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 T - 5.3.2 Environmental Protection Facilities The Climax water management and treatment system, which terminates at the base of 5 Dam, contains the principal EPFs in the Tenmile Creek Drainage. This system discharges treated water meeting the conditions and standards of the CDPS Permit at Outfall 001 located near the property line. Under the CDPS permit discussed in Section T -2.2, discharge of water from the site, including process water and impacted waters are required to meet discharge water quality limits. Contaminants that might be released from the potential sources discussed in Section T -5.3.1 would be captured within the Tenmile Creek watershed above or at the Mayflower TSF where water is treated prior to discharge. Individual EPFs, which are part of the water treatment system, are discussed in subsequent sections along with EPFs that are present in other areas of potential contamination above the water discharge outfall. The following controls are designated EPFs to prevent potential impacts to Tenmile Creek and Clinton Reservoir from Climax operations: • New TDL; • ETDL; • Robinson TSF and 2 Dam; • Tenmile TSF and 3 Dam; ■ Mayflower TSF and 5 Dam; ■ 5 Dam Seepwater Collection and Return System; • EPFs for Designated Chemicals for Concentrate Production; • OSF Water Management Controls; • PDWTP; • Containment for Water Treatment Chemicals; and • East and West Interceptor Systems. New TDL: Tailing delivery and deposition for future mine production will utilize the existing Tenmile and Mayflower TSFs. As presented in TR -14, the installation of a replacement 36 -inch diameter high- density polyethylene (HDPE) TDL has begun from the mill discharge sump to the Tenmile TSF. The TDL will generally follow the alignment of the existing ETDL. The portion of the existing 42 -inch diameter reinforced concrete pipe (RCP) ETDL from the SDP to the Mayflower TSF may be evaluated for rehabilitation and use or may be replaced to convey tailing from the Tenmile TSF to the Mayflower TSF. ETDL: The existing ETDL is planned to convey impacted water sources to the SDP and to serve as an emergency tailing conveyance line should the main delivery line from the Mill to the first discharge point have to be taken out of service for a short period. This line is constructed of 36 -inch and 42 -inch RCP that isolates the impacted water from the environment until it is delivered to the SDP or deposited in one of the TSFs. Where grades are excessive, concrete drop structures are installed. The tailing delivery system is shown in Figure AM -06- T-01 Robinson TSF and 2 Dam: As discussed in Section T- 5.2.1, the Robinson TSF encompasses approximately 650 acres. 1 Dam and a small portion of the southern part of this TSF are located in the upper Eagle River Watershed and are discussed in Section T -5.2. The remainder of the TSF and 2 Dam are within the Tenmile Creek Watershed. The Robinson TSF contains mill tailing material. As discussed in Section T- 5.2.1, tailing material from the Climax mill circuit is recognized as potentially acid producing. The Robinson TSF has been decommissioned and, as noted previously, is in the final stages of closure reclamation. However, even when reclaimed, Robinson TSF remains both a potential source of contamination and an important EPF. EPP: Version R2 T -26 December 2011