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Section 9 <br />Suiface Water <br />Document review, drainage facility design, and recommendations for the Van 4 Mine; <br />and designs of storm water collection, conveyance, and detention facilities <br />components for the Van 4 Mine are provided in the Drainage Report for, Van 4 Mine, <br />Montrose County, Colorado. This report is included as Attachment I. <br />9.2 Stormwater Runoff Detention Basins <br />Off-site stormwater runoff at the Van 4 Mine is routed around the surface facilities so <br />that no off-site runoff encounters the development rock. Stormwater that falls directly <br />onto the facilities is routed around the facilities in a series of berms and detained in <br />stormwater detention basins at the base of the development rock pile. In May 2008, a <br />Colorado Board Registered Professional Engineer visited the mine and completed a <br />stormwater evaluation 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 the mine, and followed up to provide that the facilities are <br />adequately sized. In many cases the stormwater diversion structures and detention <br />basins are larger than the required size to detain the 100-year, 24-hour storm. These <br />calculations are provided in the drainage report for the Van 4 Mine. <br />9.3 Stormwater Management Plan, Maintenance, and Inspection <br />Program <br />In accordance with the CDPS General Permit - Stormivater Discharges Associated zvith <br />Metal Mining Industnj, the Van 4 Mine has developed a stormwater management plan <br />to: <br />¦ Identify all potential sources of pollution which may reasonably be expected to <br />affect the quality of stormwater discharges associated with industrial activity from <br />the facility; <br />¦ Describe and ensure the implementation of practices which are to be used to reduce <br />the pollutants in stormwater discharges associated with industrial activity at the <br />facility; <br />¦ Ensure the practices are selected, installed, implemented, and maintained in <br />accordance with good engineering practices, including the installation, <br />implementation and maintenance requirements; and <br />¦ Provide instructions on implementation of the Stormwater Management Plan <br />(SWMP) as written and guidance on updating it upon changes of the facility or <br />processes as a condition of the permit. <br />A copy of both the CDPS general stormwater permit and the SWMP are included in <br />Attachment D. Specific permit requirements for the Van 4 Mine are described in the <br />SWMP. <br />• <br />9-2 <br />7:164886-Denison Mines\Task Order 4- EPP Sunday Mines Group-VanCVan4TINAL ReporhFINAL -Environmental Protection Plan Van4.doc