On January 25, 2018, the U.S. Environmental Protection Agency (“EPA”) withdrew its 1995 “once in always in” guidance. Under that guidance, facilities classified as “major sources” of hazardous air pollutants (“HAP”) as of the “first compliance date” of a maximum achievable control technology (“MACT”) standard under Section 112 of the Clean Air Act are required to comply permanently with the MACT standard. Now, EPA’s current policy is that a major source that limits its potential to emit (“PTE”) to below major source thresholds can become an area source and will no longer be subject to the major source MACT.
The Clean Air Act defines “major source” as “any stationary source or group of stationary sources located within a contiguous area and under common control that emits or has the potential to emit considering controls, in the aggregate, 10 tons per year or more of any hazardous air pollutant or 25 tons per year or more of any combination of hazardous air pollutants.” This definition expressly allows PTE to be calculated “considering controls,” and does not address the timing for when a source will be classified as a major source. As a result, EPA found that its “once in always in” policy “created an artificial time limit” contrary to the plain language of the Clean Air Act and must be withdrawn.
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