Water & Drought

Why the state is in such a hurry to fix Oroville Dam

See pouring of concrete foundation as part of Oroville Dam spillway repair

Pumped concrete is being put down at Oroville Dam this week (July 11, 2017) as part of the new concrete foundation and drainage system for the Lake Oroville flood control spillway. Demolition and rock cleaning continues, as does work on the emerge
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Pumped concrete is being put down at Oroville Dam this week (July 11, 2017) as part of the new concrete foundation and drainage system for the Lake Oroville flood control spillway. Demolition and rock cleaning continues, as does work on the emerge

California officials are trying to speed up repairs on Oroville Dam’s battered flood-control spillway.

The Department of Water Resources have asked federal regulators to let it demolish and replace an additional 240 feet of the spillway’s 3,000-foot concrete chute before the rains comes this fall, leaving less work for next year.

That 240-foot section originally was going to be replaced next summer as part of the two-year plan for repairing the spillway, whose massive structural problems in February sparked the emergency evacuation of 188,000 downstream residents.

Now DWR officials believe that 240-foot section, in the upper portion of the spillway, should be replaced this year to make certain the entire spillway can be rebuilt by the fall of 2018. Erin Mellon, spokeswoman for DWR’s parent agency the Natural Resources Agency, said officials want to leave little to chance next year.

“Next year’s construction season could be impacted if we have drought, or if we have excess rainfall,” she said. Officials are “making sure that we can fit in as much as we can this year.”

DWR officials made the request to blast the additional 240 feet in a letter to the Federal Energy Regulatory Commission, which licenses Oroville Dam and must approve all aspects of the spillway reconstruction project.

“After recent schedule evaluations and meetings with the contractor, we have determined it necessary to remove and reconstruct an additional 240 feet ... of the upper chute to ensure the project can be completed in two construction seasons,” DWR project manager Ted Craddock wrote. The letter was sent Monday and posted on FERC’s website Tuesday.

Mellon said the request for additional demolition this summer reflects a fine-tuning of the construction schedule, not a dramatic overhaul. If OK’d by the federal agency, it would increase the portion of the spillway demolished and replaced this season by about 10 percent.

“It was always in flux,” she said of the construction calendar. “This is getting closer to the final design plan.”

DWR’s contractor, Kiewit Corp., is demolishing and rebuilding the lower two-thirds of the spillway this year, including the portion heavily damaged in February. The upper portion escaped significant damage but will be replaced anyway next year.

State officials say this year’s repairs will be sufficient to make the spillway operational when the rainy season resumes in November. Mellon said the latest wrinkle in the construction plan won’t change that.

DWR’s desire to speed up the timetable this year did create a hiccup with federal officials. A portion of the spillway in the vicinity of the 240-foot section was demolished without FERC’s approval, bringing a rebuke from the federal agency and a temporary halt in all blasting. Demolition has since resumed, Mellon said.

How much concrete, rebar and pipe will it take to rebuild the lower spillway at Lake Oroville? Check out these numbers.

Dale Kasler: 916-321-1066, @dakasler

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