[Federal Register Volume 87, Number 35 (Tuesday, February 22, 2022)]
[Proposed Rules]
[Pages 9545-9562]
[FR Doc No: 2022-02948]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R04-OAR-2021-0841; EPA-HQ-OAR-2021-0663; FRL-9421-01-R4]

Air Plan Disapproval; AL, MS, TN; Interstate Transport
Requirements for the 2015 8-Hour Ozone National Ambient Air Quality
Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule and withdrawal of proposed rule.

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SUMMARY: Pursuant to the Federal Clean Air Act (CAA or the Act), the
Environmental Protection Agency (EPA or Agency) is proposing to
disapprove State Implementation Plan (SIP) submittals from Alabama,
Mississippi,

and Tennessee regarding the interstate transport requirements for the
2015 8-hour ozone national ambient air quality standards (NAAQS or
standard). The ``Good Neighbor'' or ``Interstate Transport'' provision
requires that each state's implementation plan 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. These disapprovals, if finalized, will establish a 2-
year deadline for EPA to promulgate a Federal Implementation Plan (FIP)
to address the relevant interstate transport requirements, unless EPA
approves a subsequent SIP submittal that meets these requirements.
Disapproval does not start a mandatory sanctions clock.

DATES: Comments. Comments on this proposed rule must be received on or
before April 25, 2022.
    Withdrawal: As of February 22, 2022, the proposed rule published
December 30, 2019, at 84 FR 71854, is withdrawn.

ADDRESSES: You may submit comments, identified by Docket No. EPA-R04-
OAR-2021-0841, through the Federal eRulemaking Portal at https://www.regulations.gov following the online instructions for submitting
comments.
    Instructions: All submissions received must include the Docket No.
EPA-R04-OAR-2021-0841 for this rulemaking. Comments received may be
posted without change to https://www.regulations.gov/, including any
personal information provided. For detailed instructions on submitting
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 staff, the EPA Docket Center and Reading Room are open
to the public by appointment only to reduce the risk of transmitting
COVID-19. The 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 EPA
online at https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: Evan Adams of the Air Regulatory
Management Section, Air Planning and Implementation Branch, Air and
Radiation Division, U.S. Environmental Protection Agency, Region 4, 61
Forsyth Street SW, Atlanta, Georgia 30303-8960. Mr. Adams can be
reached by telephone at<PHONE_NUMBER>, or via electronic mail at
[email protected].

SUPPLEMENTARY INFORMATION: Public Participation: Submit your comments,
identified by Docket No. EPA-R04-OAR-2021-0841, at https://www.regulations.gov. Once submitted, comments cannot be edited or
removed from the docket. 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. 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-R04-OAR-2021-0841
and EPA-HQ-OAR-2021-0663. Docket No. EPA-R04-OAR-2021-0841 contains
information specific to Alabama, Mississippi, and Tennessee, including
this 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-R04-OAR-2021-0841. 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. The 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 EPA online at https://www.epa.gov/dockets.
    EPA continues to carefully and continuously monitor information
from the Centers for Disease Control and Prevention (CDC), local area
health departments, and Federal partners so that EPA can respond
rapidly as conditions change regarding COVID-19.
    The indices to Docket No. EPA-R04-OAR-2021-0841 and Docket No. EPA-
R04-OAR-2021-0841 are available electronically at www.regulations.gov.
While all documents in each docket are listed in their respective
index, some information may not be publicly available due to docket
file size restrictions or content (e.g., CBI).

Table of Contents

I. Background
    A. Description of Statutory Background
    B. Description of EPA's Four Step Interstate Transport
Regulatory Process
    C. Background on EPA's Ozone Transport Modeling Information
    D. EPA's Approach To Evaluating Interstate Transport SIPs for
the 2015 8-hour Ozone NAAQS
II. SIP Submissions and EPA's Evaluation
    A. Alabama
    B. Mississippi
    C. Tennessee
III. Proposed Actions
IV. Statutory and Executive Order Reviews

I. Background

    The following provides background for EPA's proposed actions
related to the interstate transport requirements for the 2015 8-hour
ozone NAAQS for the states of Alabama, Mississippi, and Tennessee.

A. Description of Statutory Background

    On October 1, 2015, 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 ``good neighbor'' or ``interstate transport''
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). 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 EPA's Four Step Interstate Transport Regulatory
Process

    EPA is using the 4-step interstate transport framework (or 4-step
framework) to evaluate the states' implementation plan submittals
addressing the interstate transport provision for the 2015 8-hour ozone
NAAQS. 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\ 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 (August 8, 2011).
    \5\ Cross-State Air Pollution Rule Update for the 2008 Ozone
NAAQS, 81 FR 74504 (October 26, 2016).
    \6\ In 2019, the United States Court of Appeals for the District
of Columbia Circuit (D.C. Circuit) remanded 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 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\ 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 CSAPR rulemakings, other regional rulemakings
addressing ozone transport include the ``NOX SIP Call,''
63 FR 57356 (October 27, 1998), and the ``Clean Air Interstate
Rule'' (CAIR), 70 FR 25162 (May 12, 2005).
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C. Background on EPA's Ozone Transport Modeling Information

    In general, EPA has performed nationwide air quality modeling to
project ozone design values which are used in combination with measured
data to identify nonattainment and maintenance receptors. To quantify
the contribution of emissions from specific upwind states on 2023 ozone
design values for the identified downwind nonattainment and maintenance
receptors, EPA performed nationwide, state-level ozone source
apportionment modeling for 2023. The source apportionment modeling
provided contributions to ozone at receptors from precursor emissions
of anthropogenic nitrogen oxides (NOX) and volatile organic
compounds (VOCs) in individual upwind states.
    EPA has released several documents containing projected design
values, contributions, and information relevant to evaluating
interstate transport with respect to the 2015 8-hour ozone NAAQS.
First, on January 6, 2017, EPA published a notice of data availability
(NODA) in which the Agency requested comment on preliminary interstate
ozone transport data including projected ozone design values and
interstate contributions for 2023 using a 2011 base year platform.\8\
In the NODA, 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, EPA released a memorandum
(October 2017 memorandum) containing updated modeling data for 2023,
which incorporated changes made in response to comments on the NODA,
and 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, EPA issued a memorandum (March 2018 memorandum)
noting that the same 2023 modeling data released in the October 2017
memorandum could also be useful for identifying potential downwind air
quality problems with respect to the 2015 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\ 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\ See 82 FR 1733, 1735 (January 6, 2017).
    \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 (``October 2017 memorandum''),
available in Docket No. EPA-HQ-OAR-2021-0663 or at https://www.epa.gov/interstate-air-pollution-transport/interstate-air-pollution-transport-memos-and-notices.
    \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 No. EPA-HQ-OAR-2021-0663 or at https://www.epa.gov/interstate-air-pollution-transport/interstate-air-pollution-transport-memos-and-notices.
    \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
(``October 2018 memorandum''), available in Docket No. EPA-HQ-OAR-
2021-0663 or at https://www.epa.gov/airmarkets/memo-and-supplemental-information-regarding-interstate-transport-sips-2015-ozone-naaqs.
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    Since the release of the modeling data shared in the March 2018
memorandum, 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 EPA, MJOs, and states to develop a new, more recent
emissions platform for use by EPA and states in regulatory modeling as
an improvement over the dated 2011-based platform that EPA had used to
project ozone design values and contribution data provided in the 2017
and 2018 memoranda. EPA used the 2016v1 emissions to project ozone
design values and contributions for 2023. On October 30, 2020, in the
Notice of Proposed Rulemaking for the Revised CSAPR Update, EPA
released and accepted public comment on 2023 modeling that used the
2016v1 emissions platform.\15\ 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 8-hour ozone NAAQS.\16\
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    \14\ The results of this modeling, as well as the underlying
modeling files, are included in Docket No. EPA-HQ-OAR-2021-0663.
    \15\ See 85 FR 68964, 68981 (October 30, 2020).
    \16\ See the Air Quality Modeling Technical Support Document for
the Final Revised Cross-State Air Pollution Rule Update, included in
Docket No. EPA-HQ-OAR-2021-0663.
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    Following the Revised CSAPR Update final rule, EPA made further
updates to the 2016 emissions platform to include mobile emissions from
EPA's Motor Vehicle Emission Simulator (MOVES) 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
Preparation of Emissions Inventories for the 2016v2 North American
Emissions Modeling Platform technical support document (TSD) for this
proposed rule and is included in Docket No. EPA-HQ-OAR-2021-0663. EPA
performed air quality modeling of the 2016v2 emissions using the most
recent public release version of the Comprehensive Air Quality Modeling
with Extensions (CAMx) photochemical modeling, version 7.10.\18\ EPA
proposes to primarily rely on modeling based on the updated and newly
available 2016v2 emissions platform in evaluating these submissions
with respect to Steps 1 and 2 of the 4-step interstate transport
framework. By using the updated modeling results, EPA is using the most
current and technically appropriate information for this proposed
rulemaking. Section II of this notice and the Air Quality Modeling TSD
included in Docket No. EPA-HQ-OAR-2021-0663 for this proposal contain
additional detail on the modeling performed using the 2016v2 emissions
modeling.
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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\ Ramboll Environment and Health, January 2021, www.camx.com.
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    In this notice, EPA is accepting public comment on this updated
2023 modeling, which uses the 2016v2 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 8-hour ozone NAAQS Transport SIP Proposed
Actions. Comments on EPA's air quality modeling should be submitted in
Docket No. EPA-R04-OAR-2021-0841. Comments are not being accepted in
Docket No. EPA-HQ-OAR-2021-0663.
    States may have chosen to rely on the results of 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 II, EPA
evaluates how Alabama, Mississippi, and Tennessee used air quality
modeling information in their submissions.

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

    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 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 NOx 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, 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. 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, 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 concepts as may have been identified or suggested in the
past, EPA will evaluate whether the state adequately justified the
technical and legal basis for doing so.
    EPA notes that certain potential concepts included in an attachment
to the March 2018 memorandum require unique consideration, and these
ideas do not constitute agency guidance with respect to transport
obligations for the 2015 8-hour ozone NAAQS. Attachment A to the March
2018 memorandum identified a ``Preliminary List of Potential
Flexibilities'' that could potentially inform SIP development.\19\
However, 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 EPA sought ``feedback from interested
stakeholders.'' \20\ 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 is EPA specifically
recommending that states

use these approaches.'' \21\ 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, EPA will thoroughly review the technical and legal
justifications for doing so.
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    \19\ March 2018 memorandum, Attachment A.
    \20\ Id. at A-1.
    \21\ 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 EPA must implement the interstate
transport provision in a manner ``consistent with the provisions of
[title I of the CAA.]'' See 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).\22\ 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). See 938 F.3d 303, 313.
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    \22\ 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 August 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 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 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 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). 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,\23\ 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.\24\
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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    \23\ EPA notes that the court in Maryland did not have occasion
to evaluate circumstances in which 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.
    \24\ 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 August 3, 2018).
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    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 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, EPA must act on SIP submittals using the
information available at the time it takes such action. In this
circumstance, 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 23054, 23074; see also Wisconsin, 938 F.3d at 322. Consequently,
in this proposal 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, EPA identifies monitoring sites that are projected to
have problems attaining and/or maintaining the NAAQS in the 2023
analytic year. Where 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 EPA's 4-step interstate
transport framework. For sites that are identified as a nonattainment
or maintenance receptor in 2023, EPA proceeds to the next step of the
4-step interstate transport framework by identifying the upwind state's
contribution to those receptors.
    EPA's approach to identifying ozone nonattainment and maintenance
receptors in this action is consistent with the approach used in
previous transport rulemakings. 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.\25\
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    \25\ See North Carolina v. EPA, 531 F.3d 896, 910-11 (D.C. Cir.
2008) (holding that 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, 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 EPA defined nonattainment receptors as those areas
that both currently measure nonattainment and that EPA projects will be
in nonattainment in the future analytic year (i.e., 2023).\26\
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    \26\ 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, EPA identifies a receptor to be a
``maintenance'' receptor for purposes of

defining interference with maintenance, consistent with the method used
in 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).\27\ Specifically, 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. 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). 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.
---------------------------------------------------------------------------

    \27\ See 76 FR 48208 (August 8, 2011). The 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.
3. Step 2 of the 4-Step Interstate Transport Framework
    In Step 2, 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 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).
    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 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. EPA
continues to find 1 percent to be an appropriate threshold. For ozone,
as EPA found in the CAIR, CSAPR, and CSAPR Update, a portion of the
nonattainment problems from anthropogenic sources in the U.S. result
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. 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 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).
(a) EPA's Experience With Alternative Step 2 Thresholds
    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, 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.
    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 threshold at Step
2.\28\ (The memorandum also indicated that any higher alternative
threshold, such as 2 ppb, would likely not be appropriate.) However,
EPA also provided 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, 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.
---------------------------------------------------------------------------

    \28\ See August 2018 memorandum at 4.
---------------------------------------------------------------------------

    For instance, in nearly all submittals, the states did not provide
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, 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.\29\ It was at 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 8-hour ozone NAAQS.
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    \29\ 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.
---------------------------------------------------------------------------

    Furthermore, 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 8-hour ozone
NAAQS raises substantial policy consistency and practical
implementation concerns.\30\ 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
implementation plan 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 would 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.
---------------------------------------------------------------------------

    \30\ EPA notes that Congress has placed on 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.
---------------------------------------------------------------------------

    Further, it is not clear that national ozone transport policy is
best served by allowing for less stringent thresholds at Step 2. EPA
recognized in the August 2018 memorandum that there was some similarity
in the amount of total upwind contribution captured (on a nationwide
basis) between 1 percent and 1 ppb. However, 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 7 percent of total upwind state
contribution was lost according to the modeling underlying the August
2018 memorandum; \31\ in EPA's updated modeling, the amount lost is 5
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 the NAAQS threshold.
---------------------------------------------------------------------------

    \31\ See August 2018 memorandum at 4.
---------------------------------------------------------------------------

    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. See 76
FR 48208, 48237-38 (August 8, 2011).
    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, EPA's experience
since the issuance of that memorandum has revealed substantial
programmatic and policy difficulties in attempting to implement this
approach. Nonetheless, EPA is not at this time rescinding the August
2018 memorandum. As discussed further below, the basis for disapproval
of Alabama, Mississippi, and Tennessee's SIP submissions with respect
to the Step 2 analysis is, in the Agency's view, warranted even under
the terms of the August 2018 memorandum. 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, EPA
may determine to rescind the August 2018 memorandum in the future.
4. Step 3 of the 4-Step Interstate Transport Framework
    Consistent with 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. 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 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 EPA has not prescribed a particular method for this assessment,
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.\32\
---------------------------------------------------------------------------

    \32\ As examples of general approaches for how such an analysis
could be conducted for their sources, states could look to the CSAPR
Update, 81 FR 74504, 74539-51; CSAPR, 76 FR 48208, 48246-63; CAIR,
70 FR 25162, 25195-229; or the NOX SIP Call, 63 FR 57356,
57399-405. See also Revised CSAPR Update, 86 FR 23054, 23086-23116.
Consistently across these rulemakings, EPA has developed emissions
inventories, analyzed different levels of control stringency at
different cost thresholds, and assessed resulting downwind air
quality improvements.
---------------------------------------------------------------------------

5. Step 4 of the 4-Step Interstate Transport Framework
    At Step 4, states (or 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
implementation plan so that it is permanent and federally enforceable.
See CAA section 110(a)(2)(D) (``Each such [SIP] shall . . . contain
adequate provisions . . . .''). See also CAA section 110(a)(2)(A);
Committee for a Better Arvin v. EPA, 786 F.3d 1169, 1175-76 (9th Cir.
2015) (holding that measures relied on by a state to meet CAA
requirements must be included in the SIP).

II. SIP Submissions and EPA's Evaluation

A. Alabama

    The following section provides information related to Alabama's SIP
submission addressing interstate transport requirements for the 2015 8-
hour ozone NAAQS, and EPA's analysis of Alabama's submission.
1. Summary of Alabama's 2015 Ozone Interstate Transport SIP Submission
    On August 20, 2018,\33\ Alabama submitted a SIP revision addressing
the CAA section 110(a)(2)(D)(i)(I) good neighbor interstate transport
requirements for the 2015 8-hour ozone NAAQS.\34\ The SIP submission
provided Alabama's analysis of its impact to downwind states and
concluded that emissions from the State will not significantly
contribute to nonattainment or interfere with maintenance of the 2015
8-hour ozone NAAQS in other states, based on modeling results included
in EPA's March 2018 memorandum. Alabama's submission relied on the
results of EPA's modeling of 2023 using a 2011 base year, as contained
in the March 2018 memorandum (which the State attached to its
submittal), to identify downwind nonattainment and maintenance
receptors that may be impacted by emissions from sources in the State
at Step 1 of the 4-step framework.\35\
---------------------------------------------------------------------------

    \33\ The August 20, 2018, SIP submission provided by ADEM was
received by EPA on August 27, 2018.
    \34\ On August 20, 2018, Alabama submitted multiple SIP
revisions under one cover letter. EPA is only acting on Alabama's
2015 ozone good neighbor interstate transport SIP requirements in
this notice.
    \35\ EPA notes that Alabama's SIP submission is not organized
around EPA's 4-step framework for assessing good neighbor
obligations, but EPA summarizes the submission using that framework
for clarity here.
---------------------------------------------------------------------------

    Alabama Department of Environmental Management (ADEM) reviewed this
modeling, concurred with the results, and determined that the future
year projections were appropriate for the purposes of evaluating
Alabama's impact on nonattainment and maintenance receptors in other
states at Step 1. Alabama used this information to find that emissions
from Alabama would not contribute above 1 percent of the NAAQS at any
projected nonattainment or maintenance receptors at Step 2 of the 4-
step framework (using EPA's approach to defining such receptors).
    Alabama's August 20, 2018, submittal also identified existing SIP-
approved regulations and Federal programs \36\ that ADEM noted regulate
ozone-precursor emissions from sources in the State, including CSAPR
trading programs.\37\ Alabama's submission acknowledges that CSAPR does
not address interstate transport for the 2015 ozone standard but does
provide residual NOX emissions reductions and notes the
adoption of CSAPR NOX ozone season trading programs into the
Alabama SIP on August 31, 2016, and October 6, 2017.\38\ Alabama notes
that the implementation of the existing SIP-approved regulations and
Federal programs provide for a decline in ozone precursors emissions in
the State. Alabama also stated that ozone-precursor emissions would
continue to decline in the State.
---------------------------------------------------------------------------

    \36\ Alabama's submission cites the following SIP approved
regulations: Administrative Code Rule 335-3-6, ``Control of Organic
Emissions'', 335-3-8, ``Control of Nitrogen Oxides Emissions'', 335-
3-14-.01, ``General Provisions'', 335-3-14-.02, ``Permit
Procedures'', 335-3-14-.03, ``Standards for Granting Permits'', 335-
3-14- .04, ``Air Permits Authorizing Construction in in Clean Air
Areas [Prevention of Significant Deterioration Permitting (PSD)]''
and 335-3-14-.05, ``Air Permits Authorizing Construction in or Near
Nonattainment Areas.'' Alabama's Submission cites the following
Federal Rules: EPA's Tier 1 and 2 mobile source rules, EPA's nonroad
Diesel Rule, EPA's 2007 Heavy-duty Highway Rule, New Source
Performance Standards, National Emission Standards for Hazardous Air
Pollutants, and CSAPR.
    \37\ Alabama's SIP references CSAPR, which covers the
NOX ozone season trading program established in EPA's
2011 CSAPR, 76 FR 48208 (August 8, 2011). In addition, Alabama's
submittal includes a reference to the SIP-approved rules that
adopted the CSAPR Update, 81 FR 74504 (October 26, 2016). See 82 FR
46674 (October 6, 2017).
    \38\ See 81 FR 59869 (August 31, 2016), 82 FR 46674 (October 6,
2017) (adopting Alabama Administrative Code Rule 335-3-8, ''Control
of Nitrogen Oxides Emissions'' and adopting revisions to Rule 335-3-
8 into the SIP).
---------------------------------------------------------------------------

    Based on the information from Alabama's transport SIP, ADEM
concluded that emissions from Alabama sources will not significantly
contribute to nonattainment or interfere with maintenance of the 2015
8-hour ozone NAAQS in any other state.
2. Prior Notices Related to Alabama's SIP Submission
    Previously, EPA proposed approval of Alabama's interstate transport
provisions for the 2015 8-hour ozone NAAQS as addressed in Alabama's
August 20, 2018 SIP submission and based on the contribution modeling
provided in the March 2018 memorandum. See 84 FR 71854 (December 30,
2019). When EPA completed updated modeling of 2023 in 2020 using a
2016-based emissions modeling platform (2016v1), it became evident that
Alabama was projected to be linked to downwind nonattainment and
maintenance receptors (see footnote 40 below). As a result, EPA
deferred acting on Alabama's SIP submittal when it published a
supplemental proposal in 2021 to approve four other southeastern
states' good neighbor SIP submissions using the updated 2023 modeling.
See 86 FR 37942, 37943 (July 19, 2021). The updated 2023 modeling using
an updated 2016-based emissions modeling platform (2016v2) confirms the
prior 2016-based modeling of 2023 in that it continues to show Alabama
is linked to at least one downwind nonattainment or maintenance
receptor. Based on this updated modeling using the 2016-based emissions
modeling platform, discussed in section I.C above, EPA is now
withdrawing its 2019 proposed approval on Alabama's September 13, 2018,
interstate transport SIP as published on December 30, 2019, at 84 FR
71854.
3. EPA's Evaluation of Alabama's 2015 Ozone Interstate Transport SIP
Submission
    EPA is proposing to find that Alabama's August 20, 2018, SIP
submission does not meet Alabama'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 EPA's evaluation of the SIP
submission using the 4-step interstate transport framework, and EPA is
therefore proposing to disapprove Alabama's SIP submission.
(a) Results of EPA's Step 1 and Step 2 Modeling and Findings for
Alabama
    As described in section I, EPA performed updated air quality
modeling to project design values and contributions for 2023. These
data were examined to determine if Alabama contributes 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. As shown in Table 1,
the data \39\ indicate that in 2023, emissions from Alabama contribute
greater than 1 percent of the standard to a nonattainment receptor in
Harris County, Texas (ID#: 482010055) and a maintenance-only receptor
in Denton County, Texas (ID#: 481210034).\40\
---------------------------------------------------------------------------

    \39\ The ozone design values and contributions at individual
monitoring sites nationwide are provided in the file
``2016v2_DVs_state_contributions.xlsx'' which is included in Docket
No. EPA-HQ-OAR-2021-0663.
    \40\ These modeling results are consistent with the results of a
prior round of 2023 modeling using the 2016v1 emissions platform
which became available to the public in the fall of 2020 in the
Revised CSAPR Update, as noted in section I. That modeling showed
that Alabama had a maximum contribution greater than 0.70 ppb to at
least one nonattainment or maintenance-only receptor in 2023. These
modeling results are included in the file ``Ozone Design Values And
Contributions Revised CSAPR Update.xlsx'' in Docket No. EPA-HQ-OAR-
2021-0663.

                       Table 1--Alabama Linkage Results Based on EPA Updated 2023 Modeling
----------------------------------------------------------------------------------------------------------------
                                                                   2023 Average    2023 Maximum       Alabama
         Receptor ID               Location       Nonattainment/   design value    design value    contribution
                                                   maintenance         (ppb)           (ppb)           (ppb)
----------------------------------------------------------------------------------------------------------------
482010055....................  Harris County,    Nonattainment..            71.0            72.0            0.88
                                Texas.
481210034....................  Denton County,    Maintenance....            70.4            72.2            0.71
                                Texas.
----------------------------------------------------------------------------------------------------------------

(b) Evaluation of Information Provided by Alabama Regarding Step 1
    At Step 1 of the 4-step interstate transport framework, Alabama
relied on EPA modeling included in the March 2018 memorandum to
identify nonattainment and maintenance receptors in 2023. As described
in section II.A.3.a, EPA has recently updated this modeling using the
most current and technically appropriate information. EPA proposes to
rely on EPA's most recent modeling to identify nonattainment and
maintenance receptors in 2023. That information establishes that there
are two receptors to which Alabama is projected to be linked in 2023.
(c) Evaluation of Information Provided by Alabama Regarding Step 2
    At Step 2 of the 4-step interstate transport framework, Alabama
relied on EPA modeling released in the March 2018 memorandum to
identify upwind state linkages to nonattainment and maintenance
receptors in 2023. As described in section I.C of this notice, EPA has
recently updated modeling to identify upwind state contributions to
nonattainment and maintenance receptors in 2023. In this action, EPA
proposes to rely on the Agency's most recently available modeling to
identify upwind contributions and ``linkages'' to downwind air quality
problems in 2023 using a threshold of 1 percent of the NAAQS. See
section I.D for a general explanation of the use of 1 percent of the
NAAQS.
    As shown in Table 1, updated EPA modeling identifies Alabama's
maximum contribution to downwind nonattainment and maintenance
receptors as greater than 1 percent of the standard (i.e., 0.70 ppb).
Therefore, the State is linked to a downwind air quality problem at
Steps 1 and 2. Because the entire technical basis for Alabama's
interstate transport SIP submission is that Alabama is not linked at
Step 2, and thus Alabama's SIP contains 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, EPA proposes to disapprove Alabama's SIP submission based
on EPA's finding that such a linkage does exist.\41\
---------------------------------------------------------------------------

    \41\ To the extent that Alabama's submittal included information
regarding emissions controls that could be interpreted as relevant
to a step 3 analysis, EPA evaluates that information in section
II.A.3.d.
---------------------------------------------------------------------------

    Although Alabama did not rely on the 1 ppb threshold in its SIP
submittal, EPA recognizes that the most recently available EPA modeling
at the time Alabama submitted its SIP submittal indicated that Alabama
did not contribute above 1 percent of the NAAQS to a projected downwind
nonattainment or maintenance receptor. Therefore, Alabama may not have
considered analyzing the reasonableness and appropriateness of a 1 ppb
threshold at Step 2 of the 4-step interstate transport framework per
the August 2018 memorandum. However, EPA's August 2018 memorandum
provided that whether use of a 1 ppb threshold is appropriate must be
based on an evaluation of state-specific circumstances, and no such
evaluation was included in the submittal. EPA's experience with the
alternative Step 2 thresholds is further discussed in section I.D.3.a.
As discussed there, EPA is considering withdrawing the August 2018
memorandum.
(d) Evaluation of Information Provided by Alabama 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 effectively evaluate 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. 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 EPA has not directed states that they
must conduct a Step 3 analysis in precisely the manner 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 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. Alabama did not conduct
such an analysis in its SIP submission.
    Based on Alabama's finding that emissions from Alabama do not
contribute above 1 percent of the NAAQS at any monitors that are
projected to be in nonattainment or maintenance, the SIP submission
identified SIP-approved provisions and Federal programs in the context
that no further emissions reductions were necessary, and determined
that the SIP contained adequate provisions to prohibit emissions that
will significantly contribute to nonattainment or interfere with
maintenance of the 2015 8-hour ozone NAAQS in any other state. However,
the State did not analyze total ozone precursors that continue to be
emitted from sources and other emissions activity within the State,
evaluate the emissions reduction potential of any additional controls
using cost or other metrics, nor evaluate any resulting downwind air
quality improvements that could result from such controls.
    Among the Federal programs referenced in Alabama's submission was
the NOX ozone season trading program of CSAPR for the 2008
ozone standard, which ADEM adopted into the Alabama SIP.\42\ This
reference suggests that Alabama may have intended to rely on its
electric generating units (EGUs) being subject to CSAPR Update (which
reflected a stringency at the nominal marginal cost threshold of
$1,400/ton (in 2011 dollars) for the 2008 8-hour ozone NAAQS) to argue
that it has already implemented all cost-effective emissions reductions
at EGUs.
---------------------------------------------------------------------------

    \42\ See 81 FR 59869 (August 31, 2016), 82 FR 46674 (October 6,
2017) (adopting Alabama Administrative Code Rule 335-3-8, ''Control
of Nitrogen Oxides Emissions'' and adopting revisions to Rule 335-3-
8 into the SIP).
---------------------------------------------------------------------------

    EPA does not support the concept that reliance on CSAPR Update is
appropriate to conclude that no further emissions reductions are
necessary under Step 3 for the 2015 8-hour ozone NAAQS. First, CSAPR
Update did not regulate non-electric generating units (non-EGUs), and
thus this analysis, even for the 2008 ozone NAAQS, was incomplete, and
EPA acknowledged at the time that CSAPR Update was not a full remedy
for interstate transport under that NAAQS. See Wisconsin, 938 F.3d at
318-20. Second, relying on CSAPR Update's (or any other CAA program's)
determination of cost-effectiveness without further Step 3 analysis is
not approvable. Cost-effectiveness must be assessed in the context of
the specific CAA program; assessing cost-effectiveness in the context
of ozone transport should reflect a more comprehensive evaluation of
the nature of the interstate transport problem, the total emissions
reductions available at several cost thresholds, and the air quality
impacts of the reductions at downwind receptors. While EPA has not
established a benchmark cost-effectiveness value for 2015 8-hour ozone
NAAQS interstate transport obligations, it is reasonable to expect
control measures or strategies to address interstate transport under
this NAAQS to reflect higher marginal control costs because the 2015 8-
hour ozone NAAQS is a more stringent and more protective air quality
standard. As such, the marginal cost threshold of $1,400/ton for the
CSAPR Update (which addresses the 2008 ozone 8-hour NAAQS and is in
2011 dollars) is not an appropriate cost threshold and cannot be
approved as a benchmark to use for interstate transport SIP submissions
for the 2015 8-hour ozone NAAQS. In addition, the updated EPA modeling
captures all existing CSAPR trading programs in the baseline, and that
modeling confirms that these control programs were not sufficient to
eliminate the Alabama's linkage at Steps 1 and 2 under the 2015 8-hour
ozone NAAQS even if the CSAPR Update provisions had been adopted into
Alabama's SIP. The State was therefore obligated at Step 3 to assess
additional control measures using a multifactor analysis.
    As mentioned above, EPA has newly available information that
indicates sources in Alabama are linked to downwind air quality
problems for the 2015 ozone standard. Therefore, EPA proposes to
disapprove Alabama's August 20, 2018, interstate transport SIP
submission on the separate, additional basis that the SIP submittal did
not assess additional emissions control opportunities.
(e) Evaluation of Information Provided by Alabama 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 in section
II.A.3.d, Alabama's SIP submission did not contain an evaluation of
additional emissions control opportunities (or establish that no
additional controls are required), thus, no information was provided at
Step 4. As a result, EPA proposes to disapprove Alabama's August 20,
2018, 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).
4. Conclusion for Alabama
    Based on EPA's evaluation of Alabama's SIP submission and after
consideration of updated EPA modeling using the 2016-based emissions
modeling platform, EPA is proposing to find that the 2015 8-hour ozone
NAAQS good neighbor interstate transport portion of Alabama's August
20, 2018, 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.

B. Mississippi

    The following section provides information related to Mississippi's
SIP submission addressing interstate transport requirements for the
2015 8-hour ozone NAAQS, and EPA's analysis of Mississippi's
submission.
1. Summary of Mississippi's 2015 Ozone Interstate Transport SIP
Submission
    On September 3, 2019, the Mississippi Department of Environmental
Quality (MDEQ) submitted a SIP revision addressing the CAA section
110(a)(2)(D)(i)(I) interstate transport requirements for the 2015 8-
hour ozone NAAQS.\43\ The SIP

submission provided Mississippi's analysis of its impact to downwind
states and concluded that emissions from the State will not
significantly contribute to nonattainment or interfere with maintenance
of the 2015 8-hour ozone NAAQS in other states.
---------------------------------------------------------------------------

    \43\ The September 3, 2019, SIP submission provided by MDEQ was
received by EPA on September 6, 2019.
---------------------------------------------------------------------------

    MDEQ's submission relied on the results of EPA's modeling for the
2015 8-hour ozone NAAQS, contained in the March 2018 memorandum, to
identify projected downwind nonattainment and maintenance receptors and
contribution linkages in 2023 that may be impacted by emissions from
sources in Mississippi at Steps 1 and 2 of the 4-step interstate
transport framework,\44\ respectively. MDEQ reviewed EPA's March 2018
modeling and found that the modeled contributions for Mississippi were
below 1 percent of the NAAQS for all nonattainment and maintenance
receptors, except the Deer Park nonattainment receptor in Harris
County, Texas (Monitor ID: 482011039). The SIP submission identified
Mississippi as linked to the Deer Park receptor with an upwind
contribution of 0.79 ppb.
---------------------------------------------------------------------------

    \44\ EPA notes that Mississippi's September 2, 2019, SIP
submission is not organized around EPA's 4-step interstate transport
framework for assessing good neighbor obligations, but EPA
summarizes the submission using that framework for clarity here.
---------------------------------------------------------------------------

    In its submittal, MDEQ discussed EPA's August 2018 memorandum,
explaining that 0.79 ppb is 1.12 percent of the 2015 8-hour ozone
NAAQS, which is greater than the 1 percent contribution threshold of
0.70 ppb but less than a 1 ppb alternative contribution threshold. The
SIP submission also states that the Deer Park receptor design value was
projected to be greater than the 2015 ozone standard in 2023, but that
the actual 2015-2017 design value was below the NAAQS at 68 ppb. Based
on the modeling in the March 2018 memo, along with application of a 1
ppb alternative contribution threshold and information regarding 2015-
2017 monitored values at the Deer Park receptor, MDEQ concluded that
sources in Mississippi were not linked to downwind nonattainment or
maintenance receptors at Step 2, and therefore, the State does not
significantly contribute to nonattainment in another state for the 2015
ozone standard. Further, MDEQ stated that the SIP contains adequate
provisions to prohibit sources and other types of emissions activities
within the State from contributing to nonattainment in another state
with respect to the 2015 8-hour ozone NAAQS.
    In its submission, MDEQ treated the Deer Park receptor as a
maintenance receptor because the most recent measured design value at
the time of its submission (i.e., the 2017 design value of 68 ppb) was
below the level of the NAAQS at this monitor. Based on MDEQ's
interpretation of EPA's October 19, 2018, memorandum, the State
eliminated the Deer Park monitor site in Harris County, Texas, as a
maintenance receptor in 2023 (although EPA's modeling of 2023 released
with the October 2017 memorandum had identified this monitoring site as
a nonattainment receptor).
    To support eliminating the Deer Park monitor as a receptor, MDEQ's
demonstration included: (1) Evaluating ozone season temperatures in the
period 2014-2017 in Harris County to determine if conditions were
conducive for ozone formation; (2) assessing monitored ozone design
values from 2011-2017 at the Deer Park monitor; and (3) reviewing ozone
precursor emission trends in the Houston Area, Texas (statewide), and
Mississippi (statewide). In its demonstration, MDEQ stated that
temperatures in 2015 and 2016 were above average, and in 2014 and 2017
temperatures were near normal. Based on this information, MDEQ
concluded that conditions were conducive to ozone formation during this
three-year time period (i.e., 2015 to 2017). MDEQ's submission also
states that design values from 2011 to 2017 at the Deer Park receptor
showed a downward trend and that design values have been meeting the
2015 8-hour ozone NAAQS since 2015. Further, according to the
submittal, ozone precursor emissions in Texas and Mississippi both
showed a downward trend based on data from 2008, 2011, and 2014. Based
on the downward trend in emissions and the fact that the Deer Park
monitor was measuring attainment in 2015, 2016, and 2017, MDEQ
determined that the Deer Park receptor should be eliminated as a
maintenance receptor. Thus, based on the elimination of the Deer Park
receptor, along with application of a 1 ppb threshold, Mississippi
concluded that the State did not significantly interfere with
maintenance (prong 2) in another state for the 2015 ozone standard.
    In summary, MDEQ concluded that sources in the State do not
significantly contribute to nonattainment or interfere with maintenance
in another state, that no further emission reductions were necessary,
and that Mississippi's SIP contains adequate provisions to prevent
sources and other types of emissions activities within the State from
contributing significantly to nonattainment or interfering with
maintenance in another state with respect to the 2015 8-hour ozone
NAAQS.
2. EPA's Evaluation of Mississippi's 2015 Ozone Interstate Transport
SIP Submission
    EPA is proposing to find that Mississippi's September 3, 2019, SIP
submission does not meet Mississippi'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 EPA's evaluation of the SIP submission using the 4-step
interstate transport framework, and EPA is therefore proposing to
disapprove Mississippi's submission.
(a) Evaluation of Information Provided by Mississippi Regarding Step 1
    At Step 1 of the 4-step interstate transport framework, MDEQ relied
on EPA modeling released in the March 2018 memorandum to identify
nonattainment and maintenance receptors in 2023.
    In its submittal, MDEQ attempted to utilize the October 2018
memorandum along with 2014 to 2017 ozone design values (the most recent
data available at the time of submittal) to eliminate the Deer Park
receptor in Harris County, Texas (Monitor ID: 482011039) as a
maintenance receptor. Table 2 of the submittal correctly indicates that
this monitoring site was a projected nonattainment receptor, not a
maintenance-only receptor, in 2023 based on the EPA's modeling data
included in the March 2018 memorandum. However, in its submittal, the
State relied on the 2014 to 2017 design values at the Deer Park
receptor (i.e., 69 ppb, 67 ppb, and 68 ppb, respectively) as the basis
for stating that this receptor met EPA's definition of a maintenance
receptor. Based on this information, the State applied an alternative
definition of a maintenance receptor utilizing the potential concepts
included in the October 2018 memorandum. This memorandum included a
description of the approach that EPA has historically used to identify
maintenance-only receptors \45\ and identified potential alternate ways
to define maintenance receptors based on certain criteria suggested in
the memorandum including an evaluation of meteorology conductive to
ozone formation, review of ozone monitored concentrations, and
precursor emissions trends.
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    \45\ See section I.D, above for a discussion of EPA's approach
to identify maintenance receptors.

---------------------------------------------------------------------------

    EPA recognized in the October 2018 memorandum that states could
potentially, with sufficient justification, establish an approach to
addressing maintenance receptors that gives independent significance to
prong 2 in some manner different than EPA's approach. In addition, the
October 2018 memorandum identified two potential concepts that states
could use to identify maintenance receptors: (1) States may, in some
cases, eliminate a site as a maintenance receptor if the site is
currently measuring clean data, or (2) in some cases, use a design
value from the base period that is not the maximum design value. For
either of these alternative methods, to adequately consider areas
struggling to meet the NAAQS, EPA also indicated that it expects states
to include with their SIP demonstration technical analyses showing that
the following three criteria are met:
     Meteorological conditions in the area of the monitoring
site were conducive to ozone formation during the period of clean data
or during the alternative base period design value used for
projections; \46\
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    \46\ See Attachment A of EPA's October 2018 memorandum formation
to assess whether particular summers had ozone-conducive or
unconducive meteorology within the 10-year period 2008 through 2017.
The memorandum states that meteorological conditions including
temperature, humidity, winds, solar radiation, and vertical mixing
affect the formation and transport of ambient ozone concentrations.
The memorandum suggests generally that above average temperatures
are an indication that meteorology is conducive to ozone formation
and below average temperatures indicate that conditions are
unconducive to ozone formation. Within a particular summer season,
the degree that meteorology is conducive for ozone formation can
vary from region to region and fluctuate with time within a
particular region.
---------------------------------------------------------------------------

     Ozone concentrations have been trending downward at the
site since 2011 (and ozone precursor emissions of NOX and
VOC have also decreased); and
     Emissions are expected to continue to decline in the
upwind and downwind states out to the attainment date of the receptor.

EPA's October 2018 memorandum explained that the intent of these
analyses is to demonstrate that monitoring sites that would be
identified as maintenance receptors under EPA's historical approach
could nonetheless be shown to be very unlikely to violate the NAAQS in
the future analytic year.
    However, the analysis provided by Mississippi in its submission has
not met the criteria laid out in the guidance. With respect to the
first criterion (meteorological conditions), MDEQ assessed ozone design
values at the Deer Park site in Houston from 2014 to 2017 and anomalies
(i.e., difference compared to the long-term mean) of average
temperatures in June, July, and August, summarized from EPA's October
2018 memorandum, to determine whether particular summers had ozone-
conducive or unconducive meteorology during the period of clean data.
MDEQ stated that temperatures were above average in 2015 and 2016 when
the Deer Park monitor measured ozone concentrations below the 2015 8-
hour ozone NAAQS and near normal in 2014 and 2017. However, MDEQ's
review of meteorological conditions in the vicinity of the Deer Park
monitor was limited to temperature anomalies and 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 2015 and 2016 and unconducive in 2014
and 2017.
    With respect to the second criterion, MDEQ's submission included
information related to ozone design values and ozone precursors.
Specifically, the submission included an assessment of ozone design
values at the Deer Park monitor from 2011 to 2017, which showed a
downward trend in ozone concentrations. However, MDEQ's SIP submission
did not include a discussion of the 2018 design value, which showed a
violation of the 2015 standard at 71 ppb, even though that data was
available and could have been considered in the State's analysis at the
time of the submission in 2019.\47\ In addition, the 2019 and 2020
design values, 75 ppb and 78 ppb, respectively, also exceeded the
NAAQS. The preliminary design value for 2021 is 74 ppb.\48\ Although
not available at the time of the SIP submission, these more recent data
suggest a continuous trend in measured ozone concentrations above the
2015 ozone standard at the Deer Park monitor. Even though MDEQ's review
of ozone monitoring data may have shown a decrease in measured
concentration from 2011 to 2017, EPA notes a significant increase
between the 2017 and 2018 4th highest daily maximum concentration, from
68 ppb to 85 ppb. MDEQ's SIP submission did not consider the 2018 4th
high daily maximum concentration as part of its trends analysis even
though the information was available at the time the SIP was submitted
to EPA. Thus, at the time of the submission, the Deer Park monitor had
a 3-year design value of 71 ppb, which violated the 70 ppb ozone
standard. Thus, under the terms of the October 2018 memorandum,
Mississippi's SIP submission does not adequately establish a basis for
eliminating the Deer Park monitoring site as an ozone transport
receptor.
---------------------------------------------------------------------------

    \47\ The data are given in ``2010_thru_2020 Ozone Design
Values.xlsx,'' which is included in Docket No. EPA-HQ-OAR-2021-0663.
    \48\ This is based on preliminary 2021 data available from the
Air Quality System (AQS) as of January 3, 2022. The design values
for 2021 have not been certified by state agencies.
---------------------------------------------------------------------------

    MDEQ also assessed total ozone precursor emissions data in 2008,
2011, and 2014, which MDEQ claimed indicated a decrease in ozone
precursor (NOX and VOC) emissions in the Houston
metropolitan statistical area, Texas (statewide), and Mississippi
(statewide). While EPA acknowledges the general downward trends in
NOX and VOC emissions, the Deer Park monitor ozone
concentrations design values through 2020 show recent measured ozone
concentrations that exceed the 2015 ozone standard. Further, even
accounting for emissions trends, EPA's latest air quality modeling, as
presented below, shows that there are now three receptors to which
Mississippi contributes in 2023, not just one. Thus, the apparent
downward trend in ozone precursors in Texas and Mississippi alone
cannot support elimination of either the Deer Park monitor as a
receptor (under the information Mississippi relied on) or the three
Texas receptors to which EPA now finds Mississippi to be contributing.
See section II.B.2.c and Table 2 below for results of EPA's 2016v2 Step
1 and Step 2 modeling and findings for Mississippi.
    With respect to the third criterion, MDEQ stated that, ``[b]ased on
national and regional emissions trends, and current regulations on
point sources and mobile sources, emissions are expected to continue to
decline in the upwind and downwind states.'' However, the State did not
cite any specific regulations controlling sources of ozone precursors
or mobile sources or quantify the NOX emission reduction
potential of current regulations for point and mobile sources.
    Based on the reasons stated above, EPA does not believe
Mississippi's SIP submission provided sufficient justification to
eliminate the Deer Park monitor as a maintenance receptor.
(b) Evaluation of Information Provided by Mississippi Regarding Step 2
    At Step 2 of the 4-step interstate transport framework, Mississippi
relied on EPA's modeling released in the March 2018 memorandum to
identify upwind state linkages to nonattainment and maintenance
receptors in 2023.

    As described in section I.C of this notice, EPA has recently
updated modeling to identify upwind state contributions to
nonattainment and maintenance receptors in 2023. In this proposal, EPA
relies on the Agency's most recently available modeling to identify
upwind contributions and ``linkages'' to downwind air quality problems
in 2023 using a threshold of 1 percent of the NAAQS. See section I.D
for general explanation of the use of 1 percent of the NAAQS. As shown
in Table 2, updated EPA modeling identifies Mississippi's maximum
contribution to downwind nonattainment and maintenance receptors to be
greater than 1 percent of the standard (i.e., 0.70 ppb). Therefore, the
State is linked to a downwind air quality problem at Steps 1 and 2.
    MDEQ relied on EPA's August 2018 memorandum in an attempt justify
using a 1 ppb alternative contribution threshold at Step 2 as a basis
to assert that Mississippi would not be ``linked'' to any projected
downwind nonattainment or maintenance receptors. As discussed in EPA's
August 2018 memorandum, EPA had suggested that, with appropriate
additional analysis, it may be reasonable for states to use a 1 ppb
contribution threshold, as an alternative to a 1 percent threshold, at
Step 2 of the 4-step interstate transport framework, for the purposes
of identifying linkages to downwind receptors. However, based on EPA's
updated modeling, the State is projected to contribute greater than
both the 1 percent and alternative 1 ppb thresholds. While EPA does
not, in this action, approve of the State's application of the 1 ppb
threshold, based on its 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
is inconsequential to EPA's proposed action on this SIP.
    In addition, MDEQ's SIP does not include a technical analysis to
sufficiently justify use of an alternative 1 ppb threshold at the Deer
Park monitor. Echoing EPA's August 2018 memorandum, MDEQ stated that
the amount of upwind collective contribution captured with the 1
percent and 1 ppb thresholds is generally comparable. In this
memorandum, EPA also 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. In this regard, MDEQ did not provide any further technical
justification to make that determination.
    MDEQ also referred to an EPA Guidance on Significant Impact Levels
for Ozone and Fine Particles in the Prevention of Significant
Deterioration Permitting Program (``SILs Guidance'') as additional
justification for use of a 1 ppb threshold. However, MDEQ did not
provide discussion or analysis containing information specific to
Mississippi or the receptors to which its emissions are potentially
linked, which is necessary to thoroughly evaluate the state-specific
circumstances that could support approval. In addition, the State did
not explain the relevance or applicability of a SILs Guidance to which
it made reference. EPA's SILs guidance relates to a different provision
of the CAA regarding implementation of the prevention of significant
deterioration (PSD) permitting program, i.e., a program that applies in
areas that have been designated attainment \49\ or unclassifiable for
the NAAQS, and it is not applicable to the good neighbor provision,
which requires states to eliminate significant contribution or
interference with maintenance of the NAAQS at known and ongoing air
quality problem areas in other states.
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    \49\ Pursuant to section 107(d) of the CAA, EPA must designate
areas as either ``nonattainment,'' ``attainment,'' or
``unclassifiable.'' Historically for ozone, the EPA has designated
most areas that do not meet the definition of nonattainment as
``unclassifiable/attainment.'' This category includes areas that
have air quality monitoring data meeting the NAAQS and areas that do
not have monitors but for which the EPA has no evidence that the
areas may be violating the NAAQS or contributing to a nearby
violation. In the designations for the 2015 ozone NAAQS, the EPA
reversed the order of the label to be ``attainment/unclassifiable''
to better convey the definition of the designation category and so
that the category is more easily distinguished from the separate
unclassifiable category. An ``attainment'' designation is reserved
for a previous nonattainment area that has been redesignated to
attainment as a result of the EPA's approval of a CAA section 175A
maintenance plan submitted by the state air agency.
---------------------------------------------------------------------------

    The analytical gaps identified indicate that the submittal's use of
a 1 ppb threshold for the State is not approvable. EPA's experience
with the alternative Step 2 thresholds is further discussed in section
I.D.3.a. As discussed there, EPA is considering withdrawing the August
2018 memorandum.
    Despite the linkage EPA determines exists at Step 2, the State
argued in its submittal that it should not be considered to
significantly contribute to nonattainment or interfere with maintenance
of the NAAQS in other states. EPA finds that conclusion is not
approvable at Steps 1 or 2. Therefore, based on EPA's evaluation of the
information submitted by Mississippi, and based on EPA's most recent
modeling results for 2023, EPA proposes to find that Mississippi 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.
(c) Results of EPA's 2016v2 Step 1 and Step 2 Modeling and Findings for
Mississippi
    As described in section I, EPA performed air quality modeling using
the 2016v2 emissions platform to project design values and
contributions for 2023. These data were examined to determine if
Mississippi contributes 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. As shown in Table 2, the data \50\ indicate that
in 2023, emissions from Mississippi contribute greater than 1 percent
of the standard to nonattainment or maintenance-only receptors in
Denton County, Texas (Monitor ID: 481210034), Harris County, Texas
(Monitor ID: 482010055), and Brazoria County, Texas (Monitor ID:
480391004).\51\ Note that each of these monitors is currently measuring
nonattainment based on 2020 design values of 72 ppb, 76 ppb, and 73 ppb
at the Denton County, Harris County, and Brazoria County receptors,
respectively.
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    \50\ The ozone design values and contributions at individual
monitoring sites nationwide are provided in the file
``2016v2_DVs_state_contributions.xlsx'' which is included in Docket
No. EPA-HQ-OAR-2021-0663.
    \51\ These modeling results are consistent with the results of a
prior round of 2023 modeling using a the 2016v1 emissions platform
that became available to the public in the fall of 2020 in the
Revised CSAPR Update, as noted in section I.

                     Table 2--Mississippi Linkage Results Based on EPA Updated 2023 Modeling
----------------------------------------------------------------------------------------------------------------
                                                                   2023 average    2023 maximum     Mississippi
         Receptor ID               Location       Nonattainment/   design value    design value    contribution
                                                   maintenance         (ppb)           (ppb)           (ppb)
----------------------------------------------------------------------------------------------------------------
481210034....................  Denton County,    Maintenance....            70.4            72.2            1.14
                                Texas.
482010055....................  Harris County,    Nonattainment..            71.0            72.0            1.04
                                Texas.
480391004....................  Brazoria County,  Maintenance....            70.1            72.3            0.92
                                Texas.
----------------------------------------------------------------------------------------------------------------

(d) Evaluation of Information Provided by Mississippi 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 effectively evaluate 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. 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 EPA has not directed states that
they must conduct a Step 3 analysis in precisely the manner 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. Mississippi did not
conduct such an analysis in its SIP submission. Mississippi did not
include an accounting of sources or other emissions activity in the
State along with an analysis of potential NOX emissions
control technologies, their associated costs, estimated emissions
reductions, and downwind air quality improvements.
    EPA's evaluation of Mississippi's submittal, in conjunction with
its 2016-based modeling of 2023, indicates that ozone-precursor
emissions from Mississippi are linked to downwind air quality problems
for the 2015 ozone standard at Steps 1 and 2. However, Mississippi's
SIP submittal does not include a Step 3 analysis. EPA proposes to find
that Mississippi was required to analyze emissions from the sources and
other emissions activity from within the State to determine whether its
contributions were significant, and EPA proposes to disapprove its
submission because Mississippi's submittal failed to do so.
(e) Evaluation of Information Provided by Mississippi 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,
Mississippi's SIP submittal 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, EPA proposes to disapprove Mississippi's 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).
3. Conclusion for Mississippi
    Based on EPA's evaluation of Mississippi's SIP submission, EPA is
proposing to find that Mississippi's September 3, 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.

C. Tennessee

    The following section provides information related to Tennessee's
SIP submission addressing interstate transport requirements for the
2015 8-hour ozone NAAQS, and EPA's analysis of Tennessee's submission.
1. Summary of Tennessee's 2015 Ozone Interstate Transport SIP
Submission
    On September 13, 2018, Tennessee submitted a SIP revision
addressing the CAA section 110(a)(2)(D)(i)(I) interstate transport
requirements for the 2015 8-hour ozone NAAQS.52 53 The SIP
submission provided Tennessee's analysis of its impact to downwind
states and concluded that emissions from the State will not
significantly contribute to nonattainment or interfere with maintenance
of the 2015 8-hour ozone NAAQS in other states. Tennessee's submission
relied on EPA's modeling results for the 2015 8-hour ozone NAAQS,
contained in the March 2018 memorandum, to identify downwind
nonattainment and maintenance receptors that may be impacted by
emissions from sources in the State at Steps 1 and 2 of the 4-step
framework.\54\ The Tennessee Department of Environmental Control (TDEC)
reviewed EPA's 2023 modeling, concurred with the results, and
determined that EPA's future year NOX projections were
reasonable and account

for source shutdowns, new controls, and fuel switches. TDEC summarized
the State's upwind contribution to 26 nonattainment and maintenance
receptors and noted Tennessee's largest impact on any potential
downwind receptor in 2023 would be 0.31 ppb and 0.65 ppb, respectively.
Tennessee found that--based on EPA's 2023 modeling--emissions from
Tennessee do not contribute above 1 percent of the NAAQS or above 1 ppb
at any monitors that are projected to be in nonattainment or
maintenance.
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    \52\ The September 13, 2019, SIP submission provided by TDEC was
received by EPA on September 17, 2018.
    \53\ On September 18, 2018, Tennessee submitted multiple SIP
revisions under one cover letter. EPA is only acting on Tennessee's
2015 ozone good neighbor interstate transport SIP requirements in
this notice.
    \54\ EPA notes that Tennessee's SIP submission is not organized
around EPA's 4-step framework for assessing good neighbor
obligations, but EPA summarizes the submission using that framework
for clarity here.
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    Tennessee's September 13, 2018, SIP submittal asserted that
NOX emissions are considered the primary cause of formation
of ozone in the southeast United States, and emphasized a significant
reduction in NOX emissions reductions from coal-fired EGUs
and other large NOX sources leading to improvements in air
quality, including reductions attributable to previous transport
rulemakings.\55\ Additionally, TDEC identifies existing SIP-approved
provisions, Federal regulations and programs, court settlements, and
statewide source shutdowns that TDEC believes limit ozone precursor
emissions in the State.\56\
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    \55\ The Tennessee SIP revision specifically cites the Federal
NOX Budget Trading Program, CAIR, and CSAPR. In addition,
the Tennessee SIP revision discusses Tennessee rule 1200-03-27-.12
(NOX SIP Call requirements for Stationary Boilers and
Combustion Turbines), which had not been approved into the SIP at
the time of the September 13, 2018, submittal. EPA finalized
approval of TAPR 1200-03-27-.12 into the Tennessee SIP on March 2,
2021. See 86 FR 12092.
    \56\ See page 9 through 12 of Tennessee's September 13, 2018,
SIP submission for a list of SIP-approved State rules and Federal
rules. This can be found in Docket No. EPA-R04-OAR-2021-0841.
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    Based on the information contained in Tennessee's transport SIP,
TDEC concluded that Tennessee does not significantly contribute to
nonattainment or interfere with maintenance in another state of the
2015 8-hour ozone NAAQS, and that the SIP provides for adequate
measures to control ozone precursor emissions.
2. Prior Notices Related to Tennessee's SIP Submission
    Previously, EPA proposed approval of Tennessee's interstate
transport provisions for the 2015 8-hour ozone NAAQS as addressed in
Tennessee's September 13, 2018, SIP submission and based on the
contribution modeling provided in the March 2018 memorandum. See 84 FR
71854 (December 30, 2019). When EPA completed updated modeling of 2023
in 2020 using a 2016-based emissions modeling platform (2016v1), it
became evident that Tennessee was projected to be linked to downwind
nonattainment and maintenance receptors (see footnote 57 below). As a
result, EPA deferred acting on Tennessee's SIP submittal when it
published a supplemental proposal in 2021 to approve four other
southeastern states' good neighbor SIP submissions, using the updated
2023 modeling. See 86 FR 37942, 37943 (July 19, 2021). The updated 2023
modeling presented in this proposal using an updated 2016-based
emissions modeling platform (2016v2) confirms the prior 2016-based
modeling of 2023 in that it continues to show Tennessee is linked to at
least one downwind nonattainment or maintenance receptor. Based on this
updated modeling using the 2016-based emissions modeling platform,
discussed in section I.C above, EPA is now withdrawing its 2019
proposed approval on Tennessee's September 13, 2018, interstate
transport SIP as published on December 30, 2019 at 84 FR 71854.
3. EPA's Evaluation of Tennessee's 2015 Ozone Interstate Transport SIP
Submission
    EPA is proposing to find that Tennessee's September 13, 2018, SIP
submission 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 EPA's evaluation of the SIP submission using the 4-step
interstate transport framework, and EPA is therefore proposing to
disapprove Tennessee's SIP submission.
(a) Results of EPA's Step 1 and Step 2 Modeling and Findings for
Tennessee
    As described in section I, EPA performed updated air quality
modeling to project design values and contributions for 2023. These
data were examined to determine if Tennessee contributes 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. As shown in Table
3, the data \57\ indicate that in 2023, emissions from Tennessee
contribute greater than 1 percent of the standard to the maintenance-
only receptor in Denton County, Texas (ID#: 481210034).\58\
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    \57\ The ozone design values and contributions at individual
monitoring sites nationwide are provided in the file
``2016v2_DVs_state_contributions.xlsx'' which is included in Docket
No. EPA-HQ-OAR-2021-0663.
    \58\ These modeling results are consistent with the results of a
prior round of 2023 modeling using the 2016v1 emissions platform
which became available to the public in the fall of 2020 in the
Revised CSAPR Update, as noted in section I. That modeling showed
that Tennessee had a maximum contribution greater than 0.70 ppb to
at least one nonattainment or maintenance-only receptor in 2023.
These modeling results are included in the file ``Ozone Design
Values And Contributions Revised CSAPR Update.xlsx'' in Docket No.
EPA-HQ-OAR-2021-0663.

                      Table 3--Tennessee Linkage Results Based on EPA Updated 2023 Modeling
----------------------------------------------------------------------------------------------------------------
                                                                   2023 Average    2023  Maximum     Tennessee
         Receptor ID               Location       Nonattainment/   design value    design value    contribution
                                                   maintenance         (ppb)           (ppb)           (ppb)
----------------------------------------------------------------------------------------------------------------
481210034....................  Denton County,    Maintenance....            70.4            72.2            0.94
                                Texas.
----------------------------------------------------------------------------------------------------------------

(b) Evaluation of Information Provided by Tennessee Regarding Step 1
    At Step 1 of the 4-step interstate transport framework, Tennessee
relied on EPA modeling included in the March 2018 memorandum to
identify nonattainment and maintenance receptors in 2023. As described
previously in section II.C.3.a, EPA has recently updated this modeling
using the most current and technically appropriate information. EPA
proposes to rely on EPA's most recent modeling to identify
nonattainment and maintenance receptors in 2023. That information
establishes that there is one receptor to which Tennessee is projected
to be linked in 2023.
(c) Evaluation of Information Provided by Tennessee Regarding Step 2
    At Step 2 of the 4-step interstate transport framework, Tennessee
relied on EPA modeling released in the March 2018 memorandum to
identify upwind state linkages to nonattainment and maintenance
receptors in 2023. As described in section I.C of this notice,

EPA has recently updated modeling to identify upwind state
contributions to nonattainment and maintenance receptors in 2023. In
this proposal, EPA relies on the Agency's most recently available
modeling to identify upwind contributions and ``linkages'' to downwind
air quality problems in 2023 using a threshold of 1 percent of the
NAAQS. See section I.D for a general explanation of the use of 1
percent of the NAAQS.
    As shown in Table 3, updated EPA modeling identifies Tennessee's
maximum contribution to a downwind maintenance receptor as greater than
1 percent of the standard (i.e., 0.70 ppb). Therefore, the State is
linked to a downwind air quality problem at Steps 1 and 2. Because the
entire technical basis for Tennessee's submittal is that the State is
not linked at Step 2, EPA proposes to disapprove Tennessee's SIP
submission based on EPA's finding that a linkage does exist.\59\
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    \59\ To the extent the Tennessee submittal included information
regarding emissions controls that could be interpreted as relevant
to a Step 3 analysis, EPA evaluates that information in section
II.C.3.d.
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    Tennessee references a 1 ppb threshold in its submittal, citing to
EPA's SILs Guidance as justification for the use of a 1 ppb threshold.
However, Tennessee did not provide additional discussion or analysis
containing information specific to Tennessee or the receptors to which
its emissions are potentially linked, which is necessary to evaluate
the state-specific circumstances that could support approval of an
alternative threshold. Nevertheless, EPA recognizes that the most
recently available EPA modeling at the time Tennessee submitted its SIP
submittal indicated the State did not contribute above 1 percent of the
NAAQS to a projected downwind nonattainment or maintenance receptor.
Therefore, the State may not have considered conducting an in-depth
analysis as to the reasonableness and appropriateness of a 1 ppb
threshold at Step 2 of the 4-step interstate transport framework per
the August 2018 memorandum. However, EPA's August 2018 memorandum
provided that whether use of a 1 ppb threshold is appropriate must be
based on an evaluation of state-specific circumstances. Tennessee
provided no such analysis. Further, the State did not explain the
relevance of the SILs Guidance to which it made reference. This
guidance relates to a different provision of the CAA regarding
implementation of the PSD permitting program, i.e., a program that
applies in areas that have been designated attainment \60\ or
unclassifiable for the NAAQS, and it is not applicable to the good
neighbor provision, which requires states to eliminate significant
contribution or interference with maintenance of the NAAQS at known and
ongoing air quality problem areas in other states.
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    \60\ See footnote 49.
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    EPA's experience with the alternative Step 2 thresholds is further
discussed in section I.D.3.a above. As discussed there, EPA is
considering withdrawing the August 2018 memorandum.
(d) Evaluation of Information Provided by Tennessee 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 effectively evaluate 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. 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. Tennessee did not
conduct such an analysis in its SIP submission.
    The State did not analyze total ozone precursors that continue to
be emitted from sources and other emissions activity within the State,
evaluate the emissions reduction potential of any additional controls
using cost or other metrics, nor evaluate any resulting downwind air
quality improvements that could result from such controls. Instead,
Tennessee included in its submittal a list of existing emissions
control programs and measures in the State. However, EPA's modeling
already takes account of such measures. Despite these existing
emissions controls, the State is projected in the most recent modeling
to be linked to at least one downwind nonattainment or maintenance
receptor. The State was therefore obligated at Step 3 to assess
additional control measures using a multifactor analysis.
    As mentioned above, EPA has newly available information that
indicates sources in Tennessee are linked to downwind air quality
problems for the 2015 ozone standard. Therefore, EPA proposes to
disapprove Tennessee's September 18, 2018, SIP submission on the
separate, additional basis that the SIP submittal did not assess
additional emissions control opportunities.
(e) Evaluation of Information Provided by Tennessee 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 in section
II.C.3.d, Tennessee's SIP submission did not contain an evaluation of
additional emissions control opportunities (or establish that no
additional controls are required), thus, no information was provided at
Step 4. As a result, EPA proposes to disapprove Tennessee's September
18, 2018, 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).
4. Conclusion for Tennessee
    Based on EPA's evaluation of Tennessee's SIP submission and after
consideration of updated EPA modeling using the 2016-based emissions

modeling platform, EPA is proposing to find that the portion of
Tennessee's September 13, 2018, 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.

III. Proposed Actions

    EPA is proposing to disapprove the 2015 ozone good neighbor
interstate transport SIP revisions from Alabama, dated August 20, 2018;
from Mississippi, dated September 3, 2019; and from Tennessee, dated
September 13, 2018. Under CAA section 110(c)(1), if finalized, these
disapprovals would establish a 2-year deadline for EPA to promulgate a
FIP for Alabama, Mississippi, and Tennessee 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 EPA
approves a SIP that meets these requirements. However, under the CAA, a
good neighbor SIP disapproval does not start a mandatory sanctions
clock.

IV. Statutory and Executive Order Reviews

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

    These proposed actions are not significant regulatory actions and
were therefore not submitted to the Office of Management and Budget for
review.

B. Paperwork Reduction Act (PRA)

    These proposed actions do not impose an information collection
burden under the PRA because they do not contain any information
collection activities.

C. Regulatory Flexibility Act (RFA)

    These actions merely propose to disapprove SIP submissions as not
meeting the CAA for Alabama, Mississippi, and Tennessee. EPA certifies
that these proposed rules will not have a significant economic impact
on a substantial number of small entities under the RFA (5 U.S.C. 601
et seq.)

D. Unfunded Mandates Reform Act (UMRA)

    These proposed actions do not contain any unfunded mandate as
described in UMRA, 2 U.S.C. 1531-1538, and do not significantly or
uniquely affect small governments. These proposed actions impose no
enforceable duty on any state, local, or tribal governments or the
private sector.

E. Executive Order 13132: Federalism

    These proposed actions do not have federalism implications. They
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

    These proposed actions do not have tribal implications as specified
in Executive Order 13175. These proposed actions do not apply on any
Indian reservation land, any other area where 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
these actions.

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

    EPA interprets Executive Order 13045 as applying only to those
regulatory actions that concern environmental health or safety risks
that EPA has reason to believe may disproportionately affect children,
per the definition of ``covered regulatory action'' in section 2-202 of
the Executive Order. These proposed actions are not subject to
Executive Order 13045 because they merely propose to disapprove SIP
submissions from Alabama, Mississippi, and Tennessee as not meeting the
CAA.

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

    These proposed actions are not subject to Executive Order 13211,
because they are not significant regulatory actions under Executive
Order 12866.

I. National Technology Transfer and Advancement Act

    This proposed rulemaking does not involve technical standards.

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

    EPA believes the human health or environmental risk addressed by
these proposed actions will not have potential disproportionately high
and adverse human health or environmental effects on minority, low-
income or indigenous populations. These proposed actions merely propose
to disapprove SIP submissions 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 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 EPA complete discretion whether to invoke
the exception in (ii).\61\
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    \61\ 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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    EPA anticipates that this proposed rulemaking, if finalized, would
be ``nationally applicable'' within the meaning of CAA section
307(b)(1) because it would take final action on SIP submittals for the
2015 8-hour ozone NAAQS for the states of Alabama, Mississippi, and
Tennessee, which are located in three different Federal judicial
circuits (the Eleventh Circuit, the Fifth Circuit, and the Sixth
Circuit, respectively). It would apply uniform, nationwide analytical
methods, policy judgments, and interpretation with respect to the same
CAA obligations, i.e., implementation of good neighbor requirements
under CAA section 110(a)(2)(D)(i)(I) for the 2015 8-hour ozone NAAQS
for states across the country, and final action would be based on this
common core of determinations, described in further detail below.
    If EPA takes final action on this proposed rulemaking, in the
alternative, 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), EPA interprets and
applies section 110(a)(2)(d)(i)(I) of the CAA for the 2015 8-hour 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, 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 8-hour ozone NAAQS. 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, EPA proposes to determine and apply a set of
nationally consistent policy judgments to apply the 4-step framework.
EPA has selected a nationally uniform analytic year (2023) for this
analysis and is applying a nationally uniform approach to nonattainment