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ro c' v.c�` r <br /> �v <br /> I �4ro0e.d DC�u� �o '{�.� r Steyne�l t�✓L r� ✓( � �Tt2 <br /> C d 1 U v l-It <br /> by <br /> -22- <br /> As stated earlier, 3 sandstone units in the Mesaverde Group have the <br /> potential to be considered aquifers. In the Coal Basin affected area; T I/ <br /> the Upper sandstone is approximately 50 feet thick, the Middle sandston <br /> is about 120 feet thick, and the Rollins sandstone is about 140 feet 1 A <br /> thick. To better understand the stratigraphic relationships between CUB fig, <br /> these sandstones and the coal seams being mined, see Figure II-D-1 of the tf . <br /> permit application. Generally, the Rollins sandstone immediately <br /> underlies the "B" seam and the Middle sandstone immediately underlies the L� ' <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 U.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/l. <br /> The most prominent aquifer in the vicinity of the Mid-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 this alluvial aquifer, and the <br /> alluvium of several of the smaller drainages (see Map IV-C-1 and Map <br /> III-E-1 of the permit application) . Depths of these wells range from <br /> 10-75 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 high, <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 /> �G <br /> 1 . from the surface water during periods of high flow, �� <br /> 2. from the adjacent bedrock strata, and 7 <br /> 3. from direct infiltration of precipitation and snowmelt <br /> The alluvial aquifer probably disttiarges to the following locations: <br /> i . the surface .eater during periods of low flow, <br /> 2. the adjacent bedrock strata, and <br /> 3. the alluvial aquifer of the Crystal. River, farther downstream. <br />