A federal appeals court on Friday upheld a judge’s 2019 ruling that ordered Ameren Missouri to install pollution controls at its Rush Island power plant south of Festus, a decision likely to force the St. Louis-based electric utility to rethink its long-term plans or spend hundreds of millions retrofitting a 1970s-era coal plant.
The utility did win a partial victory, though. The U.S. Court of Appeals for the Eighth Circuit rejected one portion of the district court’s ruling, which ordered Ameren to also install pollution controls at another coal plant to make up for the harmful sulfur dioxide emissions that environmental regulators said Rush Island had emitted.
The ruling is the latest in a lawsuit filed at the request of the U.S. Environmental Protection Agency over a decade ago accusing Ameren of violating the Clean Air Act by making upgrades to its Rush Island plant that increased sulfur dioxide emissions without proper permits. The government’s lawsuit accused Ameren of installing new equipment in 2007 and 2010 that allowed Rush Island to burn more coal and thus emit more sulfur dioxide.
The case plodded through the court system until 2019, when U.S. District Judge Rodney Sippel ordered Ameren to install sulfur dioxide control equipment, commonly known as scrubbers, at its Rush Island plant. In addition, he ordered Ameren to install another type of sulfur dioxide pollution control at Labadie, one of the largest coal plants in the country, to make up for the harm from Rush Island’s excess pollution.
The appeals court ruling, however, has raised questions about Rush Island’s financial viability given the hundreds of millions new pollution controls would cost. It’s unknown how much of the expense state regulators will allow the utility to pass on to ratepayers for a construction project that would likely take years. Ameren might instead look at other power generation investments or the timeline for shuttering its coal plants.