The Honorable Scott Walker 

Governor of Wisconsin 

115 East Capitol 

Madison, Wisconsin 53702 

Dear Governor Walker: 

Thank you for your recommendations dated September 16, 2015 on air quality designations for the State 

of Wisconsin for the 2010 revision to the primary National Ambient Air Quality Standard (NAAQS) for 

sulfur dioxide (S02). Reducing levels of S02 pollution is an important part of the U.S. Environmental 

Protection Agency's commitment to a clean, healthy environment. Exposure to S02 can cause a range 

of adverse health effects, including narrowing of the airways which can cause difficulty breathing and 

increased asthma symptoms. This letter is to notify you of EPA's preliminary intentions regarding your 

recommended designations. 

On June 3, 2010, EPA strengthened the health-based or "primary" standard for S02 by establishing a 

standard for 1-hour average S02 concentrations at a level of 75 parts per billion. Within one year after a 

new or revised standard is established, the Clean Air Act requires the Governor of each state to submit 

to EPA a list of all areas in the state, with recommendations for whether each area meets the standard. 

Through an interactive process, EPA considers the recommendations and then promulgates designations 

for all areas across the country. On July 25, 2013, EPA designated 29 areas in 16 states as 

nonattainment based on monitored violations, but did not at that time designate other areas. Pursuant to 

a March 2, 2015, court-ordered schedule, 1 EPA must complete the remaining S02 designations by three 

specific deadlines: July 2, 2016, December 31,2017, and December 31,2020. 

This current round of designations, to be completed by July 2, 2016, addresses two groups of areas: 

(1) areas that have newly monitored violations of the 2010 S02 NAAQS based on the most recent three 

calendar years of certified monitored ambient air quality data, and (2) areas that contain any stationary 

source that had not been announced as of March 2, 2015, for retirement and that according to EPA's Air 

Markets Database emitted in 2012 either (i) more than 16,000 tons of S02 or (ii) more than 2,600 tons of 

S02 with an annual average emission rate of at least 0.45 pounds ofS02/MMBTU. 

1 Sierra Club v. McCarthy, No. 3-13-cv-3953 (Sl) (N.D. Cal. Mar. 2, 2015). 

Recycled/Recyclable • Printed with Vegetable Oil Based Inks on 100% Recycled Paper (100% Post-Consumer) 
Because the March 2, 2015 consent decree directs EPA to evaluate data collected for the most recent 3 

years, EPA initially identified Brown County as an area that would potentially be subject to an 

obligation for us to designate by July 2, 2016. Ambient air quality data for Brown County collected 

between 2012 and 2014 indicated a violation ofthe 2010 S02 NAAQS. However, your staffpromptly 

evaluated Brown County's 2015 data and certified it as accurate on January 29,2016. As a result, 

complete, quality assured, and certified data for 2013 to 2015 for Brown County, Wisconsin indicate 

compliance with the 2010 SOz NAAQS. Therefore, EPA intends to designate this area at a later date, by 

either December 31, 2017, or December 31, 2020. 

The enclosed Technical Support Document provides a detailed analysis that supports our intended 

designation decisions. If your state has additional information that EPA should consider prior to 

finalizing these designations, please submit it to us by April 19, 2016. We also will be publishing a 

notice in the Federal Register announcing a 30-day period for the public to provide input on EPA's 

intended designation decisions. We will promulgate the designations for these areas by July 2, 2016. 

We will designate all other previously undesignated areas in the state on a schedule consistent with the 

prescribed timing of the court order, i.e., by December 31, 2017, or December 31, 2020. 

We look forward to a continued dialogue with you and your staff as we work together to complete the 

area designations and implement the 2010 primary SOz standard. For additional information regarding 

designations under the SOz standard, please visit our website at www.epa.gov/so2designations. Should 

you have any questions, please do not hesitate to call me, or have your staff contact me at 312-886-3000, 

or George Czerniak, Director, Air and Radiation Division, at 312-353-2212 or czemiak.george@epa.gov. 

Sincerely, 

r.:i?drJ--4:-

Robert A. Kaplan 

Acting Regional Administrator 

Enclosure 

cc: Cathy Stepp, Secretary 

Wisconsin Department of Natural Resources 

Gail Good, Director 

Bureau of Air Management 

Wisconsin Department ofNatural Resources