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• for the sedimentation ponds (A-I) are shown on Energy Mine <br />No. 3 Surface Water Hydrology (Energy Fuels Map 8). Ditches <br />have been utilized to modify the natural tributary area to <br />some of the ponds in order to take better advantage of more <br />desirable pond sites. <br />Hydrology <br />Triangular hydrographs were computed for the ponds by using <br />the peak rate of runoff and adjusting the time base to obtain <br />the design volume. The time base of the hydrographs were <br />divided by 2.67 to obtain the time of the rising limb, in <br />accordance with the SCS National Engineering Hydrology <br />Handbook, (Section 4, Hydrology, Chapter 16). As an example, <br />the inflow hydrograph to Pond A is shown on the LRCWE Plate <br />II, Sedimentation Ponds, Hydrology and Hydraulics. That same <br />• drawing summarizes the tributary area, AMC-II curve number, <br />and the volume and peak rate of runoff for the 10-year, <br />25-year and 100-year floods for each pond. <br />OUTLET WORKS <br />Primary Outlet Works <br />Riser type outlets were designed for the ponds to achieve a <br />minimum of 24 hours of detention time for the 10-year, <br />24-hour inflow flood. A Type 3 riser constructed of <br />corrugated metal pipe was designed for each of the ponds. The <br />Type 3 riser has one or two holes whose size and elevation <br />vary for each pond. The riser is detailed on the LRCWE Plate <br />I, Sedimentation Ponds. For all of the ponds, the top of the <br />riser elevation was set at the 10-year flood elevation. <br />• <br />f (~ Leonard Rice Consulting Water Engineers. Inc. <br />