The suit, filed against Allegheny and its subsidiaries in US District Court in western Pennsylvania, seeks to force the company to lower emissions levels at three of its coal-fired power plants: Mitchell, Hatfield’s Ferry and the Armstrong Power Plant, all located in Pennsylvania.

“We are calling on Allegheny Energy to put in place equipment and operational changes that will enable its plants to perform in a manner that meets the highest standards for environmental protection,” Pennsylvania Department of Environmental Protection (DEP) secretary Kathleen McGinty said.

“We hope Allegheny Energy will work with us expeditiously to clean up their plants and protect public health.”

The states allege Allegheny Energy made “major upgrades” to the power plants in question but did not upgrade the plant’s pollution controls in tandem, a move they feel should have been required by law. The DEP claims modifications were made between 1993 and 1995 without their approval, a violation of state and federal laws.

“For a little more than a decade the plants have continued to produce emission levels above and beyond what should be produced by today’s standards,” said DEP spokesman Kurt Knaus.

Allegheny Energy is disputing the DEP’s allegations. “We believe we are in compliance with state and federal regulations on emissions from our power stations,” said spokesman Allen Staggers.

Work already done at the plants is classified only as “routine maintenance, repairs or replacement,” which is permitted by law to be completed without the requirement of new emission control installation, Staggers said.

This is not the first time Allegheny has come under fire for its practices; Citizens for Pennsylvania’s Future (PennFuture) also recently filed suit against the company citing Clean Air Act violations.