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After repairs, Oroville Dam deemed safe to operate

Ken James/Calif. Dept. of Water Resources Oroville Dam project
Workers from Kiewit Infrastructure lift and lower a slab anchor into a hole in the roller-compacted concrete on the middle chute of the Lake Oroville main spillway in Butte County, Calif., on June 25, 2018.
A team of experts will conduct ongoing monitoring and assessment of the facility, which almost collapsed in 2017.

A team of dam safety experts concluded a more than two-year review by determining that the reconstructed Oroville Dam complex in Northern California is safe to operate and that no more urgent repairs are needed.

The state Department of Water Resources initiated the needs assessment in January 2018, less than a year after the dam nearly collapsed amid heavy storms in February 2017.

The review supported several risk-reduction projects the DWR is already implementing, including installing new water pressure measurement devices to improve seepage monitoring and completion of a state-of-the-art seismic stability analysis, according to an agency news release.

DWR also is acting on recommendations to raise the nearby Parish Camp Saddle Dam by three feet, line the Palermo Canal in Butte County to reduce leakage and improve rock slope stability, and install new remote starter and power connections to the spillway radial gates to improve reliability, the release stated.

The DWR notes that since conditions can change over time, the agency will conduct ongoing monitoring and assessment of the Oroville complex.

“Public safety is at the core of DWR’s mission, and we are committed to continually evaluating the performance and safety of State Water Project facilities, including Oroville Dam,” DWR director Karla Nemeth said. “The comprehensive needs assessment report is an important step in our efforts to ensure the ongoing safety and reliability of facilities that provide water and flood control for millions of Californians.”

State officials are scheduled to present the review to an area citizens’ committee this morning during a virtual meeting.

Dam rebuilt

Crews in 2019 wrapped up a two-year, $1.1 billion emergency rebuild of the Oroville Dam. The dam is the centerpiece of the State Water Project, whose contractors irrigate about 750,000 acres of Central Valley farmland and serve more than 26 million customers, according to the project’s website.

A forensic team commissioned to study the dam’s near-failure issued a 584-page report in early 2018 that largely blamed a culture of complacency within the DWR that insulated the agency from access to industry knowledge and technical expertise to safeguard the dam and its mile-long spillway.

The latest needs assessment was done by a team that included engineers, hydrologists and other experts knowledgeable about Oroville Dam, as well as experts in risk analysis, according to the agency. An Independent Review Board oversaw the study, and a community-led group of elected officials and local organizations provided input.

The assessment comes amid a statewide effort to reduce risks to State Water Project facilities from major earthquakes and extreme weather. As part of the assessment, the DWR announced it will evaluate the concrete spillway and foundation at the Castaic Dam in Los Angeles County.

“Castaic Dam’s spillway assessments will help DWR prioritize further maintenance and potential improvements to continue the safe and reliable operation of State Water Project facilities,” said Ted Craddock, the project’s deputy director. “The Castaic facilities play an important role in water supply management in Southern California and also provide recreational opportunities for surrounding communities.”

The spillway assessments are expected to be completed by 2024, at which time the agency will modernize the dam’s structures, officials said.

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