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HYDROLOGIC DOCUMENTATION <br />a SMALL AREA EXEMPTION <br />EAST LOADOUT <br />NORTHEAST AREA <br />The following calculations demonstrate the rock filled dam or silt fence are adequately sized to handle and <br />treat the runoff and sediment volume from the north slope area and that the diversion berm is adequate to <br />divert runoff to the rock dam or silt fence. <br />Runoff volume and peak discharge calculations were performed utilizing the pond utility in the SEDCAD+ <br />computer model consistent with the methodology previously discussed in the Exhibit. The rock dam filter, <br />silt fence and diversion berm were designed to handle the peak discharge from a 10-year, 24-hour storm <br />event. <br />I.I Hydrologic Inputs <br />The CN numbers used were obtained from Procedures for Determining Peak Flows in Colorado and <br />Technical Release No. 55. Based on soil type and vegetation cover, curve numbers were determined for <br />the following condition. <br />Disturbed <br />• <br />Soil Type: B <br />Ground Cover: <30%, poor <br />Cover Type: Herbaceous <br />CN: 80 <br />All other hydrology inputs are shown on [he attached SEDCAD+ computer printouts. <br />1.2 Hydrology Results <br />Peak Discharge: 1.1 cfs <br />1.3 Berm Desien <br />The berm was designed using Manning's Equation for open channel Flow assuming a V-shaped channel. <br />The results are summarized as follows: <br />Channel slope <br />Side Slopes: <br />Manning's n: <br />Velocity: <br />Depth of Flow <br />Freeboard: <br />Berm Height: <br />2.0% <br />3: I left, 4: I right <br />0.035 <br />2.0 fps <br />0.4 ft <br />1.6 ft <br />2.0 ft. <br />• <br />