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Mona toma Do not locate on fill sites or on or near steep slopes if is expected that much of the water will exit through the bottom, or modify the bottom to prevent excessive infiltration. Energy dissipation at the inlet to minimi7c erosion • Vegetate the slopes and botwm for the same reason • Freeboard of I foot • Side slopes of at least 2:1 unless vertical retaining walls are used • Incorporate bypass or overflow for large events • Provide dedicated access to the basin bottom (minimum 4:1) for maintenance vehicles • With a riser smicnire, include an anti-vortex device and a debris barrier. Conduct uupectioes semiannually and after each significant storm. Remove floatables and carry erosion problems in the pond slopes and bottom. Pay particular attention to the outlet control orifice(s) for signs of clogging. If the orifice is located in a Type 2 catch basin, remove sediments if they are within 18 in. of the orifice plate. REFERENCES Austin (City of), 1988, "Environmental Criteria Manual". Galli, J., pens. a>mm_, Metropolitan Washington Council of Governments GKY, 1989, "Outlet Hydraulics of Extended Detention Facilities", for the Northern Virginia Planning District Commis- sion gan, P., pers. commall ., Washington Department of Ecology (formally with the City of Austin) Metropolitan Washington Council of Govcrnmcnts(MWCOG), 1983, "Nationwide Urban Runoff Program Pollution Removal Capability of Urban Bcst Management Practices in the Washington Metropolitan Arca", available from NMS, PB84-245497. Northern Virginia Planning District Commission (NVPDC), 1987, "BMP Handbook for the Occoquan Watershed" Randall, C.W„ et al., 1982, "Urban Runoff Pollutant Removal by Sedimentation", in Proceedings of the Conference on Stormwater Detention Facilities, Henniker, NH, ASCE, pp 205-209 Urban Drainage & Flood Control District, Denver, Colorado, "Urban Storm Drainage Criteria Manual - Volume 3 - Best Management Practices - Storwwata Quality", Sgxcmber, 1992. Whipple, W. and J. Hunter, 1981, "Settleability of Urban Runoff Pollution", J. Water Pollution Control Federation, 53 (12): 1726-1731. TG5 s:w Municipal Handbook 5-41 1vi"2 - D R A