A federal appeals court on Friday decided that an Environmental Protection Agency rule that left coal- and oil-fired power plants off the hook for tough mercury controls violated the Clean Air Act. The decision cheered opponents of Duke Energy's planned Cliffside power plant in western North Carolina who were recently disappointed by the state's decision to permit the facility.

The ruling [PDF] by the D.C. Circuit Court of Appeals invalidates EPA's so-called "Clean Air Mercury Rule," which would have allowed dangerously high levels of mercury pollution to be emitted by some coal-fired power plants under a pollution cap-and-trade program. The court found that EPA illegally removed power plants from the most protective requirements of the Clean Air Act simply because it believed it had the authority to do so, a move that led the court to comment:

"This explanation deploys the logic of the Queen of Hearts."

As a consequence of the decision, air permits for new coal plants such as Cliffside will have to be based on a case-by-case analysis of the best available technology for controlling mercury and other hazardous pollution. Last month, the Southern Environmental Law Center -- which sued EPA over the mercury cap-and-trade rule on behalf of several public-health organizations -- notified North Carolina regulators about the court's expected decision and called on them to consider the tougher mercury regulations when developing its final permit, advice the state Division of Air Quality failed to heed.

N.C. Waste Awareness and Reduction Network Director Jim Warren (who last week debated Duke Energy executive Tom Williams on North Carolina Public Radio) points out that DAQ's permit for Cliffside doesn't require analysis of what's known as "maximum available control technology" (MACT) for mercury and doesn't require Duke Energy to install mercury-specific pollution control equipment, noting:

The D.C. Circuit's ruling means that DAQ must rescind the final Cliffside air permit, go back to the drawing board to conduct a case-specific MACT analysis, and issue a revised draft permit for public comment before finalizing a new permit.