[Federal Register Volume 83, Number 135 (Friday, July 13, 2018)]
[Proposed Rules]
[Pages 32606-32615]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-14947]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R03-OAR-2017-0615; FRL-9980-65-Region 3]


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

AGENCY: Environmental Protection Agency (EPA).

ACTION: 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 
Commonwealth of Pennsylvania through the Pennsylvania Department of 
Environmental Protection (PADEP), to EPA on October 11, 2017, for the 
purpose of providing for attainment of the 2010 sulfur dioxide 
(SO<INF>2</INF>) primary national ambient air quality standard (NAAQS) 
in the Indiana, Pennsylvania SO<INF>2</INF> nonattainment area 
(hereafter referred to as the ``Indiana Area'' or ``Area''). The 
Indiana Area is comprised of Indiana County and a portion of Armstrong 
County (Plumcreek Township, South Bend Township, and Elderton Borough) 
in Pennsylvania. The major sources of SO<INF>2</INF> in the Indiana 
Area emitting over 2,000 tpy of SO<INF>2</INF> include several large 
electric generating units (EGUs): Keystone Plant, Conemaugh Plant, 
Homer City Generation, and Seward Generation Station (hereafter 
referred to as ``Keystone,'' ``Conemaugh,'' ``Homer City,'' and 
``Seward''). The 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) requirements, enforceable emission limitations and 
control measures, a reasonable further progress (RFP) plan, a modeling 
demonstration of SO<INF>2</INF> attainment, and contingency measures 
for the Indiana Area. As part of approving the attainment plan, EPA is 
also proposing to approve into the Pennsylvania SIP SO<INF>2</INF> 
emission limits and associated compliance parameters for Keystone, 
Conemaugh, Homer City and Seward and proposes to find Pennsylvania has 
measures in place to address nonattainment new source review. EPA 
proposes to approve Pennsylvania's attainment plan and concludes that 
the Indiana Area will attain the 2010 1-hour primary SO<INF>2</INF> 
NAAQS by the applicable attainment date and that the plan meets all 
applicable requirements under the Clean Air Act (CAA).

DATES: Written comments must be received on or before August 13, 2018.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R03-
OAR-2017-0615 at http://www.regulations.gov, or via email to 
<a href="/cdn-cgi/l/email-protection#bdcecdd4d8d1dfd8cfdad8cf93cec8cedcd3fdd8cddc93dad2cb"><span class="__cf_email__" data-cfemail="c1b2b1a8a4ada3a4b3a6a4b3efb2b4b2a0af81a4b1a0efa6aeb7">[email protected]</span></a>. 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 http://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Megan Goold, (215) 814-2027, or by 
email at <a href="/cdn-cgi/l/email-protection#97f0f8f8fbf3b9faf2f0f6f9d7f2e7f6b9f0f8e1"><span class="__cf_email__" data-cfemail="65020a0a09014b080002040b250015044b020a13">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Background for EPA's Proposed Action
II. Pennsylvania's Attainment Plan Submittal for the Indiana Area
III. EPA's Analysis of Pennsylvania's Attainment Plan for the 
Indiana 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
IV. EPA's Proposed Action
V. Incorporation by Reference
VI. 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 primary SO<INF>2</INF> 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), codified at 40 CFR 50.17. This action also 
revoked the existing 1971 primary annual 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 
SO<INF>2</INF> emissions ranging from five 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 SO<INF>2,</INF> 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)-(2) of the CAA. On August 5, 
2013, EPA promulgated initial air quality designations for 29 areas for 
the 2010 SO<INF>2</INF> NAAQS (78 FR 47191), which

[[Page 32607]]

became effective on October 4, 2013, based on violating air quality 
monitoring data for calendar years 2009-2011, where there were 
sufficient data to support a nonattainment designation.\2\
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    \1\ 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 SO<INF>2</INF> standard was retained. 
Currently, the 24-hour and annual standards are only revoked for 
certain of those areas the EPA has already designated for the 2010 
1-hour SO<INF>2</INF> NAAQS. See 40 CFR 50.4(e).
    \2\ EPA is continuing its designation efforts for the 2010 
SO<INF>2</INF> NAAQS. Pursuant to a court-order finalized March 2, 
2015, in 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 Indiana Area was designated as 
nonattainment for the 2010 SO<INF>2</INF> NAAQS for an area that 
encompasses the primary SO<INF>2</INF> emitting sources of Keystone, 
Conemaugh, Homer City, and Seward. The October 4, 2013 final 
designation triggered a requirement for Pennsylvania to submit by April 
4, 2015, a SIP revision with an attainment plan for how the Area would 
attain the 2010 SO<INF>2</INF> NAAQS as expeditiously as practicable, 
but no later than October 4, 2018, in accordance with CAA sections 
172(c) and 191-192.
    For a number of areas, including the Indiana Area, EPA published a 
notice on March 18, 2016, effective April 18, 2016, that Pennsylvania 
and other pertinent states had failed to submit the required 
SO<INF>2</INF> 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 11, 
2017, and EPA's subsequent letter dated October 13, 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 having missed the April 4, 
2015 deadline. Additionally, under CAA section 110(c), the March 18, 
2016, finding triggered a requirement that EPA promulgate a federal 
implementation plan (FIP) within two years of the effective date of the 
finding unless, by that time, the state has made the necessary complete 
submittal and EPA has approved the submittal as meeting applicable 
requirements. This FIP obligation will no longer apply if and when EPA 
makes final the approval action proposed here.
    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. 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 SO<INF>2</INF> SIPs and fundamental 
principles for SIP control strategies. Id. at 13545-49, 13567-68.
    On April 23, 2014, EPA issued recommended guidance (hereafter 2014 
SO<INF>2</INF> Nonattainment Guidance) for how state submissions could 
address the statutory requirements for SO<INF>2</INF> attainment 
plans.\3\ In this guidance, EPA described the statutory requirements 
for an attainment plan, which include: An accurate base year emissions 
inventory of current emissions for all sources of SO<INF>2</INF> 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) and (c)(6)); 
demonstration of RFP (172(c)(2)); implementation of RACM, including 
RACT (172(c)(1)); new source review (NSR) 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 SO<INF>2</INF> nonattainment plans, 
published on October 5, 2017 at 82 FR 46434.
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    \3\ See ``Guidance for 1-Hour SO<INF>2</INF> 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 the 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, the 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 ensures equivalent or greater emission 
reductions of such air pollutant.
    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). SO<INF>2</INF> 
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 SO<INF>2</INF> 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 (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 SO<INF>2</INF> 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 
SO<INF>2</INF> Nonattainment Guidance, pp. 22 to 39. The guidance 
recommends that--should states and sources utilize longer averaging 
times--the longer term

[[Page 32608]]

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 SO<INF>2</INF> Nonattainment Guidance provides an 
extensive discussion of EPA's rationale for concluding that 
appropriately set comparably stringent limitations based on averaging 
times as long as 30 days can be found to provide for attainment of the 
2010 SO<INF>2</INF> NAAQS. In evaluating this option, EPA considered 
the nature of the standard, conducted detailed analyses of the impact 
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. 22-39, and Appendices 
B, C, and D.
    As specified in 40 CFR 50.17(b), the 1-hour primary SO<INF>2</INF> 
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 SO<INF>2</INF> 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 
evaluates whether such plans ``provide for attainment,'' based on 
modeling of projected allowable emissions and in light of the NAAQS' 
form for determining attainment at monitoring sites follows.
    For SO<INF>2</INF> attainment plans based on 1-hour emission 
limits, the standard approach is to conduct modeling using fixed 
emission rates. The maximum modeled emission rate that results in 
attainment is labeled the ``critical emission value.'' The modeling 
process for identifying this critical emission value inherently 
considers the numerous variables that affect ambient concentrations of 
SO<INF>2</INF>, 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.
    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 emission value,'' which, if 
coincident with meteorological conditions conducive to high 
SO<INF>2</INF> 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 (and inherent level of emissions 
variability) 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,'' \4\ 
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 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.
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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 hourly values (e.g., the 
fourth highest maximum daily hourly 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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    To illustrate this point, EPA conducted a statistical analysis 
using a range of scenarios using actual plant data. The analysis is 
described in Appendix B of EPA's 2014 SO<INF>2</INF> Nonattainment 
Guidance. Based on the analysis described in its 2014 SO<INF>2</INF> 
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

[[Page 32609]]

attainment'' of the NAAQS. For SO<INF>2</INF>, as for other pollutants, 
it is generally impossible to design a nonattainment plan in the 
present that will guarantee that attainment will occur in the future. A 
variety of factors can cause a well-designed attainment plan to fail 
and unexpectedly not result in attainment, for example if meteorology 
occurs that is more conducive to poor air quality than was anticipated 
in the plan. Therefore, in determining whether a plan meets the 
requirement to provide for attainment, EPA's task is commonly to judge 
not whether the plan provides absolute certainty that attainment will 
in fact occur, but rather whether the plan provides an adequate level 
of confidence of prospective NAAQS attainment. From this perspective, 
in evaluating use of a 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 EPA to consider when evaluating 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 SO<INF>2</INF> NAAQS.
    The 2014 SO<INF>2</INF> 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 (i.e., 
using 1-hour historical emission values from the emissions database to 
calculate 30-day average emission values). 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 (critical 
emission value) to determine a longer term average emission limit that 
may be considered comparably stringent.\5\
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    \5\ For example, if the critical emission value is 1000 pounds 
of SO<INF>2</INF> 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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    The 2014 SO<INF>2</INF> 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.
    Preferred air quality models for use in regulatory applications are 
described in Appendix A of the EPA's Guideline on Air Quality Models 
(40 CFR part 51, appendix W).\6\ In 2005, the EPA promulgated AERMOD as 
the Agency's preferred near-field dispersion modeling for a wide range 
of regulatory applications addressing stationary sources (for example 
in estimating SO<INF>2</INF> concentrations) in all types of terrain 
based on extensive developmental and performance evaluation. 
Supplemental guidance on modeling for purposes of demonstrating 
attainment of the SO<INF>2</INF> standard is provided in Appendix A to 
the 2014 SO<INF>2</INF> Nonattainment Guidance. 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 SO<INF>2</INF> 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 SO<INF>2</INF> 
NAAQS. For a short-term (i.e., 1-hour) standard, the 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 SO<INF>2</INF>.
    The meteorological data used in the analysis should generally be 
processed with the most recent version of 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 
SO<INF>2</INF> National Ambient Air Quality Standard'' (U.S. EPA, 
2010a).

II. Pennsylvania's Attainment Plan Submittal for the Indiana Area

    In accordance with section 172(c) of the CAA, the Pennsylvania 
attainment plan for the Indiana Area includes: (1) An emissions 
inventory for SO<INF>2</INF> for the plan's base year (2011); and (2) 
an attainment demonstration. The attainment demonstration includes the 
following: Analyses that locate, identify, and quantify sources of 
emissions contributing to violations of the 2010 SO<INF>2</INF> NAAQS; 
a determination that the control strategy for the primary 
SO<INF>2</INF> sources within the nonattainment areas constitutes RACM/
RACT; a dispersion modeling analysis of an emissions control strategy 
for the primary SO<INF>2</INF> sources (Keystone, Conemaugh, Homer 
City, and Seward), showing attainment of the SO<INF>2</INF> NAAQS by 
the October 4, 2018, attainment date; requirements for RFP toward 
attaining the SO<INF>2</INF> NAAQS in the Area; contingency measures; 
the assertion that Pennsylvania's existing SIP-approved NSR program 
meets the applicable requirements for SO<INF>2</INF>; and the request 
that emission limitations

[[Page 32610]]

and compliance parameters for Keystone, Conemaugh, Homer City, and 
Seward be incorporated into the SIP.

III. EPA's Analysis of Pennsylvania's Attainment Plan for the Indiana 
Area

    Consistent with CAA requirements (see section 172), an attainment 
demonstration for an SO<INF>2</INF> nonattainment area must include a 
showing that the area will attain the 2010 SO<INF>2</INF> 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 meets all 
applicable requirements of the CAA, and EPA is proposing to approve the 
plan submitted by Pennsylvania to ensure ongoing attainment in the 
Indiana Area.

A. Pollutants Addressed

    Pennsylvania's SO<INF>2</INF> attainment plan evaluates 
SO<INF>2</INF> emissions for the Indiana Area comprised of Indiana 
County and a portion of Armstrong County (Plumcreek Township, South 
Bend Township, and Elderton Borough) that is designated nonattainment 
for the 2010 SO<INF>2</INF> NAAQS. There are no precursors to consider 
for the SO<INF>2</INF> attainment plan. SO<INF>2</INF> 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, SO<INF>2</INF> 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 
SO<INF>2</INF> emissions for the Indiana 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 
SO<INF>2</INF> 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 SO<INF>2</INF> Nonattainment 
Guidance notes that the base year inventory should include all sources 
of SO<INF>2</INF> 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 as the designation of nonattainment was based on data from 2009-
2011. Actual emissions from all the sources of SO<INF>2</INF> in the 
Indiana Area were reviewed and compiled for the base year emissions 
inventory requirement. The primary SO<INF>2</INF>-emitting point 
sources located within the Indiana Area are Keystone, Conemaugh, Homer 
City, and Seward, all coal-fired power plants. Keystone and Conemaugh 
each have two pulverized coal-fired (PC) boilers; Homer City has three 
coal-fired boilers; and Seward has two circulating fluidized bed (CFB) 
waste coal-fired boilers. More information about the emissions 
inventory for the Indiana Area (and analysis of the inventory) can be 
found in Pennsylvania's October 11, 2017, submittal as well as EPA's 
emissions inventory Technical Support Document (TSD), which can be 
found under Docket ID No. EPA-R03-OAR-2017-0615 and online at 
www.regulations.gov.
    Table 1 shows the level of emissions, expressed in tons per year 
(tpy), in the Indiana Area for the 2011 base year by emissions source 
category. The point source category includes all sources within the 
Area.

  Table 1--2011 Base Year SO2 Emissions Inventory for the Indiana Area
------------------------------------------------------------------------
                                                          SO2 Emissions
                Emission source category                      (tpy)
 
------------------------------------------------------------------------
Point..................................................      144,269.017
Area...................................................          555.610
Non-road...............................................            1.025
On-road................................................            7.730
Total..................................................      144,833.382
------------------------------------------------------------------------

    EPA has evaluated Pennsylvania's 2011 base year emissions inventory 
for the Indiana Area and has made the preliminary determination that 
this inventory was developed in a manner 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 
Indiana Area as it meets CAA requirements.
    The attainment demonstration also provides for a projected 
attainment year inventory that includes estimated emissions for all 
emission sources of SO<INF>2</INF> 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. The 
projected 2018 emissions are shown in Table 2. Pennsylvania's submittal 
asserts that the SO<INF>2</INF> emissions are expected to decrease by 
approximately 75,340 tons, or 40%, by 2018 from the 2011 base year. 
More information about the projected emissions for the Indiana Area can 
be found in Pennsylvania's October 11, 2017, submittal which can be 
found under Docket ID No. EPA-R03-OAR-2017-0615 and online at 
www.regulations.gov.

  Table 2--2018 Anticipated Actual Projected SO2 Emission Inventory for
                            the Indiana Area
------------------------------------------------------------------------
                                                          SO2 Emissions
                Emission source category                      (tpy)
 
------------------------------------------------------------------------
Point..................................................       68,545.292
Area...................................................          944.688
Non-road...............................................            0.460
On-road................................................            3.260
Total..................................................       69,493.700
------------------------------------------------------------------------

C. Air Quality Modeling

    The SO<INF>2</INF> attainment demonstration provides air quality 
dispersion modeling analyses to demonstrate that control strategies 
chosen to reduce SO<INF>2</INF> source emissions will bring the Area 
into attainment by the statutory attainment date of October 4, 2018. 
The modeling analyses, conducted pursuant to recommendations outlined 
in Appendix W to 40 CFR part 51 (EPA's Modeling Guidance), are used to 
assess the control strategy for a nonattainment area and establish 
emission limits that will provide for attainment. The analysis requires 
five years of meteorological data 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

[[Page 32611]]

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. A modeling 
analysis that provides for attainment under all scenarios of operation 
for each source must therefore consider the worst case scenario of both 
the meteorology (e.g. predominant wind directions, stagnation, etc.) 
and the maximum allowable emissions.
    PADEP provided two sets of modeling analyses: One analysis was 
developed in accordance with EPA's Modeling Guidance and the 2014 
SO<INF>2</INF> Nonattainment Guidance, and was prepared using the 
default option in EPA's preferred dispersion modeling system, AERMOD; a 
second modeling analysis also utilized AERMOD but included a procedure 
called AERMOIST, an alternative model option which accounts for 
additional plume rise associated with the latent heat release of 
condensation due to moisture in a stack's plume. AERMOIST is currently 
not approved by EPA for regulatory use. A more detailed discussion of 
PADEP's modeling analysis for the Indiana Area can be found in 
Pennsylvania's October 11, 2017 submittal.
    In addition to submitting the Indiana Area attainment plan to EPA 
on October 11, 2017, PADEP also submitted a request to EPA to review 
AERMOIST for use in the Indiana Area attainment plan. EPA has completed 
a review and determined that the AERMOIST procedure is not an 
appropriate option for use in the Indiana attainment plan for the 
following reasons: (1) There is no multi-monitor database of 
SO<INF>2</INF> monitoring data available for the four major sources of 
SO<INF>2</INF> in the Indiana Area to conduct a source-specific 
statistical test to determine if AERMOIST provides a definitive 
improvement over the current regulatory default version of AERMOD; (2) 
AERMOIST was universally applied to all the major sources in the 
Indiana Area regardless of whether the source plumes are actually 
saturated; and (3) there is a lack of supporting analysis for using 
relative humidity measurements in AERMOIST. For these reasons, EPA is 
rejecting the AERMOIST modeling analysis for the Indiana Area 
attainment plan. A detailed discussion of the deficiencies of the 
AERMOIST modeling analysis submitted for the Indiana Area can be found 
in EPA's AERMOIST modeling TSD for the Indiana which can be found under 
Docket ID No. EPA-R03-OAR-2017-0615 and available online at 
www.regulations.gov.
    EPA has reviewed the default AERMOD analysis without the AERMOIST 
module submitted for the Indiana Area. The Indiana Area was divided 
into two separate modeling domains. Refer to EPA's Modeling TSD for the 
Indiana Area under Docket ID EPA-R03-OAR-2017-0615, available at 
www.regulations.gov for EPA's review of the modeling domains. One 
domain included portions of Armstrong County which only addressed 
emissions from Keystone as a source. The other domain covered all of 
Indiana County and addressed emissions from all four sources in the 
nonattainment area. For both domains, background concentrations 
included impacts from non-modeled sources. Each separate model domain 
used its own (different) background concentration.
    AERMOD was used to determine the critical emission values (CEV) for 
Conemaugh, Keystone, and Seward where the modeled 1-hour emission rates 
demonstrate compliance with the 2010 1-hour SO<INF>2</INF> NAAQS. The 
SO<INF>2</INF> emission rates for Homer City were based on the unit 1, 
unit 2, and unit 3 combined mass-based SO<INF>2</INF> emission limits 
established in Plan Approval 32-00055H,\8\ which authorized the 
installation of Novel Integrated Desulfurization (NID) systems, often 
referred to as Dry Flue Gas Desulphurization (FGD) systems on unit 1 
and unit 2. This 1-hour SO<INF>2</INF> limit was based on air 
dispersion modeling that demonstrated compliance with the 2010 1-hour 
SO<INF>2</INF> NAAQS. The CEV rates used in the demonstration analysis 
for each of the four sources are summarized in the following table. The 
modeled emission rate in grams per second was converted to pounds per 
hour, which is the CEV limit.\9\
---------------------------------------------------------------------------

    \8\ Plan Approval 32-00055H was issued on April 2, 2012, and 
modified on April 4, 2013, by the DEP.
    \9\ Based on the National Institute of Standards and Technology 
conversion: 1 pound = 453.59237 grams.

     Table 3--Critical Emission Values From Indiana, PA SIP Modeling
                              Demonstration
------------------------------------------------------------------------
                                           Modeled rate   CEV limit (lbs/
                Facility                       (g/s)            hr)
------------------------------------------------------------------------
Conemaugh Generating Station............          426.00        3,381.00
Homer City Generating Station, Unit 1...          195.30        1,550.02
Homer City Generating Station, Unit 2...          195.30        1,550.02
Homer City Generating Station, Unit 3...          410.76        3,260.02
Keystone Generating Station.............        1,223.58        9,711.10
Seward Generating Station...............          640.00        5,079.44
------------------------------------------------------------------------

    Using the EPA conversion factor for the SO<INF>2</INF> NAAQS, the 
final 1-hour CEV model run design values for the Armstrong County 
portion (196.28 [mu]g/m\3\) and the Indiana County portion (196.44 
[mu]g/m\3\) of the Indiana Area are less than 75 ppb.\10\
---------------------------------------------------------------------------

    \10\ The SO<INF>2</INF> NAAQS level is expressed in ppb but 
AERMOD gives results in [mu]g/m\3\. The conversion factor for 
SO<INF>2</INF> (at the standard conditions applied in the ambient 
SO<INF>2</INF> reference method) is 1ppb = approximately 2.619 
[mu]g/m\3\.
    See Pennsylvania's SO<INF>2</INF> Round 3 Designations Proposed 
Technical Support Document at https://www.epa.gov/sites/production/files/2017-08/documents/35_pa_so2_rd3-final.pdf.
---------------------------------------------------------------------------

    PADEP also provided air dispersion modeling with randomly 
reassigned emissions (RRE) to provide support for establishing longer 
term emission limits for Keystone and Seward that would provide for 
attainment of the NAAQS. EPA's 2014 SO<INF>2</INF> Nonattainment 
Guidance and Section I of this proposed rulemaking provide an extensive 
discussion of EPA's rationale for concluding that emission limits that 
are appropriately set based on averaging times longer than 1 hour and 
up to as long as 30 days can be found to provide for attainment of the 
2010 SO<INF>2</INF> NAAQS. When determining longer term emission 
limits, EPA's 2014 SO<INF>2</INF> Nonattainment Guidance states,

    ``[T]he EPA is not precluding states from using other approaches 
to determine appropriate longer term average limits. However, the 
EPA would recommend in all cases that the analysis begin with 
determination of the critical emission values. A comparison of the 
1-hour limit and the proposed longer term limit, in particular an 
assessment of whether the longer term

[[Page 32612]]

average limit may be considered to be of comparable stringency to a 
1-hour limit at the critical emission value, would be a critical 
element of a demonstration that any longer term average limits in 
the SIP will help provide adequate assurance that the plan will 
provide for attainment and maintenance of the 1-hour NAAQS.''

    As discussed in the RACM/RACT section below, a 24-hour block 
average SO<INF>2</INF> emission limit for Keystone and a rolling 30-day 
average SO<INF>2</INF> emission limit for Seward were developed by 
conducting additional modeling with SO<INF>2</INF> emissions 
distributions representative of future operations which were derived 
for each facility by evaluating emissions for 2014-2016. For each 
facility, the emissions were randomly reassigned to develop 100 hourly 
emission files for use in 100 AERMOD simulations. These AERMOD 
simulations included CEV rates for three facilities, and hourly 
emissions for either Seward or Keystone. EPA believes that the 
distribution of emissions modeled in the 100 RRE methodology, which 
were based on historical operating levels and scaled to conform with 
the longer term limits, are a reasonable representation of an allowable 
emissions distribution for both Seward and Keystone. EPA believes that 
the 100 RRE analyses and model results for Keystone and Seward provide 
adequate assurance that the longer term emission limits for both of 
these facilities will result in attainment of the 2010 SO<INF>2</INF> 
NAAQS by the attainment date. A more detailed discussion of the RRE 
modeling is provided in EPA's Modeling TSD for the Indiana Area under 
Docket ID EPA-R03-OAR-2017-0615, available at www.regulations.gov.
    EPA has reviewed the modeling that Pennsylvania submitted to 
support the attainment demonstration for the Indiana Area and has 
determined that the default AERMOD modeling is consistent with CAA 
requirements, Appendix W to 40 CFR part 51, and EPA's 2014 
SO<INF>2</INF> Guidance for SO<INF>2</INF> attainment demonstration 
modeling. Because the AERMOD analysis employing AERMOIST has not been 
approved by EPA for use in the attainment demonstration for the Indiana 
Area, EPA is not proposing to approve the modeling submitted by PADEP 
which employed AERMOIST. EPA is proposing to approve the default non-
AERMOIST modeling, including the CEV and RRE simulations, provided in 
the attainment plan and EPA believes that the modeling reasonably 
demonstrates that the Indiana Area will attain the 2010 1-hour primary 
SO<INF>2</INF> NAAQS by the attainment date.

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. Section 172(c)(6) requires SIPs to contain 
enforceable emission limitations and control measures as may be 
necessary or appropriate to provide for NAAQS attainment. 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.''
    Pennsylvania's October 11, 2017, submittal discusses federal and 
state measures that Pennsylvania asserts will provide emission 
reductions leading to attainment and maintenance of the 2010 
SO<INF>2</INF> NAAQS. With regards to state rules, Pennsylvania cites 
its low sulfur fuel rules, which were SIP-approved on July 10, 2014 (79 
FR 39330). Pennsylvania's low sulfur fuel oil provisions apply to 
refineries, pipelines, terminals, retail outlet fuel storage 
facilities, commercial and industrial facilities, and facilities with 
units burning regulated fuel oil to produce electricity and domestic 
home heaters. These low sulfur fuel oil rules reduce the amount of 
sulfur in fuel oils used in combustion units, thereby reducing 
SO<INF>2</INF> emissions and the formation of sulfates that cause 
decreased visibility.
    Pennsylvania's submittal discusses that the main SO<INF>2</INF> 
emitting sources at Conemaugh, Homer City, Keystone, and Seward are all 
equipped with FGD systems (wet limestone scrubbers, dry FGD, or in-
furnace limestone injection systems) to reduce SO<INF>2</INF> 
emissions. Table 4 lists the control technology at each of the main 
SO<INF>2</INF> emitting sources at each facility.

                  Table 4--Control Technology at the Four Major SO2 Sources in the Indiana Area
----------------------------------------------------------------------------------------------------------------
                                                                                                      Control
                Facility                             Unit                     SO2 control          installation
                                                                                                       date
----------------------------------------------------------------------------------------------------------------
Conemaugh...............................  031--Main Boiler 1........  Wet limestone scrubber....           ~1994
                                          031--Main Boiler 2........  Wet limestone scrubber....           ~1995
Homer City..............................  031--Boiler 1.............  Dry FGD...................      11/18/2015
                                          032--Boiler 2.............  Dry FGD...................       5/23/2016
                                          033--Boiler 3.............  Wet limestone scrubber....           ~2002
Keystone................................  031--Boiler 1.............  Wet limestone scrubber....       9/24/2009
                                          032--Boiler 2.............  Wet limestone scrubber....      11/22/2009
Seward..................................  034--CFB Boiler 1.........  In-furnace limestone                 ~2004
                                                                       injection.
                                          035--CFB Boiler 2.........  In-furnace limestone                 ~2004
                                                                       injection.
----------------------------------------------------------------------------------------------------------------

    With these controls installed, Pennsylvania's submittal discusses 
facility-specific control measures, namely SO<INF>2</INF> emission 
limits for Conemaugh, Homer City, and Seward, and new SO<INF>2</INF> 
emission limits for Keystone. Keystone's new limits were developed 
through air dispersion modeling (default AERMOD) submitted by PADEP. 
The modeling analysis is discussed in section III.C. Air Quality 
Modeling of this proposed rulemaking and in the Modeling TSD. In order 
to ensure that the Indiana Area demonstrates attainment with the 
SO<INF>2</INF> NAAQS, PADEP asserts that the following combination of 
emission limits at the four facilities is sufficient for the Indiana 
Area to meet the SO<INF>2</INF> NAAQS and serve as RACM/RACT:
    <bullet> Conemaugh's current SO<INF>2</INF> emission limits 
contained in the Title V Operating Permit (TVOP) 32-00059 because the 
emission limits for Conemaugh determined by the modeling as necessary 
for SO<INF>2</INF> attainment would be less stringent;
    <bullet> Seward's current SO<INF>2</INF> emission limit in TVOP 32-
00040 because the emission limits for Seward determined by the modeling 
as necessary for SO<INF>2</INF> attainment would be less stringent;
    <bullet> Homer City's current SO<INF>2</INF> emission limits 
established in Plan Approval 32-00055H and Plan Approval 32-00055I; and

[[Page 32613]]

    <bullet> A new, more stringent combined SO<INF>2</INF> emission 
limit for Keystone Unit 1 and Unit 2 of 9,600 pounds per hour (lbs/hr) 
block 24-hour average limit.
    The emission limits for each of the SO<INF>2</INF>-emitting 
facilities are listed in Table 5.

                            Table 5--SO2 Emission Limits for Indiana Area Facilities
----------------------------------------------------------------------------------------------------------------
                                                           Emission limit (lbs/
             Facility                 Source description            hr)                  Averaging period
----------------------------------------------------------------------------------------------------------------
Conemaugh.........................  Unit 1...............  1,656 (TVOP 32-       3-hour block.
                                    Unit 2...............   00059).
Homer City........................  Unit 1...............  6,360 (Plan Approval  1-hour block.
                                    Unit 2...............   32-00055H) and
                                    Unit 3...............   limits specified in
                                                            Plan Approval 32-
                                                            00055I.
Keystone..........................  Unit 1...............  9,600 (New limit      24-hour block.
                                    Unit 2...............   based on default
                                                            AERMOD).
Seward............................  Unit 1...............  3,038.4 (TVOP 32-     30-day rolling.
                                    Unit 2...............   00040).
----------------------------------------------------------------------------------------------------------------

    The emission limits for Conemaugh, Keystone and Seward have 
averaging times greater than 1-hour (ranging between three hours and 30 
days). The default non-AERMOIST modeling analysis for the Indiana Area 
was used to establish CEVs for each facility. These (1-hour) CEVs were 
used for developing longer than 1-hour emission limits for Seward, 
Conemaugh, and Keystone. SO<INF>2</INF> limits at Conemaugh are set to 
a 3-hour block average. This average is roughly in line with the CEV 
modeled limit and the ratio from Appendix C in EPA's 2014 
SO<INF>2</INF> Nonattainment Guidance. Keystone's limits were set to a 
24-hour block average based on the 100 RRE simulation method discussed 
in Section III.C. Air Quality Modeling in this proposed rulemaking. A 
similar approach was used to establish a 30-day rolling average for 
Seward. Appendices C-1a and C-4 of Pennsylvania's October 11, 2017 SIP 
submittal provide a detailed explanation of the longer term emission 
limits. EPA believes the 100 RRE iteration approach used in 
Pennsylvania's submittal for determining longer term emission limits 
for Seward and Keystone can be used to demonstrate compliance with the 
2010 SO<INF>2</INF> NAAQS. EPA's analysis of the default AERMOD 
modeling analysis using longer term emission limits shows, as discussed 
in detail in the Modeling TSD, that the emission limits listed in Table 
5 are sufficient for the Indiana Area to attain the 1-hour 
SO<INF>2</INF> NAAQS. EPA's analysis of the longer term emission limits 
is discussed in more detail in the Modeling TSD for the Indiana Area 
under Docket ID EPA-R03-OAR-2017-0615, available at 
www.regulations.gov.
    The emission limits or compliance parameters, such as contingency 
measures, or both, were established through Consent Orders and 
Agreements (COAs) and Consent Orders (COs) between PADEP and the 
respective facility (see Appendices B-1 through B-4 of the October 11, 
2017, SIP submittal). The collective emission limits and all related 
compliance parameters (i.e. the measures which include system audits, 
record-keeping and reporting, and corrective actions) have been 
proposed for incorporation into the SIP to make these changes 
permanently federally enforceable. PADEP affirms that the 
implementation of existing and new emission limits and corresponding 
compliance parameters for the four EGUs will enable the Indiana Area to 
attain and maintain the SO<INF>2</INF> NAAQS.
    EPA is proposing to approve Pennsylvania's determination that the 
proposed SO<INF>2</INF> control strategy at Keystone, Conemaugh, Homer 
City, and Seward constitutes RACM/RACT for each SO<INF>2</INF> source 
in the Indiana Area based on the modeling analysis previously 
described. EPA finds Pennsylvania's control strategy for RACM/RACT 
including emission limits and compliance parameters for the four EGUs 
will enable the Indiana Area to attain and maintain the NAAQS.
    Furthermore, PADEP requests that the unredacted portions of the 
COAs, COs, Plan Approvals, and TVOP submitted by PADEP with the 
attainment plan be approved into the Pennsylvania SIP. Including the 
emission limits listed in the CO for Keystone, the Plan Approval for 
Homer City, and the TVOPs for Conemaugh and Seward (see Table 4), and 
corresponding compliance parameters found in the COAs and COs for 
Keystone, Conemaugh, Homer City, and Seward in the Pennsylvania SIP 
means that these measures will become permanent and enforceable SIP 
measures to meet the requirements of the CAA. EPA, therefore, proposes 
to approve Pennsylvania's October 11, 2017 SIP submittal as meeting the 
RACM/RACT requirements of section 172(c)(1) and the enforceable 
emission limitation and control measures requirements of section 
172(c)(6) of the CAA.

E. RFP Plan

    Section 172(c)(2) of the CAA requires that an attainment plan 
includes 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 in the 1994 SO<INF>2</INF> Guidelines 
Document \11\ and repeated in the 2014 SO<INF>2</INF> 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 SO<INF>2</INF> 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 SO<INF>2</INF> as adherence to an ambitious compliance schedule 
in both the 1994 SO<INF>2</INF> Guideline Document and the 2014 
SO<INF>2</INF> Nonattainment Guidance. EPA finds the control measures 
included in Pennsylvania's submittal demonstrate attainment for the 
Area with the 2010 SO<INF>2</INF> NAAQS based on the modeling submitted 
by

[[Page 32614]]

Pennsylvania. The permits and compliance orders submitted by 
Pennsylvania for inclusion in the SIP require these control measures 
and resulting emission reductions to be achieved as expeditiously as 
practicable. As a result, based on air quality modeling reviewed by 
EPA, this is projected to yield a sufficient reduction in 
SO<INF>2</INF> emissions from the major sources in the Indiana Area 
resulting in modeled attainment of the SO<INF>2</INF> NAAQS for the 
Indiana Area. Therefore, EPA has determined that PADEP's SO<INF>2</INF> 
attainment plan for the Indiana Area fulfills the RFP requirements for 
the Indiana Area. EPA does not anticipate future nonattainment, or that 
the Area will not attain the NAAQS by the October 4, 2018 attainment 
date. EPA proposes to approve Pennsylvania's attainment plan with 
respect to the RFP requirements.
---------------------------------------------------------------------------

    \11\ SO<INF>2</INF> Guideline Document, U.S. Environmental 
Protection Agency, Office of Air Quality Planning and Standards, 
Research Triangle Park, N.C. 27711, EPA-452/R-94-008, February 1994. 
Located at: http://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, 
SO<INF>2</INF> presents special considerations. As stated in the final 
2010 SO<INF>2</INF> NAAQS promulgation on June 22, 2010 (75 FR 35520) 
and in the 2014 SO<INF>2</INF> Nonattainment Guidance, EPA concluded 
that because of the quantifiable relationship between SO<INF>2</INF> 
sources and control measures, it is appropriate that state agencies 
develop a comprehensive program to identify sources of violations of 
the SO<INF>2</INF> NAAQS and undertake an aggressive follow-up for 
compliance and enforcement.
    The COAs or COs for Conemaugh, Homer City, Keystone, and Seward 
(see Appendices B-1 through B-4 of the October 11, 2017 submittal) each 
contain the following measures that are designed to keep the Indiana 
Area from triggering an exceedance or violation of the SO<INF>2</INF> 
NAAQS: (1) Upon execution of the COA or CO, if SO<INF>2</INF> emissions 
from the combined SO<INF>2</INF> emitting sources at the facility 
exceed 99% of the SO<INF>2</INF> emissions limit for the facility 
(listed in Table 3), within 48 hours the facility is required to 
undertake a full system audit of the SO<INF>2</INF> emitting sources 
and submit a written report to PADEP within 15 days, and corrective 
actions shall be identified by PADEP as necessary; and (2) Upon 
execution of the COA or CO, if the Strongstown monitor (ID 42-063-0004) 
measures a 1-hour concentration exceeding 75 ppb, PADEP will notify the 
facility in the Area, and the facility in the Area is required to 
identify whether any of the SO<INF>2</INF>-emitting sources at the 
respective facility were running at the time of the exceedance, and 
within a reasonable time period leading up to the exceedance, not to 
exceed 24 hours. If any of the SO<INF>2</INF>-emitting sources were 
running at the time of the exceedance, the facility must then analyze 
the meteorological data on the day the daily exceedance occurred to 
ensure that the daily exceedance was not due to SO<INF>2</INF> 
emissions from the respective facility. The facility's findings must be 
submitted to PADEP within 30 days of being notified of the exceedance.
    Additionally, if PADEP identifies a daily maximum SO<INF>2</INF> 
concentration exceeding 75 ppb at a PADEP-operated SO<INF>2</INF> 
ambient air quality monitor in the Indiana Area, within five days, 
PADEP will contact Conemaugh, Homer City, Keystone, and Seward to 
trigger the implementation of the daily exceedance report contingency 
measure described in section VIII.C. of the October 11, 2017 submittal. 
If necessary, section 4(27) of the Pennsylvania Air Pollution Control 
Act (APCA) authorizes PADEP to take any action it deems necessary or 
proper for the effective enforcement of APCA and the rules and 
regulations promulgated under APCA. Such actions include the issuance 
of orders and the assessment of civil penalties. A more detailed 
description of the contingency measures can be found in section VIII of 
the October 11, 2017 submittal as well as the COAs and COs included in 
the submittal and included for incorporation by reference into the SIP.
    EPA is proposing to find that Pennsylvania's October 11, 2017 
submittal includes sufficient measures to expeditiously identify the 
source of any violation of the SO<INF>2</INF> NAAQS and for aggressive 
follow-up including enforcement measures within PADEP's authority as 
necessary. Therefore, EPA proposes that the contingency measures 
submitted by Pennsylvania follow the 2014 SO<INF>2</INF> Nonattainment 
Guidance and meet the section 172(c)(9) requirements.

G. New Source Review <SUP>12</SUP>
---------------------------------------------------------------------------

    \12\ 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 undesignated areas and in areas that meet 
the NAAQS--designated ``attainment areas''--as well as areas where 
there is insufficient information to determine if the area meets the 
NAAQS--designated ``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--designated ``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. Pennsylvania has a 
fully implemented Nonattainment New Source Review (NNSR) program for 
criteria pollutants in 25 Pennsylvania Code Chapter 127, Subchapter E, 
which was approved into the Pennsylvania SIP on December 9, 1997 (62 FR 
64722). On May 14, 2012 (77 FR 28261), EPA approved a SIP revision 
pertaining to the pre-construction permitting requirements of 
Pennsylvania's NNSR program to update the regulations to meet EPA's 
2002 NSR reform regulations. EPA then approved an update to 
Pennsylvania's NNSR regulations on July 13, 2012 (77 FR 41276). These 
rules provide for appropriate NSR as required by CAA sections 172(c)(5) 
and 173 and 40 CFR 51.165 for SO<INF>2</INF> sources undergoing 
construction or major modification in the Indiana Area without need for 
modification of the approved rules. Therefore, EPA concludes that the 
Pennsylvania SIP meets the requirements of section 172(c)(5) for this 
Area.

IV. EPA's Proposed Action

    EPA is proposing to approve Pennsylvania's SIP revision for the 
Indiana Area, as submitted through PADEP to EPA on October 11, 2017, 
for the purpose of demonstrating attainment of the 2010 1-hour 
SO<INF>2</INF> NAAQS. Specifically, EPA is proposing to approve the 
base year emissions inventory, a modeling demonstration of 
SO<INF>2</INF> attainment, an analysis of RACM/RACT, enforceable 
emission limitations and control measures, a RFP plan, and contingency 
measures for the Indiana Area and is proposing that the Pennsylvania 
SIP has met requirements for NSR for the 2010 1-hour SO<INF>2</INF> 
NAAQS. Additionally, EPA is proposing to approve into the Pennsylvania 
SIP specific SO<INF>2</INF> emission limits,

[[Page 32615]]

compliance parameters, and contingency measures established for the 
SO<INF>2</INF> sources impacting the Indiana Area.
    EPA has determined that Pennsylvania's SO<INF>2</INF> attainment 
plan for the 2010 1-hour SO<INF>2</INF> NAAQS for Indiana County meets 
the applicable requirements of the CAA. Thus, EPA is proposing to 
approve Pennsylvania's attainment plan for the Indiana Area as 
submitted on October 11, 2017. EPA's analysis for this proposed action 
is discussed in Section III 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 promulgate and 
implement a FIP under CAA section 110(c).

V. Incorporation by Reference

    In this proposed rule, 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 the portions of the COAs or COs entered 
between Pennsylvania and Conemaugh, Homer City, Keystone, and Seward 
that are not redacted, as well as the unredacted portions of the TVOPs 
or Plan Approval included in the October 11, 2017 submittal. These 
include emission limits and associated compliance parameters (i.e. the 
measures which include system audits, record-keeping and reporting, and 
corrective actions). EPA has made, and will continue to make, these 
materials generally available through http://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).

VI. 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:
    <bullet> 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);
    <bullet> is not an Executive Order 13771 (82 FR 9339, February 2, 
2017) regulatory action because SIP approvals are exempted under 
Executive Order 12866;
    <bullet> does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
    <bullet> 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.);
    <bullet> 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);
    <bullet> does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
    <bullet> is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
    <bullet> is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
    <bullet> 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
    <bullet> 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 SO<INF>2</INF> 
attainment plan for the Indiana nonattainment 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: June 27, 2018.
Cecil Rodrigues,
Acting Regional Administrator, Region III.
[FR Doc. 2018-14947 Filed 7-12-18; 8:45 am]
BILLING CODE 6560-50-P


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