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1EPA’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. Currently, the 24-hour and 

annual standards are only revoked for certain of 

those areas the EPA has already designated for the 

2010 1-hour SO2 NAAQS. See 40 CFR 50.4(e). 

petty officer who has been designated 

by the Captain of the Port Buffalo to act 

on his behalf. 

(4) Vessel operators desiring to enter 

or operate within the safety zone must 

contact the Captain of the Port Buffalo 

or his on-scene representative to obtain 

permission to do so. The Captain of the 

Port Buffalo or his on-scene 

representative may be contacted via 

VHF Channel 16. Vessel operators given 

permission to enter or operate in the 

safety zone must comply with all 

directions given to them by the Captain 

of the Port Buffalo, or his on-scene 

representative. 

Dated: July 5, 2018. 

Joseph S. Dufresne, 

Captain, U.S. Coast Guard, Captain of the 

Port Buffalo. 

[FR Doc. 2018–14993 Filed 7–12–18; 8:45 am] 

BILLING CODE 9110–04–P 

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. 

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 (SO2) primary 

national ambient air quality standard 

(NAAQS) in the Indiana, Pennsylvania 

SO2 nonattainment area (hereafter 

referred to as the ‘‘Indiana Area’’ or 

‘‘Area’’). The Indiana Area is comprised 

of Indiana County and a portion of 

Armstrong County (Plumcreek 

Township, South Bend Township, and 

Elderton Borough) in Pennsylvania. The 

major sources of SO2 in the Indiana 

Area emitting over 2,000 tpy of SO2

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 SO2 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 

SO2 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 SO2 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 

spielberger.susan@epa.gov. 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 goold.megan@epa.gov. 

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 SO2 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 SO2

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 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)–(2) of the CAA. On August 5, 

2013, EPA promulgated initial air 

quality designations for 29 areas for the 

2010 SO2 NAAQS (78 FR 47191), which 


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2EPA is continuing its designation efforts for the 

2010 SO2 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). 

3See ‘‘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. 

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

Effective on October 4, 2013, the 

Indiana Area was designated as 

nonattainment for the 2010 SO2 NAAQS 

for an area that encompasses the 

primary SO2 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 SO2 NAAQS as expeditiously as 

practicable, but no later than October 4, 

2018, in accordance with CAA sections 

172(c) and 191–192. 

For a number of areas, including the 

Indiana Area, EPA published a notice 

on March 18, 2016, effective April 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 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 

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 include: An 

accurate base year emissions inventory 

of current emissions for all sources of 

SO2 within the nonattainment area 

(172(c)(3)); an attainment demonstration 

that includes a modeling analysis 

showing that the enforceable emissions 

limitations and other control measures 

taken by the state will provide for 

expeditious attainment of the NAAQS 

(172(c) 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 SO2 nonattainment plans, 

published on October 5, 2017 at 82 FR 

46434. 

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). 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 (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 


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4An ‘‘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. 

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 

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 SO2 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 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 

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 SO2 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 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. 

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 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 (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. 

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 SO2

Nonattainment Guidance. Based on the 

analysis described in 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 


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5For 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. 

6The EPA published revisions to the Guideline 

on Air Quality Models on January 17, 2017. 

attainment’’ of the NAAQS. For SO2, 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 welldesigned 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 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 (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

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. 

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 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 2014 SO2 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. 

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, 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 SO2. 

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 SO2 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 SO2 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 

SO2 NAAQS; a determination that the 

control strategy for the primary SO2

sources within the nonattainment areas 

constitutes RACM/RACT; a dispersion 

modeling analysis of an emissions 

control strategy for the primary SO2

sources (Keystone, Conemaugh, Homer 

City, and Seward), showing attainment 

of the SO2 NAAQS by the October 4, 

2018, attainment date; requirements for 

RFP toward attaining the SO2 NAAQS 

in the Area; contingency measures; the 

assertion that Pennsylvania’s existing 

SIP-approved NSR program meets the 

applicable requirements for SO2; and 

the request that emission limitations 


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7The 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. 

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 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 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 SO2 attainment plan 

evaluates SO2 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 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 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 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

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 as the designation of 

nonattainment was based on data from 

2009–2011. Actual emissions from all 

the sources of SO2 in the Indiana Area 

were reviewed and compiled for the 

base year emissions inventory 

requirement. The primary SO2-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

Emission source category SO2 Emissions 

(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 

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. The projected 2018 

emissions are shown in Table 2. 

Pennsylvania’s submittal asserts that the 

SO2 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

Emission source category SO2 Emissions 

(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 SO2 attainment demonstration 

provides air quality dispersion 

modeling analyses 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 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 


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8Plan Approval 32–00055H was issued on April 

2, 2012, and modified on April 4, 2013, by the DEP. 9Based on the National Institute of Standards and 

Technology conversion: 1 pound = 453.59237 

grams. 

10The SO2 NAAQS level is expressed in ppb but 

AERMOD gives results in mg/m3. The conversion 

factor for SO2 (at the standard conditions applied 

in the ambient SO2 reference method) is 1ppb = 

approximately 2.619 mg/m3. 

See Pennsylvania’s SO2 Round 3 Designations 

Proposed Technical Support Document at https://

www.epa.gov/sites/production/files/2017-08/ 

documents/35_pa_so2_rd3-final.pdf. 

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 SO2

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 SO2

monitoring data available for the four 

major sources of SO2 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 SO2 NAAQS. The SO2

emission rates for Homer City were 

based on the unit 1, unit 2, and unit 3 

combined mass-based SO2 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 SO2 limit was 

based on air dispersion modeling that 

demonstrated compliance with the 2010 

1-hour SO2 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

TABLE 3—CRITICAL EMISSION VALUES FROM INDIANA, PA SIP MODELING DEMONSTRATION

Facility Modeled rate 

(g/s) 

CEV limit 

(lbs/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 SO2 NAAQS, the final 1-hour CEV 

model run design values for the 

Armstrong County portion (196.28 mg/ 

m3) and the Indiana County portion 

(196.44 mg/m3) of the Indiana Area are 

less than 75 ppb.10

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 SO2 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 SO2 NAAQS. 

When determining longer term emission 

limits, EPA’s 2014 SO2 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 


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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 

SO2 emission limit for Keystone and a 

rolling 30-day average SO2 emission 

limit for Seward were developed by 

conducting additional modeling with 

SO2 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 SO2 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 SO2 Guidance for SO2

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 SO2

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 

SO2 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 SO2 emissions and the 

formation of sulfates that cause 

decreased visibility. 

Pennsylvania’s submittal discusses 

that the main SO2 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 SO2 emissions. Table 

4 lists the control technology at each of 

the main SO2 emitting sources at each 

facility. 

TABLE 4—CONTROL TECHNOLOGY AT THE FOUR MAJOR SO2 SOURCES IN THE INDIANA AREA

Facility Unit SO2 control 

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 injection ................. ∼2004 

035—CFB Boiler 2 .................................. In-furnace limestone injection ................. ∼2004 

With these controls installed, 

Pennsylvania’s submittal discusses 

facility-specific control measures, 

namely SO2 emission limits for 

Conemaugh, Homer City, and Seward, 

and new SO2 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 SO2

NAAQS, PADEP asserts that the 

following combination of emission 

limits at the four facilities is sufficient 

for the Indiana Area to meet the SO2

NAAQS and serve as RACM/RACT: 

• Conemaugh’s current SO2 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 SO2

attainment would be less stringent; 

• Seward’s current SO2 emission 

limit in TVOP 32–00040 because the 

emission limits for Seward determined 

by the modeling as necessary for SO2

attainment would be less stringent; 

• Homer City’s current SO2 emission 

limits established in Plan Approval 32– 

00055H and Plan Approval 32–00055I; 

and 


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11SO2 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. 

• A new, more stringent combined 

SO2 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 

SO2-emitting facilities are listed in 

Table 5. 

TABLE 5—SO2 EMISSION LIMITS FOR INDIANA AREA FACILITIES

Facility Source description Emission limit 

(lbs/hr) Averaging period 

Conemaugh ......................................... Unit 1 ...................................................

Unit 2 ...................................................

1,656 (TVOP 32–00059) ..................... 3-hour block. 

Homer City ........................................... Unit 1 ...................................................

Unit 2 ...................................................

Unit 3 ...................................................

6,360 (Plan Approval 32–00055H) and 

limits specified in Plan Approval 32– 

00055I.

1-hour block. 

Keystone .............................................. Unit 1 ...................................................

Unit 2 ...................................................

9,600 (New limit based on default 

AERMOD).

24-hour block. 

Seward ................................................. Unit 1 ...................................................

Unit 2 ...................................................

3,038.4 (TVOP 32–00040) .................. 30-day rolling. 

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. SO2

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 

SO2 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 

SO2 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 SO2

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 

SO2 NAAQS. 

EPA is proposing to approve 

Pennsylvania’s determination that the 

proposed SO2 control strategy at 

Keystone, Conemaugh, Homer City, and 

Seward constitutes RACM/RACT for 

each SO2 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 

SO2 Guidelines Document 11 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 postcontrol 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. EPA finds the control 

measures included in Pennsylvania’s 

submittal demonstrate attainment for 

the Area with the 2010 SO2 NAAQS 

based on the modeling submitted by 


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12The 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. 

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 SO2 emissions from the 

major sources in the Indiana Area 

resulting in modeled attainment of the 

SO2 NAAQS for the Indiana Area. 

Therefore, EPA has determined that 

PADEP’s SO2 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. 

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 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 SO2 NAAQS: (1) Upon execution of 

the COA or CO, if SO2 emissions from 

the combined SO2 emitting sources at 

the facility exceed 99% of the SO2

emissions limit for the facility (listed in 

Table 3), within 48 hours the facility is 

required to undertake a full system 

audit of the SO2 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 

SO2-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 SO2-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 SO2

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 SO2 concentration 

exceeding 75 ppb at a PADEP-operated 

SO2 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 SO2 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 SO2 Nonattainment Guidance and 

meet the section 172(c)(9) requirements. 

G. New Source Review 12

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 preconstruction 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 SO2 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 SO2

NAAQS. Specifically, EPA is proposing 

to approve the base year emissions 

inventory, a modeling demonstration of 

SO2 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 SO2

NAAQS. Additionally, EPA is proposing 

to approve into the Pennsylvania SIP 

specific SO2 emission limits, 


sradovich on DSK3GMQ082PROD with PROPOSALS
Federal Register / Vol. 83, No. 135 / Friday, July 13, 2018 / Proposed Rules 32615 

compliance parameters, and 

contingency measures established for 

the SO2 sources impacting the Indiana 

Area. 

EPA has determined that 

Pennsylvania’s SO2 attainment plan for 

the 2010 1-hour SO2 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: 

• Is not a ‘‘significant regulatory 

action’’ subject to review by the Office 

of Management and Budget under 

Executive Orders 12866 (58 FR 51735, 

October 4, 1993) and 13563 (76 FR 3821, 

January 21, 2011); 

• is not an Executive Order 13771 (82 

FR 9339, February 2, 2017) regulatory 

action because SIP approvals are 

exempted under Executive Order 12866; 

• does not impose an information 

collection burden under the provisions 

of the Paperwork Reduction Act (44 

U.S.C. 3501 et seq.); 

• is certified as not having a 

significant economic impact on a 

substantial number of small entities 

under the Regulatory Flexibility Act (5 

U.S.C. 601 et seq.); 

• does not contain any unfunded 

mandate or significantly or uniquely 

affect small governments, as described 

in the Unfunded Mandates Reform Act 

of 1995 (Pub. L. 104–4); 

• does not have federalism 

implications as specified in Executive 

Order 13132 (64 FR 43255, August 10, 

1999); 

• is not an economically significant 

regulatory action based on health or 

safety risks subject to Executive Order 

13045 (62 FR 19885, April 23, 1997); 

• is not a significant regulatory action 

subject to Executive Order 13211 (66 FR 

28355, May 22, 2001); 

• is not subject to requirements of 

Section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (15 U.S.C. 272 note) because 

application of those requirements would 

be inconsistent with the CAA; and 

• does not provide EPA with the 

discretionary authority to address, as 

appropriate, disproportionate human 

health or environmental effects, using 

practicable and legally permissible 

methods, under Executive Order 12898 

(59 FR 7629, February 16, 1994). 

In addition, this proposed rule, 

concerning the SO2 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 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

50 CFR Part 218 

RIN 0648–XG273 

Taking and Importing Marine 

Mammals; Taking Marine Mammals 

Incidental to U.S. Navy Operations of 

Surveillance Towed Array Sensor 

System Low Frequency Active Sonar 

in the Western and Central North 

Pacific Ocean and Eastern Indian 

Ocean 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Receipt of application for 

rulemaking and letter of authorization; 

request for comments and information. 

SUMMARY: NMFS has received a request 

from the U.S. Navy (Navy) for 

authorization to take marine mammals 

incidental to the use of Surveillance 

Towed Array Sensor Systems Low 

Frequency Active (SURTASS LFA) 

sonar systems onboard U.S. Navy 

surveillance ships for training and 

testing activities conducted under the 

authority of the Secretary of the Navy in 

the western and central North Pacific 

and eastern Indian oceans beginning 

August 2019. Pursuant to the 

implementing regulations of the Marine 

Mammal Protection Act (MMPA), NMFS 

is announcing our receipt of the Navy’s 

request for the development and 

implementation of regulations 

governing the incidental taking of 

marine mammals and inviting 

information, suggestions, and comments 

on the Navy’s application and request. 

DATES: Comments and information must 

be received no later than August 13, 

2018. 

ADDRESSES: Comments on the 

application should be addressed to Jolie 

Harrison, Chief, Permits and 

Conservation Division, Office of 

Protected Resources, National Marine 

Fisheries Service. Physical comments 

should be sent to 1315 East-West 

Highway, Silver Spring, MD 20910– 

3225 and electronic comments should 

be sent to ITP.Youngkin@noaa.gov. 


sradovich on DSK3GMQ082PROD with PROPOSALS