# 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, D i rector



### 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) subm itted to the Environmental Protection Agency (EPA) for approva l the 2006 PM2 .s Infrastructure State Implementation Plan (I-SIP) certification. As part of its certification that the Wyoming S IP was adequate to meet the requirements of the prevention of significant deteriorati on (PSD) prong of the Clean A ir 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 upd ate its permitting program to include an NNSR program. The AQD is wri ting to clarify this portion of the 2007 submi ssion (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 wi ll issue the permit in accordance with the requirements of 40 CFR part 5 1, Appendix S. The AQD would also like to clarify the ambiguity within the portion of the August 19, 201 1 certification that addresses the signifi cant contribution to nonattainment and interference with maintenance prongs of the C l ean Ai r Act Section 11 O(a)(2)(D)(i)(I). In the 2011 certi ficat ion , the AQD again referenced its May 3 , 2007 interstate transport SIP as evidence that the Wyoming S IP meets the requiremen t s 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 submi ss ion 's analysis (distance , topography, population data, the nature of pollution problems in the nearest no nattainment areas)

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### 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 PM 2. 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 E li zabeth Lyon, A s sistant Attorney General Jeni Cederle , AQD Mike Morris , AQD Adam Clark, EPA R8 \