SIERRA 

CLUB 

FOUNDED 1892 

December 14, 2015 

Scott Mathias 

Associate Director 

Air Quality Policy Division 

U.S. Environmental Protection Agency 

Research Triangle Park, NC 27711 

Re: Updated Air Dispersion Modeling of Sulfur Dioxide Pollution in Texas and 

Louisiana 

Dear Associate Director Mathias: 

On September 17, 2014, Sierra Club submitted air dispersion modeling conducted 

by Wingra Engineering, S.C. that demonstrated that sulfur dioxide ("S02") emissions 

from the Big Brown Steam Electric Station, Limestone Electric Generating Station, 

Monticello Steam Electric Station, and the W.A. Parish Electric Generating Station in 

Texas have caused downwind S02 ambient air concentrations to exceed the 75 parts per 

billion National Ambient Air Quality Standard ("NAAQS"), which translates to 196.2 

micrograms per cubic meter (" J..Lg/m3

"). Sierra Club also submitted modeling 

demonstrating that emissions from the Dolet Hills Power Station in Louisiana cause 

downwind S02 ambient air concentrations to exceed the 20 I 0 standard. 

Enclosed, please find the results of updated modeling analyses for the Big Brown, 

Monticello, W.A. Parish, and Limestone facilities in Texas, the Dolet Hills plant in 

Louisiana, and the corresponding modeling input and output files for each report. These 

updates address questions posed by EPA Region 6 Staff. 1 

Using the most recent emissions data for each facility, the modeling shows: 

1 Also on September 17, 2015, Sierra Club submitted modeling demonstrating that the Martin 

Lake Electric Generating Station in Texas and the Big Cajun II Power Plant in Louisiana each 

cause exceedances of the 20 l 0 S02 NAAQS, and should therefore be designated as 

nonattainment. No updates to those reports were necessary, and Sierra Club continues to urge 

EPA to designate the areas surrounding Martin Lake and Big Cajun II as nonattainment. 
Mr. Scott Mathias 

September 17, 2015 

Page 2 

• Big Brown in Texas causes concentrations as high as 387.9 ~J.g/m3 

• Limestone in Texas causes concentrations as high as 255.1 ~J.g/m 3 

• Monticello in Texas causes concentrations as high as 237.2 ~J. g/ 3 

• W.A. Parish in Texas causes concentrations as high as 231.2 ~J.g/m3 

• Dolet Hills in Louisiana causes concentrations as high as 218.7 ~J.g/m3 

The modeling also demonstrates that the exceedances in the areas surrounding 

these facilities are even greater when nearby sources of S02 are taken into account. 

Accordingly, the area surrounding Big Brown, Limestone, Monticello, and W.A. Parish 

in Texas, and Dolet Hills in Louisiana should each be designated nonattainrnent under the 

NAAQS. 

We urge EPA to consider this information as it undertakes area designations in 

Texas and Louisiana for the 2010 revised primary S02 NAAQS. This information is 

being provided to both EPA's Office of Ai"r Quality Planning and Standards. In the 

meantime, please let me know if I can provide any additional information. 

Thank you for your attention to and consideration of this matter, and please do not 

hesitate to contact me if you would like to discuss further. 

Sin ~ 

Joshua rr 

Staff Attom'ey 

Sierra Club 

85 Second St., Second Floor 

San Francisco, CA 941 08 

Phone: (415) 977-5560 

Fax: (415) 977-5793 

joshua.smith@sierraclub.org