For the first time, the Bay Program is counting on air pollution reductions to reduce water pollution.

When state and federal officials agreed to slash nitrogen loads entering the Chesapeake by 110 million pounds a year, they built in an assumption that 8 million pounds would come from air pollution controls. The remaining 102 million pounds was allocated to six states in the watershed and the District of Columbia.

The 8 million figure stems from EPA estimates of Bay benefits if Congress enacts the Bush administration’s Clear Skies Initiative, which would require power plants to reduce emissions of nitrogen oxides, a byproduct of fossil fuel combustion, two thirds by 2018, with the bulk of the reductions required by 2008.

Clear Skies would cap the total amount of pollution allowed from the nation’s electricity producing power plants. Individual plants could either install new pollution control technology, or purchase credits from those that exceed their pollution control goals.

The legislation has been opposed by many environmental groups that say greater reductions could be achieved by exercising existing regulatory authority in the Clean Air Act.

Proponents say the legislation’s market-based approach will help achieve dramatic pollution reductions faster and cheaper than traditional regulatory programs, and is less likely to be tied up in litigation.

“It’s a quicker and cleaner way to get those reductions,” Don Welsh, EPA Region III administrator, told state officials at a March meeting where they agreed on new nutrient reductions for the Bay.

Because the proposed law sets emission limits—rather than relying on a lengthy regulatory process to establish limits—Welsh said he was confident that Clear Skies would achieve the promised reductions by the 2010 cleanup deadline.

If they become a reality, it would reduce some of the burden on wastewater treatment plants, farmers, cities and others who have borne the brunt of the region’s nutrient control efforts.

“We wish you well with the Clear Skies proposal,” said Kathleen McGinty, acting secretary of the Pennsylvania Department of Environmental Protection. “And we hope Clear skies achieves not only 8 million pounds, but more.”

Clear Skies is aimed at sharply reducing three major pollutants stemming from power plants. Besides a 67 percent reduction in nitrogen oxides, it would require a 73 percent reduction in sulfur dioxide emissions and a 69 percent reduction in mercury emissions, measured from a 2000 baseline.

It it patterned after the successful “cap and trade” program established in the 2000 Clean Air Act that required the utility sector to slash sulfur dioxide emissions in half, then capped the emissions at those lower levels. It allowed power plants to achieve and maintain the reductions by using an emission trading program, which was credited with helping to achieve the reductions faster than predicted, and at a fraction of the expected cost.

The EPA contends that the sweeping reductions would provide a host of benefits. Sulfur dioxide is a key component of acid rain and contributes to regional haze. Besides contributing to water pollution, nitrogen oxide is a main component of summertime smog, and also contributes to acid rain. Mercury is a toxin that bioaccumulates in fish and humans.

Power plants—the target of the legislation—account for the vast majority of sulfur dioxide emissions, about a third of the mercury emissions, but only about a quarter of the nitrogen oxide emissions.

If it were to pass, it would be the first time the Bay Program attempted to account for any nitrogen reductions stemming from an air pollution program.

Scientists have estimated that between a quarter and a third of all nitrogen entering the Bay stems from air pollution. By some estimates, roughly 75 million of the 285 million pounds that enter the Bay from its watershed originate from the air. (About 20 million additional pounds are estimated to land directly on the Bay.)

Clear Skies achieves only a small reduction in that figure because it just addresses power plant emissions, which account for a quarter of nitrogen oxide emissions. Further, nitrogen oxides account for only a portion of airborne nitrogen reaching the Bay; unregulated ammonia emissions, largely from agriculture, also contribute to the problem.

Over the years, the airborne contributions to the Bay’s nitrogen problem have remained relatively unchanged. Although power plants have reduced nitrogen oxide emissions, the amount coming from cars has increased as people drive farther.

Recent regulations have aimed at further cutting emissions from cars, trucks, trains and other sources, but the effect of those actions won’t be felt for more than a decade. Also, some nitrogen oxide control programs—aimed at reducing summer smog—are only in place during warm months, whereas nitrogen is a year-round problem for the Bay and other coastal waters.

Further complicating the picture is the emissions of ammonia have increased, largely because of the increase in intensive animal agriculture.

Whether the Bay can actually count on even the 8-million-pound reduction from Clear Skies is far from certain.

Critics charge the bill undercuts existing programs which, if aggressively implemented, could achieve further reductions. Part of the goal of Clear Skies is to encourage reductions by providing regulatory certainty to the utility sector. To do that, the law changes some parts of the Clean Air Act. For instance, downwind states would lose their ability to seek reductions from upwind polluters.

“We need tough enforcement of the Clean Air Act, said David Hawkins, director of the Natural Resources Defense Council’s Climate Center. “Instead, the White House is siding with power plant owners and other big polluters.”

Also, critics complain the bill does not address carbon dioxide, a key greenhouse gas.

During the 2000 presidential election, then-candidate Bush had said he would support so-called “four pollutant” legislation which would also control carbon dioxide, but dropped that support after the election, saying it could harm the nation’s energy production.

Clear Skies, or a similar bill, could be the most significant air pollution legislation to pass Congress for several years. As a result, many advocates of reducing greenhouse gas emissions, including many lawmakers and environmental groups, are reluctant to support a bill that does not reduce carbon dioxide.

“The president promised in his campaign to support a four-pollutant cleanup law; instead he is giving a proposal that is for polluters,” Hawkins said.

Sen. James Inhofe, R-OK, chair of the Senate Environment and Public Works Committee which will handle the legislation, has said the votes probably exist in the Senate to add carbon dioxide reductions into the bill.

That would set the stage for a contentious conference committee that would have to work out differences with legislation passed by the House, which likely would not include carbon dioxide.

If a situation develops where the Senate will only approve legislation that includes carbon dioxide, and the White House refuses to support anything with carbon dioxide, there will be no law.

Roy Hoagland, Virginia director of the Chesapeake Bay Foundation, said relying on Clear Skies for nitrogen reductions was little more than “a wing and a prayer” by the Bay Program. He said that the CBF has no position on Clear Skies.

The full 110-million-pound reduction of nitrogen is needed to meet new water quality standards that have been developed for the Chesapeake, according to computer model estimates. As a result, if Clear Skies doesn’t become law, the states will have to find other ways to make up the 8 million pounds that officials are counting on.