On January 25, 2018, EPA announced that it was withdrawing its “once in, always in” policy for the classification of major sources of hazardous air pollutants (HAPs) under Section 112 of the Clean Air Act. Under its new guidance, sources of HAPs that have been classified as “major sources” may be reclassified as minor or “area” sources when a facility limits its potential to emit below the major source HAP thresholds.

In 1995, EPA issued a guidance memorandum that established a policy, commonly known as the “once in, always in” policy, under which “facilities may switch to area source status at any time until the ‘first compliance date’ of the standard.” See “Potential to Emit for MACT Standards – Guidance on Timing Issues,” John Seitz, Director, Office of Air Quality Planning and Standards, U.S. EPA, May 16, 1995. Under that guidance, sources with potential HAP emissions over the major source thresholds (10 tons/yr single HAP and 25 tons/yr all HAPs) were considered major HAP sources forever if they did not limit their potential HAP emissions to minor source levels prior to the compliance deadline established in a relevant MACT standard under 40 C.F.R. Part 63. Thus, a facility could be considered a major HAP source and subject to MACT standards and Title V permitting if their potential HAP emissions, assuming it was operating at maximum production rates 24 hours/day, 365 days/year, would exceed the major source thresholds -- even if actual emissions were de minimis.

Under EPA’s new guidance, that policy is withdrawn and sources can become minor or area sources at any time by accepting appropriate federally enforceable limits.

EPA anticipates that it will soon publish its new guidance in the Federal Register. With this guidance, facilities that have been considered major HAP sources, but have actual HAP emissions below major source levels, might want to consider obtaining limits to avoid major source MACT requirements and Title V licensing. Click here for a copy of EPA’s Press Release and its new guidance.