[Federal Register Volume 84, Number 125 (Friday, June 28, 2019)]
[Rules and Regulations]
[Pages 30920-30933]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-13736]


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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.

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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 (404) 562-8726 or via electronic mail at 
[email protected].

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

[[Page 30921]]

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\
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    \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.
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    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

[[Page 30922]]

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

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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));

[[Page 30924]]

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.

[[Page 30925]]

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

[[Page 30926]]

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-

[[Page 30927]]

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

[[Page 30928]]

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

[[Page 30929]]

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

[[Page 30930]]

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

[[Page 30931]]

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

[[Page 30932]]

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

[[Page 30933]]

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