Permitting Requirements for Nonattainment Areas in Wisconsin
Areas that currently are or have been designated as being in "nonattainment" of a national ambient air quality standard (NAAQS) have more restrictive permitting requirements, and sources in those areas may be subject to more stringent regulations known as Reasonably Available Control Technology (RACT) standards. This page shows current Wisconsin nonattainment areas and summarizes the applicable permitting requirements for major sources of emissions within these areas. It also contains information about nonattainment area history to assist in determining RACT applicability for specified sources of nitrogen oxides (NOx) and select source categories of volatile organic compounds (VOC). The contents of this page are intended to provide a general overview of the applicable requirements. For more detailed information about RACT applicability, state permitting regulations or for questions related to a specific permit, contact the Air Management Program.
For information about the EPA's reclassification of the nonattainment areas to Serious, see the “2015 ozone standard reclassification” near the bottom of this page.
Interactive Map
Click on a county below for a summary of applicable permitting requirements based on nonattainment area designations. The map also provides relevant information for determining NOx RACT applicability for all sources and VOC RACT applicability for the following source categories: miscellaneous industrial adhesives (s. NR 422.128), plastic parts coatings (s. NR 422.084) and metal parts coatings (s. NR 422.151).
Note: Graphical representations of attainment/nonattainment areas are approximate. For the most precise rule applicability information, type a specific address into the search bar on the map and then click on the map.
Explanation of Information Provided in the Map Legend
Nonattainment New Source Review
Major emission sources for construction permitting purposes in areas that meet or attain the NAAQS are covered by the prevention of significant deterioration (PSD) permitting program. In contrast, major emission sources in nonattainment areas are covered by the nonattainment new source review (NNSR) permitting program.
In general, the NNSR program is more stringent than the PSD program because the goal of NNSR is to accommodate business expansion without exacerbating nonattainment of the NAAQS. The emissions threshold for determining whether a source is subject to major source permitting is usually lower for NNSR than PSD. Projects covered by PSD are required to control emissions to a level defined as the best available control technology (BACT), which allows consideration of the economic feasibility of the controls. However, projects covered by NNSR are required to control emissions to the level defined as the lowest achievable emission rate (LAER), which does not consider economic feasibility.
Major construction covered by NNSR also requires the permit applicant to offset the project's emissions according to a ratio that depends on the severity of nonattainment. Permit applicants can use internal offsets by establishing emission reductions from their own operations, or an applicant can use emission reduction credits. The offsets must represent surplus, permanent, quantifiable and federally enforceable emissions reductions.
The map above shows, based on nonattainment status, which permitting program currently applies in each area in Wisconsin, along with the associated major source threshold and offset ratio (as applicable).
NOx RACT
Nitrogen oxides (NOx) RACT requirements apply to specified categories of equipment at facilities located in certain areas that are or have been classified as Moderate, Serious, Severe or Extreme nonattainment and emit NOx above an applicability threshold. The level of nonattainment classification determines the applicability threshold. More information on emission regulations and applicability is available on the NOx RACT page.
VOC RACT for Industrial Adhesives and Plastic and Metal Parts Coatings
Some VOC RACT requirements apply to specific facility types located in areas that are currently or were previously classified as Moderate or higher nonattainment for ozone and emit VOCs above an applicability threshold. The facilities subject to these requirements conduct operations using adhesives (s. NR 422.128), plastic parts coatings (s. NR 422.084) or metal parts coatings (s. NR 422.151). Additional VOC RACT rules covering other source categories also apply throughout the state. More information on regulations and applicability can be found on the VOC RACT page.
2015 Ozone Standard Reclassification
Effective January 16, 2025, the EPA will reclassify the areas in Wisconsin that remain in nonattainment of the 2015 ozone NAAQS. These areas, which include all of Milwaukee and Ozaukee counties and parts of Washington, Waukesha, Racine, Sheboygan and Kenosha counties will be re-classified from moderate to serious nonattainment. The DNR is required by the Clean Air Act to implement more stringent controls on nitrogen oxides (NOx) and volatile organic compound (VOC) emissions until the affected areas attain the NAAQS.
The reclassification will affect the stringency of the more restrictive permitting requirements that will apply in the areas. It may also affect the applicability of NOx RACT to certain facilities as well as operation permit requirements.
FAQs
The Air Management Program is proactively working with facilities, the EPA and neighboring states on strategies to protect the air quality and reduce the impact on businesses. For more information on the 2015 ozone standard reclassification, view the list of frequently asked questions below.
What is ground-level ozone?
Ozone in the upper atmosphere filters out harmful ultraviolet rays from the sun. However, elevated concentrations of ozone at ground level can have an adverse impact on health. Ground-level ozone is not directly emitted into the air; it is created by photochemical reactions between heat and sunlight and ozone precursors such as volatile organic compounds (VOCs) and oxides of nitrogen (NOx). To learn more about ozone, visit the ozone page.
What is the 2015 ozone standard?
The Clean Air Act requires the EPA to set national ambient air quality standards (NAAQS) for ozone and five other pollutants considered harmful to public health and the environment. The law also requires the EPA to periodically review the standards to ensure that they provide adequate health and environmental protection and to update those standards as necessary.
The EPA last revised the ozone NAAQS in 2015, setting the standard at a level of 70 ppb.
What does it mean to be in “nonattainment?”
The Clean Air Act requires areas of the country that do not meet a NAAQS to be designated as nonattainment. The law requires certain regulatory programs to be implemented in nonattainment areas to reduce emissions and facilitate future attainment of the NAAQS by specified dates.
What parts of Wisconsin are currently in nonattainment of the 2015 ozone standard?
Wisconsin has three areas that remain in nonattainment of the 2015 ozone NAAQS: the Milwaukee area (which includes all of Milwaukee and Ozaukee counties and parts of Washington, Waukesha and Racine counties) and parts of Sheboygan and Kenosha counties.
What happens when an ozone nonattainment area is reclassified or “bumped up?”
Ozone nonattainment areas are subject to a five-step classification process (Marginal, Moderate, Serious, Severe and Extreme). The classification of an area depends on its ozone concentrations and how long it has remained in nonattainment. The Clean Air Act specifies regulatory requirements for each classification. The higher the classification, the more stringent the requirements. If an area fails to attain the attainment date associated with its current classification, the area is then reclassified or “bumped up” to the next classification.
Why are Wisconsin’s ozone nonattainment areas being reclassified?
All of Wisconsin’s 2015 ozone NAAQS nonattainment areas are currently classified as Moderate and had an attainment date of August 3, 2024. Because none of these areas attained the standard by that date, the Clean Air Act requires the EPA to reclassify them to the next classification (Serious). Reclassification of areas that fail to meet an attainment date is a requirement of federal law; neither states nor the EPA have the option to defer this action. There are many other states with ozone nonattainment areas that have been or will be, similarly reclassified.
What is the effective date of reclassification?
The EPA reclassified Wisconsin’s nonattainment areas from Moderate to Serious on December 17, 2024, this action will be effective January 16, 2025.
What will be the impact of the reclassification on stationary sources?
The reclassification to Serious will affect the stringency of permitting requirements in the 2015 ozone NAAQS nonattainment areas. The major source threshold for NOx and VOC emissions will be lowered to 50 tons per year (from 100 tons per year) for both construction and operation permitting. There will also be more stringent requirements for major new sources or major modifications of existing sources. The lower thresholds and more stringent requirements are required by the Clean Air Act.
Why are there more stringent permitting requirements for NOx and VOC emissions in nonattainment areas?
Ground-level ozone is formed when NOx and VOCs react in the atmosphere in the presence of sunlight. Therefore, limiting emissions of these ozone-causing pollutants helps decrease ozone levels.
What are the new major source thresholds, and how will they affect current sources?
The reclassification to Serious may affect the source status of facilities located in the nonattainment areas under Wisconsin’s air pollution control permitting programs. This is because the reclassification will lower the major source threshold to 50 tons per year of each NOx and VOC (down from 100 tons per year).
Any facility with a potential to emit (PTE) above the major source threshold for NOx or VOC must have or apply for a Title V operation permit or apply for a synthetic minor operation permit to reduce PTE to below the major source threshold.
Some sources that were synthetic minor sources or natural minor sources may become major sources when reclassification occurs and potentially be subject to additional requirements when constructing new emissions units or modifying existing ones that emit these air pollutants.
What are the registration permit thresholds for facilities located in a Serious nonattainment area?
Registration Operation Permits (ROPs) are general permits available for facilities willing and able to limit their emissions below established thresholds in order to benefit from the ROP’s streamlined permitting and compliance demonstration processes. The ROP thresholds are based on a percentage of the major source thresholds. When the new major source thresholds take effect, the ROP thresholds on facility emissions of NOx and VOC decrease as follows:
Registration Permit NOx (TPY) VOC (TPY) Type A 12.5 12.5 Type B 25 25 Type C 12.5 12.5 Type G 40 40 Facilities operating under a ROP must compare the actual emissions of NOx and VOC against the emissions thresholds corresponding to Serious nonattainment. If the actual emissions are above the new thresholds, the facility must apply for a different type of ROP, or a source-specific operation permit and associated construction permit. The ROP thresholds on facility emissions for all other pollutants remain unchanged.
What are the impacts of reclassification on operation permitting?
Facilities located in a nonattainment area that are classified as a non-major source prior to the Serious “bump up” should review their actual and potential emissions of NOx and VOC to determine whether a permitting action is required to address the change in major source thresholds for NOx and VOC.
Any source with a PTE above major source thresholds must submit a Title V permit application or an application to obtain a permit that reduces the facility PTE below the major source thresholds.
Visit the How to Apply for Air Permits webpage for additional information on permit applications or permit revisions.
What are the impacts of reclassification on construction permitting?
In addition to lowering the major source threshold for NOx and VOC for nonattainment new source review (NNSR) to 50 tons per year (from 100 tons per year), reclassification also increases the NNSR offset ratio to 1:2:1 (from 1.15:1).
Besides reduced major source thresholds, what other rule changes could affect facilities due to reclassification?
Emissions of NOx and emissions of VOC in ozone nonattainment areas that are classified as “moderate” or higher must be controlled through the implementation of Reasonably Available Control Technology Regulations (RACT).
The reclassification to Serious may affect the applicability of NOx RACT. Facilities operating any fuel combustion equipment listed in s. NR 428.22 are required to maintain NOx emissions below the levels specified in the rule if the MTE from the affected units is over the major source threshold, which is now 50 ton per year. More information on NOx RACT is available on the NOx RACT page.
The reclassification to Serious will not affect VOC RACT applicability. Additional information on VOC RACT is available on the VOC RACT page.
What is the DNR doing to address ozone nonattainment?
The DNR has been, and will continue to be, very engaged on this issue. Much of the ozone measured in Wisconsin’s nonattainment areas originates from outside of the state, or from sources beyond state authority to regulate (like transportation). The DNR is actively working with the EPA and neighboring states on strategies to address these emissions. In addition, the Air Management Program works to ensure the required regulatory programs are being implemented in the most efficient and cost-effective way to minimize the impact on sources and the public.
How can a facility contribute to the reduction of NOx and VOC emissions?
NOx emissions can be reduced by improving the fuel combustion process, the incorporation of NOx control equipment and/or transitioning to renewable sources of energy.
VOCs are emitted from a variety of processes, including biogenic and anthropogenic. Facilities can reduce VOC emissions by using materials with low or no VOC content (i.e. water-based paints), reducing material usage, improving application processes, collecting used solvents, and applying non-destructive VOC control techniques such as adsorbents and scrubbers.
Facilities in the nonattainment area that make permanent and quantifiable VOC or NOx emission reductions may be eligible to create emission reduction credits (ERCs). ERCs can be banked and sold to facilities looking to expand or start up operations within the nonattainment area. More information is available on the ERC page.
More information
Refer to air permit options for more information about construction permits.
- Prevention of Significant Deterioration requirements: ch. NR 405, Wis. Adm. Code
- Nonattainment NSR requirements: ch. NR 408, Wis. Adm. Code
- Construction permit requirements (apply to projects in all areas): ch. NR 406, Wis. Adm. Code
Contact Information
Questions regarding permitting requirements for nonattainment areas in Wisconsin and state implementation plans (SIPs) should be sent by email to: DNRAMNonattainment@wisconsin.gov