Update at 6:50 p.m.
In light of the possibility of the auxiliary spillway’s imminent collapse, Butte County Sheriff Kory Honea said during a news conference tonight 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,” Butte County Sheriff Kory Honea said.
“This is a very dynamic situation. This is a situation that could change very, very rapidly,” he said.
“We recognize that this has caused a significant problem with traffic, in terms of exiting the area.”
“I’m hopeful that the lake level will drop significantly in a very timely fashion and relieve pressure on the spillway,” Honea said.
He wasn’t sure when residents would be able to return home. “We have to assess the safety of the spillway before we let the public back in,” Honea said.
Update at 6:30 p.m.
Operators at the Oroville Dam say they are concerned that erosion on the emergency spillway “threatens to undermine the concrete weir and allow large, uncontrolled releases.”
But, according to a news release from the California Department of Water Resources, operators’ doubling of the flow down the damaged main spillway to 100,000 cubic feet per second has helped drop the lake level and slow the erosion. The next several hours will be “crucial in determining whether the concrete structure at the head of the auxiliary spillway remains intact and prevents larger, uncontrolled flows,” according to the release.
For now, authorities say the river channels are holding the water that’s being released. The design of Oroville Dam is such that both the main and emergency spillways are separate from the main dam structure. Oroville Dam itself is sound, according to DWR.
Update at 6 p.m.
Roads leading out of Oroville are becoming jammed with traffic as people evacuate the area due to the possibility of failure of the alternate spillway at Oroville Dam.
The evacuation order was extended to include Marysville and Yuba Counties around 5:45 p.m., according to Caltrans.
State route 70 northbound, which runs past Oroville, was jammed as of 5:45 p.m. So was Highway 99, an alternate north-south route eight 10 miles to the east. And so was state route 162 heading east, away from the Feather River, and many of the surface streets nearby, according to satellite feeds from Google Maps.
Highway 49 in Nevada County had been turned into one-way traffic, according to Caltrans.
Local and state officials have ordered residents of Oroville and other towns below the Oroville Dam to evacuate, saying a failure of the dam’s emergency spillway is imminent.
“A hazardous situation is developing with the Oroville Dam auxiliary spillway,” authorities with the California Department of Forestry and Fire Protection said in an urgent release Sunday afternoon. “Operation of the auxiliary spillway has lead to severe erosion that could lead to a failure of the structure.
“Failure of the auxiliary spillway structure will result in an uncontrolled release of flood waters from Lake Oroville,” the statement continues, noting “This is NOT a drill.”
California Department of Water Resources officials had decided to use the earthen emergency spillway to take pressure off the regular concrete spillway, which developed a giant crater last week.
That crater has been growing daily.
The emergency spillway suffered erosion and could fail, according to DWR. If that happens, the water behind that barrier will come down the hill and down the river.
Flow through the broken main spillway was increased to 100,000 cubic feet per second in an effort to lower the water level in the lake more rapidly.
The evacuation order, which was also posted at the Butte County Sheriff’s Office Facebook Page, does not specify which areas of Oroville should be evacuated, simply that those in “low level” locations must flee.