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IX. <br />This section of the Findings document contains a description of the hydrologic <br />environment, a discussion of the probable hydrologic consequences of the Red <br />Canyon mining operation and an assessment of the cumulative hydrologic impact <br />of all mining in the Tongue Creek Drainage Basin. Ground water and surface <br />water are addressed separately below. <br />Ground Water <br />Description of the Environment <br />The appiicant's description of ground water is contained in Sections 2.04.5(1) <br />and 2.04.7 of the permit application, and in Volume 8, the 1982 addendum <br />(Kimball, et. al., 1982). There are four geologic units in the vicinity of <br />the proposed mine area which could potentially be called aquifers. They are, <br />in ascending order, the Rollins Sandstone, the "D" coal seam, the "E" coal <br />seam, and the unconsolidated glacial/alluvial material which mantles much of <br />the surface. Water wells have been completed in all of these aquifers in the <br />vicinity of the mine. The most used aquifer in the area is the unconsolidated <br />glacial/alluvial geologic unit. Generally, the bedrock aquifers do not yield <br />sufficient quantities of potable water for economical large-scale <br />development. The four potential aquifers are discussed in greater detail <br />below. <br />The Rollins Sandstone occurs about 150 feet below the lowest proposed mine <br />workings ("D" seam). The proposed mining operations will not impact the <br />aquifer. The strata separating the sandstone from the mine workings consist <br />of shales, siltstones, coals, and laterally discontinuous sandstones. These <br />units provide a sufficient barrier to prevent vertical hydrologic <br />communication between the aquifer and the mine workings. <br />Therefore, the Rollins Sandstone aquifer will not be affected by the operation <br />and will not be discussed further in this document. <br />The "D" coal seam is the lowest aquifer which will be disturbed by the <br />proposed mining operation. The aquifer subcrops below the glacial/alluvial <br />aquifer and continues, at a dip of 5-6o to the north, deep into the Piceance <br />Basin. Monitoring well water level data indicate that ground water in the "D" <br />seam aquifer flows updip and discharges into the overlying glacial/alluvial <br />aquifers. That is, pressures in the aquifer force water to flow against the <br />prevailing dip direction. Recharge probably occurs around the rim of the <br />Piceance Basin where the aquifer outcrops. Permeability in the coal seam is <br />mainly the result of post-depositional fracturing and cleating. The applicant <br />has determined that the transmissivity of the aquifer is 16.7 ft2/day and <br />the storage coeffitient is 4.4 x 10-5. These values indicate that the <br />aquifer is confined and has low permeability. The "D" seam aquifer contains a <br />sodium bicarbonate type water with total dissolved solids (TDS) concentrations <br />ranging from 1,184 mg/1 to 2,308 mg/1. Because of the aquifer's low <br />permeability and poor water quality, it is not suitable for large scale <br />development. <br />-24- <br />