90 FR 116 pgs. 25968-25975 - Finding of Failure To Attain; Air Plan Approval; Indiana; Huntington County Sulfur Dioxide Attainment Plan
Type: PRORULEVolume: 90Number: 116Pages: 25968 - 25975
Pages: 25968, 25969, 25970, 25971, 25972, 25973, 25974, 25975Docket number: [EPA-R05-OAR-2023-0564; FRL-12835-01-R5]
FR document: [FR Doc. 2025-11268 Filed 6-17-25; 8:45 am]
Agency: Environmental Protection Agency
Official PDF Version: PDF Version
[top]
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 (SO 2 ) 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 SO 2 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 arra.sarah@epa.gov. 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, selbst.elizabeth@epa.gov. 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
[top] On June 22, 2010 (75 FR 35520), EPA published a revised primary SO 2 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 SO 2 .
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 SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 NAAQS.
On January 9, 2018, EPA finalized the third round of initial area designations for the 2010 SO 2 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 SO 2 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 SO 2 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 SO 2 Nonattainment Area SIP Submissions" ("April 2014 SO 2 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 SO 2 nonattainment areas.
Under EPA regulations in 40 CFR 50.17, the 2010 SO 2 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 SO 2 NAAQS of 196.4 micrograms per cubic meter. An SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 NAAQS by the attainment date.
The consequences for an SO 2 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 SO 2 NAAQS.
[top] In section III. of this preamble, EPA is proposing to approve IDEM's revised SO 2 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
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 SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 Nonattainment Area Plans
Nonattainment area SO 2 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 SO 2 SIPs and fundamental principles for SIP control strategies. Id. at 13545-49, 13567-68.
In the April 2014 SO 2 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 SO 2 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
[top] This section describes EPA's evaluation of the air quality dispersion modeling IDEM provided as part of its SIP submission. EPA is proposing to
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 SO 2 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 SO 2 emissions in the area is the Isolatek facility, which is the primary source of violations of the 2010 SO 2 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 SO 2 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 SO 2 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.
[top] 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
Footnotes:
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 SO 2 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 SO 2 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 SO 2 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 SO 2 NAAQS relies on Isolatek meeting the one-hour SO 2 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 SO 2 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 SO 2 emissions from Cupola #1 and Cupola #2 and monthly average hourly SO 2 emissions from Blow Chamber #3 and Blow Chamber #4 on a quarterly basis to IDEM and must report any exceedances of the SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 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 SO 2 monitor is located approximately 74 miles east-southeast of Isolatek and is the closest monitor within the region. The hour-by-season averaged SO 2 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 SO 2 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 SO 2 emissions limits contained in the SIP revision yielded a highest 4th high one-hour daily maximum SO 2 concentration of 195.9 micrograms per cubic meter which is below the 2010 SO 2 NAAQS level of 196.4 micrograms per cubic meter.
[top] 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 SO 2 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 SO 2 NAAQS.
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 SO 2 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 SO 2 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 SO 2 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 SO 2 emissions in the nonattainment area is from non-EGU point sources. IDEM compiled actual SO 2 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.
| Sector | Huntington County Emissions (tons per year) | Huntington Township Emissions (tons per 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 |
| Year | Actual (Reported) SO 2 emissions (tpy) by Facility | Isolatek | Teijin 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.
| Sector | Huntington County 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.
[top] The Isolatek facility, identified by EPA as the largest source of SO 2 emissions contributing to violations of the 2010 SO 2 NAAQS in Huntington, Indiana, was required by the State to increase the height of its stack, enclose
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 SO 2 sources undergoing construction or major modification in nonattainment areas such as the Huntington Township area. Although these rules predated promulgation of the 2010 SO 2 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 SO 2 Attainment Plan SIP for Huntington, Indiana to provide for reasonable further progress toward attainment. For SO 2 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 SO 2 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 SO 2 emission limits for the Isolatek facility, represent implementation of control measures as expeditiously as practicable. This plan provides for attainment of the 2010 SO 2 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 SO 2 planning that influence the suitability of alternative means of addressing the requirement in CAA section 172(c)(9) for contingency measures for SO 2 . An appropriate means of satisfying this requirement for SO 2 nonattainment area planning is for the State to have a comprehensive SO 2 enforcement program that identifies sources of violations of the SO 2 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 SO 2 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 SO 2 nonattainment area as fulfilling this requirement to provide for attainment of the 2010 SO 2 NAAQS by the attainment date, in this unique circumstance because control measures are now in place and effective, the area is attaining the 2010 SO 2 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 SO 2 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 SO 2 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);
[top] • 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 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