UPDATE: Threat remains at Oroville Dam as lake level drops slightly

Update 5:30 a.m. Monday

Lake Oroville has dropped about 3.5 feet overnight after officials doubled the flows down the Feather River on Sunday.

Still, downstream communities facing the threat of uncontrolled flooding remain evacuated from their homes with no word on when they'll be allowed to return.

LIVE UPDATES: Oroville Dam crisis

As of 5 a.m., evacuations in Butte County remain in place and Highways 70 and 99 are closed starting about 7 miles south of Chico. Evacuations in Sutter and Yuba counties also remain in place.

The Salvation Army Chico Corps will begin providing food Monday to those who went to the Silver Dollar Fairgrounds in Chico.

Another evacuation shelter opened late Sunday at the Yolo County Fairgrounds, 1250 East Gum Ave. in Woodland.

A California Department of Water Resources spokesman said another update on conditions would be available later in the morning.

Oroville Dam crisis in Northern California: What we know

Original story

Some 180,000 people living downstream of Oroville Dam were ordered to evacuate late Sunday afternoon as officials said an emergency spillway was dangerously eroding and a failure could cause uncontrolled floodwaters to pour out of the lake.

The 4:20 p.m. order triggered a chaotic exodus, filling highways as evacuees headed north and west toward higher ground. An emergency shelter at the Silver Dollar Fairgrounds in Chico, 24 miles north, had to open a new facility. Several other shelters were established. The estimate of evacuees is based on a USA TODAY Network analysis of populations in affected communities.

The emergency spillway had never been activated, but was pressed into service because the dam’s main concrete spillway has been crumbling since a hole developed in it last Tuesday. Both spillways sit off to the side of the main dam structure. Officials said the main structure remains sound.

Read more: Here's a list of emergency shelters for Oroville Dam evacuees

In an effort to contain the potential disaster, operators with the California Department of Water Resources on Sunday doubled the flows into the main spillway, despite its bottom being largely washed out. At 100,000 cubic feet exiting per second, the lake level dropped quickly. That relieved some pressure on the emergency chute.

Officials were hopeful those measures would save it, and that efforts to backfill with bags of rocks could shore it up on Monday.

In light of the possibility of the auxiliary spillway’s imminent collapse, Butte County Sheriff Kory Honea said during a news conference Sunday night that he had no choice but to order an evacuation.

“I didn’t have the luxury of waiting to see if all was OK. We need to get people moving quickly and to save lives in case the worst case came to fruition,” Honea said.

“This is a very dynamic situation. This is a situation that could change very, very rapidly,” he said.

It was unclear Sunday night when residents might be allowed to return home. It also wasn’t clear how many had defied the order or been unable to leave.

Read more: Amid California dam evacuations, big risks and a costly infrastructure failure

Janita Bowen and her 18-month-old daughter were stuck in Oroville without a ride out of town, she said Sunday night via Facebook Messenger.

“It's very scary. We even ran after cars, and they still wouldn't help us,” Bowen said. She said she and her baby and boyfriend had plenty of food and water and their power was still on.

Roads in the area were shut down. She had spoken with police and they were aware of her situation, “but the police say there is no guarantee help can come,” Bowen said.

Billy Morrison, 26, who lives in the Thermalito area on the west side of Oroville, said he, his father and their two dogs were still in their house at 8 p.m.

Police had knocked on their door and warned them to evacuate around 7:30 p.m.

Shortly after the first evacuation order was issued around 3 p.m., Morrison said they tried to pick up his grandmother. Normally she’s just a five-minute drive away, but “it was chaos. We couldn’t even manage to get there,” Morrison said via Twitter. He said she had a vehicle and could leave under her own power.

Morrison said he wanted to evacuate, but his dad overruled him.

“It seems all my neighbors have left except us,” Morrison said. “We are waiting on the condition of the emergency spillway since it’s still holding, but if it is getting ready to give way, we will be headed out.”

After the initial crush of traffic, residents along the evacuation route said it had slowed some.

Todd York, owner of York Cattle and Performance Quarter Horses, said northbound traffic up highways 70 and 99 had thinned out by around 7:30 p.m.

York said earlier in the day he evacuated many of his horses from lower elevations in the valley to higher ground at his main ranch headquarters on Table Mountain Road northwest of Oroville Dam.

He didn’t wait for the Butte County Sheriff’s Office to issue evacuation orders because he said he could see the problem developing.

“I’ve been saying all along we don’t trust the (Department of Water Resources),” York said, speaking of the state agency that operates the dam. “I don’t trust anything the DWR is saying.”

Last week, DWR crews began to clear trees, rocks and other debris from the hillside near the dam where water coming down the spillway would flow.

Officials stressed Thursday there was “no imminent or expected threat to public safety or the integrity of Oroville Dam.”

The next day, reservoir operators were saying if the current releases from the nearly full reservoir could be maintained, it was less likely the lake would rise to the point where the emergency spillway would be needed.

But if it did happen, it was probably going to be Saturday, they said, adding that it was within the agency’s contingency plans and posed no flood threat downstream.

The spillway had not been used in the dam’s 48-year history. Lake Oroville came within a foot of spilling into it in January 1997, officials said.

At the Silver Dollar Fairgrounds in Chico, the Red Cross set up about 700 cots. Volunteers on Sunday night handed out pizza, juice, water, diapers, blankets and other snacks.

Robert Baker sat on a green cot at the shelter. The emergency broadcast warning had flashed once on the television soon after 4 p.m. He understood it was not a test.

“We knew what it meant,” he said.

Baker’s family will join the several hundred other residents in the evacuation shelter.

“I’m worried about my home, but family is what matters. They’re important,” Baker said.

Vera Russell and her husband Abdullah Costanza could only grab the essentials from their home when they received the evacuation warning.

Their mobile home sits near the Feather River – very much in the danger zone.

Costanza said he would have stayed at his home.

“But not with her, I’m responsible for her. She’s my wife and my reason.”