Ameren will shutter a Jefferson County coal plant found in violation of federal clean air laws rather than install what it says are expensive pollution controls, the company announced Tuesday. 

The St. Louis-based electrical utility will close the Rush Island Energy Center, built in the mid-1970s, by the spring of 2024, if not sooner. Ameren revealed the plan in a federal court filing. 

“The decision to accelerate the retirement of the Rush Island Energy Center comes after carefully considering our legal, operational, and regulatory alternatives, as well as the impact on customer costs and system reliability,” Ameren Missouri’s chairman and president, Marty Lyons, said in a statement. “We remain committed to reliable and affordable electric service for the benefit of our customers and communities, while reducing emissions and building on our longstanding commitment to environmental stewardship.”

Andy Knott, interim central region director for the Sierra Club’s Beyond Coal Campaign, said in a release that Ameren Missouri should shutter Rush Island as soon as possible. 

“The financial and health interest of Ameren’s customers is best served by the utility replacing any needed capacity with a combination of renewable energy, energy efficiency and demand side response,” Knott said. 

Rush Island is a two-unit coal plant situated on the Mississippi River south of St. Louis. It wasn’t expected to close for another 15 years, according to plans Ameren filed with Missouri regulators. But it has been in court for years because of failings under the Clean Air Act. 

Rush Island’s two units, put into operation in 1976 and 1977, are just old enough they were not required to install pollution controls under a 1977 update to the Clean Air Act requiring newly constructed power plants to install pollution controls. Older coal plants were grandfathered into the rule until they made upgrades beyond routine maintenance in a way that increased emissions. 

Once Ameren overhauled the coal plant units in 2007 and 2010, it fell under the requirement, but it failed to apply for that permit, according to court filings. 

U.S. District Court Judge for the Eastern District of Missouri Rodney Sippel ordered Ameren in 2019 to obtain that permit, install scrubbers and meet standards for sulfur dioxide emissions. Earlier this year, the 8th Circuit U.S. Court of Appeals upheld that ruling, though it struck down a requirement that Ameren also install scrubbers at the Labadie Energy Center in Franklin County.

In its filing, Ameren said retiring Rush Island early would be more beneficial to the environment than installing scrubbers and environmental advocates had urged it to do so.

Ameren also noted that Missouri lawmakers this year passed legislation, known as securitization, that allows utilities to refinance and shutter coal power plants before the end of their lifespan without taking a financial hit. Customers pay the utility a return on its investment. 

The filing said the Midcontinent Independent System Operator, the regional grid Ameren belongs to, is evaluating the effects shuttering Rush Island could have on reliability of the grid. The company expects that analysis to be done in early 2022. 

If closing Rush Island isn’t expected to have a significant effect on grid reliability, Ameren said it could choose to cease operations at the coal plant sooner. 

Knott said Ameren should not consider replacing Rush Island with fracked natural gas because of rising costs and the potent polluting effects of methane, one of the primary components of natural gas. 

“This is a major decision point for whether Ameren Missouri will act on climate which it acknowledges is due to human activity, or whether it doubles down on fossil fuels in spite of the science it says it supports,” Knott said. “To that end, Ameren Missouri executives should work vigorously to retire its coal flet before 2030 in order to mitigate the worst impacts of our changing climate.”