At least 188,000 people were asked to evacuate their homes in Northern California after authorities warned an emergency spillway in the country’s tallest dam was in danger of failing Sunday and unleashing uncontrolled flood waters on towns below.
Lake Oroville, about 150 miles northeast of San Francisco, is one of the state’s largest man-made lakes, and the 770-foot-tall Oroville Dam is the tallest in the U.S.
Sunday’s evacuation order came because of concerns the dam’s emergency spillway could fail. Over five hours later, hundreds of cars carrying panicked and angry people were sitting in gridlocked traffic.
“The police came and told us to evacuate,” said Kaysi Levias who was with her husband, Greg, at a gas station as they attempted to flee.
Officials warned residents that the spillway could fail within an hour.
“I’m just shocked,” Greg Levias said. “Pretty mad.”
“Not giving us more warning,” said Kaysi, finishing his sentence.
“We’ve never been through this before,” said Kaysi Levias. “We have two boys and our dog. All the stuff we could fit in the trunk — clothes and blankets.”
“This is very serious” California Department of Forestry and Fire Protection spokesman Scott McClean told the SF Gate as he was stuck in massive amounts of traffic. “I’m just trying to get through traffic.”
What they couldn’t fit they piled as high as they could in their downstairs Yuba City apartment and joined the line of traffic attempting to leave the city where they had moved just three weeks ago.
The cities of Oroville, Gridley, Live Oak, Marysville, Wheat land, Yuba City, Plumas Lake and Olivehurst were all under evacuation orders. The order was sent out at around 4 p.m. after engineers discovered a hole that was eroding back toward the top of the spillway.
The erosion at the head of the emergency spillway threatens to undermine the concrete weir and allow large, uncontrolled releases of water from Lake Oroville, the California Department of Water Resources said. Those potential flows could overwhelm the Feather River and other downstream waterways, channels and levees.
Officials say Oroville Lake levels had decreased by Sunday night as they let water flow from its heavily damaged main spillway but noted that water was still spilling over the dam.
Butte County Sheriff Koney Honea said engineers with the Department of Water Resources informed him shortly after 6 p.m. that the erosion on the emergency spillway at the Oroville Dam was not advancing as fast as they thought.
“Unfortunately they couldn’t advise me or tell me specifically how much time that would take so we had to make the very difficult and critical decision to initiate the evacuation of the Orville area and all locations south of that,” he said. “We needed to get people moving quickly to save lives if the worst case scenario came into fruition.”
Honea said there is a plan to plug the hole by using helicopters to drop rocks into the crevasse.
The California Department of Water Resources said it was releasing as much as 100,000 cubic feet per second from the main, heavily damaged spillway to try to drain the lake.
Department of Water Resources spokesman Kevin Dossey told the Sacramento Bee the emergency spillway was rated to handle 250,000 cubic feet per second, but it began to show weakness Sunday at a small fraction of that. Flows through the spillway peaked at 12,600 cubic feet per second at 1 a.m. Sunday and were down to 8,000 cubic feet per second by midday.
Water began flowing over the emergency spillway at the dam on Saturday after heavy rainfall damaged the main spillway.
Unexpected erosion chewed through the main spillway earlier this week, sending chunks of concrete flying and creating a 200-foot-long, 30-foot-deep hole that continues growing. Engineers don’t know what caused the cave-in, but Chris Orrock, a spokesman for the state Department of Water Resources, said it appears the dam’s main spillway has stopped crumbling even though it’s being used for water releases.
Northern California is set for another round of rain on Wednesday. The storms are expected to bring about 4 inches of rain to parts of the Central Valley, according to the SF Gate.
“We need to do everything we can to maximize our ability to move water our of this reservoir — not just for the coming storm but for the coming storms,” said Bill Croyle, acting director of department of water resources. “Our planning is both short term and long term.”