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Wed March 5, 2014
Outside Experts Weigh In On Columbia River’s Damaged Wanapum Dam
Teams of engineers are scrambling to figure out what’s gone wrong with the Wanapum Dam on the Columbia River near Vantage.
The dam’s problem is on a structure called the ogee, a big piece of concrete anchored to the bottom of the river. It’s like a river speed bump; it has a big curve on the top where the water flows over it. 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 yet sure how deep the crack goes back into the massive concrete hump.
“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 Chuck Berrie, who helps manage the dam for the Grant County Public Utility District.
‘A Two Inch-Thick Crack Can Be Significant’
Now that the crack appears to be stabilized, Berrie said, crews 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 also 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 has worked on it or knows about it. Shogren 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.”
‘Sunny-Day Scenario’: No Clear Cause
What’s caused the mighty crack in the Wanapum Dam is the big question. John Osteraas, a national disaster expert who has dealt with the aftermath of Hurricane Katrina and the Oklahoma City bombing, 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,” Osteraas said.
What troubles Osteraas is that the dam failed with no clear cause. It’s 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,” Osteraas said.
Worst-Case Scenario? Few Details Available
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.
Grant County’s Chuck Berrie wouldn’t say whether the dam is failing, but said even if the dam did fail, “it’s not right that it would create a tidal wave downstream. That is not a situation or scenario that would occur at all.”
And Berrie 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, a major employer in the area who 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,” Allen said.
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.