Document ID: EPA-R04-OAR-2020-0003-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Kentucky; Redesignation of the Jefferson County 2010 1-Hour Sulfur Dioxide Nonattainment Area to Attainment
Posted Date: 2020-05-15T04:00Z

[Federal Register Volume 85, Number 95 (Friday, May 15, 2020)]
[Proposed Rules]
[Pages 29381-29391]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-10063]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[EPA-R04-OAR-2020-0003; FRL-10009-11-Region 4]

Air Plan Approval and Designation of Areas; KY; Redesignation of 
the Jefferson County 2010 1-Hour Sulfur Dioxide Nonattainment Area to 
Attainment

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: In a letter dated December 9, 2019, the Commonwealth of 
Kentucky, through the Kentucky Division of Air Quality (KDAQ) on behalf 
of the Louisville Metro Air Pollution Control District (LMAPCD), 
submitted a request for the Environmental Protection Agency (EPA) to 
redesignate the Jefferson County sulfur dioxide (SO2) 
nonattainment area (hereinafter referred to as the ``Jefferson County 
Area'' or ``Area'') to attainment for the 2010 1-hour SO2 
primary national ambient air quality standard (NAAQS) and to approve an 
accompanying state implementation plan (SIP) revision containing a 
maintenance plan for the Area. EPA is proposing to determine that the 
Jefferson County Area has attained the 2010 1-hour SO2 
NAAQS; to approve the SIP revision containing the Commonwealth's plan 
for maintaining attainment of the 2010 1-hour SO2 standard 
and to incorporate the maintenance plan into the SIP; and to 
redesignate the Jefferson County Area to attainment for the 2010 1-hour 
SO2 NAAQS.

DATES: Comments must be received on or before June 15, 2020.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R04-
OAR-2020-0003 at http://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. EPA may publish any comment 
received to its public docket. Do not submit electronically any 
information you consider to be Confidential Business Information (CBI) 
or other information whose disclosure is restricted by statute. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e., on the web, cloud, or other file sharing 
system). For additional submission methods, the full EPA public comment 
policy, information about CBI or multimedia submissions, and general 
guidance on making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Madolyn Sanchez, Air Regulatory 
Management Section, Air Planning and Implementation Branch, Air and 
Radiation Division, U.S. Environmental Protection Agency, Region 4, 61 
Forsyth Street SW, Atlanta, Georgia 30303-8960. Ms. Sanchez may be 
reached by phone at (404) 562-9644 or via electronic mail at 
sanchez.madolyn@epa.gov.

SUPPLEMENTARY INFORMATION:

I. What are the actions EPA is proposing to take?

    EPA is proposing to take the following three separate but related 
actions: (1) To determine that the Jefferson County Area has attained 
the 2010 1-hour SO2 NAAQS; (2) to approve Kentucky's plan 
for maintaining the 2010 1-hour SO2 NAAQS in the Area 
through 2032 and incorporate it into the SIP; and (3) to redesignate 
the Jefferson County Area to attainment for the 2010 1-hour 
SO2 NAAQS. The Jefferson County Area is comprised of the 
portion of Jefferson County encompassed by the polygon with the 
vertices using Universal Traverse Mercator (UTM) coordinates in UTM 
zone 16 with datum NAD83 as follows: (1) Ethan Allen Way extended to 
the Ohio River at UTM Easting (m) 595738, UTM Northing 4214086 and 
Dixie Highway (US60 and US31W) at UTM Easting (m) 597515, UTM Northing 
4212946; (2) Along Dixie Highway from UTM Easting (m) 597515, UTM 
Northing 4212946 to UTM Easting (m) 595859, UTM Northing 4210678; (3) 
Near the adjacent property lines of Louisville Gas and Electric-Mill 
Creek Electric Generating Station and Kosmos Cement where they join 
Dixie Highway at UTM Easting (m) 595859, UTM Northing 4210678 and the 
Ohio River at UTM Easting (m) 595326, UTM Northing 4211014; (4) Along 
the Ohio River from UTM Easting (m) 595326, UTM Northing 4211014 to UTM 
Easting (m) 595738, UTM Northing 4214086. The Area consists primarily 
of the Louisville Gas & Electric (LG&E) Mill Creek Generating Station 
(Mill Creek) and the area surrounding the monitor immediately north of 
that facility. Mill Creek is the only point source of SO2 
emissions within the Jefferson County Area.

[[Page 29382]]

    EPA is proposing to determine that the Jefferson County Area has 
attained the 2010 1-hour SO2 NAAQS. EPA is also proposing to 
approve Kentucky's SIP revision containing the maintenance plan for the 
Jefferson County Area in accordance with the requirements of section 
175A of the Clean Air Act (CAA or Act). The maintenance plan submitted 
with Kentucky's request for redesignation is intended to help keep the 
Jefferson County Area in attainment of the 2010 1-hour SO2 
NAAQS through the year 2032.
    EPA is also proposing to determine that the Jefferson County Area 
has met the requirements for redesignation under section 107(d)(3)(E) 
of the CAA. Accordingly, EPA is proposing to approve a request to 
change the legal designation of the portion of Jefferson County that is 
designated nonattainment to attainment for the 2010 1-hour 
SO2 NAAQS.

II. Background

    On June 2, 2010, EPA revised the primary SO2 NAAQS, 
establishing a new 1-hour SO2 standard of 75 parts per 
billion (ppb). See 75 FR 35520 (June 22, 2010).\1\ Under EPA's 
regulations at 40 CFR part 50, the 2010 1-hour SO2 NAAQS is 
met at a monitoring site when the 3-year average of the annual 99th 
percentile of daily maximum 1-hour average concentrations is less than 
or equal to 75 ppb (based on the rounding convention in 40 CFR part 50, 
appendix T). See 40 CFR 50.17. Ambient air quality monitoring data for 
the 3-year period must meet a data completeness requirement. A year 
meets data completeness requirements when all four quarters are 
complete, and a quarter is complete when at least 75 percent of the 
sampling days for each quarter have complete data. A sampling day has 
complete data if 75 percent of the hourly concentration values, 
including state-flagged data affected by exceptional events which have 
been approved for exclusion by the Administrator, are reported.\2\
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    \1\ On February 25, 2019, EPA retained the existing 2010 primary 
NAAQS for SO2 of 75 parts per billion (ppb) based on the 
3-year average of the 99th percentile of the annual distribution of 
1-hour daily maximum concentrations. See 84 FR 9866.
    \2\ See 40 CFR part 50, appendix T, section 3(b).
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    Upon promulgation of a new or revised NAAQS, the CAA requires EPA 
to designate as nonattainment any area that does not meet (or that 
contributes to ambient air quality in a nearby area that does not meet) 
the NAAQS. EPA designated the Jefferson County Area as nonattainment 
for the 2010 1-hour SO2 NAAQS, effective on October 4, 2013, 
based on 2009-2011 complete, quality assured, and certified ambient air 
quality data. See 78 FR 47191 (August 5, 2013). Under the CAA, 
nonattainment areas must attain the NAAQS as expeditiously as 
practicable but not later than five years after the October 4, 2013, 
effective date of the designation. See CAA section 192(a). Therefore, 
the Jefferson County Area's applicable attainment date was no later 
than October 4, 2018.
    EPA's 2010 SO2 nonattainment designation for the Area 
triggered an obligation for Kentucky to develop a nonattainment SIP 
revision addressing certain requirements under title I, part D, subpart 
1 (hereinafter ``Subpart 1''), and to submit that SIP revision to EPA 
in accordance with the deadlines in title I, part D, subpart 5 
(hereinafter ``Subpart 5''). Subpart 1 contains the general 
requirements for nonattainment areas for criteria pollutants, including 
requirements to develop a SIP that provides for the implementation of 
reasonably available control measures (RACM), requires reasonable 
further progress (RFP), includes base-year and attainment-year 
emissions inventories, a SIP-approved nonattainment new source review 
(NNSR) permitting program, enforceable emission limitations and other 
such control measures, and provides for the implementation of 
contingency measures. This SIP revision was due within 18 months 
following the October 4, 2013, effective date of designation (i.e., 
April 4, 2015). See CAA section 191(a). Kentucky submitted a 
nonattainment SIP revision to EPA on June 23, 2017.\3\
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    \3\ EPA published a notice on March 18, 2016 (81 FR 14736), 
announcing its finding that Kentucky (and other pertinent states) 
had failed to submit the required SO2 nonattainment plan 
by the submittal deadline. The finding initiated a deadline under 
CAA section 179(a) for the potential imposition of NNSR offset and 
highway funding sanctions. However, pursuant to Kentucky's submittal 
of June 23, 2017 (received by EPA on July 6, 2017), and EPA's 
subsequent letter dated October 10, 2017, to Kentucky finding the 
submittal to be complete and noting the termination of these 
sanctions deadlines, the sanctions under section 179(a) were not and 
will not be imposed as a result of Kentucky having missed the April 
4, 2015, submittal deadline.
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    On June 28, 2019 (84 FR 30920), EPA approved Kentucky's June 23, 
2017, SO2 nonattainment SIP revision. EPA determined that 
the nonattainment SIP revision met the applicable requirements of 
sections 110, 172, 191, and 192 of the CAA and nonattainment regulatory 
requirements at 40 CFR part 51 (including Kentucky's attainment 
modeling demonstration for the Jefferson County Area). As discussed in 
Section V below, the attainment modeling demonstration inputs included 
SO2 emission limits and compliance parameters (monitoring, 
recordkeeping, and reporting) at Mill Creek established in the 
facility's title V permit 145-97- TV(R3) at Plant-wide Specific 
condition S1-Standards, S2-Monitoring and Record Keeping, and S3-
Reporting. EPA incorporated these limits and parameters into the SIP as 
part of its final action on Kentucky's nonattainment SIP revision, thus 
making them permanent and enforceable controls.

III. What are the criteria for redesignation?

    The CAA provides the requirements for redesignating a nonattainment 
area to attainment. Specifically, section 107(d)(3)(E) of the CAA 
allows for redesignation provided that the following criteria are met: 
(1) The Administrator determines that the area has attained the 
applicable NAAQS; (2) the Administrator has fully approved the 
applicable implementation plan for the area under section 110(k); (3) 
the Administrator determines that the improvement in air quality is due 
to permanent and enforceable reductions in emissions resulting from 
implementation of the applicable SIP and applicable federal air 
pollutant control regulations, and other permanent and enforceable 
reductions; (4) the Administrator has fully approved a maintenance plan 
for the area as meeting the requirements of section 175A; and (5) the 
state containing such area has met all requirements applicable to the 
area for purposes of redesignation under section 110 and part D of the 
CAA.
    On April 16, 1992 (57 FR 13498), EPA provided guidance on 
redesignations in the General Preamble for the Implementation of title 
I of the CAA Amendments of 1990 and supplemented this guidance on April 
28, 1992 (57 FR 18070). EPA has provided further guidance on processing 
redesignation requests in the following documents:
    1. ``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'');
    2. ``State Implementation Plan (SIP) Actions Submitted in Response 
to Clean Air Act (CAA) Deadlines,'' Memorandum from John Calcagni, 
Director, Air Quality Management Division, October 28, 1992;
    3. ``Part D New Source Review (Part D NSR) Requirements for Areas 
Requesting Redesignation to Attainment,'' Memorandum from Mary D. 
Nichols, Assistant Administrator for

[[Page 29383]]

Air and Radiation, October 14, 1994; and
    4. ``Guidance for 1-Hour SO2 Nonattainment Area SIP 
Submissions,'' Memorandum from Stephen D. Page, April 23, 2014 
(hereinafter referred to as the ``SO2 Nonattainment Area 
Guidance'').
    EPA's SO2 Nonattainment Area Guidance discusses the CAA 
requirements that air agencies need to address when implementing the 
2010 SO2 NAAQS in areas designated as nonattainment for the 
standard. The guidance includes recommendations for air agencies to 
consider as they develop SIPs to satisfy the requirements of sections 
110, 172, 175A, 191, and 192 of the CAA to show future attainment and 
maintenance of the 2010 SO2 NAAQS. Additionally, the 
SO2 nonattainment guidance provides recommendations for air 
agencies to consider as they develop redesignation requests and 
maintenance plans to satisfy the requirements of sections 107(d)(3)(E) 
and 175A.

IV. Why is EPA proposing these actions?

    Through a letter dated December 9, 2019, Kentucky submitted a 
request for EPA to redesignate the Jefferson County Area to attainment 
for the 2010 1-hour SO2 NAAQS and submitted an associated 
SIP revision containing a maintenance plan. EPA's evaluation indicates 
that the Jefferson County Area meets the requirements for redesignation 
as set forth in section 107(d)(3)(E), including the maintenance plan 
requirements under section 175A of the CAA. As a result of this 
evaluation, EPA is proposing to determine that the Area has attained 
the 2010 1-hour SO2 NAAQS based upon air monitoring data for 
2016-2018 and air quality dispersion modeling analyses. EPA is also 
proposing to approve Kentucky's maintenance plan for maintaining the 
2010 1-hour SO2 NAAQS in the Area and incorporate it into 
the SIP and to redesignate the Jefferson County Area to attainment for 
the 2010 1-hour SO2 NAAQS.

V. What is EPA's analysis of the redesignation request and SIP 
revision?

    The five redesignation criteria provided under CAA section 
107(d)(3)(E) are discussed in greater detail for the Jefferson County 
Area in the following paragraphs.

Criterion (1)--The Administrator Uetermines Uhat the Urea Has Attained 
the NAAQS

    For redesignating a nonattainment area to attainment, the CAA 
requires EPA to determine that the area has attained the applicable 
NAAQS (CAA section 107(d)(3)(E)(i)). As discussed in section VIII.A of 
the SO2 Nonattainment Area Guidance, there are generally two 
components needed to support an attainment determination for 
SO2, which should be considered interdependently. The first 
component relies on air quality monitoring data. For SO2, 
any available monitoring data would need to indicate that all monitors 
in the affected area are meeting the standard as stated in 40 CFR 50.17 
using data analysis procedures specified in 40 CFR part 50, Appendix T. 
The second component relies on air quality modeling. If there are no 
air quality monitors located in the affected area, or there are air 
quality monitors located in the area, but analyses show that none of 
the monitors are located in the area of maximum ambient air 
SO2 concentration,\4\ then air quality dispersion modeling 
will generally be needed to estimate SO2 concentrations in 
the area. Such dispersion modeling should be conducted to estimate 
SO2 concentrations throughout the nonattainment area using 
actual emissions and meteorological information for the most recent 
three calendar years. However, EPA may also make determinations of 
attainment based on the modeling from the attainment demonstration for 
the applicable SIP for the affected area, eliminating the need for 
separate actuals-based modeling to support the determination that an 
area is currently attaining. If the air agency has previously submitted 
a modeled attainment demonstration using allowable emissions, no 
further modeling is needed as long as the source characteristics are 
still reasonably represented and so long as emissions are at or below 
allowable levels. In a case such as this, where both monitoring and 
modeling evidence are available, EPA will consider both types of 
evidence.
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    \4\ See section VIII.A of the SO2 Nonattainment Area 
Guidance.
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    Kentucky's pre- and post-modification attainment demonstration 
modeling indicates that the Watson Lane Elementary School (Watson Lane) 
monitor is not sited in the area of maximum concentration for Mill 
Creek, and therefore, the clean monitoring data at the monitor does not 
on its own demonstrate that the Area is attaining the standard. EPA's 
proposed determination that the Jefferson County Area is attaining the 
SO2 NAAQS is also based on the modeled attainment 
demonstration that includes permanent and enforceable SO2 
emissions limits at Mill Creek showing attainment of the 2010 1-hour 
SO2 NAAQS. The modeled attainment demonstration accounts for 
more efficient wet flue gas desulfurization (FGD) control equipment at 
Mill Creek that became operational in stages from 2014 to 2016, as well 
as revised SO2 emission limits.\5\ EPA approved the 
attainment demonstration for the Jefferson County Area on June 28, 
2019, and incorporated the new SO2 emission limits including 
monitoring, recordkeeping, and reporting parameters into the SIP, 
making them permanent and enforceable. See 84 FR 30920. Monitoring data 
from the Watson Lane monitor and Kentucky's approved modeled attainment 
demonstration are discussed below.
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    \5\ See the ``Criterion (3)'' section of this notice for 
additional information.
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Monitoring Data
    For SO2, a monitoring site may be considered to be 
attaining the 2010 1-hour SO2 NAAQS if it meets the NAAQS as 
determined in accordance with 40 CFR 50.17 and Appendix T of part 50, 
based on three complete, consecutive calendar years of quality-assured 
air quality monitoring data. Specifically, to attain the NAAQS at each 
monitoring site, the 3-year average of the annual 99th percentile 
(fourth highest value) of daily maximum 1-hour average concentrations 
measured at each monitor within an area must be less than or equal to 
75 ppb. The data must be collected and quality-assured in accordance 
with 40 CFR part 58 and recorded in the EPA Air Quality System (AQS). 
The monitors should have remained at the same location for the duration 
of the monitoring period required for demonstrating attainment.
    Kentucky currently operates one ambient SO2 monitor in 
the Area, the Watson Lane SO2 monitor (AQS ID: 21-111-0051). 
This monitor is located less than 2 kilometers (km) east of Mill Creek. 
The original nonattainment designation was based on the 2009-2011 
design value of 112 ppb at this monitor. As shown in Table 1, the 
design values at this monitor have decreased since the 2014-2016 design 
value, and the quality-assured, complete, and certified 2016-2018 3-
year design value is 19 ppb, well below the 2010 1-hour SO2 
standard of 75 ppb.

[[Page 29384]]

There have been no 1-hour values recorded above the standard since 
March 2015. The first three-year period for which the design value for 
the Area fell below the standard was 2015-2017.

                                               Table 1--Jefferson County Area SO2 Monitored Design Values
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                                                           2009-2011   2010-2012   2011-2013   2012-2014   2013-2015   2014-2016   2015-2017   2016-2018
            Monitoring station (AQS Site ID)                Design      Design      Design      Design      Design      Design      Design      Design
                                                             value       value       value       value       value       value       value     value \6\
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Watson Lane Elementary School (21-111-0051).............     112 ppb      123ppb        ND *        ND *        ND *      76 ppb      31 ppb      19 ppb
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* The Watson Lane monitor did not collect a valid design value during 2011-2013, 2012-2014, and 2013-2015 due to incomplete data in 2013.

    Preliminary monitoring data from the Watson Lane monitor for 2019 
indicates that the 2017-2019 preliminary design value is 15 ppb.\7\ EPA 
is proposing to determine that the Jefferson County Area has attained 
the 2010 1-hour SO2 NAAQS based on the modeling analysis 
discussed below, as well as the quality-assured, complete, and 
certified ambient air monitoring data for the 2016-2018 period that 
does not indicate a NAAQS violation. If, before EPA takes final action, 
monitoring data or other evidence causes EPA to conclude that the Area 
is not continuing to meet the standard, EPA will not go forward with 
the redesignation. As discussed in more detail below, Kentucky has 
committed to continue monitoring ambient SO2 concentrations 
in this Area in accordance with 40 CFR part 58. Any future changes to 
the state or local air monitoring station (SLAMS) network in the Area 
will be submitted to EPA for approval in Kentucky's annual ambient air 
monitoring network plan, as required by 40 CFR 58.10.
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    \6\ The 2018 data is available at https://www.epa.gov/outdoor-air-quality-data/monitor-values-report.
    \7\ Preliminary 2019 data is available at https://www.epa.gov/outdoor-air-quality-data/monitor-values-report.
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Kentucky's EPA-Approved Modeling Analysis
    As discussed in Section VIII.A. of the SO2 Nonattainment 
Area Guidance, air quality dispersion modeling will generally be needed 
to demonstrate attainment in addition to attaining air quality 
monitoring data (in accordance with 40 CFR 50.17 and Appendix T of part 
50) if the existing monitor is not located in the area of maximum 
ambient air SO2 concentration. The SO2 attainment 
demonstration submitted by Kentucky on June 23, 2017, provided an air 
quality dispersion modeling analysis demonstrating that the control 
strategies chosen by the Commonwealth and LMAPCD to reduce 
SO2 emissions at Mill Creek provide for attainment of the 
standard. The source characteristics in KDAQ's attainment demonstration 
still reflect current conditions. On June 28, 2019 (84 FR 30920), EPA 
approved this attainment demonstration along with LMAPCD's control 
strategies at the facility. Details regarding the control strategies 
and emissions reductions are provided in the Criterion (3) Section of 
this notice. Details regarding the modeling analysis are discussed in 
the following paragraphs.
    Kentucky's modeling analysis was developed in accordance with EPA's 
Guideline on Air Quality Models (Modeling Guideline) \8\ and the 
SO2 Nonattainment Area Guidance, and was prepared using 
EPA's preferred dispersion modeling system, the American Meteorological 
Society/Environmental Protection Agency Regulatory Model (AERMOD) 
consisting of the AERMOD (version 15181) \9\ model and multiple data 
input preprocessors as described below. Kentucky used regulatory 
default options and the rural land use designation in the AERMOD 
modeling. Appendix A in Kentucky's December 9, 2019, submittal provides 
a summary of the modeling procedures and options, including details 
explaining how they applied the Auer technique to determine that the 
rural dispersion coefficients were appropriate for the modeling.
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    \8\ See 40 CFR part 51 Appendix W (EPA's Guideline on Air 
Quality Models) (January 17, 2017) located at https://www3.epa.gov/ttn/scram/appendix_w/2016/AppendixW_2017.pdf.
    \9\ Version 15181 of the AERMOD Modeling System was the current 
EPA-recommended regulatory version at the time the modeling was 
performed in 2016-2017, and therefore, was appropriate for the 
modeling analysis.
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    The pre-processors AERMET (version 15181) and AERMINUTE (version 
15272) were used to process five years (i.e., 2011-2015) of 1-minute 
meteorological data from the Louisville Muhammad Ali International 
Airport station in Louisville, Kentucky, located about 20 km to the 
northeast of Mill Creek. Twice daily upper-air meteorological 
information came from the Wilmington Air Park, Wilmington, Ohio station 
located about 240 km to the northeast. The surface characteristics 
surrounding the meteorological surface station were processed using 
AERSURFACE version 13016 following EPA-recommended procedures and were 
determined to be representative of the facility by the Commonwealth.
    The AERMOD pre-processor AERMAP (version 11103) was used to 
generate terrain inputs for the receptors, based on a digital elevation 
mapping database from the National Elevation Dataset developed by the 
U.S. Geological Survey. Model receptors were located throughout the 
Area using a grid with 100-meter spacing between receptors.
    Mill Creek is the only SO2 emitting major point source 
in the Area and the only emission source that was explicitly modeled in 
the attainment modeling analysis for the Jefferson County Area. All 
minor area sources and other major point sources (located outside the 
nonattainment area boundary) were accounted for with the background 
concentration discussed below. Mill Creek operates four coal-fired 
boiler units (U1 thru U4) that emit from three stacks. Unit 1 and Unit 
2 have a joint stack (S33) while Unit 3 and Unit 4 have separate stacks 
(S4 and S34, respectively). The Commonwealth evaluated the emissions 
from Mill Creek and derived a set of three SO2 critical 
emission values (CEVs), one for each stack, from AERMOD modeling 
simulations to show compliance with the 2010 SO2 NAAQS. The 
AERMOD modeling analysis resulted in the following CEVs: Stack S33, 
which serves Units 1 and 2, was modeled at 225.4 grams/second (g/s) 
equivalent to 1,789 lb/hr; stack S4, which serves Unit 3, was modeled 
at 152.6 g/s equivalent to 1,211 lb/hr; and stack S34, which serves 
Unit 4, was modeled at 183.6 g/s equivalent to 1,457 lb/hr. In each 
case, the modeled emission rate corresponds to 0.29 pounds per million 
British thermal units (lb/MMBtu) times the maximum heat input capacity 
(MMBtu/

[[Page 29385]]

hr) of the unit(s) associated with each stack. This form of an emission 
limit, in lb/MMBtu, is a frequent form of emission limit associated 
with electric generating units. The Commonwealth determined from these 
AERMOD modeling simulations that an hourly emission limit of 0.29 lb/
MMBtu would suffice to ensure modeled attainment of the SO2 
NAAQS. However, the Commonwealth opted to apply a 30-day average limit, 
following EPA's SO2 Nonattainment Area Guidance for setting 
longer term average limits. The Commonwealth determined that a 30-day 
average limit of 0.20 lb/MMBtu could be considered comparably stringent 
to a 1-hour limit of 0.29 lb/MMBtu. A comprehensive discussion of the 
procedures used by the Commonwealth to determine the longer-term 
average limit is contained in EPA's rulemaking notices associated with 
the approval of the nonattainment SIP revision for the Jefferson County 
Area. See 83 FR 56002 (November 9, 2018) and 84 FR 30920 (June 28, 
2019).
    Kentucky selected background SO2 concentrations that 
vary by season and hour of day \10\ using local SO2 
monitoring data from the Green Valley Road monitor (AQS ID: 18-043-
1004) located in New Albany, Indiana, approximately 29 km north of the 
Mill Creek facility, for the period 2013-2015. The season-by-hour 
background values ranged from 2.13 ppb to 20.67 ppb. These background 
concentrations from the nearby ambient air monitor are used to account 
for SO2 impacts from all sources that are not specifically 
included in the AERMOD modeling analysis. A comprehensive discussion of 
the background concentrations and how they are used to account for 
SO2 emissions from all the sources not explicitly modeled is 
contained in EPA's notice of proposed rulemaking for the nonattainment 
SIP revision. See 83 FR 56002 (November 9, 2018).
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    \10\ Use of 99th percentile background concentrations that vary 
by season and hour of the day is an acceptable approach that is 
described in Appendix A, Section 8, of EPA's SO2 
Nonattainment Area Guidance.
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    The AERMOD modeling resulted in a maximum modeled design value of 
190.1 micrograms per cubic meter or 72.6 ppb, including the background 
concentrations, which is below the 1-hour SO2 NAAQS of 75 
ppb. The modeling used hourly SO2 emissions for each Mill 
Creek stack equivalent to the hourly SO2 emission rate of 
0.29 lb/MMBtu, which was used to derive the 30-day average emission 
limit for the four coal-fired boilers at Mill Creek. Mill Creek 
completed the phased installation of improved FGD SO2 
controls in 2016 and became subject to the new 30-day SO2 
emission limits on April 5, 2017, which reduced SO2 
emissions by approximately 89 percent from 2014 emission levels.\11\ 
Furthermore, the Watson Lane monitoring data corroborate the 
significant SO2 reductions from Mill Creek. EPA previously 
evaluated the modeling procedures, inputs, and results and finalized a 
determination that the Commonwealth's modeling analysis demonstrates 
that the 30-day emissions limits on Mill Creek assure that there will 
be no violations of the NAAQS within the Area.
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    \11\ Mill Creek's annual SO2 emissions have dropped 
from 28,149 tons in 2014 to 3,752 tons in 2018. Additionally, Mill 
Creek emitted a total of 2,923 tons in 2019. See https://ampd.epa.gov/ampd/.
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    All emissions limits and related compliance parameters have been 
incorporated into the Jefferson County portion of the Kentucky SIP, 
making these changes permanent and federally enforceable. More details 
on the pre-construction and post-construction operations at Mill Creek 
are included in Kentucky's June 23, 2017, nonattainment SIP submission 
and in EPA's rulemaking on that submittal.\12\
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    \12\ See 84 FR 30920 (June 28, 2019) (final rule), 83 FR 56002 
(November 9, 2018) (proposed rule). Kentucky's 2017 SIP submittal is 
included in the Docket for this proposed rulemaking.
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    On June 28, 2019, EPA approved the modeled attainment demonstration 
described above and concluded that it is consistent with CAA 
requirements, EPA's Modeling Guideline, and EPA's guidance for 
SO2 attainment demonstration modeling. The modeled controls 
have been fully implemented as of June 8, 2016, when the last of the 
new FGD SO2 controls began operation. Mill Creek became 
subject to the revised SO2 emission limits in the Title V 
permit on April 5, 2017. Emissions and air quality are at or below the 
levels modeled in Kentucky's attainment demonstration.\13\ Therefore, 
EPA proposes to find that air quality modeling supports the conclusion 
that the Area has attained the 2010 1-hour SO2 NAAQS.
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    \13\ A comparison of the Mill Creek unit-level potential to emit 
to the 2018 actual emissions indicate that SO2 emissions 
at Mill Creek are below the levels modeled in the 2017 attainment 
demonstration modeling. See Kentucky's December 9, 2019, 
redesignation and maintenance submission and https://ampd.epa.gov/ampd/. Furthermore, the monitoring data trends corroborate the 
existence of the substantial air quality benefits from the 
SO2 reductions at Mill Creek. The Watson Lane monitor has 
recorded decreasing SO2 concentrations from an annual 
99th percentile value of 148.6 ppb in 2014, 54.2 ppb in 2015, 26.1 
ppb in 2016, 13.7 ppb in 2017, and 16.4 ppb in 2018. The quality-
assured, complete, and certified 2016-2018 3-year design value for 
the Watson Lane monitor is 19 ppb, which is below the 1-hour 
SO2 standard.
---------------------------------------------------------------------------

Criterion (2)--The Administrator Has Fully Approved the Applicable 
Implementation Plan for the Area Under Section 110(k); and Criterion 
(5)--Kentucky Has Met all Applicable Requirements Under Section 110 and 
Part D of Title I of the CAA

    To redesignate a nonattainment area to attainment, the CAA requires 
EPA to determine that the state has met all applicable requirements 
under section 110 and part D of title I of the CAA (CAA section 
107(d)(3)(E)(v)) and that the state has a fully approved SIP under 
section 110(k) for the area (CAA section 107(d)(3)(E)(ii)). EPA 
proposes to find that Kentucky has met all applicable SIP requirements 
for the Jefferson County Area under section 110 of the CAA (general SIP 
requirements) for purposes of redesignation. Additionally, EPA proposes 
to find that the Kentucky SIP satisfies the criterion that it meets 
applicable SIP requirements for purposes of redesignation under part D 
of title I of the CAA in accordance with section 107(d)(3)(E)(v). 
Further, EPA proposes to determine that the SIP is fully approved with 
respect to all requirements applicable for purposes of redesignation in 
accordance with section 107(d)(3)(E)(ii). In making these proposed 
determinations, EPA ascertained which requirements are applicable to 
the Area and, if applicable, that they are fully approved under section 
110(k). SIPs must be fully approved only with respect to requirements 
that were due prior to submittal of the complete redesignation request.

A. The Jefferson County Area Has Met all Applicable Requirements Under 
Section 110 and Part D of the CAA

1. General SIP Requirements
    General SIP elements and requirements are delineated in section 
110(a)(2) of title I, part A of the CAA. These requirements include, 
but are not limited to, the following: Submittal of a SIP that has been 
adopted by the state after reasonable public notice and hearing; 
provisions for establishment and operation of appropriate procedures 
needed to monitor ambient air quality; implementation of a source 
permit program; provisions for the implementation of part C 
requirements (Prevention of Significant Deterioration (PSD)) and 
provisions for the implementation of part D requirements (NNSR permit 
programs); provisions for air pollution modeling; and provisions for 
public and local agency participation in planning and emission control 
rule development.

[[Page 29386]]

    Section 110(a)(2)(D) requires that SIPs contain certain measures to 
prevent sources in a state from significantly contributing to air 
quality problems in another state. To implement this provision, EPA has 
required certain states to establish programs to address the interstate 
transport of air pollutants. The section 110(a)(2)(D) requirements for 
a state are not linked with a particular nonattainment area's 
designation and classification in that state. EPA believes that the 
requirements linked with a particular nonattainment area's designation 
and classifications are the relevant measures to evaluate in reviewing 
a redesignation request. The transport SIP submittal requirements, 
where applicable, continue to apply to a state regardless of the 
designation of any one particular area in the state. Thus, EPA does not 
believe that the CAA's interstate transport requirements should be 
construed to be applicable requirements for purposes of redesignation.
    In addition, EPA interprets the other section 110(a)(2) elements 
that are neither connected with nonattainment plan submissions nor 
linked with an area's attainment status not to be ``applicable'' 
requirements for purposes of redesignation. The area will still be 
subject to these requirements after the area is redesignated. The 
section 110(a)(2) and part D requirements which are linked with a 
particular area's designation and classification are the relevant 
measures to evaluate in reviewing a redesignation request. This 
approach is consistent with EPA's existing policy on applicability 
(i.e., for redesignations) of conformity and oxygenated fuels 
requirements, as well as with section 184 ozone transport requirements. 
See Reading, Pennsylvania, proposed and final rulemakings (61 FR 53174-
53176, October 10, 1996), (62 FR 24826, May 7, 2008); Cleveland-Akron-
Loraine, Ohio, final rulemaking (61 FR 20458, May 7, 1996); and Tampa, 
Kentucky, final rulemaking (60 FR 62748, December 7, 1995). See also 
the discussion on this issue in the Cincinnati, Ohio, redesignation (65 
FR 37890, June 19, 2000), and in the Pittsburgh, Pennsylvania, 
redesignation (66 FR 50399, October 19, 2001). Nonetheless, EPA has 
approved Kentucky's SIP revisions related to the section 110 
requirements for the 2010 SO2 NAAQS, with the exception of 
the interstate transport elements at section 110(a)(2)(D)(i)(I). See 81 
FR 87817 (December 6, 2016), 84 FR 11652 (March 28, 2019), and 84 FR 
13800 (April 8, 2019).
2. Title I, Part D, Applicable SIP Requirements
    Subpart 1 of part D, comprised of CAA sections 171-179B, sets forth 
the basic nonattainment requirements applicable to all nonattainment 
areas. All areas that were designated nonattainment for the 
SO2 NAAQS were designated under Subpart 1 of the CAA in 
accordance with the deadlines in Subpart 5. For purposes of evaluating 
this redesignation request, the applicable Subpart 1 SIP requirements 
are contained in section 172(c)(1)-(9), section 176, and sections 191 
and 192. A thorough discussion of the requirements contained in 
sections 172(c) can be found in the General Preamble for Implementation 
of Title I. See 57 FR 13498 (April 16, 1992).
a. Subpart 1 Section 172 Requirements
    Section 172 requires states with nonattainment areas to submit 
plans providing for timely attainment and meeting a variety of other 
requirements. As discussed in section V.A, above, EPA's longstanding 
interpretation of the attainment-related nonattainment planning 
requirements of section 172 is that once an area is attaining the 
NAAQS, those requirements are not ``applicable'' for purposes of CAA 
section 107(d)(3)(E)(ii) and therefore need not be approved into the 
SIP before EPA can redesignate the area. In the 1992 General Preamble 
for Implementation of Title I, EPA set forth its interpretation of 
applicable requirements for purposes of evaluating redesignation 
requests when an area is attaining a standard. See 57 FR 13498, 13564 
(April 16, 1992). EPA noted that the requirements for RFP and other 
measures designed to provide for attainment do not apply in evaluating 
redesignation requests because those nonattainment planning 
requirements ``have no meaning'' for an area that has already attained 
the standard. Id. This interpretation was also set forth in the 
Calcagni Memorandum.
    As discussed above, EPA previously approved Kentucky's 
nonattainment SIP for the Jefferson County Area. See 84 FR 30920 (June 
28, 2019). The nonattainment SIP for the Area satisfied the section 
172(c)(1) requirements for RACT/RACM; 172(c)(2) requirements related to 
RFP; 172(c)(3) requirements for a comprehensive and accurate emissions 
inventory; 172(c)(6) requirements for permanent and enforceable control 
measures necessary to provide for attainment of the NAAQS by the 
attainment date; and section 172(c)(9) requirements for contingency 
measures.
    Section 172(c)(4) requires the identification and quantification of 
allowable emissions for major new and modified stationary sources to be 
allowed in an area, and section 172(c)(5) requires source permits for 
the construction and operation of new and modified major stationary 
sources anywhere in the nonattainment area. EPA has a longstanding 
interpretation that because NNSR is replaced by PSD upon redesignation, 
nonattainment areas seeking redesignation to attainment need not have a 
fully approved part D NNSR program in order to be redesignated. See 
memorandum from Mary Nichols, Assistant Administrator for Air and 
Radiation, dated October 14, 1994, entitled ``Part D New Source Review 
Requirements for Areas Requesting Redesignation to Attainment.'' 
However, LMAPCD currently has a fully-approved part D NNSR program in 
place in Regulation 2.04 (Construction or Modification of Major Sources 
In or Impacting Upon Non-Attainment Areas (Emission Offset 
Requirements)) of the Louisville Air Pollution Control District 
Regulations. LMAPCD's PSD program will become effective in the Area 
upon redesignation to attainment.
    Section 172(c)(7) requires the SIP to meet the applicable 
provisions of section 110(a)(2). As noted above, EPA believes that 
Kentucky's SIP meets the requirements of section 110(a)(2) applicable 
for purposes of redesignation.
    Finally, section 172(c)(8) allows a state to use equivalent 
modeling, emission inventory, and planning procedures if such use is 
requested by the state and approved by EPA. Kentucky has not requested 
the use of equivalent techniques under section 172(c)(8).
b. Subpart 1 Section 176--Conformity Requirements
    Section 176(c) of the CAA requires states to establish criteria and 
procedures to ensure that federally supported or funded projects 
conform to the air quality planning goals in the applicable SIP. The 
requirement to determine conformity applies to transportation plans, 
programs, and projects that are developed, funded, or approved under 
title 23 of the United States Code (U.S.C.) and the Federal Transit Act 
(transportation conformity) as well as to all other federally supported 
or funded projects (general conformity). Because EPA does not consider 
SO2 a transportation related pollutant, only the 
requirements related to general conformity apply to the Jefferson 
County Area. The

[[Page 29387]]

Commonwealth of Kentucky adopted general conformity criteria and 
procedures as a revision to the Kentucky SIP. EPA approved Kentucky's 
general conformity SIP on July 27, 1998 (63 FR 40044). Thus, the 
requirements of CAA section 176 have been satisfied.

B. The Jefferson County Area Has a Fully Approved Applicable SIP Under 
Section 110(k) of the CAA

    EPA has fully approved the applicable Kentucky SIP for the 
Jefferson County Area under section 110(k) of the CAA for purposes of 
redesignation. EPA may rely on prior SIP approvals in approving a 
redesignation request (see Calcagni Memorandum at p. 3, Southwestern 
Pennsylvania Growth Alliance v. Browner, 144 F.3D 984, 989-90 (6th Cir. 
1998); Wall, 265 F.3d 426) plus any additional measures it may approve 
in conjunction with a redesignation action. See 68 FR 25426 (May 12, 
2003) and citations therein.

Criterion (3)--The Air Quality Improvement in the Jefferson County Area 
is due to Permanent and Enforceable Reductions in Emissions Resulting 
From Implementation of the SIP and Applicable Federal Air Pollution 
Control Regulations and Other Permanent and Enforceable Reductions

    To redesignate a nonattainment area to attainment, the CAA requires 
EPA to determine that the air quality improvement in the area is due to 
permanent and enforceable reductions in emissions resulting from 
implementation of the SIP, applicable Federal air pollution control 
regulations, and other permanent and enforceable reductions (CAA 
section 107(d)(3)(E)(iii)). EPA proposes to determine that Kentucky has 
demonstrated that the observed air quality improvement in the Jefferson 
County Area is due to permanent and enforceable reductions in 
SO2 emissions resulting from implementation of the SIP, 
namely SO2 control measures at Mill Creek since the 
nonattainment designation.
    When EPA designated the Jefferson County Area as a nonattainment 
area for the 2010 1-hour SO2 NAAQS, EPA determined that 
operations at Mill Creek were the primary cause of the 2010 1-hour 
SO2 NAAQS violations in the Area. See 78 FR 47191.\14\ The 
June 23, 2017, Jefferson County Area nonattainment SIP revision was 
based on this determination and successfully reduced ambient 
concentrations below the 1-hour SO2 NAAQS by only requiring 
emissions reductions at Mill Creek.
---------------------------------------------------------------------------

    \14\ See Final Technical Support Document, July 2013, Kentucky 
First Round of Nonattainment Area Designations for the 2010 
SO2 Primary NAAQS, Prepared by EPA Region 4. This 
document is available at Docket ID: EPA-HQ-OAR-2012-0233-0308.
---------------------------------------------------------------------------

    Mill Creek consists of four coal-fired boilers (U1-U4). Kentucky's 
control strategy for the Jefferson County Area consists of replacing 
FGD control equipment with more efficient FGD controls at Mill Creek, 
addressing SO2 emissions for all four units (U1, U2, U3 and 
U4). Unit 1 and Unit 2 share a common stack (S33) while Unit 3 and Unit 
4 have separate stacks (S4 and S34, respectively). Unit 4's new FGD 
went into service on December 9, 2014; the new combined FGD for Units 1 
and 2 went into service on May 27, 2015; and Unit 3's new FGD went into 
service on June 8, 2016.
    Kentucky established an emission limit of 0.20 lb/MMBtu for each 
coal-fired unit at Mill Creek on a 30-day average basis in accordance 
with the SO2 Nonattainment Area Guidance for longer term 
averaging time for the purpose of demonstrating attainment for the 1-
hour SO2 standard.\15\ These emission limits apply 
independently to each of the four coal-fired units (U1 thru U4), which 
emit SO2 from three separate stacks (S33, S4, and S34). 
These SO2 limits were established in a revised title V 
operating permit 145-97-TV(R3) for Mill Creek and became effective on 
April 5, 2017. Mill Creek demonstrates compliance with the 30-day 
emission limits through a continuous emission monitoring system on each 
stack as well as the monitoring of the heat input firing rate of each 
emission unit. The 30-day SO2 emission limit was established 
to demonstrate modeled attainment of the 2010 1-hour SO2 
standard for the Jefferson County nonattainment area. Kentucky 
requested that EPA incorporate into the Jefferson County portion of the 
Commonwealth's SIP the 30-day SO2 emission limits and 
operating and compliance parameters (monitoring, recordkeeping, and 
reporting) established at Plant-wide Specific condition S1-Standards, 
S2-Monitoring and Record Keeping and S3-Reporting in title V permit 
145-97-TV(R3). On June 28, 2019, EPA took final action to incorporate 
the SO2 emission limits and operating and compliance 
parameters into the SIP with the approval of Kentucky's June 23, 2017, 
SO2 nonattainment SIP revision. See 84 FR 30920. The air 
quality improvement in the Jefferson County Area is due to permanent 
and enforceable reductions in SO2 emissions resulting from 
the emission limits incorporated into the SIP.
---------------------------------------------------------------------------

    \15\ See section IV.B.4.ii of the proposed attainment 
demonstration (83 FR 56002, November 9, 2018).
---------------------------------------------------------------------------

Criterion (4)--The Jefferson County Area Has a Fully Approved 
Maintenance Plan Pursuant to Section 175A of the CAA

    For redesignating a nonattainment area to attainment, the CAA 
requires EPA to determine that the area has a fully approved 
maintenance plan pursuant to section 175A of the CAA. See CAA section 
107(d)(3)(E)(iv). In conjunction with its request to redesignate the 
Jefferson County Area to attainment for the 2010 1-hour SO2 
NAAQS, Kentucky submitted a SIP revision to provide for the maintenance 
of the 2010 1-hour SO2 NAAQS for at least 10 years after the 
effective date of redesignation to attainment. EPA is proposing to 
determine that this maintenance plan meets the requirements for 
approval under section 175A of the CAA.
a. What is required in a maintenance plan?
    Section 175A of the CAA sets forth the elements of a maintenance 
plan for areas seeking redesignation from nonattainment to attainment. 
Under section 175A, the plan must demonstrate continued attainment of 
the applicable NAAQS for at least 10 years after the Administrator 
approves a redesignation to attainment. Eight years after the 
redesignation, the state must submit a revised maintenance plan 
demonstrating that attainment will continue to be maintained for the 10 
years following the initial 10-year period. To address the possibility 
of future NAAQS violations, the maintenance plan must contain 
contingency measures as EPA deems necessary to assure prompt correction 
of any future 2010 1-hour SO2 violations. The Calcagni 
Memorandum provides further guidance on the content of a maintenance 
plan, explaining that a maintenance plan should address five 
requirements: The attainment emissions inventory; maintenance 
demonstration; monitoring; verification of continued attainment; and a 
contingency plan. As is discussed more fully below, EPA is proposing to 
determine that Kentucky's maintenance plan includes all the necessary 
components and is thus proposing to approve it as a revision to the 
Kentucky SIP.
b. Attainment Emissions Inventory
    An attainment inventory identifies a level of emissions in the Area 
that is sufficient to attain the NAAQS. As discussed above, the last 
monitored exceedance of the NAAQS occurred in

[[Page 29388]]

2015. Phased installation of the new FGDs at Mill Creek began in 2013 
and was completed in 2016, making 2017 the first full year with all of 
the new controls in operation. The design values at the Watson Lane 
monitor have decreased since the 2014-2016 design value with a quality-
assured, complete, and certified 2016-2018 3-year design value of 19 
ppb. In its maintenance plan, LMAPCD chose 2018 as the attainment 
inventory year which is one of the three years included in the current 
attaining 3-year design value. This design value reflects the permanent 
and enforceable Mill Creek SO2 emission limits used in the 
attainment modeling.
    Actual emissions from Mill Creek are used for point source 
emissions for the attainment inventory, as it is the only point source 
in the Area, and the only source specifically modeled in the attainment 
demonstration approved in 2019. SO2 emissions data from Mill 
Creek is presented in Table 2. Kentucky interpolated emissions for all 
other sectors for 2018 from the 2011 and 2014 National Emissions 
Inventory (NEI) data for Jefferson County because the Commonwealth is 
only required to develop these inventories on a triennial period in 
accordance with the NEI and subpart A to 40 CFR part 51 and the final 
2017 NEI is not yet available. The 2018 estimated emissions were then 
apportioned to the Area based on the Area's fraction of land area 
within the county. The complete attainment emissions inventory for the 
Area is presented in Table 3.

        Table 2--2018 SO2 Emissions Inventory for LG&E Mill Creek
------------------------------------------------------------------------
                                                           SO2 emissions
               Unit                        Source              (tpy)
 
------------------------------------------------------------------------
MC_U01............................  CEMS *..............           681.3
MC_U02............................  CEMS................           571.1
MC_U03............................  CEMS................           721.1
MC_U04............................  CEMS................          1778.6
MC_Other..........................  Calculated..........            0.06
                                                         ---------------
    Total.........................  ....................        3,752.16
------------------------------------------------------------------------
* Continuous Emissions Monitoring System.

                   Table 3--2018 Attainment Emissions Inventory for the Jefferson County Area
----------------------------------------------------------------------------------------------------------------
           Source type                 Point           Area          Non-road         On-road          Total
----------------------------------------------------------------------------------------------------------------
2018 SO2 Emissions (tpy)........        3,752.16            0.46            0.01            0.28        3,752.91
----------------------------------------------------------------------------------------------------------------

    For additional information regarding the development of the 
attainment year inventory, please see Kentucky's June 23, 2017, 
nonattainment SIP submission and EPA's rulemakings on that 
submittal.\16\
---------------------------------------------------------------------------

    \16\ See 84 FR 30920 (June 28, 2019) (final rule), 83 FR 56002 
(November 9, 2018) (proposed rule). Kentucky's 2017 SIP submittal is 
included in the Docket for this proposed rulemaking.
---------------------------------------------------------------------------

c. Maintenance Demonstration
    Maintenance of the SO2 standard is demonstrated either 
by showing that future emissions will not exceed the level of the 
attainment emissions inventory year or by modeling to show that the 
future mix of sources and emission rates will not cause a violation of 
the NAAQS.
    To evaluate maintenance through 2032 and satisfy the 10-year 
interval required in CAA section 175A, Kentucky prepared attainment 
year emissions (2018) and projected emissions inventories for years 
2023, 2028, and 2032. The emissions inventories are composed of the 
following general source categories: Point, area, non-road mobile, and 
on-road mobile. Projected point source emissions were based on Mill 
Creek's 2018 attainment emissions of 3752.16 tons. Projected point 
source emissions were held constant because Kentucky does not 
anticipate any development within the Area and also does not anticipate 
any major changes at Mill Creek. The projected emissions for area, non-
road mobile, and on-road mobile emissions are from U.S. EPA's 2011 v6.3 
modeling platform and further apportioned for the Area. The emissions 
inventories were developed consistent with EPA guidance and are 
summarized in Table 4. Kentucky compared projected emissions for the 
final year of the maintenance plan (2032) to the attainment emissions 
inventory year (2018) and compared interim years (2023 & 2028) to the 
attainment emissions inventory year to demonstrate continued 
maintenance of the 2010 1-hour SO2 standard. For additional 
information regarding the development of the projected inventories, 
please see Kentucky's June 23, 2017, nonattainment SIP revision.

                    Table 4--Attainment & Projected Future Emissions Inventories for the Area
                                                      [tpy]
----------------------------------------------------------------------------------------------------------------
                                                    Attainment    Projected 2023  Projected 2028  Projected 2032
                     Sector                          2018 SO2      SO2 emissions   SO2 emissions   SO2 emissions
                                                     emissions
----------------------------------------------------------------------------------------------------------------
Nonpoint........................................            0.46            0.38            0.37            0.38
Nonroad.........................................            0.01            0.02            0.02            0.02
Onroad..........................................            0.28            0.09            0.08            0.09
Point...........................................         3752.16         3752.16         3752.16         3752.16
                                                 ---------------------------------------------------------------

[[Page 29389]]

 
    Total.......................................         3752.91         3752.65         3752.64         3752.65
----------------------------------------------------------------------------------------------------------------

    In situations where local emissions are the primary contributor to 
nonattainment, such as the Jefferson County Area, if the future 
projected emissions in the nonattainment area remain at or below the 
baseline emissions in the nonattainment area, then the related ambient 
air quality standards should not be exceeded in the future. Kentucky 
has projected emissions as described previously, and these projections 
indicate that emissions in the Jefferson County Area will remain at 
nearly the same levels as those in the attainment year inventory for 
the duration of the maintenance plan. Any increases in actual emissions 
from Mill Creek must remain below permitted levels, which were made 
permanent and enforceable through incorporation into the SIP and 
demonstrate attainment of the 1-hour SO2 NAAQS. Furthermore, 
any potential future SO2 emissions sources that may locate 
in or near the Area would be required to comply with the LMAPCD's 
approved PSD permitting programs to ensure that the Area will continue 
to meet the NAAQS.
    As discussed in the SO2 Nonattainment Area Guidance, an 
approved attainment plan that relies on air quality dispersion modeling 
using maximum allowable emissions, such as Kentucky's attainment plan 
for the Area, can generally be expected to demonstrate that the 
standard will be maintained for the requisite 10 years and beyond 
without regard to any changes in operation rate of the pertinent 
sources that do not involve increases in maximum allowable 
emissions.\17\ EPA believes that the Area will continue to maintain the 
standard at least through the year 2032 because the air quality 
modeling in the approved attainment plan showed that the Area would 
attain the standard based on maximum allowable emissions limits at Mill 
Creek that are incorporated into the SIP, these sources have fully 
implemented the permanent and enforceable modeled limits and controls, 
and the emissions reductions from these measures are reflected in the 
attaining design values for the Area. Furthermore, the Watson Lane 
monitoring data trends substantiate the SO2 reductions from 
Mill Creek facility.
---------------------------------------------------------------------------

    \17\ See SO2 Nonattainment Area Guidance at p.67.
---------------------------------------------------------------------------

d. Monitoring Network
    The Watson Lane monitor (AQS ID: 21-111-0051) is the only 
SO2 monitor located within the Jefferson County Area, and 
the 2010 1-hour SO2 nonattainment designation was based on 
data collected from 2009-2011 at this monitor. In its maintenance plan, 
LMAPCD has committed to maintaining an appropriate, well-sited 
monitoring network in the Area, in accordance with 40 CFR part 58, 
through the maintenance plan period to verify the continued maintenance 
of the 2010 SO2 NAAQS. Therefore, Kentucky has addressed the 
requirement for monitoring. Kentucky's monitoring network plan was 
submitted on June 28, 2019, and approved by EPA on October 3, 2019.
e. Verification of Continued Attainment
    LMAPCD has the legal authority to enforce and implement all 
measures necessary to attain and maintain the NAAQS. See, e.g., 
Kentucky Revised Statutes (KRS) Chapter 77 (which provides LMAPCD with 
the authority to implement and enforce orders, rules, and regulations 
necessary or proper to accomplish the purposes of the chapter, 
including taking legal action and imposing fines for violations).
    The sole point source within the nonattainment area, Mill Creek, is 
required to submit annual emissions statements to LMAPCD pursuant to 
LMAPCD Regulation 1.06. LMAPCD will use these statements, along with 
monitoring data collected as described in the previous section, to 
verify continued attainment. Monitoring data is regularly compared to 
the SO2 NAAQS and reported to the Louisville Air Pollution 
Control Board. LMAPCD will compare Mill Creek's annual emissions 
statements with the attainment inventory and the permanent and 
enforceable SO2 emissions limits for Mill Creek discussed 
above. Furthermore, any potential future SO2 emissions 
sources that may locate in or near the Area would be required to comply 
with the LMAPCD's approved PSD permitting programs to ensure that the 
Area will continue to meet the NAAQS. In addition to assuring continued 
attainment in this manner, Kentucky will verify continued attainment 
through operation of the monitoring network.
f. Contingency Measures in the Maintenance 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. 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. In cases 
where attainment revolves around compliance of a single source or a 
small set of sources with emissions limits shown to provide for 
attainment, EPA interprets ``contingency measures'' to mean that the 
state agency has a comprehensive program to identify sources of 
violations of the SO2 NAAQS and to undertake aggressive 
follow-up for compliance and enforcement, including expedited 
procedures for establishing enforceable consent agreement pending the 
adoption of revised SIPs.\18\ 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).
---------------------------------------------------------------------------

    \18\ See SO2 Nonattainment Area Guidance at p.69.
---------------------------------------------------------------------------

    The contingency plan included in the maintenance plan contains 
triggers to determine when contingency measures are needed and what 
kind of measures should be used. In the event of a single monitored 
exceedance of the 1-hour 75ppb SO2 NAAQS at the Watson Lane 
monitor, LMAPCD will expeditiously investigate and perform culpability 
analysis to determine the source that cause the exceedance and/or 
violation \19\

[[Page 29390]]

and enforce any SIP or permit limit that is violated. If all sources 
are found to be in compliance with applicable SIP and permit emission 
limits, LMAPCD shall determine the cause of the exceedance and 
determine what additional control measures are necessary to impose on 
the area's stationary sources to continue to maintain attainment of the 
SO2 NAAQS. LMAPCD shall inform any affected stationary 
sources of the monitored SO2 exceedance and the potential 
need for additional control measures. Within six months of 
notification, the source must submit a detailed plan of action 
specifying additional control measures to be implemented no later than 
18 months after the notification, or 24 months from the initial 
exceedance, whichever comes first. The additional control measures will 
be submitted to EPA for approval and incorporation into the SIP. Such 
measures may require that Mill Creek reduce load. Additional 
contingency measures include the alternative RACT/RACM of switching to 
low-sulfur fuel. LMAPCD will continue to implement all measures with 
respect to the control of SO2 which were contained in the 
SIP for the Area before redesignation.
---------------------------------------------------------------------------

    \19\ Kentucky's contingency measure trigger accounts for a 
possible exceedance or violation of the 1-hour SO2 
standard. As specified in 40 CFR 50.17(b), the 1-hour primary 
SO2 NAAQS 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 is less than or equal to 75 
ppb. In a calendar year, four days with a maximum hourly value above 
75 ppb is considered an exceedance.
---------------------------------------------------------------------------

    EPA has preliminarily concluded that the maintenance plan 
adequately addresses the five basic components of a maintenance plan: 
The attainment emissions inventory; maintenance demonstration; 
monitoring; verification of continued attainment; and a contingency 
plan. Therefore, EPA proposes to determine that the maintenance plan 
for the Area meets the requirements of section 175A of the CAA and 
proposes to incorporate the maintenance plan into the Kentucky SIP.

VI. What is the effect of EPA's proposed actions?

    Approval of Kentucky's redesignation request would change the legal 
designation of the portion of Jefferson County that is within the 
Jefferson County Area, as found at 40 CFR part 81, section 81.310, from 
nonattainment to attainment for the 2010 1-hour SO2 NAAQS. 
Approval of Kentucky's associated SIP revision would also incorporate a 
plan for maintaining the 2010 1-hour SO2 NAAQS in the 
Jefferson County Area through 2032 into the SIP.

VII. Proposed Actions

    EPA is proposing to take three separate but related actions 
regarding the redesignation request and associated SIP revision for the 
Jefferson County Area.
    First, EPA is proposing to determine that the Area has attained the 
2010 1-hour SO2 NAAQS.
    Second, EPA is proposing to approve the maintenance plan for the 
Area and to incorporate it into the SIP. As described above, the 
maintenance plan demonstrates that the Area will continue to maintain 
the 2010 1-hour SO2 NAAQS through 2032.
    Third, EPA is proposing to approve Kentucky's request for 
redesignation of the Area from nonattainment to attainment for the 2010 
1-hour SO2 NAAQS based on compliance with the redesignation 
criteria provided under CAA section 107(d)(3)(E). If finalized, 
approval of the redesignation request for the Jefferson County Area 
would change the official designation of the portion of Jefferson 
County encompassed by the polygon with the vertices using UTM 
coordinates in UTM zone 16 with datum NAD83 as follows: (1) Ethan Allen 
Way extended to the Ohio River at UTM Easting (m) 595738, UTM Northing 
4214086 and Dixie Highway (US60 and US31W) at UTM Easting (m) 597515, 
UTM Northing 4212946; (2) Along Dixie Highway from UTM Easting (m) 
597515, UTM Northing 4212946 to UTM Easting (m) 595859, UTM Northing 
4210678; (3) Near the adjacent property lines of Louisville Gas and 
Electric-Mill Creek Electric Generating Station and Kosmos Cement where 
they join Dixie Highway at UTM Easting (m) 595859, UTM Northing 4210678 
and the Ohio River at UTM Easting (m) 595326, UTM Northing 4211014; (4) 
Along the Ohio River from UTM Easting (m) 595326, UTM Northing 4211014 
to UTM Easting (m) 595738, UTM Northing 4214086, as found at 40 CFR 
part 81, from nonattainment to attainment for the 2010 1-hour 
SO2 NAAQS.

VIII. Statutory and Executive Order Reviews

    Under the CAA, redesignation of an area to attainment and the 
accompanying approval of a maintenance plan under section 107(d)(3)(E) 
are actions that affect the status of a geographical area and do not 
impose any additional regulatory requirements on sources beyond those 
imposed by state law. A redesignation to attainment does not in and of 
itself create any new requirements, but rather results in the 
applicability of requirements contained in the CAA for areas that have 
been redesignated to attainment. Moreover, the Administrator is 
required to approve a SIP submission that complies with the provisions 
of the Act and applicable Federal regulations. See 42 U.S.C. 7410(k); 
40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to 
approve state choices, provided that they meet the criteria of the CAA. 
Accordingly, these proposed actions merely propose to approve state law 
as meeting Federal requirements and do not impose additional 
requirements beyond those imposed by state law. For these reasons, 
these proposed actions:
     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) and 13563 (76 FR 3821, January 21, 2011);
     Are not Executive Order 13771 (82 FR 9339, February 2, 
2017) regulatory actions because these actions are not significant 
regulatory actions under Executive Order 12866;
     Do not impose information collection burdens under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     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.);
     Do not contain any unfunded mandates or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Public Law 104-4);
     Do not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Are not economically significant regulatory actions based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Are not significant regulatory actions subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     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; and
     Will not have disproportionate human health or 
environmental effects under Executive Order 12898 (59 FR 7629, February 
16, 1994).
    This redesignation action 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

[[Page 29391]]

implications as specified by Executive Order 13175 (65 FR 67249, 
November 9, 2000), nor will it impose substantial direct costs on 
tribal governments or preempt tribal law.

List of Subjects

40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Reporting and recordkeeping, 
Sulfur dioxide.

 40 CFR Part 81

    Environmental protection, Air pollution control, National parks, 
Wilderness areas.

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

    Dated: May 5, 2020.
Mary Walker,
Regional Administrator, Region 4.
[FR Doc. 2020-10063 Filed 5-14-20; 8:45 am]
BILLING CODE 6560-50-P