[Federal Register Volume 85, Number 14 (Wednesday, January 22, 2020)]
[Proposed Rules]
[Pages 3558-3578]
[FR Doc No: 2020-00495]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2015-0463; FRL-10003-90-Region 8]

Approval and Promulgation of Air Quality Implementation Plans;
Utah; Regional Haze State and Federal Implementation Plans

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to take
action pursuant to section 110 of the Clean Air Act (CAA or Act) on
State Implementation Plan (SIP) revisions submitted by the State of
Utah on July 3, 2019, as supplemented on December 3, 2019, to satisfy
certain regional haze requirements for the program's first
implementation period. The EPA is proposing to approve the July 2019
SIP revision that provides an alternative to best available retrofit
technology (BART) controls for nitrogen oxides (NOX) at the
PacifiCorp Hunter and Huntington power plants. The EPA proposes to find
that the Utah NOX BART Alternative for Hunter and Huntington
would provide greater reasonable progress toward natural visibility
conditions than BART, in accordance with the requirements of the CAA
and the EPA's Regional Haze Rule (RHR). In conjunction with this
proposed approval, we propose to withdraw the federal implementation
plan (FIP) that addresses NOX BART for the Hunter and
Huntington power plants. The EPA also proposes to approve the December
3, 2019 SIP supplement that would require reporting of all deviations
from compliance with the applicable requirements under BART and the
BART Alternative, including the emission limits for Hunter and
Huntington.

DATES:
    Comments: Written comments must be received on or before March 23,
2020.
    Public Hearing: A public hearing for this proposal is scheduled to
be held on Wednesday, February 12, 2020, in Price, Utah from 1 p.m.
until 5 p.m., and again from 6 p.m. until 8 p.m. mountain standard time
(MST). See the SUPPLEMENTARY INFORMATION section below for the venue
address.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2015-0463, to the Federal Rulemaking Portal: https://www.regulations.gov. Follow the online instructions for submitting
comments. Once submitted, comments cannot be edited or removed from
www.regulations.gov. The EPA may publish any comment received to its
public docket. Do not submit electronically any information you
consider to be Confidential Business Information (CBI) or other
information whose disclosure is restricted by statute. Multimedia
submissions (audio, video, etc.) must be accompanied by a written
comment. The written comment is considered the official comment and
should include discussion of all points you wish to make. The EPA will
generally not consider comments or comment contents located outside of
the primary submission (i.e., on the web, cloud, or other file sharing
system). For additional submission methods, the full EPA public comment
policy, information about CBI or multimedia submissions, and general
guidance on making effective comments, please visit http://www.epa.gov/dockets/commenting-epa-dockets.
    Docket: All documents in the docket are listed in the
www.regulations.gov index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in www.regulations.gov or in hard copy at the Air Program,
Environmental Protection Agency (EPA), Region 8, 1595 Wynkoop Street,
Denver, Colorado 80202-1129. The EPA requests that, if at all possible,
you contact the individual listed in the FOR FURTHER INFORMATION
CONTACT section to view the hard copy of the docket. You may view the
hard copy of the docket Monday through Friday, 8:00 a.m. to 4:00 p.m.,
excluding federal holidays.

FOR FURTHER INFORMATION CONTACT: Aaron Worstell, Air Program, EPA,
Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-
1129,<PHONE_NUMBER><EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Public Hearing

    A public hearing will be held at the Jennifer Leavitt Student
Center (JLSC),\1\ Utah State University Eastern, 400 North 410 East,
Price, UT 84501, on Wednesday, February 12, 2020. The hearing will
convene at 1 p.m. and run from 1 p.m. until 5 p.m., and again from 6
p.m. until 8 p.m. (MST). Persons wishing to preregister may be assigned
a time according to this schedule. Please register at https://utah-regional-haze-2020.eventbrite.com to speak at the hearing. The last day
to preregister in advance to speak at the hearing is February 3, 2020.
Additionally, requests to speak may be taken the day of the hearing at
the hearing registration desk on a first come first serve basis, as
time allows. The EPA will make every effort to accommodate all walk-in
speakers, however we highly encourage the public to preregister for the
hearing in order to be guaranteed speaking time. For questions
regarding the public hearing, please contact Clayton Bean at
<EMAIL_ADDRESS>or<PHONE_NUMBER>.
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    \1\ See https://usueastern.edu/about/map/_documents/PriceCampusMap.pdf for a detailed campus map.
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    The public hearing will provide interested parties the opportunity
to present data, views, or arguments concerning the proposed action.
The EPA may ask clarifying questions during the oral presentations, but
will not respond to the presentations at that time. Written statements
and supporting information submitted during the comment period will be
considered with the same weight as oral comments and supporting
information presented at the public hearing. The hearing officer may
limit the time available for each commenter to address the proposal to
5 minutes or less if the hearing officer determines it to be
appropriate. The limitation is to ensure that everyone who wants to
make a comment has the opportunity to do so. We will not be providing
equipment for commenters to show overhead slides or make computerized
slide presentations. Any person may provide written or oral comments
and data pertaining to our proposal at the public hearings. Verbatim
transcripts, in English, of the hearings and written statements will be
included in the rulemaking docket.
    Throughout this document wherever ``we,'' ``us,'' or ``our'' is
used, we mean the EPA.

Table of Contents

I. What action is the EPA proposing?
II. Background
    A. Requirements of the Clean Air Act and the EPA's Regional Haze
Rule
    B. Best Available Retrofit Technology (BART)
    C. BART Alternatives
    D. Requirements for Regional Haze SIPs Submitted Under 40 CFR
51.309
    E. Monitoring, Recordkeeping and Reporting
    F. Consultation With Federal Land Managers (FLMs)

    G. Summary of State Regional Haze Submittals and EPA Actions
    1. 2008 and 2011 Utah Regional Haze SIP Submissions
    2. 2012 EPA Action on 2011 and 2008 Utah Regional Haze SIP
Submissions
    3. Petitions for Review of the EPA's Approval of the
SO2 Backstop Trading Program
    4. 2015 Utah Regional Haze SIP Submissions
    5. 2016 EPA Action on 2015 Utah RH SIP Submissions
    6. Petitions for Review of EPA's 2016 SIP Disapproval and FIP
    7. 2019 Utah RH SIP Revisions
III. Utah's Regional Haze SIP Revisions
    A. Summary of the Utah NOX BART Alternative SIP
Revision
    1. Utah NOX BART Alternative
    B. Summary of Utah's Demonstration for Alternative Program
    1. List of All BART-Eligible Sources Within the State
    2. List of All BART-Eligible Sources and All BART Source
Categories Covered by the Alternative Program
    3. Analysis of BART and Associated Emission Reductions
Achievable
    4. Analysis of Projected Emissions Reductions Achievable Through
the BART Alternative
    5. A Determination That the Alternative Achieves Greater
Reasonable Progress Than Would Be Achieved Through the Installation
and Operation of BART
    6. Requirement That Emission Reductions Take Place During Period
of First Long-Term Strategy
    7. Demonstration That Emissions Reductions From Alternative
Measure Will Be Surplus
    C. Monitoring, Recordkeeping and Reporting
    D. Consultation With FLMs
IV. EPA's Evaluation and Proposed Approval of Utah's Regional Haze
SIP
    A. Basis for Proposed Approval
    B. Demonstration of Greater Reasonable Progress for the
Alternative Program
    1. A List of All BART-Eligible Sources Within the State
    2. A List of All BART-Eligible Sources and All BART Source
Categories Covered by the Alternative Program
    3. Analysis of BART and Associated Emission Reductions
    4. Analysis of Projected Emissions Reductions Achievable Through
the BART Alternative
    5. A Determination That the Alternative Achieves Greater
Reasonable Progress Than Would Be Achieved Through the Installation
and Operation of BART
    6. Requirement That Emission Reductions Take Place During Period
of First Long-Term Strategy
    7. Demonstration That Emission Reductions From Alternative
Measure Will Be Surplus
    C. Monitoring, Recordkeeping, and Reporting
    D. Consultation With FLMs
V. Clean Air Act Section 110(l)
VI. The EPA's Proposed Action
    A. 2019 Utah Regional Haze SIP Revision
    B. FIP Withdrawal
    C. Clean Air Section 110(l)
VII. Incorporation by Reference
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Executive Order 13771: Reducing Regulations and Controlling
Regulatory Costs
    C. Paperwork Reduction Act
    D. Regulatory Flexibility Act
    E. Unfunded Mandates Reform Act (UMRA)
    F. Executive Order 13132: Federalism
    G. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    H. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    J. National Technology Transfer and Advancement Act
    K. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations

I. What action is the EPA proposing?

    On July 5, 2016, the EPA promulgated a final rule titled
``Approval, Disapproval and Promulgation of Air Quality Implementation
Plans; Partial Approval and Partial Disapproval of Air Quality
Implementation Plans and Federal Implementation Plan; Utah; Revisions
to Regional Haze State Implementation Plan; Federal Implementation Plan
for Regional Haze,'' which approved, in part, a regional haze SIP
revision submitted by the State of Utah on June 4, 2015.\2\ In the July
2016 final rule, the EPA also disapproved, in part, the Utah regional
haze SIP submission, including the NOX BART Alternative
(also ``BART Alternative'' or ``Alternative'') for Hunter Units 1 and 2
and Huntington Units 1 and 2, which are BART units as explained in more
detail below. The BART Alternative relied on sulfur dioxide
(SO2), NOX, and particulate matter (PM) emission
reductions stemming from the 2015 closure of PacifiCorp's Carbon power
plant, as well as NOX reductions achieved through combustion
control upgrades at Hunter Units 1, 2, and 3 and Huntington Units 1 and
2. (Hunter Unit 3 is not a BART unit.) The combustion control upgrades
for Hunter Units 1 and 2 and Huntington Units 1 and 2 include an Alstom
TSF 2000\TM\ low-NOX firing system and two elevations of
separated overfire air (SOFA). The combustion upgrades for Hunter Unit
3 include upgraded low-NOX burners (LNB) and overfire air
(OFA). Concurrent with disapproving the NOX BART
Alternative, EPA promulgated a FIP in the July 2016 final rule that
imposed a NOX BART emission limit of 0.07 lb/MMBtu (30-day
rolling average) for each of the four BART units based on the emission
reductions achievable through the installation and operation of
selective-catalytic reduction (SCR) plus upgraded combustion controls.
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    \2\ 81 FR 43894 (July 5, 2016).
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    On July 3, 2019, Utah submitted a revised SIP that, based on new
technical information and a different regulatory test, seeks to
demonstrate that the previously submitted NOX BART
Alternative achieves greater reasonable progress than BART. The SIP
revision also includes amendments to Utah's SO2 milestone
reporting requirements under the SO2 Backstop Trading
Program pursuant to 40 CFR 51.309 so that SO2 emission
reductions resulting from the closure of the Carbon plant are not
counted under both the SO2 Backstop Trading Program and the
NOX BART Alternative. The EPA is proposing to approve the
State's July 3, 2019 SIP revision based on this new information and to
incorporate the following into Utah's SIP:
     A NOX emission limit of 0.26 lb/MMBtu (30-day
rolling average) each for Hunter Units 1 and 2 and Huntington 1 and 2.
     A NOX emission limit of 0.34 lb/MMBtu (30-day
rolling average) for Hunter Unit 3.
     A requirement to permanently close and cease operation of
the Carbon power plant by August 15, 2015.
     The associated amendments to the SO2 milestone
reporting requirements.
    Because approval of the NOX BART Alternative would
satisfy Utah's BART obligation for Hunter Units 1 and 2 and Huntington
Units 1 and 2, we are also proposing to withdraw the FIP for
NOX BART at these units.
    The EPA is also proposing to approve a December 3, 2019 SIP
supplement to the July 3, 2019 SIP revision that includes monitoring,
recordkeeping and reporting (MRR) requirements for the units subject to
the NOX BART Alternative and PM BART. The supplement also
includes amendments that require each source to submit a report of any
deviation from applicable emission limits and operating practices,
including deviations attributable to upset conditions, the probable
cause of such deviations, and any corrective actions or preventive
measures taken.
    Finally, contingent on our approval of these two SIP revisions, we
propose to find that Utah's SIP fully satisfies the

requirements of section 309 of the RHR and, therefore, that the State
has fully complied with the requirements for reasonable progress,
including BART, for the first implementation period.
    EPA is requesting comment on its proposed approval of Utah's
regional haze SIP elements related to the NOX BART
Alternative under 40 CFR 51.309(d)(4)(vii) and 51.308(e)(2)-(3), as
well as the MRR elements for the units subject to that BART Alternative
and to PM BART. EPA previously approved Utah's regional haze SIP as
meeting all other requirements of 40 CFR 51.309,\3\ and we are neither
reopening nor requesting comment on previously approved elements here.
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    \3\ See 77 FR 74355 (Dec. 14, 2012); 81 FR 43894 (July 5, 2016).
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II. Background

A. Requirements of the Clean Air Act and the EPA's Regional Haze Rule

    In section 169A of the 1977 Amendments to the CAA, Congress created
a program for protecting visibility in the nation's national parks and
wilderness areas. This section of the CAA establishes ``as a national
goal the prevention of any future, and the remedying of any existing,
impairment of visibility in mandatory Class I Federal areas which
impairment results from manmade air pollution.'' \4\ Section 169A
directs the EPA to establish regulations for states to submit SIPs to
make ``reasonable progress'' toward the national visibility goal
through long-term strategies and to implement BART at certain BART-
eligible sources. Recognizing the complexity of addressing visibility
impacts, Congress enacted section 169B in the 1990 Amendments to the
CAA, which, among other things, dedicated greater resources to
``regional haze'' and the problem of visibility impairment due to
pollution transport over large distances. Section 169B provided for the
creation of ``visibility transport'' regions and commissions, and
specifically directed the establishment of a Grand Canyon visibility
transport commission at section 169B(f).
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    \4\ 42 U.S.C. 7491(a). Areas designated as 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. 42 U.S.C. 7472(a). In accordance with section 169A of the CAA,
EPA, in consultation with the Department of Interior, promulgated a
list of 156 areas where visibility is identified as an important
value. 44 FR 69122 (November 30, 1979). The extent of a mandatory
Class I area includes subsequent changes in boundaries, such as park
expansions. 42 U.S.C. 7472(a). Although states and tribes may
designate as Class I additional areas whose visibility they consider
to be an important value, the requirements of the visibility program
set forth in section 169A of the CAA apply only to ``mandatory Class
I Federal areas.'' Each mandatory Class I Federal area is the
responsibility of a ``Federal Land Manager.'' 42 U.S.C. 7602(i).
When we use the term ``Class I area'' in this section, we mean a
``mandatory Class I Federal area.'' The list of mandatory Class I
Federal areas is located in 40 CFR part 81 subpart D.
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    The EPA promulgated a rule to address regional haze on July 1,
1999.\5\ This RHR revised the existing visibility regulations \6\ to
integrate provisions addressing regional haze and established a
comprehensive visibility protection program for Class I areas. The
requirements for regional haze, found at 40 CFR 51.308 and 40 CFR
51.309, are included in the EPA's visibility protection regulations at
40 CFR 51.300 through 40 CFR 51.309. As discussed in more detail below,
section 309 is available to certain western states, including Utah, in
lieu of certain requirements in section 308. The EPA revised the RHR
most recently on January 10, 2017.\7\
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    \5\ 64 FR 35714 (July 1, 1999) (codified at 40 CFR part 51,
subpart P).
    \6\ The EPA had previously promulgated regulations to address
visibility impairment in Class I areas that is ``reasonably
attributable'' to a single source or small group of sources, i.e.,
reasonably attributable visibility impairment (RAVI). 45 FR 80084
(December 2, 1980).
    \7\ 82 FR 3078 (January 10, 2017).
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    The CAA requires each state to develop a SIP to meet various air
quality requirements, including protection of visibility.\8\ Regional
haze SIPs must assure reasonable progress toward the national goal of
achieving natural visibility conditions in Class I areas, which, for
the first implementation period, includes satisfying the BART
requirements. A state must submit its SIP and SIP revisions to the EPA
for approval. EPA reviews SIP submissions against the requirements of
the CAA and applicable regulations. If EPA finds that a state has
failed to make a required submission or that a submission does not
satisfy the minimum criteria for completeness, or if EPA disapproves a
SIP submission in whole or in part, EPA is required to promulgate a FIP
within two years of such finding or disapproval unless the State
corrects the deficiency, and the Administrator approves the plan or
plan revision, before the Administrator promulgates such FIP.\9\ Once
approved, a SIP is enforceable by the EPA and citizens under the CAA;
that is, the SIP is federally enforceable.
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    \8\ 42 U.S.C. 7410(a), 7491, and 7492(a); CAA sections 110(a),
169A, and 169B.
    \9\ 42 U.S.C. 7410(c)(1).
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B. Best Available Retrofit Technology (BART)

    Section 169A of the CAA directs states as part of their SIPs, or
the EPA when developing a FIP in the absence of an approved regional
haze SIP, to evaluate the use of retrofit controls at certain larger,
often uncontrolled, older stationary sources in order to address
visibility impacts from these sources. Specifically, section
169A(b)(2)(A) of the CAA requires states' implementation plans to
contain such measures as may be necessary to make reasonable progress
toward the natural visibility goal, including a requirement that
certain categories of existing major stationary sources built between
1962 and 1977 procure, install, and operate the ``Best Available
Retrofit Technology'' as determined by the states through their SIPs,
or as determined by the EPA when it promulgates a FIP. Under the RHR,
states (or the EPA) are directed to conduct BART determinations for
such ``BART-eligible'' sources that may reasonably be anticipated to
cause or contribute to any visibility impairment in a Class I area.\10\
Sources that are determined to cause or contribute to such impairment
pursuant to the BART Guidelines are referred to as ``subject-to-BART''
sources and must undergo a BART determination applying the five BART
factors.\11\ Rather than requiring source-specific BART controls,
states also have the flexibility to adopt an emissions trading program
or other alternative program for their subject-to-BART sources, so long
as the alternative provides greater reasonable progress towards
improving visibility than BART (sometimes referred to as the ``better-
than-BART'' test).\12\
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    \10\ 40 CFR 51.308(e). The EPA designed the Guidelines for BART
Determinations Under the RHR (Guidelines), 40 CFR part 51, Appendix
Y, ``to help States and others (1) identify those sources that must
comply with the BART requirement, and (2) determine the level of
control technology that represents BART for each source.''
Guidelines, Section I.A. Section II of the Guidelines describes the
four steps to identify BART sources, and Section III explains how to
identify BART sources (i.e., sources that are ``subject to BART'').
    \11\ CAA section 169A(g)(2); 40 CFR 51.308(e)(1)(ii)(A).
    \12\ 40 CFR 51.308(e)(2); WildEarth Guardians v. EPA, 770 F.3d
919 (10th Cir. 2014).
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C. BART Alternatives

    States opting to submit an alternative program in lieu of source-
specific BART, whether for a SIP submitted under 40 CFR 51.308 or
51.309,\13\ must meet requirements under 40 CFR 51.308(e)(2) and, if
applicable, (e)(3). These requirements for alternative programs relate
to the ``better-than-BART'' test and fundamental elements of any
alternative program.
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    \13\ See 40 CFR 51.309(d)(4).
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    In order to demonstrate that the alternative program achieves
greater reasonable progress than source-specific

BART, a state, or the EPA if developing a FIP, must demonstrate that
its SIP meets the requirements, as applicable, in 40 CFR
51.308(e)(2)(i) through (vi). Among other things, the state or the EPA
must conduct an analysis of the best system of continuous emission
control technology available and the associated emission reductions
achievable for each source subject to BART covered by the alternative
program, termed a ``BART benchmark.'' Where the alternative program has
been designed to meet requirements other than BART, simplifying
assumptions may be used to establish a BART benchmark. The BART
benchmark is the basis for comparison in the ``better-than-BART'' test
for BART alternatives.
    Pursuant to 40 CFR 51.308(e)(2)(i)(E), the state or the EPA must
provide a determination that the alternative program achieves greater
reasonable progress than BART under 40 CFR 51.308(e)(3) or otherwise
based on the clear weight of evidence. 40 CFR 51.308(e)(3), in turn,
provides specific tests applicable under specific circumstances for
determining whether the alternative achieves greater reasonable
progress than BART. If the distribution of emissions under the
alternative program is not substantially different than for BART, and
the alternative program results in greater emissions reductions of each
relevant pollutant than BART, then the alternative program may be
deemed to achieve greater reasonable progress. If the distribution of
emissions is significantly different, the differences in visibility
improvement between BART and the alternative program must be determined
by conducting dispersion modeling for each impacted Class I area for
the best and worst 20 percent of days. This modeling demonstrates
``greater reasonable progress'' if both of the two following criteria
are met: (1) Visibility does not decline in any Class I area; and (2)
there is overall improvement in visibility when comparing the average
differences between BART and the alternative program across all the
affected Class I areas.
    Alternately, pursuant to 40 CFR 51.308(e)(2)(i)(E), a third test is
available under which States may show that the BART alternative
achieves greater reasonable progress than BART ``based on the clear
weight of evidence.'' As stated in in the EPA's revisions to the RHR
governing alternative to source-specific BART determinations, such
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. 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 program 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 program as compared to BART sources,
monitoring data and emissions inventories, and sensitivity analyses
of any models used. This array of information and other relevant
data may be of sufficient quality to inform the comparison of
visibility impacts between BART and the alternative program. In
showing that an alternative program is better than BART and when
there is confidence that the difference in visibility impacts
between BART and the alternative scenarios are expected to be large
enough, a weight of evidence comparison may be warranted in making
the comparison. The EPA will carefully consider the evidence before
us in evaluating any SIPs submitted by States employing such an
approach.\14\
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    \14\ 71 FR 60612, 60622 (Oct. 13, 2006).

    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. Pursuant to 40 CFR
51.309(e)(2)(v), states have the option of including a provision that
the emissions trading program or other alternative measure include a
geographic enhancement to the program to address the requirement under
40 CFR 51.302(c) related to BART for RAVI from the pollutants covered
under the emissions trading program or other alternative measure.
    A SIP or FIP addressing regional haze must include emission limits
and compliance schedules for each visibility-impairing pollutant
emitted from each source subject to BART. In addition to the RHR's
requirements, general SIP requirements mandate that the SIP or FIP
include all regulatory requirements related to MRR needed to make
emission limits practically enforceable.\15\
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    \15\ CAA section 110(a); 40 CFR part 51, subpart K; 40 CFR part
51, appendix V.
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D. Requirements for Regional Haze SIPs Submitted Under 40 CFR 51.309

    EPA's RHR provides two paths to address regional haze for the first
implementation period of the regional haze program. One is through 40
CFR 51.308, requiring, among other things, SIPs to include source-
specific BART determinations or BART alternatives, and to contain long-
term strategies that include enforceable emission limitations,
compliance schedules, and other measures as necessary to achieve
reasonable progress in Class I areas inside the state and in Class I
areas outside the state that may be affected by emissions from the
state. In addition to these requirements, each regional haze SIP or FIP
under section 308 must contain measures as necessary to make reasonable
progress towards the national visibility goal.\16\ The other method for
addressing regional haze for the first implementation period is through
40 CFR 51.309, which provides an option for nine states termed the
``Transport Region States'': Arizona, California, Colorado, Idaho,
Nevada, New Mexico, Oregon, Utah, and Wyoming. Among other things, by
meeting the requirements under 40 CFR 51.309, these states can be
deemed to be making reasonable progress toward the national goal of
achieving natural visibility conditions for the 16 Class I areas on the
Colorado Plateau.\17\
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    \16\ 40 CFR 51.308(d), (f).
    \17\ 40 CFR 51.309(a).
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    Section 309 requires those Transport Region States that choose to
participate to adopt regional haze strategies that are based on
recommendations from the Grand Canyon Visibility Transport Commission
(GCVTC) established under CAA 169B(f) for protecting the 16 Class I
areas on the Colorado Plateau. The purpose of the GCVTC was to assess
information about the adverse impacts on visibility in and around the
16 Class I areas on the Colorado Plateau and provided policy
recommendations to the EPA to address such impacts. The GCVTC
determined that all Transport Region States could potentially impact
the Class I areas on the Colorado Plateau. The GCVTC submitted a report
to the EPA in 1996 containing recommendations for protecting visibility
for the Class I areas on the Colorado Plateau, and the EPA codified
these recommendations in section 309 as an option available to states
as part of the RHR.\18\
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    \18\ 64 FR 35714, 35749 (July 1, 1999).
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    The EPA determined that the GCVTC strategies would provide for
reasonable progress in mitigating regional haze if supplemented by an
annex containing quantitative emission reduction milestones and
provisions for a trading program or other alternative measure for
SO2.\19\ In September 2000, the Western Regional Air
Partnership (WRAP), which is the successor organization to the GCVTC,
submitted an annex to EPA.

The annex contained SO2 emissions reduction milestones and
detailed provisions of a backstop trading program to be implemented
automatically if voluntary measures failed to achieve the
SO2 milestones (the SO2 Backstop Trading
Program). The EPA codified the annex on June 5, 2003 at 40 CFR
51.309(h).\20\
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    \19\ 64 FR 35714, 35749, 35756 (July 1, 1999).
    \20\ 68 FR 33764, 33767 (June 5, 2003).
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    Five western states, including Utah, submitted implementation plans
under section 309 in 2003.\21\ However, the EPA was challenged by the
Center for Energy and Economic Development (CEED) on the validity of
the annex provisions contained in section 309(h). In CEED v. EPA, the
D.C. Circuit Court of Appeals vacated the EPA approval of the WRAP
annex.\22\ In response to the court's decision, the EPA removed the
annex requirements from 40 CFR 51.309(h), but incorporated the
provisions allowing for an SO2 Backstop Trading Program
under the stationary source requirements in 40 CFR 51.309(d)(4).\23\
The requirements under 40 CFR 51.309(d)(4) contain general requirements
pertaining to stationary sources and market trading, and allow states
to adopt alternatives to source-specific application of BART.
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    \21\ Five states--Arizona, New Mexico, Oregon, Utah and
Wyoming--and Albuquerque-Bernalillo County, New Mexico, initially
exercised this option by submitting plans to the EPA in December
2003. Oregon elected to cease participation in 2006, and Arizona
elected to cease participation in 2010.
    \22\ Ctr. for Energy & Econ. Dev. v. EPA, 398 F.3d 653, 654 (DC
Cir. 2005).
    \23\ 71 FR 60612 (October 13, 2006).
---------------------------------------------------------------------------

    Under 40 CFR 51.309, states can satisfy the SO2 BART
requirements by adopting SO2 emissions milestones and the
SO2 Backstop Trading Program as described in
51.309(d)(4)(i)-(vi). Under this approach, states must establish
declining SO2 emissions milestones for each year of the
program through 2018. The milestones must be consistent with the
GCVTC's goal of 50 to 70 percent reduction in SO2 emissions
by 2040. The SO2 Backstop Trading Program would be
implemented if a milestone is exceeded and the program is
triggered.\24\
---------------------------------------------------------------------------

    \24\ 40 CFR 51.309(d)(4)(v).
---------------------------------------------------------------------------

    Section 51.309(d)(4) includes not only provisions for stationary
source emissions of SO2, but also a requirement that
Transport Region States' implementation plans contain any necessary
long-term strategies and BART requirements for stationary source PM and
NOX emissions. Pursuant to 40 CFR 51.309(d)(4)(vii), any
BART provisions may be submitted pursuant to either 51.308(e)(1) or
51.308(e)(2); that is, states may submit either source-specific BART
determinations or BART alternatives for PM and NOX.

E. Monitoring, Recordkeeping and Reporting

    The CAA requires that SIPs, including regional haze SIPs, contain
elements sufficient to ensure emission limits are practically
enforceable. CAA section 110(a)(2) states that the MRR provisions of
states' SIPs must:

    (A) include enforceable emission limitations and other control
measures, means, or techniques (including economic incentives such
as fees, marketable permits, and auctions of emissions rights), as
well as schedules and timetables for compliance, as may be necessary
or appropriate to meet the applicable requirements of this chapter;
. . . (C) include a program to provide for the enforcement of the
measures described in subparagraph (A), and regulation of the
modification and construction of any stationary source within the
areas covered by the plan as necessary to assure that national
ambient air quality standards are achieved, including a permit
program as required in parts C and D of this subchapter; . . . (F)
require, as may be prescribed by the Administrator--(i) the
installation, maintenance, and replacement of equipment, and the
implementation of other necessary steps, by owners or operators of
stationary sources to monitor emissions from such sources, (ii)
periodic reports on the nature and amounts of emissions and
emissions-related data from such sources, and (iii) correlation of
such reports by the State agency with any emission limitations or
standards established pursuant to this chapter, which reports shall
be available at reasonable times for public inspection.

    Accordingly, 40 CFR part 51, subpart K, Source Surveillance,
requires the SIP to provide for monitoring the status of compliance
with the regulations in it, including ``[p]eriodic testing and
inspection of stationary sources,'' \25\ and ``legally enforceable
procedures'' for recordkeeping and reporting.\26\ Furthermore, 40 CFR
part 51, appendix V, Criteria for Determining the Completeness of Plan
Submissions, states in section 2.2 that complete SIPs contain: ``(g)
Evidence that the plan contains emission limitations, work practice
standards and recordkeeping/reporting requirements, where necessary, to
ensure emission levels''; and ``(h) Compliance/enforcement strategies,
including how compliance will be determined in practice.''
---------------------------------------------------------------------------

    \25\ 40 CFR 51.212(a).
    \26\ 40 CFR 51.211.
---------------------------------------------------------------------------

F. Consultation With Federal Land Managers (FLMs)

    The statute and the RHR require that a state, or the EPA if
promulgating a FIP that fills a gap in the SIP with respect to the
applicable requirements, consult with FLMs before adopting and
submitting a required SIP or SIP revision, or a required FIP or FIP
revision.\27\ Further, the state when considering a SIP revision (or
EPA in a FIP) must include in its proposal a description of how it
addressed any comments provided by the FLMs.
---------------------------------------------------------------------------

    \27\ CAA section 169A(d); 40 CFR 51.308(i).
---------------------------------------------------------------------------

G. Summary of State Regional Haze Submittals and EPA Actions

1. 2008 and 2011 Utah Regional Haze SIP Submissions
    On May 26, 2011, the State of Utah submitted to EPA a regional haze
SIP under 40 CFR 51.309 (``2011 Utah RH SIP''). Consistent with 40 CFR
51.309(d)(4)(vii), this submittal included BART determinations for
NOX and PM at Utah's four subject-to-BART sources:
PacifiCorp's Hunter Units 1 and 2 and Huntington Units 1 and 2. All
four units are tangentially-fired fossil-fuel electric generating units
(EGUs), each with a net generating capacity of 430 MW, permitted to
burn bituminous coal. This submittal also included quantitative
emissions milestones through 2018 and a backstop trading program for
SO2 intended to meet the requirements of 40 CFR
51.309(d)(4)(i)-(vi). The SO2 backstop trading program
covers Utah, Wyoming, New Mexico and the City of Albuquerque.
    Utah had also previously submitted SIPs on December 12, 2003,
August 8, 2004, and September 9, 2008, to meet the requirements of the
RHR. These submittals were, for the most part, superseded and replaced
by the May 26, 2011 submittal as further explained in the next section.
2. 2012 EPA Action on 2011 and 2008 Utah Regional Haze SIP Submissions
    On December 14, 2012, EPA partially approved and partially
disapproved the 2011 Utah RH SIP.\28\ We approved the 2011 Utah RH SIP
as meeting the requirements of 40 CFR 51.309, with the exception of the
requirements under 40 CFR 51.309(d)(4)(vii) pertaining to
NOX and PM BART. EPA's partial disapproval action was based
on the following: (1) Utah did not take into account the five statutory
factors in its BART analyses for NOX and PM; and (2) the
2011 Utah RH SIP submission did not contain the provisions necessary to
make the BART limits practically enforceable as required by section
110(a)(2) of the CAA and 40 CFR 51, appendix V.\29\
---------------------------------------------------------------------------

    \28\ 77 FR 74355, 74357 (Dec. 14, 2012).
    \29\ Id.

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

    We also approved two sections of the 2008 Utah RH SIP submission in
the December 13, 2012 action. Specifically, we approved state rules UAR
R307-250--Western Backstop Sulfur Dioxide Trading Program and R307-
150--Emission Inventories. We took no action on the rest of the 2008
submittal as the 2011 submittal superseded and replaced all other
sections. We also took no action on the December 12, 2003 and August 8,
2004 submittals as these were superseded by the 2011 submittal.
    On November 8, 2011, we separately proposed approval of Section G--
Long-Term Strategy for Fire Programs of the May 26, 2011 submittal and
finalized our approval of that action on January 18, 2013.\30\
---------------------------------------------------------------------------

    \30\ 78 FR 4071, 4072 (Jan. 18, 2013).
---------------------------------------------------------------------------

3. Petitions for Review of the EPA's Approval of the SO2
Backstop Trading Program
    In 2013, conservation organizations challenged EPA's 2012 approval
of the SO2 Backstop Trading Program as an alternative to
BART for certain Transport Region States, including Utah, in the U.S.
Court of Appeals for the Tenth Circuit. On October 21, 2014, the Tenth
Circuit upheld EPA's action, including EPA's finding that the trading
program could serve as a BART alternative under a ``clear weight of
evidence'' standard.\31\
---------------------------------------------------------------------------

    \31\ WildEarth Guardians v. United States EPA, 770 F.3d 919, 938
(10th Cir. 2014).
---------------------------------------------------------------------------

4. 2015 Utah Regional Haze SIP Submissions
    On June 4, 2015, the State of Utah submitted to EPA a revision to
its Regional Haze SIP under 40 CFR 51.309 of the RHR (``June 2015 Utah
RH SIP'') to address the requirements under 40 CFR 51.309(d)(4)(vii)
pertaining to NOX and PM BART. Utah developed the June 2015
Utah RH SIP in response to EPA's December 14, 2012 partial disapproval
of the 2011 Utah RH SIP submission. The June 2015 Utah RH SIP evolved
from a draft SIP on which Utah sought public comment in October 2014.
After receiving extensive public comments on that draft, Utah decided
to pursue a NOX BART Alternative under the 40 CFR
51.308(e)(2) ``clear weight of evidence'' standard that takes credit
for NOX reductions due to combustion controls installed at
PacifiCorp's Hunter and Huntington power plants in addition to
NOX, SO2, and PM reductions from the August 2015
retirement of PacifiCorp's nearby Carbon power plant. The June 2015
Utah RH SIP submission also included measures to make the SIP
requirements practically enforceable and included additional
information pertaining to the PM BART determinations for Hunter and
Huntington to address deficiencies identified by EPA in our December
2012 partial disapproval.
    On October 20, 2015, Utah submitted to EPA another revision to its
Regional Haze SIP under 40 CFR 51.309 (``October 2015 Utah RH SIP'').
This SIP included an enforceable commitment to provide an additional
SIP revision by mid-March 2018 to address concerns raised in public
comments that the State would be double counting certain SO2
emissions reductions under both the Utah NOX BART
Alternative and the milestone reporting for the SO2 Backstop
Trading Program.
5. 2016 EPA Action on 2015 Utah RH SIP Submissions
    On July 5, 2016, we partially approved and partially disapproved
the revisions to the Utah SIP submitted by the State of Utah on June 4,
2015.\32\ We approved the following elements of the State's SIP
submittals: \33\
---------------------------------------------------------------------------

    \32\ 81 FR 43894 (July 5, 2016).
    \33\ EPA had already approved elements satisfying other
applicable requirements in the December 14, 2012 action: Section
XX.B.8, Figures 1 and 2, Affected Class I Areas, pp. 8-9; Section
XX.D.6.b, Table 3, BART-Eligible Sources in Utah, p. 21; Section
XX.D.6.c, Sources Subject to BART, pp. 21-23.
---------------------------------------------------------------------------

     BART determinations and emission limits for PM at Hunter
Units 1 and 2 and Huntington Units 1 and 2.
     MRR requirements for units subject to the PM emission
limits, including conditional approval of the requirement that the PM
emission limits apply at all times, subject to the state's commitment
to adopt reporting requirements for deviations from the emission
limits.
    We disapproved these aspects of the State's June 4, 2015 SIP:
     NOX BART Alternative, including emission limits
consistent with upgraded combustion controls at Hunter Units 1, 2, and
3 and Huntington Units 1 and 2, and the SO2, NOx, and PM
emission reductions resulting from the shutdown of Carbon Units 1 and
2.
     MRR requirements for units subject to the NOX
BART Alternative.
    As noted above, in June 2015 Utah submitted the NOX BART
Alternative under 40 CFR 51.308(e)(2)(i)(E)'s clear-weight-of-evidence
test. To support its conclusion that the NOX BART
Alternative makes greater reasonable progress towards the national
visibility goal, the SIP submission relied on nine metrics for
comparing the Alternative to the BART Benchmark: Aggregate emission
reductions, monitoring data, timing of emission reductions, energy and
non-air quality impacts, cost, and four visibility-related metrics
based on the results of a modeling exercise using the CALPUFF model. In
the July 2016 final rule, EPA determined that the evidence provided did
not clearly demonstrate that the BART Alternative achieves greater
visibility improvement than BART. As part of this evaluation, we
determined which metrics were relevant to the assessment of relative
visibility benefit, evaluated the strengths and weaknesses of each
metric in order to determine which merited more or less weight, and
collectively considered the weights assigned to the individual pieces
of information in determining whether, on balance, the evidence
demonstrated that the NOX BART Alternative would clearly
provide for greater reasonable progress.\34\ Based on this assessment,
we determined that the evidence before us did not satisfy the standard
articulated under 40 CFR 51.308(e)(2)(i)(E) and disapproved the
NOX BART Alternative.
---------------------------------------------------------------------------

    \34\ See 81 FR 43894, 43896-43902.
---------------------------------------------------------------------------

    We thus promulgated a FIP in the July 5, 2016 action to address the
deficiencies in the Utah regional haze SIP submissions. EPA's FIP
includes the following elements:
     NOX BART determinations and corresponding
emission limits for Hunter Units 1 and 2 and Huntington Units 1 and 2
of 0.07 lb/MMbtu (30-day rolling average) each, reflecting installation
and operation of SCR plus the existing upgraded combustion controls.
     Monitoring, recordkeeping, and reporting requirements
applicable to Hunter Units 1 and 2 and Huntington Units 1 and 2 as
needed to implement the NOX BART determinations and emission
limits.
    We took no action on the enforceable commitment to revise, at a
minimum, SIP Section XX.D.3.c and state rule R307-150 addressing double
counting of SO2 emissions, because there was no need to do
so once the NOX BART Alternative had been disapproved.
6. Petitions for Review of EPA's 2016 SIP Disapproval and FIP
    In September 2016, the State of Utah, PacifiCorp, and several other
parties challenged EPA's July 5, 2016 disapproval of the NOX
BART Alternative and promulgation of a FIP in the U.S. Court of Appeals
for the Tenth Circuit.\35\ In addition, the State and PacifiCorp (on
behalf of the co-owners of Hunter Units 1 and 2 and Huntington Units 1
and 2) submitted letters to EPA on June 30, 2017, identifying new

information that was not available at the time of EPA's action on
Utah's 2015 SIP submission, providing additional explanation of
existing information, and stating an intent to develop and submit to
EPA additional technical analyses in support of the NOX BART
Alternative.\36\ On July 14, 2017, the EPA Administrator sent letters
to the State of Utah and PacifiCorp announcing the Agency's intent to
reconsider its disapproval of the NOX BART Alternative.\37\
On this basis, EPA asked the Tenth Circuit to put the litigation in
abeyance; on September 11, 2017, the court both granted EPA's request
to abate the litigation and issued a stay of EPA's July 5, 2016 final
rule.\38\
---------------------------------------------------------------------------

    \35\ State of Utah v. EPA, No. 16-9541 (10th Cir.).
    \36\ See docket IDs EPA-R08-OAR-2015-0463-0216 (letter from
State of Utah) and EPA-R08-OAR-2015-0463-0221 (letter from
PacifiCorp).
    \37\ See docket IDs EPA-R08-OAR-2015-0463-0222 (letter to State
of Utah) and EPA-R08-OAR-2015-0463-0223 (letter to PacifiCorp).
    \38\ State of Utah v. EPA, No. 16-9541 (10th Cir.), Doc. No.
10496767.
---------------------------------------------------------------------------

7. 2019 Utah RH SIP Revisions
    On July 3, 2019, Utah submitted a SIP revision intended to replace
EPA's 2016 FIP provisions for NOX BART. The measures in the
NOX BART Alternative submitted in July 2019 are identical to
those in the Alternative submitted in June 2015 (i.e., Utah submitted
the same NOX BART Alternative in the June 2015 and July 2019
SIPs). However, while the State had previously relied on the clear-
weight-of-evidence test under 40 CFR 51.308(e)(2)(i)(E) to demonstrate
that the Alternative achieves greater reasonable progress than BART in
the June 2015 submission,\39\ the July 2019 submission relies solely on
the application of the two-prong test under 51.308(e)(3) using
photochemical grid modeling. Background on these two approaches to
demonstrating greater reasonable progress is provided in section II.C.
above.
---------------------------------------------------------------------------

    \39\ For a summary of the weight-of-evidence contained in Utah's
June 2015 SIP, and EPA's evaluation thereof, refer to the July 2016
final rule at 81 FR 43897-43902.
---------------------------------------------------------------------------

    The July 3, 2019 SIP submittal includes the emission limitations
and control measures associated with the NOX BART
Alternative. It also includes the monitoring, recordkeeping, and
reporting requirements that EPA previously approved for PM BART, but
disapproved as applied to the emission limitations and control measures
associated with the NOX BART Alternative.
    On December 3, 2019, Utah submitted a supplement to the July 2019
SIP submission that includes an amendment to the monitoring, record
keeping, and reporting requirements submitted on July 3, 2019.
Specifically, the amendments require each source to submit a report of
any deviation from applicable emission limits and operating practices,
including deviations attributable to upset conditions, the probable
cause of such deviations, and any corrective actions or preventive
measures taken.
    This proposed action pertains to the July 3, 2019 SIP submittal as
supplemented on December 3, 2019.
    Sections 110(a)(2) and 110(l) of the CAA and 40 CFR 51.102 and
appendix V to part 51 require that a state provide reasonable notice
and public hearing before adopting a SIP revision and submitting it to
EPA. Utah, after providing notice, accepted comments on the July 2019
Utah RH SIP submission from April 1, 2019 through May 15, 2019.
Similarly, Utah accepted comments on the December 3, 2019 RH SIP
supplement from October 1, 2019 to October 31, 2019.

III. Utah's Regional Haze SIP Revisions

A. Summary of the Utah NOX BART Alternative SIP Revision

    As noted elsewhere, the EPA previously approved Utah's SIP elements
satisfying the requirements of 40 CFR 51.309 to address the State's
regional haze obligations for the first implementation period, other
than emission limitations corresponding to NOX BART or an
alternative to BART for NOX and the associated MRR
requirements, and certain requirements for MRR related to PM BART.\40\
Therefore, in this action we are addressing only these outstanding
elements and certain ancillary SIP revisions necessary to effectuate
them.
---------------------------------------------------------------------------

    \40\ EPA conditionally approved Utah's MRR requirements for the
PM BART emission limitations under CAA section 110(k)(4). 81 FR at
43921.
---------------------------------------------------------------------------

    Utah's July 3, 2019 SIP RH submittal, as supplemented on December
3, 2019, includes changes to the following provisions, on which we are
proposing to take action:
     Revised SIP Section XX, Regional Haze, Parts A, Executive
Summary, and D, Long-Term Strategy for Stationary Sources (revised SIP
narrative sections including the BART Assessment for NOX); adopted by
the Utah Air Quality Board on June 24, 2019.
     Revised R307-110-28, General Requirements: State
Implementation Plan, Regional Haze (state rule that incorporates by
reference most recently amended SIP Section XX); effective August 15,
2019.
     SIP Section IX.H.21 General Requirements: Control Measures
for Area and Point Sources, Emission Limits and Operating Practices,
Regional Haze Requirements (SIP section laying out MRR requirements for
control measures); adopted by the Utah Air Quality Board on November
20, 2019.
     SIP Section IX.H.22 Source Specific Emission Limitations:
Regional Haze Requirements, Best Available Retrofit Technology (SIP
section containing emission limitations necessary for NOX
BART Alternative); adopted by the Utah Air Quality Board on November
20, 2019.
     Revised R307-110-17, General Requirements: State
Implementation Plan. Section IX, Control Measures for Area and Point
Sources, Part H, Emissions Limits (state rule that incorporates by
reference most recently amended SIP Section IX, Part H); effective on
November 25, 2019.
     Revised R307-150-3, Emission Inventories, Applicability
(state rule that addresses reporting of SO2 emissions for
Carbon power plant under the Western Backstop SO2 Trading
Program); effective June 25, 2018.
    These six provisions are related to the following two outstanding
requirements for the first implementation period: NOX BART
for Hunter Units 1 and 2 and Huntington Units 1 and 2; and MRR
requirements for the Utah NOX BART Alternative and PM BART
emission limits to make the SIP requirements practically enforceable.
1. Utah NOX BART Alternative
    To satisfy the requirement of 40 CFR 51.309(d)(4)(vii), Utah has
opted to establish an alternative to BART for NOX under 40
CFR 51.308(e)(2). The State's NOX BART Alternative consists
of upgraded combustion controls on all four subject-to-BART units,
upgraded combustion controls on Hunter Unit 3, and the shutdown of
Carbon Units 1 and 2. The emission limits in the July 3, 2019 Utah RH
SIP submittal, as supplemented on December 3, 2019, are provided in
Table 1. We further explain the components of the SIP submissions
below.

                Table 1--Emission Limits and Shutdown in the Utah BART Alternative and PM SIP \1\
----------------------------------------------------------------------------------------------------------------
                                                 PM limit 2 3  (lb/     NOX limit 4  (lb/
            Source                   Unit         MMBtu, three-run        MMBtu, 30-day           SO2 limit
                                                    test average)       rolling average)
----------------------------------------------------------------------------------------------------------------
Hunter.......................               1   0.015...............  0.26................  NA.
                                            2   0.015...............  0.26................  NA.
                                            3   NA..................  0.34................  NA.
Huntington...................               1   0.015...............  0.26................  NA.
                                            2   0.015...............  0.26................  NA.
Carbon.......................               1   Shutdown by August    Shutdown by August    Shutdown by August
                                                 15, 2015.             15, 2015.             15, 2015.
                                            2   Shutdown by August    Shutdown by August    Shutdown by August
                                                 15, 2015.             15, 2015.             15, 2015.
----------------------------------------------------------------------------------------------------------------
\1\ Obtained from the July 2019 Utah RH SIP, Section IX.H.22.
\2\ Based on annual stack testing.
\3\ The BART PM emission limits were previously approved by in our July 2016 final rule. 81 FR 43894 (July 5,
  2016).
\4\ Based on continuous emission monitoring system (CEMS) measurement.

    The State compared the NOX BART Alternative against a
BART Benchmark that consists of SCR plus upgraded combustion controls
on all four BART units. The State noted SCR plus upgraded combustion
controls would require careful consideration through a source-specific
five-factor analysis before determining it is BART for these units.
However, the State used those controls as a stringent benchmark for
comparison with the NOX BART Alternative. The State remarked
that its use of SCR plus upgraded combustion controls as a benchmark is
not a determination that this technology is BART; it is merely a
conservative approach to evaluating the effectiveness of the
alternative program. The Utah NOX BART Alternative is
generally described in SIP Section XX.D.6 with a detailed demonstration
included in the Staff Review to support the State's assertion that the
Alternative achieves greater reasonable progress than BART.
    In addition to combustion controls at the Hunter and Huntington
units, the State intends to rely on the emission reductions resulting
from the shutdown of a coal-fired power plant. Utah indicated that
PacifiCorp shut down the Carbon Power Plant in 2015, due to the high
cost to control mercury to meet the requirements of EPA's Mercury and
Air Toxics Standards (MATS).\41\ The State noted that the MATS rule was
finalized in 2011, and the Utah RH SIP contains the requirement for the
Carbon Power Plant to shut down in August 2015. The emission reductions
occur after the 2002 base year for Utah's RH SIP and thus, Utah
asserts, the reductions may be considered as part of an alternative
strategy under 40 CFR 51.308(e)(2)(iv).
---------------------------------------------------------------------------

    \41\ Utah Regional Haze State Implementation Plan, Staff Review
of Recommended Alternative to BART for NOX, May 28, 2019,
p. 24.
---------------------------------------------------------------------------

    The State's demonstration is described in more detail in section
III.B below. The State's estimates of emissions for the Utah
NOX BART Alternative and the BART Benchmark are provided in
Table 2 of section III.B.4 below. EPA developed a summary of the
emissions reductions based on Utah's emission estimates and this is
presented in Table 3 of section III.B.4 below.

B. Summary of Utah's Demonstration for Alternative Program

    As discussed above in Section II, a state may opt to implement an
alternative measure rather than to require sources subject to BART to
install, operate, and maintain source-specific BART. BART alternatives
such as the Utah NOX BART Alternative that are not emissions
trading programs must meet the requirements of 40 CFR 51.308(e)(2)(i)-
(iv).\42\ Utah has included the following information in its July 2019
SIP revision to address the regulatory criteria for an alternative
program: \43\
---------------------------------------------------------------------------

    \42\ States may address 40 CFR 51.308(e)(2)(v) at their option.
    \43\ See Staff Review.
---------------------------------------------------------------------------

1. List of All BART-Eligible Sources Within the State
    Pursuant to 40 CFR 51.308(e)(2)(i)(A), the SIP must include a list
of all BART-eligible sources within the State. Utah included a list of
BART-eligible sources and noted the following sources are all covered
by the alternative program:

 PacifiCorp Hunter, Unit 1
 PacifiCorp Hunter, Unit 2
 PacifiCorp, Huntington, Unit 1
 PacifiCorp, Huntington, Unit 2
2. List of All BART-Eligible Sources and All BART Source Categories
Covered by the Alternative Program
    Pursuant to 40 CFR 51.308(e)(2)(i)(B), each BART-eligible source in
the State must be subject to the requirements of the alternative
program, have a federally enforceable emission limitation determined by
the State and approved by EPA as meeting BART, or be otherwise
addressed under paragraphs 51.308(e)(1) or (e)(4). In this instance,
the alternative program covers all the BART-eligible sources in the
state--Hunter Units 1 and 2 and Huntington Units 1 and 2--in addition
to three non-BART units--PacifiCorp's Hunter Unit 3 and Carbon Units 1
and 2.
3. Analysis of BART and Associated Emission Reductions Achievable
    Pursuant to 40 CFR 51.308(e)(2)(i)(C), the SIP must include an
analysis of BART and associated emission reductions achievable at the
subject-to-BART units covered by the alternative program, here Hunter
Units 1 and 2 and Huntington Units 1 and 2. In the July 2019 Utah RH
SIP, the State compared the Utah NOX BART Alternative to the
most stringent NOX controls, SCR plus upgraded combustion
controls, at the four BART units, referred to here as the BART
Benchmark. This is consistent with the BART determination made by EPA
in our July 2016 final rule.\44\
---------------------------------------------------------------------------

    \44\ In the July 2016 FIP, EPA determined these same controls--
SCR plus LNB/SOFA--constitute BART for each of the four subject-to-
BART units. Utah's July 2019 SIP submittal thus refers to the BART
Benchmark controls as the ``EPA FIP''; while the controls
represented by the BART Benchmark and EPA's FIP are indeed the same,
the relevant comparison for the purpose of this analysis is between
the BART Benchmark and the BART alternative.
---------------------------------------------------------------------------

4. Analysis of Projected Emissions Reductions Achievable Through the
BART Alternative
    Pursuant to 40 CFR 51. 308(e)(2)(i)(D), the SIP must include ``[a]n
analysis of the projected emissions reductions achievable through the .
. . alternative measure.'' A summary of the State's estimates of
emissions in tons per year (tpy) for the Baseline, NOX BART
Alternative and the BART Benchmark is provided in Table 2. A summary of
the emissions reductions based on those emission estimates is presented
in Table 3. The emissions and emission reductions were projected for
the year

2025 to align with the future year modeling scenarios used to calculate
visibility benefits under the BART Benchmark and BART Alternative, as
described in the section that follows.\45\
---------------------------------------------------------------------------

    \45\ Staff Review, Table 2, p. 12. Values rounded to the nearest
ton.

                                Table 2--Estimated Emissions in 2025 Under the Baseline Scenario, BART Benchmark (BART Benchmark), and the BART Alternative \45\
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         NOX (tpy)                                        SO2 (tpy)                            PM (tpy)                         Combined
                                           -------------------------------------            -------------------------------------------------------------------------------------------------------
                   Units                                   BART                                              BART                                BART                                BART     BART
                                             Baseline    benchmark   BART alt.                Baseline    benchmark    BART alt.   Baseline    benchmark   BART alt.   Baseline    benchmark  alt.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ------
Carbon 1..................................       1,312       1,312           0        2,286       2,286           0          120         120           0       3,718       3,718           0
Carbon 2..................................       1,977       1,977           0        3,528       3,528           0          183         183           0       5,688       5,688           0
Hunter 1..................................       6,380         796       3,166        2,535       1,153       1,153          733         733         733       9,648       2,682       5,052
Hunter 2..................................       6,092         798       3,028        2,531       1,408       1,408          717         717         717       9,340       2,923       5,153
Hunter 3..................................       6,530       6,530       4,490        1,204       1,230       1,230          531         531         531       8,265       8,291       6,251
Huntington 1..............................       5,944         793       3,147        2,380       1,254       1,254          517         517         517       8,841       2,564       4,918
Huntington 2..............................       5,816         753       3,366       12,308       1,201       1,201        1,033       1,033       1,033      19,157       2,987       5,600
                                           -----------------------------------------------------------------------------------------------------------------------------------------------------
    Total.................................      34,051      12,959      17,197       26,772      12,060       6,246        3,834       3,834       3,531      64,657      28,853      26,974
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

   Table 3--EPA Summary of 2025 Projected Emission Reductions Achievable With the Utah NOX BART Alternative as
                                         Compared to the BART Benchmark
----------------------------------------------------------------------------------------------------------------
                                                              Combined emissions for all units (tpy)
                   Description                   ---------------------------------------------------------------
                                                        NOX             SO2             PM           Combined
----------------------------------------------------------------------------------------------------------------
BART Benchmark..................................          12,959          12,060           3,834          28,853
BART Alternative................................          17,197           6,246           3,531          26,974
Emission Reduction (BART Benchmark Minus BART             -4,238           5,814             303           1,879
 Alternative) \1\...............................
----------------------------------------------------------------------------------------------------------------
\1\ A negative value indicates the BART Alternative results in more emissions of the specified pollutant in
  comparison to the BART Benchmark.

5. A Determination That the Alternative Achieves Greater Reasonable
Progress Than Would Be Achieved Through the Installation and Operation
of BART
    Pursuant to 40 CFR 51.308(e)(2)(i)(E), the State must provide a
determination that the alternative program achieves greater reasonable
progress than BART under 40 CFR 51.308(e)(3) or otherwise based on the
clear weight of evidence.
    Utah noted that the Hunter, Huntington, and Carbon plants are all
located within 40 miles of each other in central Utah. Because of the
close proximity of the three plants, the geographic distribution of
emissions will not be substantially different under the alternative
program. The combined emissions of NOX, SO2, and
PM are 1,879 tons/yr lower under the alternative measure. However, the
NOX BART Alternative measure does not result in greater
emission reductions of all pollutants--SO2 emissions are
lower by 5,814 tons/yr, PM are lower by 303 tons/yr, but NOX
emissions are higher by 4,238 tons/yr. Therefore, because the
NOX BART Alternative relies on SO2 reductions,
and to a lesser extent PM reductions, in lieu of NOX
reductions, Utah determined that greater reasonable progress must be
demonstrated through the two-prong test based on dispersion modeling in
40 CFR 51.308(e)(3) or a clear weight of evidence analysis. The State
chose to make this demonstration in the July 3, 2019 submittal using
the two-prong test allowed for under 40 CFR 51.308(e)(3). To evaluate
the two prongs, Utah relied on air quality modeling performed by a
contractor for PacifiCorp using the Comprehensive Air Quality Model
with Extensions (CAMx).\46\
---------------------------------------------------------------------------

    \46\ CAMx modeling software and User's Guide are available at
http://www.camx.com/download/default.aspx. CAMx version 6.10 was
used for April to December, and CAMx version 6.40 was used for
January to March.
---------------------------------------------------------------------------

    The CAMx model is a photochemical grid model that uses and produces
complex scientific data, including emissions from all sources, with a
realistic representation of formation, transport, and processes that
cause visibility degradation, estimating downwind concentrations paired
in space and time. The EPA's guidance supports use of this particular
model for evaluation of visibility impacts from sources or source
categories, such as application of the two-prong test under 40 CFR
51.308(e)(3).\47\ The CAMx model simulates air quality over many
geographic scales and treats a wide variety of inert and chemically
active pollutants, including ozone, PM, inorganic and organic
PM2.5/PM10, and mercury and other toxics. CAMx
also has plume-in-grid and source apportionment capabilities.\48\ CAMx
has a scientifically current treatment of chemistry to simulate
transformation of emissions into visibility-impairing particles of
species such as ammonium nitrate and ammonium sulfate, and is often
employed in large-scale modeling when many sources of pollution and/or
long transport distances are involved. Photochemical grid models like
CAMx

include all emissions sources and have realistic representation of
formation, transport, and removal processes of the particulate matter
that causes visibility degradation. The use of the CAMx model for
analyzing potential cumulative air quality impacts has been well
established: The model has been used for previous visibility modeling
studies in the U.S., including SIPs.\49\ The modeling followed a
modeling protocol that was reviewed by the EPA.\50\
---------------------------------------------------------------------------

    \47\ Modeling Guidance for Demonstrating Attainment of Air
Quality Goals for Ozone, PM2.5, and Regional Haze, EPA
Office of Air Quality Planning and Standards, Research Triangle
Park, NC (November 2018). The main regional haze section of the
guidance is related to setting reasonable progress goals. However,
the guidance methods may also be applicable to other regional haze
related modeling, including, but not limited to, evaluation of
visibility impacts from sources and/or source sectors. See id. at
143-145. https://www3.epa.gov/ttn/scram/guidance/guide/O3-PM-RH-Modeling_Guidance-2018.pdf. 40 CFR pt. 51, app. Y: IV.D.5 (how to
determine visibility impacts from the BART determination); 40 CFR
51.308(e)(3) (use of dispersion modeling for BART alternatives).
    \48\ Photochemical Air Quality Modeling (https://www.epa.gov/scram/photochemical-air-quality-modeling). CAMx is a photochemical
grid model, which the EPA describes as follows: Photochemical air
quality models have become widely recognized and routinely utilized
tools for regulatory analysis and attainment demonstrations by
assessing the effectiveness of control strategies. These
photochemical models are large-scale air quality models that
simulate the changes of pollutant concentrations in the atmosphere
using a set of mathematical equations characterizing the chemical
and physical processes in the atmosphere. These models are applied
at multiple spatial scales, including from local, regional, national
and global.
    \49\ See, e.g., 84 FR 22711 (May 20, 2019) (Final action for the
Laramie River Station in the Regional Haze Plan for Wyoming); 82 FR
46903 (October 10, 2017) (Final action for the Coronado Generating
Station in the Regional Haze Plan for Arizona); 81 FR 296 (January
5, 2016) (Final action for Texas and Oklahoma Regional Haze Plans).
    \50\ Photochemical Modeling Protocol to Assess Visibility
Impacts for PacifiCorp Power Plants Located in Utah. AECOM
Environment, January 2018.
---------------------------------------------------------------------------

    The Western Air Quality Study (WAQS) \51\ developed and evaluated a
photochemical modeling platform for calendar year 2011 \52\ for use in
air quality planning studies in the western U.S. The modeling data
sets, called the ``WAQS 2011b platform,'' are available to the public
and served as the starting point for the CAMx modeling exercise. The
WAQS 2011b modeling included a 2025 future year scenario that was used
here to assess visibility impacts from the Baseline, BART Benchmark,
and NOX BART Alternative emissions scenarios.
---------------------------------------------------------------------------

    \51\ Memorandum: Recommendations on Use of Intermountain West
Data Warehouse for Air Quality 2011b Model Platform. Intermountain
West Data Warehouse--Western Air Quality Study Oversight Committee.
July 6, 2016. Available http://views.cira.colostate.edu/wiki/Attachments/Modeling/IWDW-WAQS_2011b_ModelingPlatform_Release_Memo%20July6_2016final.pdf.
    \52\ ``Western Air Quality Modeling Study Photochemical Grid
Model Final Model Performance Evaluation'', available in the docket
and at: http://views.cira.colostate.edu/wiki/Attachments/Modeling/WAQS_Base11b_MPE_Final.pdf.
---------------------------------------------------------------------------

    Because regional haze is affected by natural and anthropogenic
emissions from international sources, the WAQS 2011b modeling platform
used a series of nested model simulations from the global to the
regional scale. Global scale modeling was performed by the National
Center for Atmospheric Research (NCAR) using the Model for OZone And
Related chemical Tracers (MOZART).\53\ The WAQS 2011b used boundary
concentrations data from the NCAR MOZART simulation to perform regional
scale CAMx simulations using a coarse grid 36x36 km grid resolution for
a model domain that included most of North America, a nested 12x12 km
grid for a model domain that included all of the western U.S., and a
fine scale 4x4 grid for a model domain that included the intermountain
west region. The three nested CAMx modeling domains are illustrated in
Figure 3.1 of WAQS 2011b model evaluation report.\54\
---------------------------------------------------------------------------

    \53\ The MOZART model formulation is described at https://en.wikipedia.org/wiki/MOZART_.
    \54\ Id. 56, p. 5.
---------------------------------------------------------------------------

    The PacifiCorp CAMx modeling was based on the WAQS 2011b 4x4 grid
modeling domain, but PacifiCorp initially used a smaller modeling
domain designed to focus on the nine Class I areas within 300 km of the
Hunter and Huntington BART sources that had been used in previous Utah
DEQ CALPUFF modeling.\55\ In response to comments from the EPA Region
8, PacifiCorp expanded the size of their proposed 4x4 km grid modeling
domain to ensure that air parcel trajectories would remain within the
model domain as they were transported from the BART sources to the nine
Class I areas. The expanded PacifiCorp 4x4 km model domain included 15
Class I areas, as shown in Figure 6 of the Utah DEQ staff report.\56\
While some Class I areas are more than 300 km from the BART sources,
CAMx is accurate for long range transport and has been used by the EPA
for analysis of long range transport of ozone and fine particulates at
distances greater than 1,000 km. For completeness, the EPA recommended
that PacifiCorp evaluate model results for all 15 Class I areas in the
CAMx modeling domain.
---------------------------------------------------------------------------

    \55\ Model applications using CALPUFF for BART sources
typically--but not in all cases--have included Class I areas only up
to a distance 300 km because uncertainty in CALPUFF results
increases at distances greater than 300 km.
    \56\ Staff Review, Figure 6, p. 18.
---------------------------------------------------------------------------

    The EPA provides guidance for the use of photochemical grid models
such as CAMx for evaluating source contributions to regional haze.
Because this notice addresses requirements for BART sources as part of
the first regional haze planning period, the model results are being
evaluated using procedures designed specifically for these requirements
as outlined in the RHR and in a EPA Guidance published in 2007.\57\ The
RHR, 40 CFR 51.308(e)(3), requires that greater reasonable progress
demonstrations for BART alternatives be evaluated for the best and
worst 20% total haze days, which are selected for Class I areas using
data from the IMPROVE monitoring network.\58\ The IMPROVE network
consists of 110 monitoring sites designed to measure visibility
impairment at the 155 mandatory Class I areas. While not all Class I
areas have an IMPROVE monitor, the network was designed so that, where
needed, measurements of one monitor would be representative of the
regional haze conditions at more than one nearby Class I area.\59\
---------------------------------------------------------------------------

    \57\ Guidance for Setting Reasonable Progress Goals Under the
Regional Haze Program, available at: https://www3.epa.gov/ttn/naaqs/aqmguide/collection/cp2/20070601_wehrum_reasonable_progress_goals_reghaze.pdf.
    \58\ The IMPROVE monitoring network is described at: http://vista.cira.colostate.edu/Improve/improve-program/.
    \59\ The use of a representative IMPROVE monitor for groups of
nearby Class I areas is described at: http://vista.cira.colostate.edu/Improve/wp-content/uploads/2016/04/Chapter1.pdf.
---------------------------------------------------------------------------

    Because models can be subject to bias and error in the simulation
of the individual components of PM2.5 that contribute to
regional haze, the EPA guidance recommends that photochemical model
results be used by multiplying the model simulated change in each
component of PM2.5 by the PM2.5 concentration
measured by the IMPROVE monitoring network. The EPA has developed
software, the Speciated Model Attainment Test (SMAT), that can be used
to calculate the model relative response factor (RRF) for each
PM2.5 species in an emissions control simulation compared to
a base case simulation, and to multiply the model RRF by the observed
IMPROVE PM2.5 concentrations for a five year period at the
representative monitor for each Class I area.
    As described in the model performance evaluation report for the
WAQS 2011b platform, the model generally performed well at most sites
in the western U.S. However, CAMx was biased low for ammonia and
ammonium nitrate at some sites on the Colorado Plateau, i.e., CAMx
predicted lower concentrations of ammonia and ammonium nitrate than
were measured at some monitoring sites. Because model predictions for
ammonium nitrate at these sites are directly relevant to the comparison
of the ammonium nitrate- and ammonium sulfate-related visibility
benefits of the BART and BART Alternative scenarios, the EPA
recommended that PacifiCorp perform additional model sensitivity
simulations and performance evaluation to improve model performance for
ammonia and ammonium nitrate on the Colorado Plateau. The EPA
recommended that ammonia concentration be increased at the northern
boundary of the model domain, located in the Salt Lake City area.
Previous winter PM2.5 modeling studies performed by Utah DEQ
found that winter ammonia emissions were underestimated in the Cache
Valley in northern UT, and that model performance for ammonium nitrate
improved when ammonia emissions

were increased so that the model-simulated ammonia matched observed
ammonia concentrations. For the sensitivity study, PacifiCorp used the
Utah DEQ winter PM2.5 model results to define the ammonia
concentrations at the northern boundary of the PacifiCorp modeling
domain. Additionally, the EPA recommended changes to a model parameter
that affects ammonia dry deposition to surfaces.\60\
---------------------------------------------------------------------------

    \60\ In an email dated 9/26/2017, Chris Emery of Ramboll, the
developer of the CAMx model, identified an error in the model
settings that caused it to overestimate the deposition and removal
of gas phase ammonia in the model. The default model configuration
included a setting that specified zero surface resistance to ammonia
deposition which tends to overestimate ammonia deposition to
surfaces and to underestimate the ambient concentrations of ammonia
and ammonium nitrate. Mr. Emery recommended changing the model
configuration to include surface resistance to ammonia deposition.
---------------------------------------------------------------------------

    PacifiCorp adopted both of these recommendations and performed a
new base case model simulation and performance evaluation. This
resulted in substantial improvements in model performance for ammonia
and ammonium nitrate on the Colorado Plateau. Because the new base case
model more accurately simulates the observed ammonia and ammonium
nitrate concentrations, it is also expected to provide more accurate
predictions of the visibility benefits of changes in NOX
emissions for the EPA BART Benchmark and Utah NOX BART
Alternative. These model results are described in Appendix A of the
Utah DEQ Staff Review. The revised base case model configuration was
then used for the 2011 Typical Year model simulation, the 2025 Baseline
model simulation, and for the 2025 BART Benchmark and 2025 Utah
NOX BART Alternative model simulations, described below.
    Using the WAQS 2011b platform, CAMx was configured to simulate the
following modeling scenarios:
     2011 Typical Year. This 2011 scenario allows for the
development of RRFs that are applied to observed concentrations in
order to predict future visibility conditions. The Carbon, Hunter and
Huntington power plants were modeled at levels representative of the
period 2001 to 2003, while all other sources remain at the levels of
the 2011 WAQS base year simulation.
     2025 Baseline. Emissions from Carbon, Hunter and
Huntington are identical to the Typical Year modeling Scenario (i.e.,
2001-2003). All other emissions sources remain at the levels of the
2025 WAQS future-year simulation.
     BART Benchmark. This 2025 scenario represents the BART
Benchmark and simulates the emission control strategy for Hunter and
Huntington units required in the 2016 FIP. Specifically, emissions for
the four BART units reflect a 30-day rolling average NOX
emission limit of 0.07 lb/MMBtu consistent with the installation and
operation of SCR plus upgraded combustion controls. SO2
emissions for the Hunter and Huntington units reflect representative
emissions from 2014-2016 in order to match the BART Alternative
scenario. The BART Benchmark scenario also includes the Carbon power
plant using the same level of emissions as the Baseline scenario (i.e.,
2001-2003). All other emissions sources remain at the levels of the
2025 WAQS future-year simulation.
     Utah NOX BART Alternative. This 2025 scenario
simulates the emission control strategy for Carbon, Hunter and
Huntington units required by the BART Alternative SIP as represented in
Table 2 above. This scenario simulates representative emissions of
NOX and SO2 from Hunter and Huntington units
during the period 2014 to 2016, which include the emissions controls
required under the Alternative (i.e., the upgraded combustion
controls). For this scenario, the Carbon power plant emissions were
zero since the power plant was decommissioned in April 2015, as
required under the Alternative. All other emissions sources remain at
the levels of the 2025 WAQS future-year simulation.
    All other model inputs, including other regional emissions sources,
were held constant for the future-year (Baseline, BART Benchmark, and
BART Alternative) scenarios. Thus, any differences in the visibility
impacts between the modeled control scenarios and the Baseline, and
between the two control scenarios (i.e., BART and the BART
Alternative), are attributable solely to differences in the associated
emission inputs for the seven PacifiCorp units. The CAMx-modeled
concentrations for sulfate, nitrate, and other chemical species were
tracked for the Hunter, Huntington, and Carbon power plants using the
CAMx Particulate Source Apportionment Technology (PSAT) so that the
concentrations and visibility impacts due to the seven PacifiCorp units
could be separated out from those due to the total of all other modeled
sources. Visibility impacts were assessed at the 15 Class I areas
contained inside of the modeling domain.61 62
---------------------------------------------------------------------------

    \61\ Staff Review, pp. 17-18. Specifically, see rectangular CAMx
modeling domain with 4-kilometer grid resolution in Figure 4-1.
    \62\ By contrast, in the CALPUFF modeling supporting EPA's 2016
FIP, visibility impacts were assessed for the nine Class I areas
within 300 kilometers of the BART units. The rectangular CAMx
modeling domain was designed to be large enough to include these
nine Class I areas and to include air parcel trajectories from those
sources to the Class I areas. In response to EPA Region 8 comments
on a draft modeling protocol, the rectangular CAMx model domain was
expanded further to the east, north and south to ensure that
emissions from the sources would remain within the model domain as
they were transported from the sources to the affected Class I
areas. For completeness, results for all Class I areas located
within the rectangular CAMx domain were included in the analysis.
---------------------------------------------------------------------------

    The visibility impacts derived from the CAMx modeling results are
summarized in Tables 4 and 5 of this notice.\63\ The tables show the
projected contribution to visibility impairment due to emissions from
the seven EGUs covered by the Alternative on the 20 percent best days
and worst days respectively for the Baseline, the BART Benchmark, and
the proposed BART Alternative scenarios at each of the Class I areas
analyzed. The last two columns show the predicted visibility benefits
from the BART Alternative scenario relative to both the Baseline and
the BART Benchmark. At the bottom of each table are the average
visibility values from all the Class I areas. Negative values in the
last two columns indicate that the BART Alternative has smaller modeled
contributions to visibility impairment relative to the Baseline and the
BART Benchmark.
---------------------------------------------------------------------------

    \63\ Staff Review, pp. 16-21.
---------------------------------------------------------------------------

    Column D in Table 4 shows that emissions from the seven EGUs under
the BART Alternative will not result in degradation of visibility on
the 20 percent best days compared to the Baseline at any one of the 15
Class I areas. Similarly, Column D in Table 5 shows that, on the 20
percent worst days, visibility impairment is less under the BART
Alternative than the Baseline in each of the Class I areas. Based on
these results, the State concluded that visibility does not decline at
any of the 15 Class I areas and therefore the BART Alternative meets
prong 1 of the ``greater reasonable progress using dispersion
modeling'' test found in 40 CFR 51.308(e)(3).
    The State next made a determination that the BART Alternative meets
prong 2 of the ``greater reasonable progress using dispersion
modeling'' test found in 40 CFR 51.308(e)(3) by comparing the average
difference between the BART Alternative and the BART Benchmark.

The last row of column E in Tables 4 and 5 show the average difference
in visibility between the BART Alternative and the BART Benchmark for
the 20 percent best and worst days respectively. The negative number
indicates that the average visibility improvement of the BART
Alternative is better than the BART Benchmark in both cases. Relative
to the BART Benchmark, the BART Alternative achieves an average
visibility improvement of 0.00494 dv across all Class I areas on the 20
percent best days, and of 0.00058 dv on the 20 percent worst days.
Therefore, Utah determined that the BART Alternative meets prong 2 of
the 40 CFR 51.308(e)(3) test.
    Utah noted that the language in 40 CFR 51.308(e)(3)(i) and (ii)
indicates allowance of a straight numerical test. The State explained
that the regulation does not specify that a minimum difference in
deciview between the scenarios must be achieved to determine that a
BART Alternative achieves greater reasonable progress. Because the
modeling results show that visibility under the BART Alternative does
not decline at any of the 15 affected Class I areas compared to the
Baseline (prong 1) and will result in improved visibility, on average,
across all 15 Class I areas compared to the BART Benchmark (prong 2),
Utah asserted that the BART Alternative will achieve greater reasonable
progress than the BART Benchmark under the two-prong modeling test in
40 CFR 51.308(e)(3).

  Table 4--Visibility Impacts in 2025 for the Baseline, BART Benchmark and BART Alternative Scenarios on the 20
                                             Percent Best Days \64\
----------------------------------------------------------------------------------------------------------------
                                                                                BART
                                                  BART Benchmark       BART            BART        alternative--
          Class I area             Baseline (dv)       (dv)         alternative    alternative--       BART
                                                                       (dv)          baseline        benchmark
                                             [A]             [B]             [C]             [D]             [E]
----------------------------------------------------------------------------------------------------------------
Arches NP.......................         0.10300         0.05607         0.03851        -0.06449        -0.01756
Black Canyon of the Gunnison NM.         0.02769         0.01611         0.01162        -0.01607        -0.00449
Bryce Canyon NP.................         0.00528         0.00254         0.00228        -0.00300        -0.00026
Canyonlands NP..................         0.10300         0.05607         0.03851        -0.06449        -0.01756
Capitol Reef NP.................         0.14218         0.07222         0.07140        -0.07078        -0.00082
Flat Tops WA....................         0.02834         0.01488         0.01115        -0.01719        -0.00373
Grand Canyon NP.................         0.07136         0.03567         0.03611        -0.03525         0.00044
La Garita WA....................         0.02769         0.01611         0.01162        -0.01607        -0.00449
Maroon Bells-Snowmass WA........         0.02834         0.01488         0.01115        -0.01719        -0.00373
Mesa Verde NP...................         0.06356         0.03381         0.02749        -0.03607        -0.00632
Mount Zirkel WA.................         0.04209         0.02060         0.01471        -0.02738        -0.00589
San Pedro Parks WA..............         0.03627         0.01742         0.01593        -0.02034        -0.00149
Weminuche WA....................         0.02769         0.01611         0.01162        -0.01607        -0.00449
West Elk WA.....................         0.02834         0.01488         0.01115        -0.01719        -0.00373
Zion NP \1\.....................         0.00612         0.00291         0.00300        -0.00312         0.00009
All Class I area Average........         0.04940         0.02602         0.02108             N/A        -0.00494
----------------------------------------------------------------------------------------------------------------
\1\ Results based on incomplete dataset. Zion NP monitor did not meet the 75% data completion SMAT requirement
  for year 2011.

 Table 5--Visibility Impacts in 2025 for the Baseline, BART Benchmark, and BART Alternative Scenarios on the 20
                                             Percent Worst Days \65\
----------------------------------------------------------------------------------------------------------------
                                                                                BART
                                                  BART Benchmark       BART            BART        alternative--
          Class I area             Baseline (dv)       (dv)         alternative    alternative--       BART
                                                                       (dv)          baseline        benchmark
                                             [A]             [B]             [C]             [D]             [E]
----------------------------------------------------------------------------------------------------------------
Arches NP.......................         0.25740         0.13780         0.12584        -0.13156        -0.01196
Black Canyon of the Gunnison NM.         0.01265         0.00682         0.00540        -0.00725        -0.00142
Bryce Canyon NP.................         0.04945         0.02184         0.02470        -0.02475         0.00286
Canyonlands NP..................         0.25740         0.13780         0.12584        -0.13156        -0.01196
Capitol Reef NP.................         0.26010         0.11672         0.14568        -0.11442         0.02896
Flat Tops WA....................         0.02703         0.01387         0.01011        -0.01692        -0.00376
Grand Canyon NP.................         0.00186         0.00089         0.00056        -0.00130        -0.00033
La Garita WA....................         0.01265         0.00682         0.00540        -0.00725        -0.00142
Maroon Bells-Snowmass WA........         0.02703         0.01387         0.01011        -0.01692        -0.00376
Mesa Verde NP...................         0.06203         0.02524         0.02959        -0.03244         0.00435
Mount Zirkel WA.................         0.03312         0.01705         0.01198        -0.02114        -0.00507
San Pedro Parks WA..............         0.00154         0.00074         0.00073        -0.00081        -0.00001
Weminuche WA....................         0.01265         0.00682         0.00540        -0.00725        -0.00142
West Elk WA.....................         0.02703         0.01387         0.01011        -0.01692        -0.00376
Zion NP\1\......................         0.00155         0.00051         0.00051        -0.00104         0.00000
All Class I area Average........         0.06957         0.03471         0.03413             N/A        -0.00058
----------------------------------------------------------------------------------------------------------------
\1\ Results based on incomplete dataset. Zion NP monitor did not meet the 75% data completion SMAT requirement
  for year 2011.

6. Requirement That Emission Reductions Take Place During Period of
First Long-Term Strategy
---------------------------------------------------------------------------

    \64\ Staff Review, Table 4, p. 19.
    \65\ Staff Review, Table 5, p. 20.
---------------------------------------------------------------------------

    Pursuant to 40 CFR 51.308(e)(2)(iii), the State must ensure that
all necessary emission reductions take place during the period of the
first long-term strategy for regional haze. The RHR further provides
that, ``[t]o meet this requirement, the State must provide a detailed
description of the . . . alternative measure, including schedules for
implementation, the emission reductions required by the program, all
necessary administrative and technical procedures for implementing the
program, rules for accounting and monitoring emissions, and procedures
for enforcement.'' \66\
---------------------------------------------------------------------------

    \66\ 40 CFR 51.308(e)(2)(iii).
---------------------------------------------------------------------------

    As noted above, the December 3, 2019 supplement includes revisions
to R307-110-17, the State rule that in turn incorporates Section IX,
Control Measures for Area and Point Sources, Part H, Emissions Limits,
which includes provisions for implementing the Utah NOX BART
Alternative. In addition to the emission limitations for NOX
and PM at Hunter and Huntington \67\ and the requirement for shutdown
of the Carbon Plant listed in Table 1 above (which the State notes was
made enforceable by August 15, 2015), the SIP submission includes
compliance dates, operation and maintenance requirements, and MRR
requirements. Utah asserts that the alternative measure was fully
implemented prior to 2018.
---------------------------------------------------------------------------

    \67\ EPA previously approved the BART PM emission limits in our
July 2016 final rule. 81 FR 43894 (July 5, 2016).
---------------------------------------------------------------------------

7. Demonstration That Emissions Reductions From Alternative Measure
Will Be Surplus
    Pursuant to 40 CFR 51.308(e)(2)(iv), the SIP must demonstrate that
the emissions reductions resulting from the alternative measure will be
surplus to those reductions resulting from measures adopted to meet
requirements of the CAA as of the baseline date of the SIP. The
baseline date for regional haze SIPs is 2002.\68\ Utah developed the
2002 baseline inventory in its 2008 RH SIP for regional modeling,
evaluating the impact on Class I areas outside of the Colorado Plateau,
and BART as outlined in the EPA Guidance and the BART Guidelines,
issued on July 6, 2005. Utah noted that 2002 is the baseline inventory
that was used by other states throughout the country when evaluating
BART under the provisions of 40 CFR 51.308 and that any measure adopted
after 2002 is considered ``surplus'' under 40 CFR 51.308(e)(2)(iv).
Utah referenced other EPA actions that are consistent with this
interpretation.\69\ Utah stated that the BART Benchmark scenario
includes measures required before the baseline date of the SIP (i.e.,
2002) but does not include later measures that are credited as part of
the BART Alternative scenario.
---------------------------------------------------------------------------

    \68\ See Memorandum from Lydia Wegman and Peter Tsirigotis, 2002
Base Year Emission Inventory SIP Planning: 8-hr Ozone,
PM2.5, and Regional Haze Programs (Nov. 18, 2002),
available at https://www3.epa.gov/ttn/naaqs/aqmguide/collection/cp2/20021118_wegman_2002_base_year_emission_sip_planning.pdf.
    \69\ E.g., 79 FR 33438, 33441-33442 (June 11, 2014); 79 FR
56322, 56328 (Sept. 9, 2014).
---------------------------------------------------------------------------

    Utah explained that, to address potential concerns with double
counting SO2 emission reductions from the Carbon plant
closure under both the 308 and 309 programs, the July 2019 SIP
submission includes revisions to the applicability provisions of State
Rule State Rule R307-150, Emission Inventories, to prevent double
counting. Utah also provided explanation why the emission reductions
counted towards the NOX BART Alternative are surplus to
those needed to satisfy the requirements of the SO2 Backstop
Trading Program.\70\ The State explained that the WRAP modeling done to
support the Utah RH backstop trading program SIP included regional
SO2 emissions based on the 2018 SO2 milestone and
also included NOX and PM emissions from the Carbon plant.
Actual emissions in the three-state region (Utah, Wyoming, and New
Mexico) are calculated each year and compared to the milestones. Utah
provided the information in Table 6 below to show that since 2011,
SO2 emissions in the three-state region have been below the
2018 milestone (141,849 tpy). Utah noted that the most recent milestone
report for 2016 demonstrates that SO2 emissions are
currently 36 percent lower than the 2018 milestone. Utah stated that
the Carbon plant was fully operational in the years 2011-2013 when the
2018 milestone was initially achieved for those years. The State noted
that the SO2 emission reductions from the closure of the
Carbon plant are surplus to what is needed to meet the 2018 milestone
established in Utah's RH SIP.
---------------------------------------------------------------------------

    \70\ Staff Review at 23-25.

                                       Table 6--SO2 Milestone Trends \71\
----------------------------------------------------------------------------------------------------------------
                                                                                Three-year
                                                                                average SO2      Carbon plant
                             Year                              Milestone (tpy)   emissions \1\    SO2 emissions
                                                                                (tpy)            (tpy)
----------------------------------------------------------------------------------------------------------------
2003.........................................................          303,264          214,780            5,488
2004.........................................................          303,264          223,584            5,642
2005.........................................................          303,264          220,987            5,410
2006.........................................................          303,264          218,499            6,779
2007.........................................................          303,264          203,569            6,511
2008.........................................................          269,083          186,837            5,057
2009.........................................................          234,903          165,633            5,494
2010.........................................................          200,722          146,808            7,462
2011.........................................................          200,722          130,935            7,740
2012.........................................................          200,722          115,115            8,307
2013.........................................................          185,795          105,084            7,702
2014.........................................................          170,868           96,302            9,241
2015.........................................................          155,940           91,310            2,816
2016.........................................................          155,940           90,591                0
2017.........................................................          155,940  ...............  ...............
2018.........................................................          141,849  ...............  ...............
----------------------------------------------------------------------------------------------------------------
\1\ The three-year average is based on the emissions averaged for the current and two preceding years.

    For Hunter Unit 3, Utah also explained that PacifiCorp upgraded the
LNB controls in 2008 and that the upgrade was not required under any
applicable requirements of the CAA as of the 2002 baseline date of the
SIP; the emission reductions from the upgrade are therefore considered
surplus and creditable for the BART Alternative under 40 CFR
51.308(e)(2)(iv). Utah noted that prior to the 2008 upgrade, the
emission rate for Hunter Unit 3 was 0.46 lb/MMBtu on a 30-day rolling
average as required by Phase II of the Acid Rain Program.\72\
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    \71\ Staff Review, p 24.
    \72\ There is an error on page 25 of the Staff Review. The
reference to Hunter Unit 2 should be Unit 3 based on the section
heading as well as confirmed emission limits in Utah Approval Order
DAQE-AN0102370012-08.
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    To address potential concerns that Utah would be double counting
SO2 emissions reductions for the Carbon plant closure under
both the 40 CFR 51.308 and 309 programs, the July 2019 SIP revisions
require that the State continue to report the historical emissions for
the Carbon plant in the annual milestone reports. Specifically,
revisions to the applicability provisions of State rule R307-150
(``Emission Inventories Program'') require that Utah include emissions
of 8,005 tons/yr \73\ of SO2 for the Carbon Power Plant in
the annual milestone reports.
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    \73\ Note that this value is based on the 2012-2013 actual
annual average SO2 emissions for the Carbon power plant
as used in Utah's June 4, 2015 SIP submission. By contrast, Utah's
July 3, 2019 SIP submission uses a consistent baseline for Hunter,
Huntington and Carbon based on actual annual average emissions from
2001-2003 when the SO2 emissions for Carbon were 5,814
tons/year. That is, the revisions to the SO2 milestone
reporting requirements attribute a greater amount of tons of
SO2 to the Carbon plant than the State assumed will be
reduced from the plant's retirement, for purposes of making the
demonstration that the BART Alternative achieves greater reasonable
progress than BART. As such, Utah's analysis of its compliance with
the SO2 milestone as well as its demonstration of greater
reasonable progress for the BART Alternative are both conservative.
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C. Monitoring, Recordkeeping and Reporting

    To address EPA's partial disapproval of the 2011 Utah RH SIP for
lack of enforceable measures and MRR requirements,\74\ in 2015 Utah
added two new subsections to SIP Sections IX, H.21 (General
Requirements: Control Measures for Area and Point Sources, Emission
Limits and Operating Practices, Regional Haze Requirements) and H.22
(Source Specific Emission Limitations: Regional Haze Requirements, Best
Available Retrofit Technology).
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    \74\ 77 FR 28825, 28842 (May 16, 2012).
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    Specifically, to remedy the SIP's lack of provisions for ensuring
that emission limits are practically enforceable, under H.21 Utah added
a new definition for boiler operating day. Utah noted that state rules
R307-107-1 and R307-107-2 (applicability, timing, and reporting of
breakdowns) apply to sources subject to regional haze requirements
under H.22. Utah required that information used to determine compliance
shall be recorded for all periods when the source is in operation, and
that such records shall be kept for a minimum of five years. Under
H.21, Utah specified that emission limitations listed in H.22 shall
apply at all times and identified stack testing requirements to show
compliance with those emission limitations. Finally, H.21 also
specifies the requirements for continuous emission monitoring by
listing the requirements and cross-referencing the State's rule for
continuous emission monitoring system requirements, R307-170, as well
as 40 CFR 13 \75\ and 40 CFR 60, appendix B--Performance
Specifications. Utah included the requirements to calculate hourly
average NOX concentrations for any hour in which fuel is
combusted and a new 30-day rolling average emission rate at the end of
each boiler operating day. Utah also noted that the hourly average
NOX emission rate is valid only if the minimum number of
data points specified in R307-170 is acquired for both the pollutant
concentration monitor and diluent monitor.
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    \75\ This appears to be a typo, and the correct reference should
be to 40 CFR 60.13.
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    Under H.22, Utah provided the emission limitations associated with
the NOX BART Alternative and PM BART for Hunter Units 1
through 3 and Huntington Units 1 and 2, a requirement to perform annual
stack testing for PM, and a requirement to measure NOX via
continuous emission monitoring for the sources covered under the Utah
NOX BART Alternative. Under H.22, Utah also listed the
enforceable conditions related to closing Carbon Units 1 and 2 by
August 15, 2015, including PacifiCorp's and Utah's notification and
permit rescission obligations.
    In our 2016 final rule, EPA approved subsection H.21 and H.22 as
they pertain to PM BART, including conditional approval of the
reporting requirements. We did not act on the elements of those
subsections relating to the NOX BART Alternative, as EPA
disapproved the Alternative in that action. Utah resubmitted
subsections H.21 and H.22 as part of their July 3, 2019 SIP submittal.
In its December 3, 2019 supplemental submission, to address the issue
implicated in the conditional approval, under H.21(e) Utah required
each source to submit a report of any deviation from applicable
emission limits and operating practices, including deviations
attributable to upset conditions, the probable cause of such
deviations, and any corrective actions or preventive measures taken.

D. Consultation With FLMs

    Utah's SIP submittals do not specifically discuss how it addressed
the requirements of 40 CFR 308(i)(2) for providing the FLMs with an
opportunity for consultation at least 60 days prior to holding the
public hearing for the July 2019 RH SIP. However, we are aware that
Utah consulted with the FLMs as explained in section IV.D, and the
relevant exchange is included in the docket for this action.

IV. EPA's Evaluation and Proposed Approval of Utah's Regional Haze SIP

A. Basis for Proposed Approval

    For the reasons described below, EPA proposes to approve the Utah
2019 RH SIP revisions. Our proposed action is based on an evaluation of
Utah's regional haze SIP submittals against the regional haze
requirements at 40 CFR 51.300-51.309 and CAA sections 169A and 169B.
The revisions were also evaluated against the general SIP requirements
contained in CAA section 110, other provisions of the CAA, and our
regulations applicable to this action. The EPA proposes to approve
these SIP revisions as meeting the relevant CAA requirements. Where
appropriate, we provide additional rationale to supplement to the
state's analysis and to support our conclusions below.

B. Demonstration of Greater Reasonable Progress for the Alternative
Program

    As provided under 40 CFR 51.309(d)(4)(vii), Utah has opted to
establish an alternative measure (or program) for NOX
emissions from the four subject-to-BART units in accordance with 40 CFR
51.308(e)(2). A description of the Utah NOX BART Alternative
is provided above in section III.A.1. The RHR requires that a SIP
revision establishing a BART alternative meet three key requirements
(in addition to other elements in section 308(e)(2)) as listed below.
We have evaluated the Utah NOX BART Alternative with respect
to each of these requirements.
     A demonstration that the emissions trading program or
other alternative measure will achieve greater reasonable progress than
would have resulted from the installation and operation of BART at all
sources subject to BART in the

State and covered by the alternative program.\76\
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    \76\ 40 CFR 51.308(e)(2)(i).
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     A requirement that all necessary emissions reductions take
place during the period of the first long-term strategy for regional
haze.\77\
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    \77\ 40 CFR 51.308(e)(2)(iii).
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     A demonstration that the emissions reductions resulting
from the alternative measure will be surplus to those reductions
resulting from measures adopted to meet requirements of the CAA as of
the baseline date of the SIP.\78\
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    \78\ 40 CFR 51.308(e)(2)(iv).
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    As discussed above in section II.C, pursuant to 40 CFR
51.308(e)(2)(i), Utah must demonstrate that the alternative measure
will achieve greater reasonable progress than would have resulted from
the installation and operation of BART at all sources subject to BART
in the State and covered by the alternative program. This demonstration
has five parts, each of which is addressed in the July 2019 SIP
submittal, including the Staff Review support document.
1. List of All BART-Eligible Sources Within the State
    As discussed above in section III.B.1, Utah included a list of all
BART-eligible sources:

 PacifiCorp Hunter, Unit 1
 PacifiCorp Hunter, Unit 2
 PacifiCorp, Huntington, Unit 1
 PacifiCorp, Huntington, Unit 2

    EPA previously approved Utah's BART eligibility determinations in
our 2012 rulemaking,\79\ and we are now proposing that this same list
satisfies the requirements of 40 CFR 51.308(e)(2)(i)(A).
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    \79\ 77 FR 74355, 74357 (Dec. 14, 2012).
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2. List of All BART-Eligible Sources and All BART Source Categories
Covered by the Alternative Program
    As discussed above in section III.B.2, the Utah NOX BART
Alternative covers all of the BART-eligible sources in the State,
Hunter Units 1 and 2 and Huntington Units 1 and 2, in addition to three
non-BART units, PacifiCorp's Hunter Unit 3 and Carbon Units 1 and 2. We
propose that Utah has satisfied the requirement of 40 CFR
51.308(e)(2)(i)(B).
3. Analysis of BART and Associated Emission Reductions
    As noted above in section III.B.3, in the July 2019 Utah RH SIP
submittal, the State compared the Utah NOX BART Alternative
to a BART Benchmark that included the most stringent NOX
BART controls, SCR plus upgraded combustion controls, at the four BART
units. While the State explicitly noted that it was not determining
that SCR plus upgraded combustion controls would constitute source-
specific BART at the four subject-to-BART units, it explained that this
technology ``can be used as a stringent benchmark for comparison with
an alternative program'' and it is ``a conservative approach.'' \80\ We
are proposing to find that this is a reasonable approach to setting the
BART Benchmark for purposes of comparison to a BART alternative
program, and is consistent with the streamlined approach described in
Step 1 of the BART Guidelines. The BART Guidelines note that a
comprehensive BART analysis can be forgone if a source adopts the most
stringent controls available for the purpose of implementing BART.\81\
Moreover, when EPA established NOX BART in our 2016 FIP, we
also selected SCR plus upgraded combustion controls (with an emission
limit of 0.07 lb/MMBtu as a 30-day rolling average), which further
reinforces the reasonableness of Utah's decision to treat the most
stringent controls as the BART Benchmark.
---------------------------------------------------------------------------

    \80\ Staff Review at 12.
    \81\ 40 CFR 51, appendix Y, section IV.D.1.9.
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    Utah then used modeling projections for the year 2025 to determine
the associated emission reductions that would result under the BART
Benchmark. These results are provided above in Table 2 of this notice.
The EPA proposes to find that the methodology Utah used to develop the
projection of emissions under the BART Benchmark is reasonable because
it reflects the most stringent control option.
    We propose to find that Utah has met the requirement for an
analysis of BART and associated emission reductions achievable at
Hunter Units 1 and 2 and Huntington Units 1 and 2 under 40 CFR
51.308(e)(2)(i)(C).
4. Analysis of Projected Emissions Reductions Achievable Through the
BART Alternative
    Utah's NOX BART Alternative consists of the following
enforceable measures:
     A NOX emission limit of 0.26 lb/MMBtu (30-day
rolling average) each for Hunter Units 1 and 2 and Huntington 1 and 2.
     A NOX emission limit of 0.34 lb/MMBtu (30-day
rolling average) for Hunter Unit 3.
     A requirement to permanently close and cease operation of
the Carbon power plant by August 15, 2015.
    As discussed above in section III.B.4, a summary of Utah's
estimates of emissions for the Utah NOX BART Alternative and
the BART Benchmark is provided above in Table 2. Note that the values
in Table 2 differ from the analogous table in our 2016 proposed rule
\82\ for the following reasons. First, in addition to the BART
Benchmark and BART Alternative, the table now includes projections for
the Baseline emissions scenario. All three of these projected 2025
scenarios relate to the CAMx modeling used to demonstrate that the BART
Alternative will achieve greater progress than BART under the two-prong
test of 40 CFR 51.308(e)(3), as discussed in sections III.B.5 and
IV.B.5 of this notice. The 2025 Baseline is used in the first prong of
the two-prong test to demonstrate that visibility under the BART
Alternative does not decline at any of the 15 affected Class I areas.
Second, to ensure that the selection of baseline emissions does not
bias the determination of whether the BART Alternative achieves greater
reasonable progress, the projected emissions for all three 2025
scenarios are calculated from a consistent baseline of 2001-2003 for
all BART-eligible and non-BART units covered by the BART Alternative.
That is, when establishing emission assumptions for the 2011 Typical
Year modeling scenario, annual emission rates for the seven units were
set equal to 2001-2003 actual average emissions, and these annual
emission rates were then projected to 2025 to reflect the
NOX controls anticipated under each future year scenario.
Note that although the 2025 Baseline scenario is a projection of 2025
emissions for all other sources in the modeling domain, the Baseline
emissions for the seven units in Table 2 reflect 2001-2003 emissions.
This approach was chosen so that the 2025 Baseline reflects emissions
at the subject-to-BART units at the Hunter and Hunter power plants
prior to the installation of any controls or other measures intended to
meet BART requirements. Finally, the 2001-2003 baseline period also
aligns with that used by EPA in our evaluation of BART under the FIP in
our 2016 final rule.
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    \82\ Table 3; 81 FR 2015.
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    Relative to the 2025 Baseline, the BART Benchmark and BART
Alternative include actual SO2 reductions from Hunter and
Huntington that occurred after the 2001-2003 baseline due to scrubber
upgrades. Thus, the CAMx modeling results for the BART Benchmark and
BART Alternative shown in Tables 4 and 5 of this notice reflect these
SO2 reductions. The treatment of these SO2
reductions in the modeling does not affect the determination of greater
reasonable

progress under the two-prong test. Under prong 1, while the
SO2 reductions from Hunter and Huntington increase the
apparent overall visibility benefit of the BART Alternative relative to
the Baseline, there would not be an anticipated decline in visibility
relative to the Baseline in the absence of those SO2
reductions from Hunter and Huntington because the BART Alternative
would still result in overall NOX, SO2, and PM
emissions decreases compared to the Baseline. Under prong 2, because
the SO2 reductions from Hunter and Huntington are equal
under the BART Alternative and BART Benchmark, they do not advantage
either control scenario. Accordingly, the EPA proposes to find that the
methodology Utah used to develop the modeling scenarios, including the
projection of emissions under the Utah NOX BART Alternative,
is reasonable and that Utah has met the requirement for an analysis of
the projected emissions reductions achievable through the alternative
measure under 40 CFR 51.308(e)(2)(i)(D).
5. Determination That the Alternative Achieves Greater Reasonable
Progress Than Would Be Achieved Through the Installation and Operation
of BART
    As discussed above in section III.B.5, Utah used CAMx modeling to
assess whether the NOX BART alternative will achieve greater
reasonable progress than the BART Benchmark under the two-prong
quantitative test provided for in 40 CFR 51.308(e)(3)(i) and (ii). The
CAMx modeling results in Tables 4 and 5 show both prongs of the two-
prong test are satisfied: Visibility does not decline in any Class I
area under the BART Alternative relative to the Baseline on both the
20% best or 20% worst days, and the average visibility improvement
across all affected Class I areas is greater under the BART Alternative
than under the BART Benchmark. EPA reviewed the CAMx protocol before
the modeling was undertaken. PacifiCorp revised the modeling methods
and assumptions to address EPA's concerns. Notably, as discussed above
in section III.B.5, PacifiCorp revised the ammonia emission inventory
and related input parameters to improve the model's ability to simulate
ammonia and ammonium nitrate concentrations on the Colorado Plateau,
thus also improving the model's ability to estimate visibility impacts
resulting from NOX emissions. In addition, the analysis was
expanded to assess all 15 class I areas in the modeling domain.
    As noted above, Utah submitted the same proposed NOX
BART Alternative in its June 2015 submission under the qualitative
clear-weight-of-evidence test in 40 CFR 51.308(e)(2)(i)(E). In July
2016, EPA determined that, based on the weight-of-evidence
demonstration before us at that time, Utah had not demonstrated that
the BART Alternative resulted in greater visibility improvement than
would BART. However, as noted by the U.S. Court of Appeals for the
Tenth Circuit, under EPA's interpretation of its regulations a state
can choose either the quantitative tests (as applicable) in
51.308(e)(3) or the qualitative test in 51.308(e)(2)(i)(E).\83\ We
believe it follows that a reasonable interpretation of our regulatory
scheme allows for a situation in which certain evidence would not be
sufficient to make a showing under one ``better-than-BART'' test, but
different evidence could support that showing under a separate test.
That is, we believe that just because a certain set of evidence failed
to show that a BART alternative would achieve greater visibility
improvement under the ``clear weight of evidence'' test, that does not
necessarily mean that the alternative does not in fact make greater
reasonable progress than BART, as demonstrated through dispersion
modeling under the two-prong test in section 308(e)(3). Accordingly, we
propose to approve Utah's determination that the Utah NOX
BART Alternative would achieve greater reasonable progress than BART
under 40 CFR 51.308(e)(3).
---------------------------------------------------------------------------

    \83\ WildEarth Guardians v. EPA, 770 F.3d 919, 934 (10th Cir.
2014).
---------------------------------------------------------------------------

6. Requirement That Emission Reductions Take Place During Period of
First Long-Term Strategy
    As discussed above in section III.B.6, pursuant to 40 CFR
51.308(e)(2)(iii), the State must ensure that all necessary emission
reductions take place during the period of the first long-term strategy
for regional haze. The RHR further provides that, to meet this
requirement, the State must provide a detailed description of the
alternative measure, including schedules for implementation, the
emission reductions required by the program, all necessary
administrative and technical procedures for implementing the program,
rules for accounting and monitoring emissions, and procedures for
enforcement.\84\
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