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<br />. <br /> <br />8 <br /> <br />III. AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES OF ALTERNATIVES <br /> <br />A. General Description <br /> <br />The Dallas Creek Project is located within the Uncompahgre River <br />Basin which is bordered on the south and west by the Uncompahgre Plateau, <br />on the north by the Gunnison River, and on the south and southeast by the <br />San Juan Mountains and the Cimarron Ridge. <br /> <br />Ridgway Reservoir will extend 4.6 miles up the Uncompahgre River <br />with a surface area of approximately 1,030 acres. The capacity of the reser- <br />voir will be 80,000 acre-feet, including 20,900 acre-feet for recreational <br />purposes and 4,100 acre-feet for sediment retention. <br /> <br />The Uncompahgre River flows north from the San Juan Mountains <br />and enters the Gunnison River near Delta, Colorado. The river between Ridgway <br />Dam and the community of Colona contains poor to fair populations of rainbow <br />and brown trout and also flannelmouth, white, and bluehead suckers, sculpin, <br />and dace. Heavy sediment loads, high flows during runoff, and mineral <br />pollution are factors limiting the river's present fishery values. <br /> <br />The land area between the dam and the confluence of Cow Creek <br />and the Uncompahgre River is within the right-of-way of the Dallas Creek <br />Project. The maintenance headquarters for the project would be located immedi- <br />ately downstream from the dam, and the Cow Creek recreation area would be <br />located along the Uncompahgre River between the dam and confluence of the <br />Uncompahgre River and Cow Creek. <br /> <br />B. Hydrology <br /> <br />The alternatives being considered would not affect the 25,000 <br />acre-foot recreation/sediment pool nor the minimum flow commitments made in <br />the FES. In general, flows under no-power alternatives (Nos. 1 and 4) would <br />be lower in the winter and higher in the summer than power alternatives <br />(Nos. 2, 3, 5, 6) and reservoir surface area would be reduced by an average <br />of 26 acres with power. Flows and reservoir content are detailed in Attachment I. <br /> <br />Ridgway Reservoir would continue to increase usable water supplies <br />by an average of 39,400 acre-feet annually. This supply includes 11,200 <br />acre-feet for supplemental service lands, 22,600 acre-feet for municipal use, <br />5,500 acre-feet for light industrial use, and 100 acre-feet for use at recrea- <br />tion sites. <br /> <br />C. Water Quality <br /> <br />Heavy metals are the biggest potential water quality problem at <br />Ridgway Reservoir, particularly the elements mercury, cadmium, lead, zinc, <br />silver, and copper, which enter the reservoir primarily during periods of high <br />spring runoff. Normally, heavy metals precipitate out of streamflows before <br />reaching the reservoir, generally improving water quality. These metals then <br />become trapped with the suspended sediments settling out in the reservoir. <br />