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~• ATTACHMENT F <br />Sediment Control Plan for Temporary Spoil Stockpile <br />I. Diversion. of Undisturbed Area Runoff Around the Site <br />The diversion of undisturbed runoff will be accomplished by <br />constructing a diversion ditch between the stockpile and the <br />hillside immediately south of the stockpile. A broad based <br />dip in the access road forms the upper terminus of the diver- <br />sion ditch as shown on Attachment C. <br />The ditch is sized to handle the peak flow from a 25 yr, 24 <br />hr rainfall event of 2.2 inches. Design peak flow was esti- <br />mated using SCS technical release No. 55 (1975) as described <br />in Table 1. <br />The diversion is sized using Manning's equation for a tri- <br />angular channel as follows: <br />Design Discharge = 10 cfs <br />Manning's n = 0.03 <br />• Freeboard > 0.5 ft <br />Design slope = 1X <br />Channel side slope = 3:1 <br />Normal Depth = 1.04 ft <br />Velocity = 3.09 ft/sec <br />Channel Depth = 2.0 ft <br />Top width (with ,freeboard) 12 ft <br /> <br />-1- <br />