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• the 100-year storm event with a discharge rate of less than 3 cfs. The 10 year 24 hour runoff is fully <br />contained in the pond. The pond will remain throughout the life of mine and during the initial period <br />after reclamation until vegetation has been adequately reestablished over the mine area. <br />Surface Facilities <br />As shown in Phase 1 of Map C-6, drainage from the buildings (i.e., shop, dry, and administrative <br />offices), mine access road, and parking area will be collected in a ditch along County Road 5/10 and <br />diverted to the sediment pond via two 24-inch culverts installed under the road. The water treatment <br />area will be gradually sloped at a grade of about 2 percent toward the sediment pond. Therefore, <br />stormwater runoff and any spills from the treatment area will be captured in the sediment pond. <br />Surface drainage in the facilities areas will remain the same through phase 2 and 3 of the project as <br />shown on Map C-6. <br />(ire Pad <br />Initially, the ore pad at the site will be located within a fully bermed area that will contain all direct <br />precipitation. As the lower pad area is expanded to its full size, a new ore pad will be constructed using <br />a GCL liner and 2.5 feet of cover material consisting of compacted fine-grained and run-of--mine waste <br />rock covered with an additional 1.0 feet of compacted run-of--mine waste rock (See Appendix J). This <br />pad will be contained within a berm and all drainage will be routed to a concrete sump. The <br />containment berm will be approximately a foot high and will have gradually-sloped sides that will <br />allow for haulage buggies, trucks, and loaders to access the ore stockpile. The sump will be equipped <br />with an overflow that will drain excess water through a 6-inch HDPE pipe into the Untreated Water <br />Tank. As shown on Map C-6, these drainage controls will remain in place through Phase 2 and 3. <br />Waste Pile <br />Surface drainage controls for the waste pile will be implemented in three phases during mine <br />operations; initial (phase 1), interim (phase 2), and final (phase 3). These three phases are illustrated on <br />Map C-6. <br />• <br />Whirlwind Mine 07 (rev. April 08) D-30 <br />