UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WA S HINGTON, D

. C. 20460

The Honorable Todd Parfitt Director 

## MAR 202015

Wyoming Department ofEnvironmental Qua lity Herschler Building 122 West 25th Street Cheyenne, Wyoming 82002
Dear Mr. Parfitt: OFF ICE OF AIR AN D RADIATION

I am writing to update you on the status ofthe U

.S. Environmental Protection Agency's progress in implementing the primary National Ambient Air Quality Standard (NAAQS) for sulfur dioxide (S02) set in 2010 at 75 parts per billion (ppb) as a 1-hour average. In July 2013, the EPA identified areas in 16 states as nonattainment and expressed the intent to address designations for the remainder ofthe country in separate future actions

. On March 2, 2015, the U.S. District Court for the Northern District of California accepted as an enforceable order an agreement between the EPA and Sierra Club and Natural Resources Defense Council to resolve litigation concerning the deadline for completing the designations. The court's order directs the EPA to complete designations in three additional rounds: the first round by July 2, 2016, the second round by December 31, 2017, and the final round by December 31, 2020. The EPA will complete these designations by designating areas as either nonattainment, unclassifiable/attainment, or unclassifiable.
In the first round ofdesignations, the EPA will designate two groups of areas: 1) areas that have newly monitored violations ofthe 2010 S02 standard, and 2) areas that contain any stationary source that according to the EPA's Air Markets Database either emitted more than 16,000 tons of S02 in 2012 or emitted more than 2,600 tons ofS02 and had an emission rate of at least 0.45 lbs S02/mmbtu in 2012 and that has not been announced (as ofMarch 2, 20 15) for retirement. In the enclosure to this letter, the EPA provides the schedule we intend to follow to meet the July 2, 2016, deadline.
While there are currently no sources in Wyoming meeting the emissions criteria established in the court's order, the EPA has identified the following area in your state as one that may have a newly recorded violation ofthe 2010 S02 standard based on preliminary air quality monitoring data collected between 2012 and 2014:

I nternet Add r ess ( U RL) • http :// www

.epa.gov Recyc le d/Recycl able • Pri nted wi th Vegetab le O i l Based Ink s o n 100% Postconsume r, Process C hl orine Free Recycl ed PaperState County Air Qual i ty Systems Monitor Location 2012
- 2014 Monitor Identification Preliminary S02 N umb er Design Value (pQb) WY Carbon 56-007
- 0852 Sinclair S0 2 Station 123 The EPA will use the most recent available information when making designation and boundary decisions for the indicated area. If you would like to submit updated recommendations and supporting information for the EPA to consider for th e affected area in your s tat e, we request that you do so by

September 18,2015. The EPA has updated i ts March 24 , 2011, designation guidance for the 2010 S02 standard to support analysis of designations and boundaries for these next rounds of designations. The updated guidance can be found on the EPA's website at http://epa.gov/airquality/sul(urdioxide/guidance.html. The E PA has also provided two technical assistance documents that provide advice on the use of modeling and monitoring data when determining if an area is meeting or not meeting the 20 1 0 S02 standard. These documents can be found on th e EPA's website at http :// epa.gov/airquality/sul(urdioxide/implement.html. The court's order directs the EPA to complete the second round of area designations by December 31, 2017. These designations would address areas where states have not installed and begun operating a new

S02 monitoring network meeting the EPA's specifications referenced in our proposed rule titled, "Data Requirements Rule for the 1-hour S02 primary NAAQS" . This rule, which was proposed in the Federal Register on May 13, 2014, would direct state and tribal air agencies to provide data to characterize

current air quality i n areas with l arge sources of S02 if such areas do not ha ve suffic i ent air quality monitoring in place to identify maximum S02 concentrations. The data collected as a result of this

proposed rule would be used in the designations process. Lastly, the court ' s order directs the EP A to designate all rema i ning areas by December 31 , 2020 . The EPA will provide states with additiona l information on the designations process associated with these later deadlines at a la ter date. We look forward to continued dialogue with you a n d you r staff as we work togeth er to implement the 2010 S02 s t andard and achieve its intended public health protection. For additiona l information re ga rdin g designations for the 2010 so2 standard, please visit our website at www.epa.gov/so2designations. Shou ld you have any questions, please do not hesitate to call me or Scott Mathias of my staff at 919-541-5310 and mathias. scott@epa.gov. Sincerely, Jane t G. McCabe Act i ng Assistant Admi nis trator Enclosure cc: Shaun McGra t h

EPA Region 8 Administrator

### ENCLOSURE
TIMELINE FOR 20 I0 PRIMARY S02 NAAQS DESIGNATION PROCESS FOR AREAS ASSOCIATED WITH JULY 2, 2016, COURT-ORDERED DEADLINE* Milestone Date** Court Order March 2, 2015 States may submit updated recommendations No later than September 18 , 2015 and supporting information for area designations to the EPA The EPA notifies states concerning any o/a January 22, 2016 , but absolutely no later intended modification s to their than 120 days prior to final designations , 

### i.e., recommendations ( 120-day letters) March 2, 2016 The EPA publishes public notice of state o/a February 3 , 20 16 recommendations and the EPA's intended modifications and initiates 30

-day public comment period End of 30-day pubhc comment period o /a March 4, 2016 States provide additional information to o/a April 8 , 20 16 demonstrate why an EPA modification is inappropr iate The EPA promulgates final S02 area No later than July 2, 2016 designations (no later than l6 months from Court Order} 

## * The court's order directs the EPA to promulgate additional rounds ofdes 1gnat10ns by December 31 , 2017 , and by December 31 , 2020. 

## * * o/a 

### = on or about