Posted: Tuesday, February 14, 2017 – 3:49 PM
(AFP) A sheriff on Tuesday lifted a mandatory evacuation order in northern California, which had impacted nearly 200,000 people in an area under threat of catastrophic failure at the tallest dam in the United States.
The Butte County Sheriff’s Department announced it had reduced the evacuation order to a warning, allowing people in downstream communities from Oroville Dam — 75 miles (120 kilometers) north of Sacramento — to return home.
The sheriff’s department in a Facebook statement said it had reduced the order to a warning thanks to “lower lake levels, further inspections, ongoing work to shore up the Oroville dam emergency spillway and updated weather forecasts.”
The department urged some 188,000 impacted residents to “remain vigilant and prepared as conditions can rapidly change” — saying that authorities could issue another evacuation order if necessary.
The area was bracing for another onslaught of storms forecast to begin Thursday, but the temperature is now projected to drop, which will diminish rains and lessen the flow into the reservoir.
A giant hole opened in the dam’s main spillway last week, forcing the 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 toward the valley below, media reported.
The authorities are draining about 100,000 cubic feet (3,000 cubic meters) of water per second from the dam’s main spillway. The goal is to lower the water level by at least 50 feet (15 meters) below the top of the reservoir.
The lake level has fallen 12 feet below the top of the auxiliary spillway, which is no longer overflowing, reducing the risk of erosion.
The Oroville Dam, built in 1968, is 770 feet high, the tallest in the country.
© Agence France-Presse