Workers are rushing to fix the barrier at the nation's tallest dam after authorities ordered the evacuation of almost 200,000 people for everyone living below the lake amid concerns the spillway could fail and send water roaring downstream.
"It's weird, nearly like the calm before the storm", said Cynthia Rule who lives above the dam, and presumably out of harm's way.
At a news conference Tuesday afternoon, Butte County Sheriff Kory Honea announced the order had been changed to an evacuation warning after he said the risk of flooding had been reduced.
Water continues to rush out of a damaged spillway at the Oroville Dam. Both spillways are next to the dam, which itself is sound, engineers say.
Hundreds of families were camped out in cars and tents at Silver Dollar Fairgrounds in Chico, about 25 miles (40 km) northwest of Oroville.
The earthfill dam is just upstream and east of Oroville, a city of more than 16,000 people.
As planned with raising lake level the water pours over a concrete weir into the emergency spillway, parallel to the main spillway, with a capacity of 15,000 cubic feet per second.
"Once you have damage to a structure like that, it's catastrophic", acting Water Resources director Bill Croyle told reporters. S. and now remains intact, but the emergency spillway is compromised and at risk of failure.
"Dams, bridges, roads and all ports around the country have fallen into disrepair", he said. He also said DWR engineers will spend the coming weeks calculating whether it makes sense to fix the existing concrete structure or build an entirely new spillway nearby.
During much of the five-year drought, the lake level was far below normal, forcing officials to slash water deliveries.
Obviously, the state did not upgrade the emergency spillway and, for whatever insane reason, they refused to reinforce the dam, endangering thousands of lives in the area.
"Basically it's going to be a triage situation".
The initial cave-in of the spillway occurred Wednesday when chunks of concrete went flying from the water surging down the spillway, creating a 200-foot-long, 30-foot-deep hole. Then PG&E removed power lines from transmission towers below the dam's auxiliary spillway to ensure safety should the towers themselves destabilize due to water flow.
State Department of Water Resources spokesman Chris Orrock says lake levels are dropping at a rate of 8 feet per day.