UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION IV

Technical Support Document 

EPA’s Notice of Proposed Rulemaking 

For 

Approval and Promulgation of Air Quality Implementation Plans; Georgia: 

Atlanta; Determination of Attainment of the 1997 Annual Fine Particulate 

Standards

June 2011
2

A. BACKGROUND

On July 18, 1997 (62 FR 36852), EPA established an annual fine particulate matter 

(PM2.5) national ambient air quality standards (NAAQS) at 15.0 micrograms per cubic meter 

(μg/m3) based on a 3-year average of annual mean PM2.5 concentrations. At that time, EPA also 

established a 24-hour standard of 65 μg/m3(today’s action does not address the 24-hour 

standard). See 40 CFR 50.7. On January 5, 2005 (70 FR 944), EPA published its air quality 

designations and classifications for the 1997 PM2.5 NAAQS based upon air quality monitoring 

data from those monitors for calendar years 2001–2003. These designations became effective on 

April 5, 2005. The Atlanta Area (comprised of Barrow, Bartow, Carroll, Cherokee, Clayton, 

Cobb, Coweta, DeKalb, Douglas, Fayette, Forsyth, Fulton, Gwinnett, Hall, Heard, Henry, 

Newton, Paulding, Putnam, Rockdale, Spalding and Walton Counties) was designated 

nonattainment for the 1997 PM2.5 NAAQS. See 40 CFR 81.301.

On October 17, 2006 (71 FR 61144), EPA retained the annual PM2.5 NAAQS at 15.0 

μg/m3based on a 3-year average of annual mean PM2.5 concentrations. On November 13, 2009, 

EPA clarified the designations for the NAAQS promulgated in 1997, stating that the Atlanta

Area was designated as nonattainment for the annual standard. 

B. EPA REQUIREMENTS

A nonattainment area for the 1997 PM2.5 NAAQS is determined to have attaining data 

when the design value1for the annual standard meets the requirements stipulated in 40 CFR Part 

50, section 50.13 as follows:

The annual primary and secondary PM2.5 standards are met when the annual arithmetic 

mean concentration, as determined in accordance with appendix N of this part, is less 

than or equal to 15.0 μg/m

3

.

Upon determination by EPA that an area designated nonattainment for the PM2.5 NAAQS 

has attained the standard, 40 CFR section 51.1004(c) provides that the requirement for such area 

to submit attainment demonstrations and associated reasonably available control measures, 

reasonable further progress plans, contingency measures, and other planning state 

implementation plans (SIPs) related to attainment of the PM2.5 NAAQS shall be suspended until 

the area is redesignated to attainment, at which time the requirement no longer applies. 

However, if EPA subsequently determines that the area has violated the PM2.5 NAAQS, the 

requirement to submit such plans is reinstated.

 

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Design values are the metrics that are compared to the NAAQS levels to determine attainment. The 

annual design value is calculated as the 3-year average of annual means (referred to as the “annual standard design 

value ”). (See 40 CFR part 50 Appendix N.)
3

C. EPA’S ANALYSIS OF MONITORED DATA

EPA’s determination that the Atlanta Area has attained the 1997 PM2.5 NAAQS by its 

attainment date of April 5, 2010, is based upon complete, quality assured, quality controlled and 

certified ambient air monitoring data for the 2007-2009 period, as measured by federal reference 

method, federal equivalent method, or Approved Regional Method monitors described in 40 CFR

Part 50, Appendix N. The monitors and data used to determine the 2007-2009 annual PM2.5

design value for the Atlanta Area are included in Table 1 below.

Table 1: 2007 - 2009 Annual Average PM2.5 Concentrations for Monitors in the Atlanta, 

Georgia Nonattainment Area

Location Site 

Number

2007

98th

Percentile

(μg/m3)

2008

98th

Percentile

(μg/m3)

2009

98th

Percentile

(μg/m3)

Annual 

Average 

Concentration 

(μg/m3)

Without Data 

Substitution

Annual 

Average 

Concentration 

(μg/m3)

With Data 

Substitution

Georgia DOT 13-063-

0091

15.3 13.7 11.5 13.5 N/A

GA National 

Guard

13-067-

0003

15.3 13.5 11.2 13.4 N/A

Powder 

Springs

13-067-

0004

14.5 13.1 10.3* 12.6 13.1

South Dekalb 13-089-

0002

14.8 12.7 11.4 13.0 N/A

Police Dept. 13-089-

2001

15.1 13.1 11.7 13.3 N/A

E. Rivers 

School

13-121-

0032

15.7 13.0* 11.6* 13.4 14.2

Fire Station 

#82

13-121-

0039

N/A* 7.6* 12.1 9.8 13.8

Gwinnett 

Tech

13-135-

0002

14.2 12.4* 11.6 12.7 13.3

Gainesville 13-139-

0003

13.4 11.8* 10.2 11.8 12.8

Yorkville 13-223-

0003

14.3 11.9 9.9* 12.0 12.7

*Incomplete data

 

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Fire Station #8 was relocated to the Georgia Institute of Technology’s campus in 2007 and assigned a separate Air 

Quality System (AQS) number. It moved back to Fire Station #8 at the end of 2008 and resumed normal operation. 

The annual average design value with data substitution was calculated by combining the data records for Fire Station 

#8 and the Georgia Institute of Technology. 
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EPA’s determination that the Atlanta Area is attaining the 1997 PM2.5 NAAQS is based 

upon complete, quality assured, quality controlled and certified ambient air monitoring data for 

the 2008 - 2010 period, as measured by federal reference method, federal equivalent method, or 

Approved Regional Method monitors described in 40 CFR Part 50, Appendix N. The monitors 

and data used to determine the 2008 - 2010 annual PM2.5 design value for the Atlanta Area are 

included in Table 2 below.

Table 2: 2008 - 2010 Annual Average PM2.5 Concentrations for Monitors in the Atlanta, 

Georgia Nonattainment Area

Location Site 

Number

2008

98th

Percentile

2009

98th

Percentile

2010

98th

Percentile

Annual 

Average 

Concentration 

(μg/m3)

Without Data 

Substitution

Annual 

Average 

Concentration 

(μg/m3)

With Data 

Substitution

Georgia 

DOT

13-063-

0091

13.7 11.5 13.4 12.9 N/A

GA 

National 

Guard

13-067-

0003

13.5 11.2 12.2 12.3 N/A

Powder 

Springs

13-067-

0004

13.1 12.1* 10.3 11.9 12.3

South 

Dekalb

13-089-

0002

12.7 11.4 12.3 12.1 N/A

Police 

Dept.

13-089-

2001

13.1 11.7 12.2 12.3 N/A

E. Rivers 

School

13-121-

0032

13.0* 11.6* 12.2 12.3 13.0

Fire 

Station #83

13-121-

0039

7.6* 12.1 14.5 11.4 13.6

Gwinnett 

Tech

13-135-

0002

12.4 11.6* 12.3 12.1 12.5

Gainesville 13-139-

0003

11.8* 10.2 11.4 11.2 11.9

Yorkville 13-223-

0003

11.9 9.9* 11.2 11.0 11.6

*Incomplete data

 

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Fire Station #8 was relocated to the Georgia Institute of Technology campus in 2007 and assigned a separate AQS 

number. It moved back to Fire Station #8 at the end of 2008 and resumed normal operation. The annual average 

design value with data substitution was calculated by combining the data records for Fire Station #8 and the Georgia 

Institute of Technology. 
5

Current regulations require a statistical analysis be performed on sites where data are 

determined incomplete. This analysis attempts to qualitatively determine whether, under certain 

circumstances, the data can be considered in attainment of a particular NAAQS. 40 CFR Part 50 

Appendix N and the April 1999 document, Guideline on Data Handling Conventions for the PM 

NAAQS, describe the process for PM2.5. EPA performed a quarterly maximum data substitution 

test described in the Guideline on Data Handling Conventions for the PM NAAQS document. 

EPA Region 4 requested EPA’s Office of Air Quality Planning and Standards (OAQPS) to 

conduct a bootstrap statistical analysis on two of the sites in the metropolitan statistical area: E. 

Rivers School and Fire Station #8. At the E. Rivers School site, the roof had to be replaced 

which caused portions of two calendar quarters to be affected by low data completeness. The 

Fire Station #8 site was not operating for one of the years of this design value period (2008) as 

the monitor had to be relocated due to local influences. Even though there were legitimate 

reasons for each of these situations, EPA wanted to have a higher confidence that these sites 

would still show attainment through this analysis. Also, while this particular analysis is still 

considered in draft form, it is being used as weight of evidence.

The Powder Springs monitor (13-067-0004) in Cobb County has a 2007 - 2009, PM2.5

annual design value of 12.6 μg/m3and a current 2008 - 2010, PM2.5 annual design value of 11.9

μg/m3. Since the monitor had one incomplete quarter during the 2nd quarter of 2009, data 

substitution was conducted. A maximum quarterly value of 30.3 μg/m3was obtained from the 

second quarter of 2008. This value was substituted in for all missing data in the second quarter of 

2009. The annual means were recalculated, and the resulting annual design values are 13.1 μg/m3

and 12.3 μg/m3, respectively. This monitor is considered attaining and no further evaluation is 

necessary.

The E. Rivers School monitor (13-121-0032) in Fulton County was shutdown in the 

summer of 2009 due to renovation of the school’s roof. Because the renovation was beyond 

Georgia Environmental Protection Division’s (EPD) control, EPA Region 4 does not hold the 

state responsible for the lack of data during that time. However, the fourth quarter in 2008 is also 

incomplete. The 2007 - 2009 PM2.5 annual design value is 13.4 μg/m3and the current 2008 -

2010 PM2.5 annual design value is 12.3 μg/m3. Since the fourth quarter of 2008 is considered 

incomplete, data substitution was conducted. A maximum quarterly value of 39.9 μg/m3 was 

obtained from the fourth quarter of 2008. This value was substituted in for all missing data in the 

fourth quarter of 2008. The annual means were recalculated, and the resulting annual design 

values were 14.2 μg/m3for 2007 - 2009 and 13.0 μg/m3for 2008 - 2010. This monitor is 

considered attaining.

OAQPS conducted an additional statistical analysis for the E. Rivers School monitor 

which indicates, as a weight of evidence, that despite the prolonged shut-down, the monitor 

would have attained the 1997 annual PM2.5 NAAQS in the 2007 - 2009 design value period. To 

evaluate air quality at the E. Rivers School monitor, EPA applied statistical analysis using data 

from other sites in the Area. The approach is appropriate for this Area but may or may not be 

suitable for other areas with less than complete data. EPA will evaluate the appropriateness of 

this analytical approach on a case-by-case basis for determinations regarding each area with less 

than complete data.
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The first step in the analysis was to assess the correlation of concentrations at the E. 

Rivers School monitor with concentrations at other sites in the Area (Table 3). The monitor in 

the Area that had the highest correlation with the E. Rivers School monitor was the Georgia 

Department of Transportation (DOT) monitor (13-063-0091); therefore, subsequent analyses 

used data from this site. The second step was to develop a regression equation expressing the 

relationship between concentrations at the E. Rivers School and the Georgia DOT monitors

(Figure 1). This regression equation was used to estimate values at the E. Rivers School monitor

on days during quarters with incomplete data. A 2007 - 2009 design value for the E. Rivers 

School monitor was then calculated using these estimated values (Table 4). Under this method, 

the 2007 - 2009 design value for the E. Rivers School monitor was estimated to be 13.6 μg/m3. 

Table 3: Atlanta 2007-2009 Design Valuess, Data Capture, and Correlation with Site A 

(13-121-0032)

Figure 1: Concentrations at E. Rivers School (site 13-121-0032, labeled “v_a”) compared to 

concentrations at Georgia DOT (site 13-063-0091, labeled “v_b”)
7

v_a

0

10

20

30

40

50

60

v_b

0 10 20 30 40 50 60 70

Table 4: Imputation and Resulting Data Capture and Design Value Recalculation with Site 

A (13-121-0032)

This estimated design value was then analyzed using a statistical method, referred to as 

the “bootstrap method,” that involves the use of regression residuals. In this analysis, EPA 

repeated the regression analysis 1,000 times with different values within the probability 

distribution of E. Rivers School concentrations that could be associated with given 

concentrations at the Georgia DOT monitor (Table 5). From this analysis, EPA determined that 

the upper end of the range of potential 2007 - 2009 design values obtained did not exceed the 
8

NAAQS. No exceedances of the NAAQS resulted from application of the statistical analysis. 

Therefore, EPA concluded that for 2007 - 2009, the annual average concentration of the E. 

Rivers School monitor is below the NAAQS. 

Table 5: Bootstrapping Residuals (and Design Value Recalculations) with Site A (13-121-

0032)

The Fire Station #8 monitor (13-121-0039) was relocated for a few years to a building on 

the Georgia Institute of Technology’s campus and assigned a separate AQS identifier. It was 

moved back to the Fire Station at the end of 2008 and resumed normal operation. There were no 

data completeness issues at either site during the times each site operated. EPA Region 4 is 

combining the data record of these two sites which results in a complete data record for the 2007

- 2009 and 2008 - 2010 design value periods. The resulting design values are 13.8μg/m3and 13.6

μg/m3, respectively. 

OAQPS also conducted the additional statistical analysis for the Fire Station #8 monitor. 

The analysis indicates, as a weight of evidence, that despite the prolonged move, the monitor 

would have attained in the 2007 – 2009 design value period. To evaluate air quality at the Fire 

Station #8 monitor, EPA applied statistical analysis using data from other sites in the Area. The 

approach is appropriate for this Area but may or may not be suitable for other areas with less than 

complete data. 

The first step in the analysis was to assess the correlation of concentrations at the Fire 

Station #8 monitor with concentrations at other sites in the Area (Table 6). The monitor in the 

Area that had the highest correlation with the Fire Station #8 monitor was the South Dekalb

monitor (13-089-0002); therefore, subsequent analyses used data from this site. The second step 

was to develop a regression equation expressing the relationship between concentrations at the 

Fire Station #8 monitor and the South Dekalb monitor (Figure 2). This regression equation was 

used to estimate values at the Fire Station #8 monitor on days during quarters with incomplete

data when the monitor did not measure concentrations because the site was no longer operating. 

A 2007 - 2009 design value for the Fire Station #8 monitor was then calculated using these 

estimated values (Table 7). Under this method, the 2007 - 2009 design value for the Fire Station 

#8 monitor was estimated to be 14.1 μg/m3. 
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Table 6: Atlanta 2007-2009 Design Values, Data Capture, and Correlation with Site A (13-

121-0039)

Figure 2: Concentrations at Fire Station #8 (site 13-121-0039, labeled “v_a”) Compared to 

Concentrations at South Dekalb (site , labeled “v_b”)

v_a

0

10

20

30

40

v_b

0 10 20 30 40
10

Table 7: Imputation and Resulting Data Capture and Design Value Recalculation with Site 

A (13-121-0039)

This estimated design value was then analyzed using the bootstrap method. In this 

analysis, EPA repeated the regression analysis 1,000 times with different values within the 

probability distribution of Fire Station #8 concentrations that could be associated with given 

concentrations at the South Dekalb monitor (Table 8). From this analysis, EPA determined that 

the upper end of the range of potential 2007 - 2009 design values obtained did not exceed the 

NAAQS. No exceedances of the NAAQS resulted from application of the statistical analysis. 

Therefore, EPA concluded that for 2007 – 2009, the annual average concentration of the Fire 

Station #8 monitor is below the NAAQS. 

Table 8: Bootstrapping Residuals (and Design Value Recalculations) with Site A (13-121-

0039)

The Gwinnett Technical School monitor (13-135-0002) has a 2007 - 2009 PM2.5 annual 

design value of 12.7 μg/m3and a current 2008 - 2010 PM2.5 annual design value of 12.1 μg/m3. 

Since the monitor had one incomplete quarter during fourth quarter 2008, data substitution was 

conducted. For the 2007 - 2009 design value period, a maximum quarterly value of 30.3 μg/m3

was obtained from the fourth quarter of 2007. This value was substituted in for all missing data 

in the fourth quarter of 2008 for the 2007 - 2009 design value calculation. For the 2008 - 2010 

design value period, a maximum quarterly value of 24.7 μg/m3 was obtained from the fourth 

quarter of 2010. This value was substituted in for all missing data in the fourth quarter of 2008
11

for the 2008 - 2010 design value calculation. The annual means were recalculated, and the 

resulting annual design values are 13.3 μg/m3and 12.5 μg/m3, respectively. This monitor is 

considered attaining and no further evaluation is necessary.

The Gainesville monitor (13-139-0003) has a 2007 - 2009 PM2.5 annual design value of 

11.8 μg/m3and a current 2008 - 2010 PM2.5 annual design value of 11.2 μg/m3. Since the 

monitor had two incomplete quarters during third and fourth quarters of 2008, data substitution 

was conducted. For the 2007 - 2009 design value period, maximum quarterly values of 33.5

μg/m3and 29.2 μg/m3 were obtained from the third and fourth quarters of 2007, respectively, for 

the 2007 - 2009 design value calculation. These values were substituted in for all missing data in 

the third and fourth quarters of 2008. The annual mean was recalculated, and the resulting annual 

design value was 12.8 μg/m3. For the 2008 - 2010 design value period, maximum quarterly 

values of 32.3 μg/m3and 19.8 μg/m3 were obtained from the third and fourth quarters of 2008 for 

the 2008 - 2010 design value calculation. These values were substituted in for all missing data in 

the third and fourth quarters of 2008, respectively. The annual mean was recalculated, and the 

resulting annual design value was 11.9 μg/m3. This monitor is considered attaining and no 

further evaluation is necessary.

The Yorkville monitor (13-223-0003) has a 2007 - 2009 PM2.5 annual design value of 

12.0 μg/m3and a current 2008 - 2010 PM2.5 annual design value of 11.0 μg/m3. Since the 

monitor had one incomplete quarter during the third quarter of 2009, data substitution was 

conducted. A maximum quarterly value of 36.6 μg/m3 was obtained from the third quarter of 

2008. This value was substituted in for all missing data in the third quarter of 2009. The annual 

means were recalculated, and the resulting annual design values are 12.7 μg/m3and 11.6 μg/m3, 

respectively. This monitor is considered attaining and no further evaluation is necessary.

The monitors in the Atlanta Area that collected complete data for 2007 - 2009 and 2008 –

2010 have average concentrations that are all consistent with attainment of the 1997 annual 

PM2.5 NAAQS. Determinations of attainment are based on three years of complete, qualityassured data. Nevertheless, any such assessment should consider additional quality-assured data, 

to the extent that quality-assured data exist. In accordance with Appendix N and standard EPA 

practice, the review of data is based on the three most recent years of complete data. Appendix 

N does not provide for examining partial years of data, because various seasons of the year 

reflect various influences on PM2.5 concentrations, and a partial year’s data may not be 

representative of values that would be determined from a full year’s data set. On the basis of this 

review, EPA has concluded that this Area has met the 1997 PM2.5 NAAQS by its April 5, 2010,

attainment date using 2007 – 2009 data and continues to meet the 1997 PM2.5 NAAQS using 

2008 – 2010 data. 

D. CONCLUSIONS AND RECOMMENDED AGENCY ACTION

Quality assured, quality controlled, and certified ambient air monitoring data for 2007 -

2009 show that the design value for the Atlanta PM2.5 nonattainment Area is below 15.0 μg/m3. 

Because this value is less than or equal the 1997 annual PM2.5 NAAQS of 15 μg/m3, the Area has 

attained the 1997 annual PM2.5 standard by April 5, 2010 for this NAAQS. 

Quality assured, quality controlled, and certified ambient air monitoring data for 2008 -
12

2010 show that the design value for the Atlanta PM2.5 nonattainment Area is below 15.0 μg/m3. 

Because this value is less than or equal the 1997 annual PM2.5 NAAQS of 15 μg/m3, the Area has 

monitored continued attainment for this NAAQS.