[Federal Register Volume 77, Number 67 (Friday, April 6, 2012)]
[Rules and Regulations]
[Pages 20894-20945]
[FR Doc No: 2012-6586]

Vol. 77

Friday,

No. 67

April 6, 2012

Part II

Environmental Protection Agency

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40 CFR Part 52

 Approval and Promulgation of Implementation Plans; North Dakota;
Regional Haze State Implementation Plan; Federal Implementation Plan
for Interstate Transport of Pollution Affecting Visibility and Regional
Haze; Final Rule

Federal Register / Vol. 77 , No. 67 / Friday, April 6, 2012 / Rules
and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2010-0406; FRL-9648-3]

Approval and Promulgation of Implementation Plans; North Dakota;
Regional Haze State Implementation Plan; Federal Implementation Plan
for Interstate Transport of Pollution Affecting Visibility and Regional
Haze

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: EPA is partially approving and partially disapproving a
revision to the North Dakota State Implementation Plan (SIP) addressing
regional haze submitted by the Governor of North Dakota on March 3,
2010, along with SIP Supplement No. 1 submitted on July 27, 2010, and
part of SIP Amendment No. 1 submitted on July 28, 2011. These SIP
revisions were submitted to address the requirements of the Clean Air
Act (CAA or Act) and our rules that require states to prevent any
future and remedy any existing man-made 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''). EPA is promulgating a Federal
Implementation Plan (FIP) to address the gaps in the plan resulting
from our partial disapproval of North Dakota's Regional Haze (RH) SIP.
    In addition, EPA is disapproving a revision to the North Dakota SIP
addressing the interstate transport of pollutants that the Governor
submitted on April 6, 2009. We are disapproving it because it does not
meet the Act's requirements concerning non-interference with programs
to protect visibility in other states. To address this deficiency, we
are promulgating a FIP.

DATES: This final rule is effective May 7, 2012.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-R08-OAR-2010-0406. All documents in the docket are listed on
the www.regulations.gov Web site. Although listed in the index, some
information is not publicly available, e.g., Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. Certain other material, such as copyrighted material, is
not placed on the Internet and will be publicly available only in hard
copy form. Publicly available docket materials are available either
electronically through www.regulations.gov, or in hard copy at the Air
Program, Environmental Protection Agency (EPA), Region 8, 1595 Wynkoop
Street, Denver, Colorado 80202-1129. EPA requests that if at all
possible, you contact the individual listed in the FOR FURTHER
INFORMATION CONTACT section to view the hard copy of the docket. You
may view the hard copy of the docket Monday through Friday, 8 a.m. to 4
p.m., excluding Federal holidays.

FOR FURTHER INFORMATION CONTACT: Gail Fallon, Air Program, Mailcode 8P-
AR, Environmental Protection Agency, Region 8, 1595 Wynkoop Street,
Denver, Colorado 80202-1129,<PHONE_NUMBER>, or<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Definitions

    For the purpose of this document, we are giving meaning to certain
words or initials as follows:
     The word Act or initials CAA mean or refer to the Clean
Air Act, unless the context indicates otherwise.
     The initials ASOFA mean or refer to advanced separated
overfire air.
     The initials AVS mean or refer to Antelope Valley Station.
     The initials BACT mean or refer to Best Available Control
Technology.
     The initials BART mean or refer to Best Available Retrofit
Technology.
     The initials CAM mean or refer to compliance assurance
monitoring.
     The initials CAMx mean or refer to Comprehensive Air
Quality Model.
     The initials CCS mean or refer to Coal Creek Station.
     The initials CEMS mean or refer to continuous emission
monitoring system.
     The initials CMAQ mean or refer to Community Multi-Scale
Air Quality modeling system.
     The initials CSAPR mean or refer to Cross-State Air
Pollution Rule.
     The initials EGUs mean or refer to Electric Generating
Units.
     The words we, us or our or the initials EPA mean or refer
to the United States Environmental Protection Agency.
     The initials FIP mean or refer to Federal Implementation
Plan.
     The initials FLMs mean or refer to Federal Land Managers.
     The initials GRE mean or refer to Great River Energy.
     The initials IMPROVE mean or refer to Interagency
Monitoring of Protected Visual Environments monitoring network.
     The initials IWAQM mean or refer to Interagency Workgroup
on Air Quality Modeling.
     The initials LDSCR mean or refer to low-dust SCR.
     The initials LOS mean or refer to Leland Olds Station.
     The words Lostwood or Lostwood Wilderness Area or initials
LWA mean or refer to Lostwood National Wildlife Refuge Wilderness Area.
     The initials LNB mean or refer to low NOX
burners.
     The initials LTS mean or refer to Long-Term Strategy.
     The initials MRYS mean or refer to Milton R. Young
Station.
     The initials NAAQS mean or refer to National Ambient Air
Quality Standards.
     The words North Dakota and State mean the State of North
Dakota unless the context indicates otherwise.
     The initials NOX mean or refer to nitrogen oxides.
     The initials NPCA mean or refer to National Parks
Conservation Association.
     The initials NPS mean or refer to National Park Service.
     The initials PM mean or refer to particulate matter.
     The initials PM10 mean or refer to particulate matter with
an aerodynamic diameter of less than 10 micrometers or course
particulate matter.
     The initials PM2.5 mean or refer to particulate matter
with an aerodynamic diameter of less than 2.5 micrometers or fine
particulate matter.
     The initials PRB mean or refer to Powder River Basin.
     The initials PSAT mean or refer to Particle Source
Apportionment Technology.
     The initials PSD mean or refer to Prevention of
Signification Deterioration.
     The initials RHR mean or refer to the Regional Haze Rule.
     The initials RH SIP mean or refer to North Dakota's
Regional Haze State Implementation Plan.
     The initials RMC mean or refer to the Regional Modeling
Center at the University of California Riverside.
     The initials RP mean or refer to Reasonable Progress.
     The initials RPG mean or refer to Reasonable Progress
Goal.
     The initials SCR mean or refer to selective catalytic
reduction.
     The initials SIP mean or refer to State Implementation
Plan.
     The initials SNCR mean or refer to selective non-catalytic
reduction.
     The initials SO2 mean or refer to sulfur dioxide.
     The initials SOFA mean or refer to separated overfire air.
     The initials TRNP mean or refer to Theodore Roosevelt
National Park.

     The initials TSD mean or refer to Technical Support
Document.
     The initials URP mean or refer to Uniform Rate of
Progress.
     The initials WEP mean or refer to Weighted Emissions
Potential.
     The initials WRAP mean or refer to the Western Regional
Air Partnership.

Table of Contents

I. Background
    A. Regional Haze
    B. Interstate Transport Requirements
    C. Lawsuits
    D. Our Proposal
    1. Regional Haze
    2. Interstate Transport, Visibility Prong
    E. Public Participation
II. Final Action
    A. Regional Haze
    B. Interstate Transport, Visibility Prong
III. Changes from Proposed Rule and Reasons for the Changes
    A. NOX BART for Milton R. Young Station Units 1 and 2
and Leland Olds Station Unit 2
    B. NOX BART for Coal Creek Station (CCS) Units 1 and
2
    C. Other Resultant Changes
IV. Basis for Our Final Action
    A. Regional Haze
    B. Interstate Transport, Visibility Prong
V. Issues Raised by Commenters and EPA's Responses
    A. NOX BART for Milton R. Young Station Units 1 and 2
and Leland Olds Station Unit 2
    B. Comments on Legal Issues
    1. EPA's Authority
    2. Interstate Transport Consent Decree
    3. Other General Legal Comments
    C. Comments on Modeling
    D. Comments on Costs
    1. General
    2. Comments Regarding Our Reliance on the EPA Air Pollution
Control Cost Manual
    E. Comments on BART Determinations
    1. General Comments
    2. CCS Units 1 and 2
    a. EPA's Use of the Control Cost Manual for CCS
    b. CCS Emission Limits
    c. CCS Modeling
    d. CCS Coal Ash
    e. CCS Visibility Improvements Are Minimal
    f. Comments on Alternative NOX Emission Limits
    g. Cost Effectiveness of SNCR and SCR at CCS
    h. CCS General Comments
    3. Stanton Station Unit 1
    4. Leland Olds Station Unit 1
    F. General Comments on SO2 and PM Controls
    G. Comments on Reasonable Progress and North Dakota's Long-Term
Strategy
    H. Comments on Health and Ecosystem Benefits, and Other
Pollutants
    I. Miscellaneous Comments
    J. Comments Requesting an Extension to the Public Comment Period
    K. Comments Generally in Favor of Our Proposal
    L. Comments Generally Against Our Proposal
VI. Statutory and Executive Order Reviews

I. Background

    The CAA requires each state to develop plans, referred to as SIPs,
to meet various air quality requirements. 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).
    This action involves two separate requirements under the CAA and
EPA's regulations. One is the requirement that states have SIPs that
address regional haze, the other is the requirement that states have
SIPs that address the interstate transport of pollutants that may
interfere with programs to protect visibility in other states.

A. Regional Haze

    In 1990, Congress added section 169B to the CAA to address regional
haze issues, and we promulgated regulations addressing regional haze in
1999. 64 FR 35714 (July 1, 1999), codified at 40 CFR part 51, subpart
P. The requirements for regional haze, found at 40 CFR 51.308 and
51.309, are included in our visibility protection regulations at 40 CFR
51.300-309. The requirement to submit a regional haze SIP applies to
all 50 states, the District of Columbia and the Virgin Islands. States
were required to submit a SIP addressing regional haze visibility
impairment no later than December 17, 2007. 40 CFR 51.308(b).
    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 North Dakota, and 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 section 110(c)(1).
    North Dakota initially submitted a SIP addressing regional haze on
March 3, 2010. On July 27, 2010, North Dakota submitted a revision to
that submittal, entitled ``SIP Supplement No. 1.'' On July 28, 2011,
North Dakota submitted another revision, entitled ``SIP Amendment No.
1.''

B. Interstate Transport Requirements

    Section 110(a)(1) of the CAA requires states to submit SIPs to
address new or revised National Ambient Air Quality Standards (NAAQS)
within 3 years after promulgation of such standards, or within such
shorter period as we may prescribe. On July 18, 1997, we promulgated
the 1997 8-hour ozone NAAQS and the 1997 fine particulate
(PM2.5) NAAQS. 62 FR 38652. Section 110(a)(2) of the CAA
lists the elements that such new SIPs must address, as applicable,
including section 110(a)(2)(D)(i), which pertains to the interstate
transport of certain emissions.
    Section 110(a)(2)(D)(i) contains four distinct requirements or
``prongs'' related to the impacts of interstate transport. The SIP must
prevent sources in the state from emitting pollutants in amounts which
will: (1) Contribute significantly to nonattainment of the NAAQS in
other states; (2) interfere with maintenance of the NAAQS in other
states; (3) interfere with provisions to prevent significant
deterioration of air quality in other states; or (4) interfere with
efforts to protect visibility in other states.
    On April 25, 2005, we published a ``Finding of Failure to Submit
SIPs for Interstate Transport for the 8-hour Ozone and PM2.5
NAAQS.'' 70 FR 21147. This action included a finding that North Dakota
and other states had failed to submit SIPs to address interstate
transport of air pollution and started a 2-year clock for the
promulgation of a FIP by us, unless a state made a submission to meet
the requirements of section 110(a)(2)(D)(i), and we approved the
submission, prior to that time. Id.
    On April 6, 2009, we received a SIP revision from North Dakota to
address the interstate transport provisions of CAA 110(a)(2)(D)(i) for
the 1997 8-hour ozone NAAQS and the 1997 PM2.5 NAAQS. In
prior actions, we approved this North Dakota SIP submittal for the
first three prongs of section 110(a)(2)(D)(i). (75 FR 31290, June 3,
2010 and 75 FR 71023, November 22, 2010). This action addresses the
fourth prong.

C. Lawsuits

    In two separate lawsuits, one in U.S. District Court for the
Northern District of California and one in the U.S. District Court for
the District of Colorado, environmental groups sued us for our failure
to timely take action with respect to the interstate transport
requirements and the regional haze requirements of the CAA and our
regulations. In particular, the lawsuits alleged that we

had failed to promulgate FIPs for these requirements within the two-
year period allowed by CAA section 110(c) or, in the alternative, fully
approve SIPs addressing these requirements.
    As a result of these lawsuits, we entered into two separate consent
decrees in these two jurisdictions. The consent decree in the Northern
District of California, as modified on several occasions, required that
we sign a notice of proposed rulemaking for prong four of the
interstate transport requirements for North Dakota by September 1,
2011. As lodged with the court, but before it was entered, the proposed
consent decree in the District of Colorado required that we sign a
notice of proposed rulemaking for regional haze requirements for North
Dakota by July 21, 2011. Because the latter consent decree was not
entered by the court until September 27, 2011, and we signed our notice
of proposed rulemaking on September 1, 2011, the July 21, 2011 deadline
was mooted.
    Both consent decrees, as modified, require that we sign a notice of
final rulemaking addressing the regional haze requirements and prong
four of the interstate transport requirements by March 2, 2012. We are
meeting that requirement with the signing of this notice of final
rulemaking.

D. Our Proposal

    We signed our notice of proposed rulemaking on September 1, 2011,
and it was published in the Federal Register on September 21, 2011 (76
FR 58570). In that notice, we provided a detailed description of the
various regional haze and interstate transport requirements. We are not
repeating that description here; instead, the reader should refer to
our notice of proposed rulemaking for further detail.
    In our proposal, we proposed to take the following actions:
1. Regional Haze
    We proposed to disapprove the following parts of North Dakota's RH
SIP:
    a. North Dakota's nitrogen oxides (NOX) best available
retrofit technology (BART) determinations and emissions limits for
Milton R. Young Station (MRYS) Units 1 and 2, Leland Olds Station (LOS)
Unit 2, and Coal Creek Station (CCS) Units 1 and 2.
    b. North Dakota's determination under the reasonable progress
requirements found at section 40 CFR 51.308(d)(1) that no additional
NOX emissions controls were warranted at Antelope Valley
Station (AVS) Units 1 and 2.
    c. North Dakota's reasonable progress goals (RPGs).
    d. Portions of North Dakota's long-term strategy (LTS) that relied
on or reflected other aspects of the RH SIP that we were proposing to
disapprove.
    We proposed to approve the remaining aspects of North Dakota's RH
SIP revision that was submitted on March 3, 2010 and SIP Supplement No.
1 that was submitted on July 27, 2010. We proposed to approve the
following parts of SIP Amendment No. 1 that the State submitted on July
28, 2011:
    a. Amendments to Section <IP_ADDRESS> pertaining to Coyote Station.
    b. Amendments to Appendix A.4, the Permit to Construct for Coyote
Station.
    We proposed to not act on the remainder of the State's July 28,
2011 submittal.
    We proposed to promulgate a FIP to address the deficiencies in the
North Dakota RH SIP that we identified in our proposal. The proposed
FIP included the following elements:
    a. NOX BART determinations and emission limits for MRYS
Units 1 and 2 and Leland Olds Station Unit 2.
    b. NOX BART determination and emission limit for CCS
Units 1 and 2.
    c. A reasonable progress determination and NOX emission
limit for AVS Units 1 and 2.
    d. A five-year deadline to meet the emission limits and monitoring,
recordkeeping, and reporting requirements for the above seven units to
ensure compliance.
    e. RPGs consistent with the SIP limits proposed for approval and
proposed FIP limits.
    f. LTS elements that would reflect the other aspects of the
proposed FIP.
    We also proposed approval of a SIP revision in lieu of our regional
haze FIP if the State submitted a revision in a timely way that matched
the terms of our proposed FIP.
2. Interstate Transport, Visibility Prong
    We proposed to disapprove the portion of North Dakota's April 6,
2009, SIP revision for interstate transport in which North Dakota
intended to address the requirement of section 110(a)(2)(D)(i)(II) that
emissions from North Dakota sources not interfere with measures
required in the SIP of any other state under part C of the CAA to
protect visibility.
    Because of this proposed disapproval, we proposed a FIP to meet the
visibility protection requirement of section 110(a)(2)(D)(i)(II). To
meet this FIP duty, we proposed to find that North Dakota sources would
be sufficiently controlled to eliminate interference with the
visibility programs of other states by a combination of the measures
that we were proposing to approve as meeting the regional haze SIP
requirements combined with the additional measures that we were
proposing to impose in a FIP to meet the remaining regional haze SIP
requirements.
    We noted that acting on both the section 110(a)(2)(D)(i)(II)
requirement and the regional haze SIP requirement simultaneously would
ensure the most efficient use of resources by the affected sources and
EPA.

E. Public Participation

    We requested comments on all aspects of our proposed action and
provided a two-month comment period, with the comment period closing on
November 21, 2011. We also provided a public hearing. Initially, we
scheduled the hearing to last four hours on one day. 76 FR 58570. At
the request of the Governor of North Dakota, we expanded the time for
the public hearing to 14 hours over two days and changed the venue. 76
FR 60777 (September 30, 2011). The public hearing was held in Bismarck,
North Dakota on October 13 and 14, 2011.
    We received a significant number of comments on our proposed rule,
both from commenters, particularly citizens and environmental groups,
that supported our proposed action, and from commenters, primarily from
state and city agencies, rural power cooperatives, and industrial
facilities and groups, that were critical of our proposed action.
    In this action, we are responding to the comments we have received,
taking final rulemaking action, and explaining the bases for our
action, including any changes from our proposed action.

II. Final Action

A. Regional Haze

    With this final action we are partially approving and partially
disapproving North Dakota's RH SIP revision that was submitted on March
3, 2010, SIP Supplement No. 1 that was submitted on July 27, 2010, and
part of SIP Amendment No. 1 that was submitted on July 28, 2011.
Specifically we are disapproving:
     North Dakota's NOX BART determinations and
emissions limits for CCS Units 1 and 2.
     North Dakota's determination under the reasonable progress
requirements found at 40 CFR 51.308(d)(1) that no additional
NOX emissions controls are warranted at AVS Units 1 and 2.
     North Dakota's RPGs.
     Portions of North Dakota's LTS that rely on or reflect
other aspects of the RH SIP that we are disapproving.

    We are approving the remaining aspects of North Dakota's RH SIP
revision that was submitted on March 3, 2010 and SIP Supplement No. 1
that was submitted on July 27, 2010. We are approving the following
parts of SIP Amendment No. 1 that the State submitted on July 28, 2011:
(1) Amendments to Section <IP_ADDRESS> pertaining to Coyote Station, and
(2) amendments to Appendix A.4, the Permit to Construct for Coyote
Station. We are not taking action on the remainder of the July 28, 2011
submittal at this time.
    We are finalizing a FIP to address the deficiencies in the North
Dakota RH SIP that result from our partial disapproval of the SIP.
    The final FIP includes the following elements:
     NOX BART determination and emission limit for
CCS Units 1 and 2 of 0.13 lb/MMBtu averaged across the two units on a
30-day rolling average, and a requirement that the owners/operators
comply with this NOX BART limit within five (5) years of the
effective date of this final rule.
     A reasonable progress determination and NOX
emission limit for AVS Units 1 and 2 of 0.17 lb/MMBtu that applies
singly to each of these units on a 30-day rolling average, and a
requirement that the owner/operator meet the limit as expeditiously as
practicable, but no later than July 31, 2018.
     Monitoring, record-keeping, and reporting requirements for
the above four units to ensure compliance with these emission
limitations.
     RPGs consistent with the SIP limits approved and the final
FIP limits.
     LTS elements that reflect the other aspects of the
finalized FIP.

B. Interstate Transport, Visibility Prong

    We are disapproving a portion of a SIP revision that North Dakota
submitted for the purpose of addressing the ``good neighbor''
provisions of CAA section 110(a)(2)(D)(i) for the 1997 8-hour ozone
NAAQS and the 1997 PM2.5 NAAQS. Specifically, we are
disapproving the portion of the April 6, 2009 SIP in which North Dakota
intended to address the requirement of section 110(a)(2)(D)(i)(II) that
emissions from North Dakota sources do not interfere with measures
required in the SIP of any other state under part C of the CAA to
protect visibility. Because of this disapproval, we are promulgating a
FIP to meet this requirement of section 110(a)(2)(D)(i)(II). To meet
this FIP duty, we are finding that North Dakota sources will be
sufficiently controlled to eliminate interference with the visibility
programs of other states by a combination of the measures in the North
Dakota SIP that we are simultaneously approving as meeting the regional
haze SIP requirements combined with the additional measures that we are
imposing in a FIP to meet the remaining regional haze SIP requirements.
We note that North Dakota always has the discretion to revise its SIP
and submit the revision to us. Should such a revision meet CAA
requirements, we would replace our FIP with North Dakota's SIP
revision. We encourage the State to revise its SIP.

III. Changes From Proposed Rule and Reasons for the Changes

A. NOX BART for Milton R. Young Station Units 1 and 2 and Leland Olds
Station Unit 2

    As noted, we proposed to disapprove North Dakota's NOX
BART determinations for MRYS 1 and 2 and LOS 2 and to promulgate a FIP
for NOX BART for these units to fill the gap that would have
resulted from our disapproval. After considering a recent judicial
decision, we have decided to approve North Dakota's NOX BART
determination for MRYS 1 and 2 and LOS 2 and to not promulgate a FIP
for NOX BART for these units. We more fully describe the
reasons for this change below.
    On July 27, 2006, the U.S. District Court for the District of North
Dakota entered a consent decree between EPA, the State, and Minnkota
Power Cooperative (``Minnkota''). The consent decree resulted from an
enforcement action that EPA and the State brought against Minnkota for
alleged violations of Prevention of Significant Deterioration (PSD)
permitting requirements at MRYS 1 and 2. The consent decree called for
North Dakota to make a best available control technology (BACT)
determination for NOX for MRYS 1 and 2 but also provided a
dispute resolution procedure in the event of disagreement regarding the
BACT determination.
    In November 2010, North Dakota determined BACT for NOX
to be limits of 0.36 lb/MMBtu for MRYS 1 and 0.35 lb/MMBtu for MRYS 2
based on the use of selective non-catalytic reduction (SNCR)
technology, with separate limits during startup. In reaching this
decision, North Dakota eliminated selective catalytic reduction (SCR),
a higher performing control technology, based on a finding that SCR was
not technically feasible to control emissions from North Dakota lignite
coal. In particular, North Dakota noted that no SCR has ever been
employed on an electric generating unit (EGU) burning North Dakota
lignite, that North Dakota lignite has unique properties that have the
potential to quickly degrade the SCR catalyst, and that no catalyst
vendor supplied with the specifications for the coal at MRYS 1 and 2
would provide a guarantee of catalyst life without first conducting
slipstream or pilot tests at MRYS.
    EPA disagreed with North Dakota's findings and the selection of
selective non-catalytic reduction (SNCR) as BACT and initiated the
dispute resolution process under the consent decree. Under the consent
decree, the court was tasked with upholding North Dakota's BACT
determination unless the disputing party was able to demonstrate that
North Dakota's decision was unreasonable. We have included a copy of
the consent decree and the court's order in the docket for this action.
    On December 21, 2011, following briefing by the parties, and
consideration of North Dakota's record for its BACT determination, the
court determined that EPA had not demonstrated that North Dakota's
findings were unreasonable. The court decided that North Dakota, based
on the administrative record for its BACT determination, had a
reasonable basis for concluding that SCR is not technically feasible
for treating North Dakota lignite at MRYS. The court upheld North
Dakota's determination that SNCR is BACT.
    There are two critical principles expressed in our BART guidelines
that are relevant here. First, as part of a BART analysis, technically
infeasible control options are eliminated from further review. For
BART, EPA's criteria for determining whether a control option is
technically infeasible are substantially the same as the criteria used
for determining technical infeasibility in the BACT context. 70 FR
39165; EPA's ``New Source Review Workshop Manual,'' pages B.17-B.22.
Second, the BART guidelines indicate that states generally may rely on
a BACT determination for a source for purposes of determining BART for
that source, unless new technologies have become available or best
control levels for recent retrofits have become more stringent. 70 FR
39164. As a general rule, the selection of a recent BACT level as BART
is the equivalent of selecting the most stringent level of control, and
consideration of the five statutory BART factors becomes unnecessary.
    Over our vigorous challenge of the information and analysis relied
upon by North Dakota, the U.S. District Court upheld North Dakota's
recent BACT determination based on the same

technical feasibility criteria that apply in the BART context. In light
of the court's decision and the views we have expressed in our BART
guidelines on the relationship of BACT to BART, we have concluded that
it would be inappropriate to proceed with our proposed disapproval of
SNCR as BART and our proposed FIP to impose SCR at MRYS 1 and 2 and LOS
2. While LOS 2 was not the subject of the BACT determination, the same
reasoning that applies to MRYS 1 and 2 also applies to LOS 2. It is the
same type of boiler burning North Dakota lignite coal, and North
Dakota's views regarding technical infeasibility that the U.S. District
Court upheld in the MRYS BACT case apply to it as well. Thus, with this
action we are approving North Dakota's NOX BART
determinations for MRYS 1 and 2 and LOS 2, and no FIP for these units
is necessary. The applicable limits are 0.36 lb/MMBtu for MRYS 1 and
0.35 lb/MMBtu for MRYS 2 and 0.35 lb/MMBtu for LOS 2.
    We note, however, that the State has indicated a willingness to
pursue the conduct of a pilot study at MRYS and/or LOS to analyze the
expected replacement rate of SCR catalyst exposed to flue gas from the
combustion of North Dakota lignite at these cyclone units in a low-dust
or tail-end configuration. It is our expectation that the results of
such a study could be used to inform further evaluation of SCR as a
potential control technology when the State evaluates reasonable
progress in the next planning period for regional haze. This position
is supported by the State's December 20, 2011 letter from North Dakota
Department of Health (NDDH), L. David Glatt, to EPA, Janet McCabe.

B. NOX BART for Coal Creek Station (CCS) Units 1 and 2

    We proposed a NOX BART FIP limit for CCS 1 and 2 of 0.12
lb/MMBtu that would apply to each unit individually on 30-day rolling
average basis. We based this limit on our proposed finding that SNCR
plus separated overfire air (SOFA) plus low NOX burners
(LNB) was the best available retrofit technology. While we continue to
find that SNCR plus SOFA plus LNB is the best available retrofit
technology, we are changing the emission limit to 0.13 lb/MMBtu
averaged over both units on a 30-day rolling average basis. Evidence
submitted by commenters and our own additional research in evaluating
comments has led us to conclude that this represents a more reasonable
limit to apply on a 30-day rolling average basis.
    This limit represents a control efficiency of 48% based on the
average annual baseline emission rate of 0.22 lb/MMBtu (2003-2004)
provided in the State's BART determination. This value is slightly
lower than the 49% control efficiency we assumed in our proposal, a
value that was based on the State's analysis. Beginning in 2010, CCS 2
voluntarily started employing LNC3, the more stringent level of
combustion controls that the State evaluated in its BART determination.
Annual average Clean Air Markets data for this unit reflects a
NOX emission rate of 0.153 lb/MMBtu. We estimate that SNCR
would achieve an additional 25% reduction, equivalent to an emission
rate of 0.115 lb/MMBtu. This compares to a value of 0.108 lb/MMBtu that
the State originally estimated.
    Great River Energy (GRE), the owner of CCS, asserted in comments
that SNCR will only achieve a 20% reduction beyond LNC3. We find that
25% is a conservative and reasonable estimate. We considered several
sources of information in arriving at this value. First, the Control
Cost Manual states that in typical field applications, SNCR provides a
30% to 50% NOX reduction. The manual provides a scatter plot
with NOX reduction efficiency plotted as a function of
boiler size in MMBtu/hr.\1\ The plot supports GRE's assertion that
control efficiency could be lower than 50%, and could approach 30%, for
larger boilers such as those at CCS. Second, Fuel Tech (one of the most
recognized SNCR technology suppliers) estimates a range of 25% to 50%
NOX reduction with application of SNCR.\2\ Lastly, ICAC has
published information that supports a control efficiency of 20 to 30%
for SNCR above LNB/combustion modifications.\3\ Given this range of
control efficiencies, we have settled on a control efficiency--25%--
that is lower than the lowest value given by the Control Cost Manual,
at the low end of the range estimated by Fuel Tech, and in the middle
of the range estimated by ICAC.
---------------------------------------------------------------------------

    \1\ U.S. EPA, EPA Air Pollution Control Cost Manual, EPA/452/B-
02-001, 6th Ed., January 2002, Section 4.2, Chapter 1, p. 1-3.
    \2\ http://www.ftek.com/en-US/products/apc/noxout/.
    \3\ Institute of Clean Air Companies, White Paper Selective Non-
Catalytic Reduction (SNCR) for Controlling NOX Emissions,
February 2008, p. 9.
---------------------------------------------------------------------------

    To arrive at a final BART emission limit, we adjusted the projected
annual average of 0.115 lb/MMBtu upward by 10% and then rounded to the
nearest hundredth to arrive at 0.13 lb/MMBtu. In our experience, a 5 to
15% upward adjustment is appropriate when converting an annual average
emission rate to a limit that will apply on a 30-day rolling average to
account for the fact that shorter averaging periods result in higher
variability in emissions due to load variation, startup, shutdown, and
other factors.
    We decided to allow the averaging across Units 1 and 2 in response
to comments we received. The BART Guidelines state, ``You should
consider allowing sources to `'average'' emissions across any set of
BART-eligible emission units within a fenceline, so long as the
emission reductions from each pollutant being controlled for BART would
be equal to those reductions that would be obtained by simply
controlling each of the BART-eligible units that constitute the BART-
eligible source.'' 40 CFR part 51, appendix Y, section V. This
principle applies here.

C. Other Resultant Changes

    Because we are now approving North Dakota's NOX BART
determinations for MRYS 1 and 2 and LOS 2, the basis for our proposed
disapproval of North Dakota's RPGs is slightly changed from our
proposal. Disapproval is still warranted because North Dakota's RPGs do
not represent our final NOX BART FIP limits at CCS 1 and 2
or our final NOX reasonable progress FIP limits at AVS 1 and
2 (or the Heskett or Coyote controls that North Dakota included in the
SIP). As part of our FIP, we are finalizing RPGs that are consistent
with the controls we are imposing at CCS 1 and 2 and AVS 1 and 2, and
the Heskett and Coyote controls that North Dakota included in the SIP.
For further details regarding our rationale, please refer to our
proposal and to our response to comments.
    Similarly, because we are now approving North Dakota's
NOX BART determinations for MRYS 1 and 2 and LOS 2, the
basis for our proposed partial disapproval of North Dakota's LTS is
slightly changed from our proposal. Partial disapproval is still
warranted because we are disapproving North Dakota's NOX
BART determination for CCS 1 and 2 and NOX reasonable
progress determination for AVS 1 and 2, and the LTS does not reflect
our final NOX BART FIP limits at CCS 1 and 2 or our final
NOX reasonable progress FIP limits at AVS 1 and 2, or
corresponding compliance provisions. Except for these missing elements,
the LTS satisfies the requirements of 40 CFR 51.308(d)(3), so we are
approving the remainder of the LTS. Our FIP fills the gap left by our
partial disapproval of the LTS by specifying NOX emission
limits for CCS 1 and 2 and AVS 1 and 2, compliance schedules, and
monitoring, recordkeeping, and reporting

requirements. For further details regarding our rationale, please refer
to our proposal and our response to comments.

IV. Basis for Our Final Action

    We have fully considered all significant comments on our proposal,
and, except as noted in section III, above, have concluded that no
other changes from our proposal are warranted. Our action is based on
an evaluation of North Dakota's SIP submittals and our FIP against the
regional haze requirements at 40 CFR 51.300-51.309 and CAA sections
169A and 169B, and against the interstate transport requirements
concerning visibility at CAA section 110(a)(2)(D)(i)(II). All general
SIP requirements contained in CAA section 110, other provisions of the
CAA, and our regulations applicable to this action were also evaluated.
The purpose of this action is to ensure compliance with these
requirements. Our authority for action on North Dakota's SIP submittals
is based on CAA section 110(k). Our authority to promulgate our partial
FIP is based on CAA section 110(c).

A. Regional Haze

    We are approving most of North Dakota's RH SIP provisions because
they meet the relevant regional haze requirements. Most of the adverse
comments we received concerning our proposed partial approval of the RH
SIP pertained to North Dakota's BART and reasonable progress
determinations.
    With respect to the BART determinations that we proposed to
approve, we understand that there is room for disagreement about
certain aspects of the State's analyses. Furthermore, we may have
reached different conclusions had we been performing the determinations
in the first instance. However, the comments have not convinced us that
the State, conducting specific case-by-case analyses for the relevant
units, acted unreasonably or that we should be disapproving the State's
BART determinations that we proposed to approve.
    With respect to North Dakota's reasonable progress determinations
that we proposed to approve, we continue to disagree with the manner in
which North Dakota evaluated visibility improvement when it evaluated
single source controls and have disregarded this evaluation in our
consideration of the reasonableness of North Dakota's reasonable
progress control determinations. We also disagree with some of North
Dakota's legal conclusions about the necessity of reasonable progress
controls for certain sources--specifically, for Coyote Station for
NOX and for Heskett Station 2 for sulfur dioxide
(SO2). However, in these instances, North Dakota nonetheless
included emission limits in the SIP that reflect reasonable levels of
control for reasonable progress for this initial planning period. Here
again, we understand that there is room for disagreement about the
State's analyses and appropriate limits. And, again, we may have
reached different conclusions had we been performing the
determinations. However, the comments have not convinced us that the
State, conducting specific case-by-case analyses for the relevant
units, made unreasonable determinations for this initial planning
period or that we should be disapproving the State's reasonable
progress determinations that we proposed to approve.
    As noted, we are disapproving North Dakota's NOX BART
determination for CCS 1 and 2 and its NOX reasonable
progress determination for AVS 1 and 2 and promulgating a partial FIP
to establish the required limits and corresponding compliance
provisions. For CCS 1 and 2, the State relied on values for costs of
compliance supplied by the owner that were admittedly erroneous. As
explained in detail in our response to comments, the comments we
received have not convinced us that our disapproval of the State's
NOX BART determination for CCS 1 and 2 is unreasonable, or
that our NOX BART FIP determination and limits (as modified
in this final action) are unreasonable. In particular, we conclude that
GRE's latest cost estimates and cost effectiveness values for SNCR, as
reflected in its November 2011 comments, are not based on reasonable
assumptions and overestimate the costs of compliance. Instead, our
consideration of the five statutory BART factors leads us to conclude
that SNCR plus SOFA plus LNB is BART, with a limit of 0.13 lb/MMBtu on
a 30-day rolling average basis. Also, we continue to find that the
costs of SCR are not reasonable given the projected visibility
improvement; the comments we received on this issue have not convinced
us otherwise.
    For AVS 1 and 2, consistent with our proposal, we are disapproving
the State's determination under our reasonable progress requirements
(40 CFR 51.308(d)(1)) that no additional NOX emissions
controls are warranted, and we are finalizing a FIP with a reasonable
progress determination and a NOX emission limit for AVS 1
and 2 of 0.17 lb/MMBtu on a 30-day rolling average basis. Nothing in
the comments has convinced us that the State's determination was
reasonable or that our proposed FIP was unreasonable. As we noted in
our proposal, the costs for installation and operation of combustions
controls at AVS 1 and 2 are very reasonable ($586 and $661 per ton) and
the predicted NOX reductions are substantial--3,500 tons per
unit per year. Appropriate single-source modeling also indicates that
the visibility benefits will be substantial--0.754 deciviews. Based on
these facts, and given that North Dakota's RPGs will not meet the
uniform rate of progress (URP), it was unreasonable for North Dakota to
reject LNB at AVS 1 and 2. We have determined that the State's
rejection of this level of control, and the corresponding RPGs, are not
justifiable based on a reasonable consideration of the applicable
regulatory factors--costs of compliance, time necessary for compliance,
energy and non-air quality environmental impacts of compliance, and
remaining useful life of the source. LNB is a modest, widely-used,
cost-efficient means to achieve significant NOX reductions,
and the resultant visibility benefits will be comparable to or greater
than the benefits achieved through selected controls at several BART
units in North Dakota. We have also rejected comments that call for
more stringent controls at AVS 1 and 2 in this planning period. While
such controls may be appropriate in a later planning period, we cannot
say that the State's rejection of such controls in this planning period
was unreasonable. For further details regarding our rationale, please
refer to our proposal and our response to comments.
    Consistent with our proposal, we are approving the remaining
elements of North Dakota's RH SIP because such elements meet the
relevant requirements of our regional haze regulations.

B. Interstate Transport, Visibility Prong

    The basis for this part of our action remains unchanged from our
proposal. Nothing in the comments has convinced us that a change from
our proposal is warranted. North Dakota's April 6, 2009 transport
submittal contained only a cursory reference to CAA section
110(a)(2)(D)(i)(II)'s requirement for a SIP revision that contains
adequate provisions ``prohibiting any source or other type of emission
activity within the State from emitting any air pollutant in amounts
which will * * * interfere with measures required to be included in the
applicable implementation plan for any other State under part C [of the
CAA] to protect visibility.'' Because of the impacts on visibility from
the interstate transport of pollutants, we

interpret the ``good neighbor'' provisions of section 110 of the Act
described above as requiring states to include in their SIPs either
measures to prohibit emissions that would interfere with the RPGs
required to be set to protect Class I areas in other states, or a
demonstration that emissions from North Dakota sources and activities
will not have the prohibited impacts. North Dakota's April 6, 2009
submittal contains neither. Thus, we are disapproving it. To the extent
that the State intended to meet the requirement of section
110(a)(2)(D)(i)(II) with the RH SIP, the RH SIP submission itself is
not fully approvable.
    As required by section 110(c), we are promulgating a FIP to satisfy
the requirements of CAA section 110(a)(2)(D)(i)(II) concerning
visibility protection. As explained in section II, the FIP relies on
the combination of the North Dakota RH SIP provisions that we are
approving and the additions to the regional haze program for North
Dakota that we are promulgating in our FIP for NOX BART for
CCS 1 and 2 and NOX reasonable progress for AVS 1 and 2.
Because this combination exceeds the stringency of BART and reasonable
progress limits that were already factored into the Western Regional
Air Partnership (WRAP) modeling for RPGs, this combination meets the
visibility prong of CAA section 110(a)(2)(D)(i)(II). This combination
of regional haze controls will ensure that emissions from sources in
North Dakota do not interfere with other states' visibility programs as
required by section 110(a)(2)(D)(i)(II) of the CAA.
    For further details regarding our rationale, please refer to our
proposal and our response to comments.

V. Issues Raised by Commenters and EPA's Responses

A. NOX BART for Milton R. Young Station Units 1 and 2 and Leland Olds
Station Unit 2

    As noted in section III of this action, in a major change from our
proposal, we are now approving North Dakota's NOX BART
determinations for MRYS 1 and 2 and LOS 2, and we are not proceeding
with a FIP for NOX BART for these units. We explain the
basis for this change in section III.
    We received numerous comments that were specific to the
NOX BART determinations for MRYS 1 and 2 and LOS 2. These
related to a variety of issues--modeling and visibility improvement,
costs of compliance, technical feasibility, appropriate emission
limits, and other issues. The grounds for our decision to approve North
Dakota's NOX BART determinations for MRYS 1 and 2 and LOS 2
render irrelevant further consideration of these issues. Essentially,
we are approving the State's determination of BART based on a federal
court's ruling on our challenge to the State's BACT determination for
MRYS. In establishing BACT, the State established an emission limit
based on what it considered the maximum degree of reduction of
NOX, taking into account various factors similar to those in
a BART determination. Thus, while we disagree with the vast majority of
the comments that disputed our technical and legal analyses concerning
NOX BART for MRYS 1 and 2 and LOS 2, we generally are not
summarizing or responding to those comments to the extent they are
specific to the assessment of NOX BART for MRYS 1 and 2 and
LOS 2.\4\ However, we are responding to comments that may be relevant
to other aspects of this action.
---------------------------------------------------------------------------

    \4\ Some commenters criticized the credibility and credentials
of one of our sub-contractors. Because of their focused nature, we
have included a response to some of those comments in our docket for
this action, even though the substance of the issues is no longer
relevant to our decision.
---------------------------------------------------------------------------

B. Comments on Legal Issues

1. EPA's Authority
    Comment: Multiple commenters stated that CAA Section 169A and the
Regional Haze Rule (RHR) give the states (North Dakota in this
instance) the lead in developing their regional haze SIPs. Some
commenters went further in stating that North Dakota is given almost
complete discretion in creating its RH SIP. These commenters argued
that, because North Dakota is given such discretion, EPA lacks the
statutory authority to disapprove the State's RH SIP. Specifically,
some commenters pointed to the flexibility the State is granted in
developing its BART determination, RPGs, modeling protocol and cost
analysis. The State of North Dakota, for instance, argued that each
factor in the five-factor analysis used to make its BART determination
was appropriately weighed based on the State's own discretion. The
State therefore argues that the EPA has no basis on which to disapprove
the five-factor analysis.
    Response: Congress crafted the CAA to provide for states to take
the lead in developing implementation plans, but balanced that decision
by requiring EPA to review the plans to determine whether a SIP meets
the requirements of the CAA. EPA's review of SIPs is not limited to a
ministerial type of automatic approval of a state's decisions. EPA must
consider not only whether the State considered the appropriate factors
but acted reasonably in doing so. In undertaking such a review, EPA
does not ``usurp'' the state's authority but ensures that such
authority is reasonably exercised. EPA has the authority to issue a FIP
either when EPA has made a finding that the State has failed to timely
submit a SIP or where EPA has found a SIP deficient. Here, EPA has
authority on both grounds, and we have chosen to approve as much of the
North Dakota SIP as possible and to adopt a FIP only to fill the
remaining gap. Our action today is consistent with the statute. In
finalizing our proposed determinations, we are approving the State's
determinations in identifying BART eligible sources and largely
approving the State's BART determinations for seven different emission
units subject to BART. Also, we are largely approving the State's
reasonable progress determinations. We are, however, disapproving the
State's NOX BART determinations for two units--CCS 1 and 2--
and its NOX reasonable progress determinations for two
units--AVS 1 and 2.
    The State's NOX BART determinations for CCS 1 and 2 are
not approvable because North Dakota did not properly follow the
requirements of section 51.308(e)(1)(ii)(A). Specifically, North Dakota
did not reasonably ``take into consideration the costs of compliance,''
when it relied on cost estimates that greatly overestimated the costs
of controls. We have determined that the faults in the cost estimates
were significant enough that they resulted in BART determinations for
NOX for CCS 1 and 2 that were both unreasoned and
unjustified. Accordingly, these determinations are not approvable.
    We are disapproving the State's determination that no
NOX controls are needed at AVS 1 and 2 to achieve reasonable
progress because the State's determination is not reasonable under the
relevant statutory and regulatory requirements.
    In the absence of approvable NOX BART determinations in
the SIP for CCS 1 and 2 and in the absence of an approvable reasonable
progress determination concerning NOX controls at AVS 1 and
2, we are obliged to promulgate a FIP to satisfy the CAA requirements.
Likewise, in the absence of an approvable SIP that addresses the
requirement that emissions from North Dakota sources do not interfere
with measures required in the SIP of any other state to protect
visibility, we are obliged to promulgate a FIP to address the defect.
This authority and

responsibility exists under CAA section 110(c)(1).
    We also are required by the terms of two separate consent decrees,
one in the U.S. District Court for the District of Colorado and one in
the U.S. District Court for the Northern District of California to
ensure that North Dakota's CAA requirements for regional haze and for
110(a)(2)(D)(i)(II), respectively, are finalized by March 2, 2012.
Because we have found that the State's SIP submissions do not
adequately satisfy either requirement in full and because we have
previously found that North Dakota failed to timely submit these SIP
submissions, we have not only the authority, but a duty to promulgate a
FIP that meets those requirements.
    Our action in large part approves the RH SIP submitted by North
Dakota. The disapproval of the NOX BART and reasonable
progress determinations and imposition of the FIP is not intended to
encroach on state authority. This action is only intended to ensure
that CAA requirements are satisfied using our authority under the CAA.
    Comment: The NDDH commented that states are free to deviate from
the BART guidelines in the preparation of their BART analyses, except
for power plants with a capacity exceeding 750 megawatts (MW).
    Response: We agree that the BART guidelines are only mandatory
under the regional haze regulations for ``fossil-fuel fired power
plants having a total generating capacity greater than 750 megawatts.''
40 CFR 51.308(e)(1)(ii)(B). However, the fact that a state may deviate
from the guidelines for other BART sources does not mean that the state
has unfettered discretion to act unreasonably or inconsistently with
the CAA and our regulations. Where the BART guidelines are not
mandatory, a state must still meet the requirements of the CAA and our
regulations. In other words, the State must still adopt and apply the
best available retrofit technology, considering the statutory factors.
    Our regulations define best available retrofit technology to mean
``an emission limitation based on the degree of reduction achievable
through the application of the best system of continuous emission
reduction for each pollutant which is emitted by an existing stationary
facility.'' 40 CFR 51.301 (emphasis added). We do not consider that
this definition can simply be dismissed under the mantle of state
discretion.
    In addition, North Dakota's own regulations, which have been
submitted for our approval and which we are approving with this action,
provide as follows:

    ``33-15-25-03 Guidelines for best available retrofit technology
determinations under the Regional Haze Rule.
    Title 40, Code of Federal Regulations, part 51, appendix y, as
published in the Federal Register on July 6, 2005, is incorporated
by reference into this chapter. The owner or operator of a fossil-
fuel-fired steam electric plant with a generating capacity greater
than seven hundred fifty megawatts of electricity shall comply with
the requirements of appendix y. All other facility owners or
operators shall use appendix y as guidance for preparing their best
available control retrofit technology determinations.''

(Emphasis added.) Appendix Y contains EPA's BART guidelines. Our
approval of this regulation makes it federally enforceable.
    North Dakota appears to disavow the dictates of its own regulation:

    ``EGUs with a capacity of less than 750 MW * * * are free to
deviate from the BART Guidelines in the preparation of their BART
analyses.
    MRYS * * * may use the Guidelines as guidance only.''

State of North Dakota's November 21, 2011 comments, p. 22 (emphasis
added). But, the regulation says that EGUs less than 750 MW ``shall
use'' EPA's BART guidelines as guidance, not that they ``may use'' them
as guidance or that they are ``free to deviate'' from them.
    Given that North Dakota's own regulation, which we are making
federally enforceable with this action, requires the use of the BART
guidelines as guidance for BART analyses, we think it reasonable to
conclude that any deviation from the guidelines must be based on a
reasonable justification.
    Regardless, the BART guidelines are mandatory for CCS, which is the
one source for which we are disapproving the State's BART
determination.
    Comment: North Dakota meets the presumptive BART limits for
NOX at CCS 1 and 2, based on the 2005 BART Guidelines. EPA's
rationale for disapproving the BART determinations at CCS 1 and 2 is
therefore flawed and contrary to the BART Guidelines. EPA appears to be
undertaking a national effort to change its BART Rule without going
through notice and comment rulemaking to amend or repeal the rule. EPA
is doing so by ``applying BART determinations made for sources in one
state as a new presumptive limit for all states.'' Commenter cites 76
FR 58623 of the proposed rule, where EPA justifies a cost/ton ``that
states other than North Dakota have considered reasonable for BART,''
but is higher than the presumptive BART limits.
    Response: We disagree with the commenter. First, for each source
subject to BART, the RHR, at 40 CFR 51.308(e)(1)(ii)(A), requires that
states identify the level of control representing BART after
considering the factors set out in CAA section 169A(g), as follows:
States must identify the best system of continuous emission control
technology for each source subject to BART taking into account the
technology available, the costs of compliance, the energy and non-air
quality environmental impacts of compliance, any pollution control
equipment in use at the source, the remaining useful life of the
source, and the degree of visibility improvement that may be expected
from available control technology. 70 FR 39158. In other words, the
presumptive limits do not obviate the need to identify the best system
of continuous emission control technology on a case-by-case basis
considering the five factors. A state may not simply ``stop'' its
evaluation of potential control levels at the presumptive level of
control if more stringent control technologies or limits are
technically feasible. We do not read the BART guidelines in appendix Y
to contradict the requirement in our regulations to determine ``the
degree of reduction achievable through the application of the best
system of continuous emission reduction'' ``on a case-by-case basis,''
considering the five factors. 40 CFR 51.301 (definition of Best
Available Retrofit Technology); 40 CFR 51.308(e). Also, our
interpretation is supported by the following language in our BART
guidelines:

    While these levels may represent current control capabilities,
we expect that scrubber technology will continue to improve and
control costs continue to decline. You should be sure to consider
the level of control that is currently best achievable at the time
that you are conducting your BART analysis.

70 FR 39171. The presumptive limits are meaningful as indicating a
level of control that EPA generally considered achievable and cost
effective at the time it adopted the BART guidelines in 2005, but not a
value that a state could adopt without conducting a five factor
analysis considering more stringent, technically feasible levels of
control.
    The commenter focuses on narrow passages of the BART guidelines to
support its view that the presumptive limits represent the most
stringent BART controls that EPA can require for regional haze.
However, these passages must be reconciled with the language of the RHR
cited above, as well as other passages of the BART guidelines and
associated preamble. A central concept expressed in the guidelines is
that a

state is not required to consider the five factors if it has selected
the most stringent level of control; otherwise, a state must fully
consider the five factors in determining BART. 40 CFR part 51, appendix
Y, section IV.D.1, step 1.9. Undoubtedly, as the commenter notes, the
presumptive limits for NOX represent cost effective
controls, but it is well-understood that limits based on combustion
controls do not represent the most stringent level of control for
NOX. Thus, a state which selects combustion controls and the
associated presumptive limit for NOX as BART may only do so
after rejecting more stringent control technologies based on full
consideration of the five factors. Our interpretation reasonably
reconciles the various provisions of our regulations. We clearly
communicated our views on this subject to North Dakota while it was
developing its RH SIP, and, following our interpretation, North Dakota
conducted an analysis of control technologies that would achieve a more
stringent limit than combustion controls.
    While North Dakota conducted a five-factor analysis to determine
BART at CCS, its determination was based on erroneous values for the
costs associated with potential loss of fly ash sales due to ammonia
contamination, something the source acknowledged in June of 2011. 76 FR
58603. A BART determination based on substantially erroneous cost
values does not meet the requirements of the CAA or our regulations to
determine the best system of continuous emission control technology
considering cost and the other statutory factors. Because we cannot
approve the State's BART determination, we are authorized, and in this
case obligated, to promulgate a FIP.
    In promulgating a FIP for CCS, we arrived at an emission limit that
is more stringent than the presumptive limit based on consideration of
the five factors. Contrary to the commenter's suggestion, EPA's BART
guidelines do not establish a presumptive cost effectiveness level that
is a ``safe harbor'' or ``shield'' for state BART determinations, or
that EPA, when promulgating a FIP, may not exceed in determining BART.
Once a FIP is required, we stand in the state's shoes. In considering
the cost factor, it is reasonable for us to consider other sources of
information to inform our decision, including the cost values other
states have considered reasonable. This is not EPA establishing a new
presumptive limit or national rule; it is EPA, acting in the state's
shoes, conducting a reasonable source-specific consideration of cost
and the other regulatory factors. In addition, although not required,
we considered cost effectiveness values that the State of North Dakota
had considered to be reasonable in reaching its BART determinations.
See 76 FR 58623 (``It is also within the range of values that North
Dakota considered reasonable in its NOX BART determinations
* * *'')
    Comment: EPA has failed to articulate, or apply, a SIP review
standard that preserves state authority over BART determinations. EPA
can't rely on vague references to the overarching purpose of the
regional haze program to define what's reasonable. The CAA only
requires consideration of the five statutory factors and emission
limits that yield a reduction in visibility impairment. EPA has
contradicted prior statements in various contexts, such as reports to
Congress. EPA has provided no objective measure to gauge EPA's
assessment. EPA's vague standards result in arbitrary and capricious
decision making. EPA must articulate the standard by which it evaluates
and disapproves a SIP and must support its decision with a plausible
explanation.
    Response: Our proposal clearly laid out the bases for our proposed
disapproval of the State's BART and reasonable progress determinations,
and we have relied on the standards contained in our regional haze
regulations and the authority that Congress granted us to review and
determine whether SIPs comply with the minimum statutory and regulatory
requirements. To the extent a cost analysis relies on values that are
inaccurate, a state has not considered cost in a reasoned or reasonable
fashion. To the extent a state has considered visibility improvement
from potential emissions controls in a way that substantially
understates the improvement or does so in a way that is not consistent
with the CAA, the state has not considered visibility improvement in a
reasoned or reasonable fashion. In these circumstances, it is
reasonable for EPA to disapprove the relevant aspects of the SIP. In
determining SIP adequacy, we inevitably exercise our judgment and
expertise regarding technical issues, and it is entirely appropriate
that we do so. Courts have recognized this necessity and deferred to
our exercise of discretion when reviewing SIPs. See, e.g., Connecticut
Fund for the Env't., Inc. v. EPA, 696 F.2d 169 (2nd Cir. 1982);
Michigan Dep't. of Envtl. Quality v. Browner, 230 F.3d 181 (6th Cir.
2000); Mont. Sulphur & Chem. Co. v. United States EPA, 2012 U.S. App.
LEXIS 1056 (9th Cir. Jan. 19, 2012).
    We disagree with the argument that we must approve a BART
determination where the SIP reflects consideration of the five factors
and the BART selection will result in some improvement in visibility.
We think Congress expected more when it required the application of
``best available retrofit technology.''
    While the commenter places great emphasis on EPA's prior statements
in reports to Congress, these statements have no regulatory effect.
Also, these statements are not as supportive of commenter's position as
commenter suggests. For example, ``some flexibility'' does not suggest
unfettered flexibility; a report's suggestion that a cooperative
approach would make sense does not suggest that EPA will or must
approve unilateral decision-making by a state no matter what.
    Contrary to the commenter's assertion, we have not destroyed the
State's primacy. In fact, we have approved the vast majority of the
State's determinations. We are only rejecting the State's unreasonable
analyses and decisions. We are authorized to do so.
    Comment: The grounds invoked by EPA to disapprove the RH SIP are
legislative in nature and cannot be imposed without advance notice and
comment rulemaking. EPA's proposed action on North Dakota's SIP
articulates a number of grounds not contained in CAA section 169A that
must be met for a SIP to be ``approvable.'' These additional grounds
have never been defined or promulgated with notice and comment
rulemaking. For example, EPA's proposed action articulates a two
pronged test for BART SIP approval: first, ``a state must meet the
requirements of the CAA and our regulations for selection of BART'';
and second, ``the state's BART analysis and determination must be
reasonable in light of the overarching purpose of the regional haze
program.'' 76 FR 58577. The commenter objects to the second prong,
i.e., that ``the state's BART analysis and determination must be
reasonable in light of the overarching purpose of the regional haze
program.'' According to the commenter, this is a new ``reasonableness''
standard that is neither defined nor separately set forth in the Act.
The commenter asserts that EPA is proposing to measure a BART
determination not just against the statutory criteria but also against
EPA's own subjective view whether the result reached is reasonable
enough to meet the ``overarching goal'' of the Act. EPA's new
subjective reasonable enough requirement imposes a new legislative
standard that either goes beyond or, for

the first time, purports to define ``the requirements of the Act.''
This empowers EPA to disapprove a state BART determination and replace
it with its own on reasonableness grounds that have never been defined
or first vetted through public notice and comment.
    Response: First, even assuming that EPA's proposed action on the
North Dakota RH SIP articulated new grounds for evaluating a regional
haze SIP, the proposed action provides the public with the opportunity
to comment. As evidenced by the commenter's submission, the commenter
had the opportunity to comment on EPA's approach to evaluating the
North Dakota RH SIP and to identify any concerns associated with the
statement at issue from our proposal and other aspects of our action.
    Second, the CAA requires states to submit SIPs that contain such
measures as may be necessary to make reasonable progress toward
achieving natural visibility conditions, including BART. The CAA
accordingly requires the states to submit a regional haze SIP that
includes BART as one necessary measure for achieving natural visibility
conditions. In view of the statutory language, it is hardly a novel
idea that the reasonableness of the state's BART analysis and
determination would be evaluated in light of the purpose of the
regional haze program. In addition, our regional haze regulations, at
40 CFR 51.308(d)(ii), provide that when a state has established a RPG
that provides for a slower rate of improvement in visibility than the
URP (as has North Dakota), the state must demonstrate, based on the
reasonable progress factors--i.e., costs of compliance, time necessary
for compliance, energy and non-air quality environmental impacts of
compliance, and remaining useful life of affected sources--that the
rate of progress to attain natural visibility conditions by 2064 is not
reasonable and that the progress goal adopted by the state is
reasonable. 40 CFR 51.308(d)(iii) provides that, ``in determining
whether the State's goal for visibility improvement provides for
reasonable progress towards natural visibility conditions, the
Administrator will evaluate'' the state's demonstrations under section
51.308(d)(ii). It is clear that our regulations and the CAA require
that we review the reasonableness of the State's BART determinations in
light of the goal of achieving natural visibility conditions. This
approach is also inherent in our role as the administrative agency
empowered to review and approve SIPs. Thus, we are not establishing a
new reasonableness standard, as the commenter asserts.
    Comment: EPA established a new adequacy criterion when it found
that North Dakota's cost analysis did not provide a reasonable basis to
make a NOX BART determination for LOS 2. It was illegal for
EPA to establish a new adequacy criterion without rulemaking.
    Response: While we have decided to approve the State's
NOX BART determination for LOS 2, this comment may be
relevant to other aspects of our final action.
    Our prior response largely addresses this assertion. However, in
addition, we think the illogic of the commenter's claim is revealed
when the potential consequences of the commenter's views are examined.
The necessary product of the commenter's view is that a state could
rely on irrational values for any of the five factors, and EPA would be
powerless to disapprove the SIP. We reject that view. We are not
establishing new criteria for approval of a regional haze SIP. We are
applying the criteria and requirements already specified in the CAA and
our regulations. Cost is one of the factors a state must consider in
determining BART. If North Dakota has relied on greatly inflated cost
estimates in its consideration of the cost factor, it has not
considered cost in any meaningful sense of the word.
    It is also our opinion that the commenter, in its effort to put our
action in a specific legal box--i.e., ``illegal administrative
action''--consistently misrepresents the nature of our action. This is
a SIP review action, and we believe that EPA is not only authorized,
but required to exercise independent technical judgment in evaluating
the adequacy of the State's RH SIP, including its BART determinations,
just as EPA must exercise such judgment in evaluating other SIPs. In
evaluating other SIPs, EPA is constantly exercising judgment about SIP
adequacy, not just to meet and maintain the NAAQS, but also to meet
other requirements that do not have a numeric value. In this case,
Congress did not establish NAAQS by which to measure visibility
improvement; instead, it established a reasonable progress standard and
required that EPA assure that such progress be achieved. Here, contrary
to the commenter's assertion, we are exercising judgment within the
parameters laid out in the CAA and our regulations. Our interpretation
of our regulations and of the CAA, and our technical judgments, are
entitled to deference. See, e.g., Michigan Dep't. of Envtl. Quality v.
Browner, 230 F.3d 181 (6th Cir. 2000); Connecticut Fund for the Env't.,
Inc. v. EPA, 696 F.2d 169 (2nd Cir. 1982); Voyageurs Nat'l Park Ass'n
v. Norton, 381 F.3d 759 (8th Cir. 2004); Mont. Sulphur & Chem. Co. v.
United States EPA, 2012 U.S. App. LEXIS 1056 (9th Cir. Jan. 19, 2012).
    Comment: EPA has no statutory authority to disapprove North
Dakota's BART determination for LOS 2. CAA section 169A(b)(2) leaves
that determination expressly and exclusively in the hands of the State.
EPA's SIP approval authority under CAA section 110 only permits EPA to
confirm whether the State considered the statutory factors; it does not
authorize EPA to pass judgment on how the State considers them. The
commenter cites the American Corn Growers and UARG decisions as support
for its comments. Nor, according to the commenter, does section 110
permit EPA to propose its own emission controls. By doing so, EPA's FIP
``run[s] roughshod over the procedural prerogatives that the Act has
reserved to the States'' (citing Bethlehem Steel Corp. v. Gorsuch, 742
F.2d 1028, 1036 (7th Cir. 1984)).
    Response: While we have decided to approve the State's
NOX BART determination for LOS 2, this comment may be
relevant to other aspects of our final action. The commenter reads too
much into the language of 169A. We do not agree that the language, ``as
determined by the State,'' grants the State unlimited discretion or
``sole control'' in making a BART determination, any more than the
accompanying language, ``or the Administrator in the case of a plan
promulgated under section 7410(c) of this title,'' grants EPA unlimited
discretion in making a BART determination in a FIP.
    Instead, while States are assigned the primary statutory and
regulatory authority to determine BART, and have significant freedom to
determine the weight and significance of the statutory factors, they
have an overriding obligation to come to a reasoned determination. They
may not act unreasonably or in an arbitrary and capricious fashion, and
Congress has assigned EPA, as the reviewing agency, the role of
determining whether a State's BART determination or reasonable progress
determination is reasonable.
    The commenter's citations to legislative history are unconvincing.
Among other things, they are incomplete. The commenter ignores the
intent behind the 1977 legislation:

    ``The Administrator must promulgate regulations which assure
attainment of the national goal * * * Specifically, the regulations
must require that States which contain mandatory class I areas, and
States

whose emissions cause or contribute to visibility problems in such
areas, revise their implementation plan to include two elements. The
first element of the plan revision is that the State plan must
provide for installation of ``best available retrofit technology''
for existing major stationary sources which cause or contribute to
visibility impairment in such areas.''

95 Cong. Conf. Report H. Rept. 564, at 154.
    Commenters suggest that visibility issues are only of state and
local concern and that is why Congress left states with sole control.
This is inconsistent with the very first sentence of the statute:
``Congress hereby declares as a national goal the prevention of any
future, and the remedying of any existing, impairment of visibility in
mandatory class I Federal areas * * *'' CAA section 169A, (emphasis
added). It is also inconsistent with the legislative history, which
states:

    ``There are certain national lands, including national parks,
national monuments, national recreation areas, national primitive
areas, and national wilderness areas, in which protection of clean
air quality is obviously a critical national concern * * * Indeed,
the millions of Americans who travel thousands of miles each year to
visit Yosemite or the Grand Canyon or the North Cascades will find
little enjoyment if, for example, upon reaching the Grand Canyon it
is difficult if not impossible to see across the great chasm. If
that were to come to pass--and several of our great national parks,
including the Grand Canyon, are threatened today by such a fate--the
very values which these unique areas were established to protect
would be irreparably diminished, perhaps destroyed.''

95 Cong. House Report 294 at 137.
    Thus, we do not agree that Congress assigned us a merely
ministerial role; it is not evident how such a limited role would
assure attainment of the national goal or the actual imposition of the
best available retrofit technology where a state's BART determination
is unreasonable, arbitrary and capricious, or not in accordance with
the law.
    We also disagree that our proposal is inconsistent with the
American Corn Growers and UARG decisions. These cases dealt with EPA's
authority to issue generic regulations regarding BART determinations.
They did not address EPA's authority in reviewing a SIP.
    Contrary to the commenter's assertion, the Bethlehem Steel case is
inapplicable here. We are promulgating BART and reasonable progress
limits under the authority of CAA section 110(c), not through our
action on North Dakota's SIP. We have authority to promulgate our FIP
under 110(c) on two separate grounds: first, based on our January 2009
finding of failure to submit the RH SIP; and second, based on our
partial disapproval of the RH SIP.
    Comment: Commenter stated that EPA is incorrect to assert that NDDH
did not adequately consider all five statutory factors for LOS 2.
Commenter stated that EPA concludes, in its own BART evaluation, that
SNCR + ASOFA (NDDH's BART selection) is cost effective and provides
substantial visibility benefits. When a state has taken into
consideration the five statutory factors and selected a technology that
reduces visibility impairments, it has complied with the statute and
EPA must approve the SIP. Since EPA's own FIP analysis proves North
Dakota's choice complies with the statute, EPA has no basis to
disapprove it.
    Response: While we have decided to approve the State's
NOX BART determination for LOS 2, this comment may be
relevant to other aspects of our final action. The commenter cites no
authority in the CAA or our regulations for its assertion that a BART
determination that considers the five statutory factors is adequate as
long as it provides some reduction in visibility impairment. We know of
no such criterion. Instead, our regulations define BART as an emission
limitation based on the degree of reduction achievable through the
application of the best system of continuous emission reduction for
each pollutant which is emitted by an existing stationary facility. The
emission limitation must be established, on a case-by-case basis,
taking into consideration the technology available, the costs of
compliance, the energy and non-air quality environmental impacts of
compliance, any pollution control equipment in use or in existence at
the source, the remaining useful life of the source, and the degree of
improvement in visibility which may reasonably be anticipated to result
from the use of such technology. Given that the BART limit must reflect
the ``application of the best system of continuous emission
reduction,'' we interpret the Act to require a reasonable consideration
of the five factors, one that is not arbitrary and capricious.
    Comment: EPA's effort to impose BART determinations by federal
rulemaking impermissibly deprives source owners of the substantive
procedural rights they are otherwise afforded under State law. The
commenter notes that the State used a permit process to establish BART
limits, and that a similar source-by-source adjudication of such limits
must be provided by EPA. The commenter also asserts that EPA must allow
for examination and cross-examination of witnesses, and that,
otherwise, the process is not consistent with due process.
    Response: While the State has chosen to use the permit process to
establish BART limits for individual sources, there is nothing in the
CAA or our regulations that requires states or EPA to use permits or a
source-by-source adjudicatory proceeding to establish BART limits. Both
the CAA and our regulations require that BART limits be contained in a
SIP. In the absence of an approvable SIP, CAA section 110(c) requires
us to issue a FIP. We have issued a partial FIP pursuant to CAA section
307. CAA section 307 provides that its provisions apply in lieu of the
Administrative Procedure Act (APA). The procedures provided by CAA
section 307 are adequate to ensure due process to source owners. We
have provided a substantial opportunity for comment (a two-month long
comment period) and an extensive public hearing that lasted 14 hours
over two days. The commenter submitted over 140 pages of comments with
several attachments, and other commenters submitted comments of similar
length. It is not unusual for FIPs to include source-specific limits
and requirements. An opportunity for examination and cross-examination
of witnesses is not required by the CAA, nor is it required to ensure
due process. Individuals and entities affected by EPA's action have had
ample opportunity to challenge EPA's conclusions.
    Comment: Sole control over BART determinations for EGUs under 750
MW is left to the states. Congressional intent to exclude federal
involvement in BART determinations for smaller generating stations is
apparent from the plain text of the statute and is binding on EPA. EPA
may not disapprove a state BART determination for an EGU the size of
Leland Olds.
    Response: EPA disagrees with the suggestion that Congress intended
to totally remove EPA from review of BART determinations for EGUs less
than 750 MW. The statute merely says that for EGUs greater than 750 MW,
BART must be determined in accordance with guidelines promulgated by
EPA. That does not obviate the need for the State to select BART, after
considering the five statutory factors. And, it does not remove EPA's
review role over SIP submittals.
    Comment: North Dakota has the authority under the RHR to review the
new updated cost analyses provided by URS and Golder Associates on
behalf of GRE.

    Response: Our action does not prevent North Dakota from reviewing
GRE's updated cost analyses, or from submitting a revised SIP. States
always have the freedom to submit SIP revisions to EPA. We need not
speculate in this action whether such a revision would be approvable.
However, such a SIP revision is not the subject of this action, and we
are neither obligated nor authorized to wait for such a revision before
we finalize our proposed action. To the contrary, we have already
exceeded the statutory deadline for promulgating a FIP or approving a
SIP for regional haze, and, under two separate consent decrees, we must
finalize this action by March 2, 2012.
    GRE acknowledged in a June 2011 email that it had made errors in
its original cost estimates for NOX BART for CCS. The State
relied on those erroneous cost figures in its NOX BART
analysis and determination for CCS in its RH SIP that it submitted on
March 3, 2010. This is the main RH SIP submittal that we are acting on
today.
    Because of the magnitude of these acknowledged errors, it is
appropriate to disapprove the BART determination for CCS 1 and 2 that
is contained in the March 3, 2010 submittal. We explain in response to
a prior comment why selection of the presumptive limits without a valid
case-specific analysis supporting such limits as BART is not sufficient
to meet the requirements of the regional haze regulations. Based on our
disapproval of the SIP, and on separate grounds related to our January
2009 finding of failure to submit, we are authorized and obligated to
promulgate a FIP for NOX BART for CCS 1 and 2. CAA section
110(c). We have considered GRE's revised cost analyses in the context
of our proposed FIP and address those analyses in a subsequent
response.
    Comment: Commenter stated that EPA's action is in violation of the
10th amendment to the Constitution.
    Response: Our action does not compel North Dakota to enforce
federal law and does not intrude on authority reserved to the states.
Thus, our action is consistent with the 10th amendment to the
Constitution.
    Comment: Commenter stated that EPA's action is in violation of
Article 4 of the Constitution.
    Response: The comment does not specify which aspect of Article 4 we
are alleged to have violated. However, we conclude that our action does
not violate any aspect of Article 4 of the Constitution.
    Comment: Commenter stated that Federal Land Managers (FLMs) are
using their Air Quality Related Values Workgroup (FLAG) report, a
guidance document, in highly inappropriate ways.
    Response: This comment appears to relate to how the FLMs respond to
proposed PSD permits rather than EPA's proposed actions here.
Accordingly, we are not responding to the substance of this comment.
Contrary to the commenter's assertion, we do not consider our own
actions to be inflexible. We note that we are approving the great
majority of the State's BART and reasonable progress determinations.
2. Interstate Transport Consent Decree
    Comment: Commenter states that EPA wrongly uses the Interstate
Transport consent decree to justify action by the September 1, 2011
deadline. Commenter claims that EPA separately acknowledged that the
Interstate Transport consent decree never addressed the regional haze
plan. North Dakota has sought leave of the court that issued the
consent decree to intervene in the case. North Dakota is also seeking a
declaration from the Court that EPA is exceeding its authority under
that consent decree to use it for justification of the regional haze
proposal.
    Response: The United States District Court for the Northern
District of California rejected the commenter's arguments in an order
dated December 27, 2011. We agree that the transport consent decree
does not address the regional haze plan. However, as the court in
California recognized, we made an appropriate administrative decision
to address the CAA's transport requirements and regional haze
requirements in the same action. Given that we faced a September 1,
2011 deadline for our proposed transport action under the transport
consent decree, and faced an uncertain deadline for proposed action and
a January 26, 2011 deadline for final action under the then-lodged
regional haze consent decree, we acted in a prudent and reasonable
fashion to sign our notice of proposed rulemaking by the September 1,
2011 deadline in the transport consent decree.
    Comment: North Dakota's Interstate Transport SIP, specifically the
``visibility'' element of CAA Section 110(A)(2)(D)(i)(II), must be
approved. North Dakota commented that EPA had no reason not to act on
the visibility portion of the State's interstate transport SIP
submission according to EPA's 2006 guidance. Another commenter stated
that the EPA ``admits'' in the Proposed North Dakota RH SIP/FIP that
the State met the sole obligation of Section 110(A)(2)(D)(i)(II), and
that the EPA's reasons for disapproval therefore lack basis.
    Response: We fully explained the basis for our proposed disapproval
of North Dakota's interstate transport SIP in our proposal. See 76 FR
58641-58642. We have fully considered the comments, but nothing in the
comments has caused us to change our views. As we explained in our
proposal, our 2006 guidance was premised on a certain set of
assumptions--in particular, that states would submit their regional
haze SIPs by the regulatory deadline and that the regional haze SIPs
would be the appropriate means for states to establish that their SIPs
contained adequate provisions to prevent interference with the
visibility programs required in other states. It turned out we were
mistaken in our assumptions, and we explained in our proposal that
subsequent events have rendered our 2006 guidance inappropriate in this
specific action. Thus, we appropriately and reasonably evaluated the
State's interstate transport SIP against the statutory requirements and
found it deficient. The State disagrees with the way in which we
characterized the State's transport SIP in our proposal at 76 FR 58574,
but we were clear in our discussion later in our notice that ``North
Dakota did not explicitly state in its April 6, 2009, submittal that it
intended that its Regional Haze SIP be used to satisfy the visibility
prong * * *'' 76 FR 58641.
    Basin Electric misrepresents our proposed action. While we
indicated that the State had not explicitly indicated that it was
submitting the RH SIP to meet the interstate transport requirements,
which left us in an uncertain position, that was not the only basis for
our conclusion that the RH SIP did not meet the transport requirements.
Instead, we stated, ``Most importantly, however, EPA must review the
April 6, 2009 submission in light of the current facts and
circumstances, and the RH SIP revision that the State ultimately
submitted does not fully meet the substantive requirements of the
regional haze program * * * To the extent that the State intended to
meet the requirement of section 110(a)(2)(D)(i)(II) with the RH SIP,
the RH SIP submission itself is not fully approvable.'' 76 FR 58642.
    The State and Basin Electric assert that we should approve the RH
SIP as satisfying the transport requirements even though we are
disapproving the SIP as meeting regional haze requirements. We
disagree. Under the suggested approach, EPA would simultaneously codify
in the Code of Federal Regulations disparate and conflicting
requirements--the SIP limits

and associated requirements (or in the case of AVS, the lack thereof)
for certain EGUs and the FIP limits and associated requirements for
those same EGUs. This could lead to confusion regarding the
requirements applicable to the industrial sources affected, including
confusion in enforcement actions. Accordingly, we have decided to
finalize our proposed disapproval of North Dakota's interstate
transport SIP.
    Comment: The NDDH commented that EPA has not provided any credible
evidence that the additional emission reductions from the FIP will
produce any discernible visibility improvement in out-of-state Class I
areas and has not provided any credible evidence that these additional
emission reductions are necessary to prevent North Dakota sources from
interfering with another state's ability to protect visibility.
    Response: In our proposal, we did not claim that our FIP to address
the requirements of CAA section 110(a)(2)(D)(i)(II) would result in
visibility improvement in out-of-state areas. We did not have the time
or resources to re-do the WRAP modeling that states in the region had
relied on in assessing the impacts of emissions reductions and in
setting their RPGs. Instead, we noted that the emission limits in our
proposed FIP to address certain deficiencies in the State's BART and
reasonable progress measures in its RH SIP would exceed the emissions
reductions for BART and reasonable progress for these sources that had
been factored into the WRAP modeling for RPGs. As a result, we
concluded that the limits in the FIP, in combination with the measures
in the SIP that we had proposed to approve, would satisfy the
interstate transport requirements for visibility. We continue to find
that this is a reasonable conclusion. Although there may be other
acceptable approaches to satisfying the requirements of CAA section
110(a)(2)(D)(i)(II) that would require additional visibility modeling,
the approach that we have adopted does not require that we assess
through modeling the visibility improvement that will result from our
FIP to assure that North Dakota's emissions do not interfere with
measures required in the plans of other states to protect visibility.
3. Other General Legal Comments
    Comment: Some commenters stated that EPA cannot promulgate a FIP
until it has taken final action on the related SIP.
    Response: We have the authority to promulgate a FIP concurrently
with a disapproval action. As has been noted in past FIP promulgation
actions, if EPA ``finds that a State has failed to make a required
submission * * * or * * * disapproves a [SIP] in whole or in part,''
CAA Section 110(c)(1) establishes a two-year period within which we
must promulgate a FIP, and provides no further constraints on timing.
See, e.g., 76 FR 25178, at 25202. North Dakota failed to submit its RH
SIP to us by December 2007, as required by Congress. Two years later,
North Dakota had still not submitted its RH SIP. When we made a finding
in 2009 that North Dakota had failed to submit its RH SIP, (see 74 FR
2392), that created an obligation for us to promulgate a FIP by January
2011. We are promulgating the FIP concurrently with our disapproval
action because of the applicable statutory deadlines requiring us at
this time to promulgate regional haze BART determinations and
reasonable progress (RP) determinations to the extent North Dakota's
BART and RP determinations are not approvable.
    We also note that North Dakota made this same argument to the U.S.
District Court for the District of Colorado--in a motion opposing entry
of a consent decree containing deadlines for EPA to promulgate a FIP
for regional haze for North Dakota and in comments on the proposed
consent decree. The court rejected North Dakota's argument. First, the
court noted that we had proposed action on North Dakota's SIP in our
September 1, 2011 proposal and we were, therefore, not proposing to
take final action on the regional haze FIP before making a
determination on North Dakota's SIP revision. Second, the court
indicated that we would be authorized to promulgate the regional haze
FIP even without taking final action on North Dakota's SIP. As we had
argued, the court found that the duty to promulgate a FIP (triggered by
our 2009 finding of failure to submit an RH SIP) remains ``unless the
State corrects the deficiency, and the Administrator approves the plan
or plan revision, before the Administrator promulgates such [FIP].''
Order Entering Consent Decree, WildEarth Guardians v. Jackson, Civil
Action No. 11-cv-00001-CMA-MEH, USDC Colorado, p. 17, citing CAA
section 110(c) (emphasis and brackets added by the court).
    Comment: Commenter stated that EPA must review the ``blanket five
year compliance date'' to install and operate BART to ensure that it is
as expeditious as practicable, as required by the CAA.
    Response: We have reviewed the compliance dates for meeting BART
limits that are contained in the portions of the SIP we are approving
and in the FIP we are promulgating. These dates are reasonable given
the magnitude of the retrofits being undertaken. We note that the State
permits that we are approving as part of this action provide for
compliance as expeditiously as practicable, but in no event later than
five years.

C. Comments on Modeling

    Comment: Several commenters questioned aspects of the single-source
CALPUFF modeling that North Dakota included in the SIP and which EPA
relied upon in our evaluation of visibility impacts. Among other
things, commenters questioned (1) Whether CALPUFF overestimates nitrate
formation, (2) whether newer versions of CALPUFF would give more
accurate results, (3) the method for establishing natural visibility
background, (4) how to establish ammonia background concentrations, and
(5) the method for interpreting model results as they relate to
visibility improvement. The commenters submitted revised single-source
CALPUFF modeling results to address what they believed to be
deficiencies in the single-source CALPUFF modeling that North Dakota
included in the SIP.
    Response: While each of these comments is addressed separately in
detailed responses below, a general response is warranted. We note that
many of these comments were submitted by Minnkota and Basin Electric
and were directed specifically to EPA's proposal regarding SCR at MRYS
1 and 2 and LOS 2. As we have explained, such comments are not relevant
to our final action. Nonetheless, we are responding to most of the
comments in the event that they could be interpreted as having broader
application to the assessment of visibility improvement from potential
control options.
    The second point we note is that the source owners are essentially
questioning modeling that they conducted and submitted to the State as
part of their BART evaluations, and that the State specifically called
for and included in the SIP. The State established procedures for
single-source BART modeling used to support its SIP in the ``Protocol
for BART-Related Visibility Impairment Modeling Analyses in North
Dakota'' (the BART modeling protocol). North Dakota RH SIP, Appendix
A.1. North Dakota intended for the protocol to apply to ``visibility
modeling for both identification of sources `subject to BART' (i.e.,
BART screening), and for determining the degree of visibility
improvement related to the selection of BART controls.'' North Dakota
RH SIP, Appendix A.1, p. 1. In fact, North

Dakota specifically stated: ``[A]ll BART-related single-source modeling
for sources in North Dakota must follow the protocol outlined here.
Because of this requirement, the NDDH will not expect companies which
operate BART-eligible sources to provide individual protocols for their
BART-related modeling.'' Id., p. 3. North Dakota's protocol conforms to
the BART Guidelines.\5\ It also follows recommendations for modeling
long range transport contained in 40 CFR part 51, appendix W (``The
Guideline on Air Quality Models'') and EPA's Interagency Workgroup on
Air Quality Modeling (IWAQM) Phase 2 Summary Report and Recommendations
for Modeling Long Range Transport Impacts. Furthermore, as discussed in
Section 3 of the SIP, Plan Development and Consultation, the protocol
was developed in consultation with EPA and FLM meteorologists.
Adherence to the protocol ensures that a consistent comparison of
visibility improvement can be made for potential control technologies
across different individual units and different pollutants.
---------------------------------------------------------------------------

    \5\ There is one aspect of the protocol that does not conform to
the BART guidelines--North Dakota's inclusion of the 90th percentile
modeling results in addition to the 98th percentile. The use of the
90th percentile modeling results is not consistent with the CAA. 70
FR 39121. We provide more detail about the deficiency in the use of
the 90th percentile value in subsequent responses.
---------------------------------------------------------------------------

    As the State's single-source BART modeling followed established
guidance and was developed in consultation with FLMs and EPA, we find
that it provides a reasonable basis for making control technology
determinations. We do not agree with the sources' attempt to deviate
from the established protocol for assessing visibility impacts. This is
because it would lead to a less consistent and rational assessment of
potential control options. Nonetheless, we have considered the revised
single-source modeling and the comments submitted by the commenters in
making our final action. We conclude that nothing contained in their
modeling analysis undermines the single-source modeling that North
Dakota included in the SIP.
    Comment: Two commenters stated that the receptor-specific approach
to identifying the 98th percentile result in CALPUFF is more
technically correct than the default day-specific approach. The
commenters also supplied revised CALPUFF modeling based on the
receptor-specific approach. These modeling results suggest that
controls would achieve less visibility improvement than indicated by
North Dakota's single-source BART modeling.
    Response: We do not agree that the receptor-specific approach is
more technically correct; it is not part of the standard CALPUFF model
and merely serves to decrease the conservatism of the model predictions
through the creation of 98th percentile values that are specific to
specific receptor locations within a Class I area. The standard CALPUFF
approach considers the daily impacts within a Class I area at all
receptor points; i.e., the model predicts the highest daily value for
each day of the year from all receptors within a Class I area. The 98th
percentile reflects the eighth highest of these daily values.
    In its BART modeling protocol, North Dakota stated that ``the
context of the 98th percentile 24-hour delta-deciview prediction is
with respect to days of the year, and is not receptor specific.'' RH
SIP, Appendix A.1, Section 4.0, p. 50. In addition, in establishing the
98th percentile as a reasonable contribution threshold in the BART
Guidelines, EPA intended that the day-specific, or ``day-by-day,''
approach be used. 70 FR 39121. This was the approach EPA considered
appropriate to account for the assumptions and uncertainties in
CALPUFF; the receptor-specific approach goes beyond what EPA considers
appropriate to address these assumptions and uncertainties and would
undermine the goal of achieving natural visibility conditions.
Therefore, we do not consider the revised CALPUFF modeling results
based on the flawed receptor-specific approach that were submitted by
the commenters to be useful in assessing visibility impacts..
    Comment: Several of the commenters argue that it is inappropriate
to evaluate visibility impacts in comparison to natural background
visibility conditions. Instead, the commenters propose to evaluate
visibility impacts in comparison to current, degraded visibility
conditions. The commenters further argue that EPA's use of natural
conditions is inconsistent with section 169A of the CAA and that EPA
should amend its BART Guidelines to use current, degraded visibility
conditions.
    Response: We disagree. EPA's approach is consistent with Congress's
intent in passing section 169A, and the proposal to use degraded
visibility conditions is inconsistent with section 169A. Visibility
impacts must always be evaluated relative to some reference visibility
condition, and a given reduction in ambient PM2.5 will
result in smaller relative improvement in visibility when compared to
polluted conditions versus clean conditions. Because current degraded
visibility conditions are considerably worse than natural background
visibility, comparison of a BART source's impact relative to current
degraded visibility conditions would result in a smaller relative
benefit than would a comparison relative to natural background
visibility. EPA previously considered and responded to the same comment
in 40 CFR part 51, appendix Y, promulgated at 70 FR 39104, July 6,
2005. After receiving this comment on the BART Guidelines, EPA
considered the approach of assessing a BART-eligible source's impacts
on visibility by using current or near-term future conditions, and EPA
determined that BART visibility impacts should be evaluated in
comparison to natural background visibility. In the final rulemaking
EPA wrote (70 FR 39124):

    ``Using existing conditions as the baseline for single source
visibility impact determinations would create the following paradox:
the dirtier the existing air, the less likely it would be that any
control is required. This is true because of the nonlinear nature of
visibility impairment. In other words, as a Class I area becomes
more polluted, any individual source's contribution to changes in
impairment becomes geometrically less. Therefore the more polluted
the Class I area would become, the less control would seem to be
needed from an individual source. We agree that this kind of
calculation would essentially raise the ``cause or contribute''
applicability threshold to a level that would never allow enough
emission control to significantly improve visibility. Such a reading
would render the visibility provisions meaningless, as EPA and the
States would be prevented from assuring ``reasonable progress'' and
fulfilling the statutorily-defined goals of the visibility program.
Conversely, measuring improvement against clean conditions would
ensure reasonable progress toward those clean conditions.''

See, also, Memorandum from Gail Tonnesen, Regional Modeler, to North
Dakota Regional Haze File, dated September 1, 2011, regarding
``Modeling Single Source Visibility Impacts.'' This memorandum is
included in Appendix B of the Technical Support Document (TSD) for this
action.
    Comment: Two commenters performed new CALPUFF simulations using
EPA's current regulatory version 5.881 and submitted these modeling
results to EPA during the comment period. The commenters found lower
visibility impacts using CALPUFF version 5.8 than did the State with an
earlier CALPUFF version 5.711a.
    Response: For these new model results, the commenters did not
submit a modeling protocol for EPA review and did not provide a
complete copy of the CALPUFF input and output files. As a result, EPA
was not able to fully review the data sets used in this modeling.

Moreover, while EPA did approve the use of the Rapid Update Cycle
meteorology for modeling the Heskett facility, EPA has not approved
this alternate modeling protocol for other BART sources in North Dakota
and has not reviewed or approved other modifications to the modeling
approach that the commenters used in developing new CALPUFF results.
    From the information that the commenters provided, EPA determined
that the differences in the new CALPUFF version 5.8 modeling results
are due in part to a change in the natural background visibility that
was used in the modeling analysis. The State's modeling protocol called
for use of the 20% best natural visibility days in its BART analysis
while the commenters' new CALPUFF version 5.8 analysis used the annual
average natural visibility days. If the commenters had adopted the same
approach as North Dakota and compared CALPUFF version 5.8 visibility
impacts to the 20% best natural visibility days, the results of the new
analysis would have been more similar to the original modeling
performed by North Dakota.
    We do not find that the commenters' new modeling demonstrates that
single-source modeling performed according to North Dakota's BART
modeling protocol should be disregarded. That modeling was conducted
using the latest version of CALPUFF that was available at the time, and
we are approving the great majority of North Dakota's BART
determinations that relied on results from that modeling. In our FIP,
in which we are merely filling gaps in the SIP, we are not required to
conduct new modeling using CALPUFF version 5.8 or disregard the results
of the modeling conducted using CALPUFF version 5.711a. In fact, we
find the better course is to rely on modeling based on the same version
of the model that the State employed to ensure we are using a
consistent comparison. See, Mont. Sulphur & Chem. Co. v. United States
EPA, 2012 U.S. App. LEXIS 1056 (9th Cir. Jan. 19, 2012).
    Comment: The commenters argue that CALPUFF overstates visibility
impact due to the complexity of the chemistry affecting visibility
impairment and that EPA acknowledges that ``the simplified chemistry in
the [CALPUFF] model tends to magnify the actual visibility effects of
[a] source.'' 70 FR 39121. The commenters further state that when EPA
adopted the BART Guidelines, EPA concurred with ``the concerns of
commenters that the chemistry modules of the CALPUFF model are less
advanced than some of the more recent atmospheric chemistry
simulations.'' Id. at 39123. The commenters also assert that several
published papers or presentations show that CALPUFF over predicts
nitrate by a factor of 2 to 4 in the winter.
    Response: For the reasons already stated, EPA's reliance on the
CALPUFF modeling results that the State included in the SIP is
reasonable. In addition, EPA has acknowledged that the simplified
chemistry used in the CALPUFF model creates uncertainty in the accuracy
of the model for predicting visibility impacts for pollutants such as
NOX that are converted from the gas phase to aerosol through
complex photochemical reactions. However, it is uncertain whether the
simplified chemistry will always overpredict visibility impacts. For
example, Anderson et al. (2010) \6\ found that the CALPUFF model
frequently predicted lower nitrate concentrations compared to the
Comprehensive Air Quality Model (CAMx) photochemical grid model, which
has a much more rigorous treatment of photochemical reactions. EPA
recognized the uncertainty in the CALPUFF modeling results, and EPA
made the decision in the final BART guidelines that the model should be
used to estimate the 98th percentile visibility impairment rather than
the highest daily impact value as proposed. 70 FR 39121. We made the
decision to consider the less conservative 98th percentile (i.e., the
eighth highest 24-hour deciview impact in a year rather than the
highest) primarily because the chemistry modules in the CALPUFF model
are simplified and might in some cases predict a maximum 24-hour impact
that is an ``outlier.'' Id. If recent updates to CALPUFF cause the
model to predict lower visibility impacts, the use of the updated model
might also require EPA to reconsider the choice of the less
conservative 98th percentile for evaluating visibility impacts. In any
event, our reliance on CALPUFF modeling is reasonable for the reasons
discussed above.
---------------------------------------------------------------------------

    \6\ Anderson, B., K. Baker, R. Morris, C. Emery, A. Hawkins, E.
Snyder ``Proof-of-Concept Evaluation of Use of Photochemical Grid
Model Source Apportionment Techniques for Prevention of Significant
Deterioration of Air Quality Analysis Requirements'' Community
Modeling and Analysis System (CMAS) 2010 Annual Conference, October
11-15, 2010, Research Triangle Park, NC. http://www.cmascenter.org/conference/2010/agenda.cfm.
---------------------------------------------------------------------------

    Comment: Several commenters suggested that the State has unlimited
discretion to consider visibility or cost or other factors in any way
it wishes, even in ways that are inaccurate or inconsistent with the
purpose of the CAA.
    Response: We disagree. We have already largely addressed the
assertions in this comment in our responses to comments on our legal
authority. Furthermore, as a hypothetical example, EPA would not defer
to a state determination that the remaining useful life of a source is
one year if relevant evidence indicates the remaining useful life is 20
years. Limits on state discretion are inherent in the CAA and our
regulations; otherwise, states would be free to reach decisions that
are arbitrary and capricious or inconsistent with the purpose behind
the CAA and EPA's regulations. As we have stated, North Dakota's
cumulative modeling approach thwarts the goal stated by Congress in CAA
section 169A and underlying the RHR.
    Comment: One commenter claimed that pictorial examples demonstrate
that the visibility benefits which EPA claims can be achieved with
NOX control technologies are not perceptible. The commenter
compares archived pictures copied from the National Park Service (NPS)
Web site, along with the monitored haze index, for days having varying
levels of visibility impairment. For example, the commenter compares
two pictures from different days for which the haze index changes by
1.26 deciviews and concludes that ``no perceptible difference can be
seen * * *''
    Response: We do not expect that a 1.0 deciview change in
visibility, which is considered a ``small but noticeable change in
haziness under most circumstances'' (64 FR 35725), could be easily
perceived in a small picture on the printed page. Moreover, North
Dakota did not provide visibility improvement relative to a pre-control
baseline as recommended by the BART guideline (70 FR 39170), so many of
the estimates of visibility improvement contained in the SIP are
misleadingly low. Regardless, the BART Guidelines establish that
predicted visibility improvement below perceptibility thresholds does
not provide a basis to automatically eliminate a control option: ``Even
though the visibility improvement from an individual source may not be
perceptible, it should still be considered in setting BART because the
contribution to haze may be significant relative to other source
contributions in the Class I area. Thus, we disagree that the degree of
improvement should be contingent upon perceptibility. Failing to
consider less-than-perceptible contributions to visibility impairment
would ignore the CAA's intent to have BART requirements apply to
sources that contribute to, as well as cause, such impairment.'' 70 FR
39129. The

importance of visibility impacts below the thresholds of perceptibility
cannot be ignored given that regional haze (as contrasted with
reasonably attributable visibility impairment) is a problem that is
produced by a multitude of sources and activities which are located
across a broad geographic area.
    Comment: Commenter states that it takes a larger change in
pollutant emissions to cause a perceptible visibility change when the
change is measured against current degraded visibility conditions
rather than ``natural'' visibility conditions. Visibility benefits
estimated relative to natural background will ``tend to be five to
seven times larger'' than the benefits estimated relative to current
degraded visibility. Therefore, using the natural background conditions
overstates the visibility improvement that would be achieved by
controls at the time of installation.
    Response: As noted in our responses to other similar comments, it
is precisely this effect that leads us to conclude that the only
approach consistent with the statutory and regulatory goals when
considering visibility improvement associated with potential single-
source control options is to use natural background values in the
model. The goal is reasonable progress, not stasis.
    Comment: One commenter argues that the natural background specified
by EPA significantly exaggerates how clean natural conditions actually
are. The commenter provides a report on natural visibility background
which argues that EPA's estimate of natural conditions significantly
understates the extent of natural particulate emissions, including dust
and wildfires, which are uncontrollable.
    Response: EPA recognized that variability in natural sources of
visibility impairment cause variability in natural haze levels as
described in its ``Guidance for Estimating Natural Visibility
Conditions Under the Regional Haze Rule.'' \7\ The preamble to the BART
guidelines (70 FR 39124) describes an approach used to measure progress
toward natural visibility in Mandatory Class I Areas that includes a
URP toward natural conditions for the 20 percent worst days and no
degradation of visibility on the 20 percent best days. The use of the
20 percent worst natural conditions days in the calculation of the URP
takes into consideration visibility impairment from wild fires,
windblown dust and other natural sources of haze. The ``Guidance for
Estimating Natural Visibility'' also discusses the use of the 20
percent best and worst estimates of natural visibility, provides for
revisions to these estimates as better data becomes available,\8\ and
discusses possible approaches for refining natural conditions estimates
(pages 3-1 to 3-4).
---------------------------------------------------------------------------

    \7\ Guidance for Estimating Natural Visibility Conditions Under
the Regional Haze Rule, U.S. Environmental Protection Agency,
September 2003. http://www.epa.gov/ttncaaa1/t1/memoranda/rh_envcurhr_gd.pdf, page 1-1: ``Natural visibility conditions
represent the long-term degree of visibility that is estimated to
exist in a given mandatory Federal Class I area in the absence of
human-caused impairment. It is recognized that natural visibility
conditions are not constant, but rather they vary with changing
natural processes (e.g., windblown dust, fire, volcanic activity,
biogenic emissions). Specific natural events can lead to high short-
term concentrations of particulate matter and its precursors.
However, for the purpose of this guidance and implementation of the
regional haze program, natural visibility conditions represents a
long-term average condition analogous to the 5-year average best-
and worst-day conditions that are tracked under the regional haze
program.''
    \8\ Guidance for Estimating Natural Visibility Conditions * * *:
``The preamble further stated that `with each subsequent SIP
revision, the estimates of natural conditions for each mandatory
Federal Class I area may be reviewed and revised as appropriate as
the technical basis for estimates of natural conditions improve.' ''
---------------------------------------------------------------------------

    For the evaluation of visibility impacts for BART sources, EPA
recommended the use of the natural visibility baseline for the 20% best
days for comparison to the ``cause or contribute'' applicability
thresholds. This estimated baseline is reasonably conservative and
consistent with the goal of attaining natural visibility conditions.
While EPA recognizes that there are natural sources of haze, the use of
the 20% worst natural visibility days is inappropriate for the ``cause
or contribute'' applicability thresholds. For example, if BART source
visibility impacts were evaluated in comparison to days with very poor
natural visibility resulting from nearby wild fires or dust storms, the
BART source impacts would be significantly reduced relative to these
poor natural visibility conditions and would not be protective of
natural visibility on the best 20% days.
    The commenter and the cited report on natural visibility by Robert
Paine appear to suggest that EPA requires the use of the best 20%
visibility days for all aspects of visibility analysis. This does not
accurately characterize EPA's recommended use of the 20% worst natural
visibility days for URP calculations and the 20% best natural
visibility days for the ``cause or contribute'' applicability
thresholds. For example, natural visibility conditions at the Badlands
National Park for the best 20%, annual average, and worst 20% natural
visibility days are 2.9, 5.0, and 8.1 deciviews, respectively.\9\ By
contrast, current visibility conditions at the Badlands National Park
for the best 20%, annual average, and worst 20% days are 6.9, 11.6 and
17.1 deciviews, respectively. The URP calculation uses the worst 20%
natural visibility value of 8.1 deciviews, and this value adequately
represents the impacts of natural sources of visibility impairment.
Finally, as part of the settlement of a case brought by the Utility Air
Regulatory Group challenging the BART Guidelines,\10\ EPA agreed to
issue guidance clarifying that states may use either the 20% best or
the annual average in estimating natural visibility in the evaluation
of a BART source's impacts. This guidance makes clear that states have
the flexibility to use either approach in estimating natural background
conditions. The State was not required to use the annual average and
did not. Similarly, in issuing a FIP, we are not required to use the
annual average either.
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    \9\ Natural Haze Levels II Committee Report.
    \10\ Settlement Agreement in Utility Air Regulatory Group v.
EPA, Case No. 06-1056 in the United States Court of Appeals for the
District of Columbia Circuit, April 19, 2006.
---------------------------------------------------------------------------

    The commenter cited modeling studies that purportedly show that the
model-predicted natural haze levels are substantially larger than the
natural haze levels used by EPA. In fact, the results of those studies
compare well with EPA's natural background levels. The modeling study
by Tonnesen et al.\11\ predicted annual average natural
PM2.5 concentrations in North Dakota in the range of 1.9 to
2.5 ug/m\3\, while the Koo et al. study \12\ predicted annual average
natural PM2.5 concentrations in the range of 2.5 to 3.1 ug/
m\3\ in North Dakota. These model estimates are consistent with EPA's
estimated 2.6 ug/m\3\ annual average PM2.5 concentration at
Class I Areas in western North Dakota.
---------------------------------------------------------------------------

    \11\ Tonnesen, G., Omary, M., Wang, Z., Jung, C.J., Morris, R.,
Mansell, G., Jia, Y., Wang, B., Adelman, Z., 2006. Report for the
Western Regional Air Partnership Regional Modeling Center.
University of California Riverside, Riverside, California, November.
http://pah.cert.ucr.edu/aqm/308/reports/final/2006/WRAP-RMC_2006_report_FINAL.pdf.
    \12\ Koo, B.; Chien, C.J.; Tonnesen, G.; Morris, R.; Johnson,
J.; Sakulyanontvittaya, T.; Piyachaturawat, P.; Yarwood, G.; Natural
emissions for regional modeling of background ozone and particulate
matter and impacts on emissions control strategies, Atmos. Env.,
44:19, 2372-2382.
---------------------------------------------------------------------------

    Comment: One commenter felt that EPA's decision appears to be
driven by its desired outcome--more emission reductions--and not by any
legal basis for disapproving the North Dakota SIP.
    Response: Our decision is driven by our interpretations of the CAA
and our

regulations. We note that we are approving the vast majority of North
Dakota's decisions.
    Comment: One commenter stated that EPA should not ignore two of the
three years of CALPUFF modeling results in our review of modeling
results presented by North Dakota. The commenter suggested that this is
inconsistent with EPA's typical practice of using long-term averages
when addressing regional haze as is necessary to prevent undue
influence from short-term events or unusual meteorological events.
    Response: In our review of the single-source CALPUFF modeling
results presented by North Dakota, we cited the change in the maximum
98th percentile impact over the modeled three year meteorological
period (2001-2003). As the 98th percentile value is intended to reflect
the 8th high value in any year, it already eliminates 7 days per year
from consideration in order to account for short-term events, unusual
meteorological conditions, and any over-prediction bias in the model.
Therefore, the modeling results which we cited in our proposal are
designed to exclude influence from unusual events or meteorological
conditions and are sufficient to address the commenter's concerns. We
also note that our approach is consistent with the method used by North
Dakota in identifying subject-to-BART sources where a source is
considered to contribute to impairment if it ``exceeds the threshold
when the ninety-eighth percentile of the modeling results based on any
one year of the three years of meteorological data modeled exceeds
five-tenths deciviews.'' North Dakota RH SIP, p. 63. We find that this
is a reasonable method for the purposes of evaluating visibility
improvements associated with potential control options.
    Comment: Commenters stated that EPA should not ignore the 90th
percentile impact in our review of the CALPUFF visibility results
presented by North Dakota.
    Response: In the BART Guidelines, EPA addressed the appropriate
interpretation of CALPUFF modeling results within the context of
subject-to-BART modeling. We rejected the use of the 90th percentile
because it would be inconsistent with the Act: ``The use of the 90th
percentile value would effectively allow visibility effects that are
predicted to occur at the level of the threshold (or higher) on 36 or
37 days a year. We do not believe that such an approach would be
consistent with the language of the statute.'' 70 FR 39121. On the same
page, EPA explained that the 98th percentile was sufficient to account
for any overestimation of visibility benefits by CALPUFF.
    While the BART Guidelines do allow states to consider the
``frequency, duration, and intensity'' of a source's visibility impact
when making control determinations, the use of the 90th percentile
would over-compensate for any uncertainties in CALPUFF and would
underestimate visibility benefits from potential control options and
unduly bias the resulting analysis. When the 90th percentile is used to
assess predicted visibility improvement from a potential control
option, the 37th or 38th highest predicted improvement value from 365
predicted daily values is selected; higher predicted improvement values
on 36 or 37 days a year are ignored. This is not rational. In the
actual BART determination, a state could so dilute the predicted
visibility improvement, one of the very goals of CAA section 169A, as
to nullify its initial determination using the 98th percentile that the
source is subject to BART. Accordingly, the BART guidelines
specifically mention the use of the 98th percentile as an option to
compare pre- and post-control modeling runs; use of the 90th percentile
is not mentioned. 70 FR 39170. Moreover, the FLMs have affirmed the use
of the 98th percentile in their most recent guidance for evaluating
visibility impacts at Class I areas. FLAG 2010, p. 23.\13\
---------------------------------------------------------------------------

    \13\ The complete reference is: U.S. Forest Service, National
Park Service, and U.S. Fish and Wildlife Service. 2010. Federal land
managers' air quality related values work group (FLAG): phase I
report--revised (2010). Natural Resource Report NPS/NRPC/NRR--2010/
232. National Park Service, Denver, Colorado.
---------------------------------------------------------------------------

    Comment: One commenter stated that CALPUFF overpredicts visibility
impacts associated with nitrates due to incorrect (too high) ammonia
background. The commenter stated that monitored background ammonia data
from Wyoming shows lower concentrations. The commenter also cites a
study by Colorado Department of Public Health and Environment (CDPHE)
related to the sensitivity of the CALPUFF model to ammonia background
concentrations.
    Response: The monthly ammonia background concentrations used by
North Dakota were derived from data collected at the State's only
ammonia monitor located near Beulah and range from a low of 0.98 ppb to
a high of 2.29 ppb. (BART modeling protocol, Table 3-4). Due to their
proximity to the North Dakota sources and Class I areas, the Beulah
ammonia background concentrations are clearly more representative than
those which the commenter cites for Wyoming that ``were on the order of
only 0.1 ppb.'' We also note that, in its revised modeling, the
commenter did not use alternate ammonia background concentrations that