2018-08-22_REVISION - M1977493A - Laserfiche WebLink

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Technical Revision (TR-28) Climax Molybdenum Company Environmental Protection Plan Permit No. M-1977-493 of the system of EPFs in-place in the Eagle River Watershed is demonstrated by water quality observed at water quality monitoring locations described in the Water Quality Monitoring Plan (Appendix T-C) and in water quality within Eagle Park Reservoir. Robinson Lake functions as a process water and seepage containment, storage and return system. The Robinson Lake Pump Station returns process waters directly to the process water tank for the mill. Because the integrity of this collection and return system is essential to production of molybdenum concentrates, close observation of its operation and maintenance of the systems is a priority. The development of the Robinson Lake Operating Plan (Appendix T-D) provides additional operational safeguards to prevent an overflow condition from Robinson Lake. The 4 Dam and Robinson Dam seepage collection and pump systems will remain in place and fully functional until such time as seepage from the dam meets water quality standards for this segment of the Eagle River. The seepage collected in the 4 Dam Seepage Collection System averages only approximately 10 gallons per minute, and the system has a redundant design to provide secondary containment, as described in Section T-5.2.2. The effectiveness of this system has been provided through monitoring water quality in the East Fork Eagle River at sites described in the Water Quality Monitoring Plan (Appendix T-C). The 1 Dam EPF has been effective in controlling the release of tailing material from the TSF. The regrading, capping, and reclamation of this dam (Section T-5.2.2) have increased its present and future effectiveness. T-5.4.3 Tenmile Creek Watershed EPFs in the critical Tenmile Creek Watershed have been, and continue to be, extremely effective in containing and controlling contaminants and preventing contaminant release into the environment. As the EPFs essentially function in series from the top of the watershed, the effectiveness of the system is increased through the redundancy or secondary containment afforded by this arrangement. Each EPF serves as a protective layer for up-gradient EPFs. However, it must again be emphasized that the upper Tenmile Creek Watershed has been significantly impacted by historic placer and lode mining, milling and smelting activities, which peaked in the 1880s. Prior to construction of the Mayflower TSF and the Interceptor System, impacted waters and significant loads of contaminated sediments from these non- Climax historic operations entered Tenmile Creek and were transported downstream. The Climax water treatment system successfully treats large volumes of water. The treated discharge at Outfall 001A has consistently met all effluent limitations contained in Climax's CDPS permit. Utilizing the first and second stage treatment processes of the SDP and PDWTP with lime addition for pH adjustment is an effective and time-proven means of treatment. The EPFs that control and contain the water treatment chemicals, as with the process water and tailing circuit, have a proven track record for effectiveness at the Climax Mine. As discussed in Section T-5.3.2, water treatment chemicals have primary and secondary containment. The ETDL and TDL generally have good records for effectiveness. However, leaks/spillage can and have occurred in the past. As described in TR-20 and TR-23, there is containment in the designs and, if leaks occur, any needed repairs to the line will be made promptly. As stated previously, other EPFs (East Side Channel and TSFs) adjacent to and downgradient of the ETDL and TDL also provide containment, preventing a release outside of the water management and treatment system. The effectiveness of the Robinson, Tenmile (TR-20), and Mayflower TSFs (TR-23) is self-evident. The Robinson TSF has been used since the mid-1930s, the Tenmile TSF since the mid-1950s, and the Mayflower TSF since the mid-1970s without failure. Each TSF will contain any major point and non-point source releases of potential contaminants from upstream areas including impacted seepages from the McNulty and North 40 OSFs, spillage/leaks from the ETDL and TDL, and potentially contaminated surficial run-off from haul roads, the pit area, and the yard areas around the mill facilities. The effectiveness of the Mayflower TSF (including the 5 Dam Seepwater Collection and Return System) in the Climax water treatment and discharge system has been discussed at length. Designated chemical storage EPFs within the mill all include secondary containment as described in EPP: Version R4 T-32 August 2018