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From page 77... ... 77 This chapter shows the state DOT how to determine the removal performance of proposed BMPs. It provides state DOT practitioners with an overview of methodologies and references to compare compliance strategies with regard to pollutant removal performance. Read the entire page →
From page 78... ... 78 Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff Table 39 compares load reduction and effluent target objectives applicable to the standard and presumptive approaches previously described. BMP performance evaluations should consider evaluation metrics that are most applicable to demonstrating TMDL compliance. Read the entire page →
From page 79... ... Best Management Practice Pollutant Removal Performance 79 Best Management Practice Sizing. With respect to pollutant removal performance, structural BMP sizing can generally be grouped into two categories based on type of BMP: • Storage-based: The BMP is sized to capture a certain runoff volume within the storage capacity of the system before overflow occurs. Read the entire page →
From page 80... ... 80 Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff For calculation of load reduction, capture efficiency can be determined using long-term continuous hydrologic simulation methods (or relationships derived from continuous simulation methods) Read the entire page →
From page 81... ... Best Management Practice Pollutant Removal Performance 81 transportation-related land uses representing 10 states. The transferability of BMPDB data to state DOT scenarios and the impact of geography and land use parameters on performance are described in Geosyntec Consultants and Wright Water Engineers, Inc. Read the entire page →
From page 82... ... 82 Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff Pollutant Removal Algorithm Description Applicable Pollutants Applicable BMPs Particle Settling Effluent concentrations are determined based on particle-settling theory, associating the proportion of influent particle-size distribution classes removed based on residence time and BMP geometry. • TSS and those associated with TSS (see Pollutant Partitioning and Mass Fraction algorithm) Read the entire page →
From page 83... ... Best Management Practice Pollutant Removal Performance 83 performance is likely to be highly site-specific and may vary over time due to public awareness, materials used in the manufacturing of vehicle parts, and technological advancement. While many studies have evaluated nonstructural BMP performance (Herrera et al. Read the entire page →
From page 84... ... 84 Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff Nonstructural BMP Factors Affecting Performance Quantifiable Variables Example Evaluations Street Sweeping Type of technology and equipment used, frequency, timing in relation to rainfall, road condition, location Amount of debris and sediment removed, lane miles swept; TSS and/or metals concentrations in runoff • Street Sweeping for Pollutant Removal (Curtis 2002) • Deriving Reliable Pollutant Removal Rates for Municipal Street Sweeping and Storm Drain Cleanout Programs in the Chesapeake Bay Basin (Center for Watershed Protection 2008) Read the entire page →
From page 85... ... Best Management Practice Pollutant Removal Performance 85 to many relevant models useful for evaluating BMP performance related to TMDLs (EPA 2018C) Read the entire page →
From page 86... ... 86 Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff Tool EPA National Stormwater Calculator NCHRP Report 792 SELDM Included BMPs • Bioretention (rain garden and street planter) • Cisterns (rain harvesting) Read the entire page →
From page 87... ... Best Management Practice Pollutant Removal Performance 87 reductions are based on influent–effluent regression equations developed from the BMPDB. Hydrologic performance nomographs representing continuous simulation results are available for 343 rain gages included in each tool. Read the entire page →
From page 88... ... 88 Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff provided below to allow replication by state DOT practitioners for local conditions. For each step, the input values evaluated for the example analysis are defined. Read the entire page →
From page 89... ... Best Management Practice Pollutant Removal Performance 89 4. Define tributary area attributes: The first section of the Project Design worksheet on each tool is used to define tributary area input parameters. Read the entire page →
From page 90... ... 90 Approaches for Determining and Complying with TMDL Requirements Related to Roadway Stormwater Runoff Note: BMPs with horizontal-line reduction rates are not influenced by the infiltration rate. Bioretention with Underdrains Dry Detention Infiltration Basin Sand Filter Wet PondBioretention without Underdrains 12,5002,000 1,500 1,000 500 0 10,000 7,500 5,000 2,500 0 75,000 60,000 45,000 30,000 15,000 0 Figure 26. Read the entire page →
From page 91... ... Best Management Practice Pollutant Removal Performance 91 TKN, TN, dissolved phosphorus, TP, and TSS. If a specific pollutant or subset of pollutants is of concern for TMDL compliance evaluation, only those pollutants need to be evaluated. Read the entire page →

From page 77...

... 77 This chapter shows the state DOT how to determine the removal performance of proposed BMPs. It provides state DOT practitioners with an overview of methodologies and references to compare compliance strategies with regard to pollutant removal performance.