Revised Air Dispersion Modeling Documents Now Available

Several modeling guidance documents have been updated to include recent changes in regulations and procedures. These guidance documents describe the department’s current modeling procedures and should be used for 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 Guidelines for PSD Projects,” “Air Dispersion Modeling Checklist,” and the “PSD Dispersion Modeling Protocol Template.” The documents can be found on the Department’s website here.

Substantive updates include:

• Removal of Lead guidance from the non-PSD guidelines. The department is in the process of developing Lead implementation guidance for non-PSD modeling projects. In the interim applicants required to conduct non-PSD Lead modeling should contact the modeling group for assistance. The PSD guidelines will remain consistent with the applicable federal requirements for Lead modeling.
• Changed references to Digital Elevation Model (DEM) data to National Elevation Dataset (NED).
• Updated guidance on importing base elevations for sources and buildings as well as the order in which the elevation and downwash analyses should be conducted.

The construction permit “Form MD” was also updated to be consistent with the formatting changes to the modeling determination flowchart included in the modeling guidelines. The updated form is available here.

Any questions regarding the revised modeling guidance documents should be directed to Brad Ashton by telephone at (515) 242–6532, or by e-mail to
brad.ashton@dnr.iowa.gov.