History
Folsom Dam, Lake and Powerplant
Originally authorized in 1944 as a 355,000 acre-feet flood control unit, Folsom Dam was reauthorized in 1949 as a 1,000,000 acre-feet multiple-purpose facility. The U.S. Army Corps of Engineers constructed Folsom Dam and transferred it to Reclamation for coordinated operation as an integral part of the Central Valley Project. Construction of the dam began in October 1948 and was completed in May 1956. Water was first stored in February 1955.
Recreation facilities at the 18,000-acre park surrounding the lake-area, which is administered by the California Department of Parks and Recreation, include 50 miles of trails for hiking and horseback riding, picnicking, fishing, swimming, boating, water skiing and camping.
Reclamation constructed and operates Folsom Powerplant at the foot of Folsom Dam on the north side of the river. Concrete work at Folsom Powerplant began Oct. 24, 1952, with placement of concrete in the gravity training wall between the powerplant site and spillway stilling basin. Installation of the three, 15.5-foot diameter penstock tubes that supply water to the turbines at the Folsom Powerplant began Oct. 5, 1953.
Nimbus Dam and Powerplant
Nimbus Dam is on the American River in Sacramento County, California, 7 miles downstream from Folsom Dam. It reregulates the releases for power made through the Folsom Powerplant. Nimbus Dam is a concrete gravity dam 1,093 feet long and 87 feet high. Eighteen radial gates, each 40-feet by 24-feet, control the flows. The total volume of material used in the dam is 121,100 cubic yards. Reclamation operates the dam. Nimbus Dam and Powerplant was completed and accepted by the government in July 1955.
Lake Natoma
Nimbus Dam forms Lake Natoma, with a capacity of 8,760 acre-feet and a surface area of 540 acres. Recreation facilities administered by the California Department of Parks and Recreation provide boating, picnicking, swimming, fishing and camping.
Nimbus Powerplant, constructed and operated by Reclamation, is located on the right abutment of Nimbus Dam, on the north side of the river.
Sly Park Unit
Work on the Sly Park Unit began Nov. 20, 1952, with preparations for the Camp Creek Diversion Tunnel to carry water from Camp Creek to Sly Park. Work on the tunnel was completed by the end of October 1953.
Reclamation completed the project and transferred it to the El Dorado irrigation District (EID) for operation and maintenance in mid-1955. The Sly Park Recreation Area, operated by EID in cooperation with Reclamation, offers camping, boating, swimming, picnicking and fishing.
Sly Park Dam, on Sly Park Creek, is a zoned earthfill structure, 190 feet high, with a crest length of 760 feet. It has an auxiliary earthfill dam, 130 feet high, with a crest length of 600 feet. The total volume of the main dam and dike is 1,130,000 cubic yards.
Jenkinson Lake, formed by Sly Park Dam, has a storage capacity of 41,000 acre-feet with a surface area of 650 acres. Municipal and industrial water is furnished to the city of Placerville and nearby small communities, and irrigation water is furnished to EID.
The Camino Conduit, with a capacity of 125 cubic feet per second, extends 38,016 feet west from Sly Park Dam to the community of Camino, California, to deliver supplemental water to EID for irrigation and municipal purposes. The Camino Tunnel is 2,289 feet long with a diameter of 7 feet. It is a steel reinforced, concrete lined structure with a capacity of 125 cubic feet per second.
Camp Creek Diversion Dam is a concrete overflow weir, 20 feet high and 119 feet long. The total volume of concrete in the dam is 2,000 cubic yards, and the diversion capacity is 500 cfs. Camp Creek Dam diverts a portion of the flow of Camp Creek through the Camp Creek Tunnel, a 2,845 foot long, concrete lined tunnel with a diameter of 7 feet and a capacity of 500 cfs, into the upper part of Jenkinson Lake. Work on the dam began Feb. 25, 1953, and was completed Nov. 29, 1953. Construction has been completed on the water treatment facilities and a distribution system for irrigation and municipal purposes in western El Dorado County. These facilities were built by Reclamation and will be operated, maintained and paid for by EID. The distribution system consists of three pipelines, the El Dorado Main, Pleasant Oak Main and El Dorado Main No. 2. These pipelines extend 46.3 miles, from the vicinity of Sly Park Dam to the community of Placerville.
Construction
Construction of Folsom and Nimbus Dams blocked access to natural spawning grounds of salmon and steelhead trout. To compensate for the loss of these spawning areas, Reclamation constructed the Nimbus Fish Hatchery about a quarter of a mile downstream from Nimbus Dam.
The hatchery is on the left bank of the river, about 0.3 mile below the dam. It is operated by the State of California with Reclamation funds. All machinery, processing equipment and refrigeration systems were installed, finished and accepted Oct. 17, 1955.
The Nimbus Fish Hatchery has a capacity of 30,000,000 eggs. Water for the hatchery is supplied through a 1,415 foot long, 42-inch diameter concrete pipe that runs from the left abutment of Nimbus Dam.
Reclamation also constructed the Sly Park Unit, including Sly Park Dam and Jenkinson Lake, Camp Creek Diversion Dam and the Camino Conduit, and Camino and Camp Creek Tunnels. This provides municipal and industrial water for the nearby community of Placerville, and irrigation water for the El Dorado Irrigation District. Camp Creek Diversion Dam diverts some flow from Camp Creek to Jenkinson Lake via Camp Creek Tunnel. The Camino Tunnel and Conduit delivers water from Jenkinson Lake to EID for Irrigation and municipal use.
