1so 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/m l ). 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

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### 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/m 3

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### 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 Recycled/Recyclable . Printed with Vegetable Oil Based Inks on Recycled Paper (MInimum 30% Postconsumer)ló
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# 1000/m, 0/0, 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.



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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 pM 2.5 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/m 3 . 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/rn 3 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: PM 2.5 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 12 1 1

- 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 TestBecause the February 4, 2009 value of 91.6 g/m 3 was 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 1 4glin 3

. With respect to the Macon SE monitor, the values of 28.9 gglm 3 , 30.6 g gtm 3 , and 33.0 g/m 3 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 g g/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/in 3 becomes 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, 

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R. Douglas Neeley Chief Air Toxics and Monitoring Branch

cc: Richard Wayland, OAQPS Richard Schutt, APTMD