Late last month, the EPA withdrew the Once-In-Always-In policy for the classification of major sources of hazardous air pollutants under section 112 of the Clean Air Act.  With the new guidance, sources of hazardous air pollutants previously classified as “major sources” may be reclassified as “area sources” when the facility limits its potential to emit below major source thresholds.

The Clean Air Act defines a “major source” as a one that emits, or has the potential to emit, 10 tons per year of any hazardous air pollutant, or 25 tons per year or more of any combination of hazardous air pollutants.  Sources with emissions below this threshold are classified as “area sources.” Different control standards apply to the source depending on whether or not it is classified as a “major source” or an “area source.” In a 1995 memo, EPA established a “once in always in” policy that determined that any facility subject to major source standards would always remain subject to those standards, even if production processes changed or controls were implemented that eliminated or permanently reduced that facility’s potential to emit hazardous air pollutants.

Beginning in the mid-90s and over the years, as each National Emission Standard for Hazardous Air Pollutant (NESHAP) was adopted, each rule required that sources with potential to emit (PTE) greater than the major source thresholds for hazardous air pollutants (10 tons per year of any single HAP, 25 tons per year of total HAPs) come into compliance within three years.   In 1995,  the U.S. EPA issued its once-in-always-in policy memo.  This memo states that once the compliance date passed for a particular NESHAP, that NESHAP applies to any source with PTE greater than a major source threshold on or after that date forever more – regardless of future PTE or actual emissions. Many sources elected to obtain federally enforceable state operating permits or Title V Permits with enforceable permit conditions that limited their PTE to less than the major source thresholds for HAPs.  In Clean Air Act parlance, these sources were now area sources of HAPs, and future major source NESHAP were not applicable.  The 1995 memo required that these conditions be in place prior to the compliance date of the particular NESHAP. Examples of sources that are now area sources but still subject to major source NESHAPs under 1995 policy include:

• A source that had PTE or actual emissions of toluene greater than 10 tons per year.  The NESHAP compliance date rolls around, and the source installs an RTO reducing PTE or actual emissions to 2 tons per year.
• A source never had a permit that limits its PTE.  Gets discovered, but the 1995 policy prohibited them from taking permit conditions to make any major source NESHAP not applicable.

The January 24, 2018 memo supersedes 1995 Once In Always In policy memo.  This memo states that the 1995 memo is “…contrary to the plain language of the Clean Air Act…” and “…is withdrawn effective immediately.”  That means that any source can have its permit revised to include enforceable permit conditions that make a major source NESHAP not applicable.