To clear the air, Reliant Energy's Conemaugh Generating Station installed pollution controls in 1994 and 1995, but much of what's been removed from the sky over Indiana County is being discharged into the Conemaugh River.

That's not the way pollution cleanup is supposed to work, two environmental groups said yesterday in announcing that they have filed formal notice to sue the Houston-based energy company that is one of the largest electric power producers in the nation.

According to PennEnvironment and the Sierra Club, the 1,711-megawatt power plant in New Florence has violated the federal Clean Water Act by discharging potentially toxic levels of aluminum, boron, iron, manganese and selenium into the Conemaugh River on 200 days in the last two years.

"There's a clear, chronic history of violations," David Masur, PennEnvironment director, said of the coal-burning plant that discharges 2 million gallons of wastewater a day into the river.

Those discharges could hurt efforts to clean up the river, which has long suffered from industrial and acid mine pollution. Because of recent mine drainage treatment projects, the stream is staging a comeback as a white-water recreational and fishing spot.

The pollutant discharges were reported by Reliant in monthly monitoring submissions to the state Department of Environmental Protection, which has designated the Conemaugh River an "impaired" water body because of its high concentrations of metals.

Reliant spokeswoman Pat Hammond issued a statement saying that the company, which owns the 37-year-old power plant in a partnership with seven other companies but is its sole operator, is in compliance with a special side agreement it has with the DEP about the polluted water discharges.

According to that state agreement from the mid-1990s, Reliant is allowed to discharge water pollutants exceeding the federal limits until 2011, when it must install whatever controls are needed to meet Clean Water Act standards. Ms. Hammond said the agreement acknowledges that Reliant can't achieve the federal standards now and instead establishes them as "goals."

"The agreement recognizes that the [water pollution control] technology has not yet caught up with the waste water pollution created by the [air emissions] scrubbers," said Helen Humphreys, a DEP spokeswoman. "The company has an incentive to find a solution by 2011 because it's an industry-wide problem."

But Josh Kratka, an attorney with the National Environmental Law Center, said the state's agreement with Reliant doesn't supersede its obligations under federal law or legally modify the permit under which Reliant agreed to operate, which was set at a level to protect the water quality of the Conemaugh River.

"DEP agreed to give the company an enormous amount of time before it does anything," Mr. Kratka said. "We know a number of pollutants are coming from the scrubbers installed to reduce air emissions and too much of what they are taking out of the air is going into the river, and that's not what's supposed to happen."

He said the environmental groups have sent Reliant a formal 60-day notice of intent to sue, as required before a court action can be taken under the citizen lawsuit provision of the Clean Water Act. If Reliant doesn't fix the problem in that time or show progress toward fixing it, Mr. Kratka said a lawsuit will be filed in federal court.

In a similar case in 2001 involving a state agreement not to enforce federal water pollution law, the National Environmental Law Center and PennEnvironment sued the P.H. Glatfelter Co. in York County. That lawsuit resulted in a $2 million settlement and forced the paper mill to spend $30 million to clean up pollution in Codorus Creek.