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• <br />The aquifer used most extensively in the area foz'c~~ater supplies is <br />an uncnn.solidated glacial/alluvial formation which mantles much of <br />the surface. About 25 registered wells have been completed in this <br />aquifer near the mines. Although limited in aerial extent, the aquifer <br />has suitable characteristics for eaater resource development. Because <br />of the valley disection created by [card Creek, the aquifer is not <br />continuous from the Red Canyon F1i ne to the Tomahawk P1in e. <br />Both mines have the potential to impact ground relater resources. <br />Mine de:,~atering practices will cause piezometric surfaces to lower in <br />the coal seams, other adjacent strata, and the glacia1Ja11uvial aquifer. <br />Spoils Ieachate and degraded underground mine water could potentially <br />enter adjacent strata and cause a water quality impact. As is described <br />below, the individual impacts of the mines could potentially overlap <br />and produce a cumulative impact. N.owever, material damage is not <br />expected to occur., <br />Both operations mine coal from the same sequence of bedrock strata. <br />Both mines are wet enough to necessitate mine dewaterina. Drawdown <br />predictions presented in the Grand Piesa application suggest that the <br />drawdowns of the two mines may overlap. The bedrock strata in the <br />vicinity of the coal seams will be affected. In addition, both mines <br />will probably impact water quality in the coal seams and adjacent <br />strata. Leachate generated in the spoils at the Tomahawk will enter <br />the strata and mix reith the undisturbed ground water. The quality <br />of the ground water in the old, abandoned, undergzound mine raor7;ings <br />in the area is very poor (about 10,000 mg/1, TDS). Zt is reasonable <br />to assume that similar conditions may occur in the Red Canyon Mines. <br />Therefore, the mines could cumulatively impact the bedrock ground <br />water resources of the area. However, the potentially impacted bedrock <br />strata are generally inaccessible for water resource development. <br />From their outcrop at the mines, the strata dip to the north, eventuallu <br />becoming situated deep beneath the Piceance Basin. The poor aquifer <br />characteristics and the great depth of the strata cause water development <br />to be uneconomical. Therefore, the anticipated impacts should not <br />cause material damage to anyone's water supply. <br />Both mines have the potential to impact the glacial/alluvial aquifer <br />which mantles much of the surface. Botlr water 1eve1•s and water quality <br />could be affected. Neither mine pz'edicts that a significant impact <br />will occur. The Grand Ffesa application provided an analysis of the <br />resultant impact of the underground mine water discharging to the <br />overlying glacial/alluvial aquifez'. The impact was shoran to be <br />insignificant (see the "Probable Hydrologic Consequences" portion <br />of this document). In addition, the glacial/alluvial aquifer is not <br />continuous between the two mines. The Bisected valley of t9ard Cree}: <br />separates the aquifer, therefore, a cumulative hydrologic impact is <br />not anticipated. <br />