Oroville Spillways Incident Background

January and February 2017 were some of the wettest months on record in the 110-year history of the Feather River hydrologic record. The Feather River watershed above the Oroville reservoir received an entire year’s average runoff – 4.4 million acre-feet – in 50 days during those two months. It was during this unprecedented weather system that DWR discovered damage to Oroville’s main spillway on February 7, 2017, during routine visual inspections.

Over the next week and a half, DWR would manage multiple risks, from safeguarding the operations of Hyatt Powerplant to preserving powerlines towers to maintaining flood control releases, all while managing a rapidly-filling reservoir with a damaged main spillway.

As a large atmospheric river storm settled over the Feather River basin, massive inflows and higher than expected precipitation increased lake levels rapidly. For the first time in the Oroville spillways history, the lake reached 901 feet and activated the emergency spillway, an uncontrolled concrete weir that allows water poured over onto a bare hillside.

An evacuation order for the City of Oroville and multiple downstream communities along the Feather River was soon ordered by the Butte County Sheriff’s Office due to concerns about downhill erosion threatening the emergency spillway structure. Residents returned home a few days later after increased releases from the main spillway reduced the lake level below 901 feet.

DWR immediately mobilized a coordinated emergency response effort with local, state and federal partners, monitoring the Oroville facilities, dredging the Thermalito Diversion Pool and drafting preliminary redesigns of the Oroville spillways.

While emergency response efforts continued into the spring of 2017, DWR began a robust community engagement program to keep the public informed about the emergency response and its plans to repair and reconstruct the spillways. DWR held community meetings for impacted communities, answered hundreds of email and telephone questions and shared regular email updates to the public throughout 2017.

Please reference the timeline below for more background information.

Timeline of Events February 7-March 17, 2017

View day-by-day accounts of the Lake Oroville spillway incident below. You can also refer to our news releases for more detailed information.

Recovery Project Contract Award

In April of 2017 Kiewit Infrastructure West was officially selected as the main construction partner to help rebuild the Oroville spillways.

Kiewit is one of North America’s largest and most respected construction and engineering organizations. The employee-owned company operates through a network of offices and projects in the United States, Canada and Australia. Nearly all construction projects are staffed by one or more owners of the company. To learn more about Kiewit, visit their website.

The majority of construction workers on the Oroville spillways project hired by Kiewit were from Northern California, specifically Butte, Yuba and Sutter counties.

Kiewit was one of three original bids for the project. Below are bid amounts:

  • Kiewit Infrastructure West Co. $275,443,850
  • Barnard Ames JV: $276,965,690
  • Oroville Dam Constructors: $344,129,100

Community Engagement

In 2017, DWR held a series of community meetings in April, May, July, and December. The first series of meetings, held between April 27 and May 15, 2017 were held in Gridley, Oroville, Marysville, Yuba City, Chico, and Sacramento to provide an opportunity for community members to learn about Oroville Spillways response and recovery effort, ask questions, and provide feedback. 

*Meeting materials are available upon request.