:Oroville Dam

In 1935, work began on the Central Valley Project, 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.{{cite web

|url = http://www.water.ca.gov/swp/history.cfm

|title = History of Water Development and the State Water Project

|publisher = California Department of Water Resources

|date = October 8, 2008

|access-date = April 2, 2012

|archive-url = https://web.archive.org/web/20100823082851/http://www.water.ca.gov/swp/history.cfm

|archive-date = August 23, 2010

|url-status = dead

|df = mdy-all

}}

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 – regardless of whether it would become part of 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.{{cite web

|last = Keats

|first = Adam

|url = http://www.pcl.org/projects/2011symposium/proceedings/Keats8.pdf

|title = 2. State Water Project

|publisher = Planning and Conservation League

|work = Water Wars: Present and Future

|date = October 2007

|access-date = April 2, 2012

|url-status = dead

|archive-url = https://web.archive.org/web/20130515142259/http://www.pcl.org/projects/2011symposium/proceedings/Keats8.pdf

|archive-date = May 15, 2013

|df = mdy-all

}} 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.{{cite web

|url=http://www.water.ca.gov/orovillerelicensing/docs/app_ferc_license_2005/Vol_I_Exhibit%20C.pdf

|title=Exhibit C: Construction History and Proposed Construction Schedule

|publisher=California Department of Water Resources

|work=Oroville Facilities FERC Project No. 2100

|date=January 2005

|access-date=April 4, 2012}}

Two concrete-lined diversion tunnels, each {{convert|4400|ft|m|0|abbr=on}} long and {{convert|35|ft|m|0|abbr=on}} 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 was only to be used during floods.{{cite web

|url = http://library.thinkquest.org/trio/TTQ06035/History.html

|title = History

|publisher = Oracle ThinkQuest Education Foundation

|work = Oroville – The Forgotten Golden City

|access-date = April 2, 2012

|url-status = dead

|archive-url = https://web.archive.org/web/20130516093200/http://library.thinkquest.org/trio/TTQ06035/History.html

|archive-date = May 16, 2013

|df = mdy-all

}} In May 1963, workers poured the last of {{convert|252000|yd3|e6cuft m3|abbr=unit}} of concrete that comprised the {{convert|128|ft|m|0|abbr=on}} 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 {{convert|11|mi|km|adj=on}} 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 was washed down by the Feather River after the California Gold Rush.{{cite magazine

|last=Hoffer |first=William

|title=Taming the Feather River

|magazine=Popular Mechanics

|date=July 1985

|volume=162

|number=7

|pages=78–80}}

On December 22, 1964, disaster nearly struck when the Feather River, after days of heavy rain, reached a peak flow of {{convert|250000|cuft/s|m3/s|abbr=on}} above the Oroville Dam site. The water rose behind the partially completed embankment dam and nearly overtopped it, while a maximum of {{convert|157000|cuft/s|m3/s|abbr=on}} 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 the area.{{cite web

|url=https://archive.org/stream/x5flooddecember196161calirich/x5flooddecember196161calirich_djvu.txt

|title=Flood! December 1964 – January 1965

|via=Internet Archive

|work=California Department of Water Resources Bulletin No. 161

|year=1965

|access-date=April 2, 2012}}{{cite web

|url=https://archive.org/stream/s7californiafloodc15965calirich/s7californiafloodc15965calirich_djvu.txt

|title=California Flood Control Program, 1965

|via=Internet Archive

|work=California Department of Water Resources Bulletin No. 159-65

|year=1965

|access-date=April 2, 2012}}

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 {{convert|10000|gal|L}} of diesel fuel, completely destroying two locomotives. The burning fuel from the collision started a forest fire that burned {{convert|100|acre|ha|abbr=on}} before it could be extinguished. The crash delayed construction of the dam by a week while the train wreckage was cleared.{{cite news

|agency=Associated Press

|title=Bodies of Train Crash Victims Are Recovered

|work=Lodi News-Sentinel

|date=October 9, 1965

}} Overall, 34 men died in the construction of the dam.{{cite web

| title = The Oroville Dam Train Tunnel Collision

| url = http://djkuba.tripod.com/ODamTrainTunelWreck.html

| first = Larry |last = Matthews

}}

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".{{cite magazine

|last=Griswold |first=Wesley S.

|title=The Dam That Talks Back: World's highest earth dam will keep an eye on itself to report every stress and strain

|magazine=Popular Science

|pages=86–87

|volume=190

|number=2

|date=February 1967}} (A M_L 5.7 earthquake in 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.{{cite journal

|url=http://www.johnmartin.com/earthquakes/eqpapers/00000054.htm

|title=Reservoir-Induced Earthquakes and Engineering Policy

|last=Allen |first=Clarence R.

|journal=California Geology

|volume=35

|number=11

|date=November 1982

|access-date=April 3, 2012

|archive-url=https://web.archive.org/web/20190624062531/http://www.johnmartin.com/earthquakes/eqpapers/00000054.htm

|archive-date=June 24, 2019

|url-status=dead

}}) The embankment was finally topped out on October 6, 1967, with the last of {{convert|155|e6ST|e6t|1|abbr=off|lk=on}} 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.{{cite AV media |title=The Oroville Dam Opens |publisher=KPIX / CBS |date=May 4, 1968 |url=https://diva.sfsu.edu/collections/sfbatv/bundles/231000 |url-status=dead |archive-url=https://web.archive.org/web/20231027181507/https://diva.sfsu.edu/collections/sfbatv/bundles/231000 |archive-date=2023-10-27}} Among the notable figures present were California governor Ronald Reagan, who spoke,{{Cite web|url=https://www.reaganlibrary.gov/archives/audiovisual/ronald-reagan-gubernatorial-audiotape-collection |work=Ronald Reagan Presidential Library |publisher=National Archives and Records Administration |title=Ronald Reagan Gubernatorial Audiotape Collection|language=en-gb|access-date=2024-06-03|df=mdy-all}}{{cite web |url=https://www.reaganlibrary.gov/public/digitallibrary/gubernatorial/pressunit/p17/40-840-7408624-p17-010-2017.pdf |work=Ronald Reagan Presidential Library |publisher=National Archives and Records Administration |title=Excerpts of Speech by Governor Ronald Reagan, Oroville Dam Dedication, May 4, 1968 |date=May 2, 1968 |access-date=June 3, 2024}}{{Cite episode|url=http://www.msnbc.com/rachel-maddow/watch/oroville-dam-in-crisis-raises-alarm-in-california-874905667526|title=Oroville dam in crisis raises alarm in California |series=Rachel Maddow |network=MSNBC |date=February 11, 2017 |access-date=2024-06-03}} Chief Justice (formerly California governor) Earl Warren, Senator Thomas Kuchel, and California Representative Harold T. "Bizz" Johnson.{{cite news

|agency=Associated Press

|title=Massive Dam At Oroville Is Dedicated

|work=Merced Sun-Star

|date=May 4, 1968

}} The dedication was accompanied by a week of festivities in nearby Oroville, attended by nearly 50,000 people.{{cite news

|agency=Associated Press

|title=Oroville Dam Dedication Today

|work=The Press-Courier

|date=May 4, 1968

}}

On October 17, 2005, three environmental groups filed 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 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.{{cite news|url=http://www.orovillemr.com/general-news/20170212/state-was-warned-about-inadequacy-of-emergency-spillway|title=State was warned about inadequacy of emergency spillway|first=Paul|last=Rogers|agency=Bay Area News Group|work=Oroville Mercury-Register|date=February 13, 2017|access-date=June 3, 2024}}

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 the emergency spillway to sustain significant damage."{{cite news|url=http://www.mercurynews.com/2017/02/12/oroville-dam-feds-and-state-officials-ignored-warnings-12-years-ago/|title=Oroville Dam: Feds and state officials ignored warnings 12 years ago|newspaper=San Jose Mercury News|date=February 13, 2017|access-date=February 13, 2017}}

At around 7:30{{nbsp}}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 {{convert|35|ft|m|adj=on}} diversion tunnel, cutting lights and nearly sending three workers to their deaths in 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.{{cite news| publisher = KXTV | title = River valve damaged in 2009 could have been third way to release excess water | first = Sarah | last = Moore | url = http://www.abc10.com/news/local/river-valve-damaged-in-2009-could-have-been-fourth-way-to-release-excess-water/408086236 | archive-url = https://web.archive.org/web/20170216162915/https://www.abc10.com/news/local/river-valve-damaged-in-2009-could-have-been-fourth-way-to-release-excess-water/408086236| archive-date= February 16, 2017| date= February 17, 2017}}

The California Division of the Occupational Health and Safety Administration (Cal OSHA) concluded opening the valves without an energy-dispersion ring, which reportedly was absent, "created water flow with such great turbulence that it blocked an air vent and created a vacuum".{{cite news | url=http://www.orovillemr.com/general-news/20120912/dwr-planning-study-on-worrisome-river-valves-blamed-in-2009-oroville-dam-accident | title=DWR planning study on worrisome river valves blamed in 2009 Oroville Dam accident | work=Oroville Mercury-Register | date=September 12, 2012 | author=Barbara Arrigoni}} 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.{{cite web | url=https://www.osha.gov/pls/imis/establishment.inspection_detail?id=313228637 | title=Inspection Detail | publisher=Occupational Safety and Health Administration}}

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 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 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 the RVOS and were expected to conclude in early 2017.{{cite web | url=https://cwc.ca.gov/Documents/2017/01_January/2016_SWPReview_FinalDraft.pdf | title=Draft 2016 Annual Review of the construction and operation of the State Water Project | publisher=California Water Commission | pages=4, 5 | access-date=February 19, 2017 | archive-date=February 14, 2017 | archive-url=https://web.archive.org/web/20170214182952/https://cwc.ca.gov/Documents/2017/01_January/2016_SWPReview_FinalDraft.pdf | url-status=dead }}

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."{{cite news|last1=Bollea|first1=Drew|title=Maintenance Records Show Oroville Dam Spillway Previously Patched|url=http://sacramento.cbslocal.com/2017/02/10/maintenance-records-show-oroville-dam-spillway-previously-patched/|website=CBS Local|date=February 10, 2017|access-date=February 13, 2017}}

In July 2015, the state Division of Safety of Dams inspected the dam spillway visually "from some distance" and did not walk it.{{cite news|last1=Arthur|first1=Damon|title=Dam spillway checked from 'distance' in last inspection|url=http://www.redding.com/story/news/2017/02/09/dam-spillway-checked-distance-last-inspection/97723936/|work=Record Searchlight|access-date=February 13, 2017}}

{{Main|Oroville Dam crisis}}

File:Oroville Dam spillway damage 27 Feb 2017.jpg

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 {{convert|50000|cuft/s|m3/s|abbr=on}}, and on February 7, DWR employees noticed an unusual flow pattern. This halted spillway outflow, and DWR brought engineers onto 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.{{cite web|url=https://www.water.ca.gov/What-We-Do/Emergency-Response/Oroville-Spillways/Background |title=Oroville Spillways Incident Background |publisher=State of California |access-date=2018-04-04}} High inflows to Lake Oroville forced dam operators to continue using the damaged spillway, causing additional damage. The spillway hole continued to grow.{{cite news|url=http://www.sfgate.com/news/article/Oroville-Dam-spillway-hole-erosion-water-reservoir-10920358.php|title=Gaping hole in Oroville Dam spillway is growing, officials warn|author=Graff, Amy|work=SFGate|date=February 10, 2017|access-date=February 10, 2017}} Debris from the crater in the main spillway was carried downstream, and caused damage to the Feather River Fish Hatchery due to high turbidity.{{cite web|url=http://www.krcrtv.com/news/local/butte/fish-evacuated-from-feather-river-hatchery/326225498|title=Fish evacuated from Feather River Hatchery|date=February 11, 2017|publisher=KRCR|access-date=February 13, 2017|archive-date=November 16, 2017|archive-url=https://web.archive.org/web/20171116042816/http://www.krcrtv.com/news/local/butte/fish-evacuated-from-feather-river-hatchery/326225498|url-status=dead}}

Although engineers had hoped that using the damaged spillway could drain the lake enough to avoid use of the emergency spillway,{{Cite news|url=https://phys.org/news/2017-02-emergency-spillway-oroville-california.html|title=Sacrificing California spillway may avoid emergency releases|access-date=February 11, 2017}} they were forced to reduce its discharge from {{convert|65000|cuft/s|m3/s|abbr=on}} to {{convert|55000|cuft/s|m3/s|abbr=on}} due to potential damage to nearby power lines.{{cite news|url=http://www.sacbee.com/news/state/california/water-and-drought/article132123804.html|work=Sacramento Bee|title=Use of untested emergency spillway yet again a possibility at crippled Oroville Dam|access-date=February 12, 2017}}{{cite news|url=http://www.water.ca.gov/news/newsreleases/2017/021017oroville.pdf|title=Lake Oroville Releases Slowed to Avoid Erosion|author=CA DWR|date=February 10, 2017|access-date=February 12, 2017|archive-url=https://web.archive.org/web/20170213164326/http://www.water.ca.gov/news/newsreleases/2017/021017oroville.pdf|archive-date=February 13, 2017|url-status=dead|df=mdy-all}}

{{multiple image

|align=right

|image1=Oroville dam spillover 2017-02-11.jpg

|width1=187

|caption1=Water overflowed the parking lot past the emergency spillway (in the background), while water continued to flow through the main spillway (in the foreground), on February 11.

|image2=Oroville Emergency Spillway Carrying Water.jpg

|width2=209

|caption2=Water from the Oroville Dam flows over the emergency spillway on Sunday, February 12

}}

Shortly after 8:00 pm on February 11, 2017, the emergency spillway began carrying water for the first time since the dam's construction in 1968.{{cite news|url=https://abcnews.go.com/Technology/wireStory/latest-emergency-spillway-oroville-dam-45401080|title=The Latest: Emergency Spillway Use Likely at Oroville Dam|agency=Associated Press|work=ABC News|date=February 10, 2017|access-date=February 10, 2017|url-status=dead|archive-url=https://web.archive.org/web/20170210163002/https://abcnews.go.com/Technology/wireStory/latest-emergency-spillway-oroville-dam-45401080|archive-date=February 10, 2017|df=mdy-all}} 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 the emergency spillway.{{Cite news|url=http://www.kcra.com/article/evacuation-orders-issued-for-low-levels-of-oroville/8735215|title=Thousands from Yuba, Butte, Sutter counties evacuated|author=KCRA Staff|date=February 13, 2017|newspaper=KCRA|access-date=February 13, 2017|language=en}} The flow over the main spillway was increased to {{convert|100000|cuft/s|m3/s|abbr=on}} to try to slow erosion of the emergency spillway.{{Cite news|url=http://www.sacbee.com/news/state/california/water-and-drought/article132332499.html|title=BREAKING: Fearing collapse of emergency spillway at Oroville Dam, Oroville evacuated|work=Sacramento Bee|date=February 12, 2017|access-date=February 12, 2017}}

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.{{cite news|last1=Daniels|first1=Jeff|title=Authorities lift mandatory evacuation orders for Oroville Dam emergency|url=https://www.cnbc.com/2017/02/14/authorities-lift-mandatory-evacuation-orders-for-oroville-dam-emergency.html|access-date=14 February 2017|publisher=CNBC|date=14 February 2017}}

On May 19, 2017, the spillway was shut down for the summer, to allow demolition and repair work to begin.{{cite news|url=http://www.sfgate.com/news/article/Oroville-Dam-spillway-to-go-offline-for-rest-of-11157146.php|title=Oroville Dam spillway to go offline until fall, allowing for repairs|last=Fimrite|first=Peter|work=SFGate|date=2017-05-18|access-date=2017-06-10}} The total cost of the repair was projected to exceed $400 million, with the $275 million primary contract awarded to Kiewit Construction.{{cite news|url=http://www.popularmechanics.com/technology/infrastructure/a26787/final-cost-oroville-dam-400-million/|title=The Oroville Dam Disaster Will End Up Costing About $400 Million|work=Popular Mechanics|last=Grossman|first=David|date=2017-06-06|access-date=2017-06-10}} FEMA was expected to cover a large portion of the expenses.{{cite news|url=http://www.sacbee.com/news/investigations/the-public-eye/article154265149.html|title='A once in a lifetime opportunity'. Who made money off the Oroville Dam crisis?|last=Kasler|first=Dale|work=Sacramento Bee|date=2017-06-04|access-date=2017-06-10}}

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 the spillway failure, including a faulty drainage system, variations in concrete thickness, and corrosion in the structure's rebar".{{cite news|url=http://www.sacbee.com/news/local/article153811319.html|title=Oroville Dam update: Fracture likely caused by 'multiple factors'|last=Kasler|first=Dale|work=Sacramento Bee|date=2017-06-01|access-date=2017-06-10}}

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 the future.{{cite news|url=http://www.mercurynews.com/2017/09/18/oroville-dam-what-exactly-will-be-done-by-nov-1/|last=Johnson|first=Risa|title=Oroville Dam: What exactly will be done by Nov. 1?|work=Mercury News|date=2017-09-18|access-date=2017-09-25}}

On November 1, 2017, DWR director Grant Davis said, "Lake Oroville's main spillway is indeed ready to safely handle winter flows if needed".{{cite news|url=http://www.sacbee.com/news/state/california/water-and-drought/article182123271.html|first=Dale|last=Kasler|title=Oroville Dam ready to withstand winter rains as first phase of repairs is finished, officials say|work=Sacramento Bee|date=2017-11-01|access-date=2017-11-01}} 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 a concrete secant cutoff wall for the emergency spillway. The cost estimate at this point is over $500 million.{{cite news|url=http://www.kcra.com/article/milestone-reached-in-oroville-spillway-construction-1/13135493|author=|work=KCRA|title='Milestone' reached in Oroville spillway construction|date=2017-11-01|access-date=2017-11-01}} In October 2017, hairline cracks were found in the rebuilt spillway.{{cite news |agency=Associated Press |date=28 November 2017 |title=Big California Dam's New Spillway Already Has Cracks in It |url=https://www.usnews.com/news/best-states/california/articles/2017-11-28/officials-no-threat-from-cracks-in-new-oroville-spillway |work=U.S. News & World Report |access-date=1 January 2018 }}
{{cite news |last=Serna |first=Joseph |date=2 December 2017 |title=Costs soar and cracks revealed in Oroville Dam spillway, but officials say it's ready for winter rains |url=http://www.latimes.com/local/lanow/la-me-ln-oroville-spillway-work-20171202-story.html |work=Los Angeles Times |access-date=1 January 2018 }} 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.{{cite web|url=http://www.water.ca.gov/oroville-spillway/board_of_consultants.cfm|author=California Department of Water Resources|title=Oroville Spillways Incident, Board of Consultants|date=2017-11-20|access-date=2018-01-29|archive-url=https://web.archive.org/web/20180130204320/http://www.water.ca.gov/oroville-spillway/board_of_consultants.cfm|archive-date=January 30, 2018|url-status=dead|df=mdy-all}} Memoranda (reports) prepared by the BOC are posted at the DWR web site.{{cite web|url=http://www.water.ca.gov/oroville-spillway/bocreports.cfm|author=Board of Consultants|title=Reports from the Lake Oroville Spillways Recovery Project, Board of Consultants|date=2017-12-20|access-date=2018-01-29|archive-url=https://web.archive.org/web/20180130204431/http://www.water.ca.gov/oroville-spillway/bocreports.cfm|archive-date=January 30, 2018|url-status=dead|df=mdy-all}} 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.{{cite web|url=http://www.water.ca.gov/oroville-spillway/forensic_team.cfm|author=Independent Forensic Team|title=Preliminary and interim reports of the Lake Oroville Spillways Recovery Project, Independent Forensic Team|date=2017|access-date=2018-01-30|archive-url=https://web.archive.org/web/20180131200907/http://www.water.ca.gov/oroville-spillway/forensic_team.cfm|archive-date=January 31, 2018|url-status=dead|df=mdy-all}}

{{collapse top|title=Progression of spillway conditions, Sentinel-2 true-color satellite images}}

{{Gallery

|title=

|width=400 | height=200

|align=center

|File:Oroville Dam, California, January 30, 2017, Sentinel-6, true-color satellite image.tif | January 30, 2017, before spillways failed

|File:Oroville Dam, California, March 11, 2017, Sentinel-5, true-color satellite image.tif | March 11, 2017, after spillways failed

|File:Oroville Dam, California, July 29, 2017, Sentinel-4, true-color satellite image.tif | July 29, 2017, construction progress

|File:Oroville Dam, California, November 6, 2017, Sentinel-3, true-color satellite image.tif | November 6, 2017, construction progress

|File:Oroville Dam, California, January 30, 2018, Sentinel-2, true-color satellite image.tif | January 30, 2018, construction progress

}}

{{collapse bottom}}

File:Oroville Dam main spillway rebuild phase 2.jpg

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 the following winter.{{cite web|url=http://water.ca.gov/oroville-spillway/pdf/2017/Lake%20Oroville%202017-2018%20Flood%20Ops%20Plan_Incl%20App_V2.pdf|author=DWR|title=Lake Oroville 2017/2018 Flood Control Season Operations Plan|date=2017-10-16|access-date=2018-01-30|archive-date=October 22, 2017|archive-url=https://web.archive.org/web/20171022194758/http://water.ca.gov/oroville-spillway/pdf/2017/Lake%20Oroville%202017-2018%20Flood%20Ops%20Plan_Incl%20App_V2.pdf|url-status=dead}}

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.{{cite web |last1=Harvey |first1=Chuck |title=Kiewit Leads Phase II of Oroville Dam Spillway Repairs |url=https://www.constructionequipmentguide.com/kiewit-leads-phase-ii-of-oroville-dam-spillway-repairs/41036 |website=Construction Equipment Guide |access-date=7 August 2018}}

On April 2, 2019, due to heavy rainfall upstream, the DWR began releasing water over the newly reconstructed spillway at a rate of {{convert|8,300|cuft/s}}.{{Cite web|url=http://water.ca.gov/News/News-Releases/2019/April/DWR-Uses-Oroville-Main-Spillway|title=DWR Uses Oroville Main Spillway|publisher=California Department of Water Resources|date=April 2, 2019 |language=en|access-date=2019-04-03}} Releases were increased to {{convert|25,000|cuft/s}} on April 7 to test how the spillway performed in higher flows. They were decreased to {{convert|15,000|cuft/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.{{cite report |title=Oroville Dam Safety Comprehensive Needs Assessment Summary |date=October 1, 2020 |publisher=State of California, The Natural Resources Agency, Department of Water Resources |quote=The project is suitable for continued safe and reliable operation. No emergency remedial measures are necessary for continued safe operation. |url=https://cawaterlibrary.net/wp-content/uploads/2021/05/Pages-from-20201030_Oroville_CNA_Project_Report_Summary_Final_Accessibility-Check-FINAL.pdf |accessdate=August 14, 2022}}

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 the future.{{cite news |title=The Coming California Megastorm |first=Raymond |last=Zhong |work=The New York Times |date=August 12, 2022 |url=https://www.nytimes.com/interactive/2022/08/12/climate/california-rain-storm.html |accessdate=August 14, 2022}}

File:Edward Hyatt Powerplant during its shutdown in August 2021-5993.jpg

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.{{Cite web|url=https://www.wwdmag.com/one-water/california-shuts-down-major-hydroelectric-plant-due-low-water-levels-lake-oroville|title=California Shuts Down Major Hydroelectric Plant Due to Low Water Levels at Lake Oroville |work=Wastewater Digest |date=August 9, 2021 |first=Cristina |last=Tuser|access-date=June 3, 2024 }} 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.{{Cite web|url=https://www.mercurynews.com/2022/01/04/lake-oroville-rises-89-feet-power-plant-resumes-operation-after-december-rains/|title=Lake Oroville rises 89 feet, power plant resumes operation after December rains|date=January 4, 2022 |first=Paul |last=Rogers |work=San Jose Mercury |agency=Bay Area News Group |access-date=June 3, 2024}}

Image:Oroville.jpg

Construction of 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.{{cite web|url=http://www.water.ca.gov/swp/facilities/Oroville/hyatt.cfm |title=Edward Hyatt Powerplant |publisher=California Department of Water Resources |work=California State Water Project |date=June 17, 2009 |access-date=April 2, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120407054356/http://www.water.ca.gov/swp/facilities/Oroville/hyatt.cfm |archive-date=April 7, 2012 |df=mdy-all }} The Hyatt Powerplant is capable of pumping water back into Lake Oroville when surplus power is available. The pump-generators at Hyatt can lift up to {{convert|5610|cuft/s|m3/s}} into Lake Oroville (with a net consumption of 519 MW), while the six turbines combined use a flow of {{convert|16950|cuft/s|m3/s|abbr=on}} at maximum generation.{{cite web

|url=http://www.buttecounty.net/Administration/Projects/~/media/County%20Files/AdminOffice/Public%20Internet/Lake%20Oroville%20Facilities%20Project/Final%20FEIS/Section%202%20FEIS.ashx

|title=Section 2: Proposed Action and Alternatives

|publisher=Butte County, California

|work=Federal Energy Regulatory Commission Final Environmental Impact Statement for the Oroville Facilities Project

|pages=13–42

|access-date=April 2, 2012

|archive-date=March 3, 2012

|archive-url=https://web.archive.org/web/20120303022044/http://www.buttecounty.net/Administration/Projects/~/media/County%20Files/AdminOffice/Public%20Internet/Lake%20Oroville%20Facilities%20Project/Final%20FEIS/Section%202%20FEIS.ashx

|url-status=dead

}}

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 the Oroville–Thermalito Complex.{{cite web

|url=http://www.norcalwater.org/water-maps/oroville/

|title=Oroville Reservoir and Thermalito Facilities

|publisher=Northern California Water Association

|access-date=April 2, 2012}} 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.{{cite magazine

|last=Zmuda |first=Joseph

|title=Slaking California's mammoth thirst with the World's Largest Water: Surplus water from the north now flows to arid regions via this gigantic $2.3 billion project

|magazine=Popular Science

|date=September 1972

|volume=201

|number=3

|pages=62–64}} The Hyatt and Thermalito plants produce an average of 2,200 gigawatt hours (GWh) of electricity each year, about half of the total power produced by the SWP's eight hydroelectric facilities.{{cite web

|url=http://www.yubaaccordrmt.com/Yuba%20Accord%20Documents/Draft%20EIR-EIS%20for%20the%20Proposed%20Lower%20Yuba%20River%20Accord/Chapters/Chapter%2007-Power%20Production%20and%20Energy%20Consumption.pdf

|title=Chapter 7: Power Production and Energy Consumption

|publisher=Yuba River Management Team

|work=Proposed Lower Yuba River Accord

|date=June 2007

|access-date=April 2, 2012

|archive-date=February 22, 2014

|archive-url=https://web.archive.org/web/20140222151705/http://www.yubaaccordrmt.com/Yuba%20Accord%20Documents/Draft%20EIR-EIS%20for%20the%20Proposed%20Lower%20Yuba%20River%20Accord/Chapters/Chapter%2007-Power%20Production%20and%20Energy%20Consumption.pdf

|url-status=dead

}}{{cite web

|url = http://www.water.ca.gov/swp/benefits.cfm

|title = Benefits Of The California State Water Project

|publisher = California Department of Water Resources

|date = July 18, 2008

|access-date = April 2, 2012

|archive-url = https://web.archive.org/web/20120404075751/http://www.water.ca.gov/swp/benefits.cfm

|archive-date = April 4, 2012

|url-status = dead

|df = mdy-all

}}

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 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.{{cite web

|url = http://www.water.ca.gov/swpao/docs/bulletin/95/view/text/cha11.html

|title = Power Resources

|publisher = California Department of Water Resources

|work = Bulletin 132–95

|access-date = April 2, 2012

|url-status = dead

|archive-url = https://web.archive.org/web/20120405052816/http://www.water.ca.gov/swpao/docs/bulletin/95/view/text/cha11.html

|archive-date = April 5, 2012

|df = mdy-all

}} Water and power from the dam contribute to the irrigation of {{convert|755000|acre|ha}} in the arid San Joaquin Valley Westside and municipal supplies to some 25 million people.{{cite web

|url=http://www.water.ca.gov/swp/

|title=California State Water Project Overview

|publisher=California Department of Water Resources

|date=August 11, 2010

|access-date=April 2, 2012}} At least {{convert|2.8|e6acre-ft|e9usgal e12l|abbr=unit|}} of water is released.{{Cite web|url=https://watershed.ucdavis.edu/shed/lund/dams/Oroville/OrovilleDam.html|url-status=dead|archive-url=https://web.archive.org/web/20220907204007/https://watershed.ucdavis.edu/shed/lund/dams/Oroville/OrovilleDam.html|archive-date=2022-09-07|title=Oroville Dam|work=History of Dams |first1=Heloisa |last1=Yang |first2=Matt |last2=Haynes |first3=Stephen |last3=Winzenread |first4=Kevin |last4=Okada |publisher=Center for Watershed Sciences, University of California Davis |access-date=2018-04-30}}

Image:Oroville_dam.jpg

During the winter and early spring, Lake Oroville is required to have at least {{convert|750000|acre feet|e9usgal e9l|abbr=unit}}, or a fifth of the reservoir's storage capacity, available for flood control.{{cite web

|url=http://www.water.ca.gov/swp/facilities/Oroville/LakeDam.cfm

|title=Oroville Facilities

|publisher=California Department of Water Resources

|work=California State Water Project

|date=June 17, 2009

|access-date=April 2, 2012}} The dam is operated to maintain an objective flood-control release of {{convert|150000|cuft/s|m3/s}}, which may be further reduced during large storms when flows below the Feather's confluence with the Yuba River exceed {{convert|300000|cuft/s|m3/s}}.{{cite web

|url = http://www.auburndamcouncil.org/pages/pdf-files/6-current-floodmgmt-systems.pdf

|title = Chapter 6: Assessment of Current Flood Management Systems

|work = U.S. Army Corps of Engineers, Sacramento District: Post-Flood Assessment for 1983, 1986, 1995 and 1997

|publisher = Auburn Dam Council

|access-date = April 2, 2012

|url-status = dead

|archive-url = https://web.archive.org/web/20110725023800/http://www.auburndamcouncil.org/pages/pdf-files/6-current-floodmgmt-systems.pdf

|archive-date = July 25, 2011

|df = mdy-all

}} In the particularly devastating flood of 1997, inflows to the reservoir hit more than {{convert|331000|cuft/s|m3/s}}, but dam operators managed to limit the outflow to {{convert|160000|cuft/s|m3/s}}, sparing large regions of the Sacramento Valley from flooding.{{cite conference

|url=http://cepsym.org/Sympro1997/Roos.pdf

|title=The Great New Year's Flood of 1997

|conference=California Extreme Precipitation Symposium

|last=Roos |first=Maurice

|year=1997

|access-date=April 2, 2012

|archive-date=August 13, 2015

|archive-url=https://web.archive.org/web/20150813174715/http://cepsym.org/Sympro1997/roos.pdf

|url-status=dead

}}{{cite web

|url=http://cdec.water.ca.gov/cgi-progs/queryF?s=ORO&d=02-Jan-1997+00:00&span=24hours

|title=Oroville Dam (ORO) Data Query (REL SCH) for 01/01/1997 through 01/02/1997

|publisher=California Department of Water Resources

|work=California Data Exchange Center

|access-date=August 10, 2015

|archive-date=August 3, 2017

|archive-url=https://web.archive.org/web/20170803052610/http://cdec.water.ca.gov/cgi-progs/queryF?s=ORO&d=02-Jan-1997+00:00&span=24hours

|url-status=dead

}}

Oroville Dam completely blocks 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.{{cite web |url=https://www.wildlife.ca.gov/Fishing/Hatcheries/Feather-River |title=Feather River Fish Hatchery |publisher=California Department of Fish and Wildlife |access-date=2017-02-12}} 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 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.{{cite web |url=http://cahatcheryreview.com/wp-content/uploads/2012/08/CA%20Hatchery%20Review%20Report%20Final%207-31-12.pdf#page=92 |title=California Hatchery Review Report |publisher=California Hatchery Scientific Review Group |date=June 2012 |access-date=2017-02-12}} 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 the Feather River system.{{cite web

|url=http://www.marinebio.net/marinescience/06future/salsteelfarm.htm

|title=Mariculture: Chinook Salmon and Steelhead Trout

|publisher=MarineBio Conservation Society

|year=2003

|access-date=April 2, 2012}}{{cite news

|last = Weston

|first = Mary

|url = http://www.chicoer.com/news/ci_16285995

|archive-url = https://archive.today/20130119181745/http://www.chicoer.com/news/ci_16285995

|url-status = dead

|archive-date = January 19, 2013

|title = Salmon spawning under way at Feather River hatchery

|work = Chico Enterprise-Record

|date = October 8, 2010

|access-date = April 2, 2012

}}

{{Portal|California|Water|Renewable energy}}

• New Bullards Bar Dam
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• List of power stations in California
• List of tallest dams in the United States
• New Bidwell Bar Bridge

{{Reflist}}

• {{cite report |first1=David W. |last1=Reynolds |first2=Curtis L. |last2=Hartzell |date=September 1995 |title=Lake Oroville Runoff Enhancement Project — Final Report |url=https://www.usbr.gov/tsc/techreferences/rec/R9512.pdf |publisher=United States Department of the Interior, Bureau of Reclamation}}

{{Commons category|Oroville Dam}}

• {{Official website|https://water.ca.gov/Programs/State-Water-Project/SWP-Facilities/Oroville}}
• [https://cdec.water.ca.gov/resapp/ResDetail?resid=ORO Oroville Reservoir – Current Conditions] | California Department of Water Resources
• {{webarchive |url=https://web.archive.org/web/20150128071324/http://www.water.ca.gov/hlpco/p2100.cfm |date=January 28, 2015|title=Oroville Facilities, FERC Project No. 2100}}
• {{webarchive |url=https://web.archive.org/web/20090218104539/https://orovillerelicensing.water.ca.gov/ |date=February 18, 2009 |title=Oroville Facilities Relicensing}}

{{Generating stations in California|state=autocollapse}}

{{State Water Project}}

{{Authority control}}

Category:1968 establishments in California

Category:Buildings and structures in Butte County, California

Category:California Department of Water Resources dams

Category:California State Water Project

Category:Dams completed in 1968

Category:Dams in California

Category:Dams in the Feather River basin

Category:Earth-filled dams

Category:Energy infrastructure completed in 1968

Category:Feather River

Category:Hydroelectric power plants in California

Category:Oroville, California

Category:Underground power stations

Category:United States Army Corps of Engineers dams

Category:Water in California

Category:Dams with fish ladders