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• The total capacity of the sediment pond is acceptable. The <br />water capacity of the existing pond is 0.455 AF. The <br />required capacity of the pond is 0.49 AF which equates to a <br />0.035 AF, 1525 cubic feet, shortfall. The elevation of the <br />primary spillway is the dividing line between sediment <br />capacity and water capacity in the pond. The surface area <br />of the pond at the elevation of the primary spillway is <br />6900 SF, reference the #5 POND CERTIFICATION. By reducing <br />the outlet elevation of the primary spillway by 0.22 feet, <br />the water capactiy of pond 5 will be increased to the required <br />capacity of 0.49 AF and the sediment capacity of the pond <br />would be reduced a like amount to 0.255 AF. <br />The capacity of the revised pond 5 iaill be as follows: <br />Water Capacity <br />Sediment Capacity <br />0.490 AF <br />0.255 AF <br />Total Capacity 0.745 AF <br />C}lECK DITCH AND SPILLWAY SIZES <br />PEAK FLOW CALCULATIONS FOR EMERGENCY SPILLWAY <br />• <br /> ARHA A AREA B AREA C AREA D AREA H <br />DRAINAGE AREA (ACRES) 5.5 3.8 10.9 3.9 4.5 <br />CURVE N0. 74 74 73 73 73 <br />STORM EVENT _YR., 24 HR. 25 '25 25 25 25 <br />STORM EVENT in. 2.0 2.0 2.0 2.0 2.0 <br />RUNOFF in. 0.35 0.35 0.32 0.32 0.32 <br />WATERSHED SLOPE 0.31 0.75 0.70 0.68 0.74 <br />SLOPE ADJUSTMENT rACTOR 1.09 1.17 1.17 1.17 1.17 <br />LENGHT OF WATERSHED 400 700 1600 950 950 <br />EQUIVALENT DRAINAGE AREA 3.0 7.5 30 12 12 <br />PHAK FLOW cfs/in Fig D-2 6.25 13 35 18 18 <br />ADJUSTED PEAK FLOW <br />4.44 2.70 4.81 <br />2.11 2.43 <br />TOTAL REQIRED EMERGENCY SPILLWAY FLOW CAPACTIY <br />16.49 <br />The design of the emergency spillway is presented on page C-7 <br />and C-8. On page C-8 it is shown that the design spillway, <br />flowing at a depth of 12 inches, will handle 18.7 CFS. <br />The size of the emergency spillway as constructed is sized <br />appropriately to handle the peak flow calculated above. <br /> <br />C-16 <br />3-29-91 <br />~~ <br />