# Air Plan Approval; Connecticut; New Source Review Permit Program State Plan Revision
**AGENCY:**
Environmental Protection Agency (EPA).
**ACTION:**
Proposed rule.
**SUMMARY:**
The Environmental Protection Agency (EPA) is proposing to approve a State Implementation Plan (SIP) revision submitted by the State of Connecticut. This action consists of revisions to Connecticut's New Source Review (NSR) permit program, primarily to clarify applicability for stationary sources in nonattainment areas. This action is being taken under the Clean Air Act (CAA).
**DATES:**
Written comments must be received on or before December 29, 2025.
**ADDRESSES:**
Submit your comments, identified by Docket ID No. EPA-R01-OAR-2025-0653 at *https://www.regulations.gov,* or via email to *[email protected].* For comments submitted at *Regulations.gov* , follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from *Regulations.gov* . For either manner of submission, the EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission ( *i.e.,* on the web, cloud, or other file sharing system). For additional submission methods, please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit *https://www.epa.gov/dockets/commenting-epa-dockets.* Publicly available docket materials are available at *https://www.regulations.gov* or at the U.S. Environmental Protection Agency, EPA Region 1 Regional Office, Air and Radiation Division, 5 Post Office Square—Suite 100, Boston, MA. EPA requests that, if at all possible, you contact the contact listed in the *FOR FURTHER INFORMATION CONTACT* section to schedule your inspection.
**FOR FURTHER INFORMATION CONTACT:**
Andre Turner, U.S. Environmental Protection Agency, Region 1 Office of Air and Radiation Division, 5 Post Office Square, Suite 100, Boston, MA 02109, Phone number: (617) 918-1216, Email: *[email protected].*
**SUPPLEMENTARY INFORMATION:**
Throughout this document whenever “we,” “us,” or “our” is used, we mean EPA.
**Table of Contents**
I. Background
II. Description and Review of Submittal
III. EPA's Evaluation of CT DEEP's Submittal
1. RCSA Section 22a-174-3a(a)(2)(C)(ii)
2. RCSA Section 22a-174-3a(l)(1)(B)
3. RCSA Section 22a-174-3a(l)(1)(C)
IV. Proposed Action
V. Incorporation by Reference
VI. Statutory and Executive Order Reviews
**I. Background**
The Connecticut Department of Energy and Environmental Protection (CT DEEP) established its SIP, including its NSR permit program, in 1972 in accordance with CAA section 110 and 40 CFR part 51. Since then, there have been numerous revisions to the SIP in accordance with state and federal air permitting regulations. The most recent federally enforceable revision to Connecticut's NSR permit program was approved into the SIP by EPA on September 5, 2023, and included changes to sections 22a-174-2a and 22a-174-3a of the Regulations of Connecticut State Agencies (RCSA).
**II. Description and Review of Submittal**
On October 3, 2024, [^1] CT DEEP submitted a SIP revision containing changes to RCSA section 22a-174-3a, primarily to clarify the applicability of Connecticut's permit requirements for stationary sources in nonattainment areas. These revisions to RCSA became effective, as a matter of state enforceability, on March 14, 2024.
[^1] The Connecticut SIP cover letter lists a submittal date of June 27, 2024, however EPA received this through the online submittal system State Planning Electronic Collaboration System (SPeCS) on October 3, 2024.
The first revision made by CT DEEP is to RCSA section 22a-174-3a(a)(2)(C)(ii), which references the federal definition of a “non-road engine.” The citation to 40 CFR part 89 in this clause was amended to 40 CFR 1068.30 in order reflect the correct citation after EPA renumbering. The two other revisions relate to subsection (l) of RCSA section 22a-174-3a, which addresses permit requirements for nonattainment areas. Subparagraph (B) of subdivision (1) of subsection (l) is amended to clarify how the subsection applies to modifications. The revised text provides more detail on how changes to an existing unit may be considered a major modification. The amended text also includes references to Table 3a(k)-1, which lists the significant emission rate threshold values for pollutants and their precursors. In subparagraph (C) of the same subdivision, the text is revised to add the phrase “for such pollutant” after “nonattainment area” for clarity.
**III. EPA's Evaluation of CT DEEP's Submittal**
EPA has reviewed the following revisions to RCSA section 22a-174-3a submitted by CT DEEP.
**1. RCSA Section 22a-174-3a(a)(2)(C)(ii)**
CT DEEP revised this provision to replace the outdated reference to 40 CFR part 89 with the current federal definition of “nonroad engine” at 40 CFR 1068.30. EPA has determined that this correction does not change the applicability of the exemption for nonroad engines but ensures that the state regulation references the appropriate federal definition.
**2. RCSA Section 22a-174-3a(l)(1)(B)**
CT DEEP revised this provision to clarify the applicability of nonattainment new source review (NNSR) requirements to modifications at major stationary sources. The revised regulations clarify that the NNSR program applies to two categories of modifications:
(i) modifications to an emission unit that is itself a major stationary source that triggers NNSR when the modification results in a significant emissions increase equal to or greater than the significant emission rate thresholds of a pollutant (or their precursors) for which the area is designated as nonattainment; or
(ii) modifications to a premises that is a major stationary source that triggers NNSR when the modification results in a net emissions increase equal to or greater than the significant emission rate threshold of a pollutant (or their precursors) for which the area is designated as nonattainment.
The revisions to 22a-174-3a(l)(1)(B) do not change NNSR applicability thresholds, offset obligations, or control technology requirements, but rather clarify the circumstances that a modification may be considered major and trigger NNSR to either a unit itself or to a premises that is considered a major stationary source. EPA has determined that this revision appropriately clarifies NNSR applicability for major modifications and is consistent with EPA's 40 CFR 51.165 requirements for state NNSR programs.
**3. RCSA Section 22a-174-3a(l)(1)(C)**
CT DEEP revised this provision by adding the phrase “for such a pollutant” after “nonattainment area.” This revision clarifies that NNSR requirements apply only to nonattainment pollutants (and their precursors) at new major stationary sources and modifications at existing major stationary sources located in nonattainment areas. The revisions to 22a-174-3a(l)(1)(C) do not change NNSR applicability thresholds, offset obligations, or control technology requirements. EPA has determined that this revision clarifies NNSR applicability and is consistent with EPA's 40 CFR 51.165 requirements for state NNSR programs.
**IV. Proposed Action**
EPA is proposing to approve Connecticut's October 3, 2024, SIP submittal that addresses revisions to RCSA section 22a-174-3a. EPA is soliciting public comments on the issues discussed in this notice or on other relevant matters. These comments will be considered before taking final action. Interested parties may participate in the Federal rulemaking procedure by submitting written comments to this proposed rule by following the instructions listed in the *ADDRESSES* section of this *Federal Register* .
**V. Incorporation by Reference**
In this rule, the EPA is proposing to include in a final EPA rule regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, the EPA is proposing to incorporate by reference the changes to RCSA section 22a-174-3a as adopted on March 14, 2024, and discussed in Section II of this preamble. The EPA has made, and will continue to make, these documents generally available through *https://www.regulations.gov* and at the EPA Region 1 Office (please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section of this preamble for more information).
**VI. Statutory and Executive Order Reviews**
Under the Clean Air Act, the Administrator is required to approve a SIP submission that complies with the provisions of the Clean Air Act and applicable Federal regulations. *See* 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve state choices, provided that they meet the criteria of the Clean Air Act. Accordingly, this proposed action merely approves state law as meeting Federal requirements and does not impose additional requirements beyond those imposed by state law. For that reason, this proposed action:
• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Orders 12866 (58 FR 51735, October 4, 1993);
• Is not subject to Executive Order 14192 (90 FR 9065, February 6, 2025) because SIP actions are exempt from review under Executive Order 12866;
• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 *et seq.* );
• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 *et seq.* );
• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4);
• Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);
• Is not subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it approves a state program;
• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001); and
• Is not subject to requirements of Section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the Clean Air Act.
In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where EPA or an Indian tribe has demonstrated that a tribe has jurisdiction. In those areas of Indian country, the rule does not have tribal implications and will not impose substantial direct costs on tribal governments or preempt tribal law as specified by Executive Order 13175 (65 FR 67249, November 9, 2000).
**List of Subjects in 40 CFR Part 52**
Environmental protection, Air pollution control, Incorporation by reference, Intergovernmental relations, Nitrogen dioxide, Ozone, Reporting and recordkeeping requirements, Volatile organic compounds.
Dated: November 20, 2025.
Mark Sanborn,
Regional Administrator, EPA Region 1.