Proposed Rule2025-17051
Air Plan Approval; South Carolina; Charlotte-Gastonia-Rock Hill Area Maintenance Plan for the 2008 8-Hour Ozone NAAQS
Primary source
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Published
September 5, 2025
Issuing agencies
Environmental Protection Agency
Abstract
On September 26, 2023, the State of South Carolina, through the South Carolina Department of Environmental Services (SCDES, formerly the "South Carolina Department of Health and Environmental Control"), submitted a request for the Environmental Protection Agency (EPA) to approve a State Implementation Plan (SIP) revision containing the State's plan for maintaining the 2008 ozone National Ambient Air Quality Standard (NAAQS or standard) through 2036 for the South Carolina portion of the bi-state Charlotte-Rock Hill, North Carolina- South Carolina 2008 8-hour ozone nonattainment area (the entire area is hereinafter referred to as the "bi-State Charlotte Area" and the South Carolina portion is hereinafter referred to as the "York County Area"). EPA is proposing to approve and incorporate this maintenance plan, including the 2018 and 2036 motor vehicle emission budgets (budgets) for nitrogen oxides (NOx) and volatile organic compounds (VOC) for the York County Area, into the SIP. EPA is also notifying the public of the status of EPA's adequacy determination for the budgets for the York County Area.
Full Text
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<title>Federal Register, Volume 90 Issue 170 (Friday, September 5, 2025)</title>
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[Federal Register Volume 90, Number 170 (Friday, September 5, 2025)]
[Proposed Rules]
[Pages 42878-42885]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-17051]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R04-OAR-2024-0558; FRL-12961-01-R4]
Air Plan Approval; South Carolina; Charlotte-Gastonia-Rock Hill
Area Maintenance Plan for the 2008 8-Hour Ozone NAAQS
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: On September 26, 2023, the State of South Carolina, through
the South Carolina Department of Environmental Services (SCDES,
formerly the ``South Carolina Department of Health and Environmental
Control''), submitted a request for the Environmental Protection Agency
(EPA) to approve a State Implementation Plan (SIP) revision containing
the State's plan for maintaining the 2008 ozone National Ambient Air
Quality Standard (NAAQS or standard) through 2036 for the South
Carolina portion of the bi-state Charlotte-Rock Hill, North Carolina-
South Carolina 2008 8-hour ozone nonattainment area (the entire area is
hereinafter referred to as the ``bi-State Charlotte Area'' and the
South Carolina portion is hereinafter referred to as the ``York County
Area''). EPA is proposing to approve and incorporate this maintenance
plan, including the 2018 and 2036 motor vehicle emission budgets
(budgets) for nitrogen oxides (NOx) and volatile organic compounds
(VOC) for the York County Area, into the SIP. EPA is also notifying the
public of the status of EPA's adequacy determination for the budgets
for the York County Area.
DATES: Comments must be received on or before October 6, 2025.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-
OAR-2024-0558 at <a href="http://regulations.gov">regulations.gov</a>. 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 <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a>.
FOR FURTHER INFORMATION CONTACT: Nelsha Athauda, Multi Air Pollutant
Coordination 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. The telephone number is
(404)-562-9360. Ms. Athauda can also be reached via electronic mail at
<a href="/cdn-cgi/l/email-protection#49083d21283c2d2867072c253a2128092c3928672e263f"><span class="__cf_email__" data-cfemail="6524110d041001044b2b0009160d04250015044b020a13">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Summary of EPA's Proposed Action
II. Background
III. EPA's Evaluation of South Carolina's SIP Submittal
A. Attainment Emissions Inventory
B. Maintenance Demonstration
C. Monitoring Network
D. Verification of Continued Attainment
E. Contingency Plan
IV. EPA's Analysis of South Carolina's Proposed NOx and VOC Budgets
V. EPA's Adequacy Determination for the Proposed NOx and VOC Budgets
VI. Effect of EPA's Proposed Action
VII. Proposed Action
VIII. Statutory and Executive Order Reviews
I. Summary of EPA's Proposed Action
In accordance with the Clean Air Act, 42 U.S.C. 7401, et seq. (CAA
or Act), EPA is proposing to approve the York County Area's maintenance
plan for the 2008 8-hour ozone NAAQS, adopted by SCDES \1\ on September
26, 2023, and submitted by SCDES as a revision to the South Carolina
SIP on September 26, 2023.\2\
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\1\ On July 1, 2024, SCDES was restructured into a health
agency, the Department of Public Health, and an environmental
agency, the Department of Environmental Services (DES). In a letter
dated June 20, 2024, South Carolina represented to EPA that all the
functions, powers, and duties of the environmental divisions,
offices, and programs of the South Carolina Department of Health and
Environmental Control (SCDHEC), including the authority to
administer and enforce state implementation plans, are retained and
continued in full force and effect under DES. This letter is in the
docket for this proposed rulemaking. Throughout this proposal, the
terms, ``Department'', ``South Carolina Department of Health and
Environmental Services'', ``SCDHEC'', ``South Carolina Department of
Environmental Services'', and ``SCDES'' are interchangeable.
\2\ The September 26, 2023, SIP submission, with exception of
the supporting modeling files, is included in the docket for this
action. Due to size and compatibility limitations of the Federal
Docket Management System, the supporting modeling files are instead
available at the EPA Region 4 office. To request these files, please
contact the person listed in this Notice of Proposed Rulemaking
(NPRM) under the section titled FOR FURTHER INFORMATION CONTACT.
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The York County Area's maintenance plan for the 2008 8-hour ozone
NAAQS, submitted by SCDES on September 26, 2023, is designed to
maintain the 2008 8-hour ozone NAAQS within the York County Area
through the end of the second 10-year portion of the maintenance period
beyond redesignation (through 2036). EPA is proposing to approve the
plan because it meets all applicable requirements under CAA sections
110 and 175A. EPA is also proposing to approve the 2018 and 2036 NOx
and VOC budgets in the York County Area second maintenance plan because
they meet the applicable transportation conformity requirements under
40 CFR 93.118(e).
II. Background
On March 12, 2008, EPA promulgated a revised 8-hour ozone NAAQS of
0.075 parts per million (ppm). See 73 FR 16436 (March 27, 2008). Under
EPA's regulations at 40 CFR part 50, the 2008 8-hour ozone NAAQS is
attained when the 3-year average of the annual fourth highest daily
maximum 8-hour average ambient air quality ozone concentrations is less
than or equal to 0.075 ppm. See 40 CFR 50.15. Ambient air quality
monitoring data for the 3-year period must meet a data completeness
requirement. The ambient air quality monitoring data completeness
requirement is met when the average percent of days with valid ambient
monitoring data is greater than 90 percent, and no single year has less
[[Page 42879]]
than 75 percent data completeness as determined in Appendix I of part
50.
Upon promulgation of a new or revised NAAQS, the CAA requires EPA
to designate as nonattainment any area that is violating the NAAQS,
based on the three most recent years of complete, quality assured, and
certified ambient air quality data at the conclusion of the designation
process. The bi-state Charlotte Area was designated marginal
nonattainment for the 2008 8-hour ozone NAAQS on May 21, 2012,
(effective July 20, 2012) using 2009-2011 ambient air quality data. See
77 FR 30088 (May 21, 2012). The Area attained the standard, and on
April 17, 2015, SCDES submitted a redesignation request and the first
10-year maintenance plan for the York County Area. In the final
implementation rule for the 2008 8-hour ozone NAAQS (SIP Implementation
Rule), EPA established ozone nonattainment area attainment dates based
on Table 1 of section 181(a) of the CAA. See 80 FR 12264 (March 6,
2015). This rule established an attainment date three years after the
July 20, 2012, effective date for areas classified as marginal areas
for the 2008 8-hour ozone nonattainment designations. Therefore, the
bi-state Charlotte Area's attainment date was July 20, 2015. In 2015,
the York County Area was redesignated to attainment for the 2008 8-hour
ozone NAAQS, the 10-year maintenance plan was approved, and the public
was notified that EPA found the NOx and VOC budgets adequate. See 80 FR
76865 (December 11, 2015).
The primary guidance on maintenance plans and redesignation
requests is the September 4, 1992, memorandum from John Calcagni,
titled ``Procedures for Processing Requests to Redesignate Areas to
Attainment'' (``Calcagni Memorandum'').\3\ The Calcagni Memorandum
outlines the key elements of a maintenance plan, which include the
following: attainment emissions inventory, maintenance demonstration,
monitoring network requirements, verification of continued attainment,
and contingency plan elements.
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\3\ ``Procedures for Processing Requests to Redesignate Areas to
Attainment,'' Memorandum from John Calcagni, Director, Air Quality
Management Division, September 4, 1992 (hereinafter referred to as
the ``Calcagni Memorandum''), available at <a href="https://www.epa.gov/ground-level-ozone-pollution/procedures-processing-requests-redesignate-areas-attainment">https://www.epa.gov/ground-level-ozone-pollution/procedures-processing-requests-redesignate-areas-attainment</a>.
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On April 17, 2015, SCDES requested that EPA redesignate the South
Carolina portion of the bi-state Charlotte Area to attainment for the
2008 8-hour ozone NAAQS and submitted a SIP revision containing the
State's plan for maintaining attainment of the 2008 8-hour ozone
standard in the Area, including the 2014 and 2026 budgets for NOx and
VOC for the York County Area. In a NPRM published on October 14, 2015,
EPA proposed to determine that the bi-state Charlotte Area is
continuing to attain the 2008 8-hour ozone NAAQS; to approve and
incorporate into the South Carolina SIP the State's plan for
maintaining attainment of the 2008 8-hour ozone standard in the Area,
including the 2014 and 2026 budgets for NOx and VOC for the South
Carolina portion of the bi-state Charlotte Area; and to redesignate the
South Carolina portion of the bi-state Charlotte Area to attainment for
the 2008 8-hour ozone NAAQS. See 80 FR 61775 (October 14, 2015). EPA
approved the York County maintenance plan and the State's requests to
redesignate the York County Area to attainment for the 2008 8-hour
ozone NAAQS, effective January 11, 2016. See 80 FR 76865 (December 11,
2015).
Section 175A(b) of the CAA requires states to submit a revision to
the SIP eight years after redesignation to provide for maintenance of
the NAAQS for ten additional years following the end of the first 10-
year period. Accordingly, on September 26, 2023, South Carolina
submitted the second maintenance plan for the York County Area showing
that the Area is expected to remain in attainment of the 2008 8-hour
ozone NAAQS through 2036.
EPA has revised the ozone NAAQS once since the 2008 standards were
finalized. On October 1, 2015, the Agency revised both the primary and
secondary NAAQS for ozone to a level of 0.070 ppm (annual fourth-
highest daily maximum 8-hour average concentration, averaged over 3
years). See 80 FR 65296 (October 26, 2015). On November 16, 2017, EPA
designated areas for the 2015 8-hour ozone NAAQS. The bi-state
Charlotte Area was designated attainment for that standard with an
effective date of August 3, 2018. See 83 FR 25776 (June 4, 2018).
III. EPA's Evaluation of South Carolina's SIP Submittal
As mentioned above, on September 26, 2023, SCDES submitted the York
County Area's maintenance plan to EPA as a revision to the South
Carolina SIP. The submittal includes the maintenance plan, air quality
data, emissions inventory information, motor vehicle emissions budgets,
and appendices.
EPA has reviewed the York County Area's maintenance plan, which is
designed to maintain the 2008 8-hour ozone NAAQS within the bi-state
Charlotte Area through the end of the 20-year period beyond
redesignation, as required under CAA section 175A(b). The following is
a summary of EPA's interpretation of the section 175A requirements \4\
and EPA's evaluation of how each requirement is met.
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\4\ See Calcagni Memorandum.
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A. Attainment Emissions Inventory
For maintenance plans, a state should develop a comprehensive,
accurate inventory of actual emissions for an attainment year to
identify the level of emissions which is sufficient to maintain the
NAAQS. A state should develop this inventory consistent with EPA's most
recent guidance on emissions inventory development. For ozone, the
inventory should be based on typical summer day emissions of VOC and
NOx, as these pollutants are precursors to ozone formation.
As discussed above, EPA determined that the bi-state Charlotte Area
had attained the 2008 8-hour ozone NAAQS at the time that it
redesignated the North Carolina portion of the Area to attainment. See
80 FR 44873. The bi-state Charlotte Area continues to attain the 2008
8-hour ozone NAAQS. South Carolina selected 2018 as the base year
(i.e., attainment emissions inventory year) for developing a
comprehensive emissions inventory for NOx and VOC, for which projected
emissions could be developed for 2026 and 2036. The attainment
inventory identifies a level of emissions in the Area that is
sufficient to attain the 2008 8-hour ozone NAAQS. South Carolina began
development of the attainment inventory by first generating a baseline
emissions inventory for the State's portion of the bi-state Charlotte
Area. South Carolina estimated projected summer day emission
inventories using projected rates of growth in population, traffic,
economic activity, and other parameters. In addition to comparing the
final year of the plan (2036) to the base year (2018), South Carolina
compared an interim year (2026) to the baseline to demonstrate that the
years in between are also expected to show continued maintenance of the
2008 8-hour ozone standard.
The emissions inventory is composed of four major types of sources:
point, nonpoint, onroad mobile, and nonroad mobile. South Carolina also
included event sources (i.e., wildfires and prescribed fires) in the
inventory. The complete descriptions of how the inventories were
developed are discussed in Appendices A, B, C, D, and E of the
September 26, 2023, submittal,
[[Page 42880]]
which can be found in the docket for this proposed action.
The point source emissions were tabulated from data collected by
direct on-site measurements of emissions or mass balance calculations
utilizing approved emission factors. There are usually several emission
sources for each facility. Emissions data is collected for each point
source at a facility and the data is entered into an in-house database
system. For the projected year's inventory, point sources are adjusted
by growth factors. Growth rates for the industrial point sources were
calculated via the EPA 2016v2 modeling platform data.
For nonpoint sources, emissions were estimated by multiplying an
emission factor by some known indicator of collective activity such as
production, number of employees, or population. The emission factors
used were obtained from the Emission Inventory Improvement Program
(EIIP) Tech Reports; \5\ the Procedures document \6\ or EPA's
Compilation of Air Pollutant Emission Factors, Fifth Edition (AP-42);
\7\ and the Nonpoint Method Advisory Committee (NOMAD)
collaboration.\8\ These types of emissions were estimated on the county
level. Various sources of data, such as population growth, energy
consumption by sector, and county business patterns from the Census,
were used to determine the growth projections.
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\5\ See Air Emissions Inventory Improvement Program (EIIP)
Technical Report Series, available at: <a href="https://www.epa.gov/air-emissions-inventories/air-emissions-inventory-improvement-program-eiip">https://www.epa.gov/air-emissions-inventories/air-emissions-inventory-improvement-program-eiip</a>.
\6\ See Procedures for the Development of Emissions Factors from
Stationary Sources, available at: <a href="https://www.epa.gov/air-emissions-factors-and-quantification/procedures-development-emissions-factors-stationary">https://www.epa.gov/air-emissions-factors-and-quantification/procedures-development-emissions-factors-stationary</a>.
\7\ See AP-42, Compilation of Air Pollutant Emission Factors,
5th edition, available at: <a href="https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors-stationary-sources">https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors-stationary-sources</a>.
\8\ EPA default data for nonpoint sources was developed by EPA
with the help of the Nonpoint Method Advisory (NOMAD) committee.
NOMAD is a group of inventory developers from a variety of State and
local agencies that collaborate on the development of methodologies
to aid EPA in the development of default data for the National
Emissions Inventory (NEI).
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For onroad mobile sources, South Carolina used the EPA mobile model
MOVES3.1 \9\ to generate emissions. On January 7, 2021, EPA announced
the availability of MOVES3 for official purposes outside of California.
MOVES3 was the latest state of-the art upgrade to EPA's modeling tools
for estimating emissions from cars, trucks, buses, and motorcycles
based on the latest data and regulations and was available for use in
SIPs and transportation conformity analyses outside of California. The
notice of availability started a two-year grace period that ended on
January 7, 2023, after which MOVES3 was required to be used in new
regional-emissions and hot-spot analyses for transportation conformity
determinations outside of California.
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\9\ See 86 FR 1106.
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EPA announced availability of a new versions of the MOVES model
(MOVES4 and MOVES5) on September 12, 2023 \10\ and December 11,
2024,\11\ respectively. The CAA does not require states that have
already submitted SIP revisions or will submit SIP revisions shortly
after the release of a new model to revise these SIP revisions simply
because a new motor vehicle emissions model is now available. Because
South Carolina submitted the SIP on September 26, 2023, it used
MOVES3.1 to estimate exhaust and evaporative emissions as well as brake
and tire wear emissions from all types of on-road vehicles. The
estimation of emissions involves multiplying an activity level by an
emission factor and is done within the model. The activity level used
by MOVES3.1 is vehicle miles traveled (VMT). For the future years'
inventories, the MOVES3.1 mobile model takes into consideration
expected federal tailpipe standards, fleet turnover, and new fuels.
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\10\ See 88 FR 62567.
\11\ See 89 FR 99862.
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EPA's MOVES3.1 mobile model was also used to calculate emissions
for all nonroad sources except for railroad locomotive line haul
emissions which are not included in the nonroad portion of the MOVES3.1
model and were calculated differently.
Events sources emissions estimates were calculated by EPA using the
SMARTFIRE2 (SF2/B2) system, along with state provided inputs, including
a list of all York County wildland fires (WLFs) and prescribed fires in
2017.\12\
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\12\ See Section 7 of the 2017 National Emissions Inventory
(NEI) Technical Support Document for more details. Available at
<a href="https://www.epa.gov/air-emissions-inventories/2017-national-emissions-inventory-nei-technical-support-document-tsd">https://www.epa.gov/air-emissions-inventories/2017-national-emissions-inventory-nei-technical-support-document-tsd</a>.
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The 2018 NOx and VOC emissions for the South Carolina portion of
the Area, as well as the emissions for other years, were developed
consistent with EPA guidance and are summarized in Tables 1 through 3
of the following subsection discussing the maintenance demonstration.
See Appendices A-E of the September 26, 2023, submission for more
detailed information on the emissions inventory.
B. Maintenance Demonstration
The maintenance plan includes a maintenance demonstration that:
(i) Shows compliance with and maintenance of the 2008 8-hour ozone
NAAQS by providing information to support the demonstration that
current and future emissions of NOx and VOC remain at or below 2018
emissions levels.
(ii) Uses 2018 as the attainment year and includes future emissions
inventory projections for 2018, 2026, and 2036.
(iii) Per 40 CFR part 93, NO<INF>X</INF> and VOC Budgets were
established for the last year (2036) of the maintenance plan (see
section VII below). Additionally, SCDES opted to establish a budget for
an interim year (2026).
(iv) Provides actual (2018) and projected emissions inventories, in
tons per ozone season day (tons/OSD), for the South Carolina portion of
the bi-state Charlotte Area, as shown in Tables 1 through 3, below.
Table 1--Actual and Projected Typical Summer Day VOC Emissions (tons/OSD) for the York County Area
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Source category 2018 2026 2036
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Nonpoint........................................................ 9.54 10.15 10.76
Nonroad......................................................... 1.35 1.21 1.26
Onroad.......................................................... 2.82 1.72 1.38
Point........................................................... 3.38 3.38 3.39
Event........................................................... 0.18 0.18 0.18
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Total....................................................... 17.27 16.64 16.97
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[[Page 42881]]
Table 2--Actual and Projected Typical Summer Day NOX Emissions (tons/OSD) for the York County Area
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Source category 2018 2026 2036
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Nonpoint........................................................ 1.03 1.05 1.06
Nonroad......................................................... 1.49 0.94 0.85
Onroad.......................................................... 6.86 3.47 2.51
Point........................................................... 4.13 4.22 4.37
Event........................................................... 0.02 0.02 0.02
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Total....................................................... 13.53 9.7 8.81
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Table 3--Emission Estimates (tons/OSD) for the York County Area
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VOC NOX
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2018.................................... 17.27 13.53
2036.................................... 16.97 8.81
Difference from 2018 to 2036............ -0.30 -4.72
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Tables 1 through 3 summarize the 2018 and future projected
emissions of NO<INF>X</INF> and VOC from the York County Area. In
situations where local emissions are the primary contributor to
nonattainment, the NAAQS should not be violated in the future if
emissions from within the area remain at or below the baseline with
which attainment was achieved. South Carolina has projected emissions
as described previously and determined that emissions in the South
Carolina portion of the bi-state Charlotte Area will remain below those
in the attainment year inventory for the duration of the maintenance
plan.
A ``safety margin'' is the amount by which the total projected
emissions from all sources of a given pollutant are less than the total
emissions that would satisfy the applicable requirement for reasonable
further progress (RFP), attainment, or maintenance. See 40 CFR 93.101.
The safety margin is calculated as the difference between emissions in
an attainment year and projected emissions in the maintenance year.
South Carolina selected 2018 as the attainment emissions inventory year
for the York County Area. South Carolina calculated safety margins in
its submittal for year 2018, 2026, and 2036. Because the initial budget
year of 2018 is also the base year for the maintenance plan inventory,
there is no safety margin, therefore, no adjustments were made to the
budget for 2018. The State has allocated 100% of the 2036 safety margin
to the 2036 budgets for the York County Area. Table 4 displays the
established safety margins for the York County Area in tons per ozone
season day (OSD).
Table 4--Safety Margins for the York County Area
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NOX (tons/OSD)
VOC (tons/OSD)
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2018.............................. N/A N/A
2026.............................. 0.63 3.83
2036.............................. 0.30 4.72
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The State decided to allocate one hundred percent of the 2036
safety margins to 2036 budgets to allow for unanticipated growth in
VMT, changes and uncertainty in vehicle mix assumptions, etc., that
will influence the emission estimations. After allocation of one
hundred percent of the available 2036 safety margin, there is no
remaining 2036 safety margin for NO<INF>X</INF> and VOC emissions. This
allocation is discussed further in section IV of this proposed
rulemaking along with the budgets to be used for transportation
conformity proposes.
C. Monitoring Network
There are currently five Air Quality System (AQS) ozone monitors in
the bi-State Charlotte Area: one in Lincoln County, North Carolina; two
in Mecklenburg County, North Carolina; one in Rowan County, North
Carolina; and one in Union County, North Carolina. No monitors are
located within the South Carolina portion of the bi-State Charlotte
Area. The plan presents the design values (DV) \13\ (in ppm) for the
currently active monitors in the bi-state Charlotte Area from 2012 to
2024.
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\13\ Design values are calculated as the 3-year average of the
annual fourth-highest daily maximum 8-hour average ozone
concentration.
Table 5--8-Hour Ozone NAAQS Design Values (ppm) for Monitors in the Bi-State Charlotte Area From 2012 to 2024
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2011- 2012- 2013- 2014- 2015- 2016- 2017- 2018- 2019- 2020- 2021- 2022-
County AQS Site ID 2010- 2012 DV 2013 DV 2014 DV 2015 DV 2016 DV 2017 DV 2018 DV 2019 DV 2020 DV 2021 DV 2022 DV 2023 DV 2024 DV
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Crouse: Lincoln, NC..................... 37-109-0004............... 0.075 0.072 0.068 0.065 0.067 0.067 0.065 0.064 0.060 0.061 0.061 0.065 0.064
[[Page 42882]]
Garinger: Mecklenburg, NC............... 37-119-0041............... 0.083 0.078 0.070 0.068 0.069 0.069 0.068 0.070 0.067 0.066 0.064 0.069 0.069
University Meadows: Mecklenburg, NC..... 37-119-0046............... 0.083 0.078 0.073 0.067 \a\ \a\ 0.070 0.069 0.067 0.066 0.064 0.068 0.069
0.070 0.070
Rockwell: Rowan, NC..................... 37-159-0021............... 0.078 0.073 0.068 0.064 0.065 0.064 0.062 0.062 0.061 0.062 0.061 0.065 0.065
Monroe: Union, NC....................... 37-179-0003............... 0.073 0.070 0.068 0.065 0.068 0.067 0.068 0.068 0.063 0.062 0.061 0.067 0.066
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\a\ Monitor started in 2016 to replace County Line (ID# 37-119-1009); EPA approved combining data for the two sites to calculate a design value; value reported is a combined design value.
As shown in Table 5, the design values derived from the monitors in
the bi-State Charlotte Area have been below the level of the 2008 8-
hour ozone NAAQS since redesignation. Furthermore, the overall ozone
concentrations for the Area decreased by 14 ppb between the 2010-2012
and 2022-2024 design values at one of the Mecklenburg, NC, monitors
(AQS ID 37-119-0046). As the ozone levels have dropped and remain
relatively stable, it is reasonable to conclude that the bi-State
Charlotte Area will not exceed the 2008 8-hour ozone NAAQS during the
second 10-year maintenance period.
As noted above, all the monitors in the bi-state Charlotte Area are
in the State of North Carolina. North Carolina, through the North
Carolina Department of Air Quality (NCDAQ), has committed to continue
operation of all those monitors in compliance with 40 CFR part 58,\14\
addressing the requirement for monitoring. For further details on
monitoring, see the 2024-2025 North Carolina Annual Monitoring Network
Plan \15\ as well as EPA's approval letter for the 2024-2025 Annual
Network Plan, which can be found in the docket for this proposed
action.
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\14\ See 80 FR 29250 (May 21, 2015); 80 FR 44873 (July 28,
2015).
\15\ See docket for Volume 1 (Network Descriptions (All
Regions)) of the 2024-2025 Annual Network Plan and EPA's approval
letter for the 2024-2025 Annual Network Plan. Volume 2 (Site
Descriptions by Region) of the 2024-2025 Annual Network Plan is
available online at: <a href="https://www.deq.nc.gov/about/divisions/air-quality/air-quality-monitoring/annual-network-plan/2024-2025-annual-monitoring-network-plan-north-carolina-air-quality">https://www.deq.nc.gov/about/divisions/air-quality/air-quality-monitoring/annual-network-plan/2024-2025-annual-monitoring-network-plan-north-carolina-air-quality</a>.
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D. Verification of Continued Attainment
The State of South Carolina, through SCDES, has the legal authority
to enforce and implement the requirements of the South Carolina portion
of the Area 2008 8-hour ozone maintenance plan. This includes the
authority to adopt, implement, and enforce any subsequent emissions
control contingency measures determined to be necessary to correct
future ozone attainment problems.
Verification of continued attainment is accomplished through
operation of the ambient ozone monitoring network and the periodic
update of the York County Area's emission inventories. SCDES has been
and will continue proactive efforts including reviewing monitoring data
and evaluating trends in an effort to identify possible violations as
early as possible. In addition, to track future levels of emissions,
SCDES will continue to develop and submit to EPA updated emission
inventories for all source categories at least once every three years
consistent with the requirements of 40 CFR part 51, subpart A, and 40
CFR 51.122.
E. Contingency Plan
Section 175A of the CAA requires that a maintenance plan include
such contingency measures as EPA deems necessary to assure that the
state will promptly correct a violation of the NAAQS that occurs after
redesignation. See CAA section 175A(d). The maintenance plan should
identify the contingency measures to be adopted, a schedule and
procedure for adoption and implementation, and a time limit for action
by the state. A state should also identify specific indicators to be
used to determine when the contingency measures need to be implemented.
The maintenance plan must include a requirement that a state will
implement all measures with respect to control of the pollutant that
were contained in the SIP before redesignation of the area to
attainment in accordance with section 175A(d).
In the September 25, 2023, maintenance plan, South Carolina affirms
that all programs instituted by the State will remain enforceable and
that sources are prohibited from reducing emissions controls unless
such a change is first approved by EPA as a revision to the South
Carolina SIP that is consistent with Section 110(l) of the CAA. The
plan also states that SCDES will implement all control measures with
respect to NOx, VOCs, and ozone that were contained in the SIP for the
maintenance area before it was redesignated as attainment. The
contingency plan included in the submittal includes a triggering
mechanism to determine when contingency measures are needed and a
process of developing and implementing appropriate control measures.
The primary trigger of the contingency plan will be a certified design
value that exceeds the 2008 8-hour ozone NAAQS (i.e., when the three-
year average of the 4th highest values is equal to or greater than
0.076 ppm at any monitor in the bi-state Charlotte Area). If certified
data indicates a violating design value, the triggering event will be
the date of the design value violation, not the final QA/QC date. If
initial monitoring data indicates a possible design value violation but
later certification indicates that a NAAQS violation did not occur, a
triggering event will not have occurred, and contingency measures will
not need to be implemented.
If the primary trigger is activated, SCDES will begin analyses to
determine the emission control measures that will be necessary for
attaining or maintaining the 2008 8-hour ozone NAAQS and implement
contingency measures within 24 months of a violation trigger to bring
the area back into attainment.\16\ In the September 25, 2023,
maintenance plan, the State identified the following contingency
[[Page 42883]]
measures that may be considered for adoption upon a trigger of the
contingency plan:
---------------------------------------------------------------------------
\16\ If SCDES determines that a longer schedule is required to
implement specific contingency measures, then, upon selection of the
appropriate measures, it will seek concurrence with EPA of the
proposed schedule and provide sufficient information to demonstrate
that the proposed measures are a prompt correction of the triggering
event. Any extension would be subject to EPA's approval of the SIP
revision containing the required contingency measure.
---------------------------------------------------------------------------
<bullet> Reasonably Available Control Technology (RACT) for NOx on
existing stationary sources not subject to existing requirements;
<bullet> Implementation of diesel retrofit programs, including
incentives for performing retrofits for fleet vehicle operations;
<bullet> Alternative fuel programs for fleet vehicle operations;
<bullet> Gas can and lawnmower replacement programs;
<bullet> Voluntary engine idling reduction programs;
<bullet> Other measures deemed appropriate at the time as a result
of advances in control technologies.
Finally, the Department will monitor periodic emissions inventory
updates during the triennial National Emissions Inventory and compare
them to projected emissions. If actual emissions exceed by more than 10
percent the projected emissions in this maintenance plan, the
Department will investigate the differences and develop an appropriate
strategy for addressing these differences.
Generally, the maintenance plan for the York County Area relies on
similar contingency measures as those in the SCDES plans for the first
10-year period. The only change is that the second 10-year maintenance
plan no longer lists the ``Take a Break from Exhaust program,'' as a
potential contingency measure. EPA proposes to find that the
contingency provisions in South Carolina's second maintenance plan for
the York County Area for the 2008 8-hour Ozone NAAQS meet the
requirements of the CAA section 175A(d).
IV. EPA's Analysis of South Carolina's Proposed NOX and VOC Budgets
Under section 176(c) of the CAA, new transportation plans,
programs, and projects, such as the construction of new highways, must
``conform'' to (i.e., be consistent with) the part of the state's air
quality plan that addresses pollution from cars and trucks. Conformity
to the SIP means that transportation activities will not cause new air
quality violations, worsen existing violations, or delay timely
attainment of the NAAQS or any interim milestones. Regulations at 40
CFR part 93 set forth EPA policy, criteria, and procedures for
demonstrating and assuring conformity of such transportation activities
to a SIP. The regional emissions analysis is one, but not the only,
requirement for implementing transportation conformity. Transportation
conformity is a requirement for nonattainment and maintenance areas.
Maintenance areas are areas that were previously nonattainment for a
particular NAAQS but have since been redesignated to attainment with an
approved maintenance plan for that NAAQS.
Under the CAA, states are required to submit, at various times,
control strategy SIPs and maintenance plans for nonattainment areas.
These control strategy SIPs (including RFP and attainment demonstration
requirements) and maintenance plans create budgets for criteria
pollutants and/or their precursors to address pollution from cars and
trucks. Per 40 CFR part 93, a budget must be established for the last
year of the maintenance plan. A state may adopt budgets for other years
as well. The budget is the portion of the total allowable emissions in
the maintenance demonstration that is allocated to highway and transit
vehicle use and emissions. See 40 CFR 93.101. The budget serves as a
ceiling on emissions from an area's planned transportation system. The
budget concept is further explained in the preamble to the November 24,
1993, Transportation Conformity Rule (58 FR 62188). The preamble also
describes how to establish the budget in the SIP and how to revise the
budgets.
In the first maintenance plan for the York County Area, SCDES used
2014 for the attainment year inventory because 2014 was one of the
years in the 2012-2015 three-year design value period when the bi-state
Charlotte Area first attained the 2008 ozone NAAQS. For the second
maintenance plan, SCDES selected 2018 as the base emissions inventory.
The base year of 2018 was selected because it is one of the more recent
years for which the York County Area has an attaining design value for
the 2008 8-hour ozone NAAQS while avoiding the potential
underrepresentation of emissions caused by the response to the COVID-19
pandemic beginning in early 2020. According to the transportation
conformity rule, a maintenance plan must establish budgets for the last
year of the maintenance plan (in this case, 2036). See 40 CFR 93.118.
The state may set a budget for an interim year (in this case 2026), but
it is not a requirement. In the September 26, 2023, submittal, South
Carolina requested that EPA replace the previous 2014 and 2026
NO<INF>X</INF> and VOC budgets from the first 10-year maintenance plan
with the 2018 and 2036 budgets. If approved as proposed, the previous
2014 and 2026 budgets will no longer apply for transportation
conformity purposes. Table 6, below, provides the NO<INF>X</INF> and
VOC budgets in kilograms per day (kg/day), for 2018 and 2036.
Table 6--York County, South Carolina Area Budgets
[kg/day] *
----------------------------------------------------------------------------------------------------------------
2018 2036
----------------------------------------------------------------
NOX VOC NOX VOC
----------------------------------------------------------------------------------------------------------------
Base Emissions................................. 6224.03 2555.02 2273.63 1256.15
Safety Margin Allocated to Budget.............. N/A N/A 4281.96 272.16
----------------------------------------------------------------
Total Budget............................... 6224.03 2555.02 6555.59 1528.31
----------------------------------------------------------------------------------------------------------------
* To convert kg/day to tons/OSD, multiply the value in by 1.102 x 10-3.
As mentioned above, South Carolina has chosen to allocate the
available safety margin to the NO<INF>X</INF> and VOC budgets for 2036
for the York County Area.
Through this rulemaking, EPA is proposing to approve the budgets
for NO<INF>X</INF> and VOC for 2018 and 2036 for the York County Area
because EPA believes that the Area maintains the 2008 8-hour ozone
NAAQS with the emissions at the levels of the budgets. EPA is also
proposing to replace the previous 2014 and 2026 NO<INF>X</INF> and VOC
budgets from the first 10-year maintenance plan. If EPA finalizes that
replacement, the 2014 and 2026 budgets will no longer apply for
transportation conformity purposes. EPA intends to make its
determination on the adequacy of the 2018 and 2036 budgets for the York
County Area for
[[Page 42884]]
transportation conformity purposes in the near future by completing the
adequacy process that was started on September 26, 2023. After EPA
finds the 2018 and 2036 budgets adequate or approves them (whichever is
completed first), they must be used for future conformity
determinations. EPA is proposing to approve the budgets because they
are consistent with maintenance of the 2008 8-hour ozone NAAQS through
2036.
V. EPA's Adequacy Determination for the Proposed NOX and VOC Budgets
When reviewing submitted ``control strategy'' SIPs or maintenance
plans containing budgets, EPA may affirmatively find those budgets
adequate for use in determining transportation conformity. Once EPA
affirmatively finds the submitted budget is adequate for transportation
conformity purposes, that budget must be used by state and Federal
agencies in determining whether proposed transportation projects
conform to the SIP as required by section 176(c) of the CAA.
EPA's substantive criteria for determining adequacy of budgets are
set out in 40 CFR 93.118(e)(4). The process for determining adequacy
consists of three basic steps: Public notification of a SIP submission,
a public comment period, and EPA's adequacy determination. This process
for determining the adequacy of submitted budgets for transportation
conformity purposes was initially outlined in EPA's May 14, 1999,
guidance, ``Conformity Guidance on Implementation of March 2, 1999,
Conformity Court Decision.'' EPA adopted regulations to codify the
adequacy process in the Transportation Conformity Rule Amendments for
the ``New 8-Hour Ozone and PM<INF>2.5</INF> National Ambient Air
Quality Standards and Miscellaneous Revisions for Existing Areas;
Transportation Conformity Rule Amendments--Response to Court Decision
and Additional Rule Change,'' on July 1, 2004 (69 FR 40004). Additional
information on the adequacy process for transportation conformity
purposes is available in the proposed rule entitled, ``Transportation
Conformity Rule Amendments: Response to Court Decision and Additional
Rule Changes,'' 68 FR 38974, 38984 (June 30, 2003).
As discussed earlier, South Carolina's September 26, 2023,
maintenance plan includes NO<INF>X</INF> and VOC budgets for the York
County Area for 2018, an interim year of the maintenance plan, 2026,
and the last year of the maintenance plan, 2036. EPA is reviewing the
NO<INF>X</INF> and VOC budgets through the adequacy process. The York
County Area NO<INF>X</INF> and VOC budgets, opened for public comment
on EPA's adequacy website on October 19, 2023, found at: <a href="https://www.epa.gov/state-and-local-transportation/adequacy-review-state-implementation-plan-sip-submissions-conformity">https://www.epa.gov/state-and-local-transportation/adequacy-review-state-implementation-plan-sip-submissions-conformity</a>. The EPA public comment
period on adequacy for the budgets for 2018 and 2036 for the York
County Area closed on November 20, 2023. No comments, adverse or
otherwise, were received during EPA's adequacy process for the budgets
associated with South Carolina's maintenance plan.
EPA intends to make its determination on the adequacy of the 2018
and 2036 budgets for the York County Area for transportation conformity
purposes in the near future by completing the adequacy process that was
started on September 26, 2023. If EPA finds the 2018 and 2036 budgets
adequate or approves them, the new budgets for NO<INF>X</INF> and VOC
must be used for future transportation conformity determinations. For
required regional emissions analysis years that involve 2018 through
2036, the applicable 2018 budgets will be used and for 2036 and beyond,
the applicable budgets will be the new 2036 budgets established in the
maintenance plan, as defined in Section IV of this proposed rulemaking.
VI. Effect of EPA's Proposed Action
EPA's proposed action establishes the basis upon which EPA may take
final action on the issues being proposed for approval. Approval of
South Carolina's SIP revisions would incorporate a plan for maintaining
the 2008 8-hour ozone NAAQS in the Area through 2036 into the SIP. This
maintenance plan includes contingency measures to remedy any future
violations of the 2008 8-hour ozone NAAQS and procedures for evaluation
of potential violations. The maintenance plan also establishes NOx and
VOC budgets for 2018 and 2036 for the York County Area. The budgets are
listed in Table 4 in Section IV. Additionally, EPA is notifying the
public of the status of EPA's adequacy determination for the newly
established NOx and VOC budgets for 2018 and 2036 for the York County
Area.
VII. Proposed Action
EPA is proposing to approve the second maintenance plan for the
2008 8-hour ozone NAAQS for the South Carolina portion of the bi-state
Charlotte Area, including the NOx and VOC budgets for 2018 and 2036 (to
replace the previous NOx and VOC budgets for 2014 and 2026 from the
first 10-year maintenance plan), into the South Carolina SIP under CAA
section 175A. The maintenance plan meets all applicable requirements
for maintenance plans and related contingency provisions in CAA section
175A, including a demonstration that the bi-state Charlotte Area will
continue to maintain the 2008 8-hour ozone NAAQS until January 11,
2036, the end of the 20-year maintenance period. Further, as part of
this proposed action, EPA is describing the status of its adequacy
determination for the NOx and VOC budgets for 2018 and 2036 in
accordance with 40 CFR 93.118(f)(1). Within 24 months from the
publication date of EPA's final rule for this action (if EPA approves
this maintenance plan and the underlying budgets), or the effective
date of EPA's adequacy determination for the budgets, whichever is
earlier, the transportation partners will need to demonstrate
conformity to the new NOx and VOC budgets pursuant to 40 CFR
93.104(e)(3).
VIII. Statutory and Executive Order Reviews
Under the CAA, the Administrator is required to approve a SIP
submission that complies with the provisions of the CAA 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. Accordingly, this
proposed 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:
<bullet> Is not a significant regulatory action subject to review
by the Office of Management and Budget under Executive Order 12866 (58
FR 51735, October 4, 1993);
<bullet> Is not subject to Executive Order 14192 (90 FR 9065,
February 6, 2025) because SIP actions are exempt from review under
Executive Order 12866;
<bullet> Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
<bullet> 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.);
<bullet> 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);
<bullet> Does not have federalism implications as specified in
Executive
[[Page 42885]]
Order 13132 (64 FR 43255, August 10, 1999);
<bullet> Is not subject to Executive Order 13045 (62 FR 19885,
April 23, 1997) because it approves a state program;
<bullet> Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001); and
<bullet> 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.
Because this proposed action merely proposes to approve state law
as meeting Federal requirements and does not impose additional
requirements beyond those imposed by state law, this proposed action
for the State of South Carolina does not have Tribal implications as
specified by Executive Order 13175 (65 FR 67249, November 9, 2000).
Therefore, this proposed action will not impose substantial direct
costs on Tribal governments or preempt Tribal law. The Catawba Indian
Nation (CIN) 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 (Settlement Act), ``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.'' The CIN also retains authority to
impose regulations applying higher environmental standards to the
Reservation than those imposed by state law or local governing bodies,
in accordance with the Settlement Act.
List of Subjects in 40 CFR part 52 Environmental protection, Air
pollution control, Incorporation by reference, Intergovernmental
relations, Ozone, Reporting and recordkeeping requirements, Volatile
organic compounds.
Authority: 42 U.S.C. 7401 et seq.
Dated: August 27, 2025.
Kevin McOmber,
Regional Administrator, Region 4.
[FR Doc. 2025-17051 Filed 9-4-25; 8:45 am]
BILLING CODE 6560-50-P
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This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.