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contribution of the water supplied to the alluvial valley floor, no degradation of <br /> water quality in the alluvial valley floor is predicted. <br /> 3. Surface coal mining and reclamation operations are conducted to preserve, <br /> throughout the mining and reclamation process, the essential hydrologic <br /> functions of alluvial valley floors not within the affected area (Rule 4.24.2). <br /> None of the mining activities are located within the alluvial valley floor and the <br /> natural geologic and hydrologic characteristics of the valley floor would not be <br /> disturbed. In addition, mining operations are not expected to affect the quantity <br /> and quality of surface and ground water that supply the alluvial valley floor. <br /> Minnesota Creek Drainage - Life of Mine AVF Determination: <br /> Currently, the West Elk Mine's five-year permit boundary is situated near the <br /> Minnesota Reservoir. Mining which could potentially affect the Minnesota Creek <br /> intermountain diversion and reservoir system will not be approved until an <br /> appropriate subsidence control plan is submitted and approved. <br /> One of the locations for alluvial deposits within the life-of-mine permit area is a <br /> 90-acre tract of land on the Dry Fork, immediately above Minnesota Reservoir. <br /> These alluvial deposits range from 100 to 300 feet in width. The valley floor above <br /> the reservoir widens and there is a definite break in slope from the steep sides <br /> confining the valley floor. Numerous beaver ponds and willow thickets occupy the <br /> valley floor in !his location, and grazing is limited to isolated locations along the <br /> margins of the valley. <br /> The soils in this location are primarily deep clays. The Haplaquoll soil <br /> predominates. It is associated with beaver activity and commonly exhibits mottled <br /> conditions in subsurface horizons. The alluvial origin of this material is plausible <br /> because of the beaver activity and downstream channel blockage from a landslide <br /> and from Minnesota Reservoir dam which was placed at the blockage point. <br /> Normally the soil is saturated with water at or near the surface. Because of absence <br /> of the good aeration, organic matter content is high. <br /> The applicant states that the valley floor in this reach of the Dry Fork would be <br /> incapable of supporting agricultural activities without proper drainage. <br /> Approximately 20 percent of the total alluvial fill deposits above Minnesota <br /> Reservoir have an artificially high water table as a result of backwater conditions <br /> from the reservoir pool. This area could not be drained adequately without <br /> removing the reservoir. Even with adequate drainage on the remaining 72 acres, the <br /> agricultural development would be restricted to grasses and pasture because of the <br /> high elevations and short growing season. Furthermore, the beaver ponds and <br /> willow thickets are an important factor in the general ecological picture, since they <br /> help regulate stream flow, provide water for domestic animals and wildlife, and <br /> provide wildlife cover. A letter from the Delta Soil Conservation District dated <br /> February 17, 1981 indicates that agronomic development in this 90-acre tract is <br /> doubtful. <br /> 53 <br />