hi

) ,'.-F (~"--.

:['~- I\j ED

2010 ~.PR -7 PM 12: 46

TEXAS COMMISSION ON ENVIRONMENTAL QuAlflIn'filVISION

Bryan W. Shaw, Ph.D., Chairman

Buddy Garcia, Commissioner

Carlos Rubinstein, Commissioner

Mark R. Vickery, P.G., Executive Director

Protecting Texas by Reducing andPreventing Pollution

April 1,2010

Docket No. 2009-0801-SIP

Project No. 2009-018-SIP-NR

y",·~:·

-,...r;·, .

::: ~-~!'

Alfredo "AI" Armendariz, Ph.D., Regional Administrator

U.S. Environmental Protection Agency - Region 6

1445 Ross Avenue

Dallas, Texas 75202-2733

w -

S~2 c:' ~~ :"J~ r-~·

Dear Dr. Armendariz:

On March 10,2010, the Texas Commission on Environinental Quality (Commission) adopted a revision to the

state implementation plan (SIP) for demonstration of reasonable further progress for the Houston-GalvestonBrazoria (HGB) 1997 eight-hour ozone nonattainment area.

The Commission adopted the HGB Reasonable Further Progress (RFP) SIP revision, demonstrating that the

RFP emissions reduction requirement will be met for the six-year period (2003-2008) beginning Janumy 1 ofthe

year following the year used for the baseline emissions inventory (2002) and all remaining three-year periods

after the first six-year period (2009-2011, 2012-2014, and 2015-2017) out to the area's attainment date (2019).

This SIP revision also sets the nitrogen oxides (NOx) and volatile organic compounds (VOC) motor vehicle

emissions budgets (MVEB) for transportation conformity purposes for the milestone years 2008, 2011, 2014,

2017, and 2018.

Enclosed are the proposed revision to the SIP, a public hearing certification, a complete record of the public

hearings, and the accompanying order. I look forward to your expeditious approval ofthis SIP revision.

Sincerely,

~~;dAtv- Bryan W. Shaw, Ph.D.

Chairman

BWS/ts

Enclosures

cc: The Honorable Rick Perry, Governor ofTexas

Mr. Toby Baker, Office ofBudget, Planning and Policy, Office ofthe Governor

.Mr. MarkR. Vickery, P.G., Executive Director, Texas Commission on Environmental Quality

P.O. Box 13087 Austin, Texas 78711-3087 512-239-1000 Internet address:www.tceq.state.tx.us

'.' " 'd
Texas Commission on Environmental Quality

Public Hearings

October 28 and 29. 2009

Concerning Revisions to the

HGB Eight-Hour Ozone Reasonable Further Progress SIP

Project No. 2009-018-SIP-NR
REVISION TO THE STATE IMPLEMENTATION PLAN FOR 

THE CONTROL OF OZONE AIR POLLUTION 

HOUSTON-GALVESTON-BRAZORIA 1997 EIGHT-HOUR 

OZONE STANDARD NONATTAINMENT AREA 

TCEQ 

TEXAS COMMISSION ON ENVIRONMENTAL QUALITY 

P.O. BOX 13087 

AUSTIN, TEXAS 78711-3087 

Houston-Galveston-Brazoria Reasonable Further Progress State 

Implementation Plan Revision for the1997 Eight-Hour Ozone Standard 

PROJECT NO. 2009-018-SIP-NR 

Adopted 

March 10, 2010 
HGB Reasonable Further Progress SIP Revision for the 1997 Eight-Hour Ozone Standard 

ix

LIST OF APPENDICES 

Appendix Appendix Name

Appendix 1 HGB Reasonable Further Progress Demonstration Calculations Spreadsheet 

Appendix 2 Development of Reasonable Further Progress Point Source Inventories 

Appendix 3 Development of Reasonable Further Progress Area Source Inventories 

Appendix 4 Development of Reasonable Further Progress Non-Road Mobile Source 

Emissions Inventories for Source Categories in the EPA’s NONROAD 2005 

Model 

Appendix 5 Development of Reasonable Further Progress Non-Road Mobile Source 

Emissions Inventories for Airports 

Appendix 6 Development of Reasonable Further Progress Non-Road Mobile Source 

Emissions Inventories for Locomotives 

Appendix 7 Development of Reasonable Further Progress Non-Road Mobile Source 

Emissions Inventories for Commercial Marine Vessels 

Appendix 8 Development of Reasonable Further Progress Non-Road Mobile Source 

Emissions Inventories for Drilling Rigs 

Appendix 9 Houston-Galveston-Brazoria 1997 Eight-Hour Ozone Nonattainment Area 

Reasonable Further Progress On-Road Mobile Source Emissions Inventories 
APPENDIX 4 

DEVELOPMENT OF REASONABLE FURTHER PROGRESS NON-ROAD 

MOBILE SOURCE EMISSIONS INVENTORIES FOR SOURCE CATEGORIES 

IN THE EPA’S NONROAD 2005 MODEL 
Technical Support Document 

Development of Reasonable Further Progress (RFP) NonRoad Mobile Source Emissions Inventories for Source 

Categories in the EPA’s NONROAD2005 model

March 2009 

Prepared by the Mobile Source Programs Team 

Air Quality Division 

Texas Commission on Environmental Quality
INTRODUCTION 

This technical support document describes the methodologies used by the Texas Commission on 

Environmental Quality (TCEQ) to develop RFP emissions inventory data for all source 

categories contained within the EPA’s NONROAD 2005 model. The inventories developed 

include county level ozone season day controlled and uncontrolled emissions estimates for years 

2002, 2008, 2011, 2014, 2017, 2018 and 2019 for the eight counties in the 

Houston/Galveston/Brazoria (HGB) ozone non-attainment areas. The eight counties in HGB 

area are Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller. 

A Texas specific version of the EPA’s NONROAD 2005 model, called the Texas NONROAD 

(TexN) model, was used in calculating emissions from all non-road mobile equipments and 

recreational vehicles except aircrafts, locomotives, and commercial marines. TexN was designed 

to develop emission estimates that are consistent with the latest emission inventory data available 

for all counties in Texas, for all Source Classification Codes (SCCs) included in the NONROAD 

model. Texas-specific data files included county specific equipment population, activity, 

growth, and temporal allocation files as appropriate. 

 

The TexN model also incorporates extensive data collected to estimate equipment population 

growth and geographic allocation. Unlike the EPA’s NONROAD 2005 model, the TexN model 

utilizes unique population files for each county and analysis year. Since the population files in 

TexN for all the years (i.e., 1970-2050) are created outside the model, for every evaluation year, 

using county and SCC specific growth factors, the corresponding growth (*.grw) and geographic 

allocation (*.alo) files used in NONROAD are effectively bypassed in the TexN application. 

Several NONROAD files have not been revised for SIP development or other purposes, largely 

due to the difficulty in collecting the required data. The NONROAD default files used in TexN 

include: Emission factors(*.emf), deterioration factors (*.det ), and engine technology phase-in 

schedule (tech.dat) files. The EPA does not expect users to have local data on emission factors, 

or on deterioration factors. 

Overview of the TexN model, sources of data used in TexN and calculation procedures were 

extracted from the TexN user’s guide prepared by Eastern Research Group, Inc. and is attached 

to this RFP SIP as Attachment A. The details of activity projections for TexN equipment 

categories with non-default values can be found in Attachment A, Section 1.2.4 Forecasting and 

Back-Casting Equipment Populations. 

The TexN model includes both emission factors and county-level population and activity data. 

The model therefore estimates not just emission factors but also emissions. The emission factors 

are combined with hp-hr and fuel consumption estimates to calculate mass emission estimates at 

the county level, for different evaluation years and time periods. 

The TexN model used for this RFP analysis is available at the TCEQ’s FTP site at 

ftp://ftp.tceq.state.tx.us/pub/OEPAA/TAD/Modeling/Nonroad_EI/TexN/. This FTP site also 

contains the “Texas NONROAD (TexN) model Version 1.0 User’s Guide”. The Technical 
documentation of all aspects of the non-road modeling can be found on the EPA’s NONROAD 

modeling web page at http://www.epa.gov/omswww/nonrdmdl.htm. 

The TexN model includes more than 80 basic and 260 specific types of non-road equipment, and 

further stratifies equipment types by horsepower rating and fuel type, in the following categories: 

 airport ground support, such as terminal tractors; 

 agricultural equipment, such as tractors, combines, and balers; 

 construction equipment, such as graders and back hoes; 

 industrial and commercial equipment, such as fork lifts and sweepers; 

 recreational vehicles, such as all-terrain vehicles and off-road motorcycles; 

 residential and commercial lawn and garden equipment, such as leaf and snow 

blowers; 

 logging equipment, such as shredders and large chain saws; 

 recreational marine vessels, such as power boats; 

 underground mining equipment; and 

 oil field equipment. 

The model estimates emissions for seven exhaust pollutants: hydrocarbons (HC), nitrogen oxides 

(NOX), carbon monoxide (CO), carbon dioxide (CO2), sulfur oxides (SOX), Ammonia, and 

particulate matter (PM). The model also estimates emissions of non-exhaust HC for six modes 

— hot soak, diurnal, refueling, resting loss, running loss, and crankcase emissions. 

Although the model is capable of calculating emissions from ground support equipment (GSE), 

and other oil field equipment, the TCEQ currently estimates GSE, and oil field equipment 

outside of the NONROAD model and the TexN database has zero population levels for these 

categories. 

Federal and State Control Programs Analysis 

The effects of federal and state control programs were evaluated. The TexN model was executed 

for Ozone season daily emission for years 2002, 2008, 2011, 2014, 2017, 2018 and 2019. To 

evaluate reasonable further progress requirements, a series of TexN model runs were executed 

for both controlled and uncontrolled scenarios for each federal and state control program for each 

analysis year. The electronic data including emissions inventory summary report data files for 

each of the inventories and the NONROAD input/output files can be found at the TCEQ’s FTP 

site at ftp://ftp.tceq.state.tx.us/pub/OEPAA/TAD/Modeling/Nonroad_EI/RFP/HGB. 

The details of the applicable federal and state rules modeled, and how these rules are 

incorporated in TexN model as reported by TCEQ’s contractor, Eastern Research Group, Inc., in 

the TexN User’s guide is in Attachment D. 
Federal Controls 

The Federal Clean Air Act (FCAA) provides the EPA with the authority to establish emissions 

standards only for new engines; therefore non-road engine emissions standards phase in over 

time as older engines undergo turnover and replacement. The first of the non-road regulations 

that the EPA has issued since 1994 to control non-road mobile emission sources went into effect 

in 1996, and the last went into effect in 2008. The EPA has taken a phased-in approach when 

adopting these regulations and has issued multiple tiers for certain categories of engines. The 

TexN model used in this study incorporates the effects of all of the following “on the books” 

Federal non-road equipment regulations: 

Table 1: Existing Federal Non-Road Regulations and Phase - In Dates 

Applicable Rules Category 

Implementation Phase-In 

Period 

Phase I Small SI Rule Land-Based Spark Ignition Engines < 

25hp (except marine and recreational) 

1997 

Phase II Small SI Rule Non-Handheld SI Engines < 25hp 2001-2007 

Handheld SI < 25hp 2002-2007 

1998 HD/Non-road Rule Land-Based Diesel Engines >50 hp 1996-2000 

Or Tier I Rule 

Small Diesel Engines < 50 hp 1999-2000 

Tier 2 Standards Diesel Engines all sizes 2001-2006 

Tier 3 Standards Diesel Engines 50-750 hp 2006-2008 

Large SI Rule Spark Ignition engines > 25hp Tier 1 - 2004 

Tier 2 - 2007 

Tier 4 Standards Land-Based Diesel Engines 1996-2000 
For more details on the applicable rules and how the TexN model is designed to evaluate the 

effects of individual federal rules impacting non-road emissions for RFP analysis, please see 

Attachment D. In order to evaluate individual control reductions benefits of each federal rule, a 

series of TexN model runs were executed for controlled and uncontrolled scenarios. For a 

summary of control reductions, see Table 4. 

State Controls 

The state rules evaluated for this analysis are discussed below. 

 The Texas Low Emission Diesel Rule (TxLED) 

 Reformulated Gasoline (RFG) 

Texas Low Emission Diesel 

TexLED was implemented on January 31, 2006, for 110 counties in Texas. The TexLED 

program is incorporated as part of TexN model’s post processing function. The TexLED flag 

was activated for 2006 and later analysis for the 110 counties. Annual modeling scenarios for 

2007 and beyond receive a full credit of 6.2% NOX reduction applied to all diesel emissions in 

TexLED counties. 

Table 2: TexLED NOx Emission Reduction Benefits 

Typical Summer weekday Emissions (Tons/Day)

8-County HGB Region 

Analysis Year NOX 

2002 0.00

2008 2.87

2011 2.59

2014 2.14

2017 1.73

2018 1.59

2019 1.46
Reformulated Gasoline 

RFG benefits were calculated by running the TexN model for all spark ignition equipment 

categories and all scenario years, with RVP values set to 7.2 (representative of RFG) and 8.7 

(federal default RVP for summer fuel in Texas). The resulting difference in exhaust and 

evaporative VOC levels is reported in Table 3 for each analysis year. 

Table 3: RFG VOC Emission Reduction benefits 

Typical Summer weekday Emissions (Tons/Day)

8-County HGB Region 

Analysis Year VOC 

2002 1.84

2008 1.88

2011 1.97

2014 2.05

2017 2.14

2018 2.16

2019 2.19
Table 4: State and Federal Control Reduction Summary for NONROAD 

Mobile Source Categories that are in EPA's NONROAD2005 Model 

NOX VOC 

Typical Summer Weekday Emissions Typical Summer Weekday Emissions 

Tons/Day Tons/Day 

RFP 

Analysis 

Year 

Uncontrolled Controlled Total 

Reduction 

Uncontrolled Controlled Total 

Reduction 

2002 88.63 79.01 9.62 94.86 79.05 17.65

2008 105.38 65.80 39.59 107.12 63.01 45.99

2011 111.17 54.97 56.21 113.37 57.76 57.58

2014 117.09 43.88 73.21 119.27 55.02 66.31

2017 124.33 35.94 82.17 125.34 53.78 72.46

2018 128.11 33.68 94.46 127.18 53.58 75.77

2019 129.41 31.53 97.89 128.88 53.49 77.58

The electronic data including emissions inventory summary report data files for each of the 

inventories and the NONROAD input/output files can be found at the TCEQ’s FTP site at 

ftp://ftp.tceq.state.tx.us/pub/OEPAA/TAD/Modeling/Nonroad_EI/RFP/HGB. Electronic data set 

names and descriptions for these files are provided in the following section. 

ELECTRONIC DATA SET NAMES AND DESCRIPTIONS 

This section provides the HGB 2002, 2008, 2011, 2014, 2017, 2018, and 2019 RFP non-road 

mobile source emissions inventory electronic data descriptions. 

The electronic data includes 1) the emissions inventory summary report data files for each of the 

inventories and 2) the NONROAD input/output files. These files are posted at the following 

TCEQ’s FTP Site: ftp://ftp.tceq.state.tx.us/pub/OEPAA/TAD/Modeling/Nonroad_EI/RFP/HGB. 

The files in these compressed folders are based on every TexN runs performed with the October 

2008 version of the Texas NONROAD (TexN) model, which contains the most recently updated 

equipment population estimates. 

 

These compressed data sets contain: 

 HGB RFP Rule Benefits Analysis Excel Spreadsheet files 

HGB RFP NONROAD input/output files 

 
Please note that the TexN model accounts for adjustments such as Texas Low Emission Diesel 

(TxLED), temperature/humidity NOx correction, etc., Therefore, if the EPA’s NONROAD 2005 

model is used to replicate the emissions, the results may vary slightly because the EPA’s model 

not does not include these adjustments. 

 

Notes on Non-Road Input/Output Data Sets on the FTP Site

 

1) The NONROAD INPUT OUTPUT data are in the zip file labeled “input+output". There are 

folders for each year i.e., 

2002 HGB RFP NONROAD 

2008 HGB RFP NONROAD 

2011 HGB RFP NONROAD 

2014 HGB RFP NONROAD 

2017 HGB RFP NONROAD 

2018 HGB RFP NONROAD and 

2019 HGB RFP NONROAD 

Within each of the folders, there are 15 folders except for 2002 HGB RFP NONROAD which 

has 13 folders due to some of the controls not being applicable for 2002 base year. 

The folders are for the following scenarios: 

20XX Controlled 

20XX Controlled - no TexLED 

20XX Controlled - no RFG 

20XX Large SI Controlled 

20XX Large SI Uncontrolled 

20XX Small SI Phase I Controlled 

20XX Small SI Phase I Uncontrolled 

20XX Small SI Phase II Controlled 

20XX Small SI Phase II Uncontrolled 

20XX Tier I Controlled 

20XX Tier I Uncontrolled 

20XX Tier 2_3 Controlled 

20XX Tier2_3 Uncontrolled 

20XX Tier 4 Controlled 

20XX Tier 4 Uncontrolled 

2). Each of the above mentioned folders, contain a total of 201 separate folders, the /output/ 

folder contains the aggregate.out for that particular scenario as named in the first level folder. 

The "Aggregate.out" is a comma-separated values data set that loads very easily into Excel. 

 

3). The TexN model performs 25 separate runs of the NONROAD model per County coded 01-

25. 

 
Generally, the first 25 folders are for the county Brazoria and the second 25 folders are for 

Chambers and so on in the following order: 

 

- Brazoria 

- Chambers 

- Fort Bend 

- Galveston 

- Harris 

- Liberty 

- Montgomery 

- Waller 

 

For each county, the TexN model performs separate NONROAD runs for the following 24 diesel 

construction equipment (DCE) sub-sectors to account for different equipment population and 

activity profiles within each: 

 

1) Agricultural Activities 

2) Boring/Drilling Equipment 

3) Brick and Stone Operations 

4) City and County Road Construction 

5) Commercial Construction 

6) Concrete Operations 

7) County-Owned Construction Equipment 

8) Cranes 

9) Heavy-Highway Construction 

10) Landfill Operations 

11) Landscaping Activities 

12) Manufacturing Operations 

13) Municipal Owned Construction Equipment 

14) Transportation/Sales/Services 

15) Residential Construction 

16) Rough Terrain Forklifts 

17) Scrap/Recycling Operations 

18) Skid Steer Loaders 

19) Special Trades Contractors 

20) Trenchers 

21) Texas Department Of Transportation Equipment 

22) Utility Construction 

23) Mining and Quarry Operations 

24) Off-road Tractors, Misc. Equipment, and all Equipment < 25 hp 

 

Run #25 for each County is non-DCE equipment. 

 

Within each of these directories are /inputs/ and /outputs/ subdirectories. 

 

Each /inputs/ directory contains the following NONROAD input files: 
 

- input files with an ...opt extension 

- equipment population files with a ...pop extension 

- activity files with a ...dat extension 

 

 Each /outputs/ directory contains the following NONROAD output files: 

 

- aggregate emissions output with an ...out extension 

- output message file with an ...msg extension 

- exhaust emissions by model year with a ...bmx extension 

- evaporative emissions by model year with a ...bmv extension 

1.0 References 

1. User’s Guide for the Final NONROAD2005 Model, EPA420-R-05-013, December 2005, 

http://www.epa.gov/otaq/nonrdmdl.htm 

2. NONROAD2005 Emission Factor Model, available from 

http://www.epa.gov/otaq/nonrdmdl.htm, last validated 11-18-2006. 

3. Texas NONROAD (TexN) Model Version 1.0 User’s Guide, Eastern Research Group 

prepared for the Texas Commission on Environmental Quality, August 18, 2008. 

ftp://ftp.tceq.state.tx.us/pub/OEPAA/TAD/Modeling/Nonroad_EI/TexN/. 

4. 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. 

5. Eastern Research Group, Statewide Diesel Construction Equipment Inventory, prepared 

for the Texas Commission on Environmental Quality, August 31, 2005. 

6. 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. 

 

 
Attachment A 

TexN Overview – Data Sources and Calculation Procedures 

Source: Texas NONROAD (TexsN) Model Version 1.0 User’s Guide, Chapter 4 

Prepared by: Eastern Research Group, August 18, 2008 
1.0 TexN Overview – Data Sources and Calculation Procedures 

The TexN model consists of four basic elements: 

1) A Graphical User Interface (GUI) 

2) A MySQL database 

3) EPA’s NONROAD2005 model, and 

4) An enhanced Reporting Utility 

The TexN GUI was designed to incorporate more user-friendly features than the 

NONROAD model, accommodating the need for a finer level of emissions processing, and 

allowing for more detailed documentation of each run. The interface interacts with a MySQL5.0 

database, which enhances the user’s ability to manage data, group runs, and document scenarios. 

The database was populated with all of the equipment population and related activity data 

developed for the latest State Implementation Plans (SIPs) and other periodic inventories for 

Texas. The database automatically applies post-processing adjustments as appropriate, and 

creates output files that can be imported into the modified Reporting Utility. The Reporting 

Utility allows the user enhanced reporting options. 

This section provides a detailed overview of TexN data sources, functionality, and 

processing methodology, focusing on those features not included in the standard NONROAD 

modeling package. 

1.1 Accommodation of Construction Equipment Subcategories 

Diesel construction equipment (DCE) is usually the largest single emitter of nitrogen 

oxide (NOx) emissions in urban areas. DCE is also used in a wide variety of different tasks, with 

different activity and emissions profiles. Accordingly, the DCE emissions inventory has been 

highly disaggregated for Texas, characterizing construction equipment use for 24 sectors, 

including highway, commercial building, residential, utility, and other distinct construction 

activities or specialty equipment profiles. Each of the 24 DCE sectors is listed below. 

 Agricultural Activities 

 Boring and Drilling Equipment 

 Brick and Stone Operations 

 City and County Road Construction 

 Commercial Construction 

 Concrete Operations 

 County-Owned Construction Equipment 

 Cranes 

 Heavy Highway Construction 

 Landfill Operations 

 Landscaping Activities 

 Manufacturing Operations 

 Municipal-Owned Construction Equipment 
 Transportation/Sales/Services 

 Residential Construction 

 Rough Terrain Forklifts 

 Scrap/Recycling Operations 

 Skid Steer Loaders 

 Special Trades Construction 

 Trenchers 

 TxDOT Construction Equipment 

 Utility Construction 

 Mining and Quarry Operation 

 Off-Road Tractors, Miscellaneous Equipment, and all Equipment under 25 

horsepower 

The TexN modeling system was designed to calculate emissions for each of these sectors 

individually. 

Three factors were considered when defining the DCE categories for Texas. First, the 

categories are fundamentally different in their equipment use requirements (e.g., the tasks 

required for highway and residential projects are quite different). Second, available population 

and activity surrogates for each project category should be clearly associated with actual 

equipment use to the extent possible.1 Third, all categories, when considered together, cover the 

vast majority of DCE use in the State. 

In a previous study completed for the Houston Advanced Research Center titled Ozone 

Science and Air Modeling Research Project H43T163: Diesel Construction Equipment Activity 

and Emissions Estimates for the Dallas/Ft. Worth Region, experts from various construction 

sectors and technical representatives from the TCEQ were solicited for their opinions regarding 

the distinct types of construction project categories, the likely relative contribution of the 

different categories, and the availability of appropriate surrogate data for each category. Based 

on this input it was determined that there are two fundamentally different types of DCE 

categories – those that have significant earthwork and surfacing requirements, and those that do 

not. Earthwork project categories include: 

 Highway construction (state highway and bridge work, and city/county roads); 

 Utility installation (sewer, water, gas, power, and communication line installation 

and repair); 

 Single Family housing (residential developments/subdivisions); and, 

 Commercial structures. 

Exhaust emissions are directly related to the hp-hours of work output by an engine. The 

hp-hours are in turn associated with the amount of work performed for a given task. While the 

engine work performed during non-earthwork tasks may be difficult to quantify (e.g., pothole 

 

1

 While it is not possible to directly estimate hours of equipment use for all DCE categories, certain correlates of 

activity have been identified and collected for the different project categories, such as the linear feet of utility line 

installation per year. 
patching, or the amount of lifting performed by cranes), earthwork and surfacing tasks are 

reasonably straightforward to quantify and link to available physical quantity surrogates. 

Therefore, by developing equipment activity profiles directly in terms of physical quantities such 

as cubic yards of earth moved, it became possible to develop more precise correlates for 

equipment activity for the earthwork categories listed above. 

Non-earthwork project categories may also involve the use of DCE. Equipment use for 

these categories may involve specialized activities (e.g., landfill compacting). In other cases the 

work performed may involve earthmoving and/or surfacing, but cannot be determined from 

available surrogates (e.g. for mining activities, where production data is considered confidential 

business information). 

The following lists the non-earthwork DCE categories used in Texas: 

 Road or utility maintenance/repair activities performed by 

municipalities/counties/state agencies; 

 Landfill operations; 

 Surface mining – including stone/quarry operations, sand/aggregate pits; and, 

 Boring/drilling operations, including water wells, deep foundation work 

(piles/piers), and utility pole installation/repair. 

A database of DCE purchases in the Dallas- Fort Worth area was obtained to help 

identify other industry sectors that are also significant users of DCE. These include: 

 Special construction trades (e.g., performing post-earthwork activities such as 

concrete, electrical, heating and air conditioning installation, and other tasks); 

 Landscaping companies; 

 Agricultural entities; 

 Scrap handling and recycling facilities; 

 Concrete product manufacturers; 

 Brick and stone product manufacturers; 

 General manufacturing operations; and, 

 Transportation/Wholesale and Retail Sales/Services. 

Other DCE categories were also found to be inadequately characterized by the earthwork 

profiles. These equipment types are numerous and therefore potentially significant emitters, but 

were often difficult to link to available earthwork or surfacing surrogates. These included: 

 Cranes; 

 Rough terrain forklifts; 

 Skid steer loaders; and, 

 Trenchers. 

Population data for these equipment types were derived from an equipment sales 

database, with activity estimates provided by industry experts, for both earthwork and nonearthwork project categories. 
Table 1-1 summarizes the equipment types found within each of the 24 DCE sub sectors. 
Table 1-1. DCE Type by Sub sector 

Equipment Description SCC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2Pavers 2270002003 x x x x x x x x Tampers/Rammers 2270002006 Plate Compactors 2270002009 Rollers 2270002015 x x x x x x x x x x x Scrapers 2270002018 x x x x x x x x x x x Paving Equipment 2270002021 x x x x Surfacing Equipment 2270002024 x x x x x x x Signal Boards/Light Plants 2270002027 Trenchers 2270002030 x Bore/Drill Rigs 2270002033 x Excavators 2270002036 x x x x x x x x x x x x x x x Concrete/Industrial Saws 2270002039 Cement & Mortar Mixers 2270002042 Cranes 2270002045 x Graders 2270002048 x x x x x x x x x x x x x Off-highway Trucks 2270002051 x x x x x x x x x x Crushing/Proc. Equipment 2270002054 Rough Terrain Forklifts 2270002057 x Rubber Tire Loaders 2270002060 x x x x x x x x x x x x x x x Tractors/Loaders/Backhoes 2270002066 x x x x x x x x x x x x x x x Crawler Tractor/Dozers 2270002069 x x x x x x x x x x x x x x x Skid Steer Loaders 2270002072 x Off-Highway Tractors 2270002075 Dumpers/Tenders 2270002078 Other Construction Equipment 2270002081 
Sub sector Key: 

25) Agricultural Activities 26) Boring/Drilling Equipment 27) Brick and Stone Operations 

28) City and County Road Construction 29) Commercial Construction 30) Concrete Operations 31) County-Owned Construction Equipment 32) Cranes 

33) Heavy-Highway Construction 34) Landfill Operations 35) Landscaping Activities 36) Manufacturing Operations 37) Municipal Owned Construction Equipment 38) Transportation/Sales/Services 

39) Residential Construction 40) Rough Terrain Forklifts 41) Scrap/Recycling Operations 42) Skid Steer Loaders 43) Special Trades Contractors 

44) Trenchers 45) TxDOT Equipment 46) Utility Construction 47) Mining and Quarry Operations 48) Off-road Tractors, Misc. Equipment, and all Equipment < 25 hp 
1.2 Development of Texas-Specific Data Files 

TexN was designed to develop emission estimates (including ammonia) that are 

consistent with the latest emission inventory data available for all counties in Texas, for all SCCs 

included in the NONROAD model. The resulting emission factors are combined with hp-hr and 

fuel consumption estimates to calculate mass emission estimates at the county level, for different 

evaluation years and time periods. 

In order to develop the required Texas-specific data files, ERG developed, compiled, and 

organized the NONROAD model files needed to generate the most up-to-date county level nonroad mobile emissions inventories for the state. These data included area specific equipment 

population, activity, growth, and temporal allocation files as appropriate. Base years for these 

data included 1999, 2000, 2002, and 2004. 

ERG then developed and populated baseline and projected inventory lookup tables, 

reflecting variations in fuel properties, temperature, and selected control strategies, at the county 

and SCC level. These tables can be easily modified using the TexN GUI to perform sensitivity or 

other analyses. Look-up tables for county-specific diesel activity adjustment factors were also 

compiled for altitude, ground cover, and soil properties. Note these adjustment factors are not 

input directly into the model, but are applied as linear corrections during the post-processing of 

output files. (Details regarding these and other post-processing adjustments are provided in 

Section 1.3.) 

Using the files described above, TexN can produce emissions estimates of VOC, NOx, 

SO2, CO, PM10, and PM2.5 for any county and time period of interest. For ammonia estimates, 

selected ammonia emission factors are applied to the adjusted NONROAD output files for each 

county and SCC and for each base year. The NONROAD output files are then post-processed to 

aggregate by model year and technology groups and fuel types. Emission factors are then 

combined with the NONROAD output data, using the appropriate aggregated hp-hr and/or fuel 

consumption estimates to obtain mass emissions estimates for ammonia. 

The most recent available data was identified and collected in order to populate the 

following NONROAD model files, for each county and SCC combination, for the possible range 

of analysis years (1970 – 2050). File naming conventions are provided in parentheses. 

 Option file (*.opt - temperature and fuel specification data) 

 Equipment Population by hp bin (*.pop – equipment counts by hp bin) 

 Activity (activity.dat - hr/yr) 

 Temporal allocation (season.dat - weekday/weekend, and seasonal) 

In addition, extensive data were also collected to estimate equipment population growth 

and geographic allocation. However, due to the calculation methodology employed within TexN 

which utilizes unique population files for each county and analysis year, the corresponding 
growth (*.grw) and geographic allocation (*.alo) files used in NONROAD are effectively 

bypassed in the TexN application.2

Several NONROAD files have not been revised for SIP development or other purposes, 

largely due to the difficulty in collecting the required data. In these cases NONROAD default 

files were used for emissions estimation. These default files include: 

 Emission factors (*.emf) 

 Deterioration factors (*.det files) 

 Engine technology phase-in schedule (tech.dat) 

The following summarizes the sources of the data collected in order to generate the above 

NONROAD files. 

1.2.1 TexN Fuel Specification Data 

The NONROAD2005 model requires inputs for the following fields, in order to generate 

the primary input file (known as the OPT or Options file). 

 Gasoline Reid Vapor Pressure (RVP) 

 Gasoline oxygen weight percent 

 Gasoline sulfur weight percent 

 Diesel sulfur weight percent 

 Recreational marine diesel sulfur weight percent 

 CNG/LPG sulfur weight percent 

No Texas-specific data was identified for recreational marine diesel and CNG/LPG sulfur 

levels, so NONROAD default values were retained; 0.2637% and 0.003%, respectively. [2] 

General summer fuel specifications for Texas are summarized in Table 1-2 below, 

developed for the TCEQ for on-road modeling. 

Table 1-2. Federal and State Fuels Controls in Texas During Summer Season Period3

Program Start Year Control/Standard Geographic Coverage

Federal Controls 

on Gasoline 

Volatility1

1992 

Max RVP, 7.8 pounds per 

square inch (psi) 

Max RVP, 9.0 psi 

One-hour ozone nonattainment 

counties2

Remainder of state 

 

2

 Unlike NONROAD which utilizes one state-level population file, which is in turn allocated to the county level 

using the *.alo files, TexN contains unique population files for all 254 counties in the state. Therefore the additional 

allocation step employed by NONROAD is not required within TexN. In addition, separate population files have 

been developed for every possible Episode Year, utilizing county and SCC-specific growth factors, as discussed in 

Section 4.2.3. While NONROAD’s default growth file is retained within TexN to establish model year 

distributions, it is not used to forecast or back-cast actual equipment populations. 3

 Texas Transportation Institute, Development of On-Road, Mobile Source, 1999 Through 2035 Emissions Trends 

for all 254 Counties, prepared for the TCEQ, August 2004. 
Federal 

Reformulated 

Gasoline (RFG3

) 

1995 Performance standard 

reductions: VOC, NOx, Toxics 

One-hour ozone nonattainment 

counties for HGA, DFW 

El Paso LowRVP Gasoline4 1996 Max RVP, 7.0 psi El Paso County 

Regional LowRVP Gasoline5 2000 Max RVP, 7.8 psi 95 central and eastern Texas 

counties6

Tier 2 LowSulfur Gasoline 2005 

Refinery average 30 parts per 

million (ppm) gasoline sulfur 

content 

National 

Federal LowSulfur Highway 

Diesel7, 8

1993/2006 

500 ppm maximum sulfur 

content 

15 ppm maximum sulfur 

content 

National 

Texas LowEmission Diesel9 2005/2006 

500 ppm maximum sulfur 

15 ppm maximum sulfur 

Low aromatic HC and high 

cetane number to control NOx 

110 counties: 95 central and 

eastern Texas counties6

 and the 15 

HGA, BPA, and DFW one-hour 

ozone nonattainment counties 

1. 40 CFR § 80.27. Controls and Prohibitions on Gasoline Volatility. 

2. The 16 Texas one-hour ozone nonattainment areas and respective counties are: Beaumont/Port Arthur (BPA): Hardin, 

 Jefferson, Orange; Dallas/Fort Worth (DFW): Collin, Denton, Dallas, Tarrant; Houston/Galveston (HGA): Brazoria, 

 Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, Waller; and El Paso County. 

3. 40 CFR § 80.41 Standards and Requirements for Compliance (federal RFG). 

4. 30 TAC §§ 115.252. Control Requirements (for gasoline RVP). 

5. 30 TAC § 114.301. Control Requirements For Reid Vapor Pressure. 

6. Anderson, Angelina, Aransas, Atascosa, Austin, Bastrop, Bee, Bell, Bexar, Bosque, Bowie, Brazos, Burleson, Caldwell, 

 Calhoun, Camp, Cass, Cherokee, Colorado, Comal, Cooke, Coryell, De Witt, Delta, Ellis, Falls, Fannin, Fayette, Franklin, 

 Freestone, Goliad, Gonzales, Grayson, Gregg, Grimes, Guadalupe, Harrison, Hays, Henderson, Hill, Hood, Hopkins, Houston, 

 Hunt, Jackson, Jasper, Johnson, Karnes, Kaufman, Lamar, Lavaca, Lee, Leon, Limestone, Live Oak, Madison, Marion, 

 Matagorda, McLennan, Milam, Morris, Nacogdoches, Navarro, Newton, Nueces, Panola, Parker, Polk, Rains, Red River, 

 Refugio, Robertson, Rockwall, Rusk, Sabine, San Jacinto, San Patricio, San Augustine, Shelby, Smith, Somervell, Titus, 

 Travis, Trinity, Tyler, Upshur, Van Zandt, Victoria, Walker, Washington, Wharton, Williamson, Wilson, Wise, and Wood. 

7. 1993 sulfur limit source: “Regulatory Impact Analysis: Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel 

 Sulfur Control Requirements.” EPA, December 2000 (EPA420-R-00-026). 

8. 2006 sulfur limit source: heavy-duty 2007 rule. 

9. 30 TAC § 114.312. Low Emission Diesel (LED) Standards. 

More detailed, site-specific fuel specifications were also sought by season and year at the 

county level for inclusion within TexN. Historical gasoline and diesel fuel sampling data 

collected for the TCEQ was used to populate the needed specification table. Gasoline data were 

collected in different regions across the state for summertime fuel in 2001, 2003, 2004, and 2005 

[3, 4, 5, and 6]. Diesel samples were collected in 2003, 2004, and 2005 [3, 4, and 5]. In 

addition, one set of wintertime gasoline sampling was performed in 2006 [6]. In each of the 

studies fuel samples were collected at randomly selected retail stations in each of the 25 Texas 

Department of Transportation (TxDOT) regions of the state. In order to obtain county level 

specificity, each county in the state was assigned to one of the 25 TxDOT regions. This data 

provided gasoline RVP, oxygen weight percent, and gasoline as well as diesel sulfur weight 

percent for all locations. 

In consultation with the TCEQ, alternative data and assumptions were employed in order 

to gap fill gasoline and diesel fuel specifications for years in which there was no sampling 
performed. The following summarizes the decision rules developed to estimate gasoline and 

diesel fuel specifications for years without sampling data. 

5) 2002 summer gasoline parameters are set equal to measured 2001 values; 

6) Summer gasoline RVP values for 2006 and beyond are set equal to 6.8 for 

counties using reformulated gasoline (RFG) and El Paso, 7.8 for counties subject 

to the East Texas RVP limitation, and 8.7 for all other counties; 

7) 2000 summertime gasoline RVP levels are set equal to values from the TRW 

Petroleum Technologies Survey (formerly the National Institute for Petroleum 

and Energy Research), obtained from the TCEQ; 

8) 1999 and earlier gasoline RVP levels for non-RFG counties are set equal to 9.0, 

representing levels prior to the East Texas RVP limitation; 

9) Summertime gasoline sulfur levels for years without sampling data are set equal 

to the values in EPA’s on-road emission factor model MOBILE6.2, as shown in 

Table 1-3. 

Table 1-3. Gasoline Average Sulfur Levels (% weight) [15] 

Year RFG Conventional Gas 

1999 and earlier* 0.0300 0.0300 

2000* 0.0150 0.0300 

2001 0.0149 0.0299 

2002* 0.0129 0.0279 

2003 0.0120 0.0259 

2004 0.0120 0.0121 

2005 0.0090 0.0092 

2006* 0.0030 0.0033 

2007** 0.0030 0.0033 

2008+** 0.0030 0.0030 

* Years without sampling data 

** Data available but not yet incorporated into TexN 

10) Gasoline oxygenate levels for years without sampling data are set equal to 2.1% 

by weight for summertime RFG areas, 3.5% for wintertime RFG areas, and to 0% 

for other areas. 

11) If the sampled oxygenate content for gasoline is greater than 5.0%, then the value 

was set equal to 5.0%.4

12) For wintertime gasoline, sampled data for 2006 were used for RVP, sulfur and 

oxygenate content. For other years MOBILE6.2 defaults were used for sulfur 

content (see Table 1-2), and RVP data from TRW wintertime surveys, obtained 

from the TCEQ; 

13) For diesel fuel other than that used by recreational marine engines, the sampled 

data for 2003, 2004, and 2005 were used. (Note that diesel fuel specifications do 

not vary seasonally as do gasoline specifications, so parameter values are not 

differentiated by season.) 

 

4

 NONROAD2005 does not accept oxygenate inputs greater than 5.0% by weight [2]. 
14) Diesel sulfur levels prior to 2003 were set equal to measured 2003 values. Values 

for 2006 – 2009 were set equal to 2005 values, to account for the introduction of 

the federal non-road diesel fuel standards in 2007.5

 

15) Diesel sulfur levels beyond 2009 were set equal to the average value of 0.0015% 

by weight under the EPA Clean Air Nonroad Diesel – Tier 4 Final Rule. 

The final county level fuel specifications are summarized for each season and calendar 

year, for both gasoline and diesel fuel, in Attachment B. These data were used to generate 

NONROAD OPT files specific to each county, season, and analysis year. 

1.2.2 TexN Climate Data 

NONROAD utilizes daily high, low and average temperature data, primarily to calculate 

evaporative emissions from gasoline engines. These data are required as part of NONROAD’s 

OPT file. In addition, related data on relative humidity and atmospheric pressure are also used 

during TexN’s post-processing of NONROAD model outputs to adjust diesel NOx emissions for 

temperature and humidity effects. Ideally, these data should be specific to each county and 

episode day of interest. Although meteorological data were not available at this level for all 

counties, daily temperature, relative humidity, and atmospheric pressure information was 

available for 17 weather stations across the state, from the Texas A&M Energy Systems 

Laboratory [7]. The 17 weather stations with available data are presented in Table 1-4. 

Table 1-4. Weather Stations Providing Daily Climate Data [7] 

No. Weather 

Station City County Location 

1 ABI Abilene Taylor Abilene Regional Airport 

2 AMA Amarillo Potter Amarillo International Airport 

3 ATT Austin Travis Austin Camp Mabry 

4 BRO Brownsville Cameron Brownsville S. Padre Island International 

5 CRP Corpus Christi Nueces Corpus Christi International Airport 

6 ELP El Paso El Paso El Paso International Airport 

7 DFW Fort Worth Tarrant Dallas - Fort Worth International Airport 

8 IAH Houston Harris Houston Bush Intercontinental 

9 LBB Lubbock Lubbock Lubbock International Airport 

10 GGG Lufkin Angelina Longview E. Texas Regional Airport 

11 MAF Midland Midland Midland International Airport 

12 BPT Port Arthur Jefferson Port Arthur S.E. Texas Regional Airport 

13 SJT San Angelo Tom Green San Angelo Mathis Field 

14 SAT San Antonio Bexar San Antonio International Airport 

15 VCT Victoria Victoria Victoria Regional Airport 

16 ACT Waco McLennan Waco Regional Airport 

17 SPS Wichita Falls Wichita Wichita Falls Municipal Airport 

 

5

 The 2005 diesel sulfur values were all lower than the 500 ppm cap set by the federal non-road requirements for 

Large Refiners and Importers for the 2007 – 2009 period. For this reason 2005 sulfur levels were assumed to hold 

constant until the 2010 non-road requirements commence (15 ppm). 
Hourly temperature and relative humidity data were obtained for each of these weather 

stations for 1999, 2000, and 2002, as well as an averaged “typical meteorological year” 

developed by the Energy Systems Laboratory. This data has been provided to the TCEQ in 

electronic format. From the hourly data ERG extracted the daily minimum, maximum, and 

average temperatures, and average relative humidity. These values were then sorted into four 

seasonal groups: winter (December – February), spring (March – May), summer (June – 

August), and fall (September – November). For each of these seasonal groupings, and for each 

of the four years, averages were calculated for daily minimum, maximum, and average 

temperatures, as well as averages for relative humidity. These values are used as inputs by TexN 

for NONROAD modeling as well as post-processing adjustments for NOx, and are provided in 

Attachment B. 

1.2.3 Population, Activity, and Allocation Data 

The NONROAD model utilizes equipment population and activity data specific to each 

region of the country, allowing the user to characterize equipment emissions at the county level 

for past and future years, at different temporal scales (i.e., daily, seasonal, and annual emissions). 

The default values developed by the EPA are based on national level population and activity 

data. The model allocates equipment counts and activity to the county level using readily 

available surrogates, such as census population for lawn and garden equipment, and dollar value 

of construction projects for construction equipment. 

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 1-5 through 1-10 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 1-5. Sources of Equipment Population Data 

Equipment Types Region Data Sou

Diesel Construction Equipment > 25 hp Dallas-Fort Worth (DFW) 9-county 

nonattainment area 6

Eastern Research Group, OzonModeling Research Project H4Construction Equipment ActivEstimates for the Dallas/Ft. Wfor The Houston Advanced Re31, 2005 [8] 

Diesel Construction Equipment > 25 hp, except HGB7 cranes 

Statewide excluding 9-county DFW area Eastern Research Group, Nonr

Emissions Inventory DevelopmCommission on Environmenta2006 [14] 

Diesel Cranes Houston-Galveston-Brazoria (HGB) 

nonattainment area 

Eastern Research Group, NonrEmissions Inventory DevelopmGalveston-Brazoria Area, submGalveston Area Council, July 2

LPG Forklifts DFW 9-county area and HGB 

nonattainment areas 

Eastern Research Group, Data and Emissions Inventory PrepaCommercial and Industrial EquReport, prepared for the Texas Environmental Quality, Augus

Terminal Tractors and Transportation Refrigeration Units 

DFW 9-county nonattainment area Eastern Research Group, Data 

and Emissions Inventory PrepaCommercial and Industrial EquReport, prepared for the Texas Environmental Quality, Augus

Transportation Refrigeration Units HGB nonattainment area Eastern Research Group, Nonr

Emissions Inventory DevelopmGalveston-Brazoria Area, submGalveston Area Council, July 2

6 Includes Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, and Tarrant Counties. 7 Includes Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller Counties. 
Equipment Types Region Data Sou

Commercial Lawn and Garden Statewide Eastern Research Group, Deve

Lawn and Garden Emissions ETexas and Selected MetropolitTexas Commission on EnvironNovember 24, 2003 [12] 

Recreational Marine Statewide Eastern Research Group, Recre

Emissions Inventory, prepared Commission on Environmenta2002 [13] 

All remaining equipment –see below See below NONROAD defaults - User’s G

NONROAD2005 Model, EPADecember 2005 [1] 
Equipment population estimates were taken from NONROAD defaults for the following 

equipment categories. 

 Agricultural – all equipment/fuel types 

 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 1-6. 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 

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* 

Municipal-Owned Construction Equipment County level census projections 

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

Residential Construction Historical housing permit records and 

population growth rates from county-level 

census projections 

Rough Terrain Forklifts EDA data and dollar value outputs from TX 

REMI model* 

Scrap/Recycling Operations Dollar value outputs from TX REMI model* 

Skid Steer Loaders EDA data and dollar value outputs from TX 

REMI model* 

Special Trades Construction Dollar value outputs from TX REMI model* 

Trenchers 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 1-7. 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, SamplinInventory Preparation Plan for Selected CommerciEquipment: Phase II, Final Report, prepared for thEnvironmental Quality, August 31, 2005 [11] 

Terminal Tractors and Transportation Refrigeration Units 

9-county DFW nonattainment area Eastern Research Group, Data Collection, Samplin

Inventory Preparation Plan for Selected CommerciEquipment: Phase II, Final Report, prepared for thEnvironmental Quality, August 31, 2005 [11] 

Transportation Refrigeration Units 

HGB nonattainment area Eastern Research Group, Nonroad Mobile Source 

Development for the Houston-Galveston-Brazoria Houston-Galveston Area Council, July 28, 2006 [1

Commercial Lawn and Garden 

Statewide Eastern Research Group, Development of Commer

Emissions Estimates for the State of Texas and SelAreas, prepared for Texas Commission on Environ

November 24, 2003 [12] 

Recreational Marine Statewide Eastern Research Group, Recreational Marine Emi

prepared for the Texas Commission on Environme2002 [13] 

All remaining equipment – see below 

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

Model, EPA420-R-05-013, December 2005 [1] 

Geographic allocation surrogates were taken from NONROAD defaults for the following equipment cate

 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 Termi
Table 1-8. Sources of Equipment Activity Data 

Equipment Types Region Data 

Diesel Cranes HGB nonattainment area Eastern Research Grou

Source Emissions Invethe Houston-Galvestonsubmitted to the HoustoCouncil, July 28, 2006 

Diesel Construction Equipment > 25 hp 9-county DFW nonattainment area Eastern Research Grou

Air Modeling Research Diesel Construction EqEmissions Estimates foRegion, prepared for TResearch Center, Augu

Diesel Construction Equipment > 25 hp Remainder of State, except HGB cranes Eastern Research Grou

Emissions Inventory Dfor Texas Commission Quality, November 24, 

LPG Forklifts 9-county DFW and HGB nonattainment areas Eastern Research Grou

Sampling and EmissionPlan for Selected CommEquipment: Phase II, Ffor the Texas CommissQuality, August 31, 20

Terminal Tractors and Transportation Refrigeration Units 

9-county DFW nonattainment area Eastern Research Grou

Sampling and EmissionPlan for Selected CommEquipment: Phase II, Ffor the Texas CommissQuality, August 31, 20

Transportation Refrigeration Units HGB nonattainment area Eastern Research Grou

Source Emissions Invethe Houston-Galvestonsubmitted to the HoustoCouncil, July 28, 2006 
Equipment Types Region Data 

Commercial Lawn and Garden Statewide Eastern Research Grou

Commercial Lawn and Estimates for the State Metropolitan Areas, prCommission on EnviroNovember 24, 2003 [12

All remaining equipment – see equipment population list above 

See equipment population list above NONROAD defaults - 

Final NONROAD2005 013, December 2005 [1
Table 1-9. Activity Surrogates for Construction Equipment 

Sector 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 

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 1-10. Sources of Temporal Allocation Factors 

Equipment Types Region Data 

Diesel Construction Equipment > 25 hp 9-county DFW nonattainment area Eastern Research Grou

Air Modeling Research Diesel Construction EqEmissions Estimates foRegion, prepared for TResearch Center, Augu

Diesel Construction Equipment > 25 hp Statewide excluding 9-county DFW area Eastern Research Grou

Emissions Inventory Dfor Texas Commission Quality, November 24, 

LPG Forklifts 9-county DFW and HGB nonattainment areas Eastern Research Grou

Sampling and EmissionPlan for Selected CommEquipment: Phase II, Ffor the Texas CommissQuality, August 31, 20

All remaining equipment – see equipment population list above 

See equipment population list above NONROAD defaults - 

Final NONROAD2005 013, December 2005 [1
Once identified, data was obtained for inclusion in the TexN data files. In all but one 

instance, the required data was available in electronic format at ERG. For the remaining 

instance, ERG contacted TCEQ staff to obtain revised county level allocation factors for oil field 

equipment. See an explanation from TCEQ about the oil field equipment allocation methodology 

in Attachment C.8 Default statewide oil field equipment population estimates from NONROAD 

were subsequently allocated to the county level using these factors (see Attachment D). 

Development of Population Files by Analysis Year

Upon review of the above data sets, the commercial, utility, and heavy-highway sectors 

for diesel construction equipment were found to have highly variable population surrogate values 

from one year to the next. The variability was most pronounced for certain rural counties where 

the amount of project work can change dramatically from year to year. Accordingly, the 

surrogates used as growth indicators for these sectors (dollar value of construction for 

commercial, linear feet of installation for utility, and lane-miles of construction for heavyhighway), can also vary dramatically from one year to the next in these locations. 

In these instances equipment activity does not increase or decrease relatively smoothly 

from year to year, as assumed by the NONROAD model, reflecting regional economic patterns. 

In actuality, contractors increase the equipment population as needed to complete projects, 

subsequently removing them upon project completion. In counties containing large metropolitan 

areas, project-specific fluctuations are usually not noticeable, and changes in overall equipment 

population will likely follow economic factors for the most part, as assumed by NONROAD. 

However, in some rural counties project-specific fluctuations can be the dominant factor in 

determining overall activity levels. In these cases the yearly change in activity does not follow a 

smooth, relatively small annual increase or decrease, but more closely resembles a step function 

up or down. Such step functions create discontinuities in the NONROAD growth algorithm, and 

can result in anomalously large equipment population estimates for these construction sectors. 

For example, the data on lane-miles of construction clearly indicate that a relatively large 

highway project was performed in Blanco County in 2002-2003. If this data were used without 

adjustment in the NONROAD growth files, the model would assume a several-fold increase in 

the county’s highway equipment population beginning in 2002. More importantly, the model 

would assume that this equipment remained operating in the county in subsequent years, even as 

growth factors drop back down dramatically in 2004 and beyond. This is because the growth 

factors only impact the assumed incremental equipment purchases in the county for that year. In 

order to properly account for a drastic reduction in equipment population after completion of a 

large project in these counties, the NONROAD model’s scrap curve would have to be altered for 

each county and year, for each construction sector. 

Therefore, in order to correct for these “project-induced” discontinuities, separate 

population files were developed for every possible Analysis Year, for each county and 

equipment category. To this end growth factors (described in Section 1.2.4) were applied to the 

base year equipment population files, forecasting population totals for each SCC through 2050, 

 

8

 Email from Greg Lauderdale, TCEQ, November 13, 2007 
and back-casting estimates to 1970. In this way TexN bypasses NONROAD’s growth algorithm, 

effectively running base year equipment profiles for every scenario. (The default NONROAD 

growth file, nation.grw, is retained within TexN though, and is used to develop model year 

distributions for any given analysis year.) 

1.2.4 Forecasting and Back-Casting Equipment Populations 

A variety of growth indicators or surrogates may be used to forecast and back-cast nonroad equipment population and activity estimates, depending upon the equipment type. The 

Emissions Inventory Improvement Program (EIIP) recommends several options, as shown in 

Table 4-11. 
Table 1-11. EIIP Non-road Growth Indicator Recommendations9

The previous version of the TexN model projected emissions from 1999 through 2013, 

utilizing the most appropriate available surrogates for each DCE sub sector. This section 

documents the efforts ERG made to update the TexN model to accommodate emissions 

projections for the entire NONROAD model reporting period, from 1970-2050. Activity 

projections for TexN equipment categories with non-default values were developed from 

existing data, consistent with current projection methodologies to the extent possible. 

The TexN model contains 24 distinct “sectors” with distinct equipment population and 

activity profiles. 23 of these sectors involve diesel construction equipment (DCE) profiles 

developed specifically for TCEQ and the TexN model. A summary of the growth factor 

surrogates selected for each sector is presented in the table below. 

 

9

 GSP = Gross State Product; LTO = Landing/Take-Off cycle. 
Equipment Sector Growth Factor Surrogates 

Non-DCE Default NONROAD005 

Agricultural DCE Texas Agricultural Census for land in farms, forecast 

and back-cast using total county acreage as a 

constraint to projections 

Commercial Construction Economy.com output projections for non-residential 

construction sectors 

Heavy-Highway TxDOT Annual Expenditures (1998 - 2006), forecast 

and back-cast using Economy.Com projections for 

highway construction sector 

Residential 1970 - 1979 based on state-level growth rates from 

Comptroller's Office; 1980 - 2006 from housing 

permits by county from Texas AM Real Estate 

Center; 2007 - 2009 from statewide Comptroller Fall 

Economic Forecast (2007 publication); 2010 - 2040 

from Texas State Data Center Population Growth 

Estimates, 2041-2050 no growth assumed 

Skid Steer Loaders 1990 - 2004 from DFW area sales data; no growth 

assumed before 1990 (no significant market presence 

before this time); 2005+ from Economy.com 

projections for all construction sectors (SIC 1500s - 

1700s) 

Transportation/Sales/Services Economy.com projections for corresponding SIC 

groups 

Bore/Drill Rigs, Cranes, Rough Terrain Forklifts, 

Trenchers 

Economy.com projections for all construction sectors 

(SIC 1500s - 1700s) 

Special Trades Construction Economy.com projections for SIC 1700 series 

Manufacturing Economy.com projections for corresponding SIC 

series 

Brick and Stone Economy.com projections for corresponding SIC 

series 

Concrete Operations Economy.com projections for corresponding SIC 

series 

Landscaping TX REMI data and regression between 1999 and 

2013, forecast and back-cast based on census 

population growth rates 

Municipal and County Fleets, City and County Roads, 

Landfills 

Based on Texas State Data Center census population 

projections through 2040, linear interpolation to 2050 

Utility Contractors Economy.com projections for corresponding SIC 

codes 

TxDOT Equipment No growth assumed, all years, based on TxDOT 

purchasing cycles 

The following discusses how these growth factor surrogates were identified, selected, and 

processed for each of the 24 non-road equipment sectors. The resulting county-level growth 

factors have been provided to TCEQ in electronic form for the 2004 base year for each of the 

sectors developed for this task. 
NONROAD Default Categories

The NONROAD model contains default growth factors covering the entire period from 

1970 through 2050. These default factors were kept intact in the TexN model for two equipment 

sectors – “Non-DCE” equipment and “Other DCE” equipment. Non-DCE equipment refers to 

all equipment categories other than diesel construction. These include industrial, commercial, 

recreational, and other equipment categories. Alternative growth factors have not been 

developed for the TCEQ under previous studies. 

Other DCE equipment includes those equipment categories for which non-default profiles 

have not been developed under other studies. These equipment types are not used in earthwork 

activities, and were not included in previous sales data purchases. They include off-highway 

tractors, crushing and processing equipment, signal boards and light plants, concrete/industrial 

saws, cement and mortar mixers, plate compactors, dumpers/tenders, tampers/rammers, “other” 

construction equipment, as well as all DCE less than 25 hp. While the list is extensive, most of 

these categories are very low hp applications, and/or specialty pieces with low population 

numbers. As such, these equipment categories are responsible for a very small part of the DCE 

inventory (estimated to be 1% or less of NOx). Therefore default population, activity, and 

associated growth factors from NONROAD have been retained in the TexN model for these 

equipment. 

Agricultural DCE Applications

DCE such as crawler tractors and loaders are used to a limited extent in agricultural 

applications. In the previous version of TexN, growth for agricultural other industry groups was 

based on historical and projected dollar outputs at the state level, from the Texas REMI model, 

for the period 1999 through 2013. Alternative growth surrogates for agricultural activity at the 

county level were developed from the reported amount of land in farms from the 2002 Texas 

Agricultural Census [15]. Given the volatile nature of crop yields and prices, it was deemed that 

the amount of land in production was a better surrogate for equipment activity than agriculture 

sector economic output. However, land in agricultural production was only available every five 

years, from 1987 through 2002, as shown in Table 1 in Attachment E. 

Linear regressions were performed using the Excel’s Forecast function and above data to 

estimate land in farms at the county level for the entire modeling period. In the case of 

decreasing acreage, trend projections were capped at 0 acres. This was occasionally the case for 

highly urban counties. Increasing acreage trends were possible for highly rural counties, and 

projections were capped at the total available county size [17]. The forecast acreage values for 

each year were then divided by the 2004 value for each county to obtain county-level growth 

factors for a 2004 base year. 

Single Family Housing Construction

In the previous version of TexN, growth for single family housing construction activity 

was based on statewide housing permit totals from 1999 through 2004, and projected through 

2013 using linear regression. However, given the extreme downturn in the housing market over 

the last two years, alternative data sources were developed for this sector. 
County-level housing permit data was determined to be the best source of data for this 

sector, available from the Texas A&M Real Estate Center for the years 1980 through 2006 [16]. 

This data set contained permit information for all but 23 of the 254 counties in the state, all of 

which were rural counties. Accordingly, ERG assumed zero single family housing development 

for these counties for all years. Table 2 in Attachment E presents the county-level housing 

permit data for this time period. The 23 rural counties without permit data are listed below. 

Borden Edwards Jeff Davis McMullen Terrell 

Briscoe Glasscock Jim Hogg Mills Throckmorton 

Concho Hartley Kenedy Roberts Zapata 

Crocket Hudspeth King Sterling 

Duval Irion Loving Stonewall 

Data were missing from one or more years for 17 counties in the data set (again, all rural 

counties with very low housing construction activity). Gap filling for the missing years was 

performed by taking the county average for the years with actual data and is shown in green 

highlighting in Table 2 in Attachment E. 

Housing permits prior to 1980 were based on housing start totals for the southern region 

of the country obtained from the US Census Bureau, as shown in Table 3 in Attachment E [17]. 

County level permit totals from 1980 were therefore back-cast to earlier years using annual ratios 

from these data. 

Growth for the 2007 through 2009 period was based on state level forecasts for housing 

starts from the Texas Comptrollers Fall 2007 Forecast [18]. The housing start data for 2007, 

2008, and 2009 from this source were 129,729; 108,056; and 129,393 respectively.10

Housing construction growth for 2010 and beyond was assumed to stabilize and follow 

long-term population projections. County level census projections were obtained from Texas 

State Data Center for the years 2010 through 2040 [19].11 (The associated data file is quite large 

and is available from the TCEQ in electronic format.) 2009 housing permit estimates were 

projected forward using the annual county level population growth rates from this data set. 

Lacking other data sources, housing activity was assumed to equal 2040 estimates from 2041 

through 2050. 

Single family housing growth factors were developed for each county for the 2004 base 

year by dividing permit estimates for each year by the associated 2004 total. 

Heavy-Highway Activity

The previous version of TexN used a combination of county level highway construction 

and maintenance budgets from the Texas Comptroller’s Office and projected contract dollar 

values from McGraw Hill Construction to estimate the growth in highway construction activity. 

 

10 It was determined that Economy.com, a potential alternative source of surrogate data, showed essentially no 

downturn for this sector during the 2006 – 2008 time period. Therefore the Comptroller data was deemed more 

appropriate for this sector. 

11 Growth Scenario 0.5 was used based on Demographer recommendations from the web site. 
In order to expand the growth estimates for this sector to cover the target period, ERG first 

obtained an updated list of annual highway expenditures from the Texas Comptroller’s Office, 

for the period 1998 through 2006 [20]. Expenditures were normalized to 1998 dollars using the 

Consumer Price Index (CPI) obtained from the Bureau of Labor Statistics, and are presented 

below in Table 4 in Attachment E [21]. 

Attempts to extrapolate the Comptroller data using linear regression resulted in highly 

erratic, negative trends in key urban areas. Therefore highway construction activity prior to 1998 

and after 2006 was obtained by TCEQ staff using the Economy.com database [22]. Growth 

factors were derived at the county level for the 1978 – 2037 period using economic output (in 

real dollars) for NAICS code 2373, Highway Street and Bridge Construction.12 Activity levels 

outside this period were assumed constant. Growth factors for the entire modeling period were 

then calculated as with the other sectors for the 2004 base year. 

After development of these factors it was brought to ERG’s attention that highway 

construction and maintenance budgets have been significantly influenced by rapidly rising 

materials costs over the past few years [23]. Accordingly, using total budget dollars without 

adjusting for material cost increases will substantially overestimate highway activity growth in 

recent years. As such, ERG will provide an adjustment to the current growth factors for this 

sector to account for material cost inflation, using the TxDOT Highway Cost Index Report for 

May 2008, including the adjustments in the final iteration of the TexN model (by August 2008). 

Skid Steer Loaders

In the previous version of the TexN model, growth for skid steer loaders (and all other 

specialty equipment) was based on historical and projected dollar outputs at the state level, from 

the TX REMI model. However, a review of skid steer loader sales in the Dallas/Fort Worth area 

indicate that these equipment underwent a dramatic increase in popularity through the 1990s, 

with the increase in new sales leveling off only around 2002, as shown in Figure 1-1 below [24]. 

 

12 Data from the Economy.com database are considered confidential and are not presented here. All manipulation 

and processing of the Economy.com data were performed by authorized TCEQ personnel. 
Figure 1-1. Annual Skid Steer Loader Sales, 9-County DFW Area (1990-2004) 

0

100

200

300

400

500

600

700

800

900

1988 1990 1992 1994 1996 1998 2000 2002 2004 2006

 Source: Equipment Data Associates [24] 

ERG used the above sales data as a surrogate for skid steer loader activity for the state as 

a whole for the 1990 – 2004 time period. Given the unique surge in popularity of these 

equipment, this surrogate was deemed preferable to other options such as economic output in 

associated industries during this time. Since skid steer loaders were uncommon before this time, 

ERG assumed earlier activity was equal to 1990 levels. Activity after 2004 was assumed to 

follow gross output for all construction sectors. This data was obtained at the county level 

through 2037 by the TCEQ using the Economy.com database. County level output projections 

for each year through 2037 were summed across the NAICS industry codes shown in Table 1-12 

(representing common users of this equipment type): 

Table 1-12. Construction Sector NAICS Codes 

Sector NAICS 

Highway Construction 2373 

Residential Building Construction 2361 

Non-residential Building Construction 2362 

Special Trades Contractors 238B 

Utility System Construction 2371 

Skid steer loader activity beyond 2037 was assumed to equal 2037 levels. Growth factors 

relative to the 2004 base year were calculated based on these data as described for other sectors 

above. 

Other Specialty Equipment – Bore/Drill Rigs, Cranes, Rough Terrain Forklifts, and Trenchers

In the previous version of the TexN model, growth for other specialty equipment was 

based on historical and projected dollar outputs at the state level, from the TX REMI model. 

Unlike the skid steer loaders, the sales data available for the 9-county DFW area for these 
equipment types did not show a definitive trend. Therefore it was decided to use gross economic 

output for all construction sectors (as shown Table 5 in Attachment E), for all available years in 

the Economy.com database (1978 – 2037). TCEQ staff obtained and processed the associated 

data for these NAICS codes for all Texas counties during this period, which was then converted 

to growth factors with a 2004 base year. No growth was assumed prior to 1978 or after 2037. 

Municipal and County Fleets, City/County Road Construction, and Landfills

County level census population projections were used in the previous version of TexN to 

forecast and back-cast DCE activity for these sectors for the 1999 – 2013 period. ERG 

concluded census population continues to be the best available surrogate for these sectors. ERG 

used the county-level census population estimates from the Texas State Data Center to develop 

growth factors for the period of interest [19]. Historical population was provided for decade 

years from 1970 – 2000, as shown in Attachment E. Population estimates for non-decade years 

were estimated using linear interpolation. 

Census population estimates for 2000 through 2040 were based on the State Data 

Center’s 0.5 Scenario, and have been provided to the TCEQ in electronic format. Populations 

for 2041 through 2050 were estimated by ERG by interpolation from 2039 and 2040 values. 

Other Construction Applications

The previous version of TexN utilized project dollar values from different sources, such 

as the TX REMI model and McGraw-Hill Construction to forecast and back-cast equipment 

activity for a number of different DCE sectors, for the 1999 through 2013 period. For this effort 

gross economic output data from Economy.com was identified as the best, most consistent 

growth surrogate for these sectors, considering the broad range of projection years (1978 – 

2037), and the geographic specificity (county level estimates). Table 4-13 lists the DCE sectors 

and associated NAICS codes for which Economy.com data was used. 

Table 1-13. DCE Sectors Utilizing Economy.com Growth Surrogates 

Sector NAICS 

Commercial Building Construction 2362 

Utility System Construction 2371 

Special Trades Contractors 238X 

Manufacturing 31XX – 33XX* 

Cement and Concrete Product Manufacturing 3273 

Clay Product and Refractory Manufacturing 3271 

Transportation/Sales/Services 42XX (wholesale), 44XX – 45XX (retail), 48 

XX – 49XX (transportation and warehousing), 

81XX (other services) 

* Less cement, concrete, and clay product manufacturing 

TCEQ staff obtained and processed the county level gross output data from 

Economy.com for the above NAICS codes, and provided the associated growth factors for the 

2004 base year. 
Landscaping Services / Scrap and Recycling Facilities

The previous TexN model utilized gross output for these sectors obtained from the TX 

REMI model for the 1999 through 2013 period. Landscaping services correspond to NAICS 

code 56173, and scrap-related activities to NAICS code 562920. Unlike the Other Construction 

Applications listed above, it was not possible to extend the growth surrogates for these sectors 

beyond this time period using the Economy.com data, since queries of the database could only be 

performed for 4-digit NAICS codes (or higher levels of aggregation). For this reason ERG used 

the TX REMI model outputs for the 1999 through 2013 period, extended by linear regression 

using Excel’s Forecast function for the scrap/recycling sector. Linear regression resulted in 

unreasonable historical activity projections for the landscaping sector however (e.g., negative 

activity for certain counties in the 1970s and 1980s). Therefore census population was used for 

the remaining years for this sector, to develop growth factors for these sectors. 

Tables 6 and 7 in Attachment E provide the TX REMI model outputs (in 1996 dollars) 

for the landscaping and scrap/recycling sectors, respectively. 

TxDOT Equipment

TxDOT maintains a constant inventory of their non-road equipment fleet. As such, no 

growth (i.e., a constant equipment population) is assumed across all years for this DCE sector. 

Once growth factors were obtained for all the equipment sectors, ERG applied these 

factors to the base year equipment populations for each sector/county combination in the TexN 

model. This calculation provided forecast and back-cast equipment population totals for every 

calendar year, from 1970 through 2050. The TexN model was then modified to store the 

population data for every possible analysis year, bypassing the need to modify growth factors in 

the future. The revised model will lookup the correct population based on the analysis year 

directly input by the user, thereby avoiding recurring problems with SCCs that experience rapid 

fluctuations in their population levels.13 

1.3 Data Processing 

Given the large number of model years, hp bins, and SCCs included in the NONROAD 

output files, emissions estimation necessarily includes a large amount of data processing and 

post-processing. Therefore a set of data management tools have been developed including the 

GUI, a database for data table storage and retrieval, and a modified Access Reporting Utility. 

The following clearly documents the steps used to aggregate and combine the emission and 

activity data for each equipment category and fuel type within TexN. 

1.3.1 TexN Data Management Tools and Processes 

The TexN GUI was designed to incorporate more user-friendly features than the 

NONROAD model, accommodating the need for a finer level of emissions processing, and 

 

13 The NONROAD model’s scrappage algorithm is not capable of accurately modeling equipment populations with 

highly negative growth from year to year. This situation is common with certain types of transient activities, such as 

heavy-highway projects and boring/drilling activities. 
allowing for more detailed documentation of each run. The GUI interacts with a MySQL 

database, which enhances the user’s ability to manage data, group runs, and document scenarios. 

The database was populated with all of the population and related activity data described above. 

The database is also utilized to automatically apply post-processing adjustments as appropriate, 

and create output files that can be imported into the modified Reporting Utility. A brief 

overview of the data management and emissions calculation process is discussed below. 

The TexN GUI allows the user to group a large number of NONROAD input files and 

save them to the MySQL database as a single “scenario”. For example, the modified GUI builds 

a NONROAD OPT file for each county the user selects. Should the user choose to estimate 

emissions for DCE, an OPT file is built for each county-DCE sector combination. By 

performing a separate NONROAD model run for each county and DCE sector combination it is 

possible to apply activity and post-processing adjustments at the county and DCE sector level to 

emissions estimates. However, this approach has substantial implications for the number of OPT 

files required to estimate emissions, as is discussed in the next section. The GUI, however, 

greatly facilitates building the numerous OPT files required for regional and statewide modeling 

tasks. 

The GUI interacts with the MySQL database to dynamically generate an OPT file for 

each run required by a scenario. For example, by specifying a particular county, analysis year, 

and season, an OPT file can be constructed containing county specific fuel and temperature data 

(which are stored in the database). Similarly, data are pulled from the database to generate 

county and sector specific population and activity files as well. In this way the GUI populates 

the OPT and supporting files with the region specific data necessary for the NONROAD model 

to execute. Once the OPT and related files are generated, the interface executes the NONROAD 

model for each OPT file contained within the scenario. Once the NONROAD model is 

launched, the interface tracks the progress of the current run and launches the next run 

sequentially. The GUI also checks for error messages generated by the NONROAD model. If a 

“warning” is reported, it is recorded in the message file, but does not affect processing. 

However, if an “error” is reported, the entire scenario is stopped and the user is presented with 

information on the error that occurred. All output files created by the NONROAD model are 

retained regardless of any warning or error messages generated. 

Executing NONROAD to account for county and SCC specific data and post-processing 

adjustments can require a multitude of runs. Each county requires its own OPT file. In addition, 

DCE requires emission calculations at a sector level. There are 24 DCE sectors, each 

corresponding to a unique equipment activity profile. (As noted above, DCE sectors include 

commercial building construction, utility project work, and residential construction, among 

others.) Each county-DCE sector combination also requires its own OPT file. Furthermore, in 

order to appropriately apply temperature, humidity, and fuel property adjustments, seasonal 

emissions must be calculated separately and summed together to estimate annual emissions. A 

summary of the number of the OPT files necessary for each model run within a scenario is 

presented in Table 1-14. 
Table 1-14. Required Number of NONROAD OPT Files and Model Runs for Selected 

Modeling Scenarios 

User Selections 

Period Region Equipment 

Number 

of 

Runs* 

How the Number of Runs are Calculated 

OSD^ 

or 

One 

Season 

One 

County 

Non-Diesel 

Construction 

Equipment 

(Non-DCE) 

1 One for the selected county 

[1 segment * 1 county] 

Annual One 

County Non-DCE 4 One for each County and Season [1 segment * 1 county * 4 seasons] 

OSD^ 

or 

One 

Season 

Three 

Counties Non-DCE 3 One for each selected county [1 segment * 3 counties] 

OSD^ 

or 

One 

Season 

One 

County DCE 24

One for each of the 24 DCE sectors for the selected 

county 

[24 segments * 1 county] 

Annual One 

County DCE 96

One for each of the 4 seasons and each of the 24 

DCE sectors for the selected county 

[24 segments * 1 county * 4 seasons] 

OSD^ 

or 

One 

Season 

Three 

Counties DCE 72

One for each of the 24 DCE sectors for each of the 

selected counties 

[24 segments * 3 counties] 

Annual Statewide All 25,400

One for each of the DCE sectors and one for NonDCE equipment for each county for each season 

[(24 + 1) SCC segments * 254 counties * 4 

seasons] 

*Each run requires one option file and each of the associated input files (e.g., population, activity, etc.) 

^Ozone season day 

To give an idea of run times, using a Dell Optiplex GX280 Intel® Computer with a 

Pentium® 4 CPU 3.00GHz with 512 MB of RAM, each run takes approximately 8 – 10 minutes 

to complete. 

Once all of the runs for a scenario have executed successfully, the interface calls the postprocessing driver. The post-processing driver imports all of the NONROAD output files into the 

MySQL database. The database then post-processes of all of the data, applying adjustment 

factors to the emissions estimates in the output file to generate the final criteria pollutant and 

ammonia emissions values. Post-processing applies county specific altitude, ground cover, and 

soil adjustments to emissions estimates for the appropriate SCCs. County and year specific 

temperature and humidity adjustments are also applied, along with adjustments to account for 

TxLED impacts in the appropriate counties, for diesel-fueled equipment. Once the postprocessing adjustments are made, the database performs county-level aggregation of data by 

SCC and hp bin, summing population, activity, fuel-consumption, and emissions fields. Once 

completed, the database creates a single output file. 
This output file is then ready to be imported into the modified Reporting Utility. The 

TexN Reporting Utility has all of the basic functionality of the NONROAD Reporting Utility, 

but has been modified to accommodate ammonia emissions estimates. In addition, the TexN 

Reporting Utility allows the user to generate more reports than the NONROAD version, 

including emission totals by county and SCC, as well as totals by hp bin and SCC. 

1.3.2 Post-Processing Adjustments 

Once all of the data edits have been completed and saved by the user, TexN will create 

the necessary Option and supporting data files for NONROAD, and batch the runs needed to 

model the prescribed scenario. Once the runs for a scenario have executed successfully, the GUI 

automatically calls the post-processing driver. The post-processing driver imports all of the 

NONROAD output files, generated at the by model year level of detail, into the MySQL 

database. The database then post-processes all of the data, applying 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; and, 

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

Once post-processing adjustments are made to the NONROAD output files, the database 

performs county-level aggregation of the data by SCC and hp range, summing population, 

activity, fuel-consumption, and emissions fields. Once completed, the database creates a single 

output file. The output file contained in the database is then ready to be imported into the 

Reporting Utility. The TexN Reporting Utility has all of the basic functionality of the original 

NONROAD utility, but has been modified to accommodate ammonia emissions estimates. In 

addition, the TexN Reporting Utility allows the user to generate more reports than the 

NONROAD utility, including emission totals by county and SCC, as well as emission totals by 

hp and SCC. 

Altitude Adjustments

Altitude adjustments are applied to all pollutants, as well as equipment activity estimates 

(in hours per year), for all diesel powered equipment. In general, diesel engines are assumed to 

suffer a 1% penalty in power output, and therefore productivity, per 1,000 feet in altitude. In 

other words, an activity requiring 100 hours at sea level would require 101 hours at 1,000 in 

elevation. Representative altitudes for each county were determined from GIS data containing 

altitude for each county seat [8]. For example, Anderson County has an altitude of 470 feet, and 

a corresponding adjustment factor of 0.47%, so all diesel equipment pollutant estimates for this 

county are multiplied by 1.0047 to reflect the altitude-induced increase in diesel equipment 

activity. 
Given that the vast majority of the state is at relatively low altitude, TexN emission 

estimates are generally not sensitive to county altitude. 

Soil and Ground Cover Adjustments

Substantial variations in construction equipment productivity, and therefore activity, can 

arise depending on soil and ground cover conditions in a given county. In a previous study, 

industry experts were consulted to develop activity adjustment factors to be applied to the DCE 

activity profiles, accounting for county specific conditions [8]. Adjustments for standard soil 

and ground cover conditions were based on field experience and engineering judgment, and are 

summarized in Table 4-15. (Note these factors are only applied to DCE earthwork categories 

within TexN.) 
Table 1-15. Site Condition Activity Adjustments 

Ground Cover 

Adjustment Factor

(1.0=base conditions)

Wooded lot (dense/moderate) 1.5

Small trees, shrubs, and weed 1.3

Weed and Grass 1.0

Other Varies

Soil Type Adjustment Factor

Good common earth (loam) 1.0

Sand/Gravel 1.0

Easy digging (moist silt/clay) 1.0

Hard digging (dry clay) 1.1

Fragmented Rock 1.2

Intact Rock 1.7

Other Varies

The above factors represent the increase in the time required to complete a certain task, 

relative to base case conditions, (equivalent to an increase in work time, since engine load factors 

are assumed constant under all conditions). Ground cover adjustments are applicable to the 

Commercial and Residential DCE profiles, but only for equipment involved in land clearing 

activities (assumed to be crawler dozers). U.S. Geological Survey (USGS) data were used for 

determining ground cover characteristics [8, 26]. The ground cover categories provided in the 

USGS data for Texas were mapped to one of the four standard classifications shown in Table 4-

15. 

Average values for ground cover characteristics were developed for each county, 

weighted by relative area. Areas designated as having water or impermeable/existing structures 

were excluded, and the relative areal extent of the remaining categories was renormalized. 

Weighted average adjustment factors specific to each county are then applied to the base case 

DCE profiles within TexN to account for area-specific conditions. 

Soil type adjustments for productivity are applicable to equipment involved in earthwork 

operations as well as boring/drilling tasks. For example, excavation work in areas with 

fragmented rock will require an additional 20% increase in hp-hours compared to “easy digging” 

soil conditions. In order to characterize soil conditions across the State, the Soil Survey 

Geographic Database (SSURGO) was obtained from the U.S. Natural Resource Conservation 

Service [25]. Three soil layers were extracted from this database, including the surface layer, the 

layer found at 90 cm, and the layer found at 150 cm, near or at the maximum depth of the data 

set, to provide a cross-section for analysis. The classifications of these layers were then 

correlated with the standard soil classifications shown in Table 4-15. 

Both the spatial extent and depth of each layer were used to develop weights for the DCE 

adjustments. The productivity adjustment for each layer was weighted by the relative thickness 

of the layers, and summed to provide a weighted average adjustment for the soil as a whole. The 

inverse of the resulting county-level soil adjustment factors is shown in Figure 4-2. The 

resulting countywide activity adjustment factors are applied to the Commercial, Residential and 

Utility sector DCE profiles, as well as the Trencher and Boring/Drilling profiles. 
Figure 1-2. County Level Weighted Average Soil Adjustment Factors 
The DCE equipment profiles were evaluated to establish what portion of equipment 

activity should be subject to the soil productivity adjustments. The fraction of time each 

equipment type spends performing earthwork is summarized below in Table 4-16. 

Table 1-16. Earthwork Weighting Factors for Soil Adjustments 

DCE Sector Equipment Type 

Earthwork Fraction 

(% of time, weighted by hp-hrs) 

All Trencher 100% 

All Boring/Drilling 100% 

Excavator 100% 

Backhoe 100% 

Grader 49% Commercial 

Crawler Dozer 40% 

Utility Excavator 100% 

Excavator 100% Residential Crawler Dozer 41% 

Soil adjustments specific to each county and DCE sector were calculated as follows: 

SCCs: 2270002030, 2270002033, 2270002036, 2270002048, 2270002066, 

2270002069 

DCE Sub sectors: Commercial, Utility, Boring and Drilling, Residential, Trenchers 

Application: Varies by sector and SCC – 

 Commercial (2270002036, 2270002066) = Pollutant / Adj. Factor 

Commercial (2270002048) = Pollutant * (0.51 + 0.49/ Adj. Factor) 

Commercial (2270002069) = Pollutant * (0.60 + 0.40/ Adj. Factor) 

 Residential (2270002036) = Pollutant / Adj. Factor 

Residential (2270002069) = Pollutant * (0.59 + 0.41 / Adj. Factor) 

 Utility (2270002036) = Pollutant / Adj. Factor 

 Boring and Drilling (2270002033) = Pollutant / Adj. Factor 

 Trenchers (2270002030) = Pollutant / Adj. Factor 

The weighting factors applied to the different SCCs above reflect the percent of hp-hrs a 

specific equipment type is involved in earthwork activities, as shown in Table 4-16 above. 

As seen in Figure 4-2, although the largest soil adjustments occur in West Texas near the 

Edwards Plateau, substantial adjustments (> 10%) are applied in all non-attainment regions 

across the state. However, as shown above these adjustments are only applied to a small number 

of SCCs in a few DCE sectors. Therefore, while the activity adjustments can be substantial for 

any particular county/SCC/DCE sector combination, the overall impact on emissions is relatively 

small. 

Ground cover adjustments were only applied to crawler tractors operating in the 

Commercial and Residential DCE sectors. In this case each pollutant is multiplied by (0.955 + 

0.045 x county specific ground cover adjustment). While the ground cover adjustments can be 

substantial for crawler tractors operating in heavily wooded areas such as East Texas, the 
adjustment is only this one equipment type operating within two of the DCE sectors. 

Accordingly, overall emissions are not particularly sensitive to these cover adjustments. 

Temperature and Humidity NOx Adjustments for Diesel Engines

TCEQ identified additional temperature and humidity correction factors for adjustment of 

NOx emissions from diesel engines [14]. The NOx adjustment equations developed in this study 

are a function of temperature, humidity, and atmospheric pressure. Using the climate data 

discussed in Section 4.2.2, temperature and humidity adjustment factors were calculated for 

diesel equipment operating in each county in the State, for each season and meteorological year. 

The application of these adjustment factors is summarized below. 

16) Adjustments are applied to all diesel engines (SCC = 227XXXXXXX) 

17) Adjustments are only applied to NOx emissions 

18) Adjustments also depend upon technology type distributions, as determined by 

Analysis Year 

19) Inputs to the adjustment equations include the following: 

 County Average Temperature (T – season and meteorological yearspecific, from Climate Data – in degrees Fahrenheit) 

 County Relative Humidity (RH – season and meteorological year-specific, 

from Climate Data – in percent) 

 County Atmospheric Pressure (P – in mill bars, or mb)14

20) Adjustments utilize absolute humidity (H), which is calculated as follows: 

H = [RH x 38.017 x ea] / [P – 6.112 x ea] 

where a = [9.8245 x (T – 32)] / [0.556 x (T – 32) + 243.5] 

21) There are two adjustment equations – one equation is used for naturally-aspirated 

engines, another for turbocharged engines. 

Naturally-Aspirated Engine Adjustment: 

1 + 0.001368 x (0.556 x (T - 32) – 29.444) – 0.01512 x (H – 10.71) 

Turbo-charged Engine Adjustment: 

1 + 0.00446 x (0.556 x (T – 32) - 25) – 0.018708 x (H – 10.71) 

22) The fraction of naturally-aspirated and turbocharged engines depends upon engine 

model year and hp bin. Relative fractions were estimated based on the number of 

engine entries in EPA’s certification database. Data were available electronically 

 

14 Average station pressure was found to vary by insignificant amounts over time. For the purposes of this 

calculation, annual average pressure for each station was calculated for the 2000 meteorological year. 
from EPA for model years 1998 through 2006.15 The weighting factors applied to 

the two different adjustment equations correspond to the relative fraction of 

naturally-aspirated to turbocharged engines for a given model year, summarized 

in Table 4-17 below: 

Table 1-17. Ratio of Turbo to Naturally-Aspirated Models for Diesel Engines by hp and 

Model Year 

 Model Year 

hp Range 1999 (and older) 2000 2001 2002 2003 2004 2005+

< 25 0% 0% 0% 0% 0% 0% 0%

25 – 50 10% 14% 15% 17% 15% 14% 18%

50 - 100 28% 28% 28% 28% 47% 55% 55%

100 – 175 63% 84% 84% 84% 98% 98% 98%

175+ 100% 100% 100% 100% 100% 100% 100%

23) Given this information TexN first calculates the naturally-aspirated and 

turbocharged factors for each county and season, then weights and sums the 

factors using the relative fractions given above for each hp bin and model year, 

and applies the final weighted factors to the NOx emissions value by the 

appropriate hp bin and model year in the by model year exhaust file (BMX file).16

The above adjustments can result in substantial changes to diesel NOx emission 

estimates. For example, for a 2005 Analysis Year, from a baseline of 80 degrees F and 50% 

relative humidity, a 10% increase in humidity results in a 4% reduction in NOx emissions. 

However, although increasing temperature and decreasing relative humidity will tend to increase 

NOx emissions from diesel engines, this effect is offset by NONROAD’s downward adjustment 

of NOx emissions from gasoline 4-stroke engines. 

Adjustments for Emission Controls

Various control programs have been implemented to reduce emissions from non-road 

engines. Federal controls, such as the introduction of new emission standards, are accounted for 

by the NONROAD model. While evaporative refueling (Stage II) VOC emission controls can be 

modeled by NONROAD, these emissions are categorized as area sources by the TCEQ. For this 

reason any Stage II emission control benefits associated with non-road engine refueling are 

excluded from TexN to avoid double counting. 

 

15 Data from EPA’s certification records are not sales-weighted, and therefore may not represent the actual in-use 

distribution of naturally-aspirated and turbocharged engines. However, sales data is considered proprietary by 

manufacturers, and was not available for this analysis. 

16 The fraction of naturally-aspirated and turbocharged engines depends upon engine model year and hp bin, so 

adjustments must be applied to NONROAD’s by model year exhaust (BMX) output file. This file provides emission 

estimates for each SCC and hp bin combination, as well as by model year and engine technology type. Since there 

are no NOx emissions in the by model year evaporative emissions (BMV) file, no adjustments applied there. 
The introduction of TxLED in certain Texas counties is not accounted for by the 

NONROAD model, and is addressed during TexN post-processing. Specifically, NOx emissions 

from diesel engines were reduced by 6.2% beginning in February of the 2006 calendar year, for 

the 110 counties affected by the TxLED program. TxLED was implemented January 31, 2006. 

TexN has refined the dates for application of TxLED credits to emissions estimates beginning in 

February 2006 and beyond, as described below. 

24) The TxLED “flag” is now activated for 2006 and later analsysis years, for the 110 

counties. 

25) Annual modeling scenarios for 2007 and beyond receive the full credit of 6.2% 

NOx reduction applied to all diesel emissions in TxLED counties. 

26) If an annual modeling scenario is selected for the 2006 calendar year, the full 

6.2% diesel NOx reduction is applied to the spring, summer, and fall season 

calculations. 

27) Winter season diesel NOx emissions for 2006 are reduced by 4.1%, assuming 

adjustments for 2 of the 3 winter months (Jan, Feb, and Dec of 2006). 

28) Ozone-season daily scenarios for the 2006 calendar year receive the full 6.2% 

diesel NOx reduction adjustment. 

A detailed example showing the steps involved in the TexN emission calculation process 

is provided in Attachment F. 

Other rules and regulations that effect non-road engines include multiple Memoranda of 

Understanding and other agreements with specific fleets in different nonattainment areas, such as 

airport ground support equipment (GSE) and Port activities. Texas Emission Reduction Program 

(TERP) projects also fall under this category. However, these fleet-level control initiatives have 

to be modeled using fleet-specific equipment and activity profiles. Similarly, emissions from 

unusual construction projects that have been profiled on an individual basis previously (such as 

the construction of three large liquid natural gas depots on the Gulf Coast), must also be modeled 

on a fleet-specific basis to account for their inventory impacts. As such the effects of these 

programs and initiatives are not reflected in TexN outputs. 

1.3.3 Calculation of Ammonia Emissions 

The NONROAD model does not provide estimates for ammonia emissions. In order to 

provide ammonia estimates using TexN, a list of available ammonia emission factors for the 

different non-road mobile engine fuel types, including diesel, gasoline, and gaseous fuels 

(propane and natural gas), were identified and documented [14]. A literature review was 

performed, and contacts were made with air quality researchers from EPA’s Office of 

Transportation and Air Quality (OTAQ), the California Air Resources Board (ARB) and others 

to identify available data sources. A detailed web search was also conducted to identify 

additional sources of emissions test data and analysis. Available data were evaluated for 

applicability to non-road engine applications, and emission factors were processed and adjusted 

to account for the impact of future engine technology impacts to the extent possible. Emission 

factors in TexN are expressed in terms of grams per hp-hour of engine use, and/or grams per 

gallon of fuel consumption. 
Only a limited amount of information was identified regarding ammonia emissions from 

non-road engines. An attempt was made to identify the most representative data, considering 

fuel and engine types, as well as the influence of future emission standards on control 

technologies. The ammonia emission factors identified can be combined with activity data 

outputs from NONROAD to estimate mass emissions for each SCC and county in Texas. 

Ammonia is estimated within TexN in tons for all SCCs. 

There are four ammonia emission factors in TexN: one for diesel engines, one for spark 

ignition engines (gasoline and gaseous fuel) without three-way catalysts (TWCs), one for 

gasoline engines with TWCs, and one for natural gas/LPG engines with TWCs. The emission 

factors and corresponding technology types are presented in Table 4-18 below. 

Table 1-18. Ammonia Emission Factors Used in TexN 

Engine Type Emission Factor Units 

Diesel 0.00162 g/hp-hr 

Gasoline w/ TWC 0.0690 g/hp-hr 

CNG/LPG w/ TWC 0.1030 g/hp-hr 

Spark Ignition w/out TWC 0.15 g/gal 

Note that all emission factors are in g/hp-hr except for spark ignition engines without 

TWCs, which is in g/gal. Emissions for SCC/technology type combinations with emission 

factors in g/hp-hr are calculated in TexN by multiplying the factor by the average hp value, the 

load factor, and the activity value in the BMX file. Results are then converted from grams to 

tons for output. For those SCC/Technology Type combinations expressed in g/gal, emissions are 

calculated by multiplying the emission factor by the fuel consumption value in the BMX file, 

then multiplying by 1.1023e-6 to convert from grams to tons. 

2.0 References 

1. User’s Guide for the Final NONROAD2005 Model, EPA420-R-05-013, December 

2005, http://www.epa.gov/otaq/nonrdmdl.htm 

2. NONROAD2005 Emission Factor Model, available from 

http://www.epa.gov/otaq/nonrdmdl.htm, last validated 11-18-2006. 

3. Eastern Research Group, Sampling and Laboratory Analysis of Retail Fuel for Selected 

Texas Cities, prepared for Peter Ogbeide, Texas Commission on Environmental Quality, 

August 29, 2003. 

4. Eastern Research Group, Sampling and Laboratory Analysis of Retail Fuel for Selected 

Texas Cities – Summer 2004, prepared for Peter Ogbeide, Texas Commission on 

Environmental Quality, August 31, 2004. 

5. Eastern Research Group, Sampling and Laboratory Analysis of Retail Fuel for Selected 

Texas Cities – Summer 2005, prepared for Peter Ogbeide, Texas Commission on 

Environmental Quality, August 31, 2005. 
6. Eastern Research Group, Sampling and Laboratory Analysis of Retail Fuel for Selected 

Texas Cities – Winter 2006, prepared for Peter Ogbeide, Texas Commission on 

Environmental Quality, April 30, 2006. 

7. Texas A&M University Energy Systems Laboratory, 

http://energysystems.tamu.edu/sb5/data.html, last validated 11-22-06. 

8. 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. 

9. Eastern Research Group, Statewide Diesel Construction Equipment Inventory, prepared 

for the Texas Commission on Environmental Quality, August 31, 2005. 

10. 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. 

11. 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. 

12. 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. 

13. Eastern Research Group, Recreational Marine Emissions Inventory, prepared for the 

Texas Commission on Environmental Quality, August 28, 2002. 

14. Eastern Research Group, Nonroad Ammonia Emissions Inventory Development, 

prepared for Texas Commission on Environmental Quality, November 24, 2006 

15. EPA Office of Transportation and Air Quality, User’s Guide to MOBILE6.1 and 6.2, 

http://www.epa.gov/otaq/models/mobile6/420r03010.pdf, last validated 11-22-06. 

16. Texas A&M Real Estate Center, Texas County Building Permit Activity Data, from 

http://recenter.tamu.edu/data/bpc/. 

17. U.S. Census Bureau, New Privately Owned Housing Units Started: Annual Data, 

http://www.census.gov/const/startsan.pdf. 

18. Texas Comptroller of Public Accounts, Fall 2007 Economic Forecast, Texas Economic 

Detail, from 

http://www.window.state.tx.us/ecodata/fcst07fall/fall07economiccalendar.html. 

19. Texas State Data Center, 0.5 Growth Scenario, 

http://txsdc.utsa.edu/tpepp/2004projections/. 

20. Texas Comptroller of Public Accounts, Texas State Expenditures by County, from 

http://www.window.state.tx.us/taxbud/expbyco/. 

21. Bureau of Labor Statistics, Consumer Price Index, All Urban Consumers, South Region, 

from 

http://data.bls.gov/PDQ/servlet/SurveyOutputServlet?data_tool=dropmap&series_id=CU

UR0300SA0,CUUS0300SA0 - all consumers, South Region. 

22. Personal communication with Anusuya Iyer, TCEQ, April 25, 2008. 

23. Bob Lanham, Vice President Williams Brothers Construction, Houston Texas, personal 

communication May 23, 2008. 

24. Equipment Data Associates, Skid Steer Loader Sales Records through 2005, taken from 

Eastern Research Group, “Statewide Diesel Construction Equipment Inventory”, 

prepared for the Texas Commission on Environmental Quality, August 31, 2005, p. 3-36. 
25. Natural Resource Conservation Service, 

http://www.ncgc.nrcs.usda.gov/products/datasets/ssurgo/description.html. 

26. U.S. Geological Survey, http://edc.usgs.gov/geodata/. 

27. Environmental Protection Agency, http://www.epa.gov/fedrgstr/EPAAIR/2004/January/Day-12/a458.pdf 

28. Environmental Protection Agency, 40 CFR 89.1003(a)(1)(i) and 

http://www.epa.gov/nonroad-diesel/regulations.htm 

29. Environmental Protection Agency, http://www.epa.gov/nonroad-diesel/frm1998/nr-fr.pdf 

30. Environmental Protection Agency, http://www.epa.gov/otaq/regs/nonroad/equipld/hhsfrm/f00007.pdf 

31. Environmental Protection Agency, http://www.epa.gov/otaq/largesi.htm 

32. Environmental Protection Agency, http://www.epa.gov/nonroad-diesel/2004fr.htm 

33. Environmental Protection Agency, 

http://www.epa.gov/otaq/models/nonrdmdl/nonrdmdl2005/420r05019.pdf 

34. Environmental Protection Agency, 

http://www.epa.gov/otaq/models/nonrdmdl/nonrdmdl2004/420p04009.pdf 
Attachment B 

County Level Fuel Specifications 
Table B-1. Summertime Gasoline 

 2002 

County RVP Sulfur % Oxy Wt % 

Brazoria 6.80 0.0162 1.75 

Chambers 6.80 0.0162 1.75 

Fort Bend 6.80 0.0162 1.75 

Galveston 6.80 0.0162 1.75 

Harris 6.80 0.0162 1.75 

Liberty 6.80 0.0162 1.75 

Montgomery 6.80 0.0162 1.75 

Waller 6.80 0.0162 1.75 

 2008+ 

County RVPSulfur % Oxy Wt %

Brazoria 6.8 0.00330 2.1

Chambers 6.8 0.00330 2.1

Fort Bend 6.8 0.00330 2.1

Galveston 6.8 0.00330 2.1

Harris 6.8 0.00330 2.1

Liberty 6.8 0.00330 2.1

Montgomery 6.8 0.00330 2.1

Waller 6.8 0.00330 2.1
Table B-2. Winter time Gasoline 

 2002 

County RVP Sulfur % Oxy Wt %

Brazoria 11.3 0.0259 3.5

Chambers 11.3 0.0259 3.5

Fort Bend 11.3 0.0259 3.5

Galveston 11.3 0.0259 3.5

Harris 11.3 0.0259 3.5

Liberty 11.3 0.0259 3.5

Montgomery 11.3 0.0259 3.5

Waller 11.3 0.0259 3.5

 2008+ 

County RVP Sulfur % Oxy Wt %

Brazoria 11.3 0.00300 3.5

Chambers 11.3 0.00300 3.5

Fort Bend 11.3 0.00300 3.5

Galveston 11.3 0.00300 3.5

Harris 11.3 0.00300 3.5

Liberty 11.3 0.00300 3.5

Montgomery 11.3 0.00300 3.5

Waller 11.3 0.00300 3.5

Table B-3. Diesel Fuel Sulfur Levels (weight %) 

County 1999 - 2003 2004 2005 2006-2009 2010+

Brazoria 0.0307 0.0402 0.0351 0.0351 0.0015

Chambers 0.0307 0.0402 0.0412 0.0412 0.0015

Fort Bend 0.0307 0.0402 0.0351 0.0351 0.0015

Galveston 0.0307 0.0402 0.0351 0.0351 0.0015

Harris 0.0307 0.0402 0.0351 0.0351 0.0015

Liberty 0.0307 0.0402 0.0412 0.0412 0.0015

Montgomery 0.0307 0.0402 0.0351 0.0351 0.0015

Waller 0.0307 0.0402 0.0351 0.0351 0.0015
Table B-4. Historical Census Population by County for 8-County HGB Area 

(1970 / 80 / 90 / 2000) 

County 1970 1980 1990 2000 

Brazoria 108,312 169,587 191,707 241,767 

Chambers 12,187 18,538 20,088 26,031 

Fort Bend 52,314 130,846 225,421 354,452 

Galveston 169,812 195,940 217,399 250,158 

Harris 1,741,912 2,409,547 2,818,199 3,400,578 

Liberty 33,014 47,088 52,726 70,154 

Montgomery 49,479 128,487 182,201 293,768 

Waller 14,285 19,798 23,390 32,663 

 

Source: Texas State Data Center 
Attachment C 

TexN Emission Calculation Example 
2-1

The following provides an example illustrating the detailed calculation steps within the 

NONROAD model, as well as the post-processing adjustments applied by TexN. The derivation 

and use of each parameter in the fundamental emission equation (shown below) are discussed, as 

well as the application of the appropriate locality specific adjustments. 

Fundamental Emissions Equation: 

Emissionsp/yr =∑(MYR) ∑(HP) Pop * Power * LF * A * EFp

Where: Pop = Number of engines 

Power = Average hp (for specific hp group) 

LF = Load factor (% of rated power) 

A = Activity (hr/year) 

EFp = Emissions for pollutant p (grams/bhp-hr) 

∑(HP) = summation over each equipment hp group 

∑(MYR) = summation over each equipment model year 

The example calculation is conducted for NOx emissions for the following scenario: 

 County – Harris 

 Equipment Type – Diesel Trenchers (SCC = 2270002030) 

 Analysis Year – 2050 

 Period – Ozone Season Weekday 

In order to walk through the example calculation we recommend you run a TexN scenario for 

these conditions. 

Step 1 – Identify NONROAD Input and TexN Adjustment Parameters. First open the TexN 

scenario you developed for the above conditions. This will allow you to identify the default 

input and adjustment parameters used within the model. From the Population Tab identify 

average hp, useful life (in hrs) and population for each hp bin with non-zero populations. From 

the Activity Tab identify the load factor and activity in hours per year. And from the Fuel and 

Climate Tab identify the average summertime temperature in degrees Fahrenheit, and relative 

humidity (typical meteorological year assumed). These input parameters are listed below: 

Population Tab 

hp bin avg. hp useful life population (2050)17

25 – 50 hp 34.1 2,500 hrs 2,172.64 

50 – 75 hp 61.02 4,667 hrs 491.01 

75 – 100 hp 86.75 4,667 hrs 610.22 

Activity Tab 

load factor activity 

0.59 1,308 hrs/yr 

 

17 These figures correspond to 2050 population projections. 
2-2

Fuel and Climate 

average temperature relative humidity atmospheric pressure (mb)18

81.1 °F 75% 1,013.21 

Step 2 – Determine the Model Year Distribution for Each HP Bin. NONROAD applies its default 

scrappage and growth curves in order to allocate the population totals for each hp bin across 

model years. To develop these distributions, first calculate the median life in years for diesel 

trenchers as shown below. 

Median Life in years (< 50 hp) = Median life in hours / (activity in hours/yr x load factor) = 

2,500 / (1,306 x 0.59) = 3.24 years 

Median Life in years (> 50 hp) = 4,667 / (1,306 x 0.59) = 6.05 years 

Next, the default scrappage curve must be modified to provide the fraction of median life 

expressed in terms of engine age, as shown in Table F-1 below. The age distributions shown in 

the table are calculated by simply multiplying the fraction of median life value by the median life 

expressed in years (3.24 years for engines < 50 hp, and 6.05 years for engines >= 50 hp). 

Table C-1. Default Scrappage Curve Expressed in Years of Age (Trenchers) 

Fraction of 

Median Life 

Cumulative % 

Scrapped 

Incremental % 

Scrapped

Age Distribution 

(<50 hp) 

Age Distribution 

(>50 hp)

0 0 0 0 0

0.0294 0.5 0.5 0.095 0.178

0.0588 1 0.5 0.190 0.356

0.08705 1.5 0.5 0.282 0.526

0.1153 2 0.5 0.374 0.697

0.14235 2.5 0.5 0.461 0.861

0.1694 3 0.5 0.549 1.024

0.19535 3.5 0.5 0.633 1.181

0.2213 4 0.5 0.717 1.338

0.24615 4.5 0.5 0.797 1.489

0.271 5 0.5 0.878 1.639

0.29475 5.5 0.5 0.955 1.783

0.3185 6 0.5 1.032 1.926

0.3412 6.5 0.5 1.105 2.063

0.3639 7 0.5 1.179 2.201

0.3856 7.5 0.5 1.249 2.332

0.4073 8 0.5 1.319 2.463

0.42795 8.5 0.5 1.386 2.588

0.4486 9 0.5 1.453 2.713

0.4683 9.5 0.5 1.517 2.832

0.488 10 0.5 1.581 2.951

 

18 Atmospheric pressure is not displayed on the Fuel and Climate Tab, but is maintained in one of the TexN lookup 

tables accessible by the TexN database administrator. 
2-3

Fraction of 

Median Life 

Cumulative % 

Scrapped 

Incremental % 

Scrapped

Age Distribution 

(<50 hp) 

Age Distribution 

(>50 hp)

0.5067 10.5 0.5 1.641 3.064

0.5254 11 0.5 1.702 3.177

0.5432 11.5 0.5 1.760 3.285

0.561 12 0.5 1.817 3.393

0.5779 12.5 0.5 1.872 3.495

0.5948 13 0.5 1.927 3.597

0.6108 13.5 0.5 1.979 3.694

0.6268 14 0.5 2.031 3.791

0.6419 14.5 0.5 2.079 3.882

0.657 15 0.5 2.128 3.973

0.6713 15.5 0.5 2.175 4.060

0.6856 16 0.5 2.221 4.146

0.69905 16.5 0.5 2.265 4.228

0.7125 17 0.5 2.308 4.309

0.7252 17.5 0.5 2.349 4.386

0.7379 18 0.5 2.390 4.462

0.7498 18.5 0.5 2.429 4.534

0.7617 19 0.5 2.468 4.606

0.77285 19.5 0.5 2.504 4.674

0.784 20 0.5 2.540 4.741

0.79445 20.5 0.5 2.574 4.804

0.8049 21 0.5 2.607 4.868

0.81465 21.5 0.5 2.639 4.927

0.8244 22 0.5 2.671 4.986

0.83345 22.5 0.5 2.700 5.040

0.8425 23 0.5 2.729 5.095

0.85095 23.5 0.5 2.757 5.146

0.8594 24 0.5 2.784 5.197

0.8672 24.5 0.5 2.809 5.244

0.875 25 0.5 2.835 5.292

0.8822 25.5 0.5 2.858 5.335

0.8894 26 0.5 2.881 5.379

0.89605 26.5 0.5 2.903 5.419

0.9027 27 0.5 2.924 5.459

0.90875 27.5 0.5 2.944 5.496

0.9148 28 0.5 2.964 5.532

0.92035 28.5 0.5 2.981 5.566

0.9259 29 0.5 2.999 5.599

0.93095 29.5 0.5 3.016 5.630

0.936 30 0.5 3.032 5.660

0.94055 30.5 0.5 3.047 5.688

0.9451 31 0.5 3.062 5.716

0.9492 31.5 0.5 3.075 5.740

0.9533 32 0.5 3.088 5.765

0.957 32.5 0.5 3.100 5.787

0.9607 33 0.5 3.112 5.810

0.96395 33.5 0.5 3.123 5.830
2-4

Fraction of 

Median Life 

Cumulative % 

Scrapped 

Incremental % 

Scrapped

Age Distribution 

(<50 hp) 

Age Distribution 

(>50 hp)

0.9672 34 0.5 3.133 5.849

0.9701 34.5 0.5 3.143 5.867

0.973 35 0.5 3.152 5.884

0.9755 35.5 0.5 3.160 5.899

0.978 36 0.5 3.168 5.914

0.9802 36.5 0.5 3.175 5.928

0.9824 37 0.5 3.183 5.941

0.9843 37.5 0.5 3.189 5.953

0.9862 38 0.5 3.195 5.964

0.9878 38.5 0.5 3.200 5.974

0.9894 39 0.5 3.205 5.983

0.9907 39.5 0.5 3.209 5.991

0.992 40 0.5 3.214 5.999

0.9931 40.5 0.5 3.217 6.006

0.9942 41 0.5 3.221 6.012

0.99505 41.5 0.5 3.223 6.018

0.9959 42 0.5 3.226 6.023

0.9966 42.5 0.5 3.229 6.027

0.9973 43 0.5 3.231 6.031

0.9978 43.5 0.5 3.232 6.034

0.9983 44 0.5 3.234 6.037

0.99865 44.5 0.5 3.235 6.039

0.999 45 0.5 3.236 6.041

0.99925 45.5 0.5 3.237 6.043

0.9995 46 0.5 3.238 6.045

0.99965 46.5 0.5 3.238 6.045

0.9998 47 0.5 3.239 6.046

0.99985 47.5 0.5 3.239 6.047

0.9999 48 0.5 3.239 6.047

0.99995 49 1 3.239 6.047

1 50 1 3.240 6.048

1.00005 51 1 3.240 6.048

1.0001 52 1 3.240 6.048

1.00015 52.5 0.5 3.240 6.048

1.0002 53 0.5 3.240 6.049

1.00035 53.5 0.5 3.241 6.050

1.0005 54 0.5 3.241 6.051

1.00075 54.5 0.5 3.242 6.052

1.001 55 0.5 3.243 6.054

1.00135 55.5 0.5 3.244 6.056

1.0017 56 0.5 3.245 6.058

1.0022 56.5 0.5 3.247 6.061

1.0027 57 0.5 3.248 6.064

1.0034 57.5 0.5 3.251 6.068

1.0041 58 0.5 3.253 6.072

1.00495 58.5 0.5 3.256 6.077

1.0058 59 0.5 3.258 6.083
2-5

Fraction of 

Median Life 

Cumulative % 

Scrapped 

Incremental % 

Scrapped

Age Distribution 

(<50 hp) 

Age Distribution 

(>50 hp)

1.0069 59.5 0.5 3.262 6.089

1.008 60 0.5 3.265 6.096

1.0093 60.5 0.5 3.270 6.104

1.0106 61 0.5 3.274 6.112

1.0122 61.5 0.5 3.279 6.121

1.0138 62 0.5 3.284 6.131

1.0157 62.5 0.5 3.290 6.142

1.0176 63 0.5 3.297 6.154

1.0198 63.5 0.5 3.304 6.167

1.022 64 0.5 3.311 6.181

1.0245 64.5 0.5 3.319 6.196

1.027 65 0.5 3.327 6.211

1.0299 65.5 0.5 3.336 6.228

1.0328 66 0.5 3.346 6.246

1.03605 66.5 0.5 3.356 6.266

1.0393 67 0.5 3.367 6.285

1.043 67.5 0.5 3.379 6.308

1.0467 68 0.5 3.391 6.330

1.0508 68.5 0.5 3.404 6.355

1.0549 69 0.5 3.417 6.380

1.05945 69.5 0.5 3.432 6.407

1.064 70 0.5 3.447 6.435

1.06905 70.5 0.5 3.463 6.465

1.0741 71 0.5 3.480 6.496

1.07965 71.5 0.5 3.498 6.529

1.0852 72 0.5 3.516 6.563

1.09125 72.5 0.5 3.535 6.599

1.0973 73 0.5 3.555 6.636

1.10395 73.5 0.5 3.576 6.676

1.1106 74 0.5 3.598 6.716

1.1178 74.5 0.5 3.621 6.760

1.125 75 0.5 3.644 6.803

1.1328 75.5 0.5 3.670 6.851

1.1406 76 0.5 3.695 6.898

1.14905 76.5 0.5 3.722 6.949

1.1575 77 0.5 3.750 7.000

1.16655 77.5 0.5 3.779 7.055

1.1756 78 0.5 3.808 7.109

1.18535 78.5 0.5 3.840 7.168

1.1951 79 0.5 3.872 7.227

1.20555 79.5 0.5 3.905 7.291

1.216 80 0.5 3.939 7.354

1.22715 80.5 0.5 3.975 7.421

1.2383 81 0.5 4.011 7.489

1.2502 81.5 0.5 4.050 7.561

1.2621 82 0.5 4.089 7.633

1.2748 82.5 0.5 4.130 7.709
2-6

Fraction of 

Median Life 

Cumulative % 

Scrapped 

Incremental % 

Scrapped

Age Distribution 

(<50 hp) 

Age Distribution 

(>50 hp)

1.2875 83 0.5 4.171 7.786

1.30095 83.5 0.5 4.214 7.868

1.3144 84 0.5 4.258 7.949

1.3287 84.5 0.5 4.304 8.035

1.343 85 0.5 4.351 8.122

1.3581 85.5 0.5 4.400 8.213

1.3732 86 0.5 4.449 8.304

1.3892 86.5 0.5 4.500 8.401

1.4052 87 0.5 4.552 8.498

1.4221 87.5 0.5 4.607 8.600

1.439 88 0.5 4.662 8.702

1.4568 88.5 0.5 4.719 8.810

1.4746 89 0.5 4.777 8.918

1.4933 89.5 0.5 4.838 9.031

1.512 90 0.5 4.898 9.144

1.5317 90.5 0.5 4.962 9.263

1.5514 91 0.5 5.026 9.382

1.57205 91.5 0.5 5.093 9.507

1.5927 92 0.5 5.160 9.632

1.6144 92.5 0.5 5.230 9.763

1.6361 93 0.5 5.300 9.894

1.6588 93.5 0.5 5.374 10.032

1.6815 94 0.5 5.447 10.169

1.70525 94.5 0.5 5.524 10.313

1.729 95 0.5 5.601 10.456

1.75385 95.5 0.5 5.682 10.606

1.7787 96 0.5 5.762 10.757

1.80465 96.5 0.5 5.846 10.914

1.8306 97 0.5 5.930 11.071

1.85765 97.5 0.5 6.018 11.234

1.8847 98 0.5 6.106 11.398

1.91295 98.5 0.5 6.197 11.569

1.9412 99 0.5 6.289 11.739

1.9706 99.5 0.5 6.384 11.917

2 100 0.5 6.479 12.095

The above fractions were then aggregated by engine age in year increments to determine the 

fraction of engines in each year (see Table F-2 below). 
2-7

Table C-2. Remaining Fraction of Engines by Age 

Age < 50 hp > 50 hp

1 0.95 0.98

2 0.87 0.94

3 0.71 0.90

4 0.20 0.85

5 0.10 0.78

6 0.03 0.60

7 0.00 0.24

8 0.00 0.16

9 0.00 0.11

10 0.00 0.07

11 0.00 0.04

12 0.00 0.01

In order to determine the 2050 model year distribution, the fractions presented in Table Y must 

be combined with annual equipment sales estimates over the previous 6 years, in the case of 

engines < 50 hp, and over the previous 12 years, in the case of engines >= 50 hp. The annual 

growth in sales can be calculated from NONROAD’s default growth file, nation.grw. From this 

file we identify the last two indicator values for the diesel construction indicator code (021), as 

show below. 

2025 - 1,927 

2045 - 2,569 

The NONROAD model uses these two data points to linearly extrapolate annual sales growth 

rates up to 2050. Annual growth rates for the period from 2025 through 2050 are therefore 

calculated as [(2,569 – 1,927) / (2045 – 2025)] / 1,000 = 3.21%.19 Therefore equipment sales 

totals for units of age X are related to sales totals in the year 2050 (age 1) by the following 

equation: 

Salesage x = Salesage 1 / [1 + (x – 1) (0.0321)] = Salesage x / ax

The values for ax are shown below in Table F-3. 

 

19 The difference between the indicator code values are divided by the 1996 base year value of 1,000 – also obtained 

from the nation.grw file. 
2-8

Table C-3. Sales Adjustment Factors by Age 

Age a (x)

1 1.000

2 1.032

3 1.064

4 1.096

5 1.128

6 1.161

7 1.193

8 1.225

9 1.257

10 1.289

11 1.321

12 1.353

Dividing the total equipment population for each hp bin by the sum of the ratios of the remaining 

equipment fraction (Table F-2) and the sales adjustment factors (Table F-3) allows us to 

calculate the equipment sales totals for units sold in 2050 (age 1) for each hp bin. The general 

equation for a given hp bin is shown below, with the summation over all equipment ages with 

non-zero remaining fractions. 

Salesage 1 = Total Pop / ∑ (Remaining Fractionx / ax) 

The resulting 2050 sales totals (age = 1) are shown in Table F-4 below. 

Table C-4. 2050 (Age 1) Sales Totals by HP Bin 

< 50 hp 793.4623

50 - 75 hp 94.15786

75-100 hp 117.0177

These age 1 sales totals are then divided by the product of the sales adjustment factor and the 

remaining fraction by year to obtain the model year distribution for each hp bin, as shown in 

Table F-5. 
2-9

Table C-5. Model Year Distribution by HP Bin 

Yr < 50 hp 50 - 75 hp 75-100 hp

1 749.82 91.80 114.09

2 665.00 85.76 106.58

3 529.37 79.63 98.96

4 141.13 73.00 90.73

5 66.80 65.09 80.89

6 20.51 48.68 60.50

7 0.00 18.55 23.06

8 0.00 12.30 15.29

9 0.00 8.24 10.24

10 0.00 5.11 6.36

11 0.00 2.49 3.10

12 0.00 0.35 0.43

Total 2,172.64 491.01 610.22

Step 3 – Determine Emission Factors by HP Bin and Age. First, determine the technology mix 

for trenchers in 2050. In the tech-exh.dat file we see that diesel engine sales (SCC 

227XXXXXXX) in the 25 – 50, and 50 – 75 hp bins are designated 100% “T4” starting shortly 

after 2010. Therefore by 2050 100% of all in-use trencher engines are assumed to be T4. 

Similarly all in-use trenchers in the 75 – 100 hp range are assumed to be T4N by 2050. Next, 

identify the zero-hour NOx emission factors in the exhnox.emf file for the appropriate hp bin and 

technology type. These factors are shown below in Table F-6. 

Table C-6. Zero-Hour NOx Diesel Emission Factors (2050) 

HP Bin g/hp-hr Tech Type

< 50 hp 3.00 100% T4

50 - 75 hp 3.00 100% T4

75-100 hp 0.28 100% T4N

Next, identify the associated NOx deterioration factors by technology type. These values are 

provided in the exhnox.det file. Deterioration factors are multiplicative to the zero-hour factors, 

and are calculated as follows: 

DF = 1 + A × engine ageb

In the above equation engine age is expressed as a fraction of median life. 

For technology types T4 and T4N, A = 0.008 and b = 1, translating to a very low deterioration 

rate for these engines. In addition, deterioration is capped once the engine age equals the median 

life of the engine. By calculating engine age in terms of the fraction of median life (hrs/yr x yrs 

x load factor / median life in hours), and substituting this value into the above equation, a 
2-10

separate deterioration factor can be calculated for each engine age of interest (in years), as shown 

in Table F-7. 

Table C-7. NOx Deterioration Factors by Model Year (2050 Scenario) 

Model Yr < 50 hp >= 50 hp

2050 1.0025 1.0013

2049 1.0049 1.0026

2048 1.0074 1.0040

2047 1.0080 1.0053

2046 1.0080 1.0066

2045 1.0080 1.0079

2044 1.0080 1.0080

2043 1.0080 1.0080

2042 1.0080 1.0080

2041 1.0080 1.0080

2040 1.0080 1.0080

2039 1.0080 1.0080

By multiplying the zero-hour factors in Table F-6 by the deterioration factors above we obtain 

the age-dependent emission factors, shown in Table F-8. 

Table C-8. NOx Emission Factors by Model Year (g/hp-hr) 

Model Yr < 50 hp 50 - 75 hp 75-100 hp 

2050 3.007 3.004 0.280 

2049 3.015 3.008 0.281 

2048 3.022 3.012 0.281 

2047 3.024 3.016 0.281 

2046 3.024 3.020 0.282 

2045 3.024 3.024 0.282 

2044 3.024 3.024 0.282 

2043 3.024 3.024 0.282 

2042 3.024 3.024 0.282 

2041 3.024 3.024 0.282 

2040 3.024 3.024 0.282 

2039 3.024 3.024 0.282 

Step 4 – Determine Activity Hours per Ozone-Season Weekday. The MONTHLY packet within 

the season.dat file indicates that construction equipment in the Southwest U.S. (“SW”, which 

includes Texas), are operated 9.1% of their annual total during each summer month. 

Equivalently, 27.3% (3 summer months x 9.1%/month) of total hours per year occur during the 

summer. This corresponds to 1,306 x 0.273 = 357 hours of trencher activity per summer. From 

the Scenario output file we see that a summer NONROAD run is assumed to include 92 days in 
2-11

the entire season, or 92 / 7 = 13.14 weeks. In turn, this corresponds to 357 hrs/season / 13.14 

weeks/season = 27.17 hours per week. 

Finally, the DAILY packet of the season.dat file shows that construction equipment is assumed 

to have 16.7% of its weekly activity occur on a weekday. This corresponds to 27.17 hrs/week x 

0.167 = 4.53 hours/summer weekday. This daily activity level can be multiplied using the 

following equation to estimate tons of NOx per ozone season day, with the summation occurring 

over engine model years. 

Tons/Ozone-Season Weekday = ∑ Emission Factor (g/hp-hr) x Engine Population x 

Hours/Ozone Season Weekday x Average hp x Load Factor x 1.1023 x 10-

6 short tons/gram 

The resulting emissions estimates are provided in Table F-9 below. These estimates correspond 

to the values output from the NONROAD model before TexN adjustments are applied. 

Table C-9. NOx Emissions from Diesel Trenchers 

(Tons per Ozone-Season Weekday, 2050 Scenario) 

Equipment Age (Yrs) < 50 hp 50 - 75 hp 75-100 hp 

1 0.227 0.050 0.008 

2 0.201 0.046 0.008 

3 0.161 0.043 0.007 

4 0.043 0.040 0.007 

5 0.020 0.035 0.006 

6 0.006 0.026 0.004 

7 0.000 0.010 0.002 

8 0.000 0.007 0.001 

9 0.000 0.004 0.001 

10 0.000 0.003 0.000 

11 0.000 0.001 0.000 

12 0.000 0.000 0.000 

Total 0.658 0.266 0.044 

Step 5 – Apply Post-Processing Adjustments. Several adjustments are applied to the NONROAD 

outputs. First, temperature and humidity adjustments are applied to all diesel engines, as 

discussed in Section 4.3.2. Adjustments utilize absolute humidity (H), which is calculated as 

follows: 

H = [RH x 38.017 x ea] / [P – 6.112 x ea] 

where a = [9.8245 x (T – 32)] / [0.556 x (T – 32) + 243.5] 

Inserting the parameters specific to typical meteorological year conditions in Harris County 

identified under Step 1, a = 1.781 and H = 17.330. 
2-12

There are two adjustment equations – one equation is used for naturally-aspirated engines, 

another for turbocharged engines. 

 Naturally-Aspirated (N-A) Engine Adjustment: 

 1 + 0.001368 x (0.556 x (T - 32) – 29.444) – 0.01512 x (H – 10.71) 

 Turbo-charged Engine Adjustment: 

 1 + 0.00446 x (0.556 x (T – 32) - 25) – 0.018708 x (H – 10.71) 

Inserting the values for T (81.1) and H from above, the N-A adjustment = 0.897, and the turbo 

adjustment = 0.886. 

Next the estimated fraction of N-A and turbocharged engines (presented in Section 4.3.2) is 

shown below for model years beyond 2005. 

 N-A Turbo

< 50 hp 0.82 0.18

> 50 hp 0.45 0.55

Applying these weights to the engine adjustments results in a net adjustment of 0.895 for 

engines less than 50 hp, and 0.891 for engines greater than or equal to 50 hp. Applying 

these factors directly to the NONROAD output emissions estimates we obtain the following 

adjusted NOx values. 

< 50 hp 0.5889 TPD 

50 – 75 hp 0.2370 TPD 

75 – 100 hp 0.0391 TPD 

Total 0.8650 TPD 

Next altitude adjustments are applied directly to NOx emission estimates to reflect the slight 

increase in hp-hrs needed to accomplish a task at a higher altitude (see Section 4.3.2). 

Multiplying the 0.865 figure by the altitude adjustment factor for Harris County (1.00032) yields 

a miniscule adjustment of .0003 TPD (0.8653). 

The soil adjustment factor for Harris County of 1.222 is applied to all trencher activity, resulting 

in a one-to-one increase in hp-hrs and NOx emissions. The resulting adjustment applied to the 

0.8653 figure results in a revised NOx estimate of 1.0578 TPD. 

Finally, Harris County is within the TxLED region, so a further adjustment of (1-.062) = 0.938 is 

applied to the 1.0578 value, yielding a final adjusted emission estimate of 0.992 TPD for all 

trenchers operating in Harris County in 2050. The difference from the actual TexN output of 

0.991 TPD is attributable to rounding error. 
2-13

Attachment D 

Applicable Rules and Rate of Further Progress (RFP) Analyses 
2-14

Rate of Further Progress (RFP) Analyses 

TexN can be used to evaluate the effects of individual federal rules impacting non-road 

emissions for RFP analyses. The applicable rules are: 

 Rule #1: Emission Standards for New Nonroad Spark-ignition Engines at or 

below 19 Kilowatts - “Phase I Small SI Rule” [27] 

 Rule #2: Federal Emission Standards for Heavy-Duty and Nonroad Engines - 

“1998 HD and Nonroad Rule” [28] 

 Rule #3: Tier 1, 2 and Tier 3 Emission Standards: Control of Emissions of Air 

Pollution from Nonroad Diesel Engines - “Tier 1, 2 and 3 Rule” [29] 

 Rule #4: Final Phase II Standards for Small Nonroad SI Handheld Engines - 

“Phase II Small SI Rule” [30] 

 Rule #5: Emission Standards for New Nonroad Engines: Large Industrial SI 

Engines, Recreational Vehicles, and Diesel Recreational Marine Engines - 

“Large SI Rule” [31] 

 Rule #6: Clean Air Nonroad Diesel - Tier 4 Final Rule – “Tier 4 Rule” [32] 

In an RFP evaluation, the ozone season-daily emission reduction impact must be 

determined and report of each rule for the given region and evaluation year. Table 6-1 below 

shows the phase-in dates, equipment types and hp ranges for each rule. Each of these rules is 

discussed in more detail below. 

In order to evaluate individual rule impacts, the technology type files were modified to 

reflect phase-in of individual rules. There is a separate set of technology type files for each 

federal rule that is evaluated. Each rule has a technology type file that reflects the 

“uncontrolled” conditions and the “controlled” conditions. To create the “uncontrolled” 

technology type files, the technology type phase-in that was available immediately prior to the 

rule of evaluation was carried forward to future years, effectively zeroing out the effects of the 

rule of evaluation. The “controlled” technology type files were created by carrying forward the 

phase-in that was available at the conclusion of the phase-in of the rule of evaluation, effectively 

zeroing out the effect of subsequent rules. 

Note: In some cases, a technology would begin phase-in one year prior to the rule 

requirements. In these instances, this phase-in year is considered to be a direct consequence of 

the pending rule. Therefore, any benefits seen by an early phase-in is attributed to the pending 

rule. 
2-15

Table D-1. Phase-in Dates by Rule 

Rule Spark Ignition (Gasoline, LPG, CNG) Compr

Reference # Rule 

Sub-categories

< 25 hp > 25 hp MARINE < 25 hp MARINE > 25 hp < 50 hp > 50 hp 

1 Phase I Small SI 1997-2 

1998 HD 

and 

Nonroad 

 1998-2006 1998-2000 

Tier 1 1999-2000Tier 2 2001-2006 2001-2006 

3 

Tier 1, 

Tier 2 

and 

Tier 3 

Tier 3 2006-2008 

4 Phase II Small SI 2002-2007

Large Industrial 

Spark-Ignition 

Engines 

(Tier 1)

 2004 2004 

Large Industrial 

Spark-Ignition 

Engines 

(Tier 2)

2007 2007 

Recreational 

Vehicles 2006

5 Large SI 

Diesel 

Recreational 

Marine Engines

 

6 Tier 4 2008 2008-2013
16

Rule #1: Emission Standards for New Non-road Spark-ignition (SI) Engines 

At or Below 19 kW (~25 hp) 

This rule is applicable to new non-road SI engines at or below 19 kW (~ 25 hp) 

and manufactured during or after the 1997 model year, including farm and construction 

equipment, lawnmowers, string trimmers, edgers, chainsaws, commercial turf equipment, 

small construction equipment, and lawn and garden tractors. Exempt vehicles and 

equipment include competition or combat vehicles, research, training, investigations, 

demonstrations, and national security vehicles and equipment, engines used to propel 

marine vessels, engines used in underground mining equip, motorcycles, aircraft, and 

recreational vehicles. The standards for this rule are presented in Table 6-2 below. 

Table D-2. Phase I Small SI Rule Standards (g/bhp-hr) 

Class Year CO HC HC + NOx NOx Class Description 

I 1997+ 387 N/A 12 N/A Nonhandheld < 225 cc 

II 1997+ 387 N/A 10 N/A Nonhandheld > ~225 cc 

III 1997+ 600 220 N/A 4 Handheld < 20 cc 

IV 1997+ 600 180 N/A 4 Handheld > ~20 < 50 cc 

V 1997+ 450 120 N/A 4 Handheld > ~50 cc 

Rule #2: Federal Emission Standards for Heavy-Duty and Non-road Engines 

This rule is applicable to non-road compression ignition (CI – diesel) engines 

greater than 50 hp, and marine SI outboard manufactured as early as 1998, and personal 

watercraft and jet boat engines manufactured as early as 1999. This rule does not include 

standards for non-road SI engines greater than 25 hp or marine CI engines. The standards 

are presented below in Tables 6-3 and 6-4. 

Table D-3. 1998 Non-road CI Engine Standards in g/bhp-hr 

Rated Power Year CO HC NOx PM10

Smoke (%)

acceleration/lug

/peak modes

50 ≤hp< 100 1998+ N/A N/A 6.9 N/A 20/15/50

100 ≤hp< 175 1997+ N/A N/A 6.9 N/A 20/15/50

175 ≤hp< 750 1996+ 8.5 1 6.9 0.4 20/15/50

hp = 750+ 2000+ 8.5 1 6.9 0.4 20/15/50
17

Table D-4. 1998 Marine SI Engine Standards 

HC+NOx 

P* < 4.3 P* ≥ 4.3 Year 

g/kW-hr g/hphr g/kW-hr g/hp-hr 

1998 278 207.3 (0.917 x (151+ 557/P^0.9)) + 2.44 [ (0.917 x (151+ 557/P^0.9)) + 2.44 ] x 0.7457

1999 253 188.7 (0.833 x (151+ 557/P^0.9)) + 2.89 [ (0.833 x (151+ 557/P^0.9)) + 2.89 ] x 0.7457 

2000 208 155.1 (0.750 x (151+ 557/P^0.9)) + 3.33 [ (0.750 x (151+ 557/P^0.9)) + 3.33 ] x 0.7457 

2001 204 152.1 (0.667 x (151+ 557/P^0.9)) + 3.78 [ (0.667 x (151+ 557/P^0.9)) + 3.78 ] x 0.7457 

2002 179 133.5 (0.583 x (151+ 557/P^0.9)) + 4.22 [ (0.583 x (151+ 557/P^0.9)) + 4.22 ] x 0.7457 

2003 155 115.6 (0.500 x (151+ 557/P^0.9)) + 4.67 [ (0.500 x (151+ 557/P^0.9)) + 4.67 ] x 0.7457 

2004 130 96.9 (0.417 x (151+ 557/P^0.9)) + 5.11 [ (0.417 x (151+ 557/P^0.9)) + 5.11 ] x 0.7457 

2005 105 78.3 (0.333 x (151+ 557/P^0.9)) + 5.56 [ (0.333 x (151+ 557/P^0.9)) + 5.56 ] x 0.7457 

2006+ 81 60.4 (0.250 x (151+ 557/P^0.9)) + 6.00 [ (0.250 x (151+ 557/P^0.9)) + 6.00 ] x 0.7457 

*P = power rating in kilowatts 

Rule #3: Tier 1, 2 and 3 Diesel Engine Emission Standards 

These emission standards apply to all non-road mobile diesel engines and 

equipment of all sizes, except for locomotives, marine engines above 50 hp, underground 

mining equipment, and engines with less than 50 cc that are typically used in model 

airplanes. The standards are presented in Table 6-5 below. 

Table D-5. Tier 1, 2 and 3 Diesel Engine Standards in g/kW-hr (g/hp-hr) 

Engine Size Tier Model year NMHC + NOx CO PM10

kW < 8 Tier 1 2000 10.5 (7.8) 8.0 (6.0) 1.0 (0.75)

(hp < 11) Tier 2 2005 7.5 (5.6) 8.0 (6.0) 0.8 (0.6)

8 ≤ kW < 19 Tier 1 2000 9.5 (7.1) 6.6 (4.9) 0.8 (0.6)

(11≤hp< 25) Tier 2 2005 7.5 (5.6) 6.6 (4.9) 0.8 (0.6)

19 ≤kW< 37 Tier 1 1999 9.5 (7.1) 5.5 (4.1) 0.8 (0.6)

(25 ≤hp< 50) Tier 2 2004 7.5 (5.6) 5.5 (4.1) 0.6 (0.45)

37≤kW< 75 Tier 2 2004 7.5 (5.6) 5.0 (3.7) 

(50 ≤hp< 100) Tier 3 2008 4.7 (3.5) 5.0 (3.7) 0.4 (0.3)

75 ≤kW< 130 Tier 2 2003 6.6 (4.9) 5.0 (3.7) 

(100 ≤hp< 175) Tier 3 2007 4 (3.0) 5.0 (3.7) 0.3 (0.22)

130 ≤kW< 225 Tier 2 2003 6.6 (4.9) 3.5 (2.6) 

(175 ≤hp< 300) Tier 3 2006 4 (3.0) 3.5 (2.6) 0.2 (0.15)

225 ≤kW < 450 Tier 2 2001 6.4 (4.8) 3.5 (2.6) 

(300 ≤hp < 600) Tier 3 2006 4 (3.0) 3.5 (2.6) 0.2 (0.15)

450 ≤kW < 560 Tier 2 2002 6.4 (4.8) 3.5 (2.6) 

(600 ≤hp< 750) Tier 3 2006 4 (3.0) 3.5 (2.6) 0.2 (0.15)

kW ≥ 560 

(hp ≥ 750) Tier 2 2006 6.4 (4.8) 3.5 (2.6) 0.2 (0.15)

Rule #4: Phase II Standards for Small Non-road SI Handheld Engines 
18

The Phase II Standards for small handheld non-road spark-ignition engines apply 

to the following classes of engines shown in Table 6-6. Phase II standards are presented 

in Table 6-7. 

Table D-6. Phase II Small Non-road SI Engine Categories 

Class Type cc* 

I-A Nonhandheld cc < 66

I-B Nonhandheld 66 to 100 cc

I Nonhandheld 100 to 225 c

II Nonhandheld > ~225 cc

III Handheld < 20 cc

IV Handheld 20 to 50 cc

V Handheld > ~50 cc

 * displacement in cubic centimeters 

Table D-7. Phase II HC+NOx Standards for Handheld Engines in g/kW-hr (g/hphr) 

Model Year Class III Class IV Class V 

2002 238 (177) 196 (146) N/A 

2003 175 (130) 148 (110) N/A 

2004 113 (84) 99 (74) 143 (107) 

2005 50 (37) 50 (37) 119 (89) 

2006 50 (37) 50 (37) 96 (72) 

2007+ 50 (37) 50 (37) 72 (54) 

Rule #5: Large Industrial SI Engines, Recreational Vehicles, and Diesel 

Recreational Marine Engines 

This rule applies to large industrial spark-ignition engines powered by gasoline, 

natural gas, or propane gas, rated over 19 kW (25 hp). The rule also applies to diesel 

marine engines over 37 kW (50 hp) used in recreational boats, such as yachts and 

cruisers. This rule does not apply to spark-ignition recreational marine vessels. The 

standards are presented in Tables D-8 through D-11. 

Table D-8. Large SI Engine Standards in g/kW-hr (g/hp-hr) 

Tier/Year HC+NOx CO 

Tier I Starting in 2004 4 (3.0) 50 (37.3) 

Tier 2 Starting in 2007 2.7 (2.0) 4.4 (3.3) 
19

Table D-9. Recreational Vehicles Standards in g/kW-hr (g/hp-hr) 

Vehicle Model Year HC CO Phase-in % 

2006 100 (74.6) 275 (205.1) 50 

2007 - 2009 100 (74.6) 275 (205.1)

2010 75 (55.9) 275 (205.1) Snowmobiles 

2012 75 (55.9) 200 (149.1)

100 

Off-highway 2006 2 (1.5) 25 (18.6) 50 

Motorcycles 2007+ 2 (1.5) 25 (18.6) 100 

2006 1.5 (1.1) 35 (26.1) 50 ATVs 2007+ 1.5 (1.1) 35 (26.1) 100 

Table D-10. Permeation Standards for Recreational Vehicles 

Emission Component Implementation Date Standard Test Temperature 

Fuel Tank Permeation 2008 1.5 g/sq meters/day 28 Degrees C (82 degrees F) 

Fuel Hose Permeation 2008 15 g/sq meters/day 23 Degrees C (73 degrees F) 

Table D-11. Recreational Diesel Marine Standards in g/kW-hr (g/hp-hr) 

Engine size Implementation Date HC + NOx PM10 CO

0.5 L/cyl ≤Displacement< 0.9 L/cyl 2007 7.5 (5.59) 0.4 (0.30) 5 (3.73)

0.9 L/cyl ≤Displacement< 1.2 L/cyl 2006 7.2 (5.37) 0.3 (0.22) 5 (3.73)

1.2 L/cyl ≤Displacement< 2.5 L/cyl 2006 7.2 (5.37) 0.2 (0.15) 5 (3.73)

Displacement ≥ 2.5 L/cyl 2009 7.2 (5.37) 0.2 (0.15) 5 (3.73)

Rule #6: Tier 4 Diesel Rule 

This rule introduces new emission standards for non-road diesel engines and 

sulfur reductions for non-road diesel fuel. This rule will reduce PM emissions by 95% 

and NOx emissions by 90% and virtually eliminate sulfur oxides. The sulfur level in 

non-road diesel fuel will be reduced from 3,000 ppm to 500 ppm starting in 2007, and 

then to 15 ppm starting in 2010. The sulfur reductions make it possible for manufacturers 

to use clean engine technologies to reduce pollution, similar to those being introduced in 

on-road vehicles. These new engine standards will take effect, based on engine hp, 

beginning in 2008. This rule applies to diesel engines used primarily in most 

construction, agricultural, industrial, and airport support equipment. The standards will 

be fully phased in by 2014, though engines greater than 750 hp will have an additional 

year (2015) to comply. The Tier 4 standards are presented in Table D-12. 
20

Table D-12. Tier 4 Emissions Standards (g/bhp-hr) 

Rated Power 

First year the 

standards apply PM10 NOx

hp < 25 2008 0.3 -

25 ≤hp < 75 2013 0.02 3.5

75 ≤hp < 175 2012 - 2013 0.01 0.3

175 ≤hp <750 2011 - 2013 0.01 0.3

2011 - 2014 0.075 0.5 (gensets greater than 1,200 hp); 

2.6 (all other) hp ≥750 

2015 0.02 (gensets);

0.03 (all other engines) 0.5 (gensets only)

To use TexN to evaluate the effects of individual federal rules, after selecting the 

region and analysis year of interest go to the Period and Controls tab (as seen in Figure 

D-2) of the application and select the rule you are interested in evaluating. 

Figure D-2. Period and Controls Tab 

When the scenario is executed, NONROAD must be executed twice by the user 

for each rule evaluation. The first run will use technology type files reflecting the 

controls up to, but not including the rule of interest. These are the “uncontrolled”, or 

baseline, runs. The second run will use technology type files reflecting the controls 
21

enacted by the rule of interest, but does not include any rules subsequent to the rule of 

interest. These are the “controlled” runs. The rule impacts are calculated by subtracting 

the controlled run emissions from the uncontrolled run emissions for each rule, and then 

summing the differences across all rules for each SCC. 
22

Federal Non-Road Rule / SCC Crosswalk 

Rule #1 

226X002XXX ( hp < 25 ) 

226X003XXX ( hp < 25 ) 

226X004XXX ( hp < 25 ) 

226X005XXX ( hp < 25 ) 

226X006XXX ( hp < 25 ) 

226X007XXX ( hp < 25 ) 

226X008XXX ( hp < 25 ) 

226X010010 ( hp < 25 ) 

2285004XXX ( hp < 25 ) 

2285006XXX ( hp < 25 ) 

Rule #2 

227XXXXXXX (hp > 50 ) 

2285002XXX ( hp > 50 ) 

22820050XX ( hp < 25 ) 

2282010005 ( hp < 25 ) 

Rule #3 

2270001XXX 

2270002XXX 

2270003XXX 

2270004XXX 

2270005XXX 

2270006XXX 

2270007XXX 

2270008XXX 

2270010010 

22820200XX (hp < 50 ) 

Rule #4 

226XXXXXXX ( hp < 25 ) 

2285004XXX ( hp < 25 ) 

Rule # 5 

226XXXXXXX ( hp > 25 ) 

22820050XX ( hp > 25 ) 

2282010005 ( hp > 25 ) 

2285004XXX ( hp > 25 ) 

2285006XXX ( hp > 25 ) 

22820200XX ( hp > 50 ) 

Rule #6 

227XXXXXXX 

2285002XXX 

22820200XX 
23