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Both operations have the potential to impact ground water resources. Mine <br />dewatering practices at Red Canyon will cause piezometric surfaces to lower in <br />the coal seam aquifers. Dewatering at Tomahawk could impact both coal seam <br />and surficial aquifers. Spoils leachate and degraded underground mine water <br />(after cessation of mining) could potentially enter adjacent strata and cause <br />a water quality impact. The individual impacts of the mines could potentially <br />overlap and produce a cumulative impact, however, material damage is not <br />expected to occur. This anticipated cumulative impact is discussed below. <br />Both operations mine coal from the same sequence of bedrock strata. Both <br />mines are wet enough to necessitate mine dewatering. Drawdown predictions <br />presented in the Red Canyon application suggest that the drawdowns of the two <br />operations may overlap. The bedrock strata in the vicinity of the coal seams <br />will be affected. In addition, both operations will probably impact water <br />quality in the coal seams and adjacent strata eventually. Leachate generated <br />in the spoils at the Tomahawk Mine will enter the strata and mix with the <br />undisturbed ground water. The quality of the ground water in the old, <br />abandoned, underground mine workings in the area is very poor (about 10,000 <br />mgll, TDSl. It is reasonable to assume that similar conditions may occur in <br />the Red Canyon Mines when the workings fill with water following cessation of <br />mining. Therefore, the mines could cumulatively impact the bedrock ground <br />water resources of the area. However, the potentially impacted bedrock strata <br />are generally inaccessible for water resource development. From their outcrop <br />at the mines, the strata dip to the north, eventually plunging deep beneath <br />the Piceance Basin. The poor aquifer characteristics and the great depth of <br />the strata cause water development to be uneconomical. Therefore, the <br />anticipated impacts should not cause material damage to any developable or <br />developed water supply. <br />Both mines have the potential to impact the glacial/alluvial aquifer which <br />mantles much of the surface. Both water levels and water quality could be <br />affected. Neither applicant predicts that a significant impact will occur. <br />The Red Canyon application provided an analysis of the resultant impact of the <br />underground mine water discharging to the overlying glacial/alluvial aquifer <br />following cessation of mining. The impact was shown to be insignificant (see <br />the "Probable Hydrologic Consequences" portion of this document). In <br />addition, the glacial/alluvial aquifer is not continuous between the two <br />operations. The dissected valley of Ward Creek separates the aquifer, <br />therefore, a cumulative hydrologic impact is not anticipated. <br />Based upon the analysis presented in this CHIS and in the individual findings <br />documents, the Division makes the following finding regarding the proposed Red <br />Canyon Mines. This finding is required under Section 34-33-114(2)(c) of the <br />Act: <br />The proposed Red Canyon Mines "have been designed to prevent material damage <br />to the hydrologic balance outside the permit area." <br />-28- <br />