Analysis of 1-Hour SO2 NAAQS 

Exceedances in Savannah and Rome

Submitted to:

Jimmy Johnston

Program Manager 2

Planning & Support Program

Submitted by:

Data & Modeling Unit

Planning & Support Program

Date Submitted:

December 23, 2013
Page 2 of 32

EXECUTIVE SUMMARY

On June 2, 2010, U.S. EPA strengthened that National Ambient Air Quality Standard (NAAQS) 

for sulfur dioxide (SO2) by adopting a new 1-hour standard of 75 parts per billion (ppb)1, 

effective August 23, 2010. EPD has identified three ambient monitors that were recording 1-

hour values in excess of the standard. These monitors are: Savannah – Lathrop & Augusta, 

Savannah – East President Street, and Rome – Coosa Elementary. In order to identify the 

probable cause of these high readings, EPD conducted a set of analyses. These analyses 

included the following steps: 

1) identification of nearby SO2 sources and Q/d (emissions/distance) analysis;

2) back trajectory analysis on SO2 exceedance days, and

3) AERMOD modeling to quantify source contributions to SO2 exceedances. 

The AERMOD modeling was conducted using emissions and stack data requested by EPD and 

received from the SO2 sources in March and May, 2013, respectively. Following this request, 

additional exceedances were measured by the Savannah - Lathrop & Augusta monitor and by the 

Rome monitor. Additional back trajectory analyses were conducted on the exceedances that 

were measured prior to November, 2013. 

Based on these analyses, it appears that SO2 emissions from Southern States Phosphate & 

Fertilizer caused or contributed to the SO2 NAAQS exceedances at the Savannah - E. President 

monitor; SO2 emissions from International Paper – Savannah Mill caused or contributed to the 

SO2 NAAQS exceedances at the Savannah - Lathrop & Augusta monitor; and SO2 emissions 

from International Paper – Rome Linerboard (formerly Temple Inland – Rome) and to a lesser 

degree Plant Hammond caused or contributed to the SO2 NAAQS exceedences at the Rome -

Coosa Elementary School monitor.

Unofficial data indicates that the 3-year design value for Savannah – Lathrop & Augusta has 

violated the NAAQS.

INTRODUCTION

Two SO2 monitors in Savannah (E. President and Lathrop & Augusta) and one SO2 monitor in 

Rome (Coosa Elementary School) measured multiple exceedances of the 1-hour SO2 NAAQS 

(75 ppb) from 2011 to 2013. Based on unofficial data through November, 2013, the 3-year 

design value for the Savannah Lathrop & Augusta monitor is now 80 ppb, which is a violation of

the NAAQS. Although there were multiple exceedances of the 1-hour SO2 NAAQS at the 

Savannah - E. President and Rome – Coosa Elementary monitors, the three year design value 

remained below the NAAQS at these two sites. The purpose of this analysis is to help identify 

 

1 99th percentile of 1-hour daily maximum concentrations, averaged over 3 years
Page 3 of 32

which sources contributed to the 1-hour SO2 exceedances. This document will focus primarily 

on SO2 exceedances in 2011, 2012, and early 2013, but also includes some data for exceedances 

in later 2013. A meteorology analysis of the September exceedances at Lathrop & Augusta is 

included in Appendix A. Appendix B discusses three days in Savannah where the winds were 

north-northeast (NNE), but SO2 remained low.

Table 1 identifies the 1-hour SO2 exceedances that were included as part of these analyses. The 

technical analysis includes:

1) identification of nearby SO2 sources and Q/d (emissions/distance) analysis;

2) back trajectory analysis on SO2 exceedance days; and 

3) AERMOD modeling to quantify source contributions to SO2 exceedances.

Table 1. Exceedances of the 1-hour SO2 NAAQS included in analyses.

Site Date Time of Peak SO2 SO2 Peak (ppb)

E. President

(13-051-0021)

2/13/2011 9:00 93.0

10/20/2012 9:00 87.3

11/23/2012 9:00 96.6

11/24/2012 2:00 77.9

12/19/2012 10:00 79.3

1/21/2013 10:00 96.0

Lathrop & 

Augusta

(13-051-1002)

5/5/2011 6:00 75.8

11/24/2011 8:00 94.8

12/2/2011 10:00 94.2

10/26/2012 8:00 111.7

11/17/2012 9:00 127.6

12/14/2012 7:00 87.1

9/27/13 8:00 117.5

9/28/13 8:00 92.7

9/29/13 8:00 142.1

10/8/13 9:00 101.1

11/5/13 10:00 76.3

11/13/13 7:00 79.9

11/24/13 7:00 76.6

11/30/13 12:00 77.3

Coosa 

Elementary

School

(13-115-0003)

2/25/2011 0:00 96.0

4/3/2011 18:00 153.1

4/4/2011 15:00 115.6

4/25/2011 16:00 76.3

11/13/2011 13:00 161.8
Page 4 of 32

Site Date Time of Peak SO2 SO2 Peak (ppb)

Coosa 

Elementary

School

(13-115-0003)

11/14/2011 12:00 81.4

2/13/2012 12:00 75.9

2/23/2012 14:00 133.5

2/29/2012 21:00 160.6

3/2/2012 11:00 95.6

12/6/2013 11:00 88.0

IDENTIFICATION OF NEARBY SO2 SOURCES 

The 2011 NEI was used to identify all point sources within 50 kilometer (km) of each monitor

(Table 2, Table 3 and Table 4). The SO2 emissions were identified in tons per year (Q) and the 

distance from each point source to the associated SO2 monitor was calculated in km (d). Next, 

Q/d, cumulative Q/d, and percent of the cumulative Q/d were calculated for each source. 

Sources that had a Q/d > 20 were identified for further analysis (identified with bold). Sources 

that had a Q/d < 20 were no longer included in the analysis. The sources that were identified for 

further analysis accounted for more than 99% of the cumulative Q/d.

Table 2. Point sources within 50 km of Savannah - E. President SO2 monitor.

AIRS NO. Facility Name

SO2 

(TPY)

Distance 

[km] Q/d

Cumulative 

Q/d

Percent

Cum Q/d

05100077

Southern States Phosphate & 

Fertilizer 1211.44 1.48 819.27 819.27 43.9%

05100007 International Paper - Savannah 4232.78 7.83 540.52 1359.79 72.9%

05100006

Ga Power Company - Plant 

Kraft 2806.00 12.70 221.01 1580.80 84.8%

10300007

Georgia-Pacific Consumer 

Products LP (Savannah River 

Mill) 3724.79 32.41 114.92 1695.72 91.0%

05100008 Savannah Acid Plant LLC 120.00 2.49 48.17 1743.89 93.5%

05100010 Weyerhaeuser Company 605.44 14.53 41.67 1785.57 95.8%

05100110 Imperial-Savannah, L.P. 502.26 12.40 40.51 1826.08 98.0%

10300003 Ga Power Co Plt McIntosh 691.81 33.70 20.53 1846.60 99.1%

05100076 Colonial Terminals, Inc. 82.15 6.58 12.48 1859.09 99.7%

05100148 Arizona Chemical Corporation 31.32 7.66 4.09 1863.17 99.9%

10300014

Ga Power Company - McIntosh 

Combined Cycle Facility 18.07 33.69 0.54 1863.71 100.0%

17900001 Interstate Paper LLC 11.52 49.74 0.23 1863.94 100.0%

10300012 Effingham County Power, LLC 4.70 33.20 0.14 1864.08 100.0%

05100003

Southern LNG Company, L.L.C. -

Elba Island LNG Terminal -

(Kinder Morgan , Inc.) 0.45 4.36 0.10 1864.19 100.0%

10300004 Simpson Lumber Company, LLC 1.65 33.28 0.05 1864.24 100.0%

05100012 NuStar Asphalt Refining, LLC 0.16 8.71 0.02 1864.25 100.0%

05100046 Gulfstream Aerospace Corp 0.08 15.74 0.00 1864.26 100.0%

05100017

Ga Power Company - Plant 

Boulevard 0.02 7.76 0.00 1864.26 100.0%
Page 5 of 32

Table 3. Point sources within 50 km of Savannah - Lathrop & Augusta SO2 monitor.

AIRS NO. Facility Name

SO2 

(TPY)

Distance 

[km] Q/d

Cumulative 

Q/d

Percent

Cum Q/d

05100007 International Paper - Savannah 4232.78 1.83 2312.05 2312.05 69.5%

05100006

Ga Power Company - Plant 

Kraft 2806.00 6.61 424.80 2736.85 82.3%

05100077

Southern States Phosphate & 

Fertilizer 1211.44 6.59 183.91 2920.76 87.8%

10300007

Georgia-Pacific Consumer 

Products LP (Savannah River 

Mill) 3724.79 27.51 135.40 3056.16 91.9%

05100110 Imperial-Savannah, L.P. 502.26 6.12 82.13 3138.29 94.4%

05100010 Weyerhaeuser Company 605.44 8.02 75.46 3213.74 96.6%

05100076 Colonial Terminals, Inc. 82.15 1.77 46.38 3260.12 98.0%

05100148 Arizona Chemical Corporation 31.32 1.11 28.16 3288.27 98.9%

10300003 Ga Power Co Plt McIntosh 691.81 29.63 23.35 3311.62 99.6%

05100008 Savannah Acid Plant LLC 120.00 9.78 12.27 3323.89 100.0%

10300014

Ga Power Company - McIntosh 

Combined Cycle Facility 18.07 29.62 0.61 3324.50 100.0%

17900001 Interstate Paper LLC 11.52 46.78 0.25 3324.75 100.0%

10300012 Effingham County Power, LLC 4.70 26.70 0.18 3324.93 100.0%

05100012 NuStar Asphalt Refining, LLC 0.16 2.14 0.07 3325.00 100.0%

10300004 Simpson Lumber Company, LLC 1.65 25.24 0.07 3325.06 100.0%

17900011 SNF - Riceboro 3.12 47.96 0.07 3325.13 100.0%

05100003

Southern LNG Company, L.L.C. -

Elba Island LNG Terminal -

(Kinder Morgan , Inc.) 0.45 11.90 0.04 3325.17 100.0%

05100046 Gulfstream Aerospace Corp 0.08 8.15 0.01 3325.18 100.0%

05100017

Ga Power Company - Plant 

Boulevard 0.02 6.16 0.00 3325.18 100.0%

Table 4. Point sources within 50 km of Rome - Coosa Elementary School SO2 monitor.

AIRS NO. Facility Name

SO2 

(TPY)

Distance 

[km] Q/d

Cumulative 

Q/d

Percent

Cum Q/d

11500021

International Paper – Rome 

Linerboard (was Temple Inland 

– Rome) 2,202.81 0.77 2,854.92 2,854.92 70.5%

11500003

Ga Power Company - Plant 

Hammond 2,174.44 2.20 988.38 3,843.29 94.9%

01500011

Ga Power Company - Plant 

Bowen 5,888.85 40.15 146.69 3,989.98 98.5%

11500105

General Shale Brick, Inc. - Plant 

40 102.78 1.80 57.04 4,047.02 99.9%

01500032 Gerdau Ameristeel US Inc. 92.12 48.74 1.89 4,048.91 100.0%

05500001 Mount Vernon Mills 32.90 31.66 1.04 4,049.95 100.0%

01500061 Anheuser-Busch Inc 5.72 49.86 0.11 4,050.07 100.0%

11500077

Ball Container LLC Rome Can 

Plant 0.08 21.81 0.00 4,050.07 100.0%

11500095

Packaging Products Corporation, 

LLC 0.02 14.96 0.00 4,050.07 100.0%
Page 6 of 32

The 2008 SO2 emissions at the Port of Savannah were obtained from the environmental impact 

statement report for the Savannah Harbor Expansion Project (U.S. Army Corps of Engineers, 

Environmental Impact Statement Appendix K: Air Emission Inventory and Assessment 

Savannah Harbor Expansion Project, 2012) and are shown in Table 5. These emissions were 

estimated by evaluating the air emissions from all cargo-carrying vessels and landside cargo 

handling equipment at both the Georgia Port Authority (GPA) and privately-operated terminals 

at the port. In total, 1,177.5 tons of SO2 were emitted at the Port of Savannah, with 557.6 tons 

from the Garden City Terminal, 300.7 tons from the Elba Island LNG Terminal, and 278.7 tons 

from the Ocean Terminal and non-GPA Terminals. Since the SO2 emissions from these sources 

were smaller than the SO2 emissions from point sources that were closer to the monitors, no 

additional analysis was performed for these sources.

Table 5. SO2 emissions in the Port of Savannah by sources (tons/year)

Source SO2 Emissions (TPY)

Garden City Terminal 557.6

Ocean Terminal and non-GPA Terminals 278.7

Elba Island LNG Terminal 300.7

Shifts 27.3

Maintenance Dredging 12.4

Tourist Boats 0.9

Total 1,177.5

Due to the close proximity of the SO2 monitors in Savannah, multiple sources are included in 

both Table 3 (E. President) and Table 4 (Lathrop & Augusta). The Q/d analysis for Savannah 

indicates that Southern States Phosphate & Fertilizer (43.9%) and International Paper (29.0%) 

have the largest contribution to the E. President SO2 monitor (72.9% of the cumulative Q/d) and 

International Paper has the largest contribution to the Lathrop & Augusta SO2 monitor (69.5% of 

the cumulative Q/d). The Q/d analysis for Rome indicates that International Paper – Rome 

Linerboard has the largest contribution to the Coosa Elementary School SO2 monitor (70.5% of 

the cumulative Q/d). 

BACK TRAJECTORY ANALYSIS 

Table 6 shows the date and time for each 1-hour SO2 exceedance prior to mid-December, 2013, 

along with the relevant meteorological information. To aid in identifying sources contributing to 

each exceedance, 1-hour average wind analysis and 1-minute high resolution back trajectory 

analysis were conducted.

 
Page 7 of 32

Table 6. Days that exceeded the 1-hour SO2 NAAQS and relevant meteorological data.

Site Date Time of

SO2 Peak

Wind Speed

(m/s)

Wind Direction

(Deg)

Savannah - E. 

President

(13-051-0021)

2/13/2011 9:00 0.5 253

10/20/2012 9:00 2.7 271

11/23/2012 9:00 2.7 258

11/24/2012 2:00 2.7 268

12/19/2012 10:00 2.6 21

1/21/2013 10:00 2.7 354

Savannah -

Lathrop & 

Augusta

(13-051-1002)

5/5/2011 6:00 1.9 11

11/24/2011 8:00 2.9 27

12/2/2011 10:00 1.8 33

10/26/2012 8:00 2.5 30

11/17/2012 9:00 3.6 40

12/14/2012 7:00 2.5 23

9/27/13 8:00 3.0 35

9/28/13 8:00 2.9 36

9/29/13 8:00 2.1 31

10/8/13 9:00 3.5 35

11/5/13 10:00 2.2 26

11/13/13 7:00 3.1 36

11/24/13 7:00 3.2 35

11/30/13 12:00 1.9 28

Rome - Coosa 

Elementary

School*

(13-115-0003)

2/25/2011 0:00 5.1 210

4/3/2011 18:00 5.7 180

4/4/2011 15:00 8.0 190

4/25/2011 16:00 no data no data

11/13/2011 13:00 no data no data

11/14/2011 12:00 no data no data

2/13/2012 12:00 Calm Calm

2/23/2012 14:00 5.1 200

2/29/2012 21:00 2.1 200

3/2/2012 11:00 3.6 230

12/6/2013 11:00 no data no data

* Wind data from R.B. Russell Airport Automated Surface Observing Station

For the 1-hour wind analysis, the average wind speed and wind direction data in Table 6 was 

used to determine the origin of the air mass leading to the exceedance. Figure 1 shows the 

1-hour wind analysis plot for the Savannah - E. President monitor. Then, the plot was imported 

to ArcGIS to overlay the 1-hour wind analysis plot on a map (see Figure 2) to help examine the 

relationship between major SO2 sources and each SO2 exceedance.
Page 8 of 32

Figure 1. 1-hour wind analysis plot for Savannah - E. President monitor. The units of the x-axis 

and y-axis are kilometers (km).

Figure 2. Example of 1-hour wind analysis plot overlaid on GIS map. The radius of the circle in 

the figure is 10 km.

Figure 2 shows the result of 1-hour wind analysis for Savannah - E. President monitor. High 

SO2 incidences on 02/1311, 10/20/12, 11/23/12, and 11/24/12 and are associated with sources at 

the west side of the monitor while other exceedances on 12/19/12 and 01/21/13 are associated 

with sources at the north/northeast side of the monitor. Four possible major contributors were 

Southern States Phosphate & Fertilizer, BASF Corporation – Savannah Operations, Georgia-
Page 9 of 32

Pacific Gypsum LCC – Savannah Plant, and Savannah Acid Plant, LLC. Because SO2 emissions 

from BASF Corporation – Savannah Operations and Georgia-Pacific Gypsum LCC – Savannah 

Plant were zero on those days, these two sources were ruled out. 

Next, 1-minute high resolution back trajectory analyses were performed with 1-minute wind data 

(WS and WD) and 1-minute SO2 concentration data provided by the Ambient Monitoring 

Program staff. The back-trajectory analysis begins when the first measured 1-minute SO2

concentration exceeds 75 ppb at each monitor location. Then, 1-minute wind speed and wind 

direction measurements at the SO2 monitor site were used to calculate back trajectories. Back 

trajectories were developed for every minute the SO2 monitor exceeded 75 ppb. The extent of 

back-trajectory calculation was set to a 3 km radius from the monitoring site. All of the back 

trajectories were superimposed on a GIS map to help identify sources that may have been 

contributing to the exceedances.

Figure 3 through Figure 8 show the results of 1-minute high resolution back-trajectory analyses 

done for each SO2 exceedance day. In most cases, the trajectories show directional consistency. 

Based on an analysis of the 1-hour wind analysis plot and the 1-minute high resolution backtrajectory plots, it appears that SO2 emissions from Southern States Phosphate & Fertilizer 

caused or contributed to many of the SO2 NAAQS exceedances at the Savannah - E. President 

monitor. 

Figure 3. High resolution back trajectory for Savannah - E. President monitor on 02/13/11.
Page 10 of 32

Figure 4. High resolution back trajectory for Savannah - E. President monitor on 10/20/12.

Figure 5. High resolution back trajectory for Savannah - E. President monitor on 11/23/12.
Page 11 of 32

Figure 6. High resolution back trajectory for Savannah - E. President monitor on 11/24/12.

Figure 7. High resolution back trajectory for Savannah - E. President monitor on 12/19/12.
Page 12 of 32

Figure 8. High resolution back trajectory for Savannah - E. President monitor on 01/21/13.

Figure 9 shows the result of 1-hour wind analysis for Savannah - Lathrop & Augusta monitor. 

All of the SO2 exceedances were associated with sources on the northeast side of the monitor. 

Two possible contributors were Arizona Chemical Corporation and International Paper -

Savannah. Next, 1-minute high resolution back trajectory analyses were conducted for the days 

with SO2 exceedances (Figure 10 through Figure 15). According to the 2011 NEI, annual SO2 

emission from International Paper were 4232.78 TPY compared to 31.32 TPY from Arizona 

Chemical Corporation. Based on the wind trajectory analysis and NEI 2011 emissions, it 

appears that the SO2 emissions from International Paper – Savannah Mill may be responsible for 

many of the SO2 NAAQS exceedances at the Savannah - Lathrop & Augusta monitor. 
Page 13 of 32

Figure 9. 1-hour wind analysis for Savannah - Lathrop & Augusta monitor. The radius of the 

circle in the figure is 15 km. 

Figure 10. High resolution back trajectory for Savannah - Lathrop & Augusta monitor on 

05/05/11.
Page 14 of 32

Figure 11. High resolution back trajectory for Savannah - Lathrop & Augusta monitor on 

11/24/11.

Figure 12. High resolution back trajectory for Savannah - Lathrop & Augusta monitor on 

12/02/11.
Page 15 of 32

Figure 13. High resolution back trajectory for Savannah - Lathrop & Augusta monitor on 

10/26/12.

Figure 14. High resolution back trajectory for Savannah - Lathrop & Augusta monitor on 

11/17/12.
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Figure 15. High resolution back trajectory for Savannah - Lathrop & Augusta monitor on 

12/14/12.

Figure 16. High resolution back trajectory for Lathrop & Augusta monitor on 09/27/13.
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Figure 17. High resolution back trajectory for Savannah - Lathrop & Augusta monitor on 

09/28/13.

Figure 18. High resolution back trajectory for Savannah - Lathrop & Augusta monitor on 

09/29/13.
Page 18 of 32

Figure 19. High resolution back trajectory for Savannah - Lathrop & Augusta monitor on 

10/08/13.

Figure 20 shows the result of 1-hour wind analysis for the Rome - Coosa Elementary School 

monitor. All of the SO2 exceedances were associated with sources at the south/southwest side of 

the monitor. The two possible contributors were Plant Hammond and International Paper –

Rome Linerboard. Compared to the Savannah monitors, the wind speed is much faster resulting 

in less horizontal dispersion. Based on the wind directions and the magnitude of wind speed, it 

appears that the SO2 emissions from International Paper – Rome Linerboard caused or 

contributed to many of the SO2 NAAQS exceedances at the Coosa Elementary School monitor. 

There is one day that the SO2 emissions from Plant Hammond may have caused or contributed 

to a SO2 NAAQS exceedance. 1-minute high resolution back trajectory analyses cannot be 

conducted for the Coosa Elementary Monitor since EPD does not operate a meteorology station 

at this site.
Page 19 of 32

Figure 20. 1-hour wind analysis for Rome Coosa Elementary monitor. The radius of the circle 

in the figure is 30 km. 

AERMOD MODELING ANALYSIS

AERMOD runs were performed to help quantify the contributions from each source to the 

1-hour SO2 exceedances prior to September, 2013. In order to use the most accurate SO2 

emissions available, letters were sent to each facility included in the analysis requesting hourly 

emission data for specific exceedance days. The letters requested that:

 Southern States Phosphate & Fertilizer, International Paper - Savannah Mill, Georgia

Power Company (Plant Kraft), Georgia-Pacific Consumer Products LP (Savannah River 

Mill), Weyerhaeuser Company, Imperial-Savannah, L.P., and Georgia Power Company

(Plant McIntosh) submit hourly SO2 emissions for 02/13/11, 05/05/11, 11/24/11, 

12/02/11, 10/20/12, 10/26/12, 11/17/12, 11/23/12, 11/24/12, 12/14/12, 12/19/12, and 

01/21/13;

 Savannah Acid Plant LLC submit hourly SO2 emissions for 02/13/11, 10/20/12, 

11/23/12, 11/24/12, 12/19/12, and 01/21/13;

 Colonial Terminals, Inc. and Arizona Chemical Corporation submit hourly SO2 

emissions for 05/05/11, 11/24/11, 12/02/11, 10/26/12, 11/17/12, and 12/14/12; and

 –International Paper – Rome Linerboard, Georgia Power Company (Plant Hammond), 

Georgia Power Company (Plant Bowen), and General Shale Brick, Inc. (Plant 40) submit 

hourly SO2 emissions for 02/25/11, 02/03/11, 02/04/11, 04/25/11, 11/13/11, 11/14/11, 

02/13/12, 02/23/12, and 02/29/12.
Page 20 of 32

In addition, the letter requested SO2 emissions for one day prior to the requested date. All 

facilities provided data (see Appendix C). However, some data were more detailed than others. 

While some facilities could provide hourly SO2 emissions, others could only provide a single 

SO2 emission rate for each day. The SO2 emission files, stack temperature, and stack velocity 

were converted into AERMOD format for each facility for the days that data was requested. The 

SO2 emissions on the other days were set equal to zero.

Meteorological data was created for each monitoring site using AERMETv12345 for the period 

2011-2012. The Savannah- E. President and Savannah - Lathrop & Augusta monitoring 

locations both contain on-site meteorological measurements for wind speed and wind direction. 

The other required meteorological fields were extracted from the Savannah International Airport 

ASOS site (SAV) and the Charleston, SC station (CHS) for upper air measurements. The Rome 

- Coosa Elementary School site used surface meteorological fields from the R.B. Russell Airport 

ASOS site (RMG) in Rome and upper air observations from Peachtree City station (FFC). The

meteorological data were processed using the latest version of AERSURFACEv13016 for both 

airport and site surface characteristics and using AERMINUTEv11325 for the 1-minute ASOS 

wind observations. Receptor elevations and hill heights required by AERMOD were determined 

using the AERMAPv11103 terrain preprocessor. Terrain elevations from the USGS 30m DEM 

were used for AERMAP processing.

Each modeling domain contained a 1-km by 1-km array of receptors (11 x 11) with 100 meter 

spacing with the center receptor placed at the monitor location. AERMODv12345 was run for 

2011 and 2012 for each modeling domain. Modeled SO2 concentrations at the receptor 

corresponding to the monitor location were compared against SO2 measurements on the days 

that contained SO2 exceedances. In addition, the maximum SO2 concentration from the 1-km 

by 1-km array of receptors surrounding the monitor location were compared against SO2 

measurements on the days that contained SO2 exceedances. The maximum SO2 concentration 

was used to identify plumes that may have missed to receptor corresponding to the monitor 

location due to slight differences in the observed wind direction. Next, the contribution from 

each source was evaluated to help identify which sources were contributing to the SO2 

exceedances. Since AERMOD outputs SO2 concentrations in g/m3, the SO2 observations were 

converted from ppb to g/m3by multiplying by 2.62 (e.g., 75 ppb = 196.5 g/m3).

Generally, U.S. EPA requires 5 years of meteorological data to be used and does not require SO2 

observations and SO2 model results to be paired in time and space since AERMOD models a 

distribution of steady-state concentrations. It should be noted that this AERMOD analysis 

generally pairs the SO2 observations and SO2 model results in time and space on exceedance 

days, an analysis for which AERMOD was not designed. Therefore, matching of all measured 

and modeled concentrations should not be expected. 
Page 21 of 32

Savannah - E. President (13-051-0021)

Figure 21 contains the AERMOD receptor array used to model impacts at the Savannah - E. 

President (13-051-0021) monitor. Figure 22 contains a time series plot comparing AERMOD 

SO2 results at the monitoring site receptor, AERMOD SO2 results for the maximum receptor in 

the array, and the SO2 observations. Figure 23 contains a Q-Q plot (unpaired in time) for the 

SO2 concentrations at the monitoring site receptor and the maximum receptor in the array. 

Figure 21 contains the hourly SO2 source contributions from each facility at the receptor 

corresponding to the monitor location. Figure 25 contains the maximum hourly SO2 source 

contributions from the array of receptors for each facility. Figure 26 contains a summary of the 

daily maximum observation, daily maximum source contributions from each facility at the 

receptor corresponding to the monitor location, and the daily maximum source contributions 

from each facility from the array of receptor surrounding the monitor location.

In general, AERMOD tends to under predict the SO2 peaks when using the monitoring site 

receptor. However, the model performance is improved for the higher SO2 values when using 

the maximum receptor in the array surrounding the monitoring site. Based on the model results, 

it appears that the SO2 emissions from Southern States Phosphate & Fertilizer caused or 

contributed to many of the SO2 NAAQS exceedances at the Savannah - E. President monitor. 

Figure 21. AERMOD receptor array for Savannah - E. President (13-051-0021) monitor.
Page 22 of 32

Figure 22. AERMOD SO2 results at the Savannah - E. President monitoring site receptor 

(green), AERMOD SO2 results for the maximum receptor in the array (red), and the SO2 

observations (black).

Figure 23. Q-Q plot (unpaired in time) for the SO2 concentrations at the Savannah - E. 

President monitoring site receptor and the maximum receptor in the array.

0

50

100

150

200

250

300

350

400

02/12/1102/13/1110/19/1210/20/1211/22/1211/23/1211/24/1212/18/1212/19/12

SO2 Concentration (ug/m3)

SO2 Concentrations at E. President

OBSERVATIONS

AERMOD - Receptor

AERMOD - Max Array

0

50

100

150

200

250

300

0 50 100 150 200 250 300

SO2 AERMOD (ug/m3)

SO2 Observations (ug/m3) 

Q-Q Plot at E. President

AERMOD - Receptor

AERMOD - Max Array
Page 23 of 32

Figure 24. Hourly SO2 source contributions from each facility at the receptor corresponding to 

the Savannah - E. President monitor location.

Figure 25. Maximum hourly SO2 source contributions from each facility from the array of 

receptors surrounding the Savannah - E. President monitor.

0

50

100

150

200

250

300

350

400

02/12/1102/13/1110/19/1210/20/1211/22/1211/23/1211/24/1212/18/1212/19/12

SO2 Concentration (ug/m3)

SO2 Concentrations at E. President (Receptor)

OBSERVATIONS

Imperial

International Paper

Southern States

Savannah Acid

Weyerhaeuser

Plant Kraft

Georgia Pacific

0

50

100

150

200

250

300

350

400

02/12/1102/13/1110/19/1210/20/1211/22/1211/23/1211/24/1212/18/1212/19/12

SO2 Concentration (ug/m3)

SO2 Concentrations at E. President (Max. Array)

OBSERVATIONS

Imperial

International Paper

Southern States

Savannah Acid

Weyerhaeuser

Plant Kraft

Georgia Pacific
Page 24 of 32

Figure 26. Bar chart summary of the daily maximum observation, daily maximum source 

contributions from each facility at the receptor corresponding to the Savannah - E. President 

monitor location, and the daily maximum source contributions from each facility from the array 

of receptor surrounding the Savannah - E. President monitor location.

Savannah - Lathrop & Augusta (13-051-1002)

Figure 27 contains the AERMOD receptor array used to model impacts at the Savannah -

Lathrop & Augusta (13-051-1002) monitor. Figure 28 contains a time series plot comparing 

AERMOD SO2 results at the monitoring site receptor, AERMOD SO2 results for the maximum 

receptor in the array, and the SO2 observations. Figure 29 contains a Q-Q plot (unpaired in 

time) for the SO2 concentrations at the monitoring site receptor and the maximum receptor in the 

array. Figure 30 contains the hourly SO2 source contributions from each facility at the receptor 

corresponding to the monitor location. Figure 31 contains the maximum hourly SO2 source 

contributions from the array of receptors for each facility. Figure 32 contains a summary of the 

daily maximum observation, daily maximum source contributions from each facility at the 

receptor corresponding to the monitor location, and the daily maximum source contributions 

from each facility from the array of receptor surrounding the monitor location.

In general, AERMOD tends to under predict the SO2 peaks when using the monitoring site 

receptor as well as when using the maximum receptor in the array surrounding the monitoring 

site. Based on the model results, it appears that that the SO2 emissions from International Paper 

– Savannah Mill caused or contributed to many of the SO2 NAAQS exceedances observed at the 

Savannah - Lathrop & Augusta monitor. Although Figure 32 indicates impacts from Plant Kraft 

0

50

100

150

200

250

300

350

400 02/13/11 10/20/12 11/23/12 11/24/12 12/19/12 Average SO2 Concentration (ug/m3)

Source Contributions at E. President OBSERVATIONS

Georgia Pacific

Plant Kraft

Weyerhaeuser

Savannah Acid

Southern States

International Paper

Imperial
Page 25 of 32

on 12/02/11, it can be seen in Figure 30 and Figure 31 that the Plant Kraft impacts occur prior to 

the observed SO2 exceedance on that day.

Figure 27. AERMOD receptor array for Savannah - Lathrop & Augusta (13-051-1002) monitor. 

0

50

100

150

200

250

300

350

400

05/04/1105/05/1111/23/1111/24/1112/01/1112/02/1110/25/1210/26/1211/16/1211/17/1212/13/1212/14/12

SO2 Concentration (ug/m3)

SO2 Concentrations at Lathrop & Augusta

OBSERVATIONS

AERMOD - Receptor

AERMOD - Max Array
Page 26 of 32

Figure 28. AERMOD SO2 results at the Savannah - Lathrop & Augusta monitor site receptor 

(green), AERMOD SO2 results for the maximum receptor in the array (red), and the SO2 

observations (black).

Figure 29. Q-Q plot (unpaired in time) for the SO2 concentrations at the Savannah - Lathrop & 

Augusta monitoring site receptor and the maximum receptor in the array.

0

50

100

150

200

250

300

0 50 100 150 200 250 300

SO2 AERMOD (ug/m3)

SO2 Observations (ug/m3) 

Q-Q Plot at Lathrop & Augusta

AERMOD - Receptor

AERMOD - Max Array
Page 27 of 32

Figure 30. Hourly SO2 source contributions from each facility at the receptor corresponding to 

the Savannah - Lathrop & Augusta monitor location.

Figure 31. Maximum hourly SO2 source contributions from each facility from the array of 

receptors surrounding the Savannah - Lathrop & Augusta monitor.

0

50

100

150

200

250

300

350

400

05/04/1105/05/1111/23/1111/24/1112/01/1112/02/1110/25/1210/26/1211/16/1211/17/1212/13/1212/14/12

SO2 Concentration (ug/m3)

SO2 Concentrations at Lathrop & Augusta (Receptor)

OBSERVATIONS

Arizona Chemical

Georgia Pacific

Plant Kraft

Imperial

International Paper

Southern States

Savannah Acid

Colonial Terminals

Weyerhaeuser

0

50

100

150

200

250

300

350

400

05/04/1105/05/1111/23/1111/24/1112/01/1112/02/1110/25/1210/26/1211/16/1211/17/1212/13/1212/14/12

SO2 Concentration (ug/m3)

SO2 Concentrations at Lathrop & Augusta (Max. Array)

OBSERVATIONS

Arizona Chemical

Georgia Pacific

Plant Kraft

Imperial

International Paper

Southern States

Savannah Acid

Colonial Terminals

Weyerhaeuser
Page 28 of 32

Figure 32. Bar chart summary of the daily maximum observation, daily maximum source 

contributions from each facility at the receptor corresponding to the Savannah - Lathrop & 

Augusta monitor location, and the daily maximum source contributions from each facility from 

the array of receptor surrounding Savannah - Lathrop & Augusta monitor location.

Rome - Coosa Elementary School (13-115-0003)

Figure 33 contains the AERMOD receptor array used to model impacts at the Rome - Coosa 

Elementary School (13-115-0003) monitor. Figure 34 contains a time series plot comparing 

AERMOD SO2 results at the monitoring site receptor, AERMOD SO2 results for the maximum 

receptor in the array, and the SO2 observations. Figure 51 contains a Q-Q plot (unpaired in 

time) for the SO2 concentrations at the monitoring site receptor and the maximum receptor in the 

array. Figure 36 contains the hourly SO2 source contributions from each facility at the receptor 

corresponding to the monitor location. Figure 37 contains the maximum hourly SO2 source 

contributions from the array of receptors for each facility. Figure 38 contains a summary of the 

daily maximum observation, daily maximum source contributions from each facility at the 

receptor corresponding to the monitor location, and the daily maximum source contributions 

from each facility from the array of receptor surrounding the monitor location.

In general, AERMOD tends to slightly under predict the SO2 peaks when using the monitoring 

site receptor. However, the model tends to over predict the SO2 peaks when using the maximum 

receptor in the array surrounding the monitoring site. Based on the model results, it appears that 

the SO2 emissions from International Paper – Rome Linerboard and to a lesser degree Plant 

Hammond caused or contributed to many of the SO2 NAAQS exceedances at the Rome - Coosa 

Elementary School monitor.

0

50

100

150

200

250

300

350

400

450

500 05/05/11 11/24/11 12/02/11 10/26/12 11/17/12 12/14/12 Average SO2 Concentration (ug/m3)

Source Contributions at Lathrop & Augusta

OBSERVATIONS

Weyerhaeuser

Colonial Terminals

Savannah Acid

Southern States

International Paper

Imperial

Plant Kraft

Georgia Pacific

Arizona Chemical
Page 29 of 32

Figure 33. AERMOD receptor array for Rome - Coosa Elementary School (13-115-0003) 

monitor.

Figure 34. AERMOD SO2 results at the Rome – Coosa Elementary monitoring site receptor 

0

100

200

300

400

500

600

700

800

02/24/1102/25/1104/02/1104/03/1104/04/1104/24/1104/25/1111/12/1111/13/1111/14/1102/12/1202/13/1202/22/1202/23/1202/28/1202/29/12

SO2 Concentration (ug/m3)

SO2 Concentrations at Rome

OBSERVATIONS

AERMOD - Receptor

AERMOD - Max Array
Page 30 of 32

(green), AERMOD SO2 results for the maximum receptor in the array (red), and the SO2 

observations (black).

Figure 35. Q-Q plot (unpaired in time) for the SO2 concentrations at the Rome – Coosa 

Elementary monitoring site receptor and the maximum receptor in the array.

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800

SO2 AERMOD (ug/m3)

SO2 Observations (ug/m3) 

Q-Q Plot at Rome

AERMOD - Receptor

AERMOD - Max Array

0

100

200

300

400

500

600

700

800

02/24/1102/25/1104/02/1104/03/1104/04/1104/24/1104/25/1111/12/1111/13/1111/14/1102/12/1202/13/1202/22/1202/23/1202/28/1202/29/12

SO2 Concentration (ug/m3)

SO2 Concentrations at Rome (Receptor)

OBSERVATIONS

General Shale

Plant Hammond

Plant Bowen

Temple Inland
Page 31 of 32

Figure 36. Hourly SO2 source contributions from each facility at the receptor corresponding to 

the Rome – Coosa Elementary monitor location.

Figure 37. Maximum hourly SO2 source contributions from each facility from the array of 

receptors surrounding the Rome – Coosa Elementary monitor.

Figure 38. Bar chart summary of the daily maximum observation, daily maximum source 

contributions from each facility at the receptor corresponding to the Rome – Coosa Elementary 

0

100

200

300

400

500

600

700

800

02/24/1102/25/1104/02/1104/03/1104/04/1104/24/1104/25/1111/12/1111/13/1111/14/1102/12/1202/13/1202/22/1202/23/1202/28/1202/29/12

SO2 Concentration (ug/m3)

SO2 Concentrations at Rome (Max Array)

OBSERVATIONS

General Shale

Plant Hammond

Plant Bowen

Temple Inland

0

200

400

600

800

1000

1200

1400

1600

1800

2000 02/25/11 04/03/11 04/04/11 04/25/11 11/13/11 11/14/11 02/13/12 02/23/12 02/29/12 Average SO2 Concentration (ug/m3)

Source Contributions at Rome 

OBS (ug/m3)

Temple Inland

Plant Bowen

Plant Hammond

 General Shale
Page 32 of 32

monitor location, and the daily maximum source contributions from each facility from the array 

of receptor surrounding the Rome – Coosa Elementary monitor location.

CONCLUSIONS

Technical analyses were performed to help identify SO2 emission sources that contributed to 

SO2 exceedances in Rome and Savannah. These analyses included: 

1) identification of nearby SO2 sources and Q/d (emissions/distance) analysis;

2) back trajectory analysis on SO2 exceedance days, and

3) AERMOD modeling to quantify source contributions to SO2 exceedances. 

Based on these analyses, it appears that the SO2 emissions from Southern States Phosphate & 

Fertilizer caused or contributed to the SO2 NAAQS exceedances at the Savannah - E. President 

monitor; the SO2 emissions from International Paper – Savannah Mill caused or contributed to

the SO2 NAAQS exceedances at the Savannah - Lathrop & Augusta monitor; and the SO2 

emissions from International Paper – Rome Linerboard and to a lesser degree Plant Hammond 

caused or contributed to the SO2 NAAQS exceedances at the Rome - Coosa Elementary School 

monitor.