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; Alabama, Georgia, and Tennessee: Chattanooga; 

Determination of Attaining Data for the 1997 Annual Fine Particulate Standards

March 2011
2

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 Chattanooga Area 

(comprised of Hamilton County in Tennessee, Catoosa and Walker Counties in Georgia, and a 

portion of Jackson County in Alabama) was designated nonattainment for the 1997 PM2.5 NAAQS. 

See 40 CFR 81.301(Alabama), CFR 81.311 (Georgia), and CFR 81.343 (Tennessee).

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 Chattanooga 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.)
3

rulemaking which preliminarily makes the determination that the Chattanooga Area has attained the 

1997 PM2.5 NAAQS. EPA’s determination that the Chattanooga 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, Federal 

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 PM2.5 design value for the 

Chattanooga nonattainment area are included in the table below.

Annual PM2.5 Design Values for the Monitor in the Chattanooga Nonattainment Area

Location AQS site ID

2007

Average

(μg/m3)

2008

Average

(μg/m3)

2009

Average

(μg/m3)

2007-2009

Design 

Value

(μg/m3)

Tombras Avenue 47-065-0031 14.9 12.3 10.5 12.6

Soddy Daisy High 

School

47-065-1011 14.2 11.4 9.5 11.7

Siskin Drive 47-065-4002 14.2 11.4 9.5 11.7

Rossville 13-295-0002 13.7212.5 10.7 12.3

All monitors met the 75 percent data completeness requirement except the Rossville site (13-

295-0002) in 2007. A new roof was installed in June of 2007 at the Rossville site; therefore, no 

data were collected from June 12 – November 13, 2007. The pitched roof no longer supported 

ambient air monitors, which resulted in the establishment of a new monitoring location. Because of 

the shut-down, the Rossville site did not meet data completeness requirements for 2007. Georgia 

Environmental Protection Division (GA EPD) developed a weight-of-evidence approach for an 

alternative method of data substitution. The analysis used data from Siskin Drive and Tombras 

Avenue sites to determine the attainment status of the Rossville site. GA EPD’s analysis can be 

found in the docket.

In addition to GA EPD’s analysis, Region 4 requested the EPA Office of Air Quality 

Planning and Standards (OAQPS) run a regression analysis in order to confirm GA EPD’s analysis. 

OAQPS found that site substitution would be appropriate for data substitution. EPA sent GA EPD 

a letter in November 2010 stating:

In summary, GA EPD’s analysis successfully demonstrated a strong correlation between the 

PM2.5 data from the Rossville site (the missing data site) and the other two sites. GA EPD’s 

 

2

The Rossville site did meet 75 percent data completeness for the 2007 – 2009 time period due to roof replacement 

and subsequent relocation of the monitor. 
4

analysis is bolstered by an OAQPS regression analysis using imputed data. As a result, EPA 

Region 4 agrees that the Chattanooga MSA would qualify for a clean data determination.

The letter from Region 4 to GA EPD agrees with the data substitution analysis can be found in the 

docket for the proposed rulemaking. If data substitution is deemed appropriate, the design value for 

the nonattainment area is the highest reading monitor without data substitution. The Tombras Ave 

site (47-065-0031) is the design value monitor for the nonattainment area, with a design value of 

12.6 μg/m3.

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 Chattanooga 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 Chattanooga Area is 12.6 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 Chattanooga Area be determined to have attaining data for the 

1997 annual PM2.5 NAAQS.