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Novemlrr 1993 <br />• Disturbed <br />Soil Type: <br />Treatment: <br />Cover Conditions: <br />CN: <br />2.3 Hydrology Results <br />Rlton Creek " Sma!! A>ea Exemption • 4 <br />B <br />Straight Row and Con[oured <br />Poor <br />79 <br />Peak Discharge <br />10-year,24-hour event <br />Loadout Area 3.5 cfs <br />2.4 Ditch and Berm Design <br />The berms were designed using Manning's equation for open channel flow assuming a <br />V-shape channel. The results are summarized as follows: <br />• <br />Berm <br />Q 3.5 cfs <br />Berm slope: 0.5 <br />Sideslopes: 2H:1V <br />Mannings n: .035 <br />Depth of flow: 1.0 Eeet <br />Velocity: 1.8 fps <br />Berm height: 1.3 feet <br />Freeboard: 0.3 feet <br />(Note: The berm design is considered conservative as it assumes atwo-sided u-ditch. In <br />reality it is only aone-sided ditch). <br />2.5 Sediment Fence Requirements <br />Given the peak discharge and the permissivity of the sediment fence, the amount of sediment <br />fence surface area required to safely pass the peak discharge from a 10-year, 24hour event a•as <br />determined as follows: <br />Sediment Fence permissivity: 15ga1/min/ftz or 0.033cfs/ft' (Manufacturers Quote) <br />Required Surface Area: <br />Loadout Area 3.5 cfs / 0.033 cfs/ft= = 106 ft' <br />The required length of fences should be calatlated assuming a flow depth of 1 foot. Actual <br />fence installation should be a minimum of 1.5 feet to allow free board and a fattor of safety on <br />the permissivity. <br /> <br />The silt fence should be installed in accordance with the manufactures recommendations. <br />Designs assume regular inspections and maintenance. <br />A:VSaBTRO>.PGS TerraMat>ix/ACZ Inr. * P.O. J3ox 774018 * Steamlwat S rs s Colorado 80477 * 03 879~616D <br />n/tvvs ~o~ P^ 8 ~ (3 ~ <br />