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<br />SUMMARY (Continued) <br /> <br />found the powerp1ant size should be limited to 500 MW because of capac- <br />ity limitations and geologic stability problems at the Campbell forebay <br />site, <br /> <br />The facility would consist of an 8,900-acre-foot forebay on Campbell <br />Mesa formed by a 6,640-foot-10ng, l28-foot-high, earthfil1 dam, An <br />emergency spillway would have a capacity of 7,7S0 cubic feet per second <br />(ds). Two lS-foot-diameter buried penstocks would convey the water <br />from the lower level of the forebay to a point at the edge of Plateau <br />Creek Canyon, where the penstocks would drop vertically approximately <br />1,000 feet through tunneled shafts to an underground powerp1ant at the <br />level of the afterbay, The powerp1ant would consist of two 2S0-MW pump <br />turbines. Two 27-foot-diameter tailrace tunnels would convey the water <br />from the powerplant a distance of approximately 850 feet to the afterbay <br />reservoir. The 14, 900-acre-foot afterbay in Plateau Creek would be <br />formed by a 650-foot-long concrete arch dam with a height of 230 feet. <br />The spillway would have a capacity of 40,000 cfs. A 345-ki10volt (kV) <br />transmission line, 15. S miles long, would carry power to the Co 10rado <br />River Storage Project (CRSP) grid. Estimated capital costs for the pro- <br />posed project would be $463,8 million, including $128,4 million interest <br />during construction. Capital costs per kilowatt year are estimated at <br />$928,000. The benefit-cost ratio is estimated to be 1.4:1.0. <br /> <br />Social and economic studies indicated there could be a significant <br />impact to the area with the 500-MW plan because of the size of the con- <br />struction work force and its effects on housing, social services, and <br />the rural culture of the area, Environmental impacts would primarily be <br />the loss of some grazing land and wildlife habitat and a potentially <br />adverse effect on big game from increased human access. <br /> <br />Public contribution to the planning process was significant, lead- <br />ing to the conclusion that the McPhee Reservoir afterbay alternatives <br />were unacceptable and identifying the importance of potential effects on <br />the local economy and social system. <br /> <br />S-2 <br />