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AFP
OROVILLE
ALMOST 200,000 people were under evacuation orders in northern California Monday after a threat of catastrophic failure at the United States'tallest dam.
Officials said the danger had subsided for the moment as water levels at the Oroville Dam, 75 miles north of San Francisco, had eased. But people were still being told to stay away.
Several weeks of heavy rain had filled the 770-foot high dam to capacity.
The threat comes not from the dam itself, which the California Department of Water Resources said was not in danger of collapse, but from an emergency spillway that channels excess water.
A giant hole opened in the main spillway last week, forcing authorities to activate the emergency overflow channel on Saturday for the first time.
But it began eroding, threatening a rupture that would have sent water surging towards the valley below.
Authorities released 100,000 cubic feet of water per second from the main spillway, bringing down the level of reservoir on Sunday, the Sacramento Bee newspaper said.
Helicopters readied overnight to drop rocks into eroded areas in the emergency spillway ahead of rain that is forecast for Wednesday and Thursday that could fill the reservoir again.
The California National Guard said on Facebook that it had alerted its 23,000 members to be ready to deploy.
