[Federal Register Volume 84, Number 78 (Tuesday, April 23, 2019)]
[Proposed Rules]
[Pages 16799-16809]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-07921]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R04-OAR-2018-0665; FRL-9992-52-Region 4]


Air Plan Approval; SC; 2010 1-Hour SO2 NAAQS Transport 
Infrastructure

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve South Carolina's June 25, 2018, State Implementation Plan (SIP) 
submission pertaining to the ``good neighbor'' provision of the Clean 
Air Act (CAA or Act) for the 2010 1-hour sulfur dioxide 
(SO2) National Ambient Air Quality Standard (NAAQS). The 
good neighbor provision requires each state's implementation plan to 
address the interstate transport of air pollution in amounts that 
contribute significantly to nonattainment, or interfere with 
maintenance, of a NAAQS in any other state. In this action, EPA is 
proposing to determine that South Carolina's SIP contains adequate 
provisions to prohibit emissions within the State from contributing 
significantly to nonattainment or interfering with maintenance of the 
2010 1-hour SO2 NAAQS in any other state.

DATES: Written comments must be received on or before May 23, 2019.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-
OAR-2018-0665 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: Michele Notarianni, Air Regulatory 
Management Section, Air Planning and Implementation Branch, Air, 
Pesticides and Toxics Management Division, U.S. Environmental 
Protection Agency, Region 4, 61 Forsyth Street SW, Atlanta, Georgia 
30303-8960. Ms. Notarianni can be reached via phone number (404) 562-
9031 or via electronic mail at [email protected].

SUPPLEMENTARY INFORMATION:

[[Page 16800]]

I. Background

A. Infrastructure SIPs

    On June 2, 2010, EPA promulgated a revised primary SO2 
NAAQS with a level of 75 parts per billion (ppb), based on a 3-year 
average of the annual 99th percentile of 1-hour daily maximum 
concentrations. See 75 FR 35520 (June 22, 2010). Pursuant to section 
110(a)(1) of the CAA, states are required to submit SIPs meeting the 
applicable requirements of section 110(a)(2) within three years after 
promulgation of a new or revised NAAQS or within such shorter period as 
EPA may prescribe. These SIPs, which EPA has historically referred to 
as ``infrastructure SIPs,'' are to provide for the ``implementation, 
maintenance, and enforcement'' of such NAAQS, and the requirements are 
designed to ensure that the structural components of each state's air 
quality management program are adequate to meet the state's 
responsibility under the CAA. Section 110(a) of the CAA requires states 
to make a SIP submission to EPA for a new or revised NAAQS, but the 
contents of individual state submissions may vary depending upon the 
facts and circumstances. The content of the changes proposed in such 
SIP submissions may also vary depending upon what provisions the 
state's approved SIP already contains. Section 110(a)(2) requires 
states to address basic SIP elements such as requirements for 
monitoring, basic program requirements, and legal authority that are 
designed to assure attainment and maintenance of the NAAQS. A detailed 
history, interpretation, and rationale of these SIPs and their 
requirements can be found in, among other documents, EPA's March 7, 
2016 (81 FR 11718), notice of proposed rulemaking related to 
infrastructure SIP requirements for the 2010 1-hour SO2 
NAAQS for South Carolina in the section titled, What is EPA's approach 
to the review of infrastructure SIP submissions?
    Section 110(a)(2)(D)(i)(I) of the CAA requires SIPs to include 
provisions prohibiting any source or other type of emissions activity 
in one state from emitting any air pollutant in amounts that will 
contribute significantly to nonattainment, or interfere with 
maintenance, of the NAAQS in another state. The two clauses of this 
section are referred to as prong 1 (significant contribution to 
nonattainment) and prong 2 (interference with maintenance of the 
NAAQS).
    On June 25, 2018, the South Carolina Department of Health and 
Environmental Control (SC DHEC) submitted a revision to the South 
Carolina SIP addressing only prongs 1 and 2 of CAA section 
110(a)(2)(D)(i)(I) for the 2010 1-hour SO2 NAAQS.\1\ EPA is 
proposing to approve SC DHEC's June 25, 2018, SIP submission which 
certifies that existing SIP provisions satisfy the State's obligation 
for prongs 1 and 2 for the 2010 1-hour SO2 NAAQS. All other 
elements related to the infrastructure requirements of section 
110(a)(2) for the 2010 1-hour SO2 NAAQS for South Carolina 
are addressed in separate rulemakings.\2\
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    \1\ On May 8, 2014, SC DHEC submitted a SIP revision addressing 
all infrastructure elements with respect to the 2010 1-hour 
SO2 NAAQS with the exception of prongs 1 and 2 of CAA 
110(a)(2)(D)(i)(I).
    \2\ EPA acted on the other elements of South Carolina's May 8, 
2014, infrastructure SIP submission for the 2010 1-hour 
SO2 NAAQS on May 24, 2016 (81 FR 32651) and September 24, 
2018 (83 FR 48237).
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B. EPA's Designations for the 2010 1-Hour SO2 NAAQS

    In this action, EPA has considered information from the 2010 1-hour 
SO2 NAAQS designations process, as discussed in more detail 
in section III.C of this document. For this reason, a brief summary of 
EPA's designations process for the 2010 1-hour SO2 NAAQS is 
included here.\3\
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    \3\ While designations may provide useful information for 
purposes of analyzing transport, particularly for a more source-
specific pollutant such as SO2, EPA notes that 
designations themselves are not dispositive of whether or not upwind 
emissions are impacting areas in downwind states. EPA has 
consistently taken the position that as to impacts, CAA section 
110(a)(2)(D) refers only to prevention of `nonattainment' in other 
states, not to prevention of nonattainment in designated 
nonattainment areas or any similar formulation requiring that 
designations for downwind nonattainment areas must first have 
occurred. See e.g., Clean Air Interstate Rule, 70 FR 25162, 25265 
(May 12, 2005); Cross-State Air Pollution Rule, 76 FR 48208, 48211 
(Aug. 8, 2011); Final Response to Petition from New Jersey Regarding 
SO2 Emissions From the Portland Generating Station, 76 FR 
69052 (Nov. 7, 2011) (finding facility in violation of the 
prohibitions of CAA section 110(a)(2)(D)(i)(I) with respect to the 
2010 1-hour SO2 NAAQS prior to issuance of designations 
for that standard).
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    After the promulgation of a new or revised NAAQS, EPA is required 
to designate areas as ``nonattainment,'' ``attainment,'' or 
``unclassifiable,'' pursuant to section 107(d)(1) of the CAA. The 
process for designating areas following promulgation of a new or 
revised NAAQS is contained in section 107(d) of the CAA. The CAA 
requires EPA to complete the initial designations process within two 
years of promulgating a new or revised standard. If the Administrator 
has insufficient information to make these designations by that 
deadline, EPA has the authority to extend the deadline for completing 
designations by up to one year.
    EPA promulgated the 2010 1-hour SO2 NAAQS on June 2, 
2010. See 75 FR 35520 (June 22, 2010). EPA completed the first round of 
designations for the 2010 1-hour SO2 NAAQS on July 25, 2013, 
designating 29 areas in 16 states as nonattainment for the 2010 1-hour 
SO2 NAAQS. See 78 FR 47191 (August 5, 2013). EPA based this 
first round of final SO2 designations on monitored 
SO2 concentrations violating the 2010 1-hour SO2 
standard. Following the initial August 5, 2013, designations, three 
lawsuits were filed against EPA in different U.S. District Courts, 
alleging that the Agency had failed to perform a nondiscretionary duty 
under the CAA by not designating all portions of the country within the 
time lines set forth in section 107(d)(1)(B) of the CAA. In an effort 
intended to resolve the litigation in one of those cases, EPA and the 
plaintiffs, Sierra Club and the Natural Resources Defense Council, 
filed a proposed consent decree with the U.S. District Court for the 
Northern District of California. On March 2, 2015, the court entered 
the consent decree \4\ which requires EPA to sign for publication in 
the Federal Register notices of the Agency's promulgation of area 
designations by three specific deadlines: July 2, 2016 (``round 2''); 
December 31, 2017 (``round 3''); and December 31, 2020 (``round 
4'').\5\
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    \4\ Consent Decree, Sierra Club v. McCarthy, Case No. 3:13-cv-
3953-SI (N.D. Cal. Mar. 2, 2015).
    \5\ The term ``round'' in this instance refers to which ``round 
of designations.''
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    On August 21, 2015 (80 FR 51052), EPA separately promulgated air 
quality characterization requirements for the 2010 1-hour 
SO2 NAAQS in the Data Requirements Rule (DRR). The DRR 
required state air agencies to characterize air quality, through air 
dispersion modeling or monitoring, in areas associated with sources 
that emitted greater than 2,000 tons per year (tpy) of SO2, 
or that have otherwise been listed under the DRR by EPA or state air 
agencies. In lieu of modeling or monitoring, state air agencies, by 
specified dates, could elect to impose federally-enforceable emissions 
limitations on those sources restricting their annual SO2 
emissions to 2,000 tpy or less, or provide documentation that the 
sources have been shut down. EPA expected that the information 
generated by implementation of the DRR would help inform SO2 
designations specified in the March 2, 2015, consent decree. EPA signed 
Federal Register notices of promulgation of round 2 designations \6\

[[Page 16801]]

on June 30, 2016 (81 FR 45039 (July 12, 2016)), and on November 29, 
2016 (81 FR 89870 (December 13, 2016)), and round 3 designations \7\ on 
December 21, 2017 (83 FR 1098 (January 9, 2018)). For South Carolina, 
EPA designated all counties as attainment/unclassifiable in round 3. 
Because all counties in South Carolina are now designated for the 2010 
1-hour SO2 NAAQS, and no DRR sources in the State opted to 
monitor to inform Round 4 SO2 designations, no areas in 
South Carolina will be designated in round 4.\8\ There are no 
nonattainment areas in South Carolina for the 2010 1-hour 
SO2 NAAQS.\9\
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    \6\ EPA and state documents and public comments related to the 
round 2 final designations are in the docket at regulations.gov with 
Docket ID NO. EPA-HQ-OAR-2014-0464 and at EPA's website for 
SO2 designations at https://www.epa.gov/sulfur-dioxide-designations.
    \7\ EPA and state documents and public comments related to round 
3 final designations are in the docket at regulations.gov with 
Docket ID NO. EPA-HQ-OAR-2017-0003 and at EPA's website for 
SO2 designations at https://www.epa.gov/sulfur-dioxide-designations.
    \8\ See Technical Support Document: Chapter 37 Final Round 3 
Area Designations for the 2010 1-Hour SO2 Primary National Ambient 
Air Quality Standard for South Carolina at https://www.epa.gov/sites/production/files/2017-12/documents/37-sc-so2-rd3-final.pdf. 
See also Technical Support Document: Chapter 37 Intended Round 3 
Area Designations for the 2010 1-Hour SO2 Primary National Ambient 
Air Quality Standard for South Carolina at https://www.epa.gov/sites/production/files/2017-08/documents/38sc_so2_rd3-final.pdf.
    \9\ On August 5, 2013 (78 FR 47191) and effective October 4, 
2013, EPA designated 29 areas in 16 states as nonattainment for the 
2010 1-hour SO2 NAAQS based on violating monitors using 
air quality data for the years 2009-2011, but did not, at that time, 
designate other areas in the country. On July 12, 2016 (81 FR 
45039), effective September 12, 2016, and December 13, 2016 (81 FR 
89870), effective January 12, 2017, EPA published a final rule 
establishing air quality designations for 65 areas in 24 states for 
the 2010 SO2 NAAQS including seven nonattainment areas, 
41 attainment/unclassifiable areas, and 17 unclassifiable areas. On 
January 9, 2018 (83 FR 1098) effective April 9, 2018, EPA designated 
six areas as nonattainment; 23 areas as unclassifiable; and the rest 
of the areas covered by this round in all states, territories, and 
tribal lands as attainment/unclassifiable. No areas in South 
Carolina were designated as nonattainment in these actions. See 
https://www.epa.gov/sulfur-dioxide-designations/sulfur-dioxide-designations-regulatory-actions.
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II. Relevant Factors Used To Evaluate 2010 1-Hour SO2 Interstate 
Transport SIPs

    Interstate transport of SO2 is unlike the transport of 
fine particulate matter (PM2.5) or ozone in that 
SO2 is not a regional pollutant and does not commonly 
contribute to widespread nonattainment over a large (and often multi-
state) area. The transport of SO2 is more analogous to the 
transport of lead (Pb) because its properties result in localized 
pollutant impacts very near the emissions source. However, ambient 
concentrations of SO2 do not decrease as quickly with 
distance from the source as Pb because of the properties and typical 
release heights of SO2. Emissions of SO2 travel 
farther and have wider ranging impacts than emissions of Pb, but do not 
travel far enough to be treated in a manner similar to ozone or 
PM2.5. The approaches that EPA has adopted for ozone or 
PM2.5 transport are too regionally focused and the approach 
for Pb transport is too tightly circumscribed to the source. 
SO2 transport is therefore a unique case and requires a 
different approach.
    Given the properties of SO2, EPA agrees with South 
Carolina's selection of a spatial scale with dimensions from four to 50 
kilometers (km) from point sources--the ``urban scale''--to assess 
trends in area-wide air quality that might impact downwind states.\10\ 
SC DHEC selected the urban scale as appropriate for assessing trends in 
both area-wide air quality and the effectiveness of large-scale 
pollution control strategies at SO2 point sources. SC DHEC 
supported this transport distance threshold with references to 40 CFR 
58, Appendix D, Section 4.4.4(4) ``Urban scale'', which states that 
measurements in this scale would be used to estimate SO2 
concentrations over large portions of an urban area with dimensions 
from four to 50 km. The State also notes that 50 km is the transport 
distance threshold that EPA recommends for use with the air quality 
dispersion model called the American Meteorological Society/
Environmental Protection Agency Regulatory Model (AERMOD). AERMOD is 
EPA's preferred modeling platform for regulatory purposes (Appendix W 
of 40 CFR part 51).\11\ EPA agrees with the State's selection and 
application of the 50-km threshold as a reasonable distance to evaluate 
emission source impacts into neighboring states and to assess air 
quality monitors within 50 km of the State's border, which is discussed 
further in section III.C.
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    \10\ For the definition of spatial scales for SO2, 
please see 40 CFR part 58, Appendix D, section 4.4 (``Sulfur Dioxide 
(SO2) Design Criteria''). For further discussion on how 
EPA applies these definitions with respect to interstate transport 
of SO2, see EPA's notice of proposed rulemaking on 
Connecticut's SO2 transport SIP. 82 FR 21351, 21352, 
21354 (May 8, 2017).
    \11\ EPA established a non-binding technical assistance document 
to assist states and other parties in their efforts to characterize 
air quality through air dispersion modeling for sources that emit 
SO2 titled, ``SO2 NAAQS Designations Modeling 
Technical Assistance Document. This draft document was first 
released in spring 2013. Revised drafts were released in February 
and August of 2016 (see https://www.epa.gov/sites/production/files/2016-06/documents/so2modelingtad.pdf).
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    As discussed in sections III.C and III.D, EPA first reviewed the 
State's analysis to assess how the State evaluated the transport of 
SO2 to other states, the types of information used in the 
analysis, and the conclusions drawn by the State. EPA then conducted a 
weight of evidence analysis based on a review of the State's submission 
and other available information, including SO2 air quality 
and available source modeling for states within 50 km of the South 
Carolina border.\12\
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    \12\ This proposed approval action is based on the information 
contained in the administrative record for this action, and does not 
prejudge any future EPA action that may make other determinations 
regarding the air quality status in South Carolina and downwind 
states. Any such future action, such as area designations under any 
NAAQS, will be based on their own administrative records and the 
EPA's analyses of information that becomes available at those times. 
Future available information may include, and is not limited to, 
monitoring data and modeling analyses conducted pursuant to EPA's 
DRR and information submitted to EPA by states, air agencies, and 
third-party stakeholders such as citizen groups and industry 
representatives.
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III. South Carolina's SIP Submission and EPA's Analysis

A. State Submission

    On June 25, 2018, SC DHEC submitted a revision to the South 
Carolina SIP addressing prongs 1 and 2 of CAA section 
110(a)(2)(D)(i)(I) for the 2010 1-hour SO2 NAAQS. South 
Carolina conducted a weight of evidence analysis to examine whether 
SO2 emissions from the State adversely affect attainment or 
maintenance of the 2010 1-hour SO2 NAAQS in downwind states.
    SC DHEC reviewed the following information to support its 
conclusion that South Carolina does not significantly contribute to 
nonattainment or interfere with maintenance of the 2010 1-hour 
SO2 NAAQS in downwind states: Trends in SO2 
design values (DVs) \13\ at the State's air quality monitors from 2008-
2017; highest monitored SO2 DVs for monitors with complete, 
quality-assured data and located within South Carolina and within 
Florida, Georgia, and North Carolina; SO2 emissions trends 
both statewide (for the years 2008, 2011, and 2014) and for the State's 
title V sources (for the years 2008-2016); available SO2 
modeling data for the State's round 3 DRR-subject sources; and State 
and federal regulations and State statutes that establish requirements 
for sources

[[Page 16802]]

of SO2 emissions. South Carolina noted that federal 
regulations and competition from lower natural gas prices resulted in 
four coal-fired electric generating units (EGUs) within the State 
either shutting down or switching to cleaner fuels. The State 
identified these units and summarized the history of the shutdowns and 
switches to cleaner fuels. South Carolina also included SO2 
emissions trends for the Southeast from 2000-2016 and noted that there 
is a consistent downward trend.
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    \13\ A ``Design Value'' is a statistic that describes the air 
quality status of a given location relative to the level of the 
NAAQS. The DV for the primary 2010 1-hour SO2 NAAQS is 
the 3-year average of annual 99th percentile daily maximum 1-hour 
values for a monitoring site. The interpretation of the primary 2010 
1-hour SO2 NAAQS including the data handling conventions 
and calculations necessary for determining compliance with the NAAQS 
can be found in Appendix T to 40 CFR part 50.
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    Based on this weight of evidence analysis, the State concluded that 
emissions within South Carolina will not contribute significantly to 
nonattainment or interfere with maintenance of the 2010 1-hour 
SO2 NAAQS in any other state. The State based its 
conclusions for Prong 1 on the actual and projected downward trends of 
SO2 emissions in South Carolina, trends in SO2 
DVs for South Carolina's monitors and other states' monitors within 50 
km of the South Carolina border, DRR modeling results, and established 
federal and State control measures affecting SO2. The State 
based its conclusions for Prong 2 on emissions trends of SO2 
in South Carolina and in the Southeast and established federal and 
State control measures which reduce SO2 emissions. EPA's 
evaluation of South Carolina's submission is detailed in sections 
III.B, C, and D.

B. EPA's Evaluation Methodology

    EPA believes that a reasonable starting point for determining which 
sources and emissions activities in South Carolina are likely to impact 
downwind air quality in other states with respect to the 2010 1-hour 
SO2 NAAQS is by using information in EPA's National 
Emissions Inventory (NEI).\14\ The NEI is a comprehensive and detailed 
estimate of air emissions for criteria pollutants, criteria pollutant 
precursors, and hazardous air pollutants from air emissions sources 
that is updated every three years using information provided by the 
states and other information available to the EPA. EPA used the 2014 
NEI (version 2), the most recently available, complete, and quality 
assured dataset of the NEI. Table 1 shows that point sources in South 
Carolina contribute approximately 89 percent of the State's total 
SO2 emissions, followed by nonpoint sources at six percent 
and fires at four percent.
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    \14\ EPA's NEI is available at https://www.epa.gov/air-emissions-inventories/national-emissions-inventory.

 Table 1--Summary of 2014 NEI (Version 2) SO2 Data for South Carolina by
                             Source Category
------------------------------------------------------------------------
                                                            Percent of
                Category                     Emissions       total SO2
                                               (tpy)         emissions
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Point...................................       46,913.26              89
Nonpoint................................        2,986.99               6
Fire....................................        2,300.06               4
Onroad..................................          546.07               1
Nonroad.................................           47.85               0
                                         -------------------------------
    SO2 Emissions Total.................       52,794.23             100
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    SC DHEC provided NEI data for the years 2008, 2011, and 2014, which 
showed a decrease in SO2 emissions in the State of 
approximately 73 percent from 2008 to 2014. SC DHEC notes in its 
submission that the largest sources of SO2 emissions in 
South Carolina are power plants and other industrial facilities that 
burn fossil fuels. According to the NEI data in the State's submission 
and the 2014 NEI version 2 (shown in Table 2), the majority of 
SO2 emissions in South Carolina originate from fuel 
combustion at point sources.\15\ In 2014, the total SO2 
emissions from fuel combustion point sources in South Carolina 
comprised approximately 72 percent of the total SO2 
emissions in the State. Because emissions from the other listed source 
categories are more dispersed throughout the State, those categories 
are less likely to cause high ambient concentrations when compared to a 
point source on a ton-for-ton basis. Therefore, EPA believes that it is 
appropriate to focus the analysis on SO2 emissions from fuel 
combustion at South Carolina's point sources which are located within 
the ``urban scale,'' i.e., within 50 km of one or more state borders.
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    \15\ Residential fuel combustion is considered a nonpoint 
source, and thus, residential fuel combustion data is not included 
in the point source fuel combustion data and related calculations.

 Table 2--Summary of 2014 NEI (Version 2) SO2 Data for South Carolina by
                              Source Types
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                                                             Emissions
                        Category                               (tpy)
------------------------------------------------------------------------
Fuel Combustion: EGUs (All Fuel Types)..................       27,799.38
Fuel Combustion: Industrial Boilers/Internal Combustion        10,243.87
 Engines (All Fuel Types)...............................
Fuel Combustion: Commercial/Institutional (All Fuel                41.40
 Types).................................................
Fuel Combustion: Residential (All Fuel Types)...........          128.74
Industrial Processes (All Categories)...................        8,963.50
Mobile Sources (All Categories).........................        2,602.33
Fires (All Types).......................................        2,363.13
Waste Disposal..........................................          648.48
Solvent Processes.......................................            0.12
Miscellaneous (Non-Industrial)..........................            3.30
                                                         ---------------
    SO2 Emissions Total.................................       52,794.23
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    EPA's current implementation strategy for the 2010 1-hour 
SO2 NAAQS includes the flexibility to characterize air 
quality for stationary sources via either data collected at ambient air 
quality monitors sited to capture the points of maximum concentration, 
or air dispersion modeling. EPA's assessment of SO2 
emissions from fuel combustion at South Carolina's point sources 
located within approximately 50 km of another state and their potential 
impact on neighboring states is informed by all available data at the 
time of this rulemaking.\16\
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    \16\ EPA notes that the evaluation of other states' satisfaction 
of section 110(a)(2)(D)(i)(I) for the 2010 1-hour SO2 
NAAQS can be informed by similar factors found in this proposed 
rulemaking, but may not be identical to the approach taken in this 
or any future rulemaking for South Carolina, depending on available 
information and state-specific circumstances.
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    As discussed in section I.B., many air agencies used air dispersion 
modeling to characterize air quality in the vicinity of large 
SO2 emitting sources to identify the maximum 1-hour 
SO2 concentrations in ambient air which informed EPA's round 
2 and 3 SO2 designations. These 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. The 2010 1-hour SO2

[[Page 16803]]

standard is violated at an ambient air quality monitoring site (or in 
the case of dispersion modeling, at an ambient air quality receptor 
location) when the 3-year average of the annual 99th percentile of the 
daily maximum 1-hour average concentrations exceeds 75 ppb, as 
determined in accordance with Appendix T of 40 CFR part 50. EPA's 
preferred modeling platform for regulatory purposes is AERMOD (Appendix 
W of 40 CFR part 51).\17\ In most modeling analyses, the impacts of the 
actual emissions for one or more of the recent 3-year periods (e.g., 
2012-2014, 2013-2015, 2014-2016) were considered, and in some cases the 
modeling was of currently effective limits on allowable emissions in 
lieu of or as a supplement to modeling of actual emissions.
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    \17\ EPA established a draft non-binding technical assistance 
document to assist states and other interested parties in their 
efforts to characterize air quality through air dispersion modeling 
for sources that emit SO2 titled, ``SO2 NAAQS 
Designations Modeling Technical Assistance Document.'' This draft 
document was first released in spring 2013. Revised drafts were 
released in February and August of 2016 (see https://www.epa.gov/sites/production/files/2016-06/documents/so2modelingtad.pdf).
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    The available air dispersion modeling of large SO2 
sources can support transport related conclusions about whether sources 
in one state are potentially causing or contributing to violations of 
the 2010 1-hour SO2 standard in other states. While AERMOD 
was not designed specifically to address interstate transport, the 50-
km distance that EPA recommends for use with AERMOD aligns with the 
urban monitoring scale, and thus, EPA believes that the use of AERMOD 
provides a reliable indication of air quality for transport purposes.
    As described in this section, EPA proposes to conclude that an 
assessment of South Carolina's satisfaction of the prong 1 and 2 
requirements under section 110(a)(2)(D)(i)(I) of the CAA for the 2010 
1-hour SO2 NAAQS may be reasonably based upon evaluating the 
downwind impacts of SO2 emissions from fuel combustion at 
South Carolina's point sources located within approximately 50 km of 
another state and upon any regulations intended to address fuel 
combustion at South Carolina's point sources.

C. EPA's Prong 1 Evaluation--Significant Contribution to Nonattainment

    Prong 1 of the good neighbor provision requires states' plans to 
prohibit emissions that will significantly contribute to nonattainment 
of a NAAQS in another state. SC DHEC confirms in its submission that 
South Carolina's SIP contains adequate provisions to prevent sources 
and other types of emissions activities within the State from 
contributing significantly to nonattainment in any other state with 
respect to the 2010 1-hour SO2 standard. To evaluate South 
Carolina's satisfaction of prong 1, EPA assessed the State's 
implementation plan with respect to the following factors: (1) 
SO2 ambient air quality and emissions trends for South 
Carolina and neighboring states; (2) potential ambient impacts of 
SO2 emissions from certain facilities in South Carolina on 
neighboring states based on available air dispersion modeling results; 
(3) State statutes and SIP-approved regulations that address 
SO2 emissions; and (4) federally enforceable regulations 
that reduce SO2 emissions. A detailed discussion of South 
Carolina's SIP submission with respect to each of these factors 
follows.\18\ EPA proposes that these factors, taken together, support 
the Agency's proposed determination that South Carolina's SIP 
adequately prohibits emissions that will significantly contribute to 
nonattainment of the 2010 1-hour SO2 NAAQS in another state. 
EPA's proposed conclusion is based, in part, on the fact that the 
Agency does not have information indicating that there are violations 
of the 2010 1-hour SO2 NAAQS in the surrounding states. In 
addition, the downward trends in SO2 emissions and DVs for 
air quality monitors in the State, combined with federal and State 
regulations and statutes affecting SO2 emissions of South 
Carolina's sources, further support EPA's proposed conclusion.
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    \18\ EPA has reviewed South Carolina's submission, and where new 
or more current information has become available, is including this 
information as part of the Agency's evaluation of this submission.
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1. SO2 Air Dispersion Modeling
a. State Submission
    In its June 25, 2018, SIP revision, SC DHEC summarized how each of 
the State's sources subject to the DRR elected to comply with this rule 
by either taking a federally-enforceable limit or using either modeling 
or monitoring to characterize SO2 air quality around the 
source. Of the eight sources in the State subject to the DRR, three 
accepted federally-enforceable permit limits and five sources conducted 
dispersion modeling.\19\ SC DHEC provided a summary of the air 
dispersion modeling results for the five modeled sources: Century 
Aluminum of South Carolina \20\ (Century Aluminum); International 
Paper-Eastover Mill (IP Eastover); Resolute FP US INC (Resolute); 
Santee Cooper Cross Generating Station (Santee Cooper Cross); and SCE&G 
Wateree Station (SCE&G Wateree). IP Eastover and SCE&G Wateree were 
modeled together. Of these five sources, one source (Resolute) is 
within 50 km of another state (North Carolina) at approximately 7 km 
using the nearest property boundary to North Carolina and modeled a 
maximum 2010 1-hour SO2 DV of 69 ppb. SC DHEC notes that 
Resolute used a modeling grid which extended approximately 4 km into 
North Carolina. A summary of the modeling results for Resolute, 
including supplemental data EPA has reviewed as part of the Agency's 
analysis, is shown in Table 3 of section III.C.1.b of this action.
---------------------------------------------------------------------------

    \19\ South Carolina's DRR sources which accepted federally-
enforceable permit limits to exempt out of the DRR requirements are: 
Duke Energy Carolinas LLC--W.S. Lee Steam Station; South Carolina 
Electric & Gas (SCE&G) McMeekin Station; and WestRock CP LLC 
(formerly RockTenn). See Docket ID No. EPA-HQ-OAR-2017-0003. Thus, 
there is no available air dispersion modeling under the DRR for 
these sources.
    \20\ Century Aluminum was formerly known as Alumax of South 
Carolina.
---------------------------------------------------------------------------

b. EPA Analysis
    For the SO2 air dispersion modeling factor, EPA 
evaluated the DRR modeling data in South Carolina's June 25, 2018, 
submission for sources in the State and supplemented this data with 
available, existing DRR modeling results for sources in the adjacent 
states of Georgia and North Carolina that are within 50 km of the South 
Carolina border.\21\ The purpose of evaluating modeling results in 
adjacent states within 50 km of the South Carolina border is to 
ascertain whether these areas are attaining the 2010 1-hour 
SO2 standard and, if not, whether any nearby sources in 
South Carolina are contributing to a NAAQS violation. In addition, EPA 
identified South Carolina SO2 emission sources emitting 
greater than 100 tons of SO2 in 2017 that are not subject to 
the DRR and are located up to 50 km from South Carolina's border to 
evaluate whether the SO2 emissions from these sources could 
interact with SO2 emissions from the nearest source in a 
neighboring state

[[Page 16804]]

in such a way as to contribute significantly to nonattainment in that 
state.
---------------------------------------------------------------------------

    \21\ Appendix A.1--titled, ``AERMOD (AMS/EPA Regulatory Model)'' 
of Appendix W to 40 CFR part 51--is appropriate for SO2 
in instances where steady-state assumptions for transport distances 
up to 50 km occur. While not designed specifically to address 
interstate transport, the 50-km distance which EPA recommends for 
use with AERMOD aligns with the urban monitoring scale, and thus, 
EPA believes that the use of AERMOD provides a reliable indication 
of SO2 air quality for transport purposes.
---------------------------------------------------------------------------

    Table 3 provides a summary of the modeling results for Resolute, 
the one modeled DRR source in South Carolina which is located within 50 
km of another state (North Carolina). The modeling analyses for 
Resolute resulted in no modeled violations of the 2010 1-hour 
SO2 NAAQS within the 50-km area surrounding the facility and 
no violations of the standard within the modeling domain which extends 
into North Carolina. All other areas within 50 km of Resolute are 
contained within South Carolina's borders. As a result, no further 
analysis of any other neighboring states is necessary for assessing the 
impacts of the interstate transport of SO2 pollution from 
Resolute.
    Table 4 provides a summary of the modeling results for DRR sources 
in other neighboring states which are located within 50 km of South 
Carolina and which elected to provide air dispersion modeling under the 
DRR: Three sources in Georgia (Georgia Power Company--Plant McIntosh 
(Plant McIntosh), Georgia-Pacific Consumer Products--Savannah River 
Mill (Savannah River Mill), International Paper--Savannah (IP-
Savannah)) \22\ and two sources in North Carolina (Allen Steam 
Station--Duke Energy Carolinas, LLC (Duke-Allen) \23\ and Duke Energy's 
Marshall Steam Station (Duke-Marshall)).\24\ The predicted maximum 
impacts from the model did not violate the 2010 1-hour SO2 
NAAQS for any of the five sources.\25\
---------------------------------------------------------------------------

    \22\ Georgia Power's Plant Kraft is a DRR source located less 
than 5 km from the South Carolina border which has shut down as of 
October 13, 2015, and the operating permit was formally revoked on 
November 9, 2016. The DRR modeling results for Georgia's DRR round 3 
sources may be found at: https://www.epa.gov/sites/production/files/2017-08/documents/10_ga-so2-rd3-final.pdf.
    \23\ The Duke-Allen facility did not meet the DRR emission 
threshold of 2,000 tons or more annually. However, North Carolina 
elected to characterize the area around the source through air 
dispersion modeling.
    \24\ Given that distances are approximate, the Duke-Marshall 
facility is included in Table 4 with an approximate distance of 53 
km from the South Carolina border.
    \25\ Georgia's Plant McIntosh and Savannah River Mill were 
modeled together as shown in Table 4.

                                 Table 3--South Carolina Sources With DRR Modeling Located Within 50 km of Another State
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Approximate  distance                                2010 1-hour
            DRR source                      County            from  source to      Other facilities included   SO2 Model DV     Model grid extends into
                                                               adjacent state            in  modeling              (ppb)            another state?
--------------------------------------------------------------------------------------------------------------------------------------------------------
Resolute..........................  York.................  7 km.................  Yes--Duke-Allen (NC);                 69 *  Yes--into NC (western
                                                                                   Winthrop University;                        portion of Union County
                                                                                   General Chemicals, LLC;                     in North Carolina)
                                                                                   Guardian Industries;
                                                                                   Spring Industries--Leroy
                                                                                   Plant.
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Resolute's 2010 1-hour SO2 modeled DV is based on 2012-2014 actual emissions for Resolute and all North Carolina permitted facilities within 50 km of
  the source, and allowable emissions for all South Carolina permitted facilities within 50 km of the source.


                                 Table 4--Other State's Sources with DRR Modeling Located Within 50 km of South Carolina
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Approximate
                                                          distance from         Other facilities      2010 1-hour SO2 model DV   Model grid extends into
           DRR source                County (state)      source to South      included in modeling              (ppb)                another state?
                                                         Carolina border
--------------------------------------------------------------------------------------------------------------------------------------------------------
Plant McIntosh (Modeled with      Effingham (GA).....  Less than 5 km.....  Effingham County Power    71.6 for both Plant       Yes--into SC (western
 Savannah River Mill).                                                       (GA); SCE&G-Jasper        McIntosh and Savannah     portion of Jasper
                                                                             Generating Station        River Mill (based on      County, SC).
                                                                             (SC)--(based on           2012-2014 actual
                                                                             allowable/potential to    emissions for Plant
                                                                             emit (PTE) emissions).    McIntosh).
Savannah River Mill (Modeled      Effingham (GA).....  Less than 5 km.....  Effingham County Power    71.6 for both Plant       Yes--into SC (western
 with Plant McIntosh).                                                       (GA); SCE&G-Jasper        McIntosh and Savannah     portion of Jasper
                                                                             Generating Station        River Mill *.             County, SC).
                                                                             (SC)--.
IP--Savannah....................  Chatham (GA).......  Less than 5 km.....  None....................  66 (based on 2011-2013    Yes--into SC (western
                                                                                                       actual and allowable/     portion of Jasper
                                                                                                       PTE emissions).           County, SC).
Duke-Allen......................  Gaston (NC)........  5 km...............  Duke-Marshall...........  46.6 (based on 2013-2015  Yes--into SC (York
                                                                                                       actual SO emissions).     County and portions of
                                                                                                                                 Cherokee, Union,
                                                                                                                                 Chester, Lancaster, and
                                                                                                                                 Chesterfield Counties
                                                                                                                                 in SC).
Duke-Marshall...................  Catawba (NC).......  53 km..............  Duke-Allen..............  68 (based on 2013-2015    Yes--into SC (small
                                                                                                       actual SO emissions).     portion of York and
                                                                                                                                 Cherokee Counties in
                                                                                                                                 SC).
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Savannah River Mill's 2010 1-hour SO2 modeled DV is based on 2012-2014 actual emissions for three primary power boilers and allowable/PTE emissions
  for 13 emissions units at Savannah River Mill. (For more details, see pp. 67-68 of EPA's Technical Support Document: Chapter 10 Proposed Round 3 Area
  Designations for the 2010 1-Hour SO2 Primary National Ambient Air Quality Standard for Georgia located at https://www.epa.gov/sites/production/files/2017-08/documents/10_ga-so2-rd3-final.pdf.)


[[Page 16805]]

    As mentioned previously, EPA finds that it is appropriate to 
examine the impacts of SO2 emissions from stationary sources 
in South Carolina in distances ranging from zero km to 50 km from the 
sources. Therefore, in addition to those sources addressed in Tables 3 
and 4 of this action, EPA assessed the potential impacts of 
SO2 emissions from stationary sources not subject to the DRR 
and located up to 50 km from South Carolina's borders to evaluate 
trends in area-wide air quality. Table 5 lists sources in South 
Carolina not characterized under the DRR \26\ that emitted greater than 
100 tpy of SO2 in 2017 and are located within 50 km of the 
State's border. All three of the identified sources were located along 
the border of South Carolina and North Carolina.
---------------------------------------------------------------------------

    \26\ One source, Westrock CP, LLC accepted a permit limit to 
exempt out of being subject to the DRR.

                            Table 5--South Carolina Non-DRR SO2 Sources Emitting Greater Than 100 tpy Near Neighboring States
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                          Approximate
                                             2017 Annual     Approximate                                  distance to
                                            SO2 emissions    distance to                                    nearest       Nearest neighboring state SO2
          South Carolina source                (tons)      South Carolina   Closest neighboring state     neighboring     source & 2017 emissions (>100
                                                             border (km)                                   state SO2              tons of SO2)
                                                                                                          source (km)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Milliken & Co. Magnolia Plant............             697             5.5  North Carolina.............              23  Duke Energy Carolinas, LLC--
                                                                                                                         Cliffside Steam Station (858
                                                                                                                         tons).
Guardian Industries......................             103            22.5  North Carolina.............              53  Duke--Allen (354 tons).
WestRock CP LLC..........................           1,480              44  North Carolina.............              68  Pilkington North America, Inc.
                                                                                                                         (Pilkington) (383 tons).
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Currently, EPA does not have monitoring or modeling data suggesting 
that North Carolina is impacted by SO2 emissions from the 
Milliken & Co. Magnolia Plant or WestRock CP LLC. With regard to the 
WestRock facility, EPA believes that the 68-km distance between the 
WestRock facility in South Carolina and the Pilkington facility, the 
nearest source in North Carolina with SO2 emissions greater 
than 100 tpy, makes it unlikely that SO2 emissions from 
WestRock could interact with SO2 emissions from Pilkington 
in such a way as to contribute significantly to nonattainment in North 
Carolina.
    Allowable SO2 emissions from the Guardian Industries 
facility were included in South Carolina's modeling of the Resolute DRR 
source,\27\ which was addressed in Table 3. This modeling did not show 
any violations of the 2010 1-hour SO2 NAAQS within 50 km of 
the South Carolina border, and thus, indicates that Guardian Industries 
does not significantly contribute to nonattainment of the 2010 1-hour 
SO2 NAAQS in any other state.
---------------------------------------------------------------------------

    \27\ See pp.81-82 and p.92 of EPA's Technical Support Document: 
Chapter 37 Intended Round 3 Area Designations for the 2010 1-Hour 
SO2 Primary National Ambient Air Quality Standard for 
South Carolina located at: https://www.epa.gov/sites/production/files/2017-08/documents/38sc_so2_rd3-final.pdf.
---------------------------------------------------------------------------

    The modeling results in Tables 3 and 4 predict no violations of the 
2010 1-hour SO2 NAAQS within 50 km of the South Carolina 
border, and thus, EPA believes that these results, weighed along with 
the other factors in this document and the Agency's analysis of the 
South Carolina sources addressed in Table 5, support EPA's proposed 
conclusion that sources in South Carolina do not significantly 
contribute to nonattainment of the 2010 1-hour SO2 NAAQS in 
any other state.
2. SO2 Emissions Trends
a. State Submission
    As part of its SIP submission, South Carolina presented 
SO2 emissions trends both statewide (for the years 2008-
2014) and for the State's title V sources (for the years 2008-2016). 
Statewide SO2 emissions have decreased by approximately 73 
percent from 197,136 tpy in 2008 to 52,782 tpy in 2014,\28\ and 
SO2 emissions from South Carolina's title V sources have 
decreased by approximately 88 percent from 191,058 tpy in 2008 to 
22,422 tpy in 2016.
---------------------------------------------------------------------------

    \28\ EPA notes there is a slight difference in the 2014 NEI 
value for South Carolina's SO2 emissions between what SC 
DHEC provided based on version 1 of the NEI (52,782 tpy) and the 
value that EPA relied upon from version 2 of the NEI (52,794 tpy).
---------------------------------------------------------------------------

b. EPA Analysis
    EPA reviewed the statewide and title V source SO2 
emissions trends data provided by South Carolina and agrees that the 
data show a significant decline (73 and 88 percent, respectively, as 
noted earlier). Based on the emissions trends information in South 
Carolina's submission, EPA believes that these declining SO2 
emissions may suggest that South Carolina does not significantly 
contribute to nonattainment of the 2010 1-hour SO2 NAAQS in 
any other state, particularly given that SO2 emissions 
limits for South Carolina's title V sources are federally enforceable 
conditions established in title V permits.
3. SO2 Ambient Air Quality
a. State Submission
    In its June 25, 2018, SIP submission, SC DHEC illustrated 
graphically that the DVs from 2008 through 2017 at nine out of 10 
monitors in South Carolina in EPA's Air Quality System (AQS) \29\ 
(``AQS monitors'') have remained well below the 2010 1-hour 
SO2 NAAQS since 2008.\30\ The one monitor with data above 
the 2010 1-hour SO2 NAAQS from 2008 to 2010 attained the 
standard in 2011, and the DVs for this monitor sharply decreased 
between 2011 to 2017. SC DHEC notes that the State's AQS monitors are 
all attaining the 2010 1-hour SO2 NAAQS and the DVs at these 
monitors show a consistent downward trend. In addition, SC DHEC noted 
that the highest monitored DV in the State for the 2014-2016 time 
period is 29 ppb, which is 39 percent of the 2010 1-hour SO2 
NAAQS.
---------------------------------------------------------------------------

    \29\ EPA's AQS contains ambient air pollution data collected by 
EPA, state, local, and tribal air pollution control agencies. See 
https://www.epa.gov/air-trends/air-quality-design-values.
    \30\ Three of the 10 monitors located in South Carolina shown in 
the figure on p.8 of the State's June 25, 2018, SIP submission 
(named ``DHEC,'' ``Powdersville,'' and ``York'') have shut down.
---------------------------------------------------------------------------

    SC DHEC also included a figure displaying AQS monitors located in 
South Carolina and in other states within 50 km of the South Carolina 
border. This figure depicts a total of 14 AQS monitors (seven South 
Carolina monitors with DVs; four monitors in other states with DVs; and 
three AQS monitors in North Carolina that were established to 
characterize the air quality around specific sources subject

[[Page 16806]]

to EPA's DRR to inform the Agency's future round 4 designations for the 
2010 1-hour SO2 NAAQS in lieu of modeling (hereinafter 
referred to as ``DRR monitors''). Of the 11 monitors with DVs, 10 
monitors have had DVs at or just below the 2010 1-hour SO2 
NAAQS since the 2009-2011 DV time period, and all DVs have been below 
the standard since the 2013-2015 DV period. Two of the North Carolina 
DRR monitors within 50 km of South Carolina have annual 99th percentile 
1-hour SO2 concentrations above the 2010 1-hour 
SO2 NAAQS for 2017. SC DHEC also provided the highest 
monitored SO2 DVs for the years 2014-2016 at AQS monitors 
anywhere in Florida, Georgia, and North Carolina (i.e., 81, 60, and 23 
ppb, respectively).\31\ SC DHEC notes that the nearest SO2 
nonattainment area is the Nassau County partial area \32\ in Florida, 
which is over 150 km from the South Carolina border.
---------------------------------------------------------------------------

    \31\ EPA notes that Florida is not adjacent to South Carolina.
    \32\ The term ``partial area'' in this instance refers to when 
EPA has designated a portion a county nonattainment for a NAAQS.
---------------------------------------------------------------------------

b. EPA Analysis
    Since the time of development of South Carolina's SIP submission, 
certified AQS monitoring data has become available for South Carolina 
and the surrounding states to inform the 2015-2017 DVs. EPA has 
summarized the DVs from 2012 to 2017 for AQS monitors in South Carolina 
within 50 km of another state in Table 6 and for AQS monitors in the 
surrounding states of Georgia and North Carolina within 50 km of South 
Carolina in Table 7 using relevant data from EPA's AQS DV reports for 
recent and complete 3-year periods.

                         Table 6--2010 1-Hour SO2 DVs for AQS Monitors in South Carolina Within 50 km of Another State's Border
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                        AQS site    2010-2012    2011-2013    2012-2014    2013-2015    2014-2016    2015-2017    Approximate  distance
               County                     code       DV (ppb)     DV (ppb)     DV (ppb)     DV (ppb)     DV (ppb)     DV (ppb)    to state  border (km)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Greenville..........................    450450008         * ND         * ND         * ND            3            2            2  37 (NC)
Oconee..............................    450730001         * ND         * ND         * ND            3            2            2  3 (GA)
--------------------------------------------------------------------------------------------------------------------------------------------------------
* ND indicates ``No Data'' due to monitor startup or shutdown (operated less than three years), data quality issues, or incomplete data.

    As shown in Table 6, the 2015, 2016, and 2017 DVs for the two 
monitoring sites in South Carolina (Greenville and Oconee Counties) 
within 50 km of another state's border have remained well below the 
2010 1-hour SO2 NAAQS.
    Table 7 shows that there are three AQS monitors in Georgia (Chatham 
and Richmond Counties) and one AQS monitor in North Carolina 
(Mecklenberg County) with 3-year DVs which are located within 50 km of 
the South Carolina border. Currently, there are no AQS monitors 
indicating a violation of the 2010 1-hour SO2 NAAQS located 
within 50 km of South Carolina in the surrounding states of Georgia and 
North Carolina. Further, the DVs for the monitors in Table 7 have 
declined since 2013 for Georgia's Chatham County monitor with AQS site 
code 130511002 and since 2012 for North Carolina's Mecklenberg County 
monitor. For Georgia's Richmond County monitor and Chatham County 
monitor with AQS site code 130511002, the DVs similarly show a downward 
trend, excluding those time periods for which there is no data to 
determine a DV. Also, the most recent DVs for 2015-2017 are well below 
the 2010 1-hour SO2 NAAQS. Thus, EPA believes that these 
data support EPA's proposed conclusion that South Carolina does not 
significantly contribute to nonattainment of the 2010 1-hour 
SO2 NAAQS in any other state.

                           Table 7--2010 1-Hour SO2 DVs for AQS Monitors Within 50 km of South Carolina in Surrounding States
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                            Approximate
               State                        County           AQS site   2010-2012  2011-2013  2012-2014  2013-2015  2014-2016  2015-2017  distance to SC
                                                               code      DV (ppb)   DV (ppb)   DV (ppb)   DV (ppb)   DV (ppb)   DV (ppb)    border (km)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Georgia...........................  Chatham..............    130511002         68         79         78         70         52         48               3
                                    Chatham..............    130510021         74         66       * ND       * ND       * ND         32               2
                                    Richmond.............    132450091       * ND       * ND       * ND         61         60         52               6
North Carolina....................  Mecklenberg..........    371190041         14         10          7          7          5          5              20
--------------------------------------------------------------------------------------------------------------------------------------------------------
* ND indicates ``No Data'' due to monitor startup or shutdown (operated less than three years), data quality issues, or incomplete data.

    As previously discussed, EPA's definitions of spatial scales for 
SO2 monitoring networks indicate that distances up to 50 km 
from a stationary source would be useful for assessing trends in area-
wide air quality. Thus, EPA also evaluated monitoring data provided to 
date for DRR monitors located in states adjacent to South Carolina 
within 50 km of the State's border. These DRR monitors do not have 
three or more years of complete data to determine the DVs for these 
monitors. However, EPA evaluated the available, annual 99th percentile 
SO2 concentration data for these monitors.
    No sources in South Carolina elected to establish monitors under 
the DRR. However, Table 8 lists three DRR sources in North Carolina 
within 50 km of the South Carolina border which elected to establish 
SO2 monitors to characterize the air quality in the 
associated source areas. The Buncombe County monitor in North Carolina 
was sited in the vicinity of the Asheville Steam Electric Plant--Duke 
Energy Progress, Inc (Duke-Asheville), a DRR source. Though a single 
maximum 1-hour concentration is not directly comparable to the 2010 1-
hour SO2 NAAQS, which is in the form of the 3-year average 
of the 99th percentile of

[[Page 16807]]

daily maximum 1-hour SO2 values, EPA notes that the highest 
concentration observed at the Buncombe County monitor in 2017 was 16.6 
ppb, which is approximately 78 percent below the level of the 2010 1-
hour SO2 NAAQS. The other two DRR monitors in North Carolina 
within 50 km of South Carolina--the Brunswick and Haywood County 
monitoring sites--both exceeded the 2010 1-hour SO2 NAAQS 
based on one year of complete data for 2017. For 2018, only the Haywood 
County monitoring site exceeded the 2010 1-hour SO2 NAAQS. 
The Brunswick and Haywood County monitoring sites are sited in the area 
of maximum concentration for the DRR sources named CPI USA North 
Carolina--Southport Plant (CPI) and Evergreen Packaging Group- Canton 
Mill (Evergreen), respectively.
    EPA evaluated whether there are any sources in South Carolina 
within 50 km of the State's border which could potentially be 
contributing to the exceedances in 2017 and 2018 at the Brunswick 
County and Haywood County monitors in North Carolina. With respect to 
the Haywood County monitor, there is only one source in South Carolina 
within 50 km of the State's border in the direction of the Haywood 
County monitor. This source, Milliken Enterprise Plant, is located 
approximately 12.5 km from the South Carolina border and emitted 4.25, 
4.25, and 0.05 tons of SO2 in 2015, 2016, and 2017, 
respectively. EPA believes that the Milliken Enterprise Plant is not 
contributing to the exceedances at the Haywood County monitor due to 
the source's distance of approximately 72.5 km from the monitor and the 
declining SO2 emissions trend from 2015 to 2017. With 
respect to the Brunswick County monitor, there are two sources in South 
Carolina within 50 km of the State's border in the direction of the 
Brunswick County monitor. The two sources, Horry County Solid Waste 
Authority and Santee Cooper Myrtle Beach, are located approximately 31 
km and 37 km, respectively, from the South Carolina border in the 
direction of the Brunswick County monitor. The Horry County Solid Waste 
Authority emitted 13.12, 13.12, and 12.88 tons of SO2 in 
2015, 2016, and 2017, respectively. The Santee Cooper Myrtle Beach 
facility emitted 0.02, 0.01, and 0.03 tons of SO2 in 2015, 
2016, and 2017, respectively. EPA believes that the Horry County Solid 
Waste Authority and the Santee Cooper Myrtle Beach facility are not 
contributing to the exceedances at the Brunswick County monitor due to 
the sources' distances of approximately 79 km and 85 km, respectively, 
from the monitor. Thus, after careful review of the State's assessment, 
supporting documentation, available monitoring data, and EPA's analysis 
suggesting that there are no sources in South Carolina within 50 km of 
the Brunswick and Haywood County DRR monitors which could be 
contributing to the exceedances at the Brunswick and Haywood County DRR 
monitors, EPA proposes to conclude that these monitoring data do not 
provide evidence of South Carolina contributing significantly to 2010 
1-hour SO2 violations in the neighboring states.

 Table 8--2010 1-Hour SO2 99th Percentile Concentrations for Round 4 DRR Monitors Within 50 km of South Carolina
                                          Located in Surrounding States
----------------------------------------------------------------------------------------------------------------
                                                                     2017 99th       2018 99th
                                     Round 4                        percentile      percentile      Approximate
        County (state)          monitored source   AQS site code   concentration   concentration  distance to SC
                                                                       (ppb)           (ppb)        border (km)
----------------------------------------------------------------------------------------------------------------
Buncombe (NC).................  Duke-Asheville..       370210037            16.6             9.8              32
Brunswick (NC)................  CPI.............       370190005            82.5            55.1              50
Haywood (NC)..................  Evergreen.......       370870013           206.8           213.4              48
----------------------------------------------------------------------------------------------------------------

4. SIP-Approved Regulations and State Statutes Addressing 
SO2 Emissions
a. State Submission
    South Carolina identified State statutes and SIP-approved measures 
which help ensure that SO2 emissions in the State do not 
significantly contribute to nonattainment of the 2010 1-hour 
SO2 NAAQS in any other state. SC DHEC lists the following 
SIP-approved South Carolina regulations which establish emission limits 
and other control measures for SO2: Regulation 61-62.5, 
Standard No. 7, Prevention of Significant Deterioration; Regulation 61-
62.5, Standard No. 7.1, Nonattainment New Source Review; Regulation 61-
62.96, Nitrogen Oxides (NOX) and Sulfur Dioxide 
(SO2) Budget Trading Program; Regulation 61-62.97, Cross-
State Air Pollution Rule (CSAPR) Trading Program; and Regulation 61-
62.1, Definitions and General Requirements. In addition, SC DHEC 
promulgated Regulation 61-62.72, Acid Rain, to comply with the EPA's 
Acid Rain Program, enacted to reduce acid deposition by reducing 
SO2 and NOX emissions from fossil fuel-fired 
power plants. SC DHEC also notes that South Carolina's Pollution 
Control Act, SC Code Section 48-1-10 et seq., and State Agency Rule 
Making and Adjudication of Contested Cases, SC Code Section 1-23-10 et 
seq., provide for control of SO2 emissions in the State.\33\
---------------------------------------------------------------------------

    \33\ These South Carolina statutes are not approved into the 
State's implementation plan.
---------------------------------------------------------------------------

b. EPA Analysis
    EPA believes that South Carolina's statutes and SIP-approved 
measures which establish emission limits, permitting requirements, and 
other control measures for SO2 effectively address emissions 
of SO2 from sources in the State. For the purposes of 
ensuring that SO2 emissions at new major sources or major 
modifications at existing major sources in South Carolina do not 
contribute significantly to nonattainment or interfere with maintenance 
of the NAAQS, the State has a SIP-approved major source new source 
review (NSR) program. South Carolina's SIP-approved nonattainment NSR 
regulation is Regulation 61-62.5, Standard No. 7.1--Nonattainment New 
Source Review, which applies to the construction of any new major 
stationary source or major modification at an existing major stationary 
source in an area designated as nonattainment. The State's SIP-approved 
prevention of significant deterioration (PSD) regulation, Regulation 
61-62.5, Standard No. 7--Prevention of Significant Deterioration, 
applies to the construction of any new major stationary source or major 
modification at an existing major stationary source in an area 
designated as attainment or unclassifiable or not yet designated. 
Regulation 61-62.1, Section II--Permit Requirements governs, among 
other things, the preconstruction permitting of modifications and 
construction of minor stationary sources in South Carolina. These major 
(i.e., PSD and

[[Page 16808]]

nonattainment NSR (NNSR)) and minor NSR rules ensure that 
SO2 emissions due to major modifications at existing major 
stationary sources, modifications at minor stationary sources, and the 
construction of new major and minor sources in South Carolina will not 
contribute significantly to nonattainment of the 2010 1-hour 
SO2 NAAQS in neighboring states.
5. Federally Enforceable Regulations Addressing SO2 
Emissions in South Carolina
a. State Submission
    SC DHEC listed the following EPA rules which reduce SO2 
emissions from various sources: Acid Rain Nitrogen Oxides Emission 
Reduction Program; PSD/NNSR; Cap and Trade Programs for SO2 
under 40 CFR part 96; Regional Haze; Heavy-Duty Engine and Vehicle 
Standards and Highway Diesel Fuel Sulfur Control Requirements; Mercury 
and Air Toxics Standards; and the Cross-State Air Pollution Rule. The 
State notes that the overall effect of these rules has been a 56 
percent reduction in SO2 emissions nationally from 2010 to 
2016.
b. EPA Analysis
    EPA believes that the federal control measures for SO2 
which South Carolina lists in the State's June 2018 submission 
effectively address emissions of SO2 from sources in the 
State and help ensure that SO2 emissions from South Carolina 
do not contribute significantly to nonattainment of the 2010 1-hour 
SO2 NAAQS in another state.
6. Conclusion
    EPA proposes to determine that South Carolina's June 25, 2018, SIP 
submission satisfies the requirements of prong 1 of CAA section 
110(a)(2)(D)(i)(I). This proposed determination is based on the 
following considerations: DVs for South Carolina's AQS SO2 
monitors within 50 km of another state's border have remained well 
below the 2010 1-hour SO2 NAAQS from 2015-2017; DVs for 
Georgia's and North Carolina's regulatory monitors within 50 km of 
South Carolina's border have 2017 DVs below the 2010 1-hour 
SO2 NAAQS; modeling for the one South Carolina DRR source 
within 50 km of another state's border estimates impacts below the 2010 
1-hour SO2 NAAQS; modeling for DRR sources in the 
surrounding states of Georgia and North Carolina within 50 km of South 
Carolina indicates that the areas around these sources do not violate 
the 2010 1-hour SO2 NAAQS; downward SO2 emissions 
trends in South Carolina may suggest that the State's sources are not 
likely contributing to other states' ability to attain or maintain the 
2010 1-hour SO2 NAAQS; SO2 emissions from South 
Carolina sources not subject to the DRR which emitted over 100 tons of 
SO2 in 2017 are not likely interacting with SO2 
emissions from the nearest source in a bordering state in such a way as 
to contribute significantly to nonattainment in North Carolina; annual 
99th percentile 1-hour SO2 concentrations at the Buncombe 
County DRR monitor in North Carolina are well below the 2010 1-hour 
SO2 NAAQS; and current South Carolina statutes and SIP-
approved measures and federal emissions control programs adequately 
control SO2 emissions from sources within South Carolina.
    Based on the analysis provided by South Carolina in its SIP 
submission and EPA's analysis of the factors described in section 
III.C, EPA proposes to find that sources within South Carolina will not 
contribute significantly to nonattainment of the 2010 1-hour 
SO2 NAAQS in any other state.

D. EPA's Prong 2 Evaluation--Interference With Maintenance of the NAAQS

    Prong 2 of the good neighbor provision requires state plans to 
prohibit emissions that will interfere with maintenance of a NAAQS in 
another state.
1. State Submission
    In its June 25, 2018, SIP submission, SC DHEC states that South 
Carolina's SIP contains adequate provisions to prevent sources and 
emissions activities within South Carolina from interfering with 
maintenance of the 2010 1-hour SO2 NAAQS in any other state 
based on the downward trend in SO2 emissions in the State 
and the Southeast and on federal and state control measures. As 
discussed in section III.A, SC DHEC included statewide SO2 
emissions trends in its SIP submittal which show that SO2 
emissions have declined since approximately 2005 and are continuing to 
decline. SC DHEC included a figure showing SO2 emissions 
trends in the Southeast from 2000 to 2016 and indicated that there is a 
consistent downward trend in SO2 emissions over this time 
period. The State noted that these SO2 emissions reductions 
are primarily due to federal regulations requiring pollution control 
devices and the decreased use of coal for electricity. In addition, as 
discussed in sections III.C.4 and III.C.5, SC DHEC has statutes and 
SIP-approved measures which address sources of SO2 emissions 
in South Carolina and there are also federal measures that control 
SO2 emissions in the State.
2. EPA Analysis
    In North Carolina v. EPA, the D.C. Circuit explained that the 
regulating authority must give prong 2 ``independent significance'' 
from prong 1 by evaluating the impact of upwind state emissions on 
downwind areas that, while currently in attainment, are at risk of 
future nonattainment. North Carolina v. EPA, 531 F.3d at 910-911 (D.C. 
Cir. 2008). For the prong 2 analysis, EPA evaluated the emissions 
trends provided by South Carolina for the State and the Southeast, 
evaluated air quality data, and assessed how future sources of 
SO2 are addressed through existing SIP-approved and 
federally enforceable regulations. Given the continuing trend of 
decreasing SO2 emissions from sources within South Carolina 
and the fact that all areas in other states within 50 km of the South 
Carolina border have DVs attaining the 2010 1-hour SO2 
NAAQS, EPA believes that evaluating whether these decreases in 
emissions can be maintained over time is a reasonable criterion to 
ensure that sources within South Carolina do not interfere with its 
neighboring states' ability to maintain the 2010 1-hour SO2 
NAAQS.
    Regarding SO2 air quality trends in the southeastern 
United States, EPA notes that this region of the country has 
experienced an 82 percent decrease in the annual 99th percentile of 
daily maximum 1-hour averages between 2000 and 2017 based on 24 
monitoring sites, and the most recently available data for 2017 
indicates that the mean value at these sites was approximately 14 
ppb.\34\ When this trend is evaluated alongside the monitored 
SO2 concentrations within South Carolina as well as the 
SO2 concentrations recorded at regulatory monitors in the 
surrounding states of Georgia and North Carolina shown in Tables 6 and 
7 of this document, EPA believes that emissions trends in South 
Carolina due to sources from within the State are not significantly 
different than the overall decreasing monitored SO2 
concentration trend in the Southeast. With respect to air quality data 
trends, the current 2015-2017 DVs for AQS SO2 monitors both 
in South Carolina within 50 km of another state's border and in Georgia 
and North Carolina within 50 km of South Carolina's border are below 
the 2010 1-hour SO2 NAAQS. Further, modeling results for DRR 
sources within 50 km of South Carolina's border both

[[Page 16809]]

within the State and in the states of Georgia and North Carolina 
demonstrate attainment of the 2010 1-hour SO2 NAAQS, and 
thus, demonstrate that South Carolina's largest point sources of 
SO2 are not expected to interfere with maintenance of the 
2010 1-hour SO2 NAAQS in another state.
---------------------------------------------------------------------------

    \34\ See https://www.epa.gov/air-trends/sulfur-dioxide-trends.
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    As discussed in sections III.C.4 and III.C.5, EPA believes that 
federal and State regulations and statutes that both directly and 
indirectly reduce emissions of SO2 in South Carolina help 
ensure that the State does not interfere with maintenance of the NAAQS 
in another state. SO2 emissions from future major 
modifications and new major sources will be addressed by South 
Carolina's SIP-approved major NSR regulations described in section 
III.C.4. In addition, South Carolina has a SIP-approved minor NSR 
permit program addressing small emission sources of SO2. The 
permitting regulations contained within these programs are designed to 
ensure that emissions from these activities do not interfere with 
maintenance of the NAAQS in the State or in any other state.
3. Conclusion
    EPA proposes to determine that South Carolina's June 25, 2018, SIP 
submission satisfies the requirements of prong 2 of CAA section 
110(a)(2)(D)(i)(I). This determination is based on the following 
considerations: SO2 emissions statewide from 2008 to 2014 in 
South Carolina have declined significantly; current South Carolina 
statutes and SIP-approved measures and federal emissions control 
programs adequately control SO2 emissions from sources 
within South Carolina; South Carolina's SIP-approved PSD and minor 
source NSR permit programs will address future large and small 
SO2 sources; current DVs for AQS SO2 monitors 
both in South Carolina within 50 km of another state's border and in 
Georgia and North Carolina within 50 km of South Carolina's border are 
below the 2010 1-hour SO2 NAAQS; and modeling for DRR 
sources within 50 km of South Carolina's border both within the State 
and in Georgia and North Carolina demonstrates that South Carolina's 
largest point sources of SO2 are not expected to interfere 
with maintenance of the 2010 1-hour SO2 NAAQS in another 
state. Based on the analysis provided by South Carolina in its SIP 
submission and EPA's supplemental analysis of the factors described in 
section III.C and III.D of this document, EPA proposes to find that 
emission sources within South Carolina will not interfere with 
maintenance of the 2010 1-hour SO2 NAAQS in any other state.

IV. Proposed Action

    In light of the above analysis, EPA is proposing to approve South 
Carolina's June 25, 2018, SIP submission as demonstrating that South 
Carolina's SIP has adequate provisions prohibiting any source or other 
type of emissions activity in the State from emitting any air pollutant 
in amounts that will contribute significantly to nonattainment or 
interfere with maintenance of the 2010 1-hour SO2 NAAQS in 
another state.

V. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP 
submission that complies with the provisions of the Act and applicable 
Federal regulations. See 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in 
reviewing SIP submissions, EPA's role is to approve state choices, 
provided that they meet the criteria of the CAA. This action merely 
proposes to approve state law as meeting Federal requirements and does 
not impose additional requirements beyond those imposed by state law. 
For that reason, this proposed action:
     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);
     Is not an Executive Order 13771 (82 FR 9339, February 2, 
2017) regulatory action because SIP approvals are exempted under 
Executive Order 12866;
     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
     Does not provide EPA with the discretionary authority to 
address, as appropriate, disproportionate human health or environmental 
effects, using practicable and legally permissible methods, under 
Executive Order 12898 (59 FR 7629, February 16, 1994).
    In addition, this proposed action for South Carolina does not have 
Tribal implications as specified by Executive Order 13175 (65 FR 67249, 
November 9, 2000) because it does not have substantial direct effects 
on an Indian Tribe. The Catawba Indian Nation Reservation is located 
within the boundary of York County, South Carolina. Pursuant to the 
Catawba Indian Claims Settlement Act, S.C. Code Ann. 27-16-120, ``all 
state and local environmental laws and regulations apply to the 
[Catawba Indian Nation] and Reservation and are fully enforceable by 
all relevant state and local agencies and authorities.'' However, EPA 
has determined that this proposed rule does not have substantial direct 
effects on an Indian Tribe because this proposed action is not 
approving any specific rule, but rather proposing to determine that 
South Carolina's already approved SIP meets certain CAA requirements. 
EPA notes that these proposed actions will not impose substantial 
direct costs on Tribal governments or preempt Tribal law.

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Particulate Matter, Reporting 
and recordkeeping requirements, Sulfur oxides.


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

    Dated: April 11, 2019.
Mary S. Walker,
Acting Regional Administrator, Region 4.
[FR Doc. 2019-07921 Filed 4-22-19; 8:45 am]
BILLING CODE 6560-50-P