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<br />~0127!i <br /> <br />. <br /> <br />. <br /> <br />Draft Task 7 Technical Memorandum <br /> <br />Present wildlife habitat conditions near the existing Elkhead Reservoir are generally of <br />high quality, although considerable disturbance is evident at some locations and trees are <br />virtually absent around the perimeter of the lake. Wetlands occur in some of the backwater <br />areas of the existing reservoir and also along Elkhead Creek upstream from the existing high <br />water level of the reservoir. <br /> <br />Fluctuations in reservoir contents can have a significant impact on the ability of wetlands <br />to establish and thrive around the periphery of the lake. Fluctuations in the water surface <br />elevation and area are substantial for the Elkhead Reservoir enlargement and are on the order <br />of 40 to 50 percent for Scenarios II through V. To the degree such fluctuations can be <br />minimized, the likelihood of establishing riparian wetlands and habitats would be increased. <br /> <br />Stagecoach Enlargement <br /> <br />As with the proposed Elkhead Reservoir enlargement, the enlargement of Stagecoach <br />Reservoir would have impacts on wetlands and habitat surrounding the existing reservoir, but <br />these impacts would be far less than those associated with constructing a new reservoir. <br />Because of the relatively steep side slopes of the existing reservoir, these impacts would be <br />relatively small. Fluctuations in the surface area and water elevation of Stagecoach Reservoir <br />range between 10 to 20 percent for all scenarios. <br /> <br />The most significant impact to terrestrial habitat at this site would be the inundation of <br />wetland areas in the delta of the reservoir. These wetlands are a portion of the mitigation <br />required for the construction of the reservoir and would need to be replaced or recreated in the <br />delta of the enlarged reservoir, in addition to mitigation requirements for other impacted areas. <br /> <br />Williams Fork Reservoir <br /> <br />The valley floor at the site of the Williams Fork project is characterized by stands of <br />riparian cottonwood forest and willow shrublands along the stream. The remainder of the <br />valley floor supports a variety of wetlands and irrigated fields. The entire length of the site <br />has been used for agriculture since the turn of the century and the majority of the native plant <br />. communities have been altered by these activities. Wetlands occur along the entire length of <br />the Williams Fork River as it passes through the dam site. Wet meadows and marshes occur <br />sporadically on the floodplain in association with old meander cutoffs and oxbows. <br /> <br />Impacts associated with the development of the Williams Fork project would be <br />significant. There would be considerable inundation of large cottonwood stands and riparian <br />wetland areas. The impacted area includes important winter range for large game. The <br />Williams Fork site contains a more diverse range of habitat than thatwhich would be affected <br />by Elkhead enlargement. A substantial wetland area would be created in the delta area of this <br />new reservoir that would not be greatly impacted by fluctuations in water surface elevations. <br />Results of model Scnario V indicate that fluctuations in the water elevation at the Williams <br />Fork Reservoir would be on the order of only 3 to 4 feet. <br /> <br />PROJECT COSTS <br /> <br />General <br /> <br />Preliminary cost estimates were generated for the Elkhead and Stagecoach enlargements <br />and for the Williams Fork project. These cost estimates were intended to provide only <br /> <br />19 <br /> <br />~ <br /> <br />;t. <br />"j!, " <br />