State Capitol Building 

Des Moines, Iowa 50319 

Dear Governor Branstad: 

Thank you for your recommendations dated November 4, 2015, on air quality designations for the state 

oflowa for the 2010 revision to the primary National Ambient Air Quality Standard for sulfur dioxide. 

Reducing levels of sulfur dioxide pollution is an important part of the U.S. Environmental Protection 

Agency's commitment to a clean, healthy environment. Exposure to sulfur dioxide 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 our preliminary intentions regarding your 

staff's recommended designations. 

On June 3, 2010, the EPA strengthened the health-based or primary standard for sulfur dioxide by 

establishing a standard for one-hour average sulfur dioxide concentrations at a level of75 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 the EPA a list of all areas in the state, with recommendations for 

whether each area meets the standard. Through an interactive process, the EPA considers the 

recommendations and then promulgates designations for all areas across the country. On July 25, 2013, 

the EPA designated 29 areas in 16 states as nonattainment, but did not at that time designate other areas. 

Pursuant to a March 2, 2015, court-ordered schedule, 1 the EPA must complete the remaining sulfur 

dioxide designations by three specific deadlines: July 2, 2016, December 31, 201 7, 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 sulfur dioxide standard 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 

the EPA's Air Markets Database emitted in 2012 either (i) more than 16,000 tons of sulfur dioxide or 

(ii) more than 2,600 tons of sulfur dioxide with an annual average emission rate of at least 0.45 pounds 

of sulfur dioxide per one million British Thermal Units. 

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

®Printed on Recycled Paper 
he asterisk (

) indicates the designation for this intended unclassifiable area represents a modification 

to the designation that you have recommended. 

The enclosed technical support document provides a detailed analysis that supports our intended 

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

these designations, please submit it to us by April19, 2016. We also will be publishing a notice in the 

Federal Register announcing a 30-day period for the public to provide input on our 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 sulfur dioxide standard. For additional information 

regarding designations under the sulfur dioxide standard, please visit our website at www.epa.gov/sulfur 

dioxidedesignations. Should you have any questions, please do not hesitate to call me, or have your staff 

contact David Peter of my staff at (913) 551-7397 or peter.david@epa.gov. 

Sincerely, 

Mark Hague 

Enclosure 

cc: Chuck Gipp, Iowa Department ofNatural Resources 

Catherine Fitzsimmons, Iowa Department ofNatural Resources 

Janet G. McCabe, USEPA Headquarters 

Stephen D. Page, Research Triangle Park