Oroville Dam Spillway: Is It Safe?

Nov 3, 2017

From above, it looks miraculous. A massive canyon filled in, and near tragedy transformed into triumph, and officials, including Grant Davis, director of the California Department of Water Resources, are justly proud.

“This project is a stunning feat. I’ve been told by engineers and dam experts from across the country just how impressed they are by the amount of work completed in such an accelerated timeline,” Davis said Wednesday as he delivered on his predecessor Bill Croyle’s vow — to have a working gated spillway at Oroville Dam by Nov. 1.

While the progress certainly breaks the recent trend of snail-paced construction projects in California, officials may be exaggerating the accomplishments and downplaying remaining dangers.

There was a palpable sense of pride on the line Wednesday as DWR officials spoke on a conference call, announcing that the last load of concrete had just hours ago been poured into place and a near pristine half-mile ramp leading down from Oroville Dam was ready and able, right on time and just ahead of the rainy season.

Armies of workers, hundreds of thousands of tons of debris and concrete. The scope of work was truly monumental.

“Lake Oroville’s main spillway is indeed ready to safely handle winter flows, if needed,” Davis said.

Except the accuracy of that statement isn’t ironclad. When pressed, the assistant director of DWR’s public affairs, Erin Mellon, admitted that the newly poured concrete still needs a month to reach full strength, but dismissed concerns that it could suffer the fate of its predecessor, which broke apart in February.

“I mean, we certainly don’t want to use the spillway until the concrete is cured, but at the same time, if there was some significant weather and we needed to, we’d be confident in the work that we’ve accomplished,” she said.

It is very unlikely we’ll find out. DWR has skillfully drained Lake Oroville down to 695 feet of elevation. The lake would have to rise about 120 feet before the spillway could even be pressed into service.

Meanwhile, officials can still expel water via the Hyatt Power plant and the River Outlet Valve.

“Historically, we’ve only ever opened the gates and used the spillway in 26 of the 49 years that it’s been in existence. Only in four years have actually opened the gates before January 1st,” she added.

Even with as much as eight inches of rain expected over the Feather River Basin before Monday, Mellon said officials don’t expect any measurable rise in the lake’s level.

While the visible progress on the spillway is a wonder to behold, critics say a history of neglect and hubris among operators continues to pose possibly unacceptable risks and danger to the public. Robert Bea, a Professor Emeritus at the Center for Catastrophic Risk Management and of Civil Engineering at the University of California at Berkeley is one of the lead experts conducting an official independent analysis of February’s near disaster.

His team has identified several major concerns that he says remain unaddressed. He says evidence suggests that water is leaking through the dam, that an estimated 219 cubic yards of the dam’s core block---the earthen center---about 22 dump truck loads---has washed away, and that the floodgates controlling the spillway have deficiencies that could cause an unexpected failure.  

“We’re taking chances we don’t understand and the consequences can be severe,” Bea said.

DWR officials have refuted Bea’s findings, attributing green spots on the dams face to causes other than leakage and saying the issues with the radial gates are being monitored and maintained.

Bea said DWR officials have allowed the structure’s imposing edifice, and half century of service lull themselves into a false sense of security.

“Their thinking is conditioned by, well, we haven’t had a major failure yet,” Bea said

He said that if issues of the same caliber were detected at a nuclear power plant or on a class of jet aircraft, federal regulators would suspend the plant’s operating permit and ground the aircraft.

“For something that’s very important, that’s not an appropriate way to manage its integrity,” he added.

Without acknowledging that it needed to do more, DWR said it will conduct a comprehensive needs assessment of the entire Lake Oroville system, to be completed in September 2019. The radial headworks gates area part of that review.

As far as costs are concerned, the completed spillway work will cost about half a billion dollars. That’s atop about $150 million for other work. Because it was declared a federal disaster, the Federal Emergency Management Agency has paid 75 percent of the $102 million worth of invoices already submitted. The remainder is supposed to be paid by the irrigation districts and municipalities that receive water through the state water project.

How likely is a failure? That, according to Bea is an answer that can’t be calculated without more study. Bea said that when dealing with complex infrastructure systems on this scale—it is not ok to fly blind.

“If you can’t answer it, the guideline is, don’t operate it,” he said.

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