1995-08-11_REVISION - M1977493 (9)

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seepage from entering the impoundment. This project continued through 1995 and is scheduled for completion in 1997. All contaminated media(water, tailing, sediment, soils) will be removed to the tailing impoundments during the course of this project. In addition a grout curtain will be installed below Robinson Reservoir dam to prevent potential seepage from entering Eagle Park Reservoir. Robinson Reservoir is located directly upstream of the Eagle Park Reservoir. Robinson Reservoir is 72 acres and functions as a large collection system for seep water and toe drain discharge from the No. 1 Dam on the Robinson tailing impoundment as well as decant water from the impoundment. Robinson Reservoir also stores and recycles process water collected through the Ten Mile Tunnel and, as needed, extension from the presently inactive supply canals Nos. 1 and 2 (Figure 1 and Appendix E). Water'collected from the Ten Mile impoundment is decanted through the Ten Mile riser system ("6 Riser") to the Ten Mile Tunnel. The reservoir contains industrial process water, tailing impoundment seep water, and sediments. Robinson Reservoir has a decreed storage capacity of 3135 acre-feet. A project to convert Robinson Reservoir to a fresh water impoundment similar to the previously discussed Eagle Park Reservoir may be initiated by Climax in the future. As with the Eagle Park Reservoir project, contaminated media may be removed to the tailing impoundments. As part of this project, a specific seep water collection and return system may be constructed at the base of the No. 1 dam on the Robinson tailing impoundment. The third potential source of contamination in the upper Eagle River watershed is the 667 acre Robinson tailing impoundment. This impoundment was constructed in 1936 straddling the uppermost watersheds of Ten Mile Creek to the north northeast and the Eagle River to the west southwest(Figure 1). The largest dam, the 240 foot high No. 1 Dam, contains the impoundment upstream of Robinson Reservoir in the Eagle River drainage. A smaller dam, No. 2 Dam, is connected to the upstream portion of the Ten Mile tailing impoundment in the Ten Mile Creek drainage. While the tailing material contained within the Robinson tailing impoundment consists primarily of quartz silica and orthoclase feldspar, it also contains enough sulfur to be acknowledged by Climax as slightly acid producing. Analytical testing results are found in Appendix C. In addition to tailing material, seepage from the Robinson tailing impoundment and water discharging from the toe drain system beneath No. 1 Dam are potential sources of contamination. As discussed previously, the Robinson Reservoir acts as a collection system for these co-mingled waters, and the Robinson pump station serves to return this water to the industrial process water circuit for reuse. 17