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CHAPTER III PLAN FORMULATION The Western Area Power Administration indicated to the Bureau of Reclamation that not more than 1,000 MW of peaking power could be mar- keted from this location. Reclamation then investigated powerp1ant sizes for the Campbell-Plateau Creek Alternative ranging from l2S to 1,000 MW, It was determined that the larger the powerp1ant, the higher the benefit-cost ratio. Subsequent capacity calculations and rim sta- bility problems at the Campbell site, however, made it necessary to reduce the maximum size of the Campbell forebay and limit the maximum powerp1ant size to SOO MW or less. This plan was then evaluated with three alternative power plant sizes--12S MW, 2S0 MW, and SOO MW. The Campbell-Plateau Creek Alternative is described below with a SOO-MW pumped-storage powerplant. Following the description of this plan is an economic, environmental, and social comparative analysis of the three powerplant sizes and the no action alternative. A selection of the most feasible powerp1ant size is then made. Campbell-Plateau Creek Alternative Overview of Plan The plan would consist of a fore bay on Campbell Mesa and an after- bay on Plateau Creek just above the McPhee Reservoir maximum water sur- face elevation. The reservoir would be connected with two, lS-foot- diameter penstocks and an underground powerp1ant of SOO MW. The water supply for initial filling of the afterbay and makeup water for seepage and evaporation losses would be obtained from Plateau Creek. The plant would operate with a 9 percent plant factor (approximately 800 hours per year), Power for pumping would be obtained and transmitted through the Colorado-Ute Electric Association's proposed 34S-kV transmission line between the Aspinall and Shiprock substations. Detailed Plan The Campbell forebay would consist of an 8,900-acre-foot reservoir formed by a 6,640-foot-long, l28-foot-high, earthfi11 dam. An emergency spillway would have a capacity of 7,7S0 cfs. Two lS-foot-diameter pen- stocks would be buried beneath the forebay to a point at the edge of Plateau Creek Canyon, where they would take a vertical course through tunneled shafts to a SOO-MW underground powerp1ant at the level of the afterbay. Two 27-foot-diameter tailrace tunnels would convey the water from the powerp1ant a distance of 8S0 feet to the afterbay reservoir. The elevation difference between the two reservoirs would be approxi- mately 1,000 feet. The 14,900-acre-foot afterbay in Plateau Creek would be formed by a 6S0-foot-long, concrete arch dam 230 feet high. The spillway would have a capacity of 40,000 cubic feet per second (cfs). A 34S-kV transmission line, IS,S miles long, would carry power to the Colorado River Storage Project grid. Access roads would be built which would connect to existing Forest Service roads north of the project. 11