CALIFORNIA, USA (3rd UPDATE) – Almost 200,000 people from several California towns have been ordered to evacuate late Sunday, February 12, due to fears of a dam failure.
A hole was discovered at the emergency spillway of Oroville Dam, located in northern California, leading authorities to open up an auxiliary spillway to alleviate pressure on the 50-year-old dam, the Los Angeles Times reported.
However, the increasing amount of water in the dam is threatening to flood downstream areas.
The 770-foot dam itself was not in danger of collapse, according to officials, but the emergency spillway was causing major concern due to erosion damage on its concrete top, the Sacramento Bee newspaper said.
"Immediate evacuation" of areas downstream from the Oroville Dam has been ordered by the Butte County Sheriff's office on Sunday.
On Monday, officials said the danger had subsided for the moment as water levels at the dam, 75 miles (120 kilometers) north of Sacramento, had eased. But people were still being told to stay away.
Aerial video shows strain on California's Oroville Dam's backup spillway hours before thousands ordered to evacuate. https://t.co/47O8hzBZOS pic.twitter.com/FGuRWFpP0u — ABC News (@ABC) February 13, 2017
"This is not a drill. This is not a drill. Repeat, this is not a drill," the National Weather Service said in its advisory.
Governor Jerry Brown, meanwhile, issued an emergency order to deploy resources to the affected area.
"I've been in close contact with emergency personnel managing the situation in Oroville throughout the weekend. It's clear the circumstances are complex and rapidly changing," he said in a statement.
"The state is directing all necessary personnel and resources to deal with this very serious situation."
The damaged emergency spillway of earth-fill Oroville Dam, the tallest dam in the United States, is feared to collapse any time, local media reported.
The reservoir has been filled to capacity due to water collecting there, caused by heavy rain and snow in the area that followed years of drought.
The authorities released 100,000 cubic feet of water per second from the main spillway, bringing down the level of the reservoir Sunday, the Sacramento Bee newspaper said, quoting the water department.
The paper reported that advocacy groups had warned in 2005 that the spillway posed a danger in the event of major flooding and had recommended to the federal government that it be reinforced.
Department head Bill Croyle told a news conference near the danger zone that he was unaware of the advice, but pledged that engineers would analyze what went wrong once the crisis was over, the paper said.
The department did not respond to a request for comment on the report.
Helicopters readied overnight to drop rocks into eroded areas in the emergency spillway ahead of rain 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.
Butte County Sheriff Kory Honea told a news conference on Sunday that no more water was seeping over the spillway, adding: "We're not at the point yet where we can make decisions about whether or not it is safe to repopulate areas."
Pentagon spokesman Jeff Davis told reporters on Monday the federal military was ready, if needed, to provide air transport, water rescue, medical care and shelter.
The Oroville Dam has been in use since 1968. Less famous than America's iconic Hoover Dam near Las Vegas, Oroville is still the tallest.
The city of Oroville is located downstream, to the dam's west. It has a population of around 16,260 people. – with reports from the Agence France-Presse/Rappler.com