Finding of Failure To Attain; Air Plan Approval; Indiana; Huntington County Sulfur Dioxide Attainment Plan, 25968-25975 [2025-11268]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 90, Number 116 (Wednesday, June 18, 2025)]
[Proposed Rules]
[Pages 25968-25975]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-11268]


-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R05-OAR-2023-0564; FRL-12835-01-R5]


Finding of Failure To Attain; Air Plan Approval; Indiana; 
Huntington County Sulfur Dioxide Attainment Plan

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

-----------------------------------------------------------------------

SUMMARY: The Environmental Protection Agency (EPA) is proposing to find 
that the Huntington County, Indiana nonattainment area failed to attain 
the 2010 Sulfur Dioxide (SO2) National Ambient Air Quality 
Standard (NAAQS) by the applicable attainment date of April 9, 2023. 
EPA is also proposing to approve revisions into the Indiana State 
Implementation Plan (SIP) intended to provide for attainment of the 
2010 SO2 NAAQS for the Huntington County nonattainment area. 
These SIP submissions include Indiana's attainment demonstration and 
other planning elements required under the Clean Air Act (CAA), and a 
Commissioner's Order containing enforceable emission limits. Further, 
EPA is proposing to find that the provisions of Indiana's SIP submittal 
adequately provide for attainment of the NAAQS and that the plan meets 
all other applicable CAA requirements.

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

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-
OAR-2023-0564 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, 
PBI, or multimedia submissions, and general guidance on making 
effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Liz Selbst, Air and Radiation Division 
(AR-18J), Environmental Protection Agency, Region 5, 77 West Jackson 
Boulevard, Chicago, Illinois 60604, (312) 886-4746, 
[email protected]. The EPA Region 5 office is open from 8:30 
a.m. to 4:30 p.m., Monday through Friday, excluding Federal holidays.

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

I. Background

    On June 22, 2010 (75 FR 35520), EPA published a revised primary 
SO2 NAAQS, establishing a new one-hour standard of 75 parts 
per billion (ppb). On August 21, 2015 (80 FR 51052), EPA issued the 
Data Requirements Rule (DRR), which required State air agencies to 
characterize air quality around sources that emitted 2,000 tons per 
year (tpy) or more of SO2.

[[Page 25969]]

    EPA has identified the U.S. Mineral Wool facility, also known as 
``Isolatek,'' as an emissions source that may have been contributing to 
violations of the 2010 SO2 NAAQS based on air quality 
modeling conducted by EPA and used in support of the DRR. Isolatek is 
located in the Huntington County, Indiana nonattainment area for the 
2010 SO2 NAAQS. EPA's air quality modeling, conducted in 
2015 using estimated actual emissions from the Isolatek facility, found 
that the 3-year average of the annual 99th percentile of daily maximum 
one-hour average SO2 concentrations exceeded the 75 ppb 
level of the NAAQS. EPA's March 15, 2016, response to the initial 
submittal of DRR sources from the Indiana Department of Environmental 
Management (IDEM) is included in the docket for this rulemaking. 
Evidence of IDEM's selection of the modeling pathway to characterize 
air quality in the area surrounding the Isolatek facility on June 30, 
2016, is also included in the docket for this rulemaking.
    The Isolatek facility is the only listed DRR source in the 
Huntington area and there is no approved SO2 monitoring 
network to characterize air quality in its vicinity. IDEM did not 
include updated air quality information for the Huntington area in its 
letter of designations recommendations for the 2010 SO2 
NAAQS. Therefore, during the initial area designations process, EPA 
relied on the prior EPA air quality modeling, which indicated that the 
Huntington area may have been violating the 2010 SO2 NAAQS, 
and which led EPA to include Isolatek on the list of sources subject to 
DRR requirements. On August 22, 2017, EPA notified IDEM that we 
intended to designate the Huntington area as nonattainment, based on 
the best information available to EPA at the time of designation, which 
was EPA's air quality modeling indicating that the area may have been 
violating the 2010 SO2 NAAQS.
    On January 9, 2018, EPA finalized the third round of initial area 
designations for the 2010 SO2 NAAQS. Based on prior air 
quality modeling information, EPA designated Huntington Township, a 
partial area of Huntington County, Indiana, which includes the Isolatek 
facility, as nonattainment for the 2010 SO2 NAAQS with an 
effective date of April 9, 2018 (83 FR 1098). Pursuant to CAA section 
192(a), 42 U.S.C. 7514a(a), EPA established an attainment date of no 
later than five years after the effective date of the nonattainment 
area designation, which was April 9, 2023.

II. Proposed Finding of Failure To Attain the 2010 One-Hour SO2 NAAQS

    CAA section 179(c)(1) requires EPA to determine whether a 
nonattainment area attained an ambient air quality standard by the 
applicable attainment date based on the area's air quality as of the 
attainment date. As stated in EPA's April 23, 2014, ``Guidance for 1-
Hour SO2 Nonattainment Area SIP Submissions'' (``April 2014 
SO2 guidance''), EPA may consider ambient monitoring data, 
air quality dispersion modeling, and/or a demonstration that the 
control strategy in the SIP has been fully implemented when determining 
the attainment status of SO2 nonattainment areas.
    Under EPA regulations in 40 CFR 50.17, the 2010 SO2 
standard is met at a monitoring site (or in the case of dispersion 
modeling, at an ambient air quality receptor location) when the three-
year average of the annual 99th percentile of daily maximum one-hour 
average concentrations is less than or equal to 75 ppb, as determined 
in accordance with appendix T of 40 CFR part 50 (40 CFR 50.17(a)-(b)). 
Design values are calculated by computing the three-year average of the 
annual 99th percentile daily maximum one-hour average concentrations. 
When calculating one-hour primary standard design values based on 
modeling, the modeled concentration is compared to the one-hour 
SO2 NAAQS of 196.4 micrograms per cubic meter. An 
SO2 one-hour primary standard design value is valid if it 
encompasses three consecutive calendar years of complete monitoring 
data or modeling data. See appendix T of 40 CFR part 50.
    As of this action, and as of the statutory attainment date of April 
9, 2023, there is no approved SO2 monitoring network in the 
Huntington area. The best air quality information available to EPA to 
characterize air quality in the area on the attainment date was the air 
quality modeling that was used to support the DRR. As part of the 
State's SO2 attainment plan for this area, IDEM submitted 
control measures on November 6, 2023, that included enforceable 
allowable emissions limits for the Isolatek facility (see Section III, 
``Proposed Approval of Indiana's SIP Submittal,'' of this preamble for 
discussion of the control strategy). On February 12, 2024, IDEM 
supplemented the November 6, 2023, SIP submittal with Commissioner's 
Order 2023-Air-02, which revised Commissioner's Order 2023-Air-01, 
which had been included in the November 6, 2023, submittal. In this 
notice of proposed rulemaking, we are referring to the updated Order 
2023-Air-02 as the ``Commissioner's Order,'' which established 
compliance requirements for the one-hour SO2 emissions 
limits, which were effective on March 1, 2024. In other words, the 
control measures that EPA is proposing to approve in the following 
section of this action were not in place as of the statutory attainment 
date of April 9, 2023. Therefore, based on EPA's air quality modeling 
used to support the DRR, EPA has determined that the area may have been 
violating the 2010 SO2 NAAQS prior to full implementation of 
the control strategy. EPA is proposing to find that, as of the 
applicable attainment date of April 9, 2023, the Huntington area failed 
to attain the 2010 SO2 NAAQS by the attainment date.
    The consequences for an SO2 nonattainment area that 
fails to attain a NAAQS by the applicable attainment date are set forth 
in CAA section 179(d). Under section 179(d), a State must submit a SIP 
revision for the area meeting the requirements of CAA sections 110 and 
172, the latter of which requires, among other elements, a 
demonstration of attainment and reasonable further progress and 
contingency measures. In addition, under CAA section 179(d)(2), the SIP 
revision must include such additional measures as EPA may reasonably 
prescribe, including all measures that can be feasibly implemented in 
the area in light of technological achievability, costs, and any non-
air quality and other air quality-related health and environmental 
impacts. The State is required to submit the SIP revision within one 
year after EPA publishes a final action in the Federal Register 
determining that the nonattainment area failed to attain the 
SO2 NAAQS.
    In section III. of this preamble, EPA is proposing to approve 
IDEM's revised SO2 attainment plan for the Huntington area, 
which was submitted to EPA on November 6, 2023, and supplemented on 
February 15, 2024. (Both submittals occurred after the statutory 
attainment date of April 9, 2023). The proposed approval is based on 
air quality modeling demonstrating that the area is currently attaining 
the NAAQS as a result of the implemented control measures in the 
State's SIP and the compliance requirements established in the 
Commissioner's Order. If EPA subsequently takes final action to approve 
the subject SIP submittals, EPA is proposing to find that these SIP 
revisions, as approved, satisfy the State's obligation under CAA 
section 179(d) to submit a SIP revision to address the proposed finding 
that the

[[Page 25970]]

area failed to timely attain the 2010 SO2 NAAQS.
    Under CAA sections 172(a)(2), 179(d)(3), the new attainment date 
for each primary NAAQS nonattainment area is the date by which 
attainment can be achieved as expeditiously as practicable, but no 
later than five years after EPA publishes a final action in the Federal 
Register determining that the nonattainment area failed to attain the 
SO2 NAAQS. In this action, we are proposing to approve 
IDEM's SIP revision and proposing to find that the control measures 
identified in IDEM's November 6, 2023, and February 15, 2024, SIP 
revisions satisfy the CAA requirement to achieve attainment of the 2010 
SO2 NAAQS as expeditiously as practicable (see Section III). 
Therefore, if the proposed Finding of Failure to Attain (FFA) is 
finalized, this will establish a new attainment date for the 
Huntington, IN area of no later than five years after the effective 
date of the final FFA. However, in the following section, EPA is 
proposing to approve Indiana's SIP and, if finalized, the approved SIP 
would fulfill the new SIP submission requirement triggered by the 
finalization of this FFA. We are proposing that the new SIP submission 
requirement will be met by the SIP we are acting on below in this 
unique circumstance because control measures are now in place and 
effective, the area is attaining the 2010 primary SO2 NAAQS, 
and the State has submitted a complete and approvable attainment plan 
with all required planning elements. The new attainment date 
established 5 years after the date of the effective date of the final 
FFA also requires contingency measures under CAA section 172(c)(9). EPA 
is proposing to find that IDEM's comprehensive SO2 
enforcement program, as described in Section III.D.5 of this preamble, 
satisfies the CAA section 172(c) requirements for contingency measures.

III. Proposed Approval of Indiana's SIP Submittal

A. Indiana's Requirement To Submit a SIP Revision

    On November 3, 2020 (85 FR 69504), EPA issued a finding that 
Indiana had failed to submit a SIP provision to satisfy certain 
nonattainment area planning requirements of the CAA for the 2010 
SO2 NAAQS. The effective date of the Finding of Failure to 
Submit was December 3, 2020. Indiana was required to submit a SIP 
provision in response to the Finding of Failure to Submit under CAA 
section 179(a). This finding started a sanctions clock for EPA to issue 
Nonattainment New Source Review (NNSR) sanctions and highway sanctions 
for Huntington Township under CAA section 179(b). EPA imposed NNSR 
offset sanctions that were effective on June 3, 2022, and imposed 
highway sanctions that were effective on December 3, 2022. This action 
also started a Federal Implementation Plan (FIP) clock for EPA to fully 
approve an SO2 attainment SIP, or issue a FIP, for the 
Huntington, Indiana area within two years, by December 3, 2022, under 
CAA section 110(c).
    On November 6, 2023, IDEM submitted State rules for EPA approval as 
revisions to the Indiana SIP intended to provide for attainment of the 
2010 SO2 NAAQS in the Huntington area. The revisions 
included an Attainment Demonstration, Reasonably Available Control 
Measures/Reasonably Available Control Technology (RACM/RACT) 
requirements, Reasonable Further Progress (RFP) provisions, Contingency 
Measures, Emissions Inventories for 2017 Base Year and 2023 Attainment 
Year, and NNSR Certification. On November 27, 2023, EPA issued a 
completeness determination for the November 6, 2023, SIP submittal, 
which terminated all sanctions for this area and which is available in 
the docket for this rulemaking. On February 15, 2024, IDEM submitted a 
supplemental SIP revision including updated compliance methods 
(contained in the revised Commissioner's Order 2023-Air-02, as 
previously described in this action) for the Attainment Demonstration 
for the Huntington, Indiana SO2 nonattainment area. In this 
notice of proposed rulemaking, EPA is proposing to find that this 
supplement satisfies the CAA sections 110(a)(2)(A) and 172(c)(6) 
requirements to provide enforceable emissions limitations and control 
measures as part of an attainment demonstration. As mentioned in the 
previous section, under CAA section 179(d), States must submit a SIP 
provision within one year of EPA publishing a finding of failure to 
attain by the attainment date for any nonattainment area. The 
submission must include a demonstration of attainment, reasonable 
further progress and contingency measures, and other measures EPA may 
reasonably prescribe. Assuming EPA finalizes the proposed finding of 
failure to attain and the proposed approval of Indiana's SIP 
submissions, EPA is also proposing to find that IDEM's November 6, 
2023, and February 15, 2024, SIP submissions fully satisfy the State's 
obligation under CAA section 179(d). Lastly, EPA is proposing to 
terminate the FIP clock that was triggered by EPA's November 3, 2020, 
Finding of Failure to Submit for Huntington County.

B. Requirements for SO2 Nonattainment Area Plans

    Nonattainment area SO2 SIPs must meet the applicable 
requirements of the CAA, and specifically CAA sections 110, 172, 191 
and 192. EPA's regulations governing nonattainment area SIPs are set 
forth at 40 CFR part 51, with specific procedural requirements and 
control strategy requirements contained in subparts F and G, 
respectively. Soon after Congress enacted the 1990 amendments to the 
CAA, EPA issued comprehensive guidance on SIPs in a document entitled 
the ``General Preamble for the Implementation of Title I of the Clean 
Air Act Amendments of 1990,'' published at 57 FR 13498 (April 16, 1992) 
(General Preamble). Among other things, the General Preamble addressed 
SO2 SIPs and fundamental principles for SIP control 
strategies. Id. at 13545-49, 13567-68.
    In the April 2014 SO2 guidance, EPA described the 
statutory requirements for a complete nonattainment area SIP, which 
include: an accurate emissions inventory of current emissions for all 
sources of SO2 within the nonattainment area; an attainment 
demonstration; enforceable emissions limitations and control measures; 
demonstration of RFP; implementation of RACM (including RACT); NNSR 
provisions; and adequate contingency measures for the affected area.
    In order for EPA to fully approve a SIP as meeting the requirements 
of CAA sections 110, 172 and 191-192 and EPA's regulations at 40 CFR 
part 51, the SIP for the affected area needs to demonstrate to EPA's 
satisfaction that each of the aforementioned requirements have been 
met. Under CAA section 110(l) EPA may not approve a SIP that would 
interfere with any applicable requirement concerning NAAQS attainment 
and RFP, or any other applicable requirement; and, under section 193, 
no control requirement in effect (or required to be adopted by an 
order, settlement, agreement, or plan in effect before November 15, 
1990), in any area which is a nonattainment area for any air pollutant, 
may be modified in any manner unless the modification ensures 
equivalent or greater emission reductions of such air pollutant.

C. Review of Modeled Attainment Plan

    This section describes EPA's evaluation of the air quality 
dispersion modeling IDEM provided as part of its SIP submission. EPA is 
proposing to

[[Page 25971]]

approve Indiana's attainment plan on the basis that this modeling is 
technically sound and appropriate and provides for attainment of the 
2010 SO2 NAAQS.
1. Model Selection and General Model Inputs
    IDEM followed EPA guidance at 40 CFR part 51, appendix W, and 
selected EPA's regulatory dispersion model, AERMOD, to model 
SO2 emissions impacts in the Huntington, Indiana 
nonattainment area. IDEM used the set of regulatory default options in 
AERMOD version 22112 to develop the attainment demonstration discussed 
in this section. Version 22112 was the current version of AERMOD at the 
time the air quality modeling report was submitted (October 6, 2023) as 
part of the attainment demonstration (see section 5.0 and appendix A1 
of the attainment demonstration) and the most recent update to AERMOD 
since then did not include any bug fixes or other model code changes 
that would impact the modeled concentrations in the modeled attainment. 
AERMOD was conducted with the use of rural dispersion coefficients, 
based on a land use analysis of a 3-kilometer radius from the Isolatek 
facility showing that only 17.2% of the nearby land was classified as 
urban. IDEM used an appropriate downwash algorithm for stacks that did 
not meet EPA's Good Engineering Practice (GEP) stack height policy, 
which is further described in this section. This is consistent with 
established practice for use of AERMOD in determining NAAQS compliance 
for SIP revisions. EPA proposes to find that selection of the default 
AERMOD options and use of the rural dispersion coefficient are both 
technically appropriate.
    IDEM's attainment demonstration uses a modeling domain reflecting 
the geographic extent of the Huntington nonattainment area. The 
Thermafiber, Paperworks, and Real Alloy facilities in Wabash County, 
the Steel Dynamics facility in Whitely County, the FXI facility in 
Allen County, and the Teijin Automotive Technologies facility within 
the Huntington nonattainment area were explicitly modeled as nearby 
sources in the modeling demonstration. The Teijin Automotive 
Technologies facility is located 5.6 kilometers from Isolatek. The rest 
of the nearby sources explicitly modeled in the attainment 
demonstration are located 27-37 kilometers away from the Isolatek 
facility. Nearby sources, though not evaluated for an emission limit, 
are those sources in the vicinity of the source(s) under consideration 
for emissions limits that are not adequately represented by ambient 
monitoring data. Consistent with EPA's DRR modeling for the Huntington 
area, IDEM determined that the primary source of SO2 
emissions in the area is the Isolatek facility, which is the primary 
source of violations of the 2010 SO2 NAAQS in the 
nonattainment area. EPA's evaluation of IDEM's modeling of the Isolatek 
source is discussed further in Section III.C.3-4 of this preamble.
    The receptor network fully encompasses the Huntington nonattainment 
area. IDEM used four nested receptor grids with different densities and 
included a fenceline receptor grid with 50-meter spacing. The fine 
Cartesian grid contains receptors spaced at 100-meter intervals 
extending to approximately three kilometers away from the center of the 
facility. The extended fine Cartesian grid contains receptors spaced at 
250-meter intervals starting approximately three kilometers away from 
the center of the facility and extend to five kilometers away from the 
center of the facility. The medium Cartesian grid contains receptors 
spaced at 500-meter intervals starting approximately five kilometers 
away from the center of the facility and extend to ten kilometers away 
from the center of the facility. The coarse Cartesian grid contains 
receptors spaced at 750-meter intervals starting approximately ten 
kilometers away from the center of the facility and extend to twenty 
kilometers away from the center of the facility. The receptors 
projected to have maximum modeled concentrations were all contained 
within the 100-meter spacing fine receptor grid. EPA proposes to find 
that the receptor density is consistent with standard modeling guidance 
for adequately capturing and resolving SO2 concentration 
maxima.
    IDEM's selection of terrain data corresponds to the geographic area 
represented by the Huntington Township nonattainment area, as well as 
the locations of nearby facilities influencing SO2 
concentrations in the area. U.S. Geological Survey (USGS) National 
Elevation Dataset (NED) data were obtained in an appropriate format for 
use in AERMAP (version 18081) and used for generating the necessary 
terrain inputs. Elevations from the NED data were determined for all 
sources and structures, and both elevations and representative hill 
heights were determined for receptors. EPA proposes to find that these 
selections are technically appropriate and consistent with established 
practice in determining NAAQS compliance for SIP revisions.
    EPA's appendix W guidance requires States to evaluate whether 
physical structures may affect the dispersion of emissions from stack 
sources. Stacks that are constructed to heights lower than specified 
GEP height and within the ``zone of influence'' of a nearby structure 
have plumes that are potentially subject to the effects of downwash 
which would affect dispersion and modeled concentrations in the 
building wake, near to the source. IDEM used EPA's Building Profile 
Input Program with PRIME algorithm (BPIPPRM) to generate direction-
specific building parameters for modeling building wake effects. The 
location and height of each stack and flare to be evaluated, and the 
locations and heights of nearby structures, were processed in BPIPPRM 
(version 04274) to produce the building downwash parameters required by 
AERMOD. The actual release heights of all stacks were less than the 
calculated GEP value. Therefore, all stacks at the Isolatek facility 
were modeled at their actual release heights and were subject to 
downwash effects. EPA is proposing to determine that IDEM's application 
of the modeling guidance is appropriate for addressing stacks subject 
to downwash effects.
2. Meteorological Data
    Procedures for selecting and developing meteorological data have 
been provided in appendix W, as well as in the document ``Regional 
Meteorological Data Processing Protocol, EPA Region 5 and States,'' 
which is available in the docket for this action. These documents 
describe selection criteria for surface meteorological data that 
address the representativeness of the meteorological data collection 
site to the emission source/receptor impact area. There are two 
specific criteria to be considered: (1) the suitability of 
meteorological data for the study area, and (2) the similarity of 
surface conditions and surroundings at the emission source/receptor 
impact area compared to surface characteristics at the location of the 
meteorological instrumentation tower.
    IDEM used five years of surface meteorological data from the Fort 
Wayne National Weather Service (NWS) and upper air meteorological data 
from Wilmington, Ohio for the period of 2017-2021. This data set was 
determined to be representative of the nonattainment area's airshed and 
was the most current data set available when the modeling analysis was 
conducted. IDEM pre-processes meteorological data and provides the 
datasets for modeling

[[Page 25972]]

applicants on their website.\1\ AERMINUTE (version 15272) was used to 
process two-minute averaged ASOS (Automated Surface Observing System) 
wind data (reported every minute) from Fort Wayne and used the EPA 
recommended 0.5 meters per second calm wind threshold. Surface 
characteristic data such as albedo, Bowen ratio, and surface roughness 
were calculated using the non-regulatory surface characteristics 
preprocessor AERSURFACE. The one-minute ASOS wind data and surface 
characteristics were processed together with the surface and upper air 
meteorological data using AERMET (version 19191 for the years 2017-2020 
and version 21112 for the year 2021) to prepare the meteorological data 
for input into AERMOD. Two different versions of AERMET were used as 
the 2017-2020 data set was previously processed by IDEM when the year 
2021 was processed and the differences between AERMET versions 19191 
and 21112 would not have resulted in significant changes in 
meteorological parameters. The Fort Wayne NWS wind rose shows the 
frequency of the wind direction every ten degrees for each of the wind 
speed ranges for the five-year modeled period and demonstrates that the 
prevailing winds are from the southwest and west-southwest at the Fort 
Wayne NWS station. EPA proposes to find that the meteorological data 
set IDEM selected for the air quality modeling to support its SIP 
submission was technically appropriate.
---------------------------------------------------------------------------

    \1\ https://www.in.gov/idem/airquality/modeling/air-dispersion-meteorological-data/.
---------------------------------------------------------------------------

3. Emissions Limits and Modeled Emissions Data
    As EPA identified at the time of promulgating the DRR, the primary 
source affecting nonattainment and contributing to violations of the 
2010 SO2 NAAQS in Huntington County was the Isolatek 
facility. EPA has not identified any other sources in the area that may 
have been contributing to violations of the 2010 SO2 NAAQS. 
IDEM's SIP submission establishes permanent and enforceable emissions 
limits for this facility through a Commissioner's Order. IDEM reviewed 
detailed engineering analyses for multiple control options at the 
Isolatek facility, as described in section 5.8 of the SIP submittal. 
Construction for the control measures selected at the facility, 
including increasing the cupola stack height, enclosing screenhouses, 
and building a new elevated stack, was completed in November 2022. Data 
from stack testing conducted in December 2022 and January 2023 were 
used to establish the emission limits necessary to provide for 
attainment of the 2010 one-hour SO2 NAAQS. The attainment 
demonstration incorporates hourly modeled emission rate limits, 
contained in the Commissioner's Order, of 160.0 pounds per hour (lbs/
hr) for Cupola units EU #1 and EU #2, exhausting to shared Stack #1, 
and 20.0 lbs/hr for blow chambers EU #3 and EU #4, exhausting to Screen 
Houses CE #3 and CE #4, which exhaust to Stack #3 at the Isolatek 
facility.
    IDEM's modeled demonstration of attainment of the 2010 
SO2 NAAQS relies on Isolatek meeting the one-hour 
SO2 emissions limit established in the Commissioner's Order. 
For EPA to approve an attainment plan that relies on establishing 
emissions limits, EPA must determine that the limits are quantifiable, 
fully enforceable, replicable, and accountable. See General Preamble at 
13567-68. IDEM's February 6, 2024, SIP submission includes an IDEM 
Commissioner's Order that establishes a compliance date of March 1, 
2024, for the emissions limits included in the revised SIP. In addition 
to requiring compliance with the hourly SO2 emissions limits 
and defining stack testing parameters, this order also specifies that 
Isolatek must incorporate reporting and recordkeeping requirements into 
its part 70 Operating Permit within 90 days of EPA's approval of the 
SIP submission. Isolatek must report monthly average hourly 
SO2 emissions from Cupola #1 and Cupola #2 and monthly 
average hourly SO2 emissions from Blow Chamber #3 and Blow 
Chamber #4 on a quarterly basis to IDEM and must report any exceedances 
of the SO2 emissions limits. Based on these requirements, 
EPA is proposing to find that the emissions limits in IDEM's SIP 
revision will become permanent and enforceable upon EPA's approval of 
the SIP submission.
    Using the source-specific one-hour average emissions rates for 
Isolatek that are established in the SIP submission, IDEM demonstrated 
that the highest 4th high one-hour maximum daily SO2 
concentration, averaged across five years for the entire area defined 
by the receptor grid, is 195.9 micrograms per cubic meter and occurred 
approximately 175 meters northeast of the fenceline receptor grid. As 
the maximum modeled concentrations occurred within a one kilometer 
radius of Isolatek, receptors were not placed inside the fencelines of 
the other explicitly modeled nearby sources to determine the ambient 
impacts from Isolatek. Based on this modeling, EPA proposes to conclude 
that the permanent and enforceable emission limits for Isolatek provide 
for attainment of the 2010 SO2 NAAQS of 75 ppb (or 196.4 
micrograms per cubic meter) in the Huntington nonattainment area.
4. Background Concentrations
    IDEM's demonstration providing for modeled attainment of the 2010 
SO2 NAAQS is based on a combination of facility-specific 
emission rates and monitored background concentrations. Regional 
sources not explicitly modeled in AERMOD, but which contribute to 
ambient SO2 loadings within the nonattainment area, are 
represented via background monitoring data. IDEM identified background 
concentration estimates from the Lima, Ohio monitor as the most 
representative site in the vicinity of the modeling domain. The Lima, 
OH SO2 monitor is located approximately 74 miles east-
southeast of Isolatek and is the closest monitor within the region. The 
hour-by-season averaged SO2 background values for 2019-2021 
at this monitor range from 0.33 ppb to 1.33 ppb. EPA proposes to 
conclude that the background concentrations used in IDEM's modeled 
attainment demonstration are appropriate and consistent with EPA 
modeling guidance.
5. Summary of Results
    EPA's DRR modeling indicated that the Isolatek facility was 
contributing to violations of the 2010 SO2 NAAQS in the 
Huntington area. IDEM evaluated control options for the nonattainment 
area and established emissions limits for the Isolatek facility. 
Construction of the relevant control projects was completed in November 
2022, with a compliance date to codify the emissions limits as 
permanent and enforceable on March 1, 2024. IDEM's modeling 
demonstrated that the one-hour average hourly SO2 emissions 
limits contained in the SIP revision yielded a highest 4th high one-
hour daily maximum SO2 concentration of 195.9 micrograms per 
cubic meter which is below the 2010 SO2 NAAQS level of 196.4 
micrograms per cubic meter.
    EPA is proposing to conclude that IDEM's modeling is a technically 
sound demonstration that the Isolatek facility, as the primary source 
contributing to violations of the 2010 SO2 NAAQS, has been 
properly addressed in the State's attainment plan. EPA proposes to find 
that IDEM's modeling appropriately provides for attainment of the 2010 
SO2 NAAQS.

[[Page 25973]]

D. Review of Other Plan Requirements

1. Emissions Inventory
    CAA section 172(c)(3) requires States to provide a comprehensive, 
accurate, and current inventory of actual emissions from all sources of 
SO2 in the nonattainment area, as well as any sources 
located outside the nonattainment area which may affect attainment in 
the area. The emissions inventory and source emission rate data for an 
area serve as the foundation for air quality modeling and other 
analyses that enable States to: (1) estimate the degree to which 
different sources within a nonattainment area contribute to violations 
within the affected area; and (2) assess the prospects for attaining 
the standard based on alternative control measures. EPA's April 2014 
SO2 Guidance includes requirements for submitting emissions 
inventories that are representative of base year conditions and a 
projection to the attainment year.
    IDEM provided a comprehensive, accurate, and current inventory of 
emissions of SO2 in Huntington County. The 2017 base year 
inventory was developed using data from the National Emissions 
Inventory (NEI) and included point sources, nonpoint sources, non-road 
mobile sources, and on-road mobile sources. County level emissions data 
are summarized in Table 1 for the 2017 base year. The data indicate the 
largest contribution to SO2 emissions in the nonattainment 
area is from non-EGU point sources. IDEM compiled actual SO2 
emissions, as reported, shown in Table 2, from the two non-EGU point 
sources in Huntington County. Isolatek reports annual emissions to 
IDEM; Teijin Automotive Technologies reports to IDEM on a triennial 
basis. IDEM did not find evidence of any other large sources near the 
nonattainment area that may have been impacting air quality in the 
Huntington area. EPA is proposing to determine that IDEM's list of 
sources with potential to cause nonattainment of the NAAQS is thorough 
and complete.

    Table 1--Huntington County SO2 Emissions Data by Sector for 2017
------------------------------------------------------------------------
                                            Huntington      Huntington
                                              County         Township
                 Sector                      Emissions       Emissions
                                             (tons per       (tons per
                                               year)           year)
------------------------------------------------------------------------
On-road.................................            4.48            0.07
Non-road................................            0.75            0.42
Area....................................           10.81            6.05
Point EGU...............................            0.00            0.00
Point Non-EGU...........................          176.23          176.23
Total...................................          192.27          182.77
------------------------------------------------------------------------


  Table 2--Actual Reported SO2 Emissions From Non-EGU Point Sources in
                      Huntington County, 2011-2020
------------------------------------------------------------------------
                                               Actual (Reported) SO2
                                            emissions (tpy) by Facility
                                         -------------------------------
                  Year                                        Teijin
                                             Isolatek       Automotive
                                                           Technologies
------------------------------------------------------------------------
2011....................................          219.89  ..............
2012....................................           224.3  ..............
2013....................................          176.14           0.026
2014....................................          164.36  ..............
2015....................................          180.53            0.03
2016....................................          184.21  ..............
2017....................................           176.2  ..............
2018....................................          192.88            0.03
2019....................................          188.29  ..............
2020....................................          181.33  ..............
------------------------------------------------------------------------

    IDEM's projected emissions for the 2023 attainment year are based 
on the attainment modeling described previously in this notice in 
Section III.C. As noted in EPA's evaluation of the attainment modeling 
demonstration, the source emission rate data for Isolatek is calculated 
by the maximum allowable hourly emissions limit established in the SIP 
revision. Projected county level emissions data by sector are 
summarized in Table 3 for the 2023 attainment year.

  Table 3--Projected Huntington County SO2 Emissions Data by Sector for
                                  2023
------------------------------------------------------------------------
                                                            Huntington
                                                              County
                         Sector                              Emissions
                                                             (tons per
                                                               year)
------------------------------------------------------------------------
On-road.................................................            0.05
Non-road................................................            0.24
Area....................................................            3.41
Point EGU...............................................            0.00
Point Non-EGU...........................................          788.43
Total...................................................          792.13
------------------------------------------------------------------------

2. RACM/RACT and Emissions Limitations and Control Measures
    Section 172(c)(1) of the CAA requires States to adopt and submit 
all RACM, including RACT, as needed to attain the standards as 
expeditiously as practicable. Section 172(c)(6) requires the SIP to 
contain enforceable emission limits and control measures necessary to 
provide for timely attainment of the standard.
    The Isolatek facility, identified by EPA as the largest source of 
SO2 emissions contributing to violations of the 2010 
SO2 NAAQS in Huntington, Indiana, was required by the State 
to increase the height of its stack, enclose

[[Page 25974]]

screenhouses, and build a new elevated stack. These emissions control 
projects were completed in November 2022. Together with the permanent 
and enforceable hourly average emissions limits in IDEM's 
Commissioner's Order, EPA is proposing to find that the control 
measures implemented at the Isolatek facility provide for attainment of 
the 2010 SO2 NAAQS. Because CAA section 172(c) does not 
require the State to impose emissions control measures for 
SO2 nonattainment areas beyond the emissions reductions 
necessary to provide for attainment, EPA is proposing to find that the 
control measures implemented at the Isolatek facility satisfy the 
requirements of CAA section 172(c)(1) to reduce emissions from existing 
sources in the area as expeditiously as practicable. EPA is proposing 
to determine that the State's plan satisfies the applicable CAA 
requirements for RACM and RACT.
3. Nonattainment New Source Review (NNSR)
    EPA approved Indiana's NNSR rules on October 7, 1994 (94 FR 24837). 
These rules, which are contained in the SIP, provide for review of 
SO2 sources undergoing construction or major modification in 
nonattainment areas such as the Huntington Township area. Although 
these rules predated promulgation of the 2010 SO2 standard, 
they are written in a manner such that new sources within areas that 
become designated nonattainment for the new standard, such as the 
Huntington Township area, become subject to these nonattainment new 
source review requirements. Therefore, EPA is proposing to determine 
that this CAA requirement has been met for this area.
4. RFP
    CAA section 172(c)(2) requires Indiana's SO2 Attainment 
Plan SIP for Huntington, Indiana to provide for reasonable further 
progress toward attainment. For SO2 SIPs, which address a 
small number of affected sources, requiring expeditious compliance with 
attainment emission limits can address the RFP requirement. Isolatek 
completed construction of the new stack and other emissions control 
projects by November 2022. Furthermore, Isolatek was required by the 
Commissioner's Order to comply with enforceable and permanent control 
measures by March 1, 2024.
    In this action, EPA is proposing to approve the hourly average 
SO2 emissions limits that Isolatek was required to comply 
with, per the Commissioner's Order, into Indiana's SIP as permanent and 
enforceable. EPA is proposing to conclude that the requirements in the 
State's plan, including establishing hourly SO2 emission 
limits for the Isolatek facility, represent implementation of control 
measures as expeditiously as practicable. This plan provides for 
attainment of the 2010 SO2 NAAQS. Accordingly, EPA proposes 
to find that IDEM's plan provides for RFP.
5. Contingency Measures
    Section 172(c)(9) of the CAA requires that nonattainment plans 
include additional measures which will take effect if an area fails to 
meet RFP or fails to attain the standard by the attainment date. As 
noted previously, EPA guidance describes special features of 
SO2 planning that influence the suitability of alternative 
means of addressing the requirement in CAA section 172(c)(9) for 
contingency measures for SO2. An appropriate means of 
satisfying this requirement for SO2 nonattainment area 
planning is for the State to have a comprehensive SO2 
enforcement program that identifies sources of violations of the 
SO2 NAAQS and for the State to undertake aggressive follow-
up for compliance and enforcement. IDEM's plan provides for satisfying 
the contingency measure requirement in this manner for sources in the 
State. IDEM provided example measures that may be considered if 
enforcement of violations of the NAAQS is required, such as requiring 
alternative fuels, requiring installation of additional control 
technologies, or requiring the source to reduce operating hours. EPA is 
proposing to concur with this approach and proposes to approve IDEM's 
plan for meeting the contingency measures requirement in this manner.

IV. What action is EPA proposing?

    EPA is proposing to find, under section 179 of the CAA, that the 
Huntington County, Indiana nonattainment area failed to attain the 2010 
SO2 NAAQS by the applicable attainment date of April 9, 
2023, and that Indiana is therefore subject to the requirement under 
section 179 to submit a revision to its SIP to provide for attainment 
in that area no later than five years from the date of any final 
determination that the area failed to attain. See section 179(c)-(d). 
EPA is also proposing to approve Indiana's November 6, 2023, SIP 
attainment plan submittal and February 15, 2024, supplemental SIP 
revision for the Huntington County SO2 nonattainment area as 
fulfilling this requirement to provide for attainment of the 2010 
SO2 NAAQS by the attainment date, in this unique 
circumstance because control measures are now in place and effective, 
the area is attaining the 2010 SO2 NAAQS, and the State has 
submitted a complete and approvable attainment plan with all required 
planning elements. EPA is proposing to determine that IDEM has 
appropriately demonstrated that the plan provides for attainment of the 
2010 SO2 NAAQS in the Huntington County, Indiana 
nonattainment area and that the plan meets the other applicable 
requirements under CAA sections 172, 191, and 192. The proposed 
approval of IDEM's SO2 attainment plan, if finalized, would 
also terminate the FIP clock that was triggered by EPA's November 3, 
2020, Finding of Failure to Submit for the Huntington County area. EPA 
is soliciting public comments for 30 days following the publication of 
this proposed action in the Federal Register and will take these 
comments into consideration in our final action.

V. 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);
     Is not subject to Executive Order 14192 (90 FR 9065, 
February 6, 2025) because SIP actions are exempt from review under 
Executive Order 12866;
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);

[[Page 25975]]

     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 rulemaking does not have Tribal implications and will not 
impose substantial direct costs on Tribal governments or preempt Tribal 
law as specified by Executive Order 13175 (65 FR 67249, November 9, 
2000).

List of Subjects in 40 CFR Part 52

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

    Dated: June 9, 2025.
Anne Vogel,
Regional Administrator, Region 5.
[FR Doc. 2025-11268 Filed 6-17-25; 8:45 am]
BILLING CODE 6560-50-P