[Federal Register Volume 87, Number 35 (Tuesday, February 22, 2022)]
[Proposed Rules]
[Pages 9545-9562]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[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,

[[Page 9546]]

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December 30, 2019, at 84 FR 71854, is withdrawn.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 (404) 562-9009, or via electronic mail at 
<a href="/cdn-cgi/l/email-protection#402124212d336e2536212e002530216e272f36"><span class="__cf_email__" data-cfemail="a9c8cdc8c4da87ccdfc8c7e9ccd9c887cec6df">[email protected]</span></a>.

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

[[Page 9547]]

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 ``NO<INF>X</INF> SIP Call,'' 
63 FR 57356 (October 27, 1998), and the ``Clean Air Interstate 
Rule'' (CAIR), 70 FR 25162 (May 12, 2005).
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C. Background on 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 (NO<INF>X</INF>) 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

[[Page 9548]]

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 NO<INF>x</INF> SIP Call have 
necessitated the application of a uniform framework of policy judgments 
in order to ensure an ``efficient and equitable'' approach. See EME 
Homer City Generation, LP v. EPA, 572 U.S. 489, 519 (2014).
    In the March, August, and October 2018 memoranda, 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

[[Page 9549]]

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).
---------------------------------------------------------------------------

    In addition, in this proposal, EPA identifies a receptor to be a 
``maintenance'' receptor for purposes of

[[Page 9550]]

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

[[Page 9551]]

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.
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    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

[[Page 9552]]

additional emissions controls should be required.\32\
---------------------------------------------------------------------------

    \32\ As examples of general approaches for how such an analysis 
could be conducted for their sources, states could look to the CSAPR 
Update, 81 FR 74504, 74539-51; CSAPR, 76 FR 48208, 48246-63; CAIR, 
70 FR 25162, 25195-229; or the NO<INF>X</INF> SIP Call, 63 FR 57356, 
57399-405. See also Revised CSAPR Update, 86 FR 23054, 23086-23116. 
Consistently across these rulemakings, 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\
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    \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 NO<INF>X</INF> emissions reductions and notes the 
adoption of CSAPR NO<INF>X</INF> 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 
NO<INF>X</INF> 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

[[Page 9553]]

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,

[[Page 9554]]

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 NO<INF>X</INF> 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).
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    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

[[Page 9555]]

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.
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    \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.
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    \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.
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    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.

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[[Page 9556]]

    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:
    <bullet> 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.
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    <bullet> Ozone concentrations have been trending downward at the 
site since 2011 (and ozone precursor emissions of NO<INF>X</INF> and 
VOC have also decreased); and
    <bullet> 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 (NO<INF>X</INF> and VOC) emissions in the Houston 
metropolitan statistical area, Texas (statewide), and Mississippi 
(statewide). While EPA acknowledges the general downward trends in 
NO<INF>X</INF> 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 NO<INF>X</INF> 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.

[[Page 9557]]

    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.
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    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.

[[Page 9558]]



                     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 NO<INF>X</INF> 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.<SUP>52 53</SUP> 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 NO<INF>X</INF> projections were 
reasonable and account

[[Page 9559]]

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 
NO<INF>X</INF> emissions are considered the primary cause of formation 
of ozone in the southeast United States, and emphasized a significant 
reduction in NO<INF>X</INF> emissions reductions from coal-fired EGUs 
and other large NO<INF>X</INF> 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 
NO<INF>X</INF> Budget Trading Program, CAIR, and CSAPR. In addition, 
the Tennessee SIP revision discusses Tennessee rule 1200-03-27-.12 
(NO<INF>X</INF> 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,

[[Page 9560]]

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

[[Page 9561]]

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.
---------------------------------------------------------------------------

    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

[[Page 9562]]

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 
and maintenance receptors and a nationally uniform approach to 
contribution threshold analysis.\62\ For these reasons, the 
Administrator intends, if this proposed action is finalized, to 
exercise the complete discretion afforded to him under the CAA to make 
and publish a finding that this action is based on one or more 
determinations of nationwide scope or effect for purposes of CAA 
section 307(b)(1).\63\
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    \62\ A finding of nationwide scope or effect is also appropriate 
for actions that cover states in multiple judicial circuits. In the 
report on the 1977 Amendments that revised section 307(b)(1) of the 
CAA, Congress noted that the Administrator's determination that the 
``nationwide scope or effect'' exception applies would be 
appropriate for any action that has a scope or effect beyond a 
single judicial circuit. See H.R. Rep. No. 95-294 at 323, 324, 
reprinted in 1977 U.S.C.C.A.N. 1402-03.
    \63\ EPA may take a consolidated, single final action on all of 
the proposed SIP disapproval actions with respect to obligations 
under CAA section 110(a)(2)(D)(i)(I) for the 2015 8-hour ozone 
NAAQS. Should EPA take a single final action on all such 
disapprovals, this action would be nationally applicable, and EPA 
would also anticipate, in the alternative, making and publishing a 
finding that such final action is based on a determination of 
nationwide scope or effect.
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List of Subjects in 40 CFR Part 52

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

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

    Dated: February 3, 2022.
Daniel Blackman,
Regional Administrator, Region 4.
[FR Doc. 2022-02948 Filed 2-18-22; 8:45 am]
BILLING CODE 6560-50-P


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