Ref: 8P-AR 

The Honorable Matt Mead 

Governor of Wyoming 

State Capitol 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 8 

1595 Wynkoop Street 

DENVER, CO 80202-1129 

Phone 800-227-8917 

http://www.epa.gov/region08 

FEB 0 6 2013 

Cheyenne, Wyoming 82002 

Dear Governor Mead: 

Thank you for your recommendations dated May 24, 2011, on air quality designations for the state of 

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

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

Protection Agency's (EPA) 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 the EPA's preliminary intentions 

regarding your recommended designations. 

On June 3, 2010, the 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. The Clean Air Act 

requires the EPA to complete the initial designations process within two years of promulgating a new or 

revised standard. If the Administrator has insufficient information to make these designations, the EPA 

has the authority to extend the designation process by up to one year. On July 27,2012, the EPA 

announced that it had insufficient information to complete the designations for the 1-hour so2 standard 

within two years and extended the designations deadline to June 3, 2013. 

At this time the EPA is proceeding with designating as nonattainment most areas in locations where 

existing monitoring data from 2009-2011 indicate violations ofthe 1-hour S02 standard. The EPA 

intends to address the designations for all other areas in separate future actions. With input from a 

diverse group of stakeholders, EPA has developed a comprehensive implementation strategy for these 

future actions that focuses resources on identifying and addressing unhealthy levels of S02. The 

strategy is available at: http://www.epa.gov/airquality/sulfurdioxide/implement.html. The EPA will 

continue to work closely with you and our other partners at the state, tribal and local levels to ensure 

health-protective, commonsense implementation of the 1-hour S02 standard. 

The EPA's review ofthe most recent monitored air quality data from 2009-2011 shows no violations of 

the 2010 S02 standard in any areas in Wyoming. Consequently, the EPA is not yet prepared to propose 

designation action in Wyoming, and is, therefore, currently deferring action to designate areas in 

Wyoming. The EPA expects to be able to proceed with designation action in Wyoming once additional 
data are gathered pursuant to our comprehensive implementation strategy. In a separate future action or 

actions the EPA will notify you of our intended designations for these areas, and seek public comment 

on these actions, no later than 120 days prior to promulgating any final designations. 

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

2010 primary S02 standard. For additional information regarding initial designations on the S02 

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 Crystal Ostigaard of my staff at 

(303) 312-6602 or ostigaard.crystal@epa.gov. 

Sincerely, 

~~~~ Regional Administrator 

Enclosure 

cc: Todd Parfitt, Director, DEQ 

Steven A. Dietrich, Administrator, AQD 

Gina McCarthy, Assistant Administrator for Air and Radiation 

Stephen D. Page, Director, Office of Air Quality Planning and Standards