104 STAT. 2432 PUBLIC LAW 101-549—NOV. 15, 1990 "(A) ATTAINMENT DEMONSTRATION.—A demonstration that the plan, as revised, will provide for attainment of the ozone national ambient air quality standard by the applicable attainment date. This attainment demonstration must be based on photochemical grid modeling or any other analytical method determined by the Administrator, in the Administrator's discretion, to be at least as effective. "(B) REASONABLE FURTHER PROGRESS DEMONSTRATION. —A demonstration that the plan, as revised, will result in VOC emissions reductions from the baseline emissions described in subsection (b)(1)(B) equal to the following amount averaged over each consecutive 3-year period beginning 6 years after the date of the enactment of the Clean Air Act Amendments of 1990, until the attainment date: "(i) at least 3 percent of baseline emissions each year; or "(ii) an amount less than 3 percent of such baseline emissions each year, if the State demonstrates to the satisfaction of the Administrator that the plan reflecting such lesser amount includes all measures that can feasibly be implemented in the area, in light of technological achievability. To lessen the 3 percent requirement under clause (ii), a State must demonstrate to the satisfaction of the Administrator that the plan for the area includes the measures that are achieved in practice by sources in the same source category in nonattainment areas of the next higher classification. Any determination to lessen the 3 percent requirement shall be reviewed at each milestone under section 182(g) and revised to reflect such new measures (if any) achieved in practice by sources in the same category in any State, allowing a reasonable time to implement such measures. The emission reductions described in this subparagraph shall be calculated in accordance with subsection (b)(1)(C) and (D) (concerning creditability of reductions). The reductions creditable for the period beginning 6 years after the date of the enactment of the Clean Air Act Amendments of 1990, shall include reductions that occurred before such period, computed in accordance with subsection (b)(1), that exceed the 15-percent amount of reductions required under subsection (b)(1)(A). "(C) NOx CONTROL.—The revision may contain, in lieu of the demonstration required under subparagraph (B), a demonstration to the satisfaction of the Administrator that the applicable implementation plan, as revised, provides for reductions of emissions of VOC's and oxides of nitrogen (calculated according to the creditability provisions of subsection (b)(1)(C) and (D)), that would result in a reduction in ozone concentrations at least equivalent to that which would result from the amount of VOC emission reductions required under subparagraph (B). Within 1 year after the date of the enactment of the Clean Air Act Amendments of 1990, the Administrator shall issue guidance concerning the conditions under which NOx control may be substituted for VOC control or may be combined with VOC control in order to maximize the reduction in ozone air pollution. In accord with such guidance, a lesser
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