But water levels increased, requiring officials, for the first time in the history of the dam, to use the emergency spillway, which also suffered damage (probably due to the same issue). As of the morning of Sunday, February 12, 2017, officials were still saying that there was no danger of the dam collapsing. However, Sunday afternoon, government officials ordered the evacuation of nearly 200,000 residents in Butte, Sutter and Yuba counties in Northern California (including the cities of Oroville, Gridley, Live Oak, Marysville, Wheat land, Yuba City, Plumas Lake, and Olivehurst) in the event of a failure. According to an AP article:
The erosion at the head of the emergency spillway threatens to undermine the concrete weir and allow large, uncontrolled releases of water from Lake Oroville, the California Department of Water Resources said. Those potential flows could overwhelm the Feather River and other downstream waterways, channels and levees.
The California National Guard has reportedly notified all 23,000 if its soldiers and airmen to be ready to deploy if needed.
The latest news I've found indicates that officials have successfully been able to drop the water levels in the dam, but storms expected this Friday may fill it right back up to the brim.
News reports indicate that there is grid-lock in some of the areas under the evacuation order as people attempt to flee, and lines are backed up to buy gasoline.
Sources and References:
"188,000 under evacuation orders near Northern California dam"--Associated Press (2/12/2017)
"California prepares for catastrophe: Battle to stop a collapse at America's tallest dam as 200,000 residents flee amid fears of a 100ft-deep flood that could stretch for 40 miles"--Daily Mail (2/13/2017).
"Water Vapor Almost Busts Dam: A strange phenomenon was shredding Glen Canyon Dam. Here's how it was saved."--Popular Science (March 2003).
"Cavitation Damage in Concrete and Protection"--The Constructor.