The U.S. Environmental Protection Agency is accusing BP of several Clean Air Act violations for what the agency says were a series of unapproved changes at its Whiting, Indiana, refinery.
The EPA says the modifications caused "significant increases" in the refinery's emissions of sulfur dioxide, nitrogen oxide, particulate matter and carbon monoxide.
The EPA says BP didn't comply with Clean Air Act requirements when it modified refinery flares, the tall chimney-like structures used to burn off waste substances.
BP spokesman Scott Dean said the company has fully cooperated with the EPA and hopes to resolve what he calls "a difference of opinion" on the interpretation of rules.
Dean says the violations aren't related to a proposed 3.8 billion expansion of the Whiting plant.