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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 this 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 /> During the periods 1950-62, 1964-70, 1972-1974, and 1977, water yields from the <br /> Deep Creek diversion canal were greater than releases from Minnesota Reservoir. <br /> During water years 1978, 1979, and 1980, all water passing through the Deep Creek <br /> Ditch into Minnesota Reservoir was released from the reservoir. Assuming no <br /> seepage and transmission losses, contributions of Deep Creek Ditch flow releases <br /> from Minnesota Reservoir ranged from only 13.5 percent to 25.4 percent between <br /> 1978 and 1980. It is assumed that seepage and transmission losses in the diversion <br /> canal result in a Deep Creek Ditch yield of less than 80 percent. <br /> The applicant has stated that the records of water yield from Minnesota Reservoir <br /> are not reliable and that there is no way to develop a meaningful comparison <br /> between the Deep Creek Ditch yield and the Minnesota Reservoir yield. As a result, <br /> it is difficult to assess the quantity and frequency of "natural" water supporting <br /> alluvial functions in the 90-acre tract immediately above Minnesota Reservoir. It is <br /> conceivable that the unconsolidated deposits contained within the 90-acre tract of <br /> land on the Dry Fork of Minnesota Creek are the direct result of artificial water <br /> availability, specifically the Minnesota Reservoir Dam and the Deep Creek Diversion <br /> Ditch. However, based on the high elevation, short growing season, reduced soil <br /> 51 <br />