The impact of a 2003 Clean Air Act regulation on future powerplant upgrades remains murky at best, says a National Research Council report released July 21. An NRC committee studied models for emission levels under a 2003 Environmental Protection Agency regulation. The rule would let utilities renovate coal-fired units at a cost of up to 20% of a new unit without triggering �New Source Review� mandates for permits and pollution-control equipment.

The panel says existing NSR rules would force installing more control gear than would EPA�s 2003 regulation. But the committee also says the model estimates �have substantial uncertainty.�

EPA�s 2003 regulation has not taken effect. A federal court struck it down in March. The agency is working on another version.