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. 4) using the Time of Concentration and a worst case curve number, the peak flow was also <br />developed within SURVCADD using the SCS graphical method. <br />5) Using the maximum velocities stated earlier, ditch slopes, depth and bottom width geometry <br />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 culvert <br />watersheds were calculated, the culvert routine within SURVCADD was used to properly size the <br />culvert. For all culverts, a corrugated metal pipe was used with inlet control. In order to standardize <br />culverts, a few culvert sizes were selected for all situations although, in some cases, the culvert is over <br />designed. Although WFC commits to maintaining the culverts in good condition, we only commit to the <br />cross-sectional area needed to pass the design peak flow, not the entire area of the culvert. <br />Sedimentation Pond 007 <br />Other ponds design details are discussed in Attachments 2.05.3(3)-4, 2.05.3(3)-5, and 2.05.3(3)-6. <br />In accordance with 4.05.2 and the approved NPDES permit, WFC will use Pond 007 to prevent, to the <br />extent possible, additional contributions of sediment to stream flow or runoff outside the permit area <br />due to mining disturbance (see Map 2.05.3-1 ). Attachment 2.05.3(3)-2 gives the design calculations <br />on Sediment Pond 007. Attachment 2.05.3-3 gives the typical soil grain size distribution information. <br />Maps Att 2.05.3(3)2-1 and Att 2.05.3(3)2-2 shows 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, 24-hour <br />precipitation event and to meet all applicable State and Federal regulations for all effluent <br />limitations before discharge from the permit area. The characteristics of the mine site, <br />reclamation procedures, and on site sediment control practices are also considered in the <br />design. <br />b. The sedimentation pond was designed to provide adequate sediment storage volume in <br />compliance with the CDMG regulations. <br />c. An appropriate non-clogging dewatering device will be installed to maintain a 10-year, 24- <br />hourstorage volume. <br />(REVISED 9/2002 2.05.3(3) - 5 <br />r 1 <br />U <br />