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U.S. EPA Moves to Reverse “Once In, Always In” Policy for MACT Standards


By Andy Bowman, Attorney, Bingham Greenebaum Doll LLP

A major source of hazardous air pollutants (HAP) must meet federal emission standards based on the performance of the maximum achievable control technology (MACT) currently used by the best controlled sources in the industry. A major source of HAP is defined as a source that emits or has the potential to emit (PTE) 10 tons per year (tpy) of any single HAP or 25 tpy of any combination of HAP. If a source’s HAP emissions fall below these thresholds, Section 112 of the Clean Air Act define the source as an “area source.” Most area sources are subject to less stringent standards than MACT known as generally available control technology (GACT) or generally available management practices. Many area sources are not subject to any requirements, although U.S. EPA is scheduled to adopt new standards for 50 source groups.

Under the so-called “Once In, Always In” policy adopted by U.S. EPA in 1995, a major source may become an area source by limiting its PTE HAP to below the major source thresholds (10 tpy or more of an individual HAP or 25 tpy or more of any combination of HAP) by no later than the first compliance deadline listed under the applicable MACT standard (also referred to as National Emission Standards for Hazardous Air Pollutants or NESHAP). Thus, a source which fails to achieve area source status by the first MACT compliance deadline, must remain subject to the MACT even if it subsequently reduces HAP emissions below major source levels.

U.S. EPA has acknowledged that its 1995 “Once In, Always In” policy discourages sources from adopting new control technologies or pollution prevention techniques to reduce HAP emissions if the source must always be subject to MACT standards. U.S. EPA further determined that the Clean Air Act does not prohibit a source from becoming an area source after the first MACT compliance date.

To address this situation, U.S. EPA is proposing amendments to the general provisions of 40 CFR Part 63 which provide that a major source of HAP may become an area source at any time, including after the MACT compliance date, by limiting its PTE HAP below the major source thresholds. U.S. EPA’s policy reversal, if final adopted, will provide sources which are able to limit their PTE HAP an opportunity to reduce regulatory burdens. For a source required to obtain a Title V Operating Permit only because it is a major source of HAP, the source may also be able to switch to a lower level permit and avoid the significant administrative burdens imposed by a Title V Operating Permit. U.S. EPA is seeking comments on its proposal through March 5, 2007. The proposed rule can be found at 72 Federal Register 69 (January 3, 2007) or by searching for “EPA-HQ-OAR-2004-0094.


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