UN ITE D S TATES ENVIRONMENTA L PRO T E C TI O N A G EN CY REG I ON 8

Ref: 8P-AR
Martha Rudol ph 1595 Wyn koop S treet DENVER , CO 80202 -1 129 Phone 800-227 -8917 http://www.epa.gov/region08 

# DEC 0 3 

# 2ltL1

Co lorado Department of Pub li c Health

and Env ironment 4300 Cherry Creek Drive South De nver, Colorado 80246-1530 RE : High Wi nd PM 1

### o Exceedance in Pagosa Springs on April 3, 2009 Dear Ms. Rudo lph: This letter responds to Colorado Department of Public Health a nd Environment's (CDPH E) March 29, 20 12, submittal for app roval of a re g ional high w nnd exceptional event demonstration in southern Co l orado, which was amended on September 30, 2013
. CDP HE determined that this regional high wind event caused an exceeda nc e of the PM10 National Amb ient Air Quality Stand ards (NAAQS) at the monitor in Pagosa Springs on April 3, 2009
. The EPA has reviewed the documentation p rov ided by C DP HE to demonstrate that thi s exceedance met the criteria for an exceptional event under the Exceptional Events Rule (EER), 40 CF R 50.14
. EPA concurs, based on the weight of ev idence , that CD PHE has successfully made the demonstration necessary to comply with 40 C FR 50. 14 at the Pagosa Springs location on April 3, 2009
. In addition, CDPHE has met the sc hedul e a nd procedural requirements in section 50.14(c) with respec t to the demonstration. A more detailed assessment of CDP HE's demonstration is enclosed
. My staff has entered ' 'co ncurrenc e flags" for the April 3, 2009 Pagosa Springs data into the EPA 's Air Quality System (AQS)
. Based on thi s determination, the EPA wi ll e xclude these data from the following types of ca l cu lation s and activities:
• The E PA's A QS will not count this day as an exceedance when generating user r eports, or inc lude them in des ign values estimates, unless the AQS user specificall y indicates that they should be included. >• The EPA will accept the exclusion of this data for the purposes of selecting appropriate background concentrations for New Source Review air quality analyses. 1 • The EPA will accept the exclusion of this data for the purposes of selecting appropriate background concentrations for transportation conformity hot spot analyses. 2 The determination conveyed in this letter does not constitute final EPA action regarding any matter on wh ich tbe EPA is required to provide an opportunity for public comment. In particular. this applies to determinations regarding the attainment status or classification of this area. Final actions will take place only after the EPA completes notice and comment rulemaking on those determinations. As an additional clarification, the determination conveyed in this letter is applicable only to the PM 10 NAAQS. If you or your staffhave any questions or wish to discuss this matter further , please contact Carl Daly, Air Program Director, at (303) 312-6416.

Enclosure Sincere ly.

### ~ Shaun L. McGrath Regional Administrator

cc: William Allison, CDPHE Air Pollution Control Division Gordon Pierce. CDPI IE Air Pollution Control Division, Technical Services Program

1 1f EPA is the permitting authority, EPA will propose permits on this basis. If EPA is commenting on another permitting authority ' s proposed action, EPA's comments will be consistent with the detcm1inations in this leuer.

Applicable only to PM 1 0 and PM 2 5 2 

### @ Printed on Recycled Paper