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-:»- Ground water in the basin also occurs in unconfiner] nlluvinl aquifers. Major alluvial aquifers in the basin occur along Trout Crr~eB, Middle Creek, Toidel Creek and Fish Creek (see Map No. 1 of the Energy Fuels .lo. 3 permanent program mining application). Water in these aquifers is used for irrigation, domestic and stock watering purposes. Water in the bedrock aquifers of the Twenty hfile Park hasin is generally recharged at the outcrops near the edge of the basin. From there, water generally flows towards the center of the basin and discharges into the fish CrecF; alluvial aquifer. Locally, some of the smaller, laterally discontinuous aquifers c7iscliarge into the alluvium of Trout Creek, Middle Creek, and Foidel Creek. The alluvial aquifers are gene tally locally recharged by the bedrock aquifers and direct infiltration from precipitation, irrigation return flows, and surface runoff. The alluvial water is either discharged into the stream or adjacent aquifers, or flows out of the basin via the Trout Creek alluvium and discharges into the Yampa River alluvial system. Existing and proposed coal mines located in the Twenty Mile basin are the Pittsburg and Midway Edna mine, the Apex mine, Energy Fuels No. 1, 2 and 3 mines, and the Peabody Seneca ZZ mine. A11 of these mines exmpt the existing Apex mine and the proposed ner y Fuels No. 3 mine, are drayline -strip surface operations. The Apex and the propose Energy Fuels No. 3 mine arc underground operations. The probable hydrologic consequences of mining at the Edna mine is discussed in the ground water, surface water, and alluvial valley floor sections of this docu,~nt. It is anticipated that the hydrologic consequences of the other surface mining operations in the basin will be similar in magnitude. That is, ground water will reenter the re- graded spoils, become loaded with increased concentrations of dissolved salts, and discharge into the alluvial waters of one of the streams in the basin. As this degraded water flows through the system, it should become diluted such that it would return to an acceptable quality. However, overall quality of ground water in the basin should become slightly degraded. Presently, there is an insufficient data base to quantify the magnitude of this degradation. The hydrologic consequences of mining on the quantity of ground water are expected to be less severe on the basin as a whole. However, Iocaliz~d dewaterinq of some of the minor aquifers r.~i11 occur in the vicinity of the mine pits or underground portals. Th~~re is also the potential for slight de wa to ri m; of thc• alluvial aquifers in those situations where mining occurs immediately adjacent to, or underground of a stream. This could potentially cause a decrease in productivity of subirriyated crops grown on alluvial valley floors. To date, this has not been found to be a significant problem. The major bedrock aquifers of the area (i.e. the 'twenty ~]i1e and Trout Creek Sand- stones) are not expected to be impacted by mining in terms of water quality or quantity. They are both located above or he low the coals to be mined and are separated by sufficient stratigraphic distance that any hydrologic interconnection is unlikely. Zn conclusion, there is an insuf:icient data base available to allow for quantitative. predictions to be made regarding thz probahle cumulative hydrologic consequences of mining on the ground water resource of the Twenty Flile Park basin. However, certain qualitative predictions can he made. tJaters with elevated levels of dissolved solids will discharge from reclaimed mine spoils into the alluvial systems of streams within the basin. Zt is expected that the "dilution effect" will improve the quality of these waters to acceptable levels. However, local dewatering of minor bedrock aquifers and