STATE CAPITOL MATTHEW H. MEAD OF WYOMING CHEYENNE, WY 82002 GOVERNOR 

# o ce or t 

# e Governor

May 24, 2011

James B. Martin,- Regional Administrator EPARegion 8 Mail Code: AP-AR 1595 Wynkoop Street Denver, CO 80202-1129



### Re: I-Hour Primary National Ambient Air Quality Standard (NAAQS) for Sulfur Dioxide (S02)

Dear Mr. Martin:

The State of Wyoming is making recommendations regarding designations of the I-hour primary National Ambient Air Quality Standard (NAAQS) for sulfur dioxide (S02) that became effective on June 22, 2010.

The Department of Environmental Quality (DEQ) reviewed the most recent three years of S02 monitoring data available to make designation recommendations. The results and supporting data are found in Attachment 1to this letter. Based on a review ofthe monitoring data, the DEQ would recommend "attainment" for all counties in the State. However, the DEQ has also reviewed the March 24, 2011 Steven A. Page memo, "Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards," which sets forth a different approach to making designations relying heavily on modeling rather than monitoring. The guidance recommends a temporary unclassifiable status for most areas of the country due to a lack ofmodeling. Based on this guidance, the State is left with no option but to designate all counties of the State, as indicated in the table below, as "unclassifiable" for the current I-hour primary standard for sulfur dioxide.


### Regions I-HourPrimary 802 NAAQ8 Desienation Albany County Unclassifiable Big Horn County Unclassifiable Campbell County Unclassifiable

Carbon County Unclassifiable Converse County Unclassifiable ......:.....

FAX: (307) 632-3909 HO E (307) 777-7434,VIr.**Jarn~s** H. ,1ill'llll MilY 2,1. 20 I I Page '2

Crook County Unclassifiable Fremont County Unclassifiable Goshen County Unclassifiable Hot Springs COlmty Unclassifiable

Johnson County Unclassifiable Laramie COWlty Unclassifiable Lincoln County Unclassifiable NatronaCounty Unclassifiable Niobrara COtmty Unclassifiable Park County Unclassifiable Platte County Unclassifiable Sheridan County Unclassifiable Sublette Cotmty Unclassifiable Sweetwater County Unclassifiable Teton COtmty Unclassifiable Uinta County Unclassifiable Washakie COtmty Unclassifiable

Weston County Unclassifiable

There are portions ofthe above mentioned cotmties which are under the jurisdiction of Tribal Authorities. It is my tmderstanding that Tribal designations will be made separate from State designations.

I am not convinced that the hybrid approach described in the guidance, which gives modeling considerably more weight than monitoring, is the correct method to apply. I questions whether the hybrid approach promoted by EPA is based on sotmd science, since I have not been provided with a solid demonstration showing the accuracy of the model in predicting monitored conditions. I also question why EPA would want to undermine the validity ofmonitored data, which most states depend on for growld-truthing their air programs. It is my beliefthat there needs to be more discussion with states on how to designate areas for the new I-hour S02 standard. Wyoming looks forward to participating in such a discussion.

, I hope that the EPA will reconsider the hybrid approach in addressing designations. Ifyou have

questions concerning the details of this recommendation, please feel free to contact Steven A. Dietrich, Administrator, Department of Environmental Quality, Air Quality Division, at 307­ 777-7391.
Bestregards,Mr

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Cc: John V. Corra, Director, DEQ Steven A. Dietrich, Administrator, Air Quality Division, DEQ Christine Anderson, Air Quality Division, DEQ Cara Keslar, Air Quality Division, DEQ Chad Schlichtemeier, Air Quality Division, DEQf\.lr**Jam~s** B. l\lartlll May**~4. ~Oll**  Page -+

ATTACHMENT 1: S02 Monitored Data in Wyoming 2007-2009

The I-hourprimary S02 NAAQS is met when the three-year average ofthe 99th percentile daily maximum I-hour concentration, as determined in accordance with 40 CFR part 50 Appendix T, Interpretation ofthe Primary National Ambient Air Quality Standards for Oxides ofSulfur (Sulfur Dioxide), is the 3-year average ofthe annual 99th percentile daily maximum I-hour values for a monitoring site. The following table presents data collected from 2007-2009 that have met the data collection requirements presented in Appendix T.

MonitorNarne AQD Site ID

I 3-Year 99th Percentile Average (ppb)

Black Hills 56-005-0857 63 4 24 4 

### 5 Murphy Ridge 56-041-0101 Newcastle Refinery 56-045-0800 South Pass 56-013-0099 Wamsutter 56-037-0200 I I

State ofWyomingMap ShowingMonitorLocations Consideredin this Analysis

1 Hour Primary 502 MonUors •**Cb!~**

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