2001-06-04_REVISION - M1977493 (2)

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Introduction Exponent has been requested by Climax Molybdenum Mine to prepare a report summarizing the available surface water quality data collected in and near the Eagle Park Reservoir (EPR), and to perform an antidegradation type analysis on the outfall waters delivered from this facility to the Eagle River. While an antidegradation analysis is not required to deliver water from the EPR (see Colorado Water Quality Control Act, Sections 25-8-104C1 and 25-8-503C5), Climax undertook this analysis to satisfy agreements made with the Colorado Division of Minerals and Geology for Surety Release (SR-002). Eagle Park Reservoir is located in Eagle County, Colorado, approximately 3 miles from Freemont Pass (Colorado State Highway 91) on the East Fork Eagle River tributary to the Eagle River. The reservoir is a[ an elevation of approximately 10,700 ft. EPR was originally the site of the No. 4 tailings pond, a facility built to contain tailings from the beneficiation of oxide ores. The tailings were removed from the reservoir by 1996, and the facility was upgraded to become a water reservoir capable of storing water and, through outlet works, releasing on demand stored water to [he East Fork of the Eagle River (East Fork). A report was prepared describing the development of this facility into a surface water reservoir (Eagle Park Reservoir, Final Analytical Summary, Oct. 29, 1997, Bryce Romig, Climax Molybdenum Company). Water quality samples were taken from the reservoir and receiving streams through time. As the reservoir was filling, sampling was undertaken at several locations within EPR, commencing March 1997. Discussions of the water quality during the filling period can be found in communications between Climax Molybdenum Company (CMC) and the Colorado Division of Minerals and Geology. Once the reservoir filled, surface water sampling at four locations within the reservoir was initiated in March 1998. Surface water was first delivered from EPR on December 14, 1998. After deliveries commenced, surface water samples were taken at four locations, including the outfall from the EPR and in the East Fork (one upgradient and two downgradient of the confluence of the EPR Outlet and the East Fork). These sampling locations were maintained from the first day of water delivery and continued until February 2001. Generally, water was delivered from the reservoir during periods of low flow in the East Fork (fall, winter, and early spring). 8601631.005 0101 0601 0380 Oboultlerl WalayxojectsV 9d]_climaxlepr repon_2.doc