Roughly 188,000 people living downstream from Northern California’s Lake Oroville were ordered to immediately evacuate on Sunday afternoon after an emergency spillway releasing millions of gallons of water from the lake threatened to fail due to erosion. By late Sunday night, the situation had improved, but the evacuation order has yet to be lifted.
The lake, which is about 150 miles northeast of San Francisco, is held back by the 770-foot-tall Oroville Dam, the tallest in the country. Record storms took Lake Oroville from 80 percent full to overflowing in less than a week, as the L.A. Times explains. While the dam itself is structurally sound, last week a hole caused by erosion was discovered on the main spillway. It spread across the concrete-lined channel, and on Saturday the emergency spillway was used for the first time since the dam was completed in 1968.
Initially the system appeared to be working, but on Sunday engineers spotted a hole in the emergency spillway. At 4:20 p.m local time, an evacuation order was issued for everyone living downstream of Lake Oroville’s dam.
“They have what they expect to be an imminent failure of the axillary spillway,” said Mike Smith, a spokesman for the California Department of Forestry and Fire Protection. “What they’re expecting is as much as 30 vertical feet of the top of the spillway could fail and could fail within one to two hours. We don’t know how much water that means, but we do know that’s potentially 30 feet of depth of Lake Oroville.”
Residents of Butte, Sutter, and Yuba rushed out of the area, creating gridlock for miles. An evacuation shelter was set up in Chico, which is north of the lake, at the Silver Dollar fairgrounds. Belen Castaneda, 23, told the Times she was headed there with her family and an elderly neighbor who doesn’t speak English. “We just grabbed everything we could,” she said. “Everyone was freaking out.”
Late on Sunday night the threat decreased when water stopped flowing into the emergency spillway. Officials said they plan to use bags of rocks to plug the hole in the emergency spillway, but the situation is still precarious. Storms are forecast for later this week, and officials said they need to keep draining water from the lake for as long as possible.
California governor Jerry Brown issued an emergency order on Sunday night. “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,” Brown said in a statement. “The state is directing all necessary personnel and resources to deal with this very serious situation.”
Eight California National Guard helicopters will assist with the attempt to reconstruct the emergency spillway. All 23,000 soldiers in the California National Guard have been notified that they should be ready to deploy if needed. According to the AP, the entire California National Guard hasn’t been put on alert since the 1992 L.A. riots.