Oroville Spillways Construction and Cost Estimate Update


A drone provides an overview of the recovery effort on the upper chute of the Lake Oroville main spillway and the emergency spillway splashpad

A drone provides an overview of the recovery effort on the upper chute of the Lake Oroville main spillway and the emergency spillway splashpad on the hillside above the secant pile wall at the Butte County, California site. DWR/2018

SACRAMENTO – The Department of Water Resources (DWR) today provided an update on construction activities and estimated costs for the Oroville Spillways Emergency Recovery Project.

Main Spillway

  • November 1, 2018 is a public safety construction milestone to complete placement of all concrete on the main spillway. Dry finishing, concrete curing, joint sealing, completing sidewall backfill and site clean-up on the main spillway will continue after November 1.
  • The upper chute is 63 percent complete. Crews have placed 50 of 150 erosion-resistant concrete (ERC) structural slabs and two of 50 ERC structural walls on the uppermost 730 feet of upper chute.
  • The middle chute is 77 percent complete. Crews continue to place ERC structural slabs and walls on the middle chute. To date, crews have placed 175 of 228 slabs and 51 of 76 walls.
  • Repair work on the dentates is 45 percent complete. Placement of reinforcing steel and ERC slabs on the energy dissipaters, or dentates, at the base of the main spillway is ongoing. 

Emergency Spillway

  • Placement of roller-compacted concrete (RCC) on the southern half of the emergency spillway splashpad is 72 percent complete. Crews have temporarily stopped RCC placement for scheduled maintenance on the RCC batch plant. RCC placement will resume on Monday, Sept. 10.
  • The RCC buttress at the base of the emergency spillway will be built later this year. Drilling of steel dowels into the emergency spillway monolith structure that will support the buttress is complete.
  • Work at the emergency spillway site is not dependent on the public safety construction milestone and will continue past November 1, 2018.

Other Updates

  • Work continues on an underground transmission line project along Oro Dam Boulevard East between Glen Drive and Canyon Drive. One-way traffic controls are in place from 6 a.m. to 6 p.m. and will continue until the project is complete in mid-October.
  • The speed limit has been reduced to 25 mph on this stretch of Oro Dam Boulevard East and cars will not be allowed to stop on the road. There are several designated turn outs for cars to pull over to get a view of the Oroville spillways construction site.
  • September 6 and 7 are the next free access dates at the Lake Oroville State Recreation Area, which completes DWR’s free access program.
  • DWR will meet with the independent Board of Consultants for the 20th time on September 5 and September 6.

Cost Estimate Update: As work continues to meet the November 1, 2018 public safety construction milestone to fully reconstruct the main spillway, DWR has updated its cost estimates. The current estimate for emergency response and reconstruction of the main and emergency spillways is $1.1 billion. Cost estimates are based on actual and projected work and may be adjusted further as work continues through completion of the project in 2019.

DWR will continue to submit expenditures to the Federal Emergency Management Agency (FEMA) for reimbursement. To date, FEMA has approved reimbursement of $87.4 million of the $116.5 million submitted by DWR.


Emergency Recovery: The current estimated cost of the Oroville Spillways Emergency Recovery Project through 2019 is $940 million, with major components including:


  • $630 million for main and emergency spillways work through the contract with Kiewit Infrastructure West.
  • The updated estimate reflects additional excavation on the emergency spillway hillside to reach competent rock, additional material for construction of the splashpad, and additional crews and equipment necessary to meet the November 1 public safety construction milestone.


  • $310 million for related recovery work including debris and sediment removal, powerline replacement, permitting and development of access roads, DWR staff time, technical consultants and inter-agency support.
  • The updated estimate reflects additional staff time, technical consultants and inter-agency support to meet the November 1 public safety construction milestone, and an estimate for site restoration that will occur after construction of the spillways is complete.

Emergency Response: The estimated cost for emergency response, which ended in May of 2017, remains unchanged at $160 million. Response activities included erosion mitigation for both spillways during the incident, sediment removal, installation of temporary transmission lines, staff time, technical consultants and inter-agency support.


DWR awarded an initial $275 million contract in April 2017 to Kiewit to immediately plan and mobilize crews and equipment to begin construction in May 2017. This budget allowed Kiewit to begin necessary work while the project design was completed, and was not an estimate of the total project cost. Final plans for the main spillway were completed in July 2017 and final design plans for the emergency spillway were completed and approved in August 2018.


As with any project of considerable magnitude, cost estimates are affected by conditions onsite and direction from regulatory bodies throughout design and construction.


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


Erin Mellon, Assistant Director, Public Affairs, Department of Water Resources

(916) 651-2440 | erin.mellon@water.ca.gov