Modeling and Permitting for Annual PM10 Standard Resumes October 31

September 5, 2007

The Department of Natural Resources Air Quality Bureau will resume using the annual PM10 ambient air quality standard as a surrogate for the annual PM2.5 standard for setting air construction permit limits and conducting air dispersion modeling for New Source Review (NSR) projects beginning October 31. This practice was discontinued when the EPA revoked the annual PM10 standard in a federal rulemaking finalized October 17, 2006.

EPA’s 1997 interim PM2.5 implementation policy for NSR instructs that PM10 should be used as a surrogate for PM2.5 until the EPA sets a final implementation rule for PM2.5. Both minor and major NSR permitting provisions are affected.

This practice will discontinue when the EPA announces final PM2.5 implementation guidance and it is adopted by the DNR. The announcement is expected later this year.

Questions related to this issue may be directed to Lori Hanson at lori.hanson@dnr.iowa.gov or by calling (515) 281-8911.