Only a day after water began spilling out of Lake Oroville down a never-used emergency spillway, officials ordered residents to leave areas downstream from Oroville Dam "immediately." A hole was spotted in the auxiliary spillway, raising fears that it could collapse and send a wall of water down the Feather River. Officials said Oroville Dam itself is not at risk, but then they said that about the emergency spillway too when it began to see its first water on Saturday.
On Sunday at 4:42 p.m., the state Department of Water Resource tweeted:
EMERGENCY EVACUATION: Auxiliary spillway at Oroville Dam predicted to fail within the next hour. Oroville residents evacuate northward.— CA - DWR (@CA_DWR) February 13, 2017
An estimated 188,000 residents began to evacuate in Butte, Sutter and Yuba counties late. By Sunday night, officials said the lake level had fallen below the lip and water had stopped flowing over the emergency spillway. The evacuation order remained in effect, probably overnight.
Efforts Sunday night to manage the damage included the use of helicopters to drop boulders onto the damaged spillway and the hillside below the lip.
"I’ve been in close contact with emergency personnel managing the situation in Oroville throughout the weekend, and it’s clear the circumstances are complex and rapidly changing,” Gov. Brown said Sunday night. “I want to thank local and state law enforcement for leading evacuation efforts and doing their part to keep residents safe. The state is directing all necessary personnel and resources to deal with this very serious situation.”
The state Department of Water Resources has for days been releasing a high flow of water down the regular, damaged spillway of Oroville Dam trying to lower the level of the lake. They upped the flow today to 100,000 cubic feet per second, which is dumping a lot of water. They would like to lower the lake enough to handle the expected new inflow from weather later this week.
The dramatic photos and news video of whitewater raging below the dam are of the controlled discharge down to the main concrete spillway. The area of concern is the auxiliary spillway (below) down a raw hillside on the face of the earthen dam.
The evacuated areas include the cities of Oroville, Marysville, Gridley, Biggs, Yuba City and other towns along the rivers. An actual dam break up there would be disastrous along the Feather River and south into Sacramento. The Los Angeles Fire Department and other agencies are sending swift-water rescue teams to Butte County in case they are needed. The California National Guard has also been placed on alert status, per Twitter.
What does official urgency look like on Twitter?
ALERT!!!! Evacuation ordered for all Yuba County on the valley floor. Travel safely. https://t.co/BrRpXUJiX5— Yuba County (@YubaCounty) February 13, 2017