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-37- Effects of Mining on Surface Water The Mt. Gunnison No. 1 Mine plan is designed to minimize the impacts of the project on the surface water hydrology of the region. Disturbed area drainage is collected and treated on the site. Drainage from undisturbed land is diverted around the site. Five sedimentation ponds have been built for the surface facilities area. A system of lined ditches convey water from the disturbed areas to the ponds. All five sedimentation ponds discharge into the North Fork. The mine operation has obtained the appropriate NPDES permits. Effluent quality for the sedimentation ponds has been monitored to determine permit compliance. The applicant will also continue monitoring of surface water to determine the impact of mining on the hydrologic regime. Runoff from both the Upper and Lower permanent waste disposal sites will be routed through the sediment control system and must meet effluent limitations. Final designs for the waste rock piles, which include surface and subsurface drainage systems, allow for the collection of water leachate from the pile. Analysis of sample rock provided by WECC indicates that potential toxicity levels are below EPA standards. Consequently, it appears that if runoff were to develop from the waste piles, minimal impact will occur on the North Fork of the Gunnison River. WECC will be monitoring both ground water quality and levels under the piles, leachate quality and from the subdrains, and spring quality from the base of the Upper permanent pile site if constructed. WECC estimated that treated waste water from the mine could reach 38,000 gallons per day. However, the annual reports from WECC submitted to date indicate that discharges from fall 1983 to winter 1984 averaged about 2,000 gpd. This is about 0.01 percent of the low flow of 20 cfs observed in the North Fork for that period. For spring of 1984 the discharge averaged 7,000 gpm or 0.05 percent of the low flow of 21,6 cfs observed on September 4, 1984. This indicates that there is a great dilution occurring. This indicates that the discharge is having little if any effect on river water quality. The Mt. Gunnison Mine is not expected to significantly impact water quantity in the North Fork Valley in the first five year permit term. water used in the mine and for domestic purposes is supplied from the North Fork River during higher flows when LAECC's water rights are in priority. Also, limited mine water encountered from the workings will be available for use by the mine. WECC presented a projection of depletions to the Colorado River System to quantify impacts on aquatic species. This information was requested by the U.S. Fish and Wildlife Service (Windy Gap Study). The results of WECC's study showed a net depletion of 13.1 ac-ft per year from the North Fork of the Gunnison River. This is a small depletion in relation to the size of the mine and in comparison to the flow in the North Fork of the Gunnison River.