People of Northwest Public Radio
Wed March 5, 2014
Outside Experts Weigh In On Columbia River’s Damaged Wanapum Dam
Now to central Washington. A situation on the Columbia River is rapidly unfolding with the damaged Wanapum Dam near Vantage, Washington. Teams of engineers are scrambling to figure out what’s gone wrong with part of Wanapum’s spillway structure.
So the problem with the Wanapum Dam is on a structure called the ogee. That’s a big piece of concrete that is anchored to the bottom of the river. It has a big curve on the top where the water flows over it. It’s like a river speed bump. When the spillway gate is lifted, the water flows through from the upriver side of the dam to the downriver side over this ogee. This is how dam operators let extra water through the dam that’s not needed for power production. But the ogee is cracked all the way across its upstream face, underwater. The dam operators and engineers aren't sure how deep the crack goes back into the massive concrete hump, but that’s what they are trying to figure out.
“Right now the main focus is that particular area, but we are going to do a complete and thorough evaluation of the structure before we’re through.” Said Berrie
That’s Chuck Berrie. He helps manage the dam for the Grant County Public Utility District. He says that now that the crack appears to be stabilized they can …
“... identify exactly how deep, how wide, how far, the location of any cracking. We just don’t know all of that at this time.”
Berrie says there are three teams of engineers working on the dam – county engineers, a federal team and an independent panel of experts from across the U.S. They don’t have any answers yet and Berrie wouldn’t speculate on what they could be. Still, what’s troubling to experts on dams and concrete structures is that the ogee is not only cracked, it’s slipped a little.
Rob Shogren is the technical director at a French-owned concrete company called Lafarge International. If it’s big and it’s concrete in the west, there’s a good chance Shogren’s worked on it or knows about it. He says cracks in concrete dams aren’t unusual but …
“… a two-inch thick crack can be significant. It just depends on where it is in the structure, how deep it goes and what caused it.” Said Shogren
And what’s caused the mighty crack in the Wanapum Dam is the big question. John Osteraas is a disaster expert – he’s actually a national guru on disasters. You might have heard of a couple of his past projects: Hurricane Katrina and the Oklahoma City bombing. He doesn’t like the sound of what’s happening at Wanapum.
“We’ve certainly over history seen some fairly spectacular failures of dams. There is an enormous amount of energy stored in the water behind the dam.” Said Osteraas
What troubles Osteraas, is that the dam failed with no clear cause. What disaster experts call a “sunny day scenario.”
“When things just fail in the normal course of events, under loads and forces that we thought were within the safe region. Then we have to be much more aggressive, much more thorough in our inspection to make sure we understand the total picture.” Said Osteraas
Osteraas says a good move right now would be to reduce the water between Wanapum Dam and the next dam downriver, Priest Rapids. That would create a space between the two dams for the extra water if Wanapum was to fail. I asked Grant County’s Chuck Berrie if that was happening. He didn’t answer the question but he argues that even if part of the dam was to fail …
“It’s not right that it would create a tidal wave downstream. That is not a situation or senerio that would occur at all.” Said Berrie
And he believes if the ogee topples, the rest of the dam should remain in place.
But here’s the thing. When asked about the contingency plan for what happens if the dam does bust – county officials say they have drills and plans, but they aren't sharing a lot of specifics.
They’re certainly not sharing them with Steve Allen.
He’s a major employer in the area and lives about three miles downstream from the dam. His farmhouse overlooks the Columbia River and his 100-acre apple and cherry orchard rolls out below. His eyes betray his worry over the dam.
“If it broke, if it actually came apart my orchard would be severely affected. It’s only 10 or 15 feet above the water level. And so if a huge amount of water came into here it would affect that. It would wipe out my orchard probably.” Said Allen
Back at ground zero the Wanapum Dam, looks like it has on any normal day. There are a few orange traffic cones and signs. But that’s it.
Confidential sources within the federal government tell me that the last government review of the dam’s overall safety found no significant findings. But the coming months could get complicated for dam engineers’ Band-Aid efforts. Right now, the mighty Columbia River is at its low winter levels. But soon spring snowmelt will swell the downstream river flows and sensitive salmon runs will be making their way up stream.
Copyright 2014 Northwest News Network
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