104 STAT. 2436 PUBLIC LAW 101-549—NOV. 15, 1990 "(7) SPECIAL RULE FOR MODIFICATIONS OF SOURCES EMITTING LESS THAN 100 TONS.— In the case of any major stationary source of volatile organic compounds located in the area (other than a source which emits or has the potential to emit 100 tons or more of volatile organic compounds per year), whenever any change (as described in section lll(a)(4)) at that source results in any increase (other than a de minimis increase) in emissions of volatile organic compounds from any discrete operation, unit, or other pollutant emitting activity at the source, such increase shall be considered a modification for purposes of section 172(c)(5) and section 173(a), except that such increase shall not be considered a modification for such purposes if the owner or operator of the source elects to offset the increase by a greater reduction in emissions of volatile organic compounds concerned from other operations, units, or activities within the source at an internal offset ratio of at least 1.3 to 1. If the owner or operator does not make such election, such change shall be considered a modification for such purposes, but in applying section 173(a)(2) in the case of any such modification, the best available control technology (BACT), as defined in section 169, shall be substituted for the lowest achievable emission rate (LAER). The Administrator shall establish and publish policies and procedures for implementing the provisions of this paragraph. "(8) SPECIAL RULE FOR MODIFICATIONS OF SOURCES EMITTING lOO TONS OR MORE. —In the case of any major stationary source of volatile organic compounds located in the area which emits or has the potential to emit 100 tons or more of volatile organic compounds per year, whenever any change (as described in section 111(a)(4)) at that source results in any increase (other than a de minimis increase) in emissions of volatile organic compounds from any discrete operation, unit, or other pollutant emitting activity at the source, such increase shall be considered a modification for purposes of section 172(c)(5) and section 173(a), except that if the owner or operator of the source elects to offset the increase by a greater reduction in emissions of volatile organic compounds from other operations, units, or activities within the source at an internal offset ratio of at least 1.3 to 1, the requirements of section 173(a)(2) (concerning the lowest achievable emission rate (LAER)) shall not apply. "(9) CONTINGENCY PROVISIONS.— In addition to the contingency provisions required under section 172(c)(9), the plan revision shall provide for the implementation of specific measures to be undertaken if the area fails to meet any applicable milestone. Such measures shall be included in the plan revision as contingency measures to take effect without further action by the State or the Administrator upon a failure by the State to meet the applicable milestone. "(10) GENERAL OFFSET REQUIREMENT. — For purposes of satisfy- ing the emission offset requirements of this part, the ratio of total emission reductions of volatile organic compounds to total increase emissions of such air pollutant shall be at least 1.2 to 1. Any reference to 'attainment date in subsection (b), which is incorporated by reference into this subsection, shall refer to the attainment date for serious areas. "(d) SEVERE AREAS. —Each State in which all or part of a Severe Area is located shall, with respect to the Severe Area, make the
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