[Federal Register Volume 79, Number 153 (Friday, August 8, 2014)]
[Rules and Regulations]
[Pages 46513-46555]
[FR Doc No: 2014-18228]

Vol. 79

Friday,

No. 153

August 8, 2014

Part II

 Environmental Protection Agency

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40 CFR Part 49

 Approval of Air Quality Implementation Plans; Navajo Nation; Regional
Haze Requirements for Navajo Generating Station; Final Rule

Federal Register / Vol. 79 , No. 153 / Friday, August 8, 2014 / Rules
and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 49

[EPA-R09-OAR-2013-0009; FRL-9914-62-Region 9]

Approval of Air Quality Implementation Plans; Navajo Nation;
Regional Haze Requirements for Navajo Generating Station

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is promulgating a
source-specific Federal Implementation Plan (FIP) requiring the Navajo
Generating Station (NGS), a coal-fired power plant located on the
Navajo Nation near Page, Arizona, to achieve reductions in oxides of
nitrogen (NOX) required under the Best Available Retrofit
Technology (BART) provisions of the Clean Air Act (CAA) and the
Regional Haze Rule (RHR). On February 5, 2013, EPA issued a proposed
BART determination for NGS and an alternative to BART. In a
supplemental proposal on October 22, 2013, EPA proposed to approve a
new alternative plan, based on an agreement developed by a group of
stakeholders known as the Technical Work Group (TWG). EPA is finalizing
the alternative to BART described in our supplemental proposal. This
rule is consistent with the TWG Agreement, including a lifetime cap in
total emissions of NOX from NGS over 2009-2044 (2009-2044
NOX Cap). Our final action will achieve greater emissions
reductions than BART and is expected to significantly reduce the impact
of NGS on visibility at 11 mandatory Class I Federal areas. The
operator of NGS must implement one of several alternative operating
scenarios to achieve the necessary emission reductions to comply with
the 2009-2044 NOX Cap.

DATES: Effective date: This rule is effective on October 7, 2014.

FOR FURTHER INFORMATION CONTACT: Anita Lee, EPA Region 9, (415) 972-
3958<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: EPA has established a docket for this action
under Docket ID No. EPA-R09-OAR-2013-0009. The index to the docket for
this action is available electronically at http://www.regulations.gov
and in hard copy at EPA Region 9, 75 Hawthorne Street, San Francisco,
California. While documents in the docket are listed in the index, some
information may be publicly available only at the hard copy location
(e.g. copyrighted material, voluminous or oversized documents, etc.),
and some may not be publicly available in either location (e.g.
Confidential Business Information (CBI)). To inspect the hard copy
materials, please schedule an appointment during normal business hours
with the contact listed in the FOR FURTHER INFORMATION CONTACT section.
A reasonable fee may be charged for copies.
    Throughout this document, ``we'', ``us'', and ``our'' refer to EPA.

Table of Contents

I. Executive Summary
II. Background for the Final Rule
    A. History of NGS
    B. Summary of Statutory and Regulatory Framework for Addressing
Visibility and Sources Located in Indian Country
    C. Summary of Proposed Rule and Supplemental Proposal
    D. Summary of Legal Rationale for Compliance Flexibility
III. Summary of Final FIP Provisions
IV. Summary of Major Issues Raised by Commenters
V. Summary of Final Action
VI. Administrative Requirements
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
    K. Congressional Review Act
    L. Petitions for Judicial Review

I. Executive Summary

    EPA is taking final action pursuant to the CAA and the RHR to
require Units 1, 2, and 3 at NGS to reduce emissions of NOX
in order to reduce the impact NGS has on visibility at 11 mandatory
Class I Federal areas. We are finalizing an alternative to BART based
on agreed-upon recommendations developed by a group of diverse
stakeholders known as the Technical Work Group (TWG). Our final action
limits emissions of NOX from NGS by establishing a long-term
facility-wide cap on total NOX emissions from 2009 to 2044
and requires the implementation of one of several alternative operating
scenarios to ensure that the 2009-2044 cap is met. Generally, the
alternative operating scenarios require the closure of one unit at NGS
(or the curtailment of electricity generation by a similar amount) in
2019, and compliance with a NOX emission limit that is
achievable with the installation of selective catalytic reduction (SCR)
on two units in 2030.
    As part of our final action, EPA is also setting a source-specific
BART Benchmark against which to compare the TWG Alternative to ensure
that it will achieve greater reasonable progress than BART. The BART
Benchmark is consistent with the BART determination we proposed on
February 5, 2013, requiring all three units at NGS to meet an emission
limit achievable with SCR within five years of a final rule. EPA is not
finalizing our proposed BART determination for NGS in the regulatory
requirements of this Final Rule.
    EPA's action to finalize an alternative to BART consistent with the
TWG Agreement will achieve greater NOX emission reductions
at lower cost than BART in exchange for flexibility in the timeframe
for achieving NOX reductions. When fully implemented, this
Final Rule requires over an 80 percent reduction in NOX
emissions from NGS and is expected to significantly reduce the impact
of NGS on visibility at 11 mandatory Class I Federal areas.

II. Background for the Final Rule

A. History of NGS

    NGS is a coal-fired power plant located on the Navajo Nation Indian
Reservation near Page, Arizona. The facility consists of three 750
megawatt (MW) coal-fired electric utility steam generating units with a
total capacity of 2250 MW constructed from 1974 to 1976. The three
units at NGS are co-owned by six entities: The United States Bureau of
Reclamation (Reclamation) (24.3 percent); Salt River Project (21.7
percent), which also serves as the facility operator; Los Angeles
Department of Water and Power (21.2 percent); Arizona Public Service
(14 percent); NV Energy (11.3 percent); and Tucson Electric Power (7.5
percent).
    Federal participation in NGS was authorized in the Colorado River
Basin Project Act of 1968 as a preferred alternative to building
hydroelectric dams in the Grand Canyon for the purpose of providing
power to the Central Arizona Project (CAP).\1\ The

CAP is a 336-mile water distribution system that delivers about 1.5
million acre-feet (AF) per year of Colorado River water from Lake
Havasu in western Arizona to non-Indian agricultural (NIA) water users
in central Arizona, Indian tribes located in Arizona, and municipal
water users in Maricopa, Pinal, and Pima Counties in Arizona. The CAP
water is used to meet the terms of a number of Indian water-rights
settlements in central Arizona and to reduce groundwater usage in the
region. A portion of Reclamation's share of electricity from NGS powers
the pumps that move CAP water to its destinations along the
distribution system.
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    \1\ For more detail and for citations or references to the
information provided in this Background section, please see the
Proposed Rule at 78 FR 8274 (February 5, 2013).
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    Several tribes located in Arizona, including the Gila River Indian
Community, the Ak-Chin Indian Community, the Tohono O'odham Nation, the
San Carlos Apache Tribe, the White Mountain Apache Indian Tribe, the
Fort McDowell Yavapai Nation, the Salt River Pima-Maricopa Indian
Community, the Navajo Nation, the Yavapai-Apache Nation, the Hopi
Tribe, the Pascua Yaqui Tribe, the Yavapai-Prescott Tribe, and the
Tonto Apache Nation, have CAP water allocations or contracts. In
exchange for allocations of CAP water at reduced cost and access to
funds for the development of water infrastructure, the tribes with
water settlement agreements have released their claims to other water
in Arizona. Excess NGS power owned by Reclamation that is not used by
CAP is sold and profits are deposited into the Lower Colorado River
Basin Development Fund (Development Fund) to support the tribal water
settlement agreements. The U.S. Department of the Interior (DOI or
Interior), through Reclamation, plays an important role in the
implementation of these settlement agreements and the management of the
Development Fund.
    The coal used by NGS is supplied by the Kayenta Mine, operated by
Peabody Energy and located on reservation lands of both the Navajo
Nation and the Hopi Tribe. Taxes and royalties from NGS and the Kayenta
Mine are paid to the Navajo Nation and Hopi Tribe, contributing to the
annual revenues for both governments. EPA understands that the process
is underway to renew site leases for NGS and the Kayenta Mine, as well
as associated rights of way agreements and contracts with the Navajo
Nation and Hopi Tribe.
    Given the extent of federal and tribal interests in NGS, on January
4, 2013, EPA, DOI, and the Department of Energy (DOE) signed a joint
federal agency statement (Joint Statement) committing to collaborate on
several short- and long-term goals, including analyzing and pursuing
strategies for providing clean, affordable, and reliable power,
affordable and sustainable water, and sustainable economic development
to key stakeholders who currently depend on NGS.\2\ The Joint Statement
also recognizes the trust responsibility of the Federal government to
Indian tribes.
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    \2\ See document title ``2013--0104 Joint Federal Agency
Statement on NGS'' within document number 0005 in the docket for
this proposed rulemaking at EPA-R09-OAR-2013-0009, which can be
found at www.regulations.gov.
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B. Summary of Statutory and Regulatory Framework for Addressing
Visibility and Sources Located in Indian Country

    In our Proposed Rules, we provided a detailed discussion of the
statutory and regulatory framework for addressing visibility impairment
in the mandatory Class I Federal Areas, addressing sources located in
Indian country under the statute and the Tribal Authority Rule (TAR),
and developing BART determinations pursuant to the CAA and the BART
Guidelines set forth in Appendix Y to 40 CFR Part 51.\3\ Here, we
provide a brief summary of the statutory and regulatory framework.
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    \3\ See 78 FR 8274 (February 5, 2013) and 78 FR 62509 (October
22, 2013).
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    Title I, part C, subpart II of the CAA Amendments of 1977
establishes a visibility protection program that sets forth ``as a
national goal the prevention of any future, and the remedying of any
existing, impairment of visibility in mandatory class I Federal areas
which impairment results from man-made air pollution.'' \4\ EPA
promulgated regional haze regulations implementing the program on April
22, 1999.\5\ Consistent with the statutory requirement in 42 U.S.C.
7491(b)(2)(a), EPA's 1999 regional haze regulations include a provision
that States must require certain major stationary sources to procure,
install, and operate BART. This provision covers sources in listed
industrial categories with the potential to emit 250 or more tons per
year of an air pollutant that were ``in existence on August 7, 1977,
but which ha[ve] not been in operation for more than fifteen years as
of such date.'' These sources are considered to be ``BART-eligible.''
\6\ NGS meets these criteria and is a BART-eligible source.\7\
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    \4\ See 42 U.S.C. 7419A(a)(1).
    \5\ See 64 FR 35765 (April 22, 1999).
    \6\ See 40 CFR 51.308(e)(1).
    \7\ See 74 FR 44314 (August 28, 2009); 78 FR 8279 (February 5,
2013); see also 56 FR 50172 (October 3, 1991) addressing BART for
SO2 based on Reasonably Attributable Visibility
Impairment.
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    BART-eligible sources that are reasonably anticipated to cause or
contribute to visibility impairment are ``subject'' to the BART
requirements.\8\ Generally speaking, a BART-eligible source with a
predicted visibility impact of 0.5 deciviews (dv) or more in a Class I
area is considered to ``contribute'' to visibility impairment.\9\ NGS
contributes to visibility impairment at 11 surrounding Class I areas in
excess of this threshold, and is thus subject to BART.
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    \8\ See 70 FR 39104 at 39161 (July 6, 2005).
    \9\ Id.
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    In determining BART, States are required to take into account five
factors identified in the CAA and EPA's regulations.\10\ Those factors
are: (1) The costs of compliance, (2) the energy and non-air quality
environmental impacts of compliance, (3) any pollution control
equipment in use or in existence at the source, (4) the remaining
useful life of the source, and (5) the degree of improvement in
visibility which may reasonably be anticipated to result from the use
of such technology.\11\ EPA's guidelines for evaluating BART provide
more detail and are set forth in Appendix Y to 40 CFR Part 51.
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    \10\ 42 U.S.C. 7491(g)(2) and 40 CFR 51.308(e)(1)(A)(ii)(A).
    \11\ 40 CFR 51.308(e)(1)(ii)(A).
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    In 1998, EPA promulgated the Tribal Authority Rule (TAR) relating
to implementation of CAA programs in Indian country.\12\ In the TAR,
EPA determined that it has the discretionary authority to promulgate
``such federal implementation plan provisions as are necessary or
appropriate to protect air quality'' consistent with CAA sections
301(a) and 301(d)(4) when a tribe has not submitted or EPA has not
approved a Tribal Implementation Plan (TIP).\13\ EPA has previously
promulgated FIPs under the TAR to regulate air pollutants emitted from
NGS.\14\
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    \12\ See 40 CFR part 49; see also 59 FR 43956 (August 25, 1994)
(proposed rule); 63 FR 7254 (February 12, 1998) (final rule);
Arizona Public Service Company v. EPA, 211 F.3d 1280 (D.C. Cir.
2000), cert. den., 532 U.S. 970 (2001) (upholding the TAR).
    \13\ See 40 CFR 49.11(a).
    \14\ See 56 FR 50172 (October 3, 1991). In 1999, EPA proposed a
FIP for NGS to fill the regulatory gap that existed because Arizona
State permits and SIP rules are not applicable or enforceable in the
Navajo Nation, and the Tribe had not sought approval of a TIP
covering the plant. 64 FR 48731 (September 8, 1999). EPA then re-
proposed the FIP with some additional conditions in September 2006.
71 FR 53631 (September 12, 2006). EPA finalized that NGS FIP on
March 5, 2010. 75 FR 10174.
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    Under the CAA, compliance with emission limits determined to be
BART must be achieved as expeditiously as practicable but not later
than 5 years after the effective date of the final BART determination
(See CAA 169A(b)(2)(A) and (g)(4)). As discussed in greater detail in
our Proposed Rule, EPA

recognizes that the circumstances related to NGS create unusual and
significant challenges for a 5-year compliance schedule.\15\ Based on
those challenges and our discretion under the TAR for implementing CAA
requirements in Indian country, we considered other options that are
consistent with the CAA and RHR, and that provide for a more flexible,
extended compliance schedule.
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    \15\ Because of its complicated history and its location on the
Navajo Nation, NGS faces numerous unique complexities and the
unusual requirement to comply with NEPA for lease and other rights-
of-way approvals, which apply only to NGS and Four Corners Power
Plant, the other coal-fired power plant located on the Navajo
Nation. EPA also understands the importance of the continued
operation of NGS and the Kayenta Mine to the Navajo Nation and Hopi
Tribe as a source of direct revenues through lease payments and coal
royalties, as well as the importance of Reclamation's share of NGS
to supply water to many tribes located in Arizona in accordance with
several water settlement acts. EPA also recognizes that Reclamation
may have fewer options compared to the other owners for financing
pollution control or other large capital improvement projects at
NGS. SRP expressed concern that the owners of NGS may choose to
retire the facility if faced with the financial risk of making a
large capital investment within 5 years without also having
certainty that the lease and contract re-negotiations would conclude
in a timely and favorable manner.
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    EPA's BART regulations allow an alternative in lieu of BART,
provided the alternative results in greater reasonable progress than
would have been achieved through installation of BART.\16\ Generally,
an alternative is considered to be approvable provided it results in
greater emissions reductions and the geographic distribution in
emissions from the alternative is not substantially different than the
distribution of the emissions under BART.\17\ For a state that is
subject to the submittal deadlines in the RHR, the regulations provide
that alternatives to BART must ensure that all necessary emission
reductions occur within the period of the first long-term strategy for
regional haze (i.e., by 2018) for states that were required to submit
regional haze SIPs in December 2007.\18\ Thus, if states had submitted
timely regional haze SIPs in 2007 with BART compliance deadlines in
2012, the RHR provided more than 5 additional years for the
implementation of alternatives to BART.
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    \16\ 40 CFR 51.308(e)(2).
    \17\ 40 CFR 51.308(e)(3).
    \18\ 40 CFR 51.308(e)(2)(iii).
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C. Summary of Proposed Rule and Supplemental Proposal

    EPA published an advanced notice of proposed rulemaking (ANPR)
concerning BART for NGS and the Four Corners Power Plant in August
2009.\19\ On February 5, 2013, EPA's proposed BART determination for
NGS was published in the Federal Register and provided a thorough
discussion of the statutory and regulatory framework for addressing
visibility through application of BART for sources located in Indian
country, and of the factual background for our BART determination at
NGS.\20\ The proposal analyzed the five BART factors and proposed to
find that BART for NGS was installation of emissions controls to meet a
NOX emission limit of 0.055 lb/MMBtu based on a rolling
average of 30 boiler operating days (30-BOD average).\21\ However, in
recognition of the important role that NGS and the Kayenta Mine play in
providing employment and revenue to the Navajo Nation and Hopi Tribe,
and the role of Reclamation's share of electricity generated by NGS in
fulfilling water settlement agreements with numerous tribes located in
Arizona, we proposed that the potential economic impacts to tribes
argue for thoughtful consideration of how flexibility in the compliance
timeframe could be provided consistent with the air quality goals of
the CAA.\22\ Therefore, as discussed in our Proposed Rule, EPA proposed
to exercise our authority and discretion under section 301(d)(4) of the
CAA and 40 CFR 49.11(a) to propose an appropriate timeframe for
alternative measures to BART under the RHR for NGS. We provided a
thorough discussion of the legal rationale for setting the compliance
schedule for alternative measures in our Proposed Rule.\23\
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    \19\ See 74 FR 44314 (August 28, 2009).
    \20\ See 78 FR 8274 (February 5, 2013).
    \21\ Id. at 8288.
    \22\ Id. at 8284.
    \23\ Id. at 8289.
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    Our Proposed Rule included a framework for evaluating alternatives
to BART.\24\ As part of the framework, EPA proposed a NOX
emission credit for the previous early and voluntary installation of
low-NOX burners with separated over-fire air (LNB/SOFA) over
the 2009-2011 timeframe (LNB/SOFA credit). We proposed that the LNB/
SOFA credit supported setting a compliance timeframe based on the
flexibility under section 301(d)(4) of the CAA and 40 CFR 49.11(a).\25\
EPA proposed to find that an alternative is ``better than BART'' if the
total emissions over 2009-2044 from the alternative measure, minus the
LNB/SOFA credit, are less than the total emissions under our proposed
BART determination for the same period (i.e., the BART Benchmark).
Consistent with this framework, EPA proposed an alternative to BART,
requiring compliance with an emission limit of 0.055 lb/MMBtu on one
unit per year in 2021, 2022, and 2023 (Alternative 1). We calculated
that total emissions under Alternative 1 over 2009-2044, minus the LNB/
SOFA credit, would be less than emissions based on the BART Benchmark.
Thus, we proposed to find that Alternative 1 was ``better than BART''.
EPA recognized that there may be interest in additional flexibility
beyond the 2021-2023 timeframe. EPA evaluated two additional compliance
schedules but did not propose to approve them as ``better than BART''
alternatives because total emissions over 2009-2044 under these
compliance schedules exceeded the BART Benchmark. However, we noted
that potential technologies or other options for achieving additional
emission reductions could bridge the NOX emission reduction
deficit for alternatives to BART with compliance schedules that do not,
by themselves, meet the BART Benchmark.\26\ We invited stakeholders to
submit additional BART alternatives, consistent with our proposed
framework, for EPA's consideration.
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    \24\ Id. at 8290-92.
    \25\ 78 FR 62509 at 62511 (October 22, 2013).
    \26\ 78 FR 8274 at 8291 (February 5, 2013).
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    On July 26, 2013, a stakeholder group, known as the Technical Work
Group on NGS (TWG), submitted an agreement that had been established
among the seven diverse entities in the TWG. We refer to the July 26,
2013, document as the ``TWG Agreement.'' The TWG is composed of
representatives from Central Arizona Water Conservation District
(CAWCD), the Environmental Defense Fund (EDF), the Gila River Indian
Community (Gila River or the Community), the Navajo Nation (Navajo),
Salt River Project (SRP) on behalf of itself and the other non-federal
owners, DOI, and Western Resource Advocates (WRA). Although EPA
attended the opening session of a ``kick-off'' meeting for the TWG on
March 21, 2013, at which we described our Proposed Rule, EPA did not
otherwise participate in the TWG and was not involved in any of the
discussions leading to submittal of the TWG Agreement.
    Appendix B to the TWG Agreement contained TWG's recommendation for
an alternative to BART. In general, the alternative plan in the TWG
Agreement included closure of one unit at NGS, or curtailment of net
generating capacity by an equivalent amount, in 2019 and compliance
with a NOX emission limit of 0.07 lb/MMBtu on two units at
NGS beginning in 2030. The TWG Agreement

also included a provision requiring the operator of NGS to cease
conventional coal-fired generation at NGS by the end of 2044.
    EPA independently evaluated Appendix B to the TWG Agreement to
determine whether it complied with the framework we put forth in our
Proposed Rule, as well as the statutory and regulatory requirements in
the CAA and the RHR. On October 22, 2013, EPA published a Supplemental
Proposal describing the TWG Agreement and requesting comment.\27\ Our
Supplemental Proposal contained a detailed evaluation of Appendix B to
the TWG Agreement along with a discussion of our legal rationale for
proposing to approve requirements consistent with the TWG Agreement as
meeting the requirements for an alternative to BART. Throughout this
document, we refer to the regulations we proposed in our Supplemental
Proposal that are consistent with Appendix B of the TWG Agreement as
the ``TWG Alternative.'' Thus, in this document, the term TWG
Alternative refers to EPA's independent regulatory requirements for NGS
consistent with the TWG Agreement, rather than to Appendix B of the TWG
Agreement.
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    \27\ See 78 FR 62509 (October 22, 2013).
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    In our Supplemental Proposal, we proposed to revise the numerical
value of the BART Benchmark from our Proposed Rule. We also proposed a
2009-2044 NOX Cap based on the revised numerical value of
the BART Benchmark. In our Proposed Rule, we calculated the BART
Benchmark to be 358,974 tons of NOX. As discussed in our
Supplemental Proposal, we proposed three changes to the BART Benchmark:
(1) Correction of a transcription error; (2) correction of the date
that EPA anticipated would be 5 years following the effective date of
the final rule (i.e., July 1, 2019 instead of January 1, 2018); and (3)
application of the LNB/SOFA credit to the BART Benchmark, rather than
alternatives to BART, to represent emissions under BART if LNB/SOFA had
been installed concurrently with selective catalytic reduction (SCR) to
reduce NOX emissions.\28\ Based on these changes, EPA
proposed a 2009-2044 NOX Cap of 494,899 tons. Although EPA
revised our accounting method for the LNB/SOFA credit in our
Supplemental Proposal, EPA provided a demonstration that the method EPA
used in our Proposed Rule to compare our proposed BART determination
against BART alternatives was equivalent to the method in the
Supplemental Proposal.\29\ The application of the LNB/SOFA credit to
the BART Benchmark in the Supplemental Proposal represented what total
emissions over 2009-2044 would have been under our proposed BART
determination if the operator of NGS had elected to install LNB/SOFA
concurrently with SCR, i.e., within 5 years of a final rule, rather
than in 2009-2011. Calculation of the BART Benchmark and 2009-2044
NOX Cap in this manner is easier to apply and enforce in the
context of a cap in NOX emissions because the LNB/SOFA
credit is built into the BART Benchmark rather than subtracted each
year from actual cumulative emissions.\30\
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    \28\ Id. Tables 1 and 3 at 62515-62516.
    \29\ Id. Table 2 and footnote 32 at 62515.
    \30\ In contrast, in our Proposed Rule, we calculated the BART
Benchmark and emissions under BART alternatives using the actual
early installation dates for LNB/SOFA and then applied the LNB/SOFA
credit to BART alternatives for comparison against the BART
Benchmark. Although this method would have resulted in a lower
numerical value for the 2009-2044 NOX Cap, the LNB/SOFA
credit (representing the early emission reductions achieved over
2009-2018) would have instead been subtracted from the calculations
of cumulative emissions under the BART alternative. Although this is
functionally equivalent to the method used in the Supplemental
Proposal, this method would make annual comparisons of actual
cumulative emissions under the BART alternative against the BART
Benchmark more complicated because it would have required
adjustments every year to total emissions to subtract out the LNB/
SOFA credit. By accounting for the LNB/SOFA credit in the BART
Benchmark, the actual annual emissions from NGS can be directly
compared to the BART Benchmark without any further adjustments.
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    In addition to the enforceable 2009-2044 NOX Cap, our
Supplemental Proposal defines the operating scenarios that would be
required depending on the final outcome of NGS ownership after the
expiration of the current lease term at the end of 2019. In the TWG
Agreement, the owners of NGS committed to maintain emissions from NGS
below the 2009-2044 NOX Cap regardless of post-2019
ownership of NGS and the applicable operating scenario. As a result,
the operating scenarios in the TWG Alternative include specific actions
for achieving emission reductions in 2019 and in 2030. The TWG
Alternative also provides for an operating scenario that is less well-
defined in terms of specific actions but establishes a second
NOX emissions cap over the period of 2009-2029 (2009-2029
NOX Cap) that is equivalent to emission reductions that
would be achieved by a more well-defined operating scenario. The 2009-
2029 NOX Cap would apply in addition to the 2009-2044
NOX Cap. The Supplemental Proposal included requirements for
annual emission reporting to EPA that would also be made publicly
available as part of the compliance demonstration for the TWG
Alternative.

D. Summary of Legal Rationale for Compliance Flexibility

    In our February 5, 2013, proposal for NGS, EPA proposed an
alternative to BART that we referred to as Alternative 1. EPA proposed
to find that consideration of a compliance schedule beyond 2018 for
Alternative 1 at NGS was appropriate for a number of reasons, including
the importance of NGS to numerous Indian tribes located in Arizona and
the federal government's reliance on NGS to meet the requirements of
water settlements with several tribes. Providing this timeframe for
compliance would not, in itself, avoid or mitigate increases in water
rates for tribes located in Arizona; however, it would provide time for
the collaborating federal agencies to explore options to avoid or
minimize potential impacts to tribes, including seeking funding to
cover expenses for the federal portion of pollution control at NGS.
    In developing this framework, EPA proposed to exercise its
authority and discretion under section 301(d)(4) of the CAA, 42 U.S.C.
7601(d)(4) and the TAR, 40 CFR 49.11(a), and proposed an appropriate
timeframe for an alternative measure under the RHR for NGS. EPA
considered this timeframe to be consistent with the general
programmatic requirements. Under the RHR, States and regulated sources
had almost 20 years from the issuance of the rule in 1999 to design and
implement alternative measures to BART. For numerous reasons, including
the myriad stakeholder interests and complex governmental interests
unique to NGS, we are only now addressing the BART requirements for
NGS.
    Our proposal to require emission reductions beyond 2018 was
supported by CAA section 301(d)(4) and the TAR codified at 40 CFR
49.11(a). The TAR reflects EPA's commitment to promulgate ``such
Federal implementation plan provisions as are necessary or appropriate
to protect air quality'' in Indian country where a tribe either does
not submit a Tribal Implementation Plan (TIP) or does not receive
approval of a submitted TIP (emphasis added).
    The use of the term ``provisions as are necessary or appropriate''
indicates EPA's determination that it may only be necessary or
appropriate to promulgate a FIP of limited scope. The United States
Court of Appeals for the Tenth Circuit has previously endorsed the

application of this approach in a challenge to the FIP for the Four
Corners Power Plant, stating: ``[40 CFR 49.11(a)] provides the EPA
discretion to determine what rulemaking is necessary or appropriate to
protect air quality and requires the EPA to promulgate such
rulemaking.'' \31\ The court went on to observe: ``Nothing in section
49.11(a) requires EPA . . . to submit a plan meeting the completeness
criteria of [40 CFR part 51] Appendix V.'' \32\ While the decision in
the Tenth Circuit focused on 40 CFR part 51, Appendix V, EPA believes
the same considerations apply to the promulgation of a FIP intended to
address the objectives set forth in 40 CFR 51.308(e)(2). In particular,
EPA has discretion to determine if and when a FIP addressing the
objectives set forth in 40 CFR 51.308(e)(2) should be promulgated,
which necessarily includes discretion to determine the timing for
complying with the requirements of any such FIP.
---------------------------------------------------------------------------

    \31\ See Ariz. Public Serv. Co. v. EPA, 562 F.3d 1116 (10th Cir.
2009).
    \32\ Id.
---------------------------------------------------------------------------

III. Summary of Final FIP Provisions

    EPA is finalizing our finding that it is necessary or appropriate
to promulgate a source-specific FIP requiring NGS to achieve
NOX emission reductions required by the BART provisions of
the CAA and RHR. EPA is determining that our proposed NOX
emission limit of 0.055 lb/MMBtu, based on our analysis of the relevant
factors, establishes the appropriate BART Benchmark for determining
``better than BART.'' Further, we are finalizing our assessment that
the TWG Alternative, which establishes an enforceable 2009-2044 cap on
NOX emissions from NGS over the life of the facility is
``better than BART.'' Finally, we are finalizing the TWG Alternative as
the FIP requirements for NGS.
    EPA is promulgating four possible operating scenarios under the TWG
Alternative (see Table 1). The operator of NGS must implement one of
the four enforceable operating scenarios in order to comply with the
2009-2044 NOX Cap. The applicable operating scenario will
depend on the outcome of ownership changes related to LADWP, NV Energy,
and Navajo Nation, as well as whether the operator of NGS can increase
capacity (by no more than 189 MW) to accommodate ownership changes,
without triggering New Source Review permitting requirements, as
described in Table 1. Once the ownership outcomes are finalized, the
operator of NGS must implement the applicable Alternative as shown in
Table 1. For example, if LADWP and NV Energy both retire their
ownership shares of NGS and the Navajo Nation does not elect to
purchase an ownership share of NGS, TWG Alternative A1 applies and the
operator of NGS must implement Alternative A1 and may not elect to
implement Alternatives A2, A3, or B. By December 1, 2019, the operator
of NGS must notify EPA of the applicable Alternative (i.e., TWG
Alternative A1, A2, A3, or B).
    In addition to the enforceable 2009-2044 NOX Cap,
Alternatives A1, A2, and A3 each has enforceable emission reduction
measures in 2019 and 2030 (see Table 1). Under Alternative B, in
addition to the enforceable 2009-2044 NOX Cap, the operator
of NGS must also ensure that cumulative NOX emissions over
2009-2029 comply with the 2009-2029 NOX Cap. The 2009-2029
NOX Cap is calculated based on emissions that would have
been emitted over that period under Alternative A1. Under all
Alternatives, if, based on required annual reports submitted by the
operator of NGS to EPA, cumulative emissions of NOX from NGS
exceed the 2009-2044 NOX Cap at any time prior to December
31, 2044, the operator of NGS must permanently cease operation of NGS.
In addition, under Alternative B, if cumulative emissions of
NOX exceed the 2009-2029 NOX Cap prior to 2029,
the operator of NGS must temporarily cease operation of all units at
NGS.\33\ Under all Alternatives, the operator must permanently cease
operation of all units at NGS by December 22, 2044.
---------------------------------------------------------------------------

    \33\ The combination of the 2009-2044 and 2009-2029
NOX Caps under TWG Alternative B means that if NGS
exceeds the 2009-2029 NOX Cap prior to 2029 it must cease
operation, but the operator may re-start operation after 2030 as
long as cumulative emissions have not yet exceeded the 2009-2044
NOX Cap.
---------------------------------------------------------------------------

    Under all TWG Alternatives, the operator of NGS must report to EPA
annual emissions and heat input data and must make this information
publicly available on its Web site. In addition, under TWG Alternative
B, the operator must also submit to EPA annual Emission Reduction Plans
projecting year-by-year emissions covering the 2020-2029 and 2030-2044
periods so that there is a plan for operation of NGS that ensures that
cumulative emissions of NOX do not exceed the 2009-2029
NOX Cap and the 2009-2044 NOX Cap. Although year-
by-year emissions projected in the annual Emission Reduction Plans are
not enforceable (i.e., emissions in a given year are not required to
match projections for that year in an Emission Reduction Plan), the
requirement to submit Emission Reduction Plans is enforceable, and
provides the operator with a framework for planning for future
emissions reductions. The requirement also provides EPA and the public
the opportunity to monitor and evaluate progress of emission reductions
under TWG Alternative B.

                   Table 1--Summary of the Major Regulatory Provisions of the TWG Alternative
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
Applicability
    (Step 1)....................   If LADWP and NV Energy both exit NGS without        If LADWP
                                   selling their ownership interests (i.e., retire shares),    or NV Energy
                                   or both exit by selling to an existing NGS participant;     sells to a 3rd
                                   or one retires shares and the other sells to an existing    party, or does
                                   NGS participant; and                                        not exit NGS;
                                 ------------------------------------------------------------
    (Step 2)....................   If Navajo   If Navajo   If Navajo   n/a.
                                   Nation does not     Nation purchases    Nation purchases
                                   purchase            up to 170 MW by     up to 170 MW by
                                   ownership share     12/31/19; and       12/31/19; and
                                   by 12/31/19;
    (Step 3)....................   n/a......   If          If          n/a.
                                                       Participants        Participants
                                                       increase capacity   cannot increase
                                                       without             capacity without
                                                       triggering permit   triggering
                                                       requirements;       permitting);
Applicable Alternative..........  Then TWG            Then TWG            Then TWG            Then TWG
                                   Alternative A1      Alternative A2      Alternative A3      Alternative B
                                   applies.            applies.            applies.            applies.
                                 -------------------------------------------------------------------------------
Applicable Requirements.........   Comply with 2009-2044 NOX Cap of 494,899 tons.
                                   Permanently cease operation of all units if cumulative emissions
                                   before 2044 exceed 2009-2044 NOX Cap.

                                   Permanently cease conventional coal-fired electricity generation by
                                   December 22, 2044.
                                 -------------------------------------------------------------------------------
Additional Emission Cap.........   n/a                                                 Comply
                                                                                with 2009-2029
                                                                                NOX Cap of
                                                                                416,865 tons.
                                 ------------------------------------------------------------
Specific Requirements *.........   By 12/31/   By 12/31/   By 12/31/
                                   19 permanently      19 permanently      19 reduce net       Temporarily cease
                                   close 1 unit.       close 1 unit.       generating          operation if
                                                                           capacity by no      cumulative
                                                                           less than 561 MW.   emissions before
                                                                                2029 exceed 2009-
                                                                                2029 NOX Cap.
                                   By 12/31/   By 12/31/   By 12/31/
                                   30 meet NOX limit   19 operator may     30 meet NOX limit
                                   of 0.07 lb/MMBtu    increase capacity   of 0.07 lb/MMBtu
                                   on 2 units.         by no more than     on 2 units.
                                                       189 MW.
                                                       By 12/31/
                                                       30 meet 0.07 lb/
                                                       MMBtu on 2 units.
                                 -------------------------------------------------------------------------------
Reporting.......................   By December 1, 2019, notify EPA of applicable Alternative (A1, A2,
                                   A3, or B).
                                   Submit annual report summarizing heat input and annual and cumulative
                                   emissions of NOX.
                                   Make annual report publicly available on Web Site.
                                   Submit application to revise Part 71 Operating Permit by December 31,
                                   2020.
                                 -------------------------------------------------------------------------------
Additional Reporting............   n/a                                                 By 12/31/
                                                                                19 and annually
                                                                                thereafter submit
                                                                                Emission
                                                                                Reduction Plans
                                                                                to project year-
                                                                                by-year emissions
                                                                                to assure
                                                                                compliance with
                                                                                NOX Caps.
----------------------------------------------------------------------------------------------------------------
* All units must comply with the existing NOX emission limit of 0.24 lb/MMBtu established in a 2008 permitting
  action. See discussion in Proposed Rule at 78 FR 8284 (February 5, 2013). This limit applies to each unit
  unless otherwise stated.

    In our final rule, EPA has included several revisions to the
proposed regulatory text (40 CFR 49.5513(j)) put forth in the
Supplemental Proposal. The substantive revisions include:
    1. Revision to Sec.  49.5513(j)(3) to clarify that EPA is
finalizing a ``better than BART'' Alternative;
    2. Additions to Sec.  49.5513(j)(3) to specify that the operator
must temporarily cease operation of NGS if cumulative emissions of
NOX exceed the 2009-2029 NOX Cap of 416,865 tons
at any time prior to December 31, 2029 (under Alternative B), and must
permanently cease operation of NGS if cumulative emissions of
NOX exceed the 2009-2044 NOX Cap of 494,899 tons
at any time prior to December 31, 2044 (under all Alternatives);
    3. Additions to Sec.  49.5513(j)(3)(i)(A)(2), (B)(3), and (C)(2),
to specify that the NOX emission limit of 0.07 lb/MMBtu is
to be calculated based on a rolling average basis of 30 boiler
operating days;
    4. Correction to Sec.  49.5513(j)(3)(ii)(D), to specify that
Alternative B shall also apply if either of the Departing Participants
(i.e., LADWP or NV Energy) remains as a participant in NGS;
    5. Addition of Sec.  49.5513(j)(3)(iii), consistent with the TWG
Agreement, to require the owners of NGS to cease its operation of
conventional coal-fired generation at NGS no later than December 22,
2044;\34\
---------------------------------------------------------------------------

    \34\ See page 14 of the TWG Agreement (section IV.F). This
section of the TWG Agreement also states that ``[a]t its election,
consistent with the Lease Amendment, the Navajo Nation may continue
plant operations at NGS after December 22, 2044 consistent with EPA
approval.'' EPA is not including this provision into the regulatory
requirements at Sec.  49.5513(j)(3)(iii), however, EPA expects that
NGS would be substantially modified if the Navajo Nation elects to
continue operation of the facility after NGS ceases conventional
coal-fired generation in 2044, and that NGS must then meet all
applicable regulatory and permitting requirements in existence at
that time.
---------------------------------------------------------------------------

    6. Addition to Sec.  49.5513(j)(4)(ii), to change the annual
reporting date to begin in 2015 instead of the specific date of January
31, 2015, and specify that the report must be submitted to EPA and also
made publicly-available within 30 days of the submittal deadline
associated with the annual emission inventory required by the Part 71
Operating Permit for NGS;
    7. Addition to Sec.  49.5513(j)(4)(iii), to clarify that the Part
71 Operating Permit for NGS shall incorporate practically enforceable
limits for NOX of 0.24 lb/MMBtu, on a 30[hyphen]day rolling
average basis, for each Unit equipped with LNB/SOFA, and 0.07 lb/MMBtu,
on a rolling average basis of 30 boiler operating days, for each Unit
equipped with SCR, as federally enforceable permit conditions; and
    8. Addition of Sec.  49.5513(j)(4)(iv)(C), to specify that the
requirement to submit annual Emission Reduction Plans beginning no
later than December 31, 2019, must be incorporated into the Part 71
Operating Permit for NGS as a federally enforceable permit condition.
    9. Revision to Sec.  49.5513(j)(7) to require the owner or operator
of NGS to maintain records that document compliance with the
NOX Cap (e.g., daily emissions and heat input data) for the
life of the facility, rather than at least five years.
    10. Deletion of Sec.  49.5513(j)(7)(vi) that required record-
keeping of all major maintenance activities conducted on emission
units, air pollution control equipment, and CEMS because record-keeping
of maintenance activities are not needed to ensure compliance with the
2009-2029 and 2009-2044 NOX Caps.
    11. Revision to Sec.  49.5513(j)(11) to state that the affirmative
defense provisions of paragraphs Sec.  49.5513 (c)(2) and Sec.
49.5513(i) do not apply to paragraph Sec.  49.5513(j).\35\
---------------------------------------------------------------------------

    \35\ We note that in our Supplemental Proposal, we reported the
affirmative defense provisions as paragraphs (c)(1) and (g)(3) in
error. The correct citations are to paragraph (c)(2) and paragraph
(i) of 40 CFR 49.5513.
---------------------------------------------------------------------------

    Revision (1) above is necessary to clarify that EPA is finalizing a
``better than BART'' alternative in lieu of BART.

The BART Benchmark used to assess the ``better than BART'' alternative
is based on our proposed BART determination for NGS, and the ``better
than BART'' alternative is consistent with our Supplemental Proposal of
the TWG Alternative. Revision (3) above is necessary because EPA
inadvertently did not specify the averaging period associated with the
emission limits for NOX in our Supplemental Proposal.
Revisions (2) and (4) through (10) above are in response to comments
submitted to EPA on our Supplemental Proposal. Revision (11) above
amends a proposed provision in our Supplemental Proposal that limited
the applicability of the existing affirmative defense provisions for
startups, shutdowns, and malfunctions (from the previous FIP for NGS
codified at 40 CFR 49.5513(c)(2) and 40 CFR 49.5513(i)) to
malfunctions.\36\ In this Final Action, we are revising (j)(11) to make
clear that the existing affirmative defense provisions do not apply to
the emission limits established in the TWG Alternative.
---------------------------------------------------------------------------

    \36\ See final action for the previous FIP for NGS at 75 FR
10179 (March 5, 2010).
---------------------------------------------------------------------------

    Following the close of the public comment period, the United States
Court of Appeals for the DC Circuit issued a decision concerning
various aspects of the NESHAP for Portland cement plants issued by EPA
in 2013, including the affirmative defense provision of that rule.\37\
The court found that EPA lacked authority to establish an affirmative
defense for private civil suits and held that under the CAA, the
authority to determine civil penalty amounts lies exclusively with the
courts, not EPA. The court did not address whether such an affirmative
defense provision could be properly included in a SIP. However, the
court's holding makes it clear that the CAA does not authorize
promulgation of such a provision by EPA. In particular, the court's
decision turned on an analysis of CAA sections 113 (Federal
enforcement) and 304 (Citizen suits). These provisions apply with equal
force to a civil action brought to enforce the provisions of a FIP. The
logic of the court's decision thus applies to the promulgation of a FIP
and precludes EPA from including an affirmative defense provision in a
FIP. Therefore, we are not including an affirmative defense provision
in the final FIP.
---------------------------------------------------------------------------

    \37\ NRDC v. EPA, 2014 U.S. App. LEXIS 7281 (D.C. Cir.), in the
docket for this rulemaking.
---------------------------------------------------------------------------

    We note that, if a source is unable to comply with emission
standards as a result of a malfunction, EPA may use case-by-case
enforcement discretion, as appropriate. Further, as the DC Circuit
recognized, in an EPA or citizen enforcement action the court has the
discretion to consider any defense raised and determine whether
penalties are appropriate.\38\
---------------------------------------------------------------------------

    \38\ Id. at 24 (arguments that violations were caused by
unavoidable technology failure can be made to the courts in future
civil cases when the issue arises).
---------------------------------------------------------------------------

IV. Summary of Major Issues Raised by Commenters

    The public comment period for our Proposed Rule opened on February
5, 2013. On two occasions, we extended the comment period on our
Proposed Rule at the request of stakeholders, with a final closing date
of January 6, 2014. Although we posted the pre-publication version of
our Supplemental Proposal to the docket and to our Web site on
September 25, 2013, the public comment period for the Supplemental
Proposal officially began when it was published in the Federal Register
on October 22, 2013.\39\ We accepted public comments on our
Supplemental Proposal, concurrently with our Proposed Rule, until
January 6, 2014. Our Supplemental Proposal also included notice of five
public hearings, one on the Navajo Nation, one on the Hopi reservation
and three in the State of Arizona. The public hearings occurred during
the week of November 12, 2013. In all, 194 oral testimonies were
presented at the public hearings.
---------------------------------------------------------------------------

    \39\ See document number 0182 (Pre-publication version of
Supplemental Proposal for NGS Signed on September 25, 2013), posted
to docket on September 25, 2013 and publication of Supplemental
Proposal in Federal Register at 78 FR 62509 (October 22, 2013).
---------------------------------------------------------------------------

    We received over 77,000 written comments. Of these, over 76,800
comments came from private individuals who submitted substantially
similar comments by email or postcard. We received an additional 300
unique written comments (not including duplicates, requests for
extension of the public comment period, or requests for additional
hearings) from a variety of individuals and entities, including tribal
governments, environmental or public interest advocacy groups, water
interest groups, groups representing industry or commerce, the operator
and participants in NGS and the Kayenta Mine, elected officials, and
state and local governments.
    In this document, EPA is providing an abbreviated summary of the
major comments and EPA's responses to those comments, grouped together
by subject matter. The complete response to comments document (RTC)
includes the full summary of all substantive comments and EPA's full
responses to those comments. The RTC is included in the docket for this
rulemaking.\40\ We are not responding to comments unrelated to our
Proposed Rule or Supplemental Proposal for NGS in this document or in
the RTC.
---------------------------------------------------------------------------

    \40\ See document titled ``EPA Responses to Comments on Final
Rule for NGS'' in the docket for this rule.
---------------------------------------------------------------------------

A. General Comments From Public Hearings

    Comment: Contribution of NGS to the local and state economy and
support for TWG Alternative
    Many commenters at the public hearings preferred the TWG
Alternative because they believe that EPA's proposed BART determination
would force NGS and the Kayenta Mine to close, causing economic harm to
an area where the majority of residents are low-income and where
opportunities for employment are limited. Many commenters stressed that
NGS employs over 500 people and the Kayenta Mine has over 400
employees, and the loss of these jobs would only exacerbate the
unemployment rate in the area, which currently ranges from 47 percent
to 60 percent.
    A number of commenters noted that NGS supplies more than 90 percent
of the energy used by Central Arizona Water Conservation District
(CAWCD), which operates the Central Arizona Project (CAP), which
transfers water from the Colorado River throughout Arizona. A few
commenters urged EPA to uphold its federal trust obligations and ensure
that tribal communities continue to have access to affordable water,
and advised EPA to make a decision consistent with the legal rights
that the Gila River Indian Community and other stakeholders negotiated
and that Congress granted under the Arizona Water Settlements Act of
2004.
    A few commenters support the TWG Alternative because they believe
it is a fair compromise created by a diverse group of stakeholders that
provides a path for future operation at NGS by allowing for potential
ownership changes and by providing an extension to install SCR
technology, while still ensuring that the total emission reductions of
NOX will be greater than those achieved under EPA's proposed
BART determination.
    Response: EPA recognizes the contribution of NGS and the Kayenta
Mine to the economy of the Navajo Nation, the Hopi Tribe, the city of
Page, and the state of Arizona. In our Proposed Rule, EPA discussed the
history of NGS and the relationship between NGS, the Central Arizona
Project, and numerous tribes located in

Arizona.\41\ EPA notes that NGS is a facility that is subject to the
BART requirement of the RHR, and emissions from NGS affect visibility
at 11 national parks and wilderness areas in the Southwest. The
analyses in our Proposed Rule and Supplemental Proposal determined that
additional controls at NGS are cost-effective, will significantly
reduce the contribution of NGS to visibility impairment at numerous
Class I areas, and should not cause NGS to retire. However, for a
number of reasons, including the importance of NGS to numerous Indian
tribes located in Arizona and the federal government's reliance on NGS
to meet the requirements of water settlements with several tribes, EPA
also outlined a framework for considering ``better than BART''
alternatives that ensures emission reductions while providing
additional flexibility to the operator of NGS.\42\
---------------------------------------------------------------------------

    \41\ See 78 FR 8274, at 8275 (February 5, 2013).
    \42\ Id. and 78 FR 62509 (October 22, 2013).
---------------------------------------------------------------------------

    EPA agrees with comments that the TWG Agreement represents a
compromise between diverse stakeholders, although we recognize that the
members of the TWG did not invite all affected stakeholders to
participate in their discussions. The TWG Alternative provides
certainty for future operation of NGS, flexibility in the compliance
timeframe, and more emission reductions of NOX than would
have been achieved under EPA's proposed BART determination. Based on
our analysis in our Supplemental Proposal and consideration of all
comments received, EPA is taking action to finalize requirements
consistent with the TWG Agreement we put forth in our Supplemental
Proposal, i.e., the TWG Alternative.
    Comment: Impact of air pollutants from NGS on public health and
welfare and support for proposed BART determination.
    Several commenters favor EPA's proposed BART determination for NGS
because they believe that emissions from NGS cause health problems in
the area, including respiratory illness and heart disease. One
commenter cited a Clean Air Task Force study which states that NGS is
responsible for approximately $127 million in health costs every year.
Many of these commenters urged EPA to conduct health studies to
determine the actual impact to health in these communities.
    Some commenters favor stringent controls because they believe that
emissions from NGS adversely affect native plant species and harm
traditional dry land farming. Others assert that emissions from NGS can
be linked to high levels of mercury found in fish species located in
nearby lakes. Many commenters expressed concerns over the well-being of
the Navajo Aquifer. A number of commenters favor stringent controls
because they believe that emissions produced from NGS contribute to
climate change.
    In contrast, a few commenters questioned the extent to which
emissions from NGS impact public health and the environment, asserting
that the haze is a result of emissions from natural sources (e.g.,
volcanoes, wind/dust storms, and forest fires) and pollution produced
from nearby cities (i.e., Phoenix, Los Angeles, and Las Vegas). Another
commenter asserted that EPA's Web site states that vehicles are the
largest producers of NOX emissions in the country and
concludes that EPA is ignoring mobile sources and unfairly targeting
stationary sources.
    Some commenters preferred EPA's proposed BART determination over
the TWG Alternative because they believe that the alternative is based
on a false premise. They asserted that the closure of a single unit is
not equivalent to cleaning up all three units because the reduction in
capacity will ultimately require new electricity generation elsewhere
because the demand for power does not change.
    Response: Protection of human health and the environment is EPA's
mission and forms the basis for many Agency actions, including
establishing the National Ambient Air Quality Standards (NAAQS), and
promulgation of regulations such as the New Source Performance
Standards (NSPS) and the National Emission Standards for Hazardous Air
Pollutants (NESHAP). In addition to Clean Air Act requirements to
protect human health, in the 1977 Clean Air Act Amendments, Congress
declared as a national goal the prevention of any future, and the
remedying of any existing, impairment of visibility in mandatory class
I Federal areas which impairment results from manmade air pollution
(See CAA Sec.  169A).
    EPA agrees that visibility-impairing pollutants are among the same
pollutants that affect human and ecosystem health; however, health
studies are beyond the scope of this BART analysis. Similarly,
hazardous air pollutants (HAPs), such as mercury, are not visibility-
impairing pollutants and therefore are beyond the scope of this BART
analysis.\43\
---------------------------------------------------------------------------

    \43\ Emissions of HAPs from various source categories are
addressed generally through the NESHAP. EPA addressed mercury
emissions from power plants specifically in the final Mercury and
Air Toxics Standard (MATS). 77 FR 9304 (February 16, 2012).
---------------------------------------------------------------------------

    EPA agrees that climate change is an important issue.\44\ However,
the RHR addresses pollutants that impair visibility and is not intended
to address pollutants that contribute to climate change. EPA has
developed various programs and activities to address emissions of
greenhouse gases.\45\ On June 2, 2014, EPA signed a proposal to cut
greenhouse gas emissions from coal-fired power plants by up to 30
percent by 2030.\46\ Although regulation of greenhouse gases is
conducted under separate statutory requirements from regional haze, EPA
is mindful that this BART determination for NGS is not the only
regulatory program that affects this facility and the region.
---------------------------------------------------------------------------

    \44\ http://www.epa.gov/climatechange/basics/.
    \45\ http://www.epa.gov/climatechange/EPAactivities.html.
    \46\ See http://www2.epa.gov/carbon-pollution-standards.
---------------------------------------------------------------------------

    EPA agrees with comments that mining and combustion of coal affect
the environment. EPA notes that Reclamation has started its process to
develop an Environmental Impact Statement (EIS) required under the
National Environmental Protection Act (NEPA) for activities resulting
from the continued operation of NGS and the Kayenta Mine.\47\ The on-
going NEPA process provides numerous opportunities and the appropriate
forum to raise concerns related to the impacts of mining and use of
water from the Navajo Aquifer. We further note that representatives of
DOI attended all the public hearings on NGS held by EPA and are aware
of the issues raised by commenters during the BART process regarding
mining and the Navajo Aquifer.
---------------------------------------------------------------------------

    \47\ For more information, please see www.ngskmc-eis.net.
---------------------------------------------------------------------------

    EPA disagrees with the assertion that EPA is unfairly targeting
stationary sources of emissions and ignoring the significant
contribution of motor vehicle emissions. Consistent with title II of
the CAA, the EPA Office of Transportation and Air Quality protects
public health and air quality by, among other things, regulating air
pollution from motor vehicles, engines, and the fuels to operate
them.\48\ New cars and sport utility vehicles sold today have emission
levels of hydrocarbons, NOX, and carbon monoxide that are
98-99 percent lower than new vehicles sold in the 1960s on a per mile
basis.\49\ Similarly, standards established for heavy-duty highway and
non-road

sources require emission rate reductions on the order of 90 percent or
more for particulate matter and NOX. In 2014, EPA finalized
new vehicle emission standards and reduced the fuel sulfur content of
gasoline to achieve additional reductions in tailpipe and evaporative
emissions from passenger cars, light-duty vehicles, medium-duty
passenger cars, and some heavy-duty vehicles starting in 2017.\50\
---------------------------------------------------------------------------

    \48\ http://www.epa.gov/otaq/.
    \49\ See, e.g., 76 FR 74854, at 74900 (December 1, 2011).
    \50\ See Fact Sheet for Tier 3 Standards available at http://www.epa.gov/otaq/documents/tier3/420f14010.pdf.
---------------------------------------------------------------------------

    EPA agrees that forest fires and volcanic eruptions, when they
occur, can impact visibility to a greater extent than anthropogenic
sources of emissions. However, Congress directed EPA to develop rules
to address on-going emissions from stationary sources subject to BART
to remedy the existing impairment of visibility in Class I areas and
restore visibility to natural conditions.
    EPA disagrees with assertions that the TWG Alternative is based on
a false premise because the closure or curtailment of one unit would
just result in electricity being produced elsewhere. Closure of one
unit at NGS or the curtailment of an equivalent amount of electricity
generation is possible based on LADWP and NV Energy's intended
divestiture from NGS. Consistent with state law in California and
Nevada, additional electricity needed to replace lost generation from
NGS, associated with LADWP and NV Energy's divestiture, would come from
energy sources that emit less air pollution than a conventional coal-
fired power plant operating with SCR on all units.\51\
---------------------------------------------------------------------------

    \51\ See RTC and references therein.
---------------------------------------------------------------------------

    Comments regarding specific aspects of the TWG Alternative are
discussed in Section 9.0 of the RTC.
    Comment: Environmental and Social Justice.
    Several commenters consider the presence of NGS and several other
power plants in and around the Navajo Nation to represent an
environmental and economic justice issue. One commenter noted that a
Navajo water hauler in Kaibeto, a Navajo community near Page, pays 10
to 20 times more for water, or $13,000 per acre foot, than municipal
CAP water users in Glendale or a farmer in Tempe, who pay $551 and $41
per acre feet, respectively.
    Several commenters opined that the leaders of the Navajo Nation and
EPA have not protected the interests of the local population. A few
expressed concerns over how the alternatives were written, noting that
many tribal residents do not understand the technical language used in
the documents and therefore cannot adequately comment on the validity
of the alternatives proposed. Some commenters argued that pollution can
be controlled using existing technology and EPA should apply the same
standard to NGS as other coal-burning power plants (e.g., Four Corners
Power Plant). A few commenters argued that extending the compliance
timeframe for NGS demonstrates that the federal government considers
itself exempt from federal law. Several argued that tribal communities
do not have the funds to develop proposals and/or conduct environmental
assessments and urged that EPA uphold federal trust responsibilities
and create an equal playing field.
    Response: EPA defines Environmental Justice as ``the fair treatment
and meaningful involvement of all people regardless of race, color,
national origin, or income with respect to the development,
implementation, and enforcement of environmental laws, regulations, and
policies. EPA has this goal for all communities and persons across the
country. It will be achieved when everyone enjoys the same degree of
protection from environmental and health hazards and equal access to
the decision-making process to have a healthy environment in which to
live, learn, and work.'' \52\
---------------------------------------------------------------------------

    \52\ http://www.epa.gov/environmentaljustice/.
---------------------------------------------------------------------------

    EPA takes fair treatment and meaningful involvement seriously and
provided numerous opportunities for tribal governments, environmental
and tribal non-governmental organizations, and other interested
stakeholders to provide input in the development of our Proposed Rule,
Supplemental Proposal, and Final Rule for NGS. EPA began our public
involvement process for a BART determination for NGS in 2009, when we
published an Advanced Notice of Proposed Rulemaking (ANPR). Although we
initially provided a 30-day public comment period, at the request of
tribal governments and other interested stakeholders, we extended the
comment period for tribes another 30 days to October 28, 2009 and, to
allow additional time for government-to-government consultation on NGS,
agreed to accept comments from tribes until March 1, 2010.
    EPA received over 6,000 comments on the ANPR.\53\ During 2009
through 2012, EPA met with various stakeholders, including tribal
governments and tribal environmental groups, to discuss NGS and hear
concerns related to a BART determination for this facility.\54\ We
initially provided a 90-day comment period for the Proposed Rule on
February 5, 2013, and at the request of various stakeholders, we
provided several extensions of the public comment period, which closed
on January 6, 2014. During the 11-month comment period, EPA continued
to meet with stakeholders, at their request, to discuss our proposed
BART determination for NGS and our framework for ``better than BART''
alternatives.\55\
---------------------------------------------------------------------------

    \53\ See page 25 of the TSD to the February 5, 2013 Proposed
Rule.
    \54\ See, for example document number 0232 in the ANPR docket at
EPA-R09-OAR-2009-0598, and document numbers 0008 and 0009 in the
docket for this rule.
    \55\ See, for example, document number 0150, 0152, 0166, 0173,
0302, and 0303 in the docket for this rule.
---------------------------------------------------------------------------

    On July 26, 2013, the TWG submitted Appendix B to the TWG Agreement
to EPA for consideration. EPA posted the TWG Agreement to our docket on
the same day to provide the public an opportunity to review it.\56\ On
September 25, 2013, EPA posted our Supplemental Proposal, along with
supporting documents, to the docket to allow for pre-publication review
by interested parties.\57\ The Supplemental Proposal was published in
the Federal Register on October 22, 2013. The comment period for the
Supplemental Proposal closed on the same day as the BART proposal, on
January 6, 2014. The Supplemental Proposal also included notice of five
open house and public hearing events EPA scheduled throughout Arizona
in November 2013. The open houses allowed members of the public an
opportunity to talk with representatives from EPA and ask questions.
EPA held events at the LeChee Chapter House, located on the Navajo
Nation, as well as in Page, Arizona, and provided oral interpretation
services between English and Din[eacute] (the Navajo language). EPA
also held an event at the Hopi Day School, located in Kykotsmovi, the
seat of the Hopi tribal government.\58\ Finally, we also held events in
Phoenix and in Tucson, Arizona, to allow stakeholders in central and
southern Arizona, representing CAP water interests and several tribes
receiving CAP water, the opportunity to provide comment and talk with
representatives from EPA. Although EPA understands that the TSD

and Federal Register notices include technical information that may be
difficult to understand, EPA provided Fact Sheets and handouts, written
in plain language, at the open house and public hearing events.\59\ EPA
representatives were also present at the events to discuss and explain
our Proposals. EPA recognizes that many tribal communities do not have
the funds to develop alternative proposals or hire experts on their
behalf; however, this does not diminish such communities' ability to
participate in the rulemaking process in a meaningful way as EPA takes
seriously its responsibility to explain its proposal to all interested
parties and assesses all comments, regardless of the form of the
comment or whether or not the commenter has a technical background.
---------------------------------------------------------------------------

    \56\ See document number 0122 in docket for this rule.
    \57\ See document numbers 0182, 0183, and 0184 in the docket for
this rule.
    \58\ EPA engaged with the government of the Hopi Tribe to search
for an oral interpreter between English and the Hopi language, but
the Hopi Tribe was unable to locate anyone to provide those
services.
    \59\ See document 0219 in the docket for this rule.
---------------------------------------------------------------------------

    As stated in our Proposed Rule and Supplemental Proposal, EPA has
determined that these proposed rules, if finalized, will not have
disproportionately high and adverse human health or environmental
effects on minority or low-income populations because they increase the
level of environmental protection for all affected populations (i.e.,
require emission reductions from NGS).\60\ EPA recognizes that some
commenters may view the timeframe for compliance under EPA's framework
for BART Alternatives as an environmental justice issue. We note that
the LNB/SOFA credit, an important component of the extended timeframe,
was based on real, actual emission reductions beginning in 2009 that
were voluntary and not required by any rule or regulation. We also note
that the TWG Alternative, which calls for closure of one unit in 2019
(or equivalent curtailment) will result not only in greater reductions
of NOX than would have been achieved under BART, but also
reductions of several other pollutants, including SO2, PM,
CO2, and mercury. Thus, although the TWG Alternative
includes a compliance timeframe for achieving additional reductions in
2030, over 2009-2044, the TWG Alternative will result in reductions of
additional pollutants that affect visibility or human health, and will
provide an enforceable mechanism to ensure that NGS ceases conventional
coal-fired electricity generation at NGS by the end of 2044.
---------------------------------------------------------------------------

    \60\ See discussions under Executive Order 12898 in 78 FR 8793
(February 5, 2013) and 78 FR 62520 (October 22, 2013).
---------------------------------------------------------------------------

    EPA recognizes that numerous commenters expressed frustration
regarding social inequities related to costs and benefits of coal
mining and combustion and water availability and cost. We recommend
participating in the EIS process for NGS and Kayenta Mine to raise any
concerns related to costs, benefits, and the environmental and social
justice of coal mining and coal combustion at the Kayenta Mine and NGS.

B. Comments on Factor 1--Cost of Controls

    Comment: EPA underestimated SCR costs.
    Several commenters asserted that EPA underestimated the cost of
compliance by improperly reworking cost estimates developed for SRP by
Sargent and Lundy (S&L) in 2010 and disregarding real costs that would
be incurred. One commenter quoted the BART Guidelines and the final RHR
to assert that although the use of the Control Cost Manual is
encouraged, it is not mandated, and that EPA has discretion to use
additional sources of cost information. The commenter believes,
therefore, that the SRP estimates for the excluded cost items are
appropriate to use because they are more precise than the generic
statements that EPA relied upon in the Control Cost Manual.
    Response: EPA disagrees with the comment that we improperly
reworked and underestimated the SCR cost estimates. We note, however,
that even if we had relied only on the cost estimate provided by SRP,
EPA still would have concluded that SCR is cost-effective at NGS.
    EPA used a hybrid approach for our cost analysis that relied
primarily on the cost estimates provided by SRP, but also followed the
BART Guidelines to determine whether S&L included cost estimates for
services or equipment associated with SCR that were not allowed under
the EPA Control Cost Manual. The BART guidelines state ``[i]n order to
maintain and improve consistency, cost estimates should be based on the
OAQPS Control Cost Manual, where possible''.\61\ The capital cost
estimate EPA presented in the proposed rulemaking for SCR plus LNB/SOFA
($541 million total for Units 1-3) is only 8 percent lower than the SRP
cost estimate ($589 million). SRP's cost estimate would not have
changed our conclusion that SCR is cost-effective at NGS.
---------------------------------------------------------------------------

    \61\ The OAQPS Control Cost Manual is now referred to as the EPA
Control Cost Manual.
---------------------------------------------------------------------------

    As discussed in the TSD to the proposed rulemaking, EPA made four
adjustments to SRP's cost estimates for SCR, namely, to exclude
``Owners Construction Management, O&M Support and Contract Service,''
``Owners Legal Support and Insurance,'' and ``Allowance for Funds Used
During Construction,'' and to use an interest rate of 7 percent.\62\
Our detailed, line-by-line analysis was included in the docket for this
proposed rulemaking and provided an explanation for why we retained,
modified, or rejected each line item.\63\ Please see the RTC for
additional discussion of these four adjustments to the S&L cost
analysis.
---------------------------------------------------------------------------

    \62\ See Table 12 of the TSD to the February 5, 2013 Proposed
Rulemaking, available as document number 0014 in the docket for this
rule.
    \63\ See MS Excel document titled ``EPA cost analysis for NGS''
within document number 0004 in the docket for this rule.
---------------------------------------------------------------------------

    In our proposed rule, we presented total capital and total annual
cost estimates from EPA and SRP, as well as average and incremental
cost-effectiveness values based on EPA and SRP assumptions for total
annual cost and total annual NOX reductions. Based on SRP's
analysis, average cost-effectiveness of SCR+LNB/SOFA at NGS was less
than $3,000 per ton and incremental cost-effectiveness of SCR+LNB/SOFA
(compared to SNCR+LNB/SOFA) was approximately $5,300 per ton.\64\ EPA
stated that the cost-effectiveness values calculated by both EPA and
SRP for SCR+LNB/SOFA are lower than or within the range of other BART
evaluations where EPA or a state has determined that SCR is BART
(ranging from approximately $2,000 to $6,000 per ton). EPA has
accordingly determined that SCR is cost-effective at NGS.\65\
Therefore, even if EPA accepted the S&L cost estimates submitted by
SRP, as commenters suggest, EPA would still have determined that SCR is
cost-effective for NGS.
---------------------------------------------------------------------------

    \64\ See Table 3 of our Proposed Rule, 78 FR 8281 (February 5,
2013).
    \65\ See our Proposed Rule at 78 FR 8281 (February 5, 2013).
---------------------------------------------------------------------------

    Comment: EPA overestimated SCR costs.
    One commenter asserted that EPA overestimated the cost of
installing SCR at NGS. Although the commenter supported EPA's
adjustments to the S&L cost estimates, the commenter asserted that
further revisions are appropriate. The commenter stated that EPA
overestimated the following costs: Outage costs associated with
installation and ``preinstallation'' work; catalyst costs; and
auxiliary power. In addition, the commenter asserted that EPA
overestimated annual costs by assuming 20 years as the basis for
amortizing costs and using an inflated interest rate of 7 percent.
    Although the commenter concurs with EPA's conclusion that SCR plus
LNB/SOFA is cost-effective at $2,240

per ton of NOX removed, the commenter re-calculated cost-
effectiveness to be $1,412 per ton for Unit 1, $1,331 per ton for Unit
2, and $1,497 per ton for Unit 3.
    Response: EPA disagrees with the commenter that any revisions to
EPA's estimate of SCR costs are necessary. Even if some of the costs
projected by S&L and used by EPA may be overestimated (e.g., the
commenter points primarily to capital recovery, catalyst replacement
costs, and costs for lost power generation), EPA disagrees that we must
correct every issue of concern raised by the commenters in order to
support our determination of the BART Benchmark. EPA made four specific
corrections to the estimates provided by S&L and SRP to make the cost
calculation methodology consistent with methodologies used for BART
cost calculations nationally.\66\ As noted in other responses even if
we consider the average and incremental cost effectiveness of SCR using
SRP and S&L's full cost projections, EPA would still determine that SCR
at NGS is cost-effective. The cost-effectiveness values cited by the
commenter, below $1,500 per ton, certainly suggest that SCR could be
even more cost-effective than the values we relied upon in our
proposal, but this would not change our overall determination that SCR
is cost-effective for NGS.
---------------------------------------------------------------------------

    \66\ See, e.g., Final Regional Haze Plan for Arizona (Phase 1)
at 77 FR 72512 at 72531 (December 5, 2012); Final Regional Haze Plan
for North Dakota at 77 FR 20894 at 20916-17 (April 16, 2012); Final
Regional Haze Plan for New Mexico at 76 FR 52388 at 52399-52400
(August 22, 2011); Final Regional Haze Plan for Wyoming at 79 FR
5032 at 5082 (January 30, 2014).
---------------------------------------------------------------------------

    Comment: Updated SCR cost estimate from SRP.
    SRP contracted with S&L in 2013 to review and update the SCR cost
estimates that were prepared in 2010. S&L escalated costs for
inflation, and incorporated other minor adjustments to reflect a lower
NOX design target. SRP's revised capital cost estimates for
SCR installation on all three units total $650 million (in 2013
dollars) compared to SRP's 2010 cost estimate of $544 million.
    Response: EPA reviewed the updated 2013 cost estimates developed by
S&L and provided by SRP.\67\ In its 2013 cost report, S&L explains that
it escalated labor and material costs, and updated cost estimates based
on a revised design target of 0.03 lb/MMBtu (so that the SCR system is
deployed as a 3+1 system rather than a 2+2 catalyst layer system), and
other design features, including a low-load temperature control system
to operate SCR at lower loads. S&L escalated several costs at rates
above 6.7 or 8 percent (e.g., freight, scaffolding). S&L did not make
any revisions to the components of variable annual costs, including
maintenance labor, auxiliary power, steam, and catalyst replacement. To
be consistent with the cost estimates in our Proposed Rule, EPA
accepted most of the line item costs as adjusted by S&L and made the
same four adjustments to the 2013 cost estimates as we had applied to
the 2010 cost estimates. These changes result in an 8 percent
difference in total capital costs of SCR between EPA's 2013 estimate
and SRP's 2013 estimate and a 21 percent difference in the total annual
costs of SCR between the 2013 estimates from EPA and SRP (see Table 2).
---------------------------------------------------------------------------

    \67\ See RTC and references therein.

                            Table 2--Cost Estimates for SCR in 2010 and 2013 Dollars
----------------------------------------------------------------------------------------------------------------
                                        Total capital      Total capital    Total annual cost  Total annual cost
                                       cost  (million)    cost  (million)      (million) in       (million) in
                                           in 2010$           in 2013$            2010$              2013$
----------------------------------------------------------------------------------------------------------------
EPA Estimate........................               $496               $598                $59                $69
SRP Estimate........................                544                650                 75                 88
----------------------------------------------------------------------------------------------------------------

    In our proposed BART determination, EPA also presented the average
and incremental cost-effectiveness of controls, based on the
combination of combustion controls (LNB/SOFA) and post-combustion
controls (i.e., SNCR or SCR). Therefore, cost-effectiveness values
presented in our Proposed Rule were based on total annual cost of SCR
in combination with annual cost of LNB/SOFA (SCR+LNB/SOFA), SNCR in
combination with LNB/SOFA (SNCR+LNB/SOFA) or LNB/SOFA alone.\68\ Based
on the updated 2013 cost estimates for SCR, Table 3 shows the average
and incremental cost-effectiveness of controls, in both 2010 and 2013
dollars, based on EPA and SRP assumptions for total annual cost and
annual NOX reductions achieved by SCR. See RTC for further
detail on cost-effectiveness of SNCR+LNB/SOFA and LNB/SOFA.
---------------------------------------------------------------------------

    \68\ 78 FR 8281, February 5, 2013.

                                            Table 3--Cost Effectiveness of Controls in 2010 and 2013 Dollars
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            2010 $                                                      2013 $
                                 -----------------------------------------------------------------------------------------------------------------------
                                               EPA                           SRP                           EPA                           SRP
--------------------------------------------------------------------------------------------------------------------------------------------------------
SCR+ LNB/SOFA:
    Total Annual Cost *.........  $67.5 million...............  $80.2 million...............  $74.4 million                 $92.6 million.
    Annual NOX reduced (tpy)....  28,573......................  26,180......................  28,573                        26,180.
    NOX Limit (lb/MMBtu)........  0.055.......................  0.080.......................  0.055                         0.080.
    Average Cost Effectiveness    $2,369......................  $3,069......................  $2,605                        $3,537.
     ($/ton).
    Incremental Cost              $3,522......................  $4,889......................  $3,899                        $5,695.
     Effectiveness (vs. LNB/
     SOFA) ($/ton).
    Incremental Cost              $3,239......................  $5,357......................  $3,798                        $6,647.
     Effectiveness (vs. SNCR+LNB/
     SOFA) ($/ton).
--------------------------------------------------------------------------------------------------------------------------------------------------------
* EPA's cost effectiveness calculations represent SCR in combination with LNB/SOFA, rather than SCR alone.

    Based on the revised 2013 cost estimates for SCR+LNB/SOFA, the
revised average cost-effectiveness of SCR+LNB/SOFA is roughly 10
percent higher (based on EPA's estimates) than the average cost-
effectiveness values

reported in our Proposed Rule, and roughly 15 percent higher based on
SRP's estimates.\69\ The 2013 values for average cost-effectiveness of
SCR+LNB/SOFA based on EPA and SRP estimates are still comparable to the
range of values determined cost-effective for SCR in other BART
determinations. For these reasons, EPA continues to consider SCR+LNB/
SOFA as cost-effective at NGS.
---------------------------------------------------------------------------

    \69\ For informational purposes, EPA included the incremental
cost-effectiveness values of SCR+LNB/SOFA (estimated in 2010 and
2013) compared to LNB/SOFA and SNCR+LNB/SOFA, but we note that a
comparison of the percent change in incremental cost-effectiveness
between 2010 and 2013 is not informative because SRP did not provide
updated cost estimates (in 2013 dollars) for the other control
technologies.
---------------------------------------------------------------------------

    Comment: Cost-Effectiveness of Presumptive BART.
    One commenter stated that in establishing presumptive limits in the
BART Guidelines, EPA recognized that SCR is not cost-effective and that
combustion controls such as LNB/SOFA represent the most cost-effective
control options for most boiler types. The commenter pointed out that
in establishing presumptive limits, EPA considered controls that cost
less than $1,500 per ton to be cost-effective, and that the cost-
effectiveness for SCR at NGS, which ranges from $3,000 to $6,000 per
ton based on 2010 estimates, is well above this threshold. The
commenter concluded that EPA should have rejected SCR and proposed LNB/
SOFA as BART for NGS.
    Response: EPA disagrees with the assertion that the BART Guidelines
established a threshold for cost-effectiveness against which all future
BART determinations must compare. In developing the presumptive
NOX limits for BART in 2005, EPA did not set the cost-
effectiveness values estimated for combustion controls as the threshold
for determining whether a given control technology was or was not cost-
effective. If EPA had intended the cost-effectiveness values estimated
in 2005 to represent a threshold for BART, it is reasonable to assume
that the BART Guidelines would have included those cost-effectiveness
values as thresholds in Appendix Y, and would have required future cost
estimates to be presented in 2005 dollars for appropriate comparison to
the thresholds. The BART Guidelines do not set a numerical definition
for ``cost-effective'', and the analysis of presumptive limits uses
cost-effectiveness as a means to broadly compare control technologies,
not as a threshold for rejecting controls for an individual unit or
facility that exceed the average cost-effectiveness of combustion
controls. In addition, as discussed in the RTC, a value of $1,500 per
ton is not an appropriate or relevant value for determining cost-
effectiveness.
    Comment: Indirect costs should also be considered under Factor 1.
    The Gila River Indian Community asserted that EPA conducted the
analysis of cost-effectiveness incorrectly by not including the
indirect costs of the requirements and only considering the direct cost
of the requirements. The commenter stated that EPA did not give
sufficient consideration to the high costs to tribes associated with
indirect impacts of its proposed BART determination.
    Response: EPA disagrees with the assertion that our cost-
effectiveness analysis was incorrect because it did not include
indirect costs in the assessment of the costs of compliance. The BART
Guidelines, which States and EPA must follow in BART determinations for
fossil-fuel fired power plants greater than 750 MW,\70\ focus on the
direct costs of the pollution control equipment and other capital and
annual costs associated with the control technology alternatives. The
BART Guidelines do not require consideration of the cost of potential
indirect effects of BART control options when assessing the costs of
compliance. Therefore, EPA disagrees that our analysis for Factor 1 was
incorrect or incomplete because it did not include indirect costs to
tribes. EPA further notes that under Factor 2, the energy and non-air
quality environmental impacts analysis, the BART Guidelines
specifically require the energy impact analysis to consider direct
energy impacts (e.g., parasitic load from certain control technologies)
and to generally exclude indirect energy impacts of controls (e.g.,
energy to produce raw materials for construction of control equipment)
unless the indirect impact is unusual or significant.
---------------------------------------------------------------------------

    \70\ 40 CFR 51.308(e)(1)(ii)(B).
---------------------------------------------------------------------------

    However, because of the unique relationship between NGS, tribes,
and tribal water settlement agreements, and to inform our government-
to-government consultation with tribes, EPA did consider potential
indirect effects of control options to tribes under Factor 2. EPA
quantified the impact to electricity rates and CAP water rates, and
also assessed whether installation of SCR would result in electricity
generation costs at NGS that exceed the cost to purchase power on the
wholesale market. Therefore, although EPA appropriately did not
consider indirect costs in our analysis of Factor 1, EPA did include
consideration of indirect impacts to tribes and other entities in our
analysis of Factor 2.

C. Comments on Factor 2--Energy and Non-Air Quality Environmental
Impacts, Including Economic Impacts

    Comment: EPA's Affordability Analysis relied on invalid
assumptions.
    One commenter submitted a report, prepared by Management
Information Services, Inc. (MISI report), asserting that EPA made
several assumptions that underestimated the cost of continuing to
operate NGS with additional controls, including the assumption that no
new capital would be deployed at NGS over the next 25 years, the
assumption that the increase in the annual NGS lease cost would be $15
million per year (which is lower than actual increase in lease cost of
$43 million per year that was released after publication of our
Proposed Rule), and the use of EPA's capital cost estimates for SCR
instead of the cost estimated by S&L.
    Other commenters asserted that EPA underestimated the cost of
closing NGS and purchasing power on the wholesale market, by not
accounting for costs associated with stranded investments and
decommissioning NGS.
    Response: EPA recognizes the economic importance of NGS to the
State of Arizona, the Navajo Nation, and the Hopi Tribe. The purpose of
the Affordability Analysis in our docket was to determine whether the
control options for BART would have a detrimental impact on the
competitiveness of NGS in the western power market, affecting whether
the NGS owners would continue to operate NGS or replace NGS generation
with less expensive market power. The Affordability Analysis indicated
that, even if SCR installation was required on all three units at NGS,
power produced at NGS would remain less expensive than the cost to
replace power through wholesale purchases. Because utilities will
generally provide power to their customers in a least-cost manner and
because NGS, with the installation and operation of SCR, remained the
less expensive option, EPA determined that the operation and
installation of SCR, in and of itself, was not likely to force NGS to
close.
    In response to multiple comments expressing concern related to
simplifying assumptions or outdated data, EPA updated the Affordability
Analysis with the most current power market price curves from the U.S.
Energy Information Administration (EIA) and recent forward power market
prices in March 2014 and other more current modeling variables. These

revisions are discussed in more detail in the RTC as well as in
additional supporting documents.\71\ The updated model results,
comparing the net present value (NPV) of electricity generation costs
with air pollution controls installed compared to the costs to purchase
an equivalent amount of power on the wholesale market, are summarized
in the RTC. Overall, the combined changes do not change the conclusions
from the original Affordability Analysis that installing and operating
SCR at NGS would be less costly than closing NGS and purchasing
replacement power from the wholesale market.
---------------------------------------------------------------------------

    \71\ See RTC and references therein.
---------------------------------------------------------------------------

    Comment: EPA's failure to appropriately consider the impacts to
non-Indian agricultural (NIA) water users renders its Factor 2 analysis
arbitrary, capricious, and an abuse of discretion.
    One commenter stated that, as a result of errors and omissions,
EPA's Factor 2 analysis is arbitrary, capricious, and an abuse of
discretion. The commenter asserted that there are several problems with
the EPA analysis related to NIA users of CAP water, including erroneous
assumptions, insufficient support for conclusions, failure to consider
decreased farming profitability and increased unemployment, failure to
acknowledge the inability of NIA water users to pass along cost
increases as compared to municipal users, and other factors.
    Response: EPA recognizes that CAP water is an important resource
for NIA and other users of water in Arizona. As a result, as one of a
number of discretionary analyses EPA conducted on the indirect impacts
on major stakeholders, EPA calculated water rate increases to NIA users
of CAP water and municipal and industrial users of CAP water.
    EPA disagrees that our discussion of impacts to NIA users of CAP
water renders our Factor 2 analysis arbitrary, capricious, and an abuse
of discretion. Neither the CAA nor the BART Guidelines require
consideration of indirect costs or indirect impacts of controls in a
BART analysis. EPA, nevertheless, included an evaluation of impacts to
some of the major stakeholders in NGS in our BART analysis under Factor
2, including NIA users, as consistent with the statement in the BART
Guidelines that ``the energy impacts analysis may consider . . .
whether a given alternative would result in significant economic
disruption or unemployment'' (emphasis added).\72\
---------------------------------------------------------------------------

    \72\ See BART Guidelines at 70 FR 39169 (July 6, 2005).
---------------------------------------------------------------------------

    EPA recognizes that the information we had available to us about
NIA users of CAP water was limited, and we acknowledged in the TSD to
our Proposed Rule that we had several questions about CAP and
groundwater availability to NIA water users. EPA appreciates the
clarifications and additional information provided by NIA users of CAP
water during the comment period for our proposals. The additional
information provided during the comment period about NIA users of CAP
water does not change our conclusion under Factor 2, that the potential
economic impacts to tribes argue for flexibility in the compliance
timeframe for NGS, because this compliance flexibility also benefits
other stakeholders, including the NIA users of CAP water.
    Comment: EPA must evaluate cumulative economic impact of other
rulemakings.
    One commenter asserted that the BART proposal must take into
account the context in which the regional haze rules are being
implemented and conduct a cumulative impact analysis of all EPA
rulemakings. The commenter noted that the two remaining copper smelters
in Arizona are already subject to BART for SO2 and they also
have to make significant capital investments to comply with other
regulatory programs and initiatives such as the revised SO2
NAAQS.
    Response: EPA disagrees with the assertion that we must consider
the total cost impact of all EPA regulatory requirements in a BART
analysis. EPA recognizes that other facilities, whose water and
electricity rates may be affected by our BART determination for NGS,
may also be subject to BART for their own emissions of visibility-
impairing pollutants. As a general matter, EPA is mindful that
facilities may be affected by multiple regulatory and program
activities. We note that BART is a case-by-case determination that is
based on a source-specific analysis of five factors, which include
considerations of the unique circumstances of each affected facility,
as required under the CAA.
    Comment: Impact to the Development Fund.
    One commenter stated that the increased cost of electricity
generation associated with SCR would reduce the competitiveness of the
price of NGS power on the wholesale market and therefore reduce the
revenue that flows into the Development Fund.
    Response: As discussed in our Proposal Rule and TSD, EPA recognizes
that any electricity owned by Reclamation based on its 24.3 percent
participation in NGS that is not used by CAP is sold and revenues are
deposited into the Development Fund.\73\ This fund is authorized to pay
the delivery portion of the cost of CAP water for certain Indian tribes
and to pay the cost of constructing delivery systems to bring CAP water
to certain Indian tribes.\74\ EPA considers the potential economic
impacts to tribes, including potential impacts to the Development Fund,
as part of BART factor 2 to support the appropriateness of flexibility
in the compliance timeframe for NGS.
---------------------------------------------------------------------------

    \73\ See Proposed Rule at 78 FR 8282 (February 5, 2013) and TSD
at pages 71-72.
    \74\ See Proposed Rule at 78 FR 8283 (February 5, 2013).
---------------------------------------------------------------------------

    Comment: No basis for public health claim.
    One commenter asserted that EPA has no basis for claiming that the
NOX reductions from NGS would lead to a public health
benefit. The commenter noted that EPA establishes NAAQS at levels that
are protective of public health and welfare with an adequate margin of
safety that accounts for sensitive populations such as children and the
elderly, and that EPA has never found that any of the areas around NGS
fail to attain the NAAQS. The commenter asserted that EPA must conduct
a health risk evaluation that follows the four basic steps of the risk
assessment process: Hazard identification, dose[hyphen]response,
exposure assessment, and risk characterization.
    Response: EPA agrees that the purpose of this rule is to reduce
visibility impairment caused by emissions of NOX from NGS.
EPA has not conducted a health risk evaluation for this rulemaking that
attempts to characterize or quantify a public health benefit. Because
NOX is itself a criteria pollutant that affects public
health and is also a precursor to ozone and fine particulate matter,
which are also criteria pollutants that affect public health, we
consider it reasonable to state that other benefits could exist. We
also note that EPA does not agree that there are no health benefits
from reductions in ozone and fine particulate matter below the level of
the NAAQS. On the contrary, EPA's practice of quantifying these
benefits in regulatory impact assessments has been strongly supported
by peer-reviewed science.\75\
---------------------------------------------------------------------------

    \75\ See EPA, 2010, ``Summary of Expert Opinions on the
Existence of a Threshold in the Concentration-Response Function for
PM2.5-related Mortality Technical Support Document.''
Available from http://www.epa.gov/ttn/ecas/regdata/Benefits/thresholdstsd.pdf.

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

D. Comments on Factor 3--Existing Controls at NGS

    Comment: EPA failed to consider existing controls.
    Based on EPA's statement in the Proposed Rule that the early
installation of LNB/SOFA would not influence EPA's BART determination
and EPA's use of a baseline scenario in the visibility modeling that
did not include LNB/SOFA, the operator of the Kayenta Mine concluded
that EPA failed to consider existing controls.
    Response: EPA disagrees with the assertion that we failed to
consider existing controls. As described in our Proposed Rule and
consistent with the BART Guidelines (directing BART determinations to
conduct the five-factor analysis generally using a 2001-2003 baseline)
EPA evaluated LNB/SOFA as a separate control technology in our BART
analysis, as well as a technology that can be used in combination with
post-combustion control technologies (i.e., SNCR and SCR).\76\ We also
discussed the voluntary installation of LNB/SOFA in 2009-2011 under
Factor 3: Existing Controls at NGS.\77\
---------------------------------------------------------------------------

    \76\ See Proposed Rule at 78 FR 8280, 8284 and 8285 (February 5,
2013).
    \77\ Id. at 8284.
---------------------------------------------------------------------------

    As discussed in section 8.5 of the RTC, EPA properly considered
baseline emissions over the period 2001-2003 in our analysis of cost-
effectiveness and anticipated visibility benefits of controls.
Therefore, although we did not ``consider existing controls'' in the
exact manner preferred by the commenter, we appropriately considered
the existence of LNB/SOFA in Factor 3 of our BART analysis. In
addition, the ``better than BART'' framework that we used to assess and
finalize BART alternatives explicitly accounts for the existing LNB/
SOFA.
    Comment: EPA should determine existing controls to be BART.
    Several commenters noted that NGS spent millions of dollars on LNB/
SOFA to reduce NOX emissions to levels below the presumptive
NOX emission levels in the BART Guidelines.
    One commenter stated that installing LNB/SOFA prior to a
requirement to do so under the RHR or any other CAA requirement has
resulted in greater total NOX emission reductions in the
first regional haze planning period than would be required by the most
stringent EPA BART determination.
    Response: EPA recognizes that the early and voluntary installation
of LNB/SOFA on one unit per year in 2009-2011 at NGS resulted in
significant emission reductions from NGS. EPA agrees that the early
installation of LNB/SOFA on one unit per year was voluntary and
resulted in significant NOX reductions in the first planning
period for Regional Haze. However, based on our five-factor analysis,
we have determined that SCR+LNB/SOFA is also cost-effective and would
result in significant additional visibility improvement at a number of
Class I areas. We therefore disagree that LNB/SOFA should be determined
BART for NGS.

E. Comments on Factor 5--Anticipated Visibility Benefits

    Comment: General Comments on Visibility.
    Numerous commenters questioned the extent to which NGS impacts
visibility at Class I areas or disputed EPA's analysis that
installation of SCR at NGS would improve visibility. Many commenters
asserted that the haze is produced from emissions from other sources.
    Some commenters stated that the wind near and around the Grand
Canyon blows predominantly west to east; thus, emissions from the NGS
are pushed away from several Class I areas, not towards them.
    Response: We are aware of the studies cited by commenters
purporting to show that controls on NGS would yield little visibility
improvement, and we address them in section 7.0 of the RTC. We are also
aware of work performed by the Western Regional Air Partnership (WRAP)
suggesting that the relative contribution of nitrate from point sources
to visibility impacts is relatively small.\78\ The CAA and RHR require
that BART be installed on certain old, large stationary sources as part
of the overall approach to improving visibility at Class I areas. No
control at an individual source will be sufficient to meet the goal of
remedying existing impairment of visibility in mandatory class I
Federal areas which result from manmade air pollution, as set out in
section 169A of the CAA.
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    \78\ See, e.g. WRAP PM Source Apportionment Technology (PSAT)
results, available on WRAP Technical Support System, Source
Apportionment Web page at http://vista.cira.colostate.edu/TSS/Results/SA.aspx.
---------------------------------------------------------------------------

    On the issue of wind direction, we note that the CALPUFF modeling
uses three years of hourly meteorological input, which is based on
meteorological modeling as well as observational data from stations
throughout a large area. The input includes wind speed and direction,
and would include the particular wind direction patterns noted by the
commenter. The more sophisticated meteorological treatment in CALPUFF
enables it to track the pollutant plume from NGS, including its twists
and turns over multiple days. We consider this approach to adequately
account for variability in winds noted by the commenter.
    Comment: EPA underestimated visibility benefits of SCR.
    One commenter stated that the visibility benefits of SCR are
greater than those modeled by EPA because EPA underestimated SCR
performance and because EPA overestimated the potential increase in
sulfate emissions that may come with the addition of SCR controls by
assuming an SO2 to SO3 conversion rate that is
too high and using an erroneous value for the coal sulfur content. The
commenter stated that its own modeling shows greater visibility
improvement than demonstrated by EPA.
    Response: We disagree that EPA underestimated the visibility
benefits of SCR and we note that the commenter's assertion that the
visibility benefits are even better would not change our proposed
determination under Factor 5 that the anticipated visibility benefits
of SCR+LNB/SOFA are significant and support our proposed BART limit for
NOX, achievable with SCR+LNB/SOFA. Please see the RTC for a
detailed discussion of EPA's responses to the commenter's specific
assertions.
    Comment: EPA overestimated visibility impact of NGS by using
background ammonia concentrations that were too high.
    Several commenters argued that EPA's assumed ammonia background
concentration of 1 part per billion (ppb), the default value
recommended by the Interagency Workgroup on Air Quality Modeling
(IWAQM), is unrealistically high compared to measured values in the
area, resulting in artificially high model projections of visibility
impacts, particularly in the winter.\79\ The commenter noted that the
use of a constant value of 1.0 ppb for background ammonia concentration
fails to account for known variations in monthly or seasonal ammonia
concentration.
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    \79\ Interagency Workgroup On Air Quality Modeling (IWAQM) Phase
2 Summary Report And Recommendations For Modeling Long Range
Transport Impacts (EPA-454/R-98-019), EPA OAQPS, December 1998,
http://www.epa.gov/scram001/7thconf/calpuff/phase2.pdf.
---------------------------------------------------------------------------

    One commenter cited an analysis conducted on behalf of SRP by AECOM
and Dr. Ivar Tombach. The commenter stated that the Tombach study
compared modeled predictions of

ammonium nitrates using both EPA's and AECOM's ammonia background
concentrations to measured ammonia values, demonstrating that the EPA's
assumptions over-predict actual measured values by a factor of 10 or
more in some cases.
    One commenter noted that when the IWAQM guidance was issued 14
years ago, CALPUFF did not have the capability of accommodating monthly
ammonia background concentrations as it has since been updated to do.
The commenter asserted that EPA's reliance on a constant value is an
outdated approach.
    Response: EPA has already considered and addressed the same
arguments and data provided by commenters related to background ammonia
concentrations in other rulemakings, including our final rule for Four
Corners Power Plant.\80\ As summarized briefly below, EPA disagrees
that our use of the IWAQM default background ammonia concentration for
arid areas of 1 ppb was inappropriate. Please see the RTC for the full
response to this comment.
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    \80\ See RTC and references therein.
---------------------------------------------------------------------------

    We have carefully reviewed the comments and concluded that, on
balance, the evidence does not support using lower values for
background ammonia concentrations, as argued by the commenters, in
estimating the visibility impacts from NGS. Much of the existing
measured data cited by the commenters is from other states and may not
be representative for evaluating visibility impacts from NGS.\81\
Further, existing data sometimes represent ammonia alone rather than
total ammonia and ammonium. Because ammonium represents part of the
pool of ammonia that could be available to interact with the
SO2 and NOX emitted from stationary sources, it
should be accounted for in the value for background ammonia
concentrations used in the model. In several of the research papers
cited by commenters, the amount of measured ammonium is comparable to
and at times much greater than the amount of ammonia.\82\ Measurements
made by SRP closer to NGS over December 2009 to April 2010, which
included ammonia and ammonium, showed that depending on time and
location, typical ammonia concentrations ranged from 0.2 ppb to 0.8 ppb
and the concentration of total ammonia and ammonium ranged from 0.6 to
1.2 ppb, which is considerably higher than the 0.2 ppb winter values
used in SRP's modeling.\83\ Although some of the ammonium may not be
available to interact with pollutants from NGS, the sum of ammonia and
ammonium provides an upper bound estimate of background ammonia
concentrations, and represents a conservative estimate for modeling.
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    \81\ See e.g., SRP comments Appendix G, ``Measurements of
Ambient Background Ammonia on the Colorado Plateau and Visibility
Modeling Implications'', Prepared by Salt River Project,
Contributors: Ivar Tombach and Robert Paine, September 2010.
Referred to here as ``SRP monitoring report'', or Tombach & Paine
2010.
    \82\ See RTC and references therein.
    \83\ SRP monitoring report, or Tombach & Paine 2010, and SRP
comments Appendix C. ``Revised BART Analysis for the Navajo
Generation Station Units 1-3'' (January 2009) and Appendix I.
``Visibility Modeling Using Upgraded CALPUFF Model'' (February
2011).
---------------------------------------------------------------------------

    We further note that there are measurements of gaseous ammonia
alone that show concentrations close to or greater than the
concentration of 1 ppb, even in winter when ammonia concentrations are
expected to be lowest. Winter measurements, representing 3-week
averages, ranged from 1.1 ppb to 1.8 ppb at a monitor at the Farmington
Airport in northwestern New Mexico.\84\ Measurements from the winters
of 2011-2013 from the AMoN network ranged from 1.1 to 1.3 ppb for
Farmington, and 0.7-0.9 ppb for Chiricahua, in southeastern
Arizona.\85\
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    \84\ See RTC and references therein.
    \85\ Id.
---------------------------------------------------------------------------

    We further note that there is significant variability in the
concentrations of ammonia measured at different times and places. Even
the SRP monitoring report (Tombach & Paine, 2010, cited above)
describes a surprisingly high spatial variability in ammonia
concentrations. Because of the variability and its unknown causes, the
data collected for SRP did not lead to a clear picture of appropriate
and representative background ammonia concentrations to use with
CALPUFF.
    Finally, we note that using the background ammonia concentrations
recommended by commenters does not change our conclusion under Factor 5
because CALPUFF modeling of SCR shows substantial visibility benefits
even using the alternative assumptions.\86\ Using a background ammonia
concentration of 1 ppb ammonia, EPA modeled the greatest benefit from
SCR+LNB/SOFA to be 5.4 deciviews at Capitol Reef NP, and modeled a
visibility benefit exceeding 1 to 2 deciviews at ten additional Class I
areas. Using the ammonia concentration recommended by some commenters
(ranging from 0.2 ppb in winter to 1.0 ppb in summer), EPA modeled the
greatest benefit of SCR to be 2.3 dv, and modeled a visibility benefit
exceeding 1 deciview at nine Class I areas, with three of these nine
areas having a benefit of approximately two deciviews. Even assuming a
lower ammonia concentration, the modeling demonstrates that the
installation of SCR+LNB/SOFA at NGS would have a significant beneficial
impact on visibility at a number of Class I areas. Our conclusion as to
the appropriate BART Benchmark for NGS would not accordingly change.
---------------------------------------------------------------------------

    \86\ See RTC and references therein.
---------------------------------------------------------------------------

    Comment: EPA should have used an updated version of CALPUFF.
    Several commenters asserted that EPA erred in using CALPUFF version
5.8 in its modeling rather than the more recent CALPUFF version 6.42,
released by TRC. One commenter argued that CALPUFF version 6.42
predicts lower visibility benefits than version 5.8.
    Response: We disagree with the commenters that a new CALPUFF
version should be used for the BART determination. We relied on version
5.8 of CALPUFF because it is the version approved by EPA through a
public notice and comment rulemaking, in accordance with the Guideline
on Air Quality Models (``GAQM'', 40 CFR part 51, Appendix W, section
6.2.1.e).\87\ CALPUFF version 6.4 is not approved by EPA for regulatory
purposes, and we do not agree that the changes made to this most recent
version of CALPUFF were simple model updates to address bugs. A full
evaluation of a new model such as CALPUFF version 6.4 is needed before
it should be used for regulatory purposes as errors that are not
immediately apparent can be introduced along with new model features.
---------------------------------------------------------------------------

    \87\ See RTC and references therein.
---------------------------------------------------------------------------

    Comment: Closure of Mohave Project did not improve visibility and
shows CALPUFF is unreliable.
    One commenter discussed the findings of an analysis conducted after
the closure of the Mohave Power Project (MPP) (a 1,580 MW coal-fired
power plant) to evaluate whether the closure had resulted in improved
visibility in Grand Canyon National Park.\88\ The commenter indicated
that although CALPUFF version 5.8 modeling predicted that the plant had
a significant impact on visibility in the Grand Canyon, this study
concluded that there was ``virtually no evidence that the MPP closure
improved visibility in the Grand Canyon.'' The commenter asserted that
this study raises questions about the reliability of CALPUFF.
---------------------------------------------------------------------------

    \88\ See RTC and references therein.
---------------------------------------------------------------------------

    Response: We disagree that the Terhorst & Berkman (T&B) study cited
by the commenters raises questions about CALPUFF's reliability. The

conclusion in the T&B study on the effect of MPP closure is actually
similar to that from earlier analyses, which also predicted
improvements less than the human perceptibility threshold of 1 dv. A
response to the T&B study written by White et al., stated that the T&B
analysis is ``misleadingly presented as discrediting previous studies
and their interpretation by regulators. In reality the T&B analysis
validates a consensus on MPP's visibility impact that was established
years before its closure.'' \89\
---------------------------------------------------------------------------

    \89\ W.H. White, R.J. Farber, W.C. Malm, M. Nuttall, M.L.
Pitchford, B.A. Schichtel, Comment on ``Effect of coal-fired power
generation on visibility in a nearby national park (Terhorst and
Berkman, 2010)'', Atmospheric Environment 55 (2012) 173-178.
doi:10.1016/j.atmosenv.2012.02.076. Also available at: http://www.dri.edu/marc-pitchford?showall=&start=2.
---------------------------------------------------------------------------

    White et al., explicitly addressed the purported disagreement
between the T&B methodology and results from CALPUFF, pointing out that
the comparison was flawed in several ways. First, the ambient data
relied upon by T&B are collected only every third day; this results in
an insufficient number of days for a valid statistical comparison to
the 98th percentile results reported from CALPUFF. Another important
flaw is that when T&B translated visibility extinction into deciviews,
they used recent polluted conditions as the background for comparison,
whereas the BART Guidelines and the CALPUFF results use natural
conditions as background.\90\ When the T&B results are computed using
natural background, they are substantially larger, and generally in
agreement with CALPUFF results.
---------------------------------------------------------------------------

    \90\ EPA considered and rejected comments on the proposed BART
Guidelines that visibility impacts should be evaluated relative to
current degraded visibility conditions and concluded that ``[u]sing
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.'' (70 FR 39104 at 39124, July 6, 2005).
---------------------------------------------------------------------------

F. Comments on BART Determination for NOX

    Comment: BART limit for NGS should be 0.04 lb/MMBtu.
    One commenter argued that the final BART emission limit should be
more stringent and no higher than 0.04 lb/MMBtu. The comment noted that
permitting authorities have required lower NOX limits than
0.055 lb/MMBtu in recent BACT determinations based on SCR in
combination with combustion controls.
    Response: EPA disagrees with the commenter that the BART Benchmark
for NGS should be 0.04 lb/MMBtu. We note that the commenter has not
provided any specific information to show that NGS could demonstrate
continuous compliance with an emission limit of 0.04 lb/MMBtu. The
commenter generally argued that SCR systems are typically designed to
achieve 90 percent removal. EPA notes that although an SCR system can
be designed to a specific target, the design target is typically not
equivalent to the actual emission limit.\91\ EPA proposed a limit of
0.055 lb/MMBtu achievable with SCR+LNB/SOFA, and using a baseline
emission rate of 0.35 lb/MMBtu, this represents a removal efficiency of
84 percent.\92\ However, as noted elsewhere in the RTC, the limit of
0.055 lb/MMBtu, which accommodates startup, shutdown, and low-load
operation, is based on a design target of 0.03 lb/MMBtu. This
represents a design target removal efficiency of 91 percent for
SCR+LNB/SOFA (from a baseline of 0.35 lb/MMBtu), or 88 percent for SCR
alone (i.e., from 0.24 lb/MMBtu).
---------------------------------------------------------------------------

    \91\ EPA's Environmental Appeals Board has recognized that PSD
emission limits must be set to allow fluctuations in operations,
stating: ``To account for these possibilities, a permitting
authority must be allowed a certain degree of discretion to set the
emissions limitation at a level that does not necessarily reflect
the highest possible control efficiency, but will allow the
permittee to achieve compliance consistently.'' In Re Masonite
Corporation, 5 E.A.D. 551, 560-61 (1994).
    \92\ See RTC and references therein.
---------------------------------------------------------------------------

    EPA disagrees with the commenter's assertion that emission limits
associated with BART must meet BACT or the lowest emission rate ever
achieved with that technology at any coal-fired power plant. The BART
Guidelines state that: ``[i]n assessing the capability of the control