UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 8 

Ref: 8P-AR 

The Honorable Steve Bullock 

Governor of Montana 

Montana State Capitol Building 

P.O. Box 200801 

Helena, Montana 59620-0801 

Dear Governor Bullock: 

1595 Wynkoop Street 

DENVER, CO 80202-1129 

Phone 800-227-8917 

http://www.epa.gov/region08 

FEB 0 6 2013 

Thank you for your staffs May 27, 2011, recommendations on air quality designations for the state of 

Montana 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 7 5 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 of the 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 healthprotective, commonsense implementation ofthe 1-hour S02 standard. 

Consistent with the Clean Air Act, after carefully considering Montana's recommendations and all of 

the associated technical information for the 2010 S02 standard, including the most recent air quality data 
from 2009-2011, the EPA intends to designate as nonattainment the following area, including the 

following counties or portions of counties: 

Nonattainment Area 

Area 1 

County 

Yellowstone County (excluding Crow 

Tribe of Montana) 

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

preliminary nonattainment area decisions. In assessing the air quality for Yellowstone County, you 

requested that the EPA exclude 2010 air quality monitoring data and consider a three-year average using 

2009, 2011, and 2012 data sets, or 2011-2013 data sets for designations. Based on the available data, we 

are not at this time able to concur with the state of Montana's position that the 201 0 data are not 

representative of normal yearly emissions. Because compliance with the S02 1-hour standard is 

determined based on 3 consecutive years of complete data, the EPA does not believe it would be 

appropriate to exclude considering 201 0 data. In addition, because the deadline for promulgating the S02 

designations is June, 2013, a complete year of data for 2013 will not be available for use in designations. 

Therefore, we are proceeding with designations using the data set of2009-2011. 

The EPA will continue to work with state officials regarding the appropriate boundary for the 

nonattainment area in Montana. If you have additional information that you would like the EPA to 

consider, please submit it to us by April 8, 2013. 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 preliminary designation 

decisions. We intend to promulgate these designations for areas with monitored violations of the 201 0 

so2 standard by June, 2013. 

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. 

Enclosure 

cc: Tracy Stone-Manning, Director, DEQ 

Dave Klemp, Chief, ARMB 

Sincerely, 

!J~~ ~ Regional Administrator 

Gina McCarthy, Assistant Administrator for Air and Radiation 

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