PUBLIC LAW 101-549—NOV. 15, 1990 104 STAT. 2461 designation in the case of an area classified as moderate after the date of the enactment of the Clean Air Act Amendments of 1990. "(2) SCHEDULE FOR PLAN SUBMISSIONS. —A State shall submit ' the plsin required under subparagraph (1) no later than the following: "(A) Within 1 year of the date of the enactment of the Clean Air Act Amendments of 1990, for areas designated nonattainment under section 107(d)(4), except that the provision required under subparagraph (1)(A) shall be submitted no later than June 30, 1992. "(B) 18 months after the designation as nonattainment, for those areas designated nonattainment after the designations prescribed under section 107(d)(4). "(b) SERIOUS AREAS.— "(1) PLAN PROVISIONS. —In addition to the provisions submitted to meet the requirements of paragraph (a)(1) (relating to Moderate Areas), each State in which all or part of a Serious Area is located shall submit an implementation plan for such area that includes each of the following: "(A) A demonstration (including air quality modeling)— "(i) that the plan provides for attainment of the PM-10 national ambient air quality standard by the applicable attainment date, or "(ii) for any area for which the State is seeking, pursuant to section 188(e), an extension of the attainment date beyond the date set forth in section 188(c), that attainment by that date would be impracticable, and that the plan provides for attainment by the most expeditious alternative date practicable. "(B) Provisions to assure that the best available control measures for the control of PM-10 shall be implemented no later than 4 years after the date the area is classified (or reclassified) as a Serious Area. "(2) SCHEDULE FOR PLAN SUBMISSIONS. —A State shall submit the demonstration required for an area under paragraph (I)(A) no later than 4 years after reclassification of the area to Serious, except that for areas recleissified under section 188(b)(2), the State shall submit the attainment demonstration within 18 months after reclassification to Serious. A State shall submit the provisions described under paragraph (I)(B) no later than 18 months after reclassification of the area as a Serious Area. "(3) MAJOR SOURCES. —For any Serious Area, the terms 'major " source' and 'major stationary source' include 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, at least 70 tons per year of PM-10. "(c) MILESTONES. —(1) Plan revisions demonstrating attainment submitted to the Administrator for approval under this subpart shall contain quantitative milestones which are to be achieved every 3 years until the area is redesignated attainment and which demonstrate reasonable further progress, as defined in section 171(1), toward attainment by the applicable date. "(2) Not later than 90 days after the date on which a milestone applicable to the area occurs, each State in which all or part of such area is located shall submit to the Administrator a demonstration that all measures in the plan approved under this section have been
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