Thousands of northern Californians were told to leave their homes Sunday evening, as an emergency spillway in the country’s tallest dam was in danger of failing and unleashing uncontrolled flood waters on towns below.
The California Department of Water Resources said on Sunday afternoon the emergency spillway of the Oroville Dam in Northern California could fail within an hour unleashing uncontrolled flood waters from Lake Oroville,
Later on Sunday, Butte County Sheriff Koney Honea said engineers with the California Department of Water Resources informed him shortly after 6 p.m. local time that the erosion on the emergency spillway at the Oroville Dam is not advancing as fast as they thought. Honea said two inches of water was still coming over the dam, but that was significantly down from earlier flows. Honea said there was a plan to plug the hole by using helicopters to drop rocks into the crevasse. He said the evacuation order went out after engineers spotted a hole that was eroding back toward the top of the spillway. Honea added authorities wanted to get people moving quickly to save lives in case “the worst-case scenario came into fruition.” California officials said the cities of Gridley, Live Oak, Nicolaus, Yuba City and communities near Feathers River have been added to the evacuation order. Hundreds of cars in wall-to-wall traffic could be seen on Highway 99 as people streamed out of Oroville away from the dam.
People in downstream areas needed to leave the area immediately, the department said on Sunday afternoon.Officials earlier on Sunday stressed the dam was structurally sound and said there was no threat to the public.
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 Kevin Dossey tells 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 Oroville Dam in Northern California on Saturday for the first time in its nearly 50-year history after heavy rainfall.
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.
About 150 miles northeast of San Francisco, Lake Oroville is one of California’s largest man-made lakes, and the 770-foot-tall Oroville Dam is the nation’s tallest. 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.