In his written opinion, U.S. District Judge Terrence McVerry said the government waited far too long to try to enforce Clean Air Act regulations against EME, the power plant’s current owner. EME is a subsidiary of California-based Edison International. Chicago-based Midwest Generation operates the plant.

Filed last January in the U.S. District Court for the Western District of Pennsylvania by the U.S. Environmental Protection Agency and the states of Pennsylvania, New Jersey and New York, the suit accused the company of violating the CAA by carrying out major modifications at Homer City between 1991 and 1996 without installing state-of-the-art emissions controls.

The judge noted that New York State Electric and Gas Corp. co-owned the power plant from January 1968 to June 1998. Pennsylvania Electric Company also was a co-owner from January 1968 until March 1999, and also operated the facility during the same timeframe. EME purchased Homer City in 1999 and Midwest Gen has operated it ever since.

In August 1991, the judge recounted, NYSEG and PENELEC undertook a multimillion-dollar project to replace the economizer on Unit 2, which included modification of the backpass gas ductwork and installation of new reheat temperature control dampers and internal boiler supports and related work. In March 1994, the former owners mounted a similar project to replace the economizer on Unit 1. Additional repairs were made in 1995 and 1996 as well.

For many years, McVerry said, “environmental regulators took no action to challenge the 1991, 1994, 1995 or 1996 projects as improper.” Finally, the EPA issued a notice and finding of violation to EME/Midwest Gen on June 12, 2008.

By that time, he said, the statute of limitations had expired on many of the alleged pollution violations.

A Midwest Gen spokesman said he was pleased but not surprised by the ruling, adding it was consistent with similar recent decisions. The plaintiffs have not said if they will appeal.