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Climax Molybdenum Company HENDERSON MINE SWMP Empire, CO April 2021 5.0 BEST MANAGEMENT PRACTICES This section contains general structural and non-structural BMPs for reducing the potential of the sources identified above to contribute pollutants to storm water discharges. Site or activity specific BMPs appropriate for each potential storm water pollutant source are summarized in Table 5.1. As new potential pollution sources and/or BMPs are identified, Table 5.1 (in addition to Table 4.1, Inspection Forms in Appendix B, and the Storm Water Management Maps, as applicable) will be updated. Henderson's storm water permit requires SWMPs to include BMPs that are selected, installed, implemented and maintained in accordance with good engineering practices,that reduce pollutants in storm water discharges, and that assure compliance with the terms and conditions of COR- 040000. To that end, Henderson references the EPA's National Menu of Best Management Practices (BMPs) for Stormwater (https://www.epa.gov/npdes/national-menu-best-mana eg ment- practices-bmps-stormwater#edu) and the associated BMP guidance document titled National Management Measures to Control Nonpoint Source Pollution from Urban Areas (http://www.epa.gov/owow/nps/urbannmm/index.html) and (https://www.epa.gov/nps/urban- runoff-national-management-measures)) 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. • 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. 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. Compliance with this SWMP is a requirement of all construction projects. 5.2.1 Prevention of Erosion As compared to the sediment removal practices that are discussed below, these BMPs 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 BMPs. • Reseed disturbed soil areas with maintenance seed (if it is temporary) or Climax Seed Mix (for permanent or final construction). Page 5-1