Crews work to seal California spillway that forced evacuations

California Department of Water Resources personnel monitor water flowing through a damaged spillway on the Oroville Dam in Oroville, California

By Sharon Bernstein

OROVILLE, Calif. (Reuters) – Emergency crews early on Monday prepared loads of rock to be dropped by helicopters to seal a crumbling spillway that threatens to inundate communities along the Feather River in Northern California, local media reported.

Almost 200,000 people were ordered on Sunday to evacuate from the area below the Lake Oroville Dam, the tallest dam in the United States, after authorities said its emergency spillway could give way.

Officials said the situation seemed less dire overnight but Sacramento television station KCRA reported that helicopters from around the state were sent to drop chest-high bags of rocks to close the hole in the spillway.

The NBC affiliate showed dump trucks dropping off piles of rock, which were then loaded into the bags with backhoes. The operation to close the gap would begin as soon as it was feasible, the station said.

A damaged spillway with eroded hillside is seen in an aerial photo taken over the Oroville Dam in Oroville, California, U.S.

A damaged spillway with eroded hillside is seen in an aerial photo taken over the Oroville Dam in Oroville, California, U.S. February 11, 2017. California Department of Water Resources/William Croyle/Handout via REUTERS

The state Emergency Services Office and Department of Water Resources did not immediately respond to requests for comment.

The water department said on Twitter on Sunday afternoon that the spillway next to the dam was “predicted to fail within the next hour” but it remained standing.

The department said authorities were releasing water to lower the lake’s level after weeks of heavy rains in drought-plagued California.

Overnight, state and local officials said the immediate danger had passed with water no longer flowing over the eroded spillway but they cautioned that the situation remained unpredictable.

“Once you have damage to a structure like that it’s catastrophic,” acting Water Resources director Bill Croyle told reporters. But he stressed “the integrity of the dam is not impacted” by the damaged spillway.

The earthfill dam is just upstream and east of Oroville, a city of more than 16,000 people north of the state capital of Sacramento. At 770 feet (230 meters) high, the structure, built between 1962 and 1968, is the tallest U.S. dam, exceeding the Hoover Dam by more than 40 feet (12 meters).

‘DO NOT TRAVEL NORTH’

Officials said they feared the damaged spillway could unleash a 30-foot (9-meter) wall of water on Oroville. They said evacuation orders remained in place for some 188,000 people in the area and would be re-evaluated at dawn.

The Yuba County Office of Emergency Services urged evacuees to travel east, south or west. “DO NOT TRAVEL NORTH TOWARD OROVILLE,” the department warned on Twitter.

Evacuation centers were set up at a fairgrounds in Chico, California, about 20 miles (32 km) northwest of Oroville, but major highways leading south out of the area were jammed as residents fled the flood zone.

Javier Santiago, 42, fled with his wife, two children and several friends to the Oroville Dam Visitors Center in a public park above the dam and the danger zone.

With blankets, pillows and a little food, Santiago said: “We’re going to sleep in the car.”

The Oroville dam is nearly full following winter storms that brought relief to the state after four years of drought.

State authorities and engineers on Thursday began releasing water from the dam after noticing that large chunks of concrete were missing from the spillway.

(Additional reporting, writing by Dan Whitcomb in Los Angeles, Chris Michaud in New York and Ian Simpson in Washington; Editing by Scott Malone and Bill Trott)

Spillway on California dam in danger of collapse, evacuations ordered

65,000 cfs of water flow through a damaged spillway on the Oroville Dam in Oroville, California, U.S.

By Dan Whitcomb

(Reuters) – Residents below the tallest dam in the United States, near Oroville in Northern California, were urgently ordered to evacuate on Sunday as a spillway appeared in danger of imminent collapse.

The abrupt evacuation orders came as authorities determined that the auxiliary spillway on the Lake Oroville Dam could give way at any time, unleashing floodwaters onto rural communities along the Feather River. “Immediate evacuation from the low levels of Oroville and areas downstream is ordered,” the Butte County sheriff said in a statement posted on social media. “This is NOT A Drill.”

The Oroville dam is nearly full after weeks of heavy rains and snow brought relief to the state after some four years of devastating drought.

The California Department of Water Resources said on Twitter at about 4:30 p.m. PST that the spillway next to the dam was “predicted to fail within the next hour.”

However it was still standing nearly three hours later as the Water Resources department said crews would use helicopters to drop rocks to fill a gouge in the spillway. Authorities were also releasing water to lower the lake’s level.

The Yuba County Office of Emergency Services urged evacuees to travel only to the east, south or west. “DO NOT TRAVEL NORTH TOWARD OROVILLE,” the department said on Twitter.

Evacuation centers were set up at a fairgrounds in Chico, California, about 20 miles northwest of Oroville, but roads leading out of the area were jammed as residents sought to drive out of the flood zone.

It was not clear how many residents were affected by the evacuation order.

State authorities and engineers on Thursday began carefully releasing water from the Lake Oroville Dam some 65 miles (105 km) north of Sacramento after noticing that large chunks of concrete were missing from a spillway.

Water levels were less than 7 feet (2 meters) from the top of the dam on Friday.

California Governor Jerry Brown asked the Federal Emergency Management Agency on Friday to declare a major disaster due to flooding and mudslides brought on by the storms.

The earthfill dam is just upstream and east of Oroville, a city of more than 16,000 people.

At 770 feet (230 meters) high, the structure, built between 1962 and 1968, is the tallest dam in the United States, besting the famed Hoover Dam by more than 40 feet (12 meters).

(Reporting by Dan Whitcomb in Los Angeles; Editing by Peter Cooney and Mary Milliken)