2011-03-14_REVISION - M1977493 (62)

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CM0001630 Page 2 2.0 SITE CONDITIONS The ERV is positioned northwest of the Climax Mine and is located at the headwaters of the East Fork of the Eagle River in Eagle County, Colorado. The average elevation within the valley is . = approximately 10,900 feet above mean sea level (msl). A site map of the ERV is shown on Figure 1. The ERV covers an area of approximately 300 t acres and is bounded on the north and south by bedrock exposures of the Minturn Formation and Tertiary-aged quartz monzonite intrusives. The valley is filled with glacial soil deposits ranging in thickness from 0 to over 80 feet. Figure 2 shows the configuration of the top of the bedrock within the ERV. This surface was defined by over 140 test borings and pits used to define subsurface conditions for construction of the No. 1 Tailing Dam, Robinson Lake, Eagle Park Reservoir, and Chalk Mountain Reservoir. Site features within the ERV which may require reclamation are: i • Eagle Park Reservoir, • Seep Water Related to No. 1 Tailing Dam, • Robinson Lake, and • Chalk Mountain Reservoir. A description of these features, and summary of reclamation related issues, are presented in the following sections. Eagle Park Reservoir Eagle Park Reservoir covers a 59-acre area and has a storage capacity of approximately 2,880 acre-feet (Wheeler, 1994). The reservoir dam was originally designed to be constructed in three stages with dam crest elevations at 10,705, 10,745 and 10,790 feet msl for stages 1, 2, and 3, respectively. The first stage was completed in October of 1966. However, changes in mill operations ended the need for additional storage and stage 2 was modified prior to construction, 11 reducing the dam crest elevation from 10,745 to 10,725 feet. The existing dam was completed in 1968. The dam was designed as a zoned earthen embankment with a central impervious core, and upstream and downstream zones of random pervious and semipervious material, and a sand/gravel drainage blanket. A cutoff trench was excavated into the weathered bedrock beneath the dam. L Construction records indicate the cutoff trench was up to 80 feet deep in the valley bottom (WCC, 1978). The trench was backfilled with material similar to the central core. c Oxide tailing from the mill was deposited in the Eagle Park Reservoir beginning in the summer of 1967. Oxide tailing deposition continued until late 1968 when it was stopped due to changes in mill operations. The total volume of oxide tailing deposited in Eagle Park Reservoir is ?. =0== == Environmental