Oroville Spillways FAQ

What are the objectives of Phase One and Phase Two of the Lake Oroville Spillways Emergency Recovery project?

The objective of Phase One of the Lake Oroville Spillways Emergency Recovery Project was to ensure that by November 1, 2017, the gated flood control outlet, or main spillway, could handle reservoir releases of at least 100,000 cubic feet per second.

During Phase One, DWR and its prime construction contractor, Kiewit, removed and reconstructed more than 2,200 feet of the main spillway. A section of the upper chute and the lower chute were demolished and replaced with reinforced structural concrete slabs and walls. More than 1,000 feet of the middle chute of the main spillway was reconstructed with approximately 350,000 cubic yards of roller-compacted concrete (RCC). This is the section where the two large scour holes were filled-in, layer by layer, with RCC. DWR also patched and added additional anchoring to the uppermost 730 feet of the main spillway leading to the radial gates.

During Phase Two of the project at the main spillway, expected to begin in May 2018, the uppermost 730-feet will be removed and reconstructed with steel-reinforced structural concrete slabs and walls. The roller-compacted concrete middle chute will be brought to final design by adding a 2.5-foot layer of structural concrete, as well as replacing the current roller-compacted concrete walls with structural concrete walls

Phase One construction at Lake Oroville’s emergency spillway is still underway, with construction of the underground secant pile wall expected to be completed in March 2018. The secant pile wall is being built 730 feet downhill of the emergency spillway at depths of 35 to 65 feet. In January 2018, construction crews also completed construction of a crested cut-off wall adjacent to the spillway parking lot.

Phase Two work at the emergency spillway will include construction of a roller-compacted concrete splashpad and a roller-compacted concrete buttress in 2018. The RCC splashpad, in conjunction with the secant pile wall, will armor the existing terrain, reducing the type of uphill erosion that occurred last February if the emergency spillway were used again. The concrete buttress is a structure that will be built at the base of the emergency spillway structure to provide reinforcement.

How much will the emergency response and recovery efforts cost?

DWR is submitting combined estimated emergency response and recovery costs to the Federal Emergency Management Agency (FEMA) totaling $870 million, which coverscompletion of the project through January 2019. FEMA reimburses up to 75 percent of the requested costs for a federal emergency.To date, FEMA has approved reimbursement of $86.9 million of the $115.9 million submitted by DWR.

Emergency recovery: The estimated cost of the Lake Oroville Spillways Emergency Recovery Project through January 2019 is $710 million, with major components including:

• $500 million for main and emergency spillways work through the contract with Kiewit.
• $210 million for related recovery work including debris and sediment removal, power line replacement, staff time, technical consultants and inter-agency support.
• Emergency recovery costs are based on current and projected work and may evolve as work continues.
• Emergency response: The estimated cost for emergency response, which ended in May of 2017, is $160 million. This is nearly $115 million less than the initial emergency response cost estimate of $274 million. Response included erosion mitigation for both spillways during the incident, sediment removal, installation of temporary transmission lines, staff time, technical consultants and inter-agency support.

Why was the evacuation ordered?

The Butte County Sheriff deemed the evacuation to be necessary after receiving information regarding erosion threatening the emergency spillway from the Department of Water Resources (DWR), the Federal Energy Regulatory Commission (FERC), the Division of Safety of Dams (DSOD) and the Governor’s Office of Emergency Services (Cal OES).

How did DWR manage public safety and protection of species during the emergency incident?

The primary focus of any emergency response is the safety of residents. DWR managed multiple risks during the incident – the headcutting erosion of the damaged main spillway, the potential that further erosion of the main spillway could take out critical transmission line towers, preventing the Hyatt Powerplant from flooding because of debris backing up the diversion pool tailrace, and managing lake levels to avoid using the emergency spillway – all with public safety of downstream residents as the top priority.

Several days in to the Lake Oroville spillways incident, California Fish and Wildlife employees began to relocate juvenile fish that were negatively impacted by turbidity and poor water quality.

How often is the Lake Oroville’s main spillway used?

The main spillway has been used 26 times since the dam and spillway were built in 1969 to safely release water from Lake Oroville. The main spillway has only been used four times prior to January 1– 1982, 1984, 1997, and 2006. The rate of release from the main spillway has only exceeded 100,000 cubic feet per second in five of the 49 years.

How many jobs have been created by the response and recovery process?

At the peak of construction DWR’s prime contractor, Kiewit, employed 600 people. Most of the workers are local to the immediate region or neighboring Northern California counties.

Will DWR be reimbursed by the federal government?

DWR is submitting to the Federal Emergency Management Agency (FEMA) estimated emergency response and recovery effort costs totaling $870 million, which covers completion of the project through January 2019. FEMA reimburses up to 75 percent of the requested costs for a federal emergency. To date, FEMA has approved reimbursement of $86.9 million of the $115.9 million submitted by DWR.

What is the role of the independent Board of Consultants (BOC)?

A Board of Consultants (BOC) is required by California Water Code (Division 3, Part 1, Chapter 3, Section 6056) to evaluate and review modifications to any dam owned by DWR. In addition, FERC requires a Board of Consultants to review and comment on repairs to dams. Therefore, the Lake Oroville Spillways Emergency Recovery Project is being reviewed by the BOC.

The process for the Oroville BOC is the same as for any other dam project – except the BOC must work at an accelerated pace, in real time with repairs. DWR engineers regularly present information to the BOC, then members of the BOC comment on DWR preliminary considerations and offer direction prior to DWR making final decisions.

What is the role of the Independent Forensic Team?

The Independent Forensic Team (IFT) was formed to determine the cause of the Lake Oroville spillway incident. To ensure an independent review process, the Association of State Dam Safety Officials (ASDSO) and the United States Society of Dams selected the six team members in early March 2017.

The IFT released three documents that studied the Lake Oroville spillways incident. A May 2017 preliminary findings memo listed 24 physical factors that potentially contributed to the main spillway damage and four physical factors that may have contributed to the emergency spillway damage. A September 2017 interim memo summarized findings of the Lake Oroville spillways failure. The IFT released the final report January 5, 2018.

Is Oroville Dam at risk?

Oroville Dam is sound. The Lake Oroville spillways and Oroville Dam are separate structures. The structural integrity of Oroville Dam was never at risk during the 2017 incident and remains structurally sound.

What is the vegetation area on the face of Oroville Dam?

DWR released a report in August 2017 outlining the cause of the vegetation area. It is a seasonal band of vegetation on the face of Oroville Dam caused by rainwater. It is not a threat to the integrity of Oroville Dam.

The vegetation area was observed during construction in 1966 and 1967 before the reservoir was filled. A DSOD inspection from February 1, 1967, on the face of Oroville Dam observed ponded and perched water and seepage bands from rain water in the fill area. This is an assessment that was developed over 50 years ago, supported by decades of performance monitoring instrumentation, and is continuously concurred with by engineers inspecting the dam over time.

Sensitive seepage monitoring equipment and a vertical drain near the core of the dam would intercept and alert DWR to any abnormal seepage. These levels have remained constant since construction of Oroville Dam in the late 1960s.

The independent Board of Consultants (BOC) assigned to the Lake Oroville spillways project received a briefing on the findings and conclusions in this assessment and concurred with DWR in BOC Memo #11 and concluded the following, “The BOC completed an independent assessment of the vegetation that is on the downstream slope of the dam. The BOC notes the team’s assessment was thorough. The BOC concluded the source of water that affects the vegetation is not related to seepage originating from the reservoir and is not a dam safety concern.”

Is the vegetation assessment part of a larger, comprehensive evaluation of the dam?

Yes, the vegetation assessment will be included in the Comprehensive Needs Assessment currently underway at the Oroville Dam complex. The assessment will identify and prioritize future dam safety enhancements, after consultation with state, federal and independent experts. The assessment will be completed by the end of 2019 and will be shared with public. 

How are you managing lake levels and reservoir operations in 2017 and 2018 during construction?

The Lake Oroville 2017/2018 Winter Operations Plan will guide DWR reservoir operations at Lake Oroville from November 2017 to April 2018. To ensure public safety while construction continues, the plan calls for DWR to maintain lower-than-average lake levels during the winter months to provide space for inflows and manage releases from the substantially reconstructed main spillway.

The plan called for DWR to lower the lake level to an elevation of 700 feet by November 1, 2017, compared to the average 780 feet elevation maintained on that date in prior years. The lower level will provide more than 2.2 million acre-feet of flood reserve storage to accommodate inflows during the rainy season. In the event the reservoir rises quickly during the winter months, the operations plan identifies certain elevations at which DWR will increase outflows through the Hyatt Powerplant, the river valve outlet or the main spillway to safely manage lake levels.

Why is information labeled Critical Energy Infrastructure Information (CEII) redacted from certain documents about the Lake Oroville Spillways Emergency Recovery Project? What is CEII?

Following rules and guidelines set by the Federal Energy Regulatory Commission (FERC), DWR evaluates all public documents related to the Lake Oroville Spillways Emergency Recovery Project to identify information regarding specific engineering, vulnerability, or detailed design that could be useful to a person in planning an attack on critical infrastructure.

This information is deemed Critical Energy Infrastructure Information (CEII), and that information is redacted before the document is released publicly.

According to FERC, CEII is specific engineering, vulnerability, or detailed design information about proposed or existing critical infrastructure that: (1) relates details about the production, generation, transportation, transmission, or distribution of energy; (2) could be useful to a person in planning an attack on critical infrastructure; (3) is exempt from mandatory disclosure under the Freedom of Information Act, 5 U.S.C. 552 (2000) and the California Public Records Act, per 16 USC 824o-1(d); and (4) does not simply give the general location of the critical infrastructure.

Who is responsible for reviewing documents to determine whether they contain CEII?

DWR engineers and leadership make the final decision on what information is deemed to be labeled as CEII to protect public safety and infrastructure. DWR follows guidance from the Federal Energy Regulatory Commission on what constitutes Critical Energy Infrastructure Information.

DWR posted redacted FERC Part 12D reports. What is a FERC Part 12D report? What is its significance to the Lake Oroville spillways incident?

FERC Part 12D reports are a long-standing part of the monitoring and inspection process of hydroelectric facilities and dams under the jurisdiction of FERC.

Part 12D is a section of the report that requires an independent consult to conduct a detailed review of the design, construction, performance, and current condition assessment of an entire dam facility.

Independent consultants rely on a Potential Failure Mode Analysis (PFMA) and Supporting Technical Information Document (STID), as well as visual inspections. Independent consultants also review previous FERC Part 12D reports and then make recommendations for action by the dam owner based on their observations and analysis. These actions can include everything from maintenance to increased monitoring

DWR released FERC Part 12D reports to ensure all information is available relating to maintenance and inspections of Oroville Dam

What role did piezometers play in the original construction of Oroville Dam?

The piezometers, as well as a seepage collection and monitoring system, were installed upon initial construction of Oroville Dam to monitor and verify seepage in the dam during construction, during the lake’s first filling, and those first few years thereafter.

During construction of Oroville Dam in the 1960s, DWR installed 56 twin-tube hydraulic piezometers upstream, downstream, within the dam’s core, and in the dam’s foundation.

Engineers installed the piezometers with the understanding that the monitoring devices had a limited lifespan and would no longer function after several years. Two of the original piezometers within the dam’s core remain active and are currently monitored. However, these piezometers will eventually become non-functional and no longer monitored.

The dam’s seepage collection and monitoring system remains fully functional and provides all necessary information on seepage through the dam. The seepage collection system is designed to remain serviceable for the life of the dam.

How do you know the seepage collection system is still working?

In the fall of 2016, DWR initiated a study to analyze seepage and stability of the dam, including a thorough and thoughtful evaluation of all instrument data and future data needs.

The completed study will help DWR determine whether new piezometers or other instrumentation are appropriate. This includes assessing dam safety risk versus benefit, as installation of any instrumentation into the dam’s embankment could potentially create additional risks.

Any decision about piezometers would be reviewed and approved by the California Division of Safety of Dams (DSOD) and the Federal Energy Regulatory Commission (FERC).

Where can we find inundation maps for the Oroville area?

California’s inundation map program for dam failure is a responsibility of the Governor’s Office of Emergency Services (Cal OES) and is handled specifically under the Hazard Mitigation Program.

The Cal OES Dam Inundation Mapping and Emergency Procedure (DIMEP) Program was established by Government Code §8589.5 in 1972 following a near failure of the Lower San Fernando Dam during the Sylmar Earthquake.

The inundation map for an Oroville Dam failure can be found here. Please note that this map does NOT represent a spillway failure, only a total Oroville Dam failure.

Where can I find evacuation plans and inundation maps for the Oroville region?

Evacuation procedures and plans are developed at the county level and implemented by that county’s sheriff. Depending on the county you live in and number of resources, evacuation notices by phone and email may be available, as well as personalized evacuation maps for your address:

Butte County Office of Emergency Management

Yuba County Office of Emergency Services

Sutter County Office of Emergency Services

Will DWR share Board of Consultant memos and reports from the Independent Forensic Team?

Memos from the Board of Consultants and reports from the Independent Forensic Team are posted on our website.

Consistent with DWR policy and FERC guidelines, portions of some BOC memos are redacted to remove Critical Energy Infrastructure Information (CEII). DWR will follow this same protocol for each subsequent memo from the Board of Consultants.

Which California dams are managed by the state?

DWR’s Division of Safety of Dams maintains an alphabetical list of all California dams and reservoirs. The list includes basic information on each dam. DSOD has released extensive information about how dams in California are classified and monitored.

How often is the main spillway inspected?

The Oroville facilities, including the spillways, are inspected at least once a year by the Division of Safety of Dams, the California state regulator. The most recent inspection by DSOD prior to the February incident was conducted in August 2016. Oroville Dam and its facilities are also inspected once a year by the FERC Dam Safety Program. The most recent inspection by FERC was conducted in May 2016.

Oroville Dam and related structures including the spillways are also inspected by an independent board of expert consultants every five years. The most recent independent safety inspection was conducted in August 2014. These inspections of Oroville Dam and its spillways have concluded they were safe to operate. DWR is committed to using the information from reports and lessons learned to strengthen and improve dam safety operations, policies and procedures.

Is the California Division of Safety of Dams changing its review and inspection process for California’s dams?

In February, shortly after the incident, Governor Brown directed the California Natural Resources Agency to conduct more detailed evaluations of dam appurtenant structures, such as spillways, to include geologic assessments and hydrological modeling.

The California Division of Safety of Dams identified 93 dams that have spillways similar to Oroville Dam (size, age, type). Owners of these dams are being asked by DSOD to conduct a site-specific investigation on the integrity of the dam’s spillways.

DSOD will review and approve the dam owner’s investigation plan, and once they received the owner’s detailed evaluation, DSOD will conduct an independent review of the dam's appurtenances.

What role did weather play in the spillways incident?

January and February 2017 were the wettest months on record since the start of hydrology reports in the Feather River area more than 100 years ago. Additionally, 2016-2017 was also the wettest year on record in Northern California. This record-setting precipitation brought a massive amount of runoff to the region and Lake Oroville received an entire year’s average runoff, 4.4 million-acre feet, in about 50 days.

During the 2017 Lake Oroville spillways incident, a large winter storm, regularly referred to as an atmospheric river, brought more precipitation than was forecasted. Although DWR’s original modeling and forecasting avoided use of the emergency spillway, the larger-than-expected storm delivered higher inflows.

In total, more than five million-acre feet of water was released from Lake Oroville from February through May 2017 -- more than twice the amount that has ever been released from the main spillway.

Who approves the construction design of the new spillways?

The Federal Energy Regulatory Commission (FERC) and the California Division of Safety of Dams (DSOD) approved the Lake Oroville spillways construction plan for 2017. The independent Board of Consultants (BOC) also approved the construction plans for 2017 and provides continuous project oversight.

How does the 2017 construction design for the main spillway compare to when it was built in 1968?

Since 1968, advancements in the production of concrete and spillway designs in general have come a long way. New main spillway construction will feature a thicker slabs and walls, drain pipes and slab anchors. You can compare the original 1960s construction to new construction by looking at a construction specification fact sheet. 

How can the public stay up-to-date on construction work?

DWR shares as much of the construction progress as possible. Stay up-to-date with regular news releases from DWR about construction progress.

Aerial footage of the construction process can be watched at DWR’s YouTube channel.

Construction photographs can be found on DWR’s Facebook page.

A live feed of construction work on the main spillway can be viewed through the California State Parks website.

What is DWR doing about dust/air quality issues from construction?

DWR maintains an aggressive dust management program at the spillways construction site. Dust management includes regular watering of areas near controlled blasts, as well as wetting blast areas prior to blasting for additional dust management, and real-time dust monitors surrounding the work site perimeter to verify dust is not migrating beyond the construction site.

DWR is working with the Butte County Air Quality Management District to ensure that monitoring of dust plumes caused by heavy equipment and controlled blasting in the construction zone is compliant with local and state air quality regulations.

Is blasting that occurs at the construction site safe?

The construction blasting, known as “controlled light charge blasting,” is a safe and common practice at dam construction sites throughout the country.

Controlled light charge blasting methods are used to break up intact rock on the slopes so that it can be safely excavated. Seismographs are located throughout the project area to monitor movements and to make sure recorded vibrations are within safe levels.

DWR obtains required permits for the controlled light charge blasting from state and federal regulatory partners, as well as the Butte County Sheriff’s Department.

Why does Oroville Dam need to be re-licensed?

The license allows DWR to operate the hydroelectric power facilities and provides funding for recreation improvements around the lake. When the Oroville Dam facility is re-licensed, $500 million will be available for recreation updates throughout the life of the license. The original license expired in 2007 and has been extended each year. An alternative license agreement among more than 50 stakeholders was filed with the Federal Energy Regulatory Commission in 2006.

Also, the National Marine Fisheries Service filed its required Biological Opinion with FERC in December of 2016. The Opinion found no negative effects to fish populations from the re-licensing approval.

How much has been spent on repairs Oroville Dam in the past?

Repairs to the main spillway were conducted in 1997 and 2009. In 1997, contract amounts were for $340,000. In 2009, contract amounts were for $776,000.

Average annual expenses for maintenance and operation of Oroville Dam has been $20 million per year over the last five years. An estimated $30 million has been spent over the last five years on capital improvements to Oroville Dam.

Many parts of the main spillway are being built with roller-compacted concrete. Is this material safe and will it last until repairs are finished in 2018?

Yes, roller-compacted concrete is preferred because it dries quicker and reaches full strength faster than structural concrete. Many new dams in California are constructed entirely with roller-compacted concrete.

How much water will the reconstructed main spillway be designed to handle?

The Lake Oroville 2017/2018 Winter Operations Plan is designed to operate the partially reconstructed main spillway at no more than 100,000 cubic feet per second.

Just because the main spillway can handle high flows does not mean the department ever intends to increase releases to an unsustainable level for downstream areas. DWR works with the downstream flood districts to coordinate operations so that flows do not exceed the downstream levees.

Will DWR be requesting a modification to the Flood Control Manual?

Yes, Governor Jerry Brown sent a letter to the U.S. Army Corps of Engineers requesting an update to the 1970 flood control manual. As that process takes many years to complete, DWR worked with the Army Corps of Engineers to develop the Lake Oroville 2017/2018 Winter Operations Plan to guide reservoir operations throughout construction. DWR will continue short-term operation plan updates until the official process for updating the 1970 flood control manual is complete. The process will take several years to complete and includes input from the public.

Is DWR undergoing any internal changes?

DWR has requested additional positions to address critical work relating to infrastructure including dam safety in its 2018-19 budget proposal. The department also restructured its executive team to bolster dam and flood safety, emphasize climate resilience and incorporate lessons learned from recent impacts of extreme weather on the state’s water system.

The restructuring includes a new deputy director of flood management and dam safety and a deputy director of integrated water management and multi-benefit programs. These positions were previously combined under one deputy director. The deputy director for special initiatives, which is not a new position, is now also responsible for management of the sustainable groundwater management program.

What other ways is DWR keeping the public and local officials informed of developments?

DWR continues to conduct a robust public outreach program to update communities, elected officials and all who are interested in the spillways recovery project.

In 2017, the department conducted 12 public meetings in six communities, providing updates on construction progress, answering questions, and receiving comments. We also answered hundreds of phone calls and emails from the public and issued regular community updates via email.

From April through December of 2017, we also held bi-weekly conference calls with the news media to share up-to-date construction information. DWR also conducted regular briefings, in person and through conference calls, with elected officials and interested stakeholders.

In 2017 we also hosted construction site visits at the spillways to give elected leaders, public safety officials, and the media an up-close look at construction.

DWR also attends Butte County Board of Supervisors meetings and Oroville City Council meetings, and other county and city meetings in downstream communities. The department meets with local, state, and federal agencies in weekly meetings and participates regularly in Oroville Recreation Advisory Committee (ORAC) meetings.

What is DWR doing to address recreation facilities and future recreation projects?

The recovery efforts to reconstruct the spillways have had an impact on recreational access because of the temporary closure of the spillway boat ramp, parking lot, and Oroville Dam crest road. To off-set these temporary closures, DWR is working on nearly a dozen recreation projects that are in design, construction or scheduled to begin by the end of 2018.

The lower than average lake levels also present the best opportunity to construct low-level boat ramp expansions, which will increase year-round access for watercraft. Some of the currently scheduled recreation improvements expand existing structures, but others will result in completely new facilities. For example, two projects at Loafer Creek recreation area are entirely new boat ramp and parking lot facilities. DWR is fully committed to completing its recreation upgrade projects on an accelerated 24-month schedule. Normally, these projects take up to five years to complete. Regarding the status of the Spillway Boat Ramp, DWR intends to re-open this facility for public access once the Lake Oroville Spillways Emergency Recovery Project is complete in 2019.

Projects that are underway to off-set the temporary closure of the spillway boat ramp and parking lot includes:

• Lime Saddle Boat Ramp Parking Lot Expansion (currently under construction)
• Bidwell Canyon Boat Ramp Parking Lot and Ramp Expansion (currently under construction)
• Bidwell Canyon Stage 2 Parking Lot Expansion and Boat Ramp Lane Addition (construction later this year)
• Loafer Creek Stage 1 Parking Lot and Boat Ramp (construction later this year)
• Loafer Creek Stage 2 Parking Lot and Boat Ramp (construction later this year)
• Enterprise Boat Ramp Extension (planning/permitting in progress)
• Saddle Dam Trailhead Parking Improvements (phase 1 completed, additional construction later this year)
• Boat Ramp Shuttle Service (currently in-service and will be expanded as the recreation season heats up)

What is DWR doing to address the impacts on downstream levees?

DWR’s Department of Flood Management is completing the Feather River Conveyance Re-Evaluation study on the Feather River south of Marysville to the Sutter Bypass and in some parts of Feather River north to the Thermalito Afterbay.

DWR, USACE and the Sutter Butte Flood Control Agency are engaged in a $28.5 million repair to three miles of levees in Yuba City.

Is any action being taken to improve fish mitigation?

The Department of California Fish and Wildlife and DWR installed 5,000 cubic yards of spawning gravel near the Feather River Fish Hatchery in August 2017.

The California Department of Fish and Wildlife established production goals of 450,000 steelhead, two million spring run salmon, six million fall run salmon for mitigation, and one to two million fall run salmon for enhancement.

Is DWR changing how it shares information about reservoir releases and operations with the community?

Changes to operations and releases from the Oroville facility can be found at the Oroville Dam data exchange website. In Spring of 2017 DWR began providing advance notification of main spillway operations and significant flow changes, in coordination with Local Maintaining Agencies and County Offices of Emergency Services.

DWR has worked with individual growers to identify potential federal and state assistance for crop losses. Since 2007-2008 DWR has invested approximately $366 million for repairs and improvements in the Feather River basin to reduce flood risk and conduct system repairs.

During the 2017 February-March high water events, DWR provided over $4 million for direct assistance at six Feather River sites.

Is there a list of state, local, and other partners involved in the spillway repairs?

Visit our Partners page for descriptions and information on partner agencies and departments.

How did community members make claims with the state?

The Government Claims Program (GCP) processes claims for money or damages against the state. In general, anyone who wishes to file a lawsuit against the state or its employees for damages must first pursue an administrative remedy through the GCP claims process. Only if the claim is rejected or denied may the claim be pursued through the courts. In some cases, claims may be resolved through the GCP process.

The deadline to file claims related to the Lake Oroville spillways incident was August 11, 2017. Claims against the state had to be filed within six months of the incident. Call (800) 955-0045 or email gcinfo@dgs.ca.gov with questions about the GCP.

How do I contact DWR with a question or comment on the Lake Oroville Spillways Emergency Recovery Project? How do I stay up-to-date on social media or by email?

Phone: 1-800-248-7026

Email: Oroville@water.ca.gov

Twitter: @CA_DWR

Facebook: CADWR

YouTube Channel: www.youtube.com/user/calwater