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ASS-3 <br /> <br />Assumption: Drainage Area Assume 2/3 of surface runoff shall be <br />directed towards south collector ditch <br />and 1/3 to north collector ditch. <br />Solution: From: Peak discharge vs. drainage area in East Salt Creek <br />drainage basin. <br />10-year, 24-hour Peak Discharge <br />' q10 Ad x Qr <br />-_ 20 Ac x 1.562 x 103 x 170 cfs/SQMI = 5.31 <br />q10 <br />__ 10 Ac x 1.562 x 103 x 210 cfs/SQMI = 3.28 <br />q10 <br />25-year, 24-hour Peak Discharge <br />cfs <br />cfs <br />q25 = Ad x QP <br /> <br />__ 30 Ac x 1.562 x 103 x 190 cfs/SQMI =•8.90 cfs <br />q25 <br />Use the above peak discharges, q 0 and q25, for the inlet ditch design <br />flow and the emergency spillway design flow, respectively. <br />Reservoir Liquid Volume: <br />Sedimentation Reservoir shall contain the total volume from a <br />10-year, 24-hour precipitation event. <br />Detention time for the runoff shall depend upon the water <br />quality. Once the water quality meets or exceeds the <br />standards as set forth in the mine permit, the reservoir shall <br />be dewatered by pumping. <br />Volume Surface Runoff, Vsr = Q10 x Ad <br />12 in/ft <br />Liquid Volume: <br />Vsr = 0.39 x 30.00 0.98 Ac-Ft <br />12 = 42,688.80 Cu-Ft <br />..-. <br />