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Cowlitz River Project

Overview of the Cowlitz River Project

The Cowlitz River Project is Tacoma Power’s largest hydroelectric facility. It produces enough clean, renewable hydroelectric energy to serve more than 151,000 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.

Cowlitz River Project map

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 hydroelectric energy, 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

Would you like to receive updates about the Cowlitz River Project? Click here to sign up for our Cowlitz River Project email list.

The Mossyrock Park and Taidnapam North boat launches are available. Get updates on lake levels, river flows, and boat launch availability at MyTPU.org/LakeLevels.

Mossyrock Dam North Shore Fishing Trail Closed Due to Safety Concerns
Public access to the Mossyrock Dam North Shore Fishing Trail is closed due to safety concerns. Large rocks, nearly 3 feet wide, fell across the path, blocking access. We are evaluating our options and do not yet have a timeline for reopening the trail. We will post updates on this page.

Updates as of April 2023:

Why is Riffe Lake so low?
The Riffe Lake boat launches are unavailable due to an ongoing extreme lack of precipitation, which began in 2022. Following a dry October and November, much of the precipitation we have received has been in the form of snow. That snowpack won’t help refill Riffe Lake until the temperatures warm up enough for it to melt. This lack of available water means very low inflows into Riffe Lake. Click here to learn more.

Riffe Lake recreational access update
Public safety is a top priority for Tacoma Power, so we reduced the maximum level of Riffe Lake from 778.5 to 749 feet in 2017 due to updated seismic loading concerns for the Mossyrock Dam spillway piers (not the dam itself).

Lowering the maximum lake elevation impacted recreational access, so, in 2018, we invested approximately $850,000 into improvements at Mossyrock Park. We extended one boat launch ramp (it was usable to 737 feet and is now usable to 708 feet; the other ramp is usable to 723 feet) and built a new swim area and ADA facilities, including an ADA-accessible parking lot, trail to the swim area, and restroom.

More recently, we discussed potential improvements on the east end of the lake with local elected officials and the public. After an extensive vetting process, we chose two projects that will improve the use and safety of the Taidnapam North boat launch. Read about them here.

Mossyrock Dam seismicity studies update
Revised seismic hazard data from the United States Geological Survey indicated that the Mossyrock Dam spillway piers and gates (not the dam itself) could potentially be damaged in the event of a large earthquake. If the gate structures are damaged when the lake is at a full level, this could cause an extreme downstream flooding event. Although the earthquake probability is very low, we decided to reduce this risk by keeping Riffe Lake’s elevation to about 30 feet lower than full (778.5 feet). The drawdown began in 2017. We worked with our regulators to make this decision, and they approved our plan to voluntarily lower the level.

Our objective is to bring Riffe Lake back to full pool. We are working hard to make progress on identifying potential seismic damage to any other parts of the dam, as well as possible seismic retrofits, but this is a long and complex process. Read more about our progress here.

Satellite fish rearing facilities update
We will build three satellite fish rearing facilities as indicated in our federal license. With the partnership of the Cowlitz Fisheries Technical Committee, Tacoma Power has evaluated many potential satellite rearing facility locations and programs. We have worked for years on this project and are excited to have selected our first site; it is in the upper Cowlitz basin and is owned by Energy Northwest. The Energy Northwest location offers multiple benefits, including a cool and stable water supply, good site security, and excellent access. Read more about our selection process here. We look forward to your feedback on the proposed Energy Northwest location and would also like to know if you have ideas for locations of the other two future facilities. Please send your comments to Cowlitz Fish Facilities manager Eric Shoblom at eshoblom@cityoftacoma.org by April 27, 2023.

Sign up for Lewis County Emergency Management alerts
We conducted our annual emergency siren testing at Ike Kinswa State Park, Mayfield Lake Park, and the Cowlitz Salmon Hatchery on April 5. We perform the test on the first Wednesday of each April. Lewis County Emergency Management sends alerts before and after the test. Get ready for next year by signing up for alerts online here.

We’re hiring seasonal labor workers!
If you’re looking for a job that gets you outside, we’ve got you ($18.60 to $20.51 hourly)!

Cowlitz Seasonal Laborer (including Mayfield Lake, Mossyrock, and Taidnapam parks)
Alder Lake Park Seasonal Laborer

Check out our fish game for kids!
We’re big fans of fish at Tacoma Power! Kids can learn about which species we raise by printing and filling out this page! Scroll down to the bottom of this section for the answers…

2023 grant round for Cowlitz Hatchery-Associated Production projects: Second workshop opportunity
Do you have ideas for how to help protect and promote restoration and recovery of upper Cowlitz River basin salmonids (spring/fall Chinook, coho and winter steelhead)? Consider applying for a 2023 Hatchery-Associated Production (HAP) project grant through our Cowlitz Restoration and Recovery (CRR) Program. Hatchery-Associated Production projects include the artificial production or rearing of fish to support recovery of the CRR Program target species and populations. Conservation non-profits, Native American Tribes, regional fisheries enhancement groups, conservation districts, local and state governmental entities, and federal agencies are eligible and encouraged to apply. The funding process runs through late fall of 2023.

Learn more by visiting our HAP webpage.

Questions? Contact Tacoma Power CRR Program staff contact Melora Shelton at mshelton@cityoftacoma.org or 253.441.4994.

Kosmos Flats Oil Seep Capped
As part of our commitment to ensuring good stewardship of our environment, Tacoma Power capped the Kosmos Flats oil seep in December 2019. Read more about the project.

Fish game answers!

Sockeye
Coho
Chinook
Steelhead
Cutthroat Trout

At our Cowlitz River Project in Lewis County, we raise and release spring Chinook, fall Chinook, coho, summer-run steelhead, winter-run steelhead, and sea-run cutthroat trout. Learn more about our Cowlitz fisheries programs and check out our Cowlitz Fish Report for weekly updates.

At our Cushman Hydro Project in Mason County, we raise and release spring Chinook, winter-run steelhead, coho, and sockeye. Learn more about our Cushman fisheries program.

Public Meetings

Cowlitz Annual Program Review Virtual Public Meeting – June 1, 2022
Online/conference call | 2 to 3 p.m.
26 attendees

Tacoma Power and the Washington Department of Fish and Wildlife cordially invite you to a Cowlitz Annual Program Review public meeting on Wednesday, June 1, from 2 to 3 p.m. The meeting will be hosted virtually via Microsoft Teams. Check out the agenda.

You do not need to RSVP.

Click here to join the meeting

Or call in (audio only)
+1 253-666-4424
Phone Conference ID: 151 314 598#

Please email msundbaum@cityoftacoma.org with questions.

Cowlitz Annual Program Review and Science Conference – April 21, 2022
Online/conference call | 8 a.m. to 4 p.m.
44 attendees

Agenda
Q&A

Presentations:

Cowlitz Fisheries and Hatchery Management Plan (FHMP) Transition Plans Virtual Public Meeting – Feb. 22, 2022
Online/conference call | 3 to 5 p.m.
32 attendees

The FHMP transition plans outline how we will organize and guide the Cowlitz fisheries/hatcheries programs. They are in final draft form, and we would like to hear your thoughts about them.

We will receive public feedback at the meeting, and will also receive written feedback until 4 p.m. PST on Feb. 25, 2022. Please send your feedback to cowlitz@cityoftacoma.org.

Cowlitz Annual Program Review Virtual Public Meeting – June 23, 2021
Online/conference call | 2 to 4 p.m.
14 attendees

Please email msundbaum@cityoftacoma.org with questions.

Cowlitz Annual Program Review and Science Conference – May 19, 2021
Online/conference call | 10 a.m. to 4 p.m.
37 attendees

Presentations:

Summarize Five-Year Trends

Annual Program Review

Summary of Recent Trends and Current Status, Fisheries and Hatchery Management Plan – Transition Plans Status and Next Steps, 2022 Strategies

Please email msundbaum@cityoftacoma.org with questions.

Cowlitz River Fisheries and Hatchery Management Plan (FHMP) and Annual Project Review (APR) Virtual Public Meeting – Aug. 12, 2020
Online/conference call | 4 to 6 p.m.
21 attendees

Cowlitz River Annual Project Review (APR) Public Meeting – Aug. 14, 2019
Veterans Memorial Museum | 6 to 8 p.m.

Agenda

Cowlitz River Annual Project Review and Fisheries Science Conference – July 10, 2019
Veterans Memorial Museum | 9 a.m. to 3 p.m.
51 attendees