1

Technical Support Document 

Dallas-Fort Worth Redesignation Substitute 

1-hour and 1997 8-hour Ozone NAAQS 

Background 

Evaluation: 1-hour ozone NAAQS 

 1997 8-hour ozone NAAQS 

Conclusion 

April 2016 

FOR FURTHER INFORMATION CONTACT: Tracie Donaldson, United States 

Environmental Protection Agency Region 6, Air Quality Section (6PD-Q). 1445 Ross 

Avenue, Dallas, TX 75202-2733, 214-665-6633 
2

Background 

The EPA is proposing to approve a demonstration provided by Texas that the Dallas-Fort Worth 

ozone nonattainment area (DFW area) has attained the revoked 1-hour ozone National Ambient 

Air Quality Standards (NAAQS) and the 1997 8-hour ozone NAAQS due to permanent and 

enforceable emission reductions, and that it will maintain those NAAQS for ten years from the 

date of the EPA’s approval of this demonstration. The demonstration was provided to EPA in a 

report titled “Redesignation Substitute Report for the Dallas-Fort Worth (DFW) One-Hour and 

1997 Eight-Hour Ozone Standard Nonattainment Areas” (redesignation substitute report) 

submitted to EPA on August 18, 2015. 

The determination that the area has attained both the 1-hour ozone and the 1997 8-hour ozone 

NAAQS is based upon three years of complete, quality-assured and state-certified ambient air 

monitoring data that show the area has monitored attainment of the 1-hour ozone NAAQS for the 

2004–2006 monitoring period and the 1997 8-hour ozone NAAQS for the 2012-14 monitoring 

period. Available data for 2015 show that the area continues to attain both standards 

(http://www.tceq.state.tx.us/cgi-bin/compliance/monops/ozone_exceedance.pl). The 

determination that the area attained the 1-hour ozone NAAQS and the 1997 8-hour ozone 

NAAQS due to permanent and enforceable emission reductions, and that it will maintain those 

NAAQS for ten years from the date of the EPA’s approval of this demonstration is based on the 

EPA review of the demonstration provided by Texas and the evaluation of ozone monitoring 

data. 

In 1979, the EPA promulgated the revised 1-hour ozone standard of 0.12 parts per million (ppm) 

(44 FR 8202, February 8, 1979). For ease of communication, many reports of ozone 

concentrations are given in parts per billion (ppb); ppb = ppm × 1000. Thus, 0.12 ppm becomes 

120 ppb or 124 ppb when rounding is considered. An area exceeds the 1-hour ozone standard 

each time an ambient air quality monitor records a 1-hour average ozone concentration above 

0.12 ppm in any given day. Only the highest 1-hour ozone concentration at the monitor during 

any 24-hour day is considered when determining the number of exceedance days at the monitor. 

An area violates the 1-hour ozone standard if, over a consecutive 3-year period, more than 3 

expected exceedances occur at the same monitor. For more information, please see ‘‘National 1-

hour primary and secondary ambient air quality standards for ozone’’ (40 CFR 50.9) and 

‘‘Interpretation of the 1-Hour Primary and Secondary National Ambient Air Quality Standards 

for ozone’’ (40 CFR Part 50, Appendix H). 

The DFW four-county 1-hour ozone nonattainment area (Collin, Dallas, Denton, and Tarrant 

Counties) was designated in 1991 as moderate in accordance with the 1990 CAA Amendments 

(56 FR 56694). As a moderate nonattainment area, the four-county DFW area was required to 

demonstrate attainment of the 1-hour ozone standard by November 15, 1996. Ambient air 

monitoring data for the years 1994 through 1996, however, showed that the 1-hour ozone 

standard was exceeded more than one day per year over the three-year period. As a result, the 

EPA reclassified the four-county DFW area from a moderate to a serious nonattainment area 

(effective March 20, 1998) for failure to attain the 1-hour ozone standard by the November 1996 

deadline (63 FR 8128). The EPA required the State of Texas to submit a State Implementation 
3

Plan (SIP) revision within one year that demonstrated attainment of the one-hour ozone NAAQS 

and addressed CAA requirements for serious ozone nonattainment areas. 

On July 18, 1997, the EPA promulgated an 8-hour ozone NAAQS of 0.08 parts per million 

(ppm), known as the 1997 ozone standard. For ease of communication, many reports of ozone 

concentrations are given in parts per billion (ppb); ppb = ppm × 1000. Thus, 0.08 ppm becomes 

80 ppb or 84 ppb when rounding is considered. See 62 FR 38856 and 40 CFR 50.10. Under the 

EPA regulations at 40 CFR part 50, Appendix I, the 1997 ozone standard is attained when the 3-

year average of the annual fourth highest daily maximum 8-hour average ambient ozone 

concentration is less than or equal to 0.08 ppm (up to 84 ppb). 

On June 15, 2004, the EPA designated and classified the 9-county DFW (consisting of Collin, 

Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall and Tarrant counties) as a moderate 

nonattainment area under the 1997 8-hour ozone standard with an attainment date of no later 

than June 15, 2010 (see 69 FR 23858 and 69 FR 23951). 

The fourth-highest daily ozone concentration over a 3-year period is called the design value 

(DV). The DV indicates the severity of the ozone problem in an area; it is the ozone level around 

which a state designs its control strategy for attaining the ozone standard. A monitor’s DV is the 

fourth highest ambient concentration recorded at that monitor over the previous 3 years. An 

area’s DV is the highest of the design values from the area’s monitors. 

The EPA revoked the 1-hour ozone standard on April 30, 2004 (69 FR 23951), and, on March 6, 

2015, the EPA revoked the 1997 8-hour standard (80 FR 12264). As explained more fully in the 

March 6, 2015 rulemaking the EPA also adopted a provision allowing states to seek a 

redesignation substitute for revoked standards. The regulations allow that if a redesignation 

substitute is approved the state may seek to have “anti-backsliding” requirements for areas that 

were designated as nonattainment for the revoked standard shifted to contingency measures if 

such action is consistent with sections 110(l) and 193 of the CAA (40 CFR 51.1105(b)(2)). The 

regulations authorize EPA to approve a redesignation substitute upon a showing by the state that: 

1. The area has attained that revoked NAAQS due to permanent and enforceable emission 

reductions 

2. The area will maintain that revoked NAAQS for 10 years from the date of the EPA’s 

approval of the showing. 

The first criterion for a redesignation substitute is the same as two redesignation criteria found in 

CAA section 107(d)(3)(E)(i) and (iii). The second criterion for a redesignation substitute is 

similar to the criterion for a maintenance plan which provides for maintenance of the NAAQS 

for at least 10 years after redesignation (CAA sections 107(d)3(E)(iv) and 175A). EPA provided 

guidance on the approach to evaluating state compliance with these provisions in EPA’s 

September 4, 1992 memo “Procedures for Processing Requests to Redesignate Areas to 

Attainment” from John Calcagni. For this reason, EPA believes it is appropriate to consider that 

guidance when evaluating state compliance with the redesignation substitute requirements. (1992 

redesignations guidance, www.epa.gov/ttn/oarpg/t5/memoranda/redesignmem090492.pdf). 
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On August 18, 2015, the Texas Commission on Environmental Quality (TCEQ) provided the 

“Redesignation Substitute Report for the Dallas-Fort Worth (DFW) One-Hour and 1997 EightHour Ozone Standard Nonattainment Areas” for use by the EPA in evaluating the request for 

approval of a redesignation substitute for the 1-hour and 1997 8-hour ozone standard obligations 

for the area. In this submission, Texas also requested that the nonattainment new source review 

(NNSR) classification for the revoked 1-hour and the revoked 1997 ozone NAAQS would no 

longer apply to the area. This Technical Support Document evaluates whether the Texas Report 

supports a determination by the EPA that redesignation substitute criteria in the above referenced 

rules have been met for the DFW area and whether, if a redesignation substitute is approved, 

NNSR could cease to apply for purposes of the revoked 1-hour and the revoked 1997 ozone 

standard.

Evaluation 

1-hour ozone NAAQS 

(1) The area has attained the revoked 1-hour NAAQS due to permanent and enforceable 

emission reductions. 

a.) Is the DFW area attaining the 1-hour ozone NAAQS? 

Table 1 contains the 1-hour ozone data for the DFW 1-hour ozone nonattainment area monitors 

that show that the area is currently attaining the 1-hour ozone NAAQS, consistent with 40 CFR 

Part 50, Appendix H. This data is illustrated graphically in Figure 1. 

Table 1: Current 1-hour Ozone NAAQS Design Values for the DFW Area 

Years 1-Hour Ozone Design Value 

2004-2006 124 ppb 

2005-2007 124 ppb 

2006-2008 118 ppb 

2007-2009 115 ppb 

2008-2010 110 ppb 

2009-2011 110 ppb 

2010-2012 108 ppb 

2011-2013 108 ppb 

2012-2014 102 ppb 

Preliminary 2013-2015 102 ppb 
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Figure 1: One-Hour Ozone Design Values for the DFW Area 

For the 1-hour ozone NAAQS, the design value was used to determine the classification of a 

nonattainment area but was not used for designating an area as attainment or otherwise. 

Designation is based on the maximum number of expected exceedances over all the monitors in 

an area1

. To show that the DFW area no longer violates the 1-hour ozone NAAQS, the remainder 

of this section will be based on expected exceedances, calculated as per 40 CFR Part 50, 

Appendix H. 

The expected number of exceedances of record in a metropolitan area is the maximum expected 

number of exceedances of all the area’s regulatory monitors’ individual expected number of 

exceedances. Because ozone concentrations vary spatially, it is also prudent to investigate trends 

                                                            

1

 The expected exceedances for a monitor is defined as the number of exceedances that occurred in the calendar year 

plus an increment that accounts for missing data, averaged across three consecutive years (for example, expected 

exceedances for 2013 is averaged across 2011, 2012, and 2013). The increment is calculated by finding the number 

of days without an associated ozone measurement that may not be assumed to be less than the standard, multiplied 

by the number of observed exceedances, then divided by the number of observations. This is done for each year and 

then averaged across three years to get the expected exceedances for that individual monitor. Note that unlike the 

calculation for expected exceedances, design values are not adjusted for data completeness. 
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at all regulatory monitors in an area. Table 2: One-Hour Ozone Expected Exceedances by 

Monitor contains one-hour ozone expected number of exceedances at all regulatory monitors in 

the DFW four-county ozone nonattainment area from 2006 through 2014. In 2006, all monitors 

in the DFW four-county ozone nonattainment area had expected exceedances less than the 

threshold of 1.0 per year. The number of days with ozone concentrations above 124 ppb 

occurring in the DFW area fell 100% from seven days in 1990 to zero days in 2014. In the last 

seven years, only one day had ozone concentrations above the 124 ppb NAAQS threshold. This 

means that high ozone days are not only decreasing in frequency but they are also decreasing 

geographically across the entire region, showing an area wide trend for the one-hour ozone 

NAAQS. 

Table 2. One-Hour Ozone Expected Exceedances by Monitor for the DFW Area 

The air quality data provided by Texas is consistent with that found in the quality assured data 

found in the EPA Air Quality System (AQS), therefore, EPA proposes to find that the DFW area 

is meeting the 1-hour ozone standard. 

b.) Are the air quality improvements in the DFW area due to permanent and enforceable 

emissions reductions? 

Because Texas reasonably attributed the improvement in air quality to emission reductions which 

are permanent and enforceable, the EPA proposes to find that Texas has demonstrated that the 

observed ozone air quality improvement in the DFW area is due to permanent and enforceable 

reductions in emissions resulting from implementation of the EPA approved SIP and Federal 

measures. The EPA approved SIP includes state and local measures can be found in 40 CFR 

52.2270. 

2006 2007 2008 2009 2010 2011 2012 2013 2014

2006‐

2008

2007‐

2009

2008‐

2010

2009‐

2011

2010‐

2012

2011‐

2013

2012‐

2014

Dallas Hinton (48‐113‐0069) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Denton Airport South (48‐121‐0034) 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.3 0.0 0.0 0.0 0.0 0.0

Granbury (48‐221‐0001) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Corsicana Aiport (48‐349‐1051) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Fort Worth Northwest (48‐439‐1002) 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.3 0.0 0.0 0.0 0.0 0.0

Frisco (48‐085‐0005) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Pilot Point (48‐121‐1032) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Greenville (48‐231‐1006) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Parker County (48‐367‐0081) 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0

Keller (48‐439‐2003) 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.3 0.0 0.0 0.0 0.0 0.0

Dallas North #2 (48‐113‐0075) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Midlothian OFW (48‐139‐0016) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Cleburne Airport (48‐251‐0003) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Rockwall Heath (48‐397‐0001) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Grapevine Fairway (48‐439‐3009) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Dallas Redbird Airport Executive (48‐113‐0087) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Italy (48‐139‐1044) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Kaufman (48‐257‐0005) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Arlington (48‐439‐3011) 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.3 0.3

Eagle Mountain Lake (48‐439‐0075) 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.3 0.0 0.0 0.0 0.0 0.0

3 year Expected Exceedances (avg.)

DFW Monitoring Site (Name and AQS #)

Expected Exceedances by Year
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Texas presented data to show the long term decrease in ozone concentrations in the DFW area 

and showing that this long term decrease in ozone levels can be attributed to a suite of nitrogen 

oxide (NOX) controls and volatile organic chemical (VOC) controls with a particular emphasis 

on control of highly reactive VOCs. 

In making this demonstration, the State presented several sets of data. First, the State provided 

emissions inventory data for 2002 through 2011. Secondly, the State provided an ambient 

concentration trend analysis for ozone precursors (NOX and VOC) in the DFW area between 

2002 and 2014. Finally, the State documented the VOC and NOX emission control measures that 

have been implemented in the DFW area over the past 25 years. 

A. Emissions Reductions as Shown by Emissions Inventory (EI) Data 

The year 2012 was chosen as the base year because it is one of the three years used to determine 

the DV for the 2014 attainment year. 2011 emissions were compared to 2002 VOC and NOX

emissions when the DV was 110 ppb, to show that emission reductions have occurred in the area, 

and have resulted in the ozone air quality improvement in the area. 2006 was the first three-year 

period demonstrating attainment. By 2011, NOX emissions have dropped by 36% and VOC 

emissions by 12% from 2002 levels. 

These significant decreases resulted in the improvement in ozone levels seen at the monitors. 

The emissions for both years were derived from periodic VOC and NOX emission inventories, 

which are prepared every three years. Based on the estimated emissions, the TCEQ has 

documented several emission trends to show that permanent and enforceable emission controls in 

various source sectors are responsible for significant downward trends in VOC and NOX

emission totals in the DFW area leading to attainment. For a discussion of emission inventory 

preparation methods, see the discussion of the preparation of the 2011 base year emission 

inventories below. 

To demonstrate that VOC and NOX emissions decreased between one of the violation years 

(2002) and the attainment year (2011), the TCEQ has documented DFW’s VOC and NOX

emissions for 2002 and 2011 for all anthropogenic source sectors. Table 3 lists these emissions 

for the 2002, 2005, 2008 and 2011 EI. 

Table 3: DFW Four-County Nonattainment Area Historical Emissions 

Emissions Source Category 2002 2005 2008 2011

VOC Emissions (tpd)

Area 197.27 202.36 250.92 216.47

Non‐Road Mobile 70.11 59.57 62.11 47.54

On‐Road Mobile 118.39 102.95 91.73 76.71

Point 18.76 21.42 19.01 16.15

VOC Total 404.53 386.3 423.77 356.87

NOX Emissions (tpd)

Area 24.44 36.60 74.81 31.06
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Non‐Road Mobile 104.08 110.58 115.19 93.26

On‐Road Mobile 345.10 313.70 225.53 191.55

Point 34.57 7.94 10.4 8.38

NOX Total 508.19 468.82 425.93 324.25

Based on the 2002, 2005, 2008 and 2011 DFW area emissions information provided by the 

TCEQ, the EPA concludes that VOC and NOX emission totals have significantly declined in the 

nonattainment area during the 2002–2011 period. These emission reductions have led to 

attainment of the 1-hour ozone standard in this area. The EPA concurs with Texas’ conclusions 

that the emission controls, emissions inventories, and emissions trends support the conclusion 

that attainment in the area is due to permanent and enforceable emission reductions. 

B. Impact of Emissions Controls Implementation: Trend Analysis

To assess the impact of emission control implementation, the TCEQ determined the VOC and 

NOX ambient concentration trends in the DFW area from 2000 to 2014. Annual maxima, annual 

90th percentile and annual average daily peak 1-hour NOX values were analyzed. All three 

measures decreased markedly over the time period from 2000 to 2014, falling 32% (maximum), 

60% (90th percentile) and 61.5% (average). Strong downward trends in ambient NOX

concentrations are evidence of the effectiveness of emission controls. 

The other major class of ozone precursors is VOC. Since the mid-1990s, the TCEQ has collected 

40-minute measurements, on an hourly basis, of over 40 species of VOC using auto-GC 

instruments. The TCEQ focused on two prevalent compounds, ethylene and propylene, that are 

associated with rapid and efficient ozone formation. Yearly geometric means were computed 

from valid ambient hourly measurements. The TCEQ calculated the geometric mean by taking 

the natural logarithm of each measurement, averaging these logs, and then calculating the antilog 

of this mean log value. The geometric mean is a preferable statistic to median or arithmetic 

(ordinary) mean for evaluating the central tendency of data when the data are skewed, i.e., when 

the data are not symmetrically, or normally, distributed, but instead clustered around extreme 

high or low values. A geometric mean is more robust than an ordinary average, in that its value is 

not greatly influenced by one or a few very high or very low values. Many distributions of 

pollutant measurements, especially VOC, in the DFW area are skewed. 

Prior to 2010, only two of the nine monitors had enough valid data to calculate annual geometric 

mean ethylene. Values for ethylene are fairly low; the highest geometric mean ethylene in the 

DFW area in 2014 was below 0.6 parts per billion carbon (ppbC). While trends are generally 

variable from year to year, the geometric mean ethylene has decreased at the two monitors with 

the longest record of auto-GC data. Ethylene at the Flower Mound Shiloh (C1007) monitor had 

been steadily increasing until 2013, when the geometric mean ethylene decreased in 2014. 

Concentrations at the Arlington UT Campus (C1018), Eagle Mountain Lake (C0075) and 

Kennedale Treepoint Drive (C1062) monitors saw increases between 2013 and 2014, although 

the Arlington UT Campus (C1018) and Kennedale Treepoint Drive (C1062) monitors only have 

two years of valid data to calculate the geometric mean. 
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Like ethylene, prior to 2004 only three of the nine monitors had enough valid data to calculate 

annual geometric mean propylene. The geometric means for propylene are even lower than the 

geometric means for ethylene for most of the years, with the highest geometric mean propylene 

concentration in the DFW area in 2014 below 0.4 ppbC. All monitors have been showing a 

steady decrease in geometric mean propylene from 2000 through 2014. The Fort Worth 

Northwest (C0013) monitor saw a slight increase in propylene measurements between 2013 and 

2014. Though decreasing at different rates, these long-term decreases in ambient concentrations 

of ethylene and propylene suggest overall industrial and automobile emissions of these 

compounds have decreased considerably since 2000. 

C. Permanent and Enforceable Emissions Controls Implemented 

A broad range of control measures have been implemented for each emission source category. In 

section 3.2 of the Redesignation Substitute Report, Texas identified the permanent and 

enforceable measures that led to attainment of the 1-hour ozone NAAQS. Table 4 below from 

the report lists existing ozone control strategies that have emissions reductions for both the 1-

hour and the 1997 8-hour ozone standards. These measures are permanent and enforceable and 

are included in the EPA approved SIP (40 CFR 52.2270). 

Table 4. Existing Ozone Control Measures Applicable to the DFW 1-hour ozone Four-County 

and 1997 8-hour ozone Nine-County Nonattainment Areas (from section 3.2 of the Texas 

Report) 

Measure Description Start Date(s) 

DFW Industrial, 

Commercial, and 

Institutional (ICI) Major 

Source Rule 

30 Texas Administrative 

Code (TAC) Chapter 117, 

Subchapter B, Division 4 

Applies to major sources (50 tons per year (tpy) of 

nitrogen oxides (NOx) or more) with affected units 

in Collin, Dallas, Denton, Ellis, Johnson, Kaufman, 

Parker, Rockwall, and Tarrant Counties 

Applies to major sources (100 tpy of NOx or more) 

with affected units in Wise County 

Affected source categories included in rule: boilers; 

process heaters; stationary gas turbines, and duct 

burners used in turbine exhaust ducts; lime kilns; 

heat treat and reheat metallurgical furnaces; 

stationary internal combustion engines; 

incinerators; glass, fiberglass, and mineral wool 

melting furnaces; fiberglass and mineral wool 

curing ovens; natural gas-fired ovens and heaters; 

brick and ceramic kilns; lead smelting reverberatory 

and blast furnaces; natural gas-fired dryers used in 

organic solvent, printing ink, clay, brick, ceramic 

tile, calcining, and vitrifying processes; and woodfired boilers 

March 1, 2009 or March 1, 

2010, depending on source 

category 

Note: these NOx control 

requirements are in addition 

to the NOx control strategies 

previously implemented for 

ICI major sources in Collin, 

Dallas, Denton, and Tarrant 

Counties in March 2002 for 

the one-hour ozone National 

Ambient Air Quality 

Standards (NAAQS) 

January 1, 2017 for Wise 

County and wood-fired 

boilers in all ten counties of 

the DFW area 

DFW ICI Minor Source 

Rule 

30 TAC Chapter 117, 

Subchapter D, Division 2 

Applies to all minor sources (less than 50 tpy of 

NOx) with stationary internal combustion engines 

in Collin, Dallas, Denton, Ellis, Johnson, Kaufman, 

Parker, Rockwall, and Tarrant Counties 

March 1, 2009 for rich-burn 

gas-fired engines, diesel-fired 

engines, and dual-fuel 

engines 

March 1, 2010 for lean-burn 

gas-fired engines 
10

Measure Description Start Date(s) 

Stationary Diesel Engines 

30 TAC Chapter 117, 

Subchapter B, Division 4 

and Subchapter D, 

Division 2 and 

Subchapter C, Division 4 

Prohibition on operating stationary diesel and dualfuel engines for testing and maintenance purposes 

between 6:00 a.m. and noon in Collin, Dallas, 

Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, 

and Tarrant Counties 

April 1, 2009 

DFW Major Utility 

Electric Generation 

Source Rule 

30 TAC Chapter 117, 

Subchapter C, Division 4 

NOx control requirements for major source (50 tpy 

of NOx or more) utility electric generating facilities 

in Collin, Dallas, Denton, Ellis, Johnson, Kaufman, 

Parker, Rockwall, and Tarrant Counties 

NOx control requirements for major source (100 tpy 

of NOx or more) utility electric generating facilities 

in Wise County 

Applies to utility boilers, auxiliary steam boilers, 

stationary gas turbines, and duct burners used in 

turbine exhaust ducts used in electric power 

generating systems 

Note: these NOx control requirements are in 

addition to the NOx control strategies implemented 

for utilities in Collin, Dallas, Denton, and Tarrant 

Counties in 2001 through 2005 for the one-hour 

ozone NAAQS 

March 1, 2009 for Collin, 

Dallas, Denton, Ellis, 

Johnson, Kaufman, Parker, 

Rockwall, and Tarrant 

Counties 

January 1, 2017 for Wise 

County 

Utility Electric 

Generation in East and 

Central Texas 

30 TAC Chapter 117, 

Subchapter E, Division 1 

NOx control requirements on utility boilers and 

stationary gas turbines (including duct burners used 

in turbine exhaust ducts) at utility electric 

generation sites in East and Central Texas, 

including Parker County 

May 1, 2003 through May 1, 

2005 

DFW Cement Kiln Rule 

30 TAC Chapter 117, 

Subchapter E, Division 2 

NOx control requirements for all Portland cement 

kilns located in Ellis County 

March 1, 2009 

NOx Emission Standards 

for Nitric Acid 

Manufacturing – General 

30 TAC Chapter 117, 

Subchapter F, Division 3 

NOx emission standards for nitric acid 

manufacturing facilities (state-wide rule – no nitric 

acid facilities in DFW) 

November 15, 1999 

East Texas Combustion 

Sources 

30 TAC Chapter 117, 

Subchapter E, Division 4 

NOx control requirements for stationary rich-burn, 

gas-fired internal combustion engines (240 

horsepower and greater) 

Measure implemented to reduce ozone in DFW area 

although controls not applicable in DFW area 

March 1, 2010 

Natural Gas-Fired Small 

Boilers, Process Heaters, 

and Water Heaters 

30 TAC Chapter 117, 

Subchapter E, Division 3 

NOx emission limits on small-scale residential and 

industrial boilers, process heaters, and water heaters 

equal to or less than 2.0 million British thermal 

units per hour 

May 11, 2000 

Offset Lithographic 

Printing 

30 TAC, Chapter 115, 

Subchapter E, Division 4 

Control technology requirements for offset 

lithographic printing 

Revision to limit Volatile Organic Compounds 

(VOC) content of solvents used by offset 

December 31, 2000 for 

Collin, Dallas, Denton, and 

Tarrant Counties and March 

1, 2009 in Ellis, Johnson, 
11

Measure Description Start Date(s) 

lithographic printing facilities and to include 

smaller sources in rule applicability 

Kaufman, Parker, and 

Rockwall Counties 

March 1, 2011 for major 

printing sources (50 tons of 

VOC per year or more) and 

March 1, 2012 for minor 

printing sources (less than 50 

tons of VOC per year) 

VOC Rules – Degassing 

Operations 

30 TAC, Chapter 115, 

Subchapter F, Division 3 

VOC control requirements for degassing during, or 

in preparation of, cleaning any storage tanks and 

transport vessels 

May 21, 2011 for Collin, 

Dallas, Denton, and Tarrant 

Counties 

VOC Control Measures – 

Storage Tanks 

30 TAC Chapter 115, 

Subchapter B, Division 1 

Applies to major source storage tanks (50 tpy of 

VOC or more) in Collin, Dallas, Denton, Ellis, 

Johnson, Kaufman, Parker, Rockwall, and Tarrant 

Counties 

Applies to major source storage tanks (100 tpy of 

VOC or more) in Wise County 

Requires controls for slotted guidepoles and more 

stringent controls for other fittings on floating roof 

tanks, and control requirements or operational 

limitations on landing floating roof tanks 

Eliminates exemption for storage tanks for crude oil 

or natural gas condensate and regulates flash 

emissions from these tanks 

New inspection requirements to control flashed 

gases from storage tanks and corresponding 

recordkeeping requirements for fixed roof storage 

tanks 

March 1, 2013 

January 1, 2017 for major 

source storage tanks in Wise 

County and for new 

inspection requirements to 

control flashed gases from 

storage tanks and 

corresponding recordkeeping 

requirements for fixed roof 

storage tanks in Collin, 

Dallas, Denton, Ellis, 

Johnson, Kaufman, Parker, 

Rockwall, Tarrant and Wise 

Counties 

VOC Control Measures – 

Solvent-Using Processes 

30 TAC Chapter 115, 

Subchapter E 

Revised rules to implement RACT requirements per 

Control Techniques Guidelines issued by the United 

States Environmental Protection Agency (EPA) 

including new control, testing, monitoring and 

recordkeeping requirements for eight emission 

source categories in the DFW area: paper, film, and 

foil coatings; large appliance coatings; metal 

furniture coatings; miscellaneous metal and plastic 

parts coatings; automobile and light-duty truck 

coating; industrial cleaning solvents; miscellaneous 

industrial adhesives; and flexible package printing 

(see DFW AD SIP Revision for the 1997 EightHour Ozone Standard Nonattainment Area (2010-

022-SIP-NR)) 

March 1, 2013 for Collin, 

Dallas, Denton, Ellis, 

Johnson, Kaufman, Parker, 

Rockwall, and Tarrant 

Counties 

January 1, 2017 for Wise 

County 

Refueling – Stage I 

30 TAC, Chapter 115, 

Subchapter C, Division 2 

Captures gasoline vapors that are released when 

gasoline is delivered to a storage tank 

Vapors returned to tank truck as storage tank is 

filled with fuel, rather than released into ambient air 

1990 for Collin, Dallas, 

Denton, Ellis, Johnson, 

Kaufman, Parker, Rockwall, 

and Tarrant Counties 

January 1, 2017 for Wise 

County 
12

Measure Description Start Date(s) 

A SIP revision related to 

Stage I regulations was 

approved by the EPA, 

effective June 29, 2015 

Refueling – Stage II 

30 TAC, Chapter 115, 

Subchapter C, Division 4 

Captures gasoline vapors when vehicle is fueled at 

pump 

Vapors returned through pump hose to petroleum 

storage tank, rather than released into ambient air 

1992 (Collin, Dallas, Denton, 

and Tarrant Counties) 

A SIP revision authorizing 

the decommissioning of 

Stage II vapor control 

equipment was approved by 

the EPA on March 17, 2014. 

Facilities may continue 

operating Stage II until 

August 31, 2018 

VOC Control Measures 

30 TAC Chapter 115 

Control technology requirements for VOC sources 

for reasonably available control technology (RACT) 

and other SIP planning purposes including: storage, 

general vent gas, industrial wastewater, loading and 

unloading operations, general VOC leak detection 

and repair, solvent using processes, etc. 

December 31, 2002 and 

earlier for Collin, Dallas, 

Denton, and Tarrant Counties 

June 15, 2007 or March 1, 

2009 for Ellis, Johnson, 

Kaufman, Parker, and 

Rockwall Counties 

January 1, 2017 for Wise 

County 

Texas Emissions 

Reduction Plan (TERP 

30 TAC Chapter 114, 

Subchapter K 

Provides grant funds for on-road and non-road 

heavy-duty diesel engine replacement/retrofit. The 

first emissions reduction incentive grant projects 

funded under TERP were for fiscal years 2002 - 

2003 (September 1, 2001, through August 31, 

2003). To focus the emissions reduction benefits for 

the areas that needed them the most, applications 

were accepted only for projects in the HoustonGalveston-Brazoria (HGB) and DFW 

nonattainment areas for fiscal years 2002 through 

2003. An application period limited to the DFW, 

HGB, and Beaumont-Port Arthur areas was done in 

2006 and 2007. The allocation approach established 

by the commission for TERP included several grant 

programs for reducing emissions from mobile 

sources and encouraging the use of cleaner 

alternative fuels for transportation, including the 

Diesel Emissions Reduction Incentive Program 

providing grants to replace or upgrade heavy-duty 

on-road vehicles, non-road equipment, locomotives, 

marine vessels, and some stationary engines. 

January 2002 

Texas Low Emission 

Diesel 

30 TAC Chapter 114, 

Subchapter H, Division 2 

Requires all diesel fuel for both on-road and nonroad use to have a lower aromatic content and a 

higher cetane number 

Phased in from October 31, 

2005 through January 31, 

2006 

Texas Low Reid Vapor 

Pressure (RVP) Gasoline 

Requires all gasoline for both on-road and non-road 

use to have RVP of 7.8 pounds per square inch or 

less from May 1 through October 1 each year 

April 2000 in Ellis, Johnson, 

Kaufman, Parker, Rockwall, 

and Wise Counties 
13

Measure Description Start Date(s) 

30 TAC Chapter 114, 

Subchapter H, Division 1 

 

Vehicle Inspection/ 

Maintenance (I/M) 

30 TAC Chapter 114, 

Subchapter C 

Yearly treadmill-type testing for pre-1996 vehicles 

and computer checks for 1996 and newer vehicles 

May 1, 2002 in Collin, 

Dallas, Denton, and Tarrant 

Counties 

May 1, 2003 in Ellis, 

Johnson, Kaufman, Parker, 

and Rockwall Counties 

The DFW area meets the 

FCAA, §182(b)(4) 

requirements to implement 

an Inspection and 

Maintenance (I/M) program , 

and according to 40 CFR 

§51.350(b)(2), an I/M 

program is required to cover 

the entire urbanized area 

based on the 1990 census. 

The current I/M program in 

the DFW ozone 

nonattainment area 

sufficiently covers a 

population equal to the DFW 

urbanized area, thus 

expansion of the I/M 

program to include Wise 

County is not required. 

California Gasoline 

Engines 

California standards for non-road gasoline engines 

25 horsepower and larger 

May 1, 2004 

Transportation Control 

Measures 

Various measures in North Central Texas Council 

of Governments’ (NCTCOG) long-range 

transportation plans 

2007 

Voluntary Energy 

Efficiency/Renewable 

Energy (EE/RE) 

See Chapter 3.3.3: Energy Efficiency and 

Renewable Energy Measures 

See Chapter 3.3.3 

Voluntary Mobile 

Emissions Reduction 

Program 

Various pedestrian, bicycle, traffic, and mass transit 

voluntary measures administered by NCTCOG 

2007 

Federal On-Road 

Measures 

Series of emissions limits implemented by the EPA 

for on-road vehicles 

Included in measures: Tier 1, Tier 2, and Tier 3 

light-duty and medium-duty passenger vehicle 

standards, heavy-duty vehicle standards, low sulfur 

diesel standards, National Low Emission Vehicle 

standards, and reformulated gasoline 

Phase in through 2010 

Tier 3 phase in from 2017 

through 2025 

Federal Area/Non-Road 

Measures 

Series of emissions limits implemented by the EPA 

for area and non-road sources 

Examples: diesel and gasoline engine standards for 

locomotives and leaf-blowers 

Phase in through 2018 
14

In sum, the table above shows the breadth of controls that have been adopted and implemented in 

the DFW area. These controls have been implemented over a period of decades. Texas has 

focused on the significant reductions that have happened since 2002, demonstrating both NOX 

and VOCs have declined significantly. During this same time period ozone levels have also 

declined. Table 3 shows that both Federal Measures to control on-road and off-road emissions 

and State instituted controls such as low emission diesel for marine vessels, additional storage 

tank controls and storage tank degassing controls have all contributed to these additional 

reductions. The EPA concludes that the reductions in ozone are due to these permanent and 

enforceable measures. 

(2) The area will maintain the revoked NAAQS for 10 years from the date of the EPA’s 

approval of the showing.

Consistent with the 1992 redesignations guidance, Texas provided an attainment emissions 

inventory and projected future emissions inventories for the four-county nonattainment area. To 

demonstrate maintenance of the 1-hour ozone standard, the TCEQ projected VOC and NOX

emissions to 2028 and to several interim years, 2014, 2017, 2020, 2023, 2026 and 2028. These 

emissions were compared to the 2012 base year emissions to show that emissions of NOX and 

VOC, remain below the attainment levels for the entire demonstrated maintenance period. 

In the August 18, 2015 ozone redesignation substitute request, the TCEQ compared the VOC and 

NOX emissions for 2014, 2017, 2020, 2023, 2026 and 2028 for all major source sectors, and in 

total for the DFW four-county nonattainment area. In its ozone maintenance demonstration, the 

TCEQ presented the NOX and VOC emission totals for the 2012 base year and all projection 

years for the DFW area. The TCEQ’s maintenance demonstration shows that in 2014, 2017, 

2020, 2023, 2026 and 2028, VOC and NOX emission totals for the DFW area are projected to be 

below the 2012 VOC and NOX emissions for the area. 

NOX emissions in the DFW four-county nonattainment area are projected to decline by 51 

percent between 2012 and 2028. VOC emissions in the DFW Four-County nonattainment area 

are projected to decline by approximately 17.5 percent between 2012 and 2028. Based on 

photochemical modeling analyses showing that the formation of ozone in the DFW area is more 

sensitive to NOX than to VOC emissions, the small decrease in VOC emissions is expected to be 

much less significant than the decrease in NOX. 

Based on this analysis, emissions in the DFW four-county nonattainment area are expected to 

remain at levels consistent with attainment for the 1-hour ozone standard through 2028. 

The 2012 base year and the 2014, 2017, 2020, 2023, 2026 and 2028 future year EI summaries by 

source categories for the DFW area are shown in Table 5: DFW Four-County Nonattainment 

Area NOX Emissions by Source Category (tons per day) and Table 6: DFW Four-County 

Nonattainment Area VOC Emissions by Source Category (tons per day). Contributions from 

biogenic emissions are not included in the summary because this analysis is limited to 

anthropogenic sources. 
15

Table 5: DFW Four-County nonattainment area NOX Emissions by Source Category (tpd) 

Category 2012 2014 2017 2020 2023 2026   2028

Point Sources   8.47 8.79 29.47 29.57 29.65 29.71 29.76

Area Sources   28.54 29.41 27.79 25.96 24.9 24.68 24.68

On‐Road Mobile Sources

(MOVES 2014)    171.2 147.42 96.74 69.67 54.44 43.33 38.83

Non‐Road Mobile Sources   76.95 72.29 61.56 53.31 48.87 46.36 45.66

Total   285.16 257.91 215.56 178.51 157.86 144.08 138.93

Table 6: DFW Four-County nonattainment area VOC Emissions by Source Category (tpd) 

Category 2012 2014 2017 2020 2023 2026 2028

Point Sources   11.11 11.02 11.52 11.71 11.86 11.99 12.08

Area Sources   218.9 224.51 218.56 211.43 209.81 210.69 211.77

On‐Road Mobile Sources

(MOVES 2014)    78.56 71.20 55.59 46.81 41.53 35.85 32.94

Non‐Road Mobile Sources   41.39 36.48 32.59 31.08 31.04 31.52 32.08

Total   349.96 343.21 318.26 301.03 294.24 290.05 288.87

Trend analysis using the 2028 future year emissions shows an overall decrease of 207.32 tpd in 

combined NOX and VOC emissions for the DFW area. This net change includes a projected 

61.09 tpd decrease in VOC and a 146.23 tpd decrease in NOX from 2012 levels. 

In general, growth in point and area source emissions are projected to be offset by the continued 

introduction of cleaner on road and off road vehicles. 

The EPA proposes to conclude that the TCEQ has demonstrated maintenance of the ozone 

standard during the 10-plus year maintenance period for the DFW area through projections of 

VOC and NOX emissions that show that the emissions will remain below the 2012 base year 

levels during the maintenance period. 

 
16

1997 8-hour ozone NAAQS 

(1) The area has attained the revoked NAAQS due to permanent and enforceable emission 

reductions. 

a.) Is the DFW area attaining the 1997 8-hour ozone NAAQS? 

Table 7 contains the 8-hour ozone data for the DFW 1997 8-hour ozone nine-county 

nonattainment area monitors that show that the area is currently attaining the 1997 8-hour ozone 

NAAQS, consistent with 40 CFR Part 50, Appendix H. This data is summarized in Table 8 and 

illustrated graphically in Figure 2. 

Table 7: The DFW Nine-County Nonattainment Area Fourth High 8-hour Ozone Average 

Concentrations and Design Values (ppm) for 2012-2014

Site Name 4th Highest Daily Max Design Value 

(2012-2014) 2012 2013 2014 

Frisco C31 83 84 78 82 

Dallas Hinton St. 

C401/C60/C 82 84 78 81 

Dallas North No. 2 C63 81 83 77 80 

Dallas Redbird Airport C402 81 80 73 78 

Denton Airport South C56 83 87 81 84 

Pilot Point 82 84 79 82 

Midlothian OFW C52/C137 76 77 71 75 

Italy C1044 69 72 67 69 

Cleburne Airport C77 79 79 76 78 

Kaufman C71 70 74 70 71 

Parker County C76 78 79 74 77 

Rockwall Heath C69 77 77 73 76 

Eagle Mountain Lake C75 82 81 79 81 

Ft. Worth Northwest C13 80 81 80 80 

Keller C17 87 85 77 83 

Grapevine Fairway C70 86 86 80 84 

Arlington Municipal Airport 83 80 75 79 

Table 8: Current 1997 8-hour Ozone NAAQS Design Values for the DFW Nine-County 

Nonattainment Area 

Years 8-Hour Ozone Design Value 

2011-2013 87 ppb 

2012-2014 84 ppb 

Preliminary 2013-2015 83 ppb 
17

Figure 2: 8-Hour Ozone Design Values for the DFW Nine-County Nonattainment Area 

The air quality data provided by Texas is consistent with that found in the quality assured data 

found in the EPA Air Quality System (AQS), therefore, EPA proposes to find that the DFW area 

is meeting the 1997 8-hour ozone standard. 

b.) Are the air quality improvements in the DFW area due to permanent and enforceable 

emissions reductions? 

Because Texas reasonably attributed the improvement in air quality to emission reductions which 

are permanent and enforceable, the EPA proposes to find that Texas has demonstrated that the 

observed ozone air quality improvement in the DFW area is due to permanent and enforceable 

reductions in emissions resulting from implementation of the EPA approved SIP and Federal 

measures. The EPA approved SIP includes state and local measures and can be found in 40 CFR 

52.2270. 

Texas presented data to show the long term decrease in ozone concentrations in the DFW area 

and showing that this long term decrease in ozone levels can be attributed to a suite of nitrogen 

oxide (NOX) controls and volatile organic compound (VOC) controls with a particular emphasis 

on control of highly reactive VOCs. 
18

In making this demonstration, the State presented several sets of data. First, the State provided 

emissions inventory data for 2002 through 2011. Secondly, the State provided an ambient 

concentration trend analysis for ozone precursors (NOX and VOC) in the DFW nine-county 

nonattainment area between 2002 and the period in which the standard was attained, 2012-2014. 

Finally, the State documented the VOC and NOX emission control measures that have been 

implemented in the DFW area over the past 25 years. 

A. Emissions Reductions as Shown by Emissions Inventory (EI) Data 

The attainment EI base year is 2012 because it is one of the three years used to determine the 

design value (DV) for the 2014 attainment year. 2012 emissions were compared to 2002 VOC 

and NOX emissions when the DV was 99 ppb, to show that emission reductions have occurred in 

the area, and have resulted in the ozone air quality improvement in the area. 2014 is the first 

three-year period demonstrating attainment. By 2011 (the most recent year for EI data), NOX

emissions were estimated to have dropped by 30% and VOC emissions by 46% from 2002 

levels. 

These significant decreases resulted in the improvement in ozone levels seen at the monitors. 

The emissions for both years were derived from periodic VOC and NOX emission inventories, 

which are prepared every three years. Based on the estimated emissions, the TCEQ has 

documented several emission trends to show that permanent and enforceable emission controls in 

various source sectors are responsible for significant downward trends in VOC and NOX

emission totals in the DFW area leading to attainment. For a discussion of emission inventory 

preparation methods, see the discussion of the preparation of the 2012 base year emission 

inventories below. 

To demonstrate that VOC and NOX emissions decreased between one of the violation years 

(2002) and the attainment year (2014), the TCEQ has documented DFW’s VOC and NOX

emissions for 2002 and 2011 for all anthropogenic source sectors. Table 9 lists these emissions 

for the 2002, 2005, 2008 and 2011 EI. 

 
19

Table 9: DFW 9-County Nonattainment Area Historical Emissions 

Emissions Source 

Category 2002 2005 2008 2011 

VOC Emissions (tons per day or tpd) 

Area 197.27 202.36 250.92 216.47 

Non-Road Mobile 70.11 59.57 62.11 47.54 

On-Road Mobile 118.39 102.95 91.73 76.71 

Point 18.76 21.42 19.01 16.15 

VOC Total 404.53 386.30 391.32 356.87 

NOX Emissions (tpd) 

Area 23.69 47.52 147.25 31.34 

Non-Road Mobile 118.97 130.03 270.60 230.09 

On-Road Mobile 428.49 385.57 141.87 112.40 

Point 79.23 56.93 49.12 37.69 

NOX Total 650.38 620.05 608.84 411.52 

Based on the 2002, 2005, 2008 and 2011 DFW 9-county 1997 8-hour ozone nonattainment area 

emissions information provided by the TCEQ, the EPA concludes that VOC and NOX emission 

totals have significantly declined in the nine-county nonattainment area during the 2002–2011 

period. These emission reductions have led to attainment of the 1997 8-hour ozone standard in 

this area. The EPA concurs with Texas’ conclusions that the emission controls, emissions 

inventories, and emissions trends support the conclusion that attainment in the area is due to 

permanent and enforceable emission reductions. 

B. Impact of Emissions Controls Implementation: Trend Analysis

To assess the impact of emission control implementation, the TCEQ determined the VOC and 

NOX ambient concentration trends in the DFW area from 2000 to 2014. Annual maxima, annual 

90th percentile and annual average daily peak NOX values were analyzed. All three measures 

decreased markedly over the time period from 2000 to 2014, falling 32% (maximum), 60% (90th

percentile) and 61.5% (average). Strong downward trends in ambient NOX concentrations are 

evidence of the effectiveness of emission controls. 

The other major class of ozone precursors is VOC. Since the mid-1990s, the TCEQ has collected 

40-minute measurements, on an hourly basis, of over 40 species of VOC using auto-GC 

instruments. The TCEQ focused on two prevalent compounds, ethylene and propylene, that are 
20

associated with rapid and efficient ozone formation. Yearly geometric means were computed 

from valid ambient hourly measurements. A geometric mean was calculated by taking the natural 

logarithm of each measurement, averaging these logs, and then calculating the antilog of this 

mean log value. The geometric mean is a preferable statistic to median or arithmetic (ordinary) 

mean for evaluating the central tendency of data when the data are skewed, that is, when the data 

are not symmetrically, or normally, distributed, but instead clustered around extreme high or low 

values. It is more robust than an ordinary average, meaning its value is not greatly influenced by 

one or a few very high or very low values. Many distributions of pollutant measurements, 

especially VOC, in the DFW area are skewed, thus the geometric mean was evaluated to provide 

an assessment of VOC emissions in the DFW area.

Prior to 2010, only two of the nine monitors had enough valid data to calculate annual geometric 

mean ethylene. Values for ethylene are fairly low; the highest geometric mean ethylene in the 

DFW area in 2014 was below 0.6 parts per billion carbon (ppbC). While trends are generally 

variable from year to year, the geometric mean ethylene has decreased at the two monitors with 

the longest record of auto-GC data. Ethylene at the Flower Mound Shiloh (C1007) monitor had 

been steadily increasing until 2013, when the geometric mean ethylene decreased in 2014. 

Concentrations at the Arlington UT Campus (C1018), Eagle Mountain Lake (C0075) and 

Kennedale Treepoint Drive (C1062) monitors saw increases between 2013 and 2014, although 

the Arlington UT Campus (C1018) and Kennedale Treepoint Drive (C1062) monitors only have 

two years of valid data to calculate the geometric mean. 

Like ethylene, prior to 2004 only three of the nine monitors had enough valid data to calculate 

annual geometric mean propylene. The geometric means for propylene are even lower than the 

geometric means for ethylene for most of the years, with the highest geometric mean propylene 

concentration in the DFW area in 2014 below 0.4 ppbC. All monitors have been showing a 

steady decrease in geometric mean propylene from 2000 through 2014. The Fort Worth 

Northwest (C0013) monitor saw a slight increase in propylene measurements between 2013 and 

2014. Though decreasing at different rates, these long-term decreases in ambient concentrations 

of ethylene and propylene suggest overall industrial and automobile emissions of these 

compounds have decreased considerably since 2000. 

C. Permanent and Enforceable Emissions Controls Implemented 

A broad range of control measures have been implemented for each emission source category. In 

section 3.2 of the redesignation substitute report, Texas identified the permanent and enforceable 

measures that led to attainment of the 1997 8-hour ozone NAAQS. See the 1-hour evaluation 

part C. for Table 4 listing existing ozone control strategies that have emissions reductions for 

both the 1-hour and the 1997 8-hour ozone standards. These measures are permanent and 

enforceable and are included in the EPA approved SIP (40 CFR 52.2270). 

(2) The area will maintain the revoked NAAQS for 10 years from the date of the EPA’s 

approval of the showing.

Consistent with the 1992 redesignations guidance, Texas provided an attainment emissions 

inventory and projected future emissions inventories for the nine-county nonattainment area. To 
21

demonstrate maintenance of the 1997 8-hour ozone standard, the TCEQ projected VOC and NOX

emissions to 2028 and to several interim years, 2014, 2017, 2020, 2023, 2026 and 2028. These 

emissions were compared to the 2012 base year emissions to show that emissions of NOX and 

VOC, remain below the attainment levels for the entire demonstrated maintenance period. 

In the August 18, 2015 ozone redesignation substitute request, the TCEQ compared the VOC and 

NOX emissions for 2014, 2017, 2020, 2023, 2026 and 2028 for all major source sectors, and in 

total for the DFW nine-county nonattainment area. In its ozone maintenance demonstration, the 

TCEQ presented the NOX and VOC emission totals for the 2012 base year and all projection 

years for the DFW area. The TCEQ’s maintenance demonstration shows that in 2014, 2017, 

2020, 2023, 2026 and 2028, VOC and NOX emission totals for the DFW area are projected to be 

below the 2012 VOC and NOX emissions for the area. 

NOX emissions in the DFW nine-county nonattainment area are projected to decline by 46 

percent between 2012 and 2028. VOC emissions in the DFW nine-county nonattainment area are 

projected to decline by approximately 19 percent between 2012 and 2028. Based on 

photochemical modeling analyses showing that the formation of ozone in the DFW area is more 

sensitive to NOX than to VOC emissions, the small decrease in VOC emissions is expected to be 

much less significant than the decrease in NOX. 

Based on this analysis, emissions in the DFW nine-county nonattainment area are expected to 

remain at levels consistent with attainment for the 1997 8-hour ozone standard from 2014 

through 2028. 

The 2012 base year and the 2014, 2017, 2020, 2023, 2026 and 2028 future year EI summaries by 

source categories for the DFW area are shown in Table 10: DFW Nine-County Nonattainment 

Area NOX Emissions by Source Category (tons per day) and Table 11: DFW Nine-County 

Nonattainment Area VOC Emissions by Source Category (tons per day). Contributions from 

biogenic emissions are not included in the summary because this analysis is limited to 

anthropogenic sources. 

Table 10: NOX Emission Projections (tons per day) 

Category 2012 2014 2017 2020 2023 2026 2028 

Point Sources 30.80 31.25 62.38 62.49 62.57 62.64 62.71 

Area Sources 33.60 34.77 32.01 28.98 27.37 26.97 26.93 

On-Road 

Mobile Sources 

216.74 188.65 129.19 95.95 77.87 64.62 59.75 

Non-Road 

Mobile Sources 

92.98 86.83 72.83 62.10 56.21 52.71 51.55 

Total 374.12 341.50 296.41 249.52 224.02 206.94 200.94 

Table 11: VOC Emission Projections (tons per day) 
22

Category 2012 2014 2017 2020 2023 2026 2028 

Point Sources 27.66 28.61 29.46 29.97 30.41 30.82 31.10 

Area Sources 265.43 273.08 260.19 245.76 241.13 241.19 242.15 

On-Road Mobile 

Sources 

92.17 83.75 65.62 55.36 49.21 42.70 39.49 

Non-Road 

Mobile Sources 

46.87 41.34 36.73 34.78 34.55 35.00 35.53 

Total 432.13 426.78 392.00 365.87 355.30 349.71 348.27 

Trend analysis using the 2028 future year emissions shows an overall decrease of 257.04 tpd in 

combined NOX and VOC emissions for the DFW area. This net change includes a projected 

83.86 tpd decrease in VOC and a 173.18 tpd decrease in NOX from 2012 levels. 

In general, growth in point and area source emissions are projected to be offset by the continued 

introduction of cleaner on road and off road vehicles. 

The EPA proposes to conclude that the TCEQ has demonstrated maintenance of the ozone 

standard during the 10-plus year maintenance period for the DFW area through projections of 

VOC and NOX emissions that show that the emissions will remain below the 2012 base year 

levels during the maintenance period. 

D. The Effects of a Redesignation Substitute Final Action in DFW 

Texas has requested that EPA concur that “...the relevant nonattainment NSR provisions no 

longer apply to the areas.” See, Cover letter for the HGB and Dallas Redesignation Substitute 

Submittals. Generally, if we approve a redesignation substitute, the state may request to revise 

its SIP to revise or remove provisions for NNSR for the revoked standard, provided that such 

action is consistent with CAA sections 110(l) and 193. See, 40 CFR 51.1105(b)(2). If the EPA 

finalizes a redesignation substitute for the DFW area, EPA believes that a SIP revision in this 

particular case is not necessary because the ozone standards in question have been revoked and 

because of a provision in the Texas SIP which changes the designation of the area to what is 

listed in 40 CFR part 81. We believe a plain reading of this provision in the Texas SIP 

establishes an area’s classification and thus the related major source thresholds and offset ratios 

for Texas as 40 CFR part 81 is updated without further action by Texas. Any other antibacksliding provisions that are in the Texas SIP may only be changed through the SIP revision 

process. EPA believes that the following language in the Texas SIP supports this analysis of an 

automatic updating of the ozone classification: 

TAC Chapter 101 General Air Quality Rules, Subchapter A: General Rules , §101.1. 

Definitions. (71) Nonattainment area--A defined region within the state that is 

designated by the United States Environmental Protection Agency (EPA) as failing to 

meet the national ambient air quality standard (NAAQS or standard) for a pollutant for 

which a standard exists. The EPA will designate the area as nonattainment under the 

provisions of 42 United States Code, §7407(d). For the official list and boundaries of 
23

nonattainment areas, see 40 Code of Federal Regulations (CFR) Part 81 and pertinent 

Federal Register notices. The designations and classifications for the one-hour ozone 

national ambient air quality standards in 40 CFR Part 81 were retained for the purpose of 

anti-backsliding and upon determination by the EPA that any requirement is no longer 

required for purposes of anti-backsliding, then that requirement no longer applies.  

NNSR Offset Ratios and Major Source Thresholds are defined in TAC Chapter 116 Control of 

Air Pollution by Permits for New Construction or Modification, Subchapter A: Definitions, 

§116.12. Nonattainment and Prevention of Significant Deterioration Review Definitions (19) 

Major Stationary Source and (20) Major Modification. Both definitions refer to Table 1 below. 

TABLE I2

MAJOR SOURCE/MAJOR MODIFICATION EMISSION THRESHOLDS 

POLLUTANT designation MAJOR SOURCE SIGNIFICANT LEVEL

 OFFSET RATIO Tons/year tons/year minimum 

OZONE (VOC, NOX) 

I marginal 100 40 1.10 to 1 

II moderate 100 40 1.15 to 1 

III serious 50 25 1.20 to 1 

IV severe 25 25 1.30 to 1 

Further, DFW is still subject to Nonattainment NSR for the 2008 and 2015 Ozone Standards. 

It should also be noted that when a new classification is in place, that, in and of itself, does not 

relieve sources in the area of their obligations under previously established permit conditions. 

Conclusion

The review of the Texas redesignation substitute report found that Texas has demonstrated that: 

(1) The DFW area has attained the revoked 1-hour ozone and the revoked 1997 8-hour ozone 

NAAQS due to permanent and enforceable emission reductions 

(2) The DFW area will maintain the revoked 1-hour ozone and the revoked 1997 8-hour 

NAAQS for ten years from the date of the EPA’s approval of this demonstration. 

EPA is proposing to approve the DFW redesignation substitute for the revoked 1-hour and the 

revoked 1997 8-hour ozone NAAQS. Upon final approval of the redesignation substitute, the 

area’s NNSR classification will be determined by the next highest classification remaining for 

that area. 

                                                            

2

 Only Ozone is included here