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• <br />tc = X0.6(5 + 1)0.7 <br />1140 Y0.5 <br />where tc = time of concentration in hours <br />L = hydraulic length of watershed in feet <br />5 =maximum retention <br />= 1000 -10 <br />CN <br />Y = average land slope in percent <br />rAiere L = 7,080' <br />S = 1000 -10 = 4.49 <br />69 <br />Y = 37.O~a (Avg.) <br />• <br /> <br />therefore tc = 0.571 hours <br />Se di mentology. The SEDCAD computer program was also utilized to calculate 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 as a result of the 10-year, <br />24-hour storm (100@ Basin Trap Efficiency). <br />The Revised Universal Soil Loss Equation (RUBLE) was used to determine the sediment <br />loading to the pond to estimate sediment storage and frequency of cleanout. <br />Condition Area (ac.) R K LS C P <br />Undisturbed 318.4 30 0.24 12.7 0.005 1.0 <br />Disturbed 120.2 30 0.24 12.7 0.586 1.0 <br />Total 438,6 <br />Includes roads, topsoil removed areas, and pit/spoil areas. <br />6,585.8 tons/year x 60k delivery ratio = 3,951.5 tons/year <br />Tons/Ac/ <br />Year Tons/Year <br />0.457 145.5 <br />53.58 6,440.3 <br />6,585.8 tons/yr <br />13-5-5 <br />