The Sierra Club's Andy Knott speaks at a rally on Thursday in front of a 15-foot tall inflatable inhaler in Keiner Plaza.
Credit Sarah Skiold-Hanlin, St. Louis Public Radio & The Beacon
Ameren's 2,400-megawatt plant near Labadie, Missouri, is the state's largest coal-fired power plant.
Credit Véronique LaCapra, St. Louis Public Radio & The Beacon
Andy Knott uses an "opacity" scale to illustrate the disparity between acceptable emissions levels and those considered harmful. The darker squares represent increasing particulate matter in smokestack emissions.
Credit Sarah Skiöld-Hanlin, St. Louis Public Radio & The Beacon
The Sierra Club says Ameren has been routinely violating air quality standards at its St. Louis-area power plants.
In a Notice of Intent to Sue delivered to Ameren on Wednesday afternoon, the Sierra Club alleges the company's Labadie, Meramec, and Rush Island plants have exceeded air pollution limits almost 10,000 times since 2008.