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 system conveys storm water around the process facility and TSFs, which limits the amount of impacted waters to be treated and discharged. As agreed upon with DRMS, although these interceptors are considered to be pre -EPF systems and do not contain or control designated chemicals or process solutions, they will be managed as intemal EPFs. The interceptor system is closely monitored, inspected and maintained as part of routine site monitoring activities. Other than repair and maintenance, any future expansion or modification of the interceptors will be subject to review by DRMS, consistent with Section 6.4.21(10)(a)(ii) of the Rules. The interceptors total approximately 13 miles in length and are labeled as the West Interceptor and the East Interceptor (Figure AM- 06- T -01). These interceptors were constructed in the 1970s during construction of the Mayflower TSF to intercept and convey snowmelt and storm water around the three TSFs in the Tenmile Creek Watershed. The West Interceptor begins along the west side of the Tenmile TSF and drains directly into Tenmile Creek within the Climax property line downstream of the Mayflower TSF. The east interceptor begins at the edge of the McNulty OSF and terminates at the Clinton Gulch Reservoir. The Clinton Canal begins at Clinton Reservoir and terminates at Mayflower Creek. The total Interceptor System handles approximately 14,500 acre -feet of water annually. Clinton Reservoir offers flood protection for Mayflower TSF. Protection of Clinton Reservoir :: As the McNulty OSF is expanded, it will become necessary to truncate the upper end of the East Interceptor Canal to direct runoff from the OSF to the water management and treatment system instead of allowing this water to enter the interceptor and Clinton Reservoir. The design 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 Environmental Protection Facility Effectiveness 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 EPP: Version R2 T -29 December 2011