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Suggested Citation:"Appendix C - Reach Prioritization Example." National Academies of Sciences, Engineering, and Medicine. 2019. Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff. Washington, DC: The National Academies Press. doi: 10.17226/25473.
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Suggested Citation:"Appendix C - Reach Prioritization Example." National Academies of Sciences, Engineering, and Medicine. 2019. Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff. Washington, DC: The National Academies Press. doi: 10.17226/25473.
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Suggested Citation:"Appendix C - Reach Prioritization Example." National Academies of Sciences, Engineering, and Medicine. 2019. Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff. Washington, DC: The National Academies Press. doi: 10.17226/25473.
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Page 134
Suggested Citation:"Appendix C - Reach Prioritization Example." National Academies of Sciences, Engineering, and Medicine. 2019. Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff. Washington, DC: The National Academies Press. doi: 10.17226/25473.
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Suggested Citation:"Appendix C - Reach Prioritization Example." National Academies of Sciences, Engineering, and Medicine. 2019. Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff. Washington, DC: The National Academies Press. doi: 10.17226/25473.
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Suggested Citation:"Appendix C - Reach Prioritization Example." National Academies of Sciences, Engineering, and Medicine. 2019. Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff. Washington, DC: The National Academies Press. doi: 10.17226/25473.
×
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Page 137
Suggested Citation:"Appendix C - Reach Prioritization Example." National Academies of Sciences, Engineering, and Medicine. 2019. Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff. Washington, DC: The National Academies Press. doi: 10.17226/25473.
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Suggested Citation:"Appendix C - Reach Prioritization Example." National Academies of Sciences, Engineering, and Medicine. 2019. Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff. Washington, DC: The National Academies Press. doi: 10.17226/25473.
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Page 138

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131 A P P E N D I X C Reach Prioritization Example Caltrans Reach Prioritization Caltrans delineated each reach and its subwatershed using either the applicable TMDL report or using the U.S. Department of Agriculture’s Natural Resources Conservation Service’s Watershed Boundary Dataset Hydrologic Unit Code 8 (HUC 8) or HUC 12. Caltrans assessed each of the four primary factors and assigned a metric rating for each to further quantify the ranking. The rankings from each factor were combined to determine the overall ranking for each reach, which was used to determine the high to low prioritized reaches for planning implementation in that water body. The factors with their description of the ranking methodology are summarized below. The rating factors and methodology are identified as part of the NPDES permit for TMDL compliance in California. Table 54 provides the matrix for quantifying these factors to easily prioritize the water bodies. 1. Impairment status accounts for the degree of water body impairment, as measured by the percent pollution reduction needed to achieve the WLA based on the TMDL reports. Water bodies with more impairment are given higher priority. A watershed where the reduction goals for all stakeholders are between 75% and 100% is categorized as high, between 25% and 75% is categorized as medium, and below 25% is low priority. 2. Department contributing drainage area is the rating factor assigned to water bodies where the DOT has its right-of-way in the watershed. Water bodies where the DOT has a contribution of 5% or more of the watershed area and contributes the POC would be categorized as high priority. If more detailed information on the DOT’s contribution to the watershed is available, such as runoff coefficient or unit loading rate, a more accurate estimate of its contribution and the potential impact to receiving waters is considered. 3. Connectivity to receiving waters is a rating factor assigned to water bodies based on the connectivity or proximity of a DOT’s highway (right-of-way) to the water body. Roadway/DOT facilities that are closer in proximity to a receiving water may have a more direct impact on the immediate receiving water. Roadways located further from an impaired receiving water body would likely have a lesser impact due to attenuation and dilution effects. 4. Community Environmental Health Impact is a rating factor requiring the use of the California Office of Health Hazard Assessment (OEHHA) evaluation tool which uses the environmental, health, and socioeconomic information and divides them into 10 categories. A higher category for a community indicates a higher probability of pollution to be present at the location.

132 Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff Table 54. Impaired watershed prioritization matrix. Priority Watershed Impairment Status DOT Contribution Area in Watershed DOT’s Connectivity to Receiving Waters Community Environmental Health Impact Rating Points High 75% - 100% 5% and above Over 75% of DOT drainage area within 0.25 miles of impaired reach Top 3 categories 3 Medium 25% - 50% 1% - 5% Between 25% and 75% of DOT drainage area within 0.25 miles of impaired reach Middle 4 categories 2 Low Below 25% Below 1% Less than 25% of DOT drainage area within 0.25 miles of impaired reach Lower 3 categories 1 Note: The rating factors and prioritization matrix have been implemented by Caltrans as part of the NPDES Permit Order 2012-0011-DWQ as amended by Order WQ 2014-0006-EXEC, Order WQ 2014-0077-DWQ, and Order WQ 2015-0036-EXEC. Figure 29 presents an example of the prioritized reaches and their watersheds within the Los Angeles River Metals TMDL in the state of California. Calt rans implemented this reach prioritization process as required by the State Water Resources Control Board, to better understand the priority watersheds and effectively address water quality within the high-risk receiving watersheds. The reach prioritization list was submitted to the Los Angeles RWQCB as required by the Caltrans NPDES permit, and the SWRCB evaluated and prioritized the list further based on additional factors of importance.

Reach Prioritization Example 133 The numbering of the reaches does not indicate priority status. Figure 29. Los Angeles River Metals TMDL reach subwatersheds (Michael Baker International).

Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FAST Fixing America’s Surface Transportation Act (2015) FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) NASA National Aeronautics and Space Administration NASAO National Association of State Aviation Officials NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program NHTSA National Highway Traffic Safety Administration NTSB National Transportation Safety Board PHMSA Pipeline and Hazardous Materials Safety Administration RITA Research and Innovative Technology Administration SAE Society of Automotive Engineers SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) TCRP Transit Cooperative Research Program TDC Transit Development Corporation TEA-21 Transportation Equity Act for the 21st Century (1998) TRB Transportation Research Board TSA Transportation Security Administration U.S. DOT United States Department of Transportation

TRA N SPO RTATIO N RESEA RCH BO A RD 500 Fifth Street, N W W ashington, D C 20001 A D D RESS SERV ICE REQ U ESTED N O N -PR O FIT O R G . U .S. PO STA G E PA ID C O LU M B IA , M D PER M IT N O . 88 A pproaches for D eterm ining and Com plying w ith TM D L Requirem ents Related to Roadw ay Storm w ater R unoff N CH R P Research Report 918 TR B ISBN 978-0-309-48070-3 9 7 8 0 3 0 9 4 8 0 7 0 3 9 0 0 0 0

Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff Get This Book
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State DOTs are increasingly subject to Total Maximum Daily Load (TMDL) requirements for water quality improvement that are implemented through National Pollutant Discharge Elimination System (NPDES) permits.

As a result, state DOTs may incur significant costs to construct, operate, maintain, and monitor performance of best management practices and other stormwater treatment facilities that treat stormwater from sources outside the right-of-way, as well as stormwater from roadway sources.

TRB’s National Cooperative Highway Research Program (NCHRP) Research Report 918: Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff describes how to evaluate TMDLs and develop a plan to comply with the requirements of a TMDL. The methods provide a robust approach to determining the pollutants of concern and how to assess the contribution of the roadway while understanding other important factors that affect overall pollutant loads, including adjacent land uses and watershed conditions and characteristics.

A set of presentation slides summarizing the project that developed the report is available for download.

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