Emissions inventory development for base year and future years for 

the Atlanta PM2.5 Nonattainment Area

Direct PM2.5 emissions and PM2.5 precursor emissions (SO2 and NOx) as defined in the Clean Air 

Fine Particle Implementation Rule (72 FR 20586) were developed for base year 2008 and future years 

2017 and 2024. Most of the 2008 base year emission inventory was obtained from the National 

Emissions Inventory 2008 version 1.5 (NEI2008, http://www.epa.gov/ttnchie1/net/2008inventory.html). 

The base year and future year emissions were prepared for seven source categories separately using 

different methods. These seven source categories include: 

 EGU point sources

 Non-EGU point sources

 Area sources

 Fires

 Nonroad mobile sources

 Nonroad mobile sources - Marine, aircraft and railroad

 Onroad mobile sources

The Atlanta PM2.5 nonattainment area covers twenty-two counties, including twenty whole counties 

and two partial nonattainment counties. Portions of Heard County and Putnam County were included in 

the nonattainment area in order to include two large EGU sources (Plant Wansley and Plant Branch). All 

point sources located in the nonattainment area were included in the calculation. Emissions from area, 

fire, nonroad and onroad mobile sources were calculated first for the whole counties, as documented 

below. Then, the total emissions in the two partial counties were multiplied by the human population 

fraction in the nonattainment part of the two counties to calculate the emissions in the partial 

nonattainment area.

EGU Point Sources

Process-level emissions estimates for six EGU facilities in Atlanta PM2.5 nonattainment area during 

2008 were obtained from NEI2008 version 1.5. Such emissions were projected to year 2017 and 2024 

using corresponding growth and control factors. Different growth factors were calculated for different 

SCC based on fuel consumption projections for the Southeastern region in AEO2010 (Table 1).

Flue Gas Desulfurization (FGD) for control of SO2 was applied to individual units according to the 

schedule specified in Georgia’s Rule 391-3-1-.02 (2) (sss) with adjustments for units that started 

operation ahead of the required schedule. The dates of initial FGD operation required by the rule for the 

EGUs inside the nonattainment area range from December 31, 2008, through June 1, 2015. Bowen Units 

3 and 4 actually began FGD operation on May 1 and December 1, respectively, of 2008. Wansley 1 

started FGD operation on December 1 of 2008. Yates 1 started FGD operation prior to 2008. Selective 

Catalytic Reduction (SCR) for control of NOx was applied to individual units according to the schedule 

specified in Georgia’s Rule 391-3-1-.02 (2) (sss) with adjustments for units that started operation ahead of 

the required schedule. The dates of initial SCR operation required by the rule for the EGUs inside the 

nonattainment area range from December 31, 2008, through June 1, 2015. Units at Bowen actually began 

ozone-season SCR operation prior to 2008. Please refer to Appendix C-1 for detailed EGU control 

schedules.

Table 1. Growth factors by SCCs for EGU sources

SCC Fuel Type 2017 2024

20100101 Distillate Fuel Oil 1.352 1.447
10100501 Distillate Fuel Oil 1.352 1.447

20100201 Natural Gas 0.892 1.060

10100604 Natural Gas 0.892 1.060

10100212 Steam Coal 1.058 1.099

The control factors varied with pollutants. The SO2 control factor associated with Flue Gas 

Desulfurization (FGD) was assumed to be 95% according to VISTAS 2012 Projection Emissions 

Inventory. The NOx control factor associated with Selective Catalytic Reduction (SCR) was assumed to 

be 82.5% according to VISTAS 2012 Projection Emissions Inventory. The PM2.5 control factor 

associated with FGD was assumed to be 50% according to Table 5.4-1 on page 5.4-24 of the EPA 

document "Stationary Source Control Techniques Document for Fine Particulate Matter" (EC/R 

Incorporated, 1998). When FGD or SCR controls were already operated fully or partially at a unit during 

year 2008, the control factors were only applied to uncontrolled emissions in 2008. These periods were 

identified using CAMD hourly CEM data for NOx and SO2 emissions and heat inputs. Days without 

control operation were identified as those days on which the ratio of NOx or SO2 emissions to heat input 

exceeded 0.00004 lbs/mmBtu according to correlation analysis results. In addition, NOx emissions 

during the period from October 1st, 2008, to December 31st, 2008 from Plant Bowen Unit 3 were 

projected to future years using a different method, since the actual NOx control efficiency in this period 

was approximately 60% according to hourly CEM data analysis. Such NOx emissions were first adjusted 

to reflect before control emissions, and then apply the 82.5% NOx emissions control factor for future year 

emissions projection.

Future year emissions for Plant McDonough-Atkinson located in Cobb County were calculated 

separately since this plant will undergo significant changes in generating equipment and operation during 

the attainment demonstration period. In 2008, Plant McDonough operated two coal-fired EGU’s (Units 1 

and 2) with a combined generating capacity of 530 MW. Due to the requirements specified in Georgia’s 

Rule 391-3-1-.02 (2) (sss) for EGU controls, Georgia Power plans to shut down Unit 2 by the 4th quarter 

of 2011 and Unit 1 by the 2nd quarter of 2012. Unit 2 will be replaced with two gas-fired combined cycle 

blocks (Blocks 4 and 5) and Unit 1 will be replaced by one gas-fired combined cycle block (Block 6). 

Each block consists of two generating units, with each unit consisting of a combustion turbine and a duct 

burner. The combined generation capacity of the three blocks (six units) is 840 MW. Two of the six 

combustion turbines are permitted to burn distillate oil (0.0015 % sulfur) up to 1000 hours/year each. 

NOx emissions from each unit will be controlled by a SCR and a low-NOx burner.

The facility’s Title V permit (Permit No. 4911-067-0003-V-03-0) stipulates rolling 12-month limits 

on NOx emissions from each of the three gas-fired generating blocks. In addition, short-term average 

NOx emissions rates (in ppmvd) are stipulated for both the ozone and non-ozone seasons. The 12-month 

per block NOx limits for Blocks 4 and 5 are 217 tons NOx. The limit for Block 6 is 200 tons NOx. The 

permitted NOx emission rates are 6.0 ppmvd for May through September and 15.0 ppmvd for the rest of 

the year.

Forecasts of NOx emissions from McDonough’s Blocks 4, 5, and 6 were calculated by assuming that 

actual rolling 12-month emissions will be 75 percent of the permitted limits. Since natural gas has 

historically been more expensive than coal, it was assumed that the duration of operation for these gasfired units will not push NOx emissions beyond 75 percent of their twelve-month permit caps. It was also 

assumed that the two affected combustion turbines would burn oil for 500 hours per year each. Growth 

factors were calculated for McDonough-Atkinson using the same fuel consumption approach that is 

described above, subject to the constraint that annual emissions cannot rise above the permitted 12-month 

limits.
SO2, NOx and PM2.5 emissions during 2008, 2017 and 2024 were summarized by each EGU facility 

(Table 2).

Table 2. Emissions by EGU facilities in 2008, 2017 and 2024

FacilitySiteName AIRSID 2008 2017 2024

SO2 NOX PM25 SO2 NOX PM25 SO2 NOX PM25

Chattahoochee Energy 

Facility 14900006 5 97 89 4 86 79 5 103 94

Ga Power Company - Plant 

Bowen 01500011 149,015 25,360 2,003 8,781 7,763 1,219 9,123 8,066 1,267

Ga Power Company - Plant 

Branch 23700008 93,982 20,194 445 4,972 3,740 236 5,166 3,885 245

Ga Power Company - Plant 

McDonough/Atkinson 06700003 24,330 3,489 202 25 451 283 29 536 336

Ga Power Company - Plant 

Wansley 14900001 74,956 14,625 1,866 4,086 4,116 1,069 4,246 4,299 1,119

Ga Power Company - Plant 

Yates 07700001 68,208 12,413 333 30,648 6,557 285 31,844 6,813 297

Total 410,496 76,177 4,937 48,517 22,713 3,171 50,414 23,702 3,358

Non-EGU Point Sources

Emissions estimates for non-EGU point sources in 2008 were obtained from NEI2008 version 1.5. 

Emissions in future years 2017 and 2024 were estimated using SCC- and county-specific growth factors 

generated with the USEPA’s Economic Growth Analysis System version 5.0 (EGAS 5.0) with "Default 

REMI 6.0 SCC Configuration". Appendix C-2 contains a summary of the SCC-specific growth factors 

for Atlanta PM2.5 nonattainment area. Appendix C-3 contains a list of non-EGU point sources in Atlanta 

PM2.5 nonattainment area and facility-specific SO2, NOx, and PM2.5 emissions for 2008, 2017, and 

2024. These emissions are not subject to additional controls in the future years 2017 and 2024.

Area Sources

Emissions from area sources in 2008 were obtained from NEI2008 version 1.5. Emissions in future years 

2017 and 2024 were estimated using SCC- and county-specific growth factors generated with the 

USEPA’s Economic Growth Analysis System version 5.0 (EGAS 5.0) with "Default REMI 6.0 SCC 

Configuration". Appendix C-2 contains a summary of the SCC-specific growth factors for Atlanta PM2.5 

nonattainment area. These emissions are not subject to additional controls in the future years 2017 and 

2024. Appendix C-3 contains SCC-specific SO2, NOx, and PM2.5 emissions for 2008, 2017, and 2024.

Fires

Emissions from fires in 2008 were obtained from NEI2008 version 1.5. These estimates were 

provided by Georgia Environmental Protection Division as part of AERR2008 submission (Georgia Air 

Protection Branch, 2011). This inventory was developed using 2008 burned area data and burning permit 

data provided by Georgia Forestry Commission and the same method as used for the VISTAS2002 fire 

inventory (www.epa.gov/ttnchie1/conference/ei13/rpo/barnard_pres.pdf). Emissions in future years 2017 

and 2024 were assumed to be the same as base year 2008. Appendix C-3 contains SO2, NOx, and PM2.5 

emissions summary by fire types and county in Atlanta PM2.5 nonattainment area for 2008, 2017, and 

2024.

Nonroad Mobile Sources – NONROAD Model Category

Emissions from NONROAD model source categories in 2008, 2017 and 2024 were calculated using 

NMIM2008, which incorporates EPA’s latest NONROAD model (NONROAD2008) released in April 

2009, and reflects all of EPA’s final nonroad standards to date. The runs for 2017 and 2024 have used the 
same 2008 meteorological inputs. Defaults in NMIM 2008 were used for all runs. Appendix C-3 contains 

SCC-specific SO2, NOx, and PM2.5 emissions for 2008, 2017, and 2024. For detailed run scripts and 

output databases, please refer to Appendix C-4.

Nonroad Mobile Sources – Marine, Aircraft, and Locomotives

Emissions from aircrafts and locomotives in 2008 were obtained from NEI2008 version 1.5 

(http://www.epa.gov/ttnchie1/net/2008inventory.html). Emissions from yard locomotives were not 

included in the NEI2008, and were obtained from Eastern Regional Technical Advisory Committee 

(ERTAC) separately. There were no emissions from commercial marine vessels in the Atlanta PM2.5 

nonattainment area.

Growth and control factors that were used to develop future year emissions were provided by Pechan. 

For more information regarding the SEMAP marine, aircraft, and locomotives growth and control factors, 

please refer to Appendix C-5 (Pechan, 2011).

Growth factors for all aircraft engine and airport-related SCCs were based on landing and take-off 

operation (LTO) projections available from the Federal Aviation Administration’s Terminal Area 

Forecasts (TAF) (FAA, 2010). Growth rates for military aircraft were held constant at 2008 levels. No 

control factors have been applied to aircraft for criteria pollutant forecasts. 

Growth factors for Class I and Class II/III line haul and diesel switchyard operations were calculated 

based on freight rail sector fuel consumption forecasts. Growth factors for passenger and commuter rail 

were developed from national forecasts of intercity rail diesel consumption, and commuter rail diesel 

consumption. Control factors were based on US EPA’s locomotive engine RIA and associated emission 

factor guidance.

The SEMAP growth factors were for base year 2007 (referred as hereafter). The growth 

factors for base year 2008 were calculated as assuming the linear growth. 

refers to the number of years between base year 2007 to future years.

Appendix C-6 contains a list of specific aircraft and locomotives sources in Atlanta PM2.5 

nonattainment area and SCC-specific SO2, NOx, and PM2.5 emissions for 2008, 2017, and 2024 and the 

associated growth or control factors.

Onroad Mobile

SO2, NOx and PM2.5 emissions from onroad mobile sources in 2008 and 2024 were developed by 

Atlanta Regional Commission using MOVES2010a. MOVES was run separately for two groups of 

twenty nonattainment counties in Atlanta in inventory mode. The two groups of counties has different 

I/M program and they are the Atlanta 13 county area and the Atlanta 7 county area. Average 2008 annual 

daily meteorological inputs were used. Best available local data were used for MOVES inputs such as 

vehicle population, vehicle miles traveled (VMT) by source types, road type distribution, speed 

distributions, ramp fractions, hourly VMT fractions and age distribution. Since there is no public road in 

the nonattainment part of Heard County, MOVES was not run Heard County. MOVES was run for whole 

Putnam County, and the emissions in the partial nonattainment area were calculated using human 

population fraction. Local vehicle population and VMT were used Putnam County. Please refer to the 

document “MOVES-Based Mobile Source Emissions Modeling for the Atlanta Nonattainment Area” 

provided by the Atlanta Regional Commission in Appendix C-7 for more detailed information.
Partial County Fractions for Calculation of Partial County Emissions

The partial county fractions were calculated as the ratio of human populations in the nonattainment 

part to the total populations of Heard County or Putnam County. The human population in the 

nonattainment part of a county was estimated as the total of human population in census blocks whose 

geographical centroids fall inside the nonattainment area boundary. According to 2010 Census data, the 

human population in the nonattainment part of Heard County was 0 and the total population in Heard 

County was 11,834. Therefore, the partial county fraction for Heard County is 0/11,834 = 0. For Putnam 

County, the human population in the nonattainment part is 3484 and the total population is 21,218. The 

corresponding partial county fraction for Putnam County is therefore 3484/21,218 = 16.42%.

QA/QC

Detailed QA/QC efforts for nonpoint sources were documented in Georgia Air Protection Branch 

2011 Quality Assurance Project Plan (Georgia Air Protection Branch, 2011). Point sources emissions 

have gone through QA check in EPA EIS system. Onroad mobile source emissions were provided by 

Atlanta Regional Commission, and were reviewed by running MOVES independently at Georgia Air 

Protection Branch. All MOVES input files have been carefully checked.

Reference

EC/R Incorporated, 1998, Stationary Source Control Techniques Document for Fine Particulate Matter, 

obtained from http://www.epa.gov/ttncatc1/dir1/finepmtech.pdf , accessed on 1/19/2011.

E.H. Pechan & Associates, Inc. 2011. Growth and Control Factor Development for Aircraft, Commercial 

Marine Vessels, and Locomotives

EPA, 2010. U.S. Environmental Protection Agency, EGAS Version 5.0, available for download from 

http://www.epa.gov/ttnecas1/egas5.htm, accessed March 2010.

Georgia Air protection Branch, 2011, Quality assurance project plan for 2008 emission inventories for 

sources other than large industrial stationary point sources