Preparedness & Recovery

Oroville Dam: Six Months After Disaster, a Race to Repair Before Next Winter

Today, what could have been ground zero for America’s worst dam disaster is now a hotbed of construction activity.

by Paul Rogers, The Mercury News / August 6, 2017

(TNS) - Six months ago, relentless winter storms dumped nearly 13 inches of rain in four days on the Sierra Foothills, tearing an enormous hole in the spillway at Oroville Dam, the nation’s highest, and leading to an unprecedented emergency that prompted the evacuation of 188,000 people from nearby towns.

Today, what could have been ground zero for America’s worst dam disaster is now a hotbed of construction activity. Hundreds of construction workers are laboring 20 hours a day, six days a week with huge dump trucks, cranes, excavators, bulldozers, concrete pumps and other equipment to demolish and rebuild the 3,000-foot-long main spillway — a massive chute as wide as 15 lanes of freeway– by Nov. 1, before the next winter rain season begins anew.

“We are on target. We have done about 95 percent of the demolition that needs to take place, and we are already placing new concrete for the new spillway,” said Erin Mellon, a spokeswoman for the state Department of Water Resources, which owns the dam. “Progress is pretty substantial.”

Led by Kiewit, a contractor from Omaha, Nebraska, that built Los Vaqueros Dam in Contra Costa County in the 1990s, construction workers are also shoring up Oroville’s emergency spillway, with a new underground retaining wall being built into its hillside and layers of concrete being poured to reinforce its top.

In all, for both spillways, crews will install 8.5 million pounds of steel rebar, and 55,000 feet of drainage pipe, enough to stack 10 miles high. They will pour 946,000 cubic yards of concrete over the next year — enough to fill nearly 100,000 dump trucks.

But the crisis isn’t over. Major questions remain. And disaster could happen again.

An independent “forensics team” ordered by federal regulators to find what went wrong issued preliminary findings in May, citing defects from the dam’s construction in the 1960s to problems linked to poor maintenance and oversight by state and federal officials. Its final report is due this fall. A separate investigation by engineers at UC Berkeley concluded that construction workers laboring for former Gov. Pat Brown 50 years ago cut corners, building the main spillway on weak rock that should have been excavated, then constructing the structure as thin as four inches in some places and failing to anchor or reinforce it properly.

Those dangerous shortcomings were compounded, the Berkeley report found, by trees that were allowed to grow along the spillway walls, clogging its drainage pipes with their roots, and an attitude of “patch and pray” from Department of Water Resources crews when the main spillway repeatedly developed cracks in recent decades.

“It’s not that complicated,” said engineer Bob Bea, founder of UC Berkeley’s Center for Catastrophic Risk Management  “It’s a tragedy of neglect. It was poorly built and poorly maintained.”

Meanwhile, the price tag is expected to reach at least $500 million. The state is hoping 75 percent will be paid by the Federal Emergency Management Agency, and most of the rest will come from the agencies that receive water from the State Water Project, which include the Santa Clara Valley Water District and the Metropolitan Water District in Los Angeles.

Outside dam experts say the current repairs — which are scheduled to finish in 2018 — are only the beginning. The state Department of Water Resources needs to do far more to modernize other huge dams across California, they say, and to make additional fixes at Oroville, where the aging steel gates atop the dam’s main spillway have numerous cracks and a mysterious green spot in the face of the 770-foot-tall earthen dam has some people worried whether the dam is slowly leaking.

“There are safety issues that are still outstanding,” said Ron Stork, policy director with Friends of the River, a Sacramento environmental group. “They are going to need attention sooner or later.”

Residents of the area are watching nervously.

“In many ways things are back to normal because we don’t have an imminent threat,” said Larry Matthews, 66, who lives in Yuba City, south of Oroville. “But people have a real concern that maintenance wasn’t done correctly. They want it fixed correctly. There’s a certainly some paranoia but you can’t blame people for that.”

Matthews moved to Oroville with his family from Los Angeles in 1963 when he was 12.

“I saw that dam being built when I was a teenager,” he said. “People were proud of it. You trust the people who built it. It lasted for 49 years without any major problems. When I saw all that concrete broken on the spillway, I said “it can’t be true. It looked like somebody photoshopped it.”

After the hole developed on Feb. 7, the issue became an  international story. State officials closed the main spillway, and the lake level rose to the top. Five days later, on Feb. 12, as water poured over the emergency spillway, eroding so badly it threatened to collapse, Butte County Sheriff Kory Honea issued an emergency evacuation order with phrases like “This is NOT a drill” spread across social media, radio and TV. Chaos ensured. Matthews, who three years ago wrote a book, “The Building of the Oroville Dam,” collected up birth certificates, passports and other vital documents in a garbage bag and prepared to flee with his wife and 93-year-old mother-in-law.

“I tried to evacuate,” he said. “But the roads were so congested I couldn’t even hardly get out of the driveway.”

Stores closed. Gas stations were overwhelmed. Panicked motorists drove on the shoulders of Highways 70 and 99. Matthews sat up all night watching TV news, ready to make a run for it with his family if he saw reports that the emergency spillway was collapsing, releasing Lake Oroville, which is 10 miles long and California’s second-largest reservoir, onto the towns below.

State water officials made a gambit. They re-opened the badly damaged main spillway to lower the lake.They knew the water — flowing at 750,000 gallons per second — would rip it apart, and hoped the violently out-of-control flows would not start eroding away the face of the dam itself. The plan worked. The lake level dropped. Water stopped flowing over the emergency spillway. The dam held. And two days later the evacuation order was lifted.

“People are still concerned,” said Beth Bello, an office manager who lives in Oroville. “They are saying on Facebook ‘Is the dam leaking?’ The construction workers are doing the best they can. But I do wonder how much the state is really telling us. They should have done more in the past. It could have been prevented.”

John Laird, California’s secretary of natural resources, who oversees the Department of Water Resources, said the incident brought back memories the 1989 Loma Prieta Earthquake, which destroyed Santa Cruz’s historic downtown, where he once served as mayor.

“I knew that the dislocation I felt then,” he said, “was the dislocation being felt by the community evacuated in the Oroville area.”

Laird said the state, which has lowered the lake level by 110 feet, is committed to rebuilding the main spillway by this winter so it can handle new storms, and then finishing the job next year. The plan will be done in two stages, with the bottom 75 percent replaced now and the top replaced next year. He said the state plans to learn from the investigative reports.

“We must never let down our guard and we can always do better,” he said.

Bea, of UC Berkeley, also investigated levee failures in New Orleans after Hurricane Katrina, the BP oil spill in the Gulf of Mexico and PG&E’s 2010 pipeline explosion in San Bruno. He said the entire hillside at Oroville’s emergency spillway should be armored with concrete, the steel gates on the main spillway should be replaced, and that the state needs to do an immediate, detailed investigation into the green spot on the dam, which state officials say is a harmless natural spring.

Bea said California needs a top-to-bottom change in dam safety, with much more preventative work to avert future disasters that could kill thousands.

“There is no free lunch,” he said. “You pay a little now, or one hell of a lot later.”

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©2017 the San Jose Mercury News (San Jose, Calif.)

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