The Klamath River Renewal Program is the largest dam removal and river restoration effort in North American history. This $504 million program involved the decommissioning and removal of four hydroelectric dams on the Klamath River, spanning Oregon and California, to restore volitional fish passage and improve river health.
The removal of J.C. Boyle, Copco No. 1, Copco No. 2, and Iron Gate dams opened over 400 miles of historic spawning habitat for steelhead, salmon, and lamprey. The final dam was removed in September 2024. Restoration efforts are ongoing and have already resulted in substantial ecological growth and habitat recovery.
Restoration efforts are a key component of the program, focusing on reconnecting historically fish-bearing tributaries and restoring the natural river plan and profile. To-date completed work includes riparian area bank planting and full reservoir planting with native seeds. The team also implemented measures to protect and enhance habitats for various species, including Southern Steelhead, Western Pond Turtle, and Pacific Lamprey.
The program involved significant complexities, including coordination among 21 separate local, state, and federal entities and Tribes, a large geographic footprint spanning two states, and potential impacts on nearby water wells. The team employed proactive risk management strategies and innovative value engineering to overcome these obstacles, completing the dam removals ahead of schedule and on budget.
Hydrological factors and sediment transport dynamics played a pivotal role in the program's success. To optimize construction sequencing and enhance efficiency, the team crafted a sophisticated operational water balance model. Comprehensive sediment modeling and environmental impact assessments were undertaken to safeguard downstream ecosystems and preserve water quality. In a remarkable feat of environmental engineering, McMillen orchestrated the controlled release of roughly 5 million cubic yards of sediment from behind the dams within a single season.
Within months of the final dam removal, salmon began returning to the Klamath River in numbers not seen for over a century. Chinook salmon were observed spawning in tributaries that had been inaccessible for generations. The rapid return of these fish exceeded scientists' expectations, with some estimates suggesting that salmon populations could increase by hundreds of thousands in the coming years.
This successful restoration demonstrated the resilience of river ecosystems when given the opportunity to recover. The Klamath River Renewal Program serves as a model for large-scale river restoration efforts, showcasing the potential for accelerated ecological recovery when barriers to fish migration are removed and natural river processes are restored.
