[Federal Register Volume 87, Number 35 (Tuesday, February 22, 2022)]
[Proposed Rules]
[Pages 9533-9545]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-03183]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

EPA-R07-OAR-2021-0851; EPA-HQ-OAR-2021-0663; FRL-9425-01-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) is proposing to disapprove a 
State Implementation Plan (SIP) submittal from Missouri 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, which are 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. 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 submittal that meets these requirements. 
Disapproval does not start a mandatory sanctions clock.

DATES: Written comments must be received on or before April 25, 2022.

ADDRESSES: You may send comments, identified as Docket No. EPA-R07-OAR-
2021-0851, by any of the following methods: Federal eRulemaking Portal 
at https://

[[Page 9534]]

www.regulations.gov following the online nstructions for submitting 
comments or via email to <a href="/cdn-cgi/l/email-protection#b9cacdd6d7dc97ced0d5d5d0d8d4f9dcc9d897ded6cf"><span class="__cf_email__" data-cfemail="82f1f6edece7acf5ebeeeeebe3efc2e7f2e3ace5edf4">[email protected]</span></a>. Include Docket ID No. 
EPA-R07-OAR-2021-0851 in the subject line of the message.
    Instructions: All submissions received must include the Docket ID 
No. for this rulemaking. Comments received may be posted without change 
to https://www.regulations.gov/, including any personal information 
provided. For detailed instructions on sending comments and additional 
information on the rulemaking process, see the ``Public Participation'' 
heading of the SUPPLEMENTARY INFORMATION section of this document. Out 
of an abundance of caution for members of the public and our staff, the 
EPA Docket Center and Reading Room are open to the public by 
appointment only to reduce the risk of transmitting COVID-19. Our 
Docket Center staff also continues to provide remote customer service 
via email, phone, and webform. For further information on EPA Docket 
Center services and the current status, please visit us online at 
https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: William Stone, Environmental 
Protection Agency, Region 7 Office, Air Quality Planning Branch, 11201 
Renner Boulevard, Lenexa, Kansas 66219; telephone number: (913) 551-
7714; email address: <a href="/cdn-cgi/l/email-protection#2152554e4f440f56484d4d48404c614451400f464e57"><span class="__cf_email__" data-cfemail="36454259585318415f5a5a5f575b7653465718515940">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION: Public participation: Submit your comments, 
identified by Docket ID No. EPA-R07-OAR-2021-0851, at https://www.regulations.gov (our preferred method), or the other methods 
identified in the ADDRESSES section. Once submitted, comments cannot be 
edited or removed from the docket. The EPA may publish any comment 
received to its public docket. Do not submit to EPA's docket at https://www.regulations.gov any information you consider to be Confidential 
Business Information (CBI) or other information whose disclosure is 
restricted by statute. Multimedia submissions (audio, video, etc.) must 
be accompanied by a written comment. The written comment is considered 
the official comment and should include discussion of all points you 
wish to make. The EPA will generally not consider comments or comment 
contents located outside of the primary submission (i.e., on the web, 
cloud, or other file sharing system).
    There are two dockets supporting this action, EPA-R07-OAR-2021-0851 
and EPA-HQ-OAR-2021-0663. Docket No. EPA-R07-OAR-2021-0851 contains 
information specific to Missouri, including the notice of proposed 
rulemaking. Docket 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 8-hour ozone NAAQS which are being 
used to support this action. All comments regarding information in 
either of these dockets are to be made in Docket No. EPA-R07-OAR-2021-
0851. For additional submission methods, please contact William Stone, 
(913) 551-7714, <a href="/cdn-cgi/l/email-protection#5023243f3e357e27393c3c39313d103520317e373f26"><span class="__cf_email__" data-cfemail="a2d1d6cdccc78cd5cbcececbc3cfe2c7d2c38cc5cdd4">[email protected]</span></a>. For the full EPA public comment 
policy, information about CBI or multimedia submissions, and general 
guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. Due to public health 
concerns related to COVID-19, the EPA Docket Center and Reading Room 
are open to the public by appointment only. Our Docket Center staff 
also continues to provide remote customer service via email, phone, and 
webform. For further information and updates on EPA Docket Center 
services, please visit us online at https://www.epa.gov/dockets.
    The EPA continues to carefully and continuously monitor information 
from the Centers for Disease Control and Prevention (CDC), local area 
health departments, and our Federal partners so that we can respond 
rapidly as conditions change regarding COVID-19.
    The index to the docket for this action, Docket No. EPA-R07-OAR-
2021-0851, is available electronically at www.regulations.gov. While 
all documents in the docket are listed in the index, some information 
may not be publicly available due to docket file size restrictions or 
content (e.g., CBI).
    Throughout this document, ``we,'' ``us,'' and ``our'' means the 
EPA.

I. Background

A. Description of Statutory Background

    On October 1, 2015, the EPA promulgated a revision to the ozone 
NAAQS (2015 8-hour ozone NAAQS), lowering the level of both the primary 
and secondary standards to 0.070 parts per million (ppm).\1\ Section 
110(a)(1) of the CAA requires states to submit, within 3 years after 
promulgation of a new or revised standard, SIP submissions meeting the 
applicable requirements of 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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B. Description of the EPA's Four Step Interstate Transport Regulatory 
Process

    The EPA is using the 4-step interstate transport framework (or 4-
step framework) to evaluate the state's SIP submittals addressing the 
interstate transport provision for the 2015 8-hour ozone NAAQS. The EPA 
has addressed the interstate transport requirements of CAA section 
110(a)(2)(D)(i)(I) with respect to prior ozone NAAQS in several 
regional regulatory actions, including the Cross-State Air Pollution 
Rule (CSAPR), which addressed interstate transport with respect to the 
1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter 
standards,\4\ and the Cross-State Air Pollution Rule Update (CSAPR 
Update) \5\ and the Revised CSAPR Update, both of which addressed the 
2008 ozone NAAQS.\6\
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    \4\ See Federal Implementation Plans: Interstate Transport of 
Fine Particulate Matter and Ozone and Correction of SIP Approvals, 
76 FR 48208 (Aug. 8, 2011).
    \5\ Cross-State Air Pollution Rule Update for the 2008 Ozone 
NAAQS, 81 FR 74504 (Oct. 26, 2016).
    \6\ 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).

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    Through the development and implementation of the CSAPR rulemakings 
and prior regional rulemakings pursuant to the interstate transport 
provision,\7\ the EPA, working in partnership with states, developed 
the following 4-step interstate transport framework to evaluate a 
state's obligations to eliminate interstate transport emissions under 
the interstate transport provision for the ozone NAAQS: (1) Identify 
monitoring sites that are projected to have problems attaining and/or 
maintaining the NAAQS (i.e., nonattainment and/or maintenance 
receptors); (2) identify states that impact those air quality problems 
in other (i.e., downwind) states sufficiently such that the states are 
considered ``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.
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    \7\ In addition to the 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. Background on the EPA's Ozone Transport Modeling Information

    The EPA has released several documents containing information 
relevant to evaluating interstate transport with respect to the 2015 8-
hour ozone NAAQS. First, on January 6, 2017, the EPA published a notice 
of data availability (NODA) in which we requested comment on 
preliminary interstate ozone transport data including projected ozone 
design values (DVs) and interstate contributions for 2023 using a 2011 
base year platform.\8\ In the NODA, the EPA used the year 2023 as the 
analytic year for this preliminary modeling because that year aligns 
with the expected attainment year for Moderate ozone nonattainment 
areas for the 2015 8-hour ozone NAAQS.\9\ On October 27, 2017, we 
released a memorandum (October 2017 memorandum) containing updated 
modeling data for 2023, which incorporated changes made in response to 
comments on the NODA and noted that the modeling may be useful for 
states developing SIPs to address interstate transport obligations for 
the 2008 ozone NAAQS.\10\ On March 27, 2018, we issued a memorandum 
(March 2018 memorandum) noting that the same 2023 modeling data 
released in the 2017 memorandum could also be useful for identifying 
potential downwind air quality problems with respect to the 2015 8-hour 
ozone NAAQS at Step 1 of the 4-step interstate transport framework.\11\ 
The March 2018 memorandum also included the then newly available 
contribution modeling data for 2023 to assist states in evaluating 
their impact on potential downwind air quality problems for the 2015 8-
hour ozone NAAQS under Step 2 of the 4-step interstate transport 
framework.\12\ 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 8-hour 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.\13\
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    \8\ 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).
    \9\ 82 FR at 1735.
    \10\ See Information on the Interstate Transport State 
Implementation Plan Submissions for the 2008 Ozone National Ambient 
Air Quality Standards under Clean Air Act Section 
110(a)(2)(D)(i)(I), October 27, 2017, available in the docket ID No. 
EPA-HQ-OAR-2021-0663.
    \11\ 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.
    \12\ 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.''
    \13\ 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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    Since 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.\14\ 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 DVs 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.\15\ See 85 FR 68964, 68981. Although the 
Revised CSAPR Update addressed transport for the 2008 ozone NAAQS, the 
projected design values and contributions from the 2016v1 platform are 
also useful for identifying downwind ozone problems and linkages with 
respect to the 2015 ozone NAAQS.\16\
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    \14\ The results of this modeling, as well as the underlying 
modeling files, are included in docket ID No. EPA-HQ-OAR-2021-0663.
    \15\ See 85 FR 68964, 68981.
    \16\ See the Air Quality Modeling Technical Support Document for 
the Final Revised Cross-State Air Pollution Rule Update, included in 
the Headquarters docket ID No. EPA-HQ-OAR-2021-0663.
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    Following the Revised CSAPR Update final rule, the EPA made further 
updates to the 2016 emissions platform to include mobile emissions from 
the EPA's Motor Vehicle Emission Simulator MOVES3 model \17\ and 
updated emissions projections for electric generating units (EGUs) that 
reflect the emissions reductions from the Revised CSAPR Update, recent 
information on plant closures, and other sector trends. The construct 
of the updated emissions platform, 2016v2, is described in the 
emissions modeling technical support document (TSD) for this proposed 
rule.\18\ The EPA

[[Page 9536]]

performed air quality modeling of the 2016v2 emissions using the most 
recent public release version of the Comprehensive Air Quality Model 
with Extensions (CAMx) photochemical modeling, version 7.10. with the 
2016 base year and 2023 future year emissions developed as part of the 
2016v2 emissions platform.\19\ The EPA now proposes to rely on modeling 
based on the updated and newly available 2016v2 air quality modeling in 
evaluating these submissions with respect to Steps 1 and 2 of the 4-
step interstate transport framework. By using the updated modeling 
results, the EPA is using the most current and technically appropriate 
information for this proposed rulemaking. Section III of this document 
and the Air Quality Modeling TSD included in the docket for this 
proposal contain additional detail on the modeling performed using the 
2016v2 emissions. In this document, the EPA is accepting public comment 
on this updated 2023 modeling, which uses a 2016 emissions platform. 
Details on the air quality modeling and the methods for projecting 
design values and determining contributions in 2023 are described in 
the Air Quality Modeling TSD for 2015 Ozone NAAQS Transport SIP 
Proposed Actions. Comments on the EPA's air quality modeling should be 
submitted in the Regional docket for this action, docket ID No. EPA-
R07-OAR-2021-0851. Comments are not being accepted in docket EPA-HQ-
OAR-2021-0663.
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    \17\ Additional details and documentation related to the MOVES3 
model can be found at https://www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves.
    \18\ See Technical Support Document (TSD) Preparation of 
Emissions Inventories for the 2016v2 North American Emissions 
Modeling Platform included in the Headquarters docket ID No. EPA-HQ-
OAR-2021-0663.
    \19\ Ramboll Environment and Health, January 2021, www.camx.com.
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    States may have chosen to rely on the results of the EPA modeling 
and/or alternative modeling performed by states or Multi-Jurisdictional 
Organizations (MJOs) to evaluate downwind air quality problems and 
contributions as part of their submissions. In section III we evaluate 
how Missouri used air quality modeling information in their submission.

D. The EPA's Approach to Evaluating Interstate Transport SIPs for the 
2015 8-Hour 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 
submittals for the 2015 8-hour ozone NAAQS. These policy judgments 
reflect consistency with relevant case law and past agency practice as 
reflected in the CSAPR and related rulemakings. Nationwide consistency 
in 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 in order to ensure an ``efficient and equitable'' approach. 
See EME Homer City Generation, LP v. EPA, 572 U.S. 489, 519 (2014).
    In the March, August, and October 2018 memoranda, the EPA 
recognized that states may be able to establish alternative approaches 
to addressing their interstate transport obligations for the 2015 8-
hour ozone NAAQS that vary from a nationally uniform framework. The EPA 
emphasized in these memoranda, however, that such alternative 
approaches must be technically justified and appropriate in light of 
the facts and circumstances of each particular state's submittal. In 
general, the EPA continues to believe that deviation from a nationally 
consistent approach to ozone transport must be substantially justified 
and have a well-documented technical basis that is consistent with 
relevant case law. Where states submitted SIPs that rely on any such 
potential ``flexibilities'' as may have been identified or suggested in 
the past, the EPA will evaluate whether the state adequately justified 
the technical and legal basis for doing so.
    The EPA notes that certain concepts included in an attachment to 
the March 2018 memorandum require unique consideration, and these ideas 
do not constitute agency guidance with respect to transport obligations 
for the 2015 ozone NAAQS. Attachment A to the March 2018 memorandum 
identified a ``Preliminary List of Potential Flexibilities'' that could 
potentially inform SIP development.\20\ However, the EPA made clear in 
that Attachment that the list of ideas were not suggestions endorsed by 
the Agency but rather ``comments provided in various forums'' on which 
the EPA sought ``feedback from interested stakeholders.'' \21\ Further, 
Attachment A stated, ``EPA is not at this time making any determination 
that the ideas discussed below are consistent with the requirements of 
the CAA, nor are we specifically recommending that states use these 
approaches.'' \22\ Attachment A to the March 2018 memorandum, 
therefore, does not constitute agency guidance, but was intended to 
generate further discussion around potential approaches to addressing 
ozone transport among interested stakeholders. To the extent states 
sought to develop or rely on these ideas in support of their SIP 
submittals, the EPA will thoroughly review the technical and legal 
justifications for doing so.
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    \20\ March 2018 memorandum, Attachment A.
    \21\ Id. at A-1.
    \22\ Id.
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    The remainder of this section describes the EPA's proposed 
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 general, the states and the EPA must implement the interstate 
transport provision in a manner ``consistent with the provisions of 
[title I of the CAA.]'' CAA section 110(a)(2)(D)(i). This requires, 
among other things, that these obligations are addressed consistently 
with the timeframes for downwind areas to meet their CAA obligations. 
With respect to ozone NAAQS, under CAA section 181(a), this means 
obligations must be addressed ``as expeditiously as practicable'' and 
no later than the schedule of attainment dates provided in CAA section 
181(a)(1).\23\ Several D.C. Circuit court decisions address the issue 
of the relevant analytic year for the purposes of evaluating ozone 
transport air-quality problems. On September 13, 2019, the D.C. Circuit 
issued a decision in Wisconsin v. EPA, remanding the CSAPR Update to 
the extent that 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). 938 F.3d at 313.
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    \23\ For attainment dates for the 2015 8-hour ozone NAAQS, refer 
to CAA section 181(a), 40 CFR 51.1303, and Additional Air Quality 
Designations for the 2015 Ozone National Ambient Air Quality 
Standards, 83 FR 25776 (June 4, 2018, effective Aug. 3, 2018).
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    On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. 
EPA that cited the Wisconsin decision in holding that the EPA must 
assess the impact of interstate transport on air quality at the next 
downwind attainment date, including Marginal area attainment dates, in 
evaluating the basis for the EPA's denial of a petition under CAA 
section 126(b). Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 
2020). The court noted that ``section 126(b) incorporates the Good 
Neighbor Provision,'' and, therefore, ``EPA must find a violation [of 
section 126] if an upwind source will significantly contribute to 
downwind nonattainment

[[Page 9537]]

at the next downwind attainment deadline. Therefore, the Agency must 
evaluate downwind air quality at that deadline, not at some later 
date.'' Id. at 1204 (emphasis added). The EPA interprets the court's 
holding in Maryland as requiring the states and the Agency, under the 
good neighbor provision, to assess downwind air quality as 
expeditiously as practicable and no later than the next applicable 
attainment date,\24\ which is now the Moderate area attainment date 
under CAA section 181 for ozone nonattainment. The Moderate area 
attainment date for the 2015 8-hour ozone NAAQS is August 3, 2024.\25\ 
The EPA believes that 2023 is now the appropriate year for analysis of 
interstate transport obligations for the 2015 8-hour ozone NAAQS, 
because the 2023 ozone season is the last relevant ozone season during 
which achieved emissions reductions in linked upwind states could 
assist downwind states with meeting the August 3, 2024, Moderate area 
attainment date for the 2015 8-hour ozone NAAQS.
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    \24\ We note that the court in Maryland did not have occasion to 
evaluate circumstances in which the EPA may determine that an upwind 
linkage to a downwind air quality problem exists at steps 1 and 2 of 
the interstate transport framework by a particular attainment date, 
but for reasons of impossibility or profound uncertainty the Agency 
is unable to mandate upwind pollution controls by that date. See 
Wisconsin, 938 F.3d at 320. The D.C. Circuit noted in Wisconsin that 
upon a sufficient showing, these circumstances may warrant 
flexibility in effectuating the purpose of the interstate transport 
provision.
    \25\ See CAA section 181(a); 40 CFR 51.1303; Additional Air 
Quality Designations for the 2015 Ozone National Ambient Air Quality 
Standards, 83 FR 25776 (June 4, 2018, effective Aug. 3, 2018).
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    The EPA recognizes that the attainment date for nonattainment areas 
classified as Marginal for the 2015 8-hour ozone NAAQS was August 3, 
2021. Under the Maryland holding, any necessary emissions reductions to 
satisfy interstate transport obligations should have been implemented 
by no later than this date. At the time of the statutory deadline to 
submit interstate transport SIPs (October 1, 2018), many states relied 
upon the EPA modeling of the year 2023, and no state provided an 
alternative analysis using a 2021 analytic year (or the prior 2020 
ozone season). However, the EPA must act on SIP submittals using the 
information available at the time it takes such action. In this 
circumstance, the EPA does not believe it would be appropriate to 
evaluate states' obligations under CAA section 110(a)(2)(D)(i)(I) as of 
an attainment date that is wholly in the past, because the Agency 
interprets the interstate transport provision as forward looking. See 
86 FR 23074; see also Wisconsin, 938 F.3d at 322. Consequently, in this 
proposal the EPA will use the analytical year of 2023 to evaluate each 
state's CAA section 110(a)(2)(D)(i)(I) SIP submission with respect to 
the 2015 8-hour ozone NAAQS.
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. Where the EPA's analysis shows that a site does not fall 
under the definition of a nonattainment or maintenance receptor, that 
site is excluded from further analysis under the EPA's 4-step 
interstate transport framework. For sites that are identified as a 
nonattainment or maintenance receptor in 2023, we proceed to the next 
step of our 4-step interstate transport framework by identifying the 
upwind state's contribution to those receptors.
    The EPA's approach to identifying ozone nonattainment and 
maintenance receptors in this action is consistent with the approach 
used in previous transport rulemakings. The EPA's 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 v. EPA.\26\
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    \26\ See North Carolina v. EPA, 531 F.3d 896, 910-11 (D.C. Cir. 
2008) (holding that the EPA must give ``independent significance'' 
to each prong of CAA section 110(a)(2)(D)(i)(I)).
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    For the purpose of this proposal, 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 future analytic year (i.e., 
2023).\27\
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    \27\ See 81 FR 74504 (October 26, 2016). This same concept, 
relying on both current monitoring data and modeling to define 
nonattainment receptor, was also applied in CAIR. See 70 FR at 
25241, 25249 (January 14, 2005); see also North Carolina, 531 F.3d 
at 913-14 (affirming as reasonable EPA's approach to defining 
nonattainment in CAIR).
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    In addition, in this proposal, the EPA identifies 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).\28\ 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, 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.
---------------------------------------------------------------------------

    \28\ 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).
---------------------------------------------------------------------------

    Recognizing that nonattainment receptors are also, by definition, 
maintenance receptors, 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 
above, 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. 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. Consistent with the methodology described for 
nonattainment, those sites that are

[[Page 9538]]

currently measuring ozone concentrations below the level of the 
applicable NAAQS, but that are projected to be nonattainment based on 
the average or maximum design values, are identified as maintenance-
only receptors.
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 ppb for the 2015 8-hour ozone NAAQS), the upwind state is not 
``linked'' to a downwind air quality problem, and the EPA, therefore, 
concludes that the state does not significantly contribute 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 under CAA section 
110(a)(2)(D)(i)(I).
    The EPA is proposing to rely 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 8-hour ozone NAAQS (i.e., 0.70 
ppb) at downwind receptors. This is consistent with the Step 2 approach 
that the EPA applied in CSAPR for the 1997 ozone NAAQS, which has 
subsequently been applied in the CSAPR Update when evaluating 
interstate transport obligations for the 2008 ozone NAAQS. The EPA 
continues to find 1 percent to be an appropriate threshold. For ozone, 
as the EPA found in the Clean Air Interstate Rule (CAIR), CSAPR, and 
CSAPR Update, portion of the nonattainment problems from anthropogenic 
sources in the U.S. results from the combined impact of relatively 
small contributions from many upwind states, along with contributions 
from in-state sources and, in some cases, substantially larger 
contributions from a subset of particular upwind states. The EPA's 
analysis shows that much of the ozone transport problem being analyzed 
in this proposed rule is still the result of the collective impacts of 
contributions from many upwind states. 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. See 81 
FR at 74518. See also 86 FR at 23085 (reviewing and explaining 
rationale from CSAPR; 76 FR at 48237-38. (for selection of 1 percent 
threshold)).
    The EPA's August 2018 memorandum recognized that in certain 
circumstances, a state may be able to establish that an alternative 
contribution threshold of 1 ppb is justifiable. Where a state relies on 
this alternative threshold, and where that state determined that it was 
not linked at Step 2 using the alternative threshold, the EPA will 
evaluate whether the state provided a technically sound assessment of 
the appropriateness of using this alternative threshold based on the 
facts and circumstances underlying its application in the particular 
SIP submission.
4. Step 3 of the 4-Step Interstate Transport Framework
    Consistent with the EPA's longstanding approach to eliminating 
significant contribution or interference with maintenance, at Step 3, 
states linked at steps 1 and 2 are generally expected to prepare a 
multifactor assessment of potential emissions controls. 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 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 approval. In general, 
the emissions-reducing effects of all existing emissions control 
requirements are already reflected in the 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), states must provide a well-documented 
evaluation determining whether their emissions constitute significant 
contribution or interference with maintenance by evaluating additional 
available control opportunities by preparing a multifactor assessment. 
While the EPA has not prescribed a particular method for this 
assessment, the EPA expects states at a minimum to present a sufficient 
technical evaluation. This would typically include information on 
emissions sources, applicable control technologies, emissions 
reductions, costs, cost effectiveness, and downwind air quality impacts 
of the estimated reductions, before concluding that no additional 
emissions controls should be required.\29\
---------------------------------------------------------------------------

    \29\ 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.
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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 3 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 110(a)(2)(A); Committee for a Better Arvin v. U.S. E.P.A., 
786 F.3d 1169, 1175-76 (9th Cir. 2015) (holding that measures relied on 
by state to meet CAA requirements must be included in the SIP).

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

    On June 10, 2019, the Missouri Department of Natural Resources' Air 
Pollution Control Program (MoDNR)

[[Page 9539]]

made a SIP submission to address interstate transport of air pollution 
for the 2015 8-hour ozone NAAQS. MoDNR's good neighbor SIP submission 
for the 2015 ozone NAAQS relied on the EPA's four-step approach and 
corresponding memoranda for determining obligations for upwind states 
to limit transported air pollution to downwind states. The State 
concluded that emissions from sources or emissions activity in Missouri 
will not contribute significantly to nonattainment or interfere with 
maintenance of the 2015 ozone NAAQS in any downwind states.
    In its analysis, the state relied on the EPA's modeling released 
with the March 2018 memorandum to identify nonattainment and 
maintenance receptors in 2023 (Step 1). The State also relied on the 
EPA's modeling from the March 2018 memorandum to identify which 
monitors were then linked to emissions from Missouri. In its 
submission, the MoDNR identified all of the nonattainment and 
maintenance receptors to which Missouri was projected to contribute 
more than 0.70 ppb to the 2023 DV. Table 1 provides information on the 
six nonattainment and maintenance receptors identified by the MoDNR.

  Table 1--2023 Average and Maximum Design Values at Downwind Receptors With Missouri Contributions Larger Than
                                                    0.70 ppb
----------------------------------------------------------------------------------------------------------------
                                                                   Missouri
Site  (monitor, county, state)   2023  Average   2023  Maximum   contribution               Comments
                                   DV  (ppb)       DV  (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.
----------------------------------------------------------------------------------------------------------------

    The state analyzed each of the six receptors in Table 1 using 
information in the EPA's 2018 guidance memoranda described above. For 
the two receptors in Texas, the state observed that the total upwind 
state contribution is approximately 13 ppb to both of these Texas 
receptors and that Texas' in-state contribution to these two receptors 
is 26 ppb to the Brazoria County receptor and 22.6 ppb to the Harris 
County receptor. The MoDNR combined the contributions from initial/
boundary conditions with the contribution from biogenic emissions to 
show that the contribution from these two categories is over 52 ppb, at 
these two receptors. Based on this information, the MoDNR claimed that 
the ozone problems at these two receptors are not caused by upwind U.S. 
anthropogenic emissions from other states, but rather that in-state 
contributions, natural ozone concentrations, and international 
emissions are the likely significant contributors to the problem at 
these two sites.
    The MoDNR also noted that its contribution to the projected 2023 
ozone DV at the two Texas receptors is 0.88 ppb. The MoDNR then 
referenced statements in the EPA's August 2018 memorandum on the use of 
alternative thresholds that a 1 ppb threshold would generally capture a 
substantial amount of transported contribution from upwind states to 
the downwind monitors. The MoDNR concluded that 1 ppb is, therefore, an 
appropriate alternative screening threshold for evaluating whether 
emissions in their state are linked to the ozone problems at these two 
receptors. Based on this alternative threshold, the State determined 
that it will not contribute significantly to these nonattainment 
receptors in 2023. The MoDNR then concluded that its SIP sufficiently 
addresses the good neighbor obligation for the 2015 ozone NAAQS with 
respect to these two Texas receptors based only on its Step 2 weight of 
evidence analysis.
    For the Milwaukee, Wisconsin receptor, the MoDNR noted that its 
projected contribution to this receptor is 0.93 ppb, and thus less than 
1 ppb. The State observed that the 1 ppb threshold would capture 79.4 
percent of the total contribution from all upwind states and that the 
contribution captured by the 1 ppb threshold is 83 percent of the 
amount captured by the 0.70 ppb threshold at this receptor. The state 
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 emission 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 Wayne, Michigan site, the state observed that the 1 ppb 
threshold captures 61.8 percent of total upwind state contributions and 
the contribution captured by the 1 ppb threshold would constitute 92.2 
percent of the total contribution that would be captured by the 0.70 
ppb threshold. The state asserted that the 1 ppb threshold will capture 
a substantial amount of upwind states' contribution to the ozone 
concentrations at this site, which will lead to meaningful emission 
reductions that will help ensure attainment of the NAAQS at this 
receptor in 2023. The MoDNR noted that its projected contribution to 
the Wayne, Michigan receptor is 0.92 ppb, and thus less than 1 ppb. 
Therefore, the MoDNR concluded that its existing SIP sufficiently 
addresses the good neighbor obligation for the 2015 ozone NAAQS with 
respect to this receptor based only on this Step 2 weight of evidence 
analysis.
    For the Sheboygan, Wisconsin site, the State observed that the 1 
ppb threshold would capture 79.4 percent of the total upwind 
contributions and that a 2 ppb threshold would capture 68.2 percent of 
the total upwind state contributions. The State also observed that an 
alternative 2 ppb threshold would capture 85.9 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 nearly 70 percent of the total upwind state contributions 
and thus would result in meaningful emission reductions that will help 
to ensure attainment of the NAAQS at the site by 2023. The state also 
asserted that the primary contributors to the projected ozone 
concentrations at the monitor in Sheboygan include emissions from 
Illinois, Indiana, and Wisconsin. The MoDNR cited the EPA modeling 
projecting that emissions from these states would contribute a

[[Page 9540]]

combined 31.93 ppb in 2023 to the Sheboygan receptor.
    For the Sheboygan receptor, the MoDNR also pointed to the Lake 
Michigan Air Director's Consortium's (LADCO's) interstate transport 
modeling results for the 2015 ozone NAAQS. The State noted that LADCO's 
analysis also indicates that the ozone levels at the Wisconsin 
shoreline of Lake Michigan are heavily affected by the emissions from 
Illinois, Indiana, and Wisconsin.\30\
---------------------------------------------------------------------------

    \30\ Interstate Transport Modeling for the 2015 Ozone National 
Ambient Air Quality Standard, the technical support document (TSD), 
https://www.ladco.org/wp-content/uploads/Documents/Reports/TSDs/O3/LADCO_2015O3iSIP_TSD_13Aug2018.pdf.
---------------------------------------------------------------------------

    The MoDNR further pointed out that the other monitoring site in 
Sheboygan County (551170009), which is a few miles further inland than 
the Sheboygan nonattainment receptor, has no projected problems with 
attaining and maintaining compliance with the 2015 ozone NAAQS. The 
MoDNR concluded that the nonattainment receptor in Sheboygan is heavily 
influenced by local transport emissions and lake breeze effects over 
Lake Michigan. The State asserted that use of a 2 ppb threshold would 
capture a substantial amount of upwind states' contribution to the 
ozone concentrations at this site, which will lead to meaningful 
emission reductions that will help ensure attainment of the NAAQS at 
this monitor in 2023. The MoDNR noted that its projected contribution 
to the Sheboygan, Wisconsin receptor is 1.37 ppb, which is less than 2 
ppb. Therefore, the MoDNR concluded that its existing SIP sufficiently 
addresses the good neighbor obligation for the 2015 ozone NAAQS with 
respect to the Sheboygan receptor based only on this Step 2 weight of 
evidence analysis.
    For the Allegan, Michigan receptor, the MoDNR used an analysis 
based on information in the EPA's October 2018 memorandum on 
alternative approaches for identifying maintenance receptors to claim 
that the Allegan monitoring site will not be a receptor in 2023. 
Specifically, rather than rely upon the EPA's projected 2023 maximum 
design value for identifying maintenance receptors, the state used an 
alternative approach that included projected 2023 ozone concentrations 
based on a 2-year base period (2010-2011), a 3-year base period (2009-
2011) and a 4-year base period (2009-2012) to demonstrate that the 
Allegan monitoring site would attain the standard by 2023. To support 
the use of these alternative base periods, the State provided an 
analysis for the three consideration outlined in the August 2018 
memorandum: (i) Meteorological conditions in the area of the monitoring 
site were conducive to ozone formation during the alternative base 
period design value used for projections; (ii) ozone concentrations 
have been trending downward at the site since 2011 (and ozone precursor 
emissions of NO<INF>X</INF> and VOCs have also decreased); and (iii) 
emissions are expected to continue to decline in the upwind and 
downwind states out to the attainment date of the site. The MoDNR noted 
that ozone concentrations during the summer of 2009 were well below 
normal for the state of Michigan despite having a large number of days 
during the ozone season where they claim that meteorology was conducive 
to ozone formation. The MoDNR also noted that the summer of 2012 was 
among the most ozone conducive summers across the entire Midwestern 
portion of the country. MoDNR suggested that the variation in the 
degree of ozone conducive meteorology between 2009 and 2012 would 
counterbalance in the alternative baseline period.
    The State provided an analysis showing ozone concentrations 
trending down since 2012 at the Allegan monitor. The State also 
provided the total statewide anthropogenic NO<INF>X</INF> and VOC 
emissions (ozone precursors) in Michigan, Missouri, and two neighboring 
states that are upwind of the Allegan monitor during 2011 and 2017 
(i.e., Illinois and Indiana), which showed that emissions in all four 
of these states went down during this time period.
    The MoDNR concluded that the Allegan receptor meets all the 
criteria listed in the EPA October memorandum relating to alternative 
methods for identifying maintenance receptors. Based on this analysis, 
the MoDNR asserted that the Allegan Michigan monitor should not be a 
maintenance receptor for purposes of the 2015 ozone NAAQS. Therefore, 
the State found that the Missouri' existing SIP fully addresses the CAA 
good neighbor obligation with respect to the Allegan, Michigan 
receptor.
    Based on the analysis above, the MoDNR concluded that its current 
SIP adequately addresses the state's obligation under CAA section 
110(a)(2)(D)(i)(I) (the good neighbor provision) with respect to the 
2015 ozone NAAQS. The MoDNR stated that it has demonstrated that its 
SIP submittal ensures that emissions in Missouri will not significantly 
contribute to nonattainment or interfere with maintenance of the 2015 
ozone NAAQS in any downwind state. Based on this conclusion, the MoDNR 
concluded its analysis at Step 2 of the 4-step interstate transport 
framework and provided no analysis for steps 3 or 4.

III. EPA Evaluation

    The EPA is proposing to find that the June 10, 2019, SIP submission 
from the MoDNR does not meet the State's obligations with respect to 
prohibiting emissions that contribute significantly to nonattainment or 
interfere with maintenance of the 2015 8-hour ozone NAAQS in any other 
state based on the EPA's evaluation of the SIP submission using the 4-
step interstate transport framework, and the EPA is therefore proposing 
to disapprove Missouri's submission.

A. Missouri

1. Evaluation of Information Provided by the MoDNR Regarding Step 1
    At Step 1 of the 4-Step interstate transport framework, the MoDNR 
relied on the EPA modeling released in the March 2018 memorandum to 
identify nonattainment and maintenance receptors in 2023. As correctly 
noted in the MoDNR SIP submittal, the EPA's prior analysis indicated 
that the State was linked to six nonattainment and/or maintenance 
receptors in three downwind states in 2023 (identified in Table 1 of 
this action). In its October 2018 memorandum on alternative maintenance 
receptors, the EPA suggested that States could provide meteorological 
data, among other data, to support potential alternative methodologies 
or flexibilities to identify maintenance receptors. The MoDNR utilized 
this flexibility to eliminate the Allegan, Michigan maintenance 
receptor (monitor ID 260050003) based on the use of alternative base 
year periods. The State considered three alternative base periods as a 
basis for projecting design values in 2023. These based periods include 
(1) a 2-year base period using 4th high ozone concentrations in 2010 
and 2011, (2) a 3-year base year period from 2009-2011, and (3) a 4-
year base year period from 2009-2012. As an initial matter, design 
values, by definition are based on the average of the 4th highest 
maximum daily 8-hour ozone concentration in three consecutive years. 
The ``pseudo'' design values calculated by the State using 2 years of 
data, when data for the third year (i.e., 2009) were clearly available, 
and using 4 years of data do not constitute alternative design values. 
In this regard, the approach by the State using these two alternatives 
runs counter to the approach identified in the October 2018 memorandum: 
``. . . . EPA believes that a state may, in some

[[Page 9541]]

cases, use a design value from the base period that is not the maximum 
design value.''
    The State also provided information and analysis of meteorological 
data to attempt to establish that all years that constitute the 2011 
design value (i.e., the average of the 4th high values in 2009, 2010, 
and 2011) were conducive to ozone formation. The State's analysis noted 
that the summer of 2009 was well below normal for average temperatures, 
but highlighted that data from Western Michigan Regional Airport 
national weather service site showed that a number of days in summer of 
2009 were conducive to ozone formation. Overall, the state identified 
25 days between May and September of 2009 that it considered conducive 
to ozone formation based on the criteria that the temperature reached 
80 degrees Fahrenheit or greater, no precipitation occurred, and the 
daily average wind speed was less than 5 miles per hour. In the EPA's 
review, we find the State did not sufficiently demonstrate that all 
years within the alternative base period were conducive to ozone 
formation. As the State noted, the summer of 2009 was abnormally cool 
in Michigan. While the State also analyzed local meteorological data 
(temperature, precipitation, wind speed) near the Allegan, Michigan 
monitor to identify 25 days that it considered conducive to ozone 
formation based on surface temperatures, wind speed and precipitation, 
the State did not provide any technical analysis to demonstrate a 
statistically significant relationship between high ozone 
concentrations at the Allegan receptor and the temperature, 
precipitation, and wind speed criteria used in the submittal to define 
ozone conducive conditions for this receptor. In addition, the State's 
evaluation did not discuss or consider how other meteorological factors 
identified in the October 2018 memorandum such as humidity, solar 
radiation, vertical mixing, and/or other meteorological indicators such 
as cooling-degree days confirm whether conditions affecting the monitor 
may have been conducive to ozone formation in 2009. The supplemental 
information provided in the October 2018 memorandum, which included 
temperature anomalies by state and region of the U.S. and annual state-
wide average June-August temperature rankings, clearly highlight that 
the summer of 2009 was abnormally cool in Michigan and the Great Lakes 
Region. Therefore, the EPA finds that not all years within the 
alternative base period used by the State (i.e., 2009-2011) were 
conducive to ozone formation, especially given the abnormally cold 
temperatures seen in the summer of 2009. Accordingly, in view of the 
guidance included in the October 2020 memorandum, it was not 
appropriate for the state to have eliminated the Allegan, Michigan 
receptor as a maintenance receptor at Step 1 of the 4-step interstate 
transport framework on this basis.
    Further, the MoDNR's attempt to eliminate this receptor on the 
basis of this analysis did not provide any basis to eliminate the other 
receptors to which the EPA's modeling suggested the state was linked. 
The EPA's most recent modeling, discussed further in section III.A.3, 
confirms that the existence of several receptors to which the state is 
linked. The EPA therefore proposes to proceed to evaluate the submittal 
at Step 2.
2. Evaluation of Information Provided by the State Regarding Step 2
    As an initial matter, the EPA disagrees with the arguments made by 
MoDNR based on the ostensible ``causation'' of the projected attainment 
and maintenance problems at the receptors in Brazoria County and Harris 
County in Texas. While it is correct that impacts from various sources, 
such as in-state contributions, background ozone concentrations, and 
international emissions, are often themselves significant contributors 
to attainment and maintenance problems at receptors for the 2015 ozone 
NAAQS, this does not address the question of whether there are also 
interstate transport impacts from emissions sources or activities in 
Missouri that significantly contribute to nonattainment, or interfere 
with maintenance, in any other state. This question is not one of 
causation, but rather of whether there is significant contribution as 
contemplated in CAA section 110(a)(2)(D)(i)(I). The EPA's 4-step 
interstate transport framework is intended to evaluate whether there 
are emissions that the State must address in its SIP to meet this 
requirement for purposes of the 2015 ozone NAAQS.
    The State also utilized a 1 ppb threshold at Step 2 for the 
receptors in Wayne Michigan, Milwaukee, Wisconsin and both Texas 
receptors to evaluate whether the state was ``linked'' to a projected 
downwind nonattainment or maintenance receptor. As discussed in the 
EPA's August 2018 memorandum, with appropriate additional analysis it 
may be reasonable for states to use a 1 ppb contribution threshold, 
instead of the 1 percent of the NAAQS threshold for the purposes of 
identifying linkages to appropriate downwind receptors. In some cases, 
MoDNR argued for application of the alternative 1 ppb threshold, by 
presenting the different numerical percentages of downwind impacts that 
the respective thresholds would result in, and then asserting that the 
percentages of upwind contribution captured from the 1 ppb threshold 
would be sufficiently substantial to justify its use for Missouri.
    For the Wayne, Michigan receptor, MoDNR observed that application 
of a 1 ppb threshold would capture 61.8 percent of total upwind state 
contributions, and that the contribution captured by the 1 ppb 
threshold would constitute 92.2 percent of the total contribution that 
would be captured by application of the 0.70 ppb threshold. The State 
thus argued that use of a 1 ppb threshold instead of a 1% of the NAAQS 
threshold will capture a substantial amount of upwind states' 
contribution to the ozone concentrations at this site. Using this 
alternative threshold, MoDNR stated that the projected Missouri 
contribution to the Wayne, Michigan receptor is 0.92 ppb, and thus less 
than 1 ppb. MoDNR made a comparable argument for the Milwaukee, 
Wisconsin receptor (79.4 percent of the total contribution from all 
upwind states and that the contribution captured by the 1 ppb threshold 
is 83 percent of the amount captured by the 0.70 ppb threshold). For 
the receptors in Brazoria County and Harris County, Texas, the MoDNR 
did not provide any additional analyses to determine the 
appropriateness of the application of the 1 ppb threshold at either of 
these receptors, and simply referred to the August 2018 memorandum as 
evidence to support the use of a 1 ppb threshold at these receptors. 
Rather than a quantitative comparison, MoDNR made qualitative 
statements to the effect that a 1 ppb threshold would be appropriate 
given other considerations, such as the impacts of local or 
international sources.
    However, the EPA's memorandum did not indicate that this type of 
information alone was determinative of whether an alternative threshold 
was in fact appropriate to justify use of a threshold in lieu of the 
0.70 ppb level. Rather, the EPA determined that by capturing a 
percentage of upwind state emissions comparable to the amount captured 
at 1 percent, the alternative threshold may be appropriate, indicating 
that a more determinative conclusion of appropriateness would require 
further analysis. The MoDNR did not provide any further technical 
justification to make that determination.
    The EPA notes that in each case, the use of the alternative 1 ppb 
threshold

[[Page 9542]]

would have the result of reducing the amount of cumulative upwind state 
emissions that would be captured. While the EPA does not, in this 
action, approve of the state's application of the 1 ppb threshold, 
because the state has linkages greater than 1 ppb to projected downwind 
nonattainment or maintenance receptors, the state's use of this 
alternative threshold at Step 2 of the 4-step interstate framework 
would not alter our review and proposed disapproval of this SIP 
submittal.
    The EPA here shares further evaluation of its experience since the 
issuance of the August 2018 memorandum regarding use of alternative 
thresholds at Step 2. This experience leads the Agency to now believe 
it may not be appropriate to continue to attempt to recognize 
alternative contribution thresholds at Step 2. The August 2018 
memorandum stated that ``it may be reasonable and appropriate'' for 
states to rely on an alternative threshold of 1 ppb at Step 2.\31\ 
However, the EPA also indicated that ``air agencies should consider 
whether the recommendations in this guidance are appropriate for each 
situation.'' Following receipt and review of 49 good neighbor SIP 
submittals for the 2015 8-hour ozone NAAQS, the EPA's experience has 
been that nearly every state that attempted to rely on a 1 ppb 
threshold did not provide sufficient information and analysis to 
support a determination that an alternative threshold was reasonable or 
appropriate for that state.
---------------------------------------------------------------------------

    \31\ August 2018 memo at 4.
---------------------------------------------------------------------------

    For instance, in nearly all submittals, the states did not provide 
the EPA with analysis specific to their state or the receptors to which 
its emissions are potentially linked. In one case, the proposed 
approval of Iowa's SIP submittal, the EPA expended its own resources to 
attempt to supplement the information submitted by the state, in order 
to more thoroughly evaluate the state-specific circumstances that could 
support approval.\32\ It was at the EPA's sole discretion to perform 
this analysis in support of the state's submittal, and the Agency is 
not obligated to conduct supplemental analysis to fill the gaps 
whenever it believes a state's analysis is insufficient. The Agency no 
longer intends to undertake supplemental analysis of SIP submittals 
with respect to alternative thresholds at Step 2 for purposes of the 
2015 ozone NAAQS.
---------------------------------------------------------------------------

    \32\ Air Plan Approval; Iowa; Infrastructure State 
Implementation Plan Requirements for the 2015 Ozone National Ambient 
Air Quality Standard, 85 FR 12232 (March 2, 2020). The Agency 
received adverse comment on this proposed approval and has not taken 
final action with respect to this proposal.
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    Furthermore, the EPA's experience since 2018 is that allowing for 
alternative Step 2 thresholds may be impractical or otherwise 
inadvisable for a number of additional policy reasons. For a regional 
air pollutant such as ozone, consistency in requirements and 
expectations across all states is essential. Based on its review of 
submittals to-date and after further consideration of the policy 
implications of attempting to recognize an alternative Step 2 threshold 
for certain states, the Agency now believes the attempted use of 
different thresholds at Step 2 with respect to the 2015 ozone NAAQS 
raises substantial policy, consistency, and practical implementation 
concerns.\33\ The availability of different thresholds at Step 2 has 
the potential to result in inconsistent application of good neighbor 
obligations based solely on the strength of a state's SIP submittal at 
Step 2 of the 4-step interstate transport framework. From the 
perspective of ensuring effective regional implementation of good 
neighbor obligations, the more important analysis is the evaluation of 
the emissions reductions needed, if any, to address a state's 
significant contribution after consideration of a multifactor analysis 
at Step 3, including a detailed evaluation that considers air quality 
factors and cost. Where alternative thresholds for purposes of Step 2 
may be ``similar'' in terms of capturing the relative amount of upwind 
contribution (as described in the August 2018 memorandum), nonetheless, 
use of an alternative threshold could allow certain states to avoid 
further evaluation of potential emission controls while other states 
must proceed to a Step 3 analysis. This can create significant equity 
and consistency problems among states.
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    \33\ We note that Congress has placed on the EPA a general 
obligation to ensure the requirements of the CAA are implemented 
consistently across states and regions. See CAA section 301(a)(2). 
Where the management and regulation of interstate pollution levels 
spanning many states is at stake, consistency in application of CAA 
requirements is paramount.
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    Further, it is not clear that national ozone transport policy is 
best served by allowing for less stringent thresholds at Step 2. The 
EPA recognized in the August 2018 memo that there was some similarity 
in the amount of total upwind contribution captured (on a nationwide 
basis) between 1percent and 1 ppb. However, the EPA notes that while 
this may be true in some sense, that is hardly a compelling basis to 
move to a 1 ppb threshold. Indeed, the 1 ppb threshold has the 
disadvantage of losing a certain amount of total upwind contribution 
for further evaluation at Step 3 (e.g., roughly seven percent of total 
upwind state contribution was lost according to the modeling underlying 
the August 2018 memorandum; \34\ in the EPA's updated modeling, the 
amount lost is five percent). Considering the core statutory objective 
of ensuring elimination of all significant contribution to 
nonattainment or interference of the NAAQS in other states and the 
broad, regional nature of the collective contribution problem with 
respect to ozone, there does not appear to be a compelling policy 
imperative in allowing some states to use a 1 ppb threshold while 
others rely on a 1 percent of NAAQS threshold.
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    \34\ See August 2018 memo, at 4.
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    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 also important. Continuing to use a 1 percent of NAAQS 
approach ensures that as the NAAQS are revised and made more stringent, 
an appropriate increase in stringency at Step 2 occurs, so as to ensure 
an appropriately larger amount of total upwind-state contribution is 
captured for purposes of fully addressing interstate transport. Accord 
76 FR 48237-38.
    Therefore, notwithstanding the August 2018 memorandum's recognition 
of the potential viability of alternative Step 2 thresholds, and in 
particular, a potentially applicable 1 ppb threshold, the EPA's 
experience since the issuance of that memo has revealed substantial 
programmatic and policy difficulties in attempting to implement this 
approach. Nonetheless, the EPA is not, at this time, rescinding the 
August 2018 memorandum. The EPA invites comment on this broader 
discussion of issues associated with alternative thresholds at Step 2. 
Depending on comment and further evaluation of this issue, the EPA may 
determine to rescind the August 2018 memorandum in the future.
    MoDNR used two arguments at Step 2 for excluding the nonattainment 
receptor in Sheboygan, Wisconsin, (Monitor ID: 551170006). First, the 
State utilized a 2 ppb threshold at Step 2 to identify whether the 
state was ``linked'' to this receptor. Second, the state argued that 
any reductions from Missouri would have a de minimis or minimal effect 
on air quality improvements at this receptor due to the larger impacts 
from other states such as Wisconsin,

[[Page 9543]]

Illinois and Indiana. The EPA discusses both of these arguments in this 
section.
    In its analysis, the state argued that because a 2 ppb threshold 
would capture 68.2% of cumulative upwind state contributions at the 
Sheboygan receptor, similar to the ``approximately 70 percent of total 
upwind contribution'' captured on average nationwide at the 1 ppb 
threshold the EPA identified in the August 2018 memorandum, a 2 ppb 
threshold is appropriate to use at this receptor. While the EPA had 
determined that an alternative threshold that would capture a 
sufficient percentage of upwind state emissions comparable to the 
amount that would be captured at the level of 1 percent of the NAAQS 
may be appropriate, the Agency also indicated that more analysis would 
be needed to reach a determinative conclusion of appropriateness. As 
explained with respect to the alternative 1 ppb threshold that MoDNR 
sought to use for the for the receptors in Wayne Michigan, Milwaukee, 
Wisconsin and both Texas receptors, it did not provide any further 
technical justification to make the determination.
    As explained with respect to the potential use of an alternative 1 
ppb threshold, the EPA's experience since the issuance of the 2018 
memorandum discussing the issue has revealed substantial programmatic 
and policy difficulties in attempting to implement this approach even 
for a 1 ppb threshold. At no point did the EPA suggest that a 2 ppb 
threshold might be appropriate for this purpose under any 
circumstances. Such a threshold would be higher than the threshold that 
the EPA has historically used in interstate transport rules that courts 
have approved (i.e., 1 percent of the NAAQS at issue), or that the EPA 
has considered even potentially appropriate if it were to achieve 
functionally the same air quality impacts (i.e., 1 ppb).
    The second argument that the state used to exclude the Sheboygan, 
Wisconsin receptor in Step 2 was related to emissions from other 
states. The state argued that the primary contributors to the projected 
ozone concentrations in Sheboygan are the upwind states of Illinois and 
Indiana and the home state itself, Wisconsin. The EPA's 2018 modeling 
showed these states would contribute a combined 31.93 ppb in 2023 to 
the Sheboygan receptor. However, the state's reasoning related to 
Indiana, Illinois and Wisconsin emissions is inapplicable to the 
requirements of CAA section 110(a)(2)(D)(i)(I). The good neighbor 
provision requires states and the EPA to address interstate transport 
of air pollution that contributes to downwind states' ability to attain 
and maintain NAAQS. Whether emissions from other states also contribute 
to the same downwind air quality issue is irrelevant in assessing 
whether a downwind state has an air quality problem, or whether the 
upwind state at issue state is significantly contributing to that 
problem. The Ozone NAAQS nonattainment and maintenance problems that 
result from interstate transport are typically the result of cumulative 
impacts from multiple states. States are not obligated under CAA 
section 110(a)(2)(D)(i)(I) to reduce emissions only if doing so would 
be sufficient in isolation to resolve all downwind nonattainment or 
maintenance problems. Rather, each state is obligated to eliminate its 
own ``significant contribution'' or ``interference'' with the ability 
of other states to attain or maintain the NAAQS.
    Indeed, the D.C. Circuit in Wisconsin specifically rejected 
petitioner arguments suggesting that upwind states should be excused 
from good neighbor obligations on the basis that some other source of 
emissions (whether international or another upwind state) could be 
considered the ``but-for'' cause of downwind air quality problem. 938 
F.3d 303 at 323-324. The court viewed petitioners' arguments as 
essentially an argument ``that an upwind State `contributes 
significantly' to downwind nonattainment only when its emissions are 
the sole cause of downwind nonattainment.'' 938 F.3d 303 at 324. The 
court explained that ``an upwind State can `contribute' to downwind 
nonattainment even if its emissions are not the but-for cause.'' Id. at 
324-325. See also Catawba County v. EPA, 571 F.3d 20, 39 (D.C. Cir. 
2009) (rejecting the argument ``that `significantly contribute' 
unambiguously means `strictly cause' '' because there is ``no reason 
why the statute precludes EPA from determining that [an] addition of 
[pollutant] into the atmosphere is significant even though a nearby 
county's nonattainment problem would still persist in its absence''); 
Miss. Comm'n on Envtl. Quality v. EPA, 790 F.3d 138, 163 n.12 (D.C. 
Cir. 2015) (observing that the argument that ``there likely would have 
been no violation at all . . . if it were not for the emissions 
resulting from [another source]'' is ``merely a rephrasing of the but-
for causation rule that we rejected in Catawba County.''). Therefore, a 
state is not excused from eliminating its significant contribution on 
the basis that other states' emissions also contribute some amount of 
pollution to the same receptors to which the state is linked. As a 
result, Step 3 analysis of the 4-Step Interstate Transport Framework is 
necessary.
    Thus, the EPA proposes that MoDNR's submittal did not adequately 
justify the use of an alternative threshold or otherwise establish that 
it should not be considered linked at Step 2. The EPA proposes to apply 
the 1 percent of NAAQS threshold, consistent with the discussion in 
this subsection. Under the proposed 1 percent threshold, both in the 
modeling available to the state at the time it made its submittal, and 
under the newly available 2023 modeling discussed below, Missouri is 
linked to downwind nonattainment and maintenance receptors.\35\
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    \35\ Because the EPA finds that the MoDNR submittal's arguments 
with respect to its linkages in the modeling it relied on are not 
sufficient or technically justified to conclude the state is not 
linked to downwind receptors, the EPA can also conclude that the 
same arguments would not be meritorious even if applied with respect 
to the receptor linkages the EPA finds in its more recent 2023 
modeling using the 2016v2 emissions platform.
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3. Results of the EPA's Step 1 and Step 2 Modeling and Findings for 
Missouri
    As described in section I, the EPA performed air quality modeling 
to project design values and contributions for 2023 using the 2016v2 
emissions platform. The EPA examined these data to determine if 
emissions in Missouri contribute at or above the threshold of 1 percent 
of the 2015 8-hour ozone NAAQS (0.70 ppb) to any downwind nonattainment 
or maintenance receptor in this most recent round of modeling. As shown 
in Table 2, the data indicate that in 2023, emissions from sources in 
Missouri contribute greater than 1 percent of the NAAQS to 
nonattainment or maintenance-only receptors in Racine County and 
Kenosha County, Wisconsin, and Cook County, Illinois.\36\ Therefore, 
based on the EPA's evaluation of the information submitted by MoDNR, 
and based on the EPA's most recent modeling results for 2023, the EPA 
proposes to find that Missouri is linked at steps 1 and 2 and has an 
obligation to assess potential emissions reductions from sources or 
other emissions activity at Step 3 of the 4-Step framework.
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    \36\ Design values and contributions at individual monitoring 
sites nationwide are provide in the file: 
``2016v2_DVs_state_contributions.xlsx'' which is included in docket 
ID No. EPA-HQ-OAR-2021-0663.

[[Page 9544]]



                                        Table 2--Missouri Linkage Results Based on the EPA Updated 2023 Modeling
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                         2023 Average     2023 Maximum
               Receptor ID                           Location              Nonattainment/maintenance     design value     design value   MO contribution
                                                                                                            (ppb)            (ppb)            (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
550590025................................  Kenosha, Wisconsin..........  Maintenance.................             69.2             72.3             1.66
550590019................................  Kenosha, Wisconsin..........  Nonattainment...............             72.8             73.7             1.08
170317002................................  Cook, Illinois..............  Maintenance.................             70.1             73.0             0.94
551010020................................  Racine, Wisconsin...........  Nonattainment...............             71.3             73.2             0.92
--------------------------------------------------------------------------------------------------------------------------------------------------------

4. Evaluation of Information Provided Regarding Step 3
    At Step 3, of the 4-step interstate transport framework, a state's 
emissions are further evaluated, in light of multiple factors, 
including air quality and cost considerations, 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).
    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 
which will contribute significantly to downwind air quality problems. 
Thus, states must complete something similar to the EPA's analysis (or 
an alternative approach to defining ``significance'' that comports with 
the statute's objectives) to determine whether and to what degree 
emissions from a state should be ``prohibited'' to eliminate emissions 
that will ``contribute significantly to nonattainment in, or interfere 
with maintenance of'' the NAAQS in any other state.
    MoDNR did not conduct such an analysis in its SIP submission, as a 
result of its conclusions pursuant to Step 1 and Step 2 of its analysis 
with respect to the six receptors that the EPA previously identified. 
As explained in connection with the evaluation of MoDNR's Step 1 and 
Step 2 analyses, the EPA disagrees with those analyses and accordingly 
the State should have evaluated effectively which emissions in the 
State should be deemed ``significant'' and therefore prohibited, in its 
SIP submission. We therefore propose that MoDNR was required to analyze 
emissions from the sources and other emissions activity from within the 
state to determine whether its contributions were significant, and we 
propose to disapprove its submission because MoDNR failed to do so.
5. Evaluation of Information Provided Regarding Step 4
    Step 4 of the 4-step interstate transport framework calls for 
development of permanent and federally enforceable control strategies 
to achieve the emissions reductions determined to be necessary at step 
3 to eliminate significant contribution to nonattainment or 
interference with maintenance of the NAAQS. As mentioned previously, 
Missouri's SIP submission did not contain an evaluation of additional 
emission control opportunities (or establish that no additional 
controls are required), thus, no information was provided at step 4. As 
a result, the EPA proposes to disapprove Missouri' submittal on the 
separate, additional basis that the State has not developed permanent 
and enforceable emissions reductions necessary to meet the obligations 
of CAA section 110(a)(2)(d)(i)(I).
6. Conclusion
    Based on the EPA's evaluation of the MoDNR's SIP submission, the 
EPA is proposing to find that the MoDNR's June 10, 2019 SIP submission 
addressing CAA section 110(a)(2)(D)(i)(I) does not meet the State's 
interstate transport obligations, because it fails to contain the 
necessary provisions to eliminate emissions that will contribute 
significantly to nonattainment or interfere with maintenance of the 
2015 8-hour ozone NAAQS in any other state.

IV. Proposed Action

    We are proposing to disapprove the MoDNR's June 10, 2019 SIP 
submission pertaining to interstate transport of air pollution which 
will significantly contribute to nonattainment or interfere with 
maintenance of the 2015 8-hour ozone NAAQS in other states. Under CAA 
section 110(c)(1), disapproval would establish a 2-year deadline for 
the EPA to promulgate a FIP for Missouri to address the CAA section 
110(a)(2)(D)(i)(I) interstate transport requirements pertaining to 
significant contribution to nonattainment and interference with 
maintenance of the 2015 8-hour ozone NAAQS in other states, unless the 
EPA approves a SIP that meets these requirements. Disapproval does not 
start a mandatory sanctions clock for Missouri.

V. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 13563: Improving Regulation and Regulatory Review

    This action is not a significant regulatory action and was 
therefore not submitted to the Office of Management and Budget for 
review.

B. Paperwork Reduction Act (PRA)

    This proposed action does not impose an information collection 
burden under the PRA because it does not contain any information 
collection activities.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action merely proposes to disapprove a SIP submission as not meeting 
the CAA.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does

[[Page 9545]]

not significantly or uniquely affect small governments. The action 
imposes no enforceable duty on any state, local or tribal governments 
or the private sector.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government.

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

    This action does not have tribal implications as specified in 
Executive Order 13175. This action does not apply on any Indian 
reservation land, any other area where the EPA or an Indian tribe has 
demonstrated that a tribe has jurisdiction, or non-reservation areas of 
Indian country. Thus, Executive Order 13175 does not apply to this 
action.

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

    The EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that the EPA has reason to believe may disproportionately affect 
children, per the definition of ``covered regulatory action'' in 
section 2-202 of the Executive Order. This action is not subject to 
Executive Order 13045 because it merely proposes to disapprove a SIP 
submission as not meeting the CAA.

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

    This action is not subject to Executive Order 13211, because it is 
not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act

    This rulemaking does not involve technical standards.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    The EPA believes the human health or environmental risk addressed 
by this action will not have potential disproportionately high and 
adverse human health or environmental effects on minority, low-income 
or indigenous populations. This action merely proposes to disapprove a 
SIP submission as not meeting the CAA.

K. CAA Section 307(b)(1)

    Section 307(b)(1) of the CAA governs judicial review of final 
actions by the EPA. This section provides, in part, that petitions for 
review must be filed in the D.C. Circuit: (i) When the agency action 
consists of ``nationally applicable regulations promulgated, or final 
actions taken, by the Administrator,'' or (ii) when such action is 
locally or regionally applicable, if ``such action is based on a 
determination of nationwide scope or effect and if in taking such 
action the Administrator finds and publishes that such action is based 
on such a determination.'' For locally or regionally applicable final 
actions, the CAA reserves to the EPA complete discretion whether to 
invoke the exception in (ii).\37\
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    \37\ In deciding whether to invoke the exception by making and 
publishing a finding that an action is based on a determination of 
nationwide scope or effect, the Administrator takes into account a 
number of policy considerations, including his judgment balancing 
the benefit of obtaining the D.C. Circuit's authoritative 
centralized review versus allowing development of the issue in other 
contexts and the best use of Agency resources.
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    If the EPA takes final action on this proposed rulemaking the 
Administrator intends to exercise the complete discretion afforded to 
him under the CAA to make and publish a finding that the final action 
(to the extent a court finds the action to be locally or regionally 
applicable) is based on a determination of ``nationwide scope or 
effect'' within the meaning of CAA section 307(b)(1). Through this 
rulemaking action (in conjunction with a series of related actions on 
other SIP submissions for the same CAA obligations), the EPA interprets 
and applies section 110(a)(2)(d)(i)(I) of the CAA for the 2015 ozone 
NAAQS based on a common core of nationwide policy judgments and 
technical analysis concerning the interstate transport of pollutants 
throughout the continental U.S. In particular, the EPA is applying here 
(and in other proposed actions related to the same obligations) the 
same, nationally consistent 4-step framework for assessing good 
neighbor obligations for the 2015 ozone NAAQS. The EPA relies on a 
single set of updated, 2016-base year photochemical grid modeling 
results of the year 2023 as the primary basis for its assessment of air 
quality conditions and contributions at steps 1 and 2 of that 
framework. Further, the EPA proposes to determine and apply a set of 
nationally consistent policy judgments to apply the 4-step framework. 
The EPA has selected a nationally uniform analytic year (2023) for this 
analysis and is applying a nationally uniform approach to nonattainment 
and maintenance receptors and a nationally uniform approach to 
contribution threshold analysis.\38\ For these reasons, the 
Administrator intends, if this proposed action is finalized, to 
exercise the complete discretion afforded to him under the CAA to make 
and publish a finding that this action is based on one or more 
determinations of nationwide scope or effect for purposes of CAA 
section 307(b)(1).\39\
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    \38\ A finding of nationwide scope or effect is also appropriate 
for actions that cover states in multiple judicial circuits. In the 
report on the 1977 Amendments that revised section 307(b)(1) of the 
CAA, Congress noted that the Administrator's determination that the 
``nationwide scope or effect'' exception applies would be 
appropriate for any action that has a scope or effect beyond a 
single judicial circuit. See H.R. Rep. No. 95-294 at 323, 324, 
reprinted in 1977 U.S.C.C.A.N. 1402-03.
    \39\ The EPA may take a consolidated, single final action on all 
of the proposed SIP disapproval actions with respect to obligations 
under CAA section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS. 
Should EPA take a single final action on all such disapprovals, this 
action would be nationally applicable, and the EPA would also 
anticipate, in the alternative, making and publishing a finding that 
such final action is based on a determination of nationwide scope or 
effect.
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List of Subjects in 40 CFR Part 52

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

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

    Dated: February 9, 2022.
Meghan A. McCollister,
Regional Administrator, Region 7.
[FR Doc. 2022-03183 Filed 2-18-22; 8:45 am]
BILLING CODE 6560-50-P


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