---
kind: "section"
citation: "40 C.F.R. § 51.908"
title: "40"
number: "51.908"
heading: "What modeling and attainment demonstration requirements apply for purposes of the 8-hour ozone NAAQS?"
url: "https://uscodex.org/cfr/40/51.908"
---

# §51.908. What modeling and attainment demonstration requirements apply for purposes of the 8-hour ozone NAAQS?

- (a) **What is the attainment demonstration requirement for an area classified as moderate or higher under subpart 2 pursuant to § 51.903?** An area classified as moderate or higher under [§ 51.903](/cfr/40/51.903.md) shall be subject to the attainment demonstration requirement applicable for that classification under section 182 of the Act, except such demonstration is due no later than 3 years after the area's designation for the 8-hour NAAQS.
- (b) **What is the attainment demonstration requirement for an area subject only to subpart 1 in accordance with § 51.902(b)?** An area subject to [§ 51.902(b)](/cfr/40/51.902.md?p=b) shall be subject to the attainment demonstration under section 172(c)(1) of the Act and shall submit an attainment demonstration no later than 3 years after the area's designation for the 8-hour NAAQS.
- (c) **What criteria must the attainment demonstration meet?** An attainment demonstration due pursuant to paragraph [(a)](#a) or [(b)](#b) of this section must meet the requirements of [§ 51.112](/cfr/40/51.112.md); the adequacy of an attainment demonstration shall be demonstrated by means of a photochemical grid model or any other analytical method determined by the Administrator, in the Administrator's discretion, to be at least as effective.
- (d) For each nonattainment area, the State must provide for implementation of all control measures needed for attainment no later than the beginning of the attainment year ozone season.

## Notes

### Amendments

[69 FR 23996, Apr. 30, 2004, as amended at 70 FR 71700, Nov. 29, 2005]

### 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.

### Amendments

[69 FR 23996, Apr. 30, 2004, as amended at 70 FR 71700, Nov. 29, 2005]