The Office of Chehalis Basin (OCB) is currently studying ways the Skookumchuck Dam—which sits at the midpoint of the Skookumchuck River—might be improved to reduce flood damage in Bucoda and Centralia and/or improve fish passage in the river. The dam has operated since 1970.
OCB and the Chehalis Basin Board took interest in studying the dam after its owner, TransAlta, announced it was closing its final coal burner in 2025. The burner uses water from the reservoir behind the dam.
About the study
The study examined the feasibility of adjusting discharges from the Skookumchuck Dam as well as modifying the dam’s structure or completely removing it. OCB worked to collect survey data and build models to evaluate options for the dam in partnership with the cities of Bucoda and Centralia, Confederated Tribes of the Chehalis Reservation, and experts in flooding and aquatic species. OCB has completed the following:
Watch past webinar recordings about Skookumchuck Dam:
- Skookumchuck Dam: Exploring the Future of Flood Management & Fish Passage (March 2025)
- Skookumchuck Dam Study: Phase 2 Summary (April 2023)
- Skookumchuck Dam Study: Phase 2 Analysis (Sept 2022)
- Skookumchuck Dam Study: Phase 1 Update (March 2022)
Read the Skookumchuck Dam FAQs (March 2022).
Potential flood damage reduction benefit
Although the Skookumchuck Dam was not designed or managed to reduce flooding on the Skookumchuck River, it has provided some benefit. When the catastrophic 2007 flood occurred in the upper Basin, the reservoir behind the dam was unusually low, allowing it to hold back water that could have made flooding in Bucoda and Centralia even worse.
The study also examined how this partial, unintended flood reduction could be improved to provide greater benefit.
Limited fish passage
When the Skookumchuck Dam was built in 1970, the former Washington Department of Fisheries required the owners to build a fish hatchery and fish capture and transportation facility. The hatchery was designed to offset lost fish habitat due to the dam, which included approximately:
- 4–5 miles of Chinook salmon spawning habitat
- 8 miles of coho salmon spawning habitat
- 20 miles of steelhead trout spawning habitat
The dam prevents most fish from traveling upstream, and the only fish to travel upstream past the dam were steelhead the Department of Fish and Wildlife (WDFW) captured and hauled during spawning season through 2008. Between 2008 and 2020, no fish were transported upstream of the dam. In 2020, WDFW once again trapped and hauled steelhead above the dam.
The Phase 2 Study investigated whether changing discharges from the dam or improving the 50-year-old fish capture and transport facilities will benefit fish in the river. The study found modifying dam operations for fish passage could potentially and substantially benefit steelhead and coho, while a hypothetical removal of the dam could substantially benefit steelhead, coho, and spring and fall Chinook.
Potential impacts on water rights
During the winter, the reservoir behind the dam stores water to be discharged during the summer, creating approximately 50 cubic feet per second (cfs) of water that is available year-round. TransAlta currently holds the legal right to use the water.
TransAlta used its water right to power two electrical power generation turbines until 2020, when it shut one of them down. TransAlta continues to use water to operate the remaining turbine. Though it plans to shut down the remaining turbine in the plant in 2025, TransAlta established a water bank in 2021 allowing the company to maintain its right to beneficially use the water and sell the right to other users.
Should the dam be altered in a way that prevents TransAlta from storing enough water, the cascading result would mean a reduction in the amount of water in the water bank for TransAlta to sell. Other water right users downstream, such as municipal water suppliers or farms relying on surface water irrigation, could also see their water availability impacted. If that happens, TransAlta and other water users may have to be compensated for the lost water right. The Phase 3 Study explored potential options to maintain the existing water bank through off-channel water storage, and the anticipated effects on fish and water rights.
Next steps
At this time, there are no planned changes to the Skookumchuck Dam. The Chehalis Basin Board is evaluating different pathways for the future of the dam as part of the process to develop the long-term Chehalis Basin Strategy. If the Board recommends moving forward with a preferred option, any project will require additional design, environmental review, and permits.
Contact
For more information, please contact
Nat Kale
OCB Principal Planner
nat.kale@ecy.wa.gov
(360) 706-4277
