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Asc-3 <br />• pile and 2/3 to the south ditch. <br /> Use Q10 = 7.7 CFS North Collector Ditch <br />Q10 = 16 CFS South Collector Ditch <br />Q25 = 35 CFS Emergency Spillway <br />Reservoir Liquid Volume: <br />Sedimentation Reservoir shall contain the total volume <br />from a 10-year, 24-hour precipitation event. <br />Detention time for the runoff shall depend upon the <br />water quality. Once the water quality meets or ex- <br />ceeds the standards as set forth in the mine permit, <br />the reservoir shall be dewatered by pumping. <br />Volume Surface Runoff, Vsr = Q10 x Ad <br />12 in/ft <br />Liquid Volume: <br />Vsr = 0.58 x 30.00 = 1.45 Ac-Ft <br />12 <br />= 63,162 Cu-Ft <br />• Allow liquid volume for 1.34 10-year events: <br />= 1.95 Ac-Ft <br />Reservoir Sediment Volume: <br />Use Universal Soil Loss Equation (USLE) with an appropriate <br />Sediment Delivery Ratio. <br /> Ys = R•K•LS•CP•Dr = (USLE) x (Dr) <br />Ys = Sediment Yield (tons/acre/year) <br />R = Rainfall Factor <br />K = Soil Erodibility Factor (from Wishmeier, et al. Nomo- <br /> graph for 10% ufs, 10% S o%om, Soil Str. 3 and Mod. <br /> Permeability) <br />LS = Length Slope Factor <br />CP = Control Practice Factor <br />Dr = Sediment Delivery Ratio <br />The sediment yield method and figures used are from "Hydro- <br />logy and Sedimentology of Surface Mined Lands" , by C.T.Haan <br />and B.J. Barfield, except where indicated. <br />• <br />