98 SAN J<\CINlO BlVD. 

BAKER BOlTS LL.P. 

SUIIE 1500 

AUSTIN IEXAS 

78701·4078 

TH • I 512.322 2500 

FAX •15123???501 

BolerBon~ com 

September 17, 2015 

Ms. Janet G. McCabe 

Assistant Administrator, Office of Air and Radiation 

U.S. Environmental Protection Agency lleadquarters 

1200 Pennsylvania A venue, N. W. 

Mail Code 6101A 

Washington, DC 20460 

Dear M s. McCabe: 

AUSTIN lONDON 

B[ljJNG MOSCOW 

SPUSSftS NEWYOPY 

DAllAS PAlONTO 

DUB AI RIO DE jANEIPO 

HONG KONG PIY,\l)ll 

HOUSTON WASHINGTON 

Derek McDonold 

TEL 5 123222667 

FAX: 5123228342 

derek mcdonold@bokerbott$ com 

This letter is submitted on behalf of Major Oak Power, LLC (Major Oak) to support the 

designation or the area surrounding the Twin Oaks Power Station in Robertson County, Texas as 

attainment for the ational Ambient Air Quality Standard (NAAQS) for sulfur dioxide (S0 2) set 

in 20 I 0 at 75 parts per bill ion (equal to 196 microgram s per cubic meter (~ )) as a 1-hour 

average. We submit this intormation in response to the request round in your letter dated March 

20, 20 15, to the llonorabh.: Bryan W. 'haw. Chairman. Tc.'l:as Commi ss ion on Environmental 

Quality (TCEQ). This information supports the TCI s continut:d recommendation that the 

area be designated as unclass itiablc/attainment for the 1-hour SO~ AAQS based primarily on 

the latest monitoring data and secondarily on source modeling conducted by the TCEQ. 

Major Oak owns the Twin Oaks Power Station. The Twin Oaks plant includes two 175-

megawatt steam electric generating circulating fluidized bed (CFB) units fueled primari ly by 

lignite from an adjacent mine. The design of the fluidized bed boilers provides inherent control 

or so2 emiss ions. 

Major Oak maintains that the area surrounding our facility must be designated as 

attainment or unclass ifiable/attainment for S02• Both of these options are avai lable to EPA 

under the Clean A ir Act and we are aware or no evidence that the air near our facility exceeds 

the primary S02 NAAQS. None of' the regulatory monitors in Texas arc showing violations of 

the S02 AAQS, including one in nearby McCiennan County, Texas. An attainment or 

unclassifiable designation is clearly appropriate in these circumstances. 
BAKER BOTTS,,p 

Ms. Janet G. McCabe - 2 - September 17, 20 15 

The T CEQ's unclassifiable/attainment recommendation for Robertson County is also 

supported by dispersion modeling analysis conducted by the TCEQ. As documented in the State 

of Texas' September 20 15 submittal to EPA, I the predicted maximum so2 design value 

associated with actual S02 emissions from our plant and nearby sources is only I 00 J.l g/m3

, 

which is approximately 50% of the S02 standard of 196 f.lg/m3

. Importantly, this air qualityprotective result was reached despite including in the model S02 emissions from the Oak Grove 

power plant 2 1 kilometers away. 16 J.lg/m3 background S02 levels as measured at the nearby 

ambient monitoring station in M cC iennan County, and the inherently conservative nature of the 

dispersion modeling analysis which tends to overprcdict ambient air concentrations. Additional 

details on the modeling approach arc as follows: 

• The atmospheric dispersion modeling performed by the TCEQ was executed 111 

accordance with the guidance in the EPA draft document, ··so~ AAQ 

Designations M odeling Technical Ass istance Document, .. dated December 2013. 

The American Meteorological Society/Environmental Protection Agency 

Regulatory Model (AERMOD) was used in accordance with the guidance. Three 

years of recent representative meteorological data (20 12 to 20 14) were used. The 

meteorological data were collected at the nearest National Weather Service 

stations. The surface data were collected in College Station. Texas (Station o. 

03904) and the upper air data were collected at Fort Worth, Texas (Station o. 

03990). AERMET was used to process the data along with representative albedo, 

Bowen ratio, and surface roughness values determined with AERSURFACE. 

• The only significant sources of S02 emissions at the faci lity are two stacks 

servicing the two CFB boilers. The two stacks were modeled with actual stack 

parameters (i.e., stack height. stack exit diameter, stack exit velocity, and stack 

exit temperature). Nearby structures were accounted for and downwash 

parameters were determined with the use of the EPA program BPIP-PRM. Actual 

hourly S02 emission rates, as reported to EPA's Acid Rain Program database 

were used in the modeling. 

• The T" in Oaks facility is located in a rural selling with no other significant local 

sources of SO:!. The nearest significant source of S02 em iss ions. the Oak Grove 

Steam Electric Station (Oak Grove), is located approximately 21 kilometers from 

the Twin Oaks facility. Actual hourly S02 emissions for Oak Grove. as reported 

to EPA ·s Acid Rain Program database, were included in the modeling. 

• A representative background concentration of S0 2 was added to the resultant 

maximum modeled concentration. The background concentration data was 

1 Memorandum from Daniel Menendez to David Brymer, Subject: Modeling Analysis of Sulfur Dioxide for Major 

Oak Power, LLC - Twin Oaks (RN 100226570) (June 5, 2015). 
BAKER BOTTS II f> 

Ms. Janet G. McCabe .., - .) - September 17, 20 15 

collected at the EPA Acrometric Information Retrieval System (AIRS) monitor 

located in Waco, Texas. The receptor grid consisted of a Cartesian grid of 

receptors with I 00-meter spacing along the Twin Oaks fence line out to one 

kilometer, a Cartesian grid of receptors with a spacing of 500 meters located out 

to five kilometers, and another Cartesian grid of receptors with a spacing of one 

ki lometer located out to fifty kilometers. Receptor elevations were determined 

with the use of the EPA program AERMAP. The receptor grid and elevations 

that were used are consistent with EPA guidance. 

• Associated modeling file and the TCEQ' s umrmlr) modeling memorandum are 

attached. 

These modeling methodologies utilized by the TCEQ are also consistent where 

applicable with the guidance provided by the draft December 2013 EPA document referenced 

above and EPA' s ·'Guideline on Air Quality M odels,'· published as Appendix W to 40 CFR Part 

51. 

Notably, the facility is already wel l-controlled for S02• as it was made subject to federal 

Best Available Control Technology review when permitted. Through a combination of the 

plant's CFB technology and limestone injection, the plant is able to control S02 emissions below 

federal PSD permit limits to meet S02 emiss ion budgets and regulatory limits under the CrossState A ir Pollution Rule as applicable at this time Compliance with permit and regulatory limits 

is continuously demonstrated through a continuous emissions monitoring system. We do not 

believe that it would be reasonable to require additional post-combustion S0 2 emission controls 

for the plant. 

Major Oak appreciates your consideration of thi s information. Based on EPA ·s 

responses to prior FOIA requests, we understand that EPA has no source modeling information 

that suggests that the Twin Oaks plant causes or contributes to an exceedance of the S02 

NAAQS. If any such information is submitted to EPA, we respectfully request the opportunity 

to review it and provide our views on the modeling approach. 

If you would like to discuss further. please do not hesitate to contact Eddy Young. 

Environmental Supervisor at Twin Oaks. at 254.746.55 78 or eddv. voung({Moncstargcn.com. or 

me. 

Sincerely, 

Derek McDonald 

Attachments 
BAKER BOTTS tiP 

M s. Janet G. McCabe - 4 - September 17, 20 15 

cc: Ron Curry, Regional Administrator, EPA Region 6 

Guy Donaldson, Chief. A ir Planning Section. EPA Region 6 

Bryan W. Shaw, Ph.D., P.E., Chairman, Texas Commission on Environmental Quality 

Eddy Young, Environmental Supervisor, Twin Oaks