Appendix L 

Attainment Test 
TABLE OF CONTENTS 

I. ATTAINMENT DEMONSTRATION....................................................................................... 1 

II. MODELED ATTAINMENT TEST.......................................................................................... 2 

II. ADDITIONAL CORROBORATIVE ANALYSES AND WEIGHT OF EVIDENCE 

DETERMINATION ....................................................................................................................... 4 

A. Alternative DVF Calculatation ............................................................................................. 4 

B. Air Quality Modeling Metrics............................................................................................... 6 

C. Air Quality Modeling Results From Other Studies............................................................. 10 

D. Air Quality Trends and Additional Reductions in Emissions............................................. 12 

E. Local Measures not Modeled .............................................................................................. 14 

F. Weight of Evidence Conclusions ........................................................................................ 16 

IV. UNMONITORED AREA ANALYSIS................................................................................. 17 

ATTACHMENTS TO APPENDIX l.............................................................................................19 
LIST OF TABLES 

Table L-1: USEPA’s Recommendation for Defining “Nearby” Cells .......................................... 2 

Table L-2: Metrolina Attainment Test Results for 2009 ............................................................... 3 

Table L-3: Five-Year Average Alternative Attainment Test Results for 2009 ............................. 5 

Table L-4: Total number of grid cells for the AQI Categories. ................................................... 10 

Table L-5: Metrolina DVFs based on EAC Modeling................................................................. 11 

Table L-6: Metrolina DVFs based on the USEPA’s CAIR Modeling......................................... 11 

Table L-7: Design Values (ppb) for the North Carolina Monitors in the Metrolina Area........... 12 

Table L-8: Utility NOx Emission Reductions since 2006 Ozone Season .................................... 14 
LIST OF FIGURES 

Figure L-1: Number of days greater than 90oF versus the 4th highest 8-hour ozone value for the 

Metrolina area. ........................................................................................................................ 6 

Figure L-2: Area for which the air quality metrics were applied. ................................................. 8 

Figure L-3: Persistence and Severity for the Metrolina Area ........................................................ 9 

Figure L-4: Daily AQI counts for the Metrolina Area................................................................... 9 

Figure L-5: Hourly AQI Count for the Metrolina Area............................................................... 10 

Figure L-6: Location and size of the Duke Energy facilities located in the vicinity of the 

Metrolina nonattainment area. .............................................................................................. 13 

Figure L-7: Ozone Monitors and with Respect to the VISTAS 12 km Grid ............................... 18
1 

I. ATTAINMENT DEMONSTRATION 

 This Appendix summarizes the procedures that were used to demonstrate attainment of the 8-hour 

ozone National Ambient Air Quality Standard (NAAQS) in this State Implementation Plan (SIP) 

package. As described in the US Environmental Protection Agency’s (USEPA’s) September 2006 draft 

final Guidance On The Use Of Models And Other Analyses for Demonstrating Attainment of Air Quality 

Goals for Ozone, PM2.5, and Regional Haze (“Attainment Guidance”), an attainment demonstration 

consists of (a) analyses which estimate whether selected emissions reductions will result in ambient 

concentrations that meet the NAAQS, and (b) an identified set of control measures which will result in the 

required emissions reductions. The necessary emission reductions for both of these attainment 

demonstration components may be determined by relying on results obtained with air quality models. 

 Section 3.0 of the Attainment Guidance recommends applying both a modeled attainment test and 

a subsequent screening test to the air quality modeling results to determine if the 8-hour ozone NAAQS

will be met. Additional technical or corroboratory analyses may also be used as part of a “weight of 

evidence” determination to supplement the modeled attainment test and to further support a 

demonstration of attainment of the NAAQS. 

 The modeled attainment test, additional corroborative analyses and weight of evidence, and 

unmonitored area analysis are described in further detail in the remaining portions of this Appendix, 

detailing how the respective test or analysis was performed and applied to the attainment demonstration. 
2 

II. MODELED ATTAINMENT TEST 

 The modeled attainment test is the practice of using an air quality model to simulate baseline (i.e.,

current) and future air quality. 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 

baseline predictions is calculated at each ozone monitoring site. These monitoring site-specific ratios are 

called relative response factors (RRF). Future ozone design values (DVF) are then estimated at each 

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

response factor for each monitor. If the resulting predicted site-specific DVFs are < 82 parts per billion 

(ppb), a clear demonstration of predicted attainment is shown. If the predicted DVFs is > 82 ppb and <

87 ppb, then a weight of evidence demonstration must be submitted that supports a demonstration of 

attainment. For DVFs > 87ppb, the Attainment Guidance states that more qualitative results are less 

likely to support a conclusion differing from the outcome of the modeled attainment test. Equation L-1 

presents the modeled attainment test, applied at monitoring site “x” as described in Section 4.0 of the 

Attainment Guidance. 

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

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

 = the average (of the three) design value periods which include the baseline inventory 

year (i.e., the average of the 2000-2002, 2001-2003, and 2002-2004 design vales 

periods for the 2002 baseline inventory year). 

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

(averaged over each day of the episode) to the current 8-hr daily maximum 

concentration predicted "nearby" the monitor (averaged over each day of the episode). 

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

 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. Table 

L-1 provides the USEPA's recommendations for defining “nearby” cells for grid systems having cells of 

various sizes. Since the attainment demonstration modeling was performed using a 12-kilometer grid 

resolution, the size of the array for “nearby” cells was 3 x 3. 

Table L-1: USEPA’s Recommendation for Defining “Nearby” Cells 

Size of Cell 

(km) 

Size of the Array of 

“Nearby” Cells 

<5 7 x 7 

>5-8 5 x 5 

>8-15 3 x 3 

>15 1 x 1 

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

maximum to the mean baseline year modeling 8-hour ozone daily maximum “near” the monitor. 

(Equation L-2). 
3 

RRF = mean future yr. 8-hr daily max “near” monitor “x” Equation L-2

mean baseline yr. 8-hr daily max “near” monitor “x”

 Section 14.1.1 of USEPA’s Attainment Guidance outlines the process for determining which days 

are used in the RRF calculation. The day selection process starts by identifying all the days in the 

baseline modeling that has a modeled daily maximum 8-hour average ozone equal to or greater than 

85 ppb. If there are 10 or more days greater than 85 ppb, then 85 ppb is used as the cutoff with those days 

used in the RRF calculation. If there are fewer than 10 days with a modeled daily maximum 8-hour 

average ozone equal to or greater than 85 ppb, then the threshold is reduced by 1 ppb until there are at 

least 10 days identified for use. If there are fewer than 10 days with a modeled daily maximum 8-hour

average ozone equal to greater than 70 ppb, then all days at 70 ppb and higher are used in the RRF 

calculation and consideration of modeling another episode should be explored. 

 The DVB, for purposes of the modeled attainment test, is defined in the Attainment Guidance by 

one of four methods: 

1. The design value period (e.g., the average 4th highest value for the 3-yr period used to designate 

an area “nonattainment”, here the period from 2001 to 2003) 

2. The average 4th highest value for the 3-yr period straddling the baseline inventory year (e.g., the 

2001-2003 design value period for the 2002 baseline inventory year) 

3. The highest of the three design value periods which include the baseline inventory year (e.g., the 

2000-2002, 2001-2003, 2002-2004 design value periods for a 2002 baseline inventory year) 

4. The average of the three design value periods which 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) 

 The USEPA recommends the fourth method (average of the three design value periods straddling 

the baseline year), which is the DVB shown in Table L-2 at each ozone monitoring site in the Metrolina

region. 

 Table L-2 lists the attainment test results by monitor in the Metrolina area. The first column is 

the monitoring site, then the county the monitor is located in, followed by the DVB used for the test. The 

next series of columns are the number of days used in the calculation, the ozone level threshold needed to 

reach at least 10 days for RRF, the calculated RRF and the resulting DVF for the attainment year, 2009. 

The bold italicized DVFs are values that fall within the range where additional weight of evidence is 

needed to demonstrate attainment. Half of the monitors in the Metrolina nonattainment area have 

predicted DVFs that fall below 82 ppb and the other half fall between 82 ppb and 87 ppb. Therefore, 

additional weight of evidence is required to demonstrate attainment. The North Carolina Division of Air 

Quality (NCDAQ) and the South Carolina Department of Health and Environmental Control (SCDHEC) 

believe that the weight of evidence presented in Section III supports a demonstration of attainment. 

Table L-2: Metrolina Attainment Test Results for 2009 

Monitoring Site County DVB 

(ppb) 

Number of 

Days used 

in RRF 

Ozone 

Threshold 

(ppb) 

RRF DVF 

(ppb) 
4 

Arrowood Mecklenburg 84.7 18 85 0.892 75 

County Line Mecklenburg 97.3 13 85 0.874 85 

Crouse Lincoln 90.7 10 84 0.868 78 

Enochville Rowan 97.0 13 85 0.870 84 

Garinger (Plaza) Mecklenburg 95.3 19 85 0.883 84 

Monroe Union 87.0 10 81 0.884 76 

Rockwell Rowan 97.3 10 84 0.862 83 

York York, SC 83.0 11 84 0.861 71 

II. ADDITIONAL CORROBORATIVE ANALYSES AND WEIGHT OF EVIDENCE 

DETERMINATION 

 As part of the weight of evidence determination, the following analyses will be evaluated: 

• Alternative DVF calculations, 

• Metrics of air quality modeling results, 

• Air quality modeling results from other studies, 

• Observed air quality trends and additional reductions in emissions, and 

• Local measures not modeled. 

 The weight of evidence determination is a supplement to the modeled attainment test and further 

supports that the area will attain the NAAQS for 8-hour ozone by June 15, 2010. 

 A. Alternative DVF Calculatation 

 The NCDAQ/SCDHEC used the USEPA recommended method of calculating the DVB in its 

modeled attainment test. However, the NCDAQ has commented several times on various draft versions 

of the attainment guidance that it does not believe that a weighted DVB is appropriate and that a DVB 

calculated using a straight average minimizes the impacts of any abnormally hot/dry or cool/wet 

meteorological conditions. As part of the weight of evidence demonstration, the NCDAQ/SCDHEC 

propose an alternative method to calculate the DVB and presents the modeled attainment test results with 

this alternative DVB. 

 The USEPA recommends calculating the DVB by averaging the three design value periods that 

straddle the baseline inventory year. This methodology results in a center weighting of annual 4th highest 

ozone concentrations around the baseline inventory year because the three design value periods averaged 

contain overlapping data. When simplified, the recommended DVB calculation for this SIP modeling 

exercise can be seen in Equation L-3. 

 1*(2000 4th Highest) + 2*(2001 4th Highest) + 3*(2002 4th Highest) 

DVB = + 2*(2003 4th Highest) + 1*(2004 4th Highest) Equation L-3 

 9 
5 

 The weighting scheme of annual 4th highest ozone concentrations in the recommended DVB 

calculation weights the center, or third, year three times more than that of the first or last year and one and 

a half times more than that of the second or forth year. If this third year is an abnormally hot/dry or 

cool/wet period, the unusual meteorological conditions and resulting air quality conditions will be 

amplified upward or downward in the modeled attainment exercise. 

 To minimize potential impacts of any abnormal meteorological conditions while still considering 

ozone conditions across a 5-year span, an alternative DVB calculation--that does not weigh any of the 

years more than another but is a straight average of annual 4th highest ozone concentrations for the 5-year 

span centered on the baseline inventory year--was considered (Equation L-4). 

 2000 4th Highest + 2001 4th Highest + 2002 4th Highest 

DVB = 2003 4th Highest + 2004 4th Highest Equation L-4

 5 

 When the five-year straight average DVB is applied to the remainder of the Modeled Attainment 

Test equations, the resulting DVFs are shown in Table L-3 at each monitoring site in the Metrolina 

region. 

Table L-3: Five-Year Average Alternative Attainment Test Results for 2009 

Monitoring Site County 

DVB 

5-Year Straight 

Average 

2000-2004 

(ppb) 

RRF DVF 

(ppb) 

Arrowood Mecklenburg 83.4 0.892 74 

County Line Mecklenburg 95.6 0.874 83 

Crouse Lincoln 89.2 0.868 77 

Enochville Rowan 94.4 0.870 82 

Garinger (Plaza) Mecklenburg 93.8 0.883 82 

Monroe Union 84.6 0.884 74 

Rockwell Rowan 94.6 0.862 81 

York York, SC 79.8 0.861 68 

 In comparison to the respective DVF values found in Table L-2, the DVF values in Table L-3 are 

slightly lower at each monitoring site. These differences were expected, as 2002 was an abnormally hot 

and dry year throughout the Southeast resulting in ozone concentrations that were higher than in the 

surrounding years of 2000, 2001, 2003, and 2004. Figure L-1 below illustrates this by charting the 

number of days with temperatures greater than 90o F versus the maximum fourth highest 8-hour ozone 

value for the Metrolina area. Comparing 2002 to the surrounding years used in the DVB (2000, 2001, 

2003, and 2004), 2002 had significantly more days with greater than 90oF temperatures. Similarly, the

maximum fourth highest 8-hour ozone value was ~5 ppb higher than the surrounding years used in the 

DVB. 
6 

Figure L-1: Number of days greater than 90oF versus the 4th highest 8-hour ozone value for the 

Metrolina area. 

 Thus, the recommended DVB calculation weighted the higher air quality conditions several times 

more than in the NCDAQ alternative DVB calculations. The NCDAQ firmly believes that the nonweighted or straight five-year average approach to the DVB calculation is more appropriate and 

minimizes dramatic fluctuations in meteorological and air quality conditions from year to year. This 

would be the case whether the center weighted year was an abnormally hot/dry year or a cool/wet year. 

 While none of the monitoring sites in the Metrolina region had DVF values at or above 85 ppb in 

Table L-3 using the NCDAQ alternative DVB calculation, there are still three monitors that have DVFs 

that fall between 82 ppb and 87 ppb. This continues to indicate that some additional weight of evidence 

should still be included to demonstrate attainment. These results are not inconsistent with what was 

concluded using all recommended modeled attainment test calculations. 

 B. Air Quality Modeling Metrics 

 In Section 7.0 of the Attainment Guidance, various aspects of air quality models, modeled 

performance, and uncertainties associated with the length of modeled episodes and limited observational 

datasets are described. A series of three additional air quality modeling outputs or metrics is 

recommended to provide assurance the modeled attainment demonstration indicates attainment. These 

metrics look at the relative change between the baseline and future years modeling and help to 

demonstrate how widespread the improvement in air quality is expected in the future. Although the final 

guidance did not recommend percentage cut points that corresponds to supportive weight of evidence, an

earlier draft version of the Attainment Guidance recommends that the metrics should be at least 80% or 

higher. 

 As described in Section 7.1 of the Attainment Guidance, the collected modeling data from the 

2002 and 2009 modeling output masks were applied to the following metrics: 

Metrolina 8-hour Ozone - # Days Hi ≥90F vs Max 

4th Highest

0

10

20

30

40

50

60

19961997199819992000200120022003200420052006

# Days Hi Temp 

≥ 90F 

May-Sep

0.080

0.085

0.090

0.095

0.100

0.105

0.110

0.115

Max 4th Highest

# Days Temperature >90F Max 4th Highest
7 

1. Relative change in surface grid-hours greater than 84 ppb. This metric is termed 

Persistence-Hour and is defined as the number of grid-cells in a given region with 

predicted hourly 8-hour ozone concentrations greater than 84 ppb. The relative 

change in Persistence-Hour is presented as a percent reduction computed for the 

modeling period May through September from the baseline year case to the future 

year case. 

2. Relative change in the number of grid cells with predicted 8-hr daily maxima greater 

than 84 ppb. This metric is termed Persistence-Daily metric and is similar to 

Persistence-Hr, but uses the modeled daily maximum 8-hour ozone concentrations 

greater than 84 ppb instead of the hourly 8-hour ozone concentrations. The relative 

change in Persistence-Daily is also presented as a percent reduction computed for the 

modeling period May through September from the baseline year case to the future 

year case. 

3. Relative change in the sum of hourly predictions greater than 84 ppb. This metric is 

termed Severity-Hour and is defined as the sum of all grid-cells with predicted hourly 

8-hour ozone concentrations greater than 84 ppb. Given the definition of Persistence, 

this Severity could be considered as a weighted form of the Persistence metric. The 

relative change in Severity is also presented as a percent reduction computed for the 

modeling period May through September from the baseline year case to the future 

year case. 

 In addition to the three recommended metrics, two additional metrics were computed to create a 

comprehensive corroborative analysis. The two additional metrics are: 

4. Relative change in the sum of the predicted 8-hr daily maxima greater than 84 ppb. 

Severity-Daily metric is similar to Severity-Hour, but uses the modeled daily 

maximum 8-hour ozone concentrations greater than 84 ppb instead of the hourly 8-

hour ozone concentrations. The relative change in Severity-Daily is also presented as 

a percent reduction computed for the modeling period May through September from 

the baseline year case to the future year case. 

5. Air Quality Index (AQI) counts. The AQI Counts metric is a count of the number of

grid-cells with predicted maximum 8-hour ozone concentrations sorted within each 

of the Code Green, Yellow, Orange and Red categories, as defined by the USEPA's 

AQI Index. As with the persistence and severity metrics, the AQI counts metric can 

be applied to both hourly and daily maximum 8-hour ozone concentrations. AQI 

Counts are presented as percentages of the total number of grid-cells within the study 

region. 

 The metrics described above were applied to the modeling results for just of the nonattainment 

area. Below, Figure L-2 depicts the region for which this modeling data was extracted for both the 2002 

baseline and the 2009 attainment year modeling runs. 
8 

Figure L-2: Area for which the air quality metrics were applied. 

 The results from each of the five air quality modeling metric calculations demonstrated 

significant reductions of greater than 85% in the 2009 future year air quality modeling for days that 

modeled above the NAAQS in the Metrolina nonattainment area. Each metric demonstrated very large 

relative reductions for 2009. It is important to note that the relative reductions in all metrics well 

surpassed the draft version of the Attainment Guidance recommendation of 80% for these particular 

calculations. 

 Figure L-3 below presents the relative reductions calculated in the first four metrics described 

above. The left 2 bars are the Persistence-Hour and Persistence-Daily reductions, and the right 2 bars are 

the Severity-Hour and Severity-Daily reductions. The results demonstrate a 91.2% reduction in 

persistence of hourly maximum ozone and 88.7% reduction in persistence of daily maximum ozone. The 

severity reductions are on a similar scale of 91.6% and 89.1% reduction for hourly and daily maximum 

ozone, respectively. 
9 

Figure L-3: Persistence and Severity for the Metrolina Area 

 Equating the 89.1% relative reduction in the daily maximum ozone to AQI counts, Figure L-4 

demonstrates a drop from 257 grid cells in the Code Orange and Red levels in the 2002 baseline modeling 

to only 29 grid cells in the 2009 future modeling. Furthermore, the number of grid cells in the Code 

Yellow and above (>65 ppb) is reduced by over half, from 3,352 grid cells in 2002 to 1,536 grid cells in 

2009. 

Figure L-4: Daily AQI counts for the Metrolina Area 

% Reduction in Persistence (# Grid Cells) and 

Severity (Sum Cij_85) of Hourly & Daily Max O3

60

65

70

75

80

85

90

95

100

Persistence Severity

Hourly

Daily

% Reduction

Daily 8-hr AQI Counts

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Daily 2002 Daily 2009

% Grid Cells in Region

Yellow 

Orange 

Green 
10 

 The hourly AQI counts are equally encouraging. Figure L-5 displays the 91.2% relative 

reduction in hourly persistence in terms of the AQI counts. It corresponds to a reduction from 988 hourly 

grid cells in the Code Orange and Red levels in the baseline modeling to only 86 hourly grid cells in the 

attainment year modeling. Looking at all hourly grid cells Yellow and above, the count is reduced from 

25,890 hourly grid cells to 9,140, which translates to a 64.7% reduction. Table L-4 contains all the grid 

cell counts for both the Hourly and Daily AQI count analysis. 

Figure L-5: Hourly AQI Count for the Metrolina Area 

Table L-4: Total number of grid cells for the AQI Categories. 

 C. Air Quality Modeling Results From Other Studies 

 Another recommended weight of evidence analysis is to review other air quality modeling results 

that included the Metrolina nonattainment area to determine how other modeling results compare to the 

attainment demonstration. There are two air quality modeling studies to which results are available for 

the Metrolina area. 

 The first is the Early Action Compact (EAC) modeling that the NCDAQ performed for the EAC 

areas within North Carolina. Since the modeling domain for this analysis covered the majority of North 

Carolina, including the Metrolina nonattainment area, the modeling results can be easily compared to the 

Grid Cells Grid Cells

Daily 2002 Daily 2009 Hourly 2002 Hourly 2009

Green 7181 9543 250856 268576

Yellow 4107 2039 26900 10365

Orange 340 46 1316 131

total 11628 11628 279072 279072

Hourly 8-hr AQI Counts

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Daily 2002 Daily 2009

% Grid Cells in Region

Orange

Yellow

Green
11 

attainment demonstration. There are some differences between the two modeling exercises. One 

difference is that the EAC modeling was carried out on 4 episodes (one in 1995, two in 1996 and one in

1997) for a total of sixteen days. Another is the DVB is based on the higher of the 1999-2001 or 2001-

2003 design values. Finally, the EAC modeling did not model 2009, but there are results for 2007 and 

2012. Table L-5 displays the EAC modeling results for the Metrolina monitors for both of these future

years. 

Table L-5: Metrolina DVFs based on EAC Modeling 

2007 2012 

Monitoring Site County DVB 

(ppb) RRF DVF 

(ppb) RRF DVF (ppb) 

Arrowood Mecklenburg 092 0.891 82 0.848 78 

County Line Mecklenburg 101 0.861 87 0.802 81 

Crouse Lincoln 92 0.870 80 0.826 76 

Enochville Rowan 99 0.879 87 0.818 81 

Garinger (Plaza) Mecklenburg 98 0.888 87 0.816 80 

Monroe Union 88 0.852 75 0.795 70 

Rockwell Rowan 100 0.870 87 0.800 80 

 As can be seen from the EAC modeling, although there are still four monitors slightly above the 

8-hour ozone standard in 2007, all of the monitors are well below the standard by 2012. It should be 

noted that for the Greensboro/Winston-Salem/High Point EAC area, the EAC attainment test results 

predicted the highest monitor in the area to be at 83 ppb in 2007. However the current 2004-2006 design 

value for that area is 80 ppb, below what was projected and a year earlier. 

 Another air quality modeling exercise that contained results for the Metrolina nonattainment area 

is the USEPA’s modeling for the Clean Air Interstate Rule (CAIR). The Technical Support Document for 

the final CAIR (March 2005) provided modeling results with and without the implementation for the 

CAIR. Differences between the USEPA’s modeling and the attainment demonstration are: (1) the 

meteorology was for 2001, (2) the DVB was the weighted design values the 1999-2003 period, and (3) 

the modeling results were for 2010. These modeling results are listed in the table below. 

Table L-6: Metrolina DVFs based on the USEPA’s CAIR Modeling 

DVF (ppb) County DVB 

(ppb) 2010 Base 2010 CAIR 

Lincoln 92.3 76.1 74.5 

Mecklenburg 100.3 82.5 81.4 

Rowan 99.7 81.3 80.1 

Union 87.7 71.9 71.1 

York, SC 83.3 70.0 68.5 

 The USEPA’s results were for the highest monitor in a county where more than one monitor is 

located. The USEPA’s modeling results predicts that the Metrolina nonattainment area should be below 

the 8-hour ozone standard by 2010. Although this is one year later than the attainment year for the 

Metrolina area, the USEPA’s 2010 CAIR DVFs are 3 to 4 ppb lower than what the NCDAQ/SCDHEC 
12 

are showing in the attainment demonstration, and supports weight of evidence that the Metrolina area will 

attain the 8-hour ozone standard by its attainment year of 2009. 

 D. Air Quality Trends and Additional Reductions in Emissions 

 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 100 ppb and six out of 

the seven North Carolina monitors in the area were violating the NAAQS. Each year since, the design 

values have decreased and/or the number of violating monitors in the region has decreased. With the 

latest design value period, 2004-2006, the highest violating monitor has a value of 88 ppb and there are 

only three monitors that exceed the NAAQS (See Table L-7) 

Table L-7: Design Values (ppb) for the North Carolina Monitors in the Metrolina Area 

Monitoring Site County 2001-2003 2002-2004 2003-2005 2004-2006 

Arrowood Mecklenburg 84 81 78 80 

County Line Mecklenburg 98 92 87 88 

Crouse Lincoln 92 86 81 79 

Enochville Rowan 99 91 85 85 

Garinger (Plaza) Mecklenburg 96 91 86 88 

Monroe Union 88 85 79 78 

Rockwell Rowan 100 94 88 83 

York York, SC 84 81 75 76 

 The current ozone design values are very close to the predicted attainment year design values; 

however, there are still significant nitrogen oxides (NOx) emission reductions that are expected between 

now and the attainment year 2009. Although most of these expected NOx emission reductions have been 

included in the attainment demonstration modeling, it does not appear the model is responsive enough to 

expected emission reductions. 

 The NCDAQ/SCDHEC have estimated that there will be approximately 8.5 tons per day of NOx

emissions reduced each year from the mobile sector. These reductions are the result of Federal motor 

vehicle and equipment standards for both highway vehicles and off-road equipment. As the older 

vehicles in the fleet are retired and replaced with newer vehicles meeting the Federal standards, the NOx

emissions continue to decrease, even though vehicle miles traveled continue to increase. Similarly, as 

newer off-road equipment is purchased and older equipment is retired, the NOx emissions see a downward 

trend. 

 Another source of NOx emission reductions that are expected to occur between now and the 

attainment year are from the electric generating facilities located in and near the Metrolina nonattainment 

area. The Clean Smokestacks Act requires the two large North Carolina utilities to meet annual NOx

emission budgets for 2007 and a tighter budget for 2009. Several of the Duke Energy units are still 

expected to have controls installed over the next two years. Figure L-6 displays the location and size of 

the Duke Energy facilities located in the vicinity of the Metrolina nonattainment area. Table L-8 lists the 

units that are near the Metrolina area and shows both the year the controls are expected to come on-line 

and the estimated amount of NOx emission reductions for the ozone season. 
13 

Figure L-6: Location and size of the Duke Energy facilities located in the vicinity of the Metrolina 

nonattainment area. 
14 

Table L-8: Utility NOx Emission Reductions since 2006 Ozone Season 

Facility County Technology Operational 

Date 

Ozone Season 

Reductions 

(tons/season) 

Allen Steam Station 

 Unit 2 

 Unit 3 

Gaston SNCR 

SNCR 

Spring 2007 

Fall 2007 

~300 

Buck Steam Station 

 Units 3 & 4 

 Units 5 & 6 

Rowan Low NOx Burners 

SNCR 

Spring 2007 

Fall 2006 

~350 

Riverbend 

 Unit 4 

 Unit 5 

 Unit 6 

 Unit 7 

Gaston 

SNCR 

SNCR & Burners 

SNCR & Burners 

SNCR 

Spring 2007 

Spring 2007 

Fall 2006 

Fall 2006 

~325 

Marshall Steam Station 

 Unit 2 

 Unit 3 

 Unit 4 

Catawba SNCR 

SCR 

SNCR 

Spring 2007 

Fall 2008 

Fall 2006 

~2,300 

Total expected reduction = 3,275 tons/ozone season 

SNCR = Selective Non-Catalytic Reduction 

SCR = Selective Catalytic Reduction

 The combination of the mobile source and utility NOx emission reductions that are expected in 

the Metrolina area between the end of the 2006 ozone season and before the beginning of the attainment

year 2009 is significant. Since the 2004-2006 design values are just above the standard, the additional 

NOx emission reductions in the area should ensure that the Metrolina area would attain the NAAQS by 

the prescribed attainment year. 

 E. Local Measures not Modeled 

 As discussed in Section III of the Attainment Demonstration narrative, the Metrolina 

nonattainment area is a NOx-limited area, and the largest source of NOx emissions in this region come 

from mobile sources and electric generating facilities. A significant source of NOx emission reductions 

that has not been included in the modeling is the addition of an SCR unit at Marshall Unit 3. When the 

modeling was started, Duke Energy had installed an SNCR unit at Marshall Unit 3. However, since the 

expected 2009 Duke Energy system-wide NOx emissions is very close to the Clean Smokestack Act 

annual budget for this company, Duke Energy has announced its intent to install an SCR unit in order to 

provide a safety margin in meeting the Clean Smokestack Act NOx budget. As can be seen in Figure L-6 

in the previous section, the Marshall Steam Station is located directly north and adjacent to the Metrolina 

nonattainment area. The additional NOx emission reductions expected at this facility will have an impact 

on the ozone formation in the Metrolina area on days when the winds are coming from the 

north/northwest and on days when there is recirculation occurring. This SCR unit should be installed the 

Fall of 2008 and will be operational before the beginning of 2009. A copy of the 2007 compliance plan

for Duke Energy documenting this planned installation of the SCR at Marshall Unit 3 can be found in 

Appendix M. 

 In addition to the Marshall NOx emission reductions, the Metrolina area has a number of groups 

that work towards decreasing emissions. These measures are voluntary measures that although may not 
15 

account for large emission reductions, they are directionally correct. A few of the known measures that 

are under way in the Metrolina area are listed below. A list of known projects going on in North Carolina 

is attached at the end of this Appendix. 

• I-77 High Occupancy Vehicle (HOV) lane in Mecklenburg County. A recent evaluation 

of the HOV lanes on I-77 through Charlotte, North Carolina reported that there has been 

an observed increase of use of the HOV lanes since it has opened. It was reported that in 

November 2005, “...the HOV lane carried nearly 50 percent of the average number of 

persons who are traveling in a general-purpose lane in the morning peak hour, but in less 

than 20 percent of the number of vehicles.” Additionally, the “Average daily patronage 

on the [Charlotte Area Transit System] CATS express routes using the I-77 HOV facility 

increased by 63 percent between October 2004 and 2005 ...”. This reduction of vehicle 

miles traveled in this area was not modeled in the attainment demonstration. Having 

more people carpooling or using the transit system in Mecklenburg will reduce both VOC 

and NOx emissions. A copy of the North Carolina Department of Transportation 

(NCDOT) evaluation of the I-77 HOV lane can be found at the end of this Appendix. 

• Truck Stop Electrification in Rowan County. In 2006, 50 spaces at a truck stop in Rowan 

County were converted with Idle Aire technology. This technology provides truckers 

with electricity and air conditioning, allowing the truckers to turn off their engines while 

they rest. This results in a reduction of both NOx and VOC emissions. 

• Express Bus Route (Cabarrus/Rowan Counties). A new connecting service will be 

created between Rider and Salisbury Transit. This provided an express route between 

Kannapolis and Salisbury. Having an express route between these two cities will reduce 

the number of personal cars on the roadways, which in turn will reduce VOC and NOx

emissions. This new express route should be in operation between 2008 and 2010. 

• Pedestrian walkways and Bikeways Projects: A number of the communities are creating 

walkways and bikeways in order to provide safe pathways for pedestrians and bicyclists 

to move about busy traffic areas. These types of projects provide safe alternatives to 

driving in the city. 

• Idle Reduction Policies. North Carolina Department of Public Instruction has issued a 

policy that all school bus drivers are to refrain from idling their buses while waiting to 

pick up children at the school as well as when the buses are at the transportation yard. 

Additionally, several cities and businesses have issued idle reduction policies for their 

fleet vehicles. This reduces VOC and NOx emissions as well as fine particulate matter. 

Some of the partners passing idle reduction policies include: Town of Concord, City of 

Salisbury, and Duke Power. 

• Biodiesel use. A number of cities, counties and businesses have started using biodiesel 

for their diesel fleet. Most often B-20 is being used. B-20 will reduce VOC emissions as 

well as fine particulate matter. Some of the partners using biodiesel include: Gaston 

County Landfill, Town of Matthews, City of Monroe, Union County, NCDOT, and Duke 

Power. 

• Diesel Retrofits. A number of cities, counties and school districts have installed Diesel 

Oxidation Catalysts (DOCs) or Diesel Particulate Filters (DPFs) on their diesel 

equipment. The vehicles that have been retrofitted include schools buses, as well as 

county fleet trucks for solid waste pickup. Although these types of filters are designed to 

remove fine particulate matter, when used with ultra low sulfur diesel fuel, NOx and VOC 

emissions are also reduced. Some of the partners installing DOCs and/or DPFs include: 
16 

Cabarrus County Schools, Gaston County Schools, Iredell County Schools, Lincoln 

County Schools, Mecklenburg County Schools, Rowan County Schools, Salisbury Public 

Schools, City of Charlotte and Mecklenburg County. 

 F. Weight of Evidence Conclusions 

 The NCDAQ/SCDHEC believe that it is better to use a five-year straight average DVB in the 

attainment test since it will normalize the effects of meteorology on design values more so than a 

weighted DVB. Based on the alternative DVF calculated in this section, all of the Metrolina 

nonattainment area monitors are predicted to be below the 8-hour ozone NAAQS in 2009. Although 

three of the monitors still fall within the range for weight of evidence requirements, the monitor DVFs are 

lower than when a weighted DVB is used. 

 The air quality modeling metric analyses for the Metrolina nonattainment area demonstrate 

relative reductions well beyond the recommended 80% mark that is considered appropriate for concluding

that a proposed strategy would meet the 8-hour ozone NAAQS. Additionally, other air quality modeling 

studies have found that the Metrolina area should attain the 8-hour ozone NAAQS by the prescribed 

attainment year. 

 The observed air quality trends in conjunction with further NOx emission reductions expected in 

the Metrolina area strengthens the argument that the attainment demonstration is an acceptable 

demonstration. Finally, given the variety of additional emissions reductions that were not included in the 

development of this modeling exercise, but will occur throughout the surrounding areas before 2009, it is 

reasonable to conclude that the short lived events portrayed in the future modeled year by an extremely 

small number of remaining exceeding grid cells will be below the NAAQS in 2009. 

 The NCDAQ/SCDHEC believe that the weight of evidence provided in this section is strong 

evidence that the Metrolina nonattainment area will attain the 8-hour ozone NAAQS by 2009. 
17 

IV. UNMONITORED AREA ANALYSIS 

 The modeled attainment test does not address future air quality at locations where there is not an 

ozone monitor nearby. To guard against the possibility that air quality levels could exceed the standard in 

areas with limited monitoring, Section 3.4 of the Attainment Guidance suggest that additional review is 

“necessary, particularly in nonattainment areas where the ozone or PM2.5 monitoring network just meets

or minimally exceeds the size of the network required to report data to Air Quality System (AQS).” This 

review is intended to ensure that a control strategy leads to reductions in ozone at other locations that 

could have baseline (and future) design values exceeding the NAAQS were a monitor deployed there. 

The test is called an “unmonitored area analysis.” The purpose of the analysis is to use a combination of 

model output and ambient data to identify areas that might exceed the NAAQS if monitors were located 

there. 

 The NCDAQ, along with Local and Tribal Programs, currently operates a network of 41 ozone 

monitors. Twenty-six of these monitors were established as State and Local Air Monitoring Stations 

(SLAMS). These SLAMS monitors were selected based on specific monitoring objectives (background 

concentration, area of highest concentration, high population, source impact, transport, and rural impact) 

as required by the USEPA and siting scales (micro, middle, neighborhood, urban, and regional) 

established by the USEPA. Eight of the network monitors were further designated as National Air 

Monitoring Stations (NAMS) by the USEPA and have the primary objective to provide ozone data from 

areas of expected highest concentration and population exposure and are used to evaluate trends in 

national air quality. The remaining 14 monitors are Special Purpose Monitors that were established by

NCDAQ to evaluate models, study ozone formation and transport, and obtain a better understanding of 

ozone in North Carolina. The remaining monitor is a Tribal monitor operated by the Eastern Band of 

Cherokee Nation. 

 NCDAQ believes that the density of its monitoring network relieves the necessity of applying this 

additional analysis. With an average of one monitor per 3,077 km2

, this is one of the densest statewide 

ozone monitoring networks in the nation. Additionally, the monitor density across the Metrolina 

nonattainment area is more than twice that of the statewide monitor density (on average a monitor every 

1,278 km2

). A map of each ozone monitor and its NCDAQ/VISTAS 12-km modeling grid is provided in 

Figure L-7. As can been seen by the figure, the spatial coverage of the monitors, and their resulting “near 

by” 3x3 arrays, covers the majority of the urban areas where ozone tends to be higher. 

 Despite being confident its monitoring network is robust enough to cover the state, NCDAQ has 

looked at preliminary results from the “beta” (draft) version of the “Modeled Attainment Test Software” 

(MATS) tool. The MATS tool has been developed by the USEPA to spatially interpolate data, adjust the 

spatial fields based on model output gradients, and multiply the fields by model calculated RRFs to 

complete the unmonitored area analysis. The MATS tool is currently being “beta tested” and peer 

reviewed, with the release of a guidance document for the tool still pending. Once the final version of the 

MATS tool has been released, after sufficient peer review and proper guidance documentation for the 

analysis of the results is provided, NCDAQ will evaluate the MATS tool output. 
18 

Figure L-7: Ozone Monitors and with Respect to the VISTAS 12 km Grid 
19 

ATTACHMENTS TO APPENDIX L 

 Attached to this Appendix is supporting documentation for Section III. The following documents 

are attached: 

• NCDOT I-77 HOV evaluation report 

• Spreadsheet of measures from Cabarrus/Rowan Urban Area Metropolitan Planning Organization 

• Spreadsheet of National Diesel Data from the USEPA for North Carolina 

• Spreadsheet of Diesel Data from the NCDAQ 

• Correspondence from Centralina Council of Governments