[Federal Register Volume 81, Number 71 (Wednesday, April 13, 2016)]
[Rules and Regulations]
[Pages 21735-21747]
[FR Doc No: 2016-07911]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2015-0165; FRL-9944-68-Region 9]

Promulgation of Air Quality Implementation Plans; Arizona;
Regional Haze Federal Implementation Plan; Reconsideration

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is revising portions
of the Arizona Regional Haze Federal Implementation Plan (FIP)
applicable to the Coronado Generating Station (Coronado) and the Cholla
Power Plant (Cholla). In response to a petition for reconsideration
from the Salt River Project Agricultural Improvement and Power District
(SRP), the owner and operator of Coronado, we are replacing a plant-
wide compliance method with a unit-specific compliance method for
determining compliance with the best available retrofit technology
(BART) emission limits for nitrogen oxides (NOX) from Units
1 and 2 at Coronado. While the plant-wide limit for NOX
emissions from Units 1 and 2 was established as 0.065 lb/MMBtu, we are
now setting a unit-specific limit of 0.065 lb/MMBtu for Unit 1 and
0.080 lb/MMBtu for Unit 2. In addition, we are revising the work
practice standard in the FIP for Coronado. Finally, we are removing the
affirmative defense for malfunctions, which applied to both Coronado
and Cholla.

DATES: Effective date: This rule will be effective May 13, 2016.

ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-R09-OAR-2015-0165. All documents in the docket are
listed on the http://www.regulations.gov Web site. Although listed in
the index, some information is not publicly available, e.g.,
confidential business information (CBI) or other information whose
disclosure is restricted by statute. Certain other material, such as
copyrighted material, is not placed on the Internet and will be
publicly available only in hard copy form. Publicly available docket
materials are available electronically through http://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT: Vijay Limaye, U.S. EPA, Region 9,
Planning Office, Air Division, Air-2, 75 Hawthorne Street, San
Francisco, CA 94105; telephone number:<PHONE_NUMBER>; email address:
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,''
and ``our'' refer to the EPA.

Table of Contents

I. Definitions
II. Background
III. Proposed Action
IV. Public Comments and EPA Responses
V. Final Action
VI. Environmental Justice Considerations
VII. Statutory and Executive Order Reviews

I. Definitions

    For the purpose of this document, we are giving meaning to certain
words or initials as follows:
     The initials AAC mean or refer to the Arizona
Administrative Code.
     The initials ADEQ mean or refer to the Arizona Department
of Environmental Quality.
     The initials AMPD mean or refer to Air Markets Program
Data.
     The words Arizona and State mean the State of Arizona.
     The initials CAM mean or refer to Compliance Assurance
Monitoring.
     The word Cholla refers to the Cholla Power Plant.
     The word Coronado refers to the Coronado Generating
Station.
     The initials BART mean or refer to Best Available Retrofit
Technology.
     The initials BOD mean or refer to boiler operating day.
     The initials CAA mean or refer to the Clean Air Act.
     The initials CBI mean or refer to Confidential Business
Information.
     The initials EGU mean or refer to Electric Generating
Unit.
     The words EPA, we, us, or our mean or refer to the United
States Environmental Protection Agency.
     The initials FIP mean or refer to Federal Implementation
Plan.
     The initials LNB mean or refer to low-NOX
burners.
     The initials MMBtu mean or refer to million British
thermal units.
     The initials MOT mean or refer to minimum operating
temperature.
     The initials MW mean or refer to megawatts.
     The initials NAAQS mean or refer to National Ambient Air
Quality Standards.
     The initials NESHAP mean or refer to National Emission
Standards for Hazardous Air Pollutants.
     The initials NSPS mean or refer to Standards of
Performance for New Stationary Sources.
     The initials NOX mean or refer to nitrogen oxides.
     The initials OFA mean or refer to over fire air.
     The initials RHR mean or refer to the EPA's Regional Haze
Rule.
     The initials RMB mean or refer to RMB Consulting and
Research.
     The initials S&L mean or refer to Sargent & Lundy.
     The initials SCR mean or refer to Selective Catalytic
Reduction.
     The initials SIP mean or refer to State Implementation
Plan.
     The initials SRP mean or refer to the Salt River Project
Agricultural Improvement and Power District.
     The initials SSM mean or refer to startup, shutdown, and
malfunction.
     The initials UPL mean or refer to Upper Prediction Limit.

II . Background

A. Summary of Statutory and Regulatory Requirements

    Congress created a program for protecting visibility in the
nation's national parks and wilderness areas in 1977 by adding section
169A to the Clean Air Act (CAA). This section of the CAA establishes as
a national goal the ``prevention of any future, and the remedying of
any existing, impairment of visibility in mandatory Class I Federal
areas which impairment results from man-made air pollution.'' \1\ It
also directs states to evaluate the use of retrofit controls at certain
larger, often uncontrolled, older stationary sources in order to
address visibility impacts from these sources. Specifically, section
169A(b)(2)(A) of the CAA requires states to revise their State
Implementation Plans (SIPs) to contain such measures as may be
necessary to make reasonable progress towards the national visibility
goal, including a requirement that certain categories of existing major
stationary sources built between 1962 and 1977 procure, install, and
operate best available retrofit technology (BART) controls. These
sources are referred to as ``BART-eligible'' sources.\2\ In the 1990
CAA Amendments, Congress amended the visibility provisions in the CAA
to focus attention on the problem of regional haze, which is visibility
impairment produced by a multitude of sources and activities located
across a broad geographic area.\3\ We promulgated the Regional Haze
Rule (RHR) in 1999, which requires states to develop and implement SIPs
to ensure reasonable progress toward improving visibility in mandatory
Class I Federal areas \4\ by reducing emissions that cause or
contribute to regional haze.\5\ Under the RHR, states are directed to
conduct BART determinations for BART-eligible sources that may be
anticipated to cause or contribute to any visibility impairment in a
Class I area.\6\
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    \1\ 42 U.S.C. 7491(a)(1).
    \2\ 40 CFR 51.301.
    \3\ See CAA section 169B, 42 U.S.C. 7492.
    \4\ Areas designated as mandatory Class I Federal areas consist
of national parks exceeding 6000 acres, wilderness areas, and
national memorial parks exceeding 5000 acres, and all international
parks that were in existence on August 7, 1977. 42 U.S.C. 7472(a).
When we use the term ``Class I area'' in this action, we mean a
``mandatory Class I Federal area.''
    \5\ See generally 40 CFR 51.308.
    \6\ 40 CFR 51.308(e).
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 B. History of BART Determination for Coronado Generating Station

    The Arizona Department of Environmental Quality (ADEQ) submitted a
Regional Haze SIP (``Arizona Regional Haze SIP'') under Section 308 of
the RHR to EPA Region 9 on February 28, 2011. The Arizona Regional Haze
SIP included BART determinations for NOX, particulate matter
(PM), and sulfur dioxide (SO2) for Units 1 and 2 at
Coronado. We proposed on July 20, 2012, to approve ADEQ's BART
determinations for PM and SO2, but to disapprove its
determination for NOX at Coronado.\7\ In the same notice, we
also proposed a FIP that included a NOX BART emission limit
of 0.050 lb/MMBtu for Unit 1 and 0.080 lb/MMBtu for Unit 2 based on a
30-boiler-operating-day (BOD) rolling average.\8\ These limits
correspond to the use of Selective Catalytic Reduction (SCR) and low-
NOX burners (LNB) with over fire air (OFA) to reduce
NOX emissions. We noted that a consent decree between SRP
and the EPA required the installation of SCR and compliance with a
NOX emission limit of 0.080 lb/MMBtu (30-BOD rolling
average) at Coronado Unit 2 by June 1, 2014. In its comments on our
proposal, SRP asserted that a NOX emission rate of 0.050 lb/
MMBtu was not achievable at either of the Coronado units, due to their
startup/shutdown operating profile. In support of this assertion, SRP
submitted reports by two consultants, Sargent & Lundy (S&L) and RMB
Consulting and Research (RMB), which indicated that the Coronado units
could achieve a 30-BOD rolling average emission rate in the range of
0.053 to 0.072 lb/MMBtu per unit.\9\ The S&L report also examined
potential measures to improve the performance of the current SCR design
for Unit 2, including installation of a ``low load temperature control
system,'' (i.e., steam reheat) which would allow the SCR system to
operate during periods of low load.
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    \7\ 77 FR 42834.
    \8\ Boiler-operating day is defined as ``a 24-hour period
between 12 midnight and the following midnight during which any fuel
is combusted at any time in the unit.'' 40 CFR 52.145(f)(2).
    \9\ 77 FR 72555.
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    In the final Arizona Regional Haze FIP, we set a plant-wide
NOX emission limit for Coronado of 0.065 lb/MMBtu on a 30-
BOD rolling average, which SRP could meet by installing a low-load
temperature control system on Unit 2 and an SCR system including a low-
load temperature control system on Unit 1.\10\ We structured the
compliance determination method for this limit

such that, when one of the two units was not operating, its emissions
from the preceding 30 boiler operating days would continue to be
included in the two-unit average. Please refer to our final rule
published on December 5, 2012, for further information on the BART
determinations and compliance methodology.
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    \10\ Id.
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    In addition, we included in the FIP two additional requirements
that apply to all affected sources, including Coronado. First, we
promulgated a work practice standard that requires that pollution
control equipment be designed and capable of operating properly to
minimize emissions during all expected operating conditions.\11\
Second, we incorporated by reference into the FIP certain provisions of
the Arizona Administrative Code (AAC) that establish an affirmative
defense for excess emissions due to malfunctions.
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    \11\ Id. (codified at 40 CFR 52.145(f)(10)).
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C. Petition for Reconsideration and Stay

    We received a petition from SRP on February 4, 2013, requesting
partial reconsideration and administrative stay of our final rule under
section 307(d)(7)(B) of the CAA and section 705 of the Administrative
Procedure Act.\12\ EPA Region 9 sent a letter on April 9, 2013, to
representatives of SRP informing the company that we were granting
partial reconsideration of the final rule for the Arizona Regional Haze
FIP.\13\ In particular, we stated that we were granting reconsideration
of the compliance method for NOX emissions from Units 1 and
2 at Coronado and that we would issue a notice of proposed rulemaking
seeking comment on an alternative compliance methodology. We also noted
that, because we initially proposed different NOX emission
limits for the two units, we would seek comment on the appropriate
emission limit for each of the units.
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    \12\ Petition of Salt River Project Agricultural Improvement and
Power District for Partial Reconsideration and Stay of EPA's Final
Rule: ``Approval, Disapproval and Promulgation of Air Quality
Implementation Plans; Arizona; Regional Haze State and Federal
Implementation Plans'' (February 4, 2013).
    \13\ Letters from Jared Blumenfeld, EPA, to Norman W. Fichthorn
and Aaron Flynn, Hunton and Williams (April 9, 2013).
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III. Proposed Action

    On March 31, 2015, the EPA proposed action on reconsideration of
the compliance method and NOX emissions limits for Coronado
in the Arizona Regional Haze FIP.\14\ In particular, we proposed a
unit-specific compliance method and separate numerical emission limits
for NOX at Coronado Units 1 and 2. We also proposed to
revise the work practice requirement that applies to Coronado and to
remove the affirmative defense for malfunctions that is currently
included in the FIP for Coronado and Cholla.\15\ Finally, we proposed
to determine that these revisions to the FIP would comply with CAA
section 110(l).
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    \14\ 80 FR 17010 (March 31, 2015).
    \15\ The Cholla Power Plant (also known as the Cholla Generating
Station) is operated by the by Arizona Public Service Company (APS).
APS owns Cholla Units 1-3, while PacifiCorp owns Unit 4.
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A. Proposed Compliance Method for Unit-Specific Emission Limits

    We proposed to set a separate rolling 30-BOD lb/MMBtu limit for
each of the two Coronado Units, based on the following compliance
method:

    The 30-day rolling average NOX emission rate for each
unit shall be calculated in accordance with the following procedure:
First, sum the total pounds of NOX emitted from the unit
during the current boiler operating day and the previous twenty-nine
(29) boiler-operating days; second, sum the total heat input to the
unit in MMBtu during the current boiler operating day and the
previous twenty-nine (29) boiler-operating days; and third, divide
the total number of pounds of NOX emitted during the
thirty (30) boiler-operating days by the total heat input during the
thirty (30) boiler-operating days. A new 30-day rolling average
NOX emission rate shall be calculated for each new boiler
operating day. Each 30-day rolling average NOX emission
rate shall include all emissions that occur during all periods
within any boiler operating day, including emissions from startup,
shutdown, and malfunction.

We proposed that this method would replace the plant-wide method
promulgated in the final rule at 40 CFR 52.145(f)(5)(B)(ii), but that
all other compliance-related requirements, including the monitoring,
recordkeeping, and reporting requirements, would remain as promulgated.

B. Proposed Emission Limits for Coronado Units 1 and 2

1. Proposed Emission Limit for Coronado Unit 1
    In developing a proposed emission limit for Unit 1, we considered
information and analyses provided by SRP, including two reports
prepared by S&L and RMB concerning the achievability of various
NOX emission limits at Coronado Unit 1, as well as emission
data for Unit 1 as reported to the Air Markets Program Data (AMPD)
system.\16\ The 2013 S&L Report presented modeling results intended to
predict NOX emissions from Unit 1 under various operating
scenarios.\17\ The 2013 RMB Report applied an ``upper prediction
limit'' (UPL) technique to the results of the S&L report in order to
account for ``the impact of measurement uncertainty and other process
variation.'' \18\
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    \16\ 80 FR 17013-17016.
    \17\ Letter from Kelly J. Barr, SRP, to Deborah Jordan, EPA
(November 18, 2013), Attachment 1, Sargent and Lundy LLC Report SL-
011754, Salt River Project Coronado Generating Station Unit 1 SCR
NOX Emissions Modeling (November 14, 2013) (``2013 S&L
Report'').
    \18\ Id. Attachment 2, Technical Memorandum from RMB to SRP,
NOX Limits Compliance Monitoring Consideration on
Coronado Unit 1 (October 28, 2013) (``2013 RMB Report'') at 1.
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    In our evaluation of the 2013 S&L report, we found that the
scenarios examined by S&L were realistic depictions of load profile
scenarios historically experienced by the Coronado units. In
particular, we found that S&L's scenario 5c, which consists of low-load
cycling operations (with SCR and steam reheat assumed) and three cold
startups within a 30-day period was a reasonable and conservative
representation of expected future operations at Coronado Unit 1, in
light of the number of startup events that have historically occurred
and SRP's expectation that the Coronado units will experience greater
periods of operation in load-following service or nonoperation in the
future. Accordingly, we proposed to find that an emission rate of 0.065
lb/MMBtu, which corresponds to S&L's scenario 5c, was a reasonable
estimate of average SCR performance for Unit 1.
    We were unable to evaluate fully the RMB Report because it lacked
documentation regarding many of its components. In addition, we found
that the data set for NOX emissions from Coronado Unit 1
``is much more extensive, represents continuous data collected over a
long period of time, and covers a wider range of unit operations''
relative to the data sets for which the EPA has previously employed a
UPL analysis.\19\ This better dataset means that use of the UPL
analysis method is not necessary and use of the actual data from the
unit is more representative. Accordingly, we proposed to find that the
use of the UPL method was not appropriate for setting an emission limit
for Coronado Unit 1. We also proposed to find that it was not necessary
to raise the numerical emission limit in order to provide an additional
compliance margin due to the conservative assumptions in the 2013 S&L
Report.
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    \19\ 80 FR 17016.
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    Based on these proposed findings, we proposed to set an emission
limit for Coronado Unit 1 of 0.065 lb/MMBtu on a rolling 30-BOD basis.
Please refer to

our proposal for more information concerning the 2013 S&L and RMB
Reports, our evaluation of those reports, and the basis for our
proposed emission limit for Unit 1.
2. Proposed Emission Limit for Coronado Unit 2
    In proposing an emission limit for Coronado Unit 2, we considered
information provided by SRP concerning Unit 2's design parameters and
the installation of a low-load temperature control system for Unit 2.
We found that this information supported SRP's assertion that the
emission limit in the Consent Decree of 0.080 lb/MMBtu represents BART
for Unit 2. In particular, we noted that ``the fact that SRP has
already installed a low-load temperature-control system at this unit in
order to meet the 0.080 lb/MMBtu limit suggests that a lower limit
would not be achievable on a 30-BOD basis.'' \20\ Therefore, we
proposed to set a unit-specific NOX limit for Unit 2 of
0.080 lb/MMBtu on a rolling 30-BOD basis.
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    \20\ Id.
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C. Proposed Revision to Work Practice Standard

    In addition to the revisions to the continuously applicable numeric
emission limits for each unit, we proposed to revise the work practice
standard at 40 CFR 52.145(f)(10) to require continuous operation of
pollution control equipment at each unit at all times the unit is in
service ``in a manner consistent with technological limitations,
manufacturer's specifications, and good engineering and good air
pollution control practices for minimizing emissions.'' \21\
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    \21\ Although the preamble referred to this work practice
standard specifically in relation to the SCR on Unit 2, the proposed
regulatory text applied to all controls devices on both units, which
was the intended effect of the proposed revision.
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D. Proposed Removal of Affirmative Defense for Malfunctions

    As noted in our proposal, the Arizona Regional Haze FIP
incorporates by reference certain provisions of the ACC that establish
an affirmative defense that sources may seek to assert in an
enforcement action for violations that result from excess emissions due
to malfunctions.\22\ Subsequent to the EPA's promulgation of the FIP,
the United States Court of Appeals for the D.C. Circuit ruled that CAA
sections 113 and 304 prohibit the inclusion of affirmative defense
provisions in the EPA's regulations imposing emission limits on
sources.\23\ We explained that the logic of the court's decision
applies to the promulgation of a FIP, and precludes the EPA from
including an affirmative defense provision in a FIP. In addition, we
noted that the EPA had proposed to find AAC R18-2-310(B) and AAC R18-2-
310(C) substantially inadequate to meet CAA requirements and to issue a
SIP call with respect to these provisions (``SSM SIP Call'').\24\
Therefore, we proposed to remove the affirmative defense for
malfunctions from the Arizona Regional Haze FIP.
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    \22\ See 40 CFR 52.145(f)(11) (incorporating by reference AAC R-
18-2-101, paragraph 65; AAC R18-2-310, sections (A), (B), (D) and
(E); and AAC R18-2-310.01).
    \23\ See NRDC v. EPA, 749 F.3d 1055 (D.C. Cir. 2014).
    \24\ 79 FR 55920, 55947 (September 17, 2014).
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E. Non-Interference With Applicable Requirements

    The final element of our proposed action on reconsideration was an
analysis of whether the proposed revisions to the FIP would interfere
with any applicable requirement concerning attainment, reasonable
further progress, or any other applicable requirement of the CAA.\25\
We explained that the proposed revision to the FIP would allow for an
increase in NOX emissions of 233 tons per year (tpy)
compared to the existing FIP, but that this increase represented less
than one percent of the projected total NOX emission
reductions required under the FIP. We also noted that Coronado is
located in an area that is designated as Unclassifiable/Attainment for
all of the current National Ambient Air Quality Standards (NAAQS). We
proposed to find that a revision to the BART emission limits for
NOX would not interfere with attainment or reasonable
further progress for any air quality standard. We also proposed to find
that the revisions would not interfere with the applicable requirements
of the National Emission Standards for Hazardous Air Pollutants
(NESHAP), Standards of Performance for New Stationary Sources (NSPS),
or Compliance Assurance Monitoring (CAM) requirements. Finally, we
explained that, while the proposed revisions would alter the specific
emission limits that constitute BART for NOX at Coronado,
the effect of the proposed changes on visibility and overall
NOX emissions reductions under the FIP would be very small.
Therefore, we proposed to find that the proposed revisions would not
interfere with any applicable requirement of the CAA.
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    \25\ 80 FR 17017-17018.
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IV. Public Comments and EPA Responses

    Our proposed action provided a 45-day public comment period. During
this period, we received two comment letters: one from Earthjustice on
behalf of National Parks Conservation Association and Sierra Club and
one from SRP. In addition, after the close of the comment period, we
received a comment letter from the Eastern Arizona Counties
Organization (ECO).\26\ The significant comments and our responses are
summarized below.
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    \26\ The ECO letter was dated April 28, 2015, but was not
transmitted to the EPA until June 1, 2015.
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A. Comments on Proposed Compliance Method for Unit-Specific Emission
Limits

    Comment: SRP expressed support for the proposed compliance method.
    Response: We acknowledge SRP's support for the proposed compliance
method. We are finalizing the compliance method as proposed.

B. Comments on Proposed Emission Limits for Coronado Units 1 and 2

1. General Comments on Proposed Emission Limits for Coronado Units 1
and 2
    Comment: Earthjustice noted that the proposed emission limits are
based on an approach that is ``wholly dependent on many assumptions''
and expressed concern over several elements of the S&L analysis. First,
the commenter objected to breaking up a continuous load profile into
ill-defined ``modes.'' Second, the commenter asserted that the EPA
should not have accepted S&L's scenarios, as listed in Table 2 of the
proposal, specifically citing a lack of support for NOX
rates used by S&L for the various modes of operation. The commenter
noted that the EPA indicated only that the emission rates are
``reasonable and generally consistent'' with data reported to the Air
Markets Program Data (AMPD). The commenter indicated that it could not
find support for some of the assumed rates in the record. Third,
Earthjustice stated that there were insufficient data on how many and
what combinations of the operation modes can actually occur in a given
future 30-day period. Finally, the commenter argued that the EPA (or
the permit-issuing authority) should set separate limits for each
scenario and asserted that, in the absence of such limits ``this
bottom-up approach is clearly open for abuse whereby the limit is set
by making up a worst case assumption that may or may not occur--or may
occur, but with very low

frequency--allowing the operator to have a high NOX limit at
all times.'' Earthjustice further asserted that ``inclusion of startup,
shutdown, and malfunctions cannot be an excuse to obtain a high
emission limit simply by assuming a `worst case' future scenario with
several of these mode--regardless of the low frequency of such a
scenario.''
    Response: We partially agree with this comment. With regard to the
information supporting the assumptions made in the S&L analysis, we
have requested and received additional documentation from SRP. The full
details are included as a spreadsheet in the docket of this final
rule.\27\ To summarize, SRP examined historical operating data from
startup and shutdown events over a period extending from 2009 to 2012
and identified multiple cold starts, warm starts, and shutdowns. The
listed modes reflect actual events and operating modes from Unit 1 and
2's history and the emission rates associated with these events.
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    \27\ See spreadsheet ``Startup & Shutdown Data.xls.''
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    We are cognizant of the commenter's concern that accounting for
operating events and conditions that occur relatively infrequently
could result in an emission limit that is higher than what would be
warranted based solely on normal, steady-state operations. Such a limit
provides a larger compliance margin during periods of normal, steady-
state operations, when these operating events and conditions are not
occurring. However, we disagree with the commenter's argument that
separate limits for each mode of operation or load profile are needed.
We recognize that the EPA's SSM SIP Policy as of 2015 contemplates the
potential use of ``. . . special, alternative emission limitations that
apply during startup or shutdown if the source cannot meet the
otherwise applicable emission limitation . . .'' \28\ The EPA's SSM SIP
Policy as of 2015 reflects the EPA's interpretation of the CAA to allow
continuous emission limitations in SIPs that are composed of, for
instance, (i) specific numerical limits that apply during most of the
operations at the affected source, and (ii) other specific numerical
limits that apply during modes of operation such as startup and
shutdown. This policy thus contemplates that the ``otherwise
applicable'' numerical limit might be based on steady-state operation,
which reflects the best degree of emission control during that mode of
operation. The 2015 SSM Policy recommends seven factors that would be
relevant to developing an alternative numerical limit for specific
modes of operation, if that were appropriate.
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    \28\ 80 FR 33840, 33980 (June 11, 2015).
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    The commenter is suggesting that the FIP should take this approach
for Coronado. We acknowledge that in general this approach would be
consistent with our 2015 SSM SIP Policy, but our SSM Policy also
contemplates the use of a single appropriately set numerical limit with
a relatively long averaging period that is a weighted average of the
levels of emission control during steady-state operation, startup, and
shutdown. The EPA notes, however, that the averaging period for an
emission limitation must be appropriate for the type of SIP provision
at issue, e.g., a 30 day averaging period appropriate for purposes of
Regional Haze could be inappropriate in an attainment plan for a 24-
hour NAAQS. In this instance, Coronado Unit 1 can meet the applicable
emission limitation imposed in this FIP, precisely because that
limitation accounts for emissions from startup and shutdown. Therefore,
an alternative emission limit for startup and shutdown is not necessary
or appropriate in this instance.\29\ Furthermore, the FIP's approach of
setting a single continuously applicable BART emission limit that
applies during all modes of operation is consistent with the CAA, the
RHR and the BART Guidelines. We are not aware of any instance of BART
being implemented through separate emission limits that apply to
different modes of operation.
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    \29\ Excess emissions from malfunctions events are, by
definition, unforeseeable and extremely variable, and therefore
generally cannot be specifically accounted for within an emission
limit. Sources are required to meet the normally applicable emission
limits during malfunctions. Regulators may elect to exercise
enforcement discretion in such circumstances, and sources retain the
ability to assert any legal or equitable defenses to liability or
remedies that they may have in an enforcement proceedings,
consistent with CAA sections 113 and 304.
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    Comment: In addition to the assumptions noted in the previous
comment, Earthjustice also asserted that the assumptions regarding the
design and operation of the low-load temperature control system are
unsupported. Earthjustice quoted the following passage from the EPA's
proposal:

    As described in the S&L report, periods of low load operation
generally consist of operation between loads of 138 MW to 270 MW
(operation above 270 MW can be considered ``high'' load). Broadly
speaking, the temperature in the SCR system will fall below 599
degrees F during these periods of low load operation, which is the
minimum temperature required for effective NOX control. A
low load temperature control system increases the temperature at the
SCR inlet in order to maintain 599 degrees F, allowing operation of
the SCR system during periods of low load. Without this control
system, the Coronado Unit 2 SCR system will not operate during
periods of low load.

The commenter asserted that these are ``critical and unsupported
assumptions.'' Specifically, the commenter stated that ``the minimum
operating temperature (MOT) is a function of SCR catalyst design and
parameters such as the sulfur content of the fuel,'' and that neither
the proposal nor the S&L analysis explained why the MOT is assumed to
be 599 degrees F for the SCRs at Units 1 and 2. The commenter noted
that the record contains no documentation regarding SCR design from the
actual designer of the Unit 2 SCR. The commenter also asserted that the
correspondence between MOT and unit load (i.e., that the 599 degrees F
MOT corresponds to unit load of 270 MW) is not supported.
    Response: We agree with this comment and have requested and
received additional documentation from SRP regarding these issues.
Included in the docket is a functional description of the Unit 2 SCR
system prepared by Riley Power.\30\ It indicates that the Unit 2 SCR
was designed for a catalyst MOT of 599 degrees F. Also included in the
docket is a record of Unit 2's gross load and air preheater temperature
readings over an 18-month period from January 2011 to July 2012. As
indicated in the spreadsheet and chart attached to this documentation,
the majority of these data point to an air preheater temperature of 599
degrees F being achieved at a gross load of 270 MW.
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    \30\ See 1.1.1 SCR Reactor.pdf, Unit 2 Temperature vs. Load PI
Data.xlsx, and email from Barbara Sprungl, SRP, to Eugene Chen, EPA,
regarding SCR MOT (February 19, 2016).
---------------------------------------------------------------------------

2. Comments on Proposed Emission Limits for Coronado Unit 1
    Comment: Earthjustice commented that the proposed emission limit of
0.065 lb/MMBtu was based on Scenario 5c of the S&L analysis, as listed
in Table 2 of the proposed rule, which corresponds to a 30-day period
of continuous low-load cycling with three cold startup events. The
commenter noted that the EPA did not identify a historical 30-day
period that corresponded to this scenario. The commenter further
asserted that it had ``examined Unit 1 hourly operating data for a
three year time period, 2012-2014, from AMPD and found no instances of
scenario 5c or even 5b--i.e., two or three

cold-starts along with significant low load cycling.'' The commenter
concluded that the highest NOX limit that could be supported
by S&L's analysis was Scenario 5a, i.e., 0.0550 lb/MMBtu. Accordingly
the commenter requested that the EPA ``either fully support Scenario 5c
or accept the NOX limit associated with 5a--0.0550 lb/
MMBtu.''
    Response: We partially agree with this comment. As we stated in our
proposed rule, the particular scenario that the proposed emission limit
of 0.065 lb/MMBtu is based upon, Scenario 5c of the S&L analysis,
includes unit operating conditions (30 days of continuous low-load
cycling and three cold startup events) that have not historically
occurred in a single 30 BOD period. We disagree with the commenter's
assertion, however, that an emission limit of 0.055 lb/MMBtu would be
the appropriate emission limit.
    The commenter noted that it was unable to identify a 30-day period
with two or three cold starts along with significant low-load cycling
at Unit 1 during the period from 2012-2014. We reviewed operating data
beyond the most recent 3-year period and found three 30-day periods
with multiple startup events.\31\ As indicated in AMPD data and the
information provided by SRP in its April 24, 2014, letter, Unit 1 has
experienced 30-day periods that included two cold starts, as well as
one cold start with multiple warm starts (approximately three to six).
In general, the total amount of NOX emissions from a warm
startup is smaller than a cold startup, in large part due to the longer
duration of cold startup events. In this case, the total amount of
NOX generated by the actual historical operating scenario of
one cold startup and multiple warm startups (approximately three to
six) is similar to the total amount that would be generated under
Scenario 5c (i.e., three cold startups), and supports the use of three
cold startups as a conservative assumption concerning future operations
at Unit 1.
---------------------------------------------------------------------------

    \31\ See November 2011, April 2011, July 2009 in ``Coronado
NOX Emission Data (daily).''
---------------------------------------------------------------------------

    Similarly, the commenter asserted that it had not identified a 30-
day period of significant low-load cycling at Unit 1 during the period
from 2012-2014. We agree that historical operations at the Coronado
units do not reflect 30 consecutive days of low-load cycling
operations. As noted in our proposed rule, this assumption is based on
SRP's expectation that the Coronado units will experience greater
periods of low-load cycling operation in the future, as well as
nonoperation, given the expanded role of renewable energy and reduced
reliance on fossil fuels in electricity generation. More recent data
from the first 9 months of 2015 indicate increased low-load cycling
operations and startup events relative to historical patterns.\32\ At
most, however, this represents 3 to 5 days of continuous low-load
cycling, not 30. Therefore, 30 days of low-load cycling is likely to be
an overestimate of the number of low-load cycling days that will be
exhibited in future operations at Unit 1.
---------------------------------------------------------------------------

    \32\ See spreadsheet Coronado 2015-09 (hourly).xls.
---------------------------------------------------------------------------

    In sum, based upon historical operations, particularly the modest
amount of low-load cycling operations engaged in by the Coronado units,
Scenario 5c (i.e., an operating scenario of three cold startups and 30
days of low-load cycling), represents an upper-end estimate of low-load
Unit 1 operations and startups at Unit 1. However, for the reasons
described in response to comments from SRP below, we do not agree with
Earthjustice that a rolling 30-BOD limit of 0.065 lb/MMBtu for Unit 1,
which is based upon Scenario 5c, is insufficiently stringent.
    Comment: SRP asserted that the EPA's statement that an additional
compliance margin was not appropriate for Coronado Unit 1, given the
conservative nature of the assumptions in the S&L analysis, was
inconsistent with the EPA's acknowledgment that S&L's analysis provided
a reasonable estimate of average SCR performance. The commenter argued
that ``an emission limit that reflects `average' SCR performance--even
coupled with a 30-day averaging period--does not adequately account for
performance on either end of the spectrum--minimum emissions as well as
maximum emissions'' and that the EPA ``must establish a BART emission
limit that SRP can comply with at all times (i.e., a limit that is
closer to the maximum emissions that can be anticipated).''
    Response: We disagree with this comment. The commenter is correct,
in literal terms, that an ``average'' emission rate of 0.065 lb/MMBtu
is not the same as the maximum emission rate, and an emission limit
based on an ``average'' emission rate will not account for all possible
expected emission profiles. We do not agree, however, that this
demonstrates that the proposed limit does not adequately account for
the expected emissions on the upper end of the Unit 1's operating
spectrum. Although the proposed limit of 0.065 lb/MMBtu is based upon
an average emission rate, it represents the average emission rate of a
very conservative operating scenario. As described in previous
responses to comments, the specific set of circumstances that form the
basis for the proposed limit have not historically occurred at either
of the Coronado units.\33\ Although SRP has provided information
indicating that it expects the Coronado units to be engaged in expanded
amounts of load-following service,\34\ it has provided no evidence that
the units are likely to continuously operate at low-load cycling.\35\
Given the conservative nature of these assumptions, we consider the
proposed rolling 30-BOD emission limit of 0.065 lb/MMBtu to account
adequately for the operations of Unit 1 and, as explained further
below, to address sources of uncertainty in SRP's emission analysis
that may not have been accounted for in the S&L analysis.
---------------------------------------------------------------------------

    \33\ Specifically, three cold startup events and 30 days of low-
load cycling operations.
    \34\ See Letter from Kelly Barr, SRP, to Deborah Jordan, EPA
(April 28, 2014).
    \35\ One of the assumptions underlying Scenario 5c is low-load
cycling for 30 days, which, for purposes of developing a rolling 30-
BOD limit, represents continuous operation at low-load cycling.
---------------------------------------------------------------------------

    Comment: SRP expressed agreement with the EPA's finding that S&L's
analysis produced a reasonable estimate of average SCR performance for
Unit 1, but asserted that the S&L report was ``inadequate to determine
an emission limit that SRP can meet on a continuous basis'' because it
only addressed variability due to changes in load and ``failed to
address other factors that can and do affect emission rates.'' SRP
indicated that it had submitted evidence, including the 2013 RMB Report
showing that ``the 30-day average emissions rates from comparable units
(i.e., same furnace design, comparable size, equipped with SCR)
regularly exceed the proposed SRP limit of 0.065 lb/MMbtu.''
Specifically, SRP asserted that ``the RMB analysis plainly shows that
emissions from Unit 1 reasonably should be expected to exceed the
proposed 0.065 lb/MMbtu emission limit, even with a 30-day averaging
period.'' The commenter argued that ``failing to address the impact
that process and measurement variability can have on the reported
emissions would be inconsistent with how EPA has handled the issue in
other rulemakings.'' Based on the 2013 RMB Report and an additional
memo from RMB enclosed with the comment letter,\36\ the commenter
concluded that ``a value of 0.080 lb/MMbtu is a

reasonable estimate of the lowest achievable BART NOX limit
for Unit 1.''
---------------------------------------------------------------------------

    \36\ Technical Memorandum from RMB to SRP, Comments on Proposed
Revisions to the Regional Haze Federal Implementation Plan for
Arizona (May 15, 2015).
---------------------------------------------------------------------------

    SRP also commented that RMB provided a UPL statistical analysis
``merely as a check against its primary analysis, which is analytical
assessment of years of available emissions data from comparable
units.'' The commenter noted that:

    In its analytical assessment, RMB simply determined the 99th
percentile value of hundreds of 30-day average emission rates that
it was able to calculate from the available emission data. There was
no need to rely on a statistical tool such as the UPL to predict
what the 99th percentile would be because there are adequate data to
calculate that value directly.

The commenter concluded that the UPL was in fact not appropriate
because the 99th percentile emissions rate could be analytically
derived.

    Response: We disagree with this comment. There are two separate
issues arising from the RMB report: The NOX emission rates
achieved by comparable SCR-equipped units \37\ and the variability
derived from the RMB report (and inclusion of an appropriate compliance
margin).\38\ With regard to the former issue, although similar SCR-
equipped units examined by RMB exhibited NOX emission rates
that were routinely above 0.065 lb/MMBtu, we disagree that this
represents clear evidence that Unit 1 will exceed the proposed 30-BOD
limit of 0.065 lb/MMBtu. While the units selected by RMB for review had
similar design characteristics to Coronado Unit 1, the analysis did not
examine one crucial variable: The design emission rate of the SCR
systems. For example, S&L stated that the design target of the Pleasant
Prairie Unit 1 SCR was 0.050 lb/MMBtu. By contrast, the stated design
target of the Coronado Unit 1 SCR is 0.030 lb/MMBtu.\39\ Because the
SCR on the Coronado Unit 1 is designed to achieve a lower
NOX emission rate, we do not consider the fact the actual
NOX emission rates of these other SCR-equipped units exceed
0.065 lb/MMBtu to be directly relevant to Coronado Unit 1's ability to
meet a rolling 30-BOD limit of 0.065 lb/MMBtu.
---------------------------------------------------------------------------

    \37\ See Table 4 in 2013 RMB Report. To summarize, the mean
NOX emission rates of the similar SCR-equipped units
identified by RMB range from 0.063 to 0.092 lb/MMBtu.
    \38\ See 2013 RMB Report starting at page 7. To summarize, RMB's
analysis asserts that a 15% upward adjustment is appropriate,
followed by an additional upward rounding to the next numerical
interval, which represents an additional 10%.
    \39\ See Table 1 in 2013 S&L Report.
---------------------------------------------------------------------------

    With regard to the variability derived by the RMB report, we agree
that measurement and process variability should be accounted for in
establishing an emission limit that is achievable, and that
incorporates an appropriate compliance margin. The UPL methodology
would be one way to account for the possible impact of process and
measurement variability. As explained in our proposed rule, however, we
do not believe it is necessary or appropriate to use the UPL
methodology in this instance, given the size and scope of the data set
available. The commenter provided no assertions or arguments that
contradict our finding that use of the UPL methodology is inappropriate
in this instance. Indeed, the commenter actually acknowledges that use
of the UPL is not appropriate in this instance given the available
data.
    For similar reasons, we disagree with SRP's suggestion that we
should simply have used the 99th percentile emissions rate. As with UPL
analyses, the EPA has previously used the 99th percentile (described in
some contexts as the 99th confidence level) when establishing emission
limits for entire source categories based on emission data set
collected from a subset of the sources in each category. In such cases,
it is appropriate to take additional measures, such as use of the 99th
confidence level, to address concerns about variations not captured or
accounted for in the development of the data set. In this instance, by
contrast, the proposed 0.065 lb/MMBtu emission limit was developed from
emission data from the specific unit in question--either from CEMS data
collected from Unit 1 or from SCR vendor estimates developed
specifically for Unit 1. Although we recognize that this does not
eliminate all concerns regarding variability and uncertainty, we do not
consider the measures proposed by the commenter to be appropriate in
this instance given the substantially site-specific nature of the data
underlying the proposed emission limit. Moreover, neither S&L nor RMB
calculated a 99th percentile emission rate for Coronado Unit 1 based on
the use of SCR. Accordingly, we do not agree that use of the 99th
percentile emissions is necessary to account for process and
measurement variability.
    More broadly, while we have not explicitly quantified a portion of
the compliance margin specifically to account for process and
measurement variability (e.g., the additional 15-25 percent proposed by
the commenter), we consider the conservative nature of the operating
assumptions underlying the 0.065 lb/MMbtu limit to be sufficient to
account for this variability. As noted in previous responses, 0.065 lb/
MMbtu is based on operating assumptions that have not historically
occurred for either of the Coronado units and that have not been
demonstrated to be likely to occur on a regular basis in the future. In
addition, 0.065 lb/MMBtu is based on an assumption of a steady-state
full load emission rate of 0.040 lb/MMBtu, which is 0.01 lb/MMBtu
higher than the performance guarantee of the SCR system of 0.030 lb/
MMBtu.\40\ As noted in the S&L report, this increase above the
performance guarantee is intended to account for variations that will
occur with actual controlled emissions.\41\ We consider the
conservatism built into this assumption and the previously described
assumptions concerning startups and low-load cycling to be sufficient
to account for process and measurement variability and provide an
adequate compliance margin.
---------------------------------------------------------------------------

    \40\ 2013 S&L Report Table 1.
---------------------------------------------------------------------------

    Accordingly, we are finalizing a rolling 30-BOD NOX
emission limit of 0.065 lb/MMBtu for Coronado Unit 1, as proposed.
3. Comments on Proposed Emission Limits for Coronado Unit 2
    Comment: SRP expressed support for the EPA's proposed emission
limit of 0.080 lb/MMbtu for Coronado Unit 2. SRP noted that it had
already installed SCR and a low-load temperature control system on Unit
2 and that it was unable to meet an emission limit lower than the 0.080
lb/MMbtu limit in the Consent Decree. SRP also expressed support for
the proposed work practice standard and additional language addressing
operation using the low-load temperature control system.
    Response: We acknowledge SRP's support. We wish to clarify that the
revised work practice standard applies to both Coronado units, as does
the analogous language in Coronado's existing Title V Permit.\42\
---------------------------------------------------------------------------

    \42\ See Specific Condition II.E.2.c, Title V Operating Permit
No. 52693, issued December 6, 2011 (``The Permittee shall
continuously operate each NOx control at all times the unit it
serves is in operation consistent with technological limitations,
manufacturer's specifications, and good engineering and maintenance
practices for minimizing emissions to the extent practicable''
(emphasis added)).
---------------------------------------------------------------------------

    Comment: Earthjustice stated that it had examined emission data for
Unit 2 from the APMD for the period following installation of SCR
(i.e., roughly June 1 to December 31, 2014). The commenter provided a
table of hourly reported NOX rates for Unit 2, sorted by
gross load in the range of 138 to 270 MW, which is the load range in
which the low-load temperature control system would be expected to
operate. The commenter identified several periods of time in which Unit
2 operated in this load

range, but emitted higher NOX rates that indicated that the
SCR was not operating in this load range. Based on this information,
the commenter asserted that the low-load temperature control system is
not operating as intended.
    Further, the commenter asserted that had the low-load temperature
control system operated at this load range, the corresponding
NOX rates would have been much lower and the resulting 30-
day average NOX rates for these periods would also be lower.
Earthjustice also stated that, in order to simulate proper low-load
temperature control system operation, it had substituted the
NOX value of 0.049 lb/MMBtu (the average of 0.039 and 0.059,
the lowest and highest NOX rates corresponding to 270 MW)
for all loads in the 138-270 MW range and computed the 30-day average
NOX rate, including startup, shutdown, and malfunctions
(excluding some anomalous data). Based upon the results of this
substitution, the commenter asserted that the highest 30-day average
using these results was 0.0621 lb/MMBtu, and that the appropriate
NOX limit for Unit 2 would be 0.0650 lb/MMBtu, allowing for
a reasonable compliance margin.
    Response: We disagree with the commenter's assertion that the noted
instances indicate that the low-load temperature control system was not
operating as intended. The commenter has accurately identified certain
operating hours with load values that fall within a range of 138 to 270
MW. We agree that these instances exhibit NOX emission rates
that are consistent with nonoperation of the SCR system. We note,
however, that these instances do not correspond to periods of low-load
cycling (i.e., periods of extended operation at low-load electricity
generation). Rather, the instances identified by the commenter
correspond to startup/shutdown events.
    For example, the first instance listed by the commenter (hours 13
to 15 on June 1, 2014) are the final 3 hours of a 15-hour-long startup
event, in which Unit 2 starts at zero load, proceeds to full load, and
engages in high-load cycling on a continuous basis for the next 5
weeks.\43\ The 3 hours of low load are part of the process of ramping
the boiler up to high load and/or full load, and are not part of a
period of actual low-load operation. The other instances identified by
the commenter on July 13, July 18, July 22, September 11, September 15,
November 13, and November 17, 2014, are similarly all startup/shutdown
events. As described in our 2015 proposed rulemaking, the low-load
temperature control systems on the Coronado units function during
periods of low-load cycling by the boilers. During these periods of low
load, the boiler exhaust falls below the 600 degree F minimum operating
temperature of the SCR system. By using a portion of the steam
generated by the boiler to reheat the exhaust stream up to 600 degrees
F, the low-load temperature control system allows operation of the SCR
system during periods of low-load cycling. The availability of steam
reheat is a crucial element of this system. In a boiler startup event,
boiler steam may not be available in sufficient quantity or temperature
to allow operation of the temperature control system, because the
boiler is starting up.
---------------------------------------------------------------------------

    \43\ By comparison, a typical low-load cycling operation would
consist of the boiler starting at gross load levels above 270 MW,
dropping to below 270 for several hours, and finally returning to
load levels above 270 MW.
---------------------------------------------------------------------------

    More broadly, the commenter raises concerns regarding whether these
instances of SCR nonoperation are indicative of the low-load
temperature control system being improperly installed or operated. The
2014 AMPD data supplied by the commenter do not appear to contain any
periods of operation that correspond to low-load cycling. Therefore, it
is not possible to readily evaluate the effectiveness of the low-load
temperature control system based on these data alone. In preparing our
final action on reconsideration, we have reviewed 2015 AMPD data in
order to determine if the low-load temperature control system is being
operated during periods of low-load cycling. We have identified several
periods of low-load cycling in 2015, and note that the emission rates
achieved during these periods are consistent with operation of the SCR
system.\44\ This is consistent with the analyses provided by SRP, which
indicate that the low-load temperature control system is intended to
operate during periods of low-load cycling.\45\
---------------------------------------------------------------------------

    \44\ See Coronado 2015-09 (hourly).xls. May 24, May 27, May 28,
June 8, August 25, September 7, September 11, September 14, and
September 15, 2015. NOX emission rates observed during
these periods of low-load cycling range from 0.028 to 0.060 lb/
MMBtu, which based on the corresponding heat rates are emission
rates that indicate operation of the SCR system.
    \45\ See Letter from Kelly J. Barr, SRP, to Deborah Jordan, EPA
(April 28, 2014) page 4 and 2013 S&L Report page 6.
---------------------------------------------------------------------------

    We also disagree with the commenter's second assertion, that 30-day
NOX emission rates for Unit 2 would be lower had the low-
load temperature control system operated in these load ranges, and that
the appropriate NOX limit for Unit 2 is 0.065 lb/MMBtu. As
described in the previous paragraphs, we note that the instances
identified by the commenter correspond to startup/shutdown events and
not periods of low-load cycling. As a result, we do not consider the
information provided to be sufficient to demonstrate that the SCR
should have operated during the instances identified by the commenter,
and that a lower 0.065 lb/MMBtu limit is achievable by Unit 2.
    In sum, in our 2015 proposed action on reconsideration, we proposed
a BART limit of 0.080 lb/MMBtu for Unit 2 based on information and
analysis provided by SRP indicating that the Unit 2 SCR system was
designed to meet the 2012 Consent Decree emission limit of 0.080 lb/
MMBtu, and that SRP had since installed a low-load temperature control
system on Unit 2 to meet that emission limit. Because the information
provided by the commenter does not alter the data, analysis, or
reasoning underlying this proposed limit, we are finalizing a rolling
30-BOD limit of 0.080 lb/MMBtu for Unit 2.

C. Comments on Proposed Removal of Affirmative Defense for Malfunctions

    Comment: SRP urged the EPA to retain the affirmative defense for
excess emissions due to malfunctions as part of the Arizona Regional
Haze FIP. The commenter made several arguments in support of its
position.
    First, the commenter argued that the court's decision in NRDC v.
EPA, 749 F.3d 1055 (D.C. Cir. 2014) does not compel the EPA to remove
the affirmative defense provision from the Arizona Regional Haze FIP
because the decision applies only to an EPA rulemaking under section
112 and is not binding precedent in the Ninth Circuit. The commenter
further argued that by removing the affirmative defense provision, the
EPA ``ignores its own longstanding policy supporting affirmative
defenses in situations beyond the owner's or operator's control, as
well as decisions from other Courts of Appeals upholding affirmative
defenses.'' Referring to the EPA's 1999 SSM Guidance,\46\ the commenter
stated that ``[s]ince the early 1980s, EPA has consistently maintained
the imposition of penalties for exceedance of an emission standard that
is caused by circumstances beyond the owner's or operator's control is
not appropriate.'' Citing Arizona Public Service Co. v.

EPA, 562 F.3d 1116, 1129-30 (10th Cir. 2009), Montana Sulphur &
Chemical Co. v. EPA, 666 F.3d 1174, 1192-93 (9th Cir. 2012), and
Luminant Generation v. EPA, 714 F.3d 841, 851-53 (5th Cir. 2013), the
commenter asserted that the EPA's prior SSM policy, which interpreted
the CAA to allow affirmative defense provisions in SIPs, had been
upheld by three separate U.S. Courts of Appeals. The commenter further
argued that the EPA should not apply the D.C. Circuit decision in NRDC
``where controlling precedent from the U.S. Court of Appeals for the
Ninth Circuit condones EPA's use of affirmative defenses.''
---------------------------------------------------------------------------

    \46\ In particular, the commenter cited EPA's 1999 SSM Guidance
(Memorandum to EPA Regional Administrators, Regions I-X from Steven
A. Herman and Robert Perciasepe, USEPA, Subject: State
Implementation Plans: Policy Regarding Excess Emissions During
Malfunctions, Startup, and Shutdown (September 20, 1999).
---------------------------------------------------------------------------

    Second, SRP noted that, in the proposed SSM SIP Call, the EPA had
only proposed to interpret the CAA to bar affirmative defense type
provisions in SIPs and had also proposed to provide states 18 months to
submit SIP revisions to remove affirmative defenses for exceedances due
to malfunctions. The commenter thus asserted that the EPA should allow
the SSM SIP Call rulemaking to proceed, rather than ``predetermine the
outcome of that rulemaking by removing the affirmative defense from the
Arizona Regional Haze FIP far in advance of [the] timeline applicable
to the SIP call rulemaking.''
    Third, SRP asserted that ``[t]he U.S. Constitution also supports
retention of the affirmative defense for malfunctions.'' In particular,
the commenter noted that the U.S. Supreme Court has held that the
Eighth Amendment, including protections against excessive fines and
punishments, may apply to government action in a civil context as well
as in a criminal context. SRP claimed that significant penalties are
not proportional to an offense caused by unavoidable events, such as
excess emissions during malfunction events. Furthermore, the commenter
argued that ``imposing liability for `unavoidable' and therefore
innocent conduct would infringe on substantive due process principles
under the Fifth Amendment.'' SRP asserted that affirmative defense
provisions ``avoid unjust punishment while at the same time placing on
the source the burden of demonstrating that the offense actually was
`unavoidable' (and that punishment therefore would be unjust).'' Again
citing Montana Sulphur, the commenter asserted that providing an
affirmative defense is the ``minimum protection EPA or the state must
provide to avoid infringing constitutional rights.''
    Finally, SRP stated that the affirmative defense ``was an integral
part of the agreed-upon emission limits established in the [Coronado]
Consent Decree'' and ``was integral to the analyses submitted by SRP in
support of its Petition for Reconsideration and the proposed emission
limits SRP submitted to EPA for NOX.'' The commenter
asserted that without such an affirmative defense, ``the emission
limits identified as feasible and appropriate by S&L and RMB would have
undoubtedly been higher.'' The commenter argued that ``[i]f EPA now
removes the affirmative defense from the Arizona Regional Haze FIP for
[Coronado], EPA must modify upward the emission limits for
NOX to account for that action.''
    Response: We do not agree with SRP's arguments in favor of
retaining the affirmative defense for violations due to malfunctions in
the Arizona Regional Haze FIP or its assertion that the emission limits
should be revised upward in light of removal of the affirmative
defense.
    First, we do not agree with the commenter's suggestion that we are
free to ignore the NRDC decision in the context of promulgating or
revising a FIP. The fact that the decision pertained to a rulemaking by
the EPA under section 112 is irrelevant. As explained in our proposal,
NRDC turned on an analysis of CAA sections 113 and 304. 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 the EPA from including an
affirmative defense provision in a FIP. As explained in the final SSM
SIP Call:

    The EPA is revising its interpretation of the CAA with respect
to affirmative defenses based upon a reevaluation of the statutory
provisions that pertain to enforcement of SIP provisions in light of
recent court opinions. Section 113(b) provides courts with explicit
jurisdiction to determine liability and to impose remedies of
various kinds, including injunctive relief, compliance orders and
monetary penalties, in judicial enforcement proceedings. This grant
of jurisdiction comes directly from Congress, and the EPA is not
authorized to alter or eliminate this jurisdiction under the CAA or
any other law. With respect to monetary penalties, CAA section
113(e) explicitly includes the factors that courts and the EPA are
required to consider in the event of judicial or administrative
enforcement for violations of CAA requirements, including SIP
provisions. Because Congress has already given federal courts the
jurisdiction to determine what monetary penalties are appropriate in
the event of judicial enforcement for a violation of a SIP
provision, neither the EPA nor states can alter or eliminate that
jurisdiction by superimposing restrictions on that jurisdiction and
discretion granted by Congress to the courts. Affirmative defense
provisions by their nature purport to limit or eliminate the
authority of federal courts to determine liability or to impose
remedies through factual considerations that differ from, or are
contrary to, the explicit grants of authority in section 113(b) and
section 113(e).\47\
---------------------------------------------------------------------------

    \47\ 80 FR 33851-33852.

Therefore, the EPA cannot include any such affirmative defense
provision in a FIP.
    The commenter has offered nothing to refute this interpretation of
the CAA. Instead, the commenter suggests that the EPA should not apply
the NRDC decision in this instance because of ``controlling precedent''
from the Ninth Circuit, namely the Montana Sulphur decision. As
relevant here, that decision involved a challenge by Montana Sulphur to
the EPA's imposition of limits on flaring emissions during SSM events.
In responding to Montana Sulphur's argument that these limits were
infeasible, ``the EPA acknowledge[d] that violations are likely
inevitable, but relie[d] on the provision of an affirmative defense to
compensate for the infeasibility problem.'' \48\ Significantly,
however, Montana Sulphur did not involve a challenge to inclusion of
the affirmative defense in a FIP. On the contrary, Montana Sulphur
argued that the affirmative defense in the FIP should have been
extended to cover injunctive relief in addition to monetary
penalties.\49\ The court rejected this argument and concluded that the
EPA had reasonably interpreted the CAA to limit the extent of the
affirmative defense as part of imposing continuous limits on
emissions.\50\ However, because no party directly challenged the legal
basis for the affirmative defense itself, the court did not have
occasion to consider whether the affirmative defense in the FIP
contravened CAA sections 113 and 304. Therefore, we do not agree that
Montana Sulphur constitutes controlling precedent on the issue of
whether the EPA may promulgate an affirmative defense in a FIP.
---------------------------------------------------------------------------

    \48\ 666 F.3d at 1192-93.
    \49\ Id. at 1193. The EPA's position in that case was based on
the 1999 SSM Policy, which has now been replaced by the EPA's SSM
SIP Policy as of 2015. See 80 FR 33977-33982.
    \50\ Id.
---------------------------------------------------------------------------

    With regard to the other judicial decisions cited by the commenter,
the Luminant decision did not involve a FIP at all, but concerned the
EPA's evaluation of affirmative defense provisions in a SIP context. In
that decision, the court upheld the EPA's disapproval of an affirmative
defense provision applicable to violations due to emissions during
startup, shutdown and

maintenance events, and the EPA's approval of an affirmative defense
provision applicable to violations due to emissions during
malfunctions. In both instances, the court deferred to the EPA's then
current interpretation of the CAA as a reasonable reading of ambiguous
provisions. Subsequent to that decision, however, the DC Circuit issued
its opinion in NRDC. In our Supplemental Proposal and Final SSM SIP
Call, we explained at length why we now consider the court's reasoning
in the NRDC decision to be the better reading of the CAA.\51\ Thus, the
EPA has now changed its interpretation of the CAA with respect to the
permissibility of affirmative defense provisions in SIPs and has
directed the affected state to remove the affirmative defense provision
at issue in the Luminant decision from its SIP in the final SSM SIP
call.
---------------------------------------------------------------------------

    \51\ See 79 FR 55920, 55931-55934 (September 17, 2014) and 80 FR
33856-33857.
---------------------------------------------------------------------------

    Finally, while the Arizona Public Service case did involve a
challenge to an affirmative defense in a FIP, it did not involve a
challenge to the statutory basis for such a defense.\52\ Rather,
Arizona Public Service argued that ``the EPA must justify inclusion of
the affirmative defense with a factual basis for presuming that excess
emissions are the fault of APS, and requiring APS to prove otherwise''
and that ``the EPA offered no defense to this burden-shifting
affirmative defense.'' \53\ The court rejected both of these arguments.
However, as with Montana Sulphur, no party argued that the affirmative
defense at issue was inconsistent with the enforcement structure of CAA
sections 113 and 304, so the Arizona Public Service court did not have
occasion to consider this question. Accordingly, the Arizona Public
Service decision is not directly on point with regard to whether the
EPA is authorized to include an affirmative defense in a FIP.
Therefore, none of the cases cited by the commenter compel or persuade
the EPA to adopt an interpretation of the CAA with regard to
affirmative defenses that differs from the interpretation set forth in
the SSM SIP Call Final Rule preamble, as quoted previously.
---------------------------------------------------------------------------

    \52\ Arizona Public Service Co. v. EPA, 562 F.3d 1116, 1130
(10th Cir. 2009).
    \53\ Id. (internal quotations omitted).
---------------------------------------------------------------------------

    Second, as noted previously, the EPA has finalized the SSM SIP Call
and determined that AAC R18-2-310(B) and AAC R18-2-310(C) are
substantially inadequate to meet CAA requirements.\54\ Arizona must
submit a SIP revision to remove or revise these provisions by November
22, 2016. To the extent that the commenter disagrees with the EPA's
interpretation of the CAA in the SSM SIP Call, and disagrees with the
EPA's application of that interpretation to AAC R18-2-310(B) and AAC
R18-2-310(C), that decision may be challenged in the DC Circuit.
However, the EPA is not obligated to wait until that deadline for SIP
revisions in response to the SSM SIP Call passes to remove these
provisions from the Arizona Regional Haze FIP. On the contrary, having
made a final determination that affirmative defense provisions are
inconsistent with CAA requirements, we believe it is appropriate to
expeditiously remove the affirmative defense provision from the Arizona
Regional Haze FIP. The FIP is the EPA's own rulemaking, which it is now
conforming to the requirements of the CAA.
---------------------------------------------------------------------------

    \54\ 80 FR 33840, 33971 (June 12, 2015).
---------------------------------------------------------------------------

    Third, the commenter's constitutional arguments appear to suggest
that the existing CAA enforcement provisions are facially
unconstitutional. We do not agree. The CAA does not mandate that any
penalty be automatically assessed for a violation. Rather, the CAA
establishes a maximum civil penalty in section 113(b), but then
expressly provides in section 113(e) the criteria that the EPA (in
administrative enforcement) or the courts (in judicial enforcement)
``shall take into consideration (in addition to other factors as
justice may require).'' These criteria explicitly include consideration
of ``good faith efforts to comply.'' Whether in administrative
enforcement or judicial enforcement, there is a process through which
the alleged violator may raise any legal or equitable arguments it may
have based on the facts and circumstances of the violation. Thus, the
CAA on its face does not mandate the imposition of any penalty
automatically, much less one that is per se excessive. Notably, the
commenter does not elaborate on how or why it believes the statutory
penalty provisions of the CAA are facially unconstitutional. To the
extent that the commenter is raising an ``as applied'' claim of
unconstitutionality, any such claim can be raised in the future in the
context of a specific application of the statute in an enforcement
action.
    Fourth, we acknowledge that, as in the Montana Sulphur example
cited by the commenter, the EPA has previously provided affirmative
defense provisions as a mechanism to mitigate penalties where a
violation was beyond the control of the owner or operator. Contrary to
the commenter's suggestion, however, the EPA did not indicate that such
provisions were constitutionally mandated. These actions were premised
upon the EPA's prior interpretation of the CAA to permit such
affirmative defense provisions under very narrow circumstances. More
significantly, these actions predated the NRDC decision and, as
explained previously, the EPA no longer considers affirmative defense
provisions to be consistent with the enforcement provisions of the CAA.
Furthermore, the EPA believes that the penalty criteria in section
113(e) perform a similar function to the affirmative defense provisions
previously promulgated by the EPA. The commenter does not explain why
these explicit statutory factors do not provide sufficient protection
from the imposition of allegedly unconstitutionally excessive
penalties.
    Finally, we do not agree that removal of the affirmative defense
from the Arizona Regional Haze FIP necessitates an increase in the
emission limits for NOX for Coronado Units 1 and 2. Neither
the 2013 S&L Report nor the 2013 RMB Report indicates that it relied on
the existence of such a defense in evaluating what emission limits were
achievable at the Coronado units. Moreover, the affirmative defense in
the FIP applied only to violations due to emissions during
malfunctions, which (among other criteria) must have ``resulted from a
sudden and unavoidable breakdown of process equipment or air pollution
control equipment'' and ``not stem[med] from any activity or event that
could have been foreseen and avoided, or planned.'' \55\ Nothing in the
CAA, the RHR, or the BART Guidelines indicates that BART emissions
limits should be set at a level that accommodates all emissions during
such unforeseeable events. Finally, we note that, if Coronado were to
violate a BART emission limit due to a malfunction, SRP retains the
ability to defend itself in an enforcement action and to oppose the
imposition of particular remedies or to seek the reduction or
elimination of monetary penalties, based on the specific facts and
circumstances of the event. To the extent that a violation is the
result of a genuine malfunction, the EPA anticipates that the state,
citizen suit plaintiffs, and the EPA itself will likely exercise
enforcement discretion. To the extent that any party elects to pursue
enforcement in such circumstances, however, the CAA already authorizes
the courts to determine whether parties should be held responsible for
such violations and to impose remedies or penalties only as may be
appropriate, given the relevant

facts and circumstances. As noted previously, under CAA section 113(e),
federal courts are required to consider the enumerated statutory
factors when assessing monetary penalties, including ``such other
factors as justice may require.'' Accordingly, we do not consider it
necessary or appropriate to revise the BART emission limits due to the
removal of the affirmative defense for malfunctions.
---------------------------------------------------------------------------

    \55\ AAC R18-2-310(B)(1) and (8).
---------------------------------------------------------------------------

    It should also be noted that our removal of the affirmative defense
from the Arizona Regional Haze FIP does not alter the terms of the
Coronado Consent Decree, which includes an affirmative defense
applicable only to stipulated penalties for violations of the Consent
Decree itself.\56\ This provision of the Consent Decree affects only
whether SRP must pay stipulated penalties under the Consent Decree and
does not provide a defense to otherwise applicable CAA penalties.\57\
Thus, the provision operates as a liquidated damages clause applicable
only to the penalties imposed for violations of the Consent Decree and
does not purport to alter the jurisdiction of the courts to impose
penalties for violations of CAA requirements. Moreover, this provision
was sanctioned by the United States District Court for the District Of
Arizona, which entered the Consent Decree. Therefore, it does not raise
the same concerns about limiting the jurisdiction of courts that are
raised by the affirmative defense provision in the FIP.
---------------------------------------------------------------------------

    \56\ Consent Decree paragraph 107.
    \57\ See, e.g., id. paragraph 106.
---------------------------------------------------------------------------

    In sum, we do not agree that the affirmative defense applicable to
violations due to malfunctions should be retained in the Arizona
Regional Haze FIP or that the emission limits in the FIP should be
revised upward in light of the removal of the defense.
    Comment: Earthjustice expressed support for the EPA's proposal to
remove the affirmative defense applicable to violations due to
malfunctions from the FIP. Citing the NRDC decision relied upon by the
EPA in the proposal, the commenter asserted that affirmative defenses
for violations due to malfunctions like that previously incorporated
into the Arizona Regional Haze FIP are prohibited by the plain language
of the CAA. Earthjustice further argued that such affirmatives defenses
are unnecessary because courts do not impose penalties for truly
unavoidable and unforeseeable violations. Finally, the commenter urged
the EPA to finalize its proposal in a separate action to find the
affirmative defense for violations due to malfunctions in AAC Code R18-
2-310(C) and the similar affirmative defense for violations due to
startup and shutdown in AAC R18-2-310(B) substantially inadequate to
meet CAA requirements as part of the SSM SIP Call.
    Response: We agree with the commenter for the reasons detailed in
the previous response. We note that the EPA has already finalized the
SSM SIP Call and determined that AAC R18-2-310(B) and AAC R18-2-310(C)
are substantially inadequate to meet CAA requirements.\58\ Accordingly,
the EPA has already directed the state to remove those existing
affirmative defense provisions from the SIP, consistent with EPA's
action to remove the affirmative defense for violations during
malfunctions from the Arizona Regional Haze FIP.
---------------------------------------------------------------------------

    \58\ 80 FR 33840, 33971 (June 12, 2015).
---------------------------------------------------------------------------

D. Other Comments

    Comment: SRP asserted that the EPA should defer to Arizona's
NOX BART determination for Coronado, noting that this
determination was less stringent than the requirements of the Consent
Decree.
    Response: This comment is outside the scope of the proposed action.
The EPA is not reconsidering our prior final action disapproving
Arizona's NOX BART determinations for Coronado Units 1 and
2. Furthermore, as explained in our proposal, we are not reconsidering
our determination that BART for Coronado Units 1 and 2 is an emission
limit consistent with the use of SCR, LNB with OFA, and low-load
temperature control systems.\59\ Finally, even if this comment were
relevant to this action, we do not agree that Arizona's BART
determinations for NOX at Coronado were reasonable or that
they complied with the applicable statutory and regulatory
requirements, for the reasons set forth in our prior proposed and final
actions disapproving those determinations.\60\
---------------------------------------------------------------------------

    \59\ 80 FR 17013.
    \60\ 77 FR 42834, 77 FR 72512.
---------------------------------------------------------------------------

    Comment: ECO commented that the EPA's proposed action on
reconsideration was ``a critical step toward insuring the economic
viability'' of Coronado and urged the EPA to finalize the proposal.
    Response: We acknowledge ECO's support for our action on
reconsideration.

V. Final Action

    The EPA is taking final action to revise the Arizona Regional Haze
FIP to replace a plant-wide BART compliance method and emission limit
for NOX on Units 1 and 2 at Coronado with a single-unit
compliance method and emission limit on each of the units. For the
reasons described in our proposal and in our responses to comments
above, we are finalizing emission limits of 0.065 lb/MMBtu for Unit 1
and 0.080 lb/MMBtu for Unit 2 with compliance based on a rolling 30-BOD
basis. This revision constitutes our final action on SRP's petition for
reconsideration of the FIP. We are also finalizing our proposals to
remove the affirmative defense for malfunctions in the FIP and revise
the work practice requirement that applies to Coronado under the FIP.
    We find that this revision will not interfere with any applicable
requirement concerning attainment, reasonable further progress, or any
other applicable requirement of the CAA. The Arizona Regional Haze FIP,
as revised by this action, will result in a significant reduction in
emissions compared to current levels (roughly 5,000 tpy). Although this
revision will allow a marginal increase in emissions after December
2017 from the Coronado facility as compared to the prior FIP (roughly
233 tpy), the FIP as a whole will still result in an overall
NOX reductions from Coronado compared to those currently
allowed. In addition, the area where Coronado is located has not been
designated nonattainment for any NAAQS. Thus, the revised FIP will
ensure a significant reduction in NOX emissions compared to
current levels in an area that has not been designated nonattainment
for the relevant NAAQS at those current levels. Likewise, for the
reasons explained in our proposal and summarized in section III.D, the
revision will not interfere with any other applicable CAA requirements.

VI. Environmental Justice Considerations

    The EPA believes the human health or environmental risk addressed
by this action will not have potential disproportionately high and
adverse human health or environmental effects on minority, low-income,
or indigenous populations. We expect that Coronado will install the
same control technology in order to meet the revised emission limits as
would have been necessary to meet the previously finalized limits. As
noted previously, this revision to the FIP will allow for an increase
in NOX emissions of roughly 233 tpy compared to the original
Arizona Regional Haze FIP.\61\ Although this is a not a trivial amount
of emissions, it is relatively small compared to the facility's total

emissions. In particular, 233 tpy is equivalent to about three percent
of the 7,300 tpy of NOX that the facility is currently
allowed to emit under the Coronado Consent Decree.\62\ Furthermore,
total NOX emissions from the facility following full
implementation of the FIP will be roughly 2,275 tpy, a decrease of over
5,000 tpy compared to the amount the facility is presently allowed to
emit. In sum, while this revision will allow for a marginal increase in
emissions compared to the prior FIP, it will still ensure a significant
reduction in emissions compared to present levels. Thus, the FIP, as
revised by this action, increases the level of environmental protection
for all affected populations without having any disproportionately high
and adverse human health or environmental effects on any population,
including any minority or low-income population.
---------------------------------------------------------------------------

    \61\ 80 FR 17010.
    \62\ Coronado Consent Decree, paragraph 44.
---------------------------------------------------------------------------

VII. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders
can be found at http://www2.epa.gov/laws-regulations/laws-and-executive-orders.

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

    This action is not a significant regulatory action and was
therefore not submitted to the Office of Management and Budget (OMB)
for review. This rule applies to only two facilities and is therefore
not a rule of general applicability.

 B. Paperwork Reduction Act (PRA)

    This action does not impose an information collection burden under
the PRA. This rule applies to only two facilities. Therefore, its
recordkeeping and reporting provisions do not constitute a ``collection
of information'' as defined under 44 U.S.C. 3502(3) and 5 CFR
1320.3(c).

 C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic
impact on a substantial number of small entities. This action will not
impose any requirements on small entities. Firms primarily engaged in
the generation, transmission, and/or distribution of electric energy
for sale are small if, including affiliates, the total electric output
for the preceding fiscal year did not exceed 4 million megawatt hours.
Each of the owners of facilities affected by this rule, SRP, APS and
PacifiCorp, exceeds this threshold.

 D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain an unfunded mandate of $100 million or
more as described in UMRA, 2 U.S.C. 1531-1538, and does not
significantly or uniquely affect small governments.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have
substantial direct effects on the states, on the relationship between
the national government and the states, or on the distribution of power
and responsibilities among the various levels of government.

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

    This action does not have tribal implications, as specified in
Executive Order 13175. It will not have substantial direct effects on
any Indian tribes, on the relationship between the Federal Government
and Indian tribes, or on the distribution of power and responsibilities
between the Federal Government and Indian tribes. Thus, Executive Order
13175 does not apply to this action.

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

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

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

    This action is not subject to Executive Order 13211 because it is
not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act

    This rulemaking does not involve technical standards. The EPA is
not revising any technical standards or imposing any new technical
standards in this action.

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

    The EPA believes the human health or environmental risk addressed
by this action will not have potential disproportionately high and
adverse human health or environmental effects on minority, low-income,
or indigenous populations. The results of this evaluation are contained
in section VI previously.

K. Determination Under Section 307(d)

    Pursuant to CAA section 307(d)(1)(B), this action is subject to the
requirements of CAA section 307(d), as it revises a FIP under CAA
section 110(c).

L. Congressional Review Act (CRA)

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

M. Petitions for Judicial Review

    Under section 307(b)(1) of the Clean Air Act, petitions for
judicial review of this action must be filed in the United States Court
of Appeals for the appropriate circuit by June 13, 2016. Filing a
petition for reconsideration by the Administrator of this final rule
does not affect the finality of this rule for the purposes of judicial
review nor does it extend the time within which a petition for judicial
review may be filed, and shall not postpone the effectiveness of such
rule or action. This action may not be challenged later in proceedings
to enforce its requirements. See CAA section 307(b)(2).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by
reference, Nitrogen oxides, Reporting and recordkeeping requirements,
Visibility.

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

    Dated: March 29, 2016.
Gina McCarthy,
Administrator.
    Part 52, chapter I, title 40 of the Code of Federal Regulations is
amended as follows:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

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

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

Subpart D--Arizona

0
2. In Sec.  52.145:

0
a. Revise paragraphs (f)(3)(i) and (f)(5)(ii)(A).
0
b. Add paragraph (f)(5)(ii)(B).
0
c. Revise paragraph (f)(10).
0
d. Remove paragraph (f)(11).
    The revisions and addition read as follows:

Sec.  52.145  Visibility protection.

* * * * *
    (f) * * *
    (3) * * *
    (i) NOX emission limitations. The owner/operator of each coal-fired
unit subject to this paragraph (f) shall not emit or cause to be
emitted NOX in excess of the following limitations, in
pounds per million British thermal units (lb/MMBtu) from any coal-fired
unit or group of coal-fired units. Each emission limit shall be based
on a rolling 30-boiler-operating-day average, unless otherwise
indicated in specific paragraphs.

------------------------------------------------------------------------
                                                              Federal
      Coal fired unit or group of coal-fired units           emission
                                                            limitation
------------------------------------------------------------------------
Cholla Power Plant Units 2, 3, and 4....................           0.055
Coronado Generating Station Unit 1......................           0.065
Coronado Generating Station Unit 2......................           0.080
------------------------------------------------------------------------

* * * * *
    (5) * * *
    (ii) * * *
    (A) Cholla Power Plant. The 30-day rolling average NOX
emission rate for the group of coal-fired units identified as Cholla
Power Plant, Units 2, 3, and 4 shall be calculated for each calendar
day, even if a unit is not in operation on that calendar day, in
accordance with the following procedure: Step one, for each unit, sum
the hourly pounds of NOX emitted during the current boiler-
operating day (or most recent boiler-operating day if the unit is not
in operation), and the preceding twenty-nine (29) boiler-operating
days, to calculate the total pounds of NOX emitted over the
most recent thirty (30) boiler-operating day period for each coal-fired
unit; step two, for each unit, sum the hourly heat input, in MMBtu,
during the current boiler-operating day (or most recent boiler-
operating day if the unit is not in operation), and the preceding
twenty-nine (29) boiler-operating days, to calculate the total heat
input, in MMBtu, over the most recent thirty (30) boiler-operating day
period for each coal-fired unit; step 3, sum together the total pounds
of NOX emitted from the group of coal-fired units over each
unit's most recent thirty (30) boiler-operating day period (the most
recent 30 boiler-operating day periods for different units may be
different); step four, sum together the total heat input from the group
of coal-fired units over each unit's most recent thirty (30) boiler-
operating day period; and step five, divide the total pounds of
NOX emitted from step three by the total heat input from
step four for each group of coal-fired units, to calculate the 30-day
rolling average NOX emission rate for each group of coal-
fired units, in pounds of NOX per MMBtu, for each calendar
day. Each 30-day rolling average NOX emission rate shall
include all emissions and all heat input that occur during all periods
within any boiler-operating day, including emissions from startup,
shutdown, and malfunction.
    (B) Coronado Generating Station. Compliance with the NOX
emission limits for Coronado Unit 1 and Coronado Unit 2 in paragraph
(f)(3)(i) of this section shall be determined on a rolling 30 boiler-
operating-day basis. The 30-boiler-operating-day rolling NOX
emission rate for each unit shall be calculated in accordance with the
following procedure: Step one, sum the total pounds of NOX
emitted from the unit during the current boiler operating day and the
previous twenty-nine (29) boiler operating days; Step two, sum the
total heat input to the unit in MMBtu during the current boiler
operating day and the previous twenty-nine (29) boiler operating days;
Step three, divide the total number of pounds of NOX emitted
from that unit during the thirty (30) boiler operating days by the
total heat input to the unit during the thirty (30) boiler operating
days. A new 30-boiler-operating-day rolling average NOX
emission rate shall be calculated for each new boiler operating day.
Each 30-boiler-operating-day average NOX emission rate shall
include all emissions that occur during all periods within any boiler
operating day, including emissions from startup, shutdown, and
malfunction.
* * * * *
    (10) Equipment operations--(i) Cholla Power Plant. At all times,
including periods of startup, shutdown, and malfunction, the owner or
operator of Cholla Power Plant Units 2, 3 and 4 shall, to the extent
practicable, maintain and operate each unit including associated air
pollution control equipment in a manner consistent with good air
pollution control practices for minimizing emissions. Pollution control
equipment shall be designed and capable of operating properly to
minimize emissions during all expected operating conditions.
Determination of whether acceptable operating and maintenance
procedures are being used will be based on information available to the
Regional Administrator which may include, but is not limited to,
monitoring results, review of operating and maintenance procedures, and
inspection of each unit.
    (ii) Coronado Generating Station. At all times, including periods
of startup, shutdown, and malfunction, the owner or operator of
Coronado Generating Station Unit 1 and Unit 2 shall, to the extent
practicable, maintain and operate each unit in a manner consistent with
good air pollution control practices for minimizing emissions. The
owner or operator shall continuously operate pollution control
equipment at all times the unit it serves is in operation, and operate
pollution control equipment in a manner consistent with technological
limitations, manufacturer's specifications, and good engineering and
good air pollution control practices for minimizing emissions.
Determination of whether acceptable operating and maintenance
procedures are being used will be based on information available to the
Regional Administrator which may include, but is not limited to,
monitoring results, review of operating and maintenance procedures, and
inspection of each unit.
* * * * *
[FR Doc. 2016-07911 Filed 4-12-16; 8:45 am]
BILLING CODE 6560-50-P