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<br />• <br />Drainage Effects From Waste Piles <br />-37- <br />Effluent from several underground waste piles will enter the North Fork of the <br />Gunnison River. The area contains both historic and existing waste rock/coal <br />refuse piles. Hawk's Nest has reclaimed a four-acre site in Crystal Meadows <br />and currently is storing waste at a nineteen-acre site in the Hotchkiss <br />Landfill. Mt. Gunnison has initiated construction of a waste pile which will <br />cover twenty-two acres in extent. The Bear No. 2 Mine has a 0.7 acre waste <br />pile. The Somerset life-ofanine area includes two historic waste rock/coal <br />waste disposal areas. The Hubbard Creek site was used from 1970 through 1977 <br />and covers 0.6 acres, The East Yard site (9 acres) is currently part of the <br />surface facilities area and was used as a waste dump prior to 1969. In the <br />eventuality that Somerset would re-open, future waste rock at the Somerset <br />mine will be disposed o° at a waste disposal site established at the "C" seam <br />mine portals area (1 .2 acres). The Blue Ribbon Mine finished construction of <br />a mine bench in 1985. This bench was built using mine waste from the Mt. <br />Gunnison Mine. This area is approximately four acres in size. The Orchard <br />Palley Mine has proposed a sixteen-acre waste rock pile for the life of the <br />mine. <br />leachate would probably be a sodium sulfate type water with relatively low <br />total metal concentrations and neutral pH. The rate of discharge can be <br />estimated by multiplying the infiltration to the pile by the area of the <br />pile. Information provided in the Orchard Palley permit application estimated <br />waste pile infiltration to be 2.8 in/yr. Assuming that most of the water for <br />infiltration is the result of snowmelt, it may be assumed that this discharge <br />is limited to a 60-day period in the spring. The leachate volume is <br />calculated as: <br />The effects of the waste piles on dissolved solids concentrations in the North <br />Fork of the Gunnison can be evaluated using the preceding mass balance <br />equation. By estimating the total dissolved solids concentration of the <br />leachate and estimating the rate of discharge from the pile to the stream - <br />a11uv1a1 aquifer systems the potential effect of. waste pile effluents can be <br />determined. The total dissolved solids concentration was assumed to be a <br />conservatively high concentration of 5,000 mg/1. The chemistry of the <br />Table 10: Waste Pile Disposal Acreage in the North Fork <br />Area of Waste Disposal (Acres) <br />23.0 <br />22.0 <br />0.7 <br />10.8 <br />4.0 <br />16.0 <br />7S3 acres <br />Mine <br />Hawk's Nest <br />Mt. Gunnison No. <br />Bear No. 2 <br />Somerset <br />Blue Ribbon <br />Orchard Valley <br />(76.5 acres)(2.8 inches/year)(1/12) = 17.85 acre feet/month <br />• <br />(17.85 ac-ft/month )(43560 ft2/acre)(1 month/30 days)(1 day/24 hours) <br />fl hr/60 min)(1 min/60 sec) 0.3 cfs x 2 mos 0.6 cfs <br />leachate = 5000 mg/1 TDS <br />