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Opportunity for Comment on Proposed Modeling Determination (Form MD) Update

The DNR is proposing an update to the method used to determine when a dispersion modeling analysis will be needed for construction permitting projects at portable plants.  Form MD has been updated to incorporate the proposed change.  A 2-week informal comment period will extend from February 7 through February 21.  At the end of the comment period, the DNR will address any comments that are received and finalize the document.

The current modeling determination procedure may result in unnecessary dispersion modeling analyses for portable plants. Specifically, Section 2 (Availability of Air Resources) of Form MD indicates that previous modeling for the facility should be used to determine if pollutant concentrations are approaching the level of the NAAQS in the vicinity of the facility. These instructions were developed with stationary sources in mind.  New equipment being permitted for a portable plant may or may not operate in the same area as equipment included in previous modeling analyses. This makes it difficult to pre-determine the availability of air resources in the vicinity of portable plants.  For these reasons the DNR is proposing that Section 2 of Form MD should be left blank when this form is being used for a portable plant, and that the availability of air resources will instead be determined by the DNR on a case-by-case basis when the application is processed.  This is the same procedure currently being used for new facilities.

The updated Form is available for review on the Air Quality Bureau’s Stakeholder Involvement webpage under “Public Input.”  Please send any comments or questions to Brad Ashton at, or by phone at (515) 725-9527, by 4:30 pm on February 21.