The Clean Air Interstate Rule, the Clean Air Visibility Rule and the Acid Rain Programme control power plant emissions, but in order to facilitate their smooth implementation alongside the NSR, the EPA is proposing a draft rule to provide a nationally consistent regulatory framework.

The proposed rule would establish a uniform emissions test for existing power plants by adopting the test used under the Clean Air Act’s New Source Performance Standards (NSPS). As a result of a US Fourth Circuit Court of Appeals decision, an NSPS-style emissions test already applies for the NSR across five states and the proposed ruling would open this out nationwide.

EPA is also proposing two other options for the new emissions test for consideration. In addition to the existing NSPS test, which compares maximum hourly emissions achievable before and after a physical or operational change, the agency is proposing a second option that would adjust the NSPS test to compare maximum hourly emissions achieved after the change to those that actually had been achieved before the change.

The third option is an NSR emissions test based on the mass of emissions per unit of energy output instead of hourly emissions.

EPA will accept comment on this proposal for 60 days following publication in the Federal Register.