By Kristine Guerra, The Washington Post
In 2005, three environmental groups warned state and federal officials about what they believed was a problem with Oroville Dam’s emergency spillway, which was at risk of collapsing over the weekend as recent storms caused the adjacent massive reservoir to swell.
Their concern, which seemed to have fallen on deaf ears: The emergency spillway, which is meant to be used in urgent situations — is not really a spillway.
Rather, it’s a 1,700-foot long concrete weir that empties onto a dirt hillside. That means, in the event of severe flooding, water would erode that hillside and flood nearby communities, the groups said then.
That nearly happened on Sunday, when a hole on the emergency spillway threatened to flood the surrounding area and prompted officials to evacuate thousands of residents who remain displaced as of Monday afternoon.
(Water levels dropping but dam evacuation orders still stand, courtesy of Fox News and YouTube)
When the Oroville Dam was going through a re-licensing process, the three groups filed a motion in October 2005, urging a federal regulatory agency to require state officials to armor the emergency spillway with concrete so that in case of extreme rain and flooding, water won’t freely cascade down and erode the hillside.
The upgrade would have cost million of dollars, and no one wanted to foot the bill, said Ronald Stork, senior policy advocate for Friends of the River, one of the groups that filed the motion.
“When the dam is overfull, water goes over that weir and down the hillside, taking much of the hillside with it,” Stork told The Washington Post.
“That causes huge amounts of havoc. There’s roads, there’s transmission lines, power lines that are potentially in the way of that water going down that auxiliary spillway.”
Federal officials, however, determined that nothing was wrong and the emergency spillway, which can handle 350,000 cubic feet of water per second, “would perform as designed,” according to a July 2006 memo from John Onderdonk, then a senior civil engineer for the federal agency.
“The emergency spillway meets FERC’s engineering guidelines for an emergency spillway,” Onderdonk wrote.
“The guidelines specify that during rare flood event, it is acceptable for the emergency spillway to sustain significant damage.”
Fast forward 11 years later, the erosion of the emergency spillway became so severe this weekend with only up to 12,000 cubic feet of water per second. That’s a little more than 3 percent of what officials said the spillway can handle.
Lake Oroville’s level rose significantly after potentially record-setting rain surged through California following a long drought.
(UC Davis Civil and Environmental Engineering professor Jay Lund explains what’s going on with the Oroville Auxiliary Spillway failure. Courtesy of CBS Sacramento and YouTube)
The Oroville Dam, the tallest in the country at 770 feet, remains stable, officials said. But the structure of the spillways, which are designed to release water from the reservoir in a controlled fashion, have crumbled.
Earlier this month, a portion of the main spillway — a 3,000-foot-long structure lined in concrete — eroded because of the high volume of water spilling from the reservoir, creating a craterlike hole.
Officials with the California Department of Water Resources, which owns and operates the dam and reservoir, then decided to use the adjacent emergency spillway for the first time since the dam was built nearly 50 years ago.
Sheets of water began spilling over the emergency spillway and onto the hillside, carrying mud and debris into the nearby Feather River.
The emergency spillway appeared to be working as expected — until Sunday, when officials spotted a hole. That raised fears of a catastrophic flood that could wipe away Oroville, a town of 16,000 people, and prompted officials to evacuate nearly 200,000 area residents.
“Auxiliary spillway at Oroville Dam predicted to fail within the next hour. Oroville residents evacuate northward,” the state water agency tweeted shortly before 5 p.m. Sunday.
Ronald Stork, senior policy advocate for Friends of the RiverStork believes none of that would have happened had officials listened to his and others’ concerns and built a proper emergency spillway 12 years ago.
The two other groups that filed the 2005 motion are the Sierra Club and the South Yuba River Citizens League.
“They told us not to worry. All was good. Everything was fine. It’s all safe,” Stork said.
“First of all, they’re not supposed to fail. That’s not what we do in a first-world country. We don’t do that. We certainly don’t do that with the nation’s tallest dam. An auxiliary spillway isn’t supposed to cause lots of havoc when it’s being used.”
Construction would’ve cost at least $100 million, Stork said, and the state contractors in Southern California that buy water from Northern California would’ve had to pay for it.
The Metropolitan Water District of Southern California, which provides water to 19 million people in Los Angeles, San Diego and other areas, and the State Water Contractors, would’ve had to shoulder the cost and deemed the upgrades unnecessary, according to the Oroville Mercury Register.
(Learn More, courtesy of CBS Sacramento and YouTube)
“The people who are bearing the personal risk of being killed and having their homes washed away are the people of Northern California,” Stork said.
Pressed during a news conference Monday afternoon about the 2005 motion, Bill Croyle, acting director of the Department of Water Resources, said he’s not familiar with the conversations that happened then.
“It’s the first time it’s ever taken water,” Croyle said of the emergency spillway. “We don’t know exactly why this erosion occurred.”
Lester Snow, the agency’s director from 2004 to 2010, told the Oroville Mercury Register that he does not recall specific information about the debate over the emergency spillway 12 years ago.
“The dam and the outlet structures have always done well in tests and inspections,” Snow told the paper.
“I don’t recall the FERC process.”
The crisis seemed to have been averted by Monday. Lake Oroville had dropped to 898 feet by 4 a.m., according to the Sacramento Bee. Water flows into the emergency spillway at 901 feet.
Officials doubled the flow of water out of the main spillway to 100,000 cubic feet per second, with the hope of lowering the lake level by 50 feet to leave room for upcoming rain.
Rain is expected through the region on Wednesday and Thursday, with showers lingering on Friday and Saturday, according to the National Weather Service. Water levels also are expected to rise later this week and into early next week.
Officials said Monday that they’re continuing to monitor the spillways for further erosion.
It remains unclear Monday when residents will be allowed back to their homes. Inmates at the Butte County Jail also have been moved to Alameda County about 170 miles away.
Samantha Schmidt and Derek Hawkins contributed to this story.