1

MEMORANDUM

TO: Docket No. EPA-HQ-OAR-2012-0918 

Air Quality Designations for the 2012 Fine Particulate (PM2.5) Standard

FROM: Beth W. Palma

Air Quality Policy Division, OAQPS 

SUBJECT: Tennessee Deferred Area Air Quality Designations for the 2012 PM2.5 National 

Ambient Air Quality Standard (SAN 5706)

This memorandum provides the rationale for the U.S. Environmental Protection Agency’s 

decision to use the additional time available to it under section 107(d)(1)(B) of the Clean Air Act 

(CAA) to obtain additional information and further evaluate air quality monitoring data before 

promulgating initial area designations for the 2012 primary annual fine particle National 

Ambient Air Quality Standard (2012 annual PM2.5 NAAQS)1 in certain areas in Tennessee.

Upon promulgation of a NAAQS, section 107(d) of the CAA requires the EPA to subsequently 

promulgate area designations based on that NAAQS. Specifically, EPA must designate as 

“nonattainment” those areas that are violating a NAAQS, or that are contributing to a violation of 

the NAAQS in a nearby area. By contrast, the EPA designates as “unclassifiable/attainment” 

those areas where air quality monitoring data indicate attainment of the NAAQS, and for areas 

that do not have monitors but which the EPA has reason to believe are likely to be in attainment 

and are not contributing to nearby violations. Finally, the EPA reserves the category of 

“unclassifiable” for areas where the EPA cannot determine based on available information 

whether an area is meeting the NAAQS or contributing to a nearby violation. 

As described in more detail in the memorandum titled “Initial Area Designations for the 2012 

Revised Primary Annual Final Particle National Ambient Air Quality Standard: Tennessee Data 

Issues,” Tennessee’s monitoring program has experienced data completeness issues for several 

areas across the state.2 Given these data completeness issues, for several counties the EPA 

cannot calculate a valid design value for the 2011-2013 time period (the data that the EPA is 

using to determine areas that violate the 2012 annual PM2.5 NAAQS). Without a valid design 

value, the EPA has insufficient information to determine whether these areas are meeting or are 

not meeting the NAAQS. However, the EPA believes that forthcoming monitoring data will 

likely result in the three years of complete and valid data needed to assess compliance with the 

standard and promulgate designations for the areas identified below. Accordingly, the EPA is 

deferring designations for these areas, and using the additional time available under section 

 

1 On December 14, 2012, the EPA promulgated a revised primary annual PM2.5 NAAQS (78 FR 3086, January 15, 

2013). In that action, the EPA revised the primary annual PM2.5 standard, strengthening it from 15.0 micrograms per 

cubic meter (μg/m3) to 12.0 μg/m3.

2 Memorandum from Liz Naess, Group Leader, Air Quality Analysis Group, US EPA Office of Air Quality 

Planning and Standards, to EPA Docket EPA-HQ-OAR-2012-0918, Air Quality Designations for the 2012 PM2.5

Standards, titled, “Initial Area Designations for the 2012 Revised Primary Annual Final Particle National Ambient 

Air Quality Standard: Tennessee Data Issues.”
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107(d)(1)(B) of the CAA to assess that forthcoming data, and to promulgate initial area 

designations for the identified areas.

The EPA is deferring designations for all counties in the state of Tennessee with the exception of 

Hamilton, Marion and Sequatchie counties in the Chattanooga area. Figure 1 displays a map of 

the areas. These areas include the listed counties in Tennessee with incomplete monitoring data 

that are within these areas, and counties nearby to these Tennessee counties that the EPA 

believes should be evaluated for potential contribution to the counties with affected data. The 

EPA is deferring the designations for all counties in the state of Tennessee with the exception of 

Hamilton, Marion and Sequatchie Counties in the Chattanooga area for the 2012 annual PM2.5 

NAAQS to allow the EPA to collect and assess additional information, including air quality 

monitoring data, before providing the EPA’s intended initial area designations for these areas. 

There is already sufficient data in the Chattanooga area. The EPA is designating Hamilton, 

Marion and Sequatchie counties in the Chattanooga area as unclassifiable/attainment.

Figure 1. Map of Tennessee Counties that the EPA is Deferring

The EPA will work with Tennessee to finalize the designations for these counties as soon as 

complete certified PM2.5 monitoring data are available, which the EPA anticipates will allow for 
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prompt promulgation of these designations. When complete air quality monitoring data are 

available and have been certified, the EPA invites the affected states to submit revised 

designation and boundary recommendations, as appropriate. If at that time the EPA believes that 

it is necessary to modify a state’s recommendation and to promulgate a designation different 

from the state’s recommendation, then the EPA will notify the state at least 120 days prior to 

promulgating the final designation and the EPA will provide the state an opportunity to comment 

on the potential modification. Each state will then have an opportunity to respond to the EPA’s 

proposed designations and boundaries. Pursuant to section 107(d), the EPA cannot promulgate 

the designation for these areas less than 120 days from the date of the EPA’s announced 

intention to modify the recommendation. The EPA will promulgate the designations for these 

deferred areas at a later date, in a separate final rule.

Approach

In determining the appropriate set of neighboring counties to include with the set of monitored 

counties for which the EPA is deferring designations, the EPA conducted a hypothetical analysis 

assuming that the monitors with the incomplete data were violating the 2012 standard of 12.0 

μg/m3. The EPA is proceeding under this assumption under the precautionary principle that 

because it is unclear whether there is a violation in this area due to data incompleteness, then for 

purposes of conducting the contribution analysis the EPA will presume that there may be such a 

violation. The EPA’s contribution analysis for these hypothetical violations focused on counties 

within the same CBSA as the affected monitor because these counties would be most likely to 

contain nearby sources that contribute to any violations. Specifically, the EPA evaluated all 

counties in the same CBSA as the county with the monitors in question, in order to determine 

whether these presumptively “nearby” counties (beyond the county with the incomplete 

monitoring data) contain emissions sources that would be relatively likely to contribute to any 

hypothetical violation of the standard in the area with those monitors. Using information similar 

to the information used for determining nonattainment area boundaries,3the EPA evaluated the 

information available for these CBSAs, including Air Quality Data; Emissions and Emissionsrelated Data; Meteorology; and Geography/Topography.4 One of the EPA’s primary boundary 

considerations for determining whether to defer a final designation decision for these counties is 

whether the agency believes the emissions in those nearby counties are highly likely to 

contribute to the potential violations, and whether the meteorological data support a case that 

those emissions could significantly impact the affected monitor. Where available evidence 

indicates that emissions in adjacent counties could likely have the potential to contribute to 

monitors with data incompleteness, the EPA is deferring the designation for those counties as 

well as for the county with the affected monitor.

 

3 Memorandum dated April 16, 2013, from Gina McCarthy, Assistant Administrator, to Regional Administrators, 

Regions 1-10, titled “Initial Area Designations for the 2012 Revised Primary Annual Fine Particle National Ambient 

Air Quality Standard.” 

4 The EPA did not consider jurisdictional boundaries for purposes of deferred designations because jurisdictional 

boundaries are most helpful for nonattainment planning purposes, and this analysis concerns the preliminary 

dividing line between deferred and unclassifiable/attainment counties. No counties in Tennessee are being 

designated nonattainment pursuant to this analysis, although that could change in the future if forthcoming data 

reveal a NAAQS violation. 
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Clarksville TN-KY Area

Clarksville is located in a bi-state CBSA that includes four counties: two counties in Tennessee 

and two counties in Kentucky. Most of the urbanized portion of Clarksville is contained within 

Montgomery County, Tennessee. None of the counties in the CBSA have ever been designated 

nonattainment for the 1997 or the 2006 PM2.5 NAAQS. The Clarksville CBSA and surrounding 

counties are shown in Figure 2, along with the location of point sources and air quality monitors.

Figure 2. Clarksville CBSA with Point Sources and Air Quality Monitor Locations

There is an attaining monitor in Christian County, Kentucky with a valid design value of 10.3 

μg/m3for the 2011-2013 timeframe. Also, the PM2.5 air quality in the area has been steadily 

improving since the early 2000’s as evidenced by the downward trend of PM2.5 values measured 

at the monitors in the Clarksville area. This downward trend is shown in Figure 3. The 

Montgomery County, Tennessee monitor has an incomplete design value of 9.6 μg/m3for the 

2011-2013 timeframe.

Figure 3. Clarksville Area Air Monitor Design Value (DV) Trends
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The EPA evaluated PM2.5 and PM2.5-precursor emissions5and related data from the counties in 

the Clarksville area. Table 1 provides a summary of this data. Montgomery and Stewart Counties 

have the majority of PM2.5 and precursor emissions, population and VMT. Montgomery County 

has a monitor with invalid data and an urbanized core around the City of Clarksville. Stewart 

County has a large point source (TVA Cumberland Fossil Plant) with over 2,500 tons per year 

(tpy) of PM2.5 emissions and over 7,600 tpy of sulfur dioxide (SO2) emissions in the upwind 

direction of the Montgomery County monitor.

In Kentucky, Christian County and Trigg County are outlying areas that are located primarily 

downwind from the Montgomery County PM2.5 monitoring site. Christian County has an 

attaining PM2.5 monitor, and while the county population is nearly half that of Montgomery 

County, current growth is only about 3 percent. Trigg County has very low emissions of all 

pollutants (e.g., 28 tpy of SO2 and 389 tpy of PM2.5), and the County’s population is relatively 

small at about 5 percent for the area.

Table 1. Summary Statistics for the Clarksville, TN-KY CBSA 

 

5 County-level nitrogen oxide, volatile organic compound and ammonia emissions are not shown in the tables with 

in this memorandum because ambient PM2.5 concentrations in the southeastern U.S. tend to be impacted most 

significantly by emissions of direct PM2.5 emissions and SO2 emissions.

0

2

4

6

8

10

12

14

16

2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

Clarksville DVs

Christian Cty, KY Montgomery Cty, TN - 471251009 2012 PM2.5 NAAQS
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Montgomery Stewart Christian Trigg

State Tennessee Tennessee Kentucky Kentucky

Core urbanized 

county or outlying? Core Outlying Outlying Outlying

SO2 Emissions 

(tpy) 1,529 7,740 77 28

PM2.5 emissions 

(tpy) 1,018 2,452 947 389

Population 173,375 13,340 74,138 14,355

Population (% of 

CBSA) 63% 5% 27% 5%

VMT (Millions) 1,467 166 912 218

VMT (% of CBSA) 53% 6% 33% 8%

The EPA also evaluated the meteorology in the area by evaluating wind data collected at the Fort 

Campbell Airport. Figure 4 provides a wind rose created with five years of data from 2009-2013. 

The predominant winds blow from the southwest and south directions. Additionally, there is a 

low frequency of winds blowing from the northerly directions which limits the potential for 

transport of emissions from the Kentucky counties into Tennessee. These wind patterns do not 

support contribution of emissions from the Kentucky counties to the PM2.5 air quality in the 

Tennessee areas. Emissions from Montgomery and Stewart counties in Tennessee are most 

likely to impact the monitor in Montgomery County.
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Figure 4. Wind Rose Data for the Clarksville TN-KY Area

WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Fort Campbell Airport

2009-2012

COMMENTS: COMPANY NAME:

MODELER:

DATE:

7/28/2014

PROJECT NO.:

NORTH

SOUTH

WEST EAST

2%

4%

6%

8%

10%

WIND SPEED 

(m/s)

 >= 11.1

 8.8 - 11.1

 5.7 - 8.8

 3.6 - 5.7

 2.1 - 3.6

 0.5 - 2.1

Calms: 30.05%

TOTAL COUNT:

43443 hrs.

CALM WINDS:

30.05%

DATA PERIOD:

Start Date: 1/1/2009 - 00:00

End Date: 12/31/2013 - 23:00

AVG. WIND SPEED:

2.56 m/s

DISPLAY:

 Wind Speed

Direction (blowing from)
8

Clarksville Area Conclusion:

As a result of our technical analysis of the Clarksville CBSA, the EPA is deferring the

designations for the Tennessee counties of Montgomery and Stewart along with most of the state 

of Tennessee due to the ambient monitoring data quality issues, including an invalid 2013 design 

value at the Montgomery County monitor. The EPA agrees with the recommendation from 

Kentucky for Christian and Trigg Counties in the Clarksville Area and is designating these 

counties as unclassifiable/attainment. 

Kingsport-Bristol, TN-VA Area

Kingsport-Bristol is located in a bi-state CBSA that includes four counties and a city: two 

counties in Tennessee and two counties in Virginia, along with Bristol City which straddles the 

Tennessee and Virginia state line. Most of the urbanized portion of Kingsport-Bristol is 

contained within Sullivan and Hawkins Counties in Tennessee. None of the counties in the 

CBSA have ever been designated nonattainment for the 1997 or the 2006 PM2.5 NAAQS. The 

Kingsport-Bristol CBSA and surrounding counties are shown in Figure 5, along with the location 

of point sources and air quality monitors.

Figure 5. Kingsport-Bristol CBSA with Point Sources and Air Quality Monitor Locations

There is an attaining monitor in Bristol City on the Virginia side of the state line with a valid 

design value of 9.0 μg/m3for the 2011-2013 timeframe. Also, the PM2.5 air quality in the area 
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has been steadily improving since the early 2000’s as evidenced by the downward trend of PM2.5

values measured at the monitors in the Kingsport-Bristol area. This downward trend is shown in 

Figure 6. The Sullivan County, Tennessee monitor has an incomplete deign value of 9.3 ug/m3

for the 2011-2013 timeframe.

Figure 6. Kingsport-Bristol Area Air Monitor DV Trends

The EPA evaluated PM2.5 and PM2.5-precursor emissions and related data from the counties in 

the Kingsport-Bristol area. Table 2 provides a summary of this data. Sullivan and Hawkins 

Counties have the majority of PM2.5 and precursor emissions, population and VMT. Hawkins 

County also has four large point sources in the upwind direction of the Sullivan County monitor, 

two of which, TVA John Sevier Fossil Plant and Holston Army Ammunition Plant, have 

significant SO2 emissions of over 15,000 tpy and over 1,500 tpy, respectively.

In Virginia, Scott and Washington Counties and Bristol City have low emissions, population and 

VMT relative to Sullivan and Hawkins Counties. These are outlying areas that are located in the 

primarily downwind direction from the Sullivan County PM2.5 monitoring site. Bristol City has 

an attaining PM2.5 monitor and low population and population growth of about 3 percent. Scott 

County has very low SO2 emissions of about 40 tpy and relatively low PM2.5 emissions of 306 

tpy. Although Scott County has 18 percent of the area’s population, the recent growth trend is 

negative. Washington County has very low emissions of all pollutants (e.g., 88 tpy of SO2 and 

104 tpy of PM2.5), and the County’s population is relatively small at about 6 percent for the area. 

0

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4

6

8

10

12

14

16

2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

Kingsport DVs

Bristol City, VA Sullivan Cty., TN 2012 PM2.5 NAAQS
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Table 2. Summary Statistics for the Kingsport-Bristol, TN-VA CBSA 

Hawkins Sullivan Bristol City Scott Washington

State Tennessee Tennessee Virginia Virginia Virginia

Core urbanized

county or 

outlying?

Outlying Core Outlying Outlying Outlying

SO2 Emissions 

(tpy) 17,819 24,937 26 40 88

PM2.5 emissions 

(tpy) 892 3,036 946 306 104

Population 56,842 156,866 17,849 23,111 54,879

Population (% of 

CBSA) 18% 51% 6% 18% 6%

VMT (Millions) 537 1,748 225 275 741

VMT (% of 

CBSA) 15% 50% 6% 21% 8%

The EPA also evaluated the meteorology in the area by evaluating wind data collected at the TriCities Regional Airport. Figure 7 is a wind rose created from five years of data from 2009-2013. 

The predominant winds blow from the west and southwest directions. Additionally, there is a 

low frequency of winds blowing from the northerly directions which limits the potential for 

transport of emissions from the Virginia counties into Tennessee. These wind patterns do not 

support contribution of emissions from the Virginia areas to the PM2.5 air quality in the 

Tennessee areas. Emissions from Sullivan and Hawkins counties in Tennessee are most likely to 

impact the monitor in Sullivan County. 
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Figure 7. Wind Rose Data for the Kingsport-Bristol TN-VA Area

WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Tri-Cities Regional Airport

2009-2013

COMMENTS: COMPANY NAME:

MODELER:

DATE:

7/28/2014

PROJECT NO.:

NORTH

SOUTH

WEST EAST

2%

4%

6%

8%

10%

WIND SPEED 

(m/s)

 >= 11.1

 8.8 - 11.1

 5.7 - 8.8

 3.6 - 5.7

 2.1 - 3.6

 0.5 - 2.1

Calms: 53.14%

TOTAL COUNT:

43794 hrs.

CALM WINDS:

53.14%

DATA PERIOD:

Start Date: 1/1/2009 - 01:00

End Date: 12/31/2013 - 23:00

AVG. WIND SPEED:

1.60 m/s

DISPLAY:

 Wind Speed

Direction (blowing from)
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Kingsport-Bristol Area Conclusion:

As a result of our technical analysis of the Kingsport-Bristol CBSA, the EPA is deferring the 

designations for the Tennessee counties of Sullivan and Hawkins along with most of the State of 

Tennessee due to the ambient monitoring data quality issues, including an invalid 2013 design 

value at the Sullivan County monitor. The EPA agrees with the recommendation from Virginia 

for Scott and Washington Counties and Bristol City in Virginia, and is designating these areas as 

attainment/unclassifiable. As discussed above, any potential violation at the Sullivan County 

monitor would be strongly influenced by the point sources in Sullivan and Hawkins County, 

Tennessee. 

Memphis TN-MS-AR Area

Memphis is located in a tri-state CBSA that includes nine counties: three counties in Tennessee, 

five counties in Mississippi, and one county in Arkansas. Most of the urbanized portion of 

Memphis is contained within Shelby County, Tennessee, although there are pockets of 

urbanization that stretch into DeSoto County, Mississippi, and Crittenden County, Arkansas. 

None of the counties in the CBSA have ever been designated nonattainment for either the 1997 

or the 2006 PM2.5 NAAQS. The Memphis CBSA and surrounding counties are shown in Figure 

8, along with the location of point sources and air quality monitors.

Figure 8. Memphis TN-MS-AR CBSA with Point Sources and Air Quality Monitor Locations
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There are attaining monitors in both DeSoto County and Crittenden County with valid design 

values for the 2011-2013 timeframe of 9.6 μg/m3 and 10.6 μg/m3, respectively. Also, the PM2.5

air quality in the area has been steadily improving since the early 2000’s as evidenced by the 

downward trend of PM2.5 values measured at all of the monitors in the Memphis area, including 

the monitors in Shelby County prior to the time when data quality issues caused that data to be 

unreliable for final regulatory determinations (approximately 2008). This downward trend is 

shown in Figure 9. The Shelby County, Tennessee monitor has an incomplete design value of 9.7 

ug/m3for the 2011-2013 timeframe.

Figure 9. Memphis Area Air Monitor DV Trends

The EPA evaluated PM2.5 and PM2.5-precursor emissions and related data from the counties in 

the Memphis area. Table 3 provides a summary of this data. Shelby County has the majority of 

PM2.5 and precursor emissions, population and VMT. Shelby County also has four large sources 

just 8-12 miles upwind of the Shelby County monitor, including Cargill Corn Milling (330 tpy 

PM2.5 and 3,000 tpy SO2) and Allen Fossil Plant (415 tpy PM2.5 and 11,000 tpy SO2) as can be 

seen in the map of the Memphis area provided in Figure 8.

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14

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2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

Memphis Area Design Values

PM2.5 NAAQS Shelby, TN-0047 (N.V. since 2008)

Shelby, TN-0014 Shelby, TN-0038

Shelby, TN-1004 Crittenden, AR-0004

Crittenden, AR-0005 DeSoto, MS-0002
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Table 3. Summary Statistics for the Memphis, TN-MS-AR CBSA 

Fayette Shelby Tipton Benton Desoto Marshall Tate Tunica Crittenden

State TN TN TN MS MS MS MS MS AR

Core 

urbanized 

county or 

outlying?

Outlying Core Outlying Outlying Core Outlying Outlying Outlying Core

SO2 

Emissions 

(tpy)

429 20,010 308 36 52 63 58 107 125

Primary 

Sulfate 

Emissions 

(tpy)

10 140 8 10 29 6 6 8 11

PM2.5

emissions 

(tpy)

790 4,042 874 475 1,419 1,064 651 1,471 1,854

Population 38,413 928,792 61,160 8,712 161,732 37,098 28,970 10,741 50,952

Population 

(% of CBSA) 3% 70% 5% 1% 12% 3% 2% 1% 4%

Population 

growth (2000 

– 2010)

33% 4% 19% 9% 51% 6% 14% 16% 0.2%

VMT 

(Millions) 540 8,562 417 190 1,798 683 365 237 866

VMT (% of 

CBSA) 4% 63% 3% 1% 13% 5% 3% 2% 6%

The EPA also evaluated the meteorology in the area by evaluating wind data collected at the 

Memphis International Airport. Figure 10 is a wind rose created from five years of data from 

2009-2013. The predominant winds blow from the south and southwesterly directions, with a 

smaller component of winds blowing from the north to the south. These wind patterns suggest 

the Shelby County monitor would be impacted by emissions from these large point sources in 

Shelby County. 
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Figure 10. Wind Rose Data for the Memphis TN-MS-AR Area

WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Memphis International Airport

2009-2013

COMMENTS: COMPANY NAME:

MODELER:

DATE:

7/28/2014

PROJECT NO.:

NORTH

SOUTH

WEST EAST

3%

6%

9%

12%

15%

WIND SPEED 

(m/s)

 >= 11.1

 8.8 - 11.1

 5.7 - 8.8

 3.6 - 5.7

 2.1 - 3.6

 0.5 - 2.1

Calms: 16.22%

TOTAL COUNT:

43822 hrs.

CALM WINDS:

16.22%

DATA PERIOD:

Start Date: 1/1/2009 - 00:00

End Date: 12/31/2013 - 23:00

AVG. WIND SPEED:

3.35 m/s

DISPLAY:

 Wind Speed

Direction (blowing from)
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In addition, the EPA evaluated speciated PM2.5 information collected at the Chemical Speciation 

Network monitor in the area (Figure 11). The PM2.5 speciation data and the derived urbanincrement analysis indicate the dominance of different contributing species in each quarter. The 

peak PM2.5 concentrations occur during the 3rd quarter of the calendar year (July-September) 

when sulfate and primary organic matter are the major urban increment components of the PM2.5 

mass. Largely responsible for these peak concentrations are the emissions from Shelby County, 

which include 20,010 tpy of SO2 and 140 tpy direct sulfate. By comparison, the Mississippi and 

Arkansas counties of the CBSA have low overall emissions, and in particular they have 

emissions of SO2 and direct sulfate in the range of just 36 to 125 tpy and 6 to 29 tpy, 

respectively.

Figure 11. Quarterly Speciated Monitoring and Urban Increment Data for the Memphis Area

Memphis Area Conclusion:

As a result of our technical analysis of the Memphis CBSA, the EPA is deferring designations 

for the Tennessee counties of Shelby, Fayette and Tipton along with most of the State of 

Tennessee due to the ambient monitoring data quality issues, including an invalid 2013 design 

value at the Shelby County monitor. The EPA is designating Crittenden County, Arkansas, and 

Benton, DeSoto, Marshall, Tate and Tunica Counties in Mississippi as unclassifiable/attainment, 

which agrees with the recommendations from Mississippi and represents a slight modification6to 

the recommendation from Arkansas of attainment for Crittenden County. As discussed above, 

 

6

In its recommendation letter, Arkansas recommended Crittenden County be designated “attainment.” The EPA is 

designating Crittenden County “unclassifiable/attainment.”
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any potential violation at the Shelby County monitor would be influenced by the point sources 

within Shelby County, Tennessee, particularly the much higher level of SO2 and direct sulfate 

emissions relative to the rest of the CBSA.