SALT LAKE CITY — Chevron has agreed to pay a $284,000 fine and help buy four clean-running school buses after inspectors found pollution law violations at a Salt Lake City refinery.

The Environmental Protection Agency announced the settlement with the company Wednesday.

Inspectors say the refinery's equipment was producing higher levels of nitrogen oxide, which contributes to acid rain and ozone.

The settlement requires Chevron to upgrade pollution controls that are expected to reduce nitrogen oxide emissions by an estimated 50 tons per year.

The company also will pay $100,000 that Jordan School District will use to buy four compressed natural gas-powered buses. They are expected to conserve more than 6,000 gallons of diesel fuel each year.

The EPA said Chevron's excessive nitrogen emissions stem from changes it made to a catalytic cracker unit.

"It is critical that companies conduct business responsibly and obtain the proper permits before making infrastructure changes that increase emissions of air pollutants," said Mike Gaydosh, director of EPA's enforcement program in Denver. "This settlement will help ensure the company is operating in accordance with industry standards."

Chevron admitted no liability or guilt as part of the settlement and disputed the EPA's assertion that it caused unexpected pollution. The consent decree was filed in U.S. District Court in Salt Lake City.

"The refinery did not exceed its permit limits" for nitrogen oxide emissions, Chevron spokesman Greg Hardy told The Salt Lake Tribune.

Utah's top air-quality official, Bryce Bird, said Chevron's lower emissions "certainly will help" Utah try to achieve federal air-quality standards in a plan due later this year.