C150295 Feasibility Study - Laserfiche WebLink

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2.1.2 Study Area Description The legal description for site of Old Dillon Reservoir is the SW1 /4 of the SE1 /4 of Section 13 Township 5 South, Range 78 West of the 6th Prime MeYidian, Sumtnit County, Colorado. Old Dillon Reservoir is located noYth of Dillon Reservoir between I-70 and the Dillon Dam Road (Suminit County Road 7) in the Dillon Ranger District of the White River Narional Forest (WRNF). The site is within Sumuiit County, ColoYado in an area known as Lake Hill. (.ree Study Area, Exhibit F; Vicznity Map, Exhibit G and i~ater System Map, Exhibit H). The project axea is located in Southern Rocky Mountain eco-zone at an elevation of approxirnately 9,200 feet above mean sea level (msl). The area is within the juncture between the upper poxtions of the montane ecosystems and the lowex subalpine forest ecosystem. The dominant foxest type is Iodgepole pine (Pinu.r contorta). Porrions of the project area are developed with Interstate 70 to the north, Dillon Dam Road (County Road 7) to the south and Dillon Reservoir, a large water supply reservoir and dam to the south and east. The ODR Enlaxgement project axea is a subset of the Dillon Reservoir Foxest Health EA project aYea, which encompassed approxirnately 26,000 acres of lands requiring mountain pine beetle mitigation work on National Forest Service lands. In the suintnex of 2008, the State Engineexs Office issued an ordex to the Town of Dillon to drain Old Dillon Reservoir due to concexns oveY the integrity of the north dam. This order was accomplished in July 2008, and the reservoir is currently not available fox stoxage. Old Dillon Reservoir The existing reservoir has a surface area of about 9 acxes and is impounded by two embankments of about 5 to 7 feet high. It has an adjudicated stoYage Yight of 46 acre-feet. Prior to the zero storage restriction, the Town maintained relatively stable water levels in ODR. The Yeservoir and surYOUnding area cux~endy suppoYt a variety of Yecreation opportunities, including fishing, l~iking, mountain biking, and sightseeing. Salt Lick Gulch Salt Lick Gulch is a small, alpine, subalpine watexshed located in the Upper Blue Rivex Basin. It is tributary to the Blue River, approximately'/z mile downstream of Dillon Reservoir. Dillon Ditch Old Dillon Reservoir is fed by Dillon Ditch, which diverts watex fxom Salt Lick Gulch noxth of I-70 into the reservoir. Dillon Ditch is conveyed below I-70 in an inverted siphon. Maintenance of the ditch was postponed due to Corp of EngineeY's pexmitting pYOCess, consequently the ditch is in need of xeshaping to restore operation capacity. Outlet to Salt Lick Gulch ODR discharges into a gully that is deeply incised to wetlands adjacent to Salt Lick Gulch where the flow braids into several smaller channels. The outlet flow is conveyed under 1-70 by a culveYt owned and maintained by the Colorado Depaxtrnent of Txansportarion (CDOT) back to Salt Lick Gulch. The oudet channel appeaYS as steep gYadient stream channel with laxge xock armoring the channel substrate. 3