---
kind: "section"
citation: "40 C.F.R. § 51.904"
title: "40"
number: "51.904"
heading: "How do the classification and attainment date provisions in section 172(a) of subpart 1 of the CAA apply to areas subject to § 51.902(b)?"
url: "https://uscodex.org/cfr/40/51.904"
---

# §51.904. How do the classification and attainment date provisions in section 172(a) of subpart 1 of the CAA apply to areas subject to § 51.902(b)?

- (a) **Classification.** The Administrator may classify an area subject to [§ 51.902(b)](/cfr/40/51.902.md?p=b) as an overwhelming transport area if:
  - (1) The area meets the criteria as specified for rural transport areas under [section 182(h)](/cfr/40/182.md?p=h) of the CAA;
  - (2) Transport of ozone and/or precursors into the area is so overwhelming that the contribution of local emissions to observed 8-hour ozone concentration above the level of the NAAQS is relatively minor; and
  - (3) The Administrator finds that sources of VOC (and, where the Administrator determines relevant, NOX) emissions within the area do not make a significant contribution to the ozone concentrations measured in other areas.
- (b) **Attainment dates.** For an area subject to [§ 51.902(b)](/cfr/40/51.902.md?p=b), the Administrator will approve an attainment date consistent with the attainment date timing provision of [section 172(a)(2)(A)](/cfr/40/172.md?p=a-2-A) of the CAA at the time the Administrator approves an attainment demonstration for the area.

## Notes

### Source

Source: 69 FR 23996, Apr. 30, 2004, unless otherwise noted.

### Authority

Authority: 23 U.S.C. 101; 42 U.S.C. 7401-7671q.

### Source

Source: 36 FR 22398, Nov. 25, 1971, unless otherwise noted.