Official estimate of total project cost, Colorado River storage project, region 4-Continued GRAY CANYON UNIT Official estimate of total project cost, Colorado River storage project, region 4-Continued SPLIT MOUNTAIN UNIT Class and 01 01.01 CONSTRUCTION SCHEDULE The project units are scheduled for construction over an extended period. Each unit would be brought into operation as required to meet the needs for water-consuming uses and electric energy. In scheduling construction to make certain that project units would be in operation when needed, consideration was given to cyclic shifts in runoff conditions and to the advantages that would be gained by initially filling the reservoirs while unused apportioned water is available. The Whitewater, Echo Park, Glen Canyon, Navaho, and Flaming Gorge units are scheduled for initial construction. Details of the construction schedule are shown by the bar diagram following. The diagram also shows the years in which the generating units of the project powerplants are expected to be in operation. ALTERNATIVE FEATURES Investigations to date indicate that the system of reservoirs included in the project plan would economically obtain the greatest possible water yield and power output with minimum loss of water from evaporation. Several alternative sites for power and storage development, including the Dewey on the Colorado River, the Desolation on the Green River, and the Chinle (Bluff) on the San Juan River, have been studied and excluded from the project plan because of certain physical disadvantages. Additional attention, however, should be given other storage and power developments in the near future to assure the maximum utilization of the basin's resources. The Desolation Dam site is located on the Green River about 50 miles upstream from the town of Green River, Utah, and within the basin of the potential Gray Canyon Reservoir. A dam rising 385 feet above the present stream bed at elevation 4,400 feet would impound a reservoir with a total storage capacity of more than 8 million acrefeet. The reservoir would have a maximum water surface area of 135,000 acres and a mean area of nearly 100,000 acres. Development of the reservoir would limit the Gray Canyon Dam to a height of 250 feet above stream bed and would limit the Gray Canyon Reservoir to a capacity of less than 500,000 acre-feet. The combination of Desolation Reservoir and a reduced Gray Canyon Reservoir, as compared to the Gray Canyon development included in the project plan, would increase active storage by about 5 million acre-feet and would increase average firm energy generation by nearly 380 million kilowatthours annually. The combination, however, would also result in average annual net evaporation losses of about 330,000 acre-feet annually, about 4 times the losses that would be realized at the Echo Park site for a comparable amount of active storage. The Dewey Dam site is located on the Colorado River about 3 miles downstream from the river's confluence with the Dolores River. Here a dam 335 feet high would create a reservoir with a total storage capacity of more than 8 million acre-feet. The reservoir would have a maximum water-surface elevation of 4,410 feet and a maximum water-surface area of about 75,000 acres. A 175,000-kilowatt powerplant at the site could generate nearly a billion kilowatt-hours of firm energy annually under initial flow conditions and nearly threefourths of a billion kilowatt-hours annually under ultimate flow conditions. Over a 200-year period the reservoir would receive nearly |