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J~2~.99 DESCRIPTION OF ALTERNATIVES another White River side canyon. could provide up to 65.000 acre-feet of water storage. This alternative would be similar to the Hell's Hole Canyon Dam. with some site specific differences. Preliminary investiga- tions into this reservoir site indicated water leakage through the Bird's Nest Aquifer was possible. and the site was located over a major portion of Utah Oil Shale Tract Ub. Therefore, due to uncertainties regarding water-holding capabilities and the potential loss of oil shale mining capability, Evacuation Creek was not considered a viable alternative. ALTERNATIVE 1 : WHITE RIVER DAM AND RESERVOIR The White River Dam Project components would include: 1. An earth and rockfill dam and reservoir; 2, A hydroelectric power plant; 3. A power transmission system; 4, Recreational facilities; and 5. Access roads, Since the proposed White River Dam was described in the Draft EIS. the Utah Division of Water Resources continues to refine the engineering details. Conse- quently. some final dimensions and project details may be slightly different than presented here. BLM has reviewed the changes to date and has found that they do not affect the environmental anaiysis previously contained in the Draft EIS, except as follows: 1. Uintah County. Utah Department of Trans- portation, and White River Shale Project are pro- ceeding with plans to upgrade and realign the ex- isting Utah State Highway 45 in the vicinity of Igna- tio, This construction would eliminate the need for the new bridge once considered as a part of the White River Dam Project. since the design of the current bridge would be sufficient to accommodate the reservoir. A separate environmental assess- ment for upgrading and realigning the road and bridge was prepared by the BLM Vernal District in 1981, Consequently, the alternative upstream bridge crossing analyzed in the Draft EIS has been deleted in this Final EIS, 2, The proposed hydroelectric power plant was described in the Draft EIS at a 5- to 8-megawatt (MW) size, A 15-MW power plant, consisting of three 5-MW units Is now proposed. Simulated op- eration studies have been reviewed for the two power plant sizes and the differences in operational effects were found to be minor. No difference in acreage is anticipated in the area occupied by the power plant. In general. the 15-MW power plant would use water on an as-available basis. which would otherwise be spilled with a 8-MW power plant; therefore. reservoir fluctuations and down- stream flows would be essentially the same as analyzed in the Draft EIS. The power plant would generate an estimated 31.4 million kilowatt hours (KWH) on an average annual basis. It would be constructed and operated by the Utah Division of Water Resources or a private electric utility com- pany. or constructed by the Utah Division of Water Resources but operated by a private utility com- pany. The Rural Electrification Administration (REA) is participating with the BLM as a cooperating agency and would approve loan guarantee commitments by electrical utility companies for constructing hydroelec- tric facilities at the White River Dam and 0.5 mile of 138-kilovolt (kV) transmission line between the dam and other existing substations. REA would also be involved in the approval of a contract between private utility companies and the Utah Division of Water Re- sources to purchase electricity produced by the proj- ect. A contract between private utility companies and the Utah Division of Water Resources to operate the hydroelectric facility at the dam would also require REA approval. Location and General Description The proposed dam would be located in eastern Utah about 40 miles (64 km) southeast of Vernal, Utah. in Section 17, Township 10 South, Range 24 East (Fig- ure 2-1). The dam would be a 136-foot-high (41 m) zoned earth and rockfill structure as shown by the typical dam cross section in Figure 2-3, An outlet works. service spillway, auxiliary spillway. and a hydroelectric power plant would be constructed at the dam site, at the approximate locations shown on the general layout plan in Figure 2-4. Figure 2-5 is a visual simulation of the proposed dam and reservoir. Embankment and Foundation The dam embankment would consist of an inner core constructed of impervious materials. an outer shell from sand and gravel. and a rockfill (Figure 2-3). Some select materials for internal drains. filter mate- rial, and transition zones could also be required, A cutoff trench extending to bedrock would be required to prevent excessive seepage through the sand and gravel deposits that presently overlay much of the dam site. This cut-off trench would extend the full length of the dam. Sand-cement grout would be used to seal cracks in the bedrock if thy were found to exist. Riprap (large boulders. 1 to 3 feet in diameter, 0.3 to 0.9 m) would be placed on the upstream slope to prevent damage from wave action. Reservoir The proposed White River Dam Project would cre- 17