2012-10-05_REVISION - M1977342 (12)

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TR -18 to Permit M- 1977 -342 Environmental Protection Plan Mill EPF 1.6 — Groundwater Intercept System: Henderson operates a series of extraction wells along the north seep water collection canal to prevent potential process water influences on groundwater quality. Based on previous characterization studies, the Ute Creek alluvial channel was reported to be the primary water - bearing unit underlying and downgradient of the tailings dam. Seepage from the 1 -Dam tailings facility that is not captured in the seepage collection canals reports to the buried Ute Creek alluvial channel. The historical Ute Creek channel exits the 1 -Dam tailings facility near the Ute Creek pumping station where it is captured by the 1 -Dam interceptor well field. The interceptor wells are installed perpendicular and across the historical Ute Creek alluvial channel and glacial drift deposits and range in depth from 13 to 43 feet. Flows from all of the extraction wells are combined into a single underground header that discharges to the Ute Park pump station. The water combines with the surface seepage waters from the canals and is pumped back to the tailings pond for reuse in the milling circuit. Effectiveness: This EPF is one of several engineering controls and redundancies to prevent releases of acidic waters. Two of the pneumatic Hammerhead pumps have been retrofitted with submersible VFD electric pumps, improving pumping performance. Monitoring: Flow rates and volumes are continuously measured and recorded with the use of electronic recording devices. Monitoring of ground and surface water downstream of the Groundwater Intercept System is conducted on a routine basis (see sections 8, 9, 10, and 11 below). Mill EPF 1.7 — Ute Park Pump Station: The Ute Park pump station is an important component in the zero discharge system. Collected seepage is pumped back from the Ute Park pump station to the water pool on the tailings storage facility by turbine pumps with a total capacity of 9000 gpm. A total of approximately 115 acre -feet of storage capacity exists in the seep water collection area and the area above the seep water collection ditches in case of emergency upsets. A calculated rate of 1000 gpm of seep would fill this storage in 25.5 days before a release would be possible; sufficient time to place backup pumps into operation. Effectiveness: The pumps and their operations are discussed in depth in Appendix F. If the pump and alarm systems lose power, there is a solar and battery powered fail -safe system that closes the seep water feed channels to the pump house. Monitoring: The automatic control system and response procedures alert control personnel when seep water levels in the sump pass the start probe commands for the seep water return pumps, and when a power failure occurs which shuts down the seep water return pumps. This alarm system is described in Appendix F. Maintenance and /or updates to facilities, systems, equipment, or procedures are performed as needed to be protective of the environment and to prevent releases. 7.2.2. Designated Chemical Storage Facilities Environmental Protection Facilities for designated chemicals at the Henderson Mill site include enclosed buildings, trailers, tanks, bins and berms, singly or in combination. The ultimate emergency EPF for all designated chemicals is the tailings storage facility /seep water collection and containment system discussed in Section 7.2.1. As stated previously, the Mill site and its ancillary facilities are located within the Ute Creek drainage. Therefore, accidental release of a designated chemical or process water at the Mill which is not captured by primary, secondary, Climax Molybdenum Company Henderson Operations October, 2012 Page 20 of 40