UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION IV

Technical Support Document 

EPA’s Notice of Proposed Rulemaking 

For 

Approval and Promulgation of Implementation Plans and Designations of Areas for 

Air Quality Planning Purposes; Georgia: Macon; Determination of Attaining Data 

for the 1997 Annual Fine Particulate Standards

March 2011
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A. BACKGROUND

On July 18, 1997 (62 FR 36852), EPA established an annual fine particulate matter (PM2.5) 

national ambient air quality standard (NAAQS) at 15.0 micrograms per cubic meter (μg/m3) based 

on a 3-year average of annual mean PM2.5 concentrations (referred to as the 1997 PM2.5 NAAQS). 

At that time, EPA also established a 24-hour PM2.5 standard of 65 μg/m3. 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 Macon Area (comprised 

of Bibb County and a portion of Monroe County in Georgia) was designated nonattainment for the 

1997 PM2.5 NAAQS. See 40 CFR 81.311.

On October 17, 2006 (71 FR 61144), EPA retained the 1997 annual PM2.5 NAAQS at 15.0 

μg/m3based on a 3-year average of annual mean PM2.5 concentrations, and established a new 24-

hour PM2.5 standard of 35 μg/m3. On November 13, 2009, EPA clarified the designations for the 

NAAQS promulgated in 1997, stating that the Macon Area was designated as nonattainment for the 

annual standard but attainment for the new 24-hour PM2.5 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/m3.

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 plan 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.

C. EPA’S ANALYSIS OF MONITORED DATA

This technical support document provides information in support of EPA’s proposed 

 

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 for a 

single monitoring site or a group of monitoring sites (referred to as the “annual standard design 

value ”). (See 40 CFR part 50 Appendix N.)
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rulemaking which preliminarily makes the determination that the Macon Area has attained the 1997 

PM2.5 NAAQS. EPA’s determination that the Macon Area has attaining data for the 1997 PM2.5

NAAQS is based upon quality assured, quality controlled and certified ambient air monitoring data 

for the 2007–2009 period, as measured by Federal Reference Method (FRM), Federal equivalent 

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

Macon-Allied Chemical monitor (13-021-0007) did not meet 75 percent completeness for the first 

quarter of 2008 and the Macon SE monitor (13-021-0012) did not meet 75 percent completeness for 

the second and fourth quarters of 2008 and third quarter of 2009. Data substitution is required to 

reach 75 percent completeness level. 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. The 

complete procedure for the maximum value data substitution test can be found in the EPA guidance 

document “Guideline on Handling Conventions for the PM NAAQS,” dated April 2009.

Additionally, EPA and Georgia Environmental Protection Division (GA EPD) believe an 

error occurred in the handling of the filter collected on February 4, 2009, and thus the data from the 

filter’s analysis are invalid. On February 4, 2009, GA EPD collected a filter sample from the PM2.5

FRM at its Macon-Allied Chemical Site (13-021-0007). Results from analysis of the filter indicated 

a 24-hour PM2.5 concentration of 96.1 μg/m3. Because this value is so much higher than normal 

readings from the site, GA EPD conducted an investigation into its validity. First, visual inspection 

of the filter found no discoloration normally indicative of a used filter. Second, GA EPD conducted 

a statistical analysis of the data collected from all PM2.5 FRMs in Georgia on February 4, 2009, 

which showed the 96.1 μg/m3to be a significant outlier. Finally, GA 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 Metropolitan Statistical Area (MSA) was 10.2 μg/m3. EPA, in conjunction 

with GA EPD, conducted further analysis showing the history of all values reported since 2000 at 

both sites. Ignoring an approved exceptional event data point, it is obvious that the 96.1 μg/m3is the 

most extreme outlier.

The monitors and data used to determine the 2007–2009 annual PM2.5 design value for the 

Macon nonattainment area are included in the tables below.

Annual PM2.5 Design Values for the Monitor in the Macon Nonattainment Area Without 

Data Substitution

Location AQS site ID

2007

Average

(μg/m3)

2008

Average

(μg/m3)

2009

Average

(μg/m3)

2007-2009

Design 

Value

(μg/m3)

Macon Allied 13-021-0007 16.7 12.3 12.2 13.7

Macon SE 13-021-0012 13.2 12.1 10.6 12.0
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Annual PM2.5 Design Values for the Monitor in the Macon Nonattainment Area With Data 

Substitution

Location AQS site ID

2007

Average

(μg/m3)

2008

Average

(μg/m3)

2009

Average

(μg/m3)

2007-2009

Design 

Value

(μg/m3)

Macon Allied 13-021-0007 16.7 15.9 12.2 14.9

Macon SE 13-021-0012 13.2 14.7 12.1 13.3

Because the February 4, 2009, value was found to be invalid, the next highest value of 58.1 

μg/m3, 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 design value of 14.9 μg/m3. With respect to the Macon SE monitor, the values of 28.9 

μg/m3, 30.6 μg/m3, and 33.0 μg/m3 were substituted in for the 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 μg/m3for 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 become the official design values for each respective monitor. The 

design value for the MSA is 13.7 μg/m3from the Macon Allied monitor.

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, this review 

of data is based on the three most recent years of complete data, generally 2007–2009. 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. Nevertheless, EPA examined data that 

is available to date. For the site, the average of available 2010 data is below the NAAQS. 

Therefore, the available data for 2010 are consistent with the finding, based on 2007–2009 data, 

that the Macon Area is attaining the 1997 annual PM2.5 NAAQS. On the basis of this review, EPA 

has concluded that this area has met and continues to meet the 1997 PM2.5 NAAQS. EPA is 

soliciting public comments on the issues discussed in this document through a proposed rulemaking.

Any comments, if any are received, will be considered before final action is taken.

D. CONCLUSIONS AND RECOMMENDED AGENCY ACTION

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

2009 shows that the design value for the Macon PM2.5 nonattainment Area is 14.9 μg/m3 with data 

substitution and 13.7 μg/m3 without data substitution. The official design value is without data 

substitution, 13.7 μg/m3. Because this value is less than or equal the 1997 annual PM2.5 NAAQS of 

15 μg/m3, the area has monitored attainment for this NAAQS. EPA recommends the Macon Area
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be determined to have attaining data for the 1997 annual PM2.5 NAAQS.