 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.