Thousands in California ordered to flee area
Almost 200 000 people were under evacuation orders in northern California yesterday after damage to the overflow channel of the tallest dam in the United States raised fears the spillway could collapse.
The reservoir of the Oroville Dam, located 120km north of the state capital Sacramento, had been completely full after several weeks of heavy rain.
The 235m dam itself was not in danger of collapse, the California Department of Water Resources said, but there were major fears over the emergency spillway due to erosion damage on its concrete top after water began pouring over it on Saturday.
Authorities were releasing 2 830m³ of water a second from the main spillway, bringing down the level of the reservoir on Sunday so there was no more flow into the emergency channel, the Sacramento Bee paper cited Department of Water Resources spokesman Doug Carlson as saying.
Although the immediate threat had passed, the evacuation order remained in place as authorities evaluated the state of both the auxiliary spillway and the concrete-lined main spillway, which was also damaged, with a large gash caused by the heavy volume.
“Now that there is no more water going over the emergency spillway, although it brings stability to the situation, there are still a lot of unknowns,” Butte County Sheriff Kory Honea said on Sunday night.
“We’re not at the point yet where we can make decisions about whether or not it is safe to repopulate areas.”
About 188 000 people in downstream communities had been ordered to flee on Sunday afternoon as water was still gushing over the top of the wide auxiliary spillway.
In a Facebook post ordering the immediate evacuation of low-lying areas of the city of Oroville as well as downstream communities, the Butte County Sheriff’s department warned that a hazardous situation was developing with the Oroville Dam auxiliary spillway.
“Failure of the auxiliary spillway structure will result in an uncontrolled release of flood waters from Lake Oroville,” it said, adding three times “This is NOT A Drill”.
To the south, Yuba County also ordered residents to move to safety. “Yes, an evacuation has been ordered,” the Yuba County Office of Emergency Services said in a Facebook post.
“All Yuba County on the valley floor. The auxiliary spillway is close to failing . . . Take only routes to the east, south, or west. DO NOT TRAVEL NORTH TOWARD OROVILLE !!!!! ”
Helicopter footage from news station KCRA showed water pouring down the auxiliary spillway – parallel to the main spillway.
The water flowed through a gorge to a secondary reservoir, which was also very full, before draining into the Feather River that runs through Oroville, a city of about 20 000 people.
Governor Jerry Brown issued an emergency order to deploy resources to the affected area.