39,245 tons of sulfur dioxide

The EPA requires scrubbers on new plants. Significant upgrades to old plants can trigger the requirement. Air monitoring can also reveal that clean air standards are not being met, prompting a need to install scrubbers.

At Rush Island, Ameren made major modifications to the plant's generators in 2007 and 2010 without obtaining permits. The more than $70 million upgrades boosted the 1970s-era plant's power generation as well as emissions, right around the time its machinery was reaching the end of its intended lifespan.

In 2011, the EPA sued Ameren, alleging violations of the Clean Air Act.

In 2017, U.S. District Judge Rodney Sippel agreed, and, two years later, ordered a remedy that called for the company to equip Rush Island with scrubbers.

Ameren instead proposed closing the plant ahead of its 2039 schedule — now set for this year.

But, to counteract Rush Island's excess emissions, Sippel also called for Ameren to install pollution controls at Labadie, a condition later scrapped by a federal appeals court, because "the government never provided notice of or alleged" that the plant committed a Clean Air Act violation.

But Labadie — along with Ameren's other coal plants — did receive notice of Clean Air Act violations from the EPA in at least 2010 and 2011, when Labadie, too, was cited for "major modifications that caused a significant net emissions increase" without first obtaining proper permits.

The EPA only filed suit regarding Rush Island. The agency did not on Friday clarify why.

In 2023, Labadie accounted for 39,245 tons of sulfur dioxide based on EPA data that uses readings taken from inside the exhaust stacks of coal plants.

But the EPA uses a different measure — the air monitors — to gauge public health impacts, which could trigger scrubber requirements.

'The economics of the situation'

The EPA's current standard for SO2 pollution was established in 2010, at 75 parts per billion, a threshold set to protect public health "with an adequate margin of safety, including the health of at-risk populations with asthma," according to the agency.

Around Labadie, ambient SO2 readings seldom reach half of that amount — occasionally peaking at 38 or 44 parts per billion, for instance — based on readings from air monitors placed at locations selected by Ameren.

But critics have long complained that air monitoring around the Labadie plant is insufficient: Four monitors are placed in areas they say are unlikely to accurately register pollution from the facility. Prevailing westerly winds generally push air pollution to the east. But only one of Labadie's stations is east of the plant.

"If your monitors are not in the proper spots, it's going to show, 'Hey, everything is OK,'" said Mahfood, the former Department of Natural Resources director.

But both state and EPA regulators say that the dispersal of Labadie's emissions is influenced by different forces — from weather conditions to local topography — and that computer modeling says the current monitors around the plant would indeed pick up persistent air quality violations.

The monitor locations "really do a good job in characterizing impact from that facility," said Stephen Hall, the director of MDNR's Air Pollution Control Program. He added that "citizens can be confident" that air quality standards are being met in the area.

Mahfood says he struggles to envision major change — let alone scrubbers — coming to Labadie anytime soon.

Ultimately, he expects economic trends could be the eventual impetus for change, by making it imprudent for Ameren to keep it running, as financial woes mount for coal power and costs plunge for alternative power sources — a combination that has helped shutter coal plants from coast to coast.

"It's the economics of the situation that will probably get Ameren to move," said Mahfood. "The plant needs to go."

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