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 of this modification of the East Interceptor will be developed to ensure that impacted water will not enter the East Interceptor, and to maximize the amount of clean water intercepted. The tributary area to the East Interceptor is currently estimated at 832 acres. When the East Interceptor is truncated, Climax estimates that the tributary area will be reduced by approximately 240 acres, although the final change will depend on the location and design details associated with the modification to the East Interceptor. Although not considered EPFs, Climax will conduct visual inspections and implement other Storm Water Management Plan best management practices (BMPs) in association with its general storm water permit to manage disturbances associated with the open pit, including road construction and pit development activities near the summit of Bartlett Mountain, to prevent water quality impacts to the Clinton Gulch watershed and Clinton Reservoir from erosion and sediment. As part of its storm water management program, Climax also will utilize BMPs for blasting activities to prevent water quality impacts from flyrock entering the Clinton Gulch watershed, and will grade disturbances, including the Bartlett Mountain access road so that storm water runoff will report to the open pit or McNulty Gulch collection area for eventual treatment rather than allow runoff to the Clinton drainage. T - 5.4 Environments/ Protection Faci/ityEffectiveness Evaluation The EPFs described and discussed for the three watersheds at the Climax Mine site have been very effective in preventing releases of potential contaminants to the environment, as documented by water quality monitoring and compliance with discharge standards. T - 5.4.1 Arkansas River Watershed The mining related activities that occurred in the Storke Yard area in the past have ceased as the scope and size of operations at Climax have been reduced to mining from the open pit. Closure and reclamation tasks have been completed in the upper Arkansas River Watershed contributing to improved water quality conditions in the Arkansas River. The two pumping stations in the Arkansas Watershed are the critical EPFs in the watershed. Both are active, as they directly contain and control impacted waters. The Storke Wastewater Pump Station has been operational for approximately 30 years without major problems or releases. The 5 -Shaft Pump Station, although only operational since 1996, has performed as expected without release of impacted mine water. Prior to startup of the 5 -Shaft Pump Station, the underground mine workings were dewatered by other pump systems, thereby establishing a long history of environmental protection in the Arkansas River Watershed. If determined to be needed based on haul road design, the Ceresco Ridge Haul Road Fill Area Runoff Collection System will be designed to contain and control impacted run -off from new fill areas. This water will be directed by gravity to the Camp Area or Open Pit. Demonstration of the Mosquito Fault as a hydraulic barrier to potential process water impacts to the Arkansas was discussed with DRMS during a site inspection and in verbal and written correspondence in the fall of 1994. Subsequent geophysical evaluations were performed to establish the criteria to maintain water levels 19 feet below the apex of the Mosquito Fault. The Mosquito Fault is located approximately 350 ft west of the 5- Shaft. A pumping station installed in 5 -Shaft maintains the water level at a target elevation of 11,080 feet that does not allow the flow of impacted water to the Arkansas River Valley. The level of water in 5 -Shaft is kept below the apex of the Mosquito Fault to prevent mine water from potentially impacting the Arkansas River. Climax also monitors a well located approximately 60 feet from the 5 -shaft for changes in water level. As the mining of the open pit advances in depth, the 5 Shaft Pump Station will become obsolete and water levels will be controlled by other means. The continued operation of the Storke Wastewater Pump Station and the Ceresco Ridge collection system will be dependent upon final reclamation activities in the area, but will continue indefinitely until water quality conditions are demonstrated to no longer require collection. T - 5.4.2 Eagle River Watershed • As with the EPFs throughout the Climax Mine site, those in the upper Eagle River Watershed have been highly effective in containing and controlling the release of potential contaminants during the recent EPP: Revision R1 T -27 July 2011