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and the US Army Corps of Engineers Section 404 of the Clean Water Act permit. CEC <br />assembled an experienced multi-disciplinary team of resource specialists to assess impacts of <br />the proposal including: Lisa Sakata, Inc. - NEPA, RecYeation, Aix Quality, and Visuals <br />Impacts; Resouxce Engineexing, Inc - Water Resources; Miller Ecological Consultants, Inc. - <br />Aquatic Biology/Fisheries; Zach Perdue - Visual Impacts; Metcalf Archaeological <br />Consultants, Inc. - Cultural ResouYCes; Nancy Rednex - Botany and Tetra Tech- EngineeYing. <br />GEI Consultants (1998) (see Engineering Fea.ribility Study, Exhibit J) evaluated the feasibility of <br />construction fox the project, and Resource Engineering evaluated water supply availability for <br />the project in 2005. Tetra Tech has released the final plans at the 90% review stage in 2009 <br />(.ree ODl~ 90% Plans, Exhibit~. The plans axe curYently under Yeview by the State EngineeYs <br />Office. <br />The project includes seven elements: ''~~ <br />1) Reservoir Enlargement <br />The enlaxged reservoir would have a uYface axea of about 15.4 acres. The proposal would <br />expand the existing xeservoiY from ; acre-feet to 286 acre-feet capacity by rebuilding taller <br />dams to a height of approximately 28 to 38 feet. Construction of the xeservoir enlargement <br />would xequite about 120,000 cubic yaYds of excavation, 80,000 cubic yaxds of embankment <br />fill, 10,000 cubic yards of imported YipYap, and 1,000 feet of 24" pipe foY the outlet to the Blue <br />Rivex (new Dillon Reservoix) to the south. On-site boYrow mateYial foY the dams would be <br />excavated to the east and west of the cuxrent shoYelines. The remainder would be unpoYted <br />material. A detailed analysis of the geology was pexfoYmed by Tetra Tech in Novembex 2008 <br />(see ODK Geotech, Exhibit 1~). <br />2) Restoring the outlet from Old Dillon Reservoir to the south to the Blue River <br />(Dillon Reservoir) <br />A 24" diameter pipe would be installed fxom Old Dillon Reservoir to Dillon Reservoir, under <br />the Dillon Dam Road (Sutmiut County Road 7). The pipe will be installed in a concrete wing <br />wall with energy dissipating ripxap. <br />3) Rehabilitation and modification ofDillon Ditch arld its headgate on SaltLick Gulch <br />to serve the enlarged reservoir <br />To rehabilitate the Dillon Ditch, approximately 6,100 feet would be converted to a buried <br />24" high density polyethylene (HDPE) pipe placed within the alignment of the existing <br />ditch. Reusing the ditch alignment reduces construction impacts along the pipeline as it <br />would follow the existing disturbed prism of the Dillon Ditch. The headgate would be <br />relocated upstream in SLG. The inverted siphon under I-70 would be slip lined with <br />similar flexible pipe to allow for continuous pipeline. Installation of the slip liner would <br />require a work site that would temporarily disturb approximately 0.10 acre of ground on <br />the north edge of I-70 where the Dillon Ditch enters the inverted siphon. The temporary <br />impact site would be re-graded to natural contours and seeded with a native seed mix. An <br />access vault would be constructed on the south edge of I-70 to allow maintenance of the <br />siphon. <br />12 <br />