Revised Air Dispersion Modeling Documents Now Available

Updated modeling guidance documents are now available on the Department’s website at www.iowacleanair.com/prof/progdev/modeling.html. These guidance documents describe the department’s current modeling procedures and should be used for externally conducted modeling analyses performed by industry or their consultants.

The revised documents include the “Air Dispersion Modeling Guidelines for Non-PSD Pre-Construction Permit Applications,” “Air Dispersion Modeling Checklist,” “Air Dispersion Modeling Guidelines for PSD Projects,” and the “PSD Dispersion Modeling Protocol Template.” With the exception of the “Air Dispersion Modeling Guidelines for PSD Projects,” changes to the documents are primarily administrative. To allow for more efficient document updates in the future, tables of data such as the national ambient air quality standards (NAAQS) and the state-wide background values have been removed from the checklist and template documents and are only listed in the guideline documents. Also, terms have been reviewed for consistency throughout the documents. These changes are only intended to clarify the department’s current modeling procedures.

Substantial revisions have been made to the “Air Dispersion Modeling Guidelines for PSD Projects.” The revised document has been updated to include EPA’s promulgation of the dispersion model AERMOD and the current state-wide default background values. It now also reflects the departments current procedure for evaluation of VOC emissions, expanded the guidance on modeling fugitive emissions and conducting a visibility analysis for PSD modifications, and includes new sections on particulate matter with an aerodynamic diameter less than or equal to 2.5 microns (PM2.5), pre-construction monitoring, and condensation plumes.

Any questions regarding the revised modeling guidance documents should be directed to Lori Hanson, Department of Natural Resources, Air Quality Bureau, telephone (515) 281–8911; fax (515) 242–5094. Questions may also be submitted by e-mail to lori.hanson@dnr.iowa.gov.