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76-780: Oroville Dam is an earthfill embankment dam on the Feather River east of the city of Oroville, California , in the Sierra Nevada foothills east of the Sacramento Valley . At 770 feet (235 m) high, it is the tallest dam in the U.S. and serves mainly for water supply, hydroelectricity generation, and flood control. The dam impounds Lake Oroville , the second-largest reservoir in California, capable of storing more than 3.5 million acre-feet (1.1 × 10 ^  US gal; 4.3 × 10 m). Built by

152-496: A fish ladder to the hatchery, which is located on the north bank of the Feather River. The hatchery produces 10 million salmon smolt , along with 450,000 trout smolt, to stock in the river each year. The salmon smolt are released in two runs, with 20% for the spring run and 80% for the fall run. This facility has been successful enough that concern exists that salmon of hatchery stock are outcompeting remaining wild salmon in

228-557: A concrete secant cutoff wall for the emergency spillway. The cost estimate at this point is over $ 500 million. In October 2017, hairline cracks were found in the rebuilt spillway. Things that added to the cost included relocating power lines, dredging the river downstream of the dam, as well as the discovery that the bedrock under the spillway was weak, necessitating deeper excavations and more concrete. The DWR commissioned an independent board of consultants (BOC) to review and comment on repairs to Oroville Dam. Memoranda (reports) prepared by

304-418: A dam and the filling of the reservoir behind it places a new weight on the floor and sides of a valley. The stress of the water increases linearly with its depth. Water also pushes against the upstream face of the dam, a nonrigid structure that under stress behaves semiplastically, and causes greater need for adjustment (flexibility) near the base of the dam than at shallower water levels. Thus the stress level of

380-413: A failure, known as 'loss of crest control'." FERC water agencies responsible for the cost of the upgrades said this was unnecessary and that concerns were overblown. In 2006, a senior civil engineer sent a memorandum to his managers stating, "The emergency spillway meets FERC's engineering guidelines for an emergency spillway", and "The guidelines specify that during a rare flood event, it is acceptable for

456-700: A main line north from the Feather River Canyon to the Great Northern Railway in northern California. This route, today part of BNSF's Gateway Subdivision , joined the Oakland ;– Salt Lake City main line at the Keddie Wye , a unique combination of two steel trestles and a tunnel forming a triangle of intersecting track . In 1935, the railroad went bankrupt because of decreased freight and passenger traffic caused by

532-594: A motion with the Federal Energy Regulatory Commission (FERC) urging federal officials to require that the dam's emergency spillway be armored with concrete, rather than remain as an earthen spillway, as it did not meet modern safety standards. "In the event of extreme rain and flooding, fast-rising water would overwhelm the main concrete spillway, then flow down the emergency spillway, and that could cause heavy erosion that would create flooding for communities downstream, but also could cause

608-434: A simple embankment of well-compacted earth. A homogeneous rolled-earth dam is entirely constructed of one type of material but may contain a drain layer to collect seep water. A zoned-earth dam has distinct parts or zones of dissimilar material, typically a shell of locally plentiful material with a watertight clay core. Modern zoned-earth embankments employ filter and drain zones to collect and remove seep water and preserve

684-404: A small sustained overtopping flow can remove thousands of tons of overburden soil from the mass of the dam within hours. The removal of this mass unbalances the forces that stabilize the dam against its reservoir as the mass of water still impounded behind the dam presses against the lightened mass of the embankment, made lighter by surface erosion. As the mass of the dam erodes, the force exerted by

760-686: A thick suspension of earth, rocks and water. Therefore, safety requirements for the spillway are high, and require it to be capable of containing a maximum flood stage. It is common for its specifications to be written such that it can contain at least a one-hundred-year flood. A number of embankment dam overtopping protection systems were developed in the early 21st century. These techniques include concrete overtopping protection systems, timber cribs , sheet-piles , riprap and gabions , Reinforced Earth , minimum energy loss weirs , embankment overflow stepped spillways , and precast concrete block protection systems. All dams are prone to seepage underneath

836-461: A third-party expert to improve the safety of the river valve outlet system (RVOS) and make it operational again. In 2014, DWR embarked on an accelerated refurbishment program to respond to concerns about operational needs during the ongoing drought. The system was mostly refurbished and was used during 2014 and 2015 to meet Endangered Species Act temperature requirements for the Feather River. Some additional refurbishments were being made to portions of

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912-406: Is a good choice for sites with wide valleys. They can be built on hard rock or softer soils. For a rock-fill dam, rock-fill is blasted using explosives to break the rock. Additionally, the rock pieces may need to be crushed into smaller grades to get the right range of size for use in an embankment dam. Earth-fill dams, also called earthen dams, rolled-earth dams or earth dams, are constructed as

988-630: Is a large dam on the Indus River in Pakistan , about 50 km (31 mi) northwest of Islamabad . Its height of 485 ft (148 m) above the river bed and 95 sq mi (250 km ) reservoir make it the largest earth-filled dam in the world. The principal element of the project is an embankment 9,000 feet (2,700 m) long with a maximum height of 465 feet (142 m). The dam used approximately 200 million cubic yards (152.8 million cu. meters) of fill, which makes it one of

1064-518: Is available. The pump-generators at Hyatt can lift up to 5,610 cubic feet per second (159 m/s) into Lake Oroville (with a net consumption of 519 MW), while the six turbines combined use a flow of 16,950 cu ft/s (480 m/s) at maximum generation. Since 1969, the Hyatt plant has worked in tandem with an extensive pumped-storage operation comprising two offstream reservoirs west of Oroville. These two facilities are collectively known as

1140-437: Is released. During the winter and early spring, Lake Oroville is required to have at least 750,000 acre⋅ft (240 billion US gal; 930 billion L), or a fifth of the reservoir's storage capacity, available for flood control. The dam is operated to maintain an objective flood-control release of 150,000 cubic feet per second (4,200 m/s), which may be further reduced during large storms when flows below

1216-579: The California Department of Water Resources , Oroville Dam is one of the key features of the California State Water Project (SWP), one of two major projects passed that set up California's statewide water system . Construction was initiated in 1961, and despite numerous difficulties encountered during its construction, including multiple floods and a major train wreck on the rail line used to transport materials to

1292-647: The Great Depression and had to be reorganized. Western Pacific (WP) operated the California Zephyr passenger train with the Denver and Rio Grande Western Railroad and the Chicago, Burlington and Quincy Railroad . The WP handled the "Silver Lady" from Oakland, California, to Salt Lake City, Utah from 1949 to 1970. The Western Pacific owned several connecting short-line railroads . The largest

1368-777: The Oroville–Thermalito Complex . Water is diverted into the upper Thermalito reservoir (Thermalito Forebay) via the Thermalito Diversion Dam on the Feather River. During periods of off-peak power use, surplus energy generated at Hyatt is used to lift water from Thermalito's lower reservoir (the Thermalito Afterbay) to the forebay, which releases water back into the afterbay to generate up to 114 MW of power at times of high demand. The Hyatt and Thermalito plants produce an average of 2,200 gigawatt hours (GWh) of electricity each year, about half of

1444-537: The anadromous migrations of Chinook salmon and steelhead trout in the Feather River. In 1967, in an effort to compensate for lost habitat, the DWR and the California Department of Fish and Game completed the Feather River Fish Hatchery. The Fish Barrier Dam, built in 1962, intercepts salmon and trout before they reach the base of the impassable Thermalito Diversion Dam and forces them to swim up

1520-450: The BOC are posted at the DWR web site. The independent forensic team (IFT) was selected to determine the cause of the spillways incident, including effects of operations, management, structural design and geological conditions. According to its 2017–18 operations plan, the DWR maintained Lake Oroville at a lower-than-normal level to reduce the possibility that the spillway would have to be used

1596-737: 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

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1672-479: The Feather River system. Embankment dam Embankment dams come in two types: the earth-filled dam (also called an earthen dam or terrain dam ) made of compacted earth, and the rock-filled dam . A cross-section of an embankment dam shows a shape like a bank, or hill. Most have a central section or core composed of an impermeable material to stop water from seeping through the dam. The core can be of clay, concrete, or asphalt concrete . This type of dam

1748-609: The Feather's confluence with the Yuba River exceed 300,000 cubic feet per second (8,500 m/s). In the particularly devastating flood of 1997, inflows to the reservoir hit more than 331,000 cubic feet per second (9,400 m/s), but dam operators managed to limit the outflow to 160,000 cubic feet per second (4,500 m/s), sparing large regions of the Sacramento Valley from flooding. Oroville Dam completely blocks

1824-486: The Oroville Dam has affected riparian habitat. Multiple attempts at trying to counter the dam's impacts on fish migration have included the construction of a salmon / steelhead fish hatchery on the river, which began shortly after the dam was completed. In February 2017, the main and emergency spillways threatened to fail , leading to the evacuation of 188,000 people living near the dam. After deterioration of

1900-499: The Oroville Dam site. The water rose behind the partially completed embankment dam and nearly overtopped it, while a maximum of 157,000 cu ft/s (4,400 m/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%, averting massive damage to

1976-463: The Oroville area in 1975 is believed to have been caused by induced seismicity from the weight of the Oroville Dam and reservoir on a local fault line.) The embankment was finally topped out on October 6, 1967, with the last of 155 million short tons (140.6 million tonnes ) of material that took over 40,000 train trips to transport. On May 4, 1968, Oroville Dam was officially dedicated by

2052-533: The RVOS and were expected to conclude in early 2017. The spillway cracked in 2013. A senior civil engineer with the DWR was interviewed by the Sacramento Bee , and explained, "It’s common for spillways to develop a void because of the drainage systems under them", and "There were some patches needed and so we made repairs and everything checked out." In July 2015, the state Division of Safety of Dams inspected

2128-475: The SWP's California Aqueduct , which provides a major supply of water for irrigation in the San Joaquin Valley , as well as municipal and industrial water supplies to coastal Southern California , and has prevented large amounts of flood damage to the area—more than $ 1.3 billion between 1987 and 1999. The dam stops fish migration up the Feather River and the controlled flow of the river; as a result,

2204-686: The SWP. 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 of the California Legislature, 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

2280-576: 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

2356-730: The U.S. Bureau of Reclamation Western Pacific Railroad The Western Pacific Railroad ( reporting mark WP ) was a Class I railroad in the United States . It was formed in 1903 as an attempt to break the near-monopoly the Southern Pacific Railroad had on rail service into northern California. WP's Feather River Route directly competed with SP's portion of the Overland Route for rail traffic between Salt Lake City / Ogden, Utah , and Oakland, California , for nearly 80 years. The Western Pacific

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2432-746: The Union Pacific Corporation purchased the Western Pacific in 1982, the WP became part of a combined Union Pacific rail system: the Union Pacific Railroad, the Missouri Pacific Railroad , and the WP. The Union Pacific maintains one locomotive in its fleet, Union Pacific 1983 , in a Western Pacific influenced livery . The California Zephyr was the famous Western Pacific passenger train but

2508-474: 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 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

2584-637: The asphalt make such dams especially suited to earthquake regions. For the Moglicë Hydro Power Plant in Albania the Norwegian power company Statkraft built an asphalt-core rock-fill dam. Upon completion in 2018 the 320 m long, 150 m high and 460 m wide dam is anticipated to be the world's highest of its kind. A concrete-face rock-fill dam (CFRD) is a rock-fill dam with concrete slabs on its upstream face. This design provides

2660-549: The concrete slab as an impervious wall to prevent leakage and also a structure without concern for uplift pressure. In addition, the CFRD design is flexible for topography, faster to construct and less costly than earth-fill dams. The CFRD concept originated during the California Gold Rush in the 1860s when miners constructed rock-fill timber-face dams for sluice operations . The timber was later replaced by concrete as

2736-406: The core is separated using a filter. Filters are specifically graded soil designed to prevent the migration of fine grain soil particles. When suitable building material is at hand, transport is minimized, leading to cost savings during construction. Rock-fill dams are resistant to damage from earthquakes . However, inadequate quality control during construction can lead to poor compaction and sand in

2812-577: The crater in the main spillway was carried downstream, and caused damage to the Feather River Fish Hatchery due to high turbidity . Although engineers had hoped that using the damaged spillway could drain the lake enough to avoid use of the emergency spillway, they were forced to reduce its discharge from 65,000 cu ft/s (1,800 m/s) to 55,000 cu ft/s (1,600 m/s) due to potential damage to nearby power lines. Shortly after 8:00 pm on February 11, 2017,

2888-420: The dam by a week while the train wreckage was cleared. Overall, 34 men died in the construction of the dam. 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". (A M L 5.7 earthquake in

2964-406: The dam must be calculated in advance of building to ensure that its break level threshold is not exceeded. Overtopping or overflow of an embankment dam beyond its spillway capacity will cause its eventual failure . The erosion of the dam's material by overtopping runoff will remove masses of material whose weight holds the dam in place and against the hydraulic forces acting to move the dam. Even

3040-561: The dam site, the embankment was topped out in 1967 and the entire project was ready for use in 1968. The dam began to generate electricity shortly afterwards with completion of the Edward Hyatt Power Plant , then the country's largest underground power station . Since its completion in 1968, the Oroville Dam has allocated the flow of the Feather River from the Sacramento-San Joaquin Delta into

3116-670: The dam spillway visually "from some distance" and did not walk it. The rainy season of 2016–2017 was Northern California's wettest winter in over 100 years . Heavy rainfall resulted in record inflows from the Feather River, and the spillway was opened in January to relieve pressure on Oroville Dam. After a second series of heavy storms in February, the spillway flow was increased to 50,000 cu ft/s (1,400 m/s), and on February 7, DWR employees noticed an unusual flow pattern. This halted spillway outflow, and DWR brought engineers onto

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3192-490: The dam, but embankment dams are prone to seepage through the dam as well; for example, the Usoi landslide dam leaks 35-80 cubic meters per second. Sufficiently fast seepage can dislodge a dam's component particles, which results in faster seepage, which turns into a runaway feedback loop that can destroy the dam in a piping-type failure. Seepage monitoring is therefore an essential safety consideration. gn and Construction in

3268-456: The design was applied to irrigation and power schemes. As CFRD designs grew in height during the 1960s, the fill was compacted and the slab's horizontal and vertical joints were replaced with improved vertical joints. In the last few decades, design has become popular. The tallest CFRD in the world is the 233 m-tall (764 ft) Shuibuya Dam in China , completed in 2008. The building of

3344-578: The embankment which can lead to liquefaction of the rock-fill during an earthquake. Liquefaction potential can be reduced by keeping susceptible material from being saturated, and by providing adequate compaction during construction. An example of a rock-fill dam is New Melones Dam in California or the Fierza Dam in Albania . A core that is growing in popularity is asphalt concrete . The majority of such dams are built with rock and/or gravel as

3420-400: The emergency spillway began carrying water for the first time since the dam's construction in 1968. The water flowed directly onto the earthen hillside below the emergency spillway, as designed. However, headward erosion of the emergency spillway threatened to undermine and collapse the concrete weir . On February 12, an evacuation was ordered for low-lying areas, due to possible failure of

3496-402: The emergency spillway to sustain significant damage." At around 7:30   am on July 22, 2009, several workers were deep below the reservoir operating flow controls to test a river valve chamber in the Oroville Dam. When the flow reached 85%, suction pulled a breakaway wall downstream into a 35-foot (11 m) diversion tunnel, cutting lights and nearly sending three workers to their deaths in

3572-418: The emergency spillway. The flow over the main spillway was increased to 100,000 cu ft/s (2,800 m/s) to try to slow erosion of the emergency spillway. By 8:00 pm on the evening of February 12, the increased flow had lowered the water level, causing the emergency spillway to stop overflowing. On February 14, the sheriff of Butte County lifted the mandatory evacuation order. On May 19, 2017,

3648-481: The following winter. In a second phase of spillway repairs in 2018–19, temporary repairs on the main spillway done during phase one were being torn out and replaced with steel-reinforced structural concrete. On April 2, 2019, due to heavy rainfall upstream, the DWR began releasing water over the newly reconstructed spillway at a rate of 8,300 cubic feet per second (240 m/s). Releases were increased to 25,000 cubic feet per second (710 m/s) on April 7 to test how

3724-406: The future. Due to the low precipitation in the catchment area, water levels were below normal beginning in 2020. In August 2021, the Hyatt power plant had to be shut down because the water level fell below its water inlets. After falling to a record low of 22% capacity by September 30, winter storms increased the lake level by December and the plant was restarted on January 4, 2022. Construction of

3800-440: The future. On November 1, 2017, DWR director Grant Davis said, "Lake Oroville's main spillway is indeed ready to safely handle winter flows if needed". While this completes phase 1 of the construction, there remained a phase 2 to be completed in 2018. The second phase would include rebuilding the top section of the spillway (which was not rebuilt this season), putting slabs over the roller compacted concrete section, and constructing

3876-453: The integrity of the downstream shell zone. An outdated method of zoned earth dam construction used a hydraulic fill to produce a watertight core. Rolled-earth dams may also employ a watertight facing or core in the manner of a rock-fill dam. The frozen-core dam is a temporary earth dam occasionally used in high latitudes by circulating a coolant through pipes inside the dam to maintain a watertight region of permafrost within it. Tarbela Dam

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3952-449: The largest man-made structures in the world. Because earthen dams can be constructed from local materials, they can be cost-effective in regions where the cost of producing or bringing in concrete would be prohibitive. Rock -fill dams are embankments of compacted free-draining granular earth with an impervious zone. The earth used often contains a high percentage of large particles, hence the term "rock-fill". The impervious zone may be on

4028-747: The last link from Sacramento to Oakland, this company was absorbed into the Central Pacific Railroad in 1870. The second company to use the "western pacific" appellation was the Western Pacific Railway Company , founded in 1903. Under the direction of George Jay Gould I , the Western Pacific Railway proposed to build a standard gauge track connection to the Pacific Coast for his aspiring Gould transcontinental system . Construction

4104-503: The main spillway largely stabilized and the water level of the dam's reservoir dropped below the top of the emergency spillway, the evacuation order was lifted. The main spillway was reconstructed by November 1, 2018, and water releases were successfully tested, up to 25,000 cu ft/s (710 m/s), during April 2019. In 1935, work began on the Central Valley Project , a federal water project that would develop

4180-624: The power necessary to drive the pumps that lift the water in the aqueduct from the delta into the valley, and then from the valley over the Tehachapi Mountains into coastal Southern California. Water and power from the dam contribute to the irrigation of 755,000 acres (306,000 ha) in the arid San Joaquin Valley Westside and municipal supplies to some 25 million people. At least 2.8 million acre⋅ft (910 billion US gal; 3.5 trillion L) of water

4256-424: The primary fill. Almost 100 dams of this design have now been built worldwide since the first such dam was completed in 1962. All asphalt-concrete core dams built so far have an excellent performance record. The type of asphalt used is a viscoelastic - plastic material that can adjust to the movements and deformations imposed on the embankment as a whole, and to settlement of the foundation. The flexible properties of

4332-400: 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 ft (1,341 m) long and 35 ft (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 was to carry normal water flows, while the second one

4408-501: The reservoir begins to move the entire structure. The embankment, having almost no elastic strength, would begin to break into separate pieces, allowing the impounded reservoir water to flow between them, eroding and removing even more material as it passes through. In the final stages of failure, the remaining pieces of the embankment would offer almost no resistance to the flow of the water and continue to fracture into smaller and smaller sections of earth or rock until they disintegrate into

4484-510: The roaring current. One of the workers who was badly injured survived by clinging to a bent rail, where he was struck by tools and equipment being sucked into the tunnel. He was hospitalized for four days with head trauma, a broken leg and arm, cuts, and bruises. The California Division of the Occupational Health and Safety Administration (Cal OSHA) concluded opening the valves without an energy-dispersion ring, which reportedly

4560-448: The spillway failure, including a faulty drainage system, variations in concrete thickness, and corrosion in the structure's rebar". For 2018 the DWR planned to demolish and reconstruct the portion of the spillway which was undamaged by the flood, but which also has been identified as structurally defective. In addition, crews worked to extend a cutoff wall under the emergency spillway to prevent erosion should that structure be used again in

4636-443: The spillway performed in higher flows. They were decreased to 15,000 cubic feet per second (420 m/s) on April 9. The DWR released an assessment, dated October 1, 2020, concluding that Oroville Dam was suitable for continued safe and reliable operation. Meanwhile, the Federal Energy Regulatory Commission has demanded that California submit a plan by September 2022, for addressing the issue of greater amounts of rain predicted in

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4712-448: The spillway to inspect its integrity. The engineers found a large area of concrete and foundation erosion. This erosion feature was too massive to repair without diverting water to the emergency spillway, and halted outflow along the main spillway for a period to fix the hole. High inflows to Lake Oroville forced dam operators to continue using the damaged spillway, causing additional damage. The spillway hole continued to grow. Debris from

4788-461: The spillway was shut down for the summer, to allow demolition and repair work to begin. The total cost of the repair was projected to exceed $ 400 million, with the $ 275 million primary contract awarded to Kiewit Construction . FEMA was expected to cover a large portion of the expenses. According to an independent forensics team led by John France, the exact cause of the spillway failure remains uncertain, though they identified "24 possible causes for

4864-422: The state of California. Among the notable figures present were California governor Ronald Reagan , who spoke, 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. On October 17, 2005, three environmental groups filed

4940-558: The total power produced by the SWP's eight hydroelectric facilities. Water released from Oroville Dam travels down the Feather River before joining with the Sacramento River , eventually reaching the Sacramento-San Joaquin Delta , where the SWP's California Aqueduct diverts the fresh water for transport to the arid San Joaquin Valley and Southern California. Oroville–Thermalito hydroelectric facilities furnish about one-third of

5016-472: The underground Edward Hyatt Pump-Generating Plant was finished shortly after the completion of Oroville Dam. At the time, it was the largest underground power station in the United States, with three 132- megawatt (MW) conventional turbines and three 141 MW pump-generators for a total installed capacity of 819 MW. The Hyatt Powerplant is capable of pumping water back into Lake Oroville when surplus power

5092-404: The upstream face and made of masonry , concrete , plastic membrane, steel sheet piles, timber or other material. The impervious zone may also be inside the embankment, in which case it is referred to as a "core". In the instances where clay is used as the impervious material, the dam is referred to as a "composite" dam. To prevent internal erosion of clay into the rock fill due to seepage forces,

5168-438: Was absent, "created water flow with such great turbulence that it blocked an air vent and created a vacuum". It sanctioned the DWR with six citations, including five classified as serious, and the department was initially fined $ 141,375. Two of the "serious" citations were overturned on appeal. This river valve system was one of the first parts of the dam to be built when the dam project started in 1961, because its initial purpose

5244-452: 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 was 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 cu ft/s (7,100 m/s) above

5320-847: Was financed by the Denver and Rio Grande Western Railroad , a company in the Gould system, which had lost access to California due to the attempted acquisition of the Southern Pacific Railroad by the Rio Grande's main rival, the Union Pacific Railroad. The Western Pacific Railway acquired the Alameda and San Joaquin Railroad and began construction on what became known as the Feather River Route. Completed in 1909, it

5396-675: Was one of the original operators of the California Zephyr passenger line. In 1982, the Western Pacific was acquired by the Union Pacific Corporation and it was soon merged into the Union Pacific Railroad . The original Western Pacific Railroad (1862–1870) was established in 1862 to build the westernmost portion of the first transcontinental railroad , between Sacramento and San Jose , California (later to Oakland). After completing

5472-404: Was only to be used during floods. In May 1963, workers poured the last of 252,000 cu yd (6.8 million cu ft; 193,000 m) of concrete that comprised the 128 ft (39 m) high cofferdam , to protect the construction site from floods. This structure later served as an impervious core for the completed dam. With the cofferdam in place, an 11-mile (18 km) rail line

5548-495: 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 – regardless of whether it would become part of

5624-906: Was the Sacramento Northern Railway , which once reached from San Francisco to Chico, California. Others included the Tidewater Southern Railway , the Central California Traction , the Indian Valley Railroad and the Deep Creek Railroad . In December 1953, the Railroad retired its last steam locomotive from revenue service. At the end of 1970, WP operated 1,187 miles (1,910 km) of road and 1,980 miles (3,190 km) of track, not including its Sacramento Northern and Tidewater Southern subsidiaries. After

5700-460: Was the last major rail line connected to California. After Western Pacific Railway Company defaulted on mortgage bonds, its assets were sold in 1916 to The Western Pacific Railroad Company . The original line used 85 lb/yd rail on untreated ties, with no tie plates except on curves over one degree; in 1935 more than half of the main line still had its original rail, most of it having carried 150 million gross tons. In 1931 Western Pacific opened

5776-405: Was to divert the river while the dam was under construction. After that, it served various purposes, including as a possible emergency release valve. Since the accident, DWR had implemented a standing order that prohibited the operation of the river outlet system and significantly limited access to the river valve chamber. Following the accident, DWR entered into a 2012 agreement with Cal OSHA to hire

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