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• 5) Using the maximum velocities stated earlier, ditch slopes, depth and bottom width <br />geometry were then calculated for the channels. <br />Designs for all culverts were done in a similar manner except that once the peak flows for the <br />culvert watersheds were calculated, the standard FHA procedures were used to properly size <br />the culvert. For all culverts, a corrugated metal pipe was used with inlet control. In order to <br />standardize culverts, a few culvert sizes were selected forall situations although, in some cases, <br />the culvert is over designed. Although WFC commits to maintaining the culverts in good <br />condition, we only commit to the cross-sectional area needed to pass the design peak flow, not <br />the entire area of the culvert. <br />5. Sedimentation Pond 007 <br />Other ponds design details are discussed in Attachments 2.05.3(3)-4, 2.05.3(3)-5, 2.05.3(3)-6 <br />and 2.05.3(3)-11. In accordance with 4.05.2 and the approved NPDES permit, WFC will use <br />Pond 007 to prevent, to the extent possible, additional contributions of sediment to stream flow <br />or runoff outside the permit area due to mining disturbance (see Map 2.05.3(3)-1). Attachment <br />• 2.05.3(3)-2 gives the design calculations on Sediment Pond 007. Attachment 2.05.3(3)-3 gives <br />the typical soil grain size distribution information. Maps 2.05.3(3)-2-1 and 2.05.3(3)-2-2 shows <br />the as-built design of Pond 007. <br />The sedimentation pond is designed, constructed, and maintained to: <br />a. Provide storage for the runoff or inflow entering the pond as a result of a 10-year, <br />24-hour precipitation event and to meet all applicable State and Federal regulations <br />for all effluent limitations before discharge from the permit area. The characteristics <br />of the mine site, reclamation procedures, and on site sediment control practices are <br />also considered in the design. <br />b. The sedimentation pond was designed to provide adequate sediment storage <br />volume in compliance with the CDMG regulations. <br />c. An appropriate non-clogging dewatering device will be installed to maintain a 10- <br />year, 24-hour storage volume. <br />• (Revised July 2006) 2.05.3(310 <br />