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• Spillway Pond B <br />Determine flow velocity down 3hAv embankment <br />Pond B Emergency Spillway <br />Manning's Equation <br />Flow in a Trapezoidal Channel <br />DEPTH D 0.300 FEET <br />WIDTH W 10.000 FEET <br />Slope S 0.330 EXPRESS AS DECIMAL <br />Mannings "N" N 0.040 EXPRESS AS DECIMAL <br />SIDE SLOPE X 2.000 SLOPE = X:1 <br />AREA =(W*D) +(X *DA2)= 3.18 FEETA2 <br />WETTED PERIMETER= (W) +2 *[((X *D)A2 +DA2)A0.5] 11.34 FEET <br />R= AREA/WETTED PERIMETER 0.28 <br />V= (1.49 /N) *(RA.667) *(SA.5)= 9.17 FT /SEC <br />Q =AXV= 29.15 CFS . <br />Q REQUIRED -Peak Discharge 22.63 CFS <br />Sediment Pond B <br />Riprap Sizing - Down Face of Embankment - Pond B <br />D50 = Size of Riprap <br />D50 = ((V X SA. 17)/7.58))A2 <br />D50 = Diameter in feet <br />V = Velocity <br />S = Slope <br />D50 = 1.00 feet 12 inches <br />POND C <br />Sediment pond C receives inflow from the mine. A sediment pond is to provide adequate capacity to contain <br />or treat the run -off or inflow entering the pond as a result of a 10 -year, 24 -hour precipitation event and any <br />additional storage resulting from the inflow from any underground mine. The calculation below shows Pond C <br />has a required water capacity of 3.23 acre feet for the 10 -year event, 24 -hour event. Pond C has an as -built <br />water capacity of 3.47 acre -feet which leaves 0.24 acre -feet of storage for mine water. If the mine discharges <br />water for 8 hours at a pumping rate of 150 gallons per minute, the resultant water discharged is about 0.22 <br />acre -feet. The mine may discharge water in this fashion three or more times per week The sediment pond <br />will be dewatered between each mine discharge event to assure the pond maintains the capacity to contain <br />the 10 -year, 24 -hour precipitation event. <br />/dPPRovED <br />PR -07 5/I'2/p3 EXH -8 -7 4/03 <br />