[Federal Register Volume 89, Number 151 (Tuesday, August 6, 2024)]
[Proposed Rules]
[Pages 63860-63888]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-15826]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-HQ-OAR-2021-0663; EPA-R07-OAR-2021-0851; FRL-11688-01-R7]


Air Plan Disapproval; Missouri; Interstate Transport of Air 
Pollution for the 2015 8-Hour Ozone National Ambient Air Quality 
Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: Pursuant to the Federal Clean Air Act (CAA or the Act), the 
Environmental Protection Agency (EPA or the Agency) is proposing to 
disapprove a State Implementation Plan (SIP) revision submitted by 
Missouri (the State) on November 1, 2022 regarding interstate transport 
for the 2015 8-hour ozone national ambient air quality standards 
(NAAQS). The ``good neighbor'' or ``interstate transport'' provision 
requires that each State's SIP contain adequate provisions to prohibit 
emissions from within the State from significantly contributing to 
nonattainment or interfering with maintenance of the NAAQS in other 
States. This requirement is part of the broader set of 
``infrastructure'' requirements designed to ensure that the structural 
components of each State's air quality management program are adequate 
to meet the State's responsibilities under the CAA. Missouri previously 
submitted a SIP revision regarding ozone transport for the 2015 8-hour 
ozone NAAQS (2015 ozone NAAQS) on June 10, 2019, which the EPA 
previously disapproved. Missouri submitted a second SIP submission, 
reanalyzing its good neighbor obligations and making revisions to its 
SIP, on November 1, 2022. In this document, the EPA proposes to 
disapprove the November 1, 2022, submission as inadequate to address 
Missouri's obligations. This disapproval, if finalized, will establish 
a 2-year deadline for the EPA to promulgate a Federal Implementation 
Plan (FIP) to address the relevant interstate transport requirements, 
unless the EPA approves a subsequent SIP submission that meets these 
requirements. Disapproval does not start a mandatory sanctions clock.

DATES: Written comments must be received on or before September 20, 
2024. Virtual public hearing: The EPA will hold a virtual public 
hearing on August 21, 2024. The last day to pre-register to speak at 
the hearing will be August 19, 2024. On August 20, 2024,

[[Page 63861]]

the EPA will post a general agenda for the hearing that will list pre-
registered speakers in approximate order at https://www.epa.gov/mo/air-missouri. If you require the services of a translator or a special 
accommodation such as audio description/closed captioning, please pre-
register for the hearing and describe your needs by August 13, 2024.
    For more information on the virtual public hearing, see 
SUPPLEMENTARY INFORMATION.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R07-
OAR-2021-0851, to the Federal Rulemaking Portal: https://www.regulations.gov. Follow the online instructions for submitting 
comments. Once submitted, comments cannot be edited or removed from 
https://www.regulations.gov. The EPA may publish any comment received 
to its public docket. Do not submit electronically any information you 
consider to be Confidential Business Information (CBI) or other 
information whose disclosure is restricted by statute. Multimedia 
submissions (audio, video, etc.) must be accompanied by a written 
comment. The written comment is considered the official comment and 
should include discussion of all points you wish to make. The EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e., on the web, cloud, or other file sharing 
system). For additional submission methods, the full EPA public comment 
policy, information about CBI or multimedia submissions, and general 
guidance on making effective comments, please visit https://www2.epa.gov/dockets/commenting-epa-dockets.
    Docket: There are two dockets supporting this action, EPA-R07-OAR-
2021-0851 and EPA-HQ-OAR-2021-0663. EPA-R07-OAR-2021-0851 contains 
information specific to Missouri, including the notice of proposed 
rulemaking. Docket ID No. EPA-HQ-OAR-2021-0663 contains additional 
modeling files, emissions inventory files, technical support documents, 
and other relevant supporting documentation regarding interstate 
transport of emissions for the 2015 ozone NAAQS that are being used to 
support this action. All comments regarding information in either of 
these dockets are to be made in Docket ID No. EPA-R07-OAR-2021-0851. 
All documents in the docket are listed in the https://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available electronically in 
https://www.regulations.gov.
    To pre-register to attend or speak at the virtual public hearing, 
please use the online registration form available at https://www.epa.gov/mo/air-missouri, or contact us via email at 
[email protected]. For more information on the virtual public 
hearing, see SUPPLEMENTARY INFORMATION.

FOR FURTHER INFORMATION CONTACT: William Stone, Environmental 
Protection Agency, Region 7 Office, Air Permitting and Planning Branch, 
11201 Renner Boulevard, Lenexa, Kansas 66219; telephone number: (913) 
551-7714; email address: [email protected].

SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,'' 
``us,'' or ``our'' is used, we mean the EPA.
    Virtual public hearing: The EPA is holding a virtual public hearing 
to provide interested parties the opportunity to present data, views, 
or arguments concerning the proposal. The EPA will hold a virtual 
public hearing to solicit comments on August 21, 2024.
    The hearing will convene at 9 a.m. Central Time (CT) and will 
conclude at 3 p.m. CT. The EPA may close a session 15 minutes after the 
last pre-registered speaker has testified if there are no additional 
speakers. The EPA will announce further details, including information 
on how to register for the virtual public hearing, on the virtual 
public hearing website at https://www.epa.gov/mo/air-missouri.
    The EPA will begin pre-registering speakers and attendees for the 
hearing upon publication of this document in the Federal Register. To 
pre-register to attend or speak at the virtual public hearing, please 
use the online registration form available at https://www.epa.gov/mo/air-missouri, or contact us via email at [email protected]. The 
last day to pre-register to speak at the hearing will be August 19, 
2024. On August 20, 2024, the EPA will post a general agenda for the 
hearing that will list pre-registered speakers in approximate order at 
https://www.epa.gov/mo/air-missouri. Additionally, requests to speak 
will be taken on the day of the hearing as time allows.
    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 
hearing to run either ahead of schedule or behind schedule. Each 
commenter will have approximately 3 to 5 minutes to provide oral 
testimony. The EPA encourages commenters to provide the EPA with a copy 
of their oral testimony electronically by including it in the 
registration form or emailing it to [email protected]. 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 virtual public hearing. A transcript of 
the virtual public hearing, as well as copies of oral presentations 
submitted to the EPA, will be included in the docket for this action.
    The EPA is asking all hearing attendees to pre-register, even those 
who do not intend to speak. The EPA will send information on how to 
join the public hearing to pre-registered attendees and speakers. 
Please note that any updates made to any aspect of the hearing will be 
posted online at https://www.epa.gov/mo/air-missouri. While the EPA 
expects the hearing to go forward as set forth above, please monitor 
our website or contact us via email at [email protected] to 
determine if there are any updates. The EPA does not intend to publish 
a document in the Federal Register announcing updates.
    If you require the services of a translator or a special 
accommodation such as audio description/closed captioning, please pre-
register for the hearing and describe your needs by August 13, 2024. 
The EPA may not be able to arrange accommodations without advance 
notice.
    Preamble glossary of terms and abbreviations: The following are 
abbreviations of terms used in the preamble.

$/ppb Dollar-per-ppb
2016v1 2016-Based Emissions Modeling Platform Version 1
2016v2 2016-Based Emissions Modeling Platform Version 2
2016v3 2016-Based Emissions Modeling Platform Version 3
AQAT Air Quality Analysis Tool
CAA Clean Air Act
CAIR Clean Air Interstate Rule
CBI Confidential Business Information
CSAPR Cross State Air Pollution Rule
DV Design Value
EGU Electric Generating Unit
EPA Environmental Protection Agency
FIP Federal Implementation Plan
LADCO Lake Michigan Air Directors Consortium
LMOS Lake Michigan Ozone Study

[[Page 63862]]

MDA8 Maximum Daily Average 8-Hour
MoDNR Missouri Department of Natural Resources
MOVES3 Motor Vehicle Emission Simulator Version 3
MJO Multi-Jurisdictional Organization
NAAQS National Ambient Air Quality Standards
NOX Nitrogen Oxides
Non-EGU Non-Electric Generating Unit
NODA Notice of Data Availability
ppb Parts per Billion
ppm Parts per Million
RTC Response to Comments
SCR Selective Catalytic Reduction
SIP State Implementation Plan
SNCR Selective Non-Catalytic Reduction
SOA CC State of the Art Combustion Controls
SSM Startup, Shutdown, and Malfunction
TSD Technical Support Document

Table of Contents

I. Background
    A. Executive Summary
    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 SIPs 
for the 2015 Ozone NAAQS
    1. Selection of the Analytic Year
    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
II. Missouri SIP Submission Addressing Interstate Transport of Air 
Pollution for the 2015 Ozone NAAQS
    A. Prior Submission
    B. Summary of Missouri's 2015 Ozone Interstate Transport SIP 
Submission From November 2022
    1. Information Provided at Steps 1 and 2
    2. Information Provided at Step 3
    3. Information Provided at Step 4
III. The EPA's Evaluation of Missouri's November 2022 Submission
    A. Evaluation of Information Provided by Missouri Regarding 
Steps 1 and 2
    B. Results of the EPA's Step 1 and Step 2 Modeling and Findings 
for Missouri
    C. Evaluation of Information Provided by Missouri Regarding Step 
3
    1. Evaluation of Potential Level of Emissions Controls on 
Missouri EGUs
    2. Evaluation of Projected NOX Reductions on Downwind 
Linked Receptors
    3. Evaluation of MoDNR's Use of a ``Dollar-per-ppb'' Metric
    4. Evaluation of Conclusions Regarding Potential Controls for 
Non-EGUs
    D. Evaluation of Information Provided by Missouri Regarding Step 
4
    1. Evaluation of the Consent Agreements
    2. Evaluation of Approach of Regulating Named Sources
IV. Proposed Action
V. Statutory and Executive Order Reviews

I. Background

    On October 1, 2015, the EPA promulgated a revision to the 2015 
ozone NAAQS, lowering the level of both the primary and secondary 
standards to 0.070 parts per million (ppm) for the 8-hour standard.\1\ 
Section 110(a)(1) of the CAA requires States to submit, within three 
years after promulgation of a new or revised standard, SIP submissions 
meeting the applicable requirements of section 110(a)(2).\2\ One of 
these applicable requirements is found in CAA section 
110(a)(2)(D)(i)(I), otherwise known as the ``interstate transport'' or 
``good neighbor'' provision, which generally requires SIPs to 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).\3\
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    \1\ 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 parts per billion (ppb). For example, 0.070 ppm is 
equivalent to 70 ppb.
    \2\ SIP revisions that are intended to meet the applicable 
requirements of section 110(a)(1) and (2) of the CAA are often 
referred to as infrastructure SIPs and the applicable elements under 
section 110(a)(2) are referred to as infrastructure requirements.
    \3\ See North Carolina v. EPA, 531 F.3d 896, 909-11 (D.C. Cir. 
2008).
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A. Executive Summary

    In this notice of proposed rulemaking, the EPA is providing an 
opportunity for public comment on its proposed conclusion that the 
November 1, 2022 SIP submission (hereafter November 2022 Submission or 
Submission) from Missouri does not contain the necessary provisions to 
prohibit emissions from sources within the State from significantly 
contributing to nonattainment or interfering with maintenance of the 
2015 ozone NAAQS in downwind areas as required by the CAA. The EPA is 
proposing to disapprove the November 2022 Submission as to both Prong 1 
and 2 of CAA section 110(a)(2)(D)(i)(I) as insufficient on the basis 
that it fails to adequately support its determination of Missouri's 
good neighbor obligations for the 2015 ozone NAAQS.
    Previously, the EPA disapproved a prior submission provided by the 
Missouri Department of Natural Resources (MoDNR) to address these 
obligations. See 88 FR 9336 (February 13, 2023). Following the EPA's 
proposal to disapprove that submission and proposal for a Federal 
implementation plan (the proposed Good Neighbor Plan), signed and made 
public in February and March of 2022, respectively, the MoDNR developed 
this new Submission. Following review of a draft version of the 
submission, the EPA advised the MoDNR by letter in fall of 2022 
regarding a number of concerns with respect to its approvability. The 
MoDNR made several adjustments purporting to address the EPA's comments 
and submitted the Submission as a SIP revision on November 1, 2022, 
several months after the close of the comment periods on the proposal 
to disapprove the prior submission and the proposed Good Neighbor Plan.
    To evaluate this Submission, the EPA applied its longstanding 
approach to evaluating good neighbor obligations, the 4-step interstate 
transport framework (further detailed in section I.D. of this document) 
that the MoDNR itself used to organize its Submission. The MoDNR 
specifically worked from the EPA's proposed determinations regarding 
these obligations by applying the 4-step framework as set forth in the 
proposed Good Neighbor Plan, 87 FR 20036 (April 6, 2022), while 
presenting a series of arguments in support of a less stringent set of 
obligations.
    The EPA proposes to find that the MoDNR's November 2022 Submission 
fails to provide an adequate technical and legal basis to demonstrate 
that Missouri's good neighbor obligations are adequately addressed, and 
it unreasonably concludes that only emissions improvements relying on 
existing control installations at certain identified power plants in 
the State (which are not, in fact, permanent or enforceable 
prohibitions, as explained in section III.D.) are sufficient to 
prohibit Missouri's significant contribution for the 2015 ozone NAAQS. 
The evidence indicates that additional, cost-effective emissions 
control opportunities are available across a number of Missouri's large 
emissions sources and that the MoDNR has not conducted a sufficient 
review of those emissions control opportunities or

[[Page 63863]]

its broader source inventory. See section III.C of this document.
    The EPA would reach these conclusions regarding this Submission 
even in the absence of the Good Neighbor Plan; however, the record 
evidence that the EPA has developed in the course of developing the 
Good Neighbor Plan provides important information that assists in the 
evaluation of this Submission. The EPA always strongly encourages 
States to develop SIP revisions that can replace or forestall the need 
for FIPs. The EPA explained in the proposed Good Neighbor Plan that 
States remain free to develop SIP submissions, and consistent with 
prior good neighbor rulemakings such as the Clean Air Interstate Rule 
(CAIR) and the Cross-State Air Pollution Rule (CSAPR), the EPA provided 
States as much information as the Agency could supply at that time to 
support the ability of States to submit SIP revisions to achieve the 
emissions reductions that the EPA believed necessary to eliminate 
significant contribution. Id. at 20040. That proposal could not 
definitively establish or prejudge the necessary components of an 
approvable SIP; however, the EPA's discussion there provided notice to 
Missouri and other States of the EPA's own evidence concerning good 
neighbor impacts and available controls, and, therefore, the EPA's 
expected process for reviewing SIPs in light of that evidence. The 
MoDNR had that information available, and indeed worked from it, at the 
time it developed the Submission here.
    Specifically, in the proposed Good Neighbor Plan, the EPA explained 
that States may select emissions reductions strategies that differ from 
the emissions controls included in the proposed FIP. The EPA went on to 
state that for a State to remove all FIP provisions through an approved 
SIP revision, a State would need to address all of the required 
reductions determined through the EPA's own review of the evidence and 
addressed by the FIP for that State, though the States could go about 
achieving those reductions differently. Id. at 20149. The EPA also 
stated in the proposal that if States were to regulate their Electric 
Generating Units (EGUs), in the case of SIP submissions not adopting 
the EGU trading program, the EPA would evaluate such a transport SIP 
based on the particular control strategies selected and whether the 
strategies as a whole provide adequate and enforceable provisions 
ensuring that the identified emissions reductions (i.e., reductions 
equal to or greater than what the Group 3 trading program will achieve) 
will be achieved. Id. at 20151. Similarly, for non-Electric Generating 
Units (non-EGUs), the EPA stated that a State's SIP submission must 
provide adequate provisions to prohibit an equivalent or greater amount 
of nitrogen oxide (NOX) emissions that contribute 
significantly to nonattainment or interfere with maintenance of the 
2015 ozone NAAQS in any other State. Id.\4\
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    \4\ The EPA clarifies that this language was not intended to 
suggest that states must regulate EGUs, or the same non-EGU 
industries identified in the Good Neighbor Plan. Because 
``significant contribution'' is ultimately defined at the state 
level, a state may choose to regulate entirely different categories 
of sources from a transport FIP so long as the amount of emissions 
that constitutes ``significant contribution'' is prohibited.
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    The final Good Neighbor Plan signed on March 15, 2023, contained a 
discussion on SIP submissions similar to the proposal's discussion, 
which expanded on and clarified certain points in response to comments. 
There, the EPA reiterated that States remain free to adopt alternative 
approaches to addressing their significant contribution that differ 
from the FIP promulgated for that State. However, the EPA stated that, 
given the Agency's own extensive analysis, it did not anticipate 
revisiting its findings at Steps 1 or 2 of the transport framework. See 
88 FR 36839. Further, the EPA explained that the level of reductions 
required by the FIP provides an ``important benchmark'' for States in 
evaluating possible replacement SIPs, and that we generally anticipated 
that a SIP seeking an alternative approach to eliminating its 
significant contributions would need to establish an equivalent level 
of emissions reductions to what the FIP requires at Step 3, and any 
such replacement SIP will need to comply with CAA section 110(l). Id.
    The EPA recognizes that the MoDNR made this submission in November 
of 2022, several months after the proposed Good Neighbor Plan was 
published, and before the final Good Neighbor Plan was issued on March 
15, 2023. The information provided to States regarding what the EPA 
anticipated would likely be needed to develop a SIP that satisfies the 
2015 ozone NAAQS good neighbor obligations stated in the proposal was 
nonetheless available for the MoDNR to consider in developing this 
submission. This guidance was also consistent with the EPA's stated 
policies on approvable good neighbor SIPs across many prior transport 
rulemakings going back at least to the Clean Air Interstate Rule (CAIR) 
in 2005. See, e.g., 87 FR 55692, 55693 (September 12, 2022); 86 FR 
60602, 60607-08, 60610-11 (November 3, 2021); 86 FR 23054, 23147-48 
(April 30, 2021); 81 FR 74504, 74569 (October 26, 2016); 76 FR 48208, 
48326-28 (August 8, 2011); 70 FR 25162, 25259-62 (May 12, 2005).
    As each of these prior notices make clear, when the EPA is 
evaluating and acting on SIP submissions following the promulgation of 
a final transport FIP, the EPA has recognized that the FIP can serve an 
important purpose in helping the EPA to evaluate the sufficiency of a 
SIP submission (even when the SIPs were submitted prior to the final 
FIP). However, the EPA will always carefully evaluate any alternative 
information or arguments a State puts forward in support of a different 
understanding of their good neighbor obligations. Thus, in disapproving 
SIP submissions from New York and New Jersey regarding good neighbor 
obligations for the 2008 ozone NAAQS, following the promulgation of the 
Revised CSAPR Update (which had been submitted prior to that rule even 
being proposed), the EPA explained that neither State had provided ``a 
sufficient demonstration'' that the permanent and enforceable measures 
adopted into the States' SIPs prohibited ``significant contribution'' 
in the manner that had been determined in the Revised CSAPR Update, nor 
``provided an alternative method for doing so.'' 86 FR 60607-08, 60610-
11.
    Similarly here, while the MoDNR has not followed the approach of 
adopting emissions control measures that are either identical or 
equivalent to the proposed (or final) Good Neighbor Plan, the EPA 
continues to recognize that States may submit an alternative approach 
to meeting their good neighbor obligations, and the EPA will approve 
such submissions as compliant with the Act's requirements assuming the 
State has set forth a technically and legally justifiable approach. 
Consistent with the EPA's approach as discussed in prior rulemakings, 
the EPA will evaluate such SIP submissions on a case-by-case basis. In 
the original CSAPR rulemaking, the EPA explained that where States do 
not adopt the specific control requirements of a Good Neighbor FIP, 
they still must ``provide adequate provisions to prohibit . . . 
emissions that are determined in the Transport Rule to contribute 
significantly to nonattainment or interfere with maintenance in another 
State or States. EPA will review such a SIP on a case-by-case basis.'' 
See, e.g., 76 FR 48328. In the final Good Neighbor Plan, the EPA 
explained that although there is not a fixed, mass-based emissions 
budget established for each State in that action, there are other 
objective metrics that can guide States in developing SIPs. See 88 FR 
36842. While the State need not conduct its analysis or select 
emissions

[[Page 63864]]

control strategies in a manner identical to the EPA's approach, the end 
result must nonetheless be adequate to prohibit emissions that 
significantly contribute to nonattainment and interfere with 
maintenance.
    Further, among the factors the EPA stated in 2018 that it would 
consider in evaluating alternative approaches is whether consistency in 
obligations is maintained among States given the ``collective 
contribution'' nature of the interstate ozone pollution problem. In a 
list of ``guiding principles'' that the EPA identified for States to 
consider in an appendix to the modeling memorandum issued in March 2018 
(see note 14 infra), the EPA noted that consistency among States is ``a 
particularly acute issue with respect to regional transport issues in 
which multiple States may be implicated.'' In addition, the EPA 
encouraged ``collaboration among States linked to a common receptor and 
among linked upwind and downwind States in developing and applying a 
regionally consistent approach to identify and implement good neighbor 
obligations.''
    The MoDNR's submission does not reflect any evident collaboration 
with other States with whom it shares linked receptors, nor with the 
States in which those receptors are located. The approach the MoDNR set 
forward in its November 2022 submission would not achieve emissions 
reductions (or downwind air quality improvements) that are comparable 
to those the EPA found warranted to address Missouri's good neighbor 
obligations for the 2015 ozone NAAQS or those of the other States with 
which Missouri shares common receptor linkages. Nonetheless, the EPA is 
not proposing to disapprove this Submission simply due to a lack of 
equivalency with the Good Neighbor Plan. In this proposal, the EPA sets 
forth a thorough evaluation of all aspects of the MoDNR's November 2022 
Submission to determine whether its analytic conclusions and regulatory 
approach could be technically or legally justified.
    The MoDNR's Submission would, if approved, require a minimum level 
of emissions control performance from certain named EGUs based on the 
existing NOX-control technologies installed at those units. 
This bears some similarity to the near-term emissions control 
strategies that the EPA found appropriate for EGUs in the Good Neighbor 
Plan for States linked in the 2023 analytic year. However, the EPA has 
found that the MoDNR's approach achieves fewer emissions reductions 
than the EPA has found could be cost-effectively achieved in the near 
term at EGUs in the State, the foregone emissions reductions are not 
achieved through any other means, and the MoDNR has not justified this 
alternative level of stringency with respect to these strategies.
    Further, even though Missouri remains linked to at least one 
receptor through the 2026 analytic year in the modeling it relies on in 
its Submission (notwithstanding the MoDNR's arguments that no such 
linkages exist in 2026, which the EPA is proposing to disapprove), the 
MoDNR has not imposed any additional emissions control strategies on 
its sources that could be implemented by that year. The MoDNR instead 
argues, using a ``dollar-per-ppb'' metric, that such reductions are not 
needed from its sources because they would not be cost-effective. 
However, setting aside a number of analytic challenges associated with 
using such a metric, Missouri did not consistently apply this metric 
within its own Submission nor demonstrate how this metric would apply 
across other linked upwind States so as to provide an equitable, 
workable, or consistent standard for defining significant contribution.
    The MoDNR further argues that several particular named non-EGU 
sources in Missouri are already achieving a level of emissions control 
equivalent to what was proposed for these source types in the proposed 
Good Neighbor Plan. However, the MoDNR limited its analysis to the 
provisional list of sources in the proposed Good Neighbor Plan that the 
EPA was clear was not intended to be definitive, and the MoDNR 
conducted no comprehensive survey of the non-EGU industrial sources in 
Missouri. Despite using the proposed Good Neighbor Plan as its 
information source for identifying these potential emissions control 
requirements, the MoDNR did not establish that its non-EGU sources are 
controlled to a level equivalent to Missouri's Good Neighbor Plan FIP 
(either as finalized or proposed) or that its divergence from the EPA's 
conclusions was technically supported.
    Thus, the November 2022 Submission at times makes technically 
unsupported departures from the detailed, comprehensive analytical 
findings in the proposed Good Neighbor Plan (such as the EPA's 
evaluation of near-term emissions control strategies at EGUs), while at 
other times unreasonably limits its own analysis solely to the proposed 
Good Neighbor Plan in areas the EPA was clear were not intended to be 
definitive considering their analytical purpose (such as the non-EGU 
screening evaluation).
    Finally, the EPA has identified several reasons why the MoDNR's 
approach using certain ``Consent Agreements'' with particular named EGU 
sources is not approvable as the means for implementing those emissions 
control requirements that the MoDNR concedes would be appropriate to 
prohibit its significant contribution. Among other issues, these 
agreements are structured so that they are not yet in effect and will 
not take effect unless the EPA approves the Submission; however, if the 
EPA does not ``fully approve'' the Submission, then the covered sources 
can unilaterally withdraw from the Agreements. The Agreements 
additionally provide for their termination at any time by consent of 
the parties and include broad liability waivers. These provisions fail 
several important CAA requirements for SIPs, including that emissions 
reduction measures must be permanent and not subject to modification 
except through the prescribed processes in the Act.
    With this general overview of the MoDNR's Submission in mind, the 
EPA has identified the following specific aspects of the MoDNR's 
November 2022 Submission that are inadequate and therefore render the 
Submission not approvable under CAA section 110(k)(3), because they do 
not meet the requirements of the good neighbor provision for the 2015 
ozone NAAQS:
    The EPA is disapproving the November 2022 Submission as a whole 
because the Agency has not identified any method by which the 
Submission may be partially approved or approved on a limited or 
conditional basis. Here, we summarize these bases for disapproval, as 
guided by our 4-step interstate transport framework (the EPA further 
explains its framework in section I.D.). The EPA's full evaluation of 
the November 2022 SIP Submission can be found in section III. of this 
document.
    At Step 2, the EPA proposes to find that the MoDNR did not justify 
in the November 2022 Submission the use of a 1 ppb or 2 ppb 
contribution threshold for certain receptors to which it contributes in 
the 2016v2 modeling, and these same deficiencies in the MoDNR's 
analysis equally apply to the receptor linkages identified in the 
2016v3 modeling. The MoDNR therefore incorrectly concluded that 
Missouri is not linked (i.e., ``contributing'') to certain receptors in 
2023 and no longer linked to any receptors in 2026. (The EPA notes that 
identical arguments were addressed in the SIP Disapproval Action with 
respect to Missouri's first SIP submission and in the Good Neighbor 
Plan, and the EPA is not reopening

[[Page 63865]]

those determinations in this action.) The EPA is not disapproving the 
Submission for using the 2016v2 modeling; however, the EPA's analysis 
is informed by the 2016v3 modeling and the ``violating-monitor'' 
maintenance-receptor methodology, which reflects substantial public 
input obtained through the SIP Disapproval and Good Neighbor Plan 
rulemakings, improves upon the 2016v2 modeling, and substantiates that 
Missouri is linked to at least one receptor through the 2026 analytic 
year.
    At Step 3, the EPA proposes to find that the MoDNR conducted an 
inadequate analysis of its sources' emissions contribution to downwind 
receptors to determine what amount of those emissions ``significantly 
contribute to nonattainment'' or ``interfere with maintenance'' in the 
November 2022 Submission. The MoDNR purported to follow the multifactor 
Step 3 analysis in the proposed Good Neighbor Plan but then identified 
specific points where it reached alternative conclusions regarding its 
sources' emissions, thus resulting in the identification of a 
substantially smaller amount of emissions reduction than the EPA found 
necessary to eliminate significant contribution in the Good Neighbor 
Plan. These departures from the EPA's analysis are at odds with the 
data available to the EPA or are otherwise not adequately justified. 
The EPA's analysis confirms, consistent with the MoDNR's own 
methodology using the Air Quality Assessment Tool (AQAT), that the 
emissions reductions that would be achieved under the November 2022 
Submission produce measurably less improvement in ozone levels at the 
downwind receptors to which Missouri is linked than the Good Neighbor 
Plan.
    With respect to EGUs, the EPA finds that the MoDNR did not 
adequately explain why additional, near-term, cost-effective emissions 
reductions were not being required of its EGU sources. Further, the 
MoDNR did not adequately analyze further emissions control 
opportunities at its EGU sources or establish why these were not cost-
effective. The MoDNR's use of a ``dollar-per-ppb'' metric to dismiss 
further emissions reductions from both EGUs and non-EGUs as not cost-
effective was not adequately explained and rested on unsubstantiated 
assertions regarding emissions-control costs and downwind changes in 
ozone levels. In addition, this metric was applied inconsistently to 
sources within the State and was not coordinated with the obligations 
of States that share common receptor linkages with Missouri. The 
MoDNR's additional analysis of its non-EGU sources was not based on a 
comprehensive inventory of industrial sources in the State but rather 
drew from a list of tentatively identified facilities from the EPA's 
proposed Good Neighbor Plan that the EPA was clear was not intended to 
be definitive. (The Good Neighbor Plan establishes applicability 
criteria to define source coverage rather than identifying each covered 
source by name; it also covers new in addition to existing units 
meeting those applicability criteria. See 88 FR 36685.) The MoDNR 
failed to examine whether there was cost-effective emissions control 
potential across the State's inventory of large non-EGU NOX-
emitting sources.
    At Step 4, the EPA proposes that even as to those emissions 
reductions the MoDNR's November 2022 Submission purports to require, it 
is inadequate to meet good neighbor requirements for the 2015 ozone 
NAAQS and other requirements of the Act. First, the Consent Agreements 
with certain named EGUs are not an acceptable method for implementing 
the emissions control strategies the MoDNR identified, because these 
agreements are not in effect, the trigger by which they could come into 
effect is not appropriate and inconsistent with the timing requirements 
of the good neighbor provision, and their terms allow for modification 
or withdrawal of requirements through processes that conflict with 
several bedrock CAA requirements regarding SIP revisions. Second, the 
MoDNR's approach of regulating only certain named existing EGU sources, 
rather than regulating both existing and new sources on industry-wide 
bases, fails to analyze or address the potential for production and 
emissions shifting among sources, which the EPA has consistently 
identified is an important consideration in developing emissions 
control strategies to address transport obligations. See, e.g., 70 FR 
25261 (May 12, 2005).
    Taken together, the deficiencies identified in this summary and 
further detailed in section III. lead the EPA to propose to conclude it 
cannot approve the MoDNR's November 2022 Submission as meeting the 
requirements of the good neighbor provision for the 2015 ozone NAAQS. 
The EPA is ready to work with the MoDNR and the State of Missouri and 
any other state to develop an approvable SIP submission to meet these 
requirements.

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

    For decades, when evaluating SIPs and formulating FIPs, the 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,\5\ and the CSAPR Update \6\ and 
the Revised CSAPR Update,\7\ both of which addressed the 2008 ozone 
NAAQS.\8\ The EPA is using the 4-step framework to organize its 
evaluation of the MoDNR Air Pollution Control Program November 1, 2022, 
interstate transport SIP submission for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \5\ Federal Implementation Plans: Interstate Transport of Fine 
Particulate Matter and Ozone and Correction of SIP Approvals, 76 FR 
48208 (August 8, 2011).
    \6\ Cross-State Air Pollution Rule Update for the 2008 Ozone 
NAAQS, 81 FR 74504 (October 26, 2016).
    \7\ Revised Cross-State Air Pollution Rule Update for the 2008 
Ozone NAAQS, 86 FR 23054 (April 30, 2021).
    \8\ 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 
v. 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 v. EPA, 781 F. App'x. 4 (D.C. Cir. 2019). The 
Revised CSAPR Update was upheld in Midwest Ozone Group v. EPA, 61 
F.4th 187 (D.C. Cir. 2023).
---------------------------------------------------------------------------

    Shaped through the years by input from State air agencies \9\ and 
other stakeholders on the EPA's prior interstate transport rulemakings 
and SIP actions,\10\ as well as a number of court decisions, the EPA 
has developed and used the 4-step interstate transport framework to 
evaluate a State's obligations to eliminate interstate transport 
emissions under the interstate transport provision for the ozone

[[Page 63866]]

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 ``linked'' and 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. The 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 v. EME Homer City 
Generation, L.P., 572 U.S. 489, 524 (2014).
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    \9\ See 63 FR 57356, 57361 (October 27, 1998).
    \10\ In addition to CSAPR rulemakings, other regional 
rulemakings addressing ozone transport include the ``NOX 
SIP Call,'' 63 FR 57356 (October 27, 1998), and the ``Clean Air 
Interstate Rule'' (CAIR), 70 FR 25162 (May 12, 2005).
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C. The EPA's Ozone Transport Modeling

    In general, the EPA has performed nationwide air quality modeling 
to project ozone design values (DV), which 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 ozone design values for the identified downwind 
nonattainment and maintenance receptors at Step 2, the EPA has 
performed multiple iterations of nationwide, State-level ozone source 
apportionment modeling for 2023. The source apportionment modeling 
projected contributions to ozone at receptors from precursor emissions 
of anthropogenic NOX and volatile organic compounds (VOCs) 
in individual upwind States.
    The EPA has 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.\11\ 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 ozone NAAQS.\12\ 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 (RTC) 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.\13\ 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.\14\ 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 ozone NAAQS under Step 2 of the 4-step interstate 
transport framework.\15\ The EPA notes that the MoDNR relied upon 2023 
modeling contribution data released with the March 2018 memorandum in 
developing its 2019 SIP submission. 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.\16\
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    \11\ 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).
    \12\ 82 FR 1735 (January 6, 2017).
    \13\ 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 (October 2017 memorandum), 
available in Docket ID No. EPA-HQ-OAR-2021-0663.
    \14\ 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.
    \15\ 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.''
    \16\ 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.
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    Following the release of the modeling data shared in the March 2018 
memorandum, the EPA performed updated modeling using a 2016-based 
emissions modeling platform (i.e., 2016v1). This emissions platform was 
developed under the EPA/Multi-Jurisdictional Organization (MJO)/State 
collaborative project.\17\ 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.\18\ 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.\19\
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    \17\ 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, and is 
included in this docket, Docket ID No. EPA-R07-2021-OAR-0851. Both 
dockets are available at https://www.regulations.gov.
    \18\ See 85 FR 68964, 68981.
    \19\ 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.
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    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 (MOVES3) model \20\ and updated

[[Page 63867]]

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.\21\ The 
construct of the updated emissions platform, 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 ID 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 as part of our previous 
proposed evaluation of the MoDNR's interstate transport SIP submission 
for the 2015 ozone NAAQS, submitted on June 10, 2019, with respect to 
Steps 1 and 2 of the 4-step interstate transport framework. See 87 FR 
9533 (February 22, 2022).
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    \20\ 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.
    \21\ https://www.epa.gov/air-emissions-modeling/2016v2-platform.
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    The EPA invited and received comments on the 2016v2 emissions 
inventories and modeling used to support proposals, including the 
proposal on Missouri, related to interstate transport under the 2015 
ozone NAAQS. In response to these comments, the EPA made a number of 
updates to the 2016v2 inventories and model design to construct a 
2016v3 emissions platform that 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, which included the MoDNR's June 
2019 Submission, as well as a Federal implementation plan action 
covering 23 States, including Missouri.\22\ 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 (AQM) Final Rule TSD--2015 Ozone NAAQS 
Good Neighbor Plan,'' hereafter known as the Final Good Neighbor Plan 
AQM TSD.\23\ Additional details related to the updated 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.\24\
---------------------------------------------------------------------------

    \22\ ``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).
    \23\ ``Air Quality Modeling Final Rule Technical Support 
Document--2015 Ozone NAAQS Good Neighbor Plan'' in Docket ID No. 
EPA-R08-OAR-2023-0375, and included in this docket, Docket ID No. 
EPA-R07-OAR-2021-0851.
    \24\ ``2016v3 Emissions Modeling TSD'' in Docket ID No. EPA-HQ-
OAR-2021-0668, and included in this docket, Docket ID No. EPA-R07-
OAR-2021-0851.
---------------------------------------------------------------------------

    In this proposed action, the EPA primarily relies on modeling based 
on the updated 2016v3 emissions platform in evaluating the MoDNR's 
November 2022 Submission with respect to 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 I.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.
    Nonetheless, we note that the basis for the EPA's disapproval of 
the November 2022 Submission is not affected by the choice of modeling 
between the 2016v3 modeling or the 2016v2 modeling on which the MoDNR 
based its Submission. Both sets of modeling demonstrated linkages 
between Missouri and multiple receptors above both a 1 percent of the 
NAAQS and a 1 ppb contribution threshold. The EPA does not propose to 
disapprove the MoDNR's Submission due to its choice of modeling, but 
for failing to adequately analyze and prohibit those emissions that 
constitute ``significant contribution'' to nonattainment or maintenance 
receptors in other States.
    By this action, the EPA is not reopening the determinations made 
for Missouri in the Good Neighbor Plan regarding the definition of good 
neighbor obligations through the EPA's exercise of statutory 
responsibility under CAA section 110(c). Rather, this action is taken 
pursuant to the EPA's statutory responsibility to act on SIP 
submissions pursuant to CAA section 110(k). Any comments that are not 
relevant to the EPA's proposed basis for the disapproval of Missouri's 
November 2022 Submission will be treated as beyond the scope of this 
action.

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

    The EPA proposes to apply 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). 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 involving many smaller contributors. 
Effective policy solutions to the problem of interstate ozone transport 
going back to the NOX 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 
v. EPA, 572 U.S. 489, 519 (2014). The EPA evaluates any State's 
arguments for the use of alternative approaches or alternative sets of 
data with an eye to ensuring national consistency and avoiding 
inconsistent or inequitable results among upwind States and between 
upwind and downwind States.
    The remainder of this section describes the EPA's analytic 
framework with respect to analytic year, definition of nonattainment 
and maintenance receptors, selection of contribution threshold, and 
multifactor control strategy assessment.
1. Selection of Analytic Year
    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 Good 
Neighbor Plan, to ensure consistency and equitable treatment of all 
States. In the 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 \25\

[[Page 63868]]

before the Moderate and Serious area attainment dates for the 2015 
ozone NAAQS, which are August 3, 2024, and August 3, 2027.\26\ 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 Good Neighbor Plan, 
consistent with each of its prior good neighbor rulemakings, the EPA 
focused its analysis in the years with the last full ozone seasons 
before the attainment dates (i.e., 2023 and 2026).
---------------------------------------------------------------------------

    \25\ Ozone seasons run each year from May 1-September 30, see 40 
CFR 52.38(b)(1) and 52.40(c)(1).
    \26\ CAA section 181(a); 40 CFR 51.1303; 83 FR 25776 (June 4, 
2018, effective Aug. 3, 2018).
---------------------------------------------------------------------------

    Here, the MoDNR used the 2023 and 2026 analytic years in its 
Submission, and both the modeling it considered (2016v2) and the 
additional modeling the EPA took into account (2016v3) used those 
analytic years. Because both sets of modeling show that Missouri 
remains linked, the basis for the EPA's action in this case is not in 
relation to the acceptability of the air quality modeling or analysis 
the MoDNR used at Steps 1 and 2, but rather in relation to our findings 
that the State's approach to defining ``significant contribution'' is 
inadequate. Further, use of the 2023 and 2026 analytic years ensures 
consistency in the treatment of 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 prior datasets to ensure consistency in treatment. See Bd. 
County Commissioners of Weld County v. 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 the 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 rulemaking is, in the EPA's judgment, sufficiently 
compelling to justify this approach here.
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 9341-42 
(February 13, 2023). 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.
    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.\27\ To summarize this 
methodology:
---------------------------------------------------------------------------

    \27\ See North Carolina v. 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 areas that both currently measure 
nonattainment and that the EPA projects will be in nonattainment in the 
analytic year (i.e., 2023).\28\
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    \28\ 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 25241, 
25249 (January 14, 2005); see also North Carolina, 531 F.3d at 913-
14 (affirming as reasonable the EPA's approach to defining 
nonattainment in CAIR).
---------------------------------------------------------------------------

    In addition, the EPA identified a receptor to be a ``maintenance'' 
receptor for purposes of defining interference with maintenance, 
consistent with the method used in the CSAPR and upheld by the D.C. 
Circuit in EME Homer City Generation, L.P. v. EPA, 795 F.3d 118, 136 
(D.C. Cir. 2015) (EME Homer City II).\29\ Specifically, the EPA 
identified maintenance receptors as those receptors that would have 
difficulty maintaining the relevant NAAQS in a scenario that takes into 
account historical variability in air quality at that receptor. The 
variability in air quality was determined by evaluating the ``maximum'' 
future design value at each receptor based on a projection of the 
maximum measured design value over the relevant period. The EPA 
interprets the projected maximum future design value to be a potential 
future air quality outcome consistent with the meteorology that yielded 
maximum measured concentrations in the ambient data set analyzed for 
that receptor (i.e., ozone conducive meteorology). The EPA also 
recognizes that previously experienced meteorological conditions (e.g., 
dominant wind direction, temperatures, and air mass patterns) promoting 
ozone formation that led to maximum concentrations in the measured data 
may reoccur in the future. The maximum design value gives a reasonable 
projection of future air quality at the receptor under a scenario in 
which such conditions do, in fact, reoccur. The projected maximum 
design value is used to identify upwind emissions that, under those 
circumstances, could interfere with the downwind area's ability to 
maintain the NAAQS.
---------------------------------------------------------------------------

    \29\ See 76 FR 48208 (August 8, 2011). CSAPR Update and Revised 
CSAPR Update also used this approach. See 81 FR 74504 (October 26, 
2016) and 86 FR 23054 (April 30, 2021).
---------------------------------------------------------------------------

    Nonattainment receptors are also, by definition, maintenance 
receptors, and so the EPA often uses the term ``maintenance-only'' to 
refer to those receptors that are not nonattainment receptors. 
Consistent with the concepts for maintenance receptors, as described 
earlier, the EPA identifies ``maintenance-only'' receptors as those 
monitoring sites that have projected average design values above the 
level of the applicable NAAQS, but that are not currently measuring 
nonattainment based on the most recent official design values.\30\ In 
addition, those monitoring sites with projected average design values 
below the NAAQS, but with projected maximum design values above the 
NAAQS are also identified as ``maintenance-only'' receptors, even if 
they are currently measuring nonattainment based on the most recent 
official design values.
---------------------------------------------------------------------------

    \30\ The Agency often uses the terms maintenance receptor and 
maintenance-only receptor interchangeably when discussing 
maintenance receptors that are not also nonattainment receptors.
---------------------------------------------------------------------------

    The Agency has looked closely at measured ozone levels at ambient 
monitoring sites in 2021 and 2022 for the purposes of informing the 
identification of potential additional receptors in 2023. As explained 
in more detail in the February 13, 2022, final action disapproving 19 
States' good neighbor SIP submissions, and partially approving and 
partially disapproving

[[Page 63869]]

two States' good neighbor SIP submissions (Disapproval Action), see 88 
FR 9349-50, the EPA finds there is a basis to consider certain sites 
with elevated ozone levels that are not otherwise identified as 
receptors to be an additional type of maintenance-only receptor given 
the likelihood that ozone levels above the NAAQS could persist at those 
locations through at least 2023. These are referred to as violating-
monitor maintenance-only receptors (violating-monitor receptors). In 
this action, the EPA proposes to use certified ambient monitoring data 
as an additional method to identify maintenance-only receptors. More 
specifically, violating-monitor receptors are monitoring sites with 
measured 2021 and 2022 design values and 2021 and 2022 fourth-highest 
(4th high) maximum daily average 8-hour (MDA8) ozone concentrations 
that exceed the NAAQS, despite having model-projected average and 
maximum design values for 2023 below the NAAQS.\31\ The EPA finds these 
sites are at continuing risk of failing to maintain the 2015 ozone 
NAAQS, which justifies categorizing these sites as maintenance-only 
receptors. By applying the criteria that certified 2021 and 2022 design 
values and 2021 and 2022 4th high MDA8 ozone concentrations must all 
exceed the NAAQS the EPA gives due consideration to both measured air 
quality data and its modeling projections. This reasonably identifies 
monitoring sites as receptors in 2023 using this methodology. If sites 
do not meet these criteria, then the EPA could reasonably anticipate 
these sites to not have a problem maintaining the 2015 ozone NAAQS in 
2023 and should therefore not be considered receptors.
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    \31\ A design value is calculated using the annual 4th high MDA8 
ozone concentration averaged over 3 years.
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3. Step 2 of the 4-Step Interstate Transport Framework
    In Step 2, the EPA quantifies the contribution of each upwind State 
to each receptor in the 2023 analytic year. The contribution metric 
used in Step 2 is defined as the average impact from each State to each 
receptor on the days with the highest ozone concentrations at the 
receptor based on the 2023 modeling. If a State's contribution value 
does not equal or exceed the threshold of 1 percent of the NAAQS (i.e., 
0.70 parts per billion (ppb) for the 2015 ozone NAAQS), the upwind 
State is not ``linked'' to a downwind air quality problem, and the EPA 
therefore concludes that the State does not contribute significantly to 
nonattainment or interfere with maintenance of the NAAQS in the 
downwind States. However, if a State's contribution equals or exceeds 
the 1 percent threshold, the State's emissions are further evaluated in 
Step 3, considering both air quality and cost as part of a multi-factor 
analysis, to determine what, if any, emissions might be deemed 
``significant'' and, thus, must be eliminated pursuant to the 
requirements of CAA section 110(a)(2)(D)(i)(I).
    In this proposed action, the EPA relies in the first instance on 
the 1 percent threshold for the purpose of evaluating a State's 
contribution to nonattainment or maintenance of the 2015 ozone NAAQS 
(i.e., 0.70 ppb) at downwind receptors. This is consistent with the 
Step 2 approach that the EPA applied in the Disapproval Action and in 
the Good Neighbor Plan. The EPA has acknowledged that States may be 
able to justify use of a different threshold at Step 2. For reasons 
explained in section III.A. of this document, the MoDNR did not 
successfully make this demonstration. In addition, the EPA explained in 
both the proposed and final Disapproval Action and Good Neighbor Plan 
that the need for consistent treatment of all States counsels against 
recognizing alternative thresholds on a state-by-state basis absent an 
adequate circumstance-specific justification. See 88 FR 9373-75. 
Likewise, maintaining continuity across ozone NAAQS through consistent 
application of a 1 percent of NAAQS threshold at Step 2 is appropriate, 
so that, as the NAAQS is revised and made more protective, the 
contribution threshold is correspondingly adjusted as well. See 88 FR 
36712-17; 88 FR 9371-75. See also 86 FR 23085 (use of 1 percent 
threshold in the Revised CSAPR Update); 81 FR 74518 (basis for use of 1 
percent threshold for the 2008 ozone NAAQS in the CSAPR Update); 76 FR 
48237-38 (original determination to use 1 percent threshold for the 
1997 ozone NAAQS in the CSAPR).
    Therefore, application of a consistent contribution threshold is 
necessary 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 EPA addresses the MoDNR's arguments for the use of higher Step 
2 thresholds in section III.A.; however, to the extent those arguments 
are identical to those considered and rejected in disapproving 
Missouri's previous SIP submission, the Agency is not reopening such 
determinations.
4. Step 3 of the 4-Step Interstate Transport Framework
    Consistent with the EPA's longstanding approach to eliminating 
significant contribution and interference with maintenance, at Step 3, 
a multifactor assessment of potential emissions controls is conducted 
for States linked at Steps 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. 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 the EPA's approval of 
the SIP submission. The reason is that the emissions-reducing effects 
of all existing emissions control requirements are generally 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. 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

[[Page 63870]]

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.\32\
---------------------------------------------------------------------------

    \32\ 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 NOX 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.
---------------------------------------------------------------------------

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. For a State linked at Steps 1 and 2 to rely on an emissions 
control measure at Step 4 to address its interstate transport 
obligations, that measure must be included in the State's SIP so that 
it is permanent and federally enforceable. See CAA section 110(a)(2)(D) 
(``Each such [SIP] shall . . . contain adequate provisions . . . .''). 
See also CAA section 110(a)(2)(A); Committee for a Better Arvin v. 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).

II. Missouri SIP Submission Addressing Interstate Transport of Air 
Pollution for the 2015 Ozone NAAQS

A. Prior Submission

    On June 10, 2019, the MoDNR Air Pollution Control Program made a 
SIP submission to address interstate transport of air pollution for the 
2015 ozone NAAQS (June 2019 Submission). On February 22, 2022, the EPA 
proposed to disapprove the June 2019 Submission. 87 FR 9533. On January 
31, 2023, the EPA signed a final rulemaking, finalizing disapproval of 
19 SIP submissions, and partial approval and partial disapproval of two 
SIP submissions, for inadequately addressing the good neighbor 
provision for the 2015 ozone NAAQS including Missouri. 88 FR 9336 (Feb. 
13, 2023) (February 2023 Disapproval Action). The June 2019 Submission 
is not at issue in this proposed action, and the EPA is not reopening 
its disapproval of it.\33\
---------------------------------------------------------------------------

    \33\ The EPA's February 2023 Disapproval Action is currently 
under judicial review. E.g., State of Missouri v. EPA, No. 23-1719 
(8th Cir.); Union Electric Company, d/b/a Ameren Missouri v. EPA, 
No. 23-1751 (8th Cir.).
---------------------------------------------------------------------------

B. Summary of Missouri's 2015 Ozone Interstate Transport SIP Submission 
From November 2022

    On November 1, 2022, the MoDNR submitted another SIP submission to 
the EPA addressing the infrastructure requirements of CAA section 
110(a)(2), specifically the CAA section 110(a)(2)(D)(i)(I) interstate 
transport requirements, for the 2015 ozone NAAQS (November 2022 
Submission). The November 2022 Submission is the subject of this 
proposed action. The November 2022 Submission was deemed complete by 
operation of law on May 1, 2023.
    The November 2022 Submission contains the MoDNR's analysis of the 
State's impact on air quality in downwind States organized around the 
EPA's 4-step framework and based on the EPA's 2016v2 modeling at Steps 
1 and 2.\34\ Missouri asserts its current SIP is already addressing all 
of Missouri's good neighbor obligations under the 2015 ozone NAAQS.\35\ 
The MoDNR then includes a Step 3 analysis and some potential ozone 
season emissions reductions at Step 4, which the MoDNR's submission 
provides will become effective only if the EPA approves the November 
2022 Submission.\36\
---------------------------------------------------------------------------

    \34\ November 2022 Submission at 9-37.
    \35\ Id. at 18.
    \36\ Id. at appendix A at 3, 14-15; appendix B at 3, 14-15; 
appendix C at 3, 16-17; appendix D at 3, 15-17; appendix E at 3, 13-
14; appendix F at 3, 12-13.
---------------------------------------------------------------------------

    The MoDNR's November 2022 Submission provides background 
information on the EPA's 4-step interstate transport framework, the 
EPA's guidance for good neighbor SIPs for the 2015 ozone standard, the 
MoDNR's June 2019 Submission, the EPA's proposed disapproval of that 
Submission and the FIP that was proposed on April 6, 2022, and the 
MoDNR's decision to submit a new SIP submission addressing transport 
obligations for the 2015 ozone standard.\37\
---------------------------------------------------------------------------

    \37\ Id. at 1-4.
---------------------------------------------------------------------------

1. Information Provided at Steps 1 and 2
    In the next portion of the November 2022 Submission, the MoDNR uses 
the EPA's 2016v2 modeling results 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. In the 2016v2 modeling, Missouri contributes above 
1 percent of the NAAQS to 4 receptors, including above 1 ppb to two of 
those receptors, see table 2.
    Missouri compares its contributions in the EPA modeling released 
with the March 2018 memorandum with the EPA's 2016v2 modeling results 
for 2023 released in February 2022. In the EPA modeling released with 
the March 2018 memorandum, Missouri was linked to six nonattainment and 
maintenance receptors above one percent of the level of the 2015 ozone 
NAAQS (0.70 ppb). See table 1. In the 2016v2 modeling Missouri is not 
linked to those six receptors in 2023 but is identified as linked to 
four other receptors. See table 2. For the monitor (Site ID: 260050003) 
in Allegan, MI; the monitor (Site ID: 261630019) in Wayne, MI; the 
monitor (Site ID: 482011039) in Harris, TX; and the monitor (Site ID: 
550790085) in Milwaukee, WI; the 2016v2 modeling indicates that these 
monitors' 2023 design values would not be above the NAAQS and therefore 
they were not identified as receptors at Step 1. The 2016v2 modeling 
indicates that Missouri's contribution to the receptor ID 480391004, 
Brazoria, TX, is below the 1 percent of the NAAQS threshold and so 
Missouri is not linked to it at Step 2. For the receptor (Site ID: 
551170006) in Sheboygan, WI, the MoDNR notes that in the EPA's updated 
2016v2 modeling, this monitor is still projected to be a nonattainment 
receptor, but the EPA did not calculate any upwind State contributions 
to it because there were fewer than five days where the model-predicted 
MDA8 was above 60 ppb.\38\ Missouri is therefore not identified as 
being linked to this receptor in the 2016v2 modeling.
---------------------------------------------------------------------------

    \38\ The EPA notes this is consistent with the EPA's Modeling 
Guidance.

[[Page 63871]]



     Table 1--The EPA's March 2018 Memorandum--Downwind Receptors With Missouri Contributions Above 0.70 ppb
----------------------------------------------------------------------------------------------------------------
                                                                           Missouri
                                        2023 Projected  2023 Projected     projected
     Site (monitor, county, State)        average DV      maximum DV     contribution           Comments
                                             (ppb)           (ppb)           (ppb)
----------------------------------------------------------------------------------------------------------------
260050003, Allegan, MI................            69.0            71.7            2.61  Maintenance receptor.
261630019, Wayne, MI..................            69.0            71.0            0.92  Maintenance receptor.
484392003, Brazoria, TX...............            74.0            74.9            0.88  Nonattainment receptor.
482011039, Harris, TX.................            71.8            73.5            0.88  Nonattainment receptor.
550790085 Milwaukee, WI...............            71.2            73.0            0.93  Nonattainment receptor.
551170006, Sheboygan, WI..............            72.8            75.1            1.37  Nonattainment receptor.
----------------------------------------------------------------------------------------------------------------


         Table 2--Missouri Contributions Above 0.70 ppb to Receptors Based on the EPA's 2016v2 Modeling
----------------------------------------------------------------------------------------------------------------
                                                                  2023 Projected  2023 Projected   MO projected
         Receptor ID               Location       Nonattainment/  average design  maximum design   contribution
                                                   maintenance      value (ppb)     value (ppb)        (ppb)
----------------------------------------------------------------------------------------------------------------
550590025....................  Kenosha,          Maintenance....            69.2            72.3            1.66
                                Wisconsin.
550590019....................  Kenosha,          Nonattainment..            72.8            73.7            1.08
                                Wisconsin.
170317002....................  Cook, Illinois..  Maintenance....            70.1            73.0            0.94
551010020....................  Racine,           Nonattainment..            71.3            73.2            0.92
                                Wisconsin.
----------------------------------------------------------------------------------------------------------------

    Using what it describes as a ``weight of evidence'' approach, the 
State analyzed each of the four receptors in table 2 using 2016v2 
contribution modeling results and the EPA's August 2018 memorandum 
described in section I.C.
    For the Racine, Wisconsin receptor (Site ID: 551010020), the MoDNR 
noted that Missouri's projected contribution to this receptor is 0.92 
ppb, which is less than 1 ppb. The MoDNR observed that the 1 ppb 
threshold would capture 67 percent of the total contribution from all 
upwind States and that the contribution captured by the 1 ppb threshold 
is 92.23 percent of the amount captured by the 0.70 ppb threshold at 
this receptor. The MoDNR asserted that the 1 ppb threshold would 
capture a substantial amount of total upwind States' contribution to 
ozone concentrations at this receptor, which will lead to meaningful 
emissions reductions to ensure attainment of the NAAQS at this monitor 
in 2023. Therefore, the MoDNR relied on a 1 ppb threshold to conclude 
that its existing SIP sufficiently addresses the good neighbor 
obligation for the 2015 ozone NAAQS with respect to this receptor.
    For the Kenosha-Chiwaukee, Wisconsin receptor (Site ID: 550590025), 
the MoDNR noted that its projected contribution to this receptor is 
1.08 ppb, which is more than 1 ppb. The MoDNR observed that the 1 ppb 
threshold would capture 86.9 percent of the total upwind contributions 
and that a 2 ppb threshold would capture 71 percent of the total upwind 
State contributions. The MoDNR also observed that an alternative 2 ppb 
threshold would capture 81.7 percent of the upwind State contributions 
captured under a 1 ppb threshold. Using these data, the MoDNR asserted 
that a 2 ppb threshold is appropriate because it would capture at least 
70 percent of the total upwind State contributions and thus the burden 
should fall on States other than Missouri (i.e., only on those States 
contributing above 2 ppb) to provide emissions reductions that will 
help ensure attainment of the NAAQS at the site. The MoDNR also 
asserted that the primary contributors to the projected ozone 
concentrations at the monitor in Kenosha-Chiwaukee include emissions 
from Illinois, Indiana, and Wisconsin. The MoDNR cited the EPA's 2016v2 
modeling projecting that emissions from these States would contribute a 
combined 30.79 ppb in 2023 to the Kenosha-Chiwaukee receptor. The MoDNR 
pointed to the Lake Michigan Air Directors Consortium's (LADCO's) 
interstate transport modeling results for the 2015 ozone NAAQS to 
support these claims. The MoDNR asserted that LADCO's analysis 
indicates that the ozone levels at the Wisconsin shoreline of Lake 
Michigan are heavily affected by the emissions from Illinois, Indiana, 
and Wisconsin.\39\
---------------------------------------------------------------------------

    \39\ See ``Interstate Transport Modeling for the 2015 Ozone 
National Ambient Air Quality Standard, the TSD'', included in this 
docket, Docket ID No. EPA-R07-OAR-2021-0851. https://www.ladco.org/wp-content/uploads/Documents/Reports/TSDs/O3/LADCO_2015O3iSIP_TSD_13Aug2018.pdf.
---------------------------------------------------------------------------

    The MoDNR further pointed out that two other monitoring sites in 
Wisconsin (Site IDs: 551270006 and 551330027) further inland from Lake 
Michigan have no projected problems with attaining and maintaining 
compliance with the 2015 ozone NAAQS. Based on its assessment of this 
information, the MoDNR concluded that its existing SIP sufficiently 
addresses its good neighbor obligations for the 2015 ozone NAAQS with 
respect to the Kenosha-Chiwaukee receptor based only on this Step 2 
weight of evidence analysis.
    For the Kenosha-Water Tower, Wisconsin Site receptor (Site ID: 
550590019) the MoDNR noted that its projected contribution to this 
receptor is 1.66 ppb, which is more than 1 ppb. The MoDNR observed that 
the 1 ppb threshold would capture 88.5 percent of the total upwind 
contributions and that a 2 ppb threshold would capture 71.8 percent of 
the total upwind State contributions. The MoDNR also observed that an 
alternative 2 ppb threshold would capture 81.1 percent of the upwind 
State contributions captured under a 1 ppb threshold. Using these data, 
the MoDNR asserted that a 2 ppb threshold is appropriate because it 
would capture at least 70 percent of the total upwind State 
contributions and thus the burden should fall on States other than 
Missouri (i.e., only on those States contributing above 2 ppb) to 
provide emissions reductions that will help ensure attainment of the 
NAAQS at the site. The MoDNR then noted that its projected contribution 
of 1.66 ppb is less than 2 ppb. The MoDNR also

[[Page 63872]]

asserted that the primary contributors to the projected ozone 
concentrations at the monitor in Kenosha-Water Tower include emissions 
from Illinois, Indiana, and Wisconsin. The MoDNR cited the EPA modeling 
projecting that emissions from these States would contribute a combined 
28.47 ppb in 2023 to the Kenosha-Water Tower receptor.
    The MoDNR again asserted its interpretation that the LADCO analysis 
indicates that the ozone levels at the Wisconsin shoreline of Lake 
Michigan are heavily affected by the emissions from Illinois, Indiana, 
and Wisconsin.
    The MoDNR again pointed out that two other monitoring sites in 
Wisconsin (Site IDs: 551270006 and 551330027) further inland from Lake 
Michigan have no projected problems with attaining and maintaining 
compliance with the 2015 ozone NAAQS. The MoDNR concluded that the 
nonattainment receptor at Kenosha-Water Tower is heavily influenced by 
local transport emissions and lake breeze effects over Lake Michigan. 
Based on its assessment of this information, the MoDNR concluded that 
its existing SIP sufficiently addresses the good neighbor obligation 
for the 2015 ozone NAAQS with respect to the Kenosha-Water Tower 
receptor based only on this Step 2 weight of evidence analysis.
    For the Cook County Chicago-Evanston, Illinois receptor (Site ID: 
170317002), the MoDNR noted that its projected contribution to this 
receptor is 0.94 ppb, which is less than 1 ppb. The MoDNR observed that 
the 1 ppb threshold would capture 69.7 percent of the total 
contribution from all upwind States and that the contribution captured 
by the 1 ppb threshold is 92.9 percent of the amount captured by the 
0.70 ppb threshold at this receptor. The MoDNR asserted that the 1 ppb 
threshold would capture a substantial amount of total upwind States' 
contribution to ozone concentrations at this receptor, thus the burden 
should fall on States other than Missouri (i.e., only on those States 
contributing above 1 ppb) to provide meaningful emissions reductions to 
ensure attainment of the NAAQS at this site. Therefore, the MoDNR 
relied on a 1 ppb threshold to conclude that its existing SIP 
sufficiently addresses the good neighbor obligation for the 2015 ozone 
NAAQS with respect to this receptor.
    The MoDNR further pointed out that the other nine receptors in Cook 
County, Illinois show 40 percent less impact from Missouri in the 
2016v2 modeling than the County Chicago-Evanston, Illinois receptor. 
The MoDNR concluded that this difference indicates uncertainty on any 
conclusion that emissions from Missouri are contributing significantly 
to this single monitor in Cook County, while at the same time not 
contributing significantly to any other monitor in Cook County.\40\
---------------------------------------------------------------------------

    \40\ November 2022 Submission at 16.
---------------------------------------------------------------------------

    The MoDNR cited a 2019 Lake Michigan Ozone Study (LMOS or the 
study) relating to high ozone monitor concentrations near Lake 
Michigan. According to the MoDNR, the study recommends a finer grid 
resolution to better characterize ozone concentrations near large 
bodies of water. The MoDNR interprets the study as showing that upwind 
States' NOX emissions may have little to no impact on ground 
level ozone concentrations that are linked to downwind receptors 
because on high ozone level days the ozone concentrations in these 
areas are sensitive to emissions of VOCs and not NOX. The 
MoDNR also contends that, based on information included in the EPA's 
``Air Quality Modeling for the 2016v2 Emissions Platform Modeling TSD'' 
and the receptor specific data included in the EPA's document titled 
``CAMx 2016v2 MDA8 O3 Model Performance Stats by Site,'' the EPA's 
2016v2 modeling is ``severely underperforming'' in this region of the 
country where all of Missouri's linked receptors in the EPA's 2016v2 
modeling are located.\41\
---------------------------------------------------------------------------

    \41\ Id. at 17.
---------------------------------------------------------------------------

    For these reasons the MoDNR concludes that the weight of evidence 
analyses provided for these receptors in the November 2022 Submission 
shows that Missouri's current SIP is adequately addressing its good 
neighbor obligations with respect to each of these four receptors.\42\ 
In its conclusion of Steps 1 and 2, the MoDNR has stated it believes 
Missouri's good neighbor obligations are met at Steps 1 and 2 for the 
2015 ozone NAAQS. However, in its submission, the MoDNR goes on to 
acknowledge there are uncertainties due to model performance and recent 
year NOX emissions from Missouri EGUs that exceed the 
assurance levels of the CSAPR NOX Ozone Season Trading 
Program. Consequently, the MoDNR developed a Step 3 analysis to address 
these uncertainties (i.e., proceeding from an assumption that Missouri 
is linked at Step 2) and conducted an analysis of potential emissions 
control opportunities to ensure that the ``good neighbor obligations 
are indeed satisfied.'' \43\
---------------------------------------------------------------------------

    \42\ Id. at 18.
    \43\ Id.
---------------------------------------------------------------------------

2. Information Provided at Step 3
    In Step 3, the MoDNR begins by identifying controls that could be 
implemented at units for the 2023 ozone season. The MoDNR's evaluation 
at Step 3 gives some consideration to NOX emitting sources 
at certain EGUs, as well as certain sources in certain non-EGU sectors, 
including cement and cement products manufacturing, glass and glass 
products manufacturing, and pipeline transportation of natural gas 
industries.
    For 2023, the MoDNR made a list of 10 coal-fired EGUs currently 
equipped with Selective Catalytic Reduction (SCR) in the State. The 
MoDNR observed that four of these units have Prevention of Significant 
Deterioration permits requiring continuous operation of their 
NOX control equipment (Hawthorn unit 5A, Iatan units 1 and 
2, and John Twitty Energy Center unit 2). Based on the existence of 
these permits, the MoDNR stated that no additional NOX 
control requirements would be cost-effective for these units.\44\ The 
MoDNR observed that the six other units do not currently have 
enforceable requirements to ensure the continuous operation of their 
control equipment (i.e., SCRs) during the ozone season. The MoDNR 
claims that, based on its assessment, substantial and timely emissions 
reductions are both available and cost-effective at five units and that 
the sixth unit could choose to operate their controls less efficiently 
or not at all.\45\
---------------------------------------------------------------------------

    \44\ Id. at 19.
    \45\ Id.
---------------------------------------------------------------------------

    The MoDNR also observes that there are two EGUs in Missouri that 
have Selective Non-Catalytic Reduction (SNCR) but do not currently have 
enforceable requirements to ensure the continuous operation of their 
control equipment during ozone season. The MoDNR determined that 
substantial and timely emissions reductions are both available and cost 
effective at these two units.
    The MoDNR observed that there are nine remaining coal-fired EGUs 
that have no SCR or SNCR. At the time of submission, four of these 
units at two facilities (Rush Island and Meramec) are expected to 
retire by 2026, which is the next applicable attainment date under the 
2015 ozone NAAQS following the 2023 deadline for Moderate areas.\46\ 
The MoDNR also stated that the other five units (Labadie and Sikeston) 
are

[[Page 63873]]

expected to continue operating at least through 2026. The MoDNR claims 
that no timely reductions (i.e., by 2023) are available for any of 
these nine units.\47\ The MoDNR determined, however, that new 
enforceable requirements at the Labadie and Sikeston facilities to 
ensure the continued operation of the existing NOX controls 
(i.e., low NOX burners, etc.) would help guard against 
potential backsliding and lock in the emissions reductions these 
facilities have already achieved.
---------------------------------------------------------------------------

    \46\ The EPA notes that the next attainment date after the 
Moderate attainment date is the Serious attainment date of August 3, 
2027, but 2026 is the last year with a full ozone season before that 
date. CAA section 181(a); 40 CFR 51.1303; 83 FR 25776 (June 4, 2018, 
effective Aug. 3, 2018).
    \47\ November 2022 Submission at 21.
---------------------------------------------------------------------------

    To determine the new enforceable requirements at the coal-fired 
EGUs currently equipped with SCR (New Madrid, Thomas Hill facilities 
and John Twitty Unit 1), the MoDNR first analyzed historical 
NOX emissions rates for each unit with SCR to determine what 
the starting point for a new limit should be. The MoDNR selected what 
it identified as the third best ozone season emissions rate for five of 
the units at these facilities, as the MoDNR determined those years to 
be reflective of continuous SCR operation. Next, the MoDNR took the 
average of what it identified as the third best emissions rates for 
these units, which was 0.102 lbs/mmBtu. The MoDNR then decided that a 
compliance margin of approximately 20 percent was appropriate for this 
limit, putting the limit at 0.12 lbs/mmBtu. The MoDNR claims that this 
numeric limit combined with a stipulation that the sources continuously 
run their controls during the ozone season were enough to ensure 
meaningful reductions were achieved.\48\
---------------------------------------------------------------------------

    \48\ Id. at 25.
---------------------------------------------------------------------------

    The MoDNR attempted to use the same analysis for the units with 
SNCR, however the units only had one year of full operation using the 
control equipment. The MoDNR selected the larger emissions rate of the 
two units for that year and again added the 20 percent compliance 
margin to arrive at a numeric NOX ozone season emissions 
rate of 0.18 lbs/mmBtu.\49\ The MoDNR also used this historical 
emissions rate analysis with the 20 percent compliance margin to 
establish the limits for the units without SCR and SNCR to prevent 
backsliding, arriving at a 0.12 lbs/mmBtu rate for one facility and 
0.13 lbs/mmBtu rate for a second facility.\50\ The MoDNR acknowledged 
that for these units without existing post-combustion controls, this 
rate would not achieve new emissions reductions, but rather avoid 
potential increases in emissions.
---------------------------------------------------------------------------

    \49\ Id. at 26.
    \50\ Id.
---------------------------------------------------------------------------

    The MoDNR estimated that these limits, combined (0.12 lbs/mmBtu on 
coal-fired units with existing SCR, and 0.18 lbs/mmBtu on coal-fired 
units with existing SNCR, and anti-backsliding limits on coal-fired 
units without SCR or SNCR), would achieve ozone season NOX 
reductions of 6,713 tons annually compared to emissions levels at these 
units in 2021, assuming these units operate at the limited rate.\51\
---------------------------------------------------------------------------

    \51\ Id. at 26-27.
---------------------------------------------------------------------------

    The MoDNR then used these new emissions reductions it claims would 
be achieved through these new NOX emissions limits to 
evaluate the impact to linked downwind receptors. The MoDNR used the 
EPA's Ozone AQAT for this analysis.\52\ The MoDNR analyzed the cost of 
different control strategies for the EGUs discussed above to determine 
what controls it viewed as cost-effective.\53\ The MoDNR evaluated 
annual costs for the operation of SCR at the six units with existing 
SCR described above that do not currently have limits requiring the 
operation of SCR. This did not include capital cost because the units 
already have SCR. The MoDNR performed the same analysis for the Sioux 
facility that is equipped with SNCR. Similar to the SCR units, these 
annual costs do not include capital costs because the units are already 
equipped with these controls. The MoDNR then summed these costs and 
divided the costs by the modeled improvement in ppb at each linked 
receptor. The MoDNR identified the cost per 1 ppb improvement at the 
linked receptors as the ``cost effectiveness results.'' \54\
---------------------------------------------------------------------------

    \52\ Id. at 27-28.
    \53\ Id. at 28-29.
    \54\ Id. at 29.
---------------------------------------------------------------------------

    The MoDNR states that it considered Missouri's modeled contribution 
to the four linked receptors relative to in-state and other upwind 
States contributions, the conclusions it drew at Step 2 of their 
November 2022 Submission, and the costs and the corresponding reduction 
of ozone concentrations at the four linked receptors resulting from the 
new NOX emissions limits at certain facilities.\55\ With 
consideration of those factors, the MoDNR asserts that the projected 
emissions reductions in 2023 from the new NOX emissions 
limits would fully satisfy Missouri's good neighbor obligation for the 
2015 ozone NAAQS.\56\
---------------------------------------------------------------------------

    \55\ Id.
    \56\ Id.
---------------------------------------------------------------------------

    The MoDNR also reviewed the cost of new post-combustion controls 
included in the proposed Good Neighbor Plan (87 FR 20036, April 6, 
2022) for 2026. In the proposed Good Neighbor Plan, the additional 
emissions reductions required for EGUs in 2026 are based primarily on 
the potential retrofit of additional post-combustion controls for 
NOX on most coal-fired EGUs and a portion of oil/gas-fired 
EGUs that are currently lacking such controls. In the proposed Good 
Neighbor Plan, the EPA identified SCR retrofits for coal-fired EGUs as 
part of the strategy to eliminate significant contribution from States 
linked in the 2026 analytic year. The proposed Good Neighbor Plan also 
included new emissions limitations for non-EGU point sources including 
pipeline natural gas transportation, cement and concrete manufacturing, 
glass and glass product manufacturing, basic chemical manufacturing, 
petroleum and coal products manufacturing, and pulp, paper, and 
paperboard manufacturing. Because Missouri was among the States found 
linked through 2026 in the 2016v2 modeling, the EPA proposed in the 
Good Neighbor Plan to apply these requirements for non-EGU sources in 
the State.
    In the MoDNR's submission, it acknowledges that the EPA's 2016v2 
modeling results for 2026 show that Missouri continues to contribute 
above 1 percent of the NAAQS in 2026 to one nonattainment receptor, but 
less than 1 ppb, and also continues to contribute above 1 percent of 
the NAAQS in 2026 to three maintenance receptors: to two maintenance 
receptors above 1 percent of the NAAQS but less than 1 ppb and to one 
maintenance receptor above 1 ppb. However, the MoDNR asserts that the 
Kenosha, Wisconsin, receptor (Site ID: 550590025) will no longer be a 
maintenance receptor in 2026 due to emissions reductions under the Good 
Neighbor Plan and the new NOX limits that would be 
implemented by Missouri if the November 2022 Submission is approved by 
the EPA.\57\ The MoDNR concluded that Missouri has no remaining good 
neighbor obligations for the 2015 ozone NAAQS in 2026 because Missouri 
is projected to contribute less than 1 ppb to the other three receptors 
before considering the impact of the EPA's proposed Good Neighbor Plan 
in 26 States.\58\
---------------------------------------------------------------------------

    \57\ November 2022 Submission at 30. See also appendix A at 3, 
14-15; appendix B at 3, 14-15; appendix C at 3, 16-17; appendix D at 
3, 15-17; appendix E at 3, 13-14; appendix F at 3, 12-13.
    \58\ Id. at 30. The EPA notes that Missouri is included in the 
26 states covered by the proposed Good Neighbor Plan.
---------------------------------------------------------------------------

    The MoDNR further claims that the cost-effectiveness of the 
retrofit of SCR at the Labadie facility and Sikeston facility using the 
expected remaining life of those units is more than ten times the 
average cost-effectiveness of the State's planned controls associated 
with

[[Page 63874]]

better operation of controls at EGUs with existing SCR and SNCR. The 
MoDNR then divided the cost by the modeled improvement in ppb at each 
of the three receptors to which Missouri contributes above 1 ppb in 
2023. The MoDNR used those values and cost-effectiveness to calculate 
the cost effectiveness of the SCR retrofits for each of the three 
receptors in maintenance or nonattainment in 2026.\59\ The MoDNR 
asserted that SCR retrofits at existing coal-fired EGUs are not cost-
effective, nor required for the purpose of satisfying Missouri's good 
neighbor obligations under the 2015 ozone NAAQS.\60\
---------------------------------------------------------------------------

    \59\ November 2022 Submission at 31.
    \60\ Id.
---------------------------------------------------------------------------

    The MoDNR also purported to analyze the cost of controls included 
in the proposed Good Neighbor Plan for non-EGUs. According to the 
MoDNR, the EPA's proposed Good Neighbor Plan included proposed 
requirements for preheater/precalciner kilns at a limit of 2.8 lbs. 
NOX/ton of clinker produced. The MoDNR indicated that the 
State's rule, 10 CSR 10-6.380 Control of NOX Emissions from 
Portland Cement Kilns, covers the cement kilns identified by the EPA in 
the ``Screening Assessment of Potential Emissions Reductions, Air 
Quality Impacts, and Costs from Non-EGU Emissions Units for 2026'' 
included in Docket ID No. EPA-HQ-OAR-2021-0668-0191.\61\ The MoDNR 
further asserts that the State's rule includes a more stringent 
requirement of 2.7 lbs NOX/ton of clinker produced during 
the regulatory ozone season (May--September). The MoDNR concluded that 
no cost-effective emissions reductions in this source category in 
Missouri are available.\62\
---------------------------------------------------------------------------

    \61\ ``Screening Assessment of Potential Emissions Reductions, 
Air Quality Impacts, and Costs from Non-EGU Emissions Units for 
2026'' is also found in Docket ID No. EPA-HQ-OAR-2021-0668 and 
included in this docket, Docket ID No. EPA-R07-OAR-2021-0851.
    \62\ November 2022 Submission at 32.
---------------------------------------------------------------------------

    The MoDNR also observed that the proposed Good Neighbor Plan 
included new control requirements in the glass and glass product 
manufacturing industry. Two facilities in Missouri were listed in the 
``Screening Assessment of Potential Emissions Reductions, Air Quality 
Impacts, and Costs from Non-EGU Emissions Units for 2026'' as 
potentially subject to these proposed requirements: Pittsburg Corning 
Corporation in Sedalia, Missouri, and Piramal Glass USA Inc. in Park 
Hills, MO. The MoDNR addressed these two facilities by first 
identifying that the Piramal plant in Park Hills, Missouri, was 
expected to close in March of 2022.\63\ The MoDNR then observed that 
the EPA estimated a total cost of $5.8 million for the NOX 
controls at the Pittsburg Corning Corporation in the proposed Good 
Neighbor Plan. The MoDNR further notes that the 2020 and 2021 
NOX emissions at this facility were 17 and 44 tons, 
respectively. The MoDNR concluded from this that emissions reductions 
for the glass manufacturing sector in Missouri are not cost effective 
and that no further requirements are needed under this source category 
to address Missouri's good neighbor obligations under the 2015 ozone 
NAAQS.\64\
---------------------------------------------------------------------------

    \63\ Id. at 33.
    \64\ Id.
---------------------------------------------------------------------------

    The MoDNR observed that the EPA identified four pipeline natural 
gas transportation facilities in Missouri as potentially subject to new 
controls in the proposed Good Neighbor Plan. The EPA projected the 
average annual cost per ton NOX reduced for Missouri as 
$5,452 for this industry category. The MoDNR calculated cost 
effectiveness values in terms of annual dollars spent in Missouri per 1 
ppb improvement at the remaining three downwind linked monitors using 
the EPA's estimated cost per ton reduced figure from the proposed Good 
Neighbor Plan, similar to the analysis the MoDNR performed for the SCR 
retrofit for EGUs. The MoDNR concludes that emissions reductions for 
the pipeline natural gas transportation sector in Missouri are not 
cost-effective and that no further requirements are needed under this 
source category to address Missouri's good neighbor obligations under 
the 2015 ozone NAAQS.\65\
---------------------------------------------------------------------------

    \65\ Id.
---------------------------------------------------------------------------

3. Information Provided at Step 4
    In Step 4, the MoDNR lists several EGU sources with which the State 
has developed ``Consent Agreements'' (Agreements or the Agreements) 
with NOX emissions limits based on the MoDNR's Step 3 
analysis.\66\ First, the MoDNR explains the requirements for EGUs with 
SCR. The Agreements require each facility to operate the existing SCR 
system control devices at least 95 percent of the time during the ozone 
season when burning coal. The MoDNR asserts that the five percent 
allowance for non-operation of the SCR is necessary to account for 
operational issues that SCRs might experience such as catalyst 
maintenance, plugging issues, and potential supply issues of the SCR 
reagent.
---------------------------------------------------------------------------

    \66\ Id. at 34-37. The Agreements are included in the November 
2022 Submission in Appendices A through F.
---------------------------------------------------------------------------

    Next, the MoDNR explains the numeric limits for the controlled 
units and how the State arrived at the limit of 0.120 pounds per 
million British Thermal Units (lbs./mmBtu) for the ozone season (see 
Step 3 discussion detailed earlier in this section). The MoDNR also 
states that the Agreements contain necessary monitoring, recordkeeping, 
and reporting to verify compliance with these limits.
    Next the MoDNR explains several other additional terms in the 
Agreements. The terms include provisions for Startup, Shutdown, and 
Malfunction (SSM). The MoDNR explains what constitutes SSM for each 
facility and when the hours of operation may be excluded from the 
requirement to operate the SCR when burning coal at least 95 percent of 
the time in ozone season. The Agreement for the John Twitty plant 
defines startup as ending when the unit reaches minimum gross load 
offered to the Southwest Power Pool (the Regional Transmission 
Operator) and exempts those hours on the front end. For the New Madrid 
and Thomas Hill plants, the Agreements provide that they may exclude 
startup hours following the process in the State SSM rule, 10 CSR 10-
6.050. All three facilities are subject to the process in the State SSM 
rule to exempt hours for shutdown and malfunction when determining 
compliance with the percent operating time requirement. The MoDNR 
clarified that the SSM exemptions do not apply to the numeric emissions 
rate limit of 0.120 lbs./mmBtu.
    Next the MoDNR explained that the Agreements also include a 
``regulatory safety valve'' that suspends the numeric emissions rate 
limits under certain circumstances. The MoDNR explains that the purpose 
of this provision is to provide regulatory relief in the event that the 
SCR system could not be operated, but the unit was needed to ensure 
electric grid reliability/stability. The Agreements have several 
notification and justification requirements to use this mechanism. The 
MoDNR asserts that the regulatory safety valve was designed for use 
only during rare, unexpected grid emergency situations.
    In the next section, the MoDNR explains the requirements for EGUs 
with SNCR. The Agreement for the Sioux Energy Center is designed very 
similarly to the Agreements the MoDNR made for EGUs with SCR. The MoDNR 
asserted that the SNCR agreement stipulates a 90 percent operating time 
requirement as opposed to a 95 percent operating time requirement for 
the SCR control units, because it was necessary

[[Page 63875]]

to allow for the weekly tuning procedures for the complementary over-
fire air NOX control system at the Sioux facility. The MoDNR 
determined that a numeric emissions rate limit for the SNCR controlled 
units of 0.18 lbs/mmBtu is appropriate based on analysis of historic 
emissions rates. The MoDNR added similar SSM provisions to the 
Agreement with the John Twitty facility described above. The MoDNR also 
included the same regulatory safety valve language for this Agreement 
as described above.
    Next the MoDNR explained the Agreements with Labadie Energy Center 
and Sikeston Power station. These Agreements include numeric limits of 
0.12 lbs/mmBtu and 0.13 lbs/mmBtu respectively. Both facilities are 
required to continuously operate their currently installed control 
technologies, generally consisting of combustion-control measures. The 
MoDNR explains that both Agreements have the same SSM provisions, but 
they do not include a regulatory safety valve like the Agreements for 
the SCR and SNCR controlled units because the State determined that 
they were not necessary.

III. The EPA's Evaluation of Missouri's November 2022 Submission

A. Evaluation of Information Provided by Missouri Regarding Steps 1 and 
2

    In the November 2022 Submission, the MoDNR provided its 
interpretation of the 2016v2 modeling results for 2023 and 2026 to 
eliminate receptors and its linkages identified in the prior modeling 
released with the March 2018 memorandum, and to identify projected 
nonattainment and maintenance receptors in 2023 and 2026 as well as 
Missouri's contributions to them.
    The MoDNR utilized a 1 ppb or 2 ppb threshold at Step 2 as it found 
it needed to reach a conclusion that Missouri was not ``linked'' to 
particular downwind nonattainment or maintenance receptors. The EPA had 
suggested in its August 2018 memorandum that with appropriate 
additional analysis it may be acceptable for States to use a 1 ppb 
contribution threshold, instead of the 1 percent of the NAAQS threshold 
that the EPA has traditionally used, for the purposes of identifying 
linkages to appropriate downwind receptors, so long as appropriate 
circumstance-specific information and justification was included.
    The MoDNR argued for application of an alternative 1 ppb or 2 ppb 
threshold, depending on whether Missouri's contributions were below 1 
ppb or 2 ppb, by presenting the different numerical percentages of 
collective contribution that the respective thresholds would capture, 
and then asserting that the percentages of upwind contribution captured 
from the 1 ppb or 2 ppb threshold would be sufficiently meaningful. 
Stated differently, the MoDNR's logic is that so long as the States 
contributing above these thresholds will shoulder the burden of 
implementing their own emissions reductions to eliminate significant 
contribution to the shared receptors, it is appropriate for Missouri to 
use these thresholds for the purpose of excluding Missouri's emissions 
sources from having any such obligations. (We note that no other States 
linked to these receptors included any emissions reductions in their 
interstate transport SIP submissions for the 2015 ozone NAAQS.)
    The EPA proposes to find that the MoDNR did not justify the use of 
either an alternative contribution threshold of either 1 ppb or 2 ppb. 
As an initial matter, the MoDNR's theories for use of a 1 ppb or 2 ppb 
threshold repeat the same arguments that the EPA considered and 
rejected in acting on Missouri's first submission (June 2019 
Submission). See 87 FR 9541-43 (February 22, 2022); 88 FR 9358 
(February 13, 2023). The EPA is not reopening those determinations; 
they apply with equal force to the MoDNR's attempts to again justify a 
higher threshold here; and so are incorporated by reference.
    Second, the EPA has, in the SIP Disapproval and Good Neighbor Plan 
actions carefully evaluated a variety of issues associated with the 
August 2018 memorandum and potentially recognizing alternative Step 2 
contribution thresholds and found in these notice-and-comment 
rulemakings that, absent an adequate circumstance-specific 
justification, a 1 percent threshold is the most appropriate threshold 
for identifying States that ``contribute'' to downwind ozone receptors 
for the 2015 ozone NAAQS. 88 FR 9342; 88 FR 36678 (June 5, 2023).\67\ 
Consistency with past interstate transport actions such as CSAPR, and 
the CSAPR Update and Revised CSAPR Update rulemakings (which used a 
Step 2 threshold of 1 percent of the NAAQS for two less stringent ozone 
NAAQS), is important. Continuing to use a 1 percent of the NAAQS 
approach ensures that as the NAAQS are revised and made more stringent, 
an appropriate increase in stringency at Step 2 occurs, to ensure an 
appropriately larger amount of total upwind-State contribution is 
captured for purposes of fully addressing interstate transport. See 88 
FR 9370-72. Accord 76 FR 48237-38 (August 8, 2011). In addition, the 
Agency has explained through both its Disapproval Action and Good 
Neighbor Plan rulemakings that consistency and equity among States is 
an important consideration in addressing interstate ozone pollution, 
which weighs in favor of consistency absent a strong justification 
otherwise. See 88 FR 9371-75. Larger thresholds such as 1 ppb or 2 ppb 
would reduce the amount of cumulative upwind State emissions that would 
be captured, whereas the purpose of the threshold at Step 2 is simply 
to serve as a de minimis screening threshold, to screen in States for 
further evaluation of emissions control opportunities, or, stated 
differently, to screen out States with de minimis contributions from 
further analysis even if they do have cost-effective emissions 
reduction potential. See 88 FR 9371.
---------------------------------------------------------------------------

    \67\ The EPA identified the same concerns in proposing to 
disapprove Missouri's prior SIP submission (June 2019 Submission) 
and other states' submissions, e.g., 87 FR 9541-43. The MoDNR had 
these considerations available to it when it developed the November 
2022 Submission but did not address the concerns the EPA identified 
in continuing to put forward the use of higher thresholds in this 
Submission.
---------------------------------------------------------------------------

    The EPA has not rescinded the August 2018 memorandum, but at the 
same time, the Agency does not view that memorandum as completely 
endorsing the use of a threshold higher than 1 percent of the NAAQS. 
Rather, the memorandum invited State agencies to provide technically 
sound analytical justifications for use of a 1 ppb or any other 
threshold based on state-specific circumstances. The MoDNR in this 
Submission has not advanced new arguments that have not already been 
considered. The need for consistency in application of a threshold is 
important. The EPA did not approve the use of a 1 ppb threshold for any 
State for the 2015 ozone NAAQS. 88 FR 9370-75. Further, it is now clear 
(to a degree that it may not have been in 2018-2019 when Missouri and 
other States were developing their SIP submissions) that no States 
linked even at the higher thresholds the MoDNR asserts are appropriate 
actually proposed to implement any emissions reductions to benefit 
these or any other receptors. States' use of the higher thresholds to 
avoid implementing emissions reductions is contrary to the August 2018 
Memo, which provides that ``the use of a 1 ppb threshold to identify 
linked upwind States still provides the potential, at Step 3, for 
meaningful emission reductions in linked upwind States in order to aid 
downwind States

[[Page 63876]]

with attainment and maintenance of the 2015 ozone NAAQS.'' \68\ As the 
EPA identified in the Disapproval Action, States' reliance on 
incidental, hypothetical air quality benefits from other contributing 
States as a basis to justify use of a higher threshold to dismiss their 
own contribution is improper under the EPA's longstanding approach to 
evaluating States' obligations on a consistent and equitable basis. 
This would introduce an inter-dependency into the solution of the 
``collective contribution'' problem that ozone pollution poses and is 
inconsistent with requiring each State to eliminate its own significant 
contribution. See Response to Comments at 295-297 in the final 
Disapproval Action docket (EPA-HQ-OAR-2021-0663). In the proposed and 
final Good Neighbor Plan, the EPA evaluated all other States linked to 
these same receptors to which Missouri is linked using the 1 percent of 
NAAQS threshold. See 88 FR 36678. For these reasons, the EPA proposes 
to find that the 1 percent threshold is appropriate to use to establish 
whether Missouri's emissions ``contribute'' to other States' ozone 
receptors, and the EPA proposes that Missouri's November 2022 
Submission did not adequately justify use of any higher thresholds.
---------------------------------------------------------------------------

    \68\ August Memo at 4.
---------------------------------------------------------------------------

    In addressing Missouri's linkages in 2026, the EPA notes that the 
2016v2 modeling used by the MoDNR indicated four linkages above the 1 
percent threshold to nonattainment or maintenance receptors in that 
year. The EPA finds the MoDNR's dismissal of three of those linkages 
for being below a 1 ppb threshold is unsatisfactory for the same 
reasons described above regarding Missouri's linkages in 2023. With 
respect to Missouri's contribution of 1.53 ppb to the Kenosha-Chiwaukee 
receptor in 2026, the MoDNR argued that this site will not actually be 
a receptor, once the emissions reductions in the proposed Good Neighbor 
Plan are implemented, as well as the emissions controls the MoDNR 
purports to require in the current November 2022 Submission. This 
argument is flawed for several reasons. First, the EPA's analysis in 
the proposed Good Neighbor Plan indicated that the Kenosha-Chiwaukee 
receptor would remain a maintenance receptor after the implementation 
of retrofits of post-combustion emissions controls at EGUs in the 
linked upwind States, including Missouri.\69\ Thus, the available 
evidence at the time of the MoDNR's submission does not support the 
stated conclusion. Second, the MoDNR's argument provides no 
justification why the other States linked to this receptor should be 
subject to the full stringency of the proposed Good Neighbor Plan 
(which would include post-combustion control retrofits at EGUs and the 
non-EGU control measures) while Missouri's sources should enjoy the 
benefit of only implementing the near-term EGU emissions control 
strategies relying on existing installed control technologies that the 
MoDNR purports to require in its November 2022 Submission. (Note that 
even if the MoDNR's reasoning were applied to the EPA's 2016v3 (rather 
than 2016v2) modeling and the final (rather than proposed) Good 
Neighbor Plan (discussed further below), the EPA would reach the same 
conclusion: Missouri is linked to the Sheboygan receptor through 2026 
with a 1.68 ppb contribution, and Sheboygan is projected to remain a 
receptor through 2026, even with the full implementation of the final 
Good Neighbor Plan emissions control strategies in all of the upwind 
States, including Missouri, linked to that receptor through 2026.\70\)
---------------------------------------------------------------------------

    \69\ See ``Ozone Transport Policy Analysis TSD for the Proposed 
Rule'', Docket ID No. EPA-HQ-OAR-2021-0668-0133, at p.52 (table C-9) 
and included in this docket, Docket ID No. EPA-R07-OAR-2021-0851.
    \70\ See ``Ozone Transport Policy Analysis Final Rule TSD'' 
included in Docket ID No. EPA-HQ-OAR-2021-0668-1080, p. 68 (table C-
10) and included in this docket, Docket ID No. EPA-R07-OAR-2021-
0851.
---------------------------------------------------------------------------

    The MoDNR presents further arguments identical to arguments 
provided by the MoDNR in public comment on the proposed disapproval of 
the MoDNR's first submission:\71\ specifically, that due to claimed 
model underperformance in 2016v2 and other concerns the MoDNR has about 
modeling ozone near Lake Michigan, the weight of evidence analyses 
provided for these receptors in the November 2022 Submission shows that 
Missouri's current SIP is adequately addressing its good neighbor 
obligations with respect to each of these newly identified four 
receptors in the 2016v2 modeling.
---------------------------------------------------------------------------

    \71\ The MoDNR's comment letter on the proposed disapproval of 
Missouri's first submission is included in Docket ID No. EPA-R07-
OAR-2021-0851-0021 (``MoDNR Comment Letter''). The MoDNR raised this 
same issue in the November 2022 Submission in their comment letter 
at 7-9.
---------------------------------------------------------------------------

    The EPA addressed the MoDNR's assertions about the LMOS in 
responding to its comments on the proposed disapproval of Missouri's 
June 2019 Submission, which were nearly verbatim to the November 2022 
Submission on this topic.\72\ The EPA's response to this comment can be 
found on pages 139 and 152 to 153 of the Response to Comment document 
supporting the previous final SIP Disapproval Action.\73\ The EPA is 
not reopening its determinations in the SIP Disapproval Action on this 
topic, and incorporates that analysis by reference.
---------------------------------------------------------------------------

    \72\ The MoDNR Comment Letter at 9-11.
    \73\ See ``2015 Ozone NAAQS Interstate Transport SIP 
Disapprovals--RTC Document'' available in Docket ID No. EPA-HQ-OAR-
2021-0663.
---------------------------------------------------------------------------

    As the EPA concluded in the final SIP Disapproval Action, the EPA's 
2016v3 modeling is reliable for evaluating good neighbor obligations 
for the 2015 ozone NAAQS. As stated above, the EPA invited and received 
comments on the 2016v2 emissions inventories and modeling. In response 
to these comments, the EPA made a number of updates to the 2016v2 
emissions inventories and model design to construct a 2016v3 emissions 
platform, which was used to update the air quality modeling. Model 
performance issues noted by the MoDNR in the November 2022 Submission 
have been addressed in the EPA's 2016v3 modeling. See 88 FR 9344-45.
    The EPA found that model performance for 2016v3 modeling is 
improved over the performance for 2016v2 modeling and that the 2016v3 
modeling performed well within the range of bias and error performance 
criteria recommended in the scientific literature, which alleviates the 
performance concerns in the Midwest asserted by the MoDNR in its 
November 2022 Submission.74 75 The EPA is not reopening 
these determinations in this action and incorporates its prior analysis 
by reference.
---------------------------------------------------------------------------

    \74\ See ``Air Quality Modeling Technical Support Document 2015 
Ozone NAAQS SIP Disapproval Final Action'', table B-3--Performance 
statistics for MDA8 ozone > 60 ppb for monitor plus modeled 
receptors. Page B-11.
    \75\ The EPA directly responded to model performance concerns 
raised by the MoDNR and others on the 2016v2 modeling in the final 
SIP Disapproval Action and considered these concerns in the 
development of the 2016v3 modeling. See 88 FR 9370-71. See also 
``2015 Ozone NAAQS Interstate Transport SIP Disapprovals--RTC 
Document'' at 171-187, available in Docket ID No. EPA-HQ-OAR-2021-
0663.
---------------------------------------------------------------------------

    To be clear, the EPA is not disapproving the November 2022 
Submission for using the 2016v2 modeling. Under either the 2016v2 
modeling or the 2016v3 modeling, Missouri would be linked to at least 
one receptor in another State. Therefore, the EPA proposes to find that 
Missouri is obligated to further evaluate its emissions to determine 
what portion of its contribution, if any, constitutes ``significant'' 
contribution. In fact, the MoDNR conducted such an analysis, as 
discussed and evaluated further in section III.C.

[[Page 63877]]

B. Results of the EPA's Step 1 and Step 2 Modeling and Findings for 
Missouri

    As explained in section I., the EPA is relying on the EPA's 2016v3 
modeling and violating-monitor methodology for this action, which is 
the same set of data the EPA used for all other States in the final SIP 
Disapproval Action and the final Good Neighbor Plan, including for the 
State of Missouri.
    To summarize what was found in these prior actions for Missouri: 
based on the EPA's updated 2016v3 air quality modeling and considering 
contributions to violating-monitor receptors, Missouri is projected to 
contribute more than 1 percent of the NAAQS (i.e., 0.70 ppb), 1 ppb, 
and even 2 ppb, to multiple downwind nonattainment and maintenance 
receptors in 2023. Specifically, as shown in table 3, Missouri is 
projected to contribute 1.87 ppb to a nonattainment receptor in 
Sheboygan County, Wisconsin, (Site ID: 551170006) and 1.87, 1.39, and 
1.01 ppb to three maintenance-only receptors, respectively, in 
Wisconsin and Illinois in the 2023 analytic year. As shown in table 5, 
Missouri is also projected to contribute above 1 percent of the NAAQS 
to four violating-monitor receptors at locations in Michigan, and 
Wisconsin, in the 2023 analytic year. Furthermore, data for 2026 in 
table 4 indicate that emissions from Missouri will continue to 
contribute greater than 1 percent of the NAAQS to one maintenance-only 
receptor in Wisconsin. In addition, Missouri's contribution exceeds 1 
ppb at four receptors in 2023 and one receptor in 2026.

               Table 3: Projected Missouri Linkage Results Based on the EPA Updated 2023 Modeling
----------------------------------------------------------------------------------------------------------------
                                                                   2023 Average    2023 Maximum      Missouri
         Receptor ID               Location       Nonattainment/   design value    design value    contribution
                                                   maintenance         (ppb)           (ppb)           (ppb)
----------------------------------------------------------------------------------------------------------------
551170006....................  Sheboygan,        Nonattainment..            72.7            73.6            1.87
                                Wisconsin.
170317002....................  Cook, Illinois..  Maintenance-               68.5            71.3            1.39
                                                  Only.
551010020....................  Racine,           Maintenance-               69.7            71.5            1.19
                                Wisconsin.        Only.
550590019....................  Kenosha,          Maintenance-               70.8            71.7            1.01
                                Wisconsin.        Only.
----------------------------------------------------------------------------------------------------------------
Source: Final Good Neighbor Plan AQM TSD


               Table 4: Projected Missouri Linkage Results Based on the EPA Updated 2026 Modeling
----------------------------------------------------------------------------------------------------------------
                                                                   2026 Average    2026 Maximum      Missouri
         Receptor ID               Location       Nonattainment/   design value    design value    contribution
                                                   maintenance         (ppb)           (ppb)           (ppb)
----------------------------------------------------------------------------------------------------------------
551170006....................  Sheboygan,        Maintenance-               70.8            71.7            1.68
                                Wisconsin.        Only.
----------------------------------------------------------------------------------------------------------------
Source: Final Good Neighbor Plan AQM TSD.


                              Table 5: Missouri 2023 Linkage Results Based on Violating-Monitor Maintenance-Only Receptors
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                             Missouri
                                                                            2021 Design     2022 Design    2021 4th high   2022 4th high      modeled
                Receptor ID                           Location              value (ppb)     value (ppb)        (ppb)           (ppb)       contribution
                                                                                                                                               (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
261210039.................................  Muskegon, Michigan..........              74              79              75              82            2.95
260050003.................................  Allegan, Michigan...........              75              75              78              73            2.18
550890008.................................  Ozaukee, Wisconsin..........              71              72              72              72            1.64
550590025.................................  Kenosha, Wisconsin..........              72              73              72              71            1.54
481211032.................................  Denton, Texas...............              76              77              85              77            0.70
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: Final Good Neighbor Plan AQM TSD.

C. Evaluation of Information Provided by Missouri 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, levels 
of emissions controls, and cost considerations.
    To evaluate effectively which emissions in the State should be 
deemed ``significant'' and therefore prohibited, States generally 
should prepare an accounting of sources and other emissions activity 
for relevant pollutants and assess potential additional emissions 
reduction opportunities and resulting downwind air quality 
improvements. The EPA has consistently applied this general approach 
(i.e., Step 3 of the 4-step interstate transport framework) when 
identifying emissions contributions that the Agency has determined to 
be ``significant'' (or interfere with maintenance) in each of its prior 
Federal, 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 that 
will contribute significantly to downwind air quality problems. While 
the Good Neighbor

[[Page 63878]]

Plan has defined for purposes of a FIP the obligations for Missouri 
sources based on extensive modeling, analysis, and technical and policy 
determinations applied by the EPA, States including Missouri may 
submit, and the EPA will approve, alternative approaches to defining 
``significant contribution'' that meet the Act's requirement to 
determine whether and to what degree emissions from a State should be 
``prohibited'' to eliminate emissions that will ``contribute 
significantly to nonattainment'' or ``interfere with maintenance'' of 
the NAAQS in any other State.
    In this section, the EPA evaluates the information provided by the 
MoDNR in its submission, summarized in section II.B., in support of the 
conclusions the MoDNR draws at Step 3. Although the MoDNR has stated it 
believes its good neighbor obligations are met at Steps 1 and 2 for the 
2015 ozone NAAQS (statements with which the EPA disagrees as explained 
in the preceding section), the MoDNR then goes on to state that there 
are uncertainties due to model performance. The MoDNR also acknowledges 
that there have been recent exceedances of the assurance levels of the 
CSAPR NOX Ozone Season Trading Program by Missouri EGUs. See 
88 FR 36797-98. Consequently, the MoDNR developed a Step 3 analysis to 
address these so-called ``uncertainties'' (i.e., proceeding from an 
assumption that Missouri is linked at Step 2) and conducted an analysis 
of potential emissions control opportunities to ensure that its ``good 
neighbor obligations are indeed satisfied.'' \76\
---------------------------------------------------------------------------

    \76\ November 2022 Submission at 18.
---------------------------------------------------------------------------

    After reviewing the MoDNR's Step 3 analysis, the EPA finds several 
shortfalls in the MoDNR's analysis, including in its evaluation of 
improved emissions performance opportunities at EGUs with existing 
post-combustion controls, its evaluation of additional emissions 
control opportunities at EGUs, and its assessment of non-EGU emissions 
control opportunities, including its use of a ``weighted'' approach to 
identifying significant contribution applying a dollar-per-ppb (or ``$/
ppb'') metric.
    In general, the EPA observes that in the Good Neighbor Plan, the 
EPA as statutorily required pursuant to CAA section 110(c), and based 
on extensive record evidence, defined the amount of emissions that 
constitutes significant contribution from Missouri for purposes of the 
2015 ozone NAAQS. In the Good Neighbor Plan, the EPA defined a level of 
emissions control under Step 3, based on strategies of optimizing 
existing post-combustion controls and installing or upgrading 
combustion and post-combustion control equipment on EGU sources as well 
as installing certain controls on impactful non-EGU sources, and then, 
at Step 4, established through regulations particular implementation 
methods to achieve that level of emissions control. The EPA has 
acknowledged and continues to acknowledge that States are free to 
develop a SIP to replace a Good Neighbor Plan FIP that adopts a 
different suite of control measures if they meet good neighbor 
obligations for the 2015 ozone NAAQS. See 88 FR 36838-43 (discussing 
options for States to replace the FIP with a SIP).
    The MoDNR's submission pre-dates the final Good Neighbor Plan; 
however, in some respects, as discussed further below, the MoDNR 
modeled aspects of its analysis on the proposed Good Neighbor Plan. As 
noted further in this section, it is clear that the level of emissions 
control the MoDNR offers in the November 2022 Submission is less than 
the level of emissions control the EPA proposed and ultimately found 
necessary to meet good neighbor obligations in the final Good Neighbor 
Plan.\77\ As such, the Submission is clearly not ``equivalent'' in 
achieving the elimination of an amount of emissions that the EPA 
determined constituted ``significant contribution'' in the Good 
Neighbor Plan. See 88 FR 36838-43 (discussing options for States to 
replace the FIP with a SIP). This is most clearly evident in the 
Submission's failure to include additional emissions control strategies 
for EGUs and non-EGUs that the EPA found warranted for those States 
that remain linked to one or more out-of-state receptors through 2026, 
which, as noted in the previous section, Missouri is.
---------------------------------------------------------------------------

    \77\ The effectiveness of the Good Neighbor Plan in Missouri is 
currently administratively stayed by the EPA to comply with 
preliminary orders staying the EPA's separate Disapproval Action, 88 
FR 9336, pending judicial review. 88 FR 49295 (July 31, 2023). On 
June 27, 2024, the Supreme Court granted stay applications of the 
Good Neighbor Plan, Ohio et al. v. EPA, Nos. 23A349, 23A350, 23A351 
and 23A384, 603 U.S. __ (2024). However, the Good Neighbor Plan 
remains the EPA's final determination of Missouri's and 22 other 
states' interstate transport obligations for the 2015 ozone NAAQS. 
Neither the Good Neighbor Plan nor the Disapproval Action have been 
vacated by any court, and at this time merits litigation is 
proceeding while the Good Neighbor Plan's application in Missouri is 
stayed.
---------------------------------------------------------------------------

    The EPA finds that this aspect of the November 2022 Submission runs 
counter to the guidance the EPA has provided States in the proposed and 
final Good Neighbor Plan (and prior interstate transport rulemakings 
dating back to at least 2005) that the FIP establishes an ``important 
benchmark'' and that the EPA generally anticipates that SIP submissions 
that do not meet that benchmark are not likely to be approvable (see 
discussion in the Executive Summary of this document, section I.A.). 
However, recognizing that the MoDNR presented alternative arguments as 
to why its emissions reduction obligations to eliminate ``significant 
contribution'' should be less than what was finalized in the Good 
Neighbor Plan, and these arguments were developed before the EPA's 
final action issuing the Good Neighbor Plan, the EPA will evaluate 
additional aspects of the technical, policy, and legal merits of the 
alternative approaches the MoDNR put forward. In doing so, the EPA will 
highlight where relevant methodological choices the MoDNR made are not 
sufficiently technically justified, create inconsistencies or are not 
reconciled with the good neighbor obligations that the EPA has set for 
other States linked to shared receptors, and/or otherwise result in a 
plan submission that does not meet good neighbor obligations for the 
2015 ozone NAAQS. In the following subsections, the EPA will evaluate 
important factors considered by the MoDNR and/or the EPA within the 
Step 3 multifactor test. These include evaluation of levels of 
emissions controls on EGUs and non-EGUs in Missouri, potential air 
quality resulting from these levels of controls, and the MoDNR's use of 
a ``dollar-per-ppb'' metric to assess cost effectiveness of controls.
1. Evaluation of Potential Level of Emissions Controls on Missouri EGUs
    In Missouri's November 2022 SIP Submission, the controls the State 
identified to eliminate significant contribution (from all sources in 
the State) is an ``optimized'' emissions rate of 0.12 lb/mmBtu for 
application to certain specifically-named coal-fired EGUs with SCR 
post-combustion controls and a 0.18 lb/mmBtu rate for coal-fired EGUs 
with SNCR post-combustion controls already installed. Optimization of 
existing post-combustion controls on coal-fired EGUs is a well-
established strategy that the EPA has recently applied in multiple good 
neighbor rulemakings, including the CSAPR Update, the Revised CSAPR 
Update, and the Good Neighbor Plan. However, in the Good Neighbor Plan, 
the EPA identified that on an ozone-season average, fleetwide basis, 
sources with existing SCR controls are generally capable of achieving 
an emissions rate around 0.08 lb/mmBtu. See 88 FR 36721.
    To understand this discrepancy, the EPA evaluated the level of EGU

[[Page 63879]]

emissions controls identified by the MoDNR as well as several 
alternatives based on emissions control opportunities evaluated in the 
final Good Neighbor Plan. The emissions control opportunities evaluated 
in the Good Neighbor Plan included optimizing existing SCR and SNCR 
post-combustion NOX controls at units that currently have 
this technology and installing state of the art combustion controls 
(SOA CC) at units that currently lack them and retrofitting of SCR 
post-combustion controls at units that currently do not have those 
controls installed.
    The EPA first evaluated the 0.12 lb/mmBtu rate identified by the 
MoDNR for coal-fired EGUs with SCR. Similar to the methodology 
described in the EPA's NOX Mitigation Strategies Final Rule 
TSD, the EPA focused on the third-lowest ozone season emissions rate 
for the coal-fired EGUs with SCR systems in Missouri, and calculated a 
third best average rate, which it determined to be 0.086 lb/mmBtu 
specific to these units. This value is well below the 0.12 lb/mmBtu 
rate the MoDNR ultimately determined was appropriate for these units. 
The EPA then examined the third best average rate; however, the EPA did 
so for all units across the United States with cyclone boilers with SCR 
(similar to those in Missouri where the 0.12 lb/mmBtu rate would apply) 
and found a value of 0.073 lb/mmBtu. This value is also well below the 
0.12 lb/mmBtu rate identified by the MoDNR.
    Next, going beyond fleetwide average emissions rates, the EPA 
examined the historical operation of each individual unit for which the 
MoDNR proposed to apply the 0.12 lb/mmBtu rate to identify whether 
there was a justifiable reason for selecting an ``optimized'' rate well 
above the identified third best average rates (either using the sources 
included in the EPA's evaluation, or the subset of sources in Missouri 
that the MoDNR used). The EPA found that essentially all units have 
achieved emissions rates well below 0.12 lb/mmBtu, and in almost all 
cases below at least 0.08 lb/mmBtu on a monthly or seasonal basis.\78\ 
Thus, in general, the emissions rate the MoDNR identified for these 
sources is roughly 33 percent less stringent than appears to be 
achievable based on the relevant data.
---------------------------------------------------------------------------

    \78\ The lowest monthly rate that Thomas Hill Energy Center, 
oris code 2168 unit MB2 has achieved is 0.083 lb/mmBtu.
---------------------------------------------------------------------------

    To investigate the source of this discrepancy further, the EPA 
revisited its assessment of all coal-fired EGUs with SCR for potential 
optimization completed for the Good Neighbor Plan. The EPA examined 
costs for full operation of SCR controls for units that already have 
this technology installed.\79\ This includes the cost of catalyst 
replacement and disposal, the costs of reagent, and the cost for 
returning a partially operating SCR to full operation. The EPA 
evaluated nationwide coal-fired EGU NOX ozone season 
emissions data from 2009 through 2021 and calculated an average 
NOX ozone season emissions rate across the fleet of coal-
fired EGUs with SCR for each of these thirteen years and considered the 
third best average emissions rate. The EPA did not consider the lowest 
or second-lowest NOX emissions rates since these may reflect 
SCR systems that have all new components and therefore not 
representative of ongoing achievable NOX emissions rates 
considering broken-in components and routine maintenance schedules. The 
units identified for control under Missouri's SIP submission are 
included in the subset used in the EPA analysis. The analysis, which 
includes the costs required to increase reagent and routine 
maintenance, resulted in an optimized rate of 0.08 lb/mmBtu. Based on 
the results of this assessment, we still do not find adequate 
justification for a 0.12 lb/mmBtu rate for these sources.
---------------------------------------------------------------------------

    \79\ See ``EGU NOX Mitigation Strategies Final Rule 
TSD'' in Docket ID No. EPA-HQ-OAR-2021-0668-1092, and included in 
this docket, Docket ID No. EPA-R07-OAR-2021-0851.
---------------------------------------------------------------------------

    As discussed previously, the MoDNR initiated its analysis of Step 3 
by focusing on improvements of existing SCR operation at certain coal-
fired EGUs. The MoDNR follows an assessment similar to those developed 
by the EPA in evaluating optimization of SCRs at coal-fired EGUs in 
prior good neighbor rulemakings. In the development of its analysis to 
identify an emissions rate, however, the MoDNR excludes the best 
operating coal-fired units with SCRs in Missouri before considering the 
third best average emissions rate. In addition, in establishing the 
emissions rates in the Consent Agreements, the MoDNR added a 20 percent 
compliance margin, but the MoDNR's November 2022 Submission does not 
contain any analysis or data supporting this approach to allowing 
increased emissions far beyond the selected rate. Additionally, the 
Consent Agreements already include provisions addressing instances of 
variability from startup, shutdown, and malfunction of equipment. Thus, 
the identified emissions rate is inconsistent with a review of 
historical data for the subset of units the MoDNR considered for 
controls in the SIP Submission. The EPA's analysis of the data at the 
sources at which Missouri's November 2022 Submission proposes to apply 
the 0.12 lb/mmBtu limit shows that historical NOX emissions 
rates ranging from 0.06-0.10 lb/mmBtu are attainable for these 
units.\80\ Allowing increases above historical emissions rates by an 
additional 20-100 percent does not reflect an optimized emissions 
performance level for these coal-fired EGUs with SCR and in fact allows 
for degradation in emissions performance from observed achievable 
historical rates. The MoDNR provided no cost or feasibility information 
regarding why these rates that were previously achieved at these EGUs 
are not attainable at these EGUs going forward.
---------------------------------------------------------------------------

    \80\ See ``Historical NOX Seasonal Emission Rates for 
Units with SCR Final'' in Docket ID No. EPA-HQ-OAR-2021-0668-1106, 
and included in this docket, Docket ID No. EPA-R07-OAR-2021-0851.
---------------------------------------------------------------------------

    The MoDNR's analysis of near-term emissions control opportunities 
at EGUs was incomplete in certain other respects. The EPA agrees that 
Missouri EGUs do not have SOA CC potential upgrades available at this 
time.\81\ However, the MoDNR did not evaluate additional SCR 
optimization at oil and/or gas fired EGUs. The EPA's analysis suggests 
that there may be additional emissions reductions through cost-
effective optimization of combined cycle units in Missouri available in 
the short-term, which the MoDNR did not consider.\82\ Finally, the 
Consent Agreements for Labadie and Sikeston include ozone season 
emissions rates of 0.12 lb/mmBtu and 0.13 lb/mmBtu, respectively. 
Historical ozone season emissions rates for Sikeston for the previous 
five years ranged from 0.10-0.12 lb/mmBtu and for Labadie was 0.09 lb/
mmBtu for the same period.\83\ While the MoDNR acknowledges in its 
submission that these rates would not necessarily achieve any 
reductions in emissions, instead serving as an assurance of the 
operation of controls at the units in these facilities, the emissions 
rates in the Consent Agreements actually represent an increase of their 
historical and consistently lower emissions rates.
---------------------------------------------------------------------------

    \81\ See ``Appendix A: Final Rule State Emissions Budget 
Calculations and Engineering Analytics'' in Docket ID No. EPA-HQ-
OAR-2021-0668-1080 and included in this docket, Docket ID No. EPA-
R07-OAR-2021-0851.
    \82\ Id.
    \83\ See ``Historical NOX Seasonal Emissions Rates 
for Units with SCR Final'' in Docket ID No. EPA-HQ-OAR-2021-0668-
1106, and included in this docket, Docket ID No. EPA-R07-OAR-2021-
0851.
---------------------------------------------------------------------------

    Without adequate technical justification for applying the rates 
selected and included in the Consent

[[Page 63880]]

Agreements, and with no additional emissions controls identified to 
eliminate a comparable amount of significant contribution in 
compensation for that reduced level of emissions control, the November 
2022 Submission fails to eliminate the amount of emissions that the EPA 
has found achievable through near-term EGU control strategies and which 
comprises a portion of the amount of emissions that should be 
prohibited to eliminate significant contribution for the 2015 ozone 
NAAQS (as well as for the 2008 ozone NAAQS previously).
    However, the EPA conducted further evaluation of the consequences 
of the application of this rate with respect to estimated total 
emissions reductions in the State and the air quality effects of those 
reductions at downwind receptors.
    The EPA applied the emissions rates identified by the MoDNR as well 
as the emissions rates the Agency identified in the final Good Neighbor 
Plan to the suite of units each agency identified and calculated the 
resulting ozone season State-level EGU emissions for the State 
(including the emissions from units whose emissions rates remained 
unchanged) at various levels of stringency based on 2021 emissions.\84\ 
The resulting state-wide ozone season emissions levels for various 
levels of stringency based on the EGU fleet in 2023 and 2026 is shown 
in table 6. For 2023, both the emissions levels under the MoDNR`s 
emissions controls and the final Good Neighbor Plan represent a 
reduction in emissions from the base case. However, under the final 
Good Neighbor Plan an additional 784 tons are reduced beyond the 
emissions reductions identified by the MoDNR.
---------------------------------------------------------------------------

    \84\ See ``Ozone Transport Policy Analysis Final Rule TSD'' in 
Docket ID No. EPA-HQ-OAR-2021-0668-1080, and included in this 
docket, Docket ID No. EPA-R07-OAR-2021-0851.
---------------------------------------------------------------------------

    The difference is even more pronounced in 2026, with additional 
reductions accruing from emissions reductions commensurate with the 
installation of SCR controls under the Good Neighbor Plan. Such 
controls could achieve 4,518 additional tons of ozone-season emissions 
reductions, as under the final Good Neighbor Plan, beyond the level of 
reduction specified in the November 2022 Submission.

          Table 6--2023 and 2026 EGU Ozone Season NOX Emissions (Tons) at Various Levels of Stringency
----------------------------------------------------------------------------------------------------------------
                                                           Missouri
                                                            consent      SNCR and SCR
                                                         Agreement NOX     optimized     New SCRs added and SCR
                                          Engineering    limits (0.12-  (existing SCRs  optimized (existing SCRs
                 Year                    analysis (EA)   0.18 lb/mmBtu   optimized at   and optimized to 0.08 lb/
                                           base case     on  existing    0.08 lb/mmBtu         mmBtu rate)
                                                            units)           rate)
 
----------------------------------------------------------------------------------------------------------------
2023..................................          20,094          13,382          12,598  (not applicable)
2026..................................          18,612          11,899          11,116  7,381
----------------------------------------------------------------------------------------------------------------

    The EPA notes that these figures do not account for roughly an 
additional 2,065 tons of projected ozone-season NOX 
emissions reductions that were identified in the Good Neighbor Plan 
associated with non-EGU emissions control strategies to eliminate 
significant contribution from the State of Missouri. The EPA addresses 
the non-EGU analysis provided in the Missouri SIP submission in section 
III.C.4.
    Based on this evaluation, the EPA determines the information 
provided in the November 2022 Submission regarding the potential cost-
effective emissions control strategies at EGU sources in Missouri is 
inadequate.
2. Evaluation of Projected NOX Reductions on Downwind Linked 
Receptors
    The effects of emissions control strategies on downwind receptors 
to which upwind States are linked is one of the important factors that 
States and the EPA typically assess at Step 3 for purposes of defining 
the amount of ``significant contribution.'' Further, while the EPA does 
not view achieving precisely the same degree of projected air quality 
improvement at receptors as its FIP achieves as necessarily required 
for a SIP to be approvable, the EPA considers the Good Neighbor Plan's 
evaluation of air quality improvement to supply an important benchmark 
that allows for a reasonable assessment of the sufficiency of 
alternative programs States may put forward. The MoDNR included data in 
their submission showing the projected effect of its chosen emissions 
control strategies on ozone levels at the downwind receptors. While 
this data indicates that the MoDNR's proposed approach achieves some 
improvement in ozone levels at the identified receptors to which 
Missouri is linked, this amount of air quality improvement is less than 
the degree of improvement that occurs with the application of the level 
of emissions control that the EPA had determined in the Good Neighbor 
Plan is necessary to eliminate Missouri's significant contribution. 
This finding supports the EPA's proposed conclusion that the November 
2022 Submission is not adequate to address Missouri's good neighbor 
obligations for the 2015 ozone NAAQS.
    The EPA evaluated the air quality analysis conducted by the MoDNR 
that used the Air Quality Assessment Tool, or AQAT, from the proposed 
Good Neighbor Plan. The MoDNR utilized the AQAT to estimate the air 
quality effects of Missouri's proposed emissions reductions on the 
receptors that the MoDNR identified as potential receptors in 2023. The 
EPA independently checked the emissions reductions projected to be 
achieved at the level of emissions control identified by the MoDNR and 
then using the same AQAT (from the proposed Good Neighbor Plan) 
confirmed that the MoDNR's results are accurate.
    Next, since the final Good Neighbor Plan had updates to the air 
quality modeling that form the basis of the AQAT, we repeated the air 
quality analysis using the air quality modeling and AQAT from that 
rule. Starting with the 2021 emissions from the engineering analysis 
used in the final Good Neighbor Plan and applying the emissions rates 
identified by the MoDNR, we found slightly different emissions levels 
for 2023. We also found emissions levels for 2026, which included 
emissions changes due to retirements and/or other changes (see the 
Ozone Transport Policy Analysis Final Rule TSD from the final Good 
Neighbor Plan for details; also available in this docket). In addition 
to the emissions control level identified by the MoDNR, to ensure a 
thorough review, we evaluated several other emissions

[[Page 63881]]

levels using the engineering analysis from the final Good Neighbor Plan 
(i.e., optimization levels for existing SCR controls of 0.08 lb/mmBtu 
(or better) as well as optimization of existing SNCR controls).\85\ 
Additionally, we evaluated the potential effects of installing SCR 
controls with rates of 0.05 lb/mmBtu on all coal-fired units that are 
greater than 100 MW. The resulting analysis allows for a comparison of 
reduction in ozone levels that the MoDNR's emissions reductions 
strategies for EGUs would achieve at downwind receptors as compared to 
what the final Good Neighbor Plan's emissions reduction strategies 
would achieve. The comparative estimated air quality contributions to 
each of the potential receptors resulting from these emissions 
stringency levels can be found in table 7.
---------------------------------------------------------------------------

    \85\ See ``Ozone Transport Policy Analysis Final Rule TSD'' in 
Docket ID No. EPA-HQ-OAR-2021-0668-1080 and included in this docket, 
Docket ID No. EPA-R07-OAR-2021-0851.
---------------------------------------------------------------------------

    We observe that the emissions reductions proposed by the MoDNR 
result in some air quality improvements for each receptor. However, we 
observe that for the stringency levels identified and selected to 
eliminate significant contribution in the final Good Neighbor Plan, 
there are more emissions reductions and that these emissions reductions 
result in more air quality improvements (through reductions in the 
amount of ozone to which Missouri's emissions contribute) at the 
downwind receptors relative to the stringency level that has been 
adopted by the MoDNR in its November 2022 Submission. Based on an 
extensive record, the EPA had found the emissions reductions called for 
in the Good Neighbor Plan broadly cost-effective on industry-wide bases 
through national-scale analysis in light of the large geographic scale 
and persistent nature of the interstate ozone transport problem for the 
2015 ozone NAAQS. As discussed here and throughout section III.C., the 
MoDNR has not put forward an adequate technical justification 
explaining why Missouri's EGU and non-EGU sources should be subject to 
a substantially less stringent emissions control program delivering 
proportionately less air quality benefits to receptors in other States.
---------------------------------------------------------------------------

    \86\ This table displays contributions from Missouri to each of 
the nine receptors to which Missouri is linked in 2023. Of these 
nine monitoring sites, the 2016v3 modeling indicates that only 
Sheboygan is projected to remain a receptor to which Missouri is 
linked in 2026. In this regard, the reduction in contributions in 
2026 at sites other than the Sheboygan receptor represent incidental 
air quality benefits.

 Table 7--2026 Air Quality Contributions (ppb) Estimated Using AQAT to Each of the Receptors to Which Missouri Contributes Greater Than or Equal to 0.70
                                                   ppb at Various Levels of Emissions Reductions \86\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                           SNCR and SCR
                                                                                           optimized to                                   New SCRs added
                                                           AQ Model Base    Engineering      proposed      SNCR and SCR   New SCRs added      and SCR
   Receptor ID #          State              County            Case        Analysis (EA)   Missouri NOX    optimized \b\      and SCR     optimized with
                                                                             Base Case      limits \a\                     optimized \c\      Non-EGU
                                                                                                                                          reductions d e
--------------------------------------------------------------------------------------------------------------------------------------------------------
170317002.........  Illinois.........  Cook.............           1.258           1.316           1.242           1.233           1.192           1.169
550590019.........  Wisconsin........  Kenosha..........           0.912           0.955           0.900           0.894           0.863           0.847
551010020.........  Wisconsin........  Racine...........           1.061           1.125           1.043           1.033           0.988           0.963
551170006.........  Wisconsin........  Sheboygan........           1.689           1.778           1.664           1.650           1.587           1.552
260050003.........  Michigan.........  Allegan..........           1.969           2.068           1.942           1.927           1.857           1.818
261210039.........  Michigan.........  Muskegon.........           2.649           2.685           2.638           2.633           2.607           2.593
481211032.........  Texas............  Denton...........           0.634           0.661           0.661           0.661           0.661           0.661
550590025.........  Wisconsin........  Kenosha..........           1.381           1.449           1.362           1.352           1.303           1.276
550890008.........  Wisconsin........  Ozaukee..........           1.479           1.551           1.459           1.448           1.397           1.369
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Proposed limit is 0.12 lb/mmBtu on existing units.
\b\ Existing SCRs optimized at 0.08 lb/mmBtu rate.
\c\ Existing SCRs optimized to 0.08 lb/mmBtu rate.
\d\ Existing SCRs optimized to 0.08 lb/mmBtu rate.
\e\ This is the stringency set by the Good Neighbor Plan.

3. Evaluation of the MoDNR's Use of a ``Dollar-per-ppb'' Metric
    The EPA here evaluates the argument the MoDNR put forward as to why 
it did not believe any emissions reductions beyond the near-term EGU 
emissions control strategy it selected were needed using a ``dollar-
per-ppb'' metric. Specifically, the MoDNR utilized a formula taking the 
estimated cost of emissions reductions from control technologies 
divided by the resulting air quality improvement to (implicitly) 
apportion responsibility between upwind States and to make assertions 
regarding whether particular controls are cost-effective on a dollar-
per-unit-of-air quality-improvement basis. This approach would 
``weight'' cost-effectiveness among States based on assumptions 
regarding the proportional amount of air quality benefit the same 
emissions control strategies would deliver as coming from one State 
rather than another at each particular receptor. This is substantially 
different from the approach the EPA has taken in all of its prior good 
neighbor rules for ozone. The Supreme Court in EME Homer upheld the 
EPA's decision not to allocate responsibility among upwind States 
proportionally to each State's contribution. 572 U.S. 489, 514-19. 
Nonetheless, the Disapproval Action explained the EPA's continuing 
openness to evaluating whether States could develop this or other 
alternative methods of allocating responsibility, though no other State 
has adopted this approach or demonstrated how it could be implemented 
in practice. 88 FR 9376. This experience accords with the EPA's 
previously expressed views that this approach to defining significant 
contribution would be highly analytically challenging and would require 
a highly-coordinated approach across multiple States to have a chance 
at being successful.
    The EPA has previously evaluated Step 3 alternatives to the 
``uniform approach'' the EPA has taken in the context of past good 
neighbor rulemakings, including an evaluation of methods similar to the 
``cost per level of air quality improvement'' proposed by the MoDNR. 
The alternative methods, as well as potential issues that the Agency 
identified can be found in the ``Alternative Significant Contribution 
Approaches Evaluated TSD'' included in the CSAPR rulemaking docket,\87\ 
and included in the docket for this action. In responding to comments 
in that rulemaking about similar cost per air

[[Page 63882]]

quality improvement approaches,\88\ the Agency identified concerns that 
included, but were not limited to, requirements of an ``extremely high 
level of accuracy in both the emissions modeling. . .and the air 
quality modeling'' and that ``finer-scale emissions data from all 
sectors....and fine-scale air quality modeling could be needed to 
resolve differences in cost per air quality impact.'' The EPA explained 
that ``these data and modeling techniques do not exist and/or are too 
computationally demanding to be operationally implemented.'' The EPA 
continued, ``A second challenge for this approach was to identify a 
single reduction requirement for a particular upwind State, since the 
reduction requirements relevant to different downwind receptors would 
vary significantly.''
---------------------------------------------------------------------------

    \87\ Docket ID No. EPA-HQ-OAR-2009-0491-0077, also included in 
this docket, Docket ID No. EPA-R07-OAR-2021-0851.
    \88\ See page 743 of 3009 of the CSAPR ``Transport Rule Primary 
RTC'' document, Docket ID No. EPA-HQ-OAR-2009-0491-4513 and included 
in this docket, Docket ID No. EPA-R07-OAR-2021-0851.
---------------------------------------------------------------------------

    The MoDNR has not presented a compelling argument to resolve these 
issues. Indeed, its own Step 3 analysis is internally inconsistent, 
since it only adopts a $/ppb metric in evaluating emissions control 
opportunities available by the year 2026 and does not apply that metric 
consistently in evaluating the near-term reductions it has selected. 
Nor did the MoDNR offer any analytical basis on which to establish a 
threshold based on $/ppb below which emissions reductions would be 
deemed cost-effective; in other words, the data provided in the 
Submission do not in themselves constitute a standard or definition of 
``significant contribution.'' The MoDNR simply provided tables with 
these figures (without supporting analysis or technical justification) 
on pages 32 and 33 of the November 2022 Submission and claimed that 
these figures showed that the emissions reductions were not worth 
requiring. While the EPA uses a different Step 3 cost-effectiveness 
metric to inform ``significant contribution'' in the EPA's good 
neighbor rules ($/ton rather than $/ppb), the EPA notes that its level 
of emissions stringency identified as necessary to eliminate 
significant contribution is less (often far less) than what would 
achieve a full 1 ppb increment in ozone air quality improvement at 
downwind receptors. In other words, the dollar-based figures the MoDNR 
cites are effectively meaningless without further context. Thus, the 
MoDNR's presentation of this metric, without further technical 
justification, without coordination with other States that collectively 
contribute to the same receptors impacted by Missouri, and without 
identification of an appropriate $/ppb figure that could be 
consistently applied to define the amount of emissions that constitutes 
significant contribution, cannot be approved.
    In addition to the fact that the use of this metric is inadequately 
supported on its own terms, the MoDNR has not conducted outreach or 
coordination with other States that have either primary responsibility 
for downwind receptor areas (e.g., by virtue of being included in a 
designated nonattainment area), or with those upwind States that also 
contribute above threshold to those areas, with the goal of 
establishing a consistent methodology for defining significant 
contribution with respect to a shared ozone receptor. The need for 
regional consistency is critically important to ensure consistent 
decisions that achieve equity among States with responsibility for a 
shared ozone problem. 88 FR 9365; see also March 2018 Modeling Memo, 
Attachment A, at A-1 \89\). This is particularly the case where a State 
wishes to pursue a $/ppb approach to defining the good neighbor 
obligation. With this approach, States that perceive themselves to have 
less culpability on a ppb-impact basis for a receptor would evade 
emissions control requirements, purportedly under the theory that ppb 
improvements can be achieved more cost-effectively (on a $/ppb basis) 
by other States. However, the MoDNR's analysis failed to evaluate what 
the comparative $/ppb figures would be for other States linked to its 
receptors. The November 2022 Submission does not supply a sufficient 
basis to define what constitutes ``significant contribution'' using 
this metric.
---------------------------------------------------------------------------

    \89\ Included in the docket for this action, EPA-R07-OAR-2021-
0851.
---------------------------------------------------------------------------

    The MoDNR also referenced cost-effectiveness values that it used in 
other programs (such as regional haze) as justification for why 
additional controls were not appropriate to apply in the context of 
good neighbor obligations for the 2015 ozone NAAQS. However, the MoDNR 
did not provide information on the derivation of the cost-effectiveness 
values or further analysis and justification for why those values would 
be appropriate for this purpose. The EPA has previously explained that 
application of cost-effectiveness determinations from other contexts 
must be analytically justified in relation to the specific CAA 
obligation in question. 88 FR 9359; see also, e.g., 86 FR 23054, 23073-
74 (April 30, 2021); 87 FR 9838, 9858 (February 22, 2022). Further, the 
EPA cannot determine from the Submission what level of control the 
MoDNR considered when calculating its cost-effectiveness values. For 
example, in the case of EGUs, use of new add-on control equipment would 
allow emissions rate levels well below the 0.12 lb/mmBtu levels in the 
Missouri Consent Agreements, which would lower the cost per ton of 
emissions reduced by accounting for the greater emissions reductions 
achieved by those controls.
4. Evaluation of Conclusions Regarding Potential Controls for Non-EGUs
    As noted in section II.B., the MoDNR's submission included some 
information regarding potential control availability for non-EGU 
sources. The MoDNR's evaluation for non-EGUs is informed largely by the 
proposed Good Neighbor Plan, rather than its own comprehensive 
evaluation of non-EGU NOX emissions sources within the State 
of Missouri, potential controls for those sources, or the air quality 
effects of such controls at receptors. In a supporting memorandum for 
the proposed Good Neighbor Plan titled ``Screening Assessment of 
Potential Emissions Reductions, Air Quality Impacts, and Costs from 
Non-EGU Emissions Units for 2026'' (the Screening Assessment), the EPA 
estimated potential facilities and emissions units located in Missouri 
in the cement and cement products manufacturing, glass and glass 
products manufacturing, and pipeline transportation of natural gas 
industries--as part of a larger analysis to identify industries and 
unit types for which the EPA proposed to establish emissions limits to 
eliminate significant contribution.\90\ In its submission, the MoDNR 
provided some information about the current status of certain named, 
existing sources within the cement and cement products manufacturing 
and glass and glass products manufacturing industries but did not 
provide a like analysis concerning the pipeline transportation of 
natural gas industry's sources in Missouri, or inventory or conduct any 
further assessment of industrial sources in the State. Stating that the 
certain named, existing cement or glass sources it identified were 
already controlled or closing, the MoDNR concluded that no additional 
cost-effective controls were

[[Page 63883]]

available for its non-EGU industrial sources.
---------------------------------------------------------------------------

    \90\ The memorandum is available in the docket for this action, 
Docket ID No. EPA-R07-2021-0851. See ``Screening Assessment of 
Potential Emissions Reductions, Air Quality Impacts, and Costs from 
Non-EGU Emissions Units for 2026'' in EPA-HQ-OAR-0668-0150, also 
included in this docket, Docket ID No. EPA-R07-2021-0851.
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    In determining whether any cost-effective reductions are available 
in the State, the EPA would expect, at a minimum, for the State to 
provide the EPA with a comprehensive inventory of point source 
emissions units, including non-EGUs. This is consistent with what the 
EPA indicated it would expect in a SIP submission in previous proposed 
disapproval actions (actions proposed prior to the SIP submission the 
EPA proposes action on here), where the EPA indicated that an effective 
evaluation of emissions deemed significant could be done, in general, 
through a statewide accounting of sources and other emissions activity 
and an assessment of potential, additional emissions reduction 
opportunities statewide, as well as an assessment of the downwind 
impact of those potential reductions (akin to the EPA's own Step 3 
evaluation).\91\ In this submission, the MoDNR has not provided such an 
assessment.\92\
---------------------------------------------------------------------------

    \91\ See, e.g., ``Air Plan Disapproval; Missouri Interstate 
Transport of Air Pollution for the 2015 8-Hour Ozone National 
Ambient Air Quality Standards,'' 87 FR 9533, 9544.
    \92\ The EPA provided comment on the MoDNR's draft SIP 
submission regarding the scope of sources evaluated by the State 
that questioned the approvability of the draft submission. The EPA 
encouraged the State to consider potential emissions reductions 
beyond the subset of EGU sources already equipped with SCRs. While 
we acknowledge that the scope of sources analyzed in its final 
submission was expanded, this concern has not been fully resolved, 
as described in this section. See ``EPA Comments on Missouri State 
Implementation Plan Revision Addressing Interstate Transport for the 
2015 Ozone Standard,'' at 3.
---------------------------------------------------------------------------

    Rather, in its assessment of non-EGU emissions reduction potential 
the MoDNR relied instead on the results of the EPA's Screening 
Assessment for the proposed Good Neighbor Plan. The EPA disagrees with 
this use of the Screening Assessment. The Screening Assessment 
reflected a multistate analysis of potential industries and emissions 
unit types that may have impactful, cost-effective emissions reduction 
opportunities. While the EPA finds the Screening Assessment was 
sufficient to inform the development of the EPA's Good Neighbor Plan, 
specifically to screen for potentially impactful industries and 
emissions unit types to focus on for further evaluation of cost-
effective emissions control opportunities, the EPA does not find it 
appropriate in the context of developing a SIP to rely solely on the 
results of that Screening Assessment as the only source of data for a 
State to use in conducting an inventory of its own emissions 
sources.\93\ In the proposed Good Neighbor Plan, the EPA explained that 
there may be facilities and emissions units identified in the Screening 
Assessment that are not ultimately subject to the proposed rule under 
the proposed applicability criteria, and possibly some facilities and 
emissions units not identified in the Screening Assessment that 
ultimately become subject to the proposed rule under the proposed 
applicability criteria. The final Good Neighbor Plan reaffirms this 
point--specific emissions units subject to the final rule emissions 
limits may be different than those estimated in its final rule 
technical memorandum. In general, the Good Neighbor Plan is a 
rulemaking of general applicability that, like all prior good neighbor 
FIPs, regulates units by their type and size, rather than by specific, 
named identification, and it includes both new and existing sources in 
the scope of its coverage.\94\ See section III.D.3. below for further 
discussion. Therefore, without a fuller evaluation of its own 
emissions-source inventory information, it was inadequate for the MoDNR 
to rely solely on the Screening Assessment to limit the sources it 
needed to evaluate in its assessment of non-EGU emissions reduction 
potential.
---------------------------------------------------------------------------

    \93\ See ``Non-EGU Applicability Requirements versus Results 
from Non-EGU Screening Assessment for 2026'' and the EPA's 
``Screening Assessment of Potential Emissions Reductions, Air 
Quality Impacts, and Costs from Non-EGU Emissions Units for 2026,'' 
at 3, available in this docket, Docket ID No. EPA-R07-OAR-2021-0851.
    \94\ See ``Summary of Final Rule Applicability Criteria and 
Emissions Limits for Non-EGU Emissions Units, Assumed Control 
Technologies for Meeting the Final Emissions Limits, and Estimated 
Emissions Units, Emissions Reductions, and Costs,'' at 8, available 
in Docket ID No. EPA-R07-OAR-2021-0851.
---------------------------------------------------------------------------

    In addition, where a State's SIP is not simply adopting the 
requirements of the Good Neighbor Plan or adopting emissions control 
measures that are otherwise equivalent, the EPA would expect the State 
to fully conduct its own Step 3 analysis using inventory data, 
analysis, and emissions control measures specific to that State's 
industrial sources, which may extend beyond sources in those industrial 
categories covered by the Good Neighbor Plan to ensure the State has 
put forward a sufficiently technically supported alternative approach 
to addressing their significant contribution not already identified in 
the Good Neighbor Plan. The MoDNR's SIP submission does not provide any 
such evaluation. For example, the MoDNR's evaluation of whether there 
are cost-effective controls in the pipeline transportation of natural 
gas industry only analyzed certain sources in the State, and, for the 
reasons described in section III.C.3. (identifying concerns with 
applying a dollar-per-ppb metric), was not adequately supported in 
dismissing emissions-control opportunities for that industry.
    Without having completed a full assessment of emissions control 
opportunities for large, industrial sources in Missouri, the MoDNR has 
not provided the EPA with an adequate basis on which to conclude that 
existing emissions control measures are sufficient for the State to 
address its significant contribution. Indeed, the good neighbor 
provision is not limited even to large, industrial sources. See CAA 
section 110(a)(2)(D)(i) (calling for evaluation of ``any source or 
other type of emissions activity'' to ensure significant contribution 
is ``prohibited''). See also 88 FR 36680-81 (June 5, 2023).
    Although the EPA acknowledges that the MoDNR submitted this SIP 
prior to the EPA finalizing the Good Neighbor Plan, the Submission 
would not be approvable at Step 3 for the reasons described above under 
any scenario, whether evaluated against the proposed Good Neighbor 
Plan, or the final version, or in the absence of the Good Neighbor Plan 
altogether. The State must establish that it has evaluated its 
emissions sources comprehensively and has identified those emissions 
that constitute significant contribution. Here, the State has not met 
that burden. The EPA's evaluation at Step 3 identifies multiple 
unexplained discrepancies between the conclusions the MoDNR has reached 
and the evidence that is available to the State and the EPA regarding 
potential, cost-effective emissions control opportunities in Missouri 
at both EGUs and non-EGUs (e.g., the MoDNR's use of a ``dollar-per-
ppb'' metric to reason out of control requirements for the pipeline 
transportation of natural gas industry and dismissal of post-combustion 
retrofit opportunities at several of its EGU sources. The EPA's 
evaluation of the MoDNR's use of this metric is further explained in 
section III.C.3). The State is by no means prohibited from regulating 
differently, including regulating different sources, than how the EPA 
has chosen to regulate in the Good Neighbor Plan. However, the 
extensive record the EPA developed for that rulemaking establishes an 
important benchmark to aid in the EPA's evaluation, one on which the 
MoDNR itself purported to rely. The November 2022 Submission's analysis 
of what emissions from the State constitute ``significant 
contribution'' is

[[Page 63884]]

not a choice to regulate differently than the FIP, but an attempt to 
regulate substantially less stringently without adequate technical 
justification. As such, it is inadequate to meet the requirements of 
the Act and cannot be approved.

D. Evaluation of Information Provided by Missouri Regarding Step 4

    To meet the CAA's requirement that SIPs ``contain'' ``adequate 
provisions'' to ``prohibit'' significant contribution to nonattainment 
or interference with maintenance of the NAAQS, Step 4 of the 4-step 
interstate transport framework calls for the development of permanent 
and enforceable control strategies to achieve the emissions reductions 
determined to be necessary at Step 3. These control measures must be 
contained in the State's SIP; i.e., the State must revise its SIP to 
include these measures, such that if the EPA approves these measures 
into the SIP, they will become enforceable as a matter of Federal law. 
See generally CAA sections 110(a)(2)(A)-(E), 113, and 304. The MoDNR's 
November 2022 Submission includes Consent Agreements with six power 
plants, covering a total of thirteen EGUs. None of the Consent 
Agreements require the installation of new or additional control 
technologies. Rather, the Consent Agreements establish emissions-rate 
limits based on the operation of existing SCR controls at six units, 
the operation of existing SNCR controls at two units, and the operation 
of existing combustion-controls at five units. The Submission purports 
to incorporate these Consent Agreements into Missouri's SIP as a SIP 
revision and provides that these Consent Agreements will become 
effective and enforceable only if the EPA fully approves the 
Submission.
    This section will address why, in addition to the November 2022 
Submission's failure to adequately identify significant contribution at 
Step 3, the November 2022 Submission also fails to prohibit Missouri's 
significant contribution at Step 4, even with respect to those 
reductions Missouri's submission purports to require.
1. Evaluation of the Consent Agreements
    There are several independent reasons why the Consent Agreements 
with certain power plants are not adequate at Step 4. The terms of 
these Agreements make clear that the emissions-control requirements 
they identify are neither permanent nor enforceable. They have not been 
codified into the law of the State and contain provisions that allow 
for the State and the affected sources to modify them without following 
the statutorily-mandated process for SIP revisions and without 
requisite analysis by the EPA under CAA section 110(l). See CAA section 
110(a)(2)(D); 110(i); 110(l). While the EPA will allow for consent 
agreements or permitting requirements to be incorporated by reference 
into a State's SIP to meet SIP requirements (50 CFR part 51, appendix 
V, para. 2.1(b)), it is important that the State provides that to the 
extent such provisions are approved and incorporated into the State's 
SIP, such provisions, as approved, cannot be modified by later changes 
made to the underlying agreements or permits outside of the SIP 
revision process. Once approved by the EPA into the SIP as meeting the 
applicable SIP requirements, only changes made through the statutory 
SIP revision process may modify the approved requirements of the 
State's SIP. In this instance, the terms of the Consent Agreements 
explicitly authorize the State and the affected sources to cancel the 
agreements in toto and without the EPA's approval of such a 
modification, which would in effect negate the emissions limitations in 
their entirety. This is antithetical to the requirement that SIP 
provisions be permanent and enforceable, and not changed except 
pursuant to the statutory and regulatory processes for SIP revisions.
    The EPA commented extensively during the State level public comment 
period on the draft SIP submission and noted several issues with the 
Consent Agreements related to permanence and enforceability.\95\ The 
EPA commented that all of the Consent Agreements contain a provision 
that would allow the sources to terminate the Agreement upon mutual 
written agreement of the MoDNR and the source.\96\ In its Response to 
Comments, the MoDNR states that ``Paragraph 5 of the Consent Agreements 
clearly state that after EPA approves the good neighbor SIP that 
includes the consent agreements, any future changes to the consent 
agreements will require EPA approval before going into effect. Should 
EPA approve the SIP revision that includes these consent agreements, 
and the agreements are not terminated pursuant to paragraph 13 of the 
agreements, then the requirements will become permanent, federally 
enforceable, and applicable until a revision to the SIP is submitted 
and approved by EPA.''
---------------------------------------------------------------------------

    \95\ See ``Comments on Missouri State Implementation Plan 
Revision Addressing Interstate Transport for the 2015 Ozone 
Standard'' (August 18, 2022), available in the docket for this 
action.
    \96\ See November 2022 Submission, appendices A-F, paragraph 12.
---------------------------------------------------------------------------

    However, there remain multiple problematic provisions of the 
Consent Agreements that render them non-permanent and unenforceable, 
and these are not addressed by the MoDNR's assertion above. It is this 
language in the Agreements themselves, rather than the possibility of a 
future modification to them, that renders them not approvable as a SIP 
revision addressing good neighbor obligations for the 2015 ozone NAAQS.
    First, the Agreements are not yet even in effect. Paragraph 1 of 
the Agreements says that ``the effective date of the approval of this 
Consent Agreement by EPA as a revision to the Missouri SIP'' is the 
date from which the covered sources will begin complying with the 
Agreement. This is not approvable. The statute is clear that good 
neighbor obligations must be implemented as expeditiously as 
practicable and no later than the next attainment date. See Wisconsin, 
938 F.3d at 313-20; Maryland, 958 F.3d at 1203-04. The next attainment 
date at the time the MoDNR developed and submitted its submission, and 
presently, is the August 3, 2024, Moderate area attainment date, and 
thus the relevant analytical year is 2023, and emissions requirements 
to eliminate significant contribution should be implemented no later 
than the 2023 ozone season. See Final Disapproval, 88 FR 9340-41. The 
control requirements under the Consent Agreements are premised on 
better operating existing installed emissions controls. The EPA has 
consistently found that such emissions control strategies are capable 
of being implemented in a matter of weeks (e.g., 88 FR 36720-22; 86 FR 
23088-89; 81 FR 74561). Thus, the MoDNR, in identifying these controls 
as necessary to eliminate its significant contribution or interference 
with maintenance, was obligated by the good neighbor provision to 
require these emissions reductions by the start of the 2023 ozone 
season. It did not do so, and it did not justify why it did not do so 
based on any analysis of necessity or impossibility. See Wisconsin, 938 
F.3d at 320. Instead, the MoDNR tied the effectiveness of these 
emissions reductions to an event that is irrelevant to substantive 
compliance with the good neighbor provision, i.e., the effective date 
of any final action by the EPA to approve the Consent Agreements into 
Missouri's SIP. This was improper; as a result of this provision, even 
at this point in time, Missouri has not yet imposed enforceable 
emissions control requirements that should have been in place by the 
2023 ozone season and,

[[Page 63885]]

under the plain terms of the Consent Agreements, to this day the 
covered sources are under no obligation to comply with them.
    This appears to be the sources' understanding of these Consent 
Agreements as well; otherwise, at least one source appears to have been 
in violation of its Agreement in 2023. The EPA analyzed the 2023 ozone 
season emissions for all coal-fired units with SCR control systems in 
Missouri.\97\ Several units, including some from facilities subject to 
the Consent Agreements with the State, reached a NOX rate of 
0.05-0.08 lb/mmBtu. This range was also achieved on an average 
facility-wide level. Some units, however, did not achieve the emissions 
rate specified in the Consent Agreements. One facility did not achieve 
the emissions rate specified in the Consent Agreements, both at the 
unit level and on a facility-wide average basis. The EPA views this 
data as confirming its understanding that the Consent Agreements are 
not currently in effect or constitute binding and enforceable 
provisions of State law; otherwise, all sources would have presumably 
complied with the Agreements rather than risk committing a violation.
---------------------------------------------------------------------------

    \97\ See ``Missouri EGU Units 2023 Ozone Season Data,'' 
available in docket ID No. EPA-R07-OAR -2021-0851.
---------------------------------------------------------------------------

    Further, the EPA is not in a position to take the triggering action 
(i.e., approval) necessary to bring these agreements into effect, and 
it was improper for the State to attempt to place that onus on the 
Agency rather than comply with the attainment schedule of the CAA for 
itself. First, as explained elsewhere in this document, this November 
2022 Submission is not fully approvable for multiple reasons. Second, 
for the reasons explained in the following paragraph, anything less 
than a full approval would, per the terms of the Consent Agreements, 
render them unenforceable.
    The Consent Agreements include termination clauses that render them 
unenforceable depending on the nature of the action the EPA takes. For 
example, paragraph 13 contains four circumstances in which the sources 
could choose, unilaterally, to terminate the Agreements, each being a 
circumstance in which the EPA does not issue a ``full approval'' of the 
SIP revision or upon the effective date of a FIP for Missouri. Under 
Paragraph 13, if the EPA issues only a partial approval/disapproval or 
a limited approval, or issues a SIP Call, or upon the effective date of 
a FIP, then the sources can unilaterally withdraw from the Consent 
Agreements.
    These provisions place the EPA in a position that leaves it no 
choice but to propose to disapprove the November 2022 Submission in 
full. For the reasons explained elsewhere in section III. of this 
document, the EPA finds multiple grounds why it cannot fully approve 
this SIP submission. Even if the EPA could have explored the 
possibility of a limited or partial approval of this submission, it is 
not able to do this if doing so would render the emissions control 
measures established through the Consent Agreements unenforceable, by 
triggering the sources' ability to unilaterally withdraw from the 
Agreements. Nor does the EPA have discretion to partially approve the 
SIP submission by not including within its approval those provisions of 
the Consent Agreements such as Paragraph 13 (and others discussed later 
in this section) that are not approvable. To do so would be to render 
the SIP revision more stringent than the State intended, which the EPA 
is not authorized to do. See Bethlehem Steel Corp. v. Gorsuch, 742 F.2d 
1028 (7th Cir. 1984). In effect, Paragraph 13 leaves the EPA with this 
choice: either approve the November 2022 Submission in full and never 
bring the Good Neighbor Plan into effect for Missouri--which, for the 
reasons explained elsewhere in this document would fail to adequately 
address Missouri's good neighbor obligations for the 2015 ozone NAAQS--
or disapprove the November 2022 Submission in full, so that the Good 
Neighbor Plan can be brought into effect for Missouri and fill the gap 
in Missouri's SIP. See Ass'n of Irritated Residents v. U.S. EPA, 686 
F.3d 668, 675-76 (9th Cir. 2012); Virginia v. EPA, 108 F.3d 1397, 1408 
(D.C. Cir. 1997). The EPA is obligated under the CAA to follow the 
latter course.
    Further, the MoDNR did not make any revisions to Paragraph 12 of 
the Consent Agreements in response to the EPA's pre-submission 
comments. This provision allows for termination of the Agreement upon 
``mutual written agreement of'' the source and the MoDNR. This 
provision violates the Act's prohibition on modification of SIPs 
outside of authorized SIP revision processes. See CAA section 110(i) 
and (l). SIP provisions cannot authorize a State to make changes in the 
EPA-approved and federally enforceable SIP requirements applicable to 
sources without going through the statutorily required SIP-revision 
process. The EPA refers to SIP provisions that purport to authorize 
States to make unilateral changes to existing SIP requirements as 
impermissible ``director's discretion'' provisions. See, e.g., 86 FR 
15104, 15116 (March 22, 2021). However, the EPA interprets the CAA to 
allow two types of such provisions: (1) where the provision provides 
director's discretion for the State to make changes, but specifies that 
such changes have no effect for purposes of Federal law or alter SIP 
requirements unless and until the EPA approves the changes through a 
SIP revision pursuant to CAA requirements; or (2) where the provision 
provides director's discretion that is adequately bounded, such that at 
the time the EPA approves the SIP provision the Agency can evaluate it 
for compliance with applicable CAA requirements and evaluate the 
potential impacts of the State's exercise of that discretion. The EPA 
interprets CAA section 110(l) to allow SIP provisions with director's 
discretion of either type. In the case of an adequately bounded 
provision, the EPA considers such provisions consistent with section 
110(l) because, at the time of initial approval into the SIP, the 
Agency will already have evaluated the provision for compliance with 
applicable requirements and evaluated the potential impacts from 
exercise of the discretion. E.g., 86 FR 15116.
    In Environ. Comm. Fl. Elec. Power v. EPA, 94 F.4th 77 (D.C. Cir. 
2024), the D.C. Circuit held that the EPA impermissibly issued a SIP 
call, under CAA section 110(k)(5), in its 2015 SSM SIP Action \98\ for 
certain SIP provisions applicable to emissions during SSM events, 
including certain director's discretion type provisions that the EPA 
had previously approved. However, the Court did not foreclose that some 
director's discretion provisions may be so unbounded as to interfere 
with the Agency's ability to predict the impact on compliance with the 
CAA's requirements. Id. At 111. Further, Enviro. Comm. Fl. Elec. Power 
concerns the EPA's authority to issue a SIP call for certain provisions 
that it previously approved and not the EPA's authority to approve or 
disapprove a SIP submission in the first instance. Compare CAA section 
110(k)(3) with (k)(5).
---------------------------------------------------------------------------

    \98\ See 80 FR 33840.
---------------------------------------------------------------------------

    Here, Paragraph 12 of the Consent Agreements in effect provides 
unbounded discretion to the State to eliminate the requirements, even 
though the MoDNR has submitted these Consent Agreements as necessary to 
address Missouri's good neighbor obligations under CAA section 
110(a)(2)(D)(i) for the 2015 ozone NAAQS. The EPA has explained the 
need for emissions reductions on each day of the ozone season, 
reflecting the

[[Page 63886]]

daily, but unpredictably recurring, nature of the air pollution 
problem, and it is important that emissions control programs will be in 
operation in a continuous manner to eliminate each upwind State's 
``significant contribution'' throughout each day of each ozone season 
in perpetuity. See 88 FR 36676, 36686-87, 36752. Thus, Paragraph 12, 
which allows this upwind State and its sources to agree between 
themselves to terminate these emissions control requirements at any 
time for any reason, is unacceptably too unbounded to meet good 
neighbor obligations for the 2015 ozone NAAQS. Likewise, the EPA finds 
Paragraph 12 to be inconsistent with CAA section 110(i) and (l) because 
it permits the State not merely discretion to modify some provision 
within the overall operation of a broader regulatory scheme, but the 
ability to terminate the Agreements completely--i.e., the entirety of 
the emissions control program the State has put forward--at will. The 
EPA agrees that emissions controls on these sources are necessary 
(albeit not sufficient, see section III.) for Missouri to meet its good 
neighbor obligations and it would be inappropriate for the EPA to 
approve as SIP provisions these Consent Agreements that the State could 
eliminate without undertaking the necessary SIP revision process 
mandated by the Act.
    Despite the MoDNR's unenforceable assurances in the narrative 
portion of its Submission that it would not modify the Consent 
Agreements themselves without the EPA's approval, the operative 
language in the Agreements remains the same. Paragraph 12 remains an 
unambiguous statement authorizing termination of the Agreements upon 
agreement of the parties to them.\99\ Therefore, the EPA concludes that 
if the source and the MoDNR chose to exercise their rights in Paragraph 
12, the Consent Agreements would be terminated without review or 
approval from the EPA and the source would no longer be under any 
obligation to comply.
---------------------------------------------------------------------------

    \99\ The courts would also likely interpret this language 
similarly to the EPA. See, e.g., New York v. U.S. EPA, 525 F.Supp.3d 
340, 356 (N.D.N.Y. 2021) (`` `[T]the scope of a consent decree must 
be discerned within its four corners . . . .' '') (quoting 
Firefighters Local Union No. 1784 v. Stotts, 467 U.S. 561, 574 
(1984)).
---------------------------------------------------------------------------

    Further, Paragraph 12 violates the anti-backsliding provisions of 
section 110(l) of the CAA, which requires that the EPA shall not 
approve any revision of a plan if the revision would interfere with any 
applicable requirement concerning attainment and reasonable further 
progress. 42 U.S.C. 7410(l). The termination provision would allow a 
unilateral amendment to the SIP, potentially removing emissions and 
pollution control limits without an evaluation of whether the removal 
would be appropriate under the good neighbor provision, would interfere 
with attainment or reasonable further progress, or would interfere with 
any other applicable requirement of the Act.
    Because the SIP submission is otherwise not approvable, the EPA 
need not further evaluate the SSM, regulatory safety valve, or the 
force majeure provisions of the Consent Agreements for compliance with 
the Act. Due to the identified flaws in the Consent Agreements as 
described above, the EPA proposes that it cannot approve these 
Agreements as a revision to Missouri's SIP.
2. Evaluation of Approach of Regulating Named Sources
    The Consent Agreements only cover several specific identified 
sources. In all of the EPA's prior good neighbor rules, beginning with 
the NOX SIP Call in 1998, to ensure a robust and durable 
remedy to the problem of interstate pollution, the EPA has regulated 
sources on industry-wide bases and has regulated all existing and new 
sources meeting applicability criteria within the covered industries. 
See 88 FR 36685 (discussing Appalachian Power v. EPA, 249 F.3d 1032, 
1057-58 (D.C. Cir. 2001)); 40 CFR 51.121(f). The EPA continued this 
approach with the Good Neighbor Plan. By covering all new and existing 
emissions units meeting defined applicability criteria on an industry-
wide basis, the EPA ensures against the risk of production (and thus, 
emissions) shifting from covered to uncovered units. 88 FR 36746-47; 
see also 70 FR 25261. In EME Homer City, the Supreme Court upheld the 
EPA's approach of applying a uniform level of emissions control 
stringency across all units in a given industry (there, power plants), 
because this approach brings all sources in covered States up to a 
standard level of emissions control, thus avoiding free riding and 
inequitable outcomes among States linked to the same downwind air 
quality problems. 572 U.S. 489, 519.
    For example, the Group 3 trading program established for EGUs in 
the Good Neighbor Plan, as with all of the EPA's good neighbor rules 
covering EGUs, applies to all fossil-fuel fired EGUs over a certain 
size threshold. The EPA recognizes that certain units that were not 
identified in its Step 3 analysis, such as certain simple cycle 
combustion turbines, may have cost-effective emissions reduction 
opportunities while also being sources to which production and thus 
emissions could shift. These units are included in the emissions 
trading program and therefore, as in prior transport rules, the Good 
Neighbor Plan program continues to subject them to an allowance holding 
requirement which will likely incentivize any available cost-effective 
NOX reductions from these EGUs while forestalling the risk 
of mere emissions shifting rather than prohibition of significant 
contribution. 88 FR 36732.
    While the EPA does not require States to follow its 4-step 
framework if an alternative approach can be shown to meet the statutory 
requirement to eliminate significant contribution, the EPA has 
consistently explained that SIPs seeking to demonstrate equivalency in 
eliminating significant contribution from power plants would need to be 
evaluated based on the particular control strategies selected and 
whether the strategies as a whole provide adequate and enforceable 
provisions ensuring that the state-wide emissions reductions found to 
be necessary to eliminate significant contribution will be achieved. To 
address the applicable CAA requirements, the EPA has explained that for 
all EGUs in a State, the SIP revision should include the following 
general elements: (1) a comprehensive baseline 2023 statewide 
NOX emissions inventory (which includes existing control 
requirements), which should be consistent with the 2023 emissions 
inventory that the EPA used to calculate the required State budget in 
this final rule (unless the State can explain the discrepancy); (2) a 
list and description of control measures to satisfy the State emissions 
reduction obligation and a demonstration showing when each measure 
would be implemented to meet the 2023 and successive control periods; 
(3) fully-adopted State rules providing for such NOX 
controls during the ozone season; (4) for EGUs greater than 25 MWe, 
monitoring and reporting under 40 CFR part 75, and for other units, 
monitoring and reporting procedures sufficient to demonstrate that 
sources are complying with the SIP (see 40 CFR part 51, subpart K 
(``source surveillance'' requirements)); and (5) a projected inventory 
demonstrating that State measures along with Federal measures will 
achieve the necessary emissions reductions in time to meet the 2023 and 
successive compliance deadlines (e.g., enforceable reductions 
commensurate with installation of SCR on coal-fired EGUs by the 2027 
ozone season). See 88 FR 36841-42. See also 76 FR 48326.
    In this case, the MoDNR's approach of regulating only a subset of 
specific,

[[Page 63887]]

named EGU facilities at Step 4 (rather than regulating all EGUs in the 
State on an industry-wide basis) fails to include a sufficient analysis 
of the factors identified above to demonstrate that these measures 
effectively and durably prohibit the ``amount'' of emissions that is 
necessary to eliminate significant contribution from ``any source or 
other type of emissions activity within'' the State of Missouri. CAA 
section 110(a)(2)(D).
    Therefore, the EPA proposes to find that the Consent Agreements 
included in the State SIP are not permanent and enforceable and do not 
constitute ``adequate provisions'' to ensure that emissions 
constituting ``significant contribution'' from Missouri have been 
``prohibited.'' CAA section 110(a)(2)(D).

IV. Proposed Action

    The EPA is proposing to disapprove the November 2022 Submission 
from Missouri pertaining to interstate transport of air pollution that 
will significantly contribute to nonattainment or interfere with 
maintenance of the 2015 ozone NAAQS in other States. The EPA has 
already disapproved Missouri's first submission related to these 
requirements. See 88 FR 9336 (Feb. 13, 2023). That action is currently 
stayed as to Missouri pending judicial review. Missouri's November 2022 
Submission presents a new analysis of Missouri's understanding of what 
the good neighbor provision requires for purposes of the 2015 ozone 
NAAQS. For the reasons explained in this proposed action, the EPA has 
identified numerous shortcomings in the State's analysis with respect 
to these mandatory obligations under the Act, and so the EPA is 
proposing to disapprove the Submission. Under CAA section 110(c)(1)(B), 
this disapproval, if finalized, would establish a 2-year deadline for 
the EPA to promulgate a FIP for Missouri to address the CAA section 
110(a)(2)(D)(i)(I) interstate transport requirements pertaining to 
significant contribution to nonattainment and interference with 
maintenance of the 2015 ozone NAAQS in other States, unless the EPA 
first approves a SIP that meets these requirements. See Ass'n of 
Irritated Residents v. U.S. EPA, 686 F.3d 668, 675-76 (9th Cir. 2012). 
Accordingly, if the EPA finalizes a disapproval of Missouri's November 
2022 Submission, the EPA's obligation to promulgate a FIP pursuant to 
CAA section 110(c) could be satisfied through requirements like those 
in the Good Neighbor Plan for Missouri or other appropriate action, 
which would be the subject of additional rulemaking action. Disapproval 
does not start a mandatory sanctions clock for Missouri.

V. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP 
submission that complies with the provisions of the Act and applicable 
Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in 
reviewing SIP submissions, the EPA's role is to approve State choices, 
provided that they meet the criteria of the CAA. This action proposes 
to disapprove the State submission as not meeting Federal requirements 
and does not impose additional requirements. For that reason, this 
action:
     Is not a significant regulatory action subject to review 
by the Office of Management and Budget under Executive Orders 12866 (58 
FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandates or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of the National Technology 
Transfer and Advancement Act (NTTA) because this rulemaking does not 
involve technical standards; and
     Executive Order 12898 (Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations, 59 FR 7629, Feb. 16, 1994) directs Federal agencies to 
identify and address ``disproportionately high and adverse human health 
or environmental effects'' of their actions on minority populations and 
low-income populations to the greatest extent practicable and permitted 
by law. The EPA defines environmental justice (EJ) as ``the fair 
treatment and meaningful involvement of all people regardless of race, 
color, national origin, or income with respect to the development, 
implementation, and enforcement of environmental laws, regulations, and 
policies.'' The EPA further defines the term fair treatment to mean 
that ``no group of people should bear a disproportionate burden of 
environmental harms and risks, including those resulting from the 
negative environmental consequences of industrial, governmental, and 
commercial operations or programs and policies.'' The MoDNR did not 
evaluate EJ considerations as part of its SIP submission; the CAA and 
applicable implementing regulations neither prohibit nor require such 
an evaluation. The EPA did not perform an EJ analysis and did not 
consider EJ in this action. Due to the nature of the action being taken 
here, this action is expected to have a neutral impact on the air 
quality of the affected area. Consideration of EJ is not required as 
part of this action, and there is no information in the record 
inconsistent with the stated goal of Executive Order 12898 of achieving 
environmental justice for people of color, low-income populations, and 
Indigenous peoples.
     This action does not have Tribal implications as specified 
in Executive Order 13175. This action does not apply on any Indian 
reservation land, any other area where the EPA or an Indian tribe has 
demonstrated that a tribe has jurisdiction, or non-reservation areas of 
Indian country. Thus, Executive Order 13175 does not apply to this 
action.
    Determinations Under CAA section 307(b)(1) and (d): Section 
307(b)(1) of the CAA governs judicial review of final actions by the 
EPA. This section provides, in part, that petitions for review must be 
filed in the D.C. Circuit: (1) when the agency action consists of 
``nationally applicable regulations promulgated, or final actions 
taken, by the Administrator,'' or (2) when such action is locally or 
regionally applicable, if ``such action is based on a determination of 
nationwide scope or effect and if in taking such action the 
Administrator finds and publishes that such action is based on such a 
determination.'' For locally or regionally applicable final actions, 
the CAA reserves to the EPA complete discretion to decide whether to 
invoke the exception in (2).\100\
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    \100\ In deciding whether to invoke the exception by making and 
publishing a finding that an action is based on a determination of 
nationwide scope or effect, the Administrator takes into account a 
number of policy considerations, including his judgment balancing 
the benefit of obtaining the D.C. Circuit's authoritative 
centralized review versus allowing development of the issue in other 
contexts and the best use of agency resources.

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[[Page 63888]]

    If the EPA finalizes this proposed rulemaking, the Administrator 
intends to exercise the complete discretion afforded to him under the 
CAA to make and publish a finding that the final action, which would be 
locally or regionally applicable, is based on a determination of 
``nationwide scope or effect'' within the meaning of CAA section 
307(b)(1). Through this rulemaking action (in conjunction with a series 
of related actions on other SIP submissions for the same CAA 
obligations), the EPA interprets and applies section 110(a)(2)(D)(i)(I) 
of the CAA for the 2015 ozone NAAQS based on a common core of 
nationwide policy judgments and technical analysis concerning the 
interstate transport of pollutants throughout the continental U.S. This 
proposal, if finalized, would be based on several determinations of 
nationwide scope or effect, each of which has the purpose of ensuring 
consistency and equity in implementing the good neighbor provision for 
ozone across all States, including: (1) the determination that use of 
the same 2023 and 2026 analytical year air quality modeling and 
monitoring analytics (including the use of the violating-monitor 
receptor identification methodology) that were used in the Disapproval 
Action and the Good Neighbor Plan are appropriate for purposes of 
evaluating Missouri's November 2022 Submission; (2) the determination 
that 1 percent of NAAQS is the appropriate contribution threshold at 
Step 2 of the four-step framework nationwide; and (3) the determination 
that the MoDNR's Step 3 analysis and Step 4 implementation approach are 
inconsistent with and not adequate to replace the EPA's nationwide 
findings and the emissions control programs in the Good Neighbor Plan 
for sources in Missouri and 19 other similarly situated States that 
remain linked through the 2026 analytic year.
    These determinations would provide important bases for the action, 
if finalized, and are needed to ensure consistency and equity in the 
treatment of all States in addressing the multistate problem of 
interstate ozone pollution under the good neighbor provision for the 
2015 ozone NAAQS. Missouri seeks by its November 2022 Submission to 
avoid the implementation of the Good Neighbor Plan in Missouri, through 
a set of emissions control requirements that are demonstrably and 
substantially less stringent than what the EPA determined was needed to 
eliminate ``significant contribution'' for the 2015 ozone NAAQS in the 
Good Neighbor Plan. The Good Neighbor Plan is designed as a 
``collective approach'' to effectively address the nationwide problem 
of interstate ozone transport in an equitable and consistent manner 
across the covered States. See Kentucky Energy and Environment Cabinet 
v. EPA, No. 23-3605 (6th Cir. Nov. 9, 2023), Order at 8. The 
determinations underlying this proposed disapproval would, if 
finalized, have nationwide scope and effect, among other reasons, 
because they would ensure that the Good Neighbor Plan (until replaced 
by SIPs meeting the statutory requirements) may be implemented on a 
consistent basis for all covered States, including Missouri, and may 
deliver the full amount of relief from upwind emissions that the EPA 
has found downwind jurisdictions are due.\101\ For these reasons, the 
Administrator intends, if this proposed action is finalized, to 
exercise the complete discretion afforded to him under the CAA to make 
and publish a finding that this action is based on a determination of 
nationwide scope or effect for purposes of CAA section 307(b)(1).\102\
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    \101\ In the report on the 1977 Amendments that revised section 
307(b)(1) of the CAA, Congress noted that the Administrator's 
determination that the ``nationwide scope or effect'' exception 
applies would be appropriate for any action that has a scope or 
effect beyond a single judicial circuit. See H.R. Rep. No. 95-294 at 
323, 324, reprinted in 1977 U.S.C.C.A.N. 1402-03.
    \102\ If the EPA takes a consolidated, single final action on 
this and any other proposed SIP actions with respect to obligations 
under CAA section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS, that 
action may be nationally applicable, and the EPA would also 
anticipate that in that instance, in the alternative, the 
Administrator would make and publish a finding that such final 
action is based on a determination of nationwide scope or effect.
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    This action is subject to the provisions of CAA section 307(d). CAA 
section 307(d)(1)(V) of the CAA provides that the provisions of section 
307(d) apply to ``such other actions as the administrator may 
determine.'' Pursuant to CAA section 307(d)(1)(V), the Administrator 
determines that this action is subject to the provisions of CAA section 
307(d).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Ozone.

    Authority: 42 U.S.C. 7401 et seq.

Michael S. Regan,
Administrator.
[FR Doc. 2024-15826 Filed 8-5-24; 8:45 am]
BILLING CODE 6560-50-P