[Federal Register Volume 84, Number 97 (Monday, May 20, 2019)]
[Rules and Regulations]
[Pages 22711-22727]
[FR Doc No: 2019-09922]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2018-0606; FRL-9992-73-Region 8]

Approval and Promulgation of Air Quality Implementation Plans;
Wyoming; Revisions to Regional Haze State Implementation Plan;
Revisions to Regional Haze Federal Implementation Plan

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is finalizing
approval of State Implementation Plan (SIP) revisions submitted by the
State of Wyoming on April 5, 2018, addressing regional haze. The
revisions modify the sulfur dioxide (SO2) emissions
reporting requirements for Laramie River Station Units 1 and 2. We are
also finalizing revisions to the nitrogen oxides (NOX)
emission limits for Laramie River Units 1, 2 and 3 in the Federal
Implementation Plan (FIP) for regional haze in Wyoming. The revisions
to the Wyoming regional haze FIP also establish a SO2
emission limit averaged annually across both Laramie River Station
Units 1 and 2. These units are operated by, and owned in part by, Basin
Electric Power Cooperative (Basin Electric). The EPA is taking this
action pursuant to section 110 of the Clean Air Act (CAA).

DATES: This rule is effective June 19, 2019.

ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-R08-OAR-2018-0606. All documents in the docket are
listed on the http://www.regulations.gov website. 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, is not placed on the
internet and will be publicly available only in hard copy form.
Publicly available docket materials are available through http://www.regulations.gov, or please contact the person identified in the FOR
FURTHER INFORMATION CONTACT section for additional availability
information.

FOR FURTHER INFORMATION CONTACT: Jaslyn Dobrahner, Air Program, EPA,
Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-
1129,<PHONE_NUMBER><EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Throughout this document wherever ``we,''
``us,'' or ``our'' is used, we mean the EPA.

I. Proposed Action
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. Reasonable Progress Requirements
    E. Consultation With Federal Land Managers (FLMs)
    F. Requirements for Regional Haze SIPs Submitted Under 40 CFR
51.309
    G. Modeling
    H. Regulatory and Legal History of the 2014 Wyoming SIP and FIP
III. Public Comments and EPA Responses
IV. Final Action
V. Incorporation by Reference
VI. Statutory and Executive Order Reviews

I. Proposed Action

    On January 30, 2014, the EPA promulgated a final rule titled,
``Approval, Disapproval and Promulgation of Implementation Plans; State
of Wyoming; Regional Haze State Implementation Plan; Federal
Implementation Plan for Regional Haze,'' approving, in part, a regional
haze SIP revision submitted by the State of Wyoming on January 12,
2011.\1\ In the final rule, the EPA also disapproved, in part, the
Wyoming regional haze SIP, including the NOX BART emission
limit of 0.21 lb/MMBtu (30-day rolling average) for Laramie River Units
1, 2 and 3, and promulgated a FIP that imposed a NOX BART
emission limit of 0.07 lb/MMBtu (30-day rolling average) for each of
the three Laramie River Units, among other actions.
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    \1\ 79 FR 5032 (January 30, 2014).
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    On October 11, 2018, the EPA proposed to revise the FIP per the
terms of the settlement agreement by amending the NOX and
SO2 emission limits for Laramie River.\2\ Specifically,

the EPA proposed to: (1) Revise the NOX emission limit and
associated compliance date for Unit 1; (2) through a BART alternative,
revise the NOX emission limits for Units 2 and 3, and add a
SO2 emission limit averaged annually across Units 1 and 2
along with the associated compliance dates; and (3) require selective
catalytic reduction (SCR) on Unit 1 and selective non-catalytic
reduction (SNCR) on Units 2 and 3.\3\
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    \2\ 83 FR 51403 (October 11, 2018). Letter from Eileen T.
McDonough, U.S. Department of Justice, to Elizabeth Morrisseau,
Wyoming Attorney General's Office, and Christina F. Gomez, Denise W.
Kennedy, and Patrick R, Day, Holland & Hart LLC (notification that
both the EPA and the Department of Justice (DOJ) determined not to
withdraw their consent to the Settlement Agreement) (April 24,
2017); Settlement Agreement between Basin Electric Power
Cooperative, the State of Wyoming, and the EPA (April 24, 2017);
First Amendment to Settlement Agreement (pursuant to Paragraph 15 of
the Agreement, extended the deadline for the EPA to determine
whether to withdraw or consent to the Settlement Agreement in
Paragraph 1 to May 3, 2017); Second Amendment to Settlement
Agreement (pursuant to Paragraph 15 of the Agreement, amended the
date in Paragraph 5.b.ii. for the SO2 emission limits for
Laramie River Units 1 and 2 to commence December 31, 2018)
(September 14, 2018); Letter from Eileen T. McDonough, U.S.
Department of Justice, to Erik Petersen, Wyoming Attorney General's
Office, and Christina F. Gomez, Denise W. Kennedy, and Patrick R,
Day, Holland & Hart LLC (notification regarding recent partial
government shut-down and Paragraph 15 of the Settlement Agreement
regarding extension of deadlines caused by lapse in appropriations)
(March 28, 2019); (Settlement Agreement).
    \3\ Although we are finalizing revisions to the Wyoming regional
haze FIP, Wyoming may always submit a new regional haze SIP to the
EPA for review, and we would welcome such a submission. The CAA
requires the EPA to act within 12 months on a SIP submittal from the
time that it is determined to be complete. If Wyoming were to submit
a SIP revision meeting the requirements of the CAA and the regional
haze regulations, we would propose approval of the State's plan as
expeditiously as practicable.
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    The EPA also proposed to approve SIP revisions submitted by the
State of Wyoming on April 5, 2018, that amended the SO2
emissions reporting requirements for Laramie River Units 1 and 2 as
they pertain to the Western Backstop Sulfur Dioxide Trading Program
under 40 CFR 51.309. Wyoming was one of several states that elected to
participate in the backstop trading program. The approved SIP revisions
ensure that SO2 emission reductions under the settlement
agreement are not counted as reductions under the backstop trading
program, and address how Basin Electric is required to calculate
reportable SO2 emissions, when Basin Electric is required to
use the revised SO2 emissions calculation method, and how
the reported SO2 emissions will be used within the context
of the SO2 emissions milestone inventory.

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\
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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,
the 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.''
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    The EPA promulgated a rule to address regional haze on July 1,
1999.\5\ The Regional Haze Rule (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
51.309, are included in the EPA's visibility protection regulations at
40 CFR 51.300 through 51.309. The EPA revised the RHR on January 10,
2017.\7\
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    \5\ 64 FR 35714, 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,
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. A state must
submit its SIP and SIP revisions to the EPA for review and approval.
Once approved, a SIP is enforceable by the EPA and citizens under the
CAA; that is, the SIP is federally enforceable. If a state elects not
to make a required SIP submittal, fails to make a required SIP
submittal, or if we find that a state's required submittal is
incomplete or not approvable, then we must promulgate a FIP to fill
this regulatory gap.\9\
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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 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\ Rather than requiring
source-specific BART controls, states also have the flexibility to
adopt an emissions trading program or other alternative program as long
as the alternative provides greater reasonable progress towards
improving visibility than BART.\11\
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    \10\ 40 CFR 51.308(e). The EPA designed the Guidelines for BART
Determinations Under the Regional Haze Rule (Guidelines) 40 CFR
Appendix Y to Part 51 ``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\ 40 CFR 51.308(e)(2). WildEarth Guardians v. EPA, 770 F.3d
919 (10th Cir. 2014).
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C. BART Alternatives

    An alternative program to BART must meet requirements under 40 CFR
51.308(e)(2) and (3). 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 in 40 CFR 51.308(e)(2)(i) through (v). The state
or the EPA must conduct an analysis of the best system of continuous
emission control technology available and the associated reductions for
each source subject to BART covered by the alternative program,
commonly referred to as a ``BART benchmark.'' Visibility improvement
under the BART benchmark is compared to improvement

under an alternative using one of the three tests described below to
determine whether that alternative achieves greater reasonable progress
than source-specific BART. Where the alternative program has been
designed to meet requirements other than BART, simplifying assumptions
may be used to establish a BART benchmark.
    Pursuant to 40 CFR 51.308(e)(2)(i)(E), the state or the EPA must
also 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. Title 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
for the alternative program is not substantially different than for
BART, and the alternative program results in greater emissions
reductions of each of the pollutants covered by the alternative, then
the alternative program may be deemed to achieve greater reasonable
progress. If the distribution of emissions is significantly different,
the differences in visibility between BART and the alternative program
must be determined by conducting air quality modeling and evaluating
visibility impacts on the best and worst 20 percent of days at each
impacted Class I area. The 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. Alternatively, pursuant to 40 CFR
51.308(e)(2)(i)(E), states may show that the alternative achieves
greater reasonable progress than the BART benchmark ``based on the
clear weight of evidence'' determinations.\12\
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    \12\ 40 CFR 51.308(e)(2).
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    Generally, a SIP or FIP addressing regional haze must include
emission limits and compliance schedules for 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 monitoring, recordkeeping, and reporting for the alternative's
enforceable requirements. See CAA section 110(a); 40 CFR part 51,
subpart K.

D. Reasonable Progress Requirements

    In addition to BART requirements, as mentioned previously, each
regional haze SIP or FIP must contain measures as necessary to make
reasonable progress towards the national visibility goal. Finally, the
SIP or FIP must calculate reasonable progress goals (RPGs) for each
Class I area within the state for the plan implementation period (or
``planning period''), based on the measures included in the long-term
strategy for making reasonable progress.\13\ If an RPG provides for a
slower rate of improvement in visibility than the rate under which the
national goal of no anthropogenic visibility impact would be attained
by 2064, the SIP or FIP must demonstrate, based on the four reasonable
progress factors, why that faster rate is not reasonable and the slower
rate provided for by the SIP or FIP's state-specific RPG is
reasonable.\14\
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    \13\ 40 CFR 51.308(d).
    \14\ 40 CFR 51.308(d)(1)(ii).
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E. Consultation With Federal Land Managers (FLMs)

    The RHR requires that a state, or the EPA if promulgating a FIP
that fills a gap in the SIP with respect to this requirement, consult
with FLMs before adopting and submitting a required SIP or SIP
revision, or a required FIP or FIP revision.\15\ Further, the EPA, or
state when considering a SIP revision, must include in its proposal a
description of how it addressed any comments provided by the FLMs.
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    \15\ 40 CFR 51.308(i).
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F. Requirements for Regional Haze SIPs Submitted Under 40 CFR 51.309

    The EPA's RHR provides two paths to address regional haze. One is
40 CFR 51.308, requiring states to perform source-specific BART
determinations (or adopt a BART alternative that achieves greater
visibility improvement than BART) and determine what additional
measures are necessary to make reasonable progress. The other method
for addressing regional haze is through 40 CFR 51.309, and is an option
for nine states termed the ``Transport Region States,'' which include:
Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oregon, Utah
and Wyoming. By meeting the requirements under 40 CFR 51.309, a
Transport Region State can be deemed, for the purposes of the first
implementation period, to be making reasonable progress toward the
national goal of achieving natural visibility conditions for the 16
Class I areas on the Colorado Plateau.\16\
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    \16\ The Colorado Plateau is a high, semi-arid tableland in
southeast Utah, northern Arizona, northwest New Mexico and western
Colorado. The 16 mandatory Class I areas are: Grand Canyon National
Park, Mount Baldy Wilderness, Petrified Forest National Park,
Sycamore Canyon Wilderness, Black Canyon of the Gunnison National
Park Wilderness, Flat Tops Wilderness, Maroon Bells Wilderness, Mesa
Verde National Park, Weminuche Wilderness, West Elk Wilderness, San
Pedro Park Wilderness, Arches National Park, Bryce Canyon National
Park, Canyonlands National Park, Capital Reef National Park and Zion
National Park.
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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) 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 to provide 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 for protecting
visibility for the Class I areas on the Colorado Plateau, and the EPA
codified these recommendations as an option available to states as part
of the RHR.\17\
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    \17\ 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.\18\ In
September 2000, the Western Regional Air Partnership (WRAP), which is
the successor organization to the GCVTC, submitted an annex to the 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 EPA codified the annex on June 5, 2003,
at 40 CFR 51.309(h).\19\
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    \18\ 64 FR 35714, 35749, 35756 (July 1, 1999).
    \19\ 68 FR 33764, 33767 (June 5, 2003).
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    Five western states, including Wyoming, submitted implementation
plans under section 309 in 2003.\20\ The EPA was challenged by the
Center for Energy and Economic Development (CEED) on the validity of
the annex provisions. In CEED v. EPA, the U.S. Court of Appeals for the
District of Columbia vacated the EPA's adoption of

the WRAP annex.\21\ In response to the court's decision, the EPA
rescinded the annex requirements adopted under 40 CFR 51.309(h), but
left in place the stationary source requirements in 40 CFR
51.309(d)(4).\22\ 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
BART.
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    \20\ 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. In 2012, the EPA approved
Wyoming's SIP submittals that included the Western Backstop Sulfur
Dioxide Trading Program. 77 FR 73926 (Dec. 12, 2012).
    \21\ Ctr. for Energy & Econ. Dev. v. EPA, 398 F.3d 653, 654
(D.C. Cir. 2005).
    \22\ 71 FR 60612 (October 13, 2006).
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    Thus, rather than requiring source-specific BART controls as
explained previously in Section II.B, states have the flexibility to
adopt an emissions trading program or other alternative program if the
alternative provides greater reasonable progress than would be achieved
by the application of BART, pursuant to 40 CFR 51.308(e)(2). Under 40
CFR 51.309, some states can satisfy the SO2 BART
requirements by adopting SO2 emissions milestones and a
backstop trading program. 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 backstop trading program would be implemented if a
milestone is exceeded and the program is triggered.\23\
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    \23\ 40 CFR 51.309(d)(4)(v).
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G. Modeling

    The EPA routinely uses models as a part of our analytical
methodology to provide for regularity, uniformity and to inform our
decision-making process. The CAMx model is one such dispersion model
and in particular it is a photochemical grid model \24\ 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 this application.\25\ The CAMx model simulates air
quality over many geographic scales and treats a wide variety of inert
and chemically active pollutants, including ozone, particulate matter,
inorganic and organic PM2.5/PM10, mercury and
other toxics. CAMx also has plume-in-grid and source apportionment
capabilities.\26\ At this point in time, use of a photochemical grid
model is the best available method for predicting visibility
improvement.
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    \24\ CAMx User's Guide: Comprehensive Air Quality Model with
extensions, Version 6.50, Ramboll Environment and Health, 773 San
Marin Drive, Suite 2115, Novato, California 94998. http://www.camx.com (April 2018) (CAMx User's Guide).
    \25\ 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 (December
3, 2014). (We note that the regional haze section of this guidance
explains that other portions of the guidance are applicable to
regional haze, p. 149.). https://www3.epa.gov/ttn/scram/guidance/guide/Draft_O3-PM-RH_Modeling_Guidance-2014.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).
    \26\ 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.
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    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 starting point for assessing visibility impacts for different
levels of emissions from Laramie River was the Three-State Air Quality
Modeling Study (3SAQS) modeling platform that provides a framework for
addressing air quality impacts in Colorado, Utah and Wyoming. The 3SAQS
is a publicly available platform intended to facilitate air resources
analyses. The 3SAQS developed a base year modeling platform using the
year 2008 to leverage work completed during the West-wide Jump-start
Air Quality modeling study (WestJump), which covered the entire western
United States. For the Laramie River modeling, AECOM reduced the
modeling domain to an area within 500 kilometers of the facility and
performed additional modeling to refine the modeling domain from the
3SAQS 12-kilometer (km) grid resolution to a finer 4-km grid
resolution. The refined spatial resolution was used to more accurately
simulate the concentration gradients of gas and particulate species in
the plumes emitted from the source facilities.
    The CAMx modeling analysis established specific model
configurations and other inputs. The model requires configuration and
input data such as defined horizontal and vertical modeling
domains,\27\ gridded meteorological data, emissions data, and a set of
files for the physical and chemical reaction calculations.\28\
Meteorological inputs were developed using the Weather Research and
Forecast (WRF) Model.\29\ The Sparse Matrix Operator Kernal Emissions
(SMOKE) model was used for emissions inputs. SMOKE is an emissions
processing system that converts emission inventory data into the
formatted emissions files required by an air quality simulation
model.\30\ Collectively the three models are referred to as the CAMx
modeling system.\31\
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    \27\ AECOM, Laramie River Station Power Plant Visibility Impacts
for Two Emissions Control Scenarios: Final Report (Final Report), p.
2-1, 2-3 (May 2016).
    \28\ Final Report, p. 2-1, 2-5--2-7.
    \29\ Final Report, p. 2-4.
    \30\ Final Report, p. 2-4--2-5. In addition to the emission
inputs via SMOKE, emissions from the Laramie River Station and other
sources were input into the model as further described in the
Protocol and Final Report.
    \31\ Final Report, p. 1-1.
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    The three modeling scenarios conducted were:
     Baseline Scenario. This scenario included the actual
emission rates for all three units of LRS during the 2001 to 2003
period.\32\
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    \32\ Final Report, p. 3-4.
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     EPA FIP Scenario (BART). This scenario included the
emission rates for all three units of Laramie River Station that
correspond to the EPA proposed FIP control strategy.\33\
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    \33\ Final Report, p. 3-4--3-5.
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     Basin Electric Scenario (BART alternative). This scenario
included the emission rates for all three units of Laramie River
Station that correspond to an alternative control strategy proposed by
Basin Electric.\34\
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    \34\ Final Report, p. 3-5--3-6.
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    For the two-prong test, an existing projected 2020 emissions
database was used to estimate emissions of sources within the modeling
domains. The existing 2020 database was derived from the 3SAQS study,
which projected emissions from 2008 to 2020. Since the BART alternative
emissions reductions would not be fully in place until the end of 2018,
the 2020 emissions projections are more representative of the air
quality conditions that will be obtained while the BART alternative is
being implemented than the 2008 database. In the three 2020 CAMx
modeling scenarios, Laramie River emissions were

modeled to represent the baseline, the BART 2014 FIP, and the proposed
BART alternative.
    The CAMx-modeled concentrations for sulfur, nitrogen, and primary
particulate matter (PM) were tracked using the CAMx Particulate Source
Apportionment Technology (PSAT) tool so that the concentrations and
visibility impacts due to Laramie River could be separated out from
those due to the total of all other modeled sources. AECOM computed
visibility impairment due to Laramie River using the EPA's Modeled
Attainment Test Software (MATS) tool which bias corrects CAMx outputs
to available measurements of PM species and uses the revised
Interagency Monitoring of Protected Visual Environments (IMPROVE)
equation to calculate the 20 percent best and 20 percent worst days for
visibility impacts.\35\ Finally, a typical year modeling scenario
(2008) was developed to enable calculation of the Relative Response
Factors (RRF),\36\ which were developed from monitoring data and used
along with the EPA's MATS to correct for bias in the visibility
results.\37\
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    \35\ Visibility impairment is calculated based on the summation
of extinction due to each visibility impairing pollutant. The
concentration of each visibility impairing pollutant is either
measured or obtained from the model estimates. These concentrations
are then used to calculate the total visibility impairment based on
the light absorbing or scattering characteristic of each pollutant
specie and adjustment for relative humidity. The deciview is ``an
atmospheric haze index that expresses changes in visibility'' and
``is like the decibel scale for sound'' because it ``represents a
common change in perception.'' 64 FR at 35725.
    \36\ Final Report, p. 3-1--3-3.
    \37\ Final Report, p. 4-1--4-5.
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H. Regulatory and Legal History of the 2014 Wyoming SIP and FIP

    On January 30, 2014, the EPA promulgated a final rule titled,
``Approval, Disapproval and Promulgation of Implementation Plans; State
of Wyoming; Regional Haze State Implementation Plan; Federal
Implementation Plan for Regional Haze,'' approving, in part, a regional
haze SIP revision submitted by the State of Wyoming on January 12,
2011.\38\ In the final rule, the EPA also disapproved, in part, the
Wyoming regional haze SIP, including the SIP NOX BART
emission limit of 0.21 lb/MMBtu (30-day rolling average) for each of
the three Laramie River Units, and promulgated a FIP that imposed a
NOX BART emission limit of 0.07 lb/MMBtu (30-day rolling
average) at each of the three Laramie River Units.
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    \38\ 79 FR 5032 (January 30, 2014).
---------------------------------------------------------------------------

    The Laramie River Station is in Platte County, Wyoming, and is
comprised of three 550 megawatt (MW) dry-bottom, wall-fired boilers
(Units 1, 2 and 3) burning subbituminous coal for a total net
generating capacity of 1,650 MW. All three units are within the
statutory definition of BART-eligible units and were determined to be
subject to BART by Wyoming.
    Basin Electric, the State of Wyoming, and others challenged the
final rule. Basin Electric and Wyoming challenged our action as it
pertained to the NOX BART emission limits for Laramie River
Units 1, 2 and 3.\39\ After mediated discussions through the U.S. Court
of Appeals for the Tenth Circuit's Mediation Office, Basin Electric,
Wyoming and the EPA reached a settlement in 2017 that, if fully
implemented, would address all of Basin Electric's challenges to the
2014 final rule and Wyoming's challenges to the portion of the 2014
final rule regarding NOX BART emission limits for Laramie
River Units 1, 2 and 3.40 41
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    \39\ Basin Electric Cooperative v. EPA, No. 14-9533 (10th Cir.
March 31, 2014) and Wyoming v. EPA, No. 14-9529 (10th Cir. March 28,
2014).
    \40\ 81 FR 96450 (December 30, 2016).
    \41\ Settlement Agreement.
---------------------------------------------------------------------------

    The settlement agreement required the EPA to propose a FIP revision
to include three major items:
     First, an alternative (BART alternative) to the
NOX BART emission limits in the EPA's 2014 FIP that
includes:
    [cir] Revised NOX emission limits for Laramie River
Units 2 and 3 of 0.15 lb/MMBtu (30-day rolling average) commencing
December 31, 2018, with an interim limit of 0.18 lb/MMBtu (30-day
rolling average) commencing the date that the EPA's final revised FIP
becomes effective and ending December 31, 2018; and
    [cir] A new SO2 emission limit for Laramie River Units 1
and 2 of 0.12 lb/MMBtu (annual) averaged annually across the two units
commencing December 31, 2018.
     Second, a revised NOX emission limit for
Laramie River Unit 1 of 0.06 lb/MMBtu on a 30-day rolling average
commencing July 1, 2019, with an interim limit of 0.18 lb/MMBtu on a
30-day rolling average commencing the date that the EPA's final revised
FIP becomes effective and ending June 30, 2019.\42\
---------------------------------------------------------------------------

    \42\ These limits were voluntarily requested by Basin Electric.
---------------------------------------------------------------------------

     Third, installation of SCR on Laramie River Unit 1 by July
1, 2019, (thereby revising the compliance date of the existing FIP) and
installation of SNCR on Units 2 and 3 by December 30, 2018.
    In accordance with other terms of the 2017 settlement, Wyoming
submitted a SIP revision to the EPA on April 5, 2018, to revise the
SO2 annual reporting requirements for Laramie River Units 1
and 2 as they pertain to the backstop trading program under 40 CFR
51.309. Specifically, Wyoming determined that Basin Electric must use
SO2 emission rates of 0.159 lb/MMBtu for Laramie River Unit
1 and 0.162 lb/MMBtu for Laramie River Unit 2 and multiply those rates
by the actual annual heat input during the year for each unit to
calculate and report emissions under the SO2 backstop
trading program. The revisions ensure that the SO2 emissions
reductions that are part of the BART alternative for Units 1 and 2 are
not double-counted as reductions under the backstop trading program.

III. Public Comments and EPA Responses

    We received seven comment submissions during the public comment
period. After reviewing the comments, the EPA determined that four of
the comments are outside the scope of our proposed action and fail to
identify any material issue necessitating a response. One of the
comments was a request to extend the comment period.\43\ The remaining
two comment letters--one from the National Parks Conservation
Association, Powder River Basin Resource Council, Sierra Club, and
Wyoming Outdoor Council (submitted collectively as the ``Conservation
Organizations'') and one from Basin Electric Power Cooperative--are
summarized below with our responses.
---------------------------------------------------------------------------

    \43\ In response to the request, the EPA decided to extend the
comment period for the proposed rule until December 10, 2018; 83 FR
55656 (November 7, 2018).
---------------------------------------------------------------------------

    According to the Conservation Organizations, the EPA failed to
demonstrate that the BART alternative will achieve greater reasonable
progress toward eliminating visibility impairment than would the
implementation of BART and, as a result, the EPA may not finalize its
proposed FIP revision for the following reasons: \44\
---------------------------------------------------------------------------

    \44\ See 40 CFR 51.308(e).
---------------------------------------------------------------------------

    Comment: The Conservation Organizations argue that the EPA's
modeling is based on NOX emission rates that underestimate
the visibility benefits of BART and overestimate the visibility
benefits of the BART alternative. More specifically, the commenters
argue, the EPA incorporated an inflated NOX emission rate
for SCR in the BART scenario while failing to justify a low
NOX emission rate for SNCR in the BART alternative, thereby
biasing the analysis in favor of the BART alternative. According to the

commenters, the comparison of the two scenarios must use a rational
assessment of the emissions rates achievable with the controls
constituting ``the best system of continuous emission control
technology available'' for the relevant source(s), (i.e., the BART
benchmark and the BART alternative).\45\ The EPA failed to conduct a
rational assessment, the Conservation Organizations argue, when the EPA
assumed SCR could achieve a controlled NOX annual emission
rate of 0.05 lb/MMBtu when determining the BART scenario but using a
controlled NOX annual emission rate of 0.04 lb/MMBtu under
the BART alternative scenario thereby appearing to underestimate the
visibility benefits of SCR in the BART benchmark.\46\ Likewise,
according to the commenters, the EPA failed to justify its assumption
for the BART alternative NOX emission rate of 0.128 lb/MMBtu
at Units 2 and 3 based on the operation of SNCR thereby appearing to
overestimate the visibility benefits of the BART alternative.
Specifically, it is not reasonable, according to the commenters, to
apply the same percentage reduction from the NOX baseline
emissions of 0.16 lb/MMBtu (as assumed for the proposed FIP revision)
and 0.19 lb/MMBtu (as assumed in the 2014 FIP), because the control
effectiveness of SNCR declines as baseline emission rates are reduced.
Moreover, high furnace temperatures at Laramie River Station will
further limit the possible NOX reduction.\47\
---------------------------------------------------------------------------

    \45\ 40 CFR 51.308(e)(2)(i)(C) and (D).
    \46\ Laramie River Station Power Plant Visibility Impacts for
Two Emissions Control Scenarios: Final Report. AECOM. p. 3-4--3-5,
(May 2016).
    \47\ 79 FR 5160 (January 30, 2014).
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    Response: We disagree with the commenters' assertion that the EPA's
modeling is based on NOX emission rates that underestimate
the visibility benefits of BART and overestimate the visibility
benefits of the BART alternative. We also disagree that our selection
of NOX emission rates biased the analysis in favor of the
BART alternative.
    Regarding the NOX emission rate achievable with SCR, we
disagree that we incorporated an inflated NOX emission rate
or an ``apples-to-oranges'' comparison in the BART scenario. Instead,
we used the emission limits that would be enforceable under the BART
and BART alternative scenarios, respectively. For the BART scenario, we
used the NOX emission limit of 0.07 lb/MMBtu (30-day rolling
average) which we determined to be BART in our 2014 FIP, reflecting the
installation and operation of SCR.48 49 50 For the BART
alternative scenario, we used the enforceable NOX emission
limit of 0.06 lb/MMBtu (30-day rolling average) that Basin Electric
voluntarily agreed to for Unit 1 as part of the settlement
agreement.\51\ While the 0.06 lb/MMBtu NOX limit for Unit 1
is not a component of the BART alternative, it is part of the package
of revised emission limits that is now being considered as a
replacement for the 2014 BART determinations. In order to meet the 0.06
lb/MMBtu (30-day) limit, Basin Electric will incur additional costs
that were not included in the 2014 FIP's BART determination.\52\ We are
unaware of any provision of the CAA or RHR that would prevent a source
from voluntarily requesting, and subsequently being required to comply
with, a more stringent enforceable emission rate than prescribed under
BART, as is the case here.
---------------------------------------------------------------------------

    \48\ 83 FR 51407 (October 11, 2018), 79 FR 5039 (January 30,
2014). 40 CFR pt. 51, app. Y: IV, V (BART determinations and
enforceable limits); 40 CFR 51.308(e)(3) (BART determinations).
    \49\ Shortly after publication of our FIP, various parties filed
petitions for review of EPA's final action in the U.S. Court of
Appeals for the Tenth Circuit Order (Wyoming v. EPA, No. 14-9529 and
consolidated cases). Upon the motions of various petitioners, the
Court ordered several provisions stayed pending completion of its
review. The Court issued its order on September 9, 2014 (Doc.
01019307361), which stayed the emission limits for the Laramie River
Station Units 1, 2 and 3.
    \50\ On an annual basis, the 30-day rolling average emission
limit of 0.07 lb/MMBtu corresponded to an actual emission rate of
0.05 lb/MMBtu which is the emission rate referenced by the
commenters in their comment. Regarding the relationship between 30-
day emission limits and annual emission rates, refer to the 2014
final rule which states: When establishing a 30-day emission limit
for SCR, the annual rate must be adjusted upward to account for: (1)
A margin for compliance, (2) a shorter averaging period, and (3)
start-up and shutdown emissions. 79 FR 5167 (January 30, 2014). See
also 84 FR 10433 (March 21, 2019).
    \51\ In accordance with the relationship between 30-day emission
limits and annual emission rates (see 79 FR 5167, January 30, 2014),
the EPA assumed that the 30-day rolling average emission limit of
0.06 lb/MMBtu corresponds to an annual emission rate of 0.04 lb/
MMBtu which is the emission rate referenced by the commenters in
their comment.
    \52\ Costs are one of the five factors taken into account when
determining BART.
---------------------------------------------------------------------------

    Regarding the NOX emission rate achievable with SNCR, we
disagree that we failed to justify our assumption that SNCR can achieve
an emission rate of 0.128 lb/MMBtu (annual) at Units 2 and 3.\53\ As
noted in the modeling protocol underlying the BART alternative, the
annual emission rate of 0.128 lb/MMBtu is derived from the baseline
annual emission rate of 0.16 lb/MMBtu multiplied by an assumed 20
percent reduction with SNCR (i.e., 0.16 lb/MMBtu x [1-20%/100%] = 0.128
lb/MMBtu).\54\ As the EPA recognized in our 2014 FIP and we continue to
recognize now, ``the effectiveness of SNCR is highly dependent upon the
characteristics of each boiler, and those characteristics include
furnace temperature, furnace carbon monoxide (CO) concentration,
NOX level and other factors, but furnace temperature, CO
concentration, and NOX level are most important.'' \55\
Therefore, it is difficult to predict the exact percent reduction in
NOX that can be achieved by SNCR at a given boiler.
Accordingly, in support of the 2014 FIP we used an approximation of the
NOX reduction achievable based on the NOX inlet
concentration given as a range: 30 percent for NOX greater
than 0.25 lb/MMBtu, 25 percent for NOX between 0.20 and 0.25
lb/MMBtu, and 20 percent for NOX under 0.20 lb/
MMBtu.56 57 Thus, the assumption that SNCR can reduce
NOX by 20 percent when baseline NOX emissions are
under 0.20 lb/MMBtu--whether at a baseline of 0.19 lb/MMBtu or 0.16 lb/
MMBtu--is consistent with our 2014 FIP. Put more simply, we do not
expect any meaningful difference in the control effectiveness of SNCR
between an inlet NOX emission rate of 0.19 lb/MMBtu and 0.16
lb/MMBtu. Moreover, the assumption that SNCR can reduce NOX
by 20 percent from an annual baseline of 0.16 lb/MMBtu is consistent
with the updated chapter of the EPA's Control Cost Manual (CCM) for
SNCR.\58\ Based on observed data taken from utility boilers equipped
with SNCR, Figure 1.1c of the SNCR chapter shows a relationship between
the inlet NOX emissions (x; lb/MMBtu) and the NOX
reduction (y; %) of y = 22.554x + 16.725.\59\ For a baseline emission
rate of 0.16 lb/MMBtu, the CCM equation

yields an estimated NOX reduction of 20.3 percent, which is
nearly identical to our assumed reduction of 20 percent.
---------------------------------------------------------------------------

    \53\ 83 FR 51403 (October 11, 2018), 79 FR 5032 (January 30,
2014). 40 CFR pt. 51, app. Y ] IV, V (BART determinations and
enforceable limits); 40 CFR 51.308(e)(3) (BART determinations).
    \54\ Photochemical Modeling Protocol for the Visibility
Assessment of Basin Electric Laramie River Power Plant, and
references, p. 5-1--5-2, (Protocol). Prepared for Basin Electric,
AECOM, p. 2-4, (September 2015).
    \55\ 79 FR 5159 (January 30, 2014).
    \56\ Cost of NOX Controls on Wyoming EGUs. Andover Technology
Partners. p. 4 (October 28, 2013).
    \57\ The EPA provided further justification for the assumed
percent reductions when responding to comments in the 2014 FIP. See
79 FR 5159-5161 (January 30, 2014).
    \58\ EPA Control Cost Manual, Section 4, Chapter 1, Selective
Noncatalytic Reduction. (May 2016).
    \59\ Figure 1.1c shows significant scatter in data points
yielding a trend line with an r-squared value of 0.46 (based on
simple linear regression). This reinforces the observation that the
effectiveness of SNCR is highly dependent upon the characteristics
of each boiler and is therefore difficult to predict with a high
degree of accuracy.
---------------------------------------------------------------------------

    In our 2014 FIP, we also addressed the impact of furnace
temperature on the effectiveness of SNCR. We concluded that the high
furnace temperatures would have a negative impact on reagent
utilization,\60\ we maintained that a 20 percent reduction in
NOX would be achievable.\61\ Here again, the commenter has
not provided any new information or analysis that would support a
different conclusion regarding high furnace temperatures, and we are
not aware of any such information.
---------------------------------------------------------------------------

    \60\ Reagent utilization is the ratio of moles of reagent
reacted to the moles injected.
    \61\ 79 FR 5159-5161 (January 30, 2014).
---------------------------------------------------------------------------

    In turn, the baseline annual emission rate of 0.16 lb/MMBtu is
based on actual emissions data taken from the EPA's Clean Air Markets
Division database for calendar year 2014, the most recent calendar year
for which emissions data was available when the modeling protocol for
the BART alternative was developed in 2015.\62\ Finally, we are neither
aware of any new information nor has the commenter provided any new
information or analysis that would support a different conclusion
regarding the annual emission rate achievable with SNCR.
---------------------------------------------------------------------------

    \62\ Air Markets Program Data. https://ampd.epa.gov/ampd/.
---------------------------------------------------------------------------

    Accordingly, and in consideration of the points we make above, we
find that we have provided a rational assessment of the emissions rates
achievable with SCR and SNCR control technologies for both the BART and
BART alternative scenarios.
    Comment: The Conservation Organizations argue that the EPA used an
outdated and unrepresentative temporal allocation of Laramie River
Station's SO2 and NOX emissions, which they
assert may underestimate the plant's impacts in summer and winter
months. Specifically, the modeling protocol allocated total annual
emissions based on a fairly constant level of operations without
seasonality. However, the commenters assert the data available in the
EPA's Clean Air Markets Division database show SO2 and
NOX emissions since January 2015 exhibit strong seasonality.
By neglecting to reflect this changing temporal emissions profile, the
modeling fails to accurately project visibility impacts, according to
the commenters, and therefore the EPA lacks a basis to determine that
the BART alternative is better than BART. Additionally, the commenters'
assert that AECOM inexplicably projected future year (2020) emissions
using the 2007 National Emission Inventory (NEI), Modeling Protocol, at
2-11, rather than the more current 2011 NEI. The EPA must explain
whether the use of an outdated emissions inventory may have impacted
AECOM's modeling results.
    Response: We disagree. As noted previously, the CAMx modeling
leveraged the 3SAQS \63\ as the starting point to assess visibility
impacts from Laramie River Station. The 3SAQS developed a base year
modeling platform for the year 2008 that was in turn used in the CAMx
modeling for Laramie River Station. Emissions for all sources are the
same in the 3SAQS 2008 study, except for Laramie River Station
emissions. The modeling uses annual average 2001-2003 emissions for two
reasons.\64\ First, using 2001-2003 annual emissions provides
consistency with the baseline emissions used in the CALPUFF modeling
when establishing BART in the 2014 FIP. Second, it allows the modeling
to show the visibility benefits of all NOX and
SO2 reductions that have or will occur between 2001-2003 and
the future modeled year of 2020. In turn, the temporal profile is taken
from the same years as the annual emissions (2001-2003) as it is
intended to reflect temporal variation in daily emissions during that
time. It would not be logical to apply a temporal profile reflective of
2015-2018 emissions data for the years 2001-2003 as the commenter
proposes. Furthermore, as a practical matter, the 2015-2018 emissions
data referenced by the commenter was not available when AECOM began
development of the CAMX protocol in 2014, and so could not have been
used to establish the temporal profile for Laramie River Station.
---------------------------------------------------------------------------

    \63\ ENVIRON. 2014. Three-State Air Quality Modeling Study
(3SAQS). Final Modeling Protocol 2008 Emissions and Air Quality
Modeling Platform. ENVIRON International Corporation, Novato,
California (April 2014).
    \64\ Air Quality Modeling Protocol: Wyoming Regional Haze
Federal Implementation Plan, U.S. EPA, p. 6 (January 2014) and BART
Air Modeling Protocol, Individual Source Visibility Assessments for
BART Control Analyses, p. 7 (September 2006).
---------------------------------------------------------------------------

    Regarding the year of the NEI used to project emissions to the
future year of 2020, the initial 3SAQS platform used a base year of
2008, which was in turn the basis of the CAMx modeling.\65\ A
subsequent 3SAQS platform, using a base year of 2011 with 2011 NEI
data, was developed. However, the 2011 3SAQS modeling platform was not
yet available when AECOM began preparation of the CAMx modeling
protocol in 2014.\66\ Even still, for the reasons stated above, actual
annual emissions from 2001-2003 were used for Laramie River Station. As
such, the question of whether future year emissions were projected from
the 2007 or 2011 NEI is relevant only to other sources included in the
modeling, and the same emissions for the other sources were used in all
three scenarios. Therefore, any errors in the emissions from other
sources were mitigated by the fact that the CAMx results were used to
compare the relative visibility improvements in BART and the BART
alternative.
---------------------------------------------------------------------------

    \65\ Use of the most recent NEI is consistent with the EPA's SIP
inventory guidance. ``Draft Emissions Inventory Guidance for
Implementation of Ozone [and Particulate Matter] National Ambient
Air Quality Standards (NAAQS) and Regional Haze Regulations,''
(April 11, 2014) (2014 Draft Emissions Inventory Guidance''), pp.
13, 38 (which similarly requires use of the most current emission
for regional haze reporting purposes).
    \66\ Memorandum from Intermountain West Data Warehouse--Western
Air Quality Study Oversight Committee, Recommendations on the Use of
the Intermountain West Data Warehouse for Air Quality 2011b Model
Platform (May 17, 2016).
---------------------------------------------------------------------------

    Finally, even if the EPA had used a more recent temporal profile or
emissions inventory as suggested by the commenters, the commenters do
not provide any evidence or analysis to support a conclusion that doing
so would alter the outcome of the analysis (i.e., that the BART
alternative achieves greater reasonable progress).
    Comment: Third, the commenters state that, for the reasons
summarized below and detailed in a memorandum submitted with their
comments,\67\ the results from the EPA's Comprehensive Air Quality
Model with Extensions (CAMx) modeling do not rationally support the
EPA's proposed determination that the BART alternative would achieve
greater reasonable progress than BART:
---------------------------------------------------------------------------

    \67\ Gebhart, Howard D. Technical Comments--Laramie River
Station CAMx BART Modeling Expert Report (November 30, 2018).
---------------------------------------------------------------------------

     The Badlands National Park experiences the greatest
visibility impact from Laramie River Station emissions of all modeled
Class I areas and would suffer adverse visibility impacts from the
implementation of the BART alternative when compared to BART. Other
modeled Class I areas up to or exceeding 500 kilometers (km) away
offset the negative impact of the BART alternative on visibility in
Badlands National Park.
     the CAMx modeling software lacks the necessary precision
to make accurate concentration predictions when the sulfate
concentrations are so small (on the order of 10-4 to
10-5 micrograms per cubic meter). While the model will
produce a numerical value at

this scale, the EPA's use of those values as precise measurements of
sulfate concentrations under the modeled scenario is out of step with
accepted protocols in the field of air dispersion modeling and fails to
account for the inherent uncertainty in the model. Thus, the visibility
benefit claimed for the BART alternative is not supportable.
     the results of the EPA's modeling \68\ indicating
measurable visibility impacts at the Yellowstone-region Class I areas
because of the BART alternative are inconsistent with published data on
pollutant trajectories that show sources in eastern Wyoming, where
Laramie River Station is located, influence visibility in the western
Wyoming Yellowstone area only once in approximately every 3 years.\69\
Furthermore, the back-trajectories indicate that on the rare days when
emissions would reach the Yellowstone region, they would first pass
through and impact the Bridger and Fitzpatrick wilderness areas; yet on
the days when the AECOM 2016 modeled visibility impacts at Yellowstone,
it modeled zero impact at Bridger/Fitzpatrick.
---------------------------------------------------------------------------

    \68\ Laramie River Station Power Plant Visibility Impacts for
Two Emissions Control Scenarios: Final Report, and references, p. 6-
1--6-2, AECOM, (May 2016).
    \69\ Gebhart, Howard D. Technical Comments--Laramie River
Station CAMx BART Modeling Expert Report (November 30, 2018).
---------------------------------------------------------------------------

    Response: We disagree with the commenters' assertion that the CAMx
modeling results do not support the EPA's proposed determination that
the BART alternative would achieve greater reasonable progress than
BART.
    First, with respect to the commenters' assertions regarding the
inclusion of Class I areas up to or exceeding 500 km, the inclusion of
these Class I areas is consistent with previous analysis using CAMx
simulations.\70\ Whereas CALPUFF simulations have often been limited to
300 km (unless further considerations are taken into account in
evaluating that modeling), due to the increasing potential for model
error across long distances, CAMx more readily allows for the inclusion
of more distant Class I areas.\71\ Furthermore, while we recognize that
visibility impact at Badlands National Park under the BART alternative
scenario (0.0138 deciviews) was greater than the impact under the BART
scenario (0.0131 deciviews) on the 20 percent best days,\72\ the
regional haze regulations do not require greater visibility
improvements at every Class I area when comparing the BART alternative
to BART. Instead, the regulations require that (1) visibility does not
decline in any Class I area,\73\ and (2) there is an overall
improvement in visibility, determined by comparing the average
differences between BART and the BART alternative over all affected
Class I areas. Consistent with regulations, we determined that none of
the Class I areas experienced a decline in visibility from the baseline
under the BART alternative scenario, and there was a greater
improvement in visibility under the BART alternative compared to BART
averaged over all affected areas.\74\
---------------------------------------------------------------------------

    \70\ 81 FR 66332 (September 27, 2016), 77 FR 33642 (June 7,
2012). Indeed, as explained on the CAMx website, since 1996, CAMx
has been employed extensively by local, state, regional and federal
government agencies, academic and research institutions, and private
consultants for regulatory assessments and general research
throughout the U.S. and the world. CAMx has been used in more than
20 countries on nearly every continent. http://www.camx.com/about/us-camx-applications.aspx. Many of these applications have been
under the Clean Air Act (Regional Haze/U.S. Regional Planning
Organizations (RPOs): Midwest (MRPO); Western (WRAP/WestJump);
Central (CENRAP); Southeast (VISTAS); Oregon/Washington (Columbia
River Gorge); BART Modeling: Texas BART screening analysis, Arkansas
cumulative BART modeling; 1-Hour Ozone: OTAG, NOX SIP
Call (eastern U.S.), Texas (SIPs for Houston, Dallas-Fort Worth,
East Texas), Paso/Juarez trans-border analysis, LADCO (Great Lakes
region), Pennsylvania (SIP for Pittsburgh); 8-Hour Ozone: Texas
(Houston, Dallas-Ft Worth, San Antonio, Austin, East Texas, Waco),
Oklahoma (Oklahoma City, Tulsa), Colorado (Denver), New Mexico,
Missouri/Illinois (St. Louis), LADCO (Great Lakes region), Florida
(Tampa, Orlando, Jacksonville), Arizona (Phoenix), Southern
California (Los Angeles), Louisiana (Baton Rouge), Central
California (CCOS); Local PM: Pennsylvania (Allegheny County,
PM2.5), Utah (Salt Lake City, PM2.5), LADCO
(Great Lakes region, PM2.5), Missouri/Illinois (St. Louis
PM2.5 SIP), Idaho (Boise PM10 SIP), Southern
California (Los Angeles PM10, PM2.5); Regional
Strategies: 2001 EPA analysis of Heavy-Duty Diesel Rule, (Eastern
U.S.), 2005 EPA analysis of Clean Air Interstate Rule (Eastern
U.S.), 2010 EPA analysis of Interstate Transport Rule (Eastern
U.S.), 2010 EPA ozone non-attainment area designation modeling
(national), 2014 EPA ozone NAAQS proposal PA/RIA (national), where
the modeling domains were similar in size to the one used here, and
much larger in size, covering an entire region of the U.S. or all of
the U.S.
    \71\ 77 FR 33642 (June 7, 2012) and Technical Support Document
for Demonstration of the Transport Rule as a BART Alternative
(December 2011). See CAMx User's Guide, for example, p. 1-2 (wide
regional domain), 6-2 (Figure 6.1, map of the Eastern U.S. showing
regional modeling domain).
    \72\ 83 FR 51410 (October 11, 2018), Table 6.
    \73\ Contrary to commenters' assertion that the modeling results
for Badlands National Park suggest the results do not show the BART
alternative is better than BART, the visibility at Badlands National
Park does not decline under the BART alternative scenario on the 20
percent worst days: Compare visibility impacts for BART alternative
scenario (0.0176 deciviews) and BART scenario (0.0177 deciviews).
    \74\ 83 FR 51410 (October 11, 2018), Table 6 and Table 7.
---------------------------------------------------------------------------

    Second, with respect to the commenters' concerns regarding the
precision of the CAMx modeling software, CAMx has a scientifically
current treatment of chemistry to simulate transformation of emissions
into visibility-impairing particles and its use for modeling cumulative
air quality impacts in the U.S., including for regional haze SIPs, is
well-established; CAMx has been used in several previous EPA
assessments for evaluating greater reasonable progress.\75\ While we
agree with the commenters that modeling uncertainties such as correctly
simulating the meteorological data fields are inherent to all air
quality models and are not unique to CAMx,\76\ we disagree that the
visibility improvements associated with either the BART alternative or
the BART scenario are not supportable due to these inherent and
unavoidable uncertainties. The only changes among the modeling
scenarios was due to different emission rates for the Laramie River
Station. The uncertainties inherent in the model apply to both the BART
and the BART alternative, and thus, while there is some uncertainty in
the absolute visibility impacts and benefits, our use of CAMx here
provides an accurate assessment of the relative improvement expected
from two different control scenarios and whether the BART alternative
is better than BART. Additionally, while commenters suggest the
concentrations are out of step with accepted protocols, they fail to
cite a specific protocol.
---------------------------------------------------------------------------

    \75\ 82 FR 46903 (October 10, 2017) (Final action for the
Coronado Generating Station in the Regional Haze Plan for Arizona,
BART alternative better than BART); 81 FR 296 (January 5, 2016)
(Final action for Texas and Oklahoma Regional Haze Plans where for
Texas CAMx source apportionment modeling was performed to determine
which, if any, of the facilities had significant impacts.) 77 FR
33642 (June 7, 2012) (Final action for the Cross-State Air Pollution
Rule (CSAPR) as a BART alternative.).
    \76\ Gebhart, Howard D. Technical Comments--Laramie River
Station CAMx BART Modeling Expert Report (November 30, 2018).
---------------------------------------------------------------------------

    Indeed, given the highly complex nature of predicting how chemicals
combine in the atmosphere and impact visibility, it is not surprising
that the CAMx model performance is not completely precise and accurate.
Comments with regard to CAMx precision and accuracy have been addressed
in previous applications of CAMx for evaluating regional haze in FIPs
and in SIPs.\77\ Consistent with those applications of CAMx and the
EPA's regulations and guidance, the CAMx modeling performed for this
action used several approaches that specifically address concerns about
precision and accuracy:
---------------------------------------------------------------------------

    \77\ 82 FR 46903 (October 10, 2017).
---------------------------------------------------------------------------

     CAMx modeled concentration results were processed in order
to isolate the changes to visibility conditions as a result of
emissions

controls applied to the Laramie River Station.\78\ To convert model
concentrations into visibility estimates and account for quantifiable
model bias, the EPA's Modeled Attainment Test Software (MATS) is
used.\79\ MATS is primarily intended as a tool to implement modeling
for several CAA programs, including visibility for regional haze.\80\
The use of MATS also helps mitigate model bias by pairing model
estimates with actual measured conditions and adjusts the model
predictions based on the measured concentrations.\81\
---------------------------------------------------------------------------

    \78\ Final Report, p. ES-1.
    \79\ Modeled Attainment Test Software User's Manual. Abt
Associates for EPA (April 2014). (MATS User's Manual) https://www3.epa.gov/ttn/scram/guidance/guide/MATS_2-6-1_manual.pdf.
    \80\ MATS User's Manual, p. 9.
    \81\ Final Report, p. 4-1, ES-2.
---------------------------------------------------------------------------

     The CAMx Particulate Source Apportionment Technology
(PSAT), one of the extension tools in CAMx,\82\ was used in conjunction
with MATS to isolate Laramie River Station's visibility impacts for
each of the three modeled scenarios.\83\ PSAT was used in the modeling
analysis to tag and track the chemical transformations and transport of
particulate matter (PM) precursor emissions from the Laramie River
Station within the modeling domain, which is useful to understand model
performance.\84\ PSAT was used for each of three scenarios to track and
account for particulate matter concentrations that originate or are
formed as a result of emissions form Laramie River Station.\85\ This
approach substantially reduces the model numerical errors (sometimes
referred to as ``artifacts'' associated with very small modeled
pollutant concentrations) in the estimates of visibility impairment
caused by the Laramie River Station and improves the precision in the
model estimates of visibility benefits. As explained in the Appendix to
the Final Report, AECOM also evaluated modeling artifacts and based on
several factors determined that the PSAT analysis was not affected by
modeling artifacts and thus could be appropriately used in assessing
the merits of the scenarios.\86\ The PSAT configuration setup used the
following tracers: sulfur (sulfate tracers), nitrogen (nitrate and
ammonium tracers) and primary PM (elemental carbon, organic aerosol,
crustal PM tracers).\87\ The results of the CAMx PSAT analysis are
described in detail in the supporting documentation.\88\
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    \82\ CAMx Users Guide, p. 1-4.
    \83\ Final Report, p. ES-2.
    \84\ Ibid. p. 7-1.
    \85\ Final Report, p. 5-1.
    \86\ Appendix A to Final Report.
    \87\ Protocol p. 3-7.
    \88\ Laramie River Station Power Plant Visibility Impacts for
Two Emissions Control Scenarios: Final Report Prepared for Basin
Electric, AECOM (May 2016), and letter from Holland and Hart
regarding modeling explanation.
---------------------------------------------------------------------------

     Concerns about model accuracy and bias are further
addressed in the modeling analysis by using the scaling factors called
RRF to correct model results for bias.\89\ In the RRF approach, the
impacts of each emissions control scenario on sulfate and nitrate are
estimated by multiplying the model percent change in sulfate and
nitrate in each control strategy simulation by the measured
concentrations of sulfate and nitrate at the Class I areas.\90\ This is
the same approach that is used in all regulatory applications of CAMx
for regional haze, ozone, and PM2.5 SIPs and FIPs.\91\
---------------------------------------------------------------------------

    \89\ Photochemical Modeling Protocol for the Visibility
Assessment of Basin Electric Laramie River Power Plant. (Protocol).
Prepared for Basin Electric, AECOM, p. 4-3 (September 2015).
    \90\ 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, p. 95-
96. (December 3, 2014) and Modeling Guidance for Demonstrating Air
Quality Goals for Ozone, PM2.5 and Regional Haze. EPA Office of Air
Quality Planning and Standards, Research Triangle Park, NC (November
29, 2018).
    \91\ 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, p. 95-
96. (December 3, 2014) and Modeling Guidance for Demonstrating Air
Quality Goals for Ozone, PM2.5 and Regional Haze. EPA Office of Air
Quality Planning and Standards, Research Triangle Park, NC (November
29, 2018).
---------------------------------------------------------------------------

    Additionally, both qualitative and quantitative model performance
evaluations were performed to determine whether the meteorological
fields were sufficiently accurate for the model to properly
characterize the transport, chemistry, and removal processes. The model
performance evaluation study concluded that the application exhibited
reasonably good model performance that was as good or better than other
recent prognostic model applications used in air quality planning.\92\
Finally, a number of quality assurance files were prepared and used to
check for errors in the emission inputs.\93\
---------------------------------------------------------------------------

    \92\ Protocol p. 3.1, summarizing and citing the findings in
``Western Regional Air Partnership (WRAP) West-wide Jump Start Air
Quality Modeling Study'', WRF Application/Evaluation, February 29,
2012 (ENVIRON and Alpine 2012) (https://www.wrapair2.org/pdf/WestJumpAQMS_2008_Annual_WRF_Final_Report_February29_2012.pdf). The
modeling analysis for this final action used the modeling platform
from the West-wide Jump Start Air Quality Modeling Study
(WestJumpAQMS), and the model performance evaluation study concluded
that the WestJumpAQMS application exhibited reasonably good model
performance that was as good or better than other recent prognostic
model applications used in air quality planning and it was therefore
reasonable to proceed with their use as inputs for the WestJumpAQMS
photochemical grid modeling. That study was conducted by the WRAP to
develop a regional photochemical grid model (PGM) modeling platform
for the western states. The WRAP intended that the PGM modeling
platform would be used in several CAA applications, including
visibility. Meteorological data are key inputs for CAMx
photochemical grid modeling and these data include wind speed and
direction, temperature, water vapor concentrations (mixing ratio),
sunlight intensity, clouds and precipitation, and vertical mixing.
For PGMs such meteorological inputs are generated using prognostic
meteorological models that solve the fundamental equations of the
atmosphere. p. ES1-ES2.
    \93\ Protocol p. 2-3--2-4 and Final report.
---------------------------------------------------------------------------

    While the CAMx PSAT, RRF and other methodologies do not fully
eliminate all model error, these techniques do correct for errors and
bias consistently for each emissions control scenario evaluated here,
and this increases confidence that the model results are reliable in
estimating greater relative benefits for the BART alternative scenario
compared to the BART scenario. Additionally, the EPA's chosen
visibility modeling need not be perfect, but only reasonable,\94\ and
it was reasonable to use the CAMx model, which is a satisfactory
predictive tool, to ascertain whether it is more likely than not that
the BART alternative is better than the BART scenario, information
essential to inform the EPA's analysis and decision-making. Moreover,
40 CFR 51.308(e)(3) allows for a straight numerical test regardless of
the magnitude of the computed differences and does not specify a
minimum delta deciview difference between the modeled scenarios that
must be achieved for a BART alternative to achieve greater reasonable
progress than BART. Furthermore, the BART versus BART alternative
visibility impacts presented here represent average impacts from two
periods (the 20 percent best days and 20 percent worst days). Thus,
some of the individual day impacts are much larger than reflected in
the average and ``measure'' larger impacts than implied here.
---------------------------------------------------------------------------

    \94\ See WildEarth Guardians, 770 F.3d 919, 931 (citing San Luis
& Delta-Mendota Water Auth. v. Jewell, 747 F.3d 581, 620-21 (9th
Cir. 2014) (upholding the use of EPA's approval of the
SO2 backstop trading program and that use of an imperfect
analysis is not arbitrary or capricious).
---------------------------------------------------------------------------

    Finally, we disagree with the commenters' statement that pollutant
trajectories for air masses reaching the Yellowstone region are not
accurately reflected in the modeling. The commenter claims that
``[p]ublished back-trajectories list the frequency of transport for
Laramie River Station emissions toward Yellowstone and nearby areas at
essentially zero (less

than one day every 3 years)'' and argues that therefore, the CAMx
modeling overestimates the benefits of any emissions control scenarios
in the Yellowstone region. To support this claim, the commenter
provided an extended abstract titled ``Preliminary Back Trajectory
Analysis of GrandTReNDS Reactive Nitrogen'' that was presented at a
2014 Air & Waste Management Association conference. However, we find
the extended abstract does not support the commenters' claims for
several reasons. The commenters' extended abstract relied on mean 24-
hour data, and the abstract concluded that ``[s]trong diurnal patterns
in the winds in this region mean 24-hour data are probably not adequate
for source apportionment analyses'' \95\ and noted that the commenter
intended to address this limitation by using 4 kilometer (km)
resolution weather research and forecast (WRF) data that would be
available in the future, which were both used in the CAMx modeling.
Finally, we note that on page 13 of the extended abstract, the plots
show relatively greater transport from eastern Wyoming to Yellowstone
on the lowest concentration days at Yellowstone, which is consistent
with the finding in the CAMx modeling that the Laramie River Station
can contribute to visibility impairment on the best visibility days at
Yellowstone.
---------------------------------------------------------------------------

    \95\ Preliminary Back Trajectory Analysis of GrandTReNDS
Reactive Nitrogen. Gebhart, Kristi A., Prenni, Anthony J., Barna,
Michael G., Schichtel, Bret A.; National Park Service and Malm,
William C., Day, Derek E., Sullivan, Amy P., Levin, Ezra J.T.,
Collett Jr., Jeffrey L., Benedict, Katherine B.; Colorado State
University. Air and Waste Management Association Annual Meeting.
Extended Abstract #33458. (June 26, 2014).
---------------------------------------------------------------------------

    Furthermore, the CAMx modeling uses the finer and more accurate 4
km resolution WRF meteorological modeling that was evaluated against
surface meteorological observations of wind speed, wind direction,
temperature and humidity.\96\ Contrary to the commenters' assertions,
the 4 km WRF CAMx modeling results indicate that there were days on
which wind trajectories transported emissions from the Laramie River
Station to the Yellowstone region.\97\ Thus, we do not find that there
is adequate evidence to support the commenters' assertion that the
Laramie River Station does not contribute to visibility impairment in
the Yellowstone region.
---------------------------------------------------------------------------

    \96\ Western Regional Air Partnership (WRAP) West-wide Jump
Start Air Quality Modeling Study (WestJumpAQMS). ENVIRON
International Corporation. (February 29, 2012).
    \97\ We evaluated the CAMx PSAT plots to identify days on which
the model plume was transported from Laramie River Station to Class
I areas in western Wyoming. Specifically, the model results showed
that Laramie River Station impacted these Class I areas on the
following days: May 23-28, June 30, July 26, August 5-8, August 16-
18, August 23, September 8-9, October 11-12, November 21. See also
plots of the CAMx PSAT modeling results in electronic and physical
form in the docket #EPA-R08-OAR-2018-0606.
---------------------------------------------------------------------------

    Comment: Finally, the commenters argue that multiple features of
the EPA's modeling exacerbate the uncertainty inherent in CAMx and
compound the unreliability of the results on which the EPA relies upon
in its BART alternative determination, including: \98\
---------------------------------------------------------------------------

    \98\ Gebhart, Howard D. Technical Comments--Laramie River
Station CAMx BART Modeling Expert Report (November 30, 2018).
---------------------------------------------------------------------------

     The inherent inaccuracies of the CAMx model are multiplied
at large transport distances, which further undermines the EPA's
reliance on extremely small modeled visibility benefits and associated
changes in pollutant concentrations to conclude that the BART
alternative improves visibility at these locations;
     the EPA utilized modeled results from Yellowstone to
quantify purported visibility benefits at multiple Class I areas that
lack their own IMPROVE monitors, which further compounds the errors
introduced by the Yellowstone results; and
     the use of the particulate source apportionment technology
(PSAT) to track emissions in the EPA's modeling further compounded the
unreliability of modeled visibility ``benefits'' arising from the BART
alternative as PSAT has been shown to overestimate the true sulfate
contribution assigned to individual emission sources. Accordingly, PSAT
likely introduced ``false positives'' in the model results by modeling
visibility impacts from changing emissions at Laramie River Station
under the BART alternative that would not bear out in reality.
    Response: We disagree with the commenters' arguments that multiple
features of our modeling, including large transport distances, lack of
IMPROVE monitors, and the use of PSAT exacerbated the uncertainty
inherent in CAMx and compounded the unreliability of the results on
which we relied upon in our BART alternative determination. In fact, we
utilized multiple tools, as discussed previously, to further evaluate
the modeling results to determine whether the results represent
``real'' modeled visibility differences.
    Specifically, it is true that in some geographic areas, single
IMPROVE monitors represent multiple Class I areas, based on expected
similarities between the airsheds (Figure 1). This approach is
consistent with the EPA's Guidance for Tracking Progress Under the
Regional Haze Rule that areas without a monitor are assigned a
representative monitor,\99\ and other requirements to include all Class
I areas in the modeling domain.\100\ Therefore, the Yellowstone IMPROVE
monitor was used to represent several other Class I areas in the
analysis. We note that the IMPROVE data from the nearby Class I area is
used for the RRF correction for model bias for Class I areas that do
not have a dedicated IMPROVE monitor. This nearby monitor approach is
used by the EPA and states for all regulatory and planning requirements
for Class I areas that lack IMPROVE monitors, and the estimates
represent visibility improvements at these Class I areas.\101\
Furthermore, without data showing the monitors are not representative,
we have no reason to find that this assumption should not apply.
---------------------------------------------------------------------------

    \99\ Appendix A, Table A-2 of Guidance for Tracking Progress
Under the Regional Haze Rule (September 2003).
    \100\ 40 CFR 51.308(d)(2)(ii), (e)(3). 40 CFR pt. 51, app. Y:
I.B, I.C,2, I.F.2.(c), IV.D.5. 2014 Guidance pp. 17-19.
    \101\ 40 CFR 51.308(d)(2) (the regional haze rule provides that
for Class I areas without onsite monitoring data, the state must
establish baseline and assessment values using the most
representative available monitoring data, in consultation with the
Administrator or his or her designee). Also, consistent with the
additional requirements in Sec.  51.308(d)(4), Wyoming's regional
haze plan contains a monitoring strategy for measuring,
characterizing, and reporting of regional haze visibility impairment
that is representative of all mandatory Class I Federal areas within
the State. Our 2012 proposed rule explained that Chapter 9 of the
Wyoming regional haze SIP relies on the IMPROVE network for
compliance purposes, in addition to any additional visibility
impairment monitoring that may be needed in the future, 77 FR 33022,
33048 (June 4, 2012) (Wyoming 2011 SIP Submittal, Chapter 9, pp.
178-180, adopted by reference at 40 CFR 52.2620(e)(25) (Wyoming
State Implementation Plan for Regional Haze for 309(g)).
Specifically, as was done for the CAMx modeling for action, some
Class I areas share a single monitor because of the proximity of the
areas to each other: Bridger and Fitzpatrick are represented by the
BRID1 monitor site; North Absaroka and Washakie are represented by
the NOAB1 monitor site; and Yellowstone, Teton and Grand Teton are
represented by the YELLO2 monitor. Id. at 33029. Finally, if
commenters had concerns about the use of representative monitors,
their opportunity to comment and challenge the EPA's action was
prior to our final action on the State's 2011 SIP submittal. 79 FR
5032 (January 30, 2014) (EPA's final action on Wyoming's 2011 SIP
submittal). The CAMx modeling protocol and Final Report are
consistent with this approach, as it explains that the contractor
used Table A-2 in Appendix A of EPA's Guidance for Tracking Progress
Under the Regional Haze Rule (2003), which specifies the same
representative sites. Final Report, p. 4-4.
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BILLING CODE 6560-50-P

[GRAPHIC] [TIFF OMITTED] TR20MY19.000

BILLING CODE 6560-50-C
    We disagree with the comment that PSAT has been shown to
overestimate the true sulfate contribution assigned to individual
emission sources and that PSAT likely introduced ``false positives'' in
the model results of impacts from changing emissions at Laramie. The
commenter did not cite any specific sources or studies that PSAT can
introduce false positives. Moreover, we note that PSAT was subject to
testing and evaluation by the model developer,\102\ as well as for this
particular application.\103\ While the CAMx model and PSAT can at times
be biased either high or low for sulfate, the model relative response
factor approach, which has the effect of anchoring the future estimated
visibility results to a ``real'' measured ambient value,\104\ is used
to help correct for model bias. Additionally, we note that any errors
in the CAMx model will apply to both the BART and the BART alternative
scenarios. Thus, the effects of any systematic errors in the model are
mitigated by the fact that the CAMx and PSAT results are being used to
compare the relative visibility improvements in the BART and BART
alternative.
---------------------------------------------------------------------------

    \102\ CAMx User's Guide, p. 7-7--7-12.
    \103\ Appendix A to Final Report.
    \104\ 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, p. 95-96
(December 3, 2014).
---------------------------------------------------------------------------

    As supported by our preceding responses, it was reasonable for the
EPA to: (1) Use the CAMx modeling results as the basis for our
determination; and (2) rely on the results of the CAMx model that
predicted a visibility improvement associated with the BART alternative
relative to BART.\105\
---------------------------------------------------------------------------

    \105\ Congress' concern about modeling science led it to require
the EPA to establish uniform modeling techniques and update the
models periodically as modeling science develops. Due to the highly
technical nature of the modeling techniques, the EPA's modeling
expertise makes it particularly well suited to apply and make
determinations based on the results of the modeling analysis.
---------------------------------------------------------------------------

    Our responses regarding the uncertainties associated with the CAMx
model across large distances and ``extremely small'' modeled visibility
benefits are found elsewhere in this document.
    Finally, the commenters fail to provide an alternative analysis or
basis demonstrating that any changes made to the commenters' perceived
uncertainties inherent in CAMx or otherwise would alter the outcome of
the BART alternative analysis.
    In addition to the conservation organizations' comments, we also
received several comments from Basin Electric:
    Comment: First, the commenter stated that the EPA's BART
alternative, under the two-prong test found at 40 CFR 51.308(e)(3),
results in greater reasonable progress and demonstrated compliance with
each of the five elements of the BART alternative.\106\ Specifically,
the commenters agree with the EPA's findings that the CAMx modeling
demonstrated that emission reductions associated with the BART
alternative in the proposed FIP revision will provide greater
reasonable progress towards natural visibility conditions than the
implementation of BART alone. Furthermore, reliance on the CAMx model,
including the inclusion of Laramie River Unit 1 NOX
emissions, actual anticipated emissions, Modeled Attainment Test
Software (MATS), and PSAT plots, was appropriate according to the
commenter.
---------------------------------------------------------------------------

    \106\40 CFR 51.308(e)(2).
---------------------------------------------------------------------------

    Response: For the reasons explained elsewhere in this action, we
agree with the commenter's assertion that, under the two-pronged test
found at 40 CFR 51.308(e)(3), the BART alternative results in greater
reasonable progress than BART and complies with each of the five
elements of the BART alternative.

    Comment: Second, the commenter encouraged the EPA to consider, as
part of its approval of the revised FIP, the factors set forth in the
weight of evidence test under 40 CFR 51.308(e)(2)(i)(E), including: (1)
Earlier emission reductions, (2) reductions in SO2
emissions, (3) additional NOX emissions reductions at Unit
1, (4) overall greater reasonable progress, (5) greater visibility
benefit with lower costs, and (6) avoidance of litigation risk.
    Response: While we appreciate the commenters' encouragement to
conduct an additional analysis, the regional haze rule requires the
BART alternative to achieve greater reasonable progress under either:
(1) A determination under 40 CFR 51.308(e)(3) based on greater emission
reductions if the distribution of emissions is not substantially
different than BART; (2) a determination under 40 CFR 51.308(e)(3)
based on the use of dispersion modeling if the distribution of
emissions is significantly different; or (3) a determination under 40
CFR 51.308(e)(2)(i)(E) based on the clear weight of evidence.\107\
Thus, only one analysis is necessary to determine that the BART
alternative achieves greater reasonable progress than BART.
---------------------------------------------------------------------------

    \107\ 40 CFR 51.308(e)(2)(i)(E).
---------------------------------------------------------------------------

    Furthermore, we cannot, in fact, incorporate a new key analysis,
such as a weight of evidence determination, into our final rulemaking
without first introducing it through the public rulemaking process as
part of a proposed rule.
    Comment: Third, the commenter asserts that the regional haze
regulations support consideration of costs in the determination of a
BART alternative. Since under the CAA, a BART determination must ``take
into consideration the cost of compliance'' and a determination of
reasonable progress toward achieving the national goal of improving
visibility must ``consider the cost of compliance,'' so, too, should
BART alternatives be predicated on consideration of compliance costs
and any differential between the costs of BART and the costs of the
BART alternative. Thus, the commenter encourages the EPA to consider
that the BART alternative will achieve greater visibility benefits for
less cost than BART.
    Response: The EPA disagrees that we should perform a cost analysis
of the BART alternative emission control strategy. While the cost of
compliance is a factor under both the BART and reasonable progress
analyses (CAA 169A(g)(2) and (1), respectively), the regulatory
``greater reasonable progress'' requirements for BART alternatives
focus on whether an alternative will achieve greater visibility
improvement than BART (see 40 CFR 51.308(e)(2)(i)). Specifically, the
test on which the EPA is relying to demonstrate that the BART
alternative here makes greater reasonable progress than BART (40 CFR
51.308(e)(3)) is based solely on visibility impacts of the alternative
versus BART.
    Comment: Finally, the commenter identifies an error to the
NOX emission reduction for Unit 1 found in Table 4 of the
proposed rule. The NOX emission reduction for Unit 1 in
Table 4 is shown as 4,880 tons per year but should be 5,179 tons per
year, as correctly reflected in the text, according to the commenter.
    Response: While the modeled NOX emissions reductions of
5,179 tons per year were correctly used in the modeling analysis,\108\
we agree with the commenter that the NOX emission reduction
for Unit 1 in Table 4 of the proposed rule should read 5,179 tons per
year as reflected in the text at the bottom of page 51408. We
appreciate the commenter bringing this inadvertent error in the text of
the proposed rule to our attention.
---------------------------------------------------------------------------

    \108\ Laramie River Station Power Plant Visibility Impacts for
Two Emissions Control Scenarios: Final Report. AECOM (May 2016).
---------------------------------------------------------------------------

IV. Final Action

    In this action, the EPA is finalizing approval of SIP amendments,
shown in Table 1, to the Wyoming Air Quality Standards and Regulations,
Chapter 14, Emission Trading Program Regulations, Section 3, Sulfur
dioxide milestone inventory, revising the backstop trading program
SO2 emissions reporting requirements for Laramie River Units
1 and 2.

        Table 1--List of Wyoming Amendments That EPA Is Approving
------------------------------------------------------------------------
          Approved amended sections in April 5, 2018 submittal
-------------------------------------------------------------------------
Chapter 14, Section 3: (d), (e).
------------------------------------------------------------------------

    We are also finalizing amendments to the Wyoming regional haze FIP
contained in 40 CFR 52.2636 to remove the 2014 FIP's NOX
emission limits and instead incorporate the BART alternative and
associated NOX and SO2 emission limits for
Laramie River Units 1, 2 and 3, revise the NOX emission
limit for Unit 1, and add control technology requirements.
Specifically, the EPA is revising the NOX emission limits
and control technologies for Laramie River Units 1, 2 and 3 and adding
SO2 emission limits for Laramie River Units 1 and 2 in Table
2 of 40 CFR 52.2636(c)(1). We are also adding associated compliance
dates in 40 CFR 52.2636(d)(4) for Laramie River Units 1, 2 and 3.
Finally, we are referencing SO2 in the following sections:
Applicability (40 CFR 52.2636(a)); Definitions (40 CFR 52.2636(b));
Compliance determinations for NOX (40 CFR 52.2636(e)); Reporting (40
CFR 52.2636(h)); and Notifications (40 CFR 52.2636(i)). We are not
amending any other regulatory text in 40 CFR 52.2636.
    Although we are finalizing revisions to the Wyoming regional haze
FIP, Wyoming may always submit a new regional haze SIP to the EPA for
review, and we would welcome such a submission. The CAA requires the
EPA to act within 12 months on a SIP submittal from the time that it is
determined to be complete. If Wyoming were to submit a SIP revision
meeting the requirements of the CAA and the regional haze regulations,
we would propose approval of the State's plan as expeditiously as
practicable.

V. Incorporation by Reference

    In this document, the EPA is finalizing regulatory text that
includes incorporation by reference. In accordance with requirements of
1 CFR 51.5, the EPA is finalizing the incorporation by reference of the
SIP amendments described in Section IV of this preamble. The EPA has
made, and will continue to make, these materials generally available
through www.regulations.gov and at the EPA Region 8 Office (please
contact the person identified in the For Further Information Contact
section of this preamble for more information). Therefore, these
materials have been approved by the EPA for inclusion in the state
implementation plan, have been incorporated by reference by the EPA
into that plan, are fully federally enforceable under sections 110 and
113 of the CAA as of the effective date of the final rulemaking of the
EPA's approval, and will be incorporated by reference in the next
update to the SIP compilation.\109\
---------------------------------------------------------------------------

    \109\ 62 FR 27968 (May 22, 1997).
---------------------------------------------------------------------------

VI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 13563: Improving Regulation and Regulatory Review

    This action is not a ``significant regulatory action'' under the
terms of Executive Order 12866 \110\ and was therefore not submitted to
the Office of

Management and Budget (OMB) for review. This final rule revision
applies to only one facility in the State of Wyoming. It is therefore
not a rule of general applicability.
---------------------------------------------------------------------------

    \110\ 58 FR 51735, 51738 (October 4, 1993).
---------------------------------------------------------------------------

B. Executive Order 13771: Reducing Regulations and Controlling
Regulatory Costs

    This action is not an Executive Order 13771 regulatory action
because this action is not significant under Executive Order 12866.

C. Paperwork Reduction Act

    This action does not impose an information collection burden under
the provisions of the Paperwork Reduction Act (PRA).\111\ A
``collection of information'' under the PRA means the obtaining,
causing to be obtained, soliciting, or requiring the disclosure to an
agency, third parties or the public of information by or for an agency
by means of identical questions posed to, or identical reporting,
recordkeeping, or disclosure requirements imposed on, ten or more
persons, whether such collection of information is mandatory,
voluntary, or required to obtain or retain a benefit.\112\ Because this
final rule revises the NOX and SO2 emission
limits and associated reporting requirements for one facility, the PRA
does not apply.
---------------------------------------------------------------------------

    \111\ 44 U.S.C. 3501 et seq.
    \112\ 5 CFR 1320.3(c).
---------------------------------------------------------------------------

D. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency
to prepare a regulatory flexibility analysis of any rule subject to
notice and comment rulemaking requirements under the Administrative
Procedure Act or any other statute unless the agency certifies that the
rule will not have a significant economic impact on a substantial
number of small entities. Small entities include small businesses,
small organizations and small governmental jurisdictions.
    For purposes of assessing the impacts of this rule on small
entities, small entity is defined as: (1) A small business as defined
by the Small Business Administration's (SBA) regulations at 13 CFR
121.201; (2) a small governmental jurisdiction that is a government of
a city, county, town, school district or special district with a
population of less than 50,000; and (3) a small organization that is
any not-for-profit enterprise which is independently owned and operated
and is not dominant in its field.
    After considering the economic impacts of this final rule on small
entities, I certify that this action will not have a significant
economic impact on a substantial number of small entities under the
RFA. This rule does not impose any requirements or create impacts on
small entities as no small entities are subject to the requirements of
this rule.

E. Unfunded Mandates Reform Act (UMRA)

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public
Law 104-4, establishes requirements for federal agencies to assess the
effects of their regulatory actions on state, local and tribal
governments and the private sector. Under section 202 of UMRA, the EPA
generally must prepare a written statement, including a cost-benefit
analysis, for actions with ``Federal mandates'' that may result in
expenditures to state, local and tribal governments, in the aggregate,
or to the private sector, of $100 million or more (adjusted for
inflation) in any one year. Before promulgating an EPA rule for which a
written statement is needed, section 205 of UMRA generally requires the
EPA to identify and consider a reasonable number of regulatory
alternatives and adopt the least costly, most cost-effective, or least
burdensome alternative that achieves the objectives of the rule. The
provisions of section 205 of UMRA do not apply when they are
inconsistent with applicable law. Moreover, section 205 of UMRA allows
the EPA to adopt an alternative other than the least costly, most cost-
effective, or least burdensome alternative if the Administrator
publishes with the final rule an explanation why that alternative was
not adopted. Before the EPA establishes any regulatory requirements
that may significantly or uniquely affect small governments, including
tribal governments, it must have developed under section 203 of UMRA a
small government agency plan. The plan must provide for notifying
potentially affected small governments, enabling officials of affected
small governments to have meaningful and timely input in the
development of EPA regulatory actions with significant federal
intergovernmental mandates, and informing, educating and advising small
governments on compliance with the regulatory requirements.
    Under Title II of UMRA, the EPA has determined that this action
does not contain a federal mandate that may result in expenditures that
exceed the inflation-adjusted UMRA threshold of $100 million \113\ by
state, local or tribal governments or the private sector in any one
year. The revisions to the 2014 FIP would reduce private sector
expenditures. Additionally, we do not foresee significant costs (if
any) for state and local governments. Thus, because the revisions to
the 2014 FIP reduce annual expenditures, this final rule is not subject
to the requirements of sections 202 or 205 of UMRA. This final rule is
also not subject to the requirements of section 203 of UMRA because it
contains no regulatory requirements that might significantly or
uniquely affect small governments.
---------------------------------------------------------------------------

    \113\ Adjusted to 2014 dollars, the UMRA threshold becomes $152
million.
---------------------------------------------------------------------------

F. Executive Order 13132: Federalism

    Executive Order 13132, Federalism,\114\ revokes and replaces
Executive Orders 12612 (Federalism) and 12875 (Enhancing the
Intergovernmental Partnership). Executive Order 13132 requires the EPA
to develop an accountable process to ensure ``meaningful and timely
input by State and local officials in the development of regulatory
policies that have federalism implications.'' \115\ ``Policies that
have federalism implications'' is defined in the Executive Order to
include regulations that have ``substantial direct effects on the
States, on the relationship between the national government and the
States, or on the distribution of power and responsibilities among the
various levels of government.'' \116\ Under Executive Order 13132, the
EPA may not issue a regulation ``that has federalism implications, that
imposes substantial direct compliance costs, . . . and that is not
required by statute, unless [the federal government provides the] funds
necessary to pay the direct [compliance] costs incurred by the State
and local governments,'' or the EPA consults with state and local
officials early in the process of developing the final regulation.\117\
The EPA also may not issue a regulation that has federalism
implications and that preempts state law unless the agency consults
with state and local officials early in the process of developing the
final regulation.
---------------------------------------------------------------------------

    \114\ 64 FR 43255, 43255-43257 (August 10, 1999).
    \115\ 64 FR 43255, 43257.
    \116\ Ibid.
    \117\ Ibid.
---------------------------------------------------------------------------

    This action does not have federalism implications. The FIP
revisions will not have substantial direct effects on the states, on
the relationship between the national government and the states, or on
the distribution of power and responsibilities among the various levels
of government, as specified in Executive Order 13132. Thus, Executive

Order 13132 does not apply to this action.

G. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments

    Executive Order 13175, entitled ``Consultation and Coordination
with Indian Tribal Governments,'' requires the EPA to develop an
accountable process to ensure ``meaningful and timely input by tribal
officials in the development of regulatory policies that have tribal
implications.'' \118\ This final rule does not have tribal
implications, as specified in Executive Order 13175. It will not have
substantial direct effects on tribal governments. Thus, Executive Order
13175 does not apply to this rule. However, the EPA did send letters to
each of the Wyoming tribes explaining our regional haze proposed FIP
revision and offering consultation; however, no tribe asked for
consultation.\119\
---------------------------------------------------------------------------

    \118\ 65 FR 67249, 67250 (November 9, 2000).
    \119\ Letters to tribal governments (September 5, 2018).
---------------------------------------------------------------------------

H. Executive Order 13045: Protection of Children From Environmental
Health Risks and Safety Risks

    This action is not subject to Executive Order 13045 (62 FR 19885,
April 23, 1997). The EPA interprets Executive Order 13045 as applying
only to those regulatory actions that concern environmental health or
safety risks that the EPA has reason to believe may disproportionately
affect children, per the definition of ``covered regulatory action'' in
section 2-202 of the executive order. This action is not subject to
Executive Order 13045 because it does not concern an environmental
health risk or safety risk.

I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use

    This action is not subject to Executive Order 13211 (66 FR 28355,
May 22, 2001), because it is not a significant regulatory action under
Executive Order 12866.

J. National Technology Transfer and Advancement Act

    Section 12 of the National Technology Transfer and Advancement Act
(NTTAA) of 1995 requires federal agencies to evaluate existing
technical standards when developing a new regulation. Section 12(d) of
NTTAA, Public Law 104-113, 12(d) (15 U.S.C. 272 note) directs the EPA
to consider and use ``voluntary consensus standards'' in its regulatory
activities unless to do so would be inconsistent with applicable law or
otherwise impractical. Voluntary consensus standards are technical
standards (e.g., materials specifications, test methods, sampling
procedures and business practices) that are developed or adopted by
voluntary consensus standards bodies. NTTAA directs the EPA to provide
Congress, through OMB, explanations when the agency decides not to use
available and applicable voluntary consensus standards.
    This action involves technical standards. The EPA has decided to
use the applicable monitoring requirements of 40 CFR part 75. Part 75
already incorporates a number of voluntary consensus standards.
Consistent with the agency's Performance Based Measurement System
(PBMS), part 75 sets forth performance criteria that allow the use of
alternative methods to the ones set forth in part 75. The PBMS approach
is intended to be more flexible and cost-effective for the regulated
community; it is also intended to encourage innovation in analytical
technology and improved data quality. At this time, the EPA is not
recommending any revisions to part 75. However, the EPA periodically
revises the test procedures set forth in part 75. When the EPA revises
the test procedures set forth in part 75 in the future, the EPA will
address the use of any new voluntary consensus standards that are
equivalent. Currently, even if a test procedure is not set forth in
part 75, the EPA is not precluding the use of any method, whether it
constitutes a voluntary consensus standard or not, as long as it meets
the performance criteria specified; however, any alternative methods
must be approved through the petition process under 40 CFR 75.66 before
they are used.

K. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations

    Executive Order 12898 establishes federal executive policy on
environmental justice.\120\ Its main provision directs federal
agencies, to the greatest extent practicable and permitted by law, to
make environmental justice part of their mission by identifying and
addressing, as appropriate, disproportionately high and adverse human
health or environmental effects of their programs, policies and
activities on minority populations and low-income populations in the
United States.
---------------------------------------------------------------------------

    \120\ 59 FR 7629 (February 16, 1994).
---------------------------------------------------------------------------

    I certify that the approaches under this final rule will not have
potential disproportionately high and adverse human health or
environmental effects on minority, low-income or indigenous/tribal
populations. As explained previously, the Wyoming Regional Haze FIP, as
revised by this action, will result in a significant reduction in
emissions compared to current levels. Although this revision will allow
an increase in future emissions as compared to the 2014 FIP, the
revisions to the FIP, as a whole, will still result in overall
NOX and SO2 reductions compared to those
currently allowed. In addition, the area where Laramie River Station is
located has not been designated nonattainment for any NAAQS. Thus, the
FIP will ensure a significant reduction in NOX and
SO2 emissions compared to current levels and will not create
a disproportionately high and adverse human health or environmental
effect on minority, low-income, or indigenous/tribal populations.

L. Congressional Review Act (CRA)

    This rule is exempt from the CRA because it is a rule of particular
applicability.

M. Judicial Review

    Under section 307(b)(1) of the CAA, petitions for judicial review
of this action must be filed in the United States Court of Appeals for
the appropriate circuit by July 19, 2019. Pursuant to CAA section
307(d)(1)(B), this section is subject to the requirements of the CAA
section 307(d) as it promulgates a FIP under CAA section 110(c). Filing
a petition for reconsideration by the Administrator of this final rule
does not affect the finality of this action for purposes of judicial
review nor does it extend the time within which a petition for judicial
review may be filed and shall not postpone the effectiveness of such
rule or action. This action may not be challenged later in proceedings
to enforce its requirements. See CAA section 307(b)(2).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Nitrogen dioxide, Particulate
matter, Sulfur oxides.

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

    Dated: May 6, 2019.
Andrew R. Wheeler,
Administrator.

    40 CFR part 52 is amended as follows:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

0
1. The authority citation for part 52 continues to read as follows:

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

Subpart ZZ--Wyoming

0
2. Section 52.2620 is amended by:
0
a. In paragraph (c), revising the table entry for ``Section 3'' under
the centered table heading ``Chapter 14. Emission Trading Program
Regulations.''; and
0
b. In paragraph (e), revising the table entry for ``(20) XX''.
    The revisions read as follows:

Sec.  52.2620   Identification of plan.

* * * * *
    (c) * * *

----------------------------------------------------------------------------------------------------------------
                                                  State         EPA
        Rule No.               Rule title       effective    effective   Final rule/citation       Comments
                                                   date         date             date
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------
                                Chapter 14. Emission Trading Program Regulations
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
Section 3...............  Sulfur dioxide          2/5/2018    6/19/2019  [Insert Federal      ..................
                           milestone                                      Register
                           inventory.                                     citation], 5/20/
                                                                          2019.
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------

* * * * *
    (e) * * *

----------------------------------------------------------------------------------------------------------------
                                                  State         EPA
        Rule No.               Rule title       effective    effective   Final rule/citation       Comments
                                                   date         date             date
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
(20) XX.................  Addressing Regional     4/5/2018    6/19/2019  [Insert Federal      ..................
                           Haze Visibility                                Register
                           Protection For The                             citation], 5/20/
                           Mandatory Federal                              2019.
                           Class I Areas
                           Required Under 40
                           CFR 51.309.

                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------

0
3. Section 52.2636 is amended by:
0
a. Revising paragraphs (a)(2) and (b)(4) and (12);
0
b. Adding paragraph (b)(13);
0
c. Revising paragraph (c)(1) introductory text, Table 2, and paragraphs
(d)(2) and (3);
0
d. Adding paragraph (d)(4);
0
e. Revising the heading for paragraph (e) and paragraphs (e)(1)(i) and
(e)(1)(ii)(A) through (C);
0
f. Adding paragraph (e)(1)(ii)(D); and
0
g. Revising paragraphs (h)(1) and (i)(1).
    The revisions and additions read as follows:

Sec.  52.2636   Implementation plan for regional haze.

    (a) * * *
    (2) This section also applies to each owner and operator of the
following emissions units in the State of Wyoming for which the EPA
disapproved the State's BART determination and issued a SO2
and/or NOX BART Federal Implementation Plan:
    (i) Basin Electric Power Cooperative Laramie River Station Units 1,
2, and 3;
    (ii) PacifiCorp Dave Johnston Unit 3; and
    (iii) PacifiCorp Wyodak Power Plant Unit 1.
    (b) * * *
    (4) Continuous emission monitoring system or CEMS means the
equipment required by this section to sample, analyze, measure, and
provide, by means of readings recorded at least once every 15 minutes
(using an automated data acquisition and handling system (DAHS)), a
permanent record of SO2 and/or NOX emissions,
diluent, or stack gas volumetric flow rate.
* * * * *
    (12) SO2 means sulfur dioxide.
    (13) Unit means any of the units identified in paragraph (a) of
this section.
    (c) * * *
    (1) The owners/operators of emissions units subject to this section
shall not emit, or cause to be emitted, PM, NOX, or
SO2 in excess of the following limitations:
* * * * *

                                            Table 2 to Sec.   52.2636
[Emission limits and required control technologies for BART units for which the EPA disapproved the State's BART
                                      determination and implemented a FIP]
----------------------------------------------------------------------------------------------------------------
                                                                                SO2 emission
                                                                                NOX emission     limit--lb/MMBtu
            Source name/BART unit                  NOX Required Control        limit--lb/MMBtu      (averaged
                                                        Technology             (30-day rolling   annually across
                                                                                average)       Units 1 and 2)
----------------------------------------------------------------------------------------------------------------
Basin Electric Power Cooperative Laramie      Selective Catalytic Reduction      \4\ 0.18/0.06              0.12
 River Station/Unit 1 \1\.                     (SCR) \2\.
Basin Electric Power Cooperative Laramie      Selective Non-catalytic                0.18/0.15
 River Station/Unit 2 \1\.                     Reduction (SNCR) \3\.
Basin Electric Power Cooperative Laramie      Selective Non-catalytic                0.18/0.15               N/A
 River Station/Unit 3 \1\.                     Reduction (SNCR) \3\.
PacifiCorp Dave Johnston Unit 3.............  N/A...........................            * 0.07               N/A
PacifiCorp Wyodak Power Plant/Unit 1........  N/A...........................              0.07               N/A
----------------------------------------------------------------------------------------------------------------
\1\ The owners and operators of Laramie River Station Unit 1 shall comply with the NOX emission limit of 0.18 lb/
  MMBtu on June 19, 2019 and ending June 30, 2019. The owners and operators of Laramie River Station Unit 1
  shall comply with the NOX emission limit of 0.06 lb/MMBtu on July 1, 2019. The owners and operators of the
  Laramie River Station Units 2 and 3 shall comply with the NOX emission limit of 0.18 lb/MMBtu on June 19, 2019
  and ending on December 30, 2018. The owners and operators of Laramie River Station Units 2 and 3 shall comply
  with the NOX emission limit of 0.15 lb/MMBtu on December 31, 2018. The owners and operators of Laramie River
  Station Units 1 and 2 shall comply with the SO2 emission limit of 0.12 lb/MMBtu averaged annually across the
  two units on December 31, 2018.
\2\ By July 1, 2019.
\3\ By December 30, 2018.
\4\ These limits are in addition to the NOX emission limit for Laramie River Station Unit 1 of 0.07 MMBtu on a
  30-day rolling average.
* (Or 0.28 and shut-down by December 31, 2027).

* * * * *
    (d) * * *
    (2) The owners and operators of Laramie River Station Unit 1 shall
comply with the NOX emission limit of 0.18 lb/MMBtu on June
19, 2019 and ending June 30, 2019. The owners and operators of Laramie
River Station Unit 1 shall comply with the NOX emission
limit of 0.06 lb/MMBtu on July 1, 2019. The owners and operators of the
Laramie River Station Units 2 and 3 shall comply with the
NOX emission limit of 0.18 lb/MMBtu on June 19, 2019 and
ending on December 30, 2018. The owners and operators of Laramie River
Station Units 2 and 3 shall comply with the NOX emission
limit of 0.15 lb/MMBtu on December 31, 2018. The owners and operators
of Laramie River Station Units 1 and 2 shall comply with the
SO2 emission limit of 0.12 lb/MMBtu averaged annually across
the two units on December 31, 2018.
    (3) The owners and operators of the other BART sources subject to
this section shall comply with the emissions limitations and other
requirements of this section by March 4, 2019.
    (4)(i) The owners and operators of PacifiCorp Dave Johnston Unit 3
will meet a NOX emission limit of 0.07 lb/MMBtu (30-day
rolling average) by March 4, 2019; or
    (ii) Alternatively, the owners and operators of PacifiCorp Dave
Johnston Unit 3 will permanently cease operation of this unit on or
before December 31, 2027.
    (e) Compliance determinations for SO2 and NOX.
    (1) * * *
    (i) CEMS. At all times after the earliest compliance date specified
in paragraph (d) of this section, the owner/operator of each unit shall
maintain, calibrate and operate a CEMS, in full compliance with the
requirements found at 40 CFR part 75, to accurately measure
SO2 and/or NOX, diluent, and stack gas volumetric
flow rate from each unit. The CEMS shall be used to determine
compliance with the emission limitations in paragraph (c) of this
section for each unit.
    (ii) * * *
    (A) For any hour in which fuel is combusted in a unit, the owner/
operator of each unit shall calculate the hourly average NOX
emission rates in lb/MMBtu at the CEMS in accordance with the
requirements of 40 CFR part 75. At the end of each operating day, the
owner/operator shall calculate and record a new 30-day rolling average
emission rate in lb/MMBtu from the arithmetic average of all valid
hourly emission rates from the CEMS for the current operating day and
the previous 29 successive operating days.
    (B) At the end of each calendar year, the owner/operator shall
calculate the annual average SO2 emission rate in lb/MMBtu
across Laramie River Station Units 1 and 2 as the sum of the
SO2 annual mass emissions (pounds) divided by the sum of the
annual heat inputs (MMBtu). For Laramie River Station Units 1 and 2,
the owner/operator shall calculate the annual mass emissions for
SO2 and the annual heat input in accordance with 40 CFR part
75 for each unit.
    (C) An hourly average SO2 and/or NOX emission
rate in lb/MMBtu is valid only if the minimum number of data points, as
specified in 40 CFR part 75, is acquired by both the pollutant
concentration monitor (SO2 and/or NOX) and the
diluent monitor (O2 or CO2).
    (D) Data reported to meet the requirements of this section shall
not include data substituted using the missing data substitution
procedures of subpart D of 40 CFR part 75, nor shall the data have been
bias adjusted according to the procedures of 40 CFR part 75.
* * * * *
    (h) * * *
    (1) The owner/operator of each unit shall submit quarterly excess
emissions reports for SO2 and/or NOX BART units
no later than the 30th day following the end of each calendar quarter.
Excess emissions means emissions that exceed the emissions limits
specified in paragraph (c) of this section. The reports shall include
the magnitude, date(s) and duration of each period of excess emissions,
specific identification of each period of excess emissions that occurs
during startups, shutdowns and malfunctions of the unit, the nature and
cause of any malfunction (if known), and the corrective action taken or
preventative measures adopted.
* * * * *
    (i) * * *
    (1) The owner/operator shall promptly submit notification of
commencement of construction of any equipment which is being
constructed

to comply with the SO2 and/or NOX emission limits
in paragraph (c) of this section.
* * * * *
[FR Doc. 2019-09922 Filed 5-17-19; 8:45 am]
 BILLING CODE 6560-50-P