Dispersion Modeling Tools and Reference Documents Available

August 8, 2007

Several new tools and reference documents have been added to the dispersion modeling section of the Iowa Department of Natural Resources’ Air Quality website at:

www.iowacleanair.com/prof/progdev/modeling.html

The Volume Source Tool and Flare Tool are spreadsheets that can be used to simplify the determination of the emission rates and source parameters used to characterize these types of sources in a dispersion modeling analysis. New reference documents include a summary of EPA memorandums related to ambient air issues; a copy of the EPA’s Guideline for Determination of Good Engineering Practice Stack Height (Technical Support Document for the Stack Height Regulations) 1985 (see GEP Technical Support Document ); and an EPA Region VII memorandum clarifying Use of the Ambient Ratio Method for Modeling Significant N02 Impacts.

Additional items specific to prevention of significant deterioration (PSD) are the Soil and Vegetation Analysis Tool and the Screening Threshold Method for PSD Modeling document. The Soils and Vegetation Analysis Tool is a spreadsheet to use with modeled concentrations to predict impacts on soils and vegetation. The screening threshold document was developed by North Carolina to screen the facilities evaluated in a refined PSD modeling analysis. The DNR currently uses this procedure to minimize the number of facilities included in the modeling by determining which facilities are likely to have a significant contribution in the impact area.

If you have questions about the new website additions, call the Air Quality Bureau’s Modeling Group at (515) 242-5100.