[Federal Register Volume 84, Number 125 (Friday, June 28, 2019)]
[Rules and Regulations]
[Pages 30920-30933]
[FR Doc No: 2019-13736]

-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R04-OAR-2017-0625; FRL-9995-59-Region 4]

Air Plan Approval; KY; Attainment Plan for Jefferson County SO2
Nonattainment Area

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: The Environmental Protection Agency (EPA) is approving State
Implementation Plan (SIP) revisions, submitted under a cover letter
dated June 23, 2017, by the Commonwealth of Kentucky, through the
Kentucky Division for Air Quality on behalf of the Louisville Metro Air
Pollution Control District (LMAPCD or District or Jefferson County) to
EPA, for attaining the 1-hour sulfur dioxide (SO2) primary
national ambient air quality standard (NAAQS or standard) for the
Jefferson County SO2 nonattainment area (hereafter referred
to as the ``Jefferson County nonattainment area,'' ``nonattainment
area'' or ``Area''). The Jefferson County nonattainment area is
comprised of a portion of Jefferson County in Kentucky surrounding the
Louisville Gas and Electric Mill Creek Electric Generating Station
(hereafter referred to as ``Mill Creek'' or ``LG&E''). This plan
(hereafter called a ``nonattainment plan'' or ``SIP'' or ``attainment
SIP'') includes Kentucky's attainment demonstration and other elements
required under the Clean Air Act (CAA or Act). In addition to an
attainment demonstration, the plan addresses the requirement for
meeting reasonable further progress (RFP) toward attainment of the
NAAQS, reasonably available control measures and reasonably available
control technology (RACM/RACT), base-year and projection-year emissions
inventories, enforceable emissions limitations and control measures,
nonattainment new source review (NNSR) and contingency measures. EPA
concludes that Kentucky has appropriately demonstrated that the
nonattainment plan provisions provide for attainment of the 2010 1-hour
primary SO2 NAAQS in the Jefferson County nonattainment area
and that the nonattainment plan meets the other applicable requirements
under the CAA.

DATES: This rule is effective July 29, 2019.

ADDRESSES: EPA has established a docket for this action under Docket
Identification No. EPA-R04-OAR-2017-0625. All documents in the docket
are listed on the www.regulations.gov website. Although listed in the
index, some information is not publicly available, i.e., Confidential
Business Information or other information whose disclosure is
restricted by statute. Certain other material, such as copyrighted
material, is not placed on the internet and will be publicly available
only in hard copy form. Publicly available docket materials are
available either electronically through www.regulations.gov or in hard
copy at the Air Regulatory Management Section, Air Planning and
Implementation Branch, Air and Radiation Division (formerly the Air,
Pesticides and Toxics Management Division), U.S. Environmental
Protection Agency, Region 4, 61 Forsyth Street SW, Atlanta, Georgia
30303-8960. EPA requests that if at all possible, you contact the
person listed in the FOR FURTHER INFORMATION CONTACT section to
schedule your inspection. The Regional Office's official hours of
business are Monday through Friday 8:30 a.m. to 4:30 p.m., excluding
Federal holidays.

FOR FURTHER INFORMATION CONTACT: Richard Wong, Air Regulatory
Management Section, Air Planning and Implementation Branch, Air and
Radiation Division, U.S. Environmental Protection Agency, Region 4, 61
Forsyth Street SW, Atlanta, Georgia 30303-8960. Mr. Wong can be reached
via telephone at<PHONE_NUMBER> or via electronic mail at
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Table of Contents

I. Background and Purpose
II. Response to Comments
III. Incorporation by Reference
IV. Final Action
V. Statutory and Executive Order Reviews

I. Background and Purpose

    On June 22, 2010, EPA promulgated a new 1-hour primary
SO2 NAAQS of 75 parts per billion (ppb), which 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) and (b).
On August 5, 2013, EPA designated a first set of 29 areas of the
country as nonattainment for the 2010 SO2 NAAQS, including
the Jefferson County nonattainment area within the Commonwealth of
Kentucky. See 78 FR 47191, codified at 40 CFR part 81, subpart C. These
``round one'' area designations were effective October 4, 2013. Section
191(a) of the CAA directs states to submit SIPs for areas designated as
nonattainment for the SO2 NAAQS to EPA within 18 months of
the effective date of the designation, i.e., by no later than April 4,
2015, in this case. 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, which
is October 4, 2018, in accordance with CAA sections 191-192.
    Section 172(c) of part D of the CAA lists the required components
of a nonattainment plan submittal. The base year emissions inventory
(section 172(c)(3)) is required to show a ``comprehensive, accurate,
current inventory'' of all relevant pollutants in the nonattainment
area. The nonattainment plan must identify and quantify any expected
emissions from the construction of new sources to account for emissions
in the area that might affect RFP toward attainment, or that might
interfere with attainment and maintenance of the NAAQS, and it must
provide for a NNSR program (section 172(c)(5)). The attainment
demonstration must include a modeling

analysis showing that the enforceable emissions limitations and other
control measures taken by the state will provide for RFP and
expeditious attainment of the NAAQS (section 172(c)(2), (4), (6), and
(7)). The nonattainment plan must include an analysis and provide for
implementation of the RACM considered, including RACT (section
172(c)(1)). Finally, the nonattainment plan must provide for
contingency measures (section 172(c)(9)) to be implemented either in
the case that RFP toward attainment is not made, or in the case that
the area fails to attain the NAAQS by the attainment date.
    On April 23, 2014, EPA issued a guidance document entitled,
``Guidance for 1-Hour SO2 Nonattainment Area SIP
Submissions.'' This guidance provides recommendations for the
development of SO2 nonattainment SIPs to satisfy CAA
requirements (see, e.g., sections 172, 191, and 192). An attainment
demonstration must also meet the requirements of 40 CFR part 51,
subparts F and G, and 40 CFR part 51, appendix W (the Guideline on Air
Quality Models; ``the Guideline'' or ``Appendix W''), and include
inventory data, modeling results, and emissions reduction analyses on
which the state has based its projected attainment. The guidance also
discusses criteria EPA expects to use in assessing whether emission
limits with longer averaging times of up to 30 days ensure attainment
of the SO2 NAAQS.
    For a number of areas, including the Jefferson County nonattainment
area, EPA published a document on March 18, 2016, that certain states
had failed to submit the required SO2 nonattainment plan by
the submittal deadline. See 81 FR 14736. This finding initiated a
deadline under CAA section 179(a) for the potential imposition of new
source review and highway funding sanctions, and for EPA to promulgate
a federal implementation plan (FIP) under section 110(c) of the CAA. In
response to the requirement for SO2 nonattainment planning
submittals, Kentucky submitted SIP revisions for the Jefferson County
nonattainment area on June 23, 2017. Pursuant to Kentucky's June 23,
2017, attainment SIP revisions and EPA's subsequent completeness
determination letter dated October 10, 2017, the sanctions under
section 179(a) were not (and will not be) imposed as a result of
Kentucky's having missed the April 4, 2015, submission deadline.
Furthermore, with this current action issuing final approval of
Kentucky's SIP revisions, EPA's FIP obligation under CAA section 110(c)
no longer applies, and therefore no FIP will be imposed to address
SO2 nonattainment planning requirements for the Jefferson
County nonattainment area.
    On November 9, 2018 (83 FR 56002) (hereafter NPRM), EPA proposed to
approve Kentucky's June 23, 2017, SIP revisions which included the
nonattainment plan, and SO2 attainment demonstration, among
other SO2 nonattainment planning requirements. The
Commonwealth's SIP revisions included all the specific attainment
elements mentioned above, including new SO2 emission limits
found to be comparably stringent to a 1-hour critical emissions value
that would ensure attainment of the primary SO2 NAAQS.
Specifically, Kentucky's June 23, 2017, SIP revisions include
enforceable SO2 emission limits for Mill Creek and
compliance parameters (monitoring and reporting) established at Plant-
wide Specific conditions S1-Standards, S2-Monitoring and Record Keeping
and S3-Reporting established in title V permit 145-97-TV(R3). Please
refer to EPA's proposed approval notice which contains a detailed
discussion of the CAA requirements applicable to SO2
nonattainment SIPs, along with a comprehensive analysis and rationale
for its proposed approval of the Commonwealth's attainment SIP. See 83
FR at 56003-14.
    Comments on EPA's November 9, 2018, proposed rulemaking were due on
or before December 10, 2018. EPA received two sets of relevant comments
on the proposed approval of Kentucky's SIP revisions for the Jefferson
County nonattainment area. These comments are available in the docket
for this final rulemaking action. EPA's summary of the relevant
comments and EPA's responses are provided below.
    The remainder of this preamble summarizes EPA's final approval of
Kentucky's SIP revisions and attainment demonstration for the Jefferson
County nonattainment area and contains EPA's response to public
comments.

II. Response to Comments

    EPA received two sets of comments which are included in the docket
for this final rulemaking. Generally, the comments related to the
following topics: (1) The use of a longer-term average in emissions
limits; (2) the modeling's treatment of the Kosmos Cement Facility (a
source that is outside the nonattainment area and also hereafter
referred to as Kosmos); and (3) other comments related to the timing
and development of the emissions inventory.
    Comment 1: A Commenter has made several comments related to the use
of the 30-day rolling average SO2 emission limit for the
attainment demonstration. Some of the comments can be viewed as general
to the use of a longer-term average limit, which are being responded to
here, and some are more specific to the specific permit limit for the
Mill Creek facility, which will be addressed in a following comment
response. Regarding the general use of a longer-term average limit, the
Commenter asserts that the 720-hour rolling emissions standard that the
proposed approval purports to justify is unlawful and jeopardizes the
public health and that a 720-hour averaging period is an inadequate
proxy for the 1-hour standard required under the CAA because very brief
spikes in SO2 emissions pose serious health harms. The
Commenter also cites to the Sierra Club's Petition To The EPA
Administrator To Object To Issuance Of The Revised Title V Operating
Permit For The Mill Creek Power Plant In Louisville, Kentucky (June 2,
2017) (Docket ID # EPA-R04-OAR-2017-0625-0009) (hereafter ``Title V
Petition''), and Sierra Club comments to LMAPCD re: Notice of Action on
a Title V Operating Permit O-0127-16-V: LG&E Mill Creek Generating
Station (Jan. 25, 2017) (Docket ID # EPA-R04-OAR-2017-0625-0011)
(hereafter ``Permit Comments''). In these documents, Sierra Club
provided information about health effects of SO2 exposure
and also explained its position that the 1-hour SO2 NAAQS
requires short-term limits to effectively protect human health.\1\
---------------------------------------------------------------------------

    \1\ EPA included the Title V Petition, which included
attachments such as the Permit comments, in this docket. The
Commenter has referenced the petition and certain attachments in its
comments on the November 9, 2018, NPRM. EPA is responding to the
issues raised in the Title V Petition because the Commenter
referenced it in its comments submitted in this matter. In this
action, the EPA is addressing the issues raised in the Title V
Petition that raise substantive and technical concerns regarding the
adequacy of the SIP limits at Mill Creek and other aspects of the
SIP to satisfy SIP approval criteria. EPA considers these issues to
be appropriately addressed in this rulemaking, which acts on the SIP
submission, rather than in an action on the Title V Petition. Action
on the Title V permit or Petition may address other issues raised in
that petition, such as whether the permit terms properly reflect
requirements that apply to sources in order to assure compliance
with the applicable requirements of the Clean Air Act, including the
applicable implementation plan; as well as whether the state
followed the proper procedures in issuing the permit. In this final
action, EPA is not addressing those types of issues or taking any
action on the Title V Petition.
---------------------------------------------------------------------------

    Response 1: EPA appreciates the Commenter's concerns about the
appropriateness of approving attainment plans with emission limitations
that apply over a longer period than the 1-hour form of the 2010
SO2 NAAQS. However, as EPA explained in the

November 9, 2018, NPRM, and as is further explained below, EPA believes
that long-term averaging periods can be appropriate for purposes of
attainment planning for the SO2 NAAQS. EPA also acknowledges
the Commenter's concerns regarding health effects of SO2
exposure. EPA agrees that the NAAQS is crucial for protecting public
health around SO2 emission sources. As such, EPA established
the 1-hour SO2 NAAQS based on such health effects
information and will continue to implement the NAAQS to protect public
health and welfare based on the authority granted to EPA in the CAA.
However, EPA disagrees with the Commenter's implication that the
protection against short term SO2 concentrations, which EPA
sought by establishing this 1-hour NAAQS, cannot be achieved with, for
example, comparably stringent 30-day average emission limits in
appropriate cases.
    The following explanation of EPA's guidance with respect to longer-
term average limits was provided in its November 9, 2018, NPRM. EPA's
``Guidance for 1-hour SO2 Nonattainment Area SIP
Submissions,'' (April 2014 guidance) recommends that the emission
limits be expressed as short-term average limits (e.g., addressing
emissions averaged over one or three hours), but also describes the
option to utilize emission limitations with longer averaging times of
up to 30 days, so long as the state meets various suggested criteria.
See EPA's April 2014 guidance, pp. 22 to 39. The guidance recommends
that the longer-term average limit should be set at an adjusted level
that reflects a stringency comparable to the 1-hour average limit at
the critical emission value (CEV) shown to provide for attainment that
the plan otherwise would have set.
    EPA's April 2014 guidance provides an extensive discussion of EPA's
rationale for concluding that appropriately set comparably stringent
limitations based on averaging times as long as 30 days can be found to
provide for attainment of the 2010 primary SO2 NAAQS. In
evaluating this option, EPA considered the nature of the standard,
conducted detailed analyses of the impact of the use of 30-day average
limits on the prospects for attaining the standard, and carefully
reviewed how best to achieve an appropriate balance among the various
factors that warrant consideration in judging whether a state's
attainment plan provides for attainment. April 2014 guidance at pp. 22
to 39; and also at Appendices B, C, and D.
    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 year with 365 days
of valid monitoring data, the 99th percentile would be the fourth
highest daily maximum 1-hour value. The 2010 SO2 NAAQS,
including this form of determining compliance with the standard, was
upheld by the U.S. Court of Appeals for the District of Columbia
Circuit in Nat'l Envt'l Dev. Ass'n's Clean Air Project v. EPA, 686 F.3d
803 (D.C. Cir. 2012). Because the standard has this form, a single
exceedance of the level of the standard (75 ppb) does not constitute a
violation of the standard. Instead, at issue is whether a source
operating in compliance with a properly set longer-term average could
cause exceedances, and if so the resulting frequency and magnitude of
such exceedances. What matters is whether EPA can have reasonable
confidence that a properly set longer-term average limit will provide
that the 3-year average of the annual fourth highest daily maximum 1-
hour value will be at or below 75 ppb. A synopsis of EPA's review of
how to judge whether such plans provide for attainment, based on
modeling of projected allowable emissions and considering the form of
the NAAQS for determining attainment at monitoring sites, follows.
    For SO2 attainment plans based on 1-hour emission
limits, the standard approach is to conduct modeling using fixed
emission rates. The maximum emission rate that would be modeled to
result in attainment is labeled the CEV. The modeling process for
identifying the CEV considers the numerous variables that affect
ambient concentrations of SO2, such as meteorological data,
background concentrations, and topography. In the standard approach,
the state would then provide for attainment by setting a continuously
applicable 1-hour emission limitation at the CEV.
    EPA recognizes that some sources may have highly variable emissions
that can make it extremely difficult to ensure in practice that
emissions for any given hour do not exceed the CEV. EPA also
acknowledges the concern that longer-term emission limits can allow
short periods with emissions above the CEV, which, if coincident with
meteorological conditions conducive to high SO2
concentrations, could create the possibility of an exceedance of the
NAAQS level occurring on a day when an exceedance would not have
occurred if emissions were continuously controlled at the level
corresponding to the CEV. However, for several reasons, EPA believes
that the approach recommended in its April 2014 guidance document
suitably addresses this concern.
    First, from a practical perspective, EPA expects the actual
emission profile of a source subject to an appropriately set longer-
term average limit to be similar to the emission profile of a source
subject to an analogous 1-hour average limit. EPA expects this
similarity because it has recommended that the longer-term average
limit be set at a level that is comparably stringent to the otherwise
applicable 1-hour limit (reflecting a downward adjustment from the CEV)
and that takes the source's emissions profile into account. As a
general matter, EPA would expect that any emission limit with an
averaging time longer than 1-hour would need to reflect a downward
adjustment to compensate for the loss of stringency inherent in
applying a longer-term average limit. This expectation is based on the
idea that a limit based on the 30-day average of emissions, for
example, at a given level is likely to be a less stringent limit than a
1-hour limit at the same level, since the control level needed to meet
a 1-hour limit every hour is likely to be greater than the control
level needed to achieve the same limit on a 30-day average basis. EPA's
approach for downward adjustment is to account for the expected
variability in emissions over the averaging period (up to 30 days) to
achieve comparable stringency to the emissions and expected air quality
impacts for a 1-hour period. As a result, EPA expects either form of
emission limit to yield comparable air quality and protect the NAAQS.
    Second, from a more theoretical perspective, EPA has compared the
likely air quality with a source having maximum allowable emissions
under an appropriately set longer-term limit, as compared to the likely
air quality with the source having maximum allowable emissions under
the comparable 1-hour limit. In this comparison, in the 1-hour average
limit scenario, the source is presumed always to emit at the CEV, and
in the longer-term average limit scenario, the source is presumed
occasionally to emit more than the CEV but, on average, to emit well
below the CEV. In an average year, compliance with the 1-hour limit is
expected to result in three exceedance days (i.e., three days with
maximum hourly values above 75 ppb) and a fourth day with a maximum
hourly value at 75 ppb. By comparison, with the source complying with a
longer-term limit, it is possible that additional exceedances of the
NAAQS level would occur that would

not occur in the 1-hour limit scenario (if emissions exceed the CEV at
times when meteorology is conducive to poor air quality). However, this
comparison must also factor in the likelihood that exceedances that
would be expected in the 1-hour limit scenario would not occur in the
longer-term limit scenario. This result arises because the longer-term
limit requires lower emissions most of the time (because the limit is
set below the CEV), so a source complying with an appropriately set
longer-term limit is likely to have lower emissions at critical times
than would be the case if the source were emitting as allowed with a 1-
hour limit.
    As described in Appendix B of EPA's April 2014 guidance, EPA
conducted a statistical analysis of various scenarios using actual
plant data. In doing so, EPA found that the requirement for lower
average emissions is highly likely to yield better air quality than is
required with a comparably stringent 1-hour limit. Based on analyses
described in Appendix B, EPA expects that an emission profile with
maximum allowable emissions under an appropriately set comparably
stringent 30-day average limit is likely to have the net effect of
having a lower number of exceedances of the NAAQS level and better air
quality than an emission profile with maximum allowable emissions under
a 1-hour emission limit at the CEV. This result provides a compelling
policy rationale for allowing the use of a longer averaging period, in
appropriate circumstances where the facts indicate this result can be
expected to occur.
    The question then becomes whether this approach--which is likely to
produce a lower net number of overall exceedances of 75 ppb even though
it may produce some unmodeled exceedances on occasions when emissions
are above the CEV--meets the requirement in sections 110(a) and 172(c)
for state implementation plans to provide for attainment of the NAAQS.
For SO2, as for other pollutants, it is generally impossible
to design a nonattainment plan in the present that will guarantee that
attainment will occur in the future. A variety of factors can cause a
well-designed attainment plan to fail and unexpectedly not result in
attainment, for example if meteorology occurs that is more conducive to
poor air quality than was anticipated in the plan. Therefore, in
determining whether a plan meets the requirement to provide for
attainment, EPA's task is commonly to judge not whether the plan
provides absolute certainty that attainment will in fact occur, but
rather whether the plan provides an adequate level of confidence of
prospective NAAQS attainment. From this perspective, in evaluating use
of a longer-term limit up to 30-days, EPA must weigh the likely net
effect on air quality. Such an evaluation must consider the risk that
occasions with meteorology conducive to high concentrations will have
elevated emissions leading to exceedances of the NAAQS level that would
not otherwise have occurred and must also weigh the likelihood that the
requirement for lower emissions on average will result in days not
having exceedances that would have been expected with emissions at the
critical emission value. Additional policy considerations, such as in
this case the desirability of accommodating real world emissions
variability without significant risk of violations, are also
appropriate factors for EPA to weigh in judging whether a plan provides
a reasonable degree of confidence that the plan will lead to
attainment. Based on these considerations, especially given the high
likelihood that a continuously enforceable limit, averaged over a
period as long as 30 days, determined in accordance with EPA's April
2014 guidance, will result in attainment, EPA believes as a general
matter that such limits, if appropriately determined, can reasonably be
considered to provide for attainment of the 2010 SO2 NAAQS.
    EPA's April 2014 guidance offers specific recommendations for
determining an appropriate longer-term average limit. The recommended
method starts with determination of the 1-hour emission limit that
would provide for attainment (i.e., the critical emission value), and
applies an adjustment factor to determine the (lower) level of the
longer-term average emission limit that would be estimated to have a
stringency comparable to the otherwise necessary 1-hour emission limit.
The recommended method involves using these data to compute a complete
set of emission averages, computed according to the averaging time and
averaging procedures of the prospective emission limitation. In this
recommended method, the ratio of the 99th percentile among these
longer-term averages to the 99th percentile of the 1-hour values
represents an adjustment factor that may be multiplied by the candidate
1-hour emission limit (i.e., the critical emission value) to determine
a longer-term average emission limit that may be considered comparably
stringent. The April 2014 guidance also addresses a variety of related
topics, such as the potential utility of setting supplemental emission
limits, such as mass-based limits, to reduce the likelihood and/or
magnitude of elevated emission levels that might occur under the
longer-term emission rate limit.
    The Commenter objected in principle to EPA's proposed approval of
the use of longer-term average limits in the Commonwealth's attainment
plan, but the Commenter does not provide any critique of the specific
elements of the above rationale for EPA's proposed views. Nor does the
Commenter explain why EPA should revise its views as to the suitability
of longer-term average limits in principle as appropriate elements of
attainment plans, subject to case-specific reviews as to whether the
specific limits in specific cases satisfy EPA's recommended criteria
and whether, as a result, the specific plans may be considered to
provide for attainment. Therefore, EPA continues to believe in
principle that longer-term average limits, such as the 30-day limits
applicable here, if appropriately determined, are a suitable element of
an attainment plan that may be judged to provide for attainment.
    In this action, EPA is not changing its position regarding the
sufficiency in meeting the NAAQS of the 1-hour emissions limitations to
which other facilities are subject; EPA is merely reaffirming that
properly set longer-term average limits can also provide for
attainment, and concluding that the Commonwealth's limits, including
30-day average limits for Mill Creek, in fact provide for attainment of
the 1-hour SO2 standard.
    Comment 2: In addition to general concern with the use of a longer-
term average for compliance with the 2010 1-hour SO2
standard (see Comment 1), the Commenter expresses specific concerns
with how the emissions limits were established for Mill Creek. Those
specific comments can be subdivided into the following topics: (a) Mill
Creek's emissions are not steady-state enough to make the 720-hour
limit interchangeable with a 1-hour standard; (b) the 0.20 lb/MMBtu
[pounds per one million British Thermal Units] 720-hour average
emission limit for Mill Creek is too lax, as it was calculated opaquely
and based on a 1-hour CEV that LMAPCD and an independent expert found
to be too high to meet the NAAQS; (c) the adjustment factors to
establish the longer-term limit were inappropriately based on
operations of Mill Creek before the controls were installed (2009-2013
operations, instead of 2014-2016 for the installation of the controls--
in the Commenter's opinion, the limits were based on variability of
facility operations that are no longer valid (since new controls are in
place));

and (d) the data used to demonstrate that emissions would rarely be
above the CEV (limits established using 2009-2013 operations) were from
April 2016-March 2018, after the new controls became operational. In
the Commenter's opinion, the demonstration that those limits are
effective is invalid since the demonstration is based on operations
that were not used to set the limits in the first place.
    Response 2: For clarity, EPA will respond separately to each of the
above 4 subdivided comments.
    Response 2a: EPA does not agree with the Commenter that it is
necessary to have steady state emissions in order to establish a
longer-term emission limit that will demonstrate attainment with a 1-
hour NAAQS. The Commenter implies that unless emissions are steady
state, a 720-hour limit is not ``interchangeable'' with a 1-hour limit.
EPA disagrees. EPA's policy is designed to address situations with
variable emissions, and to offer the option for agencies to adopt a
longer-term limit that is ``interchangeable'' with a 1-hour limit in
the sense of providing comparable assurances that the standard will be
attained, notwithstanding this accommodation of variable emissions. As
we explained in our April 2014 guidance, as a general matter, EPA would
expect that any emission limit with an averaging time longer than 1-
hour would need to reflect a downward adjustment to compensate for the
loss of stringency inherent in applying a longer-term average limit.
This is why the April 2014 guidance describes a procedure for
establishing a longer-term limit that is designed to have comparably
stringency to a 1-hour average limit at the CEV. In the case of Mill
Creek, the 1-hour CEV is 0.29 lb/MMBtu, but the proposed 720-hour limit
is well below this value at 0.20 lb/MMBtu.
    The Commenter also referenced pages of the Title V Petition with a
chart described as depicting Mill Creek's SO2 emissions for
nine months in 2016 and concludes that this chart shows that a 30-day
average for Mill Creek smooths out instances of excessive 1-hour
emissions, which the Commenter contends are relatively frequent and
substantial. The Commenter's chart on page 5 of the Title V Petition
largely relies on emissions prior to the installation of the improved
flue gas desulfurization (FGD) controls and therefore does not reliably
depict the potential of Mill Creek, in compliance with its limit, to
emit above the CEV. As further explained in Response 2d below, EPA
performed an analysis of 3-1/2 years of post-control upgrade emissions
and found emissions periods above the CEV to be rare.
    Response 2b: EPA disagrees with the Commenter that the 0.20 lb/
MMBtu emission limit is too ``lax.'' First, the Commenter asserts that
the limit was calculated opaquely. As described in detail in EPA's
November 9, 2018, NPRM (see 83 FR 56010-11), LMAPCD and the
Commonwealth performed modeling to determine an appropriate CEV for
each unit, which demonstrates compliance with the 1-hour SO2
NAAQS. After this, an adjustment factor was calculated and used to
determine the appropriate 720-hour emission limit of 0.20 lb/MMBtu. As
explained in the NPRM, Kentucky used the procedures in EPA's guidance
to determine a compliance ratio (adjustment factor) of 0.69, which when
multiplied by 0.29 lbs/MMBTU yields a 30-day average limit of 0.20 lbs/
MMBTU. The detailed calculations yielding this adjustment factor were
provided in a spreadsheet that Kentucky included as an appendix to the
June 23, 2017 attainment SIP (see Appendix 4), as well as in the
supporting documents of EPA's November 9, 2018, NPRM (See Docket ID:
EPA-R04-OAR-2017-0625).
    Second, the Commenter asserts that the limit was based on a CEV
that was too high to satisfy the NAAQS. EPA disagrees with the
Commenter's assertion that the CEV in the modeling performed by LMAPCD
and the Commonwealth are too high to demonstrate compliance with the
NAAQS. As discussed below, EPA continues to believe that the modeling
provided in Kentucky's 2017 attainment demonstration is acceptable and
appropriate for demonstrating that Mill Creek's emissions limit will
provide for attainment of the NAAQS.
    The Commenter cited to an independent expert report and previous
comments by LMAPCD, which were included in the Title V Petition. EPA
has evaluated the independent expert report and has found aspects of
the modeling that deviate from EPA's recommended procedures in the
Modeling Guidance for SO2 Nonattainment Areas (Nonattainment
Modeling Guidance),\2\ the Guideline on Air Quality Models (Guideline)
in 40 CFR part 51, Appendix W, and common modeling practices. These
deviations from EPA's recommended procedures create uncertainty in the
results and the conclusions presented in the report. Areas where the
modeling deviates from EPA's recommended procedures include: (1) Three
years (2010-2012) of meteorology data were used to perform the
modeling, whereas Kentucky's SIP attainment modeling used five years of
meteorology (2011-2015) as recommended in Section 7.2 of the
Nonattainment Modeling Guidance and Section 8.4 of the Guideline to
ensure that worst-case meteorological conditions are adequately
represented in the model results; (2) actual stack heights of 182.9
meters (600 feet) for Mill Creek's boilers were used in the modeling,
whereas the Commonwealth's attainment SIP modeling more appropriately
used the Good Engineering Practice (GEP) stack heights of 142.88 meters
(469 feet) that were determined in accordance provisions of EPA's stack
height regulations in 40 CFR 51.100; (3) an older version of the AERMOD
modeling system (version 12345) was used, whereas the attainment SIP
modeling used the most recent version of AERMOD (version 15181) that
was available at the time the attainment demonstration (developed in
2016-2107); and (4) flagpole heights of 1.5 meters were used for all
modeled receptors to reflect a representative inhalation level, whereas
the Commonwealth's SIP attainment modeling followed common AERMOD
modeling practice of placing receptors at ground level, which EPA
believes is more appropriate.
---------------------------------------------------------------------------

    \2\ Appendix A of EPA's April 23, 2014, ``Guidance for 1-Hour
SO2 Nonattainment Area SIP Submissions.
---------------------------------------------------------------------------

    The Commenter asserts that LMAPCD previously recognized that the
720-hour emission limit of 0.20 lb/MMBtu was too high, citing to the
Title V Petition. It appears that the Commenter is referencing a
discussion on pages 8-9 that references an October 12, 2015 letter from
LG&E to LMAPCD.\3\ The letter states LG&E's understanding, based on
information and data provided by LMAPCD to LG&E, that the modeled CEV
translates to a one-hour limit of 0.24 lbs/MMBtu (and a 0.17 lbs/MMBtu
30-day limit). EPA is uncertain of the basis of this limit, and the
information and data referred to in this letter. It appears that
Commenter is referencing this limit to suggest that LMAPCD, at one
time, contemplated a more stringent limit, but LMAPCD is making no such
contention in the context of the attainment SIP that EPA is approving
today. To the extent that LMAPCD previously considered a different
limit, it is not uncommon for state and local technical analyses to
evolve during the development of plans and permitting such changes do
not, standing alone, lend support to a contention that the state or
local final plan is inadequate.

Regardless, as discussed in the NPRM and the Responses to Comment 2,
EPA has evaluated the 0.20 lb/MMBtu 30-day rolling average limit and is
determining that the limit is sufficient to demonstrate attainment of
the standard.
---------------------------------------------------------------------------

    \3\ Docket ID #EPA-R04-OAR-2017-0625-0011; Exh. B2.
---------------------------------------------------------------------------

    Response 2c: The commenter correctly notes that the adjustment
factor was determined based on the emissions data from the years 2009-
2013. Furthermore, the commenter correctly observes that this period
precedes the upgrades in the Mill Creek control systems needed to
comply with the SIP limits, and the Commenter accurately notes
statements in the April 2014 guidance indicating that installation of
control equipment is prone to increase the variability of emissions.
    For this attainment SIP, as for most SIP submittals addressing a
need for additional emission control, the adequacy of the SIP depends
on the adequacy of the projection of the future. At issue here in
particular is the adequacy of the projection of future variability of
emissions at Mill Creek. The April 2014 guidance addresses a number of
factors to be considered in order to make the best feasible projection
of the variability of emissions once the SIP is implemented. The
November 9, 2018, NPRM (See 83 FR 56010) addresses how EPA weighed
these factors. Kentucky preferred to use data from Mill Creek to
evaluate Mill Creek emissions variability, and the data from 2009 to
2013 were the most robust data available for a period with stable
operation (i.e., for a period without changes in the applicable control
system or instability associated with the startup of the improved
control system). The period from 2014 to 2016 included some operations
before the control upgrades \4\ and some post-upgrade, so that use of
these data could be more of an assessment of the variability between
the existing and improved control systems rather than an assessment of
variability of emissions within the improved control system.
Furthermore, the national average data provided in Appendix D of the
April 2014 guidance suggest that plants that already have controls
comparable to those being required for Mill Creek have variability
comparable to the variability projected for Mill Creek. That is, if
Kentucky had chosen to project variability at Mill Creek based on
variability of another already well controlled plant, it likely would
have found a similar adjustment factor as it found with the pre-upgrade
emissions data for pre-upgrade Mill Creek emissions data. Consequently,
EPA continues to believe that these data were the best data available
at the time to estimate the variability of the emissions to be expected
at Mill Creek and calculate the adjustment factor needed to establish a
longer-term emission limit.
---------------------------------------------------------------------------

    \4\ In this notice, the phrase ``control upgrades'' refers to
the replacement of existing wet FGD systems operating at 90% control
efficiency with the new wet FGD system operating at 98 percent
efficiency for all four Mill Creek units.
---------------------------------------------------------------------------

    An additional pertinent factor is that during 2009 to 2013, Mill
Creek did have existing wet-FGD scrubbers. The typical effect of
control on variability can be inferred from Appendix D of the April
2014 guidance, showing national average adjustment factors for
uncontrolled facilities and for facilities with a few types of control.
EPA would expect that upgrading a control would have less effect on
variability than installing a fully new control system. Therefore, EPA
would expect Mill Creek to experience less change in variability than
facilities that went from no control to full control; indeed, EPA
believes that the 2009 to 2013 data should be reasonably indicative of
variability following implementation of the control upgrades.
    Nevertheless, additional data are now available for a period after
the completion of the control upgrades at Mill Creek. EPA analyzed
these data, to obtain further insight into how well Kentucky's
assessment served as a forecast of post-control emissions variability.
For each unit, this analysis used emissions data after completion of
the control upgrade until the end of 2018, which at the time of the
analysis was the most recent available data. (Specifically, the first
data point was taken 30 days after completion of the upgrade, to avoid
being influenced by any potential instability in operation of the newly
upgraded equipment.) On average, these data sets comprise 3-1/2 years
for each unit, which is less than the 5 years that Kentucky analyzed
but sufficient to likely be adequately robust. In addition, while this
analysis generally used hourly emissions data reported to EPA for
emissions trading program purposes, EPA excluded a handful of data
points reflecting data substitution, where missing parameter data
result in the reporting of extreme emission rates.\5\ EPA analyzed
these data in accordance with the data handling procedures that it
understands that Kentucky will be using to assess compliance with these
limits. The results of this analysis, as expected, indicated that the
upgrading of control systems had only a relatively modest effect on
variability. A spreadsheet providing the full details of EPA's analysis
is included in the docket for this rulemaking (See Docket ID: EPA-R04-
OAR-2017-0625).\6\
---------------------------------------------------------------------------

    \5\ This analysis excluded SO2 emissions data with
Code 12, ``Maximum or Minimum Value from Default or Span Record.''
    \6\ See Mill Creek Analysis revised.xlsx in the Docket for this
final rulemaking (Docket ID: EPA-R04-OAR-2017-0625).
---------------------------------------------------------------------------

    The modeling provided by Kentucky showed a modeled design value
somewhat below the NAAQS, specifically at 190.1 micrograms per cubic
meter ([micro]g/m\3\) as compared to the NAAQS at 196.4 [micro]g/m\3\.
Thus, even if a modestly lower adjustment factor were applied
(suggesting that a modestly higher hourly limit would correspond to a
30-day average limit of 0.20 lb/MMBtu), the plan would still provide
for attainment.
    In summary, Kentucky used the most appropriate data available at
the time it was preparing the attainment SIP. Kentucky applied an
adjustment factor slightly more restrictive than the pertinent national
average adjustment factor provided in EPA's guidance, suggesting that
development of an adjustment factor based on data from another plant
would have yielded a similar adjustment factor. The fact that the
facility had existing wet-FGD scrubbers during the period Kentucky
analyzed would be expected to improve its suitability for assessing
variability following implementation of the SIP. The plan provides a
modest margin for uncertainties for example in the appropriate
adjustment factor. For this set of reasons, EPA concludes that,
notwithstanding the upgrade of emission controls since the time used
for determining an adjustment factor, Kentucky has applied an
adjustment factor that is likely to be sufficiently reliable to warrant
a conclusion that the adjusted limit Kentucky established is comparably
stringent to the modeled 1-hour CEV and therefore provides for
attainment of the 1-hour SO2 standard.
    Response 2d: Contrary to the Commenter's stated view, EPA believes
that our own analysis of the post-upgrade 2016-2018 data, as summarized
in the EPA's November 9, 2018, NPRM is valid. At issue here is whether
the establishment of a 30-day average limit is likely to provide a
sufficient constraint on 1-hour emission levels for EPA to anticipate
that occasions of emissions above the CEV will be infrequent. The best
data for assessing the likely frequency of 1-hour emissions higher than
the CEV during periods of compliance with the longer-term limit are
data during periods of compliance with the longer-term limit. Thus,
EPA's

analysis, using recent data during which the facility met the longer-
term limit, provides the most valid assessment of the pertinent
question, and indeed provides a substantially more valid analysis than
would have been obtained following the commenter's suggestion to use
data from a period with routine long-term average values above the 30-
day average limit.
    Regardless of whether the Commenter agrees with how the 720-hour
permit limit was set, the analysis of the newer emissions data
demonstrates, based on the current operation after the control
upgrades, that the frequency of time the emissions are over the CEV is
expected to be minimal. In addition to the analysis of post-control
data that was summarized in EPA's November 9, 2018, NPRM, the Agency
has further evaluated the data with the addition of the most recent 9
months of emissions data. In summary, EPA has now looked at post-
upgrade data through December 2018.\7\ This analysis confirms our
belief as proposed that the frequency of time that emissions are over
the CEV is minimal.\8\ In this current analysis, during periods that
the units met the 30-day average limit of 0.20 lb/MMBtu, the
frequencies with which emissions from Unit 1, Unit 2, Unit 3, and Unit
4 were higher than the 1-hour critical emission rate were 0.1 percent,
0.2 percent, 0.1 percent, and 0.5 percent, respectively. This analysis
supports EPA's conclusion that the 30-day average limit of 0.20 lb/
MMBtu in title V permit 145-97-TV(R3) for EGU U1, U2, U3 and U4 for
Mill Creek is sufficient to demonstrate attainment without additional
conditions to limit the frequency of elevated emissions or the
imposition of shorter-term averaging periods (e.g., 24 hours).
---------------------------------------------------------------------------

    \7\ For Units 1, 2, and 3, the facility met the new limit for
the entire period after completion of the control upgrade. For these
units, EPA did not examine the first 30 days after the upgrade, to
disregard any instability of operation, but EPA examined the full
period from 30 days after upgrade through December 31, 2018. For
Unit 4, the unit did not meet the new limit until a corresponding
limit under the Mercury and Air Toxics Standards took effect, on
April 16, 2016. Therefore, for this analysis for Unit 4, EPA
examined the data from April 16, 2016 to December 31, 2018.
    \8\ See Mill Creek Analysis revised.xlsx in the Docket for this
final rulemaking (Docket ID: EPA-R04-OAR-2017-0625).
---------------------------------------------------------------------------

    Comment 3: A Commenter expresses concern about EPA's November 9,
2018, NPRM and the treatment of emissions from Kosmos in relation to
the attainment demonstration for the Jefferson County nonattainment
area. Generally, the Commenter believes that Kosmos should be
considered a source to evaluate for an emission limit as part of the
SIP, and not treated as either a ``nearby'' source or an ``other''
source considered in the background. Specifically, the Commenter claims
that considering Kosmos as a background source is unsound and unlawful,
in conflict with EPA's guidance at 40 CFR part 51 Appendix W. The
Commenter references air dispersion modeling performed by LMAPCD to
site a monitor in the vicinity of Kosmos (proposed Kosmosdale monitor)
using the AERMOD model to support its claim that Kosmos should be
explicitly modeled to have its emissions impact characterized. The
Commenter indicates that the results of this modeling appear to show
violations of the 1-hour SO2 NAAQS both inside and outside
the nonattainment area boundary and appear to show that Kosmos causes a
significant concentration gradient inside the nonattainment area, which
is demonstrated using either normalized or not normalized emissions.
    Response 3: Since EPA continues to believe that Kentucky's
attainment modeling is appropriate, in which Kosmos' emissions impacts
are adequately represented by modeling accounting for Kosmos as a
background source, the Agency does not agree with the Commenter's
assertion that Kosmos should be evaluated for an emissions limit to be
included in the SIP or treated as a ``nearby source,'' as defined in
Section 8.3.1 of EPA's Guideline on Air Quality Models contained in 40
CFR part 51, Appendix W (Appendix W). EPA's rationale for finding that
Kentucky's treatment of Kosmos as an ``other source'' and addressing
its impacts with a representative ambient background concentration to
be appropriate is fully discussed in Section IV.B.5 of EPA's November
9, 2018, NPRM. The following discussion briefly summarizes EPA's
independent analysis, presented in the November 9, 2018, NPRM, that was
done to assess the Commonwealth's conclusion that the Green Valley
background monitor adequately represents background concentrations of
SO2 within this nonattainment area, and any impact from
Kosmos. In accordance with Section 8.3.1.a.i of Appendix W, EPA
evaluated whether Kosmos would cause a significant concentration
gradient in the vicinity of the Mill Creek source. EPA applied the rule
of thumb criterion discussed in Section 8.3.3.b.ii of Appendix W, which
provides that the magnitude of a concentration gradient will be
greatest in the proximity of the source and will generally not be
significant at distances greater than 10 times the height of the
stack(s) at that source without consideration of terrain influences.
The height of the cement kiln stack at Kosmos is 75 feet (approximately
23 meters), and there are no significant terrain features located near
Kosmos or within the nonattainment area boundary. Therefore,
concentration gradients should be comparatively modest beyond 230
meters from the stack. The closest edge of the nonattainment boundary
is approximately 480 meters from the stack, which is more than twice
the distance of this general rule of thumb. Therefore, EPA determined
that the SO2 emissions from Kosmos would not result in a
significant concentration gradient within the nonattainment area
boundary and therefore can be treated as an ``other source'' in the
attainment demonstration modeling. EPA also evaluated whether the Green
Valley background monitor data is appropriate to represent the
potential SO2 concentration impacts from Kosmos within the
nonattainment area. Based upon an assessment of wind patterns in the
Louisville area, the SO2 emissions sources in the vicinity
of the Green Valley monitor, and comparing those sources to the Kosmos
source, EPA determined that the Green Valley monitor reasonably
indicates the impact of Kosmos on the nonattainment area.\9\
---------------------------------------------------------------------------

    \9\ The complete details of this analysis are presented in
Section IV.B.5 of EPA's NPRM (83 FR 56012).
---------------------------------------------------------------------------

    Additionally, EPA considered whether Kosmos should be evaluated for
an emission limit to include in the SIP as recommended by the
Commenter, and ultimately concluded that the Commonwealth's treatment
of Kosmos is acceptable and Kosmos did not need to be a ``Source
Subject to SIP Emissions Limit Evaluation for Compliance with Ambient
Standards'' as specified in Table 8-1 of Appendix W. SO2 is
a source-oriented pollutant and concentrations are often due to a
single large industrial source or group of sources with localized
impacts that usually have a limited number of sources affecting areas
of air quality which are relatively well defined. Emissions control
measures for such sources result in swift and dramatic improvement in
air quality. In 2013, EPA designated those areas that were determined
to be impacting or contributing to a violation at an ambient air
quality monitor (known as round 1 designations). At the time of
designations for Jefferson County, Kentucky, it was determined that
Mill Creek was the primary cause and contributor to the violation at
the Watson Lane monitor (AQS ID: 21-111-

0051) based on best available ambient air quality data, emissions and
other information that informed EPA's final designation of
nonattainment around the Mill Creek facility and the Watson Lane
monitor. EPA considered evidence of source-receptor relationships
between specific emissions sources and high SO2 values at
violating monitors in determining the appropriate contributing areas
and the appropriate extent of the nonattainment area boundary in round
1 designations. This included assessing meteorological data nearest to
the then violating Watson Lane monitor to determine which wind vectors
were associated with 1-hour SO2 concentrations exceeding the
NAAQS level. Mill Creek was the largest SO2 emission source
near the Watson Lane monitor, located approximately 1.5 kilometers (km)
southwest of the monitor. EPA's review of meteorological data as well
as emission data indicated that the majority of the NAAQS level-
exceeding hours at the monitor occurred during times when the wind blew
from the direction of Mill Creek (i.e., from southwest of the monitor)
supporting EPA's conclusion that Mill Creek was likely causing the
monitored violations. Therefore, EPA established the boundary around
Mill Creek and the Watson Lane monitor based on technical evidence that
Mill Creek was causing violations of the SO2 standard at the
monitor. EPA considered jurisdictional boundaries for the purposes of
providing a clearly defined legal boundary and to help identify the
areas appropriate for carrying out the air quality planning and
enforcement functions for nonattainment areas. Kosmos was not the focal
point for round 1 designations. In EPA's round 1 designation Technical
Support Document (TSD) for Kentucky, EPA explained that areas and
sources that we were not then yet prepared to conclude are contributing
to the monitored violations were not being included in initial
nonattainment areas. EPA did not receive any additional information or
comments during the 30-day public comment period for the 2013 round 1
designations asserting that Kosmos was causing or contributing to the
violation at the monitor, nor did any petitioner timely challenge the
designation for the portion of Jefferson County. That opportunity to
bring such a challenge has long since passed. See EPA's response to
Comment #6.
    Mill Creek is the only SO2 emitting major point source
in the nonattainment area and the only emission source explicitly
modeled in the attainment modeling analysis submitted by the
Commonwealth for the Jefferson County nonattainment area. All minor
area sources and other major point sources (located outside the
nonattainment area boundary) were accounted for with the background
concentration as discussed in Section IV.B.5. of the November 9, 2018,
NPRM. Decreasing trends in Mill Creek SO2 emissions and
ambient monitor concentrations in the nonattainment area at the Watson
Lane monitor since 2013 support the Commonwealth's focus on Mill Creek.
From 2013 to 2017, actual SO2 emissions from Mill Creek
reported in EPA's Clean Air Market program database decreased from
28,150 tons per year (tpy) to 3,040 tpy due to the new Mill Creek
emissions controls, while the Watson Lane ambient monitor design
concentrations decreased from 148.6 ppb to 13.7 ppb during the same 5-
year period. Despite the Mill Creek and Kosmos sources being in close
proximity to each other, the nature of each source and their specific
locations provide for distinct spatial patterns of modeled
concentration impacts from Mill Creek's emissions, which are emitted
from relatively tall stacks (469 feet) \10\ and Kosmos' emissions,
which are emitted from a relatively short stack (75 feet). The modeling
to site the Kosmos monitor conducted by LMAPCD and referenced by the
Commenter (in which both Kosmos and Mill Creek were modeled with
allowable emissions to find the area of maximum impact from Kosmos'
emissions), shows that the highest modeled concentrations were observed
outside the nonattainment area southwest of Kosmos' property boundary
(in the opposite direction from the nonattainment area and the Watson
Lane monitor).\11\ In contrast, in the attainment SIP modeling provided
by the Commonwealth, where only Mill Creek emissions were explicitly
modeled and other sources, including Kosmos, were addressed in the
background concentration, the maximum area of impact from Mill Creek's
emissions in the nonattainment area is located near the Watson Lane
monitor. The results of these modeling analyses show that Mill Creek
and Kosmos have different areas of impact and that Kentucky's decision
to only evaluate the Mill Creek sources for control to bring the
Jefferson County nonattainment area back into attainment with the 1-
hour SO2 NAAQS is appropriate.
---------------------------------------------------------------------------

    \10\ The actual stack heights at Mill Creek range from 600-610
feet. However, the GEP stack heights for each stack that were used
in the modeling are 469 feet.
    \11\ As presented in the LMAPCD's 2017 Network Plan, the
Kosmosdale monitor is proposed to be installed southwest of Kosmos
within the area of maximum impact.
---------------------------------------------------------------------------

    The Commonwealth's attainment SIP demonstrates that the emissions
limits for Mill Creek provides modeled and monitored attainment for the
area and appropriately accounts for the contribution of Kosmos and
other sources consistent with EPA's Guidelines and governing
regulations (as discussed in the November 9, 2018, NPRM and supported
by additional analysis by EPA within that proposal). SO2
control measures are by definition based on what is directly and
quantifiably necessary to attain the SO2 NAAQS and it would
be unlikely for an area to implement the necessary emission controls
yet fail to attain the NAAQS. Attainment plans for SO2 must
meet the applicable requirements of the CAA, and specifically CAA
sections 110, 172, 191, and 192. As EPA has explained in the April 2014
guidance and in numerous proposed and final SIP rulemakings
implementing the SO2 NAAQS, a key element in an approvable
SIP is the required modeling demonstration showing that the remedial
control measures and strategy are adequate to bring a previously or
currently violating area into attainment. The Commonwealth's attainment
SIP required Mill Creek, the primary SO2 source in the area,
to implement a control strategy in accordance with the CAA and EPA's
technical guidance and included a modeled demonstration of attainment
by the statutory attainment deadline. During round 1 designations EPA
determined Mill Creek to be the primary source of violations at the
Watson Lane monitor. The Commonwealth's attainment plan addressed the
violations of the 2010 standard through the implementation of an
emission reduction control strategy for Mill Creek, the primary
SO2 source determined to cause measured violations at the
ambient air monitor that demonstrated modeled attainment of the 2010
standard. The plan accounted for other sources outside the
nonattainment area, including emissions from Kosmos, in the background
concentrations. As EPA explained in the November 9, 2018, NPRM and as
determined through the modeled attainment demonstration submitted by
Kentucky, the evaluation of controls for other sources within or
outside the nonattainment area is not necessary to show compliance with
2010 standard. Therefore, in the context of considering the
approvability of Commonwealth's attainment SIP including the adequacy
of control

measures to provide for modeled attainment of the air quality standard
under sections 172 and 192, EPA believes it is reasonable to focus on
the modeled results that specifically account for those control
measures at Mill Creek and their resulting reductions in SO2
emissions that demonstrate attainment in the Jefferson County
nonattainment area. For the reasons described in the November 9, 2018,
NPRM and elsewhere in this rule, EPA has concluded that the
Commonwealth's SO2 attainment plan meets the requirement in
CAA sections 172(c) and 192(a), and 40 CFR 51.112, to include a
modeling demonstration that the Mill Creek control measures included in
the plan provide for attainment for the Jefferson County Area.
    EPA notes that the LMAPCD's modeling referenced by the Commenter,
and which was not submitted by Kentucky to support its attainment
demonstration, was conducted for a different purpose than for informing
the attainment SIP demonstration. Namely, it was performed to determine
the best location to site a new ambient air monitor to characterize
future maximum concentrations near the Kosmos facility and used Kosmos'
permitted allowable emissions following procedures provided in EPA's
SO2 Designations Monitoring Technical Assistance Document
(TAD).\12\ As referenced by the Commenter, LMAPCD presented the results
of modeling with both absolute and normalized concentrations. EPA
disagrees with the Commenters assertion that LMAPCD's absolute and
normalized modeling results show that Kosmos causes a significant
concentration gradient inside the nonattainment area. For purposes of
attainment demonstrations, modeling with allowable emissions is the
type of modeling expected under Appendix W for sources being evaluated
for new SIP emissions limitations and the new allowable level typically
reflects a reduction in emissions from past actual emissions. As
explained above and in the response to Comment 6, EPA is concluding
that Kosmos is not such a source. Assuming for argument that Kosmos
could not be adequately characterized as an ``other source,'' Section
8.2.2.b. and Table 8-1 in Appendix W provide that for ``nearby
sources'' emissions reflective of actual operation over the most recent
two years shall be used in cumulative impact modeling for attainment
demonstrations or for evaluating whether nearby sources cause a
significant concentration gradient in the area. LMAPCD's modeling
referenced by the Commenter was performed using Kosmos' allowable
emissions without accounting for recent actual operation, so it is not
appropriate to assess concentration gradients or contribution to the
nonattainment area since it does not reflect actual operations. EPA
concludes that for the SIP attainment demonstration, Kosmos is
adequately represented by background emissions in Kentucky's modeling
analysis as an ``other source.'' As such, we reject the Commenter's
view that the more conservative modeling using Kosmos' allowable
emissions that is not required by EPA's rules for ``nearby sources''
must be viewed as a better and preferred characterization of impacts
from Kosmos as an ``other source.''
---------------------------------------------------------------------------

    \12\ ``SO2 NAAQS Designations Source-Oriented
Monitoring Technical Assistance Document,'' U.S. EPA Office of Air
and Radiation, Office of Air Quality Planning and Standards, Air
Quality Assessment Division, February 2016 Draft.
---------------------------------------------------------------------------

    Furthermore, the monitoring data trends during the time period
corroborate the existence of the substantial air quality benefits from
the significant SO2 reductions from Mill Creek facility. In
addition to the modeling demonstrating attainment of the SO2
standard, actual monitored 99th percentile of 1-hour daily maximum
concentrations at the Watson Lane monitor do not show violations of the
NAAQS. Based on technical and policy considerations, EPA believes that
the Kosmos facility was adequately accounted for in the attainment
demonstration modeling and was not required to be evaluated for
additional controls.
    Comment 4: A Commenter indicates that EPA's November 9, 2018, NPRM
suggests that there is no need for an Agreed Board Order (ABO) to
characterize air quality in the vicinity of Kosmos if EPA believes that
the potential impacts of Kosmos are characterized by a distant monitor.
Additionally, the Commenter argues that there is no logical reason for
LMAPCD and the state to enter into the agreement if the option of
including Kosmos as an ``other,'' or background, source was available
for SIP approval.
    Response 4: EPA does not believe that it is appropriate to draw
this conclusion from the November 9, 2018, NPRM (or this final rule).
The more appropriate conclusion to draw is that, for the purpose of
attainment demonstration modeling for the Jefferson County
nonattainment area, it is appropriate to consider Kosmos a background
source. See EPA's response to Comment 3 above for EPA's response
related to treating Kosmos as a background source. Although EPA
believes for the purpose of attainment modeling for the Jefferson
County nonattainment area it is appropriate to consider Kosmos a
background source, the Agency also supports the efforts of Kentucky and
LMAPCD to further characterize air quality in the area \13\ near Kosmos
in order to continue to verify that there are no violations of 2010 1-
hour SO2 NAAQS in either the Jefferson County nonattainment
area or in other areas potentially impacted by Kosmos' emissions. As
was mentioned in EPA's November 9, 2018, NPRM, LMAPCD and Kosmos have
entered into an ABO to evaluate the ambient concentrations of
SO2 in the vicinity of Kosmos. That evaluation is ongoing
and is separate from this action. Today's SIP approval action, however,
should not be interpreted as precluding that evaluation from
continuing, nor should it be interpreted as providing a conclusion
regarding current SO2 air quality outside the Jefferson
County nonattainment area and, specifically, in the vicinity of the
Kosmos facility.
---------------------------------------------------------------------------

    \13\ Pursuant to the CAA, the Administrator also has the
authority to address any potential or actual violation of a health-
based standard either by revising an area's designation for a
particular standard, requiring a state to revise its SIP if EPA
determines the plan to be inadequate to attain or maintain a
standard, or to work collaboratively with state to remedy any
violation of a standard. The statute authorizes the Administrator to
remedy a potential violation of any health-based standard including
the 2010 SO2 NAAQS regardless of whether those potential
violations are determined to be within an existing attainment area
or are within close proximity of a nonattainment area.
---------------------------------------------------------------------------

    EPA also notes that, if additional characterization of ambient
concentrations of SO2 in the vicinity of Kosmos raises
concerns with continued NAAQS attainment or maintenance in either the
Jefferson County area or other areas, the Commonwealth and LMAPCD have
the authority to remedy any potential violation of a NAAQS through SIP-
approved and statutory provisions.\14\
---------------------------------------------------------------------------

    \14\ LMAPCD Regulation 3.01--``Ambient Air Quality Standards,''
section 4--General Prohibition and section 5--Methods of
Measurement. Commonwealth of Kentucky 401 Kentucky Administrative
Regulation (KAR), Chapter 50 Division for Air Quality; General
Administrative Procedures--50:050 Monitoring; Chapter 53--Ambient
Air Quality--53:005 General Provisions. Kentucky Revised Statutes
(KRS) Title XVIII--Public Health Chapter 224 Environmental
Protection--Subchapter 20--Air Quality (KRS 224.20-110).
---------------------------------------------------------------------------

    Comment 5: A Commenter asserts that treatment of Kosmos as a
background source undermines the modeling that was used to site the
Kosmos monitor and implies that the significant concentration gradient
shown in the 2017 Network Plan's modeling is fictitious. The Commenter
noted that

EPA approved the 2017 Network Plan and asserts that EPA must either
determine that the concentration gradient is significant and Kosmos
should be explicitly modeled (which the Commenter claims was EPA's
position as of June 2018) or determine that the AERMOD model does not
simulate impacts from sources with short releases such as Kosmos Cement
and disregard all regulatory modeling conducted for such sources.
    Response 5: As presented in the LMAPCD's 2017 Network Plan,
modeling was performed using Kosmos' permitted maximum allowable
emissions and operations in order to determine the best location to
site a new ambient air quality monitor to characterize the future
maximum 1-hour SO2 concentrations near the Kosmos facility.
This was done in accordance with the SO2 NAAQS Designations
Source-Oriented Monitoring Technical Assistance Document (TAD) which
recommends the use of modeling to determine suitable monitor placement
characterizing areas of maximum SO2 concentrations.
Specifically, for these purposes, the SO2 NAAQS Designations
Source-Oriented Monitoring TAD references the SO2 NAAQS
Designations Modeling TAD which in Section 5 discusses the use of
allowable or potential-to-emit emissions when actual emissions are
unavailable. LMAPCD appropriately followed these modeling procedures
for siting a new ambient air monitor. However, as discussed in EPA's
response to Comment #3, since LMAPCD's modeling was performed with
maximum allowable emissions and operations and does not incorporate
actual operation of the Kosmos facility, it was not performed as
prescribed in Section 8.2.2.b., and Table 8-1 in Appendix W for
evaluating Kosmos' concentration gradient or contribution to
concentrations within the nonattainment as a nearby source.
    With respect to the Commenter's suggestion that EPA must either
determine that Kosmos must be explicitly modeled or determine that
AERMOD is not adequate to simulate impacts from short stack releases,
EPA does not agree that this action poses this dilemma. As EPA has
explained, the SIP modeling appropriately treats Kosmos as a background
source. Further, EPA is making no determination on the adequacy of
AERMOD, generally, in the context of this action. Rather the only
determination EPA is making regarding AERMOD in this action concerns
its evaluation of the appropriateness of Kentucky's use of AERMOD in
its attainment demonstration modeling, which EPA is concluding is
appropriate.
    Comment 6: A Commenter questions EPA's designation process for the
2010 SO2 NAAQS. Specifically, the Commenter claims EPA has
erroneously designated Kosmos' area as attaining the NAAQS and that
Kosmos should therefore be considered a source to evaluate for an
emissions limit as part of a SIP, rather than a nearby source or an
``other'' or background source.
    Response 6: First, for the reasons previously explained, EPA
concludes that it was not necessary to evaluate Kosmos for an emission
limit to include in the SIP, and that Kentucky has appropriately
characterized Kosmos' emissions impacts in the nonattainment area. See
EPA's response to Comment #3. Second, EPA believes that the Commenter's
reference to EPA's round 3 SO2 designations signed on
December 21, 2017 (83 FR 1098), is outside the scope of this action to
approve the nonattainment planning SIP for the Jefferson County
nonattainment area. In proposing to approve the SIP addressed in this
action, EPA did not reopen either of the designations addressing
Jefferson County, Kentucky, and this final action has no final effect
on those designations. EPA also notes that no petitioner timely
challenged the designation for Kosmos' area, and that the opportunity
to bring such a challenge has long since passed. However, for
informational purposes EPA notes that, generally, designations are
based on the best ambient air quality data available at the time of
designation to determine if an area meets or does not meet the
standard. EPA's attainment/unclassifiable designation for the remaining
portion of Jefferson County, in which the Kosmos facility resides, was
finalized in January 2018 and became effective on April 9, 2018. See 83
FR 1098 (January 8, 2018). EPA provided a 30-day public comment period
(although not required by section 107(d) of the CAA) on the Agency's
intended designations published in a notice of availability requesting
public comments from interested parties, other than the states,
territories and tribes on September 5, 2017. See 82 FR 41903.
Additionally, interested parties who had submitted comments had an
opportunity to file a petition for judicial review within 60-days after
the publication date of the final rule for EPA's designations. EPA
received no comments on its intended attainment/unclassifiable
designation for the remaining portion of Jefferson County, Kentucky nor
did the Agency receive a petition for judicial review challenging the
final attainment/unclassifiable designation for the remaining portion
of Jefferson County, Kentucky.
    Comment 7: A Commenter claims that EPA reversed its position on how
to treat Kosmos from the time that EPA provided the Commonwealth
preliminary comments on its submission when it was under review at the
state level and prior to formal submission to EPA. The Commenter points
to Louisville's March 17, 2017, prehearing SIP submittal and EPA's
April 18, 2017 \15\ letter commenting on this prehearing submittal
where EPA recommended treatment of Kosmos as a nearby source. The
Commenter suggests that these previous preliminary comments show that
EPA's November 9, 2018, NPRM to approve Kentucky's treatment of Kosmos
as a background source constitutes an arbitrary and capricious shift in
position and is not supported by the record.
---------------------------------------------------------------------------

    \15\ The Commenter included a date of April 18, 2018, for an EPA
letter. However, based on the context of its use, EPA believes the
Commenter is referring to an April 18, 2017 EPA letter, which was
also referenced in footnote 22 of the November 9, 2018, NPRM.
---------------------------------------------------------------------------

    Response 7: First, it is not uncommon during continuing discussions
with states for EPA's positions on the manner in which states address
attainment planning to evolve as technical information continues to be
developed and submitted to EPA, evaluated by Agency staff, and refined.
This is exactly what happened in this case, and EPA rejects the
assertion that the fact of such evolution alone shows that our final
approval is arbitrary and capricious. In Section IV.B.5 of the November
9, 2018 NPRM, EPA detailed its analysis of the appropriateness of
treatment of Kosmos as an ``other source'' and addressing its impacts
with a representative ambient background concentration. See also EPA's
response to Comment #3 on the rationale for the treatment of Kosmos.
The Commenter did not express any technical concerns with this analysis
in the November 9, 2018, NPRM. EPA believes the record supports EPA's
determination that the Commonwealth's treatment of Kosmos as an ``other
source'' is appropriate and does not agree that its earlier comments on
the Commonwealth's preliminary submittal show that its current approach
is arbitrary and capricious and not supported by the record.
    Comment 8: A Commenter asserts that EPA is establishing the monitor
as a means of compliance with the attainment demonstration and
expresses concerns about this assumption.
    Response 8: EPA disagrees with the Commenter's characterization of
the role of the Kosmosdale monitor. EPA concludes in this rulemaking
that Kentucky's plan provides for attainment

in the established nonattainment area, and at the same time EPA
supports Kentucky's efforts to pursue additional monitoring information
to characterize air quality outside the nonattainment area in the
vicinity of the Kosmos facility. EPA notes that its evaluation of the
Commonwealth's SIP revision is based on the CAA requirements for
attainment planning and on established guidance related to attainment
plans. As outlined in EPA's November 9, 2018, NPRM, the Agency's
proposed approval of the SO2 attainment SIP is solely based
on the Agency's determination that the plan complies with the
nonattainment planning requirements of section 172(c) of the CAA for
demonstrating attainment. LMAPCD's board order does not supplement the
Commonwealth's attainment SIP nor did the Commonwealth request the
order be incorporated into the SIP. As indicated in EPA's April 18,
2017, comment letter, EPA and the Commonwealth and LMAPCD have
discussed appropriate consideration of Kosmos. This is reflected in the
discussion in Section IV.B.5 of the November 9, 2018, NPRM regarding
the appropriate treatment of Kosmos in the attainment demonstration
modeling.
    Comment 9: A Commenter expresses concerns with connecting the
timing of the deployment of the monitor near Kosmos with the attainment
demonstration for the Jefferson County nonattainment area and notes
that the monitoring plan is not contingent on the SIP submittal.
    Response 9: EPA agrees with the Commenter that the ambient air
monitoring network plan is not contingent on a SIP submittal. The
network plan is a separate regulatory planning process. On February 1,
2018, EPA approved siting the Kosmosdale monitor (AQS ID: 21-111-0065)
to characterize the maximum ambient 1-hour SO2 concentration
near Kosmos as part of the 2017 Kentucky Ambient Air Monitoring Network
Plan.
    Comment 10: Based on a Commenter's review of EPA's November 9,
2018, NPRM, the Commenter asserts that EPA is in agreement or has
otherwise made certain determinations that Kosmos does not constitute a
source causing or contributing to 1-hour SO2 NAAQS violation
inside the nonattainment area or otherwise constitutes a source for
which consideration of SO2 emissions limitations or other
controls are necessary in order for the Jefferson County nonattainment
area to attain the 1-hour SO2 NAAQS and that therefore,
source-specific modeling of Kosmos emissions is not necessary under the
2014 SO2 Nonattainment Guidance. Further, the Commenter
claims that EPA had determined that Kosmos' emissions are adequately
represented by ambient monitoring data from the Watson Lane monitor and
that therefore, Kosmos should not be considered a ``nearby'' source for
the purposes of modeling the Mill Creek Generating Station emissions
under 40 CFR part 51, Appendix W. The Commenter also states that EPA
concluded that SO2 emissions from Kosmos would likely not
result in a significant concentration gradient within the nonattainment
area boundary.
    Response 10: EPA has in fact concluded that Kentucky's SIP
adequately shows that the nonattainment area will meet the NAAQS
throughout the area's boundaries, notwithstanding emissions from
Kosmos. However, EPA also believes that Kentucky has good reasons to
establish a monitor near Kosmos to better characterize the ambient
concentrations of SO2 in the vicinity of the facility, in
order to better understand air quality in the vicinity of Kosmos. In
the separate action to approve Kentucky's monitoring network, which is
a separate regulatory process and is not being re-opened or reevaluated
in this SIP approval action, EPA supported Kentucky's choice. As
explained in EPA's November 9, 2018, NPRM, and above in EPA's response
to Comment #3, EPA observes that the analysis supplementing the
Commonwealth's modeling analysis determined that the SO2
emission from Kosmos would not result in a significant concentration
gradient in the nonattainment area. As a result, Kosmos' emissions were
not further characterized for purposes of consideration for SIP
emission limits to demonstrate attainment for the nonattainment area or
as a nearby source. See EPA's response to Comment #3. A conclusion that
Kosmos should not be considered a ``nearby'' source or considered for a
SIP emission limit for the purpose of modeling the Mill Creek
Generating Station and the associated nonattainment area in no way
indicates that it is unreasonable for Kentucky to choose to monitor air
quality in the more immediate vicinity of from Kosmos.
    Lastly, EPA does not agree with the Commenter that EPA determined
that Kosmos' impacts are represented by ambient monitoring data at the
Watson Lane monitor at all locations. EPA's supplemented background
analysis in the November 9, 2018, NPRM supports the Commonwealth's
conclusion that the Green Valley background monitor, located 27 km
north of the nonattainment area in Indiana, adequately represents
background concentrations of SO2 within this nonattainment
area, including the impact from Kosmos. EPA also evaluated whether
Green Valley background monitor data is adequately representative of
potential SO2 concentration impacts from Kosmos within the
Jefferson County nonattainment area based on an assessment of wind
patterns in the Louisville area, the SO2 emissions sources
in the vicinity of the Green Valley monitor and comparing those sources
to the Kosmos source. EPA's rationale for finding Kentucky's treatment
of Kosmos as an ``other source'' and addressing it's impacts with a
representative ambient background concentration is fully discussed in
Section IV.B.5 of EPA's November 9, 2018, NPRM. EPA's November 9, 2018,
NPRM did not indicate that Kosmos' impacts closer to the facility are
represented by ambient air quality data from the Watson Lane monitor.
    Comment 11a: A Commenter requests that EPA delete footnote number
22 because the Commenter states that the ABO referenced in footnote 22
is not necessary for EPA's approval of the SIP. The Commenter agrees
with EPA that Kosmos is appropriately considered as a background source
and no emissions limits or other controls are necessary under the SIP
to bring the Jefferson County nonattainment area into attainment.
    Response 11a: EPA included footnote number 22 to acknowledge
information provided as part of the record respecting the attainment
SIP and does not believe there is any need to delete this footnote. See
EPA's November 9, 2018, NPRM, and EPA's response to Comment #3 for more
information on the treatment of Kosmos in the attainment demonstration.
See also EPA's response to Comment #8 as it pertains to the relevance
of EPA's footnote regarding the ABO. The Agency also supports the
efforts of Kentucky and LMAPCD to further characterize air quality in
the area near Kosmos in order to continue to verify that there are no
violations of 2010 1-hour SO2 NAAQS in the vicinity of
Kosmos.
    Comment 11b: Additionally, a Commenter requests that EPA delete
footnote number 22 because of the Commenter's assertion that the ABO
between Kosmos and LMAPCD is not necessary because current monitoring
data (presumably at the Watson Lane monitor) is attaining the NAAQS,
and thus, in the Commenter's opinion the premise on which the ABO was
based

is no longer valid. The Commenter mentions that the ABO is ``subject to
change'' and claims that the ABO will need to be revisited by LMAPCD
and Kosmos and revised as necessary and appropriate.
    Response 11b: EPA does not agree with the Commenter that footnote
22 should be deleted. EPA understands that there is continued dialog
between the LMAPCD (in consultation with Kentucky) and Kosmos regarding
the ABO and the status of installation and operation of the Kosmosdale
SO2 monitor which is approved in the ambient air monitoring
network plan to characterize the impact of SO2 emissions
from the facility to the area surrounding the facility. EPA encourages
this continued dialog and does not intend through this action to
indicate that SO2 air quality in the vicinity of Kosmos
should not be further evaluated for purposes of verifying that there
are no violations of 2010 1-hour SO2 NAAQS in either the
Jefferson County nonattainment area or in other areas potentially
impacted by Kosmos' emissions. See EPA's response to Comment #4.
    Comment 11c: A Commenter claims that footnote number 22
inaccurately summarizes the ABO and asserts that the ABO does not
require Kosmos to ``deploy'' a monitor but instead only allows
monitoring to continue until the end of [a] three-year monitoring
period if a cost agreement and access agreement can be finalized and
further only requires action by Kosmos if necessary to meet the
SO2 NAAQS. The Commenter concludes that the ABO is not
necessary for the SIP approval and thus the footnote should be deleted.
    Response 11c: EPA acknowledges that the ABO does not require Kosmos
to deploy an SO2 ambient air monitor; monitoring will be
performed by LMAPCD. The ABO establishes an agreement between Kosmos
and LMAPCD regarding access and cost responsibility of the monitoring.
As prescribed in the ABO and approved by EPA in the Kentucky Ambient
Air Monitoring Network plan, which is not being re-opened in this SIP
approval action nor related to EPA's approval of the attainment SIP,
LMAPCD will operate the air monitoring site as a State and Local Air
Monitoring Station (SLAMS) to monitor SO2 and meteorological
data to obtain 3 years of quality-assured data. See EPA's response to
Comment #8.
    Comment 12: A Commenter claims that EPA's November 9, 2018, NPRM
fails to meet the CAA's statutory deadline to issue a Federal
Implementation Plan (FIP) and that EPA must issue a FIP and must impose
sanctions on Kentucky for failing to submit a lawful SIP.
    Response 12: EPA acknowledges that it did not approve a SIP
revision or promulgate a FIP for the Jefferson County area by the
statutory deadline under CAA 110(c)(1)(A). However, with this final
action to approve Kentucky's attainment SIP, EPA is discharging the
statutory obligation under CAA section 110(k)(2) to act on the SIP, and
such approval terminates our FIP obligation under section 110(c)(1)(A)
for the Jefferson County Area. Regarding sanctions under CAA section
179, as noted in EPA's November 9, 2018, NPRM, the Commonwealth
provided the required attainment SIP submittal for the Jefferson County
Area to address SO2 nonattainment planning requirements on
June 23, 2017. EPA subsequently determined the attainment SIP submittal
complete on October 10, 2017, and thus that Kentucky corrected the
deficiency that was the basis of EPA's March 18, 2016, finding for the
Area. Because this deficiency has been corrected, section 179 sanctions
are no longer applicable, and no section 179 sanctions clock was
actually running or past due at the time the Commenter submitted its
objections. A copy of EPA's completeness determination letter is
provided in the docket for this rulemaking.
    Comment 13: A Commenter asserts that the projected 2018 attainment
year inventory is set artificially high and suggests that the limits
should be set based on certain scrubber efficiency (i.e., 89 percent).
The Commenter also refers to the RACT/RACM portion of the November 9,
2018, NPRM and indicates a discrepancy related to the emissions for
post-level control. Specifically, the Commenter argues that EPA states
that the scrubber improvement is a removal rate of 98 percent, compared
to 90 percent before the upgrades, which would equate to a post-control
level of 6,000 tpy, not the projected 13,940 tpy.
    Response 13: EPA disagrees with the Commenter that the projected
emission inventory is artificially high. The projected 2018
SO2 emissions for Mill Creek are considered conservative
based on the source's expected levels or potential to emit beyond the
October 4, 2018, attainment date. The projected emission inventory is
an estimate of emissions from all SO2 emission sources
determined to have an impact on the affected nonattainment area for the
year in which the area is expected to attain the standard, consistent
with the attainment demonstration for the affected area. This inventory
should reflect projected emissions for the attainment year for all
SO2 sources in the nonattainment area, taking into account
emission changes that are expected after the base year. The projected
inventory is not an exact measurement for post-control actual emissions
and there is no one prescribed method for developing the inventory.
Mill Creek's 2011 base year emissions for all four units was 29,944 tpy
(see Table 3 in the November 9, 2018, NPRM). LMAPCD derived the 13,490
tpy projected post-construction potential (projected inventory) by
converting the 30-day 0.20 lb/MMBtu emission rate to tpy (by
multiplying the permitted rate in lb/MMBtu times the nominal heat
capacity for each unit and the total calendar year hours). Kentucky
also subtracted Mill Creek's 2011 base year emissions to show the
contemporaneous SO2 decreases for each unit at Mill Creek.
The 0.20 lb/MMBtu emission rate is based on the FGD SO2
scrubber upgrades installed at Mill Creek and demonstrates modeled
attainment of the 2010 standard. According to 40 CFR 51.ll0(a), a
control strategy must be selected that provides the degree of emission
reductions necessary for attainment and maintenance of the NAAQS. EPA
believes the projected inventory is an appropriate estimation of the
expected improvement in emissions within the Jefferson County
nonattainment area due to the adoption and implementation of upgraded
SO2 scrubber control measures at Mill Creek. Furthermore,
the Commenter's post-control calculation of 6,000 tpy is based on
applying a reduction factor to the 2011 actual emissions rather than
the uncontrolled potential to emit.
    EPA also disagrees with the Commenter's assertion that the November
9, 2018, NPRM suggests the SO2 removal efficiency at Mill
Creek only achieved 89 percent since 2014 emission levels (see footnote
No. 23 in the November 9, 2018, NPRM). The Commenter appears to confuse
actual and allowable emissions and the application of control
efficiencies and emission reductions regarding the change in emissions
for Mill Creek post control. EPA acknowledges that the reduction in
actual emissions since 2014 mathematically equates to an 89 percent
reduction in SO2 emissions but the Agency's purpose for
footnote #24 (See 83 FR 56002 at 56013) was to show the decrease in
actual emissions since 2014 and not to make a definitive determination
of the efficiency of the SO2 scrubbers since installation of
upgrades at Mill Creek. Additionally, EPA notes that the reduction in
actual

emissions discussed in the November 9, 2018, NPRM is considered a
snapshot of the level of actual emissions since the installation of
controls and is not considered a definitive indication of the
SO2 removal capability of the scrubber upgrades.
    EPA notes that since completion of the control installations at
Mill Creek in 2016, the facility's actual SO2 emissions have
decreased from 28,149 tons in 2014 to 3,040 tons in 2017. EPA believes
the control strategy implemented at Mill Creek provides for the
attainment of the standard, which is supported by the modeled
attainment demonstration, and the steady decline in actual annual
SO2 emissions since controls were installed in 2016. The
2015-2017 design value is the latest three year average available and
Watson Lane monitor has a reading of 31 ppb, well below the 75 ppb
SO2 standard.

III. Incorporation by Reference

    In this rule, EPA is finalizing rule regulatory text that includes
incorporation by reference. In accordance with requirements of 1 CFR
51.5, EPA is finalizing the incorporation by reference into the
Jefferson County portion of the Kentucky SIP, a SO2 emission
limit and specified compliance conditions established in title V permit
145-97-TV(R3) for each coal-fired emissions unit at the LG&E Mill Creek
Generating station in Jefferson County nonattainment area.
Specifically, EPA is incorporating into the Jefferson County portion of
the Kentucky SIP Plant-wide Specific conditions S1-Standards, S2-
Monitoring and Record Keeping and S3-Reporting in title V permit 145-
97-TV(R3) for EGU U1, U2, U3 and U4. These conditions include a 0.20
lb/MMBtu 30-day SO2 emission limit for each EGU, U1, U2, U3
and U4, and associated operating and compliance conditions (monitoring,
recordkeeping and reporting) for these units and are the basis for the
attainment demonstration. EPA has made, and will continue to make,
these materials generally available through www.regulations.gov and at
EPA Region 4 office (please contact the person identified in the FOR
FURTHER INFORMATION CONTACT section of this preamble for more
information). Therefore, these materials have been approved by EPA for
inclusion in the SIP, have been incorporated by reference by EPA into
that plan, are fully federally-enforceable under sections 110 and 113
of the CAA as of the effective date of the final rulemaking of EPA's
approval, and will be incorporated by reference in the next update to
the SIP compilation.\16\
---------------------------------------------------------------------------

    \16\ See 62 FR 27968 (May 22, 1997).
---------------------------------------------------------------------------

IV. Final Action

    EPA is approving Kentucky's SO2 nonattainment SIP
submissions, which the Commonwealth submitted to EPA through a letter
dated June 23, 2017, for attaining the 2010 1-hour SO2 NAAQS
for the Jefferson County nonattainment area and for meeting other
nonattainment area planning requirements. EPA has determined that
Kentucky's nonattainment SIPs meet the applicable requirements of
sections 110, 172, 191 and 192 of the CAA and nonattainment regulatory
requirements at 40 CFR part 51. Kentucky's June 23, 2017, SIP revisions
include an attainment demonstration for the Jefferson County
nonattainment area and other nonattainment requirements for RFP, RACT/
RACM, NNSR, base-year and projection-year emission inventories,
enforceable emission limits and control measures and compliance
parameters, and contingency measures. Additionally, EPA is approving
into the Jefferson County portion of the Kentucky SIP, Mill Creek's
enforceable SO2 emission limits and compliance parameters
(monitoring, recordkeeping and reporting) established at Plant-wide
Specific condition S1-Standards, S2-Monitoring and Record Keeping and
S3-Reporting established in title V permit 145-97-TV(R3).

V. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP
submission that complies with the provisions of the Act and applicable
Federal regulations. See 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in
reviewing SIP submissions, EPA's role is to approve state choices,
provided that they meet the criteria of the CAA. This action merely
approves state law as meeting Federal requirements and does not impose
additional requirements beyond those imposed by state law. For that
reason, this action:
     Is not a significant regulatory action subject to review
by the Office of Management and Budget under Executive Orders 12866 (58
FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
     Is not an Executive Order 13771 (82 FR 9339, February 2,
2017) regulatory action because SIP approvals are exempted under
Executive Order 12866;
     Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact
on a substantial number of small entities under the Regulatory
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have Federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based
on health or safety risks subject to Executive Order 13045 (62 FR
19885, April 23, 1997);
     Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the CAA; and
     Does not provide EPA with the discretionary authority to
address, as appropriate, disproportionate human health or environmental
effects, using practicable and legally permissible methods, under
Executive Order 12898 (59 FR 7629, February 16, 1994).
    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 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.
    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the
Small Business Regulatory Enforcement Fairness Act of 1996, generally
provides that before a rule may take effect, the agency promulgating
the rule must submit a rule report, which includes a copy of the rule,
to each House of the Congress and to the Comptroller General of the
United States. EPA will submit a report containing this action and
other required information to the U.S. Senate, the U.S. House of
Representatives, and the Comptroller General of the United States prior
to publication of the rule in the Federal Register. A major rule cannot
take effect until 60 days after it is published in the Federal
Register. This action is not a ``major rule'' as defined by 5 U.S.C.
804(2).
    Under section 307(b)(1) of the CAA, petitions for judicial review
of this

action must be filed in the United States Court of Appeals for the
appropriate circuit by August 27, 2019. Filing a petition for
reconsideration by the Administrator of this final rule does not affect
the finality of this action for the purposes of judicial review nor
does it extend the time within which a petition for judicial review may
be filed, and shall not postpone the effectiveness of such rule or
action. This action may not be challenged later in proceedings to
enforce its requirements. See CAA section 307(b)(2).

List of Subjects in 40 CFR Part 52

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

    Dated: May 28, 2019.
Mary S. Walker,
Regional Administrator, Region 4.

    40 CFR part 52 is amended as follows:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

0
1. The authority citation for part 52 continues to read as follows:

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

Subpart S--Kentucky

0
2. Section 52.920 is amended by:
0
a. Adding, in paragraph (d), the entry ``Louisville Gas and Electric
Mill Creek Electric Generating Station'' at the end of the table; and
0
b. Adding, in paragraph (e), the entries ``2010 1-hour SO2
Attainment Demonstration for the Jefferson County Area,'' ``2010 1-hour
SO2 Jefferson County Nonattainment Plan for 172(c)(3) 2011
Base-Year Emissions Inventory'', and ``2010 1-hour SO2
Jefferson County Nonattainment Plan for 172(c)(5) New Source Review
Requirements'' at the end of the table.
    The additions read as follows:

Sec.  52.920   Identification of plan.

* * * * *
    (d) * * *

                                                   EPA-Approved Kentucky Source-Specific Requirements
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                State
          Name of source                  Permit No.       effective date             EPA approval date                         Explanations
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                                                      * * * * * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------
Louisville Gas and Electric Mill    145-97-TV(R3)........       6/23/2017  6/28/2019 [Insert citation of           Plant-wide Specific condition S1-
 Creek Electric Generating Station.                                         publication].                           Standards, S2-Monitoring and Record
                                                                                Keeping and S3-Reporting in title V
                                                                                permit 145-97-TV(R3) for EGU U1, U2,
                                                                                U3 and U4.
--------------------------------------------------------------------------------------------------------------------------------------------------------

* * * * *
    (e) * * *

                                                     EPA-Approved Kentucky Non-Regulatory Provisions
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                State
    Name of non-regulatory SIP      Applicable geographic  submittal date/            EPA approval date                         Explanations
             provision              or nonattainment area  effective date
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                                                      * * * * * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------
2010 1-hour SO2 Attainment          Jefferson County.....       6/23/2017  6/28/2019 [Insert citation of
 Demonstration for the Jefferson                                            publication].
 County Area.
2010 1-hour SO2 Jefferson County    Jefferson County.....       6/23/2017  6/28/2019 [Insert citation of
 Nonattainment Plan for 172(c)(3)                                           publication].
 2011 Base-Year Emissions
 Inventory.
2010 1-hour SO2 Jefferson County    Jefferson County.....       6/23/2017  6/28/2019 [Insert citation of
 Nonattainment Plan for 172(c)(5)                                           publication].
 New Source Review Requirements.
--------------------------------------------------------------------------------------------------------------------------------------------------------

[FR Doc. 2019-13736 Filed 6-27-19; 8:45 am]
 BILLING CODE 6560-50-P