Department of Environmental Quality 

To protect, conserve and enhance the quality of Wyoming's 

environment for the benefit of current and future generations. 

Matthew H. Mead, Governor 

April23, 2015 

Mr. Shaun McGrath 

Regional Administrator 

US-EPA Region 8 

1595 Wynkoop Street 

Denver, CO 80202-1129 

Todd Parfitt, Director 

RE: Certification Regarding the State of Wyoming's Application of 40 CFR part 51, 

Appendix S 

Dear Mr. McGrath: 

On August 19, 201 1, the Wyoming Department of Environmental Quality - Air Quality 

Division (AQD) submitted to the Environmental Protection Agency (EPA) for approval the 2006 

PM2.s Infrastructure State Implementation Plan (I-SIP) certification. As part of its certification 

that the Wyoming SIP was adequate to meet the requirements of the prevention of significant 

deterioration (PSD) prong of the Clean Air Act Section 11 O(a)(2)(D)(i), the AQD referred to its 

May 3, 2007 interstate transport SIP for the 1997 Ozone and PM2.s standards. The EPA 

previously approved this SIP on May 8, 2008. In the 2007 interstate transport SIP, the AQD 

noted - in regards to the PSD prong - that Wyoming did not have a nonattainment new source 

review (NNSR) program because there was not a need for one. However, the AQD added that if 

such a program became necessary, Wyoming would update its permitting program to include an 

NNSR program. 

The AQD is writing to clarify this portion of the 2007 submission (and, by reference, the 

20 11 submission), and to cettify that, in the event that the AQD receives a permit application for 

a major stationary source in a designated nonattainment area prior to receiving the EPA's 

approval for Wyoming's NNSR program, the AQD will issue the permit in accordance with the 

requirements of 40 CFR part 51, Appendix S. 

The AQD would also like to clarify the ambiguity within the portion of the August 19, 

201 1 certification that addresses the significant contribution to nonattainment and interference 

with maintenance prongs of the Clean Air Act Section 11 O(a)(2)(D)(i)(I). 

In the 2011 certification, the AQD again referenced its May 3, 2007 interstate transport 

SIP as evidence that the Wyoming SIP meets the requirements of 11 O(a)(2)(D)(i)(I) for the 2006 

PM2.s NAAQS. In drawing this parallel, the AQD considered the same factors from that 

submission's analysis (distance, topography, population data, the nature of pollution problems in 

the nearest nonattainment areas) - and the AQD's conclusions were based off of these 

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WDEQ-AQD 

40 CFR part 51, Appendix S certification 

Apri/ 23, 2015 

considerations. Ultimately, the AQD determined that Wyoming sources do not contribute 

significantly to nonattainment in, or interfere with the maintenance by, any other state with 

respect to the 2006 PM2.s NAAQS. 

The AQD would like to further clarify that Wyoming considered these factors within the 

context ofthe 2006 PM2.s NAAQS in reaching its conclusion that Wyoming's existing SIP meets 

the requirements of 11 0( a)(2)(D)(i)(I). 

If you have any further questions regarding the AQD's 2006 PM2.s I-SIP submittal, or the 

May 3, 2007 interstate transport SIP that is referenced within the 2011 submittal, please feel free 

to contact Jeni Cederle at 307-777-7740. Thank you for the opportunity to provide these 

clarifications. 

Sincerely, 

~kaDJ:J Steven A. Dietrich 

Administrator 

cc: Todd Parfitt, WDEQ Director 

Elizabeth Lyon, Assistant Attorney General 

Jeni Cederle, AQD 

Mike Morris, AQD 

Adam Clark, EPA R8 

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