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:

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.

  • Agenda
  • Presentation (coming soon)
  • Survey results (coming soon)

Please email msundbaum@cityoftacoma.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.
51 attendees

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