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 - 5.4.3 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 and discharge system, which treats large volumes of water, has an exemplary track record. The treated discharge at Outfall 001 has met effluent limitations contained in the permit and has passed Whole Effluent Toxicity (WET) tests. Unlike other more complex and technically complicated water treatment processes, utilizing the first and second stage treatment processes of the SDP and the TSFs for lime precipitation is a simple and effective means of treatment. The decant system on the Mayflower TSF can be managed to increase retention time, thus allowing time to ensure treatment process and control discharge. The sulfuric acid tank is 120 percent contained within a series of sumps, and both primary and secondary containment. 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 generally has a good record for effectiveness. However, leaks have occurred in the past. When these leaks have occurred, repairs to the line have been made promptly and as stated above, other EPFs downgradient of the ETDL serve to contain water that may escape, preventing a release outside of the water management and treatment system. The effectiveness of the Robinson, Tenmile, and Mayflower TSFs 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 contains major point and non -point source releases of potential contaminants from upstream areas including impacted seepages from the McNulty and North 40 OSFs, 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 Section T -3. T - 5.5 Specific Environmental Protection Facility Monitoring /Alarms The critical EPFs at Climax are regularly checked, inspected, or monitored either visually, analytically, or both by security and water treatment personnel that are on -site at all times. Occasional inclement weather can restrict access to some facilities for short periods of time. In the case of pump stations, mechanical and telemetric alarms also are operational should failures occur. These monitoring systems are discussed herein by EPF and watershed. System alarms for the critical EPFs are discussed in subsequent sections. Facility monitoring /alarms details are not included for potential future EPFs that have not been designed. T - 5.5.1 Arkansas River Watershed 5 -Shaft Pump Station: The 5 -Shaft Pump Station is equipped with monitoring and alarm systems. In addition to these systems, the station is visually checked regularly. A groundwater piezometer (5 -Shaft Monitoring Well) has been installed adjacent to the pump station to monitor groundwater levels adjacent to 5 -Shaft. The water levels in this piezometer are recorded on a monthly basis. Storke Wastewater Pump Station: The Storke Wastewater Pump Station is equipped with monitoring and alarm systems. As with the 5 -Shaft Pump Station, the Storke Wastewater Pump Station is checked EPP: Version R2 T -31 December 2011