Bryan W. Shaw, Ph.D., Chairman

Buddy Garcia, Commissioner

Carlos Rubinstein, Commissioner

Mark R. Vickery, P.G., ExeClih'Ue Director ..

RECEIVED - 6POl

AIRPlANNINGSe:C.

. TEX'AsCOMMI~8~~N ON ENVIRONMENtAL1~M~'ftPJ1 2:55 <~' •

Protecting Te~as by Reducing and Preventing Pollution

January 17, 2012

Alfredo Armendariz, Ph.D.

Regional Administrator

U.S. Environmental Protection Agency - Region 6

1445 Ross Avenue "

Dallas, Texas 75202-2733

Dear Dr. Armendariz:

Docket No. 2011-0363-SIP

Project No. 2010-022-SIP-NR

On December 7, 2011, the Texas Commission on Environmental Quality (Commission)

adopted revisions to the State Implementation Plan (SIP) for the Dallas-Fort Worth (DFW)

1997 eight-hour ozone National Ambient Air Quality Standard (NAAQS).

The Commission adopted revisions to the SIP to include photochemical modeling analysis, a

weight of evidence analysis, a reasonably available control technology (RACT) analysis, a

motor vehicle emissions budget for 2012, and a contingency plan to fulfill requirements ofthe

reclassification of the DFW area to serious for the 1997 eight-hour ozone NAAQS. The SIP

revision also included two concurrently adopted revisions to 30 Texas Administrative Code

Chapter 115 to address RACT into the SIP.

Enclosed are the proposed revisions to the SIP, a public hearing certification, a complete

record ofthe public hearings, and the accompanying order. I look forward to your

expeditious approval ofthese SIP revisions.

Sincerely,

{;~~~' man

BWS/tgs

Enclosures

cc: The Honorable Rick Perry, Governor of Texas

Mr. Toby Baker, Office of Budget, Planning and Policy, Office ofthe Governor

Mr. Mark R. Vickery, P.G., Executive Director, Texas Commission on Environmental

Quality

P.O. Box 13087 • Austin, Texas 78711-3087 • 512-239-1000 • '#WW.tceq.texas.gov

How is our customer service? v.rww.tceq.texas.govfgotofcustomersurvey
TEXAS COMMISSION ON ENVIRONMENTAL QUALITY

Docket No. 2011-0363-SIP

Project No. 2010-022-SIP-NR

THE STATE OF TEXAS

COUNTY OF TRAVIS

This is to certify that the attached are true and correct copies of documents for a

revision to the Texas State Implementation Plan, adopted on December 7, 2011, pursuant to

40 Code of Federal Regulations § 51.104. I am the records administrator for the Air Quality

Division ofthe Texas Commission on Environmental Quality (Commission).

~~r, rL. I;"~ DireftOT-~====~-- Air Quality Division

Texas Commission on Environmental Quality
Texas Commission on Environmental Quality

Public Hearings

July 14 and July 22, 2011

Concerning the Dallas-Fort Worth Reclassification

Attainment Demonstration SIP Revision

Project No. 2010-022-SIP-NR

Volume 1 of 2
TX132.03 Texas Dallas-Fort Worth Serious Attainment Demonstration SIP 

Revision for the 1997 Eight-Hour Ozone Standard, Texas Project Number 

2010-022-SIP-NR, submitted to EPA January 17, 2012 (TX-324, SIP), 

This document contains only the Recommendation section of this submittal. 

The entire submittal is available in Regulations.gov at: 

TX133.06 Texas Dallas-Fort Worth Reclassification Attainment Demonstration SIP Revision for 

the 1997 Eight-Hour Ozone Standard, Texas Project 2010-022-SIP-NR, submitted to EPA 

January 17, 2012 (TX-324, SIP). 799 pages 27.0 MB u5d

Regulations.gov document EPA-R06-OAR-2012-0099-0006, 

AND 

TX154.04 Texas DFW Reclassification Attainment Demonstration SIP Revision for the 1997 8-

Hour Ozone Standard, Project No. 2010-022-SIP-NR, submitted January 17, 2012 (TX-324, SIP). 

799 pages 55.3 MB s4a

Regulations.gov document EPA-R06-OAR-2013-0804-0004. 
INTRODUCTION

The Texas Commission on Environmental Quality (commission) held public hearings in Arlington on

July 14, 2011 and in Austin on July 22,2011, to receive testimony regarding the Dallas-Fort Worth

Reclassification Attainment Demonstration State Implementaion Plan (SIP) Revision.

To meet Federal Clean Air Act requirements, the adopted SIP revision includes a photochemical

modeling analysis, a weight of evidence analysis, a reasonably available control technology

analysis, a reasonably available control measures analysis, a motor vehicle emissions budget for

2012, and a contingency plan. The adopted SIP revision also incorporates concurrently adopted

revisions to 30 Texas Administrative Code Chapter 115 into the Texas SIP.

The comment period was originally scheduled to close on JUly 25, 2011, but was extended to

August 8, 2011. All testimony and comments have been reviewed and seriously considered. This

hearing record contains a complete record of the public hearings and is divided into the following

four sections:

o Public Notification and Proposal

o Written and Oral Testimony

o Evaluation of Testimony

o Staff Recommendations/Order

Additional copies of this hearing record are maintained in the TCEQ central office at 12100 Park 35

Circle, Austin, Texas 78753. For further information, please contact Kathy Singleton at (817) 588-

5914.
Texas Commission on Environmental Quality

Public Hearings

July 14 and July 22, 2011

Concerning the Dallas-Fort Worth Reclassification

Attainment Demonstration 81 PRevision

Project No. 2010-022-8IP-NR

Volume 2 of2
STAFF 

RECOMMENDATIONS
REVISIONS TO THE STATE OF TEXAS AIR QUALITY 

IMPLEMENTATION PLAN FOR THE CONTROL OF OZONE AIR 

POLLUTION

DALLAS-FORT WORTH EIGHT-HOUR OZONE

NONATTAINMENT AREA

TEXAS COMMISSION ON ENVIRONMENTAL QUALITY

P.O. BOX 13087

AUSTIN, TEXAS 78711-3087

DALLAS-FORT WORTH ATTAINMENT DEMONSTRATION 

SIP REVISION FOR THE 1997 EIGHT-HOUR OZONE 

STANDARD NONATTAINMENT AREA

Project Number 2010-022-SIP-NR 

Adoption

December 7, 2011
This page intentionally left blank
ES-1 

EXECUTIVE SUMMARY

The United States Environmental Protection Agency (EPA) published a final determination of 

failure to attain and reclassification of the Dallas-Fort Worth (DFW) area from a moderate to a 

serious nonattainment area for the 1997 eight-hour ozone National Ambient Air Quality 

Standard (NAAQS) (75 Federal Register 79302) effective on January 19, 2011. The DFW ninecounty nonattainment area includes Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, 

Rockwall, and Tarrant Counties. The EPA set January 19, 2012, as the deadline for Texas to 

submit a state implementation plan (SIP) revision addressing the serious ozone nonattainment 

area requirements of the 1990 Federal Clean Air Act (FCAA) Amendments. The area’s 2010 

eight-hour design value was 86 parts per billion (ppb). The DFW area must attain the 1997 

eight-hour ozone standard of 0.08 parts per million (or no greater than 84 ppb) as expeditiously 

as practicable but no later than the attainment date of June 15, 2013. Because the attainment 

date is early in the 2013 ozone season, the EPA has prescribed that the modeling attainment test 

be applied to the previous complete ozone season. Thus, 2012 is the attainment year used in the 

ozone modeling.

This AD SIP revision includes base case modeling of a representative eight-hour ozone 

exceedance episode that occurred during June 2006. In general, the model performance 

evaluation of the 2006 base case indicates the modeling is suitable for use in conducting the 

modeling attainment test. The modeling attainment test was applied by modeling a 2006 

baseline year and 2012 future year to project 2012 eight-hour ozone design values. Based on the 

results of the modeled attainment test, no regulatory monitors in the DFW area are projected to 

have 2012 eight-hour ozone design values greater than the 1997 eight-hour ozone NAAQS.

Table ES-1: Summary of 2006 Baseline and 2012 Future Year Anthropogenic Modeling 

Emissions for DFW lists the anthropogenic modeling emissions in tons per day (tpd) by source 

category for the 2006 baseline and 2012 future year for nitrogen oxides (NOX) and volatile 

organic compounds (VOC), ozone precursors. The differences in modeling emissions between 

the 2006 baseline and the 2012 future year reflect the net of growth and reductions from 

existing controls. The existing controls include both state and federal measures that have 

already been promulgated.

Table ES-1: Summary of 2006 Baseline and 2012 Future Year Anthropogenic 

Modeling Emissions for DFW

Category 2006 NOX tpd 2012 NOX tpd 2006 VOC tpd 2012 VOC tpd

On-Road Mobile

(MOVES2010a) 259 181 111 80

Non-Road (excl. Oil & Gas 

Drilling) 85 64 60 43

Off-Road 40 37 7 6 

Stationary Point Source 51 51 41 39

Area (excl. Oil & Gas) 16 18 213 240

Oil & Gas Production 50 10 72 113

Oil & Gas Drilling 18 9 1 1 

DFW Total 519 370 505 522

Note: VOC is reported as sum of Carbon Bond 05 (CB05) species
ES-2 

Table ES-2: Summary of Modeled 2006 Baseline and 2012 Future Year Eight-Hour Ozone 

Design Values for DFW Monitors lists the eight-hour ozone design values in ppb for the 2006 

baseline (DVB) and 2012 baseline future year for the DFW monitors. All regulatory monitors 

have model-projected 2012 eight-hour ozone design values less than the 1997 eight-hour ozone 

NAAQS. Since the modeling cannot provide an absolute prediction of future year ozone design 

values, additional information from corroborative analyses are used in assessing whether the 

area will attain the standard in 2012. 

Table ES-2: Summary of Modeled 2006 Baseline and 2012 Future Year Eight-Hour 

Ozone Design Values for DFW Monitors

Site Monitor

2006 Baseline

Design Value 

(ppb)#

Relative 

Response 

Factor

2012 Future 

Design Value 

(ppb)

DENT Denton C56 93.33 0.825 77.03

EMTL Eagle Mountain Lake C75 93.33 0.836 78.06

KELC Keller C17 91.00 0.840 76.45

GRAP Grapevine Fairway C70 90.67 0.840 76.17

FWMC Fort Worth Northwest C13 89.33 0.844 75.36

FRIC Frisco C31 87.67 0.849 74.45

WTFD Weatherford Parker County C76 87.67 0.829 72.71

DALN Dallas North C63 85.00 0.837 71.15

REDB Dallas Exec Airport C402 85.00 0.830 70.58

CLEB Cleburne C77 85.00 0.834 70.85

ARLA Arlington C61 83.33 0.844 70.32

DHIC Dallas Hinton C401 81.67 0.831 67.89

PIPT* Pilot Point C1032* 81.00* 0.831* 67.35* 

MDLT* Midlothian Tower C94* 80.50* 0.828* 66.63* 

RKWL Rockwall Heath C69 77.67 0.815 63.27

MDLO* Midlothian OFW C52* 75.00* 0.830* 62.24*

KAUF Kaufman C71 74.67 0.809 60.42

GRAN Granbury C73 83.00 0.839 69.66

GRVL Greenville C1006 75.00 0.799 59.96

* PIPT, MDLT, and MDLO did not measure enough data from 2004 through 2008 to calculate a complete DVB. The 

DVB shown uses all available data. # The 2006 Baseline Design Value (DVB) is different from the 2006 regulatory design value (DVR). Figure 3-1: 2006 

Baseline Design Value Calculation illustrates how DVBs are calculated using the three DVs containing 2006 data. 

The 2006 DVR is the average of the fourth high ozone values from 2004, 2005, and 2006.

This AD SIP revision also provides ozone reduction trends analyses and other supplementary 

data and information to demonstrate that the DFW nine-county nonattainment area will attain 

the 1997 eight-hour ozone standard by the June 15, 2013, attainment date. The EPA's April 2007 

"Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air 

Quality Goals for Ozone, PM2.5, and Regional Haze," states that supplemental analyses should be 

conducted if the maximum future design value is less than 82 ppb. The quantitative and 
ES-3 

qualitative corroborative analyses in Chapter 5: Weight of Evidence further support a conclusion 

that this SIP revision demonstrates attainment of the 1997 eight-hour ozone standard. 

This AD SIP revision also addresses RACT requirements. Concurrent with this SIP revision, the 

commission is adopting revised and new RACT requirements in response to the following 

control techniques guidelines (CTG) documents issued by the EPA from 2006 through 2008

(Rule Project Number 2010-016-115-EN): Flexible Package Printing; Industrial Cleaning 

Solvents; Large Appliance Coatings; Metal Furniture Coatings; Paper, Film, and Foil Coatings; 

Miscellaneous Industrial Adhesives; Miscellaneous Metal and Plastic Parts Coatings; and Auto 

and Light-Duty Truck Assembly Coatings. Concurrent with this AD SIP revision, the 

commission is also adopting revised and new RACT requirements for VOC storage tanks (Rule 

Project Number 2010-025-115-EN). Additional detail concerning these updated control 

measures can be found in the RACT discussion in Chapter 4, Section 4.5.3: VOC RACT 

Determination. 

This revision also includes FCAA-required SIP elements, including a reasonably available 

control measures analysis, a motor vehicle emissions budget (MVEB), and a contingency plan. 

For the MVEB, see Table 4-2: 2012 Attainment Demonstration MVEB for the Nine-County 

DFW Area. 

The EPA officially released the Motor Vehicle Emission Simulator (MOVES) model as a 

replacement to MOBILE6.2 for SIP applications on March 2, 2010. Since the MOVES model was 

released several months after on-road inventory development work had to begin for this AD SIP 

revision, its use is not required based on the EPA’s MOVES1

The TCEQ is committed to developing and applying the best science and technology towards 

addressing and reducing ozone formation as required in the DFW and other nonattainment 

areas in Texas. This AD SIP revision also includes a description of how the TCEQ continues to 

use new technology and investigate possible emission reduction strategies and other practical 

methods to make progress in air quality improvement. For more information, see Chapter 6: 

Ongoing Initiatives. 

policy guidance. However, the 

commission has included MOVES2010a (the latest version of the MOVES model) on-road 

emission inventory estimates in this AD SIP revision based on the model’s technical superiority 

to MOBILE6.2, consistency with future conformity determinations, and comments received 

regarding the proposed AD SIP revision. 

 

1 Additional information on the EPA’s MOVES policy guidance is available at 

http://www.epa.gov/otaq/models/moves/420b09046.pdf. 
i 

SECTION V: LEGAL AUTHORITY

The Texas Commission on Environmental Quality (TCEQ) has the legal authority to implement, 

maintain, and enforce the National Ambient Air Quality Standards and to control the quality of 

the state’s air, including maintaining adequate visibility.

General

The first air pollution control act, known as the Clean Air Act of Texas, was passed by the Texas 

Legislature in 1965. In 1967, the Clean Air Act of Texas was superseded by a more 

comprehensive statute, the Texas Clean Air Act (TCAA), found in Article 4477-5, Vernon’s Texas 

Civil Statutes. The legislature amended the TCAA in 1969, 1971, 1973, 1979, 1985, 1987, 1989, 

1991, 1993, 1995, 1997, 1999, 2001, 2003, 2005, 2007, 2009, and 2011. In 1989, the TCAA was 

codified as Chapter 382 of the Texas Health and Safety Code.

Originally, the TCAA stated that the Texas Air Control Board (TACB) is the state air pollution 

control agency and is the principal authority in the state on matters relating to the quality of air 

resources. In 1991, the legislature abolished the TACB effective September 1, 1993, and its 

powers, duties, responsibilities, and functions were transferred to the Texas Natural Resource 

Conservation Commission (TNRCC). With the creation of the TNRCC, the authority over air 

quality is found in both the Texas Water Code and the TCAA. Specifically, the authority of the 

TNRCC is found in Chapters 5 and 7. Chapter 5, Subchapters A - F, H - J, and L, include the 

general provisions, organization, and general powers and duties of the TNRCC, and the 

responsibilities and authority of the executive director. Chapter 5 also authorizes the TNRCC to 

implement action when emergency conditions arise and to conduct hearings. Chapter 7 gives the 

TNRCC enforcement authority. In 2001, the 77th Texas Legislature continued the existence of 

the TNRCC until September 1, 2013, and changed the name of the TNRCC to the Texas 

Commission on Environmental Quality (TCEQ). In 2009, the 81st Texas Legislature, during a 

special session, amended §5.014 of the Texas Water Code, changing the expiration date of the 

TCEQ to September 1, 2011, unless continued in existence by the Texas Sunset Act. In 2011, the 

82nd Texas Legislature continued the existence of the TCEQ until 2023.

The TCAA specifically authorizes the TCEQ to establish the level of quality to be maintained in 

the state’s air and to control the quality of the state’s air by preparing and developing a general, 

comprehensive plan. The TCAA, Subchapters A - D, also authorize the TCEQ to collect 

information to enable the commission to develop an inventory of emissions; to conduct research 

and investigations; to enter property and examine records; to prescribe monitoring 

requirements; to institute enforcement proceedings; to enter into contracts and execute 

instruments; to formulate rules; to issue orders taking into consideration factors bearing upon 

health, welfare, social and economic factors, and practicability and reasonableness; to conduct 

hearings; to establish air quality control regions; to encourage cooperation with citizens’ groups 

and other agencies and political subdivisions of the state as well as with industries and the 

federal government; and to establish and operate a system of permits for construction or 

modification of facilities.

Local government authority is found in Subchapter E of the TCAA. Local governments have the 

same power as the TCEQ to enter property and make inspections. They also may make 

recommendations to the commission concerning any action of the TCEQ that affects their 

territorial jurisdiction, may bring enforcement actions, and may execute cooperative agreements 

with the TCEQ or other local governments. In addition, a city or town may enact and enforce 
ii

ordinances for the control and abatement of air pollution not inconsistent with the provisions of 

the TCAA and the rules or orders of the commission.

Subchapters G and H of the TCAA authorize the TCEQ to establish vehicle inspection and 

maintenance programs in certain areas of the state, consistent with the requirements of the 

Federal Clean Air Act; coordinate with federal, state, and local transportation planning agencies 

to develop and implement transportation programs and measures necessary to attain and 

maintain the National Ambient Air Quality Standards; establish gasoline volatility and low 

emission diesel standards; and fund and authorize participating counties to implement vehicle 

repair assistance, retrofit, and accelerated vehicle retirement programs.

The following statutes and rules provide necessary authority to adopt and implement the state 

implementation plan (SIP). The rules listed below have previously been submitted as part of the 

SIP.

Applicable Law

All sections of each subchapter are included, unless otherwise noted.

Statutes

TEXAS HEALTH & SAFETY CODE, Chapter 382 September 1, 2011

TEXAS WATER CODE September 1, 2011

Chapter 5: Texas Natural Resource Conservation Commission

Subchapter A: General Provisions

Subchapter B: Organization of the Texas Natural Resource Conservation Commission

Subchapter C: Texas Natural Resource Conservation Commission

Subchapter D: General Powers and Duties of the Commission

Subchapter E: Administrative Provisions for Commission

Subchapter F: Executive Director (except §§5.225, 5.226, 5.227, 5.2275,5.231, 5.232, and 

5.236)

Subchapter H: Delegation of Hearings

Subchapter I: Judicial Review

Subchapter J: Consolidated Permit Processing

Subchapter L: Emergency and Temporary Orders (§§5.514, 5.5145, and 5.515 only)

Subchapter M: Environmental Permitting Procedures (§5.558 only)

Chapter 7: Enforcement

Subchapter A: General Provisions (§§7.001, 7.002, 7.0025, 7.004, and 7.005 only) 

Subchapter B: Corrective Action and Injunctive Relief (§7.032 only)

Subchapter C: Administrative Penalties

Subchapter D: Civil Penalties (except §7.109)

Subchapter E: Criminal Offenses and Penalties: §§7.177, 7.179-7.183

All of the following rules are found in 30 Texas Administrative Code, as of the following latest 

effective dates:

Rules

Chapter 7: Memoranda of Understanding, §§7.110 and 7.119

December 13, 1996 and May 2, 2002

Chapter 19: Electronic Reporting March 15, 2007
iii

Chapter 35: Subchapters A-C, K: Emergency and Temporary Orders and

Permits; Temporary Suspension or Amendment of Permit Conditions July 20, 2006

Chapter 39: Public Notice, §§39.201; 39.401; 39.403(a) and (b)(8)-(10); 

39.405(f)(1) and (g); 39.409; 39.411 (a), (b)(1)-(6), and (8)-(10) and (c)(1)-(6) 

and (d); 39.413(9), (11), (12), and (14); 39.418(a) and (b)(3) and (4); 

39.419(a), (b), (d), and (e); 39.420(a), (b) and (c)(3) and (4); 39.423 (a) and 

(b); 39.601-39.605 June 24, 2010

Chapter 55: Requests for Reconsideration and Contested Case Hearings;

Public Comment, §§55.1; 55.21(a) - (d), (e)(2), (3), and (12), (f) and (g); 

55.101(a), (b), and (c)(6) - (8); 55.103; 55.150; 55.152(a)(1), (2), and (6) and 

(b); 55.154; 55.156; 55.200; 55.201(a) - (h); 55.203; 55.205; 55.209, and 

55.211 June 24, 2010

Chapter 101: General Air Quality Rules May 15, 2011

Chapter 106: Permits by Rule, Subchapter A May 15, 2011

Chapter 111: Control of Air Pollution from Visible Emissions and Particulate 

Matter July 19, 2006

Chapter 112: Control of Air Pollution from Sulfur Compounds July 16, 1997

Chapter 113: Standards of Performance for Hazardous Air Pollutants and for 

Designated Facilities and Pollutants May 14, 2009

Chapter 114: Control of Air Pollution from Motor Vehicles December 13, 2010

Chapter 115: Control of Air Pollution from Volatile Organic Compounds February 17, 2011

Chapter 116: Permits for New Construction or Modification March 17, 2011

Chapter 117: Control of Air Pollution from Nitrogen Compounds May 15, 2011

Chapter 118: Control of Air Pollution Episodes March 5, 2000

Chapter 122: §122.122: Potential to Emit December 11, 2002

Chapter 122: §122.215: Minor Permit Revisions June 3, 2001

Chapter 122: §122.216: Applications for Minor Permit Revisions June 3, 2001

Chapter 122: §122.217: Procedures for Minor Permit Revisions December 11, 2002

Chapter 122: §122.218: Minor Permit Revision Procedures for Permit 

Revisions Involving the Use of Economic Incentives, Marketable Permits, and 

Emissions Trading June 3, 2001
i 

SECTION VI: CONTROL STRATEGY

A. Introduction (No change)

B. Ozone (Revised)

1. Dallas-Fort Worth (Revised) 

Chapter 1: General

Chapter 2: Anthropogenic Emissions Inventory (EI) Description

Chapter 3: Photochemical Modeling

Chapter 4: Control Strategies and Required Elements

Chapter 5: Weight of Evidence

Chapter 6: Ongoing and Future Initiatives

2. Houston-Galveston-Brazoria (No change)

3. Beaumont-Port Arthur (No change)

4. El Paso (No change)

5. Regional Strategies (No change)

6. Northeast Texas (No change)

7. Austin Area (No change)

8. San Antonio Area (No change)

9. Victoria Area (No change) 

C. Particulate Matter

D. Carbon Monoxide (No change)

E. Lead (No change)

F. Oxides of Nitrogen (No change)

G. Sulfur Dioxide (No change)

H. Conformity with the National Ambient Air Quality Standards (No change)

I. Site Specific (No change)

J. Mobile Sources Strategies (No change)

K. Clean Air Interstate Rule (No change)

L. Transport (No change)

M. Regional Haze (No change)
ii

TABLE OF CONTENTS

Executive Summary

Section V: Legal Authority

Section VI: Control Strategy

Table of Contents

List of Acronyms

List of Tables

List of Figures

List of Appendices

Chapter 1: General

1.1 Background

1.2 Introduction

1.2.1 One-Hour National Ambient Air Quality (NAAQS) History

1.2.1.1 March 1999

1.2.1.2 April 2000

1.2.1.3 August 2001

1.2.1.4 March 2003

1.2.1.5 EPA Determination of One-Hour Ozone Attainment

1.2.2 Eight-Hour Ozone NAAQS History

1.2.2.1 May 23, 2007

1.2.3 Existing Ozone Control Strategies

1.2.4 Current AD SIP Revision

1.2.5 2008 and 2010 Ozone Standards

1.3 Health Effects

1.4 Stakeholder Participation and Public Hearings

1.4.1 TCEQ SIP and Control Strategy Development Stakeholder Meetings

1.4.2 Dallas-Fort Worth Photochemical Modeling Technical Committee

1.5 Public Hearing and Comment Information

1.6 Social and Economic Considerations

1.7 Fiscal and Manpower Resources

Chapter 2: Anthropogenic Emissions Inventory (EI) Description

2.1 Introduction

2.2 Point Sources

2.3 Area Sources

2.4 Non-Road Mobile Sources

2.5 On-Road Mobile Sources

2.6 EI Improvement
iii

Chapter 3: Photochemical Modeling

3.0 Introduction

3.1 Overview of the Ozone Photochemical Modeling Process

3.2 Ozone Modeling

3.2.1 Base Case Modeling

3.2.2 Future Year Modeling

3.3 Episode Selection

3.3.1 EPA Guidance for Episode Selection

3.3.2 DFW Ozone Episode Selection Process

3.3.3 Summary of the Extended June 2006 Episode

3.4 Meteorological Model

3.4.1 Modeling Domains

3.4.2 Meteorological Model Configuration

3.4.3 MM5 Application and Performance

3.5 Modeling Emissions

3.5.1 Biogenic Emissions

3.5.2 2006 Base Case

3.5.2.1 Point Sources

Outside Texas

Within Texas

On-Road Mobile Sources

DFW Area

Non-DFW Portions of Texas

Outside of Texas

3.5.2.2 Non-Road and Off-Road Mobile Sources

Outside Texas

Within Texas

3.5.2.3 Area Sources

Outside Texas

Within Texas

3.5.2.4 Base Case Summary

3.5.3 2006 Baseline

3.5.3.1 Point Sources

3.5.3.2 On-Road Mobile Sources

3.5.4 2012 Future Base and Control Strategy

3.5.4.1 Point Sources

Outside Texas

Within Texas
iv

3.5.4.2 On-Road Mobile Sources

DFW Area

Non-DFW Portions of Texas

Outside of Texas

3.5.4.3 Non- and Off-Road Mobile Sources

Outside Texas

Within Texas

3.5.4.4 Area Sources

Outside Texas

Within Texas

3.5.4.5 Future Base Summary

3.5.5 2006 and 2012 Modeling Emissions Summary for DFW

3.6 Photochemical Modeling

3.6.1 Modeling Domains and Horizontal Grid Cell Size

3.6.2 Vertical Layer Structure

3.6.3 Model Configuration

3.6.4 Model Performance Evaluation

3.6.4.1 Performance Evaluations Overview

3.6.4.2 Operational Evaluations

Statistical Evaluations

Graphical Evaluations

Evaluations Based on TexAQS II Rural Monitoring Network Data

3.6.4.3 Diagnostic Evaluations

Retrospective Modeling – 1999 Backcast

Observational Modeling – Weekday/Weekend

3.7 2006 Baseline and 2012 Future Case Modeling

3.7.1 2006 Baseline Modeling

3.7.2 Future Baseline Modeling

3.7.3 Ozone Source Apportionment Tool and Anthropogenic Precursor Culpability 

Analysis

3.7.4 Future Case Modeling with Controls

3.7.5 Unmonitored Area Analysis

3.8 Modeling Archive and References

3.8.1 Modeling Archive

3.8.2 Modeling References

Chapter 4: Control Strategies and Required Elements

4.1 Introduction

4.2 Existing Control Measures
v 

4.3 Updates to Existing Control Measures

4.3.1 Updates to Coatings Control Measures

4.3.2 Updates to VOC Storage Tank Control Measures

4.3.3 Repeal of State Portable Fuel Container Rule

4.3.4 Clean Fuel Fleet Requirement

4.3.5 Stage I and Stage II Requirements

4.4 New Control Measures

4.4.1 Stationary Sources

4.4.1.1 VOC Storage

4.4.1.2 Coating and Solvent Usage

4.5 RACT Analysis

4.5.1 General Discussion

4.5.2 NOX RACT Determination

4.5.3 VOC RACT Determination

4.5.3.1 Flexible Package Printing

4.5.3.2 Industrial Cleaning Solvents

4.5.3.3 Large Appliance Coatings

4.5.3.4 Metal Furniture Coatings

4.5.3.5 Paper, Film, and Foil Coatings

4.5.3.6 Miscellaneous Industrial Adhesives

4.5.3.7 Miscellaneous Metal and Plastic Parts Coatings

4.5.3.8 Auto and Light-Duty Truck Assembly Coatings

4.6 RACM Analysis

4.6.1 General Discussion

4.6.2 Results of the RACM Analysis

4.7 MVEB

4.8 Monitoring Network

4.9 Contingency Plan

4.10 References

Chapter 5: Weight of Evidence

5.1 Introduction

5.2 Corroborative Analysis: Modeling

5.2.1 Solving Modeling Problems

5.2.1.1 Resolution of Photochemical Modeling Grids

5.2.1.2 Incommensurability and Model Performance Evaluation

5.2.1.3 Ensemble Modeling

5.2.1.4 Vertical Distribution of Ozone

5.2.1.5 Photolysis Discrepancies Due to Improper Placement of Clouds
vi

5.2.1.6 Radical Shortage

5.2.2 Model Performance Evaluations: Implications of the Model Performance of the 

Current SIP Modeling

5.2.2.1 Ozone Performance

5.2.2.2 Ozone Precursor Performance

5.2.2.3 Meteorological Performance Evaluation

5.2.2.4 Model Response to Emission Changes

5.2.2.5 Ozone Formation Sensitivity

5.2.3 Additional Modeling Analysis to Measure Progress

5.2.4 Conclusion

5.3 Air Quality Trends in the DFW Area

5.3.1 Design Values

5.3.2 Nitrogen Oxides Trends

5.3.3 Volatile Organic Compound Trends

5.3.4 VOC Trends at Auto-GC Monitors

5.3.5 VOC Trends from Canisters

5.3.6 Summary of Trends in Ozone and Ozone Precursors

5.3.7 NOX Concentrations in the Barnett Shale Region

5.4 Studies of DFW Ozone Formation, Accumulation, and Transport

5.5 Qualitative Corroborative Analysis

5.5.1 Additional Measures

5.5.1.1 VOC Storage Tank Rule

5.5.1.2 Energy Efficiency and Renewable Energy (EE/RE) Measures

Renewable Energies

Residential Building Codes and Programs

Commercial Building Codes

Federal Facilities EE/RE Projects

Political Subdivisions Projects

Electric Utility Sponsored Programs

Clean Air Interstate Rule (CAIR) and Cross-State Air Pollution Rule

5.5.1.3 TERP

5.5.1.4 LIRAP

5.5.1.5 Local Initiatives

5.5.1.6 Voluntary Measures

5.6 Conclusions

5.7 References

Chapter 6: Ongoing Initiatives

6.1 Introduction
vii

6.2 Ongoing Work

6.2.1 Barnett Shale Special Emissions Inventory

6.2.2 Statewide Drilling Rigs Emissions Inventory

6.2.3 Surface Measurements and One-Dimensional Modeling Related to Ozone 

Formation in the Suburban DFW Area

6.2.4 DFW Measurements of Ozone Production

6.2.5 Airborne Measurements to Investigate Ozone Production and Transport in the 

DFW Area During the 2011 Ozone Season

6.2.6 Quantification of Industrial Emissions of VOCs, NO2 and SO2 by Solar Occultation 

Flux (SOF) and mobile Differential Optical Absorption Spectroscopy (DOAS)
viii

LIST OF ACRONYMS

ABY adjusted base year

ACM2 Asymmetric Convective Model

ACT Alternative Control Techniques

AD attainment demonstration

AIRS Aerometric Information Retrieval System

APCA Anthropogenic Precursor Culpability Assessment

APU auxiliary power unit

AQRP Air Quality Research Program

ARD Acid Rain Database

ARLA Arlington Monitor (C61)

auto-GC automated gas chromatograph

Bcf billion cubic feet

BPA Beaumont-Port Arthur

CAIR Clean Air Interstate Rule

CAMS continuous air monitoring station

CAMx Comprehensive Air Model with Extension(s)

CARB California Air Resources Board 

CATMN Community Air Toxics Monitoring Network

CB05 Carbon Bond 05

CENRAP/RPO Central Regional Air Planning Association/Regional Planning 

Organization

CFFP Clean Fuel Fleet Program

CFR Code of Federal Regulations

CFV clean fuel vehicle

CLEB Cleburne Monitor (C77)

CLU Common Land Unit

CLVL Clarksville Monitor (C648)

CO carbon monoxide

CTG Control Techniques Guidelines

DALN Dallas North Monitor (C63)

DACM AirCheckTexas Drive a Clean Machine

DENT Denton Monitor (C56)

DERC Discrete Emission Reduction Credit

DFW Dallas-Fort Worth

DHIC Dallas Hinton Monitor (C401)

DISH DISH Airfield Monitor (C1013)

DVB baseline year design value

DVF future year design value

DVP projected design value

DVR regulatory design value

EBI Euler Backward Iterative
ix

EE/RE energy efficiency and renewable energy

EGAS5 Economic Growth Analysis System, Version 5.0

EGU electric generating unit

EI emissions inventory

EIQ emissions inventory questionnaire

EMTL Eagle Mountain Lake Monitor (C75)

EPA United States Environmental Protection Agency

EPS3 Emissions Processing System, Version 3

ERC Emission Reduction Credit

ESL environmental speed limit

ESL Energy Systems Laboratory

ETH Ethylene

FCAA Federal Clean Air Act

FIP Federal Implementation Plan

FR Federal Register

FSA Farm Service Agency

FTP File Transfer Protocol

FRIC Frisco Monitor (C31)

FWMC Fort Worth Northwest Monitor (C13)

GAPP GEWEX Americas Prediction Project

GCIP Continental-Scale International Project

GEWEX Global Energy and Water Cycle Experiment

GloBEIS Global Biosphere Emissions and Interactions System

GOES Geostationary Operational Environmental Satellite

GRAN Granbury Monitor (C73)

GRAP Grapevine Monitor (C70)

GREASD Greatly Reduced Execution and Simplified Dynamics

GRVL Greenville Monitor (C1006)

GWEI Gulf-Wide Emissions Inventory

HB House Bill

HECT Highly Reactive Volatile Organic Compound Emissions Cap and 

Trade

HGB Houston-Galveston-Brazoria

HONO nitrous acid

Hp Horsepower

HPMS Highway Performance Monitoring System

HRVOC highly reactive volatile organic compounds

I/M Inspection and Maintenance

ICI industrial, commercial, and institutional

IOLE internal olefins

IOP increment-of-progress

ISOP Isoprene

JPL Jet Propulsion Laboratory 

KAUF Kaufman Monitor (C71)
x 

KELC Keller Monitor (C17)

Km Kilometer

Kv vertical diffusivity coefficient

LCP Lambert Conformal Projection

LDAR leak detection and repair

LGVW Longview Monitor (C19)

LIRAP Low Income Vehicle Repair Assistance, Retrofit, and Accelerated 

Vehicle Retirement Program

LULC land-use/land-cover

MACT maximum achievable control technology

MDLO Midlothian OFW Monitor (C52)

MDLT Midlothian Tower Monitor (C94)

MECT Mass Emissions Cap and Trade

MM5 Fifth Generation Meteorological Model

MMS Minerals Management Services

MNB Mean Normalized Bias

MNGE Mean Normalized Gross Error

MOVES Motor Vehicle Emission Simulator

MOVES2010a Motor Vehicle Emission Simulator 2010a

MOZART Model for Ozone and Related Chemical Tracers

MPE model performance evaluation

Mph miles per hour

MVEB motor vehicle emissions budget

NAAQS National Ambient Air Quality Standard

NAM North American Model

NASA National Aeronautics and Space Administration

NCAR National Center for Atmospheric Research

NCEP National Center for Environmental Prediction

NCTCOG North Central Texas Council of Governments

NEI National Emissions Inventory

NHD National Hydrography Dataset

NLCD National Land Cover Dataset

NMIM National Mobile Inventory Model

NO nitric oxide

NO2 nitrogen dioxide

NOAH NCEP Oregon State Air Force Hydrological Research Laboratory

NOX nitrogen oxides

NOY total reactive nitrogen oxides

NTCASC North Texas Clean Air Steering Committee

O3 Ozone

OFW Old Fort Worth

OH hydroxyl radical

OLE Olefins

OSAT Ozone Source Apportionment Technology
xi

OSD ozone season day

PAMS Photochemical Assessment Monitoring Station

PAR photosynthetically active radiation

PBL Planetary Boundary Layer

PEI periodic emissions inventory

PFC portable fuel container

PiG Plume-in-Grid

PIPT Pilot Point Monitor (C1032)

PLTN Palestine Monitor (C647)

PM2.5 particulate matter 2.5 microns and less

Ppb parts per billion

ppbC parts per billion, Carbon

Ppm parts per million

PPM Piecewise Parabolic Method

PUCT Public Utility Commission of Texas

QQ quantile-quantile

RACM reasonably available control measure

RACT reasonably available control technology

RAQMS Regional Air Quality Modeling System

REDB Dallas Executive Airport Monitor (C402)

REMI Regional Economic Models, Inc.

RFG reformulated gasoline

RFP reasonable further progress

RKWL Rockwall Health Monitor (C69)

ROP rate-of-progress

Rpm revolutions per minute

RRF relative response factor

RRFD relative response factor denominator

RRFN relative response factor numerator

RRTM Rapid Radiative Transfer Model

RVP Reid vapor pressure

SAGA San Augustine Airport Monitor (C646)

SB Senate Bill

SCR selective catalytic reduction

SECO State Energy Conservation Office

SEER Seasonal Energy Efficiency Ratio

SIP state implementation plan

SO2 sulfur dioxide

STARS State of Texas Air Reporting System

TAC Texas Administrative Code 

TACB Texas Air Control Board

TCAA Texas Clean Air Act

TCEQ Texas Commission on Environmental Quality (commission)

TDM Travel Demand Model
xii

TEMP Temperature

TERP Texas Emissions Reduction Plan

TexAER Texas Air Emissions Repository

TexAQS 2000 Texas Air Quality Study 2000

TexAQS II Texas Air Quality Study 2006

TexN Texas NONROAD

TGIC Texas Geographic Information Council

THSC Texas Health and Safety Code

TIPI Texas Industrial Production Index

TNMHC total non-methane hydrocarbons 

TNRCC Texas Natural Resource Conservation Commission

TOMS Total Ozone Mapping Spectrometer

Tpd tons per day

Tpy tons per year

TREIM Texas Railroad Emission Inventory Model

TTI Texas Transportation Institute

TxLED Texas Low Emission Diesel

UH University of Houston

UPA Unpaired Peak Accuracy

USDA United States Department of Agriculture

USGS United States Geological Survey

UTC Coordinated Universal Time

VMEP Voluntary Mobile Emissions Reduction Program

VMT vehicle miles traveled

VOC volatile organic compounds

WDIR wind direction

WMBA Wamba Monitor (C645)

WSPD wind speed

WTFD Weatherford Parker County Monitor (C76)
xiii

LIST OF TABLES

Table ES-1: Summary of 2006 Baseline and 2012 Future Year Anthropogenic Modeling 

Emissions for DFW

Table ES-2: Summary of Modeled 2006 Baseline and 2012 Future Year Eight-Hour Ozone 

Design Values for DFW Monitors

Table 3-1: DFW Eight-Hour Ozone Exceedance Data during TexAQS II Modeling Episodes

Table 3-2: DFW Monitor-Specific Eight-Hour Ozone Data During the Extended June 2006 

Episode

Table 3-3: MM5 Modeling Domain Definitions

Table 3-4: June 2006 MM5 Configuration

Table 3-5: DFW Meteorological Modeling Percent Accuracy

Table 3-6: Emissions Processing Modules

Table 3-7: 2006 Base Case Episode Point Source Modeling Emissions

Table 3-8: Summary of On-Road Mobile Source Emissions Development

Table 3-9: 2006 Base Case Episode On-Road Modeling Emissions for DFW (tpd)

Table 3-10: 2006 Base Case Episode Non-Road and Off-Road Modeling Emissions for DFW

Table 3-11: 2006 DFW Nine-County Oil and Gas Production Emissions

Table 3-12: 2006 Base Case Episode Area Source Modeling Emissions for DFW

Table 3-13: 2006 Base Case Episode Anthropogenic Modeling Emissions for DFW

Table 3-14: 2006 Baseline Point Source Modeling Emissions

Table 3-15: 2012 Future Case Point Source Modeling Emissions

Table 3-16: 2012 Future Case On-Road Modeling Emissions for DFW (tpd)

Table 3-17: 2012 Future Case Non-Road and Off-Road Modeling Emissions for DFW

Table 3-18: 2012 DFW Nine-County Oil and Gas Production Emissions

Table 3-19: 2012 Future Case Episode Area Source Modeling Emissions for DFW

Table 3-20: 2012 Future Base Anthropogenic Modeling Emissions for DFW

Table 3-21: Summary of 2006 Baseline and 2012 Future Base Anthropogenic Modeling 

Emissions for DFW

Table 3-22: CAMx Modeling Domain Definitions

Table 3-23: CAMx Vertical Layer Structure

Table 3-24: Retrospective Analysis Design Values

Table 3-25: 2006 Baseline Values Used in the Modeled Attainment Test

Table 3-26: Summary of the RRF and 2012 Future Design Values

Table 3-27: APCA Source Groups and Regions

Table 4-1: Existing Ozone Control Measures Applicable to the DFW Nine-County 

Nonattainment Area

Table 4-2: 2012 Attainment Demonstration MVEB for the Nine-County DFW Area
xiv

Table 4-3: 2013 DFW Attainment Demonstration Contingency Demonstration (tpd)

Table 5-1: Changes in the Area and Population Affected by an Eight-Hour Ozone Design Value 

Greater than or Equal to 85 ppb in Response to Growth and Controls

Table 5-2: Eight-Hour Ozone Design Values by Monitor in the DFW Area

Table 5-3: One-Hour Ozone Design Values by Monitor in the DFW Area

Table 5-4: Annual Fourth Highest Eight-Hour Ozone Values and Design Values (ppb)

Table 5-5: Number of Days with an Eight-Hour Ozone Exceedance

Table 5-6: Number of Days with a One-Hour Ozone Exceedance

Table 5-7: Decreases in 90th Percentile NOX Concentrations

Table 5-8: Description of Auto-GC and Canister Monitors in the DFW Area

Table 5-9: TNMHC Yearly Median Linear Regression

Table 5-10: Regression Analysis Results for Annual Geometric Mean TNMHC at CATMN 

Monitors

Table 5-11: NOX Concentrations Statistics at Various Monitors

Table 5-12: Summary of Ozone Apportionment Between Regional Transport and Local 

Production on Exceedance Days in the DFW Area
xv

LIST OF FIGURES 

Figure 1-1: One-Hour and 1997 Eight-Hour Ozone Design Values and DFW Population

Figure 3-1: 2006 Baseline Design Value Calculation

Figure 3-2: Eight-Hour Ozone Exceedance Days in DFW

Figure 3-3: DFW Monitor Map

Figure 3-4: June 2006 Episode Eight-Hour Ozone by Monitor

Figure 3-5: Daily 48-Hour Back Trajectories from DFW (May 31 through June 15, and June 16 

through July 2, 2006)

Figure 3-6: MM5 Modeling Domains

Figure 3-7: MM5 Vertical Layer Structure

Figure 3-8: June 2006 Meteorological Modeling Performance

Figure 3-9: Example of Day-Specific Biogenic Emissions

Figure 3-10: 2006 Baseline and 2012 Future Base Anthropogenic NOX and VOC Modeling 

Emissions for DFW

Figure 3-11: DFW Photochemical Modeling Domains

Figure 3-12: Peak Eight-Hour Ozone Concentration, Observed versus Modeled for May 31 

through June 15, 2006

Figure 3-13: Peak Eight-Hour Ozone Concentration, Observed versus Modeled for June 16 

through July 2, 2006

Figure 3-14: MNGE and MNB for 2006 Episode Days

Figure 3-15: Selected DFW Performance Evaluation Monitors

Figure 3-16: Time Series of Hourly Ozone Concentrations at the Denton Airport South (C56), 

Eagle Mountain Lake (C75), and Keller (C17) Monitors

Figure 3-17: Time Series of Hourly Ozone Concentrations at the Dallas Hinton (C60), Greenville 

(C1006), and Weatherford Parker County (C76) Monitors

Figure 3-18: Scatter Plots of Hourly Ozone, NOX, OLE, and PAR at the Dallas Hinton (C401) 

Monitor

Figure 3-19: Tile Plot of Daily Maximum Eight-Hour Ozone Concentrations for June 9, June 12 

and 13, and June 30, 2006

Figure 3-20: TexAQS II Monitoring Sites Outside Ozone Nonattainment Areas

Figure 3-21: Time Series of Hourly Ozone Concentrations at the Clarksville (C648) Monitor

Figure 3-22: Time Series of Hourly Ozone Concentrations at the Palestine (C647) Monitor

Figure 3-23: Monitors Used in 1999 Retrospective Analysis

Figure 3-24: Comparison of Modeled 6:00 A.M. NOX and VOC Emissions for Wednesdays, 

Saturdays, and Sundays

Figure 3-25: Median Observed and Modeled 6:00 A.M. NOX Concentrations at DFW Monitors 

as a Percentage of Wednesday

Figure 3-26: Observed and Modeled Median Daily Peak Eight-Hour Ozone Concentrations as a 

Percentage of Wednesday
xvi

Figure 3-27: Observed 90th Percentile and Modeled Daily Peak Eight-Hour Ozone 

Concentrations as a Percentage of Wednesday

Figure 3-28: Near Monitoring Site Grid Cell Array Size

Figure 3-29: APCA Source Regions

Figure 3-30: 2006 Baseline Case Eagle Mountain Lake (C75) Eight-Hour APCA with 

MOVES2010a Results (May 31 through June 15)

Figure 3-31: 2006 Baseline Case Eagle Mountain Lake (C75) Eight-Hour APCA with 

MOVES2010a Results (June 16 through July 1)

Figure 3-32: 2012 Future Case Eagle Mountain Lake (C75) Eight-Hour APCA with 

MOVES2010a Results (May 31 through June 15)

Figure 3-33: 2012 Future Case Eagle Mountain Lake (C75) Eight-Hour APCA with 

MOVES2010a Results (June 16 through July 1)

Figure 3-34: 2006 Baseline Case Dallas Hinton (C401) Eight-Hour APCA with MOVES2010a 

Results (May 31 through June 15)

Figure 3-35: 2006 Baseline Case Dallas Hinton (C401) Eight-Hour APCA Results with 

MOVES2010a (June 16 through July 1)

Figure 3-36: 2012 Future Case Dallas Hinton (C401) Eight-Hour APCA with MOVES2010a 

Results (May 31 through June 15)

Figure 3-37: 2006 Future Case Dallas Hinton (C401) Eight-Hour APCA with MOVES2010a 

Results (June 16 through July 1)

Figure 3-38: Spatially Interpolated 2006 Baseline with MOVES2010a (left) and 2012 Future 

Case with MOVES2010a (right) Design Values for the DFW Area

Figure 5-1: Daily Peak Eight-Hour Ozone Values in the DFW Area

Figure 5-2: Ozone Design Values for the DFW Area

Figure 5-3: Eight-Hour Ozone Design Value Statistics in the DFW Area

Figure 5-4: One-Hour Ozone Design Value Statistics in the DFW Area

Figure 5-5: Number of Monitors and Ozone Exceedance Days in the DFW Area

Figure 5-6: Eight-Hour Ozone Exceedance Days per Monitor in the DFW Area

Figure 5-7: Number of Eight-Hour Ozone Exceedance Days by Monitor

Figure 5-8: Number of One-Hour Ozone Exceedance Days by Monitor

Figure 5-9: Daily Peak Hourly NOX in the DFW Area

Figure 5-10: Annual Mean Daily Peak NOX

Figure 5-11: 90th Percentile Daily Peak NOX Concentrations in the DFW Area

Figure 5-13: Locations of Auto-GC Monitors (AGC) and Canisters (MCAN and CATMN) in the 

DFW Area

Figure 5-14: Daily Peak TNMHC Concentrations in the DFW Area

Figure 5-15: 90th Percentile and Median TNMHC in the DFW Area

Figure 5-16: Quarterly Geometric Mean TNMHC at CATMN Monitors

Figure 5-17: Annual Geometric Mean TNMHC at CATMN Monitors
xvii

Figure 5-18: Wind-Roses Showing 90th Percentile NOX Concentrations by Wind Direction at 

Parker County (C76) and Eagle Mountain Lake (C75)
xviii

LIST OF APPENDICES

Appendix A: Meteorological Modeling for the DFW Attainment Demonstration SIP Revision for 

the 1997 Eight-Hour Ozone Standard

Appendix B: Emissions Modeling for the DFW Attainment Demonstration SIP Revision for the 

1997 Eight-Hour Ozone Standard

Appendix C: Photochemical Modeling for the DFW Attainment Demonstration SIP Revision for 

the 1997 Eight-Hour Ozone Standard

Appendix D: Conceptual Model for the DFW Attainment Demonstration SIP Revision for the 

1997 Eight-Hour Ozone Standard

Appendix E: Modeling Protocol for the Eight-Hour Ozone Modeling of the Dallas-Fort Worth 

Area

Appendix F: Reasonably Available Control Technology Analysis

Appendix G: Reasonably Available Control Measure Analysis

Appendix H: Local Initiatives Submitted by the North Central Texas Council of Governments

Appendix I: Appendix A: Meteorological Modeling for the HGB Attainment Demonstration SIP 

Revision for the 1997 Eight-Hour Ozone Standard 

Appendix J: On-Road Emissions Supplement to the Proposed Dallas-Fort Worth Attainment 

Demonstration State Implementation Plan Revision for the 1997 Eight-Hour Ozone Standard 

Nonattainment Area
1-1 

CHAPTER 1: GENERAL

1.1 BACKGROUND

The History of the Texas State Implementation Plan, a comprehensive overview of the state 

implementation plan (SIP) revisions submitted to the United States Environmental Protection 

Agency (EPA) by the State of Texas, is available on the Introduction to the SIP Web page

(http://www.tceq.texas.gov/airquality/sip/sipintro.html#what-is-the-history) on the Texas 

Commission on Environmental Quality’s (TCEQ) Web site (http://www.tceq.texas.gov/).

1.2 INTRODUCTION

The following history of the one-hour and eight-hour ozone standards and summaries of the 

Dallas-Fort Worth (DFW) area one-hour and 1997 eight-hour ozone SIP revisions are provided 

to give context and greater understanding of the complex issues involved in DFW’s ozone 

challenge. 

1.2.1 One-Hour National Ambient Air Quality (NAAQS) History

The EPA established the one-hour ozone NAAQS of 0.08 parts per million (ppm) in the April 

30, 1971, issue of the Federal Register (FR) (36 FR 8186). The EPA revised the one-hour ozone 

standard to 0.12 ppm in the February 8, 1979, issue of the Federal Register (44 FR 4202). The 

DFW one-hour ozone nonattainment area (Collin, Dallas, Denton, and Tarrant Counties) was 

classified in 1991 as moderate in accordance with the 1990 Federal Clean Air Act (FCAA) 

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

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

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

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

EPA reclassified the DFW area from a moderate to a serious nonattainment area (effective 

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

deadline (63 FR 8128). The EPA required the State of Texas to submit a SIP revision within one 

year that demonstrated attainment of the one-hour NAAQS and addressed FCAA requirements

for serious ozone nonattainment areas.

1.2.1.1 

The TCEQ submitted the Attainment Demonstration for the Dallas-Fort Worth Ozone 

Nonattainment Area SIP revision, which contained a rate-of-progress (ROP) demonstration, to 

the EPA on March 18, 1999. The photochemical modeling contained in the revision indicated 

that additional reductions in nitrogen oxides (NOX) emissions would be needed to attain the 

standard by November 1999. The following rules were developed and included in the SIP

revision: 

March 1999

• reasonably available control technology (RACT) for NOX point sources;

• nonattainment new source review for NOX point sources; and

• revisions resulting from the change in the major source threshold for RACT applicability for

volatile organic compounds (VOC). 

Additionally, the commission indicated that, due to time constraints, the ROP demonstration

would not incorporate all rules that were necessary to bring the DFW area into attainment by 

the November 1999 deadline and that a complete attainment demonstration (AD) would be 

submitted in the spring of 2000. The EPA determined that the AD and ROP demonstration were

incomplete.
1-2 

Additional local control strategies were necessary for the DFW area to reach attainment. To 

develop further control strategy options to augment the federal and state programs in the AD 

and ROP SIP revision, the DFW area established the North Texas Clean Air Steering Committee 

(NTCASC). The committee members include local elected officials, business leaders, and other 

community stakeholders. This committee identified specific control strategies for review by 

technical subcommittee members. 

After the attainment deadline of November 15, 1999, for serious areas under the one-hour ozone 

standard passed, the EPA had not made a determination regarding the DFW area=s attainment 

status. Furthermore, technical data became available suggesting that the DFW area was 

significantly impacted by transport and regional background levels of ozone. 

1.2.1.2 

On April 19, 2000, the commission adopted a SIP revision and associated rules for the DFW 

one-hour ozone attainment demonstration. The April 2000 One-Hour Ozone Attainment 

Demonstration SIP revision contained a number of control strategies and the following 

elements:

April 2000

• photochemical modeling of specific control measures and future state and national rules for 

attainment of the one-hour ozone standard in the DFW area by the attainment deadline of 

November 15, 2007; 

• a modeling demonstration that showed air quality in the DFW area was influenced at times 

by transport from the HGB nonattainment area (Under the EPA=s July 16, 1998, transport 

policy2

• identification of the VOC and NOX emissions reductions necessary to attain the one-hour 

ozone standard by 2007. The reductions of 141 tons per day (tpd) NOX from federal 

measures and 225 tpd NOX from state measures resulted in a total of 366 tpd NOX

reductions for the attainment demonstration; 

, if photochemical modeling demonstrated that emissions from an upwind area 

located in the same state and with a later attainment date interfered with the downwind 

area=s ability to attain, the downwind area=s attainment date could be extended to no later 

than that of the upwind area. For the DFW area, following this policy would extend the 

attainment date to November 15, 2007, the same attainment date as the HGB area.);

• a 2007 motor vehicle emissions budget (MVEB) for transportation conformity; and

• a commitment to perform and submit a mid-course review by May 1, 2004.

At the time it was submitted, the April 2000 One-Hour Ozone Attainment Demonstration SIP 

revision would have allowed the EPA to determine that the DFW area should not be reclassified 

from serious to severe under the conditions of the EPA=s July 16, 1998, transport policy. 

1.2.1.3 

The next commission action was required by legislative mandate. Senate Bill 5 (SB5), passed by 

the 77th Texas Legislature in May 2001, required the repeal of two rules contained in the April 

2000 one-hour AD SIP revision. The first rule restricted the use of construction and industrial 

equipment (non-road, heavy-duty diesel equipment rated at 50 horsepower (hp) or greater). The 

second rule required the replacement of diesel-powered construction, industrial, commercial, 

and lawn and garden equipment rated at 50 hp or greater with newer Tier 2 or Tier 3 

August 2001

 

2 Additional information on EPA’s Guidance on Extension of Attainment Dates for Downwind 

Transport Areas is available at http://www.epa.gov/ttn/oarpg/t1/memoranda/transpor.pdf.
1-3 

equipment. The Texas Emissions Reduction Plan (TERP) grant incentive program established 

by SB5 replaced the NOX emissions reductions previously claimed for the two programs. The 

commission implemented the legislative mandate of SB5 by submitting the rule repeals as part 

of a SIP revision adopted in August 2001.

1.2.1.4 

On March 5, 2003, the SIP was further revised to include the following: 

March 2003

• the adoption of revised 30 Texas Administrative Code (TAC) Chapter 117 NOX emission 

limits for cement kilns; 

• the estimation of NOX reductions from energy efficiency measures, using a methodology that 

was to be further refined before energy efficiency credit was formally requested in the SIP

revision; and

• the commitment to perform modeling with MOBILE6, the latest version of the EPA=s 

emission factor model for mobile sources.

Meanwhile, the EPA=s July 16, 1998, transport policy, on which the extension of the DFW area=s 

attainment date to November 15, 2007, was based, was challenged by environmental groups. A 

suit was filed challenging the extension of the Beaumont-Port Arthur (BPA) area=s attainment 

date based on transport from the HGB area. On December 11, 2002, the United States Fifth 

Circuit Court of Appeals ruled that the EPA was not authorized to extend the BPA area’s

attainment date based on transport. The EPA published a final action in the Federal Register on 

March 30, 2004, reclassifying the BPA area to serious with an attainment date of November 15, 

2005, and requiring a new attainment demonstration to be submitted by April 30, 2005. 

Although the court decision was specifically for the BPA area, the direct implication for the DFW 

area was that the EPA could not approve extensions of the DFW one-hour ozone attainment 

date past 1999, the date mandated by the Federal Clean Air Act (FCAA) for serious areas. In 

addition, the EPA could not approve the April 2000 One-Hour Ozone DFW Attainment 

Demonstration SIP revision. 

1.2.1.5 

Since the early 1990s, when the DFW area was designated as nonattainment for the one-hour 

ozone standard, much has been done to bring the area into attainment with federal air quality 

standards. Contributions to improved air quality in the DFW area include: TCEQ-implemented 

control strategies, local control strategies adopted by the North Central Texas Council of 

Governments (NCTCOG), and on-road and non-road mobile source measures implemented by 

the EPA. Despite the EPA’s lack of approval for multiple SIP revisions, air quality in the DFW 

area continued to improve.

EPA Determination of One-Hour Ozone Attainment

By 2006, ambient monitoring data reflected attainment of the one-hour standard. On October 

16, 2008, the EPA published final determination (73 FR 61357) that DFW area one-hour ozone 

nonattainment counties (Collin, Dallas, Denton, and Tarrant) had attained the one-hour ozone 

standard with a design value of 124 parts per billion (ppb), based on verified 2004 through 2006 

monitoring data. One-hour requirements are suspended so long as the DFW area maintains 

attainment of that standard.

1.2.2 Eight-Hour Ozone NAAQS History

In 1997, the EPA revised the NAAQS for ozone, setting it at 0.08 ppm averaged over an eighthour time frame. The final 1997 eight-hour ozone NAAQS was published in the Federal Register 

on July 18, 1997 (62 FR 38856) and became effective on September 16, 1997. On April 30, 2004, 
1-4 

the EPA finalized its designations and promulgated the first phase of its implementation rule for 

the 1997 eight-hour ozone standard (69 FR 23951). These actions became effective on June 15, 

2004. The EPA designated the nine-county (Collin, Dallas, Denton, Ellis, Johnson, Kaufman, 

Parker, Rockwall, and Tarrant Counties) DFW area as nonattainment for the standard with a 

moderate classification. The TCEQ was required to submit a SIP revision for the 1997 eight-hour 

ozone NAAQS to the EPA by June 15, 2007, and demonstrate attainment of the standard by 

June 15, 2010. In the November 29, 2005, issue of the Federal Register (70 FR 71612), the EPA 

published its second phase of the implementation rule for the 1997 eight-hour ozone NAAQS, 

which addressed the control obligations that apply to areas designated nonattainment for the 

standard.

In Phase I of its implementation rule (40 CFR '51.905(a)(ii)) and subsequent guidance, the EPA 

provided three options for areas such as the DFW area that did not have an approved one-hour 

ozone attainment plan at the time of designation:

A. Submit a one-hour AD no later than one year after designation (by June 15, 2005);

B. Submit an eight-hour ozone plan no later than one year after designation (by June 15, 2005) 

that provided a 5% increment of emissions reductions from the area=s 2002 emissions 

baseline, in addition to federal and state measures already approved by the EPA, and achieve 

those reductions by June 15, 2007; or

C. Submit an eight-hour ozone attainment demonstration by June 15, 2005.

Texas selected option B, the 5% increment-of-progress (IOP) plan, as a technically sound and 

expeditious approach to initiating the reductions ultimately needed for attainment of the eighthour ozone standard. The 5% IOP SIP revision, adopted by the commission on April 27, 2005, 

contained several elements:

• 2002 periodic emissions inventory for the nine-county DFW eight-hour ozone 

nonattainment area;

• a 5% reduction in emissions from the 2002 emissions inventory baseline;

• identification of the control measures to achieve the necessary NOX and VOC emission 

reductions; and

• MVEBs for use in transportation conformity demonstrations.

1.2.2.1 

The commission adopted the May 2007 DFW Attainment Demonstration SIP revision and the 

reasonable further progress (RFP) SIP revision for the DFW area on May 23, 2007. These SIP 

revisions were the first step in addressing the 1997 eight-hour ozone standard in the DFW area. 

May 23, 2007

This eight-hour ozone SIP revision for the DFW area contained photochemical modeling and 

weight of evidence, including corroborative analysis and additional measures not included in the 

model. In addition to the existing control strategies in the DFW area, the SIP revision included

new rules for the following sources: 

• DFW area cement kilns; 

• DFW area electric generating utilities (EGUs); 

• DFW area industrial, commercial, and institutional (ICI) major sources; 

• DFW area minor sources; and 

• East Texas combustion sources in 33 counties beyond the DFW area. 
1-5 

The SIP revision included additional commitments for Voluntary Mobile Emissions Reduction 

Program (VMEP) and transportation control measures (TCM). The revision also contained the 

reasonably available control measure (RACM) analysis, RACT analysis, contingency measures, 

emissions inventories, and MVEBs. 

On July 14, 2008, the EPA proposed conditional approval (73 FR 40203) of the May 2007 DFW 

AD SIP Revision, providing that final conditional approval was contingent upon the State of 

Texas adopting and submitting to the EPA an approvable contingency plan SIP revision for the 

DFW area. The Dallas-Fort Worth Attainment Demonstration SIP Revision for the 1997 EightHour Ozone Standard (Contingency Measures Plan) was adopted by the commission on 

November 5, 2008, and submitted to the EPA on November 15, 2008. The SIP revision 

identifies measures to satisfy the EPA’s 3% reduction contingency requirement for 2010 for the 

DFW area, to apply in the event that the DFW area fails to meet the 1997 eight-hour ozone 

standard by the attainment deadline.

An additional condition stipulated by the EPA for final approval of the May 2007 DFW AD SIP 

Revision was that the TCEQ adopt and submit rule and SIP revisions to implement an 

enforceable mechanism to limit the use of discrete emission reduction credits (DERC) in the 

DFW area by March 1, 2009. The Dallas-Fort Worth Attainment Demonstration SIP Revision 

for the 1997 Eight-Hour Ozone Standard DERC Program incorporated rulemaking that would 

amend Chapter 101, Subchapter H, Division 4: Discrete Emission Credit Banking and Trading

rules to set a limit on DERC use for the DFW area.

On January 14, 2009, the EPA published final conditional approval of components of the AD

SIP revision, including the May 2007 DFW AD SIP revision, the April 2008, and November 

2008 supplements. The approval provided conditional approval of the 2009 attainment MVEBs, 

RACM demonstration, and failure-to-attain contingency plan, full approval of local VMEP and 

TCMs, full approval of the VOC RACT demonstrations for the one-hour and 1997 eight-hour 

ozone standards, and a statement that all control measures and reductions relied upon to 

demonstrate attainment were approved by the EPA.

On March 10, 2010, the commission adopted the DFW RACT Update, 30 TAC Chapter 117 Rule 

Revision Noninterference Demonstration, and Modified Failure-to-Attain Contingency Plan SIP 

Revision. This SIP revision incorporated several actions adopted by the commission, and 

supplemented the 1997 eight-hour ozone AD by demonstrating that the revised Chapter 117 rule 

does not interfere with the DFW AD SIP Revision.

On August 25, 2010, the commission adopted a SIP revision to convert an environmental speed 

limit control strategy to a transportation control measure for the 1997 eight-hour ozone 

standard in the DFW nonattainment area.

1.2.3 Existing Ozone Control Strategies

Existing control strategies implemented to address the one-hour and eight-hour ozone 

standards are expected to continue to reduce emissions of ozone precursors in the DFW area 

and positively impact progress toward attainment of the 1997 eight-hour ozone standard. The 

one-hour and 1997 eight-hour ozone design values for the DFW area from 1991 through 2010

are illustrated in Figure 1-1: One-Hour and 1997 Eight-Hour Ozone Design Values and DFW 

Population. Both design values have decreased over the past 20 years. The 2010 one-hour ozone 

design value was 110 ppb, representing a 21% decrease from the value for 1991 (140 ppb). The 

2010 eight-hour ozone design value was 86 ppb, an 18% decrease from the 1991 value of 105 
1-6 

ppb. These decreases occurred despite a 56% increase in area population, as shown in Figure 

1-1: One-Hour and 1997 Eight-Hour Ozone Design Values and DFW Population. 

Figure 1-1: One-Hour and 1997 Eight-Hour Ozone Design Values and DFW 

Population

1.2.4 Current AD SIP Revision

The DFW 1997 eight-hour ozone standard nonattainment area is currently classified as serious 

nonattainment. In 2009, the monitored design value (complete ozone season prior to the 

attainment date) for the DFW area was 86 parts per billion (ppb). Effective January 19, 2011, 

EPA finalized a determination that the DFW nonattainment area did not attain the 1997 eighthour ozone standard by June 15, 2010, the deadline set by the Phase I implementation guidance 

for the 1997 ozone standard for areas classified as moderate (75 FR 79302). Based on that 

determination, the EPA reclassified the DFW nonattainment area to serious and set a January 

19, 2012, deadline for the state to submit an AD SIP revision that addresses the 1997 eight-hour 

ozone standard serious nonattainment area requirements, including RFP. The DFW area’s new 

attainment date for the 1997 eight-hour ozone standard is as expeditiously as practicable, but no 

later than June 15, 2013.

As required by the FCAA, the TCEQ published a notice in the Texas Register on May 21, 2010

(http://www.sos.state.tx.us/texreg/pdf/backview/0521/0521is.pdf), implementing the area’s 

contingency measures for failure to attain the 1997 eight-hour ozone standard by the June 15, 

2010, deadline. 
1-7 

Concurrent with this AD SIP revision, the commission is adopting revised and new RACT 

requirements to address the following control techniques guidelines (CTG) documents issued by 

the EPA from 2006 through 2008 (Rule Project Number 2010-016-115-EN): Flexible Package 

Printing; Industrial Cleaning Solvents; Large Appliance Coatings; Metal Furniture Coatings; 

Paper, Film, and Foil Coatings; Miscellaneous Industrial Adhesives; Miscellaneous Metal and 

Plastic Parts Coatings; and Auto and Light-Duty Truck Assembly Coatings. Concurrent with this 

AD SIP revision, the commission is also adopting revised and new RACT requirements for VOC

storage tanks (Rule Project Number 2010-025-115-EN).

This attainment demonstration includes an MVEB for 2012 that represents the on-road mobile 

source emissions that have been modeled for the attainment demonstration. The DFW area's 

metropolitan planning organization must demonstrate that the estimated emissions from 

transportation plans, programs, and projects do not exceed the MVEB. Additionally, this plan 

demonstrates that by 2012, the DFW area will meet other serious nonattainment area 

requirements, including an enhanced Inspection and Maintenance Program (which has already 

been implemented in all nine counties), Stage II vapor recovery systems at gas stations (which 

has already been implemented in Collin, Dallas, Denton, and Tarrant Counties) or widespread 

onboard refueling vapor recovery, a Clean Fuel Fleet Program (which is not required if 

emissions reductions from the National Low-Emissions Vehicle Program are more than what 

would be achieved under such a program), TCMs (which have already been implemented in all 

nine counties, and enhanced monitoring (which will be in place by June 15, 2013, the attainment 

deadline). 

The EPA officially released the Motor Vehicle Emission Simulator (MOVES) model as a 

replacement to MOBILE6.2 for SIP applications on March 2, 2010. Since the MOVES model was 

released several months after on-road inventory development work had to begin for this AD SIP 

revision, its use is not required based on EPA’s MOVES3

1.2.5 2008 and 2010 Ozone Standards 

policy guidance. However, the 

commission has included MOVES2010a (the latest version of the MOVES model) on-road 

emission inventory estimates in this AD SIP revision based on the model’s technical superiority 

to MOBILE6.2, consistency with future conformity determinations, and comments received on 

the proposed AD SIP revision. 

On March 12, 2008, the EPA lowered the primary and secondary eight-hour ozone standards to 

0.075 ppm. The governor recommended to the EPA in March 2009 that 10 counties in the DFW 

area (those counties already designated as part of the DFW 1997 eight-hour ozone standard 

nonattainment area and Hood County) be designated as a nonattainment area for the 2008 

eight-hour ozone standard. In September 2009, the EPA announced that it intended to 

reconsider the 2008 ozone standard. On January 19, 2010, the EPA proposed revisions in the 

Federal Register (75 FR 2938) to strengthen the primary eight-hour ozone standard in the 

range of 0.060 to 0.070 ppm. The EPA also proposed to establish a separate cumulative, 

seasonal secondary standard within a range of 7 to 15 ppm-hours. The EPA had originally 

intended to finalize the reconsidered ozone standard in August 2010, but rescheduled 

promulgation of the final standards to July 2011. On September 2, 2011, the President

announced that he requested the EPA withdraw the proposed reconsidered ozone standard. The 

EPA announced on September 22, 2011, it will be taking action on the 2008 ozone NAAQS, and 

area designations are expected to be complete by mid 2012. 

 

3 Additional information on the EPA’s MOVES policy guidance is available at 

http://www.epa.gov/otaq/models/moves/420b09046.pdf. 
1-8 

1.3 HEALTH EFFECTS

In 1997, the EPA revised the NAAQS for ozone from a one-hour to an eight-hour standard. To 

support the 1997 eight-hour ozone standard, the EPA provided information indicating that 

negative health effects can occur at levels lower than the previous standard and at exposure 

times longer than one hour. High concentrations of one-hour ozone were not shown to correlate 

well with mortality. Exposure to relatively high levels of ozone can aggravate asthma in some 

people. Repeated exposures to high levels of ozone can make people more susceptible to 

respiratory infection and lung inflammation and can aggravate preexisting respiratory diseases, 

such as bronchitis and emphysema.

Children are at a relatively higher risk from exposure to ozone when compared to adults, since 

they breathe more air per pound of body weight than adults and because children’s respiratory 

systems are still developing. Children also spend a considerable amount of time outdoors during 

summer and during the start of the school year (August through October) when high ozone 

levels are typically recorded. Adults most at risk to ozone exposure are people working or 

exercising outdoors and individuals with preexisting respiratory diseases.

1.4 STAKEHOLDER PARTICIPATION AND PUBLIC HEARINGS

1.4.1 TCEQ SIP and Control Strategy Development Stakeholder Meetings 

The TCEQ held an open-participation DFW 1997 Eight-Hour Ozone SIP Stakeholder Group 

meeting to discuss concepts for potential control strategies for the nine-county DFW ozone 

nonattainment area, to hear the public’s ideas on potential ozone control measures, and to 

provide the public an overview of the development of this DFW AD SIP revision. The meeting 

was held on June 24, 2010, at the Arlington City Council Chambers. In the meeting, the TCEQ 

presented attendees with an update on the DFW AD SIP revision timeline, an update on 

modeling efforts, and a draft list of potential control strategy concepts for stationary, area, and 

mobile sources. Additional information is available on the DFW Eight-Hour Ozone SIP 

Stakeholder Group Web site (http://www.tceq.texas.gov/airquality/sip/dfw_stakeholder_2.

html). 

1.4.2 Dallas-Fort Worth Photochemical Modeling Technical Committee

The Dallas-Fort Worth Photochemical Modeling Technical Committee (DFW PMTC) is a TCEQ 

advisory group organized to assist the agency in addressing technical and scientific issues 

relating to air quality modeling for the Dallas-Fort Worth (DFW) area. The committee includes 

representatives from industry, county and city government, environmental groups, and the 

public. The DFW PMTC holds meetings to share and discuss technical issues related to the 

photochemical modeling of air quality. Meeting notifications, agendas, and pertinent materials 

from those meetings will be available on the DFW Photochemical Modeling Technical 

Committee Web site (http://www.tceq.texas.gov/airquality/airmod/committee/pmtc_dfw. 

html).
1-9 

1.5 PUBLIC HEARING AND COMMENT INFORMATION

The public comment period opened on June 24, 2011, and was originally scheduled to close on 

July 25, 2011; however, the comment period was extended to August 8, 2011. The extension was

granted to allow the public 30 days to review and comment on supplemental information4

concerning on-road mobile source emissions inventories based on MOVES2010a. Notice of 

public hearings for this AD SIP revision was published in the Texas Register and various 

newspapers. Written comments were accepted via mail, fax, and through the eComments system

(http://www5.tceq.state.tx.us/rules/ecomments). 

The commission conducted public hearings in Arlington on July 14, 2011, at 10:00 a.m. and 6:30 

p.m., and in Austin on July 22, 2011, at 2:00 p.m. During the comment period, which closed on 

August 8, 2011, the commission received comments concerning the DFW attainment 

demonstration AD SIP revision from Barnett Shale Energy Education Council, COPPs for Clean 

Air, Commissioners Court of Denton County, Downwinders at Risk, Earthworks Oil and Gas 

Accountability, Fort Worth Regional Concerned Citizens, KIDS for Clean Air, Lone Star Chapter 

of the Sierra Club, North Central Texas Council of Governments (NCTCOG), North Texas Clean 

Air Steering Committee, Regional Transportation Council of the NCTCOG, State Representative 

Lon Burnham, Texas Pipeline Association, the EPA, and 393 individuals. Summaries of public 

comments and TCEQ responses are included as part of this AD SIP revision.

An electronic version of the AD SIP revision and appendices can be found at the TCEQ’s Texas 

State Implementation Plan Web page (http://www.tceq.texas.gov/airquality/sip/texas-sip).

1.6 SOCIAL AND ECONOMIC CONSIDERATIONS

For a detailed explanation of the social and economic issues involved with any of the measures, 

please refer to the preambles that precede each rule package accompanying this AD SIP

revision. 

1.7 FISCAL AND MANPOWER RESOURCES 

The state has determined that its fiscal and manpower resources are adequate and will not be 

adversely affected through the implementation of this plan.

 

4 The supplemental information was released on July 8, 2011, and is contained in Appendix J: On-Road 

Emissions Supplement to the Proposed Dallas-Fort Worth Attainment Demonstration State 

Implementation Plan Revision for the 1997 Eight-Hour Ozone Standard Nonattainment Area of this SIP 

revision.
2-1 

CHAPTER 2: ANTHROPOGENIC EMISSIONS INVENTORY (EI) DESCRIPTION 

2.1 INTRODUCTION

The 1990 Federal Clean Air Act Amendments require that attainment demonstration emissions 

inventories (EIs) be prepared for ozone nonattainment areas. Ozone is produced in the 

atmosphere when volatile organic compounds (VOC) are mixed with nitrogen oxides (NOX) in 

the presence of sunlight. The Texas Commission on Environmental Quality (TCEQ) maintains 

an EI of up-to-date information on NOX and VOC sources. The EI identifies the types of 

emissions sources present in an area, the amount of each pollutant emitted, and the types of 

process and control devices employed at each plant or source category. The EI provides data for 

a variety of air quality planning tasks, including establishing baseline emission levels, 

calculating emission reduction targets, control strategy development for reducing emissions, 

emission inputs into air quality simulation models, and tracking actual emissions. These EIs are 

critical for the efforts of state, local, and federal agencies to demonstrate attainment of the 

National Ambient Air Quality Standards.

This chapter discusses general EI development for each of the anthropogenic source categories. 

Chapter 3: Photochemical Modeling details specific EIs and emissions inputs developed for the 

Dallas-Fort Worth (DFW) area ozone photochemical modeling. 

2.2 POINT SOURCES

Stationary point source emissions data are collected annually from sites that meet the reporting 

requirements of 30 Texas Administrative Code (TAC) §101.10. These sites include, but are not 

limited to, refineries, chemical plants, bulk terminals, and utilities. To collect the data, the TCEQ 

mailed EI questionnaires (EIQs) to all sites identified as meeting the reporting requirements. 

Companies were required to report emissions data and to provide sample calculations used to 

determine the emissions. Information characterizing the process equipment, the abatement 

units, and the emission points was also required. All data submitted in the EIQ were reviewed 

for quality assurance purposes and then stored in the State of Texas Air Reporting System 

database. At the end of the annual reporting cycle, point source emissions data are reported 

each year to the United States Environmental Protection Agency (EPA) for inclusion in the 

National Emissions Inventory (NEI).

2.3 AREA SOURCES

Stationary sources that do not meet the reporting requirements for point sources are classified 

as area sources. Area sources are small-scale industrial, commercial, and residential sources that 

use materials or perform processes that generate emissions. Area sources can be characterized 

by the mechanism in which emissions are released into the atmosphere: evaporative or 

combustion. Evaporative emission sources include the following: oil and gas production 

facilities, printing processes, industrial coating and degreasing operations, gasoline service 

station underground tank filling, and vehicle refueling operations. Combustion sources include 

the following: oil and gas production facilities, stationary source fossil fuel combustion at 

residences and businesses, outdoor burning, structural fires, and wildfires. 

Emissions are calculated as county-wide totals rather than as individual facilities. The emissions 

from area sources may be calculated by applying an EPA-established emission factor (emissions 

per unit of activity) to the appropriate activity or activity surrogate responsible for generating 

emissions. Examples of activity or activity surrogate data include the following: population,

crude oil and gas production, the amount of gasoline sold in an area, employment by industry 

type, and acres of crop land. The activity data are obtained via surveys, research, and/or 
2-2 

investigations. The air emissions data from the different area source categories are collected, 

reviewed for quality assurance, stored in the Texas Air Emissions Repository database system, 

and compiled to develop the statewide area source EI. This area source periodic emissions 

inventory (PEI) is reported every third year (triennially) to the EPA for inclusion in the NEI. The 

TCEQ submitted the most recent PEI for calendar year 2008.

2.4 NON-ROAD MOBILE SOURCES

Non-road mobile sources include vehicles, engines, and equipment used for construction, 

agriculture, transportation, recreation, and many other purposes. Non-road vehicles are also 

referred to as off-road or off-highway vehicles that do not normally operate on roads or 

highways. This broad category is composed of a diverse collection of machines, many of which 

are powered by diesel engines. Examples of non-road mobile sources include, but are not limited 

to: agricultural equipment, commercial and industrial equipment, construction and mining 

equipment, lawn and garden equipment, aircraft, locomotives, and commercial marine vessels.

A Texas specific version of the EPA NONROAD 2008a model, called the Texas NONROAD 

(TexN) model, was used to calculate emissions from all non-road mobile equipment and 

recreational vehicles except aircraft, ground support equipment, and locomotives. While the 

TexN model utilizes input files and post-processing routines to estimate Texas specific 

emissions estimates, it retains the EPA NONROAD 2008a model to conduct the basic emissions 

estimation calculations. Several input files provide necessary information to calculate and 

allocate emission estimates. The inputs used in the TexN model include emission factors, base 

year equipment population, activity, load factor, meteorological data, average lifetime, 

scrappage function, growth estimates, emission standard phase-in schedule, and geographic and 

temporal allocation. 

Emissions for the source categories that are not in the EPA NONROAD 2008a model are 

estimated using other EPA-approved methods and guidance documents. Airport emissions are 

calculated using the Federal Aviation Administration’s Emissions and Dispersion Modeling 

System, version 5.1. Locomotive emission estimates for Texas are based on specific fuel usage 

data derived from railway segment level gross ton mileage activity (line haul locomotives) and 

hours of operation (yard locomotives) provided directly by the Class I railroad companies 

operating in Texas. 

2.5 ON-ROAD MOBILE SOURCES

On-road mobile sources consist of passenger cars, passenger trucks, motorcycles, buses, heavyduty trucks, and other motor vehicles traveling on public roadways. Combustion-related 

emissions are estimated for vehicle engine exhaust, and evaporative hydrocarbon emissions are 

estimated for the fuel tank and other non-tailpipe sources from the vehicle. To calculate

pollution from on-road mobile sources, emission rates are estimated as a function of county, 

vehicle type, roadway type, hour, and operating speed. These rates are then matched with 

appropriate activity from transportation data sources such as vehicle miles traveled (VMT), 

number of vehicles parked, hours spent in extended idle mode, etc.

Emission factors were developed using the latest version of the EPA's on-road model, which is 

the Motor Vehicle Emissions Simulator 2010a (MOVES2010a). Various inputs are provided to

MOVES2010a to simulate the vehicle fleet in each nonattainment area such as vehicle speeds, 

vehicle age distributions, local meteorological conditions, type of Inspection and Maintenance 

Program, and local fuel properties. Separate gasoline and diesel fuel emission factors are 

developed for the thirteen MOVES2010a vehicle types. 
2-3 

For major metropolitan areas, the primary source of vehicle activity is typically the local travel 

demand model (TDM), which is run by the Texas Transportation Institute (TTI), the Texas 

Department of Transportation (TxDOT), or the regional metropolitan planning organization

(MPO). For the Dallas-Fort Worth Attainment Demonstration State Implementation Plan 

(SIP) Revision for the 1997 Eight-Hour Ozone Standard, the TCEQ contracted with the North 

Central Texas Council of Governments (NCTCOG) to develop the on-road mobile source 

emission inventories. The DFW TDM has been validated using a large number of traffic counts

collected in the area by TxDOT. In accordance with federal guidelines, VMT estimates from the 

DFW area TDM are calibrated to outputs from the Highway Performance Monitoring System

(HPMS). VMT is allocated to the appropriate vehicle types based on roadside classification 

counts collected in the local area by TxDOT. Prior to matching the VMT estimates with 

MOVES2010a emission rates, hourly operating speeds for each roadway segment are postprocessed from the TDM output based on vehicle volume-to-capacity ratios.

2.6 EI IMPROVEMENT

The TCEQ EI reflects years of emissions data improvement, including extensive point and area 

source inventory reconciliation with ambient emissions monitoring data. The following projects 

have significantly improved the DFW point source and area source inventory.

• Houston Advanced Research Center project H51C identified thousands of tons of VOC flash 

emissions from upstream oil and gas operations in the DFW area, which the TCEQ added to 

the area source inventory. 

• TCEQ Work Order Nos. 582-7-84003-FY-10-26 and 582-7-84005-FY-10-29 quantified 

nitrogen oxides (NOX) and volatile organic compounds (VOC) emissions from various oil 

and gas processes and produced water storage tanks at upstream oil and gas operations in 

the DFW area, which the TCEQ has added to the area source inventory. 

• The TCEQ conducted the first phase of a special inventory of companies that own or operate 

leases or facilities associated with Barnett Shale oil and gas operations. The TCEQ conducted 

the special emissions inventory under the authority of 30 TAC §101.10(b)(3) to determine 

the location, number, and type of emission sources associated with upstream and midstream 

oil and gas operations in the Barnett Shale. The results of the first phase were used to 

improve the compressor engine population profile in the DFW area. This improved profile 

was used in determining the area source emissions estimates for this source category. This 

inventory was the first phase of a planned two-phase special inventory. The second phase of 

this special inventory requested companies with 2009 production or transmission of oil or 

gas from the Barnett Shale formation to complete standardized forms detailing source 

emissions data, source location, information on receptors located within one-quarter mile of 

a source, and authorization information. For more information on phase two of this 

inventory, see Chapter 6: Ongoing Initiatives, Section 6.2.1: Barnett Shale Special 

Emissions Inventory. 

In addition to these projects, the TCEQ Emissions Inventory Guidelines (RG-360A), a 

comprehensive guidance document that explains all aspects of the point source EI process, is 

updated and published annually. The latest version of this document is available on the TCEQ’s 

Point Source Emissions Inventory Web site 

(http://www.tceq.state.tx.us/implementation/air/industei/psei/psei.html). Currently, six 

technical supplements provide detailed guidance on determining emissions from potentially 

underreported VOC emissions sources such as cooling towers, flares, and storage tanks. 
3-1 

CHAPTER 3: PHOTOCHEMICAL MODELING

3.0 INTRODUCTION

This chapter describes modeling conducted in support of the Dallas-Fort Worth (DFW) 

Attainment Demonstration (AD) State Implementation Plan (SIP) Revision for the 1997 EightHour Ozone Standard. The DFW ozone nonattainment area consists of Collin, Dallas, Denton, 

Ellis, Johnson, Kaufman, Parker, Rockwall, and Tarrant Counties. The 1990 Federal Clean Air 

Act Amendments require that attainment demonstrations be based on photochemical grid 

modeling or any other analytical methods determined by the United States Environmental 

Protection Agency (EPA) to be at least as effective. The EPA’s April 2007 “Guidance on the Use 

of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, 

PM2.5, and Regional Haze” (EPA, 2007; hereafter referred to as “modeling guidance”) 

recommends procedures for air quality modeling for attainment demonstrations of the eighthour ozone National Ambient Air Quality Standard (NAAQS).

The modeling guidance recommends several qualitative methods for preparing attainment 

demonstrations that acknowledge the limitations and uncertainties of photochemical models 

when used to project ozone concentrations into future years. First, the modeling guidance 

recommends using model results in a relative sense and applying the model response to the 

observed ozone data. Second, the modeling guidance recommends using available air quality, 

meteorology, and emissions data to develop a conceptual model for eight-hour ozone formation 

and to use that analysis in episode selection. Third, the modeling guidance recommends using 

other analyses, i.e., weight of evidence, to supplement and corroborate the model results and 

support the adequacy of a proposed control strategy package.

The 1990 FCAA amendments established five classifications for ozone nonattainment areas 

based on the magnitude of the regional one-hour ozone design value. Based on the monitored 

one-hour ozone design value at that time, four counties in the DFW area (Collin, Dallas, Denton, 

and Tarrant) were classified as a moderate nonattainment area. As published in the October 16, 

2008, edition of the Federal Register (FR), the EPA determined the four-county DFW area to be 

in attainment of the one-hour ozone standard based on 2004 through 2006 monitored data (73 

FR 61357).

With the change of the ozone NAAQS from a one-hour standard to an eight-hour standard in 

2004, the EPA classified the DFW area as a moderate ozone nonattainment area with an 

attainment date of June 15, 2010. Five additional counties (Ellis, Johnson, Kaufman, Parker, 

and Rockwall) were added to the four original one-hour standard nonattainment counties to 

create the nonattainment area for the 1997 eight-hour standard. Ozone AD SIP revisions 

addressing the 1997 eight-hour ozone standard were required to be submitted to the EPA by 

June 15, 2007. In May 2007, photochemical modeling and other analyses conducted by the 

Texas Commission on Environmental Quality (TCEQ) were included in the AD SIP revision 

submitted to the EPA supporting the DFW area’s attainment of the eight-hour ozone standard 

by June 15, 2010. The EPA published final conditional approval of the May 2007 DFW AD SIP 

Revision on January 14, 2009 (74 FR 1903).

In 2009, the monitored design value (complete ozone season prior to the attainment date) for 

the DFW area was 86 parts per billion (ppb), 2 ppb above the attainment level. The EPA 

published the final rule to determine the DFW area’s failure to attain the 1997 eight-hour ozone 

standard and reclassify the DFW area as a serious nonattainment area on December 10, 2010 

(75 FR 79302). The attainment date for the serious classification is June 15, 2013. The EPA has 
3-2 

prescribed that the attainment test be applied to the 2012 previous ozone season to determine 

compliance with the 2013 attainment date. 

This AD SIP revision uses photochemical modeling in combination with corroborative analyses 

to support a conclusion that the DFW nine-county nonattainment area will attain the 0.08 parts 

per million (ppm) 1997 eight-hour ozone standard by June 15, 2013. Also, the limited data 

collected in the DFW area during Texas Air Quality Study 2006 (TexAQS II) is used to evaluate 

the model’s performance and to improve understanding of the physical and chemical processes 

leading to ozone formation.

3.1 OVERVIEW OF THE OZONE PHOTOCHEMICAL MODELING PROCESS

The modeling system is composed of a meteorological model, several emissions processing 

models, and a photochemical air quality model. The meteorological and emissions models 

provide the major inputs to the air quality model. 

Ozone is a secondary pollutant; it is not generally emitted directly into the atmosphere. Ozone is 

created in the atmosphere by a complex set of chemical reactions between sunlight and several 

primary (directly emitted) pollutants. The reactions are photochemical and require ultraviolet 

energy from sunlight. The majority of primary pollutants directly involved in ozone formation 

fall into two groups, nitrogen oxides (NOX) and volatile organic compounds (VOC). In addition, 

carbon monoxide (CO) is also an ozone precursor, but much less effective than either NOX or 

VOC in forming ozone. As a result of these multiple factors, higher concentrations of ozone are 

most common during the summer with concentrations peaking during the day and falling 

during the night and early morning hours.

Ozone chemistry is complex, involving hundreds of chemical compounds and chemical 

reactions. As a result, ozone cannot be evaluated using simple dilution and dispersion 

algorithms. Due to this chemical complexity, the modeling guidance strongly recommends using 

photochemical computer models to simulate ozone formation and evaluate the effectiveness of 

future control strategies. Computer simulations are the most effective tools to address both the 

chemical complexity and the future case evaluation.

3.2 OZONE MODELING

Ozone modeling involves two major phases, the base case modeling phase and the future year 

modeling phase. The purpose of the base case modeling phase is to evaluate the model’s ability 

to adequately replicate measured ozone and ozone precursor concentrations during recent 

periods with high ozone concentrations. The purpose of the future year modeling phase is to 

predict attainment year ozone design values at each monitor and to evaluate the effectiveness of 

controls in reaching attainment. The TCEQ developed a modeling protocol describing the 

process to be followed to evaluate the ozone in the urban area and submitted the plan to the EPA 

as prescribed in the modeling guidance.

3.2.1 Base Case Modeling

Base case modeling involves several steps. First, recent ozone episodes are analyzed to 

determine what factors were associated with ozone formation in the area and whether those 

factors were consistent with the conceptual model and the EPA’s episode selection criteria. Once 

an episode is selected, emissions and meteorological data are generated and quality assured. 

Then the meteorological and emissions (NOX, VOC, and CO) data are input to the photochemical 

model and the ozone photochemistry is simulated, resulting in predicted ozone and ozone 

precursor concentrations.
3-3 

Base case modeling results are evaluated by comparing them to the observed measurements of 

ozone and ozone precursors. Typically this step is an iterative process incorporating feedback 

from successive evaluations to ensure that the model is adequately replicating observations 

throughout the modeling episode. The adequacy of the model in replicating observations is 

assessed based on compliance with statistical and graphical measures as recommended in the 

modeling guidance. Additional analyses using special study data are included when available. 

Satisfactory performance of the base case modeling provides a degree of reliability that the 

model can be used to predict future year ozone concentrations (future year design values), as 

well as to evaluate the effectiveness of possible control measures.

3.2.2 Future Year Modeling

Future year modeling involves several steps. The procedure for predicting a future year ozone 

design value (attainment test) involves determining the ratio of the future year to the baseline 

year modeled ozone concentrations. This ratio is called the relative response factor (RRF). 

Whereas the emissions data for the base case modeling are episode-specific, the emissions data 

for the baseline year are based on typical ozone season emissions. Similarly, the emissions data 

for the future year are developed applying growth and control factors to the baseline year 

emissions. The growth and control factors are developed based on the projected growth in the 

demand for goods and services and the reduction in emissions expected from state, local, and 

federal control programs.

Both the baseline and future years are modeled using their respective ozone season emissions 

and the base case episode meteorological data as inputs. The same meteorological data are used 

for modeling both the baseline and future years, and thus, the ratio of future year modeled 

ozone concentrations to the baseline year concentrations provides a measure of the response of 

ozone concentrations to the change in emissions from projected growth and controls. 

A future year ozone design value is calculated by multiplying the RRF by a baseline year ozone 

design value (DVB). The DVB is the average of the regulatory design values for the three 

consecutive years containing the baseline year (see Figure 3-1: 2006 Baseline Design Value 

Calculation). A calculated future year ozone design value of less than or equal to 0.08 ppm (84 

ppb) signifies modeled attainment. When the calculated future year ozone design value is 

greater than 84 ppb, additional controls may be needed and the model can be used to test the 

effectiveness of various control measures in developing a control strategy.
3-4 

Figure 3-1: 2006 Baseline Design Value Calculation

3.3 EPISODE SELECTION

3.3.1 EPA Guidance for Episode Selection

The primary criteria for selecting ozone episodes for eight-hour ozone attainment 

demonstration modeling is set forth in the modeling guidance and shown below:

• Select periods reflecting a variety of meteorological conditions that frequently correspond to 

observed eight-hour daily maximum ozone concentrations greater than 84 ppb at different 

monitoring sites.

• Select periods during which observed eight-hour ozone concentrations are close to the eighthour ozone design values at monitors with a DVB greater than or equal to 85 ppb.

• Select periods for which extensive air quality/meteorological data sets exist.

• Model a sufficient number of days so that the modeled attainment test can be applied at all 

of the ozone monitoring sites that are in violation of the NAAQS.

3.3.2 DFW Ozone Episode Selection Process 

An episode selection analysis was performed to identify time periods with eight-hour ozone 

exceedance days that met the primary selection criteria. The short time frame available to 

develop this modeling demonstration necessitated reviewing the applicability of ozone episodes 

that the TCEQ recently modeled or analyzed. Six high eight-hour ozone episodes from 2005 and 

2006 were modeled from TexAQS II for the most recent Houston-Galveston-Brazoria (HGB) AD 

(TCEQ, 2010). These periods were investigated first since much of the meteorological and 

emissions inventory data can be leveraged to the DFW area. The extensive monitoring data 

collected during TexAQS II, including data from radar wind profilers, make these periods even 

more attractive.

Table 3-1: DFW Eight-Hour Ozone Exceedance Data during TexAQS II Modeling Episodes

shows the episodes modeled for the HGB attainment demonstration adopted in 2010 by the 

TCEQ, as well as one additional episode, the extended June 2006 period. The table also shows 
3-5 

the maximum eight-hour ozone exceedance in the DFW area for each episode. There were more 

days with more monitors above the eight-hour ozone standard in the June periods in 2005 and 

2006 in the DFW nonattainment area than in any of the other episodes. Additional special study 

monitors were installed just prior to June 2006, along with radar wind profilers, which are 

important for meteorological modeling performance (Knoderer and MacDonald, 2007).

Table 3-1: DFW Eight-Hour Ozone Exceedance Data during TexAQS II Modeling 

Episodes

Episode Dates Days ≥ 

85 ppb

Max eight-hour

O3 (ppb) in DFW

2005ep0 May 19 - Jun 3, 2005 4 101

2005ep1 Jun 17 - 30, 2005 9 117

2005ep2 Jul 26 - Aug 8, 2005 6 115

2006ep0 May 31 - Jun 15, 2006 11 107

2006ep0ext* May 31 - Jul 2, 2006 17 107

2006ep1a Aug 13 - Sep 15, 2006 6 102

2006ep1b Sep 16 - Oct 11, 2006 0 81

*2006ep0ext not modeled for Houston

In 2008, the Austin and San Antonio areas optimized the TCEQ meteorological modeling setup 

of the June 2006 episode with alternative physics options to be more representative of noncoastal Texas. The modeling period was also extended to July 2, 2006, to include additional 

exceedance days, of which there were 17 with maximum eight-hour ozone concentrations in 

excess of 84 ppb in the DFW area (Emery et al., 2009a). Based on these results the TCEQ 

focused on the extended June episode (2006ep0ext), improving model performance for the 

DFW area and central Texas (Emery et al., 2009b).

Figure 3-2: Eight-Hour Ozone Exceedance Days in DFW shows the frequency distribution of 

days with measured daily maximum eight-hour ozone concentrations greater than 84 ppb for 

the period 1991 through 2010. The distribution for the DFW area is bi-modal with peaks in the 

frequency of exceedance days, one peak occurs in late spring, and another in summer.
3-6 

Figure 3-2: Eight-Hour Ozone Exceedance Days in DFW

The extended June 2006 episode is the focus of episode development because of the number of 

ozone exceedances, availability of special-study monitoring data, availability of existing highquality modeling databases, and the variety of meteorological conditions. 

3.3.3 Summary of the Extended June 2006 Episode

Table 3-2: DFW Monitor-Specific Eight-Hour Ozone Data During the Extended June 2006 

Episode) shows that each of these key monitors (see Figure 3-3: DFW Monitor Map) has at least 

eight days with an eight-hour concentration of 85 ppb during the 33 day episode. While these 

key monitors did not observe ten days with ozone measured in excess of 85 ppb, they did 

measure almost twenty days of eight-hour concentrations of 70 ppb or greater, which can be 

used for the RRF calculation. All but the Greenville monitor (C1006) had at least 10 days at 70 

ppb or above, although its northeast location is not in the typical path of high ozone. 
3-7 

Figure 3-3: DFW Monitor Map

Table 3-2: DFW Monitor-Specific Eight-Hour Ozone Data During the Extended 

June 2006 Episode

Site Monitor Max 8-hour

Ozone (ppb)

Days ≥ 

90 ppb

Days ≥

85 ppb

Days ≥

70 ppb

Site-specific 

Baseline Design 

Value (ppb)

EMTL Eagle Mountain Lake 

C75 107 5 8 18 93.3

DENT Denton Airport South 

C56 106 5 9 17 93.3

KELC Keller C17 103 4 8 19 91.0

GRAP Grapevine Fairway C70 95 3 5 14 90.7

FWMC Ft. Worth Northwest 

C13 101 5 8 17 89.3

WTFD Parker County C76 101 3 5 15 87.7

FRIC Frisco C31 94 1 7 14 87.7

CLEB Cleburne Airport C77 98 2 2 15 85.0

REDB Dallas Exec. Airport C402 91 1 2 17 85.0

DALN Dallas North No.2 C63 86 0 2 12 85.0
3-8 

Site Monitor Max 8-hour

Ozone (ppb)

Days ≥ 

90 ppb

Days ≥

85 ppb

Days ≥

70 ppb

Site-specific 

Baseline Design 

Value (ppb)

ARLA Arlington Municipal 

Airport C61 91 1 3 11 83.3

GRAN+ Granbury C73 92 2 3 12 83.0

DHIC Dallas Hinton St. C401 84 0 0 14 81.7

RKWL Rockwall Heath C69 78 0 0 11 77.7

GRVL+ Greenville C1006 78 0 0 8 75.0

KAUF Kaufman C71 78 0 0 11 74.7

PIPT# Pilot Point C1032 101 4 9 14 81.0#

MDLT# Midlothian Tower C94 98 1 2 14 80.5#

MDLO# Midlothian OFW C52 96 1 1 11 77.7#

ITHS*# Italy High School C650 89 0 1 10 NA#

Values are sorted in descending order of monitor-specific baseline design values. # PIPT, MDLT, and MDLO did not measure enough data from 2004 through 2008 to calculate a complete DVB. The 

DVB shown uses all available data.

* Italy High School C650 was a non-regulatory monitor (deactivated 11/07/2006).

+ Granbury C73 and Greenville C1006 are outside the 1997 eight-hour ozone NAAQS DFW nonattainment area.

The 2010 Dallas-Fort Worth Conceptual Model, Appendix D: Conceptual Model for the DFW 

Attainment Demonstration SIP Revision for the 1997 Eight-Hour Ozone Standard, describes 

the general meteorological conditions that are typically present on days when the eight-hour 

ozone concentration exceeds the 1997 eight-hour ozone NAAQS. High ozone is typically formed 

in the DFW area on days with slower wind speeds out of the east and southeast. These prevailing 

winds also typically bring higher background ozone levels into the DFW area. High background 

ozone concentrations are then amplified as an air mass moves over the urban core of Dallas and 

Tarrant Counties, both of which contain large amounts of NOX emissions. Those emissions are 

then transported across the DFW area to the northwest, where the highest eight-hour ozone 

concentrations are observed.

The 2006 modeling episode showed that these conditions were present on the high ozone days. 

High pressure developed over the area from June 5 through June 10, which resulted in mostly 

sunny days with high temperatures above 90 degrees Fahrenheit. High pressure also caused 

winds that were calm or light out of the southeast. With light winds a gradual buildup of ozone 

and ozone precursors developed over the Dallas – Fort Worth nonattainment area, peaking in 

an eight-hour ozone concentration of 106 ppb at the Eagle Mountain Lake (C75) and Denton 

Airport South (C56) monitor sites on June 9 (see Figure 3-4: June 2006 Episode Eight-Hour 

Ozone by Monitor). 
3-9 

Figure 3-4: June 2006 Episode Eight-Hour Ozone by Monitor

High pressure began to erode away as a weak frontal boundary approached from the north. As 

wind speeds increased over the area, causing ozone dilution and lowering the eight-hour ozone 

concentrations over the area. As winds switched directions and began blowing from the eastnortheast on the backside of the frontal boundary, ozone concentrations again increased. Winds 

from the east-northeast have the potential for long range transport from the direction of the 

Ohio River Valley. Transport from the east-northeast likely contributed to an eight-hour ozone 

concentration of 107 ppb at the Eagle Mountain Lake (C75) monitor site on June 14. Over the 

next few days, low pressure moved in to the area from the Gulf of Mexico. This low pressure 

caused an increase in cloudiness and wind speed, which reduced the potential for ozone 

formation. High pressure returned to the area from June 27 through June 30. With the resultant

high temperatures and low wind speeds, conditions were again favorable for ozone formation.

Back trajectories from the Eagle Mountain Lake (C75) monitor extending backwards in time for 

48 hours and terminating at 500 meters above ground level (AGL) are shown for every day of 

the extended June 2006 episode in Figure 3-5: Daily 48-Hour Back Trajectories from DFW 

(May 31 through June 15, and June 16 through July 2, 2006). The left panel shows the May 31 

through June 15, 2006, period while the right panel shows the June 16 through July 2, 2006, 

period. The trajectories depict air coming from north, east, and southerly directions. Westerly 

winds are not common during the summer months in the DFW area, thus, there are no 

trajectories coming from the west to northwest (see Appendix D: Conceptual Model for the DFW 

Attainment Demonstration SIP Revision for the 1997 Eight-Hour Ozone Standard). These 

trajectories illustrate that the extended June 2006 episode includes periods of synoptic flow 

from each of the directions commonly associated with high eight-hour ozone concentrations as 

described in the DFW conceptual model.
3-10

Figure 3-5: Daily 48-Hour Back Trajectories from DFW (May 31 through June 15, 

and June 16 through July 2, 2006)

3.4 METEOROLOGICAL MODEL

The TCEQ is using the Fifth Generation Meteorological Model (MM5, version 3.7.3) developed 

jointly by the National Center for Atmospheric Research (NCAR) and Pennsylvania State 

University (Grell et al., 1994). This model, supported by a broad user community including the 

Air Force Weather Agency, national laboratories, and academia, is being used extensively for 

regulatory air quality modeling analyses throughout the United States.

3.4.1 Modeling Domains

MM5 was configured with three two-way nested outer grids (108 kilometer (km), 36 km, and 12 

km horizontal resolution) to cover the United States and regional areas of interest. A one-way 

nested 4 km fine grid covering the eastern half of Texas was used, as shown in Figure 3-6: MM5 

Modeling Domains. The extent of each of the MM5 modeling domains was selected to 

accommodate the embedding of the commensurate air quality modeling domains (see Section 

3.6 Photochemical Modeling).

Vertically, MM5 is structured with 43 layers from the surface to approximately 20 km (Figure 

3-7: MM5 Vertical Layer Structure). Twenty layers are within the first 3,000 meters in order to 

resolve boundary layer phenomena. The same MM5 vertical layering structure is used for all of 

the domains.
3-11

Figure 3-6: MM5 Modeling Domains

Table 3-3: MM5 Modeling Domain Definitions

Domain Easting Range (km) Northing Range (km) East/West 

Grid Points

North/South 

Grid Points

108 km (-2808, 2808) (-2268, 2268) 53 43

36 km (-1296, 2160) (-1728, 972) 97 76

12 km (-648, 1080) (-1548, -360) 145 100

4 km (72, 372) (-1380, -648) 166 184
3-12

Figure 3-7: MM5 Vertical Layer Structure

3.4.2 Meteorological Model Configuration

Based on past TCEQ modeling efforts, the modeling guidance, support from external experts, 

and other demonstrations including sensitivity tests and model performance evaluation, the 

MM5 was configured with parameterizations and improved input data to optimize the 

performance of the wind field (i.e., wind speed and direction). Wind speed and direction are the 

most important parameters predicted by the meteorological model for air quality modeling 

purposes because the wind field determines the transport and dispersion of pollutants. The preprocessing of the MM5 input data followed the standard progression using the TERRAIN, 

REGRID, and INTERPF (NCAR, 2005) programs. The NESTDOWN program was used to 

interpolate from the 12 km domain output to the 4 km domain input.

In developing the meteorological modeling of the June 2006 episode for the 2010 HGB 

Attainment Demonstration SIP Revision for the 1997 Eight-Hour Ozone Standard (2009-017-

SIP-NR), the TCEQ focused on parameterizations to improve performance of the coastal wind 

field (TCEQ, 2010). Land use characteristics and sea surface temperatures on all domains were 

updated with high resolution satellite measurements. In 2008, the Austin and San Antonio 

areas optimized the TCEQ meteorological modeling of the June 2006 episode to be more 

representative for central Texas and extended the time period to July 2 (Emery et al., 2009a). 

Model options were chosen to remove spurious convection and improve the performance of the 

wind field through analysis nudging (Stauffer and Seaman, 1990; Stauffer et al., 1991; Stauffer 

and Seaman, 1994) on all domains using the National Center for Environmental Prediction 

(NCEP) North American Model (NAM) gridded output for winds, temperature, and water vapor.

The TCEQ continued this work on the extended June 2006 episode, which resulted in an MM5 

configuration that yielded good performance in the DFW and central Texas areas (Emery et al., 
3-13

2009b). Observational nudging (blending observations with predicted parameters) using 

TexAQS II radar profiler data and one-hour surface analysis nudging improved wind 

performance. Switching from the NOAH (NCEP Oregon State Air Force Hydrological Research 

Laboratory) Land-Surface Model to the five-layer soil model also improved the representation of 

precipitation, temperature, and planetary boundary layer (PBL) depths. 

The TCEQ continued to improve upon the performance of MM5 for the extended June 2006 

episode through a series of sensitivities. The final MM5 parameterization schemes and options 

selected are shown in Table 3-4: June 2006 MM5 Configuration. The selection of these schemes 

and options was based on the previous modeling experiences described above, MM5 community 

use, and features of the ozone episode being modeled.

Table 3-4: June 2006 MM5 Configuration

Domain Nudging Type PBL Cumulus Radiation LandSurface Microphysics

108 and 36 km 3-D and Surface 

Analysis MRF Grell RRTM / Dudhia

5-layer soil 

model Simple Ice

12 km 3-D, Surface 

Analysis, & Obs MRF Grell RRTM / 

Dudhia

5-layer soil 

model Simple Ice

4 km 3-D, Surface 

Analysis, & Obs Eta None RRTM / 

Dudhia

5-layer soil 

model Simple Ice

Notes: PBL = Planetary Boundary Layer; RRTM = Rapid Radiative Transfer Model; MRF = Medium Range Forecast; 

Eta (Mellor and Yamada, 1974)

MM5 output was post-processed using the MM5CAMx version 4.8 utility to convert the MM5 

meteorological fields to the Comprehensive Air Quality Model with Extensions (CAMx) grid and 

input format (Environ, 2010). The MM5CAMx utility was used with the Asymmetric Convective 

Model (ACM2) vertical diffusivity methodology and a minimum vertical diffusivity coefficient 

(Kv) of 1.0. The nocturnal Kvs were also modified on a land-use basis to set the minimum Kv 

within the first 200 vertical meters of the model using the KVPATCH program (Environ, 2005).

The patch was applied to limit the build-up of NOX concentrations in the urban area at night and 

loss of ozone due to titration (Environ, 2011).

The 2010 HGB AD SIP Revision, Appendix A: Meteorological Modeling for the HGB 

Attainment Demonstration SIP Revision for the 1997 Eight-Hour Ozone Standard provides 

details on the development of the satellite-based land-use/land-cover (LULC) and sea surface 

temperature data used in this DFW meteorological modeling (TCEQ, 2010).

3.4.3 MM5 Application and Performance

The final MM5 modeling configuration was applied to the May 28, 2006, 06:00 Coordinated 

Universal Time (UTC) through July 3, 2006, 07:00 UTC period spanning the eight-hour ozone 

episode. 

A detailed performance evaluation of the June 2006 meteorological modeling episode is 

included in Appendix A: Meteorological Modeling for the DFW Attainment Demonstration SIP 

Revision for the 1997 Eight-Hour Ozone Standard of this SIP revision. In addition, all 

performance evaluation products are available on the TCEQ File Transfer Protocol (FTP) site

(ftp://amdaftp.tceq.texas.gov/pub/DFW8H2/mm5).
3-14

As mentioned, the wind speed and direction are deemed to be the most important 

meteorological parameters input to the air quality model. The MM5 modeled wind field was 

evaluated by comparing the hourly modeled and measured wind speed and direction for all 

monitors in the DFW area. Figure 3-8: June 2006 Meteorological Modeling Performance

exhibits the percent of hours for which the average absolute difference between the modeled and 

measured wind speed and direction, for specific monitors and a DFW area average, was within 

the specified accuracy benchmarks (e.g., wind speed difference less than or equal to two meters 

per second (WSPD ≤ 2 m/s)). Table 3-5: DFW Meteorological Modeling Percent Accuracy

provides an additional evaluation of MM5 predictions to stricter benchmarks (Emery et al., 

2001).

Figure 3-8: June 2006 Meteorological Modeling Performance

Notes: WDIR = Wind Direction; WSPD = Wind Speed; TEMP = Temperature

Table 3-5: DFW Meteorological Modeling Percent Accuracy

DFW Area Wind Direction (°) 

Error ≤ 30 / 20 / 10

Wind Speed (m/s) 

Error ≤ 2 / 1 / 0.5 

Temperature (°C) 

Error ≤ 2 / 1 / 0.5

Area Average* 92 / 84 / 63 99 / 85 / 48 92 / 67 / 39

Eagle Mountain Lake 

C75 77 / 67 / 40 93 / 64 / 35 84 / 56 / 29

Denton Airport South 

C56 82 / 70 / 42 81 / 45 / 25 88 / 57 / 31

Dallas North No. 2 C63 83 / 70 / 44 96 / 62 / 32 94 / 79 / 52

Fort Worth NW C13 77 / 67 / 42 96 / 74 / 43 89 / 62 / 36

Weatherford C76 75 / 64 / 37 92 / 63 / 33 85 / 56 / 29

92

77

82 83

77 75

84

80

99

93

81

96 96

92

95

89

92

84

88

94

89

85

88

93

0

10

20

30

40

50

60

70

80

90

100

DFW Average Eagle Mtn

Lake

Denton Dallas N Fort Worth 

NW

Weatherford Frisco Midlothian 

Tower

Percent of Hours within Accuracy Threshold

June 2006 Meteorological Modeling Performance Statistics

WDIR ≤ 30 ° WSPD ≤ 2 m/s TEMP ≤ 2 °C
3-15

DFW Area Wind Direction (°) 

Error ≤ 30 / 20 / 10

Wind Speed (m/s) 

Error ≤ 2 / 1 / 0.5 

Temperature (°C) 

Error ≤ 2 / 1 / 0.5

Frisco C31 84 / 71 / 48 95 / 69 / 38 88 / 55 / 28

Midlothian Tower C94 80 / 62 / 35 89 / 60 / 33 93 / 70 / 40

* Area Average calculated from mean modeled DFW area parameter – mean observed DFW area parameter

3.5 MODELING EMISSIONS

For the stationary emission source types, which consist of point and area sources, routine 

emission inventories provided the major inputs for the emissions modeling processing. 

Emissions from mobile and biogenic sources were derived from relevant emission models. 

Specifically, link-based on-road mobile source emissions were derived from a travel demand 

model coupled with the EPA Motor Vehicle Emissions Simulator 2010a (MOVES2010a)

emission factor model, and non-road mobile source emissions were derived from the EPA’s 

National Mobile Inventory Model (NMIM), or the Texas NONROAD (TexN) mobile source 

models. The on-road and non-road emissions were processed to air quality model-ready format 

using version three of the Emissions Processing System (EPS3; Environ, 2007). Biogenic 

emissions were derived from the Global Biosphere Emissions and Interactions System 

(GloBEIS3.13.1) model, which outputs air quality model-ready emissions.

Appendix B: Emissions Modeling for the DFW Attainment Demonstration SIP Revision for the 

1997 Eight-Hour Ozone Standard provides details on the development and processing of the 

emissions using the various EPS3 modules. The modules, listed in Table 3-6: Emissions 

Processing Modules, are used to create the chemically speciated, temporally (hourly) allocated, 

and spatially distributed emission files needed for the air quality model. Model-ready emissions 

were developed for the May 31, 2006, through July 2, 2006, period. The following sections give 

a brief description of the development of each type of emissions.

Table 3-6: Emissions Processing Modules

EPS3 Module Description

PREAM Prepare area and non-link based mobile sources emissions for further 

processing

LBASE Spatially allocate link-based mobile source emissions among grid cells

PREPNT Group point source emissions into elevated and low-level for further 

processing

CNTLEM Apply controls to model strategies, apply adjustments, etc.

TMPRL Apply temporal profiles to hourly allocate emissions

CHMSPL Chemically speciate emissions into nitrogen oxide (NO), nitrogen dioxide (NO2), 

and various CB05-VOC species

GRDEM Spatially distribute emissions by grid cell using source category surrogates

MRGUAM Merge and adjust multiple gridded files for model-ready input

PIGEMS Assigns PiGs and merges elevated point source files

Notes: CB05 = the 2005 version of the Carbon Bond chemical mechanism; PiG = Plume-in-Grid

3.5.1 Biogenic Emissions

The TCEQ used version 3.1 of the GloBEIS3.13.1 model to develop the biogenic emissions. 

GloBEIS3.1 tables were modified to accept land cover classes from newly acquired updated land 

cover. Detailed locality-specific land cover data input to the model is used to generate the mix 

and density of vegetative species. Photosynthetically active radiation (PAR) was derived from 
3-16

solar radiation data taken from Geostationary Operational Environmental Satellite (GOES) 

imagery and input to the GloBEIS3.1 model. Further, the GloBEIS3.1 model used hourly 

temperature data generated from weather station data.

Biogenic Emissions Landuse Data, version 3 (BELD3; Kinnee et al., 1997), a vegetation database 

for the entire North American continent prepared specifically for creating biogenic emissions 

inventories, was used for the 36 km domain and the portion of the 12 km domain outside Texas. 

For the land-use data in the 12 km domain within Texas, the TCEQ used the Texas vegetation

database (Wiedinmyer et al., 2001), which was derived from Texas Parks and Wildlife 

Department vegetation data, agricultural statistics from the National Agricultural Statistics 

Survey, and 1999 field surveys. Within the 4 km nested domain, a new land-cover dataset from 

the Texas A&M Spatial Sciences Laboratory was used for land cover input (Popescu et al., 

2008). LandSat Thematic Mapper satellite images, with acquisition dates between the years 

2000 and 2002, were classified with respect to the Texas Land Classification System 

implemented by the Texas Geographic Information Council (TGIC) in 1999 by utilizing an 

object-based classification scheme. The Texas A&M land cover data was enhanced with the use 

of the 2001 National Land Cover Dataset (NLCD) derived by the United States Geological Survey 

(USGS), Common Land Unit (CLU) data provided by the United States Department of 

Agriculture (USDA) – Farm Service Agency (FSA), and the National Hydrography Dataset 

(NHD) produced by the USGS.

The episode-specific PAR data input to GloBEIS3.1 were obtained from the Web site operated by 

the Global Energy and Water Cycle Experiment (GEWEX) Continental-Scale International 

Project (GCIP) and GEWEX Americas Prediction Project (GAPP)

(http://metosrv2.umd.edu/~srb/gcip/cgi-bin/historic.cgi?auth=no). The episode-specific 

temperature data were obtained from weather stations throughout the United States, including 

data from the National Weather Service, the EPA Aerometric Information Retrieval System 

(AIRS) air quality database, the National Buoy Data Center, the Texas A&M Crop Weather 

Program, the Louisiana Agricultural Information Service, and the Texas Coastal Oceanographic 

Observation Network.

GloBEIS3.1 was run for each day of the modeling episode. Figure 3-9: Example of Day-Specific 

Biogenic Emissions shows the typical magnitude and distribution of biogenic VOC and NOX

emissions in the 4 km modeling domain.
3-17

Figure 3-9: Example of Day-Specific Biogenic Emissions

Since biogenic emissions are associated with meteorological features, the same episode dayspecific emissions were used as input for the 2006 baseline and 2012 future air quality 

modeling.

3.5.2 2006 Base Case

3.5.2.1 

Point source modeling emissions were developed from regional inventories such as the Central 

States Regional Air Planning Association/Regional Planning Organization (CENRAP/RPO) 

emissions database and EPA’s Acid Rain Database (ARD), state inventories including the State 

of Texas Air Reporting System (STARS), and local inventories. Data were processed with EPS3 

to generate model-ready emissions, and similar procedures were used to develop each base case 

episode. 

Point Sources

Outside Texas

Point source emissions data for the regions of the modeling domains outside Texas were 

obtained from a number of different sources. Emissions from point sources in the Gulf of 

Mexico (e.g., oil and gas production platforms) were obtained from the 2005 Gulf-Wide 

Emissions Inventory (GWEI) provided by the Minerals Management Services (MMS) as 

monthly totals. Canadian emissions were obtained from EPA modeling emission files developed 
3-18

for the 2001 Clean Air Interstate Rule (CAIR) base case analysis (EPA, 2005) and Mexican 

emissions data were obtained from Phase III of the Mexican National Emissions Inventory 

(National Emissions Inventory (NEI); http://www.epa.gov/ttn/chief/net/mexico.html). The 

Gulf of Mexico, Canadian, and Mexican inventories were not grown to 2006 due to the lack of 

historical operations data, applied controls, and/or a projection methodology.

For the non-Texas United States within the modeling domains, hourly NOX emissions for major 

electric generating units (EGUs) were obtained from the ARD for each hour of each episode day. 

Emissions for non-ARD sources in states beyond Texas were obtained from the modeling 

emissions files used for the 2002 CENRAP/RPO base cases for the Revisions to the State 

Implementation Plan (SIP) Concerning Regional Haze, with the exception of Arkansas, 

Louisiana, and Oklahoma. State-specific 2005 point source annual emissions for non-ARD 

sources were provided by Arkansas and Oklahoma. Louisiana provided their 2004 annual point 

source emissions since the 2005 annual emissions are incomplete due to hurricane Katrina. The 

EPA’s Economic Growth Analysis System Version 5.0 (EGAS5) was used to grow these 

emissions to 2006. 

Within Texas

Hourly NOX emissions from EGUs within Texas were obtained from the ARD for each episode 

day. Emissions from non-ARD sources were obtained from a STARS emissions extract for the 

year 2006. In addition, agricultural and forest fire emissions for 2006 were obtained from a 

TCEQ-funded study (Environ, 2008b), which treated fires as point sources. For the HGB area, 

2006 event-specific tank landing loss emissions were obtained from a special inventory survey 

requested by the TCEQ; the average of the non-zero days was used in this AD SIP revision. 

Highly reactive volatile organic compounds (HRVOC), ethylene, propylene, butenes, and 1,3-

butadiene, emissions were reconciled with ambient measurements by comparing concentrations 

measured by automated gas chromatographs (auto-GCs) in the area with concentrations 

expected at those locations based on the reported inventory. Appendix B: Emissions Modeling 

for the HGB Attainment Demonstration SIP Revision for the 1997 Eight-Hour Ozone Standard

provides more details on the reconciliation of HRVOC emissions. 

Table 3-7: 2006 Base Case Episode Point Source Modeling Emissions provides the state and 

nine-county DFW point source emissions for June 7, 2006, (a Wednesday) within the 33-day 

base case episode. Acid rain point source emissions are unique for each day of the base case 

episode. Non-ARD emissions are an average of reported ozone season day emissions for the 

entire period of June through August and are the same for each episode day.
3-19

Table 3-7: 2006 Base Case Episode Point Source Modeling Emissions

Point Source Type DFW NOX 

(tpd)

DFW 

VOC

(tpd)

Texas 

NOX

5 

(tpd)

Texas 

VOC5 

(tpd)

ARD1 9.4 0.9 519.6 32.9

Non-ARD2 41.6 40.0 744.7 602.2

Tank Landing3 6.6

HRVOC4 19.3

Totals 51.0 40.9 1264.3 661.0

Notes: 1. ARD emissions listed are for Wednesday, June 7, 2006.

2. Non-ARD emissions listed are for ozone season day (OSD) weekday, OSD weekend days are slightly 

less.

3. Tank landing emissions listed are episode-specific average for days with non-zero emissions.

4. HRVOC reconciled emissions listed are the amounts added to those reported via the emissions 

reconciliation procedure.

5. Note that the entire state of Texas is not included in the modeling domain.

2006 on-road mobile source inputs were developed using MOVES2010a, which is the EPA’s 

latest available on-road emissions model. The vehicle activity data sets that were used in 

conjunction with MOVES2010a are:

On-Road Mobile Sources

• the travel demand model (TDM) managed by the North Central Texas Council of 

Governments (NCTCOG) for the DFW area;

• Highway Performance Monitoring System (HPMS) data collected by the Texas Department 

of Transportation (TxDOT) for the non-DFW portions of Texas contained within the 

modeling domain; and

• the EPA default information included with the MOVES2010a database for the non-Texas 

United States portions of the modeling domain.

The output from these emission modeling applications were processed through EPS3 to 

generate the on-road speciated and gridded inputs for photochemical modeling applications.

DFW Area

For the nine-county DFW area, link-based on-road emissions were developed by NCTCOG using 

2006 TDM output and MOVES2010a emission rates to generate average summer and school 

season on-road emissions for five day types: Monday, weekday (Tuesday-Thursday average), 

Friday, Saturday, and Sunday. For the 2006 base case episode, the summer season day-type 

emissions were used. 

Non-DFW Portions of Texas

For the Texas counties outside of the DFW area, on-road emissions were developed by the Texas 

Transportation Institute (TTI) using MOVES2010a emission rates and 2006 local HPMS data. 

Average summer emissions by vehicle type and roadway type were estimated for the four day 

types of weekday (Monday through Thursday average), Friday, Saturday, and Sunday. 
3-20

Outside of Texas

For the non-Texas United States portions of the modeling domain, the TCEQ used 

MOVES2010a in default mode to generate 2006 average summer emissions for the weekday and 

weekend day types available from the model.

Table 3-8: Summary of On-Road Mobile Source Emissions Development contains additional 

detail about the on-road mobile inventory development in different regions of the modeling 

domain.

Table 3-8: Summary of On-Road Mobile Source Emissions Development

On-Road Inventory 

Development Parameter DFW Non-DFW Texas Non-Texas States/Counties

VMT Source and 

Resolution

TDM Roadway

Links

HPMS Data Sets

19 Roadway Types

MOVES2010a

12 Roadway Types

Season

Types

Summer and

School Seasons

Summer Season

Only

Summer Season

Only

Day

Types

Monday, Weekday, 

Friday, Saturday, and 

Sunday

Weekday, Friday, 

Saturday, and 

Sunday

Weekday and

Weekend

Roadway Speed 

Distribution

Varies by Hour and 

Link

Varies by Hour and 

Roadway Type

MOVES2010a

Default

MOVES2010a Fuel and

Source Use Types

Gasoline and Diesel

13 Source Use Types

Gasoline and Diesel

13 Source Use Types

Gasoline and Diesel

13 Source Use Types

Note: VMT= vehicle miles traveled

Table 3-9: 2006 Base Case Episode On-Road Modeling Emissions for DFW (tpd) summarizes 

the on-road mobile source emissions for the 2006 base case episode for the nine-county DFW 

area.

Table 3-9: 2006 Base Case Episode On-Road Modeling Emissions for DFW (tpd)

On-Road 

Day Type NOX tpd VOC tpd

Weekday 259.11 111.02

Friday 264.31 114.61

Saturday 189.98 103.25

Sunday 168.95 96.60

Monday 252.43 109.12

Notes: Only summer season emissions are reported. 

3.5.2.2 

Non-road mobile sources include vehicles, engines, and equipment used for construction, 

agriculture, transportation, recreation, and many other purposes. Off-road mobile sources are 

aircraft, locomotives, and marine vessels. Non- and off-road mobile source modeling emissions 

were developed using the EPA NMIM, the EPA NEI, TexN, and data from the TCEQ’s Texas Air 

Emissions Repository (TexAER). The output from these emission modeling applications and 

databases were processed through EPS3 to generate the air quality model-ready non- and offroad mobile source emission files.

Non-Road and Off-Road Mobile Sources
3-21

Outside Texas

For the non-Texas United States within the modeling domains, the TCEQ used the EPA’s 

NMIM. NMIM generates average summer weekday non-road mobile source category emissions 

by county and was run for 2006. For the off-road mobile source categories (aircraft, locomotive, 

and marine) in the non-Texas states, the TCEQ used the EPA’s 2002 NEI with EGAS5 growth 

factors and national controls for locomotives and marine vessels to generate 2006 average 

summer weekday off-road mobile source category emissions. Summer weekend day emissions 

for the non- and off-road mobile source categories were developed as part of the EPS3 

processing using category specific weekly activity profiles.

Within Texas

The TCEQ used the TexN model to generate average summer weekday non-road mobile source 

category emissions by county for 2006, except for oil and gas drilling rigs. The county-level 

drilling rig emissions were based on 2008 emissions (ERG, 2009), adjusted to 2006 according 

to the ratio of active drill rig counts in 2006 and 2008 from Baker Hughes (Baker Hughes, 

2010) and RigData (RigData, 2009). The drill rig emissions were also adjusted according to the 

non-road engine tier mix in the TexN model (higher emissions in 2006 than 2008). More 

information on the development of the oil and gas drilling inventory can be found in Appendix 

B.

County-level off-road emissions for 2006 were estimated by adjusting the 2005 TexAER 

emissions with the Texas-specific Regional Economic Models, Inc. – Economic Growth Analysis 

System (REMI-EGAS) growth factors, except for the aircraft/airport emissions, locomotive 

emissions, and marine vessels in the HGB and Beaumont-Port Arthur (BPA) areas. The 2012 

emissions for marine vessels in the HGB and BPA areas were developed using emission trends 

provided by the HGB and BPA Port Authorities (Starcrest, 2000). No marine vessels 

(commercial shipping) operate in the DFW nonattainment area. The 2006 aircraft/airport 

emissions in the DFW area were provided by contract (North Central Texas Council of 

Governments (NCTCOG), 2011) and are airport-specific rather than county-level. The 

locomotive emissions were calculated using the Texas Railroad Emission Inventory Model 

(TREIM) model for 2006, specific for switchers and line-hauls (ERG, 2007). Summer weekend 

day emissions for the non- and off-road mobile source categories were developed as part of the 

EPS3 processing using category specific weekly activity profiles.

Table 3-10: 2006 Base Case Episode Non-Road and Off-Road Modeling Emissions for DFW

summarizes the non-road and off-road mobile source weekday emissions for the 2006 base case 

episode for the nine-county DFW area.

Table 3-10: 2006 Base Case Episode Non-Road and Off-Road Modeling Emissions 

for DFW

Source Category Type 2006 NOX tpd 2006 VOC tpd

Non-Road 103.3 61.2

Airports 11.0 5.1

Locomotives 28.7 1.7

Marine 0.0 0.0

Total 142.9 67.9

Note: VOC is reported as sum of CB05 species
3-22

3.5.2.3 

Area source modeling emissions were developed using the EPA NEI and the TCEQ’s TexAER

database. The emissions information in these databases was processed through EPS3 to 

generate the air quality model-ready area source emission files.

Area Sources

Outside Texas

For the non-Texas United States within the modeling domains, the TCEQ used the EPA’s 2002 

NEI with EGAS5 growth factors to generate 2006 daily area source emissions.

Within Texas

The TCEQ used data from the 2005 TexAER database (TCEQ, 2011) for non-oil and gas sources. 

The 2005 TexAER data were projected to 2006 using the Texas-specific REMI-EGAS growth 

factors for the 2006 base case episode. 

For oil and gas production sources, county-specific 2006 oil and gas emissions were calculated 

based on a TCEQ-contracted research project (ERG, 2010). The emissions were calculated 

according to 2006 county-specific oil and gas production information from the Railroad 

Commission of Texas and emission factors compiled in the 2010 ERG report. Emissions and 

specificity of the 2006 base case oil and gas emissions are detailed in Table 3-11: 2006 DFW 

Nine-County Oil and Gas Production Emissions. Previous oil and gas modeling inventories 

contained only two source categories: onshore and offshore oil and gas. Detailed information on 

the development of the oil and gas production emissions inventory is described in Appendix B.

Table 3-11: 2006 DFW Nine-County Oil and Gas Production Emissions

Oil & Gas Category 2006 NOX tpd 2006 VOC tpd

2-Cycle Lean Burn Compressor 1.3 0.0

4-Cycle Lean Burn Compressor 0.8 0.2

4-Cycle Rich Burn Compressor 46.2 1.0

4-Cycle Rich Burn Compressor w/ Catalyst 0.6 0.1

Oil Fugitives (grouped) 0.0 0.0

Gas Fugitives (grouped) 0.0 2.5

Crude Tanks 0.0 0.2

Condensate Tanks 0.0 40.6

Oil Heaters 0.0 0.0

Gas Heaters 1.2 0.1

Dehydrators 0.0 1.3

Pumpjacks 0.1 0.0

Oil Loading 0.0 0.0

Condensate Loading 0.0 0.3

Oil Well Completions 0.0 0.1

Gas Well Completions 0.0 3.0

Oil Well Blowdowns 0.0 0.1

Gas Well Blowdowns 0.0 0.7

Pneumatic Devices 0.0 21.5

Produced Water 0.0 0.5

Total 50.1 72.1
3-23

Table 3-12: 2006 Base Case Episode Area Source Modeling Emissions for DFW summarizes the 

area source weekday emissions for the 2006 base case episode for the nine-county DFW area.

Table 3-12: 2006 Base Case Episode Area Source Modeling Emissions for DFW

Area Source Category 2006 NOX tpd 2006 VOC tpd

Oil and Gas Production 50.1 72.1

Petro Transport & Refueling 0.0 42.9

Architectural Coating 0.0 34.4

Solvent Use 0.0 57.5

Surface Cleaning 0.0 1.0

Industrial Fuel Use 13.5 0.5

Residential Fuel Use 2.2 0.1

Auto Refinishing 0.0 3.9

Waste Treatment 0.0 10.1

Graphic Arts 0.0 1.4

Pesticide Use 0.0 0.0

Leaking Underground Storage Tank 0.0 3.0

Traffic Marking 0.0 0.5

Surface Coating 0.0 49.7

Open Burning 0.5 2.9

Dry Cleaning 0.0 3.8

Asphalt Paving 0.0 0.7

Food/Brewing 0.0 0.9

Area Source Total 66.3 285.3

3.5.2.4 

Table 3-13: 2006 Base Case Episode Anthropogenic Modeling Emissions for DFW

Base Case Summary

 summarizes 

the typical weekday emissions in the nine-county DFW area by source type for the base case 

episode.
3-24

Table 3-13: 2006 Base Case Episode Anthropogenic Modeling Emissions for DFW

Category 2006 NOX tpd 2006 VOC tpd

On-Road Mobile (MOVES2010a) 259 111

Non-Road (excl. Oil & Gas Drilling) 85 60

Off-Road 40 7 

Point Source 51 41

Area (excl. Oil & Gas Production) 16 213

Oil & Gas Production 50 72

Oil & Gas Drilling 18 1 

DFW Total 519 505

Notes: 1. Point source emissions are based on non-startup Wednesday ARD emissions.

2. On-road emissions are summer season-specific weekday emissions.

3. Non-road, off-road and area emissions are year-specific OSD emissions.

4. Off-road emissions consist of airport and locomotive emissions.

5. VOC is reported as sum of CB05 species.

3.5.3 2006 Baseline

The baseline modeling emissions are based on typical ozone season emissions, whereas the base 

case modeling emissions are episode day-specific. The biogenic emissions are an exception in 

that the same episode day-specific emissions are used in the 2006 baseline and base case. In 

addition, the 2006 baseline non-road and off-road and area source modeling emissions are the 

same as used for the 2006 base case episode, since they are based on typical ozone season 

emissions. Unlike the base case, fire emissions were not included in the 2006 baseline as they 

are not typical ozone season day emissions.

3.5.3.1 

For the non-ARD point sources, the 2006 baseline emissions are the same as the modeling 

emissions used for the June 2006 episode, with a couple of exceptions. The 2006 baseline ARD 

EGUs emissions were estimated using the average of the 2006 third quarter hourly ARD 

emissions to more accurately reflect EGU emissions during the peak ozone season. The HRVOC 

emissions reconciliation and tank landing losses in the HGB area developed for the 2006 base 

case were used for the 2006 baseline. For the Gulf of Mexico, Canada, and Mexico, the 2006 

baseline used the same emissions as the base cases.

Point Sources

Table 3-14: 2006 Baseline Point Source Modeling Emissions provides the state and the ninecounty DFW point source emissions for the 2006 typical baseline day. The non-ARD emissions 

are the same as the base case, since they are ozone season day averages. The averaged baseline 

ARD emissions are not the same as any specific day in the base case, but typical of the entire 

episode.

Table 3-14: 2006 Baseline Point Source Modeling Emissions

Point Source Type DFW NOX 

tpd

DFW VOC 

tpd

Texas 

NOX tpd

Texas 

VOC5 tpd

ARD1 9.1 0.9 548.6 29.8

Non-ARD2 41.6 40.0 744.7 602.2

Tank Landing3 6.6
3-25

Point Source Type DFW NOX 

tpd

DFW VOC 

tpd

Texas 

NOX tpd

Texas 

VOC5 tpd

HRVOC4 19.3

Totals 50.7 40.9 1293.3 657.9

Notes: 1. ARD emissions listed are for Wednesday, June 7, 2006.

2. Non-ARD emissions listed are for OSD weekday, OSD weekend days are slightly less.

3. Tank landing emissions listed are episode-specific average for days with non-zero emissions.

4. HRVOC reconciled emissions listed are the amounts added to those reported via the emissions 

reconciliation procedure.

5. Note that the entire state of Texas is not included in the modeling domain.

3.5.3.2 

The 2006 baseline on-road mobile source emissions are the same as used for the June 2006 

base case episode. These are the summer season modeling emissions for each of the day types: 

Monday, weekday, Friday, Saturday, and Sunday.

On-Road Mobile Sources

3.5.4 2012 Future Base and Control Strategy

The biogenic emissions used for the 2012 future base and control strategy modeling are the 

same episode day-specific emissions used in the base case. In addition, similar to the 2006 

baseline, no fire emissions were included in the 2012 future base and control strategy modeling. 

Appendix B provides extensive details of the 2012 modeling emissions development.

3.5.4.1 

Outside Texas

Point Sources

The non-ARD point source emissions data in the regions outside Texas were derived from a 

combination of the modeling emissions files used for the 2018 CENRAP/RPO and the 2006 

CENRAP/RPO (grown from the 2002 CENRAP/RPO base case files) Revisions to the State 

Implementation Plan (SIP) Concerning Regional Haze files. Since growth and controls were 

included in the 2018 files, the TCEQ computed and modeled the average of the 2006 and 2018 

files for the 2012 regional non-ARD file. For the Gulf, Canada, and Mexico, the 2012 modeled 

emissions were the same as the emissions used in the 2006 baseline. The CAIR Phase 1 emission 

caps were used for the ARD EGU point source 2012 emissions.

Within Texas

Controls pertinent to existing DFW, HGB, and BPA AD SIP revisions were applied to the 2008 

STARS future base emissions of the appropriate point source categories (e.g., Mass Emissions 

Cap and Trade program (MECT), HRVOC Emissions Cap and Trade program (HECT), Ellis 

County Cement Kiln Cap, and East Texas Combustion Rule), and those specific units were 

modeled at the previous SIP rule limitations. The remaining non-ARD emissions were projected 

from the 2008 STARS future base to 2012 using the larger of the Texas Industrial Production 

Index (TIPI), the Texas-specific REMI-EGAS growth factors, or the Emissions Banking and 

Trading Registry (the sum of the banked Emissions Reduction Credits (ERCs) and Discrete 

Emissions Reduction Credits (DERCs)) in the nonattainment areas, including DFW. This 

growth was constrained by the lesser of the Emissions Banking and Trading Registry or the 

TIPI-REMI-EGAS growth. The projected growth determines how many future tons of emissions 

will be needed by 2012, and the bank determines how many tons of emissions are available for 

purchase to allow for that growth in the DFW nonattainment area. An additional limitation on 

annual DERC usage for DFW, the DERC Flow Control rule (30 TAC 101.379), did not constrain 

growth for these four years because of low projected industrial growth.
3-26

Similar to the 2012 emissions for ARD sources outside Texas, the ARD sources within Texas 

used the TCEQ CAIR Phase 1 allocations.5

Table 3-15: 2012 Future Case Point Source Modeling Emissions

The eight-county HGB area is subject to the more 

stringent MECT rule. The 2012 emissions for ARD sources within the HGB area used the MECT 

allocations which are more stringent, with the excess being allocated to the other ARD EGUs in 

the state. Newly-permitted ARD sources were limited to the CAIR 9.5% set-aside for growth. 

The 2012 tank landing emissions and the HRVOC reconciliation for the HGB area were the same 

as the 2006 baseline. 

provides the state and ninecounty DFW point source emissions for the 2012 future case day. Compared to the 2006 

baseline (Table 3-14), the future case shows a statewide reduction in NOX and VOC emissions 

due to controls. DFW NOX emissions are higher due to the CAIR cap allocating significantly 

more NOX emissions to DFW EGUs than reported in recent years.

 

5 On July 6, 2011, the EPA finalized its CAIR replacement rule, known as the Cross-State Air 

Pollution Rule (CSAPR) requiring 27 states to reduce power plant emissions. CSAPR yields 10% 

more NOX emission reductions outside Texas and 18% more in Texas in 2012 than would CAIR. 

Modeling the higher 2012 CAIR Phase I NOX allocations is a more conservative approach for 

projecting attainment. However, a 2012 modeling sensitivity was conducted using CSAPR 

allocations for the entire country and is detailed in Appendix C, Section 5.5.1.5.
3-27

Table 3-15: 2012 Future Case Point Source Modeling Emissions

Point Source Type DFW 

NOX tpd

DFW VOC 

tpd

Texas 

NOX tpd

Texas 

VOC5 tpd

ARD1 18.9 0.8 487.6 16.5

Non-ARD2 32.0 38.6 706.2 565.0

Tank Landing3 6.6

HRVOC5 19.3

Totals 50.9 39.4 1193.8 607.4

Notes: 1. ARD emissions listed are for Wednesday, June 7, 2006.

2. Non-ARD emissions listed are for OSD weekday, OSD weekend days are slightly less.

3. Tank landing emissions listed are episode-specific average for days with non-zero emissions.

4. HRVOC reconciled emissions listed are the amounts added to those reported via the emissions 

reconciliation procedure.

5. Note that the entire state of Texas is not included in the modeling domain.

For the nine-county DFW area, the point source NOX and VOC emissions are comparable for the 

2006 baseline and the 2012 future base. 

3.5.4.2 

2012 on-road mobile source inputs were developed using MOVES2010a in combination with the 

following vehicle activity data sets:

On-Road Mobile Sources

• the TDM managed by NCTCOG for the DFW area;

• HPMS data collected by TxDOT for the non-DFW portions of Texas contained within the 

modeling domain; and

• the EPA default information included with the MOVES2010a database for the non-Texas 

United States portions of the modeling domain.

The output from these emission modeling applications were processed through EPS3 to 

generate the on-road speciated and gridded inputs for photochemical modeling applications.

DFW Area

For the nine-county DFW area, link-based on-road emissions were developed by the NCTCOG 

using 2012 TDM output and MOVES2010a emission rates to generate average summer and 

school season on-road emission for five day types: Monday, weekday (Tuesday-Thursday 

average), Friday, Saturday, and Sunday. For the 2012 future case, the summer season day-type 

emissions were used. 

Non-DFW Portions of Texas

For the Texas counties outside of the DFW area, on-road emissions were developed by the Texas 

Transportation Institute (TTI) using MOVES2010a emission rates and local HPMS data 

projected out to 2012. Average summer emissions by vehicle type and roadway type were 

estimated for the four day types of weekday (Monday through Thursday average), Friday, 

Saturday, and Sunday. 
3-28

Outside of Texas

For the non-Texas United States portions of the modeling domain, the TCEQ used 

MOVES2010a in default mode to generate 2012 average summer emissions for the weekday and 

weekend day types available from the model.

Table 3-16: 2012 Future Case On-Road Modeling Emissions for DFW (tpd) summarizes the onroad mobile source emissions for each of the 2012 future case day types for the nine-county 

DFW area.

Table 3-16: 2012 Future Case On-Road Modeling Emissions for DFW (tpd)

On-Road 

Day Type NOX tpd VOC tpd

Weekday 181.40 80.48

Friday 182.24 81.87

Saturday 136.68 74.80

Sunday 124.84 71.37

Monday 175.33 78.97

Note: Only summer season emissions are reported.

For the nine-county DFW area, the on-road mobile source NOX emissions are reduced by about 

30% from the 2006 baseline (259.1 tpd) to the 2012 future case (181.4 tpd), and the VOC 

emissions are decreased about 28% from the 2006 baseline (111.0 tpd) to the 2012 future case

(80.5 tpd).

3.5.4.3 

Outside Texas

Non- and Off-Road Mobile Sources

For the non-Texas United States within the modeling domains, the TCEQ used the EPA’s NMIM 

to generate average summer weekday non-road mobile source category emissions by county for 

2012. For the off-road mobile source categories, aircraft, locomotive, and marine, in the states 

beyond Texas, the TCEQ used the EPA’s 2002 NEI with EGAS5 growth factors and national 

controls for locomotives and marine vessels to generate 2012 average summer weekday off-road 

mobile source category emissions. Summer weekend day emissions for the non-road and offroad mobile source categories were developed as part of the EPS3 processing using category 

specific weekly activity profiles.

Within Texas

The TCEQ used the TexN model to generate average summer weekday non-road mobile source 

category emissions by county for 2012, except for oil and gas drilling rigs. The county-level 

drilling rig emissions were based on 2008 emissions (ERG, 2009), adjusted to 2010 according 

to the ratio of active drill rig counts in 2008 and 2010 from Baker Hughes (Baker Hughes, 2010) 

and RigData (RigData, 2009). A 10% growth was assumed from 2010 to 2012 for the Barnett 

Shale and Haynesville Shale counties. Growth of 20%was assumed in the developing Eagle Ford 

Shale in south and central Texas. Also, 10% growth was assumed from 2010 to 2012 for all other 

Texas counties. Drill rig emissions were also adjusted according to the non-road engine tier mix 

in the TexN model (cleaner in 2012). More information on the development of the oil and gas 

drilling inventory can be found in Appendix B.

The 2012 aircraft/airport emissions in the DFW area were provided by contract (NCTCOG, 

2011) and are airport specific rather than county level. The 2012 emissions for marine vessels in 

the HGB and BPA areas were developed using emission trends provided by the HGB and BPA 
3-29

Port Authorities (Starcrest, 2000). No marine vessels (commercial shipping) operate in the 

DFW nonattainment area. The locomotive emissions were calculated using the TREIM model 

for 2012, specific for switchers and link-based line-hauls (ERG, 2007). Summer weekend day 

emissions for the non-road and off-road mobile source categories were developed as part of the 

EPS3 processing using category specific weekly activity profiles.

Table 3-17: 2012 Future Case Non-Road and Off-Road Modeling Emissions for DFW

summarizes the non-road and off-road mobile source weekday emissions for the 2012 future 

case for the nine-county DFW area.

Table 3-17: 2012 Future Case Non-Road and Off-Road Modeling Emissions for 

DFW

Source Category Type 2012 NOX tpd 2012 VOC tpd

Non-Road 72.5 43.3

Airports 10.1 4.3

Locomotives 26.8 1.7

Marine 0.0 0.0

Total 109.5 49.3

For the nine-county DFW area, the non-road and off-road mobile source NOX emissions are 

reduced by about 23% from the 2006 baseline (142.9 tpd) to the 2012 future base (109.5 tpd) 

and the VOC emissions are decreased about 27% from the 2006 baseline (67.9 tpd) to the 2012 

future base (49.3 tpd).

3.5.4.4 

Outside Texas

Area Sources

For the non-Texas United States within the modeling domains, the TCEQ used the EPA’s 2002 

NEI with EGAS5 growth factors to generate 2012 daily area source emissions.

Within Texas

The 2012 county-level area source emissions were estimated by adjusting the 2005 TexAER 

emissions with the Texas-specific REMI-EGAS growth factors, except for the oil and gas 

emissions category.

For oil and gas production sources, county-specific 2010 oil and gas emissions were calculated 

according to June 2010 county-specific oil and gas production information from the Railroad 

Commission of Texas and emission factors based on equipment surveys (ERG, 2010; TCEQ, 

2009), the East Texas Combustion rule (TCEQ, 2007b), and the 2007 DFW Minor Source rules 

(TCEQ, 2007a). A 10% growth in production and drilling emissions was assumed from 2010 to 

2012 for the Barnett Shale and Haynesville Shale counties as wells continue to be drilled. 

Growth in production and drilling emissions of 20% was assumed in the developing Eagle Ford 

Shale in south and central Texas. A 10% growth in production and drilling emissions was 

assumed from 2010 to 2012 for all other Texas counties as oil/gas well drilling continues. Table 

3-18: 2012 DFW Nine-County Oil and Gas Production Emissions details the emissions for the 

2012 future case oil and gas emissions. More information on the development of the oil and gas 

emissions inventory is described in Appendix B.
3-30

Table 3-18: 2012 DFW Nine-County Oil and Gas Production Emissions

Oil & Gas Category 2012 NOX tpd 2012 VOC tpd

2-Cycle Lean Burn Compressor 0.3 0.1

4-Cycle Lean Burn Compressor 0.5 0.3

4-Cycle Rich Burn Compressor 1.2 0.1

4-Cycle Rich Burn Compressor w/ Catalyst 4.6 3.2

Oil Fugitives (grouped) 0.0 0.1

Gas Fugitives (grouped) 0.0 6.7

Crude Tanks 0.0 0.4

Condensate Tanks 0.0 33.5

Oil Heaters 0.0 0.0

Gas Heaters 3.0 0.2

Dehydrators 0.0 3.6

Pumpjacks 0.1 0.0

Oil Loading 0.0 0.0

Condensate Loading 0.0 0.3

Oil Well Completions 0.0 0.1

Gas Well Completions 0.0 3.3

Oil Well Blowdowns 0.0 0.1

Gas Well Blowdowns 0.0 1.7

Pneumatic Devices 0.0 57.2

Produced Water 0.0 2.2

Total 9.7 113.1

Table 3-19: 2012 Future Case Episode Area Source Modeling Emissions for DFW summarizes 

the area source weekday emissions for the 2012 future case episode for the nine-county DFW

area.

Table 3-19: 2012 Future Case Episode Area Source Modeling Emissions for DFW

Area Source Category 2012 NOX tpd 2012 VOC tpd

Oil and Gas Production 9.7 113.1

Petro Transport & Refueling 0.0 45.0

Architectural Coating 0.0 40.5

Solvent Use 0.0 64.1

Surface Cleaning 0.0 1.3

Industrial Fuel Use 15.3 0.6

Residential Fuel Use 2.4 0.1

Auto Refinishing 0.0 4.6

Waste Treatment 0.0 11.2

Graphic Arts 0.0 1.5

Pesticide Use 0.0 0.0

Leaking Underground Storage Tank 0.0 3.1

Traffic Marking 0.0 0.5
3-31

Area Source Category 2012 NOX tpd 2012 VOC tpd

Surface Coating 0.0 58.5

Open Burning 0.5 3.2

Dry Cleaning 0.0 4.1

Asphalt Paving 0.0 0.8

Food/Brewing 0.0 1.0

Area Source Total 27.9 353.1

For the nine-county DFW area, the area source NOX emissions decreased by about 58% from the 

2006 baseline (66.3 tpd) to the 2012 future base (27.9 tpd), and the VOC emissions increased 

about 24% from the 2006 baseline (285.3 tpd) to the 2012 future base (353.1 tpd).

3.5.4.5 

Table 3-20: 2012 Future Base Anthropogenic Modeling Emissions for DFW

Future Base Summary

summarizes the 

typical weekday emissions in the nine-county DFW area by source type for the 2012 future base 

modeling.

Table 3-20: 2012 Future Base Anthropogenic Modeling Emissions for DFW

Category 2012 NOX tpd 2012 VOC tpd

On-Road Mobile 181 80

Non-Road (excl. Oil & Gas Drilling) 64 43

Off-Road 37 6 

Point Source 51 39

Area (excl. Oil & Gas Production) 18 240

Oil & Gas Production 10 113

Oil & Gas Drilling 9 1 

DFW Total 370 522

Notes: 1. Point source emissions are based on non-startup Wednesday ARD emissions

2. On-road emissions are summer season-specific weekday emissions

3. Non-road, off-road and area emissions are year-specific OSD emissions

4. Off-road emissions consist of airport and locomotive emissions

5. VOC is reported as sum of CB05 species

3.5.5 2006 and 2012 Modeling Emissions Summary for DFW

Table 3-21: Summary of 2006 Baseline and 2012 Future Base Anthropogenic Modeling 

Emissions for DFW summarizes the typical weekday anthropogenic emissions in the ninecounty DFW area by source type for the 2006 baseline and 2012 future base modeling

emissions. Oil and gas production and drilling have also been separated.
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Table 3-21: Summary of 2006 Baseline and 2012 Future Base Anthropogenic 

Modeling Emissions for DFW

Category 2006 NOX tpd 2012 NOX tpd 2006 VOC tpd 2012 VOC tpd

On-Road Mobile

(MOVES2010a) 259 181 111 80

Non-Road (excl. Oil & 

Gas Drilling) 85 64 60 43

Off-Road 40 37 7 6 

Point Source 51 51 41 39

Area (excl. Oil & Gas) 16 18 213 240

Oil & Gas Production 50 10 72 113

Oil & Gas Drilling 18 9 1 1 

DFW Total 519 370 505 522

Figure 3-10: 2006 Baseline and 2012 Future Base Anthropogenic NOX and VOC Modeling 

Emissions for DFW graphically compares the anthropogenic NOX and VOC modeling emissions 

for the nine-county DFW area.

Figure 3-10: 2006 Baseline and 2012 Future Base Anthropogenic NOX and VOC 

Modeling Emissions for DFW
3-33

3.6 PHOTOCHEMICAL MODELING

To ensure that a modeling study can be successfully used as technical support for an AD SIP 

revision, the air quality model must be scientifically sound and appropriate for the intended 

application and freely accessible to all stakeholders. In a regulatory environment, it is crucial 

that oversight groups (e.g., the EPA), the regulated community, and the public have access to 

and have reasonable assurance of the suitability of the model. The following three prerequisites 

were identified for selecting the air quality model to be used in the DFW attainment 

demonstration. The model must:

• have a reasonably current, peer-reviewed, scientific formulation;

• be available at no or low cost to stakeholders; and

• be consistent with air quality models being used for Texas SIP development.

The only model to meet all three of these criteria is the Comprehensive Air Quality Model with 

extensions (CAMx). The model is based on well-established treatments of advection, diffusion, 

deposition, and chemistry. Another important feature is that NOX emissions from large point 

sources can be treated with the PiG submodel, which helps avoid the artificial diffusion that 

occurs when large, hot, point source emissions are introduced into a grid volume. The model 

software and the CAMx user's guide are publicly available (Environ, 2010). In addition, the 

TCEQ has many years of experience with CAMx. CAMx was used for the modeling conducted in 

the HGB and BPA nonattainment areas, previous DFW attainment demonstrations, as well as 

for modeling being conducted in other areas of Texas (e.g., San Antonio).

CAMx Version 5.20.1 was used for this modeling study. Some of the features in this version 

include the ability to process in parallel on multiple processors and the following probing tools 

for sensitivity analysis:

• Process Analysis, which provides in-depth details of ozone formation, showing the various 

physical and chemical processes that determine the modeled ozone concentrations at 

specified locations and times;

• Ozone Source Apportionment Technology (OSAT), which estimates the contribution of 

emissions from multiple geographical areas and source categories (including biogenic 

emissions) to ozone formation; and 

• Anthropogenic Precursor Culpability Assessment (APCA), which reallocates ozone 

apportioned to non-controllable biogenic emissions to the controllable portion of precursors 

that participated in ozone formation.

3.6.1 Modeling Domains and Horizontal Grid Cell Size

Figure 3-11: DFW Photochemical Modeling Domains depicts the modeling domains used in 

CAMx. All domains were projected in a Lambert Conformal Projection (LCP) with origin at 100 

degrees west and 40 degrees north. The horizontal configuration of the CAMx modeling 

domains consists of a grid of 4 km by 4 km cells (4 km) encompassing the DFW nonattainment 

counties (blue box), nested within a grid of 12 km cells covering most of Texas and Louisiana 

(green box), nested within a grid of 36 km cells covering the eastern part of the United States 

(black box). The size of the 36 km outer domain was selected to minimize the effect of boundary 

conditions on predicted ozone concentrations at the finer grid resolutions. The domain 

specifications are detailed in Table 3-22: CAMx Modeling Domain Definitions. 
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Figure 3-11: DFW Photochemical Modeling Domains

Table 3-22: CAMx Modeling Domain Definitions

Domain Easting Range (km) Northing Range (km) East/West 

Grid Points

North/South Grid 

Points

36 km (-108, 1512) (-1584, 828) 69 67

12 km (-12, 1056) (-1488, -420) 89 89

4 km (140, 436) (-940, -680) 74 65

3.6.2 Vertical Layer Structure

The vertical configuration of the CAMx modeling domains consists of 28 layers of varying 

depths as shown in Table 3-23: CAMx Vertical Layer Structure. 
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Table 3-23: CAMx Vertical Layer Structure

CAMx Layer MM5 Layer Top (m AGL1) Center (m AGL1) Thickness (m)

28 38 15179.1 13637.9 3082.5

27 36 12096.6 10631.6 2930.0

26 32 9166.6 8063.8 2205.7

25 29 6960.9 6398.4 1125.0

24 27 5835.9 5367.0 937.0

23 25 4898.0 4502.2 791.6

22 23 4106.4 3739.9 733.0

21 21 3373.5 3199.9 347.2

20 20 3026.3 2858.3 335.9

19 19 2690.4 2528.3 324.3

18 18 2366.1 2234.7 262.8

17 17 2103.3 1975.2 256.2

16 16 1847.2 1722.2 256.3

15 15 1597.3 1475.3 249.9

14 14 1353.4 1281.6 243.9

13 13 1209.8 1139.0 143.6

12 12 1068.2 998.3 141.6

11 11 928.5 859.5 137.8

10 10 790.6 745.2 90.9

9 9 699.7 654.7 90.1

8 8 609.5 564.9 89.3

7 7 520.2 476.0 88.5

6 6 431.7 387.8 87.8

5 5 343.9 300.4 87.0

4 4 256.9 213.7 86.3

3 3 170.5 127.7 85.6

2 2 84.9 59.4 51.0

1 1 33.9 16.9 33.9

3.6.3 Model Configuration

The TCEQ used CAMx version 5.20.1, which includes a number of upgrades and features from 

previous versions. The following CAMx 5.20.1 options were employed:

• parallel processing of the chemistry and transport algorithms;

• CB05 chemical mechanism with Euler Backward Iterative (EBI) chemistry solver;

• Piecewise Parabolic Method (PPM) advection solver;

• improved vertical transport solvers; and

• updated PiG treatment of larger point sources of NOX using the Greatly Reduced Execution 

and Simplified Dynamics (GREASD) Lagrangian module.

In addition to the CAMx inputs developed from the meteorological and emissions modeling, 

inputs were needed for initial and boundary conditions, spatially resolved surface characteristic 
3-36

parameters, spatially resolved albedo/haze/ozone (i.e., opacity) and photolysis rates, and a 

chemistry parameters file.

The TCEQ contracted with Environ (Environ, 2008b), who collaborated with the National 

Aeronautics and Space Administration’s (NASA) Jet Propulsion Laboratory (JPL) to derive 

episode-specific boundary conditions from the Model for Ozone and Related Chemical Tracers 

(MOZART) global air quality model. Boundary conditions were developed for each grid cell 

along all four edges of the 36 km domain at each vertical layer (28) for each episode hour. This 

work also produced initial conditions for the episode. The TCEQ used these episode-specific 

initial and boundary conditions for this modeling study. The top-boundary condition input has 

been removed as of CAMx version 5.20.

Surface characteristic parameters, including roughness, vegetative distribution, and water/land 

boundaries, were input to CAMx via a land-use file. The land-use file provides the fractional 

contribution (0 to 1) of eleven land-use categories, as defined by the USGS LULC database. For 

the 36 km and 12 km domains, the TCEQ used the land-use files developed by Environ for the 

DFW AD SIP revision approved by the EPA in 2009, which were derived from the most recent 

USGS LULC database. For the 4 km domain the TCEQ used updated land-use files developed by 

Texas A&M University (Popescu et al., 2008), which were derived from more highly resolved 

LULC data collected by the Texas Forest Service and the University of Texas – Center for Space 

Research.

The spatially resolved opacity and photolysis rates are input to CAMx via a photolysis rates file 

and an opacity file, which are specific to the chemistry parameters file for the CB05 mechanism, 

and also input to CAMx. The TCEQ used episode-specific satellite data from the Total Ozone 

Mapping Spectrometer (TOMS) to prepare the photolysis rates and opacity files.

3.6.4 Model Performance Evaluation

The CAMx model configuration was applied to the 2006 base case using the episode-specific 

meteorological parameters and emissions, including MOVES2010a-based on-road emissions

unless otherwise noted. The CAMx modeling results were compared to the measured ozone and 

ozone precursor concentrations, which resulted in a number of modeling iterations involving 

improvements to the meteorological and emissions modeling and subsequent CAMx modeling. 

A detailed performance evaluation for the 2006 base case modeling episode is included in 

Appendix C: Photochemical Modeling for the DFW Attainment Demonstration SIP Revision 

for the 1997 Eight-Hour Ozone Standard. In addition, all performance evaluation products are 

available on the TCEQ FTP site (ftp://amdaftp.tceq.texas.gov/).

3.6.4.1 

The performance evaluation of the base case modeling demonstrates the adequacy of the model 

to correctly replicate the relationship between levels of ozone and the emissions of NOX and 

VOC. The model’s ability to suitably replicate this relationship is necessary to have confidence in 

the model’s prediction of the future year ozone and its response of ozone to various control 

measures. As recommended in the EPA modeling guidance, the TCEQ conducted two types of 

performance evaluations, operational and diagnostic. 

Performance Evaluations Overview

3.6.4.2 

Statistical measures including the Unpaired Peak Accuracy (UPA), the Mean Normalized Bias 

(MNB), and the Mean Normalized Gross Error (MNGE) were calculated by comparing 

monitored (measured) and four-cell bi-linearly interpolated modeled ozone concentrations for 

all episode days and monitors. Graphical measures including time series and scatter plots of 

Operational Evaluations
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hourly measured and bi-linearly interpolated modeled ozone and where applicable, some ozone 

precursors such as nitric oxide (NO), NO2, ethylene, and isoprene (ISOP), concentrations were 

developed for each regulatory monitor. In addition, tile plots of modeled daily maximum eighthour ozone concentrations were developed and overlaid with the measured daily maximum 

eight-hour ozone concentrations. Detailed operational evaluations for the 2006 base case 

modeling episode are included in Appendix C. 

Statistical Evaluations

The statistical evaluations presented focus on the comparison of the measured and modeled 

eight-hour ozone concentrations. Figure 3-12: Peak Eight-Hour Ozone Concentration, Observed 

versus Modeled for May 31 through June 15, 2006, and Figure 3-13: Peak Eight-Hour Ozone 

Concentration, Observed versus Modeled for June 16 through July 2, 2006, compare the 

observed and modeled daily maximum eight-hour ozone concentrations for each episode day of 

the 2006 base case. Figure 3-14: MNGE and MNB for 2006 Episode Days show the MNGE and 

MNB for monitored eight-hour ozone concentrations greater than 40 ppb for each episode day 

of the 2006 base case. Although there are no recommended criteria for the eight-hour UPA, 

MNGE, and MNB, the one-hour levels recommended by the EPA (i.e., plus or minus (±) 20%, 

30%, and ± 15%, respectively) were used for statistical evaluations.

The error bars on the daily peak measured eight-hour ozone concentrations in Figure 3-12 and 

Figure 3-13 represent the ± 20% UPA range for comparison with the daily maximum modeled 

eight-hour ozone concentrations. For the 33 episode days only seven days have daily maximum 

modeled eight-hour ozone concentrations outside the ± 20% UPA range. None of those seven 

days observed an eight-hour ozone exceedance (≥ 85 ppb). 

Figure 3-12: Peak Eight-Hour Ozone Concentration, Observed versus Modeled for 

May 31 through June 15, 2006
3-38

Figure 3-13: Peak Eight-Hour Ozone Concentration, Observed versus Modeled for 

June 16 through July 2, 2006

The area depicted in Figure 3-14: MNGE and MNB for 2006 Episode Days with MNGE ≤ 30% 

and MNB within ± 15% represents the joint condition for which both the MNGE and MNB are 

within acceptable ranges. The episode days labeled in red indicate those days for which daily 

peak measured eight-hour ozone concentrations were greater than or equal to 80 ppb.
3-39

Figure 3-14: MNGE and MNB for 2006 Episode Days

For the 33 days of the 2006 base case episode with daily maximum measured eight-hour ozone 

concentrations greater than or equal to 80 ppb, 26 days meet the joint condition of having both 

the MNGE ≤ 30% and MNB within ± 15%. Only two of the days not meeting the MNGE and 

MNB conditions are eight-hour ozone exceedance days. June 18 experienced a slow-moving 

frontal passage, which was difficult for the meteorological model to replicate. July 1 was a cloudy 

day that limited ozone production but the meteorological model predicted fewer clouds, and 

thus more ozone. The average daily maximum monitored ozone for those 33 days was 79.0 ppb, 

and the corresponding average daily maximum modeled ozone concentration was 79.3 ppb. The 

average MNB and MNGE were -0.3% and 14.7%, respectively.

Considering almost all days conformed to the UPA, MNGE, and MNB recommended criteria 

(and only two eight-hour exceedance days did not), the model suitably simulates the frequency 

and magnitude of daily maximum eight-hour ozone concentrations at the various monitors.

Graphical Evaluations

A detailed graphical evaluation of modeling results is presented in Appendix C. A selection of 

graphical evaluations is presented in this section. 

Six monitors in the nine-county DFW area were chosen for the evaluation on the basis of 

measured eight-hour ozone, geographic region, and source influences. Figure 3-15: Selected 

DFW Performance Evaluation Monitors is a map of the selected monitors. Eagle Mountain 
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Lake (C75), Denton Airport South (C56), and Keller (C17) frequently measure the highest eighthour ozone concentrations. Dallas Hinton (C401) and Keller (C17) are within the urban areas of 

Dallas and Fort Worth. Greenville (C1006) is east of the urban areas, frequently upwind, and 

outside of the nonattainment area. Weatherford Parker County (C76) is west of the urban areas 

and near oil and gas sources of the Barnett Shale.

 Figure 3-15: Selected DFW Performance Evaluation Monitors

DENT = Denton; DHIC = Dallas Hinton; EMTL = Eagle Mountain Lake; GRVL = Greenville; KELC = Keller; WTFD = 

Weatherford Parker County

Time series comparing hourly measured (red dots) and modeled (blue line) ozone 

concentrations are shown below for the six selected monitors. Included on the time-series 

graphic is the modeled maximum and minimum hourly ozone concentration within the three by 

three grid cell array around the monitor (green shading). Each day of the episode (May 31 

through July 2, 2006) is separated by dashed vertical lines.

Figure 3-16: Time Series of Hourly Ozone Concentrations at the Denton Airport South (C56),

Eagle Mountain Lake (C75), and Keller (C17) Monitors exhibits that relatively high ozone 

concentrations were measured at these monitors on several days during this episode. In general, 

the modeled ozone concentrations, including the three by three cell maximum-minimum range, 

replicate the diurnal pattern of the observations well. During the early morning hours at the 
3-41

Denton Airport South (C56) monitor, the model over-predicts ozone concentrations. 

Meteorological conditions including vertical mixing may be contributing to the overnight overprediction of hourly ozone. NOX concentrations (not shown) appear well simulated overnight. At 

all three monitors, the model under-predicts the peak ozone concentrations, especially on June 

9, 14, 18, and 28.

Figure 3-16: Time Series of Hourly Ozone Concentrations at the Denton Airport 

South (C56), Eagle Mountain Lake (C75), and Keller (C17) Monitors

Figure 3-17: Time Series of Hourly Ozone Concentrations at the Dallas Hinton (C60), 

Greenville (C1006), and Weatherford Parker County (C76) Monitors provides a comparison of 

measured and modeled hourly ozone concentrations at two rural monitors and an urban 

monitor. At the Dallas Hinton urban monitor, modeled concentrations replicate the diurnal 

pattern of the observations well with some over-prediction overnight. At the Greenville (C1006) 

monitor the model matches the daytime pattern well but poorly overestimates the nighttime 
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ozone concentrations. NOX concentrations (not shown) appear well simulated overnight so 

background transport and vertical mixing could be contributors. On the west side of the DFW 

area at the Weatherford Parker County (C76) monitor hourly ozone concentrations replicate the 

diurnal pattern very well throughout the episode. 

Figure 3-17: Time Series of Hourly Ozone Concentrations at the Dallas Hinton 

(C60), Greenville (C1006), and Weatherford Parker County (C76) Monitors

Scatter plots comparing the hourly measured and modeled concentrations of ozone (O3), NOX, 

olefins (OLE), and alkanes (PAR) are included in the performance evaluation. OLE is a CAMx 

chemical surrogate representing olefinic VOC, such as propylene, but excluding ethylene and 

certain compounds known as internal olefins, such as butenes (internal olefins are represented 

in CB05 by the surrogate species IOLE). Both ethylene and propylene are HRVOC and can 

contribute to the fast production of ozone. The DFW area does not have large ethylene and 

propylene emitters, unlike the Houston Ship Channel, but vehicles do emit small amounts. PAR 
3-43

is a CAMx chemical surrogate representing alkanes (paraffins), such as butane or n-octane, 

which can be emitted from oil and gas and other sources. Monitor sites included in the graphical 

representation were the three monitors with the highest daily maximum monitored eight-hour 

ozone concentrations and the two sites measuring VOCs with auto-GCs, Dallas Hinton (C60) 

and Fort Worth Northwest (C13).

Included on the scatter plots is the measured versus modeled quantile-quantile (QQ) plot, which 

first sorts independently both the measured and modeled concentrations, then plots the sorted 

values together. QQ plot data, shown as red dots, provide a measure of how close the modeled 

and measured distributions of values are to each other. If the red dots lie close to the diagonal 

one-to-one line, the model generates the correct proportions of small, medium, and large 

concentration values.

Figure 3-18: Scatter Plots of Hourly Ozone, NOX, OLE, and PAR at the Dallas Hinton (C401) 

Monitor shows the scatter plots for Dallas Hinton (C401). For ozone, the model compares 

favorably with the hourly observations throughout the range of concentrations. NOX

concentrations are slightly over-predicted from 15 to 30 ppb and then under-predicted for the 

highest concentrations. For OLE, the model under-predicts the lowest concentrations (less than 

1 ppb). The model consistently over-predicts PAR concentrations at Dallas Hinton (C401). The 

OLE and PAR plots are on a logarithmic scale. 
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 Figure 3-18: Scatter Plots of Hourly Ozone, NOX, OLE, and PAR at the Dallas 

Hinton (C401) Monitor

Tile plots of the of the daily maximum modeled eight-hour ozone concentrations are also 

included in the performance evaluation. Selected episode days are shown on which several 

monitors measured daily maximum eight-hour ozone concentrations greater than 84 ppb. 

Included on the tile plots are the monitor locations represented by small circles, color coded for 

the measured ozone concentration. The same scale is used for the measured and modeled 

maximum daily eight-hour ozone concentrations.

Tile plots of daily maximum eight-hour ozone concentrations for June 9, June 12 and 13, and 

June 30, 2006, are shown below in Figure 3-19: Tile Plot of Daily Maximum Eight-Hour Ozone 

Concentrations for June 9, June 12 and 13, and June 30, 2006. The model replicates the areas 

of highest eight-hour ozone for the selected days, although it slightly under-predicts the daily 

maximum eight-hour ozone concentrations on June 9 and June 30, 2006. 
3-45

Figure 3-19: Tile Plot of Daily Maximum Eight-Hour Ozone Concentrations for 

June 9, June 12 and 13, and June 30, 2006

Overall, the graphical evaluation of model performance at key monitors on key episode days 

indicates the modeling adequately replicates the features that produced high ozone during this 

episode.

Evaluations Based on TexAQS II Rural Monitoring Network Data

The TexAQS II study included a number of additional surface monitoring sites, which began 

collecting data in the summer of 2005 and continued until late October, 2006. Figure 3-20: 

TexAQS II Monitoring Sites Outside Ozone Nonattainment Areas depicts the active ozone 

monitors during the extended June 2006 episode. Data from the Clarksville (C648, CLVL), 

Wamba (C645, WMBA), Longview (C19, LGVW), Palestine (C647, PLTN), and San Augustine 

Airport (C646, SAGA) monitors are of particular importance to the DFW area as their locations 

allow measurement of background concentrations during the typical east through south flow on 

high eight-hour ozone days. Performance of the base case modeling at the Clarksville (C648) 
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and Palestine (C647) monitors is shown and discussed below. A full discussion of model 

performance at these and other rural monitors is provided in Appendix C.

Figure 3-20: TexAQS II Monitoring Sites Outside Ozone Nonattainment Areas

All of the monitors, except for Palestine (C647), are within the 12 km CAMx domain. While finer 

scale modeling (4 km or less) is necessary to capture plumes and pollutant concentration 

gradients in the urban areas, the performance of the model at regional sites can be examined to 

evaluate incoming background air. At the Clarksville (C648) monitor (Figure 3-21: Time Series 

of Hourly Ozone Concentrations at the Clarksville (C648) Monitor), the model follows the 

general diurnal pattern and trend of hourly ozone throughout the episode. The model underpredicts the highest concentrations and over-predicts the nighttime concentrations near the end 

of the episode. At the Palestine (C647) monitor (Figure 3-22: Time Series of Hourly Ozone 

Concentrations at the Palestine (C647) Monitor), the model replicates the diurnal pattern of 

hourly ozone very well during the first part of the episode. After June 16, the overnight modeled 
3-47

concentrations poorly match the observed lows when strong southerly flow occurs. The cause of 

this discrepancy is still being evaluated.

Figure 3-21: Time Series of Hourly Ozone Concentrations at the Clarksville (C648) 

Monitor

Figure 3-22: Time Series of Hourly Ozone Concentrations at the Palestine (C647) 

Monitor

3.6.4.3 

While most model performance evaluation (MPE) focuses on how well the model reproduces 

observations in the base case, a second and perhaps more important aspect of model 

performance is how well the model predicts changes as a result of modifications to its input

(Smith, 2010). The former type of MPE is static in the sense that it is based on a fixed set of 

observations which never change, while evaluating the model’s response to perturbations in its 

inputs is dynamic in the sense that the change in the model’s output is evaluated. Dynamic MPE 

is much less often performed than static MPE, simply because there is often little observational 

data available that reflects quantifiable changes in model inputs that can be directly related to 

air quality measurements. Since the attainment demonstration is based on modeling the future 

by changing the model’s inputs such as growth and controls, it is imperative to pursue dynamic 

MPE. The EPA’s modeling guidance recommends assessing the model’s response to emission 

changes. Two such dynamic MPEs are described below: retrospective model analysis and 

weekday/weekend analysis. 

Diagnostic Evaluations
3-48

Retrospective Modeling – 1999 Backcast

The goal of this diagnostic analysis is to use the model to forecast (actually backcast) a previous 

year when air quality was known, and compare the model’s predictions with those observations. 

Retrospective modeling is usually difficult to implement in practice because of the need to create

an inventory, but a 1999 inventory was already available from previous modeling applications so 

little additional inventory development was necessary. Instead of using the 1999 modeling 

application to model 2006, 1999 was back-cast from 2006 for several reasons, including a 

longer episode, better meteorological inputs, and improved inventories and boundary 

conditions available for 2006.

The development of the “predicted” 1999 inventory was analogous to developing a future 

inventory for an attainment test. Most of the 2006 baseline anthropogenic inventory was 

replaced with the available 1999 base case inventory (a 1999 baseline inventory would have been 

preferable, but was not available). As with future-case modeling, the 2006 biogenic emissions 

were not replaced, and the predictive modeling was conducted using the 2006 meteorology. The 

1999 and 2006 inventories used the MOBILE6.2 model for on-road emissions in this analysis as 

a 1999 MOVES2010a-based on-road emission inventory was not developed. 

Since the model predictions of a typical future design value are based on a (baseline year design 

value) DVB, which is the average of three regulatory design values (EPA, 2007), the quantity 

forecast in this test is not a specific future year’s design value but rather the year’s DVB. Thus, 

the regulatory design values for 1999, 2000, and 2001 were averaged in the same manner as the 

2006 DVB was calculated as the average of the 2006, 2007, and 2008 regulatory design values. 

Only monitors that had at least one regulatory design value in both the 1999 through 2001 and 

the 2006 through 2008 periods were used. Figure 3-23: Monitors Used in 1999 Retrospective 

Analysis shows the locations of the eight monitors used in this analysis.
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Figure 3-23: Monitors Used in 1999 Retrospective Analysis

Once the model was run with the 1999 baseline emissions, RRFs were calculated. In a 

retrospective analysis, RRFs are generally expected to be greater than one because ozone has 

decreased since the retrospective year. Table 3-24: Retrospective Analysis Design Values shows 

the observed DVBs, calculated RRFs, and the projected 1999 design values (DVPs).
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Table 3-24: Retrospective Analysis Design Values

Monitor 2006 DVB

(ppb)

1999 DVB

(ppb)

Observed 

2006 to 1999 

RRF

Modeled 

2006 to 1999 

RRF

1999 DVP

(ppb)

DENT - Denton C56 93.3 101.5 1.088 1.161 108.4

KELC - Keller C17 91.0 96.3 1.059 1.147 104.4

FWMC - Fort Worth NW C13 89.3 98.3 1.101 1.127 100.7

FRIC - Frisco C31 87.7 100.3 1.144 1.131 99.2

DALN - Dallas North C63 85.0 93.0 1.094 1.128 95.9

REDB - Dallas Exec Airport C402 85.0 88.0 1.035 1.142 97.1

DHIC - Dallas Hinton C401 81.7 92.0 1.126 1.127 92.0

MDLT - Midlothian Tower C94 80.5 92.3 1.147 1.146 92.3

Average 86.7 95.2 1.099 1.139 98.7

For five of the eight sites (Frisco (C31), Dallas Hinton (C401), Dallas North (C63), Midlothian 

Tower (C94), and Fort Worth Northwest (C13)), the projections were within 3 ppb of the 1999 

calculated baseline values. For the other three sites (Dallas Executive Airport – Redbird (C402), 

Denton Airport South (C56), and Keller (C17)), the model-projected 1999 DVs were higher than 

the observed values. The stronger response at those monitors could be due to emission 

inventory changes and the difference in meteorology from 2006 to 1999. Overall the modeled 

response was close to the actual airshed’s response to 1999-2006 emission changes, which 

provides confidence in the model’s ability to forecast the attainment year.

Observational Modeling – Weekday/Weekend

Weekend emissions of NOX in urban areas tend to be lower than weekday emissions because of 

lower vehicle miles travelled. The effect is most pronounced on weekend mornings, especially 

Sundays, since commuting is much lower than weekdays. This analysis examines the 

performance of the model in replicating the observed weekday/weekend effect. 

The inventories in this analysis used the MOBILE6.2 on-road emissions estimates. The 

magnitude of emission differences between weekday and weekend day-types using MOBILE6.2 

or MOVES2010a is approximately the same. Thus, the results of this analysis are not expected to 

change by using MOVES2010a. 

Figure 3-24: Comparison of Modeled 6:00 A.M. NOX and VOC Emissions for Wednesdays, 

Saturdays, and Sundays shows a comparison of modeled 6:00 A.M. NOX and VOC emissions 

for Wednesdays, Saturdays, and Sundays. Early morning emissions tend to be especially 

important in determining peak eight-hour ozone levels (MacDonald, 2010), so the 

weekday/weekend differences should manifest themselves noticeably in the relative levels of 

weekday and weekend ozone concentrations. Because there are relatively few Saturdays, 

Sundays, and Wednesdays (chosen to represent typical weekdays) in the episode, the TCEQ 

employed a novel approach which allowed each day of the episode to be treated as a Saturday, 

Sunday, and Wednesday, providing a total of 33 of each day type. This approach is possible since 

meteorology is independent of day-of-week, so by simply replacing the emissions of any episode 

day with Saturday (or Sunday or Wednesday) emissions we can obtain a valid representation of 

that day. The actual modeling procedure involved a series of runs using the 2006 baseline that 

were designed to ensure that each day-type was preceded by the appropriate predecessor daytype. Each Sunday was modeled following a Saturday, each Saturday followed a Friday, and each 
3-51

Wednesday followed a Wednesday (baseline modeled Tuesday emissions are very similar to 

Wednesdays). 

Figure 3-24: Comparison of Modeled 6:00 A.M. NOX and VOC Emissions for 

Wednesdays, Saturdays, and Sundays

For comparison with the modeled emissions, median monitored 6:00 A.M. NOX concentrations 

were calculated for every Wednesday, Saturday, and Sunday between May 15 and October 15 in 

the years 2005 through 2009. This approach gives approximately 125 observations for each type 

of day (less for some monitors because of missing data). Figure 3-25: Median Observed and 

Modeled 6:00 A.M. NOX Concentrations at DFW Monitors as a Percentage of Wednesday

shows observed and modeled 6:00 A.M. NOX concentrations at 11 sites in the DFW area. All sites 

show observed and modeled NOX concentrations that decline monotonically from Wednesday 

through Saturday to Sunday, except for the Midlothian Old Fort Worth (OFW) (C52) and 

Midlothian Tower (C94) observations which show essentially no change from Saturday to 

Sunday. The modeled values have somewhat greater variability than their observed 

counterparts, with all sites showing declines between 30% and 70% from Wednesday to Sunday, 

while all the observed sites dropped by between 40% and 70%.

0

5

10

15

20

25

Wkd Sat Sun Wkd Sat Sun

Onroad Mobile Stationary Points

Area Sources Non-Road

Offroad Mobile Total 

6 AM NOX

Emissions

6 AM VOC 

Emissions

(excluding biogenics )

Tons

(excluding Biogenics)
3-52

Figure 3-25: Median Observed and Modeled 6:00 A.M. NOX Concentrations at DFW 

Monitors as a Percentage of Wednesday

Figure 3-26: Observed and Modeled Median Daily Peak Eight-Hour Ozone Concentrations as a 

Percentage of Wednesday shows observed and modeled median daily peak eight-hour ozone 

concentrations as a percentage of Wednesdays for 19 DFW-area sites. The observed Saturday 

ozone concentrations (as a percent of Wednesday) are spread between a 10% increase and a 7% 

decrease, with more sites increasing than decreasing. Sunday concentrations ranged between a 

2% increase and a 16% decrease from Wednesday, with all but three sites showing a decrease. 

The modeled values consistently decreased between 2% and 4% on Saturday and between 4% 

and 7% on Sunday (compared with Wednesday), and showed very little spread compared with 

the observations. 

Part of the apparent discrepancy between the observed and modeled concentrations can be 

attributed to the comparison of observations from the entire ozone season with a modeled 

episode that was selected specifically to represent a period of especially high ozone 

concentrations. When the median observation concentrations are replaced with 90th percentile 

concentrations (representing high ozone days), the behavior of the observed and modeled 

concentrations is more consistent as seen in Figure 3-27: Observed 90th Percentile and 

Modeled Daily Peak Eight-Hour Ozone Concentrations as a Percentage of Wednesday. The 

observed 90th percentile concentrations range between a 4% increase and an 11% decrease on 

Saturday (compared with Wednesday), while on Sunday, all sites decrease from Wednesday, 

between 2% and 18%. In conclusion, the model is successfully replicating the observed weekdayweekend trends, especially for the higher ozone days.

0%

20%

40%

60%

80%

100%

120%

Wkd Sat Sun Wkd Sat Sun

ARLA DALN DENT DHIC FWMC GRAP

GRVL KAUF MDLO MDLT REDB

Median observed 6 AM 

NOX concentration as a 

percent of Wednesday

Median modeled 6 AM 

NOX concentration as a 

percent of Wednesday
3-53

Figure 3-26: Observed and Modeled Median Daily Peak Eight-Hour Ozone 

Concentrations as a Percentage of Wednesday
3-54

Figure 3-27: Observed 90th Percentile and Modeled Daily Peak Eight-Hour Ozone 

Concentrations as a Percentage of Wednesday

Finally, the modeled concentrations exhibit very little site-to-site variability compared with the 

observations. The reason for this small variation is that the modeling procedure applied 

Wednesday, Saturday, and Sunday emissions to exactly the same set of days. Thus, the day-today and site-to-site meteorological variability, which clearly affects the observed concentrations, 

is absent in the modeled concentrations. Thus, the modeling technique isolated the signal 

(model response to weekday-weekend emission changes) from the noise (meteorological 

variability), allowing a clean assessment of the model’s response to the emission variability.

3.7 2006 BASELINE AND 2012 FUTURE CASE MODELING 

3.7.1 2006 Baseline Modeling

The TCEQ selected 2006 as the baseline year for conducting the attainment modeling. The 

typical 2006 OSD emissions were modeled for all episode days. Days with modeled 

concentrations above 70 ppb were used for the modeled attainment test, per the EPA’s modeling 

guidance (EPA, 2007). Figure 3-28: Near Monitoring Site Grid Cell Array Size shows a map of 

the 4 km domain depicting the regulatory monitors and the extent of the three by three grid cell 

arrays around each monitor. The maximum concentrations from the three by three grid cell 

arrays were used in the modeled attainment test. Table 3-25: 2006 Baseline Values Used in the 

Modeled Attainment Test details the monitor-specific DVB, average baseline modeled 

concentrations and the number of days above the 70 ppb threshold. 
3-55

Figure 3-28: Near Monitoring Site Grid Cell Array Size

Table 3-25: 2006 Baseline Values Used in the Modeled Attainment Test

Site Monitor 2006 DVB (ppb)* 2006 Modeled 

Average (ppb)

Modeled Days 

Averaged

DENT Denton C56 93.33 87.16 10

EMTL Eagle Mountain Lake C75 93.33 86.95 10

KELC Keller C17 91.00 88.33 10

GRAP Grapevine Fairway C70 90.67 88.26 10

FWMC Fort Worth Northwest C13 89.33 88.02 10
3-56

Site Monitor 2006 DVB (ppb)* 2006 Modeled 

Average (ppb)

Modeled Days 

Averaged

FRIC Frisco C31 87.67 83.34 10

WTFD Weatherford Parker County C76 87.67 81.45 10

DALN Dallas North C63 85.00 81.00 10

REDB Dallas Exec Airport C402 85.00 80.49 10

CLEB Cleburne C77 85.00 80.39 9 

ARLA Arlington C61 83.33 85.01 10

DHIC Dallas Hinton C401 81.67 81.02 10

PIPT† Pilot Point C1032† 81.00† 84.23 10

MDLT† Midlothian Tower C94† 80.50† 79.49 10

RKWL Rockwall Heath C69 77.67 74.55 10

MDLO† Midlothian OFW C52† 75.00† 81.17 10

KAUF Kaufman C71 74.67 75.02 7 

GRAN# Granbury C73 83.00 80.38 10

GRVL# Greenville C1006 75.00 73.54 9 

* DVB values 85 ppb or greater are shown in red.

† PIPT, MDLT, and MDLO did not measure enough data from 2004 through 2008 to calculate a complete DVB. The 

DVB shown uses all available data.

# Granbury C73 and Greenville C1006 are outside the 1997 eight-hour ozone NAAQS DFW nonattainment area.

Three monitors in the DFW area did not have 10 modeled days above 70 ppb. These monitors 

are not located where the highest area ozone concentrations are typically observed, which is 

indicated by the 2006 DVB and the number of days above ozone concentration thresholds in 

Table 3-2. 

3.7.2 Future Baseline Modeling

Similar to the 2006 baseline modeling, the 2012 modeling was conducted for each of the episode 

days. The projected 2012 ozone season day emissions were used, as previously summarized in 

Table 3-21. Using the same days as used in the 2006 baseline modeling, the average of the 2012 

modeled maximum daily eight-hour ozone concentrations within the three by three grid cell 

array about each monitor were calculated. The RRF at each regulatory monitor was calculated as 

the ratio of the baseline/future modeled averages, and the 2012 future year design value (DVF) 

at each monitor was estimated as per the EPA’s modeling guidance by multiplying the 2006 DVB

by the RRF. Table 3-26: Summary of the RRF and 2012 Future Design Values details the 2006 

DVB, RRF, and 2012 DVF at each of the regulatory monitors.

Table 3-26: Summary of the RRF and 2012 Future Design Values

Site Monitor 2006 DVB (ppb)* RRF 2012 DVF (ppb)*

DENT Denton C56 93.33 0.825 77

EMTL Eagle Mountain Lake C75 93.33 0.836 78

KELC Keller C17 91.00 0.840 76

GRAP Grapevine Fairway C70 90.67 0.840 76

FWMC Fort Worth Northwest C13 89.33 0.844 75
3-57

Site Monitor 2006 DVB (ppb)* RRF 2012 DVF (ppb)*

FRIC Frisco C31 87.67 0.849 74

WTFD Weatherford Parker County C76 87.67 0.829 72

DALN Dallas North C63 85.00 0.837 71

REDB Dallas Exec Airport C402 85.00 0.830 70

CLEB Cleburne C77 85.00 0.834 70

ARLA Arlington C61 83.33 0.844 70

DHIC Dallas Hinton C401 81.67 0.831 67

PIPT† Pilot Point C1032† 81.00† 0.831† 67† 

MDLT† Midlothian Tower C94† 80.50† 0.828† 66† 

RKWL Rockwall Heath C69 77.67 0.815 63

MDLO† Midlothian OFW C52† 75.00† 0.830† 62† 

KAUF Kaufman C71 74.67 0.809 60

GRAN# Granbury C73 83.00 0.839 69

GRVL# Greenville C1006 75.00 0.799 59

* DVB and DVF values 85 ppb or greater are shown in red.

† PIPT, MDLT, and MDLO did not measure enough data from 2004 through 2008 to calculate a complete DVB. The 

DVB shown uses all available data. The DVF was calculated using the DVB shown. 

# Granbury C73 and Greenville C1006 are outside the 1997 eight-hour ozone NAAQS DFW nonattainment area.

The 2012 baseline attainment modeling projects no DFW area regulatory monitors to have a 

2012 DVF greater than 84 ppb.

3.7.3 Ozone Source Apportionment Tool and Anthropogenic Precursor Culpability 

Analysis

The TCEQ applied the OSAT and APCA CAMx tools to the 2006 and 2012 baseline modeling. 

For both types of analyses, emission source groups such as on-road mobile (using 

MOVES2010a), non-road and off-road mobile, and biogenics, and emission source regions such 

as the DFW area, east Texas, and non-Texas were defined. OSAT keeps track of the origin of the 

NOX and VOC precursors creating the ozone, which can then be apportioned to specific sources 

groups and regions. APCA is similar to OSAT, but it recognizes that the biogenics source 

category is not controllable. Where OSAT would apportion ozone production to biogenic 

emissions, APCA reallocates that ozone production to the controllable or anthropogenic 

emissions that combined with the biogenic emissions to create ozone. Only ozone created from 

both biogenic NOX and VOC precursors is apportioned to the biogenic emission source group by 

APCA. 

APCA results of the June 2006 baseline and 2012 future cases are presented here for the Eagle 

Mountain Lake (C75) and Dallas Hinton (C401) monitors. The results are graphed as layered 

area plots for every rolling eight-hour average for the source groups and regions listed in Table 

3-27: APCA Source Groups and Regions. Figure 3-29: APCA Source Regions exhibits the 

geographic regions applied in the APCA analysis. Appendix C contains a more detailed analysis 

of the APCA results, including additional monitors. 
3-58

Table 3-27: APCA Source Groups and Regions

Figure Legend Abbreviation Description of Source Group and Region

IC Initial Condition

WSTBC West Boundary Condition

ESTBC East Boundary Condition

STHBC South Boundary Condition

NTHBC North Boundary Condition

TOPBC Top Boundary Condition

Non-Texas All emission source types outside Texas

West Texas All emission source types in west Texas

South Texas All emission source types in south-central Texas

East Texas All emission source types in east Texas

DFW Biogenics DFW Biogenic sources 

DFW EI & Ships DFW Elevated point sources

DFW On-Road DFW On-road sources

DFW Non-Road DFW Non-Road sources

DFW Area DFW Area sources

DFW O&G PROD/DRILL DFW Oil and Gas production and drilling sources

DFW Other DFW Low-level point sources
3-59

Figure 3-29: APCA Source Regions

Each layer in the figures below represents a source group or type’s contribution to the total 

modeled ozone concentration. The layers are ordered according to the legend at the top of the 

figure (Initial Conditions on the bottom; DFW Other at the top). The layer corresponding to the 

initial model conditions disappears after the first few days of the episode are modeled, as 

expected. Layers corresponding to boundary conditions can give an indication of wind direction 

and possibly transport on individual episode days. 

At EMTL (Figure 3-30: 2006 Baseline Case Eagle Mountain Lake (C75) Eight-Hour APCA with 

MOVES2010a Results (May 31 through June 15), Figure 3-31: 2006 Baseline Case Eagle 

Mountain Lake (C75) Eight-Hour APCA with MOVES2010a Results (June 16 through July 1), 

Figure 3-32: 2012 Future Case Eagle Mountain Lake (C75) Eight-Hour APCA with 

MOVES2010a Results (May 31 through June 15), and Figure 3-33: 2012 Future Case Eagle 

Mountain Lake (C75) Eight-Hour APCA with MOVES2010a Results (June 16 through July 1)) 

and Dallas Hinton (C401) (Figure 3-34: 2006 Baseline Case Dallas Hinton (C401) Eight-Hour 

APCA with MOVES2010a Results (May 31 through June 15), Figure 3-35: 2006 Baseline Case 

Dallas Hinton (C401) Eight-Hour APCA Results with MOVES2010a (June 16 through July 1), 

Figure 3-36: 2012 Future Case Dallas Hinton (C401) Eight-Hour APCA with MOVES2010a 

Results (May 31 through June 15) and Figure 3-37: 2006 Future Case Dallas Hinton (C401) 
3-60

Eight-Hour APCA with MOVES2010a Results (June 16 through July 1)) non-Texas, SouthCentral Texas, and DFW sources contribute significantly to the total ozone. West Texas and 

DFW Oil and Gas sources contribute more at Eagle Mountain Lake (C75) than Dallas Hinton 

(C401) on certain days as expected based on EMTL’s proximity to oil and gas sources as well as 

the West Texas geographic region. Dallas Hinton (C401) appears to receive more contribution 

from East Texas sources. From 2006 through 2012, the contribution from local DFW sources 

decreases, including on-road, non-road, and oil and gas emission sources. Natural gas 

compressor engine rules from the 2007 DFW AD SIP revision required additional NOX controls 

from these oil and gas sources starting in 2009 (TCEQ, 2007a). Less contribution was also 

observed from the non-DFW source regions in 2012 than the 2006 non-DFW source regions.

Figure 3-30: 2006 Baseline Case Eagle Mountain Lake (C75) Eight-Hour APCA with 

MOVES2010a Results (May 31 through June 15)

Figure 3-31: 2006 Baseline Case Eagle Mountain Lake (C75) Eight-Hour APCA with 

MOVES2010a Results (June 16 through July 1)
3-61

Figure 3-32: 2012 Future Case Eagle Mountain Lake (C75) Eight-Hour APCA with 

MOVES2010a Results (May 31 through June 15)

Figure 3-33: 2012 Future Case Eagle Mountain Lake (C75) Eight-Hour APCA with 

MOVES2010a Results (June 16 through July 1)
3-62

Figure 3-34: 2006 Baseline Case Dallas Hinton (C401) Eight-Hour APCA with 

MOVES2010a Results (May 31 through June 15)

Figure 3-35: 2006 Baseline Case Dallas Hinton (C401) Eight-Hour APCA Results 

with MOVES2010a (June 16 through July 1)
3-63

Figure 3-36: 2012 Future Case Dallas Hinton (C401) Eight-Hour APCA with 

MOVES2010a Results (May 31 through June 15)

Figure 3-37: 2006 Future Case Dallas Hinton (C401) Eight-Hour APCA with 

MOVES2010a Results (June 16 through July 1)

3.7.4 Future Case Modeling with Controls

No new controls are being modeled with this AD SIP revision. Two rulemakings are being 

incorporated into this AD SIP revision as RACT: (1) a rulemaking (Rule Project No. 2010-016-

115-EN) to update existing control requirements for certain coatings and other solvent usage 

operations to implement RACT for certain source categories addressed in Control Techniques 

Guidelines documents issued by the EPA from 2006 through 2008; and (2) a rulemaking (Rule 

Project Number 2010-025-115-EN) to update existing control requirements for the storage of 

VOC to implement RACT for the petroleum liquid storage CTG emission source category. Both 
3-64

rulemakings have compliance dates in March 2013, so neither rulemaking was included in the 

model for this SIP revision.

3.7.5 Unmonitored Area Analysis

EPA guidance (EPA, 2007) recommends that areas not near monitoring locations (unmonitored 

areas) be subjected to an “unmonitored area (UMA) analysis” to demonstrate that these areas 

are expected to reach attainment by the area’s attainment year, in this case 2012. The standard 

attainment test is applied only at monitor locations, and the UMA analysis is intended to 

identify any areas not near a monitoring location that are at risk of not meeting the attainment 

date. Recently, the EPA provided Modeled Attainment Test Software (MATS) that can be used to 

conduct UMA analyses but has not specifically recommended using its software in EPA 

guidance, instead stating that “States will be able to use the EPA-provided software or are free to 

develop alternative techniques that may be appropriate for their areas or situations.”

The TCEQ chose to use its own procedure to conduct the UMA analysis instead of MATS for 

several reasons. Both procedures incorporate modeled predictions into a spatial interpolation 

procedure; however, the TCEQ Attainment Test for Unmonitored areas (TATU) is already 

integrated into the TCEQ’s model post-processing stream while MATS requires that modeled 

concentrations be exported to a personal computer-based platform. Additionally, MATS 

requires input in latitude/longitude, while TATU works directly off the LCP data used in TCEQ 

modeling applications. Finally, MATS uses the Voronoi Neighbor Averaging (VNA) technique 

for spatial interpolation, while TATU relies on the more familiar kriging geospatial interpolation 

technique. More information about TATU is provided in Appendix C, Attachment 2: Spatial 

Interpolation for Attainment Demonstration. 

Figure 3-38: Spatially Interpolated 2006 Baseline with MOVES2010a (left) and 2012 Future 

Case with MOVES (right) Design Values for the DFW Area shows two color contour maps of 

ozone concentrations produced by TATU, one for the 2006 baseline with MOVES2010a

emissions (left) and one for the 2012 future case with MOVES2010a emissions (right). The 

figure shows the extent and magnitude of the expected improvements in ozone design values, 

with zero grid cells at or above 85 ppb in the future case plot. The maximum design value in the 

domain is predicted at 81.8 ppb.
3-65

Figure 3-38: Spatially Interpolated 2006 Baseline with MOVES2010a (left) and 

2012 Future Case with MOVES2010a (right) Design Values for the DFW Area

3.8 MODELING ARCHIVE AND REFERENCES

3.8.1 Modeling Archive

The TCEQ has archived all modeling documentation and modeling input/output files generated 

as part of the DFW SIP modeling analysis. Interested parties can contact the TCEQ for 

information regarding data access or project documentation. Most modeling files and 

performance evaluation products may be found on TCEQ’s modeling FTP Web site. 

3.8.2 Modeling References

Baker Hughes, 2010. Baker Hughes Investor Relations - Rig Counts, 

http://investor.shareholder.com/bhi/rig_counts/rc_index.cfm. 

Emery, C., E. Tai, and G. Yarwood, 2001. Enhanced Meteorological Modeling and Performance 

Evaluation for Two Texas Ozone Episodes, Final Report to the Texas Natural Resource 

Conservation Commission under TNRCC Umbrella Contract No. 582-0-31984, Environ 

International Corporation, Novato, CA. 

Environ, 2007. User’s Guide Emissions Processor, Version 3, Environ International 

Corporation, Novato, CA.

Environ, 2008. Description from MM5CAMx README file contained in 

mm5camx.21feb08.tar.gz archive, http://www.camx.com/files/mm5camx.21feb08.tar.gz, 

Environ Holdings, Inc.

Environ, 2008b. Boundary Conditions and Fire Emissions Modeling, Final Report to the Texas 

Commission on Environmental Quality (TCEQ), Contract No. 582-7-84005-FY08-06, Environ 

International Corporation, Novato, CA.

Environ, 2009. User’s Guide Comprehensive Air Quality Model with Extensions (CAMx), 

Version 4.53, Environ International Corporation, Novato, CA.
3-66

Environ, 2011. Improving the Representation of Vertical Mixing Processes in CAMx, Final 

Report to the Texas Commission on Environmental Quality (TCEQ), Contract No.

582‐11‐10365‐FY11‐02, 

http://www.tceq.texas.gov/assets/public/implementation/air/am/contracts/reports/pm/58211

10365FY1102-20110822-environ-vertical_mixing_final_report.pdf, Environ International 

Corporation, Novato, CA.

EPA, 2005. Modeling files obtained via data request from the EPA in support of the Clean Air 

Interstate Rule Notice of Data Availability Technical Support Document, as documented at 

http://www.epa.gov/cair/technical.html.

EPA, 2007. Guidance on the Use of Models and Other Analyses for Demonstrating Attainment 

of Air Quality Goals for Ozone, PM2.5, and Regional Haze, 

http://www.epa.gov/scram001/guidance/guide/final-03-pm-rh-guidance.pdf.

EPA, 2008. Approval and Promulgation of Air Quality Implementation Plans; Texas; 

Dallas/Fort Worth 1-Hour Ozone Nonattainment Area; Determination of Attainment of the 1-

Hour Ozone Standard, http://edocket.access.gpo.gov/2008/pdf/E8-24592.pdf. 

EPA, 2010. Determination of Nonattainment and Reclassification of 1997 8-hour Ozone 

Nonattainment Areas: Dallas/Fort Worth, TX, 

http://www.regulations.gov/search/Regs/home.html#documentDetail?R=0900006480b2c08e 

ERG, 2007. Tier-Specific Locomotive Engine Update, Final Report to the Texas Commission on 

Environmental Quality (TCEQ), Contract No. 582-7-84003-FY07-04, Eastern Research Group, 

Inc., Morrisville, NC.

ERG, 2010. Characterization of Oil and Gas Production Equipment and Develop a Methodology 

to Estimate Statewide Emissions, Final Report to the Texas Commission on Environmental 

Quality (TCEQ), Contract No. 582-7-84003-FY10-26, 

http://www.tceq.texas.gov/assets/public/implementation/air/am/contracts/reports/ei/582078

4003FY1026-20101124-ergi-oilGasEmissionsInventory.pdf, Eastern Research Group, Inc., 

Morrisville, NC.

Feldman, M.S., T. Howard, E. McDonald-Buller, G. Mullins, D.T. Allen, A. Webb, Y. Kimura, 

2007. Applications of Satellite Remote Sensing Data for Estimating Dry Deposition in Eastern 

Texas. Atmospheric Environment, 41(35): 7562-7576.

Grell, G., J. Dudhia, and D. Stauffer, 1994. A Description of the Fifth Generation Penn 

State/NCAR Mesoscale Model (MM5), Technical Report NCAR/TN-398+STR, National Center 

of Atmospheric Research (NCAR) Tech Note.

Kinnee et al., 1997. United States Land Use Inventory for Estimating Biogenic Ozone Precursor 

Emissions. Ecological Applications 7(1): 46-58.

MacDonald, Nicole and Hakami, A, 2010. Temporal Source Apportionment of Policy-Relevant 

Air Quality Metrics, Presented at the 9th CMAS Conference Oct. 11-13, 2010, Chapel, Hill, N.C.

Mellor, G. L., and T. Yamada, 1974: A hierarchy of turbulence closure models for planetary 

boundary layers. J. Atmos. Sci., 31, 1791–1806.
3-67

NCAR, 2005. MM5 On-line Tutorial Home Pages, http://www.mmm.ucar.edu/mm5/On-LineTutorial/teachyourself.html, NCAR, Colorado.

NCEP, 2009. Global Energy and Water Cycle Experiment (GEWEX) Continental International 

Project (GCIP) National Centers for Environmental Prediction (NCEP) Eta Model Output, 

Computational and Information Systems Laboratory (CISL) Research Data Archive (RDA): 

ds609.2 Home Page, http://dss.ucar.edu/datasets/ds609.2/, NCEP.

NCTCOG, 2011. Development of Annual Emissions Inventories and Activity Data for Airports in 

the 12-County Dallas-Fort Worth Area, Report to TCEQ, North Central Texas Council of 

Governments Transportation 

Department, ftp://amdaftp.tceq.state.tx.us/pub/Offroad_EI/Airports/DFW/NCTCOG_DFW_A

irport_EI_Report_August_2011.pdf. 

Popescu, Sorin C., Jared Stukey, Mark Karnauch, Jeremiah Bowling, Xuesong Zhang, William 

Booth, and Nian-Wei Ku, 2008. The New Central Texas Land Use Land Cover Classification 

Project, Final Report to the TCEQ, Contract No. 582-5-64593-FY08-23, 

http://www.tceq.state.tx.us/assets/public/implementation/air/am/contracts/reports/oth/5820

564593FY0823-20081230-tamu-New_Central_TX_LULC.pdf, Texas A & M University, College 

Station, Texas.

RigData, 2009. RigData Barnett Shale Rig Count, 

http://www.barnettshalenews.com/documents/RigData%20Barnett%20Shale%20Rig%20Coun

t%20Booklet%20Barnett%20Shale%20EXPO%203-11-2009.pdf. 

Robinson, R., T. Gardiner, and B. Lipscombe, 2008. Measurements of VOC Emissions from 

Petrochemical Industry Sites in the Houston Area Using Differential Absorption Lidar (DIAL) 

During Summer 2007, Draft. Submitted to Russell Nettles, TCEQ, by Rod Robinson, Tom 

Gardiner, and Bob Lipscombe of the National Physical Laboratory, Teddington, Middlesex UK 

TW11 0LW, February 8, 2008, pp. 86. 

Smith, Jim and Estes, M., 2010. Dynamic Model Performance Evaluation Using WeekdayWeekend and Retrospective Analysis, Presented at the 9th CMAS Conference Oct. 11-13, 2010, 

Chapel, Hill, N.C.

Starcrest, 2000. Houston-Galveston Area Vessel Emissions Inventory, Starcrest Consulting 

Group, Houston, Texas.

Stauffer, D. R. and N. L. Seaman, 1990. Use of Four-Dimensional Data Assimilation in a 

Limited-Area Mesoscale Model. Part I: Experiments with Synoptic-Scale Data. Monthly 

Weather Review, 118: 1250-1277.

Stauffer, D.R. and N.L. Seaman, 1994. Multiscale four-dimensional data assimilation. Journal of 

Applied Meteorology, 33: 416-434.

Stauffer, D. R., N. L. Seaman, and F. S. Binkowski, 1991. Use of Four-Dimensional Data 

Assimilation in a Limited-Area Mesoscale Model. Part II: Effects of Data Assimilation Within 

the Planetary Boundary Layer. Monthly Weather Review, 119: 734-754.

TCEQ, 2007a. Revisions to the State Implementation Plan (SIP) for the Control of Ozone Air 

Pollution, Dallas-Fort Worth Eight-Hour Ozone Nonattainment Area Attainment 

Demonstration, TCEQ, Austin, Texas.
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TCEQ, 2007b. East Texas Combustion Rule, Title 30 TAC Chapter 117.3300, 

http://www.tceq.state.tx.us/permitting/air/rules/state/117/3300/r7e4_etexhp.html. 

TCEQ, 2009. TCEQ Air Modeling and Data Analysis (AMDA) Section public web site, 

http://www.tceq.state.tx.us/implementation/air/airmod/data/DFW8h2/DFW8h2.html.

TCEQ, 2010. Adopted HGB Attainment Demonstration SIP Revision for the 1997 Eight-Hour 

Ozone Standard (2009-017-SIP-NR), Texas Commission on Environmental Quality, March 

2010, http://www.tceq.state.tx.us/implementation/air/sip/texas-sip/hgb/hgb-latest-ozone. 

TCEQ, 2011, Texas Air Emissions Repository (TexAER) web site, 

http://www5.tceq.state.tx.us/texaer/. 

Wiedinmyer, C., A. Guenther, M. Estes, I.W. Strange, G. Yarwood, and D. Allen, 2001. A Land 

Use Database and Examples of Biogenic Isoprene Emission Estimates for the State of Texas, 

USA. Atmospheric Environment, 35: 6465-6477.
4-1 

CHAPTER 4: CONTROL STRATEGIES AND REQUIRED ELEMENTS

4.1 INTRODUCTION

The Dallas-Fort Worth (DFW) nonattainment area for the 1997 eight-hour ozone National 

Ambient Air Quality Standard (NAAQS), which consists of Collin, Dallas, Denton, Tarrant, Ellis, 

Johnson, Kaufman, Parker, and Rockwall Counties, includes a wide variety of major and minor 

industrial, commercial, and institutional entities. The Texas Commission on Environmental 

Quality (TCEQ) has implemented stringent and innovative regulations that address emissions of 

nitrogen oxides (NOX) and volatile organic compounds (VOC) from these sources. This chapter 

describes existing ozone control measures and ozone control measures being adopted 

concurrently with this state implementation plan (SIP) revision for the DFW area, as well as 

how Texas meets the following serious ozone nonattainment area SIP requirements: reasonably 

available control technology (RACT), reasonably available control measures (RACM), motor 

vehicle emissions budget (MVEB), and contingency measures.

4.2 EXISTING CONTROL MEASURES

Since the early 1990s, a broad range of control measures have been implemented for each 

emission source category for ozone planning in the DFW area. Table 4-1: Existing Ozone Control 

Measures Applicable to the DFW Nine-County Nonattainment Area lists the existing ozone 

control strategies that have been implemented for the one-hour and 1997 eight-hour ozone 

standards in the DFW area.

Table 4-1: Existing Ozone Control Measures Applicable to the DFW Nine-County 

Nonattainment Area

Measure Description Start Date(s)

DFW Industrial, 

Commercial, and 

Institutional (ICI) Major 

Sources Rule

Applies to all major sources (50 tons per year 

(tpy) of NOX or more) with affected units

Affected source categories included in rule: 

boilers; process heaters; stationary gas turbines; 

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; and natural 

gas-fired dryers used in organic solvent, printing 

ink, clay, brick, ceramic tile, calcining, and 

vitrifying processes

Note: these NOX control requirements are in 

additional to the NOX control strategies 

implemented for ICI major sources in Collin, 

Dallas, Denton, and Tarrant Counties in March 

2002 for the one-hour ozone NAAQS

March 1, 2009, or 

March 1, 2010, 

depending on source 

category
4-2 

Measure Description Start Date(s)

DFW ICI Minor Source 

Rule

Applies to all minor sources (less than 50 tpy of 

NOX) with stationary internal combustion engines

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

DFW Major Utility 

Electric Generation 

Source Rule

NOX control requirements for DFW utility electric 

generating facilities

Applies to utility boilers electric generation 

facilities with affected sources and auxiliary 

steam boilers, and stationary gas turbines for 

RACT purposes

Note: these NOX control requirements are in 

additional to the NOX control strategies 

implemented in for utilities in Collin, Dallas, 

Denton, and Tarrant Counties in 2001 through 

2005 for the one-hour ozone NAAQS

March 1, 2009

Utility Electric 

Generation in East and 

Central Texas 

NOX control requirements on utility boilers and 

stationary gas turbines at utility electric 

generation sites in East and Central Texas, 

including Parker County

May 1, 2003, through 

May 1, 2005

DFW Cement Kiln Rule NOX control requirements for all Portland cement 

kilns located in Ellis County

March 1, 2009

NOX Emission Standards 

for Nitric Acid 

Manufacturing – General

NOX emission standards for nitric acid 

manufacturing facilities (state-wide rule – no

nitric acid facilities in DFW)

November 15, 1999

East Texas Combustion 

Sources

NOX control requirements for stationary richburn, gas-fired internal combustion engines (240 

horsepower (hp) 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 

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
4-3 

Measure Description Start Date(s)

General VOC Control 

Measures 

Additional control technology requirements for 

VOC sources for RACT purposes including: 

storage, general vent gas, industrial wastewater, 

loading and unloading operations, general VOC 

leak detection and repair (LDAR), solvent using 

processes, etc (see Appendix D: Reasonably 

Available Control Technology Analysis for more 

details)

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 

Offset Lithographic 

Printing 

Control technology requirements for offset 

lithographic printing

Revision to limit VOC content of solvents used by 

offset lithographic printing facilities and to 

include smaller sources in rule applicability

December 31, 2000, in 

Collin, Dallas, Denton, 

and Tarrant Counties 

and March 1, 2009, in 

Ellis, Johnson, 

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 

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

Voluntary Energy 

Efficiency/Renewable 

Energy

Energy efficiency and renewable energy projects 

encouraged by Senate Bill (SB) 7 from 76th 

session of Texas Legislature and SB 5 from 77th 

session of Texas Legislature

September 1, 1999, 

and September 1, 

2001

Automotive Windshield 

Washer Fluid 

VOC content limitation on automotive windshield 

washer fluid sold, supplied, distributed, or 

manufactured for use in Texas

January 1, 1995

Refueling – Stage I 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
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Measure Description Start Date(s)

Refueling – Stage II 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)

Federal Area/Non-Road 

Measures

Series of emissions limits implemented by the 

United States Environmental Protection Agency 

(EPA) for area and non-road sources

Examples: diesel and gasoline engine standards 

for locomotives and leaf-blowers

Through 2007

Texas Emissions 

Reduction Plan (TERP)

Provides grant funds for on-road and non-road 

heavy-duty diesel engine replacement/retrofit

January 2002

California Gasoline 

Engines

California standards for non-road gasoline 

engines 25 hp and larger

May 1, 2004

Texas Low Emission 

Diesel (TxLED)

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

higher cetane number 

Phase in began 

October 31, 2005

Texas Low Reid Vapor 

Pressure (RVP) Gasoline

Requires all gasoline for both on-road and nonroad use to have RVP of 7.8 pounds per square 

inch or less from May 1 through October 1 each 

year

April 2000

Voluntary Mobile 

Emissions Reduction 

Program (VMEP)

Voluntary measures administered by the North 

Central Texas Council of Governments (NCTCOG)

(see Appendix H: NCTCOG Submittal of On-Road 

and Non-Road Mobile Emissions Reductions 

Benefit of the May 2007 DFW AD SIP Revision for 

more details)

2007

Federal On-Road 

Measures

Series of emissions limits implemented by the 

EPA for on-road vehicles

Included in measures: Tier 1 and Tier 2 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

Vehicle Inspection/ 

Maintenance (I/M)

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
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Measure Description Start Date(s)

Environmental Speed 

Limit (ESL)

Five miles per hour (mph) below what was posted 

before May 1, 2002, on roadways where speeds 

were 65 mph or higher

ESLs adopted by the commission in April 2000 

converted to Transportation Control Measures

(TCMs) by the TCEQ in August 2010

September 2001

Transportation Control 

Measures

Various measures in NCTCOG’s long-range 

transportation plans (see Chapter 4: Required 

Control Strategy Elements, of the May 2007 DFW 

AD SIP Revision) 

2007

Voluntary Energy 

Efficiency/Renewable 

Energy

Energy efficiency and renewable energy projects 

encouraged by SB 5 and SB 7 from the 80th 

session of the Texas Legislature

December 2000

4.3 UPDATES TO EXISTING CONTROL MEASURES

4.3.1 Updates to Coatings Control Measures

Concurrent with this AD SIP revision, the commission is adopting rulemaking (Rule Project 

Number 2010-016-115-EN) to update existing control requirements for certain coatings and 

other solvent usage operations to implement RACT for the following source categories 

addressed in Control Techniques Guidelines (CTG) documents issued by the EPA from

2006through 2008: 

• Flexible Package Printing, Group II, issued in 2006; 

• Large Appliance Coatings, Group III, issued in 2007; 

• Metal Furniture Coatings, Group III, issued in 2007; 

• Paper, Film, and Foil Coatings, Group III, issued in 2007; 

• Miscellaneous Metal and Plastic Parts Coatings, Group IV, issued in 2008; and

• Auto and Light-Duty Truck Assembly Coatings, Group IV, issued in 2008. 

The pleasure craft and the plastic parts coating subcategories in the 2008 Miscellaneous Metal 

and Plastic Parts Coatings CTG document represent new control measures, as discussed in 

Section 4.4: New Control Measures. Additional detail concerning these updated control 

measures can be found in the RACT discussion in Section 4.5.3: VOC RACT Determination of 

this chapter.

4.3.2 Updates to VOC Storage Tank Control Measures

Concurrent with this AD SIP revision, the commission is adopting rulemaking (Rule Project 

Number 2010-025-115-EN) to update existing control requirements for the storage of VOC to 

implement RACT for the petroleum liquid storage CTG emission source category. This 

rulemaking revises existing rules to include additional requirements for low-leaking storage 

tank fittings and to limit situations when floating roof storage tanks are allowed to emit VOC 

because the roof is not floating on the liquid. Additional detail concerning these updated control 

measures can be found in the RACT discussion in Section 4.5.3 of this chapter.
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4.3.3 Repeal of State Portable Fuel Container Rule

The EPA adopted a federal portable fuel container (PFC) rule in the February 26, 2007, issue of 

the Federal Register (72 FR 8432) that set a national standard for gasoline, diesel, and kerosene 

PFCs. The rule requires all PFCs manufactured on or after January 1, 2009, to comply with the 

federal standards. The new federal PFC regulations are consistent with the revised PFC 

regulations adopted by the California Air Resources Board (CARB) on September 15, 2005. The

Texas PFC regulations were inconsistent with the new federal standards, because they were

based on previous PFC testing methods adopted by CARB in 2001. Therefore, the state repealed 

its PFC regulations (rule project number 2008-032-115-EN) on February 10, 2010, to rely on the 

implementation of the federal PFC regulations to control VOC emissions from PFCs used within 

the state. According to an EPA analysis entitled, Federal Register Rule vs. Texas Register Rule 

Portable Fuel Containers, the federal PFC rule is more stringent than the repealed Texas PFC 

rule.

4.3.4 Clean Fuel Fleet Requirement

Participation in a Clean Fuel Fleet Program (CFFP) is required by § 246 of the FCAA for 

nonattainment areas with 1980 populations greater than 250,000 that are classified as serious 

or above for ozone. In accordance with this requirement, a CFFP was instituted by rule for the 

Dallas-Fort Worth, Houston-Galveston-Brazoria, and El Paso ozone nonattainment areas 

beginning on September 1, 1998. The CFFP required that a certain percentage of fleet purchases 

after model year 1998 be clean fuel vehicles (CFVs) that meet the standards set forth in §243 of 

the FCAA.

The most recent federal standards for both light-duty and heavy-duty vehicles have eclipsed the 

CFV standards because subsequent to September 1, 2005, any new vehicle purchase ranging 

from 0-26,000 pounds gross vehicle weight rating would have either equaled or, in most cases, 

exceeded CFV standards. In a letter to manufacturers (EPA, 2005), the EPA stated that 

“subsequent to publishing its CFV regulations, EPA has promulgated new emission standards 

that are generally more stringent than or equivalent to the CFV emission standards for lightduty vehicles, light-duty trucks, and heavy-duty engines.” This EPA letter, dated July 21, 2005, 

applied to fleet purchases that began with the 2006 model year (September 1, 2005).

During the 79th Session of the Texas Legislature in 2005, Senate Bill 1032 repealed the Texas 

Clean Fleet Program in its entirety because the federal standards already in place at that time 

eclipsed the CFV standards referenced in the FCAA. On April 26, 2006, the TCEQ formally 

repealed the Texas Clean Fleet Program because no additional benefit could be achieved from 

new vehicle purchases under CFFP. A revision to the Texas Clean Fleet SIP that reflected the 

repeal of the Texas Clean Fleet Program was submitted to the EPA on May 15, 2006. FCAA 

§182(c)(4) allows the EPA to approve measures that substitute for the initial requirement to 

implement a CFFP as long as the EPA determines the substitute will accomplish equal long-term 

reductions attributable to the CFFP. However, the EPA has not provided guidance on how states 

are to address the Clean Fuel Fleet substitution requirement in their AD SIP revision submittals, 

where more stringent federal standards exist. Since new vehicle purchases subsequent to the 

date of repeal would meet more stringent federal emission standards, cancellation of the Texas 

Clean Fleet Program does not necessitate action to substitute this program with a separate 

emission reduction measure containing equivalent benefits. Such a substitution would only be 

warranted if a net increase in emissions would occur due to repeal or cancellation of an existing 

program.
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4.3.5 Stage I and Stage II Requirements

The Stage I vapor recovery rules regulate the filling of gasoline storage tanks at gasoline stations 

by tank trucks. To comply with Stage I requirements, a vapor balance system is typically used to 

capture the vapors from the gasoline storage tanks that would otherwise be displaced to the 

atmosphere as these tanks are filled with gasoline. The captured vapors are routed back to the 

tanker truck and processed by a vapor control system when the tanker truck is subsequently 

refilled at a gasoline terminal or gasoline bulk plant. The effectiveness of Stage I vapor recovery 

rules depends on the captured vapors being: 1) effectively contained within the gasoline tanker 

truck during transit and 2) controlled when the transport vessel is refilled at a gasoline terminal 

or gasoline bulk plant. 

The Stage II vapor recovery program involves use of technology that prevents gasoline vapors 

from escaping during refueling of on-road motor vehicles. The EPA mandates that Stage II 

refueling requirements apply to all public and private refueling facilities dispensing 10,000 

gallons or more of gasoline per month. The federal throughput constitutes a minimum 

threshold, but a state may be more stringent in adopting a throughput standard. The TCEQ 

applies a more stringent throughput standard in the applicable ozone nonattainment counties 

by requiring all facilities constructed after November 15, 1992, to install Stage II vapor recovery 

regardless of throughput.

An additional five counties (Ellis, Johnson, Kaufman, Parker, and Rockwall) may be required to 

meet Stage II requirements because the DFW area was reclassified as a serious ozone 

nonattainment area. The EPA currently allows states to revise the SIP to allow the removal of 

Stage II gasoline vapor recovery equipment if the state can demonstrate that widespread use of 

on onboard refueling vapor recovery has occurred at the gasoline dispensing facilities dedicated 

to corporate or commercial fleets. ORVR systems are passive systems that force gasoline vapors 

displaced from a vehicle’s fuel tank during refueling to be directed to a carbon-canister holding 

system and ultimately to the engine where they are consumed. The EPA is in the process of 

proposing a rule that will provide a formula for states to demonstrate when ORVR widespread 

use would occur in the general fleet. If the EPA rule is promulgated and Texas can demonstrate 

ORVR widespread use, then Stage II would not be required in the additional five DFW counties.

A Stage II AD SIP revision, which may include an ORVR widespread use demonstration based 

on the EPA’s final rule, is due to the EPA on December 10, 2013.

4.4 NEW CONTROL MEASURES 

4.4.1 Stationary Sources

4.4.1.1 

In addition to the revised control requirements discussed in Section 4.3.2: Updates to VOC 

Storage Tank Control Measures of this chapter, concurrent with this AD SIP revision, the 

commission is adopting new rules (Rule Project Number 2010-025-115-EN) to control flash 

emissions from crude oil and condensate storage tanks with uncontrolled VOC emissions that 

equal or exceed 50 tons per year (tpy) to implement RACT for major stationary sources in 

serious nonattainment areas. Additional detail concerning these new control measures can be

found in the RACT discussion in Section 4.5.3 of this chapter.

VOC Storage

4.4.1.2 

In addition to the revised control requirements discussed in Section 4.3.1: Updates to Coatings 

Control Measures of this chapter, concurrent with this AD SIP revision, the commission is 

adopting new rules (Rule Project Number 2010-016-115-EN) for certain coatings and solvent 

Coating and Solvent Usage
4-8 

usage operations to implement RACT for source categories addressed in the following CTG 

documents issued by the EPA from 2006 through 2008:

• Industrial Cleaning Solvents, Group II, issued in 2006; 

• Miscellaneous Industrial Adhesives, Group IV, issued in 2008; and

• Miscellaneous Metal and Plastic Parts Coatings, Group IV, issued in 2008. 

Additional detail concerning these new control measures can be found in the RACT discussion 

in Section 4.5.3 of this chapter. Only the pleasure craft and plastic parts coating categories 

represent new control measures from the 2008 Miscellaneous Metal and Plastic Parts Coatings 

CTG document. As discussed in Section 4.3.1 of this chapter, the rulemaking also updates the 

existing control requirements for miscellaneous metals parts.

4.5 RACT ANALYSIS

4.5.1 General Discussion

The DFW area is currently classified as a serious nonattainment area for the 1997 eight-hour 

ozone NAAQS (75 FR 79302, December 20, 2010). Under the 1997 eight-hour ozone standard, 

the DFW area is required to meet the mandates of FCAA, §172(c)(1) and §182(b)(2) and 182(f). 

According to EPA’s final rule to implement the 1997 eight-hour ozone NAAQS (40 CFR §51.912, 

November 29, 2005), states containing areas classified as moderate nonattainment and above

must submit an AD SIP revision demonstrating that their current rules fulfill the RACT 

requirements for all CTG emission source categories and all non-CTG major sources of NOX and 

VOC. The major source threshold for serious nonattainment areas is a potential to emit 50 tpy 

or more of either NOX or VOC.

In the September 17, 1979, issue of the Federal Register (44 FR 53762), RACT is defined as the 

lowest emissions limitation that a particular source is capable of meeting by the application of 

control technology that is reasonably available considering technological and economic 

feasibility. RACT requirements for nonattainment areas classified as moderate and above are 

included in the FCAA to assure that significant source categories at major sources of ozone 

precursor emissions are controlled to a reasonable extent but not necessarily to best available 

control technology levels expected of new sources or to maximum achievable control technology 

(MACT) levels required for major sources of hazardous air pollutants. While RACT and RACM 

have similar consideration factors like technological and economic feasibility, there is a 

significant distinction between RACM and RACT. To be considered RACM, a control measure 

must advance attainment of the NAAQS for that area (see FCAA, §172(c)(1)). Advancing 

attainment of the area is not a consideration when evaluating RACT because the benefit of 

implementing RACT is presumed under the FCAA.

Under the current state rules, the DFW area is subject to some of the most stringent NOX and 

VOC emission control requirements in the country, and for many source categories, the existing 

rules are more stringent than recommended RACT standards for those categories. The EPA 

previously approved the RACT analysis as submitted in the May 2007 DFW AD SIP Revision (74 

FR 1903, January 14, 2009) and noted that the DFW VOC rules in 30 Texas Administrative 

Code (TAC) Chapter 115 and NOX rules in Chapter 117 were previously determined to meet the 

FCAA RACT requirements. Therefore, controls to satisfy RACT for most major sources under 

the 1997 eight-hour ozone nonattainment designation were implemented by the TCEQ and 

previously approved by the EPA, see Appendix F: Reasonably Available Control Technology 

Analysis. 
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4.5.2 NOX RACT Determination

The TCEQ's analysis demonstrates that the current NOX rules and controls for the DFW area 

fulfill the FCAA requirements for NOX RACT. The 30 TAC Chapter 117 rules represent one of the 

most comprehensive NOX control strategies in the nation and encompass both RACT and 

beyond-RACT levels of control. The current EPA-approved Chapter 117 rules fulfill RACT 

requirements for all CTG and Alternative Control Techniques (ACT) NOX emission source 

categories. For all non-CTG/ACT major NOX emission source categories for which controls are 

technologically and economically feasible, RACT is fulfilled by the EPA-approved Chapter 117 

rules or other federally enforceable measures. Additional details regarding the RACT analysis 

are provided in Appendix F of this AD SIP revision. 

4.5.3 VOC RACT Determination

The TCEQ's analysis demonstrates that the current EPA-approved 30 TAC Chapter 115 VOC 

rules and controls for the DFW area, or the Chapter 115 VOC rules being adopted concurrently 

with this AD SIP revision (Rule Project Numbers 2010-016-115-EN and 2010-025-115-EN) 

satisfy the FCAA requirements for RACT for all CTG and ACT VOC emission source categories. 

For all non-CTG/ACT major VOC emission source categories for which VOC controls are 

technologically and economically feasible, RACT is fulfilled by EPA-approved Chapter 115 rules,

other federally enforceable measures, or the Chapter 115 VOC rules being adopted concurrently 

with this AD SIP revision (Rule Project Number 2010-025-115-EN). Additional VOC controls on 

certain major sources were determined to be either not economically feasible or not 

technologically feasible. Additional details regarding the RACT analysis are provided in 

Appendix F of this AD SIP revision. 

Concurrent with this SIP revision, the commission is adopting rules in Chapter 115, Subchapter 

B, Division 1 to implement RACT for VOC storage (Rule Project Number 2010-025-115-EN). To 

implement RACT for the petroleum liquid storage CTG emission source category, these rules 

include additional requirements for low-leaking storage tank fittings and limit situations when 

floating roof tanks are allowed to emit VOC because the roof is not floating on the liquid. To 

implement RACT for major stationary sources, these rules require control of flash emissions 

from crude oil and condensate storage tanks with uncontrolled VOC emissions that equal or 

exceed 50 tpy. Additional discussion regarding the RACT requirements for VOC storage tanks is 

provided in Appendix F of this AD SIP revision. 

The EPA issued 11 CTG documents from 2006 through 2008 with recommendations for VOC 

controls on a variety of consumer and commercial products. Some of the new CTG 

recommendations are updates to previously issued CTG documents and some are 

recommendations for new categories. The TCEQ evaluated these new CTG documents to 

determine if additional VOC controls were necessary to fulfill requirements. 

The RACT analysis included in the DFW RACT SIP revision adopted March 10, 2010, addresses 

the following CTG documents: 

• Flat Wood Paneling Coatings, Group II, issued in 2006; 

• Offset Lithographic and Letterpress Printing, Group II, issued in 2006; and

• Fiberglass Boat Manufacturing Materials, Group IV, issued in 2008. 

The RACT analysis included in this AD SIP revision addresses the following CTG documents:

• Flexible Package Printing, Group II, issued in 2006; 

• Industrial Cleaning Solvents, Group II, issued in 2006; 
4-10

• Large Appliance Coatings, Group III, issued in 2007; 

• Metal Furniture Coatings, Group III, issued in 2007; 

• Paper, Film, and Foil Coatings, Group III, issued in 2007; 

• Miscellaneous Industrial Adhesives, Group IV, issued in 2008; 

• Miscellaneous Metal and Plastic Parts Coatings, Group IV, issued in 2008; and

• Auto and Light-Duty Truck Assembly Coatings, Group IV, issued in 2008. 

The following sections provide a brief summary of the TCEQ's determinations regarding these 

eight CTG documents. Additional details regarding the evaluation of the eight CTG documents 

are provided in Appendix F of this AD SIP revision. 

4.5.3.1 

The TCEQ has determined that portions of the Flexible Package Printing CTG recommendations 

are RACT for the DFW area. Concurrent with this AD SIP revision, the commission is adopting

rulemaking to limit the VOC content of coatings used by flexible package printing operations in 

the DFW area (Rule Project 2010-016-115-EN). The rulemaking implements the CTG 

recommendations to reduce the VOC content of coatings and imposes work practices for 

cleaning materials used during flexible package printing.

Flexible Package Printing

4.5.3.2 

The TCEQ has determined that portions of the Industrial Cleaning Solvents CTG 

recommendations are RACT for the DFW area. Concurrent with this AD SIP revision, the 

commission is adopting rulemaking to implement the CTG recommendations to limit the VOC 

content of industrial cleaning solvents used in the DFW area (Rule Project 2010-016-115-EN).

The TCEQ revised the proposed rules for industrial cleaning solvents in response to comments 

received on the proposed rules and this AD SIP revision. Additional details regarding these 

changes are provided in Appendix F of this AD SIP revision.

Industrial Cleaning Solvents

4.5.3.3 

The TCEQ has determined that portions of the Large Appliance Coatings CTG recommendations 

are RACT for the DFW area. Concurrent with this AD SIP revision, the commission is adopting

rulemaking to limit the VOC content of large appliance coatings in the DFW area (Rule Project 

2010-016-115-EN). The rulemaking implements the CTG recommendations to reduce the VOC 

content of coatings and imposes work practices for cleaning materials used during large 

appliance coating. The TCEQ revised the proposed rules for large appliance coatings in response 

to comments received on the proposed rules and this AD SIP revision. Additional details 

regarding these changes are provided in Appendix F.

Large Appliance Coatings

4.5.3.4 

The TCEQ has determined that portions of the Metal Furniture Coatings CTG recommendations 

are RACT for the DFW area. Concurrent with this AD SIP revision, the commission is adopting

rulemaking to limit the VOC content of metal furniture coatings used in the DFW area (Rule 

Project 2010-016-115-EN). The rulemaking implements the CTG recommendations to reduce 

the VOC content of coatings and imposes work practices for cleaning materials used during 

metal furniture coating. The TCEQ revised the proposed rules for metal furniture coatings in 

response to comments received on the proposed rules and this AD. Additional details regarding 

these changes are provided in Appendix F.

Metal Furniture Coatings
4-11

4.5.3.5 

The TCEQ has determined that portions of the Paper, Film, and Foil Coatings CTG 

recommendations are RACT for the DFW area. Concurrent with this AD SIP revision, the 

commission is adopting rulemaking to limit the VOC content of paper, film, and foil coatings in 

the DFW area (Rule Project 2010-016-115-EN). The rulemaking implements the CTG 

recommendations to reduce the VOC content of coatings and imposes work practices for 

cleaning materials used during paper, film, and foil coating.

Paper, Film, and Foil Coatings

4.5.3.6 

The TCEQ has determined that portions of the Miscellaneous Industrial Adhesives CTG 

recommendations are RACT for the DFW area. Concurrent with this AD SIP revision, the 

commission is adopting rulemaking to implement the CTG recommendations to limit the VOC 

content of miscellaneous industrial adhesives used in the DFW area (Rule Project 2010-016-115-

EN). The TCEQ revised the proposed rules for miscellaneous industrial adhesives in response to 

comments received on the proposed rules and this AD SIP revision. Additional details regarding 

these changes are provided in Appendix F.

Miscellaneous Industrial Adhesives

4.5.3.7 

The TCEQ has determined that portions of the Miscellaneous Metal and Plastic Parts Coatings 

CTG recommendations are RACT for the DFW area. Concurrent with this AD SIP revision, the 

commission is adopting rulemaking to limit the VOC content of miscellaneous metal and plastic 

parts coatings used in the DFW area (Rule Project 2010-016-115-EN). The rulemaking 

implements the CTG recommendations to reduce the VOC content of coatings and imposes work 

practices for cleaning materials used during miscellaneous metal and plastic parts coating. The 

TCEQ revised the proposed rules for miscellaneous metal and plastic parts coatings in response 

to comments received on the proposed rules and this AD SIP revision. Additional details 

regarding these changes are provided in Appendix F.

Miscellaneous Metal and Plastic Parts Coatings

4.5.3.8 

The TCEQ has determined that portions of the Auto and Light-Duty Truck Assembly Coatings 

CTG recommendations are RACT for the DFW area. Concurrent with this AD SIP revision, the 

commission is adopting rulemaking to limit the VOC content of auto and light-duty truck 

assembly coatings used in the DFW area (Rule Project 2010-016-115-EN). The rulemaking 

implements the CTG recommendations to reduce the VOC content of coatings and imposes work 

practices for cleaning materials used during auto and light-duty truck assembly coating.

Auto and Light-Duty Truck Assembly Coatings

4.6 RACM ANALYSIS

4.6.1 General Discussion

States are required by FCAA, §172(c)(1) to “provide for implementation of all reasonably 

available control measures as expeditiously as practicable” and to include RACM analyses in the 

AD SIP revision. In the General Preamble for implementation of the FCAA Amendments of 1990 

published in the April 16, 1992, issue of the Federal Register (57 FR 13498), the EPA explains 

that it interprets §172(c)(1) of the FCAA as a requirement that states incorporate into their SIP 

all reasonably available control measures that would advance a region’s attainment date. 

However, the state is obligated to adopt only those measures that are reasonably available for 

implementation in light of local circumstances.

The TCEQ used a two-step process to develop the list of potential stationary and mobile source 

control strategies evaluated during the RACM analysis. First, the TCEQ compiled a list of 

potential control strategy concepts based on an initial evaluation of the existing control
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strategies in the DFW area and existing sources of VOC and NOX in the DFW area. The EPA 

allows states the option to consider control measures outside the ozone nonattainment area that 

can be shown to advance attainment; however, consideration of these sources is not a 

requirement of the FCAA. Sources of VOC within 100 kilometers (km) of the DFW area and 

sources of NOX within 200 km of the DFW area were also considered for this initial evaluation. 

Draft lists of potential control strategy concepts for stationary and mobile sources were 

developed from this initial evaluation. The draft lists of potential control strategy concepts were 

presented to stakeholders for comment at a stakeholder meeting held in the DFW area on June 

24, 2010. The TCEQ requested comment on the potential control strategies and invited 

stakeholders to suggest any additional strategies that might help advance attainment of the 

DFW area. The final list of potential control strategy concepts for RACM analysis includes the 

strategies presented to stakeholders in June 2010 and the strategies suggested by stakeholders 

during the informal stakeholder comment process and by the North Texas Clean Air Steering 

Committee. 

Each control measure identified through the control strategy development process was 

evaluated to determine if the measure would meet established criteria to be considered 

reasonably available. The TCEQ used the general criteria specified by the EPA in the proposed

approval of the New Jersey RACM analysis published in the January 16, 2009, issue of the 

Federal Register (74 FR 2945).

RACM is defined by the EPA as any potential control measure for application to point, 

area, on-road, and non-road emission source categories that meets the following criteria.

• The control measure is technologically feasible.

• The control measure is economically feasible.

• The control measure does not cause ‘‘substantial widespread and long-term adverse 

impacts.’’

• The control measure is not ‘‘absurd, unenforceable, or impracticable.’’

• The control measure can advance the attainment date by at least one year.

The EPA did not provide guidance in the Federal Register on how to interpret the criteria 

"advance the attainment date by at least one year." Because modeling shows that the DFW area 

will be significantly below the NAAQS and as discussed in Section 4.6.2 Results of the RACM 

Analysis, it is not possible to implement control measures quickly enough to attain the NAAQS 

earlier, sensitivity runs were not needed to evaluate RACM.

The TCEQ also considered whether each potential control measure could be implemented before 

and reduce emissions prior to the beginning of the ozone season immediately before the 

attainment date. The attainment date for the 1997 eight-hour ozone NAAQS for the DFW area is 

June 15, 2013, so suggested control measures that could not be implemented by March 1, 2012, 

were not considered RACM because the measures would not advance attainment. However, the 

DFW area must make progress toward attainment of 1997 eight-hour ozone NAAQS as 

expeditiously as practicable. Therefore, if control measures can be implemented earlier than 

March 1, 2012, and will help the area make progress toward attainment of the NAAQS earlier 

than the attainment year, the measure should be implemented as early as feasible.

The TCEQ also considered whether the control measure was similar or identical to control 

measures already in place in the DFW area. If the suggested control measure would not provide 

substantive and quantifiable benefit over the existing control measure, then the suggested 

control measure was not considered RACM because reasonable controls were already in place. 
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4.6.2 Results of the RACM Analysis

All potential control measures evaluated for both stationary and mobile sources were 

determined not to be RACM due to technological or economic feasibility, enforceability, adverse 

impacts, or ability of the measure to advance attainment of the NAAQS. In general, the inability 

to advance attainment is the primary determining factor in the RACM analyses. As discussed in 

Chapter 3: Photochemical Modeling of this AD SIP revision, modeling shows that the DFW area 

will be substantially below the 1997 eight-hour ozone NAAQS and additional control measures 

are not necessary for the area to demonstrate attainment by the attainment date. Furthermore, a 

control measure would have to be in place by March 1, 2012, in order for the measure to advance 

the attainment date; therefore, it is not possible for the TCEQ to implement any control 

measures that would provide for earlier attainment of the NAAQS. The complete list of 

stationary source potential control measures and additional information and specific details 

regarding the RACM analysis for the DFW area are provided in Appendix G: Reasonably 

Available Control Measure Analysis. 

4.7 MVEB

The MVEB refers to the maximum allowable emissions from on-road mobile sources for each 

applicable criteria pollutant or precursor as defined in the SIP. The budget must be used in 

transportation conformity analyses. Areas must demonstrate that the estimated emissions from 

transportation plans, programs, and projects do not exceed the MVEB. The attainment budget

represents the on-road mobile source emissions that have been modeled for the attainment 

demonstration using MOVES2010a. The budget reflects all of the on-road control measures 

reflected in Chapter 4 of the demonstration. The MVEB is shown in Table 4-2: 2012 Attainment 

Demonstration MVEB for the Nine-County DFW Area. For additional detail, see Appendix B: 

Emissions Inventory Development. 

Table 4-2: 2012 Attainment Demonstration MVEB for the Nine-County DFW Area

Nine-County 

DFW Area

NOX tons per 

day (tpd)

VOC

tpd

2012 MVEB 181.40 80.48

4.8 MONITORING NETWORK

States are required by 40 CFR Part 58, Subpart B, to submit an annual monitoring network 

review to the EPA by July 1 of each year. This network review is required to provide the 

framework for establishment and maintenance of an air quality surveillance system. The annual 

monitoring network review must be made available for public inspection for at least 30 days 

prior to submission to the EPA. The review and any comments received during the 30 day 

inspection period are then forwarded to the EPA for final review and approval. The TCEQ 

posted the 2011 plan from June 1 through June 30, 2011, on the TCEQ Web site

(http://www.tceq.texas.gov/). The document presents the current Texas network of ambient air 

Photochemical Assessment Monitoring Station (PAMS) monitors as well as proposed changes to 

the network from July 1, 2011, through December 31, 2011.

This network review includes posting of the TCEQ's EPA-approved PAMS Network Plan which 

focuses on ozone precursors. The reclassification of the DFW ozone nonattainment area to 

serious requires carbonyl sampling at a Type 2 PAMS site in the DFW area. Carbonyls are a class 

of VOC that are involved in ozone formation. Carbonyl measurements can be used to help 

resolve the role of ozone precursors in local ozone formation and in ozone transport, as well as 

to help evaluate model performance, control strategy effectiveness, and emissions inventory 

accuracy.
4-14

The TCEQ will conduct the required intensive carbonyl sampling at the Hinton PAMS Type 2 

Site (AQS ID 48-113-0069) each year. As preliminarily agreed upon with the EPA, Region 6, the 

TCEQ will collect a total of 240 carbonyl samples at this site at a sampling frequency of eight 

three-hour samples per day every three days during June 1 through August 31. In addition to 

this serious nonattainment area requirement, the TCEQ will also collect one 24-hour carbonyl 

sample every six days, from September 1 through May 31 at the Dallas Hinton (C401) site and 

year round at the Fort Worth Northwest (C13) site.

4.9 CONTINGENCY PLAN

AD SIP revisions for nonattainment areas are required by FCAA, §172(c)(9) to provide for 

specific measures to be implemented should a nonattainment area fail to meet reasonable 

further progress (RFP) requirements or attain the applicable NAAQS by the attainment date set 

by the EPA. These contingency measures are to be implemented without further action by the 

state or the EPA. In the General Preamble for implementation of the 1990 FCAA Amendments 

of 1990 published in the April 16, 1992, issue of the Federal Register (57 FR 13498), the EPA 

interprets the contingency requirement to mean additional emissions reductions that are 

sufficient to equal up to 3% of the emissions in the adjusted base year inventory. These 

emissions reductions should be realized in the year following the year in which the failure is 

identified (i.e., an RFP milestone year or attainment year).

This 1997 eight-hour ozone AD SIP revision uses the adjusted base year inventory as the 

inventory from which to calculate the required 3% reduction for contingency. The 3% 

contingency analysis for 2013 is based on a 3% reduction in NOX, with no emissions reductions 

coming from VOC, to be achieved between 2012 and 2013. Emissions inventories analyses were 

performed on the fleet turnover effects for the federal emissions certification programs for onroad and non-road vehicles. The emissions reductions from 2012 through 2013 were estimated 

for those programs. A summary of the 2013 contingency analysis is provided in Table 4-3: 2013 

DFW Attainment Demonstration Contingency Demonstration (tpd). The analysis demonstrates 

that the 2013 contingency reductions exceed the 3% reduction requirement; therefore, the 

attainment demonstration contingency requirement is fulfilled for the DFW area.

Table 4-3: 2013 DFW Attainment Demonstration Contingency Demonstration 

(tpd) 

Contingency Element Description NOX VOC

2012 adjusted base year (ABY) emissions inventory (EI) 630.46 481.97

Percent for contingency calculation (total of 3%) 3.00 0.00

2012 to 2013 required contingency reductions (ABY EI x (contingency percent)) 18.91 0.00

Control reductions to meet contingency requirements 

Excess reductions from 2012 attainment demonstration 0.00 0.00

Subtract 2012 attainment demonstration motor vehicle emissions budget 

safety margin from excess reductions from 2012 attainment demonstration 0.00 0.00

Federal Motor Vehicle Control Program, inspection and maintenance, 

reformulated gasoline (RFG), and on-road Texas Low Emission Diesel (TxLED) 

(Note: This list of controls is the complete list for the nine DFW nonattainment 

counties; however, RFG is required, and all control reductions are modeled 

with RFG, only in the four core counties.)

33.22 10.01

Federal non-road mobile new vehicle certification standards 7.45 5.48
4-15

Contingency Element Description NOX VOC

Non-road RFG -0.01 0.08

Non-road TxLED 0.41 0.00

Federal locomotive standards 0.53 0.05

Total attainment demonstration contingency reductions 41.60 15.62

Contingency Excess (+) or Shortfall (-) 22.69 15.62

Note: Emissions benefits calculated for contingency are based on incremental reductions from 2012 through 2013. 

The negative incremental benefit shown for non-road RFG is due to a smaller total benefit and is based on output 

from the NONROAD model.

4.10 REFERENCES 

EPA, 1993. NOX Substitution Guidance

(http://www.epa.gov/ttncaaa1/t1/memoranda/noxsubst.pdf) 

EPA, 2005. Clean-Fuel Vehicle Standards, no. CCD-05-1
5-1 

CHAPTER 5: WEIGHT OF EVIDENCE

5.1 INTRODUCTION

The corroborative analysis presented in this chapter demonstrates the progress that the DallasFort Worth (DFW) area is making towards attainment of the 1997 eight-hour ozone National 

Ambient Air Quality Standard (NAAQS) of 0.08 parts per million (ppm). The United States 

Environmental Protection Agency’s (EPA) April 2007 “Guidance on the Use of Models and 

Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and 

Regional Haze” (EPA, 2007) states that all modeled attainment demonstrations should include 

supplemental evidence that the conclusions derived from the basic attainment modeling are 

supported by other independent sources of information. This chapter details the supplemental 

evidence, i.e., the corroborative analyses, for this modeling demonstration. 

The first section of the quantitative corroborative analysis chapter discusses photochemical grid 

modeling. Modeling is one of the most important tools available for evaluating progress toward 

meeting air quality standards. Known issues with photochemical grid modeling and how the 

Texas Commission on Environmental Quality (TCEQ) addresses the issues are described in the 

first section as well as overall model performance. Finally, the diagnostic analyses performed by 

the TCEQ, and the implications of those analyses on the projected attainment status are 

provided in this section. The second section of the quantitative corroborative analysis chapter 

provides information on trends in ozone and ozone precursors observed in the DFW area. The 

third section provides an analysis of recent research into the formation, transport, and 

accumulation of ozone in the DFW area. The section also examines the quantification of 

“background ozone.” The fourth section describes air quality control measures that cannot yet 

be adequately quantified but are nonetheless expected to yield tangible air quality benefits. The 

final section details on-going initiatives that are expected to improve the scientific 

understanding of ozone formation in the DFW area.

5.2 CORROBORATIVE ANALYSIS: MODELING

Photochemical grid modeling of the DFW area is challenging due to the mix of local emissions 

sources, frequent meteorological frontal passages, the influence of transport, and the large 

geographic area covered by the 1997 eight-hour ozone DFW nonattainment region. One purpose 

of the Texas Air Quality Study 2000 (TexAQS 2000) and the Texas Air Quality Study 2006 

(TexAQS II) field studies was to address the uncertainties that affect photochemical grid

modeling and its regulatory application. Insights gleaned from the Texas Air Quality Studies and 

subsequent studies have helped resolve some of these uncertainties. 

Several studies have attempted to identify and reduce uncertainties in the photochemical grid 

models and inputs. Foremost among these efforts are the studies that have sought to quantify 

underreported industrial highly reactive volatile organic compounds (HRVOC) emissions (Wert 

et al., 2003; Xie and Berkowitz, 2007; Yarwood et al., 2004; TCEQ, 2002, 2004, 2006; Smith 

and Jarvie, 2008) and to assess the sensitivities of ozone simulations to underreporting these 

emissions (TCEQ, 2002, 2004, 2006; Byun et al., 2007; Jiang and Fast, 2004). Other modeling 

efforts have tested different chemical mechanisms in the Houston-Galveston-Brazoria (HGB) 

area’s photochemical grid modeling, to study the effects of using different mechanisms on ozone 

model performance and control strategy effectiveness (Byun et al., 2005b; Faraji et al., 2008; 

Czader et al., 2008). While HGB-focused, these modeling studies are applicable to evaluating 

the DFW model performance since many of the model inputs and configurations overlap. 

Modeling sensitivity studies have also been performed to guide selection of model parameters 

such as vertical mixing schemes, number and depth of model layers, and horizontal grid 

resolution (Kemball-Cook et al., 2005; Byun et al., 2005b; Byun et al., 2007; Bao et al., 2005). 
5-2 

Mesoscale meteorological modeling is used to drive photochemical grid models, and many 

studies have examined and reduced uncertainties in these models. One of the most successful 

efforts improved meteorological simulations of ozone episodes by using radar profiler and other 

upper level wind data to “nudge” the meteorological modeling (Nielsen-Gammon et al., 2007; 

Zhang et al. 2007; Stuart et al., 2007; Bao et al., 2005; Fast et al., 2006). Other efforts improved 

land cover data and land surface modeling (Byun et al., 2005a; Cheng et al., 2008a, 2008b), 

studied the sensitivity of ozone simulations to solar irradiance and photolysis rates (Zamora et 

al., 2005; Fast et al., 2006; Pour-Biazar et al., 2007; Byun et al., 2007; Koo et al., 2008; 

Environ, 2010) and investigated some of the meteorological model’s physics options for 

modeling Texas (Environ, 2009a).

The following list includes some of the most important findings from these meteorological 

modeling studies.

• Assimilation of radar profiler and other upper air wind data is essential to good 

meteorological modeling performance.

• Modeling parameterizations need to be chosen carefully to alleviate the common problem of 

spurious thunderstorms and clouds.

• Accurate simulation of cloud cover is crucial to getting photolysis rates correct in the 

photochemical grid model, and ozone predictions are very sensitive to photolysis rates.

• An ensemble approach to meteorological and photochemical grid modeling, many iterations 

with slightly different configurations, may be warranted, given the sensitivity of ozone 

modeling to relatively small changes in meteorology. While an ensemble approach would 

allow probabilistic attainment demonstrations to be produced, the current modeling 

guidance and regulatory framework make implementing this approach problematic. 

In the remainder of this section, modeling issues identified by the studies described above are

discussed, as well as issues raised by TCEQ-sponsored investigations and other research. Overall 

performance of the photochemical grid modeling and the implications of the model’s ability to 

accurately simulate ozone episodes are also discussed. 

5.2.1 Solving Modeling Problems

The photochemical modeling system is not a perfect tool and has inherent uncertainty (EPA, 

2007). Through model performance evaluation, several aspects of ozone modeling shortcomings 

for the DFW area have been identified. This section discusses some of these issues, and how the 

TCEQ has attempted to resolve them in this round of modeling.

5.2.1.1 

Numerous studies have investigated the effects of grid size on model behavior (Cohan et al., 

2006; Esler, 2003; Gego et al., 2005; Valari and Menut, 2008). The main interest in finer grid 

resolution is that higher resolution can increase concentrations of ozone precursors in narrow 

plumes, which can affect ozone production rate and sensitivity to volatile organic compounds 

(VOC) or nitrogen oxides (NOX) within the plumes. In a city such as Houston, using a higher 

resolution grid is warranted, given the abundance of industrial point sources, which can 

generate narrow plumes and concentrations of pollution with a larger grid cell. Researchers 

during TexAQS 2000 determined that rapid ozone formation occurring within narrow industrial 

plumes are responsible for the highest observed ozone in the HGB area and for the strong ozone 

gradients that can form. The DFW area lacks the industrial point source concentration of 

Houston, and especially sources of HRVOC. The majority of DFW area emissions forming ozone 

are from mobile, non-road, and area sources that don’t appear to form strong ozone gradients 

where a very fine modeling resolution may be needed to accurately replicate ozone. The TCEQ 

Resolution of Photochemical Modeling Grids 
5-3 

modeled the DFW area at a finer resolution (4 km) than the modeling guidance suggests (12 km) 

for urban areas. 

In general, the TCEQ has found that modeling with smaller grid sizes can create higher ozone 

production and can alleviate, in part, the commonly observed low bias for ozone. There are 

limits to this solution, however; it is inappropriate to decrease grid size indefinitely. 

Parameterizations in both the meteorological modeling and the photochemical grid modeling 

are based upon the assumption that turbulence features within the planetary boundary layer 

(PBL) are much smaller than the grid size. If the grid size is decreased to 1 km by 1 km or lower, 

the assumption likely no longer holds, and more uncertainty could be added to the modeling as 

a result of the finer resolution. 

Also, where the spatial resolution of the photochemical grid modeling is reduced, the temporal 

resolution of the meteorological and chemical processes within the model should be reduced, to 

match the shorter residence time of precursors in each grid cell. In other words, as the size of 

the box shrinks, the amount of time that a mass of air resides in the box also shrinks, affecting 

how the ozone chemistry plays out. While the Comprehensive Air Model with Extensions 

(CAMx) automatically adjusts the time step for chemical processes, the meteorological process 

time step is fixed, based upon the input data from the Fifth Generation Meteorological Model 

(MM5). Although extraction of meteorological output with higher temporal resolution may be 

possible, reduction of the time steps seems likely to cause unusual model behavior. Further, the 

reduction of time steps in regulatory photochemical grid modeling has not been well studied. In 

the future, evaluation of and potential use of smaller grid sizes and shorter time steps may be 

considered. For this round of modeling, the TCEQ has kept the size of the CAMx and MM5 

modeling grid cells at 4 km and the temporal resolution, which meets and exceeds the modeling 

guidance requirements. 

5.2.1.2 

Swall and Foley (2009) discuss the problems inherent in comparing point measurements to grid 

cell values. In statistical parlance, this problem is known as incommensurability. A portion of 

the difference between point measurements and grid cell values is due solely to the fact that 

measurements made at a monitoring station do not generally represent an average of the 

conditions for the 4 km by 4 km grid cell in which it resides. The ability of a point measurement 

to represent the average of the entire grid cell area is related to how much sub-grid variation is 

observed in the area. If sub-grid variation is small, then the point measurement and the grid cell 

value are commensurate. If the spatial gradients of the variables of interest are large, the point 

measurements are less able to reflect the average conditions of the entire grid cell, and therefore 

they are incommensurate with the grid cell value. 

Incommensurability and Model Performance Evaluation 

While the DFW area lacks the industrial point sources (especially of HRVOC) for rapid ozone 

formation like the HGB area, ozone plumes do occur and are difficult to simulate. Swall and 

Foley demonstrated that incommensurability alone is capable of degrading model performance 

in areas of steep gradients. Swall and Foley state in their discussion, “This means that, even if 

the model is performing perfectly and there is no observational error, we cannot expect that in a 

scatterplot, points representing paired modeled and observed values will lie on a one-to-one 

line. Our comparison of Gaussian and exponential correlation structures with the same effective 

range shows that this concern looms larger for correlation structures in which there is a rapid 

decrease in correlation for small distances relative to grid cell size (like the exponential).” While 

there are other causes of poor model performance as well, incommensurability is likely to be 

responsible for some of the differences between model output and point measurements. 
5-4 

5.2.1.3 

A number of researchers have discussed the benefits of using ensembles of models to create 

more accurate forecasts (Pinder et al., 2009; Zhang et al., 2007). Pinder et al. and Zhang et al. 

have noted that probabilistic attainment demonstrations could be made using ensemble 

modeling and have argued that this approach can be more scientifically sound than a 

deterministic attainment demonstration. The TCEQ acknowledges the potential soundness of 

the ensemble approach but notes that the current regulatory framework does not easily allow for 

a probabilistic attainment demonstration. With approval from the EPA Region VI, this type of 

modeling would best fit as corroborative analysis or weight of evidence according to current 

guidance (the EPA, 2007).

Ensemble Modeling 

5.2.1.4 

To improve the modeled vertical mixing, the TCEQ has implemented the results of recent 

projects and studies. In order to simulate free tropospheric ozone the TCEQ has obtained global 

model output of ozone for the appropriate time periods to use as boundary conditions (Environ, 

2009b). Where discrepancies still persist, they appear to be related to phenomena that occur 

between the outermost domain boundaries and the DFW area. 

Vertical Distribution of Ozone

To represent vertical mixing in the meteorological modeling, the TCEQ has improved the land 

cover data and sea surface temperature data in its latest round of modeling, in an attempt to 

improve the simulations of surface energy balance. The TCEQ has chosen the Eta PBL scheme 

(i.e., the Mellor-Yamada-Janjic scheme), which appears to be more effective at simulating PBL 

dynamics in the DFW area than other available schemes (Zhong et al., 2007). In addition, the 

TCEQ used the KVPATCH program to modify the vertical diffusivity coefficients on a land-use 

basis to limit the maximum within the first 200 meters of the model (Environ, 2010). 

5.2.1.5 

Researchers at the University of Alabama-Huntsville examined the effects of modeled cloud 

cover on ozone performance in the HGB area and found that some of the shortcomings in model 

performance could be corrected with better depiction of clouds (Pour-Biazar et al., 2007). 

University of Houston researchers also found that their forecasts were occasionally biased due to 

poor depiction of cloud cover (Byun et al., 2007). TCEQ-funded research found that higherorder decoupled direct method analysis of modeling sensitivities indicated substantial 

sensitivity to photolysis rates (Koo et al., 2008). TCEQ-funded research also found that the 

photochemical model’s surface ozone prediction was more responsive to the placement of subgrid clouds (simulated clouds smaller than the model grid scale, e.g., 4 km) than how photolysis 

rates were applied (Environ, 2010). 

Photolysis Discrepancies Due to Improper Placement of Clouds

The TCEQ has found similar cloud cover effects in the photochemical modeling for this state 

implementation plan (SIP) revision and other modeling efforts. The greatest discrepancies tend 

to involve the model under-predicting cloud cover, and hence, greatly over-predicting ozone on 

low ozone days. Modeled episode days for which cloud cover problems exist include June 16, 19, 

21, 22, 28, and July 1 through 2, 2006. The average mean normalized bias for these days is 

+16.9%, compared to an average mean normalized bias on exceedance days of -3.4%. TCEQ 

process analysis shows that most of the radical initiation, propagation, and termination steps 

are very sensitive to photolysis rates. Hence, improvements in cloud placement could greatly 

improve ozone and precursor performance, though the greatest improvements will likely occur 

on low ozone days. 
5-5 

5.2.1.6 

A number of researchers studying urban photochemistry in Texas and other areas have found 

that available mechanisms for simulating radical production are unable to replicate the observed 

radical formation and propagation rates (Mao et al., 2007, 2009; Chen et al., 2009). The process 

analysis section of Appendix I: Corroborative Analysis for the HGB Attainment Demonstration 

SIP Revision for the 1997 Eight-Hour Ozone Standard of the 2010 Houston-Galveston-Brazoria 

Attainment Demonstration State Implementation Plan Revision for the 1997 Eight-Hour Ozone 

Standard (TCEQ, 2010) discusses this issue in detail and compares TCEQ process analyses to 

the Mao et al. and Chen et al. work. The TCEQ modeling is consistent with the Mao et al. and 

Chen et al. findings that the current mechanisms are missing something. The atmospheric 

chemistry community as a whole has not yet resolved the problem or problems with the current 

mechanisms. Several hypotheses for the missing radical formation mechanism exist, including 

daytime nitrous acid (HONO) production from nitric acid-aerosol interactions and photolysis 

(Ziemba et al., 2009); isoprene production of hydroxyl radical (OH) (Lelieveld et al., 2008; 

North and Ghosh, 2009); formation and decomposition of electronically excited nitrogen 

dioxide (NO2) (Li et al., 2008); nitryl chloride (ClNO2) chemistry (Osthoff et al., 2008; Simon et 

al., 2008); improved aromatic chemistry (Faraji et al., 2008; Hu et al., 2007); and molecular 

chlorine reactions (Chang et al., 2002; Tanaka et al., 2003; Chang and Allen, 2006; Sarwar and 

Bhave, 2007). Given the hypotheses and the current lack of a definitive explanation, the TCEQ 

has not incorporated modified chemical mechanisms into its modeling at this time. However, 

the TCEQ continues to support investigations for improving chemical mechanisms and is 

prepared to adopt an improved mechanism when it becomes sufficiently mature.

Radical Shortage 

5.2.2 Model Performance Evaluations: Implications of the Model Performance of

the Current SIP Modeling

Model performance evaluations are presented in Chapter 3: Photochemical Modeling and in its 

associated appendices. Based upon these evaluations, the TCEQ makes the following 

conclusions.

5.2.2.1 

• The model simulates the location, spatial extent, and relative intensity of ozone relatively 

well on most of the high-ozone days.

Ozone Performance 

• The model consistently underestimates peak ozone within the highest concentration plumes.

• Process analysis and modeling sensitivity analyses show that peak eight-hour ozone is 

primarily NOX-sensitive in much of the domain and on most eight-hour ozone exceedance 

days.

• According to TCEQ process analyses, VOC-sensitive conditions occur in the urban core and 

generally during rush hour when NOX concentrations peak. On all DFW episode days 

studied, NOX-sensitive ozone formation was two to five times greater than VOC-sensitive 

ozone formation. 

• Decreases in ozone production rates and other reaction rates correlate with decreases in NO2

photolysis, implying that most of the ozone formation chemistry is highly sensitive to 

photolysis, and hence, highly sensitive to cloud-cover errors.

• Based on the Anthropogenic Precursor Culpability Assessment (APCA) source 

apportionment analyses, background ozone concentrations are important in accurately 

modeling the DFW area due to the prevalence of contributions from areas outside the DFW 

nine-county area. 
5-6 

• In rural areas, the model routinely over-predicts nighttime ozone and under-predicts NOX. 

The cause of this issue is unknown, but it could involve unreported, underreported, or 

underestimated NOX emissions or problems with vertical mixing in rural areas.

• The lack of ozonesonde, aircraft, and other upper air data in the DFW area limits the 

performance evaluation of the model above the surface layer. 

5.2.2.2 

• The modeling simulated ozone precursors relatively well, albeit with a large degree of 

scatter, and the peak concentrations for some species were underestimated.

Ozone Precursor Performance

• The diurnal patterns of NOX and NO2 concentrations were well simulated, though the peak 

concentrations were often under predicted. Nitric oxide (NO) was often underestimated for 

the peak concentrations, which were usually observed in the pre-dawn hours, i.e., during 

morning rush hour.

• The highly reactive Carbon Bond 05 species ETH and OLE, which represent ethylene, 

propylene, and other alkenes, were well simulated at Dallas Hinton (C401) and Fort Worth 

Northwest (C13) but the concentrations were generally less than 1 parts per billion (ppb).

• The performance of isoprene, represented by the Carbon Bond 05 species ISOP, was mixed, 

though concentrations were less than 1 ppb. The model showed a high bias at Fort Worth 

Northwest (C13) and a low bias at Dallas Hinton (C401). 

• The model showed a high bias for the paraffins, represented by the Carbon Bond 05 specie 

PAR at both automated gas chromatograph (auto-GC) sites. 

• Formaldehyde data measurements were not available, nor did instrumented aircraft sample 

in the DFW area during June 2006 as part of TexAQS II.

• In 2006, only two auto-GCs (Dallas Hinton (C401) and Fort Worth Northwest (C13)) were in 

operation, which limited the performance evaluation of ozone precursors, especially in the 

areas of highest observed ozone. The addition of auto-GCs at Eagle Mountain Lake (C75), 

DISH, Decatur, and Flower Mound in 2010 will aid in the understanding of ozone formation 

and future model performance evaluations in the DFW area (TCEQ, 2011).

5.2.2.3 

• The meteorological modeling successfully replicated the major features of ozone episodes in 

the DFW area much of the time, including the passages of fronts.

Meteorological Performance Evaluation

• Trajectory analyses and vertical wind profiles in the DFW area show that much of the time 

on high ozone days, the model predicted ozone and precursors at approximately the correct 

areas and the correct times.

• The model occasionally had difficulty in replicating cloud cover, resulting in high ozone on 

days when low ozone was observed or vice versa.

• Episode days with strong stagnation were more difficult to model precisely than days for 

which the winds did not stagnate. The model sometimes simulated nighttime winds that 

were too brisk, resulting in more dilution of emissions than was actually observed.

• Radar profiler data indicate that for most episode days, the PBL appeared to be modeled 

with good accuracy.

5.2.2.4 

• The base case modeling has been challenged with different emissions inventories in order to 

evaluate its dynamic response to emission changes (Gilliland et al., 2009).

Model Response to Emission Changes
5-7 

• Modeled ozone appears to decrease slightly in response to NOX emission decreases typical of 

the changes that occur on weekends. 

• Modeled ozone increases substantially in response to VOC and NOX emission increases 

commensurate with the difference between 2006 emissions and 1999 emissions in the DFW 

area. When relative response factors are calculated using 2006 as the baseline year and 1999 

as the future year, the modeled response to emission reductions is similar to the observed 

response for most monitors. However, at three monitors the model responded more to the 

2006 to 1999 emission changes than what was observed at those monitors. This finding 

implies that the current modeling appears to estimate the response to emission controls 

well. If the atmosphere responds to the emission reductions from 2006 to 2012 in a manner 

similar to its response to the emission reductions between 1999 and 2006, the actual 

decrease in ozone design value will be similar to what the model predicts.

5.2.2.5 

• DFW area peak ozone is strongly affected by regional background ozone concentrations.

Ozone Formation Sensitivity

• Local ozone production in the DFW area can be substantial. The contribution of local ozone 

production to peak ozone concentration depends strongly upon wind speed and transport 

conditions. 

• In the DFW area, ozone production occurs in NOX-sensitive conditions over most of the area. 

NOX-limited ozone formation appears to contribute more to peak area-wide ozone than 

VOC-limited ozone formation. Both VOC-sensitive and NOX-sensitive ozone formation occur 

throughout the DFW area each day, with VOC-sensitive formation occurring in the morning 

and NOX-sensitive formation occurring in the afternoon. 

• VOC-sensitive ozone formation is most notable in the urban core and in the vicinity of power 

plants where large quantities of NOX are emitted. 

• Although DFW total ozone production is similar in magnitude to HGB total ozone 

production, ozone formation in the DFW area is sensitive to a different group of precursor 

emissions. In HGB, ozone formation occurs primarily in the VOC-sensitive regime 

downwind of the industrial areas and urban core but occurs in the NOX-sensitive regime in 

much of the domain. In the DFW area, NOX-limited ozone formation appears to contribute 

more to peak area-wide ozone than VOC-limited ozone formation. 

5.2.3 Additional Modeling Analysis to Measure Progress

Table 5-1: Changes in the Area and Population Affected by an Eight-Hour Ozone Design Value 

Greater than or Equal to 85 ppb in Response to Growth and Controls shows how the area 

affected by high ozone is expected to shrink dramatically in response to the emission changes 

projected to occur between 2006 and 2012. Peak ozone drops by 17% and the area with an 

estimated ozone design value greater than the 84 ppb standard is eliminated completely. Thus, 

the 2012 population living in the DFW nine-county area is projected to be residing in attainment 

of the 1997 eight-hour ozone standard, benefiting the residents of the DFW area.

Table 5-1: Changes in the Area and Population Affected by an Eight-Hour Ozone 

Design Value Greater than or Equal to 85 ppb in Response to Growth and Controls

Run name

Eight-Hour 

Peak Ozone 

(ppb)

Area with 

design value > 

84 ppb, km2

2010 population 

in area with 

design value > 84

ppb

2006 baseline (reg2 MVS) 98 2632 4320739

2012 future year (cs03a MVS) 81 0 0 
5-8 

Run name

Eight-Hour 

Peak Ozone 

(ppb)

Area with 

design value > 

84 ppb, km2

2010 population 

in area with 

design value > 84

ppb

Percentage decrease from 2006 to 

2012 17% 100% 100%

5.2.4 Conclusion 

The photochemical grid model performed by the TCEQ for the Dallas-Fort Worth Attainment 

Demonstration for the 1997 Eight-Hour Ozone Nonattainment Area has been rigorously 

evaluated against observational data. While there are a number of shortcomings that this 

modeling has in common with other modeling exercises as discussed in Section 5.2.1: Solving 

Modeling Problems and Section 5.2.2: Model Performance Evaluations: Implications of the 

Model Performance of the Current SIP Modeling, modeling for many of the simulated ozone 

days appears to behave in a manner consistent with most of the atmospheric phenomena of 

interest. 

5.3 AIR QUALITY TRENDS IN THE DFW AREA

Despite a continuous increase in the population of the nine-county area and other factors such 

as vehicle miles traveled, the area is exhibiting decreasing trends for ozone and its precursors, 

NOX and VOC. The eight-hour ozone design values appear to show decreasing trends over the 

past 20 years. The eight-hour design value in 2010 is 18% lower than the eight-hour ozone 

design value in 1991, a percentage decrease that nearly equals the one-hour ozone design value 

decrease. In 2010, the peak one-hour ozone design value was 110 ppb, while the peak eight-hour 

ozone design value was 86 ppb, which occurred on the northwest side of the DFW area. The 

number of eight-hour ozone exceedance days over the past 20 years has also decreased 

significantly, from 26 days in 1991 to 8 days in 2010. Over the same time period the number of 

ozone monitors in the DFW area more than doubled. 

Preliminary analysis suggests that NOX measured at monitors in the Barnett Shale is well below 

what is measured in the urban DFW area. This analysis also suggests that the higher NOX

percentile concentrations are observed when the winds are from the DFW region. Caution 

should be taken when interpreting these results due to the limited amount of data collected to 

date. The NOX monitors at Parker County (C76) and Eagle Mountain Lake (C75) have only been 

operating since March 2010.

5.3.1 Design Values

Trends in ozone and its precursors demonstrate not only the substantial progress the DFW area 

has made in improving air quality but also the magnitude of the future challenge in attaining the 

NAAQS for ozone. Trends are also useful as a first look at how ozone concentrations are related 

to precursor concentrations. Ozone is a secondary pollutant, formed through a photochemical 

reaction of NOX and sunlight. VOC can amplify ozone production, causing accumulation in the 

atmosphere. Decreases in NOX and VOC demonstrate the effectiveness of regulations and 

programs to reduce emissions; however, due to its dependence on meteorological variables, 

ozone may not always exhibit trends identical to its precursors. Separating variations in 

meteorological factors from trends in ozone and its precursors can highlight whether ozone 

reductions are caused by decreases in precursor emissions or by year-to-year variability in local 

meteorology (Sullivan, et al, 2009, Camalier, et al, 2007). This section discusses trends, both 

temporal and spatial, in ozone and its precursors. 
5-9 

A design value is a statistic used to compare an area’s concentrations of a particular pollutant to 

the pollutant’s NAAQS. Design values are commonly used to characterize ambient ozone 

concentrations because they summarize the severity of a local ozone problem into a single value. 

The criteria for attainment of the ozone NAAQS have changed over the past 12 years. Until its 

revocation on April 30, 2004, the ozone NAAQS was 0.12 ppm, averaged over a one-hour period 

(U.S. EPA, 2004). An exceedance occurred when the fourth highest one-hour ozone 

concentration in a three-year period equaled or exceeded 0.125 ppm. The eight-hour NAAQS for 

ozone, set at 0.08 ppm averaged over eight hours, was adopted in 1997 but not implemented 

until 2004. A monitor exceeds the eight-hour standard when its design value, a three-year 

average of the fourth highest eight-hour ozone concentration for each year, equals or exceeds 

0.08 ppm. The design value of record for an area is the highest design value recorded at any 

monitor in the area. 

This section examines the frequency at which the NAAQS (both one-hour and eight-hour) for 

ozone are exceeded, with the understanding that the eight-hour standard of 0.08 ppm is 

currently being used for control strategy development and that the one-hour standard is no 

longer in effect. However, it is still a useful benchmark for understanding ozone behavior in the 

DFW area. While the ozone NAAQS is expressed in units of ppm, this section will use the 

familiar convention of expressing concentrations in ppb. Following EPA attainment convention, 

the eight-hour ozone NAAQS is often expressed as 85 ppb.

Daily peak eight-hour ozone concentrations for the years 1991 through 2010 in the DFW area 

are shown in Figure 5-1: Daily Peak Eight-Hour Ozone Values in the DFW Area. The majority of 

days show ozone peaks below 85 ppb, but the highest days, which set the design values, are of 

particular interest. Annual maximum values and 90th percentile values have decreased over 

time; however, the median values appear to show no change or a very slight increase. Notable in 

the figure is the decrease in the number of daily peaks exceeding 84 ppb. The bi-modal character 

of the annual ozone cycle is identifiable in several years. On an annual basis, ozone tends to peak 

first in spring and then again in the summer (Nobis, 1998).
5-10

Figure 5-1: Daily Peak Eight-Hour Ozone Values in the DFW Area

The annual cycle of ozone is apparent in Figure 5-1, as daily peak ozone tends to increase 

throughout the spring, into the summer, and then falls as winter approaches, when it reaches a 

nadir. This cycle follows the annual pattern of temperature, which also rises as summer 

approaches, peaks, then falls in winter. Temperature is likely acting as a proxy for solar 

radiation or other meteorological factors known to strongly influence ozone formation. 

The trend in design values is seen more clearly in Figure 5-2: Ozone Design Values for the DFW 

Area. While the DFW area continues to exceed the 1997 eight-hour ozone standard, the eighthour ozone design value in 2010 was 86 ppb, an 18% decrease from the 1991 design value of 105 

ppb. The 2010 value approached the 1997 eight-hour ozone NAAQS of 85 ppb. A regression of 

design values on year estimates that eight-hour ozone design values decreased at the rate of 

about 0.66 ppb (0.00066 ppm) per year, which is statistically significant at the 5% level (α = 

0.05). If this trend were to continue at that rate, attainment of the eight-hour standard should 

be reached by 2012.
5-11

Figure 5-2: Ozone Design Values for the DFW Area

The DFW area one-hour ozone design value in 2010 was 110 ppb, a 21% decrease from the 1991 

design value of 140 ppb. The one-hour design value in the DFW area has met the one-hour 

ozone NAAQS of 124 ppb since 2006. Regression of one-hour design values on year shows a 

decrease at the rate of 1.49 ppb per year, which is faster than the rate of decline of the eight-hour 

ozone design value; the slope is also statistically significant at the 5% level (α = 0.05).

The design value of record in a metropolitan area is the highest design value of all individual 

design values at monitors in an area. Because ozone varies spatially, trends at all monitors in an 

area should be investigated, not just those recording the highest design values. Table 5-2: EightHour Ozone Design Values by Monitor in the DFW Area and Table 5-3: One-Hour Ozone 

Design Values by Monitor in the DFW Area contain the eight-hour and one-hour ozone design 

values at all regulatory monitors in the DFW area from 1991 to 2010. 

Table 5-2: Eight-Hour Ozone Design Values by Monitor in the DFW Area

Monitor/CAMS #

19911992199319941995199619971998

1999

20002001200220032004200520062007

2008

20092010

Keller C17 105 99 95 96 106 104 97 92 95 97 97 98 100 98 95 94 92 87 86 86

Eagle Mountain Lake C75 95 96 94 95 96 95 89 86 85

Grapevine Fairway C70 95 100 98 93 93 92 87 84 82

Denton Airport South C56 102 101 99 97 96 93 95 94 91 85 80

Cleburne Airport C77 89 90 90 89 87 85 83 83 80

Ft. Worth Northwest C13 97 94 94 88 92 94 96 97 99 99 97 96 96 94 95 94 91 83 79 79

Arlington Municipal Airport 

C61 87 87 87 84 79 77 79

105

99

95 96

106 104 104

98 101 102 101 99 100 98 95 96 95

91 86 86

140

147

140 137 139 139 139

135 137

131 130

135 135

129

125 124 124

118 115

110

0

20

40

60

80

100

120

140

160

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Design Value

(ppb) Ozone Design Values for the DFW Area

Eight-Hour Design Value

One-Hour Design Value

One-Hour NAAQS: 124 ppb

Eight-Hour NAAQS (1997): 84 ppb
5-12

Monitor/CAMS #

19911992199319941995199619971998

1999

20002001200220032004200520062007

2008

20092010

Dallas North No.2 C63 93 89 86 87 90 89 86 80 81 78

Dallas Redbird Airport C402 91 91 92 88 84 84 85 87 88 88 85 82 78 78

Pilot Point C1032 81 77 78

Frisco C31 92 99 99 101 98 101101 99 93 88 89 91 92 88 83 79 76

Parker County C76 86 89 86 87 88 91 84 81 75

Granbury C73 84 84 81 81 84 84 81 77 75

Rockwall Heath C69 83 81 82 81 80 78 75 75 74

Midlothian Old Fort 

Worth(OFW) C52/C137 75 73 72

Italy C1044 68

Kaufman C71 70 73 73 73 75 76 73 70 67

Greenville C1006 79 79 76 70 66 64

Dallas Hinton St. C401/C60 90 88 91 93 92 91 90 89 90 87 84 74

Midlothian Tower 

C94/C158 87 92 97 88 86 82 87 84 83 78

Sunnyvale Long Creek C74 83 83 84 73

Anna C68 83 80 80

Arlington Reg. Office C57 95 86

Denton Colony 83 78 79 93 101 99 99 94 100

Dallas North C5 92 90 88 90 97 97 95 89

Denton Co. Airport C33 100 103 104

Bonnieview 71 66 67 68

*Values are sorted in descending order of design values in 2010, then 2009, 2008, etc.

Table 5-3: One-Hour 

Monitor/CAMS #

1991

1992

199319941995

Ozone Design V

19961997

alues 

199819992000

by Monito

200120022003

r in the DFW Area 2004 2005 2006

2007

2008

20092010

Eagle Mountain Lake C75 112 117 135 135 129 125 124 124 115 111 110

Keller C17 140 147 140 137 139 139 131 128 128 128 128 128 128 126 117 115 117 111 108 107

Dallas Redbird Airport C402 116 118 134 135 125 118 111 103 112 121 121 111 110 109 105 106

Ft. Worth Northwest C13 130 140 140 121 121 126 133 127 133 131 130 126 126 123 123 117 118 109 102 106

Dallas North No.2 C63 129 128 128 118 113 118 120 117 116 101 105 105

Grapevine Fairway C70 98 118 128 128 125 113 112 111 107 108 104

Denton Airport South C56 122 126 126 126 128 122 118 117 118 118 118 115 102

Frisco C31 140 140 126 129 126 132 128 133 130 130 119 113 113 113 113 111 110 102 102

Parker County C76 94 99 111 113 112 116 116 116 106 103 99 

Arlington Municipal Airport 

C61 122 120 120 117 113 113 101 100 97 

Pilot Point C1032 107 104 101 94 97 

Cleburne Airport C77 108 109 110 110 118 108 106 105 105 104 96 

Granbury C73/C681 99 109 108 107 101 104 104 104 98 98 94 

Dallas Hinton St. C401/C60 120 120 121 113 121 121 121 120 128 127 125 118 125 118 115 114 114 97 87 89 

Midlothian OFW C52/C137 98 103 98 95 88 

Rockwall Heath C69 117 102 102 98 108 101 96 93 92 92 86 

Corsicana Airport C1051 86 

Kaufman C71 81 88 89 90 91 93 87 89 87 87 84 

Italy C1044/A323 86 86 84 
5-13

Monitor/CAMS #

1991

1992

199319941995199619971998199920002001200220032004200520062007

2008

20092010

Greenville C1006

Midlothian Tower 

C94/C158

Sunnyvale Long Creek C74

Anna C68

Arlington Reg. Office C57

Denton Colony

Dallas North C5

Denton Co. Airport C33

Bonnieview

Denton C80

Terrell C83

Ennis C82

Number of Monitors

130 

130 

100 

110 

100 

8 

120 

130 

100 

141 

8 

120 

122 

117 

93 

8 

120 

122 

137 

89 

8 

135 

134 

138 

127 

134 

139 

8 

129 

134 

139 

8 

130 

125 

118 

116 

10 

128 

137 

128 

10 

128 

105 

126 

17 

117 

89 

105 

125 

18 

116 

104 

108 

18 

93 

106 

107 

105 

19 

93 

116 

107 

103 

19 

92 

114 

111 

18 

92 

114 

107 

20 

90 

104 

19 

88 

19 

79 

19 

74 

8 20 

*Values are sorted in descending order of design values in 2010, then 2009, 2008, etc.

Table 5-4: Annual Fourth Highest Eight-Hour Ozone Values and Design Values (ppb) and 

Figure 5-4: One-Hour Ozone Design Value Statistics in the DFW Area display three summary 

statistics for the eight-hour and one-hour ozone design values, respectively: the maximum, 

median, and minimum values computed across all monitors in the DFW area. These figures 

facilitate assessment of the range of design values observed within a year, as well as how these 

distributions change over time. From the figures, neither eight-hour, nor one-hour ozone design 

values exhibited a noticeable trend until about 2000, when both began falling steadily. By 2002, 

over half the monitors in the area attained the one-hour standard and by 2007, over half of the 

monitors attained the eight-hour standard, as indicated by the median value falling below the 

NAAQS in those years. (The median statistic as used here indicates that half the observed design 

values are above the median, and half below it.) Since 2006, all monitors in the DFW area met 

the one-hour ozone NAAQS.

The Keller (C17) monitor currently sets the eight-hour design value of record for the DFW area. 

The 2010 design value, 86 ppb, is calculated (as with all monitors) by averaging the 2008

through 2010 fourth highest concentrations and truncating any decimal. At Keller (C17), these 

values were 85, 90, and 85 ppb. The only other monitor above the 1997 eight-hour ozone 

NAAQS is Eagle Mountain Lake (C75) and that monitor would need a fourth-highest eight-hour 

ozone concentration of 84 ppb or greater in 2011 to violate the NAAQS. The preliminary ozone 

design value ozone for 2011 is 90 parts per billion (ppb), although 2011 data have not been 

finalized.
5-14

Figure 5-3: Eight-Hour Ozone Design Value Statistics in the DFW Area

Figure 5-4: One-Hour Ozone Design Value Statistics in the DFW Area

40

50

60

70

80

90

100

110

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Design Value

(ppb) Eight-Hour Ozone Design Value Statistics the DFW Area 

1997 Eight-Hour Ozone NAAQS: 84 ppb

MAX

Median

MIN 

40

60

80

100

120

140

160

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Design Values

(ppb)

One-Hour Ozone Design Value Statistics the DFW Area 

One-Hour Ozone NAAQS: 124 ppb

MAX

Median

MIN 
5-15

Table 5-4: Annual Fourth Highest Eight-Hour Ozone Values and Design Values 

(ppb)

Monitor 2008 2009 2010

2010 EightHour Ozone 

Design Value

2011 FourthHighest Needed to 

Violate the NAAQS

Keller C17 85 90 85 86 80

Eagle Mountain Lake C75 85 91 80 85 84

Grapevine Fairway C70 77 86 83 82 86

* Monitors are sorted in descending order by 2010 design value. The 2010 design value is the average of the 2008 

through 2010 fourth high values. 

Ozone trends can also be investigated by examining the number of days an exceedance of the 

ozone NAAQS was recorded, termed an “exceedance” day. An exceedance day for the 1997 eighthour ozone NAAQS is any day that any monitor in the area measured an eight-hour average 

ozone concentration greater than or equal to 85 ppb over any eight-hour period. An exceedance 

day for one-hour ozone is any day that any monitor in the area measures a one-hour average 

ozone concentration greater than or equal to 125 ppb for at least one hour. Previous research 

(Savanich, 2006) by the TCEQ has shown that, until 2006, the number of exceedance days was 

positively correlated with the number of monitors in a particular area. That is, as the number of 

monitors increases, so does the number of exceedance days recorded, at least until either the 

area has been saturated with monitors, so that no previously unobserved exceedances are 

detected or until ozone concentrations truly decrease. Because of this correlation, when 

examining exceedance-day trends, the number of monitors must always be considered. Thus, it 

is especially noteworthy that Figure 5-5: Number of Monitors and Ozone Exceedance Days in 

the DFW Area shows that despite an increase in the number of monitors, the number of 

exceedance days for both one-hour and eight-hour ozone has generally decreased. The decrease 

is especially pronounced for eight-hour ozone over the past four years. Since 1991, the number 

of eight-hour ozone exceedance days occurring in the DFW area has fallen 69%. No one-hour 

ozone exceedance days occurred in the DFW area in 2008, 2009, or 2010; this represents a 

100% decrease in the number of one-hour ozone exceedance days from 1991 to the present.
5-16

Figure 5-5: Number of Monitors and Ozone Exceedance Days in the DFW Area

An interesting result that follows from evaluation of exceedance days and the number of 

monitors is exhibited in Figure 5-6: Eight-Hour Ozone Exceedance Days per Monitor in the 

DFW Area. This figure illustrates that accounting for the changing population of monitors in the 

DFW area actually accentuates the decline in number of exceedance days. Whereas in 1991, the 

DFW area observed about 3.3 exceedance days on average at each monitor, by 2010, with a 

much larger monitoring network operating, the DFW area observed only 0.4 exceedance days on 

average at each monitor for a decline of 88%. The drop to 2010 from the 1995 high of the twenty 

year series, 6.3 exceedance days per monitor, is 94%. In the absence of real reductions in ozone 

in the area, an increase in the number of monitors would be expected to increase the number of 

exceedance days observed where some high ozone events missed by a smaller network would be 

detected with a larger one. This result suggests that the likelihood of high ozone events escaping 

detection is diminishing because the network is enlarging at the same time that the number of 

actual high ozone events is decreasing.

26

22

18

44

49

28

36

42

38 36

30

37

31

25

44

31

12

9

12

8 7

4 4

9

15

4

12

5

11

5 2

7

3 4 3 1 2 0 0 0 0

5

10

15

20

25

0

20

40

60

80

100

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Days Monitors Ozone Exceedance Days and Number of Monitors in the DFW Area

Number of Monitors

Eight-Hour Exceedance Days (1997 NAAQS)

One-Hour Exceedance Days
5-17

Figure 5-6: Eight-Hour Ozone Exceedance Days per Monitor in the DFW Area

Results for individual monitors, displayed in Figure 5-7: Number of Eight-Hour Ozone 

Exceedance Days by Monitor and Figure 5-8: Number of One-Hour Ozone Exceedance Days by 

Monitor, support this conclusion: the number of exceedance days at individual monitors also 

appears to be decreasing. These figures highlight two monitors, Eagle Mountain Lake (C75) 

(blue line) and Keller (C17) (red line), which recorded the highest eight-hour ozone design 

values. Figure 5-8 also highlights the two monitors, Denton Airport South (C56) (blue line) and 

Keller (C17) (red line), which recorded the highest one-hour ozone design value. There have not 

been more than seven one-hour ozone exceedance days per year at any monitor in the DFW area 

from 1991 through 2010. There have been no one-hour ozone exceedances at any monitor in the 

DFW area since 2008. Because of the large number of monitors in the DFW area, data from 

these two figures are presented in Table 5-5: Number of Days with an Eight-Hour Ozone 

Exceedance and Table 5-6: Number of Days with a One-Hour Ozone Exceedance. 
5-18

Figure 5-7: Number of Eight-Hour Ozone Exceedance Days by Monitor

Figure 5-8: Number of One-Hour Ozone Exceedance Days by Monitor

0

5

10

15

20

25

30

35

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Days Eight-Hour Ozone Exceedance Days in the DFW Area

Frisco C31 Anna C68 Dallas North C5

Dallas Hinton St. C401/C60/C Dallas North No.2 C63 Dallas Redbird Airport C402

Sunnyvale Long Creek C74 Denton C80 Denton Co. Airport C33

Denton Airport South C56 Denton Colony Pilot Point

Midlothian Tower C94/C158 Midlothian OFW C52/C137 Ennis C82

Granbury C73 Greenville C1006 Cleburne Airport C77

Terrell C83 Kaufman C71 Parker County C76

Rockwall Heath C69 Arlington Reg. Office C57 Ft. Worth Northwest C13

Grapevine Fairway C70 Arlington Municipal Airport

Eagle Mountain Lake C75

Keller C17

0

1

2

3

4

5

6

7

8

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Days One-Hour Ozone Exceedance Days in the DFW Area

Frisco C31 Anna C68

Dallas North C5 Bonnieview

Dallas Hinton St. C401/C60/C Dallas North No.2 C63

Dallas Redbird Airport C402 Denton C80

Denton Co. Airport C33 Denton Airport South C56

Denton Colony Midlothian Tower C94/C158

Midlothian OFW C52/C137 Ennis C82

Italy C1044/A323 Granbury C73

Greenville C1006 Cleburne Airport C77

Terrell C83 Kaufman C71

Corsicana Airport C1051 Parker County C76

Rockwall Heath C69 Arlington Reg. Office C57

Eagle Mountain Lake C75 Ft. Worth Northwest C13

Keller C17 Grapevine Fairway C70

Arlington Municipal Airport
5-19

Table 5-5: Number of Days with an Eight-Hour Ozone Exceedance

Monitor

19911992199319941995199619971998199920002001200220032004200520062007200820092010

Keller C17 19 3 7 31 22 13 5 13 19 12 15 23 17 6 19 16 3 4 8 4 

Grapevine Fairway C70 2 18 12 16 5 12 14 4 0 5 3

Ft. Worth Northwest C13 15 5 4 9 15 10 9 17 15 13 11 12 16 10 16 12 1 0 3 3 

Eagle Mountain Lake C75 11 14 25 11 6 13 14 3 4 6 2 

Arlington Municipal Airport 7 4 3 10 5 1 0 3 1 

Parker County C76 2 5 15 7 0 8 7 4 0 2 1 

Rockwall Heath C69 6 1 3 2 3 0 1 0 0 2 1 

Frisco C31 5 10 24 20 8 20 24 16 20 14 6 5 9 10 13 2 2 1 1 

Dallas Redbird Airport C402 11 2 10 12 5 4 2 4 5 4 7 6 2 1 1 1 

Cleburne Airport C77 3 4 8 4 6 7 3 4 2 1 0 

Dallas North No.2 C63 23 14 3 4 6 6 14 5 1 0 4 0 

Denton Airport South C56 21 23 15 16 13 11 11 17 16 6 3 3 0 

Granbury C73 1 6 4 1 1 3 4 3 0 1 0 

Pilot Point 11 0 1 0 0 

Midlothian OFW C52/C137 1 1 0 0 0 

Dallas Hinton St. C401/C60/C 11 2 4 0 8 4 9 16 16 9 4 11 7 5 12 2 0 0 0 0 

Kaufman C71 0 0 0 2 0 1 1 0 0 0 0

Greenville C1006 0 1 0 0 0 0 0 0 

Midlothian Tower C94/C158 2 2 11 21 16 0 10 5 5 1 2 1 

Sunnyvale Long Creek C74 1 3 4 0 5 0 

Anna C68 6 3 3 0 4 

Arlington Reg. Office C57 18 20 5 0 

Denton Colony 0 5 11 13 28 10 14 15 21

Dallas North C5 2 7 8 7 23 10 3 13

Denton Co. Airport C33 11 22 33 18 17

Denton C80 14

Ennis C82 2 

Terrell C83 6 

*Monitors are sorted in descending order by the number of eight-hour ozone exceedance days recorded in 2010, 

then 2009, 2008, etc.

Table 5-6: Number of Days with a One-Hour Ozone Exceedance

Monitor

19911992199319941995199619971998199920002001200220032004200520062007200820092010

Eagle Mountain Lake C75 0 2 3 1 1 2 0 1 0 0 0 

Ft. Worth Northwest C13 6 2 1 0 2 2 2 1 3 0 2 2 1 0 2 0 1 0 0 0 

Keller C17 4 1 0 7 3 2 0 2 4 0 1 4 0 0 2 0 1 0 0 0 

Denton Airport South C56 0 4 1 0 3 0 0 0 0 1 0 0 0 

Parker County C76 0 0 1 0 0 2 1 0 0 0 0 

Dallas Redbird Airport C402 0 2 3 1 0 0 0 0 1 1 0 0 0 0 0 0 

Cleburne Airport C77 0 0 1 0 1 0 0 0 0 0 0 

Grapevine Fairway C70 0 1 3 0 1 0 0 0 0 0 0 

Dallas Hinton St. C401/C60/C 1 1 1 0 1 0 1 1 2 1 1 1 2 0 0 0 0 0 0 0 

Dallas North No.2 C63 3 2 0 0 1 0 0 0 0 0 0 0 

Arlington Municipal Airport 1 0 0 0 0 0 0 0 0 
5-20

Monitor

19911992199319941995199619971998199920002001200220032004200520062007200820092010

Frisco C31 2 1 1 3 0 5 0 3 1 0 0 0 0 0 0 0 0 0 0 

Italy C1044/A323 0 0 0 

Rockwall Heath C69 1 0 0 0 0 0 0 0 0 0 0 

Granbury C73 0 0 0 0 0 0 0 0 0 0 0 

Greenville C1006 0 0 0 0 0 0 0 0 

Kaufman C71 0 0 0 0 0 0 0 0 0 0 0 

Midlothian OFW C52/C137 0 0 0 0 0 

Corsicana Airport C1051 0 0 

Midlothian Tower C94/C158 2 1 1 0 0 0 0 0 0 0 

Anna C68 0 0 0 0 0 

Arlington Reg. Office C57 2 3 1 0 

Denton Colony 0 0 2 0 5 0 2 0 5 

Dallas North C5 0 0 2 0 7 0 0 0 

Denton Co. Airport C33 1 4 6 2 5 

Bonnieview 0 0 0 0 

Denton C80 2 

Ennis C82 0 

Terrell C83 0 

*Monitors are sorted in descending order by the number of one-hour ozone exceedance days recorded in 2010, 

then 2009, 2008, etc.

A variety of analyses have been presented for understanding ozone trends in the DFW area. The 

results of these analyses generally agree that ozone concentrations have been decreasing; 

however, the DFW area still faces challenges in achieving attainment of the 1997 ozone NAAQS. 

Because ozone formation depends on a multitude of factors, these factors must be investigated 

in detail before conclusions as to causes of the observed decreases can be reached.

5.3.2 Nitrogen Oxides Trends

NOX, an ozone formation precursor, is a variable mixture of NO and NO2. NOX is primarily 

emitted by fossil fuel combustion, lightning, biomass burning, and soil (Martin et.al., 2006). 

Examples of common NOX emission sources are automobiles, diesel engines, and other small 

engines; residential water heaters; industrial heaters and flares; and industrial and commercial 

boilers. Mobile, residential, and commercial NOX sources are usually numerous, smaller sources 

distributed over a large geographic area, while industrial sources are usually large point sources, 

or numerous small sources, clustered in a small geographic area. 

Other sources of NOX that are important to air quality in the DFW area are large electric 

generating unit (EGUs) in and around the metropolitan area, as well as other areas upwind of 

the DFW area. These facilities can produce large concentrated plumes of emissions that can 

enhance ozone generation. Analyses conducted by the TexAQS II Rapid Science Synthesis Team 

indicate that NOX emissions at several EGUs decreased by factors ranging from two to four 

between 2000 and 2006. These reductions were seen at EGUs that implemented NOX control 

strategies, such as selective catalytic reduction (SCR), between 2000 and 2006, suggesting these 

control strategies were effective (RSST, 2006). 

Trends for peak daily NOX are presented in Figure 5-9: Daily Peak Hourly NOX in the DFW 

Area. Daily peak NOX concentrations in the DFW area appear to be decreasing over time. NOX
5-21

concentrations have decreased more in recent years, especially 2009, a year that also recorded 

some of the lowest ozone concentrations. The graphic also shows that maximum NOX

concentrations typically occur in winter. Although erratic, maximum NOX levels have decreased 

by 43%, to 398 ppb, from 1991 through 2009, an average of roughly 18 ppb, or nearly 3% per 

year. The years 1998, 1999, and 2000 saw anomalously high peak values greater than 900 ppb. 

The reasons for the high values are not known. Average daily peak hourly NOX has dropped at 

an even faster rate than the maximum NOX levels, falling 65%, or 4% per year, from 78 ppb to 27 

ppb, since 1991. 
5-22

Figure 5-9: Daily Peak Hourly NOX in the DFW Area

78 79 68 77 78 66 64 62 65 52 49 44 46 45 48 41 39 34 27

160 160 151158 165

146 136 132 146

111 109 98 94 97 95 85 80 7461

700

770

640

454

522

626

912

945

997

366

471 474

433

350

490

426

453

380 398

0

100

200

300

400

500

600

700

800

900

1000

Jan-91 Jan-92 Jan-93 Jan-94 Jan-95 Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09

Daily Peak Hourly NOx in the DFW Area

annual maximum

annual average 90th percentile

ppb

 

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

 

 
5-23

Figure 5-10: Annual Mean Daily Peak NOX shows the annual mean of all one-hour NOX

concentrations in the DFW area from 1991 through 2009. Only years with at least 75% data 

completeness were included in the figure. Most monitors in the area demonstrate decreasing 

NOX concentrations since the late 1990s, with the sharpest decreases occurring since 2007. 

Monitors that show the smallest decreases, or show no change, are at sites that have 

traditionally had lower NOX concentrations. 

Figure 5-10: Annual Mean Daily Peak NOX

The largest median NOX concentrations were measured at the Dallas Hinton (C401) monitor, 

which is in close proximity to Interstate 35E, and at the Fort Worth Northwest (C13) monitor 

which is near Fort Worth Meacham International Airport. The location of both monitors, in 

combination with their similar trends, suggests that they may be measuring decreases in NOX

emissions from mobile sources. Monitors located further from the center of the DFW area, 

where there are fewer NOX sources, measured the lowest median NOX concentrations. Sites 

recording the highest NOX concentrations, such as Dallas Hinton (C401), are not necessarily the 

sites with the highest ozone design values. Ozone may be destroyed through reactions with NOX

near these monitors. 

For a more robust examination of the distribution of hourly NOX concentrations, the 90th 

percentile was also analyzed (Figure 5-11: 90th Percentile Daily Peak NOX Concentrations in the 

DFW Area). All sites in the Dallas-Fort Worth area appear to exhibit gradual decreases in 90th 

percentile one-hour NOX concentrations, with the Dallas Hinton (C401) monitor showing the 

largest decrease. The Dallas Hinton (C401) monitor showed large variability in 90th percentile 

NOX concentrations from the start of monitoring in 1996 through 2001. Since 2001, 90th 

percentile NOX concentrations at Dallas Hinton (C401) have steadily decreased and are now 

Annual Mean 1-hour NOX

0

5

10

15

20

25

30

35

40

45

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

NOX, ppb

Arlington Municipal Airport Arlington Reg. Office C57

Bonnieview Dallas Hinton St. C401/C60/C

Dallas North C5 Dallas North No.2 C63

Dallas Redbird Airport C402 Denton Airport South C56

Denton Co. Airport C33 Ft. Worth Northwest C13

Grapevine Fairway C70 Italy C1044

Kaufman C71 Midlothian OFW C52/C137

Midlothian Tower C94/C158
5-24

within the range of other monitors in the area. This large decrease may be due to decreasing 

automobile emissions and implemented controls, though this conclusion has not been 

rigorously tested. 

Table 5-7: Decreases in 90th Percentile NOX Concentrations shows changes in 90th percentile 

measurements since the beginning of data collection at each monitor. While several monitors 

recorded large decreases in 90th percentile NOX from 2008 to 2009, most others observed only 

minimal changes over that same period. These large disparities in patterns of ambient NOX

concentrations across the region are appropriate for further investigation, suggesting that larger 

decreases are not due solely to variations in meteorological conditions, which would be expected 

to influence all monitors similarly, though not identically. The differences appear to be related

to the relative magnitudes of the overall concentrations: sites with the highest concentrations, 

which tend to be urban sites, showed the greatest decrease. More rural sites like Kaufman (C71) 

and Italy (C1044) may reflect slight changes in background values, while more urban sites may 

reflect local emission changes.

Similar to ozone, NOX concentrations in the DFW area appear to be decreasing over time, as 

expected as a result of the comprehensive suite of NOX-targeted controls implemented since 

2000. Stringent point source NOX standards have been adopted along with numerous state and 

federal controls affecting mobile source NOX emissions. Besides normal fleet turnover, as older 

vehicles are replaced by newer, less polluting ones in the on-road fleet, mobile source NOX

reductions since 2000 are due to improvements in the Air Check Texas motor vehicle Inspection 

and Maintenance Program, implementation of the Low Income Vehicle Repair Assistance, 

Retrofit, and Accelerated Vehicle Retirement Program (LIRAP), and expansion of the Texas 

Emissions Reduction Program (TERP) for diesel trucks and heavy-duty equipment.
5-25

Figure 5-11: 90th Percentile Daily Peak NOX Concentrations in the DFW Area

Table 5-7: Decreases in 90th Percentile NOX Concentrations

Monitor Site Start Year

Percentage 

Change from Start 

Year to 2009

Average Annual 

Percentage 

Change

Midlothian OFW C52 2004 -55 -10.9

Grapevine Fairway C70 2001 -55 -6.8

Dallas North No.2 C63 1999 -54 -5.4

Kaufman C71 2001 -53 -6.7

Dallas Hinton St. C401 1996 -46 -3.6

Dallas Redbird Airport C402 1997 -39 -3.2

Ft. Worth Northwest C13 1991 -37 -2.0

Arlington Municipal Airport 2002 -24 -3.5

Denton Airport South C56 1998 -22 -2.0

5.3.3 Volatile Organic Compound Trends

VOC emissions play a central role in ozone production. Since the mid-1990s, the TCEQ has 

collected 40-minute measurements, on an hourly basis, of some 58 VOC compounds using autoGCs. These instruments automatically measure and report chemical compounds resident in 

ambient air. Initially, there was only one auto-GC collecting data in the DFW area, Dallas 

Hinton (C401), but in 2003 a second auto-GC monitor was added at Fort Worth Northwest 

(C13). The TCEQ also deployed auto-GC monitors in DISH, Eagle Mountain Lake, and Flower 

90th Percentile NOX Concentrations in the DFW Area

0

20

40

60

80

100

120

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

NOX, ppb

Arlington Municipal Airport Arlington Reg. Office C57

Bonnieview Dallas Hinton St. C401/C60/C

Dallas North C5 Dallas North No.2 C63

Dallas Redbird Airport C402 Denton Airport South C56

Ft. Worth Northwest C13 Grapevine Fairway C70

Italy C1044 Kaufman C71

Midlothian OFW C52/C137 Midlothian Tower C94/C158
5-26

Mound in 2010. While not part of this trend analysis, the data from the 2010 auto-GCs are 

evaluated routinely.

The TCEQ has also employed two types of canister sampling in the DFW area, one that samples 

ambient air over a 24-hour period (Community Air Toxics Monitoring Network, or CATMN) and 

another that samples ambient air for a single hour at a time, usually at four different times of 

day (Multican, or MCAN). The locations of the two auto-GC monitors, as well as the canisters 

collecting VOC data in the DFW area are shown in Figure 5-13: Locations of Auto-GC Monitors 

and Canisters in the DFW Area. Some monitors shown have been deactivated (see 

Table 5-8: Description of Auto-GC and Canister Monitors in the DFW Area) but still have data 

after 1999. 

Figure 5-12: Locations of Auto-GC Monitors (AGC) and Canisters (MCAN and 

CATMN) in the DFW Area

Table 5-8: Description of Auto-GC and Canister Monitors in the DFW Area

Site Name 

(CAMS Number) Airs Code County Latitude Longitude Monitor 

Type

Currently 

Active?

Boys Club A134 481130057 Dallas 32.77917 -96.8733 CATMN N 

Dallas Hinton St. 

C401/C60/AH161 481130069 Dallas 32.81972 -96.86 AGC, 

CATMN Y 
5-27

Site Name 

(CAMS Number) Airs Code County Latitude Longitude Monitor 

Type

Currently 

Active?

Denton Airport South 

C56/A163/X157 481210034 Denton 33.19444 -97.1933 MCAN, CATMN Y 

Ft. Worth Northwest 

C13/AH302 484391002 Tarrant 32.80583 -97.3564 AGC, 

CATMN Y 

Garland Hwy Dept C197 481131006 Dallas 32.91056 -96.6692 CATMN N 

Grapevine Fairway 

C70/A301/X182 484393009 Tarrant 32.98417 -97.0636 MCAN, CATMN Y 

Greenville C1006/A198 482311006 Hunt 33.15306 -96.1153 CATMN Y 

Italy C1044/A323 481391044 Ellis 32.17556 -96.8703 CATMN Y 

Kaufman 

C71/A304/X071 482570005 Kaufman 32.565 -96.3175 MCAN, CATMN Y 

Midlothian Tower 

C94/A305/X158 481390015 Ellis 32.43667 -97.0244 MCAN, 

CATMN N 

Midlothian Wyatt Road 

C302/A306 481390017 Ellis 32.47361 -97.0425 CATMN N 

Midlothian OFW 

C52/A137 481390016 Ellis 32.48222 -97.0269 CATMN Y 

AGC = Auto-GC; CATMN = Community Air Toxics Monitoring Network; MCAN = Multican

5.3.4 VOC Trends at Auto-GC Monitors

Trends in total non-methane hydrocarbons (TNMHC) concentrations, a proxy for VOC, provide 

insight into variation in VOC levels in the DFW area over time. Though this analysis includes 

data from 2009, the data have not been verified by the EPA and are subject to change.

Figure 5-14: Daily Peak TNMHC Concentrations in the DFW Area displays daily peak hourly 

VOC values at auto-GC monitors in the DFW area. These daily peaks exhibit large variability and 

range from less than 100 parts per billion, carbon (ppbC) to more than 1,000 ppbC. Because 

TNMHC measurements are characterized by a small number of extremely high values and a 

large number of low and moderate values, plotting TNMHC on a logarithmic scale is necessary 

to display the range of data and show trends. The increasing density and introduction of the new 

color of points (gray) plotted beginning in 2003 reflect the deployment of the Fort Worth 

Northwest (C13) auto-GC monitor. To better assess trends at individual monitors, 90th 

percentile and median TNHMC concentrations by year at each auto-GC monitor are also shown. 

Because of the scales of the data involved, 90th percentile and median concentrations are 

plotted on a linear scale, while daily peak TNMHC concentrations, which are skewed by a few 

very high values, are plotted on a logarithmic scale. Only months with 75% data completeness 

were used in this analysis.

The 90th percentile TNMHC at Fort Worth Northwest (C13) is much higher than the 90th 

percentile TNMHC at Dallas Hinton (C401); however, Fort Worth Northwest (C13) shows a 

much greater decrease, 30 ppbC, over the most recent year compared to a decrease of 2 ppbC at 

Dallas Hinton (C401). Because TNMHC is a precursor to ozone formation, reductions in the 

90th percentile at both locations are beneficial to improving ozone concentrations. Although the 

Fort Worth Northwest (C13) monitor shows a much higher 90th percentile than Dallas Hinton 

(C401), its median is only slightly higher. Both medians show downward trends through 2004 

and have remained roughly constant since. 
5-28

Daily peak TNMHC concentrations at Dallas Hinton (C401) show a seasonal trend: higher 

concentrations of TNMHC in the winter and lower concentrations in the summer. Fort Worth 

Northwest (C13) also exhibits a similar seasonal trend. The higher summer VOC concentrations 

at Fort Worth Northwest (C13) could be the reason that the 90th percentile is higher at that 

monitor. 

Approximately 66% of anthropogenic emissions of TNMHC at Dallas Hinton (C401) come from 

motor vehicle emissions (Qin et al., 2007). This seasonal variation may be due to photochemical 

removal and dilution of VOC from fluctuations in depth of the atmospheric mixing layer. 

Because the mixing layer in summer is much deeper than in winter, ground-level emissions tend 

to become more diluted in the summer (Qin et al., 2007).
5-29

Figure 5-13: Daily Peak TNMHC Concentrations in the DFW Area

0

60

120

180

240

1

10

100

1000

10000

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Median, 

90th Percentile

(ppbC)

Daily Peak 

(ppbC)

Note: The 90th Percentile and median 

VOC concentrations are graphed on a 

linear scale. 

90th Percentile TNMHC at FW Northwest

90th Percentile TNMHC at Dallas Hinton

Median TNMHC at FW Northwest

Median TNMHC at Dallas Hinton

*2009 Data is subject to change.

Note: Logarithmic Scale
5-30

Figure 5-15: 90th Percentile and Median TNMHC in the DFW Area displays 90th percentile and 

median TNMHC for Dallas Hinton (C401) and Fort Worth Northwest (C13) again, but the values 

are now shown along with estimated regression lines.

Table 5-9: TNMHC Yearly Median Linear Regression reports the results of ordinary least 

squares regressions of annual 90th percentile and median TNMHC measures against an index of 

year at the two subject monitors. While all four estimated models exhibit negative slopes, 

corresponding to downward trends, only the models for Dallas Hinton (C401) are statistically 

significant at the 90% (α=0.10) level. The regression analysis statistics6

 

6 *R2 (and adjusted R2) ranges from 0 to 1 and measures the proportion of total variation in the dependent 

variable that is accounted for by the model. It is often used to assess the strength of a modeled 

relationship, usually in comparisons between and among models. There is no R2 value that is considered 

"good" or "bad."

indicate acceptable 

models for Dallas Hinton (C401) but not Fort Worth Northwest (C13), indicating that the 

negative trends detected at Fort Worth Northwest (C401) are not distinguishable from zero, or 

flat lines, with statistical confidence (α = 0.05). 

**The F statistic measures the possibility that the explanatory variable(s) are not correlated with the 

dependent variable. It is the (weighted) ratio of the variance in the dependent variable that is explained by 

the model, to the remaining unexplained variance in the dependent variable. The F statistic is compared 

to a value from an F distribution (critical value) to make a determination. If the F statistic exceeds the 

critical value, the model is considered to be acceptable.

***Significance of F is the probability that the reported F value does not exceed the critical value of F from 

the F distribution. A value of 0.05 (5% probability) or less is generally considered sufficient evidence that 

the reported F statistic exceeds the critical value of F, that the reported value of F did not occur just by 

chance, and that the model is acceptable.

 The t-statistic measures the distance, in standard deviations of the explanatory variable, that the 

slope estimate of the model differs from zero. A value greater than about 2 (positive or negative) is 

considered sufficient evidence to determine that the slope estimate is valid (statistically significant).

** ***The p-value is the probability that the slope is actually zero, given the reported t-statistic, even 

though the model reported an estimate of the slope that was not zero. A p-value of 0.05 (5% probability) 

or less is generally considered sufficient evidence that the estimate of the slope parameter is not zero 

(statistically significant).
5-31

Figure 5-14: 90th Percentile and Median TNMHC in the DFW Area

Table 5-9: TNMHC Yearly Median Linear Regression

Regression 

Statistic6

Dallas Hinton St

90th Percentile

Dallas Hinton St

Median

Fort Worth NW

90th Percentile

Ft Worth NW

Median

Adjusted R2 0.693 0.740 0.161 0.069

F 23.621 29.476 2.150 1.445

Significance F 0.001 0.000 0.202 0.283

Slope -6.209 -2.178 -3.590 -1.260

t-stat -4.860 -5.429 -1.466 -1.202

p-value 0.001 0.000 0.202 0.283

5.3.5 VOC Trends from Canisters

In addition to continuously operating auto-GC instruments in the DFW area, the TCEQ also 

collects ambient air samples using evacuated canisters at seven locations throughout the DFW 

area. Data from these canisters are useful for confirming findings from auto-GCs.

This analysis of TNMHC collected with canisters investigates 24-hour measurements of TNMHC 

and HRVOC. Twelve Community Air Toxics Monitoring Network (CATMN) canisters that collect 

24-hour measurements every sixth day have been active in the DFW area over the past 10 years. 

Two canister locations coincide with auto-GC instruments: Dallas Hinton (C401) and Fort 

Worth Northwest (C13). While comparisons with auto-GC measurements may be instructive for 

observing trends and other patterns, these instruments have different measurement durations 

and frequencies, potentially yielding incomparable results. 

Similar to the auto-GC measurements, quarterly geometric mean concentrations were calculated 

by computing the natural logarithm of each 24-hour concentration, averaging these by monitor 

63 63

68 65

59 49 49 51 53

47 45

65

57 61

54

67

51 56

220

202

218

204

219

211

181

188

168

207

153 158 154

144 146 146

128 126

0

75

150

225

300

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

(ppbC)

90th Percentile and Median TNMHC

90th Percentile TNMHC at FW Northwest

90th Percentile TNMHC at Dallas Hinton

Median TNMHC at FW Northwest

Median TNMHC at Dallas Hinton

*2009 Data is subject to change.
5-32

and quarter, then exponentiating the resulting average. Samples that were invalidated and those 

with warning codes regarding sample accuracy or precision were discarded. Quarters with less 

than 75% valid measurements (less than 12 samples) were also discarded. 2009 includes data 

only through the second quarter as the third and fourth quarter data had not been analyzed and 

quality assured in time for this analysis. Resulting quarterly geometric mean concentrations for 

each HRVOC species were plotted against time. Quarters that did not meet completeness 

criteria appear as gaps in the time series. 

Values measured at each CATMN canister in the DFW area are shown in Figure 5-16: Quarterly 

Geometric Mean TNMHC at CATMN Monitors. As with auto-GC measurements, there is a 

distinct seasonal variation at all monitoring sites, possibly due partly to differences in seasonal 

driving patterns and partly to photochemical removal and dilution due to atmospheric mixing. 

The mixing layer in the summer extends to a much higher altitude than in the winter, allowing 

more dilution of the species. 

Figure 5-15: Quarterly Geometric Mean TNMHC at CATMN Monitors

Because daily and seasonal variability in these series hamper identification of trends, annual 

geometric mean TNMHC are shown for each site in Figure 5-17: Annual Geometric Mean 

TNMHC at CATMN Monitors. Visual inspection suggests that annual geometric mean TNMHC 

concentrations in the DFW area are declining. Linear regressions presented in Table 5-10: 

Regression Analysis Results for Annual Geometric Mean TNMHC at CATMN Monitors provide 

statistical confirmation of any trends present. Incomplete data from 2009 was excluded from 

the analysis.

10

100

1000

2000 2001 2002 2003 2004 2005 2006 2007 2008

Conc_ppbC

CATMN- TNMHC 

Quarterly Geometric Mean 

Dallas Hinton St.

Denton Airport South

Midlothian Tower

Italy

Kaufman

Fort Worth NW

Grapevine

Note: Logarithmic Scale
5-33

Figure 5-16: Annual Geometric Mean TNMHC at CATMN Monitors

Of the seven sites, statistically significant trends, at the 5% level (α=0.05), were identified for 

only two, Kaufman (C71) and Dallas Hinton (C401). These two sites exhibit negative slopes of -

11.86 and -23.31, respectively, which represent quite large decreases. Two other sites exhibited 

trends significant at the 10% level (α=0.10): Midlothian Tower (C94) and Grapevine (C70). 

Midlothian Tower (C94) was the only site that exhibited an increasing trend, which is possibly 

due to increased quarry operations near that site. Regression analysis from 2004 through 2008 

for Denton Airport South (C56), when this monitor began measuring a downward trend similar 

to the other sites, confirmed the observed downward trend; these values are displayed with 

emphasis (italics) in the table. Italy (C1044) had too few years of data to estimate regression 

trends. Results for Fort Worth Northwest (C13) do not show the same significantly downward 

trend, which may be due to recent increased oil and gas extraction activities in the Barnett Shale 

formation in Tarrant and Wise Counties.

Table 5-10: Regression Analysis Results for Annual Geometric Mean TNMHC at 

CATMN Monitors

Regression 

Statistic6

Dallas

Hinton 

St

Denton 

Airport 

South 

2000-

2008

Denton 

Airport 

South 

2004-

2008

Midlothian 

Tower

Italy

*** Kaufman

Fort 

Worth 

North

-west

Grapevine

Adjusted R2 0.83 -0.11 0.69 0.76 NA 0.74 -0.27 0.63

F 35.48* 0.22 7.75 10.46** NA 12.34* 0.14 7.84**

Significance F 0.00 0.65 0.11 0.08 NA 0.04 0.73 0.07

Slope -23.31* -4.41 -25.87 34.34** NA -11.86* -4.56 -22.29**

CATMN TNMHC 

Yearly Geometric Mean

10

100

1000

2000 2001 2002 2003 2004 2005 2006 2007 2008

Conc_ppbC

Dallas Hinton St.

Denton Airport South

Midlothian Tower

Italy

Kaufman

Fort Worth NW

Grapevine

Note: Logarithmic Scale
5-34

Regression 

Statistic6

Dallas

Hinton 

St

Denton 

Airport 

South 

2000-

2008

Denton 

Airport 

South 

2004-

2008

Midlothian 

Tower

Italy

*** Kaufman

Fort 

Worth 

North

-west

Grapevine

t-stat -5.96 -0.47 -2.78 3.23 NA -3.51 -0.38 -2.80

p-value 0.00 0.65 0.11 0.08 NA 0.04 0.73 0.07 *

Significant at the α=0.05 level. **Significant at the α=0.10 level. ***Insufficient data.

Analysis of VOC data collected with auto-GCs and canisters revealed statistically significant 

decreases in total VOC at Dallas Hinton (C401). Although many VOC trends appeared to 

decrease at Fort Worth Northwest (C13), no trends at that location were found to be statistically 

significant. 

5.3.6 Summary of Trends in Ozone and Ozone Precursors

Identifying and assessing trends in ozone and its precursors provide an initial appraisal of the 

current ozone situation in the DFW area, the magnitude of progress made to date, and the scale 

of future challenges. Examination of ozone trends shows that ozone design values have 

decreased in the DFW area over the past seventeen years. The eight-hour ozone design value of 

record in 2010 was 86 ppb, an 18% decrease from the 1991 design value of 105 ppb. The 2010

value is only two ppb above the level required to attain the 1997 ozone NAAQS, 84 ppb. A 

regression analysis of design value by year estimates that eight-hour ozone design values 

decreased at the rate of 0.6 ppb per year, which is statistically significant at the 5% level (α = 

0.05). The one-hour ozone design value in 2010 was 110 ppb, well below the vacated one-hour 

ozone NAAQS of 124 ppb, and a 21% decrease from the 1991 design value of 140 ppb. Regression 

analysis of one-hour design values by year show they decreased at the rate of 1.49 ppb per year, 

which is even faster than the decline in the eight-hour ozone design values.

Examination of design values at individual monitors corroborates these decreases with over half 

of the monitors at levels below the eight-hour standard by 2008 and below the vacated one-hour 

standard by 2000. Since 1991, the number of eight-hour and one-hour ozone exceedance days 

occurring in the DFW area has fallen 69% and 100%, respectively. Decreases in exceedance days 

are apparent despite an increase in the number of monitors located throughout the DFW area. 

A variety of methods has been presented for understanding ozone trends in the DFW area. 

These methods generally agree that ozone concentrations have been decreasing; however, the 

area has not attained the 1997 ozone NAAQS. Because ozone formation depends on a multitude 

of factors, these factors must be investigated and understood in detail before conclusions as to 

the causes of the observed decreases can be reached.

Similar to ozone, NOX concentrations in the DFW area are decreasing over time. NOX

concentrations have shown larger decreases in recent years, especially 2009, a year that also 

recorded some of the lowest ozone concentrations. Maximum NOX concentrations typically 

occur in winter, and, while variable, have decreased overall by 43%, to 398 ppb, since 1991, 

though 1998, 1999, and 2000 saw peak values greater than 900 ppb. This is an average of 

roughly 18 ppb per year or nearly 3%. Average daily peak hourly NOX has dropped at an even 

faster rate, falling 65%, or 4% per year, from 78 ppb to 27 ppb, since 1991. These trends were 

corroborated with results from individual monitors, which showed decreases ranging from 24% 

to 55% from the time the monitor started operation to 2009.
5-35

VOC data collected with auto-GCs and canisters revealed statistically significant decreases in 

total VOC concentrations at Dallas Hinton (C401). As noted in Appendix D: Conceptual Model 

for the DFW Attainment Demonstration SIP Revision for the 1997 Eight-Hour Ozone Standard 

this monitor is determined to be VOC sensitive. Also, VOC trends showed decreases at Fort

Worth Northwest (C13); however, these decreases were not found to be statistically significant. 

The Fort Worth Northwest (C13) monitor is defined as transitional in terms of NOX and VOC 

sensitivity. Ozone decreases at this monitor are likely related to reductions in local NOX as the 

eight-hour design value at this monitor has dropped from 97 ppb in 2001 to 79 ppb in2010. 

NOX trends from 1991 to 2009, and VOC trends from 1999 to 2009, show that most monitors in 

the DFW area experienced decreases in both median and 90th percentile concentrations of these 

pollutants. Most strikingly, 2009 experienced not only some of the lowest ozone design values in 

seventeen years, but also some of the lowest NOX and VOC values. 

5.3.7 NOX Concentrations in the Barnett Shale Region

The Barnett Shale is a geological formation of sedimentary rock in north central Texas that 

contains oil and gas. In the past several years, the quantity of gas produced from active wells has 

grown from 79 billion cubic feet (bcf) in 2000 to 1,764 bcf in 2009 (Railroad Commission of 

Texas, 2010). The geological area containing oil and gas is estimated to extend from the city of 

Dallas in the east, west to Shackleford County, south to Coryell County, and north to the Red 

River, encompassing roughly 5,000 square miles and 24 counties in Texas. 

Because of the proximity of the Barnett Shale formation to the DFW area, questions regarding 

whether emissions from oil and gas drilling, extraction, and transport activity in this region 

could be influencing ozone in the DFW area have been asked. The following paragraphs discuss 

what is currently known about types of emissions from the region.

As stated earlier, NOX is a precursor to ozone formation, and several activities associated with oil 

and gas drilling in the Barnett Shale are sources of NOX. Furthermore, the design value setting 

monitors for the DFW area are on the eastern edge of the Barnett Shale. Before the addition of 

two new NOX monitors in the Barnett Shale area, there was no monitored information about 

localized NOX concentrations. Since the installation of the Parker County (C76) and Eagle 

Mountain Lake (C75) monitors, which are on the eastern edge of the Barnett Shale, NOX data 

from this area are available for analysis. 

The Parker County (C76) and Eagle Mountain Lake (C75) monitors are located in rural areas 

west of the DFW urban area, well within eastern Barnett Shale. The Eagle Mountain Lake (C75) 

monitor frequently sets the design value for the DFW area. With the exception of gas 

compressors and drilling associated with gas and oil operations, there are no nearby major 

sources of NOX. The Parker County (C76) monitor is less populated with fewer possible emission 

sources, other than the nearby oil and gas activity and further from the DFW area. This rural 

monitor can measure oil and gas emissions without interference from urban sources.

Though there are only data for one ozone season, the preliminary results suggests that NOX in 

the Barnett Shale area is well below the NOX concentration seen at other sites, such as the 

mobile source dominated Dallas Hinton (C401) and Fort Worth Northwest (C13) monitors. A 

more direct comparison is to another similar monitor, such as the Kaufman (C71) monitor. 

These monitors have similar emission sources nearby except that there is no oil and gas activity 

at the Kaufman (C71) monitor.
5-36

The NOX means and maxima measured at Eagle Mountain Lake (C75) and Parker County (C76) 

are very similar to those at the Kaufman (C71) monitor. Kaufman’s (C71) mean NOX

concentration is calculated at 4.36 ppb. Eagle Mountain Lake (C75) and Parker County (C76) 

mean NOX concentrations are 4.96 and 2.00 ppb, respectively. Similarly, Kaufman’s (C71) 

maximum NOX concentrations is 84.72 ppb, compared to Eagle Mountain Lake (C75) and 

Parker County (C76) maximum NOX concentrations at 50.48 and 60.80 ppb, respectively. For 

more statistics see Table 5-11: NOX Concentrations Statistics at Various Monitors. 

Table 5-11: NOX Concentrations Statistics at Various Monitors

Rank by 

Mean Monitor Name Mean, ppb Maximum, ppb Nearby Emission Types

1 Hinton 14.77 222.24 Urban/Automobile

2 Ft. Worth NW 10.24 191.87 Urban/Automobile

3 Dallas North 9.62 119.35 Urban/Automobile

4 Midlothian 7.47 189.65 Rural/Kiln

5 Denton 6.48 84.67 Small Population/Automobile/Oil & Gas

6 Keller 6.45 85.66 Suburban/Oil & Gas

7 Eagle Mt. Lake 4.96 50.48 Rural/Oil & Gas

8 Kaufman 4.36 84.72 Small Population

9 Parker Co. 2.00 60.80 Rural/Oil & Gas

Note: Monitors ranked by means and values have been rounded.

Further, to evaluate the monitors’ NOX response by wind direction, wind-roses were created at 

the 90th, 75th, and 50th percentiles. To create the wind-roses, hourly wind data were merged 

with hourly NOX data and then grouped into 16 wind bins with percentiles calculated for each 

wind bin. 

The data suggest the Parker County (C76) and Eagle Mountain Lake (C75) monitors observe 

higher concentrations at all percentiles when the wind is from the East (Figure 5-18: WindRoses Showing 90th Percentile NOX Concentrations by Wind Direction at Parker County (C76) 

and Eagle Mountain Lake (C75)). Aerial photographs were also used to find other possible NOX

sources. For example, the largest nearby NOX source at the Eagle Mountain Lake (C75) monitor 

is almost due south of the monitor. This NOX source is a compressor house less than 1.5 miles 

away. Given that proximity one would expect a large NOX signal from the south but there is 

none. At the Parker County (C76) monitor there are no known large nearby NOX sources, 

nevertheless there exists a NOX signal from the east as previously mentioned. As further 

evidence that the DFW area is most likely to contribute NOX to the Eagle Mountain Lake (C75) 

and Parker County (C76) monitors, the Kaufman (C71) monitor displays a similar NOX signal, 

but from the west, given that this monitor is on the east side of the DFW area. A probable 

explanation is that NOX from the DFW urban area is transported to these monitors.

To summarize, the two new NOX monitors in the Barnett Shale area are observing much lower 

concentrations than urban monitors but similar to the rural Kaufman (C71) monitor. The 

direction from which NOX concentrations are the highest at these new monitors is east. 
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Figure 5-17: Wind-Roses Showing 90th Percentile NOX Concentrations by Wind 

Direction at Parker County (C76) and Eagle Mountain Lake (C75)

5.4 STUDIES OF DFW OZONE FORMATION, ACCUMULATION, AND TRANSPORT

The DFW metropolitan area is one of the largest in the United States with a population of over 

five million people. Like other urban areas of its size, it experiences ozone pollution episodes 

each year. The DFW conceptual model (see Appendix C) describes in detail the characteristics of 

ozone pollution in DFW. On-road mobile source emissions are the largest source of ozone 

precursors in the DFW area, especially of NOX (see Chapter 3). Other significant precursor 

sources include the area and non-road emissions that are typical of a large urban area 

(construction activity, railroads, solvent usage, etc.), electrical power plant emissions, cement 

kilns and other manufacturing facilities, and oil and gas production, especially hydraulic 

fracturing operations in the Barnett Shale formation underlying the western portion of the 

metropolitan area. In addition to these anthropogenic sources, biogenic emissions of VOC are 

substantial, due to the isoprene-emitting oak species of trees, which are relatively abundant in 

some parts of the metropolitan area. Finally, regional background ozone plays an important role 

in ozone pollution episodes in the DFW area.

Most of the air quality studies published in the peer-reviewed literature have focused on 

determining the relative importance of the different ozone precursor emissions and of the 

regional background ozone. Several studies have examined the role of regional background 

ozone concentrations on the ozone pollution in eastern Texas in general. A literature review 

summarizing recent findings about regional background ozone in Texas and the United States 

(Estes, 2010) found that: 

• Regional background ozone in eastern Texas increases with distance from the Gulf of Mexico 

(Hardesty et al., 2007). Background ozone associated with transport from the Gulf of Mexico 

is on average consistent with natural background concentrations of 15-25 ppb (Sullivan, 

2009; Chan and Vet, 2009).

• In the DFW area, regional background ozone appears to comprise a greater percentage of the 

observed maximum concentrations than in the HGB area, in part because some of the HGB 

area’s background ozone arrives from the Gulf of Mexico and therefore is often similar in 

magnitude to natural background ozone (Nielsen-Gammon et al., 2005).

• Regional background concentrations higher than 60 ppb have been observed along the 

Louisiana-Texas border, including a few excursions above 85 ppb (Hardesty et al., 2007). 
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• Regional background ozone varies greatly during the ozone season with highest background 

ozone observed in late spring and late summer (Nielsen-Gammon et al., 2005; Tobin and 

Nielsen-Gammon, 2010).

• Regional transport studies indicate that easterly and northerly flow is on average associated 

with higher background concentrations than southerly flow (Sullivan, 2009; Chan and Vet, 

2009). [See also Appendix C: Photochemical Modeling for the DFW Attainment 

Demonstration SIP Revision for the 1997 Eight-Hour Ozone Standard, Chapter 3.4.3, and 

Chapter 4, Table 4-9, of Appendix D]. 

• While studies of regional background ozone in some cities in the United States have shown 

an upward trend in background ozone (such as Cooper et al., 2010; Chan and Vet, 2009), the 

studies performed by the TCEQ to date have not shown statistically significant upward 

trends in regional background ozone concentrations in eastern Texas.

Kemball-Cook et al. (2009), one of several recent studies, focused on the DFW metropolitan 

area. examined regional background ozone in the DFW area using both aircraft observations 

and modeling in an effort to quantify the regional background ozone contribution to the local 

ozone maxima. Estimated regional transport of background ozone, based on four upwinddownwind flights, ranged from 40 to 71 ppb, with local ozone contribution ranging from 17 to 27 

ppb. Estimates of background ozone using TCEQ ground monitors were consistent with aircraft 

data. 

Using CAMx Kemball-Cook modeled the DFW area with CAMx from June 1 through September 

30, 2002. The APCA tool was used to estimate background and local contribution. The APCA 

results were then compared to TCEQ monitoring data. The relationship between DFW daily 

maximum eight-hour ozone and estimated DFW contribution was fairly consistent among the 

CAMx results, monitoring results, and aircraft results. All estimates of background show 

relatively large contributions from background ozone due to regional transport with background 

usually exceeding local contributions (Table 5-12: Summary of Ozone Apportionment Between 

Regional Transport and Local Production on Exceedance Days in the DFW Area). This study’s

modeling and TCEQ’s monitoring date from 2002 and the aircraft data includes only a single 

flight. Therefore despite the agreement of the modeled and observed data, this study alone 

cannot definitively answer the questions about the current relative importance of local and 

background ozone contributions.

Table 5-12: Summary of Ozone Apportionment Between Regional Transport and 

Local Production on Exceedance Days in the DFW Area

Data Source Average Local Ozone 

Production

Average Regional 

Transport of Ozone

Average Maximum 8-hr 

Average Ozone

CAMx model (all 2002) 46 ppb (46%) 55 ppb (54%) 101 ppb

TCEQ monitors (all 

2002) 34 ppb (35%) 62 ppb (65%) 96 ppb

Aircraft (one flight, on 

23 August 2000) 27 ppb (28%) 71 ppb (72%) 98 ppb

A second TexAQS II aircraft study was conducted by Senff et al. (2010). While their study 

focused primarily on Houston, one flight was conducted in the DFW area. This flight measured 

ozone within the urban plume downwind of the DFW area, and contrasted ozone concentrations 

in the plume to those outside the plume, i.e., in the regional background. Senff et al. found an 

enhancement of only 10 ppb within the plume for the single flight. Since only one DFW flight 
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took place, these results cannot be used to represent the characteristics of ozone formation in 

the DFW area. However, this study conducted six flights in the Houston area including extensive 

investigation of how much the Houston urban plume can raise regional background 

concentrations in east Texas. Houston’s urban plume was found to raise the ozone 

concentrations by 10 ppb over an area of more than 40,000 km2, which indicates that Houston’s 

emissions likely play a role in elevating regional background, and thus increase the likelihood of 

ozone exceedances in the DFW area and other cities downwind of Houston.

A third study using aircraft observations was conducted in 2005 by Luria et al. (2008). In this 

study, twelve flights were made in the DFW area, though only a subset of these was suitable for 

determining the respective roles of regional background and locally produced ozone. Two flight 

days showed local ozone production of 30 to 40 ppb. TCEQ monitoring sites for the same time 

period showed local contributions of 22 to 32 ppb, with background contributions of 52 to 62 

ppb.

In addition to these aircraft measurement studies, two recent studies used photochemical grid 

modeling to estimate the effects of out-of-state emissions on DFW ozone pollution. Kim et al. 

(2009) modeled two episodes, June 19 through 23, 2005, and August 30 through September 9, 

2005, and used the decoupled direct method of sensitivity analysis to estimate the sensitivity of 

DFW ozone to emissions in three areas: within the nine-county DFW nonattainment area, 

within Texas but outside the DFW area, and outside of Texas. They evaluated the effects of 

emission reductions in each of these three areas to see how they differed in their effects upon the 

DFW area. At the Kaufman upwind monitoring site on the eastern side of the DFW metropolitan 

area, interstate and within-Texas contributions dominated the ozone concentrations with about 

half of the ozone supplied by these two categories. At the Eagle Mountain Lake downwind site, 

however, ozone was dominated by contributions from the DFW urban area. 

The Kim et al. study, however, may underestimate the contribution of local emissions to DFW 

high ozone and may overestimate the contribution from out-of-state emissions. The out-of-state 

emissions used in the modeling were derived from the National Emissions Inventory created for 

1999, but the emissions for Texas used an inventory for 2005. The out-of-state emissions 

inventory did not include any emission reductions that took place between 1999 and 2005, but 

the Texas inventory did. The effect of this discrepancy is that the out-of-state emissions may 

appear to play a larger role in DFW ozone attainment in this study than they actually do. 

Another modeling study (Kemball-Cook et al. 2010) specifically examined the effects of 

emissions from the hydraulic fracturing and other oil and gas development in the Haynesville 

Shale in northern Louisiana and northeast Texas on peak ozone concentrations observed in 

northeast Texas and the DFW area. Two episodes were modeled, May 20 through 30, 2005, and 

June 13 through 30, 2005. Ozone was modeled for a 2005 base case, 2012 future baseline, and 

three 2012 future test cases representing three levels of gas development, low, medium, and 

high. They found that the greatest effect on the DFW area was an episode average increase of 

about 2 to 3 ppb in maximum eight-hour ozone. This modest increase was found only under the 

most aggressive development scenario in the Haynesville Shale area; the two less aggressive 

scenarios found much smaller effects of 0 to 2 ppb in maximum eight-hour ozone. 

A study that combined modeling and satellite observations was performed during 2006 (Pierce 

et al., 2008). Satellite data and Regional Air Quality Modeling System (RAQMS) air quality 

modeling were used to determine the importance of background ozone production on high 

ozone (mean daily eight-hour ozone greater than 60 ppb) observed in Houston and Dallas. Most 

of the high ozone days observed in the DFW area between July and October 2006 were 

associated with enhanced background ozone production based on RAQMS modeling. Overall, 7 
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out of 15 elevated eight-hour ozone days examined in DFW during TexAQS II had enhanced 

background ozone production (> 10 ppb/day), as determined by RAQMS modeling estimates 

along the back trajectory calculated at 1:00 PM local time. On average, periods of enhanced 

background ozone production events in DFW were found to have a broad Great 

Plains/Midwest/Ohio River Valley source, with the largest net enhanced background ozone 

production (20-30 ppb/day) due to Chicago, Illinois, and Houston, Texas, NOX sources. 

5.5 QUALITATIVE CORROBORATIVE ANALYSIS

5.5.1 Additional Measures

5.5.1.1 

Concurrent with this AD SIP revision, the commission is adopting rules in 30 Texas 

Administrative Code Chapter 115, Subchapter B, Division 1 to implement reasonably available 

control technology requirements for the storage of VOC (Rule Project Number 2010-025-115-

EN). The Chapter 115 rulemaking revises existing rules to include additional requirements for 

low-leaking storage tank fittings and to limit situations when floating roof storage tanks are 

allowed to emit VOC because the roof is not floating on the liquid. The Chapter 115 rulemaking 

also requires 95% control of flash emissions from crude oil and condensate storage tanks with 

uncontrolled VOC emissions that equal or exceed 50 tons per year. The VOC emission 

reductions anticipated to result from the implementation of this rule were not included in the 

photochemical modeling for this AD SIP revision since the compliance deadline for this rule is 

March 1, 2013. 

VOC Storage Tank Rule

5.5.1.2 

Energy efficiency efforts are typically programs that reduce the amount of electricity and natural 

gas consumed by residential, commercial, industrial, and municipal energy consumers. 

Examples of energy efficiency include increasing insulation in homes, installing compact 

fluorescent light bulbs, and replacing motors and pumps with high efficiency units. Renewable 

energy efforts include programs that generate energy from resources that are replenished or are 

otherwise not consumed as with traditional fuel-based energy production. Examples of 

renewable energy include wind energy and solar energy projects.

Energy Efficiency and Renewable Energy (EE/RE) Measures

The Texas Legislature has enacted a number of EE/RE measures and programs. The following is 

a list of Texas EE/RE legislation since 1999.

• 76th Texas Legislature, 1999

• Senate Bill (SB) 7 (Regular Session)

• House Bill (HB) 2492 (Regular Session)

• HB 2960 (Regular Session)

• 77th Texas Legislature, 2001

• SB 5 (Regular Session)

• HB 2277 (Regular Session)

• HB 2278 (Regular Session)

• HB 2845 (Regular Session)

• 78th Texas Legislature, 2003 

• HB 1365 (Regular Session)

• 79th Texas Legislature, 2005 

• SB 20 (First Call Session)

• HB 2129 (Regular Session)

• HB 2481 (Regular Session)
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• 80th Texas Legislature, 2007

• HB 66 (Regular Session)

• HB 3070 (Regular Session)

• HB 3693 (Regular Session)

• SB 12 (Regular Session)

• 81st Texas Legislature, 2009 

• SB 300 (Regular Session)

• 82nd Texas Legislature, 2011 

• HB 51 (Regular Session)

• HB 2077 (Regular Session)

• SB 898 (Regular Session)

• SB 924 (Regular Session)

• SB 1125 (Regular Session)

SB 5, 77th Texas Legislature, 2001, set goals for political subdivisions in affected counties to 

implement measures to reduce energy consumption from existing facilities by 5 percent each 

year for five years from January 1, 2002, through January 1, 2006. In 2007, the 80th Texas 

Legislature passed SB 12, which extended the timeline set in SB 5 through 2007 and made the 5 

percent each year a goal instead of a requirement. The State Energy Conservation Office (SECO) 

is charged with tracking the implementation of SB 5 and SB 12. Also during the 77th Texas 

Legislature, the Energy Systems Laboratory (ESL), part of the Texas Engineering Experiment 

Station, Texas A&M University System, was mandated to provide an annual report on EE/RE 

efforts in the state as part of the TERP under Texas Health and Safety Code (THSC), 

§388.003(e). HB 2129, 79th Texas Legislature, 2005, directed the ESL to collaborate with the 

TCEQ to develop a methodology for computing emission reductions attributable to use of 

renewable energy and for the ESL to quantify annually such emission reductions. HB 2129 

directed the Texas Environmental Research Consortium to use the Texas Engineering 

Experiment Station to develop this methodology. With the TCEQ’s guidance, the ESL produces 

an annual report detailing these efforts (Statewide Air Emissions Calculations from Energy 

Efficiency, Wind and Renewables). The report:

• analyzes power production from wind and other renewable energy sources; 

• provides quantification of energy savings and NOX reductions resulting from the installation 

of wind and other renewable energy sources;

• describes methodologies developed to quantify energy savings and NOX reductions from 

energy efficiency, wind and other renewable energy initiatives; and

• provides degradation analysis for future predictions of power production of wind farms.

The ESL documents methods used to develop estimates of energy savings and NOX emissions 

reductions resulting from reductions in natural gas consumption and displaced power from 

conventional electric generation facilities. The ESL used the EPA’s Emissions and Generation 

Resource Integrated Database to spatially allocate energy use and emission reductions among 

electric generation facilities. THSC, §389.002 and §389.003 contain requirements that the 

Public Utility Commission of Texas (PUCT), SECO, and the ESL report to the TCEQ all emission 

reductions resulting from EE/RE projects in Texas. The ESL analyzed the following 

areas/programs:

Renewable Energies

The 79th Texas Legislature, 2005, amended SB 5 through SB 20, HB 2129, and HB 2481 to add, 

among other initiatives, the following renewable energy initiatives, which require: 5,880 
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megawatts of generating capacity from renewable energy by 2015; the TCEQ to develop a 

methodology for calculating emission reductions from renewable energy initiatives and 

associated credits; the ESL to assist the TCEQ in quantifying emissions reductions from EE/RE 

programs; and the PUCT to establish a target of 10,000 megawatts of installed renewable 

technologies by 2025.

Residential Building Codes and Programs

THSC, Chapter 388: Texas Building Energy Performance Standards, as adopted by the 77th 

Texas Legislature, 2001, states in §388.003(a) that single-family residential construction must 

meet the energy efficiency performance standards established in the energy efficiency chapter of 

the International Residential Code. The Furnace Pilot Light Program includes energy savings 

accomplished by retrofitting existing furnaces. Also included are Seasonal Energy Efficiency 

Ratio (SEER) 13 upgrades to single-family and multi-family buildings. In January 2006, federal 

regulations mandated that the minimum efficiency for residential air conditioners be increased 

from SEER 10 to SEER 13.

Commercial Building Codes

THSC, Chapter 388 states in § 388.003(b) that all other residential, commercial, and industrial 

construction must meet the energy efficiency performance standards established in the energy 

efficiency chapter of the International Energy Conservation Code.

Federal Facilities EE/RE Projects

Federal facilities are required to reduce energy use by Presidential Executive Order 13123 and 

the Energy Policy Act of 2005 (Public Law 109-58 EPACT20065). The ESL compiled energy 

reductions data for the federal EE/RE projects in Texas.

Political Subdivisions Projects

SECO funds loans for energy-efficiency projects for state agencies, institutions of higher 

education, school districts, county hospitals, and local governments. Political subdivisions in 

nonattainment and affected counties are required by SB 5 to report EE/RE projects to SECO. 

These projects are typically building systems retrofits, nonbuilding lighting projects, and other 

mechanical and electrical systems retrofits such as municipal water and waste water treatment 

systems. 

Electric Utility Sponsored Programs

Utilities are required by SB 7, 76th Texas Legislature, 1999, and SB 5, 77th Texas Legislature, 

2001, to report these projects to the PUCT. See THSC, §386.205 and Texas Utilities Code, 

§39.905. These projects are typically air conditioner replacements, ventilation duct tightening, 

and commercial and industrial equipment replacement.

In addition to the programs discussed and analyzed in the ESL report, local governments may 

have enacted measures beyond what has been reported to SECO and the PUCT. The TCEQ 

encourages local political subdivisions to promote EE/RE measures in their respective 

communities and to ensure these measures are fully reported to SECO and the PUCT.

HB 3693, 80th Texas Legislature, 2007, amended the Texas Education Code, Texas Government 

Code, THSC, and Texas Utilities Code. The bill:

• requires state agencies, universities and local governments to adopt energy efficiency 

programs;
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• provides additional incentives for electric utilities to expand energy conservation and 

efficiency programs;

• includes municipal-owned utilities and cooperatives in efficiency programs;

• increases incentives and provides consumer education to improve efficiency programs; and

• supports other programs such as revision of building codes and research into alternative 

technology and renewable energies.

Emissions reductions resulting from the above programs were not explicitly included in the 

photochemical modeling because local efficiency efforts may not result in local emissions 

reductions or may be offset by increased demand in electricity. The complex nature of the 

electrical grid also makes accurately quantifying emission reductions from EE/RE projects 

difficult. At any given time, it is impossible to determine exactly where on the electrical grid 

electricity comes from for any certain electrical user. The electricity for a user could be from a 

power plant in west Texas, a nearby attainment county or from within the nonattainment area. 

If electrical demand is reduced in the DFW area due to these kinds of measures, then emission 

reductions from power generation facilities may occur in any number of locations around the 

state.

Under CAIR, 28 eastern states (plus the District of Columbia) were required to comply with a 

cap on sulfur dioxide (SO2) and NOX for EGU emissions. The definition of an EGU for the CAIR 

program is approximately the same definition as that for a Federal Clean Air Act (FCAA) Title IV 

Acid Rain unit (i.e., larger than 25 megawatt and more than one-third of its generation going to 

the public grid for sale). CAIR is a cap and trade program, with each of the CAIR-applicable 

states given a calculated NOX budget and a calculated SO2 budget by the EPA. The EPA modeled 

all of these states in order to test the effectiveness of controls. A result of the EPA’s CAIR 

modeling was that Texas “significantly contributed” to the nonattainment of the particulate 

matter of 2.5 microns and less (PM2.5) standard of two counties in Illinois, therefore, Texas was 

included in CAIR for the transport of PM2.5. Texas was not covered under the CAIR program for 

1997 eight-hour ozone standard contribution.

Clean Air Interstate Rule (CAIR) and Cross-State Air Pollution Rule

CAIR was to be implemented in two phases: for NOX, Phase I covers the years 2009 through 

2014 and Phase II is for the years 2015 and later; for SO2, Phase I covers the years 2010 through 

2014 and Phase II is for the years 2015 and later. The Phase I NOX budget calculated and 

assigned to Texas was 181,014 tons per year, and the Phase II NOX budget was 150,845 tons per 

year. 

See Appendix B: Emissions Modeling for the DFW Attainment Demonstration SIP Revision for 

the 1997 Eight-Hour Ozone Standard, Section 2.2.3.1: EGUs for the procedural details that the 

TCEQ used to simulate CAIR Phase I in Texas and the regional states.

On July 11, 2008, the United States Court of Appeals District of Columbia Circuit (Court) (No. 

05-1244) vacated CAIR and the CAIR Federal Implementation Plan. On December 23, 2008, the 

Court issued a revised opinion to remand, without vacating, CAIR to the EPA. CAIR, therefore, 

remained in effect while the EPA completed rulemaking to replace the program and comply with 

the Court’s July 2008 opinion. 

For more information on the ruling, see the EPA’s CAIR Web page (http://www.epa.gov/cair/), 

or the TCEQ CAIR Web page (http://www.tceq.texas.gov/airquality/sip/caircamr.html).
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On July 6, 2011, the EPA finalized its CAIR replacement rule, known as the Cross-State Air 

Pollution Rule (CSAPR) requiring 27 states to reduce power plant emissions that contribute to 

ozone and fine particle pollution in other states. The rule, effective October 7, 2011, is intended 

to help eastern states meet FCAA obligations regarding interstate transport of air pollution for 

the 1997 ozone and PM2.5 and 2006 PM2.5 NAAQS. The rule requires reductions in ozone season 

NOX emissions that cross state lines for states under the ozone requirements and reductions in 

annual SO2 and NOX for states under the PM2.5 requirements. Texas is included in both the 

ozone and the PM2.5 program requirements. To assure emissions reductions, the EPA is 

promulgating Federal Implementation Plans (FIPs) for each of the states covered by the rule. 

Alternatively, States may choose to develop AD SIP revisions to replace the FIP after 

implementation. The rule, which was published in the Federal Register on August 8, 2011 (76 

FR 48208), requires controls to be implemented beginning in 2012. 

CSAPR was released during the comment period for this DFW AD SIP revision, so the details of 

the rule were not available at the time of modeling for this SIP. However, CSAPR yields more 

emission reductions in 2012 than would CAIR. Specifically, CSAPR reduces modeled Acid Rain 

Database (ARD) NOX emissions outside Texas by approximately 10% compared to the CAIR cap. 

In the three adjacent states of Louisiana, Arkansas, and Oklahoma, modeled CSAPR ARD NOX

emissions total 24% less than CAIR. Modeled Texas ARD sources are calculated to receive an 

18% reduction in NOX allocations with CSAPR compared to CAIR.

A 2012 modeling sensitivity was conducted using CSAPR allocations for the entire country. Note 

that CSAPR allocations used for the modeling sensitivity were those published in the CSAPR 

final rule on August 8, 2011 (76 FR 48208). On October 6, 2011, the EPA signed proposed 

revisions to the CSAPR rule that would revise allowance allocations for several states, including 

Texas. Given the timing, it was not possible to complete a 2012 modeling sensitivity using those 

proposed, revised CSAPR allocations. The 2012 modeling sensitivity using the August 8, 2011, 

allocations is detailed in Section 5.5.1.5: Alternative Modeling Emissions: Cross State Air 

Pollution Rule Point Source (CSAPR) Emissions of Appendix C. In general, ozone 

concentrations in 2012 with CSAPR were lower than with CAIR. 

5.5.1.3 

The TERP program was created in 2001 by the 77th Texas Legislature to provide grants to offset 

the incremental costs associated with reducing NOX emissions from high-emitting internal 

combustion engines. From the beginning of the TERP program in 2001, through July 20, 2011, 

the TERP program had funded over $890.5 million in grants for projects in Texas ozone 

nonattainment and near-nonattainment areas. Over $310 million has been awarded to projects 

in the DFW area since 2001, which will help reduce more than 62,000 tons of NOX emissions. Of 

that $310 million, $22 million was awarded to the North Central Texas Council of Governments 

(NCTCOG) through a third-party grant to administer additional grants in the DFW area. 

TERP

Additional funds are expected to be awarded to the DFW area in subsequent grant application 

periods that will result in further NOX reductions. HB 1796, 81st Texas Legislature, 2009, 

extended the TERP program beyond its current 2013 date to 2019, which will result in 

continued reductions in the significant emissions source categories of on-road and non-road 

engines. The TERP funding appropriation for the 2012-2013 fiscal biennium is about half of the 

funding level for the previous biennium.

5.5.1.4 

SB 12, 80th Texas Legislature, 2007, enhanced the LIRAP, also known as AirCheckTexas Drive a 

Clean Machine (DACM), to expand participation by increasing the income eligibility to 300% of 

LIRAP
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the federal poverty rate and increasing the amount of assistance toward the replacement of a 

retired vehicle. HB3272, 82nd Texas Legislature, 2011, Regular Session, further enhanced the 

LIRAP to expand participation by allowing a motorist to participate if their vehicle has been 

registered in a participating county for 12 of the 15 months preceding application for assistance. 

HB3272 also revised program requirements for vehicles available as replacements. 

The LIRAP provides $3,000 for cars of the current or previous three model-years; $3,000 for 

trucks of the current or previous two model-years; and $3,500 for hybrids, electric, natural gas, 

and all vehicles that have been certified to meet federal Tier 2, Bin 3 or cleaner standards of the 

current or previous three model-years. Replacement vehicles cannot cost more than $35,000, or 

$45,000 for hybrids, electric, natural gas, and all vehicles that have been certified to meet 

federal Tier 2, Bin 3 or cleaner standards before tax, title, and license fees. In addition, 

replacement vehicles must have an odometer reading of not more than 70,000 miles. The 

retired vehicle must be ten years or older or have failed an emissions test. The LIRAP also 

provides up to $600 for repair assistance to qualified motorists of a vehicle that has failed an 

emissions inspection. 

In the DFW area, the LIRAP is available to vehicle owners in nine counties: Collin, Dallas, 

Denton, Ellis, Johnson, Kaufman, Parker, Rockwall and Tarrant. Between December 2007 and 

May 31, 2011, the LIRAP/DACM program has repaired 8,976 vehicles and retired and replaced 

23,923 vehicles at a cost of $76,187,435. The LIRAP was appropriated $6.25 million for Fiscal 

Year (FY) 2012 and FY 2013 by the 82nd Texas Legislature.

5.5.1.5 

The NCTCOG submitted an assortment of locally implemented strategies in the DFW area 

including pilot programs, new programs, or programs with pending methodologies. These 

programs are expected to be implemented in the nine-county nonattainment area by March 

2012. Due to the continued progress of these measures, additional air quality benefits will be 

gained and will further reduce precursors to ground level ozone formation. A summary of each 

strategy is included in Appendix H: Local Initiatives Submitted by the North Central Texas 

Council of Governments. 

Local Initiatives 

5.5.1.6 

The oil and natural gas industry has in some instances voluntarily implemented controls and 

practices to reduce VOC emissions from oil and natural gas operations in the DFW area as well 

as other areas of the state. Examples of these voluntary efforts include: installing vapor recovery 

units on condensate storage tanks; using low-bleed natural gas actuated pneumatic devices; and 

implementing practices to minimize VOC emissions during well completions (i.e., “Green 

Completions”). The EPA’s Natural Gas STAR Program provides details on these and other 

practices recommended by the EPA as voluntary measures to reduce emissions from oil and 

natural gas operations and improve efficiency. Additional information on the EPA Natural Gas 

STAR Program may be found at 

Voluntary Measures

http://www.epa.gov/gasstar/. 

The preliminary results from the TCEQ’s Barnett Shale Special Inventory Phase One and Phase 

Two support that some companies are implementing such voluntary practices. For example, 

initial estimates from the survey data indicate that use of low-bleed pneumatic devices by some 

companies may be more prevalent than expected and that the TCEQ’s estimates used for the 

DFW AD SIP revision may be conservative. Additional information on the Barnett Shale Special 

Inventory Phase One and Phase Two preliminary results may be found at 

http://www.tceq.texas.gov/airquality/point-source-ei/psei.html. While these industry practices 

are not enforceable under the SIP, these voluntary efforts help reduce VOC emissions in the 
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nonattainment area. The TCEQ supports and encourages these proactive efforts to help improve 

air quality in the DFW area. 

5.6 CONCLUSIONS

The TCEQ has used several sophisticated technical tools to evaluate the past and present causes 

of high ozone in the DFW area in an effort to predict the area’s future air quality. Photochemical 

grid modeling performance has been rigorously evaluated. Historical trends in ozone and ozone 

precursor concentrations and their causes have been investigated extensively. The following 

conclusions can be reached from these evaluations. 

First, the photochemical grid modeling performs relatively well. Problems observed with the 

modeling are those that are known to exist in all photochemical modeling exercises. In spite of 

the known shortcomings, the model can be used carefully to predict ozone concentrations. The 

photochemical grid modeling predicts that the 2012 future year ozone design values in the DFW 

area will be below the 0.08 ppm eight-hour ozone standard. The dynamic model evaluations 

show that the model response to emission decreases is similar to the response observed in the 

atmosphere, suggesting that the future design value will attain the 1997 eight-hour ozone 

standard. 

Second, the ozone trend analyses show that ozone has decreased significantly since the late 

1990s. The 2010 eight-hour ozone design value has dropped to 86 ppb. NOX and VOC trends 

also show significant decreases. Significant decreases in ozone precursors coincide with the 

decreases in ozone, indicating that the ozone decreases observed in the DFW area are due to 

local and regional emission controls. 

Based on the photochemical grid modeling results and these corroborative analyses, the weight 

of evidence indicates that the DFW area will attain the 1997 eight-hour ozone standard by June 

15, 2013.

5.7 REFERENCES 

Banta R., C. Senff, J. Nielsen-Gammon, L. Darby, T. Ryerson, R. Alvarez, P. Sandberg, E. 

Williams, and M. Trainer, 2005. A bad air day in Houston. Bull. of the American Meteorological 

Society, 86(5): 657-669.

Bao, J.-W., S. A. Michelson, S. A. McKeen, and G. A. Grell, 2005. Meteorological evaluation of a 

weather-chemistry forecasting model using observations from the TEXAS AQS 2000 field 

experiment. J. Geophys. Res. 110(D21105), doi:10.1029/2004JD005024.

Berkowitz, C. M., T. Jobson, G. Jiang, C. W. Spicer, and P. V. Doskey, 2004. Chemical and 

meteorological characteristics associated with rapid increases of O3 in Houston, Texas. J. of 

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6-1 

CHAPTER 6: ONGOING INITIATIVES

6.1 INTRODUCTION

The Texas Commission on Environmental Quality (TCEQ) is committed to improving the air 

quality in the Dallas-Fort Worth (DFW) area and continues to work toward identifying and 

reducing ozone precursors. Texas is investing resources into technological research and 

development for advancing pollution control technology and refining quantification of 

emissions, improving the science for ozone modeling and analysis. Refining emissions 

quantification helps improve understanding of ozone formation, which benefits the state 

implementation plan (SIP). Additionally, the TCEQ is working with the United States 

Environmental Protection Agency, local area leaders, and the scientific community to identify 

new measures for reducing ozone precursors. This chapter describes ongoing technical work 

that will be beneficial to improving air quality in Texas and the DFW area. 

6.2 ONGOING WORK

6.2.1 Barnett Shale Special Emissions Inventory

The Barnett Shale is a geological formation that produces natural gas and is located in part of

the DFW 1997 eight-hour ozone nonattainment area. The Barnett Shale formation extends west

and south from the city of Dallas, covering 5,000 square miles. Drilling permits for wells located

in the Barnett Shale formation had been issued in 24 counties in north Texas as of 2010. The 

TCEQ has recently conducted the second phase of a special inventory under the authority of 30 

TAC §101.10(b)(3) to gather detailed information about Barnett Shale emissions sources on the 

source (unit) level, including emissions data and authorization information. 

The first phase of this inventory was completed in 2010 and gathered information about the 

location, number, and type of emission sources associated with upstream and midstream oil and 

gas operations in the Barnett Shale. The results of the first phase were used to improve the 

compressor engine population profile in the DFW area. The improved profile was used to 

determine emissions estimates for the area source category. 

The second phase of the inventory began in late 2010 and involved requesting information about 

emissions. The TCEQ contacted 279 companies in the Barnett Shale area and requested 

companies with 2009 production or transmission of oil or gas from the Barnett Shale formation 

to complete standardized forms detailing source emissions data, source location, information on 

receptors located within one-quarter mile of a source, and authorization information. Data for 

over 8,000 sites were received in 2011. 

Barnett Shale area emissions survey results were still under review at the time of the 

compilation of the inventory for this DFW AD SIP revision. For activities in the Barnett Shale 

formation, initial draft NOX special inventory emissions were commensurate to those estimated 

for this AD SIP revision, while initial draft VOC special inventory emissions were below those 

estimated for this AD SIP revision. Final results will be considered to improve emissions 

estimates in future AD SIP revisions for the DFW ozone nonattainment area.

6.2.2 Statewide Drilling Rigs Emissions Inventory

The improvement or enhancement of drilling rig emission estimates can be used for future 

attainment demonstration and reasonable further progress SIP revisions and other air quality 

analyses. The updated inventories will include controlled and uncontrolled drilling rig emissions 

from 1990 through 2040. 
6-2 

6.2.3 Surface Measurements and One-Dimensional Modeling Related to Ozone 

Formation in the Suburban DFW Area

Surface measurements of trace gas and radical mixing ratios (VOC, NOX, carbon monoxide (CO), 

hydroxyl radical, nitric and nitrous acids, etc.), meteorological properties (including boundary 

layer height), and aerosol properties (concentration, composition, and size distribution) relevant 

for ozone formation were made during a field campaign in the DFW suburban area during May 

and June of 2011. One-dimensional (1D) chemical transport modeling will be used to identify 

key VOC emissions and atmospheric reactions that lead to ozone formation in the DFW region 

and to characterize chemical and meteorological conditions in the atmospheric boundary layer 

that lead to ozone accumulation and National Ambient Air Quality Standard exceedances. The 

combination of measurements and 1D modeling output will be provided to regional, threedimensional air quality modelers to inform regional studies on the inclusion of key emissions 

and chemical processing for improved accuracy of ozone modeling in the region.

6.2.4 DFW Measurements of Ozone Production

To help reduce improve the understanding of the conditions contributing to photochemical 

ozone production in the DFW area, two new Measurements of Ozone Production Sensors 

(MOPS) were developed by Pennsylvania State University. The MOPS were deployed to 

continuously measure ozone production rates in the DFW region. The data are expected to show 

the temporal and spatial variability of in situ net ozone production rates in the DFW area, as 

well as potential NOx sensitivity. The fraction of locally produced or transported ozone will also 

be determined. The measurements of the ozone production rates are expected to improve the 

performance of photochemical models.

6.2.5 Airborne Measurements to Investigate Ozone Production and Transport in 

the DFW Area During the 2011 Ozone Season

The University of Houston (UH) aircraft-based Air Quality Monitoring Team conducted, as part 

of the Air Quality Research Program, an Airborne Measurements Investigation in the DFW area 

during the 2011 ozone season. The constituents and mechanics of ozone formation and transport 

of ozone and precursors are the primary concerns of interest for this effort. UH developed a 

Quality Assurance Project Plan for this project and collected airborne monitoring samples on 

five flight plans in and around the DFW area during the 2011 ozone season. The aircraft airborne 

sampling data will be used as a complement to ground based monitoring to better understand 

the atmospheric chemistry, meteorology, and transport of relevant pollutants in the area.

6.2.6 Quantification of Industrial Emissions of VOCs, NO2 and SO2 by Solar 

Occultation Flux (SOF) and mobile Differential Optical Absorption Spectroscopy

(DOAS) 

A measurement study was conducted that will help to locate and quantify industrial VOC 

emissions (alkanes, alkenes and partly aromatics), nitrogen dioxide, and sulfur dioxide using 

advanced measurement techniques such as the Solar Occultation Flux and mobile Differential 

Optical Absorption Spectroscopy. During part of the campaign a mobile extractive Fourier 

Transform Infrared Spectroscopy was also used. This study followed up previous measurements 

in 2006 and 2009 to obtain a trend analysis for selected sites, but was also extended to new 

areas to improve the understanding of short- and long-term variability. Thus the study 

objectives are relevant for the AQRP priority research area about emissions, emphasizing the 

need to improve the uncertainty of industrial gas emissions (VOC and NOX) that lead to the 

formation of tropospheric ozone. The study areas included locations in the Dallas area.
Appendices available upon request

Kathy Singleton

kathy.singleton@tceq.texas.gov

817.588.5914
THE STATE OF TEXAS

TEXAS COMMISSION ON ENVII~IQ!.W~'~'~A.T T'I'V nd ~ItIS'lll'9'lfUe a correct copy of a

,\h"E Ot' Texas Commission on Environmental Qualily document "'1)1, W!'ich is filed in the permanentr8COrds of the CommissiOn.

=:: '*IE GMn ~der my hand and the seel of ollice on

... 6.-t-<c{4jfC6/ov nEC 12 2011 . Bridget~c. Chief Clerk

Texas Commission on Environmental Quality

ORDER ADOPTING

REVISIONS TO THE STATE IMPLEMENTATION PLAN

Docket No. 2011-0363-SIP

On December 7,2011, the Texas Commission on Environmental Quality (Commission),

during a public meeting, considered adoption ofrevisions to the State Implementation Plan

(SIP) for the Dallas-Fort Worth (DFW) 1997 eight-hour ozone National Ambient Air Quality

Standard (NAAQS). The Commission adopts a photochemical modeling analysis, a weight of

evidence analysis, a reasonably available control technology (RACT) analysis, a motor vehicle

emissions budget for 2012, and a contingency plan to fulfill requirements ofthe

reclassification ofthe DFW area to serious for the 1997 eight-hour ozone NAAQS; and

corresponding revisions to the state implementation plan (SIP). Under Tex. Health & Safety

Code Ann. §§ 382.011, 382.012, and 382.023 (Vernon 2008), the Commission has the

authority to control the quality ofthe state's air and to issue orders consistent with the

policies and purposes ofthe Texas Clean Air Act, Chapter 382 ofthe Tex. Health & Safety

Code. Notice ofthe proposed revisions to the SIP was published for comment in the June 24,

2011, issue ofthe Texas Register (36 TexReg 3984).

Pursuant to 40 Code of Federal Regulations § 51.102 and after proper notice, the

Commission conducted public hearings to consider the revisions 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 Arlington, Texas on July 14, 2011 and Austin,

Texas on July 22, 2011.

The Commission circulated hearing notices ofits intended action to the public,

including interested persons, the Regional Administrator ofthe EPA, and all applicable local

air pollution control agencies. The public was invited to submit data, views, and

recommendations on the proposed SIP revisions, either orally or in \\Titing, at the hearings or

during the comment period. Prior to the scheduled hearings, copies ofthe proposed SIP

revisions were available for public inspection at the Commission's central office and on the

Commission's Web site.

Data, views, and recommendations ofinterested persons regarding the proposed SIP

revisions were submitted to the Commission during the comment period, and were

considered by the Commission as reflected in the analysis oftestimony incorporated by

reference to this Order. The Commission finds that the analysis oftestimony includes the

names of all interested groups or associations offering comment on the proposed SIP

revisions and their position concerning the same.
2.",CiT '0 3TAT2 3HT

81VAm '10 YTv1UO:)

s; <.,.~I;GJ$..J';m;;REFG);Rli,{i)IW.E.\ffiBl1BY THE COMMISSION that the revisions to the SIP

'os: 'i~c~r..po.,m~~~r-'l'~~., r:en,~. e~.,~m. iI1?~!,~~. are he~eby adopted. The adopte~ re~sio~s to the SIP

no," 'are m,c~tJIR!'~~§M@:~l;~n~IJJj;)~lIieOlPeras Ifset forth at length verbatim III thl5 Order.

_...-.,-_.-- IT-IS.FURT~~itl:i~~THE COMMISSION that on behalf ofthe Commission,

the Chairman shdW'itti'iii1siirll'~2ciW'8!this Order, together with the adopted revisions to the

SIP, t'S;ili.1; 'R~gr6ti';rr'Rdfui1'J.if~N~fur i>"tE:PA as a proposed revision to the Texas SIP pursuant to

the Federal Clean Air Act, codified at 42 U.S. Code Ann. §§ 7401- 7671q, as amended.

If any portion ofthis Order is for any reason held to be invalid by a court of competent

jurisdiction, the invalidity of any portion shall not affect the validity ofthe remaining

portions.

Date issued: DEC 12 2011

TEXAS COMMISSION ON

ENVIRONMENTAL QUALITY

ryan W, Shaw, Ph.D., Chairman