Crews work to backfill erosion on Oroville spillway

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OROVILLE, Calif. — California water officials continue to work around the clock to repair the emergency spillway at the Oroville Dam as they brace for more rain later this week.

Chris Orrock, a spokesman for the California Department of Water Resources, said water is not going over the emergency spillway and erosion has stopped. Lake Oroville is at 889 feet and the goal is to drop the level to around 850 feet. Lake levels reached 902 feet when water started cascading over the emergency spillway Sunday.

“Through our calculations, it looks like that will get us through the next storm,” Orrock said Tuesday morning of the 850-foot goal.

A pair of storms are expected to hit California this week, and forecasters say they will be strong enough to bring 2 to 6 inches of rains to Oroville.

Officials continue to release 100,000 cubic feet per second (cfs) down the main spillway while 20,000 to 40,000 cfs is coming into the lake. “So we are taking out a lot more water than is coming in,” Orrock said.

Helicopters dropped boulders into the holes and gouges which appeared as a result of the erosion of the emergency spillway.

“We are backfilling those holes with gravel, then putting a slurry mixture to harden those parts, so when the rain comes, it will roll down instead of furthering eroding those holes,” Orrock said.

Evacuation orders are still in place and there is no word when they will be lifted.

Orrock emphasized again that Oroville Dam has not been compromised and is not affected by the eroding emergency spillway.

“Our primary concern is the safety of the community,” he said. “We don’t want to lift the evacuation orders and have them come back and then have another incident … and have them leave again,” Orrock said.

The nearly 200,000 evacuated residents were told Monday it could be up to two weeks before they secure the eroded section of the emergency spillway enough to let them return to their homes without the threat of a catastrophic flood.

Rep. Doug LaMalfa, R-Richvale, appealed to President Trump on Monday to declare a major emergency for the area and by evening California Gov. Jerry Brown told reporters he had held a conversation with a Trump Cabinet member he declined to name.

The Federal Emergency Management Agency is providing 150,000 bottles of water, 20,000 blankets and 10,000 cots to support residents affected by the evacuation.

A day after the urgent Sunday evening evacuation, officials with the state agency responsible for operating the dam remained confounded by the failure of the spillway that was supposed to be the dam’s backup plan.

As the highest dam in America, the main structure is built of 85 million cubic yards of earth and remains sound, officials say. But just more than a week ago, a hole appeared in the concrete spillway off to its side and quickly grew as the surging water blasted off chunks of loose concrete and hurled them downhill.

With that channel damaged and storm-driven runoff swelling the reservoir, officials insisted the emergency spillway would be prepared for service. It had never been used before, and began to erode dangerously — leading to the concerns of a failure and the order to evacuate.

At a news conference around midday Monday, Bill Croyle, the state’s acting director of the Department of Water Resources, admitted his agency doesn’t have clear answers.

“I’m not sure anything went wrong,” he said. “That system has been installed since the early 1960s. It’s been monitored, but I’m not sure what caused the damage itself. It’s designed for higher flows. Lower flows can create more energy. We don’t completely understand why this erosion occurred.”

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Croyle said it could be at least 15 days or longer before the agency will be able to put a plan into place to make repairs. He said a plan has been approved, but did not go into details.

Heavy trucks were moving rocks into a staging area near the dam throughout Monday morning, and by late afternoon helicopters were carrying bags of rocks toward the eroded section of the emergency spillway.

Crews are filling in the erosion around the spillway with boulders and gravel, said Josh Janssen, a spokesman for the California Department of Forestry and Fire Protection.

He did not know the volume of rocks being placed in the eroded area. At some point, the Department of Water Resources plans to cover the boulders and gravel with concrete, he said.

“The goal is to replace the erosion and make (the spillway) stronger,” said Janssen.

The Department of Water Resources continues to let more water out of the lake at a rate of 100,000 cubic feet per second in an effort to lower the lake level to 50 feet below its capacity. That should allow room for more runoff and to accommodate coming storms, and allow the water agency to stop releases so they can make repairs to the crumbling main spillway.

By Monday evening, the lake was about 6 feet from its crest.

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Water continues to rush out of a damaged spillway at the Oroville Dam. Evacuations remain in place for residents downriver. USA TODAY NETWORK

Most residents appeared to have heeded evacuation warnings, although some remained in towns from Oroville downriver to Marysville and Yuba City. At the news conference with Croyle, Butte County Sheriff Kory Honea defended the decision to order the evacuation and keep it in place.

“It’s a dynamic situation,” he said. “We need to make sure that before we allow people back in those areas it is safe to do so.”

Honea said the Sheriff’s Office is devising a repopulation plan to let people go home in an orderly fashion when the time arrives.

Speaking from the headquarters of the Office of Emergency Services just outside Sacramento, Brown pledged Monday night more scrutiny will be placed on California’s massive infrastructure network.

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“We’ll get a lot of eyes on the problem now that we have a problem. And the response is big,” Brown said. “Things can fail, whether its levees or dams or bridges, we’ve got a lot of work to do.”

Brown specifically addressed questions about a 2005 motion to the Federal Energy Regulation Commission from environmental groups that raised concerns about the safety risks posed by the dam’s emergency spillway.

“It was not part of the record before that, at least the record I saw,” Brown said, adding he’s glad the report is being discussed.

An engineer with the Federal Energy Regulation Commission responded to the concerns in 2006, saying the emergency spillway’s design complied with the commission’s engineering guidelines.

Schools in the evacuation areas near Yuba and Sutter counties will remain closed at least through Tuesday, The Sacramento Bee reported. Many school districts were closed Monday in observance of President Lincoln’s birthday, though many will not open its doors until authorities deem the area safe, The Sacramento Bee added.

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http://www.usatoday.com/story/news/nation-now/2017/02/14/oroville-dam-spillway-fixes/97884412/?utm_source=dlvr.it&utm_medium=twitter

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