Insignificance Determination for Transportation Conformity under the PMfine

National Ambient Air Quality Standard (NAAQS) For Jackson County, Alabama 

Alabama Department of Environmental Management 

The following report shows that emissions of nitrogen oxides (NOx) and direct fine 

particles (PMfine) from mobile sources in the small portion of Jackson County designated 

by EPA as nonattainment for the annual fine particle NAAQS, are an insignificant 

contributor to nonattainment of the PMfine NAAQS. 

EPA designated a small portion of Jackson County, Alabama, as nonattainment for the 

annual PMfine NAAQS on December 17, 2004. Jackson County was designated as part of 

the Chattanooga, Tennessee, annual PMfine nonattainment area. According to EPA, the 

small portion of Jackson County which includes the Widows Creek Steam Plant was 

included in the Chattanooga nonattainment area because they believed that emissions 

from this utility contribute to nonattainment in Chattanooga. The technical support 

document for the December 17, 2004 designations states “Additionally we have included 

in our recommended nonattainment area Jackson County, AL, that is adjacent to the 

Chattanooga MSA, that is generally rural in character, and that contains an identifiable 

large emitting facility or facilities (e.g., power plants) which we believe contribute to the 

nearby nonattainment problem.” Therefore, it should be noted that the small portion of 

Jackson County was included in the Chattanooga nonattainment area because of EPA 

concerns related to utility emissions and not because of concerns related to mobile source 

emissions in the county. 

According to 40 CFR 93.109(k), there are several factors that are used to support a 

finding of insignificance for these transportation-related PMfine precursor pollutants. The 

first factor is the percentage of motor vehicle emissions in the context of the total SIP 

inventory. The second factor is the current state of the air quality in the area. The third 

factor is the absence of SIP motor vehicle emission control measures. Lastly, historical 

trends and future projections of the growth of motor vehicle emissions are reviewed. 

These factors are discussed in detail in the sections to follow. Each section supports the 

insignificance of NOx and direct PMfine emissions from mobile sources in the Jackson 

County portion of the nonattainment area under the transportation conformity rule for the 

PMfine NAAQS. 

NOx:

1. Analysis of motor vehicle NOx emissions in the Jackson County portion of the 

Chattanooga nonattainment area. 

Only a small portion of Jackson County, Alabama, was included in the Chattanooga 

PMfine non-attainment area. The small portion of the county designated nonattainment 

contains a limited number of roads. In order to determine the on-road emissions of NOx

from motor vehicles in that portion of Jackson County, the document titled “Chattanooga 

Non-Attainment Area Year 2030 Conformity Determination Report for Particulate Matter 
(PM2.5)” was used to determine how emissions were calculated for Jackson County and 

the same methodology was applied in this analysis. In order to estimate on-road mobile 

source emissions for the nonattainment portion of Jackson County, a ratio of the size of 

the nonattainment portion of Jackson County in square miles to the size of the entire 

county in square miles was calculated. The nonattainment portion of Jackson County 

was determined to be only about one percent of the total area of the entire county. The 

same ratio was applied to obtain area and non-road mobile source emissions for the 

nonattainment portion of the county. The following table shows the small percentage of 

NOx emissions from on-road mobile sources as compared to NOx emissions from all 

other sources in the Jackson County portion of the nonattainment area. Emission data 

were obtained from the VISTAS 2002 Base G2 “best and final” emissions inventory. 

Table 1: 2002 NOx (TPY) Emissions in the Nonattainment portion of Jackson 

County by Source Type 

Area 3.1 <1% 

Point 26337.4 99.9% 

Non-Road Mobile 14.18 <1% 

On-Road Mobile 6.97 <1% 

Total 26361.65 

As the above table demonstrates, NOx emissions from on-road mobile sources in the 

nonattainment portion of Jackson County are less than 1% of the total NOx emissions 

from all source categories in the same area. 

In the table below, a comparison is made of the mobile source NOx emissions from the 

nonattainment portion of Jackson County to total mobile source NOx emissions for the 

entire Chattanooga nonattainment area. 

Table 2: 2002 NOx (TPY) On-road Mobile Source Emissions in the Nonattainment 

Portion of Jackson County Compared to Total On-road Mobile Source Emissions in 

the entire Chattanooga NAA 

Jackson County NAA 

Portion 

6.97 <1% 

Chattanooga NAA 13977.73 

As the table above demonstrates, NOx emissions from on-road mobile sources in the 

Jackson County portion of the nonattainment area are less than 1% of the total NOx

emissions from on-road mobile sources in the entire Chattanooga non-attainment Area. 

2. The current state of the air quality in Jackson County. 

As stated earlier in this document, the small portion of Jackson County, Alabama, was 

included in the Chattanooga PMfine non-attainment area due to the fact that a power plant 

is located in that area and it was thought by EPA to contribute to the PMfine problem in 
Chattanooga. There are no PMfine monitors located in Jackson County. The other 

monitors in Alabama near Jackson County have monitored values below the annual 

PMfine NAAQS. Other counties surrounding the county are either in attainment or 

unclassifiable. 

3. The absence of SIP motor vehicle controls for the area. 

There are no SIP motor vehicle controls for Jackson County. 

4. Historical trends and future projections of the growth of motor vehicle emissions. 

The “Chattanooga Non-Attainment Area Year 2030 Conformity Determination Report 

for Particulate Matter (PM2.5)” was used to obtain past and future projections of the 

growth in NOx emissions from on-road mobile sources. As demonstrated in the table 

below, future emissions of NOx are expected to decrease. 

Table 3: Historical and Future Projections of NOx emissions from On-Road Mobile 

Sources in Jackson County 

2002 6.97 

2010 3.40 

2020 1.35 

2030 0.96 

Direct PMfine:

1. Analysis of motor vehicle NOx emissions in the Jackson County portion of the 

Chattanooga nonattainment area 

Only a small portion of Jackson County, Alabama, was included in the Chattanooga 

PMfine non-attainment area. The portion designated nonattainment contains a limited 

number of roads. In order to determine the on-road emissions of PMfine from motor 

vehicles in that portion of Jackson County the document titled “Chattanooga NonAttainment Area Year 2030 Conformity Determination Report for Particulate Matter 

(PM2.5)” was used to determine how emissions were calculated for Jackson County and 

the same methodology was applied in this analysis. In order to estimate on-road mobile 

source emissions for the nonattainment portion of Jackson County, a ratio of the size of 

the nonattainment portion of Jackson County in square miles to the size of the entire 

county in square miles was calculated. The nonattainment portion of Jackson County 

was determined to be only about one percent of the total area of Jackson County. The 

same ratio was applied to obtain area and non-road mobile source emissions for the 

nonattainment portion of the county. The following table shows the small percentage of 

PMfine emissions from on-road mobile sources as compared to PMfine emissions from all 

other sources in the nonattainment portion of Jackson County. Emission data were 

obtained from the VISTAS 2002 Base G2 “best and final” inventory. 
Table 4: 2002 Direct PMfine (TPY) Emissions in the Nonattainment Portion of 

Jackson County by Source Type 

Area 12.09 <1% 

Point 932.51 98.6% 

Non-Road Mobile 0.882 <1% 

On-Road Mobile 0.145 <1% 

Total 945.63 

As the above table demonstrates, direct PMfine emissions from on-road mobile sources in 

the nonattainment portion of Jackson County are less than 1% of the total direct PMfine 

emissions from all source categories in the same area. 

In the table below, a comparison is made of the mobile source direct PMfine emissions 

from the nonattainment portion of Jackson County to total mobile source PMfine 

emissions for the entire Chattanooga nonattainment area. 

Table 5: 2002 Direct PMfine (TPY) On-road Mobile Source Emissions in the 

Nonattainment Portion of Jackson County Compared to Total On-road Mobile 

Source Emissions in the entire Chattanooga NAA 

Jackson County NAA 

Portion 

0.145 <1% 

Chattanooga NAA 264.97 

As the table above demonstrates, direct PMfine emissions from on-road mobile sources in 

the Jackson County portion of the nonattainment area are less than 1% of the total direct 

PMfine emissions from on-road mobiles sources in the entire Chattanooga non-attainment 

area. 

2. The current state of the air quality in Jackson County. 

The small portion of Jackson County, Alabama was included in the Chattanooga PMfine

non-attainment area due to the fact that a power plant is located in that area and it was 

thought by EPA to contribute to the PMfine problem in Chattanooga. There are no PMfine

monitors located in Jackson County. The other monitors in Alabama near Jackson County 

have monitored values below the annual PMfine NAAQS. Other counties surrounding the 

county are either in attainment or unclassifiable. 

3. The absence of SIP motor vehicle controls for the area. 

There are no SIP motor vehicle controls for Jackson County. 

4. Historical trends and future projections of the growth of motor vehicle emissions. 
The “Chattanooga Non-Attainment Area Year 2030 Conformity Determination Report 

for Particulate Matter (PM2.5)” was used to obtain past and future projections of the 

growth in direct PMfine emissions from on-road mobile sources. As demonstrated in the 

table below, future emissions of direct PMfine are expected to decrease. 

Table 6: Historical and Future Projections of PMfine emissions from On-Road 

Mobile Sources in Jackson County 

2002 0.145 

2010 0.072 

2020 0.041 

2030 0.039 

Conclusion

Each of the factors set forth in 40 CFR 93.109(k) were reviewed for the transportationrelated PMfine precursor pollutants NOx and direct PMfine. These reviews support the 

conclusion that mobile source emissions of NOx and direct PMfine in the Jackson County 

portion of the Chattanooga, Tennessee fine particle nonattainment area are insignificant 

under the transportation conformity rule for the PMfine NAAQS.