42 U.S.C. § 7512 — Classification and attainment dates

Each area designated nonattainment for carbon monoxide pursuant to section 7407(d) of this title shall be classified at the time of such designation under table 1, by operation of law, as a Moderate Area or a Serious Area based on the design value for the area. The design value shall be calculated according to the interpretation methodology issued by the Administrator^* most recently before November 15, 1990. For each area classified under this subsection, the primary standard attainment date^* for carbon monoxide shall be as expeditiously as practicable but not later than the date provided in table 1:

At the time of publication of the notice required under section 7407 of this title (designating carbon monoxide nonattainment areas), the Administrator shall publish a notice announcing the classification of each such carbon monoxide nonattainment area^*. The provisions of section 7502(a)(1)(B) of this title (relating to lack of notice-and-comment and judicial review) shall apply with respect to such classification.

If an area classified under paragraph (1), table 1, would have been classified in another category if the design value in the area were 5 percent greater or 5 percent less than the level on which such classification was based, the Administrator may, in the Administrator’s discretion, within 90 days after November 15, 1990, by the procedure required under paragraph (2), adjust the classification of the area. In making such adjustment, the Administrator may consider the number of exceedances of the national primary ambient air quality standard for carbon monoxide in the area, the level of pollution transport between the area and the other affected areas, and the mix of sources and air pollutants in the area. The Administrator may make the same adjustment for purposes of paragraphs (2), (3), (6), and (7) of section 7512a(a) of this title.

Upon application by any State^*, the Administrator may extend for 1 additional year (hereinafter in this subpart referred to as the “Extension Year”) the date specified in table 1 of subsection (a) if—

No more than 2 one-year extensions may be issued under this paragraph for a single nonattainment area.

Any area that is designated attainment or unclassifiable for carbon monoxide under section 7407(d)(4) of this title, and that is subsequently redesignated to nonattainment for carbon monoxide under section 7407(d)(3) of this title, shall, at the time of the redesignation, be classified by operation of law in accordance with table 1 under subsections (a)(1) and (a)(4). Upon its classification, the area shall be subject to the same requirements under section 7410 of this title, subpart 1 of this part, and this subpart that would have applied had the area been so classified at the time of the notice under subsection (a)(2), except that any absolute, fixed date applicable in connection with any such requirement is extended by operation of law by a period equal to the length of time between November 15, 1990, and the date the area is classified.