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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 (SO2). 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