1

Knoxville, Tennessee

Area Designations for the 

2008 Ozone National Ambient Air Quality Standards

The table below identifies the counties or parts of counties in Tennessee that EPA is designating as 

“nonattainment” for the 2008 ozone national ambient air quality standards (2008 ozone NAAQS) as part 

of the Knoxville, TN area. In accordance with section 107(d) of the Clean Air Act, EPA must designate 

an area (county or part of a county) “nonattainment” if it is violating the 2008 ozone NAAQS or if it is 

contributing to a violation of the 2008 ozone NAAQS in a nearby area. The technical analyses 

supporting the boundaries for the individual nonattainment areas are provided below.

Table 1: Final Nonattainment Area for Knoxville, TN

Area 

Tennessee’s Recommended 

Nonattainment Counties1

EPA’s Final

Nonattainment Counties

Knoxville, TN Blount (partial) Anderson (partial)

Blount

Knox

EPA is designating the remaining counties in Tennessee that are not included in the table above or in the 

Memphis, TN-MS-AR nonattainment area (see the separate technical support document for this area) as 

“unclassifiable/attainment” for the 2008 8-hour ozone NAAQS.

The analysis below provides the basis for the Knoxville, TN nonattainment area boundary. It relies on 

EPA’s analysis of whether and which monitors are violating the 2008 ozone NAAQS, based on certified 

air quality monitoring data from 2009-2011, and an evaluation of whether nearby areas are contributing 

to such violations. EPA has evaluated contributions from nearby areas based on a weight of evidence 

analysis considering the factors identified below. EPA issued guidance on December 4, 2008, that 

identified these factors as ones EPA would consider in determining nonattainment area boundaries and 

recommended that states consider these factors in making their designations recommendations to EPA.2 

1. Air quality data (including the design value calculated for each Federal Reference Method or 

Federal Equivalent Method (FEM) monitors in the area);

2. Emissions and emissions-related data (including location of sources and population, amount of 

emissions and emissions controls, and urban growth patterns);

3. Meteorology (weather/transport patterns);

4. Geography and topography (mountain ranges or other basin boundaries);

5. Jurisdictional boundaries (e.g., counties, air districts, existing nonattainment areas, Indian 

country, metropolitan planning organizations (MPOs))

Ground-level ozone generally is not emitted directly into the air, but is created by chemical reactions 

between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. 

Because NOx and VOC emissions from a broad range of sources over a wide area typically contribute to 

violations of the ozone NAAQS, EPA believes it is important to consider whether there are contributing 

 1 Tennessee provided several alternatives but this reflects the State’s first preference. 2 The December 4, 2008 guidance memorandum “Area Designations for the 2008 Revised Ozone National Ambient Air 

Quality Standards” refers to 9 factors. In this technical support document we have grouped the emissions-related factors 

together under the heading of “Emissions and Emissions-Related Data,” which results in 5 categories of factors.
2

emissions from a broad geographic area. Accordingly, EPA chose to examine the 5 factors with respect 

to the larger of the Combined Statistical Area (CSA) or Core Based Statistical Area (CBSA) associated 

with the violating monitor(s).3 All data and information used by EPA in this evaluation are the latest 

available to EPA.

In EPA’s designations guidance for the 2008 ozone NAAQS, EPA recommended examining 

CSA/CBSAs because certain factors used to establish CSAs and CBSAs are similar to the factors EPA is 

using in this technical analysis to determine if a nearby area is contributing to a violation of the 2008 

ozone NAAQS. Congress required a similar approach in 1990 for areas classified as serious or above 

for the 1-hour ozone NAAQS and EPA used the same basic approach in the designation process for the 

1997 ozone NAAQS. Where a violating monitor is not located in a CSA or CBSA, EPA’s guidance 

recommended using the boundary of the county containing the violating monitor as the starting point for 

considering the nonattainment area’s boundary. 

 3 Lists of CBSAs and CSAs and their geographic components are provided at 

www.census.gov/population/www/metroareas/metrodef.html . The lists are periodically updated by the Office of 

Management and Budget. EPA used the most recent update, based on 2008 population estimates, issued on December 1, 

2009 (OMB Bulletin No. 10-02).
3

Technical Analysis for Knoxville, TN

Figure 1 is a map of the Knoxville, TN nonattainment area. The map also shows locations and design 

values of air quality monitors, county and other jurisdictional boundaries, the nonattainment area 

boundary for 1997 ozone NAAQS, and major transportation arteries.

Figure 1. Knoxville-Sevierville-La Follette CSA

For purposes of the 1997 8-hour ozone NAAQS, EPA designated the following counties as 

nonattainment: Anderson, Blount, Jefferson, Knox, Loudon, and Sevier Counties, and a portion of 

Cocke County, Tennessee. 

In March 2009, Tennessee recommended that Anderson, Blount, Knox, Loudon, and Sevier Counties in 

their entireties, and a portion of Cocke County be designated as the “Knoxville” nonattainment area for 

the 2008 8-hour ozone NAAQS based on air quality data from 2006-2008. In March 2009, Tennessee 

also recommended that Jefferson County be designated as the “Morristown” nonattainment area, 

separate from a Knoxville nonattainment area, for the 2008 8-hour ozone NAAQS based on air quality 

data from 2006-2008. Letter from James H. Fyke, Commissioner, State of Tennessee Department of 

Environment and Conservation to A. Stanley Meiburg, Acting Regional Administrator, US EPA Region 

4 (March 10, 2009) (on file with US EPA Region 4). 
4

In November 2011, Tennessee provided an update to their 2009 original recommendation based on 

preliminary air quality data from 2009-2011. In its updated recommendation, Tennessee recommended 

that the portions of Blount, Cocke, and Sevier Counties that comprise the Tennessee portion of the Great 

Smoky Mountains National Park be designated “nonattainment” for the 2008 ozone NAAQS. Letter 

from Robert J. Martineau Jr, Commissioner, State of Tennessee Department of Environment and 

Conservation to Gwen Keyes Fleming, Regional Administrator, US EPA Region 4 (November 8, 2011) 

(on file with US EPA Region 4). The March 2009 and November 2011 recommendations were based on 

data from FEM monitors sited and operated in accordance with 40 CFR Part 58. 

On December 9, 2011, EPA initiated the 120 day consultation process by notifying the State of 

Tennessee that based on EPA’s technical analysis of the 12-county Knoxville-Sevierville-La Follette 

CSA, EPA intended to designate five whole counties and one partial county in Tennessee (identified in 

Table 2 below) as “nonattainment” for the 2008 ozone NAAQS as part of the Knoxville, TN

nonattainment area. In this December 2011 letter, EPA also requested that if Tennessee wished to 

provide comments on EPA’s intended designation or to use early certified data for designation, they 

should provide comments or early certify by February 29, 2012. 

Table 2. State's Recommended and EPA’s Intended Designated Nonattainment Counties for Knoxville, 

TN from December 9, 2011

Knoxville, TN State-Recommended 

Nonattainment Counties*

EPA Intended

Nonattainment Counties**

Tennessee Anderson (partial)

Blount (partial)

Knox

Anderson***

Blount

Cocke (partial)

Knox

Loudon

Sevier

* Based on 2008 -2010 data

**bold italics represent counties (or portion of counties) that were not included in the final boundary for 

the nonattainment area.

*** EPA proposed nonattainment for all of Anderson County which is different from the final partial 

county designation.

In February 2012, during the 120 day comment period, Tennessee submitted an updated 

recommendation for nonattainment. In it Tennessee preferred that 2009-2011 data be used for 

designations and recommended, if 2009-2011 data could be used, nonattainment for that portion of

Blount County that contains the Great Smoky Mountains National Park and attainment for the rest of the 

area.

4

 Tennessee’s February 2012 update also recommended, if 2008-2010 data must be used, 

nonattainment for the entire counties of Blount, Knox and Loudon and that portion of Anderson County 

limited to the census tract(s) including the Tennessee Valley Authority’s (TVA’s) Bull Run Fossil Plant. 

On April 5, 2012, Tennessee submitted additional technical information to support a revised

nonattainment boundary based on 2009-2011 design values. Tennessee’s recommendations are listed 

below based on order of preference: 

 4 In a letter dated April 10, 2012, EPA approved the use of Tennessee’s 2009-2011 data which was originally certified on 

November 28, 2011. See docket for approval letter.
5

A) Portion of Blount County containing the Great Smokey Mountains National Park as 

nonattainment and the rest of the Blount and all of Anderson, Cocke, Knox, Loudon, and Sevier 

Counties as attainment; or

B) Portions of Blount, Cocke, and Sevier Counties comprising the Great Smokey Mountains 

National Park nonattainment and the rest of the Blount, Cocke, and Sevier and all of Anderson, 

Knox and Loudon Counties attainment; or 

C) Knox County and the portions of Blount, Cocke, and Sevier Counties nonattainment and the 

rest of Blount, Cocke, and Sevier and all of Anderson and Loudon Counties attainment.

Tennessee also recommended that, if 2008-2010 were used, that EPA consider the following 

recommendations, listed in order of preference: 

D) Knox County and portions of Blount, Cocke, and Sevier Counties comprising the Great 

Smokey Mountains National Park nonattainment and the rest of the Blount, Cocke, and Sevier 

and all of Anderson and Loudon Counties attainment; or

E) Knox County, portions of Blount and portions of Anderson Counties as nonattainment, and 

the rest of the area attainment. Their recommended boundary for Anderson is centered on two 

census tracts encompassing the TVA Bull Run Facility, a coal-fired power plant located in the 

southern portion of the county bordering Knox County. Their recommended boundary for Blount 

County consists of two partial nonattainment boundaries- the area north of US Highway 411 and 

the census tract encompassing the Alcoa South property and the property in between Alcoa 

South and US Highway 411 and the portion of Blount located in the Great Smokey Mountains 

National Park. The rest of Blount County would be classified as attainment/unclassifiable. The 

State attributes the violating monitor to long range transport only. 

EPA begins with the CSA or CBSA areas for purposes of evaluating what areas violate and or contribute 

to a nearby violation of the ozone NAAQS. We have refined the evaluation made available to the State 

in December 2011 by considering additional technical information provided by the states and tribes. 

After considering the information available to us for the Knoxville, TN area, EPA is designating two 

entire counties and one partial county in Tennessee (identified in Table 1 above) as “nonattainment” for 

the 2008 ozone NAAQS as part of the Knoxville, TN nonattainment area. 

Based on data from 2009-2011, only one monitor in the area is violating the NAAQS as compared with 

three violating the NAAQS based on data from 2008-2010, which was the most recent data available at

the time we notified the state of our intended modifications in December 2011. Therefore, EPA 

conducted a revised analysis on whether to include Cocke, Knox, Loudon and Sevier County as part of 

the nonattainment area. EPA also considered Tennessee’s assertion that the violations at the one 

violating monitor, which is located in Blount County, were attributable to long range transport and not 

significantly impacted by localized emissions from counties within the CSA.

Factor Assessment

Factor 1: Air Quality Data 
6

For this factor, EPA considered 8-hour ozone design values (in parts per billion (ppb)) for air quality 

monitors in counties in the Knoxville-Sevierville-La Follette, TN CSA, based on data for the 2009-2011

period (i.e., the 2011 design value), which are the most recent years with fully-certified air quality data. 

It should be noted that for EPA’s December 9, 2011, technical analysis EPA only had certified 

monitoring data for the 2008-2010 period for the Knoxville-Sevierville-La Follette, TN CSA to 

consider. The 2009-2011 monitoring data indicated a decline in the number of violating monitors (from 

3 to 1) in the Knoxville-Sevierville-La Follette, TN CSA. EPA’s updated analysis in support of this 

final designation determination considers the reduction in the number of violating monitors for this area.

A monitor’s design value is the metric or statistic that indicates whether that monitor attains a specified 

air quality standard. The 2008 ozone NAAQS are met at a monitor when the annual fourth-highest daily 

maximum 8-hour average concentration, averaged over 3 years is 75 ppb or less. A design value is only 

valid if minimum data completeness criteria are met. See 40 CFR part 50 Appendix P. Where several 

monitors are located in a county (or a designated nonattainment area or maintenance area), the design 

value for the county or area is determined by the monitor with the highest level.

The 2009-2011 design values for the 2008 ozone NAAQS for counties in the Knoxville-Sevierville-La 

Follette, TN CSA are shown in Table 3.

Table 3. Air Quality Data.

County* State Recommended 

Nonattainment? 5 2009-2011 Design Value (ppb)

Anderson, TN No 70

Blount, TN Yes (Partial) 77

Cocke, TN No N/A

Jefferson, TN No 73

Knox, TN No 71

Loudon, TN No 72

Sevier, TN No 75

*Counties with violating monitors are shown in bold.

Based on 2009-2011 monitoring data, Blount County shows a violation of the 2008 ozone NAAQS, 

therefore this county is included in the nonattainment area. For EPA’s initial boundary determination 

for the Knoxville, TN area, released December 9, 2011, EPA included Knox and Sevier Counties based 

on violating monitors in these counties for the monitoring period of 2008-2010. As mentioned above, 

Tennessee has since certified its 2009-2011 data, and thus EPA consideration of inclusion of Knox and 

Sevier Counties is based on whether or not these areas contribute to violations at the nearby monitor in 

Blount County. 

A county (or partial county) must also be designated nonattainment if it contributes to a violation in a 

nearby area. Each county without a violating monitor that is located near a county with a violating

monitor has been evaluated, as discussed below, based on the five factors to determine whether it 

contributes to the nearby violation. EPA started with the CSA or CBSA for evaluating what areas 

violate and contribute to violations of the ozone NAAQS.

 5 Tennessee provided several alternatives but this reflects the State’s first preference.
7

Factor 2: Emissions and Emissions-Related Data

EPA evaluated emissions of ozone precursors (NOx and VOC) and other emissions-related data that 

provide information on areas contributing to violating monitors.

Emissions Data

EPA evaluated county-level emission data for NOx and VOC derived from the 2008 National Emissions 

Inventory (NEI), version 1.5. This is the most recently available NEI. (See 

http://www.epa.gov/ttn/chief/net/2008inventory.html) Significant emissions levels in a nearby area 

indicate the potential for the area to contribute to observed violations. EPA also considered any 

additional information we received on changes to emissions levels that are not reflected in recent 

inventories. 

As mentioned above, EPA received additional information from Tennessee following the preliminary 

boundary determination for the Knoxville, TN nonattainment area, and this information was considered 

for this final designation. Specifically, Tennessee provided additional information regarding the 

potential impacts of long range transport of emissions on the violations at the Blount County monitor 

and also provided additional information on the reduction in emissions at the Tennessee Valley 

Authority’s (TVA’s) Bull Run facility.

The precursor emission source-category percentages used below and throughout the document were 

derived from emissions data from the 2008 NEI version 1.5 referenced above. Table 4 shows emissions 

of NOx and VOC (given in tons per year (tpy)) for violating and nearby counties that EPA considered 

for inclusion in the Knoxville, TN area. 

Table 4. Total 2008 NOx and VOC Emissions.

County* State Recommended

Nonattainment? 6 NOx (tpy) VOC (tpy)

Anderson, TN No 12,475 3,569

Blount, TN Yes (Partial) 3,593 6,749

Campbell, TN No 2,964 1,773

Cocke, TN No 1,761 2,273

Grainger, TN No 687 1,216

Hamblen, TN No 6,612 4,719

Jefferson, TN No 3,148 3,329

Knox, TN No 15,169 16,182

Loudon, TN No 3,751 3,340

Roane, TN No 10,711 3,006

Sevier, TN No 2,602 5,399

Union, TN No 432 959

Areawide: 63,905 52,514

*Counties that EPA intends to designate as nonattainment are shown in bold.

Knox County is leading all counties with 24 percent of NOx and 31 percent VOC of the CSA’s 

emissions. Anderson County emits 19 percent of the CSA’s NOx emissions with 77 percent from point 

sources. It is worth noting that TVA’s Bull Run Facility Electric Generating Unit (EGU) in Anderson 

 6 Tennessee provided several alternatives but this reflects the State’s first preference.
8

County generated 1,086 tpy of NOx with selective catalytic reduction (SCR) control during the 2008 

ozone season. Blount County is the second highest VOC contributor at 6,749 tpy, 13 percent of the 

CSA total, and the fourth highest contributor of NOx emissions at 3,593 tpy. 

Population density and degree of urbanization

EPA evaluated the population and vehicle use characteristics and trends of the area as indicators of the 

probable location and magnitude of non-point source emissions. These include ozone-creating 

emissions from on-road and off-road vehicles and engines, consumer products, residential fuel 

combustion, and consumer services. Areas of dense population or commercial development are an 

indicator of area source and mobile source NOx and VOC emissions that may contribute to ozone 

formation. Rapid population or vehicle miles travelled (VMT) growth (see below) in a county on the 

urban perimeter signifies increasing integration with the core urban area, and indicates that it may be 

appropriate to include the area associated with the area source and mobile source emissions as part of

the nonattainment area. Table 5 shows the population, population density, and population growth 

information for each county in the Area.

Table 5. Population and Growth.

County*

State 

Recommended 

Nonattainment? 7 2010 Population

2010 Population 

Density

(1000 pop/sq mi)

Absolute change 

in population

(2000-2010)

Population % 

change

(2000-2010)

Anderson No 75,129 0.22 3,897 +5%

Blount Yes (Partial) 123,010 0.22 16,793 +16%

Campbell No 40,716 0.08 853 +2%

Cocke No 35,662 0.08 2,035 +6%

Grainger No 22,657 0.07 1,920 +9%

Hamblen No 62,544 0.36 4,301 +7%

Jefferson No 51,407 0.16 6,825 +15%

Knox No 432,226 0.82 49,198 +13%

Loudon No 48,556 0.20 9,342 +24%

Roane No 54,181 0.14 2,238 +4%

Sevier No 89,889 0.15 18,190 +25%

Union No 19,109 0.08 1,250 +7%

Areawide: 1,055,086 0.23 116,842 12%

*Counties that EPA intends to designate as nonattainment are shown in bold.

Sources: U.S. Census Bureau population estimates for 2010 as of August 4, 2011 

(http://factfinder2.census.gov/faces/tableservices/jsf/pages/productview.xhtml?pid=DEC_10_PL_GCTPL2.STO5&

prodType=table)

Blount County experienced 16 percent growth in population. Blount County is home to 11 percent of 

the CSA’s population and the second most populous after Knox County. Blount County’s urban and 

agriculture development is in the northwestern half of the County. Knox County has the highest 

population density, the largest absolute change in population, and the largest population in the 12-county 

CSA. Anderson County has intermittent urbanization in Oak Ridge and Clifton on the southwestern part 

of the county, adjacent to Knoxville. 

 7 Tennessee provided several alternatives but this reflects the state’s first preference.
9

Cocke County has the lowest population of all of the counties that are being considered for inclusion in 

the Knoxville, TN nonattainment area at a 2010 population of 35,662 people. Further, Cocke County 

has an absolute change in population from 2000-2010 of 2,035 people with the lowest population 

density of the counties being considered for the nonattainment area. Also Cocke County’s population 

grew by 6 percent from 2000-2010 – one of the lowest population change in the area.

Traffic VMT data and commuting patterns

EPA evaluated the total VMT for each county. In combination with the population/population density 

data and the location of main transportation arteries (see above), this information helps identify the 

probable location of non-point source emissions. A county with high VMT is generally an integral part 

of an urban area and indicates the presence of motor vehicle emissions that may contribute to ozone 

formation that contributes to nonattainment in the area. Rapid population or VMT growth in a county on 

the urban perimeter signifies increasing integration with the core urban area, and indicates that the 

associated area source and mobile source emissions may be appropriate to include in the nonattainment 

area. Table 5 shows the total 2008 VMT for each county and number of workers for each county in the 

area.

Table 5. Traffic and VMT Data.

County* State Recommended 

Nonattainment? 8

2008 VMT**

(million miles)

Number of County 

Workers*** (2009 

data)

Percent of County 

Workers that Work 

in Counties with 

Violating 

Monitors***

Anderson No 831 41,468 3.0

Blount Yes (Partial) 1,105 39,083 51.4

Campbell No 656 7,867 1.1

Cocke No 455 7,378 N/A

Grainger No 232 2,773 N/A

Hamblen No 656 29,481 N/A

Jefferson No 819 11,256 1.2

Knox No 5,304 224,770 7.2

Loudon No 782 13,690 7.3

Roane No 743 11,637 1.7

Sevier No 1,164 35,826 3.9

Union No 134 2,341 1.5

Areawide: 12,881 427,570

*Counties (or portions of counties) that EPA is designating as nonattainment are shown in bold.

**MOBILE model VMTs are those inputs into the NEI version 1.5. 

*** Source: U.S. Census Bureau http://onthemap.ces.census.gov/

Knox County leads the CSA with the highest VMT followed by Sevier and Blount Counties. 

 8 Tennessee provided several alternatives but this reflects the state’s first preference
10

A little more than half of the workers, about 20,072 workers, live and work within Blount County. The 

second largest percentage of Blount County workers are from Loudon County. The third largest 

percentage of Blount County workers, (i.e., 16,079 workers) are from Knox County. 

Since Lenoir City in Loudon County, and Seymour in Sevier County are a part of the urbanized portion 

of the Area and a part of the MPO (see figure 2), EPA reviewed the VMT data from these cities and 

determined that, based on 2009 Census Bureau data, 290 Blount County workers are from Lenior City 

and 120 Blount County workers are from Seymour. The two cities combined workers are less than 1 

percent of Blount County’s total workforce. 

Figure 2. Urbanized Areas

Factor 3: Meteorology (weather/transport patterns)

For this factor, EPA analyzed 30-years of National Weather Service (NWS) wind speed and wind 

direction data collected at the Knoxville/McGhee Tyson Airport (Station #13891) to help determine 

transport patterns and source contributions. EPA also assessed wind direction and speed for the 2009-

2011 “ozone season” (March through October) in the Knoxville-Sevierville-La Follette, TN CSA. The 

analysis was conducted to better understand the fate and transport of precursor emissions contributing to 

ozone formation. EPA’s analysis of the NWS data indicate predominate southwest, west-southwest and 

north-northeast components for the Knoxville-Sevierville-La Follette, TN CSA. Persistent winds 
11

blowing from the north and northeast may transport ozone precursor emissions from the urbanized areas 

of Knoxville toward the Blount County monitor. 

EPA also conducted a wind back trajectory analysis using the National Oceanic and Atmospheric 

Administration’s (NOAA) Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) 

model to evaluate potential contribution from nearby areas. The HYSPLIT analysis was done on days 

that exceeded the 2008 ozone NAAQS at the Blount County monitor during the 2009-2011 timeframe. 

The results of this analysis are presented in Figure 3. As can be seen in Figure 3, many of the back 

trajectories cross over areas of Knox and Blount counties and several cross over the two census tracts in 

Anderson county that are included in the nonattainment area. These trajectories provide evidence that 

ozone precursor emissions from sources in Knox, Blount and a portion of Anderson counties may 

contribute to violations measured at the Blount county monitor.

Tennessee submitted to EPA information prepared by Walter Landsden Dortch &Davis, LLP and 

EnSafe on behalf the six Tennessee Counties of Anderson, Blount, Cocke, Knox, Loudon and Sevier. 

This submittal contains a wind direction analysis of the same 2009-2011 Knoxville Airport NWS data as 

discussed above. The submittal also contains HYSPLIT back trajectory analyses that provide similar 

information to EPA’s HYSPLIT analysis. The submittal also provides information to make the 

argument that the Blount County monitor is a “high elevation monitor” that is primarily impacted 

regional transport of ozone. However, the information shows that both downwind urban ozone 

formation from Knoxville, Knox County, Blount County and portions of Anderson County ozone 

precursor emissions and high elevation regional transport of ozone contribute to the NAAQS violations 

at the Blount County monitor. 
12

Figure 3. HYSPLIT Back Trajectories for each violating day during the 2009-2011 timeframe.

Factor 4: Geography/topography (mountain ranges or other air basin boundaries)

The geography/topography analysis evaluates the physical features of the land that might affect the air

shed and, therefore, the distribution of ozone over the area.

Regional topography consists of linear ridge and parallel lowland valleys. The Area has predominantly 

high elevations in the northern regions and lower elevations further south ranging from 700 to 1,500 

feet. The Knoxville-Sevierville-La Follette, TN CSA includes the Tennessee portion of the Great 

Smoky Mountains National Park (GSMNP). This area consists of densely forested high peaks and 

valleys. The highest point in the state is at Clingman’s Dome with an elevation of 6,643 feet. There are 

three violating monitors in the Knoxville area that are at the higher elevations and within the GSMNP. 

These monitors are Look Rock (AQS ID: 47-009-0101, 2009-2011 design value of 76 ppb) in Blount 

County, Cove Mountain (AQS ID: 47-155-0101, 2009-2011 design value of 75 ppb) in Sevier County, 

and Clingman's Dome (AQS ID: 47-155-0102, 2009-2011 design value of 75 ppb), also in Sevier 

County.

Figure 4 shows a topographical map of Knoxville and the National Park. These two monitors are 

located at a significantly higher elevation than the Knox County monitors. High elevation ozone sites 

often measure elevated ozone levels overnight due to regional transport of tropospheric ozone formed 
13

during the daytime. The regional transport mechanisms that cause these events are related to downward

transport by vertical mixing that concentrates the tropospheric ozone or by horizontal transport from 

surrounding areas (Eliasson et al, 2003). The long duration of these nocturnal events can also be 

attributed to a lack of local Nitric Oxide (NO) emissions which act to titrate the ozone and reduce the 

ambient ozone concentration as occurs in urban areas overnight (Eliasson et al, 2003) 9.

Figure 5 compares the hourly distribution of daily maximum hourly ozone values over 65 ppb for four 

sites: Look Rock, two urban Knox County Sites, and Blue Ridge Parkway, another high elevation site in 

North Carolina in the GSMNP that is further removed from urban areas. The Knoxville sites show a 

typical urban pattern of ozone events in the afternoon (approximately 12:00 pm to 6:00 pm). The Blue 

Ridge Parkway site is impacted primarily by regional transport and shows a typical high elevation site 

pattern of ozone events overnight (approximately 9:00 pm to 3:00 am). This site is not in the Knoxville 

Sevierville-La Follette CSA and is only included as an example of another high elevation site. The 

Look Rock site shows a combination of these two signals, indicating that the site is impacted by both 

downwind afternoon ozone formation from Knoxville and high elevation ozone transport. In some 

cases, these two processes could be affecting the Look Rock monitor simultaneously. 

Figure 6 shows the frequency of ozone hourly values greater than 75 ppb by wind direction and time of 

day for the Look Rock site. This figure illustrates two distinct groups of high ozone events: afternoon 

ozone from the north to northwest (Knoxville) and overnight ozone from the south to southeast (regional 

transport). The Cove Mountain site in Sevier County shows a similar pattern as the Look Rock, 

although with a slightly less pronounced urban signal.

As a result of these analyses, EPA has concluded that both downwind urban ozone formation from 

Knoxville, Knox County, Blount County and portions of Anderson County ozone precursor emissions

and high elevation regional transport of ozone contribute to the NAAQS violations at the Look Rock and 

Cove Mountain monitors.

 9 Ingegärd Eliasson, Sofia Thorsson, Yvonne Andersson-Sköld, Summer nocturnal ozone maxima in Göteborg, Sweden, 

Atmospheric Environment, Volume 37, Issue 19, June 2003, Pages 2615-2627.
14

Figure 4. Topographical map of Knoxville and the Great Smoky Mountains National Park

Figure 5. 2007-2010 Count of Daily Max Values > 65 ppb

0

10

20

30

40

50

60

70

80

Count

2007-2010 Count of Daily Max Hourly Values > 65 ppb

GREAT SMOKY MOUNTAINS NP LOOK ROCK

TOWER BLUE RIDGE PKWY MILE MARKER 410

9315 RUTLEDGE PIKE MASCOT TN 37806

4625 MILDRED DRIVE

Overlap of 

downwind

and high 

elevation 

ozone

Urban/DownwindO3 profile

High elevation/transport O3 profile
15

Figure 6. Frequency of Look Rock Ozone Hourly Values >75 ppb

Factor 5: Jurisdictional boundaries

Once EPA identified the general areas that the Agency anticipated would be included in the 

nonattainment area, EPA then considered existing jurisdictional boundaries for the purposes of 

providing a clearly defined legal boundary and to help identify the areas appropriate for carrying out the 

air quality planning and enforcement functions for nonattainment areas. Examples of jurisdictional 

boundaries include existing/prior nonattainment area boundaries for ozone or other urban-scale 

pollutants, county lines, air district boundaries, township boundaries, area covered by an MPO, state 

lines, Areas of Indian Country, and urban growth boundary. Where existing jurisdictional boundaries 

were not adequate or appropriate to describe the nonattainment area, other clearly defined and 

permanent landmarks or geographic coordinates were considered.

The Knoxville, TN area has previously established nonattainment boundaries associated with the both 

the 1-hour ozone and 1997 8-hour ozone NAAQS. The Knoxville nonattainment boundary for the 1-

hour ozone NAAQS included Knox County, Tennessee in its entirety. Whereas the Knoxville 
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nonattainment boundary for the 1997 8-hour ozone NAAQS included Anderson, Blount, Jefferson, 

Knox, Loudon, and Sevier Counties in Tennessee in their entireties, and a portion of Cocke County, 

Tennessee. 

Conclusion

Based on the assessment of factors described above, EPA has concluded that the following counties 

should be included as part of the Knoxville, TN nonattainment area because they are either violating the 

2008 ozone NAAQS or contributing to a violation in a nearby area: Blount and Knox Counties, in their 

entireties and a portion of Anderson comprising the two census tracts with the TVA Bull Run Facility 

(Census Tract Numbers 202 and 213.02 from the 2000 Census). All of these counties (or portions 

thereof) are included in the Knoxville, TN nonattainment area for the 1997 ozone NAAQS. 

The air quality monitor in Blount indicates a violation of the 2008 ozone NAAQS based on 2009-2011

design values, therefore the County is included in the nonattainment area. Knox County has an attaining 

monitor based on 2009-2011 so the county is being brought into this nonattainment area as a 

contributing county. Knox County has among the highest NOx and VOC emissions; it is the largest and 

most densely populated county; and it has the most VMT traveled in the CSA. Anderson does not have 

a violating monitor, but EPA has concluded that the TVA Bull Run Facility contributes to the 2008 

ozone NAAQS violations in the Area due to its point source emissions. Anderson County had the 

second highest NOx emissions, contributing 19 percent of the CSA’s total NOx. Given the prevalent 

wind direction (southwest, west-southwest and north-northeast), the TVA Bull Run Facility in Anderson 

County contributes to the violating monitor to Blount County, and therefore we are including the portion 

of the county in which the facility is located in the nonattainment area based on contribution. Though 

SCR controls were installed at the TVA facility, total NOx levels have fluctuated since 2006 going from 

686 tons, to as high as 1,087 tons in 2008, down to 400 tons in 2009 and recently up to 758 tons for 

2011. The Heat Input (in units of MMBtu), which indicates fuel utilization, has also fluctuated in 

conjunction with the NOx levels.