DNR Responds to EPA’s Proposed Nonattainment Boundaries for PM2.5

The DNR Air Quality Bureau submitted additional technical information to the Environmental Protection Agency (EPA) Monday to support limited, sub-county boundaries in Scott and Muscatine counties for the 24-hour PM2.5 National Ambient Air Quality Standard. This was in response to the August 18 EPA recommendation that all of Scott and Muscatine Counties in Iowa and Rock Island County, Illinois, be declared in nonattainment for PM2.5.

To address EPA concerns, the DNR undertook intensive investigation to support what it believes to be appropriate modifications to EPA’s proposed boundaries, including studying the contributions of single sources at a local scale to cumulative impacts of many sources at the regional scale. Regional modeling techniques were also used to investigate the role of the precursor gases NOx and SO2.

The DNR is working with facilities in the vicinity of the violating monitors to accelerate efforts to reduce emissions at a rate that surpasses the regulatory timeliness provided for in the Clean Air Act. Additionally the DNR plans to submit 2008 monitoring data early in 2009 with the hope that nonattainment area designations will be withdrawn before they are finalized.

The DNR also asked that Rock Island County in Illinois be excluded from EPA's nonattainment proposal.

The DNR consulted and coordinated with EPA Region VII and the Illinois EPA to develop this response. The letter and entire technical support document is posted midway down the page at www.iowacleanair.com/prof/progdev/pm25na.html.