[Federal Register Volume 86, Number 42 (Friday, March 5, 2021)]
[Proposed Rules]
[Pages 12892-12895]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-04406]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 81

[EPA-R04-OAR-2020-0482; FRL-10019-57-Region 4]


Air Plan Approval; TN: Redesignation of the Sumner County 2010 
Sulfur Dioxide Unclassifiable Area

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve a State Implementation Plan (SIP) revision submitted by the 
State of Tennessee, through the Tennessee Department of Environment and 
Conservation (TDEC), on September 29, 2020, to redesignate the Sumner 
County, Tennessee unclassifiable area (hereinafter referred to as the 
``Sumner County Area'' or ``Area'') to attainment/unclassifiable for 
the 2010 1-hour primary sulfur dioxide (SO2) national 
ambient air quality standard (hereinafter referred to as the ``2010 
SO2 1-hour NAAQS''). EPA now has sufficient information to 
determine that the Sumner County Area is attaining the 2010 1-hour 
SO2 NAAQS and, therefore, is proposing to approve the 
State's request and redesignate the Area to attainment/unclassifiable 
for the 2010 1-hour SO2 NAAQS.

DATES: Comments must be received on or before April 5, 2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-
OAR-2020-0482 at http://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. 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. 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, the full EPA public comment 
policy, information about CBI or multimedia submissions, and general 
guidance on making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Evan Adams, Air Regulatory Management 
Section, Air Planning and Implementation Branch, Air and Radiation 
Division, U.S. Environmental Protection Agency, Region 4, 61 Forsyth 
Street SW, Atlanta, Georgia 30303-8960. Mr. Adams can be reached by 
telephone at (404) 562-9009 or via electronic mail at 
adams.evan@epa.gov.

SUPPLEMENTARY INFORMATION: 

I. Background

    The Clean Air Act (CAA or Act) establishes a process for air 
quality management through the establishment and implementation of the 
national ambient air quality standards (NAAQS). On June 2, 2010, EPA 
revised the primary SO2 NAAQS, establishing a new 1-hour 
SO2 standard of 75 parts per billion (ppb). See 75 FR 35520 
(June 22, 2010).\1\ After the promulgation of a new or revised NAAQS, 
EPA is required to designate all areas of the country, pursuant to 
section 107(d)(1)-(2) of the CAA. For the 2010 1-hour SO2 
NAAQS, designations were based on EPA's application of the nationwide 
analytical approach to, and technical assessment of, the weight of 
evidence for each area, including but not limited to available air 
quality monitoring data and air quality modeling results. In advance of 
designating the Sumner County Area, EPA issued updated designations 
guidance through a March 20, 2015, memorandum from Stephen D. Page, 
Director, U.S. EPA, Office of Air Quality Planning and Standards, to 
Air Division Directors, U.S. EPA Regions 1-10 titled, ``Updated 
Guidance for Area Designations for the 2010 Primary Sulfur Dioxide 
National Ambient Air Quality Standard,'' which contained the

[[Page 12893]]

factors that EPA evaluated in determining the appropriate designations 
and associated boundaries when designating the Sumner County Area, 
including: (1) Air quality characterization via ambient monitoring or 
dispersion modeling results; (2) emissions-related data; (3) 
meteorology; (4) geography and topography; and (5) jurisdictional 
boundaries.2 3 The guidance also referenced EPA's non-
binding Monitoring Technical Assistance Document (Monitoring TAD) and 
Modeling Technical Assistance Document (Modeling TAD),\4\ which contain 
scientifically sound recommendations on how air agencies should conduct 
such monitoring or modeling.
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    \1\ On February 25, 2019 (effective April 17, 2019), based on a 
review of the full body of currently available scientific evidence 
and exposure/risk information, EPA issued a decision to retain the 
existing NAAQS for SO2. See 84 FR 9866.
    \2\ The 2015 memorandum is available at https://www.epa.gov/sites/production/files/2016-04/documents/20150320so2designations.pdf.
    \3\ This designation guidance has since been supplemented by a 
July 22, 2016, designation guidance memorandum from Stephen D. Page, 
Director, U.S. EPA, Office of Air Quality Planning and Standards, to 
Regional Air Division Directors, U.S. EPA Regions 1-10. The 2016 
memorandum is available at https://www.epa.gov/sites/production/files/2016-07/documents/areadesign.pdf.
    \4\ ``Sulfur Dioxide (SO2) National Ambient Air 
Quality Standards Designations Modeling Technical Assistance 
Document,'' August 2016 draft, available at https://www.epa.gov/sites/production/files/2016-06/documents/so2modelingtad.pdf. EPA 
released earlier drafts of this document in May 2013 and February 
2016.
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    EPA completed the first set of initial area designations for the 
2010 1-hour SO2 NAAQS in 2013 (Round 1). Pursuant to a March 
2, 2015, consent decree and court-ordered schedule,\5\ EPA finalized a 
second set of initial area designations for the 2010 1-hour 
SO2 NAAQS in 2016 (Round 2). The March 2, 2015, consent 
decree identified the following emissions criteria such that EPA must 
designate, in Round 2, an area surrounding any stationary source which 
had: (a) annual emissions in 2012 exceeding 16,000 tons of 
SO2, or (b) both an annual average emissions rate of at 
least 0.45 pounds of SO2 per one million British thermal 
units, according to EPA's Clean Air Markets Division Database, and 
annual emissions of at least 2,600 tons of SO2 in 2012. 
Sumner County, Tennessee contained one source, Tennessee Valley 
Authority (TVA) Gallatin Fossil Plant (TVA Gallatin), that met these 
Round 2 criteria. EPA evaluated the Area, using the five factors 
identified previously, during the Round 2 designations. This evaluation 
is discussed further in Section III of this notice. TVA Gallatin is 
located in north-central Tennessee in the southern portion of Sumner 
County, approximately 5 kilometers (km) southeast of the center of 
Gallatin, Tennessee. TVA Gallatin is a large Electric Generating Unit 
that was included in the list of facilities to be designated pursuant 
to the March 2, 2015, Consent Decree.6 7
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    \5\ See Sierra Club et. al. v. McCarthy, Civil Action No. 3:13-
cv-3953-SI (N.D. Cal.), and 79 FR 31325 (June 2, 2014).
    \6\ TVA Gallatin was also subject to EPA's 2015 Data 
Requirements Rule (DRR) for the 2010 SO2 1-hour NAAQS. 
See https://www.epa.gov/sites/production/files/2016-06/documents/tn.pdf for Tennessee's letter dated January 15, 2016 with the Data 
Requirements Rule (DRR) source list.
    \7\ In accordance with the DRR, 40 CFR part 51, subpart BB, 
through a letter dated June 7, 2016, Tennessee notified EPA that the 
State chose to characterize peak 1-hour SO2 
concentrations for TVA Gallatin using air quality dispersion 
modeling.
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    EPA's March 20, 2015, guidance specified the designation category 
definitions to be used in the Round 2 designations. Specifically, EPA 
defined a ``nonattainment'' area as an area that EPA has determined 
violates the 2010 1-hour SO2 NAAQS based on the most recent 
three years of quality-assured, certified ambient air quality 
monitoring data or an appropriate modeling analysis, or that EPA has 
determined contributes to a violation in a nearby area; and defined an 
``attainment'' area as an area that EPA has determined meets the 2010 
1-hour SO2 NAAQS and does not contribute to a violation of 
the NAAQS in a nearby area based on either: (a) the most recent 3 years 
of ambient air quality monitoring data from a monitoring network in an 
area that is sufficient to be compared to the NAAQS per EPA 
interpretations in the Monitoring TAD, or (b) an appropriate modeling 
analysis. As discussed further in Section III of this notice, EPA was 
unable to determine whether the Sumner County Area met the definition 
of a nonattainment area or the definition of an attainment area based 
on the available information at the time of the Round 2 designations. 
As a result, EPA designated the Sumner County Area as unclassifiable in 
the Round 2 designations published on July 12, 2016.\8\ The boundary 
for this designation was the jurisdictional boundary of Sumner County.
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    \8\ See 81 FR 45039 (July 12, 2016), codified at 40 CFR 81.343.
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    Detailed rationale, analyses, and other information supporting 
EPA's original Round 2 designation for this Area can be found in the 
Round 2 designation's technical support document (TSD) for Tennessee. 
That TSD, along with all other supporting materials for the original 
2010 1-hour SO2 NAAQS designation for Sumner County, can be 
found on EPA's SO2 designations website.\9\ In support of 
this proposed redesignation action, EPA evaluated new modeling for the 
Sumner County Area provided by Tennessee and developed a new TSD. The 
TSD for this proposed action is included in the docket.\10\
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    \9\ EPA SO2 designations website can be found at 
https://www.epa.gov/sulfur-dioxide-designations.
    \10\ The modeling files are not included in the electronic 
docket for this proposed action due to their nature, size, and 
incompatibility with the Federal Docket Management System. These 
files are available at the EPA Region 4 office for review. To 
request these files, please contact the person listed in the notice 
under the section titled FOR FURTHER INFORMATION CONTACT.
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II. What are the criteria for redesignating an area from unclassifiable 
to attainment/unclassifiable?

    Section 107(d)(3)(A) of the CAA provides that the Administrator may 
notify the Governor of any state that the designation of an area should 
be revised ``on the basis of air quality data, planning and control 
considerations, or any other air quality-related considerations the 
Administrator deems appropriate.'' \11\ The Act further provides in 
section 107(d)(3)(D) that even if the Administrator has not notified a 
state Governor that a designation should be revised, the Governor of 
any state may, on the Governor's own motion, submit a request to revise 
the designation of any area, and the Administrator must approve or deny 
the request. In keeping with CAA section 107(d)(3)(A), areas that are 
redesignated to attainment/unclassifiable \12\ must meet the 
requirements for attainment areas and, thus, must meet the relevant 
NAAQS. In addition, the area must not contribute to ambient air quality 
in a nearby area that does not meet the NAAQS. See the definitions for 
nonattainment area, attainment area, and unclassifiable area in CAA 
section 107(d)(1)(A)(i)-(iii).
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    \11\ While CAA section 107(d)(3)(E) also lists specific 
requirements for redesignations, those requirements only apply to 
redesignations of nonattainment areas to attainment and, therefore, 
are not applicable in the context of a redesignation of an area from 
unclassifiable to attainment/unclassifiable.
    \12\ Historically, EPA has designated most areas that do not 
meet the definition of nonattainment as ``unclassifiable/
attainment.'' EPA has reversed the order of the label to be 
``attainment/unclassifiable'' to better convey the definition of the 
designation category and so that the category is more easily 
distinguished from the separate unclassifiable category. See 83 FR 
1098 (January 9, 2018) and 83 FR 25776 (June 4, 2018). EPA reserves 
the ``attainment'' category for when EPA redesignates a 
nonattainment area that has attained the relevant NAAQS and has an 
approved maintenance plan.
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    In its designations under the 2010 1-hour SO2 NAAQS, EPA 
has generally defined an attainment/unclassifiable area as an area 
that, based on available information including (but not limited to) 
appropriate monitoring data and/or

[[Page 12894]]

modeling analyses, EPA has determined meets the NAAQS and determined 
that the available information indicates that the area does not likely 
contribute to ambient air quality in a nearby area that does not meet 
the NAAQS. EPA is proposing to find that the Sumner County Area now 
meets the definition of attainment/unclassifiable based upon air 
quality dispersion modeling analyses that demonstrates attainment, 
i.e., no violations of the 2010 1-hour SO2 NAAQS and not 
contributing to a nearby area that is not meeting the NAAQS. EPA 
preliminarily finds this information sufficient for the purposes of 
redesignating an area from unclassifiable to attainment/unclassifiable. 
Such redesignations are functionally similar to initial designations 
and are not subject to CAA section 107(d)(3)(E), which, amongst other 
things, requires attainment to be due to permanent and enforceable 
measures and which requires a demonstration that the area will maintain 
the NAAQS for 10 years.

III. What is EPA's rationale for proposing to redesignate the area?

    The Sumner County Area was designated unclassifiable by EPA on July 
12, 2016. EPA's rationale for the unclassifiable designation is fully 
explained in the TSD associated with that action.\13\ As discussed in 
the final TSD, the revised modeling provided by Tennessee in March 2016 
for the final designation action used allowable SO2 
emissions rates from the TVA Gallatin facility that had not yet been 
made federally enforceable. Additionally, the final modeling analysis 
did not appropriately account for background SO2 
concentrations in the Area which was considered inconsistent with EPA's 
Modeling TAD and modeling guidelines in 40 CFR part 51, Appendix W.
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    \13\ The final Round 2 designations TSD can be found at https://www.epa.gov/sites/production/files/2016-07/documents/r4_tn_final_designation_tsd_06302016.pdf.
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    Tennessee submitted an updated modeling analysis with its letter 
signed by Michelle Owenby, Director of TDEC's Division of Air Pollution 
Control, on September 29, 2020, requesting that EPA redesignate Sumner 
County, Tennessee, to attainment/unclassifiable for the 2010 1-hour 
SO2 NAAQS.\14\ This updated modeling was performed using the 
current version of EPA's recommended dispersion model, AERMOD version 
19191, with the most recent three years of actual SO2 
emissions (2017-2019) from the TVA Gallatin facility and concurrent 
meteorology data. Additionally, the updated modeling used recent 2016 
land cover data and appropriately accounted for background 
SO2 concentrations in the Area. The TSD included in the 
docket for this proposed redesignation action provides a detailed 
summary of Tennessee's modeling analysis and EPA's evaluation of the 
modeling.
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    \14\ The demonstration of attainment through air quality 
dispersion modeling requires an area to review and report annual 
SO2 emissions pursuant to DRR ongoing verification at 40 
CFR 51.1205(b). In its September 29, 2020, redesignation request 
letter, Tennessee also requested to terminate the section 51.1205(b) 
annual reporting requirement because the modeling analyses 
demonstrated a value of at least 50 percent below the 2010 1-hour 
SO2 NAAQS at all receptors. EPA will address the annual 
reporting termination request in a separate action which has no 
bearing on the proposed approval of the redesignation.
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    According to EPA's guidance on redesignations, SO2 
nonattainment areas using modeling to demonstrate attainment for a 
redesignation request are expected to use maximum allowable 
emissions.\15\ However, this statement derives from the requirements of 
CAA section 107(d)(3)(E), which applies only to the redesignation of 
nonattainment areas to attainment. For redesignations of unclassifiable 
areas, the necessary analysis is equivalent to what would be required 
in a designation in the first instance since EPA has not found the area 
to be attainment or nonattainment. In this first instance, the goal is 
to characterize existing ambient air quality. As such, it is 
appropriate to use actual emissions for estimating existing air 
quality. EPA's acceptance of modeling using actual emissions in this 
instance should not be construed to define what would be needed for a 
demonstration of attainment and maintenance for purposes of a 
redesignation of a nonattainment area to attainment.
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    \15\ ``Guidance for 1-Hour SO2 Nonattainment Area SIP 
Submissions,'' April 2014, at 67, available at https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf; ``Use of Actual Emissions in 
Maintenance Demonstrations for Ozone and Carbon Monoxide (CO) 
Nonattainment Areas,'' November 1993, at 3, available at https://www3.epa.gov/ttn/naaqs/aqmguide/collection/cp2/19931130_berry_actual_emissions_ozone_co_maintenance_demos%20.pdf.
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    After reviewing Tennessee's request under CAA section 107(d)(3)(D) 
and all available information, EPA is proposing to find that the 
modeling provided by the State comports with EPA's current Modeling TAD 
and EPA's Guideline on Air Quality Models (40 CFR part 51 Appendix W) 
and is acceptable for assessing the attainment status of the Sumner 
County Area. The State's modeling indicates that the predicted maximum 
design value at any receptor in the modeling domain is 60.5 micrograms 
per cubic meter ([micro]g/m\3\), or 23.1 ppb.\16\ EPA's review confirms 
that the modeling results appropriately characterize the air quality in 
the Sumner County Area that predicted ambient SO2 
concentrations are below the 2010 1-hour SO2 NAAQS of 196.4 
[micro]g/m\3\, or 75 ppb.\17\ Additionally, there is no evidence of 
monitored or modeled violations in the surrounding counties such that 
the source is contributing to any nearby area that does not meet the 
NAAQS. EPA is therefore proposing to approve Tennessee's redesignation 
request and proposing to redesignate the entirety of Sumner County that 
was designated as unclassifiable in July 2016 to attainment/
unclassifiable based on the currently available information that 
demonstrates attainment of the 2010 1-hour SO2 NAAQS.
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    \16\ The SO2 NAAQS and the design value compared to 
the NAAQS is the 3-year average of the annual 99th percentile of 1-
hour daily maximum concentrations.
    \17\ See the TSD in the docket for this proposed action for 
further information and analysis of the updated modeling.
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IV. Proposed Action

    EPA is proposing to approve Tennessee's September 29, 2020, 
redesignation request and to redesignate the Sumner County Area from 
unclassifiable to attainment/unclassifiable for the 2010 1-hour 
SO2 NAAQS. EPA has reviewed the modeling provided by the 
State with its redesignation request and preliminarily finds that it 
complies with EPA's current Modeling TAD and EPA's Guideline on Air 
Quality Models (40 CFR part 51 Appendix W) and is acceptable for 
assessing the attainment status of the Sumner County Area. If 
finalized, approval of the redesignation request would change the legal 
designation, found at 40 CFR part 81, of Sumner County from 
unclassifiable to attainment/unclassifiable for the 2010 1-hour 
SO2 NAAQS.

V. Statutory and Executive Order Reviews

    Under the CAA, redesignation of an area to attainment/
unclassifiable is an action that affects the status of a geographical 
area and does not impose any additional regulatory requirements on 
sources beyond those imposed by state law. A redesignation to 
attainment/unclassifiable does not create any new requirements. 
Accordingly, this proposed action merely proposes to redesignate an 
area to attainment/unclassifiable and does not impose additional 
requirements. For that reason, this proposed action:

[[Page 12895]]

     Is not a significant regulatory action subject to review 
by the Office of Management and Budget under Executive Orders 12866 (58 
FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the CAA; and
     Will not have disproportionate human health or 
environmental effects under Executive Order 12898 (59 FR 7629, February 
16, 1994).
    This proposed action does not apply on any Indian reservation land 
or in any other area where EPA or an Indian tribe has demonstrated that 
a tribe has jurisdiction. In those areas of Indian country, this 
proposed action does not have tribal implications as specified by 
Executive Order 13175 (65 FR 67249, November 9, 2000), nor will it 
impose substantial direct costs on tribal governments or preempt tribal 
law.

List of Subjects in 40 CFR Part 81

    Environmental protection, Air pollution control.

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

    Dated: February 25, 2021.
John Blevins,
Acting Regional Administrator, Region 4.
[FR Doc. 2021-04406 Filed 3-4-21; 8:45 am]
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