Oroville Dam: Catastrophe averted as evacuees return to homes down stream
Updated
.jpg/8272298 "Evacuees return in California")
Californians who were ordered to evacuate due to a threat from the tallest dam in the United States can now safely return to their homes and businesses may reopen, authorities say.
Key points:
- 188,000 evacuees now free to return home
- Warning remains and more rains are forecast
- Trucks and helicopter crews rapidly reinforced spillways with rock
A previous evacuation order has been reduced to an evacuation warning, Butte County Sheriff Kory Honea said, after water management officials drained enough water from the Oroville Dam to relieve pressure and avert a catastrophe.
The warning means that people can return home but should be prepared to evacuate again if necessary, Sheriff Honea said.
Officials had ordered 188,000 people living down river from the dam to evacuate.
Both the primary and back-up drainage channels of the dam, known as spillways, were damaged after a build-up of water that resulted from an extraordinarily wet winter in Northern California that followed years of severe drought.
When the emergency spillway showed signs of erosion, engineers feared a 10-metre-high section could fail, leading to the evacuation order on Sunday.
Both spillways are next to the dam, which itself is sound, engineers say.
"I left everything in my house. I've got a four-bedroom, two-bathroom house and I don't know what's going to happen to it," said William Rigsbay, 53, of Thermalito.
Swift action averts catastrophe
The greatest danger came from the emergency spillway, which allows water out of the reservoir when capacity is reached.
Though damaged, the primary spillway was still useable, officials said.
More rain was forecast for as early as Wednesday (local time) and through Sunday, according to the National Weather Service, but the state Department of Water Resources said the upcoming storms were unlikely to threaten the emergency spillway.
Swift action by the department to shore up both spillways while also relieving pressure on the dam averted the immediate danger of a dam failure, Sheriff Honea said.
A failure could have unleashed a wall of water three stories tall on towns below.
State officials used 40 trucks carrying 30 tons of rock per hour to reinforce the eroded area, while two helicopters dropped rock and other materials into the breach.
"We're aggressively attacking the erosion concerns that have been identified," Department of Water Resources acting director William Croyle said.
Among those who had fled the danger zone were hundreds of families camped out in cars and tents at Silver Dollar Fairgrounds in Chico, about 40 kilometres north-west of Oroville.
Reuters
Topics: dams-and-reservoirs, emergency-incidents, united-states
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