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[Federal Register Volume 81, Number 9 (Thursday, January 14, 2016)]
[Proposed Rules]
[Pages 2003-2052]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-33108]

[[Page 2003]]

Vol. 81

Thursday,

No. 9

January 14, 2016

Part II

Environmental Protection Agency

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40 CFR Part 52

Approval, Disapproval and Promulgation of Air Quality Implementation 
Plans; Partial Approval and Partial Disapproval of Air Quality 
Implementation Plans and Federal Implementation Plan; Utah; Revisions 
to Regional Haze State Implementation Plan; Federal Implementation Plan 
for Regional Haze; Proposed Rule

Federal Register / Vol. 81 , No. 9 / Thursday, January 14, 2016 / 
Proposed Rules

[[Page 2004]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2015-0463; FRL--9939-43-Region 8]

Approval, Disapproval and Promulgation of Air Quality 
Implementation Plans; Partial Approval and Partial Disapproval of Air 
Quality Implementation Plans and Federal Implementation Plan; Utah; 
Revisions to Regional Haze State Implementation Plan; Federal 
Implementation Plan for Regional Haze

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to take 
action pursuant to section 110 of the Clean Air Act (CAA or Act) on 
State Implementation Plan (SIP) revisions submitted by the State of 
Utah on June 4, 2015, and October 20, 2015 to implement the regional 
haze program. The State's SIP revisions establish an alternative to 
best available retrofit technology (BART) controls that would otherwise 
be required to control nitrogen oxides (NOX) at PacifiCorp's 
Hunter and Huntington power plants. The June 2015 SIP revision also 
includes BART determinations for particulate matter with an aerodynamic 
diameter of less than 10 micrometers (PM10) at these power 
plants and provisions for making the NOX and PM10 
BART emission limits federally enforceable. The CAA requires states to 
prevent any future and remedy any existing man-made impairment of 
visibility in national parks and wilderness areas designated as Class I 
areas. Air emissions from the four electric generating units (EGUs) at 
the two plants affected by this action cause or contribute to 
visibility impairment at nine Class I areas including Grand Canyon, 
Arches, Bryce Canyon and Zion National Parks. The EPA is issuing two 
co-proposals in order to fully evaluate the State's submittals and the 
public's input thereon. The EPA would work with the State on a revised 
State plan should a partial disapproval and FIP be finalized.

DATES: Comments: Written comments must be received on or before March 
14, 2016.
    Public Hearing: A public hearing for this proposal is scheduled to 
be held on Tuesday, January 26, 2016, at the Salt Lake City Public 
Library, Main Library, from 1 p.m. until 5 p.m., and again from 6 p.m. 
until 8 p.m. (local time).

ADDRESSES: The public hearing will be held at the Salt Lake City Public 
Library, Main Library, 210 East 400 South, Salt Lake City, Utah 84111.
    Submit your comments, identified by Docket ID No. EPA-R08-OAR-2015-
0463, to the Federal eRulemaking Portal: http://www.regulations.gov. 
Follow the online instructions for submitting comments. Once submitted, 
comments cannot be edited or removed from Regulations.gov. The EPA may 
publish any comment received to its public docket. Do not submit 
electronically any information you consider to be Confidential Business 
Information (CBI) or other information whose disclosure is restricted 
by statute. Multimedia submissions (audio, video, etc.) must be 
accompanied by a written comment. The written comment is considered the 
official comment and should include discussion of all points you wish 
to make. The EPA will generally not consider comments or comment 
contents located outside of the primary submission (i.e., on the web, 
cloud, or other file sharing system). For additional submission 
methods, the full EPA public comment policy, information about CBI or 
multimedia submissions, and general guidance on making effective 
comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.
    Instructions: Direct your comments to Docket ID No. EPA-R08-OAR-
2015-0463. The EPA's policy is that all comments received will be 
included in the public docket and may be made available online at 
http://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through www.regulations.gov 
or email. The www.regulations.gov Web site is an ``anonymous access'' 
system, which means EPA will not know your identity or contact 
information unless you provide it in the body of your comment. If you 
send an email comment directly to EPA, without going through 
www.regulations.gov your email address will be automatically captured 
and included as part of the comment that is placed in the public docket 
and made available on the Internet. If you submit an electronic 
comment, EPA recommends that you include your name and other contact 
information in the body of your comment and with any disk or CD-ROM you 
submit. If EPA cannot read your comment due to technical difficulties 
and cannot contact you for clarification, EPA may not be able to 
consider your comment. Electronic files should avoid the use of special 
characters, any form of encryption, and be free of any defects or 
viruses. For additional information about EPA's public docket visit the 
EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm. 
For additional instructions on submitting comments, go to section I, 
General Information, of the SUPPLEMENTARY INFORMATION section of this 
document.
    Docket: All documents in the docket are listed in the 
www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in www.regulations.gov or in hard copy at the Air Program, 
Environmental Protection Agency (EPA), Region 8, 1595 Wynkoop Street, 
Denver, Colorado 80202-1129. EPA requests that if at all possible, you 
contact the individual listed in the FOR FURTHER INFORMATION CONTACT 
section to view the hard copy of the docket. You may view the hard copy 
of the docket Monday through Friday, 8 a.m. to 4 p.m., excluding 
federal holidays.

FOR FURTHER INFORMATION CONTACT: Gail Fallon, Air Program, EPA, Region 
8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado, 80202-1129, 
(303) 312-6281, Fallon.Gail@epa.gov.

SUPPLEMENTARY INFORMATION:

Public Hearing

    The public hearing will provide interested parties the opportunity 
to present data, views, or arguments concerning the proposed action. 
The EPA may ask clarifying questions during the oral presentations, but 
will not respond to the presentations at that time. Written statements 
and supporting information submitted during the comment period will be 
considered with the same weight as oral comments and supporting 
information presented at the public hearing. The hearing officer may 
limit the time available for each commenter to address the proposal to 
5 minutes or less if the hearing officer determines it to be 
appropriate. The limitation is to ensure that everyone who wants to 
make a comment has the opportunity to do so. We will not be providing 
equipment for commenters to show overhead slides or make computerized 
slide presentations. Any person may provide written or oral

[[Page 2005]]

comments and data pertaining to our proposal at the public hearings. 
Verbatim transcripts, in English, of the hearings and written 
statements will be included in the rulemaking docket.

Table of Contents

I. General Information
II. Overview of Proposed Actions
    A. Brief Description of These Co-Proposals
    1. Summary of Proposal To Approve the SIP
    2. Summary of Proposal To Partially Approve and Partially 
Disapprove the SIP and Propose a FIP
III. Background and Requirements for Regional Haze SIPs and Utah 
Submittals
    A. Statutory and Regulatory Background
    1. Regional Haze
    2. Requirements of the CAA and EPA's Regional Haze Rule (RHR)
    3. Roles of Agencies in Addressing Regional Haze
    4. Development of the Requirements for 40 CFR 51.309
    5. SIP and FIP Background
    B. Requirements for Regional Haze SIPs Applicable to This 
Proposal
    1. The CAA and the Regional Haze Rule
    2. Determination of Baseline, Natural and Current Visibility 
Conditions
    3. Best Available Retrofit Technology
    4. Monitoring, Recordkeeping and Reporting
    5. Consultation With States and Federal Land Managers (FLMs)
    C. Requirements for Regional Haze SIPs Submitted Under 40 CFR 
51.309
    1. Projection of Visibility Improvement
    2. Stationary Source Reductions
    a. Sulfur Dioxide Emission Reductions
    b. Provisions for Stationary Source Emissions of Nitrogen Oxides 
and Particulate Matter
    D. General Requirements for PM10 and NOX 
Alternative Programs Under the Regional Haze Rule and the ``Better-
Than-BART Demonstration''
    E. Summary of State Regional Haze Submittals and EPA Actions
    1. 2008 and 2011 Utah RH SIPs
    2. 2012 EPA Action on 2011 and 2008 Utah RH SIPs
    3. 2013 Litigation
    4. 2015 Utah RH SIPs
IV. Utah's Regional Haze SIP
    A. Summary of Elements Under EPA's Previous Actions Upon Which 
We Are Relying
    1. Affected Class I Areas
    2. BART-Eligible Sources
    3. Sources Subject-to-BART
    B. Summary of Utah's BART Alternative and PM10 BART 
SIP Revision
    1. Utah BART Alternative
    2. PM10 BART Determinations
    3. Monitoring, Recordkeeping and Reporting
    C. Summary of Utah's Demonstration for Alternative Program
    1. A List of All BART-Eligible Sources Within the State
    2. A List of All BART-Eligible Sources and All BART Source 
Categories Covered by the Alternative Program
    3. Analysis of BART and Associated Emission Reductions 
Achievable
    4. Analysis of Projected Emissions Reductions Achievable Through 
the BART Alternative
    5. A Determination That the Alternative Achieves Greater 
Reasonable Progress Than Would Be Achieved Through the Installation 
and Operation of BART
    a. Annual Emissions Comparison for Visibility-Impairing 
Pollutants
    b. Improvement in the Number of Days With Significant Visibility 
Impairment
    c. 98th Percentile Impact (dv)
    d. Annual Average Impact (dv)
    e. 90th Percentile Impact (dv)
    f. Timing for the Emissions Reductions
    g. IMPROVE Monitoring Data
    h. Energy and Non-Air Quality Benefits
    i. Cost
    6. Requirement That Emission Reductions Take Place During Period 
of First Long-Term Strategy
    7. Demonstration That Emission Reductions From Alternative 
Program Will Be Surplus
    D. Summary of Utah's Enforceable Commitment SIP Revision
    E. Consultation With FLMs
V. EPA's Evaluation and Proposed Approval of Utah's Regional Haze 
SIP
    A. Basis for Proposed Approval
    B. Utah BART Alternative
    1. Summary of Utah BART Alternative
    2. Demonstration of Greater Reasonable Progress for the 
Alternative Program
    a. A List of All BART-Eligible Sources Within the State
    b. A List of All BART-Eligible Sources and All BART Source 
Categories Covered by the Alternative Program
    c. Analysis of BART and Associated Emission Reductions
    d. Analysis of Projected Emissions Reductions Achievable Through 
the BART Alternative
    e. A Determination That the Alternative Achieves Greater 
Reasonable Progress Than Would Be Achieved Through the Installation 
and Operation of BART
    f. Evaluation of the Weight of Evidence
    g. Requirement That Emission Reductions Take Place During Period 
of First Long-Term Strategy
    h. Demonstration That Emission Reductions From Alternative 
Program Will Be Surplus
    C. PM10 BART Determinations
    D. Monitoring, Recordkeeping, and Reporting
    E. Consultation With FLMs
VI. EPA's Evaluation and Proposed Partial Approval and Partial 
Disapproval of Utah's Regional Haze SIP
    A. Basis for Proposed Partial Disapproval and Partial Approval
    B. Utah BART Alternative
    1. Summary of Utah BART Alternative
    2. Demonstration of Greater Reasonable Progress for Alternative 
Program
    a. A List of All BART-Eligible Sources Within the State
    b. A List of All BART-Eligible Sources and All BART Source 
Categories Covered by the Alternative Program
    c. Analysis of BART and Associated Emission Reductions 
Achievable
    d. Analysis of Projected Emissions Reductions Achievable Through 
the BART Alternative
    e. A Determination That the Alternative Achieves Greater 
Reasonable Progress Than Would Be Achieved Through the Installation 
and Operation of BART
    f. Evaluation of the Weight of Evidence
    g. Evaluation That Emission Reductions Take Place During Period 
of First Long-Term Strategy
    h. Demonstration That Emission Reductions From Alternative 
Program Will Be Surplus
    C. Monitoring, Recordkeeping and Reporting for Utah's BART 
Alternative
    D. Proposed Federal Implementation Plan
    1. BART Evaluations
    a. Costs of Compliance
    b. Visibility Impact Modeling
    2. Hunter Power Plant
    a. Hunter Unit 1
    b. Hunter Unit 2
    3. Huntington Power Plant
    a. Huntington Unit 1
    b. Huntington Unit 2
    4. Federal Monitoring, Recordkeeping, and Reporting
    E. PM10 BART Determinations
    F. Consultation With FLMs
VII. EPA's Proposed Actions
    A. Proposed Approval
    B. Proposed Partial Disapproval/Approval and Federal 
Implementation Plan
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. General Information

What should I consider as I prepare my comments for EPA?

    1. Submitting Confidential Business Information (CBI). Do not 
submit CBI to EPA through http://www.regulations.gov or email. Clearly 
mark the part or all of the information that you claim to be CBI. For 
CBI information on a disk or CD-ROM that you mail to EPA, mark the 
outside of the disk or CD-ROM as CBI and then identify electronically 
within the disk or CD ROM the specific

[[Page 2006]]

information that is claimed as CBI. In addition to one complete version 
of the comment that includes information claimed as CBI, a copy of the 
comment that does not contain the information claimed as CBI must be 
submitted for inclusion in the public docket. Information so marked 
will not be disclosed except in accordance with procedures set forth in 
40 CFR part 2.
    2. Tips for preparing your comments. When submitting comments, 
remember to:
     Identify the rulemaking by docket number and other 
identifying information (subject heading, Federal Register, date, and 
page number);
     Follow directions and organize your comments;
     Explain why you agree or disagree;
     Suggest alternatives and substitute language for your 
requested changes;
     Describe any assumptions and provide any technical 
information and/or data that you used;
     If you estimate potential costs or burdens, explain how 
you arrived at your estimate in sufficient detail to allow for it to be 
reproduced;
     Provide specific examples to illustrate your concerns, and 
suggest alternatives;
     Explain your views as clearly as possible, avoiding the 
use of profanity or personal threats; and
     Make sure to submit your comments by the comment period 
deadline identified.

II. Overview of Proposed Actions

    The State of Utah submitted SIP revisions on June 4, 2015, and 
October 20, 2015, to fulfill the CAA requirement to meet the 
requirements for the Best Available Retrofit Technology (BART) in the 
Regional Haze Rule (RHR) for the pollutants NOX and 
PM10. As described more fully in Section III, the purpose of 
the RHR is to remedy and prevent impairment of visibility in Class I 
areas resulting from anthropogenic air pollution. Instead of 
establishing BART controls for NOX, Utah's SIP revisions 
contain an alternative to BART. The revisions also include BART 
controls for PM10. The idea of a BART alternative, which can 
take into account (and even encourage) plans that take into account 
state specific situations is a reasonable one, and one EPA supports 
where consistent with the CAA and RHR.
    The State's SIP contains a NOX BART Alternative and 
metrics to evaluate the BART Alternative. In light of the variety of 
metrics Utah used, this is a complicated analysis and EPA considered 
the State's BART Alternative in the context of other previous decisions 
we and the states have made. EPA carefully analyzed the SIP revisions 
and the supporting information submitted by the State. We also 
conducted additional analyses, which are included with this proposal. 
Based on a careful consideration of all of this information, EPA is 
proposing and soliciting comments on two different actions: A proposal 
to approve the State SIP in its entirety,\1\ and a proposal to 
partially approve and partially disapprove the State SIP and propose a 
FIP.\2\ EPA takes seriously its decision to co-propose these two 
actions (disapprove part of the State's plan, alongside proposing to 
approve it), as it is preferable that the regional haze program be 
implemented through state plans. As part of its oversight 
responsibilities, EPA must be able to find that the state plan is 
consistent with the requirements of the Act. In this instance, we 
developed analyses and rationale supporting both a proposed approval 
and a proposed partial approval and partial disapproval, and we solicit 
input on each proposal. EPA intends to finalize only one proposal, 
although the details of our final action may differ somewhat from what 
is presented here based on any comments and additional information we 
receive.
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    \1\ Our proposed approval for one element, reporting for PM BART 
limits, is a conditional approval based on a commitment from Utah to 
provide a SIP revision to address this element. See section V.D of 
this document for a more detailed explanation.
    \2\ In March 2015, conservation groups sued EPA in the U.S. 
District Court for the District of Colorado alleging that EPA failed 
to promulgate a regional haze FIP for Utah within the two-year 
period allowed by CAA section 110(c). See Wildearth Guardians v. 
McCarthy, Case No. 1:15-cv-oo630-MSK-KLM, at *1-2 (D. Colo. Mar. 27, 
2015). EPA entered into a consent decree resolving this dispute 
requiring EPA to sign notices of proposed and final rulemaking for 
the regional haze requirements for Utah by December 16, 2015 and 
June 1, 2016, respectively. The signing of this proposed rule 
partially fulfills EPA's obligations under the consent decree. See 
id. (Doc. 60, Motion to Enter Consent Decree filed on December 8, 
2015).
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    Deciding whether to approve the State SIP entails an evaluation of 
Utah's SIP revision with respect to three elements in the RHR: (1) 
``[a] demonstration that the emissions trading program or other 
alternative measure will achieve greater reasonable progress than would 
have resulted from the installation and operation of BART at all 
sources subject to BART in the State and covered by the alternative 
program''; \3\ (2) ``[a] requirement that all necessary emission 
reductions take place during the period of the first long-term strategy 
for regional haze''; \4\ and (3) ``[a] demonstration that the emissions 
reductions resulting from the alternative measure will be surplus to 
those reductions resulting from measures adopted to meet requirements 
of the CAA as of the baseline date of the SIP.'' \5\
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    \3\ 40 CFR 51.308(e)(2)(i).
    \4\ 40 CFR 51.308(e)(2)(iii).
    \5\ 40 CFR 51.308(e)(2)(iv).
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    For the first element, the determination that the alternative 
measure will achieve greater reasonable progress than BART, the State 
must provide the following: (1) A list of all BART-eligible sources 
within the State; (2) a list of all BART-eligible sources and all BART 
source categories covered by the alternative program; (3) an analysis 
of BART and associated emission reductions; (4) an analysis of the 
projected emission reductions achievable through the BART alternative; 
and (5) a determination that the alternative achieves greater 
reasonable progress than would be achievable through the installation 
and operation of BART. A State has several options for making the 
greater reasonable progress determination; \6\ in this instance, the 
State elected to use two separate approaches.
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    \6\ 40 CFR 51.308(e)(2)(i)(E); 40 CFR 51.308(e)(3).
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    EPA's evaluation of the BART Alternative therefore entails 
consideration of both of the State's analyses. As described in our 2006 
revisions to the RHR, concerning BART alternatives, ``[t]he State's 
discretion in this area is subject to the condition that it must be 
reasonably exercised and that its decisions be supported by adequate 
documentation of its analyses.'' \7\ As presented in section V, several 
of the metrics in the State's analyses appear to support a 
determination that a BART Alternative presented by the State achieves 
greater reasonable progress than BART. However, several other metrics 
in the State's analyses do not appear to support a conclusion that the 
BART Alternative achieves greater reasonable progress. The complexity 
of our evaluation leads us to propose and solicit comment on two 
conclusions and courses of action: (1) The State's submittal meets the 
test above and we approve the BART Alternative; or (2) the State's 
submittal falls short of meeting this test and we disapprove the BART 
Alternative and promulgate a FIP for NOX BART. We request 
comment on all aspects of each proposal.
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    \7\ 71 FR 60612, 60621 (Oct. 13, 2006).
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    Given the complexities in evaluating these co-proposals, EPA wants 
to ensure that our final decision is based on the best and most 
currently available data and information, and is taken with the fullest 
possible consideration of public input. Therefore, in addition to 
seeking comments on the co-proposals, we are

[[Page 2007]]

also asking if interested parties have additional information or 
analysis on the co-proposals, for example, analysis related to the 
modeled visibility benefits of the BART Alternative compared to BART. 
In light of any such information, we are asking whether interested 
parties think the Agency should consider BART Alternatives or BART 
control technology options that are related to what we propose and that 
could be finalized as our FIP (if we disapprove the Utah SIP submittal 
in our final action). The Agency is also asking if interested parties 
have additional information or comments on the proposed timing of 
compliance.
    The Agency will take the comments and testimony received, as well 
as any further SIP revisions received from the State prior to our final 
action, into consideration in our final promulgation. As noted above, 
additional information and comments may lead the Agency to adopt final 
SIP and/or FIP regulations that differ somewhat from the co-proposals 
presented here regarding the BART Alternative, BART control technology 
option or emission limits, or impact other proposed regulatory 
provisions. EPA's final action will fully consider these complex issues 
and the comments received, which will result in the selection of a 
final action that meets the CAA and regulatory requirements requiring 
development and implementation of plans to ensure reasonable progress 
toward improving visibility in mandatory Class I areas by reducing 
emissions that cause or contribute to regional haze.

A. Brief Description of These Co-Proposals

1. Summary of Proposal To Approve the SIP
    As explained more fully later, we are proposing to approve these 
aspects of the State's June 4, 2015 SIP submittal:
     NOX BART Alternative, including NOX 
emission reductions from Hunter Units 1, 2, and 3, Huntington Units 1 
and 2, and Carbon Units 1 and 2, and sulfur dioxide (SO2) 
and PM10 emission reductions from Carbon Units 1 and 2.
     BART determinations and emission limits for 
PM10 at Hunter Units 1 and 2 and Huntington Units 1 and 2.
     Monitoring, recordkeeping, and reporting requirements for 
units subject to the BART Alternative and the PM10 emission 
limits.
    We are proposing to approve these elements of the State's October 
20, 2015 SIP submittal:
     Enforceable commitments to revise SIP section XX.D.3.c and 
state rule R307-150 by March 2018 to clarify emission inventory 
requirements for tracking compliance with the SO2 milestone 
and properly accounting for the SO2 emission reductions due 
to the closure of the Carbon plant.
2. Summary of Proposal to Partially Approve and Partially Disapprove 
the SIP and Propose a FIP
    We are proposing to approve these elements of the State's SIP 
submittals:
     BART determinations and emission limits for 
PM10 at Hunter Units 1 and 2, and Huntington Units 1 and 2.
     Monitoring, recordkeeping, and reporting requirements for 
units subject to the PM10 emission limits.
    We are proposing to disapprove these aspects of the State's June 4, 
2015 SIP:
     NOX BART Alternative, including NOX 
emission reductions from Hunter Units 1, 2, and 3, Huntington Units 1 
and 2, and Carbon Units 1 and 2, and SO2 and PM10 
emission reductions from Carbon Units 1 and 2.
    We are proposing to disapprove the State's October 20, 2015 SIP 
submittal.
    We are proposing promulgation of a FIP to address the deficiencies 
in the Utah regional haze SIPs that are identified in this notice. The 
proposed FIP includes the following elements:
     NOX BART determinations and emission limits for 
Hunter Units 1 and 2 and Huntington Units 1 and 2.
     Monitoring, recordkeeping, and reporting requirements for 
NOX at Hunter Units 1 and 2, and Huntington Units 1 and 2.
    If we partially disapprove the SIP, and promulgate a FIP, the State 
may submit a SIP revision to supersede the FIP. If we determine that 
the SIP revision is approvable, regardless of whether or not its terms 
match those of our final FIP, we would propose to approve such a SIP 
revision. If we issue a final FIP, we encourage the State to submit a 
SIP revision to replace the FIP.

III. Background and Requirements for Regional Haze SIPs and Utah 
Submittals

A. Statutory and Regulatory Background

1. Regional Haze
    Regional haze is visibility impairment that is produced by numerous 
sources that are located across a broad geographic area and emit fine 
particles (PM2.5) (e.g., sulfates, nitrates, organic carbon 
(OC), elemental carbon (EC), and soil dust), and their precursors 
(e.g., SO2, NOX, and in some cases, ammonia 
(NH3) and volatile organic compounds (VOC)). Coarse PM also 
impairs visibility. Fine particle precursors react in the atmosphere to 
form PM2.5, which impairs visibility by scattering and 
absorbing light. Visibility impairment reduces the clarity, color, and 
visible distance that one can see, PM2.5 can also cause 
serious health effects and mortality in humans and contributes to 
environmental effects such as acid deposition and eutrophication. 
Coarse PM also can cause adverse health effects.
    Data from the existing visibility monitoring network, the 
``Interagency Monitoring of Protected Visual Environments'' (IMPROVE) 
monitoring network, show that at the time the regional haze rule was 
finalized in 1999, visibility impairment caused by air pollution 
occurred virtually all the time at most national parks and wilderness 
areas. The average visual range \8\ in many Class I areas (i.e., 
national parks, wilderness areas, and international parks meeting 
certain size criteria) in the western U.S. was 62-93 miles, but in some 
Class I areas, these visual ranges may have been impacted by natural 
wildfire and dust episodes.\9\ In most of the eastern Class I areas of 
the U.S., the average visual range was less than 19 miles, ``or about 
one-fifth of the visual range that would exist under estimated natural 
conditions.'' \10\
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    \8\ Visual range is the greatest distance, in kilometers or 
miles, at which a dark object can be viewed against the sky.
    \9\ 64 FR 35715, 35716 (July 1, 1999).
    \10\ Id.
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2. Requirements of the CAA and EPA's Regional Haze Rule (RHR)
    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.'' \11\ On

[[Page 2008]]

December 2, 1980, EPA promulgated regulations to address visibility 
impairment in Class I areas that are ``reasonably attributable'' to a 
single source or small group of sources, i.e., reasonably attributable 
visibility impairment.\12\ These regulations represented the first 
phase in addressing visibility impairment. EPA deferred action on 
regional haze that emanates from a variety of sources until monitoring, 
modeling and scientific knowledge about the relationships between 
pollutants and visibility impairment were improved.
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    \11\ 42 U.S.C. 7491(a). Areas designated as mandatory Class I 
Federal areas consist of national parks exceeding 6000 acres, 
wilderness areas and national memorial parks exceeding 5000 acres, 
and all international parks that were in existence on August 7, 
1977. 42 U.S.C. 7472(a). In accordance with section 169A of the CAA, 
EPA, in consultation with the Department of Interior, promulgated a 
list of 156 areas where visibility is identified as an important 
value. 44 FR 69122 (Nov. 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 which they consider to have 
visibility as an important value, the requirements of the visibility 
program set forth in section 169A of the CAA apply only to 
``mandatory Class I Federal areas.'' Each mandatory Class I 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.''
    \12\ 45 FR 80084, 80084 (Dec. 2, 1980).
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    Congress added section 169B to the CAA in 1990 to address regional 
haze issues. EPA promulgated a rule to address regional haze on July 1, 
1999.\13\ The RHR revised the existing visibility regulations to 
integrate into the regulation provisions addressing regional haze 
impairment 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 EPA's visibility protection 
regulations at 40 CFR 51.300 through 309. Some of the main elements of 
the regional haze requirements are summarized later in section III.C of 
this preamble. The requirement to submit a regional haze SIP applies to 
all 50 states, the District of Columbia, and the Virgin Islands. 40 CFR 
51.308(b) requires states to submit the first implementation plan 
addressing regional haze visibility impairment no later than December 
17, 2007.\14\
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    \13\ 64 FR 35714, 35714 (July 1, 1999) (codified at 40 CFR part 
51, subpart P).
    \14\ EPA's RHR requires subsequent updates to the regional haze 
SIPs. 40 CFR 51.308(g) through (i).
---------------------------------------------------------------------------

    Once EPA has found that a state has failed to make a required 
submission, EPA is required to promulgate a FIP within two years unless 
the state submits a SIP and the Agency approves it within the two-year 
period.\15\
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    \15\ 42 U.S.C. 7410(c)(1).
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3. Roles of Agencies in Addressing Regional Haze
    Successful implementation of the regional haze program requires 
long-term regional coordination among states, tribal governments, and 
various federal agencies. As noted previously, pollution affecting the 
air quality in Class I areas can be transported over long distances, 
even hundreds of kilometers. Therefore, to effectively address the 
problem of visibility impairment in Class I areas, states need to 
develop strategies in coordination with one another, taking into 
account the effect of emissions from one jurisdiction on the air 
quality in another.
    Because the pollutants that lead to regional haze can originate 
from sources located across broad geographic areas, EPA has encouraged 
the states and tribes across the United States to address visibility 
impairment from a regional perspective. Five regional planning 
organizations (RPOs) were created to address regional haze and related 
issues. The RPOs first evaluated technical information to better 
understand how their states and tribes impact Class I areas across the 
country, and then pursued the development of regional strategies to 
reduce emissions of pollutants that lead to regional haze.
    The Western Regional Air Partnership (WRAP) RPO is a collaborative 
effort of state governments, tribal governments, and various federal 
agencies established to initiate and coordinate activities associated 
with the management of regional haze, visibility and other air quality 
issues in the western United States. WRAP member state governments 
include: Alaska, Arizona, California, Colorado, Idaho, Montana, New 
Mexico, North Dakota, Oregon, South Dakota, Utah, Washington, and 
Wyoming. Tribal members include Campo Band of Kumeyaay Indians, 
Confederated Salish and Kootenai Tribes, Cortina Indian Rancheria, Hopi 
Tribe, Hualapai Nation of the Grand Canyon, Native Village of Shungnak, 
Nez Perce Tribe, Northern Cheyenne Tribe, Pueblo of Acoma, Pueblo of 
San Felipe, and Shoshone-Bannock Tribes of Fort Hall.
4. Development of the Requirements for 40 CFR 51.309
    EPA's RHR provides two paths to address regional haze. One is 40 
CFR 51.308, requiring states to perform individual point source BART 
determinations and evaluate the need for other control strategies. 
These strategies must be shown to make ``reasonable progress'' in 
improving visibility in Class I areas inside the state and in 
neighboring jurisdictions. 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, states can be deemed to 
be making reasonable progress toward the national goal of achieving 
natural visibility conditions for the 16 Class I areas on the Colorado 
Plateau.
    Section 309 requires participating states 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.\16\ The EPA established the GCVTC on 
November 13, 1991. 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 
EPA to address such impacts. Section 169B of the CAA called for the 
GCVTC to evaluate visibility research, as well as other available 
information, pertaining to adverse impacts on visibility from potential 
or projected growth in emissions from sources located in the region. 
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 EPA in 1996 with its policy recommendations for protecting 
visibility for the Class I areas on the Colorado Plateau. Provisions of 
the 1996 GCVTC report include: Strategies for addressing smoke 
emissions from wildland fires and agricultural burning; provisions to 
prevent pollution by encouraging renewable energy development; and 
provisions to manage clean air corridors (CACs), mobile sources, and 
wind-blown dust, among other things. The EPA codified these 
recommendations as an option available to states as part of the 1999 
RHR.\17\
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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 as follows: 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 Parks Wilderness, Arches National 
Park, Bryce Canyon National Park, Canyonlands National Park, Capital 
Reef National Park, and Zion National Park.
    \17\ 64 FR 35714, 35749 (July 1, 1999).
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    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\ 
Thus, the 1999 RHR required that western states submit an annex to the 
GCVTC report with quantitative milestones and detailed guidelines for 
an alternative program in order to establish the GCVTC recommendations 
as an alternative approach to fulfilling the section 308 requirements 
for compliance with the RHR. In September

[[Page 2009]]

2000, the WRAP, which is the successor organization to the GCVTC, 
submitted an annex to EPA. The annex contained SO2 emissions 
reduction milestones and detailed provisions of a backstop trading 
program to be implemented automatically if voluntary measures failed to 
achieve the SO2 milestones. 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.
    \19\ 68 FR 33764, 33767 (June 5, 2003).
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    Five western states, including Utah, submitted implementation plans 
under section 309 in 2003. EPA was challenged by the Center for Energy 
and Economic Development (CEED) on the validity of the annex 
provisions. In CEED v. EPA, the DC Circuit Court of Appeals vacated EPA 
approval of the WRAP annex.\20\ In response to the court's decision, 
EPA vacated 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).\21\ 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 the point source 
application of BART.
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    \20\ Ctr. for Energy & Econ. Dev. v. EPA, 398 F.3d 653, 654 
(D.C. Cir. 2005).
    \21\ 71 FR 60612, 60612 (Oct. 13, 2006).
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5. SIP and FIP Background
    The CAA requires each state to develop plans to meet various air 
quality requirements, including protection of visibility.\22\ The plans 
developed by a state are referred to as SIPs. A state must submit its 
SIPs and SIP revisions to EPA for approval. Once approved, a SIP is 
enforceable by EPA and citizens under the CAA, which is also known as 
being federally enforceable. If a state 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.\23\ As discussed elsewhere in this preamble, one of the 
proposals would disapprove aspects of Utah's regional haze SIP and 
promulgate a FIP to address the deficiencies in Utah's regional haze 
SIP, should we disapprove the SIP in our final action.
---------------------------------------------------------------------------

    \22\ 42 U.S.C. 7410(a), 7491, and 7492(a), 169A, and 169B.
    \23\ 42 U.S.C. 7410(c)(1).
---------------------------------------------------------------------------

B. Requirements for Regional Haze SIPs Applicable to This Proposal

1. The CAA and the Regional Haze Rule
    Regional haze SIPs must assure reasonable progress towards the 
national goal of achieving natural visibility conditions in Class I 
areas. Section 169A of the CAA and EPA's implementing regulations 
require states to establish long-term strategies for making reasonable 
progress toward meeting this goal. Implementation plans must also give 
specific attention to certain stationary sources that were in existence 
on August 7, 1977, but were not in operation before August 7, 1962, and 
require these sources, where appropriate, to install BART controls for 
the purpose of eliminating or reducing visibility impairment. The 
specific regional haze SIP requirements are discussed in further detail 
later on.
2. Determination of Baseline, Natural, and Current Visibility 
Conditions
    The RHR establishes the deciview (dv) as the principal metric or 
unit for expressing visibility.\24\ This visibility metric expresses 
uniform changes in the degree of haze in terms of common increments 
across the entire range of visibility conditions, from pristine to 
extremely hazy conditions. Visibility expressed in deciviews is 
determined by using air quality measurements to estimate light 
extinction and then transforming the value of light extinction using a 
logarithmic function. The dv is a more useful measure for tracking 
progress in improving visibility than light extinction itself because 
each dv change is an equal incremental change in visibility perceived 
by the human eye. Most people can detect a change in visibility at one 
dv.\25\
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    \24\ See 70 FR 39104, 39118 (July 6, 2005).
    \25\ The preamble to the RHR provides additional details about 
the deciview (dv) scale. 64 FR 35714, 35725 (July 1, 1999).
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    The dv is used in expressing reasonable progress goals (RPGs, which 
are interim visibility goals towards meeting the national visibility 
goal), in defining baseline, current, and natural conditions; and in 
tracking changes in visibility. The regional haze SIPs must contain 
measures that ensure ``reasonable progress'' toward the national goal 
of preventing and remedying visibility impairment in Class I areas 
caused by anthropogenic emissions that cause or contribute to regional 
haze. The national goal is a return to natural conditions, i.e. to 
reach a state at which anthropogenic sources of air pollution no longer 
impair visibility in Class I areas.
    To track changes in visibility over time at each of the 156 Class I 
areas covered by the visibility program,\26\ and as part of the process 
for determining reasonable progress, states must calculate the degree 
of existing visibility impairment at each Class I area at the time of 
each regional haze SIP submittal and review progress every five years, 
midway through each 10-year implementation period. To do this, the RHR 
requires states to determine the degree of impairment (in deciviews) 
for the average 20 percent least impaired (``best'') and 20 percent 
most impaired (``worst'') visibility days over a specified time period 
at each of their Class I areas. In addition, states must also develop 
an estimate of natural visibility conditions for the purpose of 
comparing progress toward the national goal. Natural visibility is 
determined by estimating the natural concentrations of pollutants that 
cause visibility impairment and then calculating total light extinction 
based on those estimates. In 2003, EPA provided guidance to states 
regarding how to calculate baseline, natural and current visibility 
conditions.\27\ Subsequently, the Natural Haze Levels II Committee 
developed updated estimates of natural haze for average natural 
conditions and for the averages of the best 20% and worst 20% natural 
condition days \28\ that have been used by states and EPA in visibility 
assessments.
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    \26\ 40 CFR 81.401-437.
    \27\ Guidance for Estimating Natural Visibility Conditions Under 
the Regional Haze Rule, EPA-454/B-03-005, available at http://www3.epa.gov/ttn/caaa/t1/memoranda/rh_envcurhr_gd.pdf, (hereinafter 
referred to as ``our 2003 Natural Visibility Guidance'') (Sept. 
2003) (documents identified with Internet addresses are available in 
the docket) ; Guidance for Tracking Progress Under the Regional Haze 
Rule, EPA-454/B-03-004, available at http://www3.epa.gov/ttnamti1/files/ambient/visible/tracking.pdf (hereinafter referred to as our 
``2003 Tracking Progress Guidance'') (Sept. 2003).
    \28\ ``Natural Haze Levels II: Application of the New IMPROVE 
Algorithm to Natural Species Concentrations Estimates'', Final 
Report by the Natural Haze Levels II Committee to the RPO 
Monitoring/Data Analysis Workgroup, power point presentation 
included in the docket.
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    For the first regional haze SIPs that were due by December 17, 
2007, ``baseline visibility conditions'' were the starting points for 
assessing ``current'' visibility impairment. Baseline visibility 
conditions represent the five-year averages of the degree of visibility 
impairment for the 20 percent least impaired days and the 20 percent 
most impaired days for each calendar year from 2000 to 2004. Using 
monitoring data for 2000 through 2004, states are required to calculate 
the average degree of visibility impairment for each Class I area, 
based on the average of annual values over the five-year period. The 
comparison of initial baseline visibility conditions to natural 
visibility conditions indicates the amount of improvement necessary to 
attain natural visibility, while the future comparison of baseline 
conditions to the then current conditions will indicate the

[[Page 2010]]

amount of progress made. In general, the 2000-2004 baseline period is 
considered the time from which improvement in visibility is measured.
3. Best Available Retrofit Technology
    Section 169A of the CAA directs states to evaluate the use of 
retrofit controls at certain larger, often uncontrolled, older 
stationary sources in order to address visibility impacts from these 
sources. Specifically, section 169A(b)(2)(A) of the CAA requires states 
to revise their SIPs to contain such measures as may be necessary to 
make reasonable progress towards the natural visibility goal, including 
a requirement that certain categories of existing major stationary 
sources \29\ built between 1962 and 1977 procure, install, and operate 
the ``Best Available Retrofit Technology'' as determined by the state. 
Under the RHR, states are directed to conduct BART determinations for 
such ``BART-eligible'' sources that may be anticipated to cause or 
contribute to any visibility impairment in a Class I area. 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.
---------------------------------------------------------------------------

    \29\ See 42 U.S.C. 7491(g)(7) (listing the set of ``major 
stationary sources'' potentially subject-to-BART).
---------------------------------------------------------------------------

    On July 6, 2005, EPA published the ``Guidelines for BART 
Determinations Under the Regional Haze Rule'' at appendix Y to 40 CFR 
part 51 (hereinafter referred to as the ``BART Guidelines'') to assist 
states in determining which of their sources should be subject to the 
BART requirements and in determining appropriate emission limits for 
each applicable source.\30\ In making a BART determination for a fossil 
fuel-fired electric generating plant with a total generating capacity 
in excess of 750 megawatts (MW), a state must use the approach set 
forth in the BART Guidelines. A state is encouraged, but not required, 
to follow the BART Guidelines in making BART determinations for other 
types of sources. Regardless of source size or type, a state must meet 
the requirements of the CAA and our regulations for selection of BART, 
and the state's BART analysis and determination must be reasonable in 
light of the overarching purpose of the regional haze program.
---------------------------------------------------------------------------

    \30\ 70 FR 39104, 39104 (July 6, 2005).
---------------------------------------------------------------------------

    The process of establishing BART emission limitations can be 
logically broken down into three steps: First, states identify those 
sources that meet the definition of ``BART-eligible source'' set forth 
in 40 CFR 51.301; \31\ second, states determine which of such sources 
``emits any air pollutant which may reasonably be anticipated to cause 
or contribute to any impairment of visibility in any such area'' \32\ 
(a source that fits this description is ``subject-to-BART''); and 
third, for each source subject-to-BART, states then identify the best 
available type and level of control for reducing emissions.
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    \31\ BART-eligible sources are those sources that have the 
potential to emit 250 tons or more of a visibility-impairing air 
pollutant, were not in operation prior to August 7, 1962, but were 
in existence on August 7, 1977, and whose operations fall within one 
or more of 26 specifically listed source categories. 40 CFR 51.301.
    \32\ 42 U.S.C. 7491(b)(2)(A).
---------------------------------------------------------------------------

    States must address all visibility-impairing pollutants emitted by 
a source in the BART determination process. The most significant 
visibility impairing pollutants are SO2, NOX, and 
PM. EPA has stated that states should use their best judgment in 
determining whether VOC or NH3 compounds impair visibility 
in Class I areas.
    Under the BART Guidelines, states may select an exemption threshold 
value for their BART modeling, below which a BART-eligible source would 
not be expected to cause or contribute to visibility impairment in any 
Class I area. The state must document this exemption threshold value in 
the SIP and must state the basis for its selection of that value. Any 
source with emissions that model above the threshold value would be 
subject to a BART determination review. The BART Guidelines acknowledge 
varying circumstances affecting different Class I areas. States should 
consider the number of emission sources affecting the Class I areas at 
issue and the magnitude of the individual sources' impacts. Any 
exemption threshold set by the state should not be higher than 0.5 
dv.\33\
---------------------------------------------------------------------------

    \33\ 40 CFR part 51, appendix Y, Sec.  III.A.1.
---------------------------------------------------------------------------

    In their SIPs, states must identify the sources that are subject-
to-BART and document their BART control determination analyses for such 
sources. In making their BART determinations, section 169A(g)(2) of the 
CAA requires that states consider the following factors when evaluating 
potential control technologies: (1) The costs of compliance; (2) the 
energy and non-air quality environmental impacts of compliance; (3) any 
existing pollution control technology in use at the source; (4) the 
remaining useful life of the source; and (5) the degree of improvement 
in visibility which may reasonably be anticipated to result from the 
use of such technology.
    A regional haze SIP must include source-specific BART emission 
limits and compliance schedules for each source subject-to-BART. Once a 
state has made its BART determination, the BART controls must be 
installed and in operation as expeditiously as practicable, but no 
later than five years after the date of EPA approval of the regional 
haze SIP.\34\ As noted previously, the RHR allows states to implement 
an alternative program in lieu of BART so long as the alternative 
program can be demonstrated to achieve greater reasonable progress 
toward the national visibility goal than would BART.
---------------------------------------------------------------------------

    \34\ 42 U.S.C. 7491(g)(4); 40 CFR 51.308(e)(1)(iv).
---------------------------------------------------------------------------

4. Monitoring, Recordkeeping and Reporting
    The CAA requires that SIPs, including the regional haze SIP, 
contain elements sufficient to ensure emission limits are practically 
enforceable. CAA section 110(a)(2) requires in part that the 
monitoring, recordkeeping and reporting (MRR) provisions of states' 
SIPs must include enforceable emission limitations, control measures, 
and compliance timeframes. It also requires SIPs to provide for 
enforcement of these measures, installation, maintenance, and 
replacement of equipment, emissions monitoring, periodic emissions 
reports and availability of emissions reports for public inspection.
    Accordingly, 40 CFR part 51, subpart K, Source Surveillance, 
requires the SIP to provide for monitoring the status of compliance 
with the regulations in it, including ``[p]eriodic testing and 
inspection of stationary sources,'' \35\ and ``legally enforceable 
procedures'' for recordkeeping and reporting.\36\ Furthermore, 40 CFR 
part 51, appendix V, Criteria for Determining the Completeness of Plan 
Submissions, states in section 2.2 that complete SIPs contain: ``(g) 
Evidence that the plan contains emission limitations, work practice 
standards and recordkeeping/reporting requirements, where necessary, to 
ensure emission levels''; and ``(h) Compliance/enforcement strategies, 
including how compliance will be determined in practice.''
---------------------------------------------------------------------------

    \35\ 40 CFR 51.212(a).
    \36\ 40 CFR 51.211.
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5. Consultation With States and Federal Land Managers (FLMs)
    The RHR requires that states consult with FLMs before adopting and 
submitting their SIPs.\37\ States must

[[Page 2011]]

provide FLMs an opportunity for consultation, in person and at least 60 
days prior to holding any public hearing on the SIP. This consultation 
must include the opportunity for the FLMs to discuss their assessments 
of impairment of visibility in any Class I area and to offer 
recommendations on the development of the RPGs and on the development 
and implementation of strategies to address visibility impairment. 
Further, a state must include in its SIP a description of how it 
addressed any comments provided by the FLMs. Finally, a SIP must 
provide procedures for continuing consultation between the state and 
FLMs regarding the state's visibility protection program, including 
development and review of SIP revisions, five-year progress reports, 
and the implementation of other programs having the potential to 
contribute to impairment of visibility in Class I areas.
---------------------------------------------------------------------------

    \37\ 40 CFR 51.308(i).
---------------------------------------------------------------------------

C. Requirements for Regional Haze SIPs Submitted Under 40 CFR 51.309

    The following is a summary and basic explanation of the regulations 
covered under section 51.309 of the RHR that are addressed in this 
notice.\38\
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    \38\ Utah addressed some of the requirements of 40 CFR 51.309 in 
2008 and 2011 SIP submissions. EPA took final action on some of the 
provisions in the 2008 and 2011 SIP submissions in earlier notices. 
See 40 CFR 51.309 for a complete listing of the regulations under 
which the 2008 and 2011 SIP submissions were evaluated.
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1. Projection of Visibility Improvement
    For each of the 16 Class I areas located on the Colorado Plateau, 
the SIP must include a projection of the improvement in visibility 
expressed in deciviews.\39\ An explanation of the deciview metric is 
provided in section III.C.2. States need to show the projected 
visibility improvement for the best and worst 20 percent days through 
the year 2018, based on the application of all section 309 control 
strategies.
---------------------------------------------------------------------------

    \39\ 40 CFR 51.309(d)(2).
---------------------------------------------------------------------------

2. Stationary Source Reductions
a. Sulfur Dioxide Emission Reductions
    Rather than requiring source-specific BART controls as explained 
previously in section III.C.4, states have the flexibility to adopt an 
emissions trading program or other alternative program as long as 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, states can satisfy the SO2 BART requirements by 
adopting SO2 emission milestones and a backstop trading 
program.\40\ Under this approach, states must establish declining 
SO2 emission 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.
---------------------------------------------------------------------------

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

    Pursuant to 40 CFR 51.309(d)(4)(ii) through (iv), states must 
include requirements in the SIP that allow states to determine whether 
the milestone has been exceeded. These requirements include 
documentation of the baseline emission calculation, monitoring, 
recordkeeping, and reporting of SO2 emissions, and 
provisions for conducting an annual evaluation to determine whether the 
milestone has been exceeded. SIPs must also contain requirements for 
implementing the backstop trading program in the event that the 
milestone is exceeded and the program is triggered.\41\
---------------------------------------------------------------------------

    \41\ 40 CFR 51.309(d)(4)(v).
---------------------------------------------------------------------------

    The WRAP, in conjunction with EPA, developed a model for a backstop 
trading program. In order to ensure consistency between states, states 
opting to participate in the 309 program needed to adopt rules that are 
substantively equivalent to the model rules for the backstop trading 
program to meet the requirements of 40 CFR 51.309(d)(4). The trading 
program must also be implemented no later than 15 months after the end 
of the first year that the milestone is exceeded, require that sources 
hold allowances to cover their emissions, and provide a framework, 
including financial penalties, to ensure that the 2018 milestone is 
met.
b. Provisions for Stationary Source Emissions of Nitrogen Oxides and 
Particulate Matter
    Pursuant to 40 CFR 51.309(d)(4)(vii), a section 309 SIP must 
contain any necessary long term strategies and BART requirements for PM 
and NOX. These requirements, including the process for 
conducting BART determinations either based on the consideration of the 
five statutory factors or based on an alternative program, are 
explained previously in section III.C.4 and in section III.E, 
respectively.

D. General Requirements for PM10 and NOX 
Alternative Programs Under the Regional Haze Rule and the ``Better-
Than-BART Demonstration''

    States opting to submit an alternative program must meet 
requirements under 40 CFR 51.308(e)(2) and (e)(3). These requirements 
for alternative programs relate to the ``better-than-BART'' test and 
fundamental elements of any alternative program.
    In order to demonstrate that the alternative program achieves 
greater reasonable progress than source-specific BART, a state must 
demonstrate that its SIP meets the requirements in 40 CFR 
51.308(e)(2)(i) through (v). States submitting section 309 SIPs or 
other alternative programs are required to list all BART-eligible 
sources and categories covered by the alternative program. States are 
then required to determine which BART-eligible sources are ``subject-
to-BART.'' The SIP must provide 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, or what is termed a ``BART benchmark.'' Where the alternative 
program has been designed to meet requirements other than BART, states 
may use simplifying assumptions in establishing a BART benchmark.
    Pursuant to 40 CFR 51.308(e)(2)(i)(E), the State 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. 40 CFR 51.308(e)(3), in turn, 
provides a specific test 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 emission 
reductions, 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 dispersion 
modeling for each impacted Class I area for the best and worst 20 
percent of days. The modeling would demonstrate ``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 over all of the 
affected Class I areas.
    Alternately, pursuant to 40 CFR 51.308(e)(2) States may show that 
the BART alternative achieves greater reasonable progress than the BART 
benchmark ``based on the clear weight of evidence'' determinations, 
which

``attempt to make use of all available information and data which 
can inform a

[[Page 2012]]

decision while recognizing the relative strengths and weaknesses of 
that information in arriving at the soundest decision possible. 
Factors which can be used in a weight of evidence determination in 
this context may include, but not be limited to, future projected 
emissions levels under the program as compared to under BART, future 
projected visibility conditions under the two scenarios, the 
geographic distribution of sources likely to reduce or increase 
emissions under the program as compared to BART sources, monitoring 
data and emissions inventories, and sensitivity analyses of any 
models used. This array of information and other relevant data may 
be of sufficient quality to inform the comparison of visibility 
impacts between BART and the alternative program. In showing that an 
alternative program is better than BART and when there is confidence 
that the difference in visibility impacts between BART and the 
alternative scenarios are expected to be large enough, a weight of 
evidence comparison may be warranted in making the comparison. The 
EPA will carefully consider the evidence before us in evaluating any 
SIPs submitted by States employing such an approach.'' \42\
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    \42\ 71 FR 60612, 60622 (Oct. 13, 2006).

    Finally, in promulgating the final regional haze program 
requirements and responding to concerns regarding ``impermissibly 
vague'' language in Sec.  51.308(e)(3) that would allow a State to 
``approve alternative measures that are less protective than BART,'' we 
explained that ``[t]he State's discretion in this area is subject to 
the condition that it must be reasonably exercised and that its 
decisions be supported by adequate documentation of its analyses.'' 
\43\
---------------------------------------------------------------------------

    \43\ 71 FR 60612, 60621.
---------------------------------------------------------------------------

    Under 40 CFR 51.308(e)(2)(iii) and (iv), all emission reductions 
for the alternative program must take place by 2018, and all the 
emission reductions resulting from the alternative program must be 
surplus to those reductions resulting from measures adopted to meet 
requirements of the CAA as of the baseline date of the SIP. Pursuant to 
40 CFR 51.309(e)(2)(v), states have the option of including a provision 
that the emissions trading program or other alternative measure include 
a geographic enhancement to the program to address the requirement 
under 40 CFR 51.302(c) related to BART for reasonably attributable 
visibility impairment from the pollutants covered under the emissions 
trading program or other alternative measure.

E. Summary of State Regional Haze Submittals and EPA Actions

1. 2008 and 2011 Utah RH SIPs
    On May 26, 2011, the Governor of the State of Utah submitted to EPA 
a Regional Haze SIP under 40 CFR 51.309 of the RHR (``2011 Utah RH 
SIP''). This submittal included BART determinations for NOX 
and PM10 at Utah's four subject-to-BART sources: 
PacifiCorp's Hunter Units 1 and 2 and Huntington Units 1 and 2. All 
four units are tangentially fired fossil fuel fired EGUs each with a 
net generating capacity of 430 MW, permitted to burn bituminous coal. 
This submittal also included a backstop trading program under 40 CFR 
51.309 intended to meet the requirement for controlling SO2 
by establishing a cap on emissions. The trading program covers Utah, 
Wyoming, New Mexico and the City of Albuquerque.
    Utah also submitted SIPs on December 12, 2003, August 8, 2004 and 
September 9, 2008, to meet the requirements of the RHR. These 
submittals were, for the most part, superseded and replaced by the May 
26, 2011 submittal as further explained in the next section discussing 
our action on these submittals.
2. 2012 EPA Action on 2011 and 2008 Utah RH SIPs
    On December 14, 2012, EPA partially approved and partially 
disapproved the 2011 Utah RH SIP.\44\ We approved all sections of the 
2011 Utah RH SIP as meeting the requirements of 40 CFR 51.309, with the 
exception of the requirements under 40 CFR 51.309(d)(4)(vii) pertaining 
to NOX and PM10 BART. EPA's partial disapproval 
action was based on the following: (1) Utah did not take into account 
the five statutory factors in its BART analyses for NOX and 
PM10; and (2) the 2011 Utah RH SIP did not contain the 
provisions necessary to make the BART limits practically enforceable as 
required by section 110(a)(2) of the CAA and 40 CFR 51, appendix V.\45\
---------------------------------------------------------------------------

    \44\ 77 FR 74355, 74357 (Dec. 14, 2012).
    \45\ Id.
---------------------------------------------------------------------------

    We also approved two sections of the 2008 Utah RH SIP. 
Specifically, we approved UAR R307-250--Western Backstop Sulfur Dioxide 
Trading Program and R307-150--Emission Inventories. We took no action 
on the rest of the 2008 submittal as the 2011 submittal superseded and 
replaced the remaining sections of the 2008 submittal. We also took no 
action on the December 12, 2003 and August 8, 2004 submittals as these 
were superseded by the 2011 submittal.
    On November 8, 2011, we separately proposed approval of Section G--
Long-Term Strategy for Fire Programs of the May 26, 2011 submittal and 
finalized our approval of that action on January 18, 2013.\46\
---------------------------------------------------------------------------

    \46\ 78 FR 4071, 4072 (Jan. 18, 2013).
---------------------------------------------------------------------------

3. 2013 Litigation
    In 2013, conservation groups sued EPA in the U.S. Court of Appeals 
for the Tenth Circuit on our approval of the SO2 backstop 
trading program as an alternative to BART. On October 21, 2014, the 
court upheld EPA's finding that the trading program was better than 
BART.\47\
---------------------------------------------------------------------------

    \47\ Wildearth Guardians v. United States EPA, 728 F.3d 1075, 
1083-84 (10th Cir. 2013).
---------------------------------------------------------------------------

4. 2015 Utah RH SIPs
    On June 4, 2015, the Governor of the State of Utah submitted to EPA 
a revision to its Regional Haze SIP under 40 CFR 51.309 of the RHR 
(``June 2015 Utah RH SIP''), specifically to address the requirements 
under 40 CFR 51.309(d)(4)(vii) pertaining to NOX and 
PM10 BART. Utah developed the June 2015 Utah RH SIP in 
response to EPA's December 14, 2012 partial disapproval of the 2011 
Utah RH SIP. The June 2015 Utah RH SIP evolved from a draft SIP on 
which Utah sought public comment in October 2014. After receiving 
extensive public comments, Utah decided to pursue a BART alternative 
(``Utah BART Alternative,'' ``BART Alternative,'' or ``Alternative'') 
under 40 CFR 51.308(e)(2) that takes credit for early NOX 
reductions due to combustion controls installed at PacifiCorp's Hunter 
and Huntington power plants in addition to NOX, 
SO2, and PM10 reductions from the August 2015 
retirement of PacifiCorp's nearby Carbon power plant. The June 2015 
Utah RH SIP also includes measures to make the SIP requirements 
practically enforceable and includes additional information pertaining 
to the PM10 BART determinations for Hunter and Huntington to 
address deficiencies identified by EPA in our December 2012 partial 
disapproval.
    On October 20, 2015, Utah submitted to EPA an additional revision 
to its Regional Haze SIP under 40 CFR 51.309 of the RHR (``October 2015 
Utah RH SIP''). This SIP includes an enforceable commitment to provide 
an additional SIP revision by mid-March 2018 to address concerns raised 
in public comments that the State would be double counting certain 
emissions reductions under the Utah BART Alternative in respect to 
milestone reporting for the SO2 backstop trading program.
    Sections 110(a)(2) and 110(l) of the CAA require that a state 
provide reasonable notice and public hearing

[[Page 2013]]

before adopting a SIP revision and submitting it to us. Utah, after 
providing notice, accepted comments on the June 2015 Utah RH SIP in 
April 2015 and accepted comments on the October 2015 Utah RH SIP in 
mid-August through mid-September 2015. Following the comment period and 
legal review by the Utah Attorney General's Office, the Utah Air 
Quality Board adopted the June 2015 Utah RH SIP on June 3, 2015 and the 
October 2015 Utah RH SIP on October 7, 2015. The Governor submitted the 
SIP revisions to EPA on June 4, 2015 and October 20, 2015.

IV. Utah's Regional Haze SIP

A. Summary of Elements Under EPA's Previous Actions Upon Which We Are 
Relying

    Several SIP elements that we previously approved in our December 
2012 final rule and upon which we are relying in our current action 
include the following:
1. Affected Class I Areas
    Utah provided two maps in Section XX of its 2011 RH SIP, one 
showing the locations of the 16 Class I areas on the Colorado Plateau 
and one showing the locations of the five in Utah (Arches National 
Park, Bryce Canyon National Park, Canyonlands National Park, Capitol 
Reef National Park, and Zion National Park).\48\ Utah also provided a 
comparison of the monitored 2000-2004 baseline visibility conditions in 
deciviews for the 20 percent best and 20 percent worst days to the 
projected visibility improvement for 2018 for the 16 Class I areas.\49\
---------------------------------------------------------------------------

    \48\ See Utah Regional Haze State Implementation Plan, Sec.  
XX.B.8, pp. 8-9 (Figures 1 and 2) (2011).
    \49\ See id., at Sec.  XX.K.2, p. 116 (Table 24).
---------------------------------------------------------------------------

    We determined that the State's SIP satisfies the requirements of 40 
CFR 51.309(d)(2) for this element in our December 14, 2012 rulemaking.
2. BART-Eligible Sources
    Pursuant to 40 CFR 51.308(e)(2)(i)(A), the 2011 Utah RH SIP listed 
the BART-eligible sources covered by the backstop trading program (see 
Table 1). The State identified the following BART-eligible sources in 
Utah: PacifiCorp Hunter Units 1 and 2 and PacifiCorp Huntington Units 1 
and 2.
    PacifiCorp's Hunter Power Plant (Hunter), is located in Castle 
Dale, Utah and consists of three electric utility steam generating 
units. Of the three units, only Units 1 and 2 are subject to BART. 
Hunter Units 1 and 2 have a nameplate generating capacity of 488.3 MW 
each.\50\ The boilers are tangentially fired pulverized coal boilers, 
burning bituminous coal from the Deer Creek Mine in Utah.
---------------------------------------------------------------------------

    \50\ See U.S. Energy Information Administration, Electric 
Generating Capacity for 2011 (taken from Form EIA-860). See ``EIA 
existing generating units 2011.xls'' spreadsheet in the docket.
---------------------------------------------------------------------------

    PacifiCorp's Huntington Power Plant (Huntington), is located in 
Huntington City, Utah, and consists of two electric utility steam 
generating units. Huntington Units 1 and 2 have a nameplate generating 
capacity of 498 MW each.\51\ The boilers are tangentially fired 
pulverized coal boilers, burning bituminous coal from the nearby Deer 
Creek Mine.
---------------------------------------------------------------------------

    \51\ Id.
---------------------------------------------------------------------------

    We determined that the State's SIP satisfies the requirements of 40 
CFR 51.309(e)(2)(i)(A) in our December 14, 2012 rulemaking.
3. Sources Subject-to-BART
    Pursuant to 40 CFR 51.308(e)(2)(i)(B), the 2011 Utah RH SIP 
described the State's source modeling that determined which of the 
BART-eligible sources within Utah cause or contribute to visibility 
impairment and are thus subject-to-BART (more information on subject-
to-BART sources and modeling can be found in Section XX.D.6 of the 2011 
Utah RH SIP and section V.F of our May 16, 2012 proposed rulemaking).
    Table 1 shows Utah's BART-eligible sources covered by the 309 
SO2 backstop program, Hunter Units 1 and 2, and Huntington 
Units 1 and 2, and indicates that all are subject-to-BART.
    We determined that the State's SIP satisfies the requirements of 40 
CFR 51.308(e)(2)(i)(B) in our December 14, 2012 rulemaking.

                                      Table 1--Subject-to-BART Status for Utah's Section 309 BART-Eligible Sources
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                          Generating
           Company                  Source        Unit ID    Service     BART Category     capacity       Coal type        Boiler type     Subject-  to-
                                                               date                          (MW)                                              BART?
--------------------------------------------------------------------------------------------------------------------------------------------------------
PacifiCorp...................  Hunter..........          1       1978  Fossil Fuel EGU.          430  Bituminous......  Tangential......  Yes.
PacifiCorp...................  Hunter..........          2       1980  Fossil Fuel EGU.          430  Bituminous......  Tangential......  Yes.
PacifiCorp...................  Huntington......          1       1977  Fossil Fuel EGU.          430  Bituminous......  Tangential......  Yes.
PacifiCorp...................  Huntington......          2       1974  Fossil Fuel EGU.          430  Bituminous......  Tangential......  Yes.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    We note that Section XX.D.6 in the June 2015 Utah RH SIP supersedes 
Section XX.D.6 in the 2011 Utah RH SIP and that some reformatting 
occurred. As Utah did not make substantive revisions to the SIP 
provisions addressing BART-eligible sources and subject-to-BART 
sources, XX.D.6.b and XX.D.6.c, in the 2011 SIP, we are not proposing 
any additional action on these provisions in this preamble.

B. Summary of Utah's BART Alternative and PM10 BART SIP Revision

    Utah's June 2015 RH SIPs include the following SIP provisions:
     Revised R307-110-17, General Requirements: State 
Implementation Plan. Section IX, Control Measures for Area and Point 
Sources, Part H, Emissions Limits (incorporates by reference most 
recently amended SIP Section IX, Part H into state rules)
     Revised R307-110-28, General Requirements: State 
Implementation Plan, Regional Haze (incorporates by reference most 
recently amended SIP Section XX into state rules)
     Revised SIP Section XX.D.6 Regional Haze. Long-Term 
Strategy for Stationary Sources. Best Available Retrofit Technology 
(BART) Assessment for NOX and PM (supersedes Section XX.D.6 
in the 2011 Utah RH SIP)
     New SIP Section IX.H.21 General Requirements: Control 
Measures for Area and Point Sources, Emission Limits and Operating 
Practices, Regional Haze Requirements
     New SIP Section IX.H.22 Source Specific Emission 
Limitations: Regional Haze Requirements, Best Available Retrofit 
Technology.
    The June 2015 Utah RH SIP, including the five SIP revisions listed 
previously, consists of the following three components: (1) a 
NOX BART alternative that includes NOX and 
SO2, and PM10 emission reductions from

[[Page 2014]]

Hunter Units 1-3, Huntington Units 1 and 2, and Carbon Units 1 and 2 
and PM10 emission reductions from Carbon Units 1 and 2; (2) 
BART determinations for PM10 at Hunter Units 1 and 2 and 
Huntington Units 1 and 2 based on a streamlined analysis; and (3) 
monitoring, recordkeeping and reporting requirements for the Utah BART 
Alternative and PM10 BART emission limits to make the SIP 
requirements practically enforceable. The emission limits in the June 
2015 Utah RH SIP are provided in Table 2. We further explain the three 
components of the SIP.

                Table 2--Emission Limits and Shutdown in Utah's BART Alternative and PM10 SIP\1\
----------------------------------------------------------------------------------------------------------------
                                                PM10 Limit \2\ (lb/    NOX Limit \3\ (lb/
              Source                   Unit    MMBtu, three-run test      MMBtu, 30-Day           SO2 Limit
                                                      average)          Rolling Average)
----------------------------------------------------------------------------------------------------------------
Hunter............................          1  0.015................  0.26................  NA.
  2...............................          2  0.015................  0.26................  NA.
                                            3  NA...................  0.34................  NA.
Huntington........................          1  0.015................  0.26................  NA.
                                            2  0.015................  0.26................  NA.
Carbon............................          1  Shutdown by August     Shutdown by August    Shutdown by August
                                                15, 2015.              15, 2015.             15, 2015.
                                            2  Shutdown by August     Shutdown by           Shutdown by August
                                                15, 2015.              August15, 2015.       15, 2015.
----------------------------------------------------------------------------------------------------------------
\1\ Obtained from the June 2015 Utah RH SIP, Section IX.H.22.
\2\ Based on annual stack testing.
\3\ Based on continuous emission monitoring system (CEMS) measurement.

1. Utah BART Alternative
    Utah has opted to establish an alternative measure for 
NOX under 40 CFR 51.308(e)(2). The State compared the Utah 
BART Alternative against a BART Benchmark of selective catalytic 
reduction (SCR) on all four BART units at Hunter and Huntington (Units 
1 and 2 at both plants). Utah's BART Alternative consists of the 
shutdown of Carbon Units 1 and 2 and the installation of upgraded 
NOX combustion controls (new low-NOX burners 
[LNB] and overfire air [OFA]) on Hunter Unit 3 (all non-BART units). 
The Utah BART Alternative also includes the NOX reductions 
from installation of upgraded combustion controls (new LNB and 
separated overfire air [SOFA]) at Hunter Units 1 and 2 and Huntington 
Units 1 and 2 (all BART units). The BART Benchmark includes the four 
BART units with combustion controls and SCR, Carbon's baseline 
emissions, and Hunter Unit 3's emissions with original combustion 
controls. The Utah BART Alternative is generally described in SIP 
Section XX.D.6 with a detailed demonstration included in Chapter 1 of 
Utah's Technical Support Document (TSD) to support the State's 
assertion that the alternative achieves greater reasonable progress 
than BART. The State's demonstration is also described in more detail 
in section IV.C.
    A summary of the State's estimates of emissions for the Utah BART 
Alternative and the BART Benchmark is provided in Table 3. EPA 
developed a summary of the emissions reductions based on Utah's 
emission estimates and this is presented in Table 4.
    Utah indicated that PacifiCorp announced plans to shut down the 
Carbon Power Plant in 2015 due to the high cost to control mercury to 
meet the requirements of EPA's Mercury and Air Toxics Standards 
(MATS).\52\ The State noted that the MATS rule was finalized in 2011, 
and the Utah RH SIP contains the requirement for the Carbon Power Plant 
to shut down in August 2015. Therefore, the emission reductions occur 
after the 2002 base year for Utah's RH SIP and thus, Utah asserts, the 
reductions may be considered as part of an alternative strategy under 
40 CFR 51.308(e)(2)(iv).
---------------------------------------------------------------------------

    \52\ Utah Regional Haze State Implementation Plan, p. 7 (TSD 
Chapter 1) (2011).
---------------------------------------------------------------------------

2. PM10 BART Determinations
    Utah included a streamlined analysis for PM10 BART 
determinations in accordance with section D.9 of the BART Guidelines 
for the BART units at Hunter and Huntington in the SIP TSD in Chapter 
1, Section III and referenced this analysis in SIP Section XX.D.6. In 
the TSD, Utah summarized the BART analysis submitted by PacifiCorp in 
an August 5, 2014 report.\53\
---------------------------------------------------------------------------

    \53\ For PacifiCorp BART analyses reports, see TSD Chapter 2 of 
the SIP.
---------------------------------------------------------------------------

    PacifiCorp's analysis identified three available technologies: 
Upgraded ESP and flue gas conditioning (0.040 lb/MMBtu); polishing 
fabric filter (0.015 lb/MMBtu); and replacement fabric filter (0.015 
lb/MMBtu). The 2008 Utah RH SIP and BART determination had required 
PacifiCorp to install a fabric filter baghouse with a PM10 
emission limit of 0.015 lb/MMBtu at the Hunter and Huntington BART 
units. Utah staff reviewed PacifiCorp's 2012 analysis and determined 
that the baghouse technology required in 2008 is still the most 
stringent technology available and that 0.015 lb/MMBtu represents the 
most stringent emission limit. Utah cited EPA's BART Guidelines and 
regional haze actions in Colorado, Wyoming, North Dakota and Montana to 
support these assertions.
    Utah determined that the PM10 BART emission limit for 
Hunter Units 1 and 2 and Huntington Units 1 and 2 was 0.015 lb/MMBtu 
based on a three-run test average. Utah noted that because the most 
stringent technology is in place at these units and that the 
PM10 emission limits have been made enforceable in the SIP, 
no further analysis was required.
3. Monitoring, Recordkeeping and Reporting
    To address EPA's partial disapproval of the 2011 Utah RH SIP for 
lack of enforceable measures and monitoring, recordkeeping and 
reporting requirements for the Utah BART Alternative and the 
PM10 BART determinations, Utah added two new subsections to 
SIP Sections IX, General H.21 and 22. Under H.21, Utah has detailed 
general requirements for sources subject to its regional haze program. 
Under H.22, Utah has listed source-specific regional haze requirements 
for Hunter, Huntington and Carbon.
    Specifically, under H.21, Utah added a new definition for boiler 
operating day. Utah noted that state rules R307-107-1 and R307-107-2 
(applicability, timing and reporting of breakdowns) apply to sources 
subject to regional haze requirements under H.22. Utah required that 
information used to determine compliance shall be recorded for all 
periods when the source is in operation, and that such records shall be 
kept for a minimum of five years. Under H.21, Utah specified that 
emission limitations listed in H.22 shall apply at all times

[[Page 2015]]

and identified stack testing requirements to show compliance with those 
emission limitations. Finally, under H.21, Utah also specified the 
requirements for continuous emission monitoring by listing the 
requirements and cross-referencing the State's rule for continuous 
emission monitoring system requirements, R307-170 as well as 40 CFR 
part 13 and 40 CFR part 60, appendix B--Performance Specifications. 
Utah included the requirements to calculate hourly average 
NOX concentrations for any hour in which fuel is combusted 
and a new 30-day rolling average emission rate at the end of each 
boiler operating day. Utah also noted that the hourly average 
NOX emission rate is valid only if the minimum number of 
data points specified in R307-170 is acquired for both the pollutant 
concentration monitor and diluent monitor.
    Under H.21, Utah did not provide for reporting of violations of 
PM10 emissions limitations for instances other than 
breakdowns (e.g., stack test violations). However, the State provided a 
commitment letter on December 10, 2015 to address this deficiency with 
a SIP revision within one year of EPA's final action on the June 4, 
2015 RH SIP.\54\
---------------------------------------------------------------------------

    \54\ Letter from Department of Environmental Quality, State of 
Utah to EPA, DAQP-120-15 (Dec. 10, 2015).
---------------------------------------------------------------------------

    Under H.22, Utah provided the NOX and PM10 
emission limitations for Hunter Units 1 through 3 and Huntington Units 
1 and 2, a requirement to perform annual stack testing for 
PM10, and a requirement to measure NOX via 
continuous emission monitoring for the sources covered under the Utah 
BART Alternative. Under H.22, Utah also listed the enforceable 
conditions related to closing Carbon Units 1 and 2 by August 15, 2015 
including PacifiCorp's and Utah's notification and permit rescission 
obligations.

C. Summary of Utah's Demonstration for Alternative Program

    As discussed previously in background section III.A, a state may 
opt to implement an alternative measure rather than to require sources 
subject to BART to install, operate, and maintain BART. Utah has 
included the following information in its June and October 2015 RH SIPs 
to address the regulatory criteria for an alternative program:

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

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

    Utah provided the same list of BART-eligible sources in the 2011 RH 
SIP. We determined that the State's SIP satisfies the requirements of 
40 CFR 51.309(e)(2)(i)(A) in our December 14, 2012 rulemaking.
2. A List of All BART-Eligible Sources and All BART Source Categories 
Covered by the Alternative Program
    Pursuant to 40 CFR 51.308(e)(2)(i)(B), each BART-eligible source in 
the State must be subject to the requirements of the alternative 
program or have a federally enforceable emission limitation determined 
by the State and approved by EPA as meeting BART. In this instance, the 
alternative program covers all the BART-eligible sources in the state, 
Hunter Units 1 and 2 and Huntington Units 1 and 2, in addition to three 
non-BART units, PacifiCorp's Hunter Unit 3 and Carbon Units 1 and 2.
    Utah provided the same list of BART sources subject to an 
alternative program in the 2011 RH SIP. We determined that the State's 
SIP satisfies the requirements of 40 CFR 51.309(e)(2)(i)(B) in our 
December 14, 2012 rulemaking.
3. Analysis of BART and Associated Emission Reductions Achievable
    Pursuant to 40 CFR 51.308(e)(2)(i)(C), the SIP must include an 
analysis of BART and associated emission reductions at Hunter and 
Huntington. In the June 2015 Utah RH SIP, the State compared the Utah 
BART Alternative to a BART Benchmark that included the most stringent 
NOX BART controls, SCR plus new LNBs and SOFA, at the four 
BART units.
4. Analysis of Projected Emissions Reductions Achievable Through the 
BART Alternative
    Pursuant to 40 CFR 51. 308(e)(2)(D), the SIP must include ``[a]n 
analysis of the projected emissions reductions achievable through the . 
. . alternative measure.'' A summary of the State's estimates of 
emissions in tons per year (tpy) for the Utah BART Alternative and the 
BART Benchmark is provided in Table 3. A summary of the emissions 
reductions based on those emission estimates is presented in Table 4.
---------------------------------------------------------------------------

    \55\ Utah Regional Haze State Implementation Plan, Technical 
Support Document, Ch. 1 (Reference Table 2) (2015).

                                 Table 3--Estimated Emissions Under Utah's BART Benchmark and the BART Alternative \55\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                              NOX emissions (tpy)         SO2 emissions (tpy)      PM10 emissions (tpy) \4\            Combined
                                         ---------------------------------------------------------------------------------------------------------------
                  Units                     Benchmark    Alternative    Benchmark    Alternative
                                               \2\           \3\           \2\           \3\        Benchmark    Alternative    Benchmark    Alternative
--------------------------------------------------------------------------------------------------------------------------------------------------------
Carbon 1................................         1,408             0         3,388             0           221             0         5,016             0
Carbon 2................................         1,940             0         4,617             0           352             0         6,909             0
Hunter 1 \1\............................           775         3,412         1,529         1,529           169           169         2,473         5,100
Hunter 2................................           843         3,412         1,529         1,529           169           169         2,541         5,110
Hunter 3................................         6,530         4,622         1,033         1,033           122           122         7,685         5,777
Huntington 1............................           809         3,593         1,168         1,168           176           176         2,153         4,937
Huntington 2............................           856         3,844         1,187         1,187           200           200         2,243         5,231
                                         ---------------------------------------------------------------------------------------------------------------
    Total...............................        13,161        18,882        14,451         6,446         1,409           836        29,020        26,164
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Hunter 1 controls were installed in the spring of 2014, therefore Hunter 2 actual emissions are used as a surrogate.
\2\ Most stringent NOX rate for BART-eligible units (see email and spreadsheet, ``Attachment to Utah September 16, 2015 email, BART Analysis.pdf'' in
  the docket, inadvertently omitted from Utah TSD), 2012-2013 actual emissions Carbon, 2001-2003 actual emissions Hunter 3 (EPA Acid Rain Program).
\3\ Average actual emissions 2012-13 for Hunter and Huntington units, EPA Acid Rain Program.
\4\ Actual emissions for 2012, Utah Department of Air Quality annual inventory.

[[Page 2016]]

  Table 4--EPA Summary of Emission Reductions Achievable With the Utah BART Alternative as Compared to the BART
                                                    Benchmark
----------------------------------------------------------------------------------------------------------------
                                                                    Combined emissions for all units  (tpy)
                         Description                         ---------------------------------------------------
                                                                  NOX          SO2          PM10       Combined
----------------------------------------------------------------------------------------------------------------
BART Benchmark..............................................       13,161       14,451        1,409       29,020
BART Alternative............................................       18,882        6,446          836       26,164
Emission Reduction (BART Benchmark minus BART Alternative)         -5,721        8,005          573        2,856
 \1\........................................................
----------------------------------------------------------------------------------------------------------------
\1\ A negative value indicates the BART Alternative results in more emissions of the specified pollutant in
  comparison to the BART Benchmark.

5. A Determination That the Alternative Achieves Greater Reasonable 
Progress Than Would Be Achieved Through the Installation and Operation 
of BART
    Pursuant to 40 CFR 51.308(e)(2)(i)(E), the State must provide a 
determination under 40 CFR 51.308(e)(3) or otherwise based on the clear 
weight of evidence that the alternative achieves greater reasonable 
progress than BART. 40 CFR 51.308(e)(3), in turn, provides two 
different tests for determining whether the alternative achieves 
greater reasonable progress than BART.
    Utah first used the ``greater emission reductions'' test in 40 CFR 
51.308(e)(3) to support its assertion that the BART Alternative 
achieves greater reasonable progress. In the June 2015 Utah RH SIP, the 
State noted that the Hunter, Huntington and Carbon plants are all 
located within 40 miles of each other in Central Utah. Utah stated that 
because of the close proximity of the three plants, the distribution of 
emissions would not be substantially different under the Utah BART 
Alternative than under BART. With the alternative measure resulting in 
greater aggregate emission reductions by 2,856 tons/year (tpy) 
(described in Table 4), Utah asserted that the alternative measure may 
be deemed to achieve greater reasonable progress than BART under 
51.308(e)(3).
    Utah also chose to conduct a weight-of-evidence analysis under 
51.308(e)(2) based on emissions from the Hunter, Huntington, and Carbon 
power plants and considered the following evidence: \56\
---------------------------------------------------------------------------

    \56\ Utah referenced that greater reasonable progress can be 
demonstrated using one of two methods: (1) greater emission 
reductions than under BART (40 CFR 51.308(e)(3)); or (2) based on 
the clear weight of evidence (40 CFR 51.308(e)(2)(i)(E)). Utah 
further explained that: As the U.S. Circuit Court of Appeals for the 
10th Circuit recently observed, the state is free to choose one 
method or the other. WildEarth Guardians v. E.P.A., 770 F.3d 919, 
935-37 (10th Cir. 2014). Finally, Utah noted that the court 
characterized the former approach as ``quantitative'' and the latter 
as ``qualitative,'' and specifically sanctioned the use of 
qualitative factors under the clear weight of evidence.
---------------------------------------------------------------------------

a. Annual Emissions Comparison for Visibility-impairing Pollutants
    The emissions of visibility-impairing pollutants from both the Utah 
BART Alternative and the BART Benchmark, as estimated by the State, are 
summarized in Table 3. Compared with the Utah BART Benchmark, the State 
projects that the Utah BART Alternative will result in 5,721 tpy more 
NOX emissions, 8,005 tpy fewer SO2 emissions and 
573 tpy fewer PM10 emissions. Utah also found that the 
combined emissions of NOX, SO2 and 
PM10 will be 2,856 tpy lower under the Utah BART 
Alternative.
b. Improvement in the Number of Days With Significant Visibility 
Impairment
    Utah provided modeling results to assess the improvement in the 
number of days with significant visibility impairment--that is, the 
improvement in the number of days with impacts that either cause (> 1.0 
dv) or contribute (> 0.5 dv) to visibility impairment. The State 
presented this information in a number of ways, including: (1) the 
average number of days per year for three years modeled (2001-2003) 
with impacts above the cause and contribute thresholds for the nine 
affected Class I areas under the BART Alternative as compared to under 
the BART Benchmark; and (2) the total number of days for the three 
years modeled with impacts above the thresholds for the nine Class I 
areas under the two scenarios.\57\
---------------------------------------------------------------------------

    \57\ Utah noted that EPA has proposed approval of an Alternative 
Measure for the Apache Generating Station in Arizona on similar 
``weight of evidence'' grounds. 79 FR 56322, 56327 (Sept. 19, 2014). 
Utah also noted that EPA has approved a similar Alternative Measure 
in Washington, based in part on a reduction in the number of days of 
impairment greater than 0.5 dv and 1.0 dv. 79 FR 33438, 33440-33442 
(June 11, 2014).
---------------------------------------------------------------------------

    On average for the three years modeled, the Utah BART Alternative 
causes visibility impairment (>1.0 dv) on fewer days than the BART 
Benchmark (258 days vs. 264 days, for the nine affected Class I areas). 
Similarly, on average for the three years modeled, the Utah BART 
Alternative also contributes to visibility impairment (>0.5 dv) on 
fewer days than the BART Benchmark (441 days vs. 499 days for the nine 
affected Class I areas). See Tables 5 and 6.
---------------------------------------------------------------------------

    \58\ Utah Regional Haze State Implementation Plan, Technical 
Support Document, Ch. 1 (Reference Table 5) (2015).

                         Table 5--Average (2001-2003) Number of Days >1.0 dv Impact \58\
----------------------------------------------------------------------------------------------------------------
                                                                                       BART            BART
                          Class I area                               Basecase       alternative      benchmark
----------------------------------------------------------------------------------------------------------------
Arches..........................................................             128              68              77
Black Canyon of the Gunnison....................................              36              10               9
Bryce Canyon....................................................              19               9               8
Canyonlands.....................................................             141              87              87
Capitol Reef....................................................              68              42              41
Flat Tops.......................................................              46              13              15
Grand Canyon....................................................              22              11              10
Mesa Verde......................................................              40              13              12
Zion............................................................              11               6               6
                                                                 -----------------------------------------------

[[Page 2017]]

 
    Total.......................................................             511             258             264
----------------------------------------------------------------------------------------------------------------

                         Table 6--Average (2001-2003) Number of Days >0.5 dv Impact \59\
----------------------------------------------------------------------------------------------------------------
                                                                                       BART            BART
                          Class I area                               Basecase       alternative      benchmark
----------------------------------------------------------------------------------------------------------------
Arches..........................................................             176             109             130
Black Canyon of the Gunnison....................................              75              27              34
Bryce Canyon....................................................              36              17              19
Canyonlands.....................................................             178             131             140
Capitol Reef....................................................              96              63              65
Flat Tops.......................................................              93              34              44
Grand Canyon....................................................              38              19              20
Mesa Verde......................................................              71              32              37
Zion............................................................              21              10              10
                                                                 -----------------------------------------------
    Total.......................................................             784             441             499
----------------------------------------------------------------------------------------------------------------

    As for the total number of days over the course of the three 
modeled years, the Utah BART Alternative causes visibility impairment 
(> 1.0 dv) on fewer days than the BART Benchmark (775 days vs. 793 days 
for the nine affected Class I areas). Similarly, in total for the three 
years modeled, the Utah BART Alternative also contributes to visibility 
impairment (> 0.5 dv) on fewer days than the BART Benchmark (1,323 days 
vs. 1,498 days for the nine affected Class I areas). See Tables 7 and 
8.
---------------------------------------------------------------------------

    \59\ See id., at Technical Support Document, Ch. 1 (Reference 
Table 6).
    \60\ See id., at Technical Support Document, Chapter 6.b 
(Summary of Visibility Modeling).

                          Table 7--Total (2001-2003) Number of Days >1.0 dv Impact \60\
----------------------------------------------------------------------------------------------------------------
                                                                                       BART            BART
                          Class I area                               Basecase       alternative      benchmark
----------------------------------------------------------------------------------------------------------------
Arches..........................................................             383             203             230
Black Canyon of the Gunnison....................................             108              31              28
Bryce Canyon....................................................              57              26              25
Canyonlands.....................................................             422             260             260
Capitol Reef....................................................             204             126             124
Flat Tops.......................................................             138              38              44
Grand Canyon....................................................              67              34              30
Mesa Verde......................................................             121              40              35
Zion............................................................              32              17              17
                                                                 -----------------------------------------------
    Total.......................................................           1,532             775             793
----------------------------------------------------------------------------------------------------------------

                          Table 8--Total (2001-2003) Number of Days >0.5 dv Impact \61\
----------------------------------------------------------------------------------------------------------------
                                                                                       BART            BART
                          Class I area                               Basecase       alternative      benchmark
----------------------------------------------------------------------------------------------------------------
Arches..........................................................             529             327             391
Black Canyon of the Gunnison....................................             224              81             103
Bryce Canyon....................................................             107              50              57
Canyonlands.....................................................             533             393             420
Capitol Reef....................................................             288             188             194
Flat Tops.......................................................             280             101             133
Grand Canyon....................................................             115              56              59
Mesa Verde......................................................             213              97             110
Zion............................................................              63              30              31
                                                                 -----------------------------------------------
    Total.......................................................           2,352           1,323           1,498
----------------------------------------------------------------------------------------------------------------

[[Page 2018]]

c. 98th Percentile Impact (dv)
    Utah explained that the only metric it evaluated that showed 
greater improvement for the BART Benchmark in comparison to the BART 
Alternative was the 98th percentile metric when visibility impacts were 
averaged across all Class I areas and meteorological years modeled. 
Utah's comparison of the modeled visibility impacts on the 98th 
percentile day (8th highest impacted day in a given meteorological 
year) for the most impacted year shows that the BART Benchmark would 
result in greater visibility improvement at five of the nine Class I 
areas, and is better on average across all nine Class I areas (0.11 dv 
difference). At two of the most impacted Class I areas, Canyonlands and 
Capitol Reef, Utah found that the 98th percentile metric indicates the 
BART Benchmark has 0.76 dv and 0.57 dv, respectively, greater 
improvement than the Utah BART Alternative. At other Class I areas, 
Utah found that the 98th percentile metric indicates that the BART 
Alternative provides greater visibility improvement (for example, 0.44 
dv at Flat Tops).
---------------------------------------------------------------------------

    \61\ See id.
---------------------------------------------------------------------------

    Utah noted that because high nitrate values occur primarily in the 
winter months, the BART Benchmark achieved greater modeled visibility 
improvement on certain winter days with high nitrate impacts. Utah 
stated its position that there is greater uncertainty regarding the 
effect of NOX reductions on wintertime nitrate values, and 
thus on visibility, because past NOX emission reductions 
have not resulted in corresponding reductions in monitored nitrate 
values during the winter months. Utah noted it has greater confidence 
in the visibility improvement due to reductions of SO2 
because past reductions have resulted in corresponding reductions in 
monitored sulfate values throughout the year.
d. Annual Average Impact (dv)
    As modeled by Utah, which used CALPUFF modeling results, the 
average annual dv impact is better under the Utah BART Alternative at 
five of the nine Class I areas, and is better on average across all the 
Class I areas. The average impact was calculated by averaging all daily 
modeling results for each year and then calculating a three-year 
average from the annual average. Utah's information shows that the BART 
Alternative is better than the BART Benchmark by 0.009 dv on average 
across all nine Class I areas.
e. 90th Percentile Impact (dv)
    Utah's comparison of the modeled visibility impacts at the 90th 
percentile (the 110th highest day across three years) dv impact shows 
that the Utah BART Alternative is better at seven of the nine Class I 
areas and is better averaged both across three years and across nine 
Class I areas by 0.006 dv.
f. Timing for the Emissions Reductions
    Utah provided the schedule for installation of controls as noted in 
Table 9. Utah discussed that NOX reductions at Hunter Units 
1 and 2 and Huntington Units 1 and 2 occurred between 2006 and 2014, 
earlier than was required by the Regional Haze Rule, providing a 
corresponding early and on-going visibility improvement. Utah cited the 
2014 10th Circuit Court of Appeals decision regarding the 309 program 
to support that such early reductions are properly included as weight 
of evidence in the State's analysis.

                     Table 9--Installation Schedule
------------------------------------------------------------------------
                                     Timing of control installation or
           Source/Unit                           shutdown
------------------------------------------------------------------------
Hunter 1........................  New LNB and SOFA-Spring 2014.
Hunter 2........................  New LNB and SOFA-Spring 2011.
Hunter 3........................  New LNB and OFA-Summer 2008.
Huntington 1....................  New LNB and SOFA-Fall 2010.
Huntington 2....................  New LNB and SOFA-December 2006.
Carbon 1........................  Shutdown August 2015.
Carbon 2........................  Shutdown August 2015.
------------------------------------------------------------------------

    The reductions under the Utah BART Alternative are required under 
the State SIP by August 2015, as noted in Table 5, providing an early 
and on-going visibility benefit as compared to BART.\62\ Installation 
and operation of the combustion control upgrades at Hunter and 
Huntington were made enforceable under Administrative Orders DAQE-
AN0102370012-08 and DAQE-AN0102380021-10.\63\
---------------------------------------------------------------------------

    \62\ Conforming permit amendments for the Carbon plant are due 
under the SIP by December 15, 2015. Section IX.H.22 of Utah's SIP 
requires PacifiCorp to cease operation of Carbon by August 15, 2015, 
notify the State of the permanent closure by September 15, 2015, and 
request rescission of Operating Permit #700002004 and Approval Order 
DAQE-AN0100810005-08 by September 15, 2015. The State is then 
required to rescind the operating permit and approval order by 
December 15, 2015.
    \63\ Copies of Administrative Orders DAQE-AN0102370012-08 and 
DAQE-AN0102380021-10 are included in the docket.
---------------------------------------------------------------------------

g. IMPROVE Monitoring Data
    Utah's SIP presents sulfate and nitrate monitoring data at the 
Canyonlands IMPROVE monitor that shows that ``sulfates are the dominant 
visibility impairing pollutant'' \64\ and that sulfate levels have 
decreased,\65\ and references similar results at other Class I areas in 
the TSD.\66\ Utah also presents data on trends in emissions from EGUs 
showing substantial reductions in emissions of both SO2 and 
NOX.\67\ Based on these data, Utah indicates it ``has 
confidence that the SO2 reductions will achieve meaningful 
visibility improvement,'' under the Utah BART Alternative, while ``the 
visibility improvement during the winter months due to NOX 
reductions is much more uncertain.'' \68\ Utah makes this point even 
though nitrate concentrations are highest in the winter, explaining 
that while there has been a reduction in NOX, the ammonium 
nitrate values do not show similar improvement in the winter 
months.\69\ Utah offers several possible explanations for the results, 
but does not provide any definitive conclusions.\70\
---------------------------------------------------------------------------

    \64\ Utah Regional Haze State Implementation Plan, Technical 
Support Document, Ch. 1, p. 12 (2015).
    \65\ Id. at p. 15.
    \66\ Id. at p. 12.
    \67\ Id. at p. 14.
    \68\ Id. at p.13.
    \69\ Id.
    \70\ Id. at pp. 16-19.
---------------------------------------------------------------------------

    Utah also presents data on the seasonality of park visitation and 
monitoring data for nitrate and sulfates. The data show that the 
highest measured nitrate concentrations occur in winter during the 
period of lowest park visitation, and that sulfates affect visibility 
throughout the year and are the dominant visibility impairing pollutant 
from anthropogenic sources during the high visitation period of March 
through November. Utah concludes that it has greater confidence that 
reductions in SO2 will be reflected in improved visibility 
for visitors to the Class I areas, while reductions in NOX 
will have a more uncertain benefit for visitors to Class I areas.
h. Energy and Non-Air Quality Benefits
    Utah stated that energy and non-air quality environmental impacts 
are one of the factors listed in CAA section 169A(g)(2) that must be 
considered when determining BART. The State noted that the Utah BART 
Alternative would avoid the energy penalty due to operating SCR units. 
PacifiCorp included the energy penalty in its BART analysis as part of 
the total cost for installing SCR on each of the units. The energy 
penalty costs are provided in Table 10.
---------------------------------------------------------------------------

    \71\ PacifiCorp quantified the energy penalty associated with 
SCR in its August 4, 2014 BART Analysis Update, Appendix A. See id. 
at p. 26 (Table 13 presents this information).

[[Page 2019]]

                     Table 10--SCR Energy Penalty 71
------------------------------------------------------------------------
                                                       Energy penalty
                    Source/unit                    ---------------------
                                                        kW       $/year
------------------------------------------------------------------------
Hunter Unit 1.....................................      2,090    494,247
Hunter Unit 2.....................................      2,090    494,247
Huntington Unit 1.................................      2,182    516,098
Huntington Unit 2.................................      2,182    516,098
                                                   ---------------------
    Total.........................................      8,544  2,020,690
------------------------------------------------------------------------

    Utah presented additional non-air quality benefits associated with 
the closure of the Carbon plant. First, it noted that solid wastes in 
the form of fly ash from the electrostatic precipitators and bottom ash 
conveyors which clean the residuals from the two steam generating units 
(the boilers), would be eliminated. These wastes are currently 
landfilled. The Carbon plant also runs water through the boilers as 
well as two cooling towers. This uses water and has associated 
wastewater discharge. Hauling the ash to the landfill requires 
additional fuel use and water or chemical dust suppression for 
minimization of fugitive dust. Finally, for maintenance and emergency 
purposes, Utah noted that the plant has a number of emergency 
generators, fire pumps, and ancillary equipment--all of which must be 
periodically operated, tested and maintained--with associated air 
emissions, fuel use, painting, and the like. Utah suggests that all of 
these non-air quality impacts are reduced as the result of closing the 
Carbon plant.
i. Cost
    Utah cited PacifiCorp's comments on the State's proposed SIP 
revision that the BART Alternative not only produces greater reasonable 
progress, including lower emissions and improved visibility, but that 
it does so at a significant capital cost savings to PacifiCorp and its 
customers as compared to the BART Benchmark. Utah acknowledged that it 
did not officially determine the cost of installing SCR on the four 
BART units, but that it believed the cost of installing SCR would be 
significant. On the other hand, Utah noted that the Carbon Plant has 
already been closed due to the high cost of complying with the MATS 
rule. Utah explained that the costs to Utah rate payers (and those in 
other states served by PacifiCorp) to replace the power generated by 
the Carbon Plant have already occurred; there will be no additional 
cost to achieve the co-benefit of visibility improvement. As a result, 
Utah asserted that the BART Alternative not only achieves better 
visibility improvements than would be achieved by requiring SCR as BART 
at the four EGUs, but at a significantly lower cost. The State believed 
this presents a classic ``win/win'' scenario--the BART Alternative 
results in greater reasonable progress that is achieved at a much lower 
price compared to SCR. The State also noted that cost is one of the 
factors listed in CAA section 169A(g)(2) that should be considered when 
determining BART.
6. Requirement That Emission Reductions Take Place During Period of 
First Long-Term Strategy
    Pursuant to 40 CFR 51.308(e)(2)(iii), the State must ensure that 
all necessary emission reductions take place during the period of the 
first long-term strategy for regional haze, i.e., by December 31, 2018. 
The RHR further provides that, ``[t]o meet this requirement, the State 
must provide a detailed description of the . . . alternative measure, 
including schedules for implementation, the emission reductions 
required by the program, all necessary administrative and technical 
procedures for implementing the program, rules for accounting and 
monitoring emissions, and procedures for enforcement.'' \72\
---------------------------------------------------------------------------

    \72\ 40 CFR 51.308(e)(2)(iii).
---------------------------------------------------------------------------

    As noted previously, the Utah SIP revision incorporates the 
revisions to R307-110-17, Section IX, Control Measures for Area and 
Point Sources, Part H, Emissions Limits, which includes provisions for 
implementing the Utah BART Alternative. In addition to the emission 
limitations for NOX and PM10, and the requirement 
for shutdown of the Carbon Plant listed in Table 2, the SIP includes 
compliance dates, operation and maintenance requirements, and 
monitoring, recordkeeping, and reporting requirements.
7. Demonstration That Emissions Reductions From Alternative Program 
Will Be Surplus
    Pursuant to 40 CFR 51.308(e)(2)(iv), the SIP must demonstrate that 
the emissions reductions resulting from the alternative measure will be 
surplus to those reductions resulting from measures adopted to meet 
requirements of the CAA as of the baseline date of the SIP. The 
baseline date for regional haze SIPs is 2002.\73\ Utah developed the 
2002 baseline inventory in the 2008 RH SIP for regional modeling, 
evaluating the impact on Class I areas outside of the Colorado Plateau, 
and BART as outlined in EPA Guidance and the July 6, 2005 BART Rule. 
Utah noted that 2002 is the baseline inventory that was used by other 
states throughout the country when evaluating BART under the provisions 
of 40 CFR 51.308 and that any measure adopted after 2002 is considered 
``surplus'' under 40 CFR 51.308(e)(2)(iv). Utah referenced other EPA 
actions that are consistent with this interpretation.\74\ Utah stated 
that the BART Benchmark scenario includes measures required before the 
baseline date of the SIP but does not include later measures that are 
credited as part of the BART Alternative scenario.
---------------------------------------------------------------------------

    \73\ See Memorandum from Lydia Wegman and Peter Tsirigotis, 2002 
Base Year Emission Inventory SIP Planning: 8-hr Ozone, 
PM2.5, and Regional Haze Programs (Nov. 18, 2002), 
available at http://www3.epa.gov/ttnchie1/eidocs/2002baseinven_102502new.pdf.
    \74\ 79 FR 33438, 33441-33442 (June 11, 2014); 79 FR 56322, 
56328 (Sept. 9, 2014).
---------------------------------------------------------------------------

    To address potential concerns with double counting SO2 
emissions reductions from the Carbon plant closure under both the 308 
and 309 programs, in addition to providing the explanation in the June 
2015 SIP (discussed in TSD Chapter 1, Section X), Utah's October 7, 
2015 SIP also includes enforceable commitments to address these 
concerns. The State explained how the WRAP modeling done to support the 
Utah RH backstop trading program SIP included regional SO2 
emissions based on the 2018 SO2 milestone and also included 
NOX and PM10 emissions from the Carbon plant. 
Actual emissions in the three-state region are calculated each year and 
compared to the milestones. Utah provided Table 11 to show that in 2011 
emissions were below the 2018 milestone (141,849 tpy). Utah noted that 
the most recent milestone report for 2013 demonstrates that 
SO2 emissions are currently 26 percent lower than the 2018 
milestone. Utah stated that the Carbon plant was fully operational in 
the years 2011-2013 when the emissions were below the 2018 milestone. 
The State noted that the SO2 emission reductions from the 
closure of the Carbon plant are surplus to what is needed to meet the 
2018 milestone established in Utah's RH SIP.
---------------------------------------------------------------------------

    \75\ See Utah Regional Haze State Implementation Plan, Technical 
Support Document, Ch. 1 (Reference Table 15) (2015).

[[Page 2020]]

                                        Table 11--SO2 Milestone Trends 75
----------------------------------------------------------------------------------------------------------------
                                                                                    Three-Year
                                                                     Milestone      average SO2    Carbon plant
                              Year                                     (tpy)       emissions \1\   SO2 emissions
                                                                                       (tpy)           (tpy)
----------------------------------------------------------------------------------------------------------------
2003............................................................         303,264         214,780           5,488
2004............................................................         303,264         223,584           5,642
2005............................................................         303,264         220,987           5,410
2006............................................................         303,264         218,499           6,779
2007............................................................         303,264         203,569           6,511
2008............................................................         269,083         186,837           5,057
2009............................................................         234,903         165,633           5,494
2010............................................................         200,722         146,808           7,462
2011............................................................         200,722         130,935           7,740
2012............................................................         200,722         115,115           8,307
2013............................................................         185,795         105,084           7,702
2014............................................................         170,868
2015............................................................         155,940
2016............................................................         155,940
2017............................................................         155,940
2018............................................................         141,849
----------------------------------------------------------------------------------------------------------------
\1\ The three-year average is based on the emissions averaged for the current and two preceding years.

    For Hunter Unit 3, Utah also explained that PacifiCorp upgraded the 
LNB controls in 2008 and that the upgrade was not required under the 
requirements of the CAA as of the 2002 baseline date of the SIP; the 
emission reductions from the upgrade are therefore considered surplus 
and creditable for the BART Alternative under 40 CFR 51.308(e)(2)(iv). 
Utah noted that prior to the 2008 upgrade, the emission rate for Hunter 
Unit 2 was 0.46 lb/MMBtu heat input for a 30-day rolling average as 
required by Phase II of the Acid Rain Program.\76\
---------------------------------------------------------------------------

    \76\ There is a typographical error in Chapter 1, section X.C, 
PacifiCorp Hunter Unit 3, p. 31. The reference to Hunter Unit 2 
should be Unit 3 based on the section heading as well as confirmed 
emission limits in Utah Approval Order DAQE-AN0102370012-08.
---------------------------------------------------------------------------

D. Summary of Utah's Enforceable Commitment SIP Revision

    To address potential concerns that Utah would be double counting 
SO2 emissions reductions for the Carbon plant closure under 
both the 40 CFR 51.308 and 309 programs, on October 7, 2015 the State 
adopted an enforceable commitment into the Utah RH SIP at Chapter XX, 
Section N. Utah submitted this SIP revision to EPA on October 20, 2015. 
In this commitment, the State explained that it will continue to report 
the historical emissions for the Carbon plant in the annual milestones 
reports from 2016 through the life of the backstop trading program. In 
addition, the State has committed to making revisions as necessary to 
SIP Section XX.D.3.c (``Triggering the Trading Program'') and State 
rule R307-150 (``Emission Inventories Program'') as well as any other 
applicable provisions to implement the requirement for reporting 
Carbon's historical emissions under the 309 program. The State notes it 
will follow its SIP adoption process when making these SIP revisions. 
The SIP will be adopted by the Governor-appointed Air Quality Board 
through a rulemaking process that includes public participation. Once 
approved into the SIP, the commitment will be enforceable by both EPA 
and citizens under the CAA.
    The State noted that EPA has historically recognized that, under 
certain circumstances, issuing full approval may be appropriate for a 
SIP submission that consists of, in part, an enforceable commitment. 
Utah explained that its October 2015 submission satisfies EPA's 
requirements for enforceable commitments because it has adopted such a 
commitment for what is a small portion of its regional haze program in 
relation to its regional haze obligations as a whole. In addition, 
Carbon's 8,005 tpy SO2 emissions reductions is small in 
comparison to the 2018 milestone of 141,849 tpy described in Table 7.
    On the matter of timing, the State has committed to providing the 
required subsequent SIP submittal by mid-March 2018.

E. Consultation With FLMs

    Utah's SIPs do not specifically discuss how it addressed the 
requirements of 40 CFR 308(i)(2) for providing the FLMs with an 
opportunity for consultation at least 60 days prior to holding the 
public hearing for the June 2015 RH SIP. However, we are aware that 
Utah consulted with the FLMs and explain those efforts here. The State 
held an initial public comment period for proposed SIP amendments from 
November 1 through December 22, 2014. The State provided the 
opportunity for the FLMs to review the preliminary draft SIP documents 
via email approximately 68 days prior to the public hearing that was 
held on a December 1, 2014. Copies of the email correspondence 
documenting this effort are included in the docket.
    Utah received a number of comments during the public comment period 
in late 2014. After reviewing the comments and consulting with EPA, 
Utah determined additional work was needed to develop a BART 
alternative measure that would take credit for emission reductions from 
the Carbon plant shutdown among other things. Utah held an additional 
public comment period from April 1 through April 30, 2015. One of the 
FLMs, the National Park Service, provided extensive public comments to 
Utah during this second public comment period and Utah included 
responses to these comments, along with responses to other commenters, 
in the June 2015 RH SIP submittal along with other administrative 
documentation.
    The October 2015 Utah RH SIP was provided for public comment August 
15 through September 14, 2015, and we are not aware of any prior FLM 
consultation on this SIP. The FLMs did not submit comments during this 
public comment period.

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

    As explained in section II.A, EPA is soliciting comments on two 
alternative proposals: A proposal to approve the State SIP in its 
entirety, and a proposal to partially approve and partially

[[Page 2021]]

disapprove the State SIP and to issue a FIP. The co-proposals detailed 
in this section and Section VI represent different conclusions 
regarding Utah's NOX BART Alternative and the metrics the 
State has proposed to support this alternative. As described in this 
section, EPA is proposing to approve the two Utah 2015 RH SIP 
revisions. Alternatively, as discussed in section VI, EPA is co-
proposing to disapprove the Utah's June 2015 and October 2015 RH SIP 
revisions and promulgate a FIP.
    This document is written as two separate proposals in order to 
clearly present the options and solicit comment on each. EPA intends to 
finalize only one of these co-proposals; however, we also acknowledge 
that additional information and comments may also lead the Agency to 
adopt final SIP and/or FIP regulations that differ somewhat from the 
co-proposals presented here regarding the BART Alternative, BART 
control technology option or emission limits, or impact other proposed 
regulatory provisions.

A. Basis for Proposed Approval

    For the reasons described later on, EPA proposes to approve the two 
Utah 2015 RH SIP revisions. Our proposed action is based on an 
evaluation of Utah's regional haze SIP submittals against the regional 
haze requirements at 40 CFR 51.300-51.309 and CAA sections 169A and 
169B. All general SIP requirements contained in CAA section 110, other 
provisions of the CAA, and our regulations applicable to this action 
were also evaluated. The purpose of this proposed action is to ensure 
compliance with these requirements and to provide additional rationale 
to support our conclusions.

B. Utah BART Alternative

1. Summary of Utah BART Alternative
    Utah has opted to establish an alternative measure (or program) for 
NOX in accordance with 40 CFR 51.308(e)(2). A description of 
the Utah BART Alternative is provided in section IV.B.1. The RHR 
requires that a SIP revision establishing a BART alternative include 
three elements as listed later. We have evaluated the Utah BART 
Alternative with respect to each of these elements.
     A demonstration that the emissions trading program or 
other alternative measure will achieve greater reasonable progress than 
would have resulted from the installation and operation of BART at all 
sources subject to BART in the State and covered by the alternative 
program.\77\
---------------------------------------------------------------------------

    \77\ 40 CFR 51.308(e)(2)(i).
---------------------------------------------------------------------------

     A requirement that all necessary emissions reductions take 
place during the period of the first long-term strategy for regional 
haze.\78\
---------------------------------------------------------------------------

    \78\ 40 CFR 51.308(e)(2)(iii).
---------------------------------------------------------------------------

     A demonstration that the emissions reductions resulting 
from the alternative measure will be surplus to those reductions 
resulting from measures adopted to meet requirements of the CAA as of 
the baseline date of the SIP.\79\
---------------------------------------------------------------------------

    \79\ 40 CFR 51.308(e)(2)(iv).
---------------------------------------------------------------------------

2. Demonstration of Greater Reasonable Progress for the Alternative 
Program
    As discussed previously in section III.E.1, pursuant to 40 CFR 
51.308(e)(2)(i), Utah must demonstrate that the alternative measure 
will achieve greater reasonable progress than would have resulted from 
the installation and operation of BART at all sources subject to BART 
in the State and covered by the alternative program. This 
demonstration, primarily included in Chapter 1 of the TSD of the Utah 
RH SIP,\80\ must be based on five criteria which are addressed later.
---------------------------------------------------------------------------

    \80\ As presented in this proposal, while the majority of the 
State's demonstration is contained in Chapter 1, EPA has identified 
additional information regarding the demonstration and we include 
references to the additional information.
---------------------------------------------------------------------------

a. A List of All BART-Eligible Sources Within the State
    As discussed previously in section IV.A.2, Utah included a list of 
BART-eligible sources and noted the following sources are all covered 
by the alternative program:

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

    EPA previously approved Utah's BART eligibility determinations in 
our 2012 rulemaking.\81\
---------------------------------------------------------------------------

    \81\ 77 FR 74357 (Dec. 14, 2012).
---------------------------------------------------------------------------

b. A List of All BART-Eligible Sources and All BART Source Categories 
Covered by the Alternative Program
    As discussed previously in section IV.A.3, the Utah BART 
Alternative covers all the BART-eligible sources in the state, Hunter 
Units 1 and 2 and Huntington Units 1 and 2, in addition to three non-
BART units, PacifiCorp's Hunter Unit 3 and Carbon Units 1 and 2. EPA 
previously approved Utah's BART eligibility determinations in our 2012 
rulemaking.\82\
---------------------------------------------------------------------------

    \82\ 77 FR 74355, 74357 (Dec. 14, 2012).
---------------------------------------------------------------------------

c. Analysis of BART and Associated Emission Reductions
    As noted in section IV.C.3, in the June 2015 Utah RH SIP, the State 
compared the Utah BART Alternative to a BART Benchmark that included 
the most stringent NOX BART controls, SCR plus new LNBs and 
SOFA, at the four BART units. This is consistent with the streamlined 
approach described in Step 1 of the BART Guidelines. The BART 
Guidelines note that a comprehensive BART analysis can be avoided if a 
source commits to a BART determination that consists of the most 
stringent controls available.\83\
---------------------------------------------------------------------------

    \83\ 40 CFR 51, appendix Y, section IV.D.1.9.
---------------------------------------------------------------------------

    We propose to find that Utah has met the requirement for an 
analysis of BART and associated emission reductions achievable at 
Hunter and Huntington under 40 CFR 51.308(e)(2)(i)(C).
d. Analysis of Projected Emissions Reductions Achievable Through the 
BART Alternative
    As discussed previously in section IV.C.4, a summary of Utah's 
estimates of emissions for the Utah BART Alternative and the BART 
Benchmark is provided in Table 3. We propose to find that Utah has met 
the requirement for an analysis of the projected emissions reductions 
achievable through the alternative measure under 40 CFR 
51.308(e)(2)(i)(D).
e. A Determination That the Alternative Achieves Greater Reasonable 
Progress Than Would Be Achieved Through the Installation and Operation 
of BART
Greater Reasonable Progress Based on 40 CFR 51.308(e)(3)'s Greater 
Emission Reductions Test
    EPA's evaluation of the State's demonstration based on 40 CFR 
51.308(e)(3) is located in section VI.B.2.e.
Greater Reasonable Progress Based on 40 CFR 51.308(e)(2)'s Weight-of-
Evidence Test
    Although Utah found that the BART Alternative demonstrates greater 
reasonable progress under 40 CFR 51.308(e)(3), it also chose to conduct 
a weight-of-evidence analysis under 40 CFR 51.308(e)(2) based on a BART 
Alternative involving the Hunter, Huntington, and Carbon power plants 
and considered the following evidence:
i. Annual Emissions Comparison for Visibility-Impairing Pollutants
    The emissions of visibility-impairing pollutants from both the Utah 
BART Alternative and the BART Benchmark, as estimated by Utah, are 
summarized in Table 3 in section IV.C.4. Compared with the Utah BART 
Benchmark, the State projects that the Utah BART Alternative will 
result in 5,721 tpy more

[[Page 2022]]

NOX emissions, 8,005 tpy fewer SO2 emissions, and 
573 tpy fewer PM10 emissions than the BART Benchmark. Utah 
also found that the combined emissions of NOX, 
SO2 and PM10 will be 2,856 tpy lower under the 
BART Alternative.
    We propose to concur with Utah's finding that the BART Alternative 
will achieve greater SO2 and PM10 emissions 
reductions and greater aggregate emissions reductions of all 
pollutants. We further propose to recognize that not all pollutants 
impact visibility equally and that the total emissions reductions of 
all pollutants is not necessarily a direct indicator of whether the 
BART Alternative or the BART Benchmark will achieve greater reasonable 
progress. However, for reasons described later in subsection vii for 
our evaluation of Utah's IMPROVE monitoring metric, we propose to 
concur with Utah's finding that SO2 emissions reductions 
should provide visibility benefits in all seasons and that sulfate is 
the largest contributor to visibility impairment at the affected Class 
I areas. Furthermore, we propose to find that these observations 
suggest that the BART Alternative is likely to achieve greater 
reasonable progress. We note that Utah has also provided CALPUFF 
modeling results for the BART Benchmark and BART Alternative scenarios 
to assess the relative visibility benefits of each. These modeling 
results are considered here by EPA as part of the overall weight-of-
evidence analysis.
ii. Improvement in the Number of Days With Significant Visibility 
Impairment
    As discussed previously in section IV.C.5, Utah provided modeling 
results to assess the improvement in the number of days with 
significant visibility impairment--that is, the improvement in the 
number of days with impacts that either cause (>1.0 dv) or contribute 
(>0.5 dv) to visibility impairment.
    The BART Guidelines provide that, when making a BART determination, 
a State may consider the number of days or hours that a threshold was 
exceeded.\84\ In developing the BART Guidelines, our example modeling 
analysis of a hypothetical source examined the number of days that 1.0 
dv and 0.5 dv thresholds were exceeded.\85\ In addition, we have used 
these metrics, and in particular the total number of days for the 
meteorological years modeled, in previous regional haze rulemakings 
such as for North Dakota,\86\ Montana,\87\ and Washington.\88\
---------------------------------------------------------------------------

    \84\ 40 CFR 51, appendix Y, section IV.D.5.
    \85\ 70 FR 39130 (July 6, 2005).
    \86\ 76 FR 58584 (Sept. 21, 2011).
    \87\ 77 FR 24006 (Apr. 20, 2012).
    \88\ 79 FR 33438, 33440-33441 (June 11, 2014).
---------------------------------------------------------------------------

    This metric is useful in assessing the frequency and duration of 
significant visibility impacts from a source or small group of sources. 
Therefore, for this reason and because these metrics are supported by 
our regulations and past practice, we propose to find the State's use 
of these metrics is appropriate. Moreover, we propose to find the 
difference in the total number of days impacted--18 fewer days greater 
than the causation threshold of 1.0 dv (775 days for the BART 
Alternative vs. 793 days for the BART Benchmark), and 175 fewer days 
greater than the contribution 0.5 dv threshold (1,323 days for the BART 
Alternative vs. 1,498 days for the BART Benchmark)--is an indication 
that the BART Alternative achieves greater reasonable progress.
iii. 98th Percentile Impact (dv)
    As discussed previously in section IV.C.5, Utah explained that the 
only metric it evaluated that showed greater improvement for the BART 
Benchmark in comparison to the BART Alternative was the 98th percentile 
metric (when averaged across all Class I areas and meteorological years 
modeled). Utah's comparison of the modeled visibility impacts on the 
98th percentile day (8th highest impacted day in a given meteorological 
year) for the most impacted year shows that the BART Benchmark would 
result in greater visibility improvement at five of the nine Class I 
areas, and is slightly better on average across all nine Class I areas 
(0.11 dv difference). At the most impacted Class I areas, Canyonlands 
and Capitol Reef, Utah found that the 98th percentile metric indicates 
the BART Benchmark has 0.76 dv and 0.57 dv, respectively, more 
improvement than the BART Alternative. At other Class I areas, Utah 
found that the 98th percentile metric indicates that the BART 
Alternative provides greater visibility improvement (for example, 0.44 
dv at Flat Tops).
    The 98th percentile visibility impact is a key metric recommended 
by the BART Guidelines \89\ when selecting BART controls. In addition, 
this is one of the primary metrics that EPA has relied on in evaluating 
prior regional haze actions that have included BART alternatives.\90\ 
In the BART Guidelines, EPA described this metric as an appropriate 
measure in determining the degree of visibility improvement expected 
from controls.\91\ Therefore, we propose to find that it is an 
appropriate metric for assessing the relative benefits of the Utah BART 
Alternative here.
---------------------------------------------------------------------------

    \89\ 40 CFR 51, appendix Y, section IV.D.5.
    \90\ See, e.g., 78 FR 79344 (Dec. 30, 2012)(proposed rule, FIP 
for Tesoro Refining and Intalco Refinery BART Alternatives); 79 FR 
33438 (June 11, 2014)(final rule, FIP for Tesoro Refining and 
Intalco Refinery BART Alternatives); 79 FR 56322, 56328 (Sept. 19, 
2014)(proposed approval of Arizona Apache BART Alternative); 80 FR 
19220 (April 10, 2015)(final approval of Arizona Apache BART 
Alternative); 77 FR 11827, 11837 (Feb. 28, 2012)(proposed approval 
of Maryland BART Alternative); 77 FR 39938, 39940-1 (July 6, 
2012)(final approval of Maryland BART Alternative).
    \91\ 70 FR at 39129.
---------------------------------------------------------------------------

    We note that when calculating visibility improvements for 
individual Class I areas, Utah mixed the impacts from different 
meteorological years between modeling scenarios (baseline, BART 
benchmark, and BART Alternative). This may introduce some error as the 
visibility improvements could be driven by year-to-year variability in 
meteorological conditions, as opposed to the differences in emission 
reductions between the BART Alternative and BART Benchmark. For this 
reason, in addition to considering the State's numbers, EPA also 
calculated the visibility improvements for each modeling scenario using 
consistent meteorological years.\92\ Using this method, whether the 
BART Alternative resulted in lower 98th percentile impacts depended on 
both the particular Class I area and meteorological year modeled. In 
some years and some Class I areas, particularly some of the most 
impacted Class I areas, the BART Benchmark shows better visibility 
improvement than the BART Alternative. Notably, the BART Benchmark 
shows 0.93 dv greater improvement for Canyonlands in 2002 and 0.75 dv 
greater improvement for Capitol Reef in 2001.\93\ By contrast, the BART 
Alternative shows 0.90 dv greater improvement for Arches in 2003 and 
0.43 dv greater improvement for Flat Tops in 2002.\94\ On the whole, 
when using this method, the BART Benchmark is better on average across 
all years and nine Class I areas (0.14 dv difference). See Table 12. We 
propose to find, consistent with the State's evaluation, that this 
metric favors the BART Benchmark.
---------------------------------------------------------------------------

    \92\ See EPA Calculation of 98th Percentile Improvement for Utah 
Bart Alternative spreadsheet (in docket).
    \93\ Id.
    \94\ Id.

[[Page 2023]]

   Table 12--Summary of EPA Comparison of Utah CALPUFF 98th Percentile
      Modeling Results Based on Consistent Meteorological Years 95
------------------------------------------------------------------------
                                                            Average
                                                           visibility
                                                        improvement  of
                     Class I Area                       BART  benchmark
                                                           over BART
                                                          alternative
                                                         (delta dv)\1\
------------------------------------------------------------------------
Arches...............................................              -0.21
Black Canyon of the Gunnison.........................               0.06
Bryce Canyon.........................................               0.04
Canyonlands..........................................               0.78
Capitol Reef.........................................               0.59
Flat Tops............................................              -0.15
Grand Canyon.........................................               0.06
Mesa Verde...........................................               0.12
Zion.................................................               0.02
Class I Area Average.................................               0.14
------------------------------------------------------------------------
\1\ A negative value indicates the modeling results favor the BART
  Alternative. Results are based on the three-year average of results
  for 2001, 2002 and 2003.

iv. Annual Average Impact (dv)
    As discussed previously in section IV.C.5, Utah's modeling shows 
that the average annual dv impact at all Class I areas is better under 
the Utah BART Alternative at five of the nine Class I areas, and is 
better on average across all the Class I areas. The average impact was 
calculated by averaging all daily modeling results for each year and 
then calculating a 3-year average from the annual average. Utah's 
information shows that the BART Alternative is better than the BART 
Benchmark by 0.009 dv on average across all nine Class I areas. While 
EPA has not considered this metric in the past,\96\ since the State 
includes it, we consider it here. Furthermore, the BART Guidelines 
state that, ``in determining what, if any, emission controls should be 
required, the State will have the opportunity to consider the 
frequency, duration, and intensity of a source's predicted effect on 
visibility.'' \97\ The annual average does provide an indication of the 
modeled visibility impacts for the entire year while the 98th 
percentile modeled results speak to a particular day (the 8th highest 
impacted day). Accordingly, and while we have typically relied 
primarily on the 98th percentile impacts in evaluating BART controls in 
other actions, we propose to find that the annual average impact 
provides additional useful information in considering Utah's weight of 
evidence. However, given that the difference in this metric is small 
(0.009 dv), we propose to find that it only marginally supports a 
conclusion that the BART Alternative achieves greater reasonable 
progress.
---------------------------------------------------------------------------

    \95\ Id.
    \96\ EPA final actions on BART alternatives that evaluated 
CALPUFF modeling analysis, which did not include consideration of 
annual average dv impacts include: 80 FR 19220 (April 10, 
2015)(Region 9, Apache); 79 FR 33438 (June 11, 2014)(Region 10, 
Tesoro Refining and Alcoa Intalco Operations); 77 FR 39938 (July 6, 
2012)(Region 3, Maryland HAA).
    \97\ 70 FR 39121 (July 5, 2005).
---------------------------------------------------------------------------

v. 90th Percentile Impact (dv)
    As discussed previously in section IV.C.5, Utah's comparison of the 
modeled visibility impacts at the 90th percentile (the 110th highest 
day across three years) dv impact shows that the Utah BART Alternative 
is better at seven of the nine Class I areas and is slightly better 
averaged both across three years and across nine Class I areas (0.006 
dv difference). We note that the use of the 90th percentile impacts to 
evaluate alternatives has not been EPA's practice for source-specific 
BART determinations; however, as discussed previously for the average 
dv impact metric, the BART Guidelines allow states to consider other 
visibility metrics in addition to the 98th percentile. Yet, because of 
the small difference between the two scenarios (0.006 dv), we propose 
to find that it only marginally supports a conclusion that the BART 
Alternative achieves greater reasonable progress.
vi. Timing for the Emissions Reductions
    As discussed previously in section IV.C.5, Utah noted that 
reductions under the Utah BART Alternative will occur earlier than the 
BART Benchmark. The reductions under the Utah BART Alternative are 
required under the State SIP by August 2015, as noted in Table 5, 
providing an early and on-going visibility benefit as compared to BART. 
Also notable is that combustion control upgrades at the Hunter and 
Huntington facilities have been achieving significant NOX 
reductions since the time of their installation between 2006 and 2014, 
depending on the unit. If, as proposed in section VI.C, BART for the 
four units is LNB/SOFA plus SCR, BART likely would be fully implemented 
sometime between 2019 and 2021.
    Therefore, we note that the reductions from the BART Alternative 
will occur before the BART Benchmark.
vii. IMPROVE Monitoring Data
    Utah's SIP presents sulfate and nitrate monitoring data at the 
Canyonlands IMPROVE monitor that show that ``sulfates are the dominant 
visibility impairing pollutant'' \98\ and that sulfate levels have 
decreased,\99\ and references similar results at other Class I areas in 
the TSD.\100\ Utah also presents data on trends in emissions from EGUs 
showing substantial reductions in emissions of both SO2 and 
NOX.\101\ Based on these data, Utah indicates it ``has 
confidence that the SO2 reductions will achieve meaningful 
visibility improvement,'' under the Utah BART Alternative, while ``the 
visibility improvement during the winter months due to NOX 
reductions is much more uncertain.'' \102\ Utah makes this point even 
though nitrate concentrations are highest in the winter, explaining 
that while there has been a reduction in NOX, the ammonium 
nitrate values do not show similar improvement in the winter 
months.\103\ Utah offers several possible explanations for the results, 
but does not provide any definitive conclusions.\104\
---------------------------------------------------------------------------

    \98\ Utah Regional Haze State Implementation Plan, Technical 
Support Document, Ch. 1, p. 12 (2015).
    \99\ Id. at p. 15.
    \100\ Id. at p.12.
    \101\ Id. at p. 14.
    \102\ Id. at p. 13.
    \103\ Id.
    \104\ Id. at pp. 16-19.
---------------------------------------------------------------------------

    Utah also presents data on the seasonality of park visitation and 
monitoring data for nitrate and sulfates. The data show that the 
highest measured nitrate concentrations occur in winter during the 
period of lowest park visitation, and that sulfates affect visibility 
throughout the year and are the dominant visibility impairing pollutant 
from anthropogenic sources during the high visitation period of March 
through November. Utah concludes that it has greater confidence that 
reductions in SO2 will be reflected in improved visibility 
for visitors to the Class I areas, while reductions in NOX 
will have a more uncertain benefit for visitors to Class I areas.
    We invite comment on the information and conclusions provided by 
Utah as summarized previously.
    We propose to concur with one of the State's findings. We propose 
to find that visibility benefits associated with NOX 
reductions are much more likely to occur in the winter months because 
this is when aerosol thermodynamics favors nitrate formation.\105\ By 
contrast, SO2 emissions reductions should provide

[[Page 2024]]

visibility benefits in all seasons.\106\ We also propose to find that, 
as concluded by the GCVTC, and supported by the IMPROVE monitoring data 
presented by Utah, anthropogenic visibility impairment on the Colorado 
Plateau is dominated by sulfates.107 108 Therefore, we 
propose to concur with Utah's statement that sulfate is the largest 
contributor to visibility impairment at the affected Class I areas.
---------------------------------------------------------------------------

    \105\ Fountoukis, C. & Nenes, A. ISORROPIA II: A Computationally 
Efficient Aerosol Thermodynamic Equilibrium Model for K+, 
Ca2+, Mg2+, 
NH4+, Na+, 
SO42-, NO3-, Cl-, 
H2O Aerosols, 7 Atmos. Chem. Phys., 4639-4659 (2007).
    \106\ Seinfeld, John H., Urban Air Pollution: State of the 
Science, 243 Science Magazine, No. 4892, 745, 745-752 (1989).
    \107\ While natural sources of haze from wildfires or windblown 
dust can be the largest contributor on some of the 20% haziest days, 
the RHR defines ``impairment'' as anthropogenic impairment, and 
sulfate formed from anthropogenic SO2 emissions is the 
dominant contributor to anthropogenic visibility impairment on the 
haziest days.
    \108\ The Grand Canyon Visibility Transport Commission 
Recommendations for Improving Western Vistas, June 10, 1996, p. 32. 
Available at http://www.wrapair.org/WRAP/reports/GCVTCFinal.PDF and 
included in the docket.
---------------------------------------------------------------------------

    We propose to disagree with the State's findings related to park 
visitation. While the BART Guidelines do mention visitation as 
something that can inform a control decision,\109\ EPA is proposing to 
place little weight on the State's correlation of emissions reductions 
and park visitation because nothing in the CAA suggests that visitors 
during busy time periods are entitled to experience better visibility 
than visitors during off-peak periods. On the contrary, in the Regional 
Haze provisions of the CAA, Congress declared a national goal of 
remedying all manmade visibility impairment in all class I areas, which 
includes both heavily-visited national parks and seldom-visited 
wilderness areas. We invite comment on our evaluation and the 
information and conclusions provided by Utah as summarized previously.
---------------------------------------------------------------------------

    \109\ 70 FR 39104, 39130 (July 6, 2005) (``Other ways that 
visibility improvement may be assessed to inform the control 
decisions would be to examine distributions of the daily impacts, 
determine if the time of year is important (e.g. high impacts are 
occurring during tourist season), consideration of the cost-
effectiveness of visibility improvements (i.e. the cost per change 
in deciview), using the measures of deciview improvement identified 
by the State, or simply compare the worst case days for the pre- and 
post-control runs. States may develop other methods as well.'').
---------------------------------------------------------------------------

viii. Energy and Non-Air Quality Benefits
    As discussed previously in section IV.C.5, the State noted that the 
Utah BART Alternative would avoid an annual energy penalty of 
approximately $2 million due to operating four SCR units at the Hunter 
and Huntington plants and presented additional non-air quality benefits 
associated with the closure of the Carbon plant such as waste reduction 
and decreased water usage. Because such benefits do not have direct 
bearing on whether the BART Alternative achieves greater reasonable 
progress, it is not material to our action whether we agree or disagree 
with Utah's assessment that they reduce energy and non-air quality 
impacts.
ix. Cost
    As discussed previously in section IV.C.5, the State noted that the 
Utah BART Alternative would achieve greater reasonable progress at 
lower cost to PacifiCorp than the BART Benchmark. Utah also noted that 
cost is one of the factors listed in CAA 169A(g)(2) that should be 
considered when determining BART. While we propose to find that the 
described cost difference does not have a direct bearing on whether the 
BART Alternative achieves greater reasonable progress, it is not 
material to our action whether we agree or disagree with Utah's 
conclusion that the BART Alternative would have a lower cost impact to 
PacifiCorp than the BART Benchmark (i.e., costs provided by PacifiCorp 
in its BART analyses of August 5, 2014, SIP TSD Chapter 2). However, we 
do agree.
f. Evaluation of the Weight of Evidence
    In accordance with our regulations governing BART alternatives, we 
support the use of a weight-of evidence determination as an alternative 
to the methodology set forth in section 51.308(e)(3).\110\ In 
evaluating Utah's weight-of-evidence demonstration, we have evaluated 
all nine elements of Utah's analysis, and as discussed later, rely 
primarily on the following four elements in proposing to approve the 
BART Alternative: Annual emissions comparison for two pollutants; 
improvement in the number of days with significant visibility 
impairment; IMPROVE monitoring data regarding sulfates; and the early 
timing for installation of controls. Additional elements that either 
marginally support or do not support our proposed approval of Utah's 
determination are also discussed later.
---------------------------------------------------------------------------

    \110\ 71 FR 60622 (Oct. 13, 2006).
---------------------------------------------------------------------------

    Regarding the emissions reduction comparison, the Utah BART 
Alternative will result in 8,005 tpy fewer SO2 emissions 
compared to the BART Benchmark. In addition, the combined emissions of 
NOX, SO2 and PM10 will be 2,856 tpy 
lower under the BART Alternative.
    Regarding the improvement in the number of days with significant 
visibility impairment, modeling submitted by Utah shows that the Utah 
BART Alternative will result in improved visibility at all affected 
Class I areas compared with baseline conditions. The units at issue 
will have impacts of 1.0 dv or more at the affected Class I areas on 48 
fewer days under the Utah BART Alternative as compared to BART. When 
considering impacts of 0.5 dv or more, the units at issue will impact 
the affected Class I areas on 154 fewer days under the BART Alternative 
as compared to BART.
    Regarding the IMPROVE visibility monitoring data, we propose to 
agree with the State's finding that SO2 emissions reductions 
provide visibility benefits throughout the year. We also propose to 
concur with Utah's statement that sulfate is the largest contributor to 
visibility impairment at the affected Class I areas.
    Regarding the timing of emissions reductions, these SO2 
emissions reductions were achieved in August 2015, the date in the June 
2015 Utah RH SIP requiring the closure of the Carbon plant. Combustion 
controls at the four BART units in addition to Hunter Unit 3 were 
installed between 2006 and 2014. BART likely would otherwise have been 
implemented sometime between 2019 and 2021. So the Utah BART 
Alternative provides early and on-going visibility benefits as compared 
to BART.
    Regarding other metrics that only marginally support or do not 
support our proposed approval of Utah's BART Alternative, we propose to 
find that average annual dv impact and the 90th percentile impact are 
the two metrics that marginally support a conclusion that the BART 
Alternative achieves greater reasonable progress.
    Regarding the 98th percentile visibility impact, we propose to find 
this metric does not support our proposed approval of Utah's BART 
Alternative. While the 98th percentile visibility impact is a key 
metric that EPA has primarily focused on in prior actions, we propose 
to conclude that by itself it is not a dispositive metric in weighing a 
BART Alternative. Nonetheless, as discussed in section VI, we have 
given considerable weight to this metric in previous actions where we 
have evaluated BART alternatives as it captures a source's likely 
greatest visibility impacts at a Class I area; as such, it is a useful 
comparison point for determining whether one emission control scenario 
will have a greater impact on visibility improvement than another. In 
those actions, the 98th percentile visibility impact favored the BART 
alternative and therefore there was less need to introduce and consider 
additional evidence to determine

[[Page 2025]]

whether an alternative would provide greater reasonable progress. In 
the case of the Utah BART Alternative, where the 98th percentile does 
not favor the alternative, Utah has introduced additional evidence that 
we considered in order to evaluate whether the BART Alternative, on 
balance, achieves greater reasonable progress.
    Regarding the 90th percentile visibility impact, we propose to find 
that consideration of this metric is appropriate in assessing the 
weight of evidence associated with a BART alternative. Visibility at a 
Class I area changes from day to day, and each emission control 
scenario would result in visibility improvements at the affected Class 
I areas that would differ from one day to another. The metrics related 
to the number of days with impacts greater than 0.5 dv and 1.0 dv are 
examples of the type of additional information that allows for 
consideration of the frequency and duration of visibility impacts. 
Similarly, the use of the 90th percentile impact metric allows for the 
comparison of BART and a BART alternative at a different point in the 
range of impacts. This can be useful, given the varying impacts of 
different pollutants under different meteorological conditions. The 
information provided by Utah for the 90th percentile shows that the 
BART Alternative is better at seven of the nine Class I areas for this 
metric, by amounts ranging from 0.019 to 0.140 dv, and is better when 
taking into account the impacts averaged both across three years and 
across nine Class I areas, but only by 0.006 dv. These values 
marginally support our proposed approval of Utah's BART Alternative as 
better than BART. We invite comment on this proposed assessment of how 
the 90th percentile metric should be considered in the weight of 
evidence determination. We also invite interested parties to submit 
additional information on how the impacts of the BART Alternative under 
various conditions compare to the impacts of the presumed BART 
scenario, because while the 90th percentile impact provides additional 
insight, it is not uniquely informative.
    Regarding the energy and non-air quality impacts, as well as cost, 
we propose to find these metrics do not have direct bearing on whether 
the Utah BART Alternative achieves greater reasonable progress than the 
BART Benchmark; and therefore, we have not taken them into 
consideration.
    Consistent with EPA's regulations governing BART alternatives,\111\ 
in evaluating the weight-of-evidence demonstration, we have evaluated 
all of the information and data submitted by Utah, while recognizing 
the relative strengths and weaknesses of that information to arrive at 
our proposed decision. Based on the weight-of-evidence presented, we 
propose to approve Utah's determination that the Utah BART Alternative 
would achieve greater reasonable progress than BART under 40 CFR 
51.308(e)(2)(i)(I).
---------------------------------------------------------------------------

    \111\ 71 FR 60622 (Oct. 13, 2006).
---------------------------------------------------------------------------

g. Requirement That Emission Reductions Take Place During Period of 
First Long-Term Strategy
    As discussed previously in section IV.C.6, pursuant to 40 CFR 
51.308(e)(2)(iii), the State must ensure that all necessary emission 
reductions take place during the period of the first long-term strategy 
for regional haze, i.e., by December 31, 2018. The RHR further provides 
that, to meet this requirement, the State must provide a detailed 
description of the alternative measure, including schedules for 
implementation, the emission reductions required by the program, all 
necessary administrative and technical procedures for implementing the 
program, rules for accounting and monitoring emissions, and procedures 
for enforcement.\112\
---------------------------------------------------------------------------

    \112\ 40 CFR 51.308(e)(2)(iii).
---------------------------------------------------------------------------

    As noted previously, the Utah SIP revision incorporates the 
revisions to R307-110-17, Section IX, Control Measures for Area and 
Point Sources, Part H, Emissions Limits, which includes provisions for 
implementing the Utah BART Alternative. In addition to the emission 
limitations for NOX and PM10, and the requirement 
for shutdown of the Carbon plant listed in Table 2, the SIP includes 
compliance dates, operation and maintenance requirements, and 
monitoring, recordkeeping, and reporting requirements. We propose to 
find that these provisions meet the requirements of 40 CFR 
51.308(e)(2)(iii).
h. Demonstration That Emission Reductions From Alternative Program Will 
Be Surplus
i. June 2015 Utah RH SIP
    As discussed previously in section IV.C.7, pursuant to 40 CFR 
51.308(e)(2)(iv), the SIP must demonstrate that the emissions 
reductions resulting from the alternative measure will be surplus to 
those reductions resulting from measures adopted to meet requirements 
of the CAA as of the baseline date of the SIP. The baseline date for 
regional haze SIPs is 2002.\113\ As discussed in section IV.C.7, all of 
the emission reductions required by the Utah BART Alternative result 
from measures applicable to Hunter, Huntington and Carbon that occur 
after 2002.
---------------------------------------------------------------------------

    \113\ See Memorandum from Lydia Wegman and Peter Tsirigotis, 
2002 Base Year Emission Inventory SIP Planning: 8-hr Ozone, 
PM2.5, and Regional Haze Programs, November 18, 2002. 
http://www3.epa.gov/ttnchie1/eidocs/2002baseinven_102502new.pdf.
---------------------------------------------------------------------------

    Furthermore, the State's SIP explains that the WRAP modeling that 
was done to support the Utah RH SIP included regional SO2 
emissions based on the 2018 SO2 milestone and also included 
NOX and PM10 emissions from the Carbon plant. 
Thus, WRAP did not rely on emission reductions from the Carbon plant in 
establishing the 2018 SO2 milestone.
    The State's SIP also includes SO2 trend data that 
further demonstrate emission reductions from the Carbon plant do not 
appear to be needed for meeting the 2018 milestone of 141,849 tpy. 
Actual emissions in the three-state region are calculated each year and 
compared to the milestones. As can be seen in Table 7, SO2 
emissions reported for 2011 are below the 2018 milestone and the most 
recent milestone report for 2013 demonstrates that SO2 
emissions are currently 26 percent lower than the 2018 milestone. 
Additionally, the Carbon plant was fully operational in the years 2011-
2013 when the emissions from the three-state region were below the 2018 
milestone for those years. Therefore, the SO2 emission 
reductions from the closure of the Carbon plant appear to be surplus to 
what is needed to meet the 2018 milestone established in Utah's RH SIP.
ii. October 2015 Utah RH SIP
    As discussed previously in section IV.D, Utah submitted enforceable 
commitments in its October 20, 2015 SIP to address potential concerns 
that the State would be double counting SO2 emissions 
reductions for the Carbon plant closure under both the 40 CFR 51.308 
and 309 programs.\114\
---------------------------------------------------------------------------

    \114\ Regional Haze Section XX, N. (1).
---------------------------------------------------------------------------

    EPA has historically recognized that under certain circumstances, 
it is appropriate to approve a SIP submission that consists, in part, 
of an enforceable commitment. Once EPA determines that circumstances 
warrant consideration of an enforceable commitment to meet section 
110(a)(2)(A) of the Act (and other applicable sections as relevant), 
EPA applies three factors to determine whether to approve the 
enforceable commitment: (1) Whether the commitment addresses a limited 
portion

[[Page 2026]]

of the statutorily-required program; (2) whether the state is capable 
of fulfilling its commitment; and (3) whether the commitment is for a 
reasonable and appropriate period of time. Once approved in a SIP, the 
commitments are enforceable by both EPA and citizens under the Act.
    First, Utah's revisions address a limited portion of the 
statutorily-required program. The Air Quality Board adopted revisions 
to SIP Section XX, Regional Haze, and added a new subsection N, 
``Enforceable Commitments for the Utah Regional Haze SIP'' that 
resolves specific identified issues. In this provision of the SIP, 
``[t]he State commits to resolving this double counting issue by 
revising the Utah 309 plan to specifically state that the 8,005 tons of 
SO2 emissions from the Carbon units will be added into the 
annual milestone reports from 2016 through the life of the backstop 
trading program, thereby removing any credit for that emission 
reduction in meeting the levels specified in the Utah 309 plan.'' \115\ 
Reporting Carbon's emissions in this manner is reasonable and ensures 
that these emissions reductions are only credited under the BART 
Alternative.
---------------------------------------------------------------------------

    \115\ Regional Haze SIP Section XX, N. (1).
---------------------------------------------------------------------------

    The SIP indicates the Board is capable of fulfilling these 
commitments by explaining that ``[a]ll required amendments to this SIP 
will be done through the State's SIP adoption process'' \116\ and that 
``[t]he SIP is adopted by the Governor-appointed Air Quality Board 
through a rulemaking process that includes public comment periods and 
an opportunity for a public hearing.'' \117\
---------------------------------------------------------------------------

    \116\ Regional Haze SIP Section XX, N. (4).
    \117\ Regional Haze SIP Section XX, N. (4).
---------------------------------------------------------------------------

    The SIP commits to resolve the identified issues (``SIP Section 
XX.D.3.c and [the State's rule] R307-150 will be revised . . .'' 
\118\), and any other related issues, within reasonable amount of time 
(``Utah will work with EPA and take appropriate action to resolve any 
completeness or approvability issues that arise regarding the proposed 
SIP revision by March 2018'' \119\). This will allow sufficient time 
for EPA to act on the submittal before the end of the milestone 
commitment.
---------------------------------------------------------------------------

    \118\ Regional Haze SIP Section XX, N. (3).
    \119\ Regional Haze SIP Section XX, N. (6), (3).
---------------------------------------------------------------------------

    We also propose to concur that Carbon's 8,005 tpy of SO2 
emissions reductions is a limited portion of the overall requirements 
of the 309 program and particularly in comparison to the 2018 
SO2 milestone of 141,849 tpy described in Table 7.\120\
---------------------------------------------------------------------------

    \120\ Regional Haze SIP Section XX, N. (2).
---------------------------------------------------------------------------

    Based on these considerations, we propose to approve the 
enforceable commitment SIP.
    Therefore, based on the information presented previously from the 
State's SIP and enforceable commitment SIP, we propose to concur that 
the reductions from Carbon are surplus and can be considered as part of 
an alternative strategy under 40 CFR 51.308(e)(2)(iv).

C. PM10 BART Determinations

    As discussed previously in section IV.B.2, Utah determined that the 
PM10 BART emission limit for Hunter Units 1 and 2 and 
Huntington Units 1 and 2 was 0.015 lb/MMBtu based on a three-run test 
average. Utah noted that because the most stringent technology is in 
place at these units and that the PM10 emission limits have 
been made enforceable in the SIP, no further analysis was required.
    EPA has reviewed Utah's PM10 BART streamlined five-
factor analysis and PM10 BART determinations for Hunter 
Units 1 and 2 and Huntington Units 1 and 2 and proposes to find that 
these determinations meet the requirements of 40 CFR 51.309(d)(4)(vii). 
The fabric filter baghouses installed at these BART units are 
considered the most stringent technology available. The emission limit 
of 0.015 lb/MMBtu at these units represents the most stringent emission 
limit for PM10. Utah's use of a streamlined approach to the 
five-factor analysis is reasonable as the BART Guidelines provide that 
a comprehensive BART analysis can be avoided if a source commits to a 
BART determination that consists of the most stringent controls 
available.\121\
---------------------------------------------------------------------------

    \121\ 40 CFR 51, appendix Y, section IV.D.1.9.
---------------------------------------------------------------------------

    Utah's regulatory text provides, ``[e]missions of particulate (PM) 
shall not exceed 0.015 lb/MMBtu heat input from each boiler based on a 
3-run test average.'' It further states that ``[s]tack testing for the 
emission limitation shall be performed each year on each boiler.'' 
\122\ We note that BART limits must apply at all times. See CAA section 
302(k), 40 CFR part 51, appendix Y, section V. Furthermore, EPA's 
credible evidence rule requires that a state's plan must not preclude 
the use of any credible evidence or information, which can include 
evidence and information other than the test method specified in the 
plan, that would indicate whether a source was in compliance with 
applicable requirements.\123\
---------------------------------------------------------------------------

    \122\ June 2015 Utah RH SIP, Sections IX.H.22.a.i.A-B, 
IX.H.22.b.i.A-B.
    \123\ 40 CFR 51.212(c).
---------------------------------------------------------------------------

    Consistent with these requirements, we propose to interpret Utah's 
regulatory text as imposing a PM limit of 0.015 lb/MMBtu that applies 
at all times and does not preclude the use, including the exclusive 
use, of any credible evidence or information, relevant to whether a 
source is in compliance with the limit.

D. Monitoring, Recordkeeping, and Reporting

    EPA has reviewed Utah's monitoring, recordkeeping and reporting 
measures in its June 4, 2015 SIP Section IX, Part H for the BART 
Alternative and the PM10 BART determinations and proposes to 
approve these measures as meeting the requirements of section 110(a)(2) 
of the CAA and 40 CFR 51, subpart K, Source Surveillance, with the 
exception of reporting requirements for violations of PM10 
emissions limitations. For PM10 reporting, we are proposing 
to conditionally approve this element in accordance with CAA section 
110(k)(4) based on Utah's commitment to submit specific measures to 
address the reporting requirement.\124\ Utah's letter commits to adopt 
and submit rule language that would require sources to report any 
deviation from the requirements of the RH SIP provisions, which would 
include the PM10 emission limitations. The specific language 
is detailed in Utah's commitment letter.
---------------------------------------------------------------------------

    \124\ Letter from Department of Environmental Quality, State of 
Utah to EPA, DAQP-120-15 (Dec. 10, 2015).
---------------------------------------------------------------------------

    Otherwise, the SIP includes adequate measures that pertain to 
operation of Hunter and Huntington and the closure of Carbon. EPA 
previously approved state rule provisions that Utah has also cross 
referenced in these new regional haze measures, including terms, 
conditions and definitions in R307-101-1, R307-101-2 and R307-170-4 as 
well as other continuous emission monitoring system (CEMS) requirements 
referenced in R307-107. These measures are consistent with similar 
monitoring, recordkeeping, and reporting requirements that EPA has 
approved in other states or that we have adopted in federal plans,\125\ 
and in particular contain the requirements that were missing from 
Utah's prior regional haze submittals.\126\ As described previously in 
section IV.A.3, Utah has provided the emission limitations, work 
practice standards, monitoring, recordkeeping, and reporting

[[Page 2027]]

requirements for all the units that are part of Utah's BART Alternative 
for the Hunter, Huntington, and Carbon plants.
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    \125\ 77 FR 57864; 79 FR 5032.
    \126\ 77 FR 74365-74366 (Dec. 14, 2012).
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    If we finalize our proposed approval, the regulatory text contained 
in our final rule for 40 CFR part 52 subpart TT will be consistent with 
the relevant provisions of Utah's regional haze submittals for making 
the emission limits and other requirements enforceable. If EPA 
finalizes the conditional approval of Utah's PM10 reporting 
provision, the State has one year from the date of EPA's final action 
on the June 4, 2015 SIP to submit the necessary SIP revisions. If the 
State fails to meet its commitment within the one-year period, the 
approval is treated as a disapproval. EPA proposes to find that the 
necessary SIP revisions meet EPA's criteria for conditional approvals 
\127\ as the revisions appear to involve a limited amount of technical 
work, are anticipated to be non-controversial, and can reasonably be 
accomplished within the length of time for the State's adoption 
process.
---------------------------------------------------------------------------

    \127\ See Memorandum from John Calcagni to EPA Regional 
Directors. ``Processing of State Implementation Plan (SIP) 
Submittals'' (July 1992), available at http://www3.epa.gov/ttn/oarpg/t1/memoranda/siproc.pdf.
---------------------------------------------------------------------------

E. Consultation with FLMs

    As discussed previously in section IV.G, Utah conducted FLM 
consultation during late 2014, providing over 60 days prior to the 
December 1, 2014 public hearing. Subsequently, the National Park 
Service provided extensive comments in response to a second public 
comment period in April 2015. Based on these considerations, we propose 
to find that Utah has met the requirements of 40 CFR 308(i)(2).

VI. EPA's Evaluation and Proposed Partial Approval and Partial 
Disapproval of Utah's Regional Haze SIP

    In this section, we present the second of two alternative proposed 
actions on which EPA is soliciting comment. As explained previously in 
sections II.A and V, EPA is soliciting comments on two alternative 
proposals: a proposal to approve the State SIP in its entirety, and a 
proposal to partially approve and partially disapprove the State SIP 
and to issue a FIP. The co-proposals detailed in this section and 
Section V represent different conclusions regarding Utah's 
NOX BART Alternative and the metrics the State has proposed 
to support this alternative.
    As described in this section, EPA is proposing to partially approve 
and partially disapprove Utah's June 2015 and October 2015 RH SIP 
revisions and propose a FIP. Alternatively, as discussed in section V, 
EPA is co-proposing in the alternative to approve Utah's June 2015 and 
October 2015 RH SIP revisions.
    This document is written as two separate proposals in order to 
clearly present the options and solicit comment on each. EPA intends to 
finalize only one of these co-proposals; however, we also acknowledge 
that additional information and comments may also lead the Agency to 
adopt final SIP and/or FIP regulations that differ somewhat from the 
co-proposals presented here regarding the BART Alternative, BART 
control technology option or emission limits, or impact other proposed 
regulatory provisions.

A. Basis for Proposed Partial Disapproval and Partial Approval

    For the reasons described later, EPA proposes to partially approve 
and partially disapprove the two Utah 2015 RH SIP revisions. Our 
proposed action is based on an evaluation of Utah's regional haze SIP 
submittals against the regional haze requirements at 40 CFR 51.300-
51.309 and CAA sections 169A and 169B, as well as the supplemental 
information EPA developed, such as EPA's calculations of the visibility 
improvements for each modeling scenario using consistent meteorological 
years in evaluating the 98th percentile modeling and referencing the 
topographical maps in evaluating whether distribution of emissions 
would be substantially different under the Utah BART Alternative. All 
general SIP requirements contained in CAA section 110, other provisions 
of the CAA, and our regulations applicable to this action were also 
evaluated. The purpose of this action is to ensure compliance with 
these requirements. As discussed in section V, EPA is also co-proposing 
to approve the Utah's June 2015 and October 2015 RH SIP revisions.

B. Utah BART Alternative

1. Summary of Utah BART Alternative
    Utah has opted to establish an alternative measure (or program) for 
NOX in accordance with 40 CFR 51.308(e)(2). A description of 
the Utah BART Alternative is provided in section IV.C. The RHR requires 
that a SIP revision establishing a BART alternative include three 
elements as listed later. We have evaluated the Utah BART Alternative 
with respect to each of these elements.
     A demonstration that the emissions trading program or 
other alternative measure will achieve greater reasonable progress than 
would have resulted from the installation and operation of BART at all 
sources subject to BART in the State and covered by the alternative 
program.\128\
---------------------------------------------------------------------------

    \128\ 40 CFR 51.308(e)(2)(i).
---------------------------------------------------------------------------

     A requirement that all necessary emissions reductions take 
place during the period of the first long-term strategy for regional 
haze.\129\
---------------------------------------------------------------------------

    \129\ 40 CFR 51.308(e)(2)(iii).
---------------------------------------------------------------------------

     A demonstration that the emissions reductions resulting 
from the alternative measure will be surplus to those reductions 
resulting from measures adopted to meet requirements of the CAA as of 
the baseline date of the SIP.\130\
---------------------------------------------------------------------------

    \130\ 40 CFR 51.308(e)(2)(iv).
---------------------------------------------------------------------------

2. Demonstration of Greater Reasonable Progress for Alternative Program
    As discussed previously in section III.E.1, pursuant to 40 CFR 
51.308(e)(2)(i), Utah must demonstrate that the alternative measure 
will achieve greater reasonable progress than would have resulted from 
the installation and operation of BART at all sources subject to BART 
in the State and covered by the alternative program. This 
demonstration, primarily included in Chapter 1 of the TSD of the Utah 
RH SIP,\131\ must be based on five criteria presented below.
---------------------------------------------------------------------------

    \131\ As presented in this proposal, while the majority of the 
State's demonstration is contained in Chapter 1, EPA has identified 
additional information regarding the demonstration and we include 
references to the additional information.
---------------------------------------------------------------------------

a. A List of All BART-Eligible Sources Within the State
    As discussed previously in section IV.C.1, Utah included a list of 
BART-eligible sources and noted the following sources are all covered 
by the alternative program:
     PacifiCorp Hunter, Unit 1,
     PacifiCorp Hunter, Unit 2,
     PacifiCorp, Huntington, Unit 1, and
     PacifiCorp, Huntington, Unit 2.
    EPA approved Utah's BART eligibility determinations in our 2012 
rulemaking.\132\
---------------------------------------------------------------------------

    \132\ 77 FR 74357 (Dec. 14, 2012).
---------------------------------------------------------------------------

b. A List of All BART-Eligible Sources and All BART Source Categories 
Covered by the Alternative Program
    As discussed previously in section IV.A.3, the Utah BART 
Alternative covers all the BART-eligible sources in the state, Hunter 
Units 1 and 2 and Huntington Units 1 and 2, in addition to three non-
BART units, PacifiCorp's Hunter Unit 3 and Carbon Units 1 and 2. EPA 
previously approved Utah's

[[Page 2028]]

BART eligibility determinations in our 2012 rulemaking.\133\
---------------------------------------------------------------------------

    \133\ 77 FR 74357 (Dec. 14, 2012).
---------------------------------------------------------------------------

c. Analysis of BART and Associated Emission Reductions Achievable
    As noted previously in section IV.C.3, in the June 2015 Utah RH 
SIP, Utah compared the Utah BART Alternative to a BART Benchmark which 
included the most stringent NOX BART controls, SCR plus new 
LNBs and SOFA, at the four BART units. This is consistent with the 
streamlined approach described in Step 1 of the BART Guidelines. The 
BART Guidelines note that a comprehensive BART analysis can be avoided 
if a source commits to a BART determination that consists of the most 
stringent controls available.\134\
---------------------------------------------------------------------------

    \134\ 40 CFR 51, appendix Y, section IV.D.1.9.
---------------------------------------------------------------------------

    We propose to find that Utah has met the requirement for an 
analysis of BART and associated emission reductions achievable at 
Hunter and Huntington under 40 CFR 51.308(e)(2)(i)(C).
    d. Analysis of Projected Emissions Reductions Achievable Through 
the BART Alternative
    As discussed previously in section IV.C.4, a summary of Utah's 
estimates of emissions for the Utah BART Alternative and the BART 
Benchmark is provided in Table 3. We propose to find that Utah has met 
the requirement for an analysis of the projected emissions reductions 
achievable through the alternative measure under 40 CFR 
51.308(e)(2)(i)(D).
e. A Determination That the Alternative Achieves Greater Reasonable 
Progress Than Would Be Achieved Through the Installation and Operation 
of BART
Greater Reasonable Progress Based on 40 CFR 51.308(e)(3)'s Greater 
Emission Reductions Test
    As discussed previously in section III.E.1, 40 CFR 51.308(e)(3) 
allows a state to satisfy the final step of the better-than-BART 
demonstration by showing that that ``distribution of emissions is not 
substantially different than under BART'' and that ``the alternative 
measure results in greater emission reductions.'' EPA has explained 
that when the BART alternative ``achieves greater emission reductions 
than each of the individual BART determinations'' \135\ for each of the 
pollutants, ``as well as in the aggregate,'' \136\ ``visibility 
modeling is not required to support a better-than-BART determination. . 
. .'' \137\ However, as EPA explained in responding to comments in the 
final rule for the BART Alternative for the Apache Generating Station 
in Arizona's SIP, ``where BART and the BART Alternative result in 
reduced emissions of one pollutant but increased emissions of another, 
it is not appropriate to use the `greater emission reductions' test.'' 
Instead, the proper approach is to employ a clear weight-of-evidence 
approach under 40 CFR 51.308(e)(2) in order to demonstrate that the 
alternative achieves greater reasonable progress than BART.'' \138\ We 
have not considered a total emissions profile that combines emissions 
of multiple pollutants to determine whether BART or the alternative is 
``better,'' except where every visibility impairing pollutant is 
reduced by a greater amount under the BART alternative.\139\ A 
comparison of mass emissions from multiple pollutants (such as 
NOX and SO2) is not generally informative, 
particularly in assessing whether the alternative approach provides for 
greater reasonable progress towards improving visibility. Instead, when 
emissions of one or more pollutants increases under an alternative, EPA 
has ``given the most weight to the visibility impacts based on air 
quality modeling'' \140\ and used modeling to determine whether or not 
a ``BART Alternative measure that relies on interpollutant trading 
results in greater reasonable progress.'' \141\
---------------------------------------------------------------------------

    \135\ 79 FR 9318, 9335 (Feb. 18, 2014).
    \136\ 79 FR 9318, 9335 (Feb. 18, 2014). See, e.g., 77 FR 11827, 
11837 (Feb. 28, 2012) (proposed approval of Maryland BART 
Alternative, which shows greater SO2 and NOX 
reductions from the Alternative than application of BART, the two 
pollutants covered by the Alternative); 77 FR 39938, 39940-1 (July 
6, 2012) (final approval of Maryland BART Alternative, explaining in 
responding to comments that because the emission reductions are 
greater for the Alternative than BART and the distribution of 
emissions is not substantially different, the Alternative was found 
to meet 40 CFR 51.308(e)(2) and visibility dispersion modeling was 
not needed).
    \137\ 79 FR 9318, 9335 (Feb. 18, 2014) (proposed approval of 
Arizona BART Alternative for Sundt Unit 4). See also, 79 FR 52420 
(Sept. 3, 2014) (final approval of Arizona BART Alternative for 
Sundt Unit 4); 77 FR 18052, 18073-18075 (Mar. 26, 2012) (proposed 
approval of Colorado BART Alternative, no modeling required where 
the 40 CFR 51.308(e)(3) test was met); 77 FR 76871 (Dec. 31, 2012) 
(final approval of Colorado BART Alternative).
    \138\ 80 FR 19220, 19221 (Apr. 10, 2015). See, e.g., 79 FR 
56322, 56327-28 (Sept. 19, 2014); 77 FR 18052, 18075 (Mar. 26. 
2012).
    \139\ 77 FR 18052, 18075 (Mar. 26, 2012).
    \140\ 79 FR 56322, 56328 (Sept. 19, 2014) (proposed approval of 
Arizona Apache BART Alternative); 80 FR 19220 (Apr. 10, 2015) (final 
approval of Arizona Apache BART Alternative).
    \141\ 79 FR 33438, 33441 (June 11, 2014) (final rule, FIP for 
Tesoro Refining BART Alternative); See, e.g., 79 FR 56322, 56328 
(Sept. 19, 2014) (proposed approval of Arizona Apache BART 
Alternative); 80 FR 19220 (Apr. 10, 2015) (final approval of Arizona 
Apache BART Alternative); 77 FR 11827, 11837 (Feb. 28, 2012) 
(proposed approval of Maryland BART Alternative); 77 FR 39938, 
39940-1 (July 6, 2012) (final approval of Maryland BART 
Alternative).
---------------------------------------------------------------------------

    The State's demonstration appears to satisfy the first part of the 
test under 40 CFR 51.308(e)(3) (the distribution of emissions may not 
be substantially different than under BART) since the Hunter, 
Huntington and Carbon plants are all located within close proximity of 
each other in central Utah, as discussed previously in section IV.C.5. 
EPA's interpretation of the requirement under 40 CFR 51.308(e)(3) that 
the alternative measure ``results in greater emission reductions'' has 
been that the emission reduction comparisons are pollutant specific. We 
have not looked at a total emissions profile that combines emissions of 
multiple pollutants to determine whether a BART benchmark or a BART 
alternative is ``better,'' except where every visibility impairing 
pollutant is reduced by a greater amount under the BART 
alternative.\142\ Therefore, we propose to find that the State's 
demonstration does not meet the second part of the test. While in the 
aggregate there are fewer SO2 and PM10 emissions 
for the BART Alternative, the total NOX emissions are 
greater under the BART Alternative than the BART Benchmark. Therefore, 
we propose to disapprove Section XX.D.6.c of the Utah SIP under the 
test in 40 CFR 51.308(e)(3).
---------------------------------------------------------------------------

    \142\ 79 FR 9318, 9335 (Feb. 18, 2014)(proposed approval of 
Arizona BART Alternative for Sundt Unit 4). 79 FR 52420 (Sept. 3, 
2014) (final approval of Arizona BART Alternative for Sundt Unit 4); 
77 FR 18052, 18073-18075 (Mar. 26, 2012) (proposed approval of 
Colorado BART Alternative, no modeling required where the 40 CFR 
51.308(e)(3) test was met); 77 FR 76871 (Dec. 31, 2012) (final 
approval of Colorado BART Alternative).
---------------------------------------------------------------------------

Greater Reasonable Progress Based on 40 CFR 51.308(e)(2)'s Weight-of-
Evidence Test
    Utah also chose to conduct a weight-of-evidence analysis under 40 
CFR 51.308(e)(2) based on a BART Alternative involving certain units at 
the Hunter, Huntington, and Carbon power plants, which included the 
following nine categories of evidence.
i. Annual Emissions Comparison of all Visibility-Impairing Pollutants
    The emissions of visibility-impairing pollutants from both the Utah 
BART Alternative and the BART Benchmark, as estimated by Utah, are 
summarized in Table 3 in section IV.C.4. Compared with the Utah BART 
Benchmark, the State projects that the Utah BART Alternative will 
result in 5,721 tpy more NOX emissions, 8,005 tpy fewer 
SO2 emissions and 573 tpy fewer PM10 emissions 
than the BART Benchmark. As discussed previously, Utah also

[[Page 2029]]

noted that the combined emissions of NOX, SO2 and 
PM10 will be 2,856 tpy lower under the BART Alternative than 
the BART Benchmark.
    While the total emission reductions under the Utah BART Alternative 
are less than those under the BART Benchmark, a comparison of emissions 
of multiple pollutant species of emissions is generally not 
informative, particularly when the Agency is assessing whether an 
approach provides for greater reasonable progress towards improving 
visibility. As explained in section VI.B.e, our interpretation of the 
language in 40 CFR 51.308(e)(3) (``results in greater emission 
reductions . . . may be deemed to achieve greater reasonable 
progress'') has been pollutant specific. EPA has not relied on a total 
emissions profile that combines emissions of multiple pollutants 
together to determine that either BART or a BART alternative is 
``better,'' because visibility modeling is the most appropriate method 
to assess the overall improvements in visibility impacts from control 
scenarios where reductions of multiple pollutants are considered, 
except where every visibility impairing pollutant is reduced by a 
greater amount under the alternative.\143\ As we have explained, 
``[e]ach of the five pollutants which cause or contribute to visibility 
impairment has a different impact on light extinction for a given 
particle mass, making it therefore extremely difficult to judge the 
equivalence of interpollutant trades in a manner that would be 
technically credible, yet convenient to implement in the timeframe 
needed for transactions to be efficient. This analysis is further 
complicated by the fact that the visibility impact that each pollutant 
can have varies with humidity, so that control of different pollutants 
can have markedly different effects on visibility in different 
geographic areas and at different times of the year.'' \144\ As other 
Agency actions on BART alternatives have explained, modeling assesses 
``both pollutants' chemical aerosol formation mechanisms and impacts on 
visibility,'' \145\ which allows evaluation of the ``relative 
visibility impacts from the atmospheric formation of visibility 
impairing aerosols of sulfate and nitrate.'' \146\ Since we find that 
Utah's BART Alternative provides greater emission reductions for two 
pollutants (SO2 and PM10), but find that 
NOX emissions would be greater under the BART Alternative, 
we propose to find that it is not appropriate to combine all three 
pollutants in the annual emissions comparison test to support the BART 
Alternative as the State has done. While we acknowledge that two of the 
pollutants are less under the BART Alternative, one of the pollutants 
is greater, therefore we further propose to find that the annual 
emissions comparison of all three pollutants does not show that the 
BART Alternative is better than the BART Benchmark.
---------------------------------------------------------------------------

    \143\ 79 FR 9318, 9335 (Feb. 18, 2014) (proposed approval of 
Arizona BART Alternative for Sundt Unit 4). 79 FR 52420 (Sept. 3, 
2014) (final approval of Arizona BART Alternative for Sundt Unit 4); 
77 FR 18052, 18073-18075 (Mar. 26, 2012) (proposed approval of 
Colorado BART Alternative, no modeling required where the 40 CFR 
51.308(e)(3) test was met); 77 FR 76871 (Dec. 31, 2012) (final 
approval of Colorado BART Alternative).
    \144\ 64 FR 35714, 35743 (July 1, 1999).
    \145\ 78 FR 79344, 79355 (Dec. 30, 2013).
    \146\ 79 FR 33438, 33440 (June 11, 2014).
---------------------------------------------------------------------------

ii. Improvement in the Number of Days With Significant Visibility 
Impairment
    As discussed previously in section IV.C.5, Utah provided modeling 
results to assess the improvement in the number of days with 
significant visibility impairment--that is, the improvement in the 
number of days with impacts that either cause (>1.0 dv) or contribute 
(0.5 dv) to visibility impairment.
    The BART Guidelines provide that, when making a BART determination, 
a State may consider the number of days or hours that a threshold was 
exceeded.\147\ In developing the BART Guidelines, our example modeling 
analysis of a hypothetical source examined the number of days that 1.0 
dv and 0.5 dv thresholds were exceeded.\148\ As detailed in section 
IV.C.5.b, we note the difference in the total number of days impacted--
18 fewer days greater than the causation threshold of 1.0 dv (775 days 
for the BART Alternative vs. 793 days for the BART Benchmark), and 175 
fewer days greater than the contribution 0.5 dv threshold (1,323 days 
for the BART Alternative vs. 1,498 days for the BART Benchmark. Utah's 
results show that there are fewer days with impacts over 0.5 dv for the 
BART Alternative, which indicates greater improvement in visibility. 
Therefore, the results for the 0.5 dv threshold favor the BART 
Alternative.
---------------------------------------------------------------------------

    \147\ 40 CFR 51, appendix Y, section IV.D.5.
    \148\ 70 FR 39130 (July 6, 2005).
---------------------------------------------------------------------------

    However, Utah's results for the total number of days with impacts 
over 1.0 dv on a Class I area-by-area basis are not as clear in 
supporting the BART Alternative. The modeling results for the total 
number of days with impacts greater than 1.0 dv show that the BART 
Alternative would have more days with impacts greater than 1.0 dv at 
seven of the nine Class I areas, and that only two of the Class I 
areas, would have fewer days with impacts greater than 1.0 dv compared 
to the BART Benchmark. Therefore, the Class I area-by-area results do 
not show that the BART Alternative is better than the BART Benchmark. 
Similarly, the results for the average number of days with impacts over 
1.0 dv show that most of the Class I areas have the same result under 
both the BART Alternative and Benchmark, or are within one day of 
having the same result. In this context, a difference of one day is not 
particularly significant. We therefore propose to find that these 
results do not show the BART Alternative is better.
    Utah's results in applying the number of days with impacts greater 
than 1.0 dv show the BART Alternative is better ``on average'' across 
all nine Class I areas. We agree that use of average visibility impacts 
could be acceptable as part of assessing the multiple-area impacts and 
improvements. However, in this case the visibility results for the 
individual Class I areas do not consistently support or undermine the 
BART Alternative; there is variation by Class I area. Here, averaging 
the visibility results has the effect of obscuring the impacts on the 
individual Class I areas. Additionally, we propose to not the give the 
difference in days significant weight because by itself it does not 
indicate whether benefits on those days were large or small. Therefore, 
while we note that the BART Alternative shows fewer days with impacts 
greater than 1.0 dv when looking at the average over all nine areas, we 
propose to find that averaging the number of days with impacts greater 
than 1.0 dv across all affected Class I areas is not a relevant metric 
under these circumstances. We therefore further propose to find that 
this metric does not show the BART Alternative is better.
iii. 98th Percentile Impact (dv)
    As discussed previously in section IV.C.5, Utah asserted that the 
only metric it evaluated that showed greater improvement for the BART 
Benchmark in comparison to the BART Alternative was the 98th percentile 
metric when averaged across all Class I areas and meteorological years 
modeled. Utah's comparison of the modeled visibility impacts on the 
98th percentile day (8th highest impacted day in a given meteorological 
year) for the most impacted year shows that the BART Benchmark would 
result in greater visibility improvement at five of the nine Class I 
areas, and is better on average across all nine Class I areas (0.11 dv 
difference). At the most

[[Page 2030]]

impacted Class I areas, Canyonlands and Capitol Reef, Utah found that 
the 98th percentile metric indicates the BART Benchmark has 0.76 dv and 
0.57 dv, respectively, more improvement than the BART Alternative. At 
other Class I areas, such as Arches, Utah found that the 98th 
percentile metric indicates that the BART Alternative provides greater 
visibility improvement (for example, 0.44 dv at Flat Tops).
    The 98th percentile visibility impact is a key metric recommended 
by the BART Guidelines when selecting BART controls.\149\ As noted 
previously, we described this metric as an appropriate measure for 
determining the degree of visibility improvement to be expected from 
controls.\150\ In addition, this is one of the primary metrics that EPA 
has relied on in evaluating prior regional haze actions that have 
included BART alternatives.\151\
---------------------------------------------------------------------------

    \149\ 40 CFR 51, appendix Y, section IV.D.5.
    \150\ 70 FR at 39129.
    \151\ See, e.g., 78 FR 79344 (Dec. 30, 2012)(proposed rule, FIP 
for Tesoro Refining and Intalco Refinery BART Alternatives); 79 FR 
33438 (June 11, 2014)(final rule, FIP for Tesoro Refining and 
Intalco Refinery BART Alternatives); 79 FR 56322, 56328 (Sept. 19, 
2014)(proposed approval of Arizona Apache BART Alternative); 80 FR 
19220 (Apr. 10, 2015)(final approval of Arizona Apache BART 
Alternative); 77 FR 11827, 11837 (Feb. 28, 2012)(proposed approval 
of Maryland BART Alternative); 77 FR 39938, 39940-1 (July 6, 
2012)(final approval of Maryland BART Alternative).
---------------------------------------------------------------------------

    We note that when calculating visibility improvements for 
individual Class I areas, Utah mixed the impacts from different 
meteorological years between modeling scenarios (baseline, BART 
benchmark, and BART Alternative). As discussed in section V.B.2.e, the 
State's use of different meteorological years may introduce some error 
as the visibility improvements could be driven by year-to-year 
variability in meteorological conditions, as opposed to the differences 
in emission reductions between the BART Alternative and BART Benchmark. 
For this reason, in addition to the information from the State, EPA has 
also calculated the visibility improvements for each modeling scenario 
using paired-in-time meteorological and emissions data.\152\ Using this 
method, whether the BART Alternative resulted in lower 98th percentile 
impacts depends on both the particular Class I area and meteorological 
year modeled. In some years and some Class I areas, particularly some 
of the most impacted Class I areas, the BART Benchmark shows better 
visibility improvement than the BART Alternative (for example, 0.93 dv 
greater improvement for Canyonlands and 0.75 in 2002 dv greater 
improvement for Capitol Reef in 2001).\153\ At other Class I areas, the 
98th percentile metric indicates that the BART Alternative provides 
greater visibility improvement (for example, by 0.90 dv at Arches in 
2003 and 0.43 dv at Flat Tops in 2002).\154\ On the whole, when using 
this method, the BART Benchmark is slightly better on average across 
all years and nine Class I areas (0.14 dv difference).\155\ We propose 
to find, consistent with the State's evaluation, that this metric 
favors the BART Benchmark.
---------------------------------------------------------------------------

    \152\ See EPA Calculation of 98th Percentile Improvement for 
Utah Bart Alternative spreadsheet (in docket).
    \153\ Id.
    \154\ Id.
    \155\ Id.
---------------------------------------------------------------------------

iv. Annual Average Impact (dv)
    As discussed previously in section IV.C.5, Utah's modeling shows 
that the average annual dv impact at all Class I areas is better under 
the Utah BART Alternative at five of the nine Class I areas, and is 
better on average across all the Class I areas. The average impact was 
calculated by averaging all daily modeling results for each year and 
then calculating a three-year average from the annual average. Utah's 
information shows that the BART Alternative is better than the BART 
Benchmark by 0.009 dv on average across all nine Class I areas. While 
EPA has not considered this metric in the past,\156\ since the State 
includes it,\157\ we consider it here. Furthermore, the BART Guidelines 
state that, ``in determining what, if any, emission controls should be 
required, the State will have the opportunity to consider the 
frequency, duration, and intensity of a source's predicted effect on 
visibility.'' \158\ We note that the difference in the annual average 
metric of 0.009 dv only marginally supports the BART Alternative and 
that this metric shows less or equal visibility improvement at four of 
the nine Class I areas. Because the annual average metric averages over 
all days, it does not represent the benefits of the BART Alternative on 
the maximum impact days. In previous evaluations of BART alternatives 
we have relied on either the 98th percentile metric or the average 
improvement for the worst 20% IMPROVE monitoring days to evaluate 
greater reasonable progress. Therefore, we propose to find that the 
information from the annual average metric does not support a 
conclusion that the BART Alternative achieves greater reasonable 
progress than the BART Benchmark.
---------------------------------------------------------------------------

    \156\ EPA final actions on BART Alternatives that evaluated 
CALPUFF modeling analysis, which did not include consideration of 
annual average dv impacts include: 80 FR 19220 (Apr. 10, 
2015)(Region 9, Apache); 79 FR 33438 (June 11, 2014)(Region 10, 
Tesoro Refining and Alcoa Intalco Operations); 77 FR 39938 (July 6, 
2012)(Region 3, Maryland HAA).
    \157\ See Utah Regional Haze State Implementation Plan, 
Technical Support Document, Ch. 1, p. 23 (2015).
    \158\ 70 FR 39121 (July 5, 2005).
---------------------------------------------------------------------------

v. 90th Percentile Impact (dv)
    As discussed previously in section IV.C.5, Utah's comparison of the 
modeled visibility impacts at the 90th percentile (the 110th highest 
day in a year) dv impact shows that the Utah BART Alternative is better 
at seven of the nine Class I areas and is slightly better averaged both 
across three years and across nine Class I areas (0.006 dv difference). 
We note that the use of the 90th percentile impacts to evaluate 
alternatives has not been EPA's practice for source-specific BART 
determinations; however, as discussed previously for the average dv 
impact metric, the BART Guidelines allow states to consider other 
visibility metrics in addition to the 98th percentile. Yet, because of 
the small difference between the two scenarios (0.006 dv), we propose 
to find that it is questionable whether the 90th percentile supports a 
conclusion that the BART Alternative achieves greater reasonable 
progress.

vi. Timing for the Emissions Reductions

    As discussed previously in section IV.C.5, assuming the four BART 
units receive five years to come into compliance, Utah noted that 
reductions under the Utah BART Alternative will occur earlier than the 
BART Benchmark. The reductions under the Utah BART Alternative are 
required under the State SIP by August 2015, as noted in Table 5, and 
would provide an early and on-going visibility benefit as compared to 
BART. Also notable is that combustion control upgrades at the Hunter 
and Huntington facilities have been achieving significant 
NOX reductions since the time of their installation between 
2006 and 2014, depending on the unit.\159\ Finally, if, as proposed in 
section VI.C, BART for the four units is LNB/SOFA plus SCR, BART likely 
would be fully implemented sometime between 2019 and 2021.
---------------------------------------------------------------------------

    \159\ Copies of Administrative Orders DAQE-AN0102370012-08 and 
DAQE-AN0102380021-10 are included in the docket, and include 
information regarding the schedule for installation of combustion 
controls at Hunter and Huntington.
---------------------------------------------------------------------------

    Therefore, we recognize that the reductions from the BART 
Alternative would occur before the BART Benchmark.

[[Page 2031]]

vii. IMPROVE Monitoring Data
    Utah's SIP presents sulfate and nitrate monitoring data at the 
Canyonlands IMPROVE monitor that show that ``sulfates are the dominant 
visibility impairing pollutant'' \160\ and that sulfate levels have 
decreased,\161\ and references similar results at other Class I areas 
in the TSD.\162\ Utah also presents data on trends in emissions from 
EGUs showing substantial reductions in emissions of both SO2 
and NOX.\163\ Based on these data, Utah indicates it ``has 
confidence that the SO2 reductions will achieve meaningful 
visibility improvement'', under the Utah BART Alternative,\164\ while 
``the visibility improvement during the winter months due to 
NOX reductions is much more uncertain,'' \165\ Utah makes 
this point even though nitrate concentrations are highest in the 
winter, explaining that while there has been a reduction in 
NOX, the ammonium nitrate values do not show similar 
improvement in the winter months. Utah offers several possible 
explanations for the results, but does not provide any definitive 
conclusions.\166\
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    \160\ Utah Regional Haze State Implementation Plan, Technical 
Support Document, Ch. 1, p. 12 (2015).
    \161\ Id. at p. 15.
    \162\ Id. at p. 12.
    \163\ Id. at p. 14.
    \164\ Id. at p. 13.
    \165\ Id.
    \166\ Id. at pp. 16-19.
---------------------------------------------------------------------------

    Utah also presents data on the seasonality of park visitation and 
monitoring data for nitrate and sulfates. These data show the highest 
measured nitrate concentrations occur in winter during the period of 
lowest park visitation, and that sulfates affect visibility throughout 
the year and are the dominant visibility impairing pollutant from 
anthropogenic sources during the high visitation period of March 
through November. Utah concludes that it has greater confidence that 
reductions in SO2 will be reflected in improved visibility 
for visitors to the Class I areas, while reductions in NOX 
will have a more uncertain benefit for visitors to Class I areas. We 
invite comment on the information and conclusions provided by Utah as 
summarized earlier.
    We propose to concur with one of the State's findings. We propose 
to find that visibility benefits associated with NOX 
reductions are much more likely to occur in the winter months because 
this is when aerosol thermodynamics favors nitrate formation.\167\ By 
contrast, SO2 emissions reductions should provide visibility 
benefits in all seasons.\168\ We also propose to find that, as 
concluded by the GCVTC, and supported by the IMPROVE monitoring data 
presented by Utah, anthropogenic visibility impairment on the Colorado 
Plateau is dominated by sulfates. Therefore, we propose to concur with 
Utah's statement that sulfate is the largest contributor to visibility 
impairment at the affected Class I areas.
---------------------------------------------------------------------------

    \167\ Fountoukis, C. & Nenes, A., ISORROPIA II: A 
Computationally Efficient Aerosol Thermodynamic Equilibrium Model 
for K+, Ca2+, 
Mg2+, NH4+, 
Na+, SO42-, 
NO3-, Cl-, H2O Aerosols, 
7 Atmos. Chem. Phys., 4639-4659 (2007).
    \168\ Seinfeld, John H., Urban Air Pollution: State of the 
Science, 243 Science Magazine, no. 4892, 745, 750 (1989).
---------------------------------------------------------------------------

    We propose to disagree with the State's findings related to park 
visitation. While the BART Guidelines do mention visitation as 
something that can inform a control decision,\169\ EPA is proposing to 
place little weight on the State's correlation of emissions reductions 
and park visitation because nothing in the CAA suggests that visitors 
during busy time periods are entitled to experience better visibility 
than visitors during off-peak periods. On the contrary, in the Regional 
Haze provisions of the CAA, Congress declared a national goal of 
remedying all manmade visibility impairment in all class I areas, which 
includes both heavily-visited national parks and seldom-visited 
wilderness areas. We invite comment on our evaluation and the 
information and conclusions provided by Utah as summarized previously.
---------------------------------------------------------------------------

    \169\ 70 FR 39104, 39130 (July 6, 2005) (``Other ways that 
visibility improvement may be assessed to inform the control 
decisions would be to examine distributions of the daily impacts, 
determine if the time of year is important (e.g., high impacts are 
occurring during tourist season), consideration of the cost-
effectiveness of visibility improvements (i.e., the cost per change 
in deciview), using the measures of deciview improvement identified 
by the State, or simply compare the worst case days for the pre- and 
post-control runs. States may develop other methods as well.'').
---------------------------------------------------------------------------

viii. Energy and Non-Air Quality Benefits
    EPA's evaluation of the State's information on energy and non-air 
quality benefits is located earlier in section V.B.2.e.viii.
ix. Cost
    EPA's evaluation of the Utah's cost information is located in 
section V.B.2.e.ix.
f. Evaluation of the Weight of Evidence
    In this section we evaluate Utah's SIP under 40 CFR 51.308(e)(2), 
to determine whether the State met the final step of the better-than-
BART analysis ``based on the clear weight of evidence that the trading 
program or other alternative measure achieves greater reasonable 
progress than would be achieved through the installation and operation 
of BART at the covered sources.'' 40 CFR 51.308(e)(2)(i)(E).
    As discussed previously, we evaluated Utah's demonstration and all 
available information and data presented by the State, as well as 
additional information and data EPA developed and presented in this 
notice. We propose to find that this information and data do not meet 
the requirements of 40 CFR 51.308(e)(2)(i)(E). Specifically, we propose 
that Utah's demonstration does not show by the ``clear weight of 
evidence'' that the BART alternative ``measure achieves greater 
reasonable progress than would be achieved through the installation and 
operation of BART at the covered sources.'' 40 CFR 51.308(e)(2)(i)(E). 
We have evaluated the relative strengths and weakness of the 
information and propose to find that the State's analysis and 
conclusions do not clearly show that the BART Alternative results in 
greater reasonable progress than the BART Benchmark for the following 
reasons: (1) The key metric EPA has used in evaluating alternatives 
(98th percentile) on average across all the Class I areas favors the 
BART Benchmark by 0.14 dv and not the BART Alternative; (2) the 
majority of information and data that the State asserts favor the BART 
Alternative over BART show small differences; (3) the comparison of net 
emissions reductions across three pollutants, which the State relies on 
significantly is not appropriate because not all pollutants are reduced 
under the BART Alternative and each pollutant may have different 
effects on visibility; and (4) while some information may show the 
Alternative is better than BART, the information is not adequate to 
meet the ``clear weight of evidence'' test.
    First, consistent with the Agency's practice, we have considered 
all information, but have given most weight to the visibility impacts 
based on air quality modeling.\170\ Here, the 98th percentile impacts 
from the State's CALPUFF modeling show that the

[[Page 2032]]

BART Alternative is not better than the BART Benchmark because the BART 
Benchmark would provide a 0.14 dv greater average improvement than the 
BART Alternative. In addition, Table 12 lists a comparison of 2001-2003 
three-year average 98th percentile visibility improvement for each of 
the nine Class I areas; and the results for seven of the Class I areas 
favor BART over the Alternative (Black Canyon of the Gunnison (0.06 
dv), Bryce Canyon (0.04 dv), Canyonlands (0.78 dv), Capitol Reef (0.59 
dv), Grand Canyon (0.06 dv), Mesa Verde (0.12 dv), and Zion (0.02 dv)).
---------------------------------------------------------------------------

    \170\ See, e.g., 78 FR 79344 (Dec. 30, 2012) (proposed rule, FIP 
for Tesoro Refining BART Alternative); 79 FR 33438, 33441 (June 11, 
2014) (final rule, FIP for Tesoro Refining BART Alternative); 79 FR 
56322, 56328 (Sept. 19, 2014) (proposed approval of Arizona Apache 
BART Alternative); 80 FR 19220 (Apr. 10, 2015) (final approval of 
Arizona Apache BART Alternative); 77 FR 11827, 11837 (Feb. 28, 2012) 
(proposed approval of Maryland BART Alternative); 77 FR 39938, 
39940-1 (July 6, 2012) (final approval of Maryland BART 
Alternative).
---------------------------------------------------------------------------

    Second, several metrics that the State suggests favor the BART 
Alternative over BART show only small improvements as compared to BART. 
We propose to find that the slight comparative benefits in the annual 
average impacts are not compelling evidence that the BART Alternative 
will provide for greater reasonable progress than BART. Additionally, 
we propose to find that it is questionable whether the 90th percentile 
supports a conclusion that the BART Alternative will provide for 
greater reasonable progress than BART.
    Third, regarding the energy and non-air quality impacts, as well as 
cost, for the reasons presented previously, we propose to find that 
because these metrics do not have a direct bearing on whether the Utah 
BART Alternative achieves greater reasonable progress, it is not 
material to our action whether we agree or disagree with Utah's 
assessment that they reduce energy and non-air quality impact.
    As explained previously in this section, in the aggregate the 
SO2 and PM10 emissions are lower for the BART 
Alternative. However, the NOX emissions are greater under 
the BART Alternative. Additionally, while Utah's results show that some 
of the metrics support the Alternative (e.g., there are fewer days with 
impacts over 0.5 dv for the Alternative indicating greater improvement 
in visibility under the BART Alternative; emission reductions would 
occur earlier under the Alternative; the Alternative will result in 
8,005 tpy lower SO2 emissions and 573 tpy lower 
PM10 emissions compared to the BART Benchmark; sulfate is 
the largest contributor to visibility impairment at the affected Class 
I areas), we propose to find that these metrics are not enough by 
themselves to meet the ``clear weight of evidence'' test.
    Thus, we propose to find that the BART Alternative does not meet 
the requirements in the RHR because it does not show the BART 
Alternative would achieve greater reasonable progress than the BART 
Benchmark, and therefore, we are proposing to disapprove the resultant 
BART Alternative SIP.
g. Evaluation That Emission Reductions Take Place During Period of 
First Long-Term Strategy
    EPA's evaluation of Utah's information regarding the timing of 
implementation of controls is located in section V.B.2.g.
h. Demonstration That Emission Reductions From Alternative Program Will 
Be Surplus
    EPA's evaluation of Utah's information regarding whether the 
emission reductions are surplus is located in section V.B.2.h.

C. Monitoring, Recordkeeping and Reporting for Utah's BART Alternative

    As discussed previously in section IV.B.3, Utah's June 2015 RH SIP 
includes enforceable measures and monitoring, recordkeeping and 
reporting requirements for the Utah BART Alternative and the State's 
PM10 BART determinations. Because in this co-proposal we are 
proposing to disapprove Utah's BART Alternative, we are also proposing 
to disapprove (in other words, to not make federally enforceable as 
part of the SIP) the monitoring, recordkeeping and reporting 
requirements located in SIP Sections IX.H.22 associated with the BART 
Alternative. This includes SIP Section IX.H.22, subsections a.ii, 
a.iii, b.ii, and c.i.
    Concurrently, as described earlier in section V.C, we are proposing 
to approve the remainder of the monitoring, recordkeeping and reporting 
requirements associated with Utah's PM10 BART 
determinations. This includes SIP Section IX.H.21 in its entirety and 
Section IX.H.22, subsections a.i and b.i.

D. Proposed Federal Implementation Plan

    The following explanation details the support for EPA's FIP 
proposed in conjunction with the proposed partial approval and partial 
disapproval of Utah's SIP. This FIP constitutes EPA's proposed 
determination of NOX BART for Utah's four subject-to-BART 
sources.
1. BART Evaluations
    In determining BART, the state, or EPA if promulgating a FIP, must 
consider the five statutory factors in section 169A(g)(2) of the CAA: 
(1) The costs of compliance; (2) the energy and non-air quality 
environmental impacts of compliance; (3) any existing pollution control 
technology in use at the source; (4) the remaining useful life of the 
source; and (5) the degree of improvement in visibility which may 
reasonably be anticipated to result from the use of such technology. 
See also 40 CFR 51.308(e)(1)(ii)(A). Our evaluation of BART for Hunter 
and Huntington follows the Guidelines for BART Determinations Under the 
Regional Haze Rule.
    Following the identification of subject-to-BART sources as 
described in section IV.A.3, the next step of a BART evaluation is to 
perform the BART analysis. The BART Guidelines describe the BART 
analysis as consisting of the following five steps: \171\
---------------------------------------------------------------------------

    \171\ 40 CFR 51, appendix Y, section IV.D.
---------------------------------------------------------------------------

     Step 1: Identify All Available Retrofit Control 
Technologies;
     Step 2: Eliminate Technically Infeasible Options;
     Step 3: Evaluate Control Effectiveness of Remaining 
Control Technologies;
     Step 4: Evaluate Impacts and Document the Results; and
     Step 5: Evaluate Visibility Impacts.
    The results of this five step analysis are then used to select 
BART, taking into consideration the five factors listed earlier.\172\
---------------------------------------------------------------------------

    \172\ See id. section IV.E.
---------------------------------------------------------------------------

    Immediately following this, we provide background information that 
is common to our cost of compliance analysis (under Step 4) and 
visibility impacts analysis (step 5) for all BART sources. This is 
followed by the five step analysis and proposed selection of BART 
specific to each BART source.
a. Costs of Compliance
    In accordance with the BART Guidelines, we have estimated the costs 
of compliance consistent with the EPA Air Pollution Control Cost Manual 
(CCM).\173\ In addition, we have utilized portions of the draft 2015 
revisions to the CCM chapters for the post-combustion NOX 
control technologies, selective non-catalytic reduction (SNCR) and 
selective catalytic reduction (SCR).\174\ In addition, we rely on the

[[Page 2033]]

cost of compliance estimates supplied to EPA by Andover Technology 
Partners (ATP).\175\ These estimates in turn rely on the cost estimates 
that PacifiCorp submitted to Utah in 2012 and 2014, but with those cost 
estimates adjusted in a number of cases for reasons described in the 
ATP report. All costs are presented in 2014 dollars. Refer to the ATP 
report and associated spread sheets for details on how the costs of 
compliance are calculated.
---------------------------------------------------------------------------

    \173\ EPA's CCM Sixth Edition, January 2002, EPA 452/B-02-001.
    \174\ Chapter 1, Selective Noncatalytic Reduction, --6/5/2015--
Draft for Public Comment (``the 2015 SNCR CCM''); Chapter 2 
Selective Catalytic Reduction, --6/5/2015--Draft for Public Comment 
(``the 2015 SCR CCM''). The draft CCM SNCR and SCR revisions were 
made available for public comment in a Notice of Data Availability 
(NODA) on June 12, 2015, 80 FR 33515, and on July 17, 2015, 80 FR 
42491, the public comment period was extended to September 10, 2015. 
In this co-proposal for Utah's regional haze SIP, we are not taking 
comment on the revisions to the CCM. We are only taking comment on 
the application of those revisions of the CCM to the particular 
facts and circumstances for the two subject-to-BART sources, Hunter 
and Huntington, at issue in this action.
    \175\ Cost of NOX BART Controls on Utah EGUs, from 
Andover Technology Partners, to EC/R, Inc., October 22, 2015 (ATP 
report). Andover Technology Partners is a subcontractor to EC/R 
Incorporated.
---------------------------------------------------------------------------

b. Visibility Impact Modeling
    The BART Guidelines provide that states may use the CALPUFF 
modeling system or another appropriate model to determine the 
visibility improvement expected at affected Class I areas from 
potential BART control technologies. The BART Guidelines also recommend 
that states develop a modeling protocol for modeling visibility 
improvement, and suggest that states may want to consult with EPA and 
their RPO to address any issues prior to modeling. In consultation with 
EPA, Utah developed a CALPUFF modeling protocol titled ``Air Quality 
Modeling Protocol: Utah Regional Haze State Implementation Plan'', 
February 13, 2015, to support its BART Alternative analysis (see 
Chapter 6 of the State's TSD). The Utah protocol follows 
recommendations for long-range transport described in appendix W to 40 
CFR part 51, Guideline on Air Quality Models, and in the federal 
Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 2 Summary 
Report and Recommendations for Modeling Long Range Transport Impacts, 
as recommended by the BART Guidelines (40 CFR part 51, appendix Y, 
section III.D.5). Utah's protocol also follows Federal Land Managers' 
Air Quality Related Values Workgroup--Phase I Report (revised 2010). In 
section VI.B.e, we evaluate the State's modeling approach in 
consideration of the purpose for which it is intended (i.e., analyzing 
the BART Alternative). However, because Utah's modeling is not meant to 
support analysis of control options for individual BART sources under a 
five factor analysis, EPA developed separate CALPUFF modeling for this 
purpose. While the Utah modeling assesses the combined impacts of all 
of the BART and non-BART sources included in the BART Alternative--
Carbon, Hunter, and Huntington--our modeling assesses the impacts of 
the individual BART sources. In addition, our modeling assesses the 
visibility impacts of all of the NOX BART control 
technologies found to be technologically feasible in Step 2: LNB and 
OFA, LNB and OFA with SNCR, and LNB and OFA with SCR. Beyond assessing 
impacts from individual BART sources and evaluating all technologically 
feasible control options, our modeling methodology is otherwise very 
similar to that employed by Utah. Our modeling protocol, and visibility 
impact results, can be found in the docket.\176\ Also, the visibility 
impacts for each BART source are provided later in the respective five 
factor analyses.
---------------------------------------------------------------------------

    \176\ Air Quality Modeling Protocol: Utah Regional Haze Federal 
Implementation Plan, EPA Region 8, November 2015.
---------------------------------------------------------------------------

    EPA notes that, in considering the visibility improvements 
reflected in our revised modeling, EPA interprets the BART Guidelines 
to require consideration of the visibility improvement from BART 
applied to the entire BART-eligible source. The BART Guidelines explain 
that, ``[i]f the emissions from the list of emissions units at a 
stationary source exceed a potential to emit of 250 tons per year for 
any visibility-impairing pollutant, then that collection of emissions 
units is a BART-eligible source.'' In other words, the BART-eligible 
source (the list of BART emissions units at a source) is the collection 
of units for which one must make a BART determination. The BART 
Guidelines state ``you must conduct a visibility improvement 
determination for the source(s) as part of the BART determination.'' 
This requires consideration of the visibility improvement from BART 
applied to the subject-to-BART source as a whole.
    We note, however, that while our regulations require states and EPA 
to assess visibility improvement on a source-wide basis, they provide 
flexibility to also consider unit-specific visibility improvement in 
order to more fully inform the reasonableness of a BART determination, 
but that does not replace the consideration of visibility benefit from 
the source (facility) as a whole. In making the BART determinations in 
this final action we have considered visibility improvements at the 
source, and then also at the units that comprise the source.
2. Hunter Power Plant
    As described previously in section IV.A, Hunter Units 1 and 2 were 
determined to be subject to BART, while Unit 3 is not subject to BART. 
Hunter Units 1 and 2 have a nameplate generating capacity of 488.3 MW 
each.\177\ The boilers are tangentially fired pulverized coal boilers, 
burning bituminous coal from the Deer Creek Mine in Utah.
---------------------------------------------------------------------------

    \177\ U.S. Energy Information Administration, Electric 
Generating Capacity for 2011 taken from Form EIA-860. See spread 
sheet titled ``EIA existing generating units 2011.xls'' in the 
docket.
---------------------------------------------------------------------------

    Our evaluation of BART for Hunter Units 1 and 2 follows the BART 
Guidelines. For Hunter Units 1 and 2, the BART Guidelines are mandatory 
because the combined capacity for all three units at the Hunter 
facility is greater than 750 MW. See 40 CFR 51.302(e)(1)(ii)(B) (``The 
determination of BART for fossil-fuel fired power plants having a total 
generating capacity greater than 750 megawatts must be made pursuant to 
the guidelines in appendix Y of this part''). Under the Guidelines, 
cost estimates for control technologies should be based on the CCM, 
where possible.
    The BART Guidelines establish presumptive NOX limits for 
coal-fired EGUs greater than 200 MW located at greater than 750 MW 
power plants that are operating without post-combustion controls. For 
the tangential-fired boilers burning bituminous coal at Hunter, that 
presumptive limit is 0.28 lb/MMBtu.\178\ The BART Guidelines provide 
that the five factor analysis may result in a limit that is different 
than the presumptive limit, and the presumptive limits do not obviate 
the need to determine BART on a case-by-case basis considering the five 
factors.\179\
---------------------------------------------------------------------------

    \178\ 40 CFR part 51, appendix Y, IV.E.5, Table. 1.
    \179\ See 40 CFR 51.301 (definition of BART); 40 CFR 51.308(e).
---------------------------------------------------------------------------

    PacifiCorp provided BART analyses for Hunter Unit 1 to Utah in 2012 
and 2014 which we utilize in our proposed BART evaluation here.\180\ 
Although we are using some information provided by Utah and PacifiCorp, 
we are independently evaluating all five statutory BART factors, as is 
appropriate for this co-proposed FIP.
---------------------------------------------------------------------------

    \180\ PacifiCorp BART Analysis for Hunter Units 1 (July 2, 
2012); PacifiCorp BART Analysis for Hunter Unit 2 (June 7, 2012); 
Utah's Regional Haze BART Submittal, Chapter 2 of the Technical 
Support Document (2015); PacifiCorp's BART Analysis Update for 
Hunter Units 1 and 2 and Huntington Units 1 and 2 (Aug. 5, 2014).
---------------------------------------------------------------------------

a. Hunter Unit 1
    The Hunter Unit 1 boiler is of tangential-fired design with newer 
generation low-NOX burners and separated overfire air which 
were installed in 2014. Unit 1 currently achieves an annual emission 
rate of approximately 0.21 lb/MMBtu with these combustion controls. 
Under Utah's submitted regional haze SIP, Unit 1 is subject to a state-
law NOX emission

[[Page 2034]]

limit of 0.26 lb/MMBtu on a 30-day rolling average. Prior to the 
installation of LNB and SOFA the unit operated with an actual annual 
emission rate of about 0.40 lb/MMBtu.
Step 1: Identify All Available NOX Control Technologies
    In its 2012 BART analysis for Hunter Unit 1, PacifiCorp identified 
several NOX control technologies, both for combustion 
controls and post-combustion controls.\181\ The combustion controls 
identified by PacifiCorp include: low-NOX burners and 
separated overfire air (LNB and SOFA; already installed), rotating 
overfire air, neural network optimization system, flue gas 
recirculation, gas reburn, fuel lean gas reburn, coal switching, water 
injection, and others. Post-combustion control options identified by 
PacifiCorp include: SNCR, rich reagent injection (RRI), SCR, and 
others.
---------------------------------------------------------------------------

    \181\ 2012 PacifiCorp BART analysis for Hunter Unit 1, page 2.a-
106.
---------------------------------------------------------------------------

    We note that the combustion controls, LNB and SOFA, have already 
been installed on Hunter Unit 1, and so we consider them here as ``any 
existing controls'' under the third statutory BART factor. In addition, 
the BART Guidelines recognize that ``[c]ombinations of inherently 
lower-emitting processes and add-on controls'' are a category of 
retrofit controls which can be considered.\182\ Accordingly, the 
inherently lower-emitting combustion controls, LNB and SOFA, are 
evaluated in combination with the add-on controls, SNCR and SCR.
---------------------------------------------------------------------------

    \182\ BART Guidelines, IV.D.1.
---------------------------------------------------------------------------

    We have reviewed PacifiCorp's review of NOX control 
technologies and find it to be comprehensive. We propose to adopt it to 
satisfy Step 1 and we refer the reader to the 2012 PacifiCorp BART 
analysis for details on the available NOX control 
technologies.
Step 2: Eliminate Technically Infeasible Options
    In its 2012 BART analysis,\183\ PacifiCorp eliminated available 
NOX control technologies that PacifiCorp evaluated as 
technologically infeasible for Hunter Unit 1. The remaining 
technologically feasible control technologies are the combustion 
controls, LNB and SOFA, and the post-combustion controls, SNCR and SCR.
---------------------------------------------------------------------------

    \183\ 2012 PacifiCorp BART analysis for Hunter Unit 1, pages 
2.a-106 through 2.a-123.
---------------------------------------------------------------------------

    We agree with PacifiCorp's evaluation of technologically available 
controls for Hunter Unit 1 and propose to adopt it for Step 2.
Step 3: Evaluate Control Effectiveness of Remaining Control 
Technologies
    As noted previously, Hunter Unit 1 is currently achieving an actual 
annual emission rate of approximately 0.21 lb/MMBtu with LNB and SOFA. 
This represents a 48.4 percent reduction from the baseline emission 
rate of 0.40 lb/MMBtu.
    The post-combustion control technologies, SNCR and SCR, have been 
evaluated in combination with combustion controls. That is, the inlet 
concentration to the post-combustion controls is assumed to be 0.21 lb/
MMBtu (annual). This allows the equipment and operating and maintenance 
costs of the post-combustion controls to be minimized based on the 
lower inlet NOX concentration.
    Typically, SNCR reduces NOX an additional 20 to 30 
percent above combustion controls without excessive NH3 
slip.\184\ For this analysis, the control efficiency of SNCR has been 
calculated based on the formula in the 2015 draft CCM SNCR 
chapter,\185\ which for Hunter Unit 1 yields an additional reduction of 
21.4 percent after combustion controls. When combined with LNB and 
SOFA, SNCR is anticipated to achieve an annual emission rate of 0.16 
lb/MMBtu, corresponding to an overall control efficiency of 59.4 
percent.
---------------------------------------------------------------------------

    \184\ White Paper, SNCR for Controlling NOX 
Emissions, Institute of Clean Air Companies, pp. 4 and 9, February 
2008.
    \185\ 2015 SNCR CCM, Figure 1.1c: SNCR NOX Reduction 
Efficiency Versus Baseline NOX Levels for Coal-fired 
Utility Boilers.
---------------------------------------------------------------------------

    SCR can achieve performance emission rates as low as 0.04 to 0.07 
lb/MMBtu on an annual basis.\186\ For this analysis, consistent with 
our actions elsewhere, as well with PacifiCorp's analysis, we use an 
annual emission rate of 0.05 lb/MMBtu for SCR, which when combined with 
LNB and SOFA achieves an overall control efficiency of 87.5 percent.
---------------------------------------------------------------------------

    \186\ Srivastava, R., Hall, R., Khan, S., Lani, B., & Culligan, 
K., Nitrogen Oxides Emission Control Options for Coal-Fired Utility 
Boilers, 55 J. Air & Waste Mgmt. Assoc. 1367, 1367-88 (2005).
---------------------------------------------------------------------------

    A summary of emissions projections for the control options 
evaluated is provided in Table 13.

                  Table 13--Summary of NOX BART Analysis Control Technologies for Hunter Unit 1
----------------------------------------------------------------------------------------------------------------
                                               Control
             Control option                 effectiveness   Annual  emission      Emissions         Remaining
                                                 (%)         rate (lb/MMBtu)   reduction (tpy)   emissions (tpy)
----------------------------------------------------------------------------------------------------------------
LNB/SOFA +SCR...........................              87.5              0.05             5,500               784
LNB/SOFA +SNCR..........................              59.4              0.16             3,735             2,549
LNB/SOFA................................              48.4              0.21             3,042             3,242
Baseline\1\.............................  ................              0.40  ................             6,284
----------------------------------------------------------------------------------------------------------------
\1\ Baseline emissions were determined by averaging the annual emissions from 2001 to 2003 as reported to EPA
  Air Markets Program Data, available at http://ampd.epa.gov/ampd/. The annual emissions data is presented in
  Chapter 4.a of Utah's June 2015 submittal.

Step 4: Evaluate Impacts and Document Results
    Under Step 4, the Guidelines list impact analyses in four parts: 
costs of compliance, energy impacts, non-air quality environmental 
impacts, and remaining useful life. For convenience, we combine energy 
and non-air quality environmental impacts later on.
Part 1--Costs of Compliance
    We obtained capital costs for LNB and SOFA from the 2014 PacifiCorp 
BART analysis. PacifiCorp did not report any operating and maintenance 
costs for LNB and SOFA. Similarly, we obtained capital cost estimates 
for LNB and SOFA with SNCR from the 2014 PacifiCorp BART analysis. 
However, for operating and maintenance costs we propose to rely on the 
draft 2015 draft SNCR chapter of the CCM. Refer to the ATP report for 
details. Capital costs for LNB and SOFA with SCR were also obtained 
from the 2014 PacifiCorp BART analysis. However, PacifiCorp's capital 
costs were adjusted to account for items that were double-counted or 
should not be allowed under the CCM, such as an allowance for funds 
used during construction (AFUDC).\187\ In

[[Page 2035]]

addition, the capital costs were adjusted to account for a significant 
overestimation of the catalyst volume and related costs. These 
adjustments are documented in the ATP report and associated spread 
sheet. A discussion of operating and maintenance costs of SCR is also 
included in the ATP report. For the reasons given in the report, we 
propose to adopt the cost estimates contained in it.
---------------------------------------------------------------------------

    \187\ See 79 FR 5032, 5133 (Jan. 30, 2014) (discussing reasons 
for rejecting use of AFUDC).
---------------------------------------------------------------------------

    A summary of our proposed cost estimates for all control options is 
presented in Table 14.

                                                  Table 14--Summary of NOX BART Costs on Hunter Unit 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                          Average cost
               Control option                   Total capital    Indirect annual    Direct annual     Total annual        Emissions     effectiveness ($/
                                                 investment           costs             costs             cost        reductions (tpy)        ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
LNB/SOFA....................................            $11.6M             $1.2M               $0M             $1.2M             3,042              $382
LNB/SOFA/SNCR...............................             19.0M              1.9M              1.9M              3.8M             3,735             1,016
LNB/SOFA/SCR................................            110.3M             10.5M              2.5M             13.1M             5,500             2,380
--------------------------------------------------------------------------------------------------------------------------------------------------------

Parts 2 and 3--Energy and Non-Air Quality Environmental Impacts of 
Compliance
    SNCR slightly reduces the thermal efficiency of a boiler as the 
reduction reaction uses thermal energy from the boiler, decreasing the 
energy available for power generation.\188\ Using the CCM, we have 
calculated the electrical power consumption of SNCR to be 326,000 kW-hr 
per year for Hunter Unit 1.
---------------------------------------------------------------------------

    \188\ EPA Air Pollution Control Cost Manual p. 1-21 (6th ed. 
2002), available at http://www3.epa.gov/ttncatc1/dir1/c_allchs.pdf.
---------------------------------------------------------------------------

    For SCR, the thermal efficiency is much more reduced because the 
new ductwork and the reactor's catalyst layers decrease the flue gas 
pressure. As a result, additional fan power is necessary to maintain 
the flue gas flow rate through the ductwork and reactor. Using the CCM, 
we have calculated the electrical power consumption of SCR to be 
approximately 18,541,000 kW-hr per year for Hunter Unit 1.
    Both SCR and SNCR also require some minimal electricity to service 
pretreatment and injection equipment, pumps, compressors, and control 
systems. The energy requirements described earlier are not significant 
enough to warrant elimination of either SNCR or SCR as BART. In 
addition, the cost of the additional energy requirements has been 
included in our cost effectiveness calculations.
    SNCR and SCR will slightly increase the quantity of ash that will 
need to be disposed. In addition, transportation and storage of 
chemical reagents may result in spills or releases. However, these non-
air quality environmental impacts do not warrant elimination of either 
SNCR or SCR as BART.
    There are no additional energy requirements associated with the new 
LNB and SOFA, and no significant non-air quality environmental impacts.
    In summary, we propose to determine that we have adequately 
considered these impacts by including cost of additional energy in cost 
effectiveness and assessing non-air quality environmental impacts as 
insufficient to eliminate or weigh against any of the BART options.
Part 4--Remaining Useful Life
    PacifiCorp assumes a remaining useful life of at least 20 years for 
Hunter Unit 1 in its BART analysis, and has not indicated any intention 
to retire, or curtail generation from, Hunter Unit 1. Therefore, this 
factor does not preclude any of the control options considered. In 
addition, this factor is consistent with our BART calculation of cost 
effectiveness because annualized costs have been calculated over a 20 
year period for each of the control options considered. We propose that 
this gives adequate consideration to this factor.
Step 5: Evaluate Visibility Impacts
    Table 15 presents the highest of the 98th percentile visibility 
improvements at the affected Class I areas for the three meteorological 
years modeled, 2001 through 2003. Tables 16 and 17 present the number 
of days (summed across three years) with impacts greater than the 
contribution and causation thresholds--0.5 dv and 1.0 dv, respectively.

                                Table 15--Hunter Unit 1--Visibility Improvements
----------------------------------------------------------------------------------------------------------------
                                                           LNB with SOFA    LNB with SOFA and  LNB with SOFA and
                      Class I area                          ([Delta]dv)      SNCR ([Delta]dv)   SCR ([Delta]dv)
----------------------------------------------------------------------------------------------------------------
Arches NP..............................................              0.737              0.906              1.342
Black Canyon of the Gunnison NP........................              0.198              0.241              0.345
Bryce Canyon NP........................................              0.306              0.372              0.534
Canyonlands NP.........................................              0.846              1.041              1.545
Capitol Reef NP........................................              0.639              0.750              1.113
Flat Tops WA...........................................              0.231              0.280              0.404
Grand Canyon NP........................................              0.349              0.426              0.618
Mesa Verde NP..........................................              0.235              0.286              0.426
Zion NP................................................              0.184              0.224              0.323
----------------------------------------------------------------------------------------------------------------

[[Page 2036]]

                             Table 16--Hunter Unit 1--Days Greater Than 0.5 Deciview
                                               [Three year total]
----------------------------------------------------------------------------------------------------------------
                                                           LNB with SOFA    LNB with SOFA and  LNB with SOFA and
            Class I area               Baseline (days)         (days)          SNCR (days)         SCR (days)
----------------------------------------------------------------------------------------------------------------
Arches NP...........................                293                260                259                235
Black Canyon of the Gunnison NP.....                 68                 55                 53                 41
Bryce Canyon NP.....................                 42                 37                 36                 28
Canyonlands NP......................                359                330                322                311
Capitol Reef NP.....................                175                160                156                145
Flat Tops WA........................                 77                 63                 59                 50
Grand Canyon NP.....................                 49                 43                 42                 37
Mesa Verde NP.......................                 82                 66                 63                 55
Zion NP.............................                 29                 23                 23                 22
----------------------------------------------------------------------------------------------------------------

                             Table 17--Hunter Unit 1--Days Greater Than 1.0 Deciview
                                               [Three year total]
----------------------------------------------------------------------------------------------------------------
                                                           LNB with SOFA    LNB with SOFA and  LNB with SOFA and
            Class I area               Baseline (days)         (days)          SNCR (days)         SCR (days)
----------------------------------------------------------------------------------------------------------------
Arches NP...........................                170                141                139                122
Black Canyon of the Gunnison NP.....                 22                 13                 12                  9
Bryce Canyon NP.....................                 22                 19                 18                 16
Canyonlands NP......................                240                218                202                188
Capitol Reef NP.....................                118                110                109                 94
Flat Tops WA........................                 31                 20                 18                 10
Grand Canyon NP.....................                 32                 25                 23                 18
Mesa Verde NP.......................                 32                 20                 19                 13
Zion NP.............................                 14                  9                  8                  7
----------------------------------------------------------------------------------------------------------------

    Select BART.
    A summary of our impacts analysis for Hunter Unit 1 is presented in 
Table 18.

                                                   Table 18--Summary of Hunter Unit 1 Impacts Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                          Annual                 Total                                                      Visibility impacts *
                                         emission   Emission    annual     Average cost       Incremental cost     -------------------------------------
            Control option              rate  (lb/ reduction     costs     effectiveness    effectiveness ($/ton)     Improvement     Days >     Days >
                                          MMBtu)     (tpy)    (million$)      ($/ton)                                    (dv)         0.5 dv     1.0 dv
--------------------------------------------------------------------------------------------------------------------------------------------------------
LNB with SOFA.........................       0.21      3,042       $1.2M            $382  ........................           0.846        330        218
LNB with SOFA and SNCR................       0.16      3,735        3.8M           1,016  $3,796..................           1.041        322        202
LNB with SOFA and SCR.................       0.05      5,500       13.1M           2,380  $5,268 (compared to LNB            1.545        311        188
                                                                                           with SOFA and SNCR).
                                                                                          $4,853 (compared to LNB
                                                                                           with SOFA)..
--------------------------------------------------------------------------------------------------------------------------------------------------------
* At the most impacted Class I area, Canyonlands National Park.

    In determining what to co-propose as BART, we have taken into 
consideration all five of the statutory factors required by the CAA: 
The costs of compliance, the energy and non-air quality environmental 
impacts of compliance, any existing pollution control technology in use 
at the source, the remaining useful life of the source, and the degree 
of improvement in visibility which may reasonably be anticipated to 
result from the use of such technology. Later we provide a 
justification for our selection of BART, including an explanation of 
how each of the CAA factors was used in that selection.
    As described in step 1 before, we have considered the existing 
pollution control technology in use at the source. We note that Hunter 
Unit 1 was equipped with LNB and SOFA in the spring of 2014 in order to 
meet state-law requirements in the 2011 Utah RH SIP submittal, which we 
did not approve. In this co-proposal we have to evaluate control 
technologies and baseline emissions from the correct starting point, 
that is, prior to the installation of the combustion controls pursuant 
to state-law NOX limitations.\189\ As a result, we used the 
period 2001-2003 as the appropriate period for baseline emissions, in 
order to provide a realistic depiction of annual emissions for Hunter 
Unit 1 prior to installation of combustion controls.
---------------------------------------------------------------------------

    \189\ See 79 FR 5032, 5105 (Jan. 30, 2014).
---------------------------------------------------------------------------

    We have considered the energy and non-air quality environmental 
impacts of compliance and propose to find that

[[Page 2037]]

they do not appreciably favor one control option over another, or 
preclude a particular control option from selection. And finally, we 
have considered the remaining useful life of the source and find that 
it is sufficiently long (greater than 20 years) so as not to favor or 
preclude any of the control options. As a result, the remaining 
factors--the costs of compliance and visibility improvement--are the 
primary factors that lead us to our proposed BART selection for Hunter 
Unit 1.
    In order to select BART we propose to consider the costs of 
compliance and visibility impacts by generally comparing them with BART 
determinations that have been made elsewhere. In the context of 
reasonable progress determinations, a comparison with another 
reasonable progress determination has been upheld by the Ninth Circuit 
Court of Appeals as a rational explanation for that determination.\190\ 
If this were the first BART determination under the RHR and BART 
Guidelines, which it is not, it would obviously be difficult to employ 
this precise methodology.\191\ At this point, however, the EPA thinks 
there are sufficient examples of reasonable determinations to make this 
methodology feasible.
---------------------------------------------------------------------------

    \190\ Nat'l Parks Conserv. Ass'n v. U.S. EPA, 788 F.3d 1134, 
1148-49 (9th Cir. 2014).
    \191\ Even in that initial scenario, at least cost of 
compliance, as expressed in cost-effectiveness in dollars per ton, 
can be compared with what has been found reasonable for best 
available control technology (BACT) and reasonably available control 
technology (RACT), and visibility improvement can be compared with 
the 0.5 dv subject-to-BART threshold that determines whether a BART-
eligible source causes or contributes to visibility impairment in 
Class I areas. The EPA notes that this alternate methodology would 
also support our proposed BART determinations in this action.
---------------------------------------------------------------------------

    Specifically, we propose to compare the average cost-effectiveness, 
incremental cost-effectiveness, visibility improvement, and incremental 
visibility improvement for LNB and SOFA with SCR with BART 
determinations where the EPA and States have based their determination 
on the same metrics. The most comparable determination appears to be in 
EPA's final action for Wyoming's regional haze SIP, in which EPA 
promulgated a FIP for three units at Laramie River Station and 
determined NOX BART to be LNB and SOFA with SCR for the 
three units.\192\ On a per-unit basis, the visibility improvement at 
the most impacted Class I area from this control option was 0.52 to 
0.57 dv, and across all three units the sum of the improvement was 1.62 
dv. Thus, the application of this control option to all three units of 
Laramie River Station was estimated to have a visibility benefit about 
the same as the application of this control option to Hunter Unit 1. 
The average cost-effectiveness ranged from $4,375/ton to $4,461/ton, 
considerably higher than the corresponding value for Hunter Unit 1, 
while the incremental cost-effectiveness ranged from $5,449 to $5,871/
ton which is very close to the corresponding value for Hunter Unit 1. 
Finally, the incremental visibility improvement as compared to LNB and 
SOFA with SNCR was significant, as it is for Hunter Unit 1. On the 
other hand, at Dave Johnston Units 3 and 4 (for example), where EPA 
rejected LNB and SOFA with SCR, the incremental cost-effectiveness 
value of LNB and SOFA with SCR was much higher and incremental 
visibility benefit lower than at Laramie River Station and higher than 
the same metrics at Hunter Unit 1.\193\
---------------------------------------------------------------------------

    \192\ 79 FR 5032, 5047 (Jan. 30, 2014).
    \193\ 79 FR 5032, 5049.
---------------------------------------------------------------------------

    There are other BART determinations in which SCR has been selected 
as BART (either alone or in conjunction with LNB and SOFA) based on 
similar metrics, although those determinations may not have explicitly 
discussed incremental cost-effectiveness and incremental visibility 
benefits on a per-unit basis. First, the State of Colorado selected, 
and the EPA approved, SCR as NOX BART for Public Service 
Company's Hayden Station, Units 1 and 2.\194\ Hayden Units 1 and 2 were 
equipped with first generation LNB and over-fire air (OFA) installed in 
1999.\195\ In its BART determination, Colorado considered these 
existing controls as given and analyzed as feasible controls upgraded 
LNB, SNCR, and SCR. Based on an average cost-effectiveness of $3,385/
ton and $4,064/ton, incremental cost-effectiveness (as compared with 
LNB and OFA with SNCR) of $5,326/ton and $7,331/ton, and visibility 
improvement of 1.12 dv and 0.85 dv at the most impacted Class I area, 
respectively, Colorado selected SCR as BART for Units 1 and 2. In this 
case, due to the existing controls at Hayden Station, the cost-
effectiveness values for SCR for Hayden Units 1 and 2 should be 
compared to the incremental cost-effectiveness values (as compared with 
LNB and SOFA, and with LNB and SOFA with SNCR) for SCR for Hunter Unit 
1, and similarly for incremental visibility benefits. We think they are 
comparable, particularly for Hayden Unit 2, and considering that Hunter 
Unit 1 significantly impacts several Class I areas, while Colorado 
selected SCR for Hayden based solely on the visibility improvement at 
the most impacted Class I area, Mt. Zirkel Wilderness.
---------------------------------------------------------------------------

    \194\ 77 FR 18069 (Mar. 26, 2012) (proposal); 77 FR 76871 (Dec. 
31, 2012) (final).
    \195\ Colorado Department of Health and Environment, Air 
Pollution Control Division, Best Available Retrofit Technology 
(BART) Analysis of Control Options For Public Service Company--
Hayden Station, p. 5, available at https://www.colorado.gov/pacific/sites/default/files/AP_PO_Hayden-Power-Plant_0.pdf.
---------------------------------------------------------------------------

    Another comparable determination can be found in EPA's FIP for 
Arizona Public Service's Cholla Power Plant, Units 2, 3, and 4, in 
which EPA determined that NOX BART was SCR.\196\ Similarly 
to Colorado's determination for Hayden, EPA considered the existing 
controls, LNB and OFA, at the three units and estimated average cost-
effectiveness values for SCR of $3,114/ton, $3,472/ton, and $3,395/ton, 
and incremental cost-effectiveness values (as compared to LNB and OFA 
with SNCR) of $3,257/ton, $3,811/ton, and $3,661/ton, respectively, for 
Units 2, 3, and 4. EPA's modeling showed a source-wide visibility 
improvement for SCR of 1.34 dv at the most impacted Class I area. Based 
on these metrics, EPA determined NOX BART to be SCR for the 
three units. In this case, as with Hayden, the average cost-
effectiveness of SCR at Cholla should be compared with the incremental 
cost-effectiveness of SCR (as compared with just LNB and SOFA) at 
Hunter Unit 1. The cost-effectiveness values for Hunter Unit 1 are 
somewhat higher than at Cholla, but on the other hand the source-wide 
visibility improvement at Hunter Units 1 and 2 (as obtained by summing 
the per-unit improvements from Units 1 and 2) \197\ from LNB and SOFA 
with SCR is 2.759 dv at the most impacted Class I area, with 
incremental visibility improvements of 1.29 dv and 0.932 dv over LNB 
and SOFA and LNB and SOFA with SNCR, respectively. These visibility 
improvements are very much in line with those at Cholla, and given that 
the incremental cost-effectiveness of SCR at Hunter Unit 1 is still 
reasonable, the comparison with Cholla also supports selection of SCR 
for Hunter Unit 1. We invite comment on other potentially relevant BART 
determinations and our methodology generally.
---------------------------------------------------------------------------

    \196\ 77 FR 42834 (July 20, 2012) (proposal); 77 FR 72512, 
72514-15 (Dec. 5, 2012) (final).
    \197\ We use the source-wide number here to compare with the 
Cholla determination; in addition as explained above we must 
consider source-wide visibility improvements.
---------------------------------------------------------------------------

    Based on these comparisons to Laramie River Station, Hayden 
Station, Dave Johnston Units 3 and 4, and Cholla Power Plant, we think 
that selection of LNB and SOFA with SCR as BART for Hunter Unit 1 would 
be fully consistent with these prior actions. For Hunter

[[Page 2038]]

Unit 1, LNB and SOFA with SCR is very cost-effective, at $2,380/ton on 
an average basis (counting the costs and emission reductions from the 
combination of the three control technology elements) and at $5,268/ton 
on an incremental basis compared to LNB with SOFA and SNCR. Compared to 
LNB with SOFA, the incremental cost effectiveness is $4,813/ton, which 
also compares favorably to the incremental cost effectiveness that 
supported the selection of LNB with SOFA and SCR for Laramie River 
Station. For Hunter Unit 1, LNB and SOFA with SCR provides substantial 
visibility benefits at several Class I areas that are similar to those 
from Laramie River Station and larger than those from Dave Johnson 
Units 3 and 4. For example, the visibility improvement from that 
control option installed on a single unit is 1.342 dv at Arches NP, 
1.545 dv at Canyonlands NP, and 1.113 at Capitol Reef NP. These 
comparisons show that costs are justified in light of the substantial 
visibility benefits, both total and incremental.
    In the case of Hunter, the unit level visibility improvements 
justify the most stringent level of control, SCR, for each of the two 
Hunter units. Necessarily, when we consider the source-wide visibility 
improvements, they will be larger and also justify the most stringent 
level of control. In addition, the unit level visibility improvements 
and source-wide visibility improvements (as derived by summing the unit 
level visibility improvements) at other impacted Class I areas, 
particularly Arches NP and Capitol Reef NP, support the most stringent 
level of control. Accordingly, for Hunter Unit 1, we propose to find 
that BART for NOX is LNB and SOFA with SCR, represented by 
an emission limit of 0.07 lb/MMBtu (30-day rolling average). The 
proposed BART emission limit of 0.07 lb/MMBtu allows for a sufficient 
margin of compliance for a 30-day rolling average limit that would 
apply at all times, including startup, shutdown, and malfunction.\198\ 
We are also proposing monitoring, recordkeeping, and reporting 
requirements as described in our proposed regulatory text for 40 CFR 
52.2336.
---------------------------------------------------------------------------

    \198\ Emission limits such as BART are required to be met on a 
continuous basis. See 70 FR 39104, 39172 (July 6, 2005) (stating 
that emissions limits including BART are to be met on a ``continuous 
basis'' in the BART Guidelines, section V); 42 U.S.C. 7602(k) 
(noting that emission limits are to be on ``a continuous basis'').
---------------------------------------------------------------------------

    Under 40 CFR 51.308(e)(1)(iv), ``each source subject to BART [is] 
required to install and operate BART as expeditiously as practicable, 
but in no event later than five years after approval of the 
implementation plan revision.'' In light of the considerable effort 
involved to retrofit SCR, we propose that five years is as 
expeditiously as practicable. Therefore, we propose a compliance 
deadline of five years from the date our final FIP becomes effective.
b. Hunter Unit 2
    Generally speaking, Hunter Unit 2 is identical to Hunter Unit 1. 
The Hunter Unit 2 boiler is of tangential-fired design with newer 
generation low-NOX burners and separated overfire air which 
were installed in spring 2011. Hunter Unit 2 currently achieves an 
annual emission rate of approximately 0.20 lb/MMBtu with these 
combustion controls. Under Utah's submitted regional haze SIP, Unit 1 
is subject to a state-law NOX emission limit of 0.26 lb/
MMBtu on a 30-day rolling average. Prior to the installation of LNB and 
SOFA the unit operated with an actual annual emission rate of about 
0.38 lb/MMBtu.
Step 1: Identify All Available NOX Control Technologies
    For the same reasons as for Hunter Unit 1, we propose to adopt the 
identification of available NOX control technologies in 
PacifiCorp's 2012 BART analysis to satisfy Step 1, and we refer the 
reader to the 2012 PacifiCorp BART analysis for details on those 
control technologies.
Step 2: Eliminate Technically Infeasible Options
    In its 2012 BART analysis,\199\ PacifiCorp eliminated available 
NOX control technologies that PacifiCorp evaluated as 
technologically infeasible for Hunter Unit 2. The remaining 
technologically feasible control technologies are the combustion 
controls, LNB and SOFA, and the post-combustion controls, SNCR and SCR.
---------------------------------------------------------------------------

    \199\ PacifiCorp BART Analysis for Hunter Unit 2, pp. 2.b-105--
2.a-122 (2012).
---------------------------------------------------------------------------

    As with Hunter Unit 1, we agree with PacifiCorp's evaluation of 
technologically available controls for Hunter Unit 2 and propose to 
adopt it for Step 2.
Step 3: Evaluate Control Effectiveness of Remaining Control 
Technologies
    As noted previously, Hunter Unit 2 is currently achieving an actual 
annual emission rate of approximately 0.20 lb/MMBtu with LNB and SOFA. 
This represents a 48.2 percent reduction from the baseline emission 
rate of 0.38 lb/MMBtu.
    SCR can achieve performance emission rates as low as 0.04 to 0.07 
lb/MMBtu on an annual basis.\200\ For this analysis, consistent with 
our actions elsewhere, as well with PacifiCorp's analysis, we use an 
annual emission rate of 0.05 lb/MMBtu for SCR, which when combined with 
LNB and SOFA achieves an overall control efficiency of 86.9 percent. 
For this analysis, consistent with our actions elsewhere, as well with 
PacifiCorp's analysis, we use an annual emission rate of 0.05 lb/MMBtu 
for SCR, which when combined with LNB and SOFA achieves an overall 
control efficiency of 86.9 percent.
---------------------------------------------------------------------------

    \200\ Srivastava, R., Hall, R., Khan, S., Lani, B., & Culligan, 
K., Nitrogen Oxides Emission Control Options for Coal-Fired Utility 
Boilers, 55 J. Air & Waste Mgmt. Assoc. 1367, 1385-86 (2005).
---------------------------------------------------------------------------

    As with Hunter Unit 1, we evaluated post-combustion control 
technologies, SNCR and SCR, in combination with combustion controls. 
Our evaluation is the same as for Hunter Unit 1. A summary of emissions 
projections for the control options evaluated is provided in Table 19.

                  Table 19--Summary of NOX BART Analysis Control Technologies for Hunter Unit 2
----------------------------------------------------------------------------------------------------------------
                                           Control        Annual emission       Emissions          Remaining
           Control option             effectiveness (%)   rate (lb/MMBtu)    reduction (tpy)    emissions (tpy)
----------------------------------------------------------------------------------------------------------------
LNB/SOFA+SCR........................               86.9               0.05              5,230                788
LNB/SOFA+SNCR.......................               59.2               0.16              3,562              2,457
LNB/SOFA............................               48.2               0.20              2,902              3,117
Baseline \1\........................  .................               0.38  .................              6,018
----------------------------------------------------------------------------------------------------------------
\1\ Baseline emissions were determined by averaging the annual emissions from 2001 to 2003 as reported to EPA
  Air Markets Program Data available at http://ampd.epa.gov/ampd/.

[[Page 2039]]

Step 4: Evaluate Impacts and Document Results
Part 1--Costs of Compliance
    We obtained capital costs for LNB and SOFA from the 2014 PacifiCorp 
BART analysis. PacifiCorp did not report any operating and maintenance 
costs for LNB and SOFA. Similarly, we obtained capital cost estimates 
for LNB and SOFA with SNCR from the 2014 PacifiCorp BART analysis. 
However, for operating and maintenance costs we propose to rely on the 
draft 2015 draft SNCR chapter of the CCM. Refer to the ATP report for 
details. Capital costs for LNB and SOFA with SCR were also obtained 
from the 2014 PacifiCorp BART analysis. However, PacifiCorp's capital 
costs were adjusted to account for items that were double-counted or 
should not be allowed under the CCM, such as AFUDC.\201\ In addition, 
the capital costs were adjusted to account for a significant 
overestimation of the catalyst volume and related costs. These 
adjustments are documented in the ATP report and associated spread 
sheet. A discussion of operating and maintenance costs of SCR is also 
included in the ATP report. For the reasons given in the report, we 
propose to adopt the cost estimates contained in it.
---------------------------------------------------------------------------

    \201\ See 79 FR 5032, 5133 (Jan. 30, 2014) (discussing reasons 
for rejecting use of AFUDC).
---------------------------------------------------------------------------

    A summary of our proposed cost estimates for all control options is 
presented in Table 20.

                                                  Table 20--Summary of NOX BART Costs on Hunter Unit 2
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                          Average cost
            Control option                Total capital     Indirect annual     Direct annual    Total annual cost      Emissions      effectiveness ($/
                                            investment            cost               cost                            reductions (tpy)         ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
LNB/SOFA..............................              $8.6M              $0.9M                $0M              $0.9M              2,902               $298
LNB/SOFA/SNCR.........................              16.0M               1.6M               1.9M               3.5M              3,562                968
LNB/SOFA/SCR..........................             108.1M               10.3               2.4M              12.7M              5,230              2,432
--------------------------------------------------------------------------------------------------------------------------------------------------------

Parts 2 and 3--Energy and Non-Air Quality Environmental Impacts of 
Compliance
    The energy and non-air quality impacts for Hunter Unit 2 are nearly 
identical to those for Hunter Unit 1 as discussed previously. 
Accordingly, for the same reasons as for Hunter Unit 1, we propose to 
determine that we have adequately considered these impacts by including 
cost of additional energy in cost effectiveness and assessing non-air 
quality environmental impacts as insufficient to eliminate or weigh 
against any of the BART options.
Part 4--Remaining Useful Life
    PacifiCorp assumes a remaining useful life of at least 20 years for 
Hunter Unit 2 in its BART analysis, and has not indicated any intention 
to retire, or curtail generation from, Hunter Unit 2. Therefore, this 
factor does not preclude any of the control options considered. In 
addition, this factor is consistent with our BART calculation of cost 
effectiveness because annualized costs have been calculated over a 20 
year period for each of the control options considered. We propose that 
this gives adequate consideration to this factor.
Step 5: Evaluate Visibility Impacts
    Table 21 presents the highest of the 98th percentile visibility 
improvements at the affected Class I areas for the three meteorological 
years modeled, 2001 through 2003. Tables 22 and 23 present the number 
of days (summed across three years) with impacts greater than the 
contribution and causation thresholds--0.5 dv and 1.0 dv, respectively.

                                Table 21--Hunter Unit 2--Visibility Improvements
----------------------------------------------------------------------------------------------------------------
                                                           LNB with SOFA    LNB with SOFA and  LNB with SOFA and
                      Class I area                          ([Delta]dv)      SNCR ([Delta]dv)   SCR ([Delta]dv)
----------------------------------------------------------------------------------------------------------------
Arches NP..............................................              0.569              0.711              1.080
Black Canyon of the Gunnison NP........................              0.153              0.189              0.279
Bryce Canyon NP........................................              0.234              0.291              0.429
Canyonlands NP.........................................              0.658              0.822              1.250
Capitol Reef NP........................................              0.491              0.623              0.879
Flat Tops WA...........................................              0.180              0.223              0.328
Grand Canyon NP........................................              0.275              0.340              0.506
Mesa Verde NP..........................................              0.182              0.225              0.344
Zion NP................................................              0.144              0.178              0.262
----------------------------------------------------------------------------------------------------------------

                             Table 22--Hunter Unit 2--Days Greater Than 0.5 Deciview
                                               [Three year total]
----------------------------------------------------------------------------------------------------------------
                                                           LNB with SOFA    LNB with SOFA and  LNB with SOFA and
            Class I area               Baseline (days)         (days)          SNCR (days)         SCR (days)
----------------------------------------------------------------------------------------------------------------
Arches NP...........................                293                276                268                245
Black Canyon of the Gunnison NP.....                 68                 57                 55                 49
Bryce Canyon NP.....................                 42                 39                 37                 30
Canyonlands NP......................                359                336                331                317
Capitol Reef NP.....................                175                163                161                152

[[Page 2040]]

 
Flat Tops WA........................                 77                 64                 63                 57
Grand Canyon NP.....................                 49                 46                 45                 40
Mesa Verde NP.......................                 82                 72                 66                 59
Zion NP.............................                 29                 24                 23                 22
----------------------------------------------------------------------------------------------------------------

                             Table 23--Hunter Unit 2--Days Greater Than 1.0 Deciview
                                               [Three year total]
----------------------------------------------------------------------------------------------------------------
                                                           LNB with SOFA    LNB with SOFA and  LNB with SOFA and
            Class I area               Baseline (days)         (days)          SNCR (days)         SCR (days)
----------------------------------------------------------------------------------------------------------------
Arches NP...........................                170                151                145                131
Black Canyon of the Gunnison NP.....                 22                 16                 13                 11
Bryce Canyon NP.....................                 22                 21                 19                 16
Canyonlands NP......................                240                221                218                198
Capitol Reef NP.....................                118                113                111                105
Flat Tops WA........................                 31                 20                 20                 14
Grand Canyon NP.....................                 32                 25                 25                 22
Mesa Verde NP.......................                 32                 22                 20                 14
Zion NP.............................                 14                 11                  9                  8
----------------------------------------------------------------------------------------------------------------

    Select BART.
    A summary of our impacts analysis for Hunter Unit 2 is presented in 
Table 24.

                                                   Table 24--Summary of Hunter Unit 2 Impacts Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                          Annual                  Total                                                     Visibility impacts *
                                         emission    Emission    annual     Average  cost     Incremental  cost    -------------------------------------
            Control option              rate (lb/   reduction     costs     effectiveness   effectiveness ($/ton)     Improvement     Days >     Days >
                                          MMBtu)      (tpy)    (million$)      ($/ton)                                   (dv)         0.5 dv     1.0 dv
--------------------------------------------------------------------------------------------------------------------------------------------------------
LNB with SOFA........................         0.20      2,902       $0.9M            $298  .......................           0.658        336        221
LNB with SOFA and SNCR...............         0.16      3,562        3.5M             968  $3,913.................           0.822        331        218
LNB with SOFA and SCR................         0.05      5,230       12.7M           2,432  $5,558 (compared to LNB           1.250        317        198
                                                                                            with SOFA and SNCR).
                                                                                           $5,092 (compared to LNB
                                                                                            with SOFA)..
--------------------------------------------------------------------------------------------------------------------------------------------------------
* At the most impacted Class I area, Canyonlands National Park.

    In determining what to co-propose as BART, we have taken into 
consideration all five of the statutory factors required by the CAA: 
The costs of compliance, the energy and non-air quality environmental 
impacts of compliance, any existing pollution control technology in use 
at the source, the remaining useful life of the source, and the degree 
of improvement in visibility which may reasonably be anticipated to 
result from the use of such technology. Later on we provide a 
justification for our selection of BART, including an explanation of 
how each of the CAA factors was used in that selection.
    We have considered the energy and non-air quality environmental 
impacts of compliance and propose to find that they do not appreciably 
favor one control option over another, or preclude a particular control 
option from selection. As explained for Hunter Unit 1, the existing 
pollution controls have been accounted for in our evaluation of BART, 
and also would not favor or preclude any of the control options 
considered. And finally, we have considered the remaining useful life 
of the source and find that it is sufficiently long (greater than 20 
years) so as not to favor or preclude any of the control options. As a 
result, the remaining factors--the costs of compliance and visibility 
improvement--are the primary factors that lead us to our proposed BART 
selection for Hunter Unit 2.
    In order to select BART we propose (for the same reasons as for 
Hunter Unit 1) to weigh the costs of compliance against visibility 
impacts by generally comparing them with BART determinations that have 
been made elsewhere. Specifically, we propose to compare the average 
cost-effectiveness, incremental cost-effectiveness, visibility 
improvement, and incremental visibility improvement for LNB and SOFA 
with SCR with BART determinations where the EPA and States have based 
their determination on the same metrics. The most comparable 
determinations are the same as for Hunter Unit 1: Laramie River 
Station, Hayden Station, and Cholla Power Plant.

[[Page 2041]]

    Based on these comparisons, we think LNB and SOFA with SCR for 
Hunter 2 is fully consistent with the other BART determinations. LNB 
and SOFA with SCR is very cost-effective at $2,432/ton, and provides 
substantial visibility benefits at several Class I areas. For example, 
the visibility improvement from that control option is 1.250 dv at 
Canyonlands NP and 1.080 dv at Arches NP. The incremental cost-
effectiveness of SCR, $5,558/ton, is by comparison also reasonable. 
This comparison also shows that costs are justified in light of the 
substantial visibility benefits, both total and incremental.
    In the case of Hunter, the unit level visibility improvements 
justify the most stringent level of control, SCR, for each of the two 
Hunter units. Necessarily, when we consider the source-wide visibility 
improvements, they will be larger and also justify the most stringent 
level of control. In addition, the unit level visibility improvements 
and source-wide visibility improvements (as derived by summing the unit 
level visibility improvements) at other impacted Class I areas, 
particularly Arches NP and Capitol Reef NP, support the most stringent 
level of control.
    Accordingly, for Hunter Unit 2, we propose to find that BART for 
NOX is LNB and SOFA with SCR, represented by an emission 
limit of 0.07 lb/MMBtu (30-day rolling average). The proposed BART 
emission limit of 0.07 lb/MMBtu allows for a sufficient margin of 
compliance for a 30-day rolling average limit that would apply at all 
times, including startup, shutdown, and malfunction.\202\ We are also 
proposing monitoring, recordkeeping, and reporting requirements as 
described in our proposed regulatory text for 40 CFR 52.2336.
---------------------------------------------------------------------------

    \202\ Emission limits such as BART are required to be met on a 
continuous basis. See 70 FR 39104, 39172 (July 6, 2005) (stating 
that emissions limits including BART are to be met on a ``continuous 
basis'' in the BART Guidelines, section V); 42 U.S.C. 7602(k) 
(noting that emission limits are to be on ``a continuous basis'').
---------------------------------------------------------------------------

    Under 40 CFR 51.308(e)(1)(iv), ``each source subject to BART [is] 
required to install and operate BART as expeditiously as practicable, 
but in no event later than 5 years after approval of the implementation 
plan revision.'' In light of the considerable effort involved to 
retrofit SCR, we propose that five years is as expeditiously as 
practicable. Therefore, we propose a compliance deadline of five years 
from the date our final FIP becomes effective.
3. Huntington Power Plant
    As described previously in section IV.A, Huntington Units 1 and 2 
were determined to be subject to BART. PacifiCorp's Huntington Power 
Plant (Huntington), is located in Huntington City, Utah, and consists 
of a total of the two electric utility steam generating units. 
Huntington Units 1 and 2 have a nameplate generating capacity of 498 MW 
each.\203\ The boilers are tangentially fired pulverized coal boilers, 
burning bituminous coal from the nearby Deer Creek Mine.
---------------------------------------------------------------------------

    \203\ See U.S. Energy Information Administration, Electric 
Generating Capacity for 2011 (taken from Form EIA-860). See ``EIA 
existing generating units 2011.xls'' spreadsheet in the docket.
---------------------------------------------------------------------------

    Our evaluation of BART for Huntington Unit 1 and 2 follows the 
Guidelines for BART Determinations Under the Regional Haze Rule, which 
are found in appendix Y to 40 CFR part 51. For Huntington Units 1 and 
2, the BART Guidelines are mandatory because the combined capacity for 
all units at the Huntington facility is greater than 750 MW.\204\ Under 
the Guidelines, cost estimates for control technologies should be based 
on the CCM, where possible.
---------------------------------------------------------------------------

    \204\ See 40 CFR 51.302(e)(1)(ii)(B) (``The determination of 
BART for fossil-fuel fired power plants having a total generating 
capacity greater than 750 megawatts must be made pursuant to the 
guidelines in appendix Y of this part.'').
---------------------------------------------------------------------------

    The BART Guidelines establish presumptive NOX limits for 
coal-fired EGUs greater than 200 MW located at greater than 750 MW 
power plants that are operating without post-combustion controls. For 
the tangential-fired boilers burning bituminous coal at Huntington, 
that presumptive limit is 0.28 lb/MMBtu.\205\ The BART Guidelines 
provide that the five factor analysis may result in a limit that is 
different than the presumptive limit, and the presumptive limits do not 
obviate the need to determine BART on a case-by-case basis considering 
the five factors.\206\
---------------------------------------------------------------------------

    \205\ 40 CFR part 51, appendix Y, IV.E.5, Table. 1.
    \206\ See 40 CFR 51.301 (defining BART); 40 CFR 51.308(e).
---------------------------------------------------------------------------

    PacifiCorp provided BART analyses for Huntington 1 and 2 to Utah in 
2012 and 2014 which we utilize in our proposed BART evaluation 
here.\207\ Although we are using some information provided by Utah and 
PacifiCorp, we have independently evaluated all five statutory BART 
factors.
---------------------------------------------------------------------------

    \207\ See PacifiCorp BART Analysis for Huntington Unit 1(2012); 
PacifiCorp BART Analysis for Huntington Unit 2 (2012); see also 
Chapter 2 of the Technical Support Document for Utah's Regional Haze 
BART Submittal; PacifiCorp's BART Analysis Update for Hunter Units 1 
and 2 and Huntington Units 1 and 2 (2014).
---------------------------------------------------------------------------

a. Huntington Unit 1
    The Huntington Unit 1 boiler is of tangential-fired design with 
newer generation low-NOX burners and separated overfire air 
which were installed in fall 2010. Huntington Unit 1 currently achieves 
an annual emission rate of approximately 0.22 lb/MMBtu with these 
combustion controls. Under Utah's submitted regional haze SIP, Unit 1 
is subject to a state-law NOX emission limit of 0.26 lb/
MMBtu on a 30-day rolling average. Prior to the installation of LNB and 
SOFA the unit operated with an actual annual emission rate of about 
0.37 lb/MMBtu.
Step 1: Identify All Available NOX Control Technologies
    In its 2012 BART analysis for Huntington Unit 1, PacifiCorp 
identified several NOX control technologies, both for 
combustion controls and post-combustion controls.\208\ The combustion 
controls identified by PacifiCorp include: Low-NOX burners 
and separated overfire air (LNB and SOFA overfire air; already 
installed), rotating overfire air, neural network optimization system, 
flue gas recirculation, gas reburn, fuel lean gas reburn, coal 
switching, water injection, and others. Post-combustion control options 
identified by PacifiCorp include: SNCR, RRI, SCR, and others.
---------------------------------------------------------------------------

    \208\ PacifiCorp BART Analysis for Huntington Unit 1, p. 2.c-60 
(2012).
---------------------------------------------------------------------------

    We note that the combustion controls, LNB and SOFA, have already 
been installed on Huntington Unit 1, and so we consider them here as 
``any existing controls'' under the third statutory factor. In 
addition, the BART Guidelines recognize that ``[c]ombinations of 
inherently lower-emitting processes and add-on controls'' are a 
category of retrofit controls which can be considered.\209\ 
Accordingly, the inherently lower-emitting combustion controls, LNB and 
SOFA, are evaluated in combination with the add-on controls, SNCR and 
SCR.
---------------------------------------------------------------------------

    \209\ 40 CFR part 51 appendix Y.
---------------------------------------------------------------------------

    We have reviewed PacifiCorp's review of NOX control 
technologies and find it to be comprehensive. We propose to adopt it to 
satisfy Step 1 and we refer to the 2012 PacifiCorp BART analysis for 
details on the available NOX control technologies.
Step 2: Eliminate Technically Infeasible Options
    In its 2012 BART analysis,\210\ PacifiCorp eliminated available 
NOX control technologies that PacifiCorp evaluated as 
technologically infeasible for Huntington Unit 1. The remaining 
technologically feasible control technologies are the combustion

[[Page 2042]]

controls, LNB and SOFA, and the post-combustion controls, SNCR and SCR.
---------------------------------------------------------------------------

    \210\ PacifiCorp BART Analysis for Huntington Unit 1, pp. 2.c-
61--2.c-77 (2012).
---------------------------------------------------------------------------

    We agree with PacifiCorp's evaluation of technologically available 
controls for Huntington Unit 1 and propose to adopt it for Step 2.
Step 3: Evaluate Control Effectiveness of Remaining Control 
Technologies
    As noted previously, Huntington Unit 1 is currently achieving an 
actual annual emission rate of approximately 0.22 lb/MMBtu with LNB and 
SOFA. This represents a 41.5 percent reduction from the baseline 
emission rate of 0.37 lb/MMBtu.
    The post-combustion control technologies, SNCR and SCR, have been 
evaluated in combination with combustion controls. That is, the inlet 
concentration to the post-combustion controls is assumed to be 0.22 lb/
MMBtu (annual). This allows the equipment and operating and maintenance 
costs of the post-combustion controls to be minimized based on the 
lower inlet NOX concentration.
    Typically, SNCR reduces NOX an additional 20 to 30 
percent above combustion controls without excessive NH3 
slip.\211\ For this analysis, the control efficiency of SNCR has been 
calculated based on the formula in the 2015 draft CCM SNCR 
chapter,\212\ which for Huntington Unit 1 yields an additional 
reduction of 21.7 percent after combustion controls. When combined with 
LNB and SOFA, SNCR is anticipated to achieve an annual emission rate of 
0.17 lb/MMBtu, corresponding to an overall control efficiency of 54.2 
percent.
---------------------------------------------------------------------------

    \211\ Institute of Clean Air Companies, White Paper, SNCR for 
Controlling NOX Emissions, pp. 4, 9 (Feb. 2008).
    \212\ See [DRAFT] 2015 SNCR CCM (July 2015), Figure 1.1c: SNCR 
NOX Reduction Efficiency Versus Baseline NOX 
Levels for Coal-fired Utility Boilers.
---------------------------------------------------------------------------

    SCR can achieve performance emission rates as low as 0.04 to 0.07 
lb/MMBtu on an annual basis.\213\ For this analysis, consistent with 
our actions elsewhere, as well with PacifiCorp's analysis, we use an 
annual emission rate of 0.05 lb/MMBtu for SCR, which when combined with 
LNB and SOFA achieves an overall control efficiency of 86.7 percent.
---------------------------------------------------------------------------

    \213\ Srivastava, R., Hall, R., Khan, S., Lani, B., & Culligan, 
K., Nitrogen Oxides Emission Control Options for Coal-Fired Utility 
Boilers, 55 J. Air & Waste Mgmt. Assoc. 1367, 1367-88 (2005).
---------------------------------------------------------------------------

    A summary of emissions projections for the control options 
evaluated is provided in Table 25.

                Table 25--Summary of NOX BART Analysis Control Technologies for Huntington Unit 1
----------------------------------------------------------------------------------------------------------------
                                                      Control         Annual         Emissions       Remaining
                 Control option                    effectiveness   emission rate     reduction       emissions
                                                        (%)         (lb/MMBtu)         (tpy)           (tpy)
----------------------------------------------------------------------------------------------------------------
LNB/SOFA +SCR...................................            86.7            0.05           5,092             784
LNB/SOFA +SNCR..................................            54.2            0.17           3,185           2,692
LNB/SOFA........................................            41.5            0.22           2,440           3,436
Baseline \1\....................................  ..............            0.37  ..............           5,876
----------------------------------------------------------------------------------------------------------------
\1\ Baseline emissions were determined by averaging the annual emissions from 2001 to 2003 as reported to EPA
  Air Markets Program Data available at http://ampd.epa.gov/ampd/.

Step 4: Evaluate Impacts and Document Results
Part 1--Costs of Compliance
    We obtained capital costs for LNB and SOFA from the 2014 PacifiCorp 
BART analysis. PacifiCorp did not report any operating and maintenance 
costs for LNB and SOFA. Similarly, we obtained capital cost estimates 
for LNB and SOFA with SNCR from the 2014 PacifiCorp BART analysis. 
However, for operating and maintenance costs we propose to rely on the 
draft 2015 draft SNCR chapter of the CCM. Refer to the ATP report for 
details. Capital costs for LNB and SOFA with SCR were also obtained 
from the 2014 PacifiCorp BART analysis. However, PacifiCorp's capital 
costs were adjusted to account for items that were double-counted or 
should not be allowed under the CCM, such as AFUDC.\214\ In addition, 
the capital costs were adjusted to account for a significant 
overestimation of the catalyst volume and related costs. These 
adjustments are documented in the ATP report and associated spread 
sheet. A discussion of operating and maintenance costs of SCR is also 
included in the ATP report. For the reasons given in the report, we 
propose to adopt the cost estimates contained in it.
---------------------------------------------------------------------------

    \214\ See 79 FR 5032, 5133 (Jan. 30, 2014) (discussing reasons 
for rejecting use of AFUDC).
---------------------------------------------------------------------------

    A summary of our proposed cost estimates for all control options is 
presented in Table 26.

                                                Table 26--Summary of NOX BART Costs on Huntington Unit 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                             Emissions     Average Cost
                     Control option                        Total capital     Indirect      Direct annual   Total annual     reductions     effectiveness
                                                            investment      annual cost        cost            cost            (tpy)          ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
LNB/SOFA................................................           $8.1M           $0.8M             $0M           $0.8M           2,440            $332
LNB/SOFA/SNCR...........................................           15.5M            1.5M            2.0M            3.5M           3,185           1,098
LNB/SOFA/SCR............................................          107.8M           10.3M            2.5M           12.8M           5,092           2,515
--------------------------------------------------------------------------------------------------------------------------------------------------------

Parts 2 and 3--Energy and Non-Air Quality Environmental Impacts of 
Compliance
    SNCR slightly reduces the thermal efficiency of a boiler as the 
reduction reaction uses thermal energy from the boiler, decreasing the 
energy available for power generation.\215\ Using the CCM, we have 
calculated the electrical power consumption of SNCR to be 361,000 kW-hr 
per year for Huntington Unit 1.
---------------------------------------------------------------------------

    \215\ EPA Air Pollution Control Cost Manual, pp. 1-21 (6th ed. 
2002).
---------------------------------------------------------------------------

    For SCR, the thermal efficiency is much more reduced because the 
new ductwork and the reactor's catalyst layers decrease the flue gas 
pressure. As

[[Page 2043]]

a result, additional fan power is necessary to maintain the flue gas 
flow rate through the ductwork and reactor. Using the CCM, we have 
calculated the electrical power consumption of SCR to be approximately 
18,617,000 kW-hr per year for Huntington Unit 1.
    Both SCR and SNCR require some minimal electricity to service 
pretreatment and injection equipment, pumps, compressors, and control 
systems. The energy requirements described earlier are not significant 
enough to warrant elimination of either SNCR or SCR as BART. In 
addition, the cost of the additional energy requirements has been 
included in our cost effectiveness calculations.
    SNCR and SCR will slightly increase the quantity of ash that will 
need to be disposed. In addition, transportation and storage of 
chemical reagents may result in spills or releases. However, these non-
air quality environmental impacts do not warrant elimination of either 
SNCR or SCR as BART.
    There are no additional energy requirements associated with the new 
LNB and SOFA, and no significant non-air quality environmental impacts.
    In summary, we propose to determine that we have adequately 
considered these impacts by including cost of additional energy in cost 
effectiveness and assessing non-air quality environmental impacts as 
insufficient to eliminate or weigh against any of the BART options.
Part 4--Remaining Useful Life
    PacifiCorp assumes a remaining useful life of at least 20 years for 
Huntington Unit 1 in its BART analysis, and has not indicated any 
intention to retire, or curtail generation from, Huntington Unit 1. 
Therefore, this factor does not preclude any of the control options 
considered. In addition, this factor does not impact our BART 
calculation of cost effectiveness because annualized costs have been 
calculated over a 20 year period for each of the control options 
considered. We propose that this gives adequate consideration to this 
factor.
Step 5: Evaluate Visibility Impacts
    Table 27 presents the highest of the 98th percentile visibility 
improvements at the affected Class I areas for the three meteorological 
years modeled, 2001 through 2003. Tables 28 and 29 present the number 
of days (summed across three years) with impacts greater than the 
contribution and causation thresholds--0.5 dv and 1.0 dv, respectively.

                              Table 27--Huntington Unit 1--Visibility Improvements
----------------------------------------------------------------------------------------------------------------
                                                                                   LNB with SOFA   LNB with SOFA
                          Class I Area                             LNB with SOFA     and SNCR         and SCR
                                                                    ([Delta]dv)     ([Delta]dv)     ([Delta]dv)
----------------------------------------------------------------------------------------------------------------
Arches NP.......................................................           0.684           0.907           1.488
Black Canyon of the Gunnison NP.................................           0.156           0.205           0.328
Bryce Canyon NP.................................................           0.222           0.292           0.473
Canyonlands NP..................................................           0.851           1.133           1.881
Capitol Reef NP.................................................           0.493           0.651           1.108
Flat Tops WA....................................................           0.181           0.239           0.383
Grand Canyon NP.................................................           0.200           0.262           0.419
Mesa Verde NP...................................................           0.215           0.284           0.462
Zion NP.........................................................           0.150           0.198           0.320
----------------------------------------------------------------------------------------------------------------

                           Table 28--Huntington Unit 1--Days Greater Than 0.5 Deciview
                                               [Three year total]
----------------------------------------------------------------------------------------------------------------
                                                                                   LNB with SOFA
                  Class I Area                       Baseline      LNB with SOFA     and SNCR      LNB with SOFA
                                                      (days)          (days)          (days)      and SCR (days)
----------------------------------------------------------------------------------------------------------------
Arches NP.......................................             237             221             210             180
Black Canyon of the Gunnison NP.................              45              33              30              23
Bryce Canyon NP.................................              36              26              25              19
Canyonlands NP..................................             277             249             244             210
Capitol Reef NP.................................             131             117             116              99
Flat Tops WA....................................              64              41              37              27
Grand Canyon NP.................................              40              35              34              27
Mesa Verde NP...................................              63              46              41              30
Zion NP.........................................              21              16              16              14
----------------------------------------------------------------------------------------------------------------

                           Table 29--Huntington Unit 1--Days Greater than 1.0 Deciview
                                               [Three year total]
----------------------------------------------------------------------------------------------------------------
                                                                                   LNB with SOFA
                  Class I Area                       Baseline      LNB with SOFA     and SNCR      LNB with SOFA
                                                      (days)          (days)          (days)      and SCR (days)
----------------------------------------------------------------------------------------------------------------
Arches NP.......................................             146             121             117              86
Black Canyon of the Gunnison NP.................              16               7               7               3
Bryce Canyon NP.................................              19              13               9               5
Canyonlands NP..................................             175             153             143             117
Capitol Reef NP.................................              91              74              69              55

[[Page 2044]]

 
Flat Tops WA....................................              17               9               8               3
Grand Canyon NP.................................              19              13              12               9
Mesa Verde NP...................................              22              13              10               4
Zion NP.........................................              11               8               6               4
----------------------------------------------------------------------------------------------------------------

    Select BART.
    A summary of our impacts analysis for Huntington Unit 1 is 
presented in Table 30.

                                                 Table 30--Summary of Huntington Unit 1 Impacts Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                        Annual                    Total                                                     Visibility impacts *
                                       emission     Emission      annual     Average cost      Incremental cost    -------------------------------------
           Control option             rate (lb/    reduction      costs      effectiveness   effectiveness ($/ton)    Improvement     Days >     Days >
                                        MMBtu)       (tpy)      (million$)      ($/ton)                                  (dv)         0.5 dv     1.0 dv
--------------------------------------------------------------------------------------------------------------------------------------------------------
LNB with SOFA......................         0.22        2,440        $0.8M            $332  ......................           0.851        249        153
LNB with SOFA and SNCR.............         0.17        3,185         3.5M           1,098  3,609.................           1.113        244        143
LNB with SOFA and SCR..............         0.05        5,092        12.8M           2,515  $4,879 (compared to              1.881        210        117
                                                                                             LNB with SOFA and
                                                                                             SNCR).
                                                                                            $4,522 (compared to
                                                                                             LNB with SOFA).
--------------------------------------------------------------------------------------------------------------------------------------------------------
* At the most impacted Class I area, Canyonlands National Park.

    In determining what to co-propose as BART, we have taken into 
consideration all five of the statutory factors required by the CAA: 
The costs of compliance, the energy and non-air quality environmental 
impacts of compliance, any existing pollution control technology in use 
at the source, the remaining useful life of the source, and the degree 
of improvement in visibility which may reasonably be anticipated to 
result from the use of such technology. Later on we provide a 
justification for our selection of BART, including an explanation of 
how each of the CAA factors was used in that selection.
    As described in step 1 previously, we have considered the existing 
pollution control technology in use at the source. We note that 
Huntington Unit 1 was equipped with LNB and SOFA in the fall of 2010 in 
order to meet state-law requirements in the 2011 Utah RH SIP submittal, 
which we did not approve. In this co-proposal we have to evaluate 
control technologies and baseline emissions from the correct starting 
point, that is, prior to the installation of the combustion controls 
pursuant to state-law NOX limitations.\216\ As a result, we 
used the period 2001-2003 as the appropriate period for baseline 
emissions, in order to provide a realistic depiction of annual 
emissions for Huntington Unit 1 prior to installation of combustion 
controls.
---------------------------------------------------------------------------

    \216\ See 79 FR 5032, 5105-1 (Jan. 30, 2012).
---------------------------------------------------------------------------

    We have considered the energy and non-air quality environmental 
impacts of compliance and propose to find that they do not appreciably 
favor one control option over another, or preclude a particular control 
option from selection. And finally, we have considered the remaining 
useful life of the source and find that it is sufficiently long 
(greater than 20 years) so as not to favor or preclude any of the 
control options. As a result, the remaining factors--the costs of 
compliance and visibility improvement--are the primary factors that 
lead us to our proposed BART selection for Huntington Unit 1.
    Having already considered the other factors, in order to select 
BART we propose to weigh the costs of compliance against visibility 
impacts by generally comparing them with BART determinations that have 
been made elsewhere. Specifically, we propose to compare the average 
cost-effectiveness, incremental cost-effectiveness, visibility 
improvement, and incremental visibility improvement for LNB and SOFA 
with SCR with BART determinations where the EPA and States have based 
their determination on the same metrics. The most comparable 
determinations are the same as for Hunter Unit 1. The most comparable 
determination appears to be in EPA's final action for Wyoming's 
regional haze SIP, in which EPA promulgated a FIP for three units at 
Laramie River Station and determined BART to be LNB and SOFA with SCR 
for the three units.\217\ On a per-unit basis, the visibility 
improvement from that control option was 0.52 to 0.57 dv, and across 
all three units the sum of the improvement was 1.62 dv. The average 
cost-effectiveness ranged from $4,375/ton to $4,461/ton, while the 
incremental cost-effectiveness ranged from $5,449 to $5,871/ton. 
Finally, the incremental visibility improvement as compared to LNB and 
SOFA with SNCR was significant. On the other hand, at Dave Johnston 
Units 3 and 4 (for example), where EPA rejected LNB and SOFA with SCR, 
the incremental cost-effectiveness value of LNB and SOFA with SCR was 
much higher and incremental visibility benefit lower than at Laramie 
River Station.\218\
---------------------------------------------------------------------------

    \217\ 79 FR 5032, 5047 (Jan. 30, 2014).
    \218\ 79 FR 5032, 5049.

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

[[Page 2045]]

    There are other BART determinations in which SCR has been selected 
as BART (either alone or in conjunction with LNB and SOFA) based on 
similar metrics, although those determinations may not have explicitly 
discussed incremental cost-effectiveness and incremental visibility 
benefits on a per-unit basis. First, the State of Colorado selected, 
and the EPA approved, SCR as NOX BART for Public Service 
Company's Hayden Station, Units 1 and 2.\219\ Hayden Units 1 and 2 were 
equipped with first generation LNB and over-fire air (OFA) installed in 
1999.\220\ In its BART determination, Colorado considered these 
existing controls as given and analyzed as feasible controls upgraded 
LNB, SNCR, and SCR. Based on an average cost-effectiveness of $3,385/
ton and $4,064/ton, incremental cost-effectiveness (as compared with 
LNB and OFA with SNCR) of $5,326/ton and $7,331/ton, and visibility 
improvement of 1.12 dv and 0.85 dv at the most impacted Class I area, 
respectively, Colorado selected SCR as BART for Units 1 and 2. In this 
case, due to the existing controls at Hayden Station, the cost-
effectiveness values for SCR for Hayden Units 1 and 2 should be 
compared to the incremental cost-effectiveness values (as compared with 
LNB and SOFA, and with LNB and SOFA with SNCR) for SCR for Huntington 
Unit 1, and similarly for incremental visibility benefits. We think 
they are comparable, particularly for Hayden Unit 2, and considering 
that Huntington Unit 1 significantly impacts several Class I areas, 
while Colorado selected SCR for Hayden based solely on the visibility 
improvement at the most impacted Class I area, Mt. Zirkel Wilderness.
---------------------------------------------------------------------------

    \219\ 77 FR 18069 (Mar. 26, 2012) (proposal); 77 FR 76871 (Dec. 
31, 2012) (final).
    \220\ Colorado Department of Health and Environment, Air 
Pollution Control Division, Best Available Retrofit Technology 
(BART) Analysis of Control Options For Public Service Company--
Hayden Station, p. 5, available at https://www.colorado.gov/pacific/sites/default/files/AP_PO_Hayden-Power-Plant_0.pdf.
---------------------------------------------------------------------------

    Another comparable determination can be found in EPA's FIP for 
Arizona Public Service's Cholla Power Plant, Units 2, 3, and 4, in 
which EPA determined that NOX BART was SCR.\221\ Similarly 
to Colorado's determination for Hayden, EPA considered the existing 
controls, LNB and OFA, at the three units and estimated average cost-
effectiveness values for SCR of $3,114/ton, $3,472/ton, and $3,395/ton, 
and incremental cost-effectiveness values (as compared to LNB and OFA 
with SNCR) of $3,257/ton, $3,811/ton, and $3,661/ton, respectively, for 
Units 2, 3, and 4. EPA's modeling showed a source-wide visibility 
improvement for SCR of 1.34 dv at the most impacted Class I area. Based 
on these metrics, EPA determined NOX BART to be SCR for the 
three units. In this case, as with Hayden, the average cost-
effectiveness of SCR at Cholla should be compared with the incremental 
cost-effectiveness of SCR (as compared with just LNB and SOFA) at 
Huntington Unit 1. The cost-effectiveness values for Huntington Unit 1 
are somewhat higher than at Cholla, but on the other hand the source-
wide visibility improvement at Huntington Units 1 and 2 (as obtained by 
summing the per-unit improvements from Units 1 and 2) \222\ from LNB 
and SOFA with SCR is 2.759 dv at the most impacted Class I area, with 
incremental visibility improvements of 1.29 dv and 0.932 dv over LNB 
and SOFA and LNB and SOFA with SNCR, respectively. These visibility 
improvements are very much in line with those at Cholla, and given that 
the incremental cost-effectiveness of SCR at Huntington Unit 1 is still 
reasonable, the comparison with Cholla also supports selection of SCR 
for Huntington Unit 1. We invite comment on other potentially relevant 
BART determinations and our methodology generally.
---------------------------------------------------------------------------

    \221\ 77 FR 42834 (July 20, 2012) (proposal); 77 FR 72512, 
72514-15 (Dec. 5, 2012) (final).
    \222\ We use the source-wide number here to compare with the 
Cholla determination; in addition as explained above we must 
consider source-wide visibility improvements.
---------------------------------------------------------------------------

    Based on these comparisons, we think LNB and SOFA with SCR is very 
cost-effective at $2,515/ton, and provides substantial visibility 
benefits at several Class I areas. For example, the visibility 
improvement from that control option is 1.488 dv at Arches NP, 1.881 dv 
at Canyonlands NP, and 1.108 dv at Capitol Reef NP. The incremental 
cost-effectiveness of SCR, $4,879/ton, is by comparison with the 
Laramie River Station BART determination also reasonable. This 
comparison also shows that costs are justified in light of the 
substantial visibility benefits, both total and incremental.
    In the case of Huntington, the unit level visibility improvements 
justify the most stringent level of control, SCR, for each of the two 
Huntington units. Necessarily, when we consider the source-wide 
visibility improvements, they will be larger and also justify the most 
stringent level of control.
    Accordingly, for Huntington Unit 1, we propose to find that BART 
for NOX is LNB and SOFA with SCR, represented by an emission 
limit of 0.07 lb/MMBtu (30-day rolling average). The proposed BART 
emission limit of 0.07 lb/MMBtu allows for a sufficient margin of 
compliance for a 30-day rolling average limit that would apply at all 
times, including startup, shutdown, and malfunction.\223\ We are also 
proposing monitoring, recordkeeping, and reporting requirements as 
described in our proposed regulatory text for 40 CFR 52.2336.
---------------------------------------------------------------------------

    \223\ Emission limits such as BART are required to be met on a 
continuous basis. See 70 FR 39104, 39172 (July 6, 2005) (stating 
that emissions limits including BART are to be met on a ``continuous 
basis'' in the BART Guidelines, section V); 42 U.S.C. 7602(k) 
(noting that emission limits are to be on ``a continuous basis'').
---------------------------------------------------------------------------

    Under 40 CFR 51.308(e)(1)(iv), ``each source subject to BART [is] 
required to install and operate BART as expeditiously as practicable, 
but in no event later than 5 years after approval of the implementation 
plan revision.'' In light of the considerable effort involved to 
retrofit SCR, we propose that five years is as expeditiously as 
practicable. Therefore, we propose a compliance deadline of five years 
from the date our final FIP becomes effective.
b. Huntington Unit 2
    Generally, Huntington Unit 2 is identical to Unit 1. The Huntington 
Unit 2 boiler is of tangential-fired design with newer generation low-
NOX burners and separated overfire air which were installed 
in winter 2006. Huntington Unit 2 currently achieves an annual emission 
rate of approximately 0.21 lb/MMBtu with these combustion controls. 
Under Utah's submitted regional haze SIP, Unit 2 is subject to a state-
law NOX emission limit of 0.26 lb/MMBtu on a 30-day rolling 
average. Prior to the installation of LNB and SOFA the unit operated 
with an actual annual emission rate of about 0.39 lb/MMBtu.
Step 1: Identify All Available NOX Control Technologies
    For the same reasons as for Huntington Unit 1, we propose to adopt 
the identification of available NOX control technologies in 
PacifiCorp's 2012 BART analysis to satisfy Step 1, and we refer the 
reader to the 2012 PacifiCorp BART analysis for details on the 
available NOX control technologies.
Step 2: Eliminate Technically Infeasible Options
    In its 2012 BART analysis,\224\ PacifiCorp eliminated available 
NOX control technologies that PacifiCorp evaluated as 
technologically infeasible for Huntington Unit 2. The remaining 
technologically feasible control technologies are the combustion

[[Page 2046]]

controls, LNB and SOFA, and the post-combustion controls, SNCR and SCR.
---------------------------------------------------------------------------

    \224\ PacifiCorp BART Analysis for Huntington Unit 2, pp. 2.a-
106--2.a-124 (2012).
---------------------------------------------------------------------------

    We agree with PacifiCorp's evaluation of technologically available 
controls for Huntington Unit 2 and propose to adopt it for Step 2.
Step 3: Evaluate Control Effectiveness of Remaining Control 
Technologies
    As noted previously, Huntington Unit 2 is currently achieving an 
actual annual emission rate of approximately 0.21 lb/MMBtu with LNB and 
SOFA. This represents a 44.6 percent reduction from the baseline 
emission rate of 0.39 lb/MMBtu.
    The post-combustion control technologies, SNCR and SCR, have been 
evaluated in combination with combustion controls. That is, the inlet 
concentration to the post-combustion controls is assumed to be 0.21 lb/
MMBtu (annual). This allows the equipment and operating and maintenance 
costs of the post-combustion controls to be minimized based on the 
lower inlet NOX concentration.
    Typically, SNCR reduces NOX an additional 20 to 30 
percent above combustion controls without excessive NH3 
slip.\225\ For this analysis, the control efficiency of SNCR has been 
calculated based on the formula in the 2015 draft CCM SNCR 
chapter,\226\ which for Huntington Unit 2 yields an additional 
reduction of 21.5 percent after combustion controls. When combined with 
LNB and SOFA, SNCR is anticipated to achieve an annual emission rate of 
0.17 lb/MMBtu, corresponding to an overall control efficiency of 56.6 
percent.
---------------------------------------------------------------------------

    \225\ Institute of Clean Air Companies, White Paper, SNCR for 
Controlling NOX Emissions, pp. 4 and 9 (Feb. 2008).
    \226\ EPA Selective Noncatalytic, Reduction Cost Manual Draft 
for Public Comment, p. 1-6 (Figure 1.1c: SNCR NOX 
Reduction Efficiency Versus Baseline NOX Levels for Coal-
fired Utility Boilers) (June 5, 2015).
---------------------------------------------------------------------------

    SCR can achieve performance emission rates as low as 0.04 to 0.07 
lb/MMBtu on an annual basis.\227\ For this analysis, consistent with 
our actions elsewhere, as well with PacifiCorp's analysis, we use an 
annual emission rate of 0.05 lb/MMBtu for SCR, which when combined with 
LNB and SOFA achieves an overall control efficiency of 87.0 percent.
---------------------------------------------------------------------------

    \227\ Srivastava, R., Hall, R., Khan, S., Lani, B., & Culligan, 
K., Nitrogen Oxides Emission Control Options for Coal-Fired Utility 
Boilers, 55 J. Air & Waste Mgmt Assoc. 55, 1367, 1367-88 (2005).
---------------------------------------------------------------------------

    A summary of emissions projections for the control options 
evaluated is provided in Table 31.

                Table 31--Summary of NOX BART Analysis Control Technologies for Huntington Unit 2
----------------------------------------------------------------------------------------------------------------
                                                      Control         Annual         Emissions       Remaining
                 Control option                    effectiveness   emission rate     reduction       emissions
                                                        (%)         (lb/MMBtu)         (tpy)           (tpy)
----------------------------------------------------------------------------------------------------------------
LNB/SOFA +SCR...................................            87.0            0.05           5,023             747
LNB/SOFA +SNCR..................................            56.6            0.17           3,264           2,506
LNB/SOFA........................................            44.6            0.21           2,576           3,194
Baseline\1\.....................................              --            0.39              --           5,770
----------------------------------------------------------------------------------------------------------------
\1\ Baseline emissions were determined by averaging the annual emissions from 2001 to 2003 as reported to EPA
  Air Markets Program Data available at http://ampd.epa.gov/ampd/.

Step 4: Evaluate Impacts and Document Results
Part 1--Costs of Compliance
    We obtained capital costs for LNB and SOFA from the 2014 PacifiCorp 
BART analysis. PacifiCorp did not report any operating and maintenance 
costs for LNB and SOFA. Similarly, we obtained capital cost estimates 
for LNB and SOFA with SNCR from the 2014 PacifiCorp BART analysis. 
However, for operating and maintenance costs we propose to rely on the 
draft 2015 draft SNCR chapter of the CCM. Refer to the ATP report for 
details. Capital costs for LNB and SOFA with SCR were also obtained 
from the 2014 PacifiCorp BART analysis. However, PacifiCorp's capital 
costs were adjusted to account for items that were double-counted or 
should not be allowed under the CCM, such as AFUDC.\228\ In addition, 
the capital costs were adjusted to account for a significant 
overestimation of the catalyst volume and related costs. These 
adjustments are documented in the ATP report and associated spread 
sheet. A discussion of operating and maintenance costs of SCR is also 
included in the ATP report. For the reasons given in the report, we 
propose to adopt the cost estimates contained in it.
---------------------------------------------------------------------------

    \228\ See 79 FR 5032, 5133 (discussing reasons for rejecting use 
of AFUDC).
---------------------------------------------------------------------------

    A summary of our proposed cost estimates for all control options is 
presented in Table 32.

                                                Table 32--Summary of NOX BART Costs on Huntington Unit 2
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                             Emissions     Average cost
                     Control option                        Total capital     Indirect      Direct annual   Total annual     reductions     effectiveness
                                                            investment     annual costs        costs           cost            (tpy)          ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
LNB/SOFA................................................           $9.4M           $0.9M             $0M           $0.9M           2,576            $365
LNB/SOFA/SNCR...........................................           16.7M            1.6M            1.9M            3.5M           3,264           1,075
LNB/SOFA/SCR............................................          109.4M           10.4M            2.4M           12.9M           5,023           2,563
--------------------------------------------------------------------------------------------------------------------------------------------------------

Parts 2 and 3--Energy and Non-Air Quality Environmental Impacts of 
Compliance
    The energy and non-air quality impacts for Huntington Unit 2 are 
nearly identical to those for Huntington Unit 1 as discussed 
previously. Accordingly, for the same reasons as for Huntington Unit 1, 
we propose to determine that we have adequately considered these 
impacts by including cost of additional energy in cost effectiveness 
and assessing non-air quality environmental impacts as insufficient to 
eliminate or weigh against any of the BART options.

[[Page 2047]]

Part 4--Remaining Useful Life
    PacifiCorp assumes a remaining useful life of at least 20 years for 
Huntington Unit 2 in its BART analysis, and has not indicated any 
intention to retire, or curtail generation from, Huntington Unit 2. 
Therefore, this factor does not preclude any of the control options 
considered. In addition, this factor does not impact our BART 
calculation of cost effectiveness because annualized costs have been 
calculated over a 20 year period for each of the control options 
considered. We propose that this gives adequate consideration to this 
factor.
Step 5: Evaluate Visibility Impacts
    Table 33 presents the highest of the 98th percentile visibility 
improvements at the affected Class I areas for the three meteorological 
years modeled, 2001 through 2003. Tables 34 and 35 present the number 
of days (summed across three years) with impacts greater than the 
contribution and causation thresholds--0.5 dv and 1.0 dv, respectively.

                              Table 33--Huntington Unit 2--Visibility Improvements
----------------------------------------------------------------------------------------------------------------
                                                                                   LNB with SOFA   LNB with SOFA
                          Class I Area                             LNB with SOFA     and SNCR         and SCR
                                                                    ([Delta]dv)     ([Delta]dv)     ([Delta]dv)
----------------------------------------------------------------------------------------------------------------
Arches NP.......................................................           0.625           0.816           1.316
Black Canyon of the Gunnison NP.................................           0.143           0.184           0.292
Bryce Canyon NP.................................................           0.205           0.266           0.424
Canyonlands NP..................................................           0.776           1.016           1.657
Capitol Reef NP.................................................           0.449           0.584           0.955
Flat Tops WA....................................................           0.168           0.217           0.343
Grand Canyon NP.................................................           0.183           0.236           0.371
Mesa Verde NP...................................................           0.199           0.258           0.414
Zion NP.........................................................           0.136           0.176           0.281
----------------------------------------------------------------------------------------------------------------

                           Table 34--Huntington Unit 2--Days Greater Than 0.5 Deciview
                                               [Three year total]
----------------------------------------------------------------------------------------------------------------
                                                                                   LNB with SOFA
                  Class I Area                       Baseline      LNB with SOFA     and SNCR      LNB with SOFA
                                                      (days)          (days)          (days)      and SCR (days)
----------------------------------------------------------------------------------------------------------------
Arches NP.......................................             237             223             214             186
Black Canyon of the Gunnison NP.................              45              35              32              26
Bryce Canyon NP.................................              36              26              26              23
Canyonlands NP..................................             277             254             244             220
Capitol Reef NP.................................             131             119             116             104
Flat Tops WA....................................              64              44              39              31
Grand Canyon NP.................................              40              36              35              30
Mesa Verde NP...................................              63              48              43              31
Zion NP.........................................              21              17              16              15
----------------------------------------------------------------------------------------------------------------

                           Table 35--Huntington Unit 2--Days Greater Than 1.0 Deciview
                                               [Three year total]
----------------------------------------------------------------------------------------------------------------
                                                                                   LNB with SOFA
                  Class I Area                       Baseline      LNB with SOFA     and SNCR      LNB with SOFA
                                                      (days)          (days)          (days)      and SCR (days)
----------------------------------------------------------------------------------------------------------------
Arches NP.......................................             146             122             118              98
Black Canyon of the Gunnison NP.................              16               8               7               4
Bryce Canyon NP.................................              19              15              13               6
Canyonlands NP..................................             175             153             149             126
Capitol Reef NP.................................              91              75              70              59
Flat Tops WA....................................              17               9               8               4
Grand Canyon NP.................................              19              13              13               9
Mesa Verde NP...................................              22              13              13               6
Zion NP.........................................              11               8               6               4
----------------------------------------------------------------------------------------------------------------

    Select BART.
    A summary of our impacts analysis for Huntington Unit 2 is 
presented in Table 36.

[[Page 2048]]

                                                 Table 36--Summary of Huntington Unit 2 Impacts Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                      Annual                                                                              Visibility impacts *
                                     emission     Emission      Total      Average cost     Incremental cost   -----------------------------------------
          Control option            rate (lb/    reduction      annual     effectiveness    effectiveness ($/     Improvement    Days  >0.5   Days  >1.0
                                      MMBtu)       (tpy)      costs ($)       ($/ton)             ton)               (dv)            dv           dv
--------------------------------------------------------------------------------------------------------------------------------------------------------
LNB with SOFA....................         0.21        2,576        $0.9M            $365  ....................           0.776          254          153
LNB with SOFA and SNCR...........         0.17        3,264         3.5M           1,075  $3,730..............           1.016          244          149
LNB with SOFA and SCR............         0.05        5,023        12.9M           2,563  $5,326..............           1.657          220          126
                                                                                          (compared to LNB
                                                                                           with SOFA and SNCR).
                                                                                          $4,877 (compared to
                                                                                           LNB with SOFA).
--------------------------------------------------------------------------------------------------------------------------------------------------------
* At the most impacted Class I area, Canyonlands National Park.

    In determining what to co-propose as BART, we have taken into 
consideration all five of the statutory factors required by the CAA: 
The costs of compliance, the energy and non-air quality environmental 
impacts of compliance, any existing pollution control technology in use 
at the source, the remaining useful life of the source, and the degree 
of improvement in visibility which may reasonably be anticipated to 
result from the use of such technology. Later on we provide a 
justification for our selection of BART, including an explanation of 
how each of the CAA factors was used in that selection.
    We have considered the energy and non-air quality environmental 
impacts of compliance and propose to find that they do not appreciably 
favor one control option over another, or preclude a particular control 
option from selection. The existing pollution controls have been 
accounted for in our evaluation of BART, and also would not favor or 
preclude any of the control options considered. And finally, we have 
considered the remaining useful life of the source and find that it is 
sufficiently long (greater than 20 years) so as not to favor or 
preclude any of the control options. As a result, the remaining 
factors--the costs of compliance and visibility improvement--are the 
primary factors that lead us to our proposed BART selection for 
Huntington Unit 2.
    In order to select BART we propose to weigh the costs of compliance 
against visibility impacts by generally comparing them with BART 
determinations that have been made elsewhere. Specifically, we propose 
to compare the average cost-effectiveness, incremental cost-
effectiveness, visibility improvement, and incremental visibility 
improvement for LNB and SOFA with SCR with BART determinations where 
the EPA and States have based their determination on the same metrics. 
The most comparable determinations are the same as for Huntington Unit 
1: The Laramie River Station, Hayden Station, and Cholla Power Plant 
determinations.
    Based on these comparisons, we think LNB and SOFA with SCR is very 
cost-effective at $2,563/ton, and provides substantial visibility 
benefits at several Class I areas. For example, the visibility 
improvement from that control option is 1.316 at Arches NP and 1.657 dv 
Canyonlands NP. The incremental cost-effectiveness of SCR, $5,326/ton, 
is by comparison also reasonable. This comparison also shows that costs 
are justified in light of the substantial visibility benefits, both 
total and incremental.
    In the case of Huntington, the unit level visibility improvements 
justify the most stringent level of control, SCR, for each of the two 
Huntington units. Necessarily, when we consider the source-wide 
visibility improvements, they will be larger and also justify the most 
stringent level of control. In addition, the unit level visibility 
improvements and source-wide visibility improvements at other impacted 
Class I areas, particularly Arches NP and Capitol Reef NP, support the 
most stringent level of control.
    Accordingly, for Huntington Unit 2, we propose to find that BART 
for NOX is LNB and SOFA with SCR, represented by an emission 
limit of 0.07 lb/MMBtu (30-day rolling average). The proposed BART 
emission limit of 0.07 lb/MMBtu allows for a sufficient margin of 
compliance for a 30-day rolling average limit that would apply at all 
times, including startup, shutdown, and malfunction.\229\ We are also 
proposing monitoring, recordkeeping, and reporting requirements as 
described in our proposed regulatory text for 40 CFR 52.2336.
---------------------------------------------------------------------------

    \229\ Emission limits such as BART are required to be met on a 
continuous basis. See 70 FR 39104, 39172 (July 6, 2005) (stating 
that emissions limits including BART are to be met on a ``continuous 
basis'' in the BART Guidelines, section V); 42 U.S.C. 7602(k) 
(noting that emission limits are to be on ``a continuous basis'').
---------------------------------------------------------------------------

    Under Sec.  51.308(e)(1)(iv), ``each source subject to BART [is] 
required to install and operate BART as expeditiously as practicable, 
but in no event later than 5 years after approval of the implementation 
plan revision.'' In light of the considerable effort involved to 
retrofit SCR, we propose that five years is as expeditiously as 
practicable. Therefore, we propose a compliance deadline of five years 
from the date our final FIP becomes effective.
4. Federal Monitoring, Recordkeeping, and Reporting
    We have explained earlier in section III.C.4 that the CAA and 40 
CFR part 51, subpart K require that SIPs, including the regional haze 
SIP, contain certain elements sufficient to ensure emission limits are 
practically enforceable. EPA is proposing to disapprove Utah's 
NOX BART Alternative along with the associated monitoring, 
recordkeeping and reporting requirements in SIP sections IX.H.21 and 
H.22. EPA is proposing regulatory language as part of our FIP that 
specifies monitoring, recordkeeping, and reporting requirements for all 
BART sources. For purposes of consistency, EPA is proposing to adopt 
language that is the same as we have adopted for other states in Region 
8.

E. PM10 BART Determinations

    As discussed earlier in section IV.B.2, Utah determined that the 
PM10 BART emission limit for Hunter Units 1 and 2 and 
Huntington Units 1 and 2 was 0.015 lb/MMBtu based on a three-run test 
average. Utah noted that because the most stringent technology is in 
place at

[[Page 2049]]

these units and that the PM10 emission limits have been made 
enforceable in the SIP, no further analysis was required.
    EPA has reviewed Utah's PM10 BART streamlined five-
factor analysis and PM10 BART determinations for Hunter 
Units 1 and 2 and Huntington Units 1 and 2 and proposes to find that 
these determinations meet the requirements of 40 CFR 51.309(d)(4)(vii). 
The fabric filter baghouses installed at these BART units are 
considered the most stringent technology available. The emission limit 
of 0.015 lb/MMBtu at these units represents the most stringent emission 
limit for PM10 and is within the range of PM10 
BART limits that EPA has approved in other states.\230\ Utah's use of a 
streamlined approach to the five-factor analysis is reasonable as the 
BART Guidelines provide that a comprehensive BART analysis can be 
avoided if a source commits to a BART determination that consists of 
the most stringent controls available.\231\
---------------------------------------------------------------------------

    \230\ For example, Wyoming, Naughton Unit 3, Jim Bridger Units 1 
through 4, Dave Johnston Units 3 and 4, and Wyodak Unit 1. See 40 
CFR 52.2636; 79 FR 5220, (Jan. 30, 2014).
    \231\ 40 CFR 51, appendix Y, section IV.D.1.9.
---------------------------------------------------------------------------

    Utah's regulatory text provides, ``[e]missions of particulate (PM) 
shall not exceed 0.015 lb/MMBtu heat input from each boiler based on a 
3-run test average.'' \232\ It further states that ``[s]tack testing 
for the emission limitation shall be performed each year on each 
boiler.'' \233\ We note that BART limits must apply at all times.\234\ 
Furthermore, EPA's credible evidence rule requires that a state's plan 
must not preclude the use of any credible evidence or information, 
which can include evidence and information other than the test method 
specified in the plan, that would indicate whether a source was in 
compliance with applicable requirements.\235\
---------------------------------------------------------------------------

    \232\ Utah Regional Haze State Implementation Plan: Emission 
Limits & Operating Practices, Sections IX.H.22.a.i.A-B, 
IX.H.22.b.i.A-B (2015).
    \233\ Id.
    \234\ See 42 U.S.C. 7602(k); 40 CFR part 51, appendix Y, section 
V.
    \235\ 40 CFR 51.212(c).
---------------------------------------------------------------------------

    Consistent with these requirements, we propose to interpret Utah's 
regulatory text as imposing a PM10 limit of 0.015 lb/MMBtu 
that applies at all times and does not preclude the use, including the 
exclusive use, of any credible evidence or information, relevant to 
whether a source is in compliance with the limit.

F. Consultation With FLMs

    As discussed previously in section IV.G, Utah conducted FLM 
consultation during late 2014, providing over 60 days prior to the 
December 1, 2014 public hearing. Subsequently, the National Park 
Service provided extensive comments in response to a second public 
comment period in April 2015. Based on these considerations, we propose 
to find that Utah has met the requirements of 40 CFR 308(i)(2).

VII. EPA's Proposed Actions

    EPA is proceeding with co-proposals on Utah's June 3, 2015 and 
October 20, 2015 regional haze SIP revisions. Later on is a summary of 
our proposed actions. As noted above, EPA intends to finalize only one 
proposal, although it may differ from what is presented here based on 
any comments and additional information we receive.

A. Proposed Approval

    We are proposing to approve the regional haze SIP revisions 
submitted by the State of Utah on June 3, 2015 and October 20, 2015:
    1. We are proposing to approve these aspects of the State's June 4, 
2015, which rely on elements from prior approvals \236\:
---------------------------------------------------------------------------

    \236\ As necessary for our proposed approval, we propose to fill 
gaps in the 2015 Utah RH SIP submittals with the following already-
approved sections from the 2011 Utah RH SIP: Section XX.B.8, Figures 
1 and 2, Affected Class I Areas, pp. 8-9; Section XX.D.6.b, Table 3, 
BART-Eligible Sources in Utah, p. 21; Section. XX.D.6.c, Sources 
Subject to BART, pp. 21-23.
---------------------------------------------------------------------------

     NOX BART Alternative that includes 
NOX, and SO2, emission reductions from Hunter 
Units 1 through 3, Huntington 1 and 2, and Carbon Units 1 and 2, and 
PM10 emission reductions from Carbon Units 1 and 2.
     BART determinations and emission limits for 
PM10 at Hunter Units 1 and 2 and Huntington Units 1 and 2.
     Monitoring, recordkeeping and reporting requirements for 
units subject to the BART Alternative and the PM10 emission 
limits, including conditional approval of the recordkeeping 
requirements for the PM10 emission limits.
    2. We are proposing to approve these elements of the State's 
October 20, 2015 SIP submittal:
     Enforceable commitments to revise, at a minimum, SIP 
Section XX.D.3.c and State rule R307-150 by March 2018 to clarify 
emission inventory requirements for tracking compliance with the 
SO2 milestone and properly accounting for the SO2 
emission reductions due to the closure of the Carbon plant.

B. Proposed Partial Disapproval/Approval and Federal Implementation 
Plan

    1. We are proposing to approve these elements of the State's SIP 
submittals, which rely on elements from prior approvals:\237\
---------------------------------------------------------------------------

    \237\ Id.
---------------------------------------------------------------------------

     BART determinations and emission limits for 
PM10 at Hunter Units 1 and 2 and Huntington Units 1 and 2.
     Monitoring, recordkeeping, and reporting requirements for 
units subject to the PM10 emission limits, including 
conditional approval of the recordkeeping requirements for the 
PM10 emission limits.
    2. We are proposing to disapprove these aspects of the State's June 
4, 2015 SIP:
     NOX BART Alternative that includes 
NOX, and SO2, emission reductions from Hunter 
Units 1 through 3, Huntington 1 and 2, and Carbon Units 1 and 2, and 
PM10 emission reductions from Carbon Units 1 and 2.
     Monitoring, recordkeeping and reporting requirements for 
units subject to the BART Alternative.
     The enforceable commitments to revise, at a minimum, SIP 
Section XX.D.3.c and State rule R307-150 by March 2018.
    3. We are proposing that if we finalize our co-proposal to 
disapprove the NOX BART Alternative, we will promulgate a 
FIP to address the deficiencies in the Utah regional haze SIPs. The 
proposed FIP includes the following elements:
     NOX BART determinations and limits for Hunter 
Units 1 and 2, Huntington Units 1 and 2.
     Monitoring, recordkeeping, and reporting requirements 
applicable to Hunter Units 1 and 2, and Huntington Units 1 and 2.

VIII. 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 \238\ and was therefore not submitted to 
the Office of Management and Budget (OMB) for review. This proposed 
rule applies to only two facilities containing four BART units. It is 
therefore not a rule of general applicability.
---------------------------------------------------------------------------

    \238\ 58 FR 51735, 51738 (Oct. 4, 1993).
---------------------------------------------------------------------------

B. Paperwork Reduction Act

    This proposed action does not impose an information collection 
burden under the provisions of the Paperwork Reduction Act (PRA).\239\ 
Because this proposed rule applies to just two facilities, the PRA does 
not apply.
---------------------------------------------------------------------------

    \239\ 44 U.S.C. 3501 et seq.

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

[[Page 2050]]

C. 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 proposed 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 proposed 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 small entities are not subject to the requirements of 
this rule. Under the full approval approach in this proposed rule, EPA 
would approve all elements of the State's submittals as meeting the 
federal regional haze requirements and therefore EPA's action does not 
impose any requirements.\240\ Under the partial approval approach, EPA 
would disapprove the state's SIP submittal and promulgate a FIP that 
consists of imposing federal controls to meet the BART requirement for 
emissions on four specific BART units at two facilities in Utah. The 
net result of this action is that EPA is proposing direct emission 
controls on selected units at only two sources, and those sources are 
large electric generating plants that are not owned by small entities, 
and therefore the owners are not a small entities under the RFA.
---------------------------------------------------------------------------

    \240\ See, e.g., Mid-Tex Elec. Coop., Inc. v. FERC, 773 F.2d 327 
(D.C. Cir. 1985) (hereinafter Mid-Tex).
---------------------------------------------------------------------------

D. 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, EPA 
generally must prepare a written statement, including a cost-benefit 
analysis, for final rules 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 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 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 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, EPA has determined that this proposed rule 
does not contain a federal mandate that may result in expenditures that 
exceed the inflation-adjusted UMRA threshold of $100 million \241\ by 
State, local, or Tribal governments or the private sector in any one 
year. The private sector expenditures that would result from the 
approach to promulgate a FIP would include BART controls for all four 
units at the Hunter and Huntington plants would be $51.5 million \242\ 
per year. Additionally, we do not foresee significant costs (if any) 
for state and local governments. Thus, because the annual expenditures 
associated with the approach to promulgate a FIP are less than the 
threshold of $100 million in any one year, this proposed rule is not 
subject to the requirements of sections 202 or 205 of UMRA. This 
proposed 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.
---------------------------------------------------------------------------

    \241\ Adjusted to 2014 dollars, the UMRA threshold becomes $152 
million.
    \242\ Andover Technology Partners, Cost of NOX BART 
Controls on Utah EGUs, to EC/R, Inc. (Oct. 22, 2015).Andover 
Technology Partners is a subcontractor to EC/R Incorporated.
---------------------------------------------------------------------------

E. Executive Order 13132: Federalism

    Executive Order 13132, Federalism,\243\ revokes and replaces 
Executive Orders 12612 (Federalism) and 12875 (Enhancing the 
Intergovernmental Partnership). Executive Order 13132 requires 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.'' \244\ ``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.'' \245\ Under Executive Order 13132, 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 EPA consults with state and local officials early in 
the process of developing the final regulation.\246\ 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.
---------------------------------------------------------------------------

    \243\ 64 FR 43255, 43255-43257 (Aug. 10, 1999).
    \244\ 64 FR 43255, 43257.
    \245\ Id.
    \246\ Id.
---------------------------------------------------------------------------

    This action does not have federalism implications. Neither of the 
two approaches presented in this proposed rule will 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. Under the full approval approach, this 
proposed action would merely approve the state SIP as federally 
enforceable. Under the partial approval approach, this proposed action 
would merely address the State not fully meeting its

[[Page 2051]]

obligation under the CAA to adequately address the visibility 
requirements of Part C of Title I of the CAA in its SIP and to prohibit 
emissions from interfering with other states measures to protect 
visibility. Thus, Executive Order 13132 does not apply to this action.

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

    Executive Order 13175, entitled ``Consultation and Coordination 
with Indian Tribal Governments'', requires 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.'' \247\ This proposed 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.
---------------------------------------------------------------------------

    \247\ 65 FR 67249, 67250 (Nov. 9, 2000).
---------------------------------------------------------------------------

G. 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) because the environmental health or safety risks 
addressed by this action do not present a disproportionate risk to 
children. Note, however, that emissions reductions achieved as a result 
of this rule, under either proposal, will have a positive benefit on 
children's health, as they are especially vulnerable to impacts from 
emissions.

H. 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.

I. 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 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 EPA to provide 
Congress, through OMB, explanations when the Agency decides not to use 
available and applicable voluntary consensus standards.
    This proposed rulemaking does not involve technical standards. 
Therefore, EPA is not considering the use of any voluntary consensus 
standards.

J. 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.\248\ 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.
---------------------------------------------------------------------------

    \248\ 59 FR 7629, 7629 (Feb. 16, 1994).
---------------------------------------------------------------------------

    I certify that the approaches under this proposed rule will not 
have potential disproportionately high and adverse human health or 
environmental effects on minority, low-income or indigenous/tribal 
populations. The results of this evaluation are available in the 
docket. Both approaches would result in overall emission reductions for 
NOX, SO2 and PM10 and therefore an 
increase in the level of environmental protection for all affected 
populations. EPA, however, will consider any input received during the 
public comment period regarding environmental justice considerations.

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

List of Subjects in 40 CFR Part 52

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

    Dated: December 16, 2015.
Shaun L. McGrath,
Regional Administrator, Region 8.

    For the reasons discussed in the preamble, the Environmental 
Protection Agency proposes to amend 40 CFR part 52 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 TT--Utah

0
2. Add Sec.  52.2336 to read as follows:

Sec.  52.2336  Federal implementation plan for regional haze.

    (a) Applicability. (1) This section applies to each owner and 
operator of the following emissions units in the State of Utah:
    (i) PacifiCorp Hunter Plant Units 1 and 2; and
    (ii) PacifiCorp Huntington Plant Units 1 and 2.
    (b) Definitions. Terms not defined here shall have the meaning 
given them in the Clean Air Act or EPA's regulations implementing the 
Clean Air Act. For purposes of this section:
    (1) BART means Best Available Retrofit Technology.
    (2) BART unit means any unit subject to a Regional Haze emission 
limit in table 1 of this section.
    (3) 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 NOX emissions, diluent, or stack gas 
volumetric flow rate.
    (4) FIP means Federal Implementation Plan.
    (5) The term lb/MMBtu means pounds per million British thermal 
units of heat input to the fuel-burning unit.
    (6) NOX means nitrogen oxides.
    (7) Operating day means a 24-hour period between 12 midnight and 
the following midnight during which any fuel is combusted at any time 
in the BART unit. It is not necessary for fuel to be combusted for the 
entire 24-hour period.
    (8) The owner/operator means any person who owns or who operates, 
controls, or supervises a unit identified in paragraph (a) of this 
section.
    (9) Unit means any of the units identified in paragraph (a) of this 
section.
    (c) Emissions limitations. (1) The owners/operators of emissions 
units subject to this section shall not emit, or cause to be emitted, 
NOX in excess of the following limitations:

[[Page 2052]]

       Table 1--to Sec.   52.2336--Emission Limits for BART Units
------------------------------------------------------------------------
                                                           NOX emission
                                                            limit--lb/
                  Source name/BART unit                   MMBtu  (30-day
                                                              rolling
                                                             average)
------------------------------------------------------------------------
PacifiCorp Hunter Plant/Unit 1 \1\......................            0.07
PacifiCorp Hunter Plant/Unit 2 \1\......................            0.07
PacifiCorp Huntington Plant/Unit 1 \1\..................            0.07
PacifiCorp Huntington Plant/Unit 2 \1\..................            0.07
------------------------------------------------------------------------
\1\ The owners and operators of PacifiCorp Hunter Units 1 and 2 and
  Huntington Units 1 and 2, shall comply with the NOX emission limit for
  BART of 0.07 lb/MMBtu and other requirements of this section by [date
  five years from the effective date of the final rule].

    (2) These emission limitations shall apply at all times, including 
startups, shutdowns, emergencies, and malfunctions.
    (d) Compliance date. (1) The owners and operators of PacifiCorp 
Hunter Units 1 and 2 shall comply with the NOX emission 
limit of 0.07 lb/MMBtu and other requirements of this section by [date 
five years from the effective date of the final rule]. The owners and 
operators of PacifiCorp Huntington Units 1 and 2 shall comply with the 
NOX emission limit of 0.07 lb/MMBtu and other requirements 
of this section by [date five years from the effective date of the 
final rule].
    (e) Compliance determinations for NOX. (1) For all BART 
units:
    (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 
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) Method. (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 rate 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) An hourly average 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 
(NOX) and the diluent monitor (O2 or 
CO2).
    (C) 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.
    (f) Recordkeeping. The owner/operator shall maintain the following 
records for at least five years:
    (1) All CEMS data, including the date, place, and time of sampling 
or measurement; parameters sampled or measured; and results.
    (2) Records of quality assurance and quality control activities for 
emissions measuring systems including, but not limited to, any records 
required by 40 CFR part 75.
    (3) Records of all major maintenance activities conducted on 
emission units, air pollution control equipment, and CEMS.
    (4) Any other CEMS records required by 40 CFR part 75.
    (g) Reporting. All reports under this section shall be submitted to 
the Director, Office of Enforcement, Compliance and Environmental 
Justice, U.S. Environmental Protection Agency, Region 8, Mail Code 
8ENF-AT, 1595 Wynkoop Street, Denver, Colorado 80202-1129.
    (1) The owner/operator of each unit shall submit quarterly excess 
emissions reports for 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.
    (2) The owner/operator of each unit shall submit quarterly CEMS 
performance reports, to include dates and duration of each period 
during which the CEMS was inoperative (except for zero and span 
adjustments and calibration checks), reason(s) why the CEMS was 
inoperative and steps taken to prevent recurrence, and any CEMS repairs 
or adjustments. The owner/operator of each unit shall also submit 
results of any CEMS performance tests required by 40 CFR part 75.
    (3) When no excess emissions have occurred or the CEMS has not been 
inoperative, repaired, or adjusted during the reporting period, such 
information shall be stated in the quarterly reports required by 
paragraphs (g)(1) and (2) of this section.
    (h) Notifications. (1) The owner/operator shall promptly submit 
notification of commencement of construction of any equipment which is 
being constructed to comply with the NOX emission limits in 
paragraph (c) of this section.
    (2) The owner/operator shall promptly submit semi-annual progress 
reports on construction of any such equipment.
    (3) The owner/operator shall promptly submit notification of 
initial startup of any such equipment.
    (i) Equipment operation. At all times, the owner/operator shall 
maintain each unit, including associated air pollution control 
equipment, in a manner consistent with good air pollution control 
practices for minimizing emissions.
    (j) Credible evidence. Nothing in this section shall preclude the 
use, including the exclusive use, of any credible evidence or 
information, relevant to whether a source would have been in compliance 
with requirements of this section if the appropriate performance or 
compliance test procedures or method had been performed.

[FR Doc. 2015-33108 Filed 1-13-16; 8:45 am]
 BILLING CODE 6560-50-P
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