## 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; Alaba ma, Georgia, and Tennessee: Chattanooga ; 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 )

na tional 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 b ecame 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 PM 2.5 NAAQS.

See 40 CFR 81. 30 1(Alabama), CFR 81. 311 (Georgia), and CFR 81. 343 (Tennessee)

.

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 Chattanooga Area was designated 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 sta ndard 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 equal 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 asso ciated reasonably 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 p rovides information in support of EPA’s proposed

1 Design values are the metrics that are compared to the NAAQS levels to determine at tainment. 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 PM 2.5 NAAQS. EPA’s determination that the Chattanooga A rea ha s attaining data for the

1997 PM 2.5 NAAQS is based upon quality assured, quality controlled and certified ambient air monitoring data for the 200 7

– 200 9 period, as measured by Federal reference method, Federal equivalent method, or Approved Regional Method monitors described in 40 CFR Part 50

, Appe ndix

N. The monitor s and data used to determine the 2007

– 2009 annual PM 2.5 design value for the Chattanooga nonattainment area are includ ed in the t able below.

Annual PM 2.5 Design Value s for the Monitor in the Chattanooga Nonattainment Area

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 )

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 13.7 2 12.5 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 20 07. 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 Ros sville 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 th at site substitution would be appropriate for data substitution. EPA sent G A EPD

a letter i n November 2010 stating:

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

PM 2.5 data from the Rossville site (the missing d ata 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 agree s 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 T ombras Ave site (47

- 065

- 0031) is the design value monitor for the nonattainment area, with a design value of

12.6 μg/m 3

.

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 accordance 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 reflect

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 available 2010 data is b elow the NAAQS

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

– 200 9 data,

that the Chattanooga A

rea is attaining the 1997 annual PM 2.5 NAAQS . On the basis of this revie w, 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 . CONCLUSIONS AND RE COMMENDED 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 Chattanooga A rea is 1 2 .6 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 Chattanooga A rea be determined to have attaining data for the

1997 annual PM 2.5 NAAQS.