UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 8

Ref: 8P-AR

The Honorable Steve Bullock Governor ofMontana 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 062013

Thank you for your staffsMay 27, 2011, recommendations on air quality designations for the state of Montanafor the 2010 revision to the primary National Ambient Air Quality Standard for sulfur dioxide (S02). Reducing levels ofsulfur dioxide pollution is an importantpart ofthe U. S. Environmental Protection Agency's (EPA) commitmentto a clean, healthy environment. Exposure to S02 can cause a range ofadverse health effects, including narrowing ofthe airways which can cause difficulty breathing and increased asthma symptoms. This letter is to notify you ofthe EPA'spreliminary intentions regarding your recommended designations.

On June 3, 2010, the EPA strengthenedthe health-based or "primary" standard for S02by establishing a standard for 1-hour average S02 concentrations at a level of7 5parts perbillion. The Clean Air Act requires the EPA to complete the initial designations process withintwo years ofpromulgating a new or revised standard. Ifthe Administratorhas 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 informationto complete the designations for the 1-hour so2standard within two years and extendedthe 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 ofstakeholders, EPA has developed a comprehensive implementation strategy for these future actions that focuses resources on identifying and addressing unhealthy levels ofS02. The strategy is available at: http:/ /www.epa.gov/airquality/sulfurdioxide/implement.html. The EPA will continue to work closely with you and ourotherpartners 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 mostrecent air quality datafrom 2009-2011, the EPA intends to designate as nonattainment the following area, including the following counties orportions ofcounties:

Nonattainment Area Area 1 County Yellowstone County (excluding Crow Tribe ofMontana)

The enclosed draft Technical Support Documentprovides 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 onthe available data, we
are not at this time able to concur with the state ofMontana's position that the 2010 data are not representative ofnormal yearly emissions. Because compliance withthe S02 1-hour standard is determined based on 3 consecutive years ofcomplete data, the EPA does not believe it would be appropriate to exclude considering 2010 data. In addition, because the deadline for promulgating the S02 designations is June, 2013, a complete year ofdatafor 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 areain Montana. Ifyou have additional informationthat youwould like the EPAto consider, please submit it to us by April 8, 2013. We also will be publishing a notice inthe Federal Register announcing a 30-dayperiod for the public to provide input on EPA'spreliminary designation decisions. We intend to promulgate these designations for areas with monitored violations ofthe 2010 so2 standard by June, 2013.

We look forward to a continued dialogue with you and your staffas we work together to implement the 2010 primary S02 standard. For additional informationregarding initial designations onthe S02 standard, please visit our website at www.epa.gov/so2designations. Shouldyouhave any questions, please do not hesitate to call me, orhave your staffcontact Crystal Ostigaard ofmy staffat (303) 312-6602 or ostigaard.crystal@epa.gov.

Enclosure

cc: Tracy Stone-Manning, Director, DEQ Dave Klemp, Chief, ARMB Sincerely,

# !J~~**~** Regional Administrator

GinaMcCarthy, Assistant Administrator for Air and Radiation Stephen D. Page, Director, Office ofAir Quality Planning and Standards