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 Tenmile TSF and 3 Dam: The Tenmile TSF, including 3 Dam, currently encompasses approximately 620 acres and is located adjacent to and just downstream of the Robinson TSF. Once Tenmile TSF has reached its planned capacity of tailing material, it will encompass approximately 650 acres. The Tenmile TSF was constructed in the 1950s and contains tailing material that, as discussed previously, is considered acid producing. Future operations at Climax will first utilize the Tenmile TSF for tailing disposal. Approximately 29 million tons of additional tailing may be deposited in the Tenmile TSF. Mill tailing in slurry form is delivered to the TSF by the TDL. Clarified water is removed from the TSF through a decant system at Tenmile Decant via the Tenmile Tunnel (to the Robinson Lake or Mayflower TSF as discussed in Section T- 5.2.1). A water pool is maintained at the upstream end of the Tenmile TSF for process water storage, storm water management, and as the first stage in the water treatment system. The Tenmile TSF is considered both a source of potential contamination and an EPF. The integrity of the TSF and 3 Dam provides containment of the tailing material. The Tenmile TSF also provides control for contaminants that might be released from upgradient sources. Mayflower TSF and 5 Dam: The last TSF downstream in the Tenmile Creek Watershed is the Mayflower TSF. This TSF and its dam (5 Dam) currently encompass approximately 380 acres and along with the 5 Dam Seepwater Collection and Pump System is the final control on Tenmile Creek within the Climax property boundary. At the end of mining, the projected size of Mayflower TSF is approximately 900 acres. The Mayflower TSF was constructed in the mid 1970s. It was utilized for tailing deposition until Climax ceased mill operations. The TSF has significant existing and future storage capacity that is planned for use as the primary tailing deposition area when Climax recommences production. Currently, and during Phase I Deposition, the TSF is the second stage of the Climax water treatment system. In the early 1990s, the beach areas of the TSF and 5 Dam were capped with rock and soil material excavated from the eastern edge of the TSF. The water pool area is maintained and continues to be used for treatment of discharged mine waters. As with the Robinson and Tenmile TSFs, the Mayflower TSF is both a potential source of contamination and a critical EPF. As a potential source, the Mayflower TSF contains tailing material that is considered potentially acid producing. It should be noted, however, that the long -term use of this TSF strictly as a water treatment facility has served to add significant amounts of lime to the impoundment. Another source of potential contamination is seepage emanating from the toe of 5 Dam. This seepwater is slightly acidic with elevated sulfate and metals. As an EPF, the Mayflower TSF, including 5 Dam, is crucial. Along with the final pH adjustment at the Mayflower pH Control (Acid Dosing) Station, the TSF acts as the final stage water treatment system for Climax process water, mine water, and seepage waters. Mayflower TSF also provides containment of contaminated materials or designated chemicals if they are accidentally released up- gradient of the TSF. In addition, the Mayflower TSF contains, mixes, and treats impacted waters from several historic mines and smelter sites as well as non -point run -off waters which contact mine wastes within a large portion of the historic Consolidated Tenmile Mining District. 5 Dam Seepwater Collection and Retum System: The seepwater collection and retum system below 5 Dam (Mayflower TSF) is an important EPF at the Climax Mine. Although it has been discussed previously in some detail as part of the Climax water treatment and discharge system EPF, it is discussed again here as a specific EPF. Seepage from the dam is routed to concrete ponds. Collected seepage is pumped back by vertical turbine pumps to the 3 Dam Pump Station or the water pool on the Mayflower TSF. This pump system is located within the Mayflower Pump Station below the TSF. During upset conditions, seepage can be temporarily contained within the 5 million gallon concrete pond system. EPFs for Designated Chemicals for Concentrate Production: The EPFs for the designated chemicals used for milling and production of concentrate at Climax include enclosed buildings, tanks, bins, and sumps, singly or in combination. However, the final end point EPF for designated chemicals is the Mayflower TSF and the associated water treatment and discharge system. As stated previously, the mill site and its ancillary facilities are located within the upper Tenmile Creek watershed. Therefore, a release EPP: Version R2 T -27 December 2011