News Flash: EPA Loosens "Once In, Always In" Policy for MACT Standards

Posted by Earl Parker on Feb 1, 2018 10:30:00 AM

Since the early 1990's, industrial facilities have become accustomed to being required to comply to specific reporting, record keeping, and other Maximum Achievable Control Technology (MACT) standards that were defined in their Title V Operating Permit for any "major source". 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 (HAPs).  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.”

Last week, the EPA 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.  This decision allows industrial facilities the opportunity to reduce HAPs emissions to below major source levels and no longer be required to comply with the major source MACT standards.

The EPA anticipates that it will soon publish a Federal Register notice to take comment on adding regulatory text that will reflect the EPA’s plain language reading of the statute as discussed in this memorandum. More information is available online at

It is important to ensure that any reclassified emissions point will not be able to exceed the major source emissions levels. Creating an enforceable emissions limit and having the right particulate monitoring capabilities will help to do this. The “once in always in” policy has been a major reason that companies chose not to implement voluntary pollution abatement and prevention efforts, or to pursue technological innovations that would reduce hazardous air pollution emissions. This change could result in more pro-active or preventative emission monitoring solutions to be considered by former or existing companies classified as major sources.

Click here to learn more and read the entire memo.

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