Oroville Dam - History

History

In 1935, work began on the Central Valley Project (CVP), a federal water project that would develop the Sacramento and San Joaquin river systems for irrigation of the highly fertile Central Valley. However, after the end of World War II in 1945, the state experienced an economic boom that led to rapid urban and commercial growth in the central and southern portions of the state, and it became clear that California's economy could not depend solely on a state water system geared primarily towards agriculture. A new study of California's water supplies by the Division of Water Resources (now California Department of Water Resources, DWR) was carried out under an act of the California State Legislature in 1945.

In 1951, California State Engineer A.D. Edmonston proposed the Feather River Project, the direct predecessor to the SWP, which included a major dam on the Feather River at Oroville, and aqueducts and pumping plants to transfer stored water to destinations in central and southern California. The proposed project was strongly opposed by voters in Northern California and parts of Southern California that received water from the Colorado River, but was supported by other Southern Californians and San Joaquin Valley farmers. However, major flooding in the 1950s prompted the 1957 passage of an emergency flood-control bill that provided sufficient funding for construction for a dam at Oroville, whether it would be part of the SWP or not. Groundbreaking on the dam site occurred in May 1957 with the relocation of the Western Pacific Railroad tracks that ran through the Feather River canyon. The Burns-Porter Act, which authorized the SWP, was not passed until November 8, 1960 – and only by a slim margin. Engineer Donald Thayer of the DWR was commissioned to design and head construction of Oroville Dam, and the primary work contract was awarded to Oro Dam Constructors Inc., a joint venture led by Oman Construction Co.

Two concrete-lined diversion tunnels, each 4,400 feet (1,300 m) long and 35 feet (11 m) in diameter, were excavated to channel the Feather River around the dam site. One of the tunnels was located at river level and would carry normal water flows, while the second one would only be used during floods. In May 1963, workers poured the last of 252,000 cubic yards (193,000 m3) of concrete that comprised the 128-foot (39 m) high cofferdam, which would protect the construction site from floods. This structure would later serve as an impervious core for the completed dam. With the cofferdam in place, an 11-mile (18 km) rail line was constructed to move earth and rock to the dam site. An average of 120 train cars ran along the line each hour, transporting fill that was mainly excavated from enormous piles of hydraulic mining debris that were washed down by the Feather River after the California Gold Rush.

On December 22, 1964, disaster nearly struck when the Feather River, after days of heavy rain, reached a peak flow of 250,000 cubic feet per second (7,100 m3/s) above the Oroville Dam site. The water rose behind the partially completed embankment dam and nearly over topped it, while a maximum of 157,000 cubic feet per second (4,400 m3/s) poured from the diversion tunnels. This Christmas flood of 1964 was one of the most disastrous floods on record in Northern California, but the incomplete dam was able to reduce the peak flow of the Feather River by nearly 40 percent, averting massive amounts of damage to the area. Ten months later, four men died in a tragic accident on the construction rail line. On October 7, 1965, two 40-car work trains, one fully loaded and the other empty, collided head-on at a tunnel entrance, igniting 10,000 US gallons (38,000 l) of diesel fuel, completely destroying the two locomotives. The burning fuel from the collision started a forest fire that burned 100 acres (40 ha) before it could be extinguished. The crash delayed construction of the Dam by a week while the train wreckage was being cleaned up.

Oroville Dam was designed to withstand the strongest possible earthquake for the region, and was fitted with hundreds of instruments that serve to measure water pressure and settlement of the earth fill used in its construction, earning it the nickname "the dam that talks back". (It is believed that a M_W 5.7 earthquake in the Oroville area in 1975 was caused by induced seismicity from the weight of the Oroville Dam and reservoir itself on a local fault line.) The embankment was finally topped out on October 6, 1967, with the last of 155 million tons (140.6 million t) of material that took over 40,000 train trips to transport. On May 4, 1968 Oroville Dam was officially dedicated by the state of California. Among the notable figures present were Chief Justice (formerly California governor) Earl Warren, Senator Thomas Kuchel, and California Representative Harold T. "Bizz" Johnson. The dedication was accompanied by a week of festivities in nearby Oroville, attended by nearly 50,000 people.