40 C.F.R. § 51.1303 : Protection of Environment — ENVIRONMENTAL PROTECTION AGENCY — AIR PROGRAMS — REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS — Provisions for Implementation of the 2015 Ozone National Ambient Air Quality Standards — Application of classification and attainment date provisions in CAA section 181 to areas subject to Section 51.1302

(a) In accordance with CAA section 181(a)(1), each area designated nonattainment for the 2015 ozone NAAQS shall be classified by operation of law at the time of designation. The classification shall be based on the 8-hour design value for the area at the time of designation, in accordance with Table 1 of this paragraph (a). A state may request a higher or lower classification as provided in paragraphs (b) and (c) of this section. For each area classified under this section, the attainment date for the 2015 NAAQS shall be as expeditious as practicable, but not later than the date provided in Table 1 as follows:

TABLE 1 TO PARAGRAPH (A)-CLASSIFICATIONS AND ATTAINMENT DATES FOR 2015 8-HOUR OZONE NAAQS (0.070 PPM) FOR AREAS SUBJECT TO § 51.1302

Area class	8-hour ozone design value (ppm)	Primary standard attainment date (years after the effective date of designation for 2015 primary NAAQS)
Marginal	from up to*	0.071 0.081	3
Moderate	from up to*	0.081 0.093	6
Serious	from up to*	0.093 0.105	9
Severe-15	from up to*	0.105 0.111	15
Severe-17	from up to*	0.111 0.163	17
Extreme	equal to or above	0.163	20

*But not including.

(b) A state may request, and the Administrator must approve, a higher classification for an area for any reason in accordance with CAA section 181(b)(3).

(c) A state may request, and the Administrator may in the Administrator's discretion approve, a higher or lower classification for an area in accordance with CAA section 181(a)(4).

40 C.F.R. §51.1303

83 FR 10382, 5/8/2018