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• ��c�•hoc � e-o-�.a-ro �e �,r c,._ � J � �5 <br /> r n <br /> -22- <br /> As stated earlier, 3 sandstone units in the Miesaverde Group have the <br /> potential to be considered aquifers. In the C G <br /> Coal Basin affected area_.,7j' <br /> toe Upper sandstone is approximately 50 feet thick, the Middle sandston <br /> is about 120 feet thick, and the Rollins sandstone is about 140 feet ` .� <br /> thick. To better understand the stratigraphic relationships between r;,�' 3 'r` <br /> these sandstones and the coal seams being mined, see Figure II-0-1 of the <br /> permit application. Generally, the Rollins sandstone immediately <br /> underlies the "B" seam and the Middle sandstone immediately underlies the <br /> "V" seam. All of these sandstone units outcrop on the eastern wall of <br /> Coal Basin (see Map III-C-1 of the permit application) . This is where <br /> recharge to the aquifers probably occurs. From the outcrop, the <br /> sandstones dip to the west under Huntsman Ridge, and eventually, extend <br /> deep under the P•iceance Basin. On the western side of Huntsman Ridge, <br /> the sandstones are located about 2,000-3,000 feet beneath the surface <br /> (see Plate II of the permit application) . There are no known users of <br /> this ground water primarily because of this great depth. The water <br /> yields that could be expected from these sandstones are too small to <br /> justify the great cost of drilling to this depth. Also, because of this <br /> great depth, no site-specific data has been collected regarding the <br /> hydraulic characteristics or water quality of these potential aquifers. <br /> However, the applicant estimates that permeabilities in the sandstone <br /> aquifers range from 0.01 to 1 foot per day with transmissivities ranging <br /> from 0.5 to 150 square feet per day. During a U.S.G.S. survey, only one <br /> well was located in the Mesaverde Group in the vicinity of the mine. It <br /> is not known specifically what stratigraphic unit this well is completed <br /> in. 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/J . <br /> The most prominent aquifer in the vicinity of the laid-Continent <br /> operations is the alluvial aquifer of Coal Creek. Yields in this aquifer <br /> are reported to average 20 gpm. Mid-Continent has completed 9 <br /> observation and production wells into tnis alluvial aquifer, and the <br /> alluvium of several of the smaller drainages (see Map IV-0-1 and Map <br /> III-E-1 of the permit application) . Depths of these wells range from <br /> 1U-75 feet. The water quality of the aquifer is generally a calcium, <br /> sodium, magnesium-bicarbonate type with an average total dissolved solids <br /> concentration of 347 mg/l . Iron and magnesium concentrations are hign, <br /> but the water is still suitable for domestic uses (see Section III-E-2 of <br /> this permit application) . The alluvial aquifer is probably recharged by <br /> 3 mechanisms : <br /> 1 , from the surface 'water during periods of high flow, �,e'� <br /> 2. from the adjacent bedrock strata, and ! <br /> 3. from direct infiltration of precipitation and snowmelt <br /> The alluvial aquifer probably discharges to the following locations : <br /> 1 . the surface water during periods of low 'iGw, <br /> 2. -he adjacent bedrock strata, and <br /> 3. the alluvial aquifer of the Crystal. River, farther downstream. <br />