[Federal Register Volume 85, Number 150 (Tuesday, August 4, 2020)]
[Proposed Rules]
[Pages 47134-47151]
[FR Doc No: 2020-16443]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R04-OAR-2019-0447; FRL-10012-92-Region 4]

Air Plan Approval; MS; BART SIP and Regional Haze Progress Report

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve, through parallel processing, a draft Mississippi State
Implementation Plan (SIP) revision, submitted through a letter dated
April 23, 2020, addressing best available retrofit technology (BART)
determinations for 14 electric generating units (EGUs) (``draft BART
SIP''). These EGUs were initially addressed in EPA's prior limited
approval and limited disapproval actions on Mississippi's regional haze
SIP because of deficiencies arising from the State's reliance on the
Clean Air Interstate Rule (CAIR) to satisfy certain regional haze
requirements. EPA proposes to approve the draft BART SIP and finds that
it corrects the deficiencies that led to the limited approval and
limited disapproval of the State's regional haze SIP; to withdraw the
limited disapproval of the regional haze SIP; and to replace the prior
limited approval with a full approval of the regional haze SIP as
meeting all regional haze requirements of the Clean Air Act (CAA or
Act) for the first implementation period. In addition, EPA is proposing
to approve the State's first periodic report describing progress
towards reasonable progress goals (RPGs) established for regional haze
and the associated determination that the State's regional haze SIP is
adequate to meet these RPGs for the first implementation period
(``Progress Report''). The State submitted the

progress report as a SIP revision by letter dated October 4, 2018.

DATES: Comments must be received on or before September 3, 2020.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-
OAR-2019-0447, at http://www.regulations.gov. Follow the online
instructions for submitting comments. Once submitted, comments cannot
be edited or removed from Regulations.gov. 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. 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 http://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Michele Notarianni or Gobeail
McKinley, 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. Ms. Notarianni can be reached via telephone at (404) 562-
9031 or electronic mail at<EMAIL_ADDRESS>Ms. McKinley can
be reached via telephone at<PHONE_NUMBER> or electronic mail at
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

I. Parallel Processing

    Parallel processing refers to a process that utilizes concurrent
state and federal proposed rulemaking actions. Generally, the state
submits a copy of the proposed regulation or other revisions to EPA
before conducting its public hearing and completing its public comment
process under state law. EPA reviews this proposed state action and
prepares a notice of proposed rulemaking (NPRM) under federal law.\1\
If, after the state completes its public comment process and after
EPA's public comment process has run, the state changes its final
submittal from the proposed submittal, EPA evaluates those changes and
decides whether to publish another NPRM in light of those changes or to
proceed to taking final action on its proposed action and describe the
state's changes in its final rulemaking action. Any final rulemaking
action by EPA will occur only after the final submittal has been
adopted by the state and formally provided to EPA.
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    \1\ Although not the case in this proposed rulemaking, in some
instances, EPA's NPRM is published in the Federal Register during
the same time frame that the state is holding its public hearing and
conducting its public comment process. The state and EPA then
provide for concurrent public comment periods on both the state
action and federal action.
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    In its previously submitted regional haze SIP,\2\ the Mississippi
Department of Environmental Quality (MDEQ) relied on CAIR \3\ to meet
BART requirements for the 14 BART-eligible units, located at seven
facilities, formerly subject to that trading program.\4\ Mississippi's
newly submitted draft BART SIP addresses BART for these EGUs in lieu of
relying on CAIR as an alternative to BART. Because the draft BART SIP
has not yet completed the State's public notice-and-comment process,
Mississippi has requested that EPA parallel process the SIP revision
with the State's rulemaking proceedings. Mississippi submitted the
draft BART SIP to EPA on April 23, 2020,\5\ and noticed it for public
comment on the same date. The State's public comment period closed on
May 23, 2020.
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    \2\ In this notice, EPA is using ``regional haze SIP'' and
``regional haze plan'' interchangeably.
    \3\ CAIR created regional cap-and-trade programs to reduce
sulfur dioxide (SO2) and nitrogen oxide (NOX)
emissions in 27 eastern states (and the District of Columbia),
including Mississippi, that contributed to downwind nonattainment or
interfered with maintenance of the 1997 8-hour ozone national
ambient air quality standards (NAAQS) or the 1997 fine particulate
matter (PM2.5) NAAQS.
    \4\ See 77 FR 38191 (June 27, 2012); 77 FR 33642 (June 7, 2012).
    \5\ EPA received MDEQ's April 23, 2020, draft BART SIP on April
24, 2020.
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    After Mississippi submits the final BART SIP (including a response
to all public comments raised during the State's public participation
process), EPA will evaluate the submittal. If the State changes the
final submittal from the draft BART SIP that EPA is proposing to
approve today, EPA will evaluate those changes for significance. If EPA
finds any such changes to be significant, then the Agency intends to
determine whether to re-propose based on the revised submission or to
proceed to take final action on the BART SIP as changed by the State.

II. Background

A. Regional Haze and the Regional Haze Plan

    Regional haze is visibility impairment that is produced by a
multitude of sources and activities which are located across a broad
geographic area and emit PM2.5 (e.g., sulfates, nitrates,
organic carbon, elemental carbon, and soil dust), and their precursors
(e.g., SO2, NOX, and in some cases, ammonia
(NH3) and volatile organic compounds (VOC)). Fine particle
precursors react in the atmosphere to form PM2.5 which
impairs visibility by scattering and absorbing light. Visibility
impairment (i.e., light scattering) reduces the clarity, color, and
visible distance that one can see. PM2.5 can also cause
serious health effects (including premature death, heart attacks,
irregular heartbeat, aggravated asthma, decreased lung function, and
increased respiratory symptoms) and mortality in humans and contributes
to environmental effects such as acid deposition and eutrophication.
    Data from the existing visibility monitoring network, the
``Interagency Monitoring of Protected Visual Environments'' (IMPROVE)
monitoring network, show that visibility impairment caused by air
pollution occurs virtually all the time at most national park and
wilderness areas. The average visual range \6\ in many Class I areas
\7\ in the western United States is 100-150 kilometers (km), or about
one-half to two-thirds of the visual range that would exist without
anthropogenic air pollution. In most of the eastern Class I areas of
the United States, the average visual range is less than 30 km, or
about one-fifth of the visual range that would exist under estimated
natural conditions. See 64 FR 35714, 35715 (July 1, 1999). CAA programs

have reduced emissions of haze-causing pollution, lessening visibility
impairment and resulting in improved average visual ranges.\8\
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    \6\ Visual range is the greatest distance, in km or miles, at
which a dark object can be viewed against the sky.
    \7\ Areas designated as mandatory Class I areas consist of
national parks exceeding 6,000 acres, wilderness areas and national
memorial parks exceeding 5,000 acres, and all international parks
that were in existence on August 7, 1977. See 42 U.S.C. 7472(a). In
accordance with section 169A of the CAA, EPA, in consultation with
the Department of Interior, promulgated a list of 156 areas where
visibility is identified as an important value. See 44 FR 69122
(November 30, 1979); 40 CFR part 81 Subpart D. The extent of a
mandatory Class I area includes subsequent changes in boundaries,
such as park expansions. See 42 U.S.C. 7472(a). Although states and
tribes may designate as Class I additional areas which they consider
visibility as an important value, the requirements of the visibility
program set forth in section 169A of the CAA apply only to
``mandatory Class I Federal areas.'' Each mandatory Class I area is
the responsibility of a ``Federal Land Manager.'' See 42 U.S.C.
7602(i). When the term ``Class I area'' is used in this action, it
means a ``mandatory Class I Federal area.''
    \8\ An interactive ``story map'' depicting efforts and recent
progress by EPA and states to improve visibility at national parks
and wilderness areas is available at: http://arcg.is/29tAbS3.
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    In section 169A of the 1977 Amendments to the CAA, Congress created
a program for protecting visibility in the nation's national parks and
wilderness areas. This section of the CAA establishes as a national
goal the prevention of any future, and the remedying of any existing,
anthropogenic impairment of visibility in 156 national parks and
wilderness areas designated as mandatory Class I federal areas.
Congress added section 169B to the CAA in 1990 to address regional haze
issues, and EPA subsequently promulgated the Regional Haze Rule
(RHR).\9\ The RHR established a requirement to submit a regional haze
SIP which applies to all 50 states, the District of Columbia, and the
Virgin Islands.\10\ Each jurisdiction was required to submit a SIP
addressing regional haze requirements for the first implementation
period no later than December 17, 2007.\11\
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    \9\ See 64 FR 35713 (July 1, 1990).
    \10\ 40 CFR 51.300(b).
    \11\ 40 CFR 51.308(b).
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    On September 22, 2008, Mississippi submitted a SIP revision to
address regional haze in Class I areas impacted by emissions from
Mississippi and subsequently amended that submittal on May 9, 2011. As
discussed further in Section II.B.2, EPA finalized a limited approval
and a limited disapproval of the Mississippi regional haze SIP in June
2012 because of deficiencies \12\ in the regional haze SIP arising from
the State's reliance on CAIR to meet certain regional haze
requirements, including BART.
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    \12\ The deficiencies resulting from Mississippi's reliance on
CAIR to satisfy BART relate to those BART determinations and to the
use of those determinations as an element of the required long-term
strategy for achieving RPGs. Mississippi's reliance on CAIR did not
affect its reasonable progress control analysis because the State
determined in its regional haze SIP that no controls were necessary
for reasonable progress given the areas of influence and
consultation with neighboring states. See 77 FR 11879, 11888
(February 28, 2012) for further information on the reasonable
progress evaluation.
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B. BART

1. Statutory and Regulatory Requirements
    Section 169A of the CAA directs states to evaluate the use of
retrofit controls at certain larger, often uncontrolled, older
stationary sources in order to address visibility impacts from these
sources. Specifically, section 169A(b)(2) of the CAA requires states to
revise their SIPs to contain such measures as may be necessary to make
reasonable progress towards the natural visibility goal, including a
requirement that certain categories of existing major stationary
sources built between 1962 and 1977 procure, install, and operate
``Best Available Retrofit Technology'' as determined by the state. On
July 6, 2005, EPA published the Guidelines for BART Determinations
Under the Regional Haze Rule at Appendix Y to 40 CFR part 51
(hereinafter referred to as the ``BART Guidelines'') to assist states
in the BART evaluation process. Under the RHR and the BART Guidelines,
the BART evaluation process consists of three steps: (1) An
identification of all BART-eligible sources, (2) an assessment of
whether the BART-eligible sources are subject to BART, and (3) a
determination of the BART controls.\13\ States must conduct BART
determinations for all ``BART-eligible'' sources that may reasonably be
anticipated to cause or contribute to any visibility impairment in a
Class I area, or in the alternative, adopt an emissions trading program
or other alternative program as long as the alternative provides
greater reasonable progress towards improving visibility than BART. In
making a BART determination for a fossil fuel-fired electric generating
plant with a total generating capacity in excess of 750 megawatts, a
state must use the approach set forth in the BART Guidelines. A state
is generally encouraged, but not required, to follow the BART
Guidelines in other aspects.
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    \13\ See 40 CFR 51.308(e); BART Guidelines, I.F.
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    In the first step of the BART evaluation process, states are
required to identify all the BART-eligible sources within their
boundaries by utilizing the three eligibility criteria in the Act and
the RHR: (1) One or more emission units at the facility fit within one
of the 26 categories listed in the BART Guidelines; (2) the emission
unit(s) began operation on or after August 6, 1962, and was in
existence on August 6, 1977; and (3) the potential emissions of any
visibility-impairing pollutant from the units exceed 250 tons per year
(tpy).\14\ With respect to the third criterion, states must address all
visibility-impairing pollutants emitted by a BART-eligible source,
which is the collection of emissions units whose potential to emit for
a visibility-impairing pollutant is greater than 250 tpy. The most
significant visibility-impairing pollutants are SO2,
NOX, and particulate matter (PM).\15\ States should use
their best judgment in determining whether VOC or NH3
compounds impair visibility in Class I areas.\16\ Sources that meet all
three criteria are BART-eligible.
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    \14\ See CAA section 169A(b)(2)(A), (g)(7); 40 CFR 51.301
(definition of ``Existing stationary facility''); see also BART
Guidelines, II.
    \15\ See 70 FR 39160.
    \16\ See BART Guidelines, II.A.3, III.A.2.
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    The second phase of the BART evaluation is to identify those BART-
eligible sources that may reasonably be anticipated to cause or
contribute to visibility impairment at any Class I area, i.e., those
sources that are subject to BART. Section III of the BART Guidelines
allows states to exempt BART-eligible sources from further BART review
(i.e., deem them not subject to BART) via modeling and emissions
analyses demonstrating that the sources may not reasonably be
anticipated to cause or contribute to any visibility impairment in any
Class I area. For such sources, a state need not make a BART
determination.
    For states using modeling to determine whether single sources are
subject to BART, the BART Guidelines note that the first step is to set
a contribution threshold to assess whether the impact of a single
source is sufficient to cause or contribute to visibility impairment at
a Class I area.\17\ Under the BART Guidelines, states may select an
exemption threshold value for their BART modeling below which a BART-
eligible source would not be expected to cause or contribute to
visibility impairment in any Class I area. The state must document this
exemption threshold value in the SIP and must state the basis for its
selection of that value. Any source with emissions that model above the
threshold value would be subject to a BART determination review. The
BART Guidelines acknowledge varying circumstances affecting different
Class I areas. States should consider the number of emissions sources
affecting the Class I areas at issue and the magnitude of the
individual sources' impacts. Generally, the exemption threshold set by
the state should not be higher than 0.5 deciview (dv).\18\ States

are also free to use a lower threshold if, for instance, they conclude
that the location of a large number of BART-eligible sources in
proximity of a Class I area justifies this approach.
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    \17\ See BART Guidelines, III.A.3 (``Option 1: Individual Source
Attribution Approach (Dispersion Modeling)'').
    \18\ A dv is the unit of measurement on the dv index scale for
quantifying in a standard manner human perceptions of visibility.
See 40 CFR 51.301. The BART Guidelines state that ``[a] single
source that is responsible for a 1.0 deciview change or more should
be considered to `cause' visibility impairment.'' The BART
Guidelines also state that ``the appropriate threshold for
determining whether a source `contributes to visibility impairment'
may reasonably differ across states,'' but, ``[a]s a general matter,
any threshold that you use for determining whether a source
`contributes' to visibility impairment should not be higher than 0.5
deciviews.'' See BART Guidelines, III.A.1.
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    Once a state has determined which sources are subject to BART, the
state must determine BART for these sources in the third and final step
of the BART evaluation process. In making BART determinations, section
169A(g)(2) of the CAA requires that states consider the following
factors: (1) The costs of compliance; (2) the energy and non-air
quality environmental impacts of compliance; (3) any existing pollution
control technology in use at the source; (4) the remaining useful life
of the source; and (5) the degree of improvement in visibility which
may reasonably be anticipated to result from the use of such
technology. States are free to determine the weight and significance to
be assigned to each factor, but must reasonably consider all five
factors.
    A regional haze SIP must include source-specific BART emissions
limits and compliance schedules for each source subject to BART. Once a
state has made its BART determination, the BART controls must be
installed and in operation as expeditiously as practicable, but no
later than five years after the date of EPA approval of the regional
haze SIP. See CAA section 169A(g)(4); 40 CFR 51.308(e)(1)(iv). In
addition to what is required by the RHR, general SIP requirements
mandate that the SIP must also include all regulatory requirements
related to monitoring, recordkeeping, and reporting for the BART
controls on the source. See CAA section 110(a)(2).
2. Draft BART SIP
a. Relationship to EPA's Transport Rules
    Like many other states formerly subject to CAIR, Mississippi had
relied on CAIR in its regional haze SIP to meet certain requirements of
EPA's RHR, including BART requirements for emissions of SO2
and NOX from its BART-eligible EGUs in the State.\19\ This
reliance was consistent with EPA's regulations at the time that
Mississippi developed its regional haze SIP. See 70 FR 39104 (July 6,
2005). However, in 2008, the United States Court of Appeals for the
District of Columbia Circuit (D.C. Circuit) invalidated CAIR, although
it ultimately remanded the rule to EPA without vacatur to preserve the
environmental benefits CAIR provided. See North Carolina v. EPA, 550
F.3d 1176, 1178 (D.C. Cir. 2008).
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    \19\ In addition to relying on CAIR to satisfy BART
SO2 and NOX requirements, these sources also
modeled their coars PM (PM10) emissions and found that
those emissions do not contribute to visibility impairment in any
Class 1 area. See 77 FR 11890.
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    On August 8, 2011 (76 FR 48208), acting on the D.C. Circuit's
remand, EPA promulgated the Cross-State Air Pollution Rule (CSAPR) to
replace CAIR and issued Federal Implementation Plans (FIPs) to
implement the rule in CSAPR-subject states.\20\ Although Mississippi
was covered under CAIR's annual NOX and SO2
trading programs, only CSAPR's ozone-season NOX program
applied to the State. See 40 CFR 52.1284.\21\ Implementation of CSAPR
was scheduled to begin on January 1, 2012, when CSAPR would have
superseded the CAIR program. However, numerous parties filed petitions
for review of CSAPR, and at the end of 2011, the D.C. Circuit issued an
order staying CSAPR pending resolution of the petitions and directing
EPA to continue to administer CAIR. Order of December 30, 2011, in EME
Homer City Generation, L.P. v. EPA, D.C. Cir. No. 11-1302. EPA
ultimately began implementation of CSAPR on January 1, 2015.\22\
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    \20\ CSAPR requires substantial reductions of SO2 and
NOX emissions from EGUs in 27 states in the Eastern
United States that significantly contribute to downwind
nonattainment of the 1997 PM2.5 and ozone NAAQS, 2006
PM2.5 NAAQS, and the 2008 8-hour ozone NAAQS.
    \21\ See also 76 FR 48208 (Mississippi FIP for 1997 ozone
NAAQS); 81 FR 74504 (October 26, 2016) (Mississippi FIP for 2008
ozone 8-hour ozone NAAQS).
    \22\ See 79 FR 71663.
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    During this same timeframe, EPA also finalized a limited approval
and a limited disapproval of the Mississippi regional haze SIP in June
2012 because of deficiencies in the regional haze SIP arising from the
State's reliance on CAIR as an alternative to BART for the State's
BART-eligible EGUs.\23\ See 77 FR 38191 (June 27, 2012) (limited
approval); 77 FR 33642 (June 7, 2012) (limited disapproval). In the
limited disapproval action, EPA did not subject Mississippi to a FIP.
Mississippi had requested that EPA not issue a FIP and instead provide
the State with additional time to correct the deficiencies in its
regional haze SIP through a SIP revision.\24\
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    \23\ The State's analysis of reasonable progress controls was
not dependent on CAIR, and thus not affected by CAIR's invalidation.
See 77 FR 11879, 11888 (February 28, 2012) (finding no controls were
necessary for reasonable progress given the areas of influence and
consultation with neighboring states).
    \24\ See 77 FR 33654.
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    Accordingly, Mississippi began working on a new SIP submission to
address the limited disapproval of the State's regional haze SIP and
the change from CAIR and CSAPR. One important impact of the transition
from CAIR to CSAPR was that Mississippi previously relied on CAIR as an
alternative to BART for both SO2 and NOX because
it participated in trading programs for both pollutants under CAIR;
however, because Mississippi is only part of the CSAPR seasonal
NOX program (and not part of the SO2 program), it
could not rely on CSAPR to satisfy BART for SO2. Thus, the
State worked with the BART-eligible EGUs formerly subject to CAIR to
determine how these facilities would now address BART.\25\ These 14
BART-eligible units are located at the following seven facilities:
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    \25\ EPA previously approved the State's identification of BART-
eligible sources in its limited approval action. EPA is not
reexamining these BART-eligibility findings in this rulemaking, and
any comments on this issue are beyond the scope of this notice.
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     Cooperative Energy \26\--Plant Moselle (Plant Moselle);
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    \26\ Cooperative Energy was formerly known as South Mississippi
Electric Power Association.
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     Cooperative Energy--R. D. Morrow Sr. Generating Plant
(Plant Morrow);
     Entergy Mississippi, Inc.--Baxter Wilson Plant (Baxter
Wilson);
     Entergy Mississippi, Inc.--Gerald Andrus Plant (Gerald
Andrus);
     Mississippi Power Company--Plant Chevron (Plant Chevron);
     Mississippi Power Company--Plant Daniel (Plant Daniel);
and
     Mississippi Power Company--Plant Watson (Plant Watson).
    As explained further in Section III of this notice, the draft BART
SIP proposes to find that these 14 BART-eligible EGUs are exempt from
BART because visibility modeling and/or supplemental analyses
demonstrate that they are not reasonably anticipated to cause or
contribute to visibility impairment in any Class I area.
b. Pollutants Addressed
    As described earlier, the BART Guidelines direct states to address
SO2, NOX, and direct PM (including both
PM10 and PM2.5) emissions as visibility-impairing
pollutants, and to exercise judgment in determining whether VOC or
NH3 emissions from a source impair visibility in an area.
See 70 FR 39160. Mississippi had previously determined that VOC from
anthropogenic sources and NH3 from point sources are not
significant visibility-impairing pollutants in Mississippi for the
first implementation period. The State continues to rely on these
findings in its draft BART SIP. EPA previously approved these findings
in our earlier limited approval, and the Agency is not

reexamining this issue in this rulemaking.\27\
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    \27\ See 77 FR 11887-88 (discussing analysis by the State and
the Visibility Improvement State and Tribal Association of the
Southeast (VISTAS)).
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c. Dispersion Modeling Methodology
    Consistent with the BART Guidelines, Mississippi requested that
each of its seven BART-eligible facilities formerly subject to CAIR
develop and submit dispersion modeling to assess the extent of their
contribution to visibility impairment at surrounding Class I areas. The
BART Guidelines allow states to use the CALPUFF \28\ modeling system
(CALPUFF) or another appropriate model to predict the visibility
impacts from a single source on a Class I area, and therefore, to
determine whether an individual source may reasonably be anticipated to
cause or contribute to impairment of visibility in Class I areas (i.e.,
whether it is subject to BART). The BART Guidelines also recommend that
states develop a modeling protocol for making individual source
attributions.
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    \28\ EPA's reference to CALPUFF encompasses the entire CALPUFF
modeling system, which includes the CALMET, CALPUFF, and CALPOST
models and other pre and post processors. The different versions of
CALPUFF have corresponding versions of CALMET, CALPOST, etc. which
may not be compatible with previous versions (e.g., the output from
a newer version of CALMET may not be compatible with an older
version of CALPUFF). The different versions of the CALPUFF modeling
system are available from the model developer at: http://www.src.com/calpuff/download/download.htm.
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    The VISTAS states, including Mississippi, developed a ``Protocol
for the Application of CALPUFF for BART Analyses'' (VISTAS BART
Modeling Protocol).\29\ Mississippi, in coordination with VISTAS, used
this modeling protocol to apply CALPUFF to determine whether individual
sources in Mississippi were subject to or exempt from BART. EPA
previously approved the use of this modeling methodology by
Mississippi,\30\ and the Agency believes that the continued use of this
modeling methodology in the draft BART SIP remains appropriate.
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    \29\ The VISTAS BART Modeling Protocol, December 22, 2005,
Revision 3.2 (August 31, 2006), is included in Appendix L.8 of the
BART SIP.
    \30\ See 77 FR 11888-89.
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d. Contribution Threshold
    In its prior regional haze submissions, MDEQ used a contribution
threshold of 0.5 dv for determining which BART-eligible units
(including the 14 units addressed by the draft BART SIP) are subject to
BART. EPA previously approved the use of this 0.5 dv BART contribution
threshold, and the Agency is not reexamining this issue in this
rulemaking.\31\
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    \31\ The factors supporting the Agency's original approval of
the 0.5 dv BART contribution threshold have not changed. See 77 FR
11889 (Feb. 28, 2012). In fact, there are now fewer BART-eligible
sources (due to the removal of all BART-eligible units at Plant
Morrow and Unit 2 at Baxter Wilson) and less visibility-impairing
pollutants emitted from BART-eligible sources than existed in the
record at the time of EPA's earlier limited approval (due to
SO2 scrubbers installed at Plant Daniel and removal of
fuel oil burning capabilities for Unit 1 at Gerald Andrus and Unit 1
at Baxter Wilson). These changes are discussed further in Section
III of this notice.
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C. Progress Report Requirements

    The RHR requires each state to submit progress reports that
evaluate progress towards the RPGs for each mandatory Class I area
within the state and for each Class I area outside the state which may
be affected by emissions from within the state. See 40 CFR 51.308(g).
In addition, the provisions of 40 CFR 51.308(h) require a state to
submit, at the same time as each progress report, a determination of
the adequacy of the state's existing regional haze plan. The first
progress report is due five years after submittal of the initial
regional haze plan and must be submitted as a SIP revision. Mississippi
submitted its progress report for the first implementation period to
EPA on October 4, 2018.

III. Summary and EPA's Evaluation of Mississippi's BART SIP

A. Summary of Mississippi's BART SIP

    The draft BART SIP sets forth MDEQ's subject-to-BART determinations
for the BART-eligible sources formerly subject to CAIR, and finds that
none of these sources is subject to BART. Table 1 identifies these
BART-eligible sources, the highest modeled impact at the Class I area
nearest each source,\32\ and the State's determination regarding
whether the sources are subject to BART.
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    \32\ MDEQ followed the VISTAS BART Modeling protocol which
specifies that BART exemption modeling should be performed for Class
I areas located within 300 km of each BART-eligible source. The
Class I areas listed in Table 1 are the only Class I areas located
within 300 km of each BART-eligible source with the exception of
Baxter Wilson, which has no Class I areas within 300 km and is
located 310 km from Breton.

                               Table 1--Mississippi EGUs Subject-to-BART Modeling
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                                                                             Maximum 24-
                                                                              hour 98th
                                     BART-eligible                           percentile
           Facility name                 units       Nearest Class I Area    visibility       Subject to BART?
                                                                             impact \33\
                                                                                (dv)
----------------------------------------------------------------------------------------------------------------
Baxter Wilson.....................            1, 2  Breton Wilderness               0.49*  No.
                                                     Area (Breton) (LA).
Gerald Andrus.....................               1  Caney Creek                     0.15*  No.
                                                     Wilderness Area
                                                     (Caney Creek) (AR).
Plant Chevron.....................      1, 2, 3, 4  Breton (LA)..........            0.27  No.
Plant Daniel......................            1, 2  Breton (LA)..........            0.39  No.
Plant Morrow......................            1, 2  Breton (LA)..........           N/A**  N/A**.
Plant Moselle.....................               3  Breton (LA)..........            0.05  No.
Plant Watson......................            4, 5  Breton (LA)..........            0.44  No.
----------------------------------------------------------------------------------------------------------------
* These visibility impacts for Baxter Wilson and Gerald Andrus are based on burning natural gas only as these
  facilities have removed the ability to burn fuel oil at Unit 1 for each facility. In addition, as explained
  further below, the visibility impact for Baxter Wilson was modeled based on emissions from both Unit 1 and
  Unit 2, but Unit 2 at Baxter Wilson has since been removed.
** ``N/A'' indicates that there is no visibility impact from Plant Morrow Units 1 and 2 because these BART-
  eligible units were removed from service.

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

    \33\ EPA's BART Guidelines recommend comparing visibility
improvements between control options using the 98th percentile of
24-hour delta dv, which is equivalent to the facility's 8th highest
visibility impact day. See 70 FR 39162 (July 6, 2005). The 98th
percentile is recommended rather than the maximum value to allow for
uncertainty in the modeled impacts and to avoid undue influence from
unusual meteorological conditions. The ``delta'' refers to the
difference between total dv impact from the facility plus natural
background, and dv of natural background alone, so ``delta
deciviews'' is the estimate of the facility's impact relative to
natural visibility conditions. The VISTAS BART Modeling Protocol
interprets EPA's recommended use of the 98th percentile value as the
highest of the three annual 98th percentile values at a particular
Class I area or the 22nd highest value in the combined 3-year
period, whichever is more conservative (p.14).
---------------------------------------------------------------------------

    The original modeling for each of these plants was generally
performed in the early 2010s, using data from an earlier period (e.g.,
2001-03 or 2003-05) and earlier versions of the CALPUFF model. For four
facilities (Baxter Wilson, Gerald Andrus, Plant Chevron, and Plant
Moselle), the State supplemented the original modeling with new
analyses of emissions changes for SO2, NOX, and
PM10 \34\ since the BART baseline period. For each plant,
recent emissions have either remained roughly equivalent to or
decreased relative to the baseline period modeled. Accordingly, the
State concluded that the prior modeling results remain valid for
determining whether the sources are subject to BART.\35\
---------------------------------------------------------------------------

    \34\ PM10 includes PM2.5, thus, MDEQ
evaluated PM10 emissions data in the supplemental
emissions analyses in the draft BART SIP.
    \35\ In addition, as further explained in Section III.B.2, EPA
has also evaluated the potential impacts of updates to the CALPUFF
model, and found that such updates are unlikely to result in
significantly different visibility impacts.
---------------------------------------------------------------------------

    For Plant Daniel and Plant Watson, the sources conducted updated
modeling with recent emissions data and the current version of CALPUFF.
Finally, Plant Morrow's BART-eligible units are permanently retired,
and thus there is no need to determine whether this source is subject
to BART.
    The following subsections discuss in more detail MDEQ's assessment
of the BART exemption modeling for each of the seven facilities.
1. Mississippi Power Company--Chevron Cogenerating Plant Units 1, 2, 3,
and 4
    Units 1, 2, 3, and 4 at Plant Chevron, located in Pascagoula,
Mississippi, and owned and operated by Mississippi Power Company, have
been identified by MDEQ as BART-eligible. Plant Chevron is located
approximately 48 km north of Breton. Plant Chevron is an electric
generating facility with four gas-fired combined cycle turbines. All
four units each have the potential to emit more than 250 tpy of
NOX emissions. Plant Chevron performed CALPUFF modeling in
2011 on these four units utilizing CALPUFF version 5.754 Level 060202.
The modeling analysis predicted a maximum annual 98th percentile 24-
hour average visibility impact of 0.27 dv over the three years modeled
on Breton, and a 22nd highest day's visibility impact over all three
years of 0.24 dv.
    As explained previously, because the original modeling was
conducted years ago, MDEQ also performed a supplemental emissions
analysis for this facility. MDEQ compared more current (2016-2018)
SO2, NOX, and PM10 emissions values
from annual emissions reports submitted by Plant Chevron with the 2003-
2005 baseline emissions values and showed that recent emissions have
remained roughly equivalent to or decreased relative to the baseline
period modeled. Therefore, MDEQ concluded that it is not necessary to
remodel using recent emissions. Table 2 compares the maximum 24-hour
emissions rates for 2003-2005 that were modeled in 2011 against updated
maximum 24-hour emissions rates for 2016-2018. The State found that:
(1) The maximum SO2 emissions rates from all four units
combined were slightly higher, but still quite low, in the updated
period compared to the baseline period (approximately 8 pounds per hour
(lb/hr) vs 4 lb/hr); (2) the maximum NOX emissions rates
from all four units combined were significantly lower in the updated
period compared to the baseline period (approximately 420 lb/hr vs 558
lb/hr); and (3) the maximum PM10 emissions rates from all
four units combined were approximately the same (9 lb/hr). The 2011
CALPUFF modeling found that most of the visibility impact from this
facility was from nitrates, so the recent decrease in NOX
emissions would suggest a corresponding decrease in visibility impact
on Breton.
    In addition, Table 3 compares the annual 2003-2005 baseline
emissions of SO2, NOX, and PM10 to
2016-2018 annual emissions. Annual emissions are not an input into
CALPUFF modeling, but MDEQ elected to consider them. The annual
emissions comparison provides a general indication of overall trends in
emissions between the baseline period that was used in the 2011
modeling and more recent emissions. The annual emissions of
NOX and SO2 are higher in the 2016-2018 period
and PM10 emissions are lower.

                                Table 2--Plant Chevron Modeled (2003-2005) and 2016-2018 Maximum 24-Hour Emissions Rates
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Maximum 24-hour emissions rates (lb/hr) (2003-  Maximum 24-hour emissions rates (lb/hr) (2016-
                                                                               2005)                                           2018)
                      Emission unit                      -----------------------------------------------------------------------------------------------
                                                                SO2             NOX            PM10             SO2             NOX            PM10
--------------------------------------------------------------------------------------------------------------------------------------------------------
Unit 1..................................................            0.75          119.58            1.90            0.17           90.91            1.88
Unit 2..................................................            0.78          122.64            1.95            0.17           88.84            1.83
Unit 3..................................................            1.00          159.23            2.55            4.11          119.64            2.47
Unit 4..................................................            0.98          156.84            2.50            3.66          120.56            2.49
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................            3.51          558.29            8.90            8.11          419.95            8.67
--------------------------------------------------------------------------------------------------------------------------------------------------------

     Table 3--Plant Chevron Baseline (2001-2003) and Current (2016-2018) Period Annual Emissions Comparison
----------------------------------------------------------------------------------------------------------------
                                                                     Combined annual emission (tons) units 1-4
                              Year                               -----------------------------------------------
                                                                        SO2             NOX            PM10
----------------------------------------------------------------------------------------------------------------
2001............................................................            1.61        1,238.26           66.14

2002............................................................            1.55        1,181.77           62.59
2003............................................................            1.44        1,264.50           67.65
2016............................................................            8.01        1,430.36           29.50
2017............................................................            7.77        1,274.89           26.30
2018............................................................            5.76        1,240.95           26.11
----------------------------------------------------------------------------------------------------------------

    In sum, MDEQ concluded that Plant Chevron Units 1, 2, 3, and 4 are
not subject to BART, and thus, no further BART analysis is required
because Plant Chevron's 2011 modeling found that its visibility impact
was 0.27 dv which is significantly less than 0.5 dv, and there have
been no significant increases in SO2, NOX, or
PM10 emissions since the modeled baseline period.
Specifically, there have been no significant increases in the maximum
24-hour SO2 nor PM10 emissions rates, and the
maximum 24-hour NOX emissions rates have declined.
2. Mississippi Power Company--Plant Victor J Daniel Units 1 and 2
    Units 1 and 2 at Plant Daniel, located in Escatawpa, Mississippi,
and owned and operated by Mississippi Power Company, have been
identified by MDEQ as BART-eligible. Plant Daniel is approximately 63
km northeast of Breton. Plant Daniel is an electric generating facility
with two coal-fired steam EGUs. Each of the units have the potential to
emit over 250 tpy of SO2, NOX, and
PM10. Plant Daniel controls SO2 emissions from
these units through scrubbers (i.e., wet flue gas desulfurization (FGD)
systems) installed to comply with EPA's Mercury and Air Toxics
Standards (MATS).\36\ Scrubber operation began in September 2015.
Mississippi Power Company performed updated CALPUFF modeling on Units 1
and 2 using recent emissions data (i.e., from September 2015-August
2018) and the current EPA-approved version of CALPUFF. The modeling
analysis predicted a maximum annual 98th percentile 24-hour average
visibility impact of 0.39 dv over the three years modeled, and a 22nd
highest day's visibility impact over all three years of 0.33 dv. MDEQ
concluded that Plant Daniel's Units 1 and 2 are not subject to BART,
and thus, no further BART analysis is required because the 98th
percentile 24-hour average visibility impact of 0.39 dv is below the
State's 0.5 dv contribution threshold for BART.
---------------------------------------------------------------------------

    \36\ See June 15, 2020, email from MDEQ to EPA Region 4 that
includes an October 30, 2015 title V permit renewal application
addendum for Plant Daniel addressing MATS requirements. These
documents are included in the docket for this proposed action.
---------------------------------------------------------------------------

3. Entergy Mississippi Inc.--Baxter Wilson Plant Units 1 and 2
    Units 1 and 2 at Baxter Wilson, located in Vicksburg, Mississippi,
and owned and operated by Entergy Mississippi, Inc., have been
identified by MDEQ as BART-eligible. Baxter Wilson is located
approximately 310 km northwest of Breton. Baxter Wilson is an electric
generating facility that currently has one natural gas-fired unit (Unit
1). The initial CALPUFF modeling was performed in 2012 with CALPUFF
version 5.8 Level 070623. The modeling used the maximum 24-hour
emissions rates over the three-year baseline period of 2001-2003
assuming that both Units 1 and 2 fired only natural gas. This modeling
indicated a maximum 98th percentile 24-hour impact of 0.49 dv over the
three years modeled and a 22nd highest day's visibility impact over all
three years of 0.39 dv, both of which are below the contribution
threshold of 0.5 dv.
    Since the modeling was performed, the facility has undergone
changes. Unit 1 at Baxter Wilson originally was a dual fuel oil and
gas-fired unit, but the fuel oil tanks have been rendered unusable, and
the capability to burn fuel oil is in the process of being removed.\37\
Unit 2, the larger unit, permanently retired thereby reducing
SO2, NOX, and PM emissions from the plant.\38\
Given these changes and the fact that the original modeling was
conducted years ago, MDEQ also performed a supplemental emissions
analysis for this facility. MDEQ compared more current (2016-2018)
SO2, NOX, and PM10 emissions values
from annual emissions reports submitted by Baxter Wilson with the 2001-
2003 baseline emissions values and showed that recent emissions have
remained roughly equivalent to or decreased relative to the baseline
period modeled. Therefore, MDEQ concluded that it is not necessary to
remodel using recent emissions. Table 4 compares the maximum 24-hour
emissions rates for 2001-2003 that were modeled with updated rates for
2016-2018. Because the facility can no longer burn fuel oil, all
emissions values in Table 4 reflect the burning of natural gas. The
State found that the combined current emissions rates from Units 1 and
2 have decreased considerably relative to the baseline values modeled
for SO2, NOX, and PM10 because Unit 2
has shut down. In particular, current NOX emissions rates
are approximately one-fifth of the modeled emissions rates.
---------------------------------------------------------------------------

    \37\ See May 27, 2020, email from MDEQ to EPA Region 4 that
includes a September 8, 2019, letter providing an update on the
removal of fuel oil capabilities at Gerald Andrus and Baxter Wilson.
These documents are included in the docket for this proposed action.
    \38\ Unit 2 at Baxter Wilson was decommissioned in June 2018. A
copy of the Acid Rain and CSAPR Trading Programs Retired Unit
Exemption Form is located in Appendix L.7.2 of the draft BART SIP.
---------------------------------------------------------------------------

    In addition, Table 5 compares the annual baseline emissions of
2001-2003 to 2016-2018 annual emissions. Table 5 reflects annual
emissions from burning both natural gas and fuel oil. MDEQ concludes
that the current annual emissions are much less than the baseline
emissions for all pollutants.

                        Table 4--Baxter Wilson Modeled 2001-2003 and 2016-2018 Maximum 24-Hour Emissions Rates--Natural Gas Only
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Maximum 24-hour emissions rates (lb/hr) (2001-  Maximum 24-hour emissions rates (lb/hr) (2016-
                                                                               2003)                                           2018)
                      Emission unit                      -----------------------------------------------------------------------------------------------
                                                                SO2             NOX            PM10             SO2             NOX            PM10
--------------------------------------------------------------------------------------------------------------------------------------------------------
Unit 1..................................................            2.71           2,030           35.69            3.67           1,337           36.17
Unit 2..................................................            2.40           4,674           49.77               0               0               0
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................            5.11           6,704           85.46            3.67           1,337           36.17
--------------------------------------------------------------------------------------------------------------------------------------------------------

 Table 5--Baxter Wilson Baseline (2001-2003) and Current (2016-2018) Period Annual Emissions Comparison--Natural
                                                Gas and Fuel Oil
----------------------------------------------------------------------------------------------------------------
                                                                          Combined annual emission (tons)
                              Year                               -----------------------------------------------
                                                                        SO2             NOX            PM10
----------------------------------------------------------------------------------------------------------------
2001............................................................       34,117.18       14,274.82        2,796.09
2002............................................................            8.34        6,375.26          102.94
2003............................................................            1.99        1,325.02           24.51
2016............................................................            2.49        1,550.71           25.19
2017............................................................            2.65          794.41           25.06
2018............................................................            3.08        1,111.63           34.08
----------------------------------------------------------------------------------------------------------------

    MDEQ concluded that Baxter Wilson is not subject to BART, and no
further BART analysis is required because the maximum 98th percentile
24-hour average visibility impact of 0.49 dv is below the State's 0.5
dv contribution threshold for BART, and recent maximum 24-hour
emissions rates and annual emissions of SO2, NOX,
and PM have declined since the 2001-2003 modeled baseline period.
4. Entergy Mississippi Inc.--Gerald Andrus Plant Unit 1
    Gerald Andrus Unit 1, located in Greenville, Mississippi, and owned
and operated by Entergy Mississippi, Inc., has been identified by MDEQ
as BART-eligible. Gerald Andrus is located approximately 290 km east of
Caney Creek. Gerald Andrus is an electric generating facility that
currently has one natural gas-fired unit (Unit 1). The initial CALPUFF
modeling performed in 2012 for Unit 1 using CALPUFF Version 5.8 Level
070623 was based on Unit 1 only firing natural gas. This modeling
demonstrated a maximum 98th percentile 24-hour average visibility
impact over the three years modeled of 0.15 dv and a 22nd highest day's
visibility impact over all three years of 0.12 dv based on burning
natural gas.
    As with Baxter Wilson, the facility has undergone changes since the
original modeling. Namely, Unit 1 at Gerald Andrus originally was a
dual fuel oil- and gas-fired unit. As of April 23, 2020, Gerald Andrus
removed the capability to utilize fuel oil.\39\ Given this change and
the fact that the original modeling was conducted years ago, MDEQ also
performed a supplemental emissions analysis for this facility. MDEQ
compared more current (2016-2018) SO2, NOX, and
PM10 emissions values from annual emissions reports
submitted by Gerald Andrus with the 2001-2003 baseline emissions values
and showed that recent emissions have remained roughly equivalent to or
decreased relative to the baseline period modeled. Therefore, MDEQ
concluded that it is not necessary to remodel using recent emissions.
The comparison of 2001-2003 modeled maximum 24-hour emissions rates to
updated 2016-2018 maximum 24-hour emissions rates of SO2,
NOX, and PM10 is shown in Table 6. Because the
facility has removed the ability to burn fuel oil, all emissions values
in Table 6 reflect the burning of natural gas. The State's evaluation
found that the maximum 24-hour SO2 emissions rates from
2016-2018 were essentially the same as the modeled value (approximately
3.8 lb/hr vs. 3.7 lb/hr), and that recent maximum 24-hour
PM10 and NOX emissions rates were less than the
modeled emissions rates. In addition, Table 7 compares the annual 2001-
2003 baseline emissions to 2016-2018 annual emissions of
SO2, NOX, and PM10. Table 7 reflects
annual emissions from burning both natural gas and fuel oil. MDEQ
concluded that the current annual emissions are much less than the
baseline emissions for all pollutants.
---------------------------------------------------------------------------

    \39\ See May 27, 2020, email from MDEQ to EPA Region 4 with a
September 8, 2019, letter providing an update on the removal of fuel
oil capabilities at Gerald Andrus and Baxter Wilson. These documents
are included in the docket for this proposed action.

                        Table 6--Gerald Andrus Modeled 2001-2003 and 2016-2018 Maximum 24-Hour Emissions Rates--Natural Gas Only
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Maximum 24-hour emissions rates (lb/hr) (2001-  Maximum 24-hour emissions rates (lb/hr) (2016-
                                                                               2003)                                           2018)
                      Emission unit                      -----------------------------------------------------------------------------------------------
                                                                SO2             NOX            PM10             SO2             NOX            PM10
--------------------------------------------------------------------------------------------------------------------------------------------------------
Unit 1..................................................            3.66           3,971            54.2            3.83           1,813           47.13
--------------------------------------------------------------------------------------------------------------------------------------------------------

 Table 7--Gerald Andrus Baseline (2001-2003) and Current (2016-2018) Period Annual Emissions Comparison--Natural
                                                Gas and Fuel Oil
----------------------------------------------------------------------------------------------------------------
                                                                          Combined annual emission (tons)
                              Year                               -----------------------------------------------
                                                                        SO2             NOX            PM10
----------------------------------------------------------------------------------------------------------------
2001............................................................       32,725.12        8,417.70        2,108.27
2002............................................................            8.44        4,809.19          103.72
2003............................................................       12,568.21        6,626.94        1,096.43
2016............................................................            2.22          763.67           26.36
2017............................................................            1.53          436.82           17.26
2018............................................................            3.15        1,138.78           36.39
----------------------------------------------------------------------------------------------------------------

    MDEQ concluded that Gerald Andrus is not subject to BART, and no
further BART analysis is required because the 98th percentile 24-hour
average visibility impact of 0.15 dv is well below the State's 0.5 dv
threshold contribution for BART, 2016-2018 annual emissions of
SO2, NOX, and PM have declined from 2001-2003
levels, and the maximum 24-hour emissions rates of SO2,
NOX, and PM10 have remained equivalent to
(SO2) or lower than (NOX and PM10)
those in the 2001-2003 modeled baseline period.
5. Cooperative Energy--R. D. Morrow Sr. Generating Plant Units 1 and 2
    Plant Morrow Units 1 and 2, located in Purvis, Mississippi, and
owned and operated by Cooperative Energy, were previously identified by
MDEQ as BART-eligible. Plant Morrow is located approximately 138 km
from Breton. On November 17, 2018, Units 1 and 2 were permanently
retired.\40\ MDEQ concluded that there are no other units at Plant
Morrow that are BART-eligible, and therefore, the facility has no
further BART obligations.
---------------------------------------------------------------------------

    \40\ A copy of the Acid Rain and CSAPR Trading Programs Retired
Unit Exemption Form is located in Appendix L.4.2 of the draft BART
SIP.
---------------------------------------------------------------------------

6. Cooperative Energy--Plant Moselle Unit 3
    Plant Moselle Unit 3, located in Moselle, Mississippi, and owned
and operated by Cooperative Energy, has been identified by MDEQ as
BART-eligible. Plant Moselle is located approximately 170 km north of
Breton. Plant Moselle is an electric generating facility that currently
has one natural gas-fired unit (Unit 3). Plant Moselle conducted
CALPUFF modeling for Unit 3 in 2011 using CALPUFF Version 5.8 Level
070623. The modeling analysis demonstrated a maximum 98th percentile
24-hour average visibility impact over the three years modeled of 0.05
dv, and a 22nd highest day's visibility impact over all three years of
0.042 dv.
    Given that the original modeling was conducted years ago, MDEQ also
performed a supplemental emissions analysis for this facility. MDEQ
compared more current (2016-2018) SO2, NOX, and
PM10 emissions values from annual emissions reports
submitted by Plant Moselle with the 2001-2003 baseline emissions values
and showed that recent emissions have remained roughly equivalent to or
decreased relative to the baseline period modeled. Therefore, MDEQ
concluded that it is not necessary to remodel using recent emissions.
The comparison of modeled 2001-2003 maximum 24-hour emissions rates of
SO2, NOX, and PM10 to updated 2016-
2018 maximum 24-hour emissions rates is shown in Table 8. The State's
evaluation found that the 2016-2018 maximum 24-hour SO2
emissions rate was equivalent to the modeled value (0.25 lb/hr vs. 0.24
lb/hr). MDEQ notes maximum 24-hour average NOX and
PM10 emissions rates from 2016-2018 are less than the
modeled emissions rates. In addition, Table 9 compares the annual 2001-
2003 baseline emissions of SO2, NOX, and
PM10 to 2016-2018 annual emissions. MDEQ concluded that the
2016-2018 annual emissions of SO2, NOX, and
PM10 are less than the baseline emissions.

                                 Table 8--Plant Moselle Modeled 2001-2003 and 2016-2018 Maximum 24-Hour Emissions Rates
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Maximum 24-hour emissions rates emissions (lb/  Maximum 24-hour emissions rates emissions (lb/
                                                                          hr) (2001-2003)                                 hr) (2016-2018)
                 Emissions period (date)                 -----------------------------------------------------------------------------------------------
                                                                SO2             NOX            PM10             SO2             NOX            PM10
--------------------------------------------------------------------------------------------------------------------------------------------------------
Unit 3..................................................            0.24          245.25            6.50            0.25          217.25            3.21
--------------------------------------------------------------------------------------------------------------------------------------------------------

     Table 9--Plant Moselle Baseline (2001-2003) and Current (2016-2018) Period Annual Emissions Comparison
----------------------------------------------------------------------------------------------------------------
                                                                              Annual emissions (tons)
                              Year                               -----------------------------------------------
                                                                        SO2             NOX            PM10
----------------------------------------------------------------------------------------------------------------
2001............................................................            0.85          249.56            6.59
2002............................................................            0.63          317.39            7.80
2003............................................................            0.56          344.65            6.93
2016............................................................            0.11           56.35            1.37
2017............................................................            0.09           43.42            1.14
2018............................................................            0.11           58.79            1.36
----------------------------------------------------------------------------------------------------------------

    MDEQ concluded that Plant Moselle is not subject to BART, and no
further BART analysis is required because the 98th percentile 24-hour
average visibility impact of 0.05 dv is well below the State's 0.5 dv
contribution threshold for BART, 2016-2018 annual emissions of
SO2, NOX, and PM10 have declined from
2001-2003 levels, and maximum 24-hour emissions rates of
SO2, NOX and PM10 have remained
equivalent to (SO2) or declined (NOX and
PM10) since the 2001-2003 baseline period modeled.
7. Mississippi Power Company--Plant Watson Units 4 and 5
    Plant Watson Units 4 and 5, located in Gulfport, Mississippi, and
owned and operated by Mississippi Power Company, have been identified
by MDEQ as being BART-eligible. Plant Watson is 45 km from Breton.
Plant Watson is an electric generating facility that has two natural-
gas fired units (Units 4 and 5). These units were previously capable of
firing coal and fuel oil. Plant Watson conducted CALPUFF modeling in
2012 for Units 4 and 5 using CALPUFF Version 5.8 Level 070623 and
assuming that these units would convert to firing only natural gas. The
modeling analysis demonstrated a maximum 98th percentile 24-hour
average visibility impact of 0.48 dv over the three years modeled, and
a 22nd highest day's visibility impact over all three years of 0.46 dv.
Since the 2012 CALPUFF modeling was conducted, Units 4 and 5 were
modified in 2015 by removing all liquid burning equipment and
dismantling the coal handling systems. Now both units are physically
limited to burn natural gas only.\41\ Although the 2012 modeled values
are below the State's contribution threshold for sources that are
subject to BART, these changes at Plant Watson reduced annual emissions
of visibility-impairing pollutants such that the source elected to
model using more recent emissions. On behalf of Mississippi Power
Company, Southern Company Services performed updated CALPUFF modeling
on Units 1 and 2 using current emissions (i.e., 2017-2019) and the
current EPA-approved version of CALPUFF. The modeling analysis
predicted a maximum annual 98th percentile 24-hour average visibility
impact of 0.44 dv over the three years modeled, and a 22nd highest
day's visibility impact over all three years of 0.41 dv. MDEQ concluded
that Plant Watson's Units 4 and 5 are not subject to BART, and thus, no
further BART analysis is required because the 98th percentile 24-hour
average visibility impact of 0.44 dv is below the State's 0.5 dv
contribution threshold for BART.
---------------------------------------------------------------------------

    \41\ In an April 9, 2015, letter to MDEQ, Mississippi Power
Company requested a modification to its title V permit for Plant
Watson to reflect actions to render Units 4 and 5 incapable of
combusting any solid or liquid fuels. These activities included the
removal of liquid fuel burning equipment and the permanent
dismantlement of the coal handling system. MDEQ issued a revised
title V permit and acid rain permit on December 29, 2016. These
documents are located in the docket for this proposed action for
informational purposes.
---------------------------------------------------------------------------

B. EPA's Evaluation of Mississippi's BART SIP

1. Overview
    EPA proposes to find that the draft BART SIP corrects the
deficiencies arising from Mississippi's prior reliance on CAIR to meet
certain regional haze requirements that resulted in EPA's limited
disapproval of Mississippi's regional haze plan. Because this was the
sole deficiency leading to EPA's prior limited disapproval, the Agency
is also proposing to withdraw that limited disapproval and to fully
approve the State's regional haze SIP.
    As discussed above, Plant Morrow's BART-eligible Units 1 and 2
permanently retired in 2018, and EPA therefore proposes to approve the
State's finding that this source is exempt from further BART analysis.
The remaining six facilities all modeled below the State's BART
contribution threshold of 0.5 dv. As explained previously, modeling for
four facilities (Baxter Wilson, Gerald Andrus, Plant Chevron, and Plant
Moselle) was conducted in the early 2010s with earlier versions of
CALPUFF. For these facilities, EPA evaluated potential impacts of
changes to the CALPUFF modeling system, and, as discussed in Section
III.B.2, EPA believes that the modeling system changes do not
significantly affect the modeling results for these sources. In
addition, EPA agrees with the State's analyses of the modeling results
and the supplemental emissions analyses, as discussed in Section
III.B.3, below. Thus, EPA proposes to approve the State's determination
that Baxter Wilson, Gerald Andrus, Plant Chevron, Plant Daniel, Plant
Moselle, and Plant Watson are not subject to BART, and no further BART
analysis is required of these sources.
2. Assessment of CALPUFF Modeling System Changes
    MDEQ opted to rely on existing BART exemption modeling for four
sources, Baxter Wilson, Gerald Andrus, Plant Chevron, and Plant
Moselle, which utilized older versions of the CALPUFF modeling system.
For this reason, EPA assessed whether the updates to the CALPUFF
modeling system could affect the modeling results for these four
sources such that they would become subject to BART. EPA first
considered the changes to the CALPUFF modeling system and an earlier
analysis prepared by an EPA contractor, and found that these changes
are generally unlikely to result in significant differences in modeled
visibility impacts. Second, EPA analyzed Plant Watson's modeling
results under both the current CALPUFF model and the older version of
the model used by Baxter Wilson, Gerald Andrus, and Plant Moselle. This
analysis accounts for the significant similarities between the
emissions profiles of Plant Watson and the other plants, and further
corroborates that using the updated CALPUFF model is unlikely to result
in the other plants becoming subject to BART. Thus, EPA proposes to
find that it is not necessary

to remodel Baxter Wilson, Gerald Andrus, Plant Chevron, and Plant
Moselle using the current EPA-approved version of CALPUFF.
CALPUFF Modeling System Versions Used for Mississippi's BART-Eligible
Sources
    The initial BART exemption modeling utilized CALPUFF and CALMET
Version 5.8 Level 070623 for all sources except Plant Chevron, which
utilized CALPUFF version 5.754 Level 060202 and CALMET version 5.7. The
EPA-approved version of the CALPUFF modeling system has since been
updated to Version 5.8.5 Level 151214.\42\ Specific updates to the
CALPUFF and CALMET models since Version 5.8 are summarized below:
---------------------------------------------------------------------------

    \42\ See EPA, CALPUFF Modeling System, available at: https://www3.epa.gov/ttn/scram/7thconf/calpuff/Previous_SCRAM_CALPUFF_
Posting_Reference.pdf.
---------------------------------------------------------------------------

     December 4, 2013--CALPUFF and CALMET updated from Version
5.8 to Version 5.8.4 Level 130731. Changes are described in Model
Change Bulletins E, F, and G.\43\ This update included bug fixes only
and no enhancements or new features.
---------------------------------------------------------------------------

    \43\ Bulletins E, F, and G are available at https://www3.epa.gov/ttn/scram/models/calpuff/calpuff_mcb_e.txt, https://www3.epa.gov/ttn/scram/models/calpuff/calpuff_mcb_f.txt, and https://www3.epa.gov/ttn/scram/models/calpuff/calpuff_mcb_g.txt,
respectively.
---------------------------------------------------------------------------

     July 26, 2016--CALPUFF and CALMET updated to Version 5.8.5
Level 151214 which is the current EPA-approved version of the models.
This was the version of CALUFF used in revised modeling for Plants
Watson and Daniel. Changes are described in Model Change Bulletin
H.\44\ This update included program fixes to the PRIME downwash
algorithm along with updates to eliminate specific compilation and list
file errors.
---------------------------------------------------------------------------

    \44\ https://www3.epa.gov/ttn/scram/models/calpuff/calpuff_mcb_h.txt.
---------------------------------------------------------------------------

    A December 3, 2013, memorandum prepared by an EPA contractor
summarized the changes to the CALPUFF modeling system described in
Model Change Bulletins E, F, and G, and the potential effect of those
changes on predicted pollutant impacts for several scenarios and source
types.\45\ This memorandum broadly concluded that the changes to the
CALPUFF modeling system resulted in no difference, or almost no
difference (+/- 1 percent (%)), in predicted values for most scenarios
and source types evaluated.
---------------------------------------------------------------------------

    \45\ AMEC, AERMOD Technical Assistance--Modification of CALPUFF
and CALMET Final Report (December 3, 2013), available at: https://www3.epa.gov/ttn/scram/models/calpuff/CALPUFF_Update_Memo_12032013.pdf.
---------------------------------------------------------------------------

    In addition to the differences in CALPUFF versions, three sources
(Baxter Wilson, Gerald Andrus, and Plant Chevron) used Version 6.292
Level 110406 of the CALPOST processor (one of the components of the
CALPUFF modeling framework), while four sources (Plant Daniel, Plant
Morrow, Plant Moselle, and Plant Watson) used Version 6.221 Level
080724. Use of either version of CALPOST is consistent with EPA policy
in this context.\46\
---------------------------------------------------------------------------

    \46\ This context refers to calculating visibility using the new
IMPROVE equation through CALPOST Method 8. See p.71 of the November
2012 Plant Watson modeling report (Appendix B). This modeling report
is included in the docket for this rulemaking. The IMPROVE Equation
is available at: http://npshistory.com/publications/air-quality/flag-2010.pdf.
---------------------------------------------------------------------------

Further Evaluation of CALPUFF Model Changes at Baxter Wilson, Gerald
Andrus, Plant Chevron, and Plant Moselle
    EPA also performed a specific assessment of the potential impacts
of these updates to the EPA-approved version of the CALPUFF modeling
system on the visibility results for Baxter Wilson, Gerald Andrus,
Plant Chevron, and Plant Moselle. Because the emissions profile and
visibility impact for Plant Watson is similar to these four sources,
and Plant Watson also used an earlier version of CALPUFF, EPA analyzed
Plant Watson modeling information using the earlier and current
versions of CALPUFF as a point of comparison to illustrate the effect
of the CALPUFF model changes. Emissions from Baxter Wilson, Gerald
Andrus, Plant Chevron, and Plant Moselle were all dominated primarily
by NOX and secondarily by PM10, similar to Plant
Watson. The predicted visibility impacts from these five facilities on
the nearest Class I areas were dominated by NOX emissions,
accounting for 86% of the visibility impacts from Plant Watson and 90%
to 98% of the visibility impacts from the remaining facilities.\47\ The
magnitude of NOX emissions from Baxter Wilson, Gerald
Andrus, and Plant Watson are greater than the magnitude of
NOX emissions from Plants Chevron and Moselle. With the
noted similarities in the emissions profiles and predicted visibility
impacts in the initial modeling performed for these facilities, the
updated modeling performed for Plant Watson using the current EPA-
approved version of CALPUFF and recent emissions data provides insight
on the potential effects of updates to the CALPUFF modeling system on
predicted visibility impacts for Baxter Wilson, Gerald Andrus, Plant
Chevron, and Plant Moselle.
---------------------------------------------------------------------------

    \47\ Breton is the nearest Class I area for Plant Watson, Baxter
Wilson, Plant Chevron, and Plant Moselle, and Caney Creek is the
nearest Class I area for Gerald Andrus.
---------------------------------------------------------------------------

    The modeling performed for Plant Watson in 2020 using 2017-2019
emissions data and the current EPA-approved version of CALPUFF
indicated similar visibility impacts as those predicted by the 2012
modeling: 91% of the visibility impacts at Breton due to the facility
are the result of NOX emissions, 8% of the visibility
impacts are the result of PM10 emissions, and only 1% of the
visibility impacts are the result of SO2 emissions. A
comparison of emissions utilized in the initial modeling for Plant
Watson compared to the emissions utilized in the revised modeling for
Plant Watson is presented in Table 10 along with the contribution to
visibility impacts from each pollutant.

                    Table 10--Emissions Rates Modeled and Visibility Impacts for Plant Watson
----------------------------------------------------------------------------------------------------------------
                                                                                Change in 2012
                                   2012 Modeling   2020 Modeling   2012 Modeling   2020 Modeling      to 2020
            Pollutant              contribution    contribution   emissions rate  emissions rate      modeled
                                   to visibility   to visibility      (lb/hr)         (lb/hr)        emissions
                                    impacts (%)     impacts (%)                                      rates (%)
----------------------------------------------------------------------------------------------------------------
SO2.............................               1               1            4.99            4.08             -18
NOX.............................              86              91        2,491.39        2,141.34             -14
PM10............................              13               8           62.32           66.94              +7
----------------------------------------------------------------------------------------------------------------

    The 2017-2019 emissions rates used in the 2020 BART exemption
modeling for Plant Watson changed relative to the 2003-2005 emissions
rates used in the source's initial 2012 modeling as follows:
NOX emissions decreased by 14%; PM10 emissions
increased by 7%; and SO2 emissions decreased by 18%; in
addition, SO2 emissions remained substantially lower than
NOX and PM10 emissions.
    The 2020 modeling for Plant Watson indicated that the maximum 98th
percentile 24-hour average visibility impact at Breton over the three
years modeled decreased by 10% relative to the initial 2012 modeling.
The 2020 modeling also indicated that the 22nd highest day's visibility
impact over the three years modeled decreased by 11% relative to the
initial 2012 modeling. This information is presented in Table 11. Table
11 indicates that the 10-11% reduction in predicted visibility impacts
is closely correlated to the 14% reduction in the NOX
emissions rate. These results suggest that the reductions in predicted
visibility impacts are primarily due to the 14% reductions in
NOX emissions rather than the updates to CALPUFF.

                  Table 11--Comparison of Initial Modeling to Revised Modeling for Plant Watson
----------------------------------------------------------------------------------------------------------------
                                                     Max 98th      22nd highest
                                                    percentile      day over 3     NOX emissions  PM10 emissions
                                                   over 3 years    years modeled   rate (lb/hr)    rate (lb/hr)
                                                   modeled (dv)        (dv)
----------------------------------------------------------------------------------------------------------------
Initial 2012 Modeling...........................           0.482           0.457         2,491.4            62.3
Revised 2020 Modeling...........................           0.436           0.408         2,141.3            66.9
2012 to 2020 Change (%).........................           -9.5%          -10.7%          -14.1%           +7.4%
----------------------------------------------------------------------------------------------------------------

    The updated modeling performed for Plant Watson using the current
EPA-approved version of CALPUFF and recent emissions data suggests that
the updates to the CALPUFF model did not significantly affect predicted
visibility impacts for Plant Watson. Instead, the predicted changes in
visibility from Plant Watson between the initial and revised modeling
appear to be driven by NOX emissions reductions. With the
noted similarities in the emissions profiles and predicted visibility
impacts between Plant Watson and Baxter Wilson, Gerald Andrus, Plant
Chevron, and Plant Moselle, the updates to CALPUFF are also not
expected to have a significant impact on predicted visibility impacts
from these other facilities. Revised modeling performed with the
current EPA-approved version of CALPUFF and recent emissions for these
facilities would likely result in visibility impacts the same as or
less than the values from the 2011/2012 modeling shown in Table 12
because recent emissions have either remained equivalent to or
decreased since the 2011/2012 modeling. Therefore, the reduction in
NOX and PM10 emissions shown in Table 12 would
suggest a corresponding decrease in visibility impact at the nearest
Class I area.

 Table 12--2011/2012 Visibility Modeling Results and Changes in Recent NOX and PM10 Emissions for Baxter Wilson, Gerald Andrus, Plant Chevron, and Plant
                                                                         Moselle
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                NOX         Percent (%)        PM10
                                                                             2011/2012     contribution    change in NOX   contribution   Percent change
                 Facility                       Nearest class I area        modeled DV     to visibility  emissions \49\   to visibility      in PM10
                                                                            impact \48\     impact (%)                      impact (%)    emissions \50\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Baxter Wilson.............................  Breton......................            0.49              96             -80               3             -58
Gerald Andrus.............................  Caney Creek.................            0.15              98             -54               2             -13
Plant Chevron.............................  Breton......................            0.27              90             -25               9               0
Plant Moselle.............................  Breton......................            0.05              92             -11               7             -57
--------------------------------------------------------------------------------------------------------------------------------------------------------

    As previously noted, Plant Chevron used a different version of
CALPUFF (Version 5.754) than Plant Watson used in its initial modeling
(Version 5.8). While EPA did not specifically analyze the changes from
CALPUFF Version 5.754 to 5.8 (or from 5.754 to the current version),
EPA nonetheless believes that updating the modeling for Plant Chevron
is not necessary. As previously shown, the updates to Version 5.8 of
the CALPUFF model did not significantly affect predicted visibility
impacts for Plant Watson. Instead, the predicted changes in visibility
from Plant Watson between the initial and revised modeling appear to be
driven by NOX emissions reductions. If EPA assumes a similar
relationship also holds true for Plant Chevron, then the Agency would
expect updated modeling to show decreased visibility impact for Plant
Chevron. That is, the 2011 modeling for Plant Chevron indicated a
maximum 98th percentile 24-hour impact of 0.27 dv over the three years
modeled, which is well below the value of 0.5 dv. The reduction in
NOX emissions shown in Table 12 for Plant Chevron would
suggest a corresponding decrease in visibility impact at Breton.
Specifically, if EPA assumed that any visibility impact changes would
be solely due to changes in NOX emissions, then the
visibility impact of updated modeling would be approximately 0.21
dv.\51\ In

addition, while EPA is not aware of evidence indicating that CALPUFF
Version 5.754 underpredicts visibility impacts relative to the current
CALPUFF version, even were this to be true, the Agency thinks it is
extremely unlikely that would cause the visibility impact to rise above
0.5 dv, given that Plant Chevron initially modeled 0.27 dv and the
subsequent emission reductions at the source.
---------------------------------------------------------------------------

    \48\ The maximum 98th percentile 24-hour visibility impact over
the three years modeled.
    \49\ Percent decrease in NOX emissions from the
emissions used in the 2012 modeling to emissions that would be used
in the 2020 modeling. Detailed emissions data for each of the four
facilities are presented in Section III.A.
    \50\ Percent decrease in PM10 emissions from the
emissions used in the 2012 modeling to emissions that would be used
in the 2020 modeling. Detailed emissions data for each of the four
facilities are presented in Section III.A.
    \51\ The basis for the estimated impact of 0.21 dv due to
NOX reductions alone is as follows. The 2011 CALPUFF
modeling for Plant Chevron indicated that 90% of visibility impacts
at Breton were from NOX emissions which equates to
approximately 0.243 dv (90% of the total estimated impact of 0.27
dv). The remaining 10% of visibility impacts are due to
PM10 and SO2 emissions which equates to
approximately 0.027 dv (10% of 0.27 dv). To approximate the impact
of the 25% reduction in NOX emissions from Plant Chevron,
EPA decreased the portion of the visibility impacts due to
NOX emissions (0.243 dv) by 25% (0.243 * (1-0.25) = 0.182
dv). The PM10 and SO2 portion of the
visibility impacts remains at 0.027 dv. Thus, the revised estimated
total visibility impact from Plant Chevron on Breton is 0.21 dv
(0.182 + 0.027 = 0.209 dv (rounded to 0.21)).
---------------------------------------------------------------------------

3. Evaluation of Supplemental Emissions Analyses and Operational
Changes at Baxter Wilson, Gerald Andrus, Plant Chevron, and Plant
Moselle
    EPA agrees with the supplemental emission analyses performed by
MDEQ for Baxter Wilson, Gerald Andrus, Plant Chevron and Plant Moselle.
Baxter Wilson
    Even though the 2012 modeling for Baxter Wilson indicated
visibility impacts below but near the 0.5 dv threshold (0.49 dv), there
have been operational changes that have significantly reduced the
emissions from this facility, including the shutdown of the larger of
the two units at this facility. These changes have resulted in
substantial reductions in both annual and maximum 24-hour emissions of
SO2, NOX, and PM10 relative to the
baseline period modeled as shown in Tables 4 and 5.
Gerald Andrus
    The 2012 modeling for the Gerald Andrus indicated visibility
impacts of 0.15 dv, which is well below the 0.5 dv threshold. As shown
in Table 6 above, recent maximum 24-hour emissions rates of
SO2 are essentially the same as those modeled in 2012 while
NOX and PM10 maximum 24-hour emissions rates have
decreased substantially. Overall the recent annual emissions of
SO2, NOX, and PM10 have drastically
reduced at Gerald Andrus as shown in Table 7.
Plant Chevron
    The 2011 modeling for Plant Chevron indicated visibility impacts of
0.27 dv, which is well below the 0.5 dv threshold. While recent annual
emissions of SO2 have increased relative to the baseline
period modeled, the magnitude of the facility's current maximum 24-hour
SO2 emissions rate remains relatively low (8 lb/hr) compared
to its NOX emissions rates (420 lb/hr) for all four units
combined (see Table 2), and CALPUFF predicted that visibility impacts
from Chevron were dominated by NOX emissions. During the
same period, maximum 24-hour NOX emissions rates have
decreased by about 25% while PM10 maximum 24-hour emissions
rates are essentially unchanged.
Plant Moselle
    The 2011 modeling for Plant Moselle indicated visibility impacts of
0.05 dv which is well below the 0.5 dv threshold. As shown in Table 8
above, recent maximum 24-hour emissions rates of NOX,
SO2, and PM10 are equivalent to or less than
those modeled in 2011.
    Based on the State's submission and EPA's analysis in this section
and Section III.B.2, EPA proposes to approve MDEQ's finding that the
four facilities (i.e., Baxter Wilson, Gerald Andrus, Plant Chevron, and
Plant Moselle) remain exempt from further BART review.
4. Evaluation of Updated Modeling at Plant Daniel and Plant Watson
    Plant Daniel and Plant Watson have updated BART exemption modeling
using current emissions of SO2, NOX, and PM to
reflect the emissions changes as a result of the operational changes at
each plant. The updated BART exemption modeling also used a newer
version of CALPUFF, which is the current EPA-approved version. EPA
believes the updated modeling analyses for Plant Daniel and Plant
Watson properly reflect additional emissions controls and operational
changes that have reduced emissions since the original modeling was
conducted. For both facilities, the updated modeling shows that the two
facilities model below the BART contribution threshold. Therefore, EPA
proposes to approve MDEQ's finding that these facilities are also
exempt from further BART review.
5. Federal Land Manager (FLM) Review
    MDEQ provided the draft BART SIP to the FLMs to review in
accordance with 40 CFR 51.308(i)(2), and the FLMs have not provided any
comments. MDEQ's draft BART SIP references the procedures for
continuing consultation between the State and FLMs on the
implementation of the State's visibility protection program in
accordance with 40 CFR 51.308(i)(4) that are contained in Section 11 of
the State's September 22, 2008, regional haze plan.\52\ These
procedures remain in effect for the draft BART SIP.
---------------------------------------------------------------------------

    \52\ The draft BART SIP references Section 10, but EPA believes
the State meant to refer to Section 11.
---------------------------------------------------------------------------

6. Summary
    In summary, EPA proposes to approve the draft BART SIP and finds
that it corrects the deficiencies that led to the limited approval and
limited disapproval of the State's regional haze SIP; to withdraw the
limited disapproval of Mississippi's regional haze SIP; and to fully
approve Mississippi's regional haze SIP as meeting all regional haze
requirements of the CAA for the first implementation period, replacing
the prior limited approval.

IV. Summary and EPA's Evaluation of Mississippi's Progress Report and
Adequacy Determination

A. Regional Haze Progress Report

    This section includes EPA's analysis of Mississippi's Progress
Report and an explanation of the basis for the Agency's proposed
approval. EPA cannot take final action to approve Mississippi's
Progress Report unless the Agency finalizes its proposal to approve the
draft BART SIP because the existing regional haze SIP contains a
deficiency in its current strategy to achieve RPGs.
1. Control Measures
    In its Progress Report, Mississippi summarizes the status of the
emissions reduction measures that were relied upon by the State in its
regional haze plan. The measures include, among other things,
applicable federal programs (e.g., federal consent agreements, federal
control strategies for EGUs, Maximum Achievable Control Technology
standards, and mobile source rules). Additionally, MDEQ highlighted
control programs and measures that were not relied upon in its regional
haze plan which provide further assurances that visibility impacts from
Mississippi's sources are addressed (e.g., EPA's MATS Rule and measures
taken by certain sources to address the 2010 1-hour SO2
NAAQS). In the Progress Report, MDEQ also reviewed the status of BART
requirements for the non-EGU BART-subject sources in the State--Chevron
Pascagoula Refinery (Chevron Refinery) and Mississippi Phosphates
Corporation (MPC)--both located in Pascagoula, Mississippi, and notes
that it will address BART for the aforementioned BART-eligible EGUs in
a separate SIP submittal.\53\
---------------------------------------------------------------------------

    \53\ Subsequent to submittal of the Progress Report, Mississippi
addressed EGU BART in its draft BART SIP, which is discussed in
Section III of this notice.

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

    As discussed in Section II of this notice, a number of states,
including Mississippi, submitted regional haze plans that relied on
CAIR to meet certain regional haze requirements. EPA finalized a
limited disapproval of Mississippi's regional haze plan due to this
reliance on CAIR. In its draft BART SIP, Mississippi determined that
none of its seven BART-eligible facilities with EGUs formerly subject
to CAIR are subject to BART.
    Mississippi's draft BART SIP explains the status of each BART-
eligible EGU formerly subject to CAIR. Table 1 identifies the 14 BART-
eligible units (located at seven facilities) and the highest modeled
impact at the nearest Class I area for each facility. Section III of
this notice explains the status of each BART-eligible EGU in greater
detail.
    In the State's regional haze plan and Progress Report, Mississippi
focuses its assessment on SO2 emissions from coal-fired
boilers at EGUs and industrial boilers because of VISTAS' findings that
ammonium sulfate accounted for 69-87% of the visibility-impairing
pollution in all of the VISTAS states, except one coastal area, based
on 2000 to 2004 data. The emissions sensitivity analyses conducted by
VISTAS predicted that reductions in SO2 emissions from EGU
and non-EGU industrial point sources would result in the greatest
improvements in visibility in the Class I areas in the VISTAS region,
more than any other visibility-impairing pollutant. Thus, Mississippi
concluded that reducing SO2 emissions from EGU and non-EGU
point sources would have the greatest visibility benefits for the Class
I areas impacted by Mississippi sources.\54\
---------------------------------------------------------------------------

    \54\ See 77 FR 11887 (February 28, 2012).
---------------------------------------------------------------------------

    Because many states had not yet defined their criteria for
identifying sources to evaluate for reasonable progress at the time
Mississippi was developing its September 22, 2008, regional haze plan,
Mississippi initially applied its criteria for identifying emissions
units eligible for a reasonable progress control analysis as a
screening tool to identify Class I areas outside of the State
potentially impacted by Mississippi sources.\55\ Mississippi only
identified SO2 emissions from E.I. DuPont Delisle (DuPont)
and Plant Watson as potentially impacting visibility at Breton in
Louisiana for reasonable progress during the first implementation
period.\56\ However, when Louisiana completed its reasonable progress
assessments and finalized its regional haze SIP submittal, it did not
identify any Mississippi sources as impacting Breton using Louisiana's
evaluation criteria. Thus, MDEQ concluded, and EPA agreed, that no
further evaluation of Dupont and Plant Watson was needed for reasonable
progress and MDEQ updated its 2008 regional haze plan in the May 9,
2011, amendment with this conclusion.\57\
---------------------------------------------------------------------------

    \55\ As noted earlier, Breton in Louisiana, Sipsey in Alabama,
and Caney Creek in Arkansas are the closest Class I areas to
Mississippi. With respect to reasonable progress, Louisiana,
Alabama, and Arkansas did not identify any Mississippi sources as
having an impact on the visibility at Breton, Sipsey, and Caney
Creek, respectively.
    \56\ See 77 FR 11888 (February 28, 2012). See also page 14 of
the Progress Report.
    \57\ See 77 FR 11888 (February 28, 2012).
---------------------------------------------------------------------------

    EPA proposes to find that Mississippi has adequately addressed the
applicable provisions under 40 CFR 51.308(g) regarding the
implementation status of control measures because the State described
the implementation of measures within Mississippi, including BART for
NOX, SO2, and PM at its BART-subject sources for
non-EGUs in its Progress Report and for EGUs in its draft BART SIP.
2. Emissions Reductions
    As discussed in Section IV.A.1. of this notice, Mississippi focused
its assessment in its regional haze plan and Progress Report on
SO2 emissions from coal-fired boilers at point sources in
Mississippi because of VISTAS' findings that ammonium sulfate is the
primary component of visibility-impairing pollution in the VISTAS
states based upon 2000 to 2004 data.\58\ In its Progress Report, MDEQ
provides a bar graph with Mississippi's EGU SO2 emissions
from 2002 to 2017 and states that these emissions have decreased from
65,741 tons in 2002 to 2,569 tons in 2017. MDEQ notes that these
emissions are trending downward overall, with significant decreases
from 2014 to 2016 (following increases in 2013 and 2014 due to
emissions from Plant Watson) and consistently low values in 2016 and
2017 due to the conversion of Plant Watson from coal to natural gas in
2015.\59\
---------------------------------------------------------------------------

    \58\ The Progress Report also documents that sulfates continue
to be the biggest single contributor to regional haze at Breton. See
Section IV.A.5 for additional information.
    \59\ The Progress Report identifies Plant Watson as ``Watson
Electric'' on page 10 in Figure 1 and in the associated note. The
Progress Report notes that Plant Watson converted to natural gas in
2014 on page 16; the correct date is 2015 as stated on page 10.
---------------------------------------------------------------------------

    Mississippi includes cumulative VOC, PM2.5,
PM10, SO2, and NOX emissions data from
2002, 2007, and 2014 for EGUs and non-EGUs in the State, along with the
2018 emissions projections from its 2008 regional haze plan. The 2007
actual emissions data were developed through the Southeastern Modeling,
Analysis and Planning (SEMAP) partnership. At the time of Progress
Report development, the 2014 National Emissions Inventory (NEI) was the
latest available inventory.\60\ EPA's NEI is a comprehensive and
detailed estimate of air emissions for criteria pollutants, criteria
pollutant precursors, and hazardous air pollutants from air emissions
sources that is updated every three years using information provided by
the states and other information available to EPA.\61\
---------------------------------------------------------------------------

    \60\ See EPA's website for additional data and documentation for
the 2014 version of the NEI (https://www.epa.gov/air-emissions-inventories/2014-national-emissions-inventory-nei-data).
    \61\ EPA's NEI is available at https://www.epa.gov/air-emissions-inventories/national-emissions-inventory.
---------------------------------------------------------------------------

    According to MDEQ, EGU emissions are near or below the 2018
projections for all pollutants except SO2. As noted in
Section III.A.7., Plant Watson converted from coal to natural gas in
2015, and the source's SO2 emissions dropped from 70,667
tons in 2014 to 5.1 tons in 2017 and 4.6 tons in 2018. MDEQ notes that
this change in emissions from 2014 to 2018 at Plant Watson brings the
State's EGU SO2 emissions closer to the 2018 value of 15,213
tons projected in the regional haze plan (see Table 13).\62\ The
emissions reductions identified by Mississippi are due, in part, to the
implementation of measures included in the State's regional haze plan.
---------------------------------------------------------------------------

    \62\ Progress Report, page 11, Table 3.
---------------------------------------------------------------------------

    Since the time of SIP development and submission, more recent
emissions data has become available for Mississippi's EGUs and non-EGUs
from the 2017 NEI, which are reflected in Tables 13 and 14. For
Mississippi's EGUs, actual emissions from the NEI for 2017 are below
the 2018 projected emissions shown in Table 13 for all pollutants
except VOC and NOX. Of particular note is that 2017 actual
SO2 emissions of the State's EGUs are well below (2,877 tpy)
the 2018 projected value of 15,213 tpy of SO2.

                            Table 13--EGU Emissions Inventory Summary for Mississippi
                                                      [tpy]
----------------------------------------------------------------------------------------------------------------
           Year/source                  VOC             NOX            PM2.5           PM10             SO2
----------------------------------------------------------------------------------------------------------------
2002 (VISTAS)...................             648          43,135           1,138           1,633          67,429
2007 (SEMAP)....................             669          48,150           1,426           2,165          75,563
2014 (NEI)......................             349          21,686           1,829           2,359          90,733
2018 (Projected)................           1,274          21,535           7,252           7,412          15,213
2017 (NEI)......................           2,515          30,214           2,752           3,213           2,877
----------------------------------------------------------------------------------------------------------------

    Emissions from the State's non-EGU point sources are below the 2018
emissions projections for all pollutants as shown in Table 14.

                          Table 14--Non-EGU Emissions Inventory Summary for Mississippi
                                                      [tpy]
----------------------------------------------------------------------------------------------------------------
           Year/source                  VOC             NOX            PM2.5           PM10             SO2
----------------------------------------------------------------------------------------------------------------
2002 (VISTAS)...................          43,204          61,526           9,906          19,472          35,960
2007 (SEMAP)....................          33,917          50,033           7,305          10,203          19,415
2014 (NEI)......................          28,885          31,761           9,363          10,769          13,450
2018 (Projected)................          45,335          61,252          10,719          22,837          25,674
2017 (NEI)......................          24,840          13,498           6,226           7,376           5,500
----------------------------------------------------------------------------------------------------------------

    Emissions data for 2018 has also become available for the State's
EGUs since the time that Mississippi submitted its Progress Report, and
EPA notes that Mississippi's EGUs emitted 3,189.7 tons of
SO2 in 2018,\63\ well below the projected 2018 value.
---------------------------------------------------------------------------

    \63\ Mississippi's EGUs emitted 13,041.3 tons of NOX
in 2018. See EPA's Air Markets Program Data website, located at:
https://ampd.epa.gov/ampd/.
---------------------------------------------------------------------------

    In the Progress Report, MDEQ also detailed emissions reductions at
the State's two non-EGU BART-subject sources, Chevron Refinery and MPC.
In the State's regional haze plan, Chevron Refinery and MPC modeled
visibility impacts at Breton of 3.89 dv and 0.81 dv, respectively. To
satisfy a 2005 consent decree, Chevron Refinery installed numerous
controls on its units by 2008 which resulted in a modeled visibility
improvement of 2.99 dv at Breton.\64\ With respect to MPC, the Progress
Report summarized the upgrades made at the source under a November 9,
2010, Permit to Construct Air Emissions Equipment that included Best
Available Control Technology emissions limits for SO2 and
sulfuric acid mist. The facility filed for bankruptcy on October 24,
2014, fully ceased operations in December of 2014, and has been
permanently shut down and declared a Superfund site.\65\
---------------------------------------------------------------------------

    \64\ See Progress Report, pp. 13-14 and the 2005 consent decree
in U.S. v. Chevron, available at: https://www.epa.gov/sites/production/files/documents/chevron-cd.pdf. Table 6 of the Progress
Report identifies emissions reductions from the BART-eligible units
covered by the consent decree.
    \65\ For more information on MPC as a Superfund site, see
https://cumulis.epa.gov/supercpad/SiteProfiles/index.cfm?fuseaction=second.Cleanup&id=0403508#bkground.
---------------------------------------------------------------------------

    Based on the information provided in the Progress Report, EPA
proposes to find that Mississippi has adequately addressed the
applicable provisions of 40 CFR 51.308(g) regarding emissions
reductions.
3. Visibility Conditions
    40 CFR 51.308(g)(3) requires that states with Class I areas within
their borders provide information on current visibility conditions and
the difference between current visibility conditions and baseline
visibility conditions expressed in terms of five-year averages of these
annual values. Because there are no Class I areas in Mississippi, the
State is not required to provide an assessment of visibility conditions
under 40 CFR 51.308(g)(3) as noted in the Progress Report.
4. Emissions Tracking
    In its Progress Report, Mississippi presents EGU SO2
emissions data (from 2002 to 2017), and data from statewide actual
emissions inventories for 2007 (SEMAP) and 2014 (NEI) and compares
these data to the baseline emissions inventory for 2002 (actual
emissions) and the projected emissions for 2018 from the State's
regional haze plan. These emissions inventories, shown in Tables 15-18
include the following source classifications: Point, area, biogenic
(e.g., VOC from vegetation, emissions from fires), non-road mobile, and
on-road mobile sources. The pollutants inventoried for these categories
are VOC, NOX, PM2.5, PM10,
NH3, and SO2.
    The 2014 emissions for VOC, NOX, and NH3 are
all below the projected 2018 emissions for these pollutants. The
increases in total PM10 and PM2.5 from 2007 to
2014 (shown in Tables 16 and 17) are due to different methodologies for
these years in calculating unpaved road emissions in the emission
inventories. MDEQ notes that according to data from the Mississippi
Department of Transportation, the number of miles of unpaved roads in
the State have decreased from 22,547 miles in 2006 to 18,857 miles in
2014. The increase in SO2 emissions from 105,657 tons in
2007 to 108,429 tons in 2014 was due to emissions from Plant Watson
prior to the source converting to natural gas in 2015. As noted in
Section IV.A.2, the overall SO2 emissions from EGUs
decreased substantially following this conversion.

                                            Table 15--2002 Actual Emissions Inventory Summary for Mississippi
                                                                          [tpy]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                     Source category                            VOC             NOX            PM2.5           PM10             NH3             SO2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Point...................................................          43,852         104,661          11,044          21,106           1,359         103,389
Area....................................................         131,808           4,200          50,401         343,377          58,721             771
On-Road Mobile..........................................          86,811         110,672           2,089           2,828           3,549           4,566
Nonroad Mobile..........................................          41,081          88,787           4,690           5,010              23          11,315
Biogenic................................................       1,544,646          20,305               0               0               0               0
Fires...................................................          13,621           3,326          13,763          14,686             177              99
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................       1,861,820         331,952          81,896         387,007          63,829         120,139
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                                            Table 16--2007 Actual Emissions Inventory Summary for Mississippi
                                                                          [tpy]
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                     Source category                            VOC             NOX            PM2.5           PM10             NH3             SO2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Point...................................................          34,586          98,183           8,731          12,368           1,640          94,978
Area....................................................          74,755           6,091          42,758         326,350          58,774             344
On-Road Mobile..........................................           4,516         117,225           4,061           5,030           1,809             920
Nonroad Mobile..........................................          35,315          48,321           3,105           3,308              35           3,088
Biogenic................................................       1,544,646          20,305               0               0               0               0
Fires...................................................         178,431          12,454          66,621          78,612          12,413           6,327
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................       1,872,249         302,579         125,276         425,668          74,671         105,657
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                                            Table 17--2014 Actual Emissions Inventory Summary for Mississippi
                                                                          [tpy]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                     Source category                            VOC             NOX            PM2.5           PM10             NH3             SO2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Point...................................................          29,234          53,477          11,192          13,128           2,891         104,183
Area....................................................          47,959          19,504         122,136         977,608          64,986             951
On-Road Mobile..........................................          28,852          72,763           2,336           4,438           1,428             399
Nonroad Mobile..........................................          22,408          14,631           1,434           1,510              23              34
Biogenic................................................       1,515,263          14,157               0               0               0               0
Fires...................................................          69,792           6,156          26,913          31,758           4,855           2,863
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................       1,713,509         180,658         164,012       1,028,442          74,184         108,429
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                                          Table 18--2018 Projected Emissions Inventory Summary for Mississippi
                                                                          [tpy]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                     Source category                            VOC             NOX            PM2.5           PM10             NH3             SO2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Point...................................................          46,452          71,804          17,172          30,046           1,591          54,367
Area....................................................         140,134           4,483          53,222         375,495          69,910             746
On-Road Mobile..........................................          31,306          30,259             810           1,607           4,520             435
Nonroad Mobile..........................................          28,842          68,252           3,203           3,452              29           6,683
Biogenic................................................       1,544,646          20,305               0               0               0               0
Fires...................................................          14,747           3,840          15,669          17,013             285             240
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................       1,806,127         198,943          90,076         427,613          76,335          62,471
--------------------------------------------------------------------------------------------------------------------------------------------------------

    As discussed in Section IV.A.2, the Progress Report also contains
other emissions data, including a figure displaying Mississippi's EGU
SO2 emissions from 2002 to 2017 and two tables summarizing
EGU and non-EGU actual emissions data for 2002, 2007, and 2014, along
with the 2018 emissions projections for the State's regional haze plan
(see Tables 13 and 14 of this notice). MDEQ states that EGU
SO2 emissions have decreased from 65,741 tons in 2002 to
2,569 tons in 2017.
    EPA is proposing to find that Mississippi adequately addressed the
provisions of 40 CFR 51.308(g) regarding emissions tracking because the
State compared the most recent updated emission inventory data at the
time of SIP development with the baseline emissions used in the
modeling for the regional haze plan. Furthermore, Mississippi evaluated
EPA Air Markets Program Data \66\ SO2 emissions data from
2002-2017 for EGUs in the State because ammonium sulfate is the primary
component of visibility-impairing pollution in the VISTAS states and
EGUs are the largest source of SO2 in the State.
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    \66\ EPA Air Markets Program Data is available at: https://ampd.epa.gov/ampd/.

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5. Assessment of Changes Impeding Visibility Progress
    In its Progress Report, Mississippi documented that sulfates, which
are formed from SO2 emissions, continue to be the biggest
single contributor to regional haze for Breton, and therefore focused
its analysis on large SO2 emissions from point sources.\67\
In its September 22, 2008, regional haze SIP submittal, Mississippi
notes that ammonium sulfate is the largest contributor to visibility
impairment for Class I in the southeastern United States based upon
2000 to 2004 data, and that reducing SO2 emissions would be
the most effective means of reducing ammonium sulfate.\68\ In
addressing the requirements at 40 CFR 51.308(g)(5), Mississippi shows
in the Progress Report that the overall contribution of sulfates toward
visibility impairment at Breton \69\ over the 2008-2012 period is 66%
for the 20 percent haziest days and 54 percent for the 20 percent
clearest days. Although the State concludes that sulfates continue to
be the major component to visibility impairment at Breton, it also
examines other potential pollutants of concern affecting visibility at
this Class I area. Furthermore, the Progress Report shows that
SO2 emissions reductions from 2002-2017 for EGUs in
Mississippi overall are decreasing, and with the conversion of Plant
Watson to natural gas in 2015, are estimated to well exceed the
projected emission reductions from 2002-2018 in the State's regional
haze plan.
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    \67\ See Figures 2 and 3 in the Progress Report.
    \68\ See page 15 of Mississippi's September 22, 2008, regional
haze SIP narrative.
    \69\ While Mississippi does not have any Class I areas, MDEQ
reviewed particle speciation data for Breton because it is the
closest Class I area.
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    MDEQ summarized the changes in emissions from 2002 to 2014, the
latest complete emissions inventory for all source categories in the
State. For VOC, NH3, and NOX, the actual
emissions decreased from 2002 to 2014. For SO2, total
emissions in the State decreased from 2002, with a slight increase from
2007, due to the point source category. MDEQ explains that the increase
in SO2 emissions was due to emissions from Plant Watson
which, as noted previously, converted from coal to natural gas in 2015
and emitted 5.1 tons and 4.6 tons of SO2 in 2017 and 2018,
respectively.\70\ For PM2.5 and PM10, increases
in statewide PM2.5 and PM10 emissions occurred
from 2002 to 2014 due to increases in area source emissions for these
pollutants. The increase in 2014 is due to an increase in the unpaved
road dust category created by different methodologies used to calculate
unpaved road emissions over the years. MDEQ notes that according to
data from the Mississippi Department of Transportation, the number of
miles of unpaved roads in the State have decreased from 22,547 miles in
2006 to 18,857 miles in 2014. Thus, MDEQ concludes that here have been
no emissions changes that would impede progress and no significant
changes in anthropogenic emissions within the State that have limited
or impeded progress over the review period.
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    \70\ As noted in Section IV.A.2, the conversion of Plant Watson
from coal to natural gas in 2015 contributed to significant
SO2 emissions decreases. In addition, 2017 Mississippi
EGU SO2 emissions were 3,841 tons, which are well below
the 2018 projected 15,213 tons shown in Table 13 of section IV.A.2
of this rulemaking.
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    EPA proposes to find that Mississippi has adequately addressed the
provisions of 40 CFR 51.308(g) regarding an assessment of significant
changes in anthropogenic emissions for the reasons discussed in this
section.
6. Assessment of Current Strategy
    Mississippi believes that its regional haze plan is sufficient to
enable potentially impacted Class I areas to meet their RPGs. MDEQ
based this conclusion on the data provided in the Progress Report,
including the emissions reductions of visibility-impairing pollutants
from EGU and non-EGU point sources achieved in the State (summarized in
Section IV.A.2).\71\
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    \71\ See Tables 3 and 4 on page 11 of the Progress Report which
are reproduced as Tables 13 and 14 in this notice, with the addition
of ``2017 (NEI)'' emissions to Tables 13 and 14.
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    Mississippi asserts that it consulted with other states during the
development of its regional haze plan for reasonable progress,
including Alabama and Louisiana, and that these states indicated that
Mississippi sources have no impact on the visibility at Sipsey in
Alabama and at Breton in Louisiana, respectively. As discussed above,
MDEQ assessed the particle speciation data for Breton indicating that
sulfates continue to be the dominant contributor to regional haze in
this area.
    EPA proposes to find that Mississippi has adequately addressed the
provisions of 40 CFR 51.308(g) regarding the strategy assessment. In
its Progress Report, Mississippi assesses the particle speciation data
at Breton and affirms that the focus of the State's regional haze plan
on addressing SO2 emissions in the State continues to be
most effective strategy to improve visibility at Breton. Mississippi
documents the overall downward emissions trends in key pollutants, with
a focus on SO2 emissions from EGUs in the State and
determined that its regional haze plan is sufficient to enable Class I
areas outside the State potentially impacted by the emissions from
Mississippi to meet their RPGs.\72\ EPA's proposed approval of the
strategy assessment is also based on the fact that CAIR was in effect
in Mississippi through 2014, providing some of the emission reductions
relied upon in Mississippi's regional haze plan through that date; the
implementation of CSAPR, which by the end of the first regional haze
implementation period, reduced emissions of NOX from EGUs
formerly subject to CAIR in Mississippi; and the significant reductions
of SO2 from EGUs formerly subject to CAIR in the State due
to retirements, emissions controls, and permanent conversions to
natural gas as described in Section III.A.
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    \72\ Visibility conditions for 2009-2013 are below the 2018 RPGs
for Sipsey in Alabama. See 83 FR 64797, 64800 (December 18, 2018).
For Caney Creek, visibility conditions for 2012-2016 are below the
revised 2018 RPG for the 20 percent worst days and below 2000-2004
baseline conditions for the 20 percent best days. See 84 FR 11697,
11707 (March 28, 2019).
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7. Review of Current Monitoring Strategy
    EPA notes that the primary monitoring network for regional haze
nationwide is the IMPROVE network, which monitors visibility conditions
in Class I areas. The Visibility Information Exchange Web System
(VIEWS) \73\ website has been maintained by VISTAS and the other
regional planning organizations to provide ready access to the IMPROVE
data and data analysis tools.
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    \73\ The VIEWS website is located at: http://views.cira.colostate.edu/fed/SiteBrowser/Default.aspx?appkey=SBCF_VisSum.
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    In its Progress Report, Mississippi states that no modifications to