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-42- <br />The total estimated water consumed by all of the mines presently operating in <br />the North Fork of the Gunnison Drainage Basin is 396 acre-feet per year, This <br />is approximately 0.145 of the mean annual yield of the river, This indicates <br />that the total coal mining activities within the North Fork of the Gunnison <br />Drainage Basin has a very minor impact on the quantity of water available in <br />the Basin. <br />Flooded Workings Study <br />A projection of flooded workings water quality was made, in the unlikely event <br />that water would discharge through the permanent seals into the North Fork of <br />the Gunnison drainage. The quality of mine water may best be represented by <br />data from the Oliver mine adit. The Oliver mine workings have been flooded <br />for several decades and chemical equilibria are probably dominated by reduced <br />conditions. <br />Concentrations of selected major ions from the Oliver mine adit water samples <br />collected between 1979 and 1982 indicate same seasonal trends in water <br />quality. Solute concentrations tend to be slightly lower during the spring <br />than in the fall during any given year. This is probably attributable to <br />snowmelt recharge of shallow ground water systems that contribute the majority <br />of the inflow to the main. <br />The Oliver mine adit samples are dominated by sodium and bicarbonate ions. <br />Total dissolved solids concentrations range between 1050 and 1900 mg/1. A <br />comparison of water quality constituents with the most recent stream standards <br />for the North Fork of the Gunnison River is given in Table 3. The North Fork <br />will be the receiving drainage for any discharge from the Mt. Gunnison Mine. <br />The standards for boron were exceeded slightly on three occasions. The <br />standards for total iron, selenium and zinc were exceeded on just one <br />occasion. None of the exceedances were of a magnitude that was likely to <br />result in degradation of stream quality in the North Fork of the Gunnison <br />below the standards. <br />CUMULATIVE HYDROLOGIC EFFECTS ON GROUND WATER <br />An assessment of the probable hydrologic consequences of the mining operation <br />and an assessment of the probable cumulative impact of all anticipated mining <br />in the general area on the hydrologic balance has been made. Pursuant to Rule <br />2.07.6 (2 )(c ), the Division finds that the Orchard Valley mining operation has <br />been designed to prevent material damage to the hydrologic balance outside the <br />permit area. <br /> <br />