The world's leading sustainability consultancy 

Baker Botts, LL.P. 

S02 Air Dispersion Modeling 

Report for Coleto Creek 

Power Station 

September 2015 

ERM Project No. 0311696 

www.erm.com 

~ ERM 
Baker Botts, L.L.P. 

S02 Air Dispersion Modeling 

Report for Coleto Creek Power 

Station 

September, 2015 

ERM Project No. 0311696 

Robert G. Fraser 

Partner-in-Charge 

Richard P. Hame l 

Project Ma11ager 

Environmental Resources Management 

One Beacon Street, 5th Floor 

Boston, MA 02108 

T: 617-646-7800 

F: 617-267-6447 
TABLE OF CONTENTS 

1.0 fNffiODUCTION 

1.1 PROJECT OVERVIEW 

1.2 0 VER VIEW OF METHODOLOGY 

2.0 FACILITY DESCRIPTION AND REGULATORY SETTING 

2.1 FACILITY LOCATION 

2.2 S02 ATTAINMENT STATUS 

2.3 SOURCE PARAMETERS AND EMISSION RATES 

3.0 AIR DISPERSION MODELING ANALYSIS 

1-1 

1-1 

1-2 

2-1 

2-1 

2-1 

2-4 

3-1 

3.1 MODEL SELECTION AND APPLICATION 3-1 

3.2 THE1-HOURS02NAAQS 3-1 

3.3 METEOROLOGICAL DATA 3-1 

3.4 RECEPTOR GRID 3-3 

3.5 GOOD ENGINEERING PRACTICE STACK HEIGHT ANALYSIS 3-3 

3.6 AMBIENT S02 BACKGROUND DATA FOR CUMULATIVE MODELING 3-5 

3.7 REVIEW OF NON-FACILITY SOURCES FOR CUMULATIVE INVENTORY 3-6 

4.0 MODELING RESULTS 

4.1 CONCLUSIONS 

5.0 REFERENCES 

ii 

4-1 

4-1 
LIST OF TABLES 

Table 2-1 Cole to Creek Statiort Unit No. 1 -Stack Parameters 

Table 3-1 

Table 3-2 

Table 3-3 

Table 3-4 

Table 4-1 

Characteristics of the Victoria Regional Airport Meteorological Data 

Summary of Coleto Creek Power Statio11 GEP Aualysis 

Compariso11 of S02 Emissious 11ear Coleto Creek and Monitor 

Seasonal Diurual S02 Couceutratious at Corpus Christi Monitor (pglm3) 

1-hour S02 Modeling Results for Coleto Creek Power Station 

LIST OF FIGURES 

Figure 1-1 

Figure 2-1 

Figure 2-2 

Figure 3-1 

Figure 3-2 

Figure 3-3 

Figure 3-4 

Figure 3-5 

Figure 3-6 

Figure 4-1 

Coleto Creek Power Station Surrormdiugs and Land Use 

Coleto Creek Power Statiou Site Piau 

Coleto Creek Power Statiou Local Topography 

Relative Location of Coleto Creek and Victoria Regional Airport 

Three-year Wind Rose (2012-2014): Victoria Regional Airport 

Near-Field Model Receptors 

Far-Field Model Receptors 

Structures Iucluded in tire Coleto Creek GEP Analysis 

Relative Location of Coleto Creek Power Station and Corpus Christi 

Monitor 

Cole to Creek Power Station 1-ltour S02 Impact Contours 

LIST OF APPENDICES 

APPENDIX A ELECTRONIC MODELING ARCHIVE 

iii 

2-4 

3-2 

3-4 

3-5 

3-6 

4-1 

1-4 

2-2 

2-3 

3-8 

3-9 

3-10 

3-11 

3-12 

3-13 

4-2 
1.0 INTRODUCTION 

ERM Consulting & Engineering, Inc. (ERM), presents this air dispersion modeling report to 

Baker Botts, L.L.P (Baker Botts) demonstrating that maximum model-predicted S02 impacts 

from GOF Suez Coleto Creek Power Station (Coleto Creek) are in attaimnent with the 1-hour 

Sulfur Dioxide (S02) National Ambient Air Quality Standard (NAAQS). This analysis was 

conducted in compliance with the 1-Hour S02 Data Requirements Rule and applicable EPA and 

TCEQ air quality modeling guidance. The results of this analysis confirm that the ambient air 

quality in Goliad County in the vicinity of Coleto Creek, currently undesignated for the 1-hour 

S02 NAAQS, is within the standard and should be identified as "attainment" in the next cycle 

of designations. 

This modeling report describes the methodology that was used to evaluate potential impacts of 

S02 emissions from Coleto Creek on ambient air quality. Copies of the modeling files are 

provided in Appendix A, the Electronic Modeling Arch ive. 

1.1 Project Overview 

TCEQ has recommended that EPA designate Goliad County as unclassifiablef attainment for 

the 1-hr S02 NAAQS based on existing ambient air monitoring data. On March 20,2015, EPA 

notified TCEQ that EPA would make an attainment determination for Goliad County on July 2, 

2016, based on updated recommendations and supporting information submitted to EPA by 

September 16, 2015. Unlike previous NAAQS attainment demonstrations, which have been 

based on existing ambient air monitoring data, EPA has proposed to make 1-hour S02 NAAQS 

attainment determinations using ambient air monitoring data and/ or air dispersion modeling. 

In situations where air modeling is used to make this de termination, the approach described in 

EPA's draft "Modeling Technical Assistance Document" (TA0) 1, which sets forth a significantly 

different tedtnical approach compared to conventional regulatory modeling prescribed by 40 

CFR Part 51, Appendix W (EPA's Guideliue 011 Air Quality Models) could be used. This approach 

would also meet the requirements of EPA's 1-Hour S02 Data Requirements Rule (ORR). 

EP J\ distinguishes the approaches described in the S02 Modeling TAD to" reflect a view that 

designations are intended to address current actua l air quality (i.e., modeling simulates a 

monitor), and thus are unlike attainment planning modeling, which must provide assurances 

that attainment will occur." EPA's proposed approach would utilize several distinctive 

technical approaches, including but not limited to the following: 

• Simulating actual emissions and exhaust conditions (e.g., temperature and flowrate) on an 

hourly basis reflecting actual operations for a specified historical time period; 

• Representing actual stack heights, irrespective of the GEP regulations; 

• Limiting modeled ambient air receptors to locations where monitoring could actually take 

place by excluding waterways, roadways, railways, restricted access property, and other 

1 http./ I l'p<l .t•ov I oagpsOOl/sulfurdioxidc l pdfs/S02Mod elingT AD. pdf 

ERM 1-1 COLETO CREEK/ 03116%- SEPTEMBER 2015 
locations that would conventionally be considered "ambient air" for regulatory and 

permitting purposes; and 

• Simulating a three-year period of meteorological and background monitoring data, 

concurrent with the actual operating conditions and emissions, to meet EPA's objective that 

"modeling simulates monitoring" in this context. 

Some of the above methodologies are specifically discussed in the Data Requirements Rule, 

while the less commonly used modeling approaches such as plume depletion are not. 

ERM performed a cumulative modeling ana lysis evaluating the impacts on ambient a ir quality 

from S02 emissions at Coleto Creek. In addition, although the approach for considering 

cumulative ambient impacts with other major sources in the region is not specifically covered in 

the rule, ERM considered all other major sources of S02 within 50 kilometers for inclusion in the 

modeling. 

As discussed in this report, ERM's approach to the modeling analysis used those refinements 

directly addressed in the rule, i.e. the use of actual hourly emissions, actual stack heights, and 

seasonal diurnal ambient background concentrations. 

As shown in this modeling report, model-predicted S02impacts from Coleto Creek emission 

sources, w hen combined with ambient air concentrations taken from a nearby representative 

monitor, a.re 111J.lg/m3 (42.4 ppb), well below the 1-hour SOz NAAQS of 196.5 J.lg/m3 (75 ppb). 

The analyses show that there is no significant impact to attainment of the 2010 SOz NAAQS 

in Goliad County, or in any other county, from Coleto Creek. The analyses also show that 

compliance of the SOz standard in Goliad County is not significantly impacted by any other 

S02 emission source. 

This first section of this report describes the modeling methodology that was followed. Section 2 

provides a description of the facility and tl1e emissions included in tl1e modeling. Model 

selection and the methodology used in the modeling are described in Section 3. The modeling 

results are presented in Section 4. References a rc provided in Section 5. 

1.2 Overview of Metl10dologt} 

ERM's assessments were conducted in a manner consistent with United States Environmental 

Protection Agency (EPA) and Texas Commission on Environmental Quality (TCEQ) air quality 

regulations and modeling guidelines, including the following EPA documents: 

• Guideline 011 Air Qunlihj Models - 40 CFR Part 51, Appendix W, Revised November 9, 2005. 

• AERMOD flllplelllel/tntioll Guide, Revised March 19, 2009; 

• "S02 NAAQS Designations Modeling Technica l Assistance Document (Draft)," December 

2013; 

• "S02 NAAQS Designations Monitoring Technical Assistance Document (Draft)," December 

2013; 

ERM 1-2 COLI O CREEK / 0311 696 - SEPTEMBER 2015 
• "Data Requirements Rule for the 1-Hour Sulfur Dioxide (S0 2) Primary National Ambient 

Air Quality Standa rd (NAAQS)," Pre-publication Final rule, August 11, 2015); and 

• "Guidance fo r 1-hour S0 2 Nonattainment Area SIP Submissions," April 23, 2014. 

As well as: 

• "Air Qua lity Modeling Guidelines, APDG 6232", TCEQ April, 2015. 

The steps that were undertaken by ERM to cond uct the air d ispersion modeling analyses are 

summarized below: 

• Compiled information on the parame ters and characteristics for the main boiler stack 

emissions a t Cole to Creek; 

• Developed a comprehensive receptor grid to capture the maximum off-site impacts from 

Coleta Creek sources using AERMAP (v.11103); 

• Reviewed regiona l ambient background monitors to determine the most appropriate 

ambient background concentration da ta fo r S02 to represent sources not explicitly included 

in the modeling runs; 

• Developed 3 years (2012-2014) of meteorological data using surface observations from 

Victoria Regiona l Airport in Victoria, TX with upper air data from Corpus Christi 

International /\irport in Corpus Christi, TX using the most recent ve rsion (v.15181) of 

AERMET, the me teorological data processor for AERMOD, and its two pre processors: 

AERSURFACE (v.13016) and AERMINUTE (v.14237); 

• Reviewed a ll major sources of ~ within 50 kilometers of Coleta Creek for possible 

inclusion in the cumulative modeling a na lysis using the 2011 National Emission Inventory 

Database2, based on guidance included in the S0 2 Modeling TAD. 

• Conducted an air dispersion modeling ana lysis using the most recent version of EPA's 

regulatory dispersion model, AERMOD (v.15181) and 3 years (2012-2014) of actual 

emissions da ta from Coleta Creek, consistent with the methodology described in the S02 

Data Requirements Rule and S02 Modeling TAD. 

• Summarized the results and compared them with the 1-hour S02 NAAQS to de termine a 

recommended a tta inment designation for the vicinjty of Coleta Creek. 

2 http:/ / w ww.cpa.gov I tlnch il'l / nct/2011 invcntorv.html 

ERM 1-3 COLETO CREEK / 0311696 - SEPTEMBER 2015 
Figure 1-1 

ERM 

Coleto Creek Power Station Surrouudiugs and Laud Use 

GOF Suez 

Coleto Creek Station 

Fannin. TX 

\v 

ERM 

1-4 COLETOCREEK /03116% -SEPTEMBER 2015 
2.0 FACILITY DESCRIPTION AND REGULATORY SETTING 

2.1 Facilittj Location 

The Coleta Creek Power Station is located in the town of Fannin, Texas. The station is located 

about 2 miles northeast of downtown Fannin. The site is accessed by FM 2987 off US. Route 59. 

The station is approximately 90 miles southeast of San Antonio, Texas and 65 miles north of 

Corpus Christi, Texas. Approximate site coordinates are 28.713° North Latitude, 97.214° West 

Longitude. The Universal Transverse Mercator (''UTM") coordinates of the facility a re 674,410 

Easting and 3,177,477 Northing (using North American Datum of 1983- NAD83) in UTM Zone 

14. The base elevation of the facility is 106' (32.309m) above sea level. A full scale site plan of 

Coleta Creek is shown in Figure 2.1, and Figure 2.2 shows the site location marked on a United 

States Geological Survey ("USGS") 7.5-minute topographic map. 

2.2 S02 Attainment Status 

In July 2013, EPA issued a rule designating 29 counties or partial counties as non-attainment for 

1-hour S02. However, the vast majority of the country was not designated by EPA at that time. 

None of the counties surrounding Coleta Creek, including Goliad, the county in which Coleta 

Creek is located, have been designated as attainment or non-attainment for the 1-hour S02 

NAAQS. 

ERM 2-1 COU:"TO CREEK/ 0311696- SEPTEMBER 2015 
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Figure 2-2 Coleto Creek Power Station Local Topography 

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ERM 

Logond 

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Local Topography Around 

Coleto Creek Station 

GOF Suez 

Coleto Creek Stahon 

FaMin. TX 

~ ERM 

COLF.TO CRE£K / 0311696 - SEPTEMBER 2015 
2.3 Source Parameters aud Emission Rates 

For this 1-hour S02 NAAQS modeling demonstration, the only significant source of S02 

emissions at the facility was Unit No.1. Per the 1-hour S02 Data Requirements Rule and S02 

Modeling TAD, the most recent 3 years of actual emissions data, along with the actual stack 

height of Unit No.1, were used in the modeling. The following provides a description of all 

Coleta Creek S02 emission sources. Table 2-1 summarizes the characteristics of Coleta Creek 

Unit #1. The actual emissions data used in the modeling are described below: 

• Unit No. 1(Source 10: CC_01). This unit is a coal fired utility boiler that produces steam for 

the generation of electricity. For this unit, three years (2012-2014) of actual hourly emissions, 

stack temperature, and exhaust flow rate data were input into the model. These data were 

provided by GDF Suez based on CEMS data collected at the site. As per the 1-hour S02 Data 

Requirements Rule, the actual height of the stack was represented in the model. 

Other sources a t the site include emergency engines and fire pumps. These sources are used 

exclusively in emergency situations except for approximately one hourjweek testing and were 

excluded from the modeling. The exclusion of the emergency engines from the 1-hour S02 

modeling is based on US EPA guidance provided in the March 1, 2011 memorandum, 

"Additional Clarification Regarding Application of Appendix W Modeling Guidance for the 1-

hour N02 National Ambient Air Quality Standard" for intermittent sources such as emergency 

generators. In the memo, US EPA states the following: 

"Given the implications of the probabilistic fonn of the 1-hour N02 NAA QS discussed above, we are 

concemed that assumi11g continuous operation of iutermitte11t emissions would effectively impose an 

additional level of stringenC1J beyond that level intended by the standard itself As a result, we feel it 

would be inappropriate to impleme11t the 1-lwur N02 standard in such a manner and recommend 

that compliance demonstrations for the 1-hour N02 NAAQS be based 011 emission scenarios that can 

logically be assumed to be relatively continuous or which occur frequently enough to contribute 

significantly to the annual distribution of daily maximum 1-hour concentrations." 

While the memorand um addresses the 1-hour N02 NAAQS, the form of the S02 Standard is 

nearly identical and the same reasoning is commonly applied to the b·eatment of intermittent 

sources in 1-hour S02NAAQS modeling. Therefore the engines were not included in the 

modeling demonstration. 

Table 2-1 Coleta Creek Power Statiou Uuit No. 1 - Stack Parameters 

Descriptio11 Model Stack Height Exit Exit Velocity Stack 

Source Temperature Diameter 

<ft> I (m) (F) I (K) (/f/sec) I (mfs) (ft.) I (tn) 

Unit 1 Boiler1 CC_Ol 409 1124.66 -- I -- --- I -- 20.0 1 6.1o 

1. Exit temperature and exit velocity varied on an hourly basis based on actual emissions data. 

ERM 2-4 COLETO CREEK I 0311696 · SEPTEMBER 2015 
3.0 AIR DISPERSION MODELING ANALYSIS 

ERM conducted the modeling analysis for Coleto Creek to quantify ambient impacts of S02 

relative to the 1-hour NAAQ5 following the proposed approach described in the 502 Modeling 

TAD. 

3.1 Model Selection and Application 

The latest version of U5EPA's AERMOD model (v.15181) was used for predicting ambient 

impacts for 1-hour S02. Regulatory default options were used in the analysis. Model predicted 

impacts were combined with an ambient background concentration and compared to the 1-hour 

S02 NAAQS to de termine the recommended attainment status of the area in the vicinity of the 

facili ty. 

3.2 The 1-Tiour 502 NAAQS 

This study focuses on the maximum model-predicted 1-hour 502 impacts of Coleta Creek and 

compares them to the 1-hour S02 NAAQS. The new standard came into effect in August, 2010. 

The form of the standard is the 99th percentile of the 3-year average 1-hour daily maximum 

concentration, and the standard was set to 75 ppb (196.5 ~Lg/m ). 

3.3 M eteorological Data 

Guidance for regulatory air quality modeling recommends the use of one year of on-site 

meteorological data or five years of representative off-site meteorological data. The 502 

Modeling TAD however, specifies that three years of meteorological data concurrent to the 

actual emissions data being input into the mode l be used. Since on-site data a re not available for 

the Coleta Creek site, meteorological data ava ilable from the National Weather Service (NW5) 

were used in this analysis. 

Three years (2012-2014} of surface observations from the NW5 tower at Victoria Regional 

Airport in Victoria, TX (WBAN No. 12912) and concurrent upper air data from Corpus Christi, 

TX (WBAN No. 12924) were processed with the most recent version of J\ERMET (v.15181) the 

meteorological preprocessor for AERMOD, along with the two pre-processors to AERMET: 

AERSURFACE (v.13016) and AERMINUTE (v.14237). AERMET was applied to create the two 

meteorological data files required for input to AERMOD. 

AERMET requires specification of site characteristics including surface roughness (zo), albedo 

(r), and Bowen ratio (Bo). These parameters were developed according to the guidance 

provided by EPA in the AERMOD Implementation Guide (AIG) (EPA, 2008a) using 

AERSURFACE. The area within 1 km of the facility was broken into 12 sectors of 30 degrees 

each to analyze the surface characteristics in each 30 degree arc a round the main stack. 

AERMET uses the surface characteristics in the sector from which the wind approaches the 

stack as part of the meteorological data processing for each hour. 

ERM 3-1 COl RTO CREEK/ 0311696 ·SEPTEMBER 2015 
In AERSURFACE, the various land cover categories are linked to a set of seasonal surface 

characteristics. As s uch, AERSURFACE requires specification of the seasonal category for each 

month of the year. The following five seasona l categories are offered by AERSURFACE: 

1. Midsummer with lush vegetation; 

2. Autumn with unharvested cropland; 

3. Late autumn after frost and harvest, or winter with no snow; 

4. Winter with continuous snow on ground; and 

5. Transitional spring with partial green coverage or short annuals. 

The AERSURFACE run was performed using the monthly temporal resolution option. The 

seasons were broken down as follows: 

• January, December: Winter with no snow. 

• February, March, April: Transitional spring. 

• May, June, July, August, September: Midsummer 

• October, November: Autumn 

The precipitation was assigned to each month in each of the 3 years based on an analysis of 30 

years of precipitation at Victoria Regional Airport: If a given month had monthly rainfall totals 

lower than the 30th percentile of all years, the month was assigned" dry" for the purpose of 

Bowen Ratio calculations. If it had monthly rainfall above the 70th percentile, is was assigned 

"wet" . Otherwise, the month was assigned" Average". 

Additionally, 1-minute ASOS wind data, collected at the Victoria Regional Airport 

meteorologica l tower, were processed using the AERMINUTE pre-processor for AERMET. The 

data characteristics of Victoria Airport are shown in Table 3-1. Figure 3-1 shows the relative 

location of Victoria Airport and Coleto Creek, and Figure 3-2 shows the 3-year wind rose for 

Victoria Airport. 

Table 3-1 Characteristics of the Victoria Regional Airport Meteorological Data 

Dista11ce from Coleto Creek Statio11 20.1 miles 

Average Wi11d Speed 4.37m/s 

Perce11t Calm Hours 2.29% 

Data Complete11ess 98.75% 

All files associa ted with the meteorological data processing are incl uded in Appendix A: The 

Electronic Modeling Archjve. 

ER!vl 3-2 COLETO CR!iEK / 0311696 ·SEPTEMBER 2015 
3.4 Receptor Grid 

A comprehensive Cartesian receptor grid extending out to approximately 20 kilomete rs (km) 

from Coleto Creek was used in the AERMOD modeling ana lysis to assess maximum groundlevell-hour S02 concentrations. The S02 Mode ling TAD sta tes that the receptor grid must be 

s ufficient to determine ambient air quality in the vicinity of the source being studied. The 20-

kilometer receptor grid is more than s ufficient to resolve the maximum 1-hour S0 2 impacts, and 

it clearly illustrates decreasing S0 2 concentration gradients in relation to the plant in a ll 

directions out to the edge of the grid 

The Cartesian receptor grid consisted of the following receptor spacing: 

• 50-meter spacing along the facility fence line; 

• 100-meter spacing extending from the fence line to 3 kilometers; 

• 200-meter spacing extending from 3 to 5 kilometers; 

• 500-meter spacing extending from 5 to 10 kilometers; and 

• 1,000-me ter spacing extend ing from 10 to 20 kilometers. 

The above receptor da ta was used without modification in the modeling. Pe r the S0 2 Modeling 

TAD, a number of receptors located over the Cole to Creek Reservoir could have been excluded 

from the modeling doma in because ambient monitors could not reasonably be placed at these 

locations, but these receptors were retained in this analysis as a measure of conservatism. 

Terrain elevations from National Eleva tion Data ("NED" ) from USGS were processed using the 

most recent version of AERMAP (v.11103) to develop the receptor terrain eleva tions required by 

AERMOD. NED data fil es contain profiles of terrain e leva tions, which in conjunction with 

receptor locations are used to generate receptor height scales. The height scale is the terrain 

e levation in the vicinity of a receptor that has the greatest influence on dispersion a t that 

loca tion and is used for model computa tions in complex terrain areas. The near-field (within 5 

kilome ters) and far-field (full 20 km grid) receptor grids are shown in Figures 3-3 and 3-4, 

respectively. 

3.5 Good Engineering Practice Stack Heiglzt Aunlysis 

Good engineering practice ("GEP") stack height is defined as the stack height necessary to 

ensure that emissions from the stack do not result in excessive concentrations of any air 

pollu tant as a result of atmospheric downwash, wakes, or eddy effects created by the source, 

nearby structures, or terrain features. 

A GEP stack height ana lysis was performed for the Unit 1 stack using the Building Profile Input 

Program (BPIP) in accordance with USEPA's guidelines (USEPA 1985). Per the guidelines, the 

physical GEP height, (HcEP), is determined from the dimensions of all buildings which are 

within the region of influence using the following equations, de pending on the construction 

data of the stack: 

ERiv1 3-3 COLETO CREEK / 03116% ·SEPTEMBER 2015 
(1) For stacks in existence on Janua ry 12, 1979 and for which the owner or operator had 

obtained all applicable permits or approva ls required, 

I IcFr = 2.5H, 

provided the owner or operator produces evidence that this equation was actually relied 

on in establishing an emission limitation; 

(2) For all other stacks: 

Hem' = H + 1.5L 

where: 

I I = height of the structure within SL of the stack which maximizes HcEr; and 

L = lesser dimension (height or projected w idth) of the structure. 

For a squat structure, i.e., height less than projected width, the formula reduces to: 

HcEr = 2.5H 

ln the absence of influencing structures, a " default" GEP stack height is creditable up to 65 

meters (213 feet). 

A summary of the GEP stack height analyses is presented in Table 3-2. As described in the S02 

Modeling TAD, when modeling actual emissions in order to determine the attainment status of 

the fa cility when compared to the 1-hour S02 NAAQS, the full height of all stacks is allowed in 

the modeling regardless of their GEP Formula Heights. Therefore, the stack was modeled with 

its actua l stack height in the analysis. The heights and locations of all structures included in the 

GEP analysis, as well as the main stack, are shown in Figure 3-5. 

Table 3-2 Stmunary of Cole to Creek Station GEP Analysis 

Emissiou Stack Coutrolliug Btlildi,gs I Bttildi"g Projected GEP Fonnllla Height Sottru (m) Structtlres Heigltt (m) Width (m) Height (m) 

CC_Ol 124.66 Unit 1 Generator Bldg. 85.04 68.73 188.13 

ERM 3-4 COI.ETO CREEK / 0311696-SEPTEMBER 2015 
3.6 Ambie11t SOz Backgrou11d Data for Cumulative Modeliug 

It was assumed after initial modeling that model-predicted impacts from Coleta Creek would 

exceed the 1-hour S~ Significant Impact Level (SIL) of 7.9 J.lg/m3. As a result, ambient 

background data from the closest, most representative S02 monitor to Coleta Creek was 

downloaded from the EPA AirData ambient monitoring website3. A review of the data showed 

that the most representative monitor for use in the modeling is the Tuloso Corpus Christi 

monitor located at 9860 La Branch in Corpus Christi (Monitor 10# 48-355-0026). This monitor is 

somewhat conservative for use in this analysis, being sited much closer to industrial activity 

than Coleta Creek is to other sources of S02. To confirm that the monitor did not understate the 

background in the vicinity of Cole ta Creek, the EPA 2011 National Emissions Inventory was 

reviewed for 502 emissions near the facility and the monitor. Table 3-3 shows the results. The 

table shows that the monitor had over 300 tons of S02 emissions within 10 km and nearly 1000 

tons within 25 km, while Coleta Creek had only 2.5 tons ofS02emissions within 25 kilometers. 

Despite the conservatism of the monitor, it was used for this modeling analysis. 

Table 3-3 Comparison of S0 2 Emissions near Cole to Creek aud Monitor 

Site SOz tpy (NEI 2011) witlri11: 

0-10 km 10-25 km 25-50km 

Coleto Creek 0.0 2.5 482.1 

Corpus Christi Monitor 322.7 623.6 60.7 

EPA guidance a llows simulation of background values that vary by season and hour of day that 

could simula te a lower value than the 99th percentile. The modeling was performed with a set 

of seasonal diurnal values developed using the metl1odology described in the USEPA March 

1st, 2011 Clarification Memorandum for 1-hour N02 Mode ling. Though tlUs memorandum 

primarily addresses N02 modeling, page 20 describes the process for developing seasonal 

diurnal background va lues for S02 as weU. 

The loca tion of the selected ambient monitor relative to Coleto Creek is shown in Figure 3-6. 

The seasonal diurnal values used are shown in Table 3-4. 

3 https: // ofmext.epd.gov /AQDt\IRS/agdmrs.html 

ERM 3-5 COLETO CREEK I 0311696 -SEPTEMBER 2015 
Table 3-4 Seasoual Diurual 502 Couceutratious at Corpus Christi Mouitor (pfY'm3) 

Hortr1 Wiuter Spri11g Summer Fall 

1 3.53 1.46 1.40 3.42 

2 3.37 1.52 1.49 4.14 

3 2.92 1.57 1.34 2.91 

<I 3.95 1.81 1.48 3.23 

5 3.26 1.69 1.26 4.45 

6 3.39 1.87 1.39 3.33 

7 3.42 1.52 1.63 3.52 

8 3.81 1.99 '1.77 3.68 

9 3.65 1.99 1.43 3.43 

10 4.12 2.32 1.55 2.98 

11 4.96 2.82 2.02 4.09 

12 5.57 2.80 2.71 4.85 

13 5.87 3.07 2.59 4.42 

14 4.74 3.00 3.25 4.10 

15 4.96 4.87 3.35 4.65 

16 5.18 4.33 -1.58 5.().1 

17 6.59 3.92 3.18 3.89 

18 4.71 3.72 2.9-1 4.19 

19 4.18 219 2.-11 4.61 

20 8.05 2.17 3.2-1 5.58 

21 5.34 2.06 1.84 3.64 

22 4.80 3.26 1.61 3.38 

23 4.63 1.72 1.64 2.92 

24 3.81 1.94 1.63 3.22 

1. Hours in AERMOD are defined as hour-ending. 

3.7 Review of Non-Facility Sources fo r Cumulative Iuveuto1·y 

Section 4.1 of the S02 Modeling TAD discusses the criteria for the addition of major SOz sources 

in the region fo r cumula tive modeling purposes when determining the recommended 

attainment status of the area surrounding a facility as described in the 1-hour S02 Data 

Requireme nts Rule. The TAD describes sources that should be included in the modeling as 

those expected to have an impact on the air quality in the vicinity of the source being studied, in 

this case Cole ta Creek. Additionally, the TAD states that except in cases where numerous 

smaller sources are close together in the study area, conside ration of sources to include should 

begin at sources with emissions in excess of the threshold selected in the Data Requirements 

Rule (2000 tpy). 

The 2011 EPA National Emissions Inventories (NEI) was reviewed to determine candidate 

major sources. For the p urpose of this study, a ll major sources of S02 within 50 kilometers of 

Coleta Creek that had at least 2000 tons of S02 emissions were considered for inclusion in the 

modeling. No facilities within 50 kilometers were found to have emitted at least 2000 tons of 

ERM 3-6 COLETO CRE.EK / 0311696 · SEPTEMBER 2015 
S02 in 2011. In fact, the only source with greater than 100 tons of S02 within 50 miles of Coleto 

Creek was Seadrift Coke LP, located 46.6 km away in Seadrift, TX, with 410 tons. Seadrift Coke 

was not explicitly included in the modeling for the following reasons: 

• Seadrift Coke had emissions far lower than that of the 502 Data Requ irements Rule 

threshold. 

• The March ~1 , 2011 EPA clarification memorandum for modeling N02 and 5024 states 

that" .. Even accounting for some terrain influences on the location and gradients of 

maximum 1-hour concentrations, these considerations suggest that the emphasis on 

determining which nearby sources to include in the modeling analysis should focus on 

the area withjn about 10 kilometers of the project location in most cases ... " Seadrift Coke 

is more than 4 times that distance from Coleto Creek. 

• The relative locations of the facilities: Wind blowing from Coleto Creek to Seadrift Coke 

is on a bearing of 118 degrees, while wind blowing from Seadrift Coke to Coleto would 

be on a bearing of 298 degrees. A review of the 3 years of wind data {2012-2014} used in 

the modeling shows that the wind blows between the two facilities only about 7 percent 

of the time, and of that 7 percent only a total of 6 hours out of the 3 years of data had 

sufficient wind speed (12.9 m/ s} to carry a plume from one facility to the other in one 

hour. 

• The concentration gradient from Coleto Creek impacts drops sharply to the east of the 

facility (See Figure 4-1), such that the impacts from Coleto Creek would not be expected 

to interact with those from Seadrift Coke. 

• The Corpus Christi ambient monitor was shown to be conservative in Section 3.6 

Therefore, no othe r facilities were explicitly included in the modeling, but instead a 

conservative ambient concentration from the Corpus Christi monitor was added to the impacts 

from Coleto Creek to represent other sources in the area. 

• http:// www.epa.gov / scram001/ guidance/ clarification/ Add itionaJ_ Clari!ications_A ppcndixW _Hourly-N02-

NAAQS_FlNAL_03-01-20ll.pdf 

ERM 3-7 COLETO CR!lEK / 0311696 • SEPTE..v!BER 2015 
Figure 3-1 

sf~~~ AntoniO 

ERM 

Relative Locatiort of Cole to Creek aud Victoria Regioual Airport 

l egend * Coleto Creek Station 

A Meteorological Tower 

3-8 

Relative Location of 

Coleto Creek Station and 

Meteorological Site 

GDF Suez. 

Coleto Creek Station 

Fannin, TX 

\j 

ERM 

COLETO CREEK/ 031 1696-SEPTEMBER 2015 
Figure 3-2 Three-year Wind Rose (2012-2014): Victoria Regioual Airport 

ll>O~P\.OT 

3-Year Wind Rose: VIctoria Regional Airport 

2012-2014 

l-

~>IIS 

Resullanl V ec101 

11 5dog 32% 

NORTH 

' 

; soUTH 

DATA PERIOO 

Stan Date: 1 '112012- 00:00 

End Date: 1213112014 • 23:00 

CO!.'PANY tiA>.IE 

ERM 

UOOEL£R 

R. Hamel 

·-- ------------------~------- CALMWWOS JOT AI. COUIIT 

2.29% 25976 hrs. 

AVG WINO SPEED Q.\TE 

4.37 m!S 8/10/2015 

WRPtOT Votw L.._, Enwonmoroat Sol!wolt 

ERM 3-9 

DSP'-'Y 

Wind Speed 

Dlrecllon (blowing from) 

J 

EAST 

WINO SPEED 

fin'S ) 

• ,. II 10 

• 8.80·11 10 

• 5.70 8.80 

• 360-570 

D 210 -J.6o 

D ono-210 

Calms 2 29'• 

~ ERM PROJECT NO 

COLEW CREEK / 031 16%- SEPTEMBER 2015 
Figure 3-3 

EHM 

2015 

Near-Field Model Receptors 

Legend 

o Risk Receptors 

* Unit 

3-10 

Near Field (5 km) 

Receptors used in 

Coleto Creek 

GDF Suez 

Cole to Creek Station 

Fannin, TX 

\_, 

ERM 

COLETO CREEK I 031 1696 • S~IBER 
Figure 3-4 

ERM 

2015 

Far-Field Model Receptors 

3-11 

GDF Suez 

Coleto Creek Station 

Fannin. TX 

\v 

ERM 

CQLJ,-ro CREEK / 0311696 -SEPTEMBER 
Figure 3-5 Structures I11cluded i11 tlte Co leto Creek GEP Analysis 

PROJECT TillE: 

Buildings Included In the Coleto Creek GEP Analysis 

0 

on 

:::: "' - .., 

0 

on 

v ::::-

;;; 

COIAMHITS. 

ERM 

2015 

H

Magt

chi,.Sho~ . • 28' D 

Fabrbtlon ___...?. 

Building ~ HgL • 106' 

674

1

350 

SOURCES 

1 

Unit I Stocl< Hg ~; 409' 

11ECEPTORS: 

7644 

/ 

6741

400 

UTM East !m) 

COW'AHYW.ME. 

ERM 

MOOELER 

R. Hamel 

SCALE· 

0 

DATE 

8/1112015 

3-12 

1:1.500 

0.05 km 

'"'-

Ge11<111101 Bldg. 

Tltr I HgL • 100' 

Tltr 2 Hg1. • 202' Tltr 3 Hgt • 263' 

ERM 

~ 

PROJECT NO 

COLt"TO CREEK I 0311696 • SEPTBIBER 
Figure 3-6 

ERM 

2015 

Relative Locatiotr of Coleta Creek Station and Corpus Christi Monitor 

Coleto Creek Station 

¢ 502 Monttor 

3-13 

Relative Location of 

Coleto Creek Station and 

Corpus Christi S<n Monitor 

\._, GOF Suez 

Cole to Creek Station 

Fannm. TX ERM 

COLCIO CREEK I 0311696 • SF.PTEMBER 
4.0 MODELING RESULTS 

The modeling results are shown in Table 4-1 below. The modeled design value 

represents the modeled 3-year average of the 99th percentile, maximum daily 1-hour 

average impact for Coleto Creek, which is then added to the ambient background 

concentra tion and the total impact compared to the NAAQS to demonstrate attainment. 

Contours of the predicted impacts, as well as the location of the maximum predicted 

impact of 111.0 JJ.g/ m3, are shown in Figure 4-1. The table shows that model predicted 

impacts from Coleto Creek, when modeled using the most recent three years of actual 

emissions data and added to a representative ambient background concentration, are 

below the level of the 1-hour S02 NAAQS. 

Table 4-1 1-hour S02 Modeliug Results for Coleta Creek Statiou 

Coleta Creek 

Coleta Creek 

1-llr. S0 2 Below Source a11d 

Only Background NAAQS NAAQS? 

Coleto Creek Station 106.8 11g/m3 111.0 11g/m3 196.5 11g/ m3 

Yes 

(40.8 ppb) (42.4 ppb) (75 ppb) 

4.1 Conclusions 

The air dispersion modeling performed as described in this report confirms that the SOz 

emissions from Coleto Creek Power Station, when added to conservative ambient 

background concentration, result in maximum predicted impacts below the 1-hour 

S02 National Ambient Air Quality Standard. Therefore, an attainment designation for 

Goliad County and the surrounding area is recommended. 

ERM 4-1 COI.IITO CREEK/ 0311696- SEPTEMBER 2015 
Figure 4-1 

E.RM 

Coleta Creek Statiou l-lwur S02 Impact Contours 

+ Max. Predicted Impact 

[:::::J Fence Line 

Impact Contours 

4-2 

AERMOD Predicted 1-hour S02 

Impact Contours 

GOF Suez 

Coleto Crll1lk Station 

Fannin. TX "-' ERM 

COLETO CREEK I 0311696 ·SEPTEMBER 2015 
5.0 REFERENCES 

U.S. Environmental Protection Agency. (USEPA 2005) Guideline on Air Quality Models 

(GAQM, 40CFR Appendix W), November, 2005 

U.S. Environmental Protection Agency. (USEPJ\ 2009) AERMOD Implementation Guide, 

AERMOD Implementation Workgroup. March 19, 2009. 

U.S. Environmenta l Protection Agency. (USEPA 2011) USEPA memo entitled" Additional 

Clarification Rega rding Application of Appendix W Modeling Guidance for the 1-hour N02 

National Ambient Air Quality Standard", USEPA, Office of Air Quality Planning and 

Standards, Rale igh, NC. March 1, 2011. 

U.S. Environmental Protection Agency. (USEPA 2014) "S02 NAAQS Designations Modeling 

Technical Assistance Document (Draft)," December 2013; 

U.S. Environmental Protection Agency. (USEPA 2014) "S~ NAAQS Designations Monitoring 

Technical Assistan ce Document (Draft)," December 2013; 

U.S. Environmental Protection Agency. (USEPA 2014) "Data Requirements Rule for the 1-Hour 

Sulfur Dioxide (S02) Primary National Ambient Air Quality Standard (NAAQS)," Final rule, 

August 11, 2015; 

U.S. Environmental Protection Agency. (USEPA 2014) "Guidance for 1-hour S02 

Nonattainment Area SIP Submissions," April 23, 2014; and 

Texas Commission on Environmental Quality (fCEQ 2015) "Air Quality Modeling Guidelines, 

APDG 6232", April, 2015. 
Appendix A 

Electronic Modeling Archive