In a period of 16 months, four dams built between 1903 and 1962 came down as part of a monumental effort to clear 35 miles of the Klamath River spanning Oregon and California. The project owner, the Klamath River Renewal Corp., describes it as the largest dam removal effort in U.S.—and possibly world—history.
After demolition of the first dam last year, all work concluded in September, clearing 35 river miles of infrastructure and debris while opening more than 400 miles for salmon passage for the first time since the structures were built.
“It was a very humbling experience,” says Dan Petersen, project manager for contractor Kiewit Corp., which led the estimated $450-million removal under a guaranteed maximum price contract. “Whenever you’re working around huge volumes of water, it reminds you how small we are and the power of the world.”
Work finished several weeks early, but there was no incentive payment to Kiewit, according to the project owner.
Being able to harness and navigate that power required careful planning, Petersen says. With reservoirs tied to the four dams, Kiewit and Klamath River Renewal Corp. managed water levels to not only draw down reservoirs to naturally clear sediment, with some of it trapped for a century, but also to ensure safety and effective demolition of the structures.
The 50-year licenses of original dam owner PacifiCorp to operate them expired in 2006. The utility entered into a settlement agreement for removal in 2016 after 10 years of negotiation involving federal, state and local governments, two tribal nations and nine conservation and fishing groups.
To enable the project to move forward, PacifiCorp transferred the licenses to the removal firm, with costs paid for by PacificCorp customer surcharges and water bond funds under Proposition 1 for the three California dams. The demolition pricetag is deemed a fraction of the cost estimated for dam relicensing by bringing them to proper code, according to the utility.
The combined heights of the JC Boyle dam in Oregon, and the Copco No. 1, Copco No. 2 and Iron Gate dams in California reached 425 ft with a total generation capacity of 163 MW.
Kiewit structured water levels in late 2023 to remove the smallest of the four, 42-ft-high Copco No. 2, fully in the dry in fall 2023, removing the other three together throughout 2024—with all work completed in October.
An initial 65,000 pounds of seed have been planted on 2,200 acres of land as part of the river restoration effort.
Photo courtesy of Shane Anderson/Swiftwater Films
Working in Tandem
Each dam was different, but their dismantling occurred virtually simultaneously.
Copco No. 2 required the team to balance reservoirs and maintain flows below the dam. “It was really cool to be able to do that in the dry that first season,” Petersen says.
Mark Bransom, Klamath River Renewal Corp. CEO, calls removing the concrete dam, with five bays and five gates, ahead of the others “somewhat opportunistic” as crews were doing work at the base of Copco No. 1 that required reservoir cycling. “We were turning the water off below Copco No. 1 and could then work in the dry,” he says about the downstream Copco No. 2.
The water cycling allowed the construction team to work safely, but it also maintained the biological minimum flows. Crews diverted flow released from Copco No. 1 into a tunnel system, a combination of two segments drilled and blasted through rock on the side of a hill.
The other three dams were all removed in 2024, a logistics management decision that increased project efficiency, Bransom says.
JC Boyle was a 63-ft-high earth embankment and concrete mix structure. Petersen says it was not very large or impressive but it conveyed water more than three miles to a powerhouse via a 2.5-mile-long concrete canal perched on the side of the cliff over the top of the Klamath Reservoir. He says the need for a hydraulic hammer fitted to an excavator that uses percussion to break up concrete was not typical work.
Copco No. 1 was a 144-ft-high, narrow concrete arch dam. Kiewit used a combination of blasting and mechanical hoe ramming for demolition. “The big thing with that was the timing aspect and being able to minimize impact to fish,” Petersen says. “We wanted one season of impact. From the time we got going, we did the blasting and that allowed us to dislodge and haul as quickly as possible.”
The trickiest challenge at Copco No. 1, built in 1918, was drilling a 10-ft-dia tunnel through the base of the 100-ft-thick concrete foundation to allow for the water drawdown, while leaving a 10-ft-long plug at the end of the tunnel to release when it was time to send water through the dam.
The team also created modular bridges on site—two that were 60 ft long and each rated for 100 tons—that allowed them to separate from the powerhouse 200 ft downstream and the water flows.
“Once we got the bridges on, we could turn the powerhouse on and give us a full season worth of work to get the tunnel in and make the schedule,” Petersen says. “It was a bit of a challenge, but a great solution.”
The team investigated using a diversion tunnel built in 1911 and 1912 during the original construction of the dam, but that tunnel had not been used or inspected for over 100 years. After underwater inspection, the team decided it could not trust that tunnel and opted instead for the tunnel through the base of Copco No. 1.
A test blast at Copco No. 1 dam.
Photo courtesy of Shane Anderson/Swiftwater Films
'Everything Went Well'
That led to an “interesting experience,” Bransom said, as crews discovered the original project randomly placed railroad steel into the matrix, even while still tieing in with rebar. “As we were drilling and shooting this 10-ft-diameter tunnel we were setting the charges on the shots to rubbleize the concrete and then started to encounter random rail steel,” Bransom says. “We had to recalibrate the charges. Once we got that all worked out and dialed in, the blasting concrete did work quickly, and we were back on track.”
The project team had only one chance to get the concrete plug proportions right for the tunnel blast, says Petersen. “You are never getting back in that tunnel. It makes your heart kind of hurt and was very exciting to be part of. Everything went well.”
The 175-ft-high Iron Gate required millions of yards of excavation on a fully earthen embankment dam with a clay core. Just on that dam, Kiewit had 17 haul trucks, with the largest in the 70.5-ton class and 30 excavators at peak, also including some of the largest in construction. Petersen says the team also used specialty track line excavators that allowed crews to connect additional pieces of equipment to use on a winch line for demolition work.
“Iron Gate maybe didn’t have the dental demolition work of Copco,” Petersen says, “but the big bulk of materials and the orchestration of that [was logistically challenging].”
Crews had to carefully watch the pace of removal to ensure the dam could still handle a 100-year storm event, especially as work progressed earlier and quicker at JC Boyle and Copco No. 1. “There was a pretty sophisticated water management and planning effort to accommodate removal of the three remaining dams,” Bransom says.
The team used an existing diversion tunnel at Iron Gate, but added significant air venting to minimize risk of it caving in, and shotcrete to reline the inside. “It worked really well,” Bransom says.
While other dam projects around the world use differing strategies for drawdown of reservoirs, “we took the approach to really just open [them] up and let the reservoirs drain out and mobilize and evacuate the sediment,” he says.
The release of sediment built up for 60 to 100 years will “jumpstart recovery of the once-prolific salmon-producing river’s natural configuration and channels,” according to the National Oceanic and Atmospheric Administration's fisheries division. “We want to give the river as much chance as we can to do its work while the sediment is ready to move,” says Jim Simondet, Klamath branch supervisor in the fisheries’ west coast region.
The fine sediment filled with organic material in the Klamath River made this possible. “The river is undoing a century of being impacted by these dams,” says Shari Witmore, a branch fisheries biologist. “It’s moving all that sediment faster and more efficiently than we ever could.”
Working on four different dams under the same umbrella was a lesson in teamwork, Petersen says, especially with around 140 craft and staff in a remote location. “I learned so much by doing that,” he says, related to individual sites under an administrative team. “The team over the last two years fed off each other and I will try to apply that on the next jobs.”
Resource Environmental Solutions is undertaking land and waterway restoration in the 2,200-acre Klamath River basin moonscape after dams were completely removed in early October.
Courtesy of Swiftwater Films
Moving on to Restoration
With final pieces of the dam now being removed, Kiewit will transfer the project to the riverbed and land restoration contractor, Texas-based Resource Environmental Solutions. The restoration company then will transfer restored areas to the two states.
“Dam removal is the best way to bring a river back to life,” Ann Willis, California director of American Rivers, said in a statement. “It shows that we can right historic wrongs and make big, bold dreams a reality for our rivers and communities.”
Bransom says vegetation management has been ongoing, and teams have collected billions of seeds for the revegetation effort. Crews have already taken advantage of residual moisture from reservoirs to get an initial 65,000 pounds of seed on 2,200 acres of land.
The Klamath Tribes have praised the dam removals in helping to eventually return salmon to the area for the first time since 1907, but note more work to be done. “We have much more essential restoration work to complete on the Upper Klamath Basin headwaters, watershed, wetlands and Riparian areas to produce cold, clean, clear water in order to support all fisheries, aquatic species, subsistence and medicinal plants and roots all critically important to continue supporting the tribes’ culture and traditional lifeways,” said tribes' chair William Ray Jr., in a statement.
Getting to this point has been a long process. The restoration firm "has benefited from the relationship we have developed with the tribes, who have been at this for several decades,” Bransom says. “We want to acknowledge that while given the responsibility to play a small role, the project is really a project for and by the tribes.”
Over the next few months, plants will be installed as part of the project’s adaptive management goals, which means the team is working with whatever the drained reservoir gives them. “The system was very dynamic early on and things have started to settle down and we are seeing the stabilization of banks and streams readapting to their channels,” he says. “Now we can pick the proper locations for habitat complexity to work.”
The renewal company hopes to transition to maintenance and monitoring in late 2025, and is set to remain in existence through 2028 or 2029, depending on how restoration meets conditions of its various permits. At that point the corporation will dissolve and all project lands will transfer to the states or to their third-party designees.
