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Proposed Ozone Background Data Addition and Restricted Operating Hours Guidance Updates
Posted: 08/06/2014

The DNR is proposing to update available background data and to revise two dispersion modeling guidance documents to provide additional clarification on some aspects of the guidance. The details of these proposed changes are as follows:

• Default background ozone concentration data will be added to the available background data provided on the DNR website to aid in the modeling of nitrogen dioxide (NO2) analyses when utilizing the Ozone Limiting Method (OLM) or Plume Volume Molar Ratio Method (PVMRM) options encompassed in AERMOD.

• The Air Dispersion Modeling Checklist will be updated to include the use of the default background ozone concentration data when using OLM or PVMRM. Users will be asked to provide additional clarification should they choose different ozone data.

• The DNR Suggested Methodology for Modeling Restricted Hours of Operation guidance will be updated to clarify the correct procedure to use to find the 5-year average of annual fine particulate (PM2.5) concentrations when there is an associated annual limitation on operating hours for the PM2.5 source(s) in which averaging times of month or 24-hours are used.

These additions and revisions are intended to provide improved modeling guidance to applicants submitting projects that include emissions of NO2 and PM2.5. The draft documents are available for informal public review on the Air Quality Bureau’s Stakeholder Involvement website.

Please contact Jennifer Krzak at or by phone at (515) 725-9532, with any questions or comments by August 20, 2014. DNR will consider any comments received on the proposed changes prior to finalizing the guidance documents and making them available on the Website.

This list serve article is intended for consultants, industries, environmental groups, general public, and other entities regulated under the Clean Air Act. It was written by the DNR Air Quality Bureau to share regulatory news, program updates and technical guidance.