EPA reissued a policy (originally from 2017) that it will not “second-guess” industry’s own emissions projections when determining if a facility modification triggers NSR, so long as the projection is made in accordance with regulations. This memo restores the 2017 guidance (which had been revoked in 2022) on the Actual-to-Projected-Actual Applicability Test. Under the reinstated policy, a facility may account for planned operational practices or controls to keep emissions increases below NSR thresholds, and the projected emissions values themselves are not treated as enforceable limits up front. In other words, EPA will not require an NSR permit or penalize a source based solely on its pre-project emissions estimate – enforcement would only occur if post-project actual emissions data later show a significant increase beyond allowed levels. This update formally reverses the 2022 rescission and provides regulatory certainty by immediately reinstating the 2017 NSR applicability policy.

See New Source Review (NSR) Actual-to-Projected Actual Memorandum | US EPA