Air Plan Approval; Indiana; Regional Haze Plan for the Second Implementation Period, 25944-25960 [2025-11259]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 90, Number 116 (Wednesday, June 18, 2025)]
[Proposed Rules]
[Pages 25944-25960]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-11259]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R05-OAR-2021-0963; FRL-12589-01-R5]


Air Plan Approval; Indiana; Regional Haze Plan for the Second 
Implementation Period

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve the Indiana regional haze state implementation plan (SIP) 
revision submitted by the Indiana Department of Environmental 
Management (IDEM or Indiana) on December 29, 2021, as satisfying 
applicable requirements under the Clean Air Act (CAA) and EPA's 
Regional Haze Rule (RHR) for the program's second implementation 
period. EPA proposes to find that IDEM's SIP submission addresses the 
requirement that States must periodically revise their long-term 
strategies for making reasonable progress towards the national goal of 
preventing any future, and remedying any existing, anthropogenic 
impairment of visibility, including regional haze, in mandatory Class I 
Federal areas, and also addresses other applicable requirements for the 
second implementation period of the regional haze program. EPA is 
taking this action pursuant to sections 110 and 169A of the CAA.

DATES: Written comments must be received on or before July 18, 2025.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-
OAR-2021-0963 at https://www.regulations.gov or via email to 
[email protected]. For comments submitted at Regulations.gov, 
follow the online instructions for submitting comments. Once submitted, 
comments cannot be edited or removed from the docket. EPA may publish 
any comment received to its public docket. Do not submit to EPA's 
docket at https://www.regulations.gov any information you consider to 
be confidential business information (CBI), Proprietary Business 
Information (PBI), or other information whose disclosure is restricted 
by statute. Multimedia submissions (audio, video, etc.) must be 
accompanied by a written comment. The written comment is considered the 
official comment and should include discussion of all points you wish 
to make. EPA will generally not consider comments or comment contents 
located outside of the primary submission (i.e., on the web, cloud, or 
other file sharing system). For additional submission methods, please 
contact the person identified in the FOR FURTHER INFORMATION CONTACT 
section. For the full EPA public comment policy, information about CBI 
or multimedia submissions, and general guidance on making effective 
comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Charles Hatten, Air and Radiation 
Division (AR-18J), Environmental Protection Agency, Region 5, 77 West 
Jackson Boulevard, Chicago, Illinois 60604, (312) 886-6031, 
[email protected]. The EPA Region 5 office is open from 8:30 a.m. 
to 4:30 p.m., Monday through Friday.

SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,'' 
``us,'' or ``our'' is used, we mean EPA.

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Table of Contents

I. What Action is EPA Proposing?
II. Background and Requirements for Regional Haze Plans
    A. Regional Haze Background
    B. Roles of Agencies in Addressing Regional Haze
III. Requirements for Regional Haze Plans for the Second 
Implementation Period
    A. Reasonable Progress Goals (RPGs)
    B. Monitoring Strategy and Other SIP Requirements
    C. Requirements for Periodic Reports Describing Progress Towards 
the RPGs
    D. Requirements for State and Federal Land Manager Coordination
IV. EPA's Evaluation of Indiana's Regional Haze Submission for the 
Second Implementation Period
    A. Background on Indiana's First Implementation Period SIP 
Submission
    B. Indiana's Second Implementation Period SIP Submission and 
EPA's Evaluation
    C. Identification of Class I Areas
    D. Calculations of Baseline, Current, and Natural Visibility 
Conditions; Progress to Date; and the Uniform Rate of Progress
    E. Long-Term Strategy for Regional Haze
    1. Selection of Sources for Analysis
    2. Emission Measures Necessary to Make Reasonable Progress
    3. Indiana's Long-Term Strategy
    4. EPA's Evaluation of Indiana's Compliance with 40 CFR 
51.308(f)(2)(i)
    5. Consultation with States
    6. Five Additional Factors
    F. RPGs
    G. Monitoring Strategy and Other Implementation Plan 
Requirements
    H. Requirements for Periodic Reports Describing Progress Towards 
the RPGS
    I. Requirements for State and Federal Land Manager Coordination
V. Proposed Action
VI. Statutory and Executive Order Reviews

I. What action is EPA proposing?

    On December 29, 2021, IDEM submitted a SIP revision to address 
regional haze requirements for the second implementation period. IDEM 
submitted this SIP revision to satisfy the requirements pursuant to CAA 
sections 169A and 169B and 40 CFR 51.308(f) related to the regional 
haze program. EPA proposes to find that Indiana's regional haze SIP 
submission for the second implementation period meets the applicable 
statutory and regulatory requirements and thus proposes to approve 
Indiana's submission into its SIP.

II. Background and Requirements for Regional Haze Plans

    A detailed history and background of the regional haze program is 
provided in multiple prior EPA proposal actions.\1\ For additional 
background on the 2017 RHR revisions, please refer to Section III. 
Overview of Visibility Protection Statutory Authority, Regulation, and 
Implementation of ``Protection of Visibility: Amendments to 
Requirements for State Plans'' of the 2017 RHR.\2\ The following is an 
abbreviated history and background of the regional haze program and 
2017 RHR as it applies to the current action.
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    \1\ See 90 FR 13516 (March 24, 2025).
    \2\ See 82 FR 3078 (January 10, 2017, located at https://www.federalregister.gov/documents/2017/01/10/2017-00268/protection-of-visibility-amendments-to-requirements-for-State-plans#h-16).
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A. Regional Haze Background

    In the 1977 CAA Amendments, Congress created a program for 
protecting visibility in the nation's mandatory Class I Federal areas, 
which include certain national parks and wilderness areas.\3\ CAA 169A. 
The CAA establishes as a national goal the ``prevention of any future, 
and the remedying of any existing, impairment of visibility in 
mandatory class I Federal areas which impairment results from manmade 
air pollution.'' CAA 169A(a)(1).
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    \3\ Areas statutorily designated as mandatory Class I Federal 
areas consist of national parks exceeding 6,000 acres, wilderness 
areas and national memorial parks exceeding 5,000 acres, and all 
international parks that were in existence on August 7, 1977. CAA 
162(a). There are 156 mandatory Class I areas. The list of areas to 
which the requirements of the visibility protection program apply is 
in 40 CFR part 81, subpart D.
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    Regional haze is visibility impairment that is produced by a 
multitude of anthropogenic sources and activities which are located 
across a broad geographic area and that emit pollutants that impair 
visibility. Visibility impairing pollutants include fine and coarse 
particulate matter (PM) (e.g., sulfates, nitrates, organic carbon, 
elemental carbon, and soil dust) and their precursors (e.g., sulfur 
dioxide (SO2), nitrogen oxides (NOX), and, in 
some cases, volatile organic compounds (VOC) and ammonia 
(NH3)). Fine particle precursors react in the atmosphere to 
form fine particulate matter (PM2.5), which impairs 
visibility by scattering and absorbing light. Visibility impairment 
reduces the perception of clarity and color, as well as visible 
distance.\4\
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    \4\ There are several ways to measure the amount of visibility 
impairment, i.e., haze. One such measurement is the deciview, which 
is the principal metric used by the RHR. Under many circumstances, a 
change in one deciview will be perceived by the human eye to be the 
same on both clear and hazy days. The deciview is unitless. It is 
proportional to the logarithm of the atmospheric extinction of 
light, which is the perceived dimming of light due to its being 
scattered and absorbed as it passes through the atmosphere. 
Atmospheric light extinction (b\ext\) is a metric used to for 
expressing visibility and is measured in inverse megameters (Mm-1). 
The formula for the deciview is 10 ln (b\ext\)/10 Mm-1). 40 CFR 
51.301.
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    To address regional haze visibility impairment, the 1999 RHR 
established an iterative planning process that requires both States in 
which Class I areas are located and States ``the emissions from which 
may reasonably be anticipated to cause or contribute to any impairment 
of visibility'' in a Class I area to periodically submit SIP revisions 
to address such impairment. CAA 169A(b)(2); \5\ see also 40 CFR 
51.308(b), (f) (establishing submission dates for iterative regional 
haze SIP revisions); (64 FR 35714 at 35768, July 1, 1999).
    On January 10, 2017 (82 FR 3078), EPA promulgated revisions to the 
RHR, that apply for the second and subsequent implementation periods. 
The reasonable progress requirements as revised in the 2017 rulemaking 
(referred to here as the 2017 RHR Revisions) are codified at 40 CFR 
51.308(f).

B. Roles of Agencies in Addressing Regional Haze

    Because the air pollutants and pollution affecting visibility in 
Class I areas can be transported over long distances, successful 
implementation of the regional haze program requires long-term, 
regional coordination among multiple jurisdictions and agencies that 
have responsibility for Class I areas and the emissions that impact 
visibility in those areas. To address regional haze, States need to 
develop strategies in coordination with one another, considering the 
effect of emissions from one jurisdiction on the air quality in 
another. Five regional planning organizations (RPOs),\6\ which include 
representation from State and Tribal governments, EPA, and FLMs, were 
developed in the lead-up to the first implementation period to address 
regional haze. RPOs evaluate technical information to better understand 
how emissions from State and Tribal lands impact Class I areas across 
the country, pursue the development of regional strategies to reduce 
emissions of particulate matter and other pollutants leading to 
regional haze, and help States meet the consultation requirements of 
the RHR.
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    \6\ RPOs are sometimes also referred to as ``multi-
jurisdictional organizations,'' or MJOs. For the purposes of this 
notice, the terms RPO and MJO are synonymous.
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    The Lake Michigan Air Directors Consortium (LADCO) is an RPO that 
includes the States of Illinois, Indiana, Michigan, Minnesota, Ohio, 
and Wisconsin. LADCO's work is a collaborative effort of State 
governments, Tribal governments, and various Federal agencies 
established to

[[Page 25946]]

initiate and coordinate activities associated with the management of 
regional haze, visibility, and other air quality issues in the Midwest. 
Along with the six LADCO States, participants in LADCO's Regional Haze 
Technical Workgroup include EPA, the U.S. National Park Service (NPS), 
the U.S. Fish and Wildlife Service (FWS), and the U.S. Forest Service 
(USFS).

III. Requirements for Regional Haze Plans for the Second Implementation 
Period

    Under the CAA and EPA's regulations, all 50 States, the District of 
Columbia, and the U.S. Virgin Islands are required to submit regional 
haze SIPs satisfying the applicable requirements for the second 
implementation period of the regional haze program by July 31, 2021. 
Each State's SIP must contain a long-term strategy for making 
reasonable progress toward meeting the national goal of remedying any 
existing and preventing any future anthropogenic visibility impairment 
in Class I areas. CAA 169A(b)(2)(B). To this end, 40 CFR 51.308(f) lays 
out the process by which States determine what constitutes their long-
term strategies, with the order of the requirements in 40 CFR 
51.308(f)(1) through (3) generally mirroring the order of the steps in 
the reasonable progress analysis \7\ and (f)(4) through (6) containing 
additional, related requirements. Broadly speaking, a State first must 
identify the Class I areas within the State and determine the Class I 
areas outside the State in which visibility may be affected by 
emissions from the State. These are the Class I areas that must be 
addressed in the State's long-term strategy. See 40 CFR 51.308(f), 
(f)(2). For each Class I area within its borders, a State must then 
calculate the baseline (five-year average period of 2000-2004), 
current, and natural visibility conditions (i.e., visibility conditions 
without anthropogenic visibility impairment) for that area, as well as 
the visibility improvement made to date and the ``uniform rate of 
progress'' (URP). The URP is the linear rate of progress needed to 
attain natural visibility conditions, assuming a starting point of 
baseline visibility conditions in 2004 and ending with natural 
conditions in 2064. This linear interpolation is used as a tracking 
metric to help States assess the amount of progress they are making 
towards the national visibility goal over time in each Class I area. 
See 40 CFR 51.308(f)(1). Each State having a Class I area and/or 
emissions that may affect visibility in a Class I area must then 
develop a long-term strategy that includes the enforceable emission 
limitations, compliance schedules, and other measures that are 
necessary to make reasonable progress in such areas. A reasonable 
progress determination is based on applying the four factors in CAA 
section 169A(g)(1) to sources of visibility-impairing pollutants that 
the State has selected to assess for controls for the second 
implementation period. Additionally, as further explained below, the 
RHR at 40 CFR 51.308(f)(2)(iv) separately provides five ``additional 
factors'' \8\ that States must consider in developing their long-term 
strategies. See 40 CFR 51.308(f)(2). A State evaluates potential 
emission reduction measures for those selected sources and determines 
which are necessary to make reasonable progress. Those measures are 
then incorporated into the State's long-term strategy. After a State 
has developed its long-term strategy, it then establishes RPGs for each 
Class I area within its borders by modeling the visibility impacts of 
all reasonable progress controls at the end of the second 
implementation period, i.e., in 2028, as well as the impacts of other 
requirements of the CAA. The RPGs include reasonable progress controls 
not only for sources in the State in which the Class I area is located, 
but also for sources in other States that contribute to visibility 
impairment in that area. The RPGs are then compared to the baseline 
visibility conditions and the URP to ensure that progress is being made 
towards the statutory goal of preventing any future and remedying any 
existing anthropogenic visibility impairment in Class I areas. 40 CFR 
51.308(f)(2)-(3). There are additional requirements in the rule, 
including FLM consultation, that apply to all visibility protection 
SIPs and SIP revisions. See e.g., 40 CFR 51.308(i).
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    \7\ EPA explained in the 2017 RHR Revisions that we were 
adopting new regulatory language in 40 CFR 51.308(f) that, unlike 
the structure in 51.308(d), ``tracked the actual planning 
sequence.'' (82 FR 3091, January 10, 2017).
    \8\ The five ``additional factors'' forr consideration in 
section 40 CFR 51.308(f)(2)(iv) are distinct from the four factors 
listed in CAA section 169A(g)(1) and 40 CFR 51.308(f)(2)(i) that 
states that must consider and apply to sources in determining 
reasonable progress.
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    While States have discretion to choose any source selection 
methodology that is reasonable, whatever choices they make should be 
reasonably explained. To this end, 40 CFR 51.308(f)(2)(i) requires that 
a State's SIP submission include ``a description of the criteria it 
used to determine which sources or groups of sources it evaluated.'' 
The technical basis for source selection, which may include methods for 
quantifying potential visibility impacts such as emissions divided by 
distance metrics, trajectory analyses, residence time analyses, and/or 
photochemical modeling, must also be appropriately documented, as 
required by 40 CFR 51.308(f)(2)(iii).
    Once a State has selected the set of sources, the next step is to 
determine the emissions reduction measures for those sources that are 
necessary to make reasonable progress for the second implementation 
period.\9\ This is accomplished by considering the four factors--``the 
costs of compliance, the time necessary for compliance, and the energy 
and non-air quality environmental impacts of compliance, and the 
remaining useful life of any existing source subject to such 
requirements.'' CAA 169A(g)(1). EPA has explained that the four-factor 
analysis is an assessment of potential emission reduction measures 
(i.e., control options) for sources; ``use of the terms `compliance' 
and `subject to such requirements' in section 169A(g)(1) strongly 
indicates that Congress intended the relevant determination to be the 
requirements with which sources would have to comply to satisfy the 
CAA's reasonable progress mandate.'' 82 FR 3078 at 3091, January 10, 
2017. Thus, for each source it has selected for four-factor 
analysis,\10\ a State must consider a ``meaningful set'' of technically 
feasible control options for reducing emissions of visibility impairing 
pollutants. Id. at 3088.
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    \9\ The CAA provides that, ``[i]n determining reasonable 
progress there shall be taken into consideration'' the four 
statutory factors. CAA 169A(g)(1). However, in addition to four-
factor analyses for selected sources, groups of sources, or source 
categories, a state may also consider additional emission reduction 
measures for inclusion in its long-term strategy, e.g., from other 
newly adopted, on-the-books, or on-the-way rules and measures for 
sources not selected for four-factor analysis for the second 
planning period.
    \10\ ``Each source'' or ``particular source'' is used here as 
shorthand. While a source-specific analysis is one way of applying 
the four factors, neither the statute nor the RHR requires states to 
evaluate individual sources. Rather, states have ``the flexibility 
to conduct four-factor analyses for specific sources, groups of 
sources or even entire source categories, depending on state policy 
preferences and the specific circumstances of each state.'' 82 FR 
3078 at 3088, January 10, 2017.
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    EPA has also explained that, in addition to the four statutory 
factors, States have flexibility under the CAA and RHR to reasonably 
consider visibility benefits as an additional factor alongside the four 
statutory factors.\11\ Ultimately, while States have discretion

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to reasonably weigh the factors and to determine what level of control 
is needed, 40 CFR 51.308(f)(2)(i) provides that a State ``must include 
in its implementation plan a description of . . . how the four factors 
were taken into consideration in selecting the measure for inclusion in 
its long-term strategy.''
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    \11\ See, e.g., Responses to Comments on Protection of 
Visibility: Amendments to Requirements for State Plans; Proposed 
Rule (81 FR 26942, May 4, 2016), Docket Number EPA-HQ-OAR-2015-0531, 
U.S. Environmental Protection Agency at 186; 2019 Guidance at 36-37.
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    As explained above, 40 CFR 51.308(f)(2)(i) requires States to 
determine the emission reduction measures for sources that are 
necessary to make reasonable progress by considering the four factors. 
Pursuant to 40 CFR 51.308(f)(2), measures that are necessary to make 
reasonable progress towards the national visibility goal must be 
included in a State's long-term strategy and in its SIP.\12\ If the 
outcome of a four-factor analysis is that an emissions reduction 
measure is necessary to make reasonable progress towards remedying 
existing or preventing future anthropogenic visibility impairment, that 
measure must be included in the SIP.
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    \12\ States may choose to, but are not required to, include 
measures in their long-term strategies beyond just the emission 
reduction measures that are necessary for reasonable progress. For 
example, states with smoke management programs may choose to submit 
their smoke management plans to EPA for inclusion in their SIPs but 
are not required to do so. See, e.g., 82 FR 3078 at 3108-09, January 
10, 2017, (requirement to consider smoke management practices and 
smoke management programs under 40 CFR 51.308(f)(2)(iv) does not 
require states to adopt such practices or programs into their SIPs, 
although they may elect to do so).
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    The characterization of information on each of the factors is also 
subject to the documentation requirement in 40 CFR 51.308(f)(2)(iii). 
The reasonable progress analysis is a technically complex exercise, and 
also a flexible one that provides States with bounded discretion to 
design and implement approaches appropriate to their circumstances. 
Given this flexibility, 40 CFR 51.308(f)(2)(iii) plays an important 
function in requiring a State to document the technical basis for its 
decision making so that the public and EPA can comprehend and evaluate 
the information and analysis the State relied upon to determine what 
emission reduction measures must be in place to make reasonable 
progress. The technical documentation must include the modeling, 
monitoring, cost, engineering, and emissions information on which the 
State relied to determine the measures necessary to make reasonable 
progress.
    Additionally, the RHR at 40 CFR 51.308(f)(2)(iv) separately 
provides five ``additional factors'' \13\ that States must consider in 
developing their long-term strategies: (1) Emission reductions due to 
ongoing air pollution control programs, including measures to address 
reasonably attributable visibility impairment; (2) measures to reduce 
the impacts of construction activities; (3) source retirement and 
replacement schedules; (4) basic smoke management practices for 
prescribed fire used for agricultural and wildland vegetation 
management purposes and smoke management programs; and (5) the 
anticipated net effect on visibility due to projected changes in point, 
area, and mobile source emissions over the period addressed by the 
long-term strategy.
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    \13\ The five ``additional factors'' for consideration in 40 CFR 
51.308(f)(2)(iv) are distinct from the four factors listed in CAA 
section 169A(g)(1) and 40 CFR 51.308(f)(2)(i) that states must 
consider and apply to sources in determining reasonable progress.
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    Because the air pollution that causes regional haze crosses State 
boundaries, 40 CFR 51.308(f)(2)(ii) requires a State to consult with 
other States that also have emissions that are reasonably anticipated 
to contribute to visibility impairment in a given Class I area. If a 
State, pursuant to consultation, agrees that certain measures (e.g., a 
certain emission limitation) are necessary to make reasonable progress 
at a Class I area, it must include those measures in its SIP. 40 CFR 
51.308(f)(2)(ii)(A). Additionally, the RHR requires that States that 
contribute to visibility impairment at the same Class I area consider 
the emission reduction measures the other contributing States have 
identified as being necessary to make reasonable progress for their own 
sources. 40 CFR 51.308(f)(2)(ii)(B). If a State has been asked to 
consider or adopt certain emission reduction measures, but ultimately 
determines those measures are not necessary to make reasonable 
progress, that State must document in its SIP the actions taken to 
resolve the disagreement. 40 CFR 51.308(f)(2)(ii)(C). Under all 
circumstances, a State must document in its SIP submission all 
substantive consultations with other contributing States. 40 CFR 
51.308(f)(2)(ii)(C).

A. Reasonable Progress Goals (RPGs)

    RPGs ``measure the progress that is projected to be achieved by the 
control measures States have determined are necessary to make 
reasonable progress based on a four-factor analysis.'' 82 FR 3078 at 
3091, January 10, 2017.
    For the second implementation period, the RPGs are set for 2028. 
RPGs are not enforceable targets, 40 CFR 51.308(f)(3)(iii). While 
States are not legally obligated to achieve the visibility conditions 
described in their RPGs, 40 CFR 51.308(f)(3)(i) requires that ``[t]he 
long-term strategy and the RPGs must provide for an improvement in 
visibility for the most impaired days since the baseline period and 
ensure no degradation in visibility for the clearest days since the 
baseline period.''
    RPGs may also serve as a metric for assessing the amount of 
progress a State is making towards the national visibility goal. To 
support this approach, the RHR requires States with Class I areas to 
compare the 2028 RPG for the most impaired days to the corresponding 
point on the URP line (representing visibility conditions in 2028 if 
visibility were to improve at a linear rate from conditions in the 
baseline period of 2000-2004 to natural visibility conditions in 2064). 
If the most impaired days RPG in 2028 is above the URP (i.e., if 
visibility conditions are improving more slowly than the rate described 
by the URP), each State that contributes to visibility impairment in 
the Class I area must demonstrate, based on the four-factor analysis 
required under 40 CFR 51.308(f)(2)(i), that no additional emission 
reduction measures would be reasonable to include in its long-term 
strategy. 40 CFR 51.308(f)(3)(ii). To this end, 40 CFR 51.308(f)(3)(ii) 
requires that each State contributing to visibility impairment in a 
Class I area that is projected to improve more slowly than the URP 
provide ``a robust demonstration, including documenting the criteria 
used to determine which sources or groups [of] sources were evaluated 
and how the four factors required by paragraph (f)(2)(i) were taken 
into consideration in selecting the measures for inclusion in its long-
term strategy.''

B. Monitoring Strategy and Other SIP Requirements

    The provisions of 40 CFR 51.308(f)(6) require States to have 
certain strategies and elements in place for assessing and reporting on 
visibility. Individual requirements under this section apply either to 
States with Class I areas within their borders, States with no Class I 
areas but that are reasonably anticipated to cause or contribute to 
visibility impairment in any Class I area, or both. Compliance with the 
monitoring strategy requirement may be met through a State's 
participation in the Interagency Monitoring of Protected Visual 
Environments (IMPROVE) monitoring network, which is used to measure 
visibility impairment caused by air pollution at the 156 Class I areas 
covered by the visibility program. 40 CFR 51.308(f)(6), (f)(6)(i), 
(f)(6)(iv).
    All States' SIPs must provide for procedures by which monitoring 
data and other information are used to determine the contribution of 
emissions

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from within the State to regional haze visibility impairment in 
affected Class I areas, as well as a statewide inventory documenting 
such emissions. 40 CFR 51.308(f)(6)(ii), (iii), (v). All States' SIPs 
must also provide for any other elements, including reporting, 
recordkeeping, and other measures, that are necessary for States to 
assess and report on visibility. 40 CFR 51.308(f)(6)(vi).

C. Requirements for Periodic Reports Describing Progress Towards the 
RPGs

    The provisions of 40 CFR 51.308(f)(5) require a State's regional 
haze SIP revision to address the requirements of paragraphs 40 CFR 
51.308(g)(1) through (5) so that the plan revision due in 2021 will 
serve also as a progress report addressing the period since submission 
of the progress report for the first implementation period. The 
regional haze progress report requirement is designed to inform the 
public and EPA about a State's implementation of its existing long-term 
strategy and whether such implementation is in fact resulting in the 
expected visibility improvement. See 81 FR 26942, 26950, May 4, 2016, 
(82 FR 3078 at 3119, January 10, 2017). To this end, every State's SIP 
revision for the second implementation period is required to assess 
changes in visibility conditions and describe the status of 
implementation of all measures included in the State's long-term 
strategy, including Best Available Retrofit Technology (BART) and 
reasonable progress emission reduction measures from the first 
implementation period, and the resulting emissions reductions. 40 CFR 
51.308(g)(1) and (2).

D. Requirements for State and Federal Land Manager Coordination

    CAA section 169A(d) requires that before a State holds a public 
hearing on a proposed regional haze SIP revision, it must consult with 
the appropriate FLM or FLMs; pursuant to that consultation, the State 
must include a summary of the FLMs' conclusions and recommendations in 
the notice to the public. Consistent with this statutory requirement, 
the RHR also requires that States ``provide the [FLM] with an 
opportunity for consultation, in person and at a point early enough in 
the State's policy analyses of its long-term strategy emission 
reduction obligation so that information and recommendations provided 
by the [FLM] can meaningfully inform the State's decisions on the long-
term strategy.'' 40 CFR 51.308(i)(2). For EPA to evaluate whether FLM 
consultation meeting the requirements of the RHR has occurred, the SIP 
submission should include documentation of the timing and content of 
such consultation. The SIP revision submitted to EPA must also describe 
how the State addressed any comments provided by the FLMs. 40 CFR 
51.308(i)(3). Finally, a SIP revision must provide procedures for 
continuing consultation between the State and FLMs regarding the 
State's visibility protection program, including development and review 
of SIP revisions, five-year progress reports, and the implementation of 
other programs having the potential to contribute to impairment of 
visibility in Class I areas. 40 CFR 51.308(i)(4).

IV. EPA's Evaluation of Indiana's Regional Haze Submission for the 
Second Implementation Period

A. Background on Indiana's First Implementation Period SIP Submission

    Indiana submitted its regional haze SIP to EPA for the first 
implementation period, 2007-2018, on January 14, 2011, and supplemented 
it on March 10, 2011. The requirements for regional haze SIPs for the 
first implementation period are contained in 40 CFR 51.308(d) and (e). 
See 40 CFR 51.308(b).
    On May 29, 2012, EPA finalized a limited approval of Indiana's 2011 
SIP submission as satisfying the requirements for BART in 40 CFR 
51.308(e) for non-electric generating units (EGUs) and for PM from 
EGUs. EPA also approved the submission's BART limits for the Alcoa 
Warrick facility, its identification of Class I areas that the State's 
emissions affect, its demonstration that the State had consulted with 
other States in establishing RPGs, and identification of emissions 
reductions needed in Indiana to meet those goals. 77 FR 34218, June 11, 
2012. On May 30, 2012, EPA issued a limited disapproval of Indiana's 
2011 SIP submission because of deficiencies arising from the remand of 
the Clean Air Interstate Rule (CAIR). In the same rulemaking, EPA 
promulgated a Federal Implementation Plan (FIP) to replace Indiana's 
reliance on CAIR with the Cross-State Air Pollution Rule (CSAPR). 77 FR 
33642, June 7, 2012.
    Pursuant to 40 CFR 51.308(g), Indiana was also responsible for 
submitting a five-year progress report as a SIP revision for the first 
implementation period, which it did on March 30, 2016. EPA approved 
this five-year progress report as a revision to the Indiana SIP at 40 
CFR 52.770(e) on January 23, 2018 (83 FR 4847, February 2, 2018).
    On November 27, 2017, Indiana submitted a revision to its 2011 
Regional Haze SIP submission to change reliance on CAIR to reliance on 
CSAPR, which EPA approved on August 28, 2019, converting EPA's limited 
approval/limited disapproval to a full approval and withdrawing the FIP 
provisions that addressed the limited disapproval. 84 FR 46889, 
September 6, 2019.

B. Indiana's Second Implementation Period SIP Submission and EPA's 
Evaluation

    In accordance with CAA sections 169A and the RHR at 40 CFR 
51.308(f), Indiana submitted a SIP revision on December 29, 2021, to 
address its regional haze obligations for the second implementation 
period, which runs through 2028. Indiana provided a draft of its 
regional haze SIP to the FLMs for consultation on May 18, 2021. Indiana 
then provided a public comment period before submitting its SIP 
revision to EPA.\14\
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    \14\ Indiana included the comments in appendices W, X, Ya, Yb, 
and Z, and provided responses in appendices P, Q, R, S, T, U, and V 
of its 2021 Regional Haze SIP submission.
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    The following sections describe Indiana's SIP submission, including 
Indiana's assessment of progress made since the first implementation 
period, in reducing emissions of visibility impairing pollutants, and 
the visibility improvement progress at nearby Class I areas. These 
sections also contain EPA's evaluation of Indiana's submission against 
the requirements of the CAA and the RHR for the second implementation 
period of the regional haze program.

C. Identification of Class I Areas

    The provisions of section 169A(b)(2) of the CAA require each State 
in which any Class I area is located or ``the emissions from which may 
reasonably be anticipated to cause or contribute to any impairment of 
visibility'' in a Class I area to have a plan for making reasonable 
progress toward the national visibility goal. The RHR implements this 
statutory requirement at 40 CFR 51.308(f), which provides that each 
State's plan ``must address regional haze in each mandatory Class I 
Federal area located within the State and in each mandatory Class I 
Federal area located outside the State that may be affected by 
emissions from within the State,'' and (f)(2), which requires each 
State's plan to include a long-term strategy that addresses regional 
haze in such Class I areas.
    Indiana has no Class I areas within its borders that are among the 
156 mandatory Class I Federal areas where EPA deemed visibility to be 
an important value. See 40 CFR part 81, subpart D. Thus, IDEM only 
considered

[[Page 25949]]

out-of-state mandatory Class I Federal areas.
    Indiana is a member of LADCO and participated in its regional 
approach for developing a strategy for making reasonable progress 
towards the national visibility goal in the northern Midwest Class I 
areas. IDEM reviewed technical analyses conducted by LADCO to determine 
which Class I areas outside the State are affected by Indiana emission 
sources. For the second regional haze implementation period, to 
determine LADCO member State contributions to impaired visibility in 
all Class I areas, LADCO used the Comprehensive Air Quality Model with 
extensions applying Particulate Matter Source Apportionment Tool. LADCO 
tagged emissions from individual States and several multi-state regions 
as well as individual point sources and inventory source groups to 
apportion emissions to States and regions. This included 27 tagged 
source categories, nine of which were source categories or individual 
sources in Indiana: (1) Indiana non-point sources, (2) Rockport EGUs, 
(3) Gibson EGUs, (4) all other Indiana EGUs, (5) Indiana cement 
manufacturing facilities, (6) Indiana iron and steel facilities, (7) 
Indiana plastics and resin manufacturing facilities, (8) Indiana 
aluminum production facilities, and (9) all other Indiana point 
sources. LADCO assessed relative visibility impacts in 2028 by 
projecting representative emissions inventories and known emission 
controls from 2016.\15\ A group of RPOs, States, and EPA established 
2016 as the base year for a national air quality modeling platform for 
future ozone, PM2.5, and regional haze SIP development 
because of fairly typical ozone conditions and wildfire conditions.\16\ 
LADCO relied upon EPA's inventory estimates for 2016 and 2028 for most 
emission sectors as described in EPA's September 19, 2019, 
``Availability of Modeling Data and Associated Technical Support 
Document for the EPA's Updated 2028 Visibility Air Quality Modeling,'' 
(EPA's Updated 2028 Visibility Air Quality Modeling).\17\ For EGUs, 
LADCO used forecasts from the Eastern Regional Technical Advisory 
Committee (ERTAC) based on continuous emissions monitoring data from 
2016 instead of the Integrated Planning Model used in EPA's 2016 
modeling platform. LADCO also incorporated state-reported changes to 
EGUs received through September 2020 to estimate 2028 EGU emissions, 
which was considered by LADCO to be the best available information on 
EGU forecasts for the Midwest and Eastern U.S. available at the time.
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    \15\ See section 24 and appendix L of Indiana's 2021 SIP 
submittal for details of the analysis and source-apportioned 
visibility contributions at Class I areas within the LADCO region 
for regional haze second planning period that are documented in 
LADCO's ``Modeling and Analysis for Demonstrating Reasonable 
Progress for the Regional Haze Rule 2018-2028 Planning Period: 
Technical Support Document,'' June 17, 2021.
    \16\ See ``Base Year Selection Workgroup Final Report,'' 
produced by the Inventory Collaborative Base Year Selection 
Workgroup, April 5, 2017. https://www.wrapair2.org/pdf/2017-12-12_Base_Year_Selection_Report_V1.1.pdf.
    \17\ EPA, Office of Air Quality Planning and Standards, 
``Availability of Modeling Data and Associate Technical Support 
Document for EPA's Updated 2028 Visibility Air Quality Modeling,'' 
September 19, 2019. https://www.epa.gov/sites/default/files/2019-10/documents/updated_2028_regional_haze_modeling-tsd-2019_0.pdf.
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    Based on LADCO's source apportionment modeling results for 2028, 
IDEM identified 17 out-of-state Class I areas where Indiana's 
contribution to the total light extinction was 1.5 percent or greater. 
IDEM also included three additional Class I areas below the 1.5 percent 
threshold: Boundary Waters Canoe Area Wilderness (Minnesota) and 
Voyageurs National Park (Minnesota) since they are part of the LADCO 
region, as well as Caney Creek (Arkansas) based on a request for inter-
state consultation from Arkansas. IDEM found that the 1.5 percent 
threshold provided adequate geographic coverage of potential visibility 
impacts from Indiana on surrounding Class I areas and that the modeling 
of those areas would be representative of Class I areas further from 
the State. These Class I areas, along with Indiana's 2028 projected 
contributions to the total light extinction, are: Mammoth Cave National 
Park in Kentucky (11.2 percent); Sipsey Wilderness Area in Alabama 
(5.90 percent); Dolly Sods and Otter Creek Wilderness Areas in West 
Virginia (5.56 percent); Great Smoky Mountains National Park and Joyce-
Kilmer-Slickrock Wilderness Area in Tennessee (5.29 percent); 
Shenandoah National Park in Virginia (5.14 percent); Cohutta Wilderness 
Area in Georgia (4.83 percent); Mingo Wilderness Area in Missouri (4.16 
percent); Seney Wilderness Area in Michigan (4.01 percent); James River 
Face Wilderness Area in Virginia (3.75 percent); Linville Gorge 
Wilderness Area in North Carolina (2.84 percent); Lye Brook Wilderness 
Area in Vermont (2.33 percent); Brigantine Wilderness Area in New 
Jersey (2.30 percent); Shining Rock Wilderness Area in North Carolina 
(2.17 percent); Upper Buffalo Wilderness Area in Arkansas (2.02 
percent); Hercules-Glades Wilderness Area in Missouri (2.01 percent); 
Swanquarter National Wildlife Refuge in North Carolina (1.85 percent); 
Isle Royale National Park in Michigan (1.85 percent); Caney Creek 
Wilderness Area in Arkansas (1.10 percent); Boundary Waters Canoe Area 
Wilderness in Minnesota (0.74 percent); and Voyageurs National Park in 
Minnesota (0.49 percent).\18\ At each of these Class I areas, EPA notes 
that the visibility conditions in LADCO's modeling as well as EPA's 
Updated 2028 Visibility Air Quality Modeling are projected to be below 
their respective glidepaths in 2028 as depicted in Section 23 of 
Indiana's 2021 Regional Haze SIP submission. Visibility conditions at 
the Class I areas most impacted by Indiana are projected to be below 
their respective glidepaths in 2028 at Mammoth Cave National Park by 
2.16 deciviews (dv), Sipsey Wilderness Area by 2.44 dv, Dolly Sods and 
Otter Creek Wilderness Areas by 4.33 dv, Great Smoky Mountains National 
Park and Joyce-Kilmer-Slickrock Wilderness Area by 5.43 dv, and 
Shenandoah National Park by 4.98 dv. IDEM addressed each of these Class 
I areas as well as requests from their host RPOs and States in 
Indiana's 2021 Regional Haze SIP Sections 22-25 and appendix AA.
---------------------------------------------------------------------------

    \18\ The list of Class I areas impacted by Indiana, including 
the 2028 projections for total light extinction and Indiana's 
contribution, is found in Table 23-1 of Indiana's 2021 Regional Haze 
SIP submittal.
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D. Calculations of Baseline, Current, and Natural Visibility 
Conditions; Progress to Date; and the Uniform Rate of Progress

    The provisions of 40 CFR 51.308(f)(1) require States to determine 
the following for ``each mandatory Class I Federal area located within 
the State'': baseline visibility conditions for the most impaired and 
clearest days, natural visibility conditions for the most impaired and 
clearest days, progress to date for the most impaired and clearest 
days, the differences between current visibility conditions and natural 
visibility conditions, and the URP. This section also provides the 
option for States to propose adjustments to the URP line for a Class I 
area to account for visibility impacts from anthropogenic sources 
outside the United States and/or the impacts from wildland prescribed 
fires that were conducted for certain, specified objectives. 40 CFR 
51.308(f)(1)(vi)(B).
    Indiana has no mandatory Class I areas within its borders to which 
the requirements of the visibility protection program apply in 40 CFR 
part 81,

[[Page 25950]]

subpart D, and therefore, 40 CFR 51.308(f)(1) and its requirements do 
not apply.

E. Long-Term Strategy for Regional Haze

    Each State having a Class I area within its borders or emissions 
that may affect visibility in a Class I area must develop a long-term 
strategy for making reasonable progress towards the national visibility 
goal. CAA 169A(b)(2)(B). After considering the four statutory factors, 
all measures that are determined to be necessary to make reasonable 
progress must be in the long-term strategy. In developing its long-term 
strategies, a State must also consider the five additional factors in 
40 CFR 51.308(f)(2)(iv). As part of its reasonable progress 
determinations, the State must describe the criteria used to determine 
which sources or group of sources were evaluated (i.e., subjected to 
four-factor analysis) for the second implementation period and how the 
four factors were taken into consideration in selecting the emission 
reduction measures for inclusion in the long-term strategy. 40 CFR 
51.308(f)(2)(iii).
1. Selection of Sources for Analysis
    States may rely on technical information developed by the RPOs of 
which they are members to select sources for four-factor analysis and 
to conduct that analysis, as well as to satisfy the documentation 
requirements under 40 CFR 51.308(f). States may also satisfy the 
requirement of 40 CFR 51.308(f)(2)(ii) to engage in interstate 
consultation with other States that have emissions that are reasonably 
anticipated to contribute to visibility impairment in a given Class I 
area under the auspices of intra- and inter-RPO engagement.
    In developing a process for selecting sources for possible 
additional control measures during the second planning period, IDEM 
considered NOX, SO2, and NH3 emissions 
as precursors to the formation of ammonium sulfate, ammonium nitrate, 
and organic carbon that can impair visibility. Of these precursors, 
LADCO's June 17, 2021, Technical Support Document ``Modeling and 
Analysis for Demonstrating Reasonable Progress for the Regional Haze 
Rule 2018-2028 Planning Period,'' (LADCO's 2021 TSD) \19\ provided an 
analysis of the IMPROVE monitoring data. The analysis demonstrated that 
NOX and SO2 emissions lead to the formation of 
the particulate species of nitrate and sulfate that currently 
contribute more to visibility impairment in the LADCO Class I Areas 
than PM2.5, NH3, and VOC. The LADCO Class I Areas 
consist of Boundary Waters Canoe Area Wilderness and Voyageurs National 
Park in Minnesota, as well as Isle Royale National Park and Seney 
Wilderness Area in Michigan. For this reason, Indiana chose to focus on 
potential reductions in emissions of NOX and SO2, 
which Indiana found would be a reasonable approach for the second 
implementation period as noted in the ``Guidance on Regional Haze State 
Implementation Plans for the Second Implementation Period,'' EPA Office 
of Air Quality Planning and Standards, Research Triangle Park, August 
20, 2019 (``2019 Guidance'') at page 12.\20\
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    \19\ LADCO's 2021 TSD is contained in appendix L of Indiana's 
2021 Regional Haze SIP submittal.
    \20\ https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period.
---------------------------------------------------------------------------

    In selecting sources for a potential four-factor analysis, IDEM 
followed the methodology in LADCO's October 14, 2020, technical 
memorandum ``Description of the Sources and Methods Used to Support Q/d 
Analysis for the 2nd Regional Haze Planning Period'' \21\ and section 5 
of the LADCO's 2021 TSD. IDEM generated a list of sources based on 
total process-level emissions (Q) divided by distance (d) to the 
nearest Class I area, where Q/d was used as a surrogate quantitative 
metric of visibility impact in lieu of air quality modeling results. 
For Q, total emissions refer to the sum of NOX and 
SO2, and IDEM chose to use data from the National Emissions 
Inventory, EPA's Emissions Inventory System \22\ for 2016-2018, and 
Clean Air Markets Program Data (CAMPD) \23\ for 2018 to represent the 
most current operations at the time as a reflection of decreasing 
emissions overall. For Q/d, the distance to the closest Class I area 
for all selected sources was Mammoth Cave. IDEM chose a Q/d threshold 
of five to capture a variety of higher emitting sources that were 
representative of 85 percent of SO2 and 77 percent of 
NOX emissions from Indiana sources and to screen out sources 
with either lower emissions or located at farther distances from the 
Class I areas with lower visibility impacts.\24\ This process 
identified 20 sources for a possible four-factor analysis: 11 power 
generating stations and nine non-EGUs (such as steel mills, cement 
kilns, a plastics manufacturer, an aluminum smelter, and electric 
services operations).
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    \21\ LADCO's October 14, 2020, technical memorandum 
``Description of the Sources and Methods Used to Support Q/d 
Analysis for the 2nd Regional Haze Planning Period'' is included in 
appendix M of Indiana's 2021 Regional Haze SIP submittal.
    \22\ EPA's 2016-2018 Emissions Inventory System data is included 
in appendix O of Indiana's 2021 Regional Haze SIP submittal. EPA's 
Emissions Inventory System data is publicly available at https://www.epa.gov/air-emissions-inventories/emissions-inventory-system-eis-gateway.
    \23\ The 2018 CAMPD information is included in appendix E of 
Indiana's 2021 Regional Haze SIP submittal. CAMPD information is 
publicly available at https://campd.epa.gov/.
    \24\ Based on 2018 emissions. See Indiana's 2021 Regional Haze 
SIP submission, Table 7-1 and appendix N. The 2018 Indiana Emissions 
Summary Data from sources reporting under Indiana Administrative 
Code Title 326, Article 2, Rule 6 is included in the docket and is 
publicly available at https://www.in.gov/idem/airquality/reporting/emissions-summary-data/.
---------------------------------------------------------------------------

    IDEM's source selection approach identified the following 36 EGUs 
units at the 11 power generating stations: Indiana Michigan Power 
Company, dba American Electric Power--Rockport Plant (AEP--Rockport), 
Boilers MB1 and MB2; Duke Energy, Inc.--Gibson Generating Station 
(Duke--Gibson), Units 1, 2, 3, 4, and 5; AES Indiana--Petersburg 
Generating Station (AES--Petersburg), Units 1, 2, 3, and 4; Indiana-
Kentucky Electric Corporation (IKEC) and Ohio Valley Electric 
Corporation--Clifty Creek Station (IKEC--Clifty Creek), Units 1, 2, 3, 
4, 5, and 6; Duke Energy Indiana, LLC--Cayuga Generating Station 
(Duke--Cayuga), Units 1 and 2; Southern Indiana Gas and Electric 
Company (SIGECO)--A.B. Brown Generating Station (SIGECO--A.B. Brown), 
Units 1 and 2; Alcoa Power Generating, Inc.--Warrick Power Plant 
(Alcoa--Warrick Power Plant), Unit 4; SIGECO--F.B. Culley Generating 
Station (SIGECO--F.B. Culley), Units 2 and 3; Hoosier Energy REC, 
Inc.--Merom Generating Station (Hoosier Energy--Merom), Units 1SG1, 
2SG1; Northern Indiana Public Service Company, LLC (NIPSCO)--R.M. 
Schahfer Generating Station (NIPSCO--R.M. Schahfer), Units 14, 15, 16A, 
16B, 17, and 18; and Duke Energy Indiana, LLC--R. Gallagher Generating 
Station (Duke--Gallagher), Units 2 and 4.
    The nine non-EGU facilities are: Warrick Newco LLC (Alcoa--Warrick 
Operations); Cleveland-Cliffs Steel, LLC--Burns Harbor, LLC (Burns 
Harbor); Lehigh Cement Company, LLC--Mitchell Plant, Lawrence County 
(Lehigh Cement--Mitchell Plant); Cokenergy LLC; Cleveland-Cliffs Steel, 
LLC--Indiana Harbor East (Indiana Harbor East); Lone Star Industries, 
Inc. dba Buzzi Unicem USA--Greencastle Plant (Lone Star Industries--
Greencastle); United States Steel Corporation--Gary Works (U.S. Steel--
Gary Works); Cleveland-Cliffs Steel, LLC--Indiana Harbor West (Indiana

[[Page 25951]]

Harbor West); and SABIC Innovative Plastics--Mt. Vernon LLC.\25\
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    \25\ Since the time that IDEM evaluated these sources, some 
facilities have changed names. ArcelorMittal USA LLC--Indiana Harbor 
East is now Cleveland-Cliffs Steel, LLC--Indiana Harbor East. 
ArcelorMittal USA LLC--Indiana Harbor West is now Cleveland-Cliffs 
Steel, LLC--Indiana Harbor West. Arcelor Mittal--Burns Harbor, LLC 
is now Cleveland-Cliffs Steel, LLC--Burns Harbor. Alcoa Warrick 
Operations LLC is now Warrick Newco LLC. Lehigh Cement Company LLC--
Mitchell Plant is now Heidelberg Materials US Cement LLC--Mitchell 
Plant.
---------------------------------------------------------------------------

    During the FLM consultation process, NPS and USFS provided IDEM 
with their lists of sources for potential four-factor analyses based on 
Q/d; however, none of the additional sources identified by NPS or USFS 
met IDEM's threshold of Q/d greater than five.\26\ NPS later agreed 
that the units IDEM identified represented a reasonable group of 
sources for potential four-factor analyses. The FLM consultation on 
source selection is further discussed in Section 2.2 of EPA's April 22, 
2025 Technical Support Document (TSD) for this proposed rulemaking, 
which is included in the docket.
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    \26\ The lists of sources suggested for a four-factor analysis 
by NPS and USFS appear in appendix N of Indiana's 2021 Regional Haze 
SIP submittal. Comments from NPS are provided in appendix W of 
Indiana's 2021 Regional Haze SIP submission.
---------------------------------------------------------------------------

    IDEM further refined the list of selected sources by considering 
whether units would continue to operate or whether they had existing 
effective controls such that a full four-factor analysis would likely 
result in a conclusion that no further controls are necessary. Applying 
these criteria, IDEM determined a full four-factor analysis was not 
necessary for the 36 EGUs identified. IDEM selected the remaining nine 
non-EGU facilities for a four-factor analysis as described below. Of 
the emission units that met Indiana's Q/d source selection criteria, 
eight EGUs and one non-EGU facility are no longer operating: Duke--
Gallagher Units 2 and 4 ; NIPSCO--R.M. Schahfer Units 14 and 15 ; AES--
Petersburg Unit 1 (2021) and Unit 2 ; SIGECO--A.B. Brown Units 1 and 2, 
and Lehigh Cement--Mitchell Kilns 1, 2, and 3.
    For the units that are no longer operating, permitting changes,\27\ 
Unit Exemption forms,\28\ and verification from the regional 
transmission organization \29\ are included in the docket.\30\ Any 
major stationary source upon restart is subject to permitting as a new 
source and must comply with requirements pertaining to Federal New 
Source Review and Prevention of Significant Deterioration requirements 
as well as Indiana Administrative Code (IAC), Title 326, Article 2.\31\
---------------------------------------------------------------------------

    \27\ The following permits are available in the docket and on 
IDEM's website: Duke--Gallagher Units 2 and 4, title V permit 043-
44081-00004, https://permits.air.idem.in.gov/44081f.pdf; NIPSCO--
R.M. Schahfer Units 14 and 15, title V permit 073-45762-00008, 
https://permits.air.idem.in.gov/45762f.pdf; AES--Petersburg Unit 1, 
title V permit 125-44230-00002, https://permits.air.idem.in.gov/44230f.pdf and Unit 2 title V permit 125-46357-00002, https://permits.air.idem.in.gov/46357f.pdf; SIGECO--A.B. Brown Units 1 and 
2, title V permit 129-47510-00010, https://permits.air.idem.in.gov/47510f.pdf; and Lehigh Cement--Mitchell, Kilns 1, 2, and 3, title V 
permit 093-47798-00002, https://permits.air.idem.in.gov/47798f.pdf.
    \28\ The EGUs no longer operating have been certified by the 
source owner or operator under the provisions for Unit Exemptions in 
the Acid Rain Program and/or CSAPR NOX and SO2 
Trading Programs.. See 40 CFR 72.8, 40 CFR 97.405, 40 CFR 97.505, 40 
CFR 97.605, CFR 97.705, 40 CFR 97.805. Copies of Unit Exemption 
forms for each of these units are included in the docket.
    \29\ The list of generators from the Midwest Independent System 
Operator (MISO) regional transmission organization is available in 
the docket.
    \30\ Publicly available information that EPA considered in 
addition to the information provided in Indiana's 2021 Regional Haze 
SIP submission and referenced by citations in the notice of proposed 
rulemaking is included in the docket, designated by files names 
preceded by ``Indiana.''
    \31\ Indiana Administrative Code is publicly available at 
https://iar.iga.in.gov/code/2026/326.
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    For the remaining EGUs continuing to operate, IDEM examined the 
facilities for existing effective controls in determining that a full 
four-factor analysis would likely result in the conclusion that no 
further controls are necessary for reasonable progress in the second 
implementation period as described in Section 2 of EPA's April 22, 
2025, TSD.
    Citing to the flexibility allowed under the RHR, Indiana plans to 
reexamine the EGUs in the third planning period because the State has 
found that the landscape for the EGU sector has changed dramatically 
since the last planning period and is continuing to change in the 
second implementation period. In addition, IDEM states, ``fuel costs 
have upended the order in which resources are dispatched by [MISO] to 
meet the region's power generation needs and maintain adequate power 
grid management in the future. Coal fired units that were previously 
dispatched first are now dispatched last. This change in economic 
driven dispatching is expected to result in less reliance on the 
remaining coal fired EGUs and accelerated retirement. As such, Indiana 
believes that conducting four-factor analyses for EGUs during the next 
planning period would result in a better use of resources because much 
of what the State would require based on four-factor analyses conducted 
for the EGUs would become moot as the EGU sector remains in flux as 
sources continue to shutdown units, convert to natural gas, and rely 
more on renewable energy.'' See responses 2 and 3, appendix V of 
Indiana's 2021 Regional Haze SIP submission.
    EPA has provided clarification regarding when it is appropriate to 
forgo a four-factor analysis for sources with existing effective 
control measures. As explained in the 2019 Guidance, Section 3(f), ``A 
source may already have effective controls in place as a result of a 
previous regional haze SIP or to meet another CAA requirement.'' 
Section 3(f) goes on to provide ``examples, which are intended to 
illustrate (in a non-exhaustive fashion) scenarios in which EPA 
believes it may be reasonable for a State not to select a particular 
source for further analysis.''
    As discussed below, IDEM provided information to demonstrate that 
the EGUs have existing effective control measures as described in the 
examples in the 2019 Regional Haze Guidance, Section 3(f).\32\ In 
addition to IDEM's analysis of emissions from 2007 to 2019, EPA also 
considered limits contained in existing permits \33\ and 2018 to 2023 
CAMPD information showing that each unit has consistently implemented 
their existing measures and have achieved, using those measures, a 
reasonably consistent emission rate. With emission limits in the title 
V permits, provisions in Federal consent decrees, historical data 
showing relatively consistent or declining NOX and 
SO2 annual emissions and emission rates, as well as 2028 
projections, the overall emissions are not expected to increase in the 
future. As such, IDEM determined that the existing control measures are 
not necessary to prevent future emission increases and thus not 
necessary to make reasonable progress in the second implementation 
period and that pursuing additional emission reductions through the 
addition of new emission control equipment or emissions limitations is 
not reasonable as a cost-effective method. Section 2.4 of EPA's April 
22, 2025, TSD provides a detailed summary of IDEM's assessment of the 
EGUs continuing to operate.
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    \32\ See also Table 8.3 and appendix F of Indiana's 2021 
Regional Haze SIP submission.
    \33\ IDEM's Air Quality Permits are publicly available at 
https://www.in.gov/ai/appfiles/idem-caats/.
---------------------------------------------------------------------------

    After addressing the EGUs as described above and in EPA's April 22, 
2025 TSD, Indiana provided site-specific four-factor analyses for the 
remaining nine non-EGU facilities identified by IDEM's Q/d source 
selection threshold: Alcoa--Warrick Operations; Burns Harbor; Lehigh 
Cement--Mitchell; Cokenergy LLC;

[[Page 25952]]

Indiana Harbor East; Lone Star Industries--Greencastle; U.S. Steel--
Gary Works; Indiana Harbor West; and SABIC Innovative Plastics--Mt. 
Vernon LLC. The background and four-factor analysis for each of the 
nine units is described below.
2. Emission Measures Necessary To Make Reasonable Progress
    The provisions of 40 CFR 51.308(f)(2)(i) require States to evaluate 
and determine the emission reduction measures that are necessary to 
make reasonable progress by applying the four statutory factors to 
sources in a control analysis. The emission reduction measures that are 
necessary to make reasonable progress must be included in the long-term 
strategy. 40 CFR 51.308(f)(2).
    IDEM's evaluation of each of the nine non-EGU facilities identified 
through its Q/d source selection process is described in Section 2.5 
and 3 of EPA's April 22, 2025 TSD. Each of the four-factor analyses 
provided for these facilities considered all four statutory factors and 
appropriately followed the methods in the EPA Air Pollution Control 
Cost Manual.\34\
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    \34\ See the EPA's Air Pollution Control Cost Manual available 
at https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution.
---------------------------------------------------------------------------

    In addition to the four-factor analyses and evaluations provided by 
IDEM, EPA also considered limits contained in existing permits and 
information from Indiana's Emissions Summary Data \35\ showing that 
each unit has consistently implemented their existing measures and have 
achieved, using those measures, reasonably consistent emission rates. 
With limits in the title V permits, provisions in Federal consent 
decrees, historical data showing relatively consistent or declining 
NOX and SO2 annual emissions, and emission rates 
as well as 2028 projections of overall emissions not expected to 
increase in the future, IDEM determined that the existing emission 
control measures for each of the non-EGUs are not necessary to prevent 
future emission increase in the second implementation period and thus 
not necessary for reasonable progress. As such, IDEM determined that 
additional control measures are not necessary to make reasonable 
progress in the second implementation period and that pursuing 
additional emission reductions through the addition of new emission 
control equipment or emissions limitations is not cost effective.
---------------------------------------------------------------------------

    \35\ Indiana's Emissions Summary Data for 2008--2022 is 
available in the docket and at https://www.in.gov/idem/airquality/reporting/emissions-summary-data/.
---------------------------------------------------------------------------

3. Indiana's Long-Term Strategy
    Each State's long-term strategy must include the enforceable 
emission limitations, compliance schedules, and other measures that are 
necessary to make reasonable progress. 40 CFR 51.308(f)(2). After 
considering information regarding existing effective controls, analyses 
under the four statutory factors in 40 CFR 51.308(f)(2)(i), and the 
five additional factors in 40 CFR 51.308(f)(2)(iv) in addition to other 
requirements in 40 CFR 51.308(f)(2)(ii) described below, Indiana 
developed the State's long-term strategy for the second implementation 
planning period. The measures below represent reductions beyond those 
planned in the first implementation planning period, as well as 
emission reductions due to ongoing air pollution control programs, 
including those that were factored into LADCO's 2028 modeling. The 
following measures are already permanent and federally enforceable.
    On-the-books controls in the second implementation period include:
     Tier 2 Motor Vehicle Emissions and Gasoline Standards Rule 
(40 CFR 80, 85, and 86)
     Tier 3 Motor Vehicle Emission and Fuel Standards (40 CFR 
79, 80, 85, 86, 600, 1036, 1037, 1039, 1042, 1048, 1054, 1065, 1066)
     Tier 4 Non-road Engines and Diesel Fuel Rule (40 CFR 9, 
69, 80 86, 89, 94, 1039, 1048, 1051, 1065, 1068)
     Heavy-Duty Diesel Engine and Highway Diesel Fuel Rule (40 
CFR 69, 80, 86)
     Data Requirements Rule for the 2010 SO2 NAAQS 
(40 CFR 51, Subpart BB)
     Mercury and Air Toxics Standards (MATS) (40 CFR 63, 
subpart UUUUU)
     Boiler Maximum Achievable Control Technology (MACT) (40 
CFR 63, Subpart DDDDD
    On-the-way controls that reflect additional emission reductions 
expected by 2028 include:
     Revised CSAPR Update (40 CFR 97, subpart GGGGG)
4. EPA's Evaluation of Indiana's Compliance With 40 CFR 51.308(f)(2)(i)
    EPA proposes to find that Indiana has satisfied the requirements of 
40 CFR 51.308(f)(2)(i) related to evaluating sources and determining 
the emission reduction measures that are necessary to make reasonable 
progress by considering the four statutory factors. Indiana's selection 
of sources and evaluation of control measures was reasonable and 
consistent with the requirements of 40 CFR 51.308(f)(2)(i). Considering 
the four statutory factors, the projected 2028 visibility conditions 
for Class I areas influenced by emissions from Indiana sources all 
being below the URP in 2028, the historical emissions data, the 
emissions reductions, and the current control technologies, EPA also 
finds Indiana reasonably concluded that no additional measures are 
necessary to make reasonable progress in the second planning period. As 
detailed further below, EPA proposes to approve Indiana's long-term 
strategy under 40 CFR 51.308(f)(2).
    In line with recent proposals from EPA,\36\ it is the Agency's 
policy that, where visibility conditions for a Class I area impacted by 
a State are below the URP and the State has considered the four 
statutory factors, the State will have presumptively demonstrated 
reasonable progress for the second planning period for that area. In 
developing the regulations required by CAA section 169A(b), EPA 
established the concept of the URP for each Class I area. As discussed 
above, for each Class I area, there is a regulatory requirement to 
compare the projected visibility impairment (represented by the 
reasonable progress goal, or ``RPG'') at the end of each planning 
period to the URP (e.g., in 2028 for the second planning period).\37\
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    \36\ 90 FR 16478; 16483-16484, April 18, 2025.
    \37\ We note that RPGs are a regulatory construct that we 
developed to address statutory mandate in section 169B(e)(1), which 
required our regulations to include ``criteria for measuring 
`reasonable progress' toward the national goal.'' Under 40 CFR 
51.308(f)(3)(ii), RPGs measure the progress that is projected to be 
achieved by the control measures a state has determined are 
necessary to make reasonable progress. Consistent with the 1999 RHR, 
the RPGs are unenforceable, though they create a benchmark that 
allows for analytical comparisons to the URP and mid-implementation-
period course corrections if necessary. 82 FR at 3091-3092.
---------------------------------------------------------------------------

    EPA's new policy is that so long as the Class I areas impacted by a 
State are below the URP in 2028 and the State considers the four 
factors, the State will have presumptively demonstrated it has already 
made reasonable progress for the second planning period for that area. 
Indeed, we believe this policy also recognizes the considerable 
improvements in visibility impairment that have been made by a wide 
variety of State and federal programs in recent decades.
    Applying this new policy in our evaluation of Indiana's SIP and as 
further detailed in the paragraphs that follow, EPA agrees with 
Indiana's determination that, for the second planning period, no 
additional measures are necessary to achieve reasonable

[[Page 25953]]

progress towards natural visibility at Class I areas impacted by 
emissions from Indiana sources.
    The SIP submittal included evaluations for 20 emissions sources, 
including consideration of the four statutory factors for nine non-EGU 
facilities and consideration of existing measures at a further 11 power 
generating stations. Based on these evaluations and analyses, the State 
determined that no additional measures were necessary for reasonable 
progress. In reaching this determination, Indiana also considered the 
emissions reductions and visibility improvements that have already 
occurred in the second planning period in nearby Class I areas.
    For Indiana's source selection methodology, IDEM targeted the 
sources with the highest potential to impair visibility at mandatory 
Class I areas. IDEM included a thorough description of its source 
selection methodology. Starting with LADCO's Q/d methodology and 
focusing on SO2 and NOX as the predominant 
species contributing to visibility impairment in the LADCO Class I 
areas, IDEM queried data for all sources reporting to the National 
Emissions Inventory, EPA's Emissions Inventory System for 2016--2018, 
and CAMPD \38\ for 2018 to represent the most current operations at the 
time. IDEM appropriately chose a Q/d threshold of 5 to capture a 
variety of higher emitting sources and to screen out sources with 
either lower emissions or located at farther distances from the Class I 
areas. As noted in section IV.E.1, above, this process identified 20 
sources for a possible four-factor analysis. Overall, the sources 
selected by IDEM for potential four-factor analysis accounted for 81 
percent of the total emissions for SO2 and NOX 
for all sources reporting under Indiana's Emission Reporting Rule at 
Title 326, Article 2, Rule 6 of the Indiana Administrative Code (326 
IAC 2-6) in 2018, including 85 percent of SO2 and 77 percent 
of NOX.
---------------------------------------------------------------------------

    \38\ The 2018 CAMPD information that IDEM relied upon is 
included in appendix E of Indiana's 2021 Regional Haze SIP 
submittal.
---------------------------------------------------------------------------

    In determining which facilities to evaluate through a four-factor 
analysis, IDEM refined the list of sources selected using its Q/d 
threshold by providing adequate justification for no further analysis 
where sources had existing effective controls. For EGUs that are now no 
longer operating, IDEM provided information on emissions from 2009 to 
2019 and results of source apportionment modeling to demonstrate 
statewide emission reductions and projections for SO2 and 
NOX. Compared to the 2018 inventories used in IDEM's source 
selection process,\39\ the emissions reductions from the sources no 
longer operating represent decreases of SO2 by over 7,000 
tons per year (tpy) and NOX by over 9,000 tpy from all the 
sources IDEM selected with Q/d greater than five. These include: Duke--
Gallagher Units 2 and 4 (1,149 ton SO2 and 535 tons 
NOX); NIPSCO--R.M. Schahfer Units 14 and 15 (375 tons 
SO2 and 2,429 tons NOX); AES--Petersburg Unit 1 
and 2 (1,412 tons SO2 and 2,773 tons NOX); 
SIGECO--A.B. Brown Units 1 and 2 (3,527 tons SO2 and 2,112 
tons NOX); and Lehigh Cement--Mitchell Kilns 1, 2, and 3 
(700 tons SO2 and 1,800 tons NOX).
---------------------------------------------------------------------------

    \39\ 2018 CAMPD and 2018 Indiana Emissions Inventory Summary 
Data are available in the docket and at https://campd.epa.gov/; 
https://www.in.gov/idem/airquality/reporting/emissions-summary-data/.
---------------------------------------------------------------------------

    For the selected EGUs continuing to operate, IDEM appropriately 
examined the facilities for existing effective controls, trends in 
SO2 and NOX emissions, and LADCO's 2028 projected 
emissions in determining that a four-factor analysis would not likely 
result in the conclusion that further controls are necessary for 
reasonable progress. In evaluating IDEM's reasoning, EPA also 
considered trends in annual emissions and emission rates from 2018--
2023 CAMPD, emission limits in current title V permits, and the fact 
that the projected 2028 visibility conditions for Class I areas 
influenced by emissions from Indiana sources are below the URP in 2028. 
The EGUs continuing to operate include: AEP--Rockport Boiler MB1 and 
MB2; Duke--Gibson Units 1, 2, 3, 4, 5; AES--Petersburg Units 3, 4; 
IKEC--Clifty Creek Units 1, 2, 3, 4, 5, 6; Duke--Cayuga Units 1, 2; 
Alcoa--Warrick Power Plant Unit 4; SIGECO--F.B. Culley Units 2, 3; 
Hoosier Energy--Merom Units 1SG1, 2SG1; and NIPSCO--R.M. Schahfer Units 
16A, 16B, 17, 18. As summarized below, IDEM adequately documented that 
these EGUs are effectively controlled for SO2 and 
NOX for the second implementation period in determining that 
a full four-factor analysis would likely result in the conclusion that 
no further controls are necessary for reasonable progress.
     AEP--Rockport Boiler MB1 and MB2: The SO2 and 
NOX emission limits and plant-wide tonnage caps are in a 
Federal consent decree,\40\ SO2 emission rates are below the 
0.2 pounds per million British thermal units (lbs/MMBtu) for coal-fired 
EGUs in MATS, and NOX emission rates are below the 0.08 lbs/
MMBtu level for units with selective catalytic reduction (SCR) under 
the Federal ``Good Neighbor Plan''.\41\
---------------------------------------------------------------------------

    \40\ Fifth Joint Modification To Consent Decree with the United 
States District Court for the Southern District of Ohio in the 
lawsuit entitled United States, et al. v. American Electric Power 
Service Corp., et al., Civil Action Nos. 99-1182 (EAS) and 99-1250 
(EAS), (AEP Consent Decree). The AEP Consent Decree is available in 
the docket and at https://www.epa.gov/sites/default/files/documents/americanelectricpower-cd_1.pdf. See also 84 FR 26705, June 7, 2019.
    \41\ Federal ``Good Neighbor Plan'' for the 2015 Ozone National 
Ambient Air Quality Standards,'' Final Rule, 88 FR 36654, June 5, 
2023. On October 29, 2024, EPA issued a final rule to 
administratively stay the effectiveness of the Good Neighbor Plan's 
requirements for all sources covered by that rule as promulgated 
where an administrative stay was not already in place, including 
Indiana. 89 FR 87960, November 6, 2024.
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     Duke--Gibson Units 1, 2, 3, 4, and 5: The SO2 
emission rates for all units are below the MATS, NOX 
emission rates are below the 0.08 lbs/MMBtu level for units with SCR 
under the Good Neighbor Plan, and the flue gas desulfurization (FGD) 
and SCR systems achieve high control efficiencies.
     AES--Petersburg Units 3 and 4: The FGD systems achieve 
high percentages of SO2 control efficiency, actual 
SO2 emission rates for both units are below the MATS, and 
SO2 and NOX emission caps and limits are in place 
under a 2020 Federal consent decree.
     IKEC--Clifty Creek Units 1, 2, 3, 4, 5, and 6: The FGD 
systems achieve 98 percent control efficiency, the SCR and OFA systems 
achieve 70-90 percent control efficiency on an annual basis, 
SO2 limits are contained Indiana's SIP at 40 CFR 52.770(d), 
actual SO2 emission rates for all six units are below MATS, 
and NOX emissions are progressively constrained on an annual 
basis under the Revised CSAPR Update Rule. While NPS provided an 
estimate for cost effectiveness of the addition of SCR to Unit 6 at 
$6,100/ton of NOX removed, IDEM determined that additional 
emission reductions through the addition of new emission control 
equipment would not be cost-effective.
     Duke--Cayuga Units 1 and 2: The SO2 emission 
rates are below the MATS, and the FGD and SCR systems achieve control 
efficiencies near 90 percent or more.
     Alcoa--Warrick Power Plant: Unit 4 is subject to BART 
emission limitations from the first implementation period on a 
pollutant specific basis and is currently operating controls to meet 
those BART emission limits, SO2 and NOX controls 
are in place, and actual SO2 emission rates are below MATS.
     SIGECO--F.B. Culley Units 2 and 3: Federally enforceable 
SO2 and NOX emission limits and conditions 
regarding operation of the FGD and SCR control systems are contained in 
the

[[Page 25954]]

Federal consent decree and in Indiana's SIP at 52.770(c)(190), 
SO2 emission rates are below the MATS, and the FGD system 
achieves a control efficiency of 99 percent.
     Hoosier Energy--Merom Units 1SG1 and 2SG1: The FGD and SCR 
control systems achieve greater than 90 percent control efficiency, 
SO2 emission rates are below MATS, and NOX 
emission rates are below the 0.08 lbs/MMBtu level for units with SCR 
under the Good Neighbor Plan.
     NIPSCO--R.M. Schahfer: Units 16A and 16B are natural gas 
turbines emitting less than 1 tpy SO2 and 17 tpy 
NOX. For Units 17 and 18, FGD systems achieve 99 percent 
control efficiency, SO2 emission rates are below MATS, and 
NOX emission rates are below 0.199 lbs/MMBtu for units with 
low NOX burners (LNB) under the Good Neighbor Plan.
    In addition to demonstrating that these EGUs are effectively 
controlled for the second implementation period, Indiana's analysis of 
emissions from 2007 to 2019 and projected emissions from 2028 
projections, in addition to the CAMPD information from 2018 to 2023 
that EPA considered along with control measures in Federal consent 
decrees and title V permits, showed each unit had consistently 
implemented their existing measures, had demonstrated declining trends 
in total annual emissions at each facility, and emissions were not 
projected to increase through 2028. Additionally, the projected 2028 
visibility conditions for Class I areas influenced by emissions from 
Indiana sources are below the URP in 2028.\42\ As such, IDEM adequately 
demonstrated that additional measures for these units are not necessary 
to make reasonable progress during the second implementation period.
---------------------------------------------------------------------------

    \42\ See Indiana's 2021 Regional Haze SIP submission, Table 23-1 
and appendix L.
---------------------------------------------------------------------------

    Indiana's long-term strategy included Federal on-the-books and on-
the-way controls. Indiana did not rely on additional measures as part 
of the long-term strategy to make reasonable progress in the second 
planning period for the units that IDEM identified through its Q/d 
source selection process. For the units no longer operating, emission 
reductions have already taken place during the second implementation 
period. For the EGUs continuing to operate, IDEM sufficiently 
demonstrated that existing effective controls are in place as described 
in the 2019 Guidance, section 3(f) in determining that a full four-
factor analysis would likely result in the conclusion that no further 
controls are necessary for reasonable progress. IDEM's analysis of 
emissions from 2007 to 2019 and 2028 projections, CAMPD information 
from 2018 to 2023, limits contained in existing permits and Federal 
consent decrees, and the fact that projected 2028 visibility conditions 
for Class I areas influenced by emissions from Indiana sources are 
below the URP in 2028 support IDEM's determination that additional 
measures at these EGUs are not necessary to make reasonable progress 
for the second implementation period.
    For the nine non-EGU facilities, Indiana provided a thorough 
analysis of existing measures or a full four-factor analysis that 
appropriately followed the methods in the EPA Air Pollution Control 
Cost Manual.\43\ IDEM documented the range of cost effectiveness for 
control options considered technically feasible in the four-factor 
analyses.
---------------------------------------------------------------------------

    \43\ See EPA Air Pollution Control Cost Manual, available at 
https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution.

                       Table 1--Estimated Cost Effectiveness of Control Options Evaluated
----------------------------------------------------------------------------------------------------------------
               Facility                          Unit                Control option         Cost effectiveness
----------------------------------------------------------------------------------------------------------------
Alcoa--Warrick Operations............  Potlines 2 through 6...  FGD....................  $16,800 per ton of SO2
                                       Anode Baking Ring        FGD....................  $45,000 per ton of SO2
                                        Furnace and A-446 Dry
                                        Alumina Scrubbers.
Burns Harbor.........................  Battery Nos. 1 and 2...  Spray Dryer Absorber     $5,300-$6,300 per ton
                                                                 (SDA).                   of SO2
                                       Clean Coke Oven Gas      Desulfurization........  $4,000 per ton of SO2
                                        Export Line and Flare.
                                       Power Station Boilers    SDA....................  $16,100 to 42,000 per
                                        Nos. 7 through 12.                                ton of SO2
                                                                Dry Sorbent Injection    $8,800 to $16,700 per
                                                                 (DSI).                   ton of SO2
Indiana Harbor East..................  80'' Hot Strip Mill      Ultra-low NOX Burners    $6,900 to $9,100 per
                                        Walking Beam Furnaces    (ULNB).                  ton of NOX
                                        Nos. 5 and 6.
                                       Sinter Plant Windbox...  SDA....................  $28,900 per ton of SO2
                                                                DSI....................  $38,200 per ton of SO2
Lone Star Industries--Greencastle....                           DSI....................  $10,035 per ton to
                                                                                          remove 47 tons of SO2
                                                                                          per year
                                                                Selective Non-Catalytic  $1,679 per ton to
                                                                 Reduction.               remove 685 tons of NOX
                                                                                          per year
U.S. Steel--Gary Works...............  84'' Hot Strip Mill      LNB....................  $14,142/ton to reduce
                                        Reheat Furnaces.                                  211 tons of NOX
                                       Waste Heat Boiler Nos.   LNB....................  $6,130 and $6,344 per
                                        1 and 2.                                          ton to reduce 58 and
                                                                                          56 tons of NOX per
                                                                                          year, respectively
SABIC Innovative Plastics--Mt. Vernon  Co-generation Unit.....  SCR....................  $25,691 per ton to
 LLC.                                                                                     remove 101 tons of NOX
                                                                                          per year
                                       Phosgene Carbonyl        Wet Packed Tower         $12,449 per ton to
                                        Sulfide Vent Oxidizer    Absorber.                remove 542 tons of SO2
                                        and Flare.                                        per year
----------------------------------------------------------------------------------------------------------------

    For the other units evaluated at the non-EGU facilities, the 
analyses thoroughly demonstrated that no reasonable set of 
SO2 or NOX control measures were identified 
beyond what is currently installed and operated as described in Section 
3 of EPA's April 22, 2025 TSD.
    The emission reductions that have already occurred during the 
second implementation period at Duke--Gallagher, NIPSCO--R.M. Schahfer, 
AES--Petersburg, SIGECO--A.B. Brown, and Lehigh Cement--Mitchell 
represent permanent reductions in SO2 and NOX 
from Indiana sources that have reduced visibility impairment at 
impacted Class I areas. These decreases in emissions represent over 
7,000 tpy SO2 and over 9,000 tpy NOX from all the 
sources IDEM selected with Q/d greater than five based on 2018 
emissions. With a relatively small potential for additional emission 
reductions identified in the four-factor analyses compared to emission 
reductions that

[[Page 25955]]

have already taken place, IDEM provided a reasoned basis for its 
conclusions that pursuing additional emission reductions through the 
addition of new emission control measures or emissions limitations is 
not cost-effective for the second implementation period. The trends in 
NOX and SO2 emissions noted in IDEM's progress 
report discussed below and its analysis of emissions from 2007 to 2019 
and 2028 projections, along with the 2018 to 2023 emissions data 
considered by EPA demonstrate how Indiana's long-term strategy will 
continue to make significant emissions reductions during the second 
implementation period. Indiana's SIP revision shows that these measures 
will achieve substantial SO2 and NOX emission 
reductions beyond those included in its first implementation period. 
The reductions in emissions that have already occurred during the 
second implementation period, along with on-the-books and on-the-way 
control measures, contribute to Indiana's emission reductions and the 
associated visibility improvements at the affected Class I areas for 
the second implementation planning period.
    EPA proposes to find that Indiana has satisfied the requirements of 
40 CFR 51.308(f)(2)(i) related to evaluating sources and determining 
the emission reduction measures that are necessary to make reasonable 
progress by applying the four statutory factors to sources in a control 
analysis. Indiana's SIP submission reasonably applied the Q/d source 
selection process in relying on the closest Class I area and the 
emissions of SO2 and NOX. IDEM examined a 
reasonable set of sources, including sources identified by FLMs. In 
addition, IDEM adequately explained its decision to focus on the two 
pollutants--SO2 and NOX--that currently drive 
visibility impairment within the LADCO region. EPA proposes to find 
that Indiana adequately supported its conclusions for its top-impacting 
sources in determining that no additional controls are necessary for 
reasonable progress in the second implementation period. EPA is basing 
this proposed finding on the State's examination of its largest 
operating EGU and non-EGU sources, particularly the State's 
consideration of the four statutory factors, the projected 2028 
visibility conditions for Class I areas influenced by emissions from 
Indiana sources all being below the URP in 2028, the historical 
emissions data, the emission reductions that have already taken place 
during the second implementation period, and the current control 
technologies.
5. Consultation With States
    The consultation requirements of 40 CFR 51.308(f)(2)(ii), provide 
that States must consult with other States that are reasonably 
anticipated to contribute to visibility impairment in a Class I area to 
develop coordinated emission management strategies containing the 
emission reductions measures that are necessary to make reasonable 
progress. The provisions of 40 CFR 51.308(f)(2)(ii)(A) and (B) require 
States to consider the emission reduction measures identified by other 
States as necessary for reasonable progress and to include agreed upon 
measures in their SIPs, respectively. The provisions of 40 CFR 
51.308(f)(2)(ii)(C) speak to what happens if States cannot agree on 
what measures are necessary to make reasonable progress. States may 
satisfy the requirement of 40 CFR 51.308(f)(2)(ii) to engage in 
interstate consultation with other States that have emissions that are 
reasonably anticipated to contribute to visibility impairment in a 
given Class I area under the auspices of intra- and inter-RPO 
engagement.
    Although Indiana has no mandatory Class I Federal areas within its 
borders, Indiana has previously been shown to have sources with 
emissions that impact visibility at downwind Class I Federal areas. 
Indiana consulted with other States to develop a coordinated emission 
management approach to its regional haze SIP and to address Indiana's 
impact on nearby Class I areas. IDEM participated in the LADCO and 
inter-RPO processes which developed the technical information needed 
for such coordinated strategies.
    Indiana participated in the LADCO Regional Haze Technical Workgroup 
meetings with other LADCO States, FLMs, and EPA Region 5. Indiana also 
consulted with other States and Tribes, receiving and responding to 
letters \44\ from Arkansas, Missouri, Metro 4/SESARM/VISTAS,\45\ MANE-
VU,\46\ Arkansas, Missouri. IDEM replied with emissions analysis and 
modeling results to demonstrate Indiana is meeting the State's regional 
haze obligations to the surrounding States with Class I areas and that 
no further analysis is necessary for the sources identified by the 
States and RPOs. IDEM did not receive any replies disagreeing with 
their responses. Section 4 of EPA's April 22, 2025 TSD provides a 
detailed summary of Indiana's consultation with States.
---------------------------------------------------------------------------

    \44\ See Section 3.4, 23, and appendix K and AA of Indiana's 
2021 Regional Haze SIP submittal.
    \45\ Metro 4/SESARM/VISTAS refers to the Southeastern States Air 
Resources Managers, Inc. (SESARM) and the Visibility Improvement 
State and Tribal Association of the Southeast (VISTAS) as the RPO 
for Alabama, Florida, Georgia, Kentucky, Mississippi, North 
Carolina, South Carolina, Tennesse, Virginia, West Virginia, the 
Eastern Band of Cherokee Indians, and Knox County, Tennessee 
(representing the 17 Southeastern local air agencies).
    \46\ The Mid-Atlantic/Northeast Visibility Union (MANE-VU) is 
the RPO for the Northeastern and Mid-Atlantic states and Tribal 
governments, which include Connecticut, Delaware, the District of 
Columbia, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, 
New York, Pennsylvania, Penobscot Indian Nation, Rhode Island, St. 
Regis Mohawk Tribe, and Vermont.
---------------------------------------------------------------------------

    EPA proposes to find that Indiana has satisfied the consultation 
requirements of 40 CFR 51.308(f)(2)(ii). Indiana has met the 
requirements of 40 CFR 51.308(f)(2)(ii)(A) and (B) with its 
participation in the LADCO consultation process plus its individual 
consultation meetings with contributing States. There were no 
disagreements with another State; therefore, 40 CFR 51.308(f)(2)(ii)(C) 
does not apply to Indiana.
    The requirements of 40 CFR 51.308(f)(2)(iii) provide that a State 
must document the technical basis for its decision making to determine 
the emission reductions measures that are necessary to make reasonable 
progress. The documentation requirement of 40 CFR 51.308(f)(2)(iii) 
provides that States may meet their obligations to document the 
technical bases on which they are relying to determine the emission 
reductions measures that are necessary to make reasonable progress 
through an RPO, as long as the process has been ``approved by all State 
participants.'' Indiana adequately documented the technical basis, 
including the modeling, monitoring, engineering, costs, and emissions 
information that was relied on in determining the emission reduction 
measures that are necessary to make reasonable progress.
    For modeling, IDEM documented the modeling done by LADCO to 
determine visibility projections and contributions to impairment at the 
Class I areas. Indiana included justification for the 2016 base year 
selection and the 2028 emission projections based on ERTAC forecasts 
and state-reported changes.
    For monitoring, IDEM described how ambient air quality monitoring 
data were analyzed to produce a conceptual understanding of the air 
quality problems contributing to haze as well as to project visibility 
conditions in 2028 through LADCO's modeling and EPA's Updated 2028 
Visibility Air Quality Modeling. IDEM noted that LADCO relied upon the 
IMPROVE monitoring data to track the chemical composition

[[Page 25956]]

of PM2.5 in haze at Class I areas in the LADCO region, which 
included ammonium nitrate, ammonium sulfate, elemental carbon, organic 
carbon, sea salt, and inorganic soil. IDEM also documented IMPROVE 
monitoring data for several Class I areas from the 2000-2004, 2009-
2013, 2014-2018 monitored baselines along with graphs depicting their 
respective glidepaths and monitored visibility for the 20 percent most 
impaired days on an annual basis over the same time period.
    For emissions information, IDEM provided data for 2007 through 
2019, the most recent data years available at the time, from various 
sources for each unit screened in using Indiana's Q/d source selection 
threshold. Emissions data were obtained from EPA's Emissions Inventory 
System, CAMPD, and the National Emissions Inventory (NEI). 
Additionally, EPA considered 2011-2022 information from Indiana's 
Emissions Summary Data and 2018-2022 emissions from CAMPD. Data from 
2016 for annual emissions of NOX, SO2, 
PM2.5, and NH3 that was used in LADCO's modeling 
relied upon the 2016 inventory developed by the National Emissions 
Inventory Collaborative described above as well as forecasts from ERTAC 
with state-reported changes to EGUs through 2020. The pollutants 
inventoried by Indiana for the photochemical modeling included 
NOX, SO2, VOCs, PM2.5, and 
PM10 data collected through Indiana's emissions reporting 
rules. Since ammonia emissions are not reported to Indiana, modeled 
estimates were provided by LADCO.
    For engineering and costs, Indiana provided site-specific four-
factor analyses that evaluated potential engineering designs and costs 
for various NOX and SO2 emission control systems 
for the nine non-EGU facilities as previously mentioned.
    EPA proposes to find that such documentation of the technical basis 
of the long-term strategy, including the modeling, monitoring, 
engineering, costs, and emissions information discussed above, 
satisfies the requirements of 40 CFR 51.308(f)(2)(iii).
    The provisions of 40 CFR 51.308(f)(2)(iii) require that the 
emissions information considered to determine the measures that are 
necessary to make reasonable progress include information on emissions 
for the most recent year for which the State has submitted triennial 
emissions data to EPA (or a more recent year), with a 12-month 
exemption period for newly submitted data. As previously mentioned 
above, IDEM participated in the development of technical analyses, 
including emission inventory information, by LADCO and its member 
States, and is relying in part on those analyses to satisfy the 
emission inventory requirements. Emissions for the 2016 base year and 
the 2028 projected year used in LADCO's modeling address elements of 40 
CFR 51.308(f)(6)(v) of the Regional Haze Rule, which requires that 
States provide recent and future year emissions inventories of 
pollutants anticipated to contribute to visibility impairment in any 
Class I areas. Indiana's 2021 Regional Haze SIP revision for the second 
implementation period also included 2017 NEI emission data, which 
corresponds to the year of the most recent triennial NEI at the time of 
Indiana's 2021 Regional Haze SIP submission, as required under 40 CFR 
51.308(f)(2)(iii) of the Regional Haze Rule. Based on IDEM's 
consideration and analysis of the 2017 emission data in its SIP 
submission, EPA proposes to find that Indiana has satisfied the 
emissions information requirement in 40 CFR 51.308(f)(2)(iii).
6. Five Additional Factors
    In addition to the four statutory factors, States must also 
consider the five additional factors listed in 40 CFR 51.308(f)(2)(iv) 
in developing their long-term strategies. EPA proposes to find that 
Indiana adequately considered those factors in developing this 
submission.
    As required by 40 CFR 51.308(f)(2)(iv)(A), Indiana considered 
emission reductions due to ongoing air pollution control programs. IDEM 
documented significant emission reductions based on current emission 
control strategies at its sources that have reduced visibility 
impairment at all surrounding Class I areas. IDEM noted ongoing Federal 
emission control programs that have reduced and will continue to reduce 
visibility-impairing pollutants from Indiana point sources, as well as 
on-road and non-road mobile sources, in the second implementation 
period. For point sources, these programs included Federal provisions 
for title V permitting actions; Boiler MACT; Mercury and Air Toxics 
Standards for power plants; Data Requirements Rule for the 2010 
SO2 NAAQS; and Revised CSAPR Update. For on-road mobile 
sources, Indiana cited to Federal regulations for the Tier 2 Motor 
Vehicle Emissions and Gasoline Standards Rule, Tier 3 Motor Vehicle 
Emission and Fuel Standards, and Heavy-Duty Diesel Engine and Highway 
Diesel Fuel Rule. For non-road mobile sources, IDEM cited to Federal 
regulations for the Tier 4 Nonroad Engines and Diesel Fuel Rule.
    As required by 40 CFR 51.308(f)(2)(iv)(B), Indiana's consideration 
of measures to mitigate the impacts of construction activities in its 
SIP submission referred to the State's title V permit program as well 
as LADCO's inclusion of building construction, road construction, 
agricultural dust, and road dust in the modeling, which identified 
contributions to visibility impairment for consideration by the States.
    Pursuant to 40 CFR 51.308(f)(2)(iv)(C), Indiana's SIP submission 
addressed schedules for source retirements and replacements.
    In considering smoke management for prescribed burns as required in 
40 CFR 51.308(f)(2)(iv)(D), Indiana's Open Burning Rule at 326 IAC 4-1 
addresses open burning, including prescribed burns used for 
agricultural and wildland vegetation management purposes. Under 326 IAC 
4-1-3, burning of vegetation for agricultural maintenance purposes is 
exempt from the open burning rules on agricultural land, farms, 
orchards, nursery, tree farms, cemeteries, and drainage ditches. 
Burning of natural growth for the purpose of land management, such as 
wildlife habitat maintenance, forestry purposes, natural area 
management, and ecosystem management generally requires IDEM approval. 
The exceptions are for burning conducted on properties owned by the 
Indiana Department of Natural Resources, municipal or county 
governments, the US Department of Interior, the US Department of 
Agriculture, or USFS. Indiana's rules provide that such prescribed 
burns are not allowed during unfavorable meteorological conditions, 
including high winds, temperature inversions, air stagnation, or when a 
pollution alert or ozone action day has been declared. To ensure smoke 
from such activities is accounted for in the visibility projections, 
IDEM noted that LADCO's modeling included a sector for wild and 
prescribed fires.
    As required by 40 CFR 51.308(f)(2)(iv)(E), Indiana considered the 
anticipated net effect on visibility improvements due to projected 
changes in emissions from point, area, and mobile sources during the 
second implementation period addressed by the long-term strategy. The 
visibility improvement expected during the second implementation period 
was estimated using LADCO's 2016 base year and 2028 future year 
inventory components to simulate 2016 and 2028 air quality. As 
described above, for EGUs, projected changes for 2028

[[Page 25957]]

emissions in LADCO's modeling platform were based on ERTAC forecasts 
and state-reported changes. For most other emission sectors, LADCO 
relied upon EPA's 2016 and 2028 inventory estimates for projected 
changes in sectors such as agriculture, on-road and non-road mobile, 
rail, commercial marine, point and nonpoint oil and gas, residential 
wood combustion, wild and prescribed fires, and Mexico and Canada 
anthropogenic emissions. The projected changes in EPA's 2016 and 2028 
inventory estimates take into account Federal on-the-books controls 
such as those listed in Indiana's long-term strategy, above.
    IDEM also demonstrated that visibility conditions in the LADCO 
Class I Areas have shown continued improvement relative to baseline 
conditions. As depicted in LADCO's 2021 TSD, 2016 visibility impairment 
conditions at the LADCO Class I Areas on the 20 percent most impaired 
days as well as the 20 percent clearest days were below their 
respective glidepaths. By the end of the second implementation period 
in 2028, both LADCO's projections and EPA's Updated 2028 Visibility Air 
Quality Modeling show 2028 visibility conditions will remain below the 
URP glidepaths for the LADCO Class I Areas.
    After weighing the four-factor analyses and the five additional 
required factors, Indiana determined that the existing emission 
controls for the sources identified above IDEM's Q/d threshold are 
effective for the second implementation period and that additional 
measures are not necessary to meet second implementation period 
regional haze SIP requirements. IDEM's process for selecting sources 
for four-factor analyses represented 81 percent of the total 
SO2 and NOX emissions for all sources reporting 
under 326 IAC 2-6, including 85 percent of SO2 and 77 
percent of NOX. IDEM provided an analytical means for 
refining the list of sources selected by evaluating EGUs and non-EGUs 
for demonstration of existing effective controls or four-factor 
analysis. For the add-on controls evaluated for the units selected for 
four-factor analyses, Indiana determined that the controls evaluated 
were not cost effective to achieve emission reductions during the 
second implementation period. IDEM reflected upon the steady and 
significant improvement in visibility at each of the Class I areas 
impacted by sources in Indiana and noted that LADCO's modeling shows 
continued improvement with 2028 projections below their URP glidepaths 
in 2028. As discussed under the progress report elements below, from 
2007 to 2019, SO2 emissions from all Indiana EGUs decreased 
by 210,180 tons or 81 percent while NOX emissions decreased 
by 46,360 tons or 50 percent. The decreasing trend continues with the 
permanent emission reductions that have already occurred during the 
second implementation period, representing over 7,000 tpy of 
SO2 and over 9,000 tpy of NOX from all the 
sources identified by IDEM's Q/d selection process based on 2018 
emissions.
    Given all these factors, Indiana demonstrated that Federal on-the-
books and on-the-way controls are sufficient to make reasonable 
progress in the second implementation period. EPA proposes to find that 
Indiana reasonably considered and satisfied the requirements for each 
of the five additional factors in 40 CFR 51.308(f)(2)(iv) in developing 
its long-term strategy.

F. RPGs

    The provisions of 40 CFR 51.308(f)(3) contain the requirements 
pertaining to RPGs for each Class I area. Under 40 CFR 51.308(f)(3)(i), 
a State, in which a mandatory Class I area is located, is required to 
establish RPGs--one each for the most impaired and clearest days--
reflecting the visibility conditions that will be achieved at the end 
of the implementation period as a result of the emission limitations, 
compliance schedules and other measures required under paragraph (f)(2) 
to be in States' long-term strategies, as well as implementation of 
other CAA requirements. The long-term strategies as reflected by the 
RPGs must provide for an improvement in visibility on the most impaired 
days relative to the baseline period and ensure no degradation on the 
clearest days relative to the baseline period. The provisions of 40 CFR 
51.308(f)(3)(ii) apply in circumstances in which a Class I area's RPG 
for the most impaired days represents a slower rate of visibility 
improvement than the uniform rate of progress calculated under 40 CFR 
51.308(f)(1)(vi). Under 40 CFR 51.308(f)(3)(ii)(A), if the State in 
which a mandatory Class I area is located establishes an RPG for the 
most impaired days that provides for a slower rate of visibility 
improvement than the URP, the State must demonstrate that there are no 
additional emission reduction measures for anthropogenic sources or 
groups of sources in the State that would be reasonable to include in 
its long-term strategy. The provisions of 40 CFR 51.308(f)(3)(ii)(B) 
requires that if a State contains sources that are reasonably 
anticipated to contribute to visibility impairment in a Class I area in 
another State, and the RPG for the most impaired days in that Class I 
area is above the URP, the upwind State must provide the same 
demonstration. Because Indiana has no Class I areas within its borders 
to which the requirements of the visibility protection program apply in 
40 CFR part 81, subpart D, Indiana is subject only to 40 CFR 
51.308(f)(3)(ii)(B), but not 40 CFR 51.308(f)(3)(i) or (f)(3)(ii)(A).
    Under 40 CFR 51.308(f)(3)(ii)(B), a State that contains sources 
that are reasonably anticipated to contribute to visibility impairment 
in a Class I area in another State for which a demonstration by the 
other State is required under 40 CFR 51.308(f)(3)(ii)(B) must 
demonstrate that there are no additional emission reduction measures 
that would be reasonable to include in its long-term strategy. Section 
23 of Indiana's SIP submission shows that at the Class I areas impacted 
by emissions from Indiana, the 2028 projected visibility impairment is 
not above the adjusted URP glidepaths for the 20 percent most impaired 
days and ensures no degradation on the 20 percent clearest days. 
Therefore, EPA proposes that the demonstration requirement under 40 CFR 
51.308(f)(3)(ii)(B) as it pertains to these areas is not triggered.
    EPA proposes to determine that Indiana has satisfied the applicable 
requirements of 40 CFR 51.308(f)(3) relating to RPGs.

G. Monitoring Strategy and Other Implementation Plan Requirements

    The requirements of 40 CFR 51.308(f)(6) specify that each 
comprehensive revision of a State's regional haze SIP must contain or 
provide for certain elements, including monitoring strategies, 
emissions inventories, and any reporting, recordkeeping and other 
measures needed to assess and report on visibility. A main requirement 
of this subsection is for States with Class I areas to submit 
monitoring strategies for measuring, characterizing, and reporting on 
visibility impairment. Compliance with this requirement may be met 
through participation in the IMPROVE network.
    As noted above, Indiana does not have any mandatory Class I Federal 
areas located within its borders to which the requirements of the 
visibility protection program apply in 40 CFR part 81, subpart D. 
Therefore, 40 CFR 51.308(f)(6)(i), (ii), and (iv) do not apply.
    The provisions of 40 CFR 51.308(f)(6)(iii) require States with no 
Class I areas to include procedures by which monitoring data and other

[[Page 25958]]

information are used in determining the contribution of emissions from 
within the State to regional haze visibility impairment at Class I 
areas in other States. States with Class I areas must establish a 
monitoring program and report data to EPA that is representative of 
visibility at the Class I Federal areas. The IMPROVE network meets this 
requirement. Indiana stated that, as a participant in LADCO, it 
reviewed information about the chemical composition of baseline 
monitoring data at Class I Federal areas in the LADCO region to 
understand the sources of haze causing pollutants. IDEM does not 
operate any monitoring sites under the Federal IMPROVE program and, 
therefore, does not require approval of its monitoring network under 
the Regional Haze Rule. IDEM relies upon participation in the IMPROVE 
network as part of the State's monitoring strategy for regional haze to 
review progress and trends in visibility at Class I areas that may be 
affected by emissions from Indiana, for comprehensive periodic 
revisions of this implementation plan, and for periodic reports 
describing progress towards the RPGs for those areas.
    The provisions of 40 CFR 51.308(f)(6)(v) require SIPs to provide 
for a statewide inventory of emissions of pollutants that are 
reasonably anticipated to cause or contribute to visibility impairment, 
including emissions for the most recent year for which data are 
available. In appendix O of its SIP submission, Indiana provided 
statewide emission inventories for 2016-2018 in EPA's Emissions 
Inventory System, as the most recent years available at the time of the 
State's SIP submission. EPA's Emissions Inventory System is used to 
develop the NEI, which provides for, among other things, a triennial 
state-wide inventory of pollutants that are reasonably anticipated to 
cause or contribute to visibility impairment. Indiana's SIP submission 
at Section 5.13 and 5.15 also provided a summary of SO2, 
NOX, PM2.5, VOCs, and NH3 emissions 
for 2016 that LADCO used in developing Q/d metrics and the 2016 base 
year emissions inventory to project emissions to year 2028. 
Additionally, as described in further detail under the progress report 
elements, IDEM provided more recent data through 2019 from CAMPD to 
depict trends in EGU emissions, which demonstrated an 81 percent 
decrease in SO2 emissions and a 50 percent decrease in 
NOX emissions from 2007 to 2019.
    The provisions of 40 CFR 51.308(f)(6)(v) also require States to 
include estimates of future projected emissions and include a 
commitment to update the inventory periodically. For future projected 
emissions, Indiana relied on the LADCO modeling and analysis, which 
estimated 2028 projected emissions of SO2 and NOX 
for specific facilities and emission groups in the LADCO States to 
provide an assessment of expected future year air quality based on 2016 
emissions as well as ERTAC and State forecasts. In addition, Indiana 
annually updates its Emissions Summary Data for pollutants anticipated 
to cause or contribute to visibility impairment in Class I areas to 
support future regional haze progress reports and SIP revisions.
    EPA proposes to find that Indiana has met the requirements of 40 
CFR 51.308(f)(6) as described above, including through its continued 
participation in LADCO, its own statewide Emissions Summary Data, and 
its emissions reporting to EPA's Emissions Inventory System.

H. Requirements for Periodic Reports Describing Progress Towards the 
RPGs

    The provisions of 40 CFR 51.308(f)(5) require that periodic 
comprehensive revisions of States' regional haze plans also address the 
progress report requirements of 40 CFR 51.308(g)(1) through (5). The 
purpose of these requirements is to evaluate progress towards the 
applicable RPGs for each Class I area within the State and each Class I 
area outside the State that may be affected by emissions from within 
that State. The provisions of 40 CFR 51.308(g)(1) and (2) apply to all 
States and require a description of the status of implementation of all 
measures included in a State's first implementation period regional 
haze plan and a summary of the emission reductions achieved through 
implementation of those measures. The provisions of 40 CFR 51.308(g)(3) 
apply only to States with Class I areas within their borders and 
requires such States to assess current visibility conditions, changes 
in visibility relative to baseline (2000-2004) visibility conditions, 
and changes in visibility conditions relative to the period addressed 
in the first implementation period progress report. The provisions of 
51.308(g)(4) apply to all States and requires an analysis tracking 
changes in emissions of pollutants contributing to visibility 
impairment from all sources and sectors since the period addressed by 
the first implementation period progress report. This provision further 
specifies the year or years through which the analysis must extend 
depending on the type of source and the platform through which its 
emission information is reported. Finally, 40 CFR 51.308(g)(5), which 
also applies to all States, requires an assessment of any significant 
changes in anthropogenic emissions within or outside the State have 
occurred since the period addressed by the first implementation period 
progress report, including whether such changes were anticipated and 
whether they have limited or impeded expected progress towards reducing 
emissions and improving visibility.
    Indiana's previous progress report, which was a 5-year progress 
report submitted as a SIP revision for the first implementation period 
on March 30, 2016,\47\ included NOX and SO2 
emission inventories from CAMPD for 2005, 2009, 2013 for EGUs, 
Indiana's Emissions Summary Data from 2005--2014 for contributing 
sources, as well as inventories from 2005 and 2011 with 2018 
projections for the sources categories of point, mobile, non-road, EGU, 
and area sources. Based on Indiana's Emissions Summary Data covering 
the period 2010 to 2014 for contributing sources, Indiana's 2016 5-year 
progress report showed a decrease in SO2 emissions by 28 
percent and a decrease in NOX emissions by 12 percent. Over 
the longer period from 2005 to 2014, IDEM documented a decrease in 
SO2 emissions by 64 percent and NOX emissions by 
42 percent. See 82 FR 57694, December 7, 2017, and 83 FR 4847, February 
2, 2018.
---------------------------------------------------------------------------

    \47\ Indiana's March 30, 2016 Five-Year Progress Report is 
available in the docket for EPA-R05-OAR-2016-0211.
---------------------------------------------------------------------------

    For the second implementation period SIP submission, the 2019 
Guidance recommends the progress report cover the first full year that 
was not incorporated into the previous progress report through a year 
that is as close as possible to the submission date of the SIP. 2019 
Guidance at 55. Indiana's 2021 progress report covered the measures and 
emissions reductions achieved from 2007 through 2019 in Indiana's 
Emissions Summary Data, from 2016-2018 in EPA's Emissions Inventory 
System for 2016-2018, and from 2007-2019 in CAMPD.
    To address the progress report elements of 51.308(g)(1), Indiana 
described the status of implementation of all measures in the long-term 
strategy under its first implementation period regional haze plan. 
These measures included several Federal measures, including CAIR and 
its successor CSAPR, to which Indiana attributed the majority of 
reductions in visibility-impairing emissions from the largest point-
source sector, EGUs, during the first implementation period. Federal

[[Page 25959]]

measures for point sources also included BART, MATS, Boiler MACT, and 
the Data Requirements Rule for the 2010 SO2 NAAQS. 
Additional on-the-books control measures that generated further 
emission reductions addressed mobile sources, such as Federal on-road 
provisions under the Tier 2 Motor Vehicle Emissions and Gasoline 
Standards Rule, Tier 3 Motor Vehicle Emissions and Fuel Standards, and 
Heavy-Duty Diesel Engine and Highway Diesel Fuel Rule. Non-road Federal 
measures for mobile sources included the Tier 4 Non-road Engines and 
Diesel Fuel Rule.
    As required by 40 CFR 51.308(g)(2), Indiana provided a summary of 
the emission reductions achieved through the measures outlined above 
from the first implementation period. As a result of these measures, 
Indiana's Emissions Summary Data from 2007 to 2019 from across all 
emission categories for all contributing sources, discussed more fully 
below, show that Indiana's SO2 emissions decreased by 90 
percent from 836,260 to 82,677 tons, and NOX emissions 
decreased by 65 percent from 271,556 to 94,002 tons. The most 
significant emissions reductions from Indiana's SIP strategies resulted 
from CAIR and CSAPR, MATS, and the Data Requirements Rule for the 2010 
SO2 NAAQS. CAMPD information shows that the EGU sector 
experienced an 82 percent reduction in SO2 from 263,766 tons 
in 2014 to 47,834 tons in 2019, and a 50 percent reduction in 
NOX from 95,284 tons in 2014 to 47,219 tons in 2019. Over 
the longer period from 2007 to 2019, the EGUs reporting to CAMPD 
achieved a 93 percent decrease in SO2 from 655,139 to 47,834 
tons as well as a 72 percent decrease in NOX from 168,916 to 
47,219 tons. EPA proposes to find that Indiana has met the requirements 
of 40 CFR 51.308(g)(1) and (2) because its SIP submission describes the 
measures included in the long-term strategy from the first 
implementation period, as well as the status of their implementation 
and the emission reductions achieved through such implementation.
    The provisions of 40 CFR 51.308(g)(3) do not apply because Indiana 
has no mandatory Class I Federal areas within its borders as described 
above.
    To address 40 CFR 51.308(g)(4), Indiana documented the change in 
emissions of SO2 and NOX from all sources and 
activities in the State. Graph 26-1 and appendix E of Indiana's SIP 
submission documents changes in emissions of each of these pollutants 
for biogenics, fires, non-point, non-road, on-road, and point source 
categories for each year from 2007 through 2019, the most recent data 
year available at the time for category level emissions in Indiana's 
Emissions Summary Data. Indiana's tracking showed an overall decline in 
emission reductions from 2007 to 2019, with a 90 percent reduction in 
SO2 and 65 percent reduction in NOX. IDEM also 
provided data in appendix E of its SIP submission, as noted earlier, 
with respect to EGUs that report to CAMPD from 2007 to 2019, the most 
recent year available at the time, tracking the change in emissions and 
chronicling the decrease in SO2 by 93 percent from 655,139 
to 47,834 tons as well as the decrease in NOX by 72 percent 
from 168,916 to 47,219 tons. EPA proposes to find that Indiana has 
satisfied the requirements of 40 CFR 51.308(g)(4) by tracking the 
change in emissions of SO2 and NOX from all 
contributing sources since the first progress report.
    To address 40 CFR 51.308(g)(5), Indiana documented significant 
changes in anthropogenic emissions since the first implementation 
period plan, within and outside of the State through LADCO and the 
interstate consultation process, as an indicator of whether they were 
anticipated and whether they limited or impeded progress in improving 
visibility. Within the State, Indiana compared emissions from all 
contributing sources in the State for each year from 2007 to 2019 to 
identify changes in anthropogenic emissions, finding that overall 
emissions significantly decreased for NOX and 
SO2. As previously mentioned, these changes were anticipated 
and attributed to CSAPR as it replaced CAIR, MATS, and the Data 
Requirements Rule for the 2010 SO2 NAAQS. With the 
significant decreases in anthropogenic emissions of SO2 and 
NOX across all source categories, Indiana did not find any 
changes in anthropogenic emissions within or outside the State that 
occurred from 2007 to 2019 that would limit or impede progress in 
reducing pollutant emissions and improving visibility. Indiana noted 
that further improvements in visibility are anticipated with the 
emission reductions to be realized from the Revised CSAPR Update along 
with the emission reductions occuring during the second implementation 
period as mentioned previously. The emissions trend data in Indiana's 
SIP submission support an assessment that anthropogenic haze-causing 
pollutant emissions in Indiana have decreased during the reporting 
period and that changes in emissions have not limited or impeded 
progress in reducing pollutant emissions and improving visibility. EPA 
proposes to find that Indiana has met the requirements of 40 CFR 
51.308(g)(5).
    In section 28.1 of its SIP submission, Indiana committed to submit 
a 5-year progress report for the second implementation period to 
evaluate progress towards the reasonable progress goal for each 
mandatory Class I Federal area located within and outside the State 
that may be affected by emissions from within the State as required by 
40 CFR 51.308(g). Indiana also committed to revising its regional haze 
SIP and submitting it to EPA on schedule as required by 40 CFR 
51.308(f).

I. Requirements for State and Federal Land Manager Coordination

    CAA section 169A(d) requires States to consult with FLMs before 
holding the public hearing on a proposed regional haze SIP and to 
include a summary of the FLMs' conclusions and recommendations in the 
notice to the public. In addition, 40 CFR 51.308(i)(2)'s FLM 
consultation provision requires a State to provide FLMs with an 
opportunity for consultation that is early enough in the State's policy 
analyses of its emission reduction obligation so that information and 
recommendations provided by the FLMs' can meaningfully inform the 
State's decisions on its long-term strategy. If the consultation has 
taken place at least 120 days before a public hearing or public comment 
period, the opportunity for consultation will be deemed early enough. 
Regardless, the opportunity for consultation must be provided at least 
60 days before a public hearing or public comment period at the State 
level. The requirements of 40 CFR 51.308(i)(2) also provide two 
substantive topics on which FLMs must be provided an opportunity to 
discuss with States: assessment of visibility impairment in any Class I 
area and recommendations on the development and implementation of 
strategies to address visibility impairment. In 40 CFR 51.308(i)(3), 
States, in developing their implementation plans, are required to 
include a description of how they addressed FLMs' comments.
    In developing its SIP submission, IDEM participated with the FLMs 
in an early consultation process regarding source selection as well as 
a formal consultation process on a full draft regional haze SIP. 
Additionally, through LADCO, IDEM consulted directly and indirectly 
with the FLMs through emails, webinars, and conference calls early in 
the SIP planning and

[[Page 25960]]

development process.\48\ On June 16, 2020, IDEM began the early 
consultation process on the State's source selection process and 
selection of sources for four-factor analyses. On May 18, 2021, Indiana 
initiated a formal consultation process with the FLMs, providing a full 
draft of its Regional Haze SIP and offering an opportunity for 
consultation in person. IDEM initiated the early consultation process 
more than 120 days before the first public comment period on Indiana's 
plan and began the formal consultation process at least 60 days prior 
to the first public comment period on Indiana's plan, as required by 40 
CFR 51.308(i)(2). IDEM's response to the FLMs' comments from are 
included as appendix U of Indiana's SIP submission as required by 40 
CFR 51.308(i)(3). Section 2.2 of EPA's April 22, 2025 TSD provides more 
information on the FLM consultation.
---------------------------------------------------------------------------

    \48\ IDEM documented the FLM consultation process in Section 3.3 
and appendix K and N of its SIP submission.
---------------------------------------------------------------------------

    On September 28, 2021, Indiana announced the opportunity for public 
comment and public hearing regarding the State's proposed SIP 
submission for the second implementation period on IDEM's website for 
public notices and for regional haze.\49\ The public notice included 
the FLMs' comments in the proposed SIP submission. An in-person and 
virtual public hearing was held on October 28, 2021.\50\ The public 
comment period ended November 15, 2021. Following the public comment 
period, Indiana submitted its SIP revision to EPA on December 29, 2021.
---------------------------------------------------------------------------

    \49\ IDEM's website for public notices is https://www.in.gov/idem/public-notices/ and https://www.in.gov/idem/sips/regional-haze/ 
for regional haze.
    \50\ IDEM documented the verbal comments received during the 
public hearing in the transcript contained in appendix Z of its SIP 
submission. IDEM also included the written public comments along 
with an index in appendix Ya and Yb of its SIP submission. In 
addition, IDEM summarized the comments and included IDEM's responses 
in appendix V.
---------------------------------------------------------------------------

    IDEM considered input from the FLMs and the public that were 
provided during the FLM consultation period and public notice period 
when finalizing this SIP revision.
    As required by 40 CFR 51.308(i)(4), Indiana committed to continue 
consultation with States and FLMs on the development and review of any 
future plan revisions and progress reports, as well as other programs 
having the potential to contribute to visibility impairment in the 
mandatory Class I areas. Given IDEM's actions recounted above and in 
EPA's April 22, 2025, TSD, EPA proposes to find that Indiana has 
satisfied the requirements of 40 CFR 51.308(i) to consult with the FLMs 
on its regional haze SIP for the second implementation period.

V. Proposed Action

    EPA proposes to approve Indiana's December 29, 2021, SIP submission 
as satisfying the regional haze requirements for the second 
implementation period contained in 40 CFR 51.308(f).

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 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);
     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 subject to Executive Order 13045 (62 FR 19885, 
April 23, 1997) because it approves a State program;
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001); and
     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.
    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, Nitrogen oxides, Ozone, Particulate matter, Sulfur oxides.

    Dated: June 6, 2025.
Anne Vogel,
Regional Administrator, Region 5.
[FR Doc. 2025-11259 Filed 6-17-25; 8:45 am]
BILLING CODE 6560-50-P