[Federal Register Volume 78, Number 111 (Monday, June 10, 2013)]
[Proposed Rules]
[Pages 34737-34794]
[FR Doc No: 2013-13611]

Vol. 78

Monday,

No. 111

June 10, 2013

Part III

Environmental Protection Agency

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

40 CFR Part 52

Approval, Disapproval and Promulgation of Implementation Plans; State
of Wyoming; Regional Haze State Implementation Plan; Federal
Implementation Plan for Regional Haze; Proposed Rule

Federal Register / Vol. 78 , No. 111 / Monday, June 10, 2013 /
Proposed Rules

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

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2012-0026, FRL-9820-4]

Approval, Disapproval and Promulgation of Implementation Plans;
State of Wyoming; Regional Haze State Implementation Plan; Federal
Implementation Plan for Regional Haze

AGENCY: Environmental Protection Agency.

ACTION: Proposed rule.

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

SUMMARY: EPA is proposing to partially approve and partially disapprove
a State Implementation Plan (SIP) submitted by the State of Wyoming on
January 12, 2011, that addresses regional haze. This SIP revision was
submitted to address the requirements of the Clean Air Act (CAA or
``the Act'') and our rules that require states to prevent any future
and remedy any existing anthropogenic impairment of visibility in
mandatory Class I areas caused by emissions of air pollutants from
numerous sources located over a wide geographic area (also referred to
as the ``regional haze program''). States are required to assure
reasonable progress toward the national goal of achieving natural
visibility conditions in Class I areas. EPA is taking this action
pursuant to section 110 of the CAA.
    EPA is also proposing a Federal Implementation Plan (FIP) to
address the deficiencies identified in our proposed partial disapproval
of Wyoming's regional haze SIP. In lieu of our proposed FIP, or a
portion thereof, we will propose approval of a SIP revision as
expeditiously as practicable if the State submits such a revision and
the revision matches the terms of our proposed FIP. We will also review
and take action on any regional haze SIP submitted by the state to
determine whether such SIP is approvable, regardless of whether or not
its terms match those of the FIP. We encourage the State to submit a
SIP revision to replace the FIP, either before or after our final
action.

DATES: Comments: Written comments must be received at the address below
on or before August 9, 2013. Public Hearing: A public hearing for this
proposal is scheduled to be held on Monday, June 24, 2013, at the
Hershchler Building, Room 1699, 122 W. 25th St., Cheyenne, Wyoming
82002. The public hearing will be held from 1 p.m. until 5 p.m., and
again from 6 p.m. until 8 p.m.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2012-0026, by one of the following methods:
     http://www.regulations.gov. Follow the on-line
instructions for submitting comments.
     Email<EMAIL_ADDRESS>     Fax:<PHONE_NUMBER> (please alert the individual listed in
the FOR FURTHER INFORMATION CONTACT if you are faxing comments).
     Mail: Carl Daly, Director, Air Program, Environmental
Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop Street,
Denver, Colorado 80202-1129.
     Hand Delivery: Carl Daly, Director, Air Program,
Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595
Wynkoop, Denver, Colorado 80202-1129. Such deliveries are only accepted
Monday through Friday, 8:00 a.m. to 4:30 p.m., excluding Federal
holidays. Special arrangements should be made for deliveries of boxed
information.
    Instructions: Direct your comments to Docket ID No. EPA-R08-OAR-
2012-0026. EPA's policy is that all comments received will be included
in the public docket without change 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 http://www.regulations.gov or email. The http://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 http://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 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 http://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 http://www.regulations.gov or in hard copy at the Air Program,
Environmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595
Wynkoop, 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, 8:00 a.m.
to 4:00 p.m., excluding Federal holidays.

FOR FURTHER INFORMATION CONTACT: Laurel Dygowski, Air Program, U.S.
Environmental Protection Agency, Region 8, Mailcode 8P-AR, 1595
Wynkoop, Denver, Colorado 80202-1129,<PHONE_NUMBER>,
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Definitions

    For the purpose of this document, we are giving meaning to certain
words or initials as follows:

    i. The words or initials Act or CAA mean or refer to the Clean
Air Act, unless the context indicates otherwise.
    ii. The initials AFRC mean or refer to air-fuel ratio controls.
    iii. The initials BART mean or refer to Best Available Retrofit
Technology.
    iv. The initials CAMx mean or refer to Comprehensive Air Quality
Model.
    v. The initials CMAQ mean or refer to Community Multi-Scale Air
Quality modeling system.
    vi. The initials CEMS mean or refer to continuous emission
monitoring systems.
    vii. The initials EC mean or refer to elemental carbon.
    viii. The initials EGUs mean or refer to Electric Generating
Units.
    ix. The initials EGR mean or refer to exhaust gas recirculation.
    x. The words EPA, we, us or our mean or refer to the United
States Environmental Protection Agency.
    xi. The initials ESP mean or refer to electrostatic
precipitator.
    xii. The initials FGC mean or refer to flue gas conditioning.
    xiii. The initials FGD mean or refer to flue gas
desulfurization.
    xiv. The initials FGR mean or refer to external flue gas
recirculation.

    xv. The initials FIP mean or refer to Federal Implementation
Plan.
    xvi. The initials FLMs mean or refer to Federal Land Managers.
    xvii. The initials FS mean or refer to the U.S. Forest Service.
    xviii. The initials IMPROVE mean or refer to Interagency
Monitoring of Protected Visual Environments monitoring network.
    xix. The initials IWAQM mean or refer to Interagency Workgroup
on Air Quality Modeling.
    xx. The initials LEC mean or refer to low-emission combustion.
    xxi. The initials LNB mean or refer to low NOX
burner.
    xxii. The initials LTS mean or refer to the long-term strategy.
    xxiii. The initials MW mean or refer to megawatts.
    xxiv. The initials NH3 mean or refer to ammonia.
    xxv. The initials NOX mean or refer to nitrogen oxides.
    xxvi. The initials NPS mean or refer to National Park Service.
    xxvii. The initials OC mean or refer to organic carbon.
    xxviii. The initials OFA mean or refer to overfire air.
    xxix. The initials PM2.5 mean or refer to particulate matter
with an aerodynamic diameter of less than 2.5 micrometers.
    xxx. The initials PM10 mean or refer to particulate matter with
an aerodynamic diameter of less than 10 micrometers.
    xxxi. The initials PSAT mean or refer to Particle Source
Apportionment Technology.
    xxxii. The initials PSD mean or refer to Prevention of
Signification Deterioration.
    xxxiii. The initials RAVI mean or refer to Reasonably
Attributable Visibility Impairment.
    xxxiv. The initials RHR mean or refer to the Regional Haze Rule.
    xxxv. The initials RMC mean or refer to the Regional Modeling
Center at the University of California Riverside.
    xxxvi. The initials RPGs mean or refer to Reasonable Progress
Goals.
    xxxvii. The initials RPOs mean or refer to regional planning
organizations.
    xxxviii. The initials SCR mean or refer to selective catalytic
reduction.
    xxxix. The initials SIP mean or refer to State Implementation
Plan.
    xl. The initials SNCR mean or refer to selective non-catalytic
reduction.
    xli. The initials SO2 mean or refer to sulfur dioxide.
    xlii. The initials SOFA mean or refer to separated overfire air.
    xliii. The initials TSD mean or refer to Technical Support
Document.
    xliv. The initials ULNB mean or refer to ultra-low
NOX burners.
    xlv. The initials URP mean or refer to Uniform Rate of Progress.
    xlvi. The initials VOC mean or refer to volatile organic
compounds.
    xlvii. The initials WAQSR mean or refer to Wyoming Air Quality
Standards and Regulations.
    xlviii. The initials WEP mean or refer to Weighted Emissions
Potential.
    xlix. The initials WRAP mean or refer to the Western Regional
Air Partnership.
    l. The words Wyoming and State mean the State of Wyoming.

Table of Contents

I. General Information
    A. What should I consider as I prepare my comments for EPA?
II. EPA's Prior Action
III. Overview of Proposed Actions
IV. SIP and FIP Background
V. Background
    A. Regional Haze
    B. Requirements of the CAA and EPA's Regional Haze Rule (RHR)
    C. Roles of Agencies in Addressing Regional Haze
VI. Requirements for the Regional Haze SIPs
    A. The CAA and the Regional Haze Rule
    B. Determination of Baseline, Natural, and Current Visibility
Conditions
    C. Determination of Reasonable Progress Goals
    D. Best Available Retrofit Technology
    E. Long-Term Strategy
    F. Coordinating Regional Haze and Reasonably Attributable
Visibility Impairment
    G. Monitoring Strategy and Other Implementation Plan
Requirements
    H. Consultation With States and Federal Land Managers (FLMs)
VII. EPA's Evaluation of Wyoming's Regional Haze SIP
    A. Affected Class I Areas
    B. Baseline Visibility, Natural Visibility, and Uniform Rate of
Progress
    C. BART Determinations
    1. BART-Eligible Sources
    2. Sources Subject-to-BART
    a. Modeling Methodology
    b. Contribution Threshold
    c. Sources Identified by Wyoming as Subject-to-BART
    3. BART Determinations and Federally Enforceable Limits
    a. Costs of Compliance
    b. Visibility Improvement Modeling
    c. Summary of BART Determinations and Federally Enforceable
Limits
    i. FMC Westvaco--Units NS-1A and NS-1B
    ii. General Chemical Green River--Boilers C and D
    iii. Basin Electric Laramie River Station--Units 1-3
    iv. PacifiCorp Dave Johnston--Units 3 and 4
    v. PacifiCorp Jim Bridger Units 1-4
    vi. PacifiCorp Naughton Units 1-3
    vii. PacifiCorp Wyodak--Unit 1
    D. Reasonable Progress Requirements
    1. Visibility Impairing Pollutants and Sources
    2. Four-Factor Analyses
    a. Stationary Sources
    b. Summary of Reasonable Progress Determinations and Limits
    i. Oil and Gas Area Sources
    ii. Mountain Cement Company Laramie Plant--Kiln
    3. Reasonable Progress Goals
    E. Long Term Strategy
    1. Emission Inventories
    2. Consultation and Emissions Reductions for Other States' Class
I Areas
    3. Mandatory Long-Term Strategy Requirements
    a. Reductions Due to Ongoing Air Pollution Programs
    b. Measures To Mitigate the Impacts of Construction Activities
    c. Smoke Management
    d. Emission Limitations and Schedules for Compliance
    e. Source Retirement and Replacement Schedules
    f. Enforceability of Wyoming's Measures
    g. Anticipated Net Effect on Visibility Due to Projected Changes
    4. Our Conclusions on Wyoming's Long-Term Strategy
    F. Coordination of RAVI and Regional Haze Rule Requirements
    G. Monitoring Strategy and Other Implementation Plan
Requirements
    H. Consultation With FLMs
    I. Periodic SIP Revisions and 5-Year Progress Reports
VIII. Federal Implementation Plan
    A. Disapproval of the State's NOX BART Determinations
and Federal Implementation Plan for NOX BART
Determinations and Limits
    1. Disapproval of the State's Basin Electric Laramie River Units
1-3 NOX BART Determination and FIP To Address
NOX BART
    2. Disapproval of the State's PacifiCorp Dave Johnston Unit 3
and Unit 4 NOX BART Determination and FIP To Address
NOX BART
    3. Proposals in the Alternative for PacifiCorp Jim Bridger Units
1 and 2 NOX BART
    4. Disapproval of the State's PacifiCorp Naughton Units 1and 2
NOX BART Determination and FIP to Address NOX
BART
    5. Disapproval of the State's PacifiCorp Wyodak Unit 1
NOX BART Determination and FIP to Address NOX
BART
    B. Disapproval of the State's NOX Reasonable Progress
Determinations and Federal Implementation Plan for NOX
Reasonable Progress Determinations and Limits
    1. PacifiCorp Dave Johnston--Units 1 and 2
    C. Reasonable Progress Goals
    D. Federal Monitoring, Recordkeeping, and Reporting Requirements
    E. Federal Implementation Plan for the Long-Term Strategy
    F. Federal Implementation Plan for Coordination of RAVI and
Regional Haze Long-Term Strategy
IX. EPA's Proposed Action
X. Statutory and Executive Order Reviews

I. General Information

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

    1. Submitting 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 in 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
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:
    a. Identify the rulemaking by docket number and other identifying
information (subject heading, Federal Register date and page number).
    b. Follow directions--The agency may ask you to respond to specific
questions or organize comments by referencing a Code of Federal
Regulations (CFR) part or section number.
    c. Explain why you agree or disagree; suggest alternatives and
substitute language for your requested changes.
    d. Describe any assumptions and provide any technical information
and/or data that you used.
    e. If you estimate potential costs or burdens, explain how you
arrived at your estimate in sufficient detail to allow for it to be
reproduced.
    f. Provide specific examples to illustrate your concerns, and
suggest alternatives.
    g. Explain your views as clearly as possible, avoiding the use of
profanity or personal threats.
    h. Make sure to submit your comments by the comment period deadline
identified.

II. EPA's Prior Action

    We signed a notice of proposed rulemaking on May 15, 2012, and it
was published in the Federal Register on June 4, 2012 (77 FR 33022).
    In our proposal, we proposed to disapprove the following:
     The State's nitrogen oxides (NOX) best
available retrofit technology (BART) determinations for PacifiCorp Dave
Johnston Unit 3, PacifiCorp Jim Bridger Units 1 and 2, PacifiCorp
Wyodak Unit 1, and Basin Electric Laramie River Station Units 1, 2, and
3.
     The State's NOX reasonable progress
determination for PacifiCorp Dave Johnston Units 1 and 2.
     The State's Reasonable Progress Goals (RPGs).
     The State's monitoring, recordkeeping, and reporting
requirements in Chapter 6.4 of the SIP.
     Portions of the State's long-term strategy (LTS) that rely
on or reflect aspects of the regional haze SIP that we are
disapproving.
     The State's SIP because it does not contain the necessary
provisions to meet the requirements for the coordination of the review
of the reasonably attributable visibility impairment (RAVI) and the
regional haze LTS.
    We proposed to approve the remaining aspects of the State's January
12, 2011 SIP submittal. We also sought comment on two alternative
proposals related to the State's NOX BART determination for
PacifiCorp Jim Bridger Units 1 and 2.
    We proposed the promulgation of a FIP to address the deficiencies
in the Wyoming regional haze SIP that we identified in the proposal.
The proposed FIP included the following elements:
     NOX BART determinations and limits for
PacifiCorp Dave Johnston Unit 3, PacifiCorp Jim Bridger Units 1 and 2,
PacifiCorp Wyodak Unit 1, and Basin Electric Laramie River Station
Units 1, 2, and 3.
     NOX reasonable progress determination and
limits for PacifiCorp Dave Johnston Units 1 and 2.
     RPGs consistent with the SIP limits proposed for approval
and the proposed FIP limits.
     Monitoring, recordkeeping, and reporting requirements
applicable to all BART and reasonable progress sources for which there
is a SIP or FIP emissions limit.
     LTS elements pertaining to emission limits and compliance
schedules for the proposed BART and reasonable progress FIP emission
limits.
     Provisions to ensure the coordination of the RAVI and
regional haze LTS.
    In lieu of our proposed FIP, or a portion thereof, we stated that
we would propose approval of a SIP revision if the State submits such a
revision and the revision matches the terms of our proposed FIP. We
encouraged the State to submit a SIP revision to replace the FIP,
either before or after our final action.
    We requested comments on all aspects of our proposed action and
provided a 60-day comment period, with the comment period closing on
August 3, 2012. We also held two public hearings. The public hearings
were held on June 26, 2012, in Cheyenne, Wyoming and June 28, 2012, in
Rock Springs, Wyoming.
    The Conservation Organizations \1\ and the National Park Service
submitted comments during the public comment period pertaining to,
among other things, the cost analyses that the State relied upon in its
SIP and that EPA subsequently relied on to make its proposed rulemaking
decision. The commenters asserted that the State overestimated the
costs for some control technologies and underestimated the costs for
other control technologies. Based on our review of these comments and
upon further review of the State's cost and visibility analyses, we
determined that the State's analyses are flawed in several respects and
are therefore inconsistent with the BART Guidelines and statutory
requirements, as discussed further in this notice. As a result, EPA
conducted its own cost analyses for the BART and reasonable progress
electric generating units (EGUs), and also revised its modeling of the
visibility improvement for these sources in order to be comparable to
the revised costs analyses as explained in section V.II.C.3. The
revised costs and visibility modeling are explained in further detail
in section VII.C.3. Because we have developed new cost and visibility
improvement modeling analyses, we are re-proposing action on Wyoming's
SIP in order to give the public the opportunity to comment on our
updated cost and visibility analyses and our proposed determinations
based on this new information.
---------------------------------------------------------------------------

    \1\ The Conservation Organizations refers to comments submitted
on behalf of Powder River Basin Resource Council, Wyoming Outdoor
Council, Greater Yellowstone Coalition, Sierra Club, National Parks
Conservation Association, and WildEarth Guardians.
---------------------------------------------------------------------------

III. Overview of Proposed Actions

    EPA is proposing to partially approve and partially disapprove a
regional haze SIP submitted by the State of Wyoming on January 12,
2011. Specifically, we are proposing to disapprove the following:
     The State's NOX BART determinations for
PacifiCorp Dave Johnston Units 3 and 4, PacifiCorp Naughton Units 1 and
2, PacifiCorp Wyodak Unit 1, and Basin Electric Laramie River Units 1,
2, and 3.
     The State's NOX reasonable progress
determinations for PacifiCorp Dave Johnston Units 1 and 2.
     Wyoming's RPGs.
     The State's monitoring, recordkeeping, and reporting
requirements in Chapter 6.4 of the SIP.
     Portions of the State's LTS that rely on or reflect other
aspects of the regional haze SIP.
     The provisions necessary to meet the requirements for the
coordination of the review of the RAVI and the regional haze LTS.
    We are proposing to approve the remaining aspects of the State's
January 12, 2011SIP submittal. However, we are also seeking comment on
an alternative proposal, related to the State's NOX BART
determinations, for PacifiCorp Jim Bridger Units 1 and 2, that would

involve disapproval and the promulgation of a FIP.
    We are proposing the promulgation of a FIP to address the
deficiencies in the Wyoming regional haze SIP that we have identified
in this notice. The proposed FIP includes the following elements:
     NOX BART determinations and limits for
PacifiCorp Dave Johnston Units 3 and 4, PacifiCorp Naughton Units 1 and
2, PacifiCorp Wyodak Unit 1, and Basin Electric Laramie River Units 1,
2, and 3.
     NOX reasonable progress determinations and
limits for PacifiCorp Dave Johnston Units 1 and 2.
     RPGs consistent with the SIP limits proposed for approval
and the proposed FIP limits.
     Monitoring, recordkeeping, and reporting requirements
applicable to all BART and reasonable progress sources for which there
is a SIP or FIP emissions limit.
     LTS elements pertaining to emission limits and compliance
schedules for the proposed BART and reasonable progress FIP emission
limits.
     Provisions to ensure the coordination of the RAVI and
regional haze LTS.
    In lieu of our proposed FIP, or a portion thereof, we will propose
approval of a SIP revision as expeditiously as practicable if the State
submits such a revision and the revision matches the terms of our
proposed FIP. We will also review and take action on any regional haze
SIP submitted by the state to determine whether such SIP is approvable,
regardless of whether or not its terms match those of the FIP. We
encourage the State to submit a SIP revision to replace the FIP, either
before or after our final action.

IV. SIP and FIP Background

    The CAA requires each state to develop plans to meet various air
quality requirements, including protection of visibility. CAA sections
110(a), 169A, and 169B. The plans developed by a state are referred to
as SIPs. A state must submit its SIPs and SIP revisions to us for
approval. Once approved, a SIP is enforceable by EPA and citizens under
the CAA, 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 unapprovable, then we must promulgate a FIP
to fill this regulatory gap. CAA section 110(c)(1). As discussed
elsewhere in this notice, we are proposing to disapprove aspects of
Wyoming's regional haze SIP. We are proposing a FIP to address the
deficiencies in Wyoming's regional haze SIP.

V. Background

A. Regional Haze

    Regional haze is visibility impairment that is produced by a
multitude of sources and activities which are located across a broad
geographic area and emit fine particles (PM2.5) (e.g.,
sulfates, nitrates, organic carbon (OC), elemental carbon (EC), and
soil dust), and their precursors (e.g., sulfur dioxide
(SO2), NOX, and in some cases, ammonia
(NH3) and volatile organic compounds (VOC)). Fine particle
precursors react in the atmosphere to form PM2.5, which
impairs visibility by scattering and absorbing light. Visibility
impairment 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.
    Data from the existing visibility monitoring network, the
``Interagency Monitoring of Protected Visual Environments'' (IMPROVE)
monitoring network, show that visibility impairment caused by air
pollution occurs virtually all the time at most national park and
wilderness areas. The average visual range \2\ in many Class I areas
(i.e., national parks and memorial parks, wilderness areas, and
international parks meeting certain size criteria) in the western
United States is 100-150 kilometers, or about one-half to two-thirds of
the visual range that would exist without anthropogenic air pollution.
In most of the eastern Class I areas of the United States, the average
visual range is less than 30 kilometers, or about one-fifth of the
visual range that would exist under estimated natural conditions. 64 FR
35715 (July 1, 1999).
---------------------------------------------------------------------------

    \2\ Visual range is the greatest distance, in kilometers or
miles, at which a dark object can be viewed against the sky.
---------------------------------------------------------------------------

B. 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 \3\ which
impairment results from manmade air pollution.'' On December 2, 1980,
EPA promulgated regulations to address visibility impairment in Class I
areas that is ``reasonably attributable'' to a single source or small
group of sources, i.e., ``reasonably attributable visibility
impairment.'' 45 FR 80084. 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.
---------------------------------------------------------------------------

    \3\ 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
(November 30, 1979). The extent of a mandatory Class I area includes
subsequent changes in boundaries, such as park expansions. 42 U.S.C.
7472(a). Although states and tribes may designate as Class I
additional areas 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 action, we mean a
``mandatory Class I Federal area.''
---------------------------------------------------------------------------

    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. 64 FR 35714 (July 1, 1999), codified at 40 CFR part 51, subpart
P. 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 51.300-309. Some of the main elements of the regional haze
requirements are summarized in section III 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.\4\
---------------------------------------------------------------------------

    \4\ EPA's regional haze regulations require subsequent updates
to the regional haze SIPs. 40 CFR 51.308(g)-(i).
---------------------------------------------------------------------------

    Few states submitted a regional haze SIP prior to the December 17,
2007 deadline, and on January 15, 2009, EPA found that 37 states
(including Wyoming), the District of Columbia, and the Virgin Islands,
had failed to submit SIPs addressing the regional haze requirements. 74
FR 2392. 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. CAA Sec.
110(c)(1).

C. Roles of Agencies in Addressing Regional Haze

    Successful implementation of the regional haze program will require
long-term regional coordination among states, tribal governments, and
various federal agencies. As noted above, 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 developed 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.

VI. Requirements for Regional Haze SIPs

    The following is a summary of the requirements of the RHR. See 40
CFR 51.308 for further detail regarding the requirements of the rule.

A. 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
below.

B. Determination of Baseline, Natural, and Current Visibility
Conditions

    The RHR establishes the deciview as the principal metric or unit
for expressing visibility. See 70 FR 39104, 39118. 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 deciview is a more useful measure for
tracking progress in improving visibility than light extinction itself
because each deciview change is an equal incremental change in
visibility perceived by the human eye. Most people can detect a change
in visibility at one deciview.\5\
---------------------------------------------------------------------------

    \5\ The preamble to the RHR provides additional details about
the dv. 64 FR 35714, 35725 (July 1, 1999).
---------------------------------------------------------------------------

    The deciview is used in expressing RPGs (which are interim
visibility goals towards meeting the national visibility goal),
defining baseline, current, and natural conditions, and 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 air pollution by reducing anthropogenic emissions that
cause regional haze. The national goal is a return to natural
conditions, i.e., anthropogenic sources of air pollution would 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 (40 CFR 81.401-437), 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 periodically
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 of the 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. We have provided guidance to states regarding how
to calculate baseline, natural and current visibility conditions.\6\
---------------------------------------------------------------------------

    \6\ Guidance for Estimating Natural Visibility Conditions Under
the Regional Haze Rule, September 2003, EPA-454/B-03-005, available
at http://www.epa.gov/ttncaaa1/t1/memoranda/Regional Haze_
envcurhr_gd.pdf, (hereinafter referred to as ``our 2003 Natural
Visibility Guidance''); and Guidance for Tracking Progress Under the
Regional Haze Rule, (September 2003, EPA-454/B-03-004, available at
http://www.epa.gov/ttncaaa1/t1/memoranda/rh_tpurhr_gd.pdf,
(hereinafter referred to as our ``2003 Tracking Progress
Guidance'').
---------------------------------------------------------------------------

    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 degree of visibility impairment for the 20
percent least impaired days and 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 amount of progress made. In general, the 2000-2004
baseline period is considered the time from which improvement in
visibility is measured.

C. Determination of Reasonable Progress Goals

    The vehicle for ensuring continuing progress towards achieving the
natural visibility goal is the submission of a series of regional haze
SIPs from the states that establish two RPGs (i.e., two distinct goals,
one for the ``best'' and one for the ``worst'' days) for every Class I
area for each (approximately) 10-year implementation period. See 40 CFR
51.308(d), (f). The RHR does not mandate specific milestones or rates
of progress, but instead calls for states to establish goals that
provide for ``reasonable progress'' toward achieving natural visibility
conditions. In setting RPGs, states must provide for an improvement in
visibility for the most impaired days over the (approximately) 10-year
period of the SIP, and ensure no degradation in visibility for the
least impaired days over the same period. Id.
    In establishing RPGs, states are required to consider the following
factors established in section 169A of the CAA and in our RHR at 40 CFR
51.308(d)(1)(i)(A): (1) The costs of compliance; (2) the time necessary
for compliance; (3) the energy and non-air quality environmental
impacts of compliance; and (4) the remaining useful life of any
potentially affected sources. States must demonstrate in their SIPs how
these factors are considered when selecting the RPGs for the best and
worst days for each applicable Class I area. In setting the RPGs,
states must also consider the rate of progress needed to reach natural
visibility conditions by 2064 (referred to as the ``uniform rate of
progress'' (URP) or the ``glidepath'') and the emission reduction
measures needed to achieve that rate of progress over the 10-year
period of the SIP. Uniform progress towards achievement of natural
conditions by the year 2064 represents a rate of progress, which states
are to use for analytical comparison to the amount of progress they
expect to achieve. In setting RPGs, each state with one or more Class I
areas (``Class I state'') must also consult with potentially
``contributing states,'' i.e., other nearby states with emission
sources that may be affecting visibility impairment at the state's
Class I areas. 40 CFR 51.308(d)(1)(iv). In determining whether a
state's goals for visibility improvement provide for reasonable
progress toward natural visibility conditions, EPA is required to
evaluate the demonstrations developed by the state pursuant to
paragraphs 40 CFR 51.308(d)(1)(i) and (d)(1)(ii). 40 CFR
51.308(d)(1)(iii).

D. 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 \7\ 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.
---------------------------------------------------------------------------

    \7\ The set of ``major stationary sources'' potentially subject-
to-BART is listed in CAA section 169A(g)(7).
---------------------------------------------------------------------------

    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. 70 FR 39104. 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.
    The process of establishing BART emission limitations can be
logically broken down into three steps: First, states identify those
sources which meet the definition of ``BART-eligible source'' set forth
in 40 CFR 51.301;\8\ 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'' (a
source which 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.
---------------------------------------------------------------------------

    \8\ 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.
---------------------------------------------------------------------------

    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 emissions 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
deciview. 40 CFR part 51, appendix Y, section 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. CAA
section 169(g)(4) and 40 CFR 51.308(e)(1)(iv). In addition to what is
required by the RHR, general SIP requirements mandate that the SIP must
also include all regulatory requirements related to monitoring,
recordkeeping, and reporting for the BART controls on the source. See
CAA section 110(a). As noted above, 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.

E. Long-Term Strategy

    Consistent with the requirement in section 169A(b) of the CAA that
states include in their regional haze SIP a 10- to 15-year strategy for
making reasonable progress, section 51.308(d)(3) of the RHR requires
that states include a LTS in their regional haze SIPs. The LTS is the
compilation of all control measures a state will use during the
implementation period of the specific SIP submittal to meet applicable
RPGs. The LTS must include ``enforceable emissions limitations,
compliance schedules, and other measures as necessary to achieve the
reasonable progress goals'' for all Class I areas within, or affected
by emissions from, the state. 40 CFR 51.308(d)(3).
    When a state's emissions are reasonably anticipated to cause or
contribute to visibility impairment in a Class I area located in
another state, the RHR requires the impacted state to coordinate with
the contributing states in order to develop coordinated emissions
management strategies. 40 CFR 51.308(d)(3)(i). In such cases, the
contributing state must demonstrate that it has included, in its SIP,
all measures necessary to obtain its share of the emission reductions
needed to meet the RPGs for the Class I area. Id. at (d)(3)(ii). The
RPOs have provided forums for significant interstate consultation, but
additional consultations between states may be required to sufficiently
address interstate visibility issues. This is especially true where two
states belong to different RPOs.
    States should consider all types of anthropogenic sources of
visibility impairment in developing their long-term strategy, including
stationary, minor, mobile, and area sources. At a minimum, states must
describe how each of the following seven factors listed below are taken
into account in developing their LTS: (1) Emission reductions due to
ongoing air pollution control programs, including measures to address
RAVI; (2) measures to mitigate the impacts of construction activities;
(3) emissions limitations and schedules for compliance to achieve the
RPG; (4) source retirement and replacement schedules; (5) smoke
management techniques for agricultural and forestry management purposes
including plans as currently exist within the state for these purposes;
(6) enforceability of emissions limitations and control measures; and
(7) the anticipated net effect on visibility due to projected changes
in point, area, and mobile source emissions over the period addressed
by the LTS. 40 CFR 51.308(d)(3)(v).

F. Coordinating Regional Haze and Reasonably Attributable Visibility
Impairment

    As part of the RHR, EPA revised 40 CFR 51.306(c) regarding the LTS
for RAVI to require that the RAVI plan must provide for a periodic
review and SIP revision not less frequently than every three years
until the date of submission of the state's first plan addressing
regional haze visibility impairment, which was due December 17, 2007,
in accordance with 40 CFR 51.308(b) and (c). On or before this date,
the state must revise its plan to provide for review and revision of a
coordinated LTS for addressing RAVI and regional haze, and the state
must submit the first such coordinated LTS with its first regional haze
SIP. Future coordinated LTS's, and periodic progress reports evaluating
progress towards RPGs, must be submitted consistent with the schedule
for SIP submission and periodic progress reports set forth in 40 CFR
51.308(f) and 51.308(g), respectively. The periodic review of a state's
LTS must report on both regional haze and RAVI impairment and must be
submitted to EPA as a SIP revision.

F. Monitoring Strategy and Other Implementation Plan Requirements

    Section 51.308(d)(4) of the RHR includes the requirement for a
monitoring strategy for measuring, characterizing, and reporting of
regional haze visibility impairment that is representative of all
mandatory Class I Federal areas within the state. The strategy must be
coordinated with the monitoring strategy required in section 51.305 for
RAVI. Compliance with this requirement may be met through
``participation'' in the IMPROVE network, i.e., review and use of
monitoring data from the network. The monitoring strategy is due with
the first regional haze SIP, and it must be reviewed every five years.
The monitoring strategy must also provide for additional monitoring
sites if the IMPROVE network is not sufficient to determine whether
RPGs will be met.
    The SIP must also provide for the following:
     Procedures for using monitoring data and other information
in a state with mandatory Class I areas to determine the contribution
of emissions from within the state to regional haze visibility
impairment at Class I areas both within and outside the state;
     Procedures for using monitoring data and other information
in a state with no mandatory Class I areas to determine the
contribution of emissions from within the state to regional haze
visibility impairment at Class I areas in other states;
     Reporting of all visibility monitoring data to the
Administrator at least annually for each Class I area in the state, and
where possible, in electronic format;
     Developing a statewide inventory of emissions of
pollutants that are reasonably anticipated to cause or contribute to
visibility impairment in any Class I area. The inventory must include
emissions for a baseline year, emissions for the most recent year for
which data are available, and estimates of future projected emissions.
A state must also make a commitment to update the inventory
periodically; and
     Other elements, including reporting, recordkeeping, and
other measures necessary to assess and report on visibility.
    The RHR requires control strategies to cover an initial
implementation period extending to the year 2018, with a comprehensive
reassessment and revision of those strategies, as appropriate, every 10
years thereafter. Periodic SIP revisions must meet the core
requirements of section 51.308(d) with the exception of BART. The
requirement to evaluate sources for BART applies only to the first
regional haze SIP. Facilities subject-to-BART must continue to comply
with the BART provisions of section 51.308(e), as noted above. Periodic
SIP revisions will assure that the statutory requirement of reasonable
progress will continue to be met.

G. Consultation With States and Federal Land Managers (FLMs)

    The RHR requires that states consult with FLMs before adopting and
submitting their SIPs. 40 CFR 51.308(i). States must 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 assessment 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.

VII. EPA's Evaluation of Wyoming's Regional Haze SIP

A. Affected Class I Areas

    Pursuant to 40 CFR 51.308(d), the State identified seven mandatory
Class I areas in Wyoming: Grand Teton National Park, Yellowstone
National Park, Bridger Wilderness, Fitzpatrick Wilderness, North
Absaroka Wilderness, Teton Wilderness, and Washakie Wilderness.

B. Baseline Visibility, Natural Visibility, and Uniform Rate of
Progress

    As required by 40 CFR 51.308(d)(2), Wyoming provided baseline
visibility, natural visibility, and the URP for each Class I area in
the State. Natural background visibility, as defined in our 2003
Natural Visibility Guidance, is estimated by calculating the expected
light extinction using default estimates of natural concentrations of
fine particle components adjusted by site-specific estimates of
humidity. This calculation uses the IMPROVE equation, which is a
formula for estimating light extinction from the estimated natural
concentrations of fine particle components (or from components measured
by the IMPROVE monitors). As documented in our 2003 Natural Visibility
Guidance, EPA allows states to use ``refined'' or alternative
approaches to this guidance to estimate the values that characterize
the natural visibility conditions of Class I areas.
    One alternative approach is to develop and justify the use of
alternative estimates of natural concentrations of fine particle
components. Another alternative is to use the ``new IMPROVE equation''
that was adopted for use by the IMPROVE Steering Committee in December
2005.\9\ The purpose of this refinement to the ``old IMPROVE equation''
is to provide more accurate estimates of the various factors that
affect the calculation of light extinction.
---------------------------------------------------------------------------

    \9\ The IMPROVE program is a cooperative measurement effort
governed by a steering committee composed of representatives from
Federal agencies (including representatives from EPA and the FLMs)
and regional planning organizations. The IMPROVE monitoring program
was established in 1985 to aid the creation of Federal and State
implementation plans for the protection of visibility in Class I
areas. One of the objectives of IMPROVE is to identify chemical
species and emission sources responsible for existing anthropogenic
visibility impairment. TheIMPROVE program has also been a key
participant in visibility-related research, including the
advancement of monitoring instrumentation, analysis techniques,
visibility modeling, policy formulation and source attribution field
studies.
---------------------------------------------------------------------------

    Wyoming used the new IMPROVE equation to calculate natural
conditions and baseline visibility. The natural condition for each
Class I area represents the visibility goal expressed in deciviews for
the 20% worst days and the 20% best days that would exist if there were
only naturally occurring visibility impairment. In accordance with 40
CFR 51.308(d)(2)(iii), the State calculated natural visibility
conditions based on available monitoring information and appropriate
data analysis techniques and in accordance with our 2003 Natural
Visibility Guidance. The State also calculated the number of deciviews
by which baseline conditions exceed natural conditions at each of its
Class I areas to meet the requirements of 40 CFR 51.308(d)(2)(iv)(A).
    Wyoming established the baseline visibility for the best and worst
visibility days for each Class I area based on data from the IMPROVE
monitoring sites. Each IMPROVE monitor collects particulate
concentration data which are converted into reconstructed light
extinction through a complex calculation using the IMPROVE equation
(see Chapter 13 of the SIP for more information on reconstructed light
extinction and the IMPROVE equation). Per 40 CFR 51.308(d)(2)(i), the
State calculated baseline visibility using a five-year average (2000 to
2004) of IMPROVE data for both the 20% best and 20% worst days. The
State's baseline calculations were made in accordance with our 2003
Tracking Progress Guidance.
    Pursuant to 40 CFR 51.308(d)(1)(i)(B), the State calculated the URP
for each of its Class I areas. For the 20% worst days, the URP is the
calculation of the deciview reduction needed to achieve natural
conditions by 2064. For the 20% worst days, the State calculated the
URP in deciviews per year using the following formula: URP = [Baseline
Condition--Natural Condition]/60 years. In order to determine the
uniform progress needed by 2018 to be on the path to achieving natural
visibility conditions by 2064, the State multiplied the URP by the 14
years in the first planning period (2004-2018).
    Table 1 shows the baseline visibility, natural conditions, and URP
for each of the Class I areas. As indicated by the table, some Class I
areas share a single monitor because of the proximity of the areas to
each other.

                                   Table 1--Baseline Visibility, Natural Conditions, and URP for Wyoming Class I Areas
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                             20% Worst Days                                                                20% Best Days
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Reduction
                                                             2000-2004                       Needed to     2064 Natural        Delta         2000-2004
          Wyoming Class I areas            Monitor name      Baseline        2018 URP     Reach 2018 URP    Conditions    Baseline--2064     Baseline
                                                            (deciview)      (deciview)         (delta       (deciview)        Natural       (deciview)
                                                                                deciview)                      Conditions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Yellowstone National Park, Grand Teton             YELL2            11.8            10.5             1.3            6.44            5.36            2.58
 National Park, Teton Wilderness........

North Absaroka Wilderness...............           NOABI            11.5            10.4             1.1            6.83            4.67            2.0
Washakie Wilderness.....................
Bridger Wilderness, Fitzpatrick                    BRID1            11.1            10.0             1.1            6.45            4.65            2.1
 Wilderness.............................
--------------------------------------------------------------------------------------------------------------------------------------------------------

    We have reviewed Wyoming's baseline visibility, natural conditions,
and URP. We find they have been calculated correctly and are proposing
to approve them.

C. BART Determinations

    BART is an element of Wyoming's LTS for the first implementation
period. As discussed in more detail in section VI.D of this notice, the
BART evaluation process consists of three components: (1) An
identification of all the BART-eligible sources; (2) an assessment of
whether those BART-eligible sources are in fact subject-to-BART; and
(3) a determination of any BART controls. Wyoming addressed these steps
as follows:
1. BART-Eligible Sources
    The first step of a BART evaluation is to identify all the BART-
eligible sources within the state's boundaries. Wyoming identified its
BART-eligible sources by using the approach set out in the BART
Guidelines (70 FR 39158). This approach provides three criteria for
identifying BART-eligible sources: (1) One or more emission units at
the facility fit within one of the 26 categories listed in the BART
Guidelines; (2) the emission unit or units began operation on or after
August 6, 1962, and were in existence on August 6, 1977; and (3)
combined potential emissions of any visibility-impairing pollutant from
the units that meet the criteria in (1) and (2) are 250 tons or more
per year. Wyoming reviewed source permits and emission data from 2001-
2003 to identify facilities in the BART source categories with
potential emissions of 250 tons per year or more for any visibility-
impairing pollutant from any unit or units that were in existence on
August 7, 1977 and began operation on or after August 7, 1962. The BART
Guidelines direct states to address SO2\10\, NOX,
and direct PM (including both PM10 and PM2.5)
emissions as visibility-impairing pollutants and to exercise their
``best judgment to determine whether VOC or NH3 emissions
from a source are likely to have an impact on visibility in an area.''
(70 FR 39162).
---------------------------------------------------------------------------

    \10\ Wyoming has elected to submit its RH SIP pursuant to the
requirements of 40 CFR 51.309. For states electing to submit under
section 309, States do not have to do a BART analysis for
SO2. SO2 controls are included in the backstop
trading program under 40 CFR 51.309(d)(4).
---------------------------------------------------------------------------

    The State analyzed the emissions from VOC and NH3 from
sources in the State and eliminated them from further consideration for
BART controls. The State evaluated the BART-eligible sources and
determined emissions of VOC and NH3 were negligible. Thus,
the State has eliminated VOC and NH3 from further
consideration for BART controls. We agree with the State that emissions
of VOC and NH3 are negligible and propose to accept this
determination.
    The State determined that the following were BART-eligible sources:
PacifiCorp Jim Bridger, P4 Production, PacifiCorp Naughton, OCI
Wyoming, FMC Granger, Dyno Nobel, FMC Westvaco, Sinclair Casper
Refinery, Basin Electric Laramie River, Black Hills Neil Simpson 1,
PacifiCorp Wyodak, Sinclair--Sinclair Refinery, PacifiCorp Dave
Johnston, and General Chemical Green River.
    We have reviewed this information and propose to accept this
determination.
2. Sources Subject-to-BART
    The second step of the BART evaluation is to identify those BART-
eligible sources that may reasonably be anticipated to cause or
contribute to any visibility impairment at any Class I area, i.e.,
those sources that are subject-to-BART. The BART Guidelines allow
states to consider exempting some BART-eligible sources from further
BART review because they may not reasonably be anticipated to cause or
contribute to any visibility impairment in a Class I area. Consistent
with the BART Guidelines, Wyoming performed dispersion modeling on the
BART-eligible sources to assess the extent of their contribution to
visibility impairment at surrounding Class I areas.
a. Modeling Methodology
    The BART Guidelines provide that states may use the CALPUFF \11\
modeling system or another appropriate model to predict the visibility
impacts from a single source on a Class I area and to, therefore,
determine whether an individual source is anticipated to cause or
contribute to impairment of visibility in Class I areas, i.e., ``is
subject to BART.'' The Guidelines state that CALPUFF is the best
regulatory modeling application currently available for predicting a
single source's contribution to visibility impairment (70 FR 39162).
---------------------------------------------------------------------------

    \11\ Note that our reference to CALPUFF encompasses the entire
CALPUFF modeling system, which includes the CALMET, CALPUFF, and
CALPOST models and other pre and post processors. The different
versions of CALPUFF have corresponding versions of CALMET, CALPOST,
etc. which may not be compatible with previous versions (e.g., the
output from a newer version of CALMET may not be compatible with an
older version of CALPUFF). The different versions of the CALPUFF
modeling system are available from the model developer at http://www.src.com/verio/download/download.htm.
---------------------------------------------------------------------------

    The BART Guidelines also recommend that states develop a modeling
protocol for making individual source attributions, and suggest that
states may want to consult with EPA and their RPO to address any issues
prior to modeling. Wyoming used the CALPUFF model for Wyoming BART
sources in accordance with a protocol it developed titled BART Air
Modeling Protocol Individual Source Visibility Impairment Analysis,
March 2006, which was approved by EPA and is included in Chapter 6 of
the State's TSD. The Wyoming protocol follows

recommendations for long-range transport described in appendix W to 40
CFR part 51, Guideline on Air Quality Models, and in EPA's 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.A.3). To determine if each BART-eligible source has a
significant impact on visibility, Wyoming used the CALPUFF model to
estimate daily visibility impacts above estimated natural conditions at
each Class I area within 300 km of any BART-eligible facility. The
emission rates used in the CALPUFF modeling were determined by Wyoming
based upon existing permits, allowable rates, and emissions reporting
data.
b. Contribution Threshold
    For states using modeling to determine the applicability of BART to
single sources, the BART Guidelines note that the first step is to set
a contribution threshold to assess whether the impact of a single
source is sufficient to cause or contribute to visibility impairment at
a Class I area. The BART Guidelines state that, ``[a] single source
that is responsible for a 1.0 deciview change or more should be
considered to `cause' visibility impairment.'' (70 FR 39104, 39161).
The BART Guidelines also state that ``the appropriate threshold for
determining whether a source contributes to visibility impairment may
reasonably differ across states,'' but, ``[a]s a general matter, any
threshold that you use for determining whether a source ``contributes''
to visibility impairment should not be higher than 0.5 deciviews.'' Id.
Further, in setting a contribution threshold, states should ``consider
the number of emissions sources affecting the Class I areas at issue
and the magnitude of the individual sources' impacts.'' The Guidelines
affirm that states are free to use a lower threshold if they conclude
that the location of a large number of BART-eligible sources in
proximity to a Class I area justifies this approach.
    Wyoming used a contribution threshold of 0.5 deciviews for
determining which sources are subject-to-BART. By using a contribution
threshold of 0.5 deciviews, Wyoming exempted seven of the fourteen
BART-eligible sources in the State from further review under the BART
requirements. Based on the modeling results, the State determined that
P4 Production, FMC Granger,\12\ and OCI Wyoming had an impact of .07
deciview, 0.39 deciview, and 0.07 deciview, respectively, at Bridger
Wilderness. Black Hills Neil Simpson 1, Sinclair Casper Refinery, and
Sinclair--Sinclair Refinery have an impact of 0.27 deciview, 0.06
deciview, and 0.12 deciview, respectively, at Wind Cave. Dyno-Nobel had
an impact of 0.22 deciview at Rocky Mountain National Park. These
sources' modeled visibility impacts fell below the State's threshold of
0.5 deciview and were determined not to be subject-to-BART.\13\ Given
the relatively limited impact on visibility from these seven sources,
we propose to agree with Wyoming that 0.5 deciviews is a reasonable
threshold for determining whether its BART-eligible sources are
subject-to-BART.
---------------------------------------------------------------------------

    \12\ The State of Wyoming performed a refined CALPUFF visibility
modeling analysis for the two BART-eligible units at the FMC Wyoming
Granger Facility and demonstrated that the predicted 98th percentile
impacts at Bridger Wilderness Area and Fitzpatrick Wilderness Area
would be below 0.5 dv for all meteorological periods modeled. This
modeling used higher-resolution meteorological data as compared to
the data used by the State for the initial screening modeling that
identified the facility as subject-to-BART.
    \13\ CALPUFF modeling results, which provide the maximum change
in visibility are summarized in the WY BART Screening Analysis
Results and the WY BART Screening Analysis Results DV Frequency,
which can also be found in Chapter 6 of the State's TSD.
---------------------------------------------------------------------------

    Because our recommended modeling approach already incorporates
choices that tend to lower peak daily visibility impact values,\14\ our
BART Guidelines state that a state should compare the 98th percentile
(as opposed to the 90th or lower percentile) of CALPUFF modeling
results against the ``contribution'' threshold established by the state
for purposes of determining BART applicability. Wyoming used a 98th
percentile comparison that we find appropriate. Further explanation on
use of the 98th versus 90th percentile value is provided at 70 FR
39121.
---------------------------------------------------------------------------

    \14\ See our BART Guidelines, Section III.A.3.
---------------------------------------------------------------------------

c. Sources Identified by Wyoming as Subject-to-BART
    Table 2 shows the sources identified by the State as subject-to-
BART and the results of the CALPUFF modeling. The results reflect the
single highest impacted year.

  Table 2--Wyoming Subject-to-BART Sources and CALPUFF Modeling Results
------------------------------------------------------------------------
                                                         State modeling
                                                         results--98th
         Facility name          Subject-to-BART units  percentile  delta-
                                                            deciview
------------------------------------------------------------------------
PacifiCorp--Jim Bridger.......  Units 1-4............               3.1
Basin Electric--Laramie River.  Units 1, 2 and 3.....               3.68
PacifiCorp--Dave Johnston.....  Units 3 and 4........               3.30
PacifiCorp--Naughton..........  Units 1-3............               4.36
PacifiCorp--Wyodak............  Unit 1...............               1.66
FMC--Westvaco.................  Units NS-1A and NS-1B               1.3
General Chemical--Green River.  Boilers C and D......               1.36
------------------------------------------------------------------------

    We are proposing to approve the State's determination of the
subject-to-BART sources.
3. BART Determinations and Federally Enforceable Limits
    The third step of a BART evaluation is to perform the BART
analysis. The BART Guidelines (70 FR 39164) describe the BART analysis
as consisting of the following five steps:
     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.
    In determining BART, the State must consider the five statutory
factors in section 169A 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).
    We find that Wyoming considered all five steps above in its BART
determinations, but we propose to find that its consideration of the
costs of compliance and visibility improvement for the EGUs was
inadequate and did not properly follow the requirements in the BART
Guidelines and statutory requirements, as explained below.
a. Costs of Compliance
    Wyoming obtained the costs of compliance for controls from the BART
applications submitted by sources that were subject to BART.\15\ EPA in
turn relied on these costs in our original proposed rule. EPA has
reviewed Wyoming's cost analyses and has identified deficiencies in
various cost assumptions and methods. Accordingly, EPA has subsequently
and independently calculated costs of compliance and performed new
visibility modeling. In many instances, the BART sources underestimated
the cost of selective non-catalytic reduction (SNCR), while
overestimating the cost of selective catalytic reduction (SCR) (both in
combination with additional combustion controls). Depending on the
particular BART source in question, we believe this was due to a number
of errors, such as: use of incorrect baseline emissions; overestimation
of the ability of SNCR to reduce NOX; underestimation of
SNCR reagent (urea) usage and cost; and underestimation of the ability
of SCR to reduce NOX.
---------------------------------------------------------------------------

    \15\ Attachment A to the Wyoming 309(g) Regional Haze SIP.
---------------------------------------------------------------------------

    EPA has identified a number of flaws in Wyoming's cost analyses for
SNCR. For example, in the case of Laramie River Units 1-3, Wyoming
significantly overestimated the ability of SNCR to reduce
NOX. The analyses submitted by the source, and in turn used
by Wyoming, assumed that after the installation of additional
combustion controls, SNCR would reduce NOX from 0.23 lb/
MMBtu to 0.12 lb/MMBtu (or by roughly 48%). However, SNCR typically
reduces NOX an additional 20 to 30% above combustion
controls without excessive NH3 slip.\16\ NOX
reduction with SNCR is known to be greater at higher NOX
emission rates than lower rates.\17\ Accordingly, EPA has estimated
that the NOX reduction from SNCR as 30% for initial
NOX greater than 0.25 lb/MMBtu, 25% for NOX from
0.20 to 0.25 lb/MMBtu and 20% for NOX less than 0.20 lb/
MMBtu.\18\ Due to the relatively recent installation of overfire air at
the Laramie River units, the actual annual emissions in 2012 dropped to
around 0.19 lb/MMBtu,\19\ even lower than the 0.23 lb/MMbtu rate
assumed by Wyoming. Therefore, EPA predicts that the reduction that can
be achieved with SNCR at the Laramie River units is 20%, which is much
lower than the 48% assumed by Wyoming. This significantly reduces the
tons reduced by SNCR which is in turn used in the calculation of cost
effectiveness. It also affects the incremental cost effectiveness
between SNCR and SCR (both in combination with additional combustion
controls). In addition, our analysis of urea prices indicates that
producer prices for urea have increased the past three years. This
increase in price is not reflected in the Wyoming estimates for SNCR.
---------------------------------------------------------------------------

    \16\ White Paper, SNCR for Controlling NOX Emissions,
Institute of Clean of Clean Air Companies, pp. 4 and 9, February
2008.
    \17\ Hofmann, J., Sun, W., ``Process for Nitrogen Oxides
Reduction to Lowest Achievable Level'', US Patent 5,229,090, July
20, 1993, Figure 6.
    \18\ Review of Estimated Compliance Costs for Wyoming Electric
Generating (EGUs)--Revision of Previous Memo, memo from Jim Staudt,
Andover Technology Partners, to Doug Grano, EC/R, Inc., February 7,
2013, page 7 (Staudt Memo).
    \19\ Staudt memo, Table 2, p. 7.
---------------------------------------------------------------------------

    EPA has also identified a number of flaws in Wyoming's cost
analyses for SCR. For example, Wyoming assumed that SCR could only
achieve a control effectiveness of 0.07 lb/MMBtu. By contrast, EPA has
determined that on an annual basis SCR can achieve emission rates of
0.05 lb/MMbtu or lower. Moreover, we note that Wyoming's SCR capital
costs on a $/kW basis often exceeded real-world industry costs. The
capital costs for SCR claimed by Wyoming for Dave Johnston 3 and 4,
Naughton Units 1-3, and Wyodak are in excess of the range of capital
costs documented by various studies for actual installations. Five
industry studies conducted between 2002 and 2007 have reported the
installed unit capital cost of SCRs, or the costs actually incurred by
owners, to range from $79/kW to $316/kW (2010 dollars). By contrast,
Wyoming's SCR costs range from $415/kW to $531/kW.\20\ These studies
show actual capital costs are much lower than Wyoming's, particularly
for the PacifiCorp units.
---------------------------------------------------------------------------

    \20\ Staudt memo, Table 1, p. 4.
---------------------------------------------------------------------------

    For all control technologies, EPA has identified instances in which

Wyoming's source-based cost analyses did not follow the methods set
forth in the EPA Control Cost Manual.\21\ For example, Wyoming included
an allowance for funds used during construction and for owners costs
and did not provide sufficient documentation such as vendor estimates
or bids.
---------------------------------------------------------------------------

    \21\ ``In order to maintain and improve consistency, cost
estimates should be based on the OAQPS Control Cost Manual, where
possible.'' 70 FR 39166.
---------------------------------------------------------------------------

    In addition, for the PacifiCorp units, Wyoming calculated the
baseline annual emissions used for determining cost effectiveness based
on allowable emissions, rated heat input, and 7,884 hours of operation
(equivalent to a 85% capacity factor), which are not representative of
actual emissions from the baseline period. By contrast, the BART
Guidelines state that the baseline emissions should ``represent a
realistic depiction of anticipated annual emissions for the source.''
\22\ Therefore, in our revised cost analyses, we have consistently used
the actual annual average emissions from 2001-2003 to represent
baseline emissions.
---------------------------------------------------------------------------

    \22\ 70 FR 39167.
---------------------------------------------------------------------------

    To address these flaws and deficiencies, EPA has developed
independent cost analyses. In our revised cost analyses, we have
followed the structure of the EPA Control Cost Manual, though we have
largely used the Integrated Planning Model cost calculations to
estimate direct capital costs and operating and maintenance costs. We
have also followed the BART Guidelines. Detailed information on the
revised costs can be found in the docket.23 24 In addition,
we received comments on our original proposed rulemaking from the
National Park Service and Conservation Organizations that expressed
similar concerns with the State's cost analyses.
---------------------------------------------------------------------------

    \23\ Review of Estimated Compliance Costs for Wyoming Electric
Generating (EGUs)--Revision of Previous Memo, memo from Jim Staudt,
Andover Technology Partners, to Doug Grano, EC/R, Inc., February 7,
2013. (Staudt Memo).
    \24\ Review of Estimated BART Compliance Costs for Wyoming
Electricity Generating Units (EGUs) memo from Jim Staudt, Andover
Technology Partners, to Doug Grano, EC/R, Inc., February 7, 2013.
---------------------------------------------------------------------------

b. Visibility Improvement Modeling
    The BART Guidelines provide that states may use the CALPUFF
modeling system or another appropriate model to determine the
visibility improvement expected at a Class I area from potential BART
control technologies applied to the source. 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. Wyoming
developed a modeling protocol titled BART Air Modeling Protocol
Individual Source Visibility Assessments for BART Control Analyses,
September 2006, for sources to use when they performed their BART
analysis (see Chapter 6 of the State's TSD). The Wyoming protocol
follows recommendations for long-range transport described in appendix
W to 40 CFR part 51, Guideline on Air Quality Models, and in EPA's
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).
    While we are able to propose approval of the State's PM BART
determinations without having additional visibility improvement
modeling for PM controls, as discussed below, additional visibility
improvement modeling to address the EGU NOX BART controls
was needed and subsequently performed by EPA and presented in our
original proposed rulemaking.\25\ Our additional modeling to support
the original proposed rule was intended to addresses two deficiencies.
First, while Wyoming took into consideration the degree of visibility
improvement for some BART NOX control options for the
PacifiCorp EGUs, such as SCR, they did not do so for SNCR. The
visibility improvement for SNCR was neither provided in the State's SIP
nor made available to EPA. Wyoming did not assess the visibility
improvement of SNCR despite having found it to be a technically
feasible control option, and having considered a number of the other
statutory factors for SNCR, such as costs of compliance and energy
impacts. Wyoming did not consider the visibility improvement associated
with SNCR, which is clearly in conflict with the requirements set forth
in section 169A(g)(2) of the CAA, as well as in the implementing
regulations,\26\ which require that states take into consideration
``the degree of improvement in visibility which may reasonably be
anticipated to result from the use of such technology.'' Because
Wyoming did not do so, and in order to be consistent with the statutory
and regulatory requirements, EPA conducted additional CALPUFF modeling
to fill this gap in the State's visibility analysis (that is, to assess
the visibility improvement associated with SNCR).
---------------------------------------------------------------------------

    \25\ A summary of EPA's modeling methodology and results for the
original proposed rulemaking can be found in the docket under EPA
BART and RP Modeling for Wyoming Sources.
    \26\ 40 CFR 51.308(e)(1)(ii)(A).
---------------------------------------------------------------------------

    Second, it was not possible for EPA, or any other party, to
ascertain the visibility improvement that would result from the
installation of the various NOX control options because
Wyoming modeled the emission reductions for multiple pollutants
together in its SIP. In other words, because the visibility improvement
associated with each of the State's control scenarios was due to the
combined emission reductions associated with SO2,
NOX, and PM controls, it was not possible to isolate what
portion of the improvement was attributable to the NOX
controls alone. In addition, because Wyoming varied SO2 and
PM emission rates along with NOX emission rates, it was not
possible to assess the incremental visibility improvement between the
various NOX controls options. For these reasons, EPA
conducted additional modeling for the EGUs in which we held
SO2 and PM emission rates constant (reflecting the
``committed controls'' identified by Wyoming), and varied only the
NOX emission rate. This allowed us to isolate the degree of
visibility improvement attributable to the NOX control
technologies. The modeling which EPA performed to support our original
proposed rule addressed these two deficiencies in the State's analysis.
    To support today's proposal, EPA has found it necessary to revise
the CALPUFF modeling we performed in association with our original
proposed rule. The revised modeling to support today's proposed rule is
intended to address two additional issues that were raised by
commenters during the comment period for the original proposed rule.
First, as discussed above in section V.II, we have revised the costs of
control submitted by the State. In the process of revising these costs,
we have calculated a new removal efficiency for the control options
under consideration to reflect updated assumptions about baseline
emissions and control effectiveness.\27\
---------------------------------------------------------------------------

    \27\ See Staudt memos.
---------------------------------------------------------------------------

    In order to align our cost and modeling analyses, these removal
efficiencies have been incorporated into our revised modeling. Second,
the emission rates we relied on in our original proposed rule for both
the baseline (i.e., pre-control) and post-control modeling scenarios
were not consistent with the BART Guidelines. For pre-control emission
rates, the BART Guidelines recommend that States use the 24-hour
average actual

emission rate from the highest emitting day of the meteorological
period modeled.\28\ By contrast, the visibility modeling performed by
PacifiCorp, and subsequently submitted by the State and utilized by EPA
in our original proposal, deviates from the BART Guidelines by using
permit limits and the maximum rated heat input to derive the modeled
emission rates. Similarly, the visibility modeling performed by Basin
Electric, and subsequently submitted by the State and utilized by EPA
in our original proposal, deviates from the BART Guidelines by using
actual annual average heat input and actual annual average emission
rates (on a lb/MMBtu basis) from 2001-2003 continuous emissions
monitoring data to derive modeled emission rates. Furthermore, the BART
Guidelines recommend that post-control emission rates be calculated as
a percentage of pre-control emission rates.\29\ The visibility modeling
performed by PacifiCorp and Basin Electric, and subsequently submitted
by the State and utilized by EPA in our original proposal, deviates
from the BART Guidelines by using post-control emission rates
calculated in a similar manner to the pre-control emission rates. Our
revised modeling remedies both of the issues identified by the
commenters and is consistent with the requirements of the BART
Guidelines. We have otherwise followed the procedures contained in the
Wyoming BART Air Modeling Protocol. A summary of EPA's revised modeling
methodology and results can be found in the docket.\30\
---------------------------------------------------------------------------

    \28\ The BART Guidelines, Section IV. (70 FR 39170) specify that
the modeling should ``[u]se the 24-hour average actual emission rate
from the highest emitting day of the meteorological period modeled
(for the pre-control scenario)''.
    \29\ The BART Guidelines, Section IV. (70 FR 39170) specify that
``[p]ost-control emission rates are calculated as a percentage of
pre-control emission rates''.
    \30\ EPA's modeling results and a summary of EPA's modeling
methodology can be found in the docket under Summary of EPA's
Revised Modeling--Including Revisions from Previous Version Posted
on 1/18/2013 and Results for Jim Bridger Units 1-4 and EPA's Revised
Modeling Results; posted to the docket on February 11, 2013.
---------------------------------------------------------------------------

    Because Wyoming relied on visibility modeling methodologies that
are inconsistent with the statutory and regulatory requirements, we do
not consider Wyoming's analyses of visibility improvement for
NOX BART to be reasonable. We propose to find that Wyoming's
analyses are inconsistent with the statutory and regulatory requirement
that Wyoming reasonably take into consideration ``the degree of
improvement in visibility which may reasonably be anticipated to result
from the use of such technology.'' Therefore, as discussed in more
detail below, we are proposing to disapprove several of the State's
NOX BART determinations that do not meet the requirements of
the CAA and regional haze regulations because they are inconsistent
with the visibility requirements.
c. Summary of BART Determinations and Federally Enforceable Limits
    For the subject-to-BART sources, the State provided BART analyses,
as well as additional technical information and materials, in
Attachment A to the SIP. Chapter 6 of the SIP provides a summary of the
five-factor analyses. As noted above, for this proposed rulemaking, EPA
performed cost analyses and NOX visibility improvement
modeling for the control technology options analyzed for the subject-
to-BART EGU sources. We are presenting the BART analyses that we based
our June 4, 2012 proposed rulemaking on, as well as EPA's revised BART
analyses, reflecting our revised cost and visibility improvement
modeling for the EGUs.
    EPA is proposing to approve the State's BART determinations for the
following units because we have determined that the State's conclusions
were reasonable despite the cost and visibility errors for the EGUs
discussed earlier: NOX and PM BART for FMC Westvaco Unit NS-
1A and NS-1B; NOX and PM BART for General Chemical Green
River Boiler C and Boiler D; \31\ PM BART for Basin Electric Laramie
River Units 1, 2, and 3; PM BART for PacifiCorp Dave Johnston Unit 3;
PM BART for PacifiCorp Dave Johnston Unit 4; NOX and PM BART
(including reasonable progress controls) for PacifiCorp Jim Bridger
Units 1-4; PM BART for PacifiCorp Naughton Units 1and 2; NOX
and PM BART for Naughton Unit 3; and PM BART for PacifiCorp Wyodak Unit
1. A summary of the State's and EPA's BART determination for each
source is provided below.
---------------------------------------------------------------------------

    \31\ FMC Westvaco and General Chemical Green River are not EGUs
and EPA did not identify the same cost and visibility improvement
modeling issues as it did for the EGUs and are thus proposing to
approve the State's BART analyses and determinations for these
units.
---------------------------------------------------------------------------

    EPA is proposing to disapprove the State's NOX BART
determinations and promulgate a FIP for the following units: PacifiCorp
Dave Johnston Units 3 and 4; PacifiCorp Naughton Units 1 and 2;
PacifiCorp Wyodak Unit 1; and Basin Electric Laramie River Units 1, 2,
and 3. After re-analyzing the costs of control and visibility
improvement associated with these units, we determined that the State's
selection of NOX BART controls could not be supported,
warranting a FIP. EPA's reasoning behind its own NOX BART
determinations and emission limitations for these units can be found in
section VIII.A of this notice.
i. FMC Westvaco--Units NS-1A and NS-1B
Background
    FMC's Westvaco facility is a trona mine and sodium products plant
located in Sweetwater County, Wyoming. FMC Westvaco has two existing
coal-fired boilers, Unit NS-1A and Unit NS-1B, that are subject to
BART. Unit NS-1A and Unit NS-1B each have a design heat input rate of
887 MMBtu/hr and were constructed in 1975. They are both wall-fired,
wet-bottom boilers burning subbituminous coal. The State's BART
determinations for these units can be found in Chapter 6.5.2 and
Attachment A of the SIP.
NOX BART Determination
    Units NS-1A and NS-1B are currently controlled with combustion air
control with a permit limit of 0.7 lb/MMBtu (3-hour rolling average).
The State determined that low NOX burners (LNBs) and
overfired air (OFA), LNBs and OFA with SNCR, and LNBs and OFA with SCR
were all technically feasible for reducing NOX emissions at
Unit NS-1A and NS-1B. The State did not identify any technically
infeasible options. The State did not identify any energy or non-air
quality environmental impacts that would preclude the selection of any
of the controls evaluated, and there are no remaining-useful-life
issues for this source. A summary of the State's NOX BART
analyses and the visibility impacts is provided in Table 3. Baseline
NOX emissions are 2,719.5 tpy for each unit based on a heat
input rate of 887 MMBtu/hr and 8,760 hours of operation per year.

                                      Table 3--Summary of FMC Westvaco Unit NS-1A and Unit NS-1B NOX BART Analysis*
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Visibility
                                                                                improvement
                                                Emission rate                                                                             (delta dv for
                                              (lb/MMBtu)  (30-      Emission                          Average cost    Incremental cost  the maximum 98th
             Control technology                  day rolling    reduction  (tpy)  Annualized costs    effectiveness     effectiveness      percentile
                                                  average)                                               ($/ton)                            impact at
                                                                                Bridger
                                                                                Wilderness Area)
--------------------------------------------------------------------------------------------------------------------------------------------------------
LNB + OFA...................................              0.35          $1,359.7          $413,145              $304  ................              0.13
LNB + OFA + SNCR............................              0.21           1,903.6         1,281,851               673            $1,597              0.19
LNB + OFA + SCR.............................              0.10           2,331.0         8,141,177             3,493            16,051              0.24
--------------------------------------------------------------------------------------------------------------------------------------------------------
*This table reflects the costs and visibility improvements per boiler.

    The visibility modeling in the State's SIP only includes the
visibility improvement at the two most impacted Class I areas: Bridger
Wilderness Area and Fitzpatrick Wilderness Area. The visibility
improvement at Bridger is listed in the Table above. For Fitzpatrick,
the visibility improvement is .09 dv for LNBs with OFA, 0.11 dv for
LNBs with SNCR, and 0.13 dv for LNBs with SCR. Given the limited
visibility improvement at the two most impacted areas, we propose to
find that it was reasonable for the State to model only those two
receptors.
    Based on its consideration of the five factors, the State
determined that LNBs plus OFA are reasonable for BART. The State
determined that the other control options were not reasonable based on
the cost effectiveness and associated visibility improvement. The State
has determined that NOX BART emission limit for FMC Westvaco
Unit NS-1A and Unit MS-1B is 0.35 lb/MMBtu (30-day rolling average).
    We agree with the State's conclusions, and we are proposing to
approve its NOX BART determinations for FMC Westvaco Unit
NS-1A and Unit NS-1B. Although the cost-effectiveness for SNCR is
reasonable, we find it reasonable for the State not to select this
control technology based on the incremental visibility improvement for
this control technology.
PM BART Determination
    Unit NS-1A and Unit NS-1B are currently controlled for PM emissions
by electrostatic precipitators (ESPs). The units each currently have a
PM emission limit of 0.05 lb/MMBtu. The State determined that fabric
filters on the wet scrubber, addition of an ESP downstream of the wet
scrubber, and replacement of the ESPs with fabric filters were
technically feasible control options. The State did not identify any
energy or non-air quality environmental impacts that would preclude the
selection of any of the controls evaluated, and there are no remaining-
useful-life issues for this source. A summary of the State's PM BART
analysis is provided in Table 4 below. Baseline PM emissions are 197
tpy for each unit based on a heat input rate of 887 MMBtu/hr and 8,760
hours of operation per year.

                                      Table 4--Summary of FMC Westvaco Unit NS-1A and Unit NS-1B PM BART Analysis*
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Emission rate
                                                                    Control       (lb/mmbtu)  (30-      Emission                          Average cost
                      Control technology                        efficiency (%)      day rolling     reduction  (tpy)  Annualized costs    effectiveness
                                                                                average)                                               ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fabric Filter on Wet Scrubber................................              21.4              0.04               41.7        $1,791,364           $42,948
ESP after Wet Scrubber.......................................              63.3              0.019             123.3         3,507,617            28,448
Replace ESP with Fabric Filter...............................              71.3              0.015             138.8         4,116,036            29,654
--------------------------------------------------------------------------------------------------------------------------------------------------------
*This table reflects the costs and visibility improvements per boiler.

    Given the high cost of controls, which are higher than what EPA, or
other states have considered reasonable for PM, FMC did not evaluate
the visibility improvement that would result from the PM controls
evaluated. Previous visibility modeling analyses from the source
indicate that the contribution in visibility degradation from PM is
minor when compared to the effects of NOX and
SO2. Results from FMC's visibility modeling screening and
analysis confirm this conclusion and are discussed in further detail
within the comprehensive visibility analysis included as part of FMC's
BART application (see Attachment A to the SIP). The State agreed with
FMC's conclusions and did not require FMC to perform additional
visibility analyses for the PM control options.
    The State determined that the current ESP control was reasonable
for PM BART. The State rejected other controls because of their high
cost-effectiveness values. The State has determined that the PM BART
emission limits for FMC Westvaco Unit NS-1A and NS-1B are 0.05 lb/
MMBtu, 45.0 lb/hr, and 197 tpy.
    We agree with the State's conclusions, and we are proposing to
approve its PM BART determinations for FMC Westvaco Unit NS-1A and Unit
NS-1B.
ii. General Chemical Green River--Boilers C and D
    General Chemical Green River is a trona mine and sodium products
plant. General Chemical's two existing coal-fired boilers, C and D, are
co-located at the facility power plant. Both boilers burn low sulfur
bituminous coal, and they supply power and process steam to mining and
ore processing operations. Both boilers are tangentially fired using
in-line coal pulverizers. The firing rate is 534 MMBtu/hr for Boiler C
and 880 MMBtu/hr for Boiler D. The State's BART determinations can be
found in Chapter 6.5.3 and Attachment A of the SIP.
NOX BART Determination
    Boiler C and Boiler D are currently controlled with LNBs plus OFA
with a permit limit of 0.7 lb/MMBtu (3-hour rolling average). On August
7, 2009, the State issued a BART permit to General Chemical that
required the source to meet a NOX emission limit of 0.32 lb/
MMBtu (30-day rolling average) for Boiler C and Boiler D. The State
assumed the source could meet this

emission limit with the installation and operation of new LNBs with the
existing OFA. Upon further investigation, the source determined it
could not meet a limit of 0.32 lbs/MMBtu with new LNBs and the existing
OFA.
    In response to the additional information provided by the source,
the State reexamined its BART determination for Boiler C and D. The
State determined that installing SOFA in addition to the existing LNBs
and OFA could achieve an emission limit of 0.28 lb/MMBtu. Because SOFA
in conjunction with the existing NOX controls could achieve
better emission reductions than new LNBs plus OFA, the State eliminated
the latter from further consideration in the BART analysis. The State
determined that SNCR and SCR were also technically feasible. The State
did not identify any technically infeasible options.
    The State did not identify any energy or non-air quality
environmental impacts that would preclude the selection of any of the
controls evaluated, and there are no remaining-useful-life issues for
this source. A summary of the State's NOX BART analysis and
visibility impacts is provided in Tables 5 and 6 below. Baseline
NOX emissions are 1,167 tpy for Boiler C and 1,816 tpy for
Boiler D based on an average of 2001-2003 actual emissions.

                                      Table 5--Summary of General Chemical--Green River Boiler C NOX BART Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Visibility
                                                                                improvement
                                                Emission rate                                                                             (delta dv for
                                              (lb/MMBtu)  (30-      Emission                          Average cost    Incremental cost  the maximum 98th
             Control technology                  day rolling    reduction  (tpy)  Annualized costs    effectiveness     effectiveness      percentile
                                                  average)                                               ($/ton)                            impact at
                                                                                Bridger
                                                                                Wilderness Area)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Existing LNBs with SOFA.....................              0.28               512          $757,711            $1,480                --              0.05
SNCR........................................              0.35               584         1,433,720             2,455            $4,782              0.08
SCR.........................................              0.14               934         2,434,809             2,607             3,156              0.14
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                      Table 6--Summary of General Chemical--Green River Boiler D NOX BART Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Visibility
                                                                                improvement
                                                Emission rate                                                                             (delta dv for
                                              (lb/MMBtu)  (30-      Emission                          Average cost    Incremental cost  the maximum 98th
             Control technology                  day rolling    reduction  (tpy)  Annualized costs    effectiveness     effectiveness      percentile
                                                  average)                                               ($/ton)                            impact at
                                                                                Bridger
                                                                                Wilderness Area)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Existing LNBs with SOFA.....................               028               737          $943,549            $1,280                --              0.07
SNCR........................................              0.35               908         1,486,581             3,176            $2,913              0.12
SCR.........................................              0.14             1,453         3,399,266             3,510             4,342              0.17
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The visibility modeling in the State's SIP only includes the
visibility improvement at the two most impacted Class I areas: Bridger
Wilderness Area and Fitzpatrick Wilderness Area. The visibility
improvement at Bridger is listed in the Table above. For Fitzpatrick,
the visibility improvement is 0.10 dv for LNBs with SOFA, 0.09 for
SNCR, and 0.12 dv for SCR for each unit. Given the limited visibility
improvement at the two most impacted areas, we propose to find that it
was reasonable for the State to model only those two receptors.
    Based on its consideration of the five factors, the State
determined that NOX BART is the existing LNBs with new SOFA,
or a comparable performing technology. The State determined that SNCR
and SCR were not reasonable based on the high cost effectiveness and
low visibility improvement. The State determined the NOX
BART emission limit for General Chemical Green River Boiler C is 0.28
lb/MMBtu (30-day rolling average) and that the NOX BART
emission limit for Boiler D is 0.28 lb/MMBtu (30-day rolling average).
    We agree with the State's conclusions, and we are proposing to
approve its NOX BART determinations for General Chemical
Green River--Boiler C and D. Although the cost-effectiveness for SNCR
and SCR is reasonable, we find it reasonable for the State not to
select this control technology based on the low visibility improvement
for these control technologies.
PM BART Determination
    Boilers C and D are currently controlled by ESPs with permit limits
of 50 lb/hr and 80 lb/hr, respectively. General Chemical addressed PM
emissions through an abbreviated analysis by using PM BART information
from FMC Westvaco, as discussed above. The facilities are similar in
size and located about ten miles apart. Baseline PM emissions are 98
tpy for Boiler C and 161 tpy for Boiler D based on the average of 2001-
2003 actual emissions. As discussed above, visibility modeling
screening and analyses for FMC Westvaco indicate that the contribution
in visibility degradation from PM for a source comparable to Boiler C
and Boiler D is minor. Additionally, costs for controlling PM from
similar boilers are high as indicated by the FMC analysis for Westvaco.
    The State accepted General Chemical's abbreviated PM BART analysis.
The State determined that the current ESP control was reasonable for PM
BART. The State rejected other controls because of their high cost-
effectiveness values. The State determined that the PM BART emission
limits for Boiler C are 0.09 lb/MMBtu, 50 lb/hr, and 219 tpy, and that
the PM BART emissions limits for Boiler D are 0.09 lb/MMBtu, 80 lb/hr,
and 350.4 tpy.
    We agree with the State's conclusions, and we are proposing to
approve its PM BART determination for General Chemical Green River
Boiler C and D.
iii. Basin Electric Laramie River Station--Units 1-3
    Basin Electric Laramie River Station is located in Platte County,
Wyoming. Laramie River Station is comprised of three 550 MW dry-bottom,
wall-fired boilers (Units 1, 2, and 3) burning

subbituminous coal for a total net generating capacity of 1,650 MW. All
three units are subject-to-BART. The State's BART determination can be
found in Chapter 6.5.8 and Attachment A of the SIP (The NOX
BART analysis is discussed in section VIII.A of this notice).
PM BART Determination
    Laramie River Units 1, 2, and 3 are currently controlled with ESPs,
each with a permit limit of 0.03 lb/MMBtu. The State determined that
fabric filters were technically feasible for Unit 3 but not Units 1 and
2. Units 1 and 2 are controlled with wet flue gas desulfurization and
fabric filters cannot be used downstream of such a system. The State
determined that flue gas treatment and GE Max-9 hybrid were technically
infeasible for all three units. Thus, the only technically feasible
control option for PM is fabric filters on Unit 3.
    The State did not identify any energy or non-air quality
environmental impacts that would preclude the selection of any of the
controls evaluated, and there are no remaining-useful-life issues for
this source. A summary of the State's PM BART analysis for Unit 3 is
provided in Table 7 below. Baseline PM emissions are 716 tpy for the
unit based on 2001-2003 actual emissions.

                                        Table 7--Summary of Basin Electric Laramie River Unit 3 PM BART Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Emission rate
                                                                     Control       (lb/MMBtu) (30-      Emission                          Average cost
                      Control technology                         efficiency  (%)     day rolling    reduction  (tpy)  Annualized costs    effectiveness
                                                                                average)                                               ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fabric Filter--Peak Rate for Lost Generating Costs............                50             0.015               358      $194,809,000           $54,707
Fabric Filter Non-Peak Rate for Lost Generating Costs.........                50             0.015               358       134,934,000            40,156
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The State did not provide visibility improvement modeling for
fabric filters, but EPA is proposing to conclude this is reasonable
based on the high cost-effectiveness of fabric filters at each of the
units, which is higher than EPA or other state have considered
reasonable for PM BART.
    Based on its consideration of the five factors, the State
determined that the current ESPs are reasonable for PM BART, as fabric
filters on Unit 3 are not cost-effective and there are no other
technically feasible controls for Units 1 and 2. The State determined
that the PM BART emission limit for each of the Laramie River Units 1,
2, and 3 is 0.03 lb/MMBtu.
    We agree with the State's conclusions, and we are proposing to
approve its PM BART determination for Basin Electric Laramie River
Units 1, 2, and 3.
iv. PacifiCorp Dave Johnston--Units 3 and 4
Background
    PacifiCorp's Dave Johnston power plant is located in Converse
County, Wyoming. Dave Johnston Power Plant is comprised of four units
burning pulverized subbituminous Powder River Basin coal. Units 3 and 4
are the only units subject-to-BART. Dave Johnston Unit 3 is a nominal
230 MW pulverized coal-fired boiler that commenced service in 1964. It
was equipped with burners in a cell configuration until 2010, but was
then converted to a dry bottom wall-fired boiler. Dave Johnston Unit 4
is a nominal 330 MW pulverized coal-fired boiler that commenced service
in 1972. It is a tangential-fired boiler. The State's BART analysis can
be found in Chapter 6.5.5 and Appendix A of the SIP (the NOX
BART determination for Dave Johnston Unit 3 and Unit 4 is discussed in
section VIII.A of this notice).
PM BART Determination
    Units 3 and 4 are currently controlled with fabric filters
installed in 2008 with an emission limit of 0.015 lb/MMBtu. The State
determined that fabric filters represent the most stringent PM control
technology and that 0.015 lb/MMBtu is the most stringent emission
limit. Consistent with the BART Guidelines, the State did not provide a
five-factor analysis because the State determined BART to be the most
stringent control technology and limit available (70 FR 39165). The
State determined that the PM BART emission limits for Unit 3 and 4 are
both 0.015 lb/MMBtu.
    We agree with the State's conclusions, and we are proposing to
approve its PM BART determination for Dave Johnston Units 3 and 4.
v. PacifiCorp Jim Bridger--Units 1-4
Background
    PacifiCorp's Jim Bridger Power Plant is located in Sweetwater
County, Wyoming. Jim Bridger is comprised of four identically sized
nominal 530 MW tangentially fired boilers burning pulverized coal for a
total net generating capacity of 2,120 MW. Jim Bridger Unit 1 was
placed in service in 1974, Unit 2 in 1975, Unit 3 in 1976, and Unit 4
in 1979. The State's BART determination can be found in Chapter 6.5.4
and Appendix A of the SIP.
Wyoming's NOX BART Determination for Jim Bridger Unit 1 and
Unit 2
    During the baseline period of 2001-2003, PacifiCorp Jim Bridger
Units 1 and 2 were equipped with early generation LNBs with permit
limits of 0.70 lb/MMBtu (3-hour fixed) and 0.42 lb/MMBtu and 0.40 lb/
MMBtu (annual limit), respectively. The State determined that new LNBs
with SOFA, new LNBs with SOFA plus SNCR, and new LNBs with SOFA plus
SCR were all technically feasible for controlling NOX
emissions. The State did not identify any technically infeasible
options.
    The State did not identify any energy or non-air quality
environmental impacts that would preclude the selection of any of the
controls evaluated, nor are there any remaining-useful-life issues for
this source. Baseline NOX emissions are 10,643 tpy for each
unit based on unit heat input rate of 6,000 MMBtu/hr and 7,884 hours of
operation. A summary of the State's NOX BART analysis and
the visibility impacts is provided in Table 8 below.\32\
---------------------------------------------------------------------------

    \32\ We are assuming the same costs for Unit 2 as the other Jim
Bridger Units. The State analyzed Unit 2 using post installation of
LNBs/OFA costs so the cost information provided in their analysis is
not consistent with an uncontrolled baseline.

                               Table 8--Summary of Wyoming's Jim Bridger Units 1 and 2 NOX BART Analysis--Costs per Boiler
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Visibility
                                                                                improvement
                                                Emission rate                                                                            (delta deciview
                                               (lb/MMBtu) (30-      Emission                          Average cost    Incremental cost   for the maximum
             Control technology                  day rolling    reduction  (tpy)  Annualized costs    effectiveness     effectiveness    98th percentile
                                                  average)                                               ($/ton)                          impact at Mt.
                                                                                Zirkel
                                                                                wilderness)
--------------------------------------------------------------------------------------------------------------------------------------------------------
New LNB with SOFA...........................              0.26             4,493        $1,144,969              $255                --         0.41/0.47
New LNB with SOFA and SNCR..................              0.20             5,913         2,710.801               459            $1,103         0.52/0.62
New LNB with SOFA and SCR...................              0.07             8,987        20,296,400             2,258             5,721         0.76/0.82
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Based on its consideration of the five factors, the State
determined new LNBs with SOFA was reasonable for NOX BART.
The State determined the NOX BART emission limit for Jim
Bridger Units 1and 2 is 0.28 lb/MMBtu (30-day rolling average).
    PacifiCorp is required to install additional controls under the
State's LTS. The State determined that based on the cost of compliance
and visibility improvement presented by PacifiCorp in the BART
applications for Jim Bridger Units 1 and 2 and taking into
consideration the logistical challenge of managing multiple pollution
control installations within the regulatory time allotted for
installation of BART by the RHR, additional controls would be required
under the LTS in order to achieve reasonable progress but would not be
requires as BART. With respect to Jim Bridger Units 1 and 2, the State
has required PacifiCorp to install SCR, or other NOX control
systems, to achieve an emission limit of 0.07 lb/MMBtu on a 30-day
rolling average. As part of Wyoming's Regional Haze plan, PacifiCorp is
required to meet the 0.07 lb/MMBtu emission rate on Unit 1 prior to
December 31, 2021 and on Unit 2 prior to December 31, 2022.
EPA's PacifiCorp Jim Bridger Units 1 and 2 NOX BART
Determination
    The EPA agrees with the State's analysis pertaining to energy or
non-air quality environmental impacts and remaining-useful-life for
this source. Baseline NOX emissions are 8,426 tpy for Unit 1
and 7,577 for Unit 2 based on the actual annual average for the years
2001-2003. A summary of the EPA's NOX BART analysis and the
visibility impacts is provided in Tables 9-12 below. The cost
effectiveness values for the Jim Bridger units vary considerably for
the same control option. This is largely due to differences in the
(actual) baseline emissions.

                                             Table 9--Summary of EPA's Jim Bridger Unit 1 NOX BART Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Visibility
                                                                                improvement
                                                Emission rate                                         Average cost                        (delta dv for
             Control technology                  (lb/MMBtu)         Emission      Annualized costs    effectiveness   Incremental cost  the maximum 98th
                                              (annual average)  reduction  (tpy)                         ($/ton)        effectiveness      percentile
                                                                                impact at Mt.
                                                                                Zirkel)
--------------------------------------------------------------------------------------------------------------------------------------------------------
New LNBs with OFA...........................              0.18             4,558        $1,167,297              $256                --              0.59
New LNBs with OFA and SNCR..................              0.14             5,332         4,402,757               826            $4,182              0.69
New LNBs with OFA and SCR...................              0.05             7,352        17,592,636             2,393             6,530              0.96
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Jim Bridger Unit 1 also impacts other Class I areas. The visibility
improvement modeled by EPA at other Class I areas is shown in Table 10
below.

                   Table 10--Jim Bridger Unit 1: Visibility Improvement at Other Class I Areas
----------------------------------------------------------------------------------------------------------------
                                                               Visibility        Visibility        Visibility
                                                               improvement       improvement       improvement
                                                              (delta dv for     (delta dv for     (delta dv for
                       Class I area                         the maximum 98th  the maximum 98th  the maximum 98th
                                                               percentile        percentile        percentile
                                                              impact) - New     impact) - New     impact) - New
                                                               LNBs + OFA      LNBs + OFA/SNCR   LNBs + OFA/SCR
----------------------------------------------------------------------------------------------------------------
Bridger...................................................              0.53              0.62              0.91
Fitzpatrick...............................................              0.22              0.26              0.36
Rawah.....................................................              0.59              0.70              0.96