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• Assumptions: <br />1) Time of Concentration = 6 min. 0.1 hrs. <br />2) Time of Travel = 0 <br />3) Drainage Acres (Ad) = 2.5 acre = 0.0039 mi.2 <br />Solution: From Table 5 - 3 - Tabular discharges for <br />Type - II storm distribution (csm/in) <br />Q = 4p (Ad) (Q) <br />Q = hydrograph coordinate discharge in <br />cfs (cubic feet per second) <br />Qp = 99/csm/in w/Tt = 0 <br />10 yr - 24 hr. Peak discharge. <br />Q10 - qp Ad 910 <br />• 910 - (991 csm/in)(0.0039 mi.2)(0.58 in) = 2.24 cfs <br />25 yr - 24 hr. Peak discharge <br />925 - qp Ad 925 <br />925 = (991 csm/in.)(0.0039 mi.~)(0.87 tn)= 3.36 cfs <br />Use the peak discharges for design of inlet ditch and emergency <br />spillway. <br />Reservoir Liquid Volume: <br />Sedimentation Reservoir shall contain the total volume from a 10 <br />year - 24 hr. precipitation event. <br />Detention time for the runoff shall depend upon its' water quality. <br />Once the water quality meets or exceeds the standards as set forth <br />in the mine permit, the reservoir shall be dewatered by pumping. <br />• Volume Surface Runoff, Vsr - 910 x AT <br />12 in/ft <br />