2014 Highway
Runoff Manual
Mark Maurer PLA, PE.
Lynn Peterson
Highway Runoff Program Manager
Secretary of Transportation
Changes to the 2014 HRM
Washington Hydrological Society
Tacoma, WA
January 15, 2014
Date, time and initials of last edit
Changes to the HRM and NPDES Permit
• Major changes to the HRM by Chapter
– Require low impact development techniques
– Make the manual more of a design manual
– Removed Chapter 6 and made it into the Temporary Sediment and Erosion
Control Manual
• Changes to the NPDES Permit and SWMPP
• HRM recertification and training
• Questions
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Date, time and initials of last edit
HRM Chapters 1 through 3
• Chapter 1
– Deleted some background and policy material
– Rewrote sections to add clarity
• Chapter 2
– Deleted some background and policy material
– Moved some of the policy material to the Environmental Procedures Manual
– Rewrote sections to add clarity
– Rewrote Appendix 2A - Engineering and Economic Feasibility for Meeting the
HRM Minimum Requirements
• Chapter 3
– Revised flow control exempt surface waters list to be consistent with Ecology
manual
– Updated the retrofit guidelines
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Date, time and initials of last edit
Changes to Chapter 4
• Chapter 4
– Moved modeling instructions into appendices
– Added references to new design tools to aid designer in tracking land cover areas
within a TDA
– Moved BMP design guidance to Chapter 5
– Added LID definition and feasibility criteria to the infiltration design criteria section
– Added flow charts for Site Suitability Criteria
– Moved soil infiltration rate determination guidance to the appendices
– Moved UIC geotechnical design guidance to the appendices
– Added Appendix 4D – Infiltration Testing and Design
– Added Appendix 4E – Continuous Simulation Modeling
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Date, time and initials of last edit
Changes to Chapter 5
• Added LID BMP requirements including a LID flowchart
• Instructions for determining LID feasibility
• Added LID requirements for site development
• Updated design to require maintenance concurrence
• Updated some BMPs to enhance maintenance operations
• Updated the Media Filter Drain BMP to add different configurations
• Revised design guidance for Continuous Inflow Biofiltration Swales to allow
their use for Enhanced Treatment
• Added design guidance for certain BMPs from Chapter 4
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Steps to determine LID feasibility per TDA for new PGIS, applicable replaced PGIS, and PGPS
LID Requirements
Can the stormwater be dispersed within the TDA?
Read Section 5-3.4 to determine whether site conditions in
TDA are appropriate for dispersion or infiltration.
• Uses a BMP menu
No
• There is no LID flow
standard for roads and
highways (collectors
and above)
No
Can infiltration be used within the TDA?
(Apply feasibility criteria and Infiltration Design
Criteria 4-5)
Yes
Apply dispersion
FC.01 – Natural Dispersion
FC.02 – Engineered Dispersion
Does dispersion meet all the runoff
treatment and flow control
requirements within the TDA?
Yes
Done
Yes
Tier 1
Use one or more of these BMPs:*
RT.02 Compost Amended Vegetated Filter
Strips (CAVFS)
RT.04 Continuous Inflow Compost-Amended
Biofiltration Swale (CABS)1
RT.07 Media Filter Drain (MFD)1,2
RT.08 Bioretention Area2
IN.01 Bioinfiltration Pond (E. WA only)
Natural Depression Storage3,4
IN.02 Infiltration Pond4
IN.03 Infiltration Trench4
IN.04 Infiltration Vault4
IN.05 Dry Well4
Tier 2
No
LID requirement met to the extent
feasible. Evaluate options for
runoff treatment and flow control.
Consider Tier 1 BMPs first before using Tier 2 BMPs
Do these BMPs meet all the runoff
treatment and flow control
requirements for the TDA?
Yes
No
LID techniques not feasible. See Figure
5.3.2 Flow Control BMP selection flow
chart
Done
See Figure 5.3.2 Flow Control BMP
selection flow chart
* See Section 5-3.6 for BMP validation and cost-effectiveness. Repeat steps for each TDA in the
project that exceeds thresholds in Figure 3-3, Step 7.
1. Model for flow control benefit through infiltration using site specific infiltration data
2. The use of underdrains is not allowed if used to meet the LID requirement.
3. Use Section 4-7 Closed Depression Analysis for modeling methods and use performance requirements for
infiltration pond.
4. Apply Pretreatment RT.24 – Presettling Basin or any basic treatment BMP listed on the next page if the
underlying soils meet or exceed Soil Suitability Criteria 7. Otherwise apply pretreatment in the form of any basic
or enhanced treatment BMP.
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Site Development LID Flow Chart
LID Site Development
Requirements
Can the stormwater be dispersed on site?
Read Section 5-3.4 to determine whether site conditions are
appropriate for dispersion or infiltration.
No
• Uses a BMP menu
No
Can infiltration be used on the site?
(Apply feasibility criteria and Infiltration Design
Criteria 4-5)
• Can use SWMMWW or
other Ecology
approved manual
Yes
Tier 1
Use one or more of these BMPs:*
BMP T5.40: Preserving Native Vegetation1
BMP T5.41: Better Site Design
RT.02 Compost Amended Vegetated Filter
Strips (CAVFS)2
RT.08 Bioretention Area3
IN.01 Bioinfiltration Pond (E. WA only)
RT.04 Continuous Inflow Compost-Amended
Biofiltration Swale (CABS)2
RT.07 Media Filter Drain (MFD)2, 3
BMP T5.11: Concentrated Flow Dispersion1
BMP T5.12: Sheet Flow Dispersion1
BMP T5.16: Tree Retention and Tree Planting1
BMP T5.18: Reverse Slope Sidewalks1
Natural Depression Storage4, 5
IN.02 Infiltration Pond5
IN.03 Infiltration Trench5
IN.04 Infiltration Vault5
IN.05 Dry Well5
Tier 2
No
BMP from Tier 1 are required unless all Tier 1 options are
determined infeasible
Yes
Apply dispersion
FC.01 – Natural Dispersion
FC.02 – Engineered Dispersion
Does dispersion meet all the runoff
treatment and flow control
requirements for the site?
Yes
Done
Does the site design include any
buildings or structures with roofs?
Yes
BMP T5.10A: Downspout Full Infiltration1
BMP T5.10B: Downspout Dispersion Systems1
BMP T5.10C: Perforated Stub-out Connections1
BMP T5.17: Vegetated Roofs1
BMP T5.19: Minimal Excavation Foundations1
BMP T5.20: Rainwater Harvesting1
LID requirement met to the extent
feasible. Evaluate options for
runoff treatment and flow control.
Do these BMPs meet all the runoff
treatment and flow control
requirements for the TDA?
Yes
No
LID techniques not feasible. See Figure
5.3.2 Flow Control BMP selection flow
chart
Done
See Figure 5.3.2 Flow Control BMP
selection flow chart
* See Section 5-3.6 for BMP validation and cost-effectiveness. Repeat steps for each TDA in the project that exceeds
thresholds in Figure 3-3, Step 7.
1. Ecology SWMMWW Volume V
2. Model for flow control benefit through infiltration using site specific infiltration data
3. The use of underdrains is not allowed if used to meet the LID requirement.
4. Use Section 4-7 Closed Depression Analysis for modeling methods and use performance requirements for infiltration
pond.
5. Apply Pretreatment RT.24 – Presettling Basin or any basic treatment BMP listed on the next page if the underlying soils
meet or exceed Soil Suitability Criteria 7. Otherwise apply pretreatment in the form of any basic or enhanced treatment
BMP.
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No
Date, time and initials of last edit
LID Requirements
2-5.2 Stormwater Facility Design Strategy
Stormwater management facilities (runoff treatment and flow control) can be utilized to
mitigate both the hydrologic impacts and the water quality impacts of a development
project by applying the following fundamental strategy:
Maintain the preproject hydrologic and water quality functions of the project site
as it undergoes development. (emphasis added)
This strategy is accomplished through the following steps:
• Step 1 Avoid and minimize impacts on hydrology and water quality.
• Step 2 Compensate for altered hydrology and water quality by mimicking natural
processes.
• Step 3 Compensate for altered hydrology and water quality by using end-of-pipe
solutions.
Steps 1 and 2 can be achieved by minimizing impervious cover; conserving or restoring
natural areas; mimicking natural drainage patterns (for example, using sheet flow,
dispersion, infiltration, or open channels); disconnecting drainage structures to avoid
concentrating runoff; and using many small redundant facilities to treat, detain, and
infiltrate stormwater. This approach to site design reduces reliance on the use of
structural management techniques.
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BMP Changes
• Continuous inflow biofitration swale RT.06
approved for enhanced treatment
• New sketches to illustrate design guidance
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BMP Changes
• Media Filter Drain RT.07
– added more options
based on modifications
made on SR 405 project
and documented through
Technology Approval
Protocol - Ecology
• Added sections to show
various MFD
configurations
• Named MFD
configurations (Type 1-5)
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HRM Tools
• Several new tools and
spreadsheets added to
HRM website
– LID Feasibility Checklist
– CAVFS LID Calculator
– MGSFlood modeling input
– Basic and wet biofiltration
swale design
– Continuous inflow
biofiltration swale design
– MFD underdrain design
– Slotted pipe flow spreader
design
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Date, time and initials of last edit
Changes to HRM Chapter 6 Temporary Sediment and
Erosion Control Manual
• Chapter 6 is now a stand-alone manual
• Revised to meet current Construction General Permit
• Added Element 13: Protect Low Impact Development BMPs
• Appendix 6A is folded into the manual
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Date, time and initials of last edit
Changes NPDES Permit
• Added TMDLs from EPA approved TMDL list
• TMDLs will only be added at permit reissuance or via administrative order
• Language clarifying that WSDOT will only have to do “Action Items” in nonpermit areas and not apply all of HRM requirements
• Eliminates toxicity testing
• Specifies an end date to on-going baseline monitoring
• Requires WSDOT participation in regional status and trends monitoring
• Updated definitions for consistency with the definitions in the Phase I and II
permits*
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Date, time and initials of last edit
Changes to the NPDES Permit Stormwater
Management Plan
• Added notification and remediation procedure for traffic accident related spills
• Eliminates requirement for consultation with the Services for projects where
ESA § 7 consultation for projects without a federal nexus
• TMDL triggered stormwater retrofits is added to the stormwater retrofit
program
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Date, time and initials of last edit
Questions?
Mark Maurer PLA, PE
WSDOT Highway Runoff Program Manager
[email protected]
http://www.wsdot.wa.gov/environment/waterquality/runoff/highwayrunoffmanual.htm
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