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C necessa ry~ to contain the design volume 1s approximately 30 feet high, To _ <br />prevent pond water from coming into direct contact with the waste materials, <br />an embankment with a protective cover is necessary along the toe of the waste <br />materials;. This fill would be placed as shown on Figure 4 before the actual <br />deposition of waste takes place. In order to analyze the effectiveness of the <br />pond, 11: was necessary to develop a stage-volume relationship for the pond. <br />The sal'ent geometric properties of the pond are presented on Table 2. A drop <br />spillway structure consisting of vertical and horizontal sections of <br />corrugats:d metal pipe was incorporated into the design to allow storm runoff <br />from events less than or equal to the 10 year, 24 hour event to pass through <br />the pond. An emergency spillway was placed 1n the center of the dam to pass <br />the peak discharge for a 100 year, 24 hour storm event (183 cfs). <br />Table 2. <br />Sediment Pond Geometry <br />C Stage Area Average Depth Capacity <br />(ft) (acres) (ft) (acre-ft) <br />~^ <br /> <br />---------------------------------------------- <br />r <br />0.00 0.000 0.00 0.00 <br />5.00 .311 2.50 .78 <br />lO.OC .6D4 6.31 3.07 <br />15.00 .896 9.82 6.82 <br />20.00 1.223 13.17 1'L.11 <br />In order to evaluate the pond design, sediment yield parameters were <br />estimated. Because of the relatively flat bench portions of the watersheds, <br />the SLO:~S method of estimating sediment yield was utilized. Each subwatershed <br />was div~:ded into flow segments that account for overland flow or flow in the <br />channel along the perimeter of the wastes. Flow 1s effectively routed down <br />the s1oE:e area of each subwatershed and then laterally along the bench to a <br />ditch as indicated by the arrows on F?~~sr~ Z. Th= flo~~ is than reta ed along <br />the dit<:h to the sediment structure at the exit point of the drainage basin. <br />Each sut~watershed. with the exception of subwatersheds 1, 2, and 13, has three <br />to five segments to account for all of the different flow components lslope, <br />bench, or stream) within the drainage basin. The subwatershed sediment input <br />, <br />~ <br />parameters are presented to Table 3. The soil erodibility factor, K, was set <br />~ <br />