ATTACHMENT G

DEVELOPMENT OF AIR EMISSIONS INVENTORIES FOR NONROAD MODEL 

CATEGORY MOBILE SOURCES (TASK 3)
Development of Air 

Emissions Inventories for 

NONROAD Model Category 

Mobile Sources (Task 3)

Final Report

TCEQ Contract No. 582-15-50416

Work Order No. 582-15-51606-03

Project No. 2015-08

Task 3

Prepared for:

Texas Commission on Environmental Quality

Air Quality Division

Prepared by:

Eastern Research Group, Inc.

March 31, 2015
ERG No. 0345.00.003 

TCEQ Contract No. 582-15-50416 

Work Order No. 582-15-51606-03 

Project No. 2015-08

Development of Air Emissions Inventories for NONROAD Model 

Category Mobile Sources (Task 3)

TCEQ Contract No. 582-15-50416 

Work Order No. 582-15-51606-03

Project No. 2015-08

Prepared by: 

Eastern Research Group, Inc. 

3508 Far West Blvd., Suite 210 

Austin, TX 78731 

Prepared for: 

Anusuya Iyer 

Texas Commission on Environmental Quality 

Emissions Assessment Section 

Bldg. E, Room 341S 

12100 Park 35 Circle 

Austin, TX 78753 

March 31, 2015
i

LIST OF ACRONYMS

AACOG Alamo Area Council of Governments

CNG Compressed Natural Gas

CO Carbon Monoxide

CO2 Carbon Dioxide

DCE Diesel Construction Equipment

DFW Dallas-Fort Worth

EDA Equipment Data Associates

EPA Environmental Protection Agency

ERG Eastern Research Group

HGB Houston-Galveston-Brazoria

HP Horsepower

LPG Liquefied Petroleum Gas

MHC McGraw Hill Corporation

NCDC National Climatic Data Center 

NH3 Ammonia

NOAA National Oceanic and Atmospheric Administration

NOX Oxides of Nitrogen

PM10 Particulate Matter < 10 microns in diameter

PM2.5 Particulate Matter < 2.5 microns in diameter

REMI Regional Economic Models, Inc.

RFG Reformulated Gasoline

RTF Rough Terrain Forklift

SCC Source Classification Code

SIP State Implementation Plan

SIP Spark Ignition

SO2 Sulfur Dioxide

TCEQ Texas Commission on Environmental Quality

TexN Texas NONROAD Model

TPD Tons Per Day

TWC Three-way Catalyst

TX Texas

TxDOT Texas Department of Transportation

TxLED Texas Low Emission Diesel

US EPA United States Environmental Protection Agency

VOC Volatile Organic Compounds
ii

TABLE OF CONTENTS

1.0 Introduction.......................................................................................................................1

2.0 Input Data Sources............................................................................................................1

2.1 Equipment Population, Allocation, and Activity Data .........................................2

2.2 Diesel Construction Equipment Population Growth Surrogates ..........................9

2.3 Meteorological Data............................................................................................10

2.4 Fuel Property Data ..............................................................................................10

2.5 Emission Factors and Control Phase-In..............................................................11

2.6 Post Processing Adjustments and Additional Controls ......................................11

3.0 Emissions Estimation......................................................................................................11

3.1 Controlled Emissions Estimates .........................................................................12

3.2 Uncontrolled Emissions Estimates .....................................................................14

3.3 Trends .................................................................................................................16

LIST OF TABLES

Table 1. Sources of Equipment Population Data ................................................................2

Table 2. Spatial Allocation Surrogates for Diesel Construction Equipment.....................4

Table 3. Sources of Geographic Allocation Data (Non-DCE)............................................ 5

Table 4. Sources of Equipment Activity Data ....................................................................6

Table 5. Activity Surrogates for Construction Equipment ................................................ 7

Table 6. Sources of Temporal Allocation Factors ..............................................................8

Table 7. DCE Growth Surrogates ........................................................................................9

Table 8. NOX Controlled Emission Estimates – DFW 4-County Area (Tons Per Day) .. 12

Table 9. VOC Controlled Emission Estimates – DFW 4-County Area (Tons Per Day) .. 12

Table 10. NOX Controlled Emission Estimates – DFW 9-County Area (Tons Per Day). 13

Table 11. VOC Controlled Emission Estimates – DFW 9-County Area (Tons Per Day) . 13

Table 12. NOX Controlled Emission Estimates – HGB Area (Tons Per Day).................. 13

Table 13. VOC Controlled Emission Estimates – HGB Area (Tons Per Day) ................. 14

Table 14. NOX Uncontrolled Emission Estimates – DFW 4-County Area (Tons 

Per Day).................................................................................................................. 14

Table 15. VOC Uncontrolled Emission Estimates – DFW 4-County Area (Tons 

Per Day).................................................................................................................. 14

Table 16. NOX Uncontrolled Emission Estimates – DFW 9-County Area (Tons 

Per Day).................................................................................................................. 15
iii

Table 17. VOC Uncontrolled Emission Estimates – DFW 9-County Area (Tons 

Per Day).................................................................................................................. 15

Table 18. NOX Uncontrolled Emission Estimates – HGB Area (Tons Per Day) ............. 15

Table 19. VOC Uncontrolled Emission Estimates – HGB Area (Tons Per Day)............. 16

List of Figures

Figure 1. DFW Controlled Emissions Trends (NOX) (Tons Per Day).............................. 16

Figure 2. DFW Controlled Emissions Trends (VOC) (Tons Per Day)..............................17

Figure 3. HGB Controlled Emissions Trends (NOX) (Tons Per Day)...............................17

Figure 4. HGB Controlled Emissions Trends (VOC) (Tons Per Day) ............................. 18
1

1.0 Introduction

The purpose of Task 3 of this Work Order was to develop a set of emissions inventories 

for all NONROAD model category mobile sources for selected years, estimating both 

controlled and uncontrolled emissions, for the Dallas-Fort Worth nine-county and 

Houston-Galveston-Brazoria eight-county 1997 eight-hour ozone nonattainment areas.

The TexN model is a tool for developing emissions estimates for nonroad mobile sources 

in Texas for the mobile source categories under the United States Environmental 

Protection Agency’s (EPA) NONROAD model. TexN has a user-friendly graphical user 

interface and stores data in a MySQL database. TexN executes EPA’s NONROAD2008a 

model and allows TCEQ staff to replace EPA default data with local specific data. 

Currently, the TexN model is used by TCEQ staff, local air quality planning agencies, 

and other nonroad mobile stakeholders in order to facilitate the use of locally developed 

activity and population data for nonroad mobile sources, and to standardize the 

emissions estimation methodologies among the different submitting agencies in Texas. 

The TCEQ supplies all interested parties with the latest model, which reflects TCEQ 

updates to specific data, and coordinates the integration of all local changes. The 

emissions estimates developed using this integrated model are used for state 

implementation plan modeling efforts, the EPA’s reporting requirements, trends 

analyses, and air quality modeling purposes.

Using the latest version of the Texas NONROAD (TexN) model1, which incorporates all 

of the latest available data updates, ERG developed both controlled and uncontrolled 

average summer weekday emissions for VOC and NOX for the analysis years 2012, 2014, 

2017, 2020, 2023, 2026, and 2028 for the DFW nine-county and HGB eight-county 

1997 eight-hour ozone nonattainment areas.

This report presents the summaries of the emissions modeling results and provides a 

very brief summary from where each of the critical model inputs were derived from. 

Please note that TCEQ has a number of reports that have been generated over the 

evolution of the TexN model that go into greater detail about the development of each of 

the model inputs and subsequent data updates.

2.0 Input Data Sources

The following sections are meant only to provide a very brief summary of where the 

TexN inputs were derived from. Additional detail may be found in the numerous 

reports for studies conducted by TCEQ throughout the life of TexN.

 

1 TexN version 1.7.1
2

2.1 Equipment Population, Allocation, and Activity Data2

The TCEQ and others have conducted several studies over the years to collect region 

specific population and activity data for selected non-road engine categories, in order to 

improve upon NONROAD default estimates. Working with TCEQ staff, ERG compiled a 

comprehensive list of the most recent data developed for different equipment types and 

regions of the State for inclusion in the TexN model. The sources of the data for each 

equipment type and region are presented in Tables 1 - 6 below. The methods used to 

estimate equipment populations and activity levels can be quite complex; in depth 

discussions of the various methodologies used are provided in the referenced studies.

Table 1. Sources of Equipment Population Data

Equipment Types Region Data Source

Diesel Construction 

Equipment > 25 hp

Dallas-Fort Worth 

(DFW) 9-county 

nonattainment 

area 3

Eastern Research Group, Ozone Science 

and Air Modeling Research Project 

H43T163: Diesel Construction 

Equipment Activity and Emissions 

Estimates for the Dallas/Ft. Worth 

Region, prepared for The Houston 

Advanced Research Center, August 31, 

2005

Diesel Construction 

Equipment > 25 hp, except 

HGB4 cranes

Statewide 

excluding 9-county 

DFW area

Eastern Research Group, Nonroad 

Ammonia Emissions Inventory 

Development, prepared for Texas 

Commission on Environmental Quality, 

November 24, 2006

Mining and Quarry, Special 

Trades, Scrap and Recycling, 

Utility, Rough Terrain 

Forklifts (RTFs), and Skid 

Steer Loaders Diesel 

Construction Equipment

Statewide Eastern Research Group, Update of 

Diesel Construction Equipment 

Emissions Estimates for the State of 

Texas, Prepared for TCEQ, August 31, 

2008.

Mining and Quarry Diesel 

Construction Equipment

Alamo Area 

Council of 

Governments area

AACOG Chapter 2, Table 2-27, 2005 

Non-road Emissions Inventory

 

2

Information taken from TexN User’s Guide unless otherwise noted. Eastern Research Group, Texas NONROAD 

(TexN) Model Version 1.0 User’s Guide, Work Order No. 582-7-84003-FY-08-09, August 18, 2008.

3

Includes Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, and Tarrant Counties.

4

Includes Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller Counties.
3

Equipment Types Region Data Source

Heavy Highway Diesel 

Construction Equipment

Statewide Eastern Research Group, Update of DCE 

Emission Estimates for the State of 

Texas Phase I and Phase II, July 31,2009

and

Eastern Research Group, Update of 

Heavy-Highway Portion of Diesel 

Construction Equipment Inventory 

Using New Data Sources, prepared for 

TCEQ, July 15, 2014.

Diesel Cranes HoustonGalvestonBrazoria (HGB) 

nonattainment 

area

Eastern Research Group, Nonroad 

Mobile Source Emissions Inventory 

Development for the HoustonGalveston-Brazoria Area, submitted to 

the Houston-Galveston Area Council, 

July 28, 2006

LPG Forklifts DFW 9-county 

area and HGB 

nonattainment 

areas

Eastern Research Group, Data 

Collection, Sampling and Emissions 

Inventory Preparation Plan for Selected 

Commercial and Industrial Equipment: 

Phase II, Final Report, prepared for the 

Texas Commission on Environmental 

Quality, August 31, 2005

Terminal Tractors and 

Transportation Refrigeration 

Units

DFW 9-county 

nonattainment 

area

Eastern Research Group, Data 

Collection, Sampling and Emissions 

Inventory Preparation Plan for Selected 

Commercial and Industrial Equipment: 

Phase II, Final Report, prepared for the 

Texas Commission on Environmental 

Quality, August 31, 2005

Transportation Refrigeration 

Units

HGB 

nonattainment 

area

Eastern Research Group, Nonroad 

Mobile Source Emissions Inventory 

Development for the HoustonGalveston-Brazoria Area, submitted to 

the Houston-Galveston Area Council, 

July 28, 2006

Commercial Lawn and 

Garden

Statewide Eastern Research Group, Development 

of Commercial Lawn and Garden 

Emissions Estimates for the State of 

Texas and Selected Metropolitan Areas, 

prepared for Texas Commission on 

Environmental Quality, November 24, 

2003

Recreational Marine Statewide (except 

HGB area)

Eastern Research Group, Recreational 

Marine Emissions Inventory, prepared 

for the Texas Commission on 

Environmental Quality, August 28, 2002
4

Equipment Types Region Data Source

Recreational Marine HGB 

nonattainment 

area

E.H. Pechan & Associates, Development 

of 2007 Recreational Marine Emissions 

Inventory: Spatial and Temporal 

Allocation In the Houston-GalvestonBrazoria 8-County Area, 20085

Agricultural Equipment Statewide E.H. Pechan & Associates, Inc.

All remaining equipment –

see below

See below NONROAD defaults - User’s Guide for 

the Final NONROAD2005 Model, 

EPA420-R-05-013, December 2005

Equipment population estimates were taken from NONROAD defaults for the following 

equipment categories.

 Commercial – all equipment/fuel types

 Logging – all equipment/fuel types

 Railroad – all equipment/fuel types

 Recreational vehicles – all equipment/fuel types

 Residential lawn and garden – all equipment/fuel types

 Industrial – all equipment/fuel types excluding LPG forklifts in DFW and 

HGB, Transportation Refrigeration Units and Terminal Tractors in DFW

 Construction and Mining – all gasoline, LPG, CNG

 Construction and Mining – diesel < 25 hp

 Construction and Mining – diesel > 25 hp:

— Tampers/Rammers

— Plate Compactors

— Signal Boards/Light Plants

— Concrete/Industrial Saws

— Crushing/Processing Equipment

— Cement/Mortar Mixers

— Dumpers/Tenders

— Off-Highway Tractors

— Other Construction Equipment

Table 2. Spatial Allocation Surrogates for Diesel Construction Equipment

Sector Surrogate

Agricultural Dollar value outputs from Texas Regional Economic 

Models, Inc. (REMI) model*

Boring and Drilling Equipment EDA data and dollar value outputs from TX REMI 

model*

Brick and Stone Operations Dollar value outputs from TX REMI model*

City and County Road Construction Project Dollar Value from Reed Construction Data

 

5 E.H. Pechan & Associates, Development of 2007 Recreational Marine Emissions Inventory: Spatial and Temporal 

Allocation in the Houston-Galveston-Brazoria 8-County Area, 2008.
5

Sector Surrogate

Commercial Construction Building footprint data from McGraw Hill 

Corporation (MHC)

Concrete Operations Dollar value outputs from TX REMI model*

County-Owned Construction 

Equipment

County level census projections

Cranes EDA data and dollar value outputs from TX REMI 

model*

Heavy Highway Construction Project lane-mile data by county from TxDOT 

Landfill Operations Landfill disposal volumes from TCEQ

Landscaping Activities Dollar value outputs from TX REMI model*

Manufacturing Operations Dollar value outputs from TX REMI model*

Mining and Quarry Operations Million Tons of Coal Production and Annual nonoffice employee hours respectively (2007)6

Municipal-Owned Construction 

Equipment

County level census projections

Transportation Sales/Services Dollar value outputs from TX REMI model*

Residential Construction County-level housing permit data from the Texas 

A&M Real Estate Center for 1980 through 2013;

County-level census projections from the Texas 

State Data Center for 2014 through 2050;

Housing start for the southern region of the country 

from the U.S. Census Bureau prior to 1980

Rough Terrain Forklifts, Special Trades 

Construction, and Trenchers

2007 Economy.com6

Scrap/Recycling Operations USA Data© (2007)6

Skid Steer Loaders EDA data and dollar value outputs from TX REMI 

model*

TxDOT Construction Equipment None – TxDOT provided complete county-level 

population data

Utility Construction Project Dollar value from Reed Construction Data 

and MHC

* State level extrapolation and county allocation using 9-county DFW population as 

basis.

Table 3. Sources of Geographic Allocation Data (Non-DCE)

Equipment Types Region Data Source

LPG Forklifts 9-county DFW area 

and HGB 

nonattainment 

areas

Eastern Research Group, Data Collection, 

Sampling and Emissions Inventory Preparation 

Plan for Selected Commercial and Industrial 

Equipment: Phase II, Final Report, prepared for 

the Texas Commission on Environmental 

Quality, August 31, 2005

 

6 Eastern Research Group, Update of Diesel Construction Equipment Emissions Estimates for the State of Texas, 

Prepared for TCEQ, August 31, 2008.
6

Equipment Types Region Data Source

Terminal Tractors 

and Transportation 

Refrigeration Units

9-county DFW 

nonattainment area

Eastern Research Group, Data Collection, 

Sampling and Emissions Inventory Preparation 

Plan for Selected Commercial and Industrial 

Equipment: Phase II, Final Report, prepared for 

the Texas Commission on Environmental 

Quality, August 31, 2005

Transportation 

Refrigeration Units

HGB 

nonattainment area

Eastern Research Group, Nonroad Mobile 

Source Emissions Inventory Development for 

the Houston-Galveston-Brazoria Area, 

submitted to the Houston-Galveston Area 

Council, July 28, 2006

Commercial Lawn 

and Garden

Statewide Eastern Research Group, Development of 

Commercial Lawn and Garden Emissions 

Estimates for the State of Texas and Selected 

Metropolitan Areas, prepared for Texas 

Commission on Environmental Quality, 

November 24, 2003

Recreational Marine Statewide Eastern Research Group, Recreational Marine 

Emissions Inventory, prepared for the Texas 

Commission on Environmental Quality, August 

28, 2002

All remaining 

equipment – see 

below

See below NONROAD defaults - User’s Guide for the Final 

NONROAD2005 Model, EPA420-R-05-013, 

December 2005

Geographic allocation surrogates were taken from NONROAD defaults for the following 

equipment categories.

 Agricultural – all equipment

 Commercial – all equipment

 Logging – all equipment

 Railroad – all equipment

 Recreational vehicles – all equipment

 Residential lawn and garden – all equipment

 Industrial – all equipment/fuel types excluding LPG forklifts in DFW and 

HGB, TRUs and Terminal Tractors in DFW

Table 4. Sources of Equipment Activity Data

Equipment Types Region Data Source

Diesel Cranes HGB 

nonattainment 

area

Eastern Research Group, Nonroad Mobile 

Source Emissions Inventory Development for 

the Houston-Galveston-Brazoria Area, 

submitted to the Houston-Galveston Area 

Council, July 28, 2006
7

Equipment Types Region Data Source

Diesel Construction 

Equipment > 25 hp

9-county DFW 

nonattainment 

area

Eastern Research Group, Ozone Science and Air 

Modeling Research Project H43T163: Diesel 

Construction Equipment Activity and Emissions 

Estimates for the Dallas/Ft. Worth Region, 

prepared for The Houston Advanced Research 

Center, August 31, 2005

Diesel Construction 

Equipment > 25 hp

Remainder of 

State, except HGB 

cranes

Eastern Research Group, Nonroad Ammonia 

Emissions Inventory Development, prepared for 

Texas Commission on Environmental Quality, 

November 24, 2006

LPG Forklifts 9-county DFW and 

HGB 

nonattainment 

areas

Eastern Research Group, Data Collection, 

Sampling and Emissions Inventory Preparation 

Plan for Selected Commercial and Industrial 

Equipment: Phase II, Final Report, prepared for 

the Texas Commission on Environmental 

Quality, August 31, 2005

Terminal Tractors 

and Transportation 

Refrigeration Units

9-county DFW 

nonattainment 

area

Eastern Research Group, Data Collection, 

Sampling and Emissions Inventory Preparation 

Plan for Selected Commercial and Industrial 

Equipment: Phase II, Final Report, prepared for 

the Texas Commission on Environmental 

Quality, August 31, 2005

Transportation 

Refrigeration Units

HGB 

nonattainment 

area

Eastern Research Group, Nonroad Mobile 

Source Emissions Inventory Development for 

the Houston-Galveston-Brazoria Area, 

submitted to the Houston-Galveston Area 

Council, July 28, 2006

Commercial Lawn 

and Garden

Statewide Eastern Research Group, Development of 

Commercial Lawn and Garden Emissions 

Estimates for the State of Texas and Selected 

Metropolitan Areas, prepared for Texas 

Commission on Environmental Quality, 

November 24, 2003

All remaining 

equipment – see 

equipment 

population list above

See equipment

population list 

above

NONROAD defaults - User’s Guide for the Final 

NONROAD2005 Model, EPA420-R-05-013, 

December 2005

Table 5. Activity Surrogates for Construction Equipment

Sector Primary Estimation Method

Agricultural Industry expert profiles

Boring and Drilling Equipment Industry expert profiles

Brick and Stone Operations Industry expert profiles

City and County Road Construction Reed Construction profile

Commercial Construction Square feet of installed building space from 

MHC

Concrete Operations Industry expert profiles

County-Owned Construction Equipment Survey findings from HARC study
8

Sector Primary Estimation Method

Cranes Industry expert profiles

Heavy Highway Construction Survey findings from H-GAC study

Landfill Operations Survey profile from TCEQ study

Landscaping Activities Industry expert profiles

Manufacturing Operations Industry expert profiles

Municipal-Owned Construction Equipment Survey findings from HARC study

Transportation Sales/Services Industry expert profiles

Residential Construction Single family housing construction profile

Rough Terrain Forklifts Industry expert profiles

Scrap/Recycling Operations Industry expert profiles

Skid Steer Loaders Industry expert profiles

Special Trades Construction Industry expert profiles

Trenchers Industry expert profiles

TxDOT Construction Equipment Engine clock hours provided by TxDOT

Utility Construction Linear feet installed from Reed Construction 

Data

Table 6. Sources of Temporal Allocation Factors

Equipment 

Types

Region Data Source

Diesel Construction 

Equipment > 25 hp

9-county DFW 

nonattainment 

area

Eastern Research Group, Ozone Science and Air 

Modeling Research Project H43T163: Diesel 

Construction Equipment Activity and Emissions 

Estimates for the Dallas/Ft. Worth Region, 

prepared for The Houston Advanced Research 

Center, August 31, 2005

Diesel Construction 

Equipment > 25 hp

Statewide 

excluding 9-county 

DFW area

Eastern Research Group, Nonroad Ammonia 

Emissions Inventory Development, prepared for 

Texas Commission on Environmental Quality, 

November 24, 2006

LPG Forklifts 9-county DFW and 

HGB 

nonattainment 

areas

Eastern Research Group, Data Collection, 

Sampling and Emissions Inventory Preparation 

Plan for Selected Commercial and Industrial 

Equipment: Phase II, Final Report, prepared for 

the Texas Commission on Environmental Quality, 

August 31, 2005

All remaining 

equipment – see 

equipment 

population list 

above

See equipment 

population list 

above

NONROAD defaults - User’s Guide for the Final 

NONROAD2005 Model, EPA420-R-05-013, 

December 2005
9

2.2 Diesel Construction Equipment Population Growth Surrogates7

The TexN model contains 25 distinct “sectors” with distinct equipment population and 

activity profiles. Diesel construction equipment (DCE) comprises most of these 

“sectors”. Two “sectors” within TexN, being miscellaneous equipment having less than 

25 horsepower and all non-DCE, use the default profiles from EPA’s NONROAD model. 

The remaining 23 of these sectors represent independent DCE profiles developed 

specifically for the TCEQ and the TexN model under numerous projects funded by the 

TCEQ. The TCEQ has focused on DCE specifically, as DCE has the single largest impact 

on total NOx emissions from all nonroad mobile equipment represented within the 

model, which is a driving precursor to ozone formation. Table 7 presents a summary of 

the growth surrogates applied to a 2012 base-year population to forecast equipment 

population for each of the DCE subsectors.

Table 7. DCE Growth Surrogates

Non-DCE* NONROAD default

DCE - Agricultural Activities 2012 Texas Agricultural Census

DCE – Boring & Drilling Equipment Economy.com 

DCE – Brick & Stone Operations Economy.com

DCE – City and County Road 

Construction

Texas State Data Center county-level census 

population

DCE – Commercial Construction Economy.com

DCE – Concrete Operations Economy.com

DCE – County-Owned Construction 

Equipment

Texas State Data Center county-level census 

population

DCE – Cranes Economy.com 

DCE – Heavy-Highway Construction Annual highway expenditures from the Texas 

Comptroller’s Office, for the period 2007 – 2013, 

appended the data to the 1998-2006 dataset 

normalized to 1998 dollars using the Consumer Price 

Index (CPI); 

Economy.com data prior to 1998 and after 2013

DCE – Landfill Operations Texas State Data Center county-level census 

population

DCE – Landscaping Activities Tx REMI model outputs up to 2013;

Texas State Data Center census population data for 

2014-2050

DCE – Manufacturing Operations Economy.com

DCE – Municipal-Owned 

Construction Equipment

Texas State Data Center county-level census 

population

DCE –

Transportation/Sales/Services

Economy.com

 

7 Eastern Research Group, Texas NONROAD Model Update and Enhancement, Work Order No. 582-11-99776-

FY14-25, July 30, 2014.
10 

Non-DCE* NONROAD default

DCE – Residential Construction County-level housing permit data from the Texas 

A&M Real Estate Center for 1980 through 2013;

County-level census projections from the Texas State 

Data Center for 2014 through 2050;

Housing start for the southern region of the country 

from the U.S. Census Bureau prior to 1980 

DCE – Rough Terrain Forklifts Economy.com 

DCE – Scrap Recycling Operations Tx REMI model outputs up to 2013;

Texas State Data Center census population data for 

2014-2050

DCE – Skid Steer Loaders Equipment Data Associates Sales

DCE – Special Trades Construction Economy.com

DCE – Trenchers Economy.com 

DCE – TxDOT Construction 

Equipment*

Zero growth per TxDOT Equipment Replacement 

Policy

DCE – Utility Construction Economy.com

DCE – Mining & Quarry Operations Economy.com

Off-road tractors, Miscellaneous , 

and all Equipment < 25 hp*

NONROAD default

2.3 Meteorological Data8

TexN utilizes high, low and average temperature data, primarily to calculate evaporative 

emissions from gasoline engines. These data are required as part of TexN’s primary 

input file. In addition, related data on relative humidity and atmospheric pressure are 

used during post-processing of the TexN model outputs to adjust diesel NOx emissions 

for ambient effects. The TexN meteorological data is based on historical climate data 

from December 1996 through June 2014 from the National Oceanic and Atmospheric 

Administration (NOAA) National Climatic Data Center (NCDC) 

(http://cdo.ncdc.noaa.gov/qclcd ascii/). 

2.4 Fuel Property Data 

In order to maintain a high confidence level in the fuel parameters used in the 

development of emission inventories, trend analysis and control strategy analysis, the 

TCEQ has undertaken a program to periodically collect and analyze fuel samples. The 

data ensures the accuracy of local specific fuel information and also provides the best 

data available to be used in analyses to support Texas State Implementation Plan (SIP) 

and control strategy development. The latest fuel sampling data, conducted in the 

summer of 20149, was incorporated into TexN for this modeling effort. 

 

8

 Eastern Research Group, Texas NONROAD Model Update and Enhancement, Work Order No. 582-11-99776-

FY14-25, July 30, 2014. 

9

 Eastern Research Group, 2014 Summer Fuel Field Study (Revised), prepared for Texas Commission on 

Environmental Health (TCEQ), Revised January 2015. 
11

2.5 Emission Factors and Control Phase-In10

The TexN model uses the default emission factor and technology type files provided 

with US EPA NONROAD model, thus using the same phase-in schedule and emission 

factors for Federal controls. However, unlike the NONROAD model which does not 

estimate ammonia emissions, there are four ammonia emission factors in TexN: one for 

diesel engines, one for spark ignition engines (gasoline and gaseous fuel) without threeway catalysts (TWCs), one for gasoline engines with TWCs, and one for natural gas/LPG 

engines with TWCs. For more information on how these emission factors were derived, 

please refer to the TexN User’s Guide (2008) and the Addendum (2009)11.

2.6 Post Processing Adjustments and Additional Controls12

TexN applies adjustment factors to the emissions estimates in the output files to 

generate the final criteria pollutant and ammonia emissions values. Post-processing 

applies county specific adjustments to emissions estimates for the appropriate SCCs. 

Depending upon the SCC and county, the following adjustments may be applied within 

the database:

 County and year specific temperature and humidity adjustments for NOx 

emissions;

 Adjustments for Texas Low Emission Diesel (TxLED) impacts;

 Altitude, correcting for decreased engine efficiency at increasing elevation;

 Soil compaction, reflecting relative ease or difficulty digging;

 Ground cover, reflecting relative ease or difficulty in land-clearing activity; 

and

 Reformulated gasoline.

3.0 Emissions Estimation

Using the latest version of the Texas NONROAD (TexN) model13, which incorporates all 

of the latest available data updates, ERG developed both controlled and uncontrolled 

average summer weekday emissions for VOC and NOX for the analysis years 2012, 2014, 

2017, 2020, 2023, 2026, and 2028 for the DFW nine-county and HGB eight-county 

1997 eight-hour ozone nonattainment areas.

 

10 Information taken from TexN User’s Guide unless otherwise noted. Eastern Research Group, Texas NONROAD 

(TexN) Model Version 1.0 User’s Guide, Work Order No. 582-7-84003-FY-08-09, August 18, 2008.

11 Eastern Research Group, Deliverable 6 – Update of TexN User’s Guide Addendum, Work Order No. 582-7-

84003-FY09-19, July 31, 2009.

12 Information taken from TexN User’s Guide unless otherwise noted. Eastern Research Group, Texas NONROAD 

(TexN) Model Version 1.0 User’s Guide, Work Order No. 582-7-84003-FY-08-09, August 18, 2008.

13 TexN version 1.7.1
12

3.1 Controlled Emissions Estimates

The controlled emissions estimates reflect the following state and federal controls:

 Small Spark Ignition Rule - Phase I (Federal),

 Small Spark Ignition Rule - Phase 2 (Federal),

 Large Spark Ignition Rule (Federal),

 Small Spark Ignition/Spark Ignition Marine Rule (Federal),

 Diesel Recreation Marine Rule (Federal),

 Tier 1 Diesel Rule (Federal),

 Tier 2/3 Diesel Rule (Federal),

 Tier 4 Diesel Rule (Federal),

 Texas Low Emission Diesel Requirements (State), and

 Reformulated Gasoline Requirements (State).

The resulting controlled emission estimates for a typical ozone season weekday for 

multiple years for each area are summarized in Tables 8 – 13.

Table 8. NOX Controlled Emission Estimates – DFW 4-County Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 7.59 7.08 5.95 4.86 4.18 3.73 3.53

Dallas 25.40 22.35 17.99 14.68 12.88 11.88 11.51

Denton 5.19 4.54 3.62 3.01 2.72 2.59 2.56

Tarrant 14.58 12.84 10.20 8.24 7.13 6.49 6.24

Grand Total 52.75 46.81 37.77 30.79 26.91 24.69 23.84

Table 9. VOC Controlled Emission Estimates – DFW 4-County Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 5.19 4.62 4.13 3.90 3.85 3.87 3.91

Dallas 18.50 15.96 14.12 13.46 13.47 13.72 13.96

Denton 3.91 3.38 2.88 2.62 2.54 2.52 2.53

Tarrant 10.06 8.63 7.47 7.00 6.94 7.02 7.13

Grand Total 37.66 32.59 28.60 26.99 26.81 27.13 27.53
13

Table 10. NOX Controlled Emission Estimates – DFW 9-County Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 7.59 7.08 5.95 4.86 4.18 3.73 3.53

Dallas 25.40 22.35 17.99 14.68 12.88 11.88 11.51

Denton 5.19 4.54 3.62 3.01 2.72 2.59 2.56

Ellis 2.66 2.44 1.95 1.50 1.25 1.08 1.01

Johnson 2.57 2.26 1.66 1.24 1.03 0.92 0.88

Kaufman 2.60 2.09 1.56 1.18 0.98 0.88 0.85

Parker 2.08 1.70 1.25 0.94 0.78 0.70 0.68

Rockwall 0.84 0.77 0.65 0.53 0.45 0.41 0.39

Tarrant 14.58 12.84 10.20 8.24 7.13 6.49 6.24

Grand Total 63.50 56.08 44.82 36.18 31.40 28.69 27.64

Table 11. VOC Controlled Emission Estimates – DFW 9-County Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 5.19 4.62 4.13 3.90 3.85 3.87 3.91

Dallas 18.50 15.96 14.12 13.46 13.47 13.72 13.96

Denton 3.91 3.38 2.88 2.62 2.54 2.52 2.53

Ellis 1.37 1.21 1.02 0.90 0.86 0.84 0.84

Johnson 0.79 0.69 0.60 0.56 0.55 0.55 0.56

Kaufman 0.94 0.82 0.72 0.67 0.66 0.66 0.67

Parker 0.99 0.89 0.76 0.69 0.67 0.66 0.67

Rockwall 1.03 0.90 0.76 0.66 0.60 0.57 0.56

Tarrant 10.06 8.63 7.47 7.00 6.94 7.02 7.13

Grand Total 42.78 37.10 32.47 30.47 30.14 30.42 30.82

Table 12. NOX Controlled Emission Estimates – HGB Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Brazoria 3.24 2.84 2.25 1.76 1.49 1.35 1.29

Chambers 0.75 0.62 0.47 0.36 0.31 0.29 0.28

Fort Bend 3.86 3.61 2.95 2.34 2.00 1.79 1.70

Galveston 2.39 2.08 1.67 1.30 1.09 0.97 0.91

Harris 36.67 32.26 25.36 20.04 17.24 15.70 15.14

Liberty 1.10 0.92 0.68 0.51 0.42 0.38 0.36

Montgomery 3.05 2.66 2.12 1.67 1.42 1.29 1.24

Waller 0.81 0.69 0.51 0.39 0.33 0.30 0.29

Grand Total 51.88 45.68 36.01 28.36 24.30 22.06 21.21
14

Table 13. VOC Controlled Emission Estimates – HGB Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Brazoria 2.67 2.34 1.94 1.69 1.56 1.49 1.46

Chambers 0.89 0.78 0.62 0.50 0.44 0.39 0.37

Fort Bend 2.07 1.86 1.68 1.61 1.61 1.64 1.67

Galveston 3.08 2.70 2.26 1.95 1.78 1.67 1.63

Harris 26.09 22.69 19.39 17.80 17.36 17.35 17.51

Liberty 0.51 0.46 0.40 0.37 0.36 0.37 0.37

Montgomery 3.69 3.29 2.82 2.52 2.38 2.32 2.30

Waller 0.38 0.34 0.30 0.27 0.26 0.26 0.26

Grand Total 39.38 34.45 29.40 26.71 25.75 25.49 25.57

3.2 Uncontrolled Emissions Estimates

To estimate the uncontrolled emissions using TexN, the Technology Type Year was set 

to 1970, essentially turning off all Federal controls. In addition, the State controls for 

TxLED and RFG were also turned off. The resulting emissions are presented in Tables

14-19.

Table 14. NOX Uncontrolled Emission Estimates – DFW 4-County Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 19.43 21.60 24.26 25.74 27.22 28.52 29.45

Dallas 60.13 65.10 71.72 74.79 77.97 80.68 82.61

Denton 12.69 13.67 15.16 16.15 17.19 18.22 18.97

Tarrant 35.90 38.85 42.32 44.17 46.09 47.78 48.94

Grand Total 128.15 139.23 153.46 160.85 168.46 175.21 179.97

Table 15. VOC Uncontrolled Emission Estimates – DFW 4-County Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 16.06 16.78 17.76 18.55 19.33 20.09 20.61

Dallas 57.82 60.50 64.29 67.35 70.44 73.44 75.47

Denton 10.82 11.27 11.91 12.44 12.96 13.48 13.83

Tarrant 30.15 31.49 33.33 34.85 36.38 37.87 38.88

Grand Total 114.85 120.04 127.29 133.18 139.12 144.88 148.78
15

Table 16. NOX Uncontrolled Emission Estimates – DFW 9-County Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 19.43 21.60 24.26 25.74 27.22 28.52 29.45

Dallas 60.13 65.10 71.72 74.79 77.97 80.68 82.61

Denton 12.69 13.67 15.16 16.15 17.19 18.22 18.97

Ellis 7.19 8.30 9.34 9.75 10.19 10.53 10.76

Johnson 7.64 8.38 8.90 9.19 9.50 9.82 10.03

Kaufman 7.79 7.73 8.35 8.80 9.27 9.75 10.09

Parker 6.42 6.42 6.86 7.18 7.51 7.85 8.10

Rockwall 2.11 2.33 2.62 2.80 2.99 3.17 3.31

Tarrant 35.90 38.85 42.32 44.17 46.09 47.78 48.94

Grand Total 159.30 172.37 189.53 198.57 207.93 216.33 222.25

Table 17. VOC Uncontrolled Emission Estimates – DFW 9-County Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Collin 16.06 16.78 17.76 18.55 19.33 20.09 20.61

Dallas 57.82 60.50 64.29 67.35 70.44 73.44 75.47

Denton 10.82 11.27 11.91 12.44 12.96 13.48 13.83

Ellis 3.55 3.78 4.03 4.19 4.35 4.50 4.60

Johnson 2.87 3.05 3.22 3.36 3.50 3.63 3.73

Kaufman 3.14 3.24 3.43 3.59 3.75 3.90 4.01

Parker 2.82 2.93 3.10 3.23 3.35 3.48 3.56

Rockwall 2.55 2.63 2.75 2.85 2.96 3.06 3.13

Tarrant 30.15 31.49 33.33 34.85 36.38 37.87 38.88

Grand Total 129.79 135.67 143.82 150.40 157.03 163.46 167.81

Table 18. NOX Uncontrolled Emission Estimates – HGB Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Brazoria 8.74 9.36 10.26 10.64 11.08 11.48 11.74

Chambers 2.10 2.18 2.33 2.44 2.57 2.69 2.77

Fort Bend 10.21 11.48 12.70 13.29 14.00 14.66 15.11

Galveston 6.33 6.70 7.38 7.55 7.74 7.90 8.02

Harris 93.60 102.60 112.36 116.37 121.24 125.65 128.71

Liberty 3.34 3.44 3.65 3.75 3.88 4.00 4.08

Montgomery 7.95 8.54 9.39 9.80 10.27 10.71 11.01

Waller 2.48 2.56 2.73 2.86 2.99 3.13 3.21

Grand Total 134.74 146.85 160.80 166.70 173.76 180.21 184.67
16

Table 19. VOC Uncontrolled Emission Estimates – HGB Area

(Tons Per Day)

County 2012 2014 2017 2020 2023 2026 2028

Brazoria 6.81 7.07 7.43 7.69 7.95 8.21 8.38

Chambers 1.82 1.87 1.94 2.00 2.06 2.12 2.16

Fort Bend 6.97 7.36 7.85 8.22 8.61 8.98 9.24

Galveston 6.79 7.00 7.32 7.56 7.79 8.02 8.18

Harris 76.65 80.32 85.22 89.00 92.94 96.79 99.36

Liberty 1.54 1.61 1.70 1.78 1.85 1.92 1.97

Montgomery 8.99 9.32 9.80 10.18 10.56 10.92 11.16

Waller 1.20 1.25 1.32 1.37 1.43 1.48 1.52

Grand Total 110.76 115.80 122.58 127.79 133.19 138.45 141.97

3.3 Trends

The following figures illustrate the trends for controlled emissions in the DFW and HGB 

areas.

Figure 1. DFW Controlled Emissions Trends (NOX) (Tons Per Day)
17

Figure 2. DFW Controlled Emissions Trends (VOC) (Tons Per Day)

Figure 3. HGB Controlled Emissions Trends (NOX) (Tons Per Day)
18

Figure 4. HGB Controlled Emissions Trends (VOC) (Tons Per Day)