NOTE: The article CAREFULLY uses the word SPILLWAY. The dam is not in danger at this moment, but the spillways are damaged.
The use of the emergency spillway, never used since the dam was built 48 years ago has also created potential damage issues for the main spillway.
The dumping of rocks by helicopter had NOT started, according to the reports show on the 11 PM news.
Threat of spillway failure at Oroville Dam prompts evacuation of 188,000 across Northern California
Fearing that the emergency spillway at Oroville Dam was on the verge of failure Sunday afternoon, authorities ordered the evacuation of more than 160,000 Northern California residents, sending panicked drivers streaming out of Oroville, Marysville and other communities as flood-control experts scrambled to prevent a catastrophe.
State water officials ramped up water releases through the dam's damaged main spillway to 100,000 cubic feet per second from 55,000 cfs earlier Sunday, easing pressure on the emergency spillway and lending hope that the situation was not immediately as dire as feared.
"The erosion has slowed, and I think we're going to be OK," state Department of Water Resources spokesman Chris Orrock said at 9 p.m.
Six helicopters were dispatched to begin dumping containers of boulders on the area of erosion adjacent to the emergency spillway, and state emergency officials were huddling through the night to respond to the crisis.
Just before 10 p.m., officials confirmed that the lake level had dropped low enough to stop water from flowing over the lip of the emergency spillway at 8:45 p.m.
"The flowing has stopped," Water Resources spokesman Doug Carlson said.
Water had topped the emergency spillway for the first time in the dam's 48-year history on Saturday, after dam operators cut back flows on the damaged main spillway. With massive storms over the Sierra and heavy snowpack, they were unable to release enough water through the main spillway to keep the reservoir from overtopping the untested emergency system.
On Sunday, just over 24 hours after water started flowing over the emergency spillway, state officials warned the structure was at risk of failure.
As residents fled along Highway 99 and streamed into gas stations and school parking lots to evacuate their families and pets, Butte County Sheriff Kory Honea said shortly after 6 p.m. that the situation appeared to be improving and that "the erosion that caused all this concern was not advancing as rapidly" as state water officials had feared.
The hillside adjacent to the emergency spillway had "eroded to within several feet" of the huge concrete structure, said Kevin Dossey, a state Department of Water Resources engineer and spokesman, but officials hoped the fact that the water flow was stopped late Sunday would allow greater inspection and work to shore up the eroded area.
Area law enforcement and emergency officials rushed to help, with 67 Sacramento sheriff's deputies dispatched to the Oroville area, a helicopter from Sacramento Metro Fire and CHP helicopters.
Sunday's evacuations came after several days of state officials saying the dam itself was not in danger and that there was no serious threat to nearby communities.
Authorities continued to maintain Sunday night that the dam itself was safe. But their assessment of danger to downstream communities from the spillway's damage changed dramatically Sunday at 4:42 p.m., when DWR issued this tweet: "EMERGENCY EVACUATION: Auxiliary spillway at Oroville Dam predicted to fail within the next hour. Oroville residents evacuate northward."
"It's uncontrolled, it's uncontrolled," DWR spokesman Orrock said when asked how much water could be released if the spillway failed.
Within hours, the evacuation area expanded through Yuba, Sutter and Butte counties, including the communities of Hallwood, Marysville, Olivehurst/Linda, Plumas Lake, Gridley, Live Oak and Yuba City. Law enforcement officials directed residents to leave, and automated emergency calls notified some that they needed to get out, as did Facebook and other social media posts.
"They were just going down the street telling everybody to leave," said Kenny Thomas, a 43-year-old Gridley resident. "They were running up and down the streets."
"This (is) NOT A Drill. This (is) NOT A Drill. This (is) NOT A Drill," Butte County sheriff's officials warned in a Facebook post.
"They have what they expect to be an imminent failure of the auxiliary 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 – some panicked and others who said they were nonchalant about the risk of flooding in an area that has seen serious flood damage in past years – streamed out onto Highway 99 and into gas stations and motels along the roadway near Sacramento International Airport.
The Homewood Suites by Hilton started getting calls around 6 p.m., said front desk agent Gao Hang. Twenty reservations were made within the hour in back-to-back phone calls.
"They didn't care about the price at all because they just need a place to go," she said. "It's not just us."
Two neighboring hotels were filling up as well, she said.
Evacuation centers were set up at areas throughout the region, including at Sutter Union High School in Sutter, where hundreds of people gathered in the parking lot waiting for a center to open where as many as 8,000 people were expected.
"This is the highest public ground in Sutter County, so we called in staff," said Superintendent and Principal Ryan Robison. "We're talking to people, keeping them calm."
Patrick Dustin, a 35-year-old Live Oak resident, got to the school with his family around 5 p.m., with a camper they already had packed with oatmeal, cookies, rice and beans and other essentials.
Dustin said that when he heard the evacuation alert for other communities, he knew it was time to move out.
"When they said Gridley, that means us, too," he said. "We've been preparing the last couple days."
Authorities emphasized there was no immediate threat to the Sacramento region, where high water along the American River has closed area parks and lured thousands of sightseers out onto levees to gape at huge waves of water.
Sacramento Mayor Darrell Steinberg said Sunday night that "there is no imminent threat" to the city if the Oroville Dam emergency spillway fails.
Steinberg said that he and City Manager Howard Chan had spoken to state Department of Water Resources officials about the situation and will meet Monday with them for an update.
The mayor said the city has emergency plans for flooding that could be initiated if the threat escalates, but he didn't currently see a need to deploy those measures.
Steinberg spokeswoman Kelly Rivas said the city's Office of Emergency Services expected that any water released in a spillway failure could be diverted from the city via the Sacramento Weir and the Fremont Weir in the Yolo Bypass.
"The flood system as a whole is capable of absorbing that level of water," Rivas said.
Chan said the earliest that Oroville flood waters would reach the Sacramento area would be 12 hours after a spillway failure.
Yolo County officials echoed the notion that its communities were safe from flooding.
"There remains no imminent threat to our city from the Oroville Dam situation, and we are not contemplating any evacuation order," West Sacramento Mayor Christopher Cabaldon said. "The expanse between us and the dam is broad and flat, enough to dissipate floodwaters in nearly all failure scenarios."