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Federal Register / Vol. 86, No. 138 / Thursday, July 22, 2021 / Proposed Rules 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.
Comments must be received on or before August 23, 2021.

DATES:

Submit your comments, identified by Docket No. EPAR06
OAR20210032, 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, 2146657341, 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.

ADDRESSES:

lotter on DSK11XQN23PROD with PROPOSALS1

FOR FURTHER INFORMATION CONTACT:

Dayana Medina, EPA Region 6 Office, Regional Haze and SO2 Section, 214
6657341, 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 COVID19. 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.

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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 110a2 lists specific requirements that infrastructure SIPs, or i-SIPs, must include to adequately address such new or revised NAAQS, as applicable. Section 110a2Di 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 110a2DiI and the third and fourth prongs are codified in section 110a2DiII. 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 states 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 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 110a1 and 110a2. Memorandum to EPA Air Division Directors, Regions 1 through 10, September 13, 2013 hereinafter 2013 i-SIP Guidance.

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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.
A. Oklahomas 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 mg/m3 and retained the secondary annual PM2.5
standard of 15 mg/m3 as well as the primary and secondary 24-hour PM2.5
standards of 35 mg/m3 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 110a2DiII 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 110a2DiII
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.
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 110a2DiII 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 2 78

FR 3085 Jan. 15, 2013.
FR 83184 November 21, 2016.
4 82 FR 27121 June 14, 2017.
5 75 FR 35520 June 22, 2010.
6 81 FR 83184.
3 81

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