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HYDROLOGIC DOCUMENTATION <br />• SMALL AREA EXEMPTION <br />EAST LOADOUT <br />NORTHWEST 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 [he Exhibit. The rack dam filter, <br />silt fence, and diversion berm were designed [o handle the peak discharge from a ]0-year, 24-hour storm <br />event. <br />1.1 Hydrolo ig c 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 />Soil Type: B <br />Ground Cover: <30010, poor <br />• Cover Type: Herbaceous <br />CN: 80 <br />1.2 Hvdrologv Results <br />Peak Discharge: 0.37 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 />1.0% <br />3: I left, 4: I right <br />0.035 <br />1.2 fps <br />0.3 ft <br />1.7 ft <br />2.0 ft <br />• <br />