# Air Plan Approval; Illinois; Moderate Attainment Plan Elements for the Chicago and Metro East Areas for the 2015 Ozone Standard
**AGENCY:**
Environmental Protection Agency (EPA).
**ACTION:**
Proposed rule.
**SUMMARY:**
The Environmental Protection Agency (EPA) is proposing to approve portions of Illinois' 2015 ozone National Ambient Air Quality Standard (NAAQS or standard) Moderate nonattainment area State Implementation Plan (SIP) submission for the Chicago and the Metro East St. Louis areas. The portions of the SIP submission that the EPA is proposing to approve are the reasonable further progress (RFP) demonstration including the associated motor vehicle emissions budgets for 2023, the motor vehicle inspection and maintenance (I/M) program, the nonattainment new source review (NNSR) program, and the updated 2017 base year emissions inventories. The EPA is proposing to approve these portions of the State's SIP submission pursuant to section 110 and part D of the Clean Air Act (CAA), and the EPA's regulations. The EPA is also initiating the adequacy process for the 2023 motor vehicle emissions budgets (budgets) for the Chicago and Metro East St. Louis Moderate ozone nonattainment RFP demonstration included in this SIP submission.
**DATES:**
Comments must be received on or before March 16, 2026.
**ADDRESSES:**
Submit your comments, identified by Docket ID No. EPA-R05-OAR-2024-0617 or EPA-R05-OAR-2024-0618 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. The EPA may publish any comment received to its public docket. Do not submit to the 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. The 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:**
Nicole Naber, Air and Radiation Division (AR-18J), Environmental Protection Agency, Region 5, 77 West Jackson Boulevard, Chicago, Illinois 60604, (312) 886-6609, *[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 the EPA.
**I. Background**
On December 28, 2015, the EPA promulgated a revised 8-hour ozone NAAQS of 0.070 parts per million (ppm). [^1] Promulgation of a revised NAAQS triggers a requirement for the EPA to designate all areas of the country as nonattainment, attainment, or unclassifiable for the NAAQS. For the ozone NAAQS, this also involves classifying any nonattainment areas at the time of designation. [^2] Ozone nonattainment areas are classified based on the severity of their ozone levels as determined by area's “design value,” which represents air quality in the area for the most recent three years. The classifications for ozone nonattainment areas are Marginal, Moderate, Serious, Severe, and Extreme. [^3]
[^1] 80 FR 65292, October 26, 2015, codified at 40 CFR 50.19.
[^2] CAA sections 107(d)(1) and 181(a)(1).
[^3] CAA section 181(a)(1).
Areas that the EPA designates nonattainment for the ozone NAAQS are subject to the general nonattainment area planning requirements of CAA section 172 and the ozone-specific planning requirements of CAA section 182. Ozone nonattainment areas in the lower classification levels have fewer and/or less stringent mandatory air quality planning and control requirements than those in higher classifications. In the EPA's December 6, 2018 (83 FR 62998), rule, “Implementation of the 2015 National Ambient Air Quality Standards for Ozone: Nonattainment Area State Implementation Plan Requirements,” known as the “SIP Requirements Rule,” the EPA set forth nonattainment area requirements for the 2015 ozone NAAQS. These requirements are codified at 40 CFR part 51 subpart CC. For Marginal areas, a State is required to submit a baseline emissions inventory, adopt provisions into the SIP requiring emissions statements from stationary sources, and implement a nonattainment new source review program for the relevant ozone NAAQS. [^4] For Moderate areas, a State needs to comply with the Marginal area requirements, plus additional Moderate area requirements, including the requirement to submit a modeled demonstration that the area will attain the NAAQS as expeditiously as practicable but no later than six years after designation, the requirement to submit an RFP plan, the requirement to adopt and implement certain emissions controls, such as Reasonably Available Control Technology (RACT) and a Basic I/M program, and the requirement for greater emissions offsets for new or modified major stationary sources under the State's NNSR program.
[^4] CAA section 182(a).
Effective June 4, 2018, the EPA designated the Chicago and Metro East St. Louis areas as Marginal nonattainment. The Chicago area includes Cook County, DuPage County, Grundy County, Kane County, Kendall County, Lake County, McHenry County, and Will County, and the Metro East area includes Madison County, Monroe County, and St. Clair County. Under CAA section 181(b)(2), Marginal nonattainment areas that fail to attain the 2015 ozone NAAQS by the applicable attainment date will be reclassified as Moderate by operation of law upon the effective date of the final determination. For Chicago and Metro East, the deadline was August 3, 2021.
On October 7, 2022 (87 FR 60897), the EPA determined that the Chicago and Metro East areas failed to attain the 2015 ozone NAAQS by the August 3, 2021, deadline, resulting in the reclassification of the areas from Marginal to Moderate ozone attainment. In that action, the EPA established January 1, 2023, as the due date for Illinois to submit all Moderate area nonattainment plan SIP requirements applicable to newly reclassified areas. More recently, on December 17, 2024 (89 FR 101901), the EPA determined the areas did not attain the standards by the Moderate attainment date, and the areas were reclassified as Serious; however, this action is only addressing Moderate elements.
**II. Evaluation of Illinois' Submittals**
The Illinois Environmental Protection Agency (Illinois EPA) submitted SIP revisions on December 18, 2024, to address Moderate area requirements for the Chicago and Metro East areas under the 2015 ozone NAAQS. These submittals contained several nonattainment plan elements, including an updated 2017 base year emissions inventory for volatile organic compounds (VOC) and oxides of nitrogen (NO <sub>X</sub> ) and a 15% RFP plan with 2023 VOC and NO <sub>X</sub> motor vehicle emissions budgets, an I/M program certification, and an NNSR certification. The submissions also included an attainment demonstration, a reasonably available control measures demonstration, and contingency measures, which are not being addressed in this action. Illinois' SIP submissions and associated supporting documents are available in the docket for this action.
**A. 2017 Base Year Emissions Inventory**
**1. Background**
CAA sections 172(c)(3) and 182(a)(1), 42 U.S.C. 7502(c)(3) and 7511a(a)(1), require States to develop and submit, as SIP revisions, comprehensive, accurate, and complete emissions inventories for all areas designated as nonattainment for the ozone NAAQS. The specific emissions inventory requirements are codified at 40 CFR 51.1315, and the term “base year inventory” is defined at 51.1300(p). For ozone, the base year inventory is an estimation of actual emissions of VOC and NO <sub>X</sub> from all sources within the boundaries of the nonattainment area.
The regulation at 40 CFR 51.1315(a) requires that the inventory year be selected consistent with the baseline year for the RFP plan as required by 40 CFR 51.1310(b), which states that the baseline emissions inventory shall be the emissions inventory for the most recent calendar year for which a complete triennial inventory is required to be submitted to the EPA under the provisions of subpart A of 40 CFR part 51, Air Emissions Reporting Requirements, 40 CFR 51.1 through 50. For areas designated as nonattainment in 2018, the most recent triennial inventory year conducted for the National Emissions Inventory (NEI) pursuant to the Air Emissions Reporting Requirements (AERR) rule is 2017. [^5]
[^5] 83 FR 62998 through 63036 at 63005, December 6, 2018.
Further, 40 CFR 51.1315(c) requires emissions values included in the base year inventory to be actual ozone season day emissions as defined by 40 CFR 51.1300(q), which states: “Ozone season day emissions mean an average day's emissions for a typical ozone season work weekday. The State shall select, subject to the EPA approval, the month(s) in the ozone season and the day(s) in the work week to be represented, considering the conditions assumed in the development of RFP plans and/or emissions budgets for transportation conformity.”
On October 22, 2020, Illinois EPA submitted a SIP revision addressing the emissions inventory requirement of CAA section 182(a)(1). The EPA approved Illinois' 2017 base year emissions inventories for the Chicago area on August 15, 2023 (88 FR 55383).
**2. Illinois' Emission Inventory Submittal**
As part of Illinois' SIP revision request, Illinois EPA updated the 2017 base year emissions inventories to incorporate improved emissions estimates where available. In Illinois' original base year emissions inventory submittal, Illinois EPA used the 2016v1 modeling platform to generate emissions data for the point and nonpoint sectors and MOVES2014 to generate emissions data for the on-road and nonroad sectors. Illinois EPA updated the 2017 base year emissions inventories for the Chicago and Metro East areas using the 2016v1 modeling platform for point and nonpoint sectors and MOVES3 for nonroad and on-road sectors. Illinois EPA did not update biogenic emissions estimates.
Illinois EPA converted annual point and nonpoint values to tons per day (tpd) following the same procedure as was used when preparing the original 2017 base year emissions inventories. Illinois EPA extracted data from the 2016v1 modeling platform to calculate the ratio of July emissions to total annual emissions for each county by sector.
Table 1, below, shows the updated 2017 ozone season day emissions in tons per ozone season day of NO <sub>X</sub> and VOC for the Chicago and Metro East nonattainment areas, respectively.
| Area | Pollutant | Point | Area | On-road | Off-road | Total |
| --- | --- | --- | --- | --- | --- | --- |
| Chicago | NO | 66.39 | 101.36 | 208.20 | 53.34 | 429.29 |
| | VOC | 45.74 | 207.57 | 58.20 | 49.99 | 361.50 |
| Metro East | NO | 10.65 | 8.72 | 17.44 | 5.25 | 42.06 |
| | VOC | 8.62 | 18.94 | 6.81 | 3.82 | 38.19 |
**3. Analysis of Illinois' 2017 Base Year Emission Inventory**
EPA has reviewed Illinois' updated 2017 base year emissions inventory for consistency with sections 172(c)(3) and 182(a)(1) of the CAA and the EPA's emission inventory requirements. The selection of 2017 as the base year comports with the RFP baseline year requirements set forth in the SIP Requirements Rule and codified at 40 CFR 51.1310(b).
Illinois EPA documented the procedures used to estimate the emissions for each of the major source types. The documentation of the emission estimation procedures is sufficient to determine that Illinois followed acceptable procedures to estimate the emissions. Accordingly, the EPA concludes that Illinois has developed inventories of NO <sub>X</sub> and VOC emissions that are comprehensive and complete and is therefore proposing to approve Illinois' updated 2017 base year emissions inventory for the Chicago and Metro East areas under the 2015 ozone NAAQS.
**B. I/M Program**
**1. Background**
CAA section 182(b)(4) requires States with ozone nonattainment areas classified as Moderate to implement a Basic motor vehicle I/M program. The goal of I/M programs is to identify and repair high-emitting vehicles to improve air quality in areas that are not attaining the NAAQS. [^6] The CAA generally requires I/M programs for areas across the country that meet certain criteria, such as air quality status, population, and/or geographic location. The CAA also directed the EPA to establish minimum performance standards for Basic and Enhanced I/M programs. States have flexibility to design their own programs if they can show that their program is as effective as the model program used in the respective performance standard. The EPA's requirements for Basic and Enhanced I/M programs are found in 40 CFR part 51, subpart S.
[^6] For more information, see *Overview of Vehicle Inspection and Maintenance (I/M) Programs* (EPA-420-F-21-067, October 2021) at *https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1013CC0.pdf.*
Illinois EPA has been operating an enhanced I/M program in the Chicago and Metro East areas since February 22, 1999 (64 FR 8517), with a subsequent approval on August 13, 2014 (79 FR 47377). These EPA-approved I/M program requirements, that are incorporated into the Illinois SIP, remain in place in both the Chicago and Metro East areas.
**2. Illinois' I/M Certification**
Consistent with the I/M regulations, a State with an existing I/M program would need to conduct and submit a performance standard modeling (PSM) analysis as well as make any necessary program revisions as part of their Moderate area SIP submission to ensure that their I/M program is operating at or above the Basic I/M performance standard level for the 2015 ozone NAAQS. When certifying that an existing I/M program meets applicable I/M requirements for a new NAAQS, it is necessary that the State ensures that an I/M program reflects the I/M rule's required elements for a Basic or Enhanced I/M program and the applicable classification for the new ozone NAAQS. If an I/M program for a previous NAAQS contains the required elements for a new NAAQS ( *e.g.,* such as on-road mobile source testing for an Enhanced I/M program) then the State may determine through the performance standard modeling analysis that an existing SIP-approved program would meet the applicable performance standard for purposes of the 2015 ozone NAAQS without modification.
Illinois EPA is certifying that the existing SIP-approved I/M programs meet the Basic I/M program requirements of CAA section 182(b)(4) for the Chicago and Metro East areas under the 2015 ozone NAAQS. The Illinois Vehicle Emission Inspection Law of 2005(625 ILCS 5/13C) authorizes the State to implement I/M programs to reduce to reduce air pollution from motor vehicles in these areas. In addition, the requirements for the State's I/M programs are found in the Illinois Administrative Code (Ill. Adm. Code) Title 35, Parts 240 and 276. The Illinois I/M programs require on-board diagnostic (OBD) testing of gasoline-fueled and hybrid motor vehicles up to 8500 pounds gross vehicle weight rating (GVWR) that are 1996 model year (MY) and newer but more than four MYs old, as well as the OBD testing of gasoline-fueled and hybrid vehicles between 8501 and 14,000 pounds GVWR that are 2007 MY and newer but more than four MYs old.
In addition, Illinois EPA conducted an I/M PSM analysis to demonstrate that Illinois' current I/M program continues to exceed the level of the EPA's Enhanced performance standard for areas designated and classified under the 8-hour ozone standard, as detailed at 40 CFR 51.351(i)(13), which states that the actual I/M program must achieve the same or lower emissions levels of NO <sub>X</sub> and VOCs as the Federal model Enhanced program to within 0.02 grams/mile (g/m). Illinois EPA performed the modeling analysis using the EPA's mobile source emissions model, MOVES4, which was the latest model version at the time the analysis was started. The performance standard modeling analysis began after the mobile emissions modeling analyses conducted to prepare other elements of the SIP submission. This modeling was conducted for analysis year 2023 in accordance with the EPA's technical guidance: “Performance Standard Modeling for New and Existing Vehicle Inspection and Maintenance (I/M) Programs Using the MOVES Mobile Source Emissions Model”, EPA-420-B-22-034, October 2022, [^7] (October 2022 Performance Standard Modeling Guidance).
[^7]*https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1015S5C.pdf.*
Table 2 below shows the results of Illinois EPA's modeling analysis comparing the average fleet emission rates of the current I/M program to that of the Enhanced I/M performance standard benchmark program for both the Chicago and Metro East nonattainment areas, respectively. In all cases, the analysis shows that the emission reductions from Illinois' actual I/M program exceed the emission reductions modeled for the benchmark program of the Enhanced I/M performance standard to within 0.02 g/m.
| Area | Pollutant | Existing I/M | Enhanced | Enhanced I/M | Does existing I/M |
| --- | --- | --- | --- | --- | --- |
| Chicago | NO | 0.984 | 1.002 | 1.022 | Yes. |
| | VOC | 0.538 | 0.533 | 0.553 | Yes. |
| Metro East | NO | 0.527 | 0.533 | 0.553 | Yes. |
| | VOC | 0.302 | 0.297 | 0.317 | Yes. |
**2. Evaluation of Illinois' I/M Program**
At the Moderate classification for the 2015 ozone NAAQS, the Chicago and Metro East areas are only required to implement Basic I/M. However, these areas continue to implement Enhanced I/M programs as adopted into the SIP under prior ozone NAAQS. The EPA's October 2022 Performance Modeling Guidance addresses the situation where a State may need to demonstrate that an area's current Enhanced I/M program satisfies the Basic I/M SIP requirement: “[I]t is reasonable to presume that if an I/M program meets the Enhanced performance standard, then it would also meet the Basic performance standard so long as the analysis years are appropriate for the two 8-hour ozone standards in question.” [^8] The guidance goes on to identify the attainment date as the appropriate analysis year for areas that have been reclassified. [^9]
[^8] October 2022 Performance Standard Modeling Guidance, p. 10.
[^9] Ibid.
The Moderate attainment date for the Chicago and Metro East areas is August 3, 2024. However, because that date falls in the middle of the ozone season, 2023 is the year that will be used to determine whether the area achieves attainment by the attainment date. Therefore, Illinois appropriately chose 2023 as the analysis year to be consistent with the year in which attainment would be determined.
EPA has reviewed Illinois' I/M program submittals and determined that the emission reductions from the current Chicago and Metro East I/M programs meet or exceed the Basic I/M performance standard. Illinois EPA documented that the modeling analysis was conducted in accordance with the EPA's October 2022 Performance Modeling Guidance. Therefore, since the Chicago and Metro East I/M programs meet the applicable I/M performance requirements and also meet the Basic I/M requirements of CAA section 182(b)(4) and 40 CFR 51 subpart S, we are proposing to approve Illinois' I/M program SIP element for the Chicago and Metro East Moderate nonattainment areas under the 2015 ozone NAAQS.
**C. 15% RFP Plan**
**1. Background**
The CAA requires that States with areas designated as nonattainment for ozone achieve RFP toward attainment of the ozone NAAQS. CAA section 172(c)(2) contains a general requirement that nonattainment plans must provide for emissions reductions that meet RFP. For areas classified Moderate, section 182(b)(1) imposes a more specific RFP requirement that a State is required to meet through a 15% reduction in VOC emissions from the baseline anthropogenic emissions within 6 years after November 15, 1990.
The SIP Requirements Rule addressed, among other things, RFP requirements as they apply to areas designated nonattainment and classified as Moderate for the 2015 ozone NAAQS. [^10] RFP requirements under the 2015 ozone NAAQS are codified at 40 CFR 51.1310. The EPA interprets the 15% VOC emission reduction requirement in CAA section 182(b)(1) such that a State that has already met the 15% requirement for VOC and NO <sub>X</sub> for an area under either the 1-hour ozone NAAQS or a prior 8-hour ozone NAAQS would not have to fulfill that requirement through reductions of VOC again. Instead, States with such areas must obtain 15% ozone precursor emission reductions from VOC and/or NO <sub>X</sub> over the first 6 years after the baseline year for the 2015 ozone NAAQS. Illinois previously met the 15% VOC reduction requirement of CAA section 182(b)(1) for the Chicago and Metro East areas under the 1-hour ozone NAAQS. Therefore, the State may rely upon both VOC and NO <sub>X</sub> emissions reductions to meet the RFP requirement for the 2015 ozone NAAQS.
[^10] 83 FR 62998 through 63036 at 63004, December 6, 2018.
The SIP Requirements Rule specifies that the baseline emissions inventory for RFP plans shall be the most recent calendar year prior to designation for which a complete triennial inventory is required to be submitted to the EPA under the provisions of subpart A of 40 CFR part 51, AERR, 40 CFR 51.1 through 50. For areas designated as nonattainment in 2018, the most recent triennial inventory year conducted for the NEI pursuant to the AERR rule is 2017. The rule also allows the use of an alternative RFP baseline year that corresponds with the year of the effective date of an area's designation, *i.e.,* 2018 for areas designated nonattainment in 2018. [^11]
[^11] 83 FR 62998 through 63036 at 63005, December 6, 2018, codified at 40 CFR 51.1310(b).
States may not take credit for VOC or NO <sub>X</sub> reductions occurring from sources outside the nonattainment area for purposes of meeting the 15% RFP requirements of CAA sections 172(c)(2), 182(b)(1) and 182(c)(2)(B). [^12]
[^12] 40 CFR 51.1310(a)(6).
Except as specifically provided in CAA section 182(b)(1)(C) and (D) and CAA section 182(c)(2)(B), all emission reductions from SIP-approved or federally promulgated measures that occur after the baseline emissions inventory year are creditable for purposes of the RFP requirements in this section, provided the reductions meet the requirements for creditability, including the need to be enforceable, permanent, quantifiable, and surplus. Further, the Administrator has determined that the four categories of control measures listed in CAA section 182(b)(1)(D) are no longer required to be calculated for exclusion in RFP analyses because due to the passage of time the effect of these exclusions would be *de minimis.*[^13]
[^13] 40 CFR 51.1310(a)(7).
**2. Illinois' 15% RFP Plan**
**Emission Inventories**
To demonstrate that the Chicago and Metro East areas have achieved 15% RFP over the 6-year attainment planning period, Illinois EPA is using a 2017 base year inventory and a 2023 RFP inventory. The procedures Illinois EPA used to develop the 2017 base year inventory are discussed in section I.A. of this preamble. A 2016 base year inventory was used to project 2023 emissions. The 2016 base year was selected because of meteorology, typical ozone conditions, and average wildfire conditions. Comparing Illinois' 2017 base year inventory to the 2016 base year inventory used to project 2023 emissions, Illinois' 2017 base year inventory VOC and NO <sub>X</sub> emissions are higher. Therefore, projected emissions reductions for both pollutants in the RFP demonstration are more conservative when compared to the 2016 inventory. For both Chicago and Metro East, these base year emissions are substituted for 2017 data in all cases, except for onroad emissions projections. For the Chicago nonattainment area, the on-road mobile emissions were updated in this document to reflect the most up to date MOVES3 modeling at the time of analysis and motor information and were used to project 2023 emissions from a 2019 base year. The 2019 base year was chosen as it had more detailed modeling information for the Chicago NAA compared to 2017. Since on-road emissions have trended downward from 2017 to 2020 based on NEI data, the 2019 base year should have lower emissions than the 2017 base year, therefore, estimates of emissions reductions between 2023 and 2019 are less than estimates between 2023 and 2017. Thus, the 2019 base year on-road mobile emissions can be conservatively substituted for 2017 data in all cases. For the Metro East nonattainment area, the on-road mobile emissions were updated in this document to reflect the most up to date MOVES3 modeling at the time of analysis and motor information and were used to project 2023 emissions from a 2017 base year. The primary source of data for point sources was the source-reported 2017 annual emissions reports. Area source emissions are estimated by multiplying an emission factor by a known indicator of activity for a source category. The 2016v1 modeling platform used projection methods for the 2023 emissions inventory that are specific to the type of emissions source. In general, future emissions are projected from the 2016 base case through running models or adjusting base year emissions based on best estimates of changes expected to occur. Two electrical generating units (EGUs) announced shutdown before 2023 but after the development of the inventory; therefore, the Eastern Regional Technical Advisory Committee provided an EGU 16.2 beta inventory forecast for 2023 that was modified to remove the 2023 emissions from these units.
2023 ozone season day emissions of NO <sub>X</sub> and VOC for the Chicago and Metro East areas are shown in Table 3.
| Area | Pollutant | Point | Area | On-road | Off-road | Total |
| --- | --- | --- | --- | --- | --- | --- |
| Chicago | NO | 66.59 | 93.11 | 150.90 | 53.34 | 345.92 |
| | VOC | 45.80 | 211.45 | 49.00 | 44.61 | 350.86 |
| Metro East | NO | 9.14 | 7.48 | 9.87 | 3.28 | 29.76 |
| | VOC | 7.97 | 18.80 | 4.79 | 2.80 | 34.35 |
**15% RFP Demonstration**
Illinois EPA demonstrated that the Chicago and Metro East Areas have achieved 15% RFP over the 6-year attainment planning period through VOC and NO <sub>X</sub> emission reductions. Illinois has documented Federal control measures and State measures adopted into the Illinois SIP that are permanent and enforceable and can be used to achieve emissions reductions. Illinois chose to count 2% VOC reductions and 13% NO <sub>X</sub> reductions for Chicago and 3% VOC reductions and 12% NO <sub>X</sub> reductions for Metro East from 2017-2023 to meet the 15% RFP requirement. Table 4 shows the calculations used to determine that emissions reductions in both areas are sufficient to meet the 15% RFP requirement.
| Step | Description | Formula | Area | Chicago | NO | VOC | Metro East | NO | VOC |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | 2017 Base Year Inventory | | 429.29 | 361.50 | 42.06 | 38.19. | | | |
| 2 | RFP Reductions totaling 15% | | 13% | 2% | 12% | 3%. | | | |
| 3 | Emissions reductions required between base and future year | Step 1 × Step 2 | 55.81 | 7.23 | 5.05 | 1.15. | | | |
| 4 | Reductions between 2017 to 2023 from Federal on-road control programs | | 57.30 | 9.20 | 7.57 | 2.02. | | | |
| 5 | Adjustments to reductions Increase for mobile source budget | | 1.49 | 1.97 | 2.52 | 0.87. | | | |
| 6 | Creditable reductions from on-road control programs | Step 4−Step 5 | 55.81 | 7.23 | 5.05 | 1.15. | | | |
| 7 | Compare creditable reductions to determine if at least 15% reduction is achieved | Is Step 6 ≥Step 3? | Yes | Yes | Yes | Yes. | | | |
| 8 | RFP Target Level | Step 1−Step 3 | 373.48 | 354.27 | 37.01 | 37.05. | | | |
| 9 | Projected 2023 emissions | | 345.92 | 350.86 | 29.76 | 34.35. | | | |
| 10 | Compare RFP target with projected 2023 emissions to determine if RFP requirements are met | Is Step 8 ≥Step 9? | Yes | Yes | Yes | Yes. | | | |
**3. Evaluation of Illinois' 15% RFP Plan**
EPA has reviewed Illinois' 15% RFP plan for consistency with sections 172(c)(2) and 182(b)(1) of the CAA and 40 CFR 51.1310. The selection of 2017 as the base year comports with the RFP baseline year requirements set forth in the SIP Requirements Rule and codified at 40 CFR 51.1310(b). The EPA has reviewed the techniques used by Illinois to derive the 2017 and 2023 emission estimates. Illinois documented the procedures used to estimate the emissions for each of the major source types. The documentation of emission estimation procedures is thorough and adequate to determine that Illinois followed acceptable procedures to estimate the emissions. Illinois has demonstrated that these emission reductions are permanent and enforceable and will result in at least 15% RFP in the Chicago and Metro East areas over the six-year attainment planning period beginning with the 2017 base year. Thus, the EPA is proposing to approve Illinois' 15% RFP plan for both areas for the 2015 ozone NAAQS.
**D. Motor Vehicle Emission Budgets**
**1. Background**
Under section 176(c) of the CAA, transportation plans, programs, or projects that receive Federal funding or support, such as the construction of new highways, must “conform” to ( *i.e.,* be consistent with) the SIP before they receive Federal funding or approval. Conformity to the SIP means that transportation activities will not cause or contribute to any new air quality violations, increase the frequency or severity of any existing air quality problems, or delay timely attainment or any required interim emissions reductions or any other milestones. Regulations at 40 CFR part 93 subpart A set forth the EPA policy, criteria, and procedures for demonstrating and ensuring conformity of transportation activities to a SIP.
Transportation conformity is a requirement for nonattainment and maintenance areas, as defined in 40 CFR 93.101. The budget in a State's SIP serves as a ceiling on emissions from an area's planned transportation system (see definition of “motor vehicle emissions budget” in 40 CFR 93.101 and how the term is used in 40 CFR 93.109 and 93.118).
**2. VOC and NO
X
Budgets for the Chicago and Metro East Areas**
The RFP plan includes VOC and NO <sub>X</sub> budgets for the Chicago and Metro East areas for 2023, the milestone year for RFP. These inventories were developed using up-to-date assumptions about vehicles mile traveled (VMT), vehicle type and age distribution, fuels used, weather inputs, other planning assumptions, and the latest approved motor vehicle emissions model at the time Illinois EPA began to prepare the SIP submission, which was MOVES3. Total on-road emissions in both the Chicago and Metro East areas are shown in Table 5.
| Area | Pollutant | 2017 | 2023 | Difference |
| --- | --- | --- | --- | --- |
| Chicago | NO | 208.20 | 150.90 | −57.30 |
| | VOC | 58.20 | 49.00 | −9.20 |
| Metro East | NO | 17.44 | 9.87 | −7.57 |
| | VOC | 6.81 | 4.79 | −2.02 |
Table 6 identifies Illinois' 2023 budgets. The budgets, agreed upon as part of the interagency consultation process, include the emission estimates calculated for 2023 with an additional safety margin allocated to those estimates to accommodate future variations in travel demand models and VMT forecasts. A State can add a safety margin to a budget based on the transportation conformity regulation at 40 CFR 93.124(a).
| Area | Pollutant | 2023 Estimated | Applied safety | Motor vehicle |
| --- | --- | --- | --- | --- |
| Chicago | NO | 150.9 | 14.88 | 165.78 |
| | VOC | 49.0 | 3.47 | 52.47 |
| Metro East | NO | 9.87 | 4.42 | 14.29 |
| | VOC | 4.79 | 1.98 | 6.77 |
**3. Evaluation of the VOC and NO
X
Budgets**
The VOC and NO <sub>X</sub> budgets for the Chicago and Metro East areas were developed as part of an interagency consultation process which includes Federal, State, and local agencies. The budgets were clearly identified and precisely quantified. Illinois has demonstrated that both the Chicago and Metro East areas can meet the 15% RFP requirement in 2023 with mobile source emissions of 165.78 tpd of NO <sub>X</sub> and 52.47 tpd of VOC and 14.29 tpd of NO <sub>X</sub> and 6.77 tpd of VOC, respectively, despite partial allocation of the RFP plan surplus reductions that can be seen in Table 4. The EPA is thus proposing to approve the 2023 VOC and NO <sub>X</sub> budgets for use in determining transportation conformity in the Chicago and Metro East areas under the 2015 ozone NAAQS.
When reviewing submitted SIPs containing budgets, the EPA reviews the budgets for adequacy. Once the EPA finds the submitted budget is adequate for transportation conformity purposes, that budget must be used by State and Federal agencies in determining whether proposed transportation projects conform to the SIP as required by section 176(c) of the CAA.
EPA's substantive criteria for determining adequacy of a budget are set out in 40 CFR 93.118(e)(4). The process for determining adequacy is found in 40 CFR 93.118(f) and consists of three basic steps: public notification of a SIP submission, a public comment period, and issuance of the EPA's adequacy finding. The regulations that allow the EPA to begin an adequacy review through a notice of proposed rulemaking in the *Federal Register* are found in 40 CFR 93.118(f)(2). This proposal notifies the public that the EPA has received a SIP submission with budgets that the EPA will review for adequacy and begins the public comment period. Comments must be submitted to the docket for this proposal by the close of the comment period on this proposal. The EPA invites the public to comment on the adequacy of these budgets as well as on its proposed approval of the budgets and on other actions the EPA is proposing in this action.
**E. NNSR Review**
**1. Background**
NNSR is a preconstruction review permit program that applies to new major stationary sources or major modifications at existing sources within a nonattainment area and is required under CAA sections 172(c)(5) and 173. NNSR permit program requirements were adopted for the 2015 ozone NAAQS at 40 CFR 51.1314 as part of the 2015 SIP Requirements Rule. The minimum SIP requirements for NNSR permitting programs for the 2015 ozone NAAQS are contained in 40 CFR 51.165. The SIP for each ozone nonattainment area must contain NNSR provisions that: (1) set major source thresholds for NO <sub>X</sub> and VOC pursuant to 40 CFR 51.165(a)(1)(iv)(A)(1)(i) through (iv) and (2); (2) classify physical changes as a major source if the change would constitute a major source by itself pursuant to 40 CFR 51.165(a)(1)(iv)(A)(3); (3) consider any significant net emissions increase of NO <sub>X</sub> as a significant net emissions increase for ozone pursuant to 40 CFR 51.165(a)(1)(v)(E); (4) consider any increase of VOC emissions in Extreme ozone nonattainment areas as a significant net emissions increase and a major modification for ozone pursuant to 40 CFR 51.165(a)(1)(v)(F); (5) set significant emissions rates for VOC and NO <sub>X</sub> as ozone precursors pursuant to 40 CFR 51.165(a)(1)(x)(A) through (C) and (E); (6) contain provisions for emissions reductions credits pursuant to 40 CFR 51.165(a)(3)(ii)(C)(1) through (2); (7) provide that the requirements applicable to VOC also apply to NO <sub>X</sub> pursuant to 40 CFR 51.165(a)(8); (8) set offset ratios for VOC and NO <sub>X</sub> pursuant to 40 CFR 51.165(a)(9)(ii) through (iv); and (9) require public participation procedures compliant with 40 CFR 51.165(i).
**2. Illinois' NNSR Certification**
Illinois affirms that the existing NNSR for new major stationary sources or major modifications located in areas that the EPA has designated as nonattainment for a particular criteria pollutant are sufficient to meet Moderate requirements. Illinois administers this program through 35 Ill. Adm. Code Part 203, Major Stationary Sources Construction and Modification. Illinois also implements a minor NSR permit program through 35 Ill. Adm. Code Part 204, Prevention of Significant Deterioration (PSD). New major stationary sources or major modifications subject to NNSR are required to obtain emission offsets for volatile organic material or nitrogen oxides at ratio of 1.15 to 1 in areas classified as Moderate nonattainment for ozone. The requirements of the NNSR program were most recently submitted to the EPA as a SIP revision for the 2008 ozone NAAQS on May 24, 2018, and approved on October 9, 2018 (83 FR 50551).
Illinois' PSD program set forth at 35 Ill. Adm. Code 204, was approved by the EPA into Illinois' SIP on September 9, 2021 (86 FR 50459) and became effective October 12, 2021. These program requirements along with the NNSR program ensure that the initial construction of new major stationary sources and major modifications of stationary sources do not cause or contribute to a violation of the 2015 ozone NAAQS.
**3. Evaluation of Illinois' NNSR Certification**
EPA has reviewed Illinois' approved NNSR rules and is proposing to approve Illinois' certification submittal because we find that the current SIP-approved NNSR program satisfies all the NNSR program requirements currently applicable to the moderate areas for the 2015 ozone NAAQS.
**V. What action is the EPA taking?**
EPA is proposing to approve portions of Illinois' attainment plan SIP revision request, dated December 18, 2024, pursuant to section 110 and part D of CAA. The Illinois attainment plan submission satisfies the base year emissions inventory, the RFP demonstration including 2023 budgets, I/M certification, and NNSR requirements of the CAA for the Chicago and Metro East nonattainment areas for the 2015 ozone NAAQS. The EPA is also initiating the adequacy process of the 2023 budgets for the Chicago and Metro East St. Louis Moderate ozone nonattainment RFP demonstration included in this SIP submission.
**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, the 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);
• 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 the 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, Nitrogen dioxide, Ozone, Reporting and recordkeeping requirements, Volatile organic compounds.
Dated: February 3, 2026.
Anne Vogel,
Regional Administrator, Region 5.