OROVILLE, Calif. (CNN) — Authorities are scrambling to drain Lake Oroville by 50 feet and repair damage to an emergency spillway before an imminent rainstorm threatens to push billions of gallons of water back into the lake.
A flash flood warning is in effect Tuesday after the spillway — which lets excess water out when the level gets too high — suffered massive damage over the weekend.
If the spillway fails, it could flood communities downstream with what one official warned could be a “30-foot wall of water.”
Water gushes over the main spillway at Oroville Dam on Feb. 11.
Helicopters have been dropping bags of rocks into the gouged portion in an effort to plug the hole.
“Our crews are working around the clock, 24/7, to try to get as much rock as possible onto the damaged spillway before the next storms come,” Cal Fire spokesman Josh Janssen said.
The lake water gushes into the emergency spillway when it reaches 901 feet. For now, officials are cautiously optimistic.
“We have the lake level at 894 feet, but that number is sure to drop,” Janssen said Tuesday. “The level was dropping about a foot every three hours. But lakes are shaped like funnels, so we could see the water level start to drop faster.”
Another deluge to come
The next wave of rainfall will come overnight Wednesday into Thursday, CNN Senior Meteorologist Dave Hennen said. A series of storms will follow and last through the weekend.
Rainfall over the next week could total 5 to 12 inches and will likely push hundreds of billions of water back into Lake Oroville, Hennen said.
Will that be enough to overwhelm the dam’s spillways?
“The simple answer is we don’t know, but that is the concern,” Hennen said.
The spillway damage forced the evacuation of 188,000 people. Mandatory evacuation orders remained in place Tuesday for Butte, Sutter and Yuba counties.
There’s no word yet on when those 188,000 people can return.
“I recognize this has displaced a lot of people, and I recognize the hardships it’s created on our communities,” Butte County Sheriff Kory Honea said of the mandatory evacuations. “We did this because our primary purpose is to ensure public safety.”
He said officials were working on a plan to get people back home safely.
Sleeping in cars, riding out the evacuation
As repairs continue, evacuees have gone to shelters, pitched tents in parking lots and found makeshift arrangements for what could stretch for days.
Pat and Keith Dailey, a couple from Yuba City, slept in their car with their four dogs at the Colusa County Fairgrounds.
“It was miserable,” Pat Dailey told CNN affiliate KGO. “We didn’t sleep. There was people walking and people talking all night long.”
But they’re staying put.
“We’re kind of on the safe side,” said her husband, Keith. “We won’t go back, until they tell us it’s safe.”
California Gov. Jerry Brown sought to assure residents during a press conference Monday: “We’re doing everything we can to get this dam in shape so (evacuees) can return and live safely without fear.”
He said he had requested federal response aid.
Tallest dam in the US
The Oroville Dam, the tallest dam in the United States, provides flood control for the region. The dam itself has no structural issues, but the two spillways that release water from the lake to prevent overflow have structural problems.
The main spillway, which is lined, or paved, has a hole almost the size of a football field and at least 40 feet deep. It can’t be fixed immediately and needs to be used through March, which marks the end of what’s been a very heavy rainy season.
It’s being used to drain the lake at a rate of 100,000 cubic feet per second in an effort to reduce the water level. Normal flows down the main spillway are about 55,000 cubic feet per second.
The emergency spillway, which is an embankment covered with trees, is a last resort and was used for the first time in its 48-year history on Saturday. Lake water began washing into it this weekend and prompted the evacuation order when officials noticed damage on the spillway.
How did we get here?
Questions remain over how it got to this point at Lake Oroville. Why weren’t more efforts made to prevent spillway erosion after concerns were raised more than 10 years ago?
California Department of Water Resources Acting Director Bill Croyle said he was “not familiar with 2005 documentation or conversation” about spillway concerns and emphasized the efforts underway to understand the current dynamics of the dam.
“We’re going to continue to work on the challenges we have,” he said.
The governor defended the state’s flood infrastructure Monday and said he welcomed “more scrutiny” as efforts continue.
Oroville as a ghost town
After the evacuations, downtown Oroville remained a ghost town. Stores sat dark and empty with sandbags stacked in front of doors. Empty gas stations had yellow tape ringed around the pump to indicate there was no more fuel.
All schools in Sutter and Yuba counties have been closed. Affected schools in Butte County are shut until Friday.
RaeLynn Jones and her fiance, who had fled their Oroville apartment near Feather River on Sunday, came back to their home Monday to pick up more of their items.
She noted that her building was unscathed, but at Feather River, the water level nearly reached the treetops. Surrounding playgrounds, gazebos and sports fields were completely submerged, she said.
Jones is staying at her fiance’s home, which is on higher ground. Nine people and three dogs are sharing the house where they’re riding out the evacuation order. With everything closed, they’re eating whatever is left in the kitchen and snacks from the gas station. For now, all they can do is wait.
Defying the evacuation
Others decided to stay put despite the evacuation order.
Brianne Lawrence, who lives across from Feather River, brought her family back after rushing out of town on Sunday and getting stuck in traffic.
She told CNN affiliate KRCR that she lives on a hill.
“It’s going to have to come up probably, at least 10 times what it is now for us to be flooded,” she said.
Her grandfather Brian Pulley is also staying put in nearby Thermalito.
“I’m ready to leave at any second,” he told KRCR, “but I don’t think the threat’s that great at the moment.”