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. In 2011, a deal was struck between the plant owner and operator, TransAlta, Governor Christine Gregoire, and Washington Stateenvironmental groups and policy makers to shut down the coal boilers. The first would be shut down in 2020, and the second in 2025, with a schedule of emissions reductions to be met along the way. The Washington State Senate approved the deal with a 36-13 vote. To complete this transition, TransAlta is receiving an expedited permit, and is also exempt from any Environmental Impact Assessment that would otherwise be required.
Gas-fired
In 2002, the plant capacity was supplemented with five natural gas-fired units. Four of them are 50-MWe gas turbine 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 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.
Fuel supply
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. Recent rail upgrades to the Centralia Power Plant, and SO2scrubber upgrades to ensure plant releases less pollution, will ensure the plant runs for at least another 15–20 years. Centralia currently burns coal from about nine 110-car coal trains each week.
Environmental and public impacts
Annually, this coal 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 7.5MMtCO2e, 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 has been 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 will cost US$20 to $30 million over the next several years. Additionally, continuous emissions monitoring systems for mercury measurement was certified by the Energy & Environmental Research Center. Currently, neither Washington State nor the U.S. federal government has regulations in place for mercury emission reductions. As part of the same agreement between TransAlta and the Washington Department of Ecology, TransAlta agreed to reduce emissions of nitrogen oxide by 20 percent beginning in 2009. This is two to five years earlier than TransAlta would have been required to reduce NOx emissions if an agreement had not been reached with the Department of Ecology. In 2012, Selective Non Catalytic Reduction system was installed to further reduce NOx at a cost of almost $20M. It is in the commissioning and testing phase through 2014. owner of Centralia plant and Washington State Ecology.
