UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 8 1595 Wynkoop Street DENVER, CO 80202-1129 Phone 800-227-8917 http://www.epa.gov/region08

Ref: 8P-AR

Steven M. Pimer, P.E. Secretary Department ofEnvironment and Natural Resources Joe Foss Building 523 East Capitol Pierre, Sou Dakota 57501-3182

Dear·

# ~I Thank

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

OnJanuary 22,2010, the EPA strengthened the health-based National Ambient Air Quality Standard for N02by setting a new I-hourN02standard at the 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 N02 NAAQS 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 or not an area is attaining the revised N02 NAAQS.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 ofSouth Dakota, as well as the rest ofthe country, as "unclassifiable/attainment" rather than "unclassifiable." Based on air quality data from 2008-20I0, all monitored areas in the country meet the 20I0 N02NAAQS. While we acknowledge that the existing N02monitoring network does not provide adequate evidence to determine whether or not the newNAAQS is met in all areas, there currently is no evidence ofviolations anywhere in the country. The "unclassifiable/attainment" designation betterreflects the current air quality conditions. We plan to redesignate areas, as appropriate, after sufficient air quality data from the new monitoring network are available.

We will designate South Dakota unclassifiable/attainmentusing the boundaries South Dakota recommended to the EPA or revised boundaries you may provide in response to this letter. In past designations for N02, for the majority ofstates, the areaofthe state where the air quality could not be classified, orwas betterthan the national standards, was given a statewide, orrest-of-state designation. However, we recommend that you carefully considerthe implications for the Prevention ofSignificant Deterioration (PSD) permitting program ofhaving the entire state designated as a single area rather 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 permitting staffbe consulted on the area boundary issues.

Ifyou have additional information that you want the EPAto 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 ourpreliminary decisions for 30 days after a notice announcing the publiccommentperiod is published in the 

### FederalRegister. We will review any infonnation we receive from the state ofSouth Dakota 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 together to implement the 2010 N02NAAQS. 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: Brian Gustafson, Administrator, AQP

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