[Federal Register Volume 86, Number 138 (Thursday, July 22, 2021)]
[Proposed Rules]
[Pages 38630-38643]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-15467]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R06-OAR-2021-0032; FRL-8688-01-R6]


Air Plan Approval; Oklahoma; Interstate Visibility Transport

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: Pursuant to the Federal Clean Air Act (CAA or the Act), the 
Environmental Protection Agency (EPA) is proposing to approve elements 
of a State Implementation Plan (SIP) submission from the State of 
Oklahoma for the 2015 Ozone National Ambient Air Quality Standard 
(NAAQS), and proposing to disapprove elements of two SIP submissions 
for the 2010 sulfur dioxide (SO2) and the 2012 fine 
particulate matter (PM2.5) NAAQS. These infrastructure SIP 
(i-SIP) submissions address how the existing SIP provides for 
implementation, maintenance, and enforcement of these NAAQS. The i-SIP 
requirements are to ensure that the Oklahoma SIP is adequate to meet 
the state's responsibilities under the CAA for these NAAQS. 
Specifically, this proposed rule addresses the interstate visibility 
transport requirements of the i-SIP for the 2010 SO2, 2012 
PM2.5, and 2015 Ozone NAAQS under CAA section 
110(a)(2)(D)(i)(II). We are also proposing to find that the 
deficiencies in the Oklahoma SIP that form the basis of our proposed 
disapproval of the interstate visibility transport portions of the 
Oklahoma i-SIP submissions for the 2010 SO2 and 2012 
PM2.5 NAAQS are

[[Page 38631]]

remedied by the existing Federal Implementation Plan (FIP) in place for 
the Oklahoma Regional Haze program, and that no further federal action 
is required to address the proposed disapproval.

DATES: Comments must be received on or before August 23, 2021.

ADDRESSES: Submit your comments, identified by Docket No. EPA-R06-OAR-
2021-0032, at https://www.regulations.gov or via email to 
medina.dayana@epa.gov. Follow the online instructions for submitting 
comments. Once submitted, comments cannot be edited or removed from 
Regulations.gov. The EPA may publish any comment received to its public 
docket. Do not submit electronically any information you consider to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Multimedia submissions (audio, 
video, etc.) must be accompanied by a written comment. The written 
comment is considered the official comment and should include 
discussion of all points you wish to make. The EPA will generally not 
consider comments or comment contents located outside of the primary 
submission (i.e., on the web, cloud, or other file sharing system). For 
additional submission methods, please contact Dayana Medina, 214-665-
7341, medina.dayana@epa.gov. For the full EPA public comment policy, 
information about CBI or multimedia submissions, and general guidance 
on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    Docket: The index to the docket for this action is available 
electronically at www.regulations.gov. While all documents in the 
docket are listed in the index, some information may not be publicly 
available due to docket file size restrictions or content (e.g., CBI).

FOR FURTHER INFORMATION CONTACT: Dayana Medina, EPA Region 6 Office, 
Regional Haze and SO2 Section, 214-665-7341, 
medina.dayana@epa.gov. Out of an abundance of caution for members of 
the public and our staff, the EPA Region 6 office will be closed to the 
public to reduce the risk of transmitting COVID-19. We encourage the 
public to submit comments via https://www.regulations.gov, as there 
will be a delay in processing mail and no courier or hand deliveries 
will be accepted. Please call or email the contact listed above if you 
need alternative access to material indexed but not provided in the 
docket.

SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,'' 
and ``our'' means the EPA.

I. Background

    Whenever a new or revised NAAQS is promulgated, the Clean Air Act 
(CAA) requires states to submit a plan for the implementation, 
maintenance, and enforcement of the standard, commonly referred to as 
infrastructure requirements. Section 110(a)(2) lists specific 
requirements that infrastructure SIPs, or i-SIPs, must include to 
adequately address such new or revised NAAQS, as applicable. Section 
110(a)(2)(D)(i) includes four distinct elements related to interstate 
transport of air pollution, commonly referred to as prongs, that must 
be addressed in i-SIP submissions. The first two prongs are codified in 
section 110(a)(2)(D)(i)(I) and the third and fourth prongs are codified 
in section 110(a)(2)(D)(i)(II). These four prongs prohibit any source 
or type of emission activities in one state from:
     Contributing significantly to nonattainment of the NAAQS 
in another state (prong 1);
     Interfering with maintenance of the NAAQS in another state 
(prong 2);
     Interfering with measures that prevent significant 
deterioration of air quality in another state (prong 3); and
     Interfering with measures that protect visibility in 
another state (prong 4 or ``visibility transport'').
    We are only addressing the prong 4 element in this proposal. In an 
effort to assist states in complying with the i-SIP requirements, EPA 
issued guidance in 2013.\1\ In the 2013 i-SIP guidance, EPA discussed 
its interpretation of prong 4 and its relationship to the Regional Haze 
program under CAA sections 169A and 169B, which require each state to 
address its share of emission reductions needed to meet reasonable 
progress goals (RPGs) for surrounding Class I areas. EPA suggested two 
options states may have to demonstrate that the requirements of prong 4 
are met. One way in which prong 4 may be satisfied for any relevant 
NAAQS is through confirmation in the state's i-SIP submission that it 
has an approved regional haze SIP that fully meets the requirements of 
40 CFR 51.308 or 51.309. Alternatively, a state may demonstrate in its 
i-SIP submission that emissions within its jurisdiction do not 
interfere with other states' plans to protect visibility. The 
demonstration should show that the state has sufficient measures that 
have been approved into its SIP to prevent emissions within its 
jurisdiction from interfering with the visibility protection plans of 
other states.
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    \1\ Stephen D. Page, Director, Office of Air Quality Planning 
and Standards. ``Guidance on Infrastructure State Implementation 
Plan (SIP) Elements under Clean Air Act Section 110(a)(1) and 
110(a)(2).'' Memorandum to EPA Air Division Directors, Regions 1 
through 10, September 13, 2013 (hereinafter ``2013 i-SIP 
Guidance'').
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A. Oklahoma's Infrastructure SIP Submittals for 2010 SO2, 2012 PM2.5, 
and 2015 Ozone NAAQS

    EPA has regulated particulate matter (PM) since the first NAAQS for 
PM were published in 1971. (36 FR 8186 (April 30, 1971)). Most 
recently, by notice dated January 15, 2013, following a periodic review 
of the NAAQS for PM2.5, EPA revised the primary annual 
PM2.5 NAAQS to 12.0 [mu]g/m\3\ and retained the secondary 
annual PM2.5 standard of 15 [mu]g/m\3\ as well as the 
primary and secondary 24-hour PM2.5 standards of 35 [mu]g/
m\3\ (2012 PM2.5 NAAQS).\2\ The primary NAAQS is designed to 
protect human health, and the secondary NAAQS is designed to protect 
the public welfare. On June 16, 2016, the Oklahoma Secretary of Energy 
and Environment submitted a SIP revision to address most of the i-SIP 
elements for this revised 2012 PM2.5 NAAQS. On November 21, 
2016, we proposed to approve all elements included in the 2012 
PM2.5 i-SIP submission except for the 110(a)(2)(D)(i)(II) 
prong 4 portion, which we proposed to disapprove.\3\ On June 14, 2017, 
we took final action to approve all elements included in this i-SIP 
submission, but deferred taking final action on the 110(a)(2)(D)(i)(II) 
prong 4 portion.\4\ In this notice, we are once again proposing to 
disapprove the prong 4 visibility transport portion of the June 16, 
2016 i-SIP submission for the 2012 PM2.5 NAAQS.
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    \2\ 78 FR 3085 (Jan. 15, 2013).
    \3\ 81 FR 83184 (November 21, 2016).
    \4\ 82 FR 27121 (June 14, 2017).
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    On June 22, 2010, we revised the primary NAAQS for SO2 
to establish a new 1-hour standard at a level of 75 parts per billion 
(ppb), based on the 3-year average of the annual 99th percentile of 1-
hour daily maximum concentrations.\5\ On January 28, 2015, the Oklahoma 
Secretary of Energy and Environment submitted a SIP revision to address 
i-SIP elements for this revised NAAQS. On November 21, 2016, we 
proposed to disapprove the 110(a)(2)(D)(i)(II) prong 4 portion of the 
2010 SO2 i-SIP submission, but we did not finalize this 
disapproval.\6\ In this notice, we are once again proposing to 
disapprove the prong 4 visibility

[[Page 38632]]

transport portion of the January 28, 2015 i-SIP submission for the 2010 
SO2 NAAQS.
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    \5\ 75 FR 35520 (June 22, 2010).
    \6\ 81 FR 83184.
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    EPA has regulated ozone since 1971, when we published the first 
NAAQS for Photochemical Oxidants (36 FR 8186 (April 30, 1971)). Most 
recently, following a periodic review of the 2008 NAAQS for ozone, the 
EPA promulgated a revision to the ozone NAAQS in 2015 lowering the 
level of both the primary and secondary standards to 0.070 parts per 
million.\7\ On October 25, 2018, the Oklahoma Secretary of Energy and 
Environment submitted a SIP revision to address i-SIP elements for this 
revised NAAQS. On March 30, 2020, we approved most infrastructure 
elements of the 2015 ozone i-SIP submission but deferred taking final 
action on the 110(a)(2)(D)(i)(II) prong 4 portion.\8\
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    \7\ 82 FR 65291 (Oct. 26, 2015). Additional information on the 
history of the NAAQS for ozone is available at https://www.epa.gov/ozone-pollution/table-historical-ozone-national-ambient-air-quality-standards-naaqs.
    \8\ See 85 FR 17502 (March 30, 2020).
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    In this notice, we refer to each of these NAAQS by the year 
promulgated, e.g., ``the 2008 ozone standard.'' For more information on 
these standards, please visit https://www.epa.gov/criteria-air-pollutants.

B. Regional Haze and Visibility Transport in Oklahoma

    On February 17, 2010, Oklahoma submitted a regional haze SIP (the 
2010 Regional Haze SIP) to the EPA that included best available 
retrofit technology (BART) requirements for SO2, 
NOX, and PM for Oklahoma sources. On December 28, 2011, we 
took final action to partially approve and partially disapprove the 
2010 Regional Haze SIP.\9\ In this final action, we disapproved 
Oklahoma's SO2 BART determinations for the Oklahoma Gas and 
Electric (OG&E) Sooner Units 1 and 2, the OG&E Muskogee Units 4 and 5, 
and the American Electric Power/Public Service Company of Oklahoma 
(AEP/PSO) Northeastern Units 3 and 4 because they do not comply with 
our regional haze regulations under 40 CFR 51.308(e). We approved 
Oklahoma's remaining SO2 BART determinations as well as all 
nitrogen oxide (NOX) and PM BART determinations. 
Additionally, we approved all remaining portions of the 2010 Regional 
Haze SIP, with the exception of (1) the long-term strategy to the 
extent it relied on the BART emission limits that we disapproved and 
(2) Oklahoma's 2018 RPGs on the 20% least impaired and 20% most 
impaired days for the Wichita Mountains Class I area.\10\
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    \9\ 76 FR 81728 (December 28, 2011).
    \10\ In a final rule published in the Federal Register on 
January 5, 2016, we disapproved Oklahoma's 2018 RPGs on the 20% 
least impaired and 20% most impaired days for the Wichita Mountains 
Class I area because Oklahoma did not adequately demonstrate that 
its RPGs provide for reasonable progress towards meeting the 
national visibility goal. Specifically, Oklahoma did not satisfy 
several of the requirements at section 51.308(d)(1) with regard to 
setting RPGs, including the requirement to adequately consult with 
other states that may reasonably be anticipated to cause or 
contribute to visibility impairment at the Wichita Mountains and the 
requirement to adequately justify RPGs that are less stringent than 
the uniform rate of progress (URP). However, that final rulemaking 
was challenged, and in December 2016, following the submittal of a 
request by the EPA for a voluntary remand of the parts of the rule 
under challenge, the Fifth Circuit Court of Appeals remanded the 
rule in its entirety without vacatur. Texas v. EPA, 829 F.3d 405 
(5th Cir. 2016).
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    In the December 28, 2011 final rule, we also evaluated whether 
Oklahoma's SIP ensures that emissions from sources within Oklahoma do 
not interfere with the visibility programs of other states with respect 
to the 1997 8-hour Ozone NAAQS and the 1997 PM2.5 NAAQS. In 
developing their respective regional haze SIPs and reasonable progress 
goals (RPGs), the Central Regional Air Planning Association (CENRAP) 
states consulted with each other through CENRAP's work groups. As a 
result of this process, the understanding was that each CENRAP state 
would take action to achieve the emissions reductions relied upon by 
other states in their reasonable progress demonstrations. CENRAP states 
consulted in the development of RPGs, using the products of the 
technical consultation process to co-develop their RPGs. In developing 
their visibility projections using photochemical grid modeling, CENRAP 
states assumed a certain level of emissions from sources within 
Oklahoma. The CENRAP modeling assumed SO2 reductions from 
the OG&E Sooner Units 1 and 2, the OG&E Muskogee Units 4 and 5, and the 
AEP/PSO Northeastern Units 3 and 4, which Oklahoma did not secure when 
making its BART determinations for these sources and were thus not 
required by the 2010 Oklahoma Regional Haze SIP. Since this modeling 
was used by other states and Oklahoma in establishing their RPGs, we 
made the finding that the Oklahoma SIP does not ensure that emissions 
from sources within Oklahoma do not interfere with measures required in 
the SIP of any other state under Part C of the CAA to protect 
visibility.\11\ In the December 28, 2011 final rule, we finalized a FIP 
(Oklahoma SO2 BART FIP) that controls SO2 
emissions from the six units to address the deficiencies identified in 
our disapproval of these SO2 BART determinations and the 
disapproval of the SIP submission addressing its prong 4 visibility 
transport obligations for the 1997 8-hour Ozone NAAQS and the 1997 
PM2.5 NAAQS.\12\
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    \11\ 76 FR 81728.
    \12\ Id.
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    On June 20, 2013, Oklahoma submitted a regional haze SIP revision 
to replace the FIP's SO2 BART requirements for the AEP/PSO 
Northeastern Units 3 and 4 and a related revision to the SIP addressing 
interstate visibility transport requirements (the 2013 Oklahoma 
Regional Haze SIP Revision). On March 7, 2014, we approved this SIP 
revision and concurrently withdrew the FIP's applicability to these two 
units.\13\ In addition to approving the SO2 BART 
determinations for the AEP/PSO Northeastern Units 3 and 4 in that final 
rule, we also approved revised NOX BART requirements for 
these two units,\14\ and approved the portion of the 2013 Oklahoma 
Regional Haze SIP Revision concerning Oklahoma's interstate visibility 
transport obligations of CAA section 110(a)(2)(D)(i)(II) with respect 
to the 1997 8-hour ozone and 1997 PM2.5 NAAQS as applied to 
this source and its associated impacts on other states' programs to 
protect visibility in Class I Areas.\15\ The FIP provisions applicable 
to the OG&E Muskogee and Sooner plants remain in place.
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    \13\ 79 FR 12944, 12954 (March 7, 2014).
    \14\ EPA approved the NOX BART determinations for the 
AEP/PSO Northeastern Units 3 and 4 and all other subject-to-BART 
sources in Oklahoma in the December 28, 2011 final rule, but 
Oklahoma revised the EPA-approved NOX BART determinations 
for Northeastern Units 3 and 4 in the 2013 Oklahoma Regional Haze 
SIP Revision to require earlier installation and compliance with 
reduced NOX emission limits prior to the original SIP-
imposed deadline. This is discussed in more detail in section III.C 
of this notice.
    \15\ 79 FR at 12945.
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II. Oklahoma Infrastructure SIP Submittals

    On January 28, 2015, Oklahoma submitted a SIP revision to address 
the infrastructure requirements for the 2010 1-hour SO2 
NAAQS, including the interstate visibility transport requirements. In 
its evaluation, Oklahoma stated that the 2010 Regional Haze SIP 
describes Oklahoma's measures to protect visibility and ensure that 
emissions do not interfere with any other state's measures to protect 
visibility. Oklahoma stated that these measures include provisions in 
the Oklahoma Administrative Code 252:100-8, Part 11. Oklahoma noted 
that EPA partially approved and

[[Page 38633]]

partially disapproved Oklahoma's Regional Haze SIP and partially 
approved and partially disapproved Oklahoma's SIP submission addressing 
its prong 4 visibility transport requirements for the 1997 8-hour Ozone 
NAAQS and the 1997 PM2.5 NAAQS on December 28, 2011. 
Oklahoma noted that in the same action, EPA promulgated a FIP 
addressing the disapproved portions of Oklahoma's 2010 Regional Haze 
SIP and the interstate visibility transport SIP revisions for the 1997 
8-hour Ozone NAAQS and the 1997 PM2.5 NAAQS, and that EPA 
found that the controls under this FIP, in combination with the 
controls required by the portion of the Oklahoma Regional Haze SIP 
submittal approved by EPA, will serve to prevent sources in Oklahoma 
from emitting pollutants in amounts that will interfere with efforts to 
protect visibility in other states. Oklahoma also noted that it 
submitted a revision to its regional haze and interstate visibility 
transport SIPs (2013 Oklahoma Regional Haze SIP Revision) on June 14, 
2013, to replace the FIP as it relates to the AEP/PSO Northeastern 
Units 3 and 4, and that EPA approved this revision effective April 7, 
2014. Oklahoma asserted that any contribution to visibility impairment 
or interference with any other state's measures to protect visibility 
attributable to SO2 emissions are addressed through 
Oklahoma's 2010 Regional Haze SIP as revised in the 2013 Oklahoma 
Regional Haze SIP Revision and through EPA's related regional haze 
actions in Oklahoma. This includes EPA's FIP action that currently 
addresses the OG&E Sooner Units 1 and 2 and the OG&E Muskogee Units 4 
and 5. Oklahoma also noted that although no additional visibility 
protection obligations are anticipated on Oklahoma's part as a result 
of the revised 2010 1-hour SO2 NAAQ, other program actions 
taken to ensure maintenance of the revised SO2 NAAQS will 
indirectly assist in avoiding interference with any other state's 
measures to protect visibility.
    On June 16, 2016, Oklahoma submitted a SIP revision to address the 
infrastructure requirements for the 2012 PM2.5 NAAQS, 
including the transport requirements. In its evaluation, Oklahoma 
stated that the 2010 Regional Haze SIP describes Oklahoma's measures to 
protect visibility and ensure that emissions do not interfere with any 
other state's measures to protect visibility. Oklahoma stated that 
these measures include provisions in the Oklahoma Administrative Code 
252:100-8, Part 11. Oklahoma noted that EPA partially approved and 
partially disapproved Oklahoma's Regional Haze SIP and partially 
approved and partially disapproved Oklahoma's SIP submission addressing 
the visibility prong of interstate transport for the 1997 8-hour Ozone 
NAAQS and the 1997 PM2.5 NAAQS on December 28, 2011. 
Oklahoma noted that in the same action, EPA promulgated a FIP 
addressing the disapproved portions of Oklahoma's 2010 Regional Haze 
SIP and the interstate visibility transport SIP submittals for the 1997 
8-hour Ozone NAAQS and the 1997 PM2.5 NAAQS, and that EPA 
found that the controls under this FIP, in combination with the 
controls required by the portion of the Oklahoma Regional Haze SIP 
submittal approved by EPA, will serve to prevent sources in Oklahoma 
from emitting pollutants in amounts that will interfere with efforts to 
protect visibility in other states. Oklahoma also noted that it 
submitted a revision to its regional haze and interstate visibility 
transport SIPs on June 14, 2013, to replace the FIP as it relates to 
the AEP/PSO Northeastern Units 3 and 4, and that EPA approved this 
revision effective April 7, 2014. In its evaluation, Oklahoma asserted 
that any contribution to visibility impairment or interference with any 
other state's measures to protect visibility attributable to emission 
of PM2.5 or its precursors (e.g., SO2) are 
addressed through Oklahoma's 2010 Regional Haze SIP as revised in the 
2013 Oklahoma Regional Haze SIP Revision and through EPA's related 
regional haze actions in Oklahoma. This includes EPA's FIP action that 
currently addresses the OG&E Sooner Units 1 and 2 and the OG&E Muskogee 
Units 4 and 5. Oklahoma also noted that although no additional 
visibility protection obligations are anticipated on Oklahoma's part as 
a result of the revised 2012 PM2.5 NAAQS, other program 
actions taken to assure maintenance of the revised PM2.5 
NAAQS will indirectly assist in avoiding interference with any other 
state's measures to protect visibility.
    On October 25, 2018, Oklahoma submitted a SIP revision to address 
the CAA section 110(a)(1) and 110(a)(2) infrastructure and transport 
requirements for the 2015 Ozone NAAQS. In its evaluation, Oklahoma 
stated that the 2010 Regional Haze SIP describes Oklahoma's measures to 
protect visibility and ensure that emissions do not interfere with any 
other state's measures to protect visibility. Oklahoma stated that 
these measures include provisions in the Oklahoma Administrative Code 
252:100-8, Part 11. Oklahoma noted that EPA partially approved and 
partially disapproved Oklahoma's Regional Haze SIP and partially 
approved and partially disapproved Oklahoma's SIP submission addressing 
the visibility prong of interstate transport for the 1997 8-hour Ozone 
NAAQS and the 1997 PM2.5 NAAQS on December 28, 2011. 
Oklahoma noted that in the same action, EPA promulgated a FIP 
addressing the disapproved portions of Oklahoma's 2010 Regional Haze 
SIP and the interstate visibility transport SIP submittals for the 1997 
8-hour Ozone NAAQS and the 1997 PM2.5 NAAQS, and that EPA 
found that the controls under this FIP, in combination with the 
controls required by the portion of the Oklahoma Regional Haze SIP 
submittal approved by EPA, will serve to prevent sources in Oklahoma 
from emitting pollutants in amounts that will interfere with efforts to 
protect visibility in other states. Oklahoma also noted that it 
submitted a revision to its regional haze and interstate visibility 
transport SIPs on June 14, 2013, to replace the FIP as it relates to 
the AEP/PSO Northeastern Units 3 and 4, and that EPA approved this 
revision effective April 7, 2014. In its evaluation, Oklahoma asserted 
that ozone from ozone precursor emissions are not believed to 
contribute significantly to visibility impairment and that Oklahoma's 
2010 Regional Haze SIP demonstrates that Oklahoma's PM2.5 
emissions do not interfere with any other state's measures to protect 
visibility. Oklahoma noted that this portion of the 2010 Regional Haze 
SIP was approved by EPA on December 28, 2011. Additionally, the 
submission includes a technical support document (TSD) \16\ intended to 
address the requirements of CAA section 110(a)(2)(D)(i)(I), which 
requires a state's SIP to contain adequate provisions prohibiting any 
source or other type of emissions activity within the state from 
emitting any air pollutant in amounts which will contribute 
significantly to nonattainment in, or interfere with maintenance by, 
any other state with respect to any such national primary or secondary 
ambient air quality standard (i.e., prongs 1 and 2). In that document, 
Oklahoma asserted that the Oklahoma Department of Environmental Quality 
(ODEQ) has determined that Oklahoma meets the

[[Page 38634]]

prong 4 visibility transport provisions for the 2015 Ozone NAAQS, as 
the state is not contributing significantly to nonattainment or 
maintenance issues in any other state.
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    \16\ See ``Oklahoma Demonstration of Compliance with the Good 
Neighbor Requirements of Clean Air Act Section 110(a)(2)(D)(i)(I) 
for the 2015 Ozone National Ambient Air Quality Standard,'' which is 
part of Oklahoma's October 25, 2018 Infrastructure SIP submittal for 
the 2015 Ozone NAAQS.
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    In summary, Oklahoma relied on the following points to support its 
conclusion that Oklahoma meets the prong 4 visibility transport 
provision for the 2015 Ozone NAAQS: (1) The modeling and technical 
analysis in the State's interstate transport SIP revision (as to 
``prongs 1 and 2'' under section 110(a)(2)(D)(i)(I)) purportedly 
demonstrating that Oklahoma does not significantly contribute to 
nonattainment or maintenance in another state for the 2015 Ozone NAAQS; 
(2) the fact that ozone formed from ozone precursor emissions is not 
believed to contribute significantly to visibility impairment; and (3) 
Oklahoma's 2010 Regional Haze SIP, which Oklahoma says demonstrates 
that PM2.5 emissions from Oklahoma do not interfere with any 
other state's measures to protect visibility.
    On December 1, 2020, EPA sent a letter to ODEQ requesting 
clarification on how the Oklahoma SIP satisfies the prong 4 interstate 
visibility transport requirement with respect to the 2015 Ozone 
NAAQS.\17\ In a letter dated January 5, 2021, ODEQ pointed out that EPA 
approved the NOX BART determinations in the 2010 Oklahoma 
Regional Haze SIP and also clarified that the SIP addressed 
NOX and VOC emissions, which are ozone precursors, using an 
approach that is consistent with what was anticipated under the CENRAP 
process for the first regional haze planning period.\18\ In the letter, 
ODEQ noted that Sections VII and IX of the 2010 Oklahoma Regional Haze 
SIP explain that the SIP requires NOX reductions resulting 
from BART and other program requirements, as well as other factors, 
that are consistent with what was anticipated under the CENRAP 
consultation process for regional haze SIP development for the first 
planning period. In the letter, ODEQ further noted that Section VIII of 
the 2010 Oklahoma Regional Haze SIP explains that the CENRAP modeling 
used to project the visibility impacts in 2018 as a result of growth 
and control of emissions from the baseline for Class I areas in CENRAP 
states included emission adjustments made by ODEQ to reflect 
presumptive BART controls for the OG&E Sooner Plant, the OG&E Muskogee 
Plant, and the AEP/PSO Northeastern Plant. For NOX 
emissions, this presumptive control level is equivalent to 0.15 lb/
MMBtu for NOX BART and is consistent with the NOX 
emission limits required by the 2010 Oklahoma Regional Haze SIP for 
subject-to-BART units at these three power plants.
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    \17\ Letter from Michael Feldman, Chief, SO2 and 
Regional Haze Section, U.S. Environmental Protection Agency, Region 
6, to Melanie Foster, Manager, Rules & Planning Section, Air Quality 
Division, Oklahoma Department of Environmental Quality, (December 1, 
2020). A copy of this letter is included in the docket associated 
with this proposed rulemaking.
    \18\ Letter from Kendal Stegmann, Director, Air Quality 
Division, Oklahoma Department of Environmental Quality, to Michael 
Feldman, Chief, SO2 and Regional Haze Section, U.S. 
Environmental Protection Agency, Region 6 (January 5, 2021). A copy 
of this letter is included in the docket associated with this 
proposed rulemaking.
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    In the January 5, 2021 letter, ODEQ also explains that the 2010 
Oklahoma Regional Haze SIP did not include additional control 
requirements to address VOC emissions under regional haze for the first 
planning period. In the letter, ODEQ points to Section VI(A) of the 
2010 Oklahoma Regional Haze SIP, which explains that ODEQ determined 
that the visibility impairing pollutants in Oklahoma include 
SO2, NOX, PM10, and PM2.5, 
while CENRAP modeling showed that anthropogenic VOCs do not 
significantly impair visibility at the Wichita Mountains. ODEQ also 
notes that Section IX(E)(4) of the 2010 Oklahoma Regional Haze SIP 
explains that the emissions inventory associated with the SIP assigns 
most emissions of VOCs to biogenic sources, which ODEQ considers to be 
natural and therefore uncontrollable. ODEQ explains that Section 
IX(E)(4) of the 2010 Oklahoma Regional Haze SIP noted that a minority 
of VOC emissions in Oklahoma originate from area, industrial, point, 
and mobile sources, and that most of these sources already employ 
controls under various federal mandates. The 2010 Oklahoma Regional 
Haze SIP explained that considering the small and uncertain 
contribution of anthropogenic sources of VOC to visibility impairment 
at the Wichita Mountains, ODEQ did not find further VOC controls 
reasonable. In the letter, ODEQ explains that these determinations 
similarly apply to the approach taken in the 2010 Oklahoma Regional 
Haze SIP regarding potential VOC-related impacts of and remedies for 
visibility impairment at other states' Class I areas, and that this 
approach is consistent with what was anticipated under the CERNAP 
process for the first regional haze planning period. Further, ODEQ 
notes that Section VIII of the 2010 Oklahoma Regional Haze SIP 
presented model output data that demonstrates that Oklahoma emissions 
are projected to impair visibility only insignificantly at all Class I 
areas in other states, and ODEQ therefore concluded that additional 
emission reduction action was not needed to protect other Class I 
areas, including for NOX and VOC as ozone precursors.
    Thus, ODEQ clarifies in the letter that the EPA-approved portion of 
the 2010 Oklahoma Regional Haze SIP addressed NOX and VOC 
emissions using an approach that is consistent with what was 
anticipated in the CENRAP process for the first regional haze planning 
period and ODEQ states that it believes that, considering the 
clarifications in the January 5, 2021 letter, and as certified in the 
October 25, 2018 submittal, the Oklahoma SIP satisfies the interstate 
visibility transport CAA requirement of section 110(a)(2)(D)(i)(II) 
with respect to the 2015 Ozone NAAQS.

III. The EPA's Evaluation

    Our 2013 i-SIP guidance addresses the requirements for prong 4 and 
lays out two ways in which a state's infrastructure SIP submittal may 
satisfy these requirements.\19\ The first method is through a state's 
confirmation in its infrastructure SIP submittal that it has a fully 
approved regional haze SIP in place. As previously discussed, EPA 
promulgated a partial approval and partial disapproval of the 2010 
Oklahoma Regional Haze SIP in 2011 because the SO2 BART 
determinations for the OG&E Sooner Units 1 and 2, the OG&E Muskogee 
Units 4 and 5, and the AEP/PSO Northeastern Units 3 and 4 did not 
comply with our regional haze regulations under 40 CFR 51.308(e), and 
EPA concurrently promulgated a FIP to address these deficiencies.\20\ 
On June 20, 2013, Oklahoma submitted a SIP revision to address this 
deficiency with respect to the AEP/PSO Northeastern Units 3 and 4, and 
the FIP with respect to these two units was withdrawn on March 7, 
2014.\21\ However, the FIP remains in place with SO2 BART 
requirements for the OG&E Sooner Units 1 and 2 and the OG&E Muskogee 
Units 4 and 5. Therefore, Oklahoma cannot rely on a fully approved 
Regional Haze SIP as the basis for meeting its prong 4 visibility 
transport obligations for the 2010 SO2, 2012 
PM2.5, and the 2015 Ozone NAAQS.
---------------------------------------------------------------------------

    \19\ See 2013 i-SIP Guidance at 32-35.
    \20\ 76 FR 81728.
    \21\ 79 FR 12954.
---------------------------------------------------------------------------

    In the absence of a fully approved Regional Haze SIP, the second 
method provided by the 2013 i-SIP guidance to meet prong 4 requirements 
is a demonstration that emissions within a state's jurisdiction do not 
interfere with

[[Page 38635]]

other states' plans to protect visibility.\22\ EPA interprets prong 4 
to be pollutant-specific such that the state need only address the 
potential for interference with visibility protection caused by the 
pollutant (including precursors) to which the new or revised NAAQS 
applies.\23\ According to the guidance, such a demonstration for the 
first planning period should establish or identify the measures in the 
approved SIP that limit visibility-impairing pollutants and ensure that 
the resulting reductions conform with any mutually agreed emission 
reductions under the relevant regional haze regional planning 
organization (RPO) process.\24\ As explained below, Oklahoma did not 
make such a demonstration in the i-SIP submittals for the 2010 
SO2 and 2012 PM2.5 NAAQS. The i-SIP submittal for 
the 2015 Ozone NAAQS as clarified by Oklahoma's January 5, 2021 letter, 
provides a demonstration identifying the measures in the approved SIP 
that limit visibility-impairing ozone precursor emissions and clarifies 
that the resulting reductions conform with mutually agreed emission 
reductions under the relevant regional haze RPO process with respect to 
the 2015 Ozone NAAQS. We discuss this in the subsections that follow.
---------------------------------------------------------------------------

    \22\ See 2013 i-SIP Guidance at 34.
    \23\ See 2013 i-SIP Guidance at 33.
    \24\ See 2013 i-SIP Guidance at 34. See also 76 FR 22036 (April 
20, 2011) (containing EPA's approval of the visibility requirement 
of 110(a)(2)(D)(i)(II) based on a demonstration by Colorado that did 
not rely on the Colorado Regional Haze SIP).
---------------------------------------------------------------------------

A. Analysis of Oklahoma's January 28, 2015 Prong 4 Submittal for the 
2010 SO2 NAAQS

    The portion of the 2015 infrastructure SIP submittal for the 2010 
1-hour SO2 NAAQS that addresses interstate visibility 
transport relied on both Oklahoma's 2010 Regional Haze SIP submittal, 
as revised in the 2013 Regional Haze SIP revision that addresses the 
AEP/PSO facility, and EPA's FIP that currently applies to the OG&E 
Sooner Units 1 and 2 and the OG&E Muskogee Units 4 and 5. As explained 
above, the prong 4 requirements are pollutant specific. Some portions 
of the 2010 Oklahoma Regional Haze SIP that address SO2 
emissions have been disapproved and thus cannot be relied upon by 
Oklahoma to satisfy the prong 4 requirements. Further, the EPA's 2013 
i-SIP guidance states, ``Under section 110(a)(2)(D(i)(II), an i-SIP 
submission cannot be approved with respect to prong 4 (visibility 
transport) until the EPA has issued final approval of SIP provisions 
that the EPA has found to adequately address any contribution of that 
state's sources to impacts on visibility program requirements in other 
states.'' \25\ Thus, Oklahoma cannot rely on the existing 
SO2 BART FIP to satisfy the prong 4 requirements for the 
2010 1-hour SO2 NAAQS. Moreover, the 2015 i-SIP submittal 
does not provide any additional information to demonstrate that the 
measures in the SIP are sufficient to prohibit emissions from sources 
within Oklahoma from interfering with measures that have been developed 
by other states to protect visibility with respect to the 2010 1-hour 
SO2 NAAQS. Therefore, while the FIP provides an appropriate 
level of SO2 control to prohibit emissions from sources 
within Oklahoma from interfering with measures that have been developed 
by other states to protect visibility (as discussed in Section III.E.), 
the SIP submittal does not; Thus, we are proposing to disapprove the 
110(a)(2)(D)(i)(II) prong 4 portion of Oklahoma's 2015 i-SIP submittal 
for the 2010 1-hour SO2 NAAQS.
---------------------------------------------------------------------------

    \25\ See 2013 i-SIP Guidance at 32-33.
---------------------------------------------------------------------------

B. Analysis of Oklahoma's June 16, 2016 Prong 4 Submittal for the 2012 
PM2.5 NAAQS

    The portion of the 2016 infrastructure SIP submittal for the 2012 
PM2.5 NAAQS that addresses interstate visibility transport 
relied on both Oklahoma's 2010 Regional Haze SIP submittal, as revised 
in the June 20, 2013 SIP revision with respect to the AEP/PSO facility, 
and EPA's FIP that currently applies to the OG&E Sooner Units 1 and 2 
and the OG&E Muskogee Units 4 and 5. The portions of Oklahoma's 2010 
Regional Haze SIP that address PM BART have been approved, but portions 
of the SIP that address PM precursor emissions (i.e., SO2) 
have not, and thus cannot be relied upon to satisfy the prong 4 
requirements. PM emissions can be emitted directly from sources and can 
also form in the atmosphere as a result of complex reactions of other 
pollutants (i.e., precursors) such as SO2 and 
NOX, which are visibility impairing pollutants themselves 
and are required to be addressed under regional haze.\26\ As discussed 
above, EPA disapproved the SO2 BART determinations for the 
OG&E Sooner Units 1 and 2, the OG&E Muskogee Units 4 and 5, and the 
AEP/PSO Northeastern Units 3 and 4, and promulgated a FIP to address 
these deficiencies.\27\ EPA approved the 2013 Oklahoma Regional Haze 
SIP Revision that addressed SO2 BART for the AEP/PSO 
Northeastern Units 3 and 4, and EPA withdrew the FIP with respect to 
these two units on March 7, 2014.\28\ However, the FIP remains in place 
with SO2 BART requirements for the OG&E Sooner Units 1 and 2 
and the OG&E Muskogee Units 4 and 5. As explained above, Oklahoma 
cannot rely upon the portions of the 2010 Oklahoma Regional Haze SIP 
that address SO2 emissions that have been disapproved or on 
the existing SO2 BART FIP to satisfy the prong 4 
requirements for the 2012 PM2.5 NAAQS. The 2016 i-SIP 
submittal does not provide any additional information to demonstrate 
that the measures in the SIP are sufficient to prohibit emissions from 
sources within Oklahoma from interfering with measures that have been 
developed by other states to protect visibility with respect to the 
2012 PM2.5 NAAQS. We are therefore proposing to disapprove 
the 110(a)(D)(2)(i)(II) prong 4 portion of Oklahoma's 2016 
infrastructure SIP submittal for the 2012 PM2.5 NAAQS.
---------------------------------------------------------------------------

    \26\ The BART Guidelines direct states to address 
SO2, NOX and direct PM (including both 
PM10 and PM2.5) emissions as visibility-
impairment pollutants, and states must exercise their ``best 
judgment to determine whether VOC or ammonia emissions from a source 
are likely to have an impact on visibility in an area.'' See 70 FR 
39162.
    \27\ 76 FR 81728.
    \28\ 79 FR 12954.
---------------------------------------------------------------------------

C. Analysis of Oklahoma's 2018 Prong 4 Submittal for the 2015 Ozone 
NAAQS

    In Oklahoma's 2018 infrastructure SIP submittal for the 2015 Ozone 
NAAQS, Oklahoma asserted that it meets the visibility transport 
provisions under section 110(a)(2)(D)(i)(II) for the 2015 Ozone NAAQS 
given that it has determined the state is not contributing 
significantly to nonattainment or maintenance issues in any other state 
under section 110(a)(2)(D)(i)(I). The analysis in the SIP submittal 
that purports to find that Oklahoma emissions do not significantly 
contribute to nonattainment or interfere with maintenance in another 
state under section 110(a)(2)(D)(i)(I) focuses on the potential impact 
of ozone-precursor emissions at certain ozone monitor locations in 
other states as related to the attainment and maintenance of the ozone 
NAAQS (i.e., prongs 1 and 2), but does not provide an analysis of 
visibility impacts at Class I areas due to emissions of ozone 
precursors as visibility pollutants (prong 4).\29\ This basis is

[[Page 38636]]

inadequate for approval of the visibility transport requirements.
---------------------------------------------------------------------------

    \29\ See 2013 i-SIP Guidance at 33 (``The EPA interprets [prong 
4] to be pollutant-specific, such that the infrastructure SIP 
submission need only address the potential for interference with 
protection of visibility caused by the pollutant (including 
precursors) to which the new or revised NAAQS applies.'')
---------------------------------------------------------------------------

    In the 2018 submittal, Oklahoma also stated that ozone formed from 
ozone precursor emissions is not believed to contribute significantly 
to visibility impairment. Oklahoma asserted that the 2010 Regional Haze 
SIP demonstrates that PM2.5 emissions from Oklahoma do not 
interfere with any other state's measures to protect visibility, and 
that this portion of the SIP was approved by EPA on December 28, 2011. 
Here, Oklahoma is referring to EPA's approval of all the PM BART 
determinations in Oklahoma's 2010 Regional Haze SIP. However, it is 
unclear in the submittal how the SIP fulfills the prong 4 requirements 
for the 2015 Ozone NAAQS.\30\
---------------------------------------------------------------------------

    \30\ Id.
---------------------------------------------------------------------------

    The EPA has not established a separate visibility transport 
standard for ozone because it does not directly impair visibility or 
substantially produce or contribute to the production of the secondary 
air contaminants that cause visibility impairment or regional haze. As 
stated above, section 110(a)(2)(D)(i)(II) prong 4 requirements apply to 
all pollutants (including precursors) for which EPA has promulgated a 
NAAQS. As such, Oklahoma is required to demonstrate to EPA that it has 
approved measures in its SIP that ensure that ozone-precursor emissions 
within its jurisdiction do not interfere with other states' visibility 
protection plans. While ozone itself does not directly impair 
visibility, ozone precursors (i.e., NOX and in some cases 
volatile organic compounds) can react to generate visibility impairing 
pollutants. Thus, the pertinent question is whether Oklahoma's SIP 
adequately controls emissions of ozone precursors that may contribute 
to visibility impairment in other states and whether the level of 
control of these emissions is consistent with mutually-agreed emissions 
reductions under the CENRAP regional haze planning process for the 
first planning period.
    As explained in Oklahoma's January 5, 2021 clarification letter, 
EPA approved all NOX BART determinations in Oklahoma's 2010 
Regional Haze SIP and these EPA-approved NOX BART 
determinations conform with the mutually-agreed emission reductions 
\31\ under the CENRAP regional haze planning process that Oklahoma and 
other Midwestern states participated in for regional haze SIP 
development for the first regional haze planning period.\32\ In the 
2013 Oklahoma Regional Haze SIP Revision, Oklahoma revised the 
NOX BART requirements for the Northeastern Units 3 and 4 
that EPA approved in the December 28, 2011 final rule.\33\ The 
revisions require earlier installation and compliance with reduced 
NOX emission limits prior to the original SIP-imposed 
deadline.\34\ Our December 2011 approval of NOX BART for 
Units 3 and 4 required that these units meet a NOX emission 
limit of 0.15 lb/MMBtu (based on a 30-day rolling average) within five 
years from the effective date of EPA's approval, or by January 27, 
2017.\35\ However, under the 2013 Oklahoma Regional Haze SIP Revision, 
which EPA approved on March 7, 2014, both units are required to meet an 
initial NOX emission limit of 0.23 lb/MMBtu (based on a 30-
day rolling average) by December 31, 2013, with additional limits of 
1,098 lb/hr per unit on a 30-day rolling average basis and a 9,620 tpy 
combined cap for both units.\36\ By April 16, 2016, one unit is 
required to be permanently shut down, while the remaining unit is 
required to meet a NOX emission limit of 0.15 lb/MMBtu 
(based on a 30-day rolling average), with an additional limit of 716 
lb/hr on a 30-day rolling average basis and a cap of 3,137 tpy on a 12-
month rolling basis. Finally, this second unit is required to shut down 
by December 31, 2026. Thus, these revised NOX BART 
determination for the Northeastern Units 3 and 4 are more stringent 
than the determinations that we previously approved given that they 
require compliance with the 0.15 lb/MMBtu limit on a more expeditious 
schedule. The Oklahoma SIP contains NOX BART determinations 
for all subject-to-BART sources in Oklahoma, which have been approved 
by EPA in previous actions and conform with the mutually-agreed 
emission reductions under the CENRAP regional haze planning process 
that Oklahoma and other Midwestern states participated in for regional 
haze SIP development for the first regional haze planning period.
---------------------------------------------------------------------------

    \31\ During consultation ODEQ indicated that Sooner Units 1 and 
2, Muskogee Units 4 and 5, and Northeastern Units 3 and 4 would have 
emission limits based on 0.15 lb of NOX per MMBtu. ODEQ's 
January 5, 2021 letter noted that Section VIII of the 2010 Oklahoma 
Regional Haze SIP explained that these emissions reductions for 
these six units were included in the CENRAP 2018 modeling 
projections that other CENRAP states relied on in developing their 
regional haze SIPs.
    \32\ 76 FR 81728.
    \33\ 76 FR at 81729.
    \34\ 78 FR 51686, 51690 (August 21, 2013).
    \35\ 76 FR 16168, 16181, 16182 (March 22, 2011).
    \36\ 79 FR at 12944.
---------------------------------------------------------------------------

    In the January 5, 2021 letter, ODEQ also explained that VOC 
emissions, which are an ozone precursor, were addressed in the 2010 
Oklahoma Regional Haze SIP in a manner consistent with what was 
anticipated under the CENRAP process for the first regional haze 
planning period. Specifically, in the 2010 Oklahoma Regional Haze SIP, 
ODEQ asserted that the emissions inventory associated with that SIP 
submittal assigns most VOC emissions to biogenic sources, which ODEQ 
considers to be uncontrollable; \37\ The CENRAP modeling shows that 
anthropogenic VOC emissions do not significantly impair visibility at 
the Wichita Mountains; \38\ And, only a minority of VOC emissions in 
Oklahoma originate from area, industrial, point, and mobile sources, 
which ODEQ asserted are sources that are already controlled under 
various federal mandates.\39\ ODEQ stated in the 2010 Oklahoma Regional 
Haze SIP that considering the small and uncertain contribution of 
anthropogenic sources of VOC to visibility impairment at the Wichita 
Mountains, ODEQ did not find further controls for VOC sources to be 
reasonable.\40\ The CENRAP modeling used to project the visibility 
impacts in 2018 for Class I areas in CENRAP states, which reflects the 
mutually-agreed emissions reductions in CENRAP states, did not assume 
additional control of VOC emissions in Oklahoma. In the December 28, 
2011 final rule on the 2010 Oklahoma Regional Haze SIP, EPA agreed with 
ODEQ's decision to not further evaluate or require additional controls 
for VOC emissions in Oklahoma.\41\ Thus, Oklahoma's approach for VOC 
emissions in the 2010 Oklahoma Regional Haze SIP has been approved by 
EPA and conforms with the mutually-agreed emission reductions under the 
CENRAP regional haze planning process that Oklahoma and other 
Midwestern states participated in for regional haze SIP development for 
the first regional haze planning period.
---------------------------------------------------------------------------

    \37\ See 2010 Oklahoma Regional Haze SIP, Section IX.E.4, page 
113. A copy of the submittal is included in the docket associated 
with this proposed rulemaking.
    \38\ Id at Section VI.A, page 69.
    \39\ Id.
    \40\ Id.
    \41\ See 76 FR at 81729 77 FR (proposed rule) and 76 FR 81728 
(final rule).
---------------------------------------------------------------------------

    Therefore, we are proposing to find that the Oklahoma SIP includes 
the necessary emission reductions to satisfy the 110(a)(2)(D)(i)(II) 
prong 4 requirements for the 2015 Ozone NAAQS and are proposing to 
approve the portion of the 2018 infrastructure SIP submittal that 
addresses interstate visibility transport for the 2015 Ozone NAAQS.

[[Page 38637]]

D. AEP/PSO Northeastern SO2 Emission Reductions Assumed in the CENRAP 
Modeling

    As discussed earlier in this notice, Oklahoma engaged in a regional 
planning process with other CENRAP states to develop their regional 
haze SIP for the first planning period. This regional planning process 
included a forum in which state representatives built emission 
inventories that assumed that specific pollution sources would be 
controlled to specific levels. This included adjustments to projected 
emissions by ODEQ to reflect the assumption that the OG&E Sooner Units 
1 and 2, the OG&E Muskogee Units 4 and 5, and the AEP/PSO Northeastern 
Units 3 and 4 would each be controlled to presumptive BART emission 
levels for SO2,\42\ which is equivalent to 0.15 lb/
MMBtu.\43\ Visibility modeling projections conducted by CENRAP 
subsequently included those emission reductions, and other states 
relied on them as part of their reasonable progress demonstrations. 
However, Oklahoma, in its subsequent 2010 Regional Haze SIP, did not 
include these promised reductions on which the other states relied on 
in developing their own RPGs and regional haze SIPs. Instead, Oklahoma 
determined that SO2 BART for these units was no additional 
control and specified an SO2 limit of 0.65 lbs/MMBtu on a 
30-day rolling average. In a final rule published on December 28, 2011, 
we disapproved the SIP's SO2 BART determinations for these 
six units because they do not comply with our regulations under 40 CFR 
51.308(e).\44\ In the same final rule, we promulgated a FIP 
establishing an emission limit of 0.06 lb/MMBtu for each of the six 
units for purposes of complying with SO2 BART.\45\
---------------------------------------------------------------------------

    \42\ 76 FR at 16189 and 76 FR at 81735.
    \43\ 70 FR 39104, 39131 (July 6, 2005).
    \44\ 76 FR at 81730.
    \45\ 76 FR 81728.
---------------------------------------------------------------------------

    On June 20, 2013, Oklahoma submitted a regional haze SIP revision 
to replace the FIP's SO2 BART requirements for the AEP/PSO 
Northeastern Units 3 and 4. On March 7, 2014, we approved this SIP 
revision and concurrently withdrew the sections of the FIP that applied 
to those two units.\46\ The 2013 Oklahoma Regional Haze SIP Revision 
requires one of the two Northeastern units to shut down no later than 
April 16, 2016, while the remaining unit is required to install dry 
sorbent injection (DSI) to meet an SO2 emission limit of 0.4 
lb/MMBtu.\47\ However, the SO2 emission reductions for the 
AEP/PSO Northeastern facility contained in the 2013 Oklahoma Regional 
Haze SIP Revision fall short of the levels assumed in other states' 
regional haze plans through the CENRAP RPO process. In order to achieve 
emission levels equivalent to the levels assumed in other states' 
regional haze plans through the CENRAP RPO process, the remaining 
Northeastern unit would have to meet an emission limit of 0.3 lb/MMBtu 
(0.15 + 0.15).\48\ To address this, the 2013 Oklahoma Regional Haze SIP 
Revision also requires the source operators to optimize the performance 
of DSI on the remaining unit to ensure that the best possible 
performance is achieved and adjust the limit accordingly. The ``AEP/PSO 
Settlement Agreement'' included in the 2013 Oklahoma Regional Haze SIP 
Revision requires the company to develop and propose a monitoring 
program to test various operating profiles and other measures in order 
to determine whether increased SO2 removal efficiencies can 
be achieved during normal operations.\49\ AEP/PSO was required to 
implement this monitoring program and to evaluate and report the 
results to EPA and ODEQ. If the evaluation demonstrated that the 
technology is capable of sustainably achieving an emission rate of less 
than 0.37 lbs/MMBtu on a 30-day rolling average basis without (i) 
altering the unit's fuel supply, (ii) incurring additional capital 
costs, (iii) increasing operating expenses by more than a negligible 
amount, and/or (iv) adversely impacting overall unit operations, ODEQ 
would have to propose to revise the emission rate for the remaining 
Northeastern unit by 60 percent of the difference between 0.40 and the 
demonstrated emission rate.\50\
---------------------------------------------------------------------------

    \46\ 79 FR 12954.
    \47\ 79 FR at 12945.
    \48\ Northeastern Units 3 and 4 are similar design capacity so 
comparing them as the same is a reasonable approximation for this 
contextual assessment. Specific assessment is included later in this 
notice and in docket materials.
    \49\ See Attachment A, paragraph 1(f) of the ``AEP/PSO 
Settlement Agreement,'' which is presented in Appendix I of the June 
20, 2013 Oklahoma Regional Haze SIP revision. A copy of the 
submittal is found in the docket for this proposed rulemaking.
    \50\ Id.
---------------------------------------------------------------------------

    If it is determined that the remaining operating unit still cannot 
meet the emission limit of 0.3 lb/MMBtu, then the 2013 Oklahoma 
Regional Haze SIP Revision contains an enforceable commitment 
obligating ODEQ to ``obtain and/or identify additional SO2 
reductions within the State of Oklahoma to the extent necessary to 
achieve the anticipated visibility benefits estimated'' by CENRAP.\51\ 
As explained in our March 7, 2014 final rule approving the 2013 
Oklahoma Regional Haze SIP Revision, any additional SO2 
emissions reductions that can be obtained or identified from the 
northeast quadrant of the State will be presumed to count toward the 
emission reductions necessary to achieve the anticipated visibility 
benefits associated with a 0.30 lb/MMBtu emission limit at Northeastern 
Power Station.\52\ Emissions reductions obtained outside the northeast 
quadrant that are technically justified will also be counted.\53\ We 
explained in our March 7, 2014 final rule that if necessary, additional 
emissions reductions are to be obtained via enforceable emission limits 
or control equipment requirements where necessary and submitted to EPA 
as a SIP revision as expeditiously as practicable, but in no event 
later than the end of the first full Oklahoma legislative session 
occurring subsequent to AEP/PSO's submission of the evaluation and 
report for the monitoring program required under the AEP/PSO Settlement 
Agreement.\54\
---------------------------------------------------------------------------

    \51\ 79 FR at 12945.
    \52\ 79 FR at 12945
    \53\ 79 FR at 12945.
    \54\ 79 FR at 12945.
---------------------------------------------------------------------------

    On June 25, 2019, AEP/PSO submitted to ODEQ the ``BART 
SO2 Monitoring Program for Northeastern Power Station Unit 
3'' (SO2 Monitoring Program), pursuant to one of the 
requirements in the AEP/PSO Settlement Agreement.\55\ Based on the 
results of the SO2 Monitoring Program, AEP/PSO concluded 
that the lowest target emission rate sustainably achieved consistent 
with the conditions in the AEP/PSO Agreement is 0.35 lb/MMBTU on a 30-
day rolling average basis, and that the resulting federally enforceable 
emission rate should be 0.37 lb/MMBtu on a 30-day rolling average 
basis.\56\ However, an emission limit of 0.37 lb/MMBtu for AEP/PSO 
Northeastern Unit 3 would still fall short of the 0.3 lb/MMBtu emission 
limit necessary to achieve emission levels equivalent to the levels 
assumed in other states' regional haze plans through the CENRAP RPO 
process.
---------------------------------------------------------------------------

    \55\ A copy of the June 25, 2019 ``BART SO2 
Monitoring Program for Northeastern Power Station Unit 3'' can be 
found in the docket for this proposed rulemaking.
    \56\ The 0.37 lb/MMBtu emission rate is 60 percent of the 
difference between 0.40 and the demonstrated emission rate (0.35 lb/
MMBtu), per the terms of the AEP/PSO Settlement Agreement.
---------------------------------------------------------------------------

    Following final disapproval of a SIP revision in whole or in part, 
EPA has an obligation under section 110(c) of the Act to either approve 
a SIP revision and/or promulgate a FIP to address the disapproval 
within 24 months. We believe EPA's FIP obligation under

[[Page 38638]]

section 110(c) could be addressed through a demonstration that the 
deficiencies in the Oklahoma SIP that form the basis of our proposed 
disapproval of the interstate visibility transport portions of the 
Oklahoma i-SIP submissions for the 2010 SO2 and 2012 
PM2.5 NAAQS are already addressed by the existing FIP in 
place for the Oklahoma Regional Haze program. As discussed in the next 
section, we have assessed whether the emissions reductions secured by 
the existing SO2 BART emission limits for the OG&E Sooner 
Units 1 and 2 and the OG&E Muskogee Units 4 and 5, required under the 
existing FIP, are sufficient to make up for any shortfall to achieve 
the necessary anticipated visibility benefits associated with a 0.30 
lb/MMBtu emission limit at Northeastern Power Station that CENRAP 
states agreed on and relied upon in their regional haze plans. We 
discuss our technical analysis in the subsection that follows.

E. Proposed Finding That EPA's Prong 4 FIP Obligations Are Satisfied 
for the 2010 SO2 and 2012 PM2.5 NAAQS

    For the reasons explained above, Oklahoma's reliance on both its 
2010 Regional Haze SIP submittal as revised in its 2013 Regional Haze 
SIP revision and EPA's FIP that applies to the OG&E Sooner Units 1 and 
2 and OG&E Muskogee Units 4 and 5 is insufficient to satisfy its prong 
4 requirements in accordance with EPA's 2013 i-SIP guidance. EPA is 
thus proposing to disapprove the submissions with regard to CAA section 
110(a)(2)(D)(i)(II). EPA's disapproval triggers its obligation to 
promulgate a FIP under CAA section 111(c)(1) to address the 
deficiencies in the state's SIP. However, as discussed below, EPA finds 
that its FIP obligation with respect to prong 4 for these two NAAQS is 
already satisfied, and no further action is required.
    The FIP we published on December 28, 2011,\57\ included 
SO2 emission limitations for the OG&E Sooner Units 1 and 2, 
the OG&E Muskogee Units 4 and 5, and the AEP/PSO Northeastern Units 3 
and 4 based on EPA's analysis of the five BART statutory factors, and 
these emission limitations reflected a level of control more stringent 
than what was assumed in the CENRAP modeling.\58\ On June 20, 2013, 
Oklahoma submitted a regional haze SIP revision to replace the FIP's 
SO2 BART requirements for the AEP/PSO Northeastern Units 3 
and 4. On March 7, 2014, we approved this SIP revision and concurrently 
withdrew the FIP's applicability to these two units.\59\ The FIP 
provisions applicable to the OG&E Sooner Units 1 and 2 and the OG&E 
Muskogee Units 4 and 5 remain in place.
---------------------------------------------------------------------------

    \57\ 76 FR 81728.
    \58\ 76 FR 16193.
    \59\ 79 FR 12954 (March 7, 2014).
---------------------------------------------------------------------------

    As discussed in the previous subsection, based on the results of 
the SO2 Monitoring Program that was required under the AEP/
PSO Settlement Agreement and part of the 2013 Regional Haze SIP 
Revision, AEP/PSO concluded that the federally enforceable emission 
rate for AEP/PSO Northeastern Unit 3 should be 0.37 lb/MMBtu on a 30-
day rolling average basis. However, this level of control falls short 
of the 0.3 lb/MMBtu emission limit necessary to achieve emission levels 
equivalent to the levels assumed in other states' regional haze plans 
through the CENRAP RPO process. To address this issue, EPA assessed 
whether the SO2 emissions reductions secured from other 
facilities under the existing FIP promulgated on December 28, 2011, 
would be sufficient to make up for the shortfall in emissions 
reductions and associated visibility benefit from the AEP/PSO 
Northeastern facility compared to what was assumed in the CENRAP 
modeling. Under the CENRAP regional haze planning process, CENRAP 
included emissions for these sources based upon Oklahoma's indications 
that the OG&E Sooner Units 1 and 2, the OG&E Muskogee Units 4 and 5, 
and the AEP/PSO Northeastern Units 3 and 4 would each be controlled to 
presumptive BART emission levels for SO2, which is 0.15 lb/
MMBtu.\60\ Further, the FIP EPA promulgated on December 28, 2011, which 
continues to apply to the OG&E Sooner Units 1 and 2 and the OG&E 
Muskogee Units 4 and 5, requires each of these four units to comply 
with an emission limit of 0.06 lb/MMBtu for purposes of complying with 
the SO2 BART requirements.\61\
---------------------------------------------------------------------------

    \60\ 76 FR at 16189 and 76 FR at 81735.
    \61\ Although the FIP requires an SO2 emission limit 
of 0.06 lb/MMBtu for the OG&E Muskogee Units 4 and 5, the company 
elected to convert the units to natural gas in 2019 to comply with 
this emission limit. Therefore, these two units have actual 
SO2 emissions near zero.
---------------------------------------------------------------------------

    In Table 1 below, we present the controlled SO2 annual 
emission levels included in the CENRAP chemical transport modeling 
using the Comprehensive Air Quality Model with Extensions (CAMx) for 
the six units and the controlled SO2 annual emission levels 
required by both the FIP for 4 units and the 2013 Oklahoma Regional 
Haze SIP Revision for the AEP/PSO Northeastern facility's 2 units.\62\ 
These SO2 annual emissions were based on annual firing rate 
information for the base period (2002) and the appropriate lb/MMBtu 
emission limit. The CENRAP CAMx modeling assumed that AEP/PSO 
Northeastern Units 3 and 4 would have combined controlled 
SO2 emissions of 5,921 tpy, while the 2013 Oklahoma Regional 
Haze SIP revision includes control requirements that result in combined 
controlled SO2 emissions of 7,895 tpy using the same annual 
firing rate information used in CENRAP's CAMx modeling. This results in 
a shortfall of 1,974 tpy between the controlled emission level assumed 
in the CENRAP CAMx modeling and the level of control required by the 
2013 SIP Revision. The CENRAP CAMx modeling also assumed that the OG&E 
Muskogee Units 4 and 5 would have combined controlled SO2 
emissions of 5,249 tpy, while the FIP requires SO2 controls 
that result in combined controlled SO2 emissions of 2,100 
tpy using the same annual firing rate information used in CENRAP's CAMx 
modeling. The FIP results in SO2 controlled emissions on 
Muskogee units that are 3,150 SO2 tpy lower than the level 
assumed in the CENRAP modeling, which is greater than the 1,974 tpy 
shortfall from the AEP/PSO Northeastern facility. Focusing on the OG&E 
Muskogee Units 4 and 5 alone, the level of SO2 control 
required by the FIP at these two units is sufficient to make up for the 
shortfall in emission reductions from the AEP/PSO Northeastern 
facility. This is significant because the OG&E Muskogee facility is 
located in the northeast quadrant of Oklahoma, which is where the AEP/
PSO Northeastern facility is located. In our final rule approving the 
2013 Oklahoma Regional Haze SIP revision, we explained that any 
additional SO2 emissions reductions that can be obtained or 
identified from the northeast quadrant of the State will be presumed to 
count toward the emission reductions necessary to achieve the 
anticipated visibility benefits associated with a 0.30 lb/MMBtu 
emission limit at Northeastern Power Station.\63\ The OG&E Sooner Units 
1 & 2 also provide additional surplus emissions (3,304 tpy of 
SO2) that provide benefit beyond the net surplus of 1,176 
tpy of SO2 from the net of Muskogee units surplus and 
Northeastern units shortfall (3,150 tpy - 1,974 tpy). The level of 
SO2 controls within EPA's FIP is therefore sufficient

[[Page 38639]]

to make up for the shortfall from the AEP/PSO Northeastern facility.
---------------------------------------------------------------------------

    \62\ See the Excel spreadsheet ``NE SIP vs FIP visibility review 
calcs.xlsx'' which can be found in the docket for this proposed 
rulemaking.
    \63\ 79 FR 12945.

                             Table 1--Comparison of Controlled SO2 Emissions Reductions in SIP/FIP vs. CENRAP CAMx Modeling
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                       CENRAP Modeling
                                                                       Annual avg.    CENRAP modeling   Controlled SO2                       SIP/FIP
                                                                     heat input rate    SO2 emission      emissions       SIP/FIP SO2     controlled SO2
                           Facility/unit                               used in CAMx        limit          assumption     emission limit  emissions (tpy)
                                                                       modeling for   assumption (lb/      (tpy) *         (lb/MMBtu)           *
                                                                      SIP (MMBtu/hr)       MMBtu)
--------------------------------------------------------------------------------------------------------------------------------------------------------
OG&E Sooner Unit 1.................................................            4,548             0.15          2,988.2             0.06          1,195.3
OG&E Sooner Unit 2.................................................            3,835             0.15          2,519.4             0.06          1,007.7
OG&E Muskogee Unit 4...............................................            4,112             0.15          2,701.7             0.06       ** 1,440.1
OG&E Muskogee Unit 5...............................................            3,877             0.15          2,547.5             0.06       ** 1,080.7
AEP/PSO Northeastern Unit 3........................................            4,506             0.15          2,960.6             0.40          7,895.0
AEP/PSO Northeastern Unit 4........................................            4,506             0.15          2,960.6                0                0
                                                                    ------------------------------------------------------------------------------------
    Total Controlled SO2 Emissions.................................  ...............  ...............           16,678  ...............           12,198
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Controlled SO2 emissions calculated based on the 2002 annual heat input rate (MMBtu/yr) of the unit used in CENRAP's CAMx modeling that was included
  in CENRAP states SIPs.
** The controlled SO2 emissions we have calculated in this table for the OG&E Muskogee Units 4 and 5 are based on the FIP emission limits and the actual
  annual heat input rate (MMBtu/yr). However, OG&E Muskogee Units 4 and 5 converted to natural gas to comply with their SO2 BART emission limits in the
  FIP. Therefore, even though the FIP requires SO2 emission limits of 0.06 lb/MMBtu, these two units are actually emitting SO2 at much lower (near
  negligible) levels.

    Since hourly emission estimates for these six units were also used 
in CALPUFF modeling that was part of the BART analyses in the 2010 
Oklahoma Regional Haze SIP, the FIP and the 2013 SIP revision, we also 
evaluated the difference in modeled emission rates and emissions used 
in the CALPUFF modeling to compare the estimated hourly emission rates 
between the 0.15 lb/MMBtu presumptive rate utilized in the CENRAP RPO 
process and the rates required by the FIP and 2013 SIP revision. The 
CALPUFF modeling provides visibility impact information for each of the 
three facilities to further support that the net changes in emissions 
at these three facilities result in a net surplus of emission 
reductions and visibility benefits that supports EPA's proposed 
conclusion that visibility transport is adequately addressed for 
SO2. Below we discuss the difference in emissions followed 
by a discussion of the modeled visibility impacts.
    Single source modeling with the CALPUFF model was conducted for 
each of these facilities using maximum firing rates (instead of the 
actual annual firing rate used in CAMx analysis). The use of maximum 
firing rate rather than the actual annual rate that was utilized in the 
CENRAP CAMx modeling results in a higher estimate of hourly emission 
rates and also annual emission rates. Since these maximum hourly 
emission rates used for CALPUFF modeling give a larger difference 
(larger potential shortfall) for the Northeastern Units 3 & 4 and also 
are the emission rates evaluated for individual visibility assessments, 
we perform our evaluation on these rates as well as the annual CAMx 
modeled rates discussed above and in Table 1. In Table 2, these 
controlled SO2 maximum hourly emission levels were 
calculated assuming the maximum heat input rate (MMBtu/hr) of each 
unit, which is also the heat input rate used in EPA's CALPUFF BART 
modeling for the FIP, multiplied by the applicable emission rate (lb/
MMBtu). A comparison of these numbers shows that even though the AEP/
PSO Northeastern Unit 3 is required to comply with an emission limit of 
0.40 lb/MMBtu under the 2013 Oklahoma Regional Haze SIP Revision, which 
is higher (less stringent) than the 0.30 lb/MMBtu level (0.15 + 0.15 
for Northeastern Units 3 and 4) needed in order to achieve hourly 
emission levels equivalent to the levels relied upon in other states' 
regional haze plans through the CENRAP RPO process, the total maximum 
hourly controlled SO2 emissions levels for the six units 
under the FIP and the 2013 Oklahoma Regional Haze SIP Revision are 
lower than the total controlled maximum hourly SO2 emissions 
levels based on the presumptive control level included in the CENRAP 
RPO consultation and modeling. In other words, the FIP and the 2013 
Oklahoma Regional Haze SIP Revision result in greater SO2 
emission reductions for these three facilities for the maximum hourly 
emissions compared to the maximum hourly emissions based on the 0.15 
lb/MMBtu emission limit used in the CENRAP RPO consultation process. 
Specifically, the combination of the FIP and the 2013 Oklahoma Regional 
Haze SIP Revision result in combined maximum hourly controlled 
SO2 emissions of 3,596.3 lb/hr from the six units, which is 
1,293.4 lb/hr less than the levels estimated from the rate (4,889.7 lb/
hr) based on the 0.15 lb of SO2/MMBtu controlled emission 
rate that Oklahoma shared in consultation and was used in the CENRAP 
RPO process, including the CENRAP CAMx modeling. This is because the 
FIP requires a greater level of SO2 control for the OG&E 
Sooner Units 1 and 2 and the OG&E Muskogee Units 4 and 5 than the 
presumptive rate included in consultation and in the CENRAP CAMx 
modeling. The more stringent level of SO2 controls required 
by EPA's FIP is therefore sufficient to make up for the shortfall from 
the AEP/PSO Northeastern facility. Using the 0.15 lb/MMBtu controlled 
emission rate from the CENRAP CAMx modeling, the maximum hourly 
emission rate using the higher firing rate (maximum firing rate) 
calculated that AEP/PSO Northeastern Units 3 and 4 would have combined 
controlled SO2 emissions of 1710.9 lb/hr, while the 2013 
Oklahoma Regional Haze SIP revision includes control requirements that 
result in combined controlled SO2 maximum hourly emissions 
of 2324.8 lb/hr, resulting in a shortfall of 613.9 lb/hr. Using the 
0.15 lb/MMBtu from the CENRAP CAMx modeling, the OG&E Muskogee Units 4 
and 5 would have combined maximum hourly controlled SO2 
emissions of 1644 lb/hr, while the FIP requires SO2 controls 
that result in combined maximum hourly controlled SO2 
emissions of 657.6 lb/hr, a difference of 986.4 lb/hr. This surplus of 
986.4 lb/hr of SO2 is greater than the 613.9 lb/hr shortfall 
from the AEP/PSO Northeastern facility. Focusing on the OG&E Muskogee 
Units 4 and 5 alone, the level of SO2 control required by 
the FIP at these two units is sufficient to make up for the shortfall 
from the AEP/PSO Northeastern facility. This is significant because the 
OG&E Muskogee facility is located in the northeast quadrant of 
Oklahoma, which is where

[[Page 38640]]

the AEP/PSO Northeastern facility is located. In our final rule 
approving the 2013 Oklahoma Regional Haze SIP revision, we explained 
that any additional SO2 emissions reductions that can be 
obtained or identified from the northeast quadrant of the State will be 
presumed to count toward the emission reductions necessary to achieve 
the anticipated visibility benefits associated with a 0.30 lb/MMBtu 
emission limit at Northeastern Power Station.\64\ The OG&E Sooner Units 
1 & 2 also provide an additional surplus of maximum hourly emission 
reductions (920.9 lb/hr of SO2) that provide benefit beyond 
the net surplus of 372.5 lb/hr of SO2 from Muskogee units 
surplus and Northeastern units shortfall (986.4 lb/hr-613.9 lb/hr). The 
level of SO2 controls within EPA's FIP is therefore 
sufficient to make up for the shortfall from the AEP/PSO Northeastern 
facility when comparing maximum hourly emissions. In the spreadsheet in 
the docket we also evaluated using these maximum hourly emission 
estimates on an annual basis (tpy) for general comparison and it also 
indicated that EPA's FIP requirements result in a net surplus of annual 
emissions.\65\
---------------------------------------------------------------------------

    \64\ 79 FR 12945.
    \65\ See ``CALPUFF tpy'' tab of the Excel spreadsheet ``NE SIP 
vs FIP visibility review calcs.xlsx,'' which can be found in the 
docket for this proposed rulemaking.

                            Table 2--Comparison of Controlled SO2 Emissions Reductions in SIP/FIP vs. CENRAP CALPUFF Modeling
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Maximum heat   CENRAP modeling  CENRAP modeling
                                                                        input rate      SO2 emission    controlled SO2    SIP/FIP SO2        SIP/FIP
                           Facility/unit                               used in BART        limit          emissions      emission limit   controlled SO2
                                                                       modeling for   assumption (lb/  assumption (lb/     (lb/MMBtu)     emissions (lb/
                                                                      FIP (MMBtu/hr)       MMBtu)           hr) *                             hr) *
--------------------------------------------------------------------------------------------------------------------------------------------------------
OG&E Sooner Unit 1.................................................            5,116             0.15           767.40             0.06           306.96
OG&E Sooner Unit 2.................................................            5,116             0.15           767.40             0.06           306.96
OG&E Muskogee Unit 4...............................................            5,480             0.15            822.0             0.06         ** 328.8
OG&E Muskogee Unit 5...............................................            5,480             0.15            822.0             0.06         ** 328.8
AEP/PSO Northeastern Unit..........................................            5,812             0.15            871.8             0.40          2,324.8
AEP/PSO Northeastern Unit..........................................            5,594             0.15            839.1                0                0
                                                                    ------------------------------------------------------------------------------------
    Total Controlled SO2 Emissions.................................  ...............  ...............          4,889.7  ...............          3,596.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Controlled SO2 emissions calculated based on the maximum heat input rate (MMBtu/hr) of the unit used in EPA's BART modeling for the FIP.
** The controlled SO2 emissions we have calculated in this table for the OG&E Muskogee Units 4 and 5 are based on the FIP emission limits. However, OG&E
  Muskogee Units 4 and 5 converted to natural gas to comply with their SO2 BART emission limits in the FIP. Therefore, even though the FIP requires SO2
  emission limits of 0.06 lb/MMBtu, these two units are actually emitting SO2 at much lower (near negligible) levels.

    We also assessed whether the visibility benefits resulting from the 
SO2 controls for the OG&E Sooner Units 1 and 2 and the OG&E 
Muskogee Units 4 and 5 under the FIP are estimated to make up for any 
visibility benefit shortfall from the AEP/PSO Northeastern Units 3 and 
4 by scaling modeled visibility improvements from the CALPUFF modeling 
that was performed as part of the 2011 Oklahoma SO2 BART 
FIP.\66\ Based on previous modeling performed for these sources and 
other sources in other Region 6 FIPs and SIPs linear scaling within the 
ranges performed is a reasonable approach to estimate impacts. We 
scaled modeled visibility improvements for Wichita Mountains as well as 
Class I areas in other states affected by Oklahoma: Caney Creek 
Wilderness Area and Upper Buffalo Wilderness Area in Arkansas and 
Hercules-Glades Wilderness Area in Missouri. We used the 2001-2003 
average of the 98th percentile of daily maximum dv as the visibility 
impact values for our calculations and assumed linear concentration and 
linear visibility impairment calculations. Based on our calculations, 
the SO2 emission reduction shortfall in the 2013 Oklahoma 
Regional Haze SIP Revision for the AEP/PSO Northeastern Units 3 and 4 
(difference between visibility impacts under the 2013 SIP requirements 
and the CENRAP consultation and modeling assumptions of 0.15 lb/MMBtu 
for each unit) is estimated to result in a visibility benefit shortfall 
of 0.096 dv for the four affected Class I areas combined (See Table 3 
below).\67\ On the other hand, the FIP's estimated visibility benefits 
in excess of the assumptions in the CENRAP consultation and modeling 
(i.e., comparing 0.15 lb/MMBtu emission limit from the CENRAP 
consultation and CAMx modeling with 0.06 lb/MMBtu emission limit 
required under the FIP) with respect to the OG&E Muskogee Units 4 and 5 
are 0.332 dv and the OG&E Sooner Units 1 and 2 are 0.190 dv for the 
four affected Class I areas combined.\68\ The excess benefit from OG&E 
Muskogee Units 4 and 5 alone is enough to more than offset the 
Northeastern shortfall at each Class I area, including the nearby areas 
in other states. In addition, the cumulative benefit at all four Class 
I areas is greater than the cumulative shortfall, resulting in an 
overall benefit of 0.236 dv (0.332 dv excess-0.096 dv shortfall = 0.236 
dv). Including the benefits from the four OG&E Muskogee and Sooner 
units results in t a net estimated excess visibility benefit of 0.425 
dv at the four affected Class I areas combined. These results are 
summarized in the Table 3 below.
---------------------------------------------------------------------------

    \66\ Our calculations are found in the Excel spreadsheet ``NE 
SIP vs FIP visibility review calcs.xlsx,'' which can be found in the 
docket for this proposed rulemaking.
    \67\ See ``Summary Visibility'' tab of the Excel spreadsheet 
``NE SIP vs FIP visibility review calcs.xlsx,'' which can be found 
in the docket for this proposed rulemaking.
    \68\ See ``Summary Visibility'' tab of the Excel spreadsheet 
``NE SIP vs FIP visibility review calcs.xlsx,'' which can be found 
in the docket for this proposed rulemaking.

[[Page 38641]]



                        Table 3--Estimated Shortfall and Excess Visibility Benefits at Affected Class I Areas Due to SO2 Controls
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                     2001-2003 Average 98th percentile value ([Delta]dv)
                                                                    ------------------------------------------------------------------------------------
                                                                         AEP/PSO                                          Sum of OG&E
                                                                       Northeastern     OG&E Sooner     OG&E Muskogee      Sooner and     Estimated net
                            Class I Area                                estimated        estimated        estimated         Muskogee          excess
                                                                        visibility       visibility       visibility       estimated        visibility
                                                                         benefit       benefit excess   benefit excess     visibility      benefit \3\
                                                                      shortfall \1\   \2\ ([Delta]dv)  \2\ ([Delta]dv)   benefit excess    ([Delta]dv)
                                                                       ([Delta]dv)                                      \2\ ([Delta]dv)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Wichita Mountains..................................................            0.033            0.097            0.091            0.187            0.154
Caney Creek........................................................            0.025            0.035            0.072            0.107            0.082
Upper Buffalo......................................................            0.017            0.033            0.094            0.127            0.110
Hercules-Glades....................................................            0.022            0.026            0.076            0.102            0.081
                                                                    ------------------------------------------------------------------------------------
    Total..........................................................            0.096            0.190            0.332            0.522            0.425
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Based on a comparison of SO2 control requirements for the AEP/PSO Northeastern facility in the 2013 Regional Haze SIP (i.e., zero emissions for one
  unit and 0.4 lb/MMBtu for the remaining unit) against the CENRAP consultation and modeling assumptions (0.15 lb/MMBtu for each unit).
\2\ Based on a comparison of SO2 control requirements in the FIP (0.06 lb/MMBtu for each unit) against the CENRAP consultation and modeling assumptions
  (0.15 lb/MMBtu for each unit).
\3\ Based on a comparison of the ``Sum of OG&E Sooner and Muskogee Estimated Visibility Benefit Excess'' column against the ``AEP/PSO Northeastern
  Estimated Visibility Benefit Shortfall'' column.

    The FIP SO2 emission limits for the OG&E Sooner Units 1 
and 2 and the OG&E Muskogee Units 4 and 5 are permanent and federally 
enforceable.\69\ Therefore, we are proposing to find that the existing 
SO2 emission limits for the OG&E Sooner Units 1 and 2 and 
the OG&E Muskogee Units 4 and 5, required under the FIP, are sufficient 
to make up for the shortfall in the 2013 Oklahoma Regional Haze SIP 
Revision to secure the emission reductions necessary to achieve the 
anticipated visibility benefits associated with a 0.30 lb/MMBtu 
emission limit at Northeastern Power Station.
---------------------------------------------------------------------------

    \69\ Due to litigation over the FIP, the deadline by which these 
units were required to meet their SO2 emission limits 
contained in the FIP is January 4, 2019. The necessary control 
equipment was installed by the compliance deadline and these units 
are currently meeting their SO2 emission limits.
---------------------------------------------------------------------------

    The CENRAP modeling did not assume there would be any PM emission 
reductions from sources in Oklahoma for the first planning period. 
Therefore, the PM BART determinations in Oklahoma's 2010 Regional Haze 
SIP, which EPA approved on December 28, 2011,\70\ conform with the 
mutually agreed emission reductions under the CENRAP regional haze 
planning process. Based on our assessment presented in the preceding 
paragraphs, we believe that the SO2 controls required by the 
existing FIP, in combination with the SO2 controls required 
by the EPA-approved 2013 Oklahoma Regional Haze SIP Revision, 
constitute an assemblage of SO2 controls that conform with 
the mutually agreed emission reductions under the CENRAP regional haze 
planning process. This ensures that the existing FIP, together with the 
approved SIP, prevents sources in Oklahoma from emitting pollutants in 
amounts that will interfere with efforts to protect visibility in other 
states with respect to the 2010 1-hour SO2 and the 2012 
PM2.5 NAAQS. Under EPA's 2013 i-SIP guidance, this is 
sufficient to satisfy prong 4 requirements for the first planning 
period.\71\ Thus, there are no additional practical consequences from 
this disapproval for the state, the sources within its jurisdiction, or 
the EPA.\72\ EPA is proposing to find that its prong 4 obligations in 
Oklahoma for the 2010 1-hour SO2 and 2012 PM2.5 
NAAQS are satisfied.
---------------------------------------------------------------------------

    \70\ 76 FR 81728.
    \71\ See 2013 i-SIP Guidance at 33.
    \72\ Id at 34-35.
---------------------------------------------------------------------------

F. Impact on Areas of Indian Country

    Following the U.S. Supreme Court decision in McGirt v. Oklahoma, 
140 S.Ct. 2452 (2020), the Governor of the State of Oklahoma requested 
approval under Section 10211(a) of the Safe, Accountable, Flexible, 
Efficient Transportation Equity Act of 2005: A Legacy for Users, Public 
Law 109-59, 119 Stat. 1144, 1937 (August 10, 2005) (``SAFETEA''), to 
administer in certain areas of Indian country (as defined at 18 U.S.C. 
1151) the State's environmental regulatory programs that were 
previously approved by the EPA outside of Indian country.\73\ The 
State's request excluded certain areas of Indian country further 
described below. In addition, the State only sought approval to the 
extent that such approval is necessary for the State to administer a 
program in light of Oklahoma Dept. of Environmental Quality v. EPA, 740 
F.3d 185 (D.C. Cir. 2014).\74\
---------------------------------------------------------------------------

    \73\ A copy of the Governor's July 22, 2020 request can be found 
in the docket for this proposed rulemaking.
    \74\ In ODEQ v. EPA, the D.C. Circuit held that under the CAA, a 
state has the authority to implement a SIP in non-reservation areas 
of Indian country in the state, where there has been no 
demonstration of tribal jurisdiction. Under the D.C. Circuit's 
decision, the CAA does not provide authority to states to implement 
SIPs in Indian reservations. ODEQ did not, however, substantively 
address the separate authority in Indian country provided 
specifically to Oklahoma under SAFETEA. That separate authority was 
not invoked until the State submitted its request under SAFETEA, and 
was not approved until EPA's decision, described in this section, on 
October 1, 2020.
---------------------------------------------------------------------------

    On October 1, 2020, the EPA approved Oklahoma's SAFETEA request to 
administer all of the State's EPA-approved environmental regulatory 
programs, including the Oklahoma SIP, in the requested areas of Indian 
country.\75\ As requested by Oklahoma, the EPA's approval under SAFETEA 
does not include Indian country lands, including rights-of-way running 
through the same, that: (1) Qualify as Indian allotments, the Indian 
titles to which have not been extinguished, under 18 U.S.C. 1151(c); 
(2) are held in trust by the United States on behalf of an individual 
Indian or Tribe; or (3) are owned in fee by a Tribe, if the Tribe (a) 
acquired that fee title to such land, or an area that included such 
land, in accordance with a treaty with the United States to which such 
Tribe was a party, and (b) never allotted the land to a member or 
citizen of the Tribe (collectively ``excluded Indian country lands'').
---------------------------------------------------------------------------

    \75\ A copy of EPA's October 1, 2020 approval can be found in 
the docket for this proposed rulemaking.
---------------------------------------------------------------------------

    EPA's approval under SAFETEA expressly provided that to the extent 
EPA's prior approvals of Oklahoma's environmental programs excluded

[[Page 38642]]

Indian country, any such exclusions are superseded for the geographic 
areas of Indian country covered by the EPA's approval of Oklahoma's 
SAFETEA request.\76\ The approval also provided that future revisions 
or amendments to Oklahoma's approved environmental regulatory programs 
would extend to the covered areas of Indian country (without any 
further need for additional requests under SAFETEA).
---------------------------------------------------------------------------

    \76\ EPA's prior approvals relating to Oklahoma's SIP frequently 
noted that the SIP was not approved to apply in areas of Indian 
country (consistent with the D.C. Circuit's decision in ODEQ v. EPA) 
located in the state. See, e.g., 85 FR 20178, 20180 (April 10, 
2020). Such prior expressed limitations are superseded by the EPA's 
approval of Oklahoma's SAFETEA request.
---------------------------------------------------------------------------

    As explained above, the EPA is proposing to disapprove the 
interstate visibility transport portions of the Oklahoma i-SIP 
submittals for the 2010 SO2 and the 2012 PM2.5 
NAAQS because they do not meet the interstate visibility transport 
requirements of CAA Section 110(a)(2)(D)(i)(II) with respect to these 
NAAQS; however, the EPA is also proposing to make the determination 
that the deficiencies forming the basis of the proposed disapproval of 
these SIPs are met through the existing Federal Implementation Plan 
(FIP) in place for the Oklahoma Regional Haze program. The FIP applies 
to all lands within the State regardless of land status. In practice, 
the FIP requirements, as discussed previously, only apply to the OG&E 
facilities, Sooner Station Units 1 and 2, and Muskogee, Units 4 and 5.
    Additionally, EPA is proposing to approve the interstate visibility 
transport element of the Oklahoma i-SIP for the 2015 Ozone NAAQS. 
Consistent with the D.C. Circuit's decision in ODEQ v. EPA and with 
EPA's October 1, 2020, SAFETEA approval, if this approval is finalized 
as proposed, this portion of the SIP will apply in certain areas of 
Indian country. Under EPA's October 1, 2020 SAFETEA approval, the SIP 
will apply to all Indian country within the State of Oklahoma, other 
than the excluded Indian country lands. Because--per the State's 
request under SAFETEA--EPA's October 1, 2020 approval does not displace 
any SIP authority previously exercised by the State under the CAA as 
interpreted in ODEQ v. EPA, the SIP will also apply to any Indian 
allotments or dependent Indian communities located outside of an Indian 
reservation over which there has been no demonstration of tribal 
authority. \77\
---------------------------------------------------------------------------

    \77\ In accordance with Executive Order 13990, EPA is currently 
reviewing our October 1, 2020 SAFETEA approval and is engaging in 
further consultation with tribal governments and discussions with 
the state of Oklahoma as part of this review. EPA also notes that 
the October 1, 2020 approval is the subject of a pending challenge 
in federal court. (Pawnee v. Regan, No. 20-9635 (10th Cir.)). 
Pending completion of EPA's review, EPA is proceeding with this 
proposed action in accordance with the October 1, 2020 approval. 
EPA's final action on the approved interstate visibility transport 
portion of the Oklahoma i-SIP for the 2015 Ozone NAAQS will address 
the scope of the state's program with respect to Indian country, and 
may make any appropriate adjustments, based on the status of our 
review at that time. If EPA's final action on Oklahoma's SIP is 
taken before our review of the SAFETEA approval is complete, EPA may 
make further changes to the approval of Oklahoma's program to 
reflect the outcome of the SAFETEA review.
---------------------------------------------------------------------------

    This action will not result in the imposition of new requirements 
for the affected sources. Rather, it proposes to approve Oklahoma's 
determination that the regional haze measures that have already been 
approved and are currently being implemented satisfy the visibility 
transport requirements for the 2015 Ozone NAAQS and also proposes to 
make the determination that the regional haze measures promulgated by 
EPA in the Oklahoma FIP that are currently being implemented address 
the deficiencies in the Oklahoma SIP with respect to visibility 
transport requirements for the 2010 SO2 and 2012 
PM2.5 NAAQS.

IV. Proposed Action

    We are proposing to approve the interstate visibility transport 
element of Oklahoma's infrastructure SIP submission for the 2015 Ozone 
NAAQS. We are also proposing to disapprove the interstate visibility 
transport elements of two SIP submissions from Oklahoma: One for the 
2010 1-hour SO2 NAAQS and the other for the 2012 
PM2.5 NAAQS. In order to address EPA's FIP obligation under 
section 110(c) of the Act, we are proposing to find that the 
deficiencies in the Oklahoma SIP that form the basis of our proposed 
disapproval of the interstate visibility transport portions of the 
Oklahoma i-SIP submissions for the 2010 SO2 and 2012 
PM2.5 NAAQS are already addressed by the existing FIP in 
place for the Oklahoma Regional Haze program, and no further federal 
action is required.

V. Statutory and Executive Order Reviews

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

    This action is not a significant regulatory action and was 
therefore not submitted to the Office of Management and Budget for 
review.

B. Paperwork Reduction Act (PRA)

    This proposed action does not impose an information collection 
burden under the PRA because it does not contain any information 
collection activities.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action merely proposes to disapprove a SIP submission as not meeting 
the CAA.

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. The action imposes no enforceable duty on any state, 
local or tribal governments or the private sector.

E. Executive Order 13132: Federalism

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

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

    This proposal to approve the interstate visibility transport 
element of the Oklahoma i-SIP submission for the 2015 Ozone NAAQS and 
to disapprove the interstate visibility transport elements of the 
Oklahoma i-SIP submissions for the 2010 1-hour SO2 NAAQS and 
the 2012 PM2.5 NAAQS (and to propose a determination that no 
further action is required to address the deficiencies identified in 
the proposed disapproval) will apply, if finalized as proposed, to 
certain areas of Indian country as discussed in the preamble, and 
therefore has tribal implications as specified in E.O. 13175 (65 FR 
67249, November 9, 2000). However, this action will neither impose 
substantial direct compliance costs on federally recognized tribal 
governments, nor preempt tribal law. This action will not impose 
substantial direct compliance costs on federally recognized tribal 
governments because no actions will be required of tribal governments. 
This action will also not preempt tribal law as no Oklahoma tribe 
implements a regulatory program under the CAA, and thus does not have 
applicable or related tribal laws. Consistent with the EPA Policy on 
Consultation and Coordination with Indian Tribes (May 4,

[[Page 38643]]

2011), the EPA has offered consultation to tribal governments that may 
be affected by this action.

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

    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 merely proposes to disapprove a SIP 
submission as not meeting the CAA.

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

    This rulemaking does not involve technical standards.

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

    EPA believes the human health or environmental risk addressed by 
this action will not have potential disproportionately high and adverse 
human health or environmental effects on minority, low-income or 
indigenous populations. This action merely proposes to disapprove a SIP 
submission as not meeting the CAA.

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Nitrogen dioxide, Ozone, 
Particulate matter, Sulfur oxides, Visibility transport.

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

    Dated: July 15, 2021.
David Gray,
Acting Regional Administrator, Region 6.
[FR Doc. 2021-15467 Filed 7-21-21; 8:45 am]
BILLING CODE 6560-50-P


