Interstate Transport for the 2015 Ozone NAAQS
Reconsideration of the Good Neighbor Plan
On January 27, 2026 EPA signed a proposal to approve State Implementation Plan (SIP) submissions from Alabama, Arizona, Kentucky, Minnesota, Mississippi, Nevada, New Mexico, and Tennessee addressing the Clean Air Act’s “interstate transport” requirements for the 2015 ozone National Ambient Air Quality Standards (NAAQS). This proposed action is the first step in following through on EPA’s March 12, 2025, announcements to work with states on SIPs to improve air quality and reconsider the “Good Neighbor Plan.” This is the first action taken as part of the Agency’s reconsideration of the Good Neighbor Plan and its associated SIP actions. EPA intends to take additional steps to further reconsider the Good Neighbor Plan and additional states impacted by that rule.
January 27, 2026 – Signed Proposed Approval of State Plans to Address Interstate Transport of Ozone Forming Air Pollutants
- Proposed Interstate Transport Plan Review for the 2015 Ozone NAAQS (pdf)
- Fact Sheet – Proposed Approval of State Plans to Address Cross-State Transport of Ozone Forming Air Pollutants (pdf)
Summary of Interstate Transport for the 2015 Ozone NAAQS
In 2022 and 2023, EPA initially took action to address the obligations of upwind states under the 2015 ozone NAAQS. This action resulted in the Final SIP Disapproval action (February 13, 2023) and the Final Good Neighbor Plan (March 15, 2023).
Following the finalization of the Good Neighbor Plan and the Final Disapproval action, multiple parties challenged both actions through multiple sets of petitions for review in several federal circuit courts. Several courts granted petitioners’ requests for a stay of the Disapproval as to their state pending judicial review of the Disapproval action. In addition, the Supreme Court granted an additional stay in June 2024. In response, EPA issued three interim final rules to comply with these court orders in July and September 2023, and in November 2024.
The three interim final rules include provisions that ensure that states’ obligations to address interstate ozone pollution with respect to the 2008 ozone NAAQS under two prior rules, the CSAPR Update and the Revised CSAPR Update, will be met while EPA continues its reconsideration of the stayed Good Neighbor Plan’s requirements.
Rule History for Interstate Transport and the 2015 Ozone NAAQS
December 3, 2024 – Notice on Remand of the Record of the Good Neighbor Plan to Respond to Certain Comments
- Notice on Remand of the Record of the Good Neighbor Plan to Respond to Certain Comments (December 10, 2024)
October 29, 2024 – Final Rule to Administratively Stay the Effectiveness of the Good Neighbor Plan
- EPA issued a final rule to administratively stay the effectiveness of the Good Neighbor Plan's requirements for all sources covered by that rule as promulgated where an administrative stay was not already in place.
January 16, 2024 – Proposed Supplemental “Good Neighbor” Action
- Proposed Supplemental “Good Neighbor” Action for the 2015 Ozone NAAQS in Five States (pdf)
- Fact Sheet: Proposed Supplemental Interstate Transport Rule (pdf)
- Economic Impact Assessment for Proposed Supplemental Rule (pdf)
- Power Plants: Addendum to EGU NOₓ Mitigation Strategies Final Rule TSD (pdf)
- Proposed Table of State Budgets for Power Plants
- Power Sector Modeling
- Power Plants: Allowance Allocation Under the Proposed Supplemental Rule (pdf)
- Ozone Transport Policy Analysis: Proposed Supplemental Rule (pdf)
- Industrial Sources: Non-EGU Sectors Proposed Rule TSD (pdf)
- Data File with Ozone Design Values (xlsx)
- Resource Adequacy and Reliability Analysis Proposed Rule Technical Support Document (pdf)
March 15, 2023 – Final Good Neighbor Plan for the 2015 Ozone National Ambient Air Quality Standards (NAAQS)
- Final Good Neighbor Plan for the 2015 Ozone NAAQS (June 5, 2023)
- Fact Sheet: Final Good Neighbor Plan for the 2015 Ozone NAAQS (pdf)
- Final Table of State Budgets for Power Plants
- Good Neighbor Plan for the 2015 Ozone NAAQS – Compliance for Industrial Sources
- The Good Neighbor Plan and Reliable Electricity (pdf)
- Regulatory Impact Analysis (pdf)
- NOₓ Emission Control Technology Installation Timing for Non-EGU Sources Report (pdf)
- Power Sector Modeling Final Rule
- 2023 and 2024 Important Dates
- Response to Four Petitions for Reconsideration
- EPA Response to Judicial Stay Orders
Implementation Factsheets for NOX Allowance Trading Program
- Prorating Emissions Budgets, Assurance Levels, and Unit-Level Allowance Allocations in the Event of an Effective Date After May 1, 2023 (pdf)
- Recall of CSAPR NOₓ Ozone Season Group 2 Allowances from Sources in States Newly Transitioning to the CSAPR NOₓ Ozone Season Group 3 Trading Program (pdf)
- Creation of an Additional Group 3 Allowance Bank for the 2023 Control Period (pdf)
Potential Allowance Auction Rule
- EPA is considering a proposed rulemaking that would add an allowance auction mechanism for power plants under the GNP.
Final Good Neighbor Plan Webinars
Implementation: Detailed webinar for power plants and market participants was held on April 19.
General overview: EPA held four, 90-minute informational webinars, each providing an overview of the final rule and an opportunity for questions and answers (March 28, March 30, April 4)
Technical Support Documents
- Response to Comments Document (pdf)
- Preparation of Emissions Inventories for the 2016v3 North American Emissions Modeling Platform (pdf)
- Air Quality Modeling Final Rule TSD (pdf)
- 2019 National Emissions Inventory: Point Source Data (pdf)
- Power Plants: Allowance Allocation Under the Final Rule (pdf)
- Power Plants: EGU NOₓ Mitigation Strategies (pdf)
- Summary of Final Rule Applicability Criteria and Emissions Limits for Non-EGU Emissions Units, Assumed Control Technologies for Meeting the Final Emissions Limits, and Estimated Emissions Units, Emissions Reductions, and Costs (pdf)
- Industrial Sources: Non-EGU Sectors Final Rule TSD (pdf)
- Resource Adequacy and Reliability Analysis Final Rule TSD (pdf)
- Ozone Transport Policy Analysis (pdf)
- Status of CAA Section Status of CAA Section 110(a)(2)(D)(i)(I) SIP Submissions for the 2015 Ozone NAAQS for States Covered by the Final Federal Implementation Plan Addressing Regional Ozone Transport for the 2015 Ozone NAAQS (pdf)
January 31, 2023 – Final Disapproval of 2015 Good Neighbor SIP Submissions
To protect air quality in communities affected by harmful ground-level ozone (or “smog”) pollution, EPA finds that certain states failed to meet their obligations under the Clean Air Act to protect communities in other states from unhealthy levels of ozone pollution. EPA has disapproved 19 state implementation plan (SIP) submissions and partially approved and partially disapproved 2 SIP submissions addressing the good neighbor provision for the 2015 ozone NAAQS.
August 19, 2022 - Good Neighbor Plan Allowance Recordation Rule
The Environmental Protection Agency is taking final action to revise certain administrative deadlines under seven allowance trading programs for nitrogen oxides and sulfur dioxide, including all Cross-State Air Pollution Rule (CSAPR) trading programs and the Texas SO2 Trading Program. EPA proposed to revise these deadlines as part of the proposed Good Neighbor Plan published April 2022.
Previous Actions - Proposed Rulemaking
May 12, 2022 - Comment Period Extension
The Environmental Protection Agency is extending the comment period on the proposed rule to June 21, 2022.
- Notice of Comment Period Extension for the Proposed Good Neighbor Plan for the 2015 Ozone NAAQS (May, 2022)
February 28, 2022 - Proposed Good Neighbor Plan for the 2015 Ozone NAAQS
The Environmental Protection Agency proposed significant steps to reduce ozone forming NOX emissions. This action would ensure that the 26 states identified in the proposal do not “significantly contribute” to problems attaining and maintaining the 2015 Ozone National Ambient Air Quality Standards (NAAQS) in downwind states through a combination of requirements for power plants and certain other industrial sources.
- Proposed Good Neighbor Plan for the 2015 Ozone NAAQS (April, 2022)
- Fact Sheet: Proposed Good Neighbor Plan for the 2015 Ozone NAAQS (pdf)
- Table of State Budgets for Power Plants
- Summary of Proposed NOX Emission Limits for Industrial Sources
- Regulatory Impact Analysis for Proposed Federal Implementation Plan Addressing Regional Ozone Transport for the 2015 Ozone National Ambient Air Quality Standard
- Power Sector Modeling Proposed Rule
Informational Stakeholder Webinars
EPA hosted three, 90-minute stakeholder webinars on March 29, March 30, and March 31. See the slides used during those sessions:
2015 Ozone Transport Proposed Rule Overview (pdf)
Technical Support Documents (TSDs)
- Preparation of Emissions Inventories for the 2016v2 North American Emissions Modeling Platform
- Air Quality Modeling
- 2019 National Emissions Inventory: Point Data Category
- Power Plants: Allowance Allocation under the Proposed Rule
- Power Plants: EGU NOₓ Mitigation Strategies
- Industrial Sources: Technical Memorandum: Screening Assessment of Potential Emissions Reductions, Air Quality Impacts, and Costs from Non-EGU Emissions Units for 2026
- Industrial Sources: Non-EGU Sectors TSD
- Ozone Transport Policy Analysis
- Status of CAA Section 110(a)(2)(D)(i)(I) SIP Submissions for the 2015 Ozone NAAQS for States Covered by the Proposed Federal Implementation Plan Addressing Regional Ozone Transport for the 2015 Ozone National Ambient Air Quality Standards Proposed Rule
Additional supporting information and data for the listed TSDs will be available in the forthcoming official docket.