### Class I Area Impact Analysis for PSD Permit Application Dwight Mallory Dwight Mallory to: ' john _notar@nps.gov' 08/02/2012 12:28 PM Cc: Andrew Chew, Patrick Flynn



### Mr. Notar,

In reference to the voice message exchanges we have had: I am contacting you in reference to a PSD permit application, submitted to U.S. EPA Region 9 on December 5. 2005, for the emergency flare at the McElmo Creek Unit Gas Compression Facility, located near Aneth, Utah. Resolute Natural Resources Company acquired the MCU facility from Exxon Mobil in 2006 and we have been working with Region 9’s permitting staff to obtain issuance of the PSD permit since that time.

You provided comments at the time the original PSD application and air modeling were submitted that no additional modeling for Class I impacts was necessary. However, since that time, EPA has promulgated new 1-hr NAAQS for NO2 and SO2, and requested that Resolute revise the modeling to account for the 1-hr NO2 and SO2 NAAQS. They also requested that Resolute contact you and allow the opportunity for you to review your comments in light of the 2010 revisions to the air emissions guidance for federal land managers.

The emissions limits of 60 TPY S02; 73 TPY CO; 13.4 TPY NOx; and 95.4 TPY VOCs applicable to the flare are unchanged since the original PSD application was submitted; and the flare’s actual emissions have decreased from the 29.2 tons S02; 66 tons CO; 12.1 tons NOx; and 90.6 tons VOC reported by EOM for 2005 to 26.7 tons SO2; 45.4 tons CO; 8.4 tons NOx; and 54.9 tons VOC for 2011. The SCREEN 3 model submitted with the PSD application estimated near-field impacts from the flare operating at 14.83 MMCFD for the entire year, or 7 times greater than the average rate for 2005.

The results of the model showed that the flare did not cause or contribute to a violation of the National Ambient Air Quality Standards
for NO2 or SO2 that were effective at the time of the PSD submittal.
The revised SCREEN 3 model demonstrated that the flare did not to cause or contribute to a 1-hour NO2 NAAQS violation, but showed that the maximum 1-hr SO2 impact for the flare exceeded the interim SIL of 3 ppb. At Region 9’s request, Resolute remodeled the SO2 emissions using EPA’s refined AEROMOD model and was able to effectively
demonstrate that the flare does not cause or contribute to a 1-hour SO2 NAAQS violation.

I have attached Appendix D of the original PSD application, which includes the original communication between yourself and Justin Harrison at Exxon Mobil concerning impacts to Class I areas. Also

### attached is a map showing the location of the project in relation to

Class I areas. Please review and let me know if any additional information or modeling is necessary.

If you would like to speak with EPA Region 9 staff, please contact Andrew Chew at (415) 947-4197.

As requested by Region IX, I have also contacted Laura Romin with USFWS to allow an opportunity for USFWS to renew their comments regarding T&E species and critical habitat impacts.

Dwight E. Mallory Environmental, Health & Safety Coordinator Resolute Energy Corporation 1675 Broadway, Suite 1950 Denver, CO 80202 Direct: 303-573-4886 X 1165 Cell: 970-302-8620 Email: dmallory@ResoluteEnergy.com

APP D from EOM PSD Ap.pdf MCU Class I Air.pdfC a n y o n l a n d s N P

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M e s a V e r d e N P W e m i n u c h e W i l d e r n e s s



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