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 Source or notes go here italic 6 pt. 2 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 Source or notes go here italic 6 pt. 3 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 Source or notes go here italic 6 pt. 4 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 Source or notes go here italic 6 pt. 5 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. Source or notes go here italic 6 pt. 6 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. Source or notes go here italic 6 pt. 7 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. Source or notes go here italic 6 pt. 8 BMP Changes • Continuous inflow biofitration swale RT.06 approved for enhanced treatment • New sketches to illustrate design guidance Source or notes go here italic 6 pt. 9 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) Source or notes go here italic 6 pt. 1 0 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 Source or notes go here italic 6 pt. 1 1 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 Source or notes go here italic 6 pt. 1 2 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* Source or notes go here italic 6 pt. 1 3 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 Source or notes go here italic 6 pt. 1 4 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 Source or notes go here italic 6 pt. 1 5
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