# Identification of plan—in part.
**AGENCY:**
Environmental Protection Agency (EPA).
**ACTION:**
Final rule.
**SUMMARY:**
The Environmental Protection Agency (EPA) is taking final action to approve a revision to the Eastern Kern Air Pollution Control District (EKAPCD or “District”) portion of the California State Implementation Plan (SIP). This revision concerns emissions of oxides of nitrogen (NO <sub>X</sub> ) from stationary gas turbines. We are approving a local rule that regulates these emissions sources under the Clean Air Act (CAA or “Act”).
**DATES:**
This rule is effective December 22, 2025.
**ADDRESSES:**
The EPA has established a docket for this action under Docket ID No. EPA-R09-OAR-2025-0060. All documents in the docket are listed on the *https://www.regulations.gov* website. Although listed in the index, some information is not publicly available, *e.g.,* Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available through *https://www.regulations.gov,* or please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section for additional availability information. If you need assistance in a language other than English or if you are a person with a disability who needs a reasonable accommodation at no cost to you, please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section.
**FOR FURTHER INFORMATION CONTACT:**
La Kenya Evans-Hopper, EPA Region IX, 75 Hawthorne St., San Francisco, CA 94105; phone: (415) 972-3245; email: *[email protected].*
**SUPPLEMENTARY INFORMATION:**
Throughout this document, “we,” “us,” and “our” refer to the EPA.
**Table of Contents**
I. Proposed Action
II. Public Comments and EPA Responses
III. EPA Action
IV. Incorporation by Reference
V. Statutory and Executive Order Reviews
**I. Proposed Action**
On June 20, 2025 (90 FR 26232), the EPA proposed to approve the following rule into the California SIP.
| Local agency | Rule No. | Rule title | Amended | Submitted |
| --- | --- | --- | --- | --- |
| EKAPCD | 425 | Stationary Gas Turbines (Oxides of Nitrogen) | 11/13/2024 | 12/12/2024 |
We proposed to approve this rule because we determined that it complies with the relevant CAA requirements. Our proposed action contains more information on the rule and our evaluation.
**II. Public Comments and EPA Responses**
The EPA's proposed action provided a 30-day public comment period. During this period, we received four anonymous comments. The full texts of these comments are available in the docket for this rulemaking. Two of the comments were positive in response to our Determination to Defer Sanctions. [^1] One comment was in support of our decision to defer offset and highway sanctions for California and encouraged the EPA to maintain oversight for the implementation of EKAPCD Rule 425—Stationary Gas Turbines (Oxides of Nitrogen), amended November 13, 2024 (“Rule 425”). The commenter stated that long-term compliance and transparency will be key to protecting public health in the Eastern Kern region. The second comment was in support of approving Rule 425 into the SIP. The EPA thanks the commenters for their comments. As discussed in more detail below, we received two additional comments addressing specific aspects of the proposed rulemaking.
[^1] “Determination to Defer Sanctions; California; Eastern Kern Air Pollution Control District; Stationary Combustion Turbines,” June 20, 2025 (90 FR 26207).
The first of these two additional comments recommended that the EPA not revise the air pollution requirements in Eastern Kern and use “the stricter CA regulations” for every State in the Union. The EPA thanks the commenter for their comment. This rulemaking is for a specific local air pollution control district within California, the EKAPCD, and air pollution control requirements outside of the EKAPCD are beyond the scope of this rule. With respect to the recommendation that the EPA not revise the air pollution requirements within EKAPCD, and instead use “stricter CA regulations” in EKAPCD, such an approach is not available in the current rulemaking. Firstly, the commenter has not identified any specific California regulations believed to be “stricter” than Rule 425. Rule 425 regulates emissions of oxides of nitrogen (NO <sub>X</sub> ) from combustion turbines. In California, local air pollution control districts typically adopt regulations for these types of emissions sources and submit them to the California Air Resources Board (CARB). CARB then decides whether to submit these rules to the EPA for inclusion in the SIP. It is the California State Government, through CARB, that maintains the California SIP and chooses which regulations and materials to submit to the EPA for including into the SIP. Rule 425 is thus the applicable California regulation for the area. Accordingly, it is not clear what other “stricter CA regulation” the commenter is referring to. There is no other applicable California regulation that has been submitted to the EPA. Although CARB may directly regulate some categories of sources, we are not aware of any CARB regulations that establish NO <sub>X</sub> emissions limitations for combustion turbines. Secondly, under the cooperative federalism framework established by the Act, the states adopt regulations and submit them to the EPA for approval into the SIP. Under section 110(k)(3) of the CAA, the EPA must approve a SIP submission if it meets the applicable requirements of the Act. Accordingly, unless the EPA has identified a deficiency with the present submission, the EPA does not have discretion to disapprove the submission. In addition, CAA section 110(c)(1)(B) specifies that the EPA may only impose its own regulations, using a Federal Implementation Plan (FIP), if the EPA has disapproved a SIP submission and identified a deficiency in that submission that prevents full approval. The EPA may not otherwise substitute its own regulations for those submitted by the state.
To the extent that the commenter may be suggesting that the EPA disapprove the submission because Rule 425 should be “stricter” to meet CAA requirements, the commenter has not specified a deficiency that would permit the EPA to disapprove the submission, and we disagree with this suggestion. Our proposed action and technical support document (TSD) contained an analysis of the rule, including its stringency, concluding that it meets the applicable requirements of the Act. As explained in our proposal, the EKAPCD is required to implement Reasonably Available Control Technology (RACT) requirements for any category of sources covered by a Control Techniques Guidelines document and for any major stationary source of volatile organic compounds (VOCs) or NO <sub>X</sub> . See CAA sections 182(b)(2) and (f). The District relies on Rule 425 to establish RACT-level controls for combustion turbines at major sources of NO <sub>X</sub> within the District.
In this action, California is correcting a deficiency that we previously identified related to the stringency of the NO <sub>X</sub> emissions limitations in Rule 425 for a single combustion turbine in the District, the Westinghouse W251B10 combustion turbine. [^2] In 2023, we determined that Rule 425 was largely consistent with the relevant CAA requirements, including the requirement to implement RACT for covered major sources, except for the Westinghouse W251B10 combustion turbine. To address the deficiency, the District amended Rule 425 by lowering the NO <sub>X</sub> emissions limitation applicable to the unit when burning gaseous fuel from 25 parts per million by volume (ppmv) to 20 ppmv and removed the liquid fuel emissions limitation of 65 ppmv. With respect to the RACT requirement, the Westinghouse W251B10 combustion turbine is currently equipped with dry low NO <sub>X</sub> combustors to control NO <sub>X</sub> emissions. The EKAPCD provided a response document with an analysis to demonstrate that it is not cost effective for this Westinghouse turbine to be retrofitted with selective catalytic reduction (SCR), and that SCR is thus not required to meet RACT for this unit. [^3] The EPA concluded that Rule 425 represents RACT level control for this unit and that the District has addressed the prior deficiency. Please see our proposal and TSD for additional details.
[^2] 88 FR 39182 (June 15, 2025).
[^3] Response to Eastern Kern Air Pollution Control District Request regarding the SIP and Rule 425 Modification, sent on January 3, 2024 (Response Document) as found in our docket at EPA-R09-OAR-2025-0060.
Nothing in the submitted comment has changed our assessment or suggested that new information should call this conclusion into question. Accordingly, the EPA concludes that the previous deficiency has been addressed, and Rule 425 meets all applicable CAA requirements regarding enforceability, RACT, and SIP revisions. Therefore, the EPA is finalizing approval of the SIP submission.
The second comment that we received addressing an aspect of the proposed rulemaking stated that “[t]he proposed EPA reporting should be included in the matter, as informative data relevant for disclosure purposes and to provide conclusive details on the history of the potentially harmful impact to the citizens in the region.” The EPA thanks the commenter for their comment. To clarify, the EPA did not propose any additional requirements beyond those found in Rule 425. As mentioned in our proposal, the revised rule includes updates to the reporting requirements section of the rule. These reports are submitted to the District. Thus, the EPA understands this comment as being supportive of our proposed approval of Rule 425 that would include approving these revised reporting requirements into the SIP.
**III. EPA Action**
No comments were submitted that change our assessment of the rule as described in our proposed action. Therefore, as authorized in section 110(k)(3) of the Act, the EPA is approving this rule into the California SIP. The November 13, 2024 version of Rule 425 will replace the previously approved version of this rule in the SIP. This approval resolves all deficiencies forming the basis for our previous limited disapproval in 2023 of the prior version of Rule 425. This action also permanently terminates all sanctions clocks and FIP clocks triggered by our June 15, 2023 limited disapproval action.
**IV. Incorporation by Reference**
In this rule, the EPA is finalizing regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, the EPA is finalizing the incorporation by reference of Eastern Kern Air Pollution Control District, Rule 425, Stationary Gas Turbines (Oxides of Nitrogen), amended on November 13, 2024, which regulates NO <sub>X</sub> emissions from stationary gas turbines. Therefore, these materials have been approved by the EPA for inclusion in the SIP, have been incorporated by reference by the EPA into that plan, are fully federally enforceable under sections 110 and 113 of the CAA as of the effective date of the final rulemaking of the EPA's approval, and will be incorporated by reference in the next update to the SIP compilation. [^4] The EPA has made, and will continue to make, these documents available through *https://www.regulations.gov* and at the EPA Region IX Office (please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section of this preamble for more information).
[^4] 62 FR 27968 (May 22, 1997).
**V. Statutory and Executive Order Reviews**
Under the CAA, the Administrator is required to approve a SIP submission that complies with the provisions of the Act and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, the EPA's role is to approve state choices, provided that they meet the criteria of the CAA. Accordingly, this 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 action:
• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Order 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 CAA.
In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where the 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).
This action is subject to the Congressional Review Act, and the EPA will submit a rule report to each House of the Congress and to the Comptroller General of the United States. This action is not a “major rule” as defined by 5 U.S.C. 804(2).
Under section 307(b)(1) of the CAA, petitions for judicial review of this action must be filed in the United States Court of Appeals for the appropriate circuit by January 20, 2026. Filing a petition for reconsideration by the Administrator of this final rule does not affect the finality of this action for the purposes of judicial review nor does it extend the time within which a petition for judicial review may be filed, and shall not postpone the effectiveness of such rule or action. This action may not be challenged later in proceedings to enforce its requirements. (See section 307(b)(2).)
**List of Subjects in 40 CFR Part 52**
Environmental protection, Air pollution control, Incorporation by reference, Intergovernmental relations, Nitrogen oxides, Ozone, Reporting and recordkeeping requirements.
Dated: November 10, 2025.
Michael Martucci,
Acting Regional Administrator, Region IX.
For the reasons stated in the preamble, the Environmental Protection Agency amends part 52, chapter I, title 40 of the Code of Federal Regulations as follows:
**PART 52—APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS**
**40 CFR Part 52**
1. The authority citation for part 52 continues to read as follows:
**Authority:**
42 U.S.C. 7401 *et seq.*
**Subpart F—California**
**40 CFR Part 52**
2. Amend § 52.220a, paragraph (c), under the subheading “Table 10-EPA-Approved Eastern Kern Air Pollution Control District Regulations; Kern County air Pollution Control District Regulations,” by revising the entry for “425”, to read as follows:
§ 52.220a
(c) * * *
| District | Title/subject | State effective date | EPA approval date | Additional explanation |
| --- | --- | --- | --- | --- |
| | | | | |
| * * * * * * * | | | | |
| 425 | Stationary Gas Turbines (Oxides of Nitrogen) | November 13, 2024 | 11/20/2025, 90 FR [INSERT
PAGE WHERE THE DOCUMENT BEGINS] | Submitted on December 12, 2024. |
| | | | | |
| * * * * * * * | | | | |