4c Using WinSLAMM to Evaluate LID Practices Hands-on Workshop. Using WinSLAMM to Evaluate LID Practices

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1 Using WinSLAMM to Evaluate LID Practices This workshop will start with a prepared WinSLAMM model file and add Low Impact Development (LID) Practices to it. The two LID Practices that will be modeled are 1) Wet Detention Pond with Water Reuse and 2) Biofiltration. The project area is a acre Industrial Development. Figures of the Development Source Areas and LID practices can be found at the end of this document. A No Management Condition Model file has been created for you. It is named LID Example No Management Condition.mdb. The parameter files used for this example will be the same used for the previous example and are listed below. The Pollutants to be analyzed are also the same and are listed below. Current File Data: Site Description: Calgary, AB LID Example, No Management Condition Seed: -42 Rain File: CO Denver Stapelton AP 4899.ran Rain Start Date: 01/01/55 Rain End Date: 12/31/55 Winter Season Date Range: December 1st March 31st Pollutant Probability Distribution File: Central.ppdx Runoff Coefficient File: v10 Central.rsv Particulate Solids Concentration File: Central.pscx Street Delivery Files: Residential LU: Central street Res and Other Urban.std Industrial LU: Central street Com Inst Indust.std Institutional LU: Central street Com Inst Indust.std Other Urban LU: Central street Res and Other Urban.std Commercial LU: Central street Com Inst Indust.std Freeways: Central Freeway.std Pollutants: Total Suspended Solids and Total Phosphorus will be analyzed in this workshop. Page 1 of 16

2 LID Practices: Approximately half of the site, which is facing away the street, will be routed to the Wet Detention Pond, and the other half will be routed to the Biofiltration devices. The single Industrial Land Use was split into two Industrial Land Use areas to represent the two drainage areas. A table showing the Source Areas within the two drainage areas is shown below. Source Area Away from Street Roof Area (acres) Paved Parking 6.95 Driveway 0.45 Sidewalk 0.14 Small Landscaped Subtotal Towards Street Roof Paved Parking 4.39 Driveway 1.81 Sidewalk Project Source Areas Description Directly connected? 3.34 Flat Roof 2.51 Flat Roof Directly connected or draining to a directly connected area Directly connected or draining to a directly connected area Directly connected or draining to a directly connected area Directly connected or draining to a directly connected area Directly connected or draining to a directly connected area Directly connected or draining to a directly connected area Directly connected or draining to a directly connected area Directly connected or draining to a directly connected area Sidewalk Draining to a Pervious Area Small Landscaped Subtotal Total Other needed information Clayey soil; Medium or High Density, No Alleys Clayey soil; Medium or High Density, No Alleys Clayey soil; Medium or High Density, No Alleys Page 2 of 16

3 Open the No Management Condition Model File. Save the model file with a new name to represent the addition of the LID practices. Change the site description. Page 3 of 16

4 Insert the Biofilter Icon downstream of the Towards Street Industrial Land Use and Insert the Wet Detention Pond Icon downstream of the Away from Street Industrial Land Use. To insert the Control Device Icon, either right click on the Away from Street Land Use Icon and select Disconnect and right click on the Towards Street Land Use Icon and select Disconnect. Or, right-click on the Junction Icon and select Disconnect. If you select Disconnect at the Junction Icon, it will disconnect all Icons attached to it. Page 4 of 16

5 The Land Uses are now disconnected from the network. If you elected to disconnect the Junction, then the Outfall Icon would also be disconnected from the Junction Icon. If this is the case, you must re-connect them before you run the model. Page 5 of 16

6 Next, add the LID Practices. Click on the Wet Detention Pond Icon (WP) then click on the white map space. Click on the Biofilter Icon (BF) then click on the white map space. Page 6 of 16

7 Then add junctions. Click on the Junction Icon, and then click on the white map space. A junction is needed between every Land Use, Control Device, and Outfall. Page 7 of 16

8 Connect the network together by dragging the tail of each Icon to the Junction. Rearrange the network as needed by dragging the Junctions or Icons. Page 8 of 16

9 Wet Detention Pond with Water Reuse The Stage-Area data for the pond is shown below. There is a 5-foot deep, 0.22 acre permanent pool. There is two feet of storage above the permanent pool. The pond side slopes are 4:1. In the model, all stages are relative. The bottom stage and area of the pond is always zero. Start the actual bottom stage of the pond at 0.01 feet. Stage Area (ft) (ac) The Initial Stage is 5 feet. The Initial Stage indicates how full the pond is at the beginning of the model run. It is usually equivalent to the permanent pool depth, but does not have to be. The Cumulative Volume is for informational purposes only. Select the Recalculate Cumulative Volume button whenever areas or stages are changes, or after you ve entered the data for the first time. The outlet structures include: 6-inch pipe at the top of the permanent pool (Stage 5), 10-ft wide Emergency Spillway 6 inches below the top of the pond (Stage 6.5) and, Irrigation of 0.05 ac-ft per day from May 1 st through September 30 th. The Wet Detention Pond form with the entered data is shown on the next page. Page 9 of 16

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11 The 0.22-acre permanent pool will be constructed in a landscaped area. Therefore, this is a change of a source area from landscaped area to water. To change the source area data, click on the Away from Street Land Use label. The Source Area Grid for that land use will appear. Subtract 0.22 acres from the Small Landscaped 1 source area and add it to the Water Body Area source area. Page 11 of 16

12 Biofiltration There are 20 Biofiltration Practices. For purposes of this workshop, we will enter the data for a typical Biofiltration practice and model 20 of them. The typical Biofiltration practice is 15-ft by 190-ft with a 5 foot buffer. There is 1-foot of gravel, covered by 3-feet of engineered soil, with ¾-foot open area storage on top. The engineered soil is 80% sand, 10% peat, and 10% compost. The outlet structures include: Infiltration into the native soil, 6-inch underdrain, 6-inches from the bottom of the gravel 3-ft vertical standpipe, with the top 6-inches from the top of the practice 5-ft wide Emergency Spillway ¼-foot from the top of the practice Evapotranspiration (in/day) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Each Biofiltration Practice will be planted with 50% grasses, 25% prairie plants, and 25% shrubs. The Biofiltration form with the entered data is shown on the next page. The Engineered Soil Media data form is shown on the subsequent page. Page 12 of 16

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14 Use the Detailed Media Characteristics form to calculate values describing the engineered soil properties for Evapotranspiration. The values calculated in the Media Data form will appear once an Engineered Media Depth is entered and/or Evapotranspiration is selected as an outlet. If some, or all, of the values are known, they can be entered in the User-Defined Soil Type row. After the values have been determined, check the appropriate box(es) at the bottom of the form to apply them to the program. Page 14 of 16

15 Running the File: Save the File and run it. The practices are reducing the runoff volume by 59 percent and the Total Suspended Solids by 76 percent. Page 15 of 16

16 The Control Practices tabs can be reviewed to determine the reduction each practice is achieving. Increasing Total Suspended Solids Reduction If time, modify the control practices to achieve an 80 percent reduction of Total Suspended Solids. The practice footprint cannot be increased; therefore, other characteristics will need to be modified. Page 16 of 16

17 Legend Drainage Area LID Model Example Project Area

18 Legend Drainage Area Source Areas Driveway Landscape Parking Roof Sidewalk Ü LID Model Example Project Area Feet

19 Legend Drainage Areas Biofilters Wet Detention Pond Ü LID Model Example Project Area Feet