Oroville–Thermalito Complex
The Oroville–Thermalito Complex is a group of reservoirs, structures, and facilities located in and around the city of Oroville in Butte County, California. The complex serves not only as a regional water conveyance and storage system, but is the headwaters for, and therefore perhaps is the most vital part of, the California Department of Water Resources' State Water Project, the world's largest publicly built and operated water and power development and conveyance system.
Background
The Oroville–Thermalito Complex was designed as an efficient water and power storage and conveyance system. All reservoirs and canals, combined, store about when at max capacity, and generate power from releases made through Hyatt Powerplant and two other generating plants in nearby Thermalito. A special fish barrier dam was built to lead salmon and steelhead, returning to spawn, into the Feather River Fish Hatchery. The California Office of Environmental Health Hazard Assessment has developed a safe eating advisory for fish caught in the Thermalito Forebay and Afterbay based on levels of mercury or PCBs found in local species.Water released from Lake Oroville is used to produce electricity via Hyatt Powerplant, located in the bedrock beneath and inside of the core of Oroville Dam. Water can either enter the Feather River through the one-unit Thermalito Diversion Dam Powerplant and the Diversion Dam's 14 radial spill gates or up to can be diverted into the Thermalito Power Canal.
From there, the water enters the Thermalito Power Canal and flows into Thermalito Forebay. At the end of the forebay, water enters the Thermalito Afterbay by way of the Thermalito Pumping–Generating Plant to produce electricity. The plant can also pump water back into the lake to be reused for power generation at Hyatt Powerplant when needed.
Makeup
Lake Oroville
is the second largest reservoir in California, and stores winter and spring runoff which is released into the Feather River at controlled intervals to meet the Project's needs. It also provides pumped-storage capacity, of flood control storage, recreation, and freshwater releases to control salinity intrusion in the Sacramento-San Joaquin Delta and for fish and wildlife protection. The Lake is perhaps the most important of all the Oroville Complex facilities, being that it serves as the headwater of the entire State Water Project.Lake Oroville has a maximum operating storage of, which, for purposes of scale, is equal to over 1.153 trillion gallons of water. The lake has a water surface area of, a maximum water surface elevation of, and 167 miles of shoreline.
Oroville Dam and spillway
The Oroville Dam is the tallest and largest dam in the United States. Completed in 1968, it stands high with a crest length long. Over 80 million cubic yards of material were needed to build the Oroville Dam. There is enough material to build a two-lane highway around the earth in the Dam. Oroville Dam was named by the California Society of Professional Engineers as one of the seven wonders of engineering in California in 1967.The dam's inner core is a thin layer made of clay material which resists seepage. Gold dredged tailings, sand & gravel left from the early 20th century gold rush dredging operations along the Feather River, make up the remainder of Oroville Dam. Beneath the dam a giant cavern almost as large as the State Capitol Building has been hollowed out to house six power generation units. Coupled with four additional units in the Thermalito Pumping–Generating Plant, they will generate more than 2.8 billion kilowatt-hours of energy annually.
Edward Hyatt Powerplant
Located in rock in the left abutment near the axis of Oroville Dam, the 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 a 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.
The facility was named for Edward Hyatt, who was State Engineer of the Division of Water Resources under the Department of Public Works. The Division was the predecessor to the Department of Water Resources.
Thermalito Diversion Pool
The Thermalito Diversion Pool, in tandem with the Diversion Dam, serves to create a tailwater pool for Hyatt Powerplant, just around the bend to the East, at the base of Oroville Dam. The diversion pool also acts as a forebay when Hyatt Powerplant is pumping water back into Lake Oroville, as well as provides recreation opportunities.Thermalito Diversion Dam
Sitting at the South end of,, the Diversion Pool reservoir, the Thermalito Diversion dam can either divert water west-ward into the Thermalito Power Canal for power generation at Thermalito Pumping–Generating Plant at the tail end of the Thermalito Forebay, or can release flow straight through, south, into the Feather River. The Diversion Dam is 143' feet tall and has a crest length of.Thermalito Diversion Dam Powerplant
The Thermalito Diversion Dam Powerplant is located at the Thermalito Diversion Dam below the left abutment of the dam. The powerplant generates electricity from water released to the Feather River to maintain fish habitat between the diversion dam and Thermalito Afterbay river outlet. It was constructed in 1985 and was completed in 1987. The powerplant has one generating unit with an installed capacity of 3.3 MW, and a maximum flow rate of.Thermalito Power Canal
The Thermalito Power Canal is a east–west oriented concrete lined canal that extends from a headworks structure, which is part of Thermalito Diversion Dam, to the Thermalito Forebay. It conveys water in either direction between Thermalito Diversion Dam and Thermalito Forebay for pumping and power generation at Hyatt Powerplant and Thermalito Pumping–Generating Plant. Construction on the canal began in 1965 and was completed in 1967. The Power Canal has a maximum generating flow of with a maximum pumping flow of.Thermalito Forebay
Thermalito Forebay is an offstream reservoir contained by the Thermalito Forebay Dam on the east and south and by Campbell Hills on the north and west. It is located about four miles west of Oroville. The forebay conveys generating and pumping flows between Thermalito Power Canal and Thermalito Powerplant, provides regulatory storage and surge damping for the Hyatt–Thermalito power complex, and serves as a recreational area. The Thermalito Forebay has a maximum operating storage of, a water surface area of at maximum storage, and a shoreline of 10 miles. Construction on the Forebay began in 1965 and was completed in 1968.Thermalito Pumping–Generating Plant
Thermalito 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 Thermalito Diversion Dam Powerplant and Hyatt 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. The Plant has 4 units: 1 generating unit and 3 pumping–generating units, with an installed capacity of 120 MW, maximum flow rate of.Plant construction began in 1964 and was completed in 1969, operation started prior to completion, in 1968. In October 2011, the plant was renamed the Ronald B. Robie Thermalito Power Plant. On Thanksgiving, November 22, 2012, there was a major fire originating in a plant lower level cable tray that forced immediate shutdown. Completion of repairs and upgrades was expected for late 2018