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• tt = L0.8C5 + 1)0.7 <br />1140 Y0.5 <br />where tc = time of concentration in hours <br />L = hydraulic Length of watershed in feet <br />S = maximum retention <br />= 1000 -10 <br />CN <br />T = average land slope in percent <br />where L.= 7,080' <br />S = 1000 -10 = 4.49 <br />69 <br />Y = 37.OX (Avg.) <br />• therefore to 0.571 hours <br />Sedimentoloav. The SED CAD computer program was utilized to celcuLa to the sediment <br />flowing into and through the principal spillway using the DEPOSITS portion of the program. <br />The results show there was no sediment flowing out of the pond es a result of the 10-yeer, <br />24-hour storm (100X Basin Trap Efficiency). <br />To determine the sediment Loading to the pond, the Average Annual "R" Xe[hod was utilized <br />to quantify the sediment storage. The amount of sediment storage is determined for a <br />defined length of time and is based on the design storm R, design storm sediment load, <br />average Annual R, and the number of years of sediment storage desired. R is the rainfall <br />erosivity factor. The equation utilized for Required Sediment Storage is: <br />Required Storage = (Annual R) (RYee rs) (Storm Sediment Load) <br />Storm R <br /> Annual R end the number of years ere input. Storm R end Storm Sediment Load are <br />• calculated for the design storm by Sedced+. <br /> 13-SA-5 Revised 08/17/92 <br />