Ameren Labadie Plant 

Labadie, Missouri 

Evaluation of Compliance with the 1-hour NAAQS for S02 

September 3, 2015 

Conducted by: 

Steven Klajka, P.E., BCEE 

Wingra Engineering, S.C. 

Madison, Wisconsin 
Evaluation of Compliance with the !-hour NAAQSfor S02 

September 3, 2015 

Page 2 

1. Introduction 

Wingra Engineering, S.C. was hired by Sierra Club to conduct an air modeling impact analysis to 

help the U.S. Environmental Protection Agency (USEPA) and state and local air agencies identify 

facilities that are likely causing exceedances of the 1-hour sulfur dioxide (S02) national ambient air 

quality standard (NAAQS). This document describes the results and procedures for an evaluation 

conducted for the Ameren Labadie Plant located in Labadie, Missouri. 

To ensure the modeling analysis reflected the cumulative concentration of S02 emissions, it included 

emissions from the following additional sources of S02 emissions located within 50 kilometers of 

the Ameren Labadie Plant: 

• Purina Animal Nutrition Center- Gray Summit, Missouri 

• N.B. West Contracting Company Inc.NC- Pacific, Missouri 

The dispersion modeling analysis predicted ambient air concentrations for comparison with the 1-

hour S02 NAAQS. The modeling was performed using the most recent version of AERMOD, 

AERMET, and AERMINUTE, with data provided to Sierra Club by regulatory air agencies or 

obtained through other publicly-available sources as documented below. The analysis was 

conducted in adherence to all available USEP A guidance for evaluating source impacts on 

attainment of the 1-hour S02 NAAQS via aerial dispersion modeling, including the AERMOD 

Implementation Guide; USEP A's Applicability of Appendix W Modeling Guidance for the 1-hour 

S02 National Ambient Air Quality Standard, August 23, 2010; modeling guidance promulgated by 

US EPA in Appendix W to 40 CFR Part 51 ; USEPA's March 2011 Modeling Guidance for S02 

NAAQS Designations; 1 and USEPA's December 2013 S02 NAAQS Designations Technical 

Assistance Document? 

2. Compliance with the 1-hour S0 2 NAAQS 

2.1 1-hour S02 NAAQS 

The 1-hour S02 NAAQS takes the form of a three-year average of the 99th percentile of the annual 

distribution of daily maximum 1-hour concentrations, which cannot exceed 75 parts per billion 

(ppb).

3 Compliance with this standard was verified using USEPA's AERMOD air dispersion model, 

which produces air concentrations in units of Jlg/m3

. The 1-hour S02 NAAQS of 75 ppb equals 

196.2 Jlg/m

3

, and this is the value used for determining whether modeled impacts exceed the 

1 http://www.epa.gov/scramOO l/so2 _ modeling__guidance.btm 2 http://www .epa.gov/oaqpsOO l/sulfurdioltide/pdfs/S02ModelingT AD.pdf 3 USEPA, Applicability of Appendix W Modeling Guidance for the !-hour S02 National Ambient Air Quality Standard, 

August 23,2010. 
Evaluation of Compliance with the /-hour NAAQSfor SOz 

September 3, 2015 

Page3 

NAAQS.4 The 991

h percentile of the annual distribution of daily maximum 1-hour concentrations 

corresponds to the fourth-highest value at each receptor for a given year. 

2.2 Modeling Results 

Model results for all sources included in the S02 analysis are summarized in Table 1. Results are 

provided for Labadie alone and for all sources combined. 

Modeling results for Ameren Labadie Plant and the other two facilities are summarized in Table 1. It 

was determined that based on either current allowable emissions or measured actual emissions, the 

Ameren Labadie Plant is estimated to create downwind S02 concentrations which exceed the 1-hour 

NAAQS. 

More specifically, the modeling results presented in Table l, show exceedances of the NAAQS by 

the plant's allowable and actual emissions. "Allowable" is the peak emission rate from each unit as 

approved by the current air quality operation permit for the facility. "Actual" arc the measured 

emissions for each hour between January 1, 2012 and December 31,2014 as taken from USEPAAir 

Markets Program Data.5 

Air quality impacts in Missouri are based on a background concentration of23.5 gl . This is the 

2011-13 design value for Monroe County, Missouri - the lowest measured background 

concentration in the state. This is the most recently available design value. See Section 5 for further 

discussion of the background concentrations used for this analysis. 

Table 1 - S 0 2 Modeling Results for Ameren Labadie Plant Modeling Analysis 

99th Percentile !-hour Daily Maximum gl ) Complies with 

Emission Rates Facility 

Impact Background Total NAAQS NAAQS? 

Allowable Labadie 2,559.7 23.5 2,583.2 196.2 No 

Acrual Labadie 212.2 23.5 235.7 196.2 No 

Actual All 212.2 23.5 235.7 196.2 No 

4 The ppb to ~glm3 conversion is round in the source code to AERMOD v. 14134, subroutine Modules. The conversion 

calculation is 75/0.3823 = 196.2 glm • 

s http://ampd.epa.gov/ampd/ 
Evaluation of Comp liance with the /-hour NAAQSfor S0 1 

September 3, 2015 

Page4 

The emissions used for the modeling analysis are summarized in Table 2. 

Table 2 - Modeled S01 Emissions 6 

Stack Unit 

lD lD 

SOl Bl 

S02 B2 

S03 B3 

S04 B4 

Stack Total All Units 

Allowable Emissions 

1-hour Average 

(lbslhr) 

29,678.4 

29,678.4 

29,3 13.6 

29,313.6 

117,984.0 

Based on the modeling results, Table 3 provides the emission reductions from current allowable 

rates necessary to achieve compliance with the 1-hour NAAQS. This assumes a one-hour averaging 

period for the emission rate and that the emission rate is binding at all times. However, given the 

conservative aspects of this modeling protocol, it is extremely likely that this limit is too high to 

protect the NAAQS. For example, startup or shutdown periods were not evaluated. During these 

periods, decreased gas velocities and temperatures may lead to greater ambient impacts at ground 

level. Further, the hypothetical emission limitation in Table 3 would allow Ameren Labadie Plant to 

consume the entire NAAQS, leaving little to no room for any other source ofS02 in the area. No 

margin of safety has been included in the hypothetical emission limitation. 

Table 3 - Required Emission Reductions from Ameren Labadie Plant for Compliance with the 1-

hour NAAQS for S01 

Acceptable Impact Required Required Required 

(NAAQS - Background) Total Facility Total Facility 

99th Percentile Reduction Based on 

Total Facility 1-hour Average Emission Rate 1-hour Daill Max Allowable Emissions (lbslhr) Emission Rate 

(Jlg/m ) (%) (lbs/mmbtu) 

172.7 93% 7,960.2 0.43 

Predicted exceedances of the !-hour NAAQS for S0 2 based on allowable emissions extend 

throughout the region to a maximum distance of 50 kilometers. 

Figure 1 shows the extent ofNAAQS violations based on allowable emissions from the A.meren 

Labadie Plant. 

Figure 2 shows the extent of NAAQS violations based on actual hourly emissions from all sources. 

6 Allowable emissions are based on the 4.8 lbs/mmbtu limitation in Title V Pennit to Operate No. OP20ll-020 issued by 
Evaluation of Compliance with the 1-hour NAAQSf or S01 

September 3, 2015 

Page 5 

2.3 Conservative Modeling Assumptions 

A dispersion modeling analysis requires the selection of numerous parameters which affect the 

predicted concentrations. For the enclosed analysis, several parameters were selected which underpredict facility impacts. 

Assumptions used in this modeling analysis which likely under-estimate concentrations include the 

following: 

• Allowable emissions are based on a limitation with an averaging period which is greater than 

the 1-bour average used for the S02 air quality standard. Emissions and impacts during any 

1-hour period may be higher than assumed for the modeling analysis. 

• No consideration of facility operation at less than 100% load. Stack parameters such as exit 

flow rate and temperature are typically lower at less than full load, reducing pollutant 

dispersion and increasing predicted air quality impacts. 

• No consideration of building or structure downwash. These downwash effects typically 

increase predicted concentrations near the facility. 

• Except for Purina Animal Nutrition Center and N.B. West Contracting, no consideration of 

other off-site sources. These other off-site sources of S02 will increase the predicted impactS. 
Evaluation of Compliance with the 1-hour NAAQSfor S01 

September 3, 2015 

Page6 

§ 

:;: 

N 

., 

·c--'...,_ 

1-hour 802 Concentrations (ug per cubic meter) - All colored areas exceed the NAAQS. 

I 

196 400 800 1200 1600 

Figure I -Regional View of Impacts Due to Allowable Emissions from Ameren Labadie Plant 
Evaluation of Compliance with the 1-hour NAAQSfor S01 

September 3, 2015 

Page 7 

~ 

g 

~ 

0 

~ 

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0 

"' Ameren Labaclie Plant 

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:[g .:= ::? 

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Purina Animal Nutrition Center 

t:.97JOC· Ca&OOO (.8'}300 690000 G91000 

UTM East (mJ 

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, N.B. West Contracting ~ # .. ,. 't 

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1-hour average S02 concentrations (ug per cubic meter) - All colored areas exceed the NAAQS. 

' 196 225 

Figure 2 - Regional View of Impacts Due to Actual Emissions from All Sources 
Evaluation of Compliance with the 1-hour NAAQS for S02 

September 3, 2015 

Page 8 

3. Modeling Methodology 

3.1 Air Dispersion Model 

The modeling analysis used USEPA's AERMOD program, v. 14134. AERMOD, as available from 

the Support Center for Regulatory Atmospheric Modeling (SCRAM) website, was used in 

conjunction with a third-party modeling software program, AERMOD View, sold by Lakes 

Environmental Software. 

3.2 Control Options 

The AERMOD model was run with the following control options: 

• 1-hour average air concentrations 

• Regulatory defaults 

• Flagpole receptors 

To reflect a representative inhalation level, a flagpole height of 1.5 meters was used for all modeled 

receptors. This parameter was added to the receptor file when running AERMAP, as described in 

Section 4.4. 

An evaluation was conducted to determine if the modeled facility was located in a rural or urban 

setting using USEPA's methodology outlined in Section 7.2.3 of the Guideline on Air Quality 

Models.

7 For urban sources, the URBAN OPT option is used in conjunction with the urban 

population from an appropriate nearby city and a default surface roughness of 1.0 meter. Methods 

described in Section 4.1 were used to determine whether rural or urban dispersion coefficients were 

appropriate for the modeling analysis. 

3.3 Output Options 

The AERMOD analysis was based on three years of recent meteorological data. The modeling 

analyses used one run with three years of sequential meteorological data from 2012-2014. Consistent 

with USEPA's Modeling Guidance for S02 NAAQS Designations, AERMOD provided a table of 

fourth-high 1-hour S02 impacts concentrations consistent with the form of the 1-hour S02 NAAQS.8 

Please refer to Table 1 for the modeling results. 

7 US EPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex 

Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51 , November 9, 2005. 8 US EPA, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, 

Attachment 3, March 24, 2011 , pp. 24-26. 
Evaluation of Compliance with the 1-hour NAAQSfor S02 

September 3, 2015 

Page 9 

4. Modellnputs 

4.1 Geographical Inputs 

The "ground floor" of all air dispersion modeling analyses is establishing a coordinate system for 

identifying the geographical location of emission sources and receptors. These geographical 

locations are used to detennine local characteristics (such as land use and elevation), and also to 

ascertain source to receptor distances and relationships. 

The Universal Transverse Mercator (UTM) NAD83 coordinate system was used for identifying the 

easting (x) and northing (y) coordinates of the modeled sources and receptors. Stack locations were 

obtained from facility permits and prior modeling files provided by the state regulatory agency. The 

stack locations were then verified using aerial photographs. 

The facility was evaluated to determine if it should be modeled using the rural or urban dispersion 

coefficient option in AERMOD. A Geographic Information System (GIS) was used to determine 

whether rural or urban dispersion coefficients apply to a site. Land use within a three-kilometer 

radius circle surrounding the facility was considered. USEPA guidance states that urban dispersion 

coefficients are used if more than 50% ofthe area within 3 kilometers has urban land uses. 

Otherwise, rural dispersion coefficients are appropriate.9 

USEPA's AERSURFACE v. 13016 was used to develop the meteorological data for the modeling 

analysis. This model was also used to evaluate surrounding land use within 3 kilometers. Based on 

the output from the AERSURF ACE, approximately 5.5% of sWTounding land use around the 

modeled facility was of urban land use types including Type 21 -Low Intensity Residential, Type 

22 - High Intensity Residential and Type 23 - Commercial I Industrial I Transportation. 

This is less than the 50% value considered appropriate for the use of urban dispersion coefficients. 

Based on the AERSURF ACE analysis, it was concluded that the rural option would be used for the 

modeling summarized in this report. Please refer to Section 4.5.3 for a discussion of the 

AERSURF ACE analysis. 

9 USEPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex 

Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51 , November 9, 2005, Section 7.2.3. 
Evaluation of Compliance with the 1-hour NAAQSfor S02 

September 3, 2015 

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4.2 Emission Rates and Source Parameters 

The modeling analysis considered S02 emissions from the Labadie, and the other two facilities. 

Other off-site sources were not considered. Concentrations were predicted for the scenarios shown in 

Tables 1 and 2: 

1) allowable emissions based on the current permit issued by the regulatory agency, and 

2) actual hourly emissions measured at the Ameren Labadie Plant each hour between 

January 1, 2012 and December 31, 2014 as taken from VSEPAAir Markets Program 

Data. 10 Actual emissions for Purina Animal Nutrition Center and N.B. West Contracting 

were reported to Missouri DNR for 20 13. 

Stack parameters and emissions used for the modeling analysis are summarized in Table 4. 

The above stack parameters and emissions were obtained from regulatory agency documents and 

databases identified in Section 2.2. The analysis was conducted based on 100% operating load using 

maximum exhaust flow rates and temperatures. Operation at less than full capacity loads was not 

considered. This assumption tends to under-predict impacts since stack parameters such as exit flow 

rate and temperature are typically lower at less than full load, reducing pollutant dispersion and 

increasing predicted air quality impacts. Stack location, height and diameter were verified using 

aerial photographs, and flue gas flow rate and temperature were verified using combustion 

calculations. 

10 http://ampd.epa.gov/ampd/ 
Evaluation of Compliance with the 1-hour NAAQSfor S01 

September 3. 2015 

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Table 4- Facility Stack Parameters and Emissions 11 

Facility 

Stack SOl 

Description Boiler l 

X Coord. [m) 688352.17 

Y Coord. [m] 4270445.59 

Base Elevation [m] 149.66 

Release Height [m] 213.36 

Gas Exit Temperature [°K] 443.065 

Gas Exit Velocity [m/s] 34.72 

Inside Diameter [m) 6.248 

Allowable Emission Rate [g/s] 3,739 

Actual Emission Rate [g/s] -

Facility 

Volume Source 

Description 

X Coord. [m] 

Y Coord. [m] 

Base Elevation [m] 

Release Height [m] 

Side Length [m] 

Building Height [m] 

Initial Lateral Dimension (m] 

Initial Vertical Dimension [m] 

Actual Emission Rate (g/s) 

Labadie 

S02 S03 

Boiler 2 Boiler 3 

688387.01 688435.47 

4270400.4 4270332.33 

149.66 149.66 

213.36 213.36 

442.49 433.204 

35.558 34.517 

6.248 6.248 

3,739 3,693 

- -

Purina 

EU 10 

Boiler 

689107.65 

4262863.7 

172 

5 

1.524 

-

1.16 

4.65 

0.0409 

S04 EOl 

Boiler 4 Generator D

688439.28 688439.28 695

4270327.43 4270327.43 426

149.66 149.66 

213.36 9.14 

441.708 866.483 3

34.946 7.112 5

6.248 0.305 0

3,693 - 

- 0.002308 0

N.B. W

EP1

N.B. West Drag 

69519

426247

159 

5 

1.52

-

1.1

4.6

0.073

11 Stack parameters obtained from Missouri DNR modeling file: Ameren Missouri Labadie Facility Hourly Emissions File Run 12-14 20 km m

Interactive sources. 
Evaluation of Compliance with the 1-hour NAAQSfor S02 

September 3, 2015 

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4.3 Building Dimensions 

This modeling analysis did not address the effects of downwash and this may under-predict impacts. 

4.4 Receptors 

For Ameren Labadie Plant, three receptor grids were employed: 

1. A 1 00-meter Cartesian receptor grid centered on Ameren Labadie Plant and extending out 5 

kilometers. 

2. A 500-meter Cartesian receptor grid centered on Ameren Labadie Plant and extending out 10 

kilometers. 

3. A 1,000-meter Cartesian receptor grid centered on Ameren Labadie Plant and extending out 50 

kilometers. 50 kilometers is the maximum distance accepted by US EPA for the use of the AERMOD 

dispersion model. 12 

A flagpole height of 1.5 meters was used for all these receptors. 

Elevations from stacks and receptors were obtained from National Elevation Dataset (NED) GeoTiff data. 

GeoTiff is a binary file that includes data descriptors and geo-referencing information necessary for 

extracting terrain elevations. These elevations were extracted from 1 arc-second (30 meter) resolution NED 

files. The USEP A software program AERMAP v. 11103 is used for these tasks. 

4.5 Meteorological Data 

To improve the accuracy of the modeling analysis, recent meteorological data for the 2012-2014 period 

were prepared using the USEPA's program AERMET which creates the model-ready surface and profile 

data files required by AERMOD. Required data inputs to AERMET included surface meteorological 

measurements, twice-daily soundings of upper air measurements, and the rnicrometeorological parameters 

surface roughness, albedo, and Bowen ratio. One-minute ASOS data were available so USEP A methods 

were used to reduce calm and missing hours.

13 The USEPA software program AERMINUTE v. 14237 is 

used for these tasks. 

This section discusses how the meteorological data was prepared for use in the 1-hour S02 NAAQS 

modeling analyses. The USEP A software program AERMET v. 14134 is used for these tasks. 

12 USEPA, Revision to the Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex 

Terrain) Dispersion Model and Other Revisions, Appendix W to 40 CFR Part 51 , Section A.l.(l), November 9, 2005. 13 USEP A, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, Attachment 

3, March 24, 2011 , p. 19. 
Evaluation of Compliance with the 1-hour NAAQSfor S02 

September 3, 2015 

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4.5.1 Surface Meteorology 

Surface meteorology was obtained for Spirit of St. Louis Airport located near the Ameren Labadie Plant. 

Integrated Surface Hourly (ISH) data for the 2012-2014 period were obtained from the National Climatic 

Data Center (NCDC). The ISH surface data was processed through AERMET Stage 1, which performs 

data extraction and quality control checks. 

4.5.2 Upper Air Data 

Upper-air data are collected by a "weather balloon" that is released twice per day at selected locations. As 

the balloon is released, it rises through the atmosphere, and radios the data back to the surface. The 

measuring and transmitting device is known as either a radiosonde, or rawindsonde. Data collected and 

radioed back include: air pressure, height, temperature, dew point, wind speed, and wind direction. The 

upper air data were processed through AERMET Stage l, which performs data extraction and quality 

control checks. 

For Ameren Labadie Plant, the concurrent 2012-2014 upper air data from twice-daily radiosonde 

measurements obtained at the most representative location were used. This location was the Lincoln, 

Illinois measurement station. These data are in Forecast Systems Laboratory (FSL) format and were 

downloaded in ASCII text format from NOAA's FSL website. 14 All reporting levels were downloaded and 

processed with AERMET. 

4.5.3 AERSURFACE 

AERSURF ACE is a program that extracts surface roughness, albedo, and daytime Bowen ratio for an area 

surrounding a given location. AERSURFACE uses land use and land cover (LULC) data in the U.S. 

Geological Survey's 1992 National Land Cover Dataset to extract the necessary micrometeorological data. 

LULC data was used for processing meteorological data sets used as input to AERMOD. 

AERSURFACE v. 13016 was used to develop surface roughness, albedo, and daytime Bowen ratio values 

in a region surrounding the meteorological data collection site. AERSURF ACE was used to develop 

surface roughness in a one kilometer radius surrounding the data collection site. Bowen ratio and albedo 

was developed for a 10 kilometer by 10 kilometer area centered on the meteorological data collection site. 

These micrometeorological data were processed for seasonal periods using 30-degree sectors. Seasonal 

moisture conditions were considered average with winter months having no continuous snow cover. 

14 Available at: http://esrl.noaa.gov/raobs/ 
Evaluation of Compliance with the 1-hour NAAQSfor S02 

September 3, 2015 

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4.5.4 Data Review 

Missing meteorological data were not filled as the data file met USEPA's 90% data completeness 

requirement. 15 The AERMOD output file shows there were 0.42% missing data. 

To confirm the representativeness of the airport meteorological data, the surface characteristics of the 

airport data collection site and the modeled source location were compared. Since the Spirit of St. Louis 

Airport is located close to Ameren Labadie Plant, this meteorological data set was considered appropriate 

for this modeling analysis. 16 Additionally, this weather station provided high quality surface measurements 

for the most recent 3-year time, and had similar land use, surface characteristics, terrain features and 

climate. 

5. Background 802 Concentrations 

Background concentrations were determined consistent with U8EPA's Modeling Guidance for 802 

NAAQ8 Designations.17

• 

18 To preserve the form of the 1-hour S02 standard, based on the 99th percentile of 

the annual distribution of daily maximum 1-hour concentrations averaged across the number of years 

modeled, the background fourth-highest daily maximum 1-hour S02 concentration was added to the 

modeled fourth-highest daily maximum 1-hour 802 concentration. 19 Background concentrations were based 

on the 2011-13 design value measured by the ambient monitors located in Missouri.20 

6. Reporting 

All files from the programs used for this modeling analysis are available to regulatory agencies. These 

include analyses prepared with AERSURFACE, AERMET, AERMAP, and AERMOD. 

15 USEPA, Meteorological Monitoring Guidance for Regulatory Modeling Applications, EPA-454/R-99-05, February 2000, 

Section 5.3.2, pp. 5-4 to 5-5. 

16 USEPA, AERMOD Implementation Guide, March 19, 2009, pp. 3-4. 17 USEP A, Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, Attachment 

3, March 24, 2011 , pp. 20-23. 18 US EPA, S02 NAAQS Designations Modeling Technical Assistance Document, Dec. 2013, section 8.1, pp 27-28. 19 USEPA, Applicability of Appendix W Modeling Guidance for the 1-hour S0 2 National Ambient Air Quality Standard, August 

23, 2010, p. 3. 

20 http://www.epa.gov/airtrends/values.html