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The Upper North Fork Feather River Project is a hydroelectric scheme in the Sierra Nevada of California, within Lassen and Plumas Counties. The project consists of three dams, five power plants, and multiple conduits and tunnels in the headwaters of the North Fork Feather River, a major tributary of the Feather—Sacramento River systems. The total installed capacity is 362.3 megawatts (MW), producing an annual average of 1,171.9 gigawatt hours (GWh). The project is also contracted for the delivery of irrigation water between March 31 and October 31 of each year. The project is owned and operated by Pacific Gas and Electric. The project is one of several on the North Fork and its tributaries, forming a hydroelectric system so extensive it has been dubbed the "Stairway of Power".〔 ==Background== The project was conceived in the early 1900s under the Great Western Power Company to provide hydroelectricity and water storage for irrigation in the Sacramento Valley. In 1908, the Big Bend or Las Plumas powerhouse was completed on the North Fork southeast of Paradise, generating 40 MW (later uprated to 70 MW) of hydroelectricity, which was sent as far away as Oakland, away. The power station replaced an earlier 1880 plant built by the Big Bend Tunnel and Mining Company for gold mining operations in the area which ultimately were unprofitable. In 1910, the Big Bend Dam, first permanent dam on the Feather River, was completed to increase the hydraulic head available to the powerhouse. During the early years of the project, few roads existed in this rugged section of the Sierra, so construction supplies were delivered via the Western Pacific Railroad, which was also under construction at the time. At its completion, the Big Bend power plant had the largest turbines, transformers and penstocks of any hydroelectric plant in the world. However, year-round generation at the plant was an impossibility due to the seasonal flow fluctuations of the river. A large storage reservoir was first proposed to be built at Big Meadows, about upstream from Big Bend, by engineer Julius M. Howells. Great Western Power Company began to buy out land in the valley for the future reservoir, but encountered bitter local opposition. The small town of Prattville in Big Meadows was burned to the ground July 4,1909; arson was suspected, but has never been proven. Construction of the Canyon Dam to impound Lake Almanor at Big Meadows began in 1910. A rough one-way road was blazed from Greenville in the same year to transport workers and construction materials to the site, where a company town called Canyondam was established.〔 Although originally conceived as a multiple-arch dam by its designers John S. Eastwood and H.H. Sinclair, concerns over the safety of this relatively new construction technique led to a change in the design. In March 1913, with over 40 percent of the dam completed, a state commission declared the structure unsafe. The partly completed dam was dynamited and a new earthfill structure, containing over of material, was built.〔 The reservoir's name is a combination of the names of the daughters of Guy C. Earl, the vice president of Great Western.〔 The construction of this reservoir – which at the time, had a capacity of – ensured a steady water supply for the powerhouse and for irrigation during the summer. A Great Western Power Company subsidiary, the Western Canal Company, would manage the distribution of water to farmers on the lower Feather River near Oroville in Butte County.〔 Between 1919 and 1921, the first Caribou Powerhouse was built on the tributary Butt Creek, and a tunnel was excavated from Lake Almanor to the creek to provide water for the powerhouse. A high dam on Butt Creek was built in 1924 to increase the total water storage and power capacity.〔 Between 1925–1927, the Canyon Dam was expanded, increasing Lake Almanor's capacity to .〔 In 1930, Pacific Gas and Electric (PG&E) acquired the Great Western Power Company and the Upper North Fork Project. However, the Western Canal Company (now known as the Western Canal Water District) continued to hold water rights to Lake Almanor and other PG&E reservoirs along the Feather River, ensuring the continuation of irrigation deliveries.〔 The third project dam, Belden Forebay, was built on the North Fork in 1958 to serve as an afterbay for the Caribou powerplant. The Caribou No. 2 powerplant was also built in 1958 to increase the total project generating capacity. In 1962, the Canyon Dam was raised again, enlarging the lake to its present capacity of .〔 Six years later, in 1968, the giant Oroville Dam was completed on the Feather River as part of the California State Water Project, forming Lake Oroville which flooded out most of the lower North Fork, including Big Bend Powerhouse and the Big Bend Dam. PG&E completed the Belden Powerhouse in 1969 to replace the lost capacity.〔 The last component of the project, Oak Flat Powerhouse, was built in 1985 to generate power from fishery releases, as federal law requires a minimum flow to be maintained in the otherwise dewatered river stretches between the dams. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Upper North Fork Feather River Project」の詳細全文を読む スポンサード リンク
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