40 CFR § 52.51 - Classification of regions.

---
identifier: "/us/cfr/t40/s52.51"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 52.51 - Classification of regions."
title_number: 40
title_name: "Protection of Environment"
section_number: "52.51"
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"
---


# 52.51 Classification of regions.

The Alabama plan was evaluated on the basis of the following classifications:

|  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
| Alabama & Tombigbee Rivers Intrastate | II | III | III | III | III |
| Columbus (Georgia)-Phenix City (Alabama) Interstate | I | III | III | III | III |
| East Alabama Intrastate | I | III | III | III | III |
| Metropolitan Birmingham Intrastate | I | II | III | I | I |
| Mobile (Alabama)-Pensacola-Panama City (Florida)-Southern Mississippi Interstate | I | I | III | III | I |
| Southeast Alabama Intrastate | II | III | III | III | III |
| Tennessee River Valley (Alabama)-Cumberland Mountains (Tennessee) Interstate | I | I | III | III | III |

[37 FR 10847, May 31, 1972]