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Table 4: Maximum Mining Impact on the North Fork of the Gunnison River <br />Discharge (CFS) TDS (mg/q <br />~~ Upstream (Q~) Downstream (Q~) Upstream (C~) Downstream (c~) <br />„i; as say. <br />32.5 37.3 95 439 gcy X54 <br />47.6 52.4 95 340 : I L S76 <br />66.0 70.8 95 276 ye7 y>7 <br />432.0 436.8 95 124 ;b I I>6 <br />~~ I'~ S3. <br />The assessment indicates that the water quality would be degraded somewhat for all flows. However, [he assessment indicates [hat <br />no significant impacts will occur on the North Fork of the Gunnison at the maximum extent of mining and no water uses will be <br />precluded. The mine discharges and TDS concentrations were estimated using conservative assumption; therefore, the actual impact <br />to the river will probably be less than the projected impact. If more reasonable assumptions were made based on a more extensive <br />database, a more precise estimate of the impact to [he river could be made. <br />Draina¢e Effects From Waste Piles <br />Effluent from several underground waste piles may enter [he North Fork of the Gunnison River. The area contains both historic and <br />existing waste rock/coal refuse piles. Hawk's Nest has reclaimed afour-acre site in Crystal Meadows and currently is storing waste <br />at a nineteen-acre site in the Hotchkiss Landfill. West Elk has constructed a waste pile which will cover twenty-two acres. The Beaz <br />No. 2 Mine has a 0.7 acre waste pile. The old Somerset mine includes two historic waste rock/coal waste disposal areas. The Hubbard <br />Creek site was used from 1970 through 1977 and covers 0.6 acres. The East Yard site (nine acres) is currently part of the surface <br />facilities azea and was used as a waste dump prior to 1969. Waste rock at the Sanborn Creek Mine is being disposed of at a waste <br />disposal site established at the C seam mine portals area (1.2 acres). The Blue Ribbon Mine finished construction of a mine bench <br />in 1985. This bench was built using mine waste from the West Elk Mine. This area is approximately four acres in size. The Bowie <br />. No. 1 Mine is constructing asixteen-acre waste rock pile for the life of the mine. The Bowie No. 2 Mine has proposed a 5.5 acre <br />waste rock pit. <br />The effects of the waste piles on dissolved solids concentrations in the North Fork of the Gunnison can be evaluated using the <br />preceding mass balance equation. By estimating the total dissolved solids concentration of the leachate and estimating the rate of <br />discharge from [he pile [o [he stream and alluvial aquifer systems, the potential effect of waste pile effluents can be determined. The <br />total dissolved solids concentration was assumed to be a conservatively high concentration of 5,000 mgJl. The chemistry of the <br />leachate would probably be a sodium sulfate type water with relatively low total metal concentrations and neutral pH. The rate of <br />discharge can be estimated by multiplying the infiltration to the pile by the area of the pile. Information provided in the Bowie No. <br />1 permit application estimated waste pile infiltration to be 2.8 in/yr. Assuming that most of the water for infiltration is [he result of <br />snowmelt, it may be assumed that this dischazge is limited to a 60-day period in the spring. The leachate volume is calculated as: <br />• 15 <br />