[Federal Register Volume 86, Number 53 (Monday, March 22, 2021)]
[Rules and Regulations]
[Pages 15104-15132]
[FR Doc No: 2021-05362]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R06-OAR-2015-0189; FRL-10019-63-Region 6]

Air Plan Approval; Arkansas; Arkansas Regional Haze and
Visibility Transport State Implementation Plan Revisions

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: Pursuant to the Clean Air Act (CAA or the Act), the
Environmental Protection Agency (EPA) is finalizing approval of a
revision to the Arkansas State Implementation Plan (SIP) submitted by
the State of Arkansas through the Arkansas Department of Energy and
Environment, Division of Environmental Quality (DEQ) on August 13,
2019. The SIP submittal addresses requirements of the Act and the
Regional Haze Rule for visibility protection in mandatory Class I
Federal areas (Class I areas) for the first implementation period. The
EPA is approving an alternative measure to best available retrofit
technology (BART) at the Domtar Ashdown Mill for sulfur dioxide
(SO2), particulate matter (PM), and nitrogen oxide
(NOX); and elements of the SIP submittal that relate to
these BART requirements at this facility. In addition, we are approving
the withdrawal from the SIP of the previously approved PM10
BART limit for Power Boiler No. 1. The EPA is also concurrently
approving Arkansas' interstate visibility transport provisions from the
August 8, 2018, regional haze SIP submittal as supplemented by the
visibility transport provisions in the October 4, 2019, interstate
transport SIP submittal, which covers the following national ambient
air quality standards (NAAQS): The 2006 24-hour fine particulate matter
(PM2.5) NAAQS; the 2012 annual PM2.5 NAAQS; the
2008 and 2015 eight-hour ozone (O3) NAAQS; the 2010 one-hour
nitrogen dioxide (NO2) NAAQS; and the 2010 one-hour
SO2 NAAQS. In conjunction with our final approval of these
SIP revisions, we are finalizing in a separate rulemaking, published
elsewhere in this issue of the Federal Register, our withdrawal of the
Federal implementation plan (FIP) provisions for the Domtar Ashdown
Mill.

DATES: This rule is effective on April 21, 2021.

ADDRESSES: The EPA has established a docket of all documents for this
action at https://www.regulations.gov under

Docket ID No. EPA-R06-OAR-2015-0189. Although listed in the index, some
information is not publicly available, e.g., Confidential Business
Information or other information whose disclosure is restricted by
statute. Certain other material, such as copyrighted material, is not
placed on the internet. Publicly available docket materials are
available electronically through https://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT: James E. Grady, EPA Region 6 Office,
Regional Haze and SO2 Section, 1201 Elm Street, Suite 500,
Dallas TX 72570,<PHONE_NUMBER><EMAIL_ADDRESS>Please call or
email Mr. Grady or Mr. Bill Deese at<PHONE_NUMBER> if you need
alternative access to material indexed but not provided in the docket.

SUPPLEMENTARY INFORMATION: Throughout this document ``we,'' ``us,'' and
``our'' mean the EPA.

Table of Contents

I. Background
    A. Regional Haze Principles
    B. Requirements of the CAA and the EPA's Regional Haze Rule
    C. BART Requirements
    D. BART Alternative Requirements
    E. Long-Term Strategy and Reasonable Progress Requirements
    F. Previous Actions on Arkansas Regional Haze
    G. Arkansas Regional Haze Phase III SIP Submittal
    H. Arkansas Visibility Transport
II. Summary of Proposed Action and Our Final Decisions
III. Public Comments and EPA Responses
    A. Demonstration That the BART Alternative Is Better-Than-BART
    B. Monitoring, Recordkeeping and Reporting Requirements
    C. Requirements for Emission Reductions To Occur During the
First Implementation Period and for a Compliance Schedule
    D. The CAA Section 110(l) Anti-Backsliding Provision
    E. Interstate Visibility Transport and Regional Haze Reasonable
Progress Requirements
    F. Comments From Domtar
IV. Final Action
    A. Arkansas Regional Haze Phase III SIP Submittal
    B. Arkansas Visibility Transport
    C. CAA Section 110(l)
V. Incorporation by Reference
VI. Statutory and Executive Order Reviews

I. Background

A. Regional Haze Principles

    Regional haze is visibility impairment that is produced by a
multitude of sources and activities that are located across a broad
geographic area and emit fine particulates (PM2.5) \1\ into
the air. Fine particulates which cause haze are sulfates
(SO42-), nitrates (NO3-),
organic carbon (OC), elemental carbon (EC), and soil dust.\2\
PM2.5 precursors consist of SO2, NOX,
volatile organic compounds (VOCs), and in some cases, ammonia
(NH3). Airborne PM2.5 can scatter and absorb the
incident light and, therefore, lead to atmospheric opacity and
horizontal visibility degradation. Regional haze limits visual distance
and reduces color, clarity, and contrast of view. PM2.5 can
cause serious adverse health effects and mortality in humans. It also
contributes to environmental effects such as acid deposition and
eutrophication. Emissions that affect visibility include a wide variety
of natural and man-made sources. Natural sources can include windblown
dust and soot from wildfires. Man-made sources can include major and
minor stationary sources, mobile sources, and area sources. Reducing
PM2.5 and its precursor gases in the atmosphere is an
effective method of improving visibility.
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    \1\ Fine particles are less than or equal to 2.5 microns
([micro]m) in diameter and usually form secondary in nature
indirectly from other sources. Particles less than or equal to 10
[micro]m in diameter are referred to as PM10. Particles
greater than PM2.5 but less than PM10 are
referred to as coarse mass. Coarse mass can contribute to light
extinction as well and is made up of primary particles directly
emitted into the air. Fine particles tend to be man-made, while
coarse particles tend to have a natural origin. Coarse mass settles
out from the air more rapidly than fine particles and usually will
be found relatively close to emission sources. Fine particles can be
transported long distances by wind and can be found in the air
thousands of miles from where they were formed.
    \2\ Organic carbon can be emitted directly as particles or
formed through reactions involving gaseous emissions. Elemental
carbon, in contrast to organic carbon, is exclusively of primary
origin and emitted by the incomplete combustion of carbon-based
fuels. Elemental carbon particles are especially prevalent in diesel
exhaust and smoke from wild and prescribed fires.
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    Data from the existing visibility monitoring network, ``Interagency
Monitoring of Protected Visual Environments'' (IMPROVE), shows that
visibility impairment caused by air pollution occurs virtually all of
the time at most national parks and wilderness areas. In 1999, the
average visual range \3\ in many mandatory Class I Federal areas \4\ in
the western United States was 100-150 kilometers (km), or about one-
half to two-thirds of the visual range that would exist under estimated
natural conditions.\5\ In most of the eastern Class I areas of the
United States, the average visual range was less than 30 km, or about
one-fifth of the visual range that would exist under estimated natural
conditions. Since the promulgation of the original Regional Haze Rule
in 1999, CAA programs have reduced emissions of haze-causing pollution,
lessening visibility impairment and resulting in improved average
visual ranges.\6\
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    \3\ Visual range is the greatest distance, in km or miles, at
which a dark object can be viewed against the sky by a typical
observer.
    \4\ Mandatory Class I Federal 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. The EPA, in consultation with the
Department of Interior, promulgated a list of 156 areas where
visibility was identified as an important value. The extent of a
mandatory Class I area includes subsequent changes in boundaries,
such as park expansions. Although states and tribes may designate
additional areas as Class I, the requirements of the visibility
program set forth in the CAA applies only to mandatory Class I
Federal areas. Each mandatory Class I Federal area is the
responsibility of a Federal Land Manager (FLM). When the term
``Class I area'' is used in this action, it means ``mandatory Class
I Federal areas.'' See 44 FR 69122 (November 30, 1979) and CAA
Sections 162(a), 169A, and 302(i).
    \5\ 64 FR 35714, 35715 (July 1, 1999).
    \6\ An interactive story map depicting efforts and recent
progress by the EPA and states to improve visibility at national
parks and wilderness areas may be visited at: http://arcg.is/29tAbS3.
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B. Requirements of the CAA and the EPA's Regional Haze Rule

    In section 169A, enacted as part of the 1977 CAA Amendments,
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, visibility impairment in mandatory Class I
Federal areas where impairment results from manmade air pollution.
Congress added section 169B to the CAA in 1990, which strengthened the
visibility protection program of the Act, and the EPA promulgated final
regulations addressing regional haze as part of the 1999 Regional Haze
Rule, which was most recently updated in 2017.\7\ The Regional Haze
Rule revised the existing 1980 visibility regulations and established a
more comprehensive visibility protection program for Class I areas. The
requirements for regional haze, found at 40 CFR 51.308 and 51.309, are
included in the EPA's broader visibility protection regulations at 40
CFR 51.300-309. The regional haze regulations require states to
demonstrate reasonable progress toward meeting the national goal of
restoring natural visibility conditions for Class I areas by 2064. The
CAA requirement in section 169A(b)(2) to submit a regional haze SIP
applies to all fifty states, the District of Columbia, and the Virgin

Islands. States were required to submit the first implementation plan
addressing visibility impairment caused by regional haze no later than
December 17, 2007.\8\
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    \7\ See the July 1, 1999 Regional Haze Rule final action (64 FR
35714), as amended on July 6, 2005 (70 FR 39156), October 13, 2006
(71 FR 60631), June 7, 2012 (77 FR 33656) and on January 10, 2017
(82 FR 3079).
    \8\ See 40 CFR 51.308(b). Also, under 40 CFR 51.308(f)-(i), the
EPA requires subsequent updates to the regional haze SIPs for each
implementation period. The next update for the second implementation
period is due by July 31, 2021.
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C. BART Requirements

    Section 169A(b)(2)(A) of the CAA directs states to evaluate the use
of BART controls at certain categories of existing major stationary
sources built between 1962 and 1977.\9\ Under 40 CFR 51.308(e)(1)(ii),
any BART-eligible source \10\ that is reasonably anticipated to cause
or contribute to visibility impairment in a Class I area is classified
as subject-to-BART.\11\ States are directed to conduct BART
determinations to address visibility impacts for each source classified
as subject-to-BART. These large, often under-controlled, older
stationary sources are then required to procure, install, and operate
the BART controls established in these determinations to reduce
visibility impairment. The determinations must be based on an analysis
of the best system of continuous emission control technology available
and associated emission reductions achievable. States are required to
identify the level of control representing BART after considering the
five statutory factors set out in CAA section 169A(g)(2) for the
potential BART controls.\12\ States must establish emission limits, a
schedule of compliance, and other measures consistent with the BART
determination process for each source subject-to-BART.
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    \9\ See 42 U.S.C. 7491(g)(7), which lists the 26 source
categories of major stationary sources potentially subject-to-BART.
    \10\ BART-eligible sources are those sources that fall within
one of 26 source categories that began operation on or after August
7, 1962, and were in existence on August 7, 1977, with potential
emissions greater than 250 tons per year (tpy). (See 40 CFR 51
Appendix Y, section II).
    \11\ Under the BART Guidelines, states may select a visibility
impact threshold, measured in deciviews (dv), 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 threshold in the SIP and specify the basis for its selection of
that value. Any source with visibility impacts 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
emission sources affecting the Class I areas at issue and the
magnitude of the individual sources' impacts. Any visibility impact
threshold set by the state should not be higher than 0.5 dv. (See 40
CFR part 51, Appendix Y, section III.A.1).
    \12\ The five statutory factors in determining BART controls
are: (1) Costs of compliance, (2) the energy and non-air quality
environmental impacts, (3) any existing control technology present
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.
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D. BART Alternative Requirements

    A State may opt to implement or require participation in an
emissions trading program or other alternative measure rather than
require sources subject-to-BART to install, operate, and maintain BART.
Such an emissions trading program or other alternative measure must
achieve greater reasonable progress than would be achieved through the
installation and operation of BART. In order to demonstrate that the
alternative program achieves greater reasonable progress than source-
specific BART, a state must demonstrate that its SIP meets the
requirements in 40 CFR 51.308(e)(2)(i) to (iv). Among other things, the
state must conduct an analysis of BART and the associated reductions
for each source subject-to-BART covered by the alternative program, and
compare the reductions and visibility improvements of the alternative
program to what would have been achieved by BART.
    Pursuant to 40 CFR 51.308(e)(2)(i)E), the state must provide a
determination under 40 CFR 51.308(e)(3) or otherwise based on the
``clear weight of evidence'' that the alternative measure achieves
greater reasonable progress than BART. 40 CFR 51.308(e)(3) provides two
specific tests applicable under specific circumstances for determining
whether the alternative measure achieves greater reasonable progress
than BART. Under the first test, if the distribution of emissions is
not substantially different than under BART, and the alternative
measure results in greater emission reductions, then the alternative
measure may be deemed to achieve greater reasonable progress. Under the
second test, if the distribution of emissions is significantly
different, then the State must conduct dispersion modeling to determine
the difference in visibility between BART and the alternative measure
for each impacted Class I area, for the twenty percent best and worst
days. The modeling would demonstrate greater reasonable progress if
both of the following two criteria are met: (i) Visibility does not
decline in any Class I area, and (ii) there is an overall improvement
in visibility, determined by comparing the average difference between
BART and the alternative over all affected Class I areas.
    Alternatively, under 40 CFR 51.308(e)(2)(i)(E), states may show
based on the ``clear weight of evidence'' that the alternative achieves
greater reasonable progress than would be achieved through the
installation and operation of BART at the covered sources. As stated in
the EPA's revisions to the Regional Haze Rule governing alternatives to
source-specific BART determinations, weight of evidence demonstrations
attempt to make use of all available information and data which can
inform a decision while recognizing the relative strengths and
weaknesses of that information in arriving at the soundest decision
possible.\13\ This array of information and other relevant data must be
of sufficient quality to inform the comparison of visibility impacts
between BART and the alternative. A weight of evidence comparison may
be warranted when there is confidence that the difference in visibility
impacts between BART and the alternative scenarios are expected to be
large enough to show that an alternative is better than BART. The EPA
will carefully consider this evidence in evaluating any SIPs submitted
by States employing such an approach.
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    \13\ See 71 FR 60612, 60622 (October 13, 2006). Factors which
can be used in a weight of evidence determination in this context
may include, but not be limited to, future projected emissions
levels under the alternative as compared to under BART; future
projected visibility conditions under the two scenarios; the
geographic distribution of sources likely to reduce or increase
emissions under the alternative as compared to BART sources;
monitoring data and emissions inventories; and sensitivity analyses
of any models used.
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    Finally, under 40 CFR 51.308(e)(2)(iii) and (iv), all emission
reductions for the alternative program must take place during the
period of the first long-term strategy for regional haze, and all the
emission reductions resulting from the alternative program must be
surplus to those reductions resulting from measures adopted to meet
requirements of the CAA as of the baseline date of the SIP.

E. Long-Term Strategy and Reasonable Progress Requirements

    In addition to BART requirements, 40 CFR 51.308(d)(3)(i) to (iv)
requires each state to include in its SIP a long-term strategy for the
planning period that addresses regional haze visibility impairment for
each Class I area located within the state and outside the state that
may be affected by emissions generated from within the state. The long-
term strategy is the vehicle for ensuring continuing reasonable
progress toward achieving natural visibility conditions. It is a
compilation of all control measures in the SIP that a state will use
during the implementation period to meet the applicable reasonable
progress goals (RPGs) established under 40 CFR 51.308(d)(1) for each
Class I

area.\14\ The RPGs established by the State provide an assessment of
the visibility improvement anticipated to result for that planning
period.\15\ Section 51.308(d)(3)(v) requires that a state consider
certain minimum factors (the long-term strategy factors) in developing
its long-term strategy for each Class I area.\16\ States have
significant flexibility in establishing RPGs during the first planning
period and must determine whether additional measures beyond BART are
needed for reasonable progress. Under CAA section 169A(g)(1), once a
set of potential control measures have been identified for a selected
source, the State must collect data on and apply the four statutory
factors that will be considered in selecting the measure(s) for that
source that are necessary to make reasonable progress. The four
statutory factors used to characterize potential emission controls are
as follows: (1) The costs of compliance; (2) the time necessary for
compliance; (3) the energy and non-air quality environmental impacts of
compliance; and (4) the remaining useful life of any potentially
affected sources. A state planning to consider visibility benefits will
also need to characterize those benefits (often referred to as the 5th
factor).\17\ States must demonstrate in their regional haze SIPs how
these factors are considered when selecting the controls for their
long-term strategies and provide an assessment of the visibility
improvement anticipated to establish RPGs for each applicable Class I
area. This is commonly referred to this as the ``reasonable progress
analysis'' or ``four-factor analysis.''
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    \14\ See 40 CFR 51.308(d)(3)(i) to (iv). For the first planning
period, contributing and impacted states must develop coordinated
emission management strategies. Impacted states must demonstrate
that they have included all measures necessary in their SIPs to
obtain their share of emission reductions needed to meet the RPGs
for a Class I area. States must document the technical basis that
they relied upon to determine the apportionment of emission
reduction obligations necessary and identify the baseline emissions
inventory on which their strategies are based. States must also
identify all anthropogenic sources of visibility impairment
considered in developing the strategy, such as major and minor
stationary sources, mobile sources, and area sources.
    \15\ The process for setting RPGs is as follows: (1) Identify
sources that impact visibility; (2) evaluate potential controls
based on consideration of the four reasonable progress factors; (3)
project the visibility conditions based on implementation of on-the-
books and additional selected controls; (4) compare the projected
visibility conditions to the uniform rate of progress (URP) needed
to attain natural visibility conditions by year 2064 for each Class
I area; (5) determine an RPG for each Class I area based on this
analysis that will improve the visibility at or beyond the URP on
the most impaired days and ensure no degradation for the least
impaired days. The Regional Haze Rule allows for the selection of an
RPG at a given Class I area that provides for a slower rate of
improvement than the URP for that area, but in that case a state
must demonstrate that the URP is not reasonable and that the RPG
selected is. See 40 CFR 51.308(d)(1)(ii).
    \16\ These factors are: (1) Emission reductions due to ongoing
air pollution control programs, including measures to address
reasonably attributable visibility impairment (RAVI); (2) measures
to mitigate the impacts of construction activities; (3) emissions
limitations and schedules for compliance to achieve the reasonable
progress goal; (4) source retirement and replacement schedules; (5)
smoke management techniques for agricultural and forestry management
purposes including plans as currently exist within the state for
these purposes; (6) enforceability of emissions limitations and
control measures; and (7) the anticipated net effect on visibility
due to projected changes in point, area, and mobile source emissions
over the period addressed by the long-term strategy.
    \17\ Guidance for Setting Reasonable Progress Goals under the
Regional Haze Program, June 1, 2007, memorandum from William L.
Wehrum, Acting Assistant Administrator for Air and Radiation, to the
EPA Regional Administrators, EPA Regions 1-10 (pp. 4-2, 5-1).
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F. Previous Actions on Arkansas Regional Haze

    The State of Arkansas submitted a regional haze SIP on September 9,
2008, intended to address the requirements of the first regional haze
implementation period. On August 3, 2010, the State submitted a SIP
revision with mostly non-substantive changes that addressed Arkansas
Pollution Control and Ecology Commission (APCEC) Regulation 19, Chapter
15.\18\ On September 27, 2011, the State submitted a supplemental
letter that clarified several aspects of the 2008 submittal. The EPA
collectively refers to the original 2008 submittal, the supplemental
letter, and the 2010 revision together as the 2008 Arkansas Regional
Haze SIP. On March 12, 2012, the EPA partially approved and partially
disapproved the 2008 Arkansas Regional Haze SIP.\19\ Specifically, the
EPA disapproved certain BART compliance dates; the State's
identification of certain BART-eligible sources and subject-to-BART
sources; certain BART determinations for NOX,
SO2, and PM10; the State's reasonable progress
analysis; and a portion of the State's long-term strategy. The
remaining provisions of the 2008 Arkansas Regional Haze SIP were
approved. The final partial disapproval started a two-year FIP clock
that obligated the EPA to either approve a SIP revision and/or
promulgate a FIP to address the disapproved portions of the SIP.\20\
Because a SIP revision addressing the deficiencies was not approved and
the FIP clock expired in April 2014, the EPA promulgated a FIP (the
Arkansas Regional Haze FIP) on September 27, 2016, to address the
disapproved portions of the 2008 Arkansas Regional Haze SIP.\21\ Among
other things, the FIP established SO2, NOX, and
PM10 emission limits under the BART requirements for nine
units at six facilities: Arkansas Electric Cooperative Corporation
(AECC) Carl E. Bailey Plant Unit 1 Boiler; AECC John L. McClellan Plant
Unit 1 Boiler; American Electric Power/Southwestern Electric Power
Company (AEP/SWEPCO) Flint Creek Plant Boiler No. 1; Entergy22 Lake
Catherine Plant Unit 4 Boiler; Entergy White Bluff Plant Units 1 and 2
Boilers and the Auxiliary Boiler; and the Domtar Ashdown Mill Power
Boilers No. 1 and 2. The FIP also established SO2 and
NOX emission limits under the reasonable progress
requirements for the Entergy Independence Plant Units 1 and 2.
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    \18\ The September 9, 2008 SIP submittal included APCEC
Regulation 19, Chapter 15, which is the state regulation that
identified the BART-eligible and subject-to-BART sources in Arkansas
and established BART emission limits for subject-to-BART sources.
The August 3, 2010 SIP revision did not revise Arkansas' list of
BART-eligible and subject-to-BART sources or revise any of the BART
requirements for affected sources. Instead, it included mostly non-
substantive revisions to the state regulation.
    \19\ See the final action on (March 12, 2012) (77 FR 14604).
    \20\ Under CAA section 110(c), the EPA is required to promulgate
a FIP within two years of the effective date of a finding that a
state has failed to make a required SIP submission or has made an
incomplete submission, or of the effective date that the EPA
disapproves a SIP in whole or in part. The FIP requirement is
terminated only if a state submits a SIP, and the EPA approves that
SIP as meeting applicable CAA requirements before promulgating a
FIP.
    \21\ See FIP final action on September 27, 2016 (81 FR 66332) as
corrected on October 4, 2016 (81 FR 68319).
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    Following petitions for reconsideration and administrative stay
submitted by the State, industry, and ratepayers, on April 14,
2017,\23\ the EPA announced our decision to reconsider several elements
of the FIP \24\ and on April 25, 2017, the EPA issued a partial
administrative stay of the effectiveness of the FIP for ninety
days.\25\ During that period, Arkansas started to address the
disapproved portions of its regional haze SIP through several phases of
SIP revisions. On July 12, 2017, the State submitted its Phase I SIP
submittal (the Arkansas Regional Haze NOX SIP revision) to
address NOX BART requirements for all electric generating

units (EGUs) and the reasonable progress requirements with respect to
NOX. These NOX provisions were previously
disapproved by the EPA in our 2012 final action on the 2008 Arkansas
Regional Haze SIP. The Arkansas Regional Haze NOX SIP
submittal replaced all source-specific NOX BART
determinations for EGUs established in the FIP with reliance upon the
Cross-State Air Pollution Rule (CSAPR) emissions trading program for
O3 season NOX as an alternative to NOX
BART. The SIP submittal addressed the NOX BART requirements
for Bailey Unit 1, McClellan Unit 1, Flint Creek Boiler No. 1, Lake
Catherine Unit 4; White Bluff Units 1 and 2, and the Auxiliary Boiler.
The revision did not address NOX BART for Domtar Ashdown
Mill Power Boilers No. 1 and 2. On February 12, 2018, we took final
action to approve the Arkansas Regional Haze NOX SIP
revision and to withdraw the corresponding NOX provisions of
the FIP.\26\
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    \23\ Copies of the petitions for reconsideration and
administrative stay submitted by the State of Arkansas; Entergy;
Arkansas Electric Cooperative Corporation (AECC); and the Energy and
Environmental Alliance of Arkansas (EEAA) are available in the
docket of this action.
    \24\ Letter from E. Scott Pruitt, Administrator, EPA, to
Nicholas Jacob Bronni and Jamie Leigh Ewing, Arkansas Attorney
General's Office (April 14, 2017). A copy of this letter is included
in the docket, https://www.regulations.gov/document?D=EPAR06-OAR-2015-0189-0240.
    \25\ See 82 FR 18994.
    \26\ See 82 FR 42627 (September 11, 2017) for the proposed
approval. See also 83 FR 5915 and 83 FR 5927 (February 12, 2018) for
the final action.
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    The State submitted its Phase II SIP revision (the Arkansas
Regional Haze SO2 and PM SIP revision) on August 8, 2018,
that addressed most of the remaining parts of the 2008 Arkansas
Regional Haze SIP that were disapproved in the March 12, 2012, action.
The August 8, 2018, SIP submittal was intended to replace the federal
SO2 and PM10 BART determinations as well as the
reasonable progress determinations established in the FIP with the
State's own determinations. Specifically, the SIP revision addressed
the applicable SO2 and PM10 BART requirements for
Bailey Unit 1; SO2 and PM10 BART requirements for
McClellan Unit 1; SO2 BART requirements for Flint Creek
Boiler No. 1; SO2 BART requirements for White Bluff Units 1
and 2; SO2, NOX, and PM10 BART
requirements for the White Bluff Auxiliary Boiler; \27\ and included a
requirement that Lake Catherine Unit 4 not burn fuel oil until
SO2 and PM BART determinations for the fuel oil firing
scenario are approved into the SIP by the EPA.\28\ The submittal
addressed the reasonable progress requirements with respect to
SO2 and PM10 emissions for Independence Units 1
and 2 and all other sources in Arkansas. In addition, it established
revised RPGs for Arkansas' two Class I areas and revised the State's
long-term strategy provisions. The submittal did not address BART and
associated long-term strategy requirements for Domtar Ashdown Mill
Power Boilers No. 1 and 2. On September 27, 2019, we took final action
to approve a portion of the Arkansas Regional Haze SO2 and
PM SIP revision and to withdraw the corresponding parts of the
FIP.29 30 The August 8, 2018, SIP also contained a
discussion of the interstate visibility transport provisions, as
discussed in more detail in Section I.H of this final action.
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    \27\ The Arkansas Regional Haze SO2 and PM SIP
revision established a new NOX emission limit of 32.2
pounds per hour (pph) for the Auxiliary Boiler to satisfy
NOX BART and replaced the SIP determination that we
previously approved in our final action on the Arkansas Regional
Haze NOX SIP revision. In the Arkansas Regional Haze
NOX SIP revision, DEQ incorrectly identified the
Auxiliary Boiler as participating in the CSAPR trading program for
O3 season NOX to satisfy the NOX
BART requirements. The new source-specific NOX BART
emission limit that we approved in our final action on the Arkansas
Regional Haze SO2 and PM SIP revision corrected that
error.
    \28\ The 2012 action disapproved SO2, NOX,
and PM BART for the fuel oil firing scenario for the Entergy Lake
Catherine Plant Unit 4, but a FIP BART determination was not
established. Instead, the FIP included a requirement that Entergy
not burn fuel oil at Lake Catherine Unit 4 until final EPA approval
of BART determinations for SO2, NOX, and PM.
In the Arkansas Regional Haze NOX SIP revision, Arkansas
relied on participation in CSAPR for O3 season
NOX to satisfy the NOX BART requirement for
its subject-to-BART EGUs, including Lake Catherine Unit 4. When we
took final action on the Arkansas Regional Haze NOX SIP
revision, we also took final action to withdraw the FIP
NOX emission limit for the natural gas firing scenario
for Lake Catherine Unit 4. In the Arkansas Regional Haze
SO2 and PM SIP revision, Entergy committed to not burn
fuel oil at Lake Catherine Unit 4 until final EPA approval of BART
for SO2 and PM. This commitment was made enforceable by
the State through an Administrative Order that was adopted and
incorporated in the Arkansas Regional Haze SO2 and PM SIP
revision.
    \29\ See 83 FR 62204 (November 30, 2018) for proposed action and
84 FR 51033 (September 27, 2019) for final approval. The Arkansas
Regional Haze SO2 and PM SIP revision also addressed
separate CAA requirements related to interstate visibility transport
under CAA section 110(a)(2)(D)(i)(II), but we did not take action on
that part of the submittal. We are acting on the interstate
visibility transport portion of the Arkansas Regional Haze
SO2 and PM SIP revision in this final action.
    \30\ See 84 FR 51056 (September 27, 2019) for the final
withdrawal action.
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G. Arkansas Regional Haze Phase III SIP Submittal

    On August 13, 2019, DEQ submitted the Arkansas Regional Haze Phase
III SIP revision (Phase III SIP revision), which we are finalizing
approval of in this action. This submittal contains an alternative
measure to address BART and the associated long-term strategy
requirements for two subject-to-BART sources (Power Boilers No. 1 and
2) at the Domtar Ashdown paper mill located in Ashdown, Arkansas. Power
Boiler No. 1 was first installed in 1967-1968. At the time of SIP
submittal and our proposed approval, the unit was permitted to burn
only natural gas.\31\ It was capable of burning a variety of other
fuels too, including bark, wood waste, tire-derived fuel (TDF),
municipal yard waste, pelletized paper fuel, fuel-oil, and reprocessed
fuel-oil, but was not authorized to do so. It was equipped with a wet
electrostatic precipitator (WESP) \32\ but the requirements to operate
the WESP were removed when the permit was modified to combust natural
gas only. In 2020, DEQ received a disconnection notice \33\ for Power
Boiler No. 1 and it is now permanently retired. Power Boiler No. 1 has
a design heat input rating of 580 million British Thermal units per
hour (MMBtu/hr) and an average steam generation rate of approximately
120,000 pounds per hour (pph). Power Boiler No. 2 was installed in 1975
and is authorized to burn a variety of fuels including coal, petroleum
coke, TDF, natural gas, wood waste, clean cellulosic biomass (e.g.
bark, wood residuals, and other woody biomass materials), and wood
chips used to absorb oil spills. It is equipped with a traveling grate;
\34\ a combustion air system that includes over-fire air; \35\ multi-
clones for PM10 removal; \36\ and two venturi scrubbers in
parallel for removal of SO2 and remaining particulates.
Power Boiler No. 2 has a heat input rating of 820 MMBtu/hr and an
average steam generation rate of approximately 600,000 pph.
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    \31\ Power Boiler No. 1 operates as natural gas only subject to
the Gas 1 subcategory defined under 40 CFR 63.7575. See DEQ Air
Permit No. 0287-AOP-R22 (page 64) in the docket of this action.
    \32\ An electrostatic precipitator is an air pollution control
device that functions by electrostatically charging particles in a
gas stream that passes through collection plates with wires. The
ionized particulate matter is attracted to and deposited on the
plates as the cleaner air passes through. A wet electrostatic
precipitator is designed to operate with water vapor saturated air
streams to remove liquid droplets such as sulfuric acid.
    \33\ See November 18, 2020 Disconnection Notice from Domtar for
Power Boiler No. 1 (SN[hyphen]03) in the docket of this action.
    \34\ A traveling grate is a moving grate used to feed fuel to
the boiler for combustion.
    \35\ Over-fire air typically recirculates a portion of the flue
gas back to both the fuel-rich zone and the combustion zone to
achieve complete burnout by encouraging the formation of nitrogen
(N2) rather than NOX.
    \36\ A cyclone separator is an air pollution control device
shaped like a conical tube that creates an air vortex as air moves
through it causing larger particles (PM10) to settle as
the cleaner air passes through. Multi-clones are a sequence of
cyclone separators in parallel used to treat a higher volume of air.
In this particular case, the cleaner air travels to the venturi
scrubbers to remove the smaller remaining particles like
PM2.5 and SO2.
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    DEQ's original BART analyses and determinations (dated October 2006
and March 2007) for Power Boilers No. 1 and 2 were included in the 2008

Arkansas Regional Haze SIP.\37\ In our 2012 partial approval/partial
disapproval action, we approved DEQ's identification of these two units
as BART-eligible; DEQ's determination that these units are subject-to-
BART; and DEQ's PM10 BART determination for Power Boiler No.
1.\38\ In that action, we also disapproved the SO2 and
NOX BART determinations for Power Boiler No. 1; and the
SO2, NOX, and PM10 BART determinations
for Power Boiler No. 2. In the 2016 Arkansas Regional Haze FIP and its
associated technical support document (TSD),\39\ the EPA promulgated
SO2, NOX, and PM10 emission limits for
these boilers. The FIP BART limits were based on consideration of the
2006 and 2007 BART analyses, a revised BART analysis (dated May
2014),\40\ and additional information provided by Domtar for the
disapproved BART determinations. On March 20, 2018, Domtar provided DEQ
with a proposed BART alternative based on changing boiler operations as
part of the company's planned re-purposing and mill transformation from
paper production to fluff pulp production. On September 5, 2018, Domtar
further revised its BART alternative approach in response to additional
boiler operation changes planned at the Ashdown Mill.\41\ In October
2018, DEQ proposed a SIP revision that included Domtar's BART
alternative approach to address the BART requirements for Power Boilers
1 and 2 at the Ashdown Mill.\42\ The October 2018 proposal included an
administrative order as the enforceable mechanism for the emission
limits established under the BART alternative; and the order also
contained monitoring, reporting, and recordkeeping requirements for the
boilers. During the State's public comment period, Domtar submitted
comments stating that while it agrees with the BART alternative
approach and with the emission limits themselves, it does not agree
with the use of the administrative order as the enforceable mechanism
of the proposed SIP revision. Domtar requested that the portion of its
New Source Review (NSR) permit containing the regional haze
requirements be included in the proposed SIP revision as the
enforceable mechanism instead of the administrative order. DEQ
addressed Domtar's request in April 2019 by proposing a supplemental
SIP revision to the October 2018 proposal. The supplemental SIP
revision proposal replaced the administrative order with the
incorporation of certain provisions of Domtar's revised NSR permit into
the SIP as the enforceable mechanism for Domtar's regional haze
requirements. On August 1, 2019, DEQ issued a final minor permit
modification letter to Domtar,\43\ which included enforceable emission
limitations and compliance schedules for the BART alternative.
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    \37\ See ``Best Available Retrofit Technology Determination
Domtar Industries Inc., Ashdown Mill (AFIN 41-00002),'' originally
dated October 31, 2006 and revised on March 26, 2007, prepared by
Trinity Consultants Inc. This was included as part of the Phase III
submittal and included in the docket of this action.
    \38\ See the March 12, 2012 final action (77 FR 14604).
    \39\ See final FIP action on September 27, 2016 (81 FR 66332) as
corrected on October 4, 2016 (81 FR 68319) and the associated TSD,
``AR020.0002-00 TSD for EPA's Proposed Action on the Arkansas
Regional Haze FIP'' in Docket No. EPA-R06-OAR-2015-0189 for the FIP
BART analysis for SO2 and NOX for Power Boiler
No. 1; and SO2, NOX, and PM10 for
Power Boiler No. 2. This was included as part of the Phase III
submittal and included in the docket of this action.
    \40\ See ``Supplemental BART Determination Information Domtar
A.W. LLC, Ashdown Mill (AFIN 41-00002),'' originally dated June 28,
2013 and revised on May 16, 2014, prepared by Trinity Consultants
Inc. in conjunction with Domtar A.W. LLC. This was included as part
of the Phase III SIP submittal and is included in the docket of this
action.
    \41\ See section III.B of the Arkansas Regional Haze Phase III
submittal and the associated September 4, 2018, ``Ashdown Mill BART
Alternative TSD'' in the docket of this action.
    \42\ The proposed October 2018 SIP revision was intended to
replace the portion of our FIP addressing Domtar and would also
resolve the claims regarding Domtar in petitions for review of the
FIP that are currently being held in abeyance, State of Arkansas v.
EPA, No. 16-4270 (8th Cir.).
    \43\ See DEQ Air permit #0287-AOP-R22 (effective August 1, 2019)
included as part of the Phase III submittal and is included in the
docket of this action.
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    DEQ submitted its third corrective regional haze SIP submittal to
the EPA on August 13, 2019, which is the subject of this final action
(the Arkansas Regional Haze Phase III SIP revision). The Phase III SIP
revision includes Domtar's BART alternative approach and revises all of
the prior BART determinations for Power Boilers No. 1 and 2 at the
Ashdown Mill. The Phase III SIP submittal also incorporates plantwide
provisions from the August 1, 2019, permit including emission limits
and conditions for implementing the BART alternative.\44\ With final
approval of the Arkansas Regional Haze Phase III SIP revision in this
action, DEQ now has a fully-approved regional haze SIP for the first
implementation period. The Arkansas Regional Haze NOX SIP
revision (Phase I SIP),\45\ the Arkansas Regional Haze SO2
and PM SIP revision (Phase II SIP),\46\ and the Arkansas Regional Haze
Phase III SIP revision together fully address all deficiencies of the
2008 Arkansas Regional Haze SIP that EPA previously identified in the
March 12, 2012 partial approval/partial disapproval action.\47\
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    \44\ See DEQ Air permit #0287-AOP-R22, Section VI, Plantwide
Conditions #32 to #43. The ``Regional Haze Program (BART
Alternative) Specific Conditions'' portion of the Plantwide
Conditions section of the permit states the following: ``For
compliance with the CAA Regional Haze Program's requirements for the
first planning period, the No. 1 and 2 Power Boilers are subject-to-
BART alternative measures consistent with 40 CFR 51.308. The terms
and conditions of the BART alternative measures are to be submitted
to EPA for approval as part of the Arkansas SIP. Upon initial EPA
approval of the permit into the SIP, the permittee shall continue to
be subject to the conditions as approved into the SIP even if the
conditions are revised as part of a permit amendment until such time
as the EPA approves any revised conditions into the SIP. The
permittee shall remain subject to both the initial SIP-approved
conditions and the revised conditions, until EPA approves the
revised conditions.''
    \45\ See final action approved on February 12, 2018 (83 FR
5927).
    \46\ See final action approved on September 27, 2019 (84 FR
51033) and the proposed approval on November 30, 2018 (83 FR 62204).
    \47\ The Arkansas Regional Haze Phase III SIP submittal did not
revise any aspects of the previous Phase I or II SIP revisions.
---------------------------------------------------------------------------

H. Arkansas Visibility Transport

    We are also addressing the interstate visibility transport element
required under CAA section 110(a)(2)(D)(i)(II) in this final action
from multiple SIP revisions for several NAAQS. Sections 110(a)(1) and
(2) of the CAA direct each state to develop and submit to the EPA a SIP
that provides for the implementation, maintenance, and enforcement of a
new or revised NAAQS.\48\ This type of SIP submission is referred to as
an infrastructure SIP. Section 110(a)(1) provides the timing and
procedural requirements for infrastructure SIPs. Specifically, each
state is required to make a new SIP submission within three years after
promulgation of a new or revised primary or secondary NAAQS. Section
110(a)(2) lists the substantive elements that states must address for
infrastructure SIPs to be approved by the EPA. Section 110(a)(2)(D)(i)
includes four distinct elements related to interstate transport of air
pollution, commonly referred to as prongs, that must be addressed in
infrastructure SIP submissions. The first two prongs are codified in
section 110(a)(2)(D)(i)(I) and the third and fourth prongs are codified
in section 110(a)(2)(D)(i)(II). These four prongs prohibit any source
or type of emission activities in one state from:
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    \48\ See the final rules promulgating the revised NAAQS: 71 FR
61144 (October 17, 2006); 77 FR 50033 (August 20, 2012); 80 FR 11573
(March 4, 2015); 80 FR 38419 (July 6, 2015); 78 FR 53269 (August 29,
2013); 73 FR 16436 (March 27, 2008). 81 FR 74504 (October 26, 2016);
75 FR 35520 (June 22, 2010); 75 FR 6474 (February 9, 2010); and 78
FR 3086 (January 15, 2013).

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     Contributing significantly to nonattainment of the NAAQS
in another state (prong 1);
     Interfering with maintenance of the NAAQS in another state
(prong 2);
     Interfering with measures that prevent significant
deterioration of air quality in another state (prong 3); and
     Interfering with measures that protect visibility in
another state (prong 4 or ``visibility transport'').
    We are only addressing the prong 4 element in this final approval.
The prong 4 element is consistent with the requirements in the regional
haze program, which explicitly require each state to address its share
of emission reductions needed to meet the RPGs for surrounding Class I
areas. The EPA most recently issued guidance that addressed prong 4 on
September 13, 2013.\49\ The 2013 guidance indicates that a state can
satisfy prong 4 requirements with a fully-approved regional haze SIP
that meets 40 CFR 51.308 or 309. Alternatively, in the absence of a
fully-approved regional haze SIP, a state may meet the prong 4
requirements through a demonstration showing that emissions within its
jurisdiction do not interfere with another air agency's plans to
protect visibility. Lastly, the guidance states that prong 4 is
pollutant-specific, so infrastructure SIPs only need to address the
particular pollutant (including precursors) for which there is a new or
revised NAAQS for which the SIP is being submitted that is interfering
with visibility protection.
---------------------------------------------------------------------------

    \49\ See ``Guidance on Infrastructure State Implementation Plan
(SIP) Elements under CAA sections 110(a)(1) and 110(a)(2)'' by
Stephen D. Page (Sept. 13, 2013), (pages 32-35).
---------------------------------------------------------------------------

    On March 24, 2017, the State submitted a SIP revision that
addressed all four infrastructure prongs from section 110(a)(2)(D)(i)
for the 2008 lead (Pb) NAAQS, the 2006 and 2012 PM2.5 NAAQS,
the 2008 O3 NAAQS, the 2010 SO2 NAAQS, and the
2010 NO2 NAAQS. We deferred taking action on the
110(a)(2)(D)(i)(II) prong 4 portion of that infrastructure SIP for a
future rulemaking with the exception of the 2008 Pb NAAQS.\50\ On
August 8, 2018, the State also included a discussion on visibility
transport in its regional haze Phase II SIP revision, but we deferred
taking action on the visibility transport requirements in that
submittal too.\51\ In the Phase II SIP revision, the State considered
all Class I areas in Arkansas and also considered those in Missouri,
which is the only State that was determined to potentially be impacted
by sources from within Arkansas for the first implementation period.
Missouri is currently not relying on emission reductions from Domtar in
its regional haze plan. DEQ concluded that Missouri is on track to
achieve its visibility goals; that observed visibility progress from
Arkansas sources are not interfering with Missouri's RPG achievements
for Hercules-Glades Wilderness and Mingo National Wildlife Refuge; and
that no additional controls on Arkansas sources are necessary to ensure
that other states' Class I areas meet their visibility goals for the
first planning period. On October 4, 2019, the State submitted the
Arkansas 2015 O3 NAAQS Interstate Transport SIP revision to
meet the requirements of CAA section 110(a)(2)(D) regarding interstate
transport for the 2015 O3 NAAQS. In that SIP submittal,
Arkansas also addressed the 2006 and 2012 PM2.5 NAAQS, the
2008 O3 NAAQS, the 2010 SO2 NAAQS, and the 2010
NO2 NAAQS prong 4 visibility transport obligations in
110(a)(2)(D)(i)(II), and we are finalizing approval of those prong 4
requirements in this action. The State's prong 4 visibility transport
analysis in the October 4, 2019 submittal supersedes the prong 4
visibility transport portion of the March 24, 2017, infrastructure SIP
submittal and supplements the August 8, 2018, Phase II Arkansas
Regional Haze SO2 and PM SIP revision \52\ for the 2006 and
2012 PM2.5 NAAQS, the 2008 and 2015 O3 NAAQS, the
2010 SO2 NAAQS, and the 2010 NO2 NAAQS. All other
applicable infrastructure SIP requirements in the October 4, 2019, SIP
submission have been or will be addressed in separate rulemakings.
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    \50\ The EPA approved the visibility transport requirement for
the 2008 Pb NAAQS only in the February 2018 final action effective
March 16, 2018 (see 83 FR 6470).
    \51\ See 84 FR 51033, 51054 (September 27, 2019).
    \52\ See 83 FR 62204 (November 30, 2018) for proposed approval
and 84 FR 51033 (September 27, 2019) for final action. The Arkansas
Regional Haze SO2 and PM SIP revision addressed separate
CAA requirements related to interstate visibility transport under
CAA section 110(a)(2)(D)(i)(II), but we did not take action on that
part of the submittal. We are acting on the prong 4 portion of the
Arkansas Regional Haze SO2 and PM SIP revision in this
final action.
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II. Summary of Proposed Action and Our Final Decisions

    On March 16, 2020, we published a Notice of Proposed Rulemaking
(NPRM) \53\ proposing to approve the Arkansas Regional Haze Phase III
SIP revision submitted by DEQ on August 13, 2019. The SIP submittal
addressed requirements of the Act and the Regional Haze Rule for
visibility protection in mandatory Federal Class I areas for the first
implementation period. The EPA proposed to approve an alternative
measure to BART for SO2, PM, and NOX at the
Domtar Ashdown Mill and elements of the SIP submittal that relate to
these BART requirements at this facility. We are finalizing our
determination in the NPRM that the Arkansas Regional Haze Phase III SIP
revision meets all of the applicable regional haze BART alternative
provisions set forth in 40 CFR 51.308(e)(2)(i) to (iv) for the Domtar
Ashdown Mill. We are also finalizing our approval of specific plantwide
permit provisions as the enforceable mechanism for the BART alternative
emission limits and conditions for implementing the BART alternative.
We are finalizing our approval of the reasonable progress components
under 40 CFR 51.308(d) relating to Domtar Power Boilers No. 1 and 2.
With the final approval of the BART alternative requirements for the
Domtar Ashdown Mill in this action, DEQ has satisfied all long-term
strategy requirements under section 40 CFR 51.308(d)(3). We also
proposed to approve Arkansas' consultation with FLMs and Missouri and
our determination that the SIP submittal satisfies the consultation
requirements under 40 CFR 51.308(i)(2) and 40 CFR 51.308(d)(3)(i). We
also agreed with DEQ's determination that the revised 2018 RPGs in the
Phase II action do not need to be further revised. We proposed to
approve Arkansas' request to withdrawal from the approved SIP the
previously approved PM10 BART limit for Power Boiler No. 1.
and the regional haze FIP provisions for the Domtar Ashdown Mill, and
we are finalizing the withdrawal of those provisions in a separate
rulemaking published elsewhere in this issue of the Federal Register.
---------------------------------------------------------------------------

    \53\ See March 16, 2020 proposed approval (85 FR 14847).
---------------------------------------------------------------------------

    The EPA also proposed to approve in its NPRM Arkansas' interstate
visibility transport provisions from the August 8, 2018, regional haze
Phase II SIP submittal as supplemented by the visibility transport
provisions in the October 4, 2019, interstate transport SIP submittal,
which cover the following six NAAQS: The 2006 24-hour PM2.5
NAAQS; the 2012 annual PM2.5 NAAQS; the 2008 and 2015 eight-
hour O3 NAAQS; the 2010 one-hour NO2 NAAQS; and
the 2010 one-hour SO2 NAAQS. We are finalizing our approval
of the prong 4 portions of these SIP submittals addressing CAA section
110(a)(2)(D)(i)(II) for these NAAQS on the basis that with our approval
of the Arkansas Regional Haze Phase III SIP revision in this notice,
Arkansas has a fully-approved regional haze SIP. The Arkansas Regional
Haze NOX SIP

revision,\54\ the Arkansas Regional Haze SO2 and PM SIP
revision,\55\ and the Arkansas Regional Haze Phase III SIP revision
together fully address the deficiencies of the 2008 Arkansas Regional
Haze SIP that were identified in the March 12, 2012, partial approval/
partial disapproval action. As an alternative basis for approval of the
State's CAA section 110(a)(2)(D)(i)(II) prong 4 submittals for these
NAAQS, we are finalizing our determination that Arkansas has provided
an adequate demonstration in the October 4, 2019 submittal that
emissions within its jurisdiction do not interfere with other air
agencies' plans to protect visibility.
---------------------------------------------------------------------------

    \54\ Final action approved on February 12, 2018 (83 FR 5927).
    \55\ See 83 FR 62204 (November 30, 2018) for proposed approval
and 84 FR 51033 (September 27, 2019) for final approval.
---------------------------------------------------------------------------

    The public comment period for the NPRM closed on April 15, 2020. We
received two sets of public comments concerning our proposed action.
The comments are included in the publicly posted docket associated with
this action at https://www.regulations.gov. We received a comment
letter with adverse comments dated April 15, 2020, submitted on behalf
of the National Parks Conservation Association, the Sierra Club, and
Earthjustice regarding our proposed approval. We also received another
comment letter dated April 15, 2020, from Domtar that was largely in
support of our proposed approval. Below we provide a summary of the
comments with our detailed responses. The complete comments can be
found in the docket associated with this final rulemaking. After
careful consideration of the public comments received, we have decided
to finalize our action with no changes from the proposed action. For
our complete, comprehensive evaluation of the Arkansas Regional Haze
Phase III SIP revision, please refer to the proposed approval (See 85
FR 14847). Our final actions regarding the NPRM are summarized in
section IV of this notice.

III. Public Comments and EPA Responses

A. Demonstration That the BART Alternative Is Better-Than-BART

    Comment A.1: The BART alternative measure submitted by the State
fails to demonstrate that the BART alternative achieves greater
reasonable progress than BART. Rather than submit a revised BART
analysis determination, DEQ's Arkansas Regional Haze Phase III SIP
includes what it asserts are approvable SIP measures in a BART
alternative for two subject-to-BART sources (Power Boilers No. 1 and 2)
at the Domtar Ashdown paper mill located in Ashdown, Arkansas. Compared
to BART, the BART alternative results in an overall (Power Boilers No.
1 and 2) increase in sulfur dioxide (SO2) emissions and
decrease in NOX emissions. While DEQ claims that the
NOX decrease mitigates the SO2 increase, the SIP
fails to demonstrate the BART alternative achieves greater reasonable
progress than BART.
    Response: We disagree with the commenter's assertion that the BART
alternative measure submitted by the State fails to demonstrate that
the BART alternative achieves greater reasonable progress than BART.
    As explained in the proposed action, the BART alternative would
result in an overall decrease in SO2, NOX, and
particulate matter (PM10) emissions from the baseline for
both power boilers at Domtar Ashdown paper mill. The BART alternative
results in greater emission reductions of NOX and
PM10 than the BART controls in the FIP. The BART alternative
controls would reduce NOX and PM10 emissions by
1,096 and 111 tons per year (tpy), respectively, from the baseline. The
BART alternative results in a smaller reduction in SO2
emissions compared to the BART controls (BART achieves 3,051 tpy
SO2 reduction) but still achieves a decrease of 1,637 tpy
SO2 from the baseline. Despite a smaller reduction in
SO2 emissions than BART (a 1,414 tpy SO2
difference), the BART alternative results in 300 tpy fewer
NOX emissions and 157 tpy fewer PM10 emissions
compared to BART. Model results show that the additional reduction in
NOX emissions under the BART alternative controls results in
more overall modeled visibility improvement across the impacted Class I
areas than BART even with the smaller reduction in SO2
emissions.
    We explained in our proposed action that greater visibility
improvement occurs because Domtar's baseline NOX emissions
are the primary driver of visibility impacts from the source and
contribute more to visibility impairment across the four-affected Class
I areas in Arkansas and Missouri for Power Boiler No. 1, and also
contribute more at Caney Creek for Power Boiler No. 2 than other
pollutants emitted by the source. DEQ first included an analysis
utilizing method 1 \56\ that shows that the BART alternative controls
achieve greater overall cumulative reductions in visibility impairment
(as expressed by the change in deciviews or [Delta]dv) from the
baseline across the four Class I areas when compared to BART (0.549
[Delta]dv for the alternative versus 0.473 [Delta]dv for BART). DEQ
then determined that the BART alternative controls reduce the overall
visibility impairment from the baseline by 0.520 [Delta]dv under its
method 2 evaluation and is greater than the overall visibility
improvement modeled under BART, which is 0.516 [Delta]dv. The DEQ noted
that the most impacted Class I area, Caney Creek (1.137 dv baseline
impairment), improved the greatest (0.384 [Delta]dv) with the BART
alternative under method 2, and would experience greater visibility
improvement under the BART alternative scenario than under the BART
scenario, which improves by 0.361 [Delta]dv.
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    \56\ Method 1 assessed visibility impairment on a per source per
pollutant basis and Method 2 allowed for interaction of the
pollutants from both boilers. See descriptions of method 1 and 2
modeling evaluations in the March 16, 2020 proposed approval (85 FR
14847, 14857-14858).
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    The State's weight of evidence analysis of visibility improvement
in the SIP was supported by our analysis of various metrics, which
reinforced that the BART alternative achieves greater reasonable
progress. We analyzed the pollutant species contribution to visibility
impacts at the Class I areas from each power boiler. Specifically, for
Power Boiler No. 1, baseline modeled nitrate (NO3-) and
nitrogen dioxide (NO2) impacts had the highest contribution
to visibility impairment at all Class I areas. For Power Boiler No. 2,
baseline modeled NO3- and NO2 impacts are the
primary driver for visibility impacts at Caney Creek, which is the
Class I area impacted the most by the Domtar units. For Power Boiler
No. 2, the visibility impacts resulting from NOX at Caney
Creek outweigh SO42- species
contributions (from SO2 precursors) to impacts at the other
three Class I areas combined. In addition to pollutant species
contributions to impacts, we also considered the ten highest impacted
days.\57\ This analysis provided a broader look at those days with the
highest impacts at each Class I area. The results were consistent with

the State's analysis based on the 98th percentile day, which was
selected as representative of the highest impact (the 8th highest day).
The average results across the top ten highest impacted days also
supported our position that it is appropriate to give greater weight to
Caney Creek impacts (0.9819 dv baseline impairment) in our
consideration of whether the BART alternative achieves greater
reasonable progress than BART since they are much larger than impacts
at the other Class I areas. The BART alternative resulted in more
visibility improvement at Caney Creek and slightly less at the other
Class I areas when compared to the BART limits, but the visibility
improvement at Caney Creek outweighed the difference in visibility
benefit at the other three Class I areas altogether. On average, the
BART alternative controls achieved greater overall visibility
improvement from the baseline compared to BART for the ten highest
impacted days (0.439 [Delta]dv for the alternative versus 0.423
[Delta]dv for BART). Our analysis of the ten highest impacted days
similarly supported the conclusion that the BART alternative provides
for greater reasonable progress than BART. Finally, we complemented the
State's analysis by evaluating the modeled number of days impacted by
Domtar over 1.0 dv and 0.5 dv for each scenario at each Class I area.
This compared the frequency and duration of higher visibility impacts
between the two control scenarios. The BART FIP limits and the BART
alternative both reduce the total modeled number of days with
visibility impacts over 1.0 dv from fifteen days in the baseline to
four days for each scenario. For the metric of days with modeled
visibility impacts over 0.5 dv, the FIP limits and the BART alternative
showed nearly identical reduction in the number of days, but very
slightly favored the FIP limits over the BART alternative (from 82 to
36 days for the FIP limits compared to 37 days for the BART
alternative). This single metric, however, on which BART performed
slightly better than the BART alternative (days impacted over 0.5 dv)
is not sufficient to outweigh the substantial evidence presented using
the other metrics as to the relatively greater benefits of the BART
alternative over BART. These different metrics reinforce the State's
analysis in the SIP that greater reasonable progress was achieved by
the BART alternative.\58\
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    \57\ The ``ten highest impacted days'' means the 8th to 17th
highest days at each Class I area. The 98th percentile means that
for a given distribution, it is equal to or higher than 98 percent
of the rest of the distribution. The 98th percentile impact day
means that only two percent of the 365 days in a calendar year, or
7.3 days (rounded up to 8 days) have higher impacts. The simplified
chemistry in the CALPUFF model tends to magnify the actual
visibility effects of that source so it is appropriate to use the
98th percentile, or 8th highest day, to not give undue weight to the
extreme tail of the distribution. This approach will effectively
capture the sources that contribute to visibility impairment in a
Class I area, while minimizing the likelihood that the highest
modeled visibility impacts might be caused by unusual meteorology or
conservative assumptions in the model. See 70 FR 39104, 39121 (July
6, 2005), Regional Haze Regulations and Guidelines for BART
Determinations.
    \58\ See discussion regarding the different metrics in the March
16, 2020 proposed approval (85 FR 14847, 14859-14860).
---------------------------------------------------------------------------

    The State's weight of evidence analysis of emission reductions and
visibility improvement (using the 98th percentile metric) as
complemented by our analysis of different metrics, justify our approval
of the State's determination that the BART alternative achieves greater
reasonable progress than BART under 40 CFR 51.308(e)(2)(i)(E). The
State followed the prescribed process for determining the level of
control required for the BART alternative for the Domtar Ashdown Mill
and adequately supported its determination with analysis that meets the
requirements under section 40 CFR 51.308(e)(2).
    Comment A.2: EPA proposes approving the Arkansas Regional Haze
Phase III SIP and relaxing the BART emission limitations established in
its 2016 FIP. The proposed facility-wide emission limitation would
allow for fewer emission reductions from the Domtar Ashdown Mill. EPA's
proposal reverses course on its FIP, failing to make reasonable
progress on reducing visibility impairment in Class I areas in
accordance with the CAA mandates and requirements.
    Response: The BART alternative establishes pollutant-specific
limits at each of the two BART sources at the Ashdown Mill. There is no
``facility-wide emission limitation'' as stated by the commenter. In
addition, we disagree with the commenter that the EPA is reversing
course on its FIP by relaxing BART limitations established in the FIP,
and thus failing to make reasonable progress and reduce visibility
impairment in Class I areas in accordance with the CAA and its
mandates.
    The BART alternative results in larger reductions in NOX
and PM emissions than required by the FIP, while SO2
emissions are not reduced to the same extent as would be required under
the FIP. As explained in our response to comment A.1 of this final
action and also in section IV of our proposed action, our analysis of
the State's weight of evidence conclusion as complemented by EPA's
analysis, demonstrate that the State has met the BART and reasonable
progress requirements for regional haze under the applicable provisions
of the CAA and the Regional Haze Rule. Thus, the proposed withdrawal of
the BART provisions in the FIP and replacement with the BART
alternative requirements in the SIP will not result in a failure to
meet the applicable requirements.
    The Arkansas Regional Haze Phase III SIP revision and concurrent
withdrawal of the corresponding parts of the FIP pertaining to Domtar
will also not reverse course from the prior FIP with respect to the
separate reasonable progress requirements for Arkansas. As mentioned in
section IV of our proposed action, we determined in our September 27,
2019 Arkansas Regional Haze SO2 and PM SIP revision that
Arkansas had fully addressed the reasonable progress requirements under
40 CFR 51.308(d)(1) for the first implementation period in that final
action. In that action, we also noted that the 2016 FIP BART
determination requirements for Domtar were still in place but we agreed
with the State that as long as those requirements continued to be
addressed by the measures in the FIP, nothing further is needed to
satisfy the reasonable progress requirements for the first
implementation period. In the Arkansas Regional Haze Phase III SIP
submittal, the State assessed whether changes would be needed with
respect to the reasonable progress analysis, based on any differences
between the SIP and FIP-based measures for Domtar. The BART alternative
analysis performed for the Domtar power boilers was based, in part, on
an assessment of the same factors that must be addressed in the
reasonable progress analysis. The FIP BART determination analysis was
compared to the proposed BART alternative controls in the Arkansas
Regional Haze Phase III SIP submittal. The BART alternative measures
for Domtar resulted in greater overall visibility improvement than the
BART requirements in the FIP and the previously approved BART
PM10 limit for Power Boiler No. 1. As a result, nothing
further is needed to satisfy the reasonable progress requirements for
the first implementation period. For these reasons, approval of the
Arkansas Regional Haze Phase III SIP revision and concurrent withdrawal
of the corresponding parts of the FIP do not interfere or reverse
course from the FIP with respect to the CAA requirements pertaining to
BART or reasonable progress under 40 CFR 51.308(d) or (e).
    Comment A.3: EPA's proposal cobbles together two pieces of
information (a comparison of emission reductions and a modeling
analysis) and fails to demonstrate that the BART alternative is clearly
better than BART. The Regional Haze Rule provides different regulatory
tests for a state to use to demonstrate that a BART alternative is
better than BART. Arkansas claims that it used the ``clear weight of
evidence test,'' but the information it provides falls under 40 CFR
51.308(e): An emission reduction comparison and modeling. The
information Arkansas provides fails to meet the requirements in 40 CFR
51.308(e). Therefore, it is

unreasonable for EPA to provide weight to the information.
    Response: We disagree with the commenter's assertion that the
information on which our approval of the State's SIP is based fails to
provide an adequate clear weight of evidence analysis to meet the
requirements in 40 CFR 51.308(e). The commenter is apparently alleging
that the analysis provided by the State instead falls under 40 CFR
51.308(e)(3) rather than under 40 CFR 51.308(e)(2)(i)(E) because it is
based on an emission reduction comparison and modeling. The argument
that the kind of data and analysis to be used under the clear weight of
evidence test must somehow be sufficiently different from what would be
required under 40 CFR 51.308(e)(3) is not a reasonable interpretation
of these regulations. EPA interprets 40 CFR 51.308(e)(2)(i)(E) as
permitting data and analysis that may be relevant under 40 CFR
51.308(e)(3) analysis to be used in supporting a clear weight of
evidence demonstration.
    Pursuant to 40 CFR 51.308(e)(2)(i)(E), the state must provide a
determination under 40 CFR 51.308(e)(3) or otherwise based on ``clear
weight of evidence'' that the alternative measure achieves greater
reasonable progress than BART. The State relied on a modeling analysis
to determine if the BART alternative could be shown to make greater
reasonable progress than BART, but that modeling was different than the
modeling described under 40 CFR 51.308(e)(3). The State used an air
quality modeling methodology approach using the maximum 98th percentile
visibility impact of three modeled years using the CALPUFF model
instead of modeled overall visibility conditions for the twenty percent
best and worst days, as would be required under 40 CFR 51.308(e)(3).
The State's approach could be considered a modified version of the two-
part modeling test under 40 CFR 51.308(e)(3) and is more appropriate to
classify under the weight of evidence analysis approach instead allowed
under 40 CFR 51.308(e)(2)(i)(E).
    The State's methodology and analysis under the clear weight of
evidence test is reasonable. The State's CALPUFF modeling approach
utilizing the 98th percentile visibility impacts is consistent with the
approach recommended by the BART guidelines \59\ for comparing
different control options at a single source when developing BART
determinations relying on the 98th percentile visibility impact as the
key metric. It is also consistent with the methodology followed in
EPA's 2016 FIP BART determination 60 61 for Domtar.
---------------------------------------------------------------------------

    \59\ See 40 CFR 51 Appendix Y section III.A.3 and IV.D.5,
``Guidelines for BART Determinations Under the Regional Haze Rule.''
    \60\ See proposed FIP on April 8, 2015 (80 FR 18979).
    \61\ See final FIP action on September 27, 2016 (81 FR 66332) as
corrected on October 4, 2016 (81 FR 68319) and the associated TSD,
``AR020.0002-00 TSD for EPA's Proposed Action on the Arkansas
Regional Haze FIP'' in Docket No. EPA-R06-OAR-2015-0189 for the FIP
BART analysis for SO2 and NOX for Power Boiler
No. 1; and SO2, NOX, and PM10 for
Power Boiler No. 2. This was included as part of the Phase III
submittal and included in the docket of this action.
---------------------------------------------------------------------------

    CALPUFF is a single source air quality model that is recommended in
the BART Guidelines. Since CALPUFF was used for this BART alternative
analysis, the modeling results were post-processed in a manner
consistent with the BART guidelines. This approach is, therefore,
acceptable and reasonable for the comparison of the proposed BART
alternative to the FIP BART determination for Domtar since it is the
same modeling used to determine BART in the FIP, and the BART
alternative is focused on only the BART sources at Domtar. The State
also considered two methods of modeling evaluation provided by Domtar
for this approach of using the maximum 98th percentile visibility
impact. Method 1 assessed visibility impairment on a per source per
pollutant basis and method 2 allowed for interaction of the pollutants
from both boilers. The State followed the same general CALPUFF modeling
protocol and used the same meteorological data inputs for the BART
alternative assessment as discussed in Appendix B to the FIP TSD. Only
the modeled emission rates changed to represent the modeled scenarios
for each method.
    DEQ determined that the visibility benefits as measured under
method 2 and the previous FIP BART determination formed an appropriate
BART benchmark for the purposes of the evaluation of Domtar's BART
alternative. We continue to agree with DEQ that because method 2
provides for the full chemical interaction of emissions from both power
boilers, method 2 analysis results are a reliable assessment of the
anticipated overall visibility improvement of controls utilizing the
98th percentile impact. Under the weight of evidence approach, we made
use of all available information and data which could inform our
decision while recognizing the relative strengths and weaknesses of
that information in arriving at the soundest decision possible.\62\
This array of information and other relevant data was of sufficient
quality to inform our comparison of visibility impacts between BART and
the BART alternative. We carefully considered this evidence in
evaluating the Arkansas Phase III SIP revision submitted by the State.
Overall, the difference in visibility impacts between the BART and the
BART alternative scenarios was large enough to show that the BART
alternative achieves greater reasonable progress than BART based on the
clear weight of the evidence.
---------------------------------------------------------------------------

    \62\ See 71 FR 60612, 60622 (October 13, 2006). Factors which
can be used in a weight of evidence determination in this context
may include, but not be limited to, future projected emissions
levels under the alternative as compared to under BART; future
projected visibility conditions under the two scenarios; the
geographic distribution of sources likely to reduce or increase
emissions under the alternative as compared to BART sources;
monitoring data and emissions inventories; and sensitivity analyses
of any models used.
---------------------------------------------------------------------------

    As explained in response to comment A.1 in section III.A of this
final action, we evaluated DEQ's analysis and additional model results
(relying primarily on the analysis of the 98th percentile impacts),\63\
the analysis of emission reductions,\64\ and the analysis of Domtar's
visibility impacts due to NO3- compared to
SO4-.\65\ In addition, we also considered our analysis of
the ten highest impacted days (8th to 17th highest) \66\ and our
analysis of the number of days impacted over 0.5 dv and 1.0 dv.\67\ All
of these metrics, except the number of days impacted over 0.5 dv (which
only very slightly favored BART), provided substantial evidence and
collectively supported the conclusion that the BART alternative
provides for greater reasonable progress than BART. For these reasons,
we are finalizing our approval of the State's weight of evidence
analysis approach and the conclusions reached by the State. In the
course of evaluating the SIP submittal, EPA developed some additional
analysis that complements and supports

the State's analysis. Taken as a whole, the record supports approval of
the State's determination that the BART alternative achieves greater
reasonable progress than BART under the clear weight of evidence
pursuant to 40 CFR 51.308(e)(2)(i)(E).
---------------------------------------------------------------------------

    \63\ See Tables 7 and 8 of the proposed approval, 85 FR 14847,
14858.
    \64\ See Tables 5 and 6 of the proposed approval, 85 FR 14847,
14856-14857.
    \65\ See Appendix C ``Supplemental BART Determination
Information Domtar A.W. LLC, Ashdown Mill (AFIN 41-00002),''
originally dated June 28, 2013 and revised on May 16, 2014, prepared
by Trinity Consultants Inc. in conjunction with Domtar A.W. LLC.
    \66\ See 85 FR 14847, 14859. This data is based on the CALPUFF
modeling provided by Domtar and relied on by the State in the Phase
III SIP. See ``EPA-CALPUFF summary for Method 2.xlsx'' for the EPA's
summary of the modeling data, available in the docket for this
action.
    \67\ See 85 FR 14847, 14860. This data is based on the CALPUFF
modeling provided by Domtar and relied on by the State in the Phase
III SIP revision. See ``EPA-CALPUFF summary for Method 2.xlsx'' for
the EPA's summary of the modeling data, available in the docket for
this action.
---------------------------------------------------------------------------

    Comment A.4: EPA fails to provide a basis to rely on a comparison
of emissions. EPA merely presents the emission reductions under BART
and the alternative, but fails to explain the strengths and weaknesses
of this information and does not assign any weight to the emission
comparison. A comparison of multiple pollutant species emission levels
alone is not informative without visibility modeling. The pollutants'
differing visibility impacts and complex interactions between them and
in the atmosphere make it extremely difficult to discern their
collective impacts without visibility modeling. EPA has consistently
relied on modeling to assess the visibility impacts under these
circumstances.
    Response: We disagree with the commenter's assertion that EPA
``merely presents the emission reductions under BART and the
alternative.'' In our proposed action,\68\ our basis for presenting the
emission reduction information laid the foundation for describing the
differences in visibility outcomes achieved between the FIP and the
BART alternative, leading EPA to agree with the State that there was a
need to support the BART alternative with visibility modeling. The
State first showed reduced emissions from the baseline and then used
the modeling to support a conclusion that the emission reduction
differences between the FIP BART benchmark and BART alternative were
acceptable because NOX precursor emissions are the main
driver contributing to the visibility impacts from this source. Thus,
the State proceeded to conduct precisely the modeling analysis the
commenter seems to assert is required, using CALPUFF. Indeed,
recognizing the potential interaction between multiple species of
visibility pollutants, the State used Method 2 in evaluating the
visibility consequences of the BART alternative compared to the BART
benchmark. EPA has relied on the modeling submitted by the State in
reaching a conclusion that the SIP submittal is approvable. While EPA
does not concede that modeling is required in all cases to conduct an
approvable ``clear weight of evidence'' analysis under
51.308(e)(2)(i)(E), modeling was in fact done in this instance to
support the analysis. This comment is thus premised on a
misunderstanding of the record.
---------------------------------------------------------------------------

    \68\ 85 FR 14847, 14857.
---------------------------------------------------------------------------

    To the extent the commenter is asserting that the emissions
comparisons alone cannot be used as even one part of a weight of
evidence demonstration, the commenter is mistaken in how a ``weight of
evidence'' analysis is conducted. The term ``weight'' connotes that
multiple pieces of evidence are brought together and analyzed as a
whole.\69\ Comparative emissions data is obviously a critical piece of
that evidentiary record, and provides a foundation on which further
analysis, such as modeling, may be conducted. To assert that EPA must
ignore emissions comparisons--or any single piece of evidence--because
it does not provide, on its own, a sufficient basis to make a ``weight
of evidence'' determination is both illogical and a misreading of EPA's
regulations. We also note that the regulations require an analysis of
emission reductions under BART and the alternative, see 40 CFR
51.308(e)(2)(i)(C) and (D).
---------------------------------------------------------------------------

    \69\ See 71 FR 60612, 60622 (October 13, 2006).
---------------------------------------------------------------------------

    Comment A.5: EPA should not provide weight to modeling data of
insufficient quality, which fails to meet the requirements of the
regulations. It is disingenuous for EPA to suggest that the CALPUFF
model is a ``modified'' version of the two-part modeling test. EPA has
consistently interpreted the two-part dispersion modeling test under 40
CFR 51.308(e)(3) to mean the Comprehensive Air Quality Model with
Extensions (CAMx) model, and not CALPUFF. EPA and states have
consistently used CAMx to assess whether a BART alternative would
result in ``greater reasonable progress'' under the two-prong test.
CAMx and CALPUFF are vastly different models and 40 CFR 51.308(e)(3)
requires a specific type of dispersion modeling. EPA's suggestion that
use of CALPUFF is acceptable because it ``is consistent with the
approach recommended by the BART guidelines for comparing different
control options at a single source when developing BART determinations
relying on the 98th percentile visibility impact as the key metric''
also fails. A comparison of control options at a single source compares
changes in the emission reductions in one pollutant, but does not
compare the complexities involved in analyzing interactions between
multiple pollutants. It is also irrelevant that only the BART sources
at Domtar are under consideration. While the FIP considered each
pollutant separately, the alternative attempts to analyze and take
credit for combined emission reductions from three pollutants as it
fails to actually assess the effect of the alternative on visibility as
compared to BART.
    Response: We disagree with the comment that CAMx must be used for
the two-part test under 40 CFR 51.308(e)(3) or that CALPUFF cannot be
used to support the determination here, which is not under 40 CFR
51.308(e)(3) in any case. The first point is irrelevant because the
State is not proceeding under 40 CFR 51.308(e)(3); however, it is worth
noting that the regulatory text does not require the use of CAMx.
CALPUFF is also an air dispersion model, and one that the Agency has
recognized as available for use for BART alternatives under 40 CFR
51.308(e)(3).\70\
---------------------------------------------------------------------------

    \70\ See 71 FR 60612, 60616.
---------------------------------------------------------------------------

    Regarding the use of CALPUFF, we did not suggest that CALPUFF was
replacing CAMx under 40 CFR 51.308(e)(3). We logically examined the
two-part analysis under 40 CFR 51.308(e)(3) in the proposed action to
show how the State arrived at classifying the approach as a weight of
evidence approach. Our choice of using the term ``modified'' to
describe the relationship of this analysis to the two-part test under
40 CFR 51.308(e)(3) was intended to describe how the State's approach
was similar to 40 CFR51.308(e)(3) in considering distribution of
emissions and visibility improvements using modeling, but different
from 40 CFR 51.308(e)(3) because the analysis based on the CALPUFF
modeling focused on the 98th percentile visibility impacts instead of
the twenty percent best and worst days required by 40 CFR 51.308(e)(3).
Therefore, the State's weight of evidence analysis is acceptable under
40 CFR 51.308(e)(2)(i)(E) and should not be judged according to 40 CFR
51.308(e)(3). The commenter's objection to 40 CFR 51.308(e)(3) not
being met is immaterial since the weight of evidence approach followed
in the SIP submittal does not fall under 40 CFR 51.308(e)(3) but under
40 CFR 51.308(e)(2)(i)(E).
    The commenter states that EPA is wrong to consider CALPUFF as
acceptable just because it ``is consistent with the approach
recommended by the BART guidelines for comparing different control
options at a single source when developing BART determinations relying
on the 98th percentile visibility impact as the key metric.'' The
commenter points out that a comparison of control options at a single
source compares changes in the emission reductions in one pollutant,

but does not compare the complexities involved in analyzing
interactions between multiple pollutants. We disagree with this point
in relation to the alternative analysis here. First, particularly for
purposes of a BART alternative analysis for a single facility (with two
BART units), EPA's regulations recognize CALPUFF to be an acceptable
model, (explaining that CALPUFF is particularly suited for BART and
BART alternative applications at a single source).\71\ Further, Method
2, incorporated by the State in its SIP submittal, is a full assessment
method where all sources and pollutants are combined into a single
CALPUFF modeling run per year for the baseline and each control
scenario. Method 2 allows for interaction of the pollutants from both
boilers, as emitted pollutants from each unit disperse and compete for
the same reactants in the atmosphere, providing modeled overall impacts
due to emissions from both units. It is because of this that method 2
analysis results are a more reliable assessment of the anticipated
overall visibility improvement of controls under each scenario. Thus,
this is an entirely suitable application of the CALPUFF model, and the
commenter is incorrect to state that the CALPUFF modeling did not
account for the interactive chemistry of visibility pollutants.
---------------------------------------------------------------------------

    \71\ See 71 FR 60616.
---------------------------------------------------------------------------

    EPA recognizes that the CALPUFF model includes simplified chemistry
to account for interactions between pollutants. The simplified
chemistry tends to magnify the actual visibility effects of a single
source; thus, it is appropriate to use the 98th percentile to avoid
overprediction and not give undue weight to the extreme tail of the
distribution. This approach will effectively capture the sources that
contribute to visibility impairment in a Class I area, while minimizing
the likelihood that the highest modeled visibility impacts might be
caused by unusual meteorology or conservative assumptions in the model.
    The EPA has previously recognized this approach of using CALPUFF as
an acceptable approach in the past when analyzing BART alternatives
that only include emission reductions at a single or small group of
BART sources. Specifically, we approved this approach for the State of
Arizona which established a BART alternative for Steam Units 2 and 3 at
Arizona Electric Power Cooperative's Apache Generating Station.\72\ See
also 70 FR 60616 (recognizing CALPUFF as particularly appropriate for
single-source applications).
---------------------------------------------------------------------------

    \72\ See Arizona's September 19, 2014 proposed approval (79 FR
56322) which was finalized on April 10, 2015 (80 FR 19220).
---------------------------------------------------------------------------

    The commenter states that the FIP considered each pollutant
separately, whereas the alternative attempts to analyze and take credit
for combined emission reductions from three pollutants, which allegedly
fails to assess the effect of the alternative on visibility as compared
to BART. The commenter is incorrect in their premise. The CALPUFF
modeling in the FIP evaluated each unit separately, but modeled the
visibility impacts from all pollutants from that unit. For example, in
evaluating the visibility benefit from NOX controls on Power
Boiler No. 1, the NOX emissions varied between each control
scenario modeled, while the SO2 and PM emissions were
included but held constant in these NOX control scenarios.
In evaluating the BART alternative, the State provided EPA with two
separate methods of using the CALPUFF modeling to evaluate visibility
impacts of the BART alternative as compared to BART, including Method 2
(described above) that modeled all pollutants from both BART units to
assess the total visibility impact from these two units.
    For these reasons, we disagree that the modeling data was of
insufficient quality and failed to meet the requirements of the
regulations.
    Comment A.6: EPA lacks authority to give one Class I area more
weight than others. EPA suggests that it is reasonable to give one of
the Class I areas ``greater weight'' when considering visibility
benefits and cherry-picks the Class I area with the greatest visibility
improvement, which is closest to Domtar. Focusing on that Class I area
serves to support a source's preferred control outcome. Showing that
one Class I area will have greater visibility benefits does nothing to
tip the weight of evidence scale in favor of the BART alternative. It
merely shows one area will see more benefits. In addition, EPA fails to
provide a basis for applying the 0.5 deciview threshold used by the
State to determine if a source contributes to visibility impairment at
a Class I area with the BART alternative analysis.
    Response: We disagree with the commenter's assertion that EPA
``cherry picks'' the Class I areas with the greatest visibility
improvement. We considered many metrics in analyzing the weight of
evidence approach by the State, including the overall visibility
improvement on average across the four impacted Class I areas. As a
whole, these factors supported a conclusion that the BART alternative
achieves greater reasonable progress than BART at the subject facility.
One metric that we analyzed was the breakdown of pollutant speciation
impacts across each Class I area due to modeled emissions from each
power boiler. We highlighted impacts at Caney Creek specifically in
this analysis because Domtar's Ashdown facility impacts this Class I
area the greatest, and this is due to NOX emissions from
Power Boiler No. 2. We also found that NOX emissions
contributed more to visibility impairment across all four Class I areas
for Power Boiler No. 1. The greater impact due to NOX
emissions is relevant because it demonstrates that the higher
SO2 emissions allowed under the BART alternative is offset
by the larger reduction in NOX emissions. This is just one
factor among many that we considered in analyzing the State's weight of
evidence approach as explained in the proposed approval and in
preceding responses in this final approval. We took into account the
visibility impacts at all impacted Class I areas (individually and on
average) and did not solely focus on the benefits at the most impacted
area.
    We disagree with the assertion that we are supporting the source's
preferred control outcome instead of addressing emissions cumulatively
across all Class I areas. The commenter points out that the court in
Nat'l Parks Conservation Ass'n v. EPA held that EPA's analysis in
reviewing SIP submittals must take into account the visibility impacts
at all impacted Class I areas rather than focusing solely on the
benefits at the most impacted areas, 803 F.3d 151, 165 (3d Cir. 2015).
However, the facts of Nat'l Parks Conservation Ass'n v. EPA, are not
analogous to the facts surrounding our proposed approval. In Nat'l
Parks Conservation Ass'n v. EPA, the court was reviewing EPA's approval
of the state's assessment of the visibility-improvement factor within
the five-factor BART analysis. The state calculated visibility
improvement that could be achieved at Class I areas by implementing
additional controls at BART-eligible sources.\73\ The state's
calculations for each source, however, took into account only the
potential impact such controls would have on the visibility in the
Class I area most severely impacted by the source. The state did not
consider ``cumulative visibility impact,'' which the EPA itself had
conceded was improper under the

visibility BART factor.\74\ The court in NPCA rejected that this flaw
in the State's analysis could be dismissed as harmless error.\75\
---------------------------------------------------------------------------

    \73\ Id. at 164.
    \74\ Id. at 165.
    \75\ Id. at 167.
---------------------------------------------------------------------------

    In this action, by contrast, both the State and EPA have evaluated
the cumulative visibility impacts across all of the affected Class I
areas. The State considered this with both of its methods of analysis,
and EPA coupled those results with our own analysis of cumulative
visibility improvement. DEQ first included an analysis utilizing method
1 that shows that the BART alternative controls achieve greater overall
cumulative reductions in visibility impairment from the baseline
cumulatively across the four Class I areas when compared to BART (0.549
[Delta]dv for the alternative versus 0.473 [Delta]dv for BART). DEQ
also determined using method 2 that the BART alternative controls
reduce the overall cumulative visibility impairment from the baseline
by 0.520 [Delta]dv, which is greater than the overall visibility
improvement modeled under BART, which is 0.516 [Delta]dv. We
complemented the State's analysis by comparing the average visibility
impact across the top ten highest impacted days at each Class I area
(average 8th to 17th highest). This analysis provided a broader look at
those days with the highest impacts at each Class I area. The results
were consistent with the State's analysis based on the 98th percentile
day, which was selected as representative of the highest impact (i.e.,
the 8th highest day). The BART alternative controls achieve greater
overall visibility improvement from the baseline compared to BART for
the ten highest impacted days (0.439 [Delta]dv for the alternative
versus 0.423 [Delta]dv for BART). Thus, visibility benefits at each
Class I area were considered and analyzed by multiple metrics that
confirmed our proposed approval of the alternative.
    The commenter argues that EPA ``fails to provide a basis for
applying the 0.5 deciview threshold used by the State to determine if a
source contributes to visibility impairment at a Class I area with the
BART alternative analysis,'' noting that numerous BART determinations
relied on lower deciview thresholds that resulted in significant
emission reducing outcomes. The meaning of this comment is not clear.
EPA did not apply a 0.5 deciview threshold to cut off its evaluation of
other Class I areas. However, it is reasonable to provide additional
analysis when one Class I area is much more heavily impacted by a
source than others. In the case of Domtar, the baseline visibility
impacts at Caney Creek are much larger than impacts at the other Class
I areas, so it is reasonable to give greater weight to visibility
benefits at Caney Creek resulting from the alternative as compared to
BART. The level of visibility benefit from controls at the other three
Class I areas are smaller than those at Caney Creek, and the baseline
visibility impacts of the source at these areas was well below the 0.5
dv threshold used by the State to determine if a source contributes to
visibility impairment at a Class I area. In making this observation, we
do not categorically dismiss or ignore impacts to other Class I areas
below 0.5 or any other threshold. We simply note that the changes in
visibility at these other Class I areas were individually very small
and collectively smaller than the comparative gain in visibility
achieved by the BART alternative at Caney Creek.
    The commenter mentioned that Congress provided no authority for EPA
to treat one Class I area differently from others. As mentioned
previously, we treated all Class I areas the same and measured the
cumulative visibility impacts across all of them using multiple
metrics. We specifically analyzed the effects at Caney Creek, since it
is the Class I area impacted the most. But that analysis does not show
favoritism and merely provides one metric for interpreting how impacts
are correlated to overall emissions from the source at each Class I
area.

B. Monitoring, Recordkeeping and Reporting Requirements

    Comment B.1: EPA lacks authority to approve the State's SIP
submission with respect to provisions pertaining to alternative test
methods. EPA proposes to allow the State to authorize alternative
sampling or monitoring methods (equivalent to methods in the permit)
that EPA would concur on, outside the SIP process. Specifically, EPA
proposes approving permit conditions 35 and 42 as a part of the SIP.
Neither the State's SIP nor EPA's proposal explains what criteria and
process EPA would use to approve an alternative method. Arkansas'
alteration or elimination of SIP requirements can have no effect for
purposes of federal law unless and until EPA ratifies that action with
a SIP revision that is subject to the SIP requirements, including
provisions for public notice and comment. Moreover, the monitoring,
recordkeeping and reporting provisions in the State's SIP are not
approvable and therefore, those methods cannot be used a basis for
assessing whether an alternative method is approvable. Based on
Arkansas' SIP provisions, there is no way for the public to assess
whether an alternative method will comply with the Act. Therefore, EPA
should not approve these provisions because they are inconsistent with
the requirements of CAA section 110(i), 110(l) and 110(k)(3).
    Response: We recognize that the commenter raises a concern that the
State's ability to authorize (with EPA concurrence) alternative test
methods in conditions 35 and 42 may be inconsistent with the Act
insofar as ``[n]either the State's SIP nor EPA's proposed approval
explains what criteria and process EPA would use to approve an
alternative method.'' In general, EPA agrees that SIP provisions cannot
authorize a State to make changes in the EPA-approved and federally
enforceable SIP requirements applicable to sources without going
through the statutorily required SIP-revision process. EPA refers to
SIP provisions that purport to authorize States to make unilateral
changes to existing SIP requirements as impermissible ``director's
discretion'' provisions. However, EPA interprets the CAA to allow two
types of such provisions: (i) Where the provision provides director's
discretion for the State to make changes, but specifies that such
changes have no effect for purposes of federal law or alter SIP
requirements unless and until the EPA approves the changes through a
SIP revision pursuant to CAA requirements; or (ii) where the provision
provides director's discretion that is adequately bounded, such that at
the time EPA approves the SIP provision the agency can evaluate it for
compliance with applicable CAA requirements and evaluate the potential
impacts of the State's exercise of that discretion. EPA interprets CAA
section 110(i) to allow SIP provisions with director's discretion of
either type. In the case of an adequately bounded provision, EPA
considers such provisions consistent with section 110(i) because, at
the time of initial approval into the SIP, the agency will already have
evaluated the provision for compliance with applicable requirements and
evaluated the potential impacts from exercise of the discretion. By
their terms, conditions 35 and 42 do not specify that DEQ must seek a
SIP revision to change the required monitoring at the source. Thus, to
be approvable, EPA would have to determine that the State's discretion
in these provisions is adequately bounded and assess the potential
impacts from the exercise of that authority.

    In response to the commenter's concerns, EPA has further evaluated
conditions 35 and 42 to determine whether they provide adequate
bounding, allowing EPA to assess the provisions for compliance with
applicable requirements and the potential impacts that could result
from DEQ's potential exercise of the discretion to authorize
alternative monitoring. In support of EPA's proposed approval of
plantwide conditions 35 and 42 into the Arkansas SIP, DEQ provided
additional information in a letter (dated December 3, 2020) to EPA to
clarify the process and standards that the State shall follow and apply
to approve the use of any alternative method under plantwide conditions
35 and 42 of the Domtar permit.\76\ DEQ notes in the letter that DEQ
has received a disconnection notice \77\ for Power Boiler No. 1 and
that it is now permanently retired. In accordance with plantwide
condition 34, Power Boiler No. 1 is in compliance with the BART
alternative limits by virtue of being permanently retired and,
therefore, not emitting any of the relevant visibility pollutants. The
numerical emission limits will still apply, even though the unit has
been taken out of service. As a result, the process to be used by DEQ
in its approval of any request for an alternative sampling or
monitoring method is only applicable to Power Boiler No. 2 under
plantwide condition 42.
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    \76\ See December 3, 2020 clarification letter to EPA from DEQ
posted in the docket of this action.
    \77\ See November 18, 2020 Disconnection Notice from Domtar for
Power Boiler No. 1 (SN-03) in the docket of this action.
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    For Power Boiler No. 2, which currently relies on a continuous
emissions monitoring system (CEMS) to monitor SO2 and
NOX emissions, DEQ explained in its letter that it will use
the criteria for alternate monitoring systems contained in 40 CFR part
75, subpart E in its evaluation of the approvability of any request for
an alternative sampling or monitoring method for SO2 and
NOX emissions. More specifically, the State explained that
any request for approval of an alternative sampling or monitoring
method under plantwide condition 42 shall meet the general
demonstration requirements for alternative monitoring systems under 40
CFR 75.40 and require Domtar (or the current owner of the Ashdown Mill)
to demonstrate adequately that the average hourly emission data for
SO2, NOX, and/or volumetric flow in the proposed
alternative sampling or monitoring has the same or better precision,
reliability, accessibility, and timeliness as that provided by the
currently applicable continuous emission monitoring system (see
criteria in 40 CFR 75.41-75.46). Furthermore, DEQ will require all
information in 40 CFR 75.48 of Domtar (or the current owner of Ashdown
Mill) in the application for certification or recertification of the
alternative monitoring system. DEQ notes that the requirements of 40
CFR part 75, subpart E shall be met by the alternative monitoring
system when compared to a contemporaneously operating, fully certified
continuous emission monitoring system or a contemporaneously operating
reference method, where the appropriate reference methods are listed in
40 CFR 75.22.
    With respect to any request for alternative sampling or monitoring
methods for PM10 under plantwide condition 42, we note that
Power Boiler No. 2 is subject to 40 CFR part 63, subpart DDDDD and
reference is made to those requirements for PM10 compliance
demonstrations in plantwide condition 41. Condition 41 clearly explains
that the applicable PM10 compliance demonstration
requirements from 40 CFR part 63 subpart DDDDD shall be utilized by
Domtar (or the current owner of Ashdown Mill). These requirements,
which are at 40 CFR 63.7505--63.7541, do not cease and are ongoing. In
response to comment B.8 in section III of this final action, we address
the alternative option provided in the permit for monitoring emissions
from Power Boiler #2 when that unit is combusting natural gas.
    DEQ explained in its letter that it expects that Domtar will work
with both DEQ and EPA in the development of equivalent testing
protocols before seeking approval from DEQ (with EPA concurrence) and
before performing the equivalency testing. The alternate sampling or
monitoring protocol submittal to DEQ must contain EPA's official letter
of documented recommendations and concurrence, as required for DEQ
approval. Although not the same as EPA approval of an alternative
sampling or monitoring requirement through a SIP revision, in the case
of a valid director's discretion provision that is already adequately
bounded, EPA considers the inclusion of consultation with EPA an extra
measure of assurance that any such alternative will be appropriate.
Given the process that DEQ will follow and standards that DEQ will
apply in evaluating any potential alternative (and EPA's consultation
in the process) EPA anticipates that DEQ's exercise of its well bounded
discretion to authorize alternative sampling or monitoring will not
result in adverse impacts, e.g., adverse impacts on regional haze
requirements that are relevant to this SIP submission.
    Based on the information contained in DEQ's December 3, 2020,
letter which forms a critical part of the record basis for EPA's
approval of this submittal, EPA has determined that conditions 35 and
42 as supplemented by the letter are adequately bounded director's
discretion provisions. In particular, EPA agrees with DEQ that the
criteria in 40 CFR part 75, subpart E for SO2 and
NOX emissions and in 40 CFR part 63, subpart DDDDD for
PM10 emissions are appropriate to evaluate the approvability
of any alternative sampling or monitoring methods and establish the
proper bounds for DEQ's exercise of discretion and EPA approval for any
future requests from the source to use alternative sampling and
monitoring methods. Further, in determining whether it is appropriate
for EPA to provide its concurrence to any future request for a change
in sampling and monitoring methods under these conditions, EPA reserves
the right to withhold its concurrence if EPA determines that the
request falls outside the process and bounds specified in DEQ's letter.
In such circumstances, the CAA would require that the State seek to
make the change through the normal SIP revision process.
    For these reasons, these permit provisions are consistent with the
requirements of CAA sections 110(i), 110(l) and 110(k)(3).
    Comment B.2: The Arkansas Regional Haze SIP for Domtar does not
satisfy the requirement to provide for periodic testing of stationary
sources and to use enforceable test methods for each emission limit
specified in the plan, and should therefore be disapproved. For
example, the SIP lacks specificity regarding test methods in permit
conditions 38 and 40. Permit condition 38 refers to 40 CFR part 60,
without identifying the specific rule provisions that apply. Similarly,
permit condition 40 fails to identify the specific AP-42 emission
factor.
    Response: We disagree with the commenter that the SIP lacks
specificity regarding test methods in permit conditions 38 and 40 for
the boilers. The commenter states that permit condition 38 refers to 40
CFR part 60 regarding utilizing CEMS without identifying the specific
rule provisions that apply. In permit condition 38, the State provided
that ``the permittee shall demonstrate compliance with the 30-boiler
operating

day rolling average SO2 and NOX limits utilizing
a continuous emissions monitor (CEMS) subject to 40 CFR part 60.''
Permit condition 38 identifies the source category type as being a
boiler and the pollutants to be monitored by CEMS as SO2 and
NOX. It is clear from the pollutant, fuel type, and the
nature of the emission unit which of the tests would apply under 40 CFR
60 for demonstrating compliance. That is sufficient information to
locate the performance specifications and quality assurance procedures
for Power Boiler No. 2 to determine how to utilize CEMS to determine
compliance with the SO2 and NOX limits of the
Arkansas Regional Haze Phase III SIP revision. The State is being all-
inclusive when referring to Part 60 to include all of the general
provisions in Subpart A related to CEMS, such as 40 CFR 60.8 for
performance tests, 40 CFR 60.13 pertaining to monitoring requirements,
and Appendix B to Part 60, which includes performance specifications
for CEMS. In addition, these permit conditions also implement APCEC
Rule 19.703--Continuous Emission Monitoring,\78\ which is already part
of the approved SIP, and applies to this source.\79\ Specific condition
54 of the permit provides additional information regarding CEMS
requirements for Power Boiler No 2. Specifically, it says, ``The
permittee shall install, calibrate, maintain and operate continuous
emissions monitoring systems for measuring SO2 emissions,
NOX emissions, and either oxygen or carbon dioxide. The CEMS
shall have readouts which demonstrate compliance with any of the
applicable limits for the pollutant in question. The permittee shall
comply with the DEQ CEMS conditions found in Appendix B. [Reg. 19.703,
40 CFR 52, Subpart E, and Ark. Code Ann. Sec.  8-4-203 as referenced by
Ark. Code Ann. Sec. Sec.  8-4-304 and 8-4-311].'' Appendix B sections
II through IV of the permit lay out specific guidelines for CEMS
operating conditions.
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    \78\ Under APCEC Rule 19.703--Continuous Emission Monitoring,
any stationary source subject to this regulation shall, as required
by federal law and upon request of the Department: (A) Install,
calibrate, operate, and maintain equipment to continuously monitor
or determine federally regulated air pollutant emissions in
accordance with applicable performance specifications in 40 CFR part
60 Appendix B as of the effective date of the federal final rule
published by EPA in the Federal Register on February 27, 2014 (79 FR
11271), and quality assurance procedures in 40 CFR part 60 Appendix
F as of the effective date of the federal final rule published by
EPA in the Federal Register on February 27, 2014 (79 FR 11274), and
other methods and conditions that the Department, with the
concurrence of the EPA, shall prescribe. Any source listed in a
category in 40 CFR part 51 Appendix P as of the effective date of
the federal final rule published by EPA in the Federal Register on
November 7, 1986 (51 FR 40675), or in 40 CFR part 60 as of August
30, 1992, shall adhere to all continuous emissions monitoring or
alternative continuous emission monitoring requirements stated
therein, if applicable. (B) Report the data collected by the
monitoring equipment to the Department at such intervals and on such
forms as the Department shall prescribe, in accordance with 40 CFR
part 51, Appendix P, Section 4.0 (Minimum Data Requirements) as of
the effective date of the federal final rule published by EPA in the
Federal Register on November 7, 1986 (51 FR 40675), and any other
applicable reporting requirements promulgated by the EPA.
    \79\ See 52.170(c) (table) for EPA-approved regulations in the
Arkansas SIP.
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    The commenter also states that permit condition 40 fails to
identify the specific AP-42 emission factors. Condition 40 refers to
``the applicable natural gas AP-42 emission factors'' and provides an
appropriate description because the applicable emission factors are
based on the nature of the emissions unit, fuel, and pollutants in
question. As explained in the proposed approval,\80\ if Power Boiler
No. 2 switches to natural gas combustion, the applicable natural gas
AP-42 emission factors of 0.6 lb SO2/MMscf, 280 lb
NOX/MMscf, and 7.6 lb PM10/MMscf in conjunction
with natural gas fuel usage records shall be used to demonstrate
compliance with the BART emission limits.\81\ Therefore, the boiler
will operate under CEMs, and these AP-42 emissions factors would only
be used for estimation of emissions if Power Boiler No. 2 burns natural
gas. We note, just as we did in the FIP, for which these provisions are
replacing,82 83 that burning only natural gas would very
likely be sufficient in itself to demonstrate that the boiler is
complying with the SO2 emission limit. SO2
emissions from combustion of natural gas are inherently very low and
are virtually eliminated during the combustion process. Any
SO2 emissions will be in trace amounts well below the BART
alternative emission limit so there should be no concern that the
alternative limit for SO2 will be met. NOX and
PM10 emissions are also expected to be lower than the BART
alternative emission limit for natural gas combustion.84 85
Using the most conservative NOX, SO2, and
PM10 AP-42 factors (highest factor) for boiler combustion
indicates that the BART alternative emission limits will be met even
when firing natural gas at full capacity. Based on this information,
any ambiguity in the use of AP-42 factors for compliance using only
natural gas is not of concern because of the characteristically lower
emissions during natural gas combustion. When natural gas is used, the
limits in the BART alternative demonstration will be met. DEQ has the
State authority to enforce these emission factors to document
compliance and EPA will have federal authority once this approval takes
effect.
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    \80\ See 85 FR 14847, 14862.
    \81\ See AP 42, Fifth Edition Compilation of Air Pollutant
Emissions Factors, Volume 1: Stationary Point and Area Sources,
section 1.4, Tables 1.4-1 and 2 pertaining to natural gas
combustion.
    \82\ See 40 CFR 52.173(c)(8)(iv) and (v). However, the FIP
regulations required burning only pipeline quality natural gas, and
no such requirement to burn only pipeline quality natural gas can be
located in the permit or the SIP for this unit. Nonetheless, there
is no indication (nor has the commenter supplied any such
information) that burning other types of natural gas would result in
SO2 emissions that would even approach the BART
alternative emission limit.
    \83\ Table 1.4-2 from Fifth Edition Compilation of Air Pollutant
Emissions Factors, Volume 1: Stationary Point and Area Sources,
section 1.4 indicates that the AP-42 factor contemplates varying
amounts of sulfur and the potential need to adjust the emission
factor. The AP-42 factor for sulfur from natural gas (0.6 lb/10\6\
scf) is based on 100% conversion of fuel sulfur to SO2.
It assumes a sulfur content for natural gas of 2,000 grains/10\6\
scf. The SO2 emission factor in this table can be
converted to other natural gas sulfur contents by multiplying the
SO2 emission factor by the ratio of the site-specific
sulfur content (grains/10\6\ scf) to 2,000 grains/10\6\ scf. To
convert the emission factors in the AP-42 tables on a volume basis
(lb/10\6\ scf) to an energy basis (lb/MMBtu) divide by a heating
value of 1,020 MMBtu/10\6\ scf. Then, multiply the result by the
heat input capacity of the boiler (MMBtu/hr) to get a mass flow rate
(lb/hr). Accordingly, an AP factor of 0.6 lb SO2/MMscf
multiplied by Power Boiler No. 2 maximum heat input of 820 MMBtu/hr
would result in 0.5 lb/hr SO2, showing that the sulfur
emissions would be very low and almost negligible. It is also more
conservative than the FIP (``pipeline quality natural gas'' would
result in 1.2 lb/hr SO2 assuming pipeline natural gas
contains 0.5 grains or less of total sulfur per 100 standard cubic
feet). These results are well below the BART alternative limit for
SO2 of 435 lb/hr.
    \84\ From Table 1.4-1 of Fifth Edition Compilation of Air
Pollutant Emissions Factors, Volume 1: Stationary Point and Area
Sources, section 1.4 we can also appropriately select the most
conservative NOX emission factor based on the design heat
input capacity for Power Boiler No. 2 of 820 MMBtu/hr. From this, we
can choose emission factors from the combustor type. The applicable
AP-42 emission factor (280 lb NOX/MMscf) is consistent
with what was used in the FIP for a large wall-fired boiler > 100
MMBtu/hr. This is the highest emission factor in the table for
NOX and results in 225 lb/hr NOX (985 tpy
NOX) which can be calculated from the heat input capacity
of the boiler (820 MMBtu/hr) similarly as explained in previous
footnote. The result is less than both the FIP NOX limit
of 345 lb/hr (1,511 tpy) and the BART alternative NOX
rate of 293 lb/hr (1,283 tpy).
    \85\ From Table 1.4-2 of Fifth Edition Compilation of Air
Pollutant Emissions Factors, Volume 1: Stationary Point and Area
Sources, section 1.4 an AP factor of 7.6 lb PM10/MMscf
represents total PM and equates to 6.1 lb/hr PM applying a heat
input capacity of 820 MMBtu/hr. This is less than the BART
alternative rate of 81.6 lb/hr PM.
---------------------------------------------------------------------------

    The State made clear in its SIP submittal that the BART alternative
SIP requirements for this source would be implemented in conjunction
with preexisting SIP requirements for monitoring, reporting, and

recordkeeping, thus ensuring that the emissions limitations applicable
to this source under the BART alternative are practically enforceable.
See Aug. 2019 SIP Submittal at 2. These provisions of Arkansas's air
regulations have been approved by EPA into Arkansas' federally
enforceable SIP.\86\ In particular, APCEC Rule 19 Chapter 7--Sampling,
Monitoring and Reporting Requirements, sets forth the powers of DEQ in
requiring sampling, monitoring, and reporting requirements at
stationary sources. Specifically, any stationary source is subject to
air emission sampling (APCEC Rule 19.702); \87\ continuous emission
monitoring (APCEC Rule 19.703); recordkeeping and reporting
requirements (APCEC Rule 19.705); \88\ and Public Availability of
Emissions Data (APCEC Rule 19.706).\89\ All of these requirements will
become federally enforceable against Domtar with EPA's final approval
of this SIP submittal. For these reasons, conditions 38 and 40 contain
sufficient specificity regarding testing for compliance for Power
Boiler No. 2.
---------------------------------------------------------------------------

    \86\ See 40 CFR 52.170(c) (table) for EPA-approved regulations
in the Arkansas SIP.
    \87\ Under APCEC Rule 19.702--Air Emissions Sampling, any
stationary source subject to this regulation shall be subject to the
following requirements: (A) Sampling Ports To provide any sampling
ports, at the request of the Department, required for federally
regulated air pollutant emissions sampling, including safe and easy
access to such ports. (B) Sampling To conduct federally regulated
air pollutant emissions sampling, at the request of the Department,
to determine the rate, opacity, composition, and/or contaminant
concentration of the emissions. All compliance testing shall be done
at the expense of the permittee by an independent firm, unless
otherwise approved by the Department. Sampling shall not be required
for those pollutants with continuous emissions monitors. (C)
Averaging Times All compliance testing averaging times shall be
consistent with the averaging times of the applicable federally
regulated air pollutant emissions limitations stated in the
applicable permit, which in no case shall be greater than the
minimum averaging times of the applicable NAAQS. (D) Process Rates
Unless otherwise approved by the Department, all federally regulated
air pollutant emissions sampling shall be performed with the
equipment being tested operating at least at ninety percent of its
permitted capacity. Emissions results shall be extrapolated to
correlate with 100 percent of permitted capacity to determine
compliance.
    \88\ Under APCEC Rule 19.705--Record Keeping and Reporting
Requirements, any stationary source subject to this regulation
shall, upon request by the Department: (A) Maintain records on the
nature and amounts of federally regulated air pollutants emitted to
the air by the equipment in question. All records, including
compliance status reports and excess emissions measurements shall be
retained for at least five (5) years, and shall be made available to
any agent of the Department or EPA during regular business hours.
(B) Supply the following information, correlated in units of the
applicable emissions limitations, to the Department: (1) General
process information related to the emissions of federally regulated
air pollutants into the air. (2) Emissions data obtained through
sampling or continuous emissions monitoring. (C) Information and
data shall be submitted to the Department by a responsible official
on such forms and at such time intervals as prescribed by applicable
federal regulations or the Department. Reporting periods shall be a
twelve-month period. (D) Each emission inventory is to be
accompanied by a certifying statement, signed by the owner(s) or
operator(s) and attesting that the information contained in the
inventory is true and accurate to the best knowledge of the
certifying official. The certification shall include the full name,
title, signature, date of signature, and telephone number of the
certifying official.
    \89\ Emissions data obtained by the Department shall be
correlated in units of applicable emissions limitations and be made
available to the public at the Department's central offices during
normal business hours.
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    Comment B.3: The provisions for recordkeeping are inadequate for
permit conditions 36 and 43. In addition to failing to require that
``owners and operators'' are subject to these provisions, these
provisions fail to specify necessary specifics to determine compliance.
For example, these provisions lack requirements that records shall be
maintained for CEMS data; quality assurance and quality control
activities for emissions measuring systems; major maintenance
activities conducted on emission units, control equipment, and CEMS;
and any other records required by the underlying requirements.
    Response: We disagree with the commenter's assertion that the
provisions for recordkeeping are inadequate for conditions 36 and 43.
The commenter cites CAA section 110(a)(2)(F), 40 CFR 51 Subpart K,\90\
and the BART guidelines \91\ in identifying the applicable
recordkeeping and reporting requirements.\92\ However, these
requirements do not mandate the level of specificity the commenter
would like to see regarding recordkeeping, and the commenter cites no
authority for the notion that that level of specificity is required.
Nor did the commenter cite any examples from other BART alternative