Condit Dam decommissioning takes the next step
Vancouver company helping mother nature restore White Salmon River’s path
Saturday, November 5, 2011
WHITE SALMON — Dale Kuykendall strolls a few hundred yards from his makeshift office to a ledge offering a jaw-dropping view of the newly unleashed White Salmon River.
It’s noon Wednesday. Exactly one week earlier, on Oct. 26, the river upstream from Condit Dam was still a flat-water reservoir. Now it’s a raw, steep-sided canyon that shifts daily, even hourly, as a century’s worth of sediment and buried logs oozes through. You can see the ghost of the original free-flowing river as it carves a new course through the sludge.
Kuykendall, a construction engineer, is the project manager for the decommissioning of Condit Dam, a project that won’t wrap up for another 12 months. His company, Vancouver-based JR Merit Industrial Contractors, won the $16 million contract with PacifiCorp to take out the dam in 2010. It’s the company’s fourth dam decommissioning project and by far its largest.
Kuykendall joined JR Merit a year ago. The company itself is a veteran of PacifiCorp dam repair and deconstruction projects across the West.
He and his team of three worked closely with PacifiCorp project manager Tom Hickey on day-to-day operations throughout the dam breaching process.
On the one hand, he said, breaching Condit wasn’t rocket science. “We’re pretty creative people with enough experience in decommissioning” to do the job, he said.
On the other hand, “This was pretty historic,” he added. “It’s unique. My team was excited to be a part of it.”
At 125 feet, Condit Dam just missed being the highest hydroelectric dam ever breached in the United States. At 210 feet, Glines Canyon Dam on Washington’s Elwha River beat it by a month when its decommissioning began in September.
On Wednesday, Kuykendall and his team were working out of their office, a house perched near the river’s east bank that PacifiCorp converted to a command center for the dam breaching. They were monitoring the continuing movement of sediment and logs downstream to the river’s mouth. An estimated 2.7 million cubic yards of sediment built up behind the dam over 98 years. A big unknown after the breaching was how quickly that sediment would be carried down to the Columbia River.
One of the constraints of monitoring the shifting mass is that it’s all but impossible to view some sections of the lower river from shore, Kuykendall said.
On Wednesday, Mark Zoller, owner of a White Salmon River rafting company, guided a dozen researchers on a float trip down the river from the powerhouse to the mouth to get a close-up look at navigation hazards and collect sediment samples. PacifiCorp wasn’t eager to publicize the voyage because the lower river is closed to all recreational boating until next year.
The company and its contractors will continue to monitor the river through the winter for log jams and sediment flows that could block fish passage. They’ll also stay vigilant to prevent accidents along unstable shores.
On Wednesday, Kuykendall was getting ready to post signs warning “Danger: Fatal Fall Hazard” along access roads near the canyon where banks could give way underfoot. The message was clear: The White Salmon both above and below the dam remains a dangerous and unstable place to be.
Planning for blast day
It’s not every day a local contractor gets the opportunity to take out a century-old dam.
But over the past several years, JR Merit, founded in 1998, has tackled numerous hydroelectric projects for PacifiCorp in the seven states where it is licensed to do business: Washington, Oregon, Idaho, California, Utah, Colorado and Montana.
The company has overseen the decommissioning of three smaller dams: The Cove Hydroelectric Project on Idaho’s Bear River, in 2006; the American Fork Hydroelectric Project in American Fork, Utah, in 2007; and the Little Sandy Dam on Oregon’s Sandy River, in 2008.
Over that same period, Merit has responded to at least 10 hydroelectric project emergencies, including repairs to two powerhouses at Swift Reservoir on the North Fork of the Lewis River east of Cougar.
Merit was among several companies invited by PacifiCorp to submit bids for the Condit breaching. As the successful bidder, it works under the oversight of Kleinfelder, a construction management contractor that prepared the bid documents. “They act as PacifiCorp’s eyes and ears on the site,” Kuykendall said.
Kuykendall and his team came up with the plan for dewatering and rerouting the river at the base of the dam so the tunneling could begin. They considered using a crane on a barge as a staging area for the heavy equipment needed, but elected to use a tower and cable system instead. “It would have required a huge crane and a huge barge,” Kuykendall said.
In advance of the blasting, Merit engineers performed concrete strength tests on the dam. “Concrete 100 years ago was not nearly as strong as today,” Kuykendall said, though the concrete in Condit Dam continued to cure and harden after the dam was built. One surprise, discovered only when drilling into the dam began, was that it contained “really big rocks and boulders” that could weaken the structure. “It’s not a homogenous mass. It’s a discontinuous mass” that could have fractured in unpredictable ways.
Kiewit Infrastructure West Co. of Vancouver, a Merit subcontractor, handled the drilling and tunneling work at the base of the dam. Workers drilled thousands of small holes in the dam for loading the explosives that allowed them to bore through the 90-foot-thick base of the dam.
“There were 15 blast days,” Kuykendall said. On each blast day except the last one, crews tunneled through about six feet of concrete. The October 26 blast took out the final 10-foot plug.
The actual detonation required precise timing, he said. “Once you stop the flow of water, the lake starts to rise.
Power generation ceased at 11:18 a.m on breach day, Hickey said.
The gates up at the dam closed at 11:55 a.m.
There was a last-minute security check.
And then 700 pounds of explosives were detonated in the tunnel, unleashing an explosion of dust and sediment and dark water that drew gasps, cheers and stunned amazement from crowds gathered to witness the dramatic spectacle.
Seismographs showed the blast occurred at 12:08 p.m.
The Merit team watched it all unfold from a video screen inside the house.
“That day went textbook precise,” Kuykendall said with a hint of pride. “My team did an excellent job. It was pretty exciting. The real relief came when we saw it was a complete success.”
Activity at the dam will slow over the winter. Contractors hope heavy winter rains will wash most of the remaining sediment downstream and make the river safe for boaters and habitable for aquatic life again.
“Upstream, Mother Nature will do a lot of the work,” Kuykendall said.
Deconstruction work will resume in the spring. Crews will block the penstock that carried the river’s flow from the wood-stave flow line a mile downhill to the powerhouse. They’ll also block the tubes that returned the flow from the powerhouse back to the river downstream.
In May, they’ll cut up the concrete dam with a hydraulic excavator and bury the 35,000 cubic feet of rubble along the bank where the flow line runs. The treated wood from the flow line will be sent to a Klickitat County landfill.
They’ll remove the coffer dam and diversion structure that diverted the river’s flow while the dam was under construction and that still holds back significant sediment deposits. Discussions are still underway about when and how those structures will be removed.
Eventually, the sides of the V-shaped river canyon will reach a stable angle of repose. Grading of the banks will begin in May or June, when the shores dry out enough to allow heavy equipment to operate.
“We’ll restore the bank so it resembles the original grade,” Kuykendall said.
In late summer, after the grading is complete, crews will plant trees, seeds and shrubs. “The steepest slopes are rocks and cliffs, so there won’t be a lot of planting there,” Kuykendall said.
JR Merit’s contract runs through November of 2012. After that, the free-flowing White Salmon River will shape its own destiny again.