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Federal Register / Vol. 86, No. 138 / Thursday, July 22, 2021 / Proposed Rules
lotter on DSK11XQN23PROD with PROPOSALS1

other states plans to protect visibility.22
EPA interprets prong 4 to be pollutantspecific 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 Oklahomas 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.
A. Analysis of Oklahomas 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 Oklahomas 2010 Regional Haze SIP
submittal, as revised in the 2013
Regional Haze SIP revision that addresses the AEP/PSO facility, and EPAs 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 EPAs 2013
i-SIP guidance states, Under section 110a2DiII, 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 states 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 110a2DiII prong 4 portion of Oklahomas 2015 i-SIP submittal for the 2010 1-hour SO2 NAAQS.
B. Analysis of Oklahomas 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 Oklahomas 2010 Regional Haze SIP
submittal, as revised in the June 20, 2013 SIP revision with respect to the AEP/PSO facility, and EPAs 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 Oklahomas 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/

22 See
2013 i-SIP Guidance at 34.
2013 i-SIP Guidance at 33.
24 See 2013 i-SIP Guidance at 34. See also 76 FR
22036 April 20, 2011 containing EPAs approval of the visibility requirement of 110a2DiII
based on a demonstration by Colorado that did not rely on the Colorado Regional Haze SIP.
23 See
VerDate Sep<11>2014

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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 110aD2iII prong 4 portion of Oklahomas 2016 infrastructure SIP
submittal for the 2012 PM2.5 NAAQS.
C. Analysis of Oklahomas 2018 Prong 4 Submittal for the 2015 Ozone NAAQS
In Oklahomas 2018 infrastructure SIP
submittal for the 2015 Ozone NAAQS, Oklahoma asserted that it meets the visibility transport provisions under section 110a2DiII 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 110a2DiI. 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 110a2DiI 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 27 76

25 See
2013 i-SIP Guidance at 3233.
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.

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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.
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