```

[Federal Register Volume 80, Number 61 (Tuesday, March 31, 2015)]
[Proposed Rules]
[Pages 17010-17020]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2015-07233]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2015-0165; FRL-9925-31-Region 9]

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

AGENCY: Environmental Protection Agency.

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
revise part of the Arizona Regional Haze (RH) Federal Implementation 
Plan (FIP) applicable to the Coronado Generating Station (Coronado). In 
response to a petition for reconsideration from the Salt River Project 
Agricultural Improvement and Power District (SRP), the owner/operator 
of Coronado, we are proposing to replace 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 the NOX emissions from Units 1 and 
2 were established as 0.065 lb/MMBtu, we are proposing a unit-specific 
limit of 0.065 lb/MMBtu for Unit 1 and 0.080 lb/MMBtu for Unit 2. In 
addition, we are proposing to revise the work practice standard in the 
FIP for Coronado. Finally, we are proposing to remove the affirmative 
defense for malfunctions from the Arizona RH FIP, which applies to both 
Coronado and the Cholla Power Plant (Cholla).

DATES: Written comments must be submitted to the designated contact on 
or before May 15, 2015. Requests for a public hearing must be received 
on or before April 15, 2015.

ADDRESSES: Submit your comments, identified by docket number EPA-R09-
OAR-2015-0165, by one of the following methods:

[[Page 17011]]

     Federal Rulemaking portal: http://www.regulations.gov. 
Follow the on-line instructions for submitting comments.
     Email: webb.thomas@epa.gov.
     Fax: 415-947-3579 (Attention: Thomas Webb).
     Mail, Hand Delivery, or Courier: Thomas Webb, EPA Region 
9, Air Division (AIR-2), 75 Hawthorne Street, San Francisco, California 
94105. Hand and courier deliveries are only accepted Monday through 
Friday, 8:30 a.m. to 4:30 p.m., excluding Federal holidays. Special 
arrangements should be made for deliveries of boxed information.
    See the SUPPLEMENTARY INFORMATION section for further instructions 
on where and how to learn more about this proposal, attend a public 
hearing, or submit comments.

FOR FURTHER INFORMATION CONTACT: Thomas Webb, U.S. EPA, Region 9, 
Planning Office, Air Division, Air-2, 75 Hawthorne Street, San 
Francisco, CA 94105. Thomas Webb can be reached at telephone number 
(415) 947-4139 and via electronic mail at webb.thomas@epa.gov.

SUPPLEMENTARY INFORMATION: 

Table of Contents

I. General Information
II. Background
III. Proposed FIP Revision
IV. EPA's Proposed Action
V. Statutory and Executive Order Reviews

I. General Information

 A. Definitions

    For the purpose of this document, we are giving meaning to certain 
words or initials as follows:
     The words or initials Act or CAA mean or refer to the 
Clean Air Act, unless the context indicates otherwise.
     The initials ADEQ mean or refer to the Arizona Department 
of Environmental Quality.
     The words Arizona and State mean the State of Arizona.
     The initials BART mean or refer to Best Available Retrofit 
Technology.
     The term Class I area refers to a mandatory Class I 
Federal area.\1\
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    \1\ Although states and tribes may designate as Class I 
additional areas which they consider to have visibility as an 
important value, the requirements of the visibility program set 
forth in section 169A of the CAA apply only to ``mandatory Class I 
Federal areas.''
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     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 MW mean or refer to megawatts.
     The initials NOX mean or refer to nitrogen 
oxides.
     The initials NP mean or refer to National Park.
     The initials OFA mean or refer to over fire air.
     The initials RMB mean or refer to RMB Consulting and 
Research.
     The initials S&L mean or refer to Sargent and Lundy, a 
consulting firm.
     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 UPL mean or refer to Upper Prediction Limit.

B. Docket

    The proposed action relies on documents, information, and data that 
are listed in the index on http://www.regulations.gov under docket 
number EPA-R09-OAR-2015-0165. Although listed in the index, some 
information is not publicly available (e.g., Confidential Business 
Information (CBI)). Certain other material, such as copyrighted 
material, is publicly available only in hard copy form. Publicly 
available docket materials are accessible either electronically at 
http://www.regulations.gov or in hard copy at the Planning Office of 
the Air Division, AIR-2, EPA Region 9, 75 Hawthorne Street, San 
Francisco, CA 94105. EPA requests that you contact the individual 
listed in the FOR FURTHER INFORMATION CONTACT section to view the hard 
copy of the docket from Monday through Friday, 9-5:00 PDT, excluding 
Federal holidays.

C. Instructions for Submitting Comments to EPA

    Written comments must be submitted on or before May 15, 2015. 
Submit your comments, identified by docket number EPA-R09-OAR-2015-
0165, by one of the following methods:
     Federal Rulemaking portal: http://www.regulations.gov. 
Follow the on-line instructions for submitting comments.
     Email: webb.thomas@epa.gov.
     Fax: 415-947-3579 (Attention: Thomas Webb).
     Mail, Hand Delivery, or Courier: Thomas Webb, EPA Region 
9, Air Division (AIR-2), 75 Hawthorne Street, San Francisco, California 
94105. Hand and courier deliveries are only accepted Monday through 
Friday, 8:30 a.m. to 4:30 p.m., excluding Federal holidays. Special 
arrangements should be made for deliveries of boxed information.
    EPA's policy is to include all comments received in the public 
docket without change. We may make comments available online at http://www.regulations.gov, including any personal information provided, 
unless the comment includes information claimed to be CBI or other 
information for which disclosure is restricted by statute. Do not 
submit information that you consider to be CBI or that is otherwise 
protected through http://www.regulations.gov or email. The http://www.regulations.gov Web site is an ``anonymous access'' system, which 
means EPA will not know your identity or contact information unless you 
provide it in the body of your comment. If you send an email comment 
directly to EPA, without going through http://www.regulations.gov, we 
will include your email address as part of the comment that is placed 
in the public docket and made available on the Internet. If you submit 
an electronic comment, EPA recommends that you include your name and 
other contact information in the body of your comment and with any disk 
or CD-ROM you submit. If EPA cannot read your comment due to technical 
difficulties and cannot contact you for clarification, EPA may not be 
able to consider your comment. Electronic files should not include 
special characters or any form of encryption, and be free of any 
defects or viruses.

 D. Submitting Confidential Business Information

    Do not submit CBI to EPA through http://www.regulations.gov or 
email. Clearly mark the part or all of the information that you claim 
as CBI. For CBI information in a disk or CD-ROM that you mail to EPA, 
mark the outside of the disk or CD-ROM as CBI and identify 
electronically within the disk or CD-ROM the specific information that 
is claimed as CBI. In addition to one complete version of the comment 
that includes information claimed as CBI, you must submit a copy of the 
comment that does not contain the information claimed as CBI for 
inclusion in the public docket. We will not disclose information so 
marked except in accordance with procedures set forth in 40 CFR part 2.

E. Tips for Preparing Your Comments

    When submitting comments, remember to:
     Identify the rulemaking by docket number and other 
identifying

[[Page 17012]]

information (e.g., subject heading, Federal Register date and page 
number).
     Explain why you agree or disagree; suggest alternatives 
and substitute language for your requested changes.
     Describe any assumptions and provide any technical 
information and/or data that you used.
     If you estimate potential costs or burdens, explain how 
you arrived at your estimate in sufficient detail to allow for it to be 
reproduced.
     Provide specific examples to illustrate your concerns, and 
suggest alternatives.
     Explain your views as clearly as possible, avoiding the 
use of profanity or personal threats.
     Make sure to submit your comments by the identified 
comment period deadline.

F. Public Hearings

    If anyone contacts EPA by April 15, 2015 requesting to speak at a 
public hearing, EPA will schedule a public hearing and announce the 
hearing in the Federal Register. Contact Thomas Webb at 
webb.thomas@epa.gov or at (415) 947-4139 to request a hearing or to 
determine if a hearing will be held.

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 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.'' \2\ 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 natural 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.\3\ 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.\4\ 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 \5\ by reducing emissions that cause or 
contribute to regional haze.\6\ 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.\7\
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    \2\ 42 U.S.C. 7491(a)(1).
    \3\ 40 CFR 51.301.
    \4\ See CAA section 169B, 42 U.S.C. 7492.
    \5\ 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.''
    \6\ See generally 40 CFR 51.308.
    \7\ 40 CFR 51.308(e).
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B. History of FIP BART Determination

    The Arizona Department of Environmental Quality (ADEQ) submitted a 
RH SIP (``Arizona RH SIP'') under Section 308 of the RHR to EPA Region 
9 on February 28, 2011. The Arizona RH SIP included BART determinations 
for NOX, particulate matter (PM), and sulfur dioxide 
(SO2) for Units 1 and 2 at the Coronado Generating Station. 
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.\8\ 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. These limits correspond to the use 
of Selective Catalytic Reduction (SCR) control technology to reduce 
NOX emissions. We noted that a consent decree between SRP 
and 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. We explained that:
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    \8\ 77 FR 42834.

    . . . the emission limit of 0.080 lb/MMBtu established in the 
consent decree was not the result of a BART five-factor analysis, 
nor does the consent decree indicate that SCR at 0.080 lb/MMBtu 
represents BART. Nonetheless, given the compliance schedule 
established in the consent decree and the preliminary information 
received from SRP regarding the status of design and construction of 
the SCR system, it appears that achieving a 0.050 lb/MMBtu emission 
rate may not be technically feasible. Even if it is feasible, 
achievement of this emission rate may not be cost-effective. 
Therefore, we are proposing an emission limit of 0.080 lb/MMBtu as 
BART for NOX at Unit 2. However, if we do not receive 
sufficient documentation establishing that achievement of a more 
stringent limit is infeasible or not cost-effective, then we may 
determine that a more stringent limit for this unit is required in 
our final action.\9\
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    \9\ 77 FR 42864.

    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 and Lundy (S&L) and RMB Consulting and Research (RMB), which 
indicated that the Coronado units could achieve a rolling 30-day 
emission rate in the range of 0.053 to 0.072 lb/MMBtu.\10\ 
Specifically, the S&L report examined the effect of multiple startup/
shutdown events on emission rates over a 30-day period for Unit 2. 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.'' We explained the purpose of this 
control system in the preamble to our final rule:
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    \10\ 77 FR 72555.

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.\11\
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    \11\ Id.

The low-load temperature-control system is referred to as both 
``pegging steam'' and ``steam reheat'' in the various documents 
submitted by SRP. During periods of low load (138 MW to 270 MW), a 
certain amount of steam is routed to the SCR inlet in order to raise 
the inlet temperature to above 599 degrees F, which allows for proper 
operation of the SCR. At loads below 138 MW, the SCR could not operate 
even with the low-load temperature-control system.
    In setting the NOX emission limits for Coronado in the 
final Arizona RH FIP, we considered the information and analyses 
contained in the S&L report

[[Page 17013]]

and the RMB report.\12\ We concluded that:
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    \12\ Id. at 72554-56.

In recognition of the work already performed by SRP to meet the 
consent decree emission limit of 0.080 lb/MMBtu for Unit 2, and to 
avoid interfering with SRP's ability to meet that requirement by the 
deadline of June 1, 2014, we have decided not to require a BART 
emission limit for Coronado 2 more stringent than 0.080 lb/MMBtu. 
Instead, we are finalizing a plant-wide NOX emission 
limit for Coronado of 0.065 lb/MMBtu on a rolling 30-day average, 
which will provide a sufficient compliance margin for startup and 
shutdown events. We are also structuring the compliance 
determination method so that, when one of the two units is not 
operating, its emissions from the preceding thirty boiler-operating-
days will continue to be included in the two-unit average. We expect 
that SRP can meet this limit 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.\13\
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    \13\ Id. at 72555.

Please see our final rule published on December 5, 2012, for further 
information on the BART determinations and compliance methodology.

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 Clean Air Act (CAA) and section 705 of the 
Administrative Procedure Act.\14\ 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 RH 
FIP.\15\ In particular, we stated that we were granting reconsideration 
of the compliance methodology 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. Today's notice of 
proposed rulemaking includes each of these elements, and constitutes 
EPA's proposed action for the reconsideration.
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    \14\ 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).
    \15\ Letters from Jared Blumenfeld, EPA, to Norman W. Fichthorn 
and Aaron Flynn, Hunton and Williams (April 9, 2013).
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III. Proposed FIP Revision

    EPA is proposing a unit-specific compliance method and separate 
emission limits for NOX on Units 1 and 2 at the Coronado 
Generating Station. We also are proposing 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.

A. Proposed Compliance Method for Unit-Specific Emission Limits

    In a letter sent to EPA on November 18, 2013, SRP outlined its 
views concerning the compliance method and emission limit at 
Coronado.\16\ Regarding the compliance method, SRP requested that EPA 
use the same approach specified in the Consent Decree, noting that this 
would ensure ``consistency across applicable requirements.'' \17\ EPA 
notes that the Consent Decree contains two different types of 
NOX emission limits: Unit-specific 30-day rolling lb/MMBtu 
limits and a 365-day plant-wide rolling NOX tonnage 
limit.\18\ For purposes of BART, we consider a 30-BOD rolling lb/MMBtu 
limit to be appropriate.\19\ Therefore, we propose to set a separate 
30-BOD rolling lb/MMBtu limit for each of the two Coronado Units, based 
on the following compliance method:
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    \16\ Letter from Kelly Barr, SRP, to Deborah Jordan, EPA 
(November 18, 2013).
    \17\ Id. at 4.
    \18\ Consent Decree in United States v. Salt River Project, CV 
08-1479-PHX-JAT (D. Az.) (entered Dec. 19, 2008) (``Coronado Consent 
Decree'').
    \19\ BART Guidelines, 40 CFR part 51, appendix Y, section V 
(``For EGUs, specify an averaging time of a 30-day rolling average, 
and contain a definition of ``boiler operating day'' that is 
consistent with the definition in the proposed revisions to the NSPS 
for utility boilers in 40 CFR part 60, subpart Da.'').

    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, 
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shutdown, and malfunction.

This method is identical to that employed for the unit-specific 30-day 
rolling lb/MMBtu limit in the Consent Decree, except that it uses the 
term ``boiler operating day'' instead of ``Unit Operating Day.'' This 
method would replace the plant-wide method promulgated in the final 
rule at 40 CFR 52.145(f)(5)(B)(ii). 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

    Because we are proposing to replace the plant-wide average emission 
rate limit for NOX with unit-specific limits, we also must 
propose separate emission limits for each of the two units at Coronado. 
However, we are not reconsidering our determination that BART for 
Coronado Units 1 and 2 is an emission limit consistent with the use of 
SCR, low-NOX burners (LNB) with over fire air (OFA), and 
low-load temperature control. Nor are we conducting a new five-factor 
analysis for these units. Rather, we are reconsidering only the 
emission limits achievable with SCR and LNB with OFA at Coronado Units 
1 and 2. Due to the different regulatory requirements that currently 
apply to these units, we have analyzed them separately.
1. Proposed Emission Limit for Coronado Unit 1
a. SRP's Analysis of Unit 1
    After EPA granted reconsideration, SRP submitted additional 
information to EPA, including two reports prepared by S&L and RMB 
concerning the achievability of various NOX emission limits 
at Coronado Unit 1.\20\ The 2013 S&L analysis presented modeling 
results intended to predict NOX emissions from Unit 1 under 
various operating scenarios.\21\ The 2013 RMB report further analyzed 
the achievable NOX emission limit at Coronado Unit 1, 
``based on the results of S&L's modeling and application of an 
appropriate compliance margin.'' \22\ In particular, RMB applied an 
``upper prediction limit'' (UPL) technique in order to account for 
``the impact of measurement

[[Page 17014]]

uncertainty and other process variation.'' \23\
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    \20\ Letter from Kelly J. Barr, SRP, to Deborah Jordan, EPA 
(November 18, 2013) and attachments.
    \21\ Attachment 1 to November 18, 2013, Letter, Sargent and 
Lundy LLC Report SL-011754, Salt River Project Coronado Generating 
Station Unit 1 SCR NOX emissions Modeling (November 14, 
2013).
    \22\ Attachment 2 to November 18, 2013 Letter, Technical 
Memorandum from RMB Consulting & Research, Inc. to Salt River 
Project NOX limits Compliance monitoring Consideration on 
Coronado Unit 1 (October 28, 2013) at 1.
    \23\ Id.
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    The 2013 S&L report consisted of an emission analysis of the SCR 
for Unit 1. Similar to the 2012 S&L report, which concerned Unit 2, the 
2013 analysis examined the effect of startup/shutdown events, low-load 
cycling, and steam reheat on emissions over a 30-day average. In 
summary, the 2013 S&L analysis examined load profile data for Unit 1 
for the period from January 1, 2011, through July 31, 2013, and 
estimated NOX emission rates with the hypothetical use of 
SCR for the various load profiles that occurred during this period. 
S&L's estimates of SCR performance and emission rate under various load 
profiles are summarized in Table 1. For greater detail, consult the 
2013 S&L report, which is included in the docket for this proposed 
rule.

              Table 1--Unit 1 Load Profile of NOX Emissions
------------------------------------------------------------------------
                                 Unit 1 emission
         Load profile            rate (lb/MMBtu)        Description
------------------------------------------------------------------------
SCR Design Target Emission                  0.030  Full load performance
 Rate.                                              guarantee per
                                                    vendor.
SCR emission rate at full                   0.040  Actual controlled NOX
 load steady state conditions.                      emissions are
                                                    expected to average
                                                    0.01 above the
                                                    design target rate.
SCR emission rate when load                 0.050  Emission expected to
 increasing by more than 10                         change as control
 MW/hour.                                           systems adjust to
                                                    changes in boiler
                                                    load, gas flow
                                                    rates, and NOX
                                                    loading.
SCR emission rate when load                 0.035  Emission expected to
 decreasing by more than 10                         change as control
 MW/hour.                                           systems adjust to
                                                    changes in boiler
                                                    load, gas flow
                                                    rates, and NOX
                                                    loading.
Emission rate during cold                   0.10   Low NOX burners (LNB)
 start, oil-firing \24\.                            only, no SCR during
                                                    startup. Unit 1
                                                    initially uses fuel
                                                    oil for startup, and
                                                    transitions to coal
                                                    to complete startup.
Emission rate during cold                   0.25   LNB only, no SCR
 start, coal-firing.                                during startup.
Emission rate during warm                   0.19   LNB only, no SCR
 start, oil-firing \25\.                            during startup. Unit
                                                    1 initially uses
                                                    fuel oil for
                                                    startup, and
                                                    transitions to coal
                                                    to complete startup.
Emission rate during warm                   0.28   LNB only, no SCR
 start, coal-firing.                                during startup.
Emission rate during low load               0.29   For low-load periods
 periods.                                           with no steam reheat
                                                    (LNB-only, no SCR
                                                    control).
SCR emission rate during                    0.10   Emission rate during
 initial shutdown.                                  shutdown with SCR
                                                    inlet >599 degrees
                                                    F, allowing for SCR
                                                    operation.
Emission rate after SCR                     0.45   LNB only. Corresponds
 shutdown.                                          to shutdown period
                                                    after SCR inlet X Emissions Modeling'', Prepared by Sargent and Lundy, 
Report SL-011754, November 14, 2013.

          Table 2--Summary of Unit 1 Emission Modeling Results
                           [Per S&L analysis]
------------------------------------------------------------------------
                                                Controlled NOX emission
       Scenario              Description         rates based on 30-day
                                                  average (lb/MMBtu)
------------------------------------------------------------------------
0.....................  Full Load high-cycle                       0.041
                         loading.
1b....................  Low-load cycling for                       0.048
                         30 days (with steam
                         reheat).
5a....................  One cold startup                           0.055
                         with low-load
                         cycling (with steam
                         reheat).
5b....................  Two cold startups                          0.061
                         with low-load
                         cycling (with steam
                         reheat).
5c....................  Three cold startups                        0.065
                         with low-load
                         cycling (with steam
                         reheat).
------------------------------------------------------------------------

    The supplemental information submitted by SRP on November 13, 2013, 
also included a report from RMB. In this report, RMB stated that it 
used equations for calculating the UPL, which is a statistical 
technique that examines an existing set of data points and predicts the 
chances (i.e., the probability) of future data points (in this case, 
emission rates). In general terms, the UPL is a value that is 
calculated from a data set that identifies the emission rate that a 
source or group of sources is meeting and would be expected to meet a 
specified percent of the time that the source is operating. For 
example, the 99 percent UPL value is the emission level that the 
source(s) would be predicted to be below during 99 out of 100 
performance tests. The UPL value is calculated using an

[[Page 17015]]

equation based on the average and variance of a data set (in this 
instance, the aforementioned emission rates), the distribution of the 
data, quantity of data points, confidence level, and common statistical 
values such as t-scores and z-scores. The underlying regulatory concept 
behind the use of UPL values is that a source should have only a very 
small risk of being determined to be in noncompliance when the emission 
control system is actually performing as expected under each type of 
normal operation that takes place. UPL values are used in a wide 
variety of industries for predictive purposes, including finance, 
manufacturing, and healthcare.
    RMB stated that it applied the equations for calculating UPL values 
to CEMS data for Unit 1, as well as to the CEMS data from three SCR-
equipped coal-fired boilers that it considered comparable to Unit 
1.\27\ To summarize, RMB calculated the 99th percentile emission rate 
for each of the four units, and compared the 99th percentile emission 
rate to the average emission rate of each respective unit. RMB 
indicated that for Unit 1, the 99th percentile emission rate was three 
to seven percent greater than average emission rates. For the three 
SCR-equipped units examined, RMB reports that the 99th percentile 
emission rate was approximately 15 percent higher than average emission 
rates. RMB then adjusted the average 30-day emission rates from the S&L 
emission modeling analysis for each operating scenario upwards by 15 
percent in order to account for the variability indicated by the UPL 
values. The results of RMB's analysis are summarized in Table 3.
---------------------------------------------------------------------------

    \27\ The CEMS data examined for Unit 1 corresponded to operation 
with low NOX burners, as Unit 1 does not presently 
operate with SCR. For the three other units, CEMS data corresponding 
to SCR operation was examined.

          Table 3--Summary of Unit 1 Emission Modeling Results
                            [Per RMB report]
------------------------------------------------------------------------
                                                Controlled NOX emission
       Scenario              Description        rate (30-day average in
                                                       lb/MMBtu)
------------------------------------------------------------------------
1b....................  Low-load cycling for                       0.055
                         30 days (with steam
                         reheat).
5a....................  One cold startup                           0.062
                         with low-load
                         cycling (with steam
                         reheat).
5b....................  Two cold startups                          0.069
                         with low-load
                         cycling (with steam
                         reheat).
5c....................  Three cold startups                        0.073
                         with low-load
                         cycling (with steam
                         reheat).
------------------------------------------------------------------------

    RMB then indicated that if the emission limit were considered a 
``never to be exceeded value,'' an additional compliance margin should 
be incorporated given that the 99th percentile value does not account 
for the entire potential range of operating conditions that may occur. 
RMB indicated that rounding upwards to the next highest reasonable 
interval, 0.080 lb/MMBtu, would provide an approximate 10 percent 
compliance margin, and proposed that this value represents the lowest 
achievable NOX emission limit for Unit 1. The full RMB 
analysis is included in the docket for this proposed rule.
    SRP provided additional information to EPA on April 28, 2014, that 
included documentation on SCR design parameters for Unit 2, the number 
of historical startup events occurring within single 30-day periods for 
Units 1 and 2, and expected future operation of Units 1 and 2.\28\
---------------------------------------------------------------------------

    \28\ Letter from Kelly J. Barr, SRP, to Deborah Jordan, EPA 
(April 28, 2014) and attachments.
---------------------------------------------------------------------------

b. EPA's Evaluation of Unit 1
    In proposing a unit-specific limit for Unit 1, we have reviewed 
each of the analyses provided by SRP including the emission 
spreadsheets developed by S&L for several load profile scenarios. In 
addition, we have compared SRP's emission estimates for certain load 
profiles with actual Unit 1 emission data as reported to the Air 
Markets Program Data (AMPD).\29\ We consider the emission rates used by 
S&L for the various load profiles to be reasonable and generally 
consistent with emission data reported to AMPD. We also consider the 
scenarios examined by S&L to be realistic depictions of load profile 
scenarios that were historically experienced by the Coronado units. 
AMPD and Energy Information Administration (EIA) records indicate 
periods of both high-load and low-load cycling, as well as 30-day 
periods with multiple shutdown periods.\30\ The greatest number of cold 
startups occurring in a single 30-day period examined by the the S&L 
load profile scenarios was three. Although we have not identified an 
actual historical 30-day period exhibiting three cold startups, we 
consider this a reasonable assumption given both the number of startup 
events that have historically occurred,\31\ as well as SRP's 
expectation that the Coronado units will experience greater periods of 
operation in load-following service or non-operation given the expanded 
role of renewable energy sources.\32\ As a result, we consider the 
emission rate of 0.065 lb/MMBtu, which corresponds to a scenario 
consisting of low-load cycling operations (with steam reheat) and 3 
cold startups within a 30-day period, to be a reasonable estimate of 
average SCR performance for Unit 1.
---------------------------------------------------------------------------

    \29\ As noted in SRP's April 28, 2014 information response, we 
requested detailed emission spreadsheets for several scenarios, 
including high-load cycling, low-load cycling, and low-load cycling 
including multiple startups.
    \30\ See spreadsheet ``Coronado 2008-11 NOX Emission 
Data (daily).xls''.
    \31\ See SRP's April 28, 2014 letter, Attachment A (Multiple 
Start Summary).
    \32\ See April 28, 2014 letter. Expanded periods of load 
following service will result in greater periods of low-load 
cycling, as well as increase the need for startup/shutdown events.
---------------------------------------------------------------------------

    With regard to the RMB analysis, we are unable to assess fully this 
analysis, as it lacked documentation regarding many of its components. 
In particular, RMB did not identify the UPL equation(s) it used or the 
emission rate characteristics, data distribution, number of emission 
rates, or t- or z-scores. RMB did not present specific evidence that 
the two SCR-equipped units are representative of how Coronado will 
perform when carefully operated after installation of SCR. In 
particular, RMB did not address the possibility that the SCR systems on 
these two units malfunctioned or were incorrectly operated during the 
data period. Accordingly, we are unable to evaluate RMB's assertions 
regarding its UPL calculations.
    More fundamentally, we do not consider a UPL analysis to be 
necessary or appropriate for use in establishing an emission limit for 
Coronado Unit 1. Because the UPL method is a statistical technique, it 
is essentially an analytical tool that can be applied to any data set

[[Page 17016]]

and produce a UPL value for a specified percentile (i.e., 95th, 98th, 
99th percentile, etc). While UPL has been used by EPA to establish 
emission standards in other rulemakings, the context for those 
rulemakings differs significantly from the context for this action. In 
general, EPA has employed the UPL method in instances where it was 
necessary to establish an emission standard based on a limited number 
of emission measurements, such as when establishing maximum available 
control technology (MACT) standards or new source performance standards 
(NSPS).\33\ The emission data available for establishing MACT standards 
are generally in the form of short-term, three-run stack tests, with 
each test-run lasting between one and four hours. These short-term 
tests represent three ``snapshots'' of a source's operation and 
generally will not represent a source's full range of operations or 
emission levels. Accordingly, when establishing an emission standard 
that applies continuously across an entire source category, EPA 
considers it necessary to account for the emissions and operations over 
a fuller range using data sets that encompass longer time periods 
(i.e., collected over several months to a year or more of operation). 
In such situations, EPA applies the UPL method to predict the emission 
levels the source is achieving at times other than when the stack 
testing is conducted. For example, it is common for EPA to establish an 
emission standard for a particular source category for which only three 
to six test results may be available. Because these three to six data 
points do not represent the full range of unit operations, the UPL 
method is employed to ``fill in the blanks'' when developing an 
emission standard that is appropriate for a broader range of 
operations. As described in a memo regarding the use of UPL in 
establishing MACT standards, ``EPA did not have emissions information 
from sources at all times each source was operating, and therefore 
determined it was necessary to apply a methodology that addressed the 
fact that the data were not complete.'' \34\ Furthermore, while EPA has 
used the UPL method in other instances besides MACT standards, such as 
in developing NSPS, the emission data sets for those rulemakings were 
also very limited, numbering at most in the dozens of test results for 
specific source subcategories.
---------------------------------------------------------------------------

    \33\ In particular, EPA has used the UPL method in the Mercury 
and Air Toxics Standard (MATS), also known as the Boiler MACT, the 
Wool Fiberglass MACT, the Phosphoric Acid and Phosphate Fertilizer 
MACT, and the Nitric Acid Plant NSPS.
    \34\ Memorandum from Susan Fairchild to Docket Number EPA-HQ-
OAR-2010-1041, ``Use of the Upper Prediction Limit for Calculating 
MACT Floors'' (July 14, 2014); see also Memo from Susan Fairchild to 
Docket No. EPA-HQ-OAR-2010-1041, ``Approach for Applying the Upper 
Prediction Limit to Limited Datasets'' (October 6, 2014).
---------------------------------------------------------------------------

    By contrast, the data set available here is much more extensive, 
represents continuous data collected over a long period of time, and 
covers a wider range of unit operations. In particular, the UPL 
analyses performed by RMB for Coronado Unit 1 and the three SCR-
equipped coal-fired boilers examined actual emission data from CEMS (or 
in the case of Coronado Unit 1, modeled emission data based on actual 
load operation) that consisted of thousands of data points collected 
continuously over periods of time ranging from eight months to over a 
year. As noted above, this is a different context than rulemakings in 
which EPA has employed the UPL method to develop category-wide emission 
standards based on, at most, a few dozen data points. Given the size 
and scope of the data set available in this instance, we propose to 
find that the use of the UPL method is not appropriate.\35\
---------------------------------------------------------------------------

    \35\ In addition, we note that we consider RMB's application of 
its UPL-estimated variability to the results of the S&L modeling 
inappropriate. The S&L modeling results already account for 
substantial degree of operational variability by assuming a 
conservative operating scenario of low-load cycling and 3 cold 
startups in a single 30-day period. Applying the UPL-estimated 
variability on top of the S&L modeling could be described, to a 
degree, as ``double counting'' operational variability.
---------------------------------------------------------------------------

    Finally, we do not agree with RMB's suggestion that the emission 
limit for Coronado Unit 1 should be rounded up to provide an additional 
compliance margin. We note that the UPL methodology used by EPA for 
MACT standard development does not include rounding up to the next 
highest reasonable interval as suggested by RMB. Given the conservative 
nature of the assumptions in the S&L analysis, we do not consider 
additional compliance margin appropriate in this instance.
    Accordingly, in evaluating an appropriate limit for Coronado Unit 
1, we have relied primarily upon the information provided in the S&L 
analysis. This analysis found that an emission rate of 0.065 lb/MMBtu 
would be appropriate for a scenario consisting of low-load cycling 
operations (with steam reheat) and three cold startups within a 30-day 
period. As described above, we consider this to be a reasonable 
estimate of SCR performance for Coronado Unit 1. We are are therefore 
proposing a limit of 0.065 lb/MMBtu on a rolling 30-BOD basis.
2. Proposed Emission Limit for Coronado Unit 2
a. SRP's Analysis of Unit 2
    SRP also provided documentation in its April 28, 2014 letter of 
Unit 2 design parameters and indicated that it is proceeding with the 
installation of a low-load temperature-control system (i.e., steam 
reheat) for Unit 2. In addition, SRP stated that the design parameters 
demonstrate that Unit 2 was properly designed to meet the 0.080 lb/
MMBtu NOX limit required by the Coronado Consent Decree. 
Based on these design parameters and emission modeling performed by 
S&L, SRP reiterated that the design of Unit 2 could not accommodate a 
NOX emission limit lower than that required by the Consent 
Decree. SRP has met certain terms of the Consent Decree by operating 
Unit 2 with SCR since June 1, 2014. Finally, in response to an inquiry 
from EPA regarding the possibility of a work practice standard for the 
SCR system on Unit 2, SRP indicated that certain language from the 
Coronado Consent Decree and the Title V operating permit requiring 
proper operation of NOX controls are sufficient to ensure 
that NOX emissions are minimized.
b. EPA's Evaluation of Unit 2
    In our final rule published on December 5, 2012, establishing the 
NOX emission limit for Coronado Units 1 and 2, we stated the 
following regarding Unit 2:

In recognition of the work already performed by SRP to meet the 
consent decree emission limit of 0.080 lb/MMBtu for Unit 2, and to 
avoid interfering with SRP's ability to meet that requirement by the 
deadline of June 1, 2014, we have decided not to require a BART 
emission limit for Coronado 2 more stringent than 0.080 lb/MMBtu.

    The information subsequently provided by SRP supports the assertion 
that the emission limit in the Consent Decree of 0.080 lb/MMBtu 
represents BART for this unit. In particular, 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. As a result, we propose to 
set a unit-specific NOX limit for Unit 2 of 0.080 lb/MMBtu, 
based on a rolling 30-BOD basis.
    In addition, we propose to revise the work practice standard at 40 
CFR 52.145(f)(10) to require the operation of the SCR at all times that 
Unit 2 is in operation, consistent with technological

[[Page 17017]]

limitations.\36\ As noted in SRP's letter dated April 28, 2014, the 
Consent Decree contains a work practice standard for Unit 2. This 
language is included in the facility's current Title V operating 
permit.\37\ We are proposing to include this same language in the BART 
FIP in order to ensure that the SCR is operated at all times during 
which it is technologically feasible to do so. In particular, we note 
that, based on the information provided by SRP, periods of low-load 
operation are a significant element of the Coronado units' operations. 
Given the installation of a low-load temperature-control system on Unit 
2, the SCR system is now capable of operating at lower loads (i.e., 
between about 138 MW and 270 MW) on Unit 2. Accordingly, we are 
proposing to revise the work practice standard in the FIP to ensure 
that the SCR system operates during these periods of low-load 
operation.
---------------------------------------------------------------------------

    \36\ See CAA Section 302(k) (defining ``emission limit'' to 
include ``any requirement relating to the operation or maintenance 
of a source to assure continuous emission reduction, and any design, 
equipment, work practice or operational standard promulgated under 
this chapter'').
    \37\ Specific Conditions II.E.2.b and c, Title V Operating 
Permit No. 52693, issued December 6, 2011.
---------------------------------------------------------------------------

C. Proposed Removal of Affirmative Defense for Malfunctions

    The Arizona RH FIP incorporates by reference certain provisions of 
the Arizona Administrative Code that establish an affirmative defense 
for excess emissions due to malfunctions.\38\ In the interim since 
EPA's promulgation of that FIP, the United States Court of Appeals for 
the DC Circuit ruled that CAA sections 113 and 304 preclude EPA from 
creating affirmative defense provisions in the Agency's own regulations 
imposing emission limits on sources.\39\ The court found that such 
affirmative defense provisions purport to alter the jurisdiction of 
federal courts to assess liability and impose penalties for violations 
of those limits in private civil enforcement cases. The court's holding 
makes it clear that the CAA does not authorize promulgation of such a 
provision by EPA. In particular, the court's decision turned on an 
analysis of CAA sections 113 (``Federal enforcement'') and 304 
(``Citizen suits''). These provisions apply with equal force to a civil 
action brought to enforce the provisions of a FIP. The logic of the 
court's decision thus applies to the promulgation of a FIP, and 
precludes EPA from including an affirmative defense provision in a FIP. 
Furthermore, in light of the DC Circuit's decision, EPA has proposed to 
find R18-2-310(B) and R18-2-310(C) substantially inadequate to meet CAA 
requirements and to issue a SIP call with respect to these 
provisions.\40\ Consistent with the reasoning of the DC Circuit and 
EPA's proposed SIP call, we are proposing to remove the affirmative 
defense provision in the Arizona Regional Haze FIP. In addition to 
Coronado, this revision would also affect Cholla.
---------------------------------------------------------------------------

    \38\ See 40 CFR 52.145(f)(11) (incorporating by reference R-18-
2-101, paragraph 65; R18-2-310, sections (A), (B), (D) and (E); and 
R18-2-310.01).
    \39\ See NRDC v. EPA, 749 F.3d 1055 (D.C. Cir. 2014).
    \40\ 79 FR 55920, 55947 (September 17, 2014).
---------------------------------------------------------------------------

D. Non-Interference With Applicable Requirements

    The CAA requires that any revision to an implementation plan shall 
not be approved by the Administrator if the revision would interfere 
with any applicable requirement concerning attainment, reasonable 
further progress, or any other applicable requirement of the CAA.\41\
---------------------------------------------------------------------------

    \41\ CAA Section 110(l), 42 U.S.C. 7410(l). In this instance EPA 
is proposing to promulgate a revision to a FIP, rather than to 
approve a revision to a SIP. Although 110(l) on its face applies 
only to EPA approvals of plan revisions, we have nonetheless 
considered whether this proposed action would interfere with the 
requirements of the CAA.
---------------------------------------------------------------------------

    EPA has promulgated health-based standards, known as the national 
ambient air quality standards (NAAQS), for seven pollutants, including 
NO2, a component of NOX, and pollutants such as 
ozone and particulate matter with a diameter less than or equal to 2.5 
micrometers (PM2.5), that are formed in the atmosphere from 
reactions between NOX and other pollutants. Using a process 
that considers air quality data and other factors, EPA designates areas 
as ``nonattainment'' if those areas violate a NAAQS or cause or 
contribute to violations of a NAAQS in a nearby area. Reasonable 
further progress, as defined in section 171 of the CAA, is related to 
attainment and means ``such annual incremental reductions in emissions 
of the relevant air pollutant . . . for the purpose of ensuring 
attainment of the applicable [NAAQS].'' Coronado is located in Apache 
County, Arizona, which is designated as Unclassifiable/Attainment for 
all of the NAAQS. Therefore, we propose to find that a revision to the 
BART emission limits for NOX will not interfere with 
attainment or reasonable further progress for any air quality standard.
    The other requirements of the CAA that are applicable to Coronado 
are:
     Standards of Performance for New Stationary Sources, 40 
CFR part 60, subpart D;
     National Emission Standards for Hazardous Air Pollutants, 
40 CFR part 63, subpart UUUUU;
     Compliance Assurance Monitoring, 40 CFR part 64;
     BART and other visibility protection requirements under 
CAA sections 110(a)(2)(J) and 169A and 40 CFR part 51, subpart P; and
     Interstate transport visibility requirements under CAA 
section 110(a)(2)(D)(i)(II).
    Today's proposed revisions would not affect the applicable 
requirements of the National Emission Standards for Hazardous Air 
Pollutants, Standards of Performance for New Stationary Sources, or 
Compliance Assurance Monitoring requirements. Therefore, we propose to 
find that these revisions would not interfere with these requirements.
    The proposed revisions would alter the specific emission limits 
that constitute BART for NOX at Coronado under CAA section 
169A and 40 CFR 51.308(e). However, we expect the effect of the 
proposed changes on visibility will be very small. In particular, we 
note that, under the BART Guidelines, the ``degree of visibility 
improvement'' expected to result from BART is evaluated through 
modeling of the highest emission rate observed on a 24-hour 
average.\42\ Although today's rule would raise the emission rate 
allowed on a 30-day rolling average, we do not expect that it would 
alter the rate on a 24-hour basis. First, the 24-hour maximum emission 
rate used in visibility modeling corresponds to operation of the SCR 
during periods of full load, steady state operation. As noted 
previously, the BART limits proposed in today's rule are still 
consistent with the application of SCR. In addition, the underlying 
assumptions regarding SCR emission rate and performance remain 
unchanged from the December 5, 2012, final rule. Second, the 
adjustments to the rolling 30-day emission limit were made to 
accommodate periods of startup and shutdown. Specifically, BART limits 
for EGUs are established based on a 30-day rolling average and must be 
met on a continuous basis, including during periods of startup, 
shutdown, and malfunction.\43\ As described previously, the SCR system 
requires a certain minimum temperature in order to operate properly. As 
a result, there will necessarily be certain periods of time during 
startup and shutdown in which the SCR system is not technologically

[[Page 17018]]

capable of operating. This does not alter any of the assumptions 
regarding the SCR system when it is in operation, such as the maximum 
24-hour emission rate, which is the basis of the visibility modeling. 
Moreover, the BART Guidelines recommend that periods of startup and 
shutdown be excluded from the visibility modeling.\44\ Therefore, the 
degree of visibility improvement would not be significantly diminished.
---------------------------------------------------------------------------

    \42\ BART Guidelines 40 CFR part 51, Appendix Y, section IV.D.5.
    \43\ See CAA section 302(k).
    \44\ Id. section III.A.3 (recommending that ``emissions 
reflecting periods of start-up, shutdown, and malfunction'' not be 
used for modeling.).
---------------------------------------------------------------------------

    With respect to the CAA's reasonable progress requirements under 
CAA section 110(a)(2)(J) and 169A, we note that in a September 3, 2014, 
final rule, we set reasonable progress goals (RPGs) for Arizona that 
accounted for the emission reductions projected to result from 
implementation of BART at Coronado (among other sources).\45\ The 
revised emission limits we are proposing today will allow for greater 
total annual NOX emissions than the FIP. We have therefore 
considered the impact of additional emissions on the RPGs. As 
summarized in Tables 4 and 5, the difference in NOX 
emissions between the Arizona RH FIP and today's proposed rule is 
approximately 233 tons per year (tpy).\46\ This amount represents less 
than one percent of the projected total NOX emission 
reductions in the FIP. Therefore, we consider its potential impact on 
the RPGs to be de minimis.
---------------------------------------------------------------------------

    \45\ 79 FR 52420, 52468-52469.
    \46\ This value assumes that the units will fully operate at the 
allowed emission rates in Table 4 and 5 for every month of the year. 
Given that the 30-BOD limits are based on conditions that occur 
infrequently (i.e., low-load cycling, 3 cold startup/shutdowns), 
during many periods the units can be expected to operate at a lower 
emission rate. As a result, this value represents a conservative 
(i.e., tending to overestimate rather than underestimate in this 
context) estimate of the difference in NOX emissions.
---------------------------------------------------------------------------

    Finally, CAA section 110(a)(2)(D)(i)(II) requires that all SIPs 
contain adequate provisions to prohibit emissions that will interfere 
with other states' required measures to protect visibility. In our 
final rule of September 3, 2014, we determined that control measures in 
the Arizona RH SIP and FIP were sufficient to fulfill this requirement 
for the 1997 8-hour ozone, 1997 PM2.5, and 2006 
PM2.5 NAAQS.\47\ As noted above, while today's proposal 
would allow for an increase in emissions of 233 tpy compared to the 
FIP, this represents less than one percent of the projected total 
NOX emission reductions in the FIP. Accordingly, we propose 
to determine that this change would not alter our determination that 
the control measures in the Arizona RH SIP and FIP are adequate to 
prevent Arizona's emissions from interfering with other states' 
required measures to protect visibility. Thus, we propose to find that 
today's proposed revisions would not interfere with any applicable 
requirement of the CAA.
---------------------------------------------------------------------------

    \47\ 79 FR 52426.

                                             Table 4--Coronado SCR Emission Rate Allowed Under 2012 EPA FIP
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Heat duty \1\      NOX emission limit                                          NOX
                                                ---------------------         \2\                              -----------------------------------------
                    Unit No.                                         --------------------- Capacity factor \1\
                                                      (MMBtu/hr)           (lb/MMBtu)                                 (lb/hr)               (tpy)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Coronado 1.....................................                 4316                0.065                 0.84               280.54                2,042
Coronado 2.....................................                 3984  ...................                 0.89               258.96  ...................
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Supplemental Cost Analysis 2012-11-15.
\2\ Emission limit per FIP final rule, 77 FR 72578.

                                    Table 5--Coronado SCR Emission Rate Allowed Under Proposed 2015 EPA FIP Revision
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Heat duty \1\      NOX emission limit                                          NOX
                    Unit No.                    ------------------------------------------ Capacity factor \1\ -----------------------------------------
                                                      (MMBtu/yr)           (lb/MMBtu)                                 (lb/hr)               (tpy)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Coronado 1.....................................                 4316                0.065                 0.84               280.54                2,275
Coronado 2.....................................                 3984                0.080                 0.89               318.72  ...................
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Supplemental Cost Analysis 2012-11-15.

IV. EPA's Proposed Action

    EPA is proposing to revise the Arizona RH 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. As described in today's action, we 
are proposing an emission limit 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 would constitute our action on SRP's petition for 
reconsideration of the FIP. We also are proposing to remove the 
affirmative defense for malfunctions in the FIP and revise the work 
practice requirement that applies to Coronado.

V. Statutory and Executive Order Reviews

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

    This action is not a significant regulatory action 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 provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. 
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 proposed 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

[[Page 17019]]

by this rule, SRP, Arizona Public Service 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

    EPA interprets EO 13045 as applying only to those regulatory 
actions that concern health or safety risks that 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. EPA is not 
proposing to revise any technical standards or impose any new technical 
standards in this action.

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

    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 
shown in Tables 4 and 5 above, the difference in NOX 
emissions between the final EPA FIP and today's proposed rule is 
approximately 233 tons per year (tpy). 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 3 
percent of the 7,300 tpy of NOX that the facility is 
presently allowed to emit under the Coronado Consent Decree.\48\ 
Furthermore, as shown in Table 5, if today's proposal is finalized, 
total NOX emissions from the facility would be roughly 2,275 
tpy, a decrease of over 5,000 tpy compared to the plant-wide cap under 
the Consent Decree. Thus, although today's proposed revision will allow 
for a marginal increase in emissions compared to the FIP, it will still 
ensure a significant reduction in emissions compared to present levels.
---------------------------------------------------------------------------

    \48\ Coronado Consent Decree, paragraph 44.
---------------------------------------------------------------------------

K. Determination Under Section 307(d)

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

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 13, 2015.
Jared Blumenfeld,
Regional Administrator, EPA Region IX.

    Part 52, chapter I, title 40 of the Code of Federal Regulations is 
proposed to be 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, revise paragraphs (f)(3)(i), (f)(5)(ii)(A) and (B), 
and (f)(10) and remove paragraph (f)(11) to 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

[[Page 17020]]

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. 2015-07233 Filed 3-30-15; 8:45 am]
 BILLING CODE 6560-50-P
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