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' REVISED <br />7/30/85 <br />' f-•. area is 11 acres. The watershed of Pond E is shown on Map 15, Fish <br />Creek Tipple Surface Facilities and Structures. <br />The hydrologic and hydraulic specifications which contributed to the <br />' design of Pond E are summarized in Table 1, Sedimentation Pond E Design <br />Specifications. Supporting calculations are presented in Tables 2 <br />' through 4. The permanent pool capacity is the volume of required <br />sediment storage. The required sediment storage volume was calculated <br />' using the MUSLE, as shown in Table 2, Sedimentation Pond E Design <br />Calculations. <br />The dewatering devise used to achieve adequate detention time is an <br />orifice set at the required sediment storage elevation on the riser <br />' pipe. The size of the orifice is set by routing the 10-year, 24-hour <br />runoff event through the impoundment so as to achieve a theoretical <br />i ' detention time of at least 24 hours, as shown on Table 4, Sedimentation <br />Pond E Riser Pipe Design Calculations. The top of the riser pipe is set <br />at the elevation of the combined volume of sediment storage and runoff <br />~~ from the 10-year, 24-hour event. A trash rack is provided at the top of <br />the riser to prevent clogging. <br />The riser pipe and outlet conduit are sized to convey the design flood <br />' event. A rating table of the outlet works is given in Table 4, <br />Sedimentation Pond E Riser Pipe Design Calculations. Anti-seep collars <br />' are installed on the outlet conduit to prevent piping. A splash basin <br />is provided at the discharge point in accordance with Rule 4.05.7. <br />' The top of the dam is set one foot above the elevation of the routed <br /> 25-year, 24-hour runoff event. The height (H) of the embankment is <br />' measured from the upstream toe to the crest elevation. Top width is set <br /> by the equation W=(H+35)/5. Side slopes are set at 3:1, which is <br />' considered stable under saturated conditions. <br />The embankment foundation area is excavated to competent strata with <br />' , side slopes of 1:1. The entire embankment area is stripped of topsoil <br />~_ <br />and other organic matter. Fill material consists of non-swelling clay, <br />1 <br />-4- <br />