Lake Oroville Spillways Construction Updates Jan. 26, 2018

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Oroville Construction Update

Crews work on the underground cut-off wall on the emergency spillway at Lake Oroville. Jan. 24, 2018, DWR.

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

Cost Update

DWR is submitting to the Federal Emergency Management Agency (FEMA) estimated emergency response and recovery effort costs totaling $870 million, which covers completion of the project through January 2019. FEMA reimburses up to 75 percent of the requested costs for a federal emergency. To date, the Agency has approved reimbursement of $86.9 million of the $115.9 million submitted by DWR.

  • Emergency recovery: The estimated cost of the Lake Oroville Spillways Emergency Recovery Project through January 2019 is $710 million, with major components including:
    • $500 million for main and emergency spillways work through the contract with Kiewit Infrastructure West. 
    •  $210 million for related recovery work including debris and sediment removal, powerline replacement, permitting and development of access roads, staff time, technical consultants and inter-agency support. 
    • Cost estimates are based on projected work and may evolve as work continues.
  • Emergency response: The estimated cost for emergency response, which ended in May of 2017, is $160 million. This is nearly $115 million less than the initial emergency response cost estimate of $274 million. Response included erosion mitigation for both spillways during the incident, sediment removal, installation of temporary transmission lines, staff time, technical consultants and inter-agency support.

Construction Update on the Main Spillway

Phase Two of construction on the main spillway is expected to start in May, but exact timing depends on weather. Phase Two work includes the following:

  • The original 730 feet of the upper chute leading to the radial gates will be removed and replaced with structural concrete.
  • A 2.5-foot layer of structural concrete will be placed over the roller-compacted concrete (RCC) middle chute. The RCC walls in the middle chute will be removed and replaced with structural concrete walls.
  • The energy dissipaters at the base of the main spillway will be hydro-blasted and resurfaced.

     In order to protect public safety, the department and its construction contractor adhere to a high quality of work and regularly evaluate the work at each step in the construction process. While the vast majority of work completed to date meets or exceeds engineering standards and specifications from the original contract, DWR’s comprehensive quality control program has identified some items for further evaluation and possible additional work. Though the items meet engineering standards and do not impact any potential use of the spillway during the current rainy season, they may not meet the exact specifications of the contract. DWR, contractors, and oversight groups will determine whether additional work is required during Phase Two of construction.

  • As anticipated, rainwater has collected on the hillside adjacent to the temporary RCC portion of the spillway. As RCC is more permeable than structural concrete, a small amount of water has seeped through the RCC walls onto the chute. DWR is monitoring and documenting the event which will inform any decisions about potential future remediation. As noted above, the RCC walls will be replaced with structural concrete walls later this year.
  • Of the 234 structural concrete slabs placed in the 2017 construction season, three have surface imperfections that may require corrective action in 2018. These slabs will not impact short-term use of the spillway. The concrete on these slabs did not cure as anticipated for the following reasons:
    • Design specifications require all concrete pours within a slab to be poured within a certain amount of time of one another to allow the slab to cure properly. An unscheduled outage of the structural concrete plant led to delays in concrete placement.
    • Hot, high winds dried the surface of the slabs before the contractor could finish final surfacing work that results in a smooth surface.
  • A small section of the structural concrete wall is 1 percent out of alignment vertically with the surrounding walls. Studies show no impact to hydraulics, however DWR and consultants are reviewing to determine whether remediation will be necessary during the next construction season.

Construction at the Emergency Spillway

  • Work continues at the emergency spillway, and the underground secant pile wall is targeted for completion in March 2018.
  • Foundation preparation continues for the roller-compacted concrete (RCC) splashpad. The RCC splashpad, in conjunction with the secant pile wall, will armor the existing terrain thereby reducing the type of uphill erosion that occurred during the 2017 Lake Oroville spillways incident. 
  • The replacement of the emergency spillway crest wall is complete, finishing up earlier this month.
  • Work at the emergency spillway also includes an RCC buttress at the base of the emergency spillway, which will begin later in 2018.

 Oversight Update

  • DWR is scheduled to meet with the Independent Board of Consultants (BOC) for the 15th time on Feb. 22 and 23. The BOC will also be reviewing the Independent Forensic Team’s final report released earlier this month.

 

To view photos and video of the Lake Oroville Spillways construction, visit DWR’s Oroville Spillway photo gallery and YouTube channel.

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For more information, follow us on Twitter or Facebook, read our news releases or visit our Oroville Spillway Incident webpage.

Contact: Erin Mellon, Assistant Director, Public Affairs, Department of Water Resources, (916) 651-2440, erin.mellon@water.ca.gov