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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 

ATLANTA FEDERAL CENTER 

61 FORSYTH STREET 

Pilot ATLANTA, GEORGIA 30303-8960 

JAN 07 2011 

Ms. Susan Zimmer-Dauphinee, Manager 

Ambient Monitoring Program 

Georgia Environmental Protection Division 

2 Martin Luther King, Jr. Drive, SE 

Suite 1152 East 

Atlanta, Georgia 30334-4100 

Ms. Zimmer-Dauphinee: 

Thank you for your letter dated May 26, 2010, requesting that the U.S. Environmental 

Protection Agency (EPA) invalidate a particulate matter less than 2.5 microns (PM2.5) sample 

from the Macon-Allied Chemical (Macon, Georgia) monitor taken during the first quarter of 

2009. The reason that the Georgia Environmental Protection Division (EPD) submitted the 

request is that the Macon-Allied Chemical monitor did not meet the 75% data recovery 

requirement and the sample, if used in a data substitution exercise, would potentially result in a 

determination that the Macon metropolitan statistical area (MSA) area would not demonstrate 

attainment of the PM23 national ambient air quality standard (NAAQS). 

Upon review of information submitted by EPD, EPA agrees that the sample is invalid. In 

addition to providing the basis for this decision, we are providing a data substitution analysis 

using valid data. The data substitution analysis shows the resulting 2009 design value of the 

Macon-Allied Chemical site to be below the PM2.5 NAAQS level of 15.0 micrograms per cubic 

meter (jig/ml). 

Sample Validation/Invalidation 

On February 4, 2009, EPD collected a filter sample from the PM2.5 federal reference 

monitor (FRM) at its Macon-Allied Chemical site, Air Quality System (AQS) 130210007. 

Results from analysis of the filter indicated a 24-hour PM23 concentration of 91.6 j.tg/m 3 . 

Because this value is so much higher than normal readings from the site, EPD conducted an 

investigation into its validity. First, visual inspection of the filter found no discoloration 

normally indicative of a used filter. Second, EPD conducted a statistical analysis of the data 

collected from all PM23 FRMs in Georgia on February 4, 2009 which showed the 91.6 J.ig/m 3 

value to be a significant outlier. Finally, EPD compared the value to other data collected in the 

area on the same day. The highest hourly value from a continuous PM2.5 monitor in the Macon 

MSA was 10.2 ig/M3. Further, continuous PM2.5 data from the next closest site in Warner 

Robins revealed an hourly high of 15.8 ig/m3 . 

EPA staff, in conjunction with EPD, provided further analysis showing the history of all 

values reported since 2000 at both sites. The analysis identified outliers and an approved 

exceptional event (2007), as well as highlighted values from the month of February for each of 

these years. Ignoring the approved exceptional event data point, it is obvious that the 91.6 jig/M3 

is the most extreme outlier (see Figures 1 and 2). 

Internet Address ((JRL)  http:I/www.epa.gov 

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Considering all of the above information, we believe that an error occurred in the 

handling of the filter collected on February 4. 2009, and concur with EPD that the data from the 

filter’s analysis are invalid. In the future we ask that the EPD review its data on a quarterly basis 

to identify data issues as soon as possible. 

Maon MllCdthŁæikat 

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Figure 1: Reported IPM u Concentrations at me acon-Awed Cheinim su irum ulLuugu 1. 

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Figure 2: Reported pM2.5 Concentrations at inc macon ar. site num LUVU wtuugu 
Data Substitution 

On December 17, 2004, EPA issued designations for the 1997 PM2.5 annual NAAQS 

based on data from 2001-2003. At that time, the Macon MSA was designated non-attainment for 

the PM23 NAAQS. The Macon MSA has two PM23 monitors which are at the Macon-Allied 

Chemical (AQS ID 13-021-0007) and Macon SE (AQS ID 13-021-0012) sites. In 2004 only the 

Macon-Allied Chemical monitor had a design value (15.2 tg/m) which was above the 24-hour 

PM23 NAAQS of 15.0 .tg/m3 . For the MSA to be redesignated to attainment both sites must 

show clean data for the most recent three year period. Forty (40) Code of Federal Regulations 

(CFR) Part 50, Appendix N describes the data handling conventions and computations necessary 

for determining when the annual and 24-hour PM23 NAAQS specified in 40 CFR Part 50.7 and 

50.13 are met. If no data were required to be substituted into the data sets to reach a 75% data 

completeness level, the 2007-2009 annual PM2.5 design value for each site would be 13.7 and 

12.0 JIg/rn3 for Macon-Allied Chemical and Macon SE, respectively (see Table 1). 

Annual Means AnnualDV 

SITE NAME AQS ID 2007 2000 21109 21101-2009 

Macon Allied’ 134021-0007 16.7 12.3 12.2 2 13.7 

Macon SE 13-021-0012 13.2 111 10.6 12.0 

’Allied design values consider collocated data where primary data aren’t 

available. 

Allied Annual Mean does not consider 916 ug/rn3 

Table 1: PM2.5 Annual Design Values with Incomplete Data 

However, data substitution is required to reach a 75% completeness level. The first data 

completeness requirement is that each primary monitor must have 75% data completeness per 

quarter in each of the three years of the design value period. Neither Macon monitor meets this 

requirement. The Macon-Allied Chemical monitor did not meet this requirement for the first 

quarter of 2008. The Macon SE monitor did not meet this requirement for the second and fourth 

quarters of 2008 and third quarter of 2009. The data substitution procedures must be separately 

applied to each site. In the instance of an attaining but incomplete design value, a quarterly 

maximum value data substitution test must be employed to determine the validity of the attaining 

design value (see Table 2). The complete procedure for the maximum value data substitution 

test can be found in the EPA guidance document ’Guideline on Data Handling Conventions for 

the PM NAAQS" dated April 1999. 

Annual Afeans AnnualDV 

SITE NAME AQS ID 2001 2008J 2009 1211-0-200 

Macon Allied’ 13-021-0007 16.7 15.9 12.2 

Macon SO 13-021-0012 1 13.2 14.7 12.1 

’Allied design values considers data substitution of 53.1ug/m3 for all missing 

data inlst Qtr 2008 

2 Macon SE Annual Mean considers data substitution for 2nd and 4th Ctrs of 2008 

and 3rd Qtr 2009- _____ 

Table 2: Maximum Value Data Substitution Test 
Because the February 4, 2009 value of 91.6 g/m 3was found to be invalid in the previous 

section, the next highest value of 58.1 gglm 3, the maximum (valid) value, was substituted in for 

all missing data in the first quarter of 2008. The maximum value data substitution test for the 

Macon-Allied Chemical monitor results in an attaining 2007-2009 design value of 14.9 14glin3 

. 

With respect to the Macon SE monitor, the values of 28.9 gglm3, 30.6 ggtm3, and 33.0 g/m3 

were substituted in for second and fourth quarters of 2008 and third quarter of 2009, respectively. 

The test using these data results in an attaining 2007-2009 design value of 13.3 gg/m’ for the 

Macon SE monitor. Because both tests resulted in design values below the NAAQS, no further 

analyses are required for either monitor and the design values calculated with incomplete data in 

Table 1 become the official design values for each respective monitor. The Macon-Allied 

Chemical monitor’s design value of 13.7 jig/in3becomes the 2007-2009 design value for the 

MSA. 

If you have any questions regarding this matter, please contact me at (404) 562-9097 or 

Darren Palmer of my staff at (404) 562-9052. 

Sincerely, 

LD,J&~ t~ aftr 

R. Douglas Neeley 

Chief 

Air Toxics and Monitoring Branch 

cc: Richard Wayland, OAQPS 

Richard Schutt, APTMD