## 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; Georg ia : Macon ; Determination of Attaining Data

for the 1997 Annual Fine Particulate Standards

March 20112

A. BACKGROUND

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

on a 3

- year average of annual mean PM 2.5 concentrations (referred to as the 1997 PM 2.5 NAAQS)

. At that time, EPA also established a 24

- hour PM 2.5 standard of 65 μg/m 3 . See 40 CFR 50.7. On January 5, 2005 (70 FR 944), EPA published 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 Macon Area (comprised

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

1997 PM 2.5 NAAQS. See 40 CFR 81. 3 11.

On October 17, 2006 (71 FR 61144), EPA retained the 1997 annual PM 2.5 NAAQS at 15.0 μg/m 3 based on a 3

- year average of annual mean PM 2.5 concentrations , and established a new 24

- hour PM 2.5 standard of 35 μg/m 3

. On November 13, 2009, EPA clarified the designations for the NAAQS promulgated in 1997, stating that the Macon Area was designat ed as nonattainment for the

annual standard but attainment for the new 24

- hour PM 2.5 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 requirements 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 equa l 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 reaso nably available control measures, reasonable further progress plans, contingency measures, and other planning state implementation plan related

to attainment of the PM 2.5 NAAQS shall b e suspended until the area is redesignated to attainment, at

which time the requirement 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.

C. EPA’S ANALYSIS OF MONITORED DATA

This technical support document provides info rmation 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 stan dard design

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

rulemaking which preliminarily makes the determination that the Macon Area has attained the 1997

PM 2.5 NAAQS. EPA’s determination that the Macon A rea ha s attaining data for the 1997 PM 2.5 NAAQS is based upon quality as sured, quality controlled and certified ambient air monitoring data

for the 200 7

– 200 9 period, as measured by Federal Reference M ethod (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. Dat a 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.

Addit ionally, 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 fi lter sample from the PM 2.5 FRM at its Macon

- Allied Chemical Site (13

- 021

- 0007). Results from analysis of the filter indicated

a 24

- hour PM 2.5 concentration of 96.1 μg/m 3 . 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 condu cted a statistical analysis of the data collected from all PM 2.5 FRMs in Georgia on February 4, 2009,

which showed the 96.1 μg/m 3 to be a significant outlier. Finally, GA EPD compared the value to other data collected in the area on the same day. The hig hest hourly value from a continuous PM 2.5 monitor in the Macon Metropolitan Statistical Area (MSA) was 10.2 μg/m 3 . EPA, in conjunction with GA EPD, conducted further analysis showing the history of all values reported since 2000 at both sites. Ignoring a n approved exceptional event data point, it is obvious that the 96.1 μg/m 3 is the

most extreme outlier.

The monitor s and data used to determine the 2007

– 2009 annual PM 2.5 design value for the

Macon nonattainment area are includ ed in the t able s below.

An nual PM 2.5 Design Value s for the Monitor in the Macon Nonattainment Area Without

Data Substitution

Location AQS site ID 200 7 Average ( μg/m 3 ) 200 8

Average ( μg/m 3 ) 200 9

Average ( μg/m 3 ) 200 7

- 200 9

Design

Value ( μg/m 3 )

Macon Allied 13

- 021

- 0007 16.7 12.3 1 2.2 13.7

Macon SE 13

- 021

- 0012 13.2 12.1 10.6 12.04

Annual PM 2.5 Design Values for the Monitor in the Macon Nonattainment Area With Data

Substitution

Location AQS site ID 2007 Average ( μg/m 3 ) 2008

Average ( μg/m 3 ) 2009

Average ( μg/m 3 ) 2007

- 2009

Desig n Value ( μg/m 3 )

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/m 3 , the maximum valid value, was substituted in for a ll 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/m 3 . With respect to the Macon SE monitor, the values of 28.9 μg/m 3 , 30.6 μg/m 3 , an d 33.0 μg/m 3 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/m 3 for the Macon SE monitor. Because both tests res ulted 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/m 3 fro m 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 exi st. In acc ordance with Appendix N and standard EPA practice, this review of data is based on the three most recent years of complete data, generally 200 7

– 200 9 . Appendix N does not provide for examining partial years of data, because various seasons of the year refle ct
various influences 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. Nevertheless, EPA examined data that

is available to date

. For the site, the average of ava ilable 2010 data is below the NAAQS

. Therefore, the available data for 20 10 are consistent with the finding, based on 200 7

– 200 9 data,

that the Macon A

rea is attaining the 1997 annual PM 2.5 NAAQS . On the basis of this review, EPA

has concluded that this a rea has met and continues to meet the 1997 PM 2.5 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 . CON CLUSIONS AND RECOMMENDED AGENCY ACTION

Q uality assured, quality controlled, and certified ambient air monitoring data for 200 7

– 200 9 show s that the design value for the Macon PM 2.5 nonattainment A rea is 14. 9 μg/m 3 with data

substitution and 13.7 μg/m 3 wit hout data substitution

. The official design value is without data

substitution

, 13.7 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 area has monitored attainment for this NAAQS

. EPA recommend s the Macon A rea5

be determined to have attaining data for the 1997 annual PM 2.5 NAAQS.