State’s only coal power plant shifting to natural gas, will serve as backup power for region

CENTRALIA  – 

Washington’s only coal power plant will transition to natural gas by 2028. As part of the transition, the Washington Department of Ecology reviewed the environmental impacts involved with the switch, and reached an agreement to mitigate those impacts with TransAlta, which operates the Centralia plant.  

The switch to natural gas will reduce greenhouse gas emissions from the Centralia plant and reduce most toxic air emissions associated with burning coal, although emissions of volatile organic compounds would increase.  

Under an agreement with Ecology, TransAlta will invest between $7 million and $21 million in clean energy projects in Lewis and Thurston counties, based on the plant’s emissions each year.  

Ecology is seeking public input on the environmental review documents and the draft air quality permit through Sept. 6. Public comments will help shape a new grant program and provide input on the environmental review for the transition to natural gas.  

Although the transition means the plant will continue to burn fossil fuels, it will operate as a peaker plant – backing up other power sources when needed.  This means that total greenhouse gas emissions will be lower than they were when the plant relied on coal-fired generation. 

TransAlta plans to end natural gas generation at the Centralia plant in 2044, ahead of a 2045 deadline in Washington’s Clean Energy Transformation Act for all power used in the state to come from clean sources.  

“Transitioning our state’s only coal power plant to natural gas will ensure reliable power while we continue to develop renewable power sources,” said Casey Sixkiller, Ecology’s director. “Washington is committed to clean energy. TransAlta has worked with Ecology on the proposed expansion of their clean energy grant program associated with the continuation of operations.” 

History 

In 1972, the Centralia Power Plant began burning coal in two boilers to generate steam. The steam spun turbines, generating more than a gigawatt of power.  

For many years, the Centralia plant was the largest single source of greenhouse gas emissions in Washington. It was also a major source of pollutants like sulfur dioxide and nitrogen dioxide.  

Under a 2011 agreement with Washington State, TransAlta committed to stop burning coal in the plant by 2025. One of the plant’s two generating units was shut down in 2020, and TransAlta planned to close the second unit at the end of 2025.  

In December 2025, TransAlta announced an agreement with Puget Sound Energy to transition the remaining generating unit to natural gas, delivering up to 723 megawatts of power when needed.  

However, that same month, the U.S. Department of Energy issued an emergency order requiring TransAlta to keep the Centralia plant operational as a coal power plant. Despite the emergency order, which has since been extended twice, the plant has not actually been called on to supply electricity to the grid since mid-December.  

Provide input  

The public comment period for the mitigated determination of nonsignificance, State Environmental Policy Act checklist, and draft air quality permit is open until 11:59 p.m. Sunday, Sept. 6, 2026. 

There are multiple ways to provide input: 

Bobbak Talebi 
Department of Ecology  
Southwest Region Office 
P.O. Box 47775 
Olympia, WA 98504-7775