2011-12-15_REVISION - M1977493 (2)

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Technical Revision (TR -18) Climax Molybdenum Company Environmental Protection Plan Permit No. M- 1977 -493 Mayflower TSF will continue to provide second stage treatment before treated water is decanted from the pool, adjusted to a target pH of 6.5 to 9.0 with sulfuric acid, merged with waters from the Interceptor System, and discharged to Tenmile Creek downstream of 5 Dam. Treated water is discharged under the CDPS Permit as discussed in Section T -2.2 and as detailed in the schematic drawings in Permit Amendment AM -06 Exhibit G. During Phase II Deposition, tailing will be delivered to the Mayflower TSF (5 Dam) through a combination of new and rehabilitated tailing delivery pipelines (TDLs). The tailing slurry will be deposited in the Mayflower TSF utilizing the upstream deposition method by operation of a header and spigot system along the crest of 5 Dam. The mill water reclaim system will continue to operate generally as described above. The additional facility required during Phase II Deposition is the Mayflower Barge and redaim water pipeline. This barge is to be located in the Mayflower TSF water pool and will deliver water from the pool to the north portal of the Tenmile Tunnel. As in Phase I Deposition, the first priority water to be delivered to the mill will be the water decanted from the water pool on Tenmile TSF. Supernatant from the Mayflower TSF water pool will be delivered to Robinson Lake at times when the upstream sources are inadequate to satisfy the mill water demand or when there is storage space available in Robinson Lake. During Phase II Deposition, the SDP will provide first stage treatment of impacted water for use at the mill, with the sludge pumped into the tailing delivery line. However, first stage treatment of other impacted water will take place in the Mayflower TSF water pool. The discharge of circumneutral tailing slurry into the water pool will be consistent with first stage treatment in the facility. Excess water in the Mayflower TSF will be decanted from the water pool and delivered to the new Property Discharge Water Treatment Plant (PDWTP). The new PDWTP will provide second stage treatment of the impacted waters to comply with discharge permit requirements. In conjunction with these operations, potential sources of contamination in the Tenmile Creek watershed include: • Designated chemicals (stored and used) for production of molybdenum disulfide concentrate; • Dust palliatives (stored and used); • Mill water reclaim circuit (including storage tanks and supply system); • Process facility /mine yard (a.k.a: Camp Area) run -off and seepage; • Underground mine and open pit water; • OSF seepage (North 40 and McNulty); • Tailing and process water delivery systems (new TDL and ETDL); • Water treatment chemicals (stored and used) for treatment of mine water (including the Lime Station and SDP); • Robinson TSF; • Tenmile TSF and 3 Dam seepage; and • Mayflower TSF and 5 Dam seepage. These potential sources of contamination are also listed in Table T -3 and are shown on Figure AM -06 -T- 01. The process water tanks near the mill facilities were demolished and removed in 2006. A new water storage tank is planned as part of the new mill facility. Climax has developed a comprehensive water quality monitoring plan to detect potential changes in water quality downgradient of mine facilities. The monitoring is designed so that changes are detected early to enable implementation of measures that may be needed to protect off site water resources such as Clinton Reservoir and Tenmile Creek, including the addition of new EPFs if necessary. The water quality monitoring plan is included as Appendix T -C. EPP: Version R2 T -25 December 2011