The DNR is seeking public input on proposed changes to our air dispersion modeling guidance. These updates are aimed at decreasing unnecessary regulatory burden related to the new annual PM2.5 NAAQS while preserving air quality protection by refocusing our modeling efforts and refining the model estimates. Proposed updates include:
- Revise modeling triggers to be on an averaging period basis for each pollutant.
- Develop site-specific background data annually that excludes the influence of smoke events, such as wild fires.
- Use site-specific PM2.5 and PM10 backgrounds in modeling determinations, if available.
- Refine model inputs, when possible, to reduce concentrations below future modeling thresholds.
- Screen out adjacent facilities if their potential to emit is less than the applicable ton per year significant emission rate.
- Cease evaluation of combined impacts on shared boundaries where public access is precluded.
Additional details about these changes, as well as draft versions of affected guidance documents are available on the DNR’s Public Participation webpage.
Please send any comments to Brad Ashton at Brad.Ashton@dnr.iowa.gov, or by phone at 515-725-9527 by 6/24/2024. The DNR will release the final guidance after reviewing, addressing, and responding to all comments that are received.