PUBLIC LAW 101-549—NOV. 15, 1990 104 STAT. 2547 comply with such promulgated standard until the date 3 years after the date of promulgation if— "(A) the promulgated standard, limitation or regulation is more stringent than the standard, limitation or regulation proposed; and "(B) the source complies with the standard, limitation, or regulation as proposed during the 3-year period immediately after promulgation. "(3) COMPUANCE SCHEDULE FOR EXISTING SOURCES. — "(A) After the effective date of any emissions standard, limitation or regulation promulgated under this section and applicable to a source, no person may operate such source in violation of such standard, limitation or regulation except, in the case of an existing source, the Administrator shall establish a compliance date or dates for each category or subcategory of existing sources, which shall provide for compliance as expeditiously as practicable, but in no event later than 3 years after the effective date of such standard, except as provided in subparagraph (B) and paragraphs (4) through (8). "(B) The Administrator (or a State with a program approved under title V) may issue a permit that grants an extension permitting an existing source up to 1 additional year to comply with standards under subsection (d) if such additional period is necessary for the installation of controls. An additional extension of up to 3 years may be added for mining waste operations, if the 4-year compliance time is insufficient to dry and cover mining waste in order to reduce emissions of any pollutant listed under subsection (b). "(4) PRESIDENTIAL EXEMPTION. —The President may exempt any stationary source from compliance with any standard or limitation under this section for a period of not more than 2 years if the President determines that the technology to implement such standard is not available and that it is in the national security interests of the United States to do so. An exemption under this paragraph may be extended for 1 or more additional periods, each period not to exceed 2 years. The President. President shall report to Congress with respect to each exemp- ^®Po^- tion (or extension thereof) made under this paragraph. "(5) EARLY REDUCTION. — "(A) The Administrator (or a State acting pursuant to a permit program approved under title V) shall issue a permit allowing an existing source, for which the owner or operator demonstrates that the source has achieved a reduction of 90 per centum or more in emissions of hazardous air pollutants (95 per centum in the case of hazardous air pollutants which are particulates) from the source, to meet an alternative emission limitation reflecting such reduction in lieu of an emission limitation promulgated under subsection (d) for a period of 6 years from the compliance date for the otherwise applicable standard, provided that such reduction is achieved before the otherwise applicable standard under subsection (d) is first proposed. Nothing in this paragraph shall preclude a State from requiring reductions in excess of those specified in this
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