1 

### TEXAS Area Designations for the 2008 Ozone National Ambient Air Quality Standards

The table below identifies the areas and associated counties or parts of counties in Texas that EPA intends to designate as nonattainment for the 200 8 ozone national ambient ai r quality standards (2008 NAAQS). In accordance with secti on 107(d) of the Clean Air Act, EPA must designate an area
“nonattainment” if it is violati ng the 2008 ozone NAAQS or if it is co ntributing to a violation of the 2008 ozone NAAQS in a nearby area. The techni cal analyses supporting the boundaries for the
individual nonattainment areas are provided below.

Intended Nonattainment Areas in Texas

Area Texas’ Recommended
Nonattainment Counties EPA’s Intended
Nonattainment Counties

Dallas-Fort Worth, TX Collin
Dallas
Denton
Ellis
Johnson
Kaufman
Parker
Rockwall
Tarrant Collin
Dallas
Denton
Ellis
Hood
Johnson
Kaufman
Parker
Rockwall
Tarrant
Wise

Houston-Galveston-Brazoria,
TX Brazoria
Chambers
Fort Bend
Galveston
Harris Liberty Montgomery
Waller Brazoria
Chambers
Fort Bend
Galveston
Harris Liberty Matagorda Montgomery
Waller

EPA intends to designate the remaining counties in Texas that are not listed in the table above as
“unclassifiable/a ttainment” for the 2008 ozone NAAQS.

The analysis below provides the basis for inte nded nonattainment area bounda ries. It relies on our analysis of whether and which monitors are viol ating the 2008 ozone NAAQS, based on certified air quality monitoring data from 2008-2010 and an evalua tion of whether nearby areas are contributing to
such violations. EPA has evaluated contributions from nearby areas based on a weight of evidence analysis considering the factors identified be low. EPA issued guidance on December 4, 2008 that2 identified these factors as ones EPA would consid er in determining nonattainment area boundaries and
recommended that states consider these factors in making their designations recommendations to EPA. 1

1. Air quality data (including the design valu e calculated for each Federal Reference Method (FRM) or Federal Equivalent Method (FEM) 2 monitor in the area);
2. Emissions and emissions-related data (including location of sources and population, amount of
emissions and emissions controls , and urban growth patterns);
3. Meteorology (weather/transport patterns);
4. Geography and topography (mountain ra nges or other basin boundaries);
5. Jurisdictional boundaries (e.g., counties, air dist ricts, existing nonattainment areas, Indian country, metropolitan planni ng organizations (MPOs))

Ground-level ozone generally is not emitted directly in to the air, but is crea ted by chemical reactions between oxides of nitrogen (NOx) and volatile orga nic compounds (VOC) in the presence of sunlight. Because NOx and VOC emissions from a broad range of sources over a wide area typically contribute to violations of the ozone standards, EPA believes it is important to consider wh ether there are contributing emissions from a broad geographic area. Accordingly, EPA chose to examine the 5 factors with respect to the larger of the Combined Sta tistical Area (CSA) or Core Based St atistical Area (CBSA) associated with the violating monitor(s). 3 All data and information used by EP A in this evaluation are the latest available to EPA and/or provide d to EPA by states or tribes.

In EPA’s designations guidance for the 2008 ozone NAAQS EPA recommended examining
CSA/CBSAs because certain f actors used to establish CSAs and CBSAs are similar to the factors EPA is using in this technical analysis to determine if a nearby area is c ontributing to a violation of the 2008 ozone NAAQS. Congress required a similar approach in 1990 for areas classified as serious or above for
the 1-hour ozone standard and EPA used the same basic approach in the designation process for the 1997 ozone NAAQS. Where a violating monitor is not located in a CSA or CBSA, EPA’s guidance recommended using the boundary of th e county containing the violating monitor as the starting point for considering the nonattainment area’s boundary.

Technical Analysis for Dallas-Fort Worth

Figure 1 is a map of the Dallas-Fort Worth intended nonattainment area. The map provides other relevant information including the locations and design values of ai r quality monitors, county and other jurisdictional boundaries, relevant statistical area boundaries, the nonattainment area boundary for 1997 ozone NAAQS, and major tr ansportation arteries.

Figure 1. Dallas-Fort Worth In tended Nonattainment Area

1 The December 4, 2008 guidance memorandum “Area Designa tions for the 2008 Revised Ozone National Ambient Air Quality Standards” re fers to 9 factors. In this technical support document we have grouped the emissions-related factors together under the heading of “Emissions and Emissions-Related Data,” which results in 5 categories of factors.

2 FRM monitors utilize a chemi-luminescent technique to measure ozone, while many FEM monitors use a technique involving ultraviolet photometry. FEM methods began to be developed in the late 1970’s/early1980’s and are now the most widely utilized methods for monitoring ozone levels. Refer to 40 CFR Part 53 for a more detailed description of FEM and
FRM methods. http://www.epa.gov/ttnamti1/files/ambient/criteri a/reference-equivale nt-methods-list.pdf

3 Lists of CBSAs and CSAs and their geographic components are provided at www.census.gov/population/www/metroareas/metrodef.html . The lists are periodically upda ted by the Office of Management and Budget. EPA used the most recent update, based on 2008 population estimates, issued on December 1, 2009 (OMB Bulletin No. 10-02).3 For purposes of the 1997 8-hour ozone NAAQS, portions of this area were designated nonattainment. The boundary for the nonattainment area for the 1997 ozone NAAQS included the entire counties of Collin, Dallas, Denton, Ellis, Johnson, Kauf man, Parker, Rockwell, and Tarrant.

In March 2009, 4 Texas recommended that the same counties be designated as nonattainment for the 2008 ozone NAAQS based on air quality data from 2006- 2008. Texas provided an update to the original
recommendation in October 2011 5 based on air quality data from 2008-2010. The State’s
recommendations are based on data from FEM monito rs sited and operated in accordance with 40 CFR
Part 58.

After considering these recommendations and based on EPA's technical analysis described below, EPA intends to designate 11 counties in Texas (identified in Table 1 below) as “nonattainment” for the 2008 ozone NAAQS as part of the Dallas/Fort Worth nonattainment area.

Table 1. Texas's Recommended and EPA’s Intended Designated Nonattainment Counties for Dallas/Fort
Worth.

4 Initial 2008 ozone NAAQS designation recommendation letter fr om Governor Perry to Acti ng Regional Administrator

Starfield, dated March 10, 2009.

5 Updated 2008 ozone NAAQS designation recommendation letter from Governor Perry to Regional Administrator

Armendariz, dated October 31, 2011.4 Dallas-Fort Worth Area State-Recommended
Nonattainment Counties EPA Intended
Nonattainment Counties

Texas Collin
Dallas
Denton
Ellis
Johnson
Kaufman
Parker
Rockwall
Tarrant Collin
Dallas
Denton
Ellis
Hood
Johnson
Kaufman
Parker
Rockwall
Tarrant
Wise

Factor Assessment



### Factor 1: Air Quality Data

For this factor, we considered 8-hour ozone design values (in ppm) for air quality monitors in counties
in the Dallas-Fort Worth area based on data for the 2008-2010 period (i.e., the 2010 design value, or DV), which are the most recent years with fully-certifi ed air quality data. A monitor’s DV is the metric
or statistic that indicates whethe r that monitor attains a specified air quality standard. The 2008 ozone NAAQS are met at a monitor when the annual fourth-highest daily maximum 8-hour average concentration, averaged over 3 years is 0.075 ppm or less. A DV is only valid if minimum data completeness criteria are met. See 40 CFR part 50 A ppendix P. Where several m onitors are located in a county (or a designated nona ttainment area or maintenance area), the DV for the county or area is determined by the monitor with the highest level.

The 2010 DVs for the ozone NAAQS for counties in Dallas-Fort Worth and nearby surrounding area are
shown in Table 2.5 Table 2. Air Quality Data.

County State Recommended
Nonattainment? 2008-2010 Design Value (ppb) Collin County, TX Yes 77 Cooke, TX No -- Dallas County, TX Yes 78 Delta, TX No -- Denton County, TX Yes 80 Ellis County, TX Yes 72 Fannin, TX No -- Grayson, TX No -- Henderson, TX No -- Hood County, TX No 75 Hunt, TX No 64 Johnson County, TX Yes 80 Kaufman County, TX Yes 67 Palo Pinto, TX No -- Parker County, TX Yes 75 Rockwall County, TX Yes 74 Somervell, TX No -- Tarrant County, TX Yes 86 Wise County, TX No --

Air quality monitors in Collin, Dallas, Denton, Johnson, and Tarrant Counties indicate a violation of the 2008 ozone NAAQS, therefore these counties are incl uded in the nonattainment area. A county (or partial county) must also be designated nonattainment if it contributes to a vi olation in a nearby area. Each county without a violating monitor that is locat ed near a county with a vi olating monitor has been evaluated, as discussed below, based on the five f actors and other relevant information to determine
whether it contributes to the nearby violation.



### Factor 2: Emissions and Emissions-Related Data

EPA evaluated emissions of ozone precursors (NO
x and VOC) and other emissions-related data that provide information on areas cont ributing to violating monitors.

Emissions Data

EPA evaluated county-level emission data for NO
x and VOC derived from the 2008 National Emissions Inventory (NEI), version 1.5. This is th e most recently available NEI. (See http://www.epa.gov/ttn/chie f/net/2008inventory.html ). Significant emissions levels in a nearby area indicate the potential for the area to contribute to observed violations. We will also consider any
additional information we receive on changes to emissions levels th at are not reflected in recent inventories. These changes include emissions reductions due to permanent and enforceable emissions controls that will be in place before final designati ons are issued and emissions increases due to new

sources.

Table 3 shows emissions of NO
x and VOC (given in tons per year or tpy) for violating and nearby
counties that we considered for inclusion in the Dallas-Fort Worth CSA.6 Table 3. Total 2008 NO
x and VOC Emissions from 2008 NEI.

County State Recommended
Nonattainment? NO
x (tpy) VOC (tpy)

Collin, TX Yes 10,322 14,503 Cooke, TX No 3,853 5,790 Dallas, TX Yes 51,023 63,473 Delta, TX No 1,016 462 Denton, TX Yes 17,421 24,932 Ellis, TX Yes 15,768 6,543 Fannin, TX No 2,165 1,207 Grayson, TX No 5,919 7,401 Henderson, TX No 3,573 6,067 Hood, TX No 5,515 9,547 Hunt, TX No 3,688 3,765 Johnson, TX Yes 31,769 10,163 Kaufman, TX Yes 5,868 3,510 Palo Pinto, TX No 3,348 7,464 Parker, TX Yes 9,550 11,708 Rockwall, TX Yes 1,859 2,047 Somervell, TX No 698 921 Tarrant, TX Yes 56,408 49,021 Wise, TX No 11,911 23,657
Area-wide: 241,674 252,181

Subsequent to development of the 2008 NEI, the Texas Commission on Envir onmental Quality (TCEQ) prepared an emissions inventory of NOx and VOC emissions resulti ng from Barnett Shale oil and gas production, transmission, processing, and rela ted activities duri ng calendar year 2009. 6 Table 4 below presents an updated Barnett Shale Area Special Inve ntory of NOX and VOC emissions from oil and gas production activities for the counties in the Dallas-For t Worth CSA. EPA also considered the additional
contribution of NOx and VOC emissions from Barnet t Shale area oil and gas pr oduction activities in its
evaluation of emissions for the Dallas-Fort Worth CSA counties.

Table 4. TCEQ 2009 Barnett Shal e Area Special Inventory.

County State Recommended
Nonattainment? NO
x (tpy) VOC (tpy)

Collin, TX Yes Cooke, TX No 76 490 Dallas, TX Yes 0 5 Delta, TX No Denton, TX Yes 429 3,523 Ellis, TX Yes 120 49 Fannin, TX No Grayson, TX No Henderson, TX No Hood, TX No 6,903 2,113

6 http://www.tceq.texas.gov/airquality/ point-source-ei/psei.html#barnett2 . Reference Barnett Shale Area Special Inventory,
Phase Two.7 County State Recommended
Nonattainment? NO
x (tpy) VOC (tpy)

Hunt, TX No Johnson, TX Yes 1,101 1,614 Kaufman, TX Yes Palo Pinto, TX No 1,226 833 Parker, TX Yes 743 2,420 Rockwall, TX Yes Somervell, TX No 1,119 221 Tarrant, TX Yes 415 1,083 Wise, TX No 2,520 6,032
Area-wide: 14,652 18,383

The counties in the Dallas-Fort Worth CSA with the highest emissions of NOx and VOC are Collin, Dallas, Denton, Ellis, Johnson, Parker, Tarrant, and Wise. Together, these counties account for 84 percent of the 2008 NEI NOx emissions and 81 per cent of the 2008 NEI VOC emissions of the entire

area.

Hood and Wise Counties also have comparatively high emissions of NOx and VOC. Based on just the 2008 NEI data, Wise County’s emissi ons of VOC at 23,657 tpy are the 4 th highest in the 19-county CSA, and Hood County’s 5,515 tpy of VOC emissions are the 8 th highest in the 19-county CSA. Wise and Hood Counties also have comparativ ely high NOx emissions, which are 6 th and 11 th highest, respectively, in the CSA.

Population density and degree of urbanization

EPA evaluated the population and vehicle use characterist ics and trends of the area as indicators of the probable location and magnitude of non-point source emissions. These include ozone-creating emissions from on-road and off-road vehicles and engines, consumer products, residential fuel combustion, and consumer services. Areas of dense population or co mmercial development are an indicator of area
source and mobile source NO
x and VOC emissions that may cont ribute to ozone formation that
contributes to nonattainment in th e area. Rapid population or VMT grow th (see below) in a county on the urban perimeter signifies increasing integration with the core urban area, and indicates that it may be appropriate to include the area asso ciated with area source and mobile source emissions as part of the nonattainment area. Table 5 shows the populatio n, population density, and population growth information for each county in the area.

Table 5. Population and Growth.

County State
Recommended
Nonattainment? 2010 Population 2010 Population Density (1000 pop/sq mi) Absolute change in population (2000-2010) Population % change (2000-2010) Collin, TX Yes 782,341 0.88 282,143 18.5 Cooke, TX No 38,734 0.04 1,979 0.4 Dallas, TX Yes 2,368,139 2.6 142,691 2.2 Delta, TX No 5,231 0.02 -106 -0.2 Denton, TX Yes 662,614 0.69 223,647 18.7 Ellis, TX Yes 149,610 0.16 37,228 13.5 Fannin, TX No 33,915 0.04 2,575 3.8 Grayson, TX No 120,877 0.12 9,891 4.6 Henderson, TX No 78,532 0.08 4,990 0.098 County State
Recommended
Nonattainment? 2010 Population 2010 Population Density (1000 pop/sq mi) Absolute change in population (2000-2010) Population % change (2000-2010) Hood, TX No 51,182 0.12 9,719 9.2 Hunt, TX No 86,129 0.10 9,199 5.7 Johnson, TX Yes 150,934 0.21 22,967 4.9 Kaufman, TX Yes 103,350 0.13 31,268 17.6 Palo Pinto, TX No 28,111 0.03 1,028 3.1 Parker, TX Yes 116,927 0.13 27,690 15.4 Rockwall, TX Yes 78,337 0.53 34,457 25.7 Somervell, TX No 8,490 0.04 1,660 14.4
Tarrant. TX Yes 1,809,034 2.01 354,603 12.2 Wise, TX No 59,127 0.06 9,727 5.9 Area-wide: 6,731,614 0.46 1,207,356 21.9 Sources: U.S. Census Bureau populati on estimates for 2010 as of August 4, 2011 ( http://factfinder2.census .gov/faces/tableservices/js f/pages/productview.xhtml?pi d=DEC_10_PL_GCTPL2.STO5& prodType=table )

The Dallas-Fort Worth area is a large metropolitan area with a total population approaching 7 million people. For the purposes of determining the bounda ry of the intended 2008 ozone nonattainment area, EPA evaluated 22 counties in the greater Dallas- Fort Worth area with a total population of 6,731,614 people and an average population dens ity of 460 people per square mile.

Dallas and Tarrant Counties have by far the highest and most dense populations. Dallas County has approximately 2.4 million people and a population dens ity of 2,600 people per square mile, and Tarrant County has approximately 1.8 million people and a popul ation density of 2,001 pe ople per square mile. Two other counties, Collin and Denton are also de nsely populated; each has more than 500,000 people and a population density exceeding 500 people per square mile.

There are an additional eight counties in this area with populations exceeding 50,000 people and/or population densities exceeding 100 pe ople per square mile. These count ies include: Ellis, Grayson, Hood, Johnson, Kaufman, Parker, and Rockwall. Thes e counties are characterized by population counts that range between approximately 60,000 and 150,000 pe ople and population densities that range from 120 to 530 people per square mile.

Ten of the counties in this area experienced population growth between 2000 and 2010 in excess of approximately 10,000 people. Of these, the population of four of these counties grew by more than 100,000 people during the past decad e: Collin County (+282,143 people), Dallas County (+142,000 people), Denton County (+223,647 peopl e), and Tarrant County (+354,6 03 people). Six additional counties experienced population growth that rang ed from approximately 10,000 to 40,000 people: Ellis, Johnson, Kaufman, Parker, Rockwall, and Wise Counties.

A final population and growth metric evaluated by EPA was the percen t change in population during the period from 2000 to 2010. During this decade, eight of the 22 counties experienced a percent change in population that exceeded 10 percent: Collin (+1 8.5%), Denton (+18.7%), Ellis (+13.5%), Kaufman (+17.6%), Parker (+15.4%), Rockwa ll (+25.7%), Somervell (+14.4%), and Tarrant (+12.2%) Counties.

The attachment to this document contains Figu re 3, Dallas-Fort Worth Ozone and Ozone Precursor Monitoring Network, and Figure 5, Population Density Change Percentage Between 2000 and 2010
Census for Dallas-Fort Worth Ozone and Ozone Precursor Monitoring Network, which present graphical information on population density a nd growth for the Dallas-Fort Worth area.9 Traffic and commuting patterns

EPA evaluated the commuting patter ns of residents in the area, as well as the total Vehicle Miles Traveled (VMT) for each county. In combination with the population/ population density data and the location of main transportation arte ries (see above), this information helps identify the probable location of non-point source emissions. A county with high VMT and/or a high number of commuters is generally an integral part of an urban area and indicates the presence of motor vehicle emissions that may contribute to ozone formation that contribute s to nonattainment in the area. Rapid population or VMT growth in a county on the urban perimeter signi fies increasing integrati on 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. Table 6 shows tr affic and commuting pattern data, including total 2008 VMT and 10-year VMT growth for each county.

Table 6. Traffic and Commuting Patterns

. County State Recommended
Nonattainment? 2008 VMT* (million miles) % Change in VMT (2002 – 2008) Collin, TX Yes 6,198 +33 Cooke, TX No 636 +16 Dallas, TX Yes 26,625 +14 Delta, TX No 72 -4 Denton, TX Yes 5,507 +27 Ellis, TX Yes 1,893 +49 Fannin, TX No 334 +9 Grayson, TX No 1,364 +3 Henderson, TX No 768 +30 Hood, TX No 443 +46 Hunt, TX No 1,046 +26 Johnson, TX Yes 1,432 +47 Kaufman, TX Yes 1,548 +38 Palo Pinto, TX No 397 +3 Parker, TX Yes 1,280 +41 Rockwall, TX Yes 676 +15 Somervell, TX No 121 +27 Tarrant. TX Yes 16,741 +17 Wise, TX No 969 +16 Area-wide: 68,050 ---- * MOBILE model VMTs are those i nputs into the NEI version 1.5.

Total VMT is an important metric as an indica tor of potential contribu tion to ground level ozone
concentrations. Commuters in the Dallas-Fort Worth area traveled a total of approximately 68 billion miles during calendar year 2008. Four counties in th e Dallas-Fort Worth area, Collin, Dallas, Denton, and Tarrant Counties, all have total VMT for calendar year 2008 in excess of 5 billion miles. Dallas and Tarrant Counties have particularly high total VMT counts at approximately 27 and 18 billion miles, respectively. An additional seven counties have 2 008 VMT counts in the range of approximately 1 – 2 billion miles; these counties are: Ellis, Grayson, Hunt, Johnson, Kauf man, Parker, and Wise Counties.

Most of the counties in the Dallas-Fort Worth area ha ve experienced high growth in VMT for the period from 2002 – 2008. The growth in VMT for 16 of these counties exceeds 14 percen t, and for 10 of those counties the growth rate exceeded 25 percent. Four counties in particular have very high VMT growth10 for this period: Ellis County (+49%), Johnson C ounty (+47%), Kaufman County (+38%), and Parker County (+41%).



### Factor 3: Meteorology ( weather/transport patterns)

EPA evaluated available meteorological data to help determine how meteorological conditions, such as weather, transport patterns and stag nation conditions, would affect the fate and transport of precursor emissions contributing to ozone formation.

The attachment to this document contains Figu re 3, Dallas-Fort Worth Ozone and Ozone Precursor Monitoring Network, including locations of major stationary sources, an d locations of ambient monitors with their design values.

EPA has performed 24-Hour wind back trajectories (w hich is an analysis of meteorological patterns) specifically on days when a number of the monitors in the Dallas-Fort Worth area have exceeded the 2008 NAAQS. These analyses were conducted to better understand the area’s me teorological transport conditions using the National Oceanic and Atmos pheric Administration Hybrid Single Particle Lagrangian Integrated Trajecto ry Model (NOAA HYSPLIT). The HYS PLIT model yields a centerline of where the air mass came from that makes up th e air mass at a specific location and time.

The HYSPLIT trajectories for 2008-2010 exceedance days at the Keller monitor in Tarrant County were conducted, and the resulting trajectori es were overlaid on Figure 3 in the attachments as Figure 5. We
also focused on this monitor and a number of other m onitors in the Dallas-Fort Worth area, including the Eagle Mountain Lake monitor in Tarrant County and the Parker County monitor. The Keller and Eagle
Mountain Lake monitors have recorded some of the hi ghest ozone levels in the region, and inclusion of the Parker County monitor represents a good cross-section of the monitors in the Dallas-Fort Worth area that have had exceedances in the 2006-2010 period. Since the 2008-2010 data for the Keller monitor is only for three years, we evaluated additional years to better understand the meteorological transport conditions that exist during ozone exceedances. Norm ally when we are developing a conceptual model understanding of what yields ozone exceedances in an area we will evaluate 5 to 10 years worth of meteorological data. Therefore we d ecided to evaluate all days that had ozone exceedances at a number of monitors that give a representa tive data set for the 2006-2010 period.

There are 3 additional figures in th e attachment that include a zoom view for the Eagle Mountain Lake monitor and a large and a zoom view for the Parker County monitor. These figures are labeled Figures 6a through 6c. These HYSLPIT trajectories are 24-Hour back trajectories for each of these monitors on days when they had exceedances of the 75 ppb standa rd. Evaluation of the back trajectories for the Keller, Eagle Mountain Lake, and Parker County m onitors indicates that the areas upwind of the monitors prior to an ozone exceedance includes the a ll nine counties included in the Dallas-Fort Worth
nonattainment area for the 1997 8-hour standard and al so Wise and Hood Counties. We note that there are some trajectories that pass over Hood County and continue to the Parker County monitor without traversing over the core Dallas-Fort Worth area. The back trajectori es for the Eagle Mountain Lake and Parker County monitors further supp ort that air that is transported from Hood a nd Wise counties ends up
in the area of the monitor when ozone exceedances are observed.

Overall, examination of the 24-hour back trajectories on high ozone da ys at select monitors in the existing Dallas-Fort Worth area indicat es that air that originates or passes through the existing 9-county11 1997 nonattainment area and Hood and Wise counties prior to ozone exceedances being observed at existing monitors.



### Factor 4: Geography/topography (mountain ranges or other air basin boundaries)

The geography/topography analys is evaluates the physical features of the land that might affect the air shed and, therefore, the distribut ion of ozone over the area. The Dallas/Fort Worth area does not have any geographical or topographical barriers significantly limiting air pollution transport within its air shed. Therefore, this factor did not play a significant role in this evaluation.



### Factor 5: Jurisdictional boundaries

Once we identified the general area s we anticipated we would reco mmend should be included in the nonattainment area, we then considered existing ju risdictional boundaries for the purposes of providing a clearly defined legal boundary and to help identify the ar eas appropriate for carry ing out the air quality planning and enforcement functions for nonattainme nt areas. Examples of jurisdictional boundaries include existing/prior nonattainment area boundaries for ozone or othe r urban-scale pollutants, county lines, air district boundaries, township boundari es, areas covered by a metropolitan planning organization, state lines, Reservation boundaries , and urban growth boundaries. Where existing jurisdictional boundaries were not ad equate or appropriate to descri be the nonattainment area, other clearly defined and permanent landmarks or geographic coordinate s were considered.

The Dallas-Fort Worth area has previously establis hed nonattainment boundaries associated with the 1- hour and 1997 8-hour ozone NAAQS. Texas has recommended the boundary for the 2008 ozone NAAQS be the same as that for the 1997 ozone NAAQS.



### Conclusion

Based on the assessment of factors described above, EPA has preliminarily conc luded that the following counties should be included as part of the Dallas- Fort Worth nonattainment area because they are have air quality monitors that indi cate a violation of the 2008 ozone NAAQS, or because they are contributing to a violation in a nearby area: Collin, Dallas, Denton, Ellis, Hood, Johnson, Kaufman, Parker, Rockwell, Tarrant, and Wise Counties. These are the same counties that were included in the
Dallas-Fort Worth nonattainment area for the 1997 ozone NAAQS, with the addition of Hood and Wise
Counties.

The air quality monitors in Colli n, Dallas, Denton, Johnson, and Tarrant Counties indicate violations of the 2008 ozone NAAQS based on the 2010 DVs, ther efore these counties are included in the
nonattainment area.

Ellis, Hood, Kaufman, Parker, Rockwell, and Wise Counties are nearby counties that do not have monitors indicating ambient ozone concentrations in excess of 75 ppb, but EPA has concluded that these
areas contribute to observed violat ions of the 2008 ozone standard in nearby counties, through emissions from point sources and other, non-point sources (e.g., vehicles and other small area sources).12 Collin, Dallas, Denton, Ellis, Hood, Johnson, Parker, Tarrant, and Wise Counties have among the highest NOx and VOC emissions in the area. Each of these counties either has a monitor indicating a violation of the 2008 ozone NAAQS or is adja cent to one or more such counties.

Collin, Dallas, Denton, Ellis, Grayson, Hood, Johnson, Ka ufman, Parker, Rockwall, Somervell, Tarrant, and Wise Counties ranked comparatively high fo r factors related to population statistics, and Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Ro ckwall, Tarrant, and Wise Counties ranked comparatively high for factors relate d to traffic and commuting patterns.

EPA’s meteorological assessment when ozone exceed ances of the 2008 ozone standard have been monitored within the greater Dallas-Fort Worth ar ea supports the cons ideration of in clusion of the existing 9-county nonattainment area (Dallas, Tarrant , Collin, Denton, Ellis, Johnson, Parker, Rockwall, and Kaufman counties) and Hood and Wise counties.

Collin County: Recommended for inclusion by Texa s and has a violating monitor, so should be
included.

Dallas County: Recommended for inclusion by Texa s and has a violating monitor, so should be
included.

Denton County: Recommended for inclusion by Texa s and has a violating monitor, so should be
included.

Ellis County: Recommended for inclusion by Texas; has 2008 NEI emissions of 15,768 tons of NOx and 6,543 tons of VOC; there ar e 160 people per square mile; has a 2010 population of 149,610 with a growth rate of 13.5 percent between 2000 and 2010; total VMT is 1.9 billion miles. Winds are often from the south so emissions from Ellis County often c ontribute to violations other counties. In addition, the number of commuters and grow th rate indicate that Ellis County should be included in the
nonattainment area.

Hood County: Has 2008 NEI emissions of 5,515 tons of NOx and 9,547 tons of VOC, with TCEQ 2009 Barnett Shale Special Inventory emissions of 6,903 tons of NOx and 2,113 tons of VOC; there are 120 people per square mile; has a 2010 population of 51,182 with a growth rate of 9.2 percent between 2000 and 2010; total VMT is 443 million miles. Emissions from this county have grown considerably, due primarily to oil and gas development. Back traj ectories show that at times Hood County emissions
contribute to observed violations in other counties. This, in conjunc tion with high growth in population, indicates this county should be in cluded in the nonattainment area.

Johnson County: Recommended for inclusion by Texa s and has a violating monitor, so should be
included.

Kaufman County: Recomme nded for inclusion by Texas; has 2008 NEI emissions of 5,868 tons of NOx and 3,510 tons of VOC; there ar e 130 people per square mile; has a 2010 population of 103,350 with a growth rate of 17.6 percent between 2000 and 2010; total VMT is 1.5 billion miles. Winds are often from the east so emissions from Kaufman County ofte n contribute to violations other counties. In addition, the VMT and growth rate indicate that Kaufman County should be included in the
nonattainment area.13 Parker County: Recommended for inclusion by Texa s; has 2008 NEI emissions of 9,550 tons of NOx and 11,708 tons of VOC; there are 130 people per square mile; has a 2010 population of 116,927 with a growth rate of 15.4 percent between 2000 and 2010; to tal VMT is 1.3 billion miles. The comparatively high emissions and population growth rate all indicate that Parker County should be included in the nonattainment area. In addition, at times back traject ories indicate that emissions from Parker County
contribute to observed vi olations in the area.

Rockwall County: Recommended for inclusion by Texas; has 2008 NEI emissions of 1,859 tons of NOx and 2,047 tons of VOC; there are 530 people per square mile; has a 2010 population of 78,337 with a growth rate of 25.7 percent between 2000 and 2010; total VMT is 676 million miles. While a small county, its population density a nd emissions indicate that this county should be included in the
nonattainment area.

Tarrant County: Recommended for inclusion by Te xas and has a violating monitor, so should be
included.

Wise County: Has 2008 NEI emissions of 11,911 tons of NOx and 23,657 tons of VOC; there are 60 people per square mile; has a 2010 population of 59,127 with a growth rate of 5.9 percent between 2000 and 2010; total VMT is 969 million. The close proxim ity of these comparatively high emissions to violating monitors indicate s that this county should be included in the nonattainment area. The high growth in these emissions is due in large part to growth in emissi ons from Barnett Shale gas production development, but also due to growth in population. Ex amination of back trajecto ries indicates that at times emissions from Wise County contribu te to observed violations in the area.14 Technical Analysis for Houston-Galveston-Brazoria

Figure 2 is a map of the Houston-Galveston-Brazoria intended nonattainment area. The map provides other relevant information including the locations a nd design values of air qua lity monitors, county and other jurisdictional boundari es, relevant statistical area boundaries, the nona ttainment area boundary for 1997 ozone NAAQS, and major transpor tation arteries. For purposes of the technical analysis, EPA
evaluated all 12 twelve counties that comprise the Houston-Baytown-H untsville CSA: Austin, Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Matagorda, Montgomery, San Jacinto, Walker, and
Waller Counties.

For purposes of the 1997 8-hour ozone NAAQS, this area was designated nonattainment. The boundary
for the nonattainment area for the 1997 ozone NAAQS included the entire counties of Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller.

In March 2009, 7 Texas recommended these same eight counties, Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller, be designated as nonattainment for the 2008

7 Initial 2008 ozone NAAQS designation recommendation letter fr om Governor Perry to Acti ng Regional Administrator

Starfield, dated March 10, 2009.15 ozone NAAQS based on air quality data from 200 6-2008. Texas provided an update to the original
recommendation in October 2011 8 based on air quality data from 2008-2010. The recommendations
from the State are based on data from FEM monitors sited and operated in accordance with 40 CFR Part
58.

After considering these recommendations and based on EPA's technical analysis described below, EPA intends to designate 9 counties in Texas (identified in Table 7 below) as “nonattainment” for the 2008 ozone NAAQS as part of the Houston nonattainment area.

Table 7. Texas’s Recommended and EPA’s Intended Designated Nonattainment Counties for HoustonGalveston-Brazoria

.Houston-GalvestonBrazoria State-Recommended
Nonattainment Counties EPA Intended
Nonattainment Counties

Texas Brazoria
Chambers
Fort Bend
Galveston
Harris Liberty Montgomery
Waller Brazoria
Chambers
Fort Bend
Galveston
Harris Liberty Matagorda Montgomery
Waller

Factor Assessment



### Factor 1: Air Quality Data

For this factor, we considered 8-hour ozone design values (in ppm) for air quality monitors in counties in the Houston-Baytown-Huntsville CSA based on data for the 2008-2010 period (i.e., the 2010 design value, or DV), which are the most recent years with fully-certified air qualit y data. A monitor’s DV is
the metric or statistic that indicates whether that monitor attains a specified air quality standard. The 2008 ozone NAAQS are met at a monitor when th e annual fourth-highestdaily maximum 8-hour average concentration, averaged ove r 3 years is 0.075 ppm or less. A DV is only valid if minimum data completeness criteria are met. See 40 CFR part 50 A ppendix P. Where several m onitors are located in a county (or a designated nona ttainment area or maintenance area), the DV for the county or area is determined by the monitor with the highest level.

The 2010 DVs for the ozone NAAQS for counties in the Houston and nearby surrounding area are
shown in Table 8.

8 Updated 2008 ozone NAAQS designation recommendation letter from Governor Perry to Administrator Jackson, dated

October 31, 2011.16 Table 8. Air Quality Data.

County State Recommended
Nonattainment? 2008-2010 Design Value (ppb) Austin, TX No -- Brazoria, TX Yes 84 Chambers, TX Yes -- Fort Bend, TX Yes -- Galveston, TX Yes 75 Harris, TX Yes 83 Liberty, TX Yes -- Matagorda, TX No -- Montgomery, TX Yes 71 San Jacinto, TX No -- Walker, TX No -- Waller, TX Yes --

Ambient monitors in Brazoria and Harris Countie s indicate a violation of the 2008 ozone NAAQS;
therefore these counties are included in the nonattainme nt area. A county (or partial county) must also be designated nonattainment if it contributes to a vi olation in a nearby area . Each county without a violating monitor that is located ne ar a county with a violating monito r has been evaluated, as discussed below, based on the five factors and other relevant information to determine whether it contributes to the nearby violation.



### Factor 2: Emissions and Emissions-Related Data

EPA evaluated emissions of ozone precursors (NO
x and VOC) and other emissions-related data that provide information on areas cont ributing to violating monitors.

Emissions Data

EPA evaluated county-level emission data for NO
x and VOC derived from the 2008 National Emissions Inventory (NEI), version 1.5. This is th e most recently available NEI. (See http://www.epa.gov/ttn/chie f/net/2008inventory.html ). Significant emissions levels in a nearby area indicate the potential for the area to contribute to observed violations. We will also consider any
additional information we receive on changes to emissions levels th at are not reflected in recent inventories. These changes include emissions reductions due to permanent and enforceable emissions controls that will be in place before final designati ons are issued and emissions increases due to new

sources.

Table 9 shows emissions of NO
x and VOC (given in tons per year or tpy) for violating and nearby
counties that we considered for inclusion in the Houston area.17 Table 9. Total 2008 NO
x and VOC Emissions.

County State Recommended
Nonattainment? NO
x (tpy) VOC (tpy)

Austin, TX No 3,829 3,422 Brazoria, TX Yes 21,894 26,294 Chambers, TX Yes 4,517 8,119 Fort Bend, TX Yes 12,786 15,803 Galveston, TX Yes 32,170 26,867 Harris, TX Yes 165,610 135,931 Liberty, TX Yes 3,345 24,137 Matagorda, TX No 7,007 19,362 Montgomery, TX Yes 8,434 14,012 San Jacinto, TX No 1,361 6,064 Walker, TX No 3,375 2,690 Waller, TX Yes 2,080 3,993 Area-wide: 266,408 286,694

An area’s total emissions of ozone precursors is one of the most im portant factors to consider in determining its contribution to observed violations of the ozone standard. Th e counties in the core Houston area with the highest emissions of NOx ar e Brazoria, Fort Bend, Galv eston, Harris, Matagorda, and Montgomery. More than 7,000 tpy of NOx emissions originates from each of these six counties, and collectively they represent approx imately 248,000 tpy of NOx, or 93 perc ent of the total NOx emissions for the Houston area. Harris County, in particular , is characterized by high NOx emissions; the 166,000 tpy of NOx originating from Harris County accounts fo r 62 percent of the total NOx inventory for the area. Significantly, each of these co unties either has an air monitor th at indicates a violation of the 2008 ozone NAAQS or is adjacent to such a county.

Likewise, the counties with the highest VOC emissions in this area are Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Matagorda, and Mont gomery. More than 7,000 tpy of VOC emissions originates from each of these eight counties, and collectively they represent approximately 270,000 tpy of VOC, or 94 percent of the total VOC emissions fo r the Houston area. Harris C ounty, in particular, is characterized by high VOC emissions; the 136,000 tpy of VOC originating from Harris County accounts for 47 percent of the total VOC inventory for the area. As with counties characterized by high NOx emissions, each of these counties eith er has an air monitor that indi cates a violation of the 2008 ozone NAAQS or is adjacent to such a county.

Population density and degree of urbanization

EPA evaluated the population and vehicle use characterist ics and trends of the area as indicators of the probable location and magnitude of non-point source emissions. These include ozone-creating emissions from on-road and off-road vehicles and engines, consumer products, residential fuel combustion, and consumer services. Areas of dense population or co mmercial development are an indicator of area
source and mobile source NO
x and VOC emissions that may cont ribute to ozone formation that
contributes to nonattainment in th e area. Rapid population or VMT grow th (see below) in a county on the urban perimeter signifies increasing integration with the core urban area, and indicates that it may be appropriate to include the area asso ciated with area source and mobile source emissions as part of the nonattainment area. Table 10 shows the populat ion, population density, and population growth information for each county in the area.18 Table 10. Population and Growth.

County State
Recommended
Nonattainment? 2010 Population 2010 Population Density (1000 pop/sq mi) Absolute change in population (2000-2010) Population % change (2000-2010) Austin, TX No 28,417 0.04 4,675 20 Brazoria, TX Yes 313,166 0.21 70,036 29 Chambers, TX Yes 35,096 0.04 8,931 34 Fort Bend, TX Yes 585,375 0.66 226,617 63 Galveston, TX Yes 291,309 0.44 40,601 16 Harris, TX Yes 4,092,459 2.30 678,528 20 Liberty, TX Yes 75,643 0.06 5,083 7 Matagorda, TX No 36,702 0.03 -1,244 -3 Montgomery, TX Yes 455,746 0.42 158,405 53 San Jacinto, TX No 26,384 0.04 3,932 18 Walker, TX No 67,861 0.08 6,117 10 Waller, TX Yes 43,205 0.08 10,367 32 Area-wide: 6,051,363 0.51 1,212,048 25 Sources: U.S. Census Bureau populati on estimates for 2010 as of August 4, 2011 ( http://factfinder2.census .gov/faces/tableservices/js f/pages/productview.xhtml?pi d=DEC_10_PL_GCTPL2.STO5& prodType=table )

The Houston area is a large metropolitan area with a total population of approximately 6 million people. For the purposes of determining the boundary of the intended 2008 ozone nonattainment area, EPA evaluated all 12 counties in the Houston-Baytown-H untsville CSA, which ha s a total population of 6,051,363 people and an average population dens ity of 510 people per square mile.

Five counties in the CSA, Brazoria, Fort Be nd, Galveston, Harris, and Montgomery, are densely populated; each has approximately 300,000 or more people and a population density exceeding 200 people per square mile. These five counties account fo r 95 percent of the total population of the Houston area. Harris County stands out from the rema ining counties in the re gion. Harris County has approximately 4.1 million people and a population dens ity of 2,300 people per square mile. Fort Bend and Montgomery Counties have moderately high popul ations and population dens ities; the population of Fort Bend County is 585,000 with a density of 660 people per square mile, and the population of Montgomery County is 456,000 people with a density of 420 people per square mile. The remaining counties in the area are predominantl y rural, with population densities at or below 80 people per square
mile.

Four of the counties in this area experienced population growth between 2000 and 2010 in excess of 70,000 people, which represents 94 percent of the tota l population growth for the area. Of these, the population of two of these counties grew by more than 200,000 people during the past decade: Fort Bend County (+226,617 people) and Ha rris County (+678,528 people).

A final population and growth metric evaluated by EPA was the percen t change in population during the period from 2000 to 2010. During this decade, all but two of the counties in the area experienced double-digit growth in percent change in populati on. The counties of Fort Bend and Montgomery had particularly high values for pe rcent change in population, at 63 and 53 percent, respectively.

The attachments to this document contains Figu re 6, Houston Ozone and Ozone Precursor Monitoring Network, and Figure 8, Population Density Change Percentage Between 2000 and 2010 Census for Houston Ozone and Ozone Precursor Monitoring Ne twork, which present graphical information on population density and growth for the Houston area.19 Traffic and commuting patterns

EPA evaluated the commuting patt erns of residents in the area, as well as the total Vehicle Miles Traveled (VMT) for each county. In combination with the population/ population density data and the location of main transportation arte ries (see above), this information helps identify the probable location of non-point source emissions. A county with high VMT and/or a high number of commuters is generally an integral part of an urban area and indicates the presence of motor vehicle emissions that may contribute to ozone formation that contribute s to nonattainment in the area. Rapid population or VMT growth in a county on the urban perimeter signi fies increasing integrati on 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. Table 11 shows tr affic and commuting pattern data, including total 2008 VMT and 10-year VMT growth for each county.

Table 11. Traffic and Commuting Patterns

. County State Recommended
Nonattainment? 2008 VMT* (million miles) % Change in VMT (2002 – 2008) Austin, TX No 542 +18 Brazoria, TX Yes 2,263 +16 Chambers, TX Yes 935 +23 Fort Bend, TX Yes 3,339 +23 Galveston, TX Yes 2,210 +10 Harris, TX Yes 40,379 +23 Liberty, TX Yes 865 +12 Matagorda, TX No 343 -1 Montgomery, TX Yes 3,982 +22 San Jacinto, TX No 317 +13 Walker, TX No 944 +11 Waller, TX Yes 759 +16 Area-wide: 56,878 ----- * MOBILE model VMTs are those inputs into the NEI version 1.5.

Total VMT is an important metric as an indica tor of potential contribu tion to ground level ozone
concentrations. Commuters in the H ouston area traveled a total of approximately 57 billion miles during calendar year 2008. Five counties in the Houston area, Brazoria, Fort Bend, Galveston, Harris, and Montgomery Counties, all have total VMT for calenda r year 2008 in excess of 2 billion miles. These five counties have a combined VMT of 52 billion miles, or 92 percent of the total VMT for the area. Harris County has a particularly hi gh total VMT count at approximately 40 billion miles, which is 71 percent of the total VMT for the entire CMSA.

All but one of the counties in the Houston area ha ve experienced high growth in VMT for the period from 2002 – 2008. The growth in VMT for 11 of these counties exceeds 10 percen t, and for 4 of those counties the growth rate exceeded 20 percent. The c ounties with the highest percent change in VMT for this period are Chambers County (+23%), Fort Bend County (+23%), Harris County (+23%), and Montgomery County (+22%). Austin, Brazoria, and Wa ller Counties each experienced growth in VMT exceeding 15 percent.20 

### Factor 3: Meteorology (weather/transport patterns)

EPA evaluated available meteorological data to help determine how meteorological conditions, such as weather, transport patterns and stag nation conditions, would affect the fate and transport of precursor emissions contributing to ozone formation. The Hous ton-Baytown-Huntsville ar ea is considered a subtropical coastal climate w ith normal recirculation occurring due to the land-sea breeze oscillation. This
land-sea breeze oscillation result s in transport of air among nume rous counties along the gulf coast region in the Houston-Baytown-Hunt sville area and this phenomena lead s to air transport of emissions to monitors in the Houston-Baytow n-Huntsville area that have previous ly monitored exceedances of the
2008 ozone standard.

The attachment to this document contains Figu re 7, Houston Ozone and Ozone Precursor Monitoring Network, including locations of major stationary sources, and locations of ambient monitors with their design values.

EPA has performed 24-Hour wind back trajectories (w hich is an analysis of meteorological patterns) specifically on days when a number of the monitors in the Houston-Baytown-Huntsville area have exceeded the 2008 NAAQS. These analyses were conducted to better understand the area’s meteorological transport conditions using the National Oceanic and At mospheric Administration Hybrid Single Particle Lagrangian Integrated Trajec tory Model (NOAA HYSPLIT). The HYSPLIT model yields a centerline of where the air mass came from that makes up the air mass at a specific location and
time.

The HYSPLIT trajectories for 2008-2010 exceedance days at the Manvel monitor in Brazoria County were conducted and the resulting trajectories were ove rlaid on Figure 7 in the attachments as Figure 9.
We also focused on this monitor and a number of other monitors in the H ouston-Baytown-Huntsville area, including the NW Harris County and Wallisvill e Road monitors in Harris County, and the Texas City monitor in Galveston County. These monitors have recorded some of the highest ozone levels in the region and represent a good cross-section of the monitors in the Houston- Baytown-Huntsville area that have had exceedances in the 2006-2010 period. Since the 2008-2010 data is only for three years we evaluated more years to better understand the meteor ological transport conditions that exist during ozone exceedances. Normally when we are developing a conceptual model understanding of what yields
ozone exceedances in an area we will evaluate 5 to 10 years worth of meteorologi cal data. Therefore, we decided to evaluate all days that had ozone excee dances at a number of monitors that give a representative data se t for the 2006-2010 period.

There are 8 figures in the attachme nt that include a large view and a zoom view for each of the four monitors (Manvel, NW Harris, Wallisville, and Te xas City) labeled as Figures 10a through 10h. These HYSLPIT trajectories are 24-Hour b ack trajectories for each of these monitors on days when they had exceedances of the 75 ppb standard. Evaluation of the back trajectories for the Manvel and NW Harris indicates that the areas upwind of the monitor pr ior to an ozone exceedance includes the 8 existing
counties in the Houston-Galveston-Brazoria nonattain ment area for the 1997 8-hour standard and also Matagorda county. We note that there are some trajectories that pass over Matagorda County and continue to the monitor without traversing over the H ouston Ship Channel. The back trajectories for the Wallisville and Texas City monitors further support th at air that is transported from Matagorda county ends up in the area of the monitor when ozone exceedances are monitored.21 Overall, examination of the 24-hour back trajectories on high ozone da ys at select monitors in the existing Houston-Galveston-Brazoria nonattainment area indicates that air orig inates or passes through the existing 8-county 1997 nonattainment area and Ma tagorda County prior to ozone exceedances being monitored at existing monitors.



### Factor 4: Geography/topography (mountain ranges or other air basin boundaries)

The geography/topography analys is evaluates the physical features of the land that might affect the airshed and, therefore, the distri bution of ozone ove r the area. The Houston area does not have any geographical or topographical barriers significantly limiting air pollution transport within its air shed. Therefore, this factor did not play a significant role in this evaluation.



### Factor 5: Jurisdictional boundaries

Once we identified the general area s we anticipated we would reco mmend should be included in the nonattainment area, we then considered existing ju risdictional boundaries for the purposes of providing a clearly defined legal boundary and to help identify the ar eas appropriate for carry ing out the air quality planning and enforcement functions for nonattainme nt areas. Examples of jurisdictional boundaries include existing/prior nonattainment area boundaries for ozone or othe r urban-scale pollutants, county lines, air district boundaries, township boundari es, areas covered by a metropolitan planning organization, state lines, Reservation boundaries , and urban growth boundaries. Where existing jurisdictional boundaries were not ad equate or appropriate to descri be the nonattainment area, other clearly defined and permanent landmarks or geographic coordinate s were considered.

The Houston-Galveston-Brazoria area has previously established nonattainment boundaries associated
with the 1-hour and 1997 8-hour ozone NAAQS. Texas has recommended that the boundary for the 2008 ozone NAAQS be the same as for the 1997 ozone NAAQS.



### Conclusion

Based on the assessment of factors described above, EPA has preliminarily conc luded that the following counties should be included as part of the Houston-Galveston-Brazoria nonattainment area because they are either violating the 2008 ozone NAAQS or contribu ting to a violation in a nearby area: Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Matagorda, Montgomery, and Waller Counties. These
are the same counties that are includ ed in the Houston-Galveston-Brazoria nonattainment area for the 1997 ozone NAAQS, with the addition of Matagorda County.

The air quality monitors in Brazoria and Harris Counties indicate violations of the 2008 ozone NAAQS based on the 2010 design values, therefore these counties are included in the nonattainment area.

Chambers, Fort Bend, Galveston, Liberty, Matagord a, Montgomery, and Waller Counties are nearby
counties that do not have monitors indicating concentratio ns of ozone in excess of 75 ppb, but EPA has
concluded that these areas contribute to the ozone concentrations in viola tion of the 2008 ozone NAAQS through emissions from point sources and other, non- point sources (e.g., vehicles and other small area sources).22 The counties in the core Houston area with the highest emissions of NOx are Brazoria, Fort Bend, Galveston, Harris, Matagorda, and Montgomery. More than 7,000 tpy of NOx emissions originates from each of these six counties, and collectively they represent approximately 248,000 tpy of NOx, or 93 percent of the total NOx emissions for the Houston area. Likewise, the counties with the highest VOC emissions in this area are Brazoria, Chambers, Fo rt Bend, Galveston, Harris , Liberty, Matagorda, and Montgomery. More than 7,000 tpy of VOC emissions orig inates from each of these eight counties, and collectively they represent approx imately 270,000 tpy of VOC, or 94 pe rcent of the total VOC emissions
for the Houston area.

Brazoria, Fort Bend, Galveston, Harris, and Mont gomery Counties ranked comparatively high for factors related to population statis tics, including total population, popul ation density, and absolute and percent growth in populati on during the past decade.

Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery and Waller Counties ranked comparatively high for factors relate d to traffic and commuting patterns, such as total VMT and percent growth in VMT

.

EPA’s meteorological assessment when ozone exceed ances of the 2008 ozone standard have been monitored within the greater Hous ton-Baytown-Huntsville area supports the consideration of inclusion of the existing 8-county nonattainment area (Harris, Galveston, Brazoria, Chambers, Fort Bend, Liberty, Montgomery, and Waller counties) and also Matagorda county.

Brazoria County: Recommended for inclusion by Te xas and has a violating monitor, so should be
included.

Chambers County: Recommended for inclusion by Texas; has 4,517 tons of NOx emissions and 8,119 tons of VOC emissions annually; there are 40 pe ople per square mile; has a 2010 population of 35,096 with a growth rate of 34 percent between 2000 and 2010; total VMT is 935 million miles. The growth in population and VMT support the State’s recommendati on to include this county as part of the
nonattainment area.

Fort Bend County: Recommended for inclusion by Texas; has 12,786 tons of NOx emissions and 15,803 tons of VOC emissions annually; there are 660 people per square mile; has a 2010 population of 585,375 with a growth rate of 63 pe rcent between 2000 and 2010; total VMT is 3.3 billion miles. Its high ranking in emissions, population and commu ting patterns all indica te it contributes to
nonattainment and should be included in the Houston-Galveston-Brazo ria nonattainment area.

Galveston County: Recommended for inclusion by Texas; has 32,170 tons of NOx emissions and 26,867 tons of VOC emissions annually; there are 440 people per square mile; has a 2010 population of 291,309 with a growth rate of 16 pe rcent between 2000 and 2010; total VMT is 2.2 billion miles. Its high ranking in emissions, population and commu ting patterns all indica te it contributes to
nonattainment and should be included in the Houston-Galveston-Brazo ria nonattainment area.

Harris County: Recommended for inclusion by Texa s and has a violating monitor, so should be
included.23 Liberty County: Recommended for inclusion by Texas; has 3,345 tons of NOx emissions and 24,137 tons of VOC emissions annually; there are 60 pe ople per square mile; has a 2010 population of 75,643 with a growth rate of 7 percent between 2000 and 2010; total VMT is 865 million miles. The growth in population and number and VMT indicate this county should be included in the Houston-GalvestonBrazoria nonattainment area.

Matagorda County: Has 7,007 tons of NOx emissions and 19,362 tons of VOC emissions annually; there are 30 people per square mile ; has a 2010 population of 36,702 with a negative growth rate of 3 percent between 2000 and 2010; total VMT is 343 m illion miles. The high emissions in Matagorda argue that it should be included in the nonattainment area. Examination of back trajectories indicates these emissions could, at times, contribute to nonatta inment in counties with violating monitors. Based on the combination of high emissions and examina tion of the meteorology through back trajectory analysis, EPA believes this county should be include d in the Houston-Galvesto n-Brazoria nonattainment

area.

Montgomery County: Recommended for inclusion by Texas; has 8,434 tons of NOx emissions and 14,012 tons of VOC emissions annually; there are 420 people per square mile; has a 2010 population of 455,746 with a growth rate of 53 pe rcent between 2000 and 2010; total VM T is 4 billion miles. Its high ranking in emissions, population and commuting patterns all indicate it co ntributes to nonattainment and
should be included in the Houston-Ga lveston-Brazoria nonattainment area.

Waller County: Recommended for inclusion by Texa s; has 2,080 tons of NOx emissions and 3,993 tons of VOC emissions annually; there are 80 people per square mile; has a 2010 population of 43,205 with a growth rate of 32 percent between 2000 and 2010; total VMT is 759 million miles. The growth in population and VMT indicate this county should be included in the Houst on-Galveston-Brazoria
nonattainment area.24 

### ATTACHMENTS

Figure 3. Dallas-Fort Worth Ozone and Ozone Precurs or Monitoring Network, with Population Density.

Figure 4. Population Density Change Percentage Between 2000 and 2010 Census for Dallas-Fort Worth Ozone and Ozone Precursor Monitoring Network.

Figure 5. Overlay of 24-hour HYSPLIT back trajector ies of all 75 ppb exceedance s at the Keller monitor for the 2008-2010 period.

Figure 6a. NOAA HYSPLIT MODEL 24-Hour Back Tr ajectory Eagle Mtn. Lake Exceedances (2006- 10) (zoom view).

Figure 6b. NOAA HYSPLIT MODEL 24-Hour Back Traj ectory Parker County Exceedances (2006-10).

Figure 6c. NOAA HYSPLIT MODEL 24-Hour Back Tr ajectory Parker County Exceedances (2006-10) (zoom view).

Figure 7. Houston Ozone and Ozone Precursor Monitoring Network, with Population Density.

Figure 8. Population Density Change Percentage Between 2000 and 2010 Census for Houston Ozone and Ozone Precursor Monitoring Network

Figure 9. Overlay of 24-hour HYSPLIT back traject ories of all 75 ppb exceed ances at the Manvel monitor for the 2008-2010 period.

Figure 10a. NOAA HYSPLIT MODEL 24-Hour Back Trajectory Manvel Exceedances (2006-10).

Figure 10b. NOAA HYSPLIT MODEL 24-Hour Back Trajectory Manvel Exceedances (2006-10) (zoom view).

Figure 10c. NOAA HYSPLIT MODEL 24-Hour Back Trajectory NW Harris Exceedances (2006-10).

Figure 10d. NOAA HYSPLIT MODEL 24- Hour Back Trajectory NW Ha rris Exceedances (2006-10) (zoom view).

Figure 10e. NOAA HYSPLIT MODEL 24-Hour Back Trajectory Walli sville Exceedances (2006-10).

Figure 10f. NOAA HYSPLIT MODEL 24-Hour Back Trajectory Walli sville Exceedances (2006-10) (zoom view).

Figure 10g. NOAA HYSPLIT MODEL 24- Hour Back Trajectory Texas City Exceedances (2006-10).

Figure 10h. NOAA HYSPLIT MODEL 24- Hour Back Trajectory Texas City Exceedances (2006-10) (zoom view).25Figure 3. Dallas-Fort Worth Ozone and Ozone PrecursorMonitoring Network, with Population Density26Figure 4. Population Density Change Percentage Between 2000 and 2010 Censusfor Dallas-Fort Worth Ozone and Ozone Precursor Monitoring Network27Figure 5. Overlay of 24-hour HYSPLIT back trajectories of all 75 ppb exceedances at the Keller monitor for the 2008-2010 period28Figure 6a. NOAA HYSPLIT MODEL 24-HourBack Trajectory Eagle Mtn. LakeExceedances (2006-10) (zoom view).29Figure 6b. NOAA HYSPLIT MODEL 24-Hour Back Trajectory ParkerCounty Exceedances (2006-10).30Figure 6c. NOAA HYSPLIT MODEL 24-HourBack Trajectory Parker County Exceedances (2006-10) (zoom view).31Figure 7. Houston Ozone and Ozone Precursor Monitoring Network, with Population Density32Figure 8. Population Density Change Percentage Between 2000 and 2010 Censusfor Houston Ozone and Ozone Precursor Monitoring Network33Figure 9. Overlay of 24-hour HYSPLIT back trajectories of all75 ppb exceedances at the Manvel monitor for the 2008-2010 period34Figure 10a. NOAA HYSPLIT MODEL24-Hour Back Trajectory Manvel Exceedances (2006-10).35Figure 10b. NOAA HYSPLIT MODEL 24-Hour Back Trajectory Manvel Exceedances (2006-10) (zoom view).36Figure 10c. NOAA HYSPLIT MODEL24-Hour Back Trajectory NWHarris Exceedances (2006-10).37Figure 10d. NOAA HYSPLIT MODEL 24-Hour Back Trajectory NWHarris Exceedances (2006-10) (zoom view).38Figure 10e. NOAA HYSPLIT MODEL24-Hour Back Trajectory Wallisville Exceedances (2006-10).39Figure 10f. NOAA HYSPLIT MODEL 24-HourBack Trajectory Wallisville Exceedances (2006-10) (zoom view).Black Polygon is theapproximateboundaries ofMatagorda County40Figure 10g. NOAA HYSPLIT MODEL 24-Hour Back Trajectory TexasCity Exceedances (2006-10).