PUBLIC LAW 101-549—NOV. 15, 1990 104 STAT. 2431 "(C) REFERENCE TO TERMS. —For purposes of this paragraph, any reference to the term 'adoption date' shall be considered a reference to the date of adoption by the State of requirements for the installation and operation of a system for gasoline vapor recovery of emissions from the fueling of motor vehicles. "(4) MOTOR VEHICLE INSPECTION AND MAINTENANCE.—For all Moderate Areas, the State shall submit, immediately after the date of the enactment of the Clean Air Act Amendments of 1990, a revision to the applicable implementation plan that includes provisions necessary to provide for a vehicle inspection and maintenance program as described in subsection (a)(2)(B) (without regard to whether or not the area was required by section 172(b)(ll)(B) (as in effect immediately before the date of the enactment of the Clean Air Act Amendments of 1990) to have included a specific schedule for implementation of such a program). "(5) 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 1.15 tol. "(c) SERIOUS AREAS. —Except as otherwise specified in paragraph (4), each State in which all or part of a Serious Area is located shall, with respect to the Serious Area (or portion thereof, to the extent specified in this subsection), make the submissions described under subsection (b) (relating to Moderate Areas), and shall also submit the revisions to the applicable implementation plan (including the plan items) described under this subsection. For any Serious Area, the terms 'major source' and 'major stationary source' include (in addition to the sources described in section 302) any stationary source or group of sources located within a contiguous area and under common control that emits, or has the potential to emit, at least 50 tons per year of volatile organic compounds. "(1) ENHANCED MONITORING. — In order to obtain more com- Regulations, prehensive and representative data on ozone air pollution, not later than 18 months after the date of the enactment of the Clean Air Act Amendments of 1990 the Administrator shall promulgate rules, after notice and public comment, for enhanced monitoring of ozone, oxides of nitrogen, and volatile organic compounds. The rules shall, among other things, cover the location and maintenance of monitors. Immediately following the promulgation of rules by the Administrator relating to enhanced monitoring, the State shall commence such actions as may be necessary to adopt and implement a program based on such rules, to improve monitoring for ambient concentrations of ozone, oxides of nitrogen and volatile organic compounds and to improve monitoring of emissions of oxides of nitrogen and volatile organic compounds. Each State implementation plan for the area shall contain measures to improve the ambient monitoring of such air pollutants. "(2) ATTAINMENT AND REASONABLE FURTHER PROGRESS DEM- ONSTRATIONS. —Within 4 years after the date of the enactment of the Clean Air Act Amendments of 1990, the State shall submit a revision to the applicable implementation plan that includes each of the following:
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