
[Federal Register Volume 82, Number 57 (Monday, March 27, 2017)]
[Rules and Regulations]
[Pages 15139-15154]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-05724]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2016-0292; FRL-9958-79-Region 9]


Approval and Revision of Air Plans; Arizona; Regional Haze State 
and Federal Implementation Plans; Reconsideration

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is taking final 
action to approve a source-specific revision to the Arizona state 
implementation plan that addresses the best available retrofit 
technology requirements for the Cholla Power Plant (Cholla). The EPA 
finds that the state implementation plan revision fulfills the 
requirements of the Clean Air Act and the EPA's Regional Haze Rule. In 
conjunction with this final approval, the EPA is taking final action to 
withdraw the federal implementation plan provisions applicable to 
Cholla. This also constitutes our action to address petitions for 
reconsideration granted by the EPA related to Cholla.

DATES: This rule is effective on April 26, 2017.

ADDRESSES: The EPA has established a docket for this action, identified 
by Docket ID Number EPA-R09-OAR-2016-0292. The index to the docket is 
available electronically at http://www.regulations.gov or in hard copy 
at the EPA Region IX office, 75 Hawthorne Street, San Francisco, 
California. While all documents in the docket are listed in the index, 
some information may be publicly available only at the hard copy 
location (e.g., copyrighted material), and some may not be publicly 
available in either location (e.g., confidential business information). 
To inspect the hard copy materials, please schedule an appointment 
during normal business hours with the contact listed below.

FOR FURTHER INFORMATION CONTACT: Anita Lee, (415) 972-3958, or by email 
at lee.anita@epa.gov.

SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,'' 
``us,'' or ``our'' is used, we mean the EPA.

Table of Contents

I. Background
II. Public Comments and the EPA's Response to Comments
    A. Comments on the BART Reassessment
    B. Comments on Visibility Benefits
    C. Comments on the CAA Section 110(l) Analysis
    D. Other Comments
III. Summary of Final Action
IV. Environmental Justice Considerations
V. Incorporation by Reference
VI. Statutory and Executive Order Reviews

I. Background

    On July 19, 2016, the EPA proposed to approve the source-specific 
regional haze state implementation plan (SIP) revision for the Cholla 
Power Plant (``Cholla SIP Revision'') submitted to the EPA by the 
Arizona Department of Environmental Quality (ADEQ).\1\ The EPA 
concurrently proposed to withdraw federal implementation plan (FIP) 
provisions applicable to Cholla and proposed that the FIP withdrawal 
would constitute the EPA's action on petitions for reconsideration of 
the FIP.
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    \1\ See 81 FR 46852, July 19, 2016.
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    This section provides a brief overview of the statutory and 
regulatory background for this action. Please refer to the proposed 
rule for additional discussion of the visibility protection provisions 
of the Clean Air Act (CAA or ``Act'') and the Regional Haze Rule (RHR), 
and the EPA's evaluation of the regional haze SIP revision for 
Cholla.\2\
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    \2\ Id.
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    In section 169A of the 1977 Amendments to the CAA, Congress created 
a program to protect visibility in the nation's national parks and 
wilderness areas. This section of the CAA established as a national 
goal the ``prevention of any future, and the remedying of any existing, 
impairment of visibility in mandatory Class I Federal areas which 
impairment results from manmade air pollution,'' and directed states to 
evaluate the best available retrofit technology (BART) to address 
visibility impairment from certain categories of major stationary 
sources built between 1962 and 1977 (known as ``BART-eligible'' 
sources).\3\ In the 1990 CAA Amendments, Congress amended the 
visibility provisions of the CAA to focus attention on the problem of 
regional haze, i.e., visibility impairment produced by a multitude of 
sources and activities located across a broad geographic area.\4\
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    \3\ See CAA section 169A(a)(1).
    \4\ See CAA section 169B.
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    In 1999, the EPA promulgated the RHR that required states to, among 
other things, conduct an analysis to determine BART for each BART-
eligible source that may be anticipated to cause or contribute to 
visibility impairment in a Class I area.\5\ States must analyze and 
consider the following five factors as part of each source-specific 
BART analysis: (1) The costs of compliance, (2) the energy and nonair 
quality environmental impacts of compliance, (3) any existing pollution 
control technology in use at the source, (4) the remaining useful life 
of the source, and (5) the degree of visibility improvement that may 
reasonably be anticipated to result from use of such technology 
(collectively known as the ``five-factor BART analysis'').\6\ In 
determining BART for fossil fuel-fired electric generating plants with 
a total generating capacity in excess of 750 megawatts (MW), states 
must use guidelines promulgated by the EPA.\7\ In 2005, the EPA 
published the

[[Page 15140]]

current version of the ``Guidelines for BART determinations under the 
Regional Haze Rule,'' codified at appendix Y to 40 CFR part 51 (``BART 
Guidelines'').\8\
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    \5\ 40 CFR 51.308(e).
    \6\ See CAA section 169A(g)(2) and the RHR at 40 CFR 
51.308(e)(1)(ii)(A).
    \7\ See CAA section 169A(b)(1) and the last sentence of 169A(b).
    \8\ See 70 FR 39104, July 6, 2005.
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    Cholla consists of four coal-fired electric generating units with a 
total plant-wide generating capacity of 1150 MW. Unit 1 is a 126 MW 
boiler that is not BART-eligible. Unit 2 (272 MW), Unit 3 (272 MW), and 
Unit 4 (410 MW) are tangentially-fired dry bottom boilers that are 
BART-eligible. Units 1, 2, and 3 are owned and operated by Arizona 
Public Service Company (APS). Unit 4 is owned by PacificCorp and 
operated by APS.
    On February 28, 2011, ADEQ submitted a regional haze SIP under 
section 308 of the RHR to the EPA (``2011 RH SIP''). This submittal 
included, among other things, BART analyses and determinations for 
Cholla Units 2, 3, and 4 for oxides of nitrogen (NOX), 
particulate matter with an aerodynamic diameter of less than 10 
micrometers (PM10), and sulfur dioxide (SO2).\9\ 
On December 5, 2012, the EPA took final action that approved in part 
and disapproved in part the 2011 RH SIP. The EPA found that ADEQ's 
overall approach in conducting its BART analyses was appropriate, but 
we also identified significant flaws in the analyses for specific BART 
factors that warranted disapproval of the NOX BART 
determination for Cholla. Specifically, the EPA found that ADEQ did not 
calculate the costs of compliance in accordance with the BART 
Guidelines, did not appropriately evaluate and consider the visibility 
benefits, did not provide sufficient explanation and rationale for its 
final BART determination, and did not include enforceable emission 
limits in the SIP.\10\ In the same action, the EPA promulgated a FIP 
for the disapproved portions of the SIP, including a NOX 
BART determination for Cholla that established an emission limit of 
0.055 pound per million British thermal units (lb/MMBtu) determined 
across the three units on a rolling 30-boiler-operating-day average, 
with a compliance date of December 5, 2017. This limit is achievable 
with the combination of low-NOX burners with separated over-
fire air (LNB+SOFA) and selective catalytic reduction (SCR). The FIP 
also established an SO2 removal efficiency requirement of 95 
percent for Units 2, 3, and 4 with a compliance date for Units 3 and 4 
of December 5, 2013, and a compliance date for Unit 2 of April 1, 2016. 
Finally, the FIP also established compliance deadlines, compliance 
determination methodologies, and requirements for equipment 
maintenance, monitoring, recordkeeping, and reporting for 
NOX, SO2 and PM10.\11\ On April 9, 
2013, the EPA granted petitions to reconsider the compliance 
determination methodology for NOX.\12\
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    \9\ The 2011 RH SIP submittal is document number 0017 in the 
docket for this rulemaking at EPA-R09-OAR-2016-0292, entitled 
``B.1.a ADEQ RH 308 SIP 2011-SIP only.''
    \10\ See generally, Ariz. Ex rel. Darwin v. U.S. EPA, 815 F.3d 
519 (9th Circuit, 2016).
    \11\ See 77 FR 72511, December 5, 2012.
    \12\ See letter from Jared Blumenfeld, EPA Region IX, to E. 
Blaine Rawson, Ray Quinney & Nebeker P.C. (on behalf of PacifiCorp), 
dated April 9, 2013; letter from Jared Blumenfeld, EPA Region IX, to 
Norman Fichthorn, Hunton and Williams LLP (on behalf of APS), dated 
April 9, 2013; and letter from Jared Blumenfeld, EPA Region IX, to 
Aaron Flynn, Hunton and Williams LLP (on behalf of APS), dated April 
9, 2013.
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    On January 15, 2015, APS and PacifiCorp submitted an ``Application 
for Significant Permit Revision and Five-Factor BART Reassessment for 
Cholla'' to ADEQ. APS and PacifiCorp committed to take specific actions 
in lieu of the FIP requirements for Cholla and requested that ADEQ 
conduct a revised BART analysis and determination (``BART 
Reassessment'') and submit it to the EPA as a revision to the Arizona 
RH SIP. Specifically, APS and PacifiCorp committed to (1) permanently 
close Cholla Unit 2 by April 1, 2016, (2) continue to operate LNB+SOFA 
on Units 3 and 4, and (3) by April 30, 2025, permanently cease burning 
coal at both units with the option to convert both units to enable 
combustion of pipeline-quality natural gas by July 31, 2025, with an 
annual average capacity factor of less than or equal to 20 percent.
    On October 22, 2015, ADEQ submitted to the EPA the Cholla SIP 
Revision that incorporates the Cholla BART Reassessment. The Cholla SIP 
Revision consists of a revised BART analysis and determination for 
NOX, an analysis under CAA section 110(l), and revisions to 
Cholla's operating permit to implement ADEQ's revised BART 
determination for NOX and the commitments by APS and 
PacifiCorp related to the retirement and repowering of units.\13\ ADEQ 
determined that if APS closed Unit 2 by April 1, 2016, no BART 
determination for Unit 2 would be necessary because the enforceable 
closure date is within the 5-year window for compliance with BART. For 
Units 3 and 4, ADEQ conducted a revised BART analysis in light of the 
commitments made by APS and PacifiCorp regarding future operation of 
those units. Based on its re-analysis of the BART factors, ADEQ 
determined BART for Cholla Units 3 and 4 to be LNB+SOFA when coal is 
combusted in those units. In the permit revision submitted as part of 
the Cholla SIP Revision, ADEQ established unit-specific emission limits 
for Cholla Units 3 and 4 of 0.22 lb/MMBtu, effective until the 
permanent cessation of coal burning on April 30, 2025, and an emission 
limit of 0.08 lb/MMBtu, effective May 1, 2025 and thereafter, that 
would apply if Units 3 or 4 are repowered to natural gas. Although 
ADEQ's BART determination for Cholla Units 3 and 4 is LNB+SOFA, the 
permit revision for Cholla sets an emission limitation achievable with 
this technology, but it does not specify that LNB+SOFA must be used.
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    \13\ The Cholla SIP Revision is document number 0019 in the 
docket for this rulemaking at EPA-R09-OAR-2016-0292, titled ``B.3. 
2015-10-22--Cholla SIP Revision.''
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    The EPA's proposed action on the Cholla SIP Revision includes a 
comprehensive summary of ADEQ's BART Reassessment for Cholla Units 3 
and 4, and the EPA's evaluation of ADEQ's submittal. In this section, 
we provide a brief summary of the EPA's evaluation of the Cholla SIP 
Revision. Please see the proposed rule for a detailed discussion of 
ADEQ's analysis and the EPA's evaluation of it.\14\
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    \14\ See 81 FR 46852 at 46854-46863, July 19, 2016.
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    In our evaluation of Cholla Unit 2, we noted that the permanent 
retirement date of April 1, 2016, in the Cholla SIP Revision coincides 
with the compliance deadlines for SO2 and PM10 in 
the FIP and precedes the compliance deadline for NOX by over 
1 year. The EPA further noted that Unit 2 permanently closed on October 
1, 2015.\15\ If Unit 2 had not retired, APS would have been required to 
install additional controls to meet the applicable SO2, 
PM10, and NOX limits. Because the requirement for 
the permanent retirement of Unit 2 will become effective and federally 
enforceable when the Cholla SIP Revision is approved into the SIP and 
the FIP provisions applicable to Cholla are withdrawn, we proposed 
approval of the requirement for permanent retirement of Unit 2 as 
meeting the requirements of the CAA and the RHR.
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    \15\ See letter from Edward Seal, APS, to Kathleen Johnson, EPA, 
and Eric Massey, ADEQ, dated October 28, 2015.
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    In our evaluation of Units 3 and 4, we found that ADEQ's BART 
Reassessment was consistent with the requirements of the CAA, the RHR, 
and the BART Guidelines and that it addressed the flaws that were the 
bases for our disapproval of the BART analysis for Cholla. 
Specifically, in its 2011 RH SIP,

[[Page 15141]]

ADEQ's cost analysis was flawed because it included certain line item 
costs that were inconsistent with the EPA Control Cost Manual (CCM). 
This approach did not comply with the direction in the BART Guidelines 
to base cost estimates on the CCM. In its BART Reassessment for Cholla, 
ADEQ relied on the cost estimates, calculated using the CCM 
methodology, that the EPA developed as part of the FIP for Cholla.
    In its 2011 RH SIP, ADEQ considered the visibility benefits of 
controls on only one unit at a time and overlooked significant benefits 
at the multiple Class I areas, thereby understating and not giving 
appropriate consideration to the full visibility benefits of the 
candidate controls. In its BART Reassessment for Cholla, based on 
modeling performed by APS and PacifiCorp, ADEQ evaluated the visibility 
impacts and potential improvements from all units together and also 
considered potential improvements at all 13 Class I areas within 300 
kilometers of Cholla.
    As discussed in our proposed rulemaking, the EPA also proposed to 
find that ADEQ appropriately considered and weighed the five BART 
factors in determining BART for Cholla. We stated that it was 
reasonable for ADEQ to conclude that the costs of SCR and selective 
noncatalytic reduction (SNCR) were not warranted by the visibility 
benefits. Specifically, we noted that we were not aware of any instance 
in which the EPA had determined SCR or SNCR to be BART where the 
average and incremental cost-effectiveness of those controls equaled or 
exceeded the average and incremental cost-effectiveness of those 
controls for Cholla Units 3 and 4. Nor were we aware of any instance in 
which the EPA disapproved a state's BART determination that rejected 
SCR or SNCR as BART based on average and incremental cost-effectiveness 
similar to those for Cholla Units 3 and 4. In addition, although we 
noted that the visibility benefits of SCR are significant, and the 
visibility benefits of SNCR are not insignificant, we determined that 
it was reasonable for ADEQ to determine that the benefits were not 
warranted given the costs of SCR and SNCR. Moreover, after 
approximately 8 years, when Units 3 and 4 cease coal combustion 
permanently and are either closed or converted to natural gas, the 
benefits of SCR and SNCR would be negligible.
    Finally, in our proposed rulemaking, we evaluated the Cholla SIP 
Revision with respect to certain other requirements of the CAA and 
proposed to find that it would not interfere with attainment of the 
national ambient air quality standards (NAAQS), reasonable further 
progress, or any other applicable requirement of the CAA. We further 
noted that the enforceable emission limitations and the requirements 
for monitoring, recordkeeping, and reporting promulgated in the FIP for 
Cholla are included in the operating permit revision for Cholla that 
ADEQ included with its Cholla SIP Revision. Therefore, these 
requirements will remain federally enforceable when the Cholla SIP 
Revision is approved and the FIP provisions are withdrawn. Based on our 
evaluation of the Cholla SIP Revision, we proposed to approve the SIP 
revision, withdraw the FIP provisions, and to find that withdrawal of 
the FIP would constitute our action on the petitions for 
reconsideration submitted by APS and PacifiCorp.

II. Public Comments and the EPA's Response to Comments

    We received four comment letters from the following organizations 
prior to the close of the comment period on September 2, 2016: (1) APS, 
(2) PacifiCorp, (3) Environmental Defense Fund and Western Resource 
Advocates, and (4) Earthjustice on behalf of National Parks 
Conservation Association and Sierra Club.\16\
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    \16\ See (1) letter from Chas Spell, Arizona Public Service, to 
Gina McCarthy, EPA, re: Arizona Public Service Company Comments on 
EPA's Proposed Rule Approval and Revision of Air Plans; Arizona; 
Regional Haze State and Federal Implementation Plans; 
Reconsideration, dated September 1, 2016; (2) letter from William K. 
Lawson, Pacificorp, to Vijay Limaye, EPA, re: Docket ID No. EPA-R09-
OAR-2016-0292 Approval and Revision of Air Plans; Arizona; Regional 
Haze State and Federal Implementation Plans; Reconsideration 
(Proposed Rule), dated September 1, 2016; (3) letter from Bruce 
Polkowsky, Graham McCahan, Environmental Defense Fund, and John 
Nielsen, Western Resource Advocates to Vijay Limaye, EPA, re: 
Comments on the proposed approval of a source-specific revision to 
the Arizona Implementation Plan for Best Available Retrofit 
Technology at Cholla Generating Station. Docket ID No. EPA-R09-OAR-
2016-0292, undated letter submitted to www.regulations.gov on 
September 2, 2016; and (4) letter from Michael Hiatt, Earthjustice 
on behalf of Kevin Dahl, Stephanie Kodish, and Nathan Miller, 
National Parks Conservation Association, and Sandy Bahr, Bill 
Corcoran, and Gloria Smith, Sierra Club, to Vijay Limaye, EPA, re: 
Arizona Regional Haze Plan--Cholla BART Reassessment, dated 
September 2, 2016.
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A. Comments on the BART Reassessment

    Comment 1: One commenter asserted that the BART Reassessment 
violates the CAA's mandatory 5-year BART compliance deadline and the 
regulatory requirement to achieve visibility improvement in the first 
planning period that ends in 2018. In addition, the commenter argued 
that the BART Guidelines at appendix Y state that in the event a source 
prefers to shut down to comply with BART, the BART requirement must 
maintain consistency with the statutory requirement to install BART 
within 5 years, and the source may not be allowed to operate beyond 5 
years without BART controls in place. The commenter further stated that 
the EPA cannot scrap its existing BART determination for Cholla, which 
has been in effect for over 3 years, and issue a new BART determination 
that would restart the 5-year BART compliance clock. One commenter 
opined that because the EPA's proposal is unlawful, the EPA should 
leave the existing BART determination for Cholla in place.
    Response 1: The EPA disagrees with the comment that the Cholla SIP 
Revision violates the 5-year compliance deadline for BART, the 
regulatory requirement to achieve visibility improvement in the first 
planning period, or the BART Guidelines. As discussed in our proposed 
rule, in the Cholla SIP Revision, ADEQ determined BART to be 
LNB+SOFA.\17\ The emission limit associated with installation and 
operation of LNB+SOFA while burning coal at Cholla Units 3 and 4 is 
0.22 lb/MMBtu. This emission limit is reflected in the Cholla permit 
revision that is included as Appendix A of the Cholla SIP Revision. The 
permit conditions will become effective and federally enforceable 30 
days following publication of this final rule in the Federal Register, 
which we anticipate will be prior to the compliance deadline 
established in the FIP of December 5, 2017. Therefore, although we 
agree with the commenter that BART emission limitations must be in 
place within 5 years of approval, we disagree with the commenter that 
ADEQ has restarted the 5-year BART compliance clock.
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    \17\ See 81 FR 46852 at 46856 (July 19, 2016).
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    In addition to its BART determination for Cholla Units 3 and 4, 
ADEQ also included a permit revision for Cholla in its SIP submittal. 
The permit revision includes the 0.22 lb/MMBtu emission limitation that 
would apply until the permanent cessation of coal combustion in Units 3 
and 4, and an emission limitation of 0.08 lb/MMBtu that would apply if 
the units are converted to natural gas. The commenter appears to have 
misconstrued these provisions related to future operation in 2025 to be 
part of ADEQ's BART determination. We consider the permit requirements 
to cease coal combustion in 2025 and comply with new emission 
limitations if Units 3 and 4 are converted to natural gas to be 
measures that strengthen the Cholla SIP Revision. The BART

[[Page 15142]]

determination for Units 3 and 4 that we are approving is the 0.22 lb/
MMBtu emission limit. This is consistent with ADEQ's response to a 
similar comment, stating: ``Although the new proposal includes 
conversion to natural gas-firing at Units 3 and 4 in 2025, ADEQ did not 
consider it as a BART control option under the BART determination 
process because it is beyond the mandatory five-year window.'' \18\ 
Furthermore, we note that because Cholla Units 3 and 4 currently cannot 
combust natural gas, there is no obligation for ADEQ to determine BART 
for those units if they are repowered to operate on natural gas.\19\ 
Therefore, we consider the 0.08 lb/MMBtu emission limit to be a SIP-
strengthening measure, and approvable as such, but we do not consider 
it to be part of the BART determination. In addition, the presence of 
an emission limit for future operation on natural gas as a SIP 
requirement is not critical to the withdrawal of the FIP. We are not 
addressing whether 0.08 lb/MMBtu would be an appropriate BART emission 
limit for these units if they were currently combusting natural gas. We 
note that because NOX emissions resulting from natural gas 
combustion are low, there have been few if any SIPs or FIPs that have 
included a determination that BART for electric generating units (EGUs) 
combusting natural gas was a lower NOX level than already 
being achieved at the source. We are approving the BART determination 
in the Cholla SIP Revision in light of the enforceable SIP requirement 
for Units 3 and 4 to cease coal combustion in 2025.
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    \18\ See Appendix F.6 Responsiveness Summary of the Cholla SIP 
Revision (page 6 of 10 in Appendix F.6).
    \19\ See SO2 emission limits for San Juan Generating 
Station (76 FR 52387, August 22, 2011) and for 6 EGUs in Oklahoma 
(76 FR 81727, December 28, 2011), and NOX emission limits 
for Jim Bridger and Naughton (79 FR 5031, January 30, 2014), where 
emission limits are higher than would be appropriate for BART if the 
units were combusting natural gas.
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    The Cholla SIP Revision also requires Cholla Units 3 and 4 to 
comply with the BART emission limit prior to the end of the first 
planning period in 2018. We further note that APS and PacifiCorp have 
already installed LNB+SOFA on Cholla Units 3 and 4.\20\ In addition, 
the regulatory requirement cited by the commenters, to achieve 
visibility improvements in the first planning period, is associated 
with alternatives to BART as put forth in 40 CFR 51.308(e)(2). The 
Cholla SIP Revision is a re-analysis of BART that is based on new facts 
since the promulgation of the FIP; it is not an alternative to BART and 
compliance deadlines associated with alternatives to BART are not 
relevant to the Cholla SIP Revision.
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    \20\ See e.g., page 3 of the Cholla SIP Revision that states the 
LNB+SOFA are currently installed on Units 3 and 4.
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    We also disagree with the commenter's assertion that a BART 
determination that has been in place for over 3 years cannot be revised 
when a new material fact has arisen, i.e., that the Cholla units will 
not continue to combust coal indefinitely, which had been an assumption 
of the original BART determination in the FIP. In the rule proposing to 
partially approve and partially disapprove the 2011 RH SIP, the EPA 
encouraged the State to submit a revised SIP to replace our FIP, and we 
noted that the EPA would work with the State to develop a revised 
plan.\21\ We anticipated that ADEQ might develop a SIP to address the 
flaws we identified in our review of the 2011 RH SIP. APS and 
PacifiCorp also petitioned the Administrator to reconsider certain 
aspects of the FIP for Cholla. We granted the petitions based on our 
intention to reconsider aspects of the compliance determination 
methodology in the FIP. Therefore, although the FIP for Cholla has been 
in place for over 3 years, the development of a revised BART analysis 
for this facility was not unexpected. As discussed elsewhere in this 
final rule, the compliance deadline for the revised BART emission limit 
for Cholla remains within the compliance deadline in the FIP of 
December 5, 2017. Thus, ADEQ did not extend the BART compliance 
deadline in the Cholla SIP Revision beyond the original compliance date 
of December 5, 2017.
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    \21\ See 77 FR 42834, July 20, 2012.
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    Finally, as discussed elsewhere in this final rule, we disagree 
with the comment asserting that our action is unlawful. Based on our 
evaluation of the Cholla SIP Revision, we have determined that ADEQ 
conducted a BART analysis for Cholla that meets the requirements of the 
CAA, the RHR, and the BART Guidelines. Therefore, we disagree that the 
BART determination promulgated in the FIP should remain in place.
    Comment 2: One commenter opined that the EPA's cost analysis for 
SNCR was flawed because the EPA based the average cost-effectiveness of 
SNCR on 8 years of operation on coal and 12 years of operation on 
natural gas. The commenter argued that the operation of SNCR on the 
units after the switch to gas in 2025 would result in over 12 years of 
additional interest and operation and maintenance costs with minimal 
pollution reduction benefits. The commenter asserted that operation of 
SNCR for the 8 years of coal combustion and then ceasing to operate 
SNCR when the units switch to natural gas would be more cost-effective. 
The commenter argued that this would reduce the average cost-
effectiveness of SNCR on Units 3 and 4 to $2,234-$2,342 per ton of 
NOX removed and the incremental cost-effectiveness (relative 
to LNB/SOFA) to $5,364-$5,458 per ton of NOX removed. The 
commenter further argued that its approach (to base the remaining 
useful life of SNCR on the time during which the facility would burn 
coal) is consistent with how the EPA considered the remaining useful 
life for other sources transitioning to gas or other fuels, and cited 
to the 2012 BART determinations for the Centralia and Boardman 
facilities. The commenter also pointed to the BART determinations for 
Healy Unit 1 in Alaska and CENC Unit 5 in Colorado, and reasonable 
progress determinations for the Craig Unit 3 in Colorado, where SNCR 
was determined to be cost-effective with average cost-effectiveness 
values that ranged from $3,526-$4,887 per ton of NOX removed 
and incremental cost-effectiveness values that ranged from $5,445-
$9,271 per ton of NOX removed.
    Response 2: In reviewing the analysis conducted by ADEQ to assess 
whether the Cholla SIP Revision is approvable, the EPA's role is to 
decide whether the SIP meets the requirements of the CAA, the RHR, and 
the BART Guidelines. In undertaking such a review, the EPA does not 
usurp a state's authority but ensures that such authority is reasonably 
exercised. The CAA and the RHR set forth five factors that a state must 
evaluate to reach a BART determination. However, the CAA and the RHR 
provide flexibility to the state in deciding how the factors in the 
analysis are weighed.
    We note that this comment does not accurately distinguish between 
the EPA's cost analysis and the cost analysis by ADEQ. The only cost 
analysis that the EPA conducted directly was in support of the 2012 FIP 
establishing a BART emission limit for Cholla achievable with the 
installation and operation of SCR. The EPA's cost analysis was based on 
20 years of operation because, at that time, there was no commitment 
from the facility owners that Cholla would cease coal combustion in the 
future. Therefore, although the commenter refers to the cost analysis 
discussed in the proposed rule as ``the EPA's cost analysis,'' the 
comment is actually about ADEQ's cost analysis for SNCR. For purposes 
of its BART Reassessment, ADEQ adapted the EPA's cost analysis from 
2012 but

[[Page 15143]]

revised the annual cost of controls to account for the planned 
cessation of coal combustion in 2025. The commenter is suggesting that 
ADEQ should have considered a control scenario that would require SNCR 
while combusting coal and would not require SNCR once the units are 
repowered to natural gas. The commenter asserts that this SNCR scenario 
would be more cost-effective than the operation of SNCR continuously 
for 20 years. Based on this consideration of cost-effectiveness, the 
commenter asserts that ADEQ should have determined SNCR, applied in 
this way, to be BART and that the EPA should not have proposed to 
approve the Cholla SIP Revision.
    In its response to a similar comment made to ADEQ during the public 
comment period for the Cholla SIP Revision, ADEQ argued that it 
appropriately calculated the cost-effectiveness of SNCR based on a 20-
year life, with 8 years of operation on coal, and 12 years of operation 
on natural gas, because it was reasonable to presume that if SNCR were 
required, the units would be required to operate for 20 years or more 
to recoup the investment.\22\ The Cholla SIP Revision established as 
BART an emission limit of 0.22 lb/MMBtu, achievable with the 
installation and operation of LNB+SOFA. Although the units must cease 
coal combustion by April 30, 2025, the Cholla SIP Revision provides the 
option for those units to be repowered to natural gas with a 
NOX emission limit of 0.08 lb/MMBtu and a 20 percent annual 
average capacity factor restriction. Emission rates from tangentially-
fired boilers combusting natural gas can be expected to range from an 
uncontrolled emission rate of 0.16 lb/MMBtu to a rate of 0.07 lb/MMBtu 
when controlled using flue gas recirculation.\23\ Thus, although Units 
3 and 4 could continue to operate well beyond 8 years if they are 
repowered to natural gas, operation of SNCR would not be required to 
meet the 0.08 lb/MMBtu emission limitation in the Cholla SIP Revision. 
Therefore, we agree with the commenter that in this case, for Cholla 
Units 3 and 4, it is reasonable to evaluate the cost-effectiveness of 
SNCR based on the period of time that SNCR would need to be in 
operation in order to comply with the applicable emission 
limitation.\24\
---------------------------------------------------------------------------

    \22\ See Appendix F.6 Responsiveness Summary of the Cholla SIP 
Revision (p. 8 of 10 in Appendix F.6). The comment submitted to ADEQ 
recommended calculating cost-effectiveness of SNCR based on a 7.4-
year life. In this document we generally refer to the period that 
Cholla Units 3 and 4 would combust coal as an 8-year period.
    \23\ See spreadsheet titled ``Natural gas EF.xlsx'' in the 
docket for this rulemaking.
    \24\ However, we also note that if ADEQ had evaluated an 
emission limit for Units 3 and 4 applicable after the units are 
repowered to natural gas, that took into account the continued 
operation of SNCR, ADEQ's evaluation of the cost-effectiveness of 
SNCR based on 8 years of operation on coal and 12 years of operation 
on natural gas would have been more appropriate. We also note that 
the commenter cited to rulemakings for two facilities, Centralia and 
Boardman, to support the contention that the cost effectiveness of 
SNCR on Cholla Units 3 and 4 should have been calculated based on 
the period of time the units would be burning coal. Although we 
generally agree with the comment, we are not evaluating whether the 
facts associated with Centralia and Boardman support this argument.
---------------------------------------------------------------------------

    However, we further note that the assertion in the comment that 
ADEQ erred because it did not evaluate the cost-effectiveness of SNCR 
based on an 8-year life is incorrect. In its response to comments on 
the Cholla BART Reassessment, ADEQ stated that if it calculated the 
cost-effectiveness of SNCR based on a shorter (i.e., 8-year) life the 
average cost-effectiveness would be less than $2,500 per ton of 
NOX removed and the incremental cost effectiveness would be 
less than $5,700 per ton of NOX removed. ADEQ responded that 
it would still reject SNCR because the incremental cost-effectiveness 
recalculated by the commenter, even at less than $5,700 per ton of 
NOX removed, would not be justified based on the slight 
incremental visibility improvement. ADEQ evaluated the incremental 
visibility improvement of SNCR against LNB+SOFA and found that the 
differences in visibility improvement at the various Class I areas 
between the two control scenarios were relatively minor in most 
cases.\25\ ADEQ noted that the cumulative incremental visibility 
improvement of SNCR (as compared to LNB+SOFA) for 13 Class I areas was 
1.32 deciviews (ranging from 0.01 to 0.28 deciview at individual Class 
I areas), with an average incremental improvement of 0.1 deciview. ADEQ 
further noted that the visibility benefits that would be associated 
with SNCR on Cholla Units 3 and 4 would last only until 2025 because 
the closure or conversion to natural gas would reduce the visibility 
benefit of SNCR.\26\ ADEQ concluded that SNCR would not be cost-
effective whether it assumed a useful life of 20 years or 8 years.\27\
---------------------------------------------------------------------------

    \25\ See Appendix F.6 Responsiveness Summary of the Cholla SIP 
Revision (p. 8 of 10 in Appendix F.6).
    \26\ Id.
    \27\ Id. (page 9 of 10 in Appendix F.6).
---------------------------------------------------------------------------

    The EPA considered ADEQ's response to the comment and continues to 
find that ADEQ's BART Reassessment for Cholla Units 3 and 4, even when 
the cost-effectiveness for SNCR is evaluated for an 8-year period, is 
consistent with the BART Guidelines and approvable.
    The commenter also refers to three facilities, Healy Unit 1, 
Colorado Energy Nations Company (CENC) Unit 5, and Craig Unit 3, to 
highlight other average and incremental cost-effectiveness values that 
have been determined to be reasonable for BART or reasonable progress. 
We considered whether these comparisons support a conclusion that ADEQ 
was unreasonable in rejecting SNCR based on the average ($2,234 to 
$2,342 per ton of NOX removed) and incremental ($5,364 to 
$5,458 per ton of NOX removed) cost-effectiveness values 
recalculated by the commenter.
    The average cost effectiveness values for the three facilities 
cited in the comment range from $3,526 to $4,887 per ton of 
NOX removed and the incremental cost effectiveness values 
range from $5,445 to $9,271 per ton of NOX removed.\28\ The 
commenter correctly notes that SNCR was required for these facilities 
at average and incremental cost-effectiveness values that exceed both 
ADEQ's and the commenter's cost-effectiveness values for SNCR at Cholla 
Units 3 and 4. Although the comment did not cite specifically to the 
Boardman facility to highlight the cost-effectiveness of SNCR, in that 
case the state required, and the EPA approved, a final BART 
determination requiring Boardman to meet an emission limit of 0.23 lb/
MMBtu achievable with new LNB and modified overfire air.\29\ The state 
rejected SNCR for Boardman, with an average cost effectiveness of 
$1,816 per ton of NOX removed, based on the small 
incremental visibility improvement of 0.18 deciview at the Mount Hood 
Wilderness Area and concerns that excess ammonia from SNCR may result 
in increased rates of ammonium sulfate formation.\30\ Thus, although 
there are examples of states requiring SNCR at higher average and 
incremental cost-effectiveness values, there are also examples of 
states rejecting SNCR at even lower cost-effectiveness values than 
those recalculated by the commenter for SNCR at Cholla. We further note 
that while the state of Colorado determined BART for CENC Unit 5 to be 
SNCR (average cost-effectiveness of $4,918 per ton), in the same 
action, the state concurrently rejected SNCR for CENC Unit 4 (average 
cost effectiveness of $3,729 per ton) and

[[Page 15144]]

determined BART for that unit to be LNB+SOFA.\31\ Therefore, although 
we agree with the commenter that states have required SNCR at average 
and incremental cost-effectiveness values that are higher than its 
recalculated values for SNCR on Cholla Units 3 and 4, there are also 
examples of states that have rejected SNCR at average and incremental 
cost-effectiveness values that are similar to, or even lower than, the 
commenter's recalculated values for SNCR.
---------------------------------------------------------------------------

    \28\ See Final Rule for Healy Unit 1 (78 FR 10546, February 14, 
2013) and final rule for CENC Unit 5 and Craig Unit 3 (77 FR 18052, 
March 26, 2012).
    \29\ See 76 FR 38997, July 5, 2011.
    \30\ See proposed rule, 76 FR 12651 at 12661, March 8, 2011.
    \31\ 77 FR 18052, March 26, 2012.
---------------------------------------------------------------------------

    Furthermore, BART determinations are emission limitations rather 
than control technology determinations. For the three units cited by 
the commenter, the final BART or reasonable progress emission limits 
achievable with SNCR were 0.20 lb/MMBtu for Healy Unit 1, 0.19 lb/MMBtu 
for CENC Unit 5, and 0.28 lb/MMBtu for Craig Unit 3.\32\ The BART 
emission limitation for Centralia, another facility cited by the 
commenter (but for other reasons), was 0.21 lb/MMBtu achievable with 
SNCR.\33\ The final BART emission limitation put forth by ADEQ for 
Cholla Units 3 and 4, 0.22 lb/MMBtu achievable with LNB+SOFA, is 
generally consistent with the emission limits put forth for other 
facilities based on SNCR.
---------------------------------------------------------------------------

    \32\ 78 FR 10546, February 14, 2013 and 77 FR 18052, March 26, 
2012.
    \33\ 77 FR 72472, December 6, 2012.
---------------------------------------------------------------------------

    Although a comparison of cost-effectiveness values from other 
facilities is generally a useful exercise to assess the reasonableness 
of particular costs, the examples in the comment do not provide 
evidence to suggest that ADEQ's weighing of the cost-effectiveness of 
SNCR on Cholla Units 3 and 4 was unreasonable. In addition, cost-
effectiveness is not the only factor in determining BART; each BART 
determination must be made on a case-by-case basis considering the 
relevant facts in each case. The CAA and the RHR provide flexibility to 
states in deciding how the five factors are weighed in determining 
BART. If the EPA were reassessing BART for Cholla Units 3 and 4 in a 
FIP action, the EPA might have weighed the factors differently than 
ADEQ and reached a different conclusion. However, the EPA has evaluated 
ADEQ's justification for rejecting SNCR based on its consideration of 
cost-effectiveness and the visibility improvements from SNCR in 
comparison to LNB+SOFA. We consider ADEQ's BART determination for 
Cholla Units 3 and 4 to be consistent with the BART Guidelines and a 
reasonable use of its discretion in weighing the BART factors.
    Comment 3: One commenter argued that the EPA inappropriately relied 
on incremental costs and incremental visibility benefits. The commenter 
asserted that where a selection of a particular technology as BART is 
supported by reasonable total costs, incremental costs should not be 
used to override that choice. The commenter further stated that the EPA 
only discussed incremental visibility benefits of SNCR relative to LNB 
and provided no way to assess the net visibility benefit of installing 
SNCR on Units 3 and 4 against the pre-LNB baseline for those units. The 
commenter opines that the EPA's lack of analysis of the net visibility 
improvements of SNCR is inconsistent with the EPA's prior action for 
Cholla.
    Response 3: In this action, the EPA is evaluating the analysis 
conducted by ADEQ to assess whether the Cholla SIP Revision meets the 
requirements of the CAA, the RHR, and the BART Guidelines. We disagree 
with the commenter's assertion that it is inappropriate to rely on 
incremental costs or incremental visibility benefits. The CAA and the 
RHR specify that the states or the EPA must consider cost and 
visibility in the five-factor analysis. With respect to the cost 
factor, in promulgating the BART Guidelines, the EPA stated, ``In 
addition, the guidelines continue to include both average and 
incremental costs. We continue to believe that both average and 
incremental costs provide information useful for making control 
determinations.'' \34\ Section IV.4.e.1 of the BART Guidelines 
specifies that states should consider incremental cost-effectiveness in 
combination with the average cost-effectiveness. The commenter did not 
cite any regulatory language that would preclude incremental cost-
effectiveness in considering the cost of compliance. With respect to 
using incremental visibility improvement, we acknowledge that the BART 
Guidelines do not explicitly address the issue of considering overall 
versus incremental visibility benefits. However, the EPA's response to 
comments when promulgating the BART Guidelines stated:
---------------------------------------------------------------------------

    \34\ See 70 FR 39104 at 39127, July 6, 2005.

    For example, a State can use the CALPUFF model to predict 
visibility impacts from an EGU in examining the option to control 
NOX and SO2 with SCR technology and a 
scrubber, respectively. A comparison of visibility impacts might 
then be made with a modeling scenario whereby NOX is 
controlled by combustion technology. If expected visibility 
improvements are significantly different under one control scenario 
than under another, then a State may use that information, along 
with information on the other BART factors, to inform its BART 
determination.\35\
---------------------------------------------------------------------------

    \35\ Id. at 39129.

    The EPA's regulations allow states to compare incremental cost-
effectiveness and incremental visibility improvements between different 
technologies. The incremental visibility benefit is one way to compare 
the visibility improvements from various controls. Other states and the 
EPA have considered incremental visibility improvements in many BART 
determinations. For this BART determination, ADEQ weighed the small 
incremental visibility improvement against the incremental cost-
effectiveness. Based on its weighing of these factors, ADEQ provided a 
reasoned justification for selecting LNB+SOFA as BART for Cholla Units 
3 and 4, and properly exercised its discretion in its process for 
weighing the small visibility improvement against the cost-
effectiveness to reject SCR and SNCR.
    Comment 4: One commenter asserted that the EPA's analysis was 
flawed because it evaluated BART controls as if there was no existing 
BART determination in place for Units 3 and 4. The commenters opined 
that the EPA failed to analyze how various pollution controls and other 
measures would improve the BART Reassessment by eliminating any 
backsliding. The commenter recommended that the EPA evaluate installing 
SNCR in the next 18 months to improve the performance of the BART 
Reassessment beginning in 2018, and recommended four additional control 
strategies to reduce NOX emissions between 2018 and 2025: 
(1) Setting an earlier deadline for Units 3 and 4 to shut down or 
switch to natural gas, (2) restricting Units 3 and 4 to the lowest 
capacity factor necessary between 2018 and 2025, (3) requiring the use 
of hybrid NOX reduction measures, e.g., SNCR in combination 
with in-duct SCR catalysts, which the commenter said can be installed 
at far lower cost and more quickly than conventional SCR, and (4) a 
combination of the listed measures with SNCR. The commenter opined that 
if this analysis had been done, it would have shown that SNCR and other 
measures would significantly improve the BART reassessment by cost-
effectively reducing NOX emissions from Units 3 and 4 prior 
to 2025.
    Response 4: The EPA's role is to evaluate whether a state 
considered the appropriate factors and acted reasonably

[[Page 15145]]

in doing so. In undertaking such a review, the EPA does not usurp a 
state's authority but ensures that such authority is reasonably 
exercised.
    The commenter suggests that the EPA should have evaluated other 
NOX control measures that would result in greater emission 
reductions from the Cholla SIP Revision and be more comparable to the 
emission reductions that would have been achieved under the FIP for 
Cholla. As with Comment 2, we note that the commenter has not 
accurately described whether it was ADEQ or the EPA that performed (or 
would perform) specific analyses. In this action, the EPA is reviewing 
the Cholla SIP Revision that was submitted for approval or disapproval. 
In that context, the issue is not whether the EPA should or will 
undertake the types of analysis recommended by the commenter, but 
whether ADEQ's failure to do so means that its BART determination 
cannot be approved. We have reviewed ADEQ's BART SIP for Cholla to 
determine whether it meets the requirements of the five-factor BART 
analysis, as outlined by the CAA, the RHR, and the BART Guidelines. 
ADEQ did not put forth a ``better-than-BART'' BART alternative pursuant 
to 40 CFR 51.308(e)(2), which would have required a comparison of 
emission reductions under BART and the BART alternative.\36\ ADEQ 
properly evaluated the new commitments by APS and PacifiCorp related to 
future operation of Cholla Units 3 and 4 in determining BART for those 
units. For the purposes of its 110(l) analysis, ADEQ compared emissions 
of NOX, SO2, and PM10 between its 2011 
RH SIP and the Cholla SIP Revision, and also compared emissions of 
NOX between the FIP and the Cholla SIP Revision.\37\ ADEQ 
appropriately concluded that the differences in emissions were not 
inconsistent with CAA section 110(l). Nothing in 110(l) of the CAA, 
RHR, or the BART Guidelines requires ADEQ to ensure that the emission 
reductions from the Cholla SIP Revision would be numerically equivalent 
to the reductions that would have been achieved under the previously 
applicable plan (i.e., the FIP). Comments on ADEQ's 110(l) analysis, 
and the EPA's responses to those comments, are provided in Section 
II.C, below.
---------------------------------------------------------------------------

    \36\ If ADEQ had done so, there would be a question posed as to 
whether it could at the same time re-determine BART in light of the 
changed plans for the operation of the Cholla units, or would have 
had to use the FIP as the benchmark. We do not address that question 
in this action.
    \37\ See Tables 5-8 in the Proposed Rule, 81 FR 46852, July 19, 
2016.
---------------------------------------------------------------------------

    The commenter also suggests that the EPA (again, the commenter 
mistakenly refers to the EPA rather than ADEQ) should have evaluated 
additional operational restrictions on Cholla Units 3 and 4, e.g., an 
earlier date for retirement or repowering to natural gas, or capacity 
restrictions between 2018 and 2025. Although an earlier retirement date 
or capacity restrictions would reduce emissions, in general, states and 
the EPA would not impose a retirement or capacity restriction unless it 
is requested by the facility operator, because capacity and retirement 
are not ``retrofit technolog[ies]'' (the term used in the CAA) or 
``system[s] of continuous emissions reductions'' (the term used in the 
RHR definition of BART). The BART Guidelines state that potentially 
applicable retrofit control alternatives typically prevent the 
formation of pollutants (e.g., LNB) or control or reduce emissions of 
pollutants after they are formed (e.g., SNCR or SCR), or are a 
combination of these processes.\38\ The BART Guidelines go on to say 
that ``we do not consider BART as a requirement to redesign the 
source,'' or to ``direct States to switch fuel forms, e.g., from coal 
to gas.'' \39\ Therefore, consideration of earlier retirement, 
repowering, or capacity restrictions that were not put forth by the 
facility operator, is not required by the BART Guidelines.
---------------------------------------------------------------------------

    \38\ See BART Guidelines at 70 FR 39104 at 39164, July 6, 2005.
    \39\ Id.
---------------------------------------------------------------------------

    The commenter also suggests that the EPA (again, the commenter 
mistakenly refers to the EPA rather than ADEQ) should have evaluated 
SNCR with in-duct SCR catalysts, or a combination of SNCR with earlier 
retirement, repowering, or capacity restrictions. ADEQ was not required 
to consider earlier retirement, repowering, or capacity restrictions to 
be consistent with the BART Guidelines, and the combination of SNCR 
with those measures does not change our determination. Regarding SNCR 
combined with in-duct SCR catalysts, the commenter stated that in-duct 
SCR catalysts can be installed at lower cost than conventional SCR. 
Although the EPA is aware that the technologies for hybrid SNCR 
combined with in-duct SCR systems have been around since the 1990s, we 
are not aware of the widespread use of these hybrid systems on 
comparably-sized boilers, and the commenter did not provide any 
supporting data or information of sufficient specificity to indicate 
that this technology should have been considered under BART or that it 
would have changed ADEQ's BART determination.\40\ Therefore, we 
continue to consider ADEQ's BART determination for Cholla Units 3 and 4 
to be consistent with the BART Guidelines, including its evaluation of 
LNB+SOFA, SNCR, and SCR.
---------------------------------------------------------------------------

    \40\ See, generally, discussion of in-duct SCR catalysts in ``I-
NOXTM Integrated NOX Reduction 
Technology-A Lower Capital Cost Solution for NOX 
Reduction,'' March 26, 2015, at http://www.mcilvainecompany.com/Decision_Tree/2015%20WEBINARS/March%202015/Stewart%20Bible,%20Fuel%20Tech%20-%20Hot%20Topic%20Hour%203-26-15.pdf.
---------------------------------------------------------------------------

    Comment 5: One commenter disagreed with the EPA's statement that a 
BART reassessment for Cholla is necessary based on new facts that have 
arisen since the EPA's final BART determination in 2012. The commenter 
further opined that even if new facts could be used to justify 
extending the BART compliance deadline, the new facts at issue here 
would not be sufficient justification. The commenter also stated that a 
business decision by the facility operator to close Unit 2 in advance 
of the 2017 BART compliance deadline for that unit should not justify 
allowing Units 3 and 4 to delay compliance past 5 years. The commenter 
argued that no statutory or regulatory provisions, related guidance, or 
prior BART determinations allow, let alone recognize, a utility's 
lowest cost option to govern the outcome of a BART determination.
    Response 5: We disagree with the assertions in this comment and 
generally find that the commenter has misunderstood our proposed action 
and the Cholla SIP Revision. The EPA did not state that a BART 
reassessment is necessary, but we did indicate that ADEQ has discretion 
to reassess BART in light of new information and to seek approval from 
the EPA for a SIP revision to replace the FIP. As stated elsewhere in 
this final rule, the Cholla SIP Revision does not extend the BART 
compliance deadline. It replaces the compliance requirements in the FIP 
with different requirements and earlier compliance dates. The 0.22 lb/
MMBtu emission limitation for NOX that ADEQ determined to be 
BART will be effective upon the effective date of this final rule and, 
therefore, earlier than the FIP's BART deadline of December 5, 2017.
    In the Cholla SIP Revision, ADEQ conducted a BART Reassessment 
based on the new facts that arose following the EPA's FIP for Cholla. 
In 2015, APS and PacifiCorp committed to several operational changes at 
Cholla that affect specific factors in the five-factor BART analysis, 
namely, the remaining useful

[[Page 15146]]

life of the facility and its corresponding effects on the cost-
effectiveness of controls. Based on the commitments from APS and 
PacifiCorp to close Unit 2 by April 1, 2016, continue operation of 
Units 3 and 4 with LNB+SOFA and permanently cease coal combustion in 
those units by April 30, 2025 with the option to convert to natural gas 
combustion by July 31, 2025 at a 20 percent or less average annual 
capacity factor, ADEQ conducted a revised BART analysis for Cholla 
Units 2, 3, and 4. ADEQ did not rely on the closure of Unit 2 to 
justify changes to the BART determination for Units 3 and 4. Rather, 
ADEQ reasonably determined that the enforceable closure of Unit 2 prior 
to December 5, 2017, satisfies the requirements of the RHR and the CAA 
for this unit. ADEQ then conducted a re-analysis of BART for Units 3 
and 4 that considered the remaining useful life of potential control 
technologies in light of the commitments made by APS and PacifiCorp 
related to those units. Based on the changes to the cost effectiveness 
of controls, ADEQ reasonably rejected SNCR and SCR as too costly in 
comparison to the small additional visibility benefits, and concluded 
that the visibility benefits of SNCR or SCR controls after 2025, when 
coal combustion ceases and assuming those units are repowered to 
natural gas, would be negligible. ADEQ's final BART determination for 
Cholla Units 3 and 4 is an emission limitation of 0.22 lb/MMBtu that 
will be effective upon the effective date of this final rule. 
Therefore, we disagree that our proposal to approve the Cholla SIP 
Revision extends any BART compliance deadlines, and we also disagree 
with the commenter that the new facts do not warrant a revised 
assessment of BART for Cholla.
    Although we agree with the commenter that the RHR and BART 
Guidelines do not require BART determinations to align with a utility's 
lowest-cost option, we also note that this action is not based on the 
SIP revision's being the lowest-cost approach. If the FIP were to 
remain in place, APS would be free (with respect to CAA requirements) 
to cease coal combustion as a way to comply with the SCR-based BART 
emission limit, based on its own considerations.\41\ In this case, APS 
and PacifiCorp have committed to cease coal combustion in Units 3 and 4 
in 2025. Although the motivation for this commitment is irrelevant for 
purposes of the RHR, the state has discretion to reassess a BART 
determination for Cholla that takes into account the shorter period of 
coal combustion because of the potential effect this has on the five 
BART factors.
---------------------------------------------------------------------------

    \41\ See BART Guidelines, 70 FR 39104 at 39171, July 6, 2005.
---------------------------------------------------------------------------

    Comment 6: One commenter stated that the BART Reassessment will 
result in significant public health and environmental benefits, 
including very significant near-term and ongoing reductions in climate-
disturbing pollution, toxic mercury, and particulate matter, and that 
the complete closure of Unit 2 has already resulted in some near-term 
benefits. The commenter described similar multi-pollutant BART 
approaches finalized elsewhere in the Southwest. The commenter cited to 
the Cholla SIP Revision to provide estimates of emission reductions 
from the BART Reassessment compared to the 2011 RH SIP: By 2046, the 
BART Reassessment will reduce cumulative SO2 emissions by 
about 170,000 tons and cumulative PM10 emissions by 15,000 
tons compared to the 2011 RH SIP. In addition, the commenter estimates 
that when fully implemented (after 2026), the BART Reassessment will 
reduce CO2 emissions by 90 percent from current annual 
emissions and reduce mercury emissions from 430 pounds to three pounds 
per year.
    Response 6: We agree with the commenter that the Cholla SIP 
Revision will result in significant near-term and ongoing environmental 
benefits. Although the BART Reassessment for Cholla focused on 
NOX reductions, emission reductions of other pollutants, as 
described by the commenter, also have occurred as a result of the 
closure of Unit 2 in 2015 and will occur after the closure or 
repowering to natural gas of Units 3 and 4 in 2025. In addition, we 
agree with the commenter that similar multi-pollutant approaches have 
been taken elsewhere, and we also note that approaches consisting of 
interim emission limitations combined with commitments to retire early 
or repower to natural gas are common, e.g., a SIP revision (to replace 
a FIP) that put forth a revised BART determination for the four units 
at the San Juan Generating Station in New Mexico involving closure of 
two units by the end of 2017 and an emission limit of 0.23 lb/MMBtu, 
achievable with SNCR, on the remaining two units; a SIP revision (to 
replace a FIP) that put forth a revised SO2 BART 
determination for two units at the Northeastern Power Station in 
Oklahoma involving closure of one unit in 2016 and interim emission 
limits and capacity restrictions leading to closure of the second unit 
by the end of 2026; a SIP revision (to replace a FIP) that put forth a 
BART alternative for two units at the Apache Generating Station in 
Arizona that involved conversion of one unit to natural gas and SNCR on 
the remaining coal-fired unit; as well as the EPA actions on the RH 
SIPs for Oregon and Washington approving the BART determinations for 
Boardman and Centralia involving interim emission limitations similar 
to those imposed on Cholla, and retirements around 2020 or 2025.\42\
---------------------------------------------------------------------------

    \42\ See 79 FR 60985, October 9, 2014 (final action on revised 
BART determination for San Juan in New Mexico); 79 FR 12944, March 
7, 2014 (final action on revised BART determination for Northeastern 
in Oklahoma); 80 FR 19220, April 10, 2015 (final action on 
alternative to BART for Apache in Arizona); 76 FR 38997, July 5, 
2011 (final action on BART determination for Boardman in Oregon); 
and 77 FR 72742, December 6, 2012 (final action on BART 
determination for Centralia in Washington).
---------------------------------------------------------------------------

    Comment 7: One commenter noted that the BART Reassessment will 
result in higher NOX emissions and visibility impacts from 
2018 to 2025 and therefore urged the EPA to examine whether those 
impacts could be mitigated through a lower continuous emission limit 
for SO2 or other measures. The commenter noted that the 
current permitted SO2 emission rates at Cholla do not 
reflect recent operating levels for SO2.
    Response 7: In this action, we are reviewing the Cholla SIP 
Revision that was submitted for approval or disapproval. In that 
context, the issue is not whether the EPA should examine the types of 
mitigation measures recommended by the commenter, but whether ADEQ's 
failure to do so means that its BART determination cannot be approved. 
The EPA must evaluate whether a state considered the appropriate 
factors and acted reasonably in doing so. In undertaking such a review, 
the EPA does not usurp a state's authority but ensures that such 
authority is reasonably exercised.
    The EPA agrees that NOX emissions and visibility impacts 
will differ between the Cholla SIP Revision and the provisions of the 
FIP that are being withdrawn, and that NOX emissions from 
Units 3 and 4 between 2018 and 2025 under the Cholla SIP Revision will 
be greater than emissions from those units under the Cholla FIP. 
However, after April 30, 2025, when APS and PacifiCorp permanently 
cease coal combustion in Units 3 and 4 with the option to convert to 
natural gas (at a 20 percent annual average capacity factor), emissions 
from the Cholla SIP Revision will be substantially lower than emissions 
from those units under the FIP. However, we acknowledge that in 
determining whether the BART Reassessment can be approved, we may

[[Page 15147]]

not take into account these greater emission reductions in 2025 and 
thereafter.
    Although a lower SO2 emission limitation before 2025 
would certainly be environmentally beneficial, we note that we have 
previously approved the SO2 BART emission limits for 
Cholla.\43\ ADEQ's new BART determination was for NOX, and 
we must approve it if it meets the requirements of the five-factor BART 
analysis, as outlined by the CAA, the RHR, and the BART Guidelines. 
ADEQ did not put forth a BART alternative pursuant to 40 CFR 
51.308(e)(2), which would have required a comparison of emission 
reductions under BART and the BART alternative. ADEQ properly evaluated 
the new commitments by APS and PacifiCorp related to future operation 
of Cholla Units 3 and 4 in determining BART for those units. For the 
purposes of its 110(l) analysis, ADEQ did compare emissions of 
NOX, SO2, and PM10 between its 2011 RH 
SIP and the Cholla SIP Revision, and compared emissions of 
NOX between the FIP and the Cholla SIP Revision.\44\ ADEQ 
appropriately concluded that the differences in emissions that it found 
would not conflict with CAA section 110(l). Nothing in 110(l) of the 
CAA, the RHR, or the BART Guidelines required ADEQ to ensure that the 
numerical emission reductions from the Cholla SIP Revision would be 
equivalent to the reductions that would have been achieved under the 
FIP. Comments and the EPA's responses on ADEQ's 110(l) analysis are 
provided elsewhere in Section II.C.
---------------------------------------------------------------------------

    \43\ See 77 FR 72511 (Dec. 5, 2012). We approved the 
SO2 BART emission limits but promulgated FIP provisions 
for the compliance testing method because the SIP lacked those 
elements.
    \44\ See Tables 5-8 in the Proposed Rule, 81 FR 46852, July 19, 
2016.
---------------------------------------------------------------------------

    Comment 8: One commenter noted that although it does not agree with 
every reason cited by the EPA in the proposed action, it urges the EPA 
to more forward to issue a final approval for the BART Reassessment.
    Response 8: We are taking final action in this document to approve 
the Cholla SIP Revision and withdraw the provisions of the FIP that 
applied to Cholla.
    Comment 9: One commenter stated that it supports the EPA's proposed 
approval of the BART Reassessment for the following reasons: (1) The 
SIP revision includes enforceable emission limits, (2) the EPA's 
proposal is based on its own analysis of Arizona's SIP and the five-
factor BART analysis, (3) the EPA appropriately considered Unit 1 as 
not BART-eligible, but included Unit 1 in the visibility modeling 
because the Cholla SIP Revision also requires that Unit 1 cease burning 
coal by April 30, 2025 with the option to repower to natural gas at a 
20 percent capacity factor, (4) the BART Reassessment will provide for 
greater reasonable progress toward the final goal of natural conditions 
earlier than the original FIP, and (5) the EPA's analysis demonstrates 
that additional controls would provide only a small visibility 
improvement at a cost that is beyond what the EPA has required of any 
other BART-eligible EGU.
    Response 9: We are taking final action in this document to approve 
the Cholla SIP Revision and withdraw the provisions of the FIP that 
applied to Cholla. However, we note that the commenter attributed to 
the EPA the analyses and conclusion that should actually be attributed 
to ADEQ.

B. Comments on Visibility Benefits

    Comment 10: One commenter expressed concern that visibility 
benefits of installing various levels of NOX control on 
Units 3 and 4 were underestimated because the modeling included 
emissions from Unit 1 (at the same level in each NOX control 
scenario for Units 3 and 4), even though there is no enforceable 
commitment to retire Unit 1. The commenter cited to a discussion in the 
preamble to the BART Guidelines related to the effect of using existing 
conditions versus natural visibility conditions as the baseline for 
single source visibility impact determinations. The commenter argued 
that the inclusion of Unit 1 in the visibility modeling for Units 3 and 
4 resulted in a decrease in the modeled benefit of installing controls 
on those units.
    Response 10: We agree with the commenter that including Unit 1 in 
the modeling reduces the estimate of the visibility benefit of controls 
on Units 3 and 4. We also agree that if Unit 1 were part of some source 
other than Cholla, it should have been excluded from the modeling. 
However, the EPA does not agree that this procedure is incorrect given 
the fact that Unit 1 is part of the single source that is Cholla. While 
Unit 1 is, in some sense, ``an existing condition'' for purposes of 
evaluating the impacts of Units 3 and 4, it is very different than the 
``existing conditions'' in the EPA statement cited by the 
commenter.\45\ The BART Guidelines describe the ambient conditions to 
use in assessing the visibility impact of a source; consistent with the 
ultimate goal of the RHR, the visibility impact is assessed relative to 
natural conditions. The preamble to the BART Guidelines explains why a 
meaningful measure of visibility impacts and potential benefits for a 
single source requires the use of pristine natural background rather 
than existing conditions, which would reflect the impact of hundreds of 
existing sources.\46\ This is not directly relevant to the issue of 
whether to include a single additional unit at the source being 
evaluated for BART. In practice, for modeling, source impacts are 
computed as delta deciviews, which is the difference in deciviews 
between the visibility due to the source combined with the natural 
background, and the visibility due to the natural background alone. In 
other words, all of the visibility impacts modeled with CALPUFF for the 
Cholla SIP Revision are relative to natural conditions, for the 
baseline and all control scenarios. The commenter seems to imply that 
including the emissions from Unit 1 is equivalent to assuming Unit 1 is 
part of natural conditions, which is not the case.
---------------------------------------------------------------------------

    \45\ See BART Guidelines, 70 FR 39104 at 39124, July 6, 2005.
    \46\ Ibid. Given the nonlinear way in which visibility 
impairment is perceived, the dirtier the background conditions, the 
less a source's emissions seem to affect it, ``Using existing 
conditions as the baseline . . . would create the following paradox: 
The dirtier the existing air, the less likely it would be that any 
control is required. . . . Such a reading would render the 
visibility provisions meaningless.''
---------------------------------------------------------------------------

    In modeling for the Cholla SIP Revision, ADEQ had to choose whether 
to include the non-BART-eligible Unit 1 emissions that do not vary 
across the control scenarios for Units 3 and 4. This choice is not 
addressed by the BART Guidelines. Some BART analyses modeled individual 
units separately, whereas other BART analyses modeled all units 
together. Unit 1 is not part of the natural background, but it is part 
of the facility's emissions. The overall BART determination encompasses 
an understanding of the visibility impacts, including the particular 
procedures followed in modeling them. Several considerations suggest 
that including all units in an analysis is a reasonable choice. 
Including Unit 1 in the modeling provides a more realistic estimate of 
overall visibility impacts for the facility as a whole, and more 
realistically accounts for the chemistry that Units 3 and 4 plumes 
experience. The Unit 1 emissions may potentially shift the chemistry 
and may affect the formation of visibility-affecting particulate matter 
from Unit 3 and 4 emissions, for example as the NOX-derived 
nitrates in the three plumes compete for available ammonia in

[[Page 15148]]

forming particulate ammonium nitrate. Another consideration, as stated 
by the commenter, is that including Unit 1 would tend to make the 
estimate of the benefit of controls on Units 3 and 4 smaller when the 
delta deciviews (relative to natural visibility conditions) are 
compared between control scenarios. This effect is expected to be small 
because the effect of including Unit 1 in the modeling would tend to be 
cancelled out when computing the benefit of controls. The benefit of 
controls is calculated by subtracting the visibility impacts (with 
controls applied) from the baseline impact; therefore, the effect of 
including Unit 1 in the modeling is captured in both terms. The EPA 
also examined this quantitatively by using the change in total 
emissions from excluding Unit 1 to scale the modeled estimates of 
visibility, and then recalculating the deciview impacts and benefits of 
controls. The estimated visibility benefits at Petrified Forest 
National Park (the Class I area most affected by emissions from Cholla) 
from the use of SCR or SNCR on Units 3 and 4 increased by approximately 
5 percent when Unit 1 was excluded.\47\ We would not consider a 5 
percent increase in the visibility benefits of SCR or SNCR to justify 
disapproving the Cholla SIP Revision. Moreover, the modeled benefits of 
LNB+SOFA on Units 3 and 4 would also be higher if Unit 1 were excluded 
from the modeling, so the change in the incremental benefit of SCR or 
SNCR would be small.
---------------------------------------------------------------------------

    \47\ See ``vis_impacts'' tab in the spreadsheet titled 
``Cholla_pefo_u1_effect.xlsx,'' in the docket for this rulemaking.
---------------------------------------------------------------------------

    In summary, although we agree with the comment that inclusion of 
Unit 1 in the visibility modeling decreases the modeled visibility 
benefits of controls on Units 3 and 4, the effect on the estimated 
visibility benefits of controls is small, and the BART Guidelines do 
not speak directly to this question. Therefore, the EPA has determined 
that ADEQ has reasonably exercised its discretion to include Unit 1 in 
its modeling analysis.
    Comment 11: One commenter recommended that the EPA consider the net 
(not incremental) benefit of installing SNCR on Units 3 and 4. The 
commenter noted that even the incremental visibility benefit of SNCR of 
0.28 deciview at the Class I area most affected by Cholla (Petrified 
Forest National Park) compares well with the net visibility benefits of 
other BART determinations made by the EPA in FIPs, which ranged from 
0.18-0.32 deciview.
    Response 11: As discussed elsewhere in this final rule, with regard 
to incremental visibility improvement, the EPA's response to comments 
for promulgating the BART Guidelines stated:

    For example, a State can use the CALPUFF model to predict 
visibility impacts from an EGU in examining the option to control 
NOX and SO2 with SCR technology and a 
scrubber, respectively. A comparison of visibility impacts might 
then be made with a modeling scenario whereby NOX is 
controlled by combustion technology. If expected visibility 
improvements are significantly different under one control scenario 
than under another, then a State may use that information, along 
with information on the other BART factors, to inform its BART 
determination.\48\

    \48\ See 70 FR 39129, July 6, 2005.
---------------------------------------------------------------------------

    The EPA's regulations allow states to compare incremental 
visibility improvements between different technologies. The incremental 
visibility benefit is one way to compare the visibility improvements 
from various controls. For this BART determination, ADEQ weighed the 
small incremental visibility improvement against the incremental cost-
effectiveness, as well as the timing and short duration of this 
benefit. Based on its weighing of these factors, ADEQ provided a 
reasoned justification for selecting LNB+SOFA as BART for Cholla Units 
3 and 4. We have concluded that ADEQ properly exercised its discretion 
in its process for weighing the small visibility improvement against 
the cost-effectiveness to reject SCR and SNCR.
    The commenter notes that even the incremental benefit of SNCR 
relative to LNB/SOFA is comparable to benefits seen in previous BART 
assessments, at least for the Class I area with the greatest impact. 
Visibility is only one of the five factors in a BART assessment, and in 
particular must be considered together with the anticipated costs of 
controls. As stated previously, the EPA's role is to decide whether the 
state's SIP is approvable by evaluating if the Cholla SIP Revision 
meets the requirements of the CAA, the RHR, and the BART Guidelines. In 
undertaking such a review, the EPA does not usurp a state's authority 
but ensures that such authority is reasonably exercised. The CAA and 
the RHR provide flexibility to the state in deciding how the factors in 
the analysis are weighed. We have concluded that ADEQ properly 
exercised its discretion in its process for weighing the small 
visibility improvement against the cost-effectiveness to reject SCR and 
SNCR.

C. Comments on the CAA Section 110(l) Analysis

    Comment 12: One commenter asserted that the EPA's proposal violates 
CAA section 110(l) anti-backsliding requirements because it weakens the 
existing BART determination for Cholla. The commenter argued that the 
BART Reassessment is inconsistent with the EPA's long-standing 
interpretation of section 110(l) of the CAA as preventing 
implementation plan revisions that would increase overall air pollution 
or worsen air quality. The commenter stated that the effect of the BART 
Assessment would be to allow Units 3 and 4 to emit an additional 4,161 
tons of NOX per year every year between 2018 and 2024, and 
would result in worse visibility conditions than the existing BART 
determination. The commenter went on to assert that the EPA's 
conclusions that the BART Reassessment complies with 110(l) are not 
justified because the EPA inappropriately discounted the timing of 
pollution reductions and the importance of promptly reducing pollution 
and improving visibility. The commenter argued that it is contrary to 
the purposes of the regional haze program and 110(l) to trade worse air 
quality and increased air pollution in the short term for potential 
benefits that may arise years from now. The commenter expressed concern 
that the EPA's BART Reassessment, if finalized, would set troubling 
precedent for the Coronado Generating Station BART Reassessment put 
forth for public comment by ADEQ in July 2016.
    The commenter argued that the EPA's proposed approval of the Cholla 
SIP Revision is contrary to the requirements of CAA section 110(l). The 
commenter cited to case law (identified in our response below) to 
support its interpretation that additional air emissions or less 
stringent requirements occurring as a result of a SIP revision per se 
constitute a violation of CAA section 110(l). Specifically, the 
commenter argued that CAA section 110(l) prohibits the EPA from 
approving a SIP revision that is less stringent than the FIP it is 
replacing, stating, ``This section prohibits states and EPA from 
revising an implementation plan if the revision would weaken the 
existing plan's requirements.'' The commenter supported its assertion 
that the SIP revision weakens the requirements of the existing FIP by 
noting that the SIP revision will allow Cholla to emit 4,161 tons per 
year more NOX between 2018 and 2025 than would have been 
allowed pursuant to the FIP. The commenter characterized the EPA's 
proposed

[[Page 15149]]

approval of the SIP revision as relying on two factors for 
demonstrating compliance with section 110(l), stating:

    According to EPA, the proposal complies with section 110(l) 
because (1) there are ``differences in the facts underlying'' the 
existing BART determination and the BART ``reassessment,'' and (2) 
the BART ``reassessment'' would ``result in greater visibility 
improvement than the existing [BART determination] beginning in 
2026, which is consistent with the long-term national goal of 
restoring natural visibility conditions at Class I areas.'' Neither 
justification demonstrates that the BART ``reassessment'' complies 
with section 110(l).

    Response 12: As discussed in more detail below, the EPA disagrees 
with the commenter's legal interpretation that CAA section 110(l) is 
violated per se by any SIP revision that allows an increase in actual 
air emissions relative to the existing implementation plan. The EPA 
also disagrees with the characterization of our proposed section 110(l) 
analysis as relying only on the two factors quoted above.
    The CAA section 110(l) states in relevant part: ``The Administrator 
shall not approve a revision of a plan if the revision would interfere 
with any applicable requirement concerning attainment and reasonable 
further progress (as defined in section 7501 of this title), and any 
other applicable requirement of this chapter.'' This language does not 
prohibit every SIP revision that weakens the existing plan's 
requirements.\49\ The statutory language of section 110(l) does not 
support the commenter's interpretation that additional air emissions or 
less stringent requirements occurring as a result of a SIP revision per 
se constitutes a violation of CAA section 110(l), and neither does the 
case law cited by the commenter.
---------------------------------------------------------------------------

    \49\ See, e.g., the EPA's action to approve a revision to the 
New Mexico SIP that addressed the BART requirement for 
NOX for the San Juan Generating Station in New Mexico, 79 
FR 60985 at 60989, October 9, 2014, stating ``Finally, contrary to 
the commenter's assertion, CAA section 110(l) does not prohibit a 
state from submitting a SIP that is less stringent than a FIP.''
---------------------------------------------------------------------------

    The cases cited by the commenter fail to support the commenter's 
view. In El Comit[eacute] para el Bienestar de Earlimart v. U.S. EPA, 
the Ninth Circuit was addressing a different issue--whether the EPA 
reasonably determined the level of emission reductions resulting from a 
particular SIP Revision. The court was not considering a SIP revision 
that allowed increased emissions.\50\ There, the EPA had consistently 
determined that a SIP provision required a 12 percent decrease in 
emissions despite the petitioner's contrary interpretation that the 
provision required a 20 percent reduction. The court deferred to the 
EPA's reasonable interpretation, and concluded ``that the EPA did not 
arbitrarily and capriciously fail to consider whether the SIP Revision 
violated Sec.  110(l) of the Act, because it reasonably interpreted the 
Pesticide Element as committing to a 12 percent reduction in VOC 
emissions from 1990 levels by 1999 in the San Joaquin Valley.'' \51\ 
The case does not support the commenter's interpretation of section 
110(l).
---------------------------------------------------------------------------

    \50\ See 786 F.3d 688 (9th Cir. 2015).
    \51\ Id. at 697 (emphasis in original).
---------------------------------------------------------------------------

    The other cases cited by the commenter also fail to support the 
commenter's interpretation. In Kentucky Resource Council v. EPA, the 
court upheld the EPA's approval of a SIP revision that moved a vehicle 
inspection and maintenance program from the SIP to a contingency 
measure.\52\ The court examined the EPA's analysis that the SIP 
revision would not ``interfere'' with attainment and reasonable further 
progress (RFP). As an initial matter, the court rejected an expansive 
reading of section 110(l), stating:
---------------------------------------------------------------------------

    \52\ 467 F.3d 986 (6th Circuit 2006)

    The statute prohibits approval of a revision that ``would 
interfere'' with an applicable requirement. Petitioner's reading of 
the phrase would substitute ``could'' for ``would.'' On this point 
it seems fairly clear that Congress did not intend that the EPA 
reject each and every SIP revision that presents some remote 
possibility for interference.\53\
---------------------------------------------------------------------------

    \53\ Id. at 994.

    In Kentucky Resource Council, the SIP substituted other emissions 
reductions to make up for the increased emissions from moving the 
vehicle inspection and maintenance program to a contingency measure. 
The issue was whether the EPA could approve this change without 
requiring an attainment demonstration and the court upheld the EPA's 
decision that a new attainment demonstration was not required in order 
to show that the SIP revision would not interfere pursuant to section 
110(l). Thus, the examination of whether the SIP revision would 
``worsen air quality'' was based on whether the area--which, unlike 
Navajo County, was designated as a nonattainment area for the relevant 
NAAQS--would have more difficulty in attaining and maintaining the 
NAAQS with the SIP revision--not, as the commenter argues here, whether 
the SIP revision would simply result in increased emissions.\54\
---------------------------------------------------------------------------

    \54\ The additional case law cited by the commenter, Alabama 
Environmental Council v. EPA 711 F.3d 1277 (11th Circuit 2013), 
which relied on the same analysis as the Kentucky Resource Council 
case, and WildEarth Guardians v. EPA 759 F.3d 1064 (9th Circuit 
2014), where the court found that petitioners had not identified any 
provision of the SIP revision at issue which weakened pollution 
controls, are similarly unavailing.
---------------------------------------------------------------------------

    The critical question under section 110(l) is not whether the SIP 
revision will cause an increase in actual emissions, it is whether that 
increase in actual emissions will interfere with attainment of the 
NAAQS or RFP, or if the SIP revision interferes with any other 
applicable requirement of the CAA. The fact that actual emissions will 
increase means that the EPA's analysis must include an evaluation of 
how that emissions increase affects attainment and RFP and other 
applicable requirements of the CAA.
    The EPA analyzed the requirements of section 110(l) in proposing to 
approve the Cholla SIP revision.\55\ The commenter fails to acknowledge 
much of the EPA's analysis. The commenter is incorrect that the EPA's 
proposal only relied on different facts and greater long term 
visibility benefits after 2026 to support approval. Rather, our 
proposal considered that fact that Navajo County, where the facility is 
located, is attaining the NAAQS for all pollutants.\56\ In addition, 
the proposal relied on the fact that the Cholla SIP revision will 
result in substantially lower SO2 and PM10 
emissions than would have been allowed by the FIP. Finally, for 
NOX emissions, the EPA's proposal stated, ``While the Cholla 
SIP Revision will require fewer NOX reductions than the FIP 
between 2018 and 2025, it will ensure that NOX emissions remain at or 
below current levels . . . until 2025 . . .'' (emphasis added).\57\ 
Based on these facts, the EPA's proposal stated:
---------------------------------------------------------------------------

    \55\ 81 FR 46852 at 46862, July 19, 2016.

    \56\ Id. at 46862.
    \57\ Id. at 46863.
---------------------------------------------------------------------------

    Thus, the Arizona SIP does not currently rely on emission 
limitations at Cholla to satisfy any attainment or RFP requirements. 
Given that the Cholla SIP Revision will result in equivalent or 
lower emissions of NOX, PM10 and 
SO2 for all future years, compared to current emission 
levels, in an area that is designated attainment or has not yet been 
designated for all NAAQS, we propose to find that the Cholla SIP 
Revision would not interfere with any applicable requirement 
concerning attainment or RFP.

    The comment letter does not appear to challenge the EPA's analysis 
that the SIP revision does not interfere with attainment or RFP for the 
reasons discussed above, but rather simply asserts that any increase in 
emissions automatically violates section 110(l).\58\
---------------------------------------------------------------------------

    \58\ As noted previously, the commenter applies an incorrect 
legal standard, insisting that any SIP revision that is less 
stringent than the existing SIP or FIP requirement violates section 
110(l).

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

[[Page 15150]]

    CAA section 110(l) also requires the EPA to evaluate if the SIP 
revision will interfere with ``any other applicable requirement of this 
chapter.'' The EPA's proposal to approve the Cholla SIP Revision also 
carefully analyzed this requirement.\59\ The commenter challenges only 
the EPA's proposal to find that the SIP revision complies with the 
requirements of the RHR. We disagree with this comment. The commenter 
notes that the Cholla SIP Revision is predicted to result in higher 
visibility impairment at Petrified Forest National Park than the FIP 
from 2018 to 2025. We agree. As discussed in our proposed rule, in its 
section 110(l) analysis, ADEQ stated that the Cholla SIP Revision would 
result in less visibility improvement between 2018 and 2025, but would 
result in greater improvements starting in 2026.\60\ This does not, 
however, support the argument that the SIP will interfere with the 
requirements of the visibility program. As discussed above, we have 
determined that the Cholla SIP Revision meets the BART requirements. We 
also proposed that the Cholla SIP Revision would not interfere with the 
RHR because the achievement of greater visibility improvement from the 
Cholla SIP Revision beginning in 2026 would be consistent with the 
long-term national goal of the RHR of restoring visibility conditions 
at Class I areas.\61\ We further noted that while the Cholla SIP 
Revision would require fewer NOX reductions than the FIP 
between 2018 and 2025, it would ensure that NOX emission 
remain at or below current levels until 2025, after which time it would 
require a substantial reduction in NOX emissions compared to 
both current levels and the FIP.\62\
---------------------------------------------------------------------------

    \59\ 81 FR 46852 at 46862, July 19, 2016.
    \60\ Id. at 46859.
    \61\ Id. at 46862.
    \62\ Id.
---------------------------------------------------------------------------

    The commenter challenges our proposed finding that the SIP revision 
meets the requirements for BART. Our proposal concluded that the Cholla 
SIP Revision is consistent with BART, and therefore does not interfere 
with an applicable requirement of the CAA and the RHR.\63\ For the 
reasons discussed in responses to other comments, ADEQ conducted an 
adequate BART analysis for Cholla. ADEQ considered the appropriate 
factors and reached a reasonable conclusion. Our analysis that the 
Cholla SIP Revision is approvable pursuant to CAA section 110(l) 
considered compliance with BART and also considered that ``the Cholla 
SIP Revision would result in greater visibility improvement than the 
existing SIP and FIP requirements beginning in 2026, which is 
consistent with the long-term national goal of restoring natural 
visibility conditions at Class I areas.'' \64\ The commenter contends 
that the EPA was justifying ``weakening'' the Arizona SIP and allowing 
``backsliding'' based on new or different facts. That is not the case. 
The EPA was evaluating whether the SIP revision complied with the 
requirements for BART, which it does. The proposal then stated:
---------------------------------------------------------------------------

    \63\ Id.
    \64\ Id.

    Furthermore, the Cholla SIP Revision would result in greater 
visibility improvement than the existing SIP and FIP requirements 
beginning in 2026, which is consistent with the long term national 
---------------------------------------------------------------------------
goal of restoring natural visibility conditions at Class I areas.

    The commenter construes this statement incorrectly, asserting that 
this statement means the EPA is justifying compliance with section 
110(l) by crediting later emission reductions to offset earlier 
emission increases. As noted earlier, section 110(l) does not prohibit 
approving a SIP revision that allows an increase in actual emissions 
provided it does not interfere with attainment of the NAAQS, RFP, or 
any other applicable requirement. All of those criteria have been met 
for the reasons discussed above. The EPA, however, noted that the 
substantial emissions reductions from the Cholla SIP Revision--both 
those occurring from the shutdown of Unit 2 in 2016 and additional 
NOX reductions in 2025--will support efforts to meet the RHR 
goal of reaching natural visibility in 2064.
    For the reasons discussed above, the EPA disagrees with the 
commenter that our approval of the Cholla SIP revision is inconsistent 
with CAA section 110(l).

D. Other Comments

    Comment 13: One commenter argued that the EPA's proposal negates 
the 2018 reasonable progress goals (RPGs) for Arizona. The EPA set 2018 
RPGs for Arizona in its Final Phase 3 Rule that relied upon the 
emission reductions required by its regional haze FIP for Arizona. The 
commenter asserted that in delaying Cholla's compliance with its BART 
obligations past 2017, the BART Reassessment necessitates the 
development of entirely new 2018 RPGs.
    Response 13: The EPA disagrees with the comment that the Cholla SIP 
Revision negates or otherwise adversely effects the 2018 RPGs for 
Arizona. The 2018 RPGs account for emission reductions expected to 
occur by the end of the first planning period. The compliance date for 
the NOX emission reductions, achievable with SCR, required 
in the FIP for Cholla was December 5, 2017. As noted in our proposed 
rule, the anticipated NOX reductions in 2018 from Units 3 
and 4 associated with the FIP would have been 4,763 tons more than the 
reductions from those units under the Cholla SIP Revision for that 
year. However, cumulative NOX reductions in 2016 and 2017, 
from the Cholla SIP Revision, would be 6,302 tons greater than the FIP 
for Cholla as a result of the closure of Unit 2.\65\ In addition, the 
closure of Unit 2 required in the Cholla SIP Revision also results in 
additional reductions in SO2 and PM10 in 2016 and 
2017.\66\ Because the NOX, SO2, and 
PM10 reductions from the Cholla SIP Revision are greater 
than the reductions that would have occurred under the FIP in 2016, 
2017, and 2018, and because the 2018 RPGs consider emission reductions 
that occur until the end of 2018, the Cholla SIP Revision aids, rather 
than negates, the 2018 RPGs.
---------------------------------------------------------------------------

    \65\ See Table 8 in our proposed rule at 81 FR 46852, 46858 
(July 19, 2016). We further note that the emission reductions in 
Table 8 associated with Unit 2 are based on the operation of Unit 2 
until April 1, 2016. Because Unit 2 closed in 2015, the actual 
emission reductions from Unit 2 in 2016 would be lower than 
estimated in our proposed rule.
    \66\ Id. Tables 6 and 7.
---------------------------------------------------------------------------

    As discussed elsewhere in this final rule, we disagree with the 
commenter's characterization that the Cholla SIP Revision is delaying 
the compliance deadline for BART beyond December 5, 2017. We are 
approving ADEQ's determination for Cholla Units 3 and 4 that BART is 
the use of LNB+SOFA. The emission limitations associated with this BART 
determination will become effective on April 26, 2017.
    Finally, although the Cholla SIP Revision will result in greater 
NOX emissions than the FIP from Cholla Units 3 and 4 between 
December 5, 2017 and April 30, 2025, the requirements in the Cholla SIP 
Revision to permanently retire Unit 2 by April 1, 2016, combined with 
the permanent cessation of coal combustion in Units 1, 3, and 4 by 
April 30, 2025 and the potential conversion of those units to natural 
gas by July 31, 2025, will aid Arizona's RPGs more than we had 
originally attributed to the FIP provisions we are withdrawing in this 
action.
    Comment 14: One commenter noted that if the EPA takes final action 
to approve the BART Reassessment and

[[Page 15151]]

withdraw the FIP for Cholla, a provision in 40 CFR 52.145(f)(5)(i)(A) 
that requires continuous emission monitoring systems (CEMS) for 
SO2 at Cholla Units 2, 3, and 4 to be in full compliance 
with the requirements in 40 CFR part 75, will be duplicative because 
that requirement is already contained in the Cholla SIP Revision. The 
commenter requests that the EPA remove Cholla completely from the final 
version of the regulatory text that will be codified at 40 CFR 52.145.
    Response 14: The EPA agrees with the comment that the Arizona RH 
FIP provisions should not contain any provisions related to Cholla 
after the EPA takes final action to withdraw the provisions in 40 CFR 
52.145 that are applicable to this facility. As stated in our proposed 
rule, ``we propose to withdraw the provisions of the Arizona Regional 
Haze FIP that apply to Cholla;'' the retention of the reference to 
Cholla in 40 CFR 52.145(f)(5)(i)(A) was inadvertent.\67\ We also agree 
with the commenter that the condition is duplicative to the requirement 
already contained in the Cholla permit revision that was submitted as 
part of the Cholla SIP Revision. Therefore, in this final action, we 
are removing from 40 CFR 52.145(f)(5)(i)(A) the sentence that reads: 
``In addition, the owner/operator of Cholla Units 2, 3, and 4 shall 
calibrate, maintain, and operate a CEMS, in full compliance with the 
requirements found in 40 CFR part 75, to accurately measure 
SO2 emissions and diluent at the inlet of the sulfur dioxide 
control device.'' The remaining provisions in 40 CFR 52.145(f)(5)(i)(A) 
will continue to exist and apply to the Coronado Generating Station.
---------------------------------------------------------------------------

    \67\ See 81 FR 46852 at 46863, July 19, 2016.
---------------------------------------------------------------------------

III. Summary of Final Action

    For the reasons described above, the EPA is taking final action to 
approve the Cholla SIP Revision. Because this approval fills the gap in 
the Arizona RH SIP that was left by the EPA's prior partial disapproval 
with respect to Cholla, we are also taking final action to withdraw the 
provisions of the FIP that applied to Cholla. This final action also 
constitutes our action on the petitions for reconsideration submitted 
by APS and PacifiCorp on the FIP.

IV. Environmental Justice Considerations

    As shown in Tables 6 and 7 of the proposed rule, the Cholla SIP 
Revision will result in lower emissions of both PM10 and 
SO2 compared to the emissions we had previously projected 
under the existing requirements beginning in 2016, with greater 
emission reductions from the Cholla SIP Revision occurring over time 
(i.e., in the periods 2017-2025, and 2026 and thereafter).\68\ As shown 
in Table 8 of the proposed rule, the Cholla SIP Revision will result in 
greater NOX emissions than the FIP between 2018 and 2025, 
but will achieve substantially lower NOX emissions than the 
FIP in 2016, 2017, and 2026 and thereafter.\69\ In addition, as noted 
in our proposed rule, Cholla is located in Navajo County, Arizona, 
which is currently designated as attainment or unclassifiable for the 
following NAAQS: Carbon monoxide, lead, nitrogen dioxide, ozone (2008 
NAAQS), PM2.5 (1997 and 2006 NAAQS), PM10, and 
SO2 (1971 NAAQS). ADEQ also noted in its submittal that it 
has recommended a designation of attainment/unclassifiable for this 
area for the 2012 PM2.5 and 2010 SO2 standards. 
Therefore, this final action will not have potential disproportionately 
high and adverse human health or environmental effects on minority, 
low-income, or indigenous populations.
---------------------------------------------------------------------------

    \68\ See 81 FR 46852 at 46857-46858, July 18, 2016.
    \69\ Id. at 46858-46859.
---------------------------------------------------------------------------

V. Incorporation by Reference

    In this rule, the EPA is finalizing regulatory text that includes 
incorporation by reference. In accordance with the requirements of 1 
CFR 51.5, the EPA is finalizing the incorporation by reference 
``Significant Permit Revision No. 61713 to Operating Permit No. 53399'' 
issued by ADEQ on October 16, 2015. Therefore, these materials have 
been approved by the EPA for inclusion in the SIP, have been 
incorporated by reference by the EPA into that plan, are fully 
federally enforceable under sections 110 and 113 of the CAA as of the 
effective date of this final rule, and will be incorporated by 
reference by the Director of the Federal Register in the next update to 
the SIP compilation.\70\ The EPA has made, and will continue to make, 
this document available electronically through www.regulations.gov and 
in hard copy at the EPA Region IX Office. Please contact the person 
identified in the FOR FURTHER INFORMATION CONTACT section of this 
preamble for more information.
---------------------------------------------------------------------------

    \70\ 62 FR 27968, May 22, 1997.
---------------------------------------------------------------------------

VI. 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 one facility 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 PRA. Burden is defined at 5 CFR 1320.3(b).

C. Regulatory Flexibility Act (RFA)

    I certify that this final 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. The two owners of Cholla, APS and PacifiCorp, exceed 
this threshold.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small governments. This action does not impose additional requirements 
beyond those imposed by state law. Accordingly, no additional costs to 
State, local, or tribal governments, or to the private sector, will 
result from this action.

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: Coordination With Indian Tribal Governments

    This action does not have tribal implications, as specified in 
Executive Order 13175, because the SIP is not approved to apply on any 
Indian reservation land or in any other area where the EPA or an Indian 
tribe has demonstrated that a tribe has jurisdiction, and will not 
impose substantial direct costs on tribal governments or preempt tribal 
law.

[[Page 15152]]

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 Executive Order 13045 as applying only to those 
regulatory actions that concern environmental 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 impose additional 
requirements beyond those imposed by state law.

H. Executive Order 13211: Actions 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 (NTTAA)

    This rulemaking does not involve technical standards.

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

    The EPA believes the human health or environmental risk addressed 
by this action will not have potentially disproportionately high and 
adverse human health or environmental effects on minority, low-income 
or indigenous populations. Although this final action to approve the 
Cholla SIP Revision will result in greater NOX emissions 
than we had previously projected to occur under the FIP it replaces 
over the 2018-2025 period, emissions of PM10 and 
SO2 will be lower under the Cholla SIP Revision beginning in 
2016, with greater emission reductions from the Cholla SIP Revision 
occurring over time (i.e., in the periods 2017-2025, and 2026 and 
thereafter). In addition, the Cholla SIP Revision will result in 
greater NOX reductions than the FIP in 2016, 2017, and 2026 
and thereafter. In addition, as noted in our proposed rule, Cholla is 
located in Navajo County, Arizona, which is currently designated as 
attainment or unclassifiable for the following NAAQS: Carbon monoxide, 
lead, nitrogen dioxide, ozone (2008 NAAQS), PM2.5 (1997 and 
2006 NAAQS), PM10, and SO2 (1971 NAAQS). ADEQ 
also noted in its submittal that it has recommended a designation of 
attainment/unclassifiable for this area for the 2012 PM2.5 
and 2010 SO2 standards. Therefore, this final action will 
not have disproportionately high and adverse human health or 
environmental effects on minority or low-income populations.

K. Congressional Review Act (CRA)

    This rule is exempt from the CRA because it is a rule of particular 
applicably. EPA is not required to submit a rule report regarding this 
action under section 801 because this is a rule of particular 
applicability that only applies to a single named facility.

L. 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 May 26, 2017. 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 section 307(b)(2)).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Nitrogen dioxide, Particulate 
matter, Reporting and recordkeeping requirements, Sulfur dioxide, 
Visibility.

    Dated: March 16, 2017.
E. Scott Pruitt,
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. Section 52.120 is amended by:
0
a. Adding in paragraph (d), under the table heading ``EPA-Approved 
Source-Specific Requirements'' an entry for ``Cholla Power Plant'' 
after the entry for ``Arizona Electric Power Cooperative's Apache 
Generating Station.''
0
b. Adding in paragraph (e), under the table heading ``Table 1--EPA-
Approved Non-Regulatory and Quasi-Regulatory Measures'' after the entry 
for ``Arizona Lead SIP Revision'', an entry for ``Arizona State 
Implementation Plan Revision to the Arizona Regional Haze Plan for 
Arizona Public Service Cholla Generating Station.''
    The additions read as follows:


Sec.  52.120  Identification of plan.

* * * * *
    (d) * * *

                                    EPA-Approved Source-Specific Requirements
----------------------------------------------------------------------------------------------------------------
                                                                             EPA approval
        Name of source         Order/permit No.       Effective date             date            Explanation
----------------------------------------------------------------------------------------------------------------
                                   Arizona Department of Environmental Quality
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
Cholla Power Plant...........  Significant       October 16, 2015........  3/27/2017,       Permit issued by
                                Permit Revision                             [INSERT          Arizona Department
                                No. 61713 to                                Federal          of Environmental
                                Operating                                   Register         Quality. Submitted
                                Permit No.                                  CITATION].       on October 22,
                                53399.                                                       2015.
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------

    (e) * * *

[[Page 15153]]



                       Table 1--EPA-Approved Non-Regulatory and Quasi-Regulatory Measures
       [Excluding certain resolutions and statutes, which are listed in tables 2 and 3, respectively] \1\
----------------------------------------------------------------------------------------------------------------
                                     Applicable
                                   geographic or
     Name of SIP provision         nonattainment     State submittal   EPA approval date        Explanation
                                   area or title/          date
                                      subject
----------------------------------------------------------------------------------------------------------------
                         The State of Arizona Air Pollution Control Implementation Plan
    Clean Air Act Section 110(a)(2) State Implementation Plan Elements (Excluding Part D Elements and Plans)
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
Arizona State Implementation     Source-Specific..  October 22, 2015.  3/27/2017,         Revised source-
 Plan Revision to the Arizona                                           [INSERT Federal    specific BART limits
 Regional Haze Plan for Arizona                                         Register           for NOX for Cholla
 Public Service Cholla                                                  CITATION].         Power Plant adopted
 Generating Station.                                                                       October 22, 2015.
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------
\1\ Table 1 is divided into three parts: Clean Air Act Section 110(a)(2) State Implementation Plan Elements
  (excluding Part D Elements and Plans), Part D Elements and Plans (other than for the Metropolitan Phoenix or
  Tucson Areas), and Part D Elements and Plans for the Metropolitan Phoenix and Tucson Areas.

* * * * *

0
3. Section 52.145 is amended by revising paragraphs (f)(1) through (5) 
and (10) to read as follows:


Sec.  52.145  Visibility protection.

* * * * *
    (f) * * *
    (1) Applicability. This paragraph (f) applies to each owner/
operator of the following coal-fired electricity generating units 
(EGUs) in the state of Arizona: Coronado Generating Station, Units 1 
and 2. The provisions of this paragraph (f) are severable, and if any 
provision of this paragraph (f), or the application of any provision of 
this paragraph (f) to any owner/operator or circumstance, is held 
invalid, the application of such provision to other owner/operators and 
other circumstances, and the remainder of this paragraph (f), shall not 
be affected thereby.
    (2) Definitions. Terms not defined below shall have the meaning 
given to them in the Clean Air Act or EPA's regulations implementing 
the Clean Air Act. For purposes of this paragraph (f): ADEQ means the 
Arizona Department of Environmental Quality.
    Boiler-operating day means a 24-hour period between 12 midnight and 
the following midnight during which any fuel is combusted at any time 
in the unit.
    Coal-fired unit means any of the EGUs identified in paragraph 
(f)(1) of this section.
    Continuous emission monitoring system or CEMS means the equipment 
required by 40 CFR part 75 and this paragraph (f).
    Emissions limitation or emissions limit means any of the Federal 
Emission Limitations required by this paragraph (f) or any of the 
applicable PM10 and SO2 emissions limits for 
Coronado Generating Station submitted to EPA as part of the Arizona 
Regional Haze SIP in a letter dated February 28, 2011, and approved 
into the Arizona State Implementation Plan on December 5, 2012.
    Flue Gas Desulfurization System or FGD means a pollution control 
device that employs flue gas desulfurization technology, including an 
absorber utilizing lime, fly ash, or limestone slurry, for the 
reduction of sulfur dioxide emissions.
    Group of coal-fired units means Units 1 and 2 for Coronado 
Generating Station.
    lb means pound(s).
    MMBtu means million British thermal unit(s).
    NOX means nitrogen oxides expressed as nitrogen dioxide 
(NO2).
    Owner(s)/operator(s) means any person(s) who own(s) or who 
operate(s), control(s), or supervise(s) one or more of the units 
identified in paragraph (f)(1) of this section.
    Operating hour means any hour that fossil fuel is fired in the 
unit.
    PM10 means filterable total particulate matter less than 10 microns 
and the condensable material in the impingers as measured by Methods 
201A and 202 in 40 CFR part 51, appendix M. Regional Administrator 
means the Regional Administrator of EPA Region IX or his/her authorized 
representative.
    SO2 means sulfur dioxide.
    SO2 removal efficiency means the quantity of SO2 removed 
as calculated by the procedure in paragraph (f)(5)(iii)(B) of this 
section.
    Unit means any of the EGUs identified in paragraph (f)(1) of this 
section.
    Valid data means data recorded when the CEMS is not out-of-control 
as defined by 40 CFR part 75.
    (3) Federal emission limitations--(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 paragraph.

------------------------------------------------------------------------
                                                              Federal
      Coal fired unit or group of coal-fired units           emission
                                                            limitation
------------------------------------------------------------------------
Coronado Generating Station Unit 1......................           0.065
Coronado Generating Station Unit 2......................           0.080
------------------------------------------------------------------------

    (ii) [Reserved]
    (4) Compliance dates. (i) The owners/operators of each unit subject 
to this paragraph (f) shall comply with the NOX emissions 
limitations and other NOX-related requirements of this 
paragraph (f) no later than December 5, 2017.
    (ii) The owners/operators of each unit subject to this paragraph 
(f) shall comply with the applicable PM10 and SO2 
emissions limits submitted to EPA as part of the Arizona Regional Haze 
SIP in a letter dated February 28, 2011, and approved into the Arizona 
State Implementation Plan on December 5, 2012, as well as the related 
compliance, recordkeeping and reporting of this paragraph (f) no later 
than June 3, 2013.
    (5) Compliance determinations for NOX and SO2--(i) Continuous 
emission monitoring system. (A) At all times after the compliance date 
specified in paragraph (f)(4) of this section, the owner/operator of 
each coal-fired unit shall maintain, calibrate, and operate a CEMS, in 
full compliance with the requirements found at 40 CFR part 75, to 
accurately measure SO2, NOX, diluent, and stack 
gas volumetric flow rate from each unit. All valid CEMS hourly data 
shall be used to determine compliance with the emission limitations for 
NOX and SO2 in paragraph (f)(3) of this section 
for each unit. When the CEMS is out-of-control

[[Page 15154]]

as defined by 40 CFR part 75, that CEMS data shall be treated as 
missing data, and not used to calculate the emission average. Each 
required CEMS must obtain valid data for at least 90 percent of the 
unit operating hours, on an annual basis.
    (B) The owner/operator of each unit shall comply with the quality 
assurance procedures for CEMS found in 40 CFR part 75. In addition to 
these 40 CFR part 75 requirements, relative accuracy test audits shall 
be calculated for both the NOX and SO2 pounds per 
hour measurement and the heat input measurement. The CEMS monitoring 
data shall not be bias adjusted. The inlet SO2 and diluent 
monitors required by this rule shall also meet the Quality Assurance/
Quality Control (QA/QC) requirements of 40 CFR part 75. The testing and 
evaluation of the inlet monitors and the calculations of relative 
accuracy for lb/hr of NOX, SO2 and heat input 
shall be performed each time the 40 CFR part 75 CEMS undergo relative 
accuracy testing.
    (ii) Compliance determinations for NOX. (A) [Reserved]
    (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.
    (C) If a valid NOX pounds per hour or heat input is not 
available for any hour for a unit, that heat input and NOX 
pounds per hour shall not be used in the calculation of the 30-day 
rolling average.
    (iii) Compliance determinations for SO2. (A) The 30-day rolling 
average SO2 emission rate for each coal-fired unit shall be 
calculated in accordance with the following procedure: Step one, sum 
the total pounds of SO2 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 day; and step three, divide the total number of 
pounds of SO2 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 SO2 emission 
rate shall be calculated for each new boiler-operating day. Each 30-day 
rolling average SO2 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) [Reserved]
    (C) If a valid SO2 pounds per hour at the outlet of the 
FGD system or heat input is not available for any hour for a unit, that 
heat input and SO2 pounds per hour shall not be used in the 
calculation of the 30-day rolling average.
    (D) If both a valid inlet and outlet SO2 lb/MMBtu and an 
outlet value of lb/hr of SO2 are not available for any hour, 
that hour shall not be included in the efficiency calculation.
* * * * *
    (10) Equipment operations. (i) [Reserved]
    (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. 2017-05724 Filed 3-24-17; 8:45 am]
BILLING CODE 6560-50-P


