# UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION 4

Technical Support Document

For

Georgia Rule (sss) Impact Analysis

EPA’s Notice of Proposed Rulemaking For :

Air Plan Approval and Air Quality Designation; GA; Redesignation of the Atlanta,

GA, 1997 Annual Fine Particulate Matter Nonattainment Area to Attainment

November 2015

### A. BACKGROUND

The Atlanta Area attained the 1997 Annual PM 2.5 

### NAAQS in 2009. Data substitution resulted in

maximum design value estimates of 14.2 μg/m 3 

### and 13.6 μg/m 3 

### for the 3

- year periods 2007

- 2009

and 2008

- 2010, respectively. See 76 FR 56701, September 14, 2011. Rule (sss) required a

phase

- in of flu e gas desulfurizat ion (FGD) controls that started achieving SO 2 

### emission

reductions from electric generating units (EGUs) in 2009. However, this state rule has not been

approved into Georgia’s SIP . Therefore

, in January 201 5

, GA EPD provided Region 4 with an

analysis to s how that the emission reductions achieved by the rule were not necessary for the

Area to achieve attainment. In this analysis, Georgia focused on the impact of SO 2 

### reductions

because in previous analyses they have been determined to be the dominant contributor to PM 2.5 

### secondary formation in the Southeast, including the Atlanta A rea. The State determined that the

maximum impact of all SO 2 

### controls installed by 2010 on EGUs subject to Rule (sss) was a

reduction in the Atlanta Area DV of 0.6 μg/m 3 

### . Thus, for the period 2008

- 2010, the maximum

DV without Rule (sss) reductions is estimated to be 14.2 μg/m 3 

### . For the period 2007

- 2009

, the

maximum impact of the Rule (sss) reductions would be less than 0.6 μg/m 3 

### since most of the

relevant controls did not start achieving emission reductions until 2009

.

B. CAA REQUIREMENT

For redesignating a nonattainment area to attainment, the CAA requires EPA to determine that

the air quality improvement in the area is due to permanent and enforceable reductions in

emissions resulting from implementation of the SIP and applicable Federal air pollution control

regulations and other permanent and enforceable reductions (CAA section 107(d)(3)(E)(iii)).

C. EPA’S ANALYSIS OF GA EPD’S SUBMITTAL

FGD controls installed by 2010

Because GA EPD performed their impact analysis based upon the pe riod 2008

- 2010, the State

looked at the four power plants in the Atlanta Area that had FGD controls installed by the end of

2009 and thus in operation for the entire year 2010. Plant Bowen had FGD installed on Units 3

and 4 by December 31, 2008 , and on Unit 2 by June 1, 2009. Plant Hammond had FGD installed

on Units 1

- 4 by December 31, 2008. Plant Wansley had FGD installed on Unit 1 by December

31, 2008, and Unit 2 by December 31, 2009. Plant Yates had FGD installed on Unit 1 by

December 31, 2008. Th ese are summarized in T able 1 below

.

### Table 1. EGUs included in the State’s Rule (sss) sensitivity analysis ( i.e., EGUs with FGD

installed by the end of 2009)

Plant Units Control

Measure Dat e Control

Measure Was

Required by GA

Rule (sss) Date Control

M easure

Began

Operation Annual

Average SO 2



### Reductions

Achieved 2008

-

2010 (tpy)

Bowen 3, 4 ; 2 FGD 12/31/08 ; 6/1/09 10/1/08; 4/1/09 119,247

Hammond 1, 2, 3, 4 FGD 12/31/08 4/1/08 27,872

Wansley 1 ; 2 FGD 12/31/08 ;

12/31/09 10/1/08; 4/1/09 53,573

Yates 1 FGD 12/31/08 10/1/99 5,157

SO 2 

### Emission Reductions A chieved

To estimate the impact of the above FGD emission controls, GA EPD first determined the

average annual SO 2 

### reduct ions that were obtained from those controls during 2008

- 2010 ( shown

in Table 1 above )

. To do this, GA EPD determined the average tons per year of SO 2 

### emitted per

megawatt of power generated at each facility, using the years 2003

- 2007 to establish a baseline.

GA EP D multiplied this factor by the actual annual power produced during the year s 2008, 2009

and 2010 to estimate plant

- wide “uncontrolled” SO 2 

### emission s during those years. GA EPD then

subtracted the actual plant

- wide SO 2 

### emissions each year from the uncontrolled number to obtain

the tons per year of SO 2 

### reduced at each pla nt. ( See Appendix 1 for detailed calculations. )

Sensitivity of Monitors to P lant SO 2 

### E missions

To be able determine the impact of the SO 2 

### emission reductions (shown in Table 1) on the PM 2.5 

### concentrations measured by the monitors in the Atlanta Area, GA EPD needed to determine the

sensitivity of each ambient monitor to the reductions in SO 2 

### emissions from each plant. The

sensitivity would show, for each monitor, the expected annual reduction in PM 2.5 

### concentration

per quantity of SO 2 

### emissions reduced at each plant.

GA EPD used the results of existing VISTAS photochemical grid modeling 1 

### to determine the

sensitivity of PM 2.5 

### concentrations in the Atlanta A rea to the reductions in SO 2 

### emissions due to

the installation and operation of scrubbers at three large coal

- fired power plants in Georgia

(Bowen Units 1 and 2, Wansley Unit 2, and Yates Units 2

- 7), as shown in Table 2 below (the

1 The sensitivity analysis was based on the Visibility Improvement State and Tribal Association of the Southeast

(VISTAS) modeling, using the base

- year emission inventory for 2002 and the projected 2009 “future year”

emissions inventory, and CMAQ version 4.5 with the CB

- IV chemical mechanism. The methodology and

procedures used in the CMAQ modeling and calculation of PM 2.5 concentrations followed the recommendations in

EPA’s modeling guidance (EPA, Guidance on the Use of Models and Other Analyses for Demonstrating Attainmen t

of Air Quality Goals for Ozone, PM 2.5 , and Regional Haze, EPA

- 454/B

- 07

- 002, April 2007).

### “existing sensitivity analysis” 2 

### ) . Modeling for these units was used because it had already been

perform ed and, therefore, no additional modeling was necessary.

Table 2

. Power p lants for which earlier sensitivity analysis was performed ( to evaluate

EGU control strategies to be implemented in 2009 and later)

Plant Units Control

Measure Dat e Control

Measure Was

Required by GA

Rule (sss) Date Control

Measure Began

Operation

Bowen 2 ; 1 FGD 6/1/09 ; 6/1/10 4/1/09; 3/1/10

Wansley 2 FGD 12/31/09 4/1/09

Yates 2, 3, 4, 5 6,

7 Conversion to

natural gas 4/16/15 5/1/99

The State then used the results of existing previous sensitivity analysis to calculate the

“normalized sensitivity” values for the SO 2 

### emissions reductions from Rule (sss) controls

installed prior to 2010 for each facility (see Table 1 for a list of these controls, Appendix 2 for

calculations, and Table 3 for the normalized sensitivity values). The normalized sensitivity

value s represent the impact on annual PM 2.5 

### concentrations due to the amount of modeled SO 2 

### emissions reductions from each facility. Thi s analysis assumes that the EGUs included in the

earlier sensitivity analysis (i.e., Table 2 units) are representative of the EGUs that had controls

installed prior to 2010 (i.e., Table 1 units). 3 

### These normalized sensitivity values were then used

by GA EPD to calculate estimate the amount that the annual PM 2.5 

### concentration would increase

in the Atlanta Area without if Rule (sss) SO 2 

### controls were not in place. 4



### Table 3 . Normalized sensitiviti es to SO 2 

### controls at each plant

Normalized Sens itivity (ng/m 3 

### /TPD)

Plant Bowen 0.973

Plant Hammond 0.973

Plant Wansley 0.947

Plant Yates 1.308

Impact of R eductions on DV

2 This sensitivity analysis had been done for the 2010 PM 2.5 Attainment demonstration for the Atlanta Area.

3 All four units at Plant Hammond had controls installed prior to 2009, so they were not included in the earlier

sensitivity analysis. In its current analysis, GA EPD conservatively used the normalized sensitivity value from Plant

Bowen to calculate the po tential impact from Plant Hammond emissions. S ubstituting the sensitivity of Plant Bowen

for Plant Hammond is conservative because Plant Hammond is located farther away from all the Atlanta monitors

than Plant Bowen and is located in the same general direc tion from the ambient monitors as Plant Bowen.

### The maximum impact on annual PM 2.5 

### concentrations at each Atlanta PM 2.5 

### monitor due to SO 2



### emission reductions that can be attributed to Rule (sss) controls installed prior to 2010 at Plant

Bowen, Plant Hammond, Plant Wansley , and Plant Yates is calculated as shown in T able 4

below.

Table 4. Annual PM 2.5 

### impact on Atlanta monitors from SO 2 

### controls on Plant Hammond,

Plant Bowen, Plant Wansley, and Plant Yates in 2008

- 2010

SO 2 

### Emission

Reduction s

(TPY) SO 2 

### Emission

Reduction s

(TPD) Normalized

Sens itivity

(ng/m 3 

### /TPD) Annual PM 2.5



### Impact

(  g/m 3 

### )

Plant Bowen 119,246.70 326.70 0.973 0.318

Plant Hammond 27,872.21 76.36 0.973 0.074

Plant Wansley 53,573.25 146.78 0.947 0.139

Plant Yates 5,156.60 14.13 1.308 0.018

TOTAL 0.550

The maximum total impact on the PM 2.5 

### annual measurements at the Atlanta A rea PM 2.5



### monitors from the application of SO 2 

### controls from Georgia’s Rule (sss) is 0.6  g/m 3 

### (rounded

up from 0.550  g/m 3 

### ). If this this quantity is added to the measured 2008

- 2010 annual PM 2.5



### design value (13.6  g/m 3 

### ) , the result would be a design value of 14.2  g/m 3 

### , well below the 1997

annual PM 2.5 

### NAAQS of 15.0  g/m 3 

### . Therefore, removal of these controls would not have

resulted in a 2008

- 2010 annual PM 2.5 

### design value over the 1997 annual PM 2.5 

### NAAQS.

D. CONCLUSIONS AND RECOMMENDED AGEN CY ACTION

T he sensitivity analysis performed by GA EPD conservatively estimates that the maximum

potential impact of measures required by Georgia Rule (sss) by 2010 was to reduce the Area

design value by 0.55 μ g/m 3 

### . Thus, with a measured 2010 design value of 13.6  g/m 3 

### , the design

value without the Georgia Rule (sss) measures in place would have been 14.2  g/m 3



### . On the

basis of this review, EPA has concluded that the Atlanta A rea would have attained the 1997

annual PM 2.5 

### NAAQS of 15.0 μ g/m 3 

### by the same time that it did even if there had been no

emission reductions achieved from the State’s Rule (sss). Therefore, EPA recommends that lack

of federal approval of Georgia Rule (sss) have no impact on the determination of whether the air

quality i mprovement in the Atlanta Area is due to permanent and enforceable reductions in

emissions resulting from implementation of the federally SIP and applicable federal air pollution

control regulations as described in the Federal Register notice of proposed r ulemaking.

### Appendix 1

– Calculations of SO 2 

### Emission Reductions Achieved through 2010 by Rule (sss)

Plant Hammond, Controlled SO 2 emissions from in 2008

- 2010

2003 2004 2005 2006 2007 2008* 2009* 2010*

Actual SO 2 Emissions (tpy) 35,900 37,700 39,500 40,600 47,800 12,500 900 2,427

Annual Power G eneration (MW) 4.79 4.11 4.64 4.27 5.09 4.32 3.73 3.23

Annual SO 2 /Gen 7,495 9,173 8,513 9,508 9,391 2,894 241 751

AVG SO 2 /gen, 2003

- 2007 8,816

Uncontrolled SO 2 Emissions 38,085 32,883 28,475

Controlled SO 2 Emissions 25,585 31,983 26,048

Avg Controlled SO 2 Emissions, 2008

- 2010 27,872

Plant Bowen, Controlled SO 2 emissions from in 2008

- 2010

2003 2004 2005 2006 2007 2008* 2009* 2010*

Actual SO 2 Emissions (tpy) 164,900 165,900 186,500 206,400 196,800 148,100 54,800 7,618

Annual Power Generation (MW) 21.9 21.9 23.3 23.7 24 23.4 22.9 24.7

Annual SO 2 /Gen 7,530 7,575 8,004 8,709 8,200 6,329 2,393 308

AVG SO 2 /gen, 2003

- 2007 8,004

Uncontrolled SO 2 Emissions 187,285 183,283 197,690

Controlled SO 2 Emissions 39,185 128,483 190,072

Avg Controlled SO 2 Emissions, 2008

- 2010 119,247

Plant Wansley ** , Controlled SO 2 emissions in 2008

- 2010

2003 2004 2005 2006 2007 2008* 2009* 2010*

Actual SO 2 Emissions (tpy) 94,000 99,000 101,500 96200 93,900 74,300 7400 2,343

Annual Power Generation (MW) 13.7 14 15.1 14.8 16.1 15.5 11.8 9.8

Annual SO 2 /Gen 6,861 7,071 6,722 6,500 5,832 4,794 627 239

AVG SO 2 /gen, 2003

- 2007 6,597

Uncontrolled SO 2 Emissions 102,259 77,849 64,654

Controlled SO 2 Emissions 27,959 70,449 62,311

Avg Controlled SO 2 Emissions, 2008

- 2010 53,573

Plant Yates (Unit 1), Controlled SO 2 emissions in 2008

- 2010

2003 2004 2005 2006 2007 2008* 2009* 2010*

Actual SO 2 Emissions (tpy) 352 175.9 286

Uncontrolled SO 2 Emissions 7,040 3,518 5,726

Controlled SO 2 Emissions 6,688 3,342 5,440

Avg Controlled SO 2 Emissions, 2008

- 2010 5,157

Source: EPA Clean Air Markets Division

* SO 2 control, required by Georgia Rule (sss), was operational on one or more EGUs for partial or full year

. ** D oes not include emissions from facility’s gas

- fired units

.

### Appendix 2

– Summary of sensitivity analysis results for SO 2 

### emission controls

. 5



### Plant Bowen and Plan Hammond 6

Site Name TPD

reduction 7 Annual Reduction in

PM 2.5 (  g/m 3 ) Normalized annual

reduction in PM 2.5 (ng/m 3 /TPD) 8

Doraville (13

- 089

- 2001) 217.72 0.1682 0.772

E. Rivers School (13

- 121

- 0032) 217.72 0.1564 0.718

Fire Station No. 8 (13

- 121

- 0039) 217.72 0.1553 0.713

Forest Park

- Georgia DOT (13

- 063

- 0091) 217.72 0.1417 0.651

Gainesville

- Fair Street School (13

- 139

- 0003) 217.72 0.1692 0.777

Gwinnett Tech (13

- 135

- 0002) 217.72 0.1717 0.788

Kennesaw

- National Guard (13

- 067

- 0003) 217.72 0.2117 0.973

South DeKalb (13

- 089

- 0002) 217.72 0.1411 0.648

Yorkville (13

- 223

- 0003) 217.72 0.1549 0.711



### Plant Wansley

Site Name TPD

reduction Annual Reduction 1 in

PM 2.5 (  g/m 3 ) Normalized annual

reduction in PM 2.5 (ng/m 3 /TPD)

Doraville (13

- 089

- 2001) 103.88 0.0858 0.826

E. Rivers School (13

- 121

- 0032) 103.88 0.0902 0.868

Fire Station No. 8 (13

- 121

- 0039) 103.88 0.0906 0.872

Forest Park

- Georgia DOT (13

- 063

- 0091) 103.88 0.0976 0.940

Gainesville

- Fair Street School (13

- 139

- 0003) 103.88 0.0612 0.589

Gwinnett Tech (13

- 135

- 0002) 103.88 0.0714 0.687

Kennesaw

- National Guard (13

- 067

- 0003) 103.88 0.0839 0.807

South DeKalb (13

- 089

- 0002) 103.88 0.0928 0.893

Yorkville (13

- 223

- 0003) 103.88 0.0983 0.947



### Plant Yates

Site Name TPD

reduction Annual Reduction 1 in

PM 2.5 (  g/m 3 ) Normalized annual

reduction in PM 2.5 (ng/m 3 /TPD)

Doraville (13

- 089

- 2001) 137.20 0.1530 1.115

E. Rivers School (13

- 121

- 0032) 137.20 0.1673 1.220

Fire Station No. 8 (13

- 121

- 0039) 137.20 0.1680 1.224

5 Scaled relative to the observed speciated 5

- year concentrations (weighted for 2000

- 2004).

6 GA EP D did not include Plant Hammond in its earlier sensitivity analysis because all four units were already re quired to

have scrubbers installed by December 31, 2008. Since Plant Hammond is located farther away , but in the same general

direction, from all the Atlanta monitors than Plant Bowen, a conservative approach is to use the Plant Bowen SO 2 normalized

sensi tivities ( from the Kennesaw

- National Guard monitor ) to represent the impact from Plant Hammond at all the Atlanta

monitors.

7 The “Tons Per Day (TPD) Reduction” values represent the reduction of SO 2 emissions compared to pre

- controlled

emissions (assuming a 95% control efficiency for the scrubbers). The values were actually calculated from the 2009

projected emissions inventory used in the VISTAS modeling. The 2009 projected emissions for each unit modeled in the

sensitivity analysis were reduced by 95% to arrive at the “TPD reduction” values presented in the table.

8 The normalized sensitivity value in the last column in Appendix 2 is calculated by dividing the values in the “Annual

Reduction in PM 2.5 ” column by the values in the “TPD reduction” column.Forest Park

- Georgia DOT (13

- 063

- 0091) 137.20 0.1795 1.308

Gainesville

- Fair Street School (13

- 139

- 0003) 137.20 0.0988 0.720

Gwinnett Tech (13

- 135

- 0002) 137.20 0.1207 0.880

Kennesaw

- National Guard (13

- 067

- 0003) 137.20 0.1589 1.158

South DeKalb (13

- 089

- 0002) 137.20 0.1641 1.196

Yorkville (13

- 223

- 0003) 137.20 0.1579 1.151



### Map of Plant s Bowen

, Hammond, Wansley and Yates relative to the ten Atlanta PM 2.5



### monitors.