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<br />Gross Reservoir has two potential enlargement sizes: 20,000 acre-foot enlargement and <br />71,000 acre-foot enlargement (Figure 7). The 20,000 acre-foot enlargement would raise <br />the existing dam by 30 feet for a total storage capacity of approximately 62,000 acre-feet <br />and would allow for continued use of the existing hydropower plant. Water to fill the <br />reservoir would come from increased diversions of Denver Water's water rights in the <br />Fraser River and Williams Fork rivers and in South Boulder Creek, primarily during the <br />spring runoff months of average and wet years. The 71,000 acre-foot enlargement would <br />raise the existing dam by 125 feet. The enlarged reservoir would have a total storage <br />capacity of approximately 113,000 acre-feet, To maximize hydropower generation, an <br />additional hydroelectric unit could be constructed, This would require enlargement of the <br />hydropower plant licensed by FERC. A 20,000 acre-foot enlargement could provide <br />approximately 5,000 acre-feet of additional firm yield and a 71,000 acre-foot <br />enlargement would provide approximately 17,000 acre-feet of firm yield. <br /> <br />Examples of potential environmental issues associated with the Gross Reservoir <br />enlargement alternatives include: <br /> <br />· On-site impacts associated with the construction ofthe dam and inundation area of <br />the reservoir enlargement. <br />· Recreation at Gross Reservoir, <br />· Socioeconomic effects to the community immediately surrounding Gross Reservoir. <br />· Aquatic resources, including wetlands, fisheries, water quality and endangered <br />species that may be affected by increased diversions from the Fraser and Williams <br />Fork rivers. <br />· Aquatic resources, including wetlands, fisheries, water quality and endangered <br />species that may be affected by increased flows in South Boulder Creek between <br />Moffat Tunnel and Gross Reservoir, and changed flows below Gross Reservoir. <br />· Resources affected by changes in hydrology in other parts of Denver Water's <br />Collection System from operation of a larger Gross Reservoir. <br /> <br />Leyden Gulch Reservoir Alternative <br /> <br />The Leyden Gulch Reservoir site is located in Jefferson County, about 5 miles north of <br />Golden, Colorado, south of Highway 72 and immediately west of Highway 93 (Figure 8). <br />The reservoir site is a valley bound by remnant alluvial fans to the north and south and <br />the Laramie hogback formation to the west. The vegetative cover is predominantly short- <br />grass prairie, with a narrow riparian corridor lacing its way down the valley, Leyden <br />Gulch in this headwater area is ephemeral, and typically flows during spring runoff and <br />during summer storm events, The reservoir site, which is primarily owned by Denver <br />Water, is used for cattle grazing, <br /> <br />19 <br />C:\Documents and Settings\vyp\Local Settings\Temporary Internet Files\OLKI50\MoffatSystem I00603.doc <br />