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Jan. 7, 2025
This email contains important information that may affect the air pollution control permitting requirements for a facility for which you are the responsible official, facility contact or permit contact.
On Dec. 17, 2024, the U.S. Environmental Protection Agency (EPA) reclassified several areas in Wisconsin to “Serious” nonattainment for the 2015 ozone National Ambient Air Quality Standards. The areas affected by the reclassification are Milwaukee and Ozaukee counties and parts of Washington, Waukesha, Racine, Sheboygan and Kenosha counties. As a result of this action, facilities located in these areas will be subject to lower limits or thresholds for nitrogen oxide (NOx) and volatile organic compound (VOC) emissions starting Jan. 16, 2025.
The reclassification reduces the major source threshold for NOx and VOC emissions from 100 tons per year (tpy) to 50 tpy. The major source thresholds for other criteria pollutants will remain unchanged. Additionally, the reclassification increases the Nonattainment New Source Review (NNSR) offset ratio to 1.2:1 (from 1.15:1) for projects that are new major sources or major modifications under the NNSR regulations in ch. NR 408, Wis. Adm. Code.
VOC reasonably available control technology (RACT) applicability will not be affected by the reclassification to Serious, although NOx RACT applicability may be affected for some sources. Additional information on VOC RACT and NOx RACT is available on the following webpages:
How Does This Action Affect The Current Operation Permit For My Facility?
Facilities holding a Part 70 (Title V) major source operation permit:
Major sources will maintain their current source classification (aka EPA Class Code) of A.
Facilities holding a state operation permit (FESOP or SOP):
Because source classification is defined on the basis of the potential to emit (PTE) of a facility relative to major source thresholds, the reclassification from moderate to serious nonattainment will affect the source classification of some facilities with a state operation permit.
The table immediately below shows the PTE thresholds of each EPA Class Code for moderate and serious ozone nonattainment. Please refer to the preliminary determination (PD) for the active operation permit, which contains information on the facility’s PTEs under its current operation permit. A copy of the PD is available through the DNR Switchboard.
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EPA Class Code
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NOx PTE Threshold (tpy)
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VOC PTE Threshold (tpy)
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Moderate
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Serious
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Moderate
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Serious
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A
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≥ 100
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≥ 50
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≥ 100
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≥ 50
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SM80
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≥ 80
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≥ 40
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≥ 80
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≥ 40
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SM
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< 80
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< 40
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< 80
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< 40
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B*
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< 100
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< 50
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< 100
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< 50
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* To have an EPA Class Code of B, the PTE and the maximum theoretical emission (MTE) of a facility must be below the PTE threshold.
If the current NOx or VOC PTE results in a change in source classification following reclassification to Serious, a facility should apply for an operation permit revision (using Form 4530-100) to reflect the change. If a facility with a changed source classification wishes to maintain its current classification, an application for an operation permit revision or a different type of permit, such as a registration operation permit (ROP), must be submitted to request a lower NOx and/or VOC PTE.
For additional information on submitting permit applications, visit the DNR’s How to Apply for Air Permits webpage.
Facilities operating under registration permit coverage:
To operate under an ROP, a facility must meet certain eligibility criteria, which include keeping actual emissions below specified thresholds for each criteria pollutant. The ROP eligibility thresholds, which are based on a percentage of the major source thresholds, will lower by 50% for NOx and VOC following the Serious reclassification as follows:
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Registration Permit
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NOx Threshold (tpy)
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VOC Threshold (tpy)
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Moderate
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Serious
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Moderate
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Serious
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Type A
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25
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12.5
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25
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12.5
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Type B
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50
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25
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50
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25
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Type C
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25
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12.5
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25
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12.5
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Type G
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80
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40
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80
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40
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If the annual emissions from a facility are over the new ROP thresholds, the facility can either apply for a different type of ROP or a source-specific construction permit and operation permit.
For additional information on submitting ROP applications, visit the DNR website.
Where Is Additional Information Available?
Visit the Permitting Requirements for Nonattainment Areas in Wisconsin webpage for details of this reclassification and responses to some of the most frequently asked questions. For other questions, contact the DNR Air Management Program at DNRAMNonAttainment@wisconsin.gov.
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