The U.S. Environmental Protection Agency (EPA) issued a guidance memorandum on January 25 withdrawing the decades-old “once in always in” policy for classifying major sources of hazardous air pollutants under section 112 of the Clean Air Act.
EPA says that with its 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 agency says the “once in always in” policy has been a longstanding disincentive for sources to implement voluntary pollution abatement and prevention efforts, or to pursue technological innovations that would reduce hazardous air pollution emissions.
EPA says that the Clean Air Act defines a “major source” as 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.
The revised policy finds that EPA had no statutory authority under the Clean Air Act to place a time limit on when a facility may be determined to be an area source. It says that a "plain language reading" of the Act "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."
EPA says that it will soon publish a Federal Register notice on its memorandum.