## 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 th e 1997 Annual Fine Particulate
Standards

June 20112

A. BACKGROUND

On July 18, 1997 (62 FR 36852), EPA established an annual fine particulate matter ( PM 2.5 ) national ambient air quality standards ( NAAQS ) at 15.0 micrograms per cubic meter ( μg/m 3 ) based on a 3

- year average of annual mean PM 2.5 concentrations. At that time, EPA also
established a 24

- hour standard of 65 μg/m 3 (today’s action does not address the 24

- hour standard). See 40 CFR 50.7. On January 5, 2005 (70 FR 944), EPA publishe d its air quality designations and classifications for the 1997 PM 2.5 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 Barr ow, 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 PM 2.5 NAAQS. See 40 CFR 81. 3 01.
On October 17, 2006 (71 FR 61144), EPA retained the annual PM 2.5 NAAQS at 15.0 μg/m 3 based on a 3

- year average of annual mean PM 2.5 concentrations . On November 13, 2009, EPA clarified the designations for the NAAQS promulgated in 1997, statin g that the Atlanta Area was designated as nonattainment for the annual standard.

B. EPA REQUIREMENTS

A nonattainment area for the 1997 PM 2.5 NAAQS is determined to have attaining data
when the design value 1 for the annual standard meet s the requireme nts s tipulated in 40 CFR P art 50, section 50. 13 as follows:

The annual primary and secondary PM 2.5 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 t hat an area designated nonattainment for the PM 2.5 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 availab le control measures, reasonable further progress plans, contingency measures, and other planning state implementation plans ( SIPs ) related to attainment of the PM 2.5 NAAQS shall b e suspended until the area is redesignated to attainment, at which time the r equirement no lon ger appl ies.

However

, if EPA subsequently determines that the area has violated the PM 2.5 N AAQS, the requirement to submit such plans is reinstated.

1 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 (referre d 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 A rea has att ained the 1997 PM 2.5 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 200 7

- 200 9 period, as measured by f ederal reference method, f ederal 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 PM 2.5 design value for the Atlanta A rea are includ ed in T able 1 below.

Table 1: 2007

- 2009 Annual Average PM 2.5 Concentrations for Monitors in the Atlanta,

Georgia Nonattainment Area

Location Site

Number 2007

98 th

P ercentile (μg/m 3 ) 2008

98 th

P ercentile (μg/m 3 ) 2009

98 th

P ercentile (μg/m 3 ) Annual

Average
Concentration (μg/m 3 )
Without Data
Substitution Annual

Average
Concentration (μg/m 3 )
With Data
Substitution Georgia DOT 13

- 063

-

0091 15.3 13.7 11.5 13.5 N/A

GA National
Gu ard 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
#8 2 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

2 Fire Station #8 was relocated to the Georgia Institute of Tech nology’s campus in 2007 and assigned a separate A ir Q uality S ystem (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

.4

EPA’s determination that the Atlanta Area is attaining the 1997 PM 2.5 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, f ederal equivalent method, or Approved Regiona l Method monitors described in 40 CFR Part 50, Appendix N. The monitors
and data used to determine the 2008

- 2010 annual PM 2.5 design value for the Atlanta Area are
included in Table 2 below.

Table 2: 2008

- 2010 Annual Average PM 2.5 Concentrations fo r Monitors in the Atlanta,

Georgia Nonattainment Area

Location Site

Number 2008

98 th

P ercentile 2009

98 th

P ercentile 2010

98 th

P ercentile Annual

Average
Concentration (μg/m 3 )
Without Data
Substitution Annual

Average
Concentration (μg/m 3 )
With Data
Substit ution 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 1 2.3 N/A

E. Rivers
School 13

- 121

-

0032 13.0 * 11.6 * 12.2 12.3 13.0

Fire
Station #8 3 13

- 121

-

0039 7.6 * 12.1 14.5 11.4 13.6

Gwinnett
Tech 13

- 135

-

0002 12.4 1 1.6 * 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

3 Fire Station #8 was relocated to the G eorgia Institute of Tech nology 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 dat a records for Fire Station #8 and the Georgia
Institute of Tech nology

.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 consi dered 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 PM 2.5 . 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 200 7

- 200 9, PM 2.5 annual design value of 12.6 μ g/m 3 and a curren t 2008

- 2010

, PM 2.5 annual design value of 11.9

μ g/m 3

. Since the monitor had one incomplete quarter during the 2 nd quarter of 2009, data substitution was conducted. A maximum quarterly value of 30.3 μ g/m 3 w as obtained from the second quarter of 2008. Thi s value was substituted in for all missing data in the second quarter of
2009. The annual mean s w ere recalculated, and the resulting annual design value s are 13.1 μ g/m 3
and 12.3 μ g/m 3 , respectively . This monitor is considered attaining and no further evalu ation 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 Regi on 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 200 7

- 200 9 PM 2.5 annual design value is 13.4 μ g/m 3 and the current 2008

- 2010 PM 2.5 annual design value is 12.3 μ g /m 3 . Since the fourth quarter of 2008 is considered incomplete, data substitution was conducted. A maximum quarterly value of 39.9 μ g/m 3 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 mean s w ere recalculated, and the resulting annual design
value s w ere 14.2 μ g/m 3 for 2007

- 2009 and 13.0 μ g/m 3 for 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 PM 2.5 NAAQS in the 2007

- 2009 design value period. To evaluate air quality at the E. Rivers School monitor, EP A applied statistical analysis using data
from other sites in the A rea. The approach is appropriate for this Area but may or m ay not be
suitable for other areas with less than complete data. EPA will evaluate the appropriateness of this analytical approac h on a case

- by

- case basis for determinations regarding each area with less than complete data

.6

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 (T able 3)

. The monitor in
the A rea that had the highest correlation with the E. Rivers School monitor was the Georgia

D epartment 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 monitor s (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 the se estimated values (Table 4)

. Under this method,
the 20 07

- 20 09 design value for the E. Rivers School monitor was estimated to be 13.6 μg/m 3

.

Table 3: Atlanta 2007

- 2009 D esign V alues s, Data Capture, and Correlation with Site A

( 13

- 121

- 0032 )

Figure 1: Concentrations at E. Rivers School (site 13

- 121

- 00 32 , labeled “v_a”) compared to

concentrations at Georgia DOT (site 13

- 063

- 0091, labeled “v_b”)7

Table 4 : Imputation and Resulting Data Capture and D esign V alue Recalculation with Site

A ( 13

- 121

- 003 2 )

This estimated design value was then analyzed using a statistical method , referred to as the “bootstrap method,” that involve s the use of regression residuals . In this analysis, EPA
repeat ed 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 mo nitor (Table 5)

. From this analysis, EPA determined that the upper end of the range of potential 2007

- 2009 design values obtained did not exceed the8

NAAQS. No exceedances of the NAAQS result ed from application of the statistical analysis. Therefore, E PA concluded that for 2007

- 2009, the annual average concentration of the E. Rivers School monitor is below the NAAQS.

Table 5 : Bootstrapping Residuals (and D esign V alue Recalculations) with Site A ( 13

- 121

-

003 2 )

The Fire Station #8 monitor (13

- 121

- 0 039) was relocated for a few years to a building on the Georgia Institute of T ech nology’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 c omplete data record for the 2007

- 200 9 and 2008

- 2010 design value period s . The resulting design value s are 13. 8μ g/m 3 and 13.6

μ g/m 3 , 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

– 2 009 design value period. To evaluate air quality at the Fire
Station #8 monitor, EP A applied statistical analysis using data from other sites in the A rea. The approach is appropriate for this Area but may or m ay 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

A rea 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 mo nitor 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 the se estimated values (Table 7)

. Under this method, the 20 07

- 20 09 design value for the Fire Station
#8 monitor was estimated to be 14.1 μg/m 3

.9

Tab le 6 : Atlanta 2007

- 2009 D esign V alue s, 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

C oncentrations at South Dekalb (site , labeled “v_b”)10

T able 7 : Imputation and Resulting Data Capture and D esign V alue Recalculation with Site

A ( 13

- 121

- 0039 )

This estimated design value was then analyzed using the bootstrap method. In this analysis, EPA repeat ed the regression analysis 1

, 000 times with d ifferent 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 result ed from application of the statistical analysis. Therefore, EPA concluded that for 2007

– 2009, the annual average concentration of the Fire
Station #8 monito r is below the NAAQS.

Table 8 : Bootstrapping Residuals (and D esign V alue Recalculations) with Site A ( 13

- 121

-

0039 )

The Gwinnett Technical S chool monitor (13

- 135

- 0002) has a 2007

- 200 9 PM 2.5 annual design value of 12.7 μ g/m 3 and a current 2008

- 201 0 PM 2.5 annual design value of 12.1 μ g/m 3

. 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 μ g/m 3

was obtained from the four th quarter of 20 07

. 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 μ g/m 3 was obtained from the four th quarter of 2010. This value was substituted in for all missing data in the fourth quarter of 200811

for the 2008

- 2010 design value calculation

. The annual mean s w ere recalculated, and the resulting annual design value s are 1 3.3 μ g/m 3 and 12.5 μ g/m 3 , r espectively . This monitor is considered attaining and no further evaluation is necessary.
The Gainesville monitor (13

- 139

- 0003) has a 200 7

- 200 9 PM 2.5 annual design value of
11. 8 μ g/m 3 and a current 2008

- 2010 PM 2.5 annual design value of 11.2 μ g/m 3

. S in ce the monitor had two incomplete quarters during third and fourth quarters of 2008, data substitution
was conducted. For the 2007

- 2009 design value period, m aximum quarterly value s of 33.5

μ g/m 3 and 29.2 μ g/m 3 were obtained from the third and fourth qua rters of 2007, respectively

, for
the 2007

- 2009 design value calculation . Th ese value s w ere substituted in for all missing data in
the third and fourth quarter s of 2008. The annual mean was recalculated, and the resulting annual design value was 1 2

. 8 μ g/m 3

. For the 2008

- 2010 design value period, m aximum quarterly
value s of 32.3 μ g/m 3 and 19.8 μ g/m 3 were obtained from the third and fourth quarters of 2008 for
the 2008

- 2010 design value calculation . Th ese value s w ere substituted in for all missing data in
the third and fourth quarter s of 2008 , respectively . The annual mean was recalculated, and the resulting annual design value was 11. 9 μ g/m 3

. This monitor is considered attaining and no further evaluation is necessary.
The Yorkville monitor (13

- 223

- 000 3) has a 200 7

- 200 9 PM 2.5 annual design value of

1 2 .0 μ g/m 3 and a current 2008

- 2010 PM 2.5 annual design value of 11.0 μ g/m 3 . Since the monitor had one incomplete quarter during the third quarter of 2009, data substitution was
conducted. A maxi mum quart erly value of 36.6 μ g/m 3 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

mean s w ere recalculated, and the result ing annual design value s are 12.7 μ g/m 3 and 11.6 μ g/m 3

, 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 o f the 1997 annual

PM 2.5 NAAQS. Determinations of attainment are based on three years of complete, quality

assured 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, th e review of data is based on the three mos t recent years of complete data

. Appendix N does not provide for examining partial years of data, because various seasons of the year
reflect various influen ces on PM 2.5 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 A rea has met the 1997 PM 2.5 NAAQS by its April 5, 201 0

, attainment date using 2007

– 2009 data and continues to meet the 1997 PM 2.5 NAAQS using
2008

– 2010 data

.

D . CONCLUSIONS AND RECOMMENDED AGENCY ACTION

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

- 2009 sho w that the design value for the Atlanta PM 2.5 nonattainment Area is below 15.0 μg/m 3

. Because this value is less than or equal the 1997 annual PM 2.5 NAAQS of 15 μg/m 3 , the A rea has
attained the 1997 annual PM 2.5 standard by April 5, 2010 for this NAAQS. Q uality assured, quality controlled, and certified ambient air monitoring data for 200 8

-12

20 10 show that the design value for the Atlanta PM 2.5 nonattainment A rea is below 15

. 0 μg/m 3

. Because this value is less than or equal the 1997 annual PM 2.5 NAAQS of 1 5 μg/m 3 , the A rea has
monitored continued attainment for this NAAQS.