1200 Sixth Avenue, Suite 900

2^ Seattle, Washington 98101-3140

J^SERSTgT^s UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

Q rz REGION 10

^yTgL PFOZ^G{\

OFFICE OF THE

REGIONAL ADMINISTRATOR

JUN 29 2011

The Honorable C. L. "Butch" Otter

Governor of the State of Idaho

Post Office Box 83720

Boise, Idaho 83720

Dear Governor Otter:

Thank you for your recommendations on air quality designations for the revised primary National

Ambient Air Quality Standard (NAAQS) for nitrogen dioxide (NO 2) throughout Idaho. This letter is to

notify you of the U.S. Environmental Protection Agency's (EPA's) response to Idaho's designation

recommendations, and to inform you of our approach for completing the designations for the revised

NO2 NAAQS.

On January 22, 2010, the EPA strengthened the health-based National Ambient Air Quality Standard

(NAAQS) for NO2 by setting a new 1-hour N02 standard at the level of 100 parts per billion (ppb). This

new standard will protect against adverse health effects associated with short-term exposure to NO2 ,

including respiratory effects that can result in admission to a hospital. The EPA also retained with no

change, the annual average NO2 standard of 53 ppb. This suite of standards will protect public health by

limiting people's ex spres to short-term peak centrations of NO2 and by limiting community-wide

NO2 concentr,to levels below those that: hav been linked to respiratory-related emergency

department visits and hospital admissions in the United States. To determine compliance with the new

standard, the EPA established new ambient air monitoring and reporting requirements for NO2 . In urban

areas, monitors are required near major roads as well as in other locations where maximum

concentrations are expected. Additional monitors will be required in some large urban areas to measure

the highest concentrations of NO2 that occur more broadly across communities.

In the preamble to the 2010 NO2 NAAQS and in the EPA's October 2010 letter to you requesting

designation recommendations, the Agency stated that it expected to designate most areas of the country

as "unclassifiable," indicating that there are insufficient data to determine whether or not an area is

attaining the revised NO2 NAAQS. This approach took into account that the new monitoring network

requirements established with the revised NO2 NAAQS will not be effective until January 2013 and that

air quality data from these new monitors would not be available to infomi these initial designations.

The Agency has reviewed your recommendations and others, and intends to designate all areas of Idaho,

as well as the rest of the country, as "unclassifiable/attainment" rather than "unclassifiable." Based on

air quality data from 2008-2010, all monitored areas in the country meet the 2010 N02 NAAQS. While

the EPA acknowledges that the existing NO2 monitoring network does not provide adequate evidence to

detellinine whether or not the new NAAQS is met in all areas, there currently is no evidence of

violations anywhere in the country. The "unclassifiable/attainment" designation better reflects the

current air quality conditions. The EPA intends to redesignate areas, as appropriate, after sufficient air

quality data from the new monitoring network are available.
The EPA intends to designate Idaho unclassifiable/attainment using the boundaries Idaho recommended

to the EPA or revised boundaries you may provide in response to this letter. In past designations for

NO2, for the majority of states, the area of the state where the air quality could not be classified, or was

better than the national standards, was given a statewide, or rest-of-state designation. However, the EPA

recommends that your state carefully consider the implications for the Prevention of Significant

Deterioration (PSD) permitting program of having the entire state designated as a single area rather than

smaller areas (e.g., counties, groups of counties, etc.). To ensure that the size of designated areas is

consistent with your state's objectives for managing air quality deterioration and economic growth, we

recommend that your permitting staff be consulted on the area boundary issues.

If your state has additional information that you want the EPA to consider with respect to the EPA's

designation, please submit it to us by August 29, 2011. We are also making the EPA's preliminary

designation decisions and supporting documentation available to the general public for review. We are

accepting public comments on our preliminary decisions for 30 days after a notice announcing the

public comment period is published in the Federal Register. We will review any information we receive

from the State of Idaho and the general public by this date, and we plan to promulgate the final

designations by October 31, 2011.

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

2010 NO2 NAAQS. Should you have any questions, please do not hesitate to call me, or have your staff

contact Claudia Vaupel at 206-553-6121.

Sincerely,

Dennis J. McLerran

Regional Administrator

p

90 `0'''

cc: Toni Hardesty

Director, Idaho Department of Environmental Quality

Martin Bauer

Air Program Manager, Idaho Department of Environmental Quality

Gina McCarthy

Assistant Administrator for Air and Radiation, EPA

Stephen D. Page

Director, Office of Air Quality Planning and Standards, EPA