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Section 9 <br />Surface Water <br />CDM also addressed comments provided by the BLM on the Tetra Tech drainage <br />report. For the other mine areas (e.g., Sunday, West Sunday, St. Jude, and Carnation <br />Mines), the following procedure was used to design the drainage facilities <br />components: <br />¦ The peak discharge was estimated for a selected storm return interval using <br />drainage basin and climatic characteristics. <br />¦ Drainage channels, berms, and catchment basins were designed to convey or <br />contain water for the selected return interval based on available AutoCAD <br />data. <br />Channel bank and bed protection was designed for the estimated flow <br />condition. <br />Document review, drainage facility design, and recommendations for the Topaz <br />Mine; in addition to the designs of storm water collection, conveyance, and detention <br />facilities components for the West Sunday, St. Jude, Carnation, and Sunday Mines are <br />provided in the Drainage Report for Denison Mines, Sunday Mines Group, San Miguel <br />County, Colorado. This report is included as Attachment P. <br />9.3 Stormwater Runoff Detention Basins <br />The surface facilities at the Sunday Mines Group sit on top of the development rock <br />• stockpiles. Off site stormwater runoff from the Sunday Mines is routed around the <br />surface facilities so that no off-site runoff encounters the ore stockpiles or <br />development rock. Stormwater that falls directly onto the facilities is routed around <br />the facilities in a series of berms and detained in stormwater detention basins at the <br />base of each development rock pile. In May 2008, a Colorado Board Registered <br />professional engineer visited the Sunday Mines and completed a stormwater <br />evaluation of the Mines to ensure that all water from a 100-year, 24-hour storm was <br />detained in the detention basins. Because the Sunday Mines are existing facilities, <br />Denison surveyed each of the Mine Sites, and followed up to ensure that the facilities <br />are adequately sized. In many cases the stormwater diversion structures and <br />detention basins are larger than the required size to detain the 100-year, 24-hour <br />storm. The drainage report, calculations, mapping, and follow up memorandum are <br />all provided in Attachment P and Q. <br />9.4 Stormwater Management Plan, Maintenance, and <br />Inspection Program <br />In accordance with the CDPS General Permit - Stormwater Discharges Associated zvitli <br />Metal Mining Industry, the Sunday Mines Group has developed a stormwater <br />management plan that discuss Best Management Practices (BMPs) that were selected, <br />installed, implemented, and maintained with good engineering practices. A copy of <br />both the CDPS general stormwater permit and the Stormwater Management Plan <br />• (SWMP) are included in Attachment F. Specific permit requirements for the Sunday <br />Mines Group is described in the SWMP. <br />9-2 <br />7:\64986-Denison Mines\Task Order 4 - EPP Sunday Mines Group\FINAL EPP\FINAL - Environmental Protection Plan Sunday Mines.doc