40 CFR § 52.321 - Classification of regions.

---
identifier: "/us/cfr/t40/s52.321"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 52.321 - Classification of regions."
title_number: 40
title_name: "Protection of Environment"
section_number: "52.321"
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"
---


# 52.321 Classification of regions.

The revised Denver Emergency Episode Plan, adopted by the State of Colorado February 28, 1996, was submitted by the Governor of Colorado with a September 16, 1997 letter.

|  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
| Pawnee Intrastate | I | III | III | III | III |
| Metropolitan Denver Intrastate | I | III | III | I | I |
| Comanche Intrastate | III | III | III | III | III |
| San Isabel Intrastate | I | III | III | III | III |
| San Luis Intrastate | III | III | III | III | III |
| Four Corners Interstate | IA | IA | III | III | III |
| Grand Mesa Intrastate | III | III | III | III | III |
| Yampa Intrastate | III | III | III | III | III |

[37 FR 10855, May 31, 1972, as amended at 39 FR 16346, May 8, 1974; 44 FR 57409, Oct. 5, 1979; 74 FR 47891, Sept. 18, 2009]