Terra Industries has agreed to pay $625,000 civil penalty to the US Environmental Protection Agency (EPA) to settle a series of alleged violations of the federal Clean Air Act at nine of its plants in Iowa, Mississippi and Oklahoma.

In addition, the company will spend an estimated $17m to install and implement new controls and technologies that are expected to reduce harmful nitrogen oxide emissions at its facilities by at least 1,200 tons per year.

EPA said the company allegedly constructed, modified and operated its various facilities without obtaining appropriate pre-construction and operating permits without installing best available control technology for controlling air pollution.

Terra also allegedly violated the Clean Air Act by failing to comply with applicable air emission limits and ongoing requirements for emissions monitoring, recordkeeping and reporting at some of its facilities.

Department of Justice Environment and Natural Resources Division assistant attorney general Ignacia Moreno said the agreement will require Terra Industries to make important improvements in pollution control technology at nine acid-producing facilities that will result in cleaner and healthier air for the benefit of communities in Iowa, Mississippi, and Oklahoma.

Terra is a US producer of nitrogen fertilizers, including anhydrous ammonia, urea, ammonia nitrate, and urea-ammonium nitrate.