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 • Storke Wastewater Pump Station; and • Ceresco Ridge Haul road Fill Area Runoff Collection System. 5 -Shaft Pump Station and Storke Pipeline: A pumping station installed in 5 -Shaft maintains the water level at an elevation that does not threaten the flow of impacted water to the Arkansas River Valley. Storm water becomes impacted as it passes through the open pit area and collects in the underground mine workings. The quantity of water entering the shaft fluctuates seasonally based on the amount of runoff into the open pit area. Generally, minimum flows occur in the late fall through winter, increase as early as April or May, and peak from mid -June through early August. The level of water in 5 -Shaft must be kept below the apex of the Mosquito Fault to prevent mine water from potentially impacting the Arkansas River. The water level is maintained by pumping water through the Storke Pipeline to the process water circuit in the Tenmile Creek Watershed. As the mining of the open pit advances in depth, the 5 -Shaft Pump Station may become obsolete where water levels will be controlled through other means. Storke Wastewater Pump Station: The Storke Wastewater Pump Station is located just below the Storke Yard and acts as a seepage collection and return system where collected impacted water is pumped to the process water circuit in the Tenmile Creek drainage. Two concrete Tined ponds at this EPF serve to collect seepage and storm water /snowmelt run -off from the yard area and return it to the Tailings Distribution House (TDH) where it mixes with mine water prior to treatment. Ceresco Ridge Haul Road Fill Area Runoff Collection System: Depending on the amount of fill needed to improve the existing Ceresco Ridge haul road, some of this material may extend into the Arkansas River watershed, and a runoff collection ditch may be needed below the additional fill placement on Ceresco Ridge. The purpose of the collection ditch will be to intercept potentially impacted runoff from this area and route the water to the camp area or open pit, where it will be sent to the water treatment system (SDP) for treatment. Climax will submit the design for this system to DRMS for review and approval prior to construction. T -5.2 Eag /e River Watershed T -5.2.1 Potential Sources of Contamination As listed in Table T -3, the sources of potential contamination in the upper watershed of the East Fork of the Eagle River within the Climax property include: • 4 Dam seepage; ■ Robinson Dam seepage; • Tenmile Tunnel and 1 Dam seepage; ■ Robinson Lake (aka: Robinson Reservoir); and ■ A portion of the Robinson TSF (1 Dam). The Oxide Pond (Eagle Park Reservoir) was first constructed in the early 1960s to impound tailing material from the oxide ore processing facility at Climax. Oxide ore processing was discontinued in 1968. The tailing material and sediments in this TSF were acidic and contained elevated levels of metals. Seepwater emanating from the toe of the dam (4 Dam) likewise was acidic (Appendix G, original 1995 EPP). In 1993, a project was initiated to convert Eagle Park Reservoir to a fresh water impoundment to allow Climax to sell the storage facility. Such a conversion of this impoundment required draining of impacted water, removal of tailing material and contaminated sediments, and prevention of Robinson Lake seepage from entering the impoundment. This project was completed in 1997. Impacted media (water, tailing, sediment, and soils) were removed to the Tenmile TSF and 2 Dam during the course of this project. Eagle Park Reservoir was released from DRMS financial warranty and was sold to a private consortium of downstream users in 1998. Eagle Park Reservoir is no longer within the affected lands EPP: Revision R1 T -16 July 2011