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Proposed Rule2024-15826

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

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Published

August 6, 2024

Issuing agencies

Environmental Protection Agency

Abstract

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.

Full Text

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<title>Federal Register, Volume 89 Issue 151 (Tuesday, August 6, 2024)</title>
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[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 [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[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 <a href="https://www.epa.gov/mo/air-missouri">https://www.epa.gov/mo/air-missouri</a>. 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: <a href="https://www.regulations.gov">https://www.regulations.gov</a>. Follow the online instructions for submitting
comments. Once submitted, comments cannot be edited or removed from
<a href="https://www.regulations.gov">https://www.regulations.gov</a>. 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 <a href="https://www2.epa.gov/dockets/commenting-epa-dockets">https://www2.epa.gov/dockets/commenting-epa-dockets</a>.
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 <a href="https://www.regulations.gov">https://www.regulations.gov</a> 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
<a href="https://www.regulations.gov">https://www.regulations.gov</a>.
To pre-register to attend or speak at the virtual public hearing,
please use the online registration form available at <a href="https://www.epa.gov/mo/air-missouri">https://www.epa.gov/mo/air-missouri</a>, or contact us via email at
<a href="/cdn-cgi/l/email-protection#19747a70776d606b7c377e7c6b78757d597c6978377e766f">[email&#160;protected]</a>. 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: <a href="/cdn-cgi/l/email-protection#9deee9f2f3f8b3eaf4f1f1f4fcf0ddf8edfcb3faf2eb">[email&#160;protected]</a>.

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 <a href="https://www.epa.gov/mo/air-missouri">https://www.epa.gov/mo/air-missouri</a>.
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 <a href="https://www.epa.gov/mo/air-missouri">https://www.epa.gov/mo/air-missouri</a>, or contact us via email at <a href="/cdn-cgi/l/email-protection#90fdf3f9fee4e9e2f5bef7f5e2f1fcf4d0f5e0f1bef7ffe6">[email&#160;protected]</a>. 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
<a href="https://www.epa.gov/mo/air-missouri">https://www.epa.gov/mo/air-missouri</a>. 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 <a href="/cdn-cgi/l/email-protection#e08d83898e94999285ce878592818c84a0859081ce878f96">[email&#160;protected]</a>. 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 <a href="https://www.epa.gov/mo/air-missouri">https://www.epa.gov/mo/air-missouri</a>. While the EPA
expects the hearing to go forward as set forth above, please monitor
our website or contact us via email at <a href="/cdn-cgi/l/email-protection#b1dcd2d8dfc5c8c3d49fd6d4c3d0ddd5f1d4c1d09fd6dec7">[email&#160;protected]</a> 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
NO<INF>X</INF> 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 NO<INF>X</INF> 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 (NO<INF>X</INF>) 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 NO<INF>X</INF>-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 NO<INF>X</INF>-
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.
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\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).
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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 ``NO<INF>X</INF>
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 NO<INF>X</INF> 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 <a href="https://www.regulations.gov">https://www.regulations.gov</a>.
\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.
---------------------------------------------------------------------------

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 <a href="https://www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves">https://www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves</a>.
\21\ <a href="https://www.epa.gov/air-emissions-modeling/2016v2-platform">https://www.epa.gov/air-emissions-modeling/2016v2-platform</a>.
---------------------------------------------------------------------------

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\
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\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 NO<INF>X</INF> 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).
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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:
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\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).
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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.
---------------------------------------------------------------------------

\31\ A design value is calculated using the annual 4th high MDA8
ozone concentration averaged over 3 years.
---------------------------------------------------------------------------

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 NO<INF>X</INF> 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. <a href="https://www.ladco.org/wp-content/uploads/Documents/Reports/TSDs/O3/LADCO_2015O3iSIP_TSD_13Aug2018.pdf">https://www.ladco.org/wp-content/uploads/Documents/Reports/TSDs/O3/LADCO_2015O3iSIP_TSD_13Aug2018.pdf</a>.
---------------------------------------------------------------------------

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' NO<INF>X</INF> 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 NO<INF>X</INF>. 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 NO<INF>X</INF> emissions from Missouri EGUs that exceed the
assurance levels of the CSAPR NO<INF>X</INF> 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 NO<INF>X</INF> 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
NO<INF>X</INF> 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 NO<INF>X</INF>
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 NO<INF>X</INF> controls
(i.e., low NO<INF>X</INF> 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
NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF>
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 NO<INF>X</INF> 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 NO<INF>X</INF> emissions limits at certain facilities.\55\ With
consideration of those factors, the MoDNR asserts that the projected
emissions reductions in 2023 from the new NO<INF>X</INF> 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
NO<INF>X</INF> 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 NO<INF>X</INF> 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.
NO<INF>X</INF>/ton of clinker produced. The MoDNR indicated that the
State's rule, 10 CSR 10-6.380 Control of NO<INF>X</INF> 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 NO<INF>X</INF>/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 NO<INF>X</INF>
controls at the Pittsburg Corning Corporation in the proposed Good
Neighbor Plan. The MoDNR further notes that the 2020 and 2021
NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF> ozone season
emissions data from 2009 through 2021 and calculated an average
NO<INF>X</INF> 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 NO<INF>X</INF> emissions rates since these may reflect
SCR systems that have all new components and therefore not
representative of ongoing achievable NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF> 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 NO<INF>X</INF>
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 NO<INF>X</INF> 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.
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\89\ Included in the docket for this action, EPA-R07-OAR-2021-
0851.
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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 NO<INF>X</INF> 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.
---------------------------------------------------------------------------

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\
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\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.
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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 NO<INF>X</INF> 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.
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\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.

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