Supplemental Air Plan Actions: Interstate Transport of Air Pollution for the 2015 8-Hour Ozone National Ambient Air Quality Standards and Supplemental Federal “Good Neighbor Plan” Requirements for the 2015 8-Hour Ozone National Ambient Air Quality Standards

Federal RegisterFeb 16, 2024

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 97

[EPA-HQ-OAR-2021-0663; EPA-HQ-OAR-2021-0668; EPA-HQ-OAR-2023-0402; FRL-11159-01-OAR]

RIN 2060-AW09

Supplemental Air Plan Actions: Interstate Transport of Air Pollution for the 2015 8-Hour Ozone National Ambient Air Quality Standards and Supplemental Federal “Good Neighbor Plan” Requirements for the 2015 8-Hour Ozone National Ambient Air Quality Standards

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule; supplemental proposed rule and withdrawal of proposed rules.

SUMMARY:

Pursuant to the Federal Clean Air Act (CAA or the Act), the Environmental Protection Agency (EPA) is proposing to partially disapprove and partially approve State Implementation Plan (SIP) submissions from Arizona, Iowa, Kansas, New Mexico, and Tennessee regarding interstate transport for the 2015 8-hour ozone national ambient air quality standards (NAAQS). This action also proposes a Federal Implementation Plan (FIP) for Arizona, Iowa, Kansas, New Mexico, and Tennessee to address these States' obligations to eliminate significant contribution to nonattainment, or interference with maintenance, of the 2015 ozone NAAQS in other states. The FIP would require fossil fuel-fired power plants in the five states to participate in an allowance-based ozone season nitrogen oxides emissions trading program beginning in 2025. The Agency is also proposing to establish nitrogen oxides emissions limitations applicable to certain other industrial stationary sources in Arizona with a compliance year no earlier than 2027. Finally, this action also includes proposed technical corrections to the regulatory text previously promulgated to establish comparable FIP requirements for emissions sources in other states.

DATES:

Comments:

Comments must be received on or before May 16, 2024.

Public hearing:

The EPA will hold a virtual public hearing on March 4, 2024. Please refer to the

SUPPLEMENTARY INFORMATION

section for additional information on the public hearing.

Information collection request:

Under the Paperwork Reduction Act (PRA), comments on the information collection provisions are best assured of consideration if the Office of Management and Budget (OMB) receives a copy of your comments on or before March 18, 2024.

ADDRESSES:

Comments:

You may send comments, identified as Docket ID No. EPA-HQ-OAR-2023-0402, by any of the following methods: Federal eRulemaking Portal:

https://www.regulations.gov/.

Follow the online instructions for submitting comments. Include Docket ID No. EPA-HQ-OAR-2023-0402 in the subject line of the message.

Instructions:

All submissions received must include the Docket ID No. for this rulemaking. Comments received may be posted without change to

https://www.regulations.gov,

including any personal information provided. For detailed instructions on sending comments and additional information on the rulemaking process,

see

the “Public Participation” heading of the

SUPPLEMENTARY INFORMATION

section of this document.

Hearing:

The virtual hearing will be held at

https://www.epa.gov/csapr/csapr-2015-ozone-naaqs.

The public hearing will convene at 9:00 a.m. and end at 6:00 p.m. Eastern Time (ET) or 1 hour after the last registered speaker has spoken. The EPA will make every effort to accommodate all individuals interested in providing oral testimony. A lunch break is scheduled from 12:00 p.m. until 1:00 p.m. Refer to the

SUPPLEMENTARY INFORMATION

section for additional information.

FOR FURTHER INFORMATION CONTACT:

Thomas Uher, Air Quality Policy Division, Office of Air Quality Planning and Standards (C539-04), Environmental Protection Agency, 109 TW Alexander Drive, Research Triangle Park, NC 27711; telephone number: (919) 541-5534; email address:

uher.thomas@epa.gov.

SUPPLEMENTARY INFORMATION:

Public participation:

Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2023-0402, at

https://www.regulations.gov

(our preferred method. Once submitted, comments cannot be edited or removed from the docket. The EPA may publish any comment received to its public docket. Do not submit to the EPA's docket at

https://www.regulations.gov

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).

There are three dockets supporting this action, EPA-HQ-OAR-2023-0402, EPA-HQ-OAR-2021-0663, and EPA-HQ-OAR-2021-0668. All comments regarding information in any of these dockets are to be made in Docket ID No. EPA-HQ-OAR-2023-0402.

The index to the docket for this action, Docket ID No. EPA-HQ-OAR-2023-0402, is available electronically at

https://www.regulations.gov.

While all documents in the docket are listed in the index, some information may not be publicly available due to docket file size restrictions or content (

e.g.,

CBI).

Preamble Glossary of Terms and Abbreviations

The following are abbreviations of terms used in the preamble.

2016v1 2016 Version 1 Emissions Modeling Platform

2016v2 2016 Version 2 Emissions Modeling Platform

2016v3 2016 Version 3 Emissions Modeling Platform

ARP Acid Rain Program

ADEQ Arizona Department of Environmental Quality

CAA or Act Clean Air Act

CAIR Clean Air Interstate Rule

CBI Confidential Business Information

CFB Circulating Fluidized Bed Units

CFR Code of Federal Regulations

CSAPR Cross-State Air Pollution Rule

DAHS Data Acquisition and Handling System

EAV Equivalent Annualized Values

EGU Electric Generating Unit

EHD Environmental Health Department

EIA Economic Impact Assessment

EPA or the Agency United States Environmental Protection Agency

FIP Federal Implementation Plan

g/hp-hr Grams per horsepower per hour

Group 2 allowances CSAPR NO

Ozone Season Group 2 allowances

Group 2 trading program CSAPR NO

Ozone Season Group 2 Trading Program

Group 3 allowances CSAPR NO

Ozone Season Group 3 allowances

Group 3 Trading Program CSAPR NO

Ozone Season Group 3 Trading Program

ICR Information Collection Request

IPM Integrated Planning Model

LNB Low-NO

Burners

MJO Multi-Jurisdictional Organization

MOVES Motor Vehicle Emission Simulator

MW Megawatts

NAA Nonattainment Area

NAAQS National Ambient Air Quality Standards

NAICS North American Industry Classification System

NMED New Mexico Environment Department

Non-EGU Non-Electric Generating Unit

NODA Notice of Data Availability

Nitrogen Oxides

NSCR Non-Selective Catalytic Reduction

OMB United States Office of Management and Budget

PBI Proprietary Business Information

ppb parts per billion

ppm parts per million

ppmvd parts per million by volume, dry

PRA Paperwork Reduction Act

PV Present Value

RFA Regulatory Flexibility Act

RIA Regulatory Impact Analysis

RICE Reciprocating Internal Combustion Engines

SC-CO2 Social Cost of Carbon

SCR Selective Catalytic Reduction

SIL Significant Impact Level

SIP State Implementation Plan

SNCR Selective Non-Catalytic Reduction

Sulfur Dioxide

TAS Treatment as State

TDEC Tennessee Department of Environmental Control

TSD Technical Support Document

tpy tons per year

UMRA Unfunded Mandates Reform Act

Violating-Monitor Receptors Violating-Monitor Maintenance-Only Receptors

VOCs Volatile Organic Compounds

Table of Contents

I. Executive Summary

A. Purpose of the Regulatory Action

B. Costs and Benefits

II. General Information

A. Does this action apply to me?

B. What action is the Agency taking?

C. What is the Agency's authority for taking this action?

D. Severability

E. Public Participation

1. Written Comments

2. Participation in Virtual Public Hearing

III. Background

A. Description of Statutory Background

B. Description of the EPA's 4-Step Interstate Transport Regulatory Process

C. The EPA's Ozone Transport Modeling

D. The EPA's Approach To Evaluating Interstate Transport for the 2015 Ozone NAAQS

1. Selection of Analytic Years

2. Step 1 of the 4-Step Interstate Transport Framework

3. Step 2 of the 4-Step Interstate Transport Framework

4. Step 3 of the 4-Step Interstate Transport Framework

5. Step 4 of the 4-Step Interstate Transport Framework

IV. SIP Submissions Addressing Interstate Transport of Air Pollution for the 2015 8-Hour Ozone NAAQS

A. SIP Summaries

1. Arizona

Prior Notices Related to Arizona's SIP Submission

2. New Mexico

a. Information Provided by New Mexico Regarding Step 1

b. Information Provided by New Mexico Regarding Step 2

c. New Mexico Letter

3. Tennessee

Prior Notices Related to Tennessee's SIP Submission

B. EPA Evaluation

1. Arizona

a. Evaluation of Information Provided by Arizona Regarding Steps 1 and 2

b. Results of the EPA's Step 1 and Step 2 Modeling and Findings for Arizona

c. Evaluation of Information Provided Regarding Step 3

d. Conclusion

2. New Mexico

a. Evaluation of Information Provided by New Mexico Regarding Step 1

b. Evaluation of Information Provided by New Mexico Regarding Step 2

c. Results of the EPA's Step 1 and Step 2 Modeling and Findings for New Mexico

d. Evaluation of Information Provided Regarding Step 3

e. NMED's July 2023 Letter

f. Conclusion

3. Tennessee

a. Evaluation of Information Provided by Tennessee Regarding Step 1

b. Evaluation of Information Provided by Tennessee Regarding Step 2

c. Results of the EPA's Step 1 and Step 2 Modeling and Findings for Tennessee

d. Evaluation of Information Provided for Tenessee Regarding Step 3

e. Conclusion

C. Proposed SIP Action

V. Other Clean Air Act Authorities for This Action

A. Correction of the EPA's Determination Regarding SIP Submissions From Iowa and Kansas and Its Impact on the EPA's FIP Authority for Iowa and Kansas

B. Application of Rule in Indian Country and Necessary or Appropriate Finding

VI. Quantifying Upwind-State NO

Emissions Reduction Potential To Reduce Interstate Ozone Transport for the 2015 Ozone NAAQS

A. Summary of Multi-Factor Test

B. Summary of Control Stringency Levels

1. EGUs

2. Non-EGUs

C. Control Stringencies Represented by Cost Threshold ($ per Ton) and Corresponding Emissions Reductions

1. EGUs

2. Non-EGUs

D. Assessing Cost, EGU and Non-EGU NO

Reductions, and Air Quality

1. EGU and Non-EGU Cost and Emissions Reductions Assessment

2. Step 3 Air Quality Assessment Methodology

3. Results for Combined EGU and Non-EGU Air Quality Assessment

4. Conclusions

VII. Regulatory Requirements and Implementation

A. Regulatory Requirements for EGUs

1. Applicability and Tentative Identification of Newly Affected Units

2. Preset State Emissions Budgets

3. Unit-Level Allowance Allocations

4. Timing Adjustments for Certain Trading Program Provisions

5. Creation of an Additional Group 3 Allowance Bank for the 2025 Control Period and Adjustment to Bank Recalibration for the 2025 Control Period

B. Regulatory Requirements for Non-EGUs

C. Submitting a SIP

1. SIP Option To Modify Allocations for 2026 Under EGU Trading Program

2. SIP Option To Modify Allocations for 2027 and Beyond Under EGU Trading Program

3. SIP Option To Replace the Federal EGU Trading Program With an Integrated State EGU Trading Program

4. SIP Revisions That Do Not Use the Trading Program

5. SIP Revision Requirements for Non-EGU or Industrial Source Control Requirements

D. Title V Permitting

VIII. Environmental Justice Considerations, Implications and Outreach

A. Environmental Justice

1. EGU Proximity Assessment

2. Non-EGU Proximity Assessment

B. Outreach

IX. Costs, Benefits, and Other Impacts of the Proposed Rule

X. Summary of Proposed Changes to Existing Regulatory Text

A. Amendments To Apply the Federal Good Neighbor Plan's Requirements to EGUs in Additional States

B. Amendments To Apply the Federal Good Neighbor Plan's Requirements to Non-EGUs in Additional States

C. Technical Corrections and Clarifications to Previously Finalized Regulatory Text

XI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 14094: Modernizing Regulatory Review

B. Paperwork Reduction Act (PRA)

1. Information Collection Request for Electric Generating Units

2. Information Collection Request for Non-Electric Generating Units

C. Regulatory Flexibility Act (RFA)

D. Unfunded Mandates Reform Act (UMRA)

E. Executive Order 13132: Federalism

F. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

G. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks

H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution or Use

I. National Technology Transfer and Advancement Act

J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations and Executive Order 14096: Revitalizing Our Nation's Commitment to Environmental Justice for All

K. Determinations Under CAA Section 307(b)(1) and (d)

I. Executive Summary

This proposed rule would resolve the interstate transport obligations of five states under CAA section 110(a)(2)(D)(i)(I), referred to as the

“good neighbor provision” or the “interstate transport provision” of the Act, for the 2015 ozone NAAQS. On October 1, 2015, the EPA revised the primary and secondary 8-hour standards for ozone to 70 parts per billion (ppb).

States were required to provide ozone infrastructure SIP submissions to fulfill interstate transport obligations for the 2015 ozone NAAQS by October 1, 2018.

See

80 FR 65291 (October 26, 2015).

The EPA proposes to make a finding that interstate transport of ozone precursor emissions from five upwind states (Arizona, Iowa, Kansas, New Mexico, and Tennessee) is interfering with maintenance of the 2015 ozone NAAQS in other states. The EPA is withdrawing its previous proposed actions on SIP submissions from Arizona and Tennessee,

proposing to partially approve and partially disapprove good neighbor SIP submissions from Arizona, New Mexico, and Tennessee, and to error-correct its prior good neighbor SIP approval actions for Iowa and Kansas to partial disapprovals.

To fulfill the EPA's responsibility to ensure that states meet their interstate transport obligations as expeditiously as practicable to meet attainment deadlines for the 2015 ozone NAAQS, the EPA also proposes FIP requirements for these five states to prohibit the emissions that interfere with maintenance of the NAAQS in other states. For states covered in this action, the EPA proposes to define new ozone season nitrogen oxides (NO

) emissions performance obligations for Electric Generating Unit (EGU) sources and to fulfill those obligations by implementing an allowance-based ozone season trading program beginning in 2025. The EPA is also proposing to establish emissions limitations beginning in 2027 for certain other industrial stationary sources (referred to generally as “non-Electric Generating Units” (non-EGUs) in Arizona. Taken together, these strategies will fully resolve the covered states' good neighbor obligations for the 2015 ozone NAAQS.

See

87 FR 37776 (June 24, 2022). (The EPA's proposed approval of Arizona's SIP); and 87 FR 9545 (February 22, 2022) (The EPA's proposed disapproval of Tennessee's SIP).

See

87 FR 22463 (April 15, 2022) (Iowa); and 87 FR 19390 (April 4, 2022) (Kansas).

The EPA proposes to implement the necessary emissions reductions as follows. The proposed FIP requirements establish ozone season NO

emissions budgets for EGUs in Arizona, Iowa, Kansas, New Mexico, and Tennessee and require EGUs in these states to participate in the revised version of the Cross-State Air Pollution Rule (CSAPR) NO

Ozone Season Group 3 Trading Program established in the final Federal Good Neighbor Plan Rule.

For states currently covered by the CSAPR NO

Ozone Season Group 2 Trading Program (

i.e.,

Iowa, Kansas, Tennessee), the EPA proposes to amend existing FIPs to transition EGU sources in these states from the Group 2 trading program to the revised Group 3 trading program, beginning with the 2025 ozone season. The EPA proposes to issue new FIPs for Arizona and New Mexico, which are not currently covered by any CSAPR NO

ozone season trading program. Under CAA section 301(d)(4), the EPA also proposes to extend the FIP requirements to apply in Indian country located within the geographical boundaries of the states included in this proposal, including Indian reservation lands and other areas of Indian country over which the EPA or a tribe has demonstrated that a tribe has jurisdiction.

Federal “Good Neighbor Plan” for the 2015 Ozone National Ambient Air Quality Standards, 88 FR 36654 (June 5, 2023).

The timeframes for implementation of these emissions-reduction strategies are, in the EPA's judgment, as expeditious as practicable and aligned to the extent possible with the attainment schedule for downwind areas in nonattainment of the 2015 ozone NAAQS. As discussed in section VI. of this document, the EPA proposes to find that the 2025 ozone season is as expeditious as practicable to implement emissions reductions associated with near-term emissions control strategies at EGUs, and the 2027 ozone season is as expeditious as practicable to implement emissions reductions associated with new post-combustion control installations at EGUs as well as from installation of new pollution controls at non-EGUs.

As identified in section VI. of this document, the EPA proposes to find that, because Iowa, Kansas, New Mexico, and Tennessee are not linked to receptors in the 2026 ozone season, the near-term EGU emissions-control strategy is sufficient to eliminate these states' interference with maintenance of the NAAQS in other states. Because Arizona remains linked to receptors through the 2026 ozone season, the EPA proposes to find that additional NO

emissions from EGUs and NO

emissions from non-EGU sources in Arizona are interfering with maintenance of the 2015 ozone NAAQS in other states and that additional cost-effective controls for NO

emissions reductions are available from EGUs and in certain industries that would result in meaningful air quality improvements at downwind receptors. Thus, in addition to more stringent EGU emissions budgets for Arizona beginning in 2027, the EPA proposes to require emissions limitations beginning in 2027 for non-EGUs located within Arizona. The Federal Good Neighbor Plan established NO

emissions limitations during the ozone season for the following unit types for sources in non-EGU industries: reciprocating internal combustion engines (RICE) in Pipeline Transportation of Natural Gas; kilns in Cement and Cement Product Manufacturing; boilers and reheat furnaces in Iron and Steel Mills and Ferroalloy Manufacturing; furnaces in Glass and Glass Product Manufacturing; boilers in Basic Chemical Manufacturing, Metal Ore Mining, Petroleum and Coal Products Manufacturing, and Pulp, Paper, and Paperboard Mills and combustors and incinerators in Solid Waste Combustors and Incinerators.

88 FR 36654, at 36817.

A. Purpose of the Regulatory Action

In this supplemental notice of proposed rulemaking, the EPA is providing an opportunity for public comment on its proposed conclusion that SIP submissions from Arizona, New Mexico, and Tennessee do not contain the necessary provisions to prohibit emissions from sources within their states from interfering with maintenance of the 2015 ozone NAAQS in downwind areas. The EPA also proposes to find it necessary to issue an error correction under the authority of CAA section 110(k)(6) of its previous approval actions for Kansas and Iowa and proposes to partially disapprove these states' interstate transport submissions. In addition, the EPA proposes to conclude that emissions from sources in Arizona, Iowa, Kansas, New Mexico, and Tennessee interfere with maintenance of the 2015 ozone NAAQS in other states, and therefore the EPA is proposing FIPs to address these states' transport obligations through expanding the coverage of the Federal Good Neighbor Plan Rule

finalized on March 15, 2023. The EPA is proposing to implement the ozone season NO

trading program requirements for EGU sources in the Federal Good Neighbor Plan as the FIPs for Arizona, Iowa, Kansas, New Mexico, and Tennessee and the emissions limits for non-EGU (industrial) sources in the Federal Good Neighbor Plan as the FIP for Arizona. These control strategies, if finalized,

will prohibit the emissions from these five states identified as interfering with maintenance of the 2015 ozone NAAQS in other states.

Federal “Good Neighbor Plan” for the 2015 Ozone National Ambient Air Quality Standards, 88 FR 36654 (June 5, 2023).

The EPA proposes to extend the coverage of the Federal Good Neighbor Plan to these five additional states based on the same data and analyses contained in that rule. In the Federal Good Neighbor Plan, the EPA identified and finalized FIPs for 23 states with emissions that significantly contribute to nonattainment or interfere with maintenance of the 2015 ozone NAAQS in other states. The EPA used the same set of nationwide air quality modeling, air quality monitoring data, and technical analysis of emissions control opportunities in defining good neighbor obligations for all states covered in that action. Consistent with the application of the EPA's 4-step interstate transport framework, which has been used in prior good neighbor rules like the CSAPR and upheld by the federal courts, the EPA applied emissions control requirements on a uniform basis across those states based on that record.

The EPA maintains that it is reasonable, appropriate, and consistent with the EPA's prior decisions to extend the Federal Good Neighbor Plan's contribution analysis and emissions control requirements to include the five states covered in this action. The EPA has not identified any factors unique to these five states that would warrant applying a different approach. These five states were not addressed in the Federal Good Neighbor Plan because the EPA was not positioned to take final rulemaking action to disapprove SIPs, error correct prior approvals to disapprovals, or promulgate FIPs for these states at that time. To maintain consistency across all states such that the allocation of responsibility for eliminating states' significant contribution and interference with maintenance of the NAAQS in downwind states is done on an equitable basis, the EPA proposes to apply to five additional states the nationwide findings and determinations contained in the Federal Good Neighbor Plan as to the original 23 states which will, if finalized, eliminate these additional states' significant contribution. Thus, in this action the EPA proposes to apply to these five states its air quality modeling and contribution information for the analytical years 2023 and 2026 at Steps 1 and 2, its analysis of emissions control opportunities for EGUs and non-EGUs and determinations of stringency, including overcontrol analysis, at Step 3, and its implementation programs at Step 4. The technical materials and record-based findings that underlie these determinations are all contained in the Federal Good Neighbor Plan record. The scope of this rulemaking is limited to the application of that record to these five additional states.

Thus, in this document, the EPA is taking comment only on (a) the EPA's proposed conclusions that SIP submissions from Arizona, New Mexico, and Tennessee do not contain the necessary provisions to prohibit emissions from sources within their respective states from interfering with maintenance of the 2015 ozone standard, (b) the EPA's proposed conclusion that the Agency must error correct its final rules approving SIPs from Iowa and Kansas to partial disapprovals, (c) the EPA's proposed conclusions that the five states identified above have emissions that interfere with maintenance of the 2015 ozone NAAQS in other states, and (d) the EPA's proposed decision to apply the Federal Good Neighbor Plan emissions-control programs as the FIP requirements to address these emissions in these five states.

Additionally, the EPA has updated its analysis of air quality improvements at Step 3 and demonstration that there is no overcontrol resulting from the inclusion of these five additional states in the Federal Good Neighbor Plan. The EPA proposes that the 2025 and 2027 ozone seasons represent appropriate compliance start-dates for these states, affording sufficient lead time for sources to plan for compliance from the standpoint of when this rulemaking will likely be finalized, which the EPA currently anticipates will be in the summer of 2024. These proposed findings are within the scope of this rulemaking and open for public comment.

The EPA is not reopening any determinations made in the Federal Good Neighbor Plan as to the 23 states covered in that action. Nor is the EPA taking comment on any aspect of the Federal Good Neighbor Plan, except to the extent of its application to these five states. In general, the record for the Federal Good Neighbor Plan Rule contains information at each step of the 4-step interstate transport framework that can be applied to these five states. Thus, the identification of receptors to which these five states are linked and the level of contribution from these states to those receptors is based on the same analytical findings using the air quality modeling and monitoring data contained in the Federal Good Neighbor Plan. In addition, the analysis underlying the EPA's determinations at Step 3 as to EGUs and non-EGUs and the appropriate degree of emissions-control stringency needed to eliminate significant contribution and interference with maintenance likewise was conducted on a region-wide basis, and in the EPA's view is reasonably applied to the emissions sources in these five states. The emissions-control requirements were established on a uniform basis for each particular industry covered in the Federal Good Neighbor Plan, and do not vary by State (except to the extent that states not linked in 2026 are not subject to the requirements that onset in 2026 and California's EGUs are not subject to the EGU trading program). Based on these findings, these programs should be extended to these five states. This is reasonable and indeed necessary to ensure consistency and equitable treatment across all states in addressing the nationwide problem of interstate ozone pollution for the 2015 ozone NAAQS.

See EME Homer City

EPA,

472 U.S. 572, 519, 524 (2014). This is also consistent with the EPA's practice throughout the history of implementing the good neighbor provision for other NAAQS. For instance, using the final analysis in the original CSAPR rulemaking, the EPA soon after conducted rulemaking to include five additional states in the CSAPR trading programs.

See

76 FR 80760 (December 27, 2011). Thus, for the same reasons, the EPA proposes to find it reasonable and appropriate to extend the uniform set of findings and determinations made in the Federal Good Neighbor Plan to these five additional states for the 2015 ozone NAAQS. The EPA is not aware of any information with respect to these states that would justify a deviation from the same set of findings and requirements that already have been made for the 23 states covered in the Federal Good Neighbor Plan with respect to these same obligations.

Finally, this action also includes proposed technical corrections to the existing regulatory text finalized in the Federal Good Neighbor Plan.

B. Costs and Benefits

Table I.B-1 summarizes the key results of the cost-benefit analysis that was prepared for this proposed rule. Table I.B-1 presents estimates of the present values (PV) and equivalent annualized values (EAV), calculated using discount rates of 3 and 7 percent as recommended by the Office of Management and Budget's (OMB) Circular A-4, of the health and climate benefits, compliance costs, and net benefits of the proposed rule, in 2016 dollars, discounted to 2023. The estimated monetized net benefits are the

estimated monetized benefits minus the estimated monetized costs of the proposed rule. These results present an incomplete overview of the effects of the rule because important categories of benefits were not monetized (

e.g.,

ecosystem effects, visibility impairment, and water quality improvements) and are therefore not reflected in the cost-benefit tables. The EPA anticipates that taking non-monetized effects into account would show the proposed rule to be more net beneficial than this table reflects.

Table I.B-1—Estimated Monetized Health and Climate Benefits, Compliance Costs, and Net Benefits of the Proposed Rule, 2025 Through 2044

[Millions 2016$, discounted to 2023]

3% Discount rate

7% Discount rate

Present Value:

Health Benefits

$330 and $1,900

$210 and $1,200.

Climate Benefits

$9.3

$9.3.

Compliance Costs

$67

$45.

Net Benefits

$270 and $1,800

$180 and $1,100.

Equivalent Annualized Value:

Health Benefits

$22 and $130

$20 and $110.

Climate Benefits

$0.6

$0.6.

Compliance Costs

$4.5

$4.2.

Net Benefits

$18 and $120

$17 and $110.

Rows may not appear to add correctly due to rounding. The EPA used 2016 dollars in both the proposal and final Revised CSAPR Update Regulatory Impact Analysis (RIA), as well as the proposal and final Federal Good Neighbor Plan RIA; to be consistent with those recent actions we continued to use 2016 dollars as the dollar year for presenting costs and benefits.

The annualized present value of costs and benefits are calculated over a 20-year period from 2025 to 2044. Monetized benefits include those related to public health associated with reductions in ozone and PM

2.5

concentrations. The health benefits are associated with two alternative estimates of the number of premature deaths and are presented at real discount rates of 3 and 7 percent. Several categories of benefits remain unmonetized and are thus not reflected in the table.

Climate benefits are calculated using four different estimates of the social cost of carbon (SC-CO

) (model average at 2.5 percent, 3 percent, and 5 percent discount rates; 95th percentile at 3 percent discount rate). For presentational purposes in this table, the climate benefits associated with the average SC-CO

at a 3-percent discount rate are used in the columns displaying results of other costs and benefits that are discounted at either a 3-percent or 7-percent discount rate.

The costs presented in this table are consistent with the costs presented in section 3 of the

Economic Impact Assessment (EIA).

To estimate these annualized costs for EGUs, the EPA uses a conventional and widely accepted approach that applies a capital recovery factor multiplier to capital investments and adds that to the annual incremental operating expenses. Costs were calculated using a 3.75 percent real discount rate consistent with the rate used in the Integrated Planning Model's (IPM) objective function for cost-minimization. For further information on the discount rate use, please

see

section 3 of the

EIA.

As shown in Table I.B-1, the PV of the monetized health benefits, associated with reductions in ozone and PM

2.5

of this proposed rule, discounted at a 3-percent discount rate, is estimated to be about $330 and $1,900 million, with an EAV of about $22 and $130 million. At a 7-percent discount rate, the PV of the monetized health benefits is estimated to be $210 and $1,200 million, with an EAV of about $20 and $110 million. The PV of the monetized climate benefits, associated with reductions in greenhouse gas (GHG) emissions, of this proposed rule, discounted at a 3-percent discount rate, is estimated to be about $9.3 million, with an EAV of about $0.6 million. The PV of the monetized compliance costs, discounted at a 3-percent rate, is estimated to be about $67 million, with an EAV of about $4.5 million. At a 7-percent discount rate, the PV of the compliance costs is estimated to be about $45 million, with an EAV of about $4.2 million.

II. General Information

A. Does this action apply to me?

This supplemental proposed rule affects EGU and non-EGU sources, and regulates the groups identified in Table II.A-1, along with their North American Industry Classification System (NAICS) code.

Table II.A-1—Regulated Groups

Industry group

NAICS

Fossil fuel-fired electric power generation

221112

Pipeline Transportation of Natural Gas

4862

Metal Ore Mining

2122

Cement and Concrete Product Manufacturing

3273

Iron and Steel Mills and Ferroalloy Manufacturing

3311

Glass and Glass Product Manufacturing

3272

Basic Chemical Manufacturing

3251

Petroleum and Coal Products Manufacturing

3241

Pulp, Paper, and Paperboard Mills

3221

Solid Waste Combustors and Incinerators

562213

This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be regulated by this proposed rule. This table lists the types of entities that the EPA is now aware could potentially be

regulated by this proposed rule. Other types of entities not listed in the table could also be regulated. To determine whether a particular entity is regulated by this proposed rule, you should carefully examine the applicability criteria found in 40 CFR 97.1004 (EGUs) or 40 CFR 52.40(c), 52.41(b), 52.42(b), 52.43(b), 52.44(b), 52.45(b), and 52.46(b) (non-EGUs). If you have questions regarding the applicability of this proposed rule to a particular entity, consult the person listed in the

FOR FURTHER INFORMATION CONTACT

section.

B. What action is the Agency taking?

The EPA evaluated whether interstate ozone transport emissions from upwind states are significantly contributing to nonattainment, or interfering with maintenance, of the 2015 ozone NAAQS in any downwind State using the same 4-step interstate transport framework that was developed in previous ozone transport rulemakings. In its previous action, the Federal Good Neighbor Plan, the EPA found that sources in 23 states had obligations to eliminate their significant contribution to nonattainment and interference with maintenance in downwind areas.

In this proposed rule, the EPA is proposing to apply that same analysis to find that emissions reductions are required from EGU sources in the additional states of Arizona, Iowa, Kansas, New Mexico, and Tennessee and from non-EGU sources in Arizona. The EPA proposes to ensure that these NO

emissions reductions are achieved by issuing FIP requirements for these five states.

88 FR 36654 (June 5, 2023).

In this rule, the EPA is proposing to find that SIP submissions from Arizona, New Mexico, and Tennessee lack adequate provisions to ensure sources and other emissions activity in their states are not interfering with maintenance of the 2015 ozone NAAQS in other states. The EPA is also proposing to error correct its previous actions on SIP submissions from Iowa and Kansas to partial disapprovals for the same reason.

87 FR 22463 (April 15, 2022) (Iowa); 87 FR 19390 (April 4, 2022) (Kansas).

In this same action, the EPA proposes FIP requirements for these five states. The EPA is proposing to incorporate Arizona, Iowa, Kansas, New Mexico, and Tennessee into the existing CSAPR NO

Ozone Season Group 3 Trading Program established in the Federal Good Neighbor Plan, beginning in the 2025 ozone season. EGUs in states not currently covered by any CSAPR trading program for seasonal NO

emissions—Arizona and New Mexico—will be added to the CSAPR NO

Ozone Season Group 3 Trading Program under this rule. EGUs in Iowa, Kansas, and Tennessee will transition from the CSAPR NO

Ozone Season Group 2 Trading Program to the CSAPR NO

Ozone Season Group 3 Trading Program. The EPA is establishing a control stringency level reflecting optimization of existing post-combustion controls and installation of state-of-the-art combustion controls on certain covered EGU sources in the emissions budgets beginning in the 2025 ozone season. In addition, for Arizona, the EPA is establishing a control stringency level reflecting installation of new Selective Catalytic Reduction (SCR) or Selective Non-Catalytic Reduction (SNCR) controls on certain covered EGU sources in its emissions budgets beginning with the 2027 ozone season.

Consistent with the emissions limitations established for non-EGU sources in the Federal Good Neighbor Plan, this supplemental action proposes to establish emissions limitations for new and existing non-EGU sources in Arizona beginning with the 2027 ozone season. The Federal Good Neighbor Plan established control requirements for the following unit types in non-EGU industries: RICE in Pipeline Transportation of Natural Gas; kilns in Cement and Cement Product Manufacturing; reheat furnaces in Iron and Steel Mills and Ferroalloy Manufacturing; furnaces in Glass and Glass Product Manufacturing; boilers in Iron and Steel Mills and Ferroalloy Manufacturing, Metal Ore Mining, Basic Chemical Manufacturing, Petroleum and Coal Products Manufacturing, and Pulp, Paper, and Paperboard Mills; and combustors and incinerators in Solid Waste Combustors and Incinerators.

See

Table II.A-1 in this document for a list of NAICS codes for the relevant industries.

In accordance with the requirements of the good neighbor provision, CAA section 110(a)(2)(D)(i)(I), this proposed rule reduces the transport of ozone and ozone precursors from emissions in upwind states to downwind areas to protect human health and the environment from negative health impacts associated with acute and chronic exposure to ozone. Ozone exposure is also associated with negative effects on ecosystems. Additional information on the air quality issues addressed by this proposed rule is included in section IX. of this document.

C. What is the Agency's authority for taking this action?

The statutory authority for this proposed action is provided by the CAA as amended (42 U.S.C. 7401

et seq.

). Specifically, sections 110 and 301 of the CAA provide the primary statutory underpinnings for this action. The most relevant portions of CAA section 110 are subsections 110(a)(1), 110(a)(2) (including 110(a)(2)(D)(i)(I)), 110(k)(2), 110(k)(3), 110(k)(6), and 110(c)(1).

CAA section 110(a)(1) provides that states must make SIP submissions “within 3 years (or such shorter period as the Administrator may prescribe) after the promulgation of a national primary ambient air quality standard (or any revision thereof),” and that these SIP submissions are to provide for the “implementation, maintenance, and enforcement” of such NAAQS.

The statute directly imposes on states the duty to make these SIP submissions, and the requirement to make the submissions is not conditioned upon the EPA taking any action other than promulgating a new or revised NAAQS.

42 U.S.C. 7410(a)(1).

See EPA

EME Homer City Generation, L.P.,

572 U.S. 489, 509-10 (2014).

The EPA has historically referred to SIP submissions made for the purpose of satisfying the applicable requirements of CAA sections 110(a)(1) and 110(a)(2) as “infrastructure SIP” or “iSIP” submissions.” CAA section 110(a)(1) addresses the timing and general requirements for iSIP submissions, and CAA section 110(a)(2) provides more details concerning the required content of these submissions.

It includes a list of specific elements that “[e]ach such plan” must address, including the requirements of the good neighbor provision.

42 U.S.C. 7410(a)(2).

The EPA's general approach to infrastructure SIP submissions is explained in greater detail in individual documents acting or proposing to act on State infrastructure SIP submissions and in guidance.

See, e.g.,

Memorandum from Stephen D. Page on Guidance on Infrastructure State Implementation Plan (SIP) Elements under Clean Air Act Sections 110(a)(1) and 110(a)(2) (September 13, 2013).

CAA section 110(c)(1) requires the Administrator to promulgate a FIP at any time within 2 years after the Administrator: (1) finds that a State has failed to make a required SIP submission; (2) finds a SIP submission to be incomplete pursuant to CAA section 110(k)(1)(C); or (3) disapproves a SIP submission. This obligation applies unless the State corrects the deficiency through a SIP revision that

the Administrator approves before the FIP is promulgated.

42 U.S.C. 7410(c)(1).

CAA section 110(a)(2)(D)(i)(I), also known as the “good neighbor” provision, provides the primary basis for this proposed action.

It requires that each State's SIP include provisions sufficient to “prohibit[ ], consistent with the provisions of this subchapter, any source or other type of emissions activity within the State from emitting any air pollutant in amounts which will—(I) contribute significantly to nonattainment in, or interfere with maintenance by, any other State with respect to any [NAAQS].”

The EPA often refers to the emissions reduction requirements under this provision as “good neighbor obligations” and submissions addressing these requirements as “good neighbor SIPs.”

42 U.S.C. 7410(a)(2)(D)(i)(I).

Id.

Once the EPA promulgates a NAAQS, the EPA must designate areas as being in “attainment” or “nonattainment” of the NAAQS, or “unclassifiable.” CAA section 107(d).

For ozone, nonattainment is further split into five classifications based on the severity of the violation—Marginal, Moderate, Serious, Severe, or Extreme. Higher classifications provide states with progressively more time to attain while imposing progressively more stringent control requirements.

See

CAA sections 181, 182.

In general, states with nonattainment areas classified as Moderate or higher must submit plans to the EPA to bring these areas into attainment according to the statutory schedule in CAA section 182.

If an area fails to attain the NAAQS by the attainment date associated with its classification, it is “bumped up” to the next classification, per the requirements in CAA section 181(b).

42 U.S.C. 7407(d).

42 U.S.C. 7511, 7511a.

42 U.S.C. 7511a.

42 U.S.C. 7511(b).

Section 301(a)(1) of the CAA gives the Administrator the general authority to prescribe such regulations as are necessary to carry out functions under the Act.

Pursuant to this section, the EPA has authority to clarify the applicability of CAA requirements and undertake other rulemaking action as necessary to implement CAA requirements. CAA section 301 affords the Agency any additional authority that may be needed to make certain other changes to its regulations under 40 CFR parts 52 and 97 to effectuate the purposes of the Act. Such changes are discussed in section X. of this document.

42 U.S.C. 7601(a)(1).

Section 110(k)(6) of the CAA gives the Administrator authority, without any further submission from a state, to revise certain prior actions, including actions to approve SIP submissions, upon determining that those actions were in error.

As discussed further in section V.A. of this document, the EPA proposes to make error corrections under CAA section 110(k)(6) with respect to its prior approvals of the 2015 ozone transport SIP submissions from the States of Iowa and Kansas.

42 U.S.C. 7410(k)(6).

Tribes are not required to submit State implementation plans. However, as explained in the EPA's regulations outlining Tribal CAA authority, the EPA is authorized to promulgate FIPs for Indian country as necessary or appropriate to protect air quality if a Tribe does not submit, and obtain the EPA's approval of, an implementation plan.

See

40 CFR 49.11(a);

see also

CAA section 301(d)(4).

In this action, the EPA proposes an “appropriate or necessary” finding under CAA section 301(d) and proposes Tribal FIP(s) as necessary to implement the relevant requirements. This is further discussed in section V.B. of this document.

42 U.S.C. 7601(d)(4).

D. Severability

The EPA regards this proposal as a complete remedy for the covered states, which will as expeditiously as practicable implement good neighbor obligations for the 2015 ozone NAAQS, consistent with the requirements of the Act.

See North Carolina

EPA,

531 F.3d 896, 911-12 (D.C. Cir. 2008);

Wisconsin

EPA,

938 F.3d 303, 313- 20 (D.C. Cir. 2019);

Maryland

EPA,

958 F.3d 1185, 1204 (D.C. Cir. 2020);

New York

EPA,

964 F.3d 1214, 1226 (D.C. Cir. 2020);

New York

EPA,

781 Fed. App'x 4, 7-8 (D.C. Cir. 2019) (all holding that the EPA must address good neighbor obligations as expeditiously as practicable and by no later than the next applicable attainment date). Yet the EPA proposes that should a court find any discrete aspect of this action, if finalized, to be invalid, the Agency believes that, like the Federal Good Neighbor Plan, the remaining aspects of this proposed rule can and should continue to be implemented to the extent possible, consistent with law.

See

88 FR 36693. In particular, this proposal would disapprove SIP submissions and promulgate a FIP for each covered state (and, pursuant to CAA section 301(d), for each area of tribal jurisdiction within the geographic boundaries of those states). Should any jurisdiction-specific aspect of the rule, once finalized be found invalid, the EPA views this rule, if finalized as proposed, as severable along those state and/or tribal jurisdictional lines, such that the proposed rule could continue to be implemented as to any remaining jurisdictions. This action proposes discrete emissions control requirements for the power sector and for each of nine other industries. Should any industry-specific aspect of the proposed rule be found invalid once final, the EPA views this rule as proposed as severable as between the different industries and different types of emissions control requirements. This is not intended to be an exhaustive list of the ways in which the proposed rule may be severable. In the event any part of the rule, if finalized, is found invalid, our intention is that the remaining portions should continue to be implemented consistent with any judicial ruling.

In a declaration dated October 28, 2023, and filed with the U.S. Supreme Court in

State of Ohio et al.

EPA,

No. 23A349, the Agency, through Joseph Goffman, the Principal Deputy Assistant Administrator performing delegated duties of Assistant Administrator for the Office of Air and Radiation, explained in greater detail why it makes sense as both a technical and legal matter that the Federal Good Neighbor Plan can continue to be implemented in each covered state despite preliminary stays of the Plan in other states. This same reasoning applies with full force with respect to the additional states that are proposed for inclusion in these programs in this action. The declaration is included in the docket for this action.

The EPA's conclusion that this proposed rule, upon finalization, is severable also reflects the important public health and environmental benefits of this rulemaking in eliminating significant contribution and to ensure to the greatest extent possible the ability of both upwind states and downwind states and other relevant stakeholders to be able to rely on this rule at final in their planning.

Cf. Wisconsin,

938 F.3d at 336-37 (“As a general rule, we do not vacate regulations when doing so would risk significant harm to the public health or the environment.”);

North Carolina

EPA,

550 F.3d 1176, 1178 (D.C. Cir. 2008) (noting the need to preserve public health benefits);

EME Homer City

EPA,

795 F.3d 118, 132 (D.C. Cir. 2015) (noting the need to avoid disruption to emissions trading market that had developed).

E. Public Participation

1. Written Comments

Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2023-0402, at

https://www.regulations.gov.

Once submitted, comments cannot be

edited or removed from the docket. The EPA may publish any comment received to its public docket. Do not submit to the EPA's docket at

https://www.regulations.gov

any information you consider to be CBI, Proprietary Business Information (PBI), 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). Please visit

https://www.epa.gov/dockets/commenting-epa-dockets

for additional submission methods; the full EPA public comment policy; information about CBI, PBI, or multimedia submissions; and general guidance on making effective comments.

2. Participation in Virtual Public Hearing

The EPA will begin pre-registering speakers for the hearing upon publication of this document in the

Federal Register.

To register to speak at the virtual hearing, please use the online registration form available at

https://www.epa.gov/csapr/csapr-2015-ozone-naaqs

or contact Ms. Pamela Long at (919) 541-0641 and/or

long.pam@epa.gov

to register to speak at the virtual hearing. The last day to pre-register to speak at the hearing will be 3 working days before the hearing. On [last working day before the hearing], the EPA will post a general agenda for the hearing that will list pre-registered speakers in approximate order at:

https://www.epa.gov/csapr/csapr-2015-ozone-naaqs.

The EPA will make every effort to follow the schedule as closely as possible on the day of the hearing; however, please plan for the hearings to run either ahead of schedule or behind schedule. Additionally, requests to speak will be taken the day of the hearing at the hearing registration desk. The EPA will make every effort to accommodate all speakers who arrive and register, although preferences on speaking times may not be able to be fulfilled. Each commenter will have 3 minutes to provide oral testimony. The EPA encourages commenters to provide the EPA with a copy of their oral testimony electronically by emailing it to Ms. Pamela Long. The EPA also recommends submitting the text of your oral comments as written comments to the rulemaking docket.

The EPA may ask clarifying questions during the oral presentations but will not respond to the presentations at that time. Written statements and supporting information submitted during the comment period will be considered with the same weight as oral comments and supporting information presented at the public hearing.

Please note that any updates made to any aspect of the hearing are posted online at

https://www.epa.gov/csapr/csapr-2015-ozone-naaqs.

While the EPA expects the hearing to go forward as set forth above, please monitor our website or contact Ms. Pamela Long at (919) 541-0641 and/or

long.pam@epa.gov

to determine if there are any updates. The EPA does not intend to publish a document in the

Federal Register

announcing updates.

The EPA will not provide audiovisual equipment for presentations unless the Agency receives special requests in advance. Commenters should notify Ms. Pamela Long when they pre-register to speak that they will need specific equipment. If you require the services of an interpreter or special accommodations such as audio description, please pre-register for the hearing with Ms. Pamela Long and describe your needs by [DATE 1 WEEK BEFORE THE PUBLIC HEARING DATE]. The EPA may not be able to arrange accommodations without advance notice.

III. Background

A. Description of Statutory Background

On October 1, 2015, the EPA promulgated a revision to the ozone NAAQS (2015 8-hour ozone NAAQS), lowering the level of both the primary and secondary standards to 0.070 parts per million (ppm) for the 8-hour standard.

Section 110(a)(1) of the CAA requires states to submit, within 3 years after promulgation of a new or revised standard, SIP submissions meeting the applicable requirements of CAA section 110(a)(2).

One of these applicable requirements is found in CAA section 110(a)(2)(D)(i)(I), otherwise known as the “good neighbor” or “interstate transport” provision, which generally requires that SIPs contain adequate provisions to prohibit in-state emissions activities from having certain adverse air quality effects on other states due to interstate transport of pollution. There are two so-called “prongs” within CAA section 110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must contain adequate provisions prohibiting any source or other type of emissions activity within the State from emitting air pollutants in amounts that will significantly contribute to nonattainment of the NAAQS in another State (Prong 1) or interfere with maintenance of the NAAQS in another State (Prong 2). The EPA and states must give independent significance to Prong 1 and Prong 2 when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I).

National Ambient Air Quality Standards for Ozone, Final Rule, 80 FR 65292 (October 26, 2015). Although the level of the standard is specified in the units of ppm, ozone concentrations are also described in ppb. For example, 0.070 ppm is equivalent to 70 ppb.

SIP submissions that are intended to meet the applicable requirements of CAA section 110(a)(1) and (2) of the CAA are often referred to as infrastructure SIPs and the applicable elements under CAA section 110(a)(2) are referred to as infrastructure requirements.

See North Carolina

EPA,

531 F.3d 896, 909-11 (D.C. Cir. 2008).

On January 31, 2023, the EPA finalized disapproval of 19 SIP submissions and partially approved and partially disapproved two SIP submissions addressing the good neighbor provision for the 2015 ozone NAAQS. The EPA's evaluation for those actions applied uniform, nationwide analytical methods, policy judgments, and interpretation with respect to the same CAA obligations,

i.e.,

implementation of good neighbor requirements under CAA section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS for states across the country. To maintain consistency across all states in light of the final analytical conclusions reached in that action and the separate Federal Good Neighbor Plan, the EPA indicated it would take subsequent action on remaining SIP submissions addressing interstate transport obligations for the 2015 ozone NAAQS.

The EPA also indicated it would address previous final actions on SIP submissions for states where the EPA's final analysis suggested the State may be significantly contributing to nonattainment or interfering with maintenance. In the Federal Good Neighbor Plan, finalized on March 15, 2023, the EPA indicated it would address these and any outstanding FIP obligations in a future action for these states, which included the five states included here and Wyoming.

The EPA finalized its approval of the SIP submission from Wyoming on December 13, 2023.

This action proposes to

address the five additional remaining SIP submissions and FIP obligations.

88 FR 36656.

88 FR 36654 at 36656.

See

Air Plan Approval; Wyoming; Interstate Transport of Air Pollution for the 2015 8-Hour Ozone National Ambient Air Quality Standards, 88 FR 54998 (August 14, 2023). The EPA signed the

final approval on December 13, 2023. 88 FR 87720 (December 19, 2023).

B. Description of the EPA's 4-Step Interstate Transport Regulatory Process

For decades, when evaluating SIPs and formulating FIPs, EPA has consistently utilized the 4-step interstate transport framework (or 4-step framework), which was developed to give meaning to the critical statutory terms in CAA section 110(a)(2)(D)(i)(I) and to provide a reasonable organization to the analysis of the complex air quality challenge of interstate ozone transport. The EPA has addressed the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) with respect to prior NAAQS using the 4-step framework in several regulatory actions, including the CSAPR, which addressed interstate transport with respect to the 1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter standards,

the CSAPR Update

and the Revised CSAPR Update, both of which addressed the 2008 ozone NAAQS.

For the 2015 ozone NAAQS, the EPA uses this framework in evaluating SIP submissions (while considering any alternative approaches states may propose) and applied this framework in the Federal Good Neighbor Plan.

See

Federal Implementation Plans: Interstate Transport of Fine Particulate Matter and Ozone and Correction of SIP Approvals, 76 FR 48208 (August 8, 2011).

Cross-State Air Pollution Rule Update for the 2008 Ozone NAAQS, 81 FR 74504 (October 26, 2016).

In 2019, the D.C. Circuit Court of Appeals remanded the CSAPR Update to the extent it failed to require upwind states to eliminate their significant contribution by the next applicable attainment date by which downwind states must come into compliance with the NAAQS, as established under CAA section 181(a).

Wisconsin

EPA,

938 F.3d 303, 313 (D.C. Cir. 2019). The Revised CSAPR Update for the 2008 Ozone NAAQS, 86 FR 23054 (April 30, 2021), responded to the remand of the CSAPR Update in

Wisconsin

and the vacatur of a separate rule, the “CSAPR Close-Out,” 83 FR 65878 (December 21, 2018), in

New York

EPA,

781 F. App'x. 4 (D.C. Cir. 2019).

See

88 FR at 9338; 88 FR at 36671.

Shaped through the years by input from State air agencies

and other stakeholders on the EPA's prior interstate transport rulemakings and SIP submission actions,

as well as a number of court decisions, the EPA has developed and used the 4-step interstate transport framework to evaluate State's obligations to eliminate interstate transport emissions under the interstate transport provision for the ozone NAAQS: (1) identify monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS (

i.e.,

nonattainment and/or maintenance receptors); (2) identify states that impact those air quality problems in other (

i.e.,

downwind) states sufficiently such that the states are considered to “contribute” (

i.e.,

are considered “linked”) to those receptors and whose emissions therefore warrant further review and analysis; (3) identify the emissions reductions necessary (if any), applying a multifactor analysis, to eliminate each linked upwind State's significant contribution to nonattainment or interference with maintenance of the NAAQS at the locations identified in Step 1; and (4) adopt permanent and enforceable measures needed to achieve those emissions reductions. EPA does not require states to use the 4-step framework in good neighbor SIP submissions, but it is a useful organizational tool that has been upheld by the Supreme Court as “permissible, workable, and equitable.”

EPA

EME Homer City Generation, L.P.,

572 U.S. 489, 524 (2014).

See

63 FR 57356, 57361 (October 27, 1998).

In addition to CSAPR rulemakings, other regional rulemakings addressing ozone transport include the “NO

SIP Call,” 63 FR 57356 (October 27, 1998), and the “Clean Air Interstate Rule” (CAIR), 70 FR 25162 (May 12, 2005).

The general steps of this framework allow for some methodological variation, and this can be seen in the evolution of the EPA's analytic process across its prior rulemakings. This also means states have some flexibility in developing analytic methods within this framework (and may also attempt to justify an alternative framework altogether). The four steps of the framework provide a reasonable organization to the analysis of the complex air quality challenge of interstate ozone transport. As discussed further throughout this document, the EPA has organized its evaluation of good neighbor obligations around this analytical framework (including the specific methodologies within each step as evolved over the course of the CSAPR rulemakings since 2011). Where states presented alternative approaches either to the EPA's methodological approaches within the framework, or organized their analysis in some manner that differed from it entirely, the EPA has evaluated those analyses on their merits to determine compliance with the good neighbor obligation or, in some cases, identified why even if those approaches were acceptable, the State still does not meet the good neighbor requirement and therefore does not have an approvable SIP submission as a whole.

C. The EPA's Ozone Transport Modeling

The EPA has performed nationwide air quality modeling to project ozone design values that are used in combination with measured data to identify nonattainment and maintenance receptors at Step 1. To quantify the contribution of emissions from individual upwind states on 2023 and 2026 ozone design values for the identified downwind nonattainment and maintenance receptors at Step 2, the EPA has performed nationwide, state-level ozone source apportionment modeling for 2023 and 2026. The source apportionment modeling provides contributions to ozone at receptors from precursor emissions of anthropogenic NO

and volatile organic compounds (VOCs) in individual upwind states. In this action, the EPA is proposing to apply the air quality modeling and contribution results that were derived using the 2016v3 modeling and monitoring data that informed the EPA's Step 1 and Step 2 determinations in the Federal Good Neighbor Plan—inclusive of the approach for identifying certain addition sites as violating-monitor maintenance-only receptors based on certified monitoring data and regulatory design values for 2021 and 2022. This section provides an overview of the modeling developments that resulted in those analytical conclusions, which are used here to make good neighbor determinations for these five additional states.

The EPA released several documents containing projected ozone design values, contributions, and information relevant to air agencies for evaluation of interstate transport with respect to the 2015 ozone NAAQS. First, on January 6, 2017, the EPA published a notice of data availability (NODA) in which the Agency requested comment on preliminary interstate ozone transport data including projected ozone design values and interstate contributions for 2023 using a 2011 base year platform.

In the NODA, the EPA used the year 2023 as the analytic year for this preliminary modeling because this year aligns with the expected attainment year for Moderate ozone nonattainment areas for the 2015 8-hour ozone NAAQS.

On October 27, 2017, the EPA released a memorandum (October 2017 memorandum) containing updated modeling data for 2023, which incorporated changes made in response

to comments on the NODA, and was intended to provide information to assist states' efforts to develop SIP submissions to address interstate transport obligations for the 2008 ozone NAAQS.

See

Notice of Availability of the Environmental Protection Agency's Preliminary Interstate Ozone Transport Modeling Data for the 2015 8-hour Ozone National Ambient Air Quality Standard (NAAQS), 82 FR 1733 (January 6, 2017).

82 FR at 1735.

See

Information on the Interstate Transport State Implementation Plan Submissions for the 2008 Ozone National Ambient Air Quality Standards under Clean Air Act section 110(a)(2)(D)(i)(I), October 27, 2017, available in docket ID No. EPA-HQ-OAR-2021-0663.

On March 27, 2018, the EPA issued a memorandum (March 2018 memorandum) noting that the same 2023 modeling data released in the October 2017 memorandum could also be useful for identifying potential downwind air quality problems with respect to the 2015 ozone NAAQS at Step 1 of the 4-step interstate transport framework.

The March 2018 memorandum also included the then newly available contribution modeling data for 2023 to assist states in evaluating their impact on potential downwind air quality problems for the 2015 8-hour ozone NAAQS under Step 2 of the 4-step interstate transport framework.

The EPA subsequently issued two more memoranda in August and October 2018, providing additional information to states developing interstate transport SIP submissions for the 2015 ozone NAAQS concerning, respectively, potential contribution thresholds that may be appropriate to apply in Step 2 of the 4-step interstate transport framework, and considerations for identifying downwind areas that may have problems maintaining the standard at Step 1 of the 4-step interstate transport framework.

See

Information on the Interstate Transport State Implementation Plan Submissions for the 2015 Ozone National Ambient Air Quality Standards under Clean Air Act section 110(a)(2)(D)(i)(I), March 27, 2018 (“March 2018 memorandum”), available in docket ID No. EPA-HQ-OAR-2021-0663.

The March 2018 memorandum, however, provided, “While the information in this memorandum and the associated air quality analysis data could be used to inform the development of these SIPs, the information is not a final determination regarding states' obligations under the good neighbor provision. Any such determination would be made through notice-and-comment rulemaking.”

See

Analysis of Contribution Thresholds for Use in Clean Air Act section 110(a)(2)(D)(i)(I) Interstate Transport State Implementation Plan Submissions for the 2015 Ozone National Ambient Air Quality Standards, August 31, 2018 (“August 2018 memorandum”), and Considerations for Identifying Maintenance Receptors for Use in Clean Air Act section 110(a)(2)(D)(i)(I) Interstate Transport State Implementation Plan Submissions for the 2015 Ozone National Ambient Air Quality Standards, October 19, 2018, available in docket ID No. EPA-HQ-OAR-2021-0663.

Following the release of the modeling data shared in the March 2018 memorandum, the EPA performed updated modeling using a 2016 base year emissions modeling platform (

i.e.,

2016 Version 1 Emissions Platform Modeling, or “2016v1”). This emissions platform was developed under the EPA/Multi-Jurisdictional Organization (MJO)/state collaborative project.

This collaborative project was a multi-year joint effort by the EPA, MJOs, and states to develop a new, more recent emissions platform for use by the EPA and states in regulatory modeling as an improvement over the dated 2011-based platform that the EPA had used to project ozone design values and contribution data provided in the 2017 and 2018 memoranda. The EPA used the 2016v1 emissions to project ozone design values and contributions for 2023. On October 30, 2020, in the Notice of Proposed Rulemaking for the Revised CSAPR Update, the EPA released and accepted public comment on 2023 modeling that used the 2016v1 emissions platform.

Although the Revised CSAPR Update addressed transport for the 2008 ozone NAAQS, the projected design values and contributions from the 2016v1 platform were also useful for identifying downwind ozone problems and linkages with respect to the 2015 ozone NAAQS.

The results of this modeling, as well as the underlying modeling files, are included in docket ID No. EPA-HQ-OAR-2021-0663. The 2016v1 emissions modeling technical support document is available in Docket ID No. EPA-HQ-OAR-2020-0272-0187. Both dockets are available at

https://www.regulations.gov.

See

85 FR 68964, 68981.

See

the Air Quality Modeling Technical Support Document for the Final Revised Cross-State Air Pollution Rule Update, included in the Headquarters docket ID No. EPA-HQ-OAR-2021-0663.

Following the final Revised CSAPR Update, the EPA made further updates to the 2016-based emissions platform to include updated onroad mobile emissions from Version 3 of the EPA's Motor Vehicle Emission Simulator (MOVES) model (MOVES3)

and updated emissions projections for EGUs that reflected the emissions reductions from the Revised CSAPR Update, recent information on plant closures, and other inventory improvements. The EPA published these emissions inventories on its website in September of 2021 and invited initial feedback from states and other interested stakeholders.

The construct of the updated emissions platform, (

i.e.,

2016 Version 2 Emissions Platform Modeling, or “2016v2”), is described in the “Technical Support Document (TSD): Preparation of Emissions Inventories for the 2016v2 North American Emissions Modeling Platform,” hereafter known as the 2016v2 Emissions Modeling TSD, and is included in Docket No. EPA-HQ-OAR-2021-0663. The EPA performed air quality modeling using the 2016v2 emissions to provide projections of ozone design values and contributions in 2023 and 2026 that reflect the effects on air quality of the 2016v2 emissions platform. The EPA used the results of the 2016v2 modeling to inform proposed and final actions on 2015 ozone NAAQS good neighbor obligations for Iowa and Kansas.

Additional details and documentation related to the MOVES3 model can be found at

https://www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves.

https://www.epa.gov/air-emissions-modeling/2016v2-platform.

The EPA was obligated by consent-decree deadline to finalize its action for Iowa and Kansas by April 30, 2022, and was unable to consider or incorporate the later comments received on the 2016v2 modeling that were used to inform the 2016v3 modeling informing the final Disapproval action and final Federal Good Neighbor Plan in early 2023.

The EPA also used the 2016v2 emissions inventories and modeling to support proposed actions for several states, including the EPA's previous proposals on Arizona and Tennesse, as well as the proposed Federal Good Neighbor Plan. In response to comments received for these rulemakings, the EPA updated the 2016v2 inventories and model design to construct another emissions platform (

i.e.,

2016 Version 3 Emissions Platform Modeling, or “2016v3”), which was used to update the air quality modeling. The EPA used this updated modeling to inform a final rulemaking taking final action on 21 interstate transport SIP submissions for the 2015 ozone NAAQS and to inform the final Federal Good Neighbor Plan.

48 49

In its final actions on both SIP disapprovals, and the Federal Good Neighbor Plan, the EPA provided an explanation of the adjustments and other modifications made to construct the 2016v3 platform. Details on the 2016v3 air quality modeling and the methods for projecting design values and determining contributions in 2023 and 2026 based on this platform are described in the TSD titled “Air Quality

Modeling Final Rule TSD—2015 Ozone NAAQS Good Neighbor Plan,” hereafter known as the Final Good Neighbor Plan AQM TSD.

Additional details related to the 2016v3 emissions platform are located in the TSD titled “Preparation of Emissions Inventories for the 2016v3 North American Emissions Modeling Platform,” hereafter known as the 2016v3 Emissions Modeling TSD, included in Docket ID No. EPA-HQ-OAR-2021-0668.

“Air Plan Disapprovals; Interstate Transport of Air Pollution for the 2015 8-Hour Ozone National Ambient Air Quality Standards,” 88 FR 9336 (February 13, 2023), and “Federal “Good Neighbor Plan” for the 2015 Ozone National Ambient Air Quality Standards,” 88 FR 36654 (June 5, 2023).

In the Federal Good Neighbor Plan, the EPA identified and finalized FIPs for 23 states. This included the 21 states included in the SIP Disapproval action, as well as Pennsylvania and Virginia. The EPA had an obligation to finalize a FIP for these two states (and Utah) following the EPA's finding of a failure to submit a SIP from these two states (84 FR 66612). The EPA has not since received SIP submissions from Pennsylvania or Virginia.

Air Quality Modeling Final Rule Technical Support Document—2015 Ozone NAAQS Good Neighbor Plan in Docket ID No. EPA-HQ-OAR-2021-0668.

2016v3 Emissions Modeling TSD in Docket ID No. EPA-HQ-OAR-2021-0668.

In this proposed action, the EPA primarily relies on modeling based on the 2016v3 emissions platform coupled with measured data in Steps 1 and 2 of the 4-step interstate transport framework, which will generally be referenced within this action as the “2016v3 modeling” for 2023 and 2026. As discussed further in section III.D.2. of this document, the EPA is also applying its findings regarding violating-monitor maintenance-only receptors in 2023 using certified monitoring data and regulatory design values for 2021 and 2022. The EPA used the 2016v3 modeling to calculate contributions to these receptors. By again using this same set of monitoring data and updated modeling results, the EPA is using the most current and technically appropriate information for this proposed rulemaking and also ensuring that its regulatory determinations for these remaining states are wholly consistent with the findings informing the EPA's final determinations for all of the states included in the final Federal Good Neighbor Plan. In this proposed action, the EPA is accepting public comment on the 2016v3 modeling and the violating-monitor methodology, solely as they relate to Arizona, Iowa, Kansas, New Mexico, and Tennessee interstate transport obligations for the 2015 ozone NAAQS. The EPA is not reopening the modeling in relation to any other State or regulatory action. Any comments received on the modeling that are not relevant to the evaluation of these states' interstate transport obligations will be treated as beyond the scope of this action.

States may have chosen to rely on the results of prior versions of EPA's modeling and/or alternative modeling performed by states or MJOs to evaluate downwind air quality problems and contributions as part of their SIP submissions. The EPA is not proposing to disapprove any State's submission in this action based on the State's choice of modeling, but, consistent with its disapproval action, based on the EPA's evaluation of the entire record, which aims to factually determine whether states are projected to significantly contribute to or interfere with maintenance in the 2023 analytical year.

See

88 FR at 9343. In section IV.B. of this document, the EPA evaluates how Arizona, Iowa, Kansas, New Mexico, and Tennessee used air quality modeling information in their SIP submissions.

A summary of the methodology and results of the 2016v3 modeling for 2023 and 2026, along with the application of the EPA's Step 1 and Step 2 methodology for identifying receptors and upwind states that contribute to those receptors can be found in the Final Good Neighbor Plan AQM TSD. That document also contains explanations as to how current measured ozone levels based on data for 2021 and 2022 at other monitoring sites (

i.e.,

monitoring sites that are not projected to be receptors in 2023 based on air quality modeling) confirm the likely continuation of elevated ozone levels in 2023 at these locations. This analysis shows that each of the five states in this action are linked at or above (

i.e.,

contributing equal to or more than) 1 percent of the NAAQS to one or more of these monitors. Kansas and Tennessee are linked only to violating-monitor receptors, and not to modeling-based receptors. In recognition that the EPA had not proposed these sites as receptors, linkages to such receptors were used only in a “confirmatory” way to inform the final Disapproval action and Good Neighbor Plan (

i.e.,

to reinforce linkage findings as to states that were otherwise linked to modeling-based receptors). In this proposed action, the EPA finds the existence of such linkages is sufficient to establish that a State contributes to such receptors and is thus an adequate basis on which to propose disapproval of the SIP submissions from Kansas and Tennesse.

D. The EPA's Approach To Evaluating Interstate Transport for the 2015 Ozone NAAQS

The EPA has applied a consistent set of policy judgments across all states for purposes of evaluating interstate transport obligations and the approvability of interstate transport SIP submissions for the 2015 ozone NAAQS under CAA section 110(a)(2)(D)(i)(I) and proposes to continue to do so in this action. These policy judgments conform with relevant case law and past Agency practice as reflected in the CSAPR and related rulemakings. Employing a nationally consistent approach is particularly important in the context of interstate ozone transport, which is a regional-scale pollution problem characterized by the collective contribution from many upwind states to geographically dispersed monitors over distances of hundreds of miles. Effective policy solutions to the problem of interstate ozone transport going back to the NO

SIP Call have necessitated the application of a uniform framework of policy judgments to ensure an “efficient and equitable” approach.

See EME Homer City Generation, LP

EPA,

572 U.S. 489, 519 (2014).

In the March, August, and October 2018 memoranda, the EPA recognized that states may be able to establish alternative approaches to addressing their interstate transport obligations for the 2015 ozone NAAQS that vary from a nationally uniform framework. The EPA emphasized in these memoranda, however, that such alternative approaches must be technically justified and appropriate in light of the facts and circumstances of each particular State's SIP submission. In general, the EPA continues to believe that deviation from a nationally consistent approach to ozone transport must have a well-documented technical basis that is consistent with CAA obligations and relevant case law. Where states submitted SIP submissions that rely on any such potential concepts as the EPA or others may have identified or suggested in the past, the EPA will evaluate whether the State adequately justified the technical and legal basis for doing so.

The EPA notes that certain potential concepts included in an attachment to the March 2018 memorandum require unique consideration, and these ideas do not constitute Agency guidance with respect to interstate transport obligations for the 2015 ozone NAAQS. Attachment A to the March 2018 memorandum identified a “Preliminary List of Potential Flexibilities” that could potentially inform SIP development. However, the EPA made clear in both the March 2018 memorandum

and in Attachment A that the list of ideas was not endorsed by the Agency but rather “comments provided in various forums” on which the EPA sought “feedback from interested stakeholders.”

Further, Attachment A stated, “EPA is not at this time making any determination that the ideas discussed below are consistent with the requirements of the CAA, nor are we specifically recommending that states

use these approaches.”

Attachment A to the March 2018 memorandum, therefore, does not constitute Agency guidance, but was intended to generate further discussion around potential approaches to addressing ozone transport among interested stakeholders. To the extent states sought to develop or rely on one or more of these ideas in support of their SIP submissions, the EPA will thoroughly review the technical and legal justifications for doing so.

March 2018 memorandum, Attachment A.

Id.

at A-1.

Id.

The remainder of this section describes the EPA's analytic framework and interpretation of the critical terms of the good neighbor provision with respect to analytic year, definition of nonattainment and maintenance receptors, selection of contribution threshold, and multifactor control strategy assessment.

1. Selection of Analytic Years

In this section, the EPA describes its process for selecting analytic years for air quality modeling and analyses performed to identify nonattainment and maintenance receptors and identify upwind State linkages. The EPA is retaining the 2023 and 2026 analytical years used to inform the obligations of the 23 states included in the Federal Good Neighbor Plan, to ensure consistency and equitable treatment of all states. In the Federal Good Neighbor Plan, the EPA evaluated air quality to identify receptors at Step 1 and evaluate interstate contributions at Step 2 for two analytic years: 2023 and 2026.

These years are the last full ozone seasons before the Moderate and Serious area attainment dates for the 2015 ozone NAAQS (ozone seasons for purposes of the Federal Good Neighbor Plan run each year from May 1-September 30,

see

40 CFR 52.38(b)(1) and 40 CFR 52.40(c)(1)). To demonstrate attainment by these deadlines, downwind states would be required to rely on design values calculated using ozone data from 2021 through 2023 and 2024 through 2026, respectively. Areas that do not attain by the deadline may be “bumped up” to a higher nonattainment classification level per CAA sections 181 and 182, thereby incurring additional ongoing obligations. Thus, in the Federal Good Neighbor Plan, consistent with each of its prior good neighbor rulemakings, the EPA focused its analysis on the last full ozone seasons before the attainment dates (

i.e.,

2023 and 2026).

While the 2023 analytic year provides a sufficient basis to act on the SIP submissions in this action, consistent with the EPA's Disapproval action,

see

88 FR 9340-41, the EPA uses the 2026 analytic year to ensure a complete Step 3 analysis in the context of developing the FIP,

see

88 FR 36694.

The Agency recognizes that in applying its 2023 and 2026 analytics to inform this action, it may be perceived as acting inconsistently with a longstanding policy of always considering a future analytic year from the standpoint of the timing of its rulemaking action. However, the EPA determined that several important, overriding considerations warrant adopting this approach in this supplemental rulemaking. As explained in section I.A. of this document, it is imperative to maintain a consistent set of analytical and policy determinations across all states in the context of addressing the interstate ozone problem; the EPA is doing so by using a consistent set of data and analytical conclusions between the states included in this action and those for which the EPA has already rendered final determinations in the final SIP Disapproval action and the Federal Good Neighbor Plan. Were the EPA to conduct a new set of air quality analyses tied to years beyond 2023 or 2026, the EPA would separately evaluate these states using different data than that which informed and defined the obligations of all other states, solely as a result of the timing of the EPA's action on these states. Where the need for parity among states or other jurisdictions in like circumstances warrants it, courts have recognized that it may be appropriate for agencies like the EPA to rely on a unified dataset to ensure consistency in treatment.

See Bd. County Commissioners of Weld County

EPA,

72 F.4th 284, 290 (D.C. Cir. 2023) (upholding as reasonable the EPA's determination that “greater parity among counties and faster turnaround [ ] make the original data a better choice than partial updating”). The importance of use of a single, already-developed dataset focused on the years 2023 and 2026 to define good neighbor obligations for all states to ensure consistency among states and for “faster turnaround” to complete this supplemental rulemaking is, in the EPA's judgment, sufficiently compelling to justify this approach here.

The EPA's use of a common and unified dataset here is consistent with all of its past good neighbor rulemakings, including those in which the EPA conducted updated air quality analysis to address remaining good neighbor obligations. In both the CSAPR Update and the Revised CSAPR Update, the EPA took action to address good neighbor FIP actions that had been remanded to the EPA. In each case, the EPA addressed the remanded obligations for all of the covered states through analysis of a new analytic year. This ensured consistency among all of the states where there were good neighbor obligations that needed to be addressed.

See, e.g.,

86 FR 23067-68 (discussing error correction for Kentucky “consistent with EPA's methodology to address the other 20 states” included in that action). Further, the EPA already had updated modeling at hand that could inform its new action.

See, e.g., id.

at 23074, 23079-80. Likewise, where all of a group of states' obligations were being addressed on remand from an action that had not been vacated (as was the case in both the CSAPR Update and the Revised CSAPR Update), it was important to reflect the emissions reductions and air quality improvements that were already being achieved from the non-vacated action in the baseline.

See, e.g., id.

at 23075. In this case, the EPA is not re-evaluating a group of states but addressing additional states in a manner that ensures consistent treatment with the first set of states. This circumstance is analogous to the supplemental rulemaking the EPA undertook soon following the original CSAPR rulemaking to add several states to those programs based on the same data and analysis that informed the CSAPR.

See

76 FR 80760 (December 27, 2011). In the EPA's judgment, the relevant considerations therefore weigh in favor of using the currently available air quality data that has already been used to define other states' obligations.

In addition, like the CSAPR supplemental rulemaking, the timing of this action is the result of procedural happenstance, rather than a substantive difference in the circumstances of any of these five states. This timing was driven by the nature of the EPA's prior proposed or final actions, or lack of such actions, that had been taken at the time the EPA completed its final, updated air quality analysis informing its final determinations on other states' obligations in the Federal Good Neighbor Plan (explained further in section III.C. of this document). This final analysis of obligations based on 2023 and 2026 analytics necessitated the EPA's reevaluation of its proposals on Arizona and Tennessee's SIP submissions, as well as the EPA's past final actions on Iowa and Kansas' SIPs.

In these circumstances, given the potential change in the status of these states, the EPA also found it would be appropriate to provide an opportunity

for public comment on the EPA's changed basis for action.

The EPA has not taken any previous proposed or final action on New Mexico's SIP submission.

Further, shifting the analysis of good neighbor obligations forward to a new analytic year for these five states would not be relevant to a proper definition of these good neighbor obligations, and switching the analytic year(s) for just these five states could create an inequitable result both amongst other upwind states and between these five states and the downwind states to which they are linked. Creating a different set of data for a later year for these states, when the Federal Good Neighbor Plan has already defined requirements and is in effect for certain other states, would introduce an interdependency, or “who goes first,” problem that the EPA's framework generally is designed to avoid.

See Ky. Energy & Env't Cabinet

EPA,

No. 23-3605 (6th Cir. Nov. 9, 2023), Slip Op. at 8. The EPA is not reopening the determinations made for the 23 upwind states covered in the Federal Good Neighbor Plan, and 2023 and 2026 were appropriately selected as the analytical years to inform the EPA's evaluation of these states.

See

88 FR at 36694-96. These years are associated with the statutory attainment schedule faced by the downwind states with designated nonattainment areas where the identified receptors are located. It is at the least reasonable, therefore, to align these five states' evaluation with the remainder of the states in the country, which will maintain parity among all jurisdictions, which is preferable to only “partially updating” the analysis in the case of a handful of states.

Weld County,

72 F.4th at 290. This is a particularly important consideration in implementing the good neighbor provision for ozone. The EPA must ensure each state is held to the elimination of its own significant contribution.

See North Carolina

EPA,

531 F.3d 896, 920-21 (D.C. Cir. 2008). And interstate ozone pollution presents a “collective contribution” problem in which the EPA must allocate a fair share of responsibility among sources across multiple states.

See Maryland

EPA,

1185 F.3d at 120304 (D.C. Cir. 2020);

id.

at 1204 (“So long as upwind sources significantly contribute to [a state's] nonattainment at its 2021 [Marginal] attainment deadline, they violate the Good Neighbor Provision.”).

As the

Maryland

court recognized, the consequences on downwind nonattainment areas from failure to obtain relief from upwind significant contribution are not just continuing poor air quality, but also regulatory requirements that apply for years into the future, including “a requirement to provide for annual emissions reductions in SIPs.”

Id.

(citing CAA section 182(b)). The relief that can be afforded through addressing the upwind states' significant contribution, as proposed in this action, will therefore potentially lessen regulatory burdens on downwind states that Congress commanded they are not to bear alone.

See

88 FR 36840 (discussing the history of downwind states' and the EPA's reliance on emissions reductions achieved through prior good neighbor rules in, for example, redesignation actions and maintenance plans);

cf. Maryland,

958 F.3d at 1200 (a state that cannot obtain relief from an upwind state's significant contribution to a continuing nonattainment designation “is stuck in regulatory limbo”). Thus, using a common dataset makes good sense in this context; it is consistent with the requirements and the purpose of the good neighbor provision, and it ensures these obligations are implemented both expeditiously and in a consistent and equitable manner.

Weld County,

72 F.4th at 290.

While use of a common dataset makes sense for the reasons stated, the EPA notes that it is not aware of other data sets, including either monitoring data or modeling projections, that would suggest alternative regulatory conclusions from those proposed here. As evidenced by the most recent certified monitoring data and design values from 2021 and 2022 used in the violating-monitor receptor-identification methodology, relatively elevated ozone levels exceeding the NAAQS continue to be observed throughout much of the continental U.S., including in the designated nonattainment areas where many of the ozone-transport receptors identified in the Federal Good Neighbor Plan are located.

The use of a common set of air quality data was upheld in

Weld County.

The court, however, went on to find that another portion of the EPA's action under review constituted impermissible retroactive rulemaking, because it “effectively backdated” a nonattainment designation, leaving a state that would have had a three-year period to reach attainment in the position of “missing a compliance deadline that passed before the underlying legal obligation was imposed.” 72 F.4th at 293. This proposed action does not operate retroactively. The EPA's use of the 2023 analytic year does not in and of itself impose any obligations on any sources or states. Rather it provides a common dataset to assess whether any state is contributing to downwind problems attaining the NAAQS. The EPA proposes to set compliance obligations based on the amount of time needed for sources to come into compliance and does not propose to impose liability on such sources for not meeting the proposed obligations at some point in the past.

See

section VII.A.4. and B. of this document. Nor would the proposed rule apply retroactively to the five states with SIP submissions proposed to be disapproved. The EPA is not proposing to backdate the date of finalization of these proposed disapprovals to sometime in the past. Rather, if the proposed disapprovals are finalized, the only legal consequence—the establishment of a duty on the EPA to promulgate a FIP—would run from the date a final action is taken. Unlike the three-year “runway” allowed to reach attainment that the court found had been impermissibly denied to the state in

Weld County,

72 F.4th at 293, the statute affords no such period following a SIP disapproval. CAA section 110(c)(1). The EPA need not wait a single day to promulgate a FIP upon issuing a disapproval of a SIP submission.

EME Homer City,

489 U.S. at 509. Nor is the EPA obligated to give states a second chance to submit a SIP before issuing a FIP.

Id.

Nonetheless, the states covered in this supplemental proposed rulemaking have been on notice since the issuance of the 2016v3 modeling and violating-monitor methodology in connection with the SIP Disapproval and Federal Good Neighbor Plan actions in winter of 2023 that they may be subject to a good neighbor FIP due to identified linkages with downwind receptors. 88 FR 36656. None of these five states has moved since that time to submit a revised SIP submission to address the relevant requirements.

For consistency, the Agency similarly conducted its overcontrol analysis for this action using the 2023 and 2026 data (

see

section VI.D. of this document). The EPA recognizes that it is appropriate to provide sufficient lead time to allow sources in these five states to comply with the proposed requirements. Based on the compliance-timing analysis conducted in the final Federal Good Neighbor Plan and applied here (as discussed in section VII. of this document), the dates proposed for the onset of these requirements for these five states fall after the 2023 and 2026 analytic years. This too is a matter of happenstance and does not justify a deviation from the definition of these states' good neighbor obligations. Similarly, assuming favorable outcomes in the ongoing litigation resulting in stays of the Federal Good Neighbor Plan for several states pending judicial review, the EPA anticipates adjusting the timing of compliance obligations if these states are eventually made subject to the Federal Good Neighbor Plan. These circumstances are analogous to an issue the EPA addressed in the final

Federal Good Neighbor Plan regarding the ability of individual sources to apply for and obtain compliance extensions. The EPA explained that where sources obtained such extensions, the EPA did not intend to conduct further analysis of whether those reductions were still required based on updated air quality analysis. As the EPA explained, the Agency did not think individual sources should gain the benefit of delaying emissions reductions simply in the hopes that they could show those reductions would be overcontrol. This would introduce an inter-dependency into the analysis, whereas each source must be held to the elimination of its portion of significant contribution. Necessity, the EPA explained, may demand some additional amount of time for compliance, but equity demands that individual sources not gain an untoward advantage from delay and reliance on other sources' timelier compliance.

See

88 FR at 36750 n.253. Thus, here, the EPA continues to conduct its overcontrol analysis using the common datasets for 2023 and 2026, to ensure consistent and equitable determinations for what constitutes “significant contribution” even if the implementation of those emissions reductions may be delayed in certain states or for certain sources.

Thus, the EPA proposes to continue to use its 2023 and 2026 analytics, to ensure parity by holding all states to a consistent set of data in defining good neighbor obligations for the 2015 ozone NAAQS, to avoid improperly shifting the burden of emissions reductions to other upwind and downwind states, and to provide for an efficient and administratively workable resolution of these remaining obligations for five additional states.

2. Step 1 of the 4-Step Interstate Transport Framework

In Step 1, the EPA identifies monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS in the 2023 analytic year. This approach reflects the EPA's interpretation of the terms “nonattainment” and “maintenance” as used in the good neighbor provision in the context of the ozone NAAQS.

See

88 FR at 9341-42. Where the EPA's analysis shows that a site does not meet the definition of a nonattainment or maintenance receptor, the EPA excludes that site from further analysis under the EPA's 4-step interstate transport framework. At Step 2 of the 4-step interstate transport framework, the EPA considers those sites identified as a nonattainment or maintenance receptor in 2023 and identifies which upwind states contribute to those receptors above the contribution threshold.

The EPA's approach to identifying ozone nonattainment and maintenance receptors in this action is the same as that used in the Federal Good Neighbor Plan.

This approach gives independent consideration to both the “contribute significantly to nonattainment” and the “interfere with maintenance” prongs of CAA section 110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's direction in

North Carolina.

To summarize this methodology:

See

Air Quality Modeling Final Rule Technical Support Document—2015 Ozone NAAQS Good Neighbor Plan in Docket ID No. EPA-HQ-OAR-2021-0668 for additional details on the EPA's evaluation nonattainment and maintenance receptor identification.

See North Carolina

EPA,

531 F.3d at 910-11 (holding that the EPA must give “independent significance” to each prong of CAA section 110(a)(2)(D)(i)(I)).

The EPA identifies nonattainment receptors as those monitoring sites that are projected to have average design values that exceed the NAAQS and that are also measuring nonattainment based on the most recent monitored design values. This approach is consistent with prior transport rulemakings, such as the CSAPR Update, where the EPA defined nonattainment receptors as those monitoring sites that both measure nonattainment based on recent monitoring data (here, using certified 2021 data to be consistent with the analysis in the Good Neighbor Plan) and that the EPA modeling projected to be in nonattainment in the analytic year (

i.e.,

2023).

60 61

The 2021 design values were the most current official design values available for use in the 2016v3 modeling. The 2021 ozone design values, by monitoring site, can be found in the file “Final GNP O3 DVs Contributions”, in Docket ID No. EPA-HQ-OAR-2021-0668.

See

81 FR 74504 (October 26, 2016). This same concept, relying on both current monitoring data and modeling to define nonattainment receptor, was also applied in CAIR.

See

70 FR at 25241, 25249 (January 14, 2005);

See also

86 FR at 23085 (use of 1 percent threshold in the Revised CSAPR Update); 81 FR at 74518 (basis for use of 1 percent threshold for the 2008 ozone NAAQS in the CSAPR Update)

;

76 FR at 48237-38 (original determination to use 1 percent threshold for the 1997 ozone NAAQS in CSAPR).

Therefore, application of a consistent contribution threshold is important to identify those upwind states that should have responsibility for addressing their contribution to the downwind nonattainment and maintenance problems to which they collectively contribute. Continuing to use 1 percent of the NAAQS as the screening metric to evaluate collective contribution from many upwind states also allows the EPA (and states) to apply a consistent framework to evaluate interstate emissions transport under the interstate transport provision from one NAAQS to the next and helps ensure that good neighbor obligations align with the stringency of the NAAQS.

The issue of the appropriate contribution threshold to apply was thoroughly addressed in the Disapproval action and the Federal Good Neighbor Plan rulemakings, and the EPA responded to numerous comments on this topic. The EPA is not reopening this issue in this action, except as to the question of whether there is any reason to regard the Step 2 contribution threshold differently for any of these five additional states. The Agency, however, sees no basis to do so.

4. Step 3 of the 4-Step Interstate Transport Framework

At Step 3 of the 4-step interstate transport framework, the EPA further evaluates a State's emissions, in light of multiple factors, including air quality and cost considerations, to determine what, if any, emissions significantly contribute to nonattainment or interfere with maintenance and, thus, must be eliminated under CAA section 110(a)(2)(D)(i)(I). This approach reflects the EPA's interpretation of the phrases “contribute significantly” or “interfere

with maintenance” as used in the good neighbor provision in the context of the ozone NAAQS.

See

88 FR at 9342-43.

Under the EPA's longstanding approach to eliminating significant contribution to nonattainment and interference with maintenance, at Step 3, a multi-factor assessment of potential emissions controls would be conducted for states linked at Step 1 and 2. The EPA's analysis at Step 3 in prior Federal actions addressing interstate transport requirements has primarily focused on an evaluation of cost-effectiveness of potential emissions controls (on a marginal cost-per-ton basis), the total emissions reductions that may be achieved by requiring such controls (if applied across all linked upwind states), and an evaluation of the air quality impacts such emissions reductions would have on the downwind receptors to which a State is linked; other factors may potentially be relevant if adequately supported.

The EPA has consistently applied this general approach to Step 3 when identifying emissions contributions that the Agency has determined to be “significant” (or interfere with maintenance) in each of its prior Federal and regional ozone transport rulemakings, and this interpretation of the statute has been upheld by the Supreme Court.

See EME Homer City,

572 U.S. 489, 519 (2014). While the EPA has not directed states that they must conduct a Step 3 analysis in precisely the manner the EPA has done in its prior regional transport rulemakings, State implementation plans addressing the obligations in CAA section 110(a)(2)(D)(i)(I) must prohibit “any source or other type of emissions activity within the State” from emitting air pollutants which will contribute significantly to downwind air quality problems. Thus, states must undertake an analysis similar to the EPA's analysis (or an alternative approach to defining “significance” that comports with the statute's objectives) to determine whether and to what degree emissions from a State should be “prohibited” to eliminate emissions that will “contribute significantly to nonattainment in or interfere with maintenance of” the NAAQS in any other state.

See

88 FR at 9342-43, 9375-76.

In general, where the EPA's or state-provided alternative air quality and contribution modeling establishes that a State is linked at Steps 1 and 2, it will be insufficient at Step 3 for a State merely to point to its existing rules requiring control measures as a basis for SIP submission approval. In general, the emissions-reducing effects of all existing emissions control requirements are already reflected in the future year projected air quality results of the modeling for Steps 1 and 2.

If the State is shown to still be linked to one or more downwind receptor(s) despite these existing controls, but that State believes it has no outstanding good neighbor obligations, the EPA expects the State to provide sufficient justification to support a conclusion that the State has adequate provisions prohibiting “any source or other type of emissions activity within the State from emitting any air pollutant in amounts which will” “contribute significantly to nonattainment in, or interfere with maintenance by,” any other State with respect to the NAAQS.

See

CAA section 110(a)(2)(D)(i)(I). While the EPA has not prescribed a particular method for this assessment, the EPA expects states at a minimum to present a sufficient technical evaluation. This would typically include information on emissions sources, applicable control technologies, emissions reductions, costs, cost-effectiveness, and downwind air quality impacts of the estimated reductions, before concluding that no additional emissions controls should be required.

As examples of general approaches for how such an analysis could be conducted for their sources, states could look to the CSAPR Update, 81 FR 74504, 74539-51; CSAPR, 76 FR 48208, 48246-63; CAIR, 70 FR 25162, 25195-229; or the NO

SIP Call, 63 FR 57356, 57399-405.

See also

Revised CSAPR Update, 86 FR 23054, 23086-23116. Consistently across these rulemakings, the EPA has developed emissions inventories, analyzed different levels of control stringency at different cost thresholds, and assessed resulting downwind air quality improvements.

As explained in section III.A. in this document, the EPA and states must give independent significance to Prong 1 (significant contribution to nonattainment) and Prong 2 (interference with maintenance) when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I).

The EPA gives effect to Prong 2 through identifying receptors that may have trouble attaining the NAAQS under varying air quality and meteorological conditions.

EME Homer City

upheld the EPA's approach to using cost to determine “amounts” with respect to both Prong 1 and 2.

EPA

EME Homer City Generation,

572 U.S. at 518-520. The EPA's use of the term “significant contribution” in its analysis at the third step of the 4-step interstate transport framework is applied for both Prongs 1 and 2. This approach to giving effect to the “interfere with maintenance” prong has been upheld twice by the D.C. Circuit.

See EME Homer City,

795 F.3d at 136;

Wisconsin,

938 F.3d at 325-27. In effect, the EPA's determination of what level of upwind contribution constitutes “interference” with a maintenance receptor is the same determination as what constitutes “significant contribution” for a nonattainment receptor. Nonetheless, this continues to give independent effect to Prong 2 because the EPA applies a broader definition for identifying maintenance receptors, which accounts for the possibility of problems maintaining the NAAQS under realistic potential future conditions. While the EPA and others may occasionally use the language of “significance” as a shorthand for determinations at the third step under both Prongs 1 and 2, this does not detract from the fact that the EPA gives Prong 2 independent effect under the 4-step interstate transport framework. Alternative approaches to defining and prohibiting emissions that “interfere with maintenance” must be, like the EPA's approach, legally and technically justified and give effect to the language of the statute in a manner that ensures states' good neighbor obligations are defined in a consistent and equitable manner.

See North Carolina

EPA,

531 F.3d 896, 909-11 (D.C. Cir. 2008).

As explained in section IV.B. and V.A. of this document, no states whose SIP submissions the EPA is proposing to partially disapprove in this action conducted an adequate analysis at Step 3, following either the EPA's approach or an alternative approach. As explained in section I.A. of this document and further detailed in section VI. of this document, the EPA is proposing to apply the same Step 3 analysis and methodology completed in the Federal Good Neighbor Plan for 23 states to the additional states of Arizona, Iowa, Kansas, New Mexico, and Tennessee. The EPA's approach to Step 3 is explained in section III.B.1.c. of the Federal Good Neighbor Plan.

88 FR 36654, at 36678.

5. Step 4 of the 4-Step Interstate Transport Framework

At Step 4, states (or the EPA) develop permanent and federally-enforceable control strategies to achieve the emissions reductions determined to be necessary at Step 3 to eliminate significant contribution to nonattainment or interference with maintenance of the NAAQS, as necessary to comply with the terms of the good neighbor provision requiring that SIPs (or FIPs) “contain adequate provisions prohibiting” such emissions. 88 FR at 9343. These control strategies

must be included in the State's SIP so that they are made permanent and federally enforceable.

See

CAA section 110(a)(2)(D) (“Each such [SIP] shall . . . contain adequate provisions—prohibiting . . .”).

See also

CAA section 110(a)(2)(A);

Committee for a Better Arvin

EPA,

786 F.3d 1169, 1175-76 (9th Cir. 2015) (holding that measures relied on by a State to meet CAA requirements must be included in the SIP submission).

As with the previous steps of the framework, as explained in section I.A. of this document and further detailed in section VII. of this document, in proposing FIPs for Arizona, Iowa, Kansas, New Mexico, and Tennessee, the EPA is proposing to implement necessary emissions reductions through the same set of permanent and enforceable measures promulgated for 23 other states in the Federal Good Neighbor Plan. The EPA's approach to Step 4 is explained in section III.B.1.d. of the Federal Good Neighbor Plan.

88 FR 36654, at 36684.

IV. SIP Submissions Addressing Interstate Transport of Air Pollution for the 2015 8-Hour Ozone NAAQS

A. SIP Summaries

1. Arizona

On September 24, 2018, the Arizona Department of Environmental Quality (ADEQ) submitted to the EPA the “Arizona State Implementation Plan Revision under Clean Air Act Sections 110(a)(1) and 110(a)(2) for the 2015 Ozone National Ambient Air Quality Standards” (“Arizona's 2018 SIP Submission”). Arizona's 2018 SIP Submission addresses the “infrastructure” requirements of CAA section 110(a)(2), including the good neighbor provisions under CAA section 110(a)(2)(D)(i)(I), for the 2015 ozone NAAQS.

Letter dated September 24, 2018, from Timothy S. Franquist, Director, Air Quality Division, ADEQ, to Michael Stoker, Regional Administrator, EPA Region IX, Subject: “Submittal of the Arizona State Implementation Plan Revision under Clean Air Act sections 110(a)(1) and 110(a)(2) for the 2015 Ozone NAAQS.”

Arizona's 2018 SIP Submission describes the 4-step interstate transport framework established by the EPA to address the good neighbor provision.

Arizona references the results of the ozone modeling completed by the EPA using CAMx version 6.40 and 2011 base year, made available in the March 2018 memorandum, to identify downwind nonattainment and maintenance receptors that may be impacted by emissions from sources in the State at Steps 1 and 2 of the 4-step interstate transport framework. Arizona noted that the modeling results cited in the March 2018 memorandum demonstrate that Arizona is not shown to contribute greater than 1 percent of the NAAQS (

i.e.,

0.70 ppb) to any of the modeled nonattainment or maintenance receptors in other states.

Despite asserting that “Arizona still maintains that the one percent threshold is poorly suited for determining contribution obligations in the Southwestern US,” Arizona relies on the contribution threshold of 1 percent of the NAAQS at Step 2.

Based on the model results cited in Arizona's 2018 iSIP Submission, Arizona finds that it does not contribute significantly to nonattainment or maintenance receptors in other states and that it is not necessary to identify emissions reductions or adopt any permanent or enforceable controls under the interstate transport provision for the 2015 ozone NAAQS.

Arizona also asserts that the Arizona SIP contains adequate provisions to ensure that air emissions in Arizona will not significantly contribute to nonattainment or interfere with maintenance of the 2015 ozone NAAQS in any other State in the future.

Arizona's 2018 SIP submission, 12.

Id.

at 13.

Id.

at 14.

Prior Notices Related to Arizona's SIP Submission

On June 24, 2022, the EPA proposed to approve Arizona's 2018 iSIP Submission as meeting the good neighbor provision for the 2015 ozone NAAQS.

Our proposed approval was based upon the conclusion that Arizona was not linked to any downwind nonattainment or maintenance receptors, which was supported by the 2016v2 modeling described in the notice of proposed rulemaking for the proposed approval.

In response to that proposed rulemaking, the EPA received one comment letter providing evidence to suggest that Arizona likely contributes significantly to interstate ozone pollution. The commenter alleged that the 2016v2 modeling arbitrarily omits Arizona contributions to monitors in El Paso County, Texas, and Doña Ana County, New Mexico, and that Arizona is likely to significantly contribute to ozone concentrations at these receptors. The commenter also incorporated by reference comments that the commenter submitted in response to the EPA's April 6, 2022, proposed FIP addressing regional ozone transport for the 2015 ozone NAAQS, identifying additional alleged flaws and omissions in the 2016v2 modeling.

87 FR 37776 (June 24, 2022).

87 FR 37776, 37782.

87 FR 20036 (April 6, 2022).

As described in section III.B. of this document, the EPA constructed its 2016v3 emissions platform to update ozone transport modeling in response to these and similar comments received on the 2016v2 modeling and to develop the 2016v3 air quality modeling. The EPA also recognized that monitoring data for 2021 and 2022 supported recognizing additional, violating-monitor receptors. The EPA used this updated air quality analysis to inform its final Disapproval and Federal Good Neighbor Plan actions.

79 80

As described later in section IV.B.1. of this document, the 2016v3 modeling and violating-monitor receptor methodology identifies Arizona's maximum contribution to numerous downwind maintenance receptors to be greater than 1 percent of the standard (

i.e.,

greater than 0.70 ppb). Because the latest available modeling indicates that Arizona is linked to downwind maintenance receptors, the EPA is now withdrawing its 2022 proposed approval of Arizona's 2018 SIP Submission with respect to CAA section 110(a)(2)(d)(i)(I).

Details on the 2016v3 air quality modeling and the methods for projecting design values and determining contributions in 2023 and 2026 are described in the TSD titled “Air Quality Modeling Final Rule TSD—2015 Ozone NAAQS Good Neighbor Plan,” hereafter known as the Final Good Neighbor Plan AQM TSD.

2. New Mexico

The EPA made a finding in 2019 that New Mexico had failed to submit a complete good neighbor SIP submission.

See

84 FR 66612 (December 4, 2019). This triggered the EPA's obligation to promulgate a FIP for New Mexico within 2 years. When the EPA failed to do so, multiple parties brought deadline-suit litigation against the Agency. This resulted in a consent decree deadline of June 1, 2024, to either promulgate a FIP for New Mexico or approve a SIP submission fully resolving New Mexico's good neighbor obligations.

WildEarth Guardians

Regan,

No. 22-cv-00174-RB-GBW (D.N.M. Aug. 16, 2022);

Sierra Club

Regan,

No. 3:22-cv-01992-JD (N.D. Cal. Jan. 24, 2023). By stipulation of the parties, that deadline has now been extended to August 30, 2024. The EPA's duty to promulgate a FIP for New

Mexico can only be suspended by the approval of a SIP submission. As discussed in section IV.B. of this document, the EPA proposes to disapprove the SIP submission New Mexico subsequently submitted, described below. This disapproval, if finalized, would not alter or reset the EPA's pre-existing obligation to promulgate a FIP for New Mexico.

On July 27, 2021, the New Mexico Environment Department (NMED) submitted a SIP submission certifying that the State's SIP satisfies requirements of interstate transport of air pollution for the 2015 ozone NAAQS. On June 9, 2021, on behalf of the City of Albuquerque Environmental Health Department (EHD), the Cabinet Secretary of NMED submitted to the EPA a certification that Albuquerque-Bernalillo County, and New Mexico as a whole, “does not cause or contribute to nonattainment or interfere with maintenance of the 2015 ozone NAAQS in any other state.”

NMED and EHD's submission contained what NMED characterized as a weight of evidence analysis of New Mexico's contribution to ozone transport receptors using the data provided in the EPA's modeling results included as an attachment to the March 2018 memorandum. New Mexico did not explicitly follow the 4-step interstate transport framework but did examine downwind air quality and New Mexico's contributions using the analytic year of 2023 to describe New Mexico's linkages to receptors. On July 5, 2023, NMED submitted a supplemental letter containing Exhibit A, for the EPA's consideration in the Agency's review of the NMED and EHD SIP submissions. The following sections describe NMED and EHD's submissions, including Exhibit A, and the information provided for each step in the process.

See

EHD SIP submission, attachment B, page 3.

a. Information Provided by New Mexico Regarding Step 1

For Step 1 of the 4-step interstate transport framework, NMED and EHD SIP submissions relied on the EPA's interstate transport modeling results that are included as an attachment to the March 2018 memorandum.

These EPA modeling results, using a 2011 base year, provided: (1) projected average design value and maximum design value for 2023 for ozone monitors to identify nonattainment or maintenance receptors and (2) projected average contribution from State emissions to the projected ozone concentrations at each ozone monitor to identify upwind state-to-downwind receptor linkages.

As explained in section IV.A.2.c., NMED's Exhibit A acknowledged the EPA's 2016v3 modeling results and linkages.

b. Information Provided by New Mexico Regarding Step 2

NMED and EHD's submission presented New Mexico's projected 2023 ozone contributions to maintenance and nonattainment receptors using the projections from the EPA's March 2018 memorandum. The State agencies state that in past rulemakings, the EPA has relied upon the 1 percent of the 2015 ozone NAAQS standard (0.70 ppb) contribution threshold when evaluating if an upwind State has a “potentially significant contribution to nonattainment or interference with maintenance”

impacts air quality in a downwind state. New Mexico began their Step 2 analysis by using the EPA's 1 percent threshold to evaluate contribution and identified that the State contributes 1 percent or more of the NAAQS to one maintenance receptor: Weld County Tower, Colorado (Monitor ID: 081230009), and one nonattainment receptor, Rocky Flats-N, Colorado (Monitor ID: 080590006).

84 85

Additionally, the EPA's March 2018 memorandum modeling indicated that upwind states contribute roughly 8 and 10 percent of the modeled 2023 design value at the Weld County receptor and the Rocky Flats-N receptor, respectively.

EHD's SIP submission Attachment B, page 7.

Id.

at Table 1, page 4.

Id.

at page 5.

However, NMED and EHD argue that New Mexico does not contribute significantly to nonattainment or interfere with maintenance at the Weld County Tower and Rocky Flats-N receptors. NMED and EHD assert that a “weight of evidence” analysis is more appropriate than relying on a single, national standard for identifying linkages and determining whether contributions from an upwind State are significant. NMED and EHD believe that New Mexico should not be linked to Colorado receptors in the EPA's transport Step 2 analysis because the majority of the contribution to these receptors comes directly from Colorado. NMED and EHD attempt to justify this position by relying on a previous transport rulemaking that determined certain monitoring sites in California were not interstate transport receptors. Specifically, New Mexico references the approval of Arizona's 2008 ozone transport SIP submission,

see

81 FR 31513. In that action, the EPA determined that Arizona did not significantly contribute to two California monitoring sites despite contributing more than 1 percent of the NAAQS, because the EPA found the total collective contribution from all upwind states was so low at these sites that they need not be considered transport receptors. New Mexico attempts to expand the application of the EPA's reasoning in the Arizona action, asserting it would also be appropriate not to link New Mexico, or the other linked upwind states, to the Colorado receptors at the 1 percent threshold.

NMED and EHD's submission also claims that the relative share of in-state versus out-of-state contribution in Colorado, topographical influences on the transport of ozone in Colorado, and other air quality information support its “weight-of-evidence” analysis. To identify the portion of ozone levels in Colorado coming from in-state emissions as opposed to upwind-state emissions, New Mexico relied on the EPA's 2018 memorandum modeling data. Based on this data, NMED and EHD determined in-state emissions outweighed the portion of emissions coming from upwind states collectively.

NMED and EHD considered the topological influences on ozone concentrations in the Denver area based on information prepared by Colorado to support the final 2015 ozone NAAQS designation of the Denver area.

NMED and EHD assert in their submissions that the receptors in Colorado are predominantly impacted from local sources and thus the minimal contributions from upwind states do not warrant further controls in New Mexico. They contend that the topography of the Denver nonattainment area (NAA) disproportionally favors the formation of ozone due to local emissions. As support for their argument, NMED and EHD point to the EPA's TSD supporting the designation of the Denver NAA: “The three key circulation patterns (drainage flow, upslope flow, and mountain-plains solenoid circulation), in conjunction with the surface topography, in the [Denver] area serve to trap emissions and produce ozone in the basin formed by the surrounding higher elevation features. Further, these circulation patterns serve to recirculate prior day emissions into the Denver area population centers as the mountain-plains solenoid flow lifts the polluted atmosphere up the mountain slopes of the Rocky Mountains to the west in warm afternoons, and then returns the polluted air to the surface as the lofted air circulates back to the east and

subsides overnight.”

New Mexico presents this information to further support their claim that the Denver NAA is significantly more impacted by emissions from within Colorado than from interstate transport.

Id.

at page 17.

See also

83 FR 25776 (June 4, 2018).

See https://www.epa.gov/sites/default/files/2018-05/documents/co_tsd_final_0.pdf.

NMED and EHD's final weight of evidence factor consisted of an assessment of ozone air quality monitoring data and design values. Here, they identify downward trends in ozone precursor emissions (NO

and VOC) from 2005 to 2018. NMED and EHD cite New Mexico's current on-the-books rules as sufficient to resolve the State's transport responsibilities and as reason to believe downward trends in emissions and ozone concentrations at the receptors for which they contribute greater than 0.70 ppb (Rock Flats-N and Well County Tower monitors) will continue to decrease. NMED included data on an overall trend of slightly increasing VOC emissions and decreasing NO

emissions in New Mexico, Utah, Wyoming, California, and Texas from 2002 to 2014. New Mexico also provided data exhibiting a decrease of VOC and NO

emissions from Colorado during the same time period. New Mexico credited the downward emissions trends to permanent and enforceable control measures. New Mexico made an argument that overall decreasing ozone concentrations and emissions trends in the state, and other upwind states, correlate with reduced contributions to nonattainment and maintenance receptors outside of New Mexico. NMED and EHD concluded that decreasing ambient ozone concentrations in Colorado is indicative of New Mexico contributing less to ozone in downwind states as time goes on.

This concluded New Mexico's analysis in its original submission. New Mexico did not conduct an analysis of emissions-control opportunities within the State at Step 3. NMED and EHD concluded it would be unreasonable for New Mexico to take further actions to address its obligations under the good neighbor provisions for the ozone NAAQS. Thus, at Step 4, NMED and EHD determined that no additional permanent and enforceable measures were necessary to reduce the State's emissions.

c. New Mexico Letter

On July 5, 2023, NMED submitted for the EPA's consideration a letter with an attachment, Exhibit A. The letter indicates its submission is in response to the EPA's indication that it may disapprove New Mexico's SIP submission. To the EPA's awareness, this letter was not subject to public notice or rulemaking process at the State level and does not in itself purport to be a SIP submission or a revision to New Mexico's SIP. As such, the EPA takes the information in the letter under advisement but does not consider this letter to be a new SIP submission in its own right or part of the SIP submission dated July 27, 2021.

In its letter, NMED asserts the EPA should account for emissions reductions that have occurred since 2020 that could resolve the State's transport obligations. NMED identified emissions reductions from two current compliance orders that resulted in a reduction of 236 tons of annual NO

emissions. NMED entered into a settlement agreement with ETC Texas Pipeline Ltd (ETC) for its Jal #3 plant, compliance order No. AQB 20-63, which was lodged on August 25, 2021. The settlement agreement mandated that the facility remove its sulfur recovery unit, which resulted in an emissions reduction of 4.8 tons of NO

per year. Additionally, NMED entered into a consent decree with ETC for its Eunice Gas Plant, compliance order No. AQB 20-64, which was lodged on September 9, 2021. The consent decree required the shutdown of the Eunice plant, except for Amanda Booster Station, resulting in emissions decrease of 231.4 tons of NO

per year. Lastly, NMED references emissions reductions anticipated from the consent decree lodged with Matador Production Company, filed on March 27, 2023. NMED is anticipating emissions reductions of a total 77 tons of NO

over 3 years and to occur before 2030.

NMED argues that the emissions reductions resulting from these compliance orders are satisfactory to fulfil the emissions reductions that would occur under the Federal Good Neighbor Plan for the 2015 Ozone Standard. NMED states that based on the formula applied under the Federal Good Neighbor Plan, the EPA identified 30 tons of emissions reductions achievable in 2023 under the current formula for EGU emissions reductions.

NMED claims that the “EPA indicated that this 30 ton per year reduction would be all that is necessary to meet its good neighbor FIP requirements.”

NMED argues that as the NO

emissions decreases outlined in the provided consent decrees are greater than the emissions reductions anticipated in the Federal Good Neighbor Plan, the State will have met its obligations for interstate transport.

Ozone Transport Policy Analysis Final Rule Technical Support Document.

Table B-3. 2024 Ozone Season NO

Emissions for States at Different Uniform Control Scenarios.

NMED's July 5, 2023, letter to the EPA, at 1.

3. Tennessee

On September 13, 2018, Tennessee submitted a SIP revision addressing the CAA section 110(a)(2)(D)(i)(I) interstate transport requirements for the 2015 8-hour ozone NAAQS.

90 91

The SIP submission provided Tennessee's analysis of its impact to downwind states and concluded that emissions from the State will not significantly contribute to nonattainment or interfere with maintenance of the 2015 8-hour ozone NAAQS in other states. Tennessee's submission relied on the EPA's modeling results for 2023 using a 2011 base year, contained in the March 2018, memorandum, to identify downwind nonattainment and maintenance receptors that may be impacted by emissions from sources in the State at Steps 1 and 2 of the 4-step interstate transport framework.

The Tennessee Department of Environmental Control (TDEC) reviewed the EPA's 2023 modeling, concurred with the results, and determined that the EPA's future year projections were reasonable and account for source shutdowns, new controls, and fuel switches. TDEC summarized the State's upwind contribution to 26 nonattainment and maintenance receptors and noted that according to the modeling, Tennessee's largest impact on any potential downwind receptor in 2023 would be 0.31 ppb to a nonattainment receptor and 0.65 ppb to a maintenance receptor. Tennessee concluded that emissions from Tennessee do not contribute above 1 percent of the NAAQS or above 1 ppb at any receptors.

The September 13, 2019, SIP submission provided by TDEC was received by the EPA on September 17, 2018.

On September 18, 2018, Tennessee submitted multiple SIP revisions under one cover letter. The EPA is only acting on Tennessee's 2015 ozone good neighbor interstate transport SIP requirements in this document.

The EPA notes that Tennessee's SIP submission is not organized around the EPA's 4-step interstate transport framework for assessing good neighbor obligations, but the EPA summarizes the submission using that framework for clarity here.

Tennessee's submission asserted that NO

emissions are considered the primary cause of formation of ozone in the southeast United States, and emphasized a significant reduction in NO

emissions reductions from coal-fired EGUs and other large NO

sources leading to improvements in air quality, including reductions attributable to

previous transport rulemakings.

Additionally, TDEC identifies existing SIP-approved provisions, Federal regulations and programs, court settlements, and statewide source shutdowns that TDEC believes limit ozone precursor emissions in the State.

The Tennessee SIP revision specifically cites the NO

Budget Trading Program, CAIR, and CSAPR. In addition, the Tennessee SIP revision discusses Tennessee rule 1200-03-27-.12 (NO

SIP Call requirements for Stationary Boilers and Combustion Turbines), which had not been approved into the SIP at the time of the September 13, 2018, submission. The EPA finalized approval of TAPR 1200-03-27-.12 into the Tennessee SIP on March 2, 2021.

See

86 FR 12092.

See

page 9 through 12 of Tennessee's September 13, 2018, SIP submission for a list of SIP-approved State rules and Federal rules. This can be found in Docket No. EPA-R04-OAR-2021-0841.

Based on the information contained in Tennessee's transport SIP submission, TDEC concluded that Tennessee does not significantly contribute to nonattainment or interfere with maintenance in another State of the 2015 8-hour ozone NAAQS, and that the SIP submission provides for adequate measures to control ozone precursor emissions.

Prior Notices Related to Tennessee's SIP Submission

Previously, the EPA proposed approval of Tennessee's September 13, 2018, SIP submission, based on the contribution modeling provided in the March 2018 memorandum.

See

84 FR 71854 (December 30, 2019). When the EPA completed updated modeling of the 2023 analytic year in 2020 using a 2016-based emissions modeling platform (2016v1), however, it became evident that Tennessee was projected to be linked to downwind nonattainment and maintenance receptors.

As a result, the EPA did not act on Tennessee's SIP submission when it published a supplemental proposal in 2021 to approve four other southeastern states' good neighbor SIP submissions, using the updated 2023 modeling.

See

86 FR 37942, 37943 (July 19, 2021).

See

“Air Quality Modeling Technical Support Document for the Final Revised Cross-State Air Pollution Rule Update”, available in Docket ID No. EPA-HQ-OAR-2021-0663.

The 2016v2 modeling comported with the 2016v1 modeling results for Tennessee, in that it continued to show Tennessee was linked to at least one downwind-maintenance-only receptor in 2023. Based on this information and the EPA's evaluation of the information and arguments put forward by the State in its submission, the EPA withdrew its December 30, 2019, proposed approval of Tennessee's September 13, 2018, interstate transport SIP submission, and the EPA proposed disapproval of Tennessee's submission.

See

87 FR 9545 (February 22, 2022).

As described in section III.C. of this document, the EPA received numerous comments on the 2016v2 modeling used in its proposed ozone transport actions, including its proposed disapproval of Tennessee's submission. The EPA incorporated this feedback and made several updates to the 2016v2 inventories and model design to construct a 2016v3 emissions platform, which the EPA used to develop the 2016v3 air quality modeling. The EPA used the 2016v3 modeling to support the final action on 21 interstate transport SIP submissions for the 2015 ozone NAAQS.

96 97

The Agency also found there were additional receptors that would struggle to attain or maintain the NAAQS in 2023, which it identified as violating-monitor receptors. The final air quality analysis modeling indicated that while Tennessee was no longer projected in the modeling to be linked to any nonattainment or maintenance receptors, the State was linked above 1 percent of the NAAQS to five violating-monitor receptors, all located in Texas.

See

2016v3 AQM TSD, at C-5.

Disapproval Action, 88 FR 9336 (February 13, 2023), and Federal Good Neighbor Plan, 88 FR 36654 (June 5, 2023).

Although the EPA identified a linkage between emissions in Tennessee and violating-monitor receptors, in recognition that it had not included such receptors in its proposed action, the EPA did not take final action on Tennessee's transport SIP submission at that time. The EPA is now withdrawing its proposed disapproval of Tennessee's September 13, 2018, interstate transport SIP submission as published on February 22, 2022, at 87 FR 9545.

B. EPA Evaluation

The EPA is proposing to find that SIP submissions from Arizona, New Mexico, and Tennessee meet the states' obligations with respect to Prong 1, prohibiting emissions that contribute significantly to nonattainment of the 2015 8-hour ozone NAAQS, but do not meet obligations with respect to Prong 2, interference with maintenance of the 2015 8-hour ozone NAAQS in any other state. This proposal is based on the EPA's evaluation of each State's SIP submission, considered in light of the state-of-the-science 2016v3 modeling for 2023 and 2026, the certified ozone monitoring data and design values for 2021 and 2022, and corresponding contribution analysis. Therefore, the EPA is proposing to partially approve with respect to Prong 1 and partially disapprove with respect to Prong 2 the SIP submissions from Arizona, New Mexico, and Tennessee.

1. Arizona

a. Evaluation of Information Provided by Arizona Regarding Steps 1 and 2

In Arizona's 2018 SIP Submission, the State cites the EPA modeling released in the March 2018 memorandum to conclude that Arizona does not contribute significantly (

i.e.,

equal to or above the 0.70 ppb threshold) to any nonattainment or maintenance receptor in another state.

In this proposal, the EPA relies on the Agency's 2016v3 modeling, which uses a more recent base year and more up-to-date emissions inventories, compared to the modeling that was released in the March 2018 memo. The 2016v3 modeling along with the violating-monitor receptor methodology are used to identify downwind receptors, calculate upwind contributions, and determine “linkages” to downwind air quality problems in 2023 using the 0.70 ppb threshold (

i.e.,

1 percent of the NAAQS). As shown in Tables IV.B-1-3, the updated EPA contribution modeling identifies Arizona's maximum contribution to a downwind nonattainment or maintenance receptor to be greater than 1 percent of the standard (

i.e.,

greater than 0.70 ppb). Because the entire technical basis for Arizona's determination with respect to CAA section 110(a)(2)(D)(i)(I) in its 2018 SIP Submission is that Arizona is not linked at Step 2, the EPA proposes to partially disapprove Arizona's SIP submission with respect to Prong 2, interference with maintenance, based on the EPA's finding that such a linkage does exist to maintenance-only receptors.

Arizona's 2018 iSIP submission, 13-14.

b. Results of the EPA's Step 1 and Step 2 Modeling and Findings for Arizona

As described in section III.B. of this document, the EPA performed air quality modeling using the 2016v3 emissions platform to project design values and contributions for 2023 and 2026. These data were examined to determine if Arizona contributes at or above the threshold of 1 percent of the 2015 ozone NAAQS (0.70 ppb) to any downwind nonattainment or maintenance receptor. As shown in Table IV.B-1, the data indicate that, in

2023, emissions from Arizona contribute greater than 1 percent of the 2015 ozone NAAQS to six maintenance-only receptors in Colorado, Nevada, New Mexico, and Texas.

Table IV.B.1-3 indicates that in 2023, emissions from Arizona contribute greater than 1 percent of the NAAQS to three violating-monitor maintenance-only receptors in Nevada and New Mexico. Furthermore, data for 2026 in Table IV.B.1-2 indicate that emissions from Arizona contribute greater than 1 percent of the 2015 ozone NAAQS to five maintenance-only receptors in Colorado and New Mexico.

100

In addition, Arizona's contribution exceeds 1 ppb at five receptors in 2023 and two receptors in 2026. Thus, whether Arizona could have sought to justify an alternative 1 ppb threshold is irrelevant to EPA's determination that Arizona is linked, as Arizona's contributions to receptors exceed even that higher alternative contribution threshold.

Final Good Neighbor Plan AQM TSD, Appendix C, available in Docket ID No EPA-HQ-OAR-2021-0668.

100

Id.

Table IV.B.1-1—Arizona Linkage Results Based on the EPA Updated 2023 Modeling

Receptor ID

Location

Nonattainment/maintenance

2023 Average

design value

(ppb)

2023 Maximum

design value

(ppb)

Arizona

contribution

(ppb)

80690011

Larimer, Colorado

Maintenance-Only

70.9

72.1

0.86

350130021

Doña Ana, New Mexico

Maintenance-Only

70.8

72.1

1.04

350130022

Doña Ana, New Mexico

Maintenance-Only

69.7

72.4

1.06

350151005

Eddy, New Mexico

Maintenance-Only

69.7

74.1

1.34

350250008

Lea, New Mexico

Maintenance-Only

69.8

72.2

1.66

481410037

El Paso, Texas

Maintenance-Only

69.8

71.4

1.69

Source: Final Good Neighbor Plan AQM TSD.

Table IV.B.1-2—Arizona Linkage Results Based on the EPA Updated 2026 Modeling

Receptor ID

Location

Nonattainment/maintenance

2026 Average

design value

(ppb)

2026 Maximum

design value

(ppb)

Arizona

contribution

(ppb)

80690011

Larimer, Colorado

Maintenance-Only

70.0

71.2

0.71

350130021

Doña Ana, New Mexico

Maintenance-Only

69.9

71.2

0.82

350130022

Doña Ana, New Mexico

Maintenance-Only

69.0

71.6

0.82

350151005

Eddy, New Mexico

Maintenance-Only

69.1

73.4

1.06

350250008

Lea, New Mexico

Maintenance-Only

69.2

71.6

1.34

Source: Final Good Neighbor Plan AQM TSD.

Table IV.B.1-3—Arizona 2023 Linkage Results Based on Violating-Monitor Maintenance-Only Receptors

Receptor ID

Location

2021

Design value

(ppb)

2022

Design value

(ppb)

2021

4th high

(ppb)

2022

4th high

(ppb)

Arizona

contribution

(ppb)

320030043

Clark, Nevada

0.77

350011012

Bernalillo, New Mexico

1.62

350130008

Doña Ana, New Mexico

1.13

Source: Final Good Neighbor Plan AQM TSD.

Therefore, based on the EPA's evaluation of the information submitted by Arizona, and based on the EPA's most recent modeling results for 2023 and 2026 using the 2016v3 emissions platform, the EPA proposes to find that Arizona is not linked to any nonattainment receptor. However, the EPA finds that Arizona is linked at Steps 1 and 2 to at least one, and in fact several, maintenance-only receptors, based on the available analytical information, which includes the modeling results from the 2016v3 platform and the violating-monitor receptor analysis.

c. Evaluation of Information Provided Regarding Step 3

To determine what, if any, emissions significantly contribute to nonattainment or interfere with maintenance and, thus, must be eliminated under CAA section 110(a)(2)(D)(i)(I), at Step 3 of the 4-step interstate transport framework, a state's emissions are further evaluated, in light of multiple factors, including air quality and cost considerations. The EPA recognizes that the modeling results released with the March 2018 memorandum indicated Arizona would not contribute at or above 1 percent of the NAAQS to any downwind receptor. Arizona's 2018 SIP Submission therefore concluded that it was not necessary to identify any emissions reductions or adopt any permanent and enforceable controls to meet the good neighbor provision for the 2015 ozone NAAQS.

101

Arizona's 2018 SIP Submission states that “Arizona believes that this SIP contains adequate provisions to ensure that air emissions in Arizona do not significantly contribute to nonattainment or interfere with maintenance of the 2015 ozone NAAQS in any other State in the future.”

102

101

Arizona's 2018 iSIP Submission, 13-14.

102

Id at 14.

However, as discussed previously in this section, the EPA's more recent air quality analysis for 2023 and 2026

indicates that sources in Arizona are in fact contributing to downwind air quality problems at several maintenance-only receptors. Based on this record, the EPA finds the State's conclusion that its SIP contains adequate provisions prohibiting emissions interfering with maintenance of the 2015 ozone NAAQS in other states to lack justification, and the EPA proposes to partially disapprove the submission.

d. Conclusion

For the reasons described in this section, the EPA proposes to partially approve Arizona's SIP submission with respect to Prong 1 of CAA section 110(a)(2)(D)(i)(I) and to partially disapprove Arizona's SIP submission with respect to Prong 2 of CAA section 110(a)(2)(D)(i)(I).

2. New Mexico

a. Evaluation of Information Provided by New Mexico Regarding Step 1

As noted earlier, NMED and EHD first relied on the modeling information from the EPA's March 2018 memorandum which used a 2011 base period with 2011 meteorology to identify nonattainment and maintenance receptors and upwind-state contribution levels at those receptors. NMED and EHD acknowledged that this modeling showed a linkage to one nonattainment and one maintenance-only receptor in the Denver area at or above 0.70 ppb. Since the time of the State's submission, the EPA updated the modeling to a 2016 base period with 2016 meteorology and updated emissions data to produce new 2023 model projections and released this new modeling in 2022 (commonly referred to as 2016v2 modeling platform). As explained in section III.C. of this document, in response to comments, the EPA further refined its modeling in the 2016v3 modeling platform, issued in 2023.

103

Under both the EPA's 2011-based modeling included in the March 2018 memorandum that New Mexico relied upon in their SIP submission and the EPA's updated 2016v3 modeling, there are receptors identified, to which New Mexico is linked above 1 percent of the NAAQS, as described in the next section.

104

103

Air Quality Modeling Final Rule Technical Support Document—2015 Ozone NAAQS Good Neighbor Plan in Docket ID No. EPA-R08-OAR-2023-0375.

104

The 2011 modeling relied on by NMED and EHD in the SIP submission identified linkages to one nonattainment receptor, the Rocky Flats-N receptor, and the one maintenance receptor, the Weld County Tower receptor, in 2023.

See

NMED SIP Submission at 4.

b. Evaluation of Information Provided by New Mexico Regarding Step 2

As in Step 1, NMED and EHD relied upon the modeling released in the EPA's March 2018 memo, and in its July 2023 letter, NMED relied on the EPA's 2016v3 modeling results to analyze projected contributions to downwind receptors. As explained in section IV.A.2. of this document, while NMED and EHD acknowledge the EPA's modeling results identifying a contribution greater than 0.70 ppb, the agencies do not find it appropriate to rely on a particular threshold (

i.e.,

0.70 ppb) at Step 2 to determine whether a State is linked (or significantly contributing) to a downwind receptor in the West, but instead they rely on a weight of evidence approach. NMED and EHD point to the EPA's past approval of Arizona's 2008 ozone good neighbor SIP submission, in which the EPA approved Arizona's SIP based on an evaluation of receptors in California to support the use of a weight of evidence approach in evaluating interstate transport and claim that the EPA determined a weight of evidence approach to be an appropriate evaluation to apply in the West.

105

NMED SIP submission at 5.

Although NMED and EHD's approach to evaluating whether an upwind State is linked to a downwind receptor differs from the EPA's broadly applied 4-step interstate transport framework by relying instead on a “weight of evidence” approach, here, we evaluate that “weight of evidence” methodology NMED has chosen to apply. While the NMED and EHD submission does not claim to establish a linkage, and instead postulates that it is inappropriate to apply a uniform standard to determine whether a State's contributions should be further evaluated in Step 3, the submission does rely on a 1 percent threshold to identify which receptors to apply a weight of evidence analysis. Therefore, while the NMED and EHD submission seems to disagree in principle with the use of a single threshold at Step 2, they have effectively moved to apply the same threshold for the same purpose the EPA would do at Step 2—rely on a 1 percent threshold to identify receptors to which a State is linked and therefore require further evaluation at Step 3 to determine whether any of the State's contributions, if any, are significant.

While the EPA does not disagree with the methodology NMED and EHD used in the submission to identify receptors where the State is linked, the EPA continues to find its 4-step interstate transport framework to be an appropriate and nationally consistent approach to evaluating interstate transport, including the application of a contribution threshold at Step 2 of the framework. As stated in the EPA's final SIP disapproval action, the EPA disagrees with the NMED and EHD submission that neither its nationwide photochemical grid modeling nor the 4-step interstate transport framework for ozone can generally be applied to states in the western region of the U.S., including contribu

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