OROVILLE, Calif. — With the first phase of the Oroville Dam reconstruction completed by their self-imposed Nov. 1 deadline, California officials are turning their attention to the massive amount of work that remains.
Construction crews will focus on dry finishing concrete, sealing concrete slab joints, completing drain lines behind the walls and general cleanup, said Niki Woodard, a Department of Water Resources spokeswoman.
Meanwhile, crews are about halfway done with an underground cut-off wall downhill from the emergency spillway that is scheduled to be built by the end of January, officials said.
The wall “will prevent uphill erosion if the emergency spillway is ever used again,” Woodard said in an email. She added that crews are also starting to prepare to build a roller-compacted concrete splashpad and buttress to ensure the structural integrity of the emergency spillway.
That project will begin next year, as will work to demolish, remove and rebuild the upper-most portion of the main spillway and bring the middle portion of the spillway to its final design with structural concrete, Woodard said.
“DWR is confident the project will be complete by the end of (Kiewit Construction’s) contract, which runs through January 2019,” she said. “Similar to this year, crews will complete reconstruction of the main spillway by Nov. 1, 2018, so it is ready to handle winter rains.”
The reconstruction will wrap up next winter with completion of the emergency buttress and splash pad and finishing work on the main spillway, she said.
Begun after the spillways’ near failure in February threatened a large portion of the eastern Sacramento Valley’s $1.5 billion agriculture industry as well as urban areas, the project proceeds as the area’s two state legislators continue to question the DWR’s management of the dam.
Assemblyman James Gallagher, R-Yuba City, and Sen. Jim Nielsen, R-Gerber, issued a joint statement Nov. 1 calling on the DWR to address sediment and debris buildup in the Feather River downstream that has resulted from the dam’s troubles. They also called for more transparency from the agency as plans are developed.
“We want to be clear that although today’s accomplishment is worthy of recognition, the work is far from complete,” they said. “It’s not enough to fix the spillways and move on. The impacts of this crisis have not been mitigated.”
Nielsen and Gallagher said a comprehensive needs assessment for the dam that is set to be finished by September 2019 “should be conducted completely independent of DWR and the other regulatory agencies that were responsible for the inspection work leading up to the collapse of the Oroville Dam spillways.”
But Woodard countered the DWR will remain involved in the assessment, working with other state and federal regulators and independent dam safety efforts to conduct it.
“As the owner of Oroville Dam, it is absolutely necessary that DWR be involved in the comprehensive needs assessment,” she said.
It’s not the first time lawmakers have criticized the agency’s management. Rep. Doug LaMalfa, R-Richvale, who represents the Oroville area, this summer questioned the DWR’s plan to draw down the lake’s surface to under 700 feet of elevation this winter.
LaMalfa argued that would leave only 850,000 acre-feet in the lake by the end of December with only about 100 days left in the winter to fill it. But state officials said they needed to drain it to leave enough room for storm runoff and still maintain safety for workers.
Lake Oroville is the main reservoir for the State Water Project, which irrigates more than 600,000 acres of Central Valley farmland and serves 20 million urban customers in the San Francisco Bay area and Southern California.
The state in April awarded the Omaha, Neb.-based Kiewit the contract for the reconstruction, even as some of its designs were still being drawn. The first phase was slated to cost $275.4 million, although DWR is expecting the final cost to come in much lower, at about $140 million to $160 million, Woodard said.
The DWR estimates the full cost of Kiewit’s work will exceed $500 million, though the estimate is likely to “evolve” as construction ramps up again next spring, Woodard said.