The U.S. Environmental Protection Agency plans to designate the area around Ameren's Labadie coal-fired power plant in Franklin and St. Charles Counties as exceeding federal air quality standards.
The EPA said in a letter to Missouri released Wednesday that the "nonattainment" area does not meet health-safety standards for sulfur dioxide pollution strengthened in 2010.
The move rejects a Missouri Department of Natural Resource recommendation, echoed by the Missouri Air Conservation Commission last September that the area be considered "unclassifiable," meaning state regulators were unable to determine whether the air quality met required levels.
"We still believe and agree with the recommendation that the MDNR made that the area should be designated at a minimum as unclassifiable," said Ameren's Steve Whitworth. A spokesman for the Department of Natural Resources said it is "reviewing" the designation.
According to the EPA letter, "exposure to sulfur dioxide can cause a range of adverse health effects, including narrowing of the airways which can cause difficulty breathing and increased asthma symptoms."
"This is good news for the people who live around the Labadie plant and live in the shadow of its pollution," said Andy Knott, senior campaign representative for the Sierra Club’s "Beyond Coal" campaign. "The Labadie coal plant is the largest source of sulfur pollution in Missouri by far, and this action by the EPA starts us down a path toward cleaning up that pollution."
Knott said if the EPA maintains that Labadie violates the air quality standard in a final ruling due by July 2, that would require the MDNR to develop a plan to clean up the pollution (which would require a rule adoption by the Missouri Air Conservation Commission).
But first, the EPA is required to give Missouri 120 days notice that it intends to reject its recommendations, so that the state may respond. The EPA is requesting responses by April 19. Additionally, a 30-day comment period now will open in short order.
The EPA documented technical data it considered from the MDNR, Ameren and the Sierra Club. To determine whether or not the sulfur dioxide levels are unhealthy, the EPA requires three years of air monitoring data or the use of computer modeling. Modeling by both the state, the Sierra Club and even some from Ameren found violations of the standard.
But in its initial recommendation, the state argued that because various modeling showed "both violations and no violations of the SO2 standards around Labadie," an "unclassifiable" designation was appropriate.
Additionally, Ameren had installed new monitors to measure sulfur dioxide levels in the air in April 2015. Data from those had shown concentrations below the standard, according to the state report and Whitworth, Ameren's senior director of environmental policy and analysis.
"We have been trying to inform the process with the best information available by installing and reporting actual air quality monitoring data, which we believe is the best approach and most accurate approach," he said. "We strongly believe that the actual air quality measurements are the critical piece of information that needs to be considered in this process."
Whitworth said there is "compelling data" from the new air monitors and an improved method of modeling currently at the beta level that the area is meeting the standards "by a large margin."
But the EPA said it could not consider that specific modeling, because that method was still being developed. The agency said it also could not consider the new monitor data because it was not collected over the required three-year period.
"Because the monitoring data from the monitors are not yet quality assured and are for a limited period, the EPA performed no further analysis on these monitoring data for designation purposes," it said in its preliminary report.
The EPA is defining the nonattainment area as bordered by the Boone and Boles Township boundaries on the east and west, Missouri Route D and Highway 94 in St. Charles County to the north, and Interstate 44 in Franklin County to the south.