UNITED STATE S E N VIRONMENTAL PROTECTION AGENCY WASH I NGTON , D

. C. 20460

The Honorable Steve M. Pimer Secretary

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## 2 02015

South Dakota Department of Environment and Natural Resources Joe Foss Building 523 E Capitol Pierre, South Dakota 57501
Dear Mr. Pimer: OF F I CE OF A I R AN D RADIAT ION

I am wr iting to update you on the status of the U.S

. Environmenta l Pro tection Agency's progress in impl ementing the primary Nati onal Ambient Air Quality Standa rd (NAAQS) for sulfur diox ide (S02) set in 20IO at 75 parts per billion (ppb) as a l-hour average. In July 20I3, the EPA identified areas in I6 states as nonattainment and expressed the intent to address designations for the remainder of the country in sep arate future actions.
On Marc h 2, 2015, the U.S. District Court for the Northern District of Cali fo rnia accepted as an enforceable order an agreement between the EPA and Sierra Club and Natural Resources Defense Counci l to reso lve li tigation concerning the deadli ne for completing the designations. The court's order directs the EPA to comp lete des ignations in three additio nal rounds : the first round by July 2, 20 I 6 , the second round by December 31 , 2017, and the final ro und by December 3 1 , 2020. The EPA wi ll complete these designations by des ignating areas as either nonattainment , unclassifiable/at tainment , or unclassi t iable.
In the first round o f desig nations , the EPA will designate two groups of areas: I) areas that have newly monitored v i olations of the 20 I 0 S02 stand ard , and 2) areas that contain any stationary source that according to the EPA's Air Markets Database either emitted more th an 16,000 tons ofS02 in 2012 or emitted more than 2 , 600 tons ofS02 and had an emission rate of at least 0.45 lbs S02immbtu in 2012 and that has not been announced (as ofMa rch 2, 20 15) for retirement. In the enclosure to this letter , the EPA provides the schedule we intend to follow to meet the Jul y 2, 2016, deadli n e
. The EPA has iden tified the following electric power plant source in your state as meeting the criteria established in the court's order:
2012 so 2 2012 so 2 S tate County Facili ty Name E missions Emissions Rate (tons) (lb/mmbtu) Big Stone Plant

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## so Grant Power Comp any 

### 12, 290 0.813

I n terne t Address ( URL ) • h ttp ://www.e p a

. gov R ecycled/R ecyclable • Prin t ed w i t h Veget a bl e Oil Ba sed I nks on 1 0 0 % Postco ns u m er, P roce ss Chlo r i n e Free Recyc le d Pap erThe EPA will use the most recen t ava i lable information when making designation and boundary decisions for the indicated area. If you would like to submit an updated recommendation and supporting information for th e EPA to consider for the affected area in your state, we request that you do so by

September 18, 2015 . The EPA has updated 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 EPA has also pro vided 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/airquality/sul(urdioxide/implement.html. The court's order directs the EPA to complete the second round of area designations by December 31, 2017. The se 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 !-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 qua li ty in areas with large sources of S02 if such areas do not have sufficient air quality monitoring in p l ace 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 d i rects t he EPA to designate all remaining areas by December 31, 2020. The EPA will provide states with additiona l information on the designat io ns 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 th e 2010 S02 standard and ach i eve i ts intended public health protection. For additional information regarding designations for the 2010 S02 standard, please visit our webs i te at www .epa . gov/so2designations. Should you have any questions, please do not hesitate to call me or Scott Mathias ofmy staff at 919-541-5310 and mathias.scott@epa.gov. Sincerely, Janet G . McCabe Acting Assistant Administrator Enclosure cc: Shaun McGrath E PA Region 8 AdministratorENCLOSURE
TIMELINE FOR 2010 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 abso lutel y no later intended modifications to thei r than 120 days prior to final designations, 

### i.e. , recommendations ( 1 20-day letters) March 2 , 20 16 The EPA publishes public not ice 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 April 8 , 2016 demonstrate why an E PA modification is inappropriate The EPA promulgates fina l S02 area No later than Jul y 2, 20 16 designations (no later than 16 months from Court Order)

.. * The court's order directs the EPA to promulgate additional rounds of des1gnat10ns by December 31, 2017 , and by December 31 , 2020.
** o/a = on or about