OROVILLE -- For another day, helicopters fly above the Oroville Dam, carrying heavy bags of sand and rock to plug up holes in the damaged spillway.
"Moving so much rock, so much material into place, it's incredible."
As work continues, onlookers from the area watch -- intrigued by the fast and necessary repairs at the nation's tallest dam.
"It's quite the operation going on here," said Larry Thompson.
Crews have been working around the clock for days, desperate to get things under control.
"We have 40 truckloads an hour, 30 tons of rock per hour is being placed. We have two helicopters that are moving every one and a half minutes. Aggressive, proactive attack to address erosion concern," said Bill Croyle, DWR's acting director.
The emergency spillway at the Oroville Dam was used this weekend for the first time since it was built 50 years ago.
On Sunday, officials noticed a massive hole caused by erosion.
The stakes were high.
If the spillway failed, a wall of water threatened to devastate nearly 200,000 people in Oroville and other communities along the feather river.
Now the risk is much lower, but the work is not over.
"Probably won't see a stop in the number of trucks and people as they switch from a response mode in a high-level monitoring to the point where we're going to recover the system. Busy construction time," said Croyle.
Water has been steadily flowing out of the main spillway in attempt to lower water levels at Lake Oroville ahead of a new round of storms headed toward Northern California.
"I want to reiterate, the spillway has been stable for four days," said Croyle.
Experts say the system can handle it, and locals are breathing a collective sight of relief.
"They saved it, yeah, they saved it," said Larry Thomson.