40 CFR § 52.1398 - Control strategy: Sulfur dioxide.

---
identifier: "/us/cfr/t40/s52.1398"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 52.1398 - Control strategy: Sulfur dioxide."
title_number: 40
title_name: "Protection of Environment"
section_number: "52.1398"
section_name: "Control strategy: Sulfur dioxide."
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"
---


# 52.1398 Control strategy: Sulfur dioxide.

(a) *Redesignation to attainment.* The EPA has determined that the Billings 2010 sulfur dioxide (SO<sub>2</sub>) nonattainment area has met the criteria under CAA section 107(d)(3)(E) for redesignation from nonattainment to attainment for the 2010 1-hour SO<sub>2</sub> NAAQS. The EPA is therefore redesignating the Billings 2010 SO<sub>2</sub> nonattainment area to attainment.

(b) The EPA is approving the maintenance plan for the Billings nonattainment area for the 2010 SO<sub>2</sub> NAAQS submitted by the State of Montana on December 14, 2015.

(c) *Redesignation to attainment.* The EPA has determined that the East Helena sulfur dioxide (SO<sub>2</sub>) nonattainment area has met the criteria under CAA section 107(d)(3)(E) for redesignation from nonattainment to attainment for the 1971 primary and secondary SO<sub>2</sub> NAAQS. The EPA is therefore redesignating the East Helena 1971 SO<sub>2</sub> nonattainment area to attainment.

(d) *Maintenance plan.* The EPA is approving the maintenance plan for the East Helena nonattainment area for the 1971 SO<sub>2</sub> NAAQS submitted by the State of Montana on October 26, 2018.

[81 FR 28720, May 10, 2016, as amended at 84 FR 47899, Sept. 11, 2019]