Water & Drought

Oroville Dam: Butte County sheriff unveils new evacuation plan to avoid traffic jams

Tempers flare in Marysville traffic

A nightmare traffic jam developed as thousands of residents fled from Marysville Sunday night
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A nightmare traffic jam developed as thousands of residents fled from Marysville Sunday night

Capitalizing “on lessons that were learned” during the massive traffic jams last month in the Oroville Dam crisis, Butte County officials on Thursday released an updated evacuation plan that aims to prevent gridlock should another crisis arise at the dam.

Last month, roads along the highway 70 and 99 corridors became severely clogged after 188,000 people in Butte, Sutter and Yuba counties were told to evacuate with barely an hour’s notice when it appeared the dam’s emergency spillway would fail.

Having seen firsthand where the choke points were, Butte County Sheriff Kory Honea said Thursday that he wants county residents to begin evacuating 12 to 24 hours before water begins flowing over the emergency spillway. The evacuations would be staggered, with people closest to the dam leaving first.

“We have a much, much better understanding of what could go wrong,” he said at a news briefing Thursday.

He said the county has worked with state emergency officials to come up with more sophisticated early-warning trigger points to avoid a last-minute scramble for safety. He directed locals to the county’s website, which has been updated to provide new evacuation routes and a way to sign up for alerts.

He said the county had developed a plan decades ago to address a catastrophic dam failure. But he acknowledged it wasn’t very sophisticated, and “years and years of complacency” living in the shadow of the nation’s tallest dam, holding back the state’s second largest reservoir, kept it from being updated.

“Over the course of time, you begin to take it for granted,” he said.

Honea said he now has lots of confidence in work that dam managers at the state Department of Water Resources are conducting to fortify the emergency spillway, which nearly gave way last month.

“That said, it’s still untested,” he said.

DWR acting director Bill Croyle said work crews were beginning to patch the battered main spillway with a spray-on form of concrete, as well as other measures to gird the structure for the coming spring runoff.

But the department, in consultation with federal officials, is still about two weeks away from choosing a design for a more permanent repair. Croyle wants the entire spillway, portions of which have eroded away in the past month, fixed in time for the rainy season that begins in October.

An enormous gash was spotted in the main spillway’s concrete chute on Feb. 7, prompting a temporary shutdown of water releases as a major storm rolled in. Water eventually rolled over the adjacent emergency spillway.

Officials ordered the two-day evacuation of 188,000 downstream residents when the emergency structure nearly failed.

Ryan Sabalow: 916-321-1264, @ryansabalow

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