An environmental activist group is suing ArcelorMittal for allegedly violating the Clean Air Act by showering nearby residents with soot and other pollutants from a Monessen coke plant on hundreds of occasions.

PennEnvironment sent a 60-day notice letter to the Chicago-based steelmaker, ArcelorMittal USA, in August. The advance notice is required under federal law, which gives citizens the right to sue if regulatory agencies haven’t.

PennEnvironment executive director David Masur said today that the company only recently offered to discuss the violations, which ArcelorMittal generally acknowledged in a statement issued after the August letter.

But, Mr. Masur said, “They haven’t really done anything to address the emissions” at the Monessen plant.

The Pennsylvania Department of Environmental Protection said DEP is “evaluating appropriate enforcement actions” but can’t comment on the lawsuit.

John Poister, a DEP spokesman, has acknowledged that the department has received numerous dust and odor complaints from residents living near the plant, and said the DEP has conducted air quality monitoring at several locations near the plant, inspected the facility and served "numerous" violation notices on the company for visible emissions and fugitive emissions.

The plant, which bakes coal at high temperatures for use in the steelmaking process, has 56 coke battery ovens and produces about 1,000 tons of coke a day. It's located 25 miles south of Pittsburgh on the Monongahela River.

ArcelorMittal USA Inc. is headquartered in Chicago. Its parent company is based in Luxembourg and has annual revenues of more than $80 billion.

First Published: October 8, 2015, 5:28 p.m.