Proposed Rule2025-17048
Air Plan Approval; Kentucky; Emissions Inventory and Nonattainment New Source Review for the Henderson-Webster Sulfur Dioxide Nonattainment Area
Primary source
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Published
September 5, 2025
Issuing agencies
Environmental Protection Agency
Abstract
The Environmental Protection Agency (EPA) is proposing to approve two State Implementation Plan (SIP) revisions submitted by the Commonwealth of Kentucky, through the Energy and Environment Cabinet (Cabinet), Division of Air Quality (DAQ) on January 26, 2024, and February 15, 2024, to certify two requirements under the Clean Air Act (CAA or Act). These revisions establish that the Kentucky SIP satisfies the nonattainment new source review (NNSR) and base year emissions inventory requirements for the 2010 1-hour sulfur dioxide (SO<INF>2</INF>) national ambient air quality standard (NAAQS) for the Henderson-Webster SO<INF>2</INF> nonattainment area (hereinafter "Henderson-Webster SO<INF>2</INF> Nonattainment Area" or "Area"). These actions are being proposed pursuant to the CAA.
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 42889-42895]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-17048]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R04-OAR-2025-0023; FRL-12899-01-R4]
Air Plan Approval; Kentucky; Emissions Inventory and
Nonattainment New Source Review for the Henderson-Webster Sulfur
Dioxide Nonattainment Area
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve two State Implementation Plan (SIP) revisions submitted by the
Commonwealth of Kentucky, through the Energy and Environment Cabinet
(Cabinet), Division of Air Quality (DAQ) on January 26, 2024, and
February 15, 2024, to certify two requirements under the Clean Air Act
(CAA or Act). These revisions establish that the Kentucky SIP satisfies
the nonattainment new source review (NNSR) and base year emissions
inventory requirements for the 2010 1-hour sulfur dioxide
(SO<INF>2</INF>) national ambient air quality standard (NAAQS) for the
Henderson-Webster SO<INF>2</INF> nonattainment area (hereinafter
``Henderson-Webster SO<INF>2</INF> Nonattainment Area'' or ``Area'').
These actions are being proposed pursuant to the CAA.
DATES: Comments must be received on or before October 6, 2025.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-
OAR-2025-0023 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: Pearlene Williams-Miles, 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) 562-9144. Ms. Williams-Miles can also be
reached via electronic mail at <a href="/cdn-cgi/l/email-protection#5b2c323737323a36283632373e28752b3e3a29373e353e1b3e2b3a753c342d"><span class="__cf_email__" data-cfemail="b5c2dcd9d9dcd4d8c6d8dcd9d0c69bc5d0d4c7d9d0dbd0f5d0c5d49bd2dac3">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
I. Background
SO<INF>2</INF> is a gas that is formed by the burning of fossil
fuels from power plants and other industrial facilities, such as
extracting metal from ore; natural sources, such as volcanoes; and
locomotives, ships, and other vehicles and heavy equipment that burn
fuel with a high sulfur content. SO<INF>2</INF> is the component of
greatest concern amongst sulfur oxides (SOx) and is used as the
indicator for the larger group of gaseous SOx. Control measures that
reduce SO<INF>2</INF>
[[Page 42890]]
can generally be expected to reduce people's exposures to all gaseous
SOx.
On June 2, 2010, EPA revised the primary SO<INF>2</INF> NAAQS.
Specifically, EPA established a 1-hour SO<INF>2</INF> standard at a
level of 75 parts per billion (ppb), based on the 3-year average of the
annual 99th percentile of 1-hour daily maximum concentrations.\1\ See
75 FR 35520 (June 22, 2010). The 1-hour standard is met at an ambient
air quality monitoring site when the 3-year average of the annual 99th
percentile of daily maximum 1-hour average concentrations does not
exceed 75 ppb, as determined in accordance with appendix T of 40 CFR
part 50. See 75 FR 35520, codified at 40 CFR 50.17(a)-(b).
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\1\ This rule became effective on August 23, 2010, and revoked
the 24-hour and annual primary SO<INF>2</INF> standards.
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Upon promulgation of a new or revised SO<INF>2</INF> NAAQS, section
107(d) of the CAA requires EPA to designate as nonattainment any area
that is violating the NAAQS (or that contributes to ambient air quality
in a nearby area that is violating the NAAQS). As part of the
designation process for the 2010 1-hour SO<INF>2</INF> NAAQS, the
Henderson-Webster SO<INF>2</INF> Nonattainment Area was designated as a
nonattainment area in the fourth round of designations on December 21,
2020.<SUP>2 3</SUP> These area designations became effective on April
30, 2021. See 86 FR 16055 (March 26, 2021). States with nonattainment
areas for the SO<INF>2</INF> NAAQS must provide nonattainment SIP
revisions meeting the applicable requirements of CAA sections 110(a),
172, 191, and 192 \4\ for the SO<INF>2</INF> NAAQS. EPA's regulations
governing nonattainment SIPs are set forth at 40 CFR part 51, with
specific procedural requirements and control strategy requirements
residing at subparts F and G, respectively.
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\2\ See Round 4 SO<INF>2</INF> Designations at <a href="https://www.epa.gov/sulfur-dioxide-designations/epa-completes-fourth-round-sulfur-dioxide-designations">https://www.epa.gov/sulfur-dioxide-designations/epa-completes-fourth-round-sulfur-dioxide-designations</a>.
\3\ The Henderson-Webster SO<INF>2</INF> Nonattainment Area is
comprised of a portion of Henderson County and a portion of Webster
County. EPA designated the Henderson-Webster SO<INF>2</INF>
Nonattainment Area in 2020 based on a violating ambient air
monitor--the Sebree data requirements rule (DRR) monitor (Air
Quality System ID: 21-101-1011)--sited to characterize the maximum
1-hour SO<INF>2</INF> concentrations in the area. (The DRR may be
found at 40 CFR 51.1205). The extent of the partial county
Henderson-Webster SO<INF>2</INF> Nonattainment Area was defined
based on air dispersion modeling during round 4 SO<INF>2</INF>
designations in 2020. See 40 CFR 81.318.
\4\ Section 191(a) of the CAA directs states to submit SIPs for
areas designated as nonattainment for the SO<INF>2</INF> NAAQS to
EPA within 18 months of the effective date of the designation. Under
CAA section 192(a) these SIPs are required to demonstrate that their
respective areas will attain the NAAQS as expeditiously as
practicable, but no later than 5 years from the effective date of
designation. In addition, sections 110(a) and 172(c), as well as EPA
regulations at 40 CFR part 51, set forth substantive elements each
SIP must contain to be approved by EPA.
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Section 172(c) directs states with nonattainment areas to submit a
SIP that contains an attainment demonstration showing that the affected
area will attain the relevant standard as expeditiously as practicable,
but no later than the applicable statutory attainment date (April 30,
2026, for the Henderson-Webster SO<INF>2</INF> Nonattainment Area).\5\
On April 23, 2014, EPA issued guidance for meeting the statutory
requirements in SO<INF>2</INF> SIPs under the 2010 revised NAAQS in a
document entitled ``Guidance for 1-Hour SO<INF>2</INF> Nonattainment
Area SIP Submissions'' \6\ (hereinafter referred to as ``2014
SO<INF>2</INF> Nonattainment Guidance'') which describes the statutory
requirements for nonattainment at CAA section 172(c), including an
accurate inventory of actual emissions from all sources in
nonattainment areas; an attainment demonstration; a demonstration of
reasonable further progress; implementation of Reasonably Available
Control Measures (RACM) (including Reasonably Available Control
Technologies (RACT)); NNSR; enforceable emissions limitations and
control measures; and adequate contingency measures for the affected
area. For EPA to fully approve a SIP revision as meeting the
requirements of CAA sections 110, 172, and 191-192 and EPA's
regulations at 40 CFR part 51, the SIP for the affected area must
demonstrate to EPA's satisfaction that each of the requirements have
been met. State air agencies with nonattainment areas for the 2010 1-
hour primary SO<INF>2</INF> NAAQS are required to submit a SIP revision
that addresses these requirements within 18 months after an area is
designated nonattainment (no later than October 30, 2022, for the
Henderson-Webster SO<INF>2</INF> Nonattainment Area).\7\ Kentucky's
January 26, 2024, and February 15, 2024, SIP revisions address the air
agency's NNSR permitting and emissions inventory obligations pursuant
to section 172(c)(5) and 172(c)(3) of the Act, respectively.
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\5\ Soon after the 1990 amendments to the CAA were enacted by
Congress, EPA issued comprehensive guidance on SIPs in a document
entitled the ``General Preamble for the Implementation of Title I of
the Clean Air Act Amendments of 1990,'' published in the Federal
Register at 57 FR 13498 (April 16, 1992) (General Preamble). Among
other things, the General Preamble addressed SO<INF>2</INF> SIPs and
fundamental principles for SIP control strategies. Id. at 13545-49,
13567-68.
\6\ See <a href="https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf">https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf</a>.
\7\ See CAA section 191(a).
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A. Nonattainment New Source Review
As mentioned above, based on the nonattainment designation for the
Henderson-Webster SO<INF>2</INF> Nonattainment Area in 2020, Kentucky
was required to develop a SIP revision addressing, among other
requirements, NNSR permitting requirements pursuant to section
172(c)(5) of the CAA for the 2010 1-hour SO<INF>2</INF> NAAQS. Section
172(c)(5) of the CAA requires each state with a nonattainment area to
submit a SIP revision requiring NNSR permits in the nonattainment area
in accordance with the permitting requirements of CAA section 173. The
NNSR requirements apply on a pollutant-specific basis with respect to
each nonattainment pollutant for which a source has the potential to
emit in amounts greater than the applicable major source threshold for
the pollutant.\8\ Kentucky's January 26, 2024, SIP revision addresses
NNSR permitting requirements for the 2010 1-hour SO<INF>2</INF> NAAQS
for the Henderson-Webster SO<INF>2</INF> Nonattainment Area. EPA's
analysis of Kentucky's SIP revision regarding the NNSR requirements for
the 1-hour SO<INF>2</INF> is provided in Section II.A, below.
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\8\ For new sources in areas that are designated nonattainment
for the 2010 SO<INF>2</INF> NAAQS, the major source threshold is 100
tpy or more of SO<INF>2</INF>. See 40 CFR 51.165(a)(l)(iv)(A)(1).
Similarly, NNSR requirements for SO<INF>2</INF> also apply to any
existing major stationary source of SO<INF>2</INF> that proposes a
major modification, i.e., a physical change or change in the method
of operation that results in a significant net emissions increase
(40 tons per year (tpy) or more) of SO<INF>2</INF>. See 40 CFR
51.165(a)(l)(x)(A).
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B. Emission Inventory
On February 15, 2024, the Cabinet submitted a second SIP revision
that addresses the base year emissions inventory requirements for the
Henderson-Webster SO<INF>2</INF> Nonattainment Area at section
172(c)(3) of the CAA. Each state with a nonattainment area should
develop a comprehensive, accurate, and current inventory of actual
emissions from all sources of a relevant pollutant, or pollutants, such
as SO<INF>2</INF>, in a nonattainment area as well as any sources
located outside the nonattainment area which may affect attainment in
the area.\9\ This inventory should be consistent with the EPA's most
recent emissions inventory data requirements as codified at 40 CFR part
51, subpart A.\10\ An emission inventory
[[Page 42891]]
for SO<INF>2</INF> is an estimation of actual SO<INF>2</INF> emissions
in an area.
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\9\ See CAA section 172(c)(3); 2014 SO<INF>2</INF> Nonattainment
Guidance at 7-8.
\10\ The air emissions reporting requirements at 40 CFR part 51,
subpart A sets out how states are to report their emission
inventories to EPA. See 2014 SO<INF>2</INF> Nonattainment Guidance
at 8.
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Emission inventories provide emissions data that inform a variety
of air quality planning tasks, including establishing baseline emission
levels, calculating emission reduction triggers necessary to attain the
NAAQS, determining emission inputs for SO<INF>2</INF> air quality
modeling analyses, and tracking emissions over time to determine
progress toward achieving air quality and emission reduction goals.
Pursuant to the CAA, states are required to submit estimates of
SO<INF>2</INF> emissions for four general classes of anthropogenic
sources: individual stationary sources such as electrical generating
units or industrial facilities (point sources); smaller stationary
sources such as small scale industrial sources, collectively referred
to as area (non-point) sources; on-road mobile sources (on-road),
including automobiles, truck, motorcycles, and the like; and off-road
mobile sources (non-road), including agricultural equipment, aircrafts,
locomotives, and the like. Kentucky's February 15, 2024, SIP revision
provides the required accounting of actual SO<INF>2</INF> emissions for
the Henderson-Webster SO<INF>2</INF> Nonattainment Area. EPA's analysis
of Kentucky's SIP SO<INF>2</INF> emissions inventory is discussed in
Section II.B, below.
II. EPA's Analysis of the Commonwealth's Submittal
A. NNSR Requirements
Kentucky's SIP-approved NNSR regulation at 401 Kentucky
Administrative Regulation (KAR) 51.052, Review of new sources in or
impacting upon nonattainment areas (401 KAR 51:052), establishes air
quality permitting requirements for the construction or modification of
major stationary sources located within, or impacting, areas designated
as nonattainment. In its January 26, 2024, SIP revision, Kentucky
certifies that the version of 401 KAR 51:052 in the SIP satisfies the
federal NNSR requirements for the Henderson-Webster SO<INF>2</INF>
Nonattainment Area at CAA sections 172(c)(5) and 173 and 40 CFR 51.165,
and thus, a modification to the Commonwealth's SIP-approved regulations
at 401 KAR 51:052 is not necessary.
The SIP-approved version of 401 KAR 51:052 addresses the NNSR
permitting requirements for the Henderson-Webster SO<INF>2</INF>
Nonattainment Area and remains adequate to meet all applicable NNSR
requirements for the 2010 1-hour SO<INF>2</INF> NAAQS. EPA is therefore
proposing to approve Kentucky's certification that 401 KAR 51:052 meets
the NNSR requirements for implementation of the 2010 1-hour
SO<INF>2</INF> NAAQS.
B. Emissions Inventory
Section 172(c)(3) of the CAA provides that nonattainment SIPs
include a comprehensive, accurate, and current inventory of actual
emissions from all sources of SO<INF>2</INF> emissions in each
nonattainment area. The emissions inventory and source emission rate
data for an area serve as the foundation for air quality modeling and
other analyses that enable states to: (1) estimate the degree to which
different sources within a nonattainment area contribute to violations
within the affected area; and (2) assess the expected improvement in
air quality within the nonattainment area due to the adoption and
implementation of control measures.\11\
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\11\ See EPA's 2014 SO<INF>2</INF> Nonattainment Guidance at 7-
8.
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According to the DAQ, at the time of SO<INF>2</INF> designations,
the Henderson-Webster SO<INF>2</INF> Nonattainment Area included the
following major stationary sources: Century Aluminum Sebree LLC
(Century Aluminum) in Henderson County, Big Rivers Electric Corporation
(BREC) Robert A. Reid Station and Henderson Municipal Power and Light
(HMP&L) Station 2 (Reid/HMP&L), and BREC Robert D. Green Station (BREC-
Green Station). The Cabinet's base year emissions inventory evaluated
years 2017 and 2018, which are two of the three years in the three-year
design value used to designate the Henderson-Webster SO<INF>2</INF>
Area as nonattainment for the 2010 1-hour SO<INF>2</INF> standard. The
Cabinet chose to use 2017 SO<INF>2</INF> actual emissions data from the
National Emissions Inventory (NEI) to represent the base year emission
levels within the Henderson-Webster SO<INF>2</INF> Nonattainment Area
for non-point and non-road source categories. Kentucky states that on-
road emissions for 2017 were developed from EPA's Motor Vehicle
Emissions Simulator (MOVES3.0.4) software program. For point sources,
Kentucky used 2018 SO<INF>2</INF> actual emissions from the
Commonwealth's inventory, KYEIS, to represent the base year emission
levels.\12\
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\12\ The Cabinet relied on their 2018 KYEIS for point source
emissions data instead of the 2017 point source NEI data because at
the time, the Commonwealth's emission data set was more recent than
the 2017 NEI point source data. The Cabinet chose not to use 2019
KYEIS point source data due to the operational changes that occurred
at the BREC Henderson Municipal Power and Light facilities in 2019.
These operational changes led to emissions reductions in the Area,
making 2019 unrepresentative of the base year emissions for point
sources. See Section 1.a.(ii) of the February 15, 2024, SIP
revision.
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Only a portion of the land area of each county is included in the
Henderson-Webster SO<INF>2</INF> Nonattainment Area. Kentucky
determined nonattainment area partial county emissions (for on-road,
non-road) by apportioning a ratio of the whole and partial county
population using the 2010 U.S. Census data to each relevant emission
source category.\13\ DAQ estimated partial county population using
census blocks data within the respective partial county boundary. Then
DAQ multiplied the whole and partial county population to obtain an
area population ratio that was then multiplied by the Henderson and
Webster County emissions data to obtain the partial county emissions
data for non-road, on-road and non-point source categories (i.e., eight
percent for Henderson County and 25 percent for Webster County). See
Appendix A of Kentucky's February 15, 2024, SIP revision. Because the
point sources are located completely within the nonattainment area, DAQ
did not apportion the population ratio to this category. Table 1 below
summarizes the level of SO<INF>2</INF> emissions, expressed in tpy for
2017 and 2018 base year in the Henderson-Webster SO<INF>2</INF>
Nonattainment Area by emission source type. Table 1 also includes total
county emissions for Henderson and Webster County for context.
Additional discussion for each emission source category is provided
below.
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\13\ Kentucky chose the 2010 census year because at the time the
emissions inventory was developed it was the most recent and
complete census database prior to the 2018 base year. Additionally,
Kentucky acknowledged there were no census tract population data for
the 2020 census at the time the emissions inventory was developed.
[[Page 42892]]
Table 1--Base Year SO2 Emissions Inventory for the Henderson-Webster SO2 Nonattainment Area
[tpy]
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Point Non-point On-road Non-road
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Henderson County
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Total County Emissions.......................... \14\ 4240.18 14.13 0.14 0.40
Area percent adjustment (eight percent)......... * N/A 1.13 0.01 0.03
Nonattainment Area Emissions.................... 4240.18 1.13 0.01 0.03
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Webster County
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Total County Emissions.......................... 4962.91 6.43 0.05 0.16
Area percent adjustment (25 percent)............ * N/A 1.61 0.01 0.04
Nonattainment Area Emissions.................... 4962.91 1.61 0.01 0.04
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Total Nonattainment Area Emissions for Webster 9203.09 2.74 0.02 0.07
and Henderson County +.........................
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* All point sources are located within the Henderson-Webster SO2 Nonattainment Area, so the area percent
adjustment does not apply.
+ Point source data: 2018 KYEIS; Nonpoint, Onroad and Nonroad data: 2017 NEI. Please see Table 15 in the
February 15, 2024, SIP revision.
C. Point Sources
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\14\ EPA notes an emissions data discrepancy between Kentucky's
EIS 2018 point source emissions (4240.18 tons) and EPA's 2018 NEI
emissions (4629.79 tons). According to DAQ, the difference between
the two databases was due to a reporting error. Because EPA uses
data provided by states to reflect data in the NEI database the
Kentucky's EIS 2018 would provide the most current data available.
For more information, please see the copy of the August 15, 2025,
letter from DAQ included in the docket.
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The primary SO<INF>2</INF> emitting stationary sources in the
Henderson-Webster SO<INF>2</INF> Nonattainment Area at the time of the
nonattainment designation were the Century Aluminum facility in
Henderson County and the BREC Green and Reid/HMP&L power plants in
Webster County, according to the February 15, 2024, SIP revision. BREC
owns all the electric generating units at BREC Reid/HMP&L Station 2 and
BREC Green Station. Kentucky obtained 2018 actual SO<INF>2</INF>
emissions data for these stationary sources from the Commonwealth's
emissions inventory database, KYEIS. Partial county emissions were not
needed for the point source emission category because the power plants
and industrial sources are located within the Henderson-Webster
SO<INF>2</INF> Nonattainment Area boundary.
<bullet> Century Aluminum is an aluminum producing facility that at
the time of the nonattainment designation consisted of four primary
SO<INF>2</INF> emission units: three primary aluminum potlines and one
anode bake furnace (ABF).\15\ Century Aluminum's title V permit
provides a potential to emit of 5,853 tons SO<INF>2</INF> per year.
According to the Cabinet, 46 percent of all SO<INF>2</INF> emissions in
the Henderson-Webster SO<INF>2</INF> Nonattainment Area are from
Century Aluminum and essentially all the SO<INF>2</INF> emitted from
the facility comes from the oxidation of sulfur that comes into the
plant in the petroleum coke and pitch raw materials. To accurately
account for total SO<INF>2</INF> emissions, Century Aluminum uses a
mass balance method based on the sulfur content of raw materials (i.e.,
raw petroleum coke and pitch). Thus, each month, Century Aluminum
compiles data on the sulfur content contained in the raw materials and
estimates the sum of SO<INF>2</INF> emissions from each emission unit
using the facility's mass balance method \16\ taking into consideration
various emission factors for each source (i.e., sum of total ABF and
potline emissions). The estimated annual SO<INF>2</INF> emissions from
2017-2019 using the mass balance method is found in Table 2 below.\17\
The 2018 emissions in Table 2 contribute to the total point source
emissions for Henderson County in Table 1 above.
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\15\ A list of all SO<INF>2</INF> emitting units at the facility
may be found in Table 5 of Kentucky's February 15, 2024, revision.
\16\ Century Aluminum's mass balance approach has historically
been termed the ``SO<INF>2</INF> Calculation Engine.'' The
SO<INF>2</INF> Calculation Engine has previously been reviewed and
approved by the Division and is currently the stipulated method
within the facility's title V permit for calculating actual 12-month
rolling average SO<INF>2</INF> emissions. An example of the mass
balance calculation using data from September of 2018 is included in
Table 3--September 2018 SO<INF>2</INF> Calculation Engine for
Century Aluminum Emissions, from Kentucky's February 15, 2024, SIP
revision.
\17\ The SO<INF>2</INF> Calculation Engine calculations equal
the actual emissions data found in Kentucky's February SIP revision,
Appendix A, a spreadsheet titled, ``Henderson-Webster Base Year
Emissions Inventory.''
Table 2--Century Aluminum Estimated SO2 Emissions
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SO2 Emission totals (tpy)
-----------------------------------------------
2017 2018 2019
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Century Aluminum................................................ 4629.26 4239.26 4314.17
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<bullet> Green Station is a power plant in Webster County. At the
time of SO<INF>2</INF> designations, Green Station consisted of two
coal-fired boilers (Units G1 and G2) with actual SO<INF>2</INF>
emissions for the 2018 base year of 4,114.50 tons of SO<INF>2</INF>
combined contributing 45 percent of the total SO<INF>2</INF> emissions
in the Henderson-Webster SO<INF>2</INF> Nonattainment Area. Both units
were converted to natural gas-fired on May 26, 2022.\18\ Table 3 below
provides the actual SO<INF>2</INF> emissions in tpy for 2017 to 2019
for BREC-Green Station. The 2018 emissions in Table 3 contribute to the
total point source emissions for Green Station in Table 1 above for
Webster County.
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\18\ See natural gas conversion documentation for BREC--Green
Station in Appendix C of Kentucky's February 15, 2024, SIP revision.
[[Page 42893]]
Table 3--BREC Green Station 2 SO2 Emissions
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SO2 Emission totals (tpy)
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Unit 2017 2018 2019
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BREC-Green Station.................. G1........................ 2,334.41 2,689.65 2,163.18
G2........................ 773.72 1,424.85 752.44
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Emission Totals................. .......................... 3,108.14 4,114.50 2,915.62
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<bullet> The Robert Reid and HMP&L Station 2, at the time of the
nonattainment designation, were permitted as a single, stationary
electric power generating source in Webster County with one title V
operating permit and four boilers. Two boilers were owned and operated
by Reid Station (Unit 1--R1 and an emergency peaking unit Reid
Combustion Turbine--RT).\19\ The remaining two coal-fired units were
owned by HMP&L (Henderson Station Unit 1 (H1) and 2 (H2)) but also
operated by BREC.
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\19\ See Permit No. V-11-003 R1 in Appendix B of Kentucky's
February 15, 2024, SIP revision.
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[cir] The Reid Station units ceased operations in May 2015 to
convert from coal-fired burners to new natural gas-fired low
NO<INF>x</INF> burners. However, due to compliance issues, the units
never converted to natural gas, nor did the facility resume
operations.\20\ Reid Station's operating authority was officially
revoked January 17, 2022, when its operating permit was merged with the
BREC Green Station title V operating permit V-19-020 R2. Unit R1 has
been removed from the permit.\21\ \22\ Reid station emitted no
SO<INF>2</INF> emissions in 2018 due to the facility's operational
shutdown in 2015. Thus, no actual 2018 SO<INF>2</INF> emissions for the
facility are reflected in the total point source emissions in Table 1.
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\20\ In 2015, Reid Station ceased operating to undergo a natural
gas conversion; however, this modification was delayed.
\21\ Reid Station Unit R1 was removed from the merged Green
Station operating permit.
\22\ See Permit No. V-19-020 R2 in Appendix B of Kentucky's
February 15, 2024, SIP revision.
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[cir] In 2018, the two HMP&L units (EU 02 and 03) were owned by the
city of Henderson, operated by BREC, and emitted a cumulative 846.55
tons of SO<INF>2</INF>. The remaining emergency diesel generator (EU
07), emergency fire pump (EU 08), and the Reid Combustion Turbine-RT
(EU 06) emitted negligible SO<INF>2</INF> emissions in 2018.\23\ The
facility retired on February 1, 2019.\24\ Table 4 shows the total
SO<INF>2</INF> emissions from the BREC HMP&L Station 2 units from 2017
through 2019. The 2018 emissions are included in the total point source
SO<INF>2</INF> emissions for Webster County provided in Table 1 above.
---------------------------------------------------------------------------
\23\ See Appendix C of Kentucky's February 15, 2024, SIP
revision.
\24\ See documentation for BREC HMP&L Station 2 in Appendix C of
Kentucky's February 15, 2024, SIP revision.
Table 4--BREC HMP&L Station 2 SO2 Emissions
----------------------------------------------------------------------------------------------------------------
SO2 Emissions totals (tpy)
---------------------------------------------------------------------------
Unit 2017 2018 2019
----------------------------------------------------------------------------------------------------------------
HMP&L............................... EU 02..................... 591.47 423.55 7.60
EU 03..................... 816.58 423.00 9.30
EU 06..................... 1.27 1.85 2.89
EU 07..................... 0.01 0.00 0.00
EU 08..................... 0.00 0.00 0.00
-----------------------------------------------
Emission Totals................. .......................... 1409.33 848.40 19.79
----------------------------------------------------------------------------------------------------------------
D. Minor Point Sources
Kentucky also identified five minor point sources in the Area.
Cumulatively, these minor point sources contributed less than one ton
of SO<INF>2</INF> emissions in 2018. Table 5 below lists the minor
point sources in the Area and their 2018 emissions. These emissions are
included in the total point source emissions in Table 1.
Table 5--2018 Minor Point Source Actual SO2 Emissions for the Henderson-
Webster SO2 Nonattainment Area
------------------------------------------------------------------------
SO2 Emissions
Minor point source (tpy)
------------------------------------------------------------------------
Henderson
------------------------------------------------------------------------
AMG Aluminum North America LLC........................ 0.01
American Tower Corp................................... 0.02
Kentucky 5 Star Energy LLC............................ 0.00
Tyson Chicken Inc.--Robards Facility.................. 0.90
------------------------------------------------------------------------
Webster
------------------------------------------------------------------------
Tyson Chicken Inc.--Sebree Feed Mill.................. 0.02
-----------------
[[Page 42894]]
Emission Total.................................... 0.95
------------------------------------------------------------------------
E. Other Emission Source Categories
On-road emission source emissions include vehicles such as
automobiles, trucks, motorcycles, and other motor vehicles traveling on
public roadways that use gasoline, diesel, and other fuels in the
Henderson-Webster SO<INF>2</INF> Nonattainment Area. As mentioned
before, Kentucky utilized MOVES3.0.4 in collaboration with the Kentucky
Transportation Cabinet \25\ to develop the on-road emission estimates
for the partial county Henderson-Webster SO<INF>2</INF> Nonattainment
Area and apportioned to the Area based on the population adjustment
percentage discussed above. Kentucky estimated the total 2017 on-road
SO<INF>2</INF> emissions for the Henderson County portion and the
Webster County portion of the Area at 0.01 tpy each; thus,
collectively, the 2017 on-road emissions for the entire Henderson-
Webster SO<INF>2</INF> Nonattainment Area is estimated to be 0.02
tpy.<SUP>26 27</SUP> A more detailed discussion of the on-road
emissions inventory development for the Area can be found in the
Commonwealth's February 15, 2024, revision.
---------------------------------------------------------------------------
\25\ See Appendix D for more information on the data used.
\26\ The emission totals in Henderson and Webster Counties were
apportioned to the Henderson-Webster SO<INF>2</INF> Nonattainment
Area using a percentage adjustment derived from 2010 Census Bureau
population data.
\27\ Emissions data can be found in Appendix A of the February
15, 2024, SIP revision.
---------------------------------------------------------------------------
The Cabinet calculated non-point and non-road emissions for the
Area using the 2017 NEI for each county and a percentage adjustment
derived from 2010 Census Bureau population data. The Cabinet estimated
the non-point emissions for the portion of Henderson County in the Area
at 1.13 tpy SO<INF>2</INF> and 0.03 tpy for non-road SO<INF>2</INF>
emissions. For the portion of Webster County in the Area, the Cabinet
estimated 1.61 tpy of SO<INF>2</INF> for non-point and 0.04 tpy
SO<INF>2</INF> for non-road SO<INF>2</INF> emissions. A more detailed
discussion of the emissions inventory development for the Area can be
found in the Commonwealth's February 15, 2024, revision.
Table 1 above summarizes the major point and minor point 2018 base
year and on-road, non-road, and non-point 2017 base year emissions,
expressed in tpy, in the Area. The Cabinet determined that point
sources account for more than 99 percent of the total SO<INF>2</INF>
emissions in the Henderson-Webster SO<INF>2</INF> Nonattainment Area.
According to Kentucky's estimates, Century Aluminum in Henderson County
accounted for 45 percent of the total SO<INF>2</INF> emissions in the
Area and BREC-Green Station accounted for 46 percent of the total. The
remaining two point sources at BREC HMP&L Station 2 contributed nine
percent, and, due to the 2015 operational shutdown, BREC Reid emitted
no SO<INF>2</INF> emissions in 2018.
EPA has analyzed Kentucky's February 15, 2024, SIP revision for
consistency with CAA section 172(c)(3). This included Kentucky's
methodology for apportioning partial county emissions, its rationale
for using 2018 base year emissions for point source and 2017 base year
emissions for the remaining source categories (on-road, non-road, and
non-point sources), and its methodology to quantify emissions estimates
for on-road and non-road sources. Based on this analysis, EPA is
proposing to approve Kentucky's base year emissions inventory for the
Henderson-Webster SO<INF>2</INF> Nonattainment Area.
III. Proposed Actions
For the reasons discussed above, EPA is proposing to approve
Kentucky's January 26, 2024, and February 15, 2024, SIP revisions
containing a certification that its existing SIP-approved NNSR program
meets the NNSR requirements for the 2010 SO<INF>2</INF> NAAQS and an
emissions inventory, respectively, for the Henderson-Webster
SO<INF>2</INF> Nonattainment Area.
IV. 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, these
proposed actions merely propose to approve state law as meeting Federal
requirements and does not impose additional requirements beyond those
imposed by state law. For that reason, these proposed actions:
<bullet> Are not significant regulatory actions subject to review
by the Office of Management and Budget under Executive Orders 12866 (58
FR 51735, October 4, 1993);
<bullet> Are not subject to Executive Order 14192 (90 FR 9065,
February 6, 2025) because SIP actions are exempt from review under
Executive Order 12866;
<bullet> Do not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
<bullet> Are 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> Do 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> Do not have federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
<bullet> Are not subject to Executive Order 13045 (62 FR 19885,
April 23, 1997) because they approve a state program;
<bullet> Are not significant regulatory actions subject to
Executive Order 13211 (66 FR 28355, May 22, 2001); and
<bullet> Are 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.
In addition, the SIP is not approved to apply on any Indian
reservation land or in any other area where EPA or an Indian tribe has
demonstrated that a tribe has jurisdiction. In those areas of Indian
country, the rule does not have Tribal implications and will not impose
substantial direct costs on Tribal governments or preempt Tribal law as
specified by Executive Order 13175 (65 FR 67249, November 9, 2000).
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Sulfur oxides.
Authority: 42 U.S.C. 7401 et seq.
[[Page 42895]]
Dated: August 27, 2025.
Kevin McOmber,
Regional Administrator, Region 4.
[FR Doc. 2025-17048 Filed 9-4-25; 8:45 am]
BILLING CODE 6560-50-P
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