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Time of Concentration The time of concentration, tc, is defined as the time required for <br />water to flow from the hydraulically most remote point in the watershed to the watershed <br />outlet. <br />The time of concentration for PECOCO was calculated using the Barfield, 1981 method. This <br />formula lends itself to overland flow to an impoundment. <br />tc = L 0.8 (S + 1) 0.7 <br />1140 Y0.5 <br />where tc = lag in hours <br />L = hydraulic length of watershed in feet <br />5 = maximum retention <br />= 1000 -10 <br />CN <br />0 Y = average land slope in percent <br />where L = 4,150' <br />S = 1000 -10 = 4.492 <br />69 <br />Y = 22% (Avg.) <br />therefore tc = 0.483 hours <br />Sedimentology 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 no sediment flowing out of the pond as a result of the 10 -year, 24 -hour <br />storm (100`n Basin Trap Efficiency). <br />The Revised Universal Soil Loss Equation (RUSLE) was used to determine the sediment <br />loading to the pond to estimate frequency ai cleanout. <br />[FOR 006573 <br />-6g -13 <br />i <br />