Air Quality State Implementation Plans; Approvals and Promulgations: Wisconsin; Moderate Attainment Plan Elements for Wisconsin's 2015 Ozone Standard Areas

Air Plan Approval; Wisconsin; Moderate Attainment Plan Elements for Wisconsin's 2015 Ozone Standard Areas

SUPPLEMENTARY INFORMATION:

Throughout this document whenever "we," "us," or "our" is used, we mean the EPA. This supplementary information section is arranged as follows:

I. Background

II. Evaluation of Wisconsin's Submittal

A. 2017 Base Year Emissions Inventory

B. 15% RFP Plan

C. Motor Vehicle Emissions Budgets

D. Motor Vehicle I/M Program

E. NNSR Review

III. What action is the EPA taking?

IV. Statutory and Executive Order Reviews

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 based on the 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⁾

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 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 an NNSR 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 the greater emissions offsets for new or modified major stationary sources under the State's NNSR program. ⁽⁵⁾ Effective August 3, 2018, the EPA finalized the Wisconsin areas' Marginal nonattainment designations for the 2015 ozone NAAQS. ⁽⁶⁾

In response to a July 10, 2020, decision by the D.C. Circuit Court, the EPA revised the 2015 ozone NAAQS Marginal nonattainment designations for the Kenosha County and Milwaukee areas, effective July 14, 2021. ⁽⁷⁾ This action expanded the original partial Kenosha County boundary designation. For the Milwaukee area, the EPA revised and expanded nonattainment designations to include the entirety of Milwaukee and Ozaukee Counties and parts of Racine, Waukesha, and Washington Counties. The Sheboygan County area remained the same as the original Marginal designation.

On October 7, 2022 (87 FR 60897), pursuant to section 181(b)(2) of the CAA, the EPA determined that the Kenosha County area, the Milwaukee area, and the Sheboygan County area failed to attain the 2015 ozone NAAQS by the August 3, 2021, Marginal area attainment deadline and thus reclassified the area from Marginal to Moderate nonattainment. In that action, the EPA established January 1, 2023, as the due date for the State to submit all Moderate area nonattainment plan SIP requirements applicable to newly reclassified areas.

II. Evaluation of Wisconsin's Submittal

Wisconsin submitted a SIP revision on April 2, 2025, to address the Marginal area requirement for baseline emissions inventories and the Moderate area requirements for Kenosha County area, the Milwaukee area, and the Sheboygan County area under the 2015 ozone NAAQS. The submittal contained several nonattainment plan elements, including a 2017 base year emissions inventory for volatile organic compounds (VOC) and oxides of nitrogen (NO _X ), a 15% RFP plan with 2023 VOC and NO _X motor vehicle emissions budgets, an I/M program certification, and an NNSR certification. The 2017 base year emissions inventories supersede and replace a prior submittal by Wisconsin on August 3, 2021, to address Marginal area requirements for the Wisconsin areas for the 2015 ozone NAAQS. Each of these nonattainment plan elements is covered in further detail below. The submission also included an attainment demonstration, a reasonably available control measures (RACM) demonstration, and contingency measures, which will be addressed in a separate action. Wisconsin's SIP submission and associated supporting documents are available in the dockets for this action, at https://www.regulations.gov, Docket ID No. EPA-R05-OAR-2025-0169 (Kenosha), EPA-R05-OAR-2025-0170 (Milwaukee), and EPA-R05-OAR-2025-0171 (Sheboygan).

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. This requirement is 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 _X from all sources within the boundaries of the nonattainment area.

The regulation at 40 CFR 51.1315(a) requires that the selected inventory year be 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 (AERR), 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 AERR rule is 2017. ⁽⁸⁾

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 means an average day's emissions for a typical ozone season work weekday. The State shall select, subject to EPA approval, the particular 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."

2. Wisconsin's Emissions Inventory Submittal

Wisconsin's 2017 base year emissions inventory submittal for the 2015 ozone NAAQS nonattainment areas includes VOC and NO _X emissions estimates for the following source categories: point sources, area sources, onroad mobile sources, and nonroad mobile sources.

Point Sources

Point sources are industrial, commercial, or institutional stationary facilities, typically located at permanent sites, which emit specific pollutants in large enough quantities to warrant individual quantification. Wisconsin created the point source emissions inventory using annually reported point source emissions, the EPA's Clean Air Markets Program Data (CAMPD), and approved EPA techniques for emissions calculations ( e.g., emission factors) for the 2017 point source emissions from State inventory databases. ⁽⁹⁾

For electric generating unit facilities in the 2015 ozone NAAQS nonattainment areas, Wisconsin estimated ozone season day operations by selecting the ozone season day with the 99th percentile highest heat input for each unit. Ozone season day emissions for VOC and NO _X were calculated by multiplying average emission rates of VOC and NO _X for the 2017 ozone season by the maximum ozone season day heat inputs. NO _X emission rates were derived from CAMPD, and VOC emission rates were derived by dividing annual VOC emissions reported to the Wisconsin Air Emissions Inventory (AEI) system by the 2017 annual heat input reported to the CAMPD database.

Wisconsin tabulated the 2017 emissions inventory for non-EGU point sources using the emissions data reported annually by each facility operator to the Wisconsin AEI. The AEI calculates emissions for each individual emissions unit or process line by multiplying fuel or process throughput by the appropriate emission factor that is derived from mass balance analysis, stack testing, continuous emissions monitoring, engineering analysis, or the EPA's WebFIRE database. ⁽¹⁰⁾ Ozone season summer day emissions were calculated for each unit at a facility by multiplying annual emissions by a factor representing the amount of time the unit is in operation during the third quarter of the calendar year, and summed each unit's emissions to determine total ozone season summer day emissions for the facility.

Area Sources

Area sources, also called nonpoint sources, are sources that fall below point source reporting levels or are too small or too numerous to be identified individually. With the exception of agricultural silage, selected categories of solvent utilization, and the Stage II refueling category, Wisconsin based its 2017 area source emission inventory estimates on the 2017 NEI. ⁽¹¹⁾ Agricultural silage and the selected categories of solvent utilization emissions estimates were adjusted by back calculations based on data from the 2020 NEI and the EPA's 2022 Emissions Modeling Platform Version 1. Stage II refueling emissions were estimated using the EPA's Motor Vehicle Emissions Simulator model (MOVES4.0.1) with the same inputs used for onroad modeling. ⁽¹²⁾ Emission calculation methodologies used in developing the 2017 area emissions inventory are available in the EPA's 2017 NEI Technical Support Document. ⁽¹³⁾ To represent area source emissions for the partial counties, emissions from the entire county were allocated to the partial county based on population data.

Onroad Mobile Sources

Onroad mobile sources are motor vehicles traveling on local highways and roads. Examples of onroad mobile sources include cars, trucks, buses, and road motorcycles. Onroad mobile source emissions data for the Kenosha County and the Milwaukee areas were developed by the Southeastern Wisconsin Regional Planning Commission (SEWRPC), the Metropolitan Planning Organization for Southeast Wisconsin. The Wisconsin Department of Transportation (WDOT) provided onroad mobile source emissions data for Sheboygan County. Onroad emissions estimates were developed using the EPA's MOVES4.0.1, which was the latest model version at the time the inventory was developed. The modeling inputs to MOVES include detailed transportation data ( e.g., average speed distributions and vehicle miles of travel by vehicle class, road type, and hour of day).

Nonroad Mobile Sources

Nonroad mobile sources are motorized mobile equipment and other engines that are primarily used off public roadways. For inventory development, these can be divided into Commercial Marine, Aircraft and Rail Locomotive (MAR) and all other nonroad categories such as construction, agricultural, and industrial equipment. For non-MAR sources, the 2017 nonroad emissions were developed using the nonroad component of the EPA's MOVES4.0.1, using the same summer day temperatures used for onroad modeling. The default MOVES monthly distribution of agricultural activity was updated to a distribution developed by the Lake Michigan Air Directors Consortium (LADCO), consistent with what the EPA used for the 2017 and 2020 NEIs. The model was run for the months of June, July, and August. Summer day emissions were calculated by dividing the total emissions over these three months by the number of days in the three months. For MAR sources, Wisconsin used annual emission estimates for each area from the EPA's 2017 NEI, and estimated summer day emissions by dividing the annual emissions by 365. Emissions for all nonroad sources were allocated from the full county to the partial counties in the Milwaukee 2015 ozone NAAQS nonattainment area based on surrogates such as population, land area, and water area, depending on the category.

Summary of the Emissions Inventory

2017 ozone season day emissions of NO _X and VOC for the Wisconsin Moderate areas are shown in Table 1.

3. Evaluation of Wisconsin's 2017 Base Year Emissions Inventory

The EPA has reviewed Wisconsin's 2017 base year emissions inventory for consistency with sections 172(c)(3) and 182(a)(1) of the CAA and the EPA's emissions 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).

The EPA has reviewed the techniques used by Wisconsin to derive the emission estimates. Wisconsin documented the procedures used to estimate the emissions for each of the major source types. The documentation of the emission estimation procedures is thorough and adequate to determine that Wisconsin followed acceptable procedures to estimate the emissions. Therefore, the EPA is proposing to approve the emissions inventories because they satisfy all Marginal and Moderate requirements, in accordance with CAA sections 172(c)(3) and 182(a).

B. 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 and above, 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 six 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. ⁽¹⁴⁾ 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 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, the EPA interprets CAA section 172(c)(2) to require States with such areas to obtain 15% ozone precursor emission reductions from VOC and/or NO _X over the first six years after the baseline year for the 2015 ozone NAAQS. Wisconsin previously met the 15% VOC reduction requirement of CAA section 182(b)(1) for the Kenosha County, Milwaukee, and Sheboygan County areas under the 1-hour ozone NAAQS. Therefore, Wisconsin may rely upon both VOC and NO _X emissions reductions to meet the RFP requirement for the 2015 ozone NAAQS.

The SIP Requirements Rule specifies that the baseline emissions inventory for RFP plans shall be the most recent calendar year prior to the 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. ⁽¹⁵⁾

States may not take credit for VOC or NO _X 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). ⁽¹⁶⁾

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. ⁽¹⁷⁾ 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. ⁽¹⁸⁾

2. Wisconsin's 15% RFP Plan

Emissions Inventories

To demonstrate that the Kenosha County, Milwaukee, and Sheboygan County nonattainment areas have achieved 15% RFP over the six-year attainment planning period, Wisconsin is using a 2017 base year inventory and a 2023 RFP inventory. The procedures Wisconsin used to develop the 2017 base year inventory are discussed in section II.A., above. Procedures used to develop the 2023 RFP inventory are as follows. Wisconsin followed the same methodology they used to calculate 2017 emissions by multiplying average emission rates of VOC and NO _X for the ozone season by the maximum ozone season day heat inputs. Non-EGU point sources were based on 2023 reported emissions to the Wisconsin AEI. Area source emissions for 2023 were estimated by extrapolating emissions for 2017 and the EPA's 2022 Emissions Modeling Platform. ⁽¹⁹⁾ Area source emissions for the partial counties were scaled from the EPA's 2022 Emissions Modeling Platform whole counties level using county population ratios. Onroad mobile source emissions estimates for 2023 were developed using the EPA's MOVES4.0.1. For non-MAR nonroad mobile sources, the 2023 nonroad emissions were developed using the nonroad component of the EPA's MOVES4.0.1, with the updated monthly distribution of agricultural activity as was done for 2017. For MAR sources, Wisconsin obtained 2022 emissions from the EPA's 2022 Emissions Modeling Platform, Version 1, and projected 2023 emissions with a linear extrapolation from the 2017 emissions and the 2022 modeling platform emissions. If the 2022 emissions were less than the 2017 emissions, the 2023 emissions were set to the 2022 emissions to avoid an underestimation. All 2023 nonroad emissions were allocated to the partial counties based on the same adjustment factors utilized for 2017 base year emissions.

2023 ozone season day emissions of NO _X and VOC for the Milwaukee area are shown in Table 2.

15% RFP Demonstration

Wisconsin demonstrated that each Moderate area has achieved 15% RFP over the six-year attainment planning period. Wisconsin has documented Federal control measures and State measures adopted into the Wisconsin SIP that are permanent and enforceable and can be used to achieve emissions reductions.

Wisconsin has implemented NO _X RACM, codified at Wis. Adm. Code NR 428.04 and 428.05, and NO _X RACT, codified at Wis. Adm. Code NR 428.22, if emission units exceed the major source threshold of 100 tons per year. Wisconsin noted in their submittal that We Energies Pleasant Prairie power plant's boilers B20-B23 were permanently shut down on or around April 10, 2018, and are included in Wisconsin construction permit 18-RAB-050-ERC. Wisconsin has also implemented VOC RACT and National Emission Standards for Hazardous Air Pollutants (NESHAPs). VOC RACT for major stationary sources is codified in Wis. Adm. Code NR 424.

The EPA mobile source regulations currently being implemented across the country include passenger vehicle, SUV, and light-duty truck emission and fuel standards; light-duty truck and medium-duty passenger vehicle evaporative standards; heavy-duty highway compression engine standards; heavy-duty spark ignition engine standards; motorcycle emission standards; Mobile Source Air Toxics fuel formulation standards; passenger vehicle standards; and portable container emission standards. The MOVES model incorporates these Federal emissions control programs into its projections. These emissions reductions measures are permanent and enforceable and are implemented nationally, including in Wisconsin's nonattainment areas.

Table 3 through Table 5 show the calculations used to determine that emissions reductions in each Moderate nonattainment area are sufficient to meet the 15% RFP requirement.

Wisconsin assumed a 9% reduction in VOC and 6% reduction in NO _X from 2017-2023 to meet the 15% RFP requirement for the Kenosha County area. Emissions reductions of 0.53 tpd VOC and 10.87 tpd NO _X can be attributed to permanent and enforceable control measures in the EGU point source category. Emission reductions of 0.18 tpd VOC and 0.96 tpd NO _X were calculated in the onroad sector. Emission reductions of 0.08 tpd VOC and 0.20 tpd NO _X were calculated in the nonroad sector.

Wisconsin assumed a 3% reduction in VOC and 12% reduction in NO _X from 2017-2023 to meet the 15% RFP requirement for the Milwaukee area. Emissions reductions of 1.78 tpd VOC can be attributed to permanent and enforceable control measures in the point source category. Emission reductions of 2.69 tpd VOC and 12.26 tpd NO _X were calculated in the onroad sector. Emission reductions of 1.59 tpd VOC and 4.44 tpd NO _X were calculated in the nonroad sector.

Wisconsin assumed a 3% reduction in VOC and 12% reduction in NO _X from 2017-2023 to meet the 15% RFP requirement for Sheboygan County. Emissions reductions of 0.23 tpd VOC and 1.73 tpd NO _X can be attributed to permanent and enforceable control measures in the point source category. Emission reductions of 0.09 tpd VOC and 0.66 tpd NO _X were calculated in the onroad sector. Emission reductions of 0.09 tpd VOC and 0.30 tpd NO _X were calculated in the nonroad sector.

3. Evaluation of Wisconsin's Moderate 15% RFP Plans

The EPA has reviewed Wisconsin's 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 Wisconsin to derive the 2017 and 2023 emission estimates. Wisconsin 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 Wisconsin followed acceptable procedures to estimate the emissions. Wisconsin has demonstrated that these emission reductions are permanent and enforceable and will result in at least 15% RFP in the Moderate areas over the six-year attainment planning period beginning with the 2017 base year. Thus, the EPA is proposing to approve Wisconsin's 15% RFP plan for the Moderate areas for the 2015 ozone NAAQS.

C. Motor Vehicle Emissions 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, and both are defined in 40 CFR 93.101. The Budgets in a State's SIP serve 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 Wisconsin Areas

The RFP plans for the Kenosha County area, Milwaukee area, and the Sheboygan County area each include VOC and NO _X Budgets for 2023, the milestone year for RFP. 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.

For the Kenosha County and the Milwaukee areas, Wisconsin worked with SEWRPC to prepare emissions inventories used to set the Budgets for the year 2023. For Sheboygan County, Wisconsin worked with WDOT to prepare emissions inventories used to set the Budgets for the year 2023. These inventories were developed using MOVES4.0.1, the latest approved motor vehicle emissions model at the time Wisconsin began to prepare this part of the SIP submission, and up-to-date assumptions about vehicle miles traveled (VMT), socioeconomic variables, fuels used, weather inputs, and other planning assumptions. Wisconsin's 2023 Budgets for the Moderate areas are shown in Table 6. Wisconsin included a 7.5% increase to the projected VMT for 2023 for the Kenosha County and the Milwaukee areas and a 15% increase to the VMT for 2023 for Sheboygan County. This approach is consistent with the total onroad emissions presented in Table 2, above, which accommodates future variations in local transportation planning parameters, VMT forecasts, and onroad fleet characteristics.

3. Evaluation of the VOC and NO _X Budgets

The VOC and NO _X Budgets for the Kenosha County, the Milwaukee, and the Sheboygan County 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. Wisconsin has demonstrated that these areas can meet the 15% RFP requirement for the 2015 ozone NAAQS, and onroad emissions will remain under RFP target levels in 2023. The EPA is thus proposing approval of the 2023 VOC and NO _X Budgets for use in determining transportation conformity in the Kenosha County, the Milwaukee, and the Sheboygan County areas under the 2015 ozone NAAQS.

When reviewing submitted SIPs containing Budgets, the EPA reviews the Budgets for adequacy. Once the EPA affirmatively finds the submitted Budgets are adequate for transportation conformity purposes, those Budgets must be used by metropolitan and Federal agencies in determining whether proposed transportation projects conform to the SIP as required by section 176(c) of the CAA.

The EPA's substantive criteria for determining adequacy of Budgets 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 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 on the adequacy of the budgets. Comments must be submitted to the docket for this proposal by the close of the comment period on this proposal.

D. Motor Vehicle I/M Program

1. Background

In accordance with CAA section 182(b)(4), the EPA's I/M rule, at 40 CFR 51 subpart S, requires certain urbanized 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. ⁽²⁰⁾ 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 benchmark program of the respective performance standard detailed in the I/M rule.

Kenosha County and the Milwaukee areas were required to adopt an Enhanced I/M program under the 1-hour ozone NAAQS. The Sheboygan County area was required to adopt a Basic I/M program under the 1-hour ozone NAAQS. The EPA fully approved Wisconsin's I/M program on August 16, 2001 (66 FR 42949) and approved revisions to the program on September 19, 2013 (78 FR 57501).

2. Wisconsin's I/M Certification

Wisconsin's I/M program has been in operation since 1984. It was originally implemented in accordance with the 1977 CAA Amendments and operated in the six counties of Kenosha, Milwaukee, Ozaukee, Racine, Washington and Waukesha. Sheboygan County was added to the program in July 1993, resulting in a seven-county program area that has remained to the present. Vehicles were originally tested by measuring tailpipe emissions using a steady-state idle test. Tampering inspections were added in 1989. The I/M program is jointly administered by Wisconsin and WDOT.

The 1990 CAA Amendments set additional requirements for I/M programs. For Moderate areas, a "Basic" program was required under section 182(b)(4). For serious or worse areas, an "Enhanced" program was required under section 182(c)(3). The EPA's requirements for Basic and Enhanced I/M programs are found in 40 CFR part 51, subpart S.

Wisconsin's I/M program transitioned to an Enhanced program in December 1995. The major enhancement involved adding new test procedures to more effectively identify high-emitting vehicles. These new test procedures included a transient emissions test in which tailpipe emissions were measured while the vehicle was driven on a dynamometer, a treadmill-type device. Improving repairs and public convenience were also major focuses of the enhancement effort.

Since July of 2001, all model year (MY) 1996 and later cars and light trucks have been inspected by scanning the vehicle's computerized second-generation on-board diagnostic (OBD) system instead of measuring tailpipe emissions. As of July 2008, the program dropped tailpipe testing entirely and has inspected all vehicles by scanning the OBDII system. This change was the result of statutory changes in the State's 2007-2009 biennial budget which exempted model years of vehicles not federally required to be equipped with the OBDII technology (MY 1995 and earlier cars and light trucks and MY 2006 and earlier heavy trucks). To help offset the emissions reductions lost from exempting the pre-OBDII vehicles, the program increased the testable fleet for MYs 2007 and later by adding gasoline-powered vehicles between 10,001 to 14,000 pounds GVWR and diesel-powered vehicles of all weights up to 14,000 pounds GVWR.

The EPA fully approved Wisconsin's Enhanced I/M program on August 16, 2001 (66 FR 42949), including the program's legal authority and administrative requirements in the Wisconsin Statutes and Wisconsin Administrative Code. On June 7, 2012, Wisconsin submitted a SIP revision to the EPA covering all the changes to the program since the EPA approved the program in 2001. This submittal included a demonstration under section 110(l) of the CAA addressing lost emission reductions associated with the program changes. The EPA approved this SIP revision on September 19, 2013 (78 FR 57501). Wisconsin is certifying that the existing SIP-approved I/M program meets the Basic I/M program requirements of CAA section 182(b)(4) for the Kenosha County and Milwaukee areas under the 2015 ozone NAAQS.

Consistent with the I/M regulations, a State with an existing I/M program would need to conduct and submit a performance standard modeling 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 onroad 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.

Wisconsin submitted an I/M performance standard modeling analysis demonstrating that Wisconsin's current motor vehicle I/M program meets the level of the EPA's Enhanced performance standard for areas designated and classified under the 8-hour ozone standard, as specified in 40 CFR 51.351(i). Wisconsin conducted the modeling analysis using the EPA's mobile source emissions model, MOVES5.0.0, which was the latest model version at the time this analysis was started. ⁽²¹⁾ This modeling was conducted for analysis year 2025 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  ⁽²²⁾ (October 2022 Performance Standard Modeling Guidance). The performance standard modeling analysis involves a comparison of emission reductions from the EPA's model program specified in 40 CFR 51.351(i) and Wisconsin's actual program. The analysis shows that the emission reductions from Wisconsin's actual I/M program meet the emission reductions modeled for the benchmark program of the Enhanced I/M performance standards.

3. Evaluation of Wisconsin's I/M Certification

The EPA's October 2022 Performance Modeling Guidance outlines the process that 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 assume 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."  ⁽²³⁾ The guidance goes on to identify the attainment date as the appropriate analysis year for areas that have been reclassified. ⁽²⁴⁾

Wisconsin's Moderate attainment date is August 3, 2024. Since the attainment date for the 2015 ozone NAAQS has passed, based on the EPA's October 2022 Performance Modeling Guidance, Wisconsin chose 2025 as the analysis year, which is within the calendar year of the demonstration's submittal. Therefore, the analysis year of 2025 is appropriate and consistent with the EPA's guidance.

To demonstrate that an I/M program meets the Enhanced performance standard, the actual I/M program must achieve the same or lower emissions levels of NO X and VOC as the Federal model Enhanced program to within 0.02 grams per mile (gpm).

As shown in Table 7, the emission rates from the Milwaukee County, Wisconsin I/M program meet the Enhanced performance standard of 40 CFR 51.351(i) to within 0.02 gpm. Since the regional characteristics included in the modeling and fleet emission rates were similar across the Milwaukee program area, the EPA guidance supports modeling a single county in the area. The Illinois-Indiana-Wisconsin area includes only a single Wisconsin county, Milwaukee County, so only that county would need to be modeled. Wisconsin conducted the performance modeling analysis using the most recent version of the EPA's mobile source emissions model, MOVES5.0.0, in accordance with the EPA's October 2022 Performance Modeling Guidance. Therefore, since Wisconsin's current I/M program meets the applicable I/M performance requirements in all areas in which the program is implemented and also meets the Basic I/M requirements of CAA section 182(b)(4), we are proposing to approve Wisconsin's I/M program SIP element for the required subject Moderate areas under the 2015 ozone NAAQS.

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 X 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 X 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 X 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 X pursuant to 40 CFR 51.165(a)(8); (8) set offset ratios for VOC and NO X 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. Wisconsin's NNSR Certification

Wisconsin affirms that the existing NNSR program meets the NNSR requirements of CAA section 182(a)(2)(C) and (b)(5) for the Moderate areas under the 2015 ozone NAAQS. Wisconsin has a long-standing and fully implemented NNSR program. This is addressed in Wis. Adm. Code Chapter NR 408. The EPA approved Wisconsin's NNSR program on January 19, 2022 (87 FR 2719). The major source thresholds for VOC and NO X established in Chapter NR 408.02(21) are consistent with the major source threshold requirements established in the CAA based on ozone nonattainment classifications. Specifically, Chapter NR 408.02(21)(a)(1) and NR 408.02(21)(b)(1) establish major source thresholds of 100 tons per year for VOC and NO X , respectively, in Marginal or Moderate ozone nonattainment areas. Further, the emission offset ratios established in Chapter NR 408.06(4) are consistent with the emission offset ratio requirements established in the CAA based on ozone nonattainment classifications. Specifically, Chapter NR 408.06(4) establishes an offset ratio of 1.15 to 1 for Moderate areas, as required by CAA section 182(b)(5).

3. Evaluation of Wisconsin's NNSR Certification

The EPA has reviewed Wisconsin's approved NNSR rules and is proposing to approve Wisconsin's certification submittal because the current SIP-approved NNSR program satisfies all the NNSR program requirements currently applicable to the Moderate areas for the 2015 ozone NAAQS.

III. What action is the EPA taking?

The EPA is proposing to approve revisions to Wisconsin's SIP pursuant to section 110 and part D of the CAA and the EPA's regulations, because Wisconsin's April 2, 2025, attainment plan submissions satisfy the base year emissions inventory, the RFP demonstration including associated motor vehicle emissions budgets, I/M, and NNSR requirements of the CAA for the Kenosha County, Milwaukee, and the Sheboygan County areas for the 2015 ozone NAAQS. The EPA is also initiating the adequacy process for the 2023 Budgets for the Kenosha County, Milwaukee, and the Sheboygan County areas included in this SIP submission.

IV. 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 these reasons, 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).

[FR Doc. 2026-06442 Filed 4-1-26; 8:45 am]

BILLING CODE 6560-50-P

⁽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).

⁽⁴⁾  CAA section 182(a).

⁽⁵⁾  CAA section 182(b).

⁽⁶⁾  83 FR 25776, June 4, 2018.

⁽⁷⁾  86 FR 31438, June 14, 2021.

⁽⁸⁾  83 FR 62998 at 63005, December 6, 2018.

⁽⁹⁾  Information on CAMPD is available on EPA's website at: https://campd.epa.gov/.

⁽¹⁰⁾  Information on WebFIRE is available on EPA's website at: https://www.epa.gov/electronic-reporting-air-emissions/webfire.

⁽¹¹⁾  Supporting documentation for the NEI is available on EPA's website at https://www.epa.gov/air-emissions-inventories/2017-national-emissions-inventory-nei-data?adlt=strict.

⁽¹²⁾  Information on MOVES4.0.1 is available on EPA's website: https://www.epa.gov/moves/moves-versions-limited-current-use.

⁽¹³⁾  The 2017 NEI Technical Support Document is available on EPA's website: https://www.epa.gov/sites/default/files/2020-04/documents/nei2017_tsd_full_30apr2020.pdf.

⁽¹⁴⁾  83 FR 62998 at 63004, December 6, 2018.

⁽¹⁵⁾  83 FR 62998 at 63005, December 6, 2018, codified at 40 CFR 51.1310(b).

⁽¹⁶⁾  40 CFR 51.1310(a)(6).

⁽¹⁷⁾  40 CFR 51.1310(a)(5).

⁽¹⁸⁾  40 CFR 51.1310(a)(7).

⁽¹⁹⁾  Similar to the 2017 inventories, Stage II refueling emissions were estimated using MOVES4.0.1 with the same inputs used for onroad modeling.

⁽²⁰⁾  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.

⁽²¹⁾  Information on MOVES5.0.0 is available on EPA's website: https://www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves.

⁽²²⁾ https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1015S5C.pdf.

⁽²³⁾  October 2022 Performance Standard Modeling Guidance, p. 10.

⁽²⁴⁾  Ibid.