EMISSIONS INVENTORY REPORTING REQUIREMENTS FOR THE DALLASFORTWORTH AND HOUSTON-GALVESTON-BRAZORIA NONATTAINMENT AREAS 

UNDER THE 2008 EIGHT-HOUR OZONE NAAQS

Docket ID: EPA-R06-OAR-2014-0554

This document provides a technical review of a revision to a Texas State Implementation Plan 

(SIP) to meet Clean Air Act (CAA) Emission Inventory (EI) reporting requirements for the Dallas-Fort

Worth (DFW) and the Houston-Galveston-Brazoria (HGB) nonattainment areas under the 2008 eighthour ozone standards submitted by Texas Commission on Environmental Quality (TCEQ) on July16, 

2014.

A. General Requirements

Under the Clean Air Act (CAA) sections 172(c)(3) and 182 (a)(1)), states are required to submit 

emissions inventory (EI) information for all relevant sources for areas that are designated nonattainment 

for any of the National Ambient Air Quality Standards (NAAQS) for each area designated nonattainment 

for a NAAQS. On March 27, 2008, the United States Environmental Protection Agency (EPA) lowered 

the primary and secondary eight-hour ozone National Ambient Air Quality Standards (NAAQS) to 0.075 

parts per million (ppm) (73 FR 16436). On May 21, 2012, the EPA published in the Federal Register(77 

FR 30088) final designations for the 2008 eight-hour ozone standard. The Dallas-Fort Worth (DFW) area 

was designated moderate nonattainment and the Houston-Galveston-Brazoria (HGB) area was designated 

marginal nonattainment. The effective date of the final rule is July 20, 2012.

EPA’s proposed 2008 ozone standard SIP requirements rule specified that states use 2011 as a 

base year to address EI requirements. The nonattainment area base year EI emission is due no later than 

24 months from the July 20, 2012 effective date and then every three years thereafter. An emissions 

inventory is an estimation of actual emissions of air pollutants in an area. Volatile organic compounds 

(VOCs) and oxides of nitrogen (NOx) are known as “ozone precursors”, as they react with oxygen and 

sunlight to form ozone. Motor vehicle exhaust and industrial emissions, gasoline vapors and chemical 

solvents emit NOx and VOCs. Controlling sources of NOx and VOC emissions can lower ozone levels in 

the ambient air. The emissions inventory for an ozone nonattainment area contains VOC and NOx 

emissions, as these pollutants are precursors to ozone formation. The EIs provide data for a variety of air 

quality planning tasks including establishing baseline emission levels calculating federally required 

emission reduction targets, emission inputs into air quality simulation models, and tracking emissions 

over time. The total EI of VOC, NOx, and other pollutants for an area are summarized from the estimates 

developed for five general categories of emissions sources: point, area, on-road mobile, non-road mobile, 

and biogenic.

B. Background
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1. Dallas-Fort Worth 

Compliance with the Ozone NAAQS from 1990 to Present

The majority of NOx emissions in the DFW area come from on-road mobile sources (cars and trucks) and 

non-road mobile sources (such as construction equipment, aircraft, and locomotives).

2008 Eight-Hour Ozone Standard (2008 to Present)

On March 27, 2008, the United States Environmental Protection Agency (EPA) strengthened the primary 

and secondary eight-hour ozone standard to 0.075 ppm (73 FR 16436). 

On May 21, 2012, the EPA published in the Federal Registerfinal designations for the 2008 eight-hour 

ozone standard (77 FR 30088). A ten-county DFW area including Collin, Dallas, Denton, Ellis, Johnson, 

Kaufman, Parker, Rockwall, Tarrant, and Wise Counties was designated nonattainment and classified 

moderate under the 2008 eight-hour ozone standard, effective July 20, 2012. The DFW area includes the 

nine counties that were designated nonattainment under the 1997 eight-hour ozone standard in addition to 

Wise County. The attainment deadline for the DFW moderate nonattainment area is December 31, 2018.

1997 Eight-Hour Ozone Standard (1997 to Present)

In July 1997, the EPA announced a revised NAAQS for ground-level ozone. The EPA phased out and 

replaced the previous one-hour standard with an eight-hour standard set at 0.08 ppm to protect the public 

health against longer exposure to this air pollutant. The eight-hour ozone standard became effective on 

September 16, 1997.

Effective June 15, 2004, Collin, Dallas, Denton, Tarrant, Ellis, Johnson, Kaufman, Parker, and Rockwall 

Counties were designated nonattainment for the 1997 eight-hour ozone standard. The area was classified 

moderate nonattainment for the standard, with an attainment deadline of June 15, 2010.

On April 27, 2005, TCEQ submitted to EPA the DFW Eight-Hour Ozone Five Percent Increment of 

Progress SIP Revision to satisfy the requirements of Phase I of the 1997 eight-hour ozone standard 

implementation rule (69 FR 23951). The revision used a 5% increment of progress from the area’s 2002 

emissions baseline beyond the reductions from federal and state measures already approved by the EPA, 

and was the first DFW SIP revision submitted under the 1997 eight-hour ozone standard.

In May 2007, the TCEQ submitted attainment demonstration and reasonable further progress (RFP) SIP 

revisions for the DFW area to the EPA. The May 2007 DFW Attainment Demonstration SIP included a 

plan for DFW compliance with the 1997 eight-hour ozone standard by June 15, 2010 (based on 2009 

ozone season monitoring). The RFP SIP revision demonstrated 15% total NOx and volatile organic 

compound (VOC) emissions reductions between 2002 and 2008, as required. The attainment 

demonstration and RFP SIP revisions relied on photochemical modeling and weight of evidence (WoE) 

analyses that examined qualitative and other factors that could not be directly included in the models, but 

that nevertheless supported the projected attainment by 2010. On March 21, 2008, the EPA found the onroad motor vehicle emissions budget (MVEB) contained in the DFW attainment demonstration adequate 

for transportation conformity purposes (73 FR 15152).

On October 7, 2008, the EPA approved the May 2007 DFW RFP SIP revision (which included an 

updated MVEB and emissions inventory)(73 FR 58475).
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On December 7, 2011, the TCEQ adopted the 2011 DFW 1997 Eight-Hour Ozone Attainment 

Demonstration SIP Revision and the 2011 DFW 1997 Eight-Hour Ozone RFP SIP Revision. The 2011 

attainment demonstration SIP revision demonstrated that the state’s control strategy would result in the 

area’s attainment of the 1997 eight-hour ozone standard by 2012, the attainment year for serious 

nonattainment areas. The 2011 attainment demonstration SIP revision used the EPA’s Motor Vehicle 

Emissions Simulator (MOVES) model to develop the on-road mobile emissions inventory and attainment 

year MVEB. The 2011 RFP SIP revision demonstrated that an emissions reduction of at least 3% per year 

would occur between milestone years 2011 and 2012. The 2011 RFP SIP revision established baseline 

emission levels, calculated reduction targets, identified control strategies to meet emission target levels, 

and tracked actual emission reductions against established emissions growth. The 2011 RFP SIP revision 

also included an MVEB for each milestone year as well as a contingency plan. As with the 2011 

attainment demonstration SIP revision, the 2011 RFP SIP revision used the EPA’s MOVES model to 

develop the base year and milestone year on-road mobile emissions inventories and the milestone year 

MVEBs.

2. Houston-Galveston-Brazoria Background and Ozone History 

Background and history of Houston-Galveston-Brazoria (HGB) area compliance with the National 

Ambient Air Quality Standards (NAAQS) for ground-level ozone. 

2008 Eight-Hour Ozone NAAQS (2008 to Present)

On March 27, 2008, EPA strengthened the primary and secondary eight-hour ozone NAAQS to 0.075 

ppm (73 FR 16436). On March 10, 2009, the governor1recommended to the EPA that only counties 

already designated nonattainment for the 1997 eight-hour ozone NAAQS (Brazoria, Chambers, Fort 

Bend, Galveston, Harris, Liberty, Montgomery, and Waller) be designated nonattainment for the 2008 

eight-hour ozone NAAQS.

On May 21, 2012, the EPA published final designations for the 2008 eight-hour ozone NAAQS in the 

Federal Register (77 FR 30088). An eight-county HGB area including Brazoria, Chambers, Fort Bend, 

Galveston, Harris, Liberty, Montgomery, and Waller Counties was designated nonattainment and 

classified marginal under the 2008 eight-hour ozone NAAQS effective July 20, 2012. The HGB area 

includes the same eight counties that were designated nonattainment under the 1997 eight-hour ozone 

NAAQS. Matagorda County was designated attainment/unclassifiable. The attainment deadline for the 

HGB marginal nonattainment area is December 31, 2015.

1997 Eight-Hour Ozone NAAQS (1997 to Present)

Note: The HGB area (Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and 

Waller Counties) is currently classified severe nonattainment for the 1997 eight-hour ozone NAAQS, 

with an attainment deadline of June 15, 2019.

On July 18, 1997, the EPA published the revised NAAQS for ground-level ozone in the Federal Register

(62 FR 38856), and it became effective on September 16, 1997. The EPA phased out and replaced the 

 

1 See the governor’s 2009 designation recommendation letter: 

http://www.epa.gov/ozonedesignations/2008standards/rec/letters/06_TX_rec.pdf
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previous one-hour ozone NAAQS with an eight-hour NAAQS set at 0.08 ppm based on the three-year 

average of the annual fourth-highest daily maximum eight-hour average ozone concentrations measured 

at each monitor within an area.

Effective June 15, 2004, Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and 

Waller Counties were designated nonattainment in the first phase of the EPA's implementation rule for 

the 1997 eight-hour ozone NAAQS (69 FR 23951) . The HGB area was classified moderate 

nonattainment for the standard, with an attainment deadline of June 15, 2010. The TCEQ was required to 

submit a state implementation plan (SIP) revision for the 1997 eight-hour ozone NAAQS to the EPA by 

June 15, 2007. The EPA addressed the control obligations that apply to areas designated nonattainment 

for the 1997 eight-hour ozone NAAQS in the second phase of the implementation rule (70 FR 71612).

On May 23, 2007, TCEQ submitted the 2007 HGB 1997 Eight-Hour Ozone Nonattainment Area SIP 

revision as the first step in addressing the 1997 eight-hour ozone NAAQS in the HGB area and the 2007 

HGB 1997 Eight-Hour Ozone Nonattainment Area Reasonable Further Progress (RFP) SIP revision, 

which demonstrated that a required 15% emissions reduction in ozone precursors (VOC and nitrogen 

oxides (NOx) would be met for the 2001 through 2008 RFP analysis period.

On June 15, 2007, the state requested that the HGB area be reclassified from a moderate to a severe 

nonattainment area for the 1997 eight-hour ozone NAAQS, with an attainment deadline of June 15, 

20192.

On December 31, 2007, the EPA published its proposal took comments on a range of dates for the state to 

submit a revised SIP (72 FR 74252). The TCEQ provided comments3to the EPA that supported the 

reclassification and justification for an April 2010 SIP submission date. 

On October 1, 2008, the EPA published approval to reclassify the HGB ozone nonattainment area from a 

moderate to a severe nonattainment area for the 1997 ozone NAAQS (73 FR 56983) effective October 

31, 2008. The EPA set April 15, 2010 as the date for the state to submit a revised SIP addressing the 

severe-ozone nonattainment requirements.

On March 10, 2010, the commission adopted two revisions to the Texas SIP for the HGB ozone 

nonattainment area. The 2010 HGB Attainment Demonstration SIP Revision for the 1997 Eight-Hour 

Ozone Standard included a photochemical modeling analysis and a weight of evidence analysis to 

demonstrate attainment of the 1997 eight-hour ozone NAAQS by the June 15, 2019 deadline.

The 2010 HGB RFP SIP Revision for the 1997 Eight-Hour Ozone Standard demonstrated that an 18% 

emissions reduction requirement will be met for the 2002 through 2008 RFP analysis period and that an 

average of 3% per year emissions reduction will occur between each of the milestone years 2008, 2011, 

2014, 2017, and 2018. This SIP revision established baseline emission levels, calculated reduction targets, 

identified control strategies to meet emission target levels, and tracked actual emission reductions against 

established emissions growth. This revision also included an MVEB for each milestone year and a 

 

2 See the governor's 2007 reclassification request letter:

http://www.tceq.state.tx.us/assets/public/implementation/air/sip/miscdocs/AR-M550U_20070616_014613.pdf

3 See the TCEQ's comments concerning the EPA's proposed redesignation

http://www.tceq.state.tx.us/assets/public/implementation/air/sip/hgb/HGB_Letter_Comments.pdf
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contingency plan. On January 25, 2011, the EPA published a notice of its determination that the MVEBs 

in the March 10, 2010 SIP revisions, which were developed using the on-road mobile source emissions 

inventories based on the EPA's MOBILE 6.2 model, were adequate for transportation conformity 

purposes (76 FR 4342). On January 2, 2014, the EPA published approval of this RFP SIP revision (79 FR 

51).

On December 7, 2011, the commission adopted the 2011 HGB RACT Analysis Update SIP Revision for 

the 1997 Eight-Hour Ozone Standard. This SIP revision updated the RACT analysis for VOC emission 

sources to include the seven CTG documents issued by the EPA from 2006 through 2008 that were not 

addressed in the 2010 HGB Attainment Demonstration SIP revision. This SIP revision incorporated 

concurrent CTG-related rulemaking that revises Chapter 115, Subchapter E to implement RACT for those 

CTG emission source categories in the HGB area.

On April 23, 2013, the commission adopted the 2013 HGB 1997 Eight-Hour Ozone Standard 

Nonattainment Area MVEB Update SIP Revision. This SIP revision updated on-road mobile source 

emissions inventories and MVEBs for the HGB area using the EPA's latest mobile emissions estimation 

model, the Motor Vehicle Emissions Simulator (MOVES2010a). This SIP revision also met the primary 

obligation of the mid-course review commitment in the 2010 HGB attainment demonstration SIP revision 

by demonstrating that the outstanding 3% contingency requirement was fulfilled. Updated on-road 

inventories and emissions analysis based on the EPA’s August 30, 2012 vehicle miles traveled offset 

guidance and a modified version of the MOVES model demonstrated compliance with the CAA 

requirements for transportation control measures in severe nonattainment areas. On January 2, 2014, the 

EPA published approval of this MVEB SIP update to the 2010 attainment demonstration SIP revision (79 

FR 57).

C. EPA’s Analysis 

EPA has reviewed the Texas submittal for consistency with the requirements of EPA regulations. The 

following is a summary of the analysis based on the information provided by Texas.

1. Base Year Emissions Inventory The 2011 Base Year Inventory is the starting point for calculating the 

reductions necessary to meet the requirements of the CAA. Sections 172 (c)(3) and 182(b)(1) of the CAA 

require that nonattainment plan provisions include an inventory of actual emissions from all sources of 

relevant pollutants in the nonattainment area. The federal Air Emissions Reporting Requirements (AERR) 

rule requires states to develop and submit periodic EIs to EPA every three years. The 2011 inventory was 

the first periodic emission inventory (PEI) submitted under AERR. Per the AERR, the 2011 PEI was 

reported to the EPA’s National Emissions Inventory (NEI) as a comprehensive and detailed estimate of 

air emissions, including ozone precursors (NOxand VOC). The year 2011 is also the year for a required 

EI submission under the existing AERR rule. As directed by the AERR, the NEI includes statewide 

coverage. Annual and summer day emissions are reported on a three-year cycle for the AERR. States can 

rely on periodic AERR EI submittals to satisfy ongoing SIP EI submission requirements every three 

years. The Texas submitted the 2011 base year inventory to EPA as part of a SIP revision for the HGB 

and DFW 8-hour ozone non-attainment area. EPA reviewed the 2011 base year inventory and determined 

that it was developed in accordance with EPA guidelines. The inventory includes all area, point, non-road 
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mobile, and on-road mobile source emissions in the HGB and DFW ozone nonattainment area. The 

inventory also includes a description of the methods used to estimate emissions:

Point Source Emissions: Industrial sources are required to submit emissions data to TCEQ annually. 

TCEQ stores the data in the State of Texas Air Reporting System (STARS) database. The 2011 base year 

point source EI data were extracted from STARS on April 1, 2014. The extracted data contain ozone 

season daily and annual NOx and VOC emissions for each site in the HGB and DFW 2008 eight-hour 

ozone nonattainment areas that submitted a 2011 emissions inventory questionnaire, including revisions 

reviewed approved, and entered on or before the extract date. A more detailed description site level 2011 

NOxand VOC emissions data can be found in chapter 2 and Appendix K of the State submittal.

Area Source Emissions: Area sources are small-scale industrial, commercial, and residential sources that 

generate emissions. TCEQ developed the 2011 area source emission inventory in according to the AERR 

reporting requirements, using a combination of methodologies and data: EPA-generated EIs, TCEQcontracted projects, TCEQ staff projects, and categories grown from the 2008 EI. EPA developed EIs for 

states to use for many source categories as part of the NEI. These source categories include but are not 

limited to industrial coatings, degreasing; residential, commercial/institutional, and industrial fuel use, 

commercial cooking; aviation fuel use; and consumer products. For some source categories, the TCEQ 

developed state-specific emissions estimates by acquiring current state specific activity data and applying 

appropriate emissions factors. These source categories include but are not limited to: storage tanks, 

structural fires, dry cleaners, automobile fires and oil and gas. Significant resources were expended to 

improve the oil and gas area source inventory production for 2011. The improvement included the 

development and refinement of a state-specific oil and gas area source emissions calculator that uses 

county-level production and local equipment activity data with local emissions requirement to estimate 

emissions for individual production categories including compressors engines, condensate and oil storage 

tanks, loading operations, heaters, and dehydrators. We have reviewed these approaches and have 

determined that they are acceptable.

Non-road Emissions Inventory: The non-road category is composed of a diverse collection of equipment, 

many of which are powered by diesel engines. Non-road emissions sources include, but are not limited to: 

agricultural equipment, locomotives, drilling equipment, lawn and garden equipment, aircraft and airport 

equipment, locomotives, drilling rigs and commercial marine vessels (CMV). For the 2011 EI, emissions 

inventories for non-road sources were developed as subcategories: NONROAD model categories; 

airports; CMVs; drilling rigs; and locomotives. TCEQ has updated the HGB and DFW non-road 

emissions by using area specific information and the latest version of models as well data obtained from 

studies and surveys of industrial and construction equipment. TCEQ conducted several equipment survey 

studies which focused on various equipment categories operating in different areas in Texas. The 

resulting survey studies data were used as inputs to more accurately estimate non-road emissions for the 

state of Texas. We find the approach and methodology used by TCEQ acceptable. A full detailed 

description of the approach is detailed in section 2.4 of the state’s submittal.

On-road Emission Inventory: On-road emission sources consist of automobiles, trucks, motorcycles, and 

other motor vehicles travelling on public roadways. On-road mobile source emissions are usually 

categorized as either combustion-related emissions or evaporative hydrocarbon emissions. Combustionrelated emissions are estimated for vehicle engine exhaust. Evaporative hydrocarbon emissions are 

estimated for the fuel tank and other evaporative leak sources on the vehicle engine exhaust. TCEQ 
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updated the on-road emissions using the latest available data, current emissions factors (developed from 

EPA’s Motor Vehicle Emissions Simulator (MOVES))4for on-road mobile sources, and the most current 

planning assumptions. On-road mobile emission models are models that predict gram per mile emissions 

of hydrocarbons (HC), carbon monoxide (CO), NOx, carbon dioxide (CO2), particulate matter (PM), and 

toxics from cars, trucks, and motorcycles under various conditions. EPA reviewed the on-road emission 

estimates approach and methodology and determined that they are acceptable. A detailed description of 

on-road emission estimates is found in section 2.5 of the TCEQ submittal.

Table 1. DFW 2011 Emissions Inventory (tons per day or tpd)

Source Type NOx VOC

Point 39.95 29.80

Area 42.64 292.49

On-road Mobile 238.87 98.36

Non-road Mobile 120.61 55.00

Total 442.08 475.65

Table 2. HGB 2011 Emissions Inventory (tpd)

Source Type NOx VOC

Point 108.44 94.83

Area 21.14 308.73

On-road Mobile 196.21 82.62

Non-road Mobile 121.11 49.93

Total 446.90 536.12

Biogenic Sources: Biogenic sources include VOC emissions from crops, lawn grass, and trees as well as a 

small amount of NOx emissions from soils. Plants are sources of VOC emissions such as isoprene, 

monoterpene, and alpha-pinene. Biogenic emissions are estimated by the EPA using its biogenic 

emissions inventory too.

D. Summary and Recommendations:

Pursuant to 40 CFR Part 51.102 and after proper notice, the TCEQ conducted public hearings to 

consider the revision to the SIP. Proper notice included prominent advertisement in the areas affected at 

least 30 days prior to the dates of the hearings. Public hearings were held in Houston on January 14, 2014 

and Arlington on January 16, 2014. Data, views, and recommendations of interested persons regarding the 

proposed SIP revision were submitted to the TCEQ during the comment period and were considered and 

incorporated by reference to the SIP revision. The TCEQ used acceptable techniques and methodologies 

 

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In March 2010, EPA replaced the MOBILE6.2 model with MOVES as the official emissions factor model for 

developing on-road mobile source category EIs. Although MOVES represents a new approach to assessing on -road 

emissions, the sources are the same, and the opportunity to use local inputs for meteorological conditions, control 

programs, and fleet characteristics remains. The primary approach to developing an on-road inventory is the same 

with either MOVES or MOBILE6.2. With both models, emission rates are produced for subsets of the on -road fleet, 

and the emission rates are multiplied by the activity level of each vehicle type or source use type.
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to develop the 2011-base year emission inventories for the 2008 ozone NAAQS for the HGB and DFW 

nonattainment areas to satisfy the EI requirements at sections 172 and 182 of the CAA.

Therefore we recommend approval of the Texas SIP to meet CAA emissions inventory reporting 

requirements for the DFW and the HGB nonattainment areas under the 2008 ozone NAAQS submitted by 

TCEQ on July16, 2014.