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Revised Air Dispersion Modeling Guidance Available

  • 9/15/2023 9:51:00 AM
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The DNR has finalized updates to guidance documents used for air dispersion modeling analyses. These updates affect the Prevention of Significant Deterioration (PSD) and non-PSD modeling guidelines, and the dispersion modeling checklist. These documents are available on the dispersion modeling webpage.

The updates include revisions based on comments received from the public during an informal comment period that ended on February 28th. The revisions made to the final guidance documents from the versions that were posted for informal public input include:

  • Clarified that sources “affected” by the project means new sources and any source that will be modified or require permit modification as a result of the project.
  • Specified that fugitive emissions from haul roads and material storage piles only need to be included in non-PSD modeling analyses if the sources were included in previous PSD modeling, or in instances where these sources were identified as the cause of an emissions impact complaint to the DNR.
  • Explained that cooling towers only need to be modeled if they are not exempt from permitting.
  • Corrected an error in the guidance describing how to use ARM2.
  • Added the ozone SIL and NAAQS for use in modeling direct ozone emissions.
  • Removed reference to conditional permits, which no longer exist in rule.

Please send any questions to Brad Ashton at, or by phone at 515-725-9527.