The Department of Water Resources (DWR) has published a summary report on the Oroville Dam Safety Comprehensive Needs Assessment (CNA), initiated in January 2018 to identify dam safety and operational needs following reconstruction of the spillways damaged in February 2017.
The Oroville-Thermalito Complex is a storage and pumping operation on the Feather River. The facilities include three power plants (Hyatt Powerplant, Thermalito Diversion Dam Powerplant, and Thermalito Pumping-Generating Plant, two of which can either pump water or generate power), the State Water Project's largest reservoir (Lake Oroville), a forebay and afterbay, a fish hatchery, and a visitors center.
As water leaves this region, it flows down Feather River and Sacramento River channels to the Sacramento-San Joaquin Delta.
Oroville Dam and Lake Oroville lie in the foothills on the western slope of the Sierra Nevada and are one mile downstream of the junction of the Feather River’s major tributaries. The lake stores winter and spring runoff that is released into the Feather River to meet the project’s needs. It also provides pumped-storage capacity, 750,000 acre-feet of flood control storage, recreation, and freshwater releases to control salinity intrusion in the Sacramento-San Joaquin Delta and for fish and wildlife enhancement.
Oroville Dam is the tallest earth-fill dam, at 770-feet, in the United States. Construction first began in 1957 on relocating what is now Highway 70 and the Western Pacific Railroad. Work on the dam site began in 1961. The embankment was topped out in 1967.
Thermalito Forebay Dam and Forebay
Constructed between 1965 and 1968, Thermalito Forebay is an offstream reservoir contained by Thermalito Forebay Dam on the south and east and by Campbell Hills on the north and west. It is located about four miles west of the city of Oroville. The forebay conveys generating and pumping flows between Thermalito Power Canal and Thermalito Pumping-Generating Plant, provides regulatory storage and surge damping for the Hyatt-Thermalito power complex, and serves as a recreational site.
Thermalito Afterbay Dam & Afterbay
Located about six miles southwest of the city of Oroville, Thermalito Afterbay is an offstream reservoir. The Afterbay provides storage for the water required by the pumpback operation to Lake Oroville, helps regulate the power system, produces controlled flow in the Feather River downstream from the Oroville-Thermalito facilities and provides recreation. Thermalito Afterbay Dam has the longest crest in the SWP system. The facility was constructed from 1965 to 1968.
Thermalito Pumping-Generating Plant
Located about four miles west of the city of Oroville in Butte County, Thermalto Pumping-Generating Plant is a principal feature of the Oroville-Thermalito pumped-storage power complex. A pumping-generating plant, the facility is operated in tandem with Hyatt Powerplant and Thermalito Diversion Dam Powerplant to produce power. Water released for power in excess of local and downstream requirements is conserved by pumpback operation during off-peak hours through both power plants into Lake Oroville. The water is subsequently released for power generation during periods of peak power demand. Construction on the plant began in 1964 and was completed in 1969, with operations starting in 1968.
Ronald B. Robie Thermalito Pumping-Generating Plant
Ronald B. Robie Thermalito Powerplant is a principal feature of the Oroville-Thermalito pumped storage power complex. The facility is operated in tandem with Hyatt Powerplant and Thermalito Diversion Dam Powerplant to produce power. Water released for power in excess of local and downstream requirements is conserved by pumpback operation during off-peak hours through both powerplants into Lake Oroville to be subsequently released for power generation during periods of peak power demand. Construction on the plant began in 1964 and was completed in 1969, with operations starting in 1968.
Thermalito Diversion Dam Powerplant
Thermalito Diversion Dam Powerplant is located at Thermalito Diversion Dam below the left abutment of the dam. It was constructed between 1985 and 1987 and generates electricity from water released to the Feather River to maintain fish habitat between the Diversion Dam and Thermalito Afterbay river outlet. The plant facilities consist of intake headworks, inlet pipes, a single penstock, an underground powerhouse with one turbine unit, a tailrace channel and outlet works.
Edward Hyatt Powerplant
Located in the rock in the left abutment near the axis of Oroville Dam, Edward Hyatt Powerplant is an underground, hydroelectric, pumping-generating facility. Construction of the plant began in 1964 and was completed in 1967. Hyatt Powerplant maximizes power production through pumped storage operation where water, released for power in excess of local and downstream requirements, is returned to storage in Lake Oroville during off-peak periods and is used for generation during peak power demands. Water from the lake is conveyed to the units through penstocks and branch lines. After passing through the units, water is discharged through the draft tubes to one free surface and one full-flow tailrace tunnel.
Feather River Fish Hatchery
Constructed between 1966 and 1967, the Feather River Fish Hatchery was built to compensate for spawning ground lost to returning salmon and steelhead trout with the construction of Oroville Dam. The first salmon and steelhead entered the hatchery in September 1967. Today, the facility accommodates an average 8,000 fish.
Salmon and steelhead raised at the hatchery are transported in oxygenerated, temperature-controlled tanks and released in Oroville Lake, in the Feather and Sacramento rivers, or in the Delta near the San Francisco Bay area. These fish account for an estimated 20 percent of the ocean sport and commercial catch in the Pacific Ocean.
The Department of Water Resources (DWR) and California State Parks announced Lake Oroville State Recreation Area’s Spillway Boat Ramp area will remain open for the Veterans Day holiday, November 11, 2019 from 5 a.m. to 11 p.m.
Butte County and DWR announced today that they have settled a lawsuit filed by Butte County for roadway damage resulting from the Oroville Spillways Incident in February 2017.