The U.S. EPA has issued a guidance memorandum withdrawing 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.
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.
Today’s memo finds that EPA must allow facilities to be reclassified as area sources once their potential to emit hazardous air pollutants falls below the levels that define major sources.
Note: 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.”