MACT floor

Maximum Achievable Control Technology (MACT) floor means:
(1) For existing sources:
(i) The average emission limitation achieved by the best performing 12 percent of the existing sources in the United States (for which the Administrator has emissions information), excluding those sources that have, within 18 months before the emission standard is proposed or within 30 months before such standard is promulgated, whichever is later, first achieved a level of emission rate or emission reduction which complies, or would comply if the source is not subject to such standard, with the lowest achievable emission rate (as defined in section 171 of the Act) applicable to the source category and prevailing at the time, in the category or subcategory, for categories and subcategories of stationary sources with 30 or more sources; or
(ii) The average emission limitation achieved by the best performing five sources (for which the Administrator has or could reasonably obtain emissions information) in the category or subcategory, for categories or subcategories with fewer than 30 sources;
(2) For new sources, the emission limitation achieved in practice by the best controlled similar source.

Source

40 CFR § 63.51

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Scoping language

Terms used in 63.50 through 63.56 that are not defined in this section have the meaning given to them in the Act, or in subpart A of this part.

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