UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 8 

Ref: 8P-AR 

The Honorable Jack Dalrymple 

Office of the Governor 

600 East Boulevard A venue 

Bismarck, North Dakota 58505 

Dear Governor Dalrymple: 

1595 Wynkoop Street 

Denver, CO 80202-1129 

Phone 800-227-8917 

www.epa.gov/region08 

FEB 1 6 2Ji6 

Thank you for your recommendations dated September 16, 2015, on air quality designations for the state 

of North Dakota for the 2010 revision to the primary National Ambient Air Quality Standard (NAAQS) 

for sulfur dioxide (S02). Reducing levels of S02 pollution is an important part of the U.S. 

Environmental Protection Agency's (EPA's) commitment to a clean, healthy environment. Exposure to 

S02 can cause a range of adverse health effects, including narrowing of the airways which can cause 

difficulty breathing and increased asthma symptoms. This letter is to notify you of the EPA's 

preliminary intentions regarding your recommended designations. 

On June 3, 2010, the EPA strengthened the health-based or "primary" standard for S02 by establishing a 

standard for 1-hour average S02 concentrations at a level of 75 parts per billion. Within one year after a 

new or revised standard is established, the Clean Air Act requires the Governor of each state to submit 

to the EPA a list of all areas in the state, with recommendations for whether each area meets the 

standard. Through an interactive process, the EPA considers the recommendations and then promulgates 

designations for all areas across the country. On July 25, 2013, the EPA designated 29 areas in 16 states 

as nonattainment, but did not at that time designate other areas. Pursuant to a March 2, 2015, courtordered schedule, 

1 the EPA must complete the remaining S02 designations by three specific deadlines: 

July 2, 2016, December 31, 2017, and December 31 , 2020. 

This current round of designations, to be completed by July 2, 2016, addresses two groups of areas: 

(1 ) areas that have newly monitored violations of the 2010 S02 NAAQS based on the most recent three 

calendar years of certified monitored ambient air quality data, and (2) areas that contain any stationary 

source that had not been announced as of March 2, 2015, for retirement and that according to the EPA's 

Air Markets Database emitted in 2012 either (i) more than 16,000 tons of S02 or (ii) more than 2,600 

tons of S02 with an annual average emission rate of at least 0.45 pounds of S02/mmBTU. 

After carefully considering North Dakota's recommendations and other available technical information, 

the EPA intends to designate as unclassifiable/attainment the following areas, including the following 

counties or portions of counties: 

1 Sierra Club v. McCarthy, No. 3-13-cv-3953 (SI) (N.D. Cal. Mar. 2, 2015). 

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Intended Unclassifiable/ Attainment Intended Unclassifiable/ Attainment 

Area Area Counties 

Central Mercer County* Mercer County (p) 

(p) indicates portion of county 

The asterisk(*) indicates the boundary for this intended unclassifiable/attainment area-represents a 

modification to the boundary that you have recommended. In this case, because you did not recommend 

a specific boundary but recommended a designation for the area around the Coyote Station, the EPA has 

established a proposed boundary using the recommendations for our March 20, 2015 "Updated 

Guidance for Area Designations for the 2010 Primary Sulfur Dioxide National Ambient Air Quality 

Standard." 

Because the EPA has insufficient information to determine whether the following areas are meeting or 

not meeting the S02 NAAQS, the EPA intends to designate these areas as unclassifiable: 

Intended Unclassifiable Area 

McLean County/Eastern Mercer 

County* 

Intended Unclassifiable Counties 

McLean County 

Mercer County (p) 

(p) indicates portion of county 

The asterisk (*) indicates the designation and boundary for this intended unclassifiable area represents a 

modification to the attainment designation and unspecified boundary that you have recommended. 

Based on ambient air quality data collected between 2012 and 2014 indicating a violation of the 2010 

S02 NAAQS, the EPA initially identified the area around the Hess Corp Tioga Gas Plant in Tioga, 

North Dakota, as one that would potentially create the obligation for us to designate by July 2, 2016. 

However, EPA has since discovered that the monitor reading violations near the Tioga Gas Plant 

contained certain performance evaluation flaws, was not certified by either the state or the EPA, and 

should ultimately be considered non-regulatory for each year in the 2012-2014 design value period. 

Similarly, the design value period between 2013 and 2015 cannot be relied upon for the purposes of 

making a designation as the 2013 and 2014 data are non-regulatory. For these reasons, the area around 

the gas plant is not subject to the July 2, 2016, deadline for designation under the court order. We intend 

to designate the area by December 31 , 2020, based on regulatory ambient monitoring near the Tioga Gas 

Plant. 

The enclosed Technical Support Document provides a detailed analysis that supports our intended 

designation decisions. If your state has additional information that the EPA should consider prior to 

finalizing these designations, please submit it to us by April 19, 2016. We also will be publishing a 

notice in the Federal Register announcing a 30-day period for the public to provide input on the EPA's 

intended designation decisions. We will promulgate the designations for these areas by July 2, 2016. We 

will designate all other previously undesignated areas in the state on a schedule consistent with the 

prescribed timing of the court order, i.e., by December 31 , 2017, or December 31, 2020. 

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We look forward to a continued dialogue with you and your staff as we work together to complete the 

area designations and implement the 2010 primary S02 standard. For additional information regarding 

designations under the S02 standard, please visit our website at www.epa.gov/so2designations. Should 

you have any questions, please do not hesitate to call me, or have your staff contact Carl Daly of my 

staff at (303) 312-6416 or daly.carl@epa.gov. 

~~' Shaun L. 

Regional Administrator 

Enclosure 

cc: Dave Glatt 

Environmental Health Section Chief, North Dakota Department of Health 

Terry O'Clair 

Director, Division of Air Quality 

Janet G. McCabe, Acting Assistant Administrator for Air and Radiation 

Stephen D. Page, Director, Office of Air Quality Planning and Standards 

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