WASHINGTON , Oct. 11 (UPI) -- The U.S. Environmental Protection Agency said a legal settlement with American Electric Power (NYSE:AEP) will force the nation's largest power-plant pollution cleanup.

American Electric Power has agreed to install $4.6 billion in pollution-control measures at 16 existing plants and pay $75 million in penalties, The New York Times (NYSE:NYT) said Thursday.

The settlement resolves a lawsuit filed by eight states and 13 citizen groups against AEP in 1999, alleging the company violated the New Source Review requirements of the Clean Air Act.

The EPA said the agreement imposes caps on emissions of pollutants from 16 plants in West Virginia, Kentucky, Virginia, Ohio and Indiana. Pollution control equipment will reduce sulfur and nitrogen oxide emissions by more than 813,000 tons per year when fully implemented.

The agreement contains a clause that protects the company from further penalties from the future modification of the plants between now and Dec. 31, 2018, the newspaper said.