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# . UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

# i~) REGION 8 

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# PR~c- ..... rt 1595Wynkoop Street DENVER, CO 80202-1129 Phone 800-227-8917 http://www.epa.gov/region08 

# JU 29 2011

Ref: 8P-AR

Richard Opper, Director Department ofEnvironmental Quality P.O. Box 200901 Building 1520 East 6th Avenue Helena, Montan 59620-090I

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# ~our recommendations on air quality designations forthe revised primary National Ambient Air Quality Standard (NAAQS) for nitrogen dioxide (N02) throughout Montana. This letter is to notify you ofthe U.S. Environmental Protection Agency's (EPA's)response to Montana's designation recommendations, and to inform you ofour approach for completing the designations for the revised N02NAAQS.

On January 22, 2010, the EPA strengthened the health-based National Ambient Air Quality Standard for N02by setting a new I-hour N02standard atthe level of 100 parts per billion (ppb). The EPA also retained with no change, the annual average N02standard of53 ppb. This suite ofstandards will protect public health by limiting people's exposures to short-term peak concentrations ofN02and by limiting community-wide N02concentrations to levels below those that have 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 N02

. In urban areas, monitors are required near majorroads 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 ofN02that occur more broadly across communities.

In the preamble to the 2010 N02NAAQS and in the EPA's October 2010 letter to you requesting designation recommendations, the agency stated that it expected to designate most areas ofthe country as "unclassifiable," indicating that there are insufficient data to determine whether ornot an area is attaining the revised N02NAAQS.This approach took into account that the new monitoring network requirements established with the revised N02NAAQS will not be effective until January 2013 and that air quality data from these new monitors would not be available to inform these initial designations.
The agency has reviewed your recommendations and others, and intends to designate all areas of Montana, as well as the rest ofthe 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 we acknowledge that the existing N02monitoring network does not provide adequateevidence to detennine whether or not the new NAAQS is met in all areas, there currently is no evidence ofviolations anywhere in the country. The "unclassifiable/attainment"designation better reflects the current air quality conditions. We plan to redesignate areas, as appropriate, after sufficientair quality data from the new monitoring network are available.

We will designate Montana unclassifiable/attainment using the boundaries Montanarecommended to the EPA or revised boundaries you may provide in response to this letter. In past designations for NO

### z , for the majority ofstates, the area ofthe 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, we recommend that you carefully considerthe implications for the Prevention ofSignificant Deterioration (PSD) pennitting program ofhaving the entire state designated as a single arearather than smaller areas (e.g., counties, groups ofcounties, etc.). To ensure that the size ofdesignated areas is consistent with your state's objectives for managing air quality deterioration and economic growth, we recommend that your pennitting staffbe consulted on the area boundary issues.

Ifyou have additional infonnation 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 petiod is published in the Federal Register. We will review any infonnation we receive from the state ofMontana 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 staffas we work togetherto implement the 20 I0 NO

### zNAAQS. Should you have any questions, please do not hesitate to call me, orhave your staff contact Carl Daly ofmy staffat (303) 312-6416.

Sincerely,

cc: Dave Klemp, Chief, ARMB

Gina McCarthy, Assistant Administrator for Airand Radiation Stephen D. Page, Director, Office ofAir Quality Planning and Standards