Officials in northern California ordered nearly 200,000 people to evacuate to safer ground Sunday as the country's tallest dam threatened to release uncontrolled floodwaters downstream.
Motorists jammed highways as thousands of residents fled the area downstream from the Oroville Dam, about 150 miles northeast of San Francisco, after authorities warned that the emergency spillway could fail, the National Weather Service said.
Hundreds of cars lined Highway 99, creating a bumper-to-bumper traffic jam as people headed north, The Associated Press said.
Raj Gill, who manages a Shell gas station in the region, was torn between evacuating and staying open to serve the steady stream of customers who passed through his establishment.
"You can't even move," he told the AP. "I'm trying to get out of here, too. I'm worried about the flooding. I've seen the pictures; that's a lot of water."
Lake Oroville, one of California's largest manmade lakes, has swelled after a month of heavy rains. On Saturday water began topping the emergency spillway on the 770-foot-tall dam, the nation's tallest, causing erosion damage that could lead to a surge of water being released, officials said.
The lake is about 75 miles north of Sacramento and about 25 miles southeast of Chico. The dam is the tallest in the United States, according to the Los Angeles Times.
Officials from California's Department of Water Resources said they planned to use helicopters to drop rocks to fill in the gouge in the spillway.
Residents of Oroville, Gridley, Live Oak, Marysville, Wheatland, Yuba City, Plumas Lake, and Olivehurst were all ordered to evacuate immediately, authorities said.
Butte County Sheriff Kory Honea said officials made the decision to nearly double the volume of water being released from the dam to stop erosion at the top of the auxiliary spillway.
"Hopefully, that will release pressure on the emergency spillway and they’ll find a repair to prevent a complete failure," Honea said Sunday. "[The] situation is dynamic and could change anytime."
The lake had been lowered to 2 feet below the top of the emergency spillway due to the increased volume of water being released through the dam's main spillway, Oroville mayor Linda Dahlmeier told ABC News.
The lake level is being lowered at a rate of about 4 inches per hour, the mayor said, adding that the erosion area has stopped progressing and stabilized.
California Gov. Jerry Brown issued an emergency order in response to the situation.
"The state is directing all necessary personnel and resources to deal with this very serious situation,” Brown said in a statement Sunday.
Moreover, the state's National Guard said it would provide eight helicopters to assist in reconstructing the emergency spillway.
The helicopters, along with two airplanes, will also be available today for search and rescue near the Oroville Dam, California National Guard Adjunct General David Baldwin said at a news conference Sunday.
He added that the California National Guard would be ready to deploy if needed.
The Mercury News, a newspaper based out of the San Jose area, reported that three environmental groups — the Friends of the River, the Sierra Club and the South Yuba Citizens League — filed a motion with the federal government in 2005, as part of Oroville Dam’s relicensing process, urging federal officials to bolster the dam's emergency spillway.
Within that motion, the groups warned that the dam did not meet modern safety standards, the Mercury News reported.
The Federal Energy Regulatory Commission rejected their request, the paper said.
(abcNEWS)