Centralia Big Hanaford power plant is a coal-fired power plant supplemented with natural-gas-fired units. It is located east of Centralia, Washington, United States in Lewis County. It is the only commercial coal-fired power plant in the State of Washington.

The plant, owned by TransAlta, is situated on 11,000 acres (4,500 ha) and at its peak, generated energy ample enough to power Los Angeles. The plant is expected to permanently close in 2025 based on an agreement and bill signed in 2011 by governor Christine Gregoire, the TransAlta Energy Transition Bill. As a result, one coal boiler was shut down in 2020 as part of beginning phase of the closure.

The two identical coal-fired generating units have a combined capacity of 1,340 MW. Both units started up for commercial operation in August 1971. (Bonneville Power Administration 1980 EIS)

In following the 2011 agreement to close the plant, the first boiler was shut down in 2020 with the second unit planned for closure in 2025. A schedule of emissions reductions were put in place to be met as the closure date nears. The Washington State Senate approved the deal with a 36–13 vote. To complete this transition, TransAlta received an expedited permit, and is also exempt from any Environmental Impact Assessment that would otherwise be required.

The energy produced until its closure is used by Puget Sound Energy (PSE) and according to 2022 figures, 14.5% of PSE's electric load came from the TransAlta coal plant, enough to supply power to 300,000 homes.

In 2002, the plant capacity was supplemented with five natural gas-fired units. Four of them are 50-MWe gas turbine (GT) units, and the fifth is a 68-MWe steam cycle unit. The entire arrangement is known as combined cycle 4-on-1 where the exhaust from the 4 GT's creates steam via Heat Recovery Steam Generators (HRSGs) to power a single steam turbine. In 2014, the gas fired portion of the plant known as the "Big Hanaford Plant" was removed from the plant footprint and parted out to various buyers.

Seventy percent of sub-bituminous coal used by the plant was delivered by truck from the nearby Centralia Coal Mine, which was a strip mine and the largest coal mine in the state of Washington, until it closed down on November 27, 2006. Coal from the Powder River Basin in Montana and Wyoming has also been transported by rail to be burned at the plant since 1989, but was only used to supplement Centralia Coal mine coal until 2006. By 2008, the plant was burning 100% Powder River basin coal. Rail upgrades and SO₂ scrubber upgrades to ensure the plant releases less pollution would have ensured the operation runs for at least another 15–20 years. Before the closure of unit 1 Centralia burned coal from about nine 110-car coal trains each week (i.e. 990 full coal cars).

Annually, the Centralia Power Plant emits 350 pounds of mercury pollution, making it the state's largest single source of mercury pollution. Mercury pollution is a bio cumulative neurotoxin which causes brain damage in humans and is especially dangerous for children and pregnant or nursing mothers. The plant also emits 979,557 t CO₂e (year 2019), making up a large portion of Washington State's total CO₂ emissions.

All of the mining area is currently being reclaimed. When TransAlta bought the plant in 2000, it agreed to reduce emissions. It installed US$200 million worth of scrubbers on the plant, which were purchased from ABB Environmental Systems. Between 2010 and 2012, the Centralia Power Plant was offline for an average of 4 months of each year. In March 2009, a proposed agreement between TransAlta and the Washington State Department of Ecology was announced, regarding a significant step forward in improving air quality in Washington. Key to the agreement is TransAlta's willingness to voluntarily reduce mercury emissions by at least 50 percent by 2012 to address air quality concerns in the region. Capture testing took place in 2009 and an activated injection product was selected. The process was expected to cost US$20 to $30 million over several years. Additionally, continuous emissions monitoring systems (CEMS) for mercury measurement was certified by the Energy & Environmental Research Center (EERC). As part of the same agreement between TransAlta and the Washington Department of Ecology, TransAlta agreed to reduce emissions of nitrogen oxide (NO_x) by 20 percent beginning in 2009. In 2012, Selective Non Catalytic Reduction (SNCR) system was installed to further reduce NO_x at a cost of almost $20M.

From the early 1970s until 2000, the plant was owned by eight utilities: PacifiCorp (47.5%), Avista Energy (15%), Seattle City Light (8%), Snohomish County PUD (8%), Tacoma Power (8%), Puget Sound Energy (7%), Grays Harbor County PUD (4%), and Portland General Electric (2.5%).

Plans to sell the plant began in 1998. In 2000, Portland General Electric sold its 2.5 percent share to Avista Energy, shortly before the plant was sold in its entirety to TransAlta Corporation for $554 million that same year.

The design and construction of the new plant were by Stone & Webster and ABB Environmental Systems.

Future plans for the site include the operating of several green energy facilities, including generating power via hydrogen and nuclear fusion, and the decommissioning of the Centralia Coal Mine is expected to incorporate renewable energy machinery as the coal plant closes. The company created a $20 million fund for training and educational work programs for remaining employees of the plant.

• Power Technology – Centralia Power Plant New CCGT Unit, WA, USA