Attachment B

TCEQ Analyses 

Contents: 

Part 1: Summary of TCEQ’s Analyses

Part 2: TCEQ’s Modeling Analyses

A. The June 5, 2015 Modeling Analysis of Sulfur Dioxide for Coleto Creek Power, 

LP – Coleto Creek Power Station (RN100226919) 

B. The June 5, 2015 Modeling Analysis of Sulfur Dioxide for Southwestern 

Public Service Company – Tolk Station Power Plant (RN100224534) 

C. The June 5, 2015 Modeling Analysis of Sulfur Dioxide for Major Oak Power, 

LLC – Twin Oaks (RN100226570)

Attachment B, Part 1: 

Summary of TCEQ’s Analyses

In a letter to the Texas Commission on Environmental Quality (TCEQ) dated March 20, 2015, 

the U.S. Environmental Protection Agency (EPA) identified 12 power plants to be evaluated in 

order to determine their impacts, if any, on compliance with the 2010 SO2 National Ambient Air 

Quality Standard (NAAQS). The TCEQ evaluated four of the 12 EPA-identified Texas sources 

meeting the consent decree criteria, being large emissions sources not announced for retirement 

as of March 2015, with 2012 SO2 emissions greater than 16,000 tons, or with 2012 emissions 

greater than 2,600 tons and an average emission rate greater than 0.45 MMBtu. 

This attachment identifies the information that the TCEQ considered in its evaluation of the 

four SO2 emissions sources, being Sandy Creek Energy Station, located in McLennan County;

Coleto Creek Power Station, located in Goliad County; Tolk Generating Station, located in Lamb 

County; and Twin Oaks Power Station, located in Robertson County. 

The TCEQ evaluated Sandy Creek Energy Station based on McLennan County monitoring data, 

with further support from modeling performed by Sandy Creek, as described in Attachment 

C: Evaluation of the Impact of Sandy Creek Energy Station SO2 Emissions. 

While the TCEQ continues to support the use of ambient air monitoring data as the appropriate 

information for use in making designation decisions, the TCEQ modeled three of the four 

sources it evaluated. The TCEQ’s analyses are contained in Attachment B, Part 2: TCEQ’s 

Modeling Analyses. 

One of the modeled facilities – Coleto Creek Power Station – provided additional information, 

contained in Attachment D: Information Submitted to the TCEQ by Coleto Creek Power 

Station. The TCEQ did not thoroughly evaluate this supplemental information due to time 

constraints.

The TCEQ’s basis for evaluation and determinations made for each of the four sources are: 

EPA Identified

Source County Basis for Evaluation Recommended 

Designation

Additional 

Information

Submitted by 

the Source

Sandy Creek 

Energy Station McLennan Available monitoring data – 

Waco Mazanec C1037 Attainment See 

Attachment C

Coleto Creek 

Power Station Goliad

Modeled maximum 

concentration 38 parts per 

billion (ppb)

Unclassifiable/ 

Attainment

See 

Attachment D 

Tolk Generating 

Station Lamb Modeled maximum concentration 64 ppb

Unclassifiable/ 

Attainment None 

Twin Oaks Power 

Station Robertson Modeled maximum concentration 38 ppb

Unclassifiable/ 

Attainment None 

The modeling files referenced in Attachment B, Part 2: TCEQ’s Modeling Analyses are available 

to the EPA from the TCEQ’s secure ftp site (https://ftps.tceq.texas.gov/). The “Help” link on 

that Web page provides instructions to sign up for an account.
Attachment B: 

TCEQ Analyses 

Part 2: TCEQ’s Modeling Analyses

A. The June 5, 2015 Modeling Analysis of Sulfur Dioxide for Coleto Creek Power, 

LP – Coleto Creek Power Station (RN100226919) 

B. The June 5, 2015 Modeling Analysis of Sulfur Dioxide for Southwestern 

Public Service Company – Tolk Station Power Plant (RN100224534)

C. The June 5, 2015 Modeling Analysis of Sulfur Dioxide for Major Oak Power, 

LLC – Twin Oaks (RN100226570)