\O ST 41

. UNITED STATES ENVIRONMENTAL PROTECTION AGENCY X\ifL REGION IX 17 :“

L PRO1 75 Hawthorne Street San Francisco, CA 94105-3901

OFFICE OF THE 

## JUL u i 

## 2013 REGIONAL ADMINISTRATOR Mr. Eric 

### Massey Director, Air Division 

### Arizona Department ofEnvironmental Quality 1110 W. Washington St. Phoenix. Arizona 85(07 

### DearMr. Massey: 

### This letterresponds to ArizonaDepartmentofEnvironmental Quality’s (ADEQ) February 13. 2013 submittal regarding 37 exceeedanccs ofthe 24—hour

### PIV1 10 standard that occurred 

### at several monitoring stations within the Phoenix PM 10 nonattainment areaon the following

### days: September ii and 12, 2011. June 16, June 27. 

### July 11. August 11, August 14. 

### and September 6, 2012. ADEQ’s submittal included documentationthatthese exceedances were caused by high 

### wind exceptional events. EPA

### has reviewedthe documentationprovided by ADEQ to demonstrate that the exceedances on these days meetthe criteria for an exceptional eventin the Exceptional Events Rule (EER). EPA 

### concurs based on the weight ofthe evidence thatthe exceedances were caused by high wind exceptional events and 

### finds thatADEQ has successfully

### made the demonstrations referred to in 40 CPR 

### 50. 14 to EPA’s satisfaction. In addition, ADEQhas metthe schedule and procedural requirements in section 50.14(c) with respect to the same data. A

### more detailed assessment ofADEQ’s demonstration is enclosed. 

### My staffhas or shortly will enter“concurrence flags” forthese 

### datainto EPA’s AQS data system. Based on these determinations. EPA will exclude these data from the following types ofcalculations and activities:

• EPA’s Air Quality Data system (AQS) will not countthese 

### days as exceedanees 

### when generating userreports, orinclude them 

### in design values estimates, unless the 

### AQS user specifically indicates 

### thatthey should be included.

• EPA will acceptthe exclusion of these 

### data forthe purposes 

### of selecting 

### appropriate background concentrations for

### New Source Review 

### airquality analyses.’


### • EPA will acceptthe exclusion ofthese data forthe purposes ofselecting appropriate background concentrations fortransportation conformity hot spot analyses. 2
o 

### The datawill continue to be publicly available, but EPA’s publications 

### and public 

### information statements onthe status ofairquality in the affected area will 

### notreflectthese data 

### in any summary statistic ofpotential regulatory application, unless 

### such inclusion is specifically noted.
liwe arethe pernlitting authority, we will proposepermits on this basis. Ifwe are commentingon anotherpermitting authority’s proposed action, ourcomments will be consistentwiththe determinations in this letter. 2Applicable only to PM 10

### and PM 2 These data may be included in statistics intendedto describe trends in actual airquality in the area.

Printed on Recycled PaperIn addition. EPA will rely on calculated values that exclude these data in proposed regulatory actions. such as a proposed designation. classification, attainment demonstration, or finding as to whether the Phoenix PM 10 nonattainment area has met the PM 10 NAAQS. These regulatory actions require EPA to provide an opportunity for public comment prior to taking a final Agency action. If EPA is pursuing one of these actions for the Phoenix PM 10 nonattainment area. EPA will open a new comment period during which EPA may receive comments on the exceptional event submission you have made and the determinations conveyed in this letter. If so, we must consider and respond to those comments before taking final regulatory action. Accordingly, the determinations conveyed in this letter do not constitute

final EPA action regarding any matter on which EPA is required to provide an opportunity for public comment. In particular. this point applies to determinations regarding the attainment status or classification of the area. Final actions will take place only after EPA completes notice and comment

rulemaking on those determinations. As an additional clarification, the determinations conveyed in this letter are applicable only to determinations incorporating the submitted data relative to the PM in NAAQS. If you have any questions or wish to discuss this matter further, please contact Deborah Jordan, Director of the Air Division at (415) 947-8715. Sincerely, / /4 1 ’kiared Blumenfeld Enclosure cc: Ms. Theresa Rigney. ADEQ