[Federal Register Volume 87, Number 159 (Thursday, August 18, 2022)]
[Rules and Regulations]
[Pages 50778-50785]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-17449]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R03-OAR-2017-0615; FRL-9607-02-R3]


Air Plan Partial Disapproval and Partial 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 revising its 
prior action that erroneously fully approved a state implementation 
plan (SIP) revision submitted by the Commonwealth of Pennsylvania (PA), 
through the Pennsylvania Department of Environmental Protection 
(PADEP), to EPA on October 11, 2017, and supplemented on February 5, 
2020. The SIP revision provided a plan for attainment of the 2010 
sulfur dioxide (SO2) primary national ambient air quality 
standard (NAAQS) in the Indiana, Pennsylvania SO2 
nonattainment area (hereafter referred to as the ``Indiana, PA NAA'' or 
``Indiana Area''). The attainment plan submission included a base year 
emissions inventory, an analysis of the reasonably available control 
technology (RACT) and reasonably available control measure (RACM) 
requirements, enforceable emission limitations and control measures, a 
reasonable further progress (RFP) plan, a modeling demonstration of 
SO2 attainment, and contingency measures for the Indiana 
Area. EPA is revising its prior action and is partially approving and 
partially disapproving the SIP. This action is being taken under the 
Clean Air Act (CAA).

DATES: This final rule is effective on September 19, 2022.

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 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 
www.regulations.gov, or please contact the person identified in the For 
Further Information Contact section for additional availability 
information.

FOR FURTHER INFORMATION CONTACT: Megan Goold, Planning & Implementation 
Branch (3AD30), Air & Radiation Division, U.S. Environmental Protection 
Agency, Region III, Four Penn Center, 1600 John F. Kennedy Boulevard, 
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 March 17, 2022 (87 FR 15166), EPA published a notice of proposed 
rulemaking (NPRM) for the Commonwealth of Pennsylvania. In the NPRM, 
EPA provided notice to the Commonwealth and the public and described 
the basis for its determination that it had erroneously fully approved 
the Indiana, PA SO2 Attainment Plan, and proposed to revise 
its formal approval of the Plan to a partial disapproval and partial 
approval. See CAA section 110(k)(6). The formal SIP revision was 
originally submitted by Pennsylvania on October 11, 2017, and later 
supplemented on February 5, 2020. EPA took final action approving this 
attainment plan on October 19, 2020 (85 FR 66240).
    On December 18, 2020, the Sierra Club, Clean Air Council, and 
PennFuture filed a petition for judicial review with the U.S. Court of 
Appeals for the Third Circuit, challenging that final approval.\1\ On 
April 5, 2021, EPA filed a motion for voluntary remand without vacatur 
of its approval of the Indiana, PA SO2 attainment plan. On 
August 17, 2021, the U.S. Court of Appeals for the Third Circuit 
granted EPA's request for remand without vacatur of the final approval 
of Pennsylvania's SO2 attainment plan for the Indiana, PA 
NAA, and required that EPA take final action in response to the remand 
no later than one year from the date of the court's order (i.e., by 
August 17, 2022). This action finalizes EPA's response to the court's 
order.
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    \1\ Sierra Club, et. al v. EPA, Case No. 20-3568 (3rd Cir.).
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II. Summary of SIP Revision and EPA Analysis

    In accordance with section 172(c) of the CAA, the Pennsylvania 
attainment plan for the Indiana Area includes an emissions inventory 
for SO2 for the plan's base year (2011) and an attainment 
demonstration. The 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 contributing to SO2 
concentrations in the Area (Keystone, Conemaugh, Homer City, and 
Seward) purporting to show 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 
new source review (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 February 5, 2020, in response to comments submitting during the 
proposal's public comment period, PADEP submitted supplemental 
information in support of the attainment plan. The February 5, 2020 
submittal included: (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 through the third quarter of 
2019. The supplemental air dispersion modeling used a more refined 
model receptor grid than that in 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). In order to allow 
for public comment on this supplemental

[[Page 50779]]

information and modeling, on March 9, 2020 (85 FR 13602), EPA published 
a notice of data availability (NODA) for the February 5, 2020, 
submittal.
    EPA now has determined that it was in error to fully approve the 
Indiana, PA SO2 attainment plan, and is revising and 
correcting its prior action in the same manner as the prior full 
approval without further submission from the Commonwealth. See CAA 
section 110(k)(6). EPA is retaining the approval of the emissions 
inventory and nonattainment new source review (NNSR) program 
requirements, and is finalizing disapproval of the attainment 
demonstration, RACM/RACT requirements, RFP requirements, and 
contingency measures.
    Other specific requirements of section 172(c) and the rationale for 
EPA's proposed and final action are explained in the NPRM, and its 
associated technical support document (TSD), and will not be restated 
here.

III. EPA's Response to Comments Received

    EPA received two sets of comments on the notice of proposed 
rulemaking for this action. A summary of the comments and EPA's 
responses are provided below. To view the full set of comments, refer 
to the docket for this action, Docket EPA-R03-OAR-2017-0615.
    Comment 1: The commenter disagrees that the SIP did not include an 
assessment showing that the longer-term average limits for Keystone and 
Seward are of comparable stringency to the one-hour Critical Emissions 
Value (CEV). The commenter believes that Appendix C of EPA's 2014 
Guidance for 1-hour SO2 Nonattainment Area SIP Submissions 
\2\ (``2014 Guidance'') is a statistical approach and is a surrogate 
approach that was justified by Appendix B, such that Appendix C is a 
theorem and Appendix B is the proof. The commenter states that the 
Randomly Reassigned Emissions (RRE) modeling approach provides a very 
robust demonstration of a comparably stringent relationship between the 
modeling results of the CEV analysis and the RRE analysis. The 
commenter believes the facts below support that the longer-term average 
limits have been shown to be comparably stringent to the one-hour CEV, 
and that the RRE modeling is thorough in testing the emissions 
distributions that had the following attributes:
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    \2\ EPA Guidance for 1-hour SO2 Nonattainment Area 
SIP Submissions, April 23, 2014, www.epa.gov/sites/default/files/2016-06/documents/20140423guidance_nonattainment_sip.pdf.
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    1. The emissions used in the RRE modeling followed Appendix C of 
the 2014 Guidance because they reflected the distribution of emissions 
expected once the attainment plan had been implemented.
    2. High emission events were modeled in a way that is 
representative of both the variability shown by the 2016 emissions data 
and of the expected distribution of emissions occurring in compliance 
with the allowable longer-term average emissions limits.
    3. High emission events (i.e., hours with emissions above the CEV) 
were randomly placed throughout the year in the modeling in order to 
examine combinations of high emissions and varying meteorology.
    4. Each of the 100 runs resulted in modeled design values below the 
NAAQS, which the commenter asserts is a stringent requirement that is 
equivalently stringent to the modeling results for the one-hour CEV 
analysis, which has the same modeling outcome.
    Therefore, the commenter asserts that Pennsylvania's RRE modeling 
did incorporate the necessary steps to establish the comparably 
stringent relationship between a modeled one-hour CEV and the longer-
term average limits.
    The commenter also asserts that the fact that its RRE modeling 
approach--which EPA used in Appendix B to test the statistical 
adjustment approach in Appendix C--results in different longer-term 
average limits than the Appendix C approach in this specific case, is 
not contrary to the 2014 Guidance because they both demonstrate 
attainment. They argue that the direct use of the submitted modeling 
approach can be viewed as the gold standard, with a very high level of 
confidence that the emissions distribution is protective of the NAAQS.
    The commenter also claims that Appendix B uses an emissions 
distribution that is expected once the plan is in place, which is the 
same type of emissions data used in the Appendix C approach. The 
commenter continues that EPA's guidance does not require the use of the 
99th percentile of historic hourly data in the future emissions 
profile.
    The commenter is also concerned that EPA is requiring a clear link 
between the modeled one-hour CEV and the longer-term average emission 
limits even though the words ``clear'' and ``link'' do not appear in 
the 2014 Guidance document. Although the commenter disagrees with the 
requirement to demonstrate a clear link between the modeled 1-hr CEV 
and the longer-term average limits, and with EPA's position that its 
modeled future emissions scenarios must represent the worst case 
emissions scenarios permissible under the limit, the commenter believes 
that the RRE modeling has satisfied those requirements because, (1) the 
CEV was used as one of the bins in the modeling, thus demonstrating a 
clear link in the commenter's view, and (2) based on the commenter's 
comparison of modeled emissions (future expected emissions), and actual 
emissions from 2017-2021 for Keystone and Seward, the sources have 
actually had a fewer number of hours above the CEV than was modeled, 
and there have been no observed one-hour emissions from either source 
equaling or exceeding the highest hourly emissions used in the peak 
modeled emissions bin.
    The commenter continues that discount factors were calculated from 
the RRE modeling of 0.989 for Keystone and 0.686 for Seward, which are 
consistent with the range of the discount values listed in Appendix D.
    Response 1: In general, the commenter is misinterpreting the 2014 
Guidance and conflating the use of Appendix B of the guidance as an 
apparent alternate method of satisfying the SIP requirements. A SIP 
requires that the plan provide for attainment of the NAAQS. Attainment 
of the NAAQS is successfully demonstrated when the affected sources 
operate within the limits in the plan such that emissions from any and 
all variable operating scenarios are in compliance with those limits 
and do not lead to NAAQS violations. Modeling the maximum one-hour 
emission rate (i.e., the maximum allowable rate or `worst-case') that 
yields a design concentration below the NAAQS is the means by which the 
SIP provides for attainment. So, a one-hour limit is the mechanism for 
providing for attainment in the SIP. In the alternative to the one-hour 
limit, the 2014 Guidance provides flexibility for developing limits 
with longer-term averages (up to 30-days). Appendix C describes the 
method to develop longer-term limits that are comparably stringent to 
the maximum one-hour limit. Appendix C uses the 99th percentile 
distribution of emissions to ensure that the longer-term limits are 
appropriately adjusted to be comparably stringent, and by extension, 
provide for attainment. Appendix B is merely a diagnostic tool using a 
statistical example as a back check to demonstrate that the 99th 
percentile consideration used in Appendix C is the appropriate means to 
show comparable stringency.

[[Page 50780]]

Appendix B is not a tool which can be decoupled from Appendix C to 
develop limits sufficient to provide for attainment. Accordingly, the 
state SIP cannot be said to provide for attainment because the longer-
term limits have not been shown to be comparably stringent to the one-
hour maximum allowable value. The worst case emissions scenario has not 
been simulated (for example by a 99th percentile evaluation of the 
emission distribution), and therefore the RRE analysis does not 
demonstrate that the longer-term limit that the commenter claims is 
proven by the RRE analysis will provide for attainment actually does 
so, when it was performed by modeling future expected operating 
scenarios that did not simulate worst case conditions. Using Appendix B 
as a standalone tool to develop emission limits, as the state has done 
here, is not appropriate without considering worst case emissions, 
which is accomplished by linking to the CEV as is reflected in Appendix 
C. The variable emissions modeling approach used by the state provides 
no direct means of assessing whether any particular long-term limit is 
of comparable stringency to any particular one-hour limit.
    The 2014 Guidance did not remove the requirement for an attainment 
demonstration to be based on maximum allowable emissions (as the 
commenter implies), nor did it recommend basing attainment modeling on 
an expected hourly distribution of emissions once the attainment plan 
had been implemented (as the commenter implies). The 2014 Guidance 
stated that ``for SO2 modeling, maximum allowable emissions 
are the basis of the emissions input to the model in accordance with 
Section 8 of Appendix W and past SO2 guidance (U.S. EPA, 
1994).'' (2014 Guidance, pg. A-5). Furthermore, the Guidance used the 
term critical emission value to refer to the hourly emission rate that 
the model predicts would result in the 5-year average of the annual 
99th percentile of daily maximum hourly SO2 concentrations 
at the level of the one-hour NAAQS, given representative meteorological 
data for the area. (2014 Guidance, pg. 23). The guidance provided a 
methodology by which the maximum allowable modeled hourly emissions CEV 
would be clearly linked to the comparably stringent longer-term average 
limit. While the terms ``clear'' and ``link'' are not included in the 
guidance document, the methods set forth in Appendix C describe a step-
by-step process by which an adjustment factor can be calculated, which 
would then be directly applied to the CEV to create a comparably 
stringent longer-term average limit. Consequently, if the CEV changed, 
the comparably stringent longer-term limit would also change as a 
result of the application of the adjustment factor.
    Regardless of whether the guidance document uses the words `clear' 
and `link,' the absence of a direct showing that the limits in 
Pennsylvania's SIP are comparably stringent to the one-hour limits 
modeled as necessary to provide for attainment means that the plan 
presumptively does not provide adequate assurance of attainment. 
Further, the commenter does not make a consistent argument that long-
term limits may be justified by modeling a significantly different 
level of emissions (i.e., not maximum allowable emissions) than the 
emissions that must be modeled to determine one-hour limits.
    Additionally, the adjustment factor as specified in the 2014 
Guidance is derived from a statistical analysis of a set of data that 
reflect the emissions variability that the controlled source is 
expected to exhibit. Specifically, the adjustment factor is calculated 
by comparing the 99th percentile of hourly emissions data (from the 
previously described data set) compared to the 99th percentile of the 
longer-term averaging period values. This comparison at the higher end 
of the distribution (99th percentile) of data values is purposeful 
because ``the goal of the analyses is to identify a longer-term average 
limit that requires a comparable degree of control, particularly at 
times of greatest emissions as would be required by the 1-hr limit that 
would otherwise be set, the EPA would expect the analyses to compare 
the corresponding longer-term average and the 1-hr values among times 
of greatest emissions'' (2014 Guidance, pg. 29). Without undertaking 
this comparison, EPA does not believe it is able to determine that a 
longer-term average limit is comparably stringent to the one-hour limit 
that would otherwise be necessary to demonstrate attainment of the one-
hour NAAQS. The state's plan has not evaluated how the modeled 
emissions compare to worst case emissions that are allowable under the 
long-term limits, either in terms of whether the SIP modeled the 
maximum allowable emissions or in terms of whether a worst case 
distribution of emissions was modeled. Therefore, EPA does not have 
evidence that the modeled emissions was a conservative distribution of 
emissions in relation to the relevant benchmark of worst case allowable 
emissions.
    EPA does not agree that the RRE modeling provided this necessary 
type of comparably stringent analysis. First, as the commenter points 
out, although the CEV was used as one of the bins of hourly emission 
values in the modeling, the state's longer-term limit was not based on 
that CEV such that if the CEV changed the longer-term limit would in 
turn change in the same direction. As noted in the proposal for this 
rule, in the supplemental modeling analysis Pennsylvania submitted for 
Seward, when Seward's CEV decreased by 579 pounds per hour (lb/hr) 
(from 5,079 lb/hr to 4,500 lb/hr), the longer-term limit derived by 
Pennsylvania from the RRE modeling remained unchanged. The air quality 
found by modeling of variable emissions is a function of the full range 
of modeled emissions, influenced by the frequency and magnitude of 
emission values in all parts of the distribution, and so the use of the 
CEV as one of the bin values provides almost no assurance that the full 
RRE modeling analysis which includes other binned emissions is linked 
in any meaningful way to the CEV.
    Additionally, the RRE approach used the entire distribution of past 
annual hourly emissions to set a longer-term average limit, rather than 
the 99th percentile of annual hourly emissions, which does not satisfy 
EPA's recommendation to use the time of greatest emissions, and thus 
fails the Appendix C test for comparable stringency (2014 Guidance, pg. 
29).
    The commenter seems to be confused about what values in the 
analysis need to be comparably stringent; the commenter claims that the 
modeling results of the RRE modeling approach are comparably stringent 
to the one-hour CEV modeling because both show design values below the 
NAAQS. The values that need to be comparably stringent are the CEV and 
the longer-term limit, not the modeled SO2 design values.
    The modeled design values are dependent on the model inputs, 
particularly the hourly emissions modeled. While EPA recommended that 
the ``comparably stringent'' assessment be based on a set of emissions 
data that can be expected to reflect the variability of emissions once 
the subject source implements its attainment plan, this recommendation 
was in conjunction with the recommendation to use the times of greatest 
emissions (which the Guidance suggests is properly simulated by using 
the 99th percentile distribution), and to begin the comparably 
stringent analysis with the CEV. The commenter seems to have 
misconstrued these recommendations and incorrectly concluded that 
modeling an historic hourly distribution

[[Page 50781]]

of emissions for a source in an attainment modeling demonstration could 
be used as a substitute to modeling maximum allowable emissions, or to 
determining the CEV and then adjusting that value to calculate a 
comparably stringent longer-term limit. Pennsylvania's RRE modeling did 
not model maximum allowable emissions, nor did it demonstrate a 
relationship between the CEV (maximum allowable hourly emission value) 
and the longer-term average limit as recommended in EPA's 2014 Guidance 
in order to enable a conclusion that the longer-term limits are 
comparably stringent to the one-hour CEV.
    Pennsylvania's RRE analysis modeled the entire distribution of 
historic hourly emissions in 100 randomly assigned model runs; and in 
the case for Seward, it set the 30-day limit at the weighted average of 
hourly emissions modeled, and in the case for Keystone, it set the 24-
hour limit at the longer-term value that was modeled 30% of the year. 
It is questionable whether either of these longer-term average limits 
are actually being tested in the RRE model runs, or whether the model 
runs only test the distribution of hourly emissions that were modeled. 
EPA is not confident that these RRE derived longer-term limits will act 
as a constraint on the distribution of future hourly emissions to the 
same degree as the Appendix C approach using the 99th percentile value, 
and therefore EPA does not have the same degree of confidence that the 
NAAQS will not be violated. The future hourly emissions distribution 
could skew towards having more frequent hourly values above or near the 
CEV, in which case the RRE modeling performed for these sources might 
not show design values complying with the NAAQS considering the 
modeling results from the RRE modeling resulted in design values 
extremely close to the 75 parts per billion (ppb) standard (as 
discussed in more detail below). Additionally, Pennsylvania's use of a 
limited number of emission bins with a high emissions ``floor'' adds a 
further disconnect from the real distribution of worse case emissions.
    Appendix B provided results of a variety of emissions scenarios for 
a suitably adjusted longer-term average limit, which consistently 
resulted in design values between 39 and 59 ppb. EPA notes on page B-3 
of the 2014 Guidance, ``in each of these simulations a substantial 
number of hours (on average, just under one percent) had emissions 
higher than the CEV. Nevertheless, given the margin between these 
values and the NAAQS level of 75 ppb, this analysis indicates that the 
likelihood of a violation occurring with these emissions values is 
extremely low.'' The RRE modeling provided by Pennsylvania in support 
of Seward's 30-day limit and Keystone's 24-hour limit resulted in 
design values just slightly below the 75 ppb NAAQS, which provides very 
little margin by which hourly emissions could vary from those modeled 
by Pennsylvania and not cause a violation. If Pennsylvania had properly 
accounted for worst case emissions allowable under the limit, it is 
quite possible that would have shown a violation.
    Combining the impacts of using the 99th percentile of emissions 
statistics, and the large margin between the resultant modeled 
concentration in Appendix B and the level of the NAAQS, EPA is 
confident that a longer-term average limit based on the Appendix C 
methodology can be protective of the NAAQS. In contrast, the state has 
provided an RRE modeled demonstration of expected future hourly 
emissions, that when modeled, results in design values that come near 
to violating the NAAQS while also reflecting compliance with the 
longer-term average limits but at emissions scenarios not 
representative of worst case emissions levels allowed under the longer-
term average limits. The State's submission does not provide confidence 
that a comparably stringent relationship (as the commenter claims) 
exists and therefore, does not provide a sufficient level of assurance 
that the longer-term average limits provide for NAAQS attainment.
    In support of its claim that the RRE modeling demonstrated 
attainment using worst case emission scenarios, the commenter provided 
an analysis which purportedly showed that more recent emissions (2017-
2021) had less hours above the CEV than the hourly emissions modeled 
for Seward and Keystone. However, no evidence was provided that the 
distribution of hourly emissions modeled by the RRE runs were 
comparable to the worst-case hourly emissions scenario that could occur 
in compliance with the longer-term emission limit. The commenter's 
comparison of binned hourly emissions values modeled to those that 
actually occurred throughout recent years, does not provide evidence of 
worst case hourly emissions scenarios for a one-hour NAAQS. In 
contrast, a different commenter provided modeling of Keystone's actual 
emissions from 2019-2021, which purportedly showed that modeled NAAQS 
violations occurred when the source was in compliance with the 24-hour 
limit of 9600 lb/hr, and that the source's hourly emissions exceeded 
the CEV during 35 hours in 2019, 69 hours in 2020, and 232 hours in 
2021. This modeling analysis demonstrates that when a different 
emissions scenario is modeled from Pennsylvania's RRE modeling, a NAAQS 
violation occurs, highlighting the importance of modeling worst case 
emissions to ensure attainment.
    The RRE modeling approach used by Pennsylvania did not reflect the 
maximum possible emissions that could occur while maintaining 
compliance with the longer-term average emission limit, nor did the 
approach provide a comparably stringent analysis. Consequently, it was 
erroneous for EPA to fully approve the Indiana, PA SO2 
Attainment Plan in 2020, and it is necessary for EPA to correct its 
error by revising its action to partially approve and partially 
disapprove the Plan.
    Comment 2: The commenter notes that the monitors do not show 
evidence of nonattainment, and noted that, even though the Strongstown 
monitor is not located in the area of the modeled maximum 
SO2 concentration, previous modeling demonstrated that the 
Strongstown monitor would be ``significantly impacted'' if elevated 
impacts occurred elsewhere in the Indiana, PA NAA. The commenter 
provided data from the Strongstown monitor showing that its monitored 
values are decreasing and approaching values from the background 
monitor in South Fayette.
    Response 2: EPA agrees that the monitors in Strongstown and South 
Fayette are reading below the standard. However, as noted by the 
commenter, the monitors are not located in the area of modeled maximum 
concentrations and therefore are not, by themselves, indicative of 
whether the area is meeting the SO2 NAAQS. Although the 
comment makes reference to the ``modeling effort,'' it is not clear 
what modeling the commenter is referring to and the commenter has not 
provided any other data to support the claim that the Strongstown 
monitor would be ``significantly impacted'' if elevated impacts 
occurred elsewhere in Indiana, PA.
    SO2 concentrations result from direct emissions from 
combustion sources so that concentrations are highest relatively close 
to sources and are much lower at greater distances due to dispersion, 
i.e., a strong concentration gradient. Given the source-oriented nature 
of this pollutant (see 75 FR at 35570, June 22, 2010), dispersion 
models are the most appropriate air quality modeling tools to predict 
the near field concentrations and gradients

[[Page 50782]]

of this pollutant. EPA has received dispersion modeling from a 
different commenter that purportedly shows modeled violations within 
the Indiana, PA NAA near the Indiana and Armstrong County border, using 
actual 2019-2021 emissions for Keystone, while the source was 
purportedly complying with the 24-hour limit of 9,600 lb/hr. 
Consequently, EPA does not regard the commenter's observations about 
the Strongstown monitor as providing persuasive evidence that the Area 
is not violating the NAAQS or that the Plan provides for attainment of 
the NAAQS.
    Comment 3: The commenter claims that EPA is acting inconsistently 
because EPA approved the use of an alternative modeling method in 
Miami, AZ, which used Appendix C to calculate an adjustment factor, and 
included a supporting Appendix B modeling demonstration, which the 
commenter claims ``definitively'' confirmed the adequacy of the 
Appendix C calculated adjustment factor. The commenter argues that 
Appendix B was used as an essential component of the SIP because 
Appendix C was used in an application not addressed in EPA's 2014 
Guidance. Further, the commenter argues that the regulatory requirement 
is attainment of the NAAQS. The commenter alleges that this disapproval 
is arbitrary and capricious because it proposes to interpret the 
guidance differently in two nonattainment areas and apply it 
inconsistently without any explanation for the inconsistency.
    Response 3: EPA disagrees that it has applied the 2014 Guidance 
inconsistently between the Indiana, PA attainment plan and the Miami, 
AZ attainment plan. As the commenter noted, a significant difference 
between the two plans is that the Arizona plan used the Appendix C 
methodology to calculate a comparably stringent longer-term average 
limit, and then provided additional modeling to analyze whether the 
longer-term emission limit derived using Appendix C was reasonably 
likely to be protective of the NAAQS. In contrast, Pennsylvania used 
RRE modeling to arrive at the longer-term average limit without 
demonstrating comparable stringency to the one-hour CEV. The Arizona 
longer-term limit was calculated by obtaining a ratio of the 99th 
percentile of hourly emissions compared to the 99th percentile of 
longer-term average values as recommended by EPA. This ratio or 
adjustment factor was then applied to the CEV, thus taking into account 
the times of greatest emissions and linking the longer-term limit to 
the maximum modeled emission value (CEV), accordingly. Although the 
Arizona plan included an RRE-type (i.e., Appendix B) assessment of 
projected air quality, EPA did not rely on that assessment and made no 
reference to it in its final rule, insofar as the SIP was approvable 
without regard to the merits of the assessment.
    In contrast, the longer-term limits for Keystone and Seward in the 
Indiana, PA attainment plan were developed using only RRE modeling, 
which modeled the entire distribution of historic hourly emissions and 
based the limit on the 24-hour values that were modeled 30% of the time 
(Keystone) and the weighted annual average (Seward), neither of which 
considered the 99th percentile statistics of the historic hourly data 
set (times of greatest emissions), and neither of which were linked to 
the maximum modeled hourly emission rate (CEV). While sources can use 
approaches other than Appendix C to derive a longer-term average limit, 
the evidence that the other approach will result in attainment needs to 
be as compelling. EPA believes that any approach used should begin with 
the CEV, and account for times of greatest emissions in setting a 
longer-term limit. EPA also has noted that supplemental limits may be 
necessary to further constrain the frequency and magnitude of these 
worst case emission episodes.
    Due to these clear differences in approaches, EPA is not acting 
inconsistently in our actions on the Indiana, PA and Miami, AZ 
attainment plans as the commenter claims; rather, EPA is applying the 
2014 Guidance consistently across rather dissimilar situations.
    Comment 4: The commenter claims that EPA's action is arbitrary and 
capricious because the disapproval is not based on a rational 
connection between the facts found and the choice made. The commenter 
asserts that the facts in the record show that Appendix B is the proof 
of the statistical analysis in Appendix C, and that using the Appendix 
B approach is a more robust, thorough way to show that a longer-term 
emission limit can be protective of the NAAQS. The commenter claims 
that the use of the Appendix B approach is consistent with EPA's 
requirements for an approvable SIP: ``. . . as the EPA explained in our 
2014 SO2 Guidance and in numerous proposed and final SIP 
actions implementing the SO2 NAAQS, a key element of an 
approvable SIP is the required modeling demonstration showing that the 
remedial control measures and strategy are adequate to bring a 
previously or currently violating area into attainment.'' 84 FR 8815, 
March 12, 2019. EPA is now seemingly self-contradictory and believes 
that Appendix B does not provide a longer-term emission limit that is 
equivalently stringent to the one-hour limit. Nothing in the record 
supports making this determination, the commenter claims.
    Response 4: EPA disagrees with the commenter and believes the 
commenter has misunderstood the purpose of Appendix B of the 2014 
Guidance. First, the EPA language quoted by the commenter is referring 
to the modeling performed to determine the CEV, which is a one-hour 
limit for SO2 emissions, rather than a longer-term limit. 
Also, as noted in the 2014 Guidance, ``Appendix B documents analyses 
that the EPA has conducted to evaluate the extent to which longer-term 
limits that have been adjusted to have comparable stringency to one-
hour limits as the critical emissions value provide for attainment.'' 
(pg. 25). Also, as noted in the Guidance, ``at issue is the likelihood 
that a source complying with a 30-day average limit reflecting the 
adjustment generally recommended in this guidance [emphasis added] 
would have sufficiently high emissions on a sufficient fraction of the 
potential exceedance days to cause an SO2 NAAQS violation.'' 
(pg. B-2). In each of the modeling simulations run by EPA in support of 
the Appendix C methodology, the estimated design values obtained were 
between 39 and 58 ppb, and thus EPA stated, ``Given the margin between 
these values and the NAAQS level of 75 ppb, this analysis indicates 
that the likelihood of a violation occurring with these emissions 
values is extremely low.'' (pg. B-3). Thus, the modeling exercise was 
conducted as a test on emission limits that were considered comparably 
stringent with the CEV (i.e., comparably stringent longer-term emission 
limits, and not simply ``longer-term'' emission limits); it was not 
used to develop the comparably stringent longer-term limits because, as 
noted, the results of the Appendix B analyses yielded a range of 
estimated design values and EPA did not select a specific modeling 
scenario result to rely upon as an attainment demonstration. Rather, 
EPA used the analysis as support that the comparably stringent longer-
term limit derived using the Appendix C methodology, notwithstanding 
infrequent hourly emissions spikes above the CEV, could nevertheless 
protect the NAAQS.
    The commenter's claim that Appendix B is a ``proof'' of the 
statistical analysis in Appendix C is not substantiated. A mathematical 
proof of a theorem should show that the theorem holds true at all times 
so long as any

[[Page 50783]]

constraints set forth by the theorem are followed (e.g., theorem only 
applies to prime numbers). In Appendix B, EPA summarizes modeling 
exercises that were conducted using the emission patterns that could be 
expected even when a source is just barely complying with a long-term 
average emission limit. (2014 Guidance, at B-4). Based on this, EPA 
concluded that these analyses indicated ``that suitably adjusted 
longer-term average limits can generally be expected to provide 
adequate confidence that the attainment plan will provide for 
attainment.'' (pg. B-2). Words such as ``generally'' and ``adequate 
confidence'' are not words used to describe a mathematical proof.
    The modeling analyses were one piece of evidence that provided more 
confidence to EPA that a comparably stringent longer-term limit (set 
using the 99th percentile of emissions statistics) can be protective of 
a one-hour NAAQS, but the Appendix B modeling analyses did not 
``prove'' that a longer-term limit set via other methods that went 
through 100 model runs with a specified hourly emissions distribution 
and that modeled attainment would provide the same level of confidence 
that the limit is protective of the one-hour NAAQS. More specifically, 
Pennsylvania modeled hourly values that, when averaged over a 24-hour 
day, equaled less than the 24-hour limit for 70% of the year for 
Keystone. That is, while the 24-hour limit for Keystone was set at 
9,600 lb/hr, the hourly emissions that were modeled averaged between 
5,000 and 8,964 lb/hr on a 24-hour basis for 70% of the year; and the 
hourly emissions that were modeled averaged 9,600 lb/hr on a 24-hour 
basis for 30% of the year. Pennsylvania did not scale the data set such 
that the modeled hourly values resulted in 24-hour averages that just 
met the 24-hour limit of 9,600 lb/hr. Therefore, it's questionable 
whether the RRE modeling actually tested the 24-hour limit for 
Keystone. If the 24-hour averaged emissions varied from those that were 
modeled, such that 50% or 100% of the 24-hour averages equaled 9,600 
lb/hr (the limit) rather than only 30%, it is uncertain that the 
modeled concentrations would still result in attainment. On the other 
hand, EPA's methods for determining a comparably stringent limit do 
provide confidence that changes in the hourly emissions distribution 
while in compliance with the longer-term limit will still provide for 
attainment. Tellingly, at no point does the guidance recommend use of 
the methods described in Appendix B as a means of determining suitable 
limits or of determining whether limits determined by other means 
(whether of comparable stringency to a one-hour limit at the CEV or 
not) will suitably provide for attainment. Thus, characterizing 
Appendix B as `proof' of the Appendix C theorem is off base.
    Comment 5: A different commenter claims that longer-term limits are 
fundamentally incapable of protecting a one-hour NAAQS. The commenter 
provided an updated analysis of Keystone's actual hourly emissions for 
the years 2018 through 2021 which showed that the source exceeded the 
CEV over 500 hours. The commenter noted that 2021 was worse than 2020. 
The analysis also showed that Seward exceeded the CEV 71 times in that 
same period (4 years). The commenter believes that the NAAQS will not 
be attained if just four hours on four days have ambient concentrations 
above 75 ppb, and thus concludes that longer-term emissions averaging 
cannot protect the NAAQS. The commenter therefore asserts that the 
current emission limits in the SIP for Keystone and Seward are 
inadequate to protect air quality.
    In addition, the commenter calculated a conversion factor for 
Keystone using Appendix C and the more recent 2018-2021 hourly 
emissions data and noted the analysis yields a limit of 8,292.5 lb/hr 
(24-hour daily average), which is below the current limit of 9,600 lb/
hr as a 24-hour daily average.
    Response 5: EPA disagrees with the commenter's assertion that a 
longer-term limit, so long as it is properly set, cannot protect a one-
hour NAAQS. But that abstract issue is not being decided in this 
action. In this case, EPA agrees with the commenter that the specific 
longer-term limits for Keystone and Seward were not set at a level that 
ensures the protection of the one-hour SO2 NAAQS, since they 
were not shown to be comparably stringent to a modeled attaining one-
hour CEV. EPA agrees with the commenter that the longer-term limits for 
Keystone and Seward do not ensure protection of the NAAQS, and with 
this action will finalize disapproval of the attainment demonstration.
    Comment 6: The commenter provided recent air quality modeling 
allegedly demonstrating that SO2 emissions from Keystone, 
Conemaugh, and Seward continue to cause nonattainment in Pennsylvania, 
both inside and outside the Indiana NAA. The air quality modeling 
submitted with the comment, which used actual emissions from Keystone 
from 2019 through 2021, purportedly demonstrates that Keystone is 
causing violations of the NAAQS (209.9 micrograms per cubic meter 
([micro]g/m\3\)). The commenter also provided annual SO2 
emissions for Keystone, which show lower annual emissions in 2020 
(13,011 tons per year), but other years range from 17,000-24,000 tons 
per year. Using actual emissions for various three-year time periods 
from 2015-2017 through 2019-2021, the commenter provided modeling 
demonstrating that Seward and Conemaugh cause violations of the NAAQS 
(244.6 [micro]g/m\3\-275.4 [micro]g/m\3\) \3\ outside the nonattainment 
area.
---------------------------------------------------------------------------

    \3\ In the Round 3 intended designations (82 FR 41903) published 
September 5, 2017, EPA endorsed a value of 196.4 [micro]g/m\3\ 
(based on calculations using all available significant figures) as 
equivalent to 75 ppb.
---------------------------------------------------------------------------

    Response 6: EPA believes that this final rule may result in 
Pennsylvania adopting tighter SO2 emission limits for both 
Keystone and Seward which will reduce their hourly emissions and better 
provide for reductions in SO2 concentrations towards 
achieving attainment of the NAAQS, subject to EPA's evaluation of any 
such future limits.
    Regarding the commenter's modeling, which seems to show modeled 
SO2 NAAQS violations in Westmoreland and Cambria counties in 
Pennsylvania outside the boundaries of the Indiana NAA, EPA notes that 
it is not basing its partial disapproval of the Indiana attainment plan 
on these modeled NAAQS violations outside of the Indiana NAA. As stated 
in the proposal for this action, EPA is planning a separate regulatory 
action under the Clean Air Act to address those modeled NAAQS 
violations.
    Comment 7: The commenter states that Conemaugh and Seward's 
SO2 pollution implicates serious environmental justice (EJ) 
concerns. The commenter provided an EJ Screen analysis which indicates 
that southeast of Seward the population is characterized by low incomes 
and generally elderly population. The commenter also overlaid the 
modeled violations of the NAAQS with the EJ screen map showing that the 
modeled violations are impacting the identified vulnerable population. 
The commenter asserts that this adds urgency to the need for attainment 
to be achieved and SO2 emissions from Conemaugh and Seward 
to be properly limited.
    Response 7: EPA's analysis in the notice of proposed rulemaking 
showed similar results to the commenter's EJ screen analysis and 
indicated communities with environmental justice concerns both inside 
and outside the Indiana nonattainment area. EPA therefore encourages 
Pennsylvania to be as expeditious as practicable in

[[Page 50784]]

developing its new attainment plan limits in order to address the 
emissions impact on the vulnerable populations both inside the current 
nonattainment area, and in adjacent areas.

IV. Final Action

    EPA is partially approving and partially disapproving the Indiana, 
PA attainment plan as a correction of its erroneous prior full approval 
action and as a revision to the Pennsylvania SIP. See CAA section 
110(k)(6). Specifically, EPA is disapproving the attainment 
demonstration, RACT/RACM determination, RFP requirements, and 
contingency measures. EPA is retaining the approval of the emissions 
inventory and the NNSR program.
    This action initiates a sanctions clock under CAA section 179, 
providing for emission offset sanctions for new sources if EPA has not 
fully approved a revised SIP attainment plan within 18 months after 
final partial disapproval, and providing for highway funding sanctions 
if EPA has not fully approved a revised plan within 6 months 
thereafter. The sanctions clock can be stopped only if the conditions 
of EPA's regulations at 40 CFR 52.31 are met. This action also 
initiates an obligation for EPA to promulgate a Federal implementation 
plan within 24 months unless Pennsylvania has submitted, and EPA has 
fully approved, a plan addressing these attainment planning 
requirements.

V. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders 
can be found at www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 13563: Improving Regulation and Regulatory Review

    This action is not a significant regulatory action and was 
therefore not submitted to the Office of Management and Budget (OMB) 
for review.

B. Paperwork Reduction Act (PRA)

    This action does not impose an information collection burden under 
the PRA, because this SIP partial approval and partial disapproval does 
not in-and-of itself create any new information collection burdens, but 
simply partially approves and partially disapproves certain State 
requirements for inclusion in the SIP.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities. This SIP 
partial approval and partial disapproval does not in-and-of itself 
create any new requirements but simply partially approves and partially 
disapproves certain pre-existing State requirements for inclusion in 
the SIP.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small governments. This action does not impose additional requirements 
beyond those imposed by state law. Accordingly, no additional costs to 
state, local, or tribal governments, or to the private sector, will 
result from this action.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government.

F. Executive Order 13175: Coordination With Indian Tribal Governments

    This action does not have tribal implications, as specified in 
Executive Order 13175, because the SIP EPA is disapproving would not 
apply on any Indian reservation land or in any other area where the EPA 
or an Indian tribe has demonstrated that a tribe has jurisdiction, and 
will not impose substantial direct costs on tribal governments or 
preempt tribal law. Thus, Executive Order 13175 does not apply to this 
action.

G. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    The EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that the EPA has reason to believe may disproportionately affect 
children, per the definition of ``covered regulatory action'' in 
section 2-202 of the Executive order. This action is not subject to 
Executive Order 13045 because this SIP partial approval and partial 
disapproval does not in-and-of itself create any new regulations, but 
simply partially approves and partially disapproves certain pre-
existing State requirements for inclusion in the SIP.

H. Executive Order 13211: Actions That Significantly Affect Energy 
Supply, Distribution, or Use

    This action is not subject to Executive Order 13211, because it is 
not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act (NTTAA)

    Section 12(d) of the NTTAA directs the EPA to use voluntary 
consensus standards in its regulatory activities unless to do so would 
be inconsistent with applicable law or otherwise impractical. The EPA 
believes that this action is not subject to the requirements of section 
12(d) of the NTTAA because application of those requirements would be 
inconsistent with the CAA.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Population

    The EPA lacks the discretionary authority to address environmental 
justice in this rule.

K. Congressional Review Act (CRA)

    This action is subject to the CRA, and the EPA will submit a rule 
report to each House of the Congress and to the Comptroller General of 
the United States. This action is not a ``major rule'' as defined by 5 
U.S.C. 804(2).

L. 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 October 17, 2022. Filing a petition for 
reconsideration by the Administrator of this final rule does not affect 
the finality of this rule 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 pertaining to the partial approval and partial disapproval 
of the Indiana, PA SO2 attainment plan, may not be 
challenged later in proceedings to enforce its requirements. (See 
section 307(b)(2).)

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations,

[[Page 50785]]

Reporting and recordkeeping requirements, Sulfur oxides.

Adam Ortiz,
Regional Administrator, Region III.

    For the reasons stated in the preamble, the EPA amends 40 CFR part 
52 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, the table in paragraph (e)(1) is amended by adding 
an entry ``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 to read as follows:


Sec.  52.2020   Identification of plan.

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

----------------------------------------------------------------------------------------------------------------
  Name of non- regulatory SIP        Applicable      State submittal
            revision              geographic area          date        EPA approval date  Additional explanation
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
Attainment Plan for the          Indiana County     10/11/17,          8/18/22, [Insert   Partial Disapproval
 Indiana, Pennsylvania            and portions of   Supplemental        Federal Register   (attainment
 Nonattainment Area for the       Armstrong County   information        Citation].         demonstration,
 2010 Sulfur Dioxide Primary      (Plumcreek         submitted 02/05/  10/19/20, 85 FR     Reasonably Available
 National Ambient Air Quality     Township, South    20, updated        66255.             Control Technology
 Standard.                        Bend Township,     redacted permits                      (RACT)/Reasonably
                                  and Elderton       submitted on 05/                      Available Control
                                  Borough).          13/20.                                Measures (RACM)
                                                                                           determination,
                                                                                           Reasonable Further
                                                                                           Progress (RFP)
                                                                                           requirements,
                                                                                           contingency measures)
                                                                                           and Partial Approval
                                                                                           (emissions inventory
                                                                                           and nonattainment new
                                                                                           source review (NNSR)
                                                                                           program) 52.2033(f).
----------------------------------------------------------------------------------------------------------------

* * * * *

0
4. Amend Sec.  52.2033 by revising paragraph (f) to read as follows:


Sec.  52.2033   Control strategy: Sulfur oxides.

* * * * *
    (f) EPA partially approves and partially disapproves the attainment 
demonstration State Implementation Plan for the Indiana, PA Sulfur 
Dioxide Nonattainment Area submitted by the Pennsylvania Department of 
Environmental Protection on October 11, 2017 and updated on February 5, 
2020, and corrected permits submitted on May 13, 2020. EPA approves the 
base year inventory and the Nonattainment New Source Review (NNSR) 
requirements, and disapproves the attainment demonstration, Reasonably 
Available Control Technology (RACT)/Reasonably Available Control 
Measures (RACM) determination, Reasonable Further Progress (RFP) 
requirements and contingency measures.

[FR Doc. 2022-17449 Filed 8-17-22; 8:45 am]
BILLING CODE 6560-50-P