Cowlitz River Project
Overview of the Cowlitz River Project
The Cowlitz River Project is Tacoma Power’s largest hydroelectric facility. It produces enough renewable electricity to serve more than 140,000 homes each year. This hydropower comes from the water stored behind the Mayfield and Mossyrock dams.
Built in 1963, Mayfield Dam forms 13-mile-long Mayfield Lake. Mossyrock Dam, built in 1968, is the tallest dam in Washington state at 606 feet above bedrock, and forms the 23.5-mile-long Riffe Lake. Watch a video detailing how we rebuilt the two Mossyrock powerhouse generators.
- Project Licensing
All four of our hydroelectric projects are licensed separately by the Federal Energy Regulatory Commission (FERC), which was created by the Federal Power Act to ensure safe and efficient operation of power plants across the U.S. Many other agencies, tribes, organizations and stakeholders are also an important part of the licensing process. In 2003, we received a 35-year federal license to operate the Cowlitz River Project.
- Fish and Wildlife Programs and Public Recreation
Along with generating clean, renewable electricity, our FERC license includes mandates for:
- Fisheries programs, including the Cowlitz Salmon Hatchery and Cowlitz Trout Hatchery where we raise coho salmon, Chinook salmon, steelhead and cutthroat trout. Details can be found starting on page 50 of the License Settlement Agreement. Also see License Documents for plans and reports submitted about fisheries issues.
- Wildlife programs including habitat protection and enhancement for nearly 14,000 acres of land. Details can be found starting on page 69 of the license.
- Access to recreational opportunities and amenities, including campgrounds, day-use areas, fishing and other outdoor activities near our reservoirs. Details can be found starting on page 65 of the license. Also see License Documents for plans and reports submitted about recreation issues.
- Cultural resource protection and education.
- Tour the Facilities
Free group tours of the Cowlitz River Project facilities are available by appointment for school, civic, business and recreational groups. To arrange a tour, please complete the request form at the bottom of our hydropower page.
- Latest News
Kosmos Flats Area Temporarily Closed for Environmental Work
Kosmos Flats, located on the east end of Riffe Lake, is temporarily closed while Tacoma Power conducts an environmental review of the area. Read more about the project.
- Public Meetings
Cowlitz River Annual Project Review (APR) Public Meeting – Aug. 14, 2019
Veterans Memorial Museum | 6 to 8 p.m.
- Presentation (coming soon)
- Survey results (coming soon)
Please email firstname.lastname@example.org to RSVP or with questions.
Cowlitz River Annual Project Review and Fisheries Science Conference – July 10, 2019
Veterans Memorial Museum | 9 a.m. to 3 p.m.
- Purpose of Annual Project Review and Fisheries and Hatchery Management Plan, Fisheries Technical Committee Meeting Look Ahead, and Next Steps
- Trends in Cowlitz River Fish Returns and Hatchery Releases
- Decision Rules 101: General Purpose and Current Rules
- Cowlitz River Habitat Programs
- Hydro Operations
- Natural Production Estimates
- Juvenile Passage – Cowlitz Falls
- Summary of Hatchery Operations – Goals vs. Actuals
- Meeting Survey
- Meeting Survey Answers