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This change in water quality could affect water use patterns in the vicinity of the mines. A TDS of 900 mg/1 is in excess of EPA domestic water quality standards. Information in the application indicates that there is little domestic use of ground water in the area. Most domestic water users obtain their water supply from the Colby municipal water line. Other users of water (stock, irrigation, and industrial) should not be significantly affected by the predicted water quality change. Monitoring of water in the mine will be conducted to verify these predictions. The applicant proposes to place mine development waste on the existing refuse pile (see Map 2.05.3(2)(b>-1 of the permit application). The existing refuse pile is largely located 1n old abandoned strip mine pits. Some additional disturbance is proposed. The refuse pile will be completely underlain by bedrock and will not be in direct contact with the unconsolidated glacial/alluvial material. The applicant has determined that significant vertical permeabilities do not exist in the strata near the mine (see pages 20-35 of Volume 8). Therefore, vertical infiltration of leachate from the refuse pile into underlying aquifers should not be a significant problem. Upon final reclamation, the potential for hydrologic impact should actually be less than before this operation, because the old strip mine pits will be reclaimed. Cumulative Hvdroloaic Impact The only other mine in the vicinity of the Grand Mesa operation which could cumulatively impact ground water resources is the Quinn Tomahawk Mine. It is located about two miles to the west of the Red Canyon Mines. The incised valley of Ward Creek separates the two operations. Both operations mine coal from the same sequence of strata. The Tomahawk Mine will have both surface and underground mining operations. Red Canyon is solely an underground operation. For more detail regarding the proposed mining plans the reader is directed to the description of operations portion of this document and of the Quinn Tomahawk Mine findings document (published by the Division on April 9, 1982>. Also discussed in the findings documents are the statements of probable hydrologic consequences of each individual mining operation. The coal being mined at both operations is situated in the lower portion of the Williams Fork Formation; which consists of interbedded sandstones, siltstones, shales, and coals. Most of these strata are laterally discontinuous. The only continuous strata are the coal seams and the underlying Rollins Sandstone. The coal seams outcrop near the mines and generally dip to the north beneath Grand Mesa, continuing deep beneath the Piceance Basin. Because of their limited aquifer potential and great depth, the strata to be disturbed by the proposed mining operations are not used extensively for water supplies. Only a few stock watering wells have been completed in the potentially affected strata. The aquifer used most extensively in the area for water supplies is an unconsolidated glacial/alluvial formation which mantles much of the surface. About 25 registered wells have been completed in this aquifer near the mines. Although limited in aerial extent, the aquifer has suitable characteristics for water resource development. Because of the valley dissection created by Ward Creek, the aquifer is not continuous from the Red Canyon Mines to the Tomahawk Mine. _P7_