Updates to Region 5 Model September 28, 2017 Urban Runoff EMC Worksheet (New Worksheet) This worksheet is taken from STEPL version 4.4 and added to the latest version of the Region 5 model. The previous version used land use specific loading rates for estimating the load. The newer version with the addition of this new worksheet allows user to estimate the load based on the rainfall and runoff Event Mean Concentration (EMC) values. Urban BMPs Urban BMPs from STEPL version 4.4 were added to the latest Region 5 model as shown in Table 1, below. Table 1. Urban BMPs in Region 5 model and default BMP efficiencies, with flow volume reduction BMPs in blue1. (Reference STEPL 4.4) BMP Default BMP efficiency numbers N P BOD Sediment No BMP 0.00 0.00 0.00 0.00 Alum Treatment 0.60 0.90 0.60 0.95 Bioretention facility 0.63 0.80 ND ND Combined BMPs-Calculated 0.00 0.00 0.00 0.00 Concrete Grid Pavement 0.90 0.90 ND 0.90 Dry Detention 0.30 0.26 0.27 0.58 Extended Wet Detention 0.55 0.69 0.72 0.86 Filter Strip-Agricultural 0.53 0.61 ND 0.65 Grass Swales 0.10 0.25 0.30 0.65 Infiltration Basin1 0.60 0.65 ND 0.75 Infiltration Devices1 ND 0.83 0.83 0.94 Infiltration Trench1 0.55 0.60 ND 0.75 LID*/Cistern1 0.00 0.00 0.00 0.00 UD*/Cistern+Rain Barrel1 0.00 0.00 0.00 0.00 LID*/Rain Barrel1 0.00 0.00 0.00 0.00 UD/Bioretention1 0.43 0.81 ND ND LID/Dry Well1 0.50 0.50 0.70 0.90 LID/Filter/Buffer Strip 0.30 0.30 0.40 0.60 UD/lnfiltration Swale1 0.50 0.65 ND 0.90 UD/lnfiltration Trench1 0.50 0.50 0.70 0.90 LID/Vegetated Swale 0.08 0.18 ND 0.48 LID/Wet Swale 0.40 0.20 ND 0.80 Oil/Grit Separator 0.05 0.05 ND 0.15 Porous Pavement1 0.85 0.65 ND 0.90 Sand Filter/Infiltration Basin1 0.35 0.50 ND 0.80 Sand Filters ND 0.38 0.40 0.83 1 ------- BMP Default BMP efficiency numbers N P BOD Sediment Settling Basin ND 0.52 0,56 0.82 Vegetated Filter Strips 0.40 0.45 0.51 0.73 Weekly Street Sweeping ND 0.06 0.06 0.16 Wet Pond 0.35 0.45 ND 0.60 Wetland Detention 0.20 0.44 0.63 0.78 WQ Inlet w/Sand Filter 0.35 ND ND 0.80 WQ Inlets 0.20 0.09 0.13 0.37 ND - No Data N - Nitrogen P - Phosphorus BOD - Biological Oxygen Demand LID - Low Impact Development Weather Stations The updated weather stations in STEPL version 4.4 were included in the latest Region 5 model. Figure 1 and Figure 2 show the spatial locations of the weather stations for the contiguous U.S. and for Alaska, Puerto Rico, and Hawaii respectively. ONTARIO aasl ^ a ffkLij %-v'A' At.fe.vi ' NCDC Precipitation Stations in BASINS (>=30 years of data) USA_ContiguoiiS_A lbers_Equ al_Area_Conic_USG3_ «rsion TETRATECH 0cNhu®h[ii*£/- v> ^ ii^ • y.jt V VNfeather Station County states C"tocan O Torroon c me XI Co" ,M>S Figure 1. National Climactic Data Center (NCDC) Precipitation Stations - Contiguous United States 2 ------- NCDC Precipitation Stations in BASINS (>=30 years of data) LSA_Contiguou5_A lber3_Equ al_Are a_Coi>io_USGS_ version 0 250 500 1,000 || TETHATECH 0 137.5 275 550 V\feather Station County Figure 2. NCDC Precipitation Stations - Alaska, Puerto Rico, and Hawaii Flow Volume Reductions for Urban LID and Infiltration Practices The same feature is also new to STEPL version 4.4. Region 5 model can now estimate flow volume reductions for urban LID and infiltration BMP practices. This is represented as gallons/year by urban land use type in a watershed. The Urban Runoff EMC worksheet contains pre-populated design storage depths for each of the available infiltration BMPs. The user enters the design runoff captured depth and percent imperviousness of the BMP drainage areas. The urban practices in Region 5 model that provide the flow volume reduction are listed in Table 2. Table 2. Urban LID and infiltration practices in Region 5 model with flow volume reductions. Land Use BMP Urban Infiltration Basin Urban Infiltration Devices Urban Infiltration Trench Urban LID*/Cistern Urban LID*/Cistern+Rain Barrel Urban LID*/Rain Barrel Urban LID/Bioretention 3 ------- Land Use BMP Urban LID/Dry Well Urban LID/Filter/Buffer Strip Urban UD/lnfiltration Swale Urban UD/lnfiltration Trench Urban LID/Vegetated Swale Urban LID/Wet Swale Urban Oil/Grit Separator Urban Porous Pavement Urban Sand Filter/Infiltration Basin Conservation Easements and Green Roofs (New Worksheets) Tetra Tech received these worksheets from EPA Region 5 and added them to the latest version as received. The Conservation Easements worksheet provides a location to add proposed easement acres and will calculate the load reduction from the easement compared to the proposed or probable land use that would have existed without the easement. The Green Roof worksheet provides for an accounting of load reductions from green roofs based on the land use type where the green roof is placed. It assumes the entire load intercepted by the green roof is eliminated. Urban Runoff Loading Rate (Existing Worksheet) The ability to enter user defined urban runoff loading rates instead of the default pollutant loads from various urban land use types (commercial, residential, etc.) was added. A new radio button was added to toggle from default land use pollutant loading rates to user defined pollutant loading rates. When set to user-defined, any of the default rates can be modified to reflect local data. Any loading rates not changed by the user will remain at the default values. 4 ------- |