[Federal Register Volume 85, Number 202 (Monday, October 19, 2020)]
[Rules and Regulations]
[Pages 66240-66257]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-23037]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R03-OAR-2017-0615; FRL-10015-78-Region 3]


Air Plan Approval; Pennsylvania; Attainment Plan for the Indiana, 
Pennsylvania Nonattainment Area for the 2010 Sulfur Dioxide Primary 
National Ambient Air Quality Standard

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is approving a state 
implementation plan (SIP) revision submitted by the Commonwealth of 
Pennsylvania. The revision is an attainment plan for the 2010 sulfur 
dioxide (SO2) primary national ambient air quality standard 
(NAAQS) in the Indiana County, Pennsylvania SO2 
nonattainment area (hereafter referred to as the ``Indiana Area'' or 
``Area''). The Indiana Area is comprised of Indiana County and a 
portion of Armstrong County (Plumcreek Township, South Bend Township, 
and Elderton Borough) in Pennsylvania. The attainment plan includes the 
base year emissions inventory, an analysis of the reasonably available 
control technology (RACT) and reasonably available control measure 
(RACM) requirements, a reasonable further progress (RFP) plan, a 
modeling demonstration showing SO2 attainment, enforceable 
emission limitations and control measures, contingency measures for the 
Indiana Area, and Pennsylvania's new source review (NSR) permitting 
program. As part of approving the attainment plan, EPA is approving 
into the Pennsylvania SIP new SO2 emission limits and 
associated compliance parameters for Keystone Plant (hereafter referred 
to as ``Keystone''), and existing SO2 emission limits and 
associated compliance parameters for Conemaugh Plant, Homer City 
Generation, and Seward Generation Station (hereafter referred to as 
``Conemaugh,'' ``Homer City,'' and ``Seward''). EPA is approving these 
revisions that demonstrate attainment of the SO2 NAAQS in 
the Indiana Area in accordance with the requirements of the Clean Air 
Act (CAA).

DATES: This final rule is effective on November 18, 2020.

ADDRESSES: EPA has established a docket for this action under Docket ID 
Number EPA-R03-OAR-2017-0615. All documents in the docket are listed on 
the https://www.regulations.gov website. Although listed in the index, 
some information is not publicly available, e.g., confidential business 
information (CBI) 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 through 
https://www.regulations.gov, or please contact the person identified in 
the FOR FURTHER INFORMATION CONTACT section for additional availability 
of information.

FOR FURTHER INFORMATION CONTACT: Megan Goold, Planning & Implementation 
Branch (3AD30), Air & Radiation Division, U.S. Environmental Protection 
Agency, Region III, 1650 Arch Street, Philadelphia, Pennsylvania 19103. 
The telephone number is (215) 814-2027. Ms. Goold can also be reached 
via electronic mail at [email protected].

SUPPLEMENTARY INFORMATION:

I. Background

    On June 2, 2010, the EPA Administrator signed a final rule 
establishing a new SO2 primary NAAQS as a 1-hour standard of 
75 parts per billion (ppb), based on a 3-year average of the annual 
99th percentile of daily maximum 1-hour average concentrations. 75 FR 
35520 (June 22, 2010), codified at 40 CFR 50.17. This action also 
provided for revocation of the existing 1971 primary annual and 24-hour 
standards, subject to certain conditions.\1\ Following promulgation of 
a new or revised NAAQS, EPA is required by the CAA to designate areas 
throughout the United States as attaining or not attaining the NAAQS; 
this designation process is described in section 107(d)(1)-(2) of the 
CAA. On August 5, 2013, EPA promulgated initial air quality 
designations for 29 areas for the 2010 SO2 NAAQS (78 FR 
47191), which became effective on October 4, 2013, based on violating 
air quality monitoring data for calendar years 2009-2011, where there 
was sufficient data to support a nonattainment designation.\2\ The 
Indiana Area was designated as nonattainment in this initial (first) 
round of designations. 78 FR 47191 (August 5, 2013).
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    \1\ EPA's June 22, 2010, final action provided for revocation of 
the 1971 primary 24-hour standard of 140 ppb and the annual standard 
of 30 ppb because they were determined not to add additional public 
health protection given a 1-hour standard at 75 ppb. 75 FR 35520. 
However, the secondary 3-hour SO2 standard was retained. 
Currently, the 24-hour and annual standards are only revoked for 
certain of those areas the EPA has already designated for the 2010 
1-hour SO2 NAAQS. 40 CFR 50.4(e).
    \2\ EPA is continuing its designation efforts for the 2010 
SO2 NAAQS. Pursuant to a court-order entered on March 2, 
2015, by the U.S. District Court for the Northern District of 
California, EPA must complete the remaining designations for the 
rest of the country on a schedule that contains three specific 
deadlines. Sierra Club, et al. v. Environmental Protection Agency, 
13-cv-03953-SI (N.D. Cal. 2015).
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    The Indiana Area consists of all of Indiana County, Pennsylvania 
and also Plumcreek Township, South Bend Township, and Elderton Borough 
in Armstrong County, Pennsylvania. The boundaries of the nonattainment 
area were defined in order to encompass the four primary SO2 
emitting sources of Keystone, Conemaugh, Homer City, and Seward. The 
October 4, 2013 effective date of the final designation triggered a 
requirement for Pennsylvania to submit, by April 4, 2015, an attainment 
plan SIP revision describing how the Area would attain the 2010 
SO2 NAAQS as expeditiously as practicable, but no later than 
October 4, 2018, in accordance with CAA sections 172(c) and 191-192.
    For a number of areas, including the Indiana Area, EPA published a 
document on March 18, 2016, finding that Pennsylvania and other states 
had failed to submit the required SO2 attainment plan by the 
April 4, 2015 deadline. 81 FR 14736. This finding triggered the CAA 
section 179(a) deadline for the potential imposition of new source 
review and highway funding sanctions. Pennsylvania submitted the 
attainment plan on October 11, 2017. EPA then sent a letter to 
Pennsylvania, dated October 13, 2017, finding that the attainment plan

[[Page 66241]]

submittal was complete, and therefore the sanctions under section 
179(a) would not be imposed as a consequence of Pennsylvania having 
missed the April 4, 2015 deadline. Additionally, EPA's March 18, 2016 
finding triggered a requirement under CAA section 110(c) that EPA 
promulgate a Federal implementation plan (FIP) within two years of the 
effective date of the finding unless, by that time, the state has made 
the necessary complete submittal and EPA has approved the submittal as 
meeting applicable requirements. This FIP obligation will no longer 
apply as a result of this action to finalize this SIP approval.
    Attainment plans for SO2 must meet the applicable 
requirements of the CAA, and specifically, CAA sections 110, 172, 191, 
and 192. The required components of any attainment plan submittal are 
listed in section 172(c) of Title I, part D of the CAA, and additional 
requirements specific to SO2 attainment plans are found in 
CAA sections 191 and 192 and in EPA's implementing regulations at 40 
CFR part 51. On April 23, 2014, EPA also issued guidance (hereafter 
``2014 SO2 Nonattainment Guidance'') recommending how state 
submissions could address the statutory requirements for SO2 
attainment plans.\3\ The 2014 SO2 Nonattainment Guidance 
describes the statutory requirements for an attainment plan, which 
include: (1) A comprehensive, accurate, current inventory of actual 
emissions from all sources of SO2 within the nonattainment 
area (172(c)(3)); (2) an attainment demonstration that includes a 
modeling analysis showing that the enforceable emissions limitations 
and other control measures taken by the state will provide for 
expeditious attainment of the NAAQS (172(c)); (3) demonstration of RFP 
(172(c)(2)); (4) implementation of RACM, including RACT (172(c)(1)); 
(5) Nonattainment NSR requirements (172(c)(5)); and (6) adequate 
contingency measures for the affected area (172(c)(9)).
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    \3\ ``Guidance for 1-Hour SO2 Nonattainment Area SIP 
Submissions'' (April 23, 2014), available at https://www.epa.gov/sites/production/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf.
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II. Summary of SIP Revision and EPA Analysis

    In accordance with section 172(c) of the CAA, the Commonwealth of 
Pennsylvania's October 2017 attainment plan for the Indiana Area 
includes: (1) An emissions inventory for SO2 for the plan's 
base year (2011); and (2) an attainment demonstration. The plan's 
attainment demonstration includes the following: (1) Analyses that 
locate, identify, and quantify sources of emissions contributing to 
violations of the 2010 SO2 NAAQS; (2) a determination that 
the control strategy for the primary SO2 sources within the 
nonattainment areas constitutes RACM/RACT; (3) a dispersion modeling 
analysis of an emissions control strategy for the primary 
SO2 sources (Keystone, Conemaugh, Homer City, and Seward), 
showing attainment of the SO2 NAAQS by the October 4, 2018 
attainment date; (4) requirements for RFP toward attaining the 
SO2 NAAQS in the Area; (5) contingency measures; (6) the 
assertion that Pennsylvania's existing SIP-approved NSR program meets 
the applicable requirements for SO2; and (7) the request 
that emission limitations and compliance parameters for Keystone, 
Conemaugh, Homer City, and Seward be incorporated into the SIP.
    On July 13, 2018 (83 FR 32606), EPA published a notice of proposed 
rulemaking (NPRM) in which EPA proposed approval of Pennsylvania's 
Indiana, PA SO2 attainment plan and SO2 emission 
limits and associated compliance parameters for the Keystone, Homer 
City, Conemaugh and Seward sources. During the public comment period, 
the Sierra Club (in conjunction with the National Parks Conservation 
Association, PennFuture, Earthjustice, and Clean Air Council) submitted 
a modeling analysis which purported to show that the emission limits in 
the attainment plan did not assure attainment because one modeled 
receptor within the nonattainment area was above the SO2 
NAAQS. Sierra Club's modeling also purported to show exceedances of the 
SO2 NAAQS outside of the nonattainment area.
    In response to this comment, on February 5, 2020, the Pennsylvania 
Department of Environmental Protection (PADEP) submitted supplemental 
information in support of the attainment plan. The February 5, 2020 
submittal includes: (1) A supplemental air dispersion modeling report; 
(2) supplemental air dispersion modeling data; (3) a supplemental air 
dispersion modeling protocol; (4) a meteorological monitoring plan; (5) 
meteorological monitoring data; (6) meteorological monitoring quality 
assurance, quality control, and audit reports; (7) Clean Air Markets 
Division (CAMD) emissions data for 2010-2018; and (8) Continuous 
Emissions Monitoring (CEM) data for 2010-2019 (3rd Quarter). The 
supplemental air dispersion modeling used a more refined model receptor 
grid than the original submittal, meteorological data collected near 
the controlling modeled source (Seward) and more recent (2016-18) 
background concentrations from the South Fayette SO2 monitor 
(the monitor used to determine background concentrations in the 
original modeling analysis). All of these updates have been fully 
described in the supplemental modeling report from the February 5, 2020 
submittal and in four separate Technical Support Documents (TSDs) 
written by EPA for this action: (1) The TSD for the Randomly Reassigned 
Emission (RRE) Modeling Analysis in the Supplemental Information to 
Address a Comment Received by the EPA on Pennsylvania's 1-hour Sulfur 
Dioxide Attainment Demonstration for the Indiana, Pennsylvania 
Nonattainment Area submitted on February 5, 2020 (hereafter referred to 
as the RRE Modeling TSD); (2) the TSD for the Modeling Portions of the 
Document Entitled ``Supplemental Information to Address a Comment 
Received by the EPA on Pennsylvania's 1-hour SO2 Attainment 
Demonstration for the Indiana, Pennsylvania Nonattainment Area'' 
(hereafter referred to as the Supplemental Modeling TSD); (3) the TSD 
Addressing Modeled Concentration Values for the Keystone Generating 
Station Included in the Indiana, PA 1-Hour SO2 Nonattainment 
Area (hereafter referred to as the Keystone Modeling TSD); and (4) the 
TSD For the Part 75 Source Emissions Contained in the Supplemental 
Information to Address a Comment Received by the EPA on Pennsylvania's 
1-hour Sulfur Dioxide Attainment Demonstration for the Indiana, 
Pennsylvania Nonattainment Area 2020 submitted on February 5, 2020 
(hereafter referred to as the Part 75 Emissions TSD).
    In order to allow for public comment on this supplemental 
information and modeling, on March 9, 2020 (85 FR 13602), EPA published 
a notice of data availability (NODA) for the February 5, 2020 
submittal. Sierra Club submitted new comments raising issues with the 
supplemental modeling, which are fully discussed later in this 
preamble.
    Other specific requirements of the Indiana Area attainment plan and 
the rationale for EPA's proposed action are explained in the NPRM and 
will not be restated here. This final action incorporates the rationale 
provided in the NPRM and the NODA, except to the extent necessary to 
reflect any changes in the rationale in response to the public 
comments.

III. Response to Comments

    EPA received multiple comments on the NPRM and adverse comments 
from two commenters on the NODA. To review the full set of comments 
received, refer to the Docket for the

[[Page 66242]]

rulemaking, as identified in the ADDRESSES section of this document. A 
summary of the comments and EPA's responses are provided below.
    Comment 1. The commenter states that the alternative limits for 
Homer City are greater than the critical emission value (CEV),\4\ with 
no explanation given. The CEV for the three units at Homer City are 
6,360 pounds per hour (lb/hr) for all three combined. There are 
multiple emissions limits in the proposal for Homer City that are 
higher than the CEV. There is a start-up limit of 9,000 lb/hr, and an 
alternative limit of 7,300 lb/hr for all units in a transition phase. 
These limits are higher than the CEV and the commenter believes they 
would thus lead to NAAQS violations. The commenter argues that the 
modeling shows that these additional limits would violate the NAAQS.
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    \4\ The CEV is the continuous 1-hour emission rate which 
modeling shows is expected to result in the 3-year average of annual 
99th percentile daily maximum 1-hour average concentrations being at 
or below 75 ppb, which in a typical year means that fewer than four 
days have maximum hourly ambient SO2 concentrations 
exceeding 75 ppb.
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    Response 1. EPA agrees with the commenter that there are multiple 
SO2 emission limits for Homer City. However, EPA disagrees 
that the modeling shows that the alternative limits would result in 
SO2 emissions concentrations that violate the NAAQS. The 
modeling does not include the alternative limits since they are 
intermittent in nature, and, as explained in more detail later in this 
preamble, Pennsylvania correctly excluded them from the modeling 
demonstration.
    The Homer City emission limits for start-up, shut down and the 
Novel Integrated Desulfurization (NID) system transitions are limited 
to 500 hours combined in any 12-month rolling period. As stated in 
EPA's March 2011 Memorandum on Additional Clarification Regarding 
Application of Appendix W Modeling Guidance for the 1-hour 
NO2 National Ambient Air Quality Standard (hereafter 
referred to as the ``March 2011 Clarification Memo'') \5\ and as 
specifically referenced in EPA's August 2010 Memorandum on the 
Applicability of Appendix W Modeling Guidance for the 1-hour 
SO2 National Ambient Air Quality Standard,\6\ EPA believes 
the most appropriate data to use for compliance demonstrations for the 
1-hour SO2 NAAQS are those based on emissions scenarios that 
are continuous enough or frequent enough to contribute significantly to 
the annual distribution of daily maximum 1-hour concentrations. EPA's 
modeling recommendations involve a degree of conservatism in the 
modeling assumptions for demonstrating compliance with the NAAQS by 
recommending the use of maximum allowable emissions. The intermittent 
nature of the actual emissions associated with these transitions, when 
coupled with the probabilistic form of the SO2 standard, 
could result in modeled impacts being significantly higher than actual 
impacts would realistically be expected to be if the maximum allowable 
emissions were modeled continuously year round.
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    \5\ Memorandum, Additional Clarification Regarding Application 
of Appendix W Modeling Guidance for the 1-hour NO2 
National Ambient Air Quality Standard. March 2011. https://www.epa.gov/sites/production/files/2015-07/documents/appwno2_2.pdf.
    \6\ Memorandum, Applicability of Appendix W Modeling Guidance 
for the 1-hour SO2 National Ambient Air Quality Standard. 
August 2010. https://www3.epa.gov/ttn/scram/guidance/clarification/ClarificationMemo_AppendixW_Hourly-SO2-NAAQS_FINAL_08-23-2010.pdf.
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    EPA is concerned that if emissions occurring during intermittent 
operations are assumed to be occurring continuously, this would impose 
an additional level of stringency beyond that intended by the level of 
the standard itself. EPA, therefore, recommended that compliance 
demonstrations for the 1-hour SO2 NAAQS be based on emission 
scenarios that can logically be assumed to be relatively continuous or 
which occur frequently enough to contribute significantly to the annual 
distribution of daily maximum 1-hour concentrations. Existing modeling 
guidelines provide sufficient discretion for states to exclude certain 
types of intermittent emissions from compliance demonstrations for the 
1-hour SO2 standard under these circumstances.
    Pennsylvania's exclusion of the alternative limits for Homer City 
(which are limited to a combined 500 hours in a 12-month rolling 
period) in the modeling demonstration follows EPA's guidance regarding 
intermittent emission scenarios. The modeling demonstration provided by 
Pennsylvania provides support that the one-hour emission limit that was 
adopted by Homer City provides for attainment of the NAAQS.
    Comment 2. The commenter asks EPA to explain why there are numerous 
values in micrograms per cubic meter ([mu]g/m\3\) that have been 
translated to 75 ppb. The commenter notes in this action EPA is using 1 
ppb = approximately 2.619 g/m\3\, \7\ and in other EPA documents, the 
conversion factor of 2.62 was used. The commenter claims that this use 
of multiple conversion factors is a hindrance in determining if an area 
has met the standard.
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    \7\ The commenter erroneously claims that EPA is using 1 ppb = 
2.619 g/m\3\. EPA believes the commenter meant to write 2.619 [mu]g/
m\3\.
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    Response 2. The commenter is correct in stating that historically 
EPA has accepted a range of values for the [mu]g/m\3\ equivalent to 75 
ppb. In the Round 3 intended designations (82 FR 41903) published 
September 5, 2017, EPA recognized the need noted by the commenter to 
identify and apply a consistent value expressed in [mu]g/m\3\ that EPA 
considers equivalent to 75 ppb. At that time, EPA endorsed a value of 
196.4 [mu]g/m\3\ (based on calculations using all available significant 
figures). To avoid confusion, EPA is expecting attainment 
demonstrations to show achievement with concentrations at or below 
precisely 196.4 [mu]g/m\3\.\8\
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    \8\ While some Round 3 designation TSDs explained that this 
value was ``equivalent . . . using a 2.619 [mu]g/m\3\ conversion 
factor'' (more precisely, using a conversion factor of approximately 
2.6187), in fact EPA here was determining the concentration value in 
[mu]g/m\3\ that is to be considered equivalent to 75 ppb, rather 
than the precise value of the conversion factor.
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    Comment 3. The commenter asserts that the longer term limits 
applicable to Seward and Keystone (1) do not follow EPA's 2014 
SO2 Nonattainment Guidance; (2) are not comparably stringent 
to the one-hour CEV; and (3) are not based on maximum allowable 
emissions. The commenter argues that approval of these longer term 
limits would be arbitrary and capricious. The commenter provides the 
following reasons as to why the emission limits have not followed EPA's 
2014 SO2 Nonattainment Guidance: (1) EPA is proposing to 
approve longer term emission limits that are higher than the comparably 
stringent emission limits that are calculated via Appendix C 
methodology; and (2) EPA is proposing to approve longer term emission 
limits that were calculated using Appendix B methodology, which was 
provided in the 2014 SO2 Nonattainment Guidance to justify 
the Appendix C methodology. The commenter therefore argues that using 
Appendix B methodology to calculate emission limits is contrary to the 
purposes of that Appendix as described in the 2014 SO2 
Nonattainment Guidance. The commenter continues that EPA is now 
proposing to approve emission limits that are based on a facility's 
actual historic emissions, instead of maximum allowable emissions. This 
is unprecedented and does not meet the requirements of 40 CFR 51.112 
and 40 CFR part 51 appendix W, which

[[Page 66243]]

mandates the use of allowable emissions.
    Response 3. EPA agrees that Pennsylvania did not employ EPA's 
SO2 Nonattainment Guidance Appendix C methodology in 
developing the longer term emission limits for the Seward and Keystone 
facilities. EPA also agrees that the longer term emission limits for 
Seward and Keystone are higher than the emission limits would be if the 
state used the Appendix C methodology. However, that does not mean that 
the longer term emission limits are not protective of the NAAQS, nor 
does it mean that the emission limits are arbitrary and capricious.
    EPA's 2014 SO2 Nonattainment guidance explains how state 
air agencies might establish emissions limitations for sources such as 
Seward and Keystone that have averaging periods that are longer than 
one hour in duration. Appendix W to 40 CFR part 51--Guideline on Air 
Quality Models, requires modeling conducted in support of SIP limits to 
be representative of maximum allowable emission rates. In most cases, 
EPA requires using the American Meteorological Society (AMS)/EPA 
Regulatory Model or AERMOD near-field dispersion modeling system. While 
uses of AERMOD for attainment planning purposes generally use a 
constant emission rate for each source throughout the duration of a 
simulation, AERMOD can also be run with time-varying emissions, varying 
for example by month or by hour.
    In formulating its 2014 guidance, EPA recognized the challenges of 
representing allowable emissions for a limit that reflects a longer-
term average. EPA recommended an approach which did not require any 
development of variable emission profiles to represent allowable 
emissions. Instead, EPA's recommended approach relies on traditional 
modeling of a constant emission rate, for purposes of determining the 
1-hour average emission rate that if adopted as a 1-hour limit would 
provide for attainment. In normal circumstances, a longer-term average 
limit at a given level is inherently less stringent than a 1-hour limit 
at the same level. Therefore, EPA's recommended approach then uses 
appropriate data, generally taken from the historical record for the 
pertinent source, to obtain a quantitative estimate of the reduction of 
a one-hour limit's stringency arising from use of the longer-term 
average. The ratio derived in this approach (found by comparing the 
99th percentile among the longer-term average values in the data set 
against the 99th percentile among the 1-hour values in the data set) 
serves as an adjustment factor. In EPA's recommended approach, this 
adjustment factor is applied to the modeled (1-hour) attaining emission 
rate, and the resulting, downward adjusted longer-term average emission 
limit is presumed to have comparable stringency to a 1-hour limit at 
the modeled emission rate. This approach is described at length in the 
body of EPA's 2014 guidance (see pages 22 to 39) and delineated as a 
step-by-step procedure in Appendix C of the guidance. Appendix B of the 
guidance presents analyses that support EPA's view that longer-term 
limits that are comparably stringent to their 1-hour counterparts may 
be expected to yield comparable air quality.\9\
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    \9\ See also work done to supplement the work described in 
appendix B. This supplemental work, done to address a comment on 
rulemaking for the Southwest Indiana SO2 nonattainment 
area objecting that the appendix B analysis is not comparable to an 
assessment of air quality with a 1-hour emission limit, provides 
further evidence that longer term limits that are appropriately 
determined can be expected to achieve comparable air quality as 
comparably stringent 1-hour limits. Documentation of this 
supplemental work is available in the docket for the Southwest 
Indiana rulemaking, at https://www.regulations.gov/document?D=EPA-R05-OAR-2015-0700-0023, as discussed in the associated rulemaking at 
85 FR 49969-49971 (August 17, 2020).
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    EPA has approved several SIPs relying on longer term average limits 
derived according to these methods. See, for example, 83 FR 4591 
(February 1, 2018) (approval of Illinois SO2 SIP); 83 FR 
25922 (June 5, 2018) (approval of New Hampshire SO2 SIP); 84 
FR 8813 (March 12, 2019) (approval of Arizona SO2 SIP); 84 
FR 30920 (June 28, 2019) (approval of Kentucky SO2 SIP); 84 
FR 51988 (October 1, 2019) (approval of Pennsylvania SO2 SIP 
for the Beaver County area); 85 FR 22593 (April 23, 2020 (approval of 
Pennsylvania SO2 SIP for the Allegheny County area), and 85 
FR 49967 (August 17, 2020) (approval of Indiana SO2 SIP). As 
part of its 2014 SO2 Nonattainment Guidance, EPA added that 
states are not precluded from using other approaches to determine 
appropriate longer-term average limits (see page 26).
    For the Indiana County area, Pennsylvania did not use the methods 
discussed in the 2014 guidance for deriving its limits, but instead 
developed a different approach. Therefore, the validity of EPA's 
recommended approach in the 2014 guidance and the validity of the 
resulting longer-term average limits when using that approach, which 
are issues in other rulemakings such as those cited previously, are not 
at issue in this rule. Instead, at issue in this rule is whether the 
particular approach applied by Pennsylvania suffices to demonstrate 
that its adopted and submitted allowable emissions limits provide for 
attainment as required in CAA sections 110, 172, and 192.
    Pennsylvania used conceptually similar approaches for assessing the 
adequacy of limits for Keystone and for Seward, though selected 
features of these analyses differ. Therefore, the following first 
discusses the analysis for Keystone and then discusses the analysis for 
Seward.
    Pennsylvania's different approach for Keystone (as for Seward) 
began at the same starting point as EPA's 2014 guidance's recommended 
approach. As recommended by EPA, Pennsylvania determined the 1-hour CEV 
(9,711 lb/hr) for Keystone using AERMOD. Then, Pennsylvania provided 
modeling addressing its proposed limit for Keystone using an approach 
which relies on a large number of AERMOD simulations and an underlying 
data set that represents recent hourly emissions variability of the 
source (referred to as RRE Modeling). This approach relies on the 
expectation that future variability of Keystone while meeting the limit 
is likely to be similar or less than historic variability given that no 
major changes are planned for the source (i.e., no new control 
equipment, fuel changes, etc.), except for the imposition of a new 24-
hour emission limit based on this attainment SIP. EPA analyzed 10 past 
years of Keystone's emissions and operational data, and the regional 
transmission organization Pennsylvania-New Jersey-Maryland (PJM) 
forecasts for future electric demand, which support these suppositions 
(see the Part 75 Emissions TSD in the docket for this rule).
    The hourly modeled emission values were based on actual emissions 
and determined through a binning approach further described in the RRE 
Modeling TSD. Keystone has had highly variable emissions in the past. 
Hourly emissions are less variable in recent years. The source's 
historic emissions profile was such that the actual emission rate for 
15% of the hours per year were above the CEV of 9,711 lb/hr, and those 
hours fell within 15 days in each month. Because of this pattern, where 
hourly values above the CEV were clustered together on a limited number 
of days rather than individually dispersed throughout the year, 
Pennsylvania created a ``rule'' in the modeling, whereby the hours over 
the CEV were modeled in clusters which Pennsylvania calls ``high 
emission event days.'' The total amount of SO2 emissions 
each day, however, are constrained by a limit

[[Page 66244]]

which restricts the total pounds of SO2 emissions, on a 24-
hour block average basis, to be at or below 9,600 lb/hr. The hours for 
which the emissions were modeled above the CEV were not randomly 
dispersed individually throughout the year because the plant did not 
and likely will not operate that way in order to meet the limit. Thus, 
these high emission events were modeled in a way that is representative 
of the variability in the historic emissions data and in compliance 
with the allowable emissions limit.
    The ``rule'' constrained the high emission events days to not 
exceed 9,604 lb/hr on a 24-hour block average; however, not every day 
was modeled with hourly emission rates resulting in a 24-hour block 
average at or near 9,604 lbs/hr. As previously described, the 
historical emissions data demonstrate that not every day is a high 
emission event day based on the historic variability of the source. 
Pennsylvania modeled about 50% of the days in a month where hourly 
SO2 emissions were always below the CEV value and about 50% 
of the days in a month as high emission event days where there were at 
least three hours over the CEV during that 24 hours. The high emission 
events days included nine days (30% of the days) in a month where the 
24-hour averages were near 9,600 lb/hr. The remaining six high emission 
event days per month experienced three hours of emissions above the 
CEV, yet emissions during the remaining hours of the day resulted in 
the 24-hour daily average falling at 6,333 lb/hr for five of the six 
days and at 8,964 lb/hr for one of the six days. However, the other 
hours in these days were assigned values at or below the CEV, 
reflecting the predominance of values below the CEV in the modeled 
emissions distribution (which in turn reflected the predominance of 
values below the CEV in the historical record), resulting in daily 
average emission rates for these days below 9,600 lb/hr. The remaining 
days (not categorized as high emission events days) had 24-hour daily 
average emissions between 5,000 lb/hr and 6,200 lb/hr.
    Pennsylvania developed 100 different annual emission profiles using 
the historic data of high emission event days, and randomly assigning 
the other hourly emissions such that the 24-hour limit of 9,600 lbs/hr 
is modeled 30% of the days across each month, which is representative 
of the variation within the historical emissions. These emission files 
provide a large array of temporally varying hourly emissions which take 
into account the ``rule'' where hourly emissions above the CEV are 
clustered together into high emission event days, representative of the 
variability in the historic emissions data and are reflective of 
historic plant operations. Each of the 100 emissions scenarios (each 
reflecting compliance with the emissions limit) were modeled with five 
years of meteorological data using AERMOD. For each of the 100 5-year 
AERMOD simulations for Keystone, the 5-year average of the 99th 
percentile of the daily maximum 1-hour SO2 modeled 
concentrations were below the NAAQS.\10\
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    \10\ See EPA's March 1, 2011 clarification memo Additional 
Clarification Regarding Application of Appendix W Modeling Guidance 
for the 1-hour NO2 National Ambient Air Quality Standard.
---------------------------------------------------------------------------

    EPA concludes that this modeling provided enough permutations of 
emissions and meteorology that we can be reasonably confident that the 
longer-term limit is protective of the NAAQS. This conclusion is based 
upon the large number of emission distribution profiles (100), the 
frequency and distribution of high emission event days, the 9,600 lb/hr 
24-hour emission limit modeled 30% of the days per month, emissions 
inputs reflective of the variability in historic plant operations, and 
meteorological data (five years of National Weather Service data).
    Pennsylvania used the same general modeling approach to support the 
30-day rolling average SO2 emission limit for Seward. First, 
Pennsylvania determined Seward's CEV of 4,500 lb/hr using AERMOD.\11\ 
Then, using 2016-2018 emissions from Seward, Pennsylvania developed a 
binned emissions dataset to be used in formulating the inventories 
modeled in 100 AERMOD simulations. Pennsylvania used a total of 13 
bins, including five bins ranging from an upper level of 2,000 lbs/hour 
to an upper level of 4,500 lbs/hour and eight bins at various ranges 
above the CEV. Hours without operation were represented as hours with 
2,000 lbs/hour, and other hours were represented with the upper level 
of the applicable bin. The dataset included 2.5% of emissions above the 
CEV (or 220 hours). This was based on how the plant historically 
operated while complying with this 30-day limit and how it is expected 
to operate into the future while in compliance with the 30-day limit. 
The hours above the CEV were distributed across four high emission 
events, where the duration of each event was 4, 7, 12, or 16 hours, 
with the frequency of those events being twice per month, monthly, 
every six months and once per year, respectively, such that these 220 
hours above the CEV were spread across 39 days.
---------------------------------------------------------------------------

    \11\ This CEV and the description provided are based on 
Pennsylvania's updated analysis which was provided to EPA on 
February 5, 2020.
---------------------------------------------------------------------------

    The remaining 97.5% of hourly emissions were below the CEV and 
randomly assigned throughout the annual emission profile. EPA analyzed 
10 past years of Seward's emissions and operational data and PJM 
forecasts for future electric demand, and understands that no major 
changes are planned for the source (i.e., no new emission limits, no 
new control equipment, fuel changes, etc.) (See the Part 75 Emissions 
TSD in the docket for this rulemaking). Therefore, EPA believes that 
the future variability of Seward while meeting the limit is likely to 
be similar to historic variability.
    Pennsylvania calculated a weighted average of the emissions in the 
binned inventory by multiplying the bin level times the percentage of 
hours in each bin and summing the results. This sum, representing the 
average of the modeled emissions, equaled 3,088 lb/hr. Despite minor 
variations resulting from the random distribution process, each of the 
100 AERMOD simulations had approximately this average level of 
emissions.
    Pennsylvania developed 100 different annual emission profiles using 
the historic data of high emission event days, and randomly assigning 
the other hourly emissions such that the average of the 30-day averages 
of each simulation was close to 3,088 lb/hr, which is representative of 
the variation within the historical emissions. Seward's SO2 
emissions limit of 3,038.4 lb/hr on a 30-day rolling average basis is 
approximately 50 lb/hr less than the approximate average emissions 
value used in the AERMOD simulations.
    Each of the 100 emissions scenarios (each with average emissions 
above the limit level) were modeled with one year of site specific 
meteorological data using AERMOD. For each of the 100 AERMOD 
simulations for Seward, the 99th percentile of the daily maximum 1-hour 
SO2 modeled concentrations were below the NAAQS.
    EPA concludes that this modeling provided enough permutations of 
emissions and meteorology that we can be reasonably confident that 
Seward's longer-term limit is protective of the NAAQS. This conclusion 
is based upon the large number of emission distribution profiles (100), 
the targeted 30-day emissions average value in each simulation being 
set slightly above the 30-day average limit, model inputs reflective of 
the variability in historic plant operations (based on EPA's review of 
10 years of emissions data) and one year of site specific 
meteorological data.

[[Page 66245]]

    Pennsylvania's modeling process is described in Appendix C-1 of the 
state submittal, in the state's February 5, 2020 supplemental modeling 
report, in EPA's TSD for the proposed rulemaking entitled ``State 
Implementation Plan Revision: Attainment Demonstration and Base Year 
Inventory Indiana, PA Nonattainment Area for the 2010 1-Hour 
SO2 NAAQS'', dated October 2017 (hereafter referred to as 
the ``October 2017 Modeling TSD''), and EPA's RRE Modeling TSD, which 
are available in the docket.\12\
---------------------------------------------------------------------------

    \12\ The analysis was updated in the February 5, 2020 submittal.
---------------------------------------------------------------------------

    In regard to the commenter's concern that Appendix B was not meant 
to provide guidance on how to develop a longer term limit, EPA agrees 
that neither the Guidance nor Appendix B stated that Appendix B was a 
recommended approach to develop longer term emission limits. 
Nevertheless, EPA believes that elements of the methodology used in 
Appendix B may be used to assess whether a longer term limit could be 
protective of the NAAQS.
    Although the analysis described in Appendix B does not use 
allowable emissions (insofar as only the maximum 30-day average 
emissions equal the 30-day average limit), the analyses in 
Pennsylvania's submittal differ in some respects from the analysis 
described in Appendix B, and EPA must evaluate Pennsylvania's submittal 
on its own merits. For reasons described previously, EPA believes that 
Pennsylvania's modeling provides a suitable demonstration that the plan 
provides for attainment. Using actual historic operations as a basis 
for developing the emission rates used in the modeling analysis is in 
EPA's opinion a reasonable approach. Past actual operations provide the 
data necessary to develop a representative and realistic range of 
emission rates to be used in the RRE simulations to assess if Seward's 
30-day rolling average limit provides for attainment. Without the 
bounds of past operations, there are an infinite number of emission 
scenarios that could fit within Seward's 30-day rolling limit (and to a 
lesser extent Keystone's 24-hour block limit). For example, Seward 
could emit 2,186,929 lbs between midnight and one in the morning then 1 
lb/hr for the next 719 hours and still meet its limit (it is impossible 
that Seward can emit at this rate, but this illustrates that there is a 
wide range of numeric operating scenarios which could still result in 
compliance with the 30-day average limit). On the other hand, Seward 
could emit 3,084 lb/hr for 720 hours with no variability and meet its 
limit. Neither of these scenarios are likely to occur, and thus EPA 
believes that Pennsylvania has appropriately used historical data to 
develop a representative distribution of potential future hourly 
emissions that can be expected to occur when complying with a longer 
term limit.
    In summary, EPA has concluded that Pennsylvania's evaluation of 
longer term limits using 100 AERMOD simulations provides reasonable 
confidence that the longer term limits for Keystone and Seward are 
protective of the NAAQS. Pennsylvania evaluated the likelihood of 
violations based on random reassignment of emission profiles designed 
to reflect the historic variability of emissions at each of these 
plants, and modeled these emission profiles using appropriate 
meteorological data (1-year of site specific meteorological data for 
Seward and five years of representative meteorological data for 
Keystone). Because an hour with emissions above the CEV will not 
necessarily experience a NAAQS exceedance, Pennsylvania's analysis 
showing the source's emissions variability, when randomly reassigned to 
different hours in the year, with a percentage of hours modeled above 
the CEV, provides evidence that the sources complying with those longer 
term emission limits will protect the NAAQS.
    Comment 4. The commenter states that the 30-day average limit for 
Seward was calculated contrary to EPA Guidance. The commenter notes 
that the conversion factor AECOM presented in worksheets of 0.47 was 
not used, and a conversion factor of 0.60 was used. The commenter 
asserts that the conversion factors of 0.47 and 0.60 are both too 
permissive. The commenter provided an analysis which they claim 
demonstrates that the conversion factor is dependent on the time period 
used to analyze Seward's emission, and that the 0.47 and 0.60 
conversion factors are inconsistent with the actual variability 
observed in Seward's emissions.
    A similar comment was received on the NODA, where the commenter 
asserted that AECOM failed to employ a conversion factor that 
``properly reflects the emissions variability'' at Seward and ignored 
EPA's 2014 Nonattainment Guidance Appendix C methodology. AECOM 
provided a conversion factor of 0.47 that was not used to calculate the 
longer term limit. Rather, the commenter asserts, AECOM used Appendix B 
methodology to calculate longer term limits, and the commenter asserts 
this is against the stated purpose of Appendix B.
    Response 4. EPA agrees that the adjustment factor (which the 
commenter refers to as the ``conversion'' factor) which was calculated 
by AECOM of 0.47 using Appendix C methodology was not used to calculate 
the longer term emission limit for Seward. However, EPA does not agree 
that an adjustment factor of 0.60 was used. Adjustment factors were not 
used to develop the emission limit for Seward. In determining whether 
the longer term limit at Seward was supportive of the NAAQS, 
Pennsylvania considered variability of the source in a different manner 
than the recommended Appendix C methodology. As described in Response 3 
of this preamble, Pennsylvania used a modeling approach which varied 
emissions and meteorology in 100 AERMOD simulations to evaluate the 
adequacy of the 30-day rolling average SO2 emission limit 
for Seward.
    EPA acknowledges that if EPA's recommended adjustment factor 
approach is used to convert a shorter term emission limit into a longer 
term emission limit, the calculated adjustment factor can vary 
depending on the time period used to analyze the source's emissions, 
though as a general matter EPA expects that different periods with 
suitably robust data sets and similar control regimes will have similar 
variability and calculated adjustment factors. However, the state did 
not use EPA's recommended approach for developing the longer term 
emission limit for Seward. The commenter did not explain why its 
objections to an adjustment factor that was not used are relevant. The 
question is not whether Pennsylvania used the correct adjustment factor 
to develop the longer term limit, but whether the longer term limit, 
which was developed without an adjustment factor, is set at a level 
which is protective of the NAAQS. Based on the information provided in 
Response 3 of this preamble, EPA concludes that the 30-day limit for 
Seward and the 24-hour block limit for Keystone are protective of the 
NAAQS, and that the commenter's objections related to the un-used 
adjustment factor are not relevant to this determination.
    Comment 5. The commenter asserts that the longer term limits for 
Seward and Keystone are fundamentally incapable of protecting the 1-
hour SO2 NAAQS. The commenter asserts that an emission limit 
with an averaging period longer than one hour is highly unlikely to 
protect the short term standard, and spikes in emissions could cause 
short term elevations in ambient SO2 levels sufficient to 
violate the NAAQS while nonetheless averaging out over a longer

[[Page 66246]]

period such that the source complies with their longer term limit. The 
commenter cites to previous EPA documents stating that compliance with 
emission limits should be determined based on an averaging time 
consistent with the NAAQS.\13\ The commenter asserts that the 30-day 
emission limit proposed for Seward is 720 times the standard. The 
commenter provided an assessment of historic hourly emissions from 2011 
to 2016 for Seward and concluded that during this period, there were 
445 hours in which emissions from the plant exceeded its CEV. The 
commenter states that because exceedances \14\ of the NAAQS can occur 
if as few as four hours over the course of a year are above 75 ppb, the 
30-day proposed emission limit cannot be protective of the NAAQS.
---------------------------------------------------------------------------

    \13\ EPA Region 7 Comments re: Sunflower Holcomb Station 
Expansion Project 4 (August 12, 2010); EPA Region 5 comments re: 
Monroe Power Plant Construction Permit 1 (February 1, 2012).
    \14\ For clarity, EPA notes that a violation of the 2010 
SO2 NAAQS occurs when the 3-year average of the 99th 
percentile of the yearly distribution of daily maximum 1-hour 
average concentrations is above 75 ppb. The 2010 SO2 
NAAQS is not a single exceedance based standard.
---------------------------------------------------------------------------

    The commenter also states that the 24-hour emission limit proposed 
for Keystone is also inadequate to protect against violations of the 
NAAQS. The commenter provided an analysis of historic hourly emissions 
data from 2011 to 2016 for Keystone \15\ and concluded that Keystone 
had exceeded its CEV 12,830 total hours over the examined period. The 
commenter argues that given the Keystone and Seward emissions limits 
are not new requirements, it is questionable that these limits will 
protect the NAAQS.
---------------------------------------------------------------------------

    \15\ EPA notes that the graph provided on page 7 of the Comment 
document indicates the commenter's analysis is based on a CEV equal 
to 9600 lb/hr, however, the CEV for Keystone is 9711 lb/hr.
---------------------------------------------------------------------------

    Response 5. The commenter is incorrect in stating that Keystone 
does not have new emission limit requirements. Prior to the attainment 
plan, the SO2 emission limit at Keystone was set at 1.2 lb/
MMBtu on a 30-day rolling average basis. A new SO2 limit was 
established in this attainment plan for Keystone of 9,600 lb/hr average 
calculated on a 24-hour block basis, a limit which went into effect on 
October 1, 2018. Therefore, the commenter's reasoning that the Keystone 
limit will not protect the NAAQS because the past emissions exceeded 
the CEV 12,830 hours in a six-year period (prior to the adoption of the 
limit) is based on faulty information. Subsequent evidence indicates, 
as expected, that imposition of the limit has led to a significant 
decline in the frequency of emissions exceeding the CEV.
    EPA disagrees with the commenter's statement that the proposed 30-
day limit for Seward and the 24-hour limit for Keystone are 
fundamentally incapable of protecting the 1-hour SO2 NAAQS. 
Pennsylvania has conducted detailed modeling supporting the view that 
the distribution of emissions that can be expected in compliance with 
its requested SIP limits will provide for attainment. The specific 
examples of earlier EPA statements cited by the commenter (i.e., those 
contained in Exhibits 1 and 2 to Appendix A of the comment submission) 
pre-date the release of EPA's 2014 SO2 Nonattainment Area 
Guidance. As such, these examples only reflect the Agency's development 
of its policy for implementing the 2010 SO2 NAAQS as of the 
dates of the issuance of the statements. At the time these statements 
were issued, EPA had not yet addressed the specific question of whether 
it might be possible to devise an emission limit with an averaging 
period longer than one-hour, using appropriate adjustments that would 
make it comparably stringent to an emission limit shown to attain one-
hour emission levels or other possible approaches, that could 
adequately ensure attainment of the SO2 NAAQS. None of the 
pre-2014 EPA documents cited by the commenter address this question; 
consequently, it is not reasonable to read any of them as rejecting 
that possibility.
    In contrast, EPA's 2014 SO2 Nonattainment Area Guidance 
specifically addressed this issue as it pertains to SIP requirements 
for SO2 nonattainment areas under the 2010 NAAQS. EPA found 
that a longer term average limit could be devised such that it is 
likely to yield attaining air quality under the one-hour NAAQS. See 
2014 SO2 Nonattainment Guidance. While EPA's guidance 
focuses on a different approach (involving establishment of a longer 
term average limit that is comparably stringent to the one-hour limit 
that would otherwise be set), EPA believes that Pennsylvania has made a 
suitable demonstration that its limits are adequate to provide for 
attainment.
    Any analysis of whether a 30-day or 24-hour average limit provides 
for attainment must consider factors for reducing the likelihood of 1-
hour average concentrations that exceed the NAAQS level as well as 
factors creating a risk of additional concentrations that exceed the 
NAAQS level. To facilitate this analysis, EPA used the concept of a CEV 
for the SO2-emitting facilities which are being addressed in 
a nonattainment SIP. The CEV is the continuous 1-hour emission rate 
which modeling shows is expected to result in the 3-year average of 
annual 99th percentile daily maximum 1-hour average concentrations 
being at or below 75 ppb, which in a typical year means that fewer than 
four days have maximum hourly ambient SO2 concentrations 
exceeding 75 ppb. See 2014 SO2 Nonattainment Guidance.
    EPA recognizes that a 30-day or 24-hour average limits can allow 
occasions in which hourly emissions from the source exceed the CEV, and 
such occasions yield the possibility of ambient concentrations 
exceeding the NAAQS level that would not be expected if emissions were 
always at the CEV. At the same time, the establishment of the longer 
term average limit at a level below the CEV means that emissions must 
routinely be lower than they would be required to be with a 1-hour 
emission limit set at the CEV.
    As described in detail in Response 3 of this preamble, the RRE 
modeling runs submitted by Pennsylvania specifically modeled ``high 
emission events'' at Keystone and Seward where the hourly emissions 
exceeded the CEV. The RRE modeling used the distribution of past hourly 
SO2 emissions, with a certain number of hours over the CEV 
(15% of the hours at Keystone and 2.5% of the hours at Seward were 
modeled with emissions over the CEV). For each facility, the emissions 
in the resulting emission profiles were randomly reassigned to develop 
100 hourly emission files for use in 100 AERMOD simulations. The AERMOD 
simulations were conducted with the same general methodology as the air 
dispersion modeling for the CEVs, except that the hourly emission 
files, for either Keystone or Seward, replaced the CEV in AERMOD. All 
of these AERMOD simulations resulted in maximum 1-hour SO2 
design concentrations equal to or less than the NAAQS, which provides 
sufficient support for EPA to assert that the longer term emission 
limits for Seward and Keystone are protective of the NAAQS.
    While the commenter claims that emissions above the CEV will cause 
NAAQS violations, no analysis has been provided to support this 
assertion. In contrast, Pennsylvania did provide a detailed modeling 
analysis which specifically showed that the longer term limits for 
Seward and Keystone, including a percentage of hours over the CEV, 
provide for attainment. A more detailed discussion of the hourly 
emissions data for Seward and Keystone and the RRE analysis is provided 
in the Part 75 Emissions TSDs, the Supplemental Modeling TSD and the

[[Page 66247]]

RRE Modeling TSD found in the docket for this action.
    Comment 6. The commenter states that EPA's justification for 
Pennsylvania's use of the Appendix B methodology for developing longer 
term emission limits is nonsensical and contrary to EPA's 2014 
SO2 Nonattainment Guidance. The commenter cites EPA's 
Guidance, which suggests that longer term emission limits are most 
appropriate where periods of hourly emissions above the CEV are a rare 
occurrence at a source, particularly if the magnitude of the emissions 
is not substantially higher than the CEV. These periods of time over 
the CEV would be unlikely to have a significant impact on air quality, 
because they would be very unlikely to occur repeatedly at the times 
when the meteorology is conducive for high ambient concentrations of 
SO2. However, the commenter indicates that in the TSD for 
the NPRM, EPA states that a survey of emissions from 2014-2016 for 
Keystone showed hourly emissions exceeded the CEV quite frequently and 
therefore Appendix B was chosen to model attainment. The commenter 
argues that reasoning is nonsensical.
    Response 6. EPA's 2014 SO2 Nonattainment Guidance 
provides recommendations, but does not require states to follow the 
guidance in each aspect of their submittal. The state may decide to use 
a different approach than recommended by EPA, and it is EPA's role to 
determine if that approach and the result is reasonable and protective 
of the NAAQS. In this case, the state used elements of the methodology 
described in Appendix B to demonstrate that the longer term limits for 
Keystone are protective of the NAAQS. Regardless of the state's 
reasoning for using that approach, EPA must judge the state's 
submittal.
    EPA's proposal that the SO2 emission limits at Keystone 
are protective of the NAAQS relies upon Pennsylvania's RRE modeling 
analysis. Pennsylvania's SO2 limits with averaging periods 
of longer than one-hour can provide sources flexibility to deal with 
the inherent variability in their SO2 emissions and emission 
control systems.
    Pennsylvania submitted RRE model simulations that calculate design 
values over the model receptor grid based on varying hourly emissions 
that for Keystone exceeded the 1-hour CEV emission rate approximately 
15% of the hours in a year. The RRE simulations allow the model to 
determine if the total contribution to the averaged design value by the 
hours exceeding the 1-hour CEV, when considered along with the hours in 
which emissions are below the 1-hour CEV, and in compliance with the 
target emission limit, would result in a modeled NAAQS violation. 
Pennsylvania developed 100 sets of hourly emission data sets where 
Keystone's peak daily average emission rate was equal to a target value 
of 9,600 lb/hr (the new SO2 24-hr emission limit), 85% of 
the hours were modeled below the CEV, and 15% of the hours were modeled 
above the CEV. The RRE evaluation shows compliance with the NAAQS since 
all 100 simulations return modeled design values less than or equal to 
75 ppb. If the modeled emission limits were not protective, the RRE 
test would show modeled design values above the 1-hour SO2 
NAAQS.
    Because Pennsylvania did not follow the approach in Appendix C from 
EPA's SO2 Nonattainment Guidance to develop the longer term 
limit for Keystone, this analysis was the evidence EPA relied on to 
determine that the longer term limit for Keystone was protective of the 
NAAQS. In any case, more recent evidence indicates that Keystone's 
compliance with its new limit will result in substantially fewer hours 
when emissions exceed the CEV. For example, in 2019, after the limit 
took effect, only 35 hours exceeded the CEV, representing 0.4% of the 
8,623 operating hours during the year.
    Comment 7. The commenter asserts that AECOM's modeling erroneously 
splits the nonattainment area into two modeling domains, and thus does 
not adequately assess the impacts of the four electric generating units 
(EGUs) together. The commenter points out that the modeled peak impact 
for Armstrong County of 192.3 [mu]g/m\3\ is due to Keystone impacts 
only, and does not include impacts from the other three EGUs. The 
commenter notes that the maximum modeled concentration from Seward \16\ 
of 194.44 [mu]g/m\3\ occurs just over the border between Indiana and 
Armstrong Counties on the Indiana County side, and that simulation 
includes all four EGUs. The commenter thinks that both results cannot 
be true: Either the maximum impact reported for Seward is incorrect 
because it considers all four EGUs or the modeling in Armstrong County 
needs to include all four EGUs. The commenter also argues that EPA used 
an incorrect rationale for approving the two separate modeling domains. 
Specifically, the commenter is concerned that the wind rose provided in 
the TSD shows that winds having a southeasterly component occur 
approximately 15% of the time, which they claim is not ``infrequent,'' 
as EPA describes in that TSD. Also, the commenter takes issue with the 
fact that the background concentrations used in the two modeling 
domains are different--while the same monitor is used, the dates from 
the monitoring values are different (2014-2016 vs. 2013-2015). The 
commenter believes that the same date range should be used.
---------------------------------------------------------------------------

    \16\ The peak model concentration of 196.44 [mu]g/m\3\ is in the 
area surrounding Keystone, it is not in the area surrounding Seward 
as the commenter wrote. The peak model concentration around Seward 
was reported at 192.75 [mu]g/m\3\ in the original state submittal.
---------------------------------------------------------------------------

    Response 7. EPA disagrees that the nonattainment area was 
erroneously split into two modeling domains and that this splitting of 
the nonattainment area into separate modeling domains would not 
correctly consider the joint impacts of all four sources included in 
the Indiana, PA SIP modeling demonstration. EPA believes that modeling 
two domains was warranted in this case based on the justification 
provided by Pennsylvania in Appendix C-1a (AECOM's SO2 NAAQS 
Compliance Modeling Report for the Indiana, PA Non-Attainment Area: 
Phase 1 Modeling (Revision No. 1)) of the state's submittal. EPA 
believes that the commenter misunderstands the model results for Seward 
and Keystone based on the fact that the commenter noted that the 
maximum modeled concentration from Seward was 194.44 [mu]g/m\3\, which 
is actually the peak modeled concentration around Keystone.\17\
---------------------------------------------------------------------------

    \17\ EPA has included in the docket for this action a TSD 
Addressing Modeled Concentration Values for the Keystone Generating 
Station Included in the Indiana, PA 1-Hour SO2 
Nonattainment Area. The TSD explains that using updated background 
concentrations, the modeled maximum concentration for Keystone is 
below 196.4 [mu]g/m\3\.
---------------------------------------------------------------------------

    EPA will further explain the reasoning for the use of the split 
modeling domains and the reasons supporting EPA's conclusion that the 
use of two modeling domains in this case is appropriate. The 
nonattainment area was divided into two modeling domains; one covering 
portions of Armstrong County surrounding Keystone, and one covering all 
of Indiana County. In the Armstrong domain, Pennsylvania modeled 
Keystone as the only source. In the Indiana domain, Pennsylvania 
modeled all four SIP sources. EPA agrees with this approach because of 
the long aerial transport distances (for SO2) between 
Keystone and the remaining SIP sources in Indiana County, and the 
prevailing wind directions in the Area.
    The distances between Keystone and the remaining SIP sources are 
greater than 10 kilometers. From EPA's March 2011 Clarification Memo, 
``. . . the

[[Page 66248]]

emphasis on determining which nearby sources to include in the modeling 
analysis should focus on the area within about 10 kilometers of the 
project location in most cases.'' The distance between Keystone and 
Homer City is approximately 20.5 kilometers, between Keystone and 
Conemaugh is approximately 38.9 kilometers and between Keystone and 
Seward Station is approximately 38.3 kilometers. Therefore, it was 
reasonable for Pennsylvania to model Keystone in a separate modeling 
domain.
    EPA's clarification memo continues, ``[T]he routine inclusion of 
all sources within 50 kilometers of the project location, the nominal 
distance for which AERMOD is applicable, is likely to produce an overly 
conservative result in most cases.'' EPA believes that including all 
four sources in the Keystone modeling domain would have been overly 
conservative.
    When modeling all four sources, the peak model concentration is 
located approximately four km northeast of Keystone. This would be the 
result of plant emissions being blown from winds out of the southwest 
(from Keystone's stack towards the peak model receptor). Emissions from 
Conemaugh, Homer City and Seward would be transported in a similar 
direction, i.e. to locations far away from the peak receptor near 
Keystone. Evaluative modeling conducted by AECOM (Appendix C1-a of the 
SIP submittal) confirmed the minimal impact of these three sources in 
the vicinity of Keystone. Specifically, the modeling shows that the 
peak modeled concentration contains a fractional contribution (0.6%) 
from the other three SIP sources even under circumstances where those 
plant's emissions would have been advected in an almost opposite 
direction. Given this result, and since it is logical to conclude that 
when winds are blowing from the southwest, emissions would not be 
transported in the northwesterly direction, EPA believes it was 
appropriate to exclude contributions from Conemaugh, Homer City and 
Seward in modeling the area around the Keystone plant.
    In regard to the commenter's concern regarding the use of different 
background concentrations in the two modeling domains, EPA believes the 
state's use of a higher background concentration in the Keystone only 
modeling domain provides a level of conservatism that, while not 
required, provides additional assurances that the Keystone limits are 
protective of the NAAQS. The higher background concentration was from a 
period of time from 2013-2015, prior to the installation of 
SO2 controls on Homer City and during a time with higher 
regional SO2 background concentrations. Homer City is the 
closest of the three sources outside the modeling domain. The inclusion 
of these potential impacts was considered to provide a more 
conservative analysis. While Pennsylvania could have used more updated 
background concentrations reflecting a decrease in impacts from Homer 
City (and from all SO2 sources), the state submitted a more 
conservative analysis to show that even if the background 
concentrations were higher than recent background data, the modeling 
results are within the NAAQS.
    For model receptors in Indiana County, all four sources were 
modeled with newer regional background reflecting reduced emissions 
from Homer City due to new SO2 controls. The use of newer 
background concentrations (2014-2016) is warranted since it provides a 
more accurate depiction of reality. Current background concentrations 
are even lower \18\ than in 2016 (mainly due to reduced regional 
SO2 emissions), providing additional support that the plan 
provides for attainment. Pennsylvania provided more recent background 
values in the Supplemental Submittal of February 5, 2020.
---------------------------------------------------------------------------

    \18\ https://www.epa.gov/air-trends/sulfur-dioxide-trends#sonat.
---------------------------------------------------------------------------

    Comment 8. GenOn (owner and operator of Conemaugh and Keystone) was 
advised by EPA that the absence of a site-specific study would not, in 
of itself, preclude the use of AERMOIST for the Indiana Area SIP 
provided that other site-specific studies conducted elsewhere 
demonstrated the applicability and effectiveness of AERMOIST in 
providing improved model results. Consequently, based on EPA's 
guidance, GenOn and their modeling contractor, AECOM, proceeded with 
the companion modeling effort that utilized AERMOIST.
    Response 8. EPA acknowledges the detailed responses regarding 
AERMOIST provided during the public comment period (see next comment). 
EPA's analysis of possible shortcomings of the AERMOIST plume module 
was outlined in a December 27, 2017 response to Pennsylvania's request 
to use AERMOIST as an alternative model under Appendix W. At that time, 
EPA had determined that use of the AERMOIST plume module was not 
approvable under section 3.2.2 of Appendix W and that the (higher) 
limits established using AERMOIST were not protective of the 1-hour 
SO2 NAAQS.
    EPA continues to believe that the use of AERMOIST is not an 
appropriate basis for evaluating emission limits in the Indiana, PA 
nonattainment area.
    Comment 9. The commenter asserts that in an EPA White Paper, EPA 
agreed with the physical and theoretical merits of the AERMOIST 
hypothesis, specifically that AERMOD does not account for the effects 
of plume moisture. Plume moisture tends to increase plume rise over 
that for a ``dry'' plume because the condensation which occurs when 
water vapor in a moist plume condenses upon leaving the stack, 
releasing heat as part of the condensation process. The commenter 
provided a presentation (which was previously shared with EPA) that 
responds to the deficiencies of AERMOIST that EPA pointed out to them. 
The commenter asserts that EPA has acknowledged that AERMOD in default 
mode is deficient in not addressing the real effect of moisture in the 
plume, so there is merit in pursuing the AERMOIST approach. Therefore, 
the commenter concludes that AERMOIST should be considered as an 
``ALPHA'' procedure, which means that as an ``experimental'' procedure, 
AERMOIST has scientific merit, but is not yet ready for regulatory 
applications.
    Response 9. EPA acknowledges the analysis provided by the commenter 
regarding the AERMOIST plume module. As noted previously, application 
of AERMOIST in the Indiana, PA modeling demonstration has not been 
justified. The commenter appears to acknowledge that AERMOIST has not 
been demonstrated to warrant being used in regulatory applications such 
as in Pennsylvania's SO2 attainment plan. The comment 
regarding designation of AERMOIST as an alpha procedure is outside the 
scope of this rulemaking.
    Comment 10. The commenter asserts that AECOM used erroneous 
assumptions and methods in their modeling analysis and EPA's reliance 
on this modeling would be arbitrary and capricious. The commenter 
claims the following aspects of the modeling analysis are incorrect:
    1. The receptor grid used by AECOM has glaring areas of no coverage 
including the area around Homer City and the area across the Indiana 
County border right next to Seward and Conemaugh. This is a particular 
problem for Seward and Conemaugh as the emissions from those sources 
cause attainment problems both inside the nonattainment area and east 
and

[[Page 66249]]

southeast of the plants (outside the nonattainment area).
    2. The AECOM modeling used fixed stack parameters and ignored 
differences in the plume loft and dispersion that would occur at 
different gas exit temperatures and velocities. AECOM plotted 
SO2 emissions vs. temperature, and SO2 emissions 
vs. gas velocity, and both data sets showed a variation in the 
variables as a function of emissions. Data from Conemaugh and Homer 
City stacks are absent. In addition, the data for Seward and Keystone 
that are presented (SO2 emissions and temperature/velocity) 
are not directly correlated, and the link that would correlate them 
(boiler operation) is not provided or taken into consideration.
    3. The emissions modeled in the randomized modeling for Keystone 
are improper because they do not account for the actual historic 
emissions practices at the plant. The data provided by the commenter 
show that approximately 25% of the hours for 2011 through 2016 were 
above the CEV, while the modeling only included emissions over the CEV 
15% of the time.
    4. Only one meteorological data source was used for modeling all 
four EGUs, rather than selecting the most appropriate meteorological 
data for each source. EPA should have insisted on a meteorological data 
sensitivity analysis to ensure the model results were not driven by the 
meteorological data source selection. Johnston airport is not in the 
nonattainment area and is a significant distance from several coal-
fired power plants and the Strongstown monitor. It lies 16 miles south-
southeast of the monitor. DEP could have considered the Jimmy Stewart 
Airport which is located in Indiana County. The model results could be 
affected by the differences in wind speed and direction at these 
airports. Wind roses for each airport were provided. EPA should do the 
modeling again using the closer meteorological data.
    To summarize, the commenter states that these modeling issues are 
not trivial and notes that when these model assumptions are used, each 
facility, itself causes exceedances of the NAAQS.
    Response 10. EPA disagrees with the commenters' points as follows:
    1. Regarding model receptors surrounding the Homer City power 
plant, this item was brought up (and fully addressed) during 
Pennsylvania's public comment period. EPA finds Pennsylvania's response 
fully adequate (see response to comment 11 in Pennsylvania's Comment 
Response Document). The modeling analysis did include model receptors 
``. . . along the public roads which pass through the facility, 
specifically, Coal Road, Power Plant Road, Cherry Run Road, and Quarter 
Center Road.'' Homer City has also properly established that it has 
ownership and imposed proper public access control protocols that 
support its modeled ambient air boundary. Additionally, due to Homer 
City's tall stacks, local peak model concentrations occur well beyond 
the plant's ambient air boundary (see Figure 5-7 of Appendix C-1a of 
the Commonwealth's submittal) indicating model receptors within the 
area highlighted by the commenters probably do not exceed the source 
generated local concentration peaks mainly due to the GEP oriented 
stack height. GEP formula height for all three stacks is 298.62 meters 
above local ground elevations.
    The commenter's concern that no model receptors outside of the 
Indiana nonattainment area boundaries were included in Pennsylvania's 
modeling demonstration showing SO2 attainment within the 
nonattainment area is outside the scope of this action. The boundaries 
of the Indiana, PA nonattainment area were set and made final in August 
2013 in ``Round One'' of EPA's designations for the 2010 SO2 
NAAQS, and these boundaries were not challenged.\19\ Pennsylvania's 
obligation under section 110(a) of the CAA is to submit ``. . . a plan 
which provides for implementation, maintenance, and enforcement of such 
primary standard in each air quality control region (or portion 
thereof) within such State.'' CAA section 110(a)(1). Section 110 
further provides that ``[i]n the case of a plan or plan revision for an 
area designated as a nonattainment area, meet the applicable 
requirements of part D of this subchapter (relating to nonattainment 
areas).'' CAA section 110(a)(2)(I). Section 172(c)(6) then requires the 
SIP for a nonattainment area to include enforceable emission 
limitations and control measures as necessary or appropriate to provide 
for NAAQS attainment ``in such area.'' CAA section 172(c)(6). In this 
case, Pennsylvania's attainment plan for the Indiana area includes 
limits on SO2 sources and a modeling demonstration showing 
that SO2 concentrations throughout the Indiana nonattainment 
area are at or below the NAAQS. While section 110(a)(2)(D) contains 
provisions requiring that a state's SIP contain provisions to avoid 
causing or contributing to nonattainment or maintenance in another 
state, the Commenter does not cite any statutory or regulatory 
requirements or EPA guidance that a state must include modeling 
receptors outside of a nonattainment area in an attainment plan. 
Further, EPA's role is limited to determining whether the submitted SIP 
meets the requirements of the CAA, see section 110(k), and 
Pennsylvania's SIP does not address areas outside the defined 
nonattainment area. Absent a clear requirement that Pennsylvania must 
include model receptors outside of the nonattainment area in its 
submission, EPA will confine its analysis to whether the attainment SIP 
demonstrates attainment within the designated nonattainment area.
---------------------------------------------------------------------------

    \19\ See https://www.epa.gov/sulfur-dioxide-designations/so2-designations-state-designations-round-1.
---------------------------------------------------------------------------

    Although some of the modeling submitted by the commenter purports 
to show SO2 concentrations outside of the boundaries of the 
Indiana, PA nonattainment area that are above the SO2 NAAQS, 
primarily in Cambria and Westmoreland Counties to the east, 
Pennsylvania was required to develop and submit an SO2 
attainment demonstration SIP only for the Indiana, PA nonattainment 
area, which does not include these counties. Prior to making its final 
round one designations, EPA invited interested parties other than the 
states and Tribes to submit comments on the proposed designations of 
these areas, including the boundaries of these areas. 78 FR 11124 
(February 15, 2013).
    2. The commenter's concern regarding not accounting for source 
variability in stack temperatures and velocities was also raised during 
the Pennsylvania public comment period. EPA believes Pennsylvania's 
response is adequate for the commenter's concern and information 
supporting their conclusions was provided as part of Pennsylvania's SIP 
package (see Comment Response Document, response to comment 12). EPA 
generally agrees with Pennsylvania's observation that while stack 
velocities (and sometimes stack temperatures) decrease under loads less 
than 100% or the facility's peak load, the emission reductions for 
boiler loads lower than 100% more than offset any reduction in stack 
plume-height and dispersion caused by lower plume lofting due to lower 
exit velocities and lower temperatures. Additional information included 
in AECOM's modeling reports clearly show stack temperatures and exhaust 
parameters are relatively uniform across different emission ranges, 
which supports using constant values in the modeling analysis.
    3. Pennsylvania analyzed the heat input for years 2014 through 2016 
for

[[Page 66250]]

Keystone. Station operations in 2016 represented the average of station 
operations over the three-year period from 2014 through 2016 (heat 
input-based capacity factors of 74%, 64% and 69% for 2014, 2015 and 
2016, respectively), therefore the 2016 emission cumulative frequency 
plot was used in the analysis to derive the emissions input to the 100 
AERMOD simulations. EPA analyzed the last ten years of heat input and 
notes that the heat input has been relatively stable.
    The commenter is evaluating the likelihood of emissions exceeding 
the CEV based on data before Pennsylvania's limit took effect. EPA has 
analyzed the hours over the CEV for the last 10 years and notes a 
downward trend. More importantly, the newly developed SIP limit for 
Keystone went into effect on October 1, 2018, which can be expected to 
cause a reduction in the frequency of emissions exceeding the CEV. 
Indeed, the available evidence indicates that this has already 
occurred. Data from 2018 and 2019 indicates that Keystone emissions are 
now exceeding the CEV for only about 1 percent of the hours. EPA 
believes the new emission limit provides a constraint that will result 
in the frequency of hourly emissions over the CEV being considerably 
less than 15% of the time. While EPA believes that the 2016 data 
provide a good basis for formulating the anticipated shape of the 
future distribution of emissions, including assessing the variability 
of emissions (particularly as it pertains to the spread among the 
emission rates in the upper portion of the distribution, which are of 
most interest for air quality planning purposes), EPA does not believe 
that modeling with 25 percent of hours exceeding the CEV would 
appropriately reflect emissions in compliance with Pennsylvania's 
limits. A more detailed discussion of EPA's analysis of Keystone's 
emissions and heat input is included in the Part 75 Emissions TSD.
    4. The use of the Johnstown-Cambria County airport as the source of 
meteorological data for the modeling analysis has been adequately 
justified. The possibility of using the Indiana County (Jimmy Stewart) 
airport data was addressed in Pennsylvania's comment response document 
(see comment 9 and response). In addition to Pennsylvania's response, 
EPA asserts that using a site in lower terrain, such as the Indiana 
County airport, may provide unrepresentative wind speeds for the 
modeling analysis. The Johnstown-Cambria County airport sits in 
elevated terrain along the Allegheny Front to the east of the Indiana, 
PA nonattainment area. Due to its elevation, the Johnstown-Cambria 
County airport experiences relatively sustained wind speeds. One of the 
reasons this airport was chosen was because its elevation is closer to 
the exit height of the elevated stacks that are included in the 
Indiana, PA modeling demonstration.
    Pennsylvania submitted additional site-specific meteorological data 
on February 5, 2020 which was collected near the Seward and Conemaugh 
stations. This meteorological data is called the Ash Landfill Tower 
data and is more representative of the meteorology in the vicinity of 
Seward and Conemaugh. EPA compared the new Ash Landfill Tower data \20\ 
to the Johnstown-Cambria County airport data which demonstrated that 
more sustained wind speeds aloft are clearly evident. Ash Landfill 
Tower wind speeds from the lowest level (10-meters) tend to be lighter 
during the overnight hours and suggest that wind speeds at lower 
elevation sites, such as the Jimmy Stewart airport the commenters 
suggested, may not be representative of wind speeds near the exit 
heights of the stacks for the four coal and waste-coal fired facilities 
in the SIP modeling demonstration (see 500-m Ash Landfill SODAR wind 
speeds vs the Johnstown-Cambria County Airport wind speeds).
---------------------------------------------------------------------------

    \20\ The Ash Landfill Tower Data was a site-specific 
meteorological monitoring data collected at a site located in 
southeast Indiana county along the Conemaugh River between the 
Conemaugh and Seward power plants. AECOM collected meteorological 
data from a multi-level instrumented tower and SODAR. A more 
complete description of this site-specific data can be found in 
AECOM's Meteorological Monitoring Station Design and Quality 
Assurance Project Plan for the Conemaugh and Seward Generating 
Stations--Indiana County, PA referenced in the NODA.
---------------------------------------------------------------------------

    Comment 11. The commenter questions the purpose of EPA's Emissions 
Inventory Technical Support Document and requests a robust analysis and 
discussion of the emissions so the public can understand why the 
emissions information provided by the state is acceptable.
    Response 11. Pennsylvania submitted their attainment and projection 
year emission inventories in accordance with EPA's 2014 SO2 
Nonattainment Guidance. The guidance states that air agencies should 
develop a comprehensive, accurate and current inventory of actual 
emissions from all sources of SO2 in the nonattainment area, 
as well as any sources located outside the nonattainment area which may 
affect attainment in the area as required under the Clean Air Act 
section 172(c)(3). EPA verified all emissions that were submitted by 
Pennsylvania against the 2011 National Emissions Inventory (NEI) 
version 2 and found them to be acceptable.

Table 1--Commonwealth Submitted SO2 Emissions Compared to 2011 NEI (tpy)
------------------------------------------------------------------------
                                       Commonwealth
    Indiana nonattainment area        submitted SO2     2011 NEI v2 SO2
     emission source category         tons per year      tons per year
                                         (tpy) *             (tpy)
------------------------------------------------------------------------
Stationary Point Sources..........         144,269.02         144,266.29
Area Sources......................             555.61            555.597
Non[dash]road Sources.............              1.025              1.025
On[dash]road Highway Sources......               7.73              7.319
                                   -------------------------------------
    Total.........................         144,833.38         144,830.23
------------------------------------------------------------------------
* Submitted with the Attainment Plan.

    For the attainment year inventory, EPA's 2014 SO2 
Nonattainment Guidance explains that the 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. For point sources, Pennsylvania 
projected emissions from 2011 to 2018 based on the anticipated 2018 
operating scenario for each facility. For the nonpoint and nonroad 
emission projections, Pennsylvania submitted projected inventories 
developed by the Mid-

[[Page 66251]]

Atlantic Regional Air Management Association (MARAMA), which are 
documented in the TSD found in Appendix A-1 of the Attainment Plan. 
Onroad emission projections were developed by Michael Baker Corp. and 
are also detailed in Appendix A of the Attainment Plan. Point Source 
emissions account for approximately 95% of the emissions in the NAA. 
EPA compared the 2018 projected actual emissions with the actual point 
source emissions in the most recent 2017 NEI for all point sources in 
the NAA, and the projected emissions are conservative (i.e. higher) 
when compared to actual emissions from the NEI. EPA also compared 
nonpoint, nonroad, and on-road emissions from the 2017 NEI and found 
the 2018 projected emissions to be conservative in comparison.

 Table 2--Facility-Specific Comparison of 2018 Anticipated SO2 Emissions
                       and 2017 NEI SO2 Emissions
------------------------------------------------------------------------
                                     2018 Anticipated
             Facility               actual SO2  (tpy)     2017 NEI SO2
                                            *                (tpy)
------------------------------------------------------------------------
KEYSTONE STATION..................          32,459.53          23,248.09
SEWARD GENERATING STATION/SEWARD..          10,118.93           7,265.86
HOMER CITY GEN LP/CENTER TWP......          16,714.31           5,748.06
CONEMAUGH STATION.................           9,248.29           4,619.78
All other point Sources...........               4.24               7.93
                                   -------------------------------------
    Total.........................          68,545.30          40,889.72
------------------------------------------------------------------------
* Submitted with the Attainment Plan in 2016.

    Comment 12. The commenter provided modeling analyses of Seward and 
Conemaugh's emission limits using the same meteorological data, the 
same stack parameters, the same background concentrations, and the same 
building downwash data as did Pennsylvania/AECOM. The commenter used 
emissions inputs from actual historical emissions from a variety of 
time periods between 2013 through quarter one of 2018 (EPA's Air 
Markets Program Database) and used a finer receptor grid around Seward 
and Conemaugh and included receptors outside the Indiana nonattainment 
area. The commenter modeled the CEVs and asserts that EPA cannot 
approve this SIP because the commenter's modeling demonstrates emission 
limits for those facilities are too lax and will not ensure attainment 
of the NAAQS. Modeling results for four separate date ranges were 
provided: 2013-2015, 2014-2016, 2015-2017, and 2013-2017.
    Response 12. EPA agrees with the commenter that their modeling 
demonstrated that the CEV for Seward was too high because one receptor 
in the southeast corner of the nonattainment area exceeded the 
standard. However, EPA does not agree that the commenter's modeling 
demonstrates that the emission limits for Seward and Conemaugh are too 
lax. As a result of this comment, on February 5, 2020, Pennsylvania 
submitted an additional analysis showing compliance within the 
southeast portion of the Indiana, PA nonattainment area (near the 
Conemaugh and Seward power plants) where the commenter's modeling 
analysis had shown a modeled violation of the 1-hour SO2 
NAAQS at one receptor. This new analysis used one year (September 2015 
through August 2016) of meteorological tower/SODAR (Sonic Detection and 
Ranging) data collected at the Ash Landfill site (located in Indiana 
County between the Conemaugh and Seward power plants), which is more 
representative of local conditions. The CEV model runs for Seward and 
Conemaugh were updated using this site-specific meteorological data and 
updated, more accurate background concentrations, plus a refined 
modeling grid to better resolve the commenter's modeled violation. The 
newly submitted CEV for Seward is 4,500 lbs/hr; the Conemaugh CEV did 
not change.
    To better understand the reduction in Seward's CEV, EPA analyzed 
the changes in the model inputs for the supplemental analysis through 
an iterative process. A summary of the changes and the resulting model 
concentrations is provided in Table 3.

                                                   Table 3--Modeling Results for Seward CEV Model Runs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                             Peak Model
                                   Seward      Meteorological                                                                              concentration
   Run iteration description     emissions          data          Peak receptor location      Receptor grid     Background  concentration    ([micro]g/
                                  (lbs/hr)                                                                                                      m3)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Commenter's Original Run......        5,079  JST 2011-15......  Laurel Ridge Terrain......  Commenter........  Original SIP (2014-16)....     213.84551
Change to Supplemental Grid...        5,079  JST 2011-16......  Laurel Ridge Terrain......  Supplemental.....  Original SIP (2014-16)....     304.07974
Change to Supplemental Grid           5,079  Ash Landfill.....  Robindale Heights.........  Supplemental.....  Original SIP (2014-16)....     220.21861
 and Ash Tower Meteorological
 data.
Change to Supplemental Grid,          5,079  Ash Landfill.....  Robindale Heights.........  Supplemental.....  Updated SIP (2016-18).....     217.81186
 Ash Tower, Updated Background
 Concentration.
All changes; Lower CEV until          4,500  Ash Landfill.....  Robindale Heights.........  Supplemental.....  Updated SIP (2016-18).....     191.85440
 compliance.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    When EPA used the same inputs as the commenter's except replaced 
the receptor grid with the Pennsylvania supplemental grid, EPA's 
analysis produced a peak concentration over 300 [micro]g/m\3\ as 
opposed to the commenter's concentration of 213 [micro]g/m\3\. In the 
next iteration, EPA used the supplemental grid, and the Ash Landfill 
meteorological data, and the concentrations in the area of the original 
modeled violation went below the NAAQS and the maximum modeled 
concentration now occurred in a location north-northeast of the 
Conemaugh and Seward power plants in East Wheatfield Township near 
Robindale Heights.
    Finally, EPA completed a model run with all the updates from the 
supplemental modeling: The Ash

[[Page 66252]]

Landfill met data, supplemental receptor grid, and updated background 
concentration from 2016-18. When all the updates were modeled, Seward's 
1-hour modeled CEV (for the supplemental run) had to be reduced (about 
11% from the original modeling analysis) to show compliance with the 
NAAQS. A detailed description of EPA's analysis can be found in the 
June 2020 Supplemental Modeling TSD (Appendix B).
    Based on the AERMOD simulations provided which show that no 
receptors in the nonattainment area exceed the NAAQS, EPA believes the 
revised CEV for Seward and the pre-existing CEV for Conemaugh are 
protective of the 1-hour SO2 NAAQS.
    Pennsylvania submitted updated RRE model simulations using the 
site-specific Ash Landfill meteorological data, updated receptor grid, 
updated background concentration, and updated operating information 
(2016-2018) at Seward. The 30-day emission limit for Seward is below 
the newly submitted CEV, and the updated RRE modeling provides evidence 
that this limit is protective of the NAAQS (as described in Response 
3). EPA solicited public comments on this updated modeling in a notice 
of data availability published on March 9, 2020 at 85 FR 13602. A more 
detailed analysis of the RRE modeling for Seward is provided in the 
February 2020 RRE Modeling TSD.
    Comment 13. The commenter asserts that the SIP is not approvable 
because the AECOM modeling is improperly based on ``representative 
future operations'' that are not enforceable. The modeling evaluated 
hourly emissions from 2014 through 2016 and assumed similar future 
operations in its 100 RRE model simulations. However, the commenter 
argues that there is no mechanism proposed (enforceable or otherwise) 
to ensure future distribution of emissions do not change such that a 
NAAQS violation would occur.
    Response 13. While the comment is somewhat ambiguous, EPA 
interprets this comment to express concerns that the modeled emissions 
reflect a variability that may not occur in the future. Other comments 
by this commenter discussed previously spoke more precisely to maximum 
allowable emissions; those comments were answered previously. EPA is 
expecting states to set limits that reflect expected normal degrees of 
variability (at the 99th percentile level).\21\ EPA does not believe 
that the constraints on operation inherent in restricting emissions 
distributions are workable, warranted, or appropriate. EPA believes 
that air quality is likely to be relatively insensitive to differences 
among normal emission distributions. In addition, the intention of 
allowing longer term SO2 limits was to provide sources some 
degree of operating flexibility while still attaining the 2010 
SO2 NAAQS. Requiring that the sources maintain a specific 
emission profile would greatly hamper any flexibility provided by a 
longer term limit.
---------------------------------------------------------------------------

    \21\ EPA uses the term ``variability'' to address the shape of 
the distribution of a facility's emissions, in particular to be a 
measure of how much variation exists between upper emission levels 
and more common emission levels. EPA's guidance recommends a 
specific procedure, delineated in appendix C, for taking one measure 
of variability, to obtain a quantitative indication of how the 
typical range of emissions from a facility influences the relative 
magnitude of long term average emissions versus 1-hour values. While 
Pennsylvania did not use this procedure, the principle in EPA's 
guidance that historic variability may be used in many cases to 
predict future variability, without the need for explicit 
limitations on variability, nevertheless applies here.
---------------------------------------------------------------------------

    EPA believes the RRE modeling provided by Pennsylvania in the 
original submittal and supplemented on February 5, 2020 provides the 
technical evidence that the longer term emission limits (i.e., 30 day 
rolling average and 24-hour average) at Seward and Keystone are 
protective of the NAAQS. EPA agrees that the future distribution of 
hourly emissions for either source will not be exactly the same as 
those modeled in the RRE demonstration, but does not agree that an 
enforceable mechanism is required to ensure that the future 
distribution of emissions do not change. EPA believes that the longer 
term limits provide the constraints necessary to protect the NAAQS.
    The commenter did not provide any analysis, modeling or otherwise, 
showing that adherence with these limits with a different emissions 
distribution would violate the NAAQS.
    The commenter may be assuming that future operations at Seward and 
Keystone would change significantly in a way that generates much higher 
hourly SO2 emissions than those observed over the RRE 
emission survey years, even while complying with their emission limits. 
If so, no justification or analysis was provided to support such an 
assumption. EPA believes that even if this source operates at higher 
heat inputs in the future, the emission limits will constrain 
operations and continue to provide protection of the NAAQS. 
Nonetheless, EPA researched the regional transmission organization's 
(PJM's) projected electric demand and analyzed historic emission trends 
at Seward and Keystone to better understand the potential for a change 
in emissions in the future. Based on the review of PJM forecasts, EPA 
contends that it is highly unlikely that Seward or Keystone will 
operate at much higher levels in the future. Furthermore, hourly 
operations and emissions data from Keystone and Seward collected under 
part 75 of the CAA also show no long-term increase in operating levels 
(total hours of operation and MMBtu/hr) over the past 10 years. Both of 
these sources of information strongly suggest that the plants will not 
increase their hours of operation or level of operation. EPA further 
finds no reason to believe that the shape of the distribution of these 
plants' emissions will change in a way that indicates greater 
variability. EPA's assessment of this data is available in the Part 75 
Emissions TSD available in the docket for this action.
    Comment 14. The commenter asserts that EPA's proposed approval 
fails to meet the CAA statutory deadline for issuing a Federal 
Implementation Plan (FIP) because the SIP was not approved by March 8, 
2018 (two years after EPA issued a finding of failure to submit), and 
EPA must impose sanctions on Pennsylvania for failing to submit a 
lawful, approvable SIP.
    Response 14. The comment raises issues that are not relevant to the 
action EPA must take here, which is to either approve or disapprove the 
submitted SIP. In regard to EPA's failure to issue a FIP, EPA believes 
that the most expeditious way to bring this area into attainment and 
maintain attainment is to approve the submitted SIP with the limits and 
restrictions adopted by the Commonwealth, making those limits and 
restrictions Federally enforceable and obviating any need for EPA to 
issue a FIP. We also note that neither the commenter nor any other 
entity has undertaken any effort to enforce a duty to promulgate a FIP 
for this area.
    EPA disagrees with the commenter that sanctions should have been 
applied in this case because, as discussed in the NPRM, the sanctions 
clock that was started by Pennsylvania not timely submitting its SIP 
was turned off when EPA determined that Pennsylvania subsequently 
submitted a complete SIP on October 13, 2017. See CAA 179(a); see also 
40 CFR 52.31(d)(5) (a sanctions clock started by a finding of failure 
to submit a required SIP will be permanently stopped upon a final 
finding that the deficiency forming the basis of the finding of failure 
to submit has been corrected).
    The result of EPA's final approval of the Indiana, PA attainment 
plan will be to make Federally enforceable the 24-hour average 
SO2 limits at Keystone Station and the contingency measures

[[Page 66253]]

for all four sources. The emission limits at Homer City, Conemaugh, and 
Seward were already Federally enforceable, and are also being 
incorporated into the SIP for purposes of permanently attaining the 
SO2 NAAQS.
    Comment 15. The commenter expresses concern with the RACM/RACT and 
contingency measures, questioning how EPA can incorporate the 
unredacted portions of Homer City's Plan approval, which lists an 
expiration date of August 28, 2017, and Seward's Title V Operating 
Permit, which lists an expiration date of February 11, 2017. The 
commenter asks EPA to explain why not all of the consent orders have 
compliance parameters and why the contingency measures appear to be 
compliance parameters.
    Response 15. EPA acknowledges that expiration dates were 
inadvertently included in the unredacted portions of Homer City's Plan 
approval and Seward's Title V Operating Permit. Pennsylvania has 
submitted corrected redacted permits which redact the expiration dates, 
such that the limits may be considered permanent. These corrected 
permits will be incorporated into the SIP, and will remain in effect 
unless and until Pennsylvania submits a SIP revision seeking changes to 
these incorporated permit terms and EPA approves such revisions after 
evaluating whether such a revision would interfere with NAAQS 
attainment, as required by CAA section 110(l). EPA also notes that the 
SO2 emission limits listed in these permits for Homer City 
and Seward did not actually expire on the dates listed in the 
originally submitted permits. Both permits were properly extended per 
the state permitting requirements and Title V of the CAA.
    Concerning the request for an explanation of why contingency 
measures appear to be compliance parameters, EPA notes that the 2014 
SO2 Nonattainment Guidance describes special features of the 
pollutant SO2 and therefore SO2 planning that 
warrant the adoption of alternative means of addressing the requirement 
in section 172(c)(9) for contingency measures. The control efficiencies 
for SO2 control measures are well understood and are far 
less prone to uncertainty than for other criteria pollutants. Because 
SO2 control measures are based on what is directly and 
quantifiably necessary to attain the SO2 NAAQS, it would be 
unlikely for an area to implement the necessary emission controls yet 
fail to attain the NAAQS. See 2014 SO2 Nonattainment Area 
Guidance, page 41. Therefore, for SO2 programs, EPA has 
explained that contingency measures can mean that the air agency has a 
comprehensive program to identify sources of violations of the 
SO2 NAAQS and to undertake an aggressive follow-up for 
compliance and enforcement, including expedited procedures for 
establishing enforceable consent agreements pending the adoption of the 
revised SIP. EPA believes that this approach continues to be valid for 
the implementation of contingency measures to address the 2010 
SO2 NAAQS, and consequently concludes that Pennsylvania's 
comprehensive enforcement program, as discussed later, satisfies the 
contingency measure requirement.
    Pennsylvania has a comprehensive enforcement program as specified 
in Section 4(27) of the Pennsylvania Air Pollution Control Act (APCA), 
35 P.S. Sec.  4004(27). Under this program, Pennsylvania is authorized 
to take any action it deems necessary or proper for the effective 
enforcement of the Act and the rules and regulations promulgated under 
the Act. Such actions include the issuance of orders (for example, 
enforcement orders and orders to take corrective action to address air 
pollution or the danger of air pollution from a source) and the 
assessment of civil penalties. Sections 9.1 and 10.1 of the APCA, 35 
P.S. Sec. Sec.  4009.1 and 4010.1, also expressly authorize 
Pennsylvania to issue orders to aid in the enforcement of the APCA and 
to assess civil penalties.
    Any person in violation of the APCA, the rules and regulations, any 
order of PADEP, or a plan approval or operating permit conditions could 
also be subject to criminal fines upon conviction under Section 9, 35 
P.S. Sec.  4009. Section 7.1 of the APCA, 35 P.S. Sec.  4007.1, 
prohibits PADEP from issuing plan approvals and operating permits for 
any applicant, permittee, or a general partner, parent or subsidiary 
corporation of the applicant or the permittee that is placed on PADEP's 
Compliance Docket until the violations are corrected to the 
satisfaction of PADEP.
    In addition to having a fully approved enforcement program, 
Pennsylvania has included contingency measures that are triggered when 
any of the four SIP sources' emissions reach a certain percentage of 
the allowable emissions or if the Strongstown monitor in the 
nonattainment area registers a daily maximum 1-hour average 
concentration exceeding 75 ppb. These measures are in line with the 
supplemental contingency measure guidance EPA mentions previously and 
are included in the Homer City COA, Seward COA, Conemaugh Order and the 
Keystone Order, and thus will be fully approved provisions within the 
SIP.
    EPA concludes, in accordance with the 2014 SO2 
Nonattainment Guidance, that Pennsylvania's enforcement program 
suffices to satisfy the contingency measure requirements for 
SO2. The magnitude of prospective benefit from 
Pennsylvania's supplemental contingency measures is unclear, but it is 
clear that these measures can only improve, and will not worsen, air 
quality. EPA believes that Pennsylvania's enforcement program, which is 
enhanced by the supplementary provisions in the COAs and Orders, 
suffice to meet Section 172(c)(9) requirements as interpreted in the 
1992 General Preamble and the 2014 SO2 Nonattainment 
Guidance.
    In regard to the commenter's question as to why all of the consent 
orders do not contain compliance parameters, the compliance parameters 
can be found in either the COA, Orders or permits that are being 
incorporated into the SIP. EPA is interpreting the term ``compliance 
parameters'' in the comment to mean any specified method for 
determining compliance with the emission limits. The compliance 
parameters for Seward, Homer City and Conemaugh are found in the 
respective redacted permits, and the compliance parameters for Keystone 
are found in the Order. The COA or Orders for Seward, Homer City and 
Conemaugh do not have compliance parameters, as they are contained in 
the redacted permits.
    Comment 1 on NODA. The commenter expresses concern with the idea 
that the newly calculated CEV for Seward of 4,500 lbs/hr, which is less 
than the original CEV of 5,079 lbs/hr, still supports the 3,038 lbs/hr 
30-day average emission limit for Seward. The commenter concludes that 
the prior Seward CEV used to calculate the emission limit in the 
original submittal was too high and accordingly that the 3,038 lbs/hour 
emission limit itself is too high.
    Response 1 on NODA. EPA recognizes the concern that the prior CEV 
calculated for Seward was higher than the newly calculated CEV, but the 
longer term limit has not changed. While this would not necessarily 
occur if Pennsylvania had followed the methodology described in 
Appendix C, they did not. Pennsylvania opted to use a different 
approach to calculate the longer term limits (their approach was the 
same in the original submittal as in the supplemental submittal). 
Pennsylvania did not rely on adjustments from the CEV as set forth by 
the approach in Appendix C. Therefore, a reduction in the CEV does not 
necessarily dictate a reduction in the longer term limit. Instead, 
Pennsylvania

[[Page 66254]]

provided an updated RRE modeling analysis demonstrating that Seward's 
30-day average emission limit of 3,038 lbs/hr is protective of the 
NAAQS.\22\
---------------------------------------------------------------------------

    \22\ PADEP did not provide an updated RRE analysis for Keystone, 
only for Seward.
---------------------------------------------------------------------------

    The supplemental modeling analysis provided on February 5, 2020 
included updated and more accurate meteorological data, a more refined 
receptor grid and updated emission profiles. These updates were 
incorporated into both the CEV AERMOD simulations and the RRE AERMOD 
simulations. EPA's February 2020 RRE Modeling TSD located in the docket 
for this rulemaking explains EPA's review of Pennsylvania's updated RRE 
analysis and is also addressed in Response 3 of this preamble.
    EPA reviewed Seward's emissions data which indicates a decline in 
emissions variability.\23\ In particular, while a comparison of 2014 to 
2016 data against 2016 to 2018 shows fairly similar or even slightly 
increasing 99th percentile 30-day average values, these data also show 
a significant decline in the 99th percentile 1-hour values. This 
decreased difference between peak 1-hour values and peak 30-day average 
values, indicating a decline in this critical measure of variability, 
appears to be an important factor in Pennsylvania's supplemental 
modeling (using emissions reflecting the more recent, less variable 
emissions) concluding that the same 30-day average limit in the 
original modeling (using emissions reflecting the older, more variable 
emissions) still suffices to show attainment. The 2017 to 2019 data 
indicate that this trend toward less variable emissions appears to be 
continuing.
---------------------------------------------------------------------------

    \23\ Clean Air Market Division data submitted to EPA from PADEP 
on February 5, 2020.
---------------------------------------------------------------------------

    Comment 2 on NODA. The commenter states that AECOM justified the 
conversion factor of 0.68 for Seward by comparing it to Table 1 of 
Appendix D of EPA's 2014 SO2 Nonattainment Guidance for 
sources with dry scrubbers (which lists the conversion factor as 0.63). 
The commenter points out that 0.63 is significantly lower than 0.68, 
yet significantly higher than the 0.47 conversion factor AECOM 
calculated using Appendix C methodology for Seward, but ultimately 
decided to not use. The commenter states that Seward is a waste coal 
plant and is less likely to operate similarly to the coal fleet as a 
whole, which may be why using Appendix C methodology supports a 
conversion factor of 0.47.
    Response 2 on NODA. A conversion factor was not used to calculate 
the longer term limit for Seward. While a ratio between the 30-day 
average limit for Seward and the CEV may be calculated, and this ratio 
may be compared to the adjustment factor that would be derived using 
the procedures in Appendix C, the concept of a conversion factor is not 
directly relevant to the calculation of Seward's longer term limit. EPA 
acknowledges that the CEV provides an upper bound for the value of a 
potential longer term limit (i.e., the longer term limit cannot be 
greater than the CEV). However, that is the extent to which the CEV was 
used in Pennsylvania's development of Seward's 30-day limit. Instead, 
Pennsylvania provided updated 100 RRE AERMOD simulations as reasonable 
evidence that the longer-term emission limit for Seward is protective 
of the NAAQS. More details on Pennsylvania's methodology for developing 
Seward's longer term limit is provided in Response 3 of this preamble, 
and in the RRE Modeling TSD.
    Comment 3 on NODA. The commenter expressed concern that the 
modeling analysis did not include areas outside the nonattainment area 
boundary. The commenter claims that by hiding areas with peak impacts 
above the NAAQS, the AECOM analysis undercalculates CEVs, and thereby 
fails to assess emission limits low enough to protect the NAAQS.
    Response 3 on NODA. As discussed in more detail in Response 10 of 
this preamble, absent a clear requirement that Pennsylvania must 
include model receptors outside of the nonattainment area in its 
submission, EPA will confine its analysis to whether the attainment SIP 
demonstrates attainment within the designated nonattainment area.
    Comment 4 on NODA. The commenter requested that EPA extend this 
public comment period due to the National Covid-19 Pandemic. 
Specifically, the commenter requested an additional 30 days after the 
President's National Emergency Order or Governor Wolf's State Emergency 
Order are pulled back.
    Response 4 on NODA. EPA is not able to extend the public comment 
period for this NODA, particularly when the request seeks an additional 
30 day period after some unknown future date when the President's or 
Governor's Emergency Order is withdrawn. EPA is under an October 30, 
2020 court-ordered deadline to take action on this SIP, and therefore 
an indeterminate delay would require an amendment of that court order, 
and EPA could not be assured that such an extension could be obtained, 
particularly when the amount of time of the extension is tied to 
Emergency Orders with indefinite end dates. Also, EPA believes that 
issuance of the President's and Governor's orders did not significantly 
hamper the public's ability to comment because the supplemental 
information and all materials necessary to evaluate that supplemental 
information were available electronically in the docket or by 
contacting EPA for this matter. For these reasons, EPA did not grant 
the commenter's request for an indefinite extension of the public 
comment period.

IV. Final Action

    EPA is approving the attainment plan for the Indiana, PA 
SO2 nonattainment area as a revision to the Pennsylvania SIP 
as submitted by PADEP to EPA on October 11, 2017 and supplemented on 
February 5, 2020. Specifically, EPA is approving the base year 
emissions inventory, a modeling demonstration of SO2 
attainment, an analysis of RACM/RACT, an RFP plan, and contingency 
measures for the Indiana Area and is finding that the Pennsylvania SIP 
revision has met the requirements for NNSR for the 2010 1-hour 
SO2 NAAQS. Additionally, EPA is approving into the 
Pennsylvania SIP the SO2 emission limits and compliance 
parameters in the following Orders, Consent Order and Agreements (COAs) 
and permits: the unredacted portion of the Order between Pennsylvania 
and Genon NE Management Company, Conemaugh Plant; the unredacted 
portions of the Consent Order and COA between Pennsylvania and Homer 
City Generation, LP; the unredacted portions of the Order between 
Pennsylvania and Genon NE Management Company, Keystone Plant; the 
unredacted portions of the COA between Pennsylvania and Seward 
Generation, LLC; the unredacted portions of the Title V Permit for 
Conemaugh Plant (provided to EPA on May 13, 2020); the unredacted 
portions of the Plan Approval for Homer City (provided to EPA on May 
13, 2020); and the unredacted portion of the Title V Operating Permit 
for Seward Station (provided to EPA on May 13, 2020).
    EPA has determined that Pennsylvania's SO2 attainment 
plan for the 2010 1-hour SO2 NAAQS for the Indiana Area 
meets the applicable requirements of the CAA and is consistent with 
EPA's 2014 SO2 Nonattainment Guidance where applicable. 
Thus, EPA is approving Pennsylvania's attainment plan for the Indiana 
Area as submitted on October 11, 2017 and supplemented on February 5, 
2020. This final action of this SIP submittal removes EPA's duty to 
implement a FIP for this Area, and

[[Page 66255]]

discharges EPA's requirement under the court order entered in Center 
for Biological Diversity, et al., v. Wheeler, No. 4:18-cv-03544 (N.D. 
Cal., Nov. 26, 2019) to sign final action on the SIP by October 30, 
2020.

V. Incorporation by Reference

    In this document, EPA is finalizing regulatory text that includes 
incorporation by reference. In accordance with requirements of 1 CFR 
51.5, EPA is finalizing the incorporation by reference of the 
unredacted portions of the Order between Pennsylvania and Genon NE 
Management Company, Conemaugh Plant; the unredacted portions of the 
Consent Order and Agreement (COA) between Pennsylvania and Homer City 
Generation, LP; the unredacted portions of the Order between 
Pennsylvania and Genon NE Management Company, Keystone Plant; the 
unredacted portions of the COA between Pennsylvania and Seward 
Generation, LLC; the unredacted portions of the Title V Permit for 
Conemaugh Plant (provided to EPA on May 13, 2020); the unredacted 
portions of the Plan Approval for Homer City (provided to EPA on May 
13, 2020); and the unredacted portion of the Title V Operating Permit 
for Seward Station (provided to EPA on May 13, 2020). EPA has made, and 
will continue to make, these materials generally available through 
https://www.regulations.gov and at the EPA Region III 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.\24\
---------------------------------------------------------------------------

    \24\ 62 FR 27968 (May 22, 1997).
---------------------------------------------------------------------------

VI. Statutory and Executive Order Reviews

A. General Requirements

    Under the CAA, the Administrator is required to approve a SIP 
submission that complies with the provisions of the CAA and applicable 
Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in 
reviewing SIP submissions, EPA's role is to approve state choices, 
provided that they meet the criteria of the CAA. Accordingly, this 
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 it is not a significant regulatory 
action 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).
    In addition, this rule does not have tribal implications as 
specified by Executive Order 13175 (65 FR 67249, November 9, 2000), 
because the SIP is not approved to apply in Indian country located in 
the state, and EPA notes that it will not impose substantial direct 
costs on tribal governments or preempt tribal law.

B. Submission to Congress and the Comptroller General

    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).

C. Petitions for Judicial Review

    Under section 307(b)(1) of the CAA, petitions for judicial review 
of this action must be filed in the United States Court of Appeals for 
the appropriate circuit by December 18, 2020. 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 approving the attainment plan for the Indiana, PA 
SO2 nonattainment area 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, Particulate matter, Reporting 
and recordkeeping requirements, Sulfur oxides.

    Dated: October 13, 2020.
Cosmo Servidio,
Regional Administrator, Region III.

    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 NN--Pennsylvania

0
2. In Sec.  52.2020:
0
a. The table in paragraph (d)(3) is amended by adding entries for 
``Conemaugh Plant, Genon NE Management Co.'', ``Title V permit 32-
00059''; ``Conemaugh Plant, Genon NE Management Co.'', ``Order''; 
``Homer City Generation'', '' Plan Approvals 32-00055H and 32-00055I''; 
``Homer City

[[Page 66256]]

Generation'', ``Consent Order and Agreement''; ``Seward Station'', 
``Title V Permit 32-00040''; ``Seward Station'', ``Consent Order and 
Agreement''; and ``Keystone Station'', ``Consent Order and Agreement'' 
at the end of the table; and
0
b. The table in paragraph (e)(1) is amended by adding an entry for 
``Attainment Plan for the Indiana, Pennsylvania Nonattainment Area for 
the 2010 Sulfur Dioxide Primary National Ambient Air Quality Standard'' 
at the end of the table.
    The additions read as follows:


Sec.  52.2020  Identification of plan.

* * * * *
    (d) * * *
    (3) * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                            State                               Additional explanation/
           Name of source                  Permit No.                 County           effective date    EPA approval date      Sec.   52.2063 citation
--------------------------------------------------------------------------------------------------------------------------------------------------------
 
                                                                      * * * * * * *
Conemaugh Plant, Genon NE            Title V permit 32-      Indiana.................        10/28/15  10/19/20, [Insert      Sulfur dioxide emission
 Management Co.                       00059.                                                            Federal Register       limits and associated
                                                                                                        citation].             compliance parameters in
                                                                                                                               unredacted portions of
                                                                                                                               the Title V permit
                                                                                                                               provided to EPA on May
                                                                                                                               13, 2020.
Conemaugh Plant, Genon NE            Order.................  Indiana.................        10/11/17  10/19/20, [Insert      Contingency measures in
 Management Co.                                                                                         Federal Register       unredacted portion of the
                                                                                                        citation].             Order.
Homer City Generation..............  Plan Approvals 32-      Indiana.................         2/28/17  10/19/20, [Insert      Sulfur dioxide emission
                                      00055H and 32-00055I.                                             Federal Register       limits and associated
                                                                                                        citation].             compliance parameters in
                                                                                                                               unredacted portions of
                                                                                                                               the Plan Approvals
                                                                                                                               provided to EPA on May
                                                                                                                               13, 2020.
Homer City Generation..............  Consent Order and       Indiana.................         10/3/17  10/19/20, [Insert      Contingency measures in
                                      Agreement.                                                        Federal Register       unredacted portion of
                                                                                                        citation].             Consent Order and
                                                                                                                               Agreement.
Seward Station.....................  Title V Permit 32-      Indiana.................          4/8/16  10/19/20, [Insert      Sulfur dioxide emission
                                      00040.                                                            Federal Register       limits and associated
                                                                                                        citation].             compliance parameters in
                                                                                                                               unredacted portions of
                                                                                                                               the Title V permit
                                                                                                                               provided to EPA on May
                                                                                                                               13, 2020.
Seward Station.....................  Consent Order and       Indiana.................         10/3/17  10/19/20, [Insert      Contingency measures in
                                      Agreement.                                                        Federal Register       unredacted portion of the
                                                                                                        citation].             Consent Order and
                                                                                                                               Agreement.
Keystone Plant.....................  Consent Order.........  Armstrong...............         10/1/18  10/19/20, [Insert      Sulfur dioxide emission
                                                                                                        Federal Register       limits established with
                                                                                                        citation].             AERMOD modeling without
                                                                                                                               AERMOIST and related
                                                                                                                               parameters in unredacted
                                                                                                                               portions of the Consent
                                                                                                                               Order dated 10/11/17.
--------------------------------------------------------------------------------------------------------------------------------------------------------

* * * * *
    (e) * * *
    (1) * * *

----------------------------------------------------------------------------------------------------------------
   Name of non-regulatory SIP        Applicable        State submittal                           Additional
            revision               geographic area          date         EPA approval date       explanation
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
Attainment Plan for the          Indiana County and  10/11/17            10/19/20, [Insert  52.2033(f).
 Indiana, Pennsylvania            portions of         Supplemental        Federal Register
 Nonattainment Area for the       Armstrong County    information         citation].
 2010 Sulfur Dioxide Primary      (Plumcreek          submitted 02/05/
 National Ambient Air Quality     Township, South     20, redacted
 Standard.                        Bend Township,      permits submitted
                                  and Elderton        on 05/13/20.
                                  Borough).
----------------------------------------------------------------------------------------------------------------


[[Page 66257]]

* * * * *

0
3. Amend Sec.  52.2033 by adding paragraph (f) to read as follows:


Sec.  52.2033  Control strategy: Sulfur oxides.

* * * * *
    (f) EPA approves the attainment demonstration State Implementation 
Plan for the Indiana, PA Nonattainment Area submitted by the 
Pennsylvania Department of Environmental Protection on October 11, 
2017, updated on February 5, 2020, and corrected permits and plan 
approvals submitted on May 13, 2020.

[FR Doc. 2020-23037 Filed 10-16-20; 8:45 am]
BILLING CODE 6560-50-P