The operators of a proposed coal-fired power plant in Virginia are planning to use a state-of-the-art system to control its emissions, in compliance with air pollution laws.

But in an unusual twist, an environmental group warns that it will challenge permits for the plant-not for polluting the air, but because the plant's emissions will contribute to water pollution when they fall back to Earth.

The Chesapeake Bay Foundation contends that the power plant, proposed for construction in Surry County by Old Dominion Electric Cooperative, would violate the law because its emissions would contribute mercury to nearby waterways, many of which are listed as "impaired" by state and federal agencies because of mercury concentrations.

The organization also said the plant would contribute nitrogen to the Bay and its tributaries, which will soon be subject to a mandatory nutrient control plan.

"We have impaired water, and we know that this pollution is going to go into those waters, and the question is whether EPA should allow that to occur," said Jon Mueller, a CBF attorney.

But if the plant's emissions comply with all of the state and federal air regulations, it would be unprecedented to say those emissions aren't allowed because they contribute to water pollution, said Jed Hockman, a spokesman for the utility, which is a nonprofit cooperative.

"We are not dealing with any water emissions," Hockman said. "We are dealing with the Clean Air Act. We refuse the assertion that the Clean Water Act can be used to govern air emissions."

Over the years, evidence has mounted that air deposition is a major source of pollution to many waterways. Most of the mercury that enters waterways today stems from air pollution, mainly the result of burning coal, and not direct discharges into the water.

A study by the U.S. Geological Survey released this summer reported that mercury was detected in every fish sample during a nationwide study. It said air deposition was the main source of mercury to most of the streams studied.

In the Chesapeake, one quarter to one third of the nitrogen entering the Bay is estimated to originate from air pollution-nitrogen oxide emissions from tailpipes and smokestacks as well as ammonia emissions from animal feedlots.

The Clean Air Act sets ambient air standards to protect human health or reduce haze. Except for acid rain, other environmental benefits of regulations are only secondary considerations.

The Clean Water Act strictly regulates, and can even prohibit, new discharges into impaired waters-those that fail to meet water quality standards. But it has never been interpreted as having the authority to regulate air emissions.

"It's never, not yet I should say, worked," said Richard Parrish, a Clean Water Act expert with the Southern Environmental Law Center. "It's a great theory, but I don't know that it is going to get very far in court."

But in the mid-1980s, Parrish noted, the EPA successfully challenged the offshore burning of hazardous waste. "EPA argued that it's a violation of the ocean dumping law, which in a sense is the Clean Water Act, to allow this stuff to come out of the stacks and settle down into the seas."

Several state officials contacted expressed skepticism about such an argument; one said a "bright line" existed between the two laws. In its draft report responding to President Barack Obama's executive order calling for a plan to clean up the Bay, the EPA discussed the ways existing air regulations could help the Bay, but offered no hint that emissions could be regulated specifically for the Chesapeake.

But in testimony given to a Congressional subcommittee two years ago, Mueller suggested that new sources of air pollution be considered "point source" dischargers to water bodies, just like wastewater treatment plants. That could prohibit, or require offsets, for new discharges. New computer models can estimate where emissions for individual sources will land.

"We simply cannot continue to act as if there is no connection between air and water when it comes to rivers, streams and the Bay contaminated with mercury," Mueller said. "The Clean Water Act is meant to protect the water from pollution. We intend to see that it does so."

If a court agreed to such a "novel" argument, Hockman said, it would have "scary" ramifications.

"If you used the Clean Water Act in the way they are discussing using it, you couldn't build anything," he said. "You couldn't have a farm, you couldn't have any industry or anything, because you would be saying anything that is put in the air would affect the water. It is kind of an odd way to look at the law."