THE ADMINISTRATOR OF THE ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

Ms. Trudy Fisher 

Executive Director 

Mississippi Department of Environmental Quality 

P.O. Box 2261 

Jackson, Mississippi 39225-2261 

Dear Ms. Fisher: 

I am pleased to respond to your July 17, 2012, letter in which you filed a petition for reconsideration on 

behalf of the state of Mississippi concerning the U.S. Environmental Protection Agency's final rule, 

"Air Quality Designations for the 2008 Ozone National Ambient Air Quality Standards." See 77 Federal 

Register 30008 (May 21, 2012). The petition requests that the EPA reconsider the nonattainment 

designation for the northern portion of DeSoto County, Miss., as part of the Memphis, TennesseeMississippi-Arkansas ozone nonattainment area. 

The EPA has carefully evaluated the issues and information in your petition. For the reasons explained 

in the EPA's final designation action and information provided in the enclosure, the EPA is denying 

your petition. The EPA continues to believe that the northern portion of DeSoto County is properly 

designated nonattainment because of its contribution to ozone nonattainment in the Memphis TennesseeMississippi-Arkansas area. 

The enclosure provides additional information on the EPA's decision to deny your petition beyond what 

is already provided in the docket for the May 21, 2012, rulemaking. The EPA considers the designation 

of nonattainment areas with appropriate boundaries to be an important step in implementing the 2008 

ozone standards. 

We appreciate the action you have taken in Mississippi to reduce ozone levels and provide cleaner, 

healthier air for millions of people. We look forward to working with you and your staff to ensure 

achievement of the 2008 ozone standards in the Memphis Tennessee-Mississippi-Arkansas area. 

In the meantime, I thank you for your interest in protecting the quality of our environment. 

This paper is printed with vegetable-oil-based inks and is 100-percent postconsumer recycled material, chlorine-free-processed and recyclable.
Enclosure 

The EPA Response to Petition for Reconsideration from Trudy Fisher, Executive Director of the 

Mississippi Department of Environmental Quality, on behalf of the State of Mississippi 

By a letter dated July 17,2012, the Mississippi Department ofEnvironmental Quality (MDEQ), on 

behalf of the State of Mississippi petitioned the EPA to reconsider the final area designation for DeSoto 

County, Mississippi in the Memphis, Tennessee-Mississippi-Arkansas (TN-MS-AR) ozone 

nonattainment area. For the reasons discussed below, the EPA is denying the Petition. For the sake of 

clarity, we have organized this response according to the structure ofthe July 17, 2012, petition. 

I. "General Objections" 

A. Reliance on Most recent Certified Data 

Issue: The Petitioner claims that the EPA should have considered the 2011 certified air quality data for 

Mississippi and Tennessee as it is the best current scientific evidence of air quality. The Petitioner notes 

that in the Responses to Significant Comments on the State and Tribal Designation Recommendations 

for the 2008 Ozone National Ambient Air Quality Standards (NAAQS) dated April 30, 2012, the EPA 

stated that they were "relying on the most recent 3 years of certified data to designate areas for the 2008 

NAAQS" but then did not consider 2009-2011 data for Mississippi and Tennessee but instead relied on 

data from 2008-2010. The Petitioner claims that 2009-2011 data "demonstrates conclusively that 

DeSoto County does not impact the air quality in Tennessee as all of the Tennessee monitors have been 

certified to be in attainment during the 2009-2011 time period." Further, the Petitioner claims that 

"despite growth in population in DeSoto County, the Tennessee monitors are not affected by 

Mississippi" which is consistent with the m.onitored attainment in the 2009-2011 monitoring period in 

Shelby County. Petition at 1. 

Response: In determining the boundaries for the Memphis nonattainment area, the EPA considered the 

most recent full set (i.e., consistent set of years) of certified air quality data for all three states that had 

counties located in the Memphis core-based statistical area (CBSA). The EPA relied on a consistent 

evaluation principle when presented with mixed years of data in an area, and consistently applied that 

principle to all multi-state areas. Specifically, the underlying principle is that the EPA cannot designate 

an area as attainment if the most recent certified data from any of the monitors in the area for the same 

3-year period indicates a violation of the NAAQS. Importantly, while evidence of one violating monitor 

is sufficient to demonstrate that the area is violating the NAAQS for a specific 3-year period, to 

demonstrate attainment of the NAAQS all monitors in the area must be meeting the NAAQS for the 

same 3-year period. Thus, an area cannot demonstrate attainment of the NAAQS based on air quality 

data from different 3-year periods for different monitors.

1 

1 We note that the EPA's reliance on 2008-2010 data for monitors in the Memphis area is consistent with our action in two 

other multi-state areas where some, but not all, of the States submitted early certified 2011 data. For the PhiladelphiaWilmington-Atlantic City, PA-NJ-DE-MD area, we relied on air quality data for 2008-2010 for monitors in all of the States 

where Pennsylvania submitted early certified 2011 data but New Jersey, Delaware and Maryland did not. Similarly, for the 

Washington DC-MD-VA area, Virginia early certified 2011 data but the District of Columbia and Maryland did not and we 

based the designation of the area on air quality data from 2008-2010. 

1 
On page 98 of the Response to Comments, the EPA "acknowledges that Tennessee has provided 

certified, quality assured air quality data for 2009-2011. Arkansas, however, has not requested early 

certification of their 2009-2011 data, and, therefore ... [such Arkansas data] cannot be used for 

designations purposes." The EPA similarly acknowledged that Mississippi submitted early certified data 

for 2011. Memphis TSD at 5. The EPA went on to describe that " [b]ecause EPA has not received 

certified data from all monitors in the area, we are using 2008-2010 air quality data for our analysis of 

the Memphis, TN-MS-AR area." Based on certified data from monitors in all three states for 2008-2010, 

the Shelby County monitor in Tennessee was violating the 2008 ozone NAAQS. While the certified data 

from 2009-2011 showed that all monitors in the Tennessee and Mississippi portions of the Memphis 

area were meeting the NAAQS, the EPA did not have certified monitoring data from 2009-2011 

showing that the Marion monitor in Crittenden County, Arkansas was also attaining the 2008 ozone 

NAAQS. (We further note that preliminary 2011 data indicated that the Marion monitor was likely 

violating the 2008 ozone NAAQS.) In the absence of certified data from the most recent 3 years 

showing that the area as a whole is attaining the standard, the EPA could not rely on certified data from 

only a portion of the area to demonstrate the Memphis area as attainment. Similarly, the EPA could not 

rely on data from 2009-2011 for Arkansas for purposes of the designation because the 2011 data for 

monitors in Arkansas were not certified in sufficient time for consideration in the designation process. 

For the same reason, it was not appropriate for the EPA to have relied upon the 2009 - 2011 data from 

Tennessee when evaluating whether all or a portion of DeSoto County was contributing to a violation of 

the NAAQS in the Memphis CBSA. While not expressly stated, it appears that the Petitioner is 

suggesting two arguments. First, ifthe EPA had relied on data from 2009-2011 from Tennessee and 

Mississippi and 2008-2010 data from Arkansas, then the area as a whole would have been designated 

attainment and no contribution analysis would be needed. Alternatively, th·ey may be suggesting that if 

the EPA had relied on air quality data for 2009-2011 for the entire area, then the violating monitor 

would have been the Marion monitor in Crittenden County, Arkansas and not the Frayser monitor in 

Shelby County, Tennessee and the contribution analysis would have shown that no portion of DeSoto 

County is contributing to the violation at the Crittenden County monitor. For the reasons provided 

above, it was not appropriate for the EPA to have evaluated mismatched data for the three states to 

determine that the entire area was in attainment, or to have alternatively evaluated data from 2009-2011 

for all three states in a contribution analysis. In addition it was not appropriate for the EPA to have 

evaluated 2009-2011 data for all three states because Arkansas did not certify their 2009-2011 data in 

sufficient time for the EPA to consider it prior to the final de~ignations. 

B. Credit for Voluntary Measures 

Issue: The Petitioner claims that in a 2007 meeting with the EPA Region 4, the EPA stressed the 

importance of local voluntary measures and that the "EPA said that .. . [such] information would be used 

for boundary determinations." The Petitioner claims that despite these representations the "EPA failed to 

recognize the significance of the reduced emissions or to give DeSoto County any consideration 

thereof." The Petitioner also claims that the EPA's approach·in making its boundary determinations is 

only specified in the Clean Air Act (CAA or Act) for serious areas. Based on this, the Petitioner claims 

that the EPA should designate DeSoto County as attainment or attainment/unclassifiable. Petition at 2. 

Response: The EPA notes that many of the points raised in this issue were previously raised by the 

Petitioner and considered during the 120-day consultation process. The ozone area boundaries for the 

2008 ozone standard were determined by the EPA Administrator during the designation process based 

on state's 2009 recommendations, subsequent updated state recommendations, communication during 

the 120 day consultation period, public comment, and the EPA's five factor analysis, which included an 

evaluation of emissions from DeSoto County, Mississippi. The EPA is not aware of any 2007 statements 

2 
that would have contradicted the EPA's consideration of information relevant to the designation process, 

or that would have committed the EPA to an attainment/unclassifiable designation for DeSoto County. 

The Petitioner is correct that for purposes of area designations required immediately following 

promulgation of the 1990 CAA Amendments, the Act in section 107(d)(4) specifies that the 

nonattainment boundary for an area classified serious, severe or extreme is to include the entire 

metropolitan statistical area or consolidated metropolitan statistical area, by default. However, the EPA 

explained in its designations guidance for both the 1997 ozone NAAQS and the 2008 ozone NAAQS 

why it believes that to comply with the CAA it is appropriate to evaluate information relevant to the 

entire CBSA to determine an appropriate boundary for a nonattainment area. See "Boundary Guidance 

on Air Quality Designations for the 8-hour National Ambient Air Quality Standards (NAAQS or 

Standard)," memorandum from JohnS. Sei~z, to Air Division Directors, March 28, 2000, pp. 3-4; "Area 

Designations for the 2008 Revised Ozone National Ambient Air Quality Standards," memorandum from 

Robert J. Meyers, to Regional Administrators, Regions I-X, December 4, 2008, p. 3. As noted in the 

2008 memorandum, the EPA believes that using the CBSA or combined statistical area (CSA) 

boundaries as the starting point for assessing appropriate boundaries is a reasonable means for 

evaluating what "nearby" areas contribute to a violation of the NAAQS.

2 In the 2000 Seitz 

memorandum, the EPA explained that it is reasonable to consider a broad area because ofthe "pervasive 

nature of ground level ozone and its precursors." Accordingly, even though there is no CAA-prescribed 

default boundary for areas designated nonattainment for the 2008 ozone NAAQS, the EPA evaluated 

information relevant to DeSoto County's contribution to monitored violations in the Memphis CBSA, 

and concluded that a portion of DeSoto County is appropriately designated nonattainment. 

C. Consistency of Designation with 2004 Designation 

Issue: The Petitioner claims that there were two flaws in the EPA's response to Mississippi's 

recommendation that DeSoto County not be included in the Memphis CBSA because it had not been 

designated as part of the Memphis area for purposes of the 1997 ozone NAAQS. First, the Petitioner 

notes that the EPA responded by saying that it must consider the most recent information available but 

then failed to do so by not considering the new air quality monitoring data from Mississippi and 

Tennessee. Petition at 2. Second, the Petitioner takes issue with the EPA's statement that there has been 

growth throughout the entire Memphis area, countering that despite the population growth and increase 

in VMT (vehicle miles travelled), "the numbers" for DeSoto County have gone down from those relied 

on for purposes of the 2004 designations for the 1997 ozone NAAQS. Petition at 2. The Petitioner 

claims that "DeSoto County should be able .to rely upon past precedent to determine what actions the 

EPA will take". Petition at 3. 

Response: With respect to the Petitioner's first general statement regarding the appropriate data set, the 

EPA addressed the issue above in response to issue LA. The EPA further notes that as part of our five 

factor analysis for the counties in the Memphis CBSA we considered a wide variety of data that was 

new since areas were designated for the 1997 ozone NAAQS in 2004. With respect to the Petitioner's 

second general statement, the EPA first notes that is unclear which "numbers" the Petitioner is referring 

to, and thus is unable to respond specifically to this point. As a general matter, however, with respect to 

2 In the "Boundary Guidance on Air Quality Designations for the 8-hour National Ambient Air Quality Standards (NAAQS 

or Standard)," memorandum from JohnS. Seitz, to Air Division Directors, March 28, 2000, EPA used the metropolitan 

statistical area (MSA) or consolidated MSA (CIMSA) as a starting point for evaluating boundary-related information and in 

the "Area Designations for the 2008 Revised Ozone National Ambient Air Quality Standards," memorandum from Robert J. 

Meyers, to Regional Administrators, Regions 1-X, December 4, 2008, EPA used the CBSA or CSA as a analytical starting 

point. 

3 
the EPA's evaluation of growth, the Agency "evaluated the commuting patterns of residents, as well as 

the total VMT for each county in the Memphis, TN-MS-AR CBSA. In combination with the 

population/population density data and the location of main transportation arteries (see above), this 

information [was used] to identify the probable location of non-point source emissions. A county with 

high VMT is generally an integral part of an urban area and indicates the presence of motor vehicle 

emissions that may contribute to ozone formation that contributes to nonattainment in the area. Rapid 

population or VMT growth in a county on the urban perimeter signifies increasing integration with the 

core urban area, and indicates that the associated area source and mobile source emissions may be 

appropriate to include in the nonattainment area." Memphis TN-MS-AR TSD at 10. These assessments 

are relevant to assessing the location of potentially contributing emissions sources for purposes of 

establishing appropriate boundaries. 

DeSoto County has, in fact, experienced growth in population and VMT since the time of the 

designations for the 1997 NAAQS in 2004.3 It is also true that reported ozone precursor emissions in 

DeSoto County have decreased overall from emissions considered in the 2004 designations for the 1997 

ozone NAAQS, and we also note that reported ozone precursor emissions for Shelby and Crittenden 

Counties have also declined. Importantly, the ozone standard being evaluated for the 2008 NAAQS 

designation is also lower (0.75 parts per million (ppm) vs. 0.8 ppm). Based on all of the latest emissionsrelated information, and other relevant information available to us in the five factor analysis, the EPA 

evaluated DeSoto County's contribution to monitored violations in the Memphis CBSA, and concluded 

that a portion of DeSoto County is appropriately designated nonattainment for the lower 0.75 ppm 2008 

ozone NAAQS. 

II. Specific factor Analysis 

Factor 1 - Air Quality Data 

Issue: The Petitioner claims that, while the EPA cited the Arkansas-Tennessee-Mississippi Ozone Study 

(ATMOS), "EPA failed to acknowledge that DeSoto County has never had the highest ozone design 

value in the Memphis area ... [and that]the ATMOS study also showed that DeSoto County had less than 

a 1 ppb [parts per billion] contribution to the ozone levels in the Memphis area. " The Petitioner claims 

that such contribution does not constitute "sufficient contribution, even when combined with the other 

nine factors, to warrant a designation of nonattainment" for DeSoto County. In addition, the Petitioner 

claims that the EPA improperly relied on only the parts ofthe ATMOS that supported the nonattainrnent 

designation and failed to rely on the parts of the study that supported Mississippi's attainment 

recommendation. Petition at 3 - 4. 

Response: Whether DeSoto has ever had the highest design value in the area was not relevant to the 

EPA's evaluation or ultimate decision. We included a portion of DeSoto County as part of the 

designated area because it contributes to a violation of the NAAQS in a nearby area, not because of a 

monitored violation in DeSoto County. We also note that this issue could have been raised during the 

comment period on the designations and was not raised by the petitioner or any other party; thus it is not 

an appropriate basis for reconsideration. 

3 The 2000 US Census data was used for the 2004 designation. The 2000 population was 1 07,199. The 2010 Census data was 

used for the 201 2 designation. The 2010 population was 161 ,252. 

4 
In the Petitioner's claim that the EPA ignored portions of the ATMOS study that support excluding 

DeSoto from the nonattainment area, the Petitioner does not point to anything specific other than 

asserting that the study shows "that DeSoto County had less than a 1 ppb [parts per billion] contribution 

to the ozone levels in the Memphis area." The EPA does not believe that other aspects ofthe ATMOS 

study referred to by the Petitioner contradict the finding that DeSoto County contributes to ambient air 

quality in the Memphis TN-MS-AR area. The EPA relied on the ATMOS for the proposition that, due to 

meteorological conditions, the monitor site with the maximum design value for the area varies from year 

to year and it is important to consider the monitoring sites as a group, as well as individually, in making 

attainment designation determinations because the_ EPA determined that the meteorological regime 

described in ATMOS remains relevant for the Area. TSD at 6. Other aspects of ATMOS, particularly 

those related to the emissions data used in the study, are no longer relevant due to the age of the data. 

Instead the EPA relied on the more recent 2008 National Emissions Inventory (NEI) data and 2010 

Census Data as described in the TSD. Finally, we note that the relevant portion of the ATMOS study 

was only one piece of information that the EPA considered as part of its five-factor analysis and 

standing alone this study does not definitively address whether all or a portion of DeSoto County should 

be included as part of the designated nonattainment area. 

Factor 2 - Emissions and Emissions Related Data 

A. Emissions Data (location of sources and contribution to ozone concentrations) 

Issue: The Petitioner claims that, in the EPA's fmal TSD, the EPA did not specifically address or 

comment on emission sources and their contribution outlined in MDEQ's TSD. Petition at 5-6. 

Response: The EPA did consider the emission source information outlined in the MDEQ TSD in making 

its decision regarding the appropriate boundaries for the Memphis Area. As the EPA stated on page 97 

of the Response to Comments, "EPA appreciates the updated technical information that Mississippi 

provided and has updated our technical support document accordingly. However, the technical 

evaluation of DeSoto County shows contribution to the air quality in the Memphis area." 

B. Population Density and Degree of Urbanization 

Issue: The Petitioner claims that the EPA should have used raw numbers to represent growth in DeSoto 

County instead of growth rate percentages because such percentages are "not reasonable measures of 

sufficient contribution." To illustrate its point, the Petitioner claims that while DeSoto County only 

experienced a population increase of 53,000 people between 2000 and 2010, given the County's 

"relatively low" starting population, this growth equates to a 48 percent growth rate for the County. The 

Petitioner claims that presenting the information as a growth rate and not in the form of raw numbers is 

unreasonable. Petition at 6. · 

Response: As indicated in Table 5 on p. 9 ofthe TSD, the EPA recognized both the absolute change in 

population as well as the percentage change in population for the counties in the CBSA. And thus, the 

Petitioner's comment is not an appropriate basis for reconsideration. 

Issue: The Petitioner claims that the EPA provided no documentation or reference in support of its 

statement that rapid growth signifies increasing integration with the core urban area. Further, the 

Petitioner claims that "if the population growth in DeSoto County were a contributing factor, then it 

would be evidenced by increased ozone readings by the DeSoto County monitor, which obviously hasn't 

occurred." Petition at 6. 

5 
Response: This issue could have been raised during the comment period and was not raised by the 

Petitioner, and thus is not an appropriate basis for reconsideration. The EPA does not believe that it is 

accurate to conclude that if population growth within the county "were a contributing factor, then it 

would be evidenced by increase ozone readings by the DeSoto County monitor." Ambient ozone levels 

are influenced by a wide array of factors, which is why the EPA performs an extensive five-factor 

analysis to determine contribution. For example, emissions of volatile organic compounds (VOC) and 

nitrogen oxides (NOx) do not necessarily form ozone close to the source of emissions but can be 

transported short or long distances before forming ozone. Moreover, whether ozone levels at a monitor 

are affected by emissions from a specific area or source is influenced by wind patterns. 

C. Traffic and Commuting Patterns 

Issue: The Petitioner reiterates claims expressed in Factor 2 A and B above. Further, the Petitioner 

claims that the 2008 NEI, on which the EPA relied, "incorrectly lists DeSoto County as having higher 

heavy duty diesel truck emissions than Crittenden County." Petition at 8 - 9. 

Response: See responses to Factor 2.A. and B. above. With ~espect to the NEI data referenced by the 

Petitioner, this issue could have been raised during the comment period and was not, and thus is not an 

appropriate basis for reconsideration. The EPA notes that this information is entered into the NEI by the 

states. This information was used because it was the best available data available during the designation 

process. Regarding the Petitioner's heavy duty diesel truck emissions claim, as noted in the TSD, the 

EPA considered the Mississippi submittal that included heavy duty diesel traffic maps and 

accompanying traffic data provided by MDEQ during the 120-day consultation period and determined 

that DeSoto County was contributing to the violating monitor in Tennessee for the reasons described in 

the TSD. The EPA was not provided with any revised NEI data during the designation process and the 

Petitioner has not provided any information to demonstrate that it was not possible to provide such 

information during the 120-day consultation period. 

D. Growth Rates and Patterns 

Issue: The Petitioner reiterates claims expressed in Factor 2.B. above. Petition at 9. 

Response: See response to Factor 2.B. above. 

E. Level of Control of Emission Sources 

Issue: The Petitioner claims that the EPA did not address the level of control of emission sources portion 

of the Emissions and Emissions Related Data Factor in the EPA TSD. The Petitioner claims that while 

there are only a few major sources to control, those sources are well controlled through their permits and 

cites specific examples where controls meet or exceed state or federal requirements. The Petitioner also 

claims that mobile and area sources are the largest category of emissions in the area and that MDEQ and 

local governments have already put measures in place to reduce those emissions. In addition, the 

Petitioner claims that a "marginal non attainment designation will not require further controls from 

mobile or area sources in DeSoto County, nor will local controls be necessary to reduce emission in the 

area." Further, the Petitioner adds that "mobile source emission will be drastically reduced over the next 

several years due to national emission control standards effecting mobile sources." Petition at 10. 

Response: The EPA notes that the Petitioner did not identify any specific information that the EPA 

failed to consider. The emissions data included in the TSD which was the most recent data available to 

the EPA at the time of designations, reflect emission control ·measures and technologies in place through 

6 
2008. TSD at 6-8. The EPA also considered MDEQ's submittals which described the voluntary control 

measures not captured by the NEI data. TSD at 5. 

With respect to the Petitioner's comments regarding additional emissions control requirements for 

marginal nonattainment areas, the EPA notes that future control requirements are not a consideration in 

the designations process. The focus of designating nonattainment areas, as prescribed in the CAA, is to 

determine areas that are violating the NAAQS, and nearby areas that contribute to the area that is 

violating the NAAQS. 

Factor 3 - Meteorology 

Issue: The Petitioner claims that the "EPA unsoundly applied its analysis of meteorology in its use of the 

HYSPLIT model and its use of wind roses as indicators of atmospheric transport." The Petitioner lists 

four factors which it claims make a "back trajectory analysis using HYSPLIT ... patently unreliable in 

determining if transport was occurring on most ozone exceedance days." In addition, the Petitioner 

claims that the EPA failed to factor in the wind direction variability indicated by the surface wind roses 

for the Memphis Area in its analysis. Finally, the Petitioner claims that the EPA failed to acknowledge 

that the DeSoto County monitor has never had the highest design value for the Area. 

Response: This issue was raised during the comment process and was addressed by the EPA in the fmal 

TSD for the Memphis area. Thus is not appropriate for reconsideration. With regard to the EPA's use of 

NOAA's HYSPLIT trajectory model, the EPA believes the back-trajectory analysis is reliable. The EPA 

acknowledges that HYSPLIT trajectory model analyses (along with any atmospheric transport model) 

have some level of uncertainty. However, the HYSPLIT trajectory model uses sound atmospheric 

transport science and archived meteorology data from the National Weather Service to provide useful 

information to evaluate pollutant transport patterns. The locations identified by individual back 

trajectories may be somewhat uncertain, but when a relatively larger number of trajectories pass over a 

given area (i.e., portions of DeSoto County), there is increased confidence in the results ofthe analysis 

(see the discussion ofthe EPA's HYSPLIT analyses in the Meteorology Factor section ofthe EPA's 

TSD). The EPA believes HYSPLIT trajectories are a useful tool for evaluating pollutant transport and 

has used them in analyses for a number of ozone nonattainment areas during the designations process for 

the 2008 NAAQS. As stated in the EPA's TSD, "HYSPLIT trajectories alone do not conclusively 

indicate contribution to monitored violations of the ozone NAAQS and therefore cannot be used to 

determine inclusion or exclusion of an area with regard to ozone designations. Rather, HYSPLIT 

trajectories are useful supporting information that compliment other meteorological information, as well 

as information concerning the other factors, (emissions, etc.)." 

With regard to the EPA's use of wind roses, figures 4a-4d in the EPA's TSD were generated using 

surface-level winds measured at the Memphis International Airport National Weather Service 

meteorology station which is approximately 12 miles south of the Frayser monitor, between DeSoto 

County and the monitor (see Figure 9 in the EPA's TSD). The EPA determined this data to be 

representative of the winds in the Memphis area. The EPA acknowledges that the wind roses show 

variability of wind directions on days where exceedances of the ozone standard were measured at the 

Frayser monitor during the 2008-2010 timeframe. However, the wind roses clearly show that winds 

were blowing from a southerly direction during a large percentage of time when exceedances were 

measured, thus providing evidence that ozone precursor emissions from DeSoto County can contribute 

to the measured ozone concentrations. 

7 
With regard to the Petitioner's claim that the EPA failed to acknowledge that DeSoto County has never 

had the highest ozone value for the Memphis area, please see EPA's response above for Section II, 

Factor 1. 

Issue: The Petitioner also claims that the EPA's finding of the possibility, or the suggestion that sources 

in DeSoto County contributed to elevated ozone locations is not the same as finding that the County 

sufficiently contributed to such ozone levels, and as such, do not provide a strong basis for the EPA's 

designation. 

Response: As described in the TSD, the EPA conducted a five factor analysis to evaluate whether 

DeSoto County contributed to violations ofthe NAAQS in the Memphis area. The use of the terms 

"possible" and "suggests contribution" referenced by the Petitioner appear in the TSD in relation to the 

EPA's evaluation of each individual factor. The EPA evaluated each factor independently and then 

reached a conclusion regarding contribution after considering a weight of the evidence of relevant 

information related to all five factors. Consequently, the terminology cited by the Petitioner from the 

analysis of individual factors does not reflect a summary assessment of whether DeSoto County 

contributed to the violations in the CBSA. For example see the Conclusion section of the December 8, 

2011 , TSD, at pages 11 and 12. 

Issue: The Petitioner claims that the EPA failed to consider the fact that the "back trajectories shown in 

the TSD travel over areas of Memphis prior to arriving at the Frayser monitor with much higher NOx 

and VOC emissions density than [do those from] Desoto County." 

Response: This issue could have been raised during the comment period and was not raised by the 

Petitioner, thus is not an appropriate basis for reconsideration. The EPA did consider the fact that the 

back trajectories which travel over DeSoto County also travel over areas of Memphis located in 

Tennessee (Shelby County). The EPA recognizes that emission sources in the Tennessee portion of 

Memphis also contribute to the measured ozone exceedances at the Frayser monitor. However, the 

EPA's assessment ofthe five factors (including emissions, meteorology, and others) presented in our 

TSD shows that DeSoto County has: the second highest emissions levels ofNOx and VOCs in the 

Memphis TN-MS-AR CBSA; large VMT; a large population increase; and winds showing transport 

toward the Frayser monitor. Based on this information, the EPA concluded that ozone precursor 

emissions from DeSoto County also contribute to the measured ozone exceedances at the Frayser 

monitor. 

Issue: The Petitioner claims that the "EPA rushed to judgment, thereby failing to base its decision on the 

best available scientific knowledge." As evidence, the Petitioner quotes the EPA's Response to 

Comments as stating that " [i]n those cases where timing constraints and the lack of additional 

information prevented a more detailed assessment, EPA believes that the default wind rose analyses, in 

conjunction with the remainder of the multi-factor analysis, can provide an adequate assessment of 

appropriate boundaries." Petition at 11 - 12. 

Response: The EPA did not rush to judgment, and used the best available information to make final 

designations decisions. The same type and quality of information was not available for all areas that the 

EPA evaluated. The EPA notes that the Petitioner's understanding ofthe quote from the Response to 

Comments document is taken out of context. This statement is referring to states, unlike Mississippi, that 

did not conduct back trajectory analysis and concludes that ~he default wind rose analysis in 

conjunction with the remainder of the multi-factor analysis can provide an adequate assessment of 

8 
appropriate boundaries." The EPA's meteorology factor discussion in the Memphis TSD provides a 

summary of the detailed technical analyses 'that were undertaken to assess pollutant transport, including 

wind roses created with Memphis International Airport National Weather Surface data, HYSPLIT 

trajectory analyses and an assessment of previous ozone modeling studies in the Memphis area. This 

detailed information shows that the EPA considered the best information available for our analysis of 

the Memphis area. 

Factor 4-Geographyffopography 

The Petitioner did not provide any comments associated with this factor. Petition at 12. 

Factor 5- Jurisdictional Boundaries 

Issue: The Petitioner claims that state and county barriers "should be given greater consideration in the 

case of DeSoto County." The Petitioner claims that because DeSoto County is in a separate state from 

the counties with the violating monitor the state is unable to address the nonattainment using the 

provisions afforded by the CAA to get back into attainment. The Petitioner then reiterates its earlier 

claims from Factors 2.B., 2.C., 2.E., and 3 above to support its position that DeSoto County should not 

be included in the nonattainment designation for Memphis. Petition at 12-13. 

Response: The EPA did consider the jurisdictional factor, and we believe the state boundary is not a 

reason to exclude DeSoto County from the nonattainment area. TSD at 15. With respect to points the 

Petitioner raised in support of this issue, the CAA clearly contemplates that nonattainment areas may be 

comprised of counties from two or more states and that these multi-state areas can work together to 

address nonattainment. See, e.g. , CAA sections 107(d)(3)(A); 107(d)(4)(A)(iv); and 182G). The EPA 

also notes that the points raised by the Petitioner to support its claim under factor five have been 

previously addressed by the EPA, including in responses to Factors 2.B., 2.C., 2.E. and 3 above. 

9