Crews nervously watched to see if all their work - caulking, sealing and re-concreting - was enough to withstand 50,000 cubic feet per second of water.
"The idea is to make sure nothing moves around while we go through the spill event," Department of Water Resources Acting Director, Bill Croyle said. "We believe we've done everything we can and more."
Since the DWR completely stopped the use of their main spillway in late February, the water levels here at the Oroville Dam have increased more than 20 feet. That is why they now need to flush it out to make room in the reservoir for future rain and snow melt.
In the meantime, crews have moved an incredible amount of sludge and debris from the bottom of the spillway.
"1.25 million cubic yards of the 1.7 that we have mapped out in the diversion pool," Croyle said at a media briefing Friday morning.
Despite major improvements, this week DWR was hit with a sudden setback.
During recent air quality testing, safety monitors found asbestos at some work sites. Experts say unlike the extremely harmful asbestos found in old building materials, the one discovered here is naturally occurring.
"Historically there are notes of asbestos in the area, all the way back to 1868," David Beadle, Certified Industrial Hygienist with Safety Management Systems LLC, said.
While they only found limited amounts of it, as a safety precaution, crews are wetting the ground near the work sites to suppress dust. DWR said no workers or residents are in danger of asbestos exposure.
For now, experts turn their attention back to the damaged spillway. They hope to use the spillway for about five days, until they reach their target reservoir elevation of 835 feet.
"As long as we don't see a catastrophic loss of a lot of concrete, then we're going to need to roll through this," Croyle said.
The DWR says this is most likely one of three spill events they will conduct between now and June 1.
They also said the release will likely increase water levels at the Feather River ten to fifteen feet, so they urge anglers and boaters to be cautious.
At the media briefing, they announced their estimated cost of repairs as of February has amounted to $100 million.
DWR officials said the Water Forensics team still pinpointing the exact cause of the original breach. Once they figure that out, they will start making the new design of the new permanent spillway