Laserfiche WebLink
0.5 (Cg-C^A< <br />where.C| ■■ Runoff coefficient for the developed subwatershed <br />am Runoff coefficient for the undeveloped subwatershed <br />A4 ■■ Area of the developed subwatershed <br />The runoff coefficient is a funcaon of land use and ranges from 0.15 for open spaces, with <br />flat slope and loose soil to 0.9 for commercial or industrial use with steep slope an^ tight <br />soil. Chow tt al. (1988) lists runoff coefficients as a function of land use and su .1 return <br />period. <br />The detention basin volume should also be large enough to be ca|»ble of reducing the <br />phosphcmis loading (due to urbaniradon) to the prcdcvelopment loading rates. Walker <br />(1985) estimated the basin volume required to reduce the watershed phosphorus loading to <br />the undevclopment level as a function of the watershed area. He suggested the basin volume <br />in acre-ft, V, to be a fraction of the developed watershed arci in acres. This fraction ranges <br />from 0.08 to 0.25. The higher range value corresponds to a single-cell basin while the lower <br />range value corresponds to a five-cell basin. <br />The larger volume calculated from the two above-mentioned criteria (runoff volume and <br />nutrient loading) has to be used to counter the impacts of urbanization on the runoff volume <br />and water quality. <br />Required Permits. The permits required for the project elements are summarized below. <br />Aeration: <br />Sedimentation Basins: <br />Chemical Treatment: <br />DNR Permit <br />DNR and ACOE Permit <br />DNR Permit