Southwestern Indiana oil refiner CountryMark is spending $18 million on new pollution controls to settle Clean Air Act violations.

The Environmental Protection Agency and the U.S. Justice Department announced Thursday that CountryMark will spend the money on improved pollution controls such as flares at its refinery in Mount Vernon, about 20 miles west of Evansville.

Officials alleged Indianapolis-based CountryMark violated the law when it expanded operations without obtaining proper permits and installing necessary pollution controls. CountryMark began a $20 million expansion of the plant in 2007, which was expected to increase its capacity to 45 million barrels a year.

The settlement is part of a larger drive by federal authorities to enforce the Clean Air Act. Officials have negotiated settlements with 32 other refineries for a total of $6 billion to curb pollutants like sulfur dioxide and nitrogen oxides that contribute to acid rain and smog. The EPA estimates the new controls have reduced pollutants by 360,000 tons a year.

The refiner would improve its flaring devices, which burn off waste gases, and limit the amount of gases sent through the flares.

"These innovative controls include ensuring that pollution control devices, such as flares, are operated properly to minimize pollution emitted into the air and to improve their overall efficiency," Cynthia Giles, assistant administrator for EPA's Office of Enforcement and Compliance Assurance, said in a statement.

The state, represented by Indiana Attorney General Greg Zoeller and the Indiana Department of Environmental Management, will also receive $110,000 in the settlement that will pay for the removal of asbestos from an old grain elevator in downtown Mt. Vernon. CountryMark will also pay $70,000 to help retrofit diesel-engine school buses.