The rain has started to return in Northern California and will continue over the next few days, but officials aren't as concerned about the upcoming weather so much as the damage already done to the Oroville Dam's already compromised main spillway.

The risk of flooding has dropped substantially, but Butte County Sheriff Kory Honea warned residents Wednesday that they remain in "an emergency situation."

Officials confident Oroville Dam will withstand new rainstorm: 'It's holding up really well'

Reconstruction continues in a race to shore up the emergency spillway, left, at Oroville Dam on Wednesday. (Brian van der Brug / Los Angeles Times)
Reconstruction continues in a race to shore up the emergency spillway, left, at Oroville Dam on Wednesday. (Brian van der Brug / Los Angeles Times)

Even as rain began to fall in Northern California on Wednesday, state officials said the storms forecast over the next few days will not be enough to test the integrity of the Oroville Dam or its two damaged spillways.

Bill Croyle, acting director of the state Department of Water Resources, called the storms "fairly small" and said the public "won't see a blip in the reservoir" levels, now dropping about eight inches an hour.

Croyle said it was not the weather he was concerned about so much as the damage done to the dam's already compromised main spillway during days of sustained heavy releases of water.

"It's holding up really well," Croyle said, but continued mass water releases could be causing hidden damage to the rocky subsurface adjacent to the concrete chute.

A swarm of trucks and helicopters dumped 1,200 tons of material per hour onto the eroded hillside that formed the dam ’s emergency spillway. One quarry worked around the clock to mine boulders as heavy as 6 tons. An army of workers mixed concrete slurry to help seal the rocks in place.

At the main spillway, a different and riskier operation was underway: Despite a large hole in the concrete chute, officials have been sending a massive amount of the swollen reservoir’s water down the spillway to the Feather River in a desperate attempt to reduce the lake’s level.

The objective is to lower the level enough so that the lake can accept runoff from the upcoming storms without reaching capacity. If the reservoir filled up again, water would overflow into the emergency spillway, which on Sunday appeared to be nearing collapse, forcing the evacuation of more than 100,000 people downstream.

Croyle said there were plans to begin to taper off the water discharges at the end of the week.

Data from the Department of Water Resources shows Shasta Dam discharges began to be sharply increased on Feb. 10 and have increased substantially every day since that.

Federal emergency officials and the Trump administration approved Gov. Jerry Brown 's requests for presidential disaster declarations for the Oroville Dam and for the 34 counties struck in January by major winter storms that caused mudslides and power outages.

"I want to thank FEMA for moving quickly to approve our requests," Brown said in a statement from his office.

At a news briefing Tuesday, White House Press Secretary Sean Spicer said President Trump has been “keeping a close eye” on the situation at Oroville.

“The situation is a textbook example of why we need to pursue a major infrastructure package in Congress,” Spicer said. “Dams, bridges, roads and all ports around the country have fallen into disrepair.”

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