PUBLIC LAW 95-95—AUG. 7, 1977
91 STAT. 707
any subsequent enactment which supersedes such provisions, or "(ii) within one year after enactment of the Clean Air Act Amendments of 1977 gives notice of intent to convert to coal as its primary e n e r ^ source because of actual or anticipated curtailment of natural gas supplies under any curtailment plan or schedule approved by the Federal Power Commission (or, in the case of intrastate natural gas supplies, approved by the appropriate State regulatory commission), and which thereby would no longer be in compliance with any requirement under an applicable implementation plan, an order may be issued by the Administrator under paragraph (1) of this subsection for such source which specifies a date for final compliance with such requirement as expeditiously as practicable, but not later than December 31, 1980. The Administrator may issue an additional order under paragraph (1) of this subsection for such source providing an additional period of such source to come into compliance with the requirement in the applicable implementation plan, which shall be as expeditiously as practicable, but in no event later than five years after the date required for compliance under the preceding sentence. "(B) In issuing an order pursuant to subparagraph (A), the Administrator shall prescribe (and may from time to time modify) emission limitations, requirements respecting pollution characteristics of coal, or other enforceable measures for control of emissions for each source to which such an order applies. Such limitations, requirements, and measures shall be those which the Administrator determines must be complied with by the source in order to assure (throughout the period before the date for final compliance established in the order) that the burning of coal by such source will not result in emissions which cause or contribute to concentrations of any air pollutant in excess of any national primary ambient air quality standard for such pollutant. "(C) The Administrator may, by regulation, establish priorities Priorities, under which manufacturers of continuous emission reduction systems necessary to carry out this paragraph shall provide such systems to users thereof, if he finds, after consultation with the States, that priorities must be imposed in order to assure that such systems are first provided to sources subject to orders under this paragraph in air quality control regions in which national primary ambient air quality standards have not been achieved. No regulation under this subparagraph may impair the obligation of any contract entered into before the date of enactment of the Clean Air Act Amendments of 1977. "(D) No order issued to a source under this paragraph with respect to an air pollutant shall be effective if the national primary ambient air quality standard with respect to such pollutant is being exceeded at any time in the air quality control region in which such source is located. The preceding sentence shall not apply to a source if, upon submission by any person of evidence satisfactory to the Administra.tor, the Administrator determines (after notice and public hearing) — "(i) that emissions of such air pollutant from such source will affect only infrequently the air quality concentrations of such pollutant in each portion of the region where such standard is being exceeded at any time; "(ii) that emissions of such air pollutant from such source will have only insignificant effect on the air quality concentrations of such pollutant in each portion of the region where such standard is being exceeded at any time; and "(iii) with reasonable statistical assurance that emissions of such air pollutant from such source will not cause or contribute
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