40 CFR § 52.1621 - Classification of regions.

---
identifier: "/us/cfr/t40/s52.1621"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 52.1621 - Classification of regions."
title_number: 40
title_name: "Protection of Environment"
section_number: "52.1621"
section_name: "Classification of regions."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "C"
subchapter_name: "AIR PROGRAMS"
part_number: "52"
part_name: "APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7401"
cfr_part: "52"
---


# 52.1621 Classification of regions.

The New Mexico plan was evaluated on the basis of the following classifications:

|  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
| Albuquerque-Mid-Rio Grande Intrastate | I | III | III | III | I |
| New Mexico Southern Border Intrastate | IA | IA | III | III | III |
| El Paso-Las Cruces-Alamogordo Interstate | I | IA | III | I | I |
| Four Corners Interstate | IA | IA | III | III | III |
| Northeastern Plains Intrastate | III | III | III | III | III |
| Pecos-Permian Basin Intrastate | III | III | III | III | III |
| Southwestern Mountains-Augustine Plains Intrastate | III | III | III | III | III |
| Upper Rio Grande Valley Intrastate | III | III | III | III | III |

[37 FR 1081, May 31, 1972, as amended at 39 FR 16347, May 8, 1974; 42 FR 20131, Apr. 18, 1977; 45 FR 24468, Apr. 10, 1980; 45 FR 67347, Oct. 10, 1980; 52 FR 5965, Feb. 27, 1987]