1998-02-25_HYDROLOGY - M1977493 - Laserfiche WebLink

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loading of trucks and the installation of special tailgates to hold liquefied tailing during the approximately 3 mile-haul. Once the lading were removed, it was determined that they were under!ain by topsoil. Climax decided to remove the long buried topsoil from the Eagle Park Reservoir basin, thus providing the following benefits: • increased reservoir storage capacity, • removal of a potential contamination source in the event that the overlying tailing had impregnated the soil with metals or acid, • supplementation of the Climax Mine topsoil inventory for use in high altitude reclamation. A total of 56,400 cubic yards of topsoil were removed and stockpiled or spread in reclamation project areas during late October of 1996. The average topsoil haul distance was 3.7 miles. The earthen dam constructed in the 1960s to impound oxide tailing was designed as a zero discharge facility. In order to convert this dam to a fresh water storage reservoir embankment, outlet facilities and spillway improvements were installed. These installations were subject to review and approval by the Dam Safety Section of the Office of the State Engineer, as was the Emergency Preparedness Plan for the reservoir. Once Eagle Park Reservoir is released from the mined land reclamation permit, the State Engineer will have ongoing jurisdiction over the safe operation of the dam. As discussed previously, dam seepage has been collected and pumped back to the impoundment for many years. It was assumed during the development of the Eagle Park Reservoir reclamation project that seepage would continue to be collected for some period of time following tailing removal until the quality of the seepage water improved and could be released to the Eagle River. Since potentially contaminated seepage water could no longer be pumped back to Eagle Park Reservoir,a new seepage water pipeline was designed and installed. Although the quality of the dam seepage improved dramatically and immediately following tailing removal and reservoir filling, the pump back system and seepage water pipeline continue to be regulated as environmental protection facilities under the Climax Mine reclamation permit. In order to protect Eagle Park Reservoir from the potential for contamination from upgradient Climax Mine process water storage facilities,a ground water cutoff and pump back system was installed above the reservoir. This system is regulated as an environmental protection facility under the reclamation permit,and a ground water monitoring well is located below the cutoff wall. Freshwater delivery into Eagle Park Reservoir commenced in the spring of 1997. Water was diverted into the reservoir from the two fresh water interceptor canals discussed previously and also entered the reservoir from the 125 acre contributing basin below the interceptors. It was anticipated,based on extensive feasibility sampling,analysis,and modeling,that initial reservoir filling would impound good quality water and that residual materials in the reservoir footprint would not pose a threat to ultimate water quality. However, Climax was prepared to manage the reservoir water to protect the Eagle River in the event that the reservoir had to be flushed by repeated cycling of fresh water until the water quality targets were achieved. As it turned out,the initial filling of the reservoir resulted in an impoundment of high quality fresh water that met all standards associated with segment 3 of the East Fork of the Eagle River by July 26, 1997. On August 26, 1998 the Division of Minerals and Geology issued conditional approval of reclamation permit revision SR-02 with the finding that Eagle Park Reservoir had been reclaimed to the approved post mining beneficial land use of developed water resources. The terms of the conditional approval require an ongoing sampling, analysis, and contingency plan for the operation of the reservoir. Thus far, the sampling results demonstrate that water quality has stabilized, with most parameters measured at or below detection limits. Reclamation of the Oxide Tailing Pond and conversion to the Eagle Park Reservoir has resulted in the establishment of an approximately 3,200 acre-foot fresh water storage reservoir with a live yield of over 2,000 acre-feet. This project was ultimately driven by the regional recognition of the potential beneficial use of stored water at the head of the Eagle River. Upstream replenishment of down valley depletions was desirable to the Eagle Valley water users, the Colorado Water Conservation Board, and other water use stakeholders in the valley. Climax recognized the long term value of their water rights and existing water storage and conveyance infrastructure in the planning and development of the Eagle Park Reservoir reclamation project. The completed reservoir stands as a model for future reclamation efforts that involve water delivery to highly sensitive receiving waters. Attachment: Photographs of Eagle Park Reservoir -2-