UNITED STATES ENVIRONMENTAL PROTECTION AGENC Y WASHING T O N , D.C. 20460

The Honorable Scott Thompson Executive Director 

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Oklahoma Department of Envi ronmental Quality 707 N Robinson Oklahoma City , Oklahoma 73102
Dear Mr. Thompson: OFFICE OF AIR AND RAD I AT I ON

I am writing to update you on the status of the U.S. Environmental Pro t ection Agency's progress in implementing the primary Natio na l Ambient Air Quality Standa rd (NAAQS) for sulfur dioxide (S02) set in 2010 at 75 parts per billion (ppb) as a 1-hour average
. In Ju ly 2013, the EPA ident ified areas in 1 6 states as nonattainment and exp r essed the intent to address designa tion s fo r the remainder of the 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 th e EPA and Sierra Club and Natural Resources Defense Council to r esolve litigation concerning the deadli n e for completing th e designations. The court's order directs the EPA to complete des ignations in three additional rounds: the first round by 1 uly 2, 2016 , the second round by December 31, 2017, and the final ro und by December 3 1 , 2020

. The EPA wi ll complete these des ignation s by designating areas as either nonattainment, unclassifiable/attainment , or unclassifiable.
In the fi r st round of designations, the EPA will des ignate two g roups of areas: 1) areas that have newly monitored v io lations of the 2010 S02 standard, and 2) areas that contai n any stationary source that according to the EPA ' s A ir Markets Database either emitted more than 1 6,000 tons ofS02 in 2012 or emitted more than 2 , 600 to ns of S02 and had an emission rate of at least 0.45 lbs S02/ mmbtu in 2012 and that has not been announced (as of March 2, 2015) for retirement. In the enclo s ure to this letter, the EPA provides the schedul e we intend to follow to meet the 1 uly 2 , 2016 , deadline.
The EPA has identified the fo ll owing electric power pl ant sources in your state as meeting the criteria es tab li shed in the court's order:

Internet Address (URL) • http ://www

. epa.gov Recycled/Recyclable • Pri nted with Vegetable O i l Based I nks on 100% Postconsumer, Process Chlorine Free Recycled Paper2012 so2 2012 so2 State County Facility Name Emissions Emissions Rate (tons) (lb/mmbtu) OK Muskogee Muskogee Generating 22,647 0.496 Station OK Noble Sooner Generating Station 15,029 0.499 OK Choctaw Hugo Plant 8,066 0.603 T he EPA will use the most recent available information when making designation and boundary decisions for the indicated areas. If you would like to submit an updated recommenda t ion and supporting information for the EPA to consider for the affected areas in your state, we reques t that you do so by September 18, 2015. The E PA has updat e d its 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 2010 S02 standard. These documents can be found on the EPA's website at http://epa.gov/airqualitvlsul[urdioxide/implement.html. The court's order directs t he EPA to complete the second round of area designations by December 31,

20 17. These designations would address ar eas where states have not installed a nd begun operating a new S02 monitoring network meeting the EPA 's specifications referenced in our proposed rule titled, ''Dat a 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 in areas with large sources of S02 if such areas do not have sufficient 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 . Last! y, the court's order directs the EPA to

designa te all remaining areas by December 31, 2020. The EPA will provide states with additional information on the designations process associated with these later deadlines at a later date. We look forward to continued dialogue with you and your staff as we work together to implement the 2010 S02 standard and achieve i ts intended public health protection. For additional information regarding designations for the 2010 so2 standard, please visit our website at www.epa.gov/so2designations . Should you have any questions, please do not h es itate to call me or Scott Mathias of my staff at 919-541-5310 and mathias.scott@epa.gov. Sincerely,**~~'(._c.__** Janet G. McCabe Acting Assistant Administrator Enclosure cc: Ron CurryEPA Region 6 AdministratorENCLOSURE
TIMELINE FOR 20 10 PRIMARY S02 NAAQS DES IGNATION PROCESS FOR AREAS ASSOC IATED WITH JULY 2, 20 16 , COU RT-ORDERED DEADLINE* Milestone Date** Court Order March 2, 2015 States may submit upda ted recommendations No later than September 18 ,2015 and supporting info rmation for area designations to the EPA The EPA notifies s tates concerning any o/a January 22,20 16 , but absolutely no later intended modifications 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, 2016 recommendations and the EPA 's intended modifications and initiates 30

- day public comment period End of 30-day public comment period o/a March 4, 2016 States provide additional information to o /a Apri l 8, 2016 demonstrate why an EPA modification is inappropriate The E PA promulgates final S02 area No later than Jul y 2, 2016 designations (no later than 16 months from Court Order) *The court ' s order directs the EPA to promulgate additional rounds of designations by December 31 , 2017, and by December 31 ,2 020.
** o/a = on or about