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• <br />• <br /> <br />HYDROLOGIC DOCUMENTATION <br />SMALL AREA EXEMPTION <br />WEST LOADOUT RAILWAY CONTAINMENT BERM <br />The following calculations demonstrate the amount of sediment fence surface area required to adequately <br />handle the runoff from the railway containment berm area and undisturbed upland areas. <br />Runoff peak discharge calculation were performed utilizing the SEDCAD+ computer model consistent with <br />the methodology previously discussed in this Exhibit. The sediment fence was designed to handle the peak <br />discharge from a 10-year, 24-hour storm event. <br />Hydrolot~nauts <br />The CN numbers used were obtained from Procedures for Determining Peak FIo~~S in Colorado and <br />Technical Release No. 55. Based on soil type and vegetation cover, curve numbers here determined for the <br />following condition. <br />Disturbed <br />Soil Type: B <br />Ground Cover: Din Road <br />Cover Type: None <br />CN: 82 <br />All other hydrology inputs are shown on the attached SEDCAD+ computer printouts. <br />Hvdroloev Results <br />Peak Discharge: <br />Sediment Fence Requirements <br />Sediment Fence Permissivity: <br />Required Surface Area: <br />Rock Dam Re uirements <br />Rock Dam Permissivih•: <br />Required Surface Area: <br />0.60 cfs <br />l~ gal/mirr/fr or 0.033 cfs/fi' <br />0.60 cfs/0.033 cfs/tY = l8 fr <br />0.069 cfs/ft' <br />0.60 cfs/0.069 cfs/ft' = 7.0 ft' <br />Discharge through [he rock dam was detemrined using a tlow velocity of 0.069 fps. This velocity was <br />derived from data obtained from the U.S. Department of the Interiors' Engineering and Design Manual for <br />Disposal of Excess Spoils. <br />"~°°°""-:° Revised - June 1997 <br />0°/1°/9 0>: f°e~ yep <br />