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I I I I .. I ,. ., I I I I '1 I I I ., I I 001960 Scoping Document I Williams Fork Hydroelectric Project FERC Project No. 2204 and other agricultural diversion facilities in the Cameo area. These active decree holders ordinarily call out the entire Colorado River, including the Williams Fork River, between September and April. Therefore, because Denver Water holds a junior right, it can only divert from the Williams Fork River during the high flow months, when the senior decrees are satisfied. In order to improve diversions from Denver Water's collection system in the Williams Fork, Fraser and Blue River basins. Denver Water enlarged the ey"isting 6,623 acre-foot reservoir to store a replacement supply of water. This replacement supply would allow Denver Water to continually divert water without injuring senior water decree holders downstream. Construction of the new concrete thin arch dam was started in 1956 and completed in 1959 to a height of 209 feet, with a corresponding capacity of 96,822 acre feet. This enlarged reservoir would store water during the high spring runoff season, typically from about mid-April through mid-July, to be released for replacement primarily in the late summer months. With controlled releases, resulting in a higher quantity of water in the summer, Denver Water could continually divert while ensuring that the senior water rights were satisfied. When planning the Williams Fork Reservoir enlargement, Denver Water determined that generating hydroelectric power at the reservoir could be both practicable and economical. Similar to the situation in the Williams Fork basin, Denver Water's decrees on the Blue River are junior to the Bureau's Green Mountain Reservoir Power Plant. Likewise, Denver Water's ability to divert water would be limited by the streamflow and the Bureau's senior call. Consequently, Denver Water and the Bureau entered into an agreement to enable Denver Water to continue diverting water out of priority at its other facilities, so long as Denver Water provided the Bureau with replacement energy and replacement water. This energy agreement and contract allows Denver Water to either replace lost energy or replace the value of the lost energy. Therefore, the enlarged Williams Fork Reservoir allows Denver Water to more fully use its junior water decrees on the Blue River. Figure 2.2 shows the location of the Green Mountain Reservoir Power Plant, the Shoshone Power Plant downstream on the Colorado River. and other water conveyance features of the Upper Colorado River basin. From the Continental Divide the flow of water is generally from east to west except for two trans-basin diversions, the Roberts and Adams Tunnels, which convey water to the eastern slope of Colorado for Denver Water and the Northern Colorado Water Conservancy District, respectively. The FERC granted Denver Water the original license for the Project on January I, 1957. Initially, the entire output of hydroelectric power generated at the Williams Fork Dam was used to repay the Bureau for loss of power production at Green Mountain Reservoir, caused by Denver Water's out of priority diversions on the Blue River. After a series of wet years, Denver Water's energy production by the Project exceeded the amount owed to the Bureau. In ]990, Denver Water began selling the excess power generated by the Project. Denver Water currently uses "banked" power generated hy the Project to compensate the Bureau for power interference. Denver Water sells all of the current power production of the Project to Tri-State Generation and Transmission Association, Inc. Denver Water's agreement with the USFWS, which addressed minimum stream flows below the Project, was incorporated into the existing Project license. The minimum flow requirements 5