1

Charlotte-Rock Hill, NC-SC 

Area Designations for the 

2008 Ozone National Ambient Air Quality Standards

The table below identifies the areas in North Carolina and South Carolina that EPA has designated as 

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

of the Charlotte-Rock Hill, NC-SC 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 this nonattainment area is provided below.

Table 1: Final Nonattainment Area for the Charlotte-Rock Hill, NC-SC Area

Area 

State Recommended Nonattainment 

Counties

EPA’s Final Designated 

Nonattainment Counties

Charlotte-Rock Hill, NC-SC * North Carolina: 

Cabarrus (partial)**

Gaston (partial)**

Iredell (partial)**

Lincoln (partial)**

Mecklenburg County

Rowan (partial)**

Union (partial)**

North Carolina:

Cabarrus (partial)**

Gaston (partial)**

Iredell (partial)**

Lincoln (partial)**

Mecklenburg County

Rowan (partial)**

Union (partial)**

South Carolina: None South Carolina: York (partial)1

* Charlotte-Rock Hill, NC-SC is a multi-state nonattainment area. 

** Recommended/designated along township boundaries. Specifically, North Carolina recommended 

that the nonattainment designations be defined as the following: Cabarrus County (part) - Central 

Cabarrus Township, Georgeville Township, Harrisburg Township, Kannapolis Township, Midland 

Township, Mount Pleasant Township, New Gilead Township, Odell Township, Poplar Tent Township,

and Rimertown Township; Gaston County (part) - Crowders Mountain Township, Dallas Township,

Gastonia Township, Riverbend Township, and South Point Township; Iredell County (part) -

Davidson Township and Coddle Creek Township; Lincoln County (part) - Catawba Springs Township,

Ironton Township, and Lincolnton Township; Rowan County (part) - Atwell Township, China Grove 

Township, Franklin Township, Litaker Township, Locke Township, Providence Township, Salisbury 

Township, Steele Township, and Unity Township; Union County (part) - Goose Creek Township,

Marshville Township, Monroe Township, Sandy Ridge Township, and Vance Township.

EPA designated the remaining counties in North Carolina and South Carolina that are not listed in the 

table above as “unclassifiable/attainment” for the 2008 ozone NAAQS. In addition, the Indian country 

of the Catawba Indian Nation is being designated as a separate “unclassifiable/attainment” area for the 

2008 ozone NAAQS.2 The Catawba Indian Nation recommended designation of a separate 

 1 Unless otherwise noted, throughout this document the reference to York County or a portion of York County is meant to 

exclude the consideration of Indian County associated with the Catawba Indian Nation.

2 The Catawba Indian Nation Reservation is located within the South Carolina portion of the bi-state Charlotte nonattainment 

area. Generally air quality State Implementation Plans (SIPs) do not apply in Indian country throughout the United States. 

However, for purposes of the Catawba Indian Nation Reservation in Rock Hill, the South Carolina SIP does apply within the 

Reservation area of Indian country. Pursuant to the Catawba Indian Claims Settlement Act, S.C. Code Ann. 27-16-120, “all 
2

unclassifiable/attainment area through their response to the EPA’s 120-day letter which was released on 

December 9, 2011. More information about EPA’s decision-making with respect to the Indian County 

associated with the Catawba Indian Nation can be found in “Appendix to the Charlotte-Rock Hill 

Technical Support Document – Catawba Indian Nation.”

The analysis below provides the basis for the Charlotte-Rock Hill, NC-SC 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.3

 

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 

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).4 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. 

 

state and local environmental laws and regulations apply to the [Catawba Indian Nation] and Reservation and are fully 

enforceable by all relevant state and local agencies and authorities.” 3 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. 4 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 Charlotte-Rock Hill, NC-SC

Figure 1 is a map of the Charlotte-Rock Hill, NC-SC nonattainment area. The map provides other 

relevant information including the locations and design values of air quality monitors, county and other 

jurisdictional boundaries, the CSA boundary, and national highways.

For purposes of the 1997 8-hour ozone NAAQS, EPA designated the entire counties of Cabarrus, 

Gaston, Lincoln, Mecklenburg, Rowan, Union Counties, in their entireties, and a portion of Iredell 

County in North Carolina; and a portion of York County (including Indian Country), in South Carolina. 

In March 2009, North Carolina recommended that the counties of Cabarrus, Gaston, Lincoln, 

Mecklenburg, Rowan, Union, and a portion of Iredell (Davidson and Coddle Creek Townships) be 

designated as “nonattainment” for the 2008 8-hour ozone NAAQS based on air quality data from 2006-

2008. Additionally, in March 2009, South Carolina recommended that the portion of York County 

encompassed by the boundaries of the Rock Hill-Fort Mill Area Transportation Study (RFATS) MPO 

and the contiguous area encompassing the York ozone monitoring station (45-091-0006) be designated 

as “nonattainment” for the 2008 8-hour ozone NAAQS based on air quality data from 2006-2008. The 

Catawba Indian Nation did not submit a recommendation at that time.

In October 2011, North Carolina submitted an update to their 2009 recommendation and did not make 

revisions to their previous recommendation. Additionally, in October 2011, South Carolina submitted 

an amendment to their 2009 recommendation, and based on preliminary air quality data from 2009-
4

2011, revised their recommendation to “attainment” designations for each county in the State, including 

York County, for the 2008 8-hour ozone NAAQS. These data are from FEM monitors sited and 

operated in accordance with 40 CFR Part 58. (Letters from Dee Freeman, North Carolina 

Environmental Secretary to A. Stanley Meiburg, Acting Regional Administrator-EPA Region 4 and 

Gwendolyn Keyes Fleming, Regional Administrator-EPA Region 4 regarding the initial and updated

nonattainment boundary recommendations for the 2008 8-hour ozone NAAQS for North Carolina

(October 28, 2011 and March 12, 2009, respectively); Letter from Mark Sanford, South Carolina 

Governor to A. Stanley Meiburg, Acting Regional Administrator-EPA Region 4 regarding initial 

nonattainment boundary recommendations for the 2008 8-hour ozone NAAQS for South Carolina 

(March 12, 2009); Letter from Robert W. King, Jr., Deputy Commissioner of the South Carolina 

Environmental Quality Control to Gwendolyn Keyes Fleming, Regional Administrator-EPA Region 4 

regarding updated nonattainment boundary recommendations for the 2008 8-hour ozone NAAQS for 

South Carolina (October 11, 2011)).

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

Carolina and South Carolina, and the Catawba Indian Nation that based on EPA’s technical analysis of 

the 13-county Charlotte-Gastonia-Salisbury CSA, EPA intended to designate six whole counties and one 

partial county in North Carolina; one partial county in South Carolina and Indian Country (associated 

with the Catawba Indian Nation) in South Carolina (identified in Table 2 below) as “nonattainment” for 

the 2008 ozone NAAQS as part of the Charlotte-Rock Hill, NC-SC nonattainment area. In this 

December 2011 letter, EPA also requested that if the States of North Carolina and South Carolina, and 

the Catawba Indian Nation 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, Tribe’s Recommended and EPA’s Intended Designated Nonattainment 

Counties for Charlotte-Rock Hill, NC-SC from December 9, 2011

Charlotte-Rock Hill, 

NC-SC

State- or Tribe-Recommended 

Nonattainment Counties and Areas 

of Indian Country

EPA Intended

Nonattainment Counties and Areas 

of Indian Country^

Catawba Indian Nation None Catawba Indian Nation

North Carolina Cabarrus 

Gaston 

Iredell (partial)

Lincoln

Mecklenburg

Rowan

Union

Cabarrus 

Gaston 

Iredell (partial)

Lincoln

Mecklenburg

Rowan

Union

South Carolina None York (partial)

^bold italics represent areas that were modified in the final boundary determination for the CharlotteRock Hill, NC-SC nonattainment area. 

The Catawba Indian Nation, and the States of North Carolina and South Carolina all submitted 

additional information to support their designation and boundary recommendations. In summary, on 

February 29, 2012, the Catawba Indian Nation provided a recommendation of 

“attainment/unclassifiable” for the area of Indian country and submitted technical information to support 

the tribe’s recommendation of attainment. North Carolina provided certified 2009-2011 monitoring 

data, and revised its previous boundary recommendation to reduce the boundaries for the nonattainment 
5

area from whole counties to partial counties for Cabarrus, Gaston, Lincoln, Rowan and Union counties. 

North Carolina’s recommended boundary for Mecklenburg County, and a portion of Iredell County was 

consistent with its previous recommendation. North Carolina provided additional technical analysis to 

support this recommendation. The State of South Carolina provided recommendations based on 

certified 2009-2011 monitoring data, along with additional technical information, and maintained the 

State’s recommendation that York County in its entirety be designated attainment. 

EPA originally started with the CSA or CBSA areas for evaluating what areas violate and contribute to 

violations of the ozone NAAQS, and for final determinations refined its evaluation based on additional 

technical information provided by the states and tribes. After considering the recommendations and 

additional technical information for the Catawba Indian Nation, North Carolina, and South Carolina, and 

based on EPA's reevaluation of the eight counties and Indian Country as described below, EPA 

designated Mecklenburg County in its entirety and portions of Cabarrus, Gaston, Iredell, Lincoln, 

Rowan, and Union Counties in North Carolina, and a portion of York County (excluding the Indian 

Country associated with the Catawba Indian Nation) in South Carolina as “nonattainment” for the 2008 

ozone NAAQS as part of the Charlotte-Rock Hill, NC-SC nonattainment area. More information about 

EPA’s decision-making with respect to Indian Country associated with the Catawba Indian Nation can 

be found in “Appendix to the Charlotte-Rock Hill Technical Support Document – Catawba Indian 

Nation.” 

Factor Assessment

Factor 1: Air Quality Data 

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

monitors in counties in the Charlotte-Gastonia-Salisbury, NC-SC 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 Charlotte-Gastonia-Salisbury, NC-SC CSA to 

consider. While the updated 2009-2011 monitoring data for the Area indicated a decline in levels 

overall from the 2008-2010 monitoring data, the 2009-2011 monitor data also indicated the violating 

monitors are in the same counties that contained violating monitors when EPA considered for the 

development of the preliminary boundary determination for the Charlotte-Rock Hill, NC-SC 

nonattainment 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 2011 design values for the ozone NAAQS for counties in the Charlotte-Gastonia-Salisbury, NC-SC

CSA and nearby surrounding area are shown in Table 3. (Counties not identified do not have monitors.)

Table 3. Air Quality Data.^
6

County State Recommended 

Nonattainment?

2009-2011 Design Value

(ppb)

Mecklenburg, NC Yes 79

Lincoln, NC Yes 71

Rowan, NC Yes 76

Union, NC Yes 70

York, SC No 64

^Bolded counties are those violating the 2008 ozone NAAQS.

Based on 2009-2011 monitoring data, Mecklenburg and Rowan Counties in North Carolina show 

violations of the 2008 ozone NAAQS, therefore Mecklenburg County, in its entirety, and a portion of 

Rowan County (including the area where the violating monitor is located) is included in the CharlotteRock Hill, NC-SC nonattainment area. 

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. 

Factor 2: Emissions and Emissions-Related Data

EPA evaluated emissions of ozone precursors (i.e., NOx and VOC emissions) and other emissionsrelated 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 the Agency received on changes to emissions levels that are not reflected in 

recent inventories. 
7

As mentioned above, EPA received additional information from the States of North Carolina, South 

Carolina and the Catawba Indian Nation for the preliminary boundary determination for the CharlotteRock Hill, NC-SC nonattainment area, and this information was considered for this final designations. 

While more refined information was provided in some cases for meteorology (and is discussed below), 

and population and vehicle miles travelled (VMT) to account for a partial county emissions (also 

discussed below), no information was provided specifically to indicate that the overall emissions data 

used by EPA from the 2008 NEI was inaccurate. EPA notes that the Agency determined it was 

appropriate to consider full county emissions for Iredell County in North Carolina and York County in 

South Carolina for the EPA’s initial determination in December 2011 for consideration of these counties 

as part of the CSA in this Area because the CSA (and not the previous nonattainment boundary) was the 

Agency’s analytical starting point for the 2008 8-hour ozone designations. Iredell and York Counties in 

their entireties (i.e., not just the partial counties that are currently included in the 1997 8-hour ozone 

nonattainment area) are within the Charlotte-Gastonia-Salisbury CSA and thus were fully considered. 

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. EPA considered the 

refined information for partial county emissions to determine the appropriateness of a partial county 

boundary for these and the other counties in the Charlotte-Gastonia-Salisbury CSA for the final 

designations. 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 Charlotte-Rock Hill, NC-SC area. 

Table 4. Total 2008 NOx and VOC Emissions. ^

County State Recommended 

Nonattainment? NOx (tpy) VOC (tpy)

Anson, NC No 1,241 1,123 

Cabarrus, NC Yes 5,361 9,074 

Chester, SC No 2,652 1,780 

Cleveland, NC No 3,393 4,799 

Gaston, NC Yes 13,002 7,326 

Iredell, NC Yes (partial) 10,261 10,815 

Lancaster, SC No 1,626 2,744 

Lincoln, NC Yes 2,097 3,320 

Mecklenburg, NC Yes 27,275 33,412 

Rowan, NC Yes 7,117 9,834 

Stanly, NC No 1,935 2,986 

Union, NC Yes 5,190 7,748 

York, SC No 7,031 11,840 

Areawide: 88,179 106,802 

^Bolded counties (or portions thereof) that are being included in the nonattainment area.

NOx Emissions: The Charlotte-Gastonia-Salisbury CSA profile reveals that mobile emissions comprise

55 percent of the total NOx in this Area, and that area sources comprise nine percent. The total of both 

mobile and area sources comprises 64 percent of the total NOx emissions in the Charlotte-GastoniaSalisbury CSA. Mecklenburg, Gaston, Iredell, Rowan, and York Counties have the largest amounts of 

total NOx emissions in the CSA with 31 percent, 15 percent, 12 percent, and 8 percent (for both Rowan 

and York Counties each) respectively. The highest percentage of NOx emissions in the CSA come from 

mobile emissions. The percent mobile emissions from the following counties within the CSA are as 

follows: Mecklenburg County – 19 percent, Iredell County – 8 percent, Rowan County – 8 percent and 
8

York County – 4 percent. For Gaston County, the highest percentage of NOx emissions within the CSA

is from point sources, with 9 percent of their total NOx emissions. 

VOC Emissions: The Charlotte-Gastonia-Salisbury CSA profile reveals that mobile emissions 

comprise 42 percent of the total VOC emissions in this Area, and that area sources comprise 38 percent

for the total VOC emissions in the Charlotte-Gastonia-Salisbury CSA. The total of both mobile and area 

sources makes up 80 percent of the total VOC emissions in the Charlotte-Gastonia-Salisbury Area. EPA 

notes that while VOC emissions were considered in the analysis for the Area, EPA also acknowledges 

the study that was submitted by North Carolina during the 120-day consultation period that indicates 

that VOC emissions are not the primary driver for ozone formation in the Charlotte-Gastonia-Salisbury 

CSA. Mecklenburg, York, Iredell, Rowan, and Cabarrus Counties have the largest amounts of total 

VOC emissions in the CSA with 31 percent, 11 percent, 10 percent, 9 percent, and 8 percent, 

respectively. The highest percentage of VOC emissions within the CSA for Mecklenburg County is 

from area sources with 14 percent of their total VOC emissions. The highest percentage of VOC 

emissions within the CSA for Iredell, Cabarrus, and Rowan Counties is from mobile sources with 6 

percent for Iredell County and 5 percent for both Cabarrus and Rowan Counties. Mecklenburg County’s 

VOC emissions for mobile sources comprise 13 percent of the CSA. York County emissions are 

primarily from mobile and area sources.

North Carolina provided additional information showing that the townships in the portions of the 

following Counties: Cabarrus (i.e., Gold Hill Township); Gaston (Cherryville Township); Iredell 

(Barringer, Bethany, Chambersburg, Concord, Cool Springs, Eagle Mills, Fallstown, New Hope, Olin, 

Sharpesburg, Shiloh, Statesville, Turnersburg, and Union Grove Townships); Lincoln (Howards Creek 

and North Brook Townships); Rowan (Cleveland, Morgan, Mount Ulla, and Scotch Irish Townships) 

and Union (Buford, Jackson, Lanes Creek and New Salem Townships) did not contain point sources or 

contained point source emissions below 100 tpy for NOx. The State also provided information that 

these same townships, with the exception of Cleveland Township, did not contain point sources or 

contained point source emissions below 100 tpy for VOC. Cleveland Township in Rowan County 

contains one point source that emits 211 tpy of VOC emissions. 

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 precursor

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 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 CharlotteGastonia-Salisbury, NC-SC CSA that EPA considered for inclusion in the Charlotte-Rock Hill, NC-SC

area.
9

Table 5. Population and Growth. ^

County

State 

Recommended 

Nonattainment?

2010 

Population

2010 

Population 

Density 

(1000 pop/sq 

mi)

Absolute 

change in 

population 

(2000-2010)

Population 

% change 

(2000-

2010)

Anson, NC No 26,948 0.05 1,637 +6% 

Cabarrus, NC Yes 178,011 0.49 45,793 +35% 

Chester, SC No 33,140 0.06 (968) -3% 

Cleveland, NC No 98,078 0.21 1,607 +2% 

Gaston, NC Yes 206,086 0.57 15,310 +8% 

Iredell, NC Yes (partial) 159,437 0.27 35,828 +29% 

Lancaster, SC No 76,652 0.14 15,259 +25% 

Lincoln, NC Yes 78,265 0.25 14,176 +22% 

Mecklenburg, 

NC Yes 919,628 1.67 218,914 +31% 

Rowan, NC Yes 138,428 0.26 7,753 +6% 

Stanly, NC No 60,585 0.15 2,339 +4% 

Union, NC Yes 201,292 0.31 75,733 +60% 

York, SC No 226,073 0.32 60,368 +36% 

Areawide: 2,402,623 0.36 493,749 +26%

^Bolded counties (or portions thereof) that are being included in the nonattainment area.

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_GCTP

L2.STO5&prodType=table)

Mecklenburg County has the largest population and is the most densely populated of all CSA counties 

with a population of 919,628 and 1,670 people/square mile. The population densities for Cabarrus, 

Gaston, Iredell, Lincoln, Mecklenburg, Rowan, Union and York Counties all are above 250 

people/square mile. Additionally, the population growth for these same counties is 22 percent and 

above.

In response to EPA’s December 9, 2011, preliminary determination for the nonattainment boundary in 

association with counties and tribal lands in the Charlotte-Gastonia-Salisbury CSA, North Carolina and 

South Carolina provided additional technical information to support a recommendation for a boundary 

that differed from EPA’s December 9, 2011, preliminary determination. More discussion on this 

information and how EPA considered it for the final designation is discussed below.

In support of North Carolina’s revised recommendations for EPA to consider partial county boundaries

for Cabarrus, Gaston, Lincoln, Rowan and Union, the State provided additional information on 

population in these townships. The following summarizes the additional information that North 

Carolina provided. 

• Cabarrus County - Based on the 2010 census, 178,011 people live in Cabarrus County, of 

which 176,580 live in the portion recommended by the State of North Carolina for 
10

nonattainment. The western portion of the county is highly populated and centered around a 

large interstate corridor, while the eastern portion of the county is mostly rural. The Gold Hill 

Township recommended for attainment has a population density of 54 people per square mile. 

The population in Cabarrus County showed an increase between 2000 and 2010 of 34.7 percent. 

By comparison, population grew by 13 percent in Gold Hill Township. A county-wide increase 

of 23.4 percent is expected between 2010 and 2020.

• Gaston County - There are 206,086 people who live in Gaston County, and 189,586 people live 

in the five townships recommended as nonattainment, which is 92 percent of the County’s 

population. The majority of the townships in Gaston County have population densities greater 

than 300 people per square mile or higher, with Gastonia being the highest at over 1200 people 

per square mile. The Cherryville Township has the lowest population density of any Gaston 

County townships, at 253 people per square mile. The population in Gaston County grew 

approximately 8.26 percent from 2000 to 2010, and an additional growth of 17.2 percent is 

expected between 2010 and 2020. The majority of this growth occurred in the eastern two-thirds 

of the county, with the largest increases observed in Riverbend and South Point Townships, 

which border Mecklenburg County. Cherryville Township’s population increased by only 776 

people, which corresponds to a 5.2 percent increase in the township’s population density.

• Iredell County - There are 159,437 people who live in Iredell County, and 65,385 people live in 

the two townships designated as nonattainment, which is 41 percent of the County’s population. 

The northern, eastern and western portions of Iredell County have population density in the 11 

townships of 250 people per square mile or less. Statesville, located in central Iredell County, has 

a population density of 814 people per square mile. The area recommended for nonattainment, 

the two townships in the southern portion of Iredell County, is densely populated, having 

population density values of 860 and 714 people per square mile. The population in Iredell 

County grew considerably from 2000 to 2010, increasing by 30 percent, and an additional 

growth of 17.2 percent is expected between 2010 and 2020. The majority of this growth 

occurred in the two southern townships recommended for nonattainment. Davidson Township’s 

population growth was 90 percent and Coddle Creek Township’s growth was 43 percent. 

Population growth in all other townships in Iredell County was less than 40 percent with most 

being less than 20 percent.

• Lincoln County - Based on the 2010 census, 78,265 people live in Lincoln County and 63,437 

people live in the three townships recommended as nonattainment, which is 81 percent of the 

County’s population. The eastern three townships within Lincoln County, where Lincolnton and

Catawba Springs are located, are densely populated, with population values of 468,286, and

347 people per square mile. This more densely populated area is located in the three eastern

townships recommended for nonattainment. The western two townships have population 

densities of 112 and 137 people per square mile. The population in Lincoln County grew 

considerably from 2000 to 2010, increasing by 22 percent, and an additional growth of 20 

percent is expected between 2010 and 2020. The majority of this growth occurred in the eastern 

half of the county. The population of the eastern-most township, Catawba Springs, increased by 

nearly 7,700 people from 2000 to 2010, which corresponds to an increase in population density 

of over 53 percent. Conversely, the two townships recommended for attainment by the State 

(i.e., Howards Creek and North Brook Townships) only grew by 1,313 and 665 people, 

respectively, from 2000 to 2010; this corresponds to a respective increase in population density 

of 17 percent and 13.1 percent for these two townships.

• Rowan County - Based on the 2010 census, 138,428 people live in Rowan County, of which 

128,675 live in the portion recommended for nonattainment. The far northwestern and far 

eastern townships in the county are mostly rural with population densities less than 100 people 

per square mile. Conversely, the areas recommended for nonattainment in general have a 
11

significantly higher population density and are more urban in nature. The four townships 

recommended to be designated attainment by the State have population density ranging from 52 

to 98 people per square mile. The population in Rowan County increased slightly between 2000 

and 2010 (5.9 percent). The townships recommended for attainment showed a combined 

population growth of 466 people during this time. Of these, Mount Ulla Township had the

highest growth - 295 people, corresponding to an increase in population density of 21 percent. 

Cleveland and Scotch Irish Townships increased 4 percent in population density, while Morgan 

Township actually decreased slightly in population. The population of Rowan County is 

projected to grow only 6.5 percent between 2010 and 2020. 

• Union County - There are 201,292 people who live in Union County as 2010, of which 173,775 

people live in the portion recommended for nonattainment by the State. The eastern and 

southern portion of the county is mostly rural; all four townships that North Carolina 

recommended to be designated attainment have population densities of 189 people per square 

mile or less. The area recommended for nonattainment is more urbanized with three of the six 

townships having a population density of greater than 500 people per square mile. The 

population in Union County showed a significant increase between 2000 and 2010, with an 

increase of 60.5 percent. Most of the increases were focused over the townships of Monroe, 

Vance, Goose Creek and Sandy Ridge. Vance Township’s population increased by 27,237 

people from 2000 to 2010, corresponding to a 109 percent increase in population density. Sandy 

Ridge Township increased in population by 29,245, a 181 percent increase in population density. 

The townships recommended for attainment by the State collectively increased by 5,144 people 

during this time. A county-wide increase in population of 26 percent is expected between 2010 

and 2020.

In support of South Carolina’s recommendation that York County, in its entirety, be designated 

attainment for the 2008 8-hour ozone NAAQS, South Carolina provided additional information 

regarding the population in the portion of York County that EPA included in the Agency’s December 9, 

2011 boundary determination for the counties and tribal lands in association Charlotte-GastoniaSalisbury CSA. EPA notes that while South Carolina’s additional technical information is provided for 

only the portion of York County that Agency is considering for nonattainment, that the Agency’s 

analytical starting point, as described in EPA’s December 2004 boundary guidance, is the entire CSA 

which includes York County in its entirety. EPA does not agree that the Agency’s use of the full county 

information for York County is a misrepresentation. To the contrary, EPA believes that use of full 

county information is consistent with the approach outlined in EPA’s December 2008 boundary 

guidance of considering all of the counties in a CSA/CBSA. Utilizing full county information, the 

absolute change in population from 2000 to 2010 in York County is calculated as 60,368. The 

population percent change is calculated as 36 percent change. This percentage presents the second 

largest percent growth over the ten year period of 2000-2010 within the CSA and demonstrates York 

County cannot be excluded from consideration of contribution to violations at monitors in the CharlotteGastonia-Salisbury CSA. 

EPA considered the more refined partial county information for the final determination on whether or 

not a partial county boundary for York County is appropriate. As noted by South Carolina, while the 

population for York County, in its entirety for 2010 of 226, 273 people, the portion of York County that 

EPA is considering for nonattainment has a majority of the County’s population at 173,881 people 

which is approximately 80 percent of the population in York County. 
12

Traffic and commuting patterns

EPA evaluated the total VMT for each county in the area. 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 Charlotte-Rock Hill, NC-SC nonattainment area. Table 6 shows traffic data, including 

total 2008 VMT data. 

Table 6. Traffic and Commuting Patterns.^

^Bolded counties (or portions thereof) that are being included in the nonattainment area.

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

Consistent with EPA’s 2008 boundary guidance, the Agency considered VMT, traffic and commuting 

from all of the counties in the CSA/CBSA for areas as the analytical starting point for the determination 

of a boundary for a nonattainment area. For this initial analysis, EPA did not assume or predetermine a 

partial county boundary for any particular county that was within the CSA. Utilizing full county 

information, Cabarrus, Gaston, Iredell, Mecklenburg, Rowan, Union, and York Counties VMT are the 

highest where each county have VMT greater than 1,790 million miles. These traffic data support a further 

consideration of inclusion of Cabarrus, Gaston, Iredell, Mecklenburg, Rowan, Union, and York Counties, or 

portions thereof, for the Charlotte-Rock Hill, NC-SC nonattainment area. 

North Carolina’s February 29, 2012, submission provided additional information on traffic and 

commuting in the Charlotte-Gastonia-Salisbury CSA, and in particular for the townships for which the 

County

State 

Recommended 

Nonattainment?

2008 VMT 

(million 

miles)

Anson, NC No 287

Cabarrus, NC Yes 1,982

Chester, SC No 562

Cleveland, NC No 1,230

Gaston, NC Yes 2,347

Iredell, NC Yes (partial) 2,558

Lancaster, SC No 656

Lincoln, NC Yes 805

Mecklenburg, 

NC Yes 11,315

Rowan, NC Yes 1,816

Stanly, NC No 605

Union, NC Yes 1,791

York, SC No 2,002

Areawide: 27,956
13

State requested exclusion from the final nonattainment area. The information provided by North 

Carolina is summarized below.

 

• Cabarrus County has 5.7 million daily VMT, according to 2010 data. Cabarrus County 

contributes 5.17 percent of the commuters who drive in to Mecklenburg County to work each 

day, most of which live in the western portion of the county. Cabarrus County ranks number 2 in 

commuting counties into Mecklenburg County. The VMT are expected to increase to 6.5 million 

by 2015 and 8.1 million by 2025. Traffic and commuting counts for Gold Hill Township are 0.3 

percent of the county-wide total of commuters traveling into Mecklenburg County.

• Gaston County has 5.7 million average daily VMT, according to 2010 data. Gaston County 

contributes 4.97 percent of the commuters who drive into Mecklenburg County to work each 

day. Gaston ranks number 4 in the commuting counties into Mecklenburg. The VMT are 

expected to increase to approximately 7.5 million by 2015 and 9.1 million by 2025. For 

Cherryville Township, there were approximately 800 trips to/from Mecklenburg County, which 

was under 3 percent of the County total and less than 0.2 percent of trips to/from Mecklenburg 

County in the entire CSA.

• Iredell County has 5.7 million average daily VMT, according to 2010 data. Iredell County 

contributes 1.91 percent of the commuters who drive into Mecklenburg County to work each 

day. Iredell County ranks number 5 in the commuting counties into Mecklenburg County. The 

VMT are expected to increase to approximately 7.3 million by 2020. Traffic counts are highest 

in the southern townships and decline substantially in the next tier of townships. The southern 

two townships are covered by the region’s Travel Demand Model, which predicts that the VMT 

will be 3.4 million by 2015, and 4.1 million in 2025.

• Lincoln County has 2.3 million average daily VMT, according to 2010 data. Lincoln County 

contributes approximately 1.49 percent of the commuters who drive into Mecklenburg County to 

work each day. Lincoln County ranks number 6 in the commuting counties into Mecklenburg 

County. The VMT are expected to increase to approximately 2.7 million by 2015 and 3.4 million 

by 2025. A significant amount of commuter traffic from the three eastern townships travels into 

Mecklenburg County. Therefore, the eastern townships may be impacting the ambient air 

quality data in this CSA and North Carolina recommends the three eastern townships be 

designated nonattainment. Commuter traffic into Mecklenburg County from the two western 

townships was an estimated 230 trips, which was less than 3 percent of the county total and less 

than 0.4 percent of the CSA total.

• Rowan County has 5.3 million daily VMT, according to 2010 data. Rowan County contributes 

0.96 percent of the commuters who drive in to Mecklenburg County to work each day, most of 

which live in the central and south-central portions of the county. Rowan County ranks number 

8 in commuting counties into Mecklenburg County. The VMT is expected to increase to 5.7 

million by 2015 and 6.9 million in 2025. The far northwestern and far eastern townships in the 

county have very low traffic counts and would have little impact on ozone concentrations in the 

CSA. Morgan, Mount Ulla and Scotch Irish Townships collectively account for approximately 

98 trips to Mecklenburg County, which represents about 2 percent of the total from Rowan 

County and 0.02 percent from the entire CSA.

• Union County has 5.2 million daily VMT, according to 2010 data. Union County contributes

6.84 percent of the commuters who drive in to Mecklenburg County to work each day, most of 

which live in the western portion of the County. Union County ranks number 1 in commuting 

counties into Mecklenburg County. The VMT are expected to increase to 6.5 million in 2015 

and 8.7 million in 2025. There is a significant amount of commuter traffic from the northern and 

western townships into Mecklenburg County. These townships (Monroe, Sandy Ridge, Vance 

and Goose Creek Townships) may be impacting the ambient air quality data in the CSA. The 4 
14

townships recommended for attainment have lower traffic counts compared to the 5 townships 

that are recommended for nonattainment. Of the 4 townships recommended to be excluded by 

the State, Jackson Township had an estimated 1563 trips to/from Mecklenburg County, which 

was 4.1 percent of the county total and 0.3 percent of the trips from the entire CSA. Traffic 

to/from Mecklenburg County for the 3 other townships (Buford, Lanes Creek, and New Salem 

Townships) was even less.

To support its recommendation of attainment for York County, in its entirety, South Carolina provided 

partial county VMT for the portion of York County that is currently in the 1997 8-hour ozone Charlotte 

nonattainment area. Specifically, South Carolina provided additional information in their February 29, 

2012, submission related to the portion of York County along the Rock Hill – Fort Mills Area 

Transportation Study (RFATS) boundary. RFATS is the MPO for the Rock Hill area. EPA notes again 

that the analytical starting point that was considered by the Agency (as consistent with EPA’s 2008 

boundary guidance) was the entire area that is located in the Charlotte-Gastonia-Salisbury CSA, which 

is York County in its entirety. Utilizing full county information, York County’s VMT is the fourth 

highest for the Charlotte-Gastonia-Salisbury CSA at 2,002 million miles. As mentioned above, EPA is 

considering the refined partial county data provided by the State to make a determination on whether or 

not a partial county boundary (as opposed to a whole county boundary) for York County is appropriate.

South Carolina used applied 2010 partial county annual average daily VMT (AADVMT) and the whole 

county York County AADVMT to determine that 82.6 percent of the York County VMT was attributed 

to the partial county portion of the 2009 model run for the Charlotte Area. Using this ratio, the VMTs 

for the partial county in York County was calculated as 1,653 million miles. EPA reviewed the most 

recent data submitted in South Carolina’s May 31, 2011, Redesignation Demonstration and Maintenance 

Plan which utilizes a ratio of 75.8 percent of the total York County 2010 VMTs as the portion of York 

County which EPA is designating as nonattainment. EPA used the Annual Average Weekday Vehicles 

Miles Travelled HPMS tool,5 a motor vehicle emission simulator converter tool, to calculate the 

AADVMT for this portion of York County. EPA’s calculation is 1,953 million miles. Regardless of 

what data set is used for the partial county information, it appears that a majority of the VMT from York 

County is from the portion of the County that is being included in the Charlotte-Rock Hill, NC-SC 

nonattainment area, and thus a partial county boundary could be appropriate for this Area.

 5 EPA’s converter tool can be found on the EPA website at: http://www.epa.gov/otaq/models/moves/tools.htm. 
15

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 Charlotte/Douglas International Airport (NWS Station 13881) to help 

determine transport patterns and source contributions. EPA assessed wind direction and speed for the 

2009-2011 “ozone season” (April through October) in the Charlotte CSA. These analyses were 

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

formation. EPA’s analysis of the NWS data indicate predominate winds blowing from the south, 

southwest, and north for the Charlotte CSA.

The counties of Rowan and Mecklenburg in the CSA have violating monitors with design values at or 

greater than 76 ppb. The prevailing winds during the 2009-2011 ozone seasons have a strong 

southwesterly component, suggesting that the part of York County that includes the majority of the 

population and commuting traffic (which is southwest of the violating monitors) should be included in 

the nonattainment area. Lincoln and Gaston Counties are also southwest and west-southwest and may 

contribute to the violating monitors in Rowan County. Prevailing winds during the ozone season also 

have strong north and south components which suggests that Union, Cabarrus and Iredell Counties may 

contribute to the violating monitors in Mecklenburg and Rowan Counties.

North Carolina provided detailed information in Appendix I of their response to EPA’s 120 Day letter, 

presenting wind back trajectories and wind roses for the Charlotte Area. North Carolina used National 

Oceanic and Atmospheric Administration’s (NOAA) Hybrid Single Particle Lagrangian Integrated 

Trajectory Model (HYSPLIT) model to develop the back trajectories for all monitors on all days with 

ozone concentrations at or above 76 ppb within the Charlotte-Gastonia-Salisbury CSA. The information 

provided is consistent with EPA’s assessment of the entire area as discussed above. 

South Carolina also provided a detailed meteorological data analysis, including a thorough back 

trajectory analysis developed with NOAA’s HYSPLIT model for each of the ozone monitors in the 

Charlotte-Gastonia-Salisbury CSA during episodes when the monitors measured exceedances of the 

ozone standard (see Appendix A of South Carolina’s February 29, 2012 response). EPA agrees with 

South Carolina’s assertion that many of the back trajectories show air masses passing over Charlotte on 

ozone exceedance days. However, some of the back trajectories also pass over York County indicating 

the potential for York county emissions to contribute to ozone exceedances during these specific events 

(e.g., June 8, 2011). Recirculation of emissions from other areas and elevated “aged ozone” from 

stagnation conditions may contribute to the ozone exceedances during these events, but nothing 

provided by South Carolina conclusively precludes transport of emissions from York County. Therefore, 

York County cannot be ruled out as a potential contributor to ozone violations at monitors in the 

Charlotte-Gastonia-Salisbury CSA.

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 

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

The Charlotte-Gastonia-Salisbury, NC-SC CSA does not have any geographical or topographical 

barriers significantly limiting air pollution transport within its air shed. Therefore, this factor did not 

play a significant role in this evaluation.
16

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 Charlotte area has previously established nonattainment boundaries associated with both the 1-hour 

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

NAAQS included Mecklenburg County, North Carolina in its entirety. Whereas the Charlotte 

nonattainment boundary for the 1997 8-hour ozone NAAQS included Cabarrus, Gaston, Lincoln, 

Mecklenburg, Rowan and Union Counties in North Carolina in their entireties, a portion of Iredell 

County, North Carolina, a portion of York County, South Carolina, and Indian Country associated with 

the Catawba Indian Nation. The States have recommended a different boundary for the 2008 ozone 

NAAQS. Additionally, the Catawba Indian Nation recommended designation of a separate 

unclassifiable/attainment area through their response to the EPA’s 120-day letter which was released on 

December 9, 2011. More information about EPA’s decision-making with respect to the Indian County 

associated with the Catawba Indian Nation can be found in “Appendix to the Charlotte-Rock Hill 

Technical Support Document – Catawba Indian Nation.” In South Carolina’s October 2011 letter, they 

revised their boundary recommendations to attainment statewide as a result of the most current air 

quality data which indicates attainment of the 2008 8-hour ozone standard. The presence of a violating 

monitor is not the only factor considered in nonattainment boundaries. However, a consideration of the 

other factors was not presented in their October 2011 letter.

Conclusion

Based on the assessment of factors described above and throughout this technical support document, 

EPA has concluded that the following counties should be included as part of the Charlotte-Rock Hill, 

NC-SC nonattainment area because they are either violating the 2008 ozone NAAQS or contributing to 

a violation in a nearby area: Mecklenburg County in its entirety and portions of Cabarrus, Gaston, 

Iredell, Lincoln, Rowan and Union Counties in North Carolina, and a portion of York County, South 

Carolina. All of these counties, or portions thereof, are included in the Charlotte nonattainment area for 

the 1997 ozone NAAQS. The air quality monitors in Mecklenburg and Rowan Counties, North Carolina 

are currently violating the 2008 ozone NAAQS based on 2011 design values, therefore these counties

(or portions thereof) are included in the nonattainment area. Portions of Cabarrus, Gaston, Iredell,

Lincoln, and Union Counties in North Carolina and a portion of York County, South Carolina are nearby 

counties that do not have violating monitors or do not contain monitors, but EPA has concluded that 

these areas contribute to the ozone concentrations in violation of the 2008 ozone NAAQS through 

emissions from mobile and area sources. Gaston, Iredell, Mecklenburg, Rowan, and York Counties have 

the highest NOx emissions in the area. Cabarrus, Iredell, Mecklenburg, Rowan, and York Counties have 

among the highest VOC emissions in the area. Lincoln, Union, and York Counties ranked relatively high 

for emissions-related data such as population, and population density; commuting; meteorology, and 

jurisdictional boundaries. 
17

Appendix to the Charlotte-Rock Hill, NC-SC Technical Support 

Document – Catawba Indian Nation

The Catawba Indian Nation Reservation, which consists of two tracts of land within York County, South 

Carolina, is being designated for the 2008 Ozone National Ambient Air Quality Standards (NAAQS) as 

a separate “unclassifiable/attainment” area from the surrounding Charlotte-Rock Hill, NC-SC 

nonattainment area (Charlotte Area). The Catawba Indian Nation recommended designation of its 

Reservation as a separate unclassifiable/attainment area through the Tribe’s February 29, 2012, response 

to the EPA’s proposed designation for the Charlotte Area (120-day letter). 

In March 2009, and in October 2011, prior to EPA’s 120-day letters, North Carolina and South Carolina 

made recommendations for their respective portions of the Charlotte Area. The Catawba Indian Nation 

did not submit a recommendation at either time. On December 9, 2011, the EPA initiated the 120-day 

consultation process by notifying the States of North Carolina and South Carolina, and the Catawba 

Indian Nation that, based on the EPA’s technical analysis of the 13-county Charlotte-Gastonia-Salisbury 

combined statistical area (CSA), EPA intended to designate six whole counties and one partial county in 

North Carolina; one partial county in South Carolina; and the Catawba Indian Nation Reservation as 

“nonattainment” for the 2008 Ozone NAAQS as part of the Charlotte Area. In this December 2011 

letter, the EPA also requested that if North Carolina or South Carolina, or the Catawba Indian Nation 

wished to provide comments on the EPA’s intended designation, it should do so by February 29, 2012. 

The Catawba Indian Nation, North Carolina, and South Carolina each submitted comments on the 

EPA’s proposed designations and provided additional information to support their designation and 

boundary recommendations. On February 29, 2012, the Catawba Indian Nation provided its 

recommendation of “attainment/unclassifiable” for the Tribe’s Reservation and submitted technical 

information to support its recommendation of attainment. 

Section 107(d)(1) of the Clean Air Act requires that the EPA designate an area nonattainment if it 

violates a NAAQS or contributes to a violation of the NAAQS in a nearby area. The EPA’s December 

20, 2011, Policy for Establishing Separate Air Quality Designations for Areas of Indian Country, 

provides a process whereby an analysis of the factors described below may be used to determine 

whether an area of Indian Country located within or next to a larger multi-jurisdictional area should be 

excluded from that area and potentially designated separately or whether it should be designated 

according to the rest of the area. Provided below is a summation of the information relied upon by the 

EPA to designate the Catawba Indian Reservation as attainment/unclassifiable for purposes of the 2008 

Ozone NAAQS, separate from the Charlotte-Rock Hill, NC-SC Area. 

Factor Assessment

Factor 1: Air Quality Data 

The air quality data analysis for Tribal areas evaluates the data pertaining to air quality in the relevant 

area of Indian country. Where such data is unavailable or incomplete, the analysis also involves 

consideration of other available information that may enable the Agency to characterize air quality in the 

area.
18

There are no monitors within the Catawba Indian Nation Reservation. The sole monitor in York County, 

located approximately 16 to 18 miles west of the Reservation, is attaining the 2008 Ozone NAAQS

based upon the 2009-2011 period (i.e., the “2011 design value,” which represents the most recent years 

with fully-certified air quality data).6 Consequently, the EPA’s designation analysis for this Reservation 

is based upon whether sources are contributing to the violating monitors in the Charlotte-GastoniaSalisbury CSA. Based on data provided by North Carolina, South Carolina and the Catawba Indian 

Nation, there is no indication that the air quality on the Catawba Indian Nation Reservation is violating 

the 2008 Ozone NAAQS. 

Factor 2: Emissions and Emissions-Related Data

EPA evaluated emissions of ozone precursors (i.e., NOx and VOC emissions) and other emissionsrelated data to determine whether sources on the Catawba Indian Nation Reservation are contributing to

violations. This analysis is comprised of three general considerations: population density and degree of 

urbanization; traffic and commuting patterns; and, source emissions data. Each of these considerations, 

as applicable to the Catawba Indian Reservation, is summarized below.

Population density and degree of urbanization

As described above, the Catawba Indian Nation Reservation is located within York County, South 

Carolina. The Tribe included information in its technical support document to distinguish the 

Reservation from the York County, South Carolina area that is being designated nonattainment as part of 

the Charlotte-Rock Hill, NC-SC area. In the Catawba Indian Nation’s February 29, 2012, letter, the 

Tribe provided information to demonstrate that the prevailing population density and degree of 

urbanization within the Reservation is not consistent with the portion of York County proposed by the 

EPA for inclusion in the Charlotte Area. The Tribe explained that while the Reservation is within York 

County, it is outside of the urban cluster of Rock Hill, and is less densely populated - and is more rural 

in character - than the York County portion of the CSA. The Tribe further explained that the Catawba 

Indian Nation consists of two tracts of land along the Catawba River with a total land base of 

approximately 1,000 acres, which comprises only 0.002 percent of the land area of York County and 

0.004 percent of the land area in the portion of York County that is being considered for nonattainment 

for the 2008 ozone NAAQS. The Tribal members living on the Reservation comprise only about 0.003 

percent of the population of York County and exhibit close to zero percent population growth. The most 

recent demographic data for the Catawba Indian Nation indicates that the population consists of 586 

Tribal members living in 312 homes within the Catawba Indian Nation Reservation.

Traffic and commuting patterns

According to information provided by the Catawba Indian Nation, of the 586 members of the Tribe, only 

340 are of working age. In addition, the unemployment rate is relatively high and many adults have 

limited or no access to transportation (the Tribe operates a public transit program for those members 

who do not have transportation). Of the Tribal members that are children, 90 percent of them travel to 

school by bus and 10 percent by car. 

 6 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 recorded level of ozone.
19

Source Emissions Data

There are currently no point sources of ozone precursors within the boundaries of the Catawba Indian 

Nation Reservation. York County, South Carolina does contain a number of major sources for NOx and 

VOC, however, these sources are all located at least two miles from the Reservation. Therefore, there is 

no indication that sources on the Catawba Indian Nation Reservation are contributing to violations in the 

surrounding state area

Factor 3: Meteorology (weather/transport patterns)

The meteorology analysis evaluates how weather and transport patterns of the area affect the fate and 

transport of emissions from sources on or nearby the relevant area of Indian country. The 

meteorological conditions on the Reservation are not distinguishable from that of the surrounding 

portions of York County, South Carolina. In response to the EPA’s proposed designation for Charlotte 

Area (120-day letter), both North Carolina and South Carolina provided thorough analyses of the wind 

and transport patterns affecting the violating monitors in the Charlotte-Gastonia-Salisbury CSA. These 

analyses included wind roses showing wind speeds and directions on each of the violating days and 

wind back-trajectories created with the National Oceanic and Atmospheric Administration’s (NOAA) 

Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) model for all monitors and 

all days at and above the 76 ppb within the Charlotte-Gastonia-Salisbury CSA. An analysis of this 

information does not provide any conclusive evidence that the Catawba Indian Nation Reservation is 

contributing to violations at the monitors in the Charlotte-Gastonia-Salisbury CSA. Also, these analyses 

do not show that violations measured at the monitors in the area would be representative of the air 

quality on the Reservation. 

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.

The Catawba Indian Country does not have any geographical or topographical barriers significantly 

limiting air pollution transport within its air shed. Therefore, this factor did not play a significant role in 

this evaluation.

Factor 5: Jurisdictional boundaries

The jurisdictional boundary analysis is conducted to evaluate whether boundaries exist to clearly

establish the area pertaining to the designation request and to enable carrying out of the air quality 

planning and enforcement functions for nonattainment areas.
20

As described above, the Catawba Indian Nation Reservation consists of two tracts of land within York 

County, South Carolina. The Catawba Indian Nation is a federally-recognized Indian Tribe, and the 

Reservation tracts are held by the Federal Government in trust for the Tribe. Pursuant to the Catawba 

Indian Claims Settlement Act, S.C. Code Ann. § 27-16-120, all State and local environmental laws and 

regulations apply to the Catawba Indian Nation members and Reservation and such laws and regulations 

are fully enforceable by all relevant State and local agencies and authorities. The Tribe, however, does 

retain authority to impose regulations applying higher environmental standards to the Reservation. Id. 

Based upon these facts, the jurisdictional boundaries of the Reservation provide sufficiently clear 

defined legal boundaries for the purpose of carrying out of the air quality planning and enforcement 

functions for adjacent nonattainment areas. In addition, the legal authority of the State of South 

Carolina and local agencies to regulate and enforce air quality standards on the Reservation is well 

defined. 

Conclusion

EPA has evaluated the additional information submitted by the Catawba Indian Nation, and has 

concluded that there is no indication that activities on the Catawba Indian Nation Reservation are 

contributing to the violations at the monitors in the Charlotte-Gastonia-Salisbury CSA. Also, there is 

no indication that violations measured at the monitors in the Charlotte-Gastonia-Salisbury CSA would 

be representative of the air quality on the Catawba Indian Nation Reservation. Therefore, the Catawba 

Indian Nation Reservation is being designated as an unclassifiable/attainment area separate from the 

Charlotte-Rock Hill, NC-SC nonattainment area for the 2008 Ozone NAAQS.