OROVILLE SPILLWAYS CONSTRUCTION: March 21 update (with photos & video)

A drone view of the construction site for a new access road just below the Lake Oroville main spillway and four energy dissipator blocks in Butte County, California. Photo taken March 19, 2018.
Kelly M. Grow/ California Department of Water Resources

Underground secant pile cutoff wall now complete; Main spillway construction to begin in May

From the Department of Water Resources:

Today the Department of Water Resources (DWR) provided an update on construction activities for the Lake Oroville Spillways Emergency Recovery Project.  

Construction at the Emergency Spillway

  • The underground secant pile cutoff wall was completed March 7, 2018 and marks a major milestone for 2018 construction. The secant pile wall is 1,450 feet long and located 730 feet downhill of the emergency spillway at depths of 35 to 65 feet.
  • On Feb. 28 crews began construction of the roller-compacted concrete (RCC) splashpad, which will cover the hillside between the emergency spillway and secant pile wall. The splashpad, in conjunction with the secant pile wall, will armor the existing terrain to significantly reduce the type of uphill erosion that occurred during the February 2017 incident.
  • Later this year, an RCC buttress will be constructed adjacent to the emergency spillway to provide further reinforcement.

Construction on the Main Spillway

Phase Two of construction on the main spillway is expected to begin in May and is dependent on weather. This year’s work includes:

  • Demolition of the original 730 feet of the upper chute leading to the radial gates and reconstruction with steel-reinforced structural concrete slabs and walls.
  • Placement of 2.5-foot, steel-reinforced structural concrete slabs over the RCC middle chute.
  • Removal of the RCC walls in the middle chute and replacement with structural concrete walls.
  • Hydro-blasting and resurfacing of the energy dissipaters at the base of the main spillway.

DWR also began conducting early preparation work on the RCC middle chute by temporarily sealing its surface. Later this spring, crews will begin resurfacing the top layer of RCC to create a uniform surface before placement of steel-reinforced structural concrete slabs.  

Additional Updates

  • At the request of the Federal Energy Regulatory Commission (FERC), DWR submitted its outline to address recommendations and findings in the Independent Forensic Team’s final report.
  • The 2017/18 Lake Oroville Winter Operations Plan will be updated after DWR’s April 1 snowpack survey. The updated Plan will account for snowpack runoff forecasts and reservoir conditions for the remainder of the rainy season.
  • DWR will meet with the Independent Board of Consultants (BOC) for the 16th time on March 28 and 29. DWR will post the BOC’s memo recapping this meeting on the Lake Oroville spillways webpage when it is received.

The latest video from Department of Water Resources …

Crews work on the cut-off wall, installing the final rebar cages into the 80-foot holes and filling with concrete. Roller-compacted concrete (RCC) continues to be laid for the splashpad between the emergency spillway concrete weir and cut-off wall. Dental concrete is poured below the dentates of the main spillway for a new construction road.

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