The federal government and the state of Illinois on Thursday filed a suit against Midwest Generation, alleging that the company violated the Clean Air Act by making “major modifications” to six coal-fired power plants without installing required pollution control equipment.

The lawsuit (PDF) was filed by the U.S. Justice Department on behalf of the Illinois attorney general’s office and the Environmental Protection Agency (EPA) in the U.S. District Court for the Northern District of Illinois. It asks the court to order the Edison International subsidiary to install and operate “state-of-the-art” air pollution control technology to reduce sulfur dioxide, nitrogen oxide, and particulate matter emissions from six Illinois power plants that have a combined capacity of more than 6,000 MW.

The federal government and the state of Illinois claim that the Clean Air Act violations have occurred for a decade. They also seek civil penalties up to the maximum amount authorized by law—from $27,500 to $37,500 per day—as well as actions by Midwest Generation to mitigate the adverse public health and environmental effects caused by the violations.

The lawsuit is the latest in a string of enforcement actions targeting emissions from coal-fired power plants in the U.S. This February, the government sued Louisiana Generating, alleging that the NRG Energy subsidiary violated the clean air rules by operating the Big Cajun 2 Power Plant without also installing and operating modern pollution control equipment after the generating units had undergone major “modifications.”

That suit came on the heels of a similar suit filed against Westar Energy. The Justice Department accused the Kansas utility of violating rules by making pollution-increasing modifications to a coal-fired power plant without also installing updated emissions control equipment. Westar denied any violation of New Source Review rules at its Jeffrey Energy Center in St. Marys, Kan., saying it believed it was complying with EPA rules when it made the disputed modifications at the 1,857-MW plant some 10 to 15 years ago.

Also in February, the Justice Department reached a settlement with Kentucky Utilities on a complaint against that company for allegedly making modifications, without installing required pollution controls, to its E.W. Brown Generating Station in Kentucky’s Mercer County more than 10 years earlier. Kentucky Utilities agreed to pay a $1.4 million civil penalty and spend about $135 million on pollution controls to resolve the alleged Clean Air Act violations.

Duke Energy was vindicated this May on four of six projects involved in a decade-long pollution controls suit affecting the company’s Midwest power plants. A jury ruled against the company on two Indiana projects, however.

The government’s latest suit concerns the Crawford Station and the Fisk Station, both in Chicago; the Joliet Station in Joliet.; the Powerton Station Pekin; the Waukegan Station in Waukegan; and the Will County Station in Romeoville.

Sources: EPA, DOJ, POWERnews, Edison International