On December 19, 2016, the Wisconsin Department of Natural Resources (WDNR) Air Management Program finalized an update to the sulfur dioxide (SO2) and nitrogen dioxide (NO2) background concentration used in dispersion modeling.  These background values are temporally varying based upon the hour of the day for each month of the year, as opposed to static background values previously used.  See August's article that discusses the temporally-varying background in more depth.  The background values and overall policy has not changed since the proposed guidance, but the final guidance has been updated to clarify some language due to questions that arose during the public comment period.

The final memorandum can be found here and response to comments can be found here until January 9, 2017.

For questions about the recently published background concentrations or regarding dispersion modeling in Wisconsin, please contact Jon Frost at (651) 275-9900 or via email.