Supplement to the North Carolina 

8-Hour Ozone Attainment Demonstration 

for the 

Charlotte-Gastonia-Rock Hill, NC-SC 

8-Hour Ozone Nonattainment Area 

(Cabarrus, Gaston, Lincoln, 

Mecklenburg, Rowan, Union Counties and 

Coddle Creek and Davidson Townships in Iredell County) 

Prepared by: 

North Carolina Department of Environment and Natural Resources 

Division of Air Quality 

April 5, 2010
(This page intentionally left blank)
Supplement to the Attainment Demonstration for the i 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

PREFACE 

This document contains a supplement to the North Carolina attainment demonstration for the 

Charlotte-Gastonia-Rock Hill, North Carolina-South Carolina 8-hour ozone nonattainment area 

that was submitted to the United States Environmental Protection Agency on June 15, 2007. 

This supplement in combination with the June 15, 2007, submittal demonstrates that this area 

will meet the National Ambient Air Quality Standard for 8-hour ozone by June 15, 2011. This 

area includes the entire counties of Cabarrus, Gaston, Lincoln, Mecklenburg, Rowan and Union; 

Coddle Creek and Davidson Townships in Iredell County; and the Rock Hill Metropolitan 

Planning Organization boundary in York County, South Carolina. 
Supplement to the Attainment Demonstration for the ii 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

TABLE OF CONTENTS 

PREFACE i

1.0 INTRODUCTION 1

2.0 AMBIENT AIR QUALITY DATA 3

3.0 WEIGHT OF EVIDENCE MODELING 8

3.1 Emission Inventory and Controls Applied ........................................................................... 8

3.1.1 Stationary Point Sources ............................................................................................... 9

3.1.2 Stationary Area Sources .............................................................................................. 10

3.1.3 Off-Road Mobile Sources ........................................................................................... 10

3.1.4 Highway Mobile Sources ............................................................................................ 11

3.1.5 Biogenic Emission Sources ......................................................................................... 11

3.1.6 Controls Applied in 2011 Modeling ........................................................................... 11

3.2 Modeling Results ............................................................................................................... 13

3.2.1 Attainment Test Introduction ...................................................................................... 13

3.2.2 2011 Modeling Results ................................................................................................... 14

4.0 MOTOR VEHICLE EMISSION BUDGETS 15

5.0 Summary 17

LIST OF TABLES 

Table 2-1 Design Values (ppm) for the North Carolina Monitors in the Metrolina Area ............. 3

Table 2-2 Predicted 2009 Design Values Compared to Actual 2009 Design Values .................... 4

Table 2-3 Fourth Highest 8-hour Ozone Values ............................................................................ 4

Table 2-4 Utility NOx Emission Reductions since 2006 Ozone Season ....................................... 7

Table 5.2-2 Attainment Test Results for 2011 ............................................................................. 15

Table 4-1 2009 Highway Mobile Source Emissions Metrolina Nonattainment Area ................. 16

Table 4-2 County Level MVEB for 2009 .................................................................................... 17

LIST OF FIGURES 

Figure 1-1 Monitor locations in the Metrolina area ....................................................................... 1

Figure 2-1 Number of Stagnation Days versus Exceedance Days ................................................. 5

Figure 2-2 Average High Temperatures versus Exceedance Days ................................................. 6

Figure 2-3 Location and size of the Duke Energy facilities located in the vicinity of the 

Metrolina nonattainment area ......................................................................................................... 7
Supplement to the Attainment Demonstration for the iii 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

LIST OF APPENDICES 

Appendix A: Memorandums 

Appendix B: Emissions Inventory Summary

Appendix C: Emissions Inventory Documentation 

Appendix D: Attainment Test Results 

Appendix E: VISTAS Supporting Documentation 

Appendix F Public Notice Report, Comments Received and Responses 
Supplement to the Attainment Demonstration for the iv 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

(This page intentionally left blank) 
Supplement to the Attainment Demonstration for the 1 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

1.0 INTRODUCTION 

On April 15, 2004, the United States Environmental Protection Agency (USEPA) designated 

areas as nonattainment for the 1997 8-hour ozone National Ambient Air Quality Standard 

(NAAQS) based upon air quality monitoring data measured during the 2001, 2002 and 2003 

ozone seasons. These designations became effective on June 15, 2004. 

The Charlotte-Gastonia-Rock Hill, North Carolina-South Carolina (referred to as the Metrolina 

area) 8-hour ozone nonattainment area was designated as a Moderate area, with a regional 2001-

2003 8-hour ozone design value of 0.100 ppm. This nonattainment area includes the entire 

counties of Cabarrus, Gaston, Lincoln, Mecklenburg, Rowan and Union; Coddle Creek and 

Davidson Townships in Iredell County; and the Rock Hill Metropolitan Planning Organization 

boundary in York County, South Carolina. 

Figure 1-1 displays where the monitors are located in the counties affected by the Metrolina 

nonattainment designation. 

Figure 1-1 Monitor locations in the Metrolina area 

The attainment date for a Moderate area is June 15, 2010, with an attainment demonstration State 

Implementation Plan (SIP) submittal date of June 15, 2007. The North Carolina Division of Air 

Quality (NCDAQ) submitted an attainment demonstration SIP on June 15, 2007, which 

demonstrated that the Metrolina nonattainment area would attain the standard by the end of 

2009. 
Supplement to the Attainment Demonstration for the 2 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

The USEPA notified North Carolina in a letter dated November 17, 2008, that they planned to 

disapprove the Metrolina attainment demonstration SIP unless North Carolina requested a 

voluntary reclassification to Serious. In that letter, the USEPA stated “Because we are now so 

close to the attainment date, we now believe that attainment will not be achieved by the required 

moderate area deadline based on the air quality measurements from the summers of 2007 and 

2008 that exceed the standard by a sizable amount. Furthermore, we believe that the area will 

not meet the requirements for a one-year extension of the attainment date.” A copy of this 

correspondence can be found in Appendix A. 

Before responding to the November 17, 2008, letter, North Carolina thoroughly considered the 

two most apparent options: the proposed disapproval of the attainment demonstration SIP and 

the voluntary reclassification to Serious. Both options presented rather negative consequences 

for the State. While the USEPA believed that it was unlikely that the Metrolina area would 

attain the 1997 ozone standard by its attainment date, North Carolina believed that the region 

could meet the requirement for requesting a one-year extension if the attainment date was not 

met and believed that disapproval of the attainment demonstration SIP was premature. 

Many of the control requirements in the Clean Air Act Amendments (CAAA) for a Serious 

nonattainment area focus on reducing Volatile Organic Compound (VOC) emissions. For 

example, stationary sources with potential annual VOC emissions greater than 50 tons per year 

must implement reasonably available control technology or RACT. The Metrolina region is 

nitrogen oxide (NOx) limited, so reductions in VOC emissions will not result in the reductions in 

ozone needed to meet the standard. Therefore, the NCDAQ did not wish to request a voluntary 

reclassification of the Metrolina area to Serious when there was still a chance that the area would 

be eligible to request a one-year extension of the attainment date. North Carolina believed that 

in these difficult economic times, it was unreasonable for the State to require business and 

industry to go through a resource intensive and burdensome process and implement costly VOC 

controls when lower ozone levels would not be achieved as a result of that exercise. 

Therefore, on December 19, 2008, North Carolina responded to the USEPA letter (see 

Appendix A) by withdrawing the attainment demonstration SIP submitted in 2007 and by 

committing to submit a revised SIP by November 30, 2009. In August 2009, the NCDAQ shared 

an internal draft of the revised attainment demonstration with the USEPA and the transportation 

partners for comment. The NCDAQ learned at the end of the comment period that the USEPA 

had issues with the attainment year as proposed in the revised SIP being 2011. 

By the time the NCDAQ learned of the USEPA’s concerns, the majority of the ozone season was 

over. Although the Metrolina area did not have a design value below the 1997 8-hour ozone 

standard for the three-year period including the 2009 data, the area did have clean data for 2009; 

i.e., the fourth highest values at all of the monitors were below the 1997 ozone standard. The 

CAAA allows the USEPA to extend the attainment date for one year even if the area has a 3-year 

design value above the standard for the attainment year, provided certain other conditions exist. 

The conditions for the extension are that an area has clean data in the designated attainment year 

and that the State has complied with all requirements and commitments in its implementation 

plan. With clean data for 2009, the area qualifies for a one-year extension of the attainment date 

once the attainment demonstration is deemed complete by the USEPA. 
Supplement to the Attainment Demonstration for the 3 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

The USEPA discussed internally various options of what the NCDAQ could submit that would 

address their concerns with the 2011 attainment date. On November 4, 2009, the NCDAQ was 

given two options to consider: 

• Option 1 - The State could re-submit the original attainment demonstration and then 

submit supplemental information. The supplemental information would include the 2009 

ambient air quality data showing the area qualifies for a one-year extension and the 2011 

modeling as weight of evidence that the Metrolina region would attain the standard by 

June 15, 2011. 

• Option 2 - The State could use the original 2009 modeling and the revised 2011 modeling 

to develop a plan to demonstrate the area would attain the standard by June 15, 2011. 

The NCDAQ chose Option 1, and on November 12, 2009, the agency re-submitted the 

attainment demonstration SIP for the Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone 

Nonattainment Area to the USEPA. This document is a supplement to the June 15, 2007 

submittal which addresses the additional weight of evidence. This supplement in combination 

with the June 2007 attainment demonstration SIP submission are what is necessary for the 

USEPA to deem the attainment demonstration complete. 

2.0 AMBIENT AIR QUALITY DATA 

Since the 8-hour ozone designation for the Metrolina area, the 8-hour ozone design values have 

improved significantly. The 2001-2003 design value period had values as high as 0.100 parts per 

million (ppm) and six out of the seven North Carolina monitors in the area were violating the 

NAAQS. Since the 2001-2003 period, the design values and the number of violating monitors in 

the region has decreased. With the latest design value period, 2007-2009, the highest monitor in 

the area has a value of 0.086 ppm and only that monitor exceeds the NAAQS (See Table 2-1). A 

design value of 0.084 ppm would be considered to be in attainment with the 1997 8-hour ozone 

standard. 

Table 2-1 Design Values (ppm) for the North Carolina Monitors in the Metrolina Area 

Monitoring Site County 2001-

2003 

2002-

2004 

2003-

2005 

2004-

2006 

2005-

2007 

2006-

2008 

2007-

2009 

Arrowood Mecklenburg 0.084 0.081 0.078 0.080 0.083 0.079 0.076 

County Line Mecklenburg 0.098 0.092 0.087 0.088 0.093 0.094 0.086 

Crouse Lincoln 0.092 0.086 0.081 0.079 0.083 0.082 0.076 

Enochville Rowan 0.099 0.091 0.085 0.085 0.090 0.088 0.083 

Garinger (Plaza) Mecklenburg 0.096 0.091 0.086 0.088 0.090 0.089 0.082 

Monroe Union 0.088 0.085 0.079 0.078 0.081 0.080 0.076 

Rockwell Rowan 0.100 0.094 0.088 0.083 0.089 0.088 0.083 

York York, SC 0.084 0.081 0.075 0.076 0.079 0.077 0.072 

*Bolded values exceeding the NAAQS 

The current ozone design values are very close to the predicted design values for 2009 included 

in the June 2007 attainment demonstration SIP submittal (See Table 2-2 below). The Metrolina 
Supplement to the Attainment Demonstration for the 4 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

area is a NOx limited area and the major sources of NOx emissions in the region are from mobile 

sources (highway and non-road) and electric generating facilities. The reduction in design values 

since the area was designated nonattainment is attributable to significant reductions in NOx 

emissions. The emission reductions from the NOx SIP call occurred between 2004 and 2007, the 

North Carolina Clean Smokestacks Act required NOx emission caps be met in 2007 and 2009, 

the initial Phase I year for the Clean Air Interstate Rule (CAIR) is 2009, and every year the 

mobile source fleet becomes cleaner and the NOx emissions from the highway and off-road 

mobile source sectors are reduced. All of these emission reductions have contributed to the 

improvement of the design values. In fact, the air quality measurements for 2009 exhibit clean 

data; i.e., the fourth highest value at each monitor is well below the 1997 8-hour ozone standard 

(See Table 2-3). 

Table 2-2 Predicted 2009 Design Values Compared to Actual 2009 Design Values 

Monitoring Site County Model Predicted 2009 

Design Values (ppm) 

Actual 2007-2009 

Design Values (ppm) 

Arrowood Mecklenburg 0.075 0.076 

County Line Mecklenburg 0.085 0.086 

Crouse Lincoln 0.078 0.076 

Enochville Rowan 0.084 0.083 

Garinger (Plaza) Mecklenburg 0.084 0.082 

Monroe Union 0.076 0.076 

Rockwell Rowan 0.083 0.083 

York York, SC 0.071 0.072 

Table 2-3 Fourth Highest 8-hour Ozone Values 

Monitoring Site County 2006 2007 2008 2009 

Arrowood Mecklenburg 0.080 0.087 0.073 0.068 

County Line Mecklenburg 0.093 0.096 0.093 0.071 

Crouse Lincoln 0.082 0.085 0.079 0.065 

Enochville Rowan 0.089 0.095 0.082 0.073 

Garinger (Plaza) Mecklenburg 0.091 0.093 0.085 0.069 

Monroe Union 0.080 0.082 0.080 0.067 

Rockwell Rowan 0.085 0.096 0.084 0.071 

York York, SC 0.078 0.080 0.075 0.062 

*Bolded values above the NAAQS 

As is demonstrated in the table above, the fourth highest 8-hour ozone values have been 

improving. In 2007, there was an observed increase of the fourth highest values which 

corresponded to a significant drought and higher than normal temperatures. The NCDAQ has 

reviewed the meteorology for 2009 and has determined that the decrease in ozone levels cannot 

be explained away due to improved meteorological conditions. In North Carolina, the most 

serious air quality episodes occur during periods of stagnation, typically over three or more 
Supplement to the Attainment Demonstration for the 5 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

consecutive days. Stagnation occurs when winds are light for an extended period of time. 

Stagnation can be enhanced by temperature inversions, where the temperature increases with 

height and vertical mixing is reduced. Pollution loading is kept even higher if there is little or no 

precipitation. Figure 2-1 shows the number of air stagnation days that occurred between April 

through September each year for the period 1998 through 2009. For this analysis, a day was 

defined as stagnant if the current day and the two previous days had upper level winds below 25 

miles per hour (mph), lower level winds below 15 mph, and no precipitation. If an inversion was 

present, the low level wind threshold was increased by ten percent. The average number of 

stagnation days for this period was approximately 25 with a variability of +/- 8 days. In 2009, 

there were 23 stagnation days which is very close to the 11-year average. 

Figure 2-1 Number of Stagnation Days versus Exceedance Days 

Another important indicator of ozone exceedances is the average high temperature. In general, 

the higher the June through August average high temperature, the greater the number of ozone 

exceedances. Figure 2-2 shows good correlation between higher temperatures and a greater 

number of exceedance days. Average high temperatures in 2009 were very near the 11-year 

average of 87.6 oF; however the corresponding number of exceedance days for 2009 does not 

show the same correlation as previous years. 

0

5

10

15

20

25

30

35

40

45

50

0

10

20

30

40

50

60

# of Stagnation Days

# of Exceedance Days

# of Exceedances(85ppb) Stagnation Days
Supplement to the Attainment Demonstration for the 6 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

 Figure 2-2 Average High Temperatures versus Exceedance Days 

In addition to comparing the meteorology for 2009 to the 11-year average, the NCDAQ reviewed 

years that had similar meteorological parameters as 2009. The number of stagnant days and 

average high temperatures in 2009 was comparable to 2005 and 2006. Despite similar 

meteorological conditions in 2009 with 2005 and 2006, the number of exceedance days was well 

below the long term average and the numbers for 2005 and 2006. Therefore, the NCDAQ 

believes that the decline in ozone levels in 2009 was likely due to emission reductions. 

Continued reductions of emissions from the mobile source sector and the utility sector will 

influence the ozone formation in this region. Based on the 2009 and 2011 modeling emissions 

inventories, the NCDAQ has estimated that there will be reductions of approximately 14.6 tons 

per day of NOx emissions each year in this region from the highway and non-road mobile 

sectors. These reductions are the result of Federal motor vehicle and equipment engine standards 

for highway vehicles and off-road equipment, respectively. 

Additionally, the overall background levels of ozone are expected to decrease as the utilities in 

the eastern United States put on additional controls to meet CAIR as well as the reductions in 

emissions of highway and non-road mobile sources throughout the country. For North Carolina, 

2009 was the final compliance year for the NOx emission caps for the Clean Smokestacks Act. 

Figure 2-3 displays the location and size of the Duke Energy facilities located in the vicinity of 

the Metrolina nonattainment area. Table 2-4 lists the units that are in and around the Metrolina 

area, the type of technology installed and the year controls came on line, and the estimated 

amount of NOx emissions reductions for the ozone season. 

81

82

83

84

85

86

87

88

89

90

91

0

10

20

30

40

50

60

Average High Temperature (F)

# of Exceedance Days

# of Exceedances (85ppb) Average JJA Max Temp (F)
Supplement to the Attainment Demonstration for the 7 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

Figure 2-3 Location and size of the Duke Energy facilities located in the vicinity of the 

Metrolina nonattainment area 

Table 2-4 Utility NOx Emission Reductions since 2006 Ozone Season 

Facility County Technology 

Optimized 

Operational 

Date 

Ozone Season 

Reductions 

(tons/season) 

Allen Steam Station 

 Unit 2 

 Unit 5 

Gaston SNCR 

SNCR 

2007 

2008 

~175 

Buck Steam Station 

 Units 3 & 4 

 Units 5 & 6 

Rowan Low NOx Burners 

SNCR 

2007 

Fall 2006 

~225 

Riverbend 

 Unit 4 

 Unit 5 

 Unit 6 

 Unit 7 

Gaston 

SNCR 

SNCR & Burners 

SNCR & Burners 

SNCR 

2007 

2008 

Fall 2006 

Fall 2006 

~170 

Marshall Steam Station 

 Unit 2 

 Unit 3 

 Unit 4 

Catawba SNCR 

SCR 

SNCR 

2007 

2008 

2007 

~1800 

Total expected reduction = ~2,370 tons/ozone season 

SNCR = Selective Non-Catalytic Reduction 

SCR = Selective Catalytic Reduction 
Supplement to the Attainment Demonstration for the 8 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

The combination of the highway and non-road mobile sources and utility NOx emission 

reductions that occurred in the Metrolina area between the end of the 2006 ozone season and 

before the beginning of the attainment year 2009 was significant. The additional NOx emission 

reductions in the area resulted in the Metrolina area having clean data for 2009, which will allow 

the State to request a one-year extension of the attainment date. 

3.0 WEIGHT OF EVIDENCE MODELING 

The modeling for the 2009 attainment year for the Metrolina nonattainment area was performed 

in conjunction with the regional haze modeling being done by the Southeast Regional Planning 

Organization, Visibility Improvement State and Tribal Association of the Southeast (VISTAS) 

and the fine particulate matter (PM2.5) and ozone modeling being done by the Association of 

Southeastern Integrated Planning (ASIP). VISTAS and ASIP are managed by the ten Southeast 

states (Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, 

Tennessee, Virginia and West Virginia). Since the regional haze and PM2.5 modeling utilizes 

annual simulations and includes an intermediate year that is the attainment year required for the 

Metrolina nonattainment area, the NCDAQ decided to use this modeling for the 2009 attainment 

year demonstration that was submitted June 2007 to the USEPA. 

The supplemental modeling for 2011 was performed by the NCDAQ. The methods and inputs 

used by the NCDAQ were the same as those used by VISTAS/ASIP, with the only exception 

being a minor alteration in the spatial distribution of the highway mobile source emissions 

inventory and the use of a 2011 emissions inventory. The models used included the 

Pennsylvania State University/National Center for Atmospheric Research Mesoscale 

Meteorological Model (MM5), the Sparse Matrix Operator Kernel Emissions (SMOKE) 

modeling system and the USEPA’s Models-3/Community Multiscale Air Quality (CMAQ) 

modeling system. 

The analysis method, model selection, episode selection and modeling domains were all 

discussed in detail in the June 2007 attainment demonstration SIP and will not be discussed in 

this supplement. The sections that follow will briefly discuss: 1) the 2011 emissions inventory 

and the controls applied; and 2) the 2011 modeling results and how this additional modeling 

supports the June 2007 attainment demonstration as weight of evidence. 

3.1 Emission Inventory and Controls Applied 

There are five different emission inventory source classifications: stationary point sources, area 

sources, off-road and on-road mobile sources, and biogenic sources. Stationary point sources are 

those sources that emit greater than a specified tonnage per year and the data is provided at the 

facility level. Stationary area sources are those sources whose emissions are relatively small but 

due to the large number of these sources, the collective emissions could be significant (e.g., dry 

cleaners, service stations, etc.). These types of emissions are estimated at the county level. Offroad mobile sources include equipment that can move but does not use the roadways (e.g., lawn 

mowers, construction equipment, railroad locomotives, aircraft, etc). The emissions from these 

sources, like stationary area sources, are estimated at the county level. On-road mobile sources 

are automobiles, trucks, and motorcycles that use the roadway system. The emissions from these 
Supplement to the Attainment Demonstration for the 9 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

sources are estimated by vehicle type and road type and are summed to the county level. 

Biogenic sources are the natural sources like trees, crops, grasses and natural decay of plants. 

The emissions from biogenic sources are estimated at the grid cell level and summed to the 

county level. 

A synopsis of the inventories used for each source classification and a summary of the controls 

applied are discussed below. The emission summaries by county for the Metrolina 

nonattainment area, as well as for the State, are in Appendix B, and the detailed discussions of 

the 2011 emissions inventory development can be found in Appendix C. 

3.1.1 Stationary Point Sources 

Point source emissions are from individual sources having a fixed location. In general, these 

sources have a potential to emit more than five tons per year of carbon monoxide (CO), NOx, 

particulate matter (PM), sulfur dioxide or VOC from a single facility. These sources must have 

permits to operate and their emissions are inventoried on a regular schedule. Large sources 

having emissions of 100 tons per year (tpy) of a criteria pollutant, 10 tpy of a single hazardous 

air pollutant (HAP), or 25 tpy total HAP are inventoried annually. Smaller sources have been 

inventoried less frequently. The point source emissions data can be grouped into the electric 

generating units (EGU) sources and the other point sources, or non-EGUs. Appendix B provides 

the average daily peak ozone season emissions in the Metrolina nonattainment area. Appendix C 

documents the 2011 point source modeling inventory development in more detail. 

As part of the regional haze modeling, VISTAS and the Midwest Regional Planning 

Organization contracted with ICF Resources, L.L.C., to generate a future year emission 

inventory for the electric generating sector of the contiguous United States using the Integrated 

Planning Model (IPM). IPM is a dynamic linear optimization model that can be used to examine 

air pollution control policies for various pollutants throughout the contiguous United States for 

the entire electric power system. The dynamic nature of IPM enables the projection of the 

behavior of the power system over a specified future period. The optimization logic determines 

the least-cost means of meeting electric generation and capacity requirements while complying 

with specified constraints including air pollution regulations, transmission bottlenecks, and plantspecific operational constraints. The versatility of IPM allows users to specify which constraints 

to exercise and to populate IPM with their own datasets. 

The IPM modeling runs took into consideration the USEPA’s Clean Air Interstate Rule (CAIR) 

implementation and North Carolina’s Clean Smokestacks Act compliance plans for Duke Energy 

and Progress Energy. The VISTAS States then modified the IPM results to account for known 

controls expected to be installed, sources that were known to be shutting down that IPM had 

operating, and sources that IPM shutdown that a State knew would continue to operate. 

The VISTAS 2012 EGU inventory was used as the starting point for the 2011 modeling 

inventory. This inventory was adjusted for 2011 based upon VISTAS States’ feedback. 

The general approach for assembling the 2012 VISTAS non-EGU point source inventory was to 

use recently updated growth and control data consistent with the USEPA’s CAIR analyses. This 
Supplement to the Attainment Demonstration for the 10 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

data was supplemented with state specific growth factors and stakeholder input on growth 

assumptions. Based on state feedback, it was determined there would be very minimal 

differences between a 2012 and 2011 non-EGU emissions inventory. Therefore, the VISTAS 

2012 non-EGU inventory was used for the 2011 modeling. 

3.1.2 Stationary Area Sources 

Stationary area sources include sources whose emissions are relatively small but due to the large 

number of these sources, the collective emissions could be significant (e.g., combustion of fuels 

for heating, structure fires, service stations, etc.). Emissions are estimated by multiplying an 

emission factor by some known indicator of collective activity, such as fuel usage, number of 

households or population. Stationary area source emissions are estimated on the county level. 

For categories other than wildland fires, the VISTAS/ASIP contractor generated the 2012 future 

year emissions inventory. Growth factors supplied from the states or the USEPA’s CAIR 

emission projections were applied to project the controlled emissions. In some cases, the 

USEPA’s Economic Growth and Analysis System Version 5 growth factors were used if no 

factor was available from either the states or the CAIR files. For wildland fires, the 2002 typical 

base year emissions were used. This is a common practice since it is difficult to predict where 

wildland fires will occur in the future. 

The 2012 VISTAS area source emissions inventory was used for the 2011 modeling since it was 

determined be a conservative estimate of emissions. Appendix B provides emission summaries 

for average peak ozone season day. Appendix C provides a detailed discussion of the area 

source inventory development. 

3.1.3 Off-Road Mobile Sources 

Off-road mobile sources, also referred to as non-road mobile sources, include equipment that can 

move but do not use the roadways, such as construction equipment, aircraft, railroad 

locomotives, lawn and garden equipment, etc. For the majority of the non-road mobile sources, 

the emissions were estimated using the USEPA’s NONROAD2005c model. For the three source 

categories not included in the NONROAD model, i.e., aircraft engines, railroad locomotives and 

commercial marine, more traditional methods of estimating the emissions were used. 

The NONROAD model takes into consideration rules that are in effect that could impact the 

emissions from these source categories. For the four largest airports in North Carolina, the 

FAA’s Terminal Area Forecast was used to project growth in aircraft emissions to 2011. For the 

commercial marine, railroad locomotives and the remaining airport emissions, the VISTAS/ASIP 

contractor calculated the 2012 emissions using detailed inventory data (both before and after 

controls) for 1996 and 2010 obtained from the USEPA’s Clean Air Interstate Rule Technical 

Support Document. When available, state specific growth factors were used. 

For the 2011 modeling, an interpolated emissions inventory between the VISTAS 2009 and 2012 

inventories was used. Average daily emission summaries can be found in Appendix B. 

Appendix C provides a detailed discussion of the non-road mobile source inventory. 
Supplement to the Attainment Demonstration for the 11 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

3.1.4 Highway Mobile Sources 

In order to accurately model the mobile source emissions in the Metrolina nonattainment area, 

the latest version of the MOBILE model available at the time of the modeling, MOBILE6.2, was 

used. Key inputs for the MOBILE model include information on the age of vehicles on the 

roads, the average speed on the roads, the mix of vehicles on the roads, any control technologies 

in place in an area to reduce emissions for motor vehicles (e.g., emissions inspection programs), 

and temperature. The MOBILE model inputs were developed through interagency consultation 

with the transportation partners for this area. 

The MOBILE model takes into consideration rules that are in effect that impact the emissions 

from this source sector. The 2011 emissions inventory was developed running the MOBILE 

model using input data reflective of 2011. The 2011 vehicle miles traveled (VMT), speeds, 

vehicle age and vehicle mix data was obtained from the North Carolina Department of 

Transportation (NCDOT). 

Emission summaries by county for the highway mobile source sector can be found in 

Appendix B. For a detailed discussion about the highway mobile source inventory development 

used in the 2011 modeling, please refer to Appendix C. 

3.1.5 Biogenic Emission Sources 

Biogenic emissions were prepared with the SMOKE-BEIS3 (Biogenic Emission Inventory 

System 3 version 0.9) preprocessor. SMOKE-BEIS3 is basically the Urban Airshed Model 

(UAM)-BEIS3 model, but also includes modifications to use MM5 data, gridded land use data, 

and science updates. The emission factors that are used in SMOKE-BEIS3 are the same as the 

emission factors in UAM-BEIS3. 

The basis for the gridded land use data used by BEIS3 is the county land use data in the Biogenic 

Emissions Landcover Database version 3 (BELD3) provided by the USEPA. A separate land 

classification scheme, based upon satellite (AVHRR, 1 km spatial resolution) and census 

information, aided in defining the forest, agriculture and urban portions of each county. 

The 2002 base year biogenic emissions were used for 2011 modeling. This is a common practice 

in air quality modeling since the same meteorology is used for both base and future year model 

runs and the biogenic emissions are very dependent on the meteorology. Variation in these 

emissions could impact the control strategies needed to demonstrate attainment. Therefore, these 

emissions are kept constant. 

3.1.6 Controls Applied in 2011 Modeling 

There are several State and Federal measures that have been enacted in recent years that are 

resulting in emissions reductions from stationary point sources, highway mobile sources and 

nonroad mobile sources. The Federal and State control measures modeled for 2011 are briefly 

discussed below. A more detailed description of these measures is in the June 2007 attainment 

demonstration SIP. 
Supplement to the Attainment Demonstration for the 12 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

The federal measures that were modeled include: 

• Tier 2 vehicle standards: In addition to NOx controls, the Tier 2 rule also reduced the 

sulfur content of gasoline to 30 ppm starting in January of 2006. Most gasoline sold in 

North Carolina prior to January 2006 had a sulfur content of about 300 ppm. 

• Heavy-duty gasoline and diesel highway vehicle standards: Second phase of standards 

and testing procedures, which began in 2007, will reduce particulate matter from heavyduty highway engines, and will also reduce highway diesel fuel sulfur content to 15 ppm 

since the sulfur damages emission control devices. The total program is expected to 

achieve a 90% reduction in particulate matter (PM) emissions and a 95% reduction in 

NOx emissions. 

• Nonroad spark-ignition engines and recreational engines standards: Tier 1 of this 

standard was implemented in 2004 and Tier 2 started in 2007, and will reduce NOx, 

Carbon Monoxide (CO), hydrocarbons and PM emissions. 

• Large nonroad diesel engine standards: Promulgated in 2004, this rule is being phased in 

between 2008 and 2014. This rule will also reduce sulfur content in nonroad diesel fuel. 

When fully implemented, this rule will reduce NOx and direct PM2.5 emissions by over 

90%. 

• NOx SIP Call in surrounding states: In October 1998, the USEPA made a finding of 

significant contribution of NOx emissions from certain states and promulgated a rule that 

set ozone season NOx budgets for the purpose of reducing regional transport of ozone. 

This rule, referred to as the NOx SIP Call, required ozone season controls to be put on 

utility and industrial boilers, as well as internal combustion engines, in 22 states in the 

Eastern United States. A NOx trading program was established, allowing sources to buy 

credits to meet their NOx budget as opposed to actually installing controls. The emission 

budgets were to be met starting in 2004. 

• Clean Air Interstate Rule: On May 12, 2005, the USEPA promulgated the “Rule To 

Reduce Interstate Transport of Fine Particulate Matter and Ozone (Clean Air Interstate 

Rule); Revisions to Acid Rain Program; Revisions to the NOX SIP Call”, referred to as 

CAIR. This rule established the requirement for States to adopt rules limiting the 

emissions of NOx and sulfur dioxide (SO2). The purpose of CAIR is to reduce interstate 

transport of precursors of fine particulate and ozone. Due to Court challenges of CAIR in 

2008, the USEPA will be making changes to this program by 2011. However, the 

existing CAIR rules will remain in place until the USEPA promulgates changes to the 

program. 

The state measures that were modeled include: 

• Clean Air Bill: This State legislation expanded the inspection and maintenance (I/M) 

program from 9 counties to 48. Vehicles are tested using the onboard diagnostic system 
Supplement to the Attainment Demonstration for the 13 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

(OBDII), an improved method of testing, which ensures proper emission system 

operation for vehicles and light trucks during their lifetime by monitoring emissionrelated components and systems for malfunction or deterioration. This program is 

designed to reduce NOx and Volatile Organic Compound (VOCs), and Carbon Monoxide 

(CO). 

• North Carolina NOx SIP Call rule: This rule was predicted to reduce summertime NOx 

emissions from power plants and other industries by 68%. 

• North Carolina Clean Smokestack Act: This legislation required coal-fired power plants 

in North Carolina to reduce annual NOx emissions by 77% by 2009 and to reduce annual 

sulfur dioxide emissions by 49% by 2009 and 73% by 2013. This legislation set a cap on 

NOx and SO2 emissions, which the public utilities cannot meet by purchasing emission 

credits. The Clean Smokestacks Act included stipulations that NOx emission reductions 

go beyond the requirements of the NOx SIP Call rule since it required year-round NOx 

controls and did not allow the purchase of credits to meet the NOx caps. 

• Heavy duty diesel engine gap filling rule: This rule required engine manufacturers to 

perform the supplemental testing requirements for heavy duty diesel engines for model 

years 2005 and 2006 due to delays in the USEPA’s rule and as a result reduced NOx and 

PM emissions. 

3.2 Modeling Results 

Since the Metrolina nonattainment area did not have a design value below the 1997 8-hour ozone 

standard but did have clean data for 2009, the USEPA has requested supplemental information to 

support the June 2007 attainment demonstration SIP. The NCDAQ utilized 2011 modeling to 

support the attainment demonstration SIP and to provide weight of evidence that the area will 

attain the standard with a one year extension of the attainment date to June 15, 2011. The 

NCDAQ applied the attainment test as outlined in the USEPA’s Guidance on the Use of Models

and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5 and 

Regional Haze, (referred to as Attainment Guidance) to the 2011 modeling results. 

An explanation of the attainment test and the modeling results are presented in the following 

sections. 

3.2.1 Attainment Test Introduction 

The modeled attainment test is the practice of using air quality modeling results for baseline and 

future years to determine if an area is expected to attain the NAAQS. For the 8-hour ozone 

NAAQS, the baseline and future model estimates are used in a “relative” rather than “absolute” 

sense. Specifically, the ratio of the air quality model’s future to current predictions is calculated 

at each ozone monitoring site. These monitoring site-specific ratios are called relative response 

factors (RRFs). Future ozone design values (DVFs) are then estimated at each monitor by 

multiplying the monitor-specific baseline ozone design value (DVB) by the modeled RRF for 

each monitor. If all of the predicted monitor-specific DVFs in a given area are less than or equal 
Supplement to the Attainment Demonstration for the 14 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

to the standard, in this case 0.084 ppm, the attainment test is passed and the area is said to 

demonstrate attainment. Equation 3.2.1-1 presents the modeled attainment test, applied at 

monitoring site “x” as described in Section 4.0 of the USEPA’s Attainment Guidance. 

 (DVF) = (RRF) x (DVB) Equation 3.2.1-1 

Where (DVB) = the baseline design value monitored at site "x", ppm 

 (RRF) = the ratio of the future 8-hour daily maximum concentration predicted "nearby" 

a monitor (averaged over each day of the episode) to the current 8-hour daily 

maximum concentration predicted "nearby" the monitor (averaged over each 

day of the episode). 

 (DVF) = the estimated future design value, ppm. 

It is important to consider an array of cells “nearby” a monitor rather than focusing on the 

individual cell containing the monitor. This allows for variations in the model performance 

where the peak ozone may not occur in the grid cell that contains the monitor but rather nearby 

the monitor. 

The RRF is calculated by taking the ratio of the future year modeling 8-hour ozone daily 

maximum to the current year modeling 8-hour ozone daily maximum “near” the monitor 

averaged over all of the episode days (Equations 3.2.1-2). 

RRF = mean future year 8-hour daily max “near” monitor “x” Equation 3.2.1-2 

mean current year 8-hour daily max “near” monitor “x” 

The DVB, for purposes of the modeled attainment test, is defined in the USEPA’s Attainment 

Guidance as the average of the three design value periods that straddle the baseline inventory 

year (e.g., the average of the 2000-2002, 2001-2003, and 2002-2004 design value periods for a 

2002 baseline inventory year). 

3.2.2 2011 Modeling Results 

As stated above, the attainment test is not based on absolute modeling results but rather relative 

responses of ozone and is only applied at the monitors. A careful review of the predicted ozone 

values in the future years along with an examination of the emission reductions are important in 

determining whether additional controls should be considered. 

Table 3.2.2-1 provides the future design values for the Metrolina nonattainment area for 2011. 

The first column is the monitoring site, followed by the base year design value. The next two 

columns are the calculated RRF and the resulting DVF for 2011. 
Supplement to the Attainment Demonstration for the 15 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

Table 3.2.2-1 Attainment Test Results for 2011 

Monitoring Site County 

DVB (ppm) 

5-year weighted 

2000-2004 

2011 

RRF DVF 

(ppm) 

Arrowood Mecklenburg 0.0847 0.854 0.072 

County Line Mecklenburg 0.0973 0.846 0.082 

Crouse Lincoln 0.0907 0.829 0.075 

Enochville Rowan 0.0970 0.837 0.081 

Garinger (Plaza) Mecklenburg 0.0953 0.862 0.082 

Monroe Union 0.0870 0.858 0.074 

Rockwell Rowan 0.0973 0.837 0.081 

York York, SC 0.0830 0.841 0.069 

As can be seen in the table above, all monitors in the Metrolina area have predicted design values 

below the standard. These results support NCDAQ’s assertion that the air quality is expected to 

continue to improve as the NOx emissions continue to decline from the point and mobile 

sources. These results provide additional weight of evidence that the area will attain the 1997 8-

hour ozone standard by June 15, 2011. 

4.0 MOTOR VEHICLE EMISSION BUDGETS 

The purpose of transportation conformity is to ensure that Federal transportation actions 

occurring in nonattainment and maintenance areas do not hinder the area from attaining and 

maintaining the 8-hour ozone standard. This means that the level of emissions estimated by the 

NCDOT or the metropolitan planning organizations for the Transportation Improvement 

Program and Long Range Transportation Plan must not exceed the motor vehicle emission 

budgets (MVEBs) as defined in this attainment demonstration. 

The NCDAQ has examined the sources of VOC emissions and their contribution to ozone 

formation in North Carolina. Although NCDAQ steadfastly believes on-road mobile VOCs are 

insignificant contributors to ozone formation in the Metrolina nonattainment area, the USEPA 

has indicated that they will not approve the attainment demonstration SIP if it does not establish 

MVEBs for VOCs. Therefore, a requirement for the supplemental analysis is that VOC MVEBs, 

for transportation conformity purposes, be set for the year 2009. 

Motor vehicle emissions estimates for the attainment demonstration have been generated at the 

county level. Developing county level MVEBs maintains consistency with the modeling 

conducted for the attainment demonstration. The NCDAQ believes that since mobile source NOx 

emissions play a significant role in the ozone formation in the Metrolina area, it is important that 

the large counties in the area meet the county level NOx MVEBs that closely represent the 

emissions that were modeled for the attainment demonstration. 
Supplement to the Attainment Demonstration for the 16 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

Although the emissions are usually expressed in terms of tons per day, the MVEBs will be set in 

terms of kilograms (kg) per day. The reason for the change is because the MOBILE model 

generates the emissions factors in grams per mile. In past conformity exercises, there have been 

some issues with conversion to tons per day, as well as concerns with how the MVEBs were 

rounded to the hundredth place. Setting MVEBs in kilograms per day will avoid these issues in 

future conformity determinations. 

The mobile inputs used to establish the MVEBs were developed through interagency 

consultation with the transportation partners for this area. These inputs were consistent with 

what was used in the attainment demonstration modeling, and do not represent a significant 

change to the emissions. 

In the attainment demonstration modeling, the vehicle miles traveled (VMT) data used for Iredell 

County was the Highway Performance Monitoring System (HPMS) VMT increased by 40%. 

Travel demand model VMT has been demonstrated to be approximately 30% higher than HPMS 

VMT, so part of the increase was to adjust Iredell County’s VMT to be more in line with what 

would be expected from the travel demand model. The additional 10% increase was to account 

for high growth expected in southern Iredell County which the transportation partners believed 

would be evident in later revisions to the travel demand model. For the MVEBs, travel demand 

model VMT was provided for the nonattainment portion of Iredell County. This VMT was 

increased by 10% to be representative of what was modeled in the attainment demonstration. 

The table below shows the North Carolina counties with their highway mobile NOx and VOC 

emissions expressed in tons per day and the corresponding kilograms per day values for 2009. 

Table 4-1 2009 Highway Mobile Source Emissions Metrolina Nonattainment Area 

County 

NOx VOC 

Tons/day Kg/day Tons/day Kg/day 

Cabarrus 8.57 7,788 8.70 7,893 

Gaston 9.48 8,602 6.47 5,870 

Iredell* 5.61 5,094 4.32 3,923 

Lincoln 3.65 3,317 3.19 2,892 

Mecklenburg 32.27 29,270 25.18 22,852 

Rowan 8.45 7,675 6.80 6,153 

Union 5.57 5,070 6.04 5,486 

Total 73.09 66,353 60.70 55,069 

* Iredell County emissions for nonattainment area only. 

The NCDAQ will set MVEBs, for transportation conformity purposes, as county budgets within 

the Metrolina nonattainment area for 2009. Table 4-2 below lists the NOx and VOC MVEBs by 

county in kilograms per day for transportation conformity purposes. It should be noted that these 

NOx MVEBs are the same as in the original attainment demonstration submittal and are being 

displayed in this supplement for completeness. Upon the USEPA’s affirmative adequacy finding 
Supplement to the Attainment Demonstration for the 17 

Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Nonattainment Area April 5, 2010 

for these county level sub-area MVEBs, they will become the applicable MVEBs for each 

county. 

Table 4-2 County Level MVEB for 2009 

County NOx MVEB 

(kilograms/day) 

VOC MVEB 

(kilogram/day) 

Cabarrus 7,788 7,893 

Gaston 8,602 5,870 

Iredell* 5,094 3,923 

Lincoln 3,317 2,892 

Mecklenburg 29,270 22,852 

Rowan 7,675 6,153 

Union 5,070 5,486 

* Iredell County MVEB for nonattainment area only 

5.0 Summary 

The air quality data for the Metrolina area has improved significantly since the area was 

designated nonattainment in 2004. The latest 3-year design value (2007-2009) for the region is 

0.086 ppm, which is just above the 1997 8-hour ozone standard, and the area had clean data for 

2009. The fourth highest values for 2007 (Table 2-3) were well above the standard for most 

monitors. This data will drop off and be replaced with the data for 2010. With the NOx 

emission reductions that have occurred in the region and throughout the State, the fourth highest 

values for 2010 are expected to be similar to what was seen in 2009. Therefore, the Metrolina 

area is expected to attain the standard by June 15, 2011. 

The 2007 attainment demonstration SIP predicted the future design values just above the 

standard and were very close to the actual design values (Table 2-2). The 2011 modeling 

demonstrates that the design values are expected to continue to improve (Table 3.2.2-1). This 

also supports the NCDAQ’s assertion that the area will attain the standard by June 15, 2011.