2012-10-05_REVISION - M1977342 (14)

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Climax Molybdenum Company HENDERSON MINE & MILL SWMP Empire & Parshall, CO December, 2011 Page 5-1 5.0 BEST MANAGEMENT PRACTICES This section contains general BMPs for source reduction, mitigation, and treatment of potential storm water pollutants. Site- or activity-specific BMPs associated with each potential storm water pollutant source are summarized in Table 5.1 at the end of this section. As new potential pollution sources and/or BMPs are identified, Table 5.1 (as well as Table 4.1, Inspection Forms in Appendix B, and the Storm Water Management Maps, as applicable) will be updated. Henderson’s stormwater permit requires SWMPs to include BMPs that are selected, installed, implemented and maintained in accordance with good engineering practices. To that end, Henderson references the EPA’s National Menu of Stormwater Best Management Practices at http://cfpub.epa.gov/npdes/stormwater/menuofbmps/ and the associated BMP guidance document titled National Management Measures to Control Nonpoint Source Pollution from Urban Areas (http://www.epa.gov/owow/nps/urbanmm/index.html) to provide guidance on BMP selection, implementation, limitations and maintenance requirements. 5.1 Storm Water Diversion A key strategy utilized by Henderson to prevent potential storm water pollution is to minimize the amount of storm water that can come into contact with disturbed land and other industrial activities. The diversion systems described below are also shown on the Figures in Appendix A as “interceptor canals”. • A storm water interceptor canal has been constructed around the west and north ends of the tailings pond and delivers un-impacted storm water around the north end of the property to the Williams Fork River; • A collection system has been constructed to divert storm water from drainages southwest of the Mill property through an underground diversion pipe to the Williams Fork River; • Diversion ditches have been constructed on the south side of the Mine office and surface operations to divert water around industrial activities to the east end of the property; and • Diversion ditches have been constructed around the west end and along the north side of the Mine property and deliver un-impacted storm water to the West Fork of Clear Creek. 5.2 Erosion and Sedimentation If projects have a potential for polluting storm water or causing sedimentation or erosion, funds shall be allocated in the project’s budget for implementing one or more of the BMPs outlined below. Additionally, compliance with this SWMP is a requirement of all construction contracts. 5.2.1 Prevention of Erosion As compared to treatment practices that are discussed below, these BMP's are intended to prevent erosion which could eventually impact water quality. Erosion and sedimentation shall be controlled through implementation of one or more of the following best management practices.