California Dam Repair Costs to Top $500M

California officials say repair costs at the nation’s tallest dam will be nearly double the original estimate of $275 million.

Department of Water Resources spokeswoman Erin Mellon said Thursday the contract with Kiewit Corp. at 770-foot Oroville Dam will grow to more than $500 million.

Kiewit project director Jeff Petersen said the project has required significantly more excavation and concrete than expected.

The main spillway and emergency spillway suffered significant damage during storms last February, prompting fears of massive flooding. Tens of thousands were evacuated but disaster was averted.

Construction crews in California began demolishing the destroyed portion of the main spillway back in May. Using heavy equipment and explosives, crews cleared away sections of concrete and rebar that had not already washed away.

By August, 500 employees will be on the site, with work spanning 20 hours a day, six days a week, said Jeanne Kuttel, chief engineer for the project with the California Department of Water Resources.

Crews aim to replace the lower portion of the spillway by Nov. 1, when winter rain and snow increase the flow of water into the lake. They’ll reinforce concrete near the top of the structure, which was not damaged then tear it out and replace it next year.

Plans for the emergency spillway call for drilling 30 to 50 feet into the ground and building a wall anchored to the bedrock in order to prevent erosion. Next year, crews will reinforce the hillside.