PacifiCorp will begin demolishing 98-year-old Condit Dam on the White Salmon River in late October, removing a barrier to passage of salmon and steelhead.
The breaching of the dam, originally planned for 2006, has been delayed repeatedly, and the estimated $32 million price tag for the project is nearly double the $17 million the Portland utility expected to pay when it first announced plans to remove the dam back in 1999.
At 125 feet, Condit will be the second-highest dam ever removed in the United States. Glines Canyon Dam on Washington’s Elwha River, at 210 feet, will be the highest U.S. dam ever removed if it comes down on schedule in September.
“This fall we will see two of the biggest river restoration projects in history, and they’re both in Washington,” said Amy Kober, spokeswoman for the environmental group American Rivers. “It’s an exciting river renaissance.”
“Decommissioning the hydroelectric project is now on a fast track” after PacifiCorp received a critical sediment management permit from the U.S. Army Corps of Engineers, one of the project’s last major hurdles, said PacifiCorp spokesman Tom Gauntt.
On Monday, the company notified the Federal Energy Regulatory Commission that it had accepted the terms of its “surrender order,” a document that sets forth the conditions the company must meet to surrender its federal dam license.
“It’s nice to have gotten all the regulatory permitting milestones out of the way,” said Todd Olson, compliance manager for PacifiCorp. “Now that we have accepted the surrender order from FERC, we turn our attention to working with the contractor to implement this project in a safe manner.”
JR Merit Industrial Contractors of Vancouver will be the general contractor on the dam decommissioning project.
The process for demolishing the dam was hammered out in a 1999 settlement agreement with conservationists, state agencies and the Yakama Tribe that has not changed significantly over a dozen years. All parties to the settlement agreed not to challenge it in court.
Prior to breaching, workers will dynamite a 12-foot by 18-foot tunnel through 80 feet of the dam’s 90-foot-thick base. On demolition day, they’ll blast through the final 10 feet. The impounded waters of Northwestern Lake behind the dam will flow through the tunnel at an initial rate of 10,000 cubic feet per second.
“It will be a controlled high-water event,” Gauntt said. “The flow that will be coming down will be more than what normally comes down, but it won’t cause any flooding.”
The 92-acre reservoir is expected to empty in about six hours.
Some 2.3 million cubic yards of sediment built up over nearly a century will be flushed downstream, killing virtually all life in the lower 3.3 miles of the river. The sediment will enter the Columbia River, which will carry it downstream all the way to Bonneville Dam.
The payoff: Lower Columbia River chinook salmon will regain free and unrestrained access to 14 miles of habitat on the White Salmon and its tributaries, and mid-Columbia River steelhead will regain access to 33 miles of habitat in the watershed. The free-flowing river also is expected to protect critical bull trout habitat and benefit bears and other wildlife that feed on salmon.
The dam’s removal also will open a stretch of white water to rafters upstream.
“We’re incredibly excited,” said Kober of American Rivers, a party to the 1999 settlement agreement. “There are a lot of people who are going to be celebrating when this dam comes down. Obviously, it served a useful purpose. But the time has come to restore the river.”
In a statement, Virgil Lewis of the Yakama Nation Tribal Council called the announcement of the dam’s decommissioning “a momentous and long-awaited day.”
“This is an essential step in restoring the ecosystem’s resources and rebuilding the natural balance that supported the Yakama people and a significant tribal fishery for millennia,” he said.
A complex project
Removing the dam proved far more complicated than PacifiCorp envisioned when it decided to decommission the dam rather than pay to install fish ladders. FERC would have required the utility to provide fish passage as a condition of relicensing the dam.
As recently as January, PacifiCorp said in a filing with FERC that it was “clearly foreseeable and arguably likely” that it would not make its October 2011 target date.
From the beginning, Skamania and Klickitat counties opposed the dam’s breaching, citing the impact of the sediment flush on the lower river and the effect the reservoir’s draining would have on cabin owners at Northwestern Lake. Early on, the counties applied for intervenor status with FERC and tried to block the dam’s removal.
In November, PacifiCorp reached a settlement with the counties, agreeing to pay them $675,000 to offset the impacts of dam removal. The utility also agreed to protect the structural integrity of Northwestern Lake Bridge by building new bridge pilings. In exchange, the counties agreed not to oppose the dam’s removal.
Before demolition occurs, PacifiCorp also must replace a section of a 2-mile-long water line that crosses the river on its route from the upper watershed to the town of White Salmon. PacifiCorp’s Olson said that project will begin immediately in order to meet the October deadline.
In all, the dam-removal project required FERC’s approval of 18 separate plans, from vegetation management to monitoring of navigation impacts resulting from the sediment flush. “We have to go out and survey the shipping channel a couple of months after we breach and then once a year for five years,” Olson said. In order not to affect navigation, the sediment must not block the top 17 feet of the Columbia River, he said.
But the biggest cause of delay, he said, had to do with satisfying the Washington Department of Ecology that the sediment release would not result in a violation of the federal Clean Water Act. “Up until late last year it was all about working with the Department of Ecology to get our clean water permit,” Olson said. “Once they started looking at it, they had some questions and we had to do some additional studies.”
To minimize mortality to a run of fall chinook that spawn in the lower river, PacifiCorp will work with the U.S. Fish and Wildlife Service, the Washington Department of Fish and Wildlife and the Yakama Tribe to collect the salmon in large seine nets beginning in August and truck them up above the dam, where they will be released into the upper river to spawn.
“The fall chinook are the most significant,” Olson said. “They will be spawning just below the decommissioning site.”
The first step
The October dam-breaching will be just the beginning of a years-long project to restore the lower White Salmon to a free-flowing state.
After the dam is breached, the river will continue to flow through the tunnel this winter. Meanwhile, contractors will assess the sediment remaining in the former reservoir.
“They’ll stabilize the slopes, make sure they are at a safe angle of repose,” Olson said. “We’ll let the river channel decide where it wants to go.”
Next spring, the dam itself will be dismantled, using conventional concrete removal techniques. The old wood stave flow line that carries water from the dam to the downstream powerhouse will be removed and the rubble from the dam will be buried under 18 inches of soil along the mile-long riverbank bench where the wood-stave conduit ran.
Two cofferdams built to reroute the White Salmon River around the construction site when the dam was built will be removed in May. The dams, made of timber and rock, are buried beneath sediment and the reservoir and also block fish passage.
The dam’s tailrace will be removed but thehistoric powerhouse, one mile downstream, with its turbines will stay.
“We’ll be sealing it off with a cement wall,” Olson said. “We’ll take measures for public safety and environmental safety, to prevent an inadvertent oil spill.”
There will be extensive planting of the project area with native vegetation.
Watching the river regain its natural flow will be fascinating to see, Kober said.
“The big blast in October is a big milestone, but it’s going to be an incredible process watching this river come back to life. We’ll be seeing many changes through the river and spring as it regains its flow and becomes a river again. Every dam removal is different, but what we’ve seen is people are pretty amazed at how fast the river comes back to life and how resilient rivers are.”