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7. ON -SITE STORMWATER MANAGEMENT <br />As documented in Section 1 of this report this project is required to meet Minimum <br />Requirements 1-5. As a result,. this project is required to use the On -Site Stormwater <br />Management BMPs from the 2019 DOE SWMMWW. <br />Per the DOE SWMMWW the BMP's must be evaluated in the order they are listed. <br />BMP's for roofs: _ <br />1. Full Dispersion: Not feasible due to the 65:35 requirement. <br />2. Downspout Infiltration Systems: <br />As previously mentioned in. this report, soil logs taken for the .septic design found <br />loamy fine sand to approximately 41 inches below grade on the eastern side of the <br />" project parcel. Therefore, infiltration is feasible in this area and is the selected BMP for <br />this project. <br />Infiltration of the,NPGIS shall be done using two infiltration trenches. According to the <br />2010 COE Manual, a 2' wide infiltration trench installed. in soil classified as :`loamy <br />sand' shall be sized with a length of 75 feet per 1,000 sf of contributing roof area. For <br />the SFR roof area of 2,102 sf, the required trench area is 316 sf. Therefore, two <br />infiltration trenches shall be used. One being 30'x3' and the other being 51'x4.5'.The <br />combined area total comes to 319.5 sf, which shall be sufficient to infiltrate all NPGI.S <br />runoff. <br />3. Downspout Dispersion Systems: <br />Minimum flow paths cannot be achieved; therefore, downspout dispersion is infeasible. <br />4. Perforated Stub -out Connections <br />High priority BMP selected, <br />- Haack 75th SFR 20-0817 <br />September 2020 <br />Revised November 2020 Page 9 <br />