1. sports
2. table tennis and ping-pong

Environment
Submitted by:
AECOM
Chelmsford, MA
60160806.005
July 2012
Human Health Risk Assessment
Pines Area of Investigation
AOC II
Docket No. V-W-’04-C-784
Environment
Submitted by:
AECOM
Chelmsford, MA
60160806.005
July 2012
Disclaimer
This document was prepared under a federal administrative order on consent and revised based on
comments received from the U.S. Environmental Protection Agency (USEPA). This document has
been approved by the USEPA, and is the final version of the document.
AECOM
Environment
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Contents
Executive Summary
1.0 Introduction.................................................................................................................... 1-1
1.1
Baseline HHRA .................................................................................................................... 1-2
1.2
Report Organization ............................................................................................................. 1-4
2.0 Site Characterization ..................................................................................................... 2-1
2.1
Pines Area of Investigation and Environs ........................................................................... 2-1
2.2
Historical Background .......................................................................................................... 2-2
2.2.1
AOC II .................................................................................................................... 2-2
2.2.2
Site Management Strategy (SMS) ....................................................................... 2-3
2.2.3
RI/FS Work Plan ................................................................................................... 2-4
2.2.4
RI Report ............................................................................................................... 2-4
2.3
Conceptual Site Model......................................................................................................... 2-5
3.0 Data Evaluation and Hazard Identification .................................................................. 3-1
3.1
Data Evaluation .................................................................................................................... 3-1
3.1.1
Chemical Data Evaluation .................................................................................... 3-3
3.1.2
Radionuclide Data Evaluation .............................................................................. 3-5
3.2
Data Compilation and Summary Statistics ......................................................................... 3-6
3.2.1
Treatment of Non-Detects .................................................................................... 3-7
3.3
Methodology for Selection of Constituents of Potential Concern ....................................... 3-7
3.3.1
Selection of Chemical COPCs ............................................................................. 3-7
3.3.2
Selection of Radionuclide COPCs ..................................................................... 3-13
3.4
Hazard Identification .......................................................................................................... 3-16
3.4.1
Chemical Hazard Identification........................................................................... 3-16
3.4.2
Radionuclide Hazard Identification ..................................................................... 3-21
3.5
Evaluation of Inorganics Data from the North Area of Yard 520 ...................................... 3-23
4.0 Dose-Response Assessment ....................................................................................... 4-1
4.1
Chemical Dose-Response Assessment ............................................................................. 4-2
4.1.1
Sources of Toxicity Values ................................................................................... 4-2
4.1.2
Noncarcinogenic Toxicity Assessment ................................................................ 4-3
4.1.3
Carcinogenic Toxicity Assessment ...................................................................... 4-6
4.1.4
Absorption ............................................................................................................. 4-8
4.1.5
Endocrine Disruption ............................................................................................ 4-9
AOC II – Docket No. V-W-’04-C-784 – HHRA
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Radionuclide Dose-Response Assessment ..................................................................... 4-10
5.0 Exposure Assessment .................................................................................................. 5-1
5.1
Conceptual Site Model......................................................................................................... 5-1
5.1.1
Setting ................................................................................................................... 5-2
5.1.2
Potential Receptors............................................................................................... 5-3
5.1.3
Suspected CCBs................................................................................................... 5-5
5.1.4
Groundwater ......................................................................................................... 5-7
5.1.5
Sediment, Surface Water, and Fish Tissue ......................................................... 5-8
5.1.6
Groundwater-to-Soil .............................................................................................. 5-9
5.2
Quantification of Potential Exposures – Chemical HHRA ................................................ 5-10
5.2.1
Estimating Potential Exposure to COPCs in Water ........................................... 5-11
5.2.2
Estimating Potential Exposures to COPCs in CCBs, Soil or Sediment ............ 5-12
5.2.3
Estimating Potential Exposures to COPCs in Air .............................................. 5-13
5.2.4
Estimating Potential Exposures to COPCs in Fish Tissue ................................ 5-13
5.3
Quantification of Potential Exposures – Radiological HHRA ........................................... 5-14
5.3.1
Residential PRGs................................................................................................ 5-14
5.3.2
Recreational Pathways – Incidental Ingestion of Sediment and External
Exposure ............................................................................................................. 5-17
5.3.3
Non-Residential PRGs ....................................................................................... 5-17
5.4
Receptor-Specific Exposure Parameters .......................................................................... 5-19
5.4.1
Resident (Adult and Child).................................................................................. 5-19
5.4.2
Recreational Child............................................................................................... 5-22
5.4.3
Recreational Fisher ............................................................................................. 5-23
5.4.4
Construction Worker ........................................................................................... 5-23
5.4.5
Outdoor Worker .................................................................................................. 5-25
5.4.6
Surface Area and Soil to Skin Adherence Factors ............................................ 5-25
5.4.7
Radionuclide Specific Exposure Parameters .................................................... 5-28
5.5
Exposure Point Concentrations ......................................................................................... 5-28
5.5.1
Measured EPCs .................................................................................................. 5-28
5.5.2
Modeled EPCs .................................................................................................... 5-30
5.6
Exposure Calculations ....................................................................................................... 5-32
6.0 Risk Characterization .................................................................................................... 6-1
6.1
Carcinogenic Risk Characterization Methods ..................................................................... 6-1
6.2
Noncarcinogenic Risk Characterization Methods ............................................................... 6-3
6.3
Risk Characterization Results ............................................................................................. 6-4
6.3.1
Chemical Risk Characterization Results .............................................................. 6-4
6.3.2
Radionuclide Risk Characterization Results ...................................................... 6-17
6.3.3
Summary of Chemical and Radionuclide Risk Characterization Results ......... 6-35
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6.4
Evaluation of the Drinking Water Pathway ....................................................................... 6-43
6.4.1
Cumulative Risk Assessment – Area of Investigation ....................................... 6-44
6.4.2
Evaluation of CCB Impact – Area Outside Municipal Water Service ................ 6-48
6.4.3
Drinking Water Pathway Evaluation Conclusions.............................................. 6-56
6.5
Uncertainty Evaluation ....................................................................................................... 6-58
6.5.1
Selection of Constituents of Potential Concern ................................................. 6-58
6.5.2
Dose-Response Assessment ............................................................................. 6-65
6.5.3
Exposure Assessment ........................................................................................ 6-68
6.5.4
Risk Characterization .......................................................................................... 6-76
6.5.5
Summary of Sources of Uncertainty in HHRA ................................................... 6-82
7.0 Summary and Conclusions .......................................................................................... 7-1
7.1
Hazard Identification ............................................................................................................ 7-1
7.2
Dose-Response Assessment .............................................................................................. 7-8
7.3
Exposure Assessment ......................................................................................................... 7-8
7.4
Risk Characterization ........................................................................................................... 7-9
7.5
Risk Assessment Results and Conclusions...................................................................... 7-11
7.5.1
Results of Chemical and Radiological Risk Assessment .................................. 7-11
7.5.2
Results of Screening Level Drinking Water Risk Assessment .......................... 7-18
7.5.3
Conclusions......................................................................................................... 7-21
8.0 References ..................................................................................................................... 8-1
AOC II – Docket No. V-W-’04-C-784 – HHRA
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List of Appendices
Appendix A
Analytical Data
Appendix B
Drinking Water Pathway Evaluation Bar Graphs
Appendix C
In-Vivo Bioavailability Study for Arsenic
Appendix D
Background Evaluation
Appendix E
UCL Derivation and Histograms
Appendix F
Chemical Risk Calculation Spreadsheets
Appendix G
HHRA Work Plan
Appendix H
Evaluation of the Potential Produce Pathway
Appendix I
Determination of %CCBs in Residential Yards
Appendix J
Evaluation of Radionuclide Data
Appendix K
Radionuclide Risk Calculation Spreadsheets
Appendix L
Response to Comments
Appendix M
Evaluation of Monitoring Well Radiological Data
Appendix N
Characterization of the Suspected CCB Dataset
Appendix O
Yard 520 Cap Construction Documentation
Appendix P
100-Year Flood Plain Maps
Appendix Q
Wetland Delineation
Appendix R
Evaluation of Additional Sampling for Arsenic
Appendix S
ProUCL Version 4.1.01 Output for Uncertainty Evaluation - Background
Appendix T
ProUCL Version 4.1.01 Output for Uncertainty Evaluation - UCLs
AOC II – Docket No. V-W-’04-C-784 – HHRA
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List of Tables
Table 2-1
DATA ON INORGANIC COMPOSITION OF COAL COMBUSTION BY-PRODUCTS - ELECTRIC
POWER RESEARCH INSTITUTE REPORT NO. 1010556 (EPRI, 2010)
Table 2-2
DATA ON INORGANIC COMPOSITION OF SUSPECTED COAL COMBUSTION BY-PRODUCTS SAMPLES COLLECTED DURING THE MUNICIPAL WATER SERVICE EXTENSION (MWSE)
Table 2-3
DATA ON INORGANIC COMPOSITION OF OTHER COMMON MATERIALS - ELECTRIC POWER
RESEARCH INSTITUTE REPORT NO. 1010556 (EPRI, 2010)
Table 3-1
MWSE AND YARD 520 SAMPLES USED IN HUMAN HEALTH RISK ASSESSMENT
Table 3-2
MONITORING WELL GROUNDWATER SAMPLES USED IN HUMAN HEALTH RISK
ASSESSMENT
Table 3-3
PRIVATE WELL GROUNDWATER SAMPLES USED IN HUMAN HEALTH RISK ASSESSMENT
Table 3-4
SEDIMENT SAMPLES USED IN HUMAN HEALTH RISK ASSESSMENT
Table 3-5
SURFACE WATER SAMPLES USED IN HUMAN HEALTH RISK ASSESSMENT
Table 3-6
BACKGROUND SURFACE SOIL SAMPLES USED IN HUMAN HEALTH RISK ASSESSMENT
Table 3-7
BACKGROUND MONITORING WELL GROUNDWATER SAMPLES USED IN HUMAN HEALTH
RISK ASSESSMENT
Table 3-8
UPGRADIENT SEDIMENT SAMPLES USED IN HUMAN HEALTH RISK ASSESSMENT
Table 3-9
UPGRADIENT SURFACE WATER SAMPLES USED IN HUMAN HEALTH RISK ASSESSMENT
Table 3-10
SELECTION OF CONSTITUENTS OF POTENTIAL CONCERN - SUSPECTED COAL
COMBUSTION BY-PRODUCTS - RESIDENTIAL AND RECREATIONAL SCENARIOS
Table 3-11
SELECTION OF CONSTITUENTS OF POTENTIAL CONCERN - SUSPECTED COAL
COMBUSTION BY-PRODUCTS - INDUSTRIAL SCENARIO
Table 3-12
SELECTION OF CONSTITUENTS OF POTENTIAL CONCERN - BACKGROUND SOIL RESIDENTIAL AND RECREATIONAL SCENARIOS
Table 3-13
SELECTION OF CONSTITUENTS OF POTENTIAL CONCERN - BACKGROUND SOIL INDUSTRIAL SCENARIO
Table 3-14
SELECTION OF CONSTITUENTS OF POTENTIAL CONCERN - MONITORING WELLS
Table 3-15
SELECTION OF CONSTITUENTS OF POTENTIAL CONCERN - SEDIMENT
Table 3-16
SELECTION OF CONSTITUENTS OF POTENTIAL CONCERN - SURFACE WATER
Table 3-17
SELECTION OF CONSTITUENTS OF POTENTIAL CONCERN - FISH TISSUE
Table 3-18
SUMMARY OF CHEMICAL COPCs
Table 3-19
SELECTION OF RADIONUCLIDE CONSTITUENTS OF POTENTIAL CONCERN - SUSPECTED
COAL COMBUSTION BY-PRODUCTS (MWSE)
Table 3-20
SELECTION OF RADIONUCLIDE CONSTITUENTS OF POTENTIAL CONCERN - COAL
COMBUSTION BY-PRODUCTS (YARD 520)
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Table 3-21
SELECTION OF RADIONUCLIDE CONSTITUENTS OF POTENTIAL CONCERN BACKGROUND SOIL
Table 3-22
SELECTION OF RADIONUCLIDE CONSTITUENTS OF POTENTIAL CONCERN - BROWN
DITCH SEDIMENT
Table 3-23
SUMMARY OF RADIONUCLIDE COPCS
Table 3-24
ESSENTIAL NUTRIENT CALCULATIONS - - SUSPECTED CCBs, BACKGROUND SOIL, AND
SEDIMENT
Table 3-25
ESSENTIAL NUTRIENT CALCULATIONS - SURFACE WATER AND GROUNDWATER
Table 3-26
COMPARISON OF MWSE SUSPECTED CCB CONCENTRATIONS TO YARD 520 CCB
CONCENTRATIONS
Table 3-27
GROUNDWATER SUMMARY STATISTICS
Table 3-28
SCREENING LEVELS FOR SELECTION OF COPCs IN CCBs, BACKGROUND SOIL, AND
SEDIMENT
Table 3-29
SCREENING LEVELS FOR SELECTION OF COPCs IN SURFACE WATER AND
GROUNDWATER
Table 3-30
SCREENING LEVELS FOR SELECTION OF COPCs IN FISH TISSUE
Table 4-1
DOSE-RESPONSE INFORMATION FOR COPC WITH POTENTIAL NONCARCINOGENIC
EFFECTS FROM CHRONIC EXPOSURE THROUGH THE ORAL ROUTE
Table 4-2
DOSE-RESPONSE INFORMATION FOR COPC WITH POTENTIAL NONCARCINOGENIC
EFFECTS FROM SUBCHRONIC EXPOSURE THROUGH THE ORAL ROUTE
Table 4-3
DOSE-RESPONSE INFORMATION FOR COPC WITH POTENTIAL NONCARCINOGENIC
EFFECTS FROM CHRONIC EXPOSURE THROUGH THE INHALATION ROUTE
Table 4-4
DOSE-RESPONSE INFORMATION FOR COPC WITH POTENTIAL NONCARCINOGENIC
EFFECTS FROM SUBCHRONIC EXPOSURE THROUGH THE INHALATION ROUTE
Table 4-5
DOSE-RESPONSE INFORMATION FOR COPC WITH POTENTIAL CARCINOGENIC EFFECTS
THROUGH THE ORAL ROUTE
Table 4-6
DOSE-RESPONSE INFORMATION FOR COPC WITH POTENTIAL CARCINOGENIC EFFECTS
THROUGH THE INHALATION ROUTE
Table 4-7
ABSORPTION ADJUSTMENT FACTORS
Table 4-8
RADIONUCLIDE SPECIFIC PARAMETERS
Table 5-1
POTENTIAL RECEPTORS, EXPOSURE MEDIA AND EXPOSURE PATHWAYS
Table 5-2
DERMAL PERMEABILITY CONSTANTS FOR GROUNDWATER AND SURFACE WATER
Table 5-3
SUMMARY OF POTENTIAL EXPOSURE ASSUMPTIONS - RESIDENT
Table 5-4
SUMMARY OF POTENTIAL EXPOSURE ASSUMPTIONS - RECREATIONAL CHILD
Table 5-5
SUMMARY OF POTENTIAL EXPOSURE ASSUMPTIONS - RECREATIONAL FISHER
Table 5-6
SUMMARY OF POTENTIAL EXPOSURE ASSUMPTIONS - CONSTRUCTION WORKER
Table 5-7
MONITORING WELL GROUNDWATER LEVELS
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Table 5-8
SUMMARY OF POTENTIAL EXPOSURE ASSUMPTIONS - OUTDOOR WORKER
Table 5-9
SOIL ADHERENCE FACTORS FOR THE ADULT RESIDENT
Table 5-10
SOIL AND SEDIMENT ADHERENCE FACTORS FOR THE CHILD
Table 5-11
SEDIMENT ADHERENCE FACTOR FOR THE RECREATIONAL FISHER
Table 5-12
SOIL ADHERENCE FACTORS FOR THE CONSTRUCTION AND OUTDOOR WORKERS
Table 5-13
SELECTION OF EXPOSURE POINT CONCENTRATIONS FOR SUSPECTED CCBs
Table 5-14
SELECTION OF EXPOSURE POINT CONCENTRATIONS FOR BACKGROUND SOILS
Table 5-15
SELECTION OF EXPOSURE POINT CONCENTRATIONS FOR BROWN DITCH SEDIMENT AND
SURFACE WATER
Table 5-16
SUSPECTED CCB AND OUTDOOR AIR EXPOSURE POINT CONCENTRATIONS
Table 5-17
BACKGROUND SOIL AND OUTDOOR AIR EXPOSURE POINT CONCENTRATIONS
Table 5-18
MONITORING WELL EXPOSURE POINT CONCENTRATIONS
Table 5-19
POND 1 (SW013) SEDIMENT EXPOSURE POINT CONCENTRATIONS
Table 5-20
POND 2 (SW014) SEDIMENT EXPOSURE POINT CONCENTRATIONS
Table 5-21
BROWN DITCH SURFACE WATER EXPOSURE POINT CONCENTRATIONS
Table 5-22
POND 1 (SW013) SURFACE WATER EXPOSURE POINT CONCENTRATIONS
Table 5-23
POND 2 (SW014) SURFACE WATER EXPOSURE POINT CONCENTRATIONS
Table 5-24
DEVELOPMENT OF DISPERSION FACTORS FOR THE SOIL TO OUTDOOR AIR PATHWAYS
Table 5-25
PARAMETERS USED IN THE DEVELOPMENT OF PARTICULATE EMISSION FACTORS FOR
THE SOIL TO OUTDOOR AIR PATHWAYS
Table 5-26
BROWN DITCH FISH TISSUE EXPOSURE POINT CONCENTRATIONS
Table 5-27
POND 1 (SW013) FISH TISSUE EXPOSURE POINT CONCENTRATIONS
Table 5-28
POND 2 (SW014) FISH TISSUE EXPOSURE POINT CONCENTRATIONS
Table 5-29
SELECTION OF EXPOSURE POINT CONCENTRATIONS FOR SUSPECTED CCBS (MWSE) RADIONUCLIDES
Table 5-30
SELECTION OF EXPOSURE POINT CONCENTRATIONS FOR CCBS (YARD 520) RADIONUCLIDES
Table 5-31
SELECTION OF RADIONUCLIDE EXPOSURE POINT CONCENTRATIONS FOR BACKGROUND
SOIL
Table 5-32
RADIONUCLIDE EXPOSURE POINT CONCENTRATIONS
Table 5-33
BROWN DITCH SEDIMENT EXPOSURE POINT CONCENTRATIONS
Table 5-34
PARTICULATE EMISSION FACTOR FOR THE CONSTRUCTION WORKER SCENARIO –
UNPAVED ROAD TRAFFIC
Table 5-35
PARTICULATE EMISSION FACTOR FOR OTHER CONSTRUCTION ACTIVITES FOR THE
CONSTRUCTION WORKER SCENARIO
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Table 6-1RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME RESIDENT - SUSPECTED CCBS AND
BROWN DITCH
Table 6-2RME
TOTAL POTENTIAL HAZARD INDEX - RME RESIDENT - SUSPECTED CCBS AND BROWN
DITCH
Table 6-3RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME RESIDENT - SUSPECTED CCBS AND
POND 1 - SW013
Table 6-4RME
TOTAL POTENTIAL HAZARD INDEX - RME RESIDENT - SUSPECTED CCBS AND POND 1 SW013
Table 6-5RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME RESIDENT - SUSPECTED CCBS AND
POND 2 - SW014
Table 6-6RME
TOTAL POTENTIAL HAZARD INDEX - RME RESIDENT SUSPECTED CCBS AND POND 2 SW014
Table 6-7RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME RESIDENT - BACKGROUND SOILS
Table 6-8RME
TOTAL POTENTIAL HAZARD INDEX - RME RESIDENT - BACKGROUND SOILS
Table 6-9RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME RECREATIONAL CHILD - SUSPECTED
CCBS AND BROWN DITCH
Table 6-10RME
TOTAL POTENTIAL HAZARD INDEX - RME RECREATIONAL CHILD - SUSPECTED CCBS AND
BROWN DITCH
Table 6-11RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME RECREATIONAL CHILD - SUSPECTED
CCBS AND POND 1 - SW013
Table 6-12RME
TOTAL POTENTIAL HAZARD INDEX - RME RECREATIONAL CHILD - SUSPECTED CCBS AND
POND 1 - SW013
Table 6-13RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME RECREATIONAL CHILD - SUSPECTED
CCBS AND POND 2 - SW004
Table 6-14RME
TOTAL POTENTIAL HAZARD INDEX - RME RECREATIONAL CHILD SUSPECTED CCBS AND
POND 2 - SW014
Table 6-15RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME RECREATIONAL FISHER - SUSPECTED
CCBS AND BROWN DITCH
Table 6-16ME
TOTAL POTENTIAL HAZARD INDEX - RME RECREATIONAL FISHER - SUSPECTED CCBS
AND BROWN DITCH
Table 6-17RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME RECREATIONAL FISHER - SUSPECTED
CCBS AND POND 1 - SW013
Table 6-18RME
TOTAL POTENTIAL HAZARD INDEX - RME RECREATIONAL FISHER - SUSPECTED CCBS
AND POND 1 - SW013
Table 6-19RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME RECREATIONAL FISHER - SUSPECTED
CCBS AND POND 2 - SW014
Table 6-20RME
TOTAL POTENTIAL HAZARD INDEX - RME RECREATIONAL FISHER - SUSPECTED CCBS
AND POND 2 - SW014
Table 6-21RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME CONSTRUCTION WORKER MONITORING WELLS
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Table 6-22RME
TOTAL POTENTIAL HAZARD INDEX - RME CONSTRUCTION WORKER - MONITORING
WELLS
Table 6-23RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME CONSTRUCTION WORKER
Table 6-24RME
TOTAL POTENTIAL HAZARD INDEX - RME CONSTRUCTION WORKER
Table 6-25RME
TOTAL POTENTIAL CARCINOGENIC RISKS - RME OUTDOOR WORKER
Table 6-26RME
TOTAL POTENTIAL HAZARD INDEX - RME OUTDOOR WORKER
Table 6-1CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE RESIDENT - SUSPECTED CCBS AND
BROWN DITCH
Table 6-2CTE
TOTAL POTENTIAL HAZARD INDEX - CTE RESIDENT - SUSPECTED CCBS AND BROWN
DITCH
Table 6-3CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE RESIDENT - SUSPECTED CCBS AND
POND 1 - SW013
Table 6-4CTE
TOTAL POTENTIAL HAZARD INDEX - CTE RESIDENT - SUSPECTED CCBS AND POND 1 SW013
Table 6-5CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE RESIDENT - SUSPECTED CCBS AND
POND 2 - SW014
Table 6-6CTE
TOTAL POTENTIAL HAZARD INDEX - CTE RESIDENT SUSPECTED CCBS AND POND 2 SW014
Table 6-7CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE RESIDENT - BACKGROUND SOILS
Table 6-8CTE
TOTAL POTENTIAL HAZARD INDEX - CTE RESIDENT - BACKGROUND SOILS
Table 6-9CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE RECREATIONAL CHILD - SUSPECTED
CCBS AND BROWN DITCH
Table 6-10CTE
TOTAL POTENTIAL HAZARD INDEX - CTE RECREATIONAL CHILD - SUSPECTED CCBS AND
BROWN DITCH
Table 6-11CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE RECREATIONAL CHILD - SUSPECTED
CCBS AND POND 1 - SW013
Table 6-12CTE
TOTAL POTENTIAL HAZARD INDEX - CTE RECREATIONAL CHILD - SUSPECTED CCBS AND
POND 1 - SW013
Table 6-13CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE RECREATIONAL CHILD - SUSPECTED
CCBS AND POND 2 - SW004
Table 6-14CTE
TOTAL POTENTIAL HAZARD INDEX - CTE RECREATIONAL CHILD SUSPECTED CCBS AND
POND 2 - SW014
Table 6-15CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE RECREATIONAL FISHER - SUSPECTED
CCBS AND BROWN DITCH
Table 6-16ME
TOTAL POTENTIAL HAZARD INDEX - CTE RECREATIONAL FISHER - SUSPECTED CCBS AND
BROWN DITCH
Table 6-17CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE RECREATIONAL FISHER - SUSPECTED
CCBS AND POND 1 - SW013
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Table 6-18CTE
TOTAL POTENTIAL HAZARD INDEX - CTE RECREATIONAL FISHER - SUSPECTED CCBS
AND POND 1 - SW013
Table 6-19CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE RECREATIONAL FISHER - SUSPECTED
CCBS AND POND 2 - SW014
Table 6-20CTE
TOTAL POTENTIAL HAZARD INDEX - CTE RECREATIONAL FISHER - SUSPECTED CCBS
AND POND 2 - SW014
Table 6-21CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE CONSTRUCTION WORKER - MONITORING
WELLS
Table 6-22CTE
TOTAL POTENTIAL HAZARD INDEX - CTE CONSTRUCTION WORKER - MONITORING WELLS
Table 6-23CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE CONSTRUCTION WORKER
Table 6-24CTE
TOTAL POTENTIAL HAZARD INDEX - CTE CONSTRUCTION WORKER
Table 6-25CTE
TOTAL POTENTIAL CARCINOGENIC RISKS - CTE OUTDOOR WORKER
Table 6-26CTE
TOTAL POTENTIAL HAZARD INDEX - CTE OUTDOOR WORKER
Table 6-27
TOTAL POTENTIAL CHEMICAL RISK
Table 6-28
TOTAL POTENTIAL HAZARD INDEX
Table 6-29
SUMMARY OF BACKGROUND INORGANIC ARSENIC INTAKE RESULTS FOR THE U.S.
POPULATION
Table 6-30
COMPARISON OF BACKGROUND U.S. DIETARY ARSENIC LADD TO PINES AREA OF
INVESTIGATION LADD
Table 6-31
COMPARISON OF ARSENIC RISK ESTIMATES TO BACKGROUND U.S. DIETARY RISK
ESTIMATES
Table 6-32RME
TOTAL POTENTIAL RME RISKS FROM RADIONUCLIDES - YARD 520 CCBS AND BROWN
DITCH SEDIMENT
Table 6-33RME
TOTAL POTENTIAL RME RISKS FROM RADIONUCLIDES - MWSE SUSPECTED CCBS AND
BROWN DITCH SEDIMENT
Table 6-34RME
TOTAL POTENTIAL RME RISKS FROM RADIONUCLIDES - BACKGROUND SOIL AND
UPGRADIENT SEDIMENT
Table 6-32CTE
TOTAL POTENTIAL CTE RISKS FROM RADIONUCLIDES - YARD 520 CCBS AND BROWN
DITCH SEDIMENT
Table 6-33CTE
TOTAL POTENTIAL CTE RISKS FROM RADIONUCLIDES - MWSE SUSPECTED CCBS AND
BROWN DITCH SEDIMENT
Table 6-34CTE
TOTAL POTENTIAL CTE RISKS FROM RADIONUCLIDES - BACKGROUND SOIL AND
UPGRADIENT SEDIMENT
Table 6-35
TOTAL POTENTIAL RISKS FROM RADIONUCLIDES
Table 6-36
TOTAL POTENTIAL RISK – CHEMICAL RISK AND RADIONUCLIDE RISK
TABLE 6-37
CUMULATIVE SCREEN OF MONITORING WELL DATA - PRIVATE WELLS - PW003
TABLE 6-38
CUMULATIVE SCREEN OF MONITORING WELL DATA - PRIVATE WELLS - PW005
TABLE 6-39
CUMULATIVE SCREEN OF MONITORING WELL DATA - PRIVATE WELLS - PW006
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TABLE 6-40
CUMULATIVE SCREEN OF MONITORING WELL DATA - PRIVATE WELLS - PW007
TABLE 6-41
CUMULATIVE SCREEN OF MONITORING WELL DATA - PRIVATE WELLS - PW008
TABLE 6-42
CUMULATIVE SCREEN OF MONITORING WELL DATA - PRIVATE WELLS - PW009
TABLE 6-43
CUMULATIVE SCREEN OF MONITORING WELL DATA - PRIVATE WELLS - PW010
TABLE 6-44
CUMULATIVE SCREEN OF MONITORING WELL DATA - PRIVATE WELLS - PW012
TABLE 6-45
CUMULATIVE SCREEN OF MONITORING WELL DATA - PRIVATE WELLS - PW013
TABLE 6-46
CUMULATIVE SCREEN OF MONITORING WELL DATA - BACKGROUND MONITORING WELLS - MW113
TABLE 6-47
CUMULATIVE SCREEN OF MONITORING WELL DATA - BACKGROUND MONITORING WELLS - MW119
TABLE 6-48
CUMULATIVE SCREEN OF MONITORING WELL DATA - BACKGROUND MONITORING WELLS - MW120
TABLE 6-49
CUMULATIVE SCREEN OF MONITORING WELL DATA - BACKGROUND MONITORING WELLS - MW121
TABLE 6-50
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS NOT SERVED BY
MUNICIPAL WATER - MW111
TABLE 6-51
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS NOT SERVED BY
MUNICIPAL WATER - MW114
TABLE 6-52
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS NOT SERVED BY
MUNICIPAL WATER - MW115
TABLE 6-53
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS NOT SERVED BY
MUNICIPAL WATER - MW116
TABLE 6-54
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS NOT SERVED BY
MUNICIPAL WATER - MW122
TABLE 6-55
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS NOT SERVED BY
MUNICIPAL WATER - MW124
TABLE 6-56
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW-3
TABLE 6-57
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW-6
TABLE 6-58
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW-8
TABLE 6-59
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW-10
TABLE 6-60
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW101
TABLE 6-61
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW102
TABLE 6-62
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW103
TABLE 6-63
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW104
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TABLE 6-64
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW105
TABLE 6-65
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW106
TABLE 6-66
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW107
TABLE 6-67
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW108
TABLE 6-68
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW109
TABLE 6-69
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW110
TABLE 6-70
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW117
TABLE 6-71
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - MW123
TABLE 6-72
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - TW-12
TABLE 6-73
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - TW-15D
TABLE 6-74
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - TW-15S
TABLE 6-75
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - TW-16D
TABLE 6-76
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - TW-16S
TABLE 6-77
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - TW-18D
TABLE 6-78
CUMULATIVE SCREEN OF MONITORING WELL DATA - MONITORING WELLS SERVED BY MUNICIPAL
WATER - TW-18S
TABLE 6-79
GROUNDWATER SCREENING LEVELS USED IN MONITORING WELL CUMULATIVE RISK SCREEN
TABLE 6-80
RESULTS OF GROUNDWATER CUMULATIVE SCREEN USING USEPA REGIONAL SCREENING LEVELS
TABLE 6-81
SUMMARY OF GROUNDWATER POTENTIAL RISKS AND HAZARDS
TABLE 6-82
GROUNDWATER SAMPLES FOR LOCATIONS NOT SERVED BY MUNICIPAL WATER
TABLE 6-83
COMPARISON OF PRIVATE WELL DATA TO RSLs
TABLE 6-84
COMPARISON OF MONITORING WELL DATA FOR LOCATIONS
TABLE 6-85
ESSENTIAL NUTRIENT CALCULATIONS - GROUNDWATER
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List of Figures
Figure 1
Area of Investigation Details
Figure 2
USGS Topographic Map
Figure 3
Areas Addressed Under AOCs
Figure 4
Results of Suspected CCB Visual Inspections
Figure 5
Human Health Conceptual Site Model
Figure 6
MWSE and Yard 520 Sample Locations
Figure 7
Monitoring Wells Sampled for Groundwater Quality
Figure 8
Private Well Sample Locations
Figure 9
Sediment Sample Locations
Figure 10
Surface Water Sample Locations
Figure 11
Background Surface Soil Sample Locations
Figure 12
Sample Locations Analyzed for Radiological Parameters
Figure 13
Constituents of Potential Concern – Construction Worker Scenario – Monitoring Wells
Figure 14
RI Sample and Measurement Locations
Figure 15
RI Monitoring Well and Private Well Locations
Figure 16
RI Groundwater and Private Well Water Sample Locations; Drinking Water Cumulative
Risk Screening Results
Figure 17
Wells in Areas not Served by Municipal Water and Distribution of Suspected CCBs Based
on Visual Inspections
Figure 18
Boron, Sulfate, Iron, and Manganese in Groundwater – First Quarter
Figure 19
Boron, Sulfate, Iron, and Manganese in Groundwater – Second Quarter
Figure 20
Boron, Sulfate, Iron, and Manganese in Groundwater – Third Quarter
Figure 21
Boron, Sulfate, Iron, and Manganese in Groundwater – Fourth Quarter
Figure 22
Redox Conditions in Groundwater
Figure 23
Estimated Boron in Groundwater Above Screening Levels
AOC II – Docket No. V-W-’04-C-784 – HHRA
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Figure 24
National Wetland Wetlands Inventory Map
Figure 25
RI Visual Inspection Locations for Suspected CCBs
Figure 26
Radon in Indiana
Figure 27
Migration of CCB-Derived Constituents to Groundwater
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List of Acronyms
AAF
Absorption Adjustment Factors
ACF
Area Correction Factor
ACS
American Cancer Society
ADAF
Age-Dependent Adjustment Factor
ADE
Average Daily Exposure
AOC I
Administrative Order on Consent, 2003 and as amended, 2004; Docket No. V-W-03-730
AOC II
Administrative Order on Consent, 2004; Docket No. V-W-’04-C-784
ARAR
Applicable or Relevant and Appropriate Requirement
ATSDR
Agency for Toxic Substances Disease Registry
bgs
Below Ground Surface
BMD
Benchmark Dose
BMDL
Benchmark Dose Lower 95% Bound
BTV
Background Threshold Value
CADD
Chronic Average Daily Dose
CalEPA
California Environmental Protection Agency
CAS
Chemical Abstracts Service
CCB
Coal Combustion By-Product
CERCLA
Comprehensive Environmental Response, Compensation and Liability Act
COC
Constituent of Concern
COPC
Constituent of Potential Concern
CSF
Cancer Slope Factor
CSM
Conceptual Site Model
CTE
Central Tendency Exposure
+D
Plus Daughters
DAF
Dermal Absorption Factor
DOC
Dissolved Organic Carbon
EDSP
Endocrine Disruptor Screening Program
EFH
Exposure Factors Handbook
ELCR
Excess Lifetime Cancer Risk
EPC
Exposure Point Concentration
EPRI
Electric Power Research Institute
FOD
Frequency of Detection
FSP
Field Sampling Plan
HEAST
Health Effects Assessment Summary Tables
HHRA
Human Health Risk Assessment
HHRAP
Human Health Risk Assessment Protocol
HI
Hazard Index
HQ
Hazard Quotient
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IDEM
Indiana Department of Environmental Management
IDNL
Indiana Dunes National Lakeshore
IEUBK
Integrated Exposure Uptake Biokinetic
IRIS
Integrated Risk Information System
LADD
Lifetime Average Daily Dose
LMS
Linearized Multi-Stage
LOAEL
Lowest Observed Adverse Effect Level
MCL
Maximum Contaminant Level
MF
Modifying Factor
MOE
Margin of Exposure
MRL
Minimum Risk Level
MWSE
Municipal Water Service Extension
NCDC
National Climatic Data Center
NCEA
National Center for Environmental Assessment
NCOPC
Not a Constituent of Potential Concern
NCP
National Contingency Plan
NIPSCO
Northern Indiana Public Service Company
NJDEP
New Jersey Department of Environmental Protection
NOAEL
No Observed Adverse Effect Level
NORM
Naturally Occurring Radioactive Material
NWI
National Wetland Inventory
NWS
National Weather Service
ORP
Oxidation Reduction Potential
OSWER
Office of Solid Waste and Emergency Response
PAH
Polycyclic Aromatic Hydrocarbon
PC
Permeability Constant
PEF
Particulate Emission Factor
PM10
Particulate Matter of 10 Microns or Less in Diameter
POD
Point of Departure
PPRTV
Provisional Peer-Reviewed Toxicity Value
PRG
Preliminary Remediation Goal
QAPP
Quality Assurance Project Plan
QA/QC
Quality Assurance/Quality Control
RAGS
Risk Assessment Guidance for Superfund
RAL
Removal Action Level
RISC
Risk Integrated System of Closure
RBA
Relative Bioavailability
RBC
Risk-Based Concentration
RCRA
Resource Conservation and Recovery Act
RfC
Reference Concentration
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RfD
Reference Dose
RI
Remedial Investigation
RI/FS
Remedial Investigation/Feasibility Study
ROW
Right-of-Way
RME
Reasonable Maximum Exposure
RSL
Regional Screening Level
RWS
Restricted Waste Site
SAB
Science Advisory Board
SAP
Sampling and Analysis Plan
SMS
Site Management Strategy
SOW
Statement of Work
SSQL
Sample-Specific Quantitation Limit
UCL
Upper Confidence Limit
UF
Uncertainty Factor
URF
Unit Risk Factor
USDA
U.S. Department of Agriculture
USEPA
U.S. Environmental Protection Agency
USFDA
U.S. Food and Drug Administration
USGS
U.S. Geological Survey
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Standard Chemical Abbreviations
Ac
Actinium
Al
Aluminum
As
Arsenic
B
Boron
Ba
Barium
Bi
Bismuth
Cl
Chloride
Co
Cobalt
Cr
Chromium
Fe
Iron
Mn
Manganese
Mo
Molybdenum
NH4
Ammonia
Pa
Protactinium
Pb
Lead
Po
Polonium
Ra
Radium
Rn
Radon
Se
Selenium
SO4
Sulfate
Sr
Strontium
Th
Thorium
Tl
Thallium,
U
Uranium
V
Vanadium
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Executive Summary
Please see Section 7, Summary and Conclusions.
AOC II – Docket No. V-W-’04-C-784 – HHRA
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1-1
Introduction
In April 2004, the United States Environmental Protection Agency (USEPA) and the Respondents
(Brown Inc., Ddalt Corp., Bulk Transport Corp., and Northern Indiana Public Service Company
(NIPSCO)) signed an Administrative Order on Consent (AOC II) (Docket No. V-W-’04-C-784) to
conduct a Remedial Investigation and Feasibility Study (RI/FS) at the Pines Area of Investigation,
located in the environs of the Town of Pines, Indiana, as set forth in Exhibit I to AOC II (AOC II, 2004).
AOC II (Section VII. 22) and its attachment, the Statement of Work (SOW) (Task 5), require the
Respondents to conduct a Human Health Risk Assessment (HHRA) as a component of the RI/FS
process. This document provides the HHRA for the Pines Area of Investigation, or the Area of
Investigation. The HHRA meets the requirements in AOC II and the SOW, and is consistent with the
National Contingency Plan (NCP) (USEPA, 1990). The HHRA has been conducted in accordance
with the USEPA approved RI/FS Work Plan (ENSR, 2005d), in which the HHRA Work Plan was
presented in Volume 5 (ENSR, 2005b). The HHRA Work Plan is also provided here as Appendix G.
The HHRA is conducted using data collected as part of the RI Field Investigation, under the Field
Sampling Plan (FSP) (ENSR, 2005d), the Municipal Water Service Extension (MWSE) Sampling and
Analysis Plan (SAP) (ENSR, 2004), and the Yard 520 SAP (ENSR, 2005e). The objectives of the RI
include (AOC II, 2004):
“(a) to determine the nature and extent of contamination at the Site and any threat to the public
health, welfare, or the environment caused by the release or threatened release of hazardous
substances, pollutants or contaminants related to coal combustion by-products (“CCB”) at or
from the Site”, and
“(b) to collect data necessary to adequately characterize…(i) whether the water service extension
installed pursuant to AOC I and AOC I as amended is sufficiently protective of current and
reasonable future drinking water use of groundwater in accordance with Federal, State, and local
requirements; (ii) whether there are significant human health risks at the Area of Investigation
associated with exposure to CCBs;….”
Therefore, this HHRA focuses on CCB-derived constituents characterized during the RI.
The SOW provides at Section 5.1:
“Respondents shall conduct a human health risk assessment that focuses on the evaluation of
current and future risks to persons coming into contact with on-site hazardous substances or
constituents as well as risks to the nearby residential, recreational and industrial worker
populations from exposure to hazardous substances or constituents in groundwater, soils,
sediments, surface water, air, and ingestion of contaminated organisms in nearby, impacted
ecosystems. The human health risk assessment shall define central tendency and reasonable
maximum estimates of exposure for current land use conditions and reasonable future land use
conditions. The human health risk assessment shall use data from the Site and nearby areas to
identify the constituents of potential concern (COPC), provide an estimate of how and to what
extent human receptors might be exposed to COPCs, and provide an assessment of the health
effects associated with these COPCs. The human health risk assessment shall assess potential
human health risk if no cleanup action is taken at the Site.
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“Respondents shall conduct the human health risk assessment in accordance with USEPA
guidance including, at a minimum: “Risk Assessment Guidance for Superfund (RAGS), Volume I
– Human Health Evaluation Manual (Part A),” Interim Final (EPA-540-1-89-002), OSWER
Directive 9285.7-01A; December 1, 1989 [USEPA, 1989a] and “Risk Assessment Guidance for
Superfund (RAGS), Volume I – Human Health Evaluation Manual (Part D, Standardized
Planning Reporting, and Review of Superfund Risk Assessments),” Interim, (EPA 540-R-97-033),
OSWER 9285.7-01D, January 1998 [USEPA, 1998a (interim); USEPA, 2001a (final)].”
The SOW indicates that the risk assessment shall also include the following elements:
1.1
•
Hazard Identification. Available information on the constituents present will be reviewed to
identify the major COPCs. COPCs will be identified based on established background levels
and human health risk-based screening levels. Constituents with detected concentrations
below established background levels and/or human health risk-based screening levels will not
be identified as COPCs.
•
Conceptual Site Model and Exposure/Pathway Analysis.
•
Characterization of the Area of Investigation and Potential Receptors.
•
Exposure Assessment. As stated in the SOW, both central tendency and reasonable
maximum estimates of exposure for current and reasonably foreseeable future land use
conditions will be developed.
•
Toxicity Assessment.
•
Risk Characterization.
•
Identification of Limitations/Uncertainties.
Ba s e line HHRA
As specified in the SOW, the HHRA has been conducted in accordance with guidance contained in
the following Office of Solid Waste and Emergency Response (OSWER) directives:
1. Clarification to the 1994 Revised Interim Soil Lead Guidance for CERCLA [Comprehensive
Environmental Response, Compensation and Liability Act] Sites and RCRA [Resource
Conservation and Recovery Act] Corrective Action Facilities. OSWER Directive 9200.4-27.
August 1998. (USEPA, 1998b);
2. Soil Screening Guidance: User’s Guide. Publication 9355.4-23. April, 1996. (USEPA,
1996a);
3. USEPA Soil Screening Guidance: Technical Background Document. OSWER Directive
9355.4-17A. May 1, 1996. (USEPA, 1996b);
4. Supplemental Guidance for Developing Soil Screening Levels for Superfund Sites. OSWER
Directive 9355.4-24. December 2002. (USEPA, 2002a);
5. Revised Interim Soil Lead Guidance for CERCLA Sites and RCRA Corrective Action
Facilities. OSWER Directive 9355.4-12. July 14, 1994. (USEPA, 1994a);
AOC II – Docket No. V-W-’04-C-784 – HHRA
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6. Guidance Manual for the Integrated Exposure Uptake Biokinetic (IEUBK) Model for Lead in
Children. Publication 9285.7-15-1. February 1994 (USEPA, 1994b), and associated,
clarifying, Short Sheets on IEUBK Model inputs, including, but not limited to, OSWER 9285.732 through 34, as listed on the OSWER lead internet site at
www.epa.gov/superfund/programs/lead/prods.htm;
7. Integrated Exposure Uptake Biokinetic (IEUBK) Model for Lead in Children. Version 0.99D,
NTIS PB94-501517, (USEPA, 1994b) or Integrated Exposure Uptake Biokinetic (IEUBK)
Model for Lead in Children. Windows version©. (USEPA, 2002b);
8. Human Health Evaluation Manual Supplemental Guidance: Standard Default Exposure
Factors. OSWER Directive 9285.6-03, March 25, 1991. (USEPA, 1991a);
9. Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions. OSWER
9655.0-30. April, 1991. (USEPA, 1991b);
10. Risk Assessment Guidance for Superfund: Volume I – Human Health Evaluation Manual:
(Part B, Development of Risk-based Preliminary Remediation Goals). Interim, OSWER
Directive 9285.6-03. December, 1991. (USEPA, 1991c);
11. Exposure Factors Handbook (EFH), Volumes I, II, and II; August 1997. (EPA/600/P95/002Fa, b, c) (USEPA, 1997a);
12. Land Use in the CERCLA Remedy Selection Process. OSWER 9355.7-04, 1995. (USEPA,
1995a); and
Note that while a number of the above-referenced guidance documents relate to lead, lead was not
identified as a COPC in this risk assessment.
In addition, the radionuclide HHRA was conducted in accordance with the following guidance, not
listed in the SOW:
Radionuclide Toxicity and Preliminary Remediation Goals for Superfund. September 7,
2010. http://epa-prgs.ornl.gov/radionuclides/. (USEPA, 2010b).
Additional and updated versions of the above guidance documents were also used in the preparation
of this HHRA.
This HHRA evaluates potential human health effects using the four step paradigm as developed by
the USEPA (USEPA, 1989a). The steps are:
•
Data Evaluation and Hazard Identification
•
Dose-Response Assessment
•
Exposure Assessment
•
Risk Characterization
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1-4
Re port Orga niza tion
A summary of the information presented in each section of the report is as follows.
•
Section 2.0 – Site Characterization. This section discusses the Area of Investigation and its
environs, describes source areas, potential migration pathways, and potentially impacted
media.
•
Section 3.0 – Data Evaluation and Hazard Identification. This section presents a summary of
the data from the RI Field Investigation for use in the HHRA, and the results of the process
used for the selection of COPCs to be quantitatively evaluated in the baseline HHRA.
•
Section 4.0 – Dose-Response Assessment. The dose-response assessment evaluates the
relationship between the magnitude of exposure (dose) and the potential for occurrence of
specific health effects (response) for each COPC. Both potential carcinogenic and
noncarcinogenic effects are considered. This section presents the quantitative doseresponse values used in the baseline HHRA. The most current USEPA verified doseresponse values are used when available.
•
Section 5.0 – Exposure Assessment. The purpose of the exposure assessment is to provide
a quantitative estimate of the magnitude and frequency of potential exposure to COPCs for a
receptor. This section presents the updated conceptual site model (CSM) originally
presented in the HHRA Work Plan (ENSR, 2005b). Potentially exposed individuals, and the
pathways through which those individuals may be exposed to COPCs, are identified based on
the physical characteristics of the area, as well as the current and reasonably foreseeable
future uses of the area and its environs. The extent of a receptor's exposure is estimated by
constructing exposure scenarios that describe the potential pathways of exposure to COPCs
and the activities and behaviors of individuals that might lead to contact with COPCs in the
environment.
•
Section 6.0 – Risk Characterization. Risk characterization integrates the results of the
exposure assessment and the dose-response assessment to derive site-specific estimates of
potentially carcinogenic and noncarcinogenic risks resulting from both current and reasonably
foreseeable future potential human exposures to COPCs. The results of the risk
characterization are used to identify, from the COPCs evaluated, a subset termed the
constituents of concern (COCs), whose potential risks result in receptor-specific risks above
-6
-4
the target risk range of 1x10 to 1x10 for potential carcinogens and above a target Hazard
Index (HI) of 1 for noncarcinogens (that act on the same target organ), as defined in USEPA
-6
guidance (USEPA, 1991b). This will allow risk managers to judge whether risks ≥10 , but ≤
-4
10 require remediation. The target risk levels used to identify COCs are based on USEPA
guidance. Specifically, USEPA provides the following guidance (USEPA, 1991b):
“EPA uses the general 10(-4) to 10(-6) risk range as a "target range" within which the
Agency strives to manage risks as part of a Superfund cleanup. Once a decision has
been made to make an action, the Agency has expressed a preference for cleanups
achieving the more protective end of the range (i.e., 10(-6)), although waste
management strategies achieving reductions in site risks anywhere within the risk
range may be deemed acceptable by the EPA risk manager. Furthermore, the upper
boundary of the risk range is not a discrete line at 1 x 10(-4), although EPA generally
uses 1 x 10(-4) in making risk management decisions. A specific risk estimate around
10(-4) may be considered acceptable if justified based on site-specific conditions,
including any remaining uncertainties on the nature and extent of contamination and
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associated risks. Therefore, in certain cases EPA may consider risk estimates slightly
greater than 1 x 10(-4) to be protective.”
And,
“Where the cumulative carcinogenic site risk to an individual based on reasonable
maximum exposure for both current and future land use is less than 10-4, and the
non-carcinogenic hazard quotient is less than 1, action generally is not warranted
unless there are adverse environmental impacts.”
In addition, IDEM offers the following guidance regarding target risk level:
The Indiana Risk Integrated System of Closure (RISC) [IDEM. 2001. Risk Integrated
System of Closure Technical Guide. February 15, 2001.], and the latest IDEM
guidance [IDEM. 2012. Remediation Closure Guide. March 22, 2012.
http://www.in.gov/idem/6683.htm] uses the target risk range of 1E-06 to 1E-04. The
IDEM residential soil screening levels are set at a 1E-05 target risk level [see
Appendix A of IDEM, 2012]. Section 7.6 of the IDEM guidance document states:
“The cumulative hazard index of chemicals that affect the same target organ should
not exceed 1, and the cumulative target risk of chemicals that exhibit the same mode
of action should not exceed 10-4. U.S. EPA risk assessment guidance views these
criteria as “points of departure”, and IDEM will generally require some further action
at sites where these risks are exceeded. Further action may include remediation, risk
management, or a demonstration utilizing appropriate lines of evidence that the risk
characterization overstates the actual risk.
Within any of the steps of the risk evaluation process described above, assumptions must be
made due to a lack of absolute scientific knowledge. Some of the assumptions are supported
by considerable scientific evidence, while others have less support. The assumptions that
introduce the greatest amount of uncertainty in this risk evaluation are discussed in Section
6.5.
•
Section 7.0 – Summary and Conclusions. This section presents a summary of the results of
the baseline HHRA.
•
Section 8.0 – This section presents the references used in the text.
Tables and figures are presented at the end of the text. Note that table numbers are based on the
Section number.
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Site Characterization
This HHRA is based on data from environmental samples collected in accordance with the RI/FS
Work Plan (ENSR, 2005d) including the Field Sampling Plan (FSP), the MWSE SAP (ENSR, 2004),
and the Yard 520 SAP (ENSR, 2005e), from the Area of Investigation (Figure 1) and presented in the
RI Report (AECOM, 2010a). Specifically, the HHRA uses data collected for suspected coal
combustion by-products (CCBs), soils, sediments, surface water, groundwater, and private well water.
2.1
P ine s Are a of In ve s tiga tion a nd En viro ns
Figure 1 identifies the Pines Area of Investigation, as defined by AOC II. The area is located primarily
in the Town of Pines, in Porter County, Indiana. The Area of Investigation is approximately 1,450
acres (2.3 square miles) in size and encompasses a variety of land types and land uses. The
estimated population of the Town of Pines is approximately 800 (U.S. Census Bureau, 2004).
The Pines Area of Investigation is located immediately west of the city limits of Michigan City, Indiana,
and about 4,500 feet south of the southern shore of Lake Michigan. The Indiana Dunes National
Lakeshore (IDNL), managed by the National Park Service, is located between Lake Michigan and the
Town of Pines. A small portion of the IDNL is included within the Area of Investigation. Figure 2 is a
U.S. Geological Survey (USGS) topographic map showing specific features in the vicinity of the Area
of Investigation.
The land use in the region varies from the relatively undeveloped areas of the IDNL, where the land
has been preserved for recreational uses, to the highly developed industrial zones such as Burns
Harbor and Michigan City. Industrial land use includes coal-fired power generating stations and fullyintegrated steel mills. Selected areas have also been developed for residential housing, including the
Town of Pines and Beverly Shores, which is located north of the Town of Pines along the shore of
Lake Michigan.
The Area of Investigation contains residential areas, the majority of which are located between US
Route 12 (West Dunes Highway) and US Highway 20. Additional residences are located mainly along
Ardendale, Railroad Avenue, and Old Chicago Road. Each house historically may have had its own
drinking water well or septic system or both. Figure 3 shows the portion of the Area of Investigation
that has been provided municipal water service. Septic systems will continue to be used (i.e., there is
no municipal sewage system).
The Area of Investigation is sectioned in the east-west direction by two major roadways, US Route 12
(West Dunes Highway) in the northern portion, and US Highway 20 in the central portion. An eastwest railroad bisects the central portion of the Area of Investigation. A major utility corridor runs
parallel and just to the north of US Route 12. The IDNL comprises the portion of the Area of
Investigation north of the utility corridor. Both residential and commercial establishments are located
along US Route 12, and the area just south of US Route 12 consists mainly of single-family homes,
located mainly along the uplands of the dune-beach complex topography that characterizes this area
of northern Indiana. South of the residential areas, and north of the railroad are wetlands
characteristic of the swale topography. These wetlands are now drained by the east and west
branches of the man-made Brown Ditch, which was constructed to improve drainage and prevent
flooding in the area. The confluence of the east and west branches of Brown Ditch is located
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approximately in the center of the Area of Investigation, where Brown Ditch then flows north into the
IDNL (Figure 2). Within the IDNL the ditch takes a turn due east and flows into Kintzele Ditch, which
then flows to Lake Michigan.
Yard 520, a closed Restricted Waste Facility permitted by the Indiana Department of Environmental
Management (IDEM), is located in the western portion of the Area of Investigation, between US Route
20 to the north and Brown Ditch and the railroad to the south. Yard 520 was previously used for the
disposal of CCBs primarily from NIPSCO’s Michigan City Generating Station, and was closed
between 2004 and 2007. Two no longer used dump sites, the Pines Landfill (owned by Waste
Management) and the Lawrence Dump are located in the area to the south of Yard 520 and the
railroad and north of Old Chicago Road (Figure 2).
In addition to the CCBs disposed of at Yard 520, suspected CCBs have also been observed in
roadbed and other areas in certain portions of the Area of Investigation. Figure 4 depicts the
information compiled about the potential locations of CCBs at the ground surface within the Area of
Investigation, based on the information presented in the RI Report (AECOM, 2010a).
2.2
His toric a l Ba c kgroun d
Between 2000 and 2004, IDEM and USEPA conducted sampling of private wells in a portion of the
Town of Pines. Boron and molybdenum were detected in some samples at concentrations above
USEPA Removal Action Levels (RALs) (USEPA, 1998c). USEPA suspected that these
concentrations above USEPA RALs were derived from CCBs because CCBs were disposed of in
Yard 520 and CCBs were reported to have been used as fill in areas within the Area of Investigation
outside of Yard 520.
To address the boron and molybdenum detections above the USEPA RALs, the Respondents agreed
to extend Michigan City’s municipal water service from Michigan City to designated areas in the Town
of Pines. This agreement was documented in an Administrative Order on Consent, referred to as
AOC I, dated February 2003 (AOC 1, 2003). Subsequent sampling of additional private wells within
the Area of Investigation indicated some concentrations near or exceeding these RALs. To address
these exceedances, the Respondents approached the USEPA about extending the municipal water
service to a larger area, under the AOC I, amended, dated April 2004 (AOC 1, 2003). The areas that
received municipal water service are identified and shown in Figure 3. In addition to extending the
municipal water service, AOC I (amended) includes a provision to offer bottled water to those
residences within the Area of Investigation not connected to municipal water.
2.2.1
AOC II
Concurrently, USEPA and the Respondents entered into AOC II (AOC II, 2004). Under AOC II, the
Respondents committed to conduct an RI/FS for the Area of Investigation. The objectives of the
RI/FS, as stated in AOC II include:
(a) To determine the nature and extent of constituents in the Area of Investigation and any threat
to the public health, welfare, or the environment caused by releases or threatened releases of
constituents related to CCBs at or from the Area of Investigation, by conducting a Remedial
Investigation.
(b) To collect data necessary to adequately characterize, for the purpose of developing and
evaluating effective remedial alternatives:
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i) Whether the water service extension installed pursuant to AOC I and AOC I as amended
is sufficiently protective of current and reasonable future drinking water use of groundwater
in accordance with Federal, State, and local requirements;
ii) Whether there are significant human health risks at the Area of Investigation associated
with exposure to CCBs; and
iii) Whether CCB-derived constituents may be causing unacceptable risks to ecological
receptors.
2.2.2
Site Management Strategy (SMS)
The first document approved by USEPA under AOC II was the Site Management Strategy (SMS)
(ENSR, 2005a). This document summarized the available information about the geology and
hydrogeology of the area and the historical placement of CCBs within the Area of Investigation,
presented a preliminary conceptual model, including a preliminary conceptual site model for the risk
assessments, identified data gaps, and outlined the general approach to the RI/FS.
The SMS also provided a description of CCBs. Generally, CCBs are the “inorganic residues that
remain after pulverized coal is burned” (USGS, 2001). There are three types of CCBs relevant to
the Area of Investigation. Their classification is based on how and when they are generated in the
coal combustion process. Bottom ash and boiler slag settle to the bottom of the combustion
chamber. Fly ash is also generated in the combustion chamber, but it is lighter and finer than the
bottom ash and boiler slag and so is transported in the flue gas and ultimately collected by air
emission controls (e.g., electrostatic precipitators or other gas scrubbing systems) (USGS, 2001).
These residues are considered to be by-products because there are many beneficial re-uses for
these materials (USGS, 2001). For example, approximately 19 million metric tons of fly ash were
used in concrete, structural fill, and waste stabilization in 1999 (USGS, 2001). Fly ash is used in
major construction projects, for example, high-strength concrete buildings, decks and piers of
highways, major dams, and concrete pavements (USGS, 2001). The use of fly ash to partially
replace portland cement in concrete significantly reduces the emissions of carbon dioxide to the
atmosphere (for example, a reduction of seven million metric tons in 1998; USGS, 2001). Five
million metric tons of bottom ash were used in 1999 primarily in structural fill, snow and ice control,
road sub-bases, and concrete (USGS, 2001). About two million metric tons of boiler slag,
representing nearly all the boiler slag produced in 1999, was used in blasting grit and roofing
applications (USGS, 2001). In addition, USEPA has used fly ash in the construction of a “green”
building in their New England Regional Laboratory located in Chelmsford, Massachusetts. The use
of fly ash in concrete construction materials in this building accounted for 126 tons of fly ash being
recycled and not disposed of as part of the waste stream (USEPA, 2007b).
The Electric Power Research Institute (EPRI) has published a report summarizing the concentration
ranges of inorganic constituents in CCBs as well as other common materials (EPRI, 2010). The
data for CCBs are from a wide variety of locations and source coals. Table 2-1 provides the EPRI
data for fly ash and bottom ash. For comparison, Table 2-2 provides similar data for the suspected
CCBs collected under the MWSE sampling program (see Section 3 for data discussion), and Table
2-3 provides information for other common materials.
At NIPSCO’s Michigan City Generating Station, management of CCBs was performed consistent
with industry and regulatory standards. Fly ash was collected from gas in the stack in emission
control devices (such as electrostatic precipitators). Prior to 1998, CCBs were flushed from the
boiler systems using water. The mixture of water and CCBs was piped to settling ponds at the
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plant. The CCBs managed this way may have been a mixture of fly ash and bottom ash. In the
settling ponds, the CCBs were allowed to settle out of the water. Approximately twice a year, the
settling ponds became filled to capacity with CCBs. At that point, the CCBs were removed from the
ponds and typically trucked to Yard 520 for disposal. At the time of disposal, the CCBs would have
been a wet slurry. In 1998, the Michigan City Generating Station switched to a system that
managed the CCBs in dry form. Also, it appears that there were occasions when NIPSCO
contracted with other entities (not Brown Inc., the owner/operator of Yard 520) for CCB-related
services. A small amount of CCBs from NIPSCO’s Bailly station was also disposed at Yard 520.
2.2.3
RI/FS Work Plan
The RI/FS Work Plan was the next USEPA-approved document under AOC II (ENSR, 2005d). The
Work Plan included an FSP designed to collect information to fill data gaps identified in the SMS, and
a Quality Assurance Project Plan (QAPP) (ENSR, 2005c). The FSP provided guidance for the RI
Field Investigation by defining in detail the sampling and data-gathering activities and methods to be
used to meet the objectives of the investigation. The FSP presented a detailed description of the field
activities planned as a part of the RI. The goal of the FSP was to collect sufficient sampling data to
support the evaluation of potential human health and ecological risks, and select an appropriate
remedy, if necessary. The QAPP presented the organization, objectives, planned activities, and
specific quality assurance/quality control (QA/QC) procedures associated with the RI/FS. Specific
protocols for sampling, sample handling and storage, chain-of-custody, and laboratory and field
analyses were described. All QA/QC procedures were structured in accordance with applicable
technical standards, USEPA’s requirements, regulations, and guidance.
2.2.3.1 HHRA Work Plan
In addition, the RI/FS Work Plan included an HHRA Work Plan (ENSR, 2005b). The HHRA Work
Plan was submitted with final USEPA approval on September 5, 2005, and provides the approach and
methodology for conducting the HHRA for the Pines Area of Investigation, including a conceptual site
model identifying potential receptors and exposure pathways. The HHRA Work Plan is provided here
as Appendix G. Many of the assumptions and approaches presented in the approved Work Plan
were altered in response to USEPA comments on the RI Report (AECOM, 2010a) and on previous
drafts of the HHRA; see Appendix L for the comment and response documents.
2.2.4
RI Report
The RI Report documents the results of the RI conducted at the Pines Area of Investigation in
accordance with AOC II and the USEPA-approved RI/FS Work Plan (ENSR, 2005d). In addition to
providing the results of the RI Field Investigation activities, the collected data have been interpreted in
the RI Report to develop a conceptual site model for the CCB-derived constituents in environmental
media at the Area of Investigation. As part of the RI Report, data validation was performed to
evaluate whether the analytical data collected for the RI were scientifically defensible, properly
documented, of known quality, and met RI objectives, according to the specifications outlined in the
USEPA-approved QAPP. The information and validated data in the RI Report serve as the basis for
conducting the HHRA. Figure 4 of this HHRA depicts the information compiled about the potential
locations of CCBs at the ground surface within the Area of Investigation, based on the information
presented in the RI Report (AECOM, 2010a). The RI Report was conditionally approved by USEPA
on November 3, 2009, and the Final RI Report was submitted on March 5, 2010.
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Conc e ptua l S ite Mod e l
To guide identification of appropriate exposure pathways and receptors for evaluation in the risk
assessment, a conceptual site model or CSM for human health was developed. The purpose of the
CSM is to identify source areas, potential migration pathways of constituents from source areas to
environmental media where exposure can occur, and to identify potential human receptors. The CSM
is meant to be a “living” model that can be updated and modified as additional data become available.
The initial CSM for the Area of Investigation is presented in the SMS and in Figure 4 of the HHRA
Work Plan (ENSR, 2005b). The CSM was revised based on USEPA comments on the RI Report and
was presented in Figure 3-20 of the RI Report (AECOM, 2010a). The CSM was used to guide the
investigation presented in the RI Report (AECOM, 2010a) and the COPC selection process in Section
3.0 of this HHRA. The CSM has been updated (see Figure 5) based on the data evaluation and
COPC selection conducted in Section 3.0 as well as on USEPA comments on the draft HHRA, and is
discussed in Section 5.0 (Exposure Assessment). The updated CSM provides the basis for the
exposure scenarios evaluated in the HHRA. Three general exposure scenarios are evaluated,
including residential (adult and child), recreational (fisher and child), and industrial (outdoor worker
and construction worker). These are discussed in more detail in Section 5.1. Media evaluated
include suspected CCBs, background soil, sediment, surface water, groundwater, private well water,
and CCBs within Yard 520. The data for these media are discussed in Section 3.
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Data Evaluation and Hazard Identification
The purpose of the hazard identification process is two-fold: 1) to evaluate the nature and extent of
CCB-derived constituents present at the Area of Investigation; and 2) to select a subset of CCBderived constituents identified as COPCs for quantitative evaluation in the risk assessment. This step
of the risk assessment involves compiling and summarizing the RI data relevant to the risk
assessment, and selecting COPCs based on a series of screening steps.
3.1
Da ta Eva lua tio n
Investigation samples from a variety of environmental media were collected from locations across the
Area of Investigation. Figure 14 displays the RI sample and measurement locations, and Figure 25
displays all of the locations evaluated in the CCB visual inspection program. The following details
some of the data collection activities germane to the human health risk assessment:
•
A total of 34 suspected CCB and 12 native soil samples were collected from utility trenches
during the installation of the municipal water service extension.
•
CCB visual inspections were conducted at over 3,800 inspection locations within rights-of-way
(ROWs), as shown on Figure 25.
•
CCB visual inspections were conducted at over 4,600 inspection locations on private
property, as shown on Figure 25.
•
Three samples of CCBs were collected from three borings drilled in the Type II (North) Area
at Yard 520.
•
A total of 25 background soil samples were collected from locations within and around the
Area of Investigation.
•
A total of five soil samples were collected from five soil borings located within the Area of
Investigation.
•
A total of 21 groundwater samples were collected from vertical profile intervals at five
monitoring well locations.
•
A total of 22 monitoring wells were installed within and around the Area of Investigation. An
additional two borings were drilled, but monitoring wells were not installed due to the limited
amount of groundwater at these locations.
•
Two staff gauges were installed in two separate ponds located in the Area of Investigation.
•
A total of 12 piezometers were installed within and around the Area of Investigation.
•
Over 375 water level measurements were collected over a period of one year during five
measuring events.
•
A total of 87 groundwater samples were collected over a period of one year during four
sampling events from the 22 installed monitoring wells.
•
A total of 38 groundwater samples were collected over a period of one year during four
sampling events from up to 11 existing Yard 520 monitoring wells.
•
A total of 92 surface water samples were collected over a period of one year during four
sampling events from 23 locations.
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•
Shallow sediment samples were collected at 19 locations. At 8 of the 19 locations, sediment
samples were collected at both shallow and deeper depths.
•
A total of 33 groundwater samples were collected from private wells over a period of one year
during four sampling events from up to nine locations.
As evident on Figures 14 and 25, and from the listing above, the surface water and sediment samples
provide adequate coverage of Brown Ditch and the other surface water environs, and the monitoring
well and private well sampling locations provide adequate coverage for groundwater. The CCB visual
inspections were conducted along every road within the Area of Investigation, and extended out into
private properties where warranted (and where access was granted). No reports have been received
of areas of CCBs within the Area of Investigation not already identified, and the identified areas
coincide with historical information discussed in the Site Management Strategy document (ENSR,
2005a). However, it must be recognized that large portions of the Area of Investigation have not been
formally surveyed (using the visual inspection method or otherwise) to determine the presence or
absence of CCBs. Therefore, the presence or absence of CCBs within the Area of Investigation
outside the MWSE and the properties subject to the visual inspection process is not known at this
time. As evidenced by the detection of trace levels of CCBs (less than 1%) in three of the five
background samples submitted for CCB analysis (see Section 3.1.1), CCBs may have been released
and transported from areas of initial deposition (e.g., the MWSE or private property) to various
unsampled portions of the Area of Investigation. However, CCB concentrations at these areas of
secondary deposition are expected to be lower than those within the MWSE. Therefore, while the
CCB samples collected during the MWSE were not taken from each area where CCBs have been
identified, they provide a robust data set that is a reasonably conservative representative of suspected
CCBs within the Area of Investigation, as discussed in more detail in Section 6.5.3.2 and in Appendix
N
The HHRA was conducted using the validated data presented in the RI Report (AECOM, 2010a). The
chemical data evaluation is presented in Section 3.1.1 and the radionuclide data evaluation is
presented in Section 3.1.2. The table below identifies the data available for evaluation in the HHRA:
Dataset
MWSE Suspected CCBs
Yard 520 CCBs – North Area
Yard 520 CCBs – South Area
Groundwater
Private Well Water
Brown Ditch Sediment
Brown Ditch Surface Water
Pond Sediment
Pond Surface Water
Dataset - Background
Surface Soil
Brown Ditch Upgradient Sediment
Brown Ditch Upgradient Surface Water
Groundwater
Analyses
Chemical Constituents
Inorganics
PAH/Dioxins
X
X (a)
X (b)
X (b)
X
X
X
X
Radionuclides
X
X (c)
X (d)
X (c)
X (c)
X
X
X
X
X
X
X
X (c)
X Data collected and available for the HHRA.
(a) Data determined not to be appropriate for use in the quantitative HHRA (see discussion in Section 3.5).
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Inorganics
PAH/Dioxins
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(b) Drinking water pathway for CCB-derived constituents is incomplete under current conditions for receptors that are provided
municipal or bottled water. The drinking water pathway for CCB-derived constituents is potentially complete for receptors
using private drinking water wells if those wells are impacted by CCBs (a detailed discussion of this can be found in
Section 6.4.2). The drinking water pathway may also be potentially complete in the future if drinking water wells are
installed and used in areas where groundwater is impacted by CCBs.
(c) Medium/constituent group found to be not of concern during the RI because sample results were below applicable
screening levels, thus, not evaluated in the quantitative HHRA (see Appendix A for a presentation of the data and Section
3.1.2 and Appendix M, which documents the basis for USEPA’s approval of removing radionuclides from the groundwater
investigation and Section 3.1.1, which discusses the results of focused PAH and dioxin sampling).
(d) Although not considered to be appropriate for evaluation of direct contact exposures, these data are included in the
quantitative HHRA at the request of USEPA.
3.1.1
Chemical Data Evaluation
Chemical analytical data are available for the following media:
•
Suspected CCBs collected from trenches during the installation of the municipal water service
extension (MWSE) project. Samples are available from the ground surface to a maximum
depth of five feet below ground surface (bgs). These samples were analyzed for inorganics.
The samples evaluated in the HHRA are listed in Table 3-1. Validated analytical data are
presented in Appendix A, Attachment 1 (Table A-1-1). Sample locations are shown in
Figure 6.
•
CCBs collected from Yard 520. Data from an investigation of the Type III (South) Area of
Yard 520, where CCBs were disposed, indicated that polycyclic aromatic hydrocarbons
(PAHs) and dioxin constituents are not present in the CCB materials at Yard 520 in
concentrations above human health screening levels (AECOM, 2010b). USEPA concurred
with this conclusion and PAHs and dioxins were eliminated from further consideration during
the RI. The comparison of the validated analytical data for these constituents to human
health based screening levels is provided in Appendix A, Attachment 2, Tables A-2-1 to
A-2-4. Inorganics were also analyzed in three samples from the Type II (North) Area of
Yard 520; these data are not quantitatively evaluated in the HHRA because there is no
exposure to the CCBs within Yard 520 and samples collected during the MWSE project
provide a better estimate of potential inorganics concentrations in the community. These
samples are discussed in more detail in Section 3.5. The samples are listed in Table 3-1.
Validated analytical data are presented in Appendix A, Attachment 3 (Table A-3-1). Sample
locations are shown in Figure 6.
•
Groundwater monitoring well data. The samples evaluated in the HHRA are listed in Table 32. Validated analytical data are presented in Appendix A, Attachment 1 (Table A-1-2).
Sample locations are shown in Figure 7.
•
Private well water data. The samples evaluated in the HHRA are listed in Table 3-3.
Validated analytical data are presented in Appendix A, Attachment 1 (Table A-1-9). Sample
locations are shown in Figure 8.
•
Brown Ditch and pond sediment. The samples evaluated in the HHRA are listed in Table 3-4.
Validated analytical data are presented in Appendix A, Attachment 1 (Table A-1-3). Sample
locations are shown in Figure 9. Note that the data for the shallow sediment samples
(0 – 0.5 ft) are used in the HHRA.
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Brown Ditch and pond surface water. The samples evaluated in the HHRA are listed in
Table 3-5. Validated analytical data are presented in Appendix A, Attachment 1
(Table A-1-4). Sample locations are shown in Figure 10.
Analytical data obtained during the RI from background or reference locations are available for the
following media:
•
Surface soils. Background surface soil samples are listed in Table 3-6; samples were
collected from 0-0.5 feet bgs. Sample locations are shown on Figure 11, and as can be seen,
they were collected from widely-spaced locations in and around the Area of Investigation.
Validated analytical data are presented in Appendix A, Attachment 1 (Table A-1-5). A total of
25 background samples were collected, of which 15 represent native granular soils and 10
represent native organic soils; three duplicate background soil samples were also collected.
The background dataset was evaluated in the HHRA using the same residential scenarios as
used for the suspected CCB dataset. The risk assessment on the background dataset has
been conducted such that a comparison between potential risks from naturally occurring
materials (i.e., background) and suspected CCBs can be made. To confirm the field visual
inspection observations about the absence of CCB materials in the background samples, a
subset of five background soil samples (SS016, SS018, SS021, SS024, and SS025),
representing 20% of the total background dataset, were submitted for microscopic analysis.
Three of the samples were native organic soils (SS016, SS018, SS025) and account for 33%
of the native organic soils dataset (3 of 10 samples); two of the samples were native granular
soils (SS021 and SS024) and account for 13% of the native granular soils dataset (2 of 15
samples). Samples were collected on February 11, 2010 from background soil material
maintained in storage and submitted for analysis by polarized light microscopy, X-ray
fluorescence, X-ray diffraction, and loss on ignition. The results are presented in the RI
Report (Appendix S) and indicate that three of the samples (SS021, SS024, and SS025)
contain less than 0.25% fly ash, and two samples contain bottom ash, one sample at 0.75%
(SS021) and one at 1% (SS024). The presence of CCB materials was not identified in two
samples (SS016 and SS018). The results indicated that no detectable amounts of fly ash
were present in the samples and that bottom ash was identified to comprise less than or
equal to 1% of the total sample material in just two of the five samples analyzed (AECOM,
2010a). The presence of even trace levels of CCBs in the majority of the background soil
samples that were analyzed for the presence of CCBs limits the usefulness of the existing
background soil data set. As a result, any comparison between the risks and hazards
calculated based on the background soil data set and those based on the CCB data set must
be viewed cautiously. (Note: Background soil samples were also collected during the MWSE
project, but not from locations identified in conjunction with USEPA oversight in the field;
therefore, data from these samples are not used in the HHRA).
•
Groundwater. Background groundwater samples are listed in Table 3-7. Validated analytical
data are presented in Appendix A, Attachment 1 (Table A-1-6). Sample locations are shown
in Figure 7.
•
Sediment. Upgradient sediment samples are listed in Table 3-8. Validated analytical data
are presented in Appendix A, Attachment 1 (Table A-1-7). Sample locations are shown in
Figure 9.
•
Surface water. Upgradient surface water samples are listed in Table 3-9. Validated analytical
data are presented in Appendix A, Attachment 1 (Table A-1-8). Sample locations are shown
in Figure 10.
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Samples were analyzed for inorganics, consistent with the USEPA-approved RI/FS Work Plan
(ENSR, 2005d). The inorganics that were included in the RI sampling were selected because of
knowledge about what may be present in CCBs, the results of the MWSE suspected CCB sampling,
information needed for general data interpretation, and based on previous sampling conducted by
USEPA for boron and molybdenum in groundwater.
3.1.2
Radionuclide Data Evaluation
Radiological analytical data for use in the HHRA are available for the following media:
•
Suspected CCBs collected from trenches during the MWSE project. A total of 10 samples
and one duplicate were analyzed for radionuclides. Five of the samples were collected from 1
to 2 feet bgs, two of the samples and the duplicate were collected from 1 to 1.5 feet bgs, and
three of the samples were collected from 2 to 3 feet bgs. The samples evaluated in the
HHRA are identified in Table 3-1. Validated analytical data for radionuclides are presented in
Appendix A, Attachment 4 (Table A-4-2). Sample locations are shown in Figure 12.
•
CCBs collected from the Type III (South) Area of Yard 520. The samples evaluated in the
HHRA are listed in Table 3-1. A total of 10 samples and one duplicate were analyzed for
radionuclides, and were collected from 8 to 12 feet bgs. Validated analytical data for
radionuclides are presented in Appendix A, Attachment 4 (Table A-4-1). Sample locations
are shown in Figure 12.
•
Brown Ditch sediment. The samples evaluated in the HHRA are identified in Table 3-4.
Validated analytical data for radionuclides are presented in Appendix A, Attachment 4 (Table
A-4-3). A total of three samples and one duplicate were analyzed for radionuclides. Sample
locations are shown in Figure 12. Note that the data for the shallow sediment samples (0 –
0.5 ft) are used in the HHRA.
•
Groundwater monitoring well data. The samples are identified in Table 3-2. Validated
radionuclide analytical data are presented in Appendix A, Attachment 4 (Table A-4-4).
Sample locations are shown in Figure 12. A total of seven samples and one duplicate from
seven monitoring wells having the highest CCB impacts were analyzed for radionuclides.
Sample results were below applicable screening levels and USEPA agreed that no further
evaluation was necessary (see Appendix M). Because the radionuclide concentrations in
groundwater were so low and based on the CSM that groundwater is likely the main pathway
for the presence of CCB-derived constituents in surface water, surface water samples were
not analyzed for radionuclides.
Radionuclide analytical data for use in the HHRA from background or reference locations are
available for the following media:
•
Surface soils. Background surface soil samples are listed in Table 3-6; all 25 background
surface soil samples and three duplicates were analyzed for radionuclide analytical
parameters. Validated analytical data for radionuclides are presented in Appendix A,
Attachment 4 (Table A-4-5). Sample locations are shown in Figure 12. It should be noted
that for use in the risk assessment, the laboratory-reported polonium-210 and lead-210
concentrations in this dataset were replaced with the reported radium-226 concentrations
because the polonium-210 and lead-210 had a high degree of error and were unrealistically
high. Polonium-210 and lead-210 are in the natural radium-226 decay chain which, in nature,
is in approximate secular equilibrium. Therefore, for background samples, the polonium-210
and lead-210 concentrations should be approximately equal to the radium-226 concentration.
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Appendix A, Attachment 4 provides the validated laboratory data as well as the substituted
values.
•
Sediment. Upgradient sediment samples are identified in Table 3-8. Two samples were
analyzed for radionuclides. Validated analytical data for radionuclides are presented in
Appendix A, Attachment 4 (Table A-4-6). Sample locations are shown in Figure 12.
•
Groundwater monitoring well data. The samples are identified in Table 3-2. Three samples
and one duplicate were analyzed for radionuclides. Validated radionuclide analytical data are
presented in Appendix A, Attachment 4 (Table A-4-7). Sample locations are shown in Figure
12. Sample results were below applicable screening levels for radionuclides and USEPA
agreed that no further evaluation was necessary (see Appendix M).
3.2
Da ta Com pila tion a nd S um m a ry S ta tis tic s
Analytical data collected in support of the RI have been compiled and tabulated in a database for
statistical analysis. The steps used to summarize the data for use in identifying COPCs in the
screening process presented in this section are discussed here. The additional steps used to
summarize the data for identifying exposure point concentrations (EPCs) are presented in Section 5.0.
Data for samples and their duplicates were averaged before summary statistics were calculated, such
that a sample and its duplicate were treated as one sample for calculation of summary statistics
(including maximum detection and frequency of detection) (USEPA, 1989b). Where both the sample
and the duplicate were not detected, the resulting values used in the statistics are the average of the
sample-specific quantitation limits (SSQLs). Where both the sample and the duplicate were detected,
the resulting values are the average of the detected results. Where one of the pair was reported as
not detected and the other was detected, the detected concentration was used.
Summary statistics for each chemical constituent in each medium sampled in the RI are presented in
Tables 3-10 to 3-16 and Table 3-27. Note that Table 3-14 contains summary statistics for monitoring
wells only (except background monitoring wells), while Table 3-27 also presents summary statistics
for all wells (RI monitoring wells, Yard 520 monitoring wells, background monitoring wells, and private
wells). Summary statistics for radionuclides are presented in Tables 3-19 to 3-22. Summary statistic
tables include the following statistics:
•
Frequency of Detection: The frequency of detection (FOD) is reported as a ratio of the
number of samples reported as detected for a specific constituent and the total number of
samples analyzed. The total number of samples reflects the averaging of duplicates
discussed above.
•
Minimum Detected Concentration: This is the minimum detected concentration for each
constituent/area/medium combination, after duplicates have been averaged.
•
Maximum Detected Concentration: This is the maximum detected concentration for each
constituent/area/medium combination, after duplicates have been averaged.
•
Mean Detected Concentration: This is the arithmetic mean concentration for each
constituent/area/medium combination, after duplicates have been averaged, based on
detected results only. Mean concentrations incorporating non-detect results are derived for
COPCs using appropriate SSQL substitution methods (USEPA, 2007a) in Section 5.
•
Minimum Reporting Limit: The minimum reporting limit, without averaging duplicates.
•
Maximum Reporting Limit: The maximum reporting limit, without averaging duplicates.
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Summary statistics were calculated for suspected CCBs using all suspected CCB samples,
regardless of depth. Three sets of summary statistics were developed for sediment and surface
water: for Brown Ditch, Pond 1 (location SW013), and Pond 2 (location SW014). Separate summary
statistics were calculated for each monitoring well to summarize the data collected over the RI
monitoring events.
3.2.1
Treatment of Non-Detects
Non-detects were not included in the calculation of summary statistics used in the COPC selection
process. For the calculation of EPCs, statistical analyses account for non-detects using various SSQL
substitution methods included in the ProUCL program, Version 4.00.02 (USEPA, 2007a). It should be
noted that since the EPCs were calculated, a new version of ProUCL (Version 4.1.01) was released.
As will be discussed in Section 5.5.1, the use of the new version has no impact on the EPCs
calculated.
A purely statistical identification of surrogate values for SSQLs (as used by ProUCL) is not appropriate
for all radionuclides. Therefore, for radioanalytical data, non-detect results for polonium-210 and lead210 were replaced with the reported radium-226 results based on the assumption of secular
equilibrium. In general, when polonium-210 and lead-210 were detected, the concentrations were
approximately equal to the radium-226 concentrations (within the error range). Appendix A,
Attachment 4, provides the validated laboratory data as well as the substituted values.
3.3
Me tho dolog y for S e le c tion of Cons titue n ts of P ote n tia l Conc e rn
COPCs are the subset of the complete set of constituents detected in media in the Area of
Investigation that are carried through the quantitative risk assessment process. Selection of COPCs
focuses the analysis on the most likely risk “drivers.” As stated in USEPA guidance (USEPA, 1993a):
“Most risk assessments are dominated by a few compounds and a few routes of exposure.
Inclusion of all detected compounds at a site in the risk assessment has minimal influence on the
total risk. Moreover, quantitative risk calculations using data from environmental media that may
contain compounds present at concentrations too low to adversely affect public health have no
effect on the overall risk estimate for the site. The use of a toxicity screen allows the risk
assessment to focus on the compounds and media that may make significant contributions to
overall risk.”
The selection of chemical COPCs is discussed in Section 3.3.1. The selection of radionuclide COPCs
is discussed in Section 3.3.2.
3.3.1
Selection of Chemical COPCs
Chemical COPCs were identified by comparing constituent-specific analytical data for environmental
media to appropriate screening levels. Several factors are typically considered in identifying COPCs,
including background, frequency of detection, toxicity, and essential nutrient status, as provided in the
approved HHRA Work Plan (ENSR, 2005b). The steps used to identify chemical COPCs are
presented below. The steps were conducted in sequential order, such that a constituent that met the
requirements of a given step was eliminated as a COPC and was not evaluated in subsequent steps.
3.3.1.1 Frequency of Detection
Per the USEPA-approved HHRA Work Plan (ENSR, 2005b), constituents that are detected in fewer
than 5% of samples, provided at least 20 samples are available, generally are not identified as
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COPCs. Based on the summary statistics developed, the suspected CCB dataset, the background
soil dataset, and the Brown Ditch surface water dataset all have enough samples to evaluate
frequency of detection. While the frequency of detection evaluation is the first step in the COPC
selection process, it is also important to note whether the constituents with low frequency of detection
are below the applicable screening levels discussed in Section 3.4.1. Therefore, the text below notes
whether constituents are eliminated from consideration based solely on frequency of detection or if
they are also eliminated based on the comparison to screening levels discussed in Section 3.4.1.
The analytical reporting limits used for the field program were appropriate for the then-current tap
water screening levels and the screening method approved by USEPA for the HHRA Work Plan
(ENSR, 2005b). However, changes to the screening method introduced by USEPA (use of 0.1x the
RSL for screening) and a change in the RSL for thallium that occurred after the field program was
complete resulted in some surface water reporting limits higher than the screening levels. Thallium
was not detected in any surface water samples. However, thallium’s maximum surface water
reporting limit is 1.9 ug/L, which exceeds its tapwater RSL-based screening level of 0.037 ug/L.
Similarly, vanadium was detected in less than half the surface water samples; however, whereas the
detected values do not exceed vanadium’s tapwater RSL-based screening level of 18 ug/L, the
maximum reporting limit is 50 ug/L, which exceeds vanadium’s tapwater RSL-based screening level.
These results suggest uncertainty associated with not selecting thallium and vanadium as surface
water COPCs. This uncertainty is discussed in Section 6.5.1.2.
Suspected CCBs
Antimony was detected at a low frequency of detection in suspected CCBs and, in addition, the
maximum detected concentration was below the screening level. Therefore, while antimony had a low
frequency of detection, it was also eliminated as a COPC based on the screening level. No chemical
constituents were eliminated as COPCs from the suspected CCB dataset based solely on frequency
of detection.
Brown Ditch Surface Water
Arsenic and lead were detected at a low frequency of detection in Brown Ditch surface water. All
detected values of lead were below the screening level, and arsenic was detected above the
screening level. Therefore, lead was eliminated as a COPC based on the screening level. Arsenic
has been retained for further evaluation as a COPC based on its USEPA carcinogen classification
(see Section 4). No constituents were eliminated as COPCs from the Brown Ditch surface water
dataset based solely on frequency of detection.
Background Soil
Background data were used as a part of the COPC selection process. Additionally, as noted
previously, the background dataset was evaluated in the HHRA under the same residential scenarios
as for the suspected CCB dataset so that a comparison between potential risks from naturally
occurring materials (i.e., background) and suspected CCBs can be made. In background soil,
beryllium, cobalt, and molybdenum were detected at a low frequency of detection. All detected values
of beryllium and molybdenum were below the screening level, while cobalt was detected above the
screening level. For the background soil dataset, therefore, beryllium and molybdenum were
eliminated as COPCs based on the screening level, and cobalt was eliminated based on low
frequency of detection. Cobalt was detected in only one of the 25 background soil samples. The
background samples were collected at widely-spaced locations over a very wide area, and so are not
clustered by location, as shown on Figure 11. The one detected concentration (23.8 mg/kg) as well
as samples with detection limits of about 10 mg/kg or greater of cobalt are of organic soils with
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moisture content greater than 50%. Therefore, “elevated” concentrations (or detection limits) of cobalt
appear to be associated with organic soils and in particular, with the wet-weight to dry-weight
correction used by the laboratory to report dry-weight concentrations, and elimination of cobalt based
on low frequency of detection is appropriate. A discussion of the uncertainties associated with
eliminating cobalt from the background dataset is presented in Section 6.5.1.2.
Summary
Only a few chemical constituents qualify for elimination based on frequency of detection. The majority
of these also have maximum detected concentrations below screening levels, as discussed in
Section 3.4.1. Arsenic in Brown Ditch surface water has been retained for further evaluation as a
COPC, despite having a low frequency of detection. Cobalt in background soil is, therefore, the only
constituent to be eliminated as a COPC based solely on frequency of detection. A discussion of the
uncertainties associated with eliminating cobalt from the background dataset is presented in
Section 6.5.1.
3.3.1.2 Comparison to Applicable Standards and/or Screening Levels
A risk-based screen was performed to identify COPCs in each medium. The methods and screening
level sources for each medium are described in this section. The maximum detected concentration in
each medium was used in this comparison step, as presented in Section 3.4.
Screening Levels for Suspected CCBs and Sediment
The USEPA Regional Screening Levels (RSLs) for soil (USEPA, 2011b), which update and replace
the USEPA Region 9 Preliminary Remediation Goals (PRGs) (identified as the basis for the screening
levels in the HHRA Work Plan), were used to identify COPCs in suspected CCBs and sediment.
-6
RSLs are risk-based concentrations in soil corresponding to a cancer risk level of 1x10 and a hazard
index of one. Although not required by the USEPA-approved HHRA Work Plan (ENSR, 2005b), RSLs
for noncarcinogens were adjusted by a factor of 0.1 to account for potential cumulative effects in the
screening process, hereinafter referred to as “adjusted RSLs”. Based on discussion with USEPA,
-6
RSLs for potential carcinogens are based on a conservative target risk level of 1x10 and were not
adjusted. The RSLs and adjusted RSLs for residential soil and industrial soil are shown in Table 3-28.
RSLs for residential soil assume daily contact by an adult and a child and assume incidental ingestion,
dermal contact, and inhalation of soil derived dusts. RSLs for industrial soil assume contact for 250
days per year by an occupational adult and assume incidental ingestion, dermal contact, and
inhalation of soil derived dusts. RSLs are not intended to represent “de facto” cleanup standards but
rather are screening levels that help determine whether further evaluation is necessary for a particular
constituent at a particular location (USEPA, 2011b).
Residential soil RSLs were adjusted and used to identify COPCs for the residential and recreational
scenarios for sediment. Industrial soil RSLs were adjusted and used to identify COPCs for the
industrial and construction worker scenarios for suspected CCBs.
Screening Levels for Groundwater and Surface Water
The published USEPA RALs (USEPA, 1998c) were used by USEPA in the area of the Town of Pines
as precautionary levels to determine whether bottled water should be offered to residents on a
temporary basis. In addition, the RALs were used by USEPA as the basis for requiring an RI/FS for
the Pines Area of Investigation. The USEPA RAL guidance notes that published numeric RALs “do
not in any way restrict the flexibility to develop and apply site-specific RALs” (USEPA, 1998c).
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RALs are not generally used in the selection of COPCs for a risk assessment, therefore, the USEPAapproved HHRA Work Plan (ENSR, 2005b) indicated that although they would be used to select
COPCs for groundwater for this risk assessment, they would not be the primary source. The general
hierarchy of screening levels for selecting COPCs in groundwater based on the HHRA Work Plan
(ENSR, 2005b) is:
1.
USEPA Primary Maximum Contaminant Levels (MCLs) (USEPA, 2011a)
2.
USEPA RALs (USEPA, 1998c)
3.
USEPA RSLs for tapwater (USEPA, 2011b), which replace and update the PRGs
However, USEPA has since requested that the screening for groundwater and surface water be
conducted using only the RSLs for tapwater, so this approach has been used instead of that outlined
in the approved HHRA Work Plan, as noted above. RSLs for noncarcinogens were adjusted by a
factor of 0.1 to account for potential cumulative effects in the screening process, based on discussion
with USEPA. The RSLs and adjusted RSLs for tapwater are shown on Table 3-29.
The potential exposure pathway to COPCs in surface water in Brown Ditch and related tributaries for
a recreational receptor is via dermal contact. The potential exposure pathway to COPCs for a
residential and a recreational receptor in surface water in the two ponds is via dermal contact and
incidental ingestion while swimming. There are no published screening levels for these potential
exposure pathways. Therefore, COPCs in surface water were conservatively selected using the
same adjusted tapwater RSLs noted above for groundwater. All the groundwater screening levels are
based on a drinking water scenario and are, therefore, protective of potential recreational and
construction worker exposures.
Screening Levels for Fish Tissue
While the USEPA RSL table replaces the USEPA Region 3 Risk-Based Concentrations (RBCs), RSLs
are not provided for fish tissue. Therefore, fish tissue screening levels (USEPA, 2011d) available on
the USEPA Region 3 website (http://www.epa.gov/reg3hwmd/risk/human/index.htm) have been used.
Modeled fish tissue concentrations (see Section 5.5.2.2) based on the maximum detected
concentration in surface water were compared to the screening levels, based on a target cancer risk
-6
level of 1x10 and a hazard quotient of 0.1. The fish tissue RSLs and adjusted RSLs are shown in
Table 3-30.
3.3.1.3 Comparison to Background
The background evaluation was conducted in accordance with USEPA guidance (USEPA, 2002d)
using the background comparison protocols provided in USEPA’s ProUCL software Version 4.00.02
(USEPA, 2007a). Since the time the background comparison was conducted, a new version of
ProUCL (Version 4.1.01) was released. To determine the potential impact on the background
evaluation, select constituents were re-run using Version 4.1.01. The results were the same as those
using Version 4.00.02. The methods used and the results of the background evaluation are presented
in Appendix D. As noted above, each step in the screening process is sequential; therefore, only
constituents with maximum detected concentrations above the adjusted RSLs described above are
considered in the background evaluation. The background evaluation was conducted as part of the
both the ecological and human health risk assessments. In some cases additional constituents were
considered for the Ecological Risk Assessment and are included in the discussion below even if
maximum detected concentrations are below the human health adjusted RSLs. Constituents that
were found to be consistent with background were eliminated as COPCs and are listed below.
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A background evaluation was not conducted for groundwater monitoring wells or surface water and
sediment in the ponds, since they are evaluated on a location by location basis.
The following chemical constituents were considered in the background evaluation for suspected
CCBs. Those listed in boldface type and noted by an asterisk (*) were found to be consistent with
background and, therefore, were eliminated as COPCs.
•
Aluminum
•
Arsenic
•
Barium
•
Boron
•
Cadmium
•
Calcium
•
Chromium
•
Cobalt
•
Copper
•
Iron
•
Lead (consistent with background; maximum detected concentration less than the
adjusted RSL) *
•
Magnesium
•
Manganese (consistent with background) *
•
Molybdenum
•
Nickel
•
Potassium
•
Selenium
•
Silicon (consistent with background; no RSL available) *
•
Sodium
•
Thallium
•
Uranium, total
•
Vanadium
•
Zinc (consistent with background; maximum detected concentration less than the
adjusted RSL) *
The following chemical constituents were considered in the background evaluation for Brown Ditch
sediment. Those listed in boldface type and noted by an asterisk (*) were found to be consistent with
background and, therefore, were eliminated as COPCs:
•
Aluminum
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Arsenic
•
Barium
•
Boron
•
Calcium
•
Copper
•
Iron
•
Lead (consistent with background; maximum detected concentration less than the
RSL) *
•
Magnesium
•
Manganese
•
Molybdenum
•
Nickel
•
Potassium
•
Selenium
•
Silicon
•
Sodium
•
Strontium
•
Vanadium
•
Zinc
3-12
The following chemical constituents were considered in the background evaluation for Brown Ditch
surface water. Those listed in boldface type and noted by an asterisk (*) were found to be consistent
with background and, therefore, were eliminated as COPCs:
•
Aluminum (consistent with background; maximum detected concentration less than
the adjusted RSL) *
•
Arsenic
•
Boron
•
Calcium
•
Iron
•
Magnesium
•
Manganese (consistent with background) *
•
Molybdenum
•
Potassium (consistent with background; no RSL available) *
•
Silica (consistent with background; no RSL available) *
•
Silicon (consistent with background; no RSL available) *
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Sodium (consistent with background; no RSL available) *
An evaluation of the potential uncertainties associated with eliminating constituents with maximum
detected concentrations greater than adjusted RSLs based on background is provided in
Section 6.5.1.
3.3.1.4 Essential Nutrients
Essential nutrients are defined as calcium, iron, magnesium, sodium, and potassium (USEPA, 1989a).
According to USEPA (1989a) essential nutrients do not need to be evaluated in a quantitative HHRA
when they are present at low concentrations (i.e., only slightly elevated above background levels)
because they are toxic only at very high doses. Screening values are not available for calcium,
magnesium, sodium, or potassium (USEPA, 2011b). Additionally, dose-response values are not
available with which to quantitatively evaluate potential health risks associated with these constituents
(see Section 4.0). RSLs are available for iron for soil and tapwater (USEPA, 2011b). Therefore, iron
concentrations were compared to RSLs as described in Section 3.4.1.2. Iron was also evaluated in
the background comparison described in Section 3.3.1.3. Calcium, magnesium, sodium, and
potassium were also evaluated in the background comparison. Potassium was found to be consistent
with background in Brown Ditch surface water; essential nutrients in other media were not found to be
consistent with background.
Because RSLs are not available, in order to determine if calcium, magnesium, potassium, and sodium
can be eliminated as COPCs, potential exposure to these essential nutrients via ingestion was further
evaluated by calculating a daily intake for comparison to dietary reference values. The daily intake
was calculated based on the maximum concentration of each constituent in each medium multiplied
by the ingestion rate appropriate to the medium. Section 5.4.1 presents residential exposure
parameters and Section 5.4.4 presents the construction worker exposure parameters. An ingestion
rate of 200 mg/day has been assumed for suspected CCBs and sediment, based on the child soil
ingestion rate (Table 5-3). For surface water, an ingestion rate of 0.05 L/day was used, consistent
with the swimming scenario for the residential child (Table 5-3). For groundwater, an ingestion rate of
0.005 L/day was used for the construction worker (Table 5-6). This maximum daily intake was
converted to a percentage of the dietary reference value (for adults and children 4 or more years of
age) for each constituent (USFDA, 2003).
As shown in Table 3-24 (suspected CCBs/background soil/sediment) and Table 3-25 (surface
water/groundwater), the maximum percentage of the dietary reference value is low (less than 1%) for
all four essential nutrients in suspected CCBs, background soil, sediment, surface water, and
groundwater. Therefore, calcium, magnesium, potassium, and sodium were all eliminated as COPCs
in these media.
3.3.2
Selection of Radionuclide COPCs
Sample results for radionuclide constituents in groundwater were below applicable water screening
levels and USEPA agreed during the RI that no further evaluation was necessary. This was
documented in the RI Report (AECOM, 2010a). The correspondence with USEPA including the data
and the comparison to screening levels is provided in Appendix M. Based on the CSM that
groundwater is likely the main pathway for the presence of CCB-derived constituents in surface water,
surface water samples were not analyzed for radionuclides.
The identification of COPCs for radionuclides in Yard 520 CCBs, MWSE suspected CCBs, sediments
(Brown Ditch and Upgradient) and background soils was not conducted in the same manner as for the
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chemical constituents. Radionuclide constituent concentrations were not simply compared against
screening levels or background concentrations for the purpose of eliminating constituents as COPCs.
The methodology used is described below.
The radionuclide constituents occur as part of several natural radioactive decay chains. These decay
chains begin with uranium-238, uranium-235, and thorium-232 as shown in the tables below. To
account for the impacts of a parent isotope and several of its short-lived decay products, the “+D” or
“+daughters” extensions are added to a parent isotope. For example, the “+D” designation is used in
the USEPA’s Health Effects Assessment Summary Tables (HEAST) (USEPA, 2001b) to provide a
radiological risk slope factor that includes contributions from the parent and short-lived daughter
isotopes which are present in equal radiological concentrations based on secular equilibrium
conditions.
Therefore, the assumption of secular equilibrium and the selection of COPCs with their “+D”
designation allows the HHRA to include contributions from decay products that were not quantified in
analytical samples. For example, the uranium-238+D slope factor includes contributions from
thorium-234 and protactinium-234m. The decay of these isotopes includes x-rays and low-energy
gamma emissions as well as some low-yield, high-energy gamma emissions. Because these
isotopes were not quantified in the samples, their contribution to the overall potential risk can only be
accounted for in the selection of the “uranium-238+D” slope factor.
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Half-life
Uranium Series (U-238 decay chain)
U-238+D
U-238
Th-234
alpha
4.5E9 year
Th-234
Pa-234m
beta
24.1 day
Pa-234m
U-234
beta
1.17 minute
Individual long-lived isotopes
U-234
Th-230
alpha
2.5E5 year
Th-230
Ra-226
alpha
8.0E4 year
Ra-226
Rn-222
alpha
1600 year
Rn-222
Po-218
alpha
3.82 day
Po-218
Pb-214
alpha
3.05 minute
Pb-214
Bi-214
beta
26.8 minute
Bi-214
Po-214
beta
19.9 minute
Po-214
Pb-210
alpha
164 microsecond
Pb-210
Bi-210
beta
22.3 year
Bi-210
Po-210
beta
5.01 day
Po-210
Pb-206
alpha
138.4 day
Parent
Daughter
Decay
Half-life
Ra-226+D
Pb-210+D
Partial Actinium Series (U-235 decay chain)
U-235+D
U-235
Th-231
alpha
7.1E8 year
Th-231
Pa-231
beta
25.6 hour
Parent
Daughter
Decay
Half-life
Thorium Series (Th-232 decay chain)
Individual long-lived isotopes
Th-232
Ra-228
alpha
1.4E10 year
Ra-228
Ac-228
beta
6.7 year
Ac-228
Th-228
beta
6.13 hour
Th-228
Ra-224
alpha
3.64 day
Ra-224
...
-
-
...
Pb-208
-
-
Ra-228+D
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Therefore, detected radionuclides were grouped according to their decay series and selected as
COPCs (without screening) for Yard 520 CCBs, MWSE suspected CCBs, sediments (Brown Ditch
and Upgradient), and background soils, using the “+D” or “+daughters” designation and slope factors
as appropriate, as listed below:
•
Uranium-238+D (not a COPC for the Upgradient sediment dataset, because it was not
detected)
•
Uranium-234
•
Thorium-230
•
Radium-226+D
•
Lead-210+D
•
Uranium-235+D (not a COPC for the Brown Ditch sediment, Upgradient sediment, or MWSE
suspected CCB dataset, because it was not detected)
•
Thorium-232
•
Radium-228+D
•
Thorium-228 (while thorium-228 is included in the radium-228 decay chain, it is not included
in the radium-228+D slope factor, and thorium-228 is, therefore, included as a separate
COPC)
While polonium-210 was detected, it is part of the lead-210 decay chain and is included as a COPC
via the lead-210+D evaluation. Polonium-210 is, therefore, not included as a separate radionuclide in
the calculations. Actinium-227 and propactinium-231 were not detected but are included as part of
the uranium-235 decay chain and are evaluated using the uranium-235 data.
3.4
Ha za rd Ide ntific a tion
This section presents the results of the COPC screening by medium and area. COPCs identified here
are included in subsequent risk calculations. The chemical hazard identification is presented in
Section 3.4.1 and the radionuclide hazard identification is presented in Section 3.4.2.
3.4.1
Chemical Hazard Identification
3.4.1.1 Suspected CCBs
Table 3-10 presents the COPC selection for constituents detected in suspected CCB samples under
the residential and recreational exposure scenarios. Fourteen constituents with maximum detected
concentrations below adjusted RSLs were not identified as COPCs. As indicated on the table,
concentrations of lead, manganese, silicon and zinc are consistent with background. Sulfur does not
have an RSL and there is no dose-response value with which to evaluate it and, therefore, is not
selected as a COPC. Calcium, magnesium, potassium, and sodium are essential nutrients and were
eliminated as COPCs using the approach presented in Section 3.3.1.4.
The following constituents were identified as COPCs in suspected CCBs for residential and
recreational exposures because their maximum detected concentrations are above the adjusted
residential soil RSLs and because they were not determined to be consistent with background:
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•
Aluminum
•
Arsenic
•
Chromium (hexavalent)
•
Cobalt
•
Iron
•
Thallium
•
Vanadium
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Table 3-11 presents the COPC selection for constituents detected in suspected CCB samples under
the industrial exposure scenario. The same background evaluation presented above for the
residential and recreational scenarios applies here. Three constituents have maximum detected
concentrations greater than the adjusted industrial RSLs and were not determined to be consistent
with background and, therefore, are identified as COPCs for suspected CCBs for industrial exposures
as follows:
•
Arsenic
•
Iron
•
Thallium
3.4.1.2 Background Soils
Table 3-12 presents the COPC selection for constituents detected in background soil samples under
the residential and recreational exposure scenarios. Note that the HHRA for background soils was
conducted only for the residential scenario.
Constituents with maximum detected concentrations below adjusted RSLs were not identified as
COPCs. Silicon and sulfur do not have RSLs and there are no dose-response values with which to
evaluate them and, therefore, they are not selected as COPCs. Calcium, magnesium, potassium, and
sodium are essential nutrients and were eliminated as COPCs using the approach presented in
Section 3.3.1.4. Although cobalt was detected at a concentration above the adjusted RSL, it was
detected only once in 25 samples and, therefore, was eliminated as a COPC based on a frequency of
detection of less than 5%. A discussion of the uncertainties associated with eliminating cobalt from
the background dataset is presented in Section 6.5.1.
The following constituents were identified as COPCs in background soils for residential and
recreational exposures because their maximum detected concentrations are above the adjusted
residential soil RSLs:
•
Aluminum
•
Arsenic
•
Iron
•
Manganese
•
Thallium
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Table 3-13 presents the COPC selection for constituents detected in background soils for the
industrial (outdoor worker and construction worker) scenario for informational purposes; the HHRA for
background soils was conducted only for the residential scenario. The following constituents were
identified as COPCs in background soils for industrial exposures because their maximum detected
concentrations are above the adjusted industrial soil RSLs:
•
Arsenic
•
Manganese
•
Thallium
3.4.1.3 Groundwater Monitoring Wells
The monitoring well data are used to evaluate the potential construction worker contact with
groundwater scenario. Table 3-14 presents the COPC selection for monitoring well groundwater for
the construction worker exposure scenario. The maximum detected concentration in each well was
compared to the adjusted tapwater RSL. A statistical background evaluation was not conducted for
groundwater. COPCs were selected on a well-by-well basis; the following COPCs were identified in
one or more of the monitoring wells:
•
Arsenic
•
Boron
•
Iron
•
Manganese
•
Molybdenum
•
Selenium
•
Strontium
•
Thallium
•
Vanadium
Not every COPC was identified as a COPC in every well; see Table 3-14. The COPCs for
groundwater are shown by well on Figure 13.
A risk-based evaluation of the residential drinking water pathway for the monitoring well data is
included in Section 6.4. COPCs were identified using a cumulative risk screening process, which is a
much more detailed evaluation than a simple comparison to adjusted RSLs, thus the COPC
identification and discussion of results for this pathway are presented in Section 6.4.
3.4.1.4 Private Wells
A risk-based evaluation of the residential drinking water pathway for the private well water data, is
presented in Section 6.4. COPCs were identified using a cumulative risk screening process, which is
a much more detailed evaluation than a simple comparison to adjusted RSLs, thus the COPC
identification and discussion of results for this pathway are presented in Section 6.4.
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3.4.1.5 Sediment
Table 3-15 presents the COPC selection for sediment for the recreational scenarios for Brown Ditch,
Pond 1 (location SW013), and Pond 2 (location SW014). While background soils were evaluated in
the HHRA, Brown Ditch Upgradient sediment data were not evaluated quantitatively in the chemical
HHRA. The following COPCs were identified for sediment in Brown Ditch because their maximum
detected concentrations are above adjusted residential soil RSLs:
•
Aluminum
•
Arsenic
•
Iron
•
Manganese
•
Vanadium
The following COPCs were identified for sediment in Pond 1 because their maximum detected
concentrations are above adjusted residential soil RSLs:
•
Arsenic
•
Iron
•
Manganese
The following COPCs were identified for sediment in Pond 2 because their maximum detected
concentrations are above adjusted residential soil RSLs:
•
Aluminum
•
Arsenic
•
Iron
•
Manganese
•
Vanadium
Note that although COPCs have been identified for sediment in the ponds and in Brown Ditch, it
cannot be determined if the presence of these COPCs is related to CCBs or if they are present at
these locations for other reasons (see the RI Report for more detailed discussion).
3.4.1.6 Surface Water
Table 3-16 presents the COPC selection for surface water for the recreational scenarios. COPCs
were selected for Brown Ditch, Pond 1 (location SW013), and Pond 2 (location SW014). While
background soils are evaluated in the HHRA, Brown Ditch Upgradient surface water data were not
evaluated quantitatively in the chemical HHRA. The following COPCs were identified for surface
water in Brown Ditch because their maximum detected concentrations are above the adjusted
tapwater RSLs, and because they are not consistent with background:
•
Arsenic
•
Boron
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Iron
•
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Note that arsenic was detected in only one sample out of 40, and meets the requirement for
elimination based on frequency of detection. However, due to its carcinogen classification, arsenic
has been retained as a COPC.
The following COPCs were identified for surface water in Pond 1 because their maximum detected
concentrations are above the adjusted tapwater RSLs:
•
Boron
•
Iron
•
Manganese
The following COPCs were identified for surface water in Pond 2 because their maximum detected
concentrations are above the adjusted tapwater RSLs:
•
Boron
•
Manganese
Note that although COPCs have been identified for surface water, it cannot be determined if the
presence of these COPCs is related to CCBs or if they are present at these locations for other
reasons (see the RI Report for more detailed discussion).
3.4.1.7 Fish Tissue
The calculation of fish tissue concentrations based on maximum detected concentrations of
constituents in surface water is described in Section 5.5.2.2. The calculated fish tissue concentrations
are then compared to the adjusted RSLs for the fish ingestion pathway (USEPA, 2011d). Table 3-17
presents the selection of COPCs for modeled fish tissue.
The following COPCs were identified because the calculated fish tissue concentrations are greater
than the adjusted calculated RSLs:
•
Brown Ditch – Arsenic, Selenium
•
Pond 1 – Manganese
•
Pond 2 – Manganese
Arsenic was detected in one surface water sample collected from Brown Ditch. Using this one data
point, the calculated fish tissue concentration is greater than the calculated adjusted RSL, as shown in
Table 3-17. Although arsenic in prepared, cooked fish has been shown to be in the organic (nontoxic) form (Schoof, et al., 1999; ATSDR, 2007), arsenic has been retained as a COPC in fish tissue
for this evaluation.
Note that although COPCs have been identified for fish tissue, it cannot be determined if the presence
of these COPCs in surface water is related to CCBs or if they are present at these locations for other
reasons (see the RI Report for more detailed discussion).
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3.4.1.8 Chemical COPC Summary
Table 3-18 presents a summary of the COPCs identified in the media discussed above. Overall, the
following 12 COPCs were identified:
•
Aluminum
•
Arsenic
•
Boron
•
Chromium (hexavalent)
•
Cobalt
•
Iron
•
Manganese
•
Molybdenum
•
Selenium
•
Strontium
•
Thallium
•
Vanadium
Not every COPC is a COPC in all media. Table 3-18 shows the media for which each COPC has
been identified.
3.4.2
Radionuclide Hazard Identification
3.4.2.1 Suspected CCBs
Table 3-19 presents the radionuclide summary statistics for the MWSE suspected CCB samples, and
Table 3-20 presents the radionuclide summary statistics for the Yard 520 CCB samples.
Radionuclindes were included as COPCs without applying a risk-based screening step as was done
for the chemical data. The following radionuclides were selected as COPCs:
•
Uranium-238+D
•
Uranium-234
•
Thorium-230
•
Radium-226+D
•
Lead-210+D
•
Uranium-235+D (not a COPC for the MWSE dataset, because it was not detected)
•
Thorium-232
•
Radium-228+D
•
Thorium-228
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3.4.2.2 Background Soils
Table 3-21 presents the radionuclide summary statistics for the background soil samples. The
following radionuclides were selected as COPCs:
•
Uranium-238+D
•
Uranium-234
•
Thorium-230
•
Radium-226+D
•
Lead-210+D
•
Uranium-235+D
•
Thorium-232
•
Radium-228+D
•
Thorium-228
3.4.2.3 Brown Ditch and Upgradient Sediment
Table 3-22 presents the radionuclide summary statistics for the Brown Ditch and Upgradient sediment
samples. The following radionuclides were selected as COPCs for both media:
•
Uranium-238+D (not a COPC for the Upgradient dataset, because it was not detected)
•
Uranium-234
•
Thorium-230
•
Radium-226+D
•
Lead-210+D
•
Thorium-232
•
Radium-228+D
•
Thorium-228
3.4.2.4 Radionuclide COPC Summary
Table 3-23 presents a summary of the COPCs identified in the media discussed above. Overall, the
following nine radionuclides were grouped according to their decay series and selected as COPCs,
using the “+D” designation and slope factors as appropriate, as listed below:
•
Uranium-238+D
•
Uranium-234
•
Thorium-230
•
Radium-226+D
•
Lead-210+D
•
Uranium-235+D
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Thorium-232
•
Radium-228+D
•
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Uranium-235 was not detected in MWSE suspected CCB samples, in Brown Ditch sediment samples,
or in Upgradient sediment samples and is, therefore, not selected as a COPC in these media.
Uranium-238 was not detected in Upgradient sediment samples and is not selected as a COPC for
Upgradient sediment.
3.5
Eva lua tion of In orga n ic s Da ta from the North Are a of Ya rd 520
USEPA has requested in the comments on the draft HHRA for the Pines Area of Investigation that the
inorganics results for three samples collected in the Type II (North) Area of Yard 520 be combined
with the MWSE SAP dataset (i.e., the 34 samples collected in the utility trenches in the Town of
Pines) and used for human health risk assessment purposes as a single CCB dataset. The following
presents the technical justification for not adding the three Yard 520 samples to the suspected CCB
dataset, which USEPA has agreed to following review of this information.
Yard 520 is a closed Restricted Waste Facility with no potential exposure pathways for direct
contact with CCBs. Yard 520 is a closed Restricted Waste Facility permitted by IDEM, and as such
is not regulated under the AOC for the Pines Area of Investigation – however, the evaluation of
constituents migrating from Yard 520 is included in the AOC (AOC II, 2004). Evaluation of direct
contact with constituents that have migrated from CCBs to groundwater is included in the risk
assessments for the Pines Area of Investigation. However, because Yard 520 is closed and capped,
there are no potential exposure pathways for direct contact with CCBs contained within Yard 520.
While trespassing activity has been noted on occasion, there are no exposures to CCBs due to the
placement and maintenance of a cap as part of the closure.
The Yard 520 Restricted Waste Site (RWS) is regulated by the State of Indiana whose laws,
regulations, and rules provide the applicable requirements for Yard 520. These laws,
regulations, and rules will serve as the applicable or relevant and appropriate requirements (ARARs)
within the meaning of Section 121 of CERCLA. The Type II Area and Type III Area were both closed
in compliance with the Applicable Requirements, including those related to capping. Specifically, the
cover consists of at least two feet of compacted final cover which is covered by at least six inches of
top soil for vegetation, in accordance with 329 IAC 10-30-3 and 329 IAC 10-28-14. The closures,
including the capping, of both the Type II Area and the Type III Area were certified by a professional
engineer licensed by the State of Indiana. The certifications were approved by IDEM. Appendix O
provides IDEM’s approval letters for the Type II Area (dated July 27, 1998) and the Type III Area
(dated August 1, 2005).
Post Closure Permits have been issued by IDEM for the Yard 520 RWS, and Post Closure
Inspections are required under the Applicable Requirements. The minimum thicknesses of both
the final cover and the vegetation layer must be maintained in accordance with 329 IAC 10-31-2.
Continued compliance with Post Closure Requirements is achieved through both unannounced IDEM
inspections and required semi-annual inspections (April and October). Post Closure Inspection
Reports are submitted annually to IDEM. Post Closure Inspection Reports (including copies of the
Closed Landfill Inspection Forms) for the years 2007, 2008, 2009, and 2010 are provided in
Appendix O.
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Therefore, the CSM for the HHRA does not identify Yard 520 as a potential exposure area for direct
contact, i.e., there is no significant human health risk from direct exposure to the CCBs in Yard 520.
The initial tiered approach envisioned sampling of CCBs in Y520, but the development and
approval of the MWSE SAP provided for direct sampling of CCBs within the Area of
Investigation. During early discussions on the SMS, Respondents suggested a tiered approach to
the evaluation/risk assessment of CCBs. Such a tiered approach would have considered analyzing
samples of CCBs from Yard 520, and using the results as a conservative surrogate for the suspected
CCBs along roadways within the Area of Investigation. Had the results indicated the potential for
elevated risks, then sampling of CCBs outside of Yard 520 would be conducted. This was the
approach taken for the evaluation of the PAHs, dioxins/furans and radionuclides. However, the
Amendment to AOC I increased the MWSE to a much larger area, and it became apparent that the
trenching for the MWSE would provide the opportunity to collect suspected CCB samples directly from
the Area of Investigation where there was potential for direct contact exposure. Therefore, the MWSE
SAP (ENSR, 2004) was developed and approved by the Agency and 34 samples of suspected CCBs
(plus appropriate duplicates) were collected and analyzed for inorganic parameters. As of the
submission of the first draft of the RI/FS Work Plan, approximately 30 suspected CCB samples had
been collected. The final MWSE SAP (October 2004) predated the final SMS (January 2005) and,
therefore, there was no description of or proposal for a tiered approach for the inorganic data in the
SMS.
Development of the Yard 520 SAP for PAHs, dioxins/furans, and radionuclides. As part of the
RI/FS Work Plan review, USEPA requested that a small set of samples of CCBs be collected and
analyzed for certain additional parameters: PAHs, dioxins/furans, and radionuclides. The
Respondents proposed that samples for these parameters be collected from Yard 520 for several
reasons: 1) these parameters can have naturally high background levels, 2) it was important to collect
samples from an area known to be only CCBs to provide an accurate assessment of their levels in
CCBs, and 3) samples collected from the MWSE project could be impacted from other sources, thus
potentially biasing the results for these specific parameters. The Yard 520 results for these additional
parameters are considered worst case because the samples were fly ash, and of the three types of
CCBs (fly ash, bottom ash, and boiler slag), fly ash is known to have higher constituent
concentrations. Also, it was proposed that samples be collected from the South Area of Yard 520 as it
is known that only fly ash was placed there, whereas other materials were placed in the North Area of
Yard 520 in addition to fly ash, thus avoiding sample results that could be biased or diluted by these
other materials. This sampling is identified and discussed in the Yard 520 SAP (ENSR, 2005e).
Request for inorganic analyses from Yard 520. Also as part of the RI/FS Work Plan review,
USEPA requested that inorganic analyses be conducted on the samples from Yard 520. In response,
and for the same reasons stated above, the Respondents noted that the presence of metals in CCBs
was being evaluated under the MWSE SAP using the samples collected from the utility trenches in the
residential areas of the Area of Investigation. The Respondents agreed to add to the RI/FS sampling
program collection of three samples of material from the North Area of Yard 520 to be analyzed for
inorganics to focus the analyte list used for the MWSE SAP and other sampling efforts in the RI. This
was in fact noted in the FSP of the RI/FS Work Plan.
The MWSE dataset is a robust dataset representative of CCBs placed within the Area of
Investigation outside of Yard 520. The RI has produced the MWSE CCB dataset which is a very
robust dataset of inorganic constituents in suspected CCBs from locations within the residential areas
of the Area of Investigation – those areas where potential exposure can take place. These samples
were collected from the road bed and fill areas encountered during the MWSE trenching, and were
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biased to consist only of CCBs to the extent practical. Using the protocols employed for the visual
inspection program, the samples in the MWSE dataset would be classified as being in the 75-100%
CCB range. The visual inspection results determined that the majority of the inspection locations on
private properties where suspected CCBs were located at the surface had a CCB content in the 125% range, some in the 25-50% range, and only a very few were classified in the 50-75% range (see
Appendix I). None of the locations were classified in the 75-100% CCB range. Therefore, although
there may be some other non-CCB material in the MWSE suspected CCB samples, they still contain
a greater amount of CCBs than samples at the surface evaluated during the visual inspections. The
samples evaluated during the visual inspection represent a wide range of areas within the Area of
Investigation. Thus the MWSE suspected CCB dataset is both a representative and a conservative
dataset for the estimation of potential direct contact exposure to CCB constituents within the Area of
Investigation. Appendix N provides a statistical evaluation of the suspected CCB dataset.
The North Area Yard 520 results are clearly different from the dataset representative of CCBs
within the Area of Investigation outside of Yard 520. Review of the MWSE CCB dataset indicates
that it is representative of one population (see Section 4.3.2 of the RI Report, and Appendix N). The
Type II (North) Area of Yard 520 results are clearly different from the MWSE dataset. This can be
seen from the data and the ranges of constituent concentrations, and from the descriptions in the
boring and test pits logs (RI Report). Table 3-26 presents a comparison of the
minimum/maximum/mean concentrations of the MWSE suspected CCB inorganics dataset and the
Yard 520 CCB inorganics dataset. The material observed during the water service installation
included a large percentage of coarse grained material (larger than silt and clay), and the sidewalls of
the trenches stayed upright during the utility work. In contrast, the material in Yard 520 was observed
to be predominantly very fine grained, soupy or muddy, and would not stay upright on an open face.
Based on descriptions from Brown Inc., the material brought to Yard 520 was a wet slurry which
needed draining/dewatering. This material would not have been suitable for fill or road sub-base,
which accounts for the material outside Yard 520 being different. The most likely explanation of the
observed differences is that the material in Yard 520 is primarily fly ash, while the material in the Town
of Pines consists of a larger portion of bottom ash and/or boiler slag. Thus while both materials are
CCBs, they are different types of CCBs with different physical and chemical characteristics. The RI
Report includes more discussion of the different types of CCBs and the differences observed within
the Area of Investigation. Fly ash is known to have higher constituent concentrations than the other
types of ash, and this difference is clear in the analytical results for the MWSE dataset and the three
Type II (North) Area of Yard 520 samples.
Therefore, to provide an HHRA that is representative of potential exposures in the Area of
Investigation, the samples from the Type II (North) Area of Yard 520 have not been included in the
quantitative risk assessment.
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Dose-Response Assessment
The purpose of the dose-response assessment is to identify the types of adverse health effects a
constituent may potentially cause, and to define the relationship between the dose of a constituent
and the likelihood and magnitude of an adverse effect (response) (USEPA, 1989a). Adverse effects
are classified by USEPA as potentially carcinogenic or noncarcinogenic (i.e., potential effects other
than cancer). Dose-response relationships are defined by USEPA for oral exposure and for exposure
by inhalation. Oral toxicity values are also used to assess dermal exposures, with appropriate
adjustments, because USEPA has not yet developed dose-response values for this route of exposure
(USEPA, 1989a). Combining the results of the toxicity assessment with information on the magnitude
of potential human exposure provides an estimate of potential risk (USEPA, 1989a). The Integrated
Risk Information System (IRIS) (USEPA, 2011e) is USEPA’s online database of toxicity values.
As stated in IRIS (USEPA, 2011e), for noncancer effects, oral reference doses and inhalation
reference concentrations (RfDs and RfCs, respectively) for effects known or assumed to be produced
through a nonlinear (possibly threshold) mode of action are developed. The oral Reference Dose
(RfD) is based on the assumption that thresholds exist for certain toxic effects such as gastrointestinal
effects. It is expressed in units of mg/kg-day. In general, the RfD is an estimate (with uncertainty
spanning perhaps an order of magnitude) of a daily exposure to the human population (including
sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a
lifetime.
As stated in IRIS (USEPA, 2011e), for potential cancer effects, descriptors that characterize the
weight of evidence for human carcinogenicity, oral slope factors, and oral and inhalation unit risks for
carcinogenic effects are developed. The quantitative risk estimates are presented in three ways. The
slope factor is the result of application of a low-dose extrapolation procedure and is presented as the
risk per (mg/kg-day). The unit risk is the quantitative estimate in terms of either risk per ug/L drinking
3
water or risk per ug/m air breathed. The third form in which risk is presented is a drinking water or air
concentration providing cancer risks of 1 in 10,000, 1 in 100,000 or 1 in 1,000,000.
Numerical toxicity values are generally obtained from USEPA databases/sources as described
Section 4.1.1. The dose-response relationship is often determined from laboratory studies conducted
under controlled conditions with laboratory animals. These laboratory studies are controlled to
minimize responses due to confounding variables, and are conducted at relatively high dose levels to
ensure that responses can be observed using as few animals as possible in the experiments.
Mathematical models or uncertainty factors are used to extrapolate the relatively high doses
administered to animals to predict potential human responses at dose levels far below those tested in
animals. Humans are typically exposed to constituents in the environment at levels much lower than
those tested in animals. These low doses may be detoxified or rendered inactive by the myriad of
protective mechanisms that are present in humans (Ames, et al., 1987) and which may not function at
the high dose levels used in animal experiments. Moreover, as noted by USEPA (USEPA, 1993c) “in
the case of systemic toxicity, however, organic homeostatic, compensating, and adaptive mechanisms
exist that must be overcome before a toxic endpoint is manifested.” Therefore, the results of these
animal studies may only be of limited use in accurately predicting a dose-response relationship in
humans (USEPA, 1989a). However, to be protective of human health, USEPA incorporates
conservative assumptions and safety factors when deriving numerical toxicity criteria from laboratory
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studies, as discussed in Section 4.1.2 below. USEPA explicitly recognizes these extrapolations from
high doses to low doses and from animal studies to predict responses in humans as uncertainties in
the risk assessment process (USEPA, 1989a).
In some cases, data from human exposure to constituents are used to develop dose-response values.
However, these data also have uncertainties because it is not possible to determine from human
exposure studies whether one or more constituents are responsible for the observed effects, and in
general it is even more difficult to determine precise exposure levels (USEPA, 1989a). Moreover,
where effects are observed in humans, they generally occur at high exposure levels (often in industrial
settings), and it is difficult to predict potential human responses at the much lower dose levels that
occur in environmental exposure scenarios (USEPA, 1989a). However, there are cases where
human toxicity has been observed at site-specific environmental levels, for example cases of arsenic
exposure in Taiwan or Bangladesh (Hughes, et al., 2011).
The chemical dose-response assessment is presented in Section 4.1 and contains four subsections.
Section 4.1.1 describes the sources of toxicity values. Section 4.1.2 describes USEPA’s approach for
developing noncarcinogenic toxicity values. Section 4.1.3 describes the toxicity values developed by
USEPA for the evaluation of potential carcinogenic effects. Section 4.1.4 discusses the methods used
to derive dermal toxicity values and presents absorption adjustment factors (AAFs) used to account
for differences in absorption in the environmental medium and in the dose-response study. The
radionuclide dose-response assessment is presented in Section 4.2.
4.1
Che m ic a l Dos e -Re s p ons e As s e s s m e nt
4.1.1
Sources of Toxicity Values
The USEPA’s guidance regarding the hierarchy of sources of human health dose-response values in
risk assessment was followed (USEPA, 2003). Sources of the published dose-response values in this
risk assessment include USEPA’s IRIS database (USEPA, 2011e), provisional peer-reviewed toxicity
values (PPRTVs), California Environmental Protection Agency (CalEPA, 2008a; 2008b), the New
Jersey Department of Environmental Protection (NJDEP, 2009) and the Health Effects Assessment
Summary Tables (HEAST) (USEPA, 1997b).
The primary (Tier 1) USEPA source of dose-response values is IRIS, an on-line computer database of
toxicological information (USEPA, 2011e). The IRIS database is updated monthly to provide the most
current USEPA verified dose-response values. As defined by the USEPA (1997b), a dose-response
value is “Work Group-Verified” if all available information on the value has been examined by an
Agency Work Group, the value has been calculated using current Work Group methodology, a
unanimous consensus has been reached on the value by the Work Group, and the value appears on
IRIS.
When a dose-response value is not available from IRIS, PPRTVs or other provisional values
published by the USEPA National Center for Environmental Assessment (NCEA) in Cincinnati are
used (Tier 2 values). PPRTVs for aluminum (USEPA, 2006b), cobalt (USEPA, 2008a), iron (USEPA,
2006c), and vanadium (USEPA, 2009b) were obtained from USEPA on January 8, 2010. The PPRTV
for vanadium is for metallic vanadium, which is unlikely to be present in suspected CCBs. Therefore,
the dose-response value available from IRIS for vanadium pentoxide was used, adjusted in the same
manner as in the USEPA RSL table (USEPA, 2011b). The USEPA now provides PPRTVs on-line
[http://hhpprtv.ornl.gov/]. The PPRTV for thallium and compounds was obtained on-line (USEPA,
2010a).
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If dose-response values were not available from IRIS (Tier 1) and PPRTVs were not available (Tier 2),
a Tier 3 source is used. Tier 3 sources include: Agency for Toxic Substances Disease Registry
(ATSDR) Minimal Risk Levels (MRLs) (ATSDR, 2008), CalEPA values (CalEPA, 2008a; 2008b), or
USEPA’s HEAST (USEPA, 1997b). A dose response value was obtained for hexavalent chromium
from the NJDEP (NJDEP, 2009). HEAST was formerly published annually by the USEPA and
provides a compilation of dose-response values available at the time of publishing. Because HEAST
is no longer updated regularly, the dose-response values provided may not represent the most current
values available. In addition, the dose-response values provided by HEAST are considered to be
provisional, i.e., the value has had some form of agency review, but does not appear on IRIS. The
HEAST values may or may not have been generated through the Agency Work Group process, but
the values generally use all available information, use current methodology, and a consensus was
reached by Agency scientists on the value. HEAST is, therefore, considered to be an unverified
source of dose-response values and should be used only if no dose-response value is available from
IRIS or the NCEA. Therefore, the hierarchy of dose-response value sources correlates in general with
the level of confidence in the values, with the values provided by IRIS or NCEA having the higher level
of confidence. While the other Tier 3 sources (i.e., ATSDR, CalEPA, NJDEP) may provide more
current dose-response values than HEAST, these values are also considered to have a lower level of
confidence than the USEPA-derived values due to the differences in derivation and review processes.
4.1.2
Noncarcinogenic Toxicity Assessment
Constituents with known or potential noncarcinogenic effects are assumed to have a dose below
which no adverse effect occurs or, conversely, above which an adverse effect may be seen. This
dose is called the threshold dose. A conservative estimate of the true threshold dose is called a No
Observed Adverse Effect Level (NOAEL). The lowest dose at which an adverse effect has been
observed is called a Lowest Observed Adverse Effect Level (LOAEL). The NOAEL, or if not available,
the LOAEL are used as the point of departure (POD) for extrapolating from experimental data to
predict a threshold level for humans. By applying uncertainty factors to the NOAEL or the LOAEL,
Reference Doses (RfDs) or Reference Concentrations (RfCs) for chronic exposure to constituents
with noncarcinogenic effects have been developed by USEPA (1997b, 2011e).
In more recent derivations, USEPA has used a benchmark dose (BMD) approach to define the POD
for an observed adverse outcome, or benchmark response, from experimental observations. The
BMD approach provides a more quantitative alternative to the first step in the dose-response
assessment than the current NOAEL/LOAEL process for noncancer health effects. Derivation of the
BMD is a two-step process: (1) response data are modeled in the range of empirical observation; and
then (2) extrapolation below the range of observation is accomplished by modeling. The POD for
BMD modeling is the BMDL, or the lower 95% bound on the dose/exposure associated with the
benchmark response (i.e., adverse response), typically 10% above the control response. Using the
lower bound accounts for the uncertainty inherent in a given study, and assures (with 95%
confidence) that the target benchmark response is not exceeded. Uncertainty factors are then applied
to the BMDL, as in the case for the NOAEL/LOAEL approach, to derive an RfD or RfC. The BMD
approach has been used for the derivation of the dose-response values for the following: boron (oral
RfD), and hexavalent chromium (inhalation RfC).
In regulatory toxicity assessment, USEPA assumes that humans are as sensitive, or more sensitive,
to the toxic effects of a constituent as the most sensitive species used in the laboratory studies.
Moreover, the RfD or RfC is developed based on the most sensitive or critical adverse health effect
observed in the study population, with the assumption that if the most critical effect is prevented, then
all other potential toxic effects are prevented. Uncertainty factors are applied to the BMDL or NOAEL
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(or LOAEL, when a NOAEL is unavailable) for this critical effect to account for uncertainties
associated with the dose-response relationship. These include using an animal study to derive a
human toxicity value, extrapolating from a LOAEL to a NOAEL, extrapolating from a subchronic
(partial lifetime) to a chronic lifetime exposure, and evaluating sensitive subpopulations. Generally, a
10-fold factor is used to account for each of these uncertainties; thus, the total uncertainty factor can
range from 10 to 10,000. In addition, an uncertainty factor or a modifying factor of up to 10 can be
used to account for inadequacies in the database or other uncertainties. The uncertainty factors for
the COPCs evaluated in this risk assessment range from 1 to 3000. USEPA’s standard uncertainty
factors and the modifying factor are identified below (USEPA, 1993c).
Standard Uncertainty Factors (UFs):
•
•
•
•
Use a 10-fold factor when extrapolating from valid experimental results in studies using
prolonged exposure to average healthy humans. This factor is intended to account for
the variation in sensitivity among the members of the human population and is
referenced as "10H".
Use an additional 10-fold factor when extrapolating from valid results of long-term
studies on experimental animals when results of studies of human exposure are not
available or are inadequate. This factor is intended to account for the uncertainty
involved in extrapolating from animal data to humans and is referenced as "10A".
Use an additional 10-fold factor when extrapolating from less than chronic results on
experimental animals when there are no useful long-term human data. This factor is
intended to account for the uncertainty involved in extrapolating from less than chronic
NOAELs to chronic NOAELs and is referenced as "10S".
Use an additional 10-fold factor when deriving an RfD from a LOAEL, instead of a
NOAEL. This factor is intended to account for the uncertainty involved in extrapolating
from LOAELs to NOAELs and is referenced as "10L".
Modifying Factor (MF):
•
Use professional judgment to determine the MF, which is an additional uncertainty factor
that is greater than zero and less than or equal to 10. The magnitude of the MF depends
upon the professional assessment of scientific uncertainties of the study and data base
not explicitly treated above; e.g., the completeness of the overall data base and the
number of species tested. The default value for the MF is 1.
The resulting RfDs and RfCs are conservative, i.e., health protective, because of the use of the
uncertainty factors and modifying factors, where applicable. For constituents with noncarcinogenic
effects, an RfD or RfC provides reasonable certainty that no noncarcinogenic health effects are
expected to occur even if daily exposures were to occur at the RfD level for a lifetime. RfDs and
exposure doses are expressed in units of milligrams of a constituent per kilogram of body weight per
day (mg/kg-day). RfCs and exposure concentrations are expressed in terms of milligrams of
3
constituent per cubic meter of air (mg/m ). The lower the RfD or RfC value, the lower is the assumed
threshold for effects, and the greater the assumed toxicity.
All twelve COPCs evaluated in this risk assessment have oral reference doses, as shown in Table 41. Six oral reference doses are based on animal studies (aluminum, chromium [hexavalent], boron,
strontium, thallium, and vanadium) with uncertainty factors ranging from 66 (boron) to 3000 (thallium).
Six oral reference doses are based on human studies (arsenic, cobalt, iron, manganese,
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molybdenum, and selenium), with uncertainty factors ranging from one (with a modifying factor or
three) for manganese to 1000 (cobalt).
Seven COPCs have inhalation reference concentrations, as shown in Table 4-3. The inhalation
reference concentration for hexavalent chromium is based on a rat study and has an uncertainty
factor of 300. The remaining six reference concentrations are based on human studies (aluminum,
arsenic, boron, cobalt, manganese, and selenium) and have uncertainty factors range from 100
(boron) to 1000 (manganese).
In identifying the appropriate RfD or RfC for use in the HHRA, the duration of exposure was
considered. Chronic dose-response values apply to exposures lasting greater than seven years,
while subchronic dose-response values apply to exposures lasting fewer than seven years (USEPA,
1989a). Therefore, for evaluation of the future construction worker whose exposure is assumed to
last one year, subchronic dose-response values were used. Subchronic dose-response values are
selected according to the same hierarchy of sources as chronic dose-response values. For many
constituents, a subchronic dose-response value may be derived from the chronic dose-response
value by removing the uncertainty factors applied for extrapolation from a subchronic study to a
chronic exposure period. Subchronic dose-response data are not available for every constituent for
which a chronic dose-response value has been derived. For a COPC lacking a subchronic RfD or
RfC or for which a subchronic RfD or RfC could not be derived by removal of the applied subchronicto-chronic extrapolation uncertainty factor, the chronic dose-response value was used. Very few
subchronic values were identified; for oral exposure, a subchronic RfD was identified for cobalt, based
on a human study with an uncertainty factor of 300 (USEPA, 2008a), chromium (hexavalent), based
on a rat study with an uncertainty factor of 100 (USEPA, 2011e) and thallium, based on a rat study
with an uncertainty factor of 1000 (USEPA, 2010a), and for inhalation exposure, a subchronic RfC
was identified for chromium (hexavalent), based on a rat study with an uncertainty factor of 100
(USEPA, 2011e) and cobalt, based on a human study with an uncertainty factor of 100 (USEPA,
2008a). For all remaining COPCs, the chronic value was used to evaluate subchronic exposures.
Table 4-1 summarizes the chronic toxicity information for COPCs with potential noncarcinogenic
effects for the oral route of exposure, and Table 4-2 summarizes the subchronic toxicity information.
For each COPC, the chemical abstracts service number (CAS number), the dose-response value
(RfD), and the reference for the toxicity value are presented. In addition, the USEPA confidence level
in the value, the uncertainty factor, the modifying factor, the study animal, study method, target organ
and critical effect upon which the toxicity value is based are also presented for each COPC, where
available. The confidence level is provided where available, and is based on the confidence in the
study and the extent of toxicity information available for that constituent. Adjustments for dermal
absorption are discussed in Section 4.1.4. It should be noted that both the chronic and the subchronic RfDs for thallium are provisional screening values derived in Appendix A of USEPA (2010a).
According to USEPA (2010a), a reference dose for thallium was not derived because the available
toxicity database contains studies that are generally of poor quality. Appendix A of USEPA (2010a)
indicates that it is inappropriate to derive provisional chronic or subchronic RfDs for thallium, but that
information is available which, although insufficient to support derivation of a provisional toxicity value,
under current guidelines, may be of limited use to risk assessors. Therefore, the screening RfDs were
conservatively used in this HHRA. The RfDs are based on a subchronic study in rats and the NOAEL
is based on hair follicle atrophy; this endpoint was selected because atrophy of hair follicles is
consistent with the atrophic changes observed in cases of human thallium poisoning and may be the
best indication for human response to thallium exposure (USEPA, 2010a). However, this endpoint is
not a “toxic” endpoint per se, and the results of the thallium risk assessment should be interpreted with
appropriate reservations.
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Table 4-3 summarizes the chronic toxicity information for COPCs with potential noncarcinogenic
effects for the inhalation route of exposure, and Table 4-4 summarizes the subchronic toxicity
information. For each COPC, the CAS number and the toxicity value (RfC) are presented. In
addition, the reference for the toxicity value, the USEPA confidence level in the value, the uncertainty
factor, the modifying factor, the study animal, study method, target organ and critical effect upon which
the toxicity value is based are also presented for each constituent. Due to the great uncertainties
involved, USEPA generally does not support use of oral toxicity values to evaluate inhalation
exposures (USEPA, 1994c); therefore, route-to-route extrapolations were not used in this HHRA.
4.1.3
Carcinogenic Toxicity Assessment
USEPA has developed new carcinogen risk assessment guidelines (USEPA, 2005a) that revise and
replace the previous carcinogen risk assessment guidelines. However, the carcinogen risk
assessments for many of the constituents listed in USEPA’s IRIS database still follow the classification
system developed in the previous guidance (USEPA, 1999). The classification system in the previous
guidance was developed according to the weight of evidence from epidemiologic and animal studies:
Group A
- Human Carcinogen (sufficient evidence of carcinogenicity in humans)
Group B
- Probable Human Carcinogen (B1 - limited evidence of carcinogenicity in humans; B2 –
sufficient evidence of carcinogenicity in animals with inadequate or lack of evidence in
humans)
- Possible Human Carcinogen (limited evidence of carcinogenicity in animals and
inadequate or lack of human data)
- Not Classifiable as to Human Carcinogenicity (inadequate or no evidence)
Group C
Group D
Group E
- Evidence of Noncarcinogenicity for Humans (no evidence of carcinogenicity in adequate
studies)
In the previous guidance, it was assumed that there is some finite level of risk associated with each
non-zero dose. The USEPA has developed computerized models that extrapolate dose-response
relations observed at the relatively high doses used in animal studies to the low dose levels
encountered by humans in environmental situations. The mathematical models developed by USEPA
assume no threshold, and use both animal and human data (where available) to develop a potency
estimate for a given constituent. The potency estimate for oral and dermal exposure, called a cancer
-1
slope factor (CSF) is expressed in units of (mg/kg-day) ; the higher the CSF, the greater the
carcinogenic potential. The potency estimate for inhalation exposures, called a unit risk factor (URF),
3 -1
is expressed in terms of (ug/m ) ; the higher the URF, the greater the carcinogenic potential.
USEPA (2005a) places greater emphasis on critically evaluating all available data from which a
default option may be invoked if needed in the absence of critical information. The guidance also
emphasizes the use of mode of action data. Mode of action is defined as a sequence of key events
and processes, starting with interaction of an agent with a cell and resulting in cancer formation.
Some modes of action are anticipated to be mutagenic and are assessed with a linear approach.
Other modes of action may be modeled with either linear or nonlinear approaches after a rigorous
analysis of available data under the guidance provided in the framework for mode of action analysis.
USEPA (2005a) uses a weight of evidence narrative rather than the classification system that was
used in the previous guidance. The following descriptors are recommended along with the weight of
evidence narrative:
•
Carcinogenic to humans – this descriptor indicates strong evidence of human carcinogenicity.
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•
Likely to be carcinogenic to humans – this descriptor is appropriate when the weight of
evidence is adequate to demonstrate carcinogenic potential to humans.
•
Suggestive evidence of carcinogenic potential – this descriptor is appropriate when the weight
of evidence is suggestive of carcinogenicity; a concern for potential carcinogenic effects in
humans is raised, but the data are judged not sufficient for a stronger conclusion.
•
Inadequate information to assess carcinogenic potential – this descriptor is appropriate when
available data are judged inadequate for applying one of the other descriptors.
•
Not likely to be carcinogenic to humans – this descriptor is appropriate when the available
data are considered robust for deciding that there is no basis for human hazard concern.
More than one descriptor can be used when a constituent’s effects differ by dose or exposure route.
While these represent important advances in carcinogen risk assessment, the approach has not
generally been implemented for constituents with toxicity values on IRIS. Therefore, the alphanumeric
system is still presented on IRIS and is included here. None of the COPCs evaluated in this HHRA
have been classified under the new system.
Table 4-5 summarizes the toxicity information for COPCs classified by the USEPA as potential
carcinogens for the oral route of exposure. For each constituent, the CAS number, USEPA
carcinogenicity class, the oral CSF and the reference are provided. In addition, the study animal and
route of exposure upon which the CSF is based are presented. Adjustments for dermal absorption
are discussed in Section 4.1.4.
Table 4-6 summarizes the toxicity information for COPCs classified by the USEPA as potential
carcinogens for the inhalation route of exposure. For each constituent, the CAS number, USEPA
carcinogenicity class, the URF, and the reference are provided. In addition, the study animal and
route of exposure upon which the URF is based are presented.
USEPA guidance for early life exposure to carcinogens (USEPA, 2005b) requires that potential risks
from constituents that act by a mutagenic mode of action be calculated differently than constituents
that do not act via a mutagenic mode of action. According to IRIS (USEPA, 2011e), hexavalent
chromium potentially acts via mutagenic mode of action via the inhalation route of exposure. IRIS
does not present an oral CSF for hexavalent chromium; therefore, a value developed by NJDEP
(2009) was used in this HHRA, as that is the value used in the RSL tables (USEPA, 2011b). While
NJDEP’s documentation indicates that there is no clear evidence of mutagenic mode of action via the
oral route of exposure, USEPA has requested that hexavalent chromium be evaluated for mutagenic
mode of action for both inhalation and oral routes of exposure. As noted in the user’s guide for the
RSLs (USEPA, 2011b), “EPA’s Office of Pesticide Programs (OPP) has concluded that the weight-of
evidence supports that Cr(VI) may act through a mutagenic mode of action following administration
via drinking water and has also recommended that Age-Dependent Adjustment Factors (ADAFs) be
applied when assessing cancer risks from early-life exposure (< 16 years of age).” Therefore, the
following Age-Dependent Adjustment Factors (ADAFs) are applied, as recommended by USEPA
(2005b):
•
Ages 0-2:
ADAF = 10;
•
Ages 2-6:
ADAF = 3;
•
Ages 6-16:
ADAF = 3;
•
>16:
ADAF = 1.
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Exposure assumptions for the child are used for the 0-2 and 2-6 year age groupings and exposure
assumptions for an adult are used for the 6-16 and greater than 16 age groupings.
However, it should be noted that USEPA’s Science Advisory Board (SAB) recently provided
comments on the draft USEPA derivation of the oral CSF for hexavalent chromium (which is similar in
nature to that derived by the NJDEP) and indicated many reservations with the assumptions, including
the presumed mutagenic mode of action, and in the derivation itself. The SAB review can be
accessed at http://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=221433.
4.1.4
Absorption
Dermal and oral absorption factors are discussed below.
4.1.4.1 Dermal Absorption
As there are no dermal dose-response values, oral dose-response values are used to evaluate
dermal exposures. The equation for calculating dermal absorption gives rise to an absorbed dose,
making it necessary to adjust the oral toxicity factor to account for an absorbed rather than an
administered dose. This adjustment accounts for the absorption efficiency in the critical study, which
forms the basis of the RfD or CSF. For example, in the case where oral absorption in the critical study
is essentially complete (i.e., 100%), the absorbed dose is equivalent to the administered dose and,
therefore, no adjustment is necessary. USEPA (2004a, Exhibit 4-1) provides recommended
adjustment factors for oral dose-response values. Several of the COPCs evaluated in this HHRA
require adjustment (chromium (hexavalent), manganese, and vanadium), as indicated in Table 4-1.
The next step is to determine dermal absorption fractions for COPCs in soil. The dermal absorption
fraction (DAF) accounts for lower absorption through the skin. USEPA (2004a) provides constituentspecific dermal absorption fractions for a limited number of constituents. Table 4-7 shows the dermal
absorption fractions for each of the COPCs. USEPA (2004a) provides a DAF of 0.03 for arsenic, as
indicated in Table 4-7. The default DAF for inorganics of 0.001 was obtained from USEPA Region 4
guidance for the remaining COPCs (USEPA, 2000).
4.1.4.2 Oral Absorption
Bioavailability is the measure of the degree to which a constituent may be systemically absorbed
following exposure. In accordance with USEPA guidance (USEPA, 1989a, 1992a), a site-specific oral
AAF for arsenic bioavailability was developed for suspected CCBs. For all other COPCs, an oral AAF
of one has been assumed. The development of the oral bioavailability factor for arsenic is discussed
below.
Development of Oral Bioavailability Factor for Arsenic
The relative bioavailability (RBA) of arsenic in samples of suspected CCBs was determined using a
juvenile swine model. The protocol used for the study and the method of analysis was developed by
USEPA Region 8 [www.epa.gov/region8/r8risk/hh_rba.html] and generally uses two test materials for
analysis. The study was conducted by Stanley Casteel at the University of Missouri. The final report
(Casteel, et al., 2007) is provided in Appendix C of this HHRA. Two test materials were evaluated,
and the RBA of each was determined. The test materials used in the study were MWSE suspected
CCB samples obtained from trenches during the installation of the municipal water service line from
locations previously sampled for arsenic that demonstrated relatively high concentrations. The RBA
for test material one was determined to be 0.72 and the RBA for test material two was determined to
be 0.50. The maximum of the values, 0.72, has been used in this HHRA as the site-specific AAF for
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arsenic, as indicated in Table 4-7. Use of the maximum RBA is consistent with how these results
have been used in other USEPA led risk assessments (for example, the Wells G&H Superfund Site,
Aberjona River Study [http://www.epa.gov/region1/superfund/sites/wellsgh/213053.pdf], and the Butte
Montana Superfund Site [http://www.epa.gov/region8/superfund/mt/sbcbutte/. Use of the maximum
RBA is relatively conservative because samples used in the study consisted of those containing
suspected CCBs with higher concentrations of arsenic; use of the maximum value does not take into
account any variability. However, only two samples were considered. Therefore, the uncertainty
analysis discusses the range of potential arsenic results based on the measured AAFo values of 0.5
and 0.72, the midpoint of the AAFo values, 0.61, and the maximum potential AAFo of 1.
Support for the Use of Absorption Factors in Agency Guidance
The use of absorption factors is recommended by USEPA for use in risk assessment when the
“medium of exposure in the site exposure assessment differs from the medium of exposure assumed
by the dose-response value” (USEPA, 1989a). In this case, the medium of exposure in the exposure
assessment is suspected CCBs while the medium of exposure assumed by the dose-response value
is drinking water (USEPA, 2011e). In other guidance (USEPA, 1992a), USEPA states:
“The applied dose, or the amount that reaches exchange boundaries of the skin, lung or
gastrointestinal tract, may often be less than the potential dose if the material is only partly
bioavailable. Where data on bioavailability are known, adjustments to the potential dose to
convert it to applied dose and internal dose may be made.
This may be done by adding a bioavailability factor (range: 0 to 1) to the dose equation. The
bioavailability factor would then take into account the ability of the constituent to be extracted
from the matrix, absorption through the exchange boundary, and any other losses between
ingestion and contact with lung or gastrointestinal tract.”
4.1.5
Endocrine Disruption
The COPCs evaluated in this risk assessment are metals and inorganics, which are not generally
associated with endocrine disrupting activities. However, a review was conducted to verify this.
Under the Food Quality Protection Act and the Safe Drinking Water Act Amendments of 1996, the
USEPA has authority to screen constituents for endocrine disruption effects to humans, fish and
wildlife. The screening of select constituents for endocrine disruption effects is in process through the
USEPA Endocrine Disruptor Screening Program (EDSP) [http://www.epa.gov/oscpmont/oscpendo/].
USEPA announced the first list of constituents to be screened under the EDSP in April of 2009.
[http://www.epa.gov/scipoly/oscpendo/pubs/final_list_frn_041509.pdf]. The list is mainly comprised of
active pesticide ingredients and inert pesticide ingredients also found in commercial pesticide
formulas. The second list of constituents to be screened came out in November of 2010 and is mainly
comprised of constituents that may be found in drinking water
[http://www.epa.gov/endo/pubs/prioritysetting/draftlist2.htm].
The decision to screen these pesticides and drinking water constituents first was based on the chance
of exposure to these constituents, and does not indicate or confirm that these constituents are
endocrine disruptors. The screening process is still in progress, and requested data from the
appropriate companies or parties is expected for most of the first and second list of constituents within
the next year [http://www.epa.gov/oscpmont/oscpendo/pubs/edspoverview/index.htm].
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For most constituents, there is insufficient data on endocrine disruption effects. From the USEPA
website:
EPA is developing requirements for the screening and testing of pesticides, commercial
chemicals, and environmental contaminants for their potential to disrupt the endocrine system.
Although EPA has some data on endocrine-disrupting pesticides, insufficient scientific data are
available for most of the chemicals produced today to allow for an evaluation of endocrine
associated risks. The science related to measuring and demonstrating endocrine disruption is
relatively new and validated testing methods are still being developed
[http://www.epa.gov/oscpmont/oscpendo/pubs/edspoverview/background.htm]
ATSDR toxicological profiles [http://www.atsdr.cdc.gov/toxprofiles/index.asp] were reviewed for each
of the COPCs included in this risk assessment. There is no ATSDR toxicological profile for
molybdenum, so the Dietary Reference Intake document developed by the National Academy of
Sciences was reviewed (NAS, 2001). Based on the review conducted, there is no evidence that the
COPCs evaluated in this HHRA are endocrine disruptors.
4.2
Ra dionuc lide Dos e -Re s pons e As s e s s m e nt
USEPA calculates radionuclide slope factors to assist risk assessors with risk-related evaluations.
Table 4-8 presents the slope factors for the radionuclide COPCs, for both the individual long-lived
isotopes and the parent/daughter inclusive “+D” decay series. Radionuclide slope factors for water,
food, and soil ingestion, inhalation, and external exposure were obtained from USEPA HEAST
(USEPA, 2001b). Half-lives for the radionuclides were also obtained from USEPA (2001b), and the
decay constants were calculated as 0.693 divided by the half-life.
Table 4-8 also presents soil-to-plant transfer factors for radionuclides. The transfer factors were
obtained from the Radionuclide Toxicity and Preliminary Remediation Goals for Superfund table dated
September 7, 2010 (USEPA, 2010b).
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Exposure Assessment
The purpose of the exposure assessment is to predict the magnitude and frequency of potential
human exposure to each of the COPCs retained for quantitative evaluation in the HHRA. The first
step in the exposure assessment process is the characterization of the setting of the site and
surrounding area. Current and potential future site uses and potential receptors (i.e., people who may
contact the environmental media of interest) are then identified. Potential exposure scenarios
identifying appropriate environmental media and exposure pathways for current and potential future
uses and receptors are then developed. Those potential exposure pathways for which COPCs are
identified and are judged to be complete are evaluated quantitatively in the risk assessment. This
information is used to develop or update the CSM.
To estimate the potential risk to human health that may be posed by the presence of COPCs in
environmental media in the Area of Investigation, it is first necessary to estimate the potential
exposure dose of each COPC for each receptor. The exposure dose is estimated for each constituent
via each exposure route/pathway by which the receptor is assumed to be exposed. Reasonable
maximum exposure (RME) scenarios, and central tendency exposure (CTE) scenarios based on
appropriate USEPA guidance are both evaluated in the quantitative risk assessment. Exposure dose
equations combine the estimates of constituent concentration in the environmental medium of interest
with assumptions regarding the type and magnitude of each receptor's potential exposure to provide a
numerical estimate of the exposure dose. The exposure dose is defined as the amount of COPC
taken into the receptor and is expressed in units of milligrams of COPC per kilogram of body weight
per day (mg/kg-day). The exposure doses are combined with the toxicity values to estimate potential
risks and hazards for each receptor.
This section contains six subsections. Section 5.1 presents the updated CSM for the Area of
Investigation and identifies the potential exposure scenarios and receptors. Section 5.2 presents
methods for quantifying potential exposures for the chemical HHRA. Section 5.3 presents methods
for quantifying potential exposure for the radionuclide HHRA. Section 5.4 presents receptor-specific
exposure parameters for both the chemical and radionuclide HHRAs. Section 5.5 identifies EPCs for
both the chemical and the radionuclide HHRAs. Section 5.6 presents the exposure calculations for
each receptor and pathway evaluated in the HHRA.
5.1
Conc e ptua l S ite Mod e l
To guide identification of appropriate exposure pathways and receptors for evaluation in the risk
assessment, a CSM for human health was developed as part of the scoping activities in the HHRA
Work Plan (ENSR, 2005b). The purpose of the CSM is to identify source areas, potential migration
pathways of constituents from source areas to environmental media where exposure can occur, and
to identify potential human receptors. The CSM is meant to be a “living” model that can be updated
and modified as additional data become available.
The initial CSM for the site is presented in Figure 4 of the HHRA Work Plan (ENSR, 2005b). The
CSM was revised based on USEPA comments on both the HHRA Work Plan and the draft RI Report
and presented in Figure 3-20 of the final RI Report (AECOM, 2010a). The CSM and the receptor area
matrix have not changed since the final RI Report based on a review of the analytical results and the
COPC selection process, with the exception that suspected CCBs have been evaluated as one
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dataset rather than separating surface and subsurface suspected CCBs for the construction worker
evaluation. However, based on USEPA comments on the October, 2010 version of the HHRA, the
fish ingestion pathway is included for the residential adult and child, and the sediment and surface
water pathways are included for the residential adult and child (note the calculations are performed
under the recreational child and the recreational fisher scenarios). The revised CSM is presented
here in Figure 5. Table 5-1 shows the receptor populations that are quantitatively evaluated in the
HHRA, and indicates the media and pathways to which each receptor is assumed to be exposed.
A detailed characterization and CSM of the geology and hydrogeology of the Area of Investigation are
presented in the RI Report (AECOM, 2010a) and are, therefore, not repeated here. The CSM
presented below focuses on the potential for human exposure to COPCs in the media investigated
during the RI.
Based on the detailed characterization of the Area of Investigation, the HHRA CSM was developed to
address which receptor populations might be exposed to CCB-derived constituents within the Area of
Investigation, and how they might be exposed. Some receptor populations may be exposed to CCBderived constituents by more than one pathway. Although there may be more than one potential
exposure pathway, USEPA guidance (USEPA, 1989a) cautions that the first step is to identify
reasonable exposure pathway combinations, and then to determine “whether it is likely that the same
individuals would consistently face the reasonable maximum exposure by more than one pathway.”
With this in mind, the CSM was developed by constructing potential exposure scenarios and
identifying the hypothetical receptors to be used in evaluating these exposures. Notably, the
exposure scenarios are constructed for hypothetical receptors that are assumed to be the most
frequently exposed and the most sensitive receptors. These receptors are not intended to represent
specific individuals.
5.1.1
Setting
The first step in developing the CSM is the characterization of the setting of the study area and
surrounding area. Current and potential future uses of the study area and potential receptors (i.e.,
residential or industrial receptors who may contact the environmental media of interest) are then
identified. Potential exposure scenarios identifying appropriate environmental media and exposure
pathways for current and potential future uses and receptors are then developed. Those potential
exposure pathways for which COPCs are identified and which are complete are evaluated
quantitatively in the risk assessment.
The Area of Investigation contains residential areas. Each house may have its own drinking water
well or septic system or both. In other areas, a municipal water distribution service has been installed.
Human receptor populations may potentially contact CCBs that are present at the ground surface due
to their use as road-base and/or fill in the area as well as CCB-derived constituents that might have
migrated from CCBs into groundwater, surface water, sediment, or air. CCB-derived constituents may
have migrated to groundwater, surface water, or sediment in two ways: 1) the infiltration and
percolation of rainwater through CCBs into the groundwater in the surficial aquifer, and potential
subsequent transport to surface water; and 2) surface run-off and erosion of CCBs into surface water
bodies. The presence of CCB-derived constituents in surface water could lead to increases in
constituent concentrations in various aquatic media (i.e., sediments, and fish tissue). CCB-derived
constituents may be entrained as dusts in outdoor air. CCB-derived constituents are not volatile;
however, it is possible for radon, a daughter product of potentially CCB-derived radionuclides, to
infiltrate the indoor air of a building. As discussed in greater detail in Section 5.3, the radiological
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HHRA was conducted by calculating PRGs using soil equations based on USEPA’s Preliminary
Remediation Goals for Radionuclides calculator: http://epa-prgs.ornl.gov/radionuclides/equations.html.
The potential radon vapor intrusion pathway was not evaluated in this HHRA. The soil PRG equations
on the USEPA calculator do not include inhalation of indoor air. Two equations are provided for
deriving air PRGs, one which includes a decay function for sources such as dust from a previous
release being resuspended, and one for a continual source such as soil. However, the use of these
equations would result in air PRGs, not soil PRGs. Furthermore, based on construction records and
the placement of fill in the area (mid-1970s), none of the homes in the Area of Investigation are built
on top of fill potentially containing CCBs, and so the pathway of radon entering a residence currently is
likely to be incomplete. There are no models available to accurately assess radon vapor intrusion
from potential sources that are not beneath a building; the USEPA PRGs acknowledge the
uncertainties with accurate prediction of exposure via this pathway. The soil equations do include
exposure to fugitive dusts 24 hours per day for residents and 8 hours per day for workers; therefore,
inhalation of radionuclides as fugitive dust is evaluated in this HHRA while inhalation of radon in
indoor air is not. However, radon is a daughter product of Ra-226 and is, therefore, included in the
HHRA through the use of the Ra-226+D slope factor, as discussed in Section 3.3.2. The uncertainty
evaluation includes a discussion of radon, its natural occurrence in northern Indiana, and the
uncertainties associated with the indoor air pathway.
5.1.2
Potential Receptors
Potential human receptor populations include residents, recreational visitors (i.e., who visit the Area of
Investigation but do not reside in the area), construction workers, and outdoor workers. Potential
receptors and how they may contact CCBs and COPCs in other environmental media are described
below, and are summarized in Figure 5.
•
Residents. Residents (adults and children) may potentially contact CCB-derived constituents
at the ground surface directly via incidental ingestion and dermal contact (dermal contact is
not included in the evaluation of potential radionuclide risk, per the USEPA’s radiological PRG
guidance; USEPA, 2010b). Additionally, residents may inhale CCB particulates entrained in
dusts. Where groundwater is used as a source of drinking water (i.e., outside the area that
has been supplied municipal water), residents may be exposed to CCB-derived constituents
that may have migrated into groundwater. The drinking water pathway is only potentially
complete for those residents who use groundwater from the surficial aquifer as a drinking
water source. Concentrations of radionuclides in groundwater were below screening levels
and USEPA agreed this pathway did not need further evaluation (see Appendix M).
Residential children who may play in the local ditches may contact COPCs in surface water
(via dermal contact) or sediment (via incidental ingestion and dermal contact). In addition,
residential children who may swim in the local ponds may contact COPCs in surface water
(via incidental ingestion and dermal contact) or sediment (via incidental ingestion and dermal
contact). As discussed below, a separate recreational receptor is included in this HHRA.
Wading and swimming pathways were also included in the evaluation of the residential child,
as discussed above. In addition, the potential exposures calculated for the recreational child
fish ingestion pathway have been added to the residential child exposures described above.
The recreational fisher wading and fish ingestion pathways have been added to the
residential adult exposures described above. Where gardens exist within areas containing
suspected CCBs, residential adults and children may potentially be exposed to COPCs in
produce. While this potential exposure pathway was not included in the USEPA-approved
work plan, potential exposure to chemicals via produce is evaluated in Appendix H at the
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request of USEPA. The produce pathway has been included in the radiological risk
assessment. Residents are also potentially exposed to external gamma radiation from
suspected CCBs.
•
Recreational Visitors. Recreational visitors may be adults who fish in the local ditches or
children who play in the local ditches or swim in the local ponds. Recreational fishers and
recreational children may contact COPCs in Brown Ditch surface water while wading (via
dermal contact) or in sediment (via incidental ingestion and dermal contact; dermal contact is
not included in the evaluation of potential radionuclide risk, per the USEPA’s radiological PRG
guidance; USEPA, 2010b), or recreational children may contact COPCs in pond surface
water while swimming (via incidental ingestion and dermal contact). Recreational visitors may
be exposed to COPCs via ingestion of fish tissue. Note that the USEPA-approved HHRA
Work Plan (ENSR, 2005b) included fish ingestion only for the recreational fisher (adult).
However, based upon USEPA comments on the RI Report, fish ingestion has been evaluated
for the recreational child as well. Recreational visitors may inhale CCB particulates entrained
in dusts from surface deposits in the Area of Investigation. Recreational visitors may use
groundwater as drinking water. The drinking water pathway is only currently potentially
complete in areas where groundwater from the surficial aquifer is used as a drinking water
source. Note that the USEPA-approved HHRA Work Plan (ENSR, 2005b) does not include a
recreational drinking water scenario. This pathway was added at the request of USEPA.
Section 6.4 presents a risk-based evaluation of the residential drinking water pathway.
Because the exposure frequency for the residential drinking water scenario is higher than for
a recreational visitor, the evaluation presented in Section 6.4 is protective of this receptor.
Concentrations of radionuclides in groundwater were below screening levels and USEPA
agreed this pathway did not need further evaluation (see Appendix M). Therefore, the
recreational visitor drinking water pathway is not quantitatively evaluated in this HHRA.
Recreational visitors are also potentially exposed to external gamma radiation from suspected
CCBs. Surface water samples were not analyzed for radionuclides because the radionuclide
concentrations in groundwater were so low and groundwater is likely the main pathway for the
presence of CCB-derived constituents in surface water, therefore, potential exposure to
radionuclides via surface water and fish tissue is not evaluated. A separate evaluation of
potential radionuclide inhalation exposures from suspected CCBs was not conducted for the
recreational visitor. As indicated by the residential evaluation, the inhalation pathway is a
minor contributor to total potential radionuclide risk. While there have been reports and some
evidence of trespassing activity on Yard 520, as discussed in Section 3.5, the cover on Yard
520 and the regular inspection and maintenance program prevent direct exposure to CCBs at
Yard 520, thus this is an incomplete exposure pathway for the recreational receptor.
•
Construction Workers. Construction workers may potentially contact CCB-derived
constituents at the surface and subsurface directly via incidental ingestion and dermal contact
(dermal contact is not included in the evaluation of potential radionuclide risk, per the
USEPA’s radiological PRG guidance; USEPA, 2010b). Construction activities are assumed
to occur over a one-year exposure duration (IDEM, 2001). Note that the MWSE dataset for
suspected CCBs is used to evaluate both surface and subsurface exposures. As discussed
previously, the dataset is more representative of subsurface exposures, and provides a
conservative estimate of surface exposures to CCB-derived constituents. Additionally,
construction workers may inhale CCB particulates entrained in dusts. Construction workers
may also directly contact COPCs in groundwater via incidental ingestion and dermal contact if
groundwater is encountered during excavation. Construction workers may use groundwater
as drinking water. The drinking water pathway is only currently potentially complete in areas
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where groundwater from the surficial aquifer is used as a drinking water source. Note that the
USEPA-approved HHRA Work Plan (ENSR, 2005b) does not include a construction worker
drinking water scenario. This pathway was added at the request of USEPA. Section 6.4
presents a risk-based evaluation of the residential drinking water pathway. Because the
exposure frequency for the residential drinking water scenario is higher than for a construction
worker, the evaluation presented in Section 6.4 is protective of this receptor. Concentrations
of radionuclides in groundwater were below screening levels and USEPA agreed this
pathway did not need further evaluation (see Appendix M). Therefore, the drinking water
pathway for the construction worker is not quantitatively evaluated in this HHRA; however, the
construction worker incidental ingestion of groundwater pathway has been quantitatively
evaluated. Construction workers are also potentially exposed to external gamma radiation
from suspected CCBs.
•
Outdoor Workers. The USEPA-approved HHRA Work Plan (ENSR, 2005b) does not include
an outdoor worker scenario. However, based on USEPA comments on the RI Report, an
outdoor worker scenario has been included. Outdoor workers may potentially contact surface
CCBs directly via incidental ingestion and dermal contact (dermal contact is not included in
the evaluation of potential radionuclide risk, per the USEPA’s radiological PRG guidance;
USEPA, 2010b). Additionally, outdoor workers may inhale CCB particulates entrained in
dusts. Outdoor workers may use groundwater as drinking water. The drinking water pathway
is only currently potentially complete in areas where groundwater from the surficial aquifer is
used as a drinking water source. Section 6.4 presents a risk-based evaluation of the
residential drinking water pathway. Because the exposure frequency for the residential
drinking water scenario is higher than for an outdoor worker, the evaluation presented in
Section 6.4 is protective of this receptor. Concentrations of radionuclides in groundwater
were below screening levels and USEPA agreed this pathway did not need further evaluation
(see Appendix M). Therefore, the drinking water pathway for the outdoor worker is not
quantitatively evaluated in this HHRA. Outdoor workers are also potentially exposed to
external gamma radiation from suspected CCBs.
Exposure scenarios are developed on the basis of the HHRA CSM presented above for each
medium.
5.1.3
Suspected CCBs
The following describes potential routes of exposure to suspected CCBs. Receptors may potentially
contact suspected CCBs that have been used as road-base and/or fill in the area. Ingestion, dermal
contact, inhalation of suspected CCB-derived dusts, exposure to gamma radiation, and ingestion of
produce are the potential exposure pathways that are evaluated in the HHRA for suspected CCBderived constituents that are identified as COPCs. Residents, visitors, and outdoor workers may
potentially be exposed to COPCs in suspected CCBs present at the ground surface, while
construction workers may potentially be exposed to COPCs in suspected CCBs present at the surface
and in the subsurface.
Samples of suspected CCBs were collected during trenching activities during the extension of the
municipal water service lines, as indicated in Figure 6. Samples were collected from the ground
surface to 5 feet bgs. These data are used as a proxy for concentrations that may be present at the
surface around the Area of Investigation and, therefore, all of the samples are used to evaluate the
residential, recreational, industrial, and the construction scenarios, regardless of depth (see Section
3.5 for a more detailed discussion). Visual inspections of where suspected CCBs are present at the
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ground surface were conducted as part of the RI activities, and Figure 4 indicates where suspected
CCBs were identified. Potential exposure to suspected CCBs is complete only in areas where
suspected CCBs were identified. While CCBs are present in Yard 520, Yard 520 is a closed RSW
that is capped and CCBs are not present at the ground surface. The minimum cap thickness at Yard
520 is 2 feet. See Appendix O for more detailed information on the Yard 520 cap construction, and
the cap inspection and maintenance program. Thus, direct exposure to CCBs in Yard 520 is an
incomplete exposure pathway, and is not quantitatively evaluated in the HHRA.
USEPA risk assessment guidance (USEPA, 1989a) assumes receptor contact with soil via various
exposure pathways (ingestion, dermal contact, and inhalation). It is important to note that this risk
assessment conservatively evaluates a hypothetical screening level scenario that assumes that all of
the assumed contact with soil for the residential, recreational, industrial, and construction worker
receptors is contact with CCBs. As seen in Figure 4, CCBs were deposited (or placed) primarily along
approximately 37% of the roadways within the municipal water service extension. However, as
evidenced by the detection of trace levels of CCBs (less than 1%) in three of the five background
samples submitted for CCB analysis (see Section 3.1.1), CCBs may have been released and
transported from areas of original deposition (or placement) to various unsampled portions of the Area
of Investigation. As noted in Figure 4, “the presence or absence of CCBs within the Area of
Investigation at locations not otherwise identified as ‘field verified suspected’ or ‘inferred suspected’
CCB locations is not known at this time. Furthermore, the hypothetical screening level risk
assessment for the resident and the outdoor worker assumes that the residential lot is comprised of
100% CCBs. As described in greater detail in Section 6.3.1, based on visual inspections, the
conservative maximum average percent of suspected CCBs over the exposure area of any residential
lot is 27% (see Appendix I). Site-specific exposure scenarios based on this factor have also been
incorporated into this HHRA. Thus, two exposure scenarios are evaluated in this risk assessment:
•
A hypothetical screening level scenario where exposure to 100% CCBs is assumed
(Note: CCB samples from the MWSE would be classified in the 75 to 100% CCB range,
and consistent with the visual inspection process [see Appendix I], were assumed to
consist of 100% CCBs), and
•
A site-specific scenario where exposure to the conservative maximum average percent
of CCBs of 27% is evaluated.
As described in Appendix I, 27% is the highest of the conservative maximum average percent
suspected CCBs calculated over the exposure area of any residential lot. The figure below shows
that the majority of exposure areas have a conservative maximum average percent CCBs of less than
14%, and the average of the conservative maximum average percent CCBs is 6%. Thus the sitespecific conservative maximum average percent CCBs of 27% is a very conservative scenario.
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Risk assessments generally assume that materials at depth can be brought to the surface in the future
due to excavation and regrading activities. Such activities may occur in the future within the Area of
Investigation, but it is unlikely that the excavated CCBs would remain at 100% through the excavation,
replacement, and regrading activities. The CCBs would mix with other materials (soil, sand) during
these activities as there are few areas where suspected CCBs have been identified to occur within the
entire 0-15 foot soil column. Therefore, the site-specific conservative maximum average percent
CCBs of 27% is also expected to be a reasonable and conservative estimate of potential future
exposures.
5.1.4
Groundwater
The Area of Investigation contains residential areas. Each house either has its own private drinking
water well or is connected to the municipal water system. Currently, two groups of residents are
distinguished with respect to potential groundwater exposures at their places of residence:
1.
Those within the area of municipal water supply service.
2.
Those outside the area of municipal water supply service and, therefore, required to obtain
drinking water from private wells.
It should be noted that human receptors may also be exposed directly to groundwater outside their
place of residence via contact with seeps. Seep-related groundwater exposures are smaller than inhome exposures and were not evaluated in the HHRA. As a result, the total groundwater risks
presented and discussed in the HHRA are underestimated to a small degree in this regard. Also, as
shown on Figure 5, groundwater may discharge to Brown Ditch and Ponds 1 and 2. The HHRA
evaluates direct contact exposures to surface water and sediment, as well as indirect exposure
through ingestion of fish tissue. It should be understood that some portion of these exposures, and
related risks and hazards, are attributable to groundwater discharge. Please see Appendix L for
additional analysis.
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The RI has shown that CCB-derived constituents have migrated to groundwater in some areas of the
Area of Investigation. In particular, CCB-derived constituents are more likely to migrate to
groundwater where there are larger amounts of suspected CCB fill material present, for example, at
Yard 520 or in certain areas where the suspected CCB fill extends substantially beyond roadways.
Figure 27 brings together information on the locations of suspected CCBs and the presence of B in
groundwater (as an indicator of CCB-derived constituents). As shown on this map, CCB-derived
constituents (as represented by elevated concentrations of B) are present downgradient from Yard
520 and in wells MW106, MW109, and MW111, all located near or downgradient from larger areas of
suspected CCBs along Idaho, East Johns, Columbia, and Delaware Avenues. There does not seem
to be substantial migration to groundwater where suspected CCBs were used in smaller volumes,
such as for only road sub-base material or driveway surfaces. Several wells are located in or
downgradient from such areas, including MW107, MW108, MW114, and PW005. These wells do not
show the presence of elevated levels of B (see Figure 27). In addition to the smaller amounts of
suspected CCBs present, the paving of roadways may reduce groundwater recharge and migration of
CCB-related constituents to groundwater. In the majority of the Area of Investigation, the levels of
constituents that may be CCB-derived are too low to determine whether they are related to CCBs or
other sources or to background. Section 4.4.7 of the RI Report provides a more detailed summary of
the results of the groundwater investigation.
Where groundwater is used as a source of drinking water (i.e., outside the area that has been
supplied municipal water), residents may be exposed to CCB-derived constituents that may have
migrated into groundwater. The drinking water pathway is only potentially complete for those
residents who use groundwater from the surficial aquifer as a drinking water source. A cumulative
risk-based evaluation of the residential drinking water pathway is included in Section 6.4.
Construction workers could potentially be exposed to CCB-derived constituents in groundwater via
incidental ingestion and dermal contact if water is encountered during excavation, both within and
outside of areas serviced by the municipal water supply. The monitoring well data are used to
evaluate this exposure pathway; locations of wells are indicated in Figure 7.
5.1.5
Sediment, Surface Water, and Fish Tissue
CCB-derived constituents may also have migrated from CCBs into surface water and sediment either
directly or via groundwater flow to surface water. Figure 9 presents the sediment sample locations
and Figure 10 presents the surface water sample locations. Recreational users of local ditches and
ponds may, therefore, be exposed to COPCs in surface water via dermal contact while wading (or via
dermal contact and incidental ingestion while swimming) and sediment via incidental ingestion, dermal
contact, and external gamma radiation. A radiological evaluation was not conducted for surface
water.
According to USEPA (2004a), “Sediments which are consistently covered by considerable amounts of
water are likely to wash off before the individual reaches the shore.” The guidance, therefore,
recommends the use of sediment samples which are near shore. However, at the request of USEPA,
the pond sediment samples were collected from depositional sediments in the deepest part of the
ponds and likely represent the most elevated concentrations within the ponds. Incidental ingestion
was not evaluated for Brown Ditch surface water due to the short exposure time for the wading
scenario, however it was evaluated for the swimming scenario for the ponds. It should be noted that
incidental surface water ingestion could occur if a child playing or wading in Brown Ditch trips and
falls, or if residents gather and consume wild asparagus or mushrooms without first washing these.
Exclusion of the incidental ingestion pathway for the wading scenario is consistent with the human
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health risk assessment conducted by USEPA Region I for the Wells G and H Superfund site (USEPA,
2004b).
Additionally, it is possible that fish may take up COPCs from surface water in Brown Ditch and the two
ponds. Therefore, recreational fishers and recreational children may potentially be exposed to
COPCs via ingestion of fish. It should be noted that Brown Ditch is not an area known for fishing and
people are rarely if ever observed fishing there. Moreover, the most common fish that may be present
in the Brown Ditch system, according to the Indian Department of Natural Resources (Bacula, 2011),
are small minnows and shiners, e.g., fathead minnow, and other species may include carp and
bullhead. These are not generally considered to be sport fish, or fish that would be caught and
consumed. Therefore, inclusion of the fishing pathway for Brown Ditch is very conservative.
Note that the sediment, surface water, and fish ingestion pathways described above were also
included for the residential receptors.
5.1.6
Groundwater-to-Soil
In their review of the RI Report, USEPA expressed concern about potential exposure to arsenic in
soils that may have originated through migration with groundwater from CCBs. In the vicinity of Yard
520 there are marked declines in concentrations of arsenic in groundwater in short distances from
Yard 520 itself. This concentration distribution indicates that attenuation processes (e.g., redox
conditions) appear to be very effective in removing arsenic from groundwater through sorption to soil
particles. Arsenic in the subsurface is commonly associated with iron minerals (that is, sorbed onto or
co-precipitated with iron hydroxide or iron sulfide minerals). Under oxidizing conditions, the iron forms
insoluble molecules and leaves the groundwater. These minerals also remove arsenic from solution.
Under reducing conditions, the iron in these minerals is reduced, the minerals dissociate, and the iron
is present as a soluble ion in the water. When the iron minerals dissolve, the arsenic that is
associated with them is also released into the groundwater.
As part of the RI, soil samples were collected near Yard 520 and other areas of CCB fill and analyzed
for arsenic to evaluate whether the observed attenuation processes could be leading to significant
concentrations of arsenic in soils. The sampling, results, and conclusions are included in the RI
Report (AECOM, 2010a), and that same information is presented here in Appendix R. The sampling
indicated that arsenic concentrations in soils beneath or downgradient from areas of CCBs are within
the range of background concentrations.
As documented in the RI Report (AECOM, 2010a) groundwater flow in the vicinity of Yard 520 is
downward through Yard 520 into the underlying native soils, then outward towards Brown Ditch.
Therefore, it should be noted that hypothetically if there were significant accumulations of arsenic in
soil downgradient from Yard 520, these would occur at the base of the surficial aquifer consistent with
where the greatest groundwater concentrations were detected, e.g., at depths greater than 20 feet
deep. Exposures to soil are unlikely to occur at these depths, as excavation work for utilities or light
construction rarely exceeds 12-15 feet bgs. If there were a component of shallow groundwater flow
leaving Yard 520, arsenic would tend to be attenuated more quickly than in the deeper groundwater,
because conditions in the shallow portions of the surficial aquifer are more oxidizing, compared to the
deeper portions. Thus, any additional loading from the groundwater to the shallow soils would be
restricted to the immediate vicinity of Yard 520.
An evaluation of the scale of the relative arsenic concentrations in groundwater compared to
concentrations in soil indicates that the two are significantly different. The highest concentration of
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arsenic detected in groundwater outside the limits of Yard 520 is 0.130 mg/L at TW-15D. The
background concentrations in soils range from 2.1 to 29.5 mg/kg. It would clearly require significant
loading of arsenic from groundwater (shallow or deep) to soil to add up to concentrations that are
similar to background soils, and even much greater loading to approach concentrations that are
significantly greater than background. Thus the contribution that of arsenic sorption to shallow or
deep soils is likely to be insignificant with respect to background soil concentrations and would not
have an impact on the risk assessment results.
For the arsenic sorbed onto the deeper soils to remobilize into the dissolved phase, certain
geochemical conditions would have to be met. For instance, some combination of changes to the pH
and/or redox potential would be required. RI data suggests that the groundwater flow and chemistry
in the vicinity of Yard 520 is at steady-state, so such changes are not expected. If such changes were
to occur, the kinetics that would convert sorbed to dissolved phase arsenic would occur very slowly
such that any remobilized arsenic concentrations would be very low, likely lower than the groundwater
concentrations currently observed. In addition, for the arsenic to persist in groundwater, these
geochemical changes would need to occur throughout the length of the groundwater flow path. Even
if local conditions were to change, it is very unlikely these changes would extend throughout the
groundwater flow system. Therefore, arsenic concentrations associated with soils are not expected to
result in any significant concentrations of remobilized dissolved phase arsenic. The sampling and
results are discussed in more detail in Section 2.16 of the RI Report (AECOM, 2010a). All of this
information, including the work plan, USEPA correspondence, results and the summary and
conclusions are provided in the approved RI Report (AECOM, 2010a). However, to aid the review of
this document, all of this information has been excerpted from the RI Report and is presented here as
Appendix R.
The results of this evaluation indicate that arsenic sorption to soils within the soil column are likely to
be insignificant in comparison to background soil concentrations. A quantitative risk assessment of
background soils has been included in the risk assessment.
5.2
Qua ntific a tio n of P o te ntia l Expos ure s – Ch e m ic a l HHRA
To estimate the potential risk to human health that may be posed by the presence of COPCs in the
Area of Investigation, it is first necessary to estimate the potential exposure dose of each COPC. The
exposure dose is estimated for each constituent via each exposure pathway by which the receptor is
assumed to be exposed. Exposure dose equations combine the estimates of constituent
concentration in the environmental medium of interest with assumptions regarding the type and
magnitude of each receptor's potential exposure to provide a numerical estimate of the exposure
dose. The exposure dose is defined as the amount of COPC taken into the receptor and is expressed
in units of milligrams of COPC per kilogram of body weight per day (mg/kg-day).
Exposure doses are defined differently for potential carcinogenic and noncarcinogenic effects. The
Chronic Average Daily Dose (CADD) is used to estimate a receptor’s potential intake from exposure
to a COPC with noncarcinogenic effects for oral and dermal exposures. According to USEPA
(1989a), the CADD should be calculated by averaging the dose over the period of time for which the
receptor is assumed to be exposed. Therefore, the averaging period is the same as the exposure
duration.
For COPCs with potential carcinogenic effects, however, the Lifetime Average Daily Dose (LADD) is
employed to estimate potential doses for oral and dermal exposures. In accordance with USEPA
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(1989a) guidance, the LADD is calculated by averaging exposure over the receptor’s assumed lifetime
(70 years). Therefore, the averaging period is the same as the receptor’s assumed lifetime.
Exposure doses for inhalation exposures are calculated following USEPA guidance (USEPA, 2009a).
Average daily doses are not calculated for inhalation exposures. Rather, average daily exposures
(ADE) (referred to as exposure concentrations in USEPA, 2009a) are calculated based on COPC
concentrations in air and exposure parameters in accordance with USEPA (2009a). As with the
CADD and the LADD, the ADE for noncarcinogens is averaged over the period of exposure while the
ADE for potential carcinogens is averaged over the receptor’s assumed lifetime (70 years).
The standardized equations for estimating a receptor’s average daily dose or exposure (both lifetime
and chronic) are presented below, followed by descriptions of receptor-specific exposure parameters
and constituent-specific parameters.
5.2.1
Estimating Potential Exposure to COPCs in Water
The following equations are used to calculate the estimated exposure.
Average Daily Dose (Lifetime and Chronic) Following Ingestion of Water (mg/kg-day):
ADD =
CW x IR x EF x ED
BWxAT
where:
ADD
=
Average Daily Dose (mg/kg-day)
CW
=
Water Concentration (mg/L)
IR
=
Water Ingestion Rate (L/day)
EF
=
Exposure Frequency (days/year)
ED
=
Exposure Duration (year)
BW
=
Body Weight (kg)
AT
=
Averaging Time (days)
Average Daily Dose (Lifetime and Chronic) Following Dermal Contact with Water (mg/kg-day):
The equation used to estimate a receptor's potential exposure via dermal contact with groundwater or
surface water is as follows.
ADD =
DAevent x EV x EF x ED x SA
BW x AT
where:
ADD
=
Average Daily Dose (dermal absorbed dose) (mg/kg-day)
DAevent
=
Absorbed Dose per Event (mg/cm -event)
SA
=
Surface Area (cm )
EV
=
Event Frequency (events/day)
EF
=
Exposure Frequency (days/year)
2
2
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ED
=
Exposure Duration (years)
BW
=
Body Weight (kg)
AT
=
Averaging Time (years)
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The calculation of the dose absorbed per unit area per event (DAevent) is as follows for inorganics:
DAevent = CW x PC x ET x CF
where:
2
DAevent
=
Absorbed Dose per Event (mg/cm -event)
CW
=
Concentration in Water (mg/L)
PC
=
Permeability Constant (cm/hr)
ET
=
Exposure Time (hr/event)
CF
=
Conversion factor (L/1000 cm )
3
The PC values were derived from USEPA (2004a) Exhibit 3-1. Table 5-2 presents the PC values.
5.2.2
Estimating Potential Exposures to COPCs in CCBs, Soil or Sediment
The following equations are used to calculate the estimated exposure.
Average Daily Dose (Lifetime and Chronic) Following Incidental Ingestion of CCBs/Soil/Sediment
(mg/kg-day):
ADD =
CS x SIR x EF x ED x AAFo x CF
BWxAT
where:
ADD
=
Average Daily Dose (mg/kg-day)
CS
=
CCB/Soil/Sediment Concentration (mg/kg soil)
SIR
=
CCB/Soil/Sediment Ingestion Rate (mg soil/day)
EF
=
Exposure Frequency (days/year)
ED
=
Exposure Duration (year)
AAFo
=
Oral Absorption Adjustment Factor (for the purposes of this HHRA this term applies
only to arsenic; see Section 4.1.4.2, referred to as oral bioavailability factor [AAF]))
(unitless)
6
CF
=
Unit Conversion Factor (kg soil/10 mg soil)
BW
=
Body Weight (kg)
AT
=
Averaging Time (days)
Average Daily Dose (Lifetime and Chronic) Following Dermal Contact with CCBs/Soil/Sediment
(mg/kg-day):
ADD =
CS x SA x AF x EF x ED x AAFd x CF
BWxAT
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where:
ADD
=
Average Daily Dose (mg/kg-day)
CS
=
CCB/Soil/Sediment Concentration (mg/kg soil)
SA
=
Exposed Skin Surface Area (cm /day)
AF
=
Adherence Factor (mg soil/cm )
EF
=
Exposure Frequency (days/year)
ED
=
Exposure Duration (year)
2
2
AAFd
=
Dermal Absorption Adjustment Factor (constituent-specific) (unitless)
CF
=
Unit Conversion Factor (kg soil/10 mg soil)
BW
=
Body Weight (kg)
AT
=
Averaging Time (days)
5.2.3
6
Estimating Potential Exposures to COPCs in Air
3
Average Daily Exposure (Lifetime and Chronic) Following Inhalation of COPC (mg/m ):
ADE =
CA x ET x EF x ED
AT
where:
3
ADE
=
Average Daily Exposure (mg/m )
CA
=
Air concentration (mg/m )
3
ET
=
Exposure time (hours/day)
EF
=
Exposure frequency (days/year)
ED
=
Exposure duration (year)
AT
=
Averaging time (hours)
5.2.4
Estimating Potential Exposures to COPCs in Fish Tissue
The equation used to estimate a receptor's potential exposure via fish consumption is:
Average Daily Dose (Lifetime and Chronic) Following Fish Consumption (mg/kg-day):
ADD =
CF x IR x EF x ED
AT x BW
where:
ADD
=
Average Daily Dose (mg/kg-day)
CF
=
Concentration in Food (mg/kg)
IR
=
Ingestion Rate (kg/day)
EF
=
Exposure Frequency (days/year)
ED
=
Exposure Duration (years)
AT
=
Averaging Time (days)
BW
=
Body Weight (kg)
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Appendix F presents the chemical exposure dose/concentration and risk calculation spreadsheets.
The risk results are discussed in Section 6.0. Note that the spreadsheets presented in Appendix F
handle averaging time in a slightly different but mathematically equivalent manner from that presented
above for the oral and dermal pathways. Averaging time for potential carcinogens is equal to the
assumed lifetime (70 years) multiplied by 365 days; averaging time for noncarcinogens is equal to the
exposure duration multiplied by 365 days. Intermediate “calculated” values are derived on the first
page of each spreadsheet to account for the averaging time to simplify the calculations on the
subsequent pages, as follows:
•
Exposure Frequency: Exposure Frequency/365 days = fraction
•
Exposure Duration (potential carcinogens): Exposure Duration/70 years = fraction
•
Exposure Duration (noncarcinogens): Exposure Duration/Exposure Duration = 1
5.3
Qua ntific a tio n of P o te ntia l Expos ure s – Ra dio logic a l HHRA
The radiological HHRA was conducted by calculating PRGs using equations based on USEPA’s
Preliminary Remediation Goals for Radionuclides calculator: http://epaprgs.ornl.gov/radionuclides/equations.shtml. Because the relationship between the potential risk and
the concentration of a radionuclide is linear, the potential risks were calculated based on the EPC, the
-6
PRG, and the PRG target risk (10 ) as follows:
Potential Risk =
EPC (pci / g)
* 10 −6
PRG(pci / g)
PRG equations are presented below.
5.3.1
Residential PRGs
Residential – Incidental Ingestion
TR x t x λ
-λt
(1 – e ) x SFs x [(IRSc x EDc) + (IRSa x EDa)/ED] x EF x ED x CF x PF
PRG =
Where:
PRG=
Preliminary Remediation Goal (pCi/g)
TR =
Target Risk (unitless; 1x10 )
t
=
Time (yrs)
λ
=
Decay Constant (yr )
-6
-1
SFs =
Slope Factor (risk/pCi)
IRS =
Ingestion Rate (mg/day)
EF =
Exposure Frequency (days/yr)
ED =
Exposure Duration (yrs)
CF =
Conversion factor (0.001 g/mg)
PF =
Percent CCBs (i.e., 27%, entered as a decimal fraction, 27/100 = 0.27)
c
=
Child
a
=
Adult
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=
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soil
Radionuclide specific parameters (λ, SFs) are discussed in Section 4.2 and presented in Table 4-8.
Residential – Inhalation of Particles
TR x t x λ
PRG =
-λt
(1 – e ) x SFi x [(IRAc x EDc) +( IRAa x EDa)/ED] x EF x ED x (1/PEF) x (ET/24) x CF x PF
Where:
PRG=
Preliminary Remediation Goal (pCi/g)
TR =
Target Risk (unitless; 1x10 )
t
=
Time (yrs)
λ
=
Decay Constant (yr )
-6
-1
SFi =
Slope Factor (risk/pCi)
IRA =
Inhalation Rate (m /day)
EF =
Exposure Frequency (days/yr)
ED =
Exposure Duration (yrs)
PEF =
Particulate Emission Factor (m /kg)
3
3
ET =
Exposure Time (hours/day)
CF =
Conversion factor (1000 g/kg)
PF =
Percent CCBs (i.e., 27%, entered as a decimal fraction, 27/100 = 0.27)
c
=
Child
a
=
Adult
i
=
Inhalation
Radionuclide specific parameters (λ, SFi) are discussed in Section 4.2 and presented in Table 4-8.
Residential – External Exposure
TR x t x λ
PRG =
-λt
(1 – e ) x SFext-sv x ACF x EF/365 x ED x [ETo + (ETi x GSFi)] x PF
Where:
PRG
=
Preliminary Remediation Goal (pCi/g)
TR
=
Target Risk (unitless; 1x10 )
t
=
Time (yrs)
λ
=
Decay Constant (yr )
SF
=
Slope Factor (risk/yr/pCi/g)
ACF
=
Area Correction Factor (unitless)
-6
-1
EF
=
Exposure Frequency (days/yr)
ED
=
Exposure Duration (yrs)
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ET
=
Exposure Time (hours/day)
GSF
=
Gamma Shielding Factor (unitless)
PF
=
Percent CCBs (i.e., 27%, entered as a decimal fraction, 27/100 = 0.27)
i
=
Indoor
o
=
Outdoor
ext-sv
=
External Exposure
Radionuclide specific parameters (λ, SF) are discussed in Section 4.2 and presented in Table 4-8.
Residential – Consumption of Homegrown Produce
TR x t x λ
PRG =
-λt
(1 – e ) x SFf x IRPadj x CF x ED x (EF/365) x TFp x PF
Where:
IRPadj =
(EDc x IRPc )+ (EDa x IRPa)
ED
and
PRG
=
Preliminary Remediation Goal (pCi/g)
TR
t
=
=
Target Risk (unitless; 1x10 )
Time (yrs)
λ
=
Decay Constant (yr )
ED
=
Exposure Duration (yrs)
EF
=
Exposure Frequency (days/yr)
SFf
=
Slope Factor (risk/pCi)
TFp
=
Plant Transfer Factor (pCi/gram-plant/Pci/gram-soil)
IRP
=
Homegrown Produce Ingestion Rate (kg/yr)
-6
-1
CF
=
Conversion factor (1000 g/kg)
PF
=
Percent CCB (i.e., 27%, entered as a decimal fraction, 27/100 = 0.27) [the
contaminated plant fraction in the PRG equation has been replaced with this percent
CCB variable for the MWSE suspected CCB and Yard 520 CCB datasets; the default
PF has been used for the background dataset]
f
=
Food
a
=
Adult
c
=
Child
IRPadj
=
Age Adjusted Produce Ingestion Factor
Radionuclide specific parameters (λ, SFf, TFp) are discussed in Section 4.2 and presented in
Table 4-8.
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Residential – Total
PRG =
1
(1/PRG ing) + (1/PRG -inh) + (1/PRG -ext) + (1/PRG prod-ing)
Where:
PRG ing
=
Preliminary Remediation Goal from Incidental Ingestion of Soil
PRG inh
=
Preliminary Remediation Goal from Inhalation of Particles Emitted from Soil
PRG ext
=
Preliminary Remediation Goal from External Exposure
PRG prod-ing
=
Preliminary Remediation Goal from Consumption of Homegrown Produce
Note that the total potential risk for the resident also includes the potential sediment risks calculated
for the recreational child and the recreational fisher, based on the sediment PRGs calculated as
described in Section 5.3.2.
5.3.2
Recreational Pathways – Incidental Ingestion of Sediment and External
Exposure
The residential equations listed above were also used in the evaluation of the recreational child and
recreational fisher for potential exposure to sediment via incidental ingestion and potential exposure to
external gamma radiation, using the applicable portions of each equation for child only or adult only
exposure. The total PRG was calculated as follows:
PRG =
1
(1/PRG ing)+ (1/PRG -ext)
Where:
PRG ing
=
Preliminary Remediation Goal from Incidental Ingestion of Sediment
PRG ext
=
Preliminary Remediation Goal from External Exposure
5.3.3
Non-Residential PRGs
Outdoor and Construction Worker – Incidental Ingestion
TR x t x λ
PRG =
-λtw
(1 – e
) x SFs x IRS x EF x ED x CF x PF
Where:
PRG=
Preliminary Remediation Goal (pci/g)
TR =
Target Risk (unitless; 1x10 )
t
=
Time (yrs)
λ
=
Decay Constant (yr )
SF =
-6
-1
Slope Factor (risk/pCi)
IRS =
Soil Ingestion Rate (mg/day)
EF =
Exposure Frequency (days/yr)
ED =
Exposure Duration (yrs)
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CF =
Conversion factor (0.001 g/mg)
s
Soil
=
PF =
5-18
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Percent CCBs (i.e., 27%, entered as a decimal fraction, 27/100 = 0.27 for the outdoor
worker, and 100% or 1 for the construction worker)
Radionuclide specific parameters (λ, SFs) are discussed in Section 4.2 and presented in Table 4-8.
Outdoor and Construction Worker – Inhalation of Particulates
TR x t x λ
PRG =
-λt
(1 – e ) x SFi x IRA x EF x ED x (1/PEF) x (ET/24) x CF x PF
Where:
PRG=
TR =
t
=
λ
=
SF =
IRA =
EF =
ED =
PEF =
ET =
CF =
i
=
PF =
Preliminary Remediation Goal (pCi/g)
-6
Target Risk (unitless; 1x10 )
Time (yrs)
-1
Decay Constant (yr )
Slope Factor risk/pCi)
3
Inhalation Rate (m /day)
Exposure Frequency (days/year)
Exposure Duration (years)
3
Particulate Emission Factor (m /kg)
Exposure Time (hours/day)
Conversion factor (1000 g/kg)
Inhalation
Percent CCBs (i.e., 27%, entered as a decimal fraction, 27/100 = 0.27 for the outdoor
worker, and 100% or 1 for the construction worker)
Radionuclide specific parameters (λ, SF) are discussed in Section 4.2 and presented in Table 4-8.
Outdoor and Construction Worker – External Exposure
PRG =
TR x t x λ
-λt
(1 – e ) x SFext-svx ACF x (EF/365) x ED x (ET/24) x PF
Where:
PRG
=
Preliminary Remediation Goal (pCi/g)
TR
=
Target Risk (unitless; 1x10 )
t
=
Time (yrs)
λ
=
Decay Constant (yr )
SF
=
Slope Factor (risk/yr/pCi/g)
ACF
=
Area Correction Factor (unitless)
-6
-1
EF
=
Exposure Frequency (days/yr)
ED
=
Exposure Duration (yrs)
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ET
=
Exposure Time (hours/day)
ext-sv
=
External Exposure
PF
=
Percent CCBs (i.e., 27%, entered as a decimal fraction, 27/100 = 0.27 for the outdoor
worker, and 100% or 1 for the construction worker)
Radionuclide specific parameters (λ, SF) are discussed in Section 4.2 and presented in Table 4-8.
Outdoor and Construction Worker – Total
PRG =
1
(1/PRGing) + (1/PRG inh) + (1/PRG ext)
Where:
PRG ing
=
Preliminary Remediation Goal from Incidental Ingestion of Soil
PRG inh
=
Preliminary Remediation Goal from Inhalation of Particles Emitted from Soil
PRG ext
=
Preliminary Remediation Goal from External Exposure
Appendix K presents the calculations.
5.4
Re c e ptor-S pe c ific Expos ure P a ra m e te rs
The following subsections present the parameters that were used to evaluate each of the potential
receptors in the HHRA. Both RME and CTE scenarios were evaluated for each receptor. Receptorspecific exposure parameters are presented below (Sections 5.4.1 to 5.4.5). Derivation of surface
area and dermal adherence factors is discussed in Section 5.4.6. Pathways to be evaluated are
presented in Figure 5 and in Table 5-1. Exposure parameters for both RME and CTE scenarios are
presented in Tables 5-3 through 5-7. Receptor specific exposure parameters that vary for the
radionuclide HHRA are presented for each receptor. Exposure parameters common to all receptors
for the radionuclide HHRA are presented in Section 5.4.7.
5.4.1
Resident (Adult and Child)
Table 5-3 presents the exposure assumptions for a residential adult and child receptor for both RME
and CTE exposures. Because of the differences in activity patterns and sensitivity to potential
constituent exposures, two age groups for the resident receptor are evaluated: the child (age 0 to 6
years, 15 kg body weight) and the adult resident (70 kg body weight) (USEPA, 1991a). The child’s
lower body weight, combined with a higher intake rate for soil exposures results in a higher dose per
kilogram of body weight than for other age groups. The child also has a longer exposure time for
inhalation exposures, resulting in a higher daily exposure. This receptor is then the most sensitive to
the noncarcinogenic health effects of constituents and is, therefore, the target receptor for the
noncarcinogenic analysis (i.e., estimated risks for this age group will be higher than for other older
child age groups or for adults). Because carcinogenic effects are assumed to be additive over a
lifetime, it is more conservative to evaluate potentially carcinogenic effects of COPCs over the period
of residence (that is, the duration an individual lives at one location). USEPA (1997a) lists 30 years as
the 95th percentile value for residence time. This estimate was derived from three studies:
•
U.S. Census Bureau, 1993 (housing survey), as cited in USEPA, 1997a;
•
Israeli and Nelson, 1992, as cited in USEPA 1997a; and
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Johnson and Capel, 1993, as cited in USEPA, 1997a.
According to the Exposure Factors Handbook (EFH) (USEPA, 1997a), while information provided by
the U.S. Census Bureau does provide information regarding population mobility, it is difficult to
determine the average residence time in a home or apartment because the surveys are not designed
to follow individual families through time. Therefore, the three listed sources, which each used a
unique approach to quantify residence time, were used to derive the estimates provided in the EFH.
According to the EFH, the three studies provide residence time estimates that are similar. Therefore,
the 95th percentile estimate of 30 years is used in the HHRA as a conservative estimate of the time a
hypothetical receptor may live in the same residence location. The resident, as both child and adult, is
thus evaluated for potential carcinogenic effects of COPCs over a 30-year residency period. For the
CTE scenario, 9 years is provided as the average residential duration (USEPA, 1997a).
The resident receptor is assumed to be exposed to COPCs in surface CCBs where present via
incidental ingestion and dermal contact, to COPCs in CCBs where present in particulates that may be
suspended in the air via inhalation, and to COPCs in CCBs where present via external exposure to
gamma radiation. For the chemical risk assessment, the resident is assumed to be potentially
exposed for 250 days per year for 30 years under the RME scenario and for 165 days per year for 9
years under the CTE scenario (USEPA, 1993b). The exposure frequency for the chemical risk
assessment under both the RME and CTE scenario was developed to reflect meteorological
conditions at the Area of Investigation, as described below. For the radiological risk assessment,
potential exposure to external gamma radiation is not expected to be affected by meteorological
conditions. Therefore, the exposure frequency for the RME scenario is 350 days per year and the
exposure frequency for the CTE scenario is 234 days per year. Exposure assumptions for the
chemical risk assessment are shown in Table 5-3. Exposure assumptions for the radiological risk
assessment are shown in Appendix K. The resident may also be exposed to CCBs where present via
ingestion of homegrown produce. The potential for exposure to arsenic in homegrown produce is
evaluated in Appendix H. The potential for exposure to radionuclides in homegrown produce is
evaluated as part of the radionuclide HHRA.
The residential child is assumed to play in either the local ditches or swim in local ponds and,
therefore, is assumed to be exposed to COPCs in surface water via dermal contact (and via incidental
ingestion while swimming) and in sediment via incidental ingestion and dermal contact for 26 days per
year (2 days per week for the 13 warmest weeks of the year) for 6 years under the RME scenario and
for 13 days per year (2 days per week for the 13 warmest weeks of the year) for 2 years under the
CTE scenario. Other exposure assumptions are shown in Table 5-3 for the chemical risk assessment
and Appendix K for the radiological risk assessment. Additionally, potential risks calculated for the
recreational fisher and recreational child for the fish ingestion pathway and potential risks calculated
for the recreational fisher for the surface water and sediment pathways are included in the total risk
estimate for the residential receptor.
Derivation of surface area and dermal adherence factors is discussed in Section 5.4.6.
The consumer-only ingestion rates for homegrown produce were taken from USEPA’s Human Health
Risk Assessment Protocol for Hazardous Waste Combustion Facilities (HHRAP), Table C-1-2
(USEPA, 2005c). The HHRAP ingestion rates were taken from Tables 13-61 through 13-65 of
USEPA’s Exposure Factors Handbook (USEPA, 1997a). The USEPA 1997 Exposure Factors
Handbook ingestion rates are based on the 1987-1988 U.S. Department of Agriculture (USDA)
National Food Consumption Survey, which is a one-week survey used to evaluate consumers of
homegrown produce.
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HHRAP ingestion rates are adjusted to account for preparation, cooking, and post cooking loss of
homegrown produce. An adult and child time-weighted average ingestion rate for above and below
ground produce of 24.6 kg/year was used in the estimation of potential risks from ingestion of
produce. Appendix H presents a comparison of the ingestion rates used in this HHRA to other
available ingestion rates.
Exposure Frequency
A meteorological factor is generally used to account for the fraction of the year during which exposure
to constituents at the ground surface may occur (Sheehan, et al., 1991; USEPA, 1989a; IDEM, 2001;
PADEP, 1997). It is reasonable to assume that direct contact with soil or CCBs will not occur for
residential receptors during inclement weather, i.e., when it is raining or snowing, when the ground is
wet or frozen, or when snow or ice (32 degrees F) are covering the ground. This does not imply that
people are not outdoors on these days; simply that soils are not available for direct contact on these
days. Thus the frequency of contact with CCBs is adjusted for these location-specific meteorological
conditions (USEPA, 1989a).
There are only a few metrics that can be used to describe the fraction of the year when meteorological
conditions are likely to limit exposure. These include temperature and the amount of precipitation per
day and per year, which includes rain, snow, and ice. The National Climatic Data Center (NCDC)
provides daily temperature and precipitation data (NCDC, 2005). Daily temperature data are also
available from the NIPSCO’s Michigan City Generating Station (NIPSCO, 2005). It is assumed that
exposure to CCBs is limited on days when the maximum temperature is less than 32 degrees F
because the ground is frozen. The number of days with precipitation greater than 0.1 inches is
selected as the best representation of when exposure is likely to be limited by snow, rain, or ice
because the ground is wet or covered by snow/ice. The choice of a precipitation target of 0.1 inches
is in keeping with guidance provided in the “Compilation of Air Pollution Emission Factors”, which
assumes that soil suspension will not occur on days with more than 0.01 inches of precipitation
(USEPA, 1995b). It is probable, however, that this metric both over- and under-estimates the
potential exposure in some conditions. For example, it is possible that some exposure to CCBs may
occur on days when it rains just over 0.1 inches in the early morning and then the ground dries during
the course of the day. Alternatively, significant rainfall, such as greater than 1 inch, is likely to saturate
the ground for consecutive days, and several inches of snow (which may fall all on one day with one
storm) may cover the ground and inhibit direct contact for several days. With both of these
considerations in mind, it is likely that a meteorological factor based on inclement days (i.e., days
where the ground surface is unavailable for direct-contact) defined as precipitation greater than 0.1
inches and maximum temperatures less than 32 degrees F is reasonable.
Based on ten years of precipitation data (1995-2004) for South Bend, Indiana, National Weather
Service (NWS) station at the Michiana Regional Airport (NCDC, 2005), and ten years of temperature
data from the Michigan City Generating Station (1994-2004), a meteorological factor was derived for
use in the exposure equations. South Bend, which is located 30 miles east of Michigan City, provides
the best data capture in the area for hourly precipitation data. Precipitation is not recorded at
Michigan City Generating Station. The station at Brenton Harbor (40 miles northeast of Michigan City,
but closer to Lake Michigan) has temperature data, but lacks precipitation data. While precipitation
data sources closer to Michigan City are available, data capture is poor (i.e., Gary Airport, Ogden
Dunes). While some difference in precipitation conditions from Michigan City to South Bend are
expected, the differences are not expected to be significant. On the average, 69.6 days/year in this
area receive 0.1 or greater inches of precipitation (NCDC, 2005), and there are typically 42.6
days/year with a maximum temperature of 32 degrees F or below (i.e., the temperature never rises
above freezing during the day). Accounting for days when both events occur (3.6 days), the number
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of inclement days, 108.6, can be calculated (69.6 + 42.6 – 3.6). It is assumed that these days are
evenly spaced throughout the course of the year. The meteorological factor is then calculated
(108.6/365 = 29.8%). Thus, it is assumed that exposure to CCBs will not occur for the residential
receptor 29.8% of the assumed days of exposure (exposure frequency) due to the ground surface
being unavailable for contact, not because receptors are not outdoors on these days. This results in
exposure frequencies of 245.9 (rounded up to 250) days per year for the RME residential scenario
and 164.4 (rounded up to 165) days per year for the CTE residential scenario.
The use of the meteorological factor does not imply that receptors are not outdoors on these days,
only that exposure to the ground during those periods of precipitation greater than 0.1 inches and
maximum temperatures less than 32 degrees F is negligible. It should be noted that this approach
has precedence in regulatory risk assessment. Indiana (IDEM, 2001) and Pennsylvania (PADEP,
1997) have modified the default exposure frequency to account for inclement weather in the
development of screening levels for use in their environmental programs. IDEM uses a residential soil
exposure frequency of 250 days/year as the default value in their Risk Integrated System of Closure
program (IDEM, 2001). A meteorological factor was used in the HHRA for the Sauget Area 2 Sites,
recently approved by USEPA Region 5 (AECOM, 2009). Additionally, an exposure frequency of 250
days per year was used by USEPA Region 5 in their HHRA for the Jacobsville Neighborhood Soil
Contamination Site (USEPA, 2006a), which is a community in Evansville, IN.
The meteorological factor is not applied in the radionuclide calculations because it is not applicable to
the external gamma pathway. While the meteorological factor is applicable to the soil and outdoor air
pathways, it has conservatively not been applied to the calculation of potential risk in the radiological
risk assessment.
5.4.2
Recreational Child
Table 5-4 presents exposure assumptions for a recreational child receptor assumed to be exposed to
CCB-derived COPCs where present in outdoor air via inhalation. In addition, the recreational child is
assumed to be exposed to COPCs in surface water via dermal contact (and via incidental ingestion
while swimming) and in sediment via incidental ingestion and dermal contact while playing in local
ditches or swimming in local ponds. Fish ingestion is not expected to be a significant pathway for
young children (aged 0 to 6). Data show that roughly 50% of children aged 0 to 9 years of age ingest
little to no fish (USPEA, 1997a). Roughly 97% of children aged 0 to 9 years ingest less than 20 grams
of fish per day (USEPA, 1997a). These statistics are for total fish consumption (freshwater, saltwater,
and shellfish). Young and older children consume less than 3 grams of freshwater finfish per day
based on the data in Table 10-6 of the EFH (USEPA, 1997a). USEPA Region I also concluded that
this pathway is unlikely to occur with any degree of frequency for young children in the Wells G and H
Superfund site HHRA (USEPA, 2004b). However, the fish ingestion pathway has been included at
the request of USEPA, assuming that fish are caught by the recreational fisher and shared with young
children. Therefore, while the pathway is unlikely, it was evaluated in the HHRA. At the further
request of USEPA, the potential risks calculated for the recreational child fish ingestion pathway were
added to the residential child potential risk. The child fish ingestion rate is assumed to be 2.5 g/day
for the RME scenario and 0.4 g/day for the CTE scenario (USEPA, 2008b); see Table 5-4. Brown
Ditch and Upgradient sediment samples were analyzed for radionuclides; the child is, therefore,
evaluated for potential exposure to radionuclides via sediment ingestion and exposure to external
gamma radiation (no outdoor shielding factors were considered).
The recreational child is assumed to be the same age as the residential child (0-6 years) and is
assumed to visit the Area of Investigation 26 days per year under the RME scenario and 13 days per
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year under the CTE scenario. The fish ingestion rate was derived based on data presented in USEPA
(2008b, Table 10-28). Other exposure assumptions are shown in Table 5-4 for the chemical risk
assessment and Appendix K for the radiological risk assessment. Derivation of surface area and
dermal adherence factors is discussed in Section 5.4.6. As the young child is the most sensitive
receptor compared to other age groups due to the young child’s higher intake combined with a lower
body weight, estimated risks for this age group will be higher than for other older child age groups or
adults.
5.4.3
Recreational Fisher
Exposure assumptions for the recreational fisher under the RME and CTE scenarios are shown in
Table 5-5. Recreational fishing may take place in local ditches or ponds. As constituents in
groundwater may migrate to these water bodies, COPCs may be present in surface water, sediment,
and fish tissue. Therefore, a recreational fisher has the potential to be exposed to COPCs through
ingestion of fish, incidental ingestion and dermal contact with sediment, and dermal contact with
surface water. The recreational fisher is also assumed to be exposed to COPCs derived from CCBs
where present in outdoor air via inhalation. Brown Ditch and Upgradient sediment samples were
analyzed for radionuclides; the fisher is, therefore, evaluated for potential exposure to radionuclides
via sediment ingestion and exposure to external gamma radiation.
The recreational fisher is assumed to fish in the Area of Investigation 26 days per year for 30 years
under the RME scenario and 3 days per year for 9 years under the CTE scenario. It is assumed that
during each day spent fishing in the Area of Investigation enough fish are caught to provide a fish
meal. This is a conservative assumption given the small size of the Brown Ditch system within the
Area of Investigation and the lack of observed fishing activity. At the request of USEPA, potential
risks calculated for the recreational fisher for fish ingestion, sediment, and surface water pathways
were also added to the residential total potential risk. Other exposure assumptions are shown in
Table 5-5 for the chemical risk assessment and Appendix K for the radiological risk assessment.
Derivation of surface area and dermal adherence factors is discussed in Section 5.4.6.
5.4.4
Construction Worker
Exposure assumptions for the construction/utility worker under the RME and CTE scenarios are
shown in Table 5-6. Exposure media of interest in the evaluation of potential risk to a future
construction worker include surface and subsurface CCBs where present and groundwater.
Construction work is assumed to occur to a depth of 12 to 15 feet bgs and includes utility maintenance
work. Water levels, which are presented in Table 5-7, have ranged from about 2 feet to about 28 feet
bgs seasonally across monitoring wells. Several wells have never had a depth to water less than
15 feet bgs, including MW105, MW-16S, MW-16D, MW-18S, and MW-18D. However, due to the
potential for water level variations over time, data from all monitoring wells have been included in the
evaluation of potential construction worker contact with groundwater. Exposure is assumed to occur
via incidental ingestion and dermal contact with CCB-derived constituents in soils, groundwater, and
via inhalation of fugitive dust from CCBs. The construction worker is also assumed to be exposed to
CCBs where present via external exposure to gamma radiation. As discussed previously, potential
exposure to radionuclides in groundwater has been eliminated as a pathway of concern.
The construction worker is assumed to work in the Area of Investigation 40 days per year (5 days per
week for 2 months) for one year (IDEM, 2001) under the RME scenario and 20 days per year 5 days
per week for 1 month) for one year under the CTE scenario (IDEM, 2001). Other exposure
assumptions are shown in Table 5-6 for the chemical risk assessment and Appendix K for the
radiological risk assessment. Derivation of surface area and dermal adherence factors is discussed in
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Section 5.4.6. The default CCB/soil ingestion rate of 330 mg/day (USEPA, 2002a) listed in Table 5-6
for the construction worker was used in the HHRA under the RME and CTE scenarios, however,
further discussion of the ingestion rate is provided below.
CCB/Soil Ingestion Rate
Incidental soil ingestion occurs at all ages as a result of hand-to-mouth activities. Default soil or CCB
ingestion rates have been used for the resident adult and child. However, currently, there are little or
no reliable quantitative data available for estimating occupational adult soil ingestion rates. USEPA
risk assessment guidance suggests a soil ingestion rate of 100 mg/day for adults in an outdoor
industrial scenario (USEPA, 2002a). While this value was also approved for use in this HHRA at the
work plan stage for the construction worker RME scenario, USEPA since has requested that the
ingestion rate be revised to 330 mg/day. The following text describes the derivation of an alternative
construction worker CCB ingestion rate, which was approved for use under the CTE scenario in the
HHRA work plan; however, USEPA has requested that the soil ingestion rate for both the RME and
CTE scenarios be revised to 330 mg/day.
CCB ingestion may occur as a result of hand-to-mouth transfer. Therefore, the amount of CCBs that
may adhere to a receptor’s hands is critical in determining the amount of CCBs that may be ingested
by that receptor. In 1993, USEPA sponsored a workshop to evaluate soil-to-skin adherence data. A
study to characterize soil-to-skin adherence was sponsored by the USEPA and conducted by John C.
Kissel and associates at the University of Washington (Kissel, et al., 1996; Holmes, et al., 1999). The
intent of this study was to resolve uncertainties and develop more accurate measures of soil-to-skin
loading rates for various occupational and recreational activities. As reported in the EFH (USEPA,
1997a), soil loading on skin surfaces as a result of various occupational and recreational activities was
directly measured. This study indicates that soil loadings vary with the type of activity and the body
parts contacted. As one would expect, adherence appears to be greatest during outdoor activities
such as farming and gardening, and more soil/dust tends to adhere to the hands and knees than to
other areas of the body.
Average hand soil loading factors are as presented in the EFH (USEPA, 1997a) for the adult outdoor
workers evaluated by Kissel and Holmes. The range of soil adherence loadings measured by Kissel
2
and Holmes falls within the USEPA range of 0.2 to 1.0 mg/cm (USEPA, 1992a).
For this evaluation, the construction worker receptor is assumed to be exposed to COPCs in surface
and subsurface CCBs during excavation activity. Based on this exposure scenario, the “farmer”
receptor provided in the EFH is considered to provide an upper-bound estimate of adherence. An
ingestion rate can be calculated by substituting the adherence value for the receptor for the estimated
value derived by Hawley (1985), as follows:
ingestion rate (mg / day )
480 mg/day
=
2
3.5 mg/ cm
soil adherence (mg / cm 2 )
2
The soil to hand adherence value for the “farmer” is 0.47 mg/cm . The calculated ingestion rate based
on this adherence factor is 64 mg/day.
Additional support for this value comes from a paper by Kissel and coworkers (Kissel, et al., 1998) that
presents the results of a study of the transfer of soil from hand to mouth by intentional licking. Soil
was loaded onto the skin by pressing the hand onto soil, and the amount transferred to the mouth was
measured. The thumb sucking, finger mouthing, and palm licking activities resulted in geometric
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mean soil mass transfers of 7.4 to 16 mg per event. The author concludes that "transfer of 10 mg or
more of soil from a hand to the oral cavity in one event is possible, but requires moderate soil loading
and more than incidental hand-to-mouth contact." However, "the fraction of soil transferred from hand
to mouth that is subsequently swallowed is unknown but may be less than 100 percent." In addition,
"the adult volunteers in this study reported that the presence of roughly 10 mg of soil in the mouth is
readily detected (and unpleasant). Repeated unintentional ingestion of that mass of soil by adults
therefore seems unlikely.”
Based on the above information, the use of a soil ingestion rate for the construction worker of 330
mg/day is likely an overestimate of potential ingestion. However, the default ingestion rate has been
used for both the RME and the CTE scenarios.
5.4.5
Outdoor Worker
Table 5-8 presents the exposure assumptions for the outdoor worker receptor for both RME and CTE
exposures. The outdoor worker is assumed to be exposed to COPCs in surface CCBs where present
via incidental ingestion and dermal contact and to COPCs in CCBs where present in particulates that
may be suspended in the air via inhalation. Additionally, the outdoor worker is assumed to be
potentially exposed to external gamma radiation. Per request of USEPA, the exposure frequency for
the chemical HHRA is assumed to be 225 days per year (USEPA, 2002a) for 25 years under the RME
scenario and 225 days per year for 7 years under the CTE scenario (USEPA, 1993b) for the outdoor
worker receptor. This is a conservative estimate, as a site-specific exposure frequency for the
chemical HHRA under both the RME and CTE scenario was developed as part of the HHRA Work
Plan to reflect meteorological conditions at the Area of Investigation, as described in Section 5.4,
above. If the meteorological factor of 29.8% was applied to the standard default industrial exposure
assumption of 250 days per year (USEPA, 1997a), an exposure frequency of 176 days per year [250(250 x 0.298) = 176] would result, which is lower than the default value requested for use by USEPA.
For the radiological risk assessment, potential exposure to external gamma radiation is not expected
to be affected by meteorological conditions. Therefore, the exposure frequency for the radiological
RME and CTE scenarios is 250 days per year. The default soil ingestion rate of 100 mg/day (USEPA
2002a) was used for the RME scenario, and a rate of 30 mg/day was used for the CTE scenario
(Calabrese, et al., 1990). Exposure assumptions for the chemical risk assessment are shown in
Table 5-8, and exposure assumptions for the radiological risk assessment are shown in Appendix K.
5.4.6
Surface Area and Soil to Skin Adherence Factors
It is assumed that while outdoors, receptors will come into dermal contact with CCBs. Adherence
estimates were calculated using the skin surface area data and soil adherence data from USEPA
(1997a and 2004a). The methods used to derive the skin surface areas and adherence factors are
described below.
5.4.6.1 Surface Area
For the adult resident, it is assumed that the head, hands, forearms, and lower legs are exposed for
potential CCB contact. For the child resident and recreational visitor, it is assumed that head, hands,
forearms, lower legs, and feet are exposed for potential CCB and sediment exposure. Table 5-9
2
presents the 50th percentile surface areas for those body parts for an adult resident (5,700 cm ) and
Table 5-10 presents the 50th percentile surface area for a child resident and recreational child
2
(2,800 cm ). The 50th percentile values are used because they correlate with the 50th percentile
body weight parameter (e.g., 70 kg for adult) recommended by the USEPA (1989a). Additionally,
these are the surface areas recommended in Exhibit 3-5 of USEPA (2004a). Note that the calculated
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values presented in Tables 5-9 and 5-10 are rounded to be consistent with Exhibit 3-5 of USEPA
(2004a).
For the recreational fisher, it is assumed that hands, forearms, lower legs, and feet are exposed to
sediment. Table 5-11 presents the 50th percentile surface areas for those body parts for a
2
recreational fisher. The total surface area assumed to be exposed is 5,669 cm .
It is assumed that construction workers and outdoor workers are required to wear shoes and long
pants. It is also assumed that the worker wears a long-sleeved shirt and/or coat during the colder
months of the year and, at a minimum, a short-sleeved shirt during the warmer months of the year.
Gloves are also likely worn in the winter. However, it is conservatively assumed that the construction
worker and outdoor worker receptor’s head, hands, and lower arms are exposed for CCB contact
throughout the year. Table 5-12 presents the surface areas for each of these body parts at the 50th
2
percentile for adults. The total surface area assumed to be exposed is 3,300 cm , which is consistent
with the value recommended in Exhibit 3-5 of USEPA (2004a) for a commercial/industrial worker.
Note that the calculated value presented in Table 5-12 is rounded to be consistent with Exhibit 3-5 of
USEPA (2004a).
5.4.6.2 Adherence Factors
To account for differences in adherence for different parts of the body, an area-weighted adherence
factor is calculated using the body part-specific adherence levels presented in Exhibit C-2 of USEPA
(2004a). For each receptor, the skin surface area of each exposed body part is multiplied by its body
part-specific adherence factor to yield a total mass adhered to that body part. The total masses are
then summed for all exposed body parts, and then divided by the total body surface area exposed to
derive the area-weighted adherence factor.
Estimates of adherence are derived from the EFH (USEPA, 1997a), which states that: “In
consideration of … the recent data from Kissel [Kissel, et al., 1996]…, changes are needed from past
USEPA recommendations [USEPA, 1992a] which used one adherence value to represent all soils,
body parts, and activities. One approach would be to select the activity from Table 6-11 which best
represents the exposure scenario of concern and use the corresponding adherence value from
Table 6-12”.
USEPA (2004a) indicates that adherence factors should be calculated by either selecting a central
tendency soil contact activity and a high-end weighted adherence factor, or by selecting a high-end
soil contact activity and using the central tendency weighted adherence factor. The guidance also
states that using a high-end soil contact activity should not be used with a high-end weighted
adherence factor, as this is not consistent with the use of an RME scenario.
From the exposure scenarios presented in Table 6-11 of USEPA (1997a) and the adherence data
presented in Exhibit C-2 of USEPA (2004a), the following approach was used to derive adherence
factors:
Adult Resident
•
RME CCB/Soil Scenario – High-end soil contact activity (Gardeners) used with geometric
2
mean adherence data = 0.07 mg/cm (consistent with recommendation in Exhibit 3-5 of
USEPA, 2004a).
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CTE CCB/Soil Scenario – Central tendency soil contact activity (Groundskeepers) used with
2
geometric mean adherence data = 0.01 mg/cm (consistent with recommendation in Exhibit
3-5 of USEPA, 2004a).
The calculations for the adult resident are presented in Table 5-9.
Child Resident/ Recreational Child
•
RME CCB/Soil Scenario – High-end soil contact activity (Children Playing in Wet Soil) used
2
with geometric mean adherence data = 0.2 mg/cm (consistent with recommendation in
Exhibit 3-5 of USEPA, 2004a; calculated value was rounded to be consistent with the
guidance value).
•
CTE CCB/Soil Scenario – Central tendency soil contact activity (Day Care Kids) used with
2
geometric mean adherence data = 0.04 mg/cm (consistent with recommendation in Exhibit
3-5 of USEPA, 2004a).
•
RME and CTE Sediment Scenario – High-end soil contact activity (Children Playing in Wet
2
Soil) used with geometric mean adherence data = 0.2 mg/cm (consistent with
recommendation in Exhibit 3-5 of USEPA, 2004a; calculated value was rounded to be
consistent with the guidance value).
The calculations for the child resident/recreational child are presented in Table 5-10.
Recreational Fisher
•
RME and CTE Sediment Scenario – Adult sediment/wet soil contact activity (Reed Gatherers)
2
used with geometric mean adherence data = 0.3 mg/cm .
The calculations for the recreational fisher are presented in Table 5-11.
Construction Worker
•
RME CCB/Soil Scenario – High-end soil contact activity (Construction Workers) used with
2
95th percentile adherence data = 0.3 mg/cm (consistent with recommendation in Equation 51 of USEPA, 2002a).
•
CTE CCB/Soil Scenario – High-end soil contact activity (Construction Workers) used with
2
geometric mean adherence data = 0.139 mg/cm (consistent with recommendation in Exhibit
C-2 of USEPA, 2004a).
The calculations for the construction worker are presented in Table 5-12.
Outdoor Worker
•
RME CCB/Soil Scenario – High-end soil contact activity (Utility Workers) used with geometric
2
mean adherence data = 0.2 mg/cm (consistent with recommendation in Exhibit 3-5 of
USEPA, 2004b)
•
CTE CCB/Soil Scenario – Central tendency soil contact activity (Groundskeepers) used with
2
geometric mean adherence data = 0.02 mg/cm (consistent with recommendation in Exhibit
3-5 of USEPA, 2004b).
The calculations for the outdoor worker are presented in Table 5-12.
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Radionuclide Specific Exposure Parameters
The USEPA risk model used for the external gamma radiation exposure pathway assumes that an
individual is exposed to a source that is effectively an infinite slab (i.e., of infinite depth). Based on the
information on the location of suspected CCBs within the Area of Investigation, for the exposure
scenarios presented here, this assumption was unrealistic and adjustments were made by applying
an area correction factor (ACF). The ACF effectively reduces the external gamma exposure by a
small amount due to the reduction in the size (area) of the source term.
2
An ACF of 0.92 was selected for exposure scenarios where an area approximation of 2000 m (1/2
acre) was assumed (construction worker and recreational scenarios). This is the recommended ACF
for Ra-226+D in Table 5.2 on the USEPA PRG website (USEPA, 2010b). The Ra-226+D ACF is a
conservative selection for all radionuclides because the Ra-226 decay chain has the most energetic
and abundant gamma emissions of any of the radionuclides evaluated.
2
An ACF of 0.87 was selected for exposure scenarios where an area approximation of 500 m (or
2
about 27% of 2000 m ) was used (residential and outdoor worker). This is the recommended ACF for
Ra-226+D in Table 5.2 on the USEPA PRG website (USEPA, 2010b). The Ra-226+D ACF is a
conservative selection for all radionuclides because the Ra-226 decay chain has the most energetic
and abundant gamma emissions of any of the radionuclides evaluated.
Indoor and outdoor exposure time fractions are also applied to the residential external gamma
exposure risk calculations. However, in all exposure scenarios, the indoor time fraction was set to
zero. Based on the information available about house construction dates and suspected CCB
placement, CCBs are not expected to be present under residential structures. The outdoor time
fractions are based on the hours of outdoor exposure assumed per day. The gamma shielding factor
for indoor exposures is also shown in the radiological risk parameter tables. However, this factor is
set to zero as indoor exposures are not expected. There is also no gamma shielding assumed for any
outdoors exposures (residential, occupational, or recreational).
5.5
Expos ure P oint Co nc e ntra tions
Exposure points are located where potential receptors may contact COPCs at or from the Area of
Investigation. The concentration of COPCs in the environmental medium that receptors may contact
must be estimated in order to determine the magnitude of potential exposure. The estimation of EPCs
in media evaluated for the HHRA is discussed below. Both measured and modeled EPCs are
discussed where applicable.
5.5.1
Measured EPCs
The EPC for a human health risk assessment is defined as the 95% upper confidence limit (UCL) on
the arithmetic mean concentration, or the maximum concentration, whichever is lower (USEPA,
2002c), for the RME scenario. The lower of the UCL and the maximum detected concentration is also
used as the EPC for the CTE scenario.
Summary statistics have been calculated for each constituent in each medium, as presented in the
tables in Section 3.0. As discussed in Section 3.0, before summary statistics were calculated,
duplicate sample analytical results were averaged, and the average used as the sample point
concentration (USEPA, 1989b).
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EPCs for suspected CCBs, background soils, Brown Ditch sediment, and Brown Ditch surface water
were generated following USEPA guidance (USEPA, 2002c; USEPA, 2007a). USEPA’s ProUCL
Version 4.00.02 software (USEPA, 2007a) was used to calculate UCLs using the Kaplan-Meier
method where non-detects are present (using SSQLs and appropriate substitution methods). Since
the time the UCLs were tabulated, a new version of ProUCL (Version 4.1.01) was released. To
determine the potential impact on UCLs, UCLs for the MWSE dataset were run using Version 4.1.01.
The UCLs were essentially equivalent, with only two UCLs varying slightly at the hundredth point.
The ProUCL-recommended UCL (95%, 97.5%, or 99%) was used as the EPC. Based on information
presented in the ProUCL guidance (USEPA, 2007a) regarding minimum sample size and frequency of
detection, UCLs were calculated where at least 10 samples and at least six detected results are
available. ProUCL version 4.00.02 recommends 10-15 or more distinct results for the most accurate
and reliable UCL calculation. Where too few samples or detects are available, the maximum detected
concentration is used as the EPC. Appendix E provides the output from ProUCL as well as
histograms for COPCs meeting the minimum data requirements.
Chemical EPCs
Table 5-13 presents the chemical EPC selection for suspected CCBs; EPCs for the hypothetical
screening level 100% CCB scenario and the site-specific 27% CCB scenario are provided. Table 5-14
presents the chemical EPC selection for background soils, and Table 5-15 presents the chemical EPC
selection for Brown Ditch sediment and surface water.
UCLs were not calculated for Pond 1 and Pond 2 sediment and surface water. One sediment sample
was collected from each pond, and the detected concentration is selected as the EPC. Four rounds of
surface water samples were collected from each pond. Therefore, the maximum detected
concentration is selected as the EPC for these media. As noted in Section 3.1.4, Brown Ditch
Upgradient sediment and surface water data are not quantitatively evaluated in the chemical risk
assessment.
UCLs were not calculated for groundwater monitoring wells, which are evaluated on a location-bylocation basis. Four rounds of samples were collected from each well; the maximum detected
concentration for each well is selected as the EPC for groundwater.
As discussed in the next section, EPCs for CCBs and background soil were used to calculate EPCs in
air. EPCs for surface water in Brown Ditch and the ponds were used to calculate EPCs for fish tissue.
Chemical EPCs used in the HHRA are presented in the following tables (the modeled EPCs shown in
these tables are discussed in the following section):
•
Table 5-16 – Suspected CCB EPCs
•
Table 5-17 – Background Soil EPCs
•
Table 5-18 – Monitoring Well EPCs (note that Table 3-27 presents summary statistics for all
groundwater, including private wells and background monitoring wells; the maximum detected
concentration is used as the EPC in the residential drinking water cumulative risk assessment
presented in Section 6.4)
•
Table 5-33 – Brown Ditch Sediment EPCs
•
Table 5-19 – Pond 1 Sediment EPCs
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•
Table 5-20 – Pond 2 Sediment EPCs
•
Table 5-21 – Brown Ditch Surface Water EPCs
•
Table 5-22 – Pond 1 Surface Water EPCs
•
Table 5-23 – Pond 2 Surface Water EPCs
5-30
Radionuclide EPCs
As discussed in Section 3.1.2, non-detect concentrations for polonium-210 and lead-210 in the
MWSE, Yard 520, and Brown Ditch sediment datasets were replaced with reported radium-226
concentrations for each sample based on the assumption of secular equilibrium. In the background
dataset, all polonium-210 and lead-210 results were replaced with reported radium-226
concentrations for each sample because the reported polonium-210 and lead-210 concentrations
were not consistent with the more reliable radium-226 results. These values were replaced prior to
the calculation of the radionuclide EPCs.
Table 5-29 presents the radionuclide EPC selection for the MWSE suspected CCB dataset; EPCs for
the hypothetical screening level 100% CCB scenario and the site-specific 27% CCB scenario are
provided. Table 5-30 presents the radionuclide EPC selection for the Yard 520 CCB dataset, and
Table 5-31 presents the radionuclide EPC selection for background soils. Table 5-32 presents the
EPCs for suspected CCBs, background soils, and sediment (Brown Ditch and Upgradient). Maximum
detected concentrations were used to evaluate radionuclides in sediment.
5.5.2
Modeled EPCs
Some pathways required modeling to derive the EPCs. These pathways include generation of fugitive
dusts from undisturbed soils as well as during construction activities, and uptake of COPCs from
surface water into fish tissue.
5.5.2.1 Outdoor and Excavation Air – Suspected CCBs
Modeling was required to calculate EPCs for the soil to outdoor air pathway. Outdoor air
concentrations for non-excavation scenarios (residential and recreational) follow the methods
recommended by USEPA (2002a). Outdoor air concentrations of particulates in the excavation
scenario (construction worker) follow the method recommended by USEPA (2002a) for unpaved road
truck traffic, although the method recommended by MADEP (1995) was presented in the USEPAapproved HHRA Work Plan (ENSR, 2005b).
PEF for Non-Excavation Scenarios
The dust concentration in air EPC calculated for use in the evaluation of outdoor air pathways is the
inverse of the Particulate Emission Factor (PEF) derived in accordance with USEPA guidance
(USEPA, 2002a). Table 5-24 calculates the dispersion factor for use in the PEF development for nonexcavation scenarios. The dispersion factor was calculated for a hypothetical residential lot that is ½
acre in size. Table 5-25 presents the PEF calculation for non-excavation scenarios. The default
fraction of vegetative cover of 0.5 acres was used to represent the majority of potential cases, where a
house and a driveway likely cover about ½ of the residential lot. Using this assumption assumes that
the remainder of the property is bare soil, which is a conservative assumption and likely overestimates
air concentrations. The PEF was also used in the evaluation of potential radionuclide risks however, it
is included as an integrated part of the PRG equation; therefore, a separate modeled air concentration
is not used in the radionuclide HHRA.
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Excavation Scenario
The dust concentration in air EPC calculated for use in the evaluation of the construction worker
excavation air pathway is the inverse of the PEF derived in accordance with Appendix E of USEPA
(2002a) for fugitive dust emissions. USEPA (2002a) Appendix E presents two fugitive dust models for
construction activities:
•
•
Fugitive dust emissions from unpaved road traffic – this PEF estimates fugitive dusts based
on unpaved road traffic
Fugitive dust emissions from other construction activities – this PEF estimates fugitive dusts
based on wind erosion, excavation soil dumping, dozing, grading, and tilling or other similar
operations.
Because most of the roads in the Area of Investigation are paved, and the majority of the locations of
suspected CCBs are small residential areas, the PEF based on unpaved road traffic is likely not
applicable. However, the PEF was calculated using both methods. Table 5-34 presents the
calculation of the PEF for unpaved road traffic, based on USEPA (2002a) defaults and suggested
6
3
values, and an area of 0.5 acres (hypothetical residential lot). The PEF is 1.09x10 m /kg, which is
3
equivalent to a dust concentration of 921 ug/m . Table 5-35 presents the PEF based on other
construction activities based on USEPA (2002a) defaults and suggested values, and an area of 0.5
7
3
acres (hypothetical residential lot). The PEF is 5.47x10 m /kg, which is equivalent to a dust
3
3
concentration of 18.3 ug/m , which is lower than the MADEP default dust concentration of 60 ug/m
(MADEP, 1995). While the PEF based on other construction activities is more applicable to conditions
found within the Area of Investigation, the unpaved road traffic PEF has been used to provide a
conservative estimate of potential risks. The uncertainty analysis will discuss the potential risks based
on the PEF for other construction activities as well as potential risks based on the MADEP dust
concentration.
Outdoor and excavation air concentrations for both the hypothetical 100% screening level scenario
and the site-specific 27% CCB scenario (residential and outdoor worker scenarios only) are presented
on Table 5-16. Outdoor and excavation air concentrations for the background scenario are presented
on Table 5-17.
The PEF was also used in the evaluation of potential radionuclide risks however, it is included as an
integrated part of the PRG equation; therefore, a separate modeled air concentration is not used in
the radionuclide HHRA.
5.5.2.2 Fish Tissue
Fish tissue EPCs for Brown Ditch (arsenic, selenium) and the ponds (manganese) were estimated
based on the estimated surface water EPC and water-to-fish uptake factors. Uptake factors of
3.46 mg/kg fish per mg/L water and 485 mg/kg fish per mg/L water were used for arsenic and
selenium, respectively (USEPA, 1998d). An uptake factor of 400 mg constituent/kg fish per
mg constituent/L water was used for manganese (WSRC, 1999). Uptake factors used in the risk
assessment are consistent with the uptake factors applied for arsenic and selenium for trophic level
three fish in USEPA documents (USEPA, 2002e), and are conservative for the fish expected to be
present in Brown Ditch and the ponds. Small minnows and shiners, e.g., fathead minnow (trophic
level two), are likely the most common fish present; other species may include carp and bullhead
(trophic level three; Bacula, 2011). Food chain multipliers of 1 for inorganics for trophic levels one and
two were obtained from USEPA (1995c); this is consistent with the recommended food chain multiplier
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of 1 for trophic levels three and four for inorganic constituents that do not biomagnify (USEPA, 1995d
and 1998e), and specifically, the recommended food chain multiplier for selenium (IDEM, 1997).
Table 5-26 presents the uptake factors and the estimated fish tissue EPCs for arsenic and selenium in
Brown Ditch, and Tables 5-27 and 5-28 present the uptake factor and the estimated fish tissue EPCs
for manganese in Pond 1 and Pond 2, respectively. The full equation for derivation of the fish tissue
EPCs is presented in each of these tables and reduces to:
Fish tissue EPC (mg/kg) =
Surface Water EPC (mg/L) x Uptake Factor [(mg constituent /kg fish)/(mg constituent /L water)]
5.6
Expos ure Ca lc ula tion s
The EPCs and exposure parameters were used to develop estimates of exposures to COPCs for
each receptor and pathway evaluated in the HHRA. Appendix F presents the exposure
dose/concentration and risk calculation spreadsheets for the chemical HHRA and Appendix K
presents the risk calculation spreadsheets for the radionuclide HHRA. The risk results are discussed
in Section 6.0.
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6-1
Risk Characterization
The potential risk to human health associated with potential exposure to COPCs in environmental
media at the Area of Investigation is evaluated in this step of the risk assessment process. Risk
characterization is the process in which the dose-response information (Section 4.0) is integrated with
quantitative estimates of human exposure derived in the Exposure Assessment (Section 5.0). The
result is a quantitative estimate of the likelihood that humans will experience any adverse health
effects given the exposure assumptions made. Two general types of health risk are characterized for
each potential exposure pathway considered: potential carcinogenic risk and potential
noncarcinogenic hazard. Potential carcinogenic risk is evaluated by averaging exposure over a
normal human lifetime, which, based on USEPA guidance (1989a), is assumed to be 70 years.
Potential noncarcinogenic hazard is evaluated by averaging exposure over the total exposure period.
Characterization of the potential health effects of potential carcinogenic and noncarcinogenic
constituents is approached in very different ways. The difference in approaches arises from the
conservative assumption that substances with possible carcinogenic action proceed by a no-threshold
mechanism, whereas other toxic actions may have a threshold, i.e., a dose below which few
individuals would be expected to respond. Thus, under the no-threshold assumption, it is necessary
to calculate a risk, but for constituents with a threshold, it is possible to simply characterize an
exposure as above or below the threshold. In risk assessment, that threshold is termed a reference
dose or reference concentration. Reference doses and reference concentrations as well as cancer
slope factors and unit risk factors were discussed in Section 4.0. The approach to carcinogenic risk
characterization is presented in Section 6.1, and the approach to noncarcinogenic risk
characterization is presented in Section 6.2. The chemical risk characterization results are presented
in Section 6.3.1. The radionuclide risk characterization is presented in Section 6.3.2. A cumulative
risk assessment for the residential drinking water pathway is presented in Section 6.4. Uncertainties
associated with the risk characterization are presented in Section 6.5. The chemical risk calculation
spreadsheets are presented in Appendix F. The radionuclide risk calculation spreadsheets are
presented in Appendix K.
6.1
Ca rc inoge nic Ris k Ch a ra c te riza tion Me thod s
The purpose of carcinogenic risk characterization is to estimate the upper-bound likelihood, over and
above the background cancer rate, that a receptor will develop cancer in his or her lifetime as a result
of exposure to a constituent in environmental media. This likelihood is a function of the dose or
concentration of a constituent (described in the Exposure Assessment, Section 5.0) and the toxicity
values, the CSF or URF (described in the Dose-Response Assessment, Section 4.0) for that
constituent. The Excess Lifetime Cancer Risk (ELCR) is the likelihood of contracting cancer over and
above the background cancer rate. The American Cancer Society (ACS) estimates that the lifetime
-1
-1
probability of contracting cancer in the U.S. is 1 in 2 (5 x 10 ) for men and 1 in 3 (3 x 10 ) for women
-6
(ACS, 2011). The risk value is also expressed as a probability (e.g., one in one million or 10 ). The
relationship between the ELCR and the estimated LADD of a constituent for oral and dermal
exposures may be expressed as:
-(CSF x LADD)
ELCR = 1-e
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When the product of the CSF and the LADD is much greater than 1, the ELCR approaches 1 (i.e., 100
percent probability). When the product is less than 0.01 (one chance in 100), the equation can be
closely approximated by:
ELCR = LADD (mg/kg-day) x CSF (mg/kg-day)
-1
The product of the CSF and the LADD is unitless, and provides an upper-bound estimate of the
potential carcinogenic risk associated with a receptor’s exposure to that constituent via that pathway.
For inhalation exposures, the ELCR is calculated as follows:
3
3 -1
ELCR = Lifetime ADE (mg/m ) x URF (ug/mg ) x 1000 ug/mg
The LADD for oral, dermal, and inhalation pathways is multiplied by the applicable ADAF where
appropriate.
Potential risks for radionuclides were calculated based on the PRGs calculated in Appendix K.
Because the relationship between the potential risk and the concentration of a radionuclide is linear,
-6
the potential risks were calculated based on the EPC, the PRG, and the PRG target risk (10 ) as
follows:
Potential Risk =
EPC (pci / g)
* 10 −6
PRG(pci / g)
The potential carcinogenic risk for each exposure pathway is calculated for each receptor. Current
regulatory risk assessments assume that carcinogenic risks are cumulative. Pathway and areaspecific risks are summed to estimate the total potential carcinogenic risk for each receptor.
Summaries of the total carcinogenic risks for each receptor group is presented in this section and
-4
-6
compared to the USEPA’s target risk range of 10 to 10 . A COPC that causes an exceedance of the
-6
10 risk level for a particular receptor is designated a COC. Per the request of USEPA, all
-6
constituents, receptors and/or pathways posting total potential risk > 1x10 are identified, The target
risk levels used for the identification of COCs are based on USEPA guidance and were identified in
-4
the approved HHRA Work Plan (ENSR, 2005b), though the work plan identified 10 as the target for
COC identification. Specifically, USEPA provides the following guidance (USEPA, 1991b):
“EPA uses the general 10(-4) to 10(-6) risk range as a "target range" within which the Agency
strives to manage risks as part of a Superfund cleanup. Once a decision has been made to
make an action, the Agency has expressed a preference for cleanups achieving the more
protective end of the range (i.e., 10(-6)), although waste management strategies achieving
reductions in site risks anywhere within the risk range may be deemed acceptable by the EPA
risk manager. Furthermore, the upper boundary of the risk range is not a discrete line at 1 x
10(-4), although EPA generally uses 1 x 10(-4) in making risk management decisions. A
specific risk estimate around 10(-4) may be considered acceptable if justified based on sitespecific conditions, including any remaining uncertainties on the nature and extent of
contamination and associated risks. Therefore, in certain cases EPA may consider risk
estimates slightly greater than 1 x 10(-4) to be protective.”
And,
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“Where the cumulative carcinogenic site risk to an individual based on reasonable maximum
exposure for both current and future land use is less than 10-4, and the non-carcinogenic
hazard quotient is less than 1, action generally is not warranted unless there are adverse
environmental impacts.”
In addition, IDEM offers the following guidance regarding target risk level:
The Indiana Risk Integrated System of Closure (RISC) [IDEM. 2001. Risk Integrated System
of Closure Technical Guide. February 15, 2001.], and the latest IDEM guidance [IDEM.
2012. Remediation Closure Guide. March 22, 2012. http://www.in.gov/idem/6683.htm] uses
the target risk range of 1E-06 to 1E-04. The IDEM residential soil screening levels are set at
a 1E-05 target risk level [see Appendix A of IDEM, 2012]. Section 7.6 of the IDEM guidance
document states: “The cumulative hazard index of chemicals that affect the same target
organ should not exceed 1, and the cumulative target risk of chemicals that exhibit the same
mode of action should not exceed 10-4. U.S. EPA risk assessment guidance views these
criteria as “points of departure”, and IDEM will generally require some further action at sites
where these risks are exceeded. Further action may include remediation, risk management,
or a demonstration utilizing appropriate lines of evidence that the risk characterization
overstates the actual risk.
By comparison, the ACS estimates that the lifetime probability of contracting cancer in the U.S. is 1 in
-1
-1
2 (5 x 10 ) for men and 1 in 3 (3 x 10 ) for women (ACS, 2011).
6.2
Nonc a rc inoge nic Ris k Cha ra c te riza tion Me thods
The potential for exposure to a constituent to result in adverse noncarcinogenic health effects is
estimated for each receptor by comparing the CADD or ADE for each COPC with the RfD or RfC,
respectively, for that COPC. The resulting ratio, which is unitless, is known as the Hazard Quotient
(HQ) for that constituent. The HQ is calculated using the following equation for oral and dermal
exposures:
HQ = CADD (mg/kg-day)
RfD (mg/kg-day)
For inhalation exposures, the HQ is calculated as follows:
3
HQ = Chronic ADE (mg/m )
3
RfC (mg/m )
The target HQ is defined as an HQ of less than or equal to one (USEPA, 1989a, 1991b). When the
HQ is less than or equal to 1, the RfD has not been exceeded, and no adverse noncarcinogenic
effects are expected. If the HQ is greater than 1, there may be a potential for adverse
noncarcinogenic health effects to occur; however, the magnitude of the HQ cannot be directly equated
to a probability or effect level.
The total Hazard Index (HI) is calculated for each exposure pathway by summing the HQs for each
individual constituent. The total HI is calculated for each potential receptor by summing the HIs for
each pathway associated with the receptor. Where the total HI is greater than 1 for any receptor, a
more detailed evaluation of potential noncarcinogenic effects based on specific health or target
endpoints (e.g., liver effects, neurotoxicity) is performed (USEPA, 1989a). The target HI is 1 on a per
target endpoint basis.
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A summary of all HIs for each receptor is presented in this section and compared to the USEPA’s
target HI of 1. The tables summarizing the HI show both the total HI and, where the total HI is greater
than one, the HI by target organ. Each COPC that causes an exceedance of the HI of 1 for a
particular receptor and for a particular target endpoint is designated a COC.
6.3
Ris k Cha ra c te riza tion Re s ults
The results of the risk characterization are presented below by receptor. Chemical results are
presented in Section 6.3.1 and radionuclide results are presented in Section 6.3.2. Section 6.3.3
provides a summary of both the chemical and radionuclide risk characterization results.
6.3.1
Chemical Risk Characterization Results
6.3.1.1 Resident
For the residential scenario, it is conservatively assumed for the hypothetical screening level 100%
CCB scenario that the receptor’s entire yard is comprised of CCBs and that all contact that would
normally be assumed to occur with soils would occur with CCBs. Based on data obtained during the
visual inspections of private properties (AECOM, 2010a), the assumption of 100% CCBs covering
100% of a residential lot is overly conservative. Therefore, a second site-specific scenario using the
conservative maximum average percent of CCBs identified by a review of the visual inspection data
was evaluated (see Appendix I). The percent of suspected CCBs mixed with other materials at each
location was estimated based on information obtained during the visual inspections of private
properties (see Section 3.7.2 of the RI Report). Based on these field observations, an average
percent of suspected CCBs in surface soils was calculated for each property (taking into account the
percent of suspected CCBs at each inspection location and the total area of each property upon which
suspected CCBs were present). The conservative maximum of the maximum average percent of
suspected CCBs in surface soils over the exposure area was 27%, as calculated in Appendix I. The
conservative average of the maximum average percent of suspected CCBs in surface soils over the
exposure area was 6%, and all but 4 properties have a maximum average percent less than 15% (i.e.,
93% of the properties have a result less than 15%). This is shown graphically in the figure below.
Therefore, the second scenario, which is still conservative, assumes that the hypothetical exposure
area of a residential lot contains 27% CCBs in surface soil.
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Risk assessments generally assume that materials at depth can be brought to the surface in the future
due to excavation and regrading activities. Such activities may occur in the future within the Area of
Investigation, but it is unlikely that the excavated CCBs would remain at 100% through the excavation,
replacement, and regrading activities. The CCBs would mix with other materials (soil, sand) during
these activities as there are few areas where suspected CCBs have been identified to occur within the
entire 0-15 foot soil column. Therefore, the site-specific conservative maximum average percent
CCBs of 27% is also expected to be a reasonable and conservative estimate of potential future
exposures.
Residents are assumed to be potentially exposed to COPCs in suspected CCBs via incidental
ingestion and dermal contact and via inhalation of particulates in outdoor air. Residents are also
assumed to be potentially exposed to COPCs in sediment via incidental ingestion and dermal contact
and in surface water via dermal contact in Brown Ditch while wading or via incidental ingestion and
dermal contact in one of the ponds while swimming. Potential fish ingestion risks calculated for the
recreational fisher and the recreational child are also included in the residential total risk estimates. In
addition, potential risks associated with exposure to background soils via incidental ingestion, dermal
contact, and dust inhalation are presented. Groundwater data were evaluated in a cumulative risk
assessment in Section 6.4. The potential produce pathway is evaluated in Appendix H.
Tables 6-1RME through 6-6RME present the total potential risks and hazard indices for suspected
CCBs, sediment, and surface water, as discussed below for the RME scenario. Three sets of
potential risks and hazards are presented based on whether the residential receptor is assumed to be
exposed to COPCs in Brown Ditch, Pond 1, or Pond 2. The potential risks associated with suspected
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CCBs are the same on each of these tables. In addition to the potential risks and hazards calculated
for the residential receptor, potential risks and hazards calculated for some recreational scenarios
were added to the residential receptor totals, including recreational fish ingestion by adults and
children and surface water and sediment exposure for adults (the residential child was evaluated for
surface water and sediment exposure). Tables 6-7RME and 6-8RME present the potential risks
associated with exposure to COPCs in background soils.
The CTE scenario results are presented on Tables 6-1CTE through 6-6CTE for potential exposure to
COPCs in suspected CCBs, sediment, and surface water, as well as fish ingestion. Tables 6-7CTE
and 6-8CTE present the potential risks associated with exposure to COPCs in background soils.
Exposure to COPCs in Suspected CCBs, Sediment, and Surface Water
RME Resident – CCBs and Brown Ditch
Table 6-1RME presents the total potential carcinogenic risks for the RME resident potentially exposed
to COPCs in suspected CCBs as well as Brown Ditch surface water, sediment, and fish tissue. The
-5
potential risks under both the hypothetical screening level 100% CCB scenario (4.8x10 ) and the site-5
-4
-6
specific 27% CCB scenario (1.8x10 ) are within USEPA’s target risk range of 10 to 10 . The
following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 (see totals
above)
•
Total potential risk (hypothetical screening level 100% and site-specific 27% CCB scenarios)
-5
is greater than 10 (see totals above)
•
Total arsenic potential risk (hypothetical screening level 100% CCB scenario [4.6x10 ] and
-5
-5
site-specific 27% CCB scenario [1.7x10 ]) is greater than 10
•
Arsenic in suspected CCBs (hypothetical screening level 100% CCB scenario [3.9x10 ] and
-5
-5
site-specific 27% CCB scenario [1.1x10 ] is greater than 10
•
Hexavalent chromium in suspected CCBs (hypothetical screening level 100% CCB scenario)
-6
-6
is greater than 10 (2.8x10 )
•
Arsenic in Brown Ditch sediment is greater than 10 for both the child (3.2x10 ) and the adult
-6
fisher (2.4x10 )
-4
-5
-5
-6
-6
Table 6-2RME presents the hazard index (by target organ). The total HI under the 100% CCB
hypothetical screening level scenario is 4.6, and under the site-specific 27% CCB scenario, is 1.5.
Therefore, a target endpoint analysis was conducted. By target organ, incidental ingestion with
suspected CCBs result in HQs above one as follows:
•
Iron (HQ = 1.06 for suspected CCBs and 1.13 total, which are essentially one) under the
hypothetical screening level 100% CCB scenario based on gastrointestinal effects. Under
the site-specific 27% CCB scenario, the iron HQ is below one (0.36)
•
Thallium (HQ = 1.64 for ingestion of suspected CCBs and 1.65 total) under the hypothetical
screening level 100% CCB scenario. Under the 27% CCB scenario, the thallium HQ is below
one (0.45). Note that the endpoint for thallium is hair follicle atrophy, and that the provisional
toxicity value provided by USEPA is not necessarily recommended for use (see discussion in
Section 4).
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Noncarcinogenic regulatory targets were not exceeded for sediment or surface water.
CTE Resident – CCBs and Brown Ditch
Table 6-1CTE presents the total potential carcinogenic risks for the CTE resident potentially exposed
to COPCs in suspected CCBs as well as Brown Ditch surface water, sediment, and fish tissue. The
-6
potential risks under both the hypothetical screening level 100% CCB scenario (4.6x10 ) and the site-6
-4
-6
specific 27% CCB scenario (1.5x10 ) are within USEPA’s target risk range of 10 to 10 . The
following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
totals above)
•
Total potential risk (hypothetical screening level 100% and site-specific 27% CCB scenarios)
-6
is greater than 10 (see totals above)
•
Total arsenic potential risk (hypothetical screening level 100% CCB scenario [4.2x10 ] and
-6
-6
site-specific 27% CCB scenario [1.4x10 ]) is greater than 10
•
Arsenic in suspected CCBs (hypothetical screening level 100% CCB scenario) is greater than
-6
-6
-6
10 (3.8x10 ) and under the site-specific 27% CCB scenario is equal to 1x10
-4
-5
-6
Table 6-2CTE presents the hazard index (by target organ). The total HI under the 100% CCB
hypothetical screening level scenario is 1.4, and under the site-specific 27% CCB scenario, is 0.44.
Therefore, a target endpoint analysis was conducted. By target organ, there are no HQs above one
for either scenario.
RME Resident – CCBs and Pond 1
Table 6-3RME presents the total potential carcinogenic risks for the RME resident potentially exposed
to COPCs in suspected CCBs as well as Pond 1 sediment, surface water, and fish tissue. The
-5
potential risks under both the hypothetical screening level 100% CCB scenario (4.4x10 ) and the site-5
-4
-6
specific 27% CCB scenario (1.3x10 ) are within USEPA’s target risk range of 10 to 10 . The
following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 (see totals
above)
•
Total potential risk (hypothetical screening level 100% CCB scenario and site-specific 27%
-5
CCB scenario) is greater than 10 (see totals above)
•
Total arsenic potential risk (hypothetical screening level 100% CCB scenario [4.1x10 ] and
-5
-5
site-specific 27% CCB scenario [1.2x10 ]) is greater than 10
•
Arsenic in suspected CCBs (hypothetical screening level 100% CCB scenario [3.9x10 ] and
-5
-5
site-specific 27% CCB scenario [1.1x10 ] is greater than 10
•
Hexavalent chromium in suspected CCBs (hypothetical screening level 100% CCB scenario)
-6
-6
is greater than 10 (2.8x10 )
•
Arsenic in Pond 1 sediment is greater than 10 for the child (1.1x10 )
-4
-5
-5
-6
-6
Table 6-4RME presents the hazard index (by target organ). The total HI under the hypothetical
screening level 100% CCB scenario is 4.7, and under the site-specific 27% CCB scenario, is 1.6.
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Therefore, a target endpoint analysis was conducted. By target organ, incidental ingestion with
suspected CCBs result in HQs above one as follows:
•
Iron (HQ = 1.06 for suspected CCBs and 1.08 total, which are essentially one) under the
hypothetical screening level 100% CCB scenario based on gastrointestinal effects. Under
the site-specific 27% CCB scenario, the iron HQ is below one (0.31)
•
Thallium (HQ = 1.64 for ingestion of suspected CCBs and 1.65 total) under the hypothetical
screening level 100% CCB scenario. Under the 27% CCB scenario, the thallium HQ is below
one (0.45). Note that the endpoint for thallium is hair follicle atrophy, and that the provisional
toxicity value provided by USEPA is not necessarily recommended for use (see discussion in
Section 4).
Noncarcinogenic regulatory targets were not exceeded for sediment or surface water.
CTE Resident – CCBs and Pond 1
Table 6-3CTE presents the total potential carcinogenic risks for the CTE resident potentially exposed
to COPCs in suspected CCBs as well as Pond 1 sediment, surface water, and fish tissue. The
-6
potential risks under both the hypothetical screening level 100% CCB scenario (4.3x10 ) and the site-6
-4
-6
specific 27% CCB scenario (1.3x10 ) are within USEPA’s target risk range of 10 to 10 . The
following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
totals above)
•
Total potential risk (hypothetical screening level 100% CCB scenario and site-specific 27%
-6
CCB scenario) is greater than 10 (see totals above)
•
Total arsenic potential risk (hypothetical screening level 100% CCB scenario [4x10 ] and
-6
-6
site-specific 27% CCB scenario [1.1x10 ]) is greater than 10
•
Arsenic in suspected CCBs (hypothetical screening level 100% CCB scenario) is greater than
-6
-6
-6
10 (3.8x10 ) and under the site-specific 27% CCB scenario is equal to 1x10
-4
-5
-6
Table 6-4CTE presents the hazard index (by target organ). The total HI under the 100% CCB
hypothetical screening level scenario is 1.5, and under the site-specific 27% CCB scenario, is 0.45.
Therefore, a target endpoint analysis was conducted. By target organ, there are no HQs above one
for either scenario.
RME Resident – CCBs and Pond 2
Table 6-5RME presents the total potential carcinogenic risks for the RME resident potentially exposed
to COPCs in suspected CCBs as well as Pond 2 sediment, surface water, and fish tissue. The
-5
potential risks under both the hypothetical screening level 100% CCB scenario (4.9x10 ) and the site-5
-4
-6
specific 27% CCB scenario (1.8x10 ) are within USEPA’s target risk range of 10 to 10 . The
following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 (see totals
above)
•
Total potential risk (hypothetical screening level 100% CCB scenario and site-specific 27%
-5
CCB scenario) is greater than 10 (see totals above)
-4
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•
Total arsenic potential risk (hypothetical screening level 100% CCB scenario [4.6x10 ] and
-5
-5
site-specific 27% CCB scenario [1.8x10 ]) is greater than 10
•
Arsenic in suspected CCBs (hypothetical screening level 100% CCB scenario [3.9x10 ] and
-5
-5
site-specific 27% CCB scenario [1.1x10 ]) is greater than 10
•
Hexavalent chromium in suspected CCBs (hypothetical screening level 100% CCB scenario)
-6
-6
is greater than 10 (2.8x10 )
•
Arsenic in Pond 2 sediment is greater than 10 for both the recreational child (4x10 ) and the
-6
adult fisher (3x10 )
-5
-5
-6
-6
Table 6-6RME presents the hazard index (by target organ). The total HI under the 100% CCB
hypothetical screening level scenario is 4.8, and under the site-specific 27% CCB scenario, is 1.7.
Therefore, a target endpoint analysis was conducted. By target organ, incidental ingestion with
suspected CCBs result in HQs above one as follows:
•
Iron (HQ = 1.06 for suspected CCBs and 1.18 total, which are essentially one) under the
hypothetical screening level 100% CCB scenario based on gastrointestinal effects. Under
the site-specific 27% CCB scenario, the iron HQ is below one (0.4)
•
Thallium (HQ = 1.64 for ingestion of suspected CCBs and 1.65 total) under the hypothetical
screening level 100% CCB scenario. Under the 27% CCB scenario, the thallium HQ is below
one (0.45). Note that the endpoint for thallium is hair follicle atrophy, and that the provisional
toxicity value provided by USEPA is not necessarily recommended for use (see discussion in
Section 4).
Noncarcinogenic regulatory targets were not exceeded for sediment or surface water.
CTE Resident – CCBs and Pond 2
Table 6-5CTE presents the total potential carcinogenic risks for the CTE resident potentially exposed
to COPCs in suspected CCBs as well as Pond 2 sediment, surface water, and fish tissue. The
-6
potential risks under both the hypothetical screening level 100% CCB scenario (4.6x10 ) and the site-6
-4
-6
specific 27% CCB scenario (1.6x10 ) are within USEPA’s target risk range of 10 to 10 . The
following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
totals above)
•
Total potential risk (hypothetical screening level 100% CCB scenario and site-specific 27%
-6
CCB scenario) is greater than 10 (see totals above)
•
Total arsenic potential risk (hypothetical screening level 100% CCB scenario [4.3x10 ] and
-6
-6
site-specific 27% CCB scenario [1.5x10 ]) is greater than 10
•
Arsenic in suspected CCBs (hypothetical screening level 100% CCB scenario) is greater than
-6
-6
-6
10 (3.8x10 ) and under the site-specific 27% CCB scenario is equal to 1x10
-4
-5
-6
Table 6-6CTE presents the hazard index (by target organ). The total HI under the hypothetical
screening level 100% CCB scenario is 1.5, and under the site-specific 27% CCB scenario is 0.48.
Therefore, a target endpoint analysis was conducted. Target-endpoint specific HQs are below one.
Noncarcinogenic regulatory targets were not exceeded for sediment or surface water.
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A screening level groundwater risk assessment is presented in Section 6.4.1.
Resident Summary
-4
No potential risks greater than 10 were identified under the RME or CTE scenarios for the resident
-5
receptors. No potential risks greater than 10 were identified under the CTE scenario for the resident
receptors.
-5
-4
Potential risks greater than 10 , but less than 10 , were identified under the RME scenario as follows
(the potential risk estimates were presented above and are not repeated for this summary):
•
Total potential risk (hypothetical screening level 100% CCB scenario and site-specific 27%
CCB scenario) for the Brown Ditch, Pond 1 and Pond 2 scenarios
•
Total arsenic potential risk (hypothetical screening level 100% CCB scenario and site-specific
27% CCB scenario) for the Brown Ditch, Pond 1 and Pond 2 scenarios
•
Arsenic in suspected CCBs (hypothetical screening level 100% CCB scenario; the site-5
specific 27% CCB scenarios are equal to 10 ) for the Brown Ditch, Pond 1 and Pond 2
scenarios
-6
-5
Potential risks greater than 10 , but less than 10 , were identified under the RME scenario as follows:
•
Hexavalent chromium in suspected CCBs (hypothetical screening level 100% CCB scenario)
for the Brown Ditch, Pond 1 and Pond 2 scenarios
•
Arsenic in Brown Ditch sediment (adult and child)
•
Arsenic in Pond 1 sediment (child)
•
Arsenic in Pond 2 sediment (adult and child)
-6
-5
Potential risks greater than 10 , but less than 10 , were identified under the CTE scenario as follows:
•
Total potential risk (hypothetical screening level 100% CCB scenarios and site-specific 27%
CCB scenario) for the Brown Ditch, Pond 1 and Pond 2 scenarios
•
Total arsenic (hypothetical screening level 100% CCB scenario and site-specific 27% CCB
scenario) for the Brown Ditch, Pond 1 and Pond 2 scenarios
•
Arsenic in suspected CCBs (hypothetical screening level 100% CCB scenario, and equal to
-6
1x10 under the site-specific 27% CCB scenario) for the Brown Ditch, Pond 1 and Pond 2
scenarios
Based on the results of the HHRA for the RME resident, iron and thallium are the only
noncarcinogenic COPCs with hazard indices above one under the screening level 100% CCB
scenario as discussed in greater detail below:
•
Iron. When the iron HQ under the screening level 100% CCB scenario is rounded to one
significant figure per USEPA guidance (USEPA, 1989a), the iron HQ on a target endpoint
basis (gastrointestinal effects) is 1. It should be noted that iron is an essential nutrient, and
that the iron HQ under the site-specific 27% CCB scenario is below one.
•
Thallium. The thallium HQ under the screening level 100% CCB scenario is 1.65. The
endpoint for thallium effects is hair follicle atrophy, and the provisional toxicity value provided
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by USEPA is not necessarily recommended for use (see discussion in Section 4). The
thallium HQ under the site-specific 27% CCB scenario is below one.
Noncarcinogenic regulatory targets were not exceeded for any of the RME site-specific 27% CCB
scenarios on a target endpoint specific basis, nor for any of the CTE residential scenarios or sediment
or surface water.
Exposure to COPCs in Background Soil
Table 6-7RME presents the total potential carcinogenic risks for the RME resident based on potential
-5
exposure to COPCs in background soils. The total potential risk (1.9x10 ) is within USEPA’s target
-4
-6
risk range of 10 to 10 . The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 (see total
above)
•
Arsenic in background soil is greater than 10 (1.9x10 )
-4
-5
-5
The potential risk from arsenic in background soils is on the same order of magnitude as the potential
risk from arsenic in suspected CCBs. While arsenic in suspected CCBs was not found to be
-5
consistent with background, potential risks from suspected CCBs are 3.9x10 (hypothetical screening
-5
-5
level 100% CCB scenario) and 1.1x10 (site-specific 27% CCB scenario) and are 1.9x10 for
background soils.
Table 6-8RME presents the hazard index (by target organ). The total HI (2.1) is greater than the
regulatory target of one. The thallium HQ (1.3) is greater than one and is similar to the thallium HQ
under the screening level 100% CCB scenario (1.65). All other target endpoint HQs for background
soil are below one. The endpoint for thallium effects is hair follicle atrophy, and the provisional toxicity
value provided by USEPA is not necessarily recommended for use (see discussion in Section 4).
Table 6-7CTE presents the total potential carcinogenic risks for the CTE resident based on potential
exposure to COPCs in background soils. The potential risks are within USEPA’s target risk range of
-4
-6
-6
10 to 10 (1.9x10 ). The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
total above)
•
Arsenic in background soil is greater than 10 (1.9x10 )
-4
-6
-5
-6
Table 6-8CTE presents the hazard index for the CTE resident. The HI of 0.7 is below the target of
one; therefore, a target endpoint analysis was not necessary.
6.3.1.2 Recreational Child
The recreational child is assumed to be a visitor in the area who may potentially be exposed to
COPCs in sediment via incidental ingestion and dermal contact, in surface water via dermal contact
while wading in Brown Ditch, via incidental ingestion and dermal contact while swimming in one of the
ponds, and via ingestion of fish caught in Brown Ditch or one of the ponds. This receptor is also
assumed to be potentially exposed to COPCs in suspected CCBs via inhalation of particulates in
outdoor air.
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The air concentrations used to evaluate this receptor are the same as those used to evaluate the
residential receptor, i.e., the effects of dilution and dispersion in the air from a hypothetical residential
lot (assumed to be comprised of CCBs) to Brown Ditch or the ponds (which would result in lower air
concentrations) has not been taken into account. Moreover, the modeled air concentrations assuming
exposure to 100% CCBs were used; the site-specific 27% CCB scenario was not included in the
recreational evaluations.
Tables 6-9RME through 6-14RME present the total potential risks and hazard indices for suspected
CCBs, sediment, and surface water, as discussed below. Three sets of potential risks and hazards
are presented, for Brown Ditch, Pond 1, and Pond 2. The potential risks associated with suspected
CCBs via inhalation are the same on each of these tables. The results for the CTE scenarios are
presented on Tables 6-9CTE through 6-14CTE.
Exposure to COPCs in Suspected CCBs, Sediment, and Surface Water
RME Recreational Child - Brown Ditch
Table 6-9RME presents the total potential carcinogenic risks for the RME recreational child potentially
exposed to COPCs in 100% CCBs via inhalation as well as to COPCs in sediment, surface water, and
-6
-4
fish tissue in Brown Ditch. The potential risk (3.4x10 ) is within USEPA’s target risk range of 10 to
-6
10 . The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
total above)
•
The total potential risk is greater than 10 (see total above)
•
Total potential arsenic risk is greater than 10 (3.4x10 )
•
Arsenic potential risk in Brown Ditch sediment is greater than 10 (3.2x10 )
-4
-5
-6
-6
-6
-6
-6
Table 6-10RME presents the hazard index (0.26), which is below one; therefore, a target endpoint
analysis was not necessary.
CTE Recreational Child - Brown Ditch
Table 6-9CTE presents the total potential carcinogenic risks for the CTE recreational child potentially
exposed to COPCs in 100% CCBs via inhalation as well as to COPCs in sediment, surface water, and
-7
-4
fish tissue in Brown Ditch. The potential risk (3x10 ) is below USEPA’s target risk range of 10 to
-6
10 . Table 6-10CTE presents the hazard index (0.06), which is below one; therefore, a target
endpoint analysis was not necessary.
RME Recreational Child - Pond 1
Table 6-11RME presents the total potential carcinogenic risks for the RME recreational child
potentially exposed to COPCs in 100% CCBs via inhalation as well as Pond 1 sediment, surface
-6
water, and fish tissue. The potential risk (1.1x10 ) is just within the low end of USEPA’s target risk
-4
-6
range of 10 to 10 . The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
total above)
•
The total potential risk is greater than/equal to 10 (see total above)
•
Total potential arsenic risk is greater than/equal to 10 (1.1x10 )
-4
-5
-6
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-6
-6
Arsenic potential risk in Pond 1 sediment is greater than/equal to 10 (1.1x10 )
Table 6-12RME presents the hazard index (0.31), which is below one; therefore, a target endpoint
analysis was not necessary.
CTE Recreational Child - Pond 1
Table 6-11CTE presents the total potential carcinogenic risks for the CTE recreational child potentially
exposed to COPCs in 100% CCBs via inhalation as well as Pond 1 sediment, surface water, and fish
-8
-4
-6
tissue. The potential risk (9.8x10 ) is below USEPA’s target risk range of 10 to 10 . Table 6-12CTE
presents the hazard index (0.06), which is below one; therefore, a target endpoint analysis was not
necessary.
RME Recreational Child - Pond 2
Table 6-13RME presents the total potential carcinogenic risks for the RME recreational child
potentially exposed to COPCs in 100% CCBs via inhalation as well as Pond 2 sediment, surface
-6
-4
-6
water, and fish tissue. The potential risk (4x10 ) is within USEPA’s target risk range of 10 to 10 .
The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
total above)
•
The total potential risk is greater than 10 (see total above)
•
Total potential arsenic risk is greater than 10 (4x10 )
•
Arsenic potential risk in Pond 2 sediment is greater than 10 (4x10 )
-4
-5
-6
-6
-6
-6
-6
Table 6-14RME presents the hazard index (0.41), which is below one; therefore, a target endpoint
analysis was not necessary.
CTE Recreational Child - Pond 2
Table 6-13CTE presents the total potential carcinogenic risks for the CTE recreational child potentially
exposed to COPCs in 100% CCBs via inhalation as well as Pond 2 sediment, surface water, and fish
-7
-4
-6
tissue. The potential risk (3.6x10 ) is below USEPA’s target risk range of 10 to 10 . Table 6-14CTE
presents the hazard index (0.1), which is below one; therefore, a target endpoint analysis was not
necessary.
Recreational Child Summary
-4
-5
No potential risks greater than 10 or 10 were identified under the RME or CTE scenarios. No
-6
potential risks greater than 10 were identified under the CTE scenario. Potential risks greater than
-6
10 were identified under the RME scenario as follows (the potential risk estimates were presented
above and are not repeated for this summary):
•
Arsenic in Brown Ditch sediment
•
Arsenic in Pond 1 sediment
•
Arsenic in Pond 2 sediment
No HIs above one were identified for any scenario; therefore, target endpoint analyses were not
necessary.
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6.3.1.3 Recreational Fisher
The recreational fisher is assumed to be potentially exposed to COPCs in suspected CCBs via
inhalation of particulates in outdoor air. The recreational fisher is also assumed to be potentially
exposed to COPCs in sediment via incidental ingestion and dermal contact and surface water via
dermal contact by wading in either Brown Ditch or one of the ponds, and via ingestion of fish caught in
Brown Ditch or one of the ponds.
The air concentrations used to evaluate this receptor are the same used to evaluate the residential
receptor, i.e., the effects of dilution and dispersion in the air from a hypothetical residential lot
(assumed to be comprised of CCBs) to Brown Ditch or the ponds (which would result in lower air
concentrations) has not been taken into account. Moreover, the modeled air concentrations assuming
exposure under the hypothetical screening level 100% CCB scenario were used; the site-specific 27%
CCB scenario was not included in the recreational evaluations.
Tables 6-15RME through 6-20RME present the total potential risks and hazard indices for suspected
CCBs, sediment, and surface water, as discussed below. Three sets of potential risks and hazards
are presented, for Brown Ditch, Pond 1, and Pond 2. The potential risks associated with suspected
CCBs are the same on each of these tables. The results for the CTE scenarios are presented on
Tables 6-15CTE through 6-20CTE.
RME Recreational Fisher - Brown Ditch
Table 6-15RME presents the total potential carcinogenic risks for the RME recreational fisher
potentially exposed to COPCs in 100% CCBs via inhalation as well as Brown Ditch sediment, surface
-6
-4
-6
water, and fish tissue. The potential risk (3.1x10 ) is within USEPA’s target risk range of 10 to 10 .
The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
total above)
•
Arsenic in Brown Ditch sediment and total potential arsenic risk are greater than 10 (2.4x10
-6
and 3.1x10 , respectively)
-4
-5
-6
-6
Table 6-16RME presents the hazard index (0.08), which is below one; therefore, a target endpoint
analysis was not necessary.
CTE Recreational Fisher - Brown Ditch
Table 6-15CTE presents the total potential carcinogenic risks for the CTE recreational fisher
potentially exposed to COPCs in 100% CCBs via inhalation as well as Brown Ditch sediment, surface
-8
-4
-6
water, and fish tissue. The potential risk (7.8x10 ) is below USEPA’s target risk range of 10 to 10 .
Table 6-16CTE presents the hazard index (0.007), which is below one; therefore, a target endpoint
analysis was not necessary.
RME Recreational Fisher - Pond 1
Table 6-17RME presents the total potential carcinogenic risks for the RME recreational fisher
potentially exposed to COPCs in 100% CCBs via inhalation as well as Pond 1 sediment, surface
-7
-4
-6
water, and fish tissue. The potential risk (8.1x10 ) is below USEPA’s target risk range of 10 to 10 .
Table 6-18RME presents the hazard index (0.2), which is below one; therefore, a target endpoint
analysis was not necessary.
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CTE Recreational Fisher - Pond 1
Table 6-17CTE presents the total potential carcinogenic risks for the CTE recreational fisher
potentially exposed to COPCs in 100% CCBs via inhalation as well as Pond 1 sediment, surface
-8
-4
-6
water, and fish tissue. The potential risk (1.9x10 ) is below USEPA’s target risk range of 10 to 10 .
Table 6-18CTE presents the hazard index (0.02), which is below one; therefore, a target endpoint
analysis was not necessary.
RME Recreational Fisher - Pond 2
Table 6-19RME presents the total potential carcinogenic risks for the RME recreational fisher
potentially exposed to COPCs in 100% CCBs as well as Pond 2 sediment, surface water, and fish
-6
-4
-6
tissue. The potential risk (3x10 ) is within USEPA’s target risk range of 10 to 10 . The following
summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
total above)
•
Arsenic in Pond 2 sediment and total potential arsenic risk are greater than 10 (3.0x10 )
-4
-6
-5
-6
Table 6-20RME presents the hazard index (0.13), which is below one; therefore, a target endpoint
analysis was not necessary.
CTE Recreational Fisher - Pond 2
Table 6-19CTE presents the total potential carcinogenic risks for the CTE recreational fisher
potentially exposed to COPCs in 100% CCBs as well as Pond 2 sediment, surface water, and fish
-8
-4
-6
tissue. The potential risk (6.9x10 ) is below USEPA’s target risk range of 10 to 10 . Table 6-20CTE
presents the hazard index (0.01), which is below one; therefore, a target endpoint analysis was not
necessary.
Recreational Fisher Summary
-4
-5
No potential risks greater than 10 or 10 were identified under the RME or CTE scenarios. No
-6
potential risks greater than 10 were identified under the CTE scenario. Potential risks greater than
-6
10 were identified under the RME scenario as follows (the potential risk estimates were presented
above and are not repeated for this summary):
•
Arsenic in Brown Ditch sediment and total potential arsenic risk for the Brown Ditch scenario
•
Arsenic in Pond 2 sediment and total potential arsenic risk for the Pond 2 scenario
No total HIs above one were identified for any scenario; therefore, target endpoint analyses were not
necessary.
6.3.1.4 Construction Worker
Construction workers are assumed to be potentially exposed to COPCs in surface and subsurface
suspected CCBs via incidental ingestion and dermal contact during excavation and via inhalation of
particulates in excavation air. Construction workers are also assumed to be potentially exposed to
COPCs in groundwater exposed during excavation via incidental ingestion and dermal contact.
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This scenario conservatively assumes that all excavation occurs through CCBs, i.e., the full depth and
length of the excavation trench excavated each day is comprised of CCBs. As the derivation of the
conservative maximum average percent of CCBs for residential properties is based on observations of
CCBs at the surface, the site-specific 27% CCB scenario was not applied to the construction worker
(i.e., it was assumed that all CCBs at depth are 100% CCBs).
-4
-6
A summary of the potential risks and hazards compared to the USEPA target risk range of 10 to 10
and a hazard index of one by target endpoint is presented below. Note that potential risks and
hazards for the incidental ingestion/dermal contact with groundwater pathway were calculated for
each monitoring well. These are presented in Tables 6-21RME and 6-21CTE and Table 6-22RME
and 6-22CTE, respectively. Table 6-23RME presents the potential carcinogenic risks for the
-7
construction worker (3.4x10 ); the highest potential risk calculated by constituent in Table 6-21RME
-8
for the groundwater pathway (1.9x10 ) is presented on this table. Potential risks are below USEPA’s
-4
-6
target risk range of 10 to 10 . Table 6-24RME presents the potential hazard index (0.2) for the
construction worker; the highest potential hazards calculated by constituent in Table 6-22RME for the
groundwater pathway (0.009) are presented on this table. The total HI is below one; therefore, a
target endpoint analysis was not necessary.
-7
As shown on Tables 6-23CTE and Table 6-24CTE, the risks (1.6x10 ) and hazards (0.1) for the CTE
scenario are also below regulatory targets; therefore, a target endpoint analysis was not necessary.
Construction Worker Summary
-4
-5
-6
No potential risks greater than 10 , 10 , or 10 were identified under the RME or CTE scenarios. No
total or target endpoint specific HIs above one were identified for any scenario.
6.3.1.5 Outdoor Worker
Outdoor workers are assumed to be potentially exposed to COPCs in suspected CCBs via incidental
ingestion and dermal contact and via inhalation of particulates in outdoor air.
-4
-6
A summary of the potential risks and hazards compared to the USEPA target risk range of 10 to 10
and a hazard index of one by target organ is presented below. Table 6-25RME presents the potential
carcinogenic risks for the outdoor worker. Potential risks under both the hypothetical screening level
-5
-6
100% CCB scenario (1.2x10 ) and site-specific 27% CCB scenario (3.4x10 ) are within USEPA’s
-4
-6
target risk range of 10 to 10 . The following bullets summarize the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
totals above)
•
Arsenic in suspected CCBs (hypothetical screening level 100% CCB scenario and site-6
specific 27% CCB scenario) and total potential risks for those scenarios are greater than 10
-5
-6
(1.2x10 and 3.4x10 , respectively).
-4
-5
Table 6-26RME presents the potential hazard index for the outdoor worker. The total HI is below one
under both the hypothetical screening level 100% CCB scenario (0.4) and the site-specific 27% CCB
scenario (0.09); therefore, target endpoint analyses were not necessary.
As shown on Tables 6-25CTE and Table 6-26CTE, the risks and hazards for the CTE scenario for
-7
both the hypothetical screening level 100% CCB scenario (8.9x10 and 0.1, respectively) and the site-7
specific 27% CCB scenario (2.4x10 and 0.03, respectively) are below regulatory targets.
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Outdoor Worker Summary
-4
-5
No potential risks greater than 10 or 10 were identified under the RME or CTE scenarios. No
-6
potential risks greater than 10 were identified under the CTE scenario. Potential risks greater than
-6
10 were identified under the RME scenario as follows (the potential risk estimates were presented
above and are not repeated for this summary):
•
Arsenic in suspected CCBs (hypothetical screening level 100% CCB scenario and sitespecific 27% CCB scenario)
No total or target endpoint specific HIs above one were identified for any scenario; therefore, target
endpoint analyses were not necessary.
6.3.1.6 Chemical Risk Characterization Summary
The results of the chemical risk assessment are presented on Tables 6-27 and 6-28 for potential
carcinogenic risk and noncarcinogenic hazard, respectively.
-4
As shown on Table 6-27, no potential risks are above 10 . As described above, potential risks
-5
-6
-5
greater than 10 and 10 were identified for some scenarios. Potential risks greater than 10 were
identified for the RME resident (hypothetical screening level 100% CCB scenario and site-specific
27% CCB scenario), for the RME resident (background soil scenario), and for the outdoor worker
(hypothetical 100% CCB scenario). All other potential risks, including the CTE residential scenarios,
-6
were within or below the 10 risk range.
As shown on Table 6-28, all target endpoint specific hazard indices are equal to or less than the
regulatory target of one, with the exception the RME residential receptor under the hypothetical
screening level 100% CCB scenario. The HI above one is based on iron and thallium in suspected
CCBs. However, when as suggested in USEPA guidance (USEPA, 1989a) the iron HQ is rounded to
one significant figure, the hazard quotient associated with iron on a target endpoint basis is 1. The
endpoint for thallium effects is hair follicle atrophy, and the provisional toxicity value provided by
USEPA is not necessarily recommended for use (see discussion in Section 4). Noncarcinogenic
regulatory targets were not exceeded for the site-specific 27% CCB scenario or for sediment or
surface water exposures.
6.3.2
Radionuclide Risk Characterization Results
As noted previously, the site-specific conservative maximum average percent of CCBs in surface soils
within a residential lot was 27% (Appendix I). Therefore, the HHRA for radionuclides assumes that
the residential lot contains 27% CCBs at the surface. For informational purposes, a hypothetical
screening level scenario assuming 100% CCBs has also been included.
Residents are assumed to be potentially exposed to radionuclide COPCs in suspected CCBs via
incidental ingestion, inhalation of particulates in outdoor air, and via external exposure to gamma
radiation. Where gardens are present, residents are also assumed to be exposed to radionuclide
COPCs in produce. Because it is unlikely that every yard contains a garden, and because a given
yard may not be large enough to support the assumed produce ingestion rate, potential risks are
calculated with and without the produce pathway. Residents are also assumed to be potentially
exposed to radionuclide COPCs in sediment via incidental ingestion. Sediment samples from Brown
Ditch and Upgradient locations were analyzed for radionuclide constituents. Samples from the ponds
were not; therefore, the results from Brown Ditch are used to represent potential risks from sediments.
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Groundwater samples were analyzed for radionuclide constituents and concentrations were found to
be below screening levels, as discussed in the RI Report (AECOM, 2010a; see Appendix M in this
document). Therefore, groundwater was not included in the radionuclide HHRA. As noted in
Section 3.1.2, because groundwater is the likely source of constituents in surface water, surface water
samples were not analyzed for radionuclide constituents and surface water is not included in the
evaluation of potential radionuclide risk.
Potential risks were calculated based on two datasets: the Yard 520 CCB dataset and the MWSE
suspected CCB dataset. The first dataset contains samples collected from Yard 520, which
represents a worst-case scenario. This scenario does not assume that a residential structure is
present on Yard 520, but rather is included as a worst-case estimate that assumes that concentrations
of CCBs found in Yard 520 could also present in the community, which data have shown is not the
case. Therefore, the 27% maximum average CCB assumption discussed above also was applied to
this very hypothetical scenario. It should be noted that there are no potential direct contact exposures
with the CCBs in Yard 520 due to the cap construction and the cap inspection and maintenance
program (see the detailed discussion in Section 3.5 and the information in Appendix O). The Yard
520 results for these additional parameters are considered worst case because the samples were fly
ash, and of the three types of CCBs (fly ash, bottom ash, and boiler slag), fly ash is known to have
higher constituent concentrations. As noted in Section 3.5, the material in the Town of Pines consists
of a larger portion of bottom ash and/or boiler slag. Thus while both materials are CCBs, they are
different types of CCBs with different physical and chemical characteristics. The RI Report includes
more discussion of the different types of CCBs and the differences observed within the Area of
Investigation. Fly ash is known to have higher constituent concentrations than the other types of ash,
and this difference is clear in the analytical results for the MWSE and Yard 520 radiological datasets.
Thus the radiological evaluation of the Yard 520 data is provided here for informational purposes only.
The MWSE radiological dataset is a more appropriate yet still conservative basis for evaluating
potential exposures.
6.3.2.1 Resident
This section summarizes the potential radiological risks for the resident receptors for both RME and
CTE scenarios.
Hypothetical RME Resident – Yard 520 CCBs and Brown Ditch
Table 6-32RME presents the total potential carcinogenic risks for the hypothetical RME resident
potentially exposed to radionuclide COPCs in CCBs from Yard 520 and Brown Ditch sediment (child
and adult fisher). The total potential risks for the hypothetical screening level 100% CCB garden
-4
-4
-4
scenario (2.8x10 ) and no garden scenario (1.2x10 ) exceed USEPA’s target risk range of 10 to
-6
-5
-5
10 . The potential risks for the site-specific 27% CCB garden (7.7x10 ) and no garden (3.3x10 )
-4
-6
scenarios are within USEPA’s target risk range of 10 to 10 . The following summarizes the potential
risks:
•
The potential risk for the Yard 520 CCB dataset under the hypothetical screening level 100%
-4
CCB no garden and garden scenarios are greater than 10 (see totals above)
•
The total potential risk for the Yard 520 CCB dataset under the site-specific 27% CCB garden
-5
and the site-specific 27% CCB no garden scenarios is greater than 10 (see totals above)
•
Potential sediment risks (adult fisher) are greater than 10 (1.2x10 ), but there are no
-6
constituents with potential risks greater than 10 ; potential sediment risks for the child are
-6
-7
below 10 (6.7x10 )
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The following constituents have potential risks greater than 10 in Yard 520 CCBs:
−
•
•
6-19
Radium-226+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-4
garden scenario (1.5x10 )
-5
The following constituents have potential risks greater than 10 in Yard 520 CCBs:
−
Lead-210+D in Yard 520 CCBs under the hypothetical screening level 100% CCB garden
-5
-5
scenario (8.2x10 ) and the site-specific 27% CCB garden scenario (2.2x10 )
−
Radium-226+D in Yard 520 CCBs under the hypothetical screening level 100% CCB no
-5
-5
garden scenario (9.7x10 ), the site-specific 27% CCB garden (4.1x10 ), and no garden
-5
(2.6x10 ) scenarios
−
Radium-228+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-5
-5
garden (4x10 ) and no garden (1.2x10 ) scenarios, and under the site-specific 27% CCB
-5
garden scenario (1.1x10 )
-6
The following constituents have potential risks greater than 10 in Yard 520 CCBs:
−
Thorium-230 in Yard 520 CCBs under the hypothetical screening level 100% CCB garden
-6
scenario (1.3x10 )
−
Thorium-232 in Yard 520 CCBs under the hypothetical screening level 100% CCB garden
-6
scenario (1.1x10 )
−
Uranium-234 in Yard 520 CCBs under the hypothetical screening level 100% CCB
-6
garden scenario (1.6x10 )
−
Uranium-238+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-6
-6
garden (3.1x10 ) and no garden (2.3x10 ) scenarios
−
Lead-210+D in Yard 520 CCBs under the hypothetical screening level 100% CCB no
-6
-6
garden scenario (9.9x10 ) and the site-specific 27% CCB no garden scenario (2.7x10 )
−
Radium-228+D in Yard 520 CCBs under the site-specific 27% CCB no garden scenario
-6
(3.2x10 )
Hypothetical CTE Resident – Yard 520 CCBs and Brown Ditch
Table 6-32CTE presents the total potential carcinogenic risks for the hypothetical CTE resident
potentially exposed to radionuclide COPCs in CCBs from Yard 520 and Brown Ditch sediment (child
and adult fisher). The potential risks for the hypothetical screening level 100% CCB garden scenario
-5
-5
-5
(5.7x10 ), no garden scenario (2.7x10 ), site-specific 27% CCB garden scenario (1.6x10 ) and no
-6
-4
-6
garden scenario (7.4x10 ) are within USEPA’s target risk range of 10 to 10 . The following
summarizes the potential risks:
•
There are no potential risks for the Yard 520 CCB dataset, either by receptor or constituent,
-4
greater than 10 (see totals above)
•
The total potential risk for the Yard 520 CCB dataset under both the hypothetical screening
level 100% CCB garden and no garden scenarios and the site-specific 27% CCB garden
-5
scenarios are greater than 10 (see totals above)
•
The total potential risk for the Yard 520 CCB dataset under the site-specific 27% CCB no
-6
garden scenario is greater than 10 (see totals above)
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•
Potential sediment risks are below 10 (adult 4.4x10 , child 6x10 )
•
The following constituents have potential risks greater than 10 in Yard 520 CCBs:
•
6-20
Environment
-6
-8
-8
-5
−
Lead-210+D in Yard 520 CCBs under the hypothetical screening level 100% CCB garden
-5
(1.5x10 ) scenario
−
Radium-226+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-5
-5
garden (2.7x10 ) and no garden (1.9x10 ) scenarios
−
Radium-228+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-5
garden scenario (1.4x10 )
-6
The following constituents have potential risks greater than 10 in Yard 520 CCBs:
−
Lead-210+D in Yard 520 CCBs under the hypothetical screening level 100% CCB no
-6
-6
garden scenario (2x10 ) and the site-specific 27% CCB garden scenario (4.1x10 )
−
Radium-226+D in Yard 520 CCBs under the site-specific 27% CCB garden (7.2x10 ) and
-6
no garden (5.2x10 ) scenarios
−
Radium-228+D in Yard 520 CCBs under the hypothetical screening level 100% CCB no
-6
-6
garden scenario (5.1x10 ) and the site-specific 27% CCB garden (3.8x10 ) and no
-6
garden (1.4x10 ) scenarios
-6
RME Resident – MWSE Suspected CCBs and Brown Ditch
Table 6-33RME presents the total potential carcinogenic risks for the RME resident potentially
exposed to radionuclide COPCs in suspected CCBs from the MWSE dataset and Brown Ditch
sediment (child and adult fisher). The total potential risks for the hypothetical screening level 100%
-4
CCB garden scenario (1.6x10 ) and the hypothetical screening level 100% CCB outdoor worker
-4
-4
-6
scenario (1.1x10 ) exceed USEPA’s target risk range of 10 to 10 . However, when the total risk for
the outdoor worker receptor is rounded to one significant figure per USEPA guidance (USEPA,
-4
1989a), the risk is equal to the upper end of the target risk range of 1x10 . The potential risks for the
-5
hypothetical screening level 100% CCB no garden scenario (7.4x10 ) and the site-specific 27% CCB
-5
-5
-4
garden (4.4x10 ) and no garden (2x10 ) scenarios are within USEPA’s target risk range of 10 to
-6
10 . The following summarizes the potential risks:
•
There are no potential risks by constituent greater than 10 for the MWSE dataset
•
The only potential risks (see totals above) by receptor greater than 10 for the MWSE dataset
is for the hypothetical screening level 100% CCB scenario assuming a residential garden, and
for the outdoor worker
•
The potential risk for the MWSE dataset under the hypothetical screening level 100% CCB no
garden, the site-specific 27% CCB garden and the site-specific 27% CCB no garden
-5
scenarios is greater than 10 (see totals above)
•
Potential sediment risks (adult fisher) are greater than 10 (1.2x10 ), but there are no
-6
constituents with potential risks greater than 10 ; potential sediment risks for the child are
-6
-7
below 10 (6.7x10 )
•
The following constituents have potential risks greater than 10 in suspected CCBs:
-4
-4
-6
-6
-5
−
Lead-210+D in suspected CCBs under the hypothetical screening level 100% CCB
-5
garden scenario (3.2x10 )
AOC II – Docket No. V-W-’04-C-784 – HHRA
July 2012
AECOM
•
6-21
Environment
−
Radium-226+D in suspected CCBs under the hypothetical screening level 100% CCB
-5
garden scenario (9.1x10 ), the hypothetical screening level 100% CCB no garden
-5
-5
scenario (5.9x10 ), the site-specific 27% CCB garden scenario (2.5x10 ), and the site-5
specific 27% CCB no garden scenario (1.6x10 )
−
Radium-228+D in suspected CCBs under the hypothetical screening level 100% CCB
-5
garden scenario (2.8x10 )
-6
The following constituents have potential risks greater than 10 :
−
Lead-210+D in suspected CCBs under the hypothetical screening level 100% CCB no
-6
-6
garden scenario (3.9x10 ), the site-specific 27% CCB garden scenario (8.5x10 ) and
-6
under the site-specific 27% CCB no garden scenario (equal to 10 )
−
Radium-228+D in suspected CCBs under the hypothetical screening level 100% CCB no
-6
-6
garden scenario (8.2x10 ) and under the site-specific 27% CCB garden (7.7x10 ) and
-6
the site-specific 27% CCB no garden (2.2x10 ) scenarios
−
Uranium-238+D in suspected CCBs under the hypothetical screening level 100% CCB
-6
-6
garden (2x10 ) and no garden scenarios (1.5x10 )
CTE Resident – MWSE Suspected CCBs and Brown Ditch
Table 6-33CTE presents the total potential carcinogenic risks for the CTE resident potentially exposed
to radionuclide COPCs in suspected CCBs from MWSE samples and Brown Ditch sediment (child
-5
and adult fisher). The potential risks for the hypothetical screening level 100% CCB garden (3.3x10 ),
-5
-6
-6
no garden (1.7x10 ), site-specific 27% CCB garden (8.9x10 ) and no garden (4.5x10 ) scenarios are
-4
-6
within USEPA’s target risk range of 10 to 10 . The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 for the MWSE
dataset (see totals above)
•
The total potential risk under both the hypothetical screening level 100% CCB garden and no
-5
garden scenarios for the MWSE dataset is greater than 10 (see totals above)
•
The total potential risk for the MWSE dataset under both the site-specific 27% CCB garden
-6
and no garden scenarios is greater than 10 (see totals above)
•
Potential sediment risks are below 10 (adult 4.4x10 , child 6x10 )
•
The following constituents have potential risks greater than 10 in suspected CCBs:
-4
-6
-8
-5
−
•
-8
Radium-226+D in suspected CCBs under the hypothetical screening level 100% CCB
-5
-5
garden (1.6x10 ), and hypothetical screening level 100% CCB no garden (1.2x10 )
scenarios
-6
The following constituents have potential risks greater than 10 :
−
Lead-210+D in suspected CCBs under the hypothetical screening level 100% CCB
-6
-6
garden (5.9x10 ) scenario, and the site-specific 27% CCB garden scenario (1.6x10 )
−
Radium-226+D in suspected CCBs under the site-specific 27% CCB garden (4.4x10 )
-6
and no garden (3.2x10 ) scenarios
−
Radium-228+D in suspected CCBs under the hypothetical screening level 100% CCB
-6
-6
garden (9.8x10 ) and no garden (3.6x10 ) scenarios, and under the site-specific 27%
-6
CCB garden (2.7x10 ) scenario
-6
AOC II – Docket No. V-W-’04-C-784 – HHRA
July 2012
AECOM
6-22
Environment
Resident Summary
-4
Potential risks greater than 10 were identified for Yard 520 CCBs and Brown Ditch sediment under
the RME hypothetical screening level 100% CCB garden and no garden scenarios. Potential risks
-4
greater than 10 were identified for MWSE suspected CCBs and Brown Ditch sediment under the
-4
RME hypothetical screening level 100% CCB garden scenario. No potential risks greater than 10
were identified for any of the site-specific 27% CCB scenarios or any of the CTE scenarios.
-4
-6
Potential risks within USEPA’s target risk range of 10 to 10 were identified for Yard 520 CCBs and
Brown Ditch sediment under the RME site-specific 27% CCB scenarios (garden and no garden), and
for MWSE suspected CCBs and Brown Ditch sediment for the RME hypothetical screening level
100% CCB no garden scenario and the site-specific 27% CCB scenarios (garden and no garden).
-4
-6
Potential risks within USEPA’s target risk range of 10 to 10 were identified for the all of the CTE
scenarios.
-4
Radionuclide-specific potential risks greater than or equal to 10 were identified under the RME
scenario as follows:
•
Yard 520 dataset: radium-226+D in Yard 520 CCBs under the hypothetical screening level
100% CCB garden scenario
-5
Radionuclide-specific potential risks greater than or equal to 10 were identified under the RME
hypothetical screening level 100% CCB scenario as follows:
•
Yard 520 dataset: lead-210+D, radium-228+D in Yard 520 CCBs under the garden scenario,
and radium-226+D and radium-228+D in Yard 520 CCBs under the no garden scenario
•
MWSE dataset: lead-210+D and radium-228+D in suspected CCBs under the garden
scenario, radium-226+D in suspected CCBs under the garden and no garden scenarios
-5
Radionuclide-specific potential risks greater than or equal to 10 were identified under the RME sitespecific 27% CCB scenario as follows:
•
Yard 520 dataset: radium 226+D in Yard 520 CCBs under the garden and no garden
scenarios, and lead-210+D and radium-228+D in Yard 520 CCBs under the garden scenario
•
MWSE dataset: radium-226+D in suspected CCBs under the garden and no garden
scenarios
-6
-5
Radionuclide-specific potential risks greater than or equal to 10 , but less than 10 , were identified
under the RME hypothetical screening level 100% CCB scenario as follows:
•
Yard 520 dataset: thorium-230, thorium-232, uranium-234, and uranium-238+D in Yard 520
CCBs under the garden scenario, and lead-210+D and uranium-238+D in Yard 520 CCBs
under the no garden scenario
•
MWSE dataset: uranium-238+D in suspected CCBs under the garden scenario, and lead210+D, radium-228+D, and uranium-238+D in suspected CCBs under the no garden scenario
-6
-5
Radionuclide-specific potential risks greater than or equal to 10 , but less than 10 were identified
under the RME site-specific 27% CCB scenario as follows:
AOC II – Docket No. V-W-’04-C-784 – HHRA
July 2012
AECOM
6-23
Environment
•
Yard 520 dataset: lead-210+D and radium-228+D in Yard 520 CCBs under the no garden
scenario
•
MWSE dataset: lead-210+D and radium-228+D in suspected CCBs under the garden and no
garden scenarios
-4
No radionuclide-specific potential risks greater than 10 were identified under the CTE scenarios.
-5
Radionuclide-specific potential risks greater than or equal to 10 were identified under the CTE
hypothetical screening level 100% CCB scenario as follows:
•
Yard 520 dataset: lead-210+D and radium-228+D in Yard 520 CCBs under the garden
scenario, and radium-226+D in Yard 520 CCBs under the garden and no garden scenarios
•
MWSE dataset: radium-226+D in suspected CCBs under the garden and no garden
scenarios
-5
No radionuclide-specific potential risks greater than or equal to 10 were identified under the CTE
site-specific 27% CCB scenario.
-6
-5
Radionuclide-specific potential risks greater than or equal to 10 , but less than 10 , were identified
under the CTE hypothetical screening level 100% CCB scenario as follows:
•
Yard 520 dataset: lead-210+D and radium-228+D in Yard 520 CCBs under the no garden
scenario
•
MWSE dataset: lead-210+D, and radium-228+D in suspected CCBs under the garden
scenario, and radium-228+D in suspected CCBs under the no garden scenario
-4
-5
-6
As described above, potential risks greater than10 , 10 and 10 were identified. Potential risks
-4
greater than 10 are associated only with the hypothetical screening level 100% CCB scenario only.
-4
The tables below summarize the potential risks; potential risks greater than 10 are highlighted in
-5
-4
orange, potential risks greater than 10 but less than 10 are highlighted in yellow, and potential risks
-6
-5
-6
greater than 10 but less than 10 are highlighted in green. Calculated risks less than 10 , which are
below USEPA’s target risk range, are not highlighted. Potential risks based on the background
scenario are also presented for comparison.
Yard 520 Dataset Hypothetical
RME Resident Scenario
Radionuclide
Pb-210+daughters
Ra-226+daughters
Ra-228+daughters
Th-228
Th-230
Th-232
U-234
U-235+daughters
U-238+daughters
Total Potential Risk
AOC II – Docket No. V-W-’04-C-784 – HHRA
Hypothetical
Screening Level
Evaluation Assuming
100% CCB
Garden No Garden
Site-Specific
Evaluation Based on
27% CCB
Garden No Garden
Background Soil
Garden No Garden
8.2E-05
1.5E-04
4.1E-05
1.3E-07
1.3E-06
1.1E-06
1.6E-06
5.9E-07
3.1E-06
1.0E-05
9.8E-05
1.2E-05
1.1E-07
9.9E-07
8.2E-07
8.6E-07
5.4E-07
2.3E-06
2.2E-05
4.2E-05
1.1E-05
4.0E-08
3.6E-07
3.0E-07
4.3E-07
1.6E-07
8.5E-07
2.9E-06
2.7E-05
3.4E-06
3.2E-08
2.8E-07
2.3E-07
2.4E-07
1.4E-07
6.4E-07
2.0E-06
1.0E-05
2.9E-06
2.0E-08
9.6E-08
1.2E-07
8.5E-08
2.8E-07
4.3E-07
7.6E-07
9.2E-06
1.9E-06
1.9E-08
8.9E-08
1.1E-07
7.1E-08
2.8E-07
3.9E-07
2.8E-04
1.2E-04
7.7E-05
3.3E-05
1.6E-05
1.2E-05
July 2012
AECOM
Environment
6-24
Radionuclide
Hypothetical
Screening Level
Evaluation
Assuming 100%
CCB
No
Garden
Garden
Site-Specific
Evaluation Based
on 27% CCB
No
Garden
Garden
Background Soil
No
Garden
Garden
Pb-210+daughters
Ra-226+daughters
Ra-228+daughters
Th-228
Th-230
Th-232
U-234
U-235+daughters
U-238+daughters
1.5E-05
2.7E-05
1.4E-05
6.0E-08
1.9E-07
1.5E-07
2.2E-07
1.1E-07
5.2E-07
2.0E-06
1.9E-05
5.1E-06
4.8E-08
1.4E-07
1.2E-07
1.3E-07
1.0E-07
4.1E-07
4.1E-06
7.2E-06
3.8E-06
1.6E-08
5.1E-08
4.2E-08
6.1E-08
3.0E-08
1.4E-07
5.5E-07
5.3E-06
1.4E-06
1.3E-08
3.9E-08
3.2E-08
3.4E-08
2.8E-08
1.1E-07
3.7E-07
1.9E-06
1.1E-06
8.8E-09
1.3E-08
1.7E-08
1.2E-08
5.5E-08
7.5E-08
1.4E-07
1.8E-06
7.8E-07
8.3E-09
1.3E-08
1.5E-08
1.0E-08
5.4E-08
7.0E-08
5.7E-05
2.7E-05
1.5E-05
7.4E-06
3.6E-06
2.8E-06
Yard 520 Dataset
Hypothetical CTE Resident
Scenario
Total Potential Risk
Radionuclide
Hypothetical
Screening Level
Evaluation
Assuming 100%
CCB
No
Garden Garden
Site-Specific
Evaluation Based
on 27% CCB
No
Garden Garden
Background Soil
No
Garden Garden
Pb-210+daughters
Ra-226+daughters
Ra-228+daughters
Th-228
Th-230
Th-232
U-234
U-235+daughters
U-238+daughters
3.2E-05
9.2E-05
2.9E-05
2.0E-07
7.9E-07
4.7E-07
9.3E-07
ND
2.0E-06
4.1E-06
6.0E-05
8.5E-06
1.6E-07
6.1E-07
3.6E-07
5.2E-07
ND
1.5E-06
8.8E-06
2.6E-05
7.9E-06
5.6E-08
2.3E-07
1.4E-07
2.6E-07
ND
5.6E-07
1.3E-06
1.7E-05
2.5E-06
4.6E-08
1.8E-07
1.1E-07
1.5E-07
ND
4.2E-07
2.0E-06
1.0E-05
2.9E-06
2.0E-08
9.6E-08
1.2E-07
8.5E-08
2.8E-07
4.3E-07
7.6E-07
9.2E-06
1.9E-06
1.9E-08
8.9E-08
1.1E-07
7.1E-08
2.8E-07
3.9E-07
1.6E-04
7.4E-05
4.4E-05
2.0E-05
1.6E-05
1.2E-05
MWSE Dataset RME Resident
Scenario
Total Potential Risk
AOC II – Docket No. V-W-’04-C-784 – HHRA
July 2012
AECOM
6-25
Environment
Radionuclide
Hypothetical
Screening Level
Evaluation
Assuming 100%
CCB
No
Garden Garden
Site-Specific
Evaluation Based
on 27% CCB
No
Garden Garden
Background Soil
No
Garden Garden
Pb-210+daughters
Ra-226+daughters
Ra-228+daughters
Th-228
Th-230
Th-232
U-234
U-235+daughters
U-238+daughters
5.9E-06
1.6E-05
9.8E-06
8.7E-08
1.1E-07
6.6E-08
1.3E-07
ND
3.3E-07
7.8E-07
1.2E-05
3.6E-06
7.1E-08
8.7E-08
5.1E-08
7.5E-08
ND
2.6E-07
1.6E-06
4.4E-06
2.7E-06
2.4E-08
3.1E-08
1.8E-08
3.6E-08
ND
9.1E-08
2.2E-07
3.2E-06
9.9E-07
1.9E-08
2.4E-08
1.4E-08
2.1E-08
ND
7.1E-08
3.7E-07
1.9E-06
1.1E-06
8.8E-09
1.3E-08
1.7E-08
1.2E-08
2.0E-07
2.8E-07
1.4E-07
1.8E-06
7.8E-07
8.3E-09
1.3E-08
1.5E-08
1.0E-08
1.0E-06
1.5E-06
3.3E-05
1.7E-05
8.9E-06
4.5E-06
3.9E-06
2.8E-06
MWSE Dataset CTE Resident
Scenario
Total Potential Risk
Exposure to Radionuclide COPCs in Background Soil
Table 6-34RME presents the total potential carcinogenic risks for the RME resident based on potential
exposure to radionuclide COPCs in background soils and upgradient sediment. The potential risks for
-5
-5
the garden scenario (1.6x10 ) and the no garden scenario (1.2x10 ) are within USEPA’s target risk
-4
-6
range of 10 to 10 . The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 (see totals
above)
•
Potential risk for the garden scenario and no garden scenario are greater than 10 (see totals
above)
•
Potential upgradient sediment risks are below 10 (adult 3.4x10 , child 1.9x10 )
•
The following constituents have potential risks greater than 10 in background soil:
-4
-5
-6
-7
-5
−
•
-7
-5
Radium-226+D in background soil is equal to 10 under the garden scenario
-6
The following constituents have potential risks greater than 10 in background soil:
−
Lead-210+D in background soil under the garden scenario (2x10 )
−
Radium-226+D in background soil under the no garden scenario (8.8x10 ),
−
Radium-228+D in background soil under the garden (2.9x10 ) and no garden scenario
-6
(1.8x10 )
-6 ,
-6
-6
The potential RME risk from radionuclides in background soils is on the same order of magnitude as
the potential RME risk from radionuclides in suspected CCBs. Potential risks for the RME resident
-5
-5
garden scenario are 8x10 (Yard 520 dataset, site-specific 27% CCB scenario) and 4x10 (MWSE
-5
dataset, site-specific 27% CCB scenario) and are 2x10 for background soils.
AOC II – Docket No. V-W-’04-C-784 – HHRA
July 2012
AECOM
6-26
Environment
Table 6-34CTE presents the total potential carcinogenic risks for the CTE resident based on potential
exposure to radionuclide COPCs in background soils and upgradient sediment. The potential risks for
-6
-6
the garden scenario (3.6x10 ) and the no garden scenario (2.8x10 ) are within USEPA’s target risk
-4
-6
range of 10 to 10 . The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
totals above)
•
The total potential risk under both the garden and no garden scenarios is greater than 10
(see totals above)
•
Potential sediment risks are below 10 (adult 1.2x10 , child 1.7x10 )
•
The following constituents have potential risks greater than 10 in background soil:
-4
-6
-8
-5
-6
-8
-6
−
Radium-226+D in background soil under the garden (1.9x10 ) and no garden (1.8x10 )
scenarios
−
Radium-228+D in background soil under the garden scenario (1.1x10 )
-6
-6
-6
6.3.2.2 Recreational Child
The recreational child is assumed to be a visitor in the area who may potentially be exposed to
radionuclide COPCs in sediment via incidental ingestion. Because the residential child is also
evaluated for external exposure to gamma radiation and inhalation of particulates from suspected
CCBs, separate calculations for these pathways were not included.
RME Recreational Child – Brown Ditch
Table 6-32RME and Table 6-33RME present the potential risks for the recreational child, based on the
Brown Ditch sediment dataset. The potential sediment risks are the same for both Yard 520 and
MWSE datasets because both are based on the Brown Ditch sediment data, and are the same for
both the hypothetical screening level 100% CCB and the site-specific 27% CCB scenarios because
the percent CCB parameter is not applicable to sediment. The potential sediment risks are presented
along with potential risks from the Yard 520 dataset in Table 6-32RME and from the MWSE dataset in
-4
-6
-7
Table 6-33RME. The potential risks are below USEPA’s target risk range of 10 to 10 (6.7x10 ).
CTE Recreational Child – Brown Ditch
Table 6-32CTE and Table 6-33CTE present the potential risks for the recreational child, based on the
Brown Ditch sediment dataset. The potential sediment risks are the same for both Yard 520 and
MWSE datasets because both are based on the Brown Ditch sediment data, and are the same for
both the hypothetical screening level 100% CCB and the site-specific 27% CCB scenarios because
the percent CCB parameter is not applicable to sediment. The potential sediment risks are presented
along with potential risks from the Yard 520 dataset in Table 6-32CTE and from the MWSE dataset in
-4
-6
-8
Table 6-33CTE. The potential risks are below USEPA’s target risk range of 10 to 10 (6x10 ).
Recreational Child Summary
-6
No potential risks greater than 10 were identified under the RME or CTE scenarios, as indicated
below. Potential upgradient sediment risks are also presented for comparison.
AOC II – Docket No. V-W-’04-C-784 – HHRA
July 2012
AECOM
6-27
Environment
Recreational Child
Radionuclide
Pb-210+daughters
Ra-226+daughters
Ra-228+daughters
Th-228
Th-230
Th-232
U-234
U-235+daughters
U-238+daughters
Total Potential Risk
Brown Ditch Sediment
RME
CTE
1.0E-07
4.0E-07
1.4E-07
3.8E-09
8.4E-09
7.2E-09
7.6E-09
ND
8.0E-09
6.7E-07
8.9E-09
3.3E-08
1.5E-08
5.6E-10
7.0E-10
6.0E-10
6.3E-10
ND
6.7E-10
6.0E-08
Upgradient Sediment
RME
CTE
2.7E-08
1.1E-07
4.9E-08
9.8E-10
2.3E-09
1.9E-09
2.0E-09
ND
ND
1.9E-07
2.4E-09
9.0E-09
5.2E-09
1.4E-10
1.9E-10
1.5E-10
1.6E-10
ND
ND
1.7E-08
Exposure to Radionuclide COPCs in Upgradient Sediment
Table 6-34RME presents the total potential carcinogenic risks for the RME recreational child based on
potential exposure to radionuclide COPCs in Upgradient sediment. The potential risks are below
-4
-6
-7
USEPA’s target risk range of 10 to 10 (1.9x10 ).
The potential RME risk from radionuclides in Upgradient sediment is on the same order of magnitude
as the potential RME risk from radionuclides in Brown Ditch sediment. Potential RME risks from
-7
-7
Brown Ditch sediment are 7x10 and are 2x10 for Upgradient sediment.
Table 6-34CTE presents the total potential carcinogenic risks for the CTE recreational child based on
potential exposure to radionuclide COPCs in Upgradient sediment. The potential risks are below
-4
-6
-8
USEPA’s target risk range of 10 to 10 (1.7x10 ).
6.3.2.3 Recreational Fisher
The recreational fisher is assumed to be a visitor in the area who may potentially be exposed to
radionuclide COPCs in sediment via incidental ingestion. Because the recreational fisher is also
evaluated for external exposure to gamma radiation and inhalation of particulates from suspected
CCBs, separate calculations for these pathways were not included.
RME Recreational Fisher – Brown Ditch
Table 6-32RME and Table 6-33RME present the potential risks for the recreational fisher, based on
the Brown Ditch sediment dataset. The potential sediment risks are the same for both Yard 520 and
MWSE datasets because both are based on the Brown Ditch sediment data, and are the same for
both the hypothetical screening level 100% CCB and the site-specific 27% CCB scenarios because
the percent CCB parameter is not applicable to sediment. The potential sediment risks are presented
along with potential risks from the Yard 520 dataset in Table 6-32RME and from the MWSE dataset in
-4
-6
Table 6-33RME. The total potential risks are within USEPA’s target risk range of 10 to 10
-6
-6
(1.2x10 ). Potential constituent risks are less than 10 .
CTE Recreational Fisher – Brown Ditch
Table 6-32CTE and Table 6-33CTE present the potential risks for the recreational fisher, based on the
Brown Ditch dataset. The potential sediment risks are the same for both Yard 520 and MWSE
AOC II – Docket No. V-W-’04-C-784 – HHRA
July 2012
AECOM
6-28
Environment
datasets because both are based on the Brown Ditch sediment data, and are the same for both the
hypothetical screening level 100% CCB and the site-specific 27% CCB scenarios because the
percent CCB parameter is not applicable to sediment. The potential sediment risks are presented
along with potential risks from the Yard 520 dataset in Table 6-32CTE and from the MWSE dataset in
-4
-6
-8
Table 6-33CTE. The potential risks are below USEPA’s target risk range of 10 to 10 (4.4x10 ).
Recreational Fisher Summary
-6
The total potential risk under the RME scenario slightly exceeds 10 , with no constituent risks above
-6
-6
10 . No potential risks greater than 10 were identified under the CTE scenario. The table below
-6
-5
summarizes the potential risks; potential risks greater than 10 but less than 10 are highlighted in
green. Potential risks based on upgradient sediment are also presented for comparison.
Recreational
Fisher
Radionuclide
Pb-210+daughters
Ra-226+daughters
Ra-228+daughters
Th-228
Th-230
Th-232
U-234
U-235+daughters
U-238+daughters
Total Potential Risk
Brown Ditch Sediment
RME
CTE
1.4E-07
9.5E-07
1.0E-07
5.1E-10
8.0E-09
6.6E-09
6.1E-09
ND
1.1E-08
1.2E-06
3.2E-09
3.2E-08
7.7E-09
3.1E-11
1.4E-10
1.2E-10
1.1E-10
ND
3.1E-10
4.4E-08
Upgradient Sediment
RME
CTE
3.8E-08
2.6E-07
3.6E-08
1.3E-10
2.2E-09
1.7E-09
1.6E-09
ND
ND
3.4E-07
8.7E-10
8.8E-09
2.7E-09
7.9E-12
3.8E-11
3.0E-11
2.8E-11
ND
ND
1.2E-08
Exposure to Radionuclide COPCs in Upgradient Sediment
Table 6-34RME presents the total potential carcinogenic risks for the RME recreational fisher based
on potential exposure to radionuclide COPCs in Upgradient sediment. The potential risks are below
-4
-6
-7
USEPA’s target risk range of 10 to 10 (3.4x10 ).
-6
Potential RME risks for the recreational fisher from Brown Ditch sediment are 1.2x10 and potential
-7
risks are 3.4x10 for Upgradient sediment.
Table 6-34CTE presents the total potential carcinogenic risks for the CTE recreational fisher based on
potential exposure to radionuclide COPCs in Upgradient sediment. The potential risks are below
-4
-6
-8
USEPA’s target risk range of 10 to 10 (1.2x10 ).
6.3.2.4 Construction Worker
Construction workers are assumed to be potentially exposed to radionuclide COPCs in surface and
subsurface suspected CCBs via incidental ingestion, via inhalation of particulates, and via external
exposure to gamma radiation.
This scenario conservatively assumes that all excavation occurs through CCBs, i.e., the full depth and
length of the excavation trench excavated each day is comprised of CCBs. As the derivation of the
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conservative maximum average percent of CCBs for residential properties is based on observations of
CCBs at the surface, the site-specific 27% CCB scenario was not applied to the construction worker.
Hypothetical RME Construction Worker – Yard 520 CCBs
Table 6-32RME presents the total potential risks for the construction worker based on the Yard 520
-6
-4
-6
CCB dataset. The potential risks (2.2x10 ) are within USEPA’s target risk range of 10 to 10 . The
following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
total above)
•
The total potential risk is greater than 10 (see total above)
•
The only constituent with a potential risk greater than 10 is Radium-226+D (1.1x10 )
-4
-5
-6
-6
-6
Hypothetical CTE Construction Worker – Yard 520 CCBs
Table 6-32CTE presents the total potential risks for the construction worker based on the Yard 520
-4
-6
CCB dataset. The potential risks are just within the low end USEPA’s target risk range of 10 to 10
-6
-6
(1.1x10 ); there are no constituents with potential risks greater than 10 .
RME Construction Worker – MWSE Suspected CCBs
Table 6-33RME presents the total potential risks for the construction worker based on the MWSE
-6
-4
suspected CCB dataset. The potential risks (1.5x10 ) are within USEPA’s target risk range of 10 to
-6
-6
10 . There are no constituents with potential risks greater than 10 .
CTE Construction Worker – MWSE Suspected CCBs
Table 6-33CTE presents the total potential risks for the construction worker based on the MWSE
-7
-4
suspected CCB dataset. The potential risks (7.4x10 ) are below USEPA’s target risk range of 10 to
-6
10 .
Construction Worker Summary
-4
-5
No potential risks greater than 10 or 10 were identified under the RME or CTE scenarios. Potential
-6
risks in the 10 range were identified under the RME and CTE scenarios, as discussed above. The
-6
only constituent risk greater than 10 was radium-226+D in the Yard 520 dataset under the RME
-6
scenario. The table below summarizes the potential risks; potential risks greater than 10 but less
-5
than 10 are highlighted in green. Potential risks based on the background scenario are also
presented for comparison.
Construction
Worker
Radionuclide
Pb-210+daughters
Ra-226+daughters
Ra-228+daughters
Th-228
Th-230
Th-232
Yard 520 CCBs
RME
CTE
8.3E-08
1.1E-06
3.9E-07
2.2E-07
7.9E-08
8.6E-08
AOC II – Docket No. V-W-’04-C-784 – HHRA
3.5E-08
5.4E-07
2.0E-07
1.1E-07
3.9E-08
4.3E-08
MWSE Suspected
CCBs
RME
CTE
3.2E-08
6.6E-07
2.8E-07
3.3E-07
4.8E-08
3.7E-08
1.3E-08
3.3E-07
1.4E-07
1.6E-07
2.4E-08
1.8E-08
Background Soil
RME
CTE
5.8E-09
9.4E-08
5.7E-08
3.8E-08
6.8E-09
1.1E-08
2.5E-09
4.7E-08
2.8E-08
1.9E-08
3.4E-09
5.6E-09
July 2012
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Environment
Construction
Worker
Radionuclide
MWSE Suspected
CCBs
RME
CTE
Yard 520 CCBs
RME
CTE
Background Soil
RME
CTE
U-234
U-235+daughters
U-238+daughters
3.6E-08
7.5E-09
4.1E-08
1.8E-08
3.8E-09
2.0E-08
2.1E-08
ND
2.6E-08
1.1E-08
ND
1.3E-08
2.9E-09
3.7E-09
6.8E-09
1.4E-09
1.9E-09
3.4E-09
Total Potential Risk
2.0E-06
1.0E-06
1.4E-06
7.1E-07
2.3E-07
1.1E-07
Exposure to Radionuclide COPCs in Background Soil
Table 6-34RME presents the total potential carcinogenic risks for the RME construction worker based
-7
on potential exposure to radionuclide COPCs in background soils (2.4x10 ), and Table 6-34CTE
-7
provides the CTE scenario results (1.2x10 ). The potential risks are below USEPA’s target risk range
-4
-6
of 10 to 10 .
6.3.2.5 Outdoor Worker
Outdoor workers are assumed to be potentially exposed to radionuclide COPCs in suspected CCBs
via incidental ingestion, via inhalation of particulates, and via external exposure to gamma radiation.
The outdoor worker is assumed to be exposed only to surface soils.
Hypothetical RME Outdoor Worker – Yard 520 CCBs
Table 6-32RME presents the total potential risks for the outdoor worker based on the Yard 520 CCB
-4
dataset. The potential risks under the hypothetical screening level 100% CCB scenario (1.8x10 ) are
-4
-6
-4
above USEPA’s target risk range of 10 to 10 , and are within USEPA’s target risk range of 10 to
-6
-5
10 under the site-specific 27% CCB scenario (4.9x10 ). The following summarizes the potential
risks:
•
Potential risk for the outdoor worker is greater than 10 under the hypothetical screening level
-5
100% CCB scenario and greater than 10 under the site-specific 27% CCB scenario for Yard
520 CCBs (see totals above)
•
The following constituents have potential risks greater than 10 in Yard 520 CCBs:
-4
-4
−
•
•
Radium-226+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-4
scenario (1.6x10 )
-5
The following constituents have potential risks greater than 10 in Yard 520 CCBs:
−
Radium-228+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-5
scenario (1.9 x10 )
−
Radium-226+D in Yard 520 CCBs under the site-specific 27% CCB scenario (4.2x10 )
-5
-6
The following constituents have potential risks greater than 10 in Yard 520 CCBs for the
RME scenarios:
−
Lead-210+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-6
-6
scenario (4.1x10 ) and the site-specific 27% CCB scenario (1.1x10 )
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−
Uranium-238+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-6
scenario (2.3x10 )
−
Radium-228+D in Yard 520 CCBs under the site-specific 27% CCB scenario (5.1x10 )
-6
Hypothetical CTE Outdoor Worker – Yard 520 CCBs
Table 6-32CTE presents the total potential risks for the hypothetical outdoor worker based on the
Yard 520 CCB dataset. The potential risks under the hypothetical screening level 100% CCB
-5
-5
scenario (5.6x10 ) and under the site-specific 27% CCB scenario (1.5x10 ) are within USEPA’s
-4
-6
target risk range of 10 to 10 . The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 (see totals
above)
•
Potential risk for the outdoor worker is greater than 10 under both the hypothetical screening
level 100% CCB and the 27% CCB scenarios (see totals above)
•
The following constituents have potential risks greater than 10 in Yard 520 CCBs for the
CTE scenarios:
•
-4
-5
-5
−
Radium-226+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-5
-5
scenario (4.3x10 ) and the site-specific 27% CCB scenario (1.2x10 )
−
Radium-228+D in Yard 520 CCBs under the hypothetical screening level 100% CCB
-5
scenario (1.1x10 )
-6
The following constituents have potential risks greater than 10 in Yard 520 CCBs:
−
-6
Radium-228+D in Yard 520 CCBs under the site-specific 27% CCB scenario (3x10 )
RME Outdoor Worker – MWSE Suspected CCBs
Table 6-33RME presents the total potential risks for the outdoor worker based on the MWSE
suspected CCB dataset. The potential risks under the hypothetical screening level 100% CCB
-4
-4
-6
scenario (1.1x10 ) are above USEPA’s target risk range of 10 to 10 , and are within USEPA’s target
-4
-6
-5
risk range of 10 to 10 under the site-specific 27% CCB scenario (3x10 ). The following
summarizes the potential risks:
•
Potential risk for suspected CCBs for the outdoor worker is greater than 10 under the
-5
hypothetical screening level 100% CCB scenario and greater than 10 under the site-specific
27% CCB scenario (see totals above)
•
There are no potential risks by constituent greater than 10
•
The following constituents have potential risks greater than 10 in suspected CCBs:
•
-4
-4
-5
−
Radium-226+D in suspected CCBs under the hypothetical screening level 100% CCB
-5
-5
scenario (9.4 x10 ) and the site-specific 27% CCB scenario (2.5x10 )
−
Radium-228+D in suspected CCBs under the hypothetical screening level 100% CCB
-5
scenario (1.3 x10 )
-6
The following constituents have potential risks greater than 10 in suspected CCBs:
−
Lead-210+D in suspected CCBs under the hypothetical screening level 100% CCB
-6
scenario (1.6x10 )
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Environment
−
Uranium-238+D in suspected CCBs under the hypothetical screening level 100% CCB
-6
scenario (1.5x10 )
−
Radium-228+D in suspected CCBs under the site-specific 27% CCB scenario (3.6x10 )
-6
CTE Outdoor Worker – MWSE Suspected CCBs
Table 6-33CTE presents the total potential risks for the outdoor worker based on the MWSE
suspected CCB dataset. The potential risks under the hypothetical screening level 100% CCB
-5
-6
scenario (3.5x10 ) and under the site-specific 27% CCB scenario (9.4x10 ) are within USEPA’s
-4
-6
target risk range of 10 to 10 . The following summarizes the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 (see totals
above)
•
Potential risk for suspected CCBs for the outdoor worker is greater than 10 under the
-6
hypothetical screening level 100% CCB scenario and greater than 10 under the site-specific
27% CCB scenario (see totals above)
•
The following constituents have potential risks greater than 10 in suspected CCBs:
-4
-5
-5
−
•
Radium-226+D in suspected CCBs under the hypothetical screening level 100% CCB
-5
scenario (2.6 x10 )
-6
The following constituents have potential risks greater than 10 in suspected CCBs:
−
Radium-228+D in suspected CCBs under the hypothetical screening level 100% CCB
-6
-6
scenario (7.9x10 ) and the site-specific 27% CCB scenario (2.1x10 )
−
Radium-226+D in suspected CCBs under the site-specific 27% CCB scenario (7.1x10 )
-6
Outdoor Worker Summary
-4
Potential risks greater than 10 were identified under the RME hypothetical screening level 100%
CCB scenario for the Yard 520 and MWSE datasets. Potential risks within USEPA’s target risk range
-4
-6
of 10 to 10 were identified for the MWSE and Yard 520 datasets under the site-specific 27% CCB
scenarios and all of the CTE scenarios.
-4
Constituent-specific potential risks greater than or equal to 10 were identified under the RME
scenario as follows:
•
Yard 520 dataset: radium-226+D in Yard 520 CCBs under the hypothetical screening level
100% CCB scenario
-5
Constituent-specific potential risks greater than or equal to 10 were identified under the RME
scenario as follows:
•
Yard 520 dataset: radium-228+D under the hypothetical screening level 100% CCB scenario,
and radium-226+D under the site-specific 27% CCB scenario
•
MSWE dataset: radium-226+D and radium-228+D under the hypothetical screening level
100% CCB scenario, and radium-226+D under the site-specific 27% CCB scenario
-6
-5
Constituent-specific potential risks greater than or equal to 10 , but less than 10 , were identified
under the RME scenario as follows:
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Environment
•
Yard 520 dataset: lead-210+D and uranium-238+D under the hypothetical screening level
100% CCB scenario, and lead-210+D and radium-228+D under the site-specific 27% CCB
scenario
•
MWSE dataset: lead-210+D and uranium-238+D under the hypothetical screening level
100% CCB scenario, and radium-228+D under the site-specific 27% CCB scenario
-5
Constituent-specific potential risks greater than or equal to 10 were identified under the CTE
scenario as follows:
•
Yard 520 dataset: radium-226+D and radium-228+D under the hypothetical screening level
100% CCB scenario, and radium-226+D under the site-specific 27% CCB scenario
•
MWSE dataset: radium-226+D under the hypothetical screening level 100% CCB scenario
-6
-5
Potential risks greater than 10 , but less than 10 , were identified under the CTE scenario as follows:
•
Yard 520 dataset: radium-228+D under the site-specific 27% CCB scenario
•
MWSE dataset: radium-228+D under the hypothetical screening level 100% CCB scenario,
and radium-226+D and radium-228+D under the site-specific 27% CCB scenario
-4
-5
-6
As described above, potential risks greater than10 , 10 and 10 were identified. Potential risks
-4
greater than 10 are associated only with the hypothetical screening level 100% CCB scenario. The
-4
tables below summarize the potential risks; potential risks greater than 10 are highlighted in orange,
-5
-4
potential risks greater than 10 but less than 10 are highlighted in yellow, and potential risks greater
-6
-5
-6
than 10 but less than 10 are highlighted in green. Calculated risks less than 10 , which are below
USEPA’s target risk range, are not highlighted. Potential risks based on the background scenario are
also presented for comparison.
Hypothetical
Outdoor Worker
Radionuclide
Pb-210+daughters
Ra-226+daughters
Ra-228+daughters
Th-228
Th-230
Th-232
U-234
U-235+daughters
U-238+daughters
Total Potential Risk
Yard 520 RME
Hypothetical
SiteScreening
Specific
Level
Evaluation
Evaluation
Based on
Assuming
100% CCB
27% CCB
4.1E-06
1.6E-04
1.9E-05
2.4E-08
2.0E-07
1.6E-07
1.4E-07
7.9E-07
2.3E-06
1.8E-04
AOC II – Docket No. V-W-’04-C-784 – HHRA
1.1E-06
4.2E-05
5.1E-06
6.4E-09
5.5E-08
4.2E-08
3.9E-08
2.1E-07
6.1E-07
4.9E-05
Yard 520 CTE
Hypothetical
SiteScreening
Specific
Level
Evaluation
Evaluation
Based on
Assuming
100% CCB
27% CCB
4.6E-07
4.3E-05
1.1E-05
1.4E-08
2.2E-08
1.6E-08
1.4E-08
2.2E-07
6.1E-07
5.6E-05
1.2E-07
1.2E-05
3.0E-06
3.8E-09
5.9E-09
4.3E-09
3.7E-09
6.0E-08
1.6E-07
1.5E-05
Background Soil
RME
CTE
2.9E-07
1.4E-05
2.9E-06
4.1E-09
1.8E-08
2.0E-08
1.1E-08
4.2E-07
4.0E-07
1.8E-05
3.3E-08
4.0E-06
1.7E-06
2.5E-09
1.9E-09
2.1E-09
1.1E-09
1.2E-07
1.1E-07
6.0E-06
July 2012
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Environment
Outdoor Worker
Radionuclide
Pb-210+daughters
Ra-226+daughters
Ra-228+daughters
Th-228
Th-230
Th-232
U-234
U-235+daughters
U-238+daughters
Total Potential
Risk
MWSE RME
Hypothetical
Screening
SiteLevel
Specific
Evaluation
Evaluation
Assuming
Based on
100% CCB
27% CCB
MWSE CTE
Hypothetical
Screening
SiteLevel
Specific
Evaluation
Evaluation
Assuming
Based on
100% CCB
27% CCB
Background Soil
RME
CTE
1.6E-06
9.4E-05
1.3E-05
3.5E-08
1.2E-07
6.7E-08
8.5E-08
ND
1.5E-06
4.3E-07
2.5E-05
3.6E-06
9.5E-09
3.3E-08
1.8E-08
2.3E-08
ND
3.9E-07
1.8E-07
2.6E-05
7.9E-06
2.1E-08
1.3E-08
6.9E-09
8.2E-09
ND
3.9E-07
4.8E-08
7.1E-06
2.1E-06
5.6E-09
3.6E-09
1.9E-09
2.2E-09
ND
1.1E-07
2.9E-07
1.4E-05
2.9E-06
4.1E-09
1.8E-08
2.0E-08
1.1E-08
4.2E-07
4.0E-07
3.3E-08
4.0E-06
1.7E-06
2.5E-09
1.9E-09
2.1E-09
1.1E-09
1.2E-07
1.1E-07
1.1E-04
3.0E-05
3.5E-05
9.4E-06
1.8E-05
6.0E-06
Exposure to Radionuclide COPCs in Background Soil
Table 6-34RME presents the total potential carcinogenic risks for the RME outdoor worker based on
-5
potential exposure to radionuclide COPCs in background soils. The potential risk (1.8x10 ) is within
-4
-6
USEPA’s target risk range of 10 to 10 . The following bullets summarize the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 (see total
above)
•
Total potential risk for the outdoor worker is greater than 10 (see total above)
•
Radium-226+D in background soils is greater than 10 (1.4x10 )
•
Radium-228+D in background soils is greater than 10 (2.9x10 )
-4
-5
-5
-5
-6
-6
The potential RME risk from radionuclides in background soils is on the same order of magnitude as
the potential risk from radionuclides in suspected CCBs. Potential risks for the RME outdoor worker
-5
-5
receptor under the site-specific 27% CCB scenario are 5x10 (Yard 520 dataset) and 3x10 (MWSE
-5
dataset) and are 2x10 for background soils.
Table 6-34CTE presents the total potential carcinogenic risks for the CTE outdoor worker based on
-6
potential exposure to radionuclide COPCs in background soils. The potential risk (6x10 ) is within
-4
-6
USEPA’s target risk range of 10 to 10 . The following bullets summarize the potential risks:
•
There are no potential risks, either by receptor or constituent, greater than 10 or 10 (see
total above)
•
Total potential risk for the outdoor worker receptor is greater than 10 (see total above)
•
Radium-226+D in background soils is greater than 10 (4x10 )
•
Radium-228+D in background soils is greater than 10 (1.7x10 )
-4
-5
-6
-6
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-6
-6
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6.3.2.6 Radionuclide Risk Characterization Summary
The results of the radionuclide risk assessment are presented on Table 6-35. As described above,
-4
-5
-6
-4
potential risks greater than10 , 10 and 10 were identified. Potential risks greater than 10 are
associated only with the hypothetical screening level 100% CCB scenario.
6.3.3
Summary of Chemical and Radionuclide Risk Characterization Results
This section provides a summary of the chemical and radionuclide risk characterization results.
6.3.3.1 Datasets Evaluated
The human health risk assessment has quantitatively evaluated chemical constituents for the
following groups of datasets:
•
MWSE suspected CCB dataset,
•
Brown Ditch, Pond 1 and Pond 2 sediment datasets
•
Brown Ditch, Pond 1 and Pond 2 surface water datasets
•
Groundwater dataset
•
Background soil dataset
and
The human health risk assessment has evaluated radionuclide constituents for the following groups of
datasets:
• MWSE suspected CCB dataset, in conjunction with:
•
Brown Ditch sediment dataset for radionuclides
•
Background soil dataset, in conjunction with:
•
Brown Ditch Upgradient sediment dataset
and
In addition, at the request of USEPA, the following datasets were evaluated:
•
Yard 520 CCB dataset for radionuclides, in conjunction with:
•
Brown Ditch sediment dataset for radionuclides (the same sediment dataset evaluated in
conjunction with the MWSE suspected CCB dataset)
As noted previously, there is no direct contact with CCBs in Yard 520 due to the cap that was placed
upon closure of the facility and the maintenance of that cap (see Appendix O). Chemical constituent
data (e.g., metals and inorganics) were not collected for risk assessment purposes from Yard 520.
Samples from the Type III (South) Area of Yard 520 were collected and analyzed for radionuclides to
use in a screening level risk evaluation. Because MWSE suspected CCB samples were analyzed for
radionuclides, and because they are representative of potential exposures to CCBs located within the
Area of Investigation, the Yard 520 sample data were not needed to evaluate risk. However, at the
request of USEPA, this risk assessment has conducted a detailed radionuclide risk assessment of the
Yard 520 data in addition to the MWSE data following USEPA guidance (USEPA, 2010b). Exposure
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6-36
to CCBs in Yard 520 is not a currently complete exposure pathway, nor will there be a complete
exposure pathway in the future due to the regulatory closure requirements administered by IDEM.
The risk assessment on the Yard 520 data at the request of USEPA does not assume that a
residential structure is present on Yard 520, but rather assumes that concentrations of CCBs found in
Yard 520 are also present in the community. Data discussed in Section 3.5 have shown that this is
not the case, thus, further discussion focuses on the risk results for the MWSE datasets.
6.3.3.2 Scenarios Evaluated
Both chemical constituent data and radionuclide data are available for the suspected CCBs collected
from the utility trenches along streets within the Area of Investigation under the MWSE program. Two
CCB exposure scenarios were evaluated for these datasets:
•
A hypothetical screening level 100% CCB scenario, and
•
A site-specific 27% CCB scenario, as derived from the CCB visual inspection results detailed
in Appendix I
The hypothetical screening level 100% CCB scenario directly uses the data for the samples collected
at depth (0-5 feet bgs – note that only one sample was collected from a depth that started at the
ground surface) under the MWSE sampling program. These CCBs were originally placed as road bed
in the mid-1970s, and have not been mixed significantly with other materials. Thus, these sample
results are representative of the suspected CCBs placed within the Area of Investigation at that time.
The results of the visual inspection program conducted under the RI have been used to identify where
within the Area of Investigation suspected CCBs are present at the surface (defined as at the ground
surface and/or within the top 6-inches of material at the ground surface), and have demonstrated that
the suspected CCBs present at the surface are mixed with other materials, such as sand and soil.
Where suspected CCBs are present at the surface, they make up less than 25% of the material for the
majority of the sample locations (see Appendix I for a detailed discussion of the CCB visual inspection
results). Thus the 100% CCB exposure scenario for the receptors assumed to be exposed to CCBs
at the ground surface (the resident receptor and the outdoor worker receptor) is indeed a hypothetical
screening level scenario. The risk results for this scenario are presented here for informational
purposes, but do not represent potential risk via exposure to suspected CCBs within the Area of
Investigation.
The results of the CCB visual inspection program were tallied for the 43 residential and potentially
residential properties where suspected CCBs were identified at the ground surface. Figure 4 and
Figure I-3 of Appendix I show the approximate location of suspected CCBs on private property. An
exposure area was defined for each property as essentially the size of the residential lot, and also
included the contiguous ROWs, as most suspected CCBs within the Area of Investigation are located
with the ROWs. In several cases where properties were large and where suspected CCBs were
located only within a subset of that larger property, the exposure area was identified as approximately
the size of a standard residential lot taking care to include all or the majority of the locations where
suspected CCBs were identified; this treatment ensured that the large areas of these properties that
did not have suspected CCBs at the surface did not “dilute out” the results for the areas where
suspected CCBs were present. For each property, the area where suspected CCBs were identified
and the total exposure area were measured. For the area on each property where suspected CCBs
were located, the average percent of suspected CCBs was calculated (assuming the maximum
observed at each inspection location), as detailed in Appendix I. Then taking into account the size of
the area with suspected CCBs and the size of the total exposure area, the average percent suspected
CCBs across the exposure area (conservatively assuming the maximum at each inspection location)
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was calculated for each of the 43 properties (Appendix I provides a step-wise description of these
calculations). The maximum of all of these results, 27%, was used here to evaluate the site-specific
maximum average 27% CCB scenario. The figure below tabulates the average percent results. As
can be seen, 27% is the maximum, the majority of the results are below 14% CCBs, and the average
is 6% CCBs. Therefore, the maximum average 27% CCB scenario provides a very conservative
estimate of potential exposure and risk for this risk assessment.
This distinction between the hypothetical screening level 100% CCB and the site-specific 27% CCB
scenarios is applicable to the receptors assumed to be exposed to suspected CCBs at the ground
surface, i.e., the resident and the outdoor worker. The construction worker is assumed to be exposed
to suspected CCBs during excavation work, thus the 100% CCB data were used to evaluate this
receptor. The recreational receptors are assumed to be exposed to CCB-derived constituents in
sediment and surface water in Brown Ditch and Ponds 1 and 2. As discussed previously, radionuclide
data are available for Brown Ditch sediment, therefore, the summed chemical constituent and
radiological data risk results focus on the Brown Ditch exposure scenarios for the resident and
recreational receptors. Because the radionuclide concentrations in groundwater were so low and
based on the CSM that groundwater is likely the main pathway for the presence of CCB-derived
constituents in surface water, surface water samples were not analyzed for radionuclides (see Section
3.1.22 as well as Appendix M regarding groundwater).
Risk assessments generally assume that materials at depth can be brought to the surface in the future
due to excavation and regrading activities. Such activities may occur in the future within the Area of
Investigation, but it is unlikely that the excavated CCBs would remain at 100% through the excavation,
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replacement, and regrading activities. The CCBs would mix with other materials (soil, sand) during
these activities as there are few areas where suspected CCBs have been identified to occur within the
entire 0-15 foot soil column. Therefore, the site-specific conservative maximum average percent
CCBs of 27% is also expected to be a reasonable and conservative estimate of potential future
exposures.
6.3.3.3 Receptor and Scenario Specific Risk Results
The summed risk results, as presented in Table 6-36, are for the following datasets:
•
Chemical constituent data for suspected CCBs, Brown Ditch sediment and Brown Ditch
surface water
•
Radionuclide data for suspected CCBs and Brown Ditch sediment
•
Chemical constituent and radionuclide data for background soils and Upgradient sediment in
the background datasets
-4
-6
The target risk range is 10 to 10 , as defined in USEPA guidance (USEPA, 1991b). As described
-4
-5
-6
above, potential risks greater than 10 , 10 and 10 are summarized below from the results
presented in the previous sections.
-4
Potential risks greater than 10 are associated only with the RME hypothetical screening level 100%
CCB scenario for radionuclides, as shown in Table 6-36.
•
The radionuclide potential risk for the hypothetical screening level 100% CCB resident garden
-4
scenario is 2x10 , as is the total potential chemical plus radionuclide risk for the garden
-4
scenario; however, no individual radionuclide or chemical constituent risk is above 10
•
The total potential chemical plus radionuclide risk for the hypothetical screening level 100%
-4
CCB resident no garden scenario is 1x10 , which is the upper end of USEPA’s target risk
range
•
The radionuclide potential risk for the hypothetical screening level 100% CCB outdoor worker
-4
scenario is 1x10 , as is the total potential chemical plus radionuclide risk, both of which are at
the upper end of USEPA’s target risk range
-5
The total potential risks for the RME resident site-specific 27% CCB scenarios are within the 10 to
-4
10 risk range, as are the total potential risks for the background dataset. The site-specific 27% CCB
scenario and background risk results are the same order of magnitude, although the MWSE dataset
risks are slightly higher than the background risks.
The recreational and construction worker RME scenario summed risks are within the low end of the
-6
-5
10 to 10 risk range.
6.3.3.4 Constituent-Specific Risk Results
Summary of Hypothetical Screening Level 100% CCB Scenario
-4
No potential risks greater than 10 were identified in the chemical HHRA. No individual radionuclides
-4
-4
were identified with potential risks greater than 10 . Total potential risks greater than 10 were
identified for the RME hypothetical screening level 100% CCB scenario for the residential garden
scenario and the outdoor worker scenario for radionuclides. Potential carcinogenic risks greater than
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-6
10 and/or greater than or equal to 10 were identified under various, but not all, hypothetical
screening level 100% CCB RME MWSE chemical and radionuclide dataset pathways and scenarios,
as described in detail in Sections 6.2 and 6.3 and summarized below.
-5
Constituents with potential risks greater than or equal to 10 were identified under the hypothetical
screening level 100% CCB RME scenario as follows:
•
•
•
•
Arsenic (residential receptor; and, outdoor worker)
Lead-210+D (residential receptor garden scenario)
Radium-226+D (residential receptor garden and no garden scenarios; and, outdoor worker)
Radium-228+D (residential receptor garden scenario; and, outdoor worker)
-6
Constituents with potential risks greater than or equal to 10 were identified under the hypothetical
screening level 100% CCB RME scenario as follows:
•
•
•
•
•
Arsenic (recreational child, recreational fisher)
Hexavalent chromium (residential receptor)
Lead-210+D (residential receptor no garden scenario; and, outdoor worker)
Radium-228+D (residential receptor no garden scenario)
Uranium-238+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-5
Constituents with potential risks greater than or equal to 10 were identified under the hypothetical
screening level 100% CCB CTE scenario as follows:
•
Radium-226+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-6
Constituents with potential risks greater than or equal to 10 were identified under the hypothetical
screening level 100% CCB CTE scenario as follows:
•
•
•
Arsenic (residential receptor)
Lead-210+D (residential receptor garden scenario)
Radium-228+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-4
No individual constituents were identified with potential risks greater than 10 . Furthermore, the
100% CCB scenario was included as a hypothetical screening level evaluation and is based on the
conservative assumption that an entire residential yard is comprised of 100% CCBs. Nonetheless,
the COPCs identified above as associated with risks ≥ 1E-06 have been identified as COCs for
potential carcinogenic effects based on the hypothetical evaluation.
Based on the results of the hypothetical screening level 100% CCB scenario HHRA for the RME
resident, iron and thallium are the only noncarcinogenic COPCs with hazard indices above one, as
discussed in greater detail below:
•
Iron. When the iron HQ under the hypothetical screening level 100% CCB scenario is
rounded to one significant figure per USEPA guidance (USEPA, 1989a), the iron HQ on a
target endpoint basis (gastrointestinal effects) is 1. It should be noted that iron is an
essential nutrient, and that the iron HQ under the site-specific 27% CCB scenario is below
one.
•
Thallium. The thallium HQ under the hypothetical screening level 100% CCB scenario is
1.65. The thallium HQ under the site-specific 27% CCB scenario is below one.
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Noncarcinogenic regulatory targets were not exceeded for any of the CTE scenarios, sediment or
surface water under RME or CTE scenarios, or construction worker contact with groundwater under
RME or CTE scenarios. The iron HQ is essentially equal to one and it is an essential nutrient. Both
the chronic and the sub-chronic RfDs for thallium are provisional screening values derived in
Appendix A of USEPA (2010a). According to USEPA (2010a), a reference dose for thallium was not
derived because the available toxicity database contains studies that are generally of poor quality.
Appendix A of USEPA (2010a) indicates that it is inappropriate to derive provisional chronic or
subchronic RfDs for thallium, but that information is available which, although insufficient to support
derivation of a provisional toxicity value, under current guidelines, may be of limited use to risk
assessors. Therefore, the screening RfDs for thallium were conservatively used in this HHRA. The
RfDs for thallium are based on a subchronic study in rats and the NOAEL is based on hair follicle
atrophy; this endpoint was selected because atrophy of hair follicles is consistent with the atrophic
changes observed in cases of human thallium poisoning and may be the best indication for human
response to thallium exposure (USEPA, 2010a). However, this endpoint is not a “toxic” endpoint per
se, and the results of the thallium risk assessment should be interpreted with appropriate reservations.
Furthermore, the thallium HQ of 1.65 is based on the hypothetical scenario that a residential yard is
comprised of 100% CCBs and the HQs are below one under the site-specific 27% CCB scenario. By
comparison, the HQ for thallium in background soils under the RME resident scenario is 1.3. Because
the levels are similar and due to the issues of relevance and confidence in the basis for the toxicity
value for thallium, no COCs have been identified for noncarcinogenic effects for the hypothetical
screening level 100% CCB scenario.
The results presented in Appendix H indicate that potential exposures and risk via the homegrown
produce consumption pathway under the hypothetical screening level 100% CCB scenario are within
the low end of the range of exposure and risk for the normal background dietary ingestion of arsenic,
indicating that carcinogenic risk from ingesting homegrown produce containing arsenic is likely not a
human health concern.
Based on the results of the hypothetical screening level evaluation assuming 100% CCBs, the
following COCs were identified under RME conditions or under CTE conditions:
RME Conditions
•
•
•
•
•
•
Arsenic (residential receptor garden and no garden scenarios, outdoor worker, recreational
child, and recreational fisher)
Hexavalent chromium (residential receptor garden and no garden scenarios)
Lead-210+D (residential receptor garden and no garden scenarios)
Radium-226+D (residential receptor garden and no garden scenarios and outdoor worker)
Radium-228+D (residential receptor garden and no garden scenarios and outdoor worker)
Uranium-238+D (residential receptor garden and no garden scenarios and outdoor worker)
CTE Conditions
•
•
•
•
Arsenic (residential receptor garden and no garden scenarios)
Lead-210+D (residential receptor garden scenario)
Radium-226+D (residential receptor garden and no garden scenarios and outdoor worker)
Radium-228+D (residential receptor garden and no garden scenarios and outdoor worker)
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Summary of Site-Specific 27% CCB Scenario
-4
No potential total or individual risks greater than 10 were identified under the site-specific 27% CCB
-5
scenario, RME or CTE. Potential carcinogenic risks greater than 10 and/or greater than or equal to
-6
10 were identified for some, but not all, site-specific 27% CCB RME pathways and scenarios, for the
MWSE chemical and radionuclide dataset, as described in detail in Sections 6.2 and 6.3 and
summarized below.
-5
Constituents with potential risks greater than or equal to 10 were identified under the site-specific
27% CCB RME scenario as follows:
•
•
Arsenic (residential receptor)
Radium-226+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-6
Constituents with potential risks greater than or equal to 10 were identified under the site-specific
27% CCB RME scenario as follows:
•
•
•
Arsenic (recreational child, recreational fisher, and outdoor worker)
Lead-210+D (residential receptor garden and no garden scenarios)
Radium-228+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-5
No constituents with potential risks greater than or equal to 10 were identified under the site-specific
27% CCB CTE scenario.
-6
Constituents with potential risks greater than or equal to 10 were identified under the site-specific
27% CCB CTE scenario as follows:
•
•
•
•
Arsenic (residential receptor)
Lead-210+D (residential receptor garden scenario)
Radium-226+D (residential receptor garden and no garden scenarios; and, outdoor worker)
Radium-228+D (residential receptor garden scenario; and, outdoor worker)
The COPCs identified above as associated with risks ≥ 1E-06 have been identified as COCs for
potential carcinogenic effects based on the site-specific 27% CCB evaluation.
Noncarcinogenic regulatory targets were not exceeded for any of the site-specific 27% CCB
scenarios, sediment or surface water scenarios, or construction worker contact with groundwater
scenarios. Therefore, no COCs have been identified for noncarcinogenic effects for the 27% CCB
scenarios.
The results presented in Appendix H indicate that potential exposures and risk via the homegrown
produce consumption pathway under the site-specific 27% CCB scenario are within the low end of the
range of exposure and risk for the normal background dietary ingestion of arsenic, indicating that
carcinogenic risk from ingesting homegrown produce containing arsenic is likely not a human health
concern.
Based on the results of the site-specific evaluation assuming 27% CCBs, the following COCs were
identified under RME conditions or under CTE conditions:
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RME Conditions
•
•
•
•
Arsenic (residential receptor garden and no garden scenarios, outdoor worker, recreational
child, and recreational fisher)
Lead-210+D (residential receptor garden and no garden scenarios)
Radium-226+D (residential receptor garden and no garden scenarios and outdoor worker)
Radium-228+D (residential receptor garden and no garden scenarios and outdoor worker)
CTE Conditions
•
•
•
•
Arsenic (residential receptor garden and no garden scenarios)
Lead-210+D (residential receptor garden scenario)
Radium-226+D (residential receptor garden and no garden scenarios and outdoor worker)
Radium-228+D (residential receptor garden scenario and outdoor worker)
Summary of Potential Background Risks
-5
-6
Potential carcinogenic risks greater than 10 and/or greater than or equal to 10 were identified for
the COPCs indentified under the site-specific 27% CCB scenario under various, but not all, RME
pathways and scenarios for the background chemical and radionuclide datasets (as described in
detail in Sections 6.2 and 6.3). All of these COPCs are the same as COPCs identified under the sitespecific 27% CCB RME scenario as summarized below.
-5
Constituents with potential risks greater than or equal to 10 were identified under the RME
background scenario as follows:
•
•
Arsenic (residential receptor)
Radium-226+D (residential receptor garden scenario; and, outdoor worker)
-6
Constituents with potential risks greater than or equal to 10 were identified under the RME
background scenario as follows:
•
•
•
Lead-210+D (residential receptor garden scenario)
Radium-226+D (residential receptor no garden scenario)
Radium-228+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-5
No constituents with potential risks greater than or equal to 10 were identified under the CTE
background scenario.
-6
Constituents with potential risks greater than or equal to 10 were identified under the CTE
background scenario as follows:
•
•
•
Arsenic (residential receptor)
Radium-226+D (residential receptor garden and no garden scenarios; and, outdoor worker)
Radium-228+D (residential receptor garden scenario; and, outdoor worker).
The HQ for thallium is greater than the noncarcinogenic regulatory target of one. As noted previously,
the endpoint for thallium effects is hair follicle atrophy, and the provisional toxicity value provided by
USEPA is not necessarily recommended for use (see discussion in Section 4). All other target
endpoint HQs for background soil are below one.
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Comparison of Risks for Background and CCB Scenarios
While arsenic in suspected CCBs was not found to be consistent with background, the potential risk
from arsenic in background soils is of the same order of magnitude as the potential risk from arsenic in
suspected CCBs under both CCB scenarios. Potential risks for arsenic from suspected CCBs are
-5
-5
4x10 (hypothetical screening level 100% CCB scenario) and 1x10 (site-specific 27% CCB scenario)
-5
and are 2x10 for background soils.
In addition, the potential residential RME risk from radionuclides in background soils is of the same
order of magnitude as the potential residential RME risk from radionuclides in suspected CCBs.
-4
Potential risks for the RME resident garden scenario are 2x10 (hypothetical screening level 100%
-5
-5
CCB scenario) and 4x10 (site-specific 27% CCB scenario) and are 2x10 for background soils.
Evaluation of Regulatory Standards for Radionuclides
In addition to the radionuclide risk assessment, an evaluation of the data with respect to regulatory
standards for radionuclides was conducted. As shown in Appendix J, USEPA guidance identifies a
standard of 5 pCi/g above background that is used to assess the combined levels of radium-226 and
radium-228. The background soil data collected during the RI were used to statistically derive a
background threshold value (BTV) for the sum of the radium isotopes, which ranges from 1 to 2 pCi/g;
therefore, the resulting 5 pCi/g plus background range is 6 to 7 pCi/g. As shown in Appendix J, all of
the results from the MWSE suspected CCB dataset, the Brown Ditch sediment dataset and the
Upgradient sediment dataset are below this 5 pCi/g plus background range.
6.4
Eva lua tion of the Drin king Wa te r P a thwa y
In April 2004, the USEPA and the Respondents (Brown Inc., Ddalt Corp., Bulk Transport Corp., and
NIPSCO) signed an Administrative Order on Consent (AOC II – Docket No. V-W-’04-C-784) to
conduct a RI/FS at the Pines Area of Investigation. The objectives of the RI include (AOC II, 2004):
“(a) to determine the nature and extent of contamination at the Site and any threat to the public
health, welfare, or the environment caused by the release or threatened release of hazardous
substances, pollutants or contaminants related to Coal Combustion By-products (“CCB”) at or
from the Site”, and
“(b) to collect data necessary to adequately characterize…(i) whether the water service extension
installed pursuant to AOC I, as amended, is sufficiently protective of current and reasonable future
drinking water use of groundwater in accordance with Federal, State, and Local requirements, (ii)
any additional human health risks at the Site associated with exposure to CCBs;….”
A risk assessment for the residential drinking water pathway using a cumulative risk-based screening
method is provided in Section 6.4.1 in order to determine whether potential risks associated with the
use of groundwater as a drinking water source are above USEPA target risk levels. The cumulative
risk assessment is conducted for all private wells, background wells, and monitoring wells, regardless
of whether they represent groundwater that is actually currently used as a drinking water source.
Therefore, the evaluation is hypothetical and used to determine whether restrictions on the use of
groundwater as a drinking water source should be considered and, therefore, the adequacy of the
coverage of the existing municipal water supply.
With respect to objectives (b) (i) and (ii) above, the RI for the Pines Area of Investigation included the
analysis of groundwater samples obtained from private wells and monitoring wells located outside of
the area where municipal water service is available. Because one purpose of the RI was to determine
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whether CCB-derived constituents pose a health risk via the drinking water pathway, a determination
must be made as to whether the groundwater in the area outside of the municipal water service has
been impacted by CCBs. All of the constituents associated with CCBs are naturally occurring
inorganic constituents (e.g., metals and salts), most of which have been shown to be present naturally
in the environmental media tested during the RI. Section 6.4.2 evaluates the groundwater data for
samples collected in areas outside of the municipal water service area to determine whether
groundwater in these areas may have been impacted by CCBs. Conclusions are provided in
Section 6.4.3.
6.4.1
Cumulative Risk Assessment – Area of Investigation
A cumulative risk assessment has been conducted for groundwater within the Area of Investigation.
Available groundwater data from private wells (Table 3-3), background wells (Table 3-7), and
monitoring wells (Table 3-2) have been used in the evaluation. Figure 15 presents the sample
locations. Analytical data are presented in Appendix A. Well-by-well summary statistics are provided
in Table 3-27, including the range of reporting limits for both detected and non-detected analytes,
minimum detected concentration, maximum detected concentration, and mean detected
concentration.
A cumulative risk screen approach has been used for the drinking water pathway. In a cumulative risk
screen, potential risks and hazards are calculated based on default screening levels. The USEPA
RSLs for tap water (USEPA, 2011b) are used in the cumulative screen. RSLs are risk-based
concentrations for various media, including tap water, corresponding to a potential carcinogenic risk
-6
level of 1x10 and a noncarcinogenic HQ of one. In a cumulative risk screen, RSLs are used to
estimate the potential carcinogenic risk and noncarcinogenic hazard associated with detected
concentrations; therefore, the RSLs for noncarcinogens do not need to be adjusted to account for
cumulative effects because the potential HQ for each constituent is calculated directly in order to
quantify potential cumulative effects. The USEPA RSL table presents the lower of the potential
carcinogenic and noncarcinogenic calculated values. However, the electronic version of the USEPA
RSL table provides RSLs for both potential carcinogenic and noncarcinogenic effects, where both
exist. Table 6-79 presents the RSLs for both potential carcinogenic and noncarcinogenic effects for
comparative purposes. Arsenic is the only constituent detected in groundwater with RSLs for both
potential carcinogenic and noncarcinogenic effects.
The RSLs incorporate agency default, conservative exposure assumptions for a residential drinking
water scenario (assuming exposure of 350 days per year for 30 years) as well as agency selected
toxicity values. Thus, the potential risks and hazards estimated using the RSLs are conservative and
are likely overestimates of potential risks and hazards. This method of screening ensures that one
may screen out constituents with low potential risk or hazard while taking into consideration the
potential for cumulative effects. The methodology for the cumulative risk screen is described below.
To perform a comprehensive cumulative risk screen, constituents are grouped into those evaluated for
potential carcinogenic effects and those evaluated for potential noncarcinogenic effects. The same
constituent may appear on both lists, as some constituents have USEPA dose-response values for
both types of effects; as noted previously, the only constituent for which this is the case in this
evaluation is arsenic. For constituents with potential carcinogenic effects, the maximum detected
-6
concentration is divided by the RSL and multiplied by 1x10 (the target risk level on which the RSLs
are based) to obtain an estimated potential carcinogenic risk. For constituents with noncarcinogenic
effects, the maximum detected concentration in each well is divided by the RSL to obtain an estimated
-6
HQ. Any constituent with a potential carcinogenic risk greater than 1x10 or an HQ greater than one
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is identified as a COPC. RSLs are not available for essential nutrients calcium, magnesium,
potassium, or sodium. Therefore, these constituents are not included in the cumulative screen and
are discussed further in Section 6.4.1.1.
As arsenic is the only potential carcinogen detected in groundwater, no further refinements to the
evaluation for potential carcinogens are needed.
The evaluation of constituents with noncarcinogenic effects uses a tiered approach. As an initial step,
the total HI is calculated by summing the individual constituent HQs regardless of target endpoint.
Where the total HI is less than one, no COPCs are identified and no further evaluation is necessary.
Where the total HI is greater than one, any individual constituent with an HQ above one is identified as
a COPC. Where the sum of the HQs for the remaining constituents is less than or equal to one, no
further evaluation is necessary and no additional COPCs are identified. Where the sum of the HQs
for the remaining constituents is above one, the constituents are grouped by similar target endpoint,
and a target endpoint-specific HI is calculated (which is the sum of the HQs). Where the target
endpoint-specific HI is less than or equal to one, no further evaluation is necessary and no additional
COPCs are identified; where it is above one, the constituents driving the risk are identified as COPCs.
Based on all the target endpoint evaluations, no constituents with individual HQs less than one have
been identified as COPCs.
Cumulative risk screens for each well are presented in Tables 6-37 to 6-78. Table 6-80 provides a
well by well summary of the COPC selection for each well, and the quantitative results are
summarized below and in Table 6-81.
6.4.1.1 Cumulative Risk Assessment Results
The results of the cumulative risk assessment for the various areas are discussed below.
Private Wells
Selected private wells were sampled outside of the area supplied municipal water. Private wells
within the area supplied municipal water were not sampled because they were abandoned as part of
the water installation project. The intent was to sample groundwater that is representative of areas
not provided municipal water, because these are the areas where the groundwater drinking water
pathway is complete.
Tables 6-80 and 6-81 present the results of the cumulative screening for the private wells, which are
presented in Tables 6-37 to 6-45. No potential carcinogens (i.e., arsenic) were detected in the private
wells. The noncarcinogenic hazard index was equal to or below one in all private wells, as shown in
Tables 6-37 to 6-45 and Table 6-81. Therefore, no COPCs were identified for private wells.
Background Wells
Tables 6-80 and 6-81 present the results of the cumulative screening for background wells, which are
presented in Tables 6-46 to 6-49. The potential carcinogenic risk in MW120 is within the USEPA
-6
-4
target risk range of 1x10 to 1x10 ; potential carcinogens were not detected in the other background
-6
wells (MW113, MW119, and MW121). The potential carcinogenic risk in MW120 exceeds 10 and
-5
10 due to arsenic. The noncarcinogenic hazard index was below one in all background wells, as
shown in Table 6-81.
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Monitoring Wells in Locations Not Served by Municipal Water
Tables 6-80 and 6-81 present the results of the cumulative screening for monitoring wells in locations
not served by municipal water, which are presented in Tables 6-50 to 6-55. Potential carcinogens
were not detected in MW114, MW115, MW116, or MW124, and the HI is below one in these wells.
In MW111, arsenic, iron, manganese, and thallium were identified as potential COPCs because the
-4
potential carcinogenic risk (arsenic) is greater than 10 , and the HQs for iron, manganese, and
thallium are greater than one. The potential HQ associated with other noncarcinogens is below one
on a target endpoint basis (see Table 6-50). MW111 is located adjacent to Brown Ditch and Illinois
Avenue, in a wetland area (see Figure 24) and an area of suspected CCB fill.
In MW122, arsenic and boron were identified as potential COPCs because the potential carcinogenic
-4
risk (arsenic) is greater than 10 , and the HQs for both arsenic and boron are greater than one. The
potential HQ associated with other noncarcinogens is below one on a target endpoint basis (see
Table 6-54). MW122 is located downgradient of Yard 520. While MW111 and MW122 are impacted
by CCBs, they are located in wetland areas that are unlikely to be developed. The location of wells in
wetland areas is discussed further in Section 6.4.4.2 and is presented on Figure 24.
Monitoring Wells in Locations Served by Municipal Water
Tables 6-80 and 6-81 present the results of the cumulative screening, which is presented in Tables
6-56 to 6-78. No COPCs were identified in the following wells where potential carcinogenic risks are
either not present, or are below the target risk range and the HI is below one:
•
MW101
•
MW102
•
MW103
•
MW105
•
MW106
•
MW107
•
MW108
•
MW109
•
MW110
•
MW117
•
MW123
•
TW-15S
•
TW-16S
•
TW-18S
COPCs were identified as follows in the remaining wells:
•
MW-3: boron
•
MW-6: arsenic (>10 ), boron
-4
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•
MW-8: arsenic (>10 ), boron
•
TW-10: boron
•
TW-12: boron
•
TW-15D: arsenic (>10 )
•
TW-16D: manganese
•
TW-18D: manganese
•
MW104: arsenic (>10 )
6-47
-4
-4
-5
The wells for which COPCs are listed above are located at and in the area immediately surrounding
Yard 520 (with the exception of MW104); this area is served by municipal water. The area
-4
-5
surrounding MW104, which has a potential risk less than 10 but greater than 10 , is also served by
municipal water. Concentrations of boron and sulfate in MW104 may be slightly above background.
However, as discussed in Section 4.5.2 of the RI Report, a number of parameters that are indicators
of septic system impacts are elevated in this well (compared to samples from most other wells).
These include: ammonia, nitrate, organic carbon, surfactants, and bacteriological parameters.
Therefore, the groundwater in this well appears primarily impacted by septic systems.
Essential Nutrients
Calcium, magnesium, potassium, and sodium are typically eliminated from further consideration in a
human health risk assessment due to lack of toxicity data, and the USEPA-approved work plan
(ENSR, 2005d) indicated that these essential nutrients would not be included in the risk assessment.
However, USEPA requested that potential exposure to these essential nutrients via ingestion be
further evaluated by calculating a daily intake for comparison to dietary reference values. The daily
intake was calculated based on the maximum concentration of each constituent in each group of wells
multiplied by the adult drinking water ingestion rate (2 liters/day). This maximum daily intake was
converted to a percentage of the dietary reference value (for adults and children 4 or more years of
age) for each constituent (USFDA, 2003).
Table 6-85 presents the comparison of the maximum daily intake to recommended daily intakes. As
indicated on the table, maximum daily intakes are lower than recommended daily intakes. It should
be noted that the maximum detected concentrations of essential nutrients in private wells were
identified in PW007 and PW008, which have been shown in the RI Report (AECOM, 2010a) to be
impacted by the Pines Landfill (owned by Waste Management).
6.4.1.2 Cumulative Drinking Water Risk Assessment Conclusions
The cumulative risk assessment shows that potential risks associated with both background and
private wells in the Area of Investigation are below or within USEPA acceptable levels for both
potentially carcinogenic and noncarcinogenic effects. Potential risks were identified for several
monitoring wells both inside and outside the municipal water service area. Figure 16 shows the
locations of the wells where COPCs have been identified. The cumulative risk assessment indicates
that there are potential risks above target risk levels associated with two monitoring wells (MW111
and MW122) outside the municipal water service area. These wells are located in wetland areas (see
Figure 24), and currently the drinking water pathway is incomplete in these areas. More discussion of
the wetland areas is provided in Section 6.4.2.2, below. Potential risks above target risk levels were
also identified for several monitoring wells within the water service area in the vicinity of Yard 520, and
one well within the water service area away from Yard 520.
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No potential risks were identified for groundwater based on the cumulative risk assessment of the RI
data for the drinking water pathway for the areas outside the areas shown on Figure 16. As the figure
indicates, potential risks have not been identified for the vast majority of the Area of Investigation, and
the potential risks are localized to the area immediately adjacent to Yard 520, and to wetland areas
downgradient of large deposits of CCBs.
6.4.2
Evaluation of CCB Impact – Area Outside Municipal Water Service
As determined in Section 6.4.1, potential risks associated with the majority of groundwater in the Area
of Investigation are within or below USEPA target risk levels. Potential risks were identified for two
wells in wetland areas (MW111 and MW122, not served by municipal water, but in areas unlikely to be
developed) and for several wells surrounding Yard 520 (served by municipal water). In this section,
an evaluation is presented to determine whether wells in the area outside the municipal water service
area are impacted by CCBs. Constituents with concentrations above screening levels are of interest
only if they are related to the presence of CCBs.
Figure 15 presents the RI groundwater sample locations. Locations shown in blue are representative
of groundwater within the municipal water service area (which is encompassed by the green outline).
Table 6-82 lists the groundwater locations outside of the municipal water service area where samples
were collected. Figure 17 shows the groundwater sample locations outside of the area of municipal
water service, and shows the surficial extent of suspected CCBs as determined by the visual
inspection of roadways and adjacent properties conducted throughout the Area of Investigation (see
Section 3.7.2 of the RI Report).
As can be seen from Table 6-82, there are many sample locations outside of the MWSE area, 3-4
rounds of samples were collected from each well, and for each sample there are approximately 23
analytes to evaluate. Therefore, a tiered approach has been used to evaluate the data. In the first
step, analytical data are compared to risk-based screening levels to identify constituents for further
evaluation in the CCB impact determination. Section 6.4.1 presented a cumulative risk assessment
for all wells, regardless of whether they are determined to be impacted by CCBs. The screening
presented below is conducted in order to determine which areas to further evaluate for potential
drinking water pathway completeness, not to determine potential risk. Because CCB-derived
constituents are also naturally occurring inorganic constituents, in the second step the constituents
identified in the initial screening are evaluated to determine whether they are CCB-derived.
As explained in greater detail below, this evaluation indicates that the drinking water pathway for CCBrelated constituents outside of the area of municipal water service is unlikely to be complete.
6.4.2.1 Risk-Based Screening
Analytical data for all of the private wells and monitoring wells located outside the area receiving
municipal water have been compared to health risk-based screening levels. Based on conversations
with USEPA, the screening for groundwater is conducted using the USEPA RSLs for tapwater
(USEPA, 2011b). As noted in the previous section, RSLs are risk-based concentrations in various
-6
media, including tapwater, corresponding to a target cancer risk level of 1x10 and a target
noncarcinogenic HQ of one. Although not required by the USEPA-approved HHRA Work Plan
(ENSR, 2005d), based on conversations with USEPA, RSLs for noncarcinogens were adjusted in the
screening process by a factor of 0.1 (i.e., an HQ of 0.1) to account for potential cumulative effects.
For comparison purposes, the available federal drinking water standards (MCLs) (USEPA, 2011a) are
also provided. The screen for private wells is presented in Table 6-83, and the screen for monitoring
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wells is presented in Table 6-84. The screening results are presented below for private wells and for
monitoring wells.
Private Well Screening Results
For the majority of the private wells sampled, four rounds of samples were collected at each well. The
results of the screening for the private well data are presented in Table 6-83. Both the tap water RSLs
and the adjusted tap water RSLs (i.e., adjusted to a target HQ of 0.1) are presented. Constituent
concentrations greater than the adjusted RSL are highlighted in blue. None of the private well
constituent concentrations are greater than the unadjusted RSLs. Table 6-83 also presents the
available MCLs (USEPA, 2011a). None of the constituent concentrations in private wells are above
the MCLs. Concentrations above the adjusted RSLs are discussed further below.
One of the private wells, PW003 located on West Dunes Highway, had no constituent concentrations
greater than the adjusted RSLs. In the remaining private wells, one or more of only three constituents
were detected in one or more samples at levels above the adjusted RSLs; these are barium (Ba), iron
(Fe), and manganese (Mn). As noted above, the purposes of the RI/FS include determining the
nature and extent of constituents related to CCBs at or from the Area of Investigation, and determining
whether there are significant human health risks in the Area of Investigation associated with exposure
to CCBs. All of the constituents associated with CCBs are naturally occurring inorganic constituents
(e.g., metals and salts), most of which are have been shown to be present naturally in the
environmental media tested during the RI. Therefore, for the purposes of the RI, the occurrence of
Ba, Fe, and Mn in the private wells is significant only if they are present as the result of CCBs.
The purpose of screening using adjusted RSLs (i.e., adjusting RSLs based on noncarcinogenic effects
by a factor of 0.1) is to account for potential cumulative effects. For the noncarcinogenic risk
assessment, noncarcinogenic risks are additive only on a similar target endpoint basis. As provided in
the notes for Table 6-83, the target endpoints are not the same and are, therefore, not additive for Ba
(kidney), Fe (gastrointestinal), and Mn (nervous system). So use of the unadjusted RSLs to evaluate
these constituents is appropriate. As noted previously, none of the concentrations reported on
Table 6-83 are above the unadjusted RSLs. Therefore, these private well concentrations do not pose
a health risk to the users, as shown using the cumulative risk screening method in Section 6.4.1.
Neither boron (B) nor molybdenum (Mo), notable constituents of CCBs and identified as CCB
indicators in groundwater in the RI, was present in any sample from any private well at a level above
the adjusted RSLs.
Monitoring Well Screening Results
The results of the screening of the monitoring well data for wells located outside the area of municipal
water service are presented in Table 6-84. Both the tapwater RSLs and the adjusted tapwater RSLs
(i.e., adjusted to a target HQ of 0.1) are presented, as well as the available federal drinking water
standards.
There were no constituents detected above adjusted RSLs in the background well MW119, or in the
two wells located to the west of the municipal water service area, MW116 and MW124.
In the remaining background wells, constituents present above the adjusted RSL, but below the
unadjusted RSL were Mn in MW121 and Fe and Mn in MW113, and there was one occurrence of
arsenic (As) above the unadjusted RSL, but below the federal drinking water standard in MW120.
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In two wells located south of the municipal water service area, MW114 and MW115, Fe and Mn were
present above the adjusted RSL, but below the unadjusted RSL.
In two wells located in wetland areas at or downgradient of CCB deposits, MW111 and MW122,
concentrations of As, B, Fe, Mn, Mo, and/or thallium (Tl) were present at concentrations in at least one
sample above either an unadjusted or adjusted RSL.
The results of the screening of these wells are discussed in more detail below by area.
6.4.2.2 Evaluation of Drinking Water Pathway Completeness
The maps in Figures 15 and 17 show the municipal water service area, and the remaining portion of
the Area of Investigation where municipal water is not available. The areas within the Pines Area of
Investigation that are not currently served by municipal water fall into different groups based on
geographic location and other factors. The completeness of the drinking water pathway in each of
these areas is discussed below.
In addition to the screening results, the groundwater chemistry in each of these areas is also
evaluated. As discussed in the RI Report, and for the purposes of this discussion, elevated levels of B
and sulfate (SO4) are used as indicators of CCBs, but both constituents are also present naturally in
groundwater at lower levels than in CCB-impacted groundwater. (See Section 4.4.5 of the RI Report
for a more detailed discussion of CCB indicator conditions in groundwater.) In addition, Fe and Mn
are present above the adjusted screening level in the majority of wells located outside of the area of
municipal water service. Figures 18 through 21 visually demonstrate the similarities and differences in
constituent concentrations among wells, incorporating their geographic location. For each well, a bar
graph has been prepared that presents the concentrations of B and SO4 (CCB indicators, shown in
green) and Fe and Mn (constituents present above adjusted screening levels in some of the
groundwater, shown in blue). The concentrations of B, Fe, and Mn are shown in mg/L; the
concentration of SO4 has been divided by 100 to transform it to a scale consistent with the other
parameters. These graphs are intended to provide a visual pattern of chemistry, similar to the radial
plots or other figures developed for the RI Report. Figures 18 through 21 present this information for
the August 2006 (first quarter), October 2006 (second quarter), January 2007 (third quarter), and April
2007 (fourth quarter) sampling rounds. Data from the April 2007 sampling round are not available for
the deep aquifer wells PW009, PW012, and PW013, as monitoring was discontinued at these
locations prior to the last round of sampling (see section on wells screened in deeper aquifer below).
The bar graphs are also presented in Appendix B, grouped by individual well.
CCB-Impacted Wells
To provide context for the discussions below, it is first necessary to understand the chemistry of CCBimpacted wells. Bar graphs for most of the wells downgradient of Yard 520 are depicted in the upper
portion of Figures 18 through 21. These graphs show that in all of these wells, concentrations of B
and SO4 are relatively high. This is a pattern that indicates impacts due to CCBs. In some of the
wells, but not all of them, Fe and/or Mn are also elevated (the blue bars). As discussed in the RI
Report (Section 4.4.4), this pattern of occurrence of Fe and Mn is not necessarily associated with
CCBs, but is likely related to redox conditions in the groundwater (for example MW122 is located in a
wetland area). Figure 22 shows the relationship between redox and both Fe and Mn. Generally,
where redox shows aerobic conditions, concentrations of Fe and Mn are relatively low. For Fe, this
transition occurs above an oxidation reduction potential (ORP) of approximately 0 mV; for Mn, above
approximately 50 mV except for at well TW-18D which doesn’t follow this pattern.
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To the east within the Area of Investigation are shown three additional wells (MW106, MW109, and
MW111) that are also impacted by CCBs. CCBs were encountered when drilling each of these wells.
Again, B and SO4 are elevated in these wells. The elevated Fe present in MW109 and MW111 is
likely associated with redox conditions; both of these wells are located in/near wetland areas and ORP
ranges from -139.5 to -89.2 mV at MW109 and -113.7 to -91.2 mV at MW111. In contrast, other wells
that are impacted by CCB-derived constituents do not contain elevated iron, for example, MW106 to
the west, and MW-6 and MW-8 located downgradient from Yard 520. Therefore, the iron and
manganese are likely not due solely to CCB impacts, but rather are associated with local redox
conditions as described in more detail in the RI Report (see Section 5.2). Figure 23 presents the
outline of estimated boron concentrations in groundwater above the risk-based adjusted and
unadjusted RSL. Also plotted on this figure are the monitoring well and private well results for Fe, with
the wells color coded based on the risk-based adjusted and unadjusted RSLs for Fe. As can be seen
from the figure, areas of higher Fe concentrations are not co-located with areas of higher B
concentrations. This further demonstrates that elevated Fe concentrations are not necessarily
associated with CCB impacts.
Background Wells
The RI included installation of monitoring wells that represent upgradient/background conditions,
unaffected by CCB-related constituents. Three of the monitoring wells installed for this purpose are
MW119, MW120, and MW121, shown in green on the map in Figures 15 and 17. MW119 and
MW120 are located to the west outside the Area of Investigation; MW120 is located within Indiana
Dunes National Lakeshore. MW121 is located near the eastern edge of the Area of Investigation. As
described in the RI Report, based on the observed water chemistry and the groundwater flow system,
none of these wells is impacted by CCB-related constituents. The RI also showed that monitoring well
MW113, located near the southern end of the Area of Investigation (see Figure 15), is also a
representative upgradient/background well. It is located upgradient of the Area of Investigation, and
suspected CCBs have not been identified in the vicinity or upgradient from the well. Boron
concentrations in these wells, which represent background conditions unaffected by CCB-related
constituents, ranged from 0.019 to 0.119 mg/L.
No COPCs were identified in the background wells based on the cumulative screen presented in
Section 6.4.1.1. There were no constituents detected above screening levels in the background well
MW119 under the direct screen shown on Table 6-84. In the remaining background wells,
constituents present above the adjusted RSL, but below the unadjusted RSL, were Mn in MW121 and
Fe and Mn in MW113. In addition, there was one occurrence of arsenic (As) above the unadjusted
RSL, but below the federal drinking water standard in MW120.
As shown on Figures 18 through 21, the background wells to the west and southeast are relatively low
in concentrations of all four parameters. MW113 to the south has elevated Fe, as shown by the blue
bar on the each of the graphs. The low B and SO4 in this well (along with other data presented in
detail in Section 4.4.1 of the RI Report) show that it is not likely impacted by CCBs. Therefore, these
Fe concentrations (ranging from 4.1 to 11.7 mg/L) are representative of a background condition. The
source of the Fe in this well is due to local geochemical conditions (redox); anaerobic conditions in the
groundwater are causing naturally-occurring iron in the surficial aquifer sands to be dissolved in
groundwater. There are many possible causes of the anaerobic conditions, including the presence of
wetlands or other organic soils, discharges from septic systems, and local land use which could
restrict infiltration of oxygen-bearing rainwater, etc. In the vicinity of MW113 in particular, the nearby
Pines Landfill (owned by Waste Management) could be reducing the amount of rainwater infiltration in
the area and/or adding an organic carbon source to the groundwater, both of which would contribute
to general reduction in oxygen in the groundwater. In addition, the surficial aquifer thins in this area
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and pinches out to the south. It is possible there is a greater relative contribution from upgradient
and/or deeper aquifers through the Valparaiso Moraine and/or lacustrine sediments, where the
groundwater is likely to be older and thus depleted in oxygen.
Wells Screened in Deeper (Confined) Aquifer(s)
A portion of the Area of Investigation that extends southward, including areas on the south end of
Ardendale Road, on Old Chicago Road, and on County Road E 1675N, is referred to as the “southern
portion” of the Area of Investigation. The southern portion was included within the Area of
Investigation because USEPA’s sampling of private wells in this area indicated B and/or Mo were
present at concentrations near or above the screening levels used by USEPA (see Section 1.3.1 of
the RI Report). However, USGS regional geologic information indicated that the sands of the surficial
aquifer in the southern portion pinch out against the lower permeability silts and clays of the
Valparaiso Moraine/lacustrine sediments, such that the surficial aquifer is either thin or absent. In
addition, wells screened in the deeper, confined aquifers in northwest Indiana were shown by the
USGS to have naturally higher concentrations of B and Mo (Buszka, et al., 2007). The southern
portion was evaluated as part of the RI, and as discussed in detail in Section 3.4.5 of the RI Report,
the following conclusions were made:
•
Based on the geologic information from multiple sources, the surficial aquifer pinches out to
the south. In the southern portion of the Area of Investigation, it is either not present, or
where present, has a limited saturated thickness and thus does not provide a sufficient source
of drinking water.
•
Based on geologic, well construction, and chemical data, private wells located in this area are
screened in the deeper confined aquifer(s).
•
The results of the suspected CCB visual inspections in the Pines Area of Investigation
showed no evidence of CCBs located in this area (see Section 3.7.2 of the RI Report).
Three private wells (PW009, PW012 and PW013) located in this southern portion of the Area of
Investigation were sampled during the RI. These are shown in red on Figures 15 and 17. Tritium
data and other results discussed in the RI Report (see Section 4.4.4), demonstrate that the private
wells PW009, PW012, and PW013 are all screened in the deep aquifer, and are not affected by
CCBs. Because of the findings of the evaluation, USEPA approved discontinuing sampling of these
wells after January 2007, and bottled water was discontinued in this area after November 2007. The
graphs for these three deep wells (Figures 18 though 21) show low concentrations of B and SO4, but
elevated concentrations of Fe. The levels of Fe (0.4 – 2.9 mg/L) and Mn (0.02 – 0.45 mg/L) in these
wells, which are above the adjusted RSLs (but not above the unadjusted RSLs), are representative of
the background/natural conditions of the deep aquifer, and not related to CCBs. Furthermore, no
COPCs were identified in these wells in the cumulative screen presented in Section 6.4.1.1.
Therefore, the drinking water pathway is not complete for CCB-related constituents in the southern
portions because the surficial aquifer is thin or non-existent and private wells are screened in the
deeper, confined aquifers.
Western Corner
West of the municipal water service area, there is a small area along Pine St., Poplar St., a portion of
West Dunes Highway, and a portion of US Highway 20 where the water service has not been
extended. Sampling locations representative of this area include MW116, PW003, and MW124, as
shown on the map in Figures 15 and 17. As shown on Tables 6-83 and 6-84, there are no
parameters in these wells that exceed the adjusted RSLs. In addition, the concentrations of CCB
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indicator constituents in these wells (B, SO4, etc.) are low and consistent with background. The
maximum concentration of B in any of these wells is 0.128 mg/L, well below the adjusted RSL of
0.730 mg/L. Therefore, the drinking water pathway for CCB-related constituents is not likely to be
complete in the western corner.
Wetland Areas
Wetlands are common in the Area of Investigation, consistent with the dune and swale topography of
the Lake Michigan lakeshore. Figure 24 presents the National Wetland Inventory (NWI) map
(USFWS, 2011) for this area overlain on the Area of Investigation (note that the overlay is
approximate). In the preparation of the NWI maps, these wetland areas have been identified via
aerial photos, but have not been officially surveyed on the ground. The IDNL Great Marsh figures
prominently on this map. Notably, wetland areas are identified in the vicinity of MW111 on the east
branch of Brown Ditch, and in the vicinity of MW122, located between Yard 520 and the West Branch
of Brown Ditch. As additional information, Appendix P provides the Flood Insurance Rate Maps for
this area of Porter County, Indiana. These maps are prepared by the National Flood Insurance
Program under the Federal Emergency Management Agency. Taken together, these maps identify
much of the area on both sides of the east and west branches of Brown Ditch as located within the
100-year flood plain. An official wetland delineation has been conducted in the vicinity of MW122; this
report is included as Appendix Q.
Wetland areas within the Area of Investigation include the low-lying areas just south of the municipal
water service area along the East and West Branch of Brown Ditch where there are currently no
homes or other development. Two wells are located in these wetland areas at or downgradient of
CCB deposits, MW111 and MW122 (shown in orange on Figures 15 and 17). B, Fe, Mn, As, Tl,
and/or Mo are present in these wells at concentrations in at least one sample above a screening level
(either adjusted or unadjusted) (see Table 6-84), and several COPCs are identified in each well under
the cumulative screen presented in Section 6.4.1.1. In certain portions of these areas, groundwater is
impacted by CCB-related constituents, as represented by elevated concentrations of B and SO4 in
wells MW122 and MW111 (see Figures 18 though 21). The interpreted distribution of elevated B is
shown on the map in Figure 23. Outside the municipal water service area, all areas where B
concentrations are elevated are within wetland areas. While it is not likely that these areas would be
developed in the future, such development cannot be ruled out entirely. Therefore, although
CCB-related constituents are present in groundwater, there is no currently no complete pathway to
drinking water receptors in the wetland areas.
South Railroad Avenue
There are three private wells (PW006, PW007, PW008) located on South Railroad Ave and one
monitoring well (MW115), see Figure 15. The RI Report shows there is no hydraulic connection
between Yard 520 and this area, that is, groundwater cannot flow from Yard 520 to reach these wells.
Specifically, continuous water level monitoring has shown that the groundwater hydraulic heads
(water levels) on the south side of Brown Ditch are always higher than the heads in the ditch.
Therefore, there is always a gradient from the south to Brown Ditch. Thus, groundwater flowing from
Yard 520 cannot migrate any further south than the ditch itself (see Section 3.6 of the RI Report).
The concentration of B in all of these wells does not exceed the adjusted RSL of 0.730 mg/L.
However, in some of the sampling locations in this area, concentrations of Ba, Fe and/or Mn are
elevated above the adjusted RSLs. In addition to the lack of hydraulic connection, the following data
show that the elevated concentrations in these wells are not likely to be due to CCB impacts:
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•
No suspected CCBs have been identified at locations upgradient from these wells (that is, to
the south), based on the results of the visual inspection of roadways and adjacent properties
conducted throughout the Area of Investigation (see Figure 17).
•
The chemistry of the groundwater samples in these wells is not consistent with the pattern
expected from CCB impacts, that is, B and SO4 are not both elevated. Boron concentrations
are relatively low, and the SO4 concentrations in some of these wells are lower than
background, rather than being elevated as would be expected if they represented CCB
impacts.
•
The chemistry of the groundwater samples in PW007, PW008, and MW115 is consistent with
the pattern expected from municipal landfill leachate, that is, chloride (Cl), ammonia (NH4),
dissolved organic carbon (DOC), etc., are elevated, as discussed in detail in the RI Report
(Section 4.4.4), a pattern that is not consistent with CCB impacts. In addition, the RI sampling
has shown that the chemistry in these wells is distinct from other wells sampled. The most
likely reason for this difference is that they are impacted by leachate from the Pines Landfill
(owned by Waste Management), which is located upgradient. Specific indications of this
conclusion are discussed in detail in Section 4.4.4 of the RI Report.
•
Note that B was present in PW007 and PW008, and in MW115 at concentrations higher than
in other private wells. As discussed in the RI Report (Section 4.4.4) and above, these wells
are located downgradient of the Pines Landfill (owned by Waste Management). The
chemistry (including B concentrations) in these wells is consistent with the chemistry in at
least one Pines Landfill monitoring well, located upgradient of these private wells and
downgradient of the Pines Landfill. Thus, it is likely that the B detected in these wells
originates from the Pines Landfill (owned by Waste Management). As shown on Figure 17,
the visual inspection did not indicate suspected CCBs in the immediate vicinity of these
private wells. Suspected CCBs are present on Railroad Ave., which is downgradient from
these wells, suggesting that their presence would not likely impact the upgradient private
wells.
Based on the RI investigations, the wells along South Railroad Ave. are not likely impacted by CCBs.
The Ba, Fe and Mn in these wells originate from upgradient conditions, including the Pines Landfill
(owned by Waste Management). Furthermore, no COPCs were identified in these wells in the
cumulative screen presented in Section 6.4.1.1. Therefore, the drinking water pathway associated
with CCB-related constituents is not likely complete along South Railroad Ave. The pattern of
occurrence of CCB-related constituents (B, SO4) compared to Fe and Mn, supporting this conclusion,
is shown on Figures 18 through 21.
Ardendale Ave.
The municipal water service along Ardendale Ave. does not extend south of US Highway 20.
Sampling locations along Ardendale outside the municipal water service area include MW114 and
PW010 (see Figures 15 and 17). Background location MW113 is located further to the south, and
upgradient, along Ardendale.
The two sampling locations, MW114 and PW010, are located on Ardendale Ave, just north and south
of Railroad Ave, respectively. Given their locations, and the presence of Brown Ditch as a barrier to
groundwater flow as detailed above, there is no possible connection between groundwater in this area
and Yard 520. Suspected CCBs have been identified in this area (see Figure 17). However, there is
no evidence that CCBs were placed in this area as significant fill; more likely CCBs have been used
along roads and as driveway surface material. The RI has shown that smaller amounts of suspected
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CCBs are unlikely to result in elevated levels (above screening levels) of CCB-related constituents in
groundwater. Instead, CCB-related constituents are present above screening levels in groundwater
only in the two areas identified during the RI with substantial deposits, located elsewhere in the Area
of Investigation (see Section 4.4.5 of the RI Report).
The groundwater chemistry in this area is not consistent with CCB-impacted areas. At MW114 and
PW010, the maximum concentration of B was 0.166 mg/L. This is well below the adjusted RSL of
0.730 mg/L. In both MW114 and PW010, Fe and Mn were detected above the adjusted RSLs, but
below the unadjusted RSLs. However, the chemistry of these wells is not consistent with the pattern
expected due to CCBs. Concentrations of both B and SO4 are similar to background (maximum B =
0.166 mg/L; maximum SO4 = 33.1 mg/L) and well below the adjusted RSL for B. The concentrations
of Fe and Mn are also consistent with background relative to background well MW113 located
upgradient from PW010 and MW114.
Parameter
B
SO4
Fe
Mn
Concentration at MW114
(mg/L)
0.112 – 0.165
2.85 – 9.27
2.69 – 3.57
0.172 – 0.233
Concentration at PW010
(mg/L)
0.106 – 0.166
23.4 – 33.1
1.19 – 5.58
0.0229 – 0.481
Concentration at MW113
(mg/L)
0.091 – 0.106
27.7 – 43.2
4.07 – 11.7
0.208 – 0.262
These data show that CCB-related constituents are not elevated in PW010 or MW114, and that the
Fe and Mn are related to background conditions in this area, discussed in more detail above.
Furthermore, no COPCs were identified in these wells in the cumulative screen. Therefore, the
drinking water pathway along Ardendale is not considered to be complete for CCB-related
constituents.
USEPA’s testing of the private well at 1693 Ardendale Ave. in 2003 reported a B concentration in this
shallow well of 1.95 mg/L. This concentration is above the adjusted RSL but well below the
unadjusted RSL for B of 7.3 mg/L. Iron was present at 7.68 mg/L and Mn was present at 0.455 mg/L,
consistent with the data presented for MW114, PW010, and MW113. Also, the concentration of Mo,
an indicator of CCBs, in this well was also low at 0.006 mg/L. This single B result in 2003 seems
anomalous compared to PW010 in the immediate vicinity and which consistently over a period of a
year (2006 – 2007) exhibited low B concentrations.
East Railroad Ave.
There are several homes along this road not connected to the municipal water service. There is one
sampling location, PW005, shown on Figures 15 and 17. Boron concentrations in this well ranged
from 0.151 to 0.174 mg/L, well below the adjusted RSL of 0.730 mg/L. The concentration of Mn in this
well is above the adjusted RSL (see Table 6-83), but is below the unadjusted RSL. As discussed
above, the Mn represents a background condition throughout much of this area, and does not
represent CCB-related impacts. Furthermore, no COPCs were identified in these wells in the
cumulative screen presented in Section 6.4.1.1. Therefore, the drinking water pathway for CCBrelated constituents is not likely complete in along East Railroad Ave.
6.4.2.3 CCB Impact Conclusions
Based on this evaluation for areas not served by municipal water, the drinking water pathway is not
likely complete for CCB-related constituents, as summarized below.
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There are only two wells (MW111 and MW122) where concentrations of B exceed adjusted RSLs.
The chemistry of these wells indicates CCB-related impacts. MW111 is adjacent to an area of CCB
fill, and MW122 is downgradient of Yard 520. Both of these monitoring wells are located in and
represent wetland areas (see Figure 24) that are currently undeveloped, and not likely to be
developed in the future due to the wetland conditions, though such development cannot be precluded.
In none of the other areas does the concentration of B exceed the adjusted RSLs. Therefore, none of
these are identified in the risk assessment screening process for further evaluation.
Concentrations of other parameters (Ba, Fe, and/or Mn) are above adjusted RSLs in some locations,
and this review has shown that they are not likely impacted by CCBs. These levels are associated
with other upgradient/background conditions and not with CCB impacts. In addition, these parameters
are present at concentrations appropriate for tapwater use, and none are present at concentrations
greater than federal drinking water standards.
Although the RI covered a 3.5-year period, the CCBs have been in place at Yard 520 and in the Area
of Investigation for several decades. Review of the groundwater elevation contours and the
constituent data over the course of the RI, as presented in the RI Report, indicates that the constituent
distribution in groundwater is largely controlled by the groundwater hydraulic gradients (direction of
groundwater flow) and location relative to Brown Ditch, and there is no indication of dramatic changes
in the gradients across the seasons sampled during the RI. Moreover, additional water level
measurements collected voluntarily by the Respondents upon the conclusion of the RI (5 rounds
between 2008 and 2011) indicate no significant changes have occurred during that time. Based on
the information provided in the RI Report, groundwater flow is not expected to change significantly in
the future in the absence of major unforeseen changes. Therefore, while the groundwater data used
in the HHRA is representative of the time period over which it was collected, there is no information
that would suggest that these conditions would change dramatically in the future, though this remains
a source of uncertainty in the risk assessment.
6.4.3
Drinking Water Pathway Evaluation Conclusions
The cumulative risk assessment shows that potential risks associated with both background and
private wells in the Area of Investigation are below or within USEPA target risk levels for both
potentially carcinogenic and noncarcinogenic effects. Potential risks were identified for several
monitoring wells including MW111 and MW122 located outside the municipal water service area in
wetland areas (unlikely to be developed though such development in the future cannot be precluded),
MW104 located within the municipal water service area, and the following wells surrounding Yard 520,
within the municipal water service area:
•
MW-3
•
MW-6
•
MW-8
•
MW-10
•
TW-12
•
TW-15D
•
TW-16D
•
TW-18D
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With the exception of the wells listed above, wells within the municipal water service area do not
appear to be significantly impacted by CCBs. With the exception of MW111 and MW122, wells
outside of the municipal water service area do not appear to be impacted by CCBs or the
concentrations are so low as to be insignificant. Because the potential risks were identified either in
areas that are unlikely to be developed or in an area served by municipal water, the drinking water
pathway is currently incomplete. Groundwater in these areas is unlikely to be used for drinking water
in the future, though future use cannot be precluded.
The cumulative risk assessment was conducted using residential screening levels and is therefore
protective of other potential drinking water scenarios (e.g., a visitor to the area). Analytical data for
private wells and RI monitoring wells were compared to RSLs using a cumulative screening approach.
A cumulative screen is in essence a risk assessment in which potential risks and hazards are
calculated based on default screening levels.
In a cumulative risk screen, RSLs are used to estimate the potential carcinogenic risk and
noncarcinogenic hazard associated with detected concentrations; therefore, the RSLs for
noncarcinogens do not need to be adjusted to account for cumulative effects because the potential
HQ for each constituent is calculated directly in order to quantify potential cumulative effects.
The RSLs incorporate agency default, conservative exposure assumptions as well as agency selected
toxicity values. Thus, the potential risks and hazards estimated using the RSLs are conservative and
are likely overestimates of potential risks and hazards.
The evaluation of the drinking water pathway was conducted in two parts, as presented above. First,
a cumulative screening approach was used to identify constituents above regulatory targets in each
-6
well for which RI data were collected. No constituents with risks greater than 10 or a total endpointspecific HI greater than one were identified in any private well. No constituents with risks greater than
-4
10 or a total endpoint-specific HI greater than one were identified in any background well. Arsenic
-5
was identified in background well MW120 with a potential risk greater than 10 . Within the municipal
-4
water service area, constituents with risks greater than 10 or a total endpoint specific HI greater
than 1 were identified only in monitoring wells in the immediate vicinity of Yard 520 (MW-3, MW-6,
-5
MW-8, TW-10, TW-12, TW-15D, TW-16D, and TW-18D). Potential risks above 10 were identified for
arsenic in MW104, within the municipal water service area; however, the chemistry of this well is not
consistent with CCB impacts. In addition, outside of the municipal water service extension,
-4
constituents with potential risks greater than 10 and a total endpoint specific HI greater than one
were identified for MW111 and MW122, which are in the limited wetland areas bordering Brown Ditch
and downgradient of significant deposits of CCBs. These wells are shown in Figure 16. Based on the
location of the few wells for which constituents above regulatory targets were identified, it was
concluded that no further risk assessment of the drinking water pathway is warranted.
One objective of the RI is to evaluate CCB-derived constituents. Therefore, the drinking water
pathway would not be complete if wells are not likely impacted by CCBs, or for which COPCs are not
identified. This analysis was conducted to determine whether wells outside the municipal water
service area are potentially impacted by CCBs. Based on that analysis, while the presence of CCBderived constituents cannot be entirely ruled out for some wells outside of the municipal water service
area, the fact that the concentrations of constituents that may be CCB-derived are so low as to not be
identified as COPCs indicates that if this pathway is complete, it is insignificant. Therefore, the
drinking water pathway for exposure to CCB-derived constituents in the area outside the municipal
water service area is likely incomplete, with the exception of MW111 and MW122. These two wells
are located in limited wetland areas (see Figure 24) that are unlikely to be developed though such
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development in the future cannot be precluded, but they are in areas that could easily be provided
municipal water if developed in the future.
Similarly, the drinking water pathway inside the area of the municipal water service may be complete
only where locations have not been connected to municipal water and where wells are screened in the
shallow surficial aquifer, and only in those areas in the immediate vicinity of Yard 520 where COPCs
have been identified. Thus, use of groundwater as drinking water outside of the immediate vicinity of
Yard 520, whether within or outside of the municipal water service area would not pose a health risk to
residents based on these results.
6.5
Unc e rta inty Eva lua tio n
Within any of the four steps of the human health risk assessment process, assumptions must be
made due to a lack of absolute scientific knowledge. Some of the assumptions are supported by
considerable scientific evidence, while others have less support. Every assumption introduces some
degree of uncertainty into the risk assessment process. Regulatory risk assessment methodology
requires that conservative assumptions be made throughout the risk assessment to ensure that public
health is protected. Therefore, when all of the assumptions are combined, it is much more likely that
risks are overestimated rather than underestimated.
The assumptions that introduce the greatest amount of uncertainty in this risk assessment are
discussed in this section. They are discussed in qualitative terms, because for most of the
assumptions there is not enough information to assign a numerical value to the uncertainty that can
be factored into the calculation of risk.
6.5.1
Selection of Constituents of Potential Concern
The analytical data collected during the RI serve as the basis for the risk assessment. As noted in
Section 3.1, numerous samples were collected from a wide variety of environmental media within and
around the Area of Investigation. While not every location was sampled, the sampling program is very
representative of the conditions within the Area of Investigation. Section 6.5.3.2 provides more
discussion of the CCB sampling results.
In the Hazard Identification step, information on the concentrations of constituents detected at the
Area of Investigation is compared to levels in environmental media, calculated to account for
conservative exposure scenarios and constituent-specific toxicity estimates, to obtain a subset of
constituents for quantitative evaluation in the risk assessment, the COPCs. The goal is to include in
the quantitative portion of the risk assessment those constituents that may pose a risk under the
scenarios evaluated. The selection of the COPCs forms the basis of the quantitative risk assessment.
6.5.1.1 Analytical Program
Generally in the site characterization phase of the site assessment, knowledge of past and current
land use is used to determine which analytical parameters are analyzed and what analytical methods
are employed for the detection of constituents in the relevant environmental media.
A comprehensive list of inorganics was included in the RI analytical program, and the inorganics were
selected because of knowledge about what may be present in CCBs, the results of the MWSE
suspected CCB sampling, information needed for general data interpretation, and due to previous
sampling by USEPA for boron and molybdenum in groundwater. Therefore, it is unlikely that
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significant quantities of constituents not on the analyte list would contribute to potential risks in the
Area of Investigation. Specific analytes are addressed below.
PAHs and Dioxins
During the RI process, data were gathered to ensure that potentially CCB-related constituents were
included in the investigation process. Data from an investigation of Yard 520, where CCBs were
disposed of, indicated that PAHs and dioxin constituents are not present in the CCB materials present
in Yard 520 at concentrations above human health screening levels (AECOM, 2010b). USEPA
concurred with this conclusion and PAHs and dioxins were eliminated from further consideration
during the RI. Because the concentrations were so low and below screening levels, the impact of
their exclusion from the quantitative risk assessment is insignificant. These samples were collected
from the South Area of Yard 520 to determine whether PAHs and dioxin constituents should be
included in the analytical program for suspected CCBs collected outside of Yard 520; these samples
were not intended to be used in the risk assessment as they were collected from areas that are not
accessible for direct contact, i.e., within a closed and capped landfill (see Appendix O for detailed
information on the cap construction and the inspection and maintenance program). Therefore, metals
data were not collected for these samples; metals data are available for the CCBs collected outside of
Yard 520. Because these samples are from locations that represent potential exposure within the
Area of Investigation, it is these data from these samples that are used in the risk assessment.
Based on field investigations conducted within the Area of Investigation, the material present in the
Type III (South) Area of Yard 520 is fly ash, while the suspected CCBs encountered in the MWSE are
composed primarily of bottom ash/boiler slag. The analytical results for radionuclides in fly ash
samples from the Type III (South) Area of Yard 520 indicate higher activity than do the samples of ash
material collected from the MWSE project. This suggests that data from the Yard 520 samples are
appropriate for conservatively estimating the activity of these constituents. Also, the (limited) metals
data obtained at the Type II (North) Area of Yard 520 from primarily fly ash (although other materials
are present), indicate higher concentrations than the samples collected from the MWSE project—
suggesting that data from Yard 520 samples also are appropriate for conservatively estimating
constituent concentrations. These differences in inorganic content between the fly ash samples in
Yard 520 and the predominantly bottom ash/boiler slag in the utility trenches are consistent with a
summary report prepared by the Electric Power Research Institute (EPRI) entitled “Comparison of
Coal Combustion Products to Other Common Materials – Chemical Characteristics” (EPRI Technical
Report No. 1020556, 2010, available for download at www.epri.com). Paralleling these results, and
based on the formation processes of the different types of CCBs (see Sections 5.3.1.1 and 5.3.1.3 of
the Site Management Strategy [SMS], dated 2005, included as part of the Remedial Investigation
[ENSR 2005a]), it can be concluded that the dioxin/PAH concentrations in the Yard 520 samples are
‘worst case,’ or at least representative of what may be present in the MWSE samples.
Hexavalent Chromium
Similarly, a subset of suspected CCB samples were analyzed for hexavalent chromium early in the
MWSE sampling program to determine if all samples should be analyzed for hexavalent chromium. It
was analyzed in 12 samples and detected in 11 samples. The sample concentrations were well
below human health risk-based screening levels current at the time, therefore USEPA concurred that
no further sampling for hexavalent chromium was necessary. Moreover, total chromium was not
detected in any groundwater or surface water samples collected. Additional discussion of hexavalent
chromium is provided in Section 6.5.2.
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Groundwater and surface water samples were analyzed for chromium (total); all results were
nondetect for chromium (total). However, no groundwater and surface water samples were analyzed
for hexavalent chromium. The maximum reporting limit of 10 micrograms per liter (ug/L) is more than
two orders of magnitude higher than the tapwater RSL for hexavalent chromium of 3.1E-02 ug/L. At
the time the RI samples were collected (2006/2007) the tap water screening level for hexavalent
chromium was 110 ug/L and the MCL for total chromium was 100 ug/L, thus the reporting limits were
appropriate for that time period. Therefore, the fact that chromium (total) was not detected in any
groundwater and surface water samples at a maximum reporting limit of 10 ug/L is insufficient to
prove absence of hexavalent chromium in these samples. Hexavalent chromium is more water
soluble than trivalent chromium, and so may occur in groundwater and surface water potentially
impacted by CCBs. However, it should be noted that hexavalent chromium is a strong oxidizer and is
expected to readily react with available organic compounds and reducing agents such as ferrous iron,
and transform from hexavalent to trivalent chromium. Absence of hexavalent chromium in analytical
results from the site groundwater and surface water samples is a data gap expected to bias low the
risk assessment results. However, the magnitude of any underestimation is expected to be low to
moderate based on the expected transformation of any hexavalent chromium to trivalent chromium
and the limited potential (in surface water) for exposure.
Mercury
Mercury was analyzed and detected in 31 of 34 MWSE samples. The maximum detected
concentration of 0.06 mg/kg is well below the adjusted RSL of 2.3 mg/kg. Therefore, because
mercury is not a major component of suspected CCBs, further analysis was not considered
necessary.
Cobalt
Cobalt was analyzed in suspected CCBs and background soil, but was not included as an analyte for
the remaining media addressed in the approved RI/FS Work Plan (ENSR, 2005d). All samples with
concentrations of about 10 mg/kg or greater of cobalt (or detection limits above 10), are of organic
soils with moisture content greater than 50%. Therefore, “elevated” concentrations (or detection
limits) of cobalt appear to be associated with organic soils and in particular, with the dry-weight to wetweight correction used by the laboratory to report wet-weight concentrations. Cobalt was detected at
a higher concentration in the background soil sample than in the MWSE samples. If cobalt was
identified as a COPC in background soil (rather than screening it out based on frequency of detection,
see below), the background hazard quotient for cobalt would be greater than the MWSE hazard
quotient for cobalt, showing that potential risks from CCBs are similar to potential background risks.
Strontium
Strontium was added to the project analyte list I the RI/FS Work Plan; it was not included as an
analyte in the MWSE sampling program. While the lack of data presents and uncertainty, it was
present in all other media at concentrations below screening levels, therefore, it is unlikely that
additional data for CCBs would have identified it as either a COPC or a risk-driver.
Silica
CCB samples were analyzed for silicon but not for silica. USEPA does not have a screening level for
silicon, however, the RSL table (USEPA, 2011b) does provide a screening level for silica in residential
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soil that is over one million parts per million. Therefore, the lack of data for silica in this risk
assessment does not significantly affect the risk assessment results.
6.5.1.2 Constituent Screening
A subset of constituents detected in a study area is generally selected for quantitative analysis for
several reasons (USEPA, 1993a). All of the constituents associated with CCBs are naturally
occurring inorganic constituents (e.g., metals and salts), most of which have been shown to be
present naturally in the environmental media tested during the RI. Thus, for the Pines Area of
Investigation, some constituents detected may be naturally occurring and their presence not related to
CCBs. Other constituents may be present at concentrations that can be assumed with reasonable
assurance not to pose a risk to human health. A review of the results of risk assessments
demonstrate that in most cases risks are attributable only to one or a few constituents, and that many
of the constituents quantitatively evaluated do not contribute significantly to total risk estimates
(USEPA, 1993a). The screening process is conducted to identify the COPCs that may contribute the
greatest to potential risk. The screening process used here is conservative. Although the excluded
constituents may pose some level of risk, that risk would contribute negligibly to the total risk.
Therefore, not quantitatively evaluating the excluded constituents will not measurably affect the
numerical estimates of hazard or risk and, thus, not affect remedial decision-making. The screening
process used for the Area of Investigation included a frequency of detection screen, a comparison to
screening levels, a background evaluation, and a quantitative evaluation of essential nutrients.
Only one constituent was eliminated as a COPC based solely on the frequency of detection screen
(cobalt in background soils). Cobalt was detected at a higher concentration in background soils (23.8
mg/kg) than in suspected CCB samples (maximum detection of 19.5 mg/kg). Cobalt was selected as
a COPC in suspected CCBs because it was detected frequently and was detected above the adjusted
RSL (2.3 mg/kg). If cobalt was identified as a COPC in background soil (rather than screening it out
based on frequency of detection), the background soil hazard quotient would be greater than the
MWSE hazard quotient, showing that potential risks from suspected CCBs are similar to potential
background risks. The cobalt EPC for suspected CCBs is 13.5 mg/kg; with only one detection, the
EPC for cobalt in the background dataset would be 23.8 mg/kg. Therefore, potential risks/hazards
from background soils for cobalt would be 1.76 times higher (23.8 mg/kg divided by 13.5 mg/kg) than
from suspected CCBs, as indicated below for the RME residential receptor:
Cobalt
Potential Carcinogenic Risk
Hazard Quotient
Suspected CCBs
2.89E-09
0.4
Background
5.09E-09
0.7
While arsenic in Brown Ditch surface water was detected infrequently, it was retained as a COPC
based on its carcinogen classification.
For the chemical risk assessment, the comparison to screening levels was conducted using USEPA
RSLs (USEPA, 2011b, 2010d). RSLs for residential soil and tap water are based on a conservative
residential scenario assuming exposure to soils and drinking water for 350 days per year for 30 years.
RSLs for the industrial scenario are also very conservative, assuming exposure to soils for 250 days
per year for 25 years. RSLs for fish tissue (USEPA, 2010d) are also conservative, assuming a
relatively high consumption rate for 350 days per year. The comparison to RSLs was conducted
-6
using a target risk level of 1x10 and a hazard quotient of 0.1. Given the conservative nature of the
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RSLs and the low risk and HQ targets on which they are based, it is unlikely that the eliminated
constituents contribute substantially to cumulative risk.
For the radiological risk assessment, detected radionuclides were grouped according to their decay
series and selected as COPCs using the “+D” or “+daughters” designation and slope factors as
appropriate. Polonium-210 was detected but is included as a COPC as part of the lead-210 decay
chain and was not included as a separate radionuclide in the calculations.
Evaluation of Reporting Limits
When the RI/FS Work Plan (ENSR, 2005d) was developed, human health risk-based screening levels
were used to identify appropriate laboratory methods for chemical analyses, based on the detection
limits achievable for each of the constituents evaluated. However, with environmental samples there
are interferences that can occur from other materials that may be present within the samples, and
these interferences can result in reporting limits that are above the expected detection limits for the
analytical method. For example, the wet nature of sediment samples generally results in higher
reporting limits than for drier solid materials such as soil. The bullets below discuss instances where
reporting limits for constituents reported as not detected are greater than RSLs:
•
In the suspected CCBs and the background soils datasets, although there were some
instances of elevated reporting limits, these were associated with constituents identified as
COPCs through the screening process. It should be noted that the analytical program
(ProUCL) that calculates the EPCs uses a statistical method to include the reporting limits for
constituents reported as not detected in the EPC calculation, so these data have been used in
the risk assessment.
•
In the sediment dataset, the maximum reporting limits for arsenic were above the adjusted
RSL, but arsenic was identified as a COPC in sediment (Brown Ditch, Pond 1, Pond 2) based
on the detected concentrations. Thallium was not detected in any of the sediment samples
and the maximum reporting limit (5.2 mg/kg) is above the residential adjusted RSL (0.078).
Based on the exposure parameters for sediment used in this HHRA, an approximate HQ for
thallium in sediment based on the maximum reporting limit is 0.5 Since total sediment
hazard indices were below 0.5, not identifying thallium as a COPC in sediment has no
significant impact on the results of the risk assessment because the total HI would not exceed
one.
•
For surface water, the maximum reporting limits for arsenic and thallium are above their
respective adjusted RSLs but below the MCLs. Similarly, the maximum reporting limit for
vanadium exceeds its adjusted RSL (vanadium does not have a MCL). As surface water
does not serve as a source of drinking water these results indicate that the exclusion of
thallium and vanadium from the risk assessment for surface water would have no significant
impact on the risk assessment. Furthermore, arsenic was selected as a COPC in Brown
Ditch surface water (and modeled fish tissue) and potential risks for recreational receptors
-6
were below 1x10 .
•
In groundwater samples, the following constituents reported as not detected had maximum
reporting limits above the adjusted RSLs:
−
Arsenic – the standard laboratory analytical techniques available for arsenic are unable to
achieve a reporting limit at or near the RSL of 0.045 ug/L. Standard arsenic reporting
limits are around 2 ug/L; most reporting limits are between 2-3.6 ug/L. Arsenic is
detected in only a few wells, and it was identified as a COPC in those wells. In the
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remaining wells, the maximum reporting limit is below the MCL of 10 ug/L for arsenic. If
arsenic is present, it could be present at a concentration less, or much less, than the
reporting limit and, therefore, also less than the MCL, thus its exclusion from the risk
assessment should not have a significant effect on the results.
−
Thallium - the standard laboratory analytical techniques available for thallium are unable
to achieve a reporting limit at or near the RSL of 0.037 ug/L. The range of thallium
reporting limits is between 1.4 to 1.9 ug/L, which is below the MCL of 2 ug/L. In five wells,
there was one sample each where one reporting limit was above the MCL. As the
remaining reporting limits were below the MCL, and acknowledging that if thallium is
present, it could be present at a concentration less, or much less, than the reporting limit,
its exclusion from the risk assessment should not have a significant effect on the results.
−
Lithium – Lithium was analyzed in a subset of wells in one round of groundwater sampling
to evaluate its utility as an indicator of CCBs. As an ancillary analyte, lithium was not
included in the list of constituents for which data quality levels were developed for the
QAPP; therefore, the reporting limits for lithium were much higher than the adjusted
screening level. It cannot be determined whether or not lithium would be expected to be
present in these samples, thus the effect that these results may have on the risk
assessment cannot be determined. As noted in Appendix M, USEPA concurred with the
decision not to continue sampling for lithium, once it was shown not to be useful as an
indicator.
Comparison to Background
The background evaluation was conducted following USEPA guidelines using ProUCL
Version 4.00.02. Since the time the background comparison was conducted, a new version of
ProUCL (Version 4.1.01) was released. To determine the potential impact on the background
evaluation, the background evaluation for lead in Brown Ditch sediment and manganese in suspected
CCBs/background surface soil were run using Version 4.1.01 (output provided in Appendix S). The
results were the same as those using Version 4.00.02. Therefore, the use of the older version of
ProUCL has no impact on the risk assessment. Because the purpose of the HHRA is to determine
whether there are potential risks due to CCBs, and the constituents in CCBs are also naturally
occurring inorganics, it is important to exclude constituents that are present in media in the Area of
Investigation naturally or due to other causes. The background evaluation process is conducted in
such a way that it is unlikely that constituents that are not consistent with background would be falsely
eliminated, and that it is more likely that constituents that are consistent with background are retained
for further evaluation in the quantitative risk assessment.
As discussed in detail in Section 3.1.1, to confirm the field visual inspection observations about the
absence of CCB materials in the background samples, a subset of five background soil samples were
submitted for microscopic analysis. Only 40 percent of the background samples contained no CCBs.
The presence of even trace levels of CCBs in the majority of the background soil samples that were
analyzed for the presence of CCBs limits the usefulness of the existing background soil data set. The
remaining 60 percent of the background samples contained less than 1% CCBs. As a result, any
comparison between the risks and hazards calculated based on the background soil data set and
those based on the CCB data set must be viewed cautiously.
The constituents that have been eliminated based on background are listed below:
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Suspected CCBs
•
Lead (consistent with background; maximum detected concentration less than the adjusted
RSL)
•
Manganese (consistent with background)
•
Silicon (consistent with background; no RSL available)
•
Zinc (consistent with background; maximum detected concentration less than the adjusted
RSL)
Brown Ditch Sediment
•
Lead (consistent with background; maximum detected concentration less than the RSL)
Brown Ditch Surface Water
•
Aluminum (consistent with background; maximum detected concentration less than the
adjusted RSL)
•
Manganese (consistent with background)
•
Potassium (consistent with background; no RSL available)
•
Silica (consistent with background; no RSL available)
•
Silicon (consistent with background; no RSL available)
•
Sodium (consistent with background; no RSL available)
For constituents listed above which also have maximum detected concentrations below adjusted
RSLs (aluminum, lead, zinc), there is little uncertainty associated with elimination based on
background because these constituents could also be eliminated based on the adjusted RSL. The
potential risks associated with essential nutrients were shown to be negligible in Section 3.3.1.4;
therefore, it is unlikely that uncertainty is associated with the elimination of potassium and sodium as
COPCs in Brown Ditch surface water. Silica and silicon are not human health risk drivers and no
RSLs are available; it is unlikely that elimination of these constituents introduces uncertainty to the
HHRA. Manganese was eliminated as a COPC from both the suspected CCB dataset and the Brown
Ditch surface water dataset based on background, and the maximum detected concentrations exceed
the adjusted RSLs.
As a conservative estimate of uncertainty, the potential HQ for manganese can be calculated by
dividing the maximum detected concentration by the RSL. The HQ estimates are conservative as
they are based on the RSL default exposure factors, which do not account for site-specific
assumptions, such as the exposure frequency default of 350 days per year for soil versus 250 days
for Area of Investigation suspected CCBs. The tapwater RSL is based on a drinking water scenario,
while the site-specific exposure potential for wading in Brown Ditch is much less (26 days per year,
dermal contact only). The conservatively estimated HQs are as follows:
•
Suspected CCBs Manganese HQ: 737 mg/kg / 1800 mg/kg (residential soil RSL) = 0.41
•
Brown Ditch Surface Water Manganese HQ: 658 ug/L / 880 ug/L (tapwater RSL) = 0.75
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The target endpoint for manganese is the nervous system. As indicated in Table 6-2RME, the total
potential HI for nervous system effects under the RME scenario for the residential receptor is 0.27; the
conservative HQ estimate of 0.41 would not would not result in an HI above one. As indicated in
Table 6-2RME, there are no other COPCs in Brown Ditch surface water with a nervous system
endpoint. Therefore, the conservative HQ estimate of 0.75 would not result in an HI above one.
Essential Nutrients
Essential nutrients, including calcium, magnesium, sodium, and potassium, are generally excluded
from the risk assessment process (USEPA, 1989a). A quantitative evaluation was conducted to
further support the exclusion of these essential nutrients from the risk assessment. Because these
constituents are essential to the human diet, it is unlikely that they pose significant hazards at the
relatively low concentrations detected in environmental media.
6.5.2
Dose-Response Assessment
The purpose of the dose-response assessment is to identify the types of adverse health effects a
constituent may potentially cause and to define the relationship between the dose of a constituent and
the likelihood or magnitude of an adverse effect (response). Risk assessment methodologies typically
divide potential health effects of concern into two general categories: effects with a threshold
(noncarcinogenic) and effects assumed to be without a threshold (potentially carcinogenic), although
there is increasing scientific evidence that many carcinogens also act via a threshold mechanism.
Toxicity assessments for both of these types of effects share many of the same sources of
uncertainty. To compensate for these uncertainties, USEPA has developed RfDs, CSFs, and
radiological slope factors that are biased to overestimate rather than under-estimate human health
risks. Several of the more important sources of uncertainty and the resulting biases are discussed
below. Relative bioavailability of arsenic is also discussed.
6.5.2.1 Animal-to-Human Extrapolation in Noncarcinogenic Dose-Response Evaluation
For many constituents, animal studies provide the only reliable information on which to base an
estimate of adverse human health effects. All twelve COPCs evaluated in this risk assessment have
oral reference doses, of which six are based on animal studies and six are based on human studies.
Seven COPCs have inhalation reference concentrations, of which one (hexavalent chromium) is
based on an animal study and six are based on human studies. Extrapolation from animals to
humans introduces a great deal of uncertainty into the risk characterization; where human studies are
available, uncertainty is reduced. In most instances, it is not known how differently a human may
react to the constituent compared to the animal species used to test the constituent. If a constituent's
fate and the mechanisms by which it causes adverse effects are known in both animals and humans,
uncertainty is reduced. When the fate and mechanism for the constituent are unknown, uncertainty
increases.
The procedures used to extrapolate from animals to humans involve conservative assumptions and
incorporate uncertainty factors such that overestimation of effects in humans is more likely than
underestimation. When data are available from several species, the lowest dose that elicits effects in
the most sensitive species is used for the calculation of the RfD. To this dose are applied uncertainty
factors, generally of 1 to 10 each, to account for intraspecies variability, interspecies variability, study
duration, and/or extrapolation of a low effect level to a no effect level. Thus, most reference doses
used in risk assessment are 100- to 10,000-fold lower than the lowest effect level found in laboratory
animals. Uncertainty factors for chronic toxicity values based on animal studies included in this risk
assessment range from 1 (manganese RfD) to 3,000 (thallium RfD), as shown in Tables 4-1 and 4-3.
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Nevertheless, because the fate of a constituent can differ in animals and humans, it is possible that
animal experiments will not reveal an adverse effect that would manifest itself in humans. This can
result in an underestimation of the effects in humans. The opposite may also be true: effects
observed in animals may not be observed in humans, resulting in an overestimation of potential
adverse human health effects.
6.5.2.2 Evaluation of Carcinogenic Dose-Response
Significant uncertainties exist in estimating dose-response relationships for potential carcinogens.
These are due to experimental and epidemiologic variability, as well as uncertainty in extrapolating
both from animals to humans and from high to low doses. Three major issues affect the validity of
toxicity assessments used to estimate potential excess lifetime cancer risks: (1) the selection of a
study (i.e., dataset, animal species, matrix the constituent is administered in) upon which to base the
calculations, (2) the conversion of the animal dose used to an equivalent human dose, and (3) the
mathematical model used to extrapolate from experimental observations at high doses to the very low
doses potentially encountered in the environment. Of the twelve chemical COPCs included in this risk
assessment, arsenic and hexavalent chromium are classified as potentially carcinogenic via the oral
route of exposure, and arsenic, hexavalent chromium, and cobalt are potentially carcinogenic via the
inhalation route of exposure. All radiological COPCs are classified as potentially carcinogenic via the
ingestion, inhalation, and external exposure routes.
Study Selection
Study selection involves the identification of a dataset (experimental species and specific study) that
provides sufficient, well-documented dose-response information to enable the derivation of a valid
CSF. Human data (e.g., from epidemiological studies) are preferable to animal data, although
adequate human datasets are relatively rare. Therefore, it is often necessary to seek dose-response
information from a laboratory species, ideally one that biologically resembles humans (e.g., with
respect to metabolism, physiology, and pharmacokinetics), and where the route of administration is
similar to the expected mode of human exposure (e.g., inhalation and ingestion). The oral cancer
slope factor and the unit risk factors for arsenic, cobalt, and hexavalent chromium are based on
human studies. The oral cancer slope factor for hexavalent chromium developed by the NJDEP
(2009) is based on a mouse study. When multiple valid studies are available, the USEPA generally
bases CSFs on the one study and site that show the most significant increase in tumor incidence with
increasing dose. In some cases this selection is done in spite of significant decreases of tumor
incidence in other organs and total tumor incidence with increasing dose. Consequently, the current
study selection criteria are likely to lead to overestimation of potential cancer risks in humans.
Interspecies Dose Conversion
The USEPA derivation of human equivalent doses by conversion of doses administered to
experimental animals requires the assumption that humans and animals are equally sensitive to the
toxic effects of a substance, if the same dose per unit body surface area is absorbed by each species.
Although such an assumption may hold for direct-acting genotoxicants, it is not necessarily applicable
to many indirect acting carcinogens and likely overestimates potential risk by a factor of 6 to 12
depending on the study species (USEPA, 1992b). Further assumptions for dose conversions involve
standardized scaling factors to account for differences between humans and experimental animals
with respect to life span, body size, breathing rates, and other physiological parameters. In addition,
evaluation of risks associated with one route of administration (e.g., inhalation) when tests in animals
involve a different route (e.g., ingestion) requires additional assumptions with corresponding additional
uncertainties. Although USEPA has formally changed its default position for scaling animal data to
humans from a per surface area basis to a per body weight basis (USEPA, 1992b), changes to
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existing CSF will only be made when the USEPA commits to a formal review of a constituent’s doseresponse profile, and as of this writing, few have been incorporated.
High-to-Low Dose Extrapolation
The concentration of constituents to which humans are potentially exposed in the environment is
usually much lower than the levels used in the studies from which dose-response relationships are
developed. Estimating potential health effects, therefore, requires the use of models that allow
extrapolation of health effects from high experimental doses in animals to low environmental doses.
These models are generally statistical in character and have little or no biological basis. Thus the use
of a model for dose extrapolation introduces uncertainty in the dose-response estimate. In addition,
these models contain assumptions that may also introduce a large amount of uncertainty. Generally
the models have been developed to err on the side of over-estimating rather than underestimating
potential health risks.
Many of the USEPA CSFs listed in IRIS are derived using the upper 95% confidence limit of the slope
predicted by the linearized multi-stage (LMS) model used to extrapolate low dose risk from high dose
experimental data. USEPA recognizes that this method produces very conservative risk estimates,
and that other mathematical models exist. USEPA states that the upper-bound estimate generated by
the LMS model leads to a plausible upper limit to the risk that is consistent with some of the proposed
mechanisms of carcinogenesis. The true risk, however, is unknown and may be as low as zero. The
LMS model is very conservative as it assumes strict linearity between the lowest dose that produced
an effect and zero dose. According to USEPA (1989a), “Because the slope factor is often an upper
95th percentile confidence limit of the probability of response based on experimental animal data used
in the multistage model, the carcinogenic risk estimate will generally be an upper-bound estimate.
This means that EPA is reasonably confident that the "true risk" will not exceed the risk estimate
derived through use of this model and is likely to be less than that predicted.” Moreover, the body has
many mechanisms to detoxify constituents, especially at low doses, and many mechanisms to repair
damages if they should occur. Therefore, many scientists believe that most constituents can cause
cancer only above a “threshold” dose. This phenomenon of a threshold for carcinogenic activity has
been demonstrated for chloroform and used as the basis for USEPA’s development of dose-response
values for chloroform (USEPA, 2011e) and is likely for arsenic (Boyce et al., 2008). The arsenic oral
CSF and inhalation unit risk factor were derived using time and dose-related formulation of the
multistage model (USEPA, 2011e). The arsenic CSF is based on a drinking water study in Taiwan,
where extremely high concentrations of arsenic are present. Extrapolating the effects at these high
concentrations (e.g., greater than 290 ug/L) to the lower levels of exposure in the United States may
distort the arsenic dose-response curve at the low end. The cobalt unit risk factor was derived by
linear extrapolation of the 95% lower confidence limit on the benchmark dose to zero exposure level.
USEPA’s current carcinogen risk assessment guidelines (USEPA, 2005a) emphasizes mode of action
data, and recognizes that some carcinogens may act in a nonlinear fashion. Therefore, it is
recognized that some carcinogens may have a threshold dose below which effects would not be seen.
There is significant epidemiological evidence that a threshold does exist for the potentially
carcinogenic effects of arsenic (Boyce, et al., 2008). Although USEPA does not currently recognize
the potential for a threshold for the carcinogenic effects of arsenic, it is mentioned here as a potential
source of uncertainty in the risk assessment. Boyce, et al. (2008) derived a threshold for no increased
bladder or lung cancer of 150 ug/L arsenic in drinking water from a study in Taiwan. Only one well
(MW-6, located near Yard 520) has arsenic concentrations above this level; the maximum detected
concentration of arsenic was 275 ug/L.
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In addition, there is considerable uncertainty about the extrapolation from mouse studies to humans
for the potential carcinogenicity of hexavalent chromium by the oral route of exposure. It should be
noted that USEPA’s Science Advisory Board (SAB) provided comments in July 2011 on the draft
USEPA derivation of the oral CSF for hexavalent chromium (which is similar in nature to that derived
by the NJDEP, and used in this risk assessment at the request of USEPA), and indicated many
reservations with the assumptions, including the presumed mutagenic MOA, and in the derivation
itself. The SAB review can be accessed at
http://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=221433. Thus, use of this toxicity value
also introduces uncertainty into the risk assessment.
6.5.2.3 Arsenic Relative Bioavailability
Bioavailability is the measure of the degree to which a constituent may be systemically absorbed
following exposure. In accordance with USEPA guidance (USEPA, 1989a, 1992a), a site-specific oral
AAF for arsenic bioavailability was developed for suspected CCBs. As discussed in Section 4.1.4.2,
the RBA of arsenic in samples of suspected CCBs was determined using a juvenile swine model. The
protocol used for the study and the method of analysis was developed by USEPA Region 8
[www.epa.gov/region8/r8risk/hh_rba.html] and generally uses two test materials for analysis. The
study was conducted by Stanley Casteel at the University of Missouri. The final report (Casteel, et al.,
2007) is provided in Appendix C of this HHRA. Two test materials were evaluated, with resulting
RBAs of 0.5 and 0.72; the maximum RBA of 0.72 was used in the HHRA. Use of the maximum RBA is
consistent with how these results have been used in other USEPA led risk assessments (for example,
the Wells G&H Superfund Site, Aberjona River Study
[http://www.epa.gov/region1/superfund/sites/wellsgh/213053.pdf], and the Butte Montana Superfund
Site [http://www.epa.gov/region8/superfund/mt/sbcbutte/. The use of the maximum RBA is
conservative because samples used in the study consisted of those containing suspected CCBs with
higher concentrations of arsenic; the use of the maximum value does not take into account any
variability. However, because only two samples were considered, the maximum test AAFo value
could be as high as 1. The potential ingestion risks and hazards associated with arsenic are linearly
related to the RBA; potential risks may therefore be lower (or higher) than those estimated in this
HHRA. The table below presents the potential arsenic ingestion risks and hazard quotients for the
RME resident based on the measured AAFo values, the midpoint between them, and the upper bound
AAFo value of 1.
Arsenic AAFo
1
0.72
0.61
0.5
Potential Carcinogenic Risk
4.79E-05
3.45E-05
2.93E-05
2.40E-05
Potential Hazard Quotient
0.88
0.63
0.53
0.44
While the use of the upper bound estimate, midpoint or the lowest AAFo would not result in changes
to the final HHRA conclusions, it is important to recognize the potential magnitude of the difference in
the risk estimates.
6.5.3
Exposure Assessment
Exposure assessment consists of three basic steps: 1) development of exposure scenarios, (2)
estimation of exposure point concentrations, and 3) estimation of human dose.
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6.5.3.1 Exposure scenarios
Exposure scenarios in a risk assessment are selected to be representative of potential exposures to
COPCs in media that may be experienced by human receptors based on current and reasonably
foreseeable land use. These exposure scenarios are developed for a hypothetical receptor, but one
that would represent the RME scenario. Therefore, exposure levels are assumed for these receptors
that are much greater than expected to typically occur in an actual population. The use of the CTE
scenarios provides an estimate of exposures more likely to represent average exposures. The CTE
risk estimates are used to put the RME risk estimates into context. Three general groups of receptors
were evaluated in this risk assessment:
•
Residential receptors were assumed to be potentially exposed to suspected CCBs via
incidental ingestion, dermal contact, inhalation of dusts, ingestion of home grown produce and
external gamma radiation. For the residential scenario, it is conservatively assumed for the
hypothetical screening level 100% CCB scenario that the receptor’s entire yard is comprised
of CCBs and that all contact that would normally be assumed to occur with soils would occur
with CCBs. Based on data obtained during the visual inspections of private properties
(AECOM, 2010a), the assumption of 100% CCBs covering 100% of a residential lot is overly
conservative. Therefore, a second site-specific scenario using the conservative maximum
average percent of CCBs identified by a review of the visual inspection data was evaluated
(see Appendix I). The percent of suspected CCBs (in 25% increments) mixed with other
materials at each location was estimated based on information obtained during the visual
inspections of private properties (see Section 3.7.2 of the RI Report). Based on these field
observations, a conservative maximum average percent of suspected CCBs in surface soils
was calculated for each property (taking into account the percent suspected CCBs at each
inspection location and the total area of each property upon which suspected CCBs were
present). The maximum of the conservative maximum average percent of CCBs in surface
soils over the exposure area was 27%, as calculated in Appendix I. The average of the
conservative maximum average percent of CCBs in surface soils over the exposure area was
6%, and all but 4 properties have a maximum average percent less than 15% (i.e., 93% of the
properties have a result less than 15%). Therefore, the site-specific scenario, which is still
conservative, assumes that the hypothetical exposure area of a residential lot contains 27%
CCBs in surface soil. As discussed in Section 5.1.3, should CCBs at-depth be brought to the
surface in the future, they would likely be mixed with sand and soil during the re-grading
process, such that the site-specific conservative maximum average percent CCBs of 27% is
also expected to be a reasonable and conservative estimate of potential future exposures.
The resident is also assumed to be potentially exposed to COPCs via dermal contact with
surface water while wading (Brown Ditch), via incidental ingestion and dermal contact while
swimming (child) or wading (adult) (Pond 1 and Pond 2), via incidental ingestion with
sediment while wading or swimming, and via fish ingestion. Given the nature of the
waterbodies, it is unlikely that swimming or wading occurs as frequently as assumed (26 days
per year). The COPCs for the pond surface water swimming scenarios are noncarcinogens.
Young children are routinely assessed as the worst case receptor for noncarcinogenic
evaluations due to higher ingestion rate and lower body, which results in higher hazard
quotients than for older receptors. Note that locations where water depth is suitable for
swimming within the Area of Investigation are limited to privately owned ponds. The HHRA
has evaluated wading in Brown Ditch, which is a more appropriate exposure scenario for this
shallow ditch.
•
Recreational receptors were assumed to be potentially exposed to suspected CCBs in dust
via inhalation, and to COPCs via dermal contact with surface water while wading (Brown
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Ditch), via incidental ingestion and dermal contact while swimming (Pond 1 and Pond 2), via
incidental ingestion of sediment while wading or swimming, and via ingestion of fish caught in
Brown Ditch or one of the ponds. Both the recreational fisher and the recreational child were
assumed to ingest fish. The USEPA-approved work plan did not include fish ingestion for the
recreational child because fish ingestion is not expected to be a significant pathway for young
children (aged 0 to 6). Data show that roughly 50% of children aged 0 to 9 years of age
ingest little to no fish (USEPA, 1997a). Roughly 97% of children aged 0 to 9 years ingest less
than 20 grams of fish per day (USEPA, 1997a). These statistics are for total fish consumption
(freshwater, saltwater, and shellfish). Young and older children consume less than 3 grams
of freshwater finfish per day based on the data in Table 10-6 of the EFH (USEPA, 1997a).
USEPA Region I also concluded that this pathway is unlikely to occur with any degree of
frequency for young children in the Wells G and H Superfund site HHRA (USEPA, 2004b).
However, in comments on the draft RI Report, USEPA requested that the recreational child
be evaluated for potential fish ingestion. Therefore, while the pathway is unlikely, it was
evaluated in the HHRA for chemical COPCs.
The HHRA did not evaluate potential exposure to recreational children via incidental ingestion
of surface water from Brown Ditch. In order to document the magnitude of uncertainty
introduced by this omission, it was assumed that recreational children were exposed via the
RME exposure parameters for surface water ingestion (see Table 5-4) to the maximum
detected concentration of each Brown Ditch surface water COPC (arsenic [2.3 ug/L], boron
[519.8 ug/L], iron [6,859 ug/L], and molybdenum [23.78 ug/L]) (see general equation in
Section 5.2.1). The risks and hazards associated with each COPC are presented below.
Arsenic
Lifetime average daily dose (LADD) = 4.7E-08 mg/kg-day
-1
Oral carcinogenic slope factor (CSF) (see Table 4-5) = 1.5 (mg/kg-day)
-1
Risk = 4.7E-08 mg/kg-day x 1.5 (mg/kg-day) = 7.0E-08
ADD = 5.5E-07 mg/kg-day
RfD (see Table 4-1) = 3E-04 mg/kg-day
HQ = (5.5E-07 mg/kg-day)/(3E-04 mg/kg-day) = 1.8E-03
Boron
ADD = 1.2E-04 mg/kg-day
RfD (see Table 4-1) = 2E-01
HQ = (1.2E-04 mg/kg-day)/(2E-01 mg/kg-day) = 6E-04
Iron
ADD = 1.6E-03 mg/kg-day
RfD (see Table 4-1) = 7E-01
HQ = (1.6E-03 mg/kg-day)/(7E-01 mg/kg-day) = 2.3E-03
Molybdenum
ADD = 5.7E-06 mg/kg-day
RfD (see Table 4-1) = 5E-03
HQ = (5.7E-06 mg/kg-day)/(5E-03 mg/kg-day) = 1.1E-03
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The risk associated with potential exposure to arsenic is well below 1E-06 and insignificant.
Similarly, the hazards associated with each of the four COPCs, as well as the total hazard
(5.8E-03) are well below 1 and insignificant. Therefore, the uncertainty associated with
omitting incidental ingestion of surface water COPCs from Brown Ditch is minimal.
•
Industrial receptors (construction workers and outdoor workers) are assumed to be exposed
to suspected CCBs via incidental ingestion, dermal contact, inhalation of dusts, and external
gamma radiation. The construction worker is also assumed to be potentially exposed to
COPCs in groundwater via incidental ingestion during excavation. The exposure frequency of
225 days/year used for the outdoor worker for the chemical risk assessment was the value
requested by USEPA and as provided in Agency guidance. This value is higher than the 176
days/year value calculated by applying a site-specific meteorological factor to the exposure
frequency. The application of a meteorological factor to develop a site-specific exposure
frequency does not assume that work is not conducted on inclement days, but rather that
surface soils are not available for contact during those inclement days. The soil ingestion rate
for the construction worker of 330 mg/day is a highend value provided in Agency guidance,
and was requested for use for both the RME and CTE scenarios by USEPA. The value is
much higher than the RME (100 mg/day) and CTE (64 mg/day) values provided in the
USEPA-approved HHRA Work Plan (see Appendix G), and derived based on information
available in the scientific literature. Thus, the potential risk results for both of these receptors
represent very conservative scenarios.
Construction workers, outdoor workers, and recreational receptors working or visiting in the area
outside the municipal water service area may also be potentially exposed to CCB-derived constituents
in groundwater used as drinking water; however, as discussed in Section 6.4, this pathway has not
been shown to be complete and, therefore, is not evaluated in the HHRA for these receptors (a
screening level drinking water risk assessment was included for the resident in Section 6.4.1).
6.5.3.2 Estimation of Exposure Point Concentrations
Sample Statistics
Exposure to COPCs is best estimated by the use of the arithmetic mean concentration of a COPC in
each medium. Because of the uncertainty associated with estimating the true average concentration,
the USEPA has required the use of the 95% UCL on the arithmetic mean as the EPC (USEPA,
2002c). Therefore, this is a very conservative estimate of the true arithmetic mean. RME EPCs in this
risk assessment represent the lower of the maximum detected concentration or the 95% UCL on the
mean (USEPA, 2002c) and were calculated using USEPA’s ProUCL software (USEPA, 2007a).
Since the time the UCLs were tabulated, a new version of ProUCL (Version 4.1.01) was released. To
determine the potential impact on UCLs, UCLs for the COPCs in the MWSE dataset were run using
Version 4.1.01 (output provided in Appendix T). The UCLs for all COPCs with the exception of
thallium were equivalent. The UCL for thallium is based on a bootstrapping method, which will result in
slight variations to the UCL each time ProUCL is run. To test this, five sets of UCLs were calculated
for thallium using ProUCL version 4.1.01 (output included in Appendix T). The various UCLs
calculated for thallium are indicated below:
•
•
•
•
•
ProUCL Version 4.00.02 1.803 mg/kg
ProUCL Version 4.1.01 Run 1 1.802 mg/kg
ProUCL Version 4.1.01 Run 2 1.823 mg/kg
ProUCL Version 4.1.01 Run 3 1.811 mg/kg
ProUCL Version 4.1.01 Run 4 1.816 mg/kg
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• ProUCL Version 4.1.01 Run 5 1.792 mg/kg
As indicated above, the various UCLs calculated are very similar, with some of the UCLs calculated
using Version 4.1.01 being slightly greater than the UCL used in the HHRA, and some being slightly
lower. Based on this evaluation, the use of the older version of ProUCL has minimal impact on the
HHRA.
The appropriate UCL is selected by ProUCL based on the distribution of the dataset, as described in
USEPA (2002c). The CTE calculations have conservatively used the lower of the maximum detected
concentration and the 95% UCL as the EPC as well. In some instances radium-226 concentrations
were substituted for reported lead-210 and polonium-210 concentrations as discussed previously (see
Section 3.1.2). These substitutions were done prior to calculating the EPCs.
Sample Location
In addition, the data used to calculate the EPCs are assumed to be representative of general area
conditions and a result of random sampling. Sample locations were selected based on previous
knowledge of where constituents had been detected, and in the case of the suspected CCB data,
from areas where CCBs had likely been used as fill based on visual inspections during the extension
of the municipal water service line. These sample locations are biased towards areas that are more
likely to contain higher concentrations of CCB-derived constituents, compared to what may be present
at the ground surface (general area conditions).
Groundwater samples were obtained from existing monitoring wells at Yard 520, and monitoring wells
installed as part of the RI. At each RI monitoring well location, a single well was installed (rather than
pairs or other clusters). At the beginning of the RI, a program of vertical profiling was conducted in
order to decide on screened intervals for the monitoring wells to be installed. As a result of that
program, it was agreed with USEPA that the monitoring wells would be installed in the “middle” of the
saturated thickness of the surficial aquifer. This interval was selected because the highest boron
concentrations were consistently detected in this zone. Thus, it is expected that concentrations
measured in monitoring wells are conservative. Correspondence related to vertical profiling is
included in Appendix E of the RI Report.
For potential exposure to CCBs, the available data were from samples collected from utility trenches
within or near roadways. These concentrations were then extended to potential receptors in
residential areas. The suspected CCBs present in residential lots are expected to be the same as
CCBs encountered in rights-of-way based on the following information:
•
Meeting minutes from the Town of Pines municipal council show that the practicing of using
CCBs from NIPSCO’s Michigan City Generating Station started in approximately 1972 and
was discontinued before 1980 (e.g., Site Management Strategy Report, Appendix F; ENSR,
2005a).
•
Correspondence between Calumet Trucking Company and the Indiana Solid Waste
Management Office indicates that a number of the larger areas on private property were
planned to be filled in 1976 with coal ash from NIPSCO’s facility (SMS Report, ENSR, 2005a).
•
Aerial photography confirms that there was no evidence of filling activities in 1970, but filling
along many of the streets was observable in photos from 1975.
•
Starting in the late 1970s, almost all shipments of CCBs from the Michigan City Generating
Station were managed at Yard 520 compared to earlier in the 1970s.
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At the Michigan City Generating Station, the source of coal and the management of coal ash
were consistent during this time period (the 1970s), such that there would not have been
significant changes in the chemistry of the coal ash during this time period (SMS Report,
Appendix D, ENSR, 2005a).
Because of these factors, the general availability and use of CCBs from the Michigan City Generating
Station for filling in the Town of Pines was restricted to a fixed time period in the 1970s. Therefore,
the CCBs present on private properties are expected to be the same in chemical composition as the
CCBs sampled in the utility trenches. For a statistical evaluation that also supports that the CCBs
have a common origin, see Appendix N.
There is extensive reliance on the visual inspection method for obtaining data (such as the percentage
of CCBs) for use in the risk assessment. It must be recognized that large portions of the Area of
Investigation have not been formally surveyed (using the visual inspection method or otherwise) to
determine the presence or absence of CCBs. Therefore, the presence or absence of CCBs within the
Area of Investigation outside the MWSE and the properties subject to the visual inspection process is
not known at this time. As evidenced by detection of tracelevels of CCBs (less than 1%) in three of
the five background samples submitted for CCB analysis (see Section 3.1.1), CCBs may have been
released and transported from areas of initial deposition (e.g., the MWSE or private property) to
various unsampled portions of the Area of Investigation. However, CCB concentrations at these
areas of secondary deposition are expected to be lower than within the MWSE. The uncertainty
associated with using CCB samples from the MWSE to represent all potential CCB locations within
the Area of Investigation is judged to be a reasonably conservative (health-protective) estimate.
Please see Appendix L for additional evaluation, including the potential background risks minus 1%
CCBs, an evaluation of the uncertainty associated with the estimate of the conservative maximum
average percent of suspected CCBs, and inclusion of manganese as a COPC in background.
Predicted EPCs
Models were used to predict outdoor air concentrations from suspected CCBs for both excavation and
non-excavation scenarios (USEPA, 2002a). Although assumptions are made about constituent
behavior in each of these models, the assumptions used are conservative in that they tend to result in
over-predictions rather than under-predictions of air concentrations. The dust concentration (921
3
ug/m , Table 5-34) selected to derive potential risks in this HHRA is based on truck traffic on unpaved
roads. Given that most of the roads in the Area of Investigation are paved, and that the majority of the
locations containing suspected CCBs are small residential areas, it is likely that this dust concentration
is overly conservative for site-specific conditions. The dust concentration calculated for other
3
construction activities (18.3 ug/m , Table 5-35) is more likely to be representative of the activities and
dust concentrations that might occur. The use of the more realistic dust concentration would result in
potential excavation air risks for the construction worker (chemical and radiological) about 50 times
lower than presented in this HHRA. The use of the MADEP dust concentration (MADEP, 1995) of 60
3
ug/m , which was approved by USEPA for use in the HHRA work plan, would result in potential
excavation air risks for the construction worker (chemical and radiological) about 15 times lower than
presented in this HHRA.
In addition, fish tissue concentrations were modeled from surface water using water to fish uptake
factors. Water to fish uptake factors introduce uncertainty into the risk assessment process. They are
often based on relatively small studies, and it is not always clear what biotransformations may occur
once the inorganic is taken into the fish. For example, based on speciation of arsenic in prepared and
cooked fish, almost all of the arsenic taken into fish from surface water is converted to an organic
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(non-toxic) form (Schoof, et al., 1999; ATSDR, 2007). However, for this risk assessment it has been
assumed that the predicted fish tissue concentration of arsenic was all in the inorganic form. Uptake
factors used in the risk assessment are consistent with the uptake factors applied for arsenic and
selenium for trophic level three fish in USEPA documents (USEPA 2002e), and are conservative for
the fish expected to be present in Brown Ditch and the ponds. Small minnows and shiners, e.g.,
fathead minnow (trophic level two), are likely the most common fish present; other species may
include carp and bullhead (trophic level three; Bacula, 2011). Thus, it is likely that the calculated fish
tissue concentrations for arsenic and selenium (Brown Ditch) and manganese (Pond 1 and Pond 2)
are overestimates.
Consideration of Future Scenarios
Section 6.4 provides an evaluation of the drinking water pathway using data available from the RI,
which are representative of current conditions. Although the RI covered a 3.5-year period, the CCBs
have been in place at Yard 520 and in the Area of Investigation for several decades. A tool such as a
predictive groundwater model could be used to estimate potential future groundwater conditions.
However, a review of the groundwater elevation contours and the constituent data over the course of
the RI, as presented in the RI Report, indicates that the constituent distribution in groundwater is
largely controlled by the groundwater elevations and location relative to Brown Ditch, and there is no
indication of dramatic changes in the elevations across the seasons sampled during the RI. Based on
the information provided in the RI Report, groundwater flow and chemistry are not expected to change
significantly in the future in the absence of major unforeseen changes. Moreover, additional water
level measurements and groundwater samples collected voluntarily by the Respondents upon the
conclusion of the RI (5 rounds between 2008 and 2011) indicate no significant changes have occurred
during that time. Therefore, while the groundwater data used in the HHRA is representative of the
time period over which it was collected, there is no information that would suggest that these
conditions would change dramatically in the future, though this remains a source of uncertainty in the
risk assessment.
6.5.3.3 Exposure Assumptions
When estimating potential human doses (i.e., intakes and external exposures) from potential exposure
to various media containing COPCs, several assumptions are made. Uncertainty may exist, for
example, in assumptions concerning rates of ingestion, frequency and duration of exposure, and
bioavailability of the constituents in the medium. Typically, when limited information is available to
establish these assumptions, a conservative (i.e., health-protective) estimate of potential exposure is
employed. Default exposure assumptions recommended by the USEPA are intended to be
conservative and representative of an individual who consistently and frequently contacts
environmental media, a scenario that rarely occurs. Most individuals will also contact media at
locations outside of the study area, while the risk assessment assumes that all exposure to
environmental media will occur within the Area of Investigation. Moreover, it is often assumed that
contact with environmental media occurs in the areas having the highest constituent concentrations
for the entire exposure frequency/duration used in the risk assessment, due to both statistical handling
of the data and the original sampling plan.
The assumptions regarding exposure frequency and duration are very conservative. For example,
while the agency default for residential exposure duration is 30 years, the average time for residing in
a household is nine years (USEPA, 1997a, Table 1-2). The use of conservative assumptions is likely
to lead to an overestimate of potential risk. Exposure frequency and duration are also a factor of the
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source size (impacted area). For residential external gamma radiation exposure assessments, this is
2
assumed to be 500 m (i.e., 27% of a half-acre residential lot).
Per the USEPA-approved HHRA Work Plan (ENSR, 2005b), a meteorological factor was used in the
risk assessment to account for the number of days when direct contact with suspected CCBs does not
occur for residents during inclement weather, i.e., when it is raining or snowing, when the ground is
wet or frozen, or when snow or ice (32 degrees F) are covering the ground. This is not to say that
residents would not be outdoors on such days, only that the soil would not be available for significant
contact either because it is wet or frozen. Thus, the exposure frequency was adjusted for these sitespecific meteorological conditions. For the chemical risk assessment, a meteorological factor of
29.8% was calculated (see Section 5.4) and applied to the residential receptor, resulting in a
residential exposure frequency of 250 days per year. It should be noted that this approach has
precedence in regulatory risk assessment: the Indiana (IDEM, 2001) and Pennsylvania (PADEP,
1997) have modified the default exposure frequency to account for inclement weather in the
development of screening levels for use in their environmental programs. IDEM uses a residential soil
exposure frequency of 250 days/year as the default value in their Risk Integrated System of Closure
program (IDEM, 2001). A meteorological factor was used in the HHRA for the Sauget Area 2 Sites,
recently approved by USEPA Region 5 (AECOM, 2009). Additionally, an exposure frequency of 250
days per year was used by USEPA Region 5 in their HHRA for the Jacobsville Neighborhood Soil
Contamination Site (USEPA, 2006a), located at a community in Evansville, IN. However, use of a
meteorological factor as discussed above is not universal. The majority of HHRAs prepared in
USEPA Region 5 do not employ this factor. As documented in MDEQ’s Part 201 regulations, MDEQ
applies a meteorological factor only for evaluation of the dermal exposure pathway, and does not
employ this factor for evaluation of the incidental ingestion exposure pathway (MDEQ 2005).
Therefore, there is uncertainty associated with use of a meteorological factor as presented in the
HHRA.
In order to evaluate the uncertainty introduced by using this factor, alternative soil-related and total
risks and hazards based on use of (1) an exposure frequency of 350 days/year for all soil-related
exposure pathways (incidental ingestion, dermal contact, and inhalation) under RME conditions, (2)
an exposure frequency of 350 days/year for just incidental ingestion and inhalation under RME
conditions, and (3) an exposure frequency of 234 days/year under CTE conditions for the same two
sets of conditions described in items 1 and 2 were calculated. Based on a review of Table 6-1RME,
the change from an exposure frequency of 250 days/year to 350 days/year for all soil-related
exposure pathways results in an increase in soil-related risks and hazards of 40 percent and an
increase in total risks and hazards of about 35 to 37 percent. A change in exposure frequency for
only the incidental ingestion and inhalation exposure pathways results in an increase in soil-related
risks of about 36 percent and in hazards of about 39 percent, and an increase in total risks of 31
percent and in total hazards of about 36 percent.
While the soil-related and total risks and hazards increase by 35 to 40 percent as described above,
the primary conclusions—identification of risks ≥ 1E-06 and hazards > 1—are largely unimpacted.
Most importantly, risks that were within EPA’s 1E-06 to 1E-04 risk range remain within the risk range
even with the increased risk resulting from a change in residential exposure frequency.
USEPA requested that the meteorological factor not be applied to the outdoor worker receptor.
Because potential exposure to gamma radiation is not expect to be affected by meteorological
conditions, the residential exposure frequency of 350 days/year and the industrial exposure frequency
of 250 days/year were used for the radiological risk assessment without adjustment.
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A site-specific bioavailability factor was developed for arsenic in CCBs based on an in vivo swine
study (Appendix C). Using a site-specific value reduces uncertainty.
Appendix H presents the produce ingestion pathway, and the derivation of the produce ingestion rates
used in the chemical and radiological risk assessments. The rates used were those recommended by
USEPA (2005c). USEPA recently issued the November 2011 edition of the Exposure Factors
Handbook (USEPA, 2011c). The EFH provides estimates of fruit and vegetable consumption by agegroup. These rates were compared to the ingestion rates used in this risk assessment. Use of the
EFH ingestion rates would lead to higher risk estimates from the potential ingestion of arsenic in
homegrown produce. However, based on the evaluation provided in Appendix H, the use of the
higher ingestion rates would not materially impact the conclusions of the evaluation. While forage
activities are not explicitly included in the ingestion estimates, the potential for receptors to ingest local
forage (berries, mushrooms) growing in areas where CCBs are present would not be expected to
significantly impact the total ingestion rates used.
6.5.4
Risk Characterization
The potential risk of adverse human health effects is characterized based on estimated potential
exposures and potential dose-response relationships. Three areas of uncertainty are introduced in
this phase of the risk assessment: the evaluation of potential exposure to multiple constituents, the
combination of upper-bound exposure estimates with upper-bound toxicity estimates, and the risk to
sensitive populations. This section also presents a comparison of arsenic exposure in the diet from
background sources to arsenic exposures in the Area of Investigation.
6.5.4.1 Risk from Multiple Constituents
Once potential exposure to and potential risk from each COPC are estimated, the total upper-bound
potential risk posed for each receptor is determined by combining the estimated potential health risk
from each of the COPCs, chemical and radiological. Presently, potential carcinogenic effects are
added unless evidence exists indicating that the COPCs interact synergistically (a combined effect
that is greater than a simple addition of potential individual effects) or antagonistically (a combined
effect that is less than a simple addition of potential individual effects) with each other. For most
combinations of constituents, little if any evidence of interaction is available. Therefore, additivity is
assumed for potential carcinogens in this HHRA (arsenic, cobalt, hexavalent chromium, and
radionuclide COPCs).
For noncarcinogenic effects, the HI should only be summed for constituents that have the same or
similar target endpoints (USEPA, 1989a). The target endpoint is defined as the most sensitive
noncarcinogenic health effect used to derive the RfD, RfC or other suitable toxicity value (USEPA,
1989a). As can be seen by the table below, a number of the COPCs have different endpoints, while
others overlap:
COPC
Noncancer Oral Endpoint
Noncancer Inhalation Endpoint
Aluminum
Nervous System
Nervous System
Arsenic
Skin, Vascular
Developmental, Vascular, Nervous System
Chromium (Hexavalent)
None reported
Respiratory
Boron
Developmental
Respiratory
Cobalt
Thyroid
Respiratory
Iron
Gastrointestinal
no RfC
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Noncancer Inhalation Endpoint
Manganese
Nervous System
Nervous System
Molybdenum
Kidney
no RfC
Selenium
Skin, Nails, Hair, Behavioral
Gastrointestinal, Vascular, Nervous System
Strontium
Skeletal
no RfC
Thallium
Hair follicle atrophy
no RfC
Vanadium
Hair
no RfC
Again, there is little evidence to suggest whether those COPCs associated with a common target
endpoint are additive, synergistic, antagonistic, or independent in terms of mechanism of action.
Whether assuming additivity leads to an underestimation or overestimation of risk is unknown. In this
risk assessment, it has been assumed that HQs from COPCs with the same target endpoint are
additive (e.g., all the HQs from the COPCs with respiratory effects are added together).
6.5.4.2 Combination of Several Upper-Bound Assumptions
Generally, the goal of a risk assessment is to estimate an upper-bound potential exposure and risk.
Most of the assumptions about exposure and toxicity used in this evaluation are representative of
statistical upper-bounds or even maxima for each parameter. The result of combining several such
upper-bound assumptions is that the final estimate of potential exposure or potential risk is extremely
conservative (health-protective).
This is best illustrated by a simple example. Assume that potential risk depends upon three variables
(soil consumption rate, COPC concentration in soil and CSF). The mean, upper 95% bound and
maximum are available for each variable.
One way to generate a conservative estimate of potential risk is to multiply the upper 95% bounds of
the three parameters in this example. Doing so assumes that the 5% of the people who are most
sensitive to the potential carcinogenic effects of a COPC will also ingest soil at a rate that exceeds the
rate for 95% of the population and that all the soil these people ingest will have a constituent
concentration that exceeds the 95% UCL concentration in the soil. The consequence of these
assumptions is that the estimated potential risk is representative of 0.0125% of the population (0.05 x
0.05 x 0.05 = 0.000125 x 100 = 0.0125%). Put another way, these assumptions overestimate risks for
99.99% of the population or 9,999 out 10,000 people. Thus, the majority of people will have a much
lower level of potential risk. The very conservative nature of the potential risks estimated by the risk
assessment process is not generally recognized. In reality, the estimates are more conservative than
outlined above, because usually more than three upper 95% assumptions are used to estimate
potential risk(s).
Alternatively, if a single upper 95% assumption of the cancer slope factor is combined with average
(50th percentile) assumptions for soil concentration and soil ingestion rate, the resulting estimates of
potential risk still over predict risk for 97.5% of the potentially exposed population (0.05 x 0.5 = 0.025 x
100 = 2.5%). This is a conservative and health protective approach that substantially overestimates
the “average” level and even the reasonable maximum level of potential risk.
The risk assessment approach used here employed upper 95% bounds or maxima for most RME
exposure and toxicity assumptions. Thus, it produces estimates of potential risk two to three orders of
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magnitude greater than the risk experienced by the average member of the potentially exposed
populations. The CTE scenarios have used average estimates of exposure where possible, but still
use the conservative toxicity values, and 95% upperbound EPC estimates; thus even the CTE risk
estimates are likely to overestimate total risk.
6.5.4.3 Risk to Sensitive Populations
The health risks estimated in the risk characterization generally apply to the receptors whose activities
and locations were described in the exposure assessment. Some people will always be more
sensitive than the average person and, therefore, will be at greater risk. Dose-response values used
to calculate risk, however, are frequently derived to account for additional sensitivity of subpopulations
(e.g., the uncertainty factor of 10 used to account for intraspecies differences). Therefore, it is unlikely
that this source of uncertainty contributes significantly to the overall uncertainty of the risk
assessment.
6.5.4.4 Comparison of Dietary Arsenic Exposure to Area of Investigation Arsenic Exposure
As noted in the RI Report and in Appendix H, and from the background soil samples collected for the
Area of Investigation, arsenic is naturally occurring in soils in the U.S. As such, it is also present in our
diet. Schoof, et al. (1999) presented data on the inorganic content of arsenic in foodstuffs collected in
a market basket survey. The analysis focused on inorganic arsenic, as the organic forms of arsenic
found predominantly in fish, but also present in other foodstuffs, are essentially non-toxic
(Schoof, et al., 1999; ATSDR, 2007). These data were used by Boyce, et al. (2008) in a probabilistic
analysis of background exposures to inorganic arsenic in the U.S. from the diet, and soil and water
ingestion.
Comparison of LADD Estimates
Table 6-29 presents a summary of estimated background exposures to inorganic arsenic, expressed
as LADD, for diet, soil, and water (Boyce, et al., 2008). These exposure estimates were generated
using a probabilistic model and, thus, mean estimates of exposure as well as various percentiles of
the distribution of background exposures can be estimated and are presented in the table. Dietary
exposure represents the majority of background exposure to inorganic arsenic, with soil exposures
representing a small fraction of the total potential background exposure. Note that Boyce, et al.
(2008) only evaluated dietary ingestion of inorganic arsenic, not total arsenic. Organic arsenic is the
more prevalent form of arsenic in foodstuffs, and total arsenic concentrations in the diet would be
much higher than the inorganic estimates used by Boyce, et al. In addition, the soil intake estimates
th
by Boyce, et al., used exposure assumptions that are lower than the USEPA defaults; the 95
percentile child soil ingestion rate used by Boyce, et al., is 124 mg/day, compared with the higher 200
mg/day assumed by USEPA and used in the HHRA for the Pines Area of Investigation. Thus the
intake estimates made by Boyce et al. are lower than those that would have been made using Agency
defaults.
Potential carcinogenic risks for the chemical HHRA at the Pines Area of Investigation are within the
-6
-4
USEPA risk range of 10 to 10 and are driven by arsenic. Potential risks for the residential scenario
-5
are in the 10 range. In order to put the potential risks from arsenic in suspected CCBs and other
media at the Area of Investigation into perspective, they are compared here to exposures to arsenic in
the American diet from background sources. The receptor with the highest risk results, the residential
receptor, was used for this conservative comparison.
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The LADD for arsenic for the residential receptor includes incidental ingestion and dermal contact with
suspected CCBs and incidental ingestion and dermal contact with sediment. The highest potential
exposures from sediment were included (Pond 2). The inhalation of suspected CCB pathway was not
included in the total. Lifetime Daily Exposure is calculated for the inhalation pathway, which cannot be
compared directly to the LADD. Furthermore, the HHRA has shown that the inhalation pathway adds
a negligible amount to the total potential exposure. Potential exposures from surface water have also
been shown in the HHRA to be negligible and are not included in the totals.
Table 6-30 compares the estimated background dietary exposure to inorganic arsenic expressed as
LADD (Boyce, et al., 2008) to the Area of Investigation LADD for arsenic for the residential scenario.
The table presents both RME and CTE LADD exposure estimates for inorganic arsenic, as well as
exposure estimates under both the hypothetical screening level 100% CCB and the site-specific 27%
CCB scenarios previously described. Note that the 100% and 27% CCB scenarios apply only to the
suspected CCB pathway, not to the sediment pathway. The ratios of the 95th percentile dietary
inorganic arsenic background exposure estimate to the Area of Investigation exposure estimates for
arsenic for the various scenarios are calculated. As can be seen on the table, background exposures
via the diet are approximately 5 times higher than potential exposures to suspected CCBs under the
hypothetical screening level 100% CCB RME scenario. Under the more realistic site-specific 27%
CCB RME scenario, background exposures to inorganic arsenic via the diet are approximately 15
times higher than potential exposure to arsenic in CCBs. Under the 100% CCB CTE scenario,
background dietary exposures are 52 times higher than potential exposure to arsenic in CCBs and
155 times higher than potential exposure to arsenic in CCBs under the 27% CCB CTE scenario. The
ratios show that compared to dietary arsenic exposures, exposure to arsenic from suspected CCBs in
the Area of Investigation is much lower.
Comparison of Risk Estimates
The assumption of linear low-dose extrapolation was used by USEPA in the development of the
current toxicity values for arsenic. However, there is much support in the scientific literature for a
threshold mechanism of action for arsenic. The information presented here is for comparison
purposes, and does not represent Agency guidance. Boyce, et al. (2008) have reviewed the literature
and developed a Margin of Exposure (MOE) approach for the evaluation of exposures to arsenic by
calculating a NOAEL for the potential carcinogenic effects of arsenic from human epidemiological
studies. Comparison of the NOAEL to the LADD provides the margin of exposure:
MOE = NOAEL/LADD
The lower the exposure or LADD, the higher the MOE. This is the opposite of the HI approach, which
is the ratio of the LADD to the reference dose, such that as the exposure or LADD increases, the HI
increases [HI = LADD/RfD]. Therefore, while a higher HI indicates higher potential exposures, the
higher the MOE, the lower the potential exposures. An MOE above one indicates that exposures are
below the threshold for potential carcinogenic effects.
Boyce, et al. (2008) derived a NOAEL for arsenic as the exposure level associated with no elevated
risk of cancer. The NOAEL is based on a threshold for no increased bladder or lung cancer of 150
ug/L arsenic in drinking water from a study in Taiwan. As described in Boyce, et al. (2008), there are
several epidemiological studies to support the selected threshold level. The drinking water
concentration of 150 ug/L was converted to a daily dose using exposure parameters suitable for the
Taiwanese population. The resulting NOAEL is 0.013 mg/kg-day.
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Therefore, in addition to the evaluation of arsenic exposures using the USEPA-derived CSF in this
HHRA, this uncertainty analysis provides an evaluation of arsenic exposures using the MOE approach
and a NOAEL of 0.013 mg/kg-day, however, it should be noted that this type of comparison does not
represent Agency policy.
Note that a point estimate approach has been used for the HHRA, so a single upper bound estimate
of exposure and risk are calculated. By contrast, Boyce, et al. (2008) have conducted a distributional
analysis of exposure and risk and, therefore, can provide percentiles of risk. The HHRA assumptions
have been selected to provide an upper-bound estimate, thus, the most appropriate comparison is
th
between the RME result for the Pines Area of Investigation and the 95 percentile values from the
Boyce, et al., (2008) study.
Table 6-31 presents the LADDs, MOEs, and ELCRs for arsenic associated with suspected CCBs and
sediment in the Area of Investigation. The table also presents the mean, 5th percentile, 50th
percentile, and 95th percentile LADDs, MOEs, and ELCRs for dietary exposure to inorganic arsenic,
as presented in Boyce, et al. (2008). The MOE for the hypothetical screening level 100% CCB RME
scenario is over 450. This indicates that potential exposure to arsenic at the Area of Investigation is
over 450 times lower than the level at which cancer risks could reasonably be expected based on the
threshold dose derived above. Under the more realistic site-specific 27% CCB scenario, the MOE
(RME) is over 1,300. Under the CTE scenario, the MOEs are over 4,500 (100% CCB) and 13,500
(27% CCB). By contrast, the MOEs for background dietary exposure range from 58 for the 95th
percentile exposure estimate to 447 for the 5th percentile exposure estimates. It is clear from this
evaluation that potential arsenic exposures at the Area of Investigation are below the level at which
cancer risks can reasonably be expected using this evaluation approach, and are much lower than
exposures to inorganic arsenic from the typical American diet.
6.5.4.5
Evaluation of the Range of Percent CCB Scenarios
This HHRA evaluated two scenarios with respect to the percent of CCBs assumed to be present at
the ground surface; a hypothetical screening level scenario assuming 100% CCBs, and a site-specific
scenario assuming 27% CCBs. As described in Appendix I, 27% is the highest of the conservative
maximum average percent suspected CCBs calculated over the exposure area of any residential lot.
The majority of exposure areas have a conservative maximum average percent CCBs of less than
15%, and the average of the conservative maximum average percent CCBs is 6%. The tables below
present the potential risk estimates based assumptions of 100%, 27%, 15%, and 6% CCBs for both
the residential receptor and the outdoor worker. While potential risks calculated for the hypothetical
-4
-5
screening level 100% CCB scenario are in the 10 and 10 range, potential risks calculated for the
-5
-6
27% and 15% scenarios are in the 10 and 10 range, and potential risks calculated for the 6%
-6
scenario are in the 10 range (with the exception of the total potential risk including a garden, which is
-5
at the 10 level). The 27% CCB assumption used in this risk assessment is conservative, and as the
tables below show, potential risks are likely lower than those presented under the site-specific 27%
CCB scenario.
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Total Potential Risk Based on Assumed
Percent of CCBs
100%
27%
15%
6%
Chemical Potential Risk
Radionuclide Potential Risk (with garden)
Radionuclide Potential Risk (without garden)
4.E-05
2.E-04
7.E-05
1.E-05
4.E-05
2.E-05
6.E-06
2.E-05
1.E-05
3.E-06
9.E-06
4.E-06
Total Potential Risk (with garden)
Total Potential Risk (without garden)
2.E-04
1.E-04
5.E-05
3.E-05
3.E-05
2.E-05
1.E-05
7.E-06
RME Resident - Suspected CCBs
Thallium was the only noncarcinogenic constituent with an HQ above one (1.65) under the RME
residential hypothetical screening level 100% CCB scenario. Thallium HQs for the other RME
resident scenarios are: 0.45 under the site-specific 27% CCB scenario, 0.25 under the 15% CCB
scenario, and 0.1 under the 6% CCB scenario.
RME Outdoor Worker - Suspected CCBs
Total Potential Risk Based on Assumed
Percent of CCBs
100%
27%
15%
6%
Chemical Potential Risk
Radionuclide Potential Risk
1.E-05
1.E-04
3.E-06
3.E-05
2.E-06
2.E-05
7.E-07
7.E-06
Total Potential Risk
1.E-04
3.E-05
2.E-05
7.E-06
6.5.4.6
Comparison of Background Radionuclide COPCs to the Radionuclide COPCs in
the Area of Investigation
Background radiation from naturally occurring radioactive materials (NORM) has been measured
throughout North America and its range of concentrations in soil and rock is well documented. These
concentrations, in turn, create variations in exposure rates and background risk. The magnitude of
variation can be significant over a short distance and also can vary with time. Understanding the
characteristics of natural background and the wide range of background values encountered in the
field is integral when evaluating the impacts of technologically-enhanced naturally occurring
radioactive material (such as CCBs) present in the natural environment. This is especially important
because regulatory exclusion limits and clean-up criteria are often set at a concentration, dose, or risk
greater than background.
Background soil concentrations for NORM isotopes were evaluated for background soil in the Area of
Investigation. These included native granular and native organic soils. These samples were analyzed
using high-resolution gamma spectroscopy which identified the gamma emitting isotopes in the U-238,
U-235, and Th-232 decay series, the same as the radionuclide COPCs. Therefore, because there are
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COPCs in the background soil, the risk cannot go to zero on a linear risk model and the CCBs are
adding only an incremental risk to the background. These background levels of NORM can result in
the release of radon within the soil and to surrounding air, and into overlying buildings. Figure 26
shows the prevalence of radon in areas of Indiana. Porter County is in Zone 2. Zone 2 counties have
a predicted average indoor radon screening level between 2 and 4 pCi/L of air. Zone 2 is considered
to be of moderate potential for indoor radon. As noted in Section 5.1.1, the radionuclide PRG
equations for soil from USEPA do not account for explicitly for radon generation. However, the
similarity of radionuclide levels between CCBs and background soils would suggest that the
contribution of CCBs to radon generation may be low or negligible, however it is not possible to
quantify this uncertainty.
6.5.5
Summary of Sources of Uncertainty in HHRA
The large number of assumptions made in the risk characterization introduces uncertainty in the
results. While this could potentially lead to underestimates of potential risk, the use of numerous
conservative (i.e., protective of human health) assumptions, as was done here, more likely
overestimates potential risks. Any one person's potential exposure and subsequent risk are
influenced by all the parameters mentioned above and will vary on a case-by-case basis. Despite
inevitable uncertainties associated with the steps used to derive potential risks, the use of numerous
health-protective assumptions will most likely lead to an overestimate of potential risks from the study
area. Moreover, when evaluating risk assessment results, it is important to put the risks into
perspective. For example, ACS estimates that the lifetime probability of contracting cancer in the U.S.
-1
-1
is 1 in 2 (5 x 10 ) for men and 1 in 3 (3 x 10 ) for women (ACS, 2011). The risk value is expressed
-6
as a probability (e.g., 10 , or one in one million). The results of the risk assessment must be carefully
interpreted considering the uncertainty and conservatism associated with the analysis, especially
where risk management decisions are made.
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Summary and Conclusions
This HHRA has been conducted as part of the RI/FS process in order to evaluate the potential risks to
human receptors posed by suspected CCB-derived COPCs in environmental media within the Area of
Investigation. The objectives of the RI include (AOC II, 2004):
“(a) to determine the nature and extent of contamination at the Site and any threat to the public
health, welfare, or the environment caused by the release or threatened release of hazardous
substances, pollutants or contaminants related to coal combustion by-products (“CCB”) at or
from the Site”, and
“(b) to collect data necessary to adequately characterize…(i) whether the water service extension
installed pursuant to AOC I and AOC I as amended is sufficiently protective of current and
reasonable future drinking water use of groundwater in accordance with Federal, State, and local
requirements; (ii) whether there are significant human health risks at the Area of Investigation
associated with exposure to CCBs;….”
Therefore, this HHRA focuses on CCB-derived constituents characterized during the RI. The SOW
provides at Section 5.1:
“Respondents shall conduct a human health risk assessment that focuses on the evaluation of
current and future risks to persons coming into contact with on-site hazardous substances or
constituents as well as risks to the nearby residential, recreational and industrial worker
populations from exposure to hazardous substances or constituents in groundwater, soils,
sediments, surface water, air, and ingestion of contaminated organisms in nearby, impacted
ecosystems. The human health risk assessment shall define central tendency and reasonable
maximum estimates of exposure for current land use conditions and reasonable future land use
conditions. The human health risk assessment shall use data from the Site and nearby areas to
identify the constituents of potential concern (COPC), provide an estimate of how and to what
extent human receptors might be exposed to COPCs, and provide an assessment of the health
effects associated with these COPCs. The human health risk assessment shall assess potential
human health risk if no cleanup action is taken at the Site.”
A baseline HHRA was conducted for the Area of Investigation in accordance with the four-step
paradigm for human health risk assessments developed by USEPA (USEPA, 1989a): 1) Hazard
Identification, 2) Dose-Response Assessment, 3) Exposure Assessment, and 4) Risk
Characterization. A summary of each step is presented below, followed by results and conclusions.
7.1
Ha za rd Ide ntific a tion
The purpose of the data evaluation and hazard identification process is two-fold: 1) to evaluate the
nature and the extent of release of CCB-derived constituents present within the Area of Investigation;
and 2) to identify a subset of these constituents as COPCs for quantitative evaluation in the risk
assessment. This step of the risk assessment involves compiling and summarizing the data for the
risk assessment and designating COPCs. A discussion of CCBs, the site setting, and the occurrence
of CCBs within the Area of Investigation is provided below, followed by a summary of the COPC
selection process and the results.
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CCBs
There are three types of CCBs relevant to the Area of Investigation, as discussed in the SMS (ENSR,
2005a). Their classification is based on how and when they are generated in the coal combustion
process. Bottom ash and boiler slag settle to the bottom of the combustion chamber. Fly ash is also
generated in the combustion chamber, but it is lighter and finer than the bottom ash and boiler slag
and so is transported in the flue gas and ultimately collected by air emission controls (e.g.,
electrostatic precipitators or other gas scrubbing systems) (USGS, 2001). These residues are
considered to be by-products because there are many beneficial re-uses for these materials (USGS,
2001). The use of fly ash to partially replace Portland cement in concrete not only increases
concrete’s strength and durability, it significantly reduces the emissions of carbon dioxide to the
atmosphere (for example, a reduction of seven million metric tons in 1998; USGS, 2001). In addition,
USEPA has used fly ash in the construction of a “green” building in their New England Regional
Laboratory located in Chelmsford, Massachusetts. The use of fly ash in concrete construction
materials in this building accounted for 126 tons of fly ash being recycled and not disposed of as part
of the waste stream (USEPA, 2007b). Bottom ash is used primarily in structural fill, snow and ice
control, road sub-bases, and concrete, and boiler slag is used in blasting grit and roofing applications
(USGS, 2001). These different beneficial uses of CCBs are based on their different physical
characteristics, and these characteristics explain in part their locations within the Area of Investigation,
as discussed in more detail below.
Site Setting
The Area of Investigation contains residential areas, the majority of which are located between US
Route 12 (West Dunes Highway) and US Highway 20. Additional residences are located mainly along
Ardendale, Railroad Avenue, and Old Chicago Road. Each house historically may have had its own
drinking water well or septic system or both. Figure 3 shows the portion of the Area of Investigation
that has been provided municipal water service in accordance with AOC I and the Amendment to
AOC I. It is expected that septic systems will continue to be used in this community (i.e., there is no
municipal sewage system). The water table of the shallow groundwater aquifer within the municipal
water service extension (MWSE) area is present near the ground surface in low lying areas, and can
be up to 25 feet bgs beneath the upland dune areas. The saturated thickness of the aquifer ranges
from less than five feet to approximately 40 feet. The RI determined that this shallow aquifer is not
present in the area in the southern portion of the Area of Investigation (e.g., the area along Old
Chicago Road).
CCBs in Yard 520
CCBs are present in Yard 520, a closed Restricted Waste Facility permitted by IDEM that is located in
the western portion of the Area of Investigation, between US Route 20 to the north and Brown Ditch
and the railroad to the south. Yard 520 was previously used for the disposal of CCBs primarily from
NIPSCO’s Michigan City Generating Station, and was closed between 2004 and 2007. Although
CCBs are present at Yard 520, direct contact with them is an incomplete exposure pathway as the
facility is capped and closed (see the information provided in Appendix O).
CCBs Within the Area of Investigation
Suspected CCBs have also been observed in roadbeds and other areas in certain portions of the
Area of Investigation. Figure 4 depicts the information compiled about the potential locations of
suspected CCBs at the ground surface within the Area of Investigation based on the information
presented in the RI Report (AECOM, 2010a). It is evident from Figure 4 that suspected CCBs are
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located in discrete areas of the Town of Pines predominantly associated with roadways, and are not
distributed throughout all areas.
It is important to note that the CCBs present in Yard 520 and suspected CCBs within the Area of
Investigation are not the same materials. The material observed during the water service installation
included a large percentage of coarse grained material (larger than silt and clay), and the sidewalls of
the trenches stayed upright during the utility work. In contrast, the material in Yard 520 was observed
to be predominantly very fine grained, soupy or muddy, and would not stay upright on an open face.
Based on descriptions from Brown Inc., the material brought to Yard 520 was a wet slurry which
needed draining/dewatering. This material would not have been suitable for fill or road sub-base,
which accounts for the material outside Yard 520 being different. The most likely explanation of the
observed differences is that the CCB material in Yard 520 is primarily fly ash, while the suspected
CCB material in the Town of Pines consists of a larger portion of bottom ash and/or boiler slag. Thus
both materials have different physical and chemical characteristics. The RI Report includes more
discussion of the different types of CCBs and the differences observed within the Area of
Investigation. Fly ash is known to have higher constituent concentrations than the other types of ash,
and this difference is clear in the analytical results for the MWSE dataset and the Yard 520 dataset
(see Appendix A; see also Tables 2-1 through 2-3).
As part of the Municipal Water Service Extension, water lines were installed along roadways, including
at locations where CCBs were suspected to be present. During the installation of the MWSE,
samples of suspected CCBs were taken for laboratory analysis when encountered in the excavation
trenches. Samples were collected within an interval from the ground surface up to a depth of
5 feet bgs.
The suspected CCBs present in residential lots are expected to be the same source and chemical
composition as the suspected CCBs encountered (and collected and analyzed) in rights-of-way during
the installation of the MWSE based on the following information:
•
Meeting minutes from the Town of Pines municipal council show that the practicing of using
CCBs from NIPSCO’s Michigan City Generating Station started in approximately 1972 and
was discontinued before 1980 (e.g., Site Management Strategy Report, Appendix F; ENSR,
2005a).
•
Correspondence between Calumet Trucking Company and the Indiana Solid Waste
Management Office indicates that a number of the larger areas on private property were
planned to be filled in 1976 with coal ash from NIPSCO’s facility (SMS Report, ENSR, 2005a).
•
Aerial photography confirms that there was no evidence of filling activities in 1970, but filling
along many of the streets was observable in photos from 1975.
•
Starting in the late 1970s, almost all shipments of CCBs from the Michigan City Generating
Station were managed at Yard 520 compared to earlier in the 1970s.
•
At the Michigan City Generating Station, the source of coal and the management of coal ash
were consistent during this time period (the 1970s), such that there would not have been
significant changes in the chemistry of the coal ash during this time period (SMS Report,
Appendix D, ENSR, 2005a).
Because of these factors, the general availability and use of CCBs from the Michigan City Generating
Station for filling in the Town of Pines was restricted to a fixed time period in the 1970s. Therefore,
the suspected CCBs present on private properties are expected to be the same in chemical
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composition as the suspected CCBs sampled in the utility trenches. For a statistical evaluation that
also supports that the suspected CCBs have a common origin, see Appendix N.
Thus, the type and source of the suspected CCBs in the utility trenches and on residential properties
within the Area of Investigation are expected to be the same. However, the concentrations of
constituents in the MWSE samples are likely representative of suspected CCBs at depth and not
necessarily constituent concentrations at the ground surface, where the suspected CCBs have been
shown to be mixed with other native and anthropogenic materials (e.g., sand, soil).
CCB Visual Inspections
A visual inspection program was developed and conducted as part of the RI. In this program, CCB
visual inspections were conducted at over 3,800 inspection locations within ROWs and at over 4,600
inspection locations on private property, as shown on Figure 25. The locations evaluated during the
visual inspection represent a wide range of areas within the Area of Investigation. The visual
inspection program is detailed in Appendix I.
The visual inspection results for locations on private properties where suspected CCBs were located
at the surface determined that the majority of the inspection locations had a suspected CCB content in
the 1-25% range, some in the 25-50% range, and only a very few in the 50-75% range (see Appendix
I). None of the locations were classified in the 75-100% CCB range.
The results of the CCB visual inspection program were tallied for the 43 properties where suspected
CCBs were identified at the ground surface. Figure 4 and Figure I-3 of Appendix I show the
approximate location of suspected CCBs on private property. An exposure area was defined for each
property as essentially the size of the residential lot, and also included the contiguous ROWs, as most
suspected CCBs within the Area of Investigation are located with the ROWs. In several cases where
properties were large and where suspected CCBs were located only within a subset of that larger
property, the exposure area was identified as approximately the size of a standard residential lot
taking care to include all or the majority of the locations where suspected CCBs were identified; this
treatment ensured that the large areas of these properties that did not have suspected CCBs at the
surface did not “dilute out” the results for the areas where suspected CCBs were present. For each
property, the area where suspected CCBs were identified and the total exposure area were
measured. For the area on each property where suspected CCBs were located, the average percent
of suspected CCBs was calculated (assuming the maximum observed at each inspection location), as
detailed in Appendix I. Then taking into account the size of the area with suspected CCBs and the
size of the total exposure area, the average percent suspected CCBs across the exposure area
(conservatively assuming the maximum at each inspection location) was calculated for each of the 43
properties (Appendix I provides a step-wise description of these calculations). The figure below
tabulates the average percent results. As can be seen, 27% is the maximum for all 43 properties, the
majority of the results are below 15% suspected CCBs, and the average is 6% suspected CCBs.
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Background Soil
All of the inorganic constituents in CCBs are naturally occurring. Samples of background soil were
collected with USEPA oversight in the field and the data used in the quantitative risk assessment so
that a comparison between potential risks from naturally occurring materials (i.e., background) and
suspected CCBs can be made. In addition, a subset of background soil samples was physically
analyzed for CCBs at the request of USEPA. The results indicate that no detectable amounts of fly
ash were present in the samples and that bottom ash was identified to comprise less than or equal to
1% of the total sample material in just two of the five samples analyzed (AECOM, 2010a).
Background soil samples were also collected during the MWSE project, however, they were not from
locations identified in conjunction with USEPA oversight in the field and, therefore, these data are not
used in the HHRA.
Analytical Data
The analytical data used in the HHRA are presented in Appendix A. Figure 14 provides a summary of
all of the RI sample locations. In accordance with AOC II, media were evaluated for inorganic
constituents (see the Appendix A). In addition, USEPA requested that samples from certain media be
analyzed for PAHs, dioxins, and radionuclides. The table below identifies the data available for
evaluation in the HHRA:
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Dataset
MWSE Suspected CCBs
Yard 520 CCBs – North Area
Yard 520 CCBs – South Area
Groundwater
Private Well Water
Brown Ditch Sediment
Brown Ditch Surface Water
Pond Sediment
Pond Surface Water
Dataset - Background
Surface Soil
Brown Ditch Upgradient Sediment
Brown Ditch Upgradient Surface Water
Groundwater
X
(a)
(b)
(c)
(d)
7-6
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Analyses
Chemical Constituents
Inorganics
PAH/Dioxins
X
X (a)
X (b)
X (b)
X
X
X
X
X
X
X
X
Radionuclides
X
X (c)
X (d)
X (c)
X (c)
X
X
X
X (c)
Data collected and available for the HHRA.
Data determined not to be appropriate for use in the quantitative HHRA (see discussion in Section 3.5).
Drinking water pathway for CCB-derived constituents is incomplete under current conditions for receptors that are provided
municipal or bottled water. The drinking water pathway for CCB-derived constituents is potentially complete for receptors
using private drinking water wells if those wells are impacted by CCBs (a detailed discussion of this can be found in
Section 6.4.2). The drinking water pathway may also be potentially complete in the future if drinking water wells are
installed and used in areas where groundwater is impacted by CCBs.
Medium/constituent group found to be not of concern during the RI because sample results were below applicable
screening levels, thus, not evaluated in the quantitative HHRA (see Appendix A for a presentation of the data and Section
3.1.2 and Appendix M, which documents the basis for USEPA’s approval of removing radionuclides from the groundwater
investigation and Section 3.1.1, which discusses the results of focused PAH and dioxin sampling).
Although not considered to be appropriate for evaluation of direct contact exposures, these data are included in the
quantitative HHRA at the request of USEPA.
The MWSE data were used as a proxy for concentrations that may be present in fill around the Area
of Investigation and, as a result, all of the samples (regardless of depth) are used to evaluate the
residential, recreational, industrial, and construction scenarios (see Exposure Assessment below).
Potential exposure to suspected CCBs is complete only in areas where suspected CCBs were
identified. The exposure scenarios are discussed in more detail in Section 7.5.1.2.
COPC Selection
Both the chemical constituent data and the radionuclide data have been quantitatively evaluated in
this HHRA. COPCs were identified using a series of screening steps, including frequency of
detection, comparison of maximum detected concentration to screening levels, comparison to
background, and essential nutrient status. Only one constituent (cobalt in background soil) was
eliminated as a COPC based on frequency of detection. The impact of eliminating cobalt from the
background dataset is insignificant, as discussed Section 6.5.1.
A number of constituents were eliminated based on comparisons to screening levels and background.
An evaluation of the potential uncertainties associated with eliminating constituents with maximum
detected concentrations greater than RSLs based on background is provided in Section 6.5.1.1; the
uncertainties were found to be insignificant. Essential nutrients (calcium, magnesium, potassium, and
sodium) were eliminated based on a comparison of maximum daily intakes to recommended daily
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intakes. Based on the COPC screening steps, the following COPCs were designated for quantitative
evaluation in the HHRA:
Chemical Constituents
•
Aluminum
•
Arsenic
•
Boron
•
Chromium (hexavalent)
•
Cobalt
•
Iron
•
Manganese
•
Molybdenum
•
Selenium
•
Strontium
•
Thallium
•
Vanadium
Not all constituents are COPCs in all media. Table 3-18 shows the media for which chemical COPCs
have been identified.
Radionuclides
Detected radionuclides were grouped according to their decay series and selected as COPCs using
the “+D” or “+daughters” designation and slope factors as appropriate. Polonium-210 was detected
but is included as a COPC as part of the lead-210 decay chain and was not included as a separate
radionuclide in the calculations. Radionuclides selected as COPCs include:
•
Uranium-238+D
•
Uranium-234
•
Thorium-230
•
Radium-226+D
•
Lead-210+D
•
Uranium-235+D
•
Thorium-232
•
Radium-228+D
•
Thorium-228
Table 3-23 shows the media for which radionuclide COPCs have been identified.
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Dos e -Re s pons e As s e s s m e nt
The purpose of the dose-response assessment is to identify the types of adverse health effects a
constituent may potentially cause, and to define the relationship between the dose of a constituent
and the likelihood or magnitude of an adverse effect (response) (USEPA, 1989a). Adverse effects are
classified by USEPA as potentially carcinogenic or noncarcinogenic (i.e., potential effects other than
cancer). Dose-response relationships are defined by USEPA for oral exposure and for exposure by
inhalation. Oral toxicity values are also used to assess dermal exposures, with appropriate
adjustments, because USEPA has not yet developed values for this route of exposure (USEPA,
1989a). The USEPA’s guidance regarding the hierarchy of sources of human health dose-response
values in risk assessment was followed (USEPA, 2003) for chemical constituents. Sources of the
published dose-response values in this risk assessment for chemical constituents include USEPA’s
IRIS database (USEPA, 2011e), PPRTVs, CalEPA (2008a; 2008b), the NJDEP (2009) and HEAST
(USEPA, 1997b). Radionuclide slope factors for ingestion of water, food, and slope factors for
inhalation, and external exposure were obtained from USEPA HEAST (USEPA, 2001b).
7.3
Expos ure As s e s s m e nt
The purpose of the exposure assessment is to predict the magnitude and frequency of potential
human exposure to each of the COPCs retained for quantitative evaluation in the HHRA. To guide
identification of appropriate exposure pathways and receptors for evaluation in this HHRA, a CSM for
human health was developed (see Figure 5). The purpose of the CSM is to identify source areas,
potential migration pathways of constituents from source areas to environmental media where
exposure can occur, and to identify potential human receptors based on current and future site uses.
Based on the CSM, three general groups of receptors are evaluated in this risk assessment:
•
Residential receptors were assumed to be potentially exposed to suspected CCBs via
incidental ingestion, dermal contact, inhalation of dusts, and via external exposure to gamma
radiation. The residential child was also assumed to wade or swim in a local water body, and
was assumed to be potentially exposed to surface water via dermal contact (and via
incidental ingestion for the swimming scenario) and sediment via incidental ingestion and
dermal contact. The residential child was also assumed to be potentially exposed to
radionuclides in Brown Ditch sediment via incidental ingestion and external exposure. As
discussed below, a separate recreational receptor is included in this HHRA. Wading and
swimming pathways were also included in the evaluation of the residential child, as discussed
above. In addition, the potential exposures calculated for the recreational child fish ingestion
pathway have been added to the residential child exposures described above, per the request
of USEPA. The recreational fisher wading and fish ingestion pathways have been added to
the residential adult exposures described above, per the request of USEPA. In a hypothetical
screening level scenario, it was conservatively assumed that the receptor’s entire residential
exposure area is comprised of CCBs and that all contact that would normally be assumed to
occur with soils would occur with CCBs – this is a hypothetical scenario that has been shown
to not be representative or even exist within the Area of Investigation by the extensive CCB
visual inspection program conducted as part of the RI. As shown in Appendix I, the
conservative maximum average percent of suspected CCBs at the ground surface was 27%,
therefore, a second site-specific scenario in the HHRA evaluates the site-specific maximum
average 27% CCB scenario. Assuming gardens are present within areas containing
suspected CCBs, residential adults and children may potentially be exposed to COPCs in
produce; this pathway was addressed directly in the radiological risk assessment, and
addressed separately in Appendix H for the chemical risk assessment. Where groundwater is
used as a source of drinking water (i.e., outside the area that has been supplied municipal
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water), residents may be exposed to CCB-derived constituents that may have migrated into
groundwater. The drinking water pathway is only potentially complete for those residents who
use groundwater from the surficial aquifer as a drinking water source.
•
Recreational receptors were assumed to be potentially exposed to suspected CCBs in dust
via inhalation, and to COPCs via dermal contact with surface water while wading or swimming
in a local water body, via incidental ingestion and dermal contact with sediment while wading
or swimming, and via ingestion of fish caught in a local water body. Both the recreational
fisher and the recreational child were assumed to ingest fish. The recreational receptors were
also assumed to be potentially exposed radionuclides in Brown Ditch sediment via incidental
ingestion and external exposure. For example, the recreational child is assumed to be 0 to 6
years of age, to wade in Brown Ditch 26 days per year for two hours each day or to swim in a
pond located along Brown Ditch 26 days per year for 2 hours each day, and to consume
approximately 13 meals each year of fish obtained from Brown Ditch or an adjacent pond.
•
Industrial receptors (construction workers and outdoor workers) were assumed to be exposed
to suspected CCBs via incidental ingestion, dermal contact, inhalation of dusts, and external
exposure to gamma radiation. The construction worker was also assumed to be potentially
exposed to COPCs in groundwater during excavation. The outdoor worker is assumed to be
exposed to materials at the ground surface and, therefore, both the hypothetical screening
level 100% CCB and the site-specific 27% CCB scenarios are evaluated for this receptor.
The construction worker scenario conservatively assumes that all excavations occur through
suspected CCBs, thus only the 100% CCB scenario was evaluated for this receptor.
EPCs for suspected CCBs (MWSE dataset), CCBs (Yard 520 dataset), sediment, surface water, and
groundwater were derived from measured data. Where possible, EPCs represent the lower of the
maximum detected concentration and the 95% UCL. Where too few data points are available, the
maximum detected concentration was selected as the EPC. EPCs for fugitive and excavation dusts
were calculated from suspected CCB or soil concentrations based on USEPA models. Fish tissue
concentrations were derived from surface water concentrations using water-to-fish uptake factors.
7.4
Ris k Cha ra c te riza tion
The potential risk to human health associated with potential exposure to COPCs in environmental
media in the Area of Investigation is evaluated in this step of the risk assessment process. Risk
characterization is the process in which the dose-response information (Section 4.0) is integrated with
quantitative estimates of human exposure derived in the Exposure Assessment (Section 5.0). The
result is a quantitative estimate of the likelihood that humans will experience any adverse health
effects given the exposure assumptions made. Two general types of health risk are characterized for
each potential exposure pathway considered: potential carcinogenic risk and potential
noncarcinogenic hazard.
The potential carcinogenic risk for each exposure pathway is calculated for each receptor. Current
regulatory risk assessments assume that carcinogenic risks are cumulative. Pathway and areaspecific risks are summed to estimate the total potential carcinogenic risk for each receptor. The total
potential carcinogenic risks for each receptor group are compared to the USEPA’s target risk range of
-4
-6
-6
10 to 10 . A COPC that poses a risk > 1x10 risk level for a particular receptor is designated a
COC. The target risk levels used for the identification of COCs are based on USEPA guidance and
-4
were identified in the approved HHRA Work Plan (ENSR, 2005b), though the work plan identified 10
as the target for COC identification. Specifically, USEPA provides the following guidance (USEPA,
1991b):
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“EPA uses the general 10(-4) to 10(-6) risk range as a "target range" within which the Agency
strives to manage risks as part of a Superfund cleanup. Once a decision has been made to
make an action, the Agency has expressed a preference for cleanups achieving the more
protective end of the range (i.e., 10(-6)), although waste management strategies achieving
reductions in site risks anywhere within the risk range may be deemed acceptable by the EPA
risk manager. Furthermore, the upper boundary of the risk range is not a discrete line at 1 x
10(-4), although EPA generally uses 1 x 10(-4) in making risk management decisions. A
specific risk estimate around 10(-4) may be considered acceptable if justified based on sitespecific conditions, including any remaining uncertainties on the nature and extent of
contamination and associated risks. Therefore, in certain cases EPA may consider risk
estimates slightly greater than 1 x 10(-4) to be protective.”
And,
“Where the cumulative carcinogenic site risk to an individual based on reasonable maximum
exposure for both current and future land use is less than 10-4, and the non-carcinogenic
hazard quotient is less than 1, action generally is not warranted unless there are adverse
environmental impacts.”
In addition, IDEM offers the following guidance regarding target risk level:
The Indiana Risk Integrated System of Closure (RISC) [IDEM. 2001. Risk Integrated System
of Closure Technical Guide. February 15, 2001.], and the latest IDEM guidance [IDEM.
2012. Remediation Closure Guide. March 22, 2012. http://www.in.gov/idem/6683.htm] uses
the target risk range of 1E-06 to 1E-04. The IDEM residential soil screening levels are set at
a 1E-05 target risk level [see Appendix A of IDEM, 2012]. Section 7.6 of the IDEM guidance
document states: “The cumulative hazard index of chemicals that affect the same target
organ should not exceed 1, and the cumulative target risk of chemicals that exhibit the same
mode of action should not exceed 10-4. U.S. EPA risk assessment guidance views these
criteria as “points of departure”, and IDEM will generally require some further action at sites
where these risks are exceeded. Further action may include remediation, risk management,
or a demonstration utilizing appropriate lines of evidence that the risk characterization
overstates the actual risk.
-5
-6
At USEPA’s request, all constituents that potentially pose a risk greater than 1 x 10 and 1 x 10 have
also been identified. By comparison, the ACS estimates that the lifetime probability of contracting
-1
-1
cancer in the U.S. is 1 in 2 (5 x 10 ) for men and 1 in 3 (3 x 10 ) for women (ACS, 2011).
The potential for exposure to a constituent to result in adverse noncarcinogenic health effects is
estimated for each receptor by comparing the dose for each COPC with the reference dose (RfD) for
that COPC. The resulting ratio, which is unitless, is known as the hazard quotient (HQ) for that
constituent. The target HQ is defined as an HQ of less than or equal to one (USEPA, 1989a). When
the HQ is less than or equal to 1, the RfD has not been exceeded, and no adverse noncarcinogenic
effects are expected. If the HQ is greater than 1, there may be a potential for adverse
noncarcinogenic health effects to occur; however, the magnitude of the HQ cannot be directly equated
to a probability or effect level. HQs for a given pathway are summed to provide a hazard index (HI).
Pathway HIs are summed to provide a total receptor HI. When the HI is less than 1, the target has not
been exceeded, and no adverse noncarcinogenic effects are expected. This initial HI summation
assumes that all the COPCs are additive in their toxicity, and is considered only a screening step
because additive toxicity may not occur. If the HI is greater than 1, further evaluation is necessary to
determine if the COPCs are additive in toxicity. This evaluation is termed a target endpoint analysis.
COPCs that cause an exceedance of a target-endpoint specific HI of 1 are designated COCs.
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Ris k As s e s s m e nt Re s ults a nd Conc lus io n s
The results of the chemical and radiological risk assessment are summarized in Section 7.5.1. The
results of the screening level drinking water risk assessment are presented in Section 7.5.2. Risk
assessment conclusions are presented in Section 7.5.3.
7.5.1
Results of Chemical and Radiological Risk Assessment
This section provides a summary of the chemical and radionuclide risk characterization results.
7.5.1.1 Datasets Evaluated
The human health risk assessment has quantitatively evaluated chemical constituents for the
following groups of datasets:
•
MWSE suspected CCB dataset,
•
Brown Ditch, Pond 1 and Pond 2 sediment datasets
•
Brown Ditch, Pond 1 and Pond 2 surface water datasets
•
Groundwater dataset
•
Background soil dataset
and
The human health risk assessment has evaluated radionuclide constituents for the following groups of
datasets:
•
MWSE suspected CCB dataset, in conjunction with:
•
Brown Ditch sediment dataset for radionuclides
•
Background soil dataset, in conjunction with:
•
Brown Ditch Upgradient sediment dataset
and
In addition, at the request of USEPA, the following datasets were evaluated:
•
Yard 520 CCB dataset for radionuclides, in conjunction with:
•
Brown Ditch sediment dataset for radionuclides (the same sediment dataset evaluated in
conjunction with the MWSE suspected CCB dataset)
As noted previously, there is no direct contact with CCBs in Yard 520 due to the cap that was placed
upon closure of the facility and the maintenance of that cap (see Appendix O). Chemical constituent
data (e.g., metals and inorganics) were not collected for risk assessment purposes from Yard 520.
Samples from the Type III (South) Area of Yard 520 were collected and analyzed for radionuclides to
use in a screening level risk evaluation. MWSE suspected CCB samples were analyzed for
radionuclides, and because they are representative of potential exposures to CCBs located within the
Area of Investigation, the Yard 520 sample data were no longer needed. However, at the request of
USEPA, this risk assessment has conducted a detailed radionuclide risk assessment of the Yard 520
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data in addition to the MWSE data following USEPA guidance (USEPA, 2010b). Because exposure
to CCBs in Yard 520 is not a currently complete exposure pathway, and it will not be a complete
exposure pathway in the future due to the regulatory closure requirements administered by IDEM, and
the CCBs in Yard 520 are not representative of the suspected CCBs present in the community, further
discussion focuses on the risk results for the MWSE datasets.
7.5.1.2 Scenarios Evaluated
Both chemical constituent data and radionuclide data are available for the suspected CCBs collected
from the utility trenches along streets within the Area of Investigation under the MWSE program.
USEPA risk assessment guidance (USEPA, 1989a) assumes receptor contact with soil via various
exposure pathways (ingestion, dermal contact, and inhalation). Two CCB exposure scenarios were
evaluated for these datasets:
•
A hypothetical screening level 100% CCB scenario, and
•
A site-specific 27% CCB scenario, as derived from the CCB visual inspection results detailed
in Appendix I
Note that this HHRA conservatively assumes in the hypothetical screening level 100% CCB scenario
that all of the assumed contact for the residential, recreational, industrial, and construction worker
receptors is contact with “soil” that is all CCBs. As seen in Figure 4, CCBs were deposited (or placed)
primarily along approximately 37% of the roadways within the municipal water service extension.
However, as evidenced by the detection of trace levels of CCBs (less than 1%) in three of the five
background samples submitted for CCB analysis (see Section 3.1.1), CCBs may have been released
and transported from areas of original deposition (or placement) to various unsampled portions of the
Area of Investigation. As noted in Figure 4, “the presence or absence of CCBs within the Area of
Investigation at locations not otherwise identified as ‘field verified suspected’ or ‘inferred suspected’
CCB locations is not known at this time.” Nonetheless, the results of the visual inspection program
conducted as part of the RI were used to identify where within the Area of Investigation suspected
CCBs are present at the surface (defined as at the ground surface and/or within the top 6 inches of
material at the ground surface), and demonstrated that the suspected CCBs present at the surface
are mixed with other materials. Where suspected CCBs are present at the surface, suspected CCBs
make up less than 25% of the material for the majority of the sample locations (see Appendix I for a
detailed discussion of the CCB visual inspection results). Thus the 100% CCB exposure scenario for
the receptors assumed to be exposed to CCBs at the ground surface (the resident receptor and the
outdoor worker receptor) is indeed a hypothetical screening level scenario. The risk results for this
scenario are presented here for informational purposes, but do not represent potential risk via
exposure to suspected CCBs within the Area of Investigation. The maximum average 27% CCB
scenario provides a site-specific but still very conservative estimate of potential exposure and risk for
this risk assessment.
This distinction between the hypothetical 100% CCB and the site-specific 27% CCB scenarios is
applicable to the receptors assumed to be exposed to CCBs at the ground surface, i.e., the resident
and the outdoor worker. The construction worker is assumed to be exposed to CCBs during
excavation work, thus the 100% CCB scenario was used to evaluate this receptor. The recreational
receptors are assumed to be exposed to CCB-derived constituents in sediment and surface water in
Brown Ditch and Ponds 1 and 2. As discussed previously, radionuclide data are available for Brown
Ditch sediment, therefore, the summed chemical constituent and radiological data risk results focus on
the Brown Ditch exposure scenarios for the resident and recreational receptors. Because the
radionuclide concentrations in groundwater were so low and based on the CSM that groundwater is
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likely the main pathway for the presence of CCB-derived constituents in surface water, surface water
samples were not analyzed for radionuclides (see Section 3.1.2 as well as Appendix M regarding
groundwater).
Furthermore, the hypothetical screening level risk assessment for the resident and the outdoor worker
assumes that the ground surface is completely covered with 100% CCBs. As discussed in the
evaluation provided in Section 6.3, and Appendix I, based on visual inspections, the conservative
maximum average percent of CCBs at the surface of any lot is 27%, and this site-specific scenario
has also been included in the quantitative HHRA for the residential and outdoor worker receptors.
7.5.1.3 Receptor and Scenario Specific Risk Results
The summed risk results, as presented in Table 6-36, are for the following datasets:
•
Chemical constituent data for suspected CCBs, Brown Ditch sediment, and Brown Ditch
surface water
•
Radionuclide data for suspected CCBs and Brown Ditch sediment
•
Chemical constituent and radionuclide data for background soils and Upgradient sediment in
the background datasets
-4
-6
The target risk range is 10 to 10 , as defined in USEPA guidance (USEPA, 1991b). As described
-4
-5
-6
above, potential risks greater than 10 , 10 and 10 are summarized below from the results
presented in the previous sections.
-4
Potential risks greater than 10 are associated only with the RME hypothetical screening level 100%
CCB scenario for radionuclides, as shown in Table 6-36.
•
The radionuclide potential risk for the hypothetical screening level 100% CCB resident garden
-4
scenario is 2x10 , as is the total potential chemical plus radionuclide risk for the garden
-4
scenario; however, no individual radionuclide or chemical constituent risk is above 10
•
The total potential chemical plus radionuclide risk for the hypothetical screening level 100%
-4
CCB resident no garden scenario is 1x10 , which is the upper end of USEPA’s target risk
range
•
The radionuclide potential risk for the hypothetical screening level 100% CCB outdoor worker
-4
scenario is 1x10 , as is the total potential chemical plus radionuclide risk, both of which are at
the upper end of USEPA’s target risk range
-5
The total potential risks for the RME resident site-specific 27% CCB scenarios are within the 10 to
-4
10 risk range, as are the total potential risks for the background dataset. The site-specific 27% CCB
scenario and background risk results are the same order of magnitude, although the site-specific 27%
CCB dataset risks are slightly higher than the background risks.
The recreational and construction worker RME scenario summed risks are within the low end of the
-6
-5
10 to 10 risk range.
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7.5.1.4 Constituent Specific Risk Results
Summary of Hypothetical Screening Level 100% CCB Scenario
-4
No potential risks greater than 10 were identified in the chemical HHRA. Total potential risks greater
-4
than 10 were identified for the RME hypothetical screening level 100% CCB scenario for the
residential garden scenario and the outdoor worker scenario for radionuclides. No individual
-4
radionuclides were identified with potential risks greater than 10 . Potential carcinogenic risks greater
-5
-6
than 10 and/or greater than or equal to 10 were identified under various, but not all, hypothetical
screening level 100% CCB RME MWSE chemical and radionuclide dataset pathways and scenarios,
as described in detail in Sections 6.2 and 6.3 and summarized below.
-5
Constituents with potential risks greater than or equal to 10 were identified under the hypothetical
screening level 100% CCB RME scenario as follows:
•
•
•
•
Arsenic (residential receptor; and, outdoor worker)
Lead-210+D (residential receptor garden scenario)
Radium-226+D (residential receptor garden and no garden scenarios; and, outdoor worker)
Radium-228+D (residential receptor garden scenario; and, outdoor worker)
-6
Constituents with potential risks greater than or equal to 10 were identified under the hypothetical
screening level 100% CCB RME scenario as follows:
•
•
•
•
•
Arsenic (recreational child, recreational fisher)
Hexavalent chromium (residential receptor)
Lead-210+D (residential receptor no garden scenario; and, outdoor worker)
Radium-228+D (residential receptor no garden scenario)
Uranium-238+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-5
Constituents with potential risks greater than or equal to 10 were identified under the hypothetical
screening level 100% CCB CTE scenario as follows:
•
Radium-226+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-6
Constituents with potential risks greater than or equal to 10 were identified under the hypothetical
screening level 100% CCB CTE scenario as follows:
•
•
•
Arsenic (residential receptor)
Lead-210+D (residential receptor garden scenario)
Radium-228+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-4
No individual constituents were identified with potential risks greater than 10 . Furthermore, the
100% CCB scenario was included as a hypothetical screening level evaluation and is based on the
conservative assumption that an entire residential yard is comprised of 100% CCBs. Nonetheless,
the COPCs identified above as associated with risks ≥ 1E-06 have been identified as COCs for
potential carcinogenic effects based on the hypothetical evaluation.
Based on the results of the hypothetical screening level 100% CCB scenario HHRA for the RME
resident, iron and thallium are the only noncarcinogenic COPCs with hazard quotients above one, as
discussed in greater detail below:
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•
Iron. When the iron HQ under the hypothetical screening level 100% CCB scenario is
rounded to one significant figure per USEPA guidance (USEPA, 1989a), the iron HQ on a
target endpoint basis (gastrointestinal effects) is 1. It should be noted that iron is an
essential nutrient, and that the iron HQ under the site-specific 27% CCB scenario is below
one.
•
Thallium. The thallium HQ under the hypothetical screening level 100% CCB scenario is
1.65. The thallium HQ under the site-specific 27% CCB scenario is below one.
Noncarcinogenic regulatory targets were not exceeded for any of the CTE scenarios, sediment or
surface water under RME or CTE scenarios, or construction worker contact with groundwater under
RME or CTE scenarios. The iron HQ is essentially equal to one and it is an essential nutrient. Both
the chronic and the sub-chronic RfDs for thallium are provisional screening values derived in
Appendix A of USEPA (2010a). According to USEPA (2010a), a reference dose for thallium was not
derived because the available toxicity database contains studies that are generally of poor quality.
Appendix A of USEPA (2010a) indicates that it is inappropriate to derive provisional chronic or
subchronic RfDs for thallium, but that information is available which, although insufficient to support
derivation of a provisional toxicity value, under current guidelines, may be of limited use to risk
assessors. Therefore, the screening thallium RfDs were conservatively used in this HHRA. The
thallium RfDs are based on a subchronic study in rats and the NOAEL is based on hair follicle
atrophy; this endpoint was selected because atrophy of hair follicles is consistent with the atrophic
changes observed in cases of human thallium poisoning and may be the best indication for human
response to thallium exposure (USEPA, 2010a). However, this endpoint is not a “toxic” endpoint per
se, and the results of the thallium risk assessment should be interpreted with appropriate reservation.
Furthermore, the thallium HQ of 1.65 is based on the hypothetical scenario that a residential yard is
comprised of 100% CCBs, and the HQs are below one under the site-specific 27% CCB scenario. By
comparison, the HQ for thallium in background soils (see below) under the RME resident scenario is
1.3. Because these HQs are so similar, and due to the issues of relevance and confidence in the
screening toxicity value for thallium, no COCs have been identified for noncarcinogenic effects for the
hypothetical screening level 100% CCB scenario.
The results presented in Appendix H indicate that potential exposures and risk via the homegrown
produce consumption pathway under the hypothetical screening level 100% CCB scenario are within
the low end of the range of exposure and risk for the normal background dietary ingestion of arsenic,
indicating that carcinogenic risk from ingesting homegrown produce containing arsenic is likely not a
human health concern.
Based on the results of the hypothetical screening level evaluation assuming 100% CCBs, the
following COCs were identified under RME conditions or under CTE conditions:
RME Conditions
•
•
•
•
•
•
Arsenic (residential receptor garden and no garden scenarios, outdoor worker, recreational
child, and recreational fisher)
Hexavalent chromium (residential receptor garden and no garden scenarios)
Lead-210+D (residential receptor garden and no garden scenarios)
Radium-226+D (residential receptor garden and no garden scenarios and outdoor worker)
Radium-228+D (residential receptor garden and no garden scenarios and outdoor worker)
Uranium-238+D (residential receptor garden and no garden scenarios and outdoor worker)
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CTE Conditions
•
•
•
•
Arsenic (residential receptor garden and no garden scenarios)
Lead-210+D (residential receptor garden scenario)
Radium-226+D (residential receptor garden and no garden scenarios and outdoor worker)
Radium-228+D (residential receptor garden and no garden scenarios and outdoor worker)
Summary of Site-Specific 27% CCB Scenario
-4
No potential total or individual risks greater than 10 were identified under the RME or CTE site-5
specific 27% CCB scenario. Potential carcinogenic risks greater than 10 and/or greater than or
-6
equal to 10 were identified for some, but not all, site-specific 27% CCB RME pathways and
scenarios, for the MWSE chemical and radionuclide dataset, as described in detail in Sections 6.2
and 6.3 and summarized below.
-5
Constituents with potential risks greater than or equal to 10 were identified under the site-specific
27% CCB RME scenario as follows:
•
•
Arsenic (residential receptor)
Radium-226+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-6
Constituents with potential risks greater than or equal to 10 were identified under the site-specific
27% CCB RME scenario as follows:
•
•
•
Arsenic (recreational child, recreational fisher, and outdoor worker)
Lead-210+D (residential receptor garden and no garden scenarios)
Radium-228+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-5
No constituents with potential risks greater than or equal to 10 were identified under the site-specific
27% CCB CTE scenario.
-6
Constituents with potential risks greater than or equal to 10 were identified under the site-specific
27% CCB CTE scenario as follows:
•
•
•
•
Arsenic (residential receptor)
Lead-210+D (residential receptor garden scenario)
Radium-226+D (residential receptor garden and no garden scenarios; and, outdoor worker)
Radium-228+D (residential receptor garden scenario; and, outdoor worker)
Carcinogenic regulatory targets were not exceeded for any of the RME or CTE site-specific 27% CCB
scenarios, sediment or surface water scenarios, or construction worker contact with groundwater
under RME or CTE scenarios. The COPCs identified above as associated with risks ≥ 1E-06 have
been identified as COCs for potential carcinogenic effects based on the site-specific 27% CCB
evaluation.
Noncarcinogenic regulatory targets were not exceeded for any of the site-specific 27% CCB
scenarios, sediment or surface water scenarios, or construction worker contact with groundwater
scenarios. Therefore, no COCs have been identified for noncarcinogenic effects for the 27% CCB
scenarios.
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The results presented in Appendix H indicate that potential exposures and risk via the homegrown
produce consumption pathway under the site-specific 27% CCB scenario are within the low end of the
range of exposure and risk for the normal background dietary ingestion of arsenic, indicating that
cancer risk from ingesting homegrown produce containing arsenic is likely not a human health
concern.
Based on the results of the site-specific evaluation assuming 27% CCBs, the following COCs were
identified under RME conditions or under CTE conditions:
RME Conditions
•
•
•
•
Arsenic (residential receptor garden and no garden scenarios, outdoor worker, recreational
child, and recreational fisher)
Lead-210+D (residential receptor garden and no garden scenarios)
Radium-226+D (residential receptor garden and no garden scenarios and outdoor worker)
Radium-228+D (residential receptor garden and no garden scenarios and outdoor worker)
CTE Conditions
•
•
•
•
Arsenic (residential receptor garden and no garden scenarios)
Lead-210+D (residential receptor garden scenario)
Radium-226+D (residential receptor garden and no garden scenarios and outdoor worker)
Radium-228+D (residential receptor garden scenario and outdoor worker)
Summary of Potential Background Risks
-5
-6
Potential carcinogenic risks greater than 10 and/or greater than or equal to 10 were identified for
the same four COPCs indentified under the site-specific 27% CCB scenario under various, but not all,
RME pathways and scenarios for the background chemical and radionuclide datasets, as described in
detail in Sections 6.2 and 6.3 and summarized below.
-5
Constituents with potential risks greater than or equal to 10 were identified under the RME
background scenario as follows:
•
•
Arsenic (residential receptor)
Radium-226+D (residential receptor garden scenario; and, outdoor worker)
-6
Constituents with potential risks greater than or equal to 10 were identified under the RME
background scenario as follows:
•
•
•
Lead-210+D (residential receptor garden scenario)
Radium-226+D (residential receptor no garden scenario)
Radium-228+D (residential receptor garden and no garden scenarios; and, outdoor worker)
-5
No constituents with potential risks greater than or equal to 10 were identified under the CTE
background scenario.
-6
Constituents with potential risks greater than or equal to 10 were identified under the CTE
background scenario as follows:
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•
•
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Arsenic (residential receptor)
Radium-226+D (residential receptor garden and no garden scenarios; and, outdoor worker)
Radium-228+D (residential receptor garden scenario; and, outdoor worker).
The HQ for thallium is greater than the noncarcinogenic regulatory target of one. As noted previously,
the endpoint for thallium effects is hair follicle atrophy, and the provisional toxicity value provided by
USEPA is not necessarily recommended for use (see discussion in Section 4). All other target
endpoint HQs for background soil are below one.
Comparison of Risks for Background and CCB Scenarios
While arsenic in suspected CCBs was not found to be consistent with background, the potential risk
from arsenic in background soils is of the same order of magnitude as the potential risk from arsenic in
suspected CCBs under both the hypothetical screening level 100% CCB scenario and the site-specific
-5
27% CCB scenario. Potential risks for the RME resident for arsenic from suspected CCBs are 4x10
-5
(hypothetical screening level 100% CCB scenario), 1x10 (site-specific 27% CCB scenario), and
-5
2x10 for background soils.
In addition, the potential residential RME risk from radionuclides in background soils is of the same
order of magnitude as the potential residential RME risk from radionuclides in suspected CCBs.
-4
Potential risks for the RME resident garden scenario are 2x10 (hypothetical screening level 100%
-5
-5
CCB scenario), 4x10 (site-specific 27% CCB scenario), and 2x10 for background soils.
Evaluation of Regulatory Standards for Radionuclides
In addition to the radionuclide risk assessment, an evaluation of the data with respect to regulatory
standards for radionuclides was conducted. As shown in Appendix J, USEPA guidance identifies a
standard of 5 pCi/g above background that is used to assess the combined levels of radium-226 and
radium-228. The background soil data collected during the RI were used to statistically derive a
background threshold value (BTV) for the sum of the radium isotopes, which ranges from 1 to 2 pCi/g;
therefore, the resulting 5 pCi/g plus background range is 6 to 7 pCi/g. As shown in Appendix J, all of
the results from the MWSE suspected CCB dataset, the Brown Ditch sediment dataset and the
Upgradient sediment dataset are below this 5 pCi/g plus background range.
7.5.2
Results of Screening Level Drinking Water Risk Assessment
This section provides a summary of the screening level drinking water risk assessment.
7.5.2.1 Methods
A cumulative risk screen was conducted to evaluate the residential drinking water pathway. The
screen used the RSLs for residential tap water (USEPA, 2011b) and, therefore, is protective of other
potential drinking water scenarios (e.g., a visitor to the area). Analytical data for private wells and RI
monitoring wells were compared to RSLs using this cumulative screening approach. A cumulative
screen is in essence a risk assessment in which potential risks and hazards are calculated based on
the default screening levels.
In a cumulative risk screen, RSLs are used to estimate the potential carcinogenic risk and
noncarcinogenic hazard associated with detected concentrations; therefore, the RSLs for
noncarcinogens do not need to be adjusted to account for cumulative effects because the potential
HQ for each constituent is calculated directly in order to quantify potential cumulative effects.
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The RSLs incorporate agency default, conservative exposure assumptions as well as agency selected
toxicity values. Thus, the potential risks and hazards estimated using the RSLs are conservative and
are likely overestimates of potential risks and hazards.
The evaluation of the drinking water pathway was conducted in two parts. First, a cumulative screen
was used to identify constituents above regulatory targets in each well for which RI data were
collected. Second, information for wells located outside of the municipal water service area was
evaluated to determine if those wells were impacted by CCB-derived constituents.
7.5.2.2 Results of the Cumulative Risk Screen
-6
No constituents with risks greater than 10 or a total endpoint-specific HI greater than one were
-4
identified in any private well. No constituents with risks greater than 10 or a total endpoint-specific HI
greater than one were identified in any background well. Arsenic was identified in background well
-5
MW120 with a potential risk greater than 10 . Within the municipal water service area, constituents
-4
with risks greater than 10 or a total endpoint specific HI greater than 1 were identified only in
monitoring wells in the immediate vicinity of Yard 520 (MW-3, MW-6, MW-8, TW-10, TW-12, TW-15D,
-5
TW-16D, and TW-18D). Potential risks above 10 were identified for arsenic in MW104, within the
municipal water service area; however, the chemistry of this well indicates septic impacts. In addition,
outside of the municipal water service extension area, constituents with potential risks greater than
-4
10 and a total endpoint specific HI greater than one were identified only for MW111 and MW122,
which are in the limited wetland areas bordering Brown Ditch and downgradient of significant deposits
of CCBs or suspected CCBs. These wells are shown in Figure 16.
7.5.2.3 Evaluation of CCB-Derived Constituents
The purpose of the RI is to evaluate only CCB-derived constituents. As such, the drinking water
pathway would not be complete if wells are not likely impacted by CCBs, or for which COPCs are not
identified. This analysis was conducted to determine whether wells outside the municipal water
service area are potentially impacted by CCBs. Based on that analysis, while the presence of CCBderived constituents cannot be entirely ruled out for some wells outside of the municipal water service
area, the fact that the concentrations of constituents that may be CCB-derived are so low as to not be
identified as COPCs suggests that if this pathway is complete, it is insignificant. Therefore, the
drinking water pathway for exposure to CCB-derived constituents in the area outside the municipal
water service area is likely incomplete, with the exception of MW111 and MW122. These two wells
are located in limited wetland areas (see Figure 24) that are unlikely to be developed, though such
development in the future cannot be precluded. However, they are in areas that could easily be
provided municipal water if developed in the future.
Similarly, the drinking water pathway within the area of the municipal water service would potentially
be complete only where locations have not been connected to municipal water and where wells are
screened in the shallow surficial aquifer, and only in those areas in the immediate vicinity of Yard 520
where COPCs have been identified. Thus, this evaluation of the drinking water pathway indicates that
CCB-derived constituents in groundwater used as drinking water outside of the immediate vicinity of
Yard 520, whether within or outside of the municipal water service area would not be expected to
pose a health risk to residents.
7.5.2.4 Future Scenario for the Groundwater Pathway
Review of the groundwater elevation contours and the constituent data over the course of the RI, as
presented in the RI Report, indicates that the constituent distribution in groundwater is largely
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controlled by the groundwater elevations and location relative to Brown Ditch, and there is no
indication of dramatic changes in the elevations across the seasons sampled during the RI. Based on
the information provided in the RI Report, groundwater flow and groundwater chemistry are not
expected to change significantly in the future in the absence of major unforeseen changes. While not
required under AOC II, the Respondents voluntarily continued collecting groundwater data since 2007.
Five rounds of groundwater and surface water sampling have been conducted since then, totaling 25
groundwater samples and 20 surface water samples, in addition to groundwater level measurements.
These data are used to track the extent of elevated boron in groundwater and show that the extent of
the boron is not expanding northward, and in some wells concentrations have decreased.
Therefore, while the groundwater data used in the HHRA is representative of the time period over
which it was collected, there is no information that would suggest that these conditions would change
dramatically in the future, though this remains a source of uncertainty in the risk assessment.
7.5.2.5 Other Potential Impacts on Groundwater Quality
The results of the extensive RI and this HHRA have shown CCB impacts to groundwater above health
risk-based screening levels only in localized areas, either in the immediate vicinity of Yard 520, or in
limited wetland areas, there are numerous other constituents present in groundwater in the area,
either due to natural or background conditions, or due to other anthropogenic activities. There are
many possible reasons unrelated to CCBs for water to be unpleasant. One of the most common is
natural levels of iron and manganese which are frequently present in groundwater. The Purdue
Extension Service can help a homeowner interpret water quality information
(http://www.ces.purdue.edu/extmedia/WQ/WQ-5.html). For iron and manganese, the Extension
Service provides the following information:
Iron originates in soils and rocks, occurs naturally in water and is needed in human and animal
diets. Iron in Indiana ground water spans a typical range from 0.1 to 3.0 ppm. At high
concentrations (more than 0.3 ppm) iron will discolor (reddish-orange; brown-black) household
fixtures, laundry and give an objectionable taste and odor to water. However, even at
concentrations far over 0.3 ppm few adverse health effects have been reported. Bacteria which
feed on iron can create an objectionable odor in the water and discharge a clear, oil-like slime,
typically noticed in toilet tanks.
Manganese ranges from 0.02 to 1.0 ppm in Indiana ground water. At levels greater than 0.05
ppm manganese tends to fall out of solution and form black flakes. These flakes will deposit
themselves in the same way iron stains and can clog pipes.
These naturally occurring levels of iron and manganese can discolor household items including
silverware, laundry, and jewelry, and can clog filters or well points. The presence of boron and/or
molybdenum in groundwater is unlikely to impart a taste or color to the water or cause these kinds of
problems.
In addition to high levels of iron and manganese, the RI revealed evidence of other sources of impacts
to groundwater in the area that could make water unpleasant, including:
•
•
•
Septic system discharges;
Use of road salt in the area;
A landfill located off Ardendale Road and south of South Railroad Avenue (Pines Landfill
owned by Waste Management).
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Conclusions
Based on the results of the HHRA as summarized above, risks ≥ 1E
-06 and hazards greater than 1
were identified under both the hypothetical screening level 100% CCB scenario and the site-specific
27% CCB scenario, and under both RME and CTE conditions, as well as at monitoring wells in the
immediate vicinity of Yard 520 and within limited wetland areas. The primary COCs identified include
arsenic, lead-210+D, radium-226+D, and radium-228+D. Hexavalent chromium and uranium-238+D
were identified as COCs only under the hypothetical 100% CCB scenario and RME conditions.
Receptors for which these COCs were identified include residential (all COCs), outdoor workers
(arsenic, radium-226+D, radium-228+D, and uranium-238+D), and recreational child and recreational
fisher (arsenic only). In addition to arsenic, the following metals were identified as COCs (based on
noncarcinogenic effects) at monitoring wells in the immediate vicinity of Yard 520 and in limited
wetland areas: boron, manganese, and thallium.
The screening level drinking water risk assessment identified potential risks above regulatory targets
in two wells (MW111 and MW122) located outside the water service area and in limited wetland areas
that are unlikely to be developed, though such development in the future cannot be precluded (the
location of wells in wetland areas is discussed further in Section 6.4.4.2 and is presented on Figure
24); and a subset of wells located in close proximity to Yard 520 (MW-3, MW-6, MW-8, TW-10,
TW-12, TW-15D, TW-16D, TW-18D), which are located inside the municipal water service area (see
Figure 16). Municipal water is available in the area of Yard 520, and it is unlikely that the wetland
areas would be developed, however, municipal water could be extended to these areas in the unlikely
event they were to be developed in the future.
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