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Evacuations ordered below Oroville Dam; failure of emergency spillway ‘expected’

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PG&E crews work to move two electric transmission line towers as a precaution before the Oroville Dam emergency spillway was needed to be used in Oroville. Authorities were worried the spillway would fail Sunday evening and flood nearby communities. (Brian van der Brug/Los Angeles Times/TNS)

OROVILLE — Residents of Oroville and nearby towns were ordered to immediately evacuate on Sunday afternoon after a “hazardous situation” developed involving an emergency spillway at the Oroville Dam.

The National Weather Service said the auxiliary spillway at the Oroville Dam was expected to fail early Sunday evening, which could send an “uncontrolled release of flood waters from Lake Oroville.”

Those in Oroville were asked to flee northward toward Chico. In Yuba County, those in the valley areas were urged to take routes to the east, south or west.

“This is not a Drill. This is not a Drill. Repeat this is not a drill,” the National Weather Service said. Authorities urged residents to contact neighbors and family members and reach out to the elderly and assist them in evacuating.

The Butte County Sheriff’s Department and the state Department of Water Resources said the failure of the auxiliary spillway was caused by “severe erosion.”

The evacuations marked a dramatic turn of events at the nation’s tallest dam. For several days, officials have been trying to figure out how to get water out of Lake Oroville after the main spillway was damaged.

The emergency spillway had never been used before — and until the last few hours it seemed to be working well.

Hours earlier at a noon news conference, California Department of Water Resources officials said Oroville Lake is draining without incident and that the amount of water it’s releasing is beginning to taper off, thanks in part to several days of sunny weather and less runoff flowing into the reservoir.

“We think by this time tomorrow … the flow over the auxiliary spillway will have ended,” said Eric See, a spokesman for the Department of Water Resources.

Diminished by years of drought conditions, the reservoir had become a symbol of the state’s worsening water crisis. But an unusually wet winter took the lake from nearly full to overflowing in less than a week.

At the same time, the nearly mile-long concrete spillway that the dam’s managers rely on to release excess water began to crumble, with erosion worsening as millions of gallons of water poured over it.

It continued to rain. Realizing the lake might rise to a level that would trigger the use of an emergency spillway, state workers began clearing the area of trees and brush that could be sent hurtling downstream.

On Saturday morning, water began washing over the dam’s emergency spillway for the first time since it was completed in 1968. Photographs showed a torrent of water rushing downhill to join the Feather River.

On Sunday, officials said that although they expected the uncontrolled spill to end, they plan to continue using the concrete spillway to create more storage in the reservoir in anticipation of rainfall later in the week.

“We’re going to continue to flow water down the spillway and lower the lake,” See said. “You’re going to see the lake dropping over the next several days.”

Officials emphasized that while erosion had carved a massive hole in the main spillway, the dam itself is structurally sound.

“Believe me, in the last several days there have been a lot of eyes on it,” said Bill Croyle, acting director of the water department. “Oroville Dam is not in any way a part of the damage that occurred.”

Officials have estimated it could cost $100 million to $200 million to repair the damage to the spillway and other features.

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