EPA Withdraws "Once In, Always In" MACT Standards

The U.S. Environmental Protection Agency (EPA) issued a guidance memorandum on January 25, 2018 to withdraw the “once in, always in” classification policy of major sources of air emissions. [1] This significant change in air permitting policy reversed the longstanding policy that did not allow reclassification of a major source facility even if emissions were reduced below the major source thresholds. Assistant Administrator of EPA’s Office of Air and Radiation stated, “It will reduce regulatory burden for industries and the states, while continuing to ensure stringent and effective controls on hazardous air pollutants.” [2]

Clean Air Act and MACT Standards

Under section 112 of the Clean Air Act, a “major source” is defined as any source that emits 10 tons per year of any Hazardous Air Pollutant (HAP) or 25 tons or more per year of any combination of HAPs. If classified as a major source, a facility is subject to Maximum Available Control Technology (MACT) standards. The EPA MACT standards grow more stringent over time. Sources below these air emission levels are classified as “area sources,” to which different, less stringent control standards apply. A 1995 EPA memorandum had established a “once in always in” policy whereby any facility determined to be a major source would always remain subjected to those standards, even if the facility permanently reduced or eliminated the potential to emit HAPs. [2]

In short, major sources that reduced emissions below the 10 and 25-ton thresholds (as frequently happens under the stringent EPA MACT standards), could not be reclassified as an area source. Reclassification would greatly benefit these facilities with more streamlined reporting and record keeping procedures [3], and lower compliance costs.

Effects on Enforcement, New Permits

Many facilities will likely seek reclassification from “major” to “area” source status because of reduction or elimination of HAP emissions. And since states have incorporated the federal major source requirements into air permits, permit modifications through state agencies would be necessary in those cases. This new guidance memorandum may also have implications for current enforcement cases. [4]