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Expected dam spillway fail prompts Calif. evacuation

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USA Today Network
Greg Toppo, USA TODAY NETWORK

Published 8:25 p.m. ET Feb. 12, 2017 | Updated 48 minutes ago

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Water could pour over an emergency spillway at Lake Oroville for the first time ever, a last-ditch alternative that California officials said they had been hoping to avoid. (Feb. 10)
AP

Residents of the northern California town of Oroville were being ordered to evacuate on Sunday after authorities there said they expected a spillway at a local dam to fail within the hour.

In a post on its Facebook page, the Butte County, Calif., Sheriff’s Department ordered an “immediate evacuation from the low levels of Oroville and areas downstream.”

Police said a “hazardous situation is developing” with the Oroville Dam auxiliary spillway, in which severe erosion could lead it to fail, resulting in an “uncontrolled release of flood waters from Lake Oroville.”

California Department of Water Resources officials had decided to use the emergency spillway to take pressure off the dam’s regular spillway, which developed a giant crater last week, The (Redding) Record Searchlight reported. That crater had been growing daily, so to take pressure off the spillway, the state began using the emergency spillway, but that has also become compromised.

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.

Residents of Oroville, located about 65 miles north of Sacramento, were ordered to evacuate northward, toward Chico, Calif.

The dam was built in 1968. Following heavy rains this winter, water on Saturday overtopped the emergency spillway for the first time since its completion, The Sacramento Bee reported Saturday.

Bill Croyle, acting director of the Department of Water Resources, said the dam itself is not threatened, but that the crisis won’t be over soon, since Northern California is on pace for its wettest winter ever. He said an estimated 2.8 million acre-feet of snow blankets mountains above the dam, putting more strain on it in months to come.

“Our next 60 to 90 days will be critical, how we route this (snow) runoff through this reservoir,” Croyle told The Bee. “There’s a lot of snow up there.”

Follow Greg Toppo on Twitter: @gtoppo

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