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Mass evacuations in California as America’s tallest dam threatens to spill

Californian authorities have ordered thousands of residents near Lake Oroville to evacuate over fears of imminent failure of the emergency spillway at the Oroville Dam.

Californian authorities have ordered thousands of residents near Lake Oroville to evacuate over fears of imminent failure of the emergency spillway at the Oroville Dam. Photo: EPA/California Department of Water Resources

Stormwaters have receded behind America’s tallest dam as engineers race to drain the rain-swollen Northern California reservoir and shore up a crumbling overflow channel before new storms sweep the region.

Authorities say they have averted the immediate danger of a catastrophic failure – one capable of unleashing a wall of water three stories tall on towns below.

Earlier residents and local officials described a panicked and chaotic scene on roads and freeways after almost 200,000 people were ordered to evacuate from the area below the Lake Oroville Dam, amid fears its emergency spillway could give way.

US emergency crews early prepared loads of rock to be dropped by helicopters to seal a crumbling spillway that threatened to inundate communities along the Feather River in Northern California.

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.

Oroville Dam evacuees

Evacuees in a California church – some 170,000 people have been told to leave for higher ground. Photo: EPA/Peter Dasilva

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.

The state Emergency Services Office and Department of Water Resources 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.

Californian Tyson Shorthorn posted this video to Instagram:

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.

Oroville Dam spillway

A long exposure picture of the Oroville Dam discharging water at 100,000 cubic feet per second. Photo: Josh Edelson/AFP/Getty

“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 230 metres high, the structure, built between 1962 and 1968, is the tallest US dam, exceeding the Hoover Dam by more than 12 metres.

Panicked residents

Jodye Manley of Olivehurst says she and her husband were having dinner Sunday at her daughter’s house in Sacramento when she got word from a city councilman friend that her area would probably be evacuated.

She says the couple got petrol and made a mad dash to get their four dogs and three cats. Manley says she and her neighbours were completely panicked and that the scene “was almost like a movie.”

She says the traffic-filled return to Sacramento was terrifying, with people thinking the spillway would go at any moment.

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.

– AAP

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