Summary

Changes how the Clean Air Act treats a plant change as a “modification” by redefining when an action “increases” emissions and by excluding certain changes from being treated as modifications. It ties an emissions increase to a change that raises the maximum hourly emission rate above any hourly maximum from the prior 10 years, and it says changes that improve emissions per unit, restore or improve reliability, or improve safety are not ‘‘modifications.’’ The bill applies those same limits to Prevention of Significant Deterioration (PSD) and nonattainment NSR tests and makes clear the new definitions do not retroactively expand the set of changes treated as modifications before enactment.

• Redefines an ‘‘increase’’ in emissions to mean a post-change maximum hourly rate higher than any hourly maximum in the prior 10 years.
• Excludes changes that reduce emissions per unit or restore/improve reliability or safety from the statutory term ‘‘modification’’ under section 111.
• Makes PSD program treatment of ‘‘modification’’ depend on the same section 111 definition and excludes changes that do not cause significant hourly or annual increases.
• Applies the same narrowed definition to nonattainment-area NSR (terms ‘‘modifications/modified’’).
• Includes a rule of construction preventing the Act from being read to expand what was a modification before enactment.
• Does not provide funding, an explicit effective date, or new agency deadlines.
• Likely reduces the number of facility changes that trigger new permitting, affecting permitting workload and compliance costs.
• Creates legal and measurement questions about applying a 10-year hourly-lookback and the scope of exclusions.