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 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 Climax 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. The Ceresco Ridge Haul Road Fill Area Runoff Collection System provides containment and control of any impacted run-off from newer fill areas. 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 piezometer located approximately 60 feet from the 5-shaft for changes in water level, on the same side of the Mosquito Fault as the 5-Shaft. The effectiveness of 5 Shaft pumping is verified by the water level in the piezometer adjacent to the shaft that shows a hydraulic gradient towards the shaft. As the mining of the open pit advances in depth, the 5 Shaft Pump Station may become obsolete during operations, and pit and underground water levels will then be controlled by an in-pit dewatering system. The long-term operation of the 5 Shaft Pump Station, 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 site, those in the upper Eagle River Watershed have been effective in containing and controlling the release of potential contaminants during the recent history of the mine. The primary EPFs in the watershed are Robinson Lake (and dam), the Robinson Lake Pump Station, and the associated seep collection and return systems below Robinson Lake. As described in Section T-5.2.2, the capacities of the collection and pumping systems in-place are adequate to provide protection of water resources in the Eagle River Watershed. Multiple improvements to the EPFs in the Eagle River Watershed have been made over the last 15 to 20 years, and include: The installation of Tim's Pond and improvements to Warren's Pump Station to capture the majority of seepage from 1 Dam and Tenmile Tunnel and pumping this water to the SDP before it enters Robinson Lake; Upgrading the Robinson Lake Seepage Collection System, including the application of an impermeable coating on the upstream side of the cut-off wall and construction of a collection pond upgradient of the wall to provide increased storage capacity. The long-term effectiveness EPP: Version R4 T-31 August 2018