OROVILLE — At least 188,000 people were asked to evacuate in Northern California after authorities warned an emergency spillway at Oroville was in danger of failing Sunday and unleashing uncontrolled flood waters on towns below.
Sunday’s evacuation orders for of Oroville, Gridley, Live Oak, Marysville, Wheatland, Yuba City, Plumas Lake, and Olivehurst were all under evacuation orders came on the heels of heavy rains that triggered the partial melting of the heaviest Sierra snowpack in 22 years.
Oroville — the state’s second largest reservoir with 3,537,577 acre feet of capacity — is the largest earth dam in California and the highest dam in the United States at 770 feet.
The San Joaquin County Office of Emergency Services was on alert Sunday when the Mokelumne River near Thornton in the north county reached flood stage and then started to recede.
Crews have been monitoring San Joaquin River levees due to heavy releases upstream. Don Pedro Reservoir, as an example on the Tuolumne River was at 98 percent capacity on Sunday as dam operators worked to keep a cushion between inflow and outflow.
The situation is being helped greatly by New Melones. On Sunday the reservoir was taking in 19,084 cubic feet of water a second — of the equivalent of 19,804 basketballs passing a specific point in a given second. The Bureau of Reclamation was only releasing 17 cubic feet per second. The reservoir in the past 10 days has increased its capacity 10 percent but is still at only 54 percent of is 2.4 million acre foot capacity.
Similar heavy rains that hammered an unusually heavy December 1996 snow triggering an early and heavy snow melt that set up heavy releases when operators feared New Melones could be breached setting up the devastating January 1997 flood that inundated 70 square miles south of Manteca,.
Bumper to bumper
traffic fleeing cities
The evacuation was ordered Sunday afternoon over concerns the dam’s emergency spillway could fail. Over five hours later, thousands of cars carrying panicked and angry people were sitting in bumper-to-bumper 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.”
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 evacuation order went out around 4 p.m. after engineers spotted 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 Kory 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.
Water began flowing over the emergency spillway at the Oroville Dam in Northern California on Saturday for the first time in its nearly 50-year history after heavy rainfall. Officials earlier Sunday stressed the dam itself was structurally sound and said there was no threat to the public.
Emergency spillway started
failed at only 10% of its
rated capacity
Residents of Oroville, a town of 16,000 people, should head north toward Chico, and other cities should follow orders from their local law enforcement agencies, the Butte County Sheriff’s office said.
The Yuba County Office of Emergency Services asked residents in the valley floor, including Marysville, a city of 12,000 people, to evacuate and take routes to the east, south, or west and avoid traveling north toward Oroville.
The California Department of Water Resources said it is releasing as much as 100,000 cubic feet per second from the main, heavily damaged spillway to try to drain the lake.
Department engineer and 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.
Unexpected erosion chewed through the main spillway during heavy rain 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.
The lake is a central piece of California’s government-run water delivery network, supplying water for agriculture in the Central Valley and residents and businesses in Southern California.
