# 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 ("S0 2 ") emissions from the Big Brown Steam Electric Station, Limestone Electric Generating Station, Monticello Steam Electric Station, and the W.A. Parish E lectric 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 trans lates 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 S0 2 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/m**3** 

### • 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/m**3** 

### • Dolet Hills 

### in Louisiana causes concentrations as high as 218.7**~J.g/m 3**  

### 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 me antime, 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