[Federal Register Volume 85, Number 79 (Thursday, April 23, 2020)]
[Rules and Regulations]
[Pages 22593-22609]
[FR Doc No: 2020-08573]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R03-OAR-2017-0730; FRL-10008-40-Region 3]

Air Plan Approval; Pennsylvania; Attainment Plan for the
Allegheny 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 Pennsylvania
Department of Environmental Protection (PADEP) on behalf of the
Allegheny County Health Department (ACHD). The SIP revision, submitted
on October 3, 2017, provides for attainment of the 2010 sulfur dioxide
(SO2) primary national ambient air quality standard (NAAQS)
in the Allegheny Pennsylvania SO2 nonattainment area
(hereafter referred to as the ``Allegheny Area'' or ``Area''). The SIP
submission includes an attainment plan, including an attainment
demonstration showing SO2 attainment in the Area, an
analysis of reasonably available control technology (RACT) and
reasonably available control measures (RACM) requirements, enforceable
emission limitations and control measures, a reasonable further
progress (RFP) plan, and contingency measures for the Allegheny Area.
EPA is approving new SO2 emission limits and associated
compliance parameters for the four major sources of SO2 in
the Allegheny Area into the Allegheny County portion of the
Pennsylvania SIP. Three of the sources (Clairton Coke Works, Edgar
Thomson, and Irvin Works) are collectively known as the U.S. Steel
(USS) Mon Valley Works, and the fourth

is the Harsco Metals Facility, also referred to as Braddock Recovery.
EPA is also approving the base year emissions inventory for the
Allegheny Area and ACHD's certification that the nonattainment new
source review (NNSR) permit program meets requirements. These revisions
to the Pennsylvania SIP are in accordance with the requirements of the
Clean Air Act (CAA).

DATES: This final rule is effective on May 26, 2020.

ADDRESSES: EPA has established a docket for this action under Docket ID
Number EPA-R03-OAR-2017-0730. 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
information.

FOR FURTHER INFORMATION CONTACT: Marilyn Powers, 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-
2308. Ms. Powers can also be reached via electronic mail at
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

I. Background

    On June 22, 2010, (75 FR 35520) EPA promulgated a new 1-hour
primary SO2 NAAQS of 75 parts per billion (ppb). 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) of the CAA. On August 5, 2013 (78 FR 47191), EPA designated
29 areas of the country, including the Allegheny Area, as nonattainment
for the 2010 SO2 NAAQS based on violating air quality
monitoring data for calendar years 2009-2011.\1\ The Allegheny Area is
entirely within Pennsylvania and is comprised of the City of Clairton,
the City of Duquesne, the City of McKeesport, the Townships of
Elizabeth, Forward, and North Versailles, and the following Boroughs:
Braddock, Dravosburg, East McKeesport, East Pittsburgh, Elizabeth,
Glassport, Jefferson Hills, Liberty, Lincoln, North Braddock, Pleasant
Hills, Port Vue, Versailles, Wall, West Elizabeth, and West Mifflin.
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    \1\ EPA is continuing its designation efforts for the 2010
SO2 NAAQS. Pursuant to a court order issued 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 (2015).
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    The Allegheny Area designation became effective on October 4, 2013.
Section 191(a) of the CAA directs states to submit SIP revisions for
designated SO2 nonattainment areas to EPA within 18 months
of the effective date of the designation, i.e., in this case by no
later than April 4, 2015. Under CAA section 192(a), these SIP
submissions are required to include measures that will bring the
nonattainment area into attainment of the NAAQS as expeditiously as
practicable, but no later than five years from the effective date of
designation. The attainment date for the Allegheny Area was therefore
October 4, 2018.
    Attainment plans for SO2 must meet sections 110, 172,
191 and 192 of the CAA. The required components of an attainment plan
submittal are listed in section 172(c) of title 1, part D of the CAA.
EPA's regulations governing SIPs are set forth at 40 CFR part 51, with
specific procedural requirements and control strategy requirements at
subparts F and G, respectively. Soon after Congress enacted the 1990
Amendments to the CAA, EPA issued comprehensive guidance on SIPs, in a
document entitled ``General Preamble for the Implementation of Title I
of the Clean Air Act Amendments of 1990,'' published at 57 FR 13498
(April 16, 1992) (General Preamble). Among other things, the General
Preamble addressed SO2 SIPs and fundamental principles for
SIP control strategies. Id. at 13545-49, 13567-68. On April 23, 2014,
EPA issued recommended guidance (hereafter 2014 SO2
Guidance) for how state submissions could address the statutory
requirements for SO2 attainment plans.\2\ In this guidance,
EPA described the statutory requirements for an attainment plan, which
include: An accurate base year emissions inventory of current emissions
for all sources of SO2 within the nonattainment area
(172(c)(3)); 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)); RFP (172(c)(2)); implementation of
RACM, including RACT (172(c)(1)); NNSR requirements (172(c)(5)); and
adequate contingency measures for the affected area (172(c)(9)).
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    \2\ See ``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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    On March 18, 2016, effective April 18, 2016, EPA published a
document that Pennsylvania and other states had failed to submit the
required SO2 attainment plans by the April 4, 2015 submittal
deadline. See 81 FR 14736. This finding initiated a deadline under CAA
section 179(a) for the potential imposition of new source review and
highway funding sanctions. Additionally, under CAA section 110(c), the
finding triggered a requirement 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 before the Administrator promulgates a FIP. Following
Pennsylvania's submittal of ACHD's attainment plan SIP on October 3,
2017, EPA sent a letter dated October 6, 2017 to Pennsylvania finding
the submittal was complete and therefore the sanctions deadline no
longer applied and sanctions under section 179(a) would not be imposed
as a consequence of Pennsylvania's having missed the original deadline.

II. Summary of EPA's Notice of Proposed Rulemaking

    On November 19, 2018 (83 FR 58206), EPA proposed approval of
Pennsylvania's October 3, 2017 SO2 attainment plan submittal
for the Allegheny Area. The notice of proposed rulemaking (NPRM)
described the requirements that nonattainment plans are designed to
meet and provided extensive discussion of EPA's rationale for proposing
to approve the Pennsylvania submittal as meeting these requirements.
Notably, the Allegheny Area attainment plan included 30-day rolling
average hourly SO2 emission limits for the following
sources: Clairton Coke Works, Edgar Thomson, Irvin Works, and Harsco
Metals. The NPRM included an extensive discussion of EPA's 2014
SO2 Guidance allowing the use of 30-day rolling average
hourly SO2 emission limits, including a full discussion of
EPA's rationale for concluding that properly set longer-term average
SO2 emission limits of up to 30 days (in particular, longer-
term

emission limits that are comparably stringent to the 1-hour limits that
would otherwise be established) can be effective in providing for
attainment. The NPRM then described EPA's review of the modeling that
Pennsylvania submitted to demonstrate that the limits adopted by ACHD
would provide for attainment of the 2010 SO2 NAAQS and
described EPA's review of whether the submittals met other applicable
requirements, such as the requirements for an emissions inventory, RFP,
NNSR, and contingency measures. On this basis, EPA proposed to conclude
that the SO2 emission limits established for Clairton, Edgar
Thomson, Irvin, and Harsco Metals assure attainment in the Allegheny
Area. More generally, EPA proposed to approve Pennsylvania's SIP
submittal as addressing the nonattainment planning requirements. The
specific attainment plan requirements and EPA's rationale for proposing
approval of the Allegheny Area attainment plan are explained in detail
in the NPRM and will not be restated here. Five commenters submitted
comments on the NPRM. One commenter supported the proposal, and one
commenter provided comments that were not germane to the proposed
rulemaking. The remaining three commenters submitted adverse comments
that are addressed in the next section. All of the comments are
included in the Docket for this rulemaking at https://www.regulations.gov, Docket ID Number EPA-R03-OAR-2017-0730.

III. Comments and EPA Responses

    Three comment letters--one anonymous, one from the Sierra Club and
one from the Clean Air Council--provided comments relevant to this
rulemaking. The comments submitted by the Clean Air Council included
comments that were originally submitted to ACHD in response to ACHD's
proposal of the Allegheny Area attainment plan, which the Clean Air
Council believed were not adequately addressed by ACHD.
    Comment 1: The commenter noted that the attainment SIP for the
Allegheny Area was due in April 2015, which Pennsylvania failed to
meet, and that EPA subsequently issued a finding of failure to submit
the SIP in March 2016. The commenter asserts that the finding triggered
a requirement that EPA promulgate a FIP by March 2018, and that not
only has EPA failed to issue a FIP, but EPA has also failed to enforce
applicable sanctions against the State.\3\
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    \3\ The commenter cited a FIP deadline of March 2018, however
the FIP deadline was actually 24 months after the effective date of
the finding, or April 18, 2018.
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    Response 1: Pennsylvania submitted an attainment plan SIP for the
Allegheny SO2 nonattainment area on October 3, 2017. EPA had
an obligation to take action on the submittal or promulgate a FIP by
April 18, 2018, as required under CAA section 110(c)(1)(A). EPA
acknowledges that it did not approve the SIP revision or promulgate a
FIP for the Allegheny Area by this date, as noted by the commenter. EPA
also notes that since issuing its proposed approval of the SIP, EPA has
become subject to a court order directing it to take final action on
the SIP no later than April 30, 2020. See Center for Biological
Diversity, et al. v. Wheeler, No. 4:18-cv-03544 (November 26, 2019).
EPA believes that the most expeditious way to bring this area into
attainment is to approve the submitted SIP with the limits and
restrictions adopted by ACHD, making those limits and restrictions
Federally-enforceable. Completion of our proposed action to approve the
SIP, which contains emissions limits and requirements that are already
effective and which the subject sources are already meeting, will
result in achieving Federally-enforceable emissions reductions needed
to attain the NAAQS far faster than would starting from scratch to
develop, adopt, and apply new emissions limits and requirements in a
FIP, the requirement for which would in any case be mooted by our final
approval of the SIP. Thus, it is reasonable to use the most expeditious
approach to a Federally-enforceable plan to bring the Area into
attainment, and that is to approve this SIP rather than promulgate a
FIP. With this final action to approve the Allegheny SO2
attainment plan SIP, we are discharging our statutory obligation under
CAA section 110(k)(2) to act on the SIP, and such approval terminates
our FIP obligation under section 110(c)(1)(A) for the Allegheny
SO2 nonattainment area. We are also discharging our
requirement under the court order to take final action on the SIP by
April 30, 2020.
    EPA disagrees that sanctions are applicable in the Allegheny Area.
As discussed in the Background section of this preamble, Pennsylvania
submitted the Allegheny attainment SIP on October 3, 2017, which was
before the deadline of October 18, 2017 for the State to correct the
deficiency that started the sanctions clock. CAA section 179(a). EPA's
letter dated October 6, 2017 to Pennsylvania indicated that the
submittal met the completeness criteria under 40 CFR part 51, and
corrected the deficiency identified in EPA's March 18, 2016 finding of
failure to submit SO2 SIPs. Under EPA's regulations
implementing mandatory sanctions clocks, as of October 6, 2017, the
sanctions clock for the Allegheny Area was stopped; therefore, the
sanctions under section 179(a) were not imposed as a consequence of
Pennsylvania having missed the original deadline for submittal of the
SIP. See 40 CFR 52.31(d)(5).
    Comment 2: The commenter states that under the Clean Air Act, the
NAAQS ``compliance'' deadline for this area was October 4, 2018, and
that it is unclear how the SIP can meet the past compliance deadline
when even those limits proposed in the ACHD submission are not
presently Federally-enforceable. The commenter also states that the
Allegheny nonattainment area is still failing to attain the standard
over five years after designation, and that EPA cannot approve an
attainment plan for an area that is ``demonstrably failing to attain
the standard, well-after the attainment deadline.'' The commenter cites
to EPA data that shows the 2015-2017 design value as 97 ppb, or roughly
30 percent above the NAAQS, and that the ``current'' 99th percentile
SO2 hourly concentration for the Allegheny Area is 130 ppb,
which would result in a 2016-2018 design value of at least 103 ppb. The
commenter points out that the 99th percentile hours for 2017 and 2018
are so high that Allegheny cannot come into attainment even if the
monitor shows zero SO2 emissions for every hour in 2019, and
that EPA ``confusingly states that the plan will somehow `ensure
ongoing attainment' and that the chosen control strategies `will bring
the Area into attainment by the statutory attainment date of October 4,
2018.' '' The commenter also says that EPA never addresses monitor data
at all, except where monitored data plays a factor in the contingency
measures for the area, and that EPA cannot approve an attainment plan
that fails to actually attain the standard by the statutorily mandated
deadline of October 4, 2018.
    Response 2: The commenter makes an assertion that is incorrect--the
CAA does not require that, before EPA can approve a SIP that provides
for attainment, it must first find that the area factually attained the
NAAQS as a result of the control strategy in the SIP. Nor does the CAA
preclude approval of a control strategy that modeling shows will
achieve NAAQS-attaining air quality merely because monitoring of
historical air quality that preceded the implementation of controls
that went into force still produces design values that do not reflect
emissions reductions

from those controls and that are consequently still above the NAAQS.
Sections 172 and 192 of the CAA require states to submit SIP revisions
that ``provide for attainment'' of the SO2 NAAQS by the
attainment date. In our proposal, we described the measures, supporting
analyses, and the rationale for finding that the SO2
attainment plan for the Allegheny Area submitted by Pennsylvania does
provide for attainment. In particular, Pennsylvania's submittal
provides modeling-based evidence that establishes that the control
measures required on the sources of emissions in the Allegheny Area are
sufficient to yield air quality that attains the NAAQS by the
attainment deadline. As discussed in the proposal, the permits required
that the Mon Valley Works facilities and the Harsco facility comply
with the control measures needed for attainment by October 4, 2018.
    The commenter submitted data showing monitored 99th percentile
SO2 concentrations from 2016 to 2018 (64 ppb, 116 ppb, and
130 ppb, respectively) that results in a design value for this three-
year period of 103 ppb. The commenter further stated that regardless of
the monitored values for 2019, the Area would not come into attainment
because of the high 99th percentile concentrations for 2017 and 2018.
The monitoring data in 2017 and 2018 cited by the commenter are
accurate. However, the available monitoring data should not be
interpreted as indicating that the attainment plan will fail to provide
for timely attainment. The monitoring data cited by the commenter were
collected before the full implementation of the measures in the
Allegheny SO2 attainment plan, which occurred by October 4,
2018. Therefore, these data measuring the air quality prior to full
implementation of the measures reflected in the modeling demonstration
are not a reliable indicator of whether air quality, after
implementation of all modeled relevant control measures, would be
expected to meet the standard at the attainment deadline. In other
words, these data are not indicative of the adequacy of the plan and
its modeling demonstration to provide for NAAQS attainment. Instead, as
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 SO2 attainment 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.\4\ Given the form of the 2010
SO2 NAAQS as the 3-year average of the 99th percentile of
the yearly distribution of 1-hour daily maximum SO2
concentrations, it is often possible that the three-year period of
monitored data will not reflect the actual air quality levels resulting
from implementation of the newer remedial control measures implemented
within that period. In such cases, as it is here, the more complete and
representative analysis for informing action on a submitted SIP should
focus on the results of newly implemented control measures required
under the plan, rather than historical concentrations that do not
reflect the results of the plan's required control measures. The former
analysis explicitly addresses whether air quality will be attaining (as
required) under the state's submitted plan, whereas the latter analysis
may have little to no bearing on what will happen as a result of the
plan. Therefore, in the context of reviewing the adequacy of those
newer control measures to provide for newly attaining air quality under
sections 172 and 192 of the CAA, we conclude that it is reasonable to
focus on the modeling results that specifically account for those
control measures and the resulting reductions in SO2
emissions, rather than on monitored data that, in this case, do not
represent air quality levels resulting from full implementation of the
control measures in the attainment plan. In the Allegheny
SO2 attainment plan, ACHD's modeling shows that
implementation of the measures included in the plan result in air
quality that attains the NAAQS, and those measures are being met by the
subject sources by the October 4, 2018 attainment date. Therefore, the
SIP meets the requirement to demonstrate that it provides for timely
attainment.
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    \4\ Air Plan Approval; KY; Attainment Plant for Jefferson County
SO2 Nonattainment Area, (Proposed rule 83 FR 56002,
November 9, 2018; Final rule 84 FR 30921, June 28, 2019), and
Approval and Promulgation of Air Quality Implementation Plans;
Arizona; Nonattainment Plan for the Miami SO2
Nonattainment Area (Proposed rule 83 FR 27938, June 15, 2018; Final
rule 84 FR 8813, March 12, 2019).
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    While the submitted modeling demonstrates attainment for the area,
EPA acknowledges that some SO2 exceedances were monitored in
2018 and 2019 that EPA believes were the result of a December 24, 2018
fire at the Clairton Coke Works which required the immediate shut down
of No. 2 and No. 5 control rooms. The shutdown of the two control rooms
resulted in the diversion of coke oven gas (COG) away from the
desulfurization process within the facility's by-products operation,
allowing SO2 to be released from various flaring stacks into
the ambient air. To mitigate the release of pollutants into the air,
U.S. Steel, owner of the Clairton Coke Works, took remedial action to
mitigate SO2 emissions by using COG diluted with natural gas
in the boilers. ACHD conducted a review of operational data for the
period following the fire and determined that the facility was in
violation of its hydrogen sulfide (H2S) permit limit. ACHD's
review of monitor data for the period following the fire showed
monitored violations. ACHD concluded that the mitigation efforts by
U.S. Steel did not fully compensate for the shutdown of the two control
rooms and the bypass of the desulfurization process. Therefore, on
February 28, 2019, ACHD issued an Enforcement Order requiring U.S.
Steel to extend coking times at all the Clairton batteries, reduce
usage of COG at boilers located at the Edgar Thomson facility, and
reduce the SO2 emissions from coke oven batteries, boilers,
and emissions stacks from all of the Mon Valley Works facilities by
either one or a combination of reducing the volume of coal in each
oven, extending the coking time further, limiting production at coke
oven batteries by temporarily hot idling coke ovens, or some other plan
submitted to ACHD to meet ACHD's stipulated reduction of SO2
emissions from the facility. The enforcement order required weekly
compliance reports to ACHD until all repairs were completed to No. 2
and No. 5 control rooms, and 100 percent of the COG exiting the control
rooms was again being desulfurized, or until June 30, 2019, whichever
was later. On March 12, 2019, following discussions with U.S. Steel,
ACHD issued an amended order (Enforcement Order #190202A) compelling
U.S. Steel to extend the time of the coking process. The control rooms
were repaired and resumed operation on April 15, 2019, and COG was
again sent to the desulfurization units on that date. A second fire
occurred on the morning of June 17, 2019. The second fire again shut
down the No. 2 and No. 5 control rooms, but both control rooms were

back in operation by the evening of the same day. The data in EPA's Air
Quality Systems (AQS) database for all of 2018 and 2019 shows three
exceedances of the NAAQS in December 2018 \5\ and seven exceedances in
early 2019, shown in Table 1 as follows:
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    \5\ Nine other monitored exceedances occurred between February
through August 2018, however, these exceedances happened prior to
the establishment of new limits, and occurred prior to and are not
related to the fires at Clairton, which occurred outside of these
time frames. The reports showing the exceedances in Table 1 have
been added to the docket for this rulemaking action.

                    Table 1--Monitored SO2 Exceedances at Liberty and North Braddock Monitors
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                                                                                Concentration,
                   Monitor                      AQS monitor        Date of         Occurrence       parts per
                                                                  exceedance         (hour)       million (ppm)
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Liberty McKeesport, PA......................      42-003-0064         12/26/18            10:00            0.079
                                              ...............         12/26/18            11:00             0.08
                                              ...............         12/28/18            10:00            0.145
                                              ...............           1/2/19            21:00            0.081
                                              ...............           1/3/19            23:00            0.085
                                              ...............           1/8/19             4:00            0.076
                                              ...............           1/8/19             0:00             0.08
                                              ...............          3/28/19             3:00            0.082
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North Braddock Braddock, PA.................      42-003-1301         1/7/2019            23.00            0.083
                                              ...............         2/4/2019            22.00            0.082
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    As shown in Table 1, the monitored exceedances occurred at the
Liberty and North Braddock monitors between December 26, 2018 and March
28, 2019, during the time when the desulfurization units were off-line.
There were no monitored exceedances that occurred that correlate to the
June 2019 fire. From October 2018, when compliance with the new
measures was required at the affected facilities, until the December
2018 fire, no exceedances of the standard were monitored. Based on
EPA's preliminary data for 2019, since April 15, 2019, when the
desulfurization units resumed operation, to the end of 2019, no
additional exceedances have been monitored.\6\ This indicates that the
additional measures required by ACHD to achieve attainment in the Area
are in fact adequate to provide for attainment.\7\
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    \6\ The 2019 data is preliminary and will not be certified until
May 2020.
    \7\ 2018 fourth quarter reports for Clairton, Edgar Thompson,
and Irvin showing no deviations from permit requirements (except for
the period during the December 2018 fire) are provided in the
docket. The Clairton report shows that the COG provided to the
pipeline to fuel the other facilities, including Harsco Metals, met
the permit limit.
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    Under the CAA, a determination of whether an area has failed to
attain is a separate action from the review of an attainment
demonstration SIP. EPA's attainment SIP review for SO2
occurs under CAA sections 110(k), 172(c) and 192(a), while a
determination of whether an SO2 nonattainment area has
failed to attain is governed by CAA section 179(c)(1). Under section
110(k)(3), EPA is required to approve a SIP submission that meets all
applicable requirements of the CAA. For the reasons described in our
proposal and elsewhere in this action, we have concluded that the
Allegheny SO2 attainment plan meets all such requirements,
including the requirement in 172(c) and 192(a) to provide for
attainment by the attainment date. This is the determination that is
the subject of this final SIP approval action.
    Separately, in a different action under section 179(c)(1) that is
beyond the scope of this final SIP approval action, EPA must determine
within six months of the attainment date whether an area has attained
the NAAQS based on the area's air quality as of the attainment date.
Accordingly, EPA will take a separate action to analyze the pertinent
information and determine whether the Allegheny SO2 Area
attained the NAAQS by the attainment date in accordance with section
179(c)(1).
    Comment 3: One commenter states that the contingency measures in
the attainment plan are ``hazy and unspecified'' and that the
``thorough analysis to identify the sources of the violation and bring
the area back into compliance with the NAAQS'' is ``wholly insufficient
to address NAAQS exceedances and ensure attainment, and that EPA
nowhere explains why such contingency measures are not already
triggered by the continuing levels of SO2 in the Allegheny
area.'' Another commenter states that ACHD should do more than what is
described in its contingency measures, particularly as the 2014
SO2 Guidance states that an air agency is not precluded from
requiring additional contingency measures that are enforceable and
appropriate for a particular source category, and should include a
``comprehensive program to identify sources of violations and undertake
an aggressive follow-up for compliance and enforcement, provide
specific contingency measures, as well as including specific
contingency measures.''
    Response 3: As EPA explained in the 2014 SO2 Guidance,
SO2 presents special considerations, compared to other
criteria pollutants.\8\ First, for some of the other criteria
pollutants, the analytical tools for quantifying the relationship
between reductions in precursor emissions and resulting air quality
improvements remain subject to significant uncertainties, in contrast
with procedures for directly-emitted pollutants such as SO2.
Second, emission estimates and attainment analyses for other criteria
pollutants can be strongly influenced by overly optimistic assumptions
about control efficiency and rates of compliance for many small
sources. This is not the case for SO2.
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    \8\ See EPA's 2014 SO2 Nonattainment Guidance, p. 41.
See also SO2 Guideline Document, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards,
Research Triangle Park, N.C. 27711, EPA-452/R-94-008, February 1994,
p. 6-40. See General Preamble for the Implementation of Title I of
the Clean Air Act Amendments of 1990 at 57 FR 13498 (April 16,
1992).
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    In contrast, the control efficiencies for SO2 control
measures are well understood and are far less prone to uncertainty.
Because SO2 control measures are, by definition, 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.

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.\9\
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    \9\ See EPA's 2014 SO2 Nonattainment Guidance, p. 41.
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    As noted in the NPRM, Section 7 of the Allegheny attainment plan
details the requirements whenever the SO2 NAAQS is exceeded.
It requires ACHD to, within 10 days of a violation, complete an
analysis to determine the source and the conditions that contributed to
the violation. The culpable source would then be required to submit,
within 10 days of notification by ACHD, a written system audit report
that details the operating parameters of all SO2 emissions
units for the time periods during which the violation occurred, along
with recommended control strategies for any unit that may have
contributed to the violation. Following a 30-day evaluation period and
a 30-day consultation period with the source, additional control
measures will be implemented as expeditiously as possible to return the
area to compliance. Further, the installation permits for the four
sources of SO2 in the Area, which are incorporated by
reference into the Allegheny portion of the Pennsylvania SIP, require
SO2 compliance testing, monitoring, and reporting to assure
compliance with the permit limits, including any instances of non-
compliance with the conditions of the permit and the corrective action
taken to restore compliance.
    Also, ACHD has a comprehensive program to identify potential
sources causing SO2 NAAQS violations, as specified in ACHD
Article XXI, Part I, Regulations 2109.01 through 2901.06, and 2901.10
(Enforcement). Under these regulations, ACHD is authorized to take any
action it deems necessary or proper for the effective enforcement of
any provision of Article XXI and the rules and regulations promulgated
under the article. Any violation authorizes ACHD to pursue the issuance
of an enforcement order as authorized under the Article (for corrective
action or shut down of a source or part of a source), the revocation of
any applicable license or installation or operating permit, or
initiation of criminal proceedings, civil penalty, or injunctive
relief. Also, the permits for the four main sources of SO2
include a requirement to record all instances of non-compliance with
the conditions of the permits upon occurrence along with the corrective
action taken to restore compliance. As explained in response to comment
2 of this action, following implementation of all the control measures
contained in this attainment plan on October 4, 2018, the Allegheny
Area did not experience any SO2 NAAQS exceedances except for
those exceedances directly traceable to the two fires and shutdowns of
the desulfurization unit at the Clairton Coke Works. ACHD took
immediate enforcement action to minimize emissions resulting from the
first fire, in accordance with the contingency measures outlined in its
attainment plan, and the desulfurization unit shutdown because of the
second fire lasted only a few hours. ACHD's implementation of some of
the contingency measures contained in its attainment plan in response
to the first fire at Clairton shows that the source-specific
enforcement response in the plan can be effective at preventing further
exceedances of the SO2 NAAQS. Since the restart of the
desulfurization unit at Clairton and the return to typical operations
at Clairton, there have been no further recorded exceedances of the
SO2 NAAQS in the Allegheny Area. Thus, the Allegheny Area is
currently meeting the 2010 SO2 NAAQS without implementation
of the contingency measures in the plan, so there is no need to trigger
contingency measures at this time. If there are no further unforeseen
breakdowns in SO2 emission controls at the four facilities,
the modeling shows that the existing control measures in the plan are
adequate to ensure attainment of the 2010 SO2 NAAQS.
    Comment 4: The commenter asserts that EPA's reliance on long-term
emission limits ensures that attainment will not be achieved because
the 2010 SO2 NAAQS is a short-term, 1-hour standard, and the
proposed 30-day averaging period for the Clairton and Irvin Plants are
fundamentally incapable of protecting the standard. The commenter
asserts that because the NAAQS is evaluated through reference to the
4th-highest daily maximum ambient concentration annually, ambient air
quality conditions can be rendered unsafe by as few as four hours of
elevated emissions over the course of a year, thus making an emission
limit with an averaging period of longer than one hour unlikely to be
able to protect this short-term standard. The commenter argued that
spikes in emissions could cause short-term elevations in ambient
SO2 levels sufficient to violate the NAAQS while nonetheless
averaging out over longer periods such that the 30-day average permit
limit is ``complied'' with. To support this contention, the commenter
provided language making similar points excerpted from two EPA letters
that were included in the attachments to the commenter's December 19,
2018 comment letter on the NPRM, specifically an August 12, 2010
comment letter from EPA Region 7 to Kansas regarding the Sunflower
Holcomb Station Expansion Project, and a February 1, 2012 comment
letter from EPA Region 5 to Michigan regarding a draft construction
permit for the Detroit Edison Monroe Power Plant. The commenter
concluded that the 30-day average emission limit proposed for the major
sources are 720 times the NAAQS and should be revised to adequately
protect the NAAQS. The commenter states the proposed long-term limits
should be rejected in favor of a plan with 1-hour emission limits to
protect the 1-hour NAAQS.
    Response 4: EPA disagrees with the commenter's statement that the
proposed 30-day limits at Clairton and Irvin are fundamentally
incapable of protecting the 1-hour SO2 NAAQS. EPA believes
as a general matter that properly set, longer-term average limits are
comparably effective in providing for attainment of the 1-hour
SO2 standard as are 1-hour limits. EPA's 2014 SO2
Guidance sets forth in detail the reasoning supporting its conclusion
that the distribution of emissions that can be expected in compliance
with a properly set longer-term average limit is likely to yield
overall air quality protection that is as good as a corresponding
hourly emissions limit set at a level that provides for attainment.
    EPA's 2014 SO2 Guidance specifically addressed this
issue as it pertains to requirements for SIPs for SO2
nonattainment areas under the 2010 NAAQS, especially with regard to the
use of appropriately set comparably stringent limitations based on
averaging times as long as 30 days. EPA found that a longer-term
average limit which is comparably stringent to a short-term average
limit is likely to yield comparable air quality; and that the net
effect of allowing emissions variability over time but requiring a
lower average emission level is that the resulting worst-case air
quality is likely to be comparable to the worst-case air quality
resulting from the corresponding higher

short-term emission limit without variability. See 2014 SO2
Guidance.
    Any accounting of whether a 30-day average limit provides for
attainment must consider factors reducing the likelihood of exceedances
as well as factors creating risk of additional exceedances. To
facilitate this analysis, EPA used the concept of a critical emission
value (CEV) for the SO2-emitting facilities which are being
addressed in a nonattainment SIP. The CEV is the continuous 1-hour
emission rate which is expected to provide for the average annual 99th
percentile maximum daily 1-hour concentration to be 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 Guidance.
    EPA recognizes that a 30-day limit can allow occasions in which
emissions exceed the CEV, and such occasions yield the possibility of
exceedances occurring that would not be expected if emissions were
always at the CEV. At the same time, the establishment of the 30-day
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 at the CEV. On those critical modeled days in which
emissions at the CEV are expected to result in concentrations exceeding
75 ppb, emissions set to comply with a 30-day average level which is
below the CEV may well result in concentrations below 75 ppb. Requiring
emissions on average to be below the CEV introduces significant chances
that emissions will be below the CEV on critical days, so that such a
requirement creates significant chances that air quality would be
better than 75 ppb on days that, with emissions at the CEV, would have
exceeded 75 ppb.
    The NPRM provides an illustrative example of the effect that
application of a limit with an averaging time longer than one hour can
have on air quality.\10\ This example illustrates both (1) the
possibility of elevated emissions (emissions above the CEV) causing
exceedances not expected with emissions at or below the CEV and (2) the
possibility that the requirement for routinely lower emissions would
result in avoiding exceedances that would be expected with emissions at
the CEV. In this example, moving from a 1-hour limit to a 30-day
average limit results in one day that exceeds 75 ppb that would
otherwise be below 75 ppb, one day that is below 75 ppb that would
otherwise be above 75 ppb, and one day that is below 75 ppb that would
otherwise be at 75 ppb. In net, the 99th percentile of the 30-day
average limit scenario is lower than that of the 1-hour limit scenario,
with a design value of 67.5 ppb rather than 75 ppb. Stated more
generally, this example illustrates several points: (1) The variations
in emissions that are accounted for with a longer-term average limit
can yield higher concentrations on some days and lower concentrations
on other days, as determined by the factors influencing dispersion on
each day, (2) one must account for both possibilities, and (3)
accounting for both effects can yield the conclusion that a properly
set longer-term average limit can provide as good or better air quality
than allowing constant emissions at a higher level. As noted in the
NPRM, and as described in Appendix B of the 2014 SO2
Guidance, EPA expects that an emission profile with a comparably
stringent 30-day average limit is likely to have a net effect of having
a lower number of exceedances and better air quality than an emissions
profile with maximum allowable emissions under a 1-hour emission limit
at the critical emission value. Thus, EPA continues to assert that
appropriately set 30-day emission limits can be protective of the 1-
hour SO2 standard.
---------------------------------------------------------------------------

    \10\ For the full discussion of the hypothetical example, see
NPRM, November 19, 2018 (83 FR 58206) at page 58209 at https://www.regulations.gov, Docket ID Number EPA-R03-OAR-2017-0730.
---------------------------------------------------------------------------

    Regarding the examples cited by the commenter to support the
contention that only one-hour limits are protective of the NAAQS, EPA's
April 2014 guidance acknowledges that EPA had previously recommended
that averaging times in SIP emission limits should not exceed the
averaging time of the applicable NAAQS. The specific examples of
earlier EPA statements cited by the commenter (i.e., those contained in
Exhibits 1 and 2 of Appendix A of the comment submission) all pre-date
the release of EPA's April 2014 SO2 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 their own
issuance. At the time of their issuance, 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 1-hour, with appropriate
adjustments that would make it comparably stringent to an emission
limit shown to attain 1-hour emission levels, 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.
However, EPA's April 2014 guidance specifically addressed this issue as
it pertains to requirements for SIPs for SO2 nonattainment
areas under the 2010 NAAQS, especially with regard to the use of
appropriately set comparably stringent limitations based on averaging
times as long as 30 days (see p. 2). EPA developed this guidance
pursuant to a lengthy stakeholder outreach process regarding
implementation strategies for the 2010 NAAQS, which had not yet
concluded (or in some cases even begun) when the documents cited by the
commenter were issued. As such, EPA's April 2014 Guidance was the first
instance in which the Agency provided recommended guidance for that
component of this action. Consequently, EPA does not view those prior
EPA statements as conflicting with the Agency's guidance addressing
this specific question of how to devise a longer-term limit that is
comparably stringent to a 1-hour CEV that has been modeled to attain
the NAAQS. Moreover, EPA notes that the commenter has not raised
specific objections to the general policy and technical rationale EPA
provided in its proposed approval or in EPA's April 2014 SO2
Guidance for why such longer-term averaging-based limits may in
specific cases be adequate to ensure NAAQS attainment.
    Additionally, ACHD requires supplementary limits to restrict
excessive frequency or magnitude of elevated emissions. As explained in
the April 2014 SO2 Guidance, in addition to establishing a
rate that is comparably stringent to the 1-hour average emission limit,
a second important factor in assessing whether a longer-term average
limit provides appropriate protection against NAAQS violations is
whether the source can be expected to comply with a long term average
limit in a manner that minimizes the frequency of occasions with
elevated emissions and magnitude of emissions on those occasions. The
2014 SO2 Guidance states that use of long term average
limits is most defensible if the frequency and magnitude of such
occasions of elevated emissions will be minimal, and that supplemental
limits on the frequency and/or magnitude of occasions of elevated
emissions can be a valuable element of a plan that protects against
NAAQS violations. Limits against excessive frequency and/or magnitude
of elevated emissions could further strengthen the justification for
the use of longer-term average limits,

with one option being shorter averaging times. Towards this end, ACHD
established 24-hour average limits to supplement the 30-day average
limits. A discussion of ACHD's evaluation of the limits and a tabular
comparison of hourly emissions values to the 30-day, the 24-hour, and
CEV limits may be found in the NPRM.
    Comment 5: EPA relies on conversion factors from CEV calculated by
reference to the sulfur content of the fuel the facilities use. Such
content can vary widely, depending on the fuel mix the facility chooses
to buy. However, nothing in the proposal requires that the historical
fuel mix be maintained, meaning that variability could increase, and
increase substantially, in the future, underscoring the inadequacy of
long-term emission limits.
    Response 5: In the 2014 SO2 Guidance, EPA notes that it
is important to recognize that some sources may have variable
emissions, for example due to variations in fuel sulfur content as the
commenter notes, that can make it extremely difficult, even with a
well-designed control strategy, to ensure in practice that stringent
hourly limits are never exceeded. It is this variability in emissions
that EPA believes justifies the use of longer-term average limits.
    EPA guidance provides for states to use historic data to assess the
emissions variability that can be anticipated upon implementation of
the plan. The state is to analyze these data to obtain a best estimate
of the degree of adjustment needed for the state's longer-term limit to
be comparably stringent to the one-hour limit that it would otherwise
be adopting. EPA does not believe that imposing limits on variability
is either appropriate or feasible. First, EPA's guidance for assessing
variability is to use three to five years of data, which suggests that
a limit on variability might require a similar amount of data. A limit
based on three to five years of data would almost certainly not be
practically enforceable. Second, a limit on variability would
necessarily impose limits on the operation of the facility. As a
general matter, EPA prefers to avoid restricting the operation of
facilities, so long as EPA has reasonable confidence that air quality
requirements are being met. The commenter gives no reason to believe
that variability will increase and provides no recommendations on how
to address the practical problems that limiting variability would
entail. Furthermore, page 31 of EPA's 2014 SO2 Guidance
acknowledges the possibility that variability can change and provides
EPA's views on how to address such situations: ``If the EPA approves an
attainment plan but subsequently learns that emissions variability at a
source is exceeding the expected variability, such that the plan proves
not to provide the expected confidence that the NAAQS is being
attained, the EPA will use its available authority to pursue any
necessary corrections of the plan.'' However, at this time, EPA
believes that ACHD has identified 1-hour limits that would provide for
attainment and has submitted 30-day average limits (supplemented with
24-hour limits) that present evidence indicates are comparably
stringent, and so EPA is concluding that these limits suffice to assure
attainment.
    Comment 6: The commenter expresses bafflement as to why EPA's
November 19, 2018 NPRM did not definitively verify that certain
controls required by the plan to be installed and operational no later
than October 4, 2018 were actually installed and operating, especially
when EPA relied upon the installation and operation of these controls
when approving the attainment plan.
    Response 6: The ACHD installation permits for Clairton, Edgar
Thomson, Irvin, and Harsco required compliance on or before October 4,
2018. These facilities were required by that date to comply with the
SO2 emission limitations and other requirements for
monitoring and recordkeeping set forth in the permits. The NPRM for
this action did not include information on the sources' actual
compliance with the required permit limits as of October 4, 2018.
However, the issue in this rulemaking is whether compliance with the
plan would result in timely attainment, as shown by the modeling.
Whether such compliance or such attainment actually occurred is best
addressed by the Clean Air Act's enforcement authorities and a
determination of attainment under section 179(c)(1) of the CAA.
    Comment 7: A commenter states that section V.D. of the proposed SIP
requires Vacuum Carbonate Units (VCU) to be implemented at only two
facilities, rather than at all facilities in the Allegheny Area, and
opines that though this would allow the Area to meet the requirement
for compliance, it does not comprise all reasonably available control
measures on SO2 emissions. The commenter further states that
if a VCU is a reasonably available measure for some plants, it should
be reasonable to many, if not all, of the facilities in the Area. To
protect the nearby residents, the commenter thinks that as a minimum,
all measures which can be reasonably enforced should be applied to all
emitting facilities in the Allegheny Area.
    Response 7: Section 172 (c)(1) of the CAA provides that ``Such plan
shall provide for the implementation of all reasonably available
control measures as expeditiously as practicable (including such
reductions in emissions from existing sources in the area as may be
obtained through the adoption, at a minimum, of reasonably available
control technology) and shall provide for attainment of the national
primary ambient air quality standards.'' EPA intends to continue
defining RACT for SO2 as that control technology which will
achieve the NAAQS within statutory timeframes. See General Preamble at
57 FR 13498, 13547 (April 16, 1992). CAA section 172(c)(6) requires
plans to include enforceable emission limitations and control measures
as may be necessary or appropriate to provide for attainment by the
attainment date. The commenter has failed to consider that VCUs were
already pre-existing at these process lines and that RACT for
SO2 is that which is necessary to attain the NAAQS. While
additional controls may be reasonably available at other plants, the
VCU upgrades at the two process lines at the Clairton facility show
attainment of the 2010 SO2 NAAQS by the attainment date, and
thus further controls are not necessary to satisfy the requirement for
RACT.
    Emission reductions needed to reach attainment in the Allegheny
Area, as determined through air dispersion modeling, are dependent on
the control measures implemented at the existing sources at USS Mon
Valley Works (upon which property Harsco Metals is located), which are
the primary sources of SO2 in the nonattainment area. The
100 and 600 VCU upgrade was initiated at the Clairton Coke Works to
reduce the content of H2S in the COG sent to all the Mon
Valley Works plants and Harsco. The 100 VCU upgrade was completed at
the Clairton Coke Works in 2016, leading to significant decreases in
sulfur content in COG. An upgrade for the 600 VCU added redundant
controls for the COG line. All the USS Mon Valley Works facilities and
Harsco must also provide source monitoring results to demonstrate
continuous efficient operation of the VCU system. The reduction of
H2S content in the COG produced at Clairton was needed for
the USS Mon Valley Works plants and Harsco to comply with their permit
limits. Emission limits at all four facilities were established through
enforceable installation permits (See Appendix K of Pennsylvania's
October

3, 2017 SIP submittal).\11\ The collective emission limits and related
compliance parameters (i.e., testing, monitoring, record keeping and
reporting) will be incorporated into the SIP as part of the attainment
plan in accordance with CAA section 172. The emission limits for each
of the SO2-emitting USS Mon Valley and Harsco facilities are
listed in Tables 3, 4 and 5 of the proposal. The compliance parameters
include continuous process monitoring of H2S content and
flow rate of the COG at the Clairton facility and the four lines which
feed the Edgar Thompson, Irvin, and Harsco facilities, as well as
record-keeping, reporting, and stack testing requirements at all
facilities.
---------------------------------------------------------------------------

    \11\ ACHD's SIP submittal can be found at https://www.regulations.gov, Docket ID Number EPA-R03-OAR-2017-0730.
---------------------------------------------------------------------------

    ACHD nonetheless evaluated potential RACT at other sources in the
Allegheny Area including Koppers Inc.--Clairton Plant, Clairton Slag--
West Elizabeth Plant, Eastman Chemical Resins Inc.--Jefferson Plant,
and Kelly Run Sanitation--Forward Township, each of which have less
than 5 tons per year (tpy) of allowable SO2 emissions. In
addition, ACHD examined several RACM options for area, nonroad and
mobile sources of SO2 in the Area. ACHD determined that no
additional controls beyond the emission limits at the four main
SO2-emitting facilities in the Allegheny Area are needed to
provide for attainment of the SO2 NAAQS in the Area. Because
of this, additional controls on other SO2 sources in the
Area are not required RACT for the Allegheny Area.\12\
---------------------------------------------------------------------------

    \12\ See Footnote 8 of this preamble.
---------------------------------------------------------------------------

    Comment 8: The commenter believes that the boundaries of the
Allegheny Area may be drawn too narrowly, due to insufficient
monitoring for SO2 throughout Allegheny County. The
commenter specifically notes that there is no monitoring station for
SO2 near Springdale, where the Cheswick Generating Station,
the largest source of SO2 in the County, is located. The
commenter believes that ACHD's continuing failure to address the
insufficient monitoring in Allegheny County means that the monitoring
data is not fully representative of air quality in the nonattainment
area. The commenter asks EPA to require ACHD to gather sufficient
information regarding ambient levels of SO2 near Springdale,
or otherwise provide sufficient evidence that there is no possibility
of the Area being in nonattainment with the NAAQS.
    Response 8: EPA notes that the boundaries of the Allegheny Area
were determined in 2013 as part of the process of designating the Area
as nonattainment, and therefore the boundaries of the Area are not
being reconsidered in this action. EPA issued its final rule
identifying the first round of designations for the 2010 SO2
NAAQS on August 5, 2013 (78 FR 47191). In the first round of
SO2 designations, EPA explained that the designations were
based on recorded air quality monitoring data at existing monitor
locations. Areas designated as nonattainment with the NAAQS were
designated based on the design value at existing monitors that showed
violations of the 1-hour SO2 standard during the three-year
period of 2009-2011. EPA designated as nonattainment 29 areas,
including the Allegheny Area, in the August 5, 2013 action. In
accordance with section 107(d)(1)(B)(ii) of the CAA, the boundaries of
the Allegheny Area were also determined as part of the designations
process. EPA determined at that time that the Allegheny Area should not
include the portion of the County containing the Cheswick plant. EPA's
technical support document (TSD) for the August 5, 2013 final rule
provides the rationale for determining both the nonattainment
designation and the boundaries of the Allegheny County area. As
explained in the TSD, the Liberty monitor in Allegheny County showed
violations of the 2010 SO2 NAAQS, based on certified 2009-
2011 air quality data and additional data from 2012 provided by
Pennsylvania and ACHD. EPA concluded that, based on the supporting
information relating to emissions, air quality data, meteorology,
geography and jurisdictional boundaries provided by Pennsylvania and
ACHD in response to EPA's 120-day letters, only a portion of Allegheny
County should be initially included in the Allegheny Area, and that the
remaining portion of the Area would be evaluated in a separate round of
designations. Prior to finalizing the Round 1 designations, EPA
provided the public with an opportunity to comment upon the proposed
designations, including the boundaries of the designated area. 78 FR
11124, 11125-26 (February 15, 2013). The commenter's opportunity to
express concerns about the boundaries of the Allegheny Area was during
this public comment period, and therefore this comment is untimely and
not germane to this final action. The commenter was again given an
opportunity to comment on the air quality status of the remaining
portion of Allegheny County that was not included in the Round 1
designation when EPA sought public input on the ``Round 3''
designations for SO2, which included the portion of
Allegheny County containing the Cheswick plant. 82 FR 41903, 41905
(September 5, 2017).
    On January 9, 2018 at 83 FR 1098, EPA published in the Federal
Register, a final rule with Round 3 designations for the 2010
SO2 NAAQS for numerous areas of the U.S., including the
remaining portion of Allegheny County where the Cheswick plant is
located. EPA designated this remaining portion as ``unclassifiable,''
meaning that under CAA section 107(d)(1) the area cannot be classified
as meeting or not meeting the NAAQS or as contributing to a nearby area
that does not meet the NAAQS based on available information. 834 FR
1154 January 9, 2018; 40 CFR 81.339. No one challenged EPA's
designation of the remaining portion of Allegheny County. Therefore,
EPA believes that this comment regarding the boundaries of the
Allegheny Area is untimely and not germane to this rule.
    Regarding the portion of the comment questioning the sufficiency of
the SO2 monitoring network in Allegheny County, and in
particular near the Cheswick plant, EPA notes that the proper place to
challenge any lack of monitors is when ACHD public notices its Annual
Network Monitoring Plan for public comment. This action does not reopen
EPA's previous designations made under the 2010 SO2
standard, however, for informational purposes only, the following
information from the 2013 Allegheny Area Round 1 designations TSD is
provided herein. As part of the analysis for the 2013 Round 1
designation of the Allegheny Area, EPA evaluated the Cheswick Power
Plant. Cheswick's emissions have been significantly reduced since
installation and operation of its SO2 control equipment,
comprised of a wet flue gas desulfurization (FGD) unit installed in
2010. In the analysis, EPA looked at Cheswick's 2011 and 2012
SO2 emissions from the Clean Air Markets Division (CAMD)
database, which indicated a large decrease in annual SO2
emissions between 2011 and 2012, primarily due to increased control
efficiency at the plant. In 2011, Cheswick's coal-fired unit ran for
6,160 hours at an annually averaged emission rate of 0.71 pounds per
Million british thermal units (lbs/MMbtu). In 2012, Cheswick's coal
unit ran slightly less at 5,715 hours with an annually averaged
emission rate of 0.15 lbs/MMbtu. In light of Cheswick's lower emission
rates, its distance of approximately 24 kilometers from the Liberty
monitor, and minimal change in the monitored values at the Liberty
monitor, EPA did

not include this source in the Allegheny nonattainment area. EPA
therefore defined the nonattainment area boundaries for the Allegheny
Area based on the information available at the time of the initial
designations and is not reopening that designation in this final SIP
approval for the Allegheny area.
    Comment 9: The commenter believes that ACHD should install and
operate an SO2 monitor at the Glassport location, which was
discontinued in 2006 but showed higher levels of SO2 than
the Liberty monitor while it was operating. The commenter states that
the lack of a monitor at this location could become material to whether
the area is determined to be in attainment, and that while EPA prefers
air modeling over air monitoring for purposes of SO2
attainment demonstrations, this does not apply to attainment
determinations. The commenter cites EPA's Final rule for the
SO2 NAAQS, at 75 FR 35520, 35553 (June 22, 2010), in which
EPA indicated it was still considering under what circumstances it may
be appropriate to rely on monitoring data alone to make attainment
determinations. The commenter refers to the requirement that design
values for purposes of an attainment determination are necessarily
based on actual data from an ambient air quality monitoring site, thus
the failure to reactivate the Glassport monitor may become relevant to
an accurate determination of air quality in this area.
    Response 9: As noted in EPA's response to comment 2 of this action,
a determination of whether an area has attained or failed to attain the
NAAQS is a separate action from the review of an attainment
demonstration SIP and is outside the scope of this action approving the
SIP. EPA's SO2 attainment SIP review occurs under CAA
sections 110(k), 172(c) and 192(a), while a determination of
attainment/nonattainment of the NAAQS is governed by CAA section
179(c)(1). Under section 110(k)(3), EPA is required to approve a SIP
submission that meets all applicable requirements of the CAA. For the
reasons described in our proposal and elsewhere in this action, we have
concluded that the Allegheny Area attainment plan meets all such
requirements, including the requirement in 172(c) and 192(a) to provide
for attainment by the attainment date. This is the determination that
is the subject of this final SIP approval action. EPA will take a
separate action to analyze the pertinent information and determine
whether the Allegheny Area attained the NAAQS by the attainment date,
in accordance with section 179(c)(1) of the CAA.
    Also, although the former Glassport monitor may have recorded
higher levels of ambient SO2 emissions than the Liberty
monitor, those readings were taken before the new SO2 limits
were imposed on the USS Mon Valley Works and Harsco facilities as part
of the attainment plan. The modeling analysis submitted by ACHD with
its attainment plan shows that with these new limits at these
facilities, the entire nonattainment area would attain the 2010
SO2 NAAQS, including at the former Glassport monitor
location.
    Comment 10: A commenter claims that ACHD should evaluate impacts of
its transported emissions of SO2 on other states' attainment
with the NAAQS, and that SO2 is a precursor to the formation
of fine particulates (PM2.5). The commenter claims that
``the Department'', i.e., ACHD, does not discuss the impact of sources
in Allegheny County on levels of SO2 or PM2.5
outside this nonattainment area, but does discuss the impact of upwind
sources (outside the County) on SO2 levels in the Allegheny
County nonattainment area. In addition, ACHD also included modeling of
upwind sources outside the nonattainment area. The commenter cites to
the attainment plan's statement that some sources outside of the NAA
have been included in the modeling demonstration in order to properly
account for transported emissions into the nonattainment area. The
commenter states that a plan must include adequate provisions
prohibiting any source from emitting any air pollutant in amounts which
will contribute significantly to nonattainment in, or interfere with
maintenance by, any other state with respect to a NAAQS as required
under section 110(a)(2)(D) of the CAA. In ACHD's Response to Comments
document dated June 13, 2017, the commenter claims that the Department
avoids the question by asserting that ``SO2 as a precursor
to PM2.5 is better addressed via PM2.5 modeling
using photochemical modeling, and development of an attainment
demonstration for the 2012 PM2.5 NAAQS for Allegheny County
is underway.'' Comment #45, page 19-20. The commenter also states that
ACHD incorrectly made an assertion that the PM2.5 attainment
plan was underway when responding to comments concerning transported
emissions from Allegheny County during the state public comment period,
and that ACHD was over two years late in meeting the CAA requirements
to address the nonattainment with the 2012 PM2.5 standard,
asserting that ACHD only made revisions to its NNSR regulations after
EPA issued a finding of failure to submit required nonattainment area
requirements.
    Response 10: Because the comment pertains to emissions that
contribute significantly to nonattainment in, or interfere with
maintenance by, any other state, EPA assumes that the commenter is
referring specifically to the CAA requirements under section
110(a)(2)(D)(i)(I), and not the other elements of section 110(a)(2)(D)
(namely 110(a)(2)(D)(i)(II), which pertains to measures required under
part C to prevent significant deterioration of air quality or to
protect visibility, and 110(a)(2)(D)(ii), which pertains to
requirements for interstate and international pollution abatement).
Section 110(a)(2)(D)(i)(I) of the CAA requires that SIPs contain
adequate provisions to prohibit any emissions source or activity in a
state from contributing significantly to nonattainment in, or
interfering with maintenance by, any other state with respect to a
primary or secondary NAAQS. The section 110(a)(2)(D)(i)(I) requirements
for a state are not linked with a particular nonattainment area's
designation and classification in that state. The requirements under
section 110(a)(2)(D)(i)(I), where applicable, continue to apply to a
state regardless of the designation of any one particular area in the
state. Therefore, for the purposes of an attainment plan, EPA disagrees
that the showing of noninterference with another state's SIP under CAA
110(a)(2)(D)(i)(I) is an element that must be addressed in a section
172(c) plan submitted for the purpose of attainment of a NAAQS within
that state. EPA believes that the requirements linked with a particular
nonattainment area's designation and classifications are the relevant
measures to evaluate in reviewing an attainment plan. Thus, EPA does
not believe that the CAA's section 110(a)(2)(D)(i)(I) interstate
transport requirements should be construed to be applicable
requirements for purposes of approval of the Allegheny Area attainment
SIP submittal.
    The requirements for nonattainment area SIPs are addressed in CAA
sections 110(k), 172(a), and 192(a), and consist of an attainment plan,
including an attainment demonstration, a base year emissions inventory,
RFP, RACM/RACT, and contingency measures. EPA's evaluation of whether
an attainment plan submittal is approvable hinges on the approvability
of these nonattainment area requirements. In taking action on
infrastructure SIPs

under section 110(a)(2) of the CAA, of which the transport element is a
part, EPA has long noted the separate requirements and the different
time frames for submission of infrastructure SIPs and nonattainment
area SIPs. In its attainment SIP, ACHD appropriately considered
emissions from outside the nonattainment area in the modeling analysis
to determine necessary limits at the SO2 emitting facilities
within the Allegheny County nonattainment area. However, an analysis of
the impacts of any SO2 or PM2.5 emissions from
sources in the Allegheny Area upon downwind areas in other states, is
outside the scope of this action to approve the Allegheny Area
attainment plan for the SO2 NAAQS. Such an analysis would be
a required part of any Pennsylvania submittal for an infrastructure SIP
under section 110(a)(2). Thus, EPA does not believe that the CAA's
interstate transport requirements should be construed to be applicable
requirements for purposes of approval of an attainment plan.
    EPA also disagrees that nonattainment area requirements related to
the PM2.5 NAAQS must be addressed in the Allegheny Area's
SO2 attainment plan. While SO2 is a precursor to
PM2.5, the SO2 attainment plan was submitted and
is being approved to show attainment with the 2010 1-hour
SO2 NAAQS. EPA agrees with ACHD's response to the comment
that the PM2.5 attainment plan will have to address all
PM2.5 precursors, including SO2, and that the
PM2.5 modeling analysis is better suited to determining
SO2's impact as a precursor to PM2.5 when
analyzing what is needed for PM2.5 attainment. Finally,
EPA's findings of failure to submit the PM2.5 attainment
plan for the 2012 PM2.5 NAAQS, and whether or not attainment
planning for PM2.5 in Allegheny County is underway, are not
relevant to this action to approve the Allegheny Area attainment plan
for SO2.
    Comment 11: The commenter suggested that there may be other
measures and control strategies to facilitate attainment of the
SO2 NAAQS, and that EPA should require ACHD to develop
additional requirements for emissions reductions from these facilities.
The commenter included several suggestions for additional emission
reductions, including the use of lower-sulfur coal, a lower percentage
of allowable leaking doors at the Clairton facility, and efficiency
initiatives.
    Response 11: EPA agrees that it may be appropriate for the
facilities to continue exploring operational and process improvements
to reduce SO2 emissions. However, EPA has determined that
the submittal, including the measures in the facility permits submitted
by Pennsylvania for incorporation into the Allegheny County portion of
the Pennsylvania SIP, represent the level of controls and measures
necessary for the Allegheny Area to attain the SO2 NAAQS,
and it is therefore not necessary to compel adoption of additional
measures in order to approve the SIP. ACHD's modeling analysis shows
these measures will achieve attainment of the SO2 NAAQS in
the Allegheny Area. See also the discussion of RACM/RACT for the
Allegheny Area in EPA's response to comment 7 of this action.
    Comment 12: ACHD should have imposed immediate deadlines for
implementing proposed control strategies and should not have waited
until the attainment date. This postponement of compliance with control
strategies until the exact attainment date contradicts EPA's policy
relating to attainment plans. The commenter claims that EPA requires
the state permitting agency to generate at least one calendar year of
compliance information, prior to the attainment date. The commenter
referenced EPA's 2014 SO2 Guidance, which states that ``EPA
would expect states to require sources to begin complying with the
attainment strategy in the SIP no later than January 1, 2017. By this
means, the plans would be able to provide at least l calendar year of
air quality monitoring data (and at least 1 calendar year of compliance
information which, when modeled, would show attainment) before the
applicable attainment deadline, indicating that the plan is in fact
providing for attainment.'' In ACHD's Response to Comments document
dated June 13, 2017, it states that ``[t]he design, construction, and
implementation of all projects for this SIP necessitate the longer
schedule than prescribed by the general NAAQS schedule,'' without
citing any evidence. EPA should require more of an explanation from the
Department for the delay in requiring control measures, which is
inconsistent with EPA's guidance document.
    Response 12: EPA's 2014 SO2 Guidance, as cited by the
commenter, sets forth the expectation that one year of compliance or
monitored data would be available as supporting evidence that modeling
performed for the attainment plan, and the control measures adopted by
the attainment plan, provide for attainment. In the case of the
measures for the sources in the Allegheny Area that were needed for
attainment, EPA proposed approval of the plan based on ACHD's submitted
modeling demonstration showing that the measures would provide for
attainment. Although one year of compliance data was not available at
the time of the proposal, EPA believes it was appropriate, despite the
Guidance recommendation on monitoring and compliance data, to propose
our action. As 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.\13\ The 2014 SO2 Guidance addresses the best
case scenario, but does not fit the current situation, so EPA has to
use its judgment as to whether the lack of one year of monitored data
which reflects the implementation of the control measures prior to the
attainment date, under these circumstances, invalidates the modeling
showing that these controls can achieve attainment. As part of this
analysis, EPA looked at the AQS data for the Liberty monitor, which is
included in the docket for this final rule. This data shows that after
October 4, 2018, the date by which the control measures in the
attainment plan were required at the Mon Valley Works and Harsco
facilities, there were no exceedances between October 4, 2018 and
December 23, 2018, which was the day just preceding the day of the fire
at the Clairton Plant. As discussed previously, outside of the time
frame during which the desulfurization plant at Clairton was not
operational due to the fire on December 24, 2018, there were no
monitored violations at the Liberty monitor. Preliminary data for 2019
also shows that outside of the time frame for the control outage from
the December 2018 fire, no monitored violations have occurred. EPA
believes that although the 2019 data is preliminary, the October
through December 2018 data and the 2019 preliminary data suggests that
compliance with the measures have been effective in showing that the
measures provide for attainment. The three quarters of preliminary data
for 2019 is included in the docket for this final rule. Fourth quarter
2019 data is normally submitted into AQS by March 31, 2020, and
certification of data is required by May 1, 2020. Because actual
monitored data (that was not impacted by the fires) show no exceedances
after the October 4, 2018 deadline to meet the new measures, it is not
necessary or

useful to look back at the reasons the measures were not required
sooner.
---------------------------------------------------------------------------

    \13\ See 2014 SO2 Guidance, p. 9.
---------------------------------------------------------------------------

    The portion of the 2014 SO2 Guidance referenced by the
commenter is there for the purpose of recommending what is preferred
for a determination of attainment under CAA section 179(c), rather than
what is necessary for assessing whether an attainment plan would
provide for attainment by the attainment date under section 172(c) of
the CAA. Therefore, the lack of one year of monitored data before the
attainment date does not invalidate this attainment plan approval
action.
    Comment 13: The commenter provided a preliminary evaluation of
ambient air quality monitoring data for the three-year period of 2016-
2018, which suggests that the Allegheny Area will be in nonattainment
due to data at the Liberty monitor. The commenter cites a predicted
design value of 101 ppb, based on the average of the fourth-highest
maximum hourly values for 2016, 2017, and 2018. The commenter asked EPA
to provide an evaluation whether the design value for 2016-2018 will in
fact be below the NAAQS, as anticipated by ACHD. This should include
substantiation regarding its projection of what the design value will
be, based on monitored data. If the numbers demonstrate that it will
exceed the standard, the commenter states that the Department should
revise the state implementation plan to require additional emissions
reductions sufficient to meet the standard.
    Response 13: Although this design value was not as anticipated by
ACHD when it responded to comments received on the proposed Allegheny
Area attainment plan, the monitoring data available at that time should
not be interpreted as indicating that the attainment plan fails to
provide for attainment. The monitoring data cited by the commenter were
collected before the full implementation of the measures in the
Allegheny SO2 attainment plan on October 4, 2018. Therefore,
these data do not show the improvement in air quality and monitored
values which were expected from full implementation of the measures
used in the modeling demonstration. As such, these data are not a
reliable indicator of whether air quality, after implementation of all
modeled, relevant control measures, would be expected to meet the
standard at the attainment deadline. In other words, these data are not
indicative of the adequacy of the plan and its modeling demonstration
to provide for NAAQS attainment. As noted previously, EPA's 2014
SO2 Guidance and actions implementing the SO2
NAAQS explain that 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. Given the form of the 2010 NAAQS as the three-year
average of the 99th percentile of the yearly distribution of 1-hour
daily maximum SO2 concentrations, it is often possible that
the three-year period of monitored data will contain some monitored
results which preceded implementation of the newer remedial control
measures. These monitored results would not reflect the air quality
levels resulting from implementation of the attainment plan control
measures. In such cases, as it is here, the more complete and
representative analysis for informing action on a submitted SIP should
focus on the results of newly implemented control measures required
under the plan and the modeling demonstration based on those control
measures, rather than pre-control, measured concentrations that do not
reflect the results of the plan's required control measures. The former
analysis explicitly addresses whether air quality will be attaining (as
required) under the state's submitted plan, whereas the latter analysis
may have little to no bearing on what will happen as a result of the
plan. Therefore, in the context of reviewing the adequacy of those
newer control measures to provide for newly attaining air quality under
sections 172 and 192 of the CAA, we conclude that it is reasonable to
rely on the modeling results that specifically account for those
control measures and the resulting reductions in SO2
emissions, rather than on monitored data that, in this case, do not
represent air quality levels resulting from full implementation of the
control measures in the attainment plan. In the Allegheny
SO2 attainment plan, ACHD's modeling shows that
implementation of the measures included in the plan result in air
quality that attains the NAAQS.
    Comment 14: The commenter claims that the Department (or ACHD) did
not adequately address the problems in the proposed revision. ACHD
correctly states that ``reasonable further progress'' contemplates
``annual incremental reductions in emissions.'' However, the data
provided in this section only demonstrates overall ambient reduction in
SO2 at the Liberty monitor. The data would have to show
annual incremental reductions in SO2 emissions specifically
at each source, in order to demonstrate reasonable further progress.
See 42 U.S.C. 7501(1). The Department confuses the concept of
``reasonable further progress'' by setting forth a chart showing
declining concentrations of SO2 at a monitoring site. But as
set forth above, that is not what the statute calls ``reasonable
further progress.'' See 42 U.S.C. 7501(1). The Department provides
further evidence of this confusion when it asserts that ``[the]
shutdown of Guardian Industries in 2015 is an additional decrease in
emissions for the NAA . . . .'' Id., page 32. Comparing decreases in
ambient concentrations with decreases in source emissions is like
comparing apples to oranges.
    At best, the Department implies there have been some emissions
reductions ``due to partially-completed projects by USS (including
projects that have not been quantified for this SIP).'' See Id. But the
Department must quantify those emissions, and it must demonstrate
``reasonable further progress'' in this proposed plan revision. The
fact that projects are only ``partially-completed,'' and the Department
has not even quantified them for this plan, demonstrates that the
Department has failed to show ``reasonable further progress.'' See Id.
    ACHD's response to the commenter was that, for RFP, ``the
definition is generally less pertinent to pollutants like
SO2 that usually have a limited number of sources affecting
areas of air quality which are relatively well defined, and emissions
control measures for such sources result in swift and dramatic
improvement in air quality. . . . Given that source controls are in
effect `single steps' for RFP for SO2, and the initial
controls are only partially in place (for an 8-month period in 2016 for
the VCU upgrades), incremental reductions cannot be classified.
Emission reductions cannot be double counted by applying them to both
the control strategy and RFP. As a method to indicate downward
progress, concentration data was used along with quantifiable
reductions in emissions.'' \14\
---------------------------------------------------------------------------

    \14\ See October 3, 2017 Pennsylvania submittal, p. 79.
---------------------------------------------------------------------------

    The commenter asserts that ACHD's argument is flawed because it is
premised on the notion that there will be a swift and dramatic
improvement in air quality, which remains to be seen, and also because
emissions reductions cannot be double-counted by applying them to both
the control strategy and RFP, and is not a defense to not doing single-
counting of additional emissions reductions from means other than VCU
upgrades, such as limiting leaking doors. Stated differently, just
because a facility has invested in an item of capital equipment to
reduce emissions does not mean that it should not be

required to explore other opportunities for emissions reductions. The
commenter believes that EPA should require more from ACHD by way of RFP
and require additional emissions reductions above and beyond those
achievable through recent projects.
    Response 14: ACHD's response to comments on its proposed attainment
plan relies on EPA's 2014 SO2 Guidance and the discussion of
the RFP requirement. As explained in the 2014 SO2 Guidance,
section 171(1) of the CAA defines RFP as ``such annual incremental
reductions in emissions of the relevant air pollutant as are required
by this part (part D) or may reasonably be required by the EPA for the
purpose of ensuring attainment of the applicable NAAQS by the
applicable attainment date.'' 2014 SO2 Guidance, pp. 40 and
41. The 2014 SO2 Guidance goes on to explain that ``[a]s EPA
has previously explained, this definition is most appropriate for
pollutants that are emitted by numerous and diverse sources, where the
relationship between any individual source and the overall air quality
is not explicitly quantified, and where the emission reductions
necessary to attain the NAAQS are inventory-wide. We have also
previously explained that the definition is generally less pertinent to
pollutants like SO2 that usually have a limited number of
sources affecting areas of air quality which are relatively well
defined, and emissions control measures for such sources result in
swift and dramatic improvement in air quality. That is, for
SO2, there is usually a single `step' between pre-control
nonattainment and post-control attainment, thus annual incremental
reductions that would be required for some other pollutants, as
discussed in the 2014 Guidance, would not be necessary prior to
attainment. Therefore, for SO2, with its discernible
relationship between emissions and air quality, and significant and
immediate air quality improvements, we explained in the General
Preamble that RFP is best construed as `adherence to an ambitious
compliance schedule.' See 74 FR 13547, April 16, 1992. This means that
the air agency needs to ensure that affected sources implement
appropriate control measures as expeditiously as practicable in order
to ensure attainment of the standard by the applicable attainment
date.'' Id. The Guidance further states that, by definition, the RFP
provision requires only such reductions in emissions as are necessary
to attain the NAAQS. If a modeling analysis for an area shows that the
SIP will timely attain the NAAQS, then the purpose of the RFP
requirement will have been fulfilled, and since the modeling for this
area makes that demonstration, additionally showing that the area will
make RFP toward attainment has no further utility. We took this view
with respect to the general RFP requirement under CAA section l
72(c)(2) in the ``General Preamble for the Implementation of Title I of
the Clean Air Act Amendments of 1990'' (General Preamble) (see 57 FR
13498, 13564, April 16, 1992). See 72 FR at 20604, 2014 SO2
Guidance, p. 54. The modeling demonstration, which takes into account
the new SO2 reduction measures at the four facilities in the
Area that were required no later than October 4, 2018, shows that the
SIP provides for the Allegheny Area to attain the 2010 SO2
NAAQS by October 4, 2018. Because the modeling for the Area shows
attainment of the NAAQS by the attainment date through timely
compliance with the new emission limits in the permits, RFP, as
interpreted for the purpose of SO2, has been met in this
Area.
    Further, as noted in EPA's response to comment 2 of this action,
preliminary monitoring data for 2019 (excluding the monitoring data
collected during the control outage caused by the December 2018 fire at
Clairton Coke Works) supports the modeling results that the SIP
provides for attainment of the Area with respect to the 2010
SO2 NAAQS.
    Comment 15: The commenter believes that there should be no
averaging period at all, given the complexity of the air shed in the
nonattainment area, and that long-term averaging for the VCU at the
Clairton facility should be rejected. The commenter also states that a
better explanation of the calculations and analysis regarding the CEV
should have been included in the submittal to provide EPA and the
public an opportunity to assess whether the long-term average is
appropriate in this case. The 2014 SO2 Guidance sets forth
the steps to establish longer-term limits that are comparably
stringent, including determination of a CEV; each of these steps should
be shown in the submittal to accurately assess whether there is
comparable stringency. The commenter also stated that ACHD did not have
enough data for its B Line VCU upgrade to determine comparable
stringency values. The commenter believes that ACHD used eight months
of data for this line, projected out to three to five years, as the
basis of its calculations of an adjustment factor for determining long
term average limits that would be comparably stringent to 1-hour limits
at the CEV. The commenter believes that this amount of data is
inadequate for this purpose and believes that ACHD should have used
data from a comparable site having three to five years of operating
data.
    Response 15: The validity of long-term average limits is addressed
in EPA's response to comment 4 of this action. With regard to the data
used in the calculations for the determination of the CEV value,
Appendix C of the 2014 SO2 Guidance shows an example
calculation and the steps needed to determine a longer-term average
emission limit. Step 1 of the calculation is to conduct dispersion
modeling to determine a source's 1-hour CEV that could be used as a
baseline for determination of a longer-term average limit that is
comparably stringent to the CEV. These values are shown in Tables 3-1
and 3-3 of the Commonwealth's submittal. Step 2 is to compile emissions
data reflecting the distribution of emissions that is expected once the
attainment plan is implemented. Emission distributions describe the
frequency with which different emission levels occur, which may be
depicted by graphing the number of hours per year (for example) that
emissions are within a particular range, as a function of emission
level. A key element of this step is selection of an appropriate
emissions data set. This step is especially important if the attainment
plan is expected to involve installation of control equipment or other
similarly significant changes in operations. The choice of control
strategy can have a significant effect on the emission distribution.
For example, installation and operation of flue gas desulfurization
equipment, particularly in the absence of requirements for continuous
operation of the equipment, can lead to an emission distribution in
which most emission values are significantly lower but occasional
values remain relatively high, thus enlarging the difference between
peak emission values and longer-term average emission values.
Consequently, if the source being addressed does not currently operate
flue gas desulfurization equipment but the attainment plan is likely to
involve installation and operation of such equipment, the current
emissions profile data for the source may not provide a suitable
representation of the variability of emissions that might be expected
after the attainment plan controls are in place.
    The 2014 SO2 Guidance states that in such cases, as
suggested by the commenter, Step 2 would involve identifying another
set of data that better reflects the source's expected emission
variability, presumably from

another comparable source that is already implementing the control
strategy that the target source anticipates using. In other cases, the
2014 SO2 Guidance states that ``the air agency may determine
that an area could attain through a control strategy that will not
significantly change the emission distribution. Where the control
strategy does not significantly change the distribution, the source's
current emission distribution may be the best indicator of the source's
post-control emission distribution. Irrespective of whether the future
emissions variability does or does not match the historic emissions
variability at a source, a critical element of Step 2 is to assure that
the data used to analyze prospective emissions variability at the
source properly reflects the emissions variability that might be
expected at the source once the SIP is implemented''. See 2014
SO2 Guidance, pp 31-32.
    Clairton Works is a distinctive source, being the nation's largest
coke works and being relatively well controlled. Thus, EPA believes
that no other source could provide a data set that could represent the
emissions variability resulting from burning COG from Clairton Works
better than data from Clairton Works itself.
    As described in Appendix D of its documentation, ACHD analyzes 2014
to 2016 data from four units at Clairton Works: Unit 1, Unit 2, Line A,
and Line B. The commenter focuses in particular on the calculations for
Line B, which the commenter incorrectly states are based on data for
the eight months in this period after an upgrade to its sulfur removal
equipment. In fact, these calculations are based on data for the entire
3-year period. EPA's 2014 SO2 Guidance, at page 29, states,
``The EPA anticipates that data sets reflecting hourly data for at
least three to five years of stable operation (i.e., without changes
that significantly alter emissions variability) would be needed to
obtain a suitably reliable analysis.'' Thus, for Line B, the ideal data
set would have reflected three to five years of data following
implementation of the control upgrade. However, such a data base, by
definition including data at least through April 2019, was not
available to ACHD for its October 2017 submittal. Almost as good would
have been a data base reflecting three to five years of data from
before the control upgrade, so long as the data could be demonstrated
to be reflective of variability after implementation of the control
upgrade. ACHD did not explain whether or why such a data base was not
available. However, ACHD did compare the emissions distributions before
and after the control upgrade, concluding that the emissions after the
control upgrade exhibit similar variability (albeit at around one
fourth the levels) as emissions before the control upgrade. ACHD
justified the use of data from the entirety of 2014 to 2016 on this
basis.
    As a general matter, EPA's recommendation to use data from a period
without significant changes in controls is intended in part to assure
that the data base purely represents variability of emissions within a
specific control regime, not variability from one control regime to
another. Although ACHD has provided information to support its
assertions that the variability of emissions at the Line B after the
control upgrade are similar to their variability before the control
upgrade, this information does not address concerns about using a data
base that mixes 28 months of relatively high (pre-upgrade) data with
eight months of relatively low (post-upgrade) data.
    EPA conducted additional analyses of ACHD's data to evaluate
whether, despite these concerns, the results of ACHD's analysis of the
Line B data might nevertheless provide a suitable estimation of the
degree of adjustment warranted to determine comparably stringent
longer-term average limits. EPA computed adjustment factors using 2014
SO2 Guidance Appendix C methods for three scenarios: (1)
Using all pertinent data for the full three years (as was done by
ACHD), (2) using only pre-upgrade data, and (3) using a three year data
set in which the post-upgrade data are adjusted according to the
average emission reduction from the upgrade, to simulate a three-year
pre-upgrade data base. A spreadsheet showing these computations is
provided in the docket, and the results for these three scenarios are
shown in Table 2.

                     Table 2--Adjustment Factors for Line B COG Using Alternative Data Sets
----------------------------------------------------------------------------------------------------------------
                                                         36 Months of
                                                        unadjusted data    28 Months of pre-    36 Months, with
                      Scenario                          (ACHD approach)    upgrade data (%)   adjustment of post-
                                                              (%)                              upgrade data (%)
----------------------------------------------------------------------------------------------------------------
30-day average......................................               83.4                82.2                78.3
24-hour average.....................................               94.4                94.2                93.5
----------------------------------------------------------------------------------------------------------------

    As these results show, ACHD's results are similar to the results
they would have obtained either using a 28-month data base using only
pre-upgrade data or using a data base with adjustments as if all 36
months of data were at pre-upgrade levels. The data suggest that the
99th percentile values for all averaging times are, not surprisingly,
during the higher, pre-upgrade period; in this respect, the analysis
appears to be more sensitive to pre-upgrade variability than to post-
upgrade variability, and the analysis predominantly reflects
variability during a 28-month period and thus is a potentially less
robust result than would be obtained with three years of data with a
constant control regime. Nevertheless, these data support ACHD's
assertion that post-upgrade variability is similar to pre-upgrade
variability, and EPA believes more broadly that ACHD's results provide
a suitable adjustment factor for determining the longer-term limits for
units firing B Line COG that are comparably stringent to the 1-hour
limits that otherwise would have been set.
    Step 3 of EPA's recommended procedure is to use the selected data
set to compute longer-term (in this case 30-day and 24-hour) average
values. Step 4 is to determine the 99th percentile of the 1-hour and
longer-term average values. Step 5 is to calculate the ratio of the
values determined in Step 4, to be used as an adjustment factor. The
values that ACHD obtained through these steps are documented in
Appendix D Tables D-4-2, D-4-3, and D-4-4. The application of these
adjustment factors to limits for units that fire COG from these four
sources are shown in Table 3-3 of the main SIP document.
    The commenter expresses concern that EPA does not have estimates of
the expected frequency or magnitude of emissions in excess of the CEV.
Such an analysis is complicated by the number of different emission
units that burn

COG from these four sets of COG origins. Nevertheless, as stated in the
NPRM, the application of 24-hour average limits as well as 30-day
limits will help assure that the frequency and magnitude of emissions
above the CEV will be modest. If the facility has no values that exceed
the 30-day and 24-hour average limits (i.e., if the facility complies
with the SIP limits), then EPA expects correspondingly few values above
the corresponding 1-hour value (i.e., the CEV) as well.
    Comment 16: The commenter requested that EPA substantially revise
the NPRM before finalizing and should ensure attainment without
ignoring monitor data showing nonattainment with the standard.
    Response 16: EPA has concluded that a revised NPRM is not warranted
because the comments do not identify a flaw in ACHD's plan which would
require a plan revision in order to meet the requirements of the CAA.
As previously explained in our response to comments 2 and 13 of this
action, in the context of reviewing the adequacy of newer control
measures to provide for newly attaining air quality under sections 172
and 192 of the CAA, we conclude that it is reasonable to focus on the
modeling results that specifically account for those control measures
and the resulting reductions in SO2 emissions, rather than
on monitored data that, in this case, do not represent air quality
levels resulting from full implementation of the control measures in
the attainment plan, which ACHD's modeling shows result in air quality
that attains the NAAQS. For the reasons described in our proposal and
in the preceding responses to comments, we find that the Allegheny
SO2 attainment plan meets all applicable requirements under
the CAA and EPA's implementing regulations. Accordingly, we are
finalizing our approval of the Allegheny SO2 attainment
plan.

IV. Final Action

    EPA is approving Pennsylvania's attainment plan SIP revision for
the Allegheny Area, as submitted by ACHD through PADEP to EPA on
October 3, 2017, for the purpose of demonstrating attainment of the
2010 1-hour SO2 NAAQS. 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 Allegheny Area and that the Pennsylvania
SIP revision has met the requirements for NNSR for the 2010 1-hour
SO2 NAAQS. Additionally, EPA is approving into the Allegheny
County portion of the Pennsylvania SIP the SO2 emission
limits and compliance parameters in the following permits, all of which
are dated September 14, 2017: ACHD Permit 0052-1017 for the Clairton
Plant; ACHD Permit 0051-1006 for the Edgar Thomson Plant; ACHD Permit
0050-1008 for the Irvin Plant, and ACHD Permit 0265-1001 for Braddock
Recovery/Harsco Metals.
    EPA has determined that Pennsylvania's SO2 attainment
plan for the 2010 1-hour SO2 NAAQS for the Allegheny Area
meets the applicable requirements of the CAA and is consistent with
EPA's 2014 SO2 Guidance. Thus, EPA is approving
Pennsylvania's attainment plan for the Allegheny Area as submitted on
October 3, 2017. This final action of this SIP submittal removes EPA's
duty to implement a FIP for this Area, and discharges EPA's requirement
under the court order to take final action on the SIP by April 30,
2020.

V. Incorporation by Reference

    In this document, EPA is finalizing regulatory text that includes
incorporation by reference. In accordance with the requirements of 1
CFR 51.5, EPA is finalizing the incorporation by reference of
SO2 emission limits and compliance parameters in ACHD
permits. EPA has made, and will continue to make, these materials
generally available 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.\15\
---------------------------------------------------------------------------

    \15\ 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 SIP approvals are exempted under
Executive Order 12866.
     Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact
on a substantial number of small entities under the Regulatory
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have Federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based
on health or safety risks subject to Executive Order 13045 (62 FR
19885, April 23, 1997);
     Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the CAA; and
     Does not provide EPA with the discretionary authority to
address, as appropriate, disproportionate human health or environmental
effects, using practicable and legally permissible methods, under
Executive Order 12898 (59 FR 7629, February 16, 1994).
    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 June 22, 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 Allegheny Area attainment plan for
the 2010 SO2 NAAQS 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, Reporting and recordkeeping requirements, Sulfur oxides.

    Dated: April 17, 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
``U.S. Steel Clairton'', ``U.S. Steel Edgar Thomson'', ``U.S. Steel
Irvin'', and ``Braddock Recovery/Harsco Metals'' at the end of the
table; and
0
b. The table in paragraph (e)(1) is amended by adding an entry for
``Allegheny Area 2010 SO2 attainment plan and base year
emissions inventory'' at the end of the table.
    The additions read as follows:

Sec.  52.2020   Identification of plan.

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

----------------------------------------------------------------------------------------------------------------
                                                                                Additional
                                                                 State                             explanation/
        Name of source            Permit No.        County     effective    EPA approval date     Sec.   52.2063
                                                                 date                                citation
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
U.S. Steel Clairton..........  Redacted          Allegheny    9/14/17     4/23/20, [insert       Sulfur dioxide
                                Installation                               Federal Register       emission
                                Permit 0052-                               citation].             limits and
                                1017.                                                             related
                                                                                parameters in
                                                                                unredacted
                                                                                portions of
                                                                                the
                                                                                Installation
                                                                                Permit.
U.S. Steel Edgar Thomson.....  Redacted          Allegheny    9/14/17     4/23/20, [insert       Sulfur dioxide
                                Installation                               Federal Register       emission
                                Permit 0051-                               citation].             limits and
                                1006.                                                             related
                                                                                parameters in
                                                                                unredacted
                                                                                portions of
                                                                                the
                                                                                Installation
                                                                                Permit.
U.S. Steel Irvin.............  Redacted          Allegheny    9/14/17     4/23/20, [insert       Sulfur dioxide
                                Installation                               Federal Register       emission
                                Permit 0050-                               citation].             limits and
                                1008.                                                             related
                                                                                parameters in
                                                                                unredacted
                                                                                portions of
                                                                                the
                                                                                Installation
                                                                                Permit.
Braddock Recovery/Harsco       Redacted          Allegheny    9/14/17     4/23/20, [insert       Sulfur dioxide
 Metals.                        Installation                               Federal Register       emission
                                Permit 0265-                               citation].             limits and
                                1001.                                                             related
                                                                                parameters in
                                                                                unredacted
                                                                                portions of
                                                                                the
                                                                                Installation
                                                                                Permit.
----------------------------------------------------------------------------------------------------------------

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

----------------------------------------------------------------------------------------------------------------
    Name of non-regulatory SIP          Applicable           State                                Additional
             revision                geographic area    submittal date   EPA approval date       explanation
----------------------------------------------------------------------------------------------------------------

                                                  * * * * * * *
Allegheny Area 2010 SO2            Cities of Clairton,        10/03/17  4/23/20, [insert     Also see:
 attainment plan and base year      Duquesne, and                        Federal Register     52.2033(d) and EPA-
 emissions inventory.               McKeesport; the                      citation].           approved redacted
                                    Townships of                                              permits for: U.S.
                                    Elizabeth,                                                Steel Clairton
                                    Forward, and North                                        (0052-1017); U.S.
                                    Versailles, and                                           Steel Edgar
                                    the following                                             Thompson (0051-
                                    Boroughs:                                                 1006); U.S. Steel
                                    Braddock,                                                 Irvin (0050-1008);
                                    Dravosburg, East                                          and Braddock
                                    McKeesport, East                                          Recovery/Harsco
                                    Pittsburgh,                                               Metals (0265-
                                    Elizabeth,                                                1001).
                                    Glassport,
                                    Jefferson Hills,
                                    Liberty, Lincoln,
                                    North Braddock,
                                    Pleasant Hills,
                                    Port Vue,
                                    Versailles, Wall,
                                    West Elizabeth,
                                    and West Mifflin.
----------------------------------------------------------------------------------------------------------------

* * * * *

0
3. Section 52.2033 is amended by adding paragraph (e) to read as
follows:

Sec.  52.2033   Control strategy: Sulfur dioxide.

* * * * *
    (e) EPA approves the 2010 1-hour SO2 attainment plan for
the City of Clairton, City of Duquesne, City of McKeesport, Borough of
Braddock, Borough of Dravosburg, Borough of East McKeesport, Borough of
East Pittsburgh,

Borough of Elizabeth, Borough of Glassport, Borough of Jefferson Hills,
Borough of Liberty, Borough of Lincoln, Borough of North Braddock,
Borough of Pleasant Hills, Borough of Port Vue, Borough of Versailles,
Borough of Wall, Borough of West Elizabeth, Borough of West Mifflin,
Elizabeth Township, Forward Township, and North Versailles Township in
Pennsylvania, submitted by the Department of Environmental Protection
on October 3, 2017.

[FR Doc. 2020-08573 Filed 4-22-20; 8:45 am]
 BILLING CODE 6560-50-P