Update: Concern at Oroville Spillway triggers evacuation orders

Oroville, Calif. — In an update issued Monday evening, Feb. 13, the California Department of Water Resources (DWR) said that the primary spillway continues to flow at 100,000 cubic feet per second (cfs) and Oroville Lake levels had dropped to 894’ feet.

After evaluating the erosion on the emergency spillway, a plan was put in place to prevent further erosion. Utilizing trucks and helicopters, crews moved large rocks and gravel to fill erosion on the emergency spillway. DWR staff continues to inspect and evaluate the emergency and primary spillways for further erosion.

DWR said that total discharges from the reservoir remain consistent with flood control releases at this time of year under these weather conditions and it does not expect the discharge from the reservoir to exceed the capacity of any channel downstream.

Counties and cities near Lake Oroville and the surrounding area had been issued evacuation orders for residents. The concern was that erosion at the head of the auxiliary spillway threatened to undermine the concrete weir and allow large, uncontrolled releases of water from Lake Oroville. Those potential flows could exceed the capacity of downstream channels.

To avert more erosion at the top of the auxiliary spillway, DWR doubled the flow down its main spillway from 55,000 cubic feet per second (cfs) to 100,000 cfs. Flow over the auxiliary spillway weir began Saturday morning, Feb. 11.

Oroville Dam itself is sound, according to DWR, and is a separate structure from the auxiliary spillway.