Is there a lesson in problems at the Oroville Dam?
Things got scary downstream of the Oroville Dam this week. And with new storms brewing in northern California, nearly 200,000 evacuees are still holding their breath.
Municipal crews worked round-the-clock听Tuesday to stave off potential disaster. Engineers kept water from Lake Oroville gushing out through a spillway, bringing the lake鈥檚 levels well down from where they peaked on Saturday, . And workers raced to patch up a second, emergency spillway that, like the first, was damaged over the weekend, threatening to unleash floodwaters on the region.
With the initial scare hardly past, however, scrutiny of the damage to the spillways has raised questions about what lessons might be gleaned from a still-precarious situation 鈥� or whether the Oroville Dam鈥檚 spillway problems were a freak accident, a matter of poor planning by regulators at a single site, or something else.
鈥淚 don鈥檛 think we know what went wrong, frankly,鈥� says Marty McCann, a Stanford University civil engineer and director of the National Performance of Dams Program. 鈥淚 would expect that there would be any number of boards that would investigate this.鈥�
鈥淏ut people are focusing on the emergency spillway,鈥� he adds, 鈥渁nd rightfully so.鈥�
In the dam鈥檚 50 years in existence, that spillway had rarely been necessary. But after the main channel for diverting excess water during major rain events听was damaged, California Department of Water Resource (DWR) engineers redirected听waters toward the second, suddenly putting it to the test.听
The sturdiness of that spillway 鈥� little more than a concrete weir that channels water听down a dirt hillside 鈥� had been called question over a decade ago by environmental groups, during the dam鈥檚 re-licensing.
In 2005, three groups filed a motion that asked federal regulators to require California to reinforce the hillside with concrete, warning that floodwaters could erode it and send rocks, soil, and debris into the Feather River below, causing damage and threatening lives downstream,
鈥淲e said, 鈥楢re you really sure that running all this water over the emergency spillway won鈥檛 cause the spillway to fail?鈥� 鈥� Ron Stork, policy director with the Sacramento-base Friends of the River, told the paper. 鈥淭hey tried to be as evasive as possible. It would have cost money to build a proper concrete spillway.鈥�
Regulators determined that the extra 鈥渁rmor鈥� wasn鈥檛 necessary, with one senior engineer at the Federal Energy Regulatory Commission pointing to guidelines specifying that 鈥渄uring a rare flood event, it is acceptable for the emergency spillway to sustain significant damage,鈥� .
The damage incurred听over the weekend, however,听appeared to have crossed the line from significant to potentially dangerous.
On Sunday, monitoring officials reported severe erosion on that spillway, even though water volumes were just 3 percent of what it was supposed to be able to handle, and triggered the mass evacuation.
That was a worrisome surprise, says Dr. McCann.
鈥淭hat just shouldn鈥檛 happen,鈥� he tells 海角大神.听
Others have wondered whether the problems might be traced to infrastructure woes. As The Atlantic noted on Monday, the American Society of Civil Engineers for maintenance of its aging dam networks, most of which were built in the 1960s or earlier. But dam safety in California is also known to be as among the country鈥檚 most robust.
Still, dams can be notoriously difficult to maintain, as large volumes of water can sometimes behave in unpredictable ways, says Gregory Baecher, a civil engineer at the University of Maryland and dam safety expert.听The kind of听erosion on the main spillway is particularly common.
鈥淭hat鈥檚 something we see a lot in dams,鈥� he tells the Monitor.
Whether the issues on the main spillway were due to aging, inadequate maintenance, or something else remains unclear, he notes. And the Oroville Dam is often seen as the 鈥減oster child鈥� for California鈥檚 water-project excellence.听
But 鈥渢his is a thing that dam-safety and hydraulic engineers worry about all the time,鈥� he says. 鈥淭he forces of water are just huge.鈥�
鈥淭he bill from lack of maintenance over the last 50 years is huge,鈥� he tells the Monitor.
鈥淚 think this does point out that we have to keep investing in maintenance of all this stuff if we鈥檙e going to be a modern economy.鈥�
