4300 Cherry Creek Drive South, EDO-AQCC-A5, Denver, CO 80246-1530 P 303-692-2000 www.colorado.gov/pacific/cdphe

John W. Hickenlooper, Governor | Larry Wolk, MD, MSPH, Executive Director and Chief Medical Officer

Dedicated to protecting and improving the health and environment of the people of Colorado

September 18, 2015

Shaun McGrath

Regional Administrator

USEPA Region VIII

1595 Wynkoop Street

Denver, CO 80202-1129

RE: 2015 Colorado Designation Recommendations for 1-hour Sulfur Dioxide NAAQS

Dear Mr. McGrath:

Pursuant to the provisions of section 107(d)(1) of the Clean Air Act, the state of Colorado 

submits to the Environmental Protection Agency the attached area designation

recommendations for the 1-Hour Sulfur Dioxide National Ambient Air Quality Standard 

(NAAQS), as revised on June 22, 2010. The Consent Decree (CD) ordered on March 2, 

2015 requires EPA to promulgate source specific designations on certain SO2 sources no 

later than July 2, 2016 (termed “Round 2” designations). This CD affects two sources in 

Colorado – the Pawnee Power Plant and Martin Drake Power Plant. The Colorado 

Department of Public Health and Environment must submit source specific designation 

recommendations, to assist EPA in promulgating “Round 2” designations, by September 

18, 2015.

The enclosed technical support document provides an overview of the designation 

process and supporting analyses for each recommendation. The technical support 

document makes a strong case that these designation recommendations are accurate 

and supportable for EPA approval. The unclassifiable designation for the area 

surrounding the Pawnee Power Plant is based on the need to develop appropriate shortterm emission rates so that air quality model results properly characterize ambient SO2 

levels surrounding the facility. The unclassifiable designation for the area surrounding 

the Drake Power Plant is based on disparate monitoring and modeling information. 

Historical ambient monitoring in the Colorado Springs metropolitan area and current 

ambient SO2 monitoring near the Drake Power Plant shows that the 1-hour SO2 NAAQS 

has not been violated. 
4300 Cherry Creek Drive South, EDO-AQCC-A5, Denver, CO 80246-1530 P 303-692-2000 www.colorado.gov/pacific/cdphe

John W. Hickenlooper, Governor | Larry Wolk, MD, MSPH, Executive Director and Chief Medical Officer

Dedicated to protecting and improving the health and environment of the people of Colorado

Conversely, third-party air quality modeling submitted to the Air Pollution Control 

Division (APCD) illustrates potential NAAQS violations. These disparities make it 

appropriate to designate the area as unclassifiable. An unclassifiable designation is 

further supported by APCD’s determination that the available meteorological data is not 

sufficiently representative of conditions at the facility to conduct accurate modeling. 

APCD is working with the facility operator, Colorado Springs Utilities, to gather 

representative meteorological data.

The enclosed area classification recommendations for the area surrounding Pawnee 

Power Plant and the area surrounding Drake Power Plant were adopted by the Colorado 

Air Quality Control Commission following a public hearing held on August 20, 2015. If 

you have any questions regarding this submittal, please contact Mike Silverstein, 

Administrator for the Air Quality Control Commission, at (303) 692-3478 or Will Allison, 

Director of the Air Pollution Control Division, at (303) 692-3114.

Sincerely,

Larry Wolk, MD, MSPH

Executive Director and Chief Medical Officer

Colorado Department of Public Health and Environment

cc. Martha Rudolph, CDPHE

Mike Silverstein, CDPHE-AQCC

Will Allison, CDPHE-APCD

Abby Fulton, EPA Region 8

Enclosure

State of Colorado, Technical Support Document for 1-Hour Sulfur Dioxide National 

Ambient Air Quality Standard Recommended Air Quality Designations for Specific 

Sources