The California Department of Water Resources (DWR) announced on Oct. 31 that it had met its goal of completely reconstructing the main spillway at Oroville Dam by Nov. 1 to be prepared for the upcoming winter.
The newly constructed spillway is now built to its original design capacity of 270,000 cubic feet per second.
Dry finishing, joint sealing, completing sidewall backfill and site clean-up on the main spillway will continue after Nov. 1. DWR says the concrete on the main spillway will have cured by Dec. 1, in time for the rainy season and use of the main spillway if necessary.
“More than 700 construction workers, many of them from Butte County and other parts of Northern California, literally worked day and night to make incredible progress during the 2018 construction season,” said Tony Meyers, DWR project manager for the Oroville Spillways Emergency Recovery Project. “Staff from nearly every corner of DWR worked on the project in some capacity over the past year and a half and their planning, execution and hard work contributed to meeting this November 1 milestone.”
The final erosion-resistant concrete (ERC) slab was placed on Oct. 11. Crews placed a total of 378 ERC structural slabs in 2018. Combined with last year’s work, 612 new concrete slabs have been installed.
Crews placed the final ERC wall on Oct. 18. Crews placed a total of 126 ERC walls in 2018.Together with last year’s work, 204 new concrete walls have been installed.
Final concrete placements on the energy dissipaters, or dentates, at the base of the main spillway were completed on Oct. 20.
The roller-compacted-concrete (RCC) splashpad was completed on Oct. 26. Crews placed about 700,000 cubic yards of RCC on the splashpad.
Crews also completed construction of the RCC buttress at the base of the emergency spillway earlier this month.
Placement of a structural concrete cap connecting the RCC buttress to the emergency spillway structure will be complete in early 2019.
DWR says it has completed an operations plan for the 2018-19 flood season that will guide reservoir operations from November 2018 through April 2019. The plan calls for DWR to maintain lower-than-average lake levels during the winter months to provide operational flexibility to ensure flood protection, meet water deliveries, meet environmental requirements, and prevent use of the emergency spillway this winter, as construction will continue on the emergency spillway into early 2019. DWR updated the plan with recommendations from the U.S. Army Corps of Engineers, Federal Energy Regulatory Commission and Division of Safety of Dams.
The Oroville Dam Safety Comprehensive Needs Assessment (CNA) Ad Hoc Group met for the second time on Oct. 30. The Ad Hoc Group consists of 12 community members appointed by State Senator Jim Nielsen and Assembly Member James Gallagher to provide community perspectives to both DWR and an Independent Review Board of dam safety experts throughout the CNA process.