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The runoff and routed hydrographs were generated using the SCS Dimensionless Unit Graph • Method. For each basin, this method requires the determination of the SCS lag time that is expressed as: Lo.a x (S + 1)0.~ ~° 1900yo.s where: tp = lag time in hours, L = length of watershed in feet, y = average watershed slope in percent, S = (1000/CN) - 10, and CN = curve number. A summary of the calculated lag time for each basin is also presented in Table 3-1. The chazacteristics of the basins were input into the Army Corps of Engineers HEC-1 computer model (COE, 1996) for the hydrologic analyses. • 3.5.3.2 Diversion Channel and Riprap Sizing The diversion channel was sized based on the flow obtained from the HEC-l computer analysis and the grading of the regraded surface. The proposed channel configuration is to be trapezoidal in shape with a 3H:1 V side slope and a bottom width of 6 feet. The diversion channel is divided into three segments based on the boundaries of the basins adjacent to the channel (see Figure 3-4). Segment 1 with an average slope of 1.7 % extends in an east direction adjacent to the evaporation pond area for approximately 174 feet before emptying into Segment 2. Segment 2 of the diversion channel has an average slope of 0.8 % and extends approximately 826 feet along the north side of the pond before emptying into Segment 3. Segment 3 with an average slope of 0.7 % and a length of approximately 406 fee[ extends past the holding pond and berm azea. An outlet erosion protection apron will be required to decrease flow velocity at the channel exit. Each segment of the diversion channel will require riprap stabilization to protect against erosion. A spreadsheet program based on the 1991 U.S. Army Corps of Engineers Method (COE, 1991) i was used to analyze channel reaches requiring riprap stabilization. In the spreadsheet program, Battle Mountain Resources, fnc. DRAFT Shepherd Miller, /nc. °:vaoze~r..~~.w~.~r~.~ 3-6 May 11, /999