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iiiiii-ii~ii~iii~ii <br />HYDROLOGIC DOCUt+lENTATZi <br />SMALL AREA E7Q~IPTION <br />YARD AREA <br />The following calculations demonstrate the amount of sediment fence, straw <br />bales or gravel berm surface area required to adequately handle the runoff from <br />the Yard Area SAE. <br />Runoff volume and peak discharge calculations were performed utilizing the <br />SEDCAD 4 computer model consistent with the methodology previously discussed in <br />this Exhibit. The sediment control structure was designed to handle the peak <br />discharge from a 10-year, 24-hour storm event. <br />1 Hydrology Inputs <br />All hydrology inputs are shown on the SEDCAD 9 computer printouts. <br />The CN numbers used for the SAE watershed were obtained from Procedures <br />for Determining Peak Flows in Colorado and Technical Release No. 55 <br />(USDA-SCS, 1960). Based on soil type and vegetation cover, curve numbers <br />were determined using Table 2-2a and 2-2 d, USDA-SCS TR-55, for the <br />following conditions: <br />Reclaimed (< 2 years) <br />Soil Type: B <br />• Ground Cover: <30$, Poor <br />Cover Type: Herbaceous <br />CN: 80 <br />2 Hydrology Results <br />Peak Discharge In <br />10-year,24-hour event <br />0.91 cfs <br />3. Sediment Fence Reouirements <br />Sediment Fence Permissivity: <br />Required Surface Area: <br />10 gal/min/f t' or 0.022 cfs/ftz <br />0.85 cfs / 0.022 cfs/ft'- 39 ft` <br />The silt fence should be installed in accordance with the manufactures <br />recommendations. Design assumes regular inspections and maintenance. <br />4. Straw Bale Requirements <br />Straw bale Permissivity: <br />Required Surface Area: <br />14 gal/min/ft~ or 0.031 cfs/ftz <br />0.90 cfs / 0.031 cfs/ft~ = 29 ft' <br />5. Gravel Berm <br />. Gravel Berm Permissivity: <br />270 gal/min/ft' or 0.60 cfs/f t~ <br />Required Surface Area: 0.91 cfs / 0.60 cfs/f t' = 1.5 ft` <br />