EPA Ends 20 Year "Once In, Always In" Policy For MACT Standards: May Effect Enforcement, New Permits

In a major change in air permitting policy, on January 25, 2018 U.S. EPA reversed its longstanding "once in, always in" policy governing what sources are subject to major source regulations for the emissions of air toxics under Section 112 of the Clean Air Act. Under a 1995 policy memorandum issued by the agency, sources that had the potential to emit above the major source thresholds at the time a standard applied to a particular source category were "always in," and had to forever comply with that standard—even if the source subsequently installed emission control equipment or switched to non-hazardous air pollutant substances, and took enforceable limits to keep emissions below those limits. The January 25 memorandum reverses that policy, and authorizes the reclassification of a major source to an area source at such time as the source takes enforceable limits on potential to emit below the major source thresholds.