Approval and Promulgation of Air Quality Implementation Plans; Pennsylvania; Attainment Plan for the Allegheny, Pennsylvania Nonattainment Area for the 2010 Sulfur Dioxide Primary National Ambient Air Quality Standard, 58206-58219 [2018-25079]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 83, Number 223 (Monday, November 19, 2018)]
[Proposed Rules]
[Pages 58206-58219]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-25079]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R03-OAR-2017-0730; FRL-9986-63-Region 3]


Approval and Promulgation of Air Quality Implementation Plans; 
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: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve a state implementation plan (SIP) revision, submitted by the 
Pennsylvania Department of Environmental Protection (PADEP) on behalf 
of the Allegheny County Health Department (ACHD), to EPA on October 3, 
2017, for the purpose of providing 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 
major sources of SO2 in the Allegheny Area are the Harsco 
Metals facility and the facilities which comprise the U.S. Steel (USS) 
Mon Valley Works: Clairton, Edgar Thomson and Irvin Plants. The 
Pennsylvania SIP submission is an attainment plan which includes the 
base year emissions inventory, an analysis of the reasonably available 
control technology (RACT) and reasonably available control measure 
(RACM)

[[Page 58207]]

requirements, enforceable emission limitations and control measures, a 
reasonable further progress (RFP) plan, a modeling demonstration of 
SO2 attainment, a nonattainment New Source Review (NNSR) 
permit program, and contingency measures for the Allegheny Area. As 
part of approving the attainment plan, EPA is also proposing to approve 
new SO2 emission limits and associated compliance parameters 
for USS Clairton, Edgar Thomson and Irvin Plants and the Harsco Metals 
facility into the Allegheny County portion of the Pennsylvania SIP. 
This action is being taken under the Clean Air Act (CAA).

DATES: Written comments must be received on or before December 19, 
2018.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R03-
OAR-2017-0730 at https://www.regulations.gov, or via email to 
[email protected]. For comments submitted at Regulations.gov, 
follow the online instructions for submitting comments. Once submitted, 
comments cannot be edited or removed from Regulations.gov. For either 
manner of submission, EPA may publish any comment received to its 
public docket. Do not submit electronically any information you 
consider to be confidential business information (CBI) or other 
information whose disclosure is restricted by statute. Multimedia 
submissions (audio, video, etc.) must be accompanied by a written 
comment. The written comment is considered the official comment and 
should include discussion of all points you wish to make. EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e. on the web, cloud, or other file sharing 
system). For additional submission methods, please contact the person 
identified in the FOR FURTHER INFORMATION CONTACT section. For the full 
EPA public comment policy, information about CBI or multimedia 
submissions, and general guidance on making effective comments, please 
visit https://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Leslie Jones Doherty, (215) 814-3409, 
or by email at [email protected].

SUPPLEMENTARY INFORMATION: 

Table of Contents

I. Background for EPA's Proposed Action
II. Requirements for SO2 Nonattainment Plans
III. Attainment Demonstration and Longer Term Averaging
IV. Pennsylvania's Attainment Plan Submittal for the Allegheny Area
V. EPA's Analysis of Pennsylvania's Attainment Plan Submittal for 
the Allegheny Area
    A. Pollutants Addressed
    B. Emissions Inventory Requirements
    C. Air Quality Modeling
    D. RACM/RACT
    E. RFP Plan
    F. Contingency Measures
    G. New Source Review
VI. EPA's Proposed Action
VII. Incorporation by Reference
VIII. Statutory and Executive Order Reviews

I. Background for EPA's Proposed Action

    On June 2, 2010, the EPA Administrator signed a final rule 
establishing a new SO2 primary NAAQS as a 1-hour standard of 
75 parts per billion (ppb), based on a 3-year average of the annual 
99th percentile of daily maximum 1-hour average concentrations. See 75 
FR 35520 (June 22, 2010), 40 CFR 50.17. This action also revoked the 
existing 1971 annual standard and 24-hour standards, subject to certain 
conditions.\1\ EPA established the NAAQS based on significant evidence 
and numerous health studies demonstrating that serious health effects 
are associated with short-term exposures to SO2 emissions 
ranging from 5 minutes to 24 hours with an array of adverse respiratory 
effects including narrowing of the airways which can cause difficulty 
breathing (bronchoconstriction) and increased asthma symptoms. For more 
information regarding the health impacts of SO2, please 
refer to the June 22, 2010, final rulemaking. See 75 FR 35520. 
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, EPA promulgated 
initial air quality designations for 29 areas for the 2010 
SO2 NAAQS (78 FR 47191), which became effective on October 
4, 2013, based on violating air quality monitoring data for calendar 
years 2009-2011, where there was sufficient data to support a 
nonattainment designation.\2\
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    \1\ With certain exceptions, EPA's June 22, 2010 final action 
revoked the two 1971 primary 24-hour standard of 140 ppb and the 
annual standard of 30 ppb because they were determined not to add 
additional public health protection given a 1-hour standard at 75 
ppb. See 75 FR 35520. However, the secondary 3-hour SO2 
standard was retained. Because Allegheny County has already been 
designated for the 2010 1-hour SO2 NAAQS and was neither 
designated nonattainment nor subject to a SIP call for the 1971 
primary standards, these standards have been revoked for this area. 
See 40 CFR 50.4(e).
    \2\ 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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    Effective on October 4, 2013, the Allegheny Area was designated as 
nonattainment for the 2010 SO2 NAAQS for an area that 
encompasses the primary SO2 emitting sources of the Harsco 
Metals facility and the USS Mon Valley Works (Clairton, Edgar Thomson 
and Irvin Plants). The Allegheny Area is comprised of a portion of 
Allegheny County which includes 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. The 
October 4, 2013 final designation triggered a requirement for 
Pennsylvania to submit a SIP revision with an attainment plan for how 
the Area would attain the 2010 SO2 NAAQS as expeditiously as 
practicable, but no later than October 4, 2018, in accordance with CAA 
sections 172 and 191-192.
    For a number of areas, including the Allegheny Area, EPA published 
a notice on March 18, 2016, that Pennsylvania and other pertinent 
states had failed to submit the required SO2 attainment plan 
by this 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. However, pursuant to 
Pennsylvania's submittal of October 3, 2017, and EPA's subsequent 
letter dated October 6, 2017 to Pennsylvania finding the submittal 
complete and noting the stopping of the sanctions' deadline, these 
sanctions under section 179(a) will not be imposed as a consequence of 
Pennsylvania's having missed the original deadline. Additionally, under 
CAA section 110(c), the finding triggers 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

[[Page 58208]]

submittal and EPA has approved the submittal as meeting applicable 
requirements.

II. Requirements for SO2 Nonattainment Area Plans

    Attainment plans must meet the applicable requirements of the CAA, 
and specifically CAA sections 172, 191, and 192. The required 
components of an attainment plan submittal are listed in section 172(c) 
of Title 1, part D of the CAA. The EPA's regulations governing 
nonattainment SIPs are set forth at 40 CFR part 51, with specific 
procedural requirements and control strategy requirements residing 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 the ``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 Nonattainment Guidance) for how state submissions could 
address the statutory requirements for SO2 attainment 
plans.\3\ In this guidance, EPA described the statutory requirements 
for an attainment plan, which includes: 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)). A synopsis of these requirements is also provided in the 
notice of proposed rulemaking on the Illinois SO2 
nonattainment plans, published on October 5, 2017 at 82 FR 46434.
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    \3\ 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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    In order for EPA to fully approve a SIP as meeting the requirements 
of CAA sections 110, 172 and 191-192 and EPA's regulations at 40 CFR 
part 51, the SIP for the affected area needs to demonstrate to EPA's 
satisfaction that each of the aforementioned requirements have been 
met. Under CAA sections 110(l) and 193, EPA may not approve a SIP that 
would interfere with any applicable requirement concerning NAAQS 
attainment and RFP, or any other applicable requirement, and no 
requirement in effect (or required to be adopted by an order, 
settlement, agreement, or plan in effect before November 15, 1990) in 
any area which is a nonattainment area for any air pollutant, may be 
modified in any manner unless it insures equivalent or greater emission 
reductions of such air pollutant.

III. Attainment Demonstration and Longer Term Averaging

    CAA section 172(c)(1) directs states with areas designated as 
nonattainment to demonstrate that the submitted plan provides for 
attainment of the NAAQS. 40 CFR part 51, subpart G further delineates 
the control strategy requirements that SIPs must meet, and EPA has long 
required that all SIPs and control strategies reflect four fundamental 
principles of quantification, enforceability, replicability, and 
accountability. General Preamble, at 13567-68. SO2 
attainment plans must consist of two components: (1) Emission limits 
and other control measures that assure implementation of permanent, 
enforceable and necessary emission controls, and (2) a modeling 
analysis which meets the requirements of 40 CFR part 51, Appendix W 
which demonstrates that these emission limits and control measures 
provide for timely attainment of the primary SO2 NAAQS as 
expeditiously as practicable, but by no later than the attainment date 
for the affected area. In all cases, the emission limits and control 
measures must be accompanied by appropriate methods and conditions to 
determine compliance with the respective emission limits and control 
measures and must be quantifiable (i.e., a specific amount of emission 
reduction can be ascribed to the measures), fully enforceable 
(specifying clear, unambiguous and measurable requirements for which 
compliance can be practicably determined), replicable (the procedures 
for determining compliance are sufficiently specific and non-subjective 
so that two independent entities applying the procedures would obtain 
the same result), and accountable (source specific limits must be 
permanent and must reflect the assumptions used in the SIP 
demonstrations). EPA's 2014 SO2 Nonattainment Guidance 
recommends that the emission limits established for the attainment 
demonstration be expressed as short-term average limits (e.g., 
addressing emissions averaged over one or three hours), but also 
describes the option to utilize emission limits with longer averaging 
times of up to 30 days so long as the state meets various suggested 
criteria. See 2014 SO2 Nonattainment Guidance, pp. 22 to 39. 
The guidance recommends that--should states and sources utilize longer 
averaging times--the longer term average limit should be set at an 
adjusted level that reflects a stringency comparable to the 1-hour 
average limit at the critical emission value shown to provide for 
attainment that the plan otherwise would have set.
    The 2014 SO2 Nonattainment Guidance provides an 
extensive discussion of EPA's rationale for positing that appropriately 
set comparably stringent limitations based on averaging times as long 
as 30 days can be found to provide for attainment of the 2010 
SO2 NAAQS. In evaluating this option, EPA considered the 
nature of the standard, conducted detailed analyses of the impact of 
use of 30-day average limits on the prospects for attaining the 
standard, and carefully reviewed how best to achieve an appropriate 
balance among the various factors that warrant consideration in judging 
whether a state's plan provides for attainment. Id. at pp. 22 to 39. 
See also id. at Appendices B, C, and D.
    As specified in 40 CFR 50.17(b), the 1-hour primary SO2 
NAAQS is met at an ambient air quality monitoring site when the 3-year 
average of the annual 99th percentile of daily maximum 1-hour average 
concentrations is less than or equal to 75 ppb. In a year with 365 days 
of valid monitoring data, the 99th percentile would be the fourth 
highest daily maximum 1-hour value. The 2010 SO2 NAAQS, 
including this form of determining compliance with the standard, was 
upheld by the U.S. Court of Appeals for the District of Columbia 
Circuit in Nat'l Envt'l Dev. Ass'n's Clean Air Project v. EPA, 686 F.3d 
803 (D.C. Cir. 2012). Because the standard has this form, a single 
exceedance does not create a violation of the standard. Instead, at 
issue is whether a source operating in compliance with a properly set 
longer term average could cause exceedances, and if so the resulting 
frequency and magnitude of such exceedances, and in particular whether 
EPA can have reasonable confidence that a properly set longer term 
average limit will provide that the average fourth highest daily 
maximum value will be at or below 75 ppb. A synopsis of how EPA judges 
whether such plans ``provide for attainment,'' based on modeling of 
projected allowable

[[Page 58209]]

emissions and in light of the NAAQS' form for determining attainment at 
monitoring sites follows.
    For SO2 plans based on 1-hour emission limits, the 
standard approach is to conduct modeling using fixed emission rates. 
The maximum emission rate that would be modeled to result in attainment 
(i.e., in an ``average year'' \4\ shows three, not four days with 
maximum hourly levels exceeding 75 ppb) is labeled the ``critical 
emission value.'' The modeling process for identifying this critical 
emissions value inherently considers the numerous variables that affect 
ambient concentrations of SO2, such as meteorological data, 
background concentrations, and topography. In the standard approach, 
the state would then provide for attainment by setting a continuously 
applicable 1-hour emission limit at this critical emission value.
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    \4\ An ``average year'' is used to mean a year with average air 
quality. While 40 CFR 50 Appendix T provides for averaging three 
years of 99th percentile daily maximum values (e.g., the fourth 
highest maximum daily concentration in a year with 365 days with 
valid data), this discussion and an example below uses a single 
``average year'' in order to simplify the illustration of relevant 
principles.
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    EPA recognizes that some sources have highly variable emissions, 
for example due to variations in fuel sulfur content and operating 
rate, that can make it extremely difficult, even with a well-designed 
control strategy, to ensure in practice that emissions for any given 
hour do not exceed the critical emission value. EPA also acknowledges 
the concern that longer term emission limits can allow short periods 
with emissions above the ``critical emissions value,'' which, if 
coincident with meteorological conditions conducive to high 
SO2 concentrations, could in turn create the possibility of 
a NAAQS exceedance occurring on a day when an exceedance would not have 
occurred if emissions were continuously controlled at the level 
corresponding to the critical emission value. However, for several 
reasons, EPA believes that the approach recommended in its guidance 
document suitably addresses this concern. First, from a practical 
perspective, EPA expects the actual emission profile of a source 
subject to an appropriately set longer term average limit to be similar 
to the emission profile of a source subject to an analogous 1-hour 
average limit. EPA expects this similarity because it has recommended 
that the longer term average limit be set at a level that is comparably 
stringent to the otherwise applicable 1-hour limit (reflecting a 
downward adjustment from the critical emissions value) and that takes 
the source's emissions profile into account. As a result, EPA expects 
either form of emission limit to yield comparable air quality.
    Second, from a more theoretical perspective, EPA has compared the 
likely air quality with a source having maximum allowable emissions 
under an appropriately set longer term limit, as compared to the likely 
air quality with the source having maximum allowable emissions under 
the comparable 1-hour limit. In this comparison, in the 1-hour average 
limit scenario, the source is presumed at all times to emit at the 
critical emission level, and in the longer term average limit scenario, 
the source is presumed occasionally to emit more than the critical 
emission value but on average, and presumably at most times, to emit 
well below the critical emission value. In an ``average year,'' 
compliance with the 1-hour limit is expected to result in three 
exceedance days (i.e., three days with hourly values above 75 ppb) and 
a fourth day with a maximum hourly value at 75 ppb. By comparison, with 
the source complying with a longer term limit, it is possible that 
additional exceedances would occur that would not occur in the 1-hour 
limit scenario (if emissions exceed the critical emission value at 
times when meteorology is conducive to poor air quality). However, this 
comparison must also factor in the likelihood that exceedances that 
would be expected in the 1-hour limit scenario would not occur in the 
longer term limit scenario. This result arises because the longer term 
limit requires lower emissions most of the time (because the limit is 
set well below the critical emission value), so a source complying with 
an appropriately set longer term limit is likely to have lower 
emissions at critical times than would be the case if the source were 
emitting as allowed with a 1-hour limit.
    As a hypothetical example to illustrate these points, suppose a 
source that always emits 1000 pounds of SO2 per hour, which 
results in air quality at the level of the NAAQS (i.e., results in a 
design value of 75 ppb). Suppose further that in an ``average year,'' 
these emissions cause the 5 highest maximum daily average 1-hour 
concentrations to be 100 ppb, 90 ppb, 80 ppb, 75 ppb, and 70 ppb. Then 
suppose that the source becomes subject to a 30-day average emission 
limit of 700 pounds per hour. It is theoretically possible for a source 
meeting this limit to have emissions that occasionally exceed 1000 
pounds per hour, but with a typical emissions profile, emissions would 
much more commonly be between 600 and 800 pounds per hour. In this 
simplified example, assume a zero background concentration, which 
allows one to assume a linear relationship between emissions and air 
quality. (A nonzero background concentration would make the mathematics 
more difficult but would give similar results.) Air quality will depend 
on what emissions happen on what critical hours, but suppose that 
emissions at the relevant times on these 5 days are 800 pounds/hour 
(lb/hr), 1100 pounds per hour, 500 pounds per hour, 900 pounds per 
hour, and 1200 pounds per hour, respectively. (This is a conservative 
example because the average of these emissions, 900 pounds per hour, is 
well over the 30-day average emission limit.) These emissions would 
result in daily maximum 1-hour concentrations of 80 ppb, 99 ppb, 40 
ppb, 67.5 ppb, and 84 ppb. In this example, the fifth day would have an 
exceedance that would not otherwise have occurred, but the third day 
would not have an exceedance that otherwise would have occurred, and 
the fourth day would have been below, rather than at, 75 ppb. In this 
example, the fourth highest maximum daily concentration under the 30-
day average would be 67.5 ppb.
    This simplified example illustrates the findings of a more 
complicated statistical analysis that EPA conducted using a range of 
scenarios using actual plant data. As described in Appendix B of EPA's 
2014 SO2 Nonattainment Guidance, EPA found that the 
requirement for lower average emissions is highly likely to yield 
better air quality than is required with a comparably stringent 1-hour 
limit. Based on analyses described in Appendix B of its 2014 
SO2 Nonattainment Guidance, EPA expects that an emission 
profile with maximum allowable emissions under an appropriately set 
comparably stringent 30-day average limit is likely to have the net 
effect of having a lower number of exceedances and better air quality 
than an emission profile with maximum allowable emissions under a 1-
hour emission limit at the critical emission value. This result 
provides a compelling policy rationale for allowing the use of a longer 
averaging period, in appropriate circumstances where the facts indicate 
this result can be expected to occur.
    The question then becomes whether this approach, which is likely to 
produce a lower number of overall exceedances even though it may 
produce some unexpected exceedances above the critical emission value, 
meets the requirement in section 110(a)(1) and 172(c)(1) for SIPs to 
``provide for attainment'' of the NAAQS. For SO2, as for 
other pollutants, it is generally impossible to design a nonattainment

[[Page 58210]]

plan in the present that will guarantee that attainment will occur in 
the future. A variety of factors can cause a well-designed attainment 
plan to fail and unexpectedly not result in attainment, for example if 
meteorology occurs that is more conducive to poor air quality than was 
anticipated in the plan. Therefore, in determining whether a plan meets 
the requirement to provide for attainment, EPA's task is commonly to 
judge not whether the plan provides absolute certainty that attainment 
will in fact occur, but rather whether the plan provides an adequate 
level of confidence of prospective NAAQS attainment. From this 
perspective, in evaluating use of a 30-day average limit, EPA must 
weigh the likely net effect on air quality. Such an evaluation must 
consider the risk that occasions with meteorology conducive to high 
concentrations will have elevated emissions leading to exceedances that 
would not otherwise have occurred, and must also weigh the likelihood 
that the requirement for lower emissions on average will result in days 
not having exceedances that would have been expected with emissions at 
the critical emissions value. Additional policy considerations, such as 
in this case the desirability of accommodating real world emissions 
variability without significant risk of violations, are also 
appropriate factors for the EPA to weigh in judging whether a plan 
provides a reasonable degree of confidence that the plan will lead to 
attainment. Based on these considerations, especially given the high 
likelihood that a continuously enforceable limit averaged over as long 
as 30 days, determined in accordance with EPA's guidance, will result 
in attainment, EPA believes as a general matter that such limits, if 
appropriately determined, can reasonably be considered to provide for 
attainment of the 2010 SO2 NAAQS.
    The 2014 SO2 Nonattainment Guidance offers specific 
recommendations for determining an appropriate longer term average 
limit. The recommended method starts with determination of the 1-hour 
emission limit that would provide for attainment (i.e., the critical 
emission value), and applies an adjustment factor to determine the 
(lower) level of the longer term average emission limit that would be 
estimated to have a stringency comparable to the otherwise necessary 1-
hour emission limit. This method uses a database of continuous emission 
data reflecting the type of control that the source will be using to 
comply with the SIP emission limits, which (if compliance requires new 
controls) may require use of an emission database from another source. 
The recommended method involves using these data to compute a complete 
set of emission averages, computed according to the averaging time and 
averaging procedures of the prospective emission limitation. In this 
recommended method, the ratio of the 99th percentile among these long 
term averages to the 99th percentile of the 1-hour values represents an 
adjustment factor that may be multiplied by the candidate 1-hour 
emission limit to determine a longer term average emission limit that 
may be considered comparably stringent.\5\ The 2014 SO2 
Nonattainment Guidance also addresses a variety of related topics, such 
as the potential utility of setting supplemental emission limits, such 
as mass-based limits, to reduce the likelihood and/or magnitude of 
elevated emission levels that might occur under the longer term 
emission rate limit.
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    \5\ For example, if the critical emission value is 1000 pounds 
of SO2 per hour, and a suitable adjustment factor is 
determined to be 70 percent, the recommended longer term average 
limit would be 700 pounds per hour.
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    Preferred air quality models for use in regulatory applications are 
described in Appendix A of EPA's Guideline on Air Quality Models (40 
CFR part 51, Appendix W).\6\ In 2005, EPA promulgated the American 
Meteorological Society/Environmental Protection Regulatory Model 
(AERMOD) as the Agency's preferred near-field dispersion modeling for a 
wide range of regulatory applications addressing stationary sources 
(for example in estimating SO2 concentrations) in all types 
of terrain based on extensive developmental and performance evaluation. 
Supplemental guidance on modeling for purposes of demonstrating 
attainment of the SO2 standard is provided in Appendix A to 
the April 23, 2014 SO2 nonattainment area SIP guidance 
document referenced above. Appendix A provides extensive guidance on 
the modeling domain, the source inputs, assorted types of 
meteorological data, and background concentrations. Consistency with 
the recommendations in this guidance is generally necessary for the 
attainment demonstration to offer adequately reliable assurance that 
the plan provides for attainment.
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    \6\ The EPA published revisions to the Guideline on Air Quality 
Models on January 17, 2017.
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    As stated previously, attainment demonstrations for the 2010 1-hour 
primary SO2 NAAQS must demonstrate future attainment and 
maintenance of the NAAQS in the entire area designated as nonattainment 
(i.e., not just at the violating monitor) by using air quality 
dispersion modeling (See Appendix W to 40 CFR part 51) to show that the 
mix of sources and enforceable control measures and emission rates in 
an identified area will not lead to a violation of the SO2 
NAAQS. For a short-term (i.e., 1-hour) standard, EPA believes that 
dispersion modeling, using allowable emissions and addressing 
stationary sources in the affected area (and in some cases those 
sources located outside the nonattainment area which may affect 
attainment in the area) is technically appropriate, efficient and 
effective in demonstrating attainment in nonattainment areas because it 
takes into consideration combinations of meteorological and emission 
source operating conditions that may contribute to peak ground-level 
concentrations of SO2.
    The meteorological data used in the analysis should generally be 
processed with the most recent version of AERMOD Meteorological 
Preprocessor (AERMET). Estimated concentrations should include ambient 
background concentrations, should follow the form of the standard, and 
should be calculated as described in section 2.6.1.2 of the August 23, 
2010 clarification memo on ``Applicability of Appendix W Modeling 
Guidance for the 1-hr SO2 National Ambient Air Quality 
Standard'' (U. S. EPA, 2010a).

IV. Pennsylvania's Attainment Plan Submittal for the Allegheny Area

    In accordance with section 172(c) of the CAA, the Pennsylvania 
attainment plan for the Allegheny County Area includes: (1) An 
emissions inventory for SO2 for the plan's base year (2011); 
(2) an attainment demonstration including analyses that locate, 
identify, and quantify sources of emissions contributing to violations 
of the 2010 SO2 NAAQS as well as a dispersion modeling 
analysis of an emissions control strategy for the primary 
SO2 sources (USS Clairton, Edgar Thomson and Irvin Plants 
and Harsco Metals) showing attainment of the SO2 NAAQS by 
the October 4, 2018 attainment date; (3) a determination that the 
control strategy for the primary SO2 source within the 
nonattainment areas constitutes RACM/RACT; (4) requirements for RFP 
toward attaining the SO2 NAAQS in the Area; (5) contingency 
measures; (6) the assertion that Pennsylvania's existing SIP-approved 
NNSR program meets the applicable requirements for SO2; and 
(7) the request that emission limitations and compliance parameters for 
Clairton, Edgar Thomson and Irvin Plants and Harsco Metals be 
incorporated into the SIP.

[[Page 58211]]

V. EPA's Analysis of Pennsylvania's Attainment Plan Submittal for the 
Allegheny Area

    Consistent with CAA requirements (see section 172), an attainment 
demonstration for a SO2 nonattainment area must include a 
showing that the area will attain the 2010 SO2 NAAQS as 
expeditiously as practicable. The demonstration must also meet the 
requirements of 40 CFR 51.112 and 40 CFR part 51, Appendix W, and 
include inventory data, modeling results, and emissions reductions 
analyses on which the state has based its projected attainment. EPA is 
proposing that the attainment plan submitted by Pennsylvania is 
sufficient, and EPA is proposing to approve the plan to ensure ongoing 
attainment.

A. Pollutants Addressed

    Pennsylvania's SO2 attainment plan evaluates 
SO2 emissions for the Allegheny Area comprised of a portion 
of Allegheny County that is designated nonattainment for the 2010 
SO2 NAAQS. There are no precursors to consider for the 
SO2 attainment plan. SO2 is a pollutant that 
arises from direct emissions, and therefore concentrations are highest 
relatively close to the sources and much lower at greater distances due 
to dispersion. Thus, SO2 concentration patterns resemble 
those of other directly emitted pollutants like lead, and differ from 
those of photochemically-formed (secondary) pollutants such as ozone. 
Pennsylvania's attainment plan appropriately considered SO2 
emissions for the Allegheny Area.

B. Emissions Inventory Requirements

    States are required under section 172(c)(3) of the CAA to develop 
comprehensive, accurate and current emissions inventories of all 
sources of the relevant pollutant or pollutants in the nonattainment 
area. These inventories provide detailed accounting of all emissions 
and emissions sources by precursor or pollutant. In addition, 
inventories are used in air quality modeling to demonstrate that 
attainment of the NAAQS is as expeditious as practicable. The 2014 
SO2 Nonattainment Guidance provides that the emissions 
inventory should be consistent with the Air Emissions Reporting 
Requirements (AERR) at Subpart A to 40 CFR part 51.\7\
---------------------------------------------------------------------------

    \7\ The AERR at Subpart A to 40 CFR part 51 cover overarching 
Federal reporting requirements for the states to submit emissions 
inventories for criteria pollutants to EPA's Emissions Inventory 
System. EPA uses these submittals, along with other data sources, to 
build the National Emissions Inventory.
---------------------------------------------------------------------------

    For the base year inventory of actual emissions, a ``comprehensive, 
accurate and current'' inventory can be represented by a year that 
contributed to the three-year design value used for the original 
nonattainment designation. The 2014 SO2 Nonattainment 
Guidance notes that the base year inventory should include all sources 
of SO2 in the nonattainment area as well as any sources 
located outside the nonattainment area which may affect attainment in 
the area. Pennsylvania appropriately elected to use 2011 as the base 
year. Actual emissions from all the sources of SO2 in the 
Allegheny Area were reviewed and compiled for the base year emissions 
inventory requirement. The primary SO2-emitting point 
sources located within the Allegheny Area are the USS Mon Valley 
Works--Clairton, Edgar Thomson and Irvin Plants with SO2 
emissions in 2011 of 1468 tons per year (tpy), 1279 tpy, and 419 tpy, 
respectively. The Harsco Metals facility which is located on the Edgar 
Thomson plant property is the next largest source with 7 tpy of 
SO2 emissions in 2011. A more detailed discussion of the 
emissions inventory for the Allegheny Area and EPA's analysis of the 
Area can be found in Pennsylvania's October 3, 2017 submittal as well 
as the emissions inventory Technical Support Document (TSD), which can 
be found under Docket ID No. EPA-R03-OAR-2017-0730 and which is 
available online at www.regulations.gov.
    Table 1 shows the level of emissions, expressed in tpy, in the 
Allegheny Area for the 2011 base year by emissions source category.

 Table 1--2011 Base Year SO2 Emissions Inventory for the Allegheny Area
------------------------------------------------------------------------
                                                         SO2 emissions
               Emission source category                      (tpy)
------------------------------------------------------------------------
Point................................................            3249.20
Area.................................................             158.85
Non-road.............................................               1.17
On-road..............................................               8.11
                                                      ------------------
  Total..............................................            3417.33
------------------------------------------------------------------------

    EPA has evaluated Pennsylvania's 2011 base year emissions inventory 
for the Allegheny Area and has made the determination that this 
inventory was developed consistent with EPA's guidance. Therefore, 
pursuant to section 172(c)(3), EPA is proposing to approve 
Pennsylvania's 2011 base year emissions inventory for the Allegheny 
Area.
    The attainment demonstration also provides for a projected 
attainment year inventory that includes estimated emissions for all 
emission sources of SO2 which are determined to impact the 
nonattainment area for the year in which the Area is expected to attain 
the NAAQS. Pennsylvania provided a 2018 projected emissions inventory 
for all known sources included in the 2011 base year inventory, and EPA 
finds Pennsylvania appropriately developed this inventory as discussed 
in the emissions inventory TSD. The projected 2018 emissions are shown 
in Table 2. Pennsylvania's submittal asserts that the SO2 
emissions are expected to decrease by approximately 618 tons, or 18%, 
by 2018 from the 2011 base year.\8\ A detailed discussion of the 
projected emissions for the Allegheny Area and EPA's analysis of 
emissions can be found in Pennsylvania's October 3, 2017 submittal as 
well as in the emissions inventory TSD, which can be found under Docket 
ID No. EPA-R03-OAR-2017-0730 and online at www.regulations.gov.
---------------------------------------------------------------------------

    \8\ Reductions in projected 2018 SO2 emissions in the 
onroad, nonroad and nonpoint source categories can be attributed to 
lower sulfur content limits for gasoline and diesel fuels for the 
onroad and nonroad sector, and more stringent sulfur content limits 
on home heating oil and other distillate/residual fuel oils for the 
nonpoint sector which limits are included in the Pennsylvania SIP. 
Reductions in projected 2018 SO2 emissions for point 
sources are a result of the limits discussed in the RACT/RACM 
section of this rulemaking.

  Table 2--2018 Projected SO2 Emission Inventory for the Allegheny Area
------------------------------------------------------------------------
                                                         SO2 emissions
               Emission source category                      (tpy)
------------------------------------------------------------------------
Point................................................            2676.52
Area.................................................             119.18
Non-road.............................................               0.44
On-road..............................................               2.96
                                                      ------------------
  Total..............................................            2799.10
------------------------------------------------------------------------

C. Air Quality Modeling

    The SO2 attainment demonstration provides an air quality 
dispersion modeling analysis to demonstrate that control strategies 
chosen to reduce SO2 source emissions will bring the Area 
into attainment by the statutory attainment date of October 4, 2018. 
The modeling analysis, which the state is to conduct in accordance with 
Appendix W to 40 CFR part 51 (EPA's Modeling Guidance), is used for the 
attainment demonstration to assess the control strategy for a 
nonattainment area and establish emission limits that will provide for 
attainment. In accordance with Appendix W, three years of prognostic 
meteorological data was used

[[Page 58212]]

to simulate the dispersion of pollutant plumes from multiple point, 
area, or volume sources across the averaging times of interest. The 
modeling demonstration typically also relies on maximum allowable 
emissions from sources in the nonattainment area. Though the actual 
emissions are likely to be below the allowable emissions, sources have 
the ability to run at higher production rates or optimize controls such 
that emissions approach the allowable emissions limits. An attainment 
plan must provide for attainment under all allowable scenarios of 
operation for each source based on the maximum allowable emissions.
    ACHD provided an analysis which was developed in accordance with 
EPA's Modeling Guidance and the 2014 SO2 Nonattainment 
Guidance, and was prepared using the EPA dispersion modeling system, 
AERMOD. This modeling demonstration also utilized the Weather Research 
and Forecasting (WRF) model to generate prognostic meteorological data. 
EPA's Mesoscale Model Interface Program (MMIF) was used to extract the 
prognostic meteorological data which was processed using AERMET, a pre-
processor to AERMOD, in accordance with 40 CFR part 51. EPA notes that 
our most recent version of 40 CFR part 51 Appendix W allows for 
prognostic meteorological data to be used in AERMOD. The prognostic 
meteorological data was extracted and processed following the 
methodology outlined in EPA's updated Appendix W and other applicable 
guidance. In the particular circumstances in this Area, in which local 
topographical influences are likely to be channeling flows in a manner 
prone to yield different flows for different facilities in the Area, 
EPA believes that the prognostic meteorological data generated by ACHD 
are likely to provide a better characterization of winds in this Area 
than application of a single hourly wind speed and direction across the 
Area. EPA also conducted its own land use survey (using the methods of 
Auer), finding that about 70 percent (%) of the Area within an area out 
to three kilometers from the main sources in the Area may be considered 
rural land use, which supports ACHD's use of rural dispersion 
coefficients in its modeling analysis. Further discussion of ACHD's 
development of these meteorological data and EPA's land use survey can 
be found in EPA's modeling TSD, which can be found under Docket ID No. 
EPA-R03-OAR-2017-0730.
    ACHD characterized USS's Clairton Coke Works fugitive coke oven 
emissions using an alternative modeling technique, which shows 
significantly better model performance over the regulatory version of 
AERMOD. Given the high temperatures of these fugitive emissions, ACHD 
recognized that the plume rise and initial plume characteristics vary 
by hour reflecting hourly variations in meteorology in a manner that is 
not addressed in simple treatments of volume sources in AERMOD. 
Therefore, ACHD used an alternate method, using EPA's Buoyant Line and 
Point Source Model (BLP), to determine hourly values of these 
parameters. Since AERMOD does not provide for volume sources to have 
heat flux or otherwise to have plume rise, ACHD used hourly release 
heights reflecting the plume height for each hour's meteorology 
estimated by the BLP Plume Rise module. Similarly, ACHD used hourly 
values which characterize the initial width and height of the release 
based on hourly plume dimensions determined by BLP. Fugitive emissions 
were then included in AERMOD for each of the multiple volume sources 
used to represent the coke batteries in the Area by using volume 
sources with hourly release heights and initial dispersion coefficients 
determined in this manner, as contained in an hourly emission rate 
file. This alternative method is referred to as the BLP/AERMOD Hybrid 
approach.
    As noted in ACHD's modeling protocol document (See Appendix A of 
Pennsylvania's October 3, 2017 submittal), the procedure for handling 
USS's coke oven fugitive emissions in the dispersion modeling analysis 
was initially developed and used for previous particulate matter 
smaller than 10 microns in diameter (PM10) SIP work 
completed by ACHD and discussed in EPA Model Clearinghouse \9\ Memos 
from 1991 through 1994 (91-III-12, 93-III-06, and 94-III-02). (See 
Modeling Protocol Addendum to Appendix A of Pennsylvania's October 3, 
2017 submittal for more information on prior Model Clearinghouse 
memos). The original algorithms were developed for the ACHD 
PM10 SIP workgroup in 1994 and are currently being used by 
ACHD with additional revisions to the BLP Plume Rise program. This 
method is considered an alternative model due to the inclusion of the 
BLP model within the AERMOD dispersion model system (starting with 
AERMOD version 15181) using the BUOYLINE source pathway keyword. ACHD 
began its SIP modeling development for the Area using AERMOD version 
15181 then switched to version 1616r for its final modeling 
demonstration, which was the current regulatory version at the time of 
submittal. Use of an alternative model needs to be approved under 
section 3.2 of Appendix W--Guideline on Air Quality Models--with 
concurrence from EPA's Model Clearinghouse.
---------------------------------------------------------------------------

    \9\ EPA Model Clearinghouse is the central point of consultation 
and coordination within the EPA for reviewing the use of air quality 
models and analytical techniques for demonstrating compliance or 
attainment with the NAAQS in regulatory applications or 
implementation plans. All case-specific approvals of alternative 
models by an EPA Regional Office require consultation and 
concurrence by the Model Clearinghouse, per Section 3.2.2 of the 
Guideline on Air Quality Models (40 CFR part 51 Appendix W).
---------------------------------------------------------------------------

    A demonstration in support of the use of the BLP/AERMOD Hybrid 
approach for source characterization of the coke oven fugitive 
emissions for PM10 was undertaken by ACHD as part of its 
2012 Annual Fine Particle Matter (particulate matter less than 2.5 
microns in diameter, PM2.5) attainment plan preparation. 
While the demonstration was used to support this approach with 
PM10 (simulating dispersion of primary particulate matter), 
in AERMOD both PM10 and SO2 are treated as inert 
pollutants, therefore, they would have similar dispersion 
characteristics and are directly scalable and comparable. Thus, EPA 
finds that this approach is applicable for all primary pollutants 
including SO2. ACHD prepared the analysis and submitted an 
alternative modeling request under section 3.2.2 (b)(2) and (d) of 
Appendix W to EPA Region 3's Regional Administrator on July 27, 2018. 
EPA staff have reviewed ACHD's analysis and found that the BLP/AERMOD 
Hybrid approach provides better model performance of the impacts from 
the coke oven fugitive emissions than the regulatory BUOYLINE source 
methodology in AERMOD. This result is consistent with the dispersion 
model performance analyses ACHD described in Appendix A-2 Modeling 
Protocol Addendum, G and I of Pennsylvania's October 3, 2017 submittal.
    EPA's review and approval of ACHD's analysis supporting the use of 
the BLP/AERMOD Hybrid approach followed the EPA Model Clearinghouse 
concurrence process as prescribed in section 3.2 of Appendix W. 
Following receipt of ACHD's analysis on July 27, 2018, EPA Region 3 
recommended approval of this alternative modeling approach to the EPA 
Model Clearinghouse on August 7, 2018. The EPA Model Clearinghouse 
concurred with Region 3's recommended approval on August 10, 2018. EPA 
Region 3 then approved the use of this alternative model by letter from 
its Regional Administrator to ACHD dated August 16, 2018. EPA is 
providing notice in this rulemaking

[[Page 58213]]

proposal that an alternative modeling approach using the BLP/AERMOD 
Hybrid approach to simulate the fugitive coke oven battery emissions 
was used for ACHD's SO2 attainment plan and that its use was 
approved by EPA. ACHD's request to use this alternative modeling 
approach, EPA Region 3's analysis of ACHD's request, and the EPA Model 
Clearinghouse concurrence is included in the docket for this rulemaking 
action and can be found under Docket ID No. EPA-R03-OAR-2017-0730 and 
online at www.regulations.gov. EPA is taking public comment on 
proposing to approve the SIP based on the approved use of ACHD's 
alternative modeling approach.
    The primary SO2 sources included in the SIP modeling 
demonstration are the Harsco Metals facility and the three USS Mon 
Valley Works facilities--Clairton, Edgar Thomson and Irvin Plants. The 
modeling properly characterized source limits, local meteorological 
data, background concentrations, and provided an adequate model 
receptor grid to capture maximum modeled concentrations. Using the EPA 
conversion factor for the SO2 NAAQS, the final modeled 
design value for the Allegheny Area (196.17 microgram per meter cubed, 
[micro]g/m\3\), is less than 75 ppb.\10\ EPA has reviewed the modeling 
that Pennsylvania submitted to support the attainment demonstration for 
the Allegheny Area and has determined that the modeling is consistent 
with CAA requirements, Appendix W, and EPA's guidance for 
SO2 attainment demonstration modeling as discussed above. 
Therefore, EPA is proposing to determine that the analysis demonstrates 
that the source limits used in the modeling demonstration show 
attainment with the 1-hour SO2 NAAQS. EPA's analysis of the 
modeling is discussed in more detail in EPA's modeling TSD, which can 
be found under Docket ID No. EPA-R03-OAR-2017-0730 and online at 
www.regulations.gov for this rulemaking. EPA proposes to conclude that 
the modeling provided in the attainment plan shows that the Allegheny 
Area will attain the 2010 1-hour primary SO2 NAAQS by the 
attainment date.
---------------------------------------------------------------------------

    \10\ The SO2 NAAQS level is expressed in ppb, but 
AERMOD gives results in micro grams per cubic meter ([micro]g/m\3\). 
The conversion factor for SO2 (at the standard conditions 
applied in the ambient SO2 reference method) is 1 ppb = 
approximately 2.619 [micro]g/m\3\. See Pennsylvania's SO2 
Round 3 Designations proposed TSD at https://www.epa.gov/sites/production/files/2017-08/documents/35_pa_so2_rd3-final.pdf.
---------------------------------------------------------------------------

D. RACM/RACT

    CAA section 172(c)(1) requires that each attainment plan provide 
for the implementation of all reasonably available control measures 
(i.e., RACM) as expeditiously as practicable and shall provide for 
attainment of the NAAQS. EPA interprets RACM, including RACT, under 
section 172, as measures that a state determines to be both reasonably 
available and contribute to attainment as expeditiously as practicable 
``for existing sources in the area.'' In addition, 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.
    Pennsylvania's October 3, 2017 submittal discusses facility-
specific control measures, namely SO2 emission limits for 
Harsco Metals and for the USS Mon Valley Works facilities--Clairton, 
Edgar Thomson and Irvin Plants, that were developed through the air 
dispersion modeling submitted by ACHD. The modeling analysis is 
discussed in section IV.C. Air Quality Modeling of this proposed 
rulemaking and in the Modeling TSD. ACHD asserts that the combination 
of controls and the resulting emission limits at the three USS 
facilities and Harsco Metals is sufficient for the Allegheny Area to 
meet the SO2 NAAQS and serve as RACT/RACM.
    Controls at the Clairton and Edgar Thomson plants represent the 
majority of SO2 reductions within the Allegheny Area. As 
noted by ACHD, the Clairton Plant is the largest coke plant in North 
America. The Clairton Plant operates 10 coke batteries and produces 
approximately 13,000 tons of coke per day along with approximately 225 
million cubic feet of coke oven gas (COG). The COG is used as fuel at 
all of the Mon Valley Works facilities. At the Clairton Plant, ACHD 
explained in its attainment plan that upgrades to the 100 and 600 
Vacuum Carbonate Units (VCUs) will reduce the content of hydrogen 
sulfide (H2S) in the downriver COG utilized at all Mon 
Valley Works plants. The 100 VCU upgrade was completed in 2016 and the 
600 VCU upgrade will add redundant controls for the downriver COG line. 
Full operation of both upgraded units will be completed on or before 
October 4, 2018 as required by permit. Source monitoring to demonstrate 
continuous efficient operation of the Clairton VCU system is also 
required to be complete by October 4, 2018. In addition, a tail gas 
recycling project at the Shell Claus off-gas Treatment (SCOT) plant 
within the Clairton plant will reroute sulfur-rich gases back into the 
by-products facility at Clairton during planned and unplanned outages 
and will be completed on or before October 4, 2018 as required by 
permit.
    In its modeling analysis, ACHD determined critical emission values 
(CEV) with an hourly average for SO2 sources. However, based 
on the variability in sulfur content of the COG, ACHD determined that 
several sources warrant a limit with a longer-term averaging period. As 
discussed previously, EPA believes that establishment of emission rate 
limits with averaging periods longer than one hour may reasonably be 
found to provide for attainment if specified criteria recommended in 
EPA's 2014 SO2 Nonattainment Guidance are met.
    The objective of ACHD's analysis of the variability of COG sulfur 
content is to determine the adjustment factor that can be multiplied 
times the modeled CEVs to compute longer term limits that will require 
a comparable degree of control as would be required by 1-hour limits at 
the CEVs. EPA's 2014 SO2 Nonattainment Guidance states that 
``. . . air agencies may determine that an area could attain through a 
control strategy that will not significantly change the emission 
distribution (as may be true, for example, for a strategy involving a 
switch to lower sulfur coal with similar sulfur content variability or 
for a strategy involving enhancement of existing control equipment). 
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.'' In 
this case, the upgrades to the VCU unit at the USS Clairton plant 
reduce the H2S content in the COG but are unlikely to cause 
significant changes in the distribution of emissions, except to the 
extent that installation of redundant sulfur capture systems is likely 
to reduce the frequency and magnitudes of emission spikes from the 
facilities burning this COG. ACHD used the most recent three years of 
operating data (2014-2016) available at the time of its analysis to 
analyze the variability in H2S content in the COG for the 
four primary COG process streams used to deliver fuel to the USS Mon 
Valley Works plants (Unit 1, Unit 2, A Line and B Line). All COG is 
produced and desulfurized at the Clairton plant and then distributed 
via pipeline to the other two plants. USS upgraded its COG sulfur 
removal systems in April 2016, therefore ACHD separately analyzed the 8 
months of data post-control to compare whether the distribution of 
hydrogen sulfide (H2S) content would

[[Page 58214]]

be similar before and after controls. After extrapolating the post-
control data, the distribution of H2S content is similar to 
the distribution before controls thus, ACHD concluded that the use of 
the full 3 years of data is representative of overall variability and, 
that these upgrades are not expected to have a significant effect on 
variability or on the degree of adjustment to yield a comparably 
stringent longer term average limit. Analyzing variability of fuel 
quality is not a direct means of analyzing the variability of emissions 
(which also factors in the variability of the quantity of fuel burned). 
On the other hand, the facilities at issue here have relatively stable 
operations, and a complete analysis would also factor in the degree to 
which the installation of redundant control systems reduces emission 
spikes and thereby reduces variability. For these reasons, EPA believes 
that ACHD's analysis should provide a reasonable approximation of the 
prospective variability of emissions following implementation of the 
controls in the attainment plan and a reasonable approximation of the 
degree of adjustment needed to determine the longer term limits that 
are comparably stringent to the 1-hour limits that would otherwise be 
established.
    In accordance with the methods EPA recommended in Appendix C to its 
2014 SO2 Nonattainment Guidance, adjustment factors were 
determined from the variability in sulfur content in each line and were 
applied to the modeled CEV for the processes using that COG to 
determine an appropriate emission limit with a 30-day averaging period 
that is of comparable stringency to the 1-hour CEV. The 30-day average 
SO2 emission limit adjustment factor is 0.717 for emission 
units burning COG from Unit 1 Line, 0.797 for units burning COG from 
Unit 2 Line, 0.848 for units burning COG from A Line, and 0.834 for 
units burning COG from B Line. As recommended in 2014 SO2 
Nonattainment Guidance, ACHD determined that for sources with a 30-day 
averaging period a supplementary 24-hour limit not to be exceeded for 3 
consecutive days should be applied in order to limit the frequency and 
magnitude of occurrences of elevated emissions. Adjustment factors for 
24-hour SO2 emission limits were calculated for each line 
and applied to the modeled CEV to determine the emission limit with a 
24-hour averaging period. The 24-hour average SO2 emission 
limit adjustment factors for emission units burning COG are 0.914 for 
Unit 1 Line COG, 0.898 for Unit 2 Line COG, 0.927 for A Line COG, and 
0.944 for B Line COG.
    Table 3 shows the modeled CEV, the 30-day and 24-hour average 
adjustment factors and the resulting comparable 30-day and 24-hour 
average SO2 emission rate, calculated by applying the 
adjustment factor to the critical emissions value, for units affected 
by COG sulfur reduction projects and units partially affected by the 
COG controls in combination with other fuels at the Clairton plant. 
Table 3 also shows new SO2 limits for units taking 
reductions to their allowable limits at the Clairton plant.

                                                   Table 3--SO2 Emission Limits for USS Clairton Plant
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                            Adjustment                                      Adjustment     Supplemental
                         Process                           CEV (lbs/hr)   factor (for 30-  New emission      Averaging    factor (for 24-  24-hour limit
                                                                            day limit)    limit (lbs/hr)      period        hour limit)      (lbs/hr)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Boiler 1................................................          142.01           0.834          118.44          30-day           0.944          134.06
                                                              (aggregate
                                                             basis) \11\
Boiler 2................................................
Boiler R1...............................................
Boiler R2...............................................
Boiler T1...............................................
Boiler T2...............................................
Battery 1 Underfiring...................................           14.52           0.717           10.41          30-day           0.914           13.27
Battery 2 Underfiring...................................           12.76           0.717            9.15          30-day           0.914           11.66
Battery 3 Underfiring...................................           14.74           0.717           10.57          30-day           0.914           13.47
Battery 13 Underfiring..................................           17.48           0.797           13.93          30-day           0.898           15.70
Battery 14 Underfiring..................................           17.60           0.797           14.03          30-day           0.898           15.80
Battery 15 Underfiring..................................           23.43           0.797           18.67          30-day           0.898           21.04
Battery 19 Underfiring..................................           36.85           0.797          229.37          30-day           0.898           33.09
Battery 20 Underfiring..................................           33.88           0.797           27.00          30-day           0.898           30.42
B Battery Underfiring...................................           29.82           0.717           21.38          30-day           0.914           27.26
C Battery Underfiring...................................           44.67           0.717           32.03          30-day           0.914           40.83
SCOT Incinerator........................................              24  ..............              24          1-hour
PEC Baghouse 1-3........................................            7.10  ..............            7.10          1-hour
PEC Baghouse 13-15......................................            7.46  ..............            7.46          1-hour
PEC Baghouse 19-20......................................            7.78  ..............            7.78          1-hour
PEC Baghouse B..........................................            7.50  ..............            7.50          1-hour
PEC Baghouse C..........................................            8.65  ..............            8.65          1-hour
Quench Tower 1..........................................            0.75  ..............            0.75          1-hour
Quench Tower B..........................................            4.09  ..............            4.09          1-hour
Quench Tower C..........................................            5.00  ..............            5.00          1-hour
Quench Tower 5A.........................................            7.56  ..............            7.56          1-hour
Quench Tower 7A.........................................            7.21  ..............            7.21          1-hour
Batteries 1-3 Hot Car...................................           10.64  ..............           10.64          1-hour
Batteries 13-15 Hot Car.................................           11.21  ..............           11.21          1-hour
Batteries 19-20 Hot Car.................................           13.73  ..............           13.73          1-hour
C Battery Hot Car.......................................            5.82  ..............            5.82          1-hour
--------------------------------------------------------------------------------------------------------------------------------------------------------
\11\ ACHD ran 16 different modeling scenarios for the various boiler stacks at the Clairton plant and used the worst case boiler impacts in its final
  analysis. Additional information can be found in ACHD's SIP submittal's Appendix I included in the docket for this rulemaking and is available online
  at www.regulations.gov.


[[Page 58215]]

    EPA's guidance advises that, to help assure attainment near sources 
with longer term limits, states should assure that occasions with 
hourly emissions above the CEV are limited in frequency and magnitude. 
The supplemental limits that ACHD has adopted, providing 24-hour 
average limits to supplement the 30-day average limits, serve this 
purpose. To evaluate these limits, ACHD analyzed SO2 
emissions from one source at the Clairton facility (Battery 20 
underfiring) at maximum flow rate and compared hourly emission values 
to the 30-day, 24-hour and CEV limits. ACHD's analysis indicates that, 
for this unit, over a two month span the 30-day limit and 24-hour 
limits were not exceeded while the CEV was exceeded four times. Actual 
flow rate for the months analyzed was 70% of the maximum flowrate in 
which the CEV would have been exceeded twice by less than 2 lb/hr in 
the time period. In addition, ACHD evaluated the hours which were above 
the CEV at either flowrate and the Liberty monitor values ranged from 
0-13 ppb at those times and meteorology was typical for the months. EPA 
does not have the emissions data to make quantitative estimates of the 
expected frequency or magnitude of emissions exceeding the CEVs, but 
EPA believes, particularly with the application of the 24-hour 
supplemental limits, that these occasions are likely to be modest in 
frequency and magnitude. Further details regarding ACHD's longer term 
limits and variability analysis can be found in Appendix D of 
Pennsylvania's October 3, 2017 submittal which can be found under 
Docket ID No. EPA-R03-OAR-2017-0730 and online at www.regulations.gov.
    For these sources with limits based on longer averaging periods, 
H2S content will be measured by a continuous source 
monitoring device and flow meter equipment that measures the actual 
hourly flow of gas. SO2 emissions will then be calculated by 
assuming complete conversion of the combusted H2S. The 
SO2 values will be calculated hourly, averaged over a 24-
hour basis (calendar day) and then averaged over a rolling 30-day 
basis. All sources utilizing a 30-day rolling average also have an 
additional shorter term 24-hour limit which may not be exceeded more 
than three consecutive days. A more detailed discussion of ACHD's 
statistical analysis that was used to develop the proposed 30-day 
average limits and supplemental 24-hour limits for the Allegheny Area 
can be found in Appendix D of Pennsylvania's October 3, 2017 submittal 
found under Docket ID No. EPA-R03-OAR-2017-0730. Additionally, EPA's 
2014 SO2 Nonattainment Guidance and section I. of this 
proposed rulemaking provide an extensive discussion of EPA's rationale 
for concluding that emission limits based on averaging times as long as 
30 days that are appropriately set, reflecting comparable stringency to 
a suitable 1-hour limit, especially when accompanied by supplemental 
limits that help minimize the frequency and magnitude of spikes in 
emissions, can be found to provide for attainment of the 2010 
SO2 NAAQS. In evaluating these longer term averaging times, 
EPA proposes to find that the emission limits with these longer term 
averaging times were appropriately set in accordance with EPA's 2014 
SO2 Nonattainment Guidance and are sufficient for the 
Allegheny Area to attain the 2010 SO2 NAAQS.
    The USS Edgar Thomson plant is an iron and steel making facility 
which mainly produces steel slabs. At the USS Edgar Thomson facility, a 
new stack and a combined flue system is planned for Riley Boilers 1, 2 
and 3. All boilers will exhaust to the new stack which is below good 
engineering practice (GEP) stack height. Specifically, the height of 
this stack, 85 meters, is lower than the formula GEP height based on 
the dimensions of nearby buildings, 97 meters.
    Actual emissions will be reduced as a result of the boilers using 
the lower H2S content COG from the USS Clairton plant in 
combination with other fuels, and thus emissions for the boilers will 
be reduced on an aggregate basis. New emission limits for the boilers 
at the Edgar Thomson plant are listed in Table 4 along with other 
sources with reduced SO2 allowable limits; all of these 
limits are established on a 1-hour basis.\12\
---------------------------------------------------------------------------

    \12\ Subsequent to ACHD's submittal of its attainment plan for 
the Area, ACHD informed EPA that the new stack at the Edgar Thompson 
plant might have different parameters than the ``new stack'' 
parameters included in the attainment plan's attainment 
demonstration modeling. The stack is part of the modeled control 
strategy discussed in sections C and D of this rulemaking. However, 
ACHD has confirmed to EPA (by email) that subsequent modeling with 
the new stack parameters (e.g. location, height, temperature, 
velocity) at the Edgar Thomson plant is consistent with the 
submitted modeling demonstration showing SO2 attainment 
by the attainment date with the same SO2 emission 
limitations in the modeling submitted with ACHD's attainment plan 
for the Area. A copy of this email dated December 8, 2017 with 
technical documentation supporting ACHD's conclusion is included in 
the docket for this rulemaking and is available online at 
www.regulations.gov.

                                                Table 4--SO2 Emission Limits for USS Edgar Thomson Plant
--------------------------------------------------------------------------------------------------------------------------------------------------------
               Process                                                           New * Emission Limit (lbs/hr)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Combustion Units
--------------------------------------------------------------------------------------------------------------------------------------------------------
Boiler 1.............................                                                                                           556.91 (aggregate basis)
Boiler 2.............................
Boiler 3.............................
Blast Furnace 1 Stoves...............                                                                                                              98.50
Blast Furnace 3 Stoves...............                                                                                                              90.00
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                  Non-Combustion Units
--------------------------------------------------------------------------------------------------------------------------------------------------------
Blast Furnace 1 Casthouse (Roof +                                                                                                                   2.01
 Fume)...............................
Blast Furnace 3 Casthouse (Roof +                                                                                                                   1.69
 Fume)...............................
BOP Process (Roof)...................                                                                                                               6.64

[[Page 58216]]

 
Continuous Casting (Roof)............                                                                                                               5.25
Casthouse Baghouse...................                                                                                                              45.10
--------------------------------------------------------------------------------------------------------------------------------------------------------
* New emission limit is equivalent to modeled CEV for Edgar Thomson sources.

    The USS Irvin plant is a secondary steel processing plant which 
receives steel slabs and performs one of several finishing processes on 
the steel slabs. Reductions in SO2 emissions at the USS 
Irvin plant are mainly a result of the COG controls reducing the sulfur 
content in the COG. The 80-inch Hot Strip Mill receives COG via the A 
Line from the Clairton plant while all other units at the Irvin plant 
receive COG via the B Line. Emission limits for units at the USS Irvin 
plant are listed in Table 5.

                                                 Table 5--SO2 Emission Limits for U.S. Steel Irvin Plant
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                            Adjustment                                      Adjustment     Supplemental
                         Process                           CEV (lbs/hr)   factor (for 30-  New emission      Averaging    factor (for 24-  24-hour limit
                                                                            day limit)    limit (lbs/hr)      period        hour limit)      (lbs/hr)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Boiler #1...............................................            9.45           0.834            7.88          30 day           0.944            8.92
Boiler #2...............................................           10.02           0.834            8.36          30 day           0.944            9.46
Boiler #3-4                                                         9.85           0.834            8.21          30 day           0.944            9.30
(aggregate).............................................
80'' Hot Strip Reheat                                             128.10           0.848          108.63          30 day           0.927          118.75
(aggregate).............................................
HPH Annealing Furnaces                                             14.39           0.834              12          30 day           0.944           13.58
(aggregate).............................................
Open Coil Annealing                                                13.79           0.834            11.5          30 day           0.944           13.02
(aggregate).............................................
Continuous Annealing....................................            9.68           0.834            8.07          30 day           0.944            9.14
#1 Galvanizing Line.....................................            0.04  ..............            0.04          1-hour  ..............  ..............
#2 Galvanizing Line.....................................            0.01  ..............            0.01          1-hour  ..............  ..............
--------------------------------------------------------------------------------------------------------------------------------------------------------

    In addition, Harsco Metals (also known as Braddock Recovery Inc) is 
located on the property of the USS Edgar Thomson plant. Harsco uses a 
rotary kiln fired with COG which is supplied by USS Clairton plant. As 
a result of the lower sulfur content in the USS-produced COG, Harsco 
has become subject to a lower SO2 limit of 1.8 lbs/hr as a 
1-hour average for the rotary kiln.
    Emission limits at all four facilities (USS Clairton, Edgar Thomson 
and Irvin Plants and Harsco Metals) were established through 
enforceable installation permits (See Appendices K of Pennsylvania's 
October 3, 2017 SIP submittal). The collective emission limits and 
related compliance parameters (i.e., testing, monitoring, record 
keeping and reporting) have been proposed for incorporation 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 facilities are listed in Tables 3, 4 and 5. The compliance 
parameters include continuous process monitoring of H2S 
content and flow rate of the COG at Clairton facility and the four 
lines which feed the Edgar Thompson and Irvin facilities; record-
keeping, reporting, and stack testing requirements at all facilities. 
ACHD affirms that the implementation of new emission limits and 
corresponding compliance parameters at the three USS Mon Valley Works 
facilities and Harsco Metals will enable the Allegheny Area to attain 
and maintain the SO2 NAAQS. The AERMOD modeling analysis 
shows, as discussed in detail in the Modeling TSD, that the emission 
limits listed in Tables 3, 4 and 5 and the limit for Harsco Metals 
(modeling the 1-hour limits where applicable and modeling the 1-hour 
equivalents where longer term average limits apply) are sufficient for 
the Allegheny Area to attain the 1-hour SO2 NAAQS.
    EPA's guidance for longer term average limits is that plans based 
on such limits can be considered to provide for attainment where 
appropriate as long as the longer term limit is comparably stringent to 
the 1-hour limit that would otherwise be set and EPA can have 
reasonable confidence that occasions of emissions above the critical 1-
hour emission rate will be limited in frequency and magnitude. ACHD has 
provided for comparable stringency by computing adjustment factors in 
accordance with the method that EPA recommended in Appendix C of its 
guidance and adopting longer term average limits (where applicable) 
that are adjusted accordingly. Also in accordance with EPA's 
recommendations, ACHD has established supplemental limits that will 
help assure that occasions of emissions above the critical 1-hour 
emission rate will be limited in frequency and magnitude. Therefore, 
EPA believes that ACHD has met EPA's recommended criteria for longer 
term average limits to be part of a plan that provides suitable 
assurances that the area will attain the standard.
    ACHD also 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. All sources have less than 5 
tpy of allowable SO2 emissions. ACHD determined that no 
additional controls would be technically or economically feasible for 
the purposes of SO2 RACT

[[Page 58217]]

at these small sources. ACHD also noted that Guardian Industries 
permanently shut down in 2015; therefore, no RACT analysis was 
performed for Guardian Industries. In addition, ACHD examined several 
RACM options for area, nonroad and mobile sources of SO2 in 
the Area and determined no additional controls are needed to provide 
for attainment in the Area, since ACHD's modeling indicates that its 
plan will provide for attainment without reduction of any portion of 
background concentrations attributable to these sources.
    EPA is proposing to approve ACHD's determination that the 
SO2 control strategies at the USS Mon Valley Works 
facilities--Clairton, Edgar Thomson and Irvin plants and Harsco Metals 
constitute RACM/RACT for each source in the Allegheny Area based on the 
modeling analysis previously described and ACHD's evaluation of 
technically and economically feasible controls.
    Pennsylvania has requested that portions of the installation 
permits for the USS Mon Valley Works facilities--Clairton, Edgar 
Thomson and Irvin plants and Harsco Metals be approved into the 
Allegheny County portion of the Pennsylvania SIP. Upon approval, the 
emission limits listed in the installation permits and corresponding 
compliance parameters found in the installation permits for Clairton, 
Edgar Thomson, Irvin and Harsco Metals will become permanent and 
enforceable SIP measures to meet the requirements of the CAA. After 
considering ACHD's submitted information, EPA, therefore, concludes 
Pennsylvania's October 3, 2017, SIP submittal for the Area meets the 
RACM/RACT and emission limitation and other control measure 
requirements of section 172(c) of the CAA.

E. RFP Plan

    Section 172(c)(2) of the CAA requires an attainment plan to include 
a demonstration that shows reasonable further progress (i.e., RFP) for 
meeting air quality standards will be achieved through generally linear 
incremental improvement in air quality. 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 EPA for the purpose of ensuring attainment of 
the applicable NAAQS by the applicable attainment date.'' As stated 
originally in the 1994 SO2 Guidelines Document \13\ and 
repeated in the 2014 SO2 Nonattainment Guidance, EPA 
continues to believe that this definition is most appropriate for 
pollutants that are emitted from numerous and diverse sources, where 
the relationship between particular sources and ambient air quality are 
not directly quantified. In such cases, emissions reductions may be 
required from various types and locations of sources. The relationship 
between SO2 and sources is much more defined, and usually 
there is a single step between pre-control nonattainment and post-
control attainment. Therefore, EPA interpreted RFP for SO2 
as adherence to an ambitious compliance schedule in both the 1994 
SO2 Guideline Document and the 2014 SO2 
Nonattainment Guidance. The control measures for attainment of the 2010 
SO2 NAAQS included in Pennsylvania's submittal were modeled 
by ACHD to achieve attainment of the NAAQS. The ACHD permits which 
require these control measures to be effective on or before October 4, 
2018 (including specific emission limits and compliance parameters) 
show the resulting emission reductions to be achieved as expeditiously 
as practicable for the Area. As a result, based on air quality 
modeling, ACHD projected these control measures will yield a sufficient 
reduction in SO2 emissions from the major sources in the 
Allegheny Area to show attainment of the SO2 NAAQS for the 
Allegheny Area. EPA has found ACHD's attainment modeling for the Area 
to be in accordance with CAA requirements. EPA finds the control 
measures proposed will be implemented as expeditiously as practicable 
by October 4, 2018 according to the terms of the permits for the 
affected facilities. Therefore, EPA has determined that Pennsylvania's 
SO2 attainment plan for the Allegheny Area fulfills the RFP 
requirements for the Allegheny Area. EPA proposes to approve 
Pennsylvania's attainment plan with respect to the RFP requirements.
---------------------------------------------------------------------------

    \13\ SO2 Guideline Document, U.S. Environmental 
Protection Agency, Office of Air Quality Planning and Standards, 
Research Triangle Park, NC 27711, EPA-452/R-94-008, February 1994. 
Located at: https://www.epa.gov/ttn/oarpg/t1pgm.html.
---------------------------------------------------------------------------

F. Contingency Measures

    In accordance with section 172(c)(9) of the CAA, contingency 
measures are required as additional measures to be implemented in the 
event that an area fails to meet the RFP requirements or fails to 
attain the standard by its attainment date. These measures must be 
fully adopted rules or control measures that can be implemented quickly 
and without additional EPA or state action if the area fails to meet 
RFP requirements or fails to meet its attainment date, and should 
contain trigger mechanisms and an implementation schedule. However, 
SO2 presents special considerations. As stated in the final 
2010 SO2 NAAQS promulgation on June 22, 2010 (75 FR 35520) 
and in the 2014 SO2 Nonattainment Guidance, EPA concluded 
that because of the quantifiable relationship between SO2 
sources and control measures, it is appropriate that state agencies 
develop a comprehensive program to identify sources of violations of 
the SO2 NAAQS and undertake an aggressive follow-up for 
compliance and enforcement.
    The contingency measures in Pennsylvania's October 3, 2017 
submittal are designed to keep the Allegheny Area from triggering an 
exceedance or violation of the SO2 NAAQS. In the attainment 
plan, ACHD states that if an ambient air quality monitor measures 
enough exceedances in a consecutive three-year period that would cause 
a design value to exceed the 75 ppb standard, ACHD would conduct a 
thorough analysis in order to identify the sources of the violation and 
bring the area back into compliance with the NAAQS. ACHD states that 
the root cause analysis will begin immediately upon verification of a 
violation, will include analysis of source and meteorological 
conditions contributing to the violation, and will take no longer than 
10 days to complete. In its plan, sources identified by ACHD as most 
likely contributing to the violation will have 10 days from 
notification to submit a written system audit report which details the 
operating parameters of all SO2 emission sources for the 
four 5-day periods up to and including the dates which the monitor 
registered exceedances of the SO2 NAAQS. According to the 
attainment plan, sources must recommend SO2 control 
strategies for each affected unit in the audit report. Once ACHD 
receives the audit report(s), a 30-day evaluation period will begin in 
which ACHD will investigate the audit findings and recommended control 
strategies. The 30-day evaluation period will be followed by a 30-day 
consultation period with the sources. Additional control measures will 
be implemented as expeditiously as possible to bring the Area back into 
compliance. If a permit modification is necessary, ACHD has the 
statutory authority under ACHD Rules and Regulations, Article XXI--Air 
Pollution Control to amend and issue a final permit. Any new emission 
limits would also be submitted to EPA as a SIP revision. In addition, 
ACHD has the regulatory authority to take any action it deems necessary 
or proper for the effective enforcement of rules and regulations; such 
actions include the

[[Page 58218]]

issuance of orders (i.e., enforcement orders and orders to take 
corrective action to address air pollution or the danger of air 
pollution from a source) and the assessment of civil penalties. ACHD's 
regulations for enforcement, ACHD Article XXI, Part I, sections 
2109.01-2109.06 and 2109.10, provide ACHD authority to enforce its 
regulations, permits and orders. Pursuant to these regulations, ACHD 
has authority, inter alia, to inspect facilities, seek penalties for 
violations, enter enforcement orders, and revoke permits. These 
regulations are included in the Pennsylvania SIP. See 67 FR 68935 
(November 14, 2002).
    EPA finds that ACHD has a comprehensive program included in the 
Pennsylvania SIP to identify sources of violations of the 
SO2 NAAQS and to undertake an aggressive follow up for 
compliance and enforcement. Therefore, EPA proposes that the 
contingency measures submitted by Pennsylvania follow the 2014 
SO2 Nonattainment Guidance and meet the section 172(c)(9) 
requirements.

G. New Source Review \14\
---------------------------------------------------------------------------

    \14\ The CAA new source review (NSR) program is composed of 
three separate programs: Prevention of significant deterioration 
(PSD), NNSR, and Minor NSR. PSD is established in part C of title I 
of the CAA and applies in areas that meet the NAAQS--``attainment 
areas''--as well as areas where there is insufficient information to 
determine if the area meets the NAAQS--``unclassifiable areas.'' The 
NNSR program is established in part D of title I of the CAA and 
applies in areas that are not in attainment of the NAAQS--
``nonattainment areas.'' The Minor NSR program addresses 
construction or modification activities that do not qualify as 
``major'' and applies regardless of the designation of the area in 
which a source is located. Together, these programs are referred to 
as the NSR programs. Section 173 of the CAA lays out the NNSR 
program for preconstruction review of new major sources or major 
modifications to existing sources, as required by CAA section 
172(c)(5). The programmatic elements for NNSR include, among other 
things, compliance with the lowest achievable emissions rate and the 
requirement to obtain emissions offsets.
---------------------------------------------------------------------------

    Section 172(c)(5) of the CAA requires that an attainment plan 
require permits for the construction and operation of new or modified 
major stationary sources in a nonattainment area. In Allegheny County, 
NNSR procedures and conditions for which new major stationary sources 
or major modifications may obtain a preconstruction permit are 
stipulated in the ACHD Rules and Regulations, Article XXI, Air 
Pollution Control, Sec.  2102.06, ``Major Sources Locating in or 
Impacting a Nonattainment Area'' which was previously approved into the 
Pennsylvania SIP, with the most recent revision effective March 30, 
2015 (80 FR 16570). ACHD Rules and Regulations, Article XXI, Air 
Pollution Control, Sec.  2102.06 also incorporates by reference 
applicable provisions of PADEP's NNSR regulations codified at 25 Pa. 
Code Chapter 127, Subchapter E. PADEP's NNSR regulations in 25 Pa. Code 
Chapter 127, Subchapter E were previously approved into the 
Pennsylvania SIP, with the most recent revision updating the 
regulations to meet EPA's 2002 NSR reform regulations effective on May 
14, 2012 (77 FR 28261). A discussion of the specific PADEP provisions 
incorporated by reference into ACHD Article XXI can be found in 
Pennsylvania's October 3, 2017 submittal found under Docket ID No. EPA-
R03-OAR-2017-0730. These rules provide for appropriate NNSR permitting 
as required by CAA sections 172(c)(5) and 173 and 40 CFR 51.165 for 
SO2 sources undergoing construction or major modification in 
the Allegheny Area without need for modification of the approved rules. 
Therefore, EPA concludes that Allegheny County's SIP-approved NNSR 
program meets the requirements of section 172(c)(5) for this Area.

VI. EPA's Proposed Action

    EPA is proposing to approve Pennsylvania's attainment plan SIP 
revision for the Allegheny Area, as submitted through ACHD and PADEP to 
EPA on October 3, 2017, for the purpose of demonstrating attainment of 
the 2010 1-hour SO2 NAAQS. Specifically, EPA is proposing to 
approve the base year emissions inventory, a modeling demonstration of 
SO2 attainment, an analysis of RACM/RACT, a RFP plan, and 
contingency measures for the Allegheny Area and is proposing that the 
Pennsylvania SIP revision has met the requirements for NNSR for the 
2010 1-hour SO2 NAAQS. Additionally, EPA is proposing to 
approve into the Pennsylvania SIP specific SO2 emission 
limits and compliance parameters in permits established for the 
SO2 sources impacting the Allegheny Area.
    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 EPA's 2014 
SO2 Nonattainment Guidance. Thus, EPA is proposing to 
approve Pennsylvania's attainment plan for the Allegheny Area as 
submitted on October 3, 2017. EPA's analysis for this proposed action 
is discussed in Section V of this proposed rulemaking. EPA is 
soliciting public comments on the issues discussed in this document. 
These comments will be considered before taking final action. Final 
approval of this SIP submittal will remove EPA's duty to implement a 
FIP for this Area.

VII. Incorporation by Reference

    In this document, EPA is proposing to include in a final EPA rule 
regulatory text that includes incorporation by reference. In accordance 
with requirements of 1 CFR 51.5, EPA is proposing to incorporate by 
reference portions of the installation permits issued by ACHD with USS 
facilities at Clairton, Edgar Thomson and Irvin and with Harsco Metals. 
This includes emission limits and associated compliance parameters, 
recording-keeping and reporting. EPA has made, and will continue to 
make, these materials generally available through https://www.regulations.gov and at the EPA Region III Office (please contact 
the person identified in the ``For Further Information Contact'' 
section of this proposed rulemaking for more information).

VIII. Statutory and Executive Order Reviews

    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 proposed 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

[[Page 58219]]

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 proposed rule, concerning the SO2 
attainment plan for the Allegheny Area in Pennsylvania, 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.

List of Subjects in 40 CFR Part 52

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

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

    Dated: November 1, 2018.
Cosmo Servidio,
Regional Administrator, Region III.
[FR Doc. 2018-25079 Filed 11-16-18; 8:45 am]
 BILLING CODE 6560-50-P