UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IX 75 Hawthorne Street San Francisco, CA 94105·3901

OFFICE OF THE REGIONAL ADMI"fISTRATOR 

## JUN 2 9 

## 2011
The Honorable Brian Sandoval Governor ofNevada 101 North Carson Street Carson City, Nevada 89701

Dear Governor Sandoval:

I am writing to notify you ofthe U.S. Environmental Protection Agency's (EPA's) intend to designate all areas ofNevada as unclassifiable/attainmentfor the revised primary National Ambient Air Quality Standard (NAAQS) for nitrogen dioxide (N02 ) using the boundaries your State recommended in January 2011 or any revised boundaries that you submitin response to this letter. I am also writing to thank you for your State's previous recommendations, to provide you an opportunity to revise your previous recommendations for area boundaries, and to inform you ofourapproach for completing the designations for the revised N02 NAAQS.

On January 22, 2010, the EPA strengthened the health-based NAAQS for N02by setting a new I-hour N02standard at the level of 100 parts perbillion (ppb). The EPA also retained the annual N02standard of53 ppb. This suite ofstandards will protectpublic health by limiting people's exposures to short-term peakconcentrations ofN02and by limiting community-wide N02 concentrations 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 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 ofN02that occur more broadly across communities.

InourNovember 2010 letter to you requesting your designation recommendations, the EPA stated that
we anticipated designating most areas ofthe country as "unclassifiable," indicating that there are insufficient data to determine whether ornot an area is attaining the revised N02 NAAQS. TheEPA believed this approach was appropriate given that: (l) the new near-road monitoring network requirements associated with the revised N02NAAQS will not be effective until January 2013, so air quality data from these new monitors would not be available to inform initial designations; and (2) the N02monitors in the existing N02network do not provide adequate evidence to determine whether or not the new NAAQS is met at otherlocations, especially those closerto N02 emission sources such as roadways.

After reviewing all the recommendations we received including Nevada's, the EPA now intends to designate all areas ofthe country as "unclassifiable/attainment."TheEPA is making this change because, based on the most recent airquality data from 2008-2010, all monitored areas in the country meet the 2010 N02NAAQS. While the EPA acknowledges that the existing N02 monitoring network

Prinud on Recycled Paperdoes not provide adequateevidence to determine whether or not the new NAAQS is met everywhere, there currently is no evidence ofviolations anywhere in the country. Based on this, the EPA believes "unclassifiable/attainment" is the most appropriate designation to use at this time. TheEPA intends to redesignate areas, as appropriate, after sufficient airquality data from the new monitoring network are available.

The EPA intends to designate all areas ofNevada as unclassifiable/attainmentusing the boundaries your State recommended to the EPA in January 2011 or any revised boundaries you may provide in response to this letter. As we did in our November 2010 letter, EPA recommends that each state carefully consider the implications ofthe boundaries it selects for its Prevention ofSignificant Deterioration permitting program for new ormodified sources to ensure that they are consistent with its objectives for managing air quality deterioration and economic growth.

Ifyour State has additional information that you wantthe EPA to consider with respect to the designations including any revisions to your State's recommended boundaries, please submitit to us by August 29,2011. We are also making the EPA'spreliminary 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 the notice oftheir availability is published in the Federal Register. We will review any information we receive from the state ofNevada and the general public by these dates. Weplan to promulgate the final designations by October31, 2011.

Thankyou again for your State'sJanuary 2011 recommendations for designations for the new I-hour N02 NAAQS. We look forward to a continued dialogue with you and your staffas we work together to implement this NAAQS. Should you have any questions, please do not hesitate to call me, or have your staffcontactDeborahJordan ofmy staffat (415) 947-8715.
Sincerely,

cc: Colleen Cripps Administrator, NDEP

Rob Bamford Bureau Chief, Bureau ofAirQualityPlanning, NDEP