Oroville Dam’s repair estimates jump to $275 million

Crews work near the Oroville Dam spillway on April 6. Crews work near the Oroville Dam spillway on April 6. Photo: Dan Reidel, Associated Press Photo: Dan Reidel, Associated Press Image 1 of / 30 Caption Close Oroville Dam’s repair estimates jump to $275 million 1 / 30 Back to Gallery

California water officials Monday awarded a $275 million contract to repair the troubled Oroville Dam to a subsidiary of one of the world’s largest construction companies that is headquartered in Omaha, Nebraska.

At $275.4 million, the bid from Kiewit Infrastructure West Co., a division of international firm Kiewit Corporation, came in about $1.5 million under a second bid and was the least expensive of three submitted.

Still, the winning bid was nearly $44 million more than the Department of Water Resources’ projection of $231.7 million.

The second-placed bid of $277 million was submitted by a subsidiary of Montana-based Barnard Construction Co. Oroville Dam Constructors, a partnership of California companies, bid $344 million.

The job involves mending two spillways that gave way in February, threatening to flood tens of thousands of homes. The work is complicated by the fact that the cause of the damage has yet to be determined.

Much of the construction will have to be done on the fly, state officials say, as the winning contractor works alongside government experts to probe deeper into the reservoir’s problems and find ways to restore the spillways in time for possible outflows next winter.

“It’s scary when you say, ‘I’m going to tell these contractors to do it right this time,’ when you really don’t know what right is,” said Bob Bea, a professor emeritus and engineering expert at UC Berkeley. “I don’t think we have a clear vision of the long-term fix.”

The state Department of Water Resources is dealing with an unprecedented infrastructure failure that has made it difficult to control water releases at the nation’s tallest dam. On Feb. 7, Lake Oroville’s main spillway cracked amid heavy outflows, prompting dam managers to rely on an emergency spillway that also partially crumbled. Fears that water would rush uncontrollably down the Feather River prompted the evacuation of 180,000 people.

State officials have resumed limited releases at the reservoir, but they have not said what went wrong and have declined to make public the opinions of their consultants, citing security concerns.

On Monday, UC Berkeley’s Center for Catastrophic Risk Management released a report authored by Bea that identified a host of problems.

First, Bea said, the main spillway at the 50-year-old reservoir was not designed to meet today’s standards. For example, the concrete was too thin and not adequately anchored, according to the report. The finding is similar to what several state consultants said before officials started making their reviews confidential.

Second, the state failed to do adequate maintenance at the site, Bea said. For instance, he said, officials did not repair cracks in the spillway that allowed water to seep in and weaken the structure.

“Complex systems fail in complex ways,” Bea said.

State officials had originally estimated the cost of the construction at $220 million, before issuing a revised estimate Monday of $231 million.. That was up from a projected $100 million to $200 million when the reservoir’s problems first surfaced.

The scope of the work is not entirely clear because the state has declined to release the contract that was put to bid, again citing security concerns.

The winning contractor, though, is expected to partially rebuild and stabilize both spillways before November. What isn’t finished by the onset of the next rainy season will be done in the summer of 2018. The large fracture in the hillside along the main spillway where water continues to pour is also scheduled to be fixed next year.

The Department of Water Resources has not said where the money will come from for the repairs. The big agencies that buy water from Lake Oroville are likely to contribute a large portion of the funding, as is the federal government.

Kurtis Alexander is a San Francisco Chronicle staff writer. Email: kalexander@sfchronicle.com Twitter: @kurtisalexander