On July 28, 2015, the Wisconsin Department of Natural Resources (WDNR) posted four (4) draft guidance documents for review and comment.  These draft guidance documents address WDNR's new policy for regulating particulate matter with an aerodynamic diameter of 2.5 microns or less (PM2.5)in Wisconsin.  The guidance documents specifically address PM2.5 inclusion in air permit applications, air dispersion modeling guidelines, and variance request procedures under NR 415.075(4).

WDNR prepared a technical support document (TSD) that examines the science behind the primary and secondary formation of PM2.5 as well as results of statewide PM2.5 monitoring and other factors related to PM2.5.  Historically, any source of particulate matter (PM) was assumed to be a source of particulate matter with an aerodynamic diameter of 10 microns or less (PM10) and PM2.5; however based on the scientific information detailed in the TSD, WDNR has concluded not all units that emit PM are sources of PM2.5.  Based on this conclusion, WDNR has developed these guidance documents to inform permit applicants of the new policy on PM2.5.

The first document, "Guidance for Including PM2.5 in Air Pollution Control Permit Applications," describes the changes being implemented in how the WDNR evaluates PM2.5 emissions in air pollution control permits, including:

  • Only combustion and high temperature industrial sources are considered to directly emit significant amounts on PM2.5.  Under the proposed guidance, PM2.5 emissions will not need to be estimated for fugitive dust sources, mechanical handling, grain handling, and other low temperature particulate sources in permit applications.
  • Except for modeling for Prevention of Significant Deterioration (PSD), nonattainment area major permit reviews, and major modifications when there are significant sources of PM2.5 (i.e., combustion and high-temperature sources), the WDNR will not perform modeling for PM2.5 in the review of permits for existing sources, new minor sources, and minor modifications of major sources.

The next two guidance documents further clarify the modeling requirements with respect to the new PM2.5 policy.  The first, "2015 Approach to Dispersion Modeling for Permits," provides updated guidance on WDNR's approach to dispersion modeling as part of the air permit review process.  This guidance breaks down the modeling requirements for all types of permit applications (attainment or nonattainment sources, PSD permits, minor construction permits, major or minor operation permit, permits in baseline or non-baseline counties, Part 70 or non-Part 70 initial permits or permit revisions or renewals, registration permits, and general permits).

The second modeling guidance, "Air Dispersion Modeling Guidelines," details the methods and techniques that should be used to perform air dispersion modeling in Wisconsin.  Specific modeling guidelines are included for major and minor PSD projects, individual operation permit actions, and registration permits.  Also included are the TSD for PM2.5 and a map detailing where urban dispersion coefficients should be used in air dispersion models for sources located in Milwaukee.

Lastly, the "Variance Request Procedures under NR 415.075(4), Wis. Adm. Code" guidance document describes variance review criteria for new and existing ledge rock quarries and industrial sand mines requesting a variance from the requirement to operate an air monitoring system under NR 415.075.  The new PM2.5 policy has the potential to impact these sources so this guidance has been posted to ensure consistency during permit review and determination as well as to educate industry and the public of the WDNR procedures in considering variance requests.

All four guidance documents, and the appropriate WDNR contact for each, are available on the WDNR website for review and public comment until August 27, 2015.  If you have any questions about these proposed guidance documents, or how they may impact your facility, please contact Jon Frost at (651) 275-9900 x6.