# .oED Sr4T,es UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 0; 

# Q '>Z REGION 10 

# s 1200 Sixth Avenue, Suite 900 

### ox^^o Seattle, Washington 98101-3140
y?44 PRO Z ^' OFFICE OF THE REGIONAL ADMINISTRATOR FEB. 6 2013 The Honorable C. L. "Butch" Otter Governor of the State of Idaho State Capitol P.O. Box 83720 Boise, Idaho 83720 Dear Governor Otter: Thank you for the recommendations provided by Toni Hardesty the Director of the Idaho Department of Environmental Quality dated May 16, 2011, on air quality designations for the State of Idaho for the 2010 revision to the primary National Ambient Air Quality Standard for sulfur dioxide (SO 2 ). 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 SO2 can cause a range of adverse health effects, including narrowing of the airways which can cause difficulty in 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 SO2 by establishing a standard for 1-hour average SO2 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 of the 1-hour SO2 standard. The EPA intends to address the designations for all other areas in separate future actions. With input from a diverse group of stakeholders, the EPA has developed a comprehensive implementation strategy for these future actions that focuses resources on identifying and addressing unhealthy levels of SO 2

. 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 SO2 standard. The EPA's review of the most recent monitored air quality data from 2009-2011 shows no violations of the 2010 SO2 standard in any areas in Idaho. Consequently, the EPA is not yet prepared to propose designation action in Idaho and is therefore currently deferring action to designate areas in Idaho. The EPA expects to proceed with designation action in Idaho 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 SO2 standard. For additional information regarding initial designations on the SO2 standard, please visit our website at www.epa.gov/so2designations . Should you have any questions, please do not hesitate to call me at (206)553-1234, or have your staff contact Debra Suzuki at (206) 553- 0985, or e-mail suzuki.debra@epa.gov

.

Dennis J. cLerran Regional Administrator

cc: Curt Fransen Director, Idaho Department of Environmental Quality Tiffany Floyd Administrator, Air Quality Division, Idaho Department of Environmental Quality Gina McCarthy Assistant Administrator, Office of Air and Radiation Stephen D. Page Director, Office of Air Quality Planning and Standards