Federal Register / Vol. 83, No. 158 / Wednesday, August 15, 2018 / Proposed Rules 40487 

obtained. Additional information 

regarding how to submit comments 

online can be found at: http://

www.prc.gov/how-to-participate. All 

comments accepted will be made 

available on the Commission’s website, 

http://www.prc.gov. 

Pursuant to 39 U.S.C. 505, Kenneth E. 

Richardson is designated as an officer of 

the Commission (Public Representative) 

to represent the interests of the general 

public in this proceeding. 

It is ordered: 

1. Interested persons may submit 

initial comments no later than 60 days 

from the date of the publication of this 

document in the Federal Register. 

2. Pursuant to 39 U.S.C. 505, the 

Commission appoints Kenneth R. 

Moeller to serve as an officer of the 

Commission (Public Representative) to 

represent the interests of the general 

public in this docket. 

3. The Secretary shall arrange for 

publication of this Order in the Federal 

Register. 

By the Commission. 

Stacy L. Ruble, 

Secretary. 

[FR Doc. 2018–17498 Filed 8–14–18; 8:45 am] 

BILLING CODE 7710–FW–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R05–OAR–2015–0700; FRL–9982– 

28—Region 5] 

Air Plan Approval; Indiana; Attainment 

Plan for Indianapolis, Southwest 

Indiana, and Terre Haute SO2

Nonattainment Areas 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve 

as a State Implementation Plan (SIP) 

revision an Indiana submission to EPA 

dated October 2, 2015. The submission 

addresses attainment of the 2010 sulfur 

dioxide (SO2) national ambient air 

quality standard (NAAQS) for the 

Indianapolis (Marion County), 

Southwest Indiana (Daviess and Pike 

Counties), and Terre Haute (Vigo 

County) areas. Indiana also submitted a 

SIP revision request for the Morgan 

County area. In this proposed action, 

EPA is not addressing the Morgan 

County portion of the SIP revision 

request, and will address it separately in 

a future action. This plan (herein called 

a ‘‘nonattainment plan’’) includes 

Indiana’s attainment demonstration and 

other elements required under the Clean 

Air Act (CAA). In addition to an 

attainment demonstration, the 

nonattainment plan addresses the 

requirement for meeting reasonable 

further progress (RFP) toward 

attainment of the NAAQS, reasonably 

available control measures and 

reasonably available control technology 

(RACM/RACT), base-year and 

projection-year emission inventories, 

enforceable emissions limitations and 

control measures, and contingency 

measures. EPA proposes to conclude 

that Indiana has appropriately 

demonstrated that the plan provisions 

provide for attainment of the 2010 SO2

NAAQS in the Indianapolis, Southwest 

Indiana, and Terre Haute areas by the 

applicable attainment date and that the 

plan meets the other applicable 

requirements under the CAA. 

DATES: Comments must be received on 

or before September 14, 2018. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R05– 

OAR–2015–0700 at http://

www.regulations.gov, or via email to 

aburano.douglas@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: 

Michelle Becker, Life Scientist, 

Attainment Planning and Maintenance 

Section, Air Programs Branch (AR–18J), 

Environmental Protection Agency, 

Region 5, 77 West Jackson Boulevard, 

Chicago, Illinois 60604, (312) 886–3901, 

becker.michelle@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Throughout this document whenever 

‘‘we,’’ ‘‘us,’’ or ‘‘our’’ is used, we mean 

EPA. The following outline is provided 

to aid in locating information in this 

preamble. 

Table of Contents 

I. Why was Indiana required to submit an 

SO2 plan for Indianapolis, Southwest 

Indiana, and Terre Haute? 

II. Requirements for SO2 Nonattainment Area 

Plans 

III. Requirements for Attainment 

Demonstrations and Longer-Term 

Averaging 

IV. Review of Indiana’s Modeled Attainment 

Plans 

A. Model Selection 

B. Meteorological Data 

C. Emissions Data 

D. Emission Limits 

1. Enforceability 

2. Longer Term Average Limits 

E. Background Concentrations 

F. Comments Made During State 

Rulemaking 

G. Summary of Results 

V. Review of Other Plan Requirements 

A. Emissions Inventory 

B. RACM/RACT 

C. New Source Review (NSR) 

D. RFP 

E. Contingency Measures 

VI. EPA’s Proposed Action 

VII. Incorporation by Reference 

VIII. Statutory and Executive Order Reviews 

I. Why was Indiana required to submit 

an SO2 plan for Indianapolis, 

Southwest Indiana, and Terre Haute? 

On June 22, 2010, EPA promulgated a 

new 1-hour primary SO2 NAAQS of 75 

parts per billion (ppb), which 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 does not 

exceed 75 ppb, as determined in 

accordance with appendix T of 40 CFR 

part 50. See 75 FR 35520, codified at 40 

CFR 50.17(a)–(b). On August 5, 2013, 

EPA designated a first set of 29 areas of 

the country as nonattainment for the 

2010 SO2 NAAQS, including the 

Indianapolis (Marion County), Morgan 

County, Southwest Indiana (Daviess and 

Pike Counties), and Terre Haute (Vigo 

County) areas within Indiana. See 78 FR 

47191, codified at 40 CFR part 81, 

subpart C. These area designations were 

effective October 4, 2013. Section 191(a) 

of the CAA directs states to submit SIPs 

for areas designated as nonattainment 

for the SO2 NAAQS to EPA within 18 

months of the effective date of the 

designation, i.e., by no later than April 

4, 2015 in this case. Under CAA section 

192(a), the states are required to 


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demonstrate that their respective areas 

will attain the NAAQS as expeditiously 

as practicable, but no later than 5 years 

from the effective date of designation, 

which is October 4, 2018. 

In response to the requirement for SO2

nonattainment plan submittals, Indiana 

submitted nonattainment plans for the 

Indianapolis, Morgan County, 

Southwest Indiana, and Terre Haute 

areas on October 2, 2015. EPA will 

address the Morgan County portion of 

the submittal in a future action. The 

remainder of this preamble describes 

the requirements that such plans must 

meet in order to obtain EPA approval, 

provides a review of the state’s plans 

with respect to these requirements, and 

describes EPA’s proposed action on the 

plans. 

II. Requirements for SO2

Nonattainment Area Plans 

Nonattainment SIPs must meet the 

applicable requirements of the CAA, 

specifically CAA sections 110, 172, 191 

and 192. 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 57 FR 

13545–13549, 13567–13568. On April 

23, 2014, EPA issued guidance for 

meeting the statutory requirements in 

SO2 SIPs submitted under the 2010 

NAAQS, in a document entitled, 

‘‘Guidance for 1-Hour SO2

Nonattainment Area SIP Submissions,’’ 

available at https://www.epa.gov/sites/ 

production/files/2016-06/documents/ 

20140423guidance_nonattainment_

sip.pdf. In this guidance EPA described 

the statutory requirements for a 

complete nonattainment area SO2 SIP, 

which includes: An accurate emissions 

inventory of current emissions for all 

sources of SO2 within the 

nonattainment area; an attainment 

demonstration; demonstration of RFP; 

implementation of RACM (including 

RACT); new source review (NSR); 

enforceable emissions limitations and 

control measures; and adequate 

contingency measures for the affected 

area. 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 EPA to fully approve a 

SIP as meeting the requirements of CAA 

sections 110, 172 and 191–192 and 

EPA’s regulations at 40 CFR part 51, the 

SIP for the affected area needs to 

demonstrate to EPA’s satisfaction that 

each of the aforementioned 

requirements have been met. Under 

CAA sections 110(l) and 193, EPA may 

not approve a SIP that would interfere 

with any applicable requirement 

concerning NAAQS attainment and 

RFP, or any other applicable 

requirement, and no requirement in 

effect (or required to be adopted by an 

order, settlement, agreement, or plan in 

effect before November 15, 1990) in any 

area which is a nonattainment area for 

any air pollutant, may be modified in 

any manner unless it ensures equivalent 

or greater emission reductions of such 

air pollutant. 

III. Requirements for Attainment 

Demonstrations and Longer-Term 

Averaging 

CAA sections 172(c)(1), 172(c)(6) and 

192(a) direct states with SO2 areas 

designated as nonattainment to 

demonstrate that the submitted plan 

provides for attainment of the NAAQS. 

40 CFR part 51, subpart G further 

delineates the control strategy 

requirements that SIPs must meet, and 

EPA has long required that all SIPs and 

control strategies reflect four 

fundamental principles of 

quantification, enforceability, 

replicability, and accountability. 

General Preamble, at 13567–68. SO2

attainment plans must consist of two 

components: (1) Emission limits and 

other control measures that assure 

implementation of permanent, 

enforceable and necessary emission 

controls, and (2) a modeling analysis 

which meets the requirements of 40 CFR 

part 51, appendix W which 

demonstrates that these emission limits 

and control measures provide for timely 

attainment of the primary SO2 NAAQS 

as expeditiously as practicable, but by 

no later than the attainment date for the 

affected area. In all cases, the emission 

limits and control measures must be 

accompanied by appropriate methods 

and conditions to determine compliance 

with the respective emission limits and 

control measures and must be 

quantifiable (i.e., a specific amount of 

emission reduction can be ascribed to 

the measures), fully enforceable 

(specifying clear, unambiguous and 

measurable requirements for which 

compliance can be practicably 

determined), replicable (the procedures 

for determining compliance are 

sufficiently specific and non-subjective 

so that two independent entities 

applying the procedures would obtain 

the same result), and accountable 

(source specific limits must be 

permanent and must reflect the 

assumptions used in the SIP 

demonstrations). 

EPA’s April 2014 guidance 

recommends that the emission limits 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 

guidance, pp. 22 to 39. The guidance 

recommends that—should states and 

sources utilize longer averaging times— 

the longer-term average limit should be 

set at an adjusted level that reflects a 

stringency comparable to the 1-hour 

average limit at the critical emission 

value shown to provide for attainment 

that the plan otherwise would have set. 

The April 2014 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 use of 30-day 

average limits on the prospects for 

attaining the standard, and carefully 

reviewed how best to achieve an 

appropriate balance among the various 

factors that warrant consideration in 

judging whether a state’s plan provides 

for attainment. Id. at pp. 22 to 39. See 

also id. at Appendices B, C, and D. 

As specified in 40 CFR 50.17(b), the 

1-hour primary SO2 NAAQS is met at an 

ambient air quality monitoring site 

when the 3-year average of the annual 

99th percentile of daily maximum 1- 

hour average concentrations is less than 

or equal to 75 parts per billion. 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 hourly 

exceedance of the 75 ppb level 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 

hourly exceedances, and if so the 

resulting frequency and magnitude of 


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1An ‘‘average year’’ is used to mean a year with 

average air quality. While 40 CFR 50 appendix T 

provides for averaging three years of 99th percentile 

daily maximum values (e.g., the fourth highest 

maximum daily concentration in a year with 365 

days with valid data), this discussion and an 

example below uses a single ‘‘average year’’ in order 

to simplify the illustration of relevant principles. 

such exceedances, and in particular 

whether EPA can have reasonable 

confidence that a properly set longer 

term average limit will provide that the 

three-year average of the annual fourth 

highest daily maximum hourly value 

will be at or below 75 ppb. A synopsis 

of how EPA judges whether such plans 

‘‘provide for attainment,’’ based on 

modeling of projected allowable 

emissions and in light of the NAAQS’ 

form for determining attainment at 

monitoring sites, follows. 

For plans for SO2 based on 1-hour 

emission limits, the standard approach 

is to conduct modeling using fixed 

emission rates. The maximum emission 

rate that would be modeled to result in 

attainment (i.e., in an ‘‘average year’’ 1

shows three, not four days with 

maximum hourly levels exceeding 75 

ppb) is labeled the ‘‘critical emission 

value.’’ The modeling process for 

identifying this critical emissions value 

inherently considers the numerous 

variables that affect ambient 

concentrations of SO2, such as 

meteorological data, background 

concentrations, and topography. In the 

standard approach, the state would then 

provide for attainment by setting a 

continuously applicable 1-hour 

emission limit at this critical emission 

value. 

EPA recognizes that some sources 

have highly variable emissions, for 

example due to variations in fuel sulfur 

content and operating rate, that can 

make it extremely difficult, even with a 

well-designed control strategy, to ensure 

in practice that emissions for any given 

hour do not exceed the critical emission 

value. EPA also acknowledges the 

concern that longer-term emission limits 

can allow short periods with emissions 

above the ‘‘critical emissions value,’’ 

which, if coincident with 

meteorological conditions conducive to 

high SO2 concentrations, could in turn 

create the possibility of a NAAQS 

exceedance occurring on a day when an 

exceedance would not have occurred if 

emissions were continuously controlled 

at the level corresponding to the critical 

emission value. However, for several 

reasons, EPA believes that the approach 

recommended in its guidance document 

suitably addresses this concern. First, 

from a practical perspective, EPA 

expects the actual emission profile of a 

source subject to an appropriately set 

longer term average limit to be similar 

to the emission profile of a source 

subject to an analogous 1-hour average 

limit. EPA expects this similarity 

because it has recommended that the 

longer-term average limit be set at a 

level that is comparably stringent to the 

otherwise applicable 1-hour limit 

(reflecting a downward adjustment from 

the critical emissions value) and that 

takes the source’s emissions profile into 

account. As a result, EPA expects either 

form of emission limit to yield 

comparable air quality. 

Second, from a more theoretical 

perspective, EPA has compared the 

likely air quality with a source having 

maximum allowable emissions under an 

appropriately set longer term limit, as 

compared to the likely air quality with 

the source having maximum allowable 

emissions under the comparable 1-hour 

limit. In this comparison, in the 1-hour 

average limit scenario, the source is 

presumed at all times to emit at the 

critical emission level, and in the 

longer-term average limit scenario, the 

source is presumed occasionally to emit 

more than the critical emission value 

but on average, and presumably at most 

times, to emit well below the critical 

emission value. In an ‘‘average year,’’ 

compliance with the 1-hour limit is 

expected to result in three exceedance 

days (i.e., three days with hourly values 

above 75 ppb) and a fourth day with a 

maximum hourly value at 75 ppb. By 

comparison, with the source complying 

with a longer-term limit, it is possible 

that additional exceedances would 

occur that would not occur in the 1- 

hour limit scenario (if emissions exceed 

the critical emission value at times 

when meteorology is conducive to poor 

air quality). However, this comparison 

must also factor in the likelihood that 

exceedances that would be expected in 

the 1-hour limit scenario would not 

occur in the longer-term limit scenario. 

This result arises because the longerterm limit requires lower emissions 

most of the time (because the limit is set 

well below the critical emission value), 

so a source complying with an 

appropriately set longer term limit is 

likely to have lower emissions at critical 

times than would be the case if the 

source were emitting as allowed with a 

1-hour limit. 

As a hypothetical example to 

illustrate these points, suppose a source 

that always emits 1000 pounds of SO2

per hour, which results in air quality at 

the level of the NAAQS (i.e., results in 

a design value of 75 ppb). Suppose 

further that in an ‘‘average year,’’ these 

emissions cause the 5 highest maximum 

daily 1-hour average concentrations to 

be 100 ppb, 90 ppb, 80 ppb, 75 ppb, and 

70 ppb. Then suppose that the source 

becomes subject to a 30-day average 

emission limit of 700 pounds per hour 

(lbs/hour). It is theoretically possible for 

a source meeting this limit to have 

emissions that occasionally exceed 1000 

lbs/hour, but with a typical emissions 

profile emissions would much more 

commonly be between 600 and 800 lbs/ 

hour. In this simplified example, 

assume a zero background 

concentration, which allows one to 

assume a linear relationship between 

emissions and air quality. (A nonzero 

background concentration would make 

the mathematics more difficult but 

would give similar results.) Air quality 

will depend on what emissions happen 

on what critical hours, but suppose that 

emissions at the relevant times on these 

5 days are 800 pounds/hour, 1,100 lbs/ 

hour, 500 lbs/hour, 900 lbs/hour, and 

1,200 lbs/hour, respectively. (This is a 

conservative example because the 

average of these emissions, 900 lbs/ 

hour, is well over the 30-day average 

emission limit.) These emissions would 

result in daily maximum 1-hour 

concentrations of 80 ppb, 99 ppb, 40 

ppb, 67.5 ppb, and 84 ppb. In this 

example, the fifth day would have an 

exceedance that would not otherwise 

have occurred, but the third day would 

not have an exceedance that otherwise 

would have occurred, and the fourth 

day would have had a concentration 

below, rather than at 75 ppb. In this 

example, the fourth highest maximum 

daily concentration under the 30-day 

average would be 67.5 ppb. 

This simplified example illustrates 

the findings of a more complicated 

statistical analysis that EPA conducted 

using a range of scenarios using actual 

plant data. As described in Appendix B 

of EPA’s April 2014 SO2 nonattainment 

planning guidance, EPA found that the 

requirement for lower average emissions 

is highly likely to yield better air quality 

than is required with a comparably 

stringent 1-hour limit. Based on 

analyses described in appendix B of its 

2014 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. 


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2For 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. 

3EPA published revisions to the Guideline on Air 

Quality Models (40 CFR part 51, appendix W) on 

January 17, 2017. 

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 sections 

110(a)(1), 172(c)(1), 172(c)(6) and 192(a) 

for SIPs to contain emissions limitations 

and control measures to ‘‘provide for 

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 weigh in 

judging whether a plan provides a 

reasonable degree of confidence that the 

plan will lead to attainment. Based on 

these considerations, especially given 

the high likelihood that a continuously 

enforceable limit averaged over as long 

as 30 days, determined in accordance 

with EPA’s guidance, will result in 

attainment, EPA believes as a general 

matter that such limits, if appropriately 

determined, can reasonably be 

considered to provide for attainment of 

the 2010 SO2 NAAQS. 

The April 2014 guidance offers 

specific recommendations for 

determining an appropriate longer-term 

average limit. The recommended 

method starts with determination of the 

1-hour emission limit that would 

provide for attainment (i.e., the critical 

emission value), and applies an 

adjustment factor to determine the 

(lower) level of the longer-term average 

emission limit that would be estimated 

to have a stringency comparable to the 

otherwise necessary 1-hour emission 

limit. This method uses a database of 

continuous emission data reflecting the 

type of control that the source will be 

using to comply with the SIP emission 

limits, which (if compliance requires 

new controls) may require use of an 

emission database from another source. 

The recommended method involves 

using these data to compute a complete 

set of emission averages, computed 

according to the averaging time and 

averaging procedures of the prospective 

emission limitation. In this 

recommended method, the ratio of the 

99th percentile among these long term 

averages to the 99th percentile of the 1- 

hour values represents an adjustment 

factor that may be multiplied by the 

candidate 1-hour emission limit to 

determine a longer term average 

emission limit that may be considered 

comparably stringent.2 The 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 EPA’s Guideline on Air 

Quality Models (40 CFR part 51, 

appendix W).3 In 2005, 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 April 23, 2014 SO2 nonattainment 

area SIP guidance document referenced 

above. Appendix A provides extensive 

guidance on the modeling domain, the 

source inputs, assorted types of 

meteorological data, and background 

concentrations. Consistency with the 

recommendations in this guidance is 

generally necessary for the attainment 

demonstration to offer adequately 

reliable assurance that the plan provides 

for attainment. 

As stated previously, attainment 

demonstrations for the 2010 SO2

NAAQS must demonstrate future 

attainment and maintenance of the 

NAAQS in the entire area designated as 

nonattainment (i.e., not just at the 

violating monitor) by using air quality 

dispersion modeling (see appendix W to 

40 CFR part 51) to show that the mix of 

sources and enforceable control 

measures and emission rates in an 

identified area will not lead to a 

violation of the SO2 NAAQS. For a 

short-term (i.e., 1-hour) standard, EPA 

believes that dispersion modeling, using 

allowable emissions and addressing 

stationary sources in the affected area 

(and in some cases those sources located 

outside the nonattainment area which 

may affect attainment in the area) is 

technically appropriate, efficient and 

effective in demonstrating attainment in 

nonattainment areas because it takes 

into consideration combinations of 

meteorological and emission source 

operating conditions that may 

contribute to peak ground-level 

concentrations of SO2. 

The meteorological data used in the 

analysis should generally be processed 

with the most recent version of 

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’’ (EPA, 2010a). 

IV. Review of Indiana’s Modeled 

Attainment Plans 

The following discussion evaluates 

various features of the modeling that 

Indiana used in its attainment 

demonstrations. 

A. Model Selection 

Indiana’s attainment demonstrations 

used AERMOD, the preferred model for 

these applications as identified in 

appendix W to CFR part 51. Indiana 

used version 14134 of this model, 

utilizing the regulatory default mode for 

all air quality modeling runs. This 

version of AERMOD was the most 

recent version at the time the state 

conducted its nonattainment planning; 

and, in any case, the results of this 

version are likely to be similar to those 

that more recent versions would 

provide. Therefore, EPA finds the use of 

this version of AERMOD acceptable. 


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4 June 27, 2018 Technical Support Document— 

‘‘Evaluation of Concentrations on Facility Property 

Attributable to Nearby Sources’’. 

The receptor grids and modeling 

domain followed the recommended 

approaches from appendix W, 

Guidelines on Air Quality Models. 

Receptor spacing for each modeled 

facility fence line was every 50 meters 

with 100-meter spacing of receptors out 

to a distance of 500 meters beyond each 

facility. The distances between modeled 

facilities contained receptors which 

were spaced at 100-meter intervals. The 

100-meter spacing receptor grid 

contained in excess of several thousand 

receptors for each modeled 

nonattainment area. The above receptor 

spacing and facility fence line receptors 

brought the total modeled receptors for 

Marion County to 17,925 receptors, 

including two additional receptors 

placed at the Marion County SO2

monitor locations; Vigo County to 7,111 

receptors, including two receptors at 

each of the Vigo County SO2 monitors; 

and Daviess and Pike to 5,354 receptors, 

including two located at Daviess and 

Pike County SO2 monitors. 

Indiana did not assess impacts within 

any one facility’s property from the 

emissions from other facilities. EPA 

reviewed Indiana’s modeling results to 

assess whether any further modeling 

was warranted to evaluate impacts 

within of other facilities on any plant’s 

property. For Southwest Indiana, peak 

impacts from the two facilities were 

well off any plant property, and 

therefore insufficient to cause a 

violation within each other’s property. 

For the Terre Haute area, since the Duke 

Wabash River Power Plant and 

sgSolutions sources were adjacent, EPA 

conducted additional modeling that 

demonstrated that neither plant 

contributed to a violation within the 

other plant’s property. Finally, in 

Indianapolis, EPA conducted additional 

modeling for the Vertellus and Rolls 

Royce facilities due to their proximity to 

one another and due to peak 

concentrations for both facilities 

occurring at their property boundaries. 

The analysis showed that collective 

impacts at on-property receptors from 

the other source and from other sources 

in Marion County were below the 

NAAQS. Further description of EPA’s 

review is provided in the technical 

support document available in the 

docket for this rulemaking.4 EPA finds 

that Indiana’s receptor grids, 

supplemented with the results of EPA’s 

additional analysis, are adequate for 

assessing whether the adopted limits 

provide for attainment throughout the 

respective areas. 

The appropriate rural or urban land 

classifications were selected by Indiana, 

with only the Indianapolis SO2 area 

being classified as urban. The remaining 

1-hour SO2 nonattainment areas 

addressed in this action, in Southwest 

Indiana and Terre Haute, were modeled 

as rural. While Indiana’s submittal does 

not discuss the rationale for these 

determinations, EPA agrees that these 

selections appropriately characterize 

these areas. The Indianapolis area has 

historically been modeled using ‘‘urban 

dispersion.’’ This combined statistical 

area includes 2.3 million people, 

including Marion County, with just 

under 1 million people. The population 

density for Marion County is 917 people 

per square kilometer, and the modeled 

area is a relatively urban portion of the 

county, thus meeting the criterion in 

appendix W that areas with at least 750 

people per square kilometer may be 

treated as urban. Conversely, Vigo, Pike, 

and Daviess Counties have population 

densities of 102, 13, and 42 people per 

square mile, respectively. Examination 

of satellite imagery for these areas 

confirms that a land use analysis of 

these areas would be expected to yield 

the same character of Indianapolis as 

urban and the other areas as rural. For 

Indianapolis, a population of 1,000,000 

(reflecting the approximate population 

of Marion County) was used in 

AERMOD to characterize the strength of 

the urban heat island effect. The use of 

urban dispersion with a 1,000,000 

population is appropriate for this 

modeling. For these reasons, EPA finds 

it appropriate to model these areas using 

the land classifications identified by 

Indiana. 

B. Meteorological Data 

Indiana used the Indianapolis 

National Weather Service (NWS) surface 

data and the Lincoln, Illinois upper air 

station (WBAN#048233) data for 

Indianapolis and Terre Haute, and the 

Evansville NWS for surface data and the 

Lincoln upper air station data for 

Southwest Indiana. These are the closest 

National Weather Service surface 

stations to each respective area. The 

State determined these stations to be the 

most representative for the respective 

modeling domains. The upper air 

stations were chosen on the basis of 

regional representativeness. EPA finds 

Indiana’s choices of surface and upper 

air meteorological stations appropriate 

based on: (1) The suitability of 

meteorological data for the study area; 

and (2) the actual similarity of surface 

conditions and surroundings at the 

emissions source/receptor impact area 

compared to the locations of the 

meteorological instrumentation towers. 

C. Emissions Data 

Indiana modeled 14 sources in the 

three nonattainment areas of 

Indianapolis (6 sources), Southwest 

Indiana (2 sources), and Terre Haute (6 

sources). The sources were physically 

located within the nonattainment area; 

Indiana excluded facilities that emitted 

less than ten tons per year, and Indiana 

found no sources outside the 

nonattainment areas with sufficient 

likely concentration gradient in the 

modeled area to warrant modeling 

explicitly. The emission limits used for 

the model for 12 of the sources 

correspond to the revised sulfur dioxide 

limitations on a 1-hour basis and are 

found in Indiana Administrative Code 

(IAC) Part 326, Article 7, and have been 

included by Indiana in this submission 

for SIP approval. The applicable 

emission limits for sgSolutions in Vigo 

County (Terre Haute) and IPL— 

Petersburg in Daviess County 

(Southwest Indiana) are established on 

a 30-day average basis and are lower 

than the modeled 1-hour attainment 

emission rates (the critical emission 

values) by virtue of application of 

adjustment factors determined and 

applied in accordance with the 2014 

SO2 Guidance. These limits are 

established and made enforceable in 326 

IAC 7. EPA finds Indiana’s choice of 

included sources appropriate, and finds 

that the modeled emission levels 

appropriately correspond to the limits 

given in 326 IAC 7, in the case of IPL— 

Petersburg and sgSolutions by modeling 

the 1-hour emission level that 

corresponds (before adjustment) to the 

30-day average limit established in 326 

IAC 7. Further discussion of the 30-day 

average limits is provided below. 

D. Emission Limits 

An important prerequisite for 

approval of an attainment plan is that 

the emission limits that provide for 

attainment be quantifiable, fully 

enforceable, replicable, and 

accountable. See General Preamble at 

13567–68. Some of the limits that 

Indiana’s plan relies on are expressed as 

30-day average limits. Therefore, part of 

the review of Indiana’s attainment plan 

must address the use of these limits, 

both with respect to the general 

suitability of using such limits for this 

purpose and with respect to whether the 

particular limits included in the plan 

have been suitably demonstrated to 

provide for attainment. The first 

subsection that follows addresses the 

enforceability of the limits in the plan, 


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and the second subsection that follows 

addresses the 30-day average limits. 

1. Enforceability 

In preparing its plans, Indiana 

adopted revisions to a previously 

approved state regulation governing 

emissions of SO2. These rule revisions 

were adopted by the Indiana 

Environmental Rules Board following 

established, appropriate public review 

procedures. In addition, the rule 

revisions provide unambiguous, 

permanent emission limits, expressed in 

lbs/hour of allowable SO2 emissions, 

that, if exceeded by a source, would be 

clear grounds for an enforcement action. 

The revised limits for significant 

contributing sources have a compliance 

date of January 1, 2017 and are codified 

in 326 IAC 7, titled ‘‘Sulfur Dioxide 

Rules.’’ Specifically, the list of rules is 

‘‘Compliance date’’ (326 IAC 7–1.1–3), 

‘‘Reporting requirements; methods to 

determine compliance’’ (7–2–1), 

‘‘Marion County sulfur dioxide emission 

limitations’’ (7–4–2.1), ‘‘Vigo County 

sulfur dioxide emission limitations’’ (7– 

4–3.1), and ‘‘Pike County sulfur dioxide 

emission limitations’’ (7–4–15). The 

rules also include associated 

monitoring, testing, and recordkeeping 

and reporting requirements. For 

example, continuous emission 

monitoring will be conducted for 

assessing compliance with the 30-day 

average limits. Specifically, 326 IAC 7– 

1–9 is being replaced by 7–4–2.1 for 

Marion County and 326 IAC 7–1–10.1 is 

being replaced by 326 IAC 7–4–15 for 

Vigo County. EPA finds these limits to 

be enforceable. A summary of the limits 

is shown in Table 1. 

As shown in this table, the emission 

limits for sgSolutions Tail Gas 

Incinerator Stack EP1 and IPLPetersburg Units 1–4 are expressed as 

30-day average limits. Other limits in 

the rule are expressed as 1-hour average 

limits. The limits are expressed as lbs/ 

hour or pounds per million British 

Thermal Units (MMBTU). EPA’s review 

of Indiana’s nonattainment plan 

addresses the use of these limits, both 

with respect to the general suitability of 

using such limits in attainment 

demonstrations, and whether Indiana 

has demonstrated that the particular 

limits included in the plan provide for 

attainment. EPA addresses Indiana’s use 

of a 30-day average emission limits 

below. 

TABLE 1—EMISSION LIMITS IN SUBMITTED INDIANA RULES

Source Emission unit description Emission limit (lbs/hour) or other 

requirements 

Emission 

limit 

(lbs/MMBTU) 

Marion County sulfur dioxide emission limitations 326 IAC 7–4–2.1 

Citizens Thermal—Perry K Source ID 

No. 00034.

(A) Boiler 11 ............................................

(B) Boiler 13 ............................................

(C) Boiler 14 ............................................

73.6 ..........................................................

80.6 ..........................................................

80.6 ..........................................................

0.2 

0.2 

0.2 

(D) Boilers 12, 15, and 16 ....................... Burn natural gas ...................................... ........................

(E) Boiler 17 ............................................ 72.6 .......................................................... 0.3 

(F) Boiler 18 ............................................ 72.6 .......................................................... 0.3 

Belmont Advanced Wastewater Treatment Plant Source ID No. 00032.Incinerator 1, Incinerator 2, Incinerator 3, 

and Incinerator 4.

Comply with SO2 limit in 40 CFR 60, 

subpart MMMM * or 40 CFR 60, subpart LLLL *.

........................

Rolls-Royce Source ID No. 00311 .......... (A) Boiler 0070–58 ..................................

(B) Boiler 0070–59 ..................................

(C) Boiler 0070–62 ..................................

(D) Boiler 0070–63 ..................................

0.07 ..........................................................

0.07 ..........................................................

0.37 ..........................................................

0.37 ..........................................................

0.0015 

0.0015 

0.0015 

0.0015 

(E) Boilers 0070–64 ................................ Burn natural gas or landfill gas ............... 0.01 

(F) Boiler 0070–65 .................................. Burn natural gas or landfill gas ............... 0.01 

(G) Generating Turbine 0070–80 ............ Burn natural gas or landfill gas ............... 0.01 

(H) 2 Gas Turbine Engines 0070–66 ...... .................................................................. 0.1 

(I) 12 Gas Turbine Engines 0070–67 ..... .................................................................. 0.05 

(J) 3 Gas Turbine Engines 0070–68c, 

0070–68d, and 0070–68e.

.................................................................. 0.05 

(K) 2 Gas Turbine Engines 0070–68a 

and 0070–68b.

Burn natural gas ...................................... ........................

(L) 3 Gas Turbine Engines 0070–69 ...... .................................................................. 0.05 

(M) Three Shack Heaters 0070–70 ........ Burn natural gas ...................................... ........................

(N) Rental Generators ............................. .................................................................. 0.0015 

(O) Engine Test Cells Plant 5 ................. .................................................................. 0.05 

(P) Engine Test Cell Plant 8 ................... .................................................................. 0.1 

(Q) Engine Test Cell N20 ........................ 18 foot vertical stack, if operating ........... ........................

(R) Engine Test Cell N21 ........................ 20 foot vertical stack, if operating ........... ........................

(S) Engine Test Cell N23 ........................ 30 foot vertical stack, if operating ........... ........................

(T) Engine Test Cell N24 ........................ 20 foot vertical stack, if operating ........... ........................

Vertellus Agriculture and Nutrition Specialties Source ID No. 00315.(A) 70K Boiler 70–2722W .......................

(B) 30K Boiler 30–2726S ........................

(C) 28K Boiler 28–186N ..........................

18.4 ..........................................................

9.8 ............................................................

9.9 ............................................................

0.20 

0.25 

0.27 

(D) Boiler CB–70K ................................... Burn natural gas ...................................... ........................

(E) BM Furnace BM2724W ..................... 1.1 ............................................................ 0.05 

(F) Box Furnace BX2707V ...................... 0.8 ............................................................ 0.05 

(G) DAB Furnace 732714 ....................... 2.8 ............................................................ 0.05 

(H) Born Heater 722804 .......................... 0.34 .......................................................... 0.05 

(I) Born Heater Furnace BXS2706Q ....... 0.3 ............................................................ 0.05 

(J) EP Furnace EP2729Q ....................... 0.15 .......................................................... 0.05 

(K) CB20 CB600–300 Boiler ................... 2.3 ............................................................ 0.09 

(L) 50K CN5–400 Boiler .......................... 5.5 ............................................................ 0.09 

(M) BD Furnace BD2714V ...................... 0.75 .......................................................... 0.05 


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TABLE 1—EMISSION LIMITS IN SUBMITTED INDIANA RULES—Continued 

Source Emission unit description Emission limit (lbs/hour) or other 

requirements 

Emission 

limit 

(lbs/MMBTU) 

(N) Heater BS2740Q ............................... 0.3 ............................................................ 0.05 

(O) Heater BT2728S ............................... 0.3 ............................................................ 0.05 

(P) Furnace HW–925.001 ....................... 12.25 ........................................................ 1.25 

(Q) CS Kettle Born Heater ...................... Burn natural gas ...................................... ........................

(R) CS Still Born Heater .......................... Burn natural gas ...................................... ........................

(S) Born Hot Oil Furnace (Process Heater) Unit 2607T.Burn natural gas ...................................... ........................

Quemetco Source ID No. 00079 ............. WESP Stack ............................................ 52.0 .......................................................... ........................

Indianapolis Power & Light Co.—Harding 

Street Generating Station Source ID 

No. 00033.

(A) Boiler 9 ..............................................

(B) Boiler 10 ............................................

(C) Boiler 50 ............................................

Do not operate ........................................

Do not operate ........................................

Burn natural gas ......................................

........................

........................

........................

(D) Boiler 60 ............................................ Burn natural gas ...................................... ........................

(E) Boiler 70 ............................................ Burn natural gas ...................................... ........................

(F) Gas Turbine 1 .................................... 29.9 .......................................................... 0.1 

(G) Gas Turbine 2 ................................... 29.9 .......................................................... 0.1 

(H) Gas Turbine 4 ................................... 87.5 .......................................................... 0.1 

(I) Gas Turbine 5 ..................................... 86.7 .......................................................... 0.1 

(J) Gas Turbine 6 .................................... Burn natural gas ...................................... ........................

(K) Emergency Generator ....................... 500 hour calendar year operating limit ... ........................

Vigo County sulfur dioxide limitations (326 IAC 7–4–3.1) 

Wabash River Combined Cycle Source 

ID No. 00147.

Combustion Turbine Unit 1A ................... 333.76 ...................................................... 0.195 

sgSolutions Source ID No. 00091 ........... (A) Tail Gas Incinerator Stack EP1 ......... 230.6 * ...................................................... ........................

(B) Process Flare Unit 2 ......................... 500 hour calendar year operating limit 

on coal/syngas.

........................

SONY Digital Audio Disc Source ID No. 

00032.

(A) #1 Kewanee Boiler ............................

(B) #2 Kewanee Boiler ............................

(C) Unit 3 Burnham Boiler .......................

(D) Unit 4 Burnham Boiler .......................

(E) Unit 5 Superior Boiler ........................

(F) Unit 6 Superior Boiler ........................

(G) Unit 18 Boiler ....................................

..................................................................

..................................................................

..................................................................

..................................................................

..................................................................

..................................................................

..................................................................

0.05 

0.05 

0.05 

0.05 

0.05 

0.05 

0.05 

Taghleef Industries Source ID No. 00045 (A) Clayton Boiler (Standby) ...................

(B) Nebraska Boiler .................................

0.03 ..........................................................

0.05 ..........................................................

0.0015 

0.0015 

(C) Nebraska-D Boiler ............................. Burn natural gas ...................................... ........................

Terre Haute Regional Hospital Source ID 

No. 00046.

(A) #1 Boiler ............................................

(B) New #2 Boiler ....................................

..................................................................

..................................................................

0.45 

0.45 

Union Hospital Source ID No. 00047 ...... 2 Keeler Boilers ....................................... .................................................................. 0.36 

Duke Energy—Wabash River Generating 

Station Source ID No. 00021.

(A) Boiler 6 ..............................................

(B) Diesel Generators 7A, 7B, and 7C ...

1,499.5 .....................................................

500 hour calendar year operating limit 

(each).

0.5 

0.05 

Pike County sulfur dioxide limitations (326 IAC 7–4–15) 

Hoosier Energy—Ratts Source ID No. 

00001.

(A) Boiler 1 ..............................................

(B) Boiler 2 ..............................................

58 .............................................................

58 .............................................................

0.05 

0.05 

(C) No. 2 Auxiliary Boiler ........................ 1.0 ............................................................ 0.05 

Indianapolis Power & Light—Petersburg 

Generating Station Source ID No. 

00002.

(A) Unit 1 .................................................

(B) Unit 2 .................................................

(C) Unit 3 .................................................

(D) Unit 4 .................................................

263.0 * ......................................................

495.4 * ......................................................

1,633.7 * ...................................................

1,548.2 * ...................................................

0.12 * 

0.12 * 

0.29 * 

0.28 * 

(E) Diesel Generators PB–2, PB–3, and 

PB–4.

500 hour calendar year operating limit 

(each).

........................

Indianapolis Power & Light—Petersburg 

Generating Station Source ID No. 

00002.

(A) Unit 1 .................................................

(B) Unit 2 .................................................

(C) Unit 3 .................................................

(D) Unit 4 .................................................

330.0 ........................................................

621.6 ........................................................

2,049.8 .....................................................

1,942.5 .....................................................

0.15 

0.15 

0.37 

0.35 

(E) Diesel Generators PB–2, PB–3, and 

PB–4.

500 hour calendar year operating limit 

(each).

........................

* Indicates emission limit for the unit is expressed as a 30-day average limit. 

2. Longer Term Average Limits 

As noted above, the 2014 SO2

Guidance discusses the option to 

establish limits with averaging times up 

to 30 days in length that are comparably 

stringent to the 1-hour average limit that 

would otherwise have been set, and 

recommends a detailed procedure for 

determining such a comparably 

stringent limit. The Guidance also notes 

that it might be appropriate to establish 

supplemental limits in order to limit the 


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magnitude and/or frequency of elevated 

emissions, as a means of further 

reducing the likelihood of elevated 

emissions occurring on those occasions 

when the meteorology is conducive to 

high concentrations of SO2. 

For both IPL-Petersburg and 

sgSolutions, Indiana closely followed 

the six-step recommendation of the 

2014 SO2 Guidance in determining an 

appropriate level for the 30-day average 

limits. As a first step in each case, 

Indiana conducted modeling which 

determined the 1-hour emission limit 

that would provide for attainment. 

Indiana conducted a series of modeling 

runs identifying baseline allowable air 

quality (in absence of emission 

reductions), evaluating the air quality 

consequences of feasible emission 

reductions, and ultimately identifying a 

set of reduced allowable emission levels 

that would provide for attainment. For 

IPL-Petersburg, these quantities were 

expressed in lbs/MMBTU, and may be 

termed the critical emissions rates. The 

critical emission rates were 0.15, 0.15, 

0.37, and 0.35 lbs/MMBTU, for IPLPetersburg Units 1–4 respectively. For 

sgSolutions, Indiana determined a 

critical emission level of 527 lbs/hour. 

For the second step of the process, for 

IPL-Petersburg, Indiana compiled 

representative emissions data sets from 

the IPL-Petersburg Unit 2 Flue Gas 

Desulfurization stack, which is the same 

control technology IPL-Petersburg will 

use for Units 1,3, and 4 in order to meet 

the emission limits associated with 

attaining the 2010 SO2 NAAQS. Indiana 

used data compiled from 2006–2010 for 

the stack. For sgSolutions, Indiana used 

the data from the Tail Gas Incinerator 

from 2009–2014 scaled to fewer 

operating hours to create the emissions 

data set. 

The third step was calculating the 30- 

day rolling averages. The analysis for 

IPL-Petersburg assessed the variability 

of the emission rate. The 30-day average 

rate was calculated by summing the 

pounds SO2 per hour values over the 

previous 720 hours (30 days) and 

dividing by the sum of the MMBTU per 

hour over the past 720 hours, yielding 

a separate 30-day average pounds of SO2

per MMBTU for each successive ending 

hour. Using this calculation ensured 

that any hours showing zero emissions 

did not affect the calculations. This 

calculation is consistent with the 

procedures used in determining 

compliance with the Mercury and Air 

Toxics Standard (MATS) rule, as 

recommended in appendix C of the 

2014 EPA SO2 Guidance. The analysis 

for sgSolutions used statistics on the 

hourly mass emission rate and the 

corresponding 720-hour average hourly 

emission rate. 

The fourth step determined 99th 

percentile values for the 1-hour values 

and 30-day average values. The 1-hour 

values were determined by compiling 

the values in step 2 over the five-year 

period. The result for the 99th 

percentile 30-day average was 

determined from the calculations in step 

3. For IPL-Petersburg, the 99th 

percentile of 1-hour values was 0.233 

lbs/MMBTU, and the 99th percentile of 

30-day average values was 0.185 lbs/ 

MMBTU. For sgSolutions, the 99th 

percentile values were 139 and 60.7 lbs/ 

hour among 1-hour and 30-day average 

values, respectively. In the fifth step the 

ratio of the values was calculated by 

dividing the 99th percentile values for 

the 30-day rolling data and the 1-hour 

data identified in the fourth step. For 

IPL-Petersburg the result was an 

adjustment factor of 79.7 percent, and 

for sgSolutions the result was an 

adjustment factor of 43.6 percent. The 

final step multiplied the modeled 

critical emissions values calculated in 

the first step by the adjustment factors 

calculated in the fifth step. This resulted 

in 30-day average limits of 0.12, 0.12, 

0.29, and 0.35 lbs/MMBTU for IPLPetersburg Units 1–4 respectively and 

230.6 lbs/hr for sgSolutions. 

Based on a review of the state’s 

submittal, these limits provide a 

reasonable alternative to establishing a 

per hour 1-hour average emission limit 

for this source. The state used an 

appropriate database and then applied 

an appropriate adjustment, yielding an 

emission limit that has comparable 

stringency to the 1-hour average limit 

that the state determined would 

otherwise have been necessary to 

provide for attainment. While the 30- 

day average limit allows for occasions in 

which emissions are higher than the 

level that would be allowed under the 

1-hour limit, the state’s limit 

compensates by requiring average 

emissions to be lower than the level that 

would otherwise have been required by 

a 1-hour average limit. 

As noted above, the April 2014 

Guidance recommends that 30-day 

average limits be accompanied by 

supplemental limits that help serve to 

minimize the frequency and/or 

magnitude of occasions with elevated 

emissions. Indiana did not use 

supplemental limits. Therefore, EPA 

examined available emissions data at 

IPL-Petersburg and at sgSolutions to 

evaluate the likely frequency and 

magnitude of spikes in emissions above 

the critical emission value while 

nevertheless complying with the 30-day 

average limit. The most pertinent data 

for IPL-Petersburg are for Unit 2, 

addressing a five-year time period 

before the relevant limit became 

effective. Approximately seven percent 

of available 30-day average values in 

this data set exceeded the 30-day 

average limit of 0.12 lbs/MMBTU. In 

this data set, approximately six percent 

of the hourly emissions values exceeded 

the critical emission rate of 0.15 lbs/ 

MMBTU; these elevated values on 

average were approximately 34 percent 

above 0.15 lbs/MMBTU. Reduction of 

emissions sufficient to meet the 0.12 

lbs/MMBTU limit consistently would 

reduce the frequency and magnitude of 

hourly emissions values above the 0.15 

lbs/MMBTU critical emissions rate, 

although the precise levels are difficult 

to predict. For sgSolutions, over a sixyear period, in a data set with no 

exceedances of the 30-day average limit 

of 230.6 lbs/hour (in which, in fact, only 

one day had daily average emissions 

above 230.6 lbs/hour), only seven hours 

(approximately 0.02 percent of the 

hours) exceeded the critical emission 

value of 527 lbs/hour, and the 

magnitude of these exceedances on 

average was only nine percent above the 

critical emission value. Based on these 

data, EPA finds that the 30-day average 

limit without supplemental limits 

should suffice in these cases to provide 

adequate assurance of attainment. 

For IPL-Petersburg, Indiana’s rule 

identifies both a set of 30-day average 

limits and a corresponding set of 1-hour 

limits (the latter set at the critical 

emission value) for the four units of this 

facility. Indiana’s rule specifies, 

‘‘Indianapolis Power & Light shall notify 

the department prior to [January 1, 

2017] to indicate if compliance . . . will 

be determined using [the specified 1- 

hour limits or the specified 30-day 

average limits] and prior to switching 

[which set of limits applies].’’ Given this 

potential under Indiana’s rules for IPL 

to choose to switch back and forth 

between a set of 30-day average limits 

and a set of 1-hour limits, EPA 

conducted additional review of the 

enforceability of the limits and of 

whether the potential to switch limits 

might adversely affect the degree to 

which these limits assure attainment. 

Regarding enforceability, the primary 

question is whether at any time the 

applicable requirements are 

unequivocally clear, such that the 

occurrence of emissions above the 

specified level unquestionably 

constitutes noncompliance. Since the 

limits themselves are clearly specified 

in Indiana’s rule, the pertinent question 

is whether the choice of limits is clear, 

i.e. whether it is always clear whether 

the 30-day average limits or the 1-hour 


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limits apply. As noted above, Indiana’s 

rule requires IPL-Petersburg to notify 

the state of its initial choice of 

applicable limits and to notify the state 

of any choice IPL makes to switch 

applicable limits. Thus, pursuant to the 

requirements of the rule, the applicable 

set of limits is always specified, Indiana 

always knows which set of limits 

applies, and this information is 

available to EPA and any other 

interested party upon request to 

Indiana. 

EPA also evaluated whether the 

option to switch applicable limits might 

yield less air quality protection than 

permanently imposing 30-day average 

limits or permanently imposing 1-hour 

limits. At any given time, IPL is subject 

to a single set of limits; IPL cannot 

excuse noncompliance with the 

applicable limits even if it is meeting 

the alternative limits. Therefore, IPL 

does not have the option to choose 

limits contemporaneously according to 

a short-term judgment as to which set of 

limits is less stringent for that time 

period. Instead, IPL must design its 

control strategy to meet the limits with 

the chosen averaging time rather than to 

aim simply to meet whichever set of 

limits might be less stringent for any 

particular period. 

A further question about switching 

limits is whether applying 1-hour limits 

for part of a year and longer-term limits 

for another part of the year provides as 

much air quality protection as applying 

a single set of limits for the entire year. 

Use of long term average limits creates 

the potential for periods with elevated 

emissions that may yield additional, 

unmodeled exceedances (i.e., 

exceedances beyond those identified in 

modeling of constant emissions), but 

also creates a compensating likelihood 

of avoiding some of the modeled 

exceedances because the downward 

adjusted long-term average limit 

requires emissions to be lower most of 

the time. At issue here is the risk that 

in a year when both types of limits 

apply, the periods subject to 30-day 

average limits might have additional, 

unmodeled exceedances while the 

periods subject to 1-hour limits might 

not avoid any of the exceedances found 

in constant emissions modeling. 

For several reasons, EPA believes that 

this concern does not apply in this case. 

Indiana’s rule requires IPL to notify 

Indiana before any change in limits and, 

in the case of a switch from 30-day 

average limits to one-hour limits, to 

complete a 30-day period in compliance 

with the 30-day average limits before 

the one-hour limits take effect. IPL 

cannot change the applicable limits 

retroactively. While IPL may change the 

prospective applicable set of limits if it 

anticipates significant changes in 

operations, the experience to date is that 

IPL has made no switches in the 

selection since electing the 30-day 

average in January 2017, and nothing in 

the record suggests that IPL is likely to 

switch which limits apply in the future. 

For these reasons, EPA believes that 

Indiana’s limits for IPL are an 

appropriate part of an attainment plan 

for Southwest Indiana that provide for 

attainment, most likely by requiring 

compliance with an appropriately 

adjusted set of 30-day average limits. 

The issue of switching limits does not 

apply to sgSolutions; this source is 

permanently subject to a 30-day average 

limit. EPA believes that the 30-day 

average limits for IPL-Petersburg and 

sgSolutions are appropriate elements of 

Indiana’s attainment plans for the 

applicable areas. 

E. Background Concentrations 

Indiana determined background 

concentrations by selecting the 99th 

percentile of a monitoring data set that 

excluded values from emission sources 

where the upwind SO2 concentration 

exceeded 10 ppb. For Indianapolis, the 

background concentration was 

generated using the hourly 

concentrations from the Harding Street 

monitor (18–097–0057). At the time 

Indiana conducted its analysis this was 

the only suitable background monitor. 

The monitor is sited about four 

kilometers northeast of the Indianapolis 

Power and Light-Harding Station 

source. For the determination of a 

background value Harding Station 

Power Plant was considered a nearby 

source and was expressly included in 

the modeling analysis, and so Indiana 

determined the Indianapolis 

background concentration from a 

Harding Street data set that excluded 

values during hours with winds from 

the south and southwest. The resulting 

background concentration was 22.5 

micrograms per cubic meter (mg/m3) (8.6 

ppb). 

In the Southwest Indiana area there 

are two monitors, one located in each of 

Pike and Daviess counties. The monitor 

with the highest background 

concentration is the Arda Lane monitor 

located in Pike County (18–125–0005) 

with a value of 25.9 mg/m3 (9.9 ppb). 

The monitor is sited about 1 kilometer 

to the south of IPL-Petersburg source 

and about 1.5 kilometers east of the 

Hoosier Plant. Indiana considered these 

two sources nearby, and determined a 

background concentration from a data 

set that excluded data when winds were 

from the northwest. There are two 

monitors located in the Terre Haute 

nonattainment area, both in Vigo 

County. 

For the Vigo County analysis, the 

controlling monitor (i.e., highest design 

value over the 2011–2013 period), 

Harrison Road monitor (18–125–0005) 

was used. The monitor is sited 

approximately 2.5 kilometers southeast 

of the Duke Energy-Wabash River 

facility, which Indiana considered 

nearby, so Indiana determined 

background concentrations from a data 

set that excluded data when winds were 

from the northwest. The result was a 

background concentration of 23.0 mg/m3

(8.8 ppb). EPA has reviewed these 

background concentrations and finds 

these values appropriate as model 

inputs. 

F. Comments Made During State 

Rulemaking 

During the preparation of its 

nonattainment plans, Indiana received 

and responded to a number of 

comments by, among others, EPA and 

the Sierra Club that EPA believes 

warrant further discussion in this 

action. 

The first comment from EPA to 

Indiana pertained to the IPL–Petersburg 

facility having a choice between hourly 

and 30-day average limits in the Pike 

county emission limit rules, and 

requesting that Indiana assure clarity as 

to which limits apply, by including 

explicit requirements for reporting and 

recordkeeping to which limits apply. 

Indiana responded to the comment by 

adding language at 326 IAC 7–4–15(e) 

requiring the source to notify IDEM 

when switching from one set of limits 

to the other. For any switch from the 1- 

hour limits to the 30-day average limits, 

IDEM’s final rule requires compliance 

with the 1-hour limit until the first 30- 

day average emission rate is calculated 

so that there is no gap in compliance. 

EPA agrees that this change in the 

rulemaking ensures clear compliance 

requirements and establishes the 30-day 

average limit (when applicable) in a 

manner (consistently requiring a 

reduced level of emissions) that 

provides the full protection against 

violations recommended in EPA’s 

guidance. 

Sierra Club expressed concerns about 

the Duke Energy facility in Gibson 

County (‘‘Gibson’’), commenting that 

Indiana should have modeled Gibson 

explicitly. Indiana responded that 

emissions reductions from the sources 

located within Pike and Daviess County 

nonattainment area were the most 

responsible for bringing the area into 

attainment. Other SO2 sources in 

surrounding counties are accounted for 

within the representative 1-hour SO2


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40496 Federal Register / Vol. 83, No. 158 / Wednesday, August 15, 2018 / Proposed Rules 

background concentration. EPA notes 

that the criterion recommended in 

appendix W of 40 CFR 51 for sources to 

be modeled explicitly are those nearby 

sources that are not adequately 

represented by ambient monitoring data, 

such as sources that cause a significant 

concentration gradient in the vicinity of 

the area of interest. Gibson is about 46 

kilometers southwest of the Southwest 

Indiana nonattainment area. At this 

distance, concentration gradients may 

be presumed to be quite small, and the 

impacts of Gibson may reasonably be 

considered accounted for in the 

background concentration for the 

Southwest Indiana nonattainment area. 

Thus, EPA agrees with Indiana’s 

conclusion that any impact from Gibson 

on the Southwest Indiana 

nonattainment area is appropriately 

captured in the background 

concentration for the Southwest Indiana 

nonattainment area, such that explicit 

modeling of this facility is unnecessary. 

In a related comment, Sierra Club 

commented that Indiana needed to 

impose SO2 limits on the Duke Energy 

facility in order to ensure that the 

Southwest Indiana nonattainment area 

(Daviess and Pike counties) attained the 

standard. Indiana’s attainment 

demonstration for the Southwest 

Indiana nonattainment area did not 

depend on emission limits for Gibson. 

Appendix W specifies the 

recommended consideration of emission 

limits for sources that are required to be 

explicitly modeled in the attainment 

demonstration. Sources such as Gibson 

that are accounted for as part of the 

monitored background concentration 

need not be modeled explicitly (as 

noted above) and in particular need not 

be considered on the basis of allowable 

emissions. That is, Appendix W advises 

consideration of distant sources such as 

Gibson on the basis of available 

monitoring data, irrespective of any 

limits on Gibson emissions that may 

apply. Indiana’s modeling analysis, in 

accordance with appendix W, 

demonstrates that the Southwest 

Indiana nonattainment area can be 

expected to attain the standard without 

regard to whether emission limits for 

Gibson are established. Thus, Indiana’s 

SIP submission is approvable without 

limits for Gibson. 

Also, several utility groups 

commented that Indiana should use a 

compliance date of October 1, 2017, 

which would allow for twelve months 

of data to demonstrate attainment of the 

standard prior to the October 2018 

attainment deadline. Indiana chose 

instead to adopt its proposed 

compliance date of January 1, 2017. 

This compliance date was 

recommended in the 2014 EPA 

Guidance because monitoring site data 

are certified annually on a calendar 

year, not a 12-month time span, so 

compliance by January 1, 2017 is 

recommended to provide for a calendar 

year of data for later informing whether 

timely attainment has occurred. EPA 

supports the decision made by Indiana 

to require compliance with the new 

limits by January 1, 2017. 

G. Summary of Results 

The final dispersion modeling results 

submitted by Indiana show design 

values, as provided in Table 2 below, 

that are less than 75 ppb. Therefore, 

Indiana’s modeling analysis 

demonstrates attainment of the 2010 

SO2 NAAQS for the Indianapolis, 

Southwest Indiana, and Terre Haute 

areas. EPA believes that Indiana’s 

modeling appropriately reflects 

allowable emissions in these areas, 

including, for sources subject to 30-day 

average limits, the 1-hour emission rates 

that upon appropriate adjustment 

correspond to the 30-day average limits 

that Indiana has adopted. EPA has 

reviewed Indiana’s attainment 

demonstrations, agrees with Indiana’s 

submitted results, and proposes to 

determine that the enforceable measures 

in Indiana’s plans provide for 

attainment of the 2010 primary SO2

NAAQS in the Indianapolis, Southwest 

Indiana, and Terre Haute nonattainment 

areas. 

TABLE 2—1-HOUR SO2 DISPERSION MODELING RESULTS

Area name Indianapolis Southwest 

Indiana Terre Haute 

Modeled Concentration (ppb) ...................................................................................................... 64.4 64.9 63.8 

Background Concentration (ppb) ................................................................................................. 8.6 9.9 8.8 

Total Concentration (ppb) ..................................................................................................... 73 74.8 72.6 

V. Review of Other Plan Requirements 

A. Emissions Inventory 

The emissions inventory and source 

emission rate data for an area serve as 

the foundation for air quality modeling 

and other analyses that enable states to: 

(1) Estimate the degree to which 

different sources within a 

nonattainment area contribute to 

violations within the affected area; and 

(2) assess the expected improvement in 

air quality within the nonattainment 

area due to the adoption and 

implementation of control measures. As 

noted above, the state must develop and 

submit to EPA a comprehensive, 

accurate and current inventory of actual 

emissions from all sources of SO2

emissions in each nonattainment area, 

as well as any sources located outside 

the nonattainment area which may 

affect attainment in the area. See CAA 

section 172(c)(3). 

Indiana provided a comprehensive, 

accurate, and current inventory of SO2

emissions for Marion (Indianapolis), 

Daviess and Pike (Southwest Indiana), 

and Vigo counties (Terre Haute). The 

following source categories were 

included: Electric-generating units 

(EGUs), non-EGUs (point), non-point 

(area), non-road, and on-road sources of 

SO2 and are summarized in Table 3. 

Indiana uploads point source emissions 

to the National Emissions Inventory 

(NEI) annually. For the 2011 base year 

inventory, emissions from EGU and 

non-EGUs are actual reported emissions. 

Data for airport, area, non-road, and onroad emissions were compiled from the 

EPA Emissions Modeling Clearinghouse 

(SO2 NAAQS Emissions Modeling 

platform 2007/2007v5) for the 2008 NEI 

and the 2018 projected inventory year. 

Data were interpolated between 2008 

and 2014 to determine the airport, area, 

non-road, and on-road emissions 2011 

inventory and between 2014–2020 for 

2018. As noted above, these inventories 

addressed sources within each 

nonattainment county and can be found 

in appendix H of the submitted 

attainment demonstration. Indiana also 

provided modeling inputs that include 

a listing of the individual sources with 

sufficient proximity to and impact on 

the nonattainment areas to warrant 

being explicitly included in the 

modeling analysis. 


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Federal Register / Vol. 83, No. 158 / Wednesday, August 15, 2018 / Proposed Rules 40497 

TABLE 3—2011 ACTUAL EMISSIONS INVENTORY

Marion 

(Indianapolis) 

(tpy) 

Daviess 

(southwest 

Indiana) 

(tpy) 

Pike 

(southwest 

Indiana) 

(tpy) 

Vigo 

(Haute Terre) 

(tpy) 

EGU ......................................................................................................... 18,998.02 0 34,728.99 55,782.42 

Point ......................................................................................................... 4,582.46 8.39 2.74 102.79 

Area ......................................................................................................... 193.21 55.63 13.60 32.51 

Non-road .................................................................................................. 125.37 1.23 1.38 9.42

On-road .................................................................................................... 121.88 3.14 1.85 13.72 

By providing a comprehensive, 

accurate, and current inventory of SO2

emissions for Marion, Pike, Daviess, and 

Vigo counties, Indiana has met the 

emission inventory requirement of CAA 

section 172(c)(3) for the Indianapolis, 

Southwest Indiana, and Terre Haute 

areas. This inventory represents 

emissions in 2011, a time when the 

areas were violating the standard. While 

section 172(c)(3) does not have a formal 

requirement for an attainment year 

inventory, the state did include 

allowable attainment year emissions in 

its modeling analysis. 

B. RACM/RACT 

In its submission, Indiana discusses 

its rationale for concluding that the 

nonattainment plans meet the RACM/ 

RACT requirements in accordance with 

EPA guidance. For most criteria 

pollutants, RACT is control technology 

as needed to meet the NAAQS that is 

reasonably available considering 

technological and economic feasibility. 

However, Indiana cites EPA guidance 

that the definition of RACT for SO2 is, 

simply, ‘‘that control technology which 

is necessary to achieve the NAAQS (40 

CFR 51.1 00(o))’’. Indiana in fact 

requires the control technology that 

modeling shows to be necessary to 

ensure attainment of the SO2 NAAQS by 

the applicable attainment date. 

Additionally, the Indiana submission 

includes limits for the individual units 

in the nonattainment areas. The limits 

are established in the attainment 

demonstration, and made permanent 

and enforceable in SIP rule 326 IAC 7, 

Sulfur Dioxide Rules. 

Indiana has determined that these 

measures suffice to provide for timely 

attainment. EPA concurs and proposes 

to conclude that the state has satisfied 

the requirements in sections 172(c)(1) 

and (6) to adopt and submit all RACT/ 

RACM and emission limitations and 

control measures as needed to attain the 

standards as expeditiously as 

practicable. 

C. New Source Review (NSR) 

EPA approved Indiana’s 

nonattainment new source review rules 

on October 7, 1994 (94 FR 24838). These 

rules provide for appropriate new 

source review for SO2 sources 

undergoing construction or major 

modification in the Indianapolis, 

Southwest Indiana, and Terre Haute 

without need for modification of the 

approved rules. Therefore, EPA 

concludes that this requirement has 

already been met for these areas. 

D. RFP 

Indiana’s adopted rules in 326 IAC 7 

require that control measures be 

implemented no later than January 1, 

2017. Indiana has concluded that this 

plan requires that affected sources 

implement appropriate control 

measures as expeditiously as practicable 

in order to ensure attainment of the 

standard by the applicable attainment 

date. Indiana concludes that this plan 

therefore provides for RFP in 

accordance with the approach to RFP 

described in EPA’s guidance. EPA 

concurs and proposes to conclude that 

the plan provides for RFP. 

E. Contingency Measures 

In its November 15, 2017 clarification 

memo, Indiana explained its rationale 

for concluding that the plans met the 

requirement for contingency measures 

in accordance with EPA guidance. 

Specifically, Indiana relies on EPA’s 

guidance, noting the special 

circumstances that apply to SO2 (as 

discussed above), and explaining on 

that basis why the contingency 

requirement in CAA section 172(c)(9) is 

met for SO2 by having a comprehensive 

program to identify sources of violations 

of the SO2 NAAQS and to undertake an 

aggressive follow-up for compliance and 

enforcement of applicable emissions 

limitations. Indiana stated that it has 

such an enforcement program as 

codified in Indiana Code Title 13, 

Articles 14 and 15, identifying violators 

and taking prompt, appropriate 

enforcement action. On this basis, EPA 

concludes that Indiana’s nonattainment 

plans satisfy contingency measure 

requirements for the Indianapolis, 

Southwest Indiana, and Terre Haute 

nonattainment areas. 

Indiana’s rules also provide for 

additional contingency measures as 

necessary, following a review of any air 

quality problems that become identified 

and following a review of options for 

mitigating the problems that arise. 

However, Indiana is not relying on these 

provisions to satisfy the requirements 

for contingency measures. 

VI. EPA’s Proposed Action 

EPA is proposing to approve Indiana’s 

SIP submission, which the state 

submitted to EPA on October 2, 2015, 

for attaining the 2010 1-hour SO2

NAAQS for the Indianapolis, Southwest 

Indiana, and Terre Haute areas. 

These SO2 nonattainment plans 

include Indiana’s attainment 

demonstration for the Indianapolis, 

Southwest Indiana, and Terre Haute SO2

nonattainment areas. These 

nonattainment plans also address 

requirements for emission inventories, 

RACT/RACM, RFP, and contingency 

measures. Indiana has previously 

addressed requirements regarding 

nonattainment area NSR. EPA has 

determined that Indiana’s SO2

nonattainment plans for Indianapolis, 

Southwest Indiana, and Terre Haute 

meet the applicable requirements of 

CAA sections 110, 172, 191, and 192. 

EPA is taking no action at this time on 

Indiana’s submittal with respect to 

Morgan County. 

EPA is taking public comments for 

thirty days following the publication of 

this proposed action in the Federal 

Register. We will take all comments into 

consideration in our final action. 

VII. Incorporation by Reference 

In this 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 

Indiana Administrative Code, Title 326, 

Article 7, ‘‘Compliance date’’ (326 IAC 

7–1.1–3), ‘‘Reporting requirements; 

methods to determine compliance’’ (7– 

2–1), ‘‘Marion County sulfur dioxide 

emission limitations’’ (7–4–2.1), ‘‘Vigo 

County sulfur dioxide emission 


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40498 Federal Register / Vol. 83, No. 158 / Wednesday, August 15, 2018 / Proposed Rules 

limitations’’ (7–4–3.1), and ‘‘Pike 

County sulfur dioxide emission 

limitations’’ (7–4–15), effective January 

1, 2107. EPA has made, and will 

continue to make, these documents 

generally available through 

www.regulations.gov, and at the EPA 

Region 5 Office. (Please contact the 

person identified in the FOR FURTHER

INFORMATION CONTACT section of this 

preamble for more information.) 

VIII. Statutory and Executive Order 

Reviews 

Under the CAA, the Administrator is 

required to approve a SIP submission 

that complies with the provisions of the 

Act 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 proposed 

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 Order 12866 58 FR 51735, 

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

January 21, 2011); 

• 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, the SIP is not approved 

to apply on any Indian reservation land 

or in any other area where EPA or an 

Indian tribe has demonstrated that a 

tribe has jurisdiction. In those areas of 

Indian country, the rule does not have 

tribal implications and will not impose 

substantial direct costs on tribal 

governments or preempt tribal law as 

specified by Executive Order 13175 (65 

FR 67249, November 9, 2000). 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Intergovernmental relations, 

Reporting and recordkeeping 

requirements, Sulfur oxides. 

Dated: August 2, 2018. 

Cathy Stepp, 

Regional Administrator, Region 5. 

[FR Doc. 2018–17582 Filed 8–14–18; 8:45 am] 

BILLING CODE 6560–50–P 


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