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range from 0.01 to 1 foot per day with transmissivities ranging from 0.5 <br /> to 150 square feet per day. During a U.S.G.S. survey, only one well was <br /> located in the Mesa Verde Group in the vicinity of the mine. It is not <br /> known specifically what stratigraphic unit this well is completed in. <br /> However, the water quality of this well was reported to be a calcium <br /> bicarbonate type with a total dissolved solids concentration of 181 mg/l. <br /> The most prominent aquifer in the vicinity of the Mid-Continent operations <br /> is the alluvial aquifer of Coal Creek. Yields in this aquifer are <br /> reported to average 20 gpm. Mid-Continent has completed 9 observation and <br /> production wells into this alluvial aquifer, and the alluvium of several <br /> of the smaller drainages. Depths of these wells range from 10-75 feet. <br /> The water quality of the aquifer is generally a calcium, sodium, <br /> magnesium-bicarbonate type with an average total dissolved solids <br /> concentration of 347 mg/l. Iron and magnesium concentrations are high, <br /> but the water is still suitable for domestic uses. <br /> The only ground water aquifers that have the potential to be impacted by <br /> mining are those used by the applicant. Several mine production wells are <br /> completed into the alluvial aquifer of Coal Creek. No wells are known to <br /> be completed in the coal-bearing strata of the Mesa Verde Group in the <br /> vicinity of the mine. <br /> The applicant proposes to mine both the Coal Basin coal seam ("B" seam) <br /> and the Dutch Creek coal seam ("V" seam) by underground mining methods. <br /> The mine entries will be located near the outcrop of the seams. No <br /> significant physical disturbance of adjacent strata will occur as a result <br /> of the mine entries. <br /> In addition, the applicant proposes to construct a tunnel which will <br /> connect the 2 seams currently being mined. This tunnel will be used to <br /> more efficiently transport coal out of the mines. The tunnel entry will <br /> be located in the underlying Mancos shale formation and will continue up <br /> the stratigraphic section until it intersects with the Dutch Creek coal <br /> seam. It will cut through 3 sandstone units that are considered potential <br /> aquifers. They are, in stratigraphically ascending order, the Cozzette, <br /> Rollins, and Middle sandstones. The waste rock generated during the <br /> construction of this tunnel will be disposed of near Dutch Creek. <br /> The mines dewater the coal seams and adjacent strata as part of normal <br /> operations. This dewatering process will cause water levels in some <br /> aquifers to be lowered. The decline in water levels should not extend <br /> more than a mile from the edge of the mine workings based on <br /> transmissivities of these strata as presented in the application. This <br /> effect should be temporary in nature. When mining is completed, the water <br /> levels in the aquifers should return to pre-mining elevations. <br /> Other effects on ground water will be a slight mixing of ground waters <br /> from previously unconnected aquifers as a result of the proposed rock <br /> tunnel and a slight degradation of alluvial water from the coal processing <br /> waste pile and the rock tunnel waste pile. None of these impacts are <br /> expected to cause material damage to ground waters in the Coal Basin area. <br /> 11 <br />