Proposed Rule2026-17503
Air Plan Approval; Mississippi; 2010 1-Hour SO2 NAAQS Transport Infrastructure
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
August 27, 2026
Issuing agencies
Environmental Protection Agency
Abstract
Pursuant to the Federal Clean Air Act (CAA or the Act), the U.S. Environmental Protection Agency (EPA or Agency) is proposing to approve a State Implementation Plan (SIP) revision submitted by the State of Mississippi, through the Mississippi Department of Environmental Quality (MDEQ), on January 27, 2022, for the purpose of complying with the "good neighbor" provision of the CAA for the 2010 1-hour sulfur dioxide (SO<INF>2</INF>) primary National Ambient Air Quality Standard (NAAQS). The good neighbor provision requires each State's implementation plan to contain adequate provisions prohibiting the interstate transport of air pollution in amounts that will contribute significantly to nonattainment, or interfere with maintenance, of a NAAQS in any other State. In this proposed rulemaking, the EPA is proposing to determine that Mississippi will not contribute significantly to nonattainment or interfere with maintenance of the 2010 1-hour SO<INF>2</INF> primary NAAQS in any other State. Therefore, the EPA is proposing to approve the January 27, 2022, SIP revision as meeting the requirements of the good neighbor provision for the 2010 1-hour SO<INF>2</INF> primary NAAQS.
Full Text
<html>
<head>
<title>Federal Register, Volume 91 Issue 165 (Thursday, August 27, 2026)</title>
</head>
<body><pre>
[Federal Register Volume 91, Number 165 (Thursday, August 27, 2026)]
[Proposed Rules]
[Pages 55305-55312]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-17503]
-----------------------------------------------------------------------
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R04-OAR-2023-0227; FRL-13502-01-R4]
Air Plan Approval; Mississippi; 2010 1-Hour SO2 NAAQS Transport
Infrastructure
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
-----------------------------------------------------------------------
SUMMARY: Pursuant to the Federal Clean Air Act (CAA or the Act), the
U.S. Environmental Protection Agency (EPA or Agency) is proposing to
approve a State Implementation Plan (SIP) revision submitted by the
State of Mississippi, through the Mississippi Department of
Environmental Quality (MDEQ), on January 27, 2022, for the purpose of
complying with the ``good neighbor'' provision of the CAA for the 2010
1-hour sulfur dioxide (SO<INF>2</INF>) primary National Ambient Air
Quality Standard (NAAQS). The good neighbor provision requires each
State's implementation plan to contain adequate provisions prohibiting
the interstate transport of air pollution in amounts that will
contribute significantly to nonattainment, or interfere with
maintenance, of a NAAQS in any other State. In this proposed
rulemaking, the EPA is proposing to determine that Mississippi will not
contribute significantly to nonattainment or interfere with maintenance
of the 2010 1-hour SO<INF>2</INF> primary NAAQS in any other State.
Therefore, the EPA is proposing to approve the January 27, 2022, SIP
revision as meeting the requirements of the good neighbor provision for
the 2010 1-hour SO<INF>2</INF> primary NAAQS.
DATES: Comments must be received on or before September 17, 2026.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-
OAR-2023-0227 at <a href="http://regulations.gov">regulations.gov</a>. Follow the online instructions for
submitting comments. Once submitted, comments cannot be edited or
removed from Regulations.gov. The EPA may publish any comment received
to its public docket. Do not submit electronically any information you
consider to be Confidential Business Information (CBI) or other
information whose disclosure is restricted by statute. Multimedia
submissions (audio, video, etc.) must be accompanied by a written
comment. The written comment is considered the official comment and
should include discussion of all points you wish to make. The EPA will
generally not consider comments or comment contents located outside of
the primary submission (i.e., on the web, cloud, or other file sharing
system). For additional submission methods, the full EPA public comment
policy, information about CBI or multimedia submissions, and general
guidance on making effective comments, please visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a>.
[[Page 55306]]
FOR FURTHER INFORMATION CONTACT: Matthew Bloemer, Muti-Air Pollutant
Coordination 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. The telephone number is
(404) 562-9653. Mr. Bloemer can also be reached via electronic mail at
<a href="/cdn-cgi/l/email-protection#b5d7d9dad0d8d0c79bd8d4c1c1ddd0c2f5d0c5d49bd2dac3"><span class="__cf_email__" data-cfemail="5e3c32313b333b2c70333f2a2a363b291e3b2e3f70393128">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: Throughout this proposed rule, the use of
``we,'' ``us,'' or ``our'' is intended to refer to the EPA. We use
multiple abbreviations and terms in this proposed rule. While this list
may not be exhaustive, for ease of reading and for reference purposes,
the EPA defines the following terms and acronyms here:
CAA Clean Air Act
CBI Confidential Business Information
CFR Code of Federal Regulations
DRR Data Requirements Rule
DV Design Value
EGU Electric Generating Unit
EIS Emissions Inventory System
EPA Environmental Protection Agency
FR Federal Register
km Kilometer
MDEQ Mississippi Department of Environmental Quality
MS Mississippi
NAAQS National Ambient Air Quality Standard
NEI National Emissions Inventory
NPRM Notice of Proposed Rulemaking
NSR New Source Review
Pb Lead
PM<INF>2.5</INF> Particulate Matter less than 2.5 [micro]m in
diameter
ppb Parts Per Billion
SIP State Implementation Plan
SO<INF>2</INF> Sulfur Dioxide
tpy Tons per year
TSD Technical Support Document
WOE Weight of Evidence
Table of Contents
I. Background
A. Infrastructure SIPs
B. 2010 1-Hour SO<INF>2</INF> NAAQS Designations Background
II. Relevant Factors Used To Evaluate 2010 1-Hour SO<INF>2</INF>
Interstate Transport SIPs
III. Mississippi's SIP Submission and the EPA's Analysis
A. State Submission
B. The EPA's Evaluation Methodology
1. The EPA's Prong 1 Evaluation--Contribute Significantly to
Nonattainment
2. The EPA's Prong 2 Evaluation--Interference With Maintenance
IV. Proposed Action
V. Statutory and Executive Order Reviews
I. Background
A. Infrastructure SIPs
On June 2, 2010, the EPA established a revised primary 1-hour
SO<INF>2</INF> NAAQS with a level of 75 parts per billion (ppb), based
on a 3-year average of the annual 99th percentile of daily maximum 1-
hour average concentrations.\1\ CAA section 110(a)(1) requires all
States to submit, within three years after promulgation of a new or
revised NAAQS, SIP submissions to provide for the implementation,
maintenance, and enforcement of the NAAQS.\2\ The EPA has historically
referred to these SIPs as ``infrastructure SIPs.'' Specifically, CAA
section 110(a)(1) provides the procedural and timing requirements for
SIP submissions. CAA section 110(a)(2) lists specific elements that all
States must meet related to a newly established or revised NAAQS, such
as requirements for monitoring, basic program requirements, and legal
authority that are designed to assure attainment and maintenance of the
NAAQS.
---------------------------------------------------------------------------
\1\ See 75 FR 35520 (June 22, 2010).
\2\ On December 10, 2024, the EPA revised the existing secondary
SO<INF>2</INF> standard to an annual standard of 10 ppb, averaged
over 3 years. See 89 FR 105692 (Dec. 27, 2024).
---------------------------------------------------------------------------
CAA section 110(a)(2)(D)(i)(I), also known as the ``good neighbor''
provision, requires a State's implementation plan to include adequate
provisions prohibiting any source or other type of emissions activity
in the State from emitting any air pollutant in amounts that will
contribute significantly to nonattainment, or interfere with
maintenance, of the NAAQS in any other State. The EPA has long
interpreted this language to enact a ``functional prohibition'' on
certain emissions from upwind States, necessitating the EPA's
independent assessment whether those emissions will occur or have been
adequately controlled in the State where they originate.\3\ The EPA
often refers to these requirements as prong 1 (significant contribution
to nonattainment of the NAAQS) and prong 2 (interference with
maintenance of the NAAQS).\4\ This notice of proposed rulemaking (NPRM)
addresses Mississippi's good neighbor obligations pursuant to prongs 1
and 2. All other applicable infrastructure SIP requirements of CAA
section 110(a)(2) for the 2010 1-hour SO<INF>2</INF> NAAQS for
Mississippi, except for prong 4, have been addressed in separate
rulemakings.\5\
---------------------------------------------------------------------------
\3\ See Genon Rema LLC v. EPA, 722 F.3d 513, 520-24 (3d Cir.
2013); Appalachian Power Co. v. EPA, 249 F.2d 1032, 1045-47 (D.C.
Cir. 2001); see also 71 FR 25328, 25335 (Apr. 28, 2006) (explaining
that the SIP/FIP process under CAA section 110 and the petitioning
process for direct Federal regulation under CAA section 126 provide
independent means of effectuating the same ``functional
prohibition'' found in CAA section 110(a)(2)(D)(i)(I)).
\4\ CAA section 110(a)(2)(D)(i) includes four distinct
components, commonly referred to as ``prongs,'' that must be
addressed in infrastructure SIP submissions. The first two prongs,
which are codified in CAA section 110(a)(2)(D)(i)(I), prohibit any
source or other type of emissions activity in one State from
contributing significantly to nonattainment of the NAAQS in another
State (prong 1) and from interfering with maintenance of the NAAQS
in another State (prong 2). The third and fourth prongs, which are
codified in CAA section 110(a)(2)(D)(i)(II), prohibit emissions
activity in one State from interfering with measures required to
prevent significant deterioration of air quality in another State
(prong 3) or from interfering with measures to protect visibility in
another State (prong 4).
\5\ The EPA took action to approve Mississippi's remaining
infrastructure elements, except for CAA section 110(a)(2)(D)(i)(II),
prong 4, on September 30, 2016 (81 FR 67178) and October 4, 2018 (83
FR 50014). The EPA will address prong 4 in a separate rulemaking.
---------------------------------------------------------------------------
B. 2010 1-Hour SO2 NAAQS Designations Background
In this proposed rulemaking, the EPA has considered information
from the 2010 1-hour SO<INF>2</INF> NAAQS designations process, as
discussed in more detail in the Technical Support Document (TSD) for
this rulemaking. For this reason, a summary of the EPA's designations
process for the 2010 1-hour SO<INF>2</INF> NAAQS is included here.\6\
---------------------------------------------------------------------------
\6\ While designations may provide useful information for
purposes of analyzing transport, the EPA notes that designations
themselves are not dispositive of whether or not upwind emissions
are impacting areas in downwind States. The EPA has consistently
taken the position that CAA section 110(a)(2)(D)(i)(I) requires
elimination of significant contribution and interference with
maintenance in other States, and this analysis is not limited to
designated nonattainment areas. Nor must designations for
nonattainment areas have first occurred before States or EPA can act
under CAA section 110(a)(2)(D)(i)(I). See, e.g., Clean Air
Interstate Rule, 70 FR 25162, 25265 (May 12, 2005); Cross State Air
Pollution Rule, 76 FR 48208, 48211 (Aug. 8, 2011); Final Response to
Petition from New Jersey Regarding SO<INF>2</INF> Emissions From the
Portland Generating Station, 76 FR 69052 (Nov. 7, 2011) (finding
facility in violation of the prohibitions of CAA section
110(a)(2)(D)(i)(I) with respect to the 2010 1-hour SO<INF>2</INF>
NAAQS prior to issuance of designations for that standard).
---------------------------------------------------------------------------
After the promulgation of a new or revised NAAQS, the EPA is
required to designate areas as ``nonattainment,'' ``attainment,'' or
``unclassifiable'' pursuant to CAA section 107(d)(1)-(2). The process
for designating areas following promulgation of a new or revised NAAQS
is contained in section 107(d) of the CAA. The EPA promulgated the 2010
1-hour SO<INF>2</INF> NAAQS on June 2, 2010.\7\ The EPA Administrator
signed the first round \8\ of designations (Round 1) \9\ for the 2010
1-
[[Page 55307]]
hour SO<INF>2</INF> NAAQS on July 25, 2013, designating 29 areas in 16
States as nonattainment for the 2010 1-hour SO<INF>2</INF> NAAQS.\10\
The Federal Register final rules of promulgation for Round 2
designations \11\ published on July 12, 2016 and on December 13, 2016.
<SUP>12 13</SUP> Round 3 designations \14\ were published on January 9,
2018 and April 5, 2018.<SUP>15 16</SUP> Round 4 designations \17\ were
published on March 26, 2021 and April 14, 2021.<SUP>18 19 20</SUP> The
Agency published the Data Requirements Rule (DRR) on August 21, 2015 to
provide expectations for collection of data, either monitoring or
modeling, for the remaining designations.<SUP>21 22</SUP> In the DRR,
the EPA identified six sources in Mississippi for which the State was
required to characterize air quality through modeling or monitoring or
impose federally enforceable controls. In Round 2 designations, the EPA
designated Lamar County as attainment/unclassifiable based on modeling,
effective August 12, 2016.\23\ In Round 3, the EPA designated Choctaw
and Jackson Counties as attainment/unclassifiable based on modeling,
effective April 9, 2018.\24\ Also, during Round 3, the EPA designated
the remaining counties without DRR sources as attainment/
unclassifiable, completing the area designations for the 2010 1-hour
SO<INF>2</INF> NAAQS in Mississippi effective April 9, 2018. Thus, no
areas in the State were designated in Round 4. Currently, there are no
nonattainment areas in Mississippi for the 2010 1-hour SO<INF>2</INF>
NAAQS based on Rounds 1 through 4.
---------------------------------------------------------------------------
\7\ See 75 FR 35520 (June 22, 2010).
\8\ The term ``round'' in this instance refers to which ``round
of designations.''
\9\ The EPA and State documents and public comments related to
the Round 1 final designations are in the docket at <a href="http://regulations.gov">regulations.gov</a>
with Docket ID No. EPA-HQ-OAR-2012-0233 and at the EPA's website for
SO<INF>2</INF> designations at <a href="https://www.epa.gov/sulfur-dioxide-designations">https://www.epa.gov/sulfur-dioxide-designations</a>.
\10\ See 78 FR 47191 (Aug. 5, 2013).
\11\ The EPA and State documents and public comments related to
the Round 2 final designations are in the docket at <a href="http://regulations.gov">regulations.gov</a>
with Docket ID No. EPA-HQ-OAR-2014-0464 and at the EPA's website for
SO<INF>2</INF> designations at <a href="https://www.epa.gov/sulfur-dioxide-designations">https://www.epa.gov/sulfur-dioxide-designations</a>.
\12\ See 81 FR 45039.
\13\ See 81 FR 89870.
\14\ The EPA and State documents and public comments related to
Round 3 final designations are in the docket at <a href="http://regulations.gov">regulations.gov</a> with
Docket ID No. EPA-HQ-OAR-2017-0003 and at the EPA's website for
SO<INF>2</INF> designations at <a href="https://www.epa.gov/sulfur-dioxide-designations">https://www.epa.gov/sulfur-dioxide-designations</a>.
\15\ See 83 FR 1098.
\16\ See 83 FR 14597.
\17\ The EPA and State documents and public comments related to
Round 4 final designations are in the docket at <a href="http://regulations.gov">regulations.gov</a> with
Docket ID No. EPA-HQ-OAR-2020-0037 and at the EPA's website for
SO<INF>2</INF> designations at <a href="https://www.epa.gov/sulfur-dioxide-designations">https://www.epa.gov/sulfur-dioxide-designations</a>.
\18\ The Round 4 2010 1-hour SO<INF>2</INF> NAAQS designations
action was signed by former EPA Administrator Andrew Wheeler on
December 21, 2020, pursuant to a court-ordered deadline of December
31, 2020. For administrative purposes only, and in compliance with
requirements of the Office of the Federal Register, former Acting
Administrator Jane Nishida re-signed the same action on March 10,
2021, for publication in the Federal Register.
\19\ See 86 FR 16055.
\20\ See 86 FR 19576.
\21\ See 80 FR 51052.
\22\ On August 21, 2015 (80 FR 51052), the EPA separately
promulgated air quality characterization requirements for the 2010
1-hour SO<INF>2</INF> NAAQS in the DRR. The DRR requires State air
agencies to characterize air quality, through air dispersion
modeling or monitoring, in areas associated with sources that
emitted in 2014 2,000 tpy or more of SO<INF>2</INF>, or that have
otherwise been listed under the DRR by the EPA or State air
agencies. In lieu of modeling or monitoring, State air agencies, by
specified dates, could elect to impose federally enforceable
emissions limitations on those sources restricting their annual
SO<INF>2</INF> emissions to less than 2,000 tpy, or provide
documentation that the sources have been shut down. The EPA used the
information generated by implementation of the DRR to help inform
round 4 designations for the 2010 1-hour SO<INF>2</INF> NAAQS.
\23\ See 81 FR 45039 (July 12, 2016) and EPA's Final Technical
Support Document: Mississippi--Area Designations for the 2010
SO<INF>2</INF> Primary National Ambient Air Quality Standard, at
<a href="https://www.epa.gov/sites/default/files/2016-07/documents/r4_ms_final_designation_tsd_06302016.pdf">https://www.epa.gov/sites/default/files/2016-07/documents/r4_ms_final_designation_tsd_06302016.pdf</a>.
\24\ See 83 FR 1098 (Jan. 9, 2018) and Technical Support
Document: Chapter 21 Final Round 3 Area Designations for the 2010 1-
Hour SO<INF>2</INF> Primary National Ambient Air Quality Standard
for Mississippi, at <a href="https://www.epa.gov/sites/default/files/2017-12/documents/21-ms-so2-rd3-final.pdf">https://www.epa.gov/sites/default/files/2017-12/documents/21-ms-so2-rd3-final.pdf</a>.
---------------------------------------------------------------------------
II. Relevant Factors Used To Evaluate 2010 1-Hour SO2 Interstate
Transport SIPs
Although SO<INF>2</INF> is emitted from a similar universe of point
and nonpoint sources as is directly emitted fine particulate matter
(PM<INF>2.5</INF>) and the precursors to ozone and PM<INF>2.5</INF>,
interstate transport of SO<INF>2</INF> is unlike the transport of
PM<INF>2.5</INF> or ozone, which disperse over a wide area and can
contribute to nonattainment or maintenance issues hundreds of miles
from precursor-emitting sources or activities. SO<INF>2</INF> emissions
usually do not undergo long-range transport in the atmosphere. The
transport of SO<INF>2</INF> relative to the 2010 1-hour SO<INF>2</INF>
NAAQS is more analogous to the transport of lead (Pb) relative to the
Pb NAAQS in that emissions of SO<INF>2</INF> typically result in 1-hour
pollutant impacts of greatest concern near the emissions source.
However, ambient 1-hour concentrations of SO<INF>2</INF> do not
decrease as quickly with distance from the source as do 3-month average
concentrations of Pb, because SO<INF>2</INF> gas is not removed by
deposition as rapidly as are Pb particles. Emitted SO<INF>2</INF> has
wider-ranging impacts than emitted Pb, but it does not have such wide-
ranging (far downwind) impacts that treatment in a manner similar to
ozone or PM<INF>2.5</INF> would be appropriate. Accordingly, the
approaches that the EPA has adopted for ozone or PM<INF>2.5</INF>
transport are too regionally focused, and the approach for Pb transport
is too tightly circumscribed to the source, to be appropriate for
assessing SO<INF>2</INF> transport. SO<INF>2</INF> transport is
therefore a unique case and necessitates an approach that lies between
these other approaches to assessing pollutant transport.
In this NPRM, and consistent with prior SO<INF>2</INF> transport
analyses, the EPA focused on a 50 kilometer (km)-wide zone around
sources of interest because the physical properties of SO<INF>2</INF>
result in relatively localized pollutant impacts near an emission
source that drop off with distance. Given the properties of
SO<INF>2</INF>, the EPA believes that significant impacts in a downwind
State are unlikely at distances greater than 50 km from a source and
thus, the EPA's review focused on areas within 50 km of the State
lines. This scale of analysis is consistent with the ``urban scale''
which is the largest appropriate spatial scale for SO<INF>2</INF>
monitors and is useful for assessing SO<INF>2</INF> transport and
trends in area-wide air quality.\25\
---------------------------------------------------------------------------
\25\ For the definition of spatial scales for SO<INF>2</INF>,
see 40 CFR part 58, appendix D, section 4.4 (``Sulfur Dioxide
(SO<INF>2</INF>) Design Criteria''). For further discussion on how
the EPA applies these definitions with respect to interstate
transport of SO<INF>2, see</INF> the EPA's proposed rulemaking on
Connecticut's SO<INF>2</INF> transport SIP. See 82 FR 21351, 21352,
21354 (May 8, 2017).
---------------------------------------------------------------------------
As discussed in section III of this document, and in further detail
in the TSD for this proposed rulemaking, the EPA reviewed Mississippi's
January 27, 2022, SO<INF>2</INF> SIP submission. Mississippi's
submission did not provide enough data to completely assess whether the
State was meeting its CAA good neighbor requirements for the 2010
SO<INF>2</INF> NAAQS. Therefore, the EPA elected to review and assess
other available information regarding SO<INF>2</INF> emissions and air
quality for sources in Mississippi to assist in this evaluation given
the availability of more recent emissions, air quality data, and air
dispersion modeling that was not available at the time of Mississippi's
submittal. The EPA independently analyzed such information to determine
whether Mississippi meets the interstate transport requirements
described in the CAA.\26\
---------------------------------------------------------------------------
\26\ This proposed rulemaking is based on the information
contained in the administrative record for this proposed rulemaking
and does not prejudge any future EPA action that may make other
determinations regarding the air quality status in Mississippi and
downwind States. Any such future action, such as area designations
under any NAAQS, would be based on separate administrative records
and the EPA's analyses of information that become available at that
time. Future available information may include, monitoring data and
modeling analyses conducted by States, air agencies, and third-party
stakeholders.
---------------------------------------------------------------------------
Consistent with our prior evaluations of other States'
SO<INF>2</INF> transport obligations, the EPA conducted a weight of
evidence (WOE) analysis evaluating
[[Page 55308]]
several sources of information, including current air quality data from
monitors as well as available emissions and/or source modeling for
sources in Mississippi and neighboring States within 50 km of the State
border. A WOE approach can be appropriate in instances, such as in this
case, to determine whether or not SO<INF>2</INF> emissions from
Mississippi contribute to nonattainment or maintenance issues in
adjoining States. A WOE analysis that is based strictly on available
data may not be sufficient in all instances for evaluating interstate
SO<INF>2</INF> transport, and additional analysis may be necessary.
Further, the term ``WOE'' does not establish the legal or technical
meaning for what constitutes significant contribution to nonattainment
or interference with maintenance for the 2010 SO<INF>2</INF> NAAQS.
Rather, the term refers to the gathering and consideration of a wide
range of information, on a case-by-case basis, to determine whether a
statutory or regulatory standard is met.
In other SO<INF>2</INF> transport SIP actions, the EPA has
generally been able to use a WOE analysis of available information to
reach a conclusion that there are no SO<INF>2</INF> nonattainment or
maintenance issues in the relevant areas of other States, or that no
sources in the upwind State are contributing to those issues. If the
available evidence indicated, however, that an upwind source, sources,
or emissions activities were contributing to an out-of-State
SO<INF>2</INF> nonattainment or maintenance problem, then further
analysis and a regulatory determination would be necessary concerning
what amount of those emissions, if any, constituted ``significant
contribution'' under prong 1 or prong 2 of the good neighbor provision.
The EPA finds there is sufficient information to allow the EPA to
make a determination that no Mississippi sources are contributing to
any out-of-State SO<INF>2</INF> nonattainment or maintenance concerns
under current and likely future conditions and emissions scenarios;
therefore, it is not necessary for purposes of this action to render a
determination concerning what amount of emissions would be
``significant'' and therefore subject to prohibition under the good
neighbor provision.\27\
---------------------------------------------------------------------------
\27\ Cf. Genon Rema v. EPA, 722 F.3d 513 (3d Cir. 2013)
(upholding the EPA grant of CAA section 126(b) petition and
establishment of direct Federal emissions control requirements on
SO<INF>2</INF> source in Pennsylvania found to be significantly
contributing to nonattainment and interfering with maintenance of
the 2010 SO<INF>2</INF> NAAQS in New Jersey).
---------------------------------------------------------------------------
III. Mississippi's SIP Submission and the EPA's Analysis
A. State Submission
Mississippi's January 27, 2022, SIP submission addresses the
requirements of CAA section 110(a)(2)(D)(i)(I) for the 2010 1-hour
SO<INF>2</INF> primary NAAQS. Mississippi conducted an analysis to
examine whether SO<INF>2</INF> emissions from Mississippi contribute
significantly to nonattainment, or interfere with maintenance of, the
2010 1-hour SO<INF>2</INF> NAAQS in downwind States.
Mississippi based its conclusions for prongs 1 and 2 on the
following information: SO<INF>2</INF> design values (DVs) \28\ for the
years 2012-2014 at monitors in Mississippi and in the neighboring
States (Alabama, Tennessee, and Louisiana); statewide SO<INF>2</INF>
actual emissions from 2008 and 2011 and emission trends in this data;
stationary source (electric generating units) actual SO<INF>2</INF>
emissions from 2002-2017 and emissions trends in this data;
Mississippi's initial work to meet the DRR requirements; State and
Federal measures that establish requirements for sources of
SO<INF>2</INF> emissions; monitored ambient air data in Mississippi and
neighboring States based on a 50 km spatial distance; available DRR air
dispersion modeling associated with relevant SO<INF>2</INF> sources in
Mississippi and in neighboring States within 50 km of Mississippi's
border; and an SO<INF>2</INF> source specific emission analysis from
stationary sources in Mississippi and neighboring States that were not
subject to the DRR that emitted over 100 tons per year (tpy) of
SO<INF>2</INF> emissions in 2018 or 2019 within 50 km of the State's
border (i.e., an analyses of non-DRR sources' current emissions
relative to the distance to the State's border).
---------------------------------------------------------------------------
\28\ A ``Design Value'' is a statistic that describes the air
quality status of a given location relative to the level of the
NAAQS. The DV for the primary 2010 1-hour SO<INF>2</INF> NAAQS is
the 3-year average of annual 99th percentile daily maximum 1-hour
values for a monitoring site. For example, the 2017 DV is calculated
based on the three-year average from 2015-2017. The interpretation
of the primary 2010 1-hour SO<INF>2</INF> NAAQS including the data
handling conventions and calculations necessary for determining
compliance with the NAAQS can be found in appendix T to 40 CFR part
50.
---------------------------------------------------------------------------
Based on this analysis, MDEQ concluded that no sources in the State
are significantly contributing to nonattainment or interfering with
maintenance of the 2010 SO<INF>2</INF> NAAQS in a neighboring State.
Thus, Mississippi determined that the SIP contains adequate provisions
to address the State's CAA good neighbor obligations.
The EPA's evaluation of Mississippi's submission is detailed in
section III.B of this document below. The EPA may elect to consider
additional information to assist in reaching a conclusion as to whether
the submission may be approved, in whole or in part, as satisfying the
Act's requirements, or does not meet the Act's requirements. Here, the
EPA may consider all relevant information, or generate new data and
analysis, to make an independent judgment in evaluating States'
compliance with the good neighbor provision, which concerns the effects
of States' emissions in other States. Therefore, the EPA elected to
supplement Mississippi's transport SIP analysis with a review and
assessment of other available information, as described below and in
more detail in the TSD for this proposed rulemaking, regarding
SO<INF>2</INF> emissions and air quality for sources in Mississippi to
assist in the EPA's evaluation and to fully assess whether Mississippi
is meeting its CAA good neighbor obligations for the 2010
SO<INF>2</INF> NAAQS.
B. The EPA's Evaluation Methodology
For this CAA section 110(a)(2)(D)(i)(I) evaluation of the 2010
SO<INF>2</INF> NAAQS, the EPA conducted a WOE analysis for prong 1 and
prong 2 separately,\29\ evaluating available information such as
SO<INF>2</INF> ambient air data, emission inventory trends, modeling,
and emission trends in Mississippi and the States that border
Mississippi. The EPA has evaluated this information and further
supplements Mississippi's analysis here to ensure there are no further
SO<INF>2</INF> emissions controls needed for meeting CAA interstate
transport requirements. To identify which sources and emissions
activities in Mississippi could potentially impact downwind air quality
in other States with respect to the 2010 1-hour SO<INF>2</INF> NAAQS,
the EPA used information in the EPA's National Emissions Inventory
(NEI) \30\ and Emissions Inventory System (EIS).\31\ The NEI is a
comprehensive and detailed estimate of air emissions for criteria
pollutants, criteria pollutant precursors, and hazardous air pollutants
[[Page 55309]]
from air emissions sources, updated every three years using information
provided by the States and other information available to the EPA. For
the identification of sources and emissions activities, the EPA largely
relied on data from the 2020 NEI because it is the most recently
available, complete, and quality assured dataset. However, in
evaluating emissions trends, both State-wide and at the facility level,
the EPA also considered data from prior NEI reports and EIS queries as
part of the overall WOE analysis.
---------------------------------------------------------------------------
\29\ In North Carolina v. EPA, 531 F.3d 896, 910-911 (D.C. Cir.
2008), modified, 550 F. 3d 1176 (D.C. Cir. 2008), the United States
Court of Appeals for the District of Columbia Circuit (D.C. Cir.)
explained that the regulating authority must give prong 2
``independent significance'' from prong 1 by evaluating the impact
of upwind State emissions on downwind areas that, while currently in
attainment, are at risk of future nonattainment.
\30\ The EPA's NEI is available and accessible to the public at
<a href="https://www.epa.gov/air-emissions-inventories/national-emissions-inventory">https://www.epa.gov/air-emissions-inventories/national-emissions-inventory</a>.
\31\ The EIS is the EPA's database used to receive and store
emissions data and generate emissions inventories. The EIS Gateway
is a web-based tool developed to provide only registered EPA, State,
local and Tribal users with access to emission inventory data for
sources in their jurisdiction.
---------------------------------------------------------------------------
As shown in table 1 below, the majority of SO<INF>2</INF> emissions
in Mississippi originate from point sources. In 2020, total
SO<INF>2</INF> emissions from point sources in Mississippi comprised
approximately 56 percent of the total SO<INF>2</INF> emissions in the
State. Nonpoint sources, on road, and nonroad emissions sources are
individually much smaller and more dispersed throughout the State and
are therefore unlikely to contribute to high ambient concentrations
when compared to point source contributions. Further analysis \32\
shows that facilities with reported emissions greater than 100 tpy
represent approximately 4 percent of the total number of Mississippi
SO<INF>2</INF> point sources but are responsible 5,411 tons of
SO<INF>2</INF>, or 84 percent of the total 2020 reported SO<INF>2</INF>
emissions originating from point sources in Mississippi.\33\ Based on
this analysis, the EPA's WOE analysis focused on SO<INF>2</INF>
emissions from Mississippi's point sources (i.e., sources emitting over
100 tpy of SO<INF>2</INF>) that are located within 50 km of one or more
State borders.\34\ The EPA's WOE analysis includes some of the same
sources included in Mississippi's non-DRR source specific analysis.
---------------------------------------------------------------------------
\32\ See the EPA's TSD for a more detailed discussion.
\33\ See Table 9 in the EPA's TSD.
\34\ See Table 10 in the EPA's TSD.
Table 1--Summary of 2020 SO2 Emissions in Mississippi by Source Category
----------------------------------------------------------------------------------------------------------------
2020 Emissions Percent total SO2 emissions
Category (tpy)
----------------------------------------------------------------------------------------------------------------
Point........................................................... 6,420 56
Nonpoint........................................................ 4,897 43
On Road......................................................... 128 1
Nonroad......................................................... 8 0
-----------------------------------------------
SO2 Emission Total.......................................... 11,453 100
----------------------------------------------------------------------------------------------------------------
As described in this section III of this document, the EPA proposes
that an assessment of Mississippi's satisfaction of the prong 1 and 2
requirements under CAA section 110(a)(2)(D)(i)(I) for the 2010 1-hour
SO<INF>2</INF> NAAQS may be reasonably based upon several factors.
These factors include 2020-2022 through 2022-2024 ambient air quality
SO<INF>2</INF> design value concentrations in Mississippi and
surrounding States, 2022 SO<INF>2</INF> emission trends data for
sources in Mississippi and neighboring States (assessing sources'
current emissions relative to distance from the border), assessment of
Mississippi's SO<INF>2</INF> point source 2022 emissions of more than
100 tpy of SO<INF>2</INF> per facility that are located within
approximately 50 km of another State, assessment of other States' point
sources emitting more than 100 tpy of SO<INF>2</INF> located within
approximately 50 km of Mississippi, evaluation of the predicted
downwind impacts projected in previous relevant modeling studies that
have been conducted for certain sources, review of wind and topographic
data to evaluate the likely direction of transport and magnitude of
SO<INF>2</INF> emissions from relevant sources, and assessment of
Federal regulations and SIP-approved regulations affecting
Mississippi's SO<INF>2</INF> sources. The EPA's evaluation is informed
by all available data at the time of this proposed rulemaking,
including the analysis Mississippi provided in its January 27, 2022,
SIP submission.\35\
---------------------------------------------------------------------------
\35\ The EPA notes that the evaluation of other States'
satisfaction of CAA section 110(a)(2)(D)(i)(I) for the 2010 1-hour
SO<INF>2</INF> NAAQS can be informed by similar factors found in
this proposed rulemaking but may not be identical to the approach
taken in this or any future rulemaking for Mississippi, depending on
available information and State-specific circumstances.
---------------------------------------------------------------------------
The EPA notes that if this information were insufficient to draw a
reasonable conclusion concerning whether Mississippi is ``significantly
contributing'' or not, then it would not be possible to propose
approval based only on this information. In other words, in general,
the absence of information concerning whether interstate transport is
occurring is not in itself sufficient justification for approving a
good neighbor SIP submission. For example, if there were inadequate
monitoring or modeling information to characterize the effects of a
large, near-border source of SO<INF>2</INF> emissions, it may be
appropriate to conduct, or ask the State to conduct, further analysis
to better characterize that source and its effects, in order to reach a
determination concerning whether the good neighbor provision is being
met.\36\ In this case, the information available to the EPA, as
analyzed in the accompanying TSD and summarized below, is fully
sufficient to conclude that under current and likely future conditions
and emissions scenarios Mississippi is not emitting and will not emit
SO<INF>2</INF> pollution in violation of the good neighbor provision
for the 2010 SO<INF>2</INF> NAAQS.
---------------------------------------------------------------------------
\36\ See, e.g., 88 FR 41344 (June 26, 2023) (proposing approval
of Tennessee's SO<INF>2</INF> good neighbor SIP submission based on
updated modeling conducted to better characterize emissions from the
Eastman Chemical facility).
---------------------------------------------------------------------------
1. The EPA's Prong 1 Evaluation--Contribute Significantly to
Nonattainment
Prong 1 of the ``good neighbor'' provision requires States' plans
to prohibit emissions that will contribute significantly to
nonattainment of the NAAQS in another State. The EPA's evaluation \37\
of whether Mississippi has met its prong 1 transport obligations was
accomplished by considering all available information including the
following: SO<INF>2</INF> ambient air quality in Mississippi and
neighboring States; SO<INF>2</INF> emissions trends for Mississippi and
neighboring States; potential ambient impacts of SO<INF>2</INF>
emissions from certain facilities \38\ in Mississippi on neighboring
States; Mississippi's SIP-approved regulations specific to
SO<INF>2</INF> emissions and to permit requirements;
[[Page 55310]]
and other SIP-approved or federally enforceable regulations which may
reduce SO<INF>2</INF> emissions either directly or indirectly.
---------------------------------------------------------------------------
\37\ A detailed review of the EPA's evaluation of emissions, air
monitoring data, other technical information, and rationale for
proposed approval of this SIP revision as meeting CAA section
110(a)(2)(D)(i)(I) for the 2010 1-hour SO<INF>2</INF> NAAQS may be
found in the TSD.
\38\ The physical properties of SO<INF>2</INF> result in
relatively localized pollutant impacts near the emissions source.
Therefore, the EPA selected a spatial scale with dimensions up to 50
km from point sources.
---------------------------------------------------------------------------
Based on the EPA's analysis, the Agency proposes to determine that
there are no SO<INF>2</INF> nonattainment issues in the relevant areas
in other States bordering Mississippi, and as such, the EPA proposes to
determine that Mississippi's SIP satisfies the requirements of prong 1
of CAA section 110(a)(2)(D)(i)(I). This proposed determination is based
on the following considerations:
<bullet> Monitors in neighboring Alabama, Louisiana, and Tennessee
within 50 km of Mississippi's border all have DVs below the standard;
there are no monitors recording violations of the 2010 1-hour
SO<INF>2</INF> NAAQS located in Mississippi within 50 km of its border;
and there are only two SO<INF>2</INF> monitors in Mississippi and
neither are violating the 2010 SO<INF>2</INF> NAAQS. Only one of the
two Mississippi monitors is within 50 km of the State's border, and the
current DVs \39\ at these two monitors are well below the 2010
SO<INF>2</INF> NAAQS and have remained well below the standard for many
years;
---------------------------------------------------------------------------
\39\ The design value is the 3-year average of the 99th
percentile 1-hour daily maximums at a monitor. A control strategy
should be designed to bring the value to attainment of the standard.
---------------------------------------------------------------------------
<bullet> Downward SO<INF>2</INF> emission trends in Mississippi and
in Alabama, Louisiana, and Tennessee, when considered together with the
other factors discussed as part of Mississippi's analysis and the EPA's
WOE, support Mississippi's conclusion that sources in the State will
not contribute significantly to any other States' nonattainment of the
2010 1-hour SO<INF>2</INF> NAAQS; and
<bullet> Source-specific analyses of sources located within 50 km
of the State border that emitted 100 tpy or more of SO<INF>2</INF>
indicate that these sources do not contribute significantly to
nonattainment in other States. These analyses draw upon available
emissions data, monitoring data, air dispersion modeling, source
retirements, wind rose data, and other relevant information to assess
the likelihood of air quality impacts from these sources to areas in
surrounding States. A detailed discussion of each source-specific
analysis is contained in section IV.B.1.iii of the EPA's TSD
accompanying this proposed rulemaking.
Below, the EPA covers some of the principal evidence that confirms
that emissions from Mississippi do not contribute significantly to
nonattainment in other States.\40\
---------------------------------------------------------------------------
\40\ Unless otherwise stated, the summaries below include
Mississippi sources listed in Table 10 of the TSD (and Tables 7 and
8 in Mississippi's submission) already established as meeting the 50
km spatial distance and 100 ton emission threshold for further
analysis. This includes references to the EPA Region 6's WOE
analysis regarding the Louisiana SO<INF>2</INF> transport
infrastructure SIP revision.
---------------------------------------------------------------------------
a. North Mississippi: The EPA evaluated two sources in north
Mississippi--Rockwool (formerly Roxul USA, Inc.) and Mississippi
Silicon. Considering the short distance (approximately 2 km) from
Rockwool to the Tennessee border, the EPA looked at available wind rose
data (2021-2023) at the Olive Branch Airport in DeSoto County,
Mississippi (the nearest wind rose west of Rockwool). This data shows
predominant wind patterns from the south, southeast, and southwest
suggesting that Rockwool emissions are most likely carried north into
Tennessee possibly interacting with the Shelby Farms monitor and
Memphis Airport. However, the EPA assessed prevention of significant
deterioration (PSD) permit modeling for Rockwool performed in 2012 \41\
and 2016,\42\ including modeling of SO<INF>2</INF> to determine
compliance with the 1-hour SO<INF>2</INF> NAAQS. The results showed
Rockwool did not cause or contribute to any violations of the 1-hour
SO<INF>2</INF> NAAQS in either Mississippi or across the border in
Tennessee. Both sets of modeling included cumulative impacts above the
1-hour SO<INF>2</INF> NAAQS, but in both analyses, the contribution
from the Rockwool facility to the modeled violations was very small
(<0.11 microgram per cubic meter ([micro]g/m\3\)), which is well below
the 1-hour SO<INF>2</INF> Significant Impact Level (SIL) of 7.8
[micro]g/m\3\.
---------------------------------------------------------------------------
\41\ The PSD Air Permit Application, Volume III, Dispersion
Modeling, Roxul USA, Inc., March 2012, Prepared by ERM.
\42\ Volume II: Update to PSD Air Quality Assessment, Roxul USA,
Inc. August 2016, Prepared by ERM.
---------------------------------------------------------------------------
For Mississippi (MS) Silicon, the EPA looked at available wind rose
data (2021-2023). This data shows predominant wind patterns from the
south and southeast suggesting that emissions are likely transported
northward into Tennessee possibly interacting with the nearest
Tennessee source, Package Corporation of America. However, the EPA also
considered 2014 \43\ and 2021 \44\ PSD permit modeling for MS Silicon
where both modeling analyses were performed to demonstrate compliance
with the 1-hour SO<INF>2</INF> NAAQS in accordance with PSD permitting
requirements. The results of the modeling show that MS Silicon did not
cause or contribute to any violations of the 1-hour SO<INF>2</INF>
NAAQS in either Mississippi or across the borders in Tennessee and
Alabama. The available modeling for MS Silicon, discussed further in
the EPA's TSD, supports a determination that the source does not
contribute significantly to nonattainment of the NAAQS in Tennessee or
Alabama.
---------------------------------------------------------------------------
\43\ Mississippi Department of Environmental Quality, Modeling
Report, Mississippi Silicon LLC, Tishomingo County, MS, November
2014, Prepared by FC&E Engineering LLC.
\44\ Mississippi Silicon Air Quality Impact Assessment, Report
in Support of Air Permit Amendment Request, August 17, 2021,
Prepared by Kennedy/Jenks Consultants.
---------------------------------------------------------------------------
b. East Mississippi: For the three Lowndes County sources--Steel
Dynamics Columbus (SDI), International Paper Columbus Mill (IP-Columbus
Mill), and the Columbus Air Force Base (AFB). These sources are
approximately 27 km, 15 km, and 17 km, respectively, from the Alabama
State border. In 2022, these sources emitted approximately 370 tpy, 215
tpy, and 239 tpy, respectively. From 2020-2022, these sources
collectively emitted 912 tpy or less per year. The distance between the
closest Lowndes County source (IP-Columbus Mill) and the nearest
Alabama source (Nucor Steel in Tuscaloosa) is 90 km. Wind rose data
showing predominant winds from the south, southeast, and north indicate
that emissions from these sources will predominately not be transported
across the Alabama border. Based on all of this, the EPA believes these
three sources in Lowndes County are not interacting in such a way that
they will significantly contribute to nonattainment or interfere with
maintenance in Alabama.
c. West Mississippi: The low SO<INF>2</INF> emissions (under 100
tpy in 2023) from IP-Vicksburg in Warren County, infrequent winds
toward Louisiana, the large distance between the closest Louisiana
source, GPI, in Ouachita Parish, and IP-Vicksburg (129 km) (suggesting
the respective plumes would be too far apart to interact), and the
Mississippi-Louisiana border (98 km), all suggest an unlikely
cumulative impact in Louisiana. Thus, the EPA believes it is unlikely
that emissions from IP-Vicksburg could contribute significantly to
nonattainment of the 2010 SO<INF>2</INF> NAAQS in Louisiana.
d. South Mississippi:
i. Lamar County
There are no nearby SO<INF>2</INF> sources in Mississippi or
Louisiana within 50 km of the Rain CII Carbon LLC (Rain-MS) facility in
Lamar County that emitted greater than 100 tpy of SO<INF>2</INF> that
could interact with the facility and create a potential cumulative
downwind transport of SO<INF>2</INF> emissions into Louisiana to cause
a violation of the 2010 standard. The closest Louisiana source--
International Paper-Bogalusa
[[Page 55311]]
Mill (IP-Bogalusa Mill)--is approximately 64 km southwest of Rain.
Additionally, available 2021-2023 wind rose data shows predominant wind
patterns from the south and north and less frequently from the
northwest and southeast in the path of Rain-MS suggesting a low
frequency of winds blowing from Rain-MS towards Louisiana. With the
distance from Rain-MS to the Louisiana border and IP-Bogalusa greater
than 50 km, the consistent trend in annual SO<INF>2</INF> emissions at
Rain-MS over the past 10 years,\45\ no evidence of modeled cumulative
impacts with the nearby R.D. Morrow DRR, and the repowering of emission
units at Morrow, the EPA believes it is unlikely that Rain-MS could
interact with these sources to contribute significantly to
nonattainment of the SO<INF>2</INF> NAAQS in Louisiana. Furthermore,
there are no nearby SO<INF>2</INF> sources in Mississippi or Louisiana
within 50 km of Rain that emitted greater than 100 tpy of
SO<INF>2</INF> that could interact with the facility and create
potential cumulative downwind impacts.\46\
---------------------------------------------------------------------------
\45\ Even though preliminary 2023 emissions at Rain show an
increase of approximately 20 tons, this increase is not a
significant outlier in the trends from the past 10 years when Rain
has shown a downward trend from 746.14 tons since 2013 and has
stable emissions between 377 and 347 tpy since 2017.
\46\ See ``Air Plan Approval; Louisiana; Interstate Transport
Requirements for the 2010 SO<INF>2</INF> NAAQS.'' 90 FR 15213 (Apr.
9, 2025) and 90 FR 29743 (July 7, 2025). See also EPA's TSD for the
Louisiana rulemaking in Docket No. EPA-R06-OAR-2013-0465.
---------------------------------------------------------------------------
ii. Jackson County
Wind rose data near Chevron Texaco Products (Chevron) petroleum
refinery in Jackson County, Mississippi indicates a low frequency of
west to east winds in the path of Chevron towards the Alabama border
and the W&T Offshore and Evonik sources in southeast Mobile County. The
80 km spatial distance between Chevron and Alabama Power Plant Barry
Generating Station and Nouryon in northwest Mobile County is also too
far for their respective plumes to interact and contribute
significantly to SO<INF>2</INF> NAAQS nonattainment in Alabama. The EPA
also believes it is unlikely that emissions from Chevron and the two
sources in the St. Bernard Parish SO<INF>2</INF> nonattainment area
(Chalmette Refining LLC and Rain CII Carbon-Louisiana) could interact
as to contribute significantly to SO<INF>2</INF> NAAQS nonattainment in
Louisiana.\47\ Based on this weight of evidence, the EPA concludes that
emissions from Chevron are not contributing significantly to
SO<INF>2</INF> NAAQS nonattainment in Alabama or Louisiana.
---------------------------------------------------------------------------
\47\ See the TSD in Docket No. EPA-R06-OAR-2013-0465 for EPA's
WOE analysis of sources in the St. Bernard Parish SO<INF>2</INF> NAA
supporting the EPA's approval of Louisiana's SO<INF>2</INF>
Interstate Transport SIP. See ``Air Plan Approval; Louisiana;
Interstate Transport Requirements for the 2010 SO<INF>2</INF>
NAAQS.'' 90 FR 29743 (July 7, 2025).
---------------------------------------------------------------------------
The Pascagoula monitor, located approximately 5 km northwest of
Chevron in Jackson County, 13 km west of the Alabama border, and 80 km
north of St. Bernard Parrish, Louisiana, measured less than 6 ppb from
2018 through 2024. This monitor was not sited to characterize the
maximum SO<INF>2</INF> concentrations from Chevron, however, the EPA
believes the low design value provides a good indication that Chevron's
SO<INF>2</INF> concentrations near the Alabama border are likely well
below the 1-hr SO<INF>2</INF> NAAQS.
Based on this evaluation, discussed further in the EPA's TSD, EPA
proposes to find that SO<INF>2</INF> sources in Mississippi will not
contribute significantly to nonattainment of the 2010 1-hour
SO<INF>2</INF> NAAQS in any other State.
2. The EPA's Prong 2 Evaluation--Interference With Maintenance
Prong 2 of the ``good neighbor'' provision requires State plans to
prohibit emissions that will interfere with maintenance of a NAAQS in
another State. The EPA's evaluation of whether Mississippi has met its
prong 2 transport obligations was accomplished by considering all
available information, with a focus on current air quality data,
SO<INF>2</INF> emission trends for Mississippi and neighboring States,
and how existing and future sources of SO<INF>2</INF> are addressed
through existing SIP-approved and other federally enforceable
regulations. This evaluation builds upon the analysis conducted for
significant contribution to nonattainment (prong 1), which considered
SO<INF>2</INF> ambient air quality in Mississippi and neighboring
States and potential ambient impacts of SO<INF>2</INF> emissions from
certain facilities in Mississippi on neighboring States.
Based on the EPA's analysis, we propose to find that SO<INF>2</INF>
levels in neighboring States near the Mississippi border do not
indicate an inability to maintain the SO<INF>2</INF> NAAQS that could
be attributed in part to sources in Mississippi. As such, the EPA
proposes to determine that Mississippi's SIP satisfies the requirements
of prong 2 of CAA section 110(a)(2)(D)(i)(I). This determination is
based on the following considerations:
<bullet> The current 2022-2024 DV for the SO<INF>2</INF> monitor in
Mississippi within 50 km of another State's border and in neighboring
States within 50 km of Mississippi's border are below the standard,
indicating that these areas are all currently in attainment of the 2010
1-hour SO<INF>2</INF> NAAQS;
<bullet> State-wide SO<INF>2</INF> emission trends in Mississippi
and surrounding States are generally declining thus resulting in
declining impacts to neighboring States;
<bullet> Source-specific analyses show that Mississippi facility-
level emissions are generally decreasing considering Federal and SIP-
approved provisions regulating SO<INF>2</INF> emission standards,
indicating that emissions are not anticipated to increase relative to
baseline emissions;
<bullet> Current Mississippi SIP-approved measures and Federal
SO<INF>2</INF> emission requirements control SO<INF>2</INF> emissions
from specific source sectors within Mississippi; and
<bullet> Mississippi's SIP-approved PSD, major New Source Review
(NSR), and minor source NSR regulations address future new and modified
SO<INF>2</INF> sources above major and minor permitting thresholds with
the intent of ensuring that the SO<INF>2</INF> NAAQS will not be
exceeded within or outside of the State because of new facility
construction or existing facility modification within the State.
Based on this evaluation, as discussed further in the EPA's TSD for
this proposed rulemaking, the Agency proposes to find that sources
within Mississippi will not interfere with maintenance of the 2010 1-
hour SO<INF>2</INF> NAAQS in any other State.
IV. Proposed Action
The EPA is proposing to approve Mississippi's January 27, 2022,
prong 1 and prong 2 infrastructure SIP addressing interstate transport
for the 2010 1-hour SO<INF>2</INF> NAAQS. Based on the EPA's WOE
analysis, and as more thoroughly discussed in the TSD, the Agency
proposes to determine that emissions from Mississippi will not
contribute significantly to nonattainment in, or interfere with
maintenance of, any other State with respect to the 2010 SO<INF>2</INF>
NAAQS. The EPA therefore proposes to find that Mississippi's SIP
contains adequate provisions consistent with CAA section
110(a)(2)(D)(i)(I).
V. Statutory and Executive Order Reviews
Under the CAA, the Administrator is required to approve a SIP
submission that complies with the provisions of the CAA and applicable
Federal regulations.\48\ Thus, in reviewing SIP
[[Page 55312]]
submissions, the EPA's role is to approve State choices, provided that
they meet the criteria of the CAA. Accordingly, this proposed
rulemaking merely proposes to approve State law as meeting Federal
requirements and does not impose additional requirements beyond those
imposed by State law. For that reason, this proposed rulemaking:
---------------------------------------------------------------------------
\48\ See 42 U.S.C. 7410(k); 40 CFR 52.02(a).
---------------------------------------------------------------------------
<bullet> Is not a significant regulatory action subject to review
by the Office of Management and Budget under Executive Order 12866 (58
FR 51735, October 4, 1993);
<bullet> Is not an Executive Order 14192 (90 FR 9065, February 6,
2025) regulatory action because this action is not significant under
Executive Order 12866;
<bullet> Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
<bullet> Is certified as not having a significant economic impact
on a substantial number of small entities under the Regulatory
Flexibility Act (5 U.S.C. 601 et seq.);
<bullet> Does not contain any unfunded mandate or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);
<bullet> Does not have federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
<bullet> Is not subject to Executive Order 13045 (62 FR 19885,
April 23, 1997) because it approves a State program;
<bullet> Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001); and
<bullet> Is not subject to requirements of section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the CAA.
In addition, the SIP is not approved to apply on any Indian
reservation land or in any other area where the EPA or an Indian Tribe
has demonstrated that a Tribe has jurisdiction. In those areas of
Indian country, the rule does not have Tribal implications and will not
impose substantial direct costs on Tribal governments or preempt Tribal
law as specified by Executive Order 13175 (65 FR 67249, November 9,
2000).
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Carbon monoxide,
Incorporation by reference, Intergovernmental relations, Lead, Nitrogen
dioxide, Ozone, Particulate matter, Reporting and recordkeeping
requirements, Sulfur oxides, Volatile organic compounds.
(Authority: 42 U.S.C. 7401 et seq.)
Dated: August 20, 2026.
Kristy Eubanks,
Deputy Regional Administrator performing the functions and duties of
the Regional Administrator, Region 4.
[FR Doc. 2026-17503 Filed 8-26-26; 8:45 am]
BILLING CODE 6560-50-P
</pre><script data-cfasync="false" src="/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.js"></script></body>
</html>Indexed from Federal Register on August 27, 2026.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.