2011-08-08_REVISION - M1977493 (33)

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• Technical Revision (TR -18) Climax Molybdenum Company Environmental Protection Plan Permit No. M- 1977 -493 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 Return System: The seepwater collection and return 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 of a designated chemical or process waters not contained at the release site ultimately would be contained at the TSFs. TR -14 described the new mill and accessory buildings for use during resumed production, however the final design and layout of the mill and accessory buildings had not been fully developed at that time. TR- 14 designated the mill building as a location for several Environmental Protection Facilities (EPFs) associated with designated chemicals. Additional details of the mill facility have now been developed and general arrangement drawings of the entire mill and of the reagent storage and containment areas are provided as Figures AM- 06 -T -06 and AM- 06 -T -07. The list of designated chemicals, their storage location, storage capacity and the presence of secondary containment is provided in Table T -2 in Section T -3.1 OSF Water Management Controls: As described in Section T -4, Climax will use best management practices to reduce the amount of impacted water requiring treatment. Climax will segregate materials when feasible and, as discussed in Section T -4, is developing construction design and monitoring plans with guidelines for overburden placement to reduce infiltration within exposed OSF surfaces to the extent practicable by promoting drainage off of OSF surfaces and performing concurrent reclamation. The OSF EPFs will consist of water management controls for the McNulty and North 40 OSFs. Specific EPFs that will be designed and submitted to DBMS for review and approval prior to OSF expansion will include one or more of the following: EPP: Revision R1 T -25 July 2011