Appendix D 

Nonroad Mobile Sources Emissions 

Inventory Documentation 
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Nonroad Mobile Sources Documentation i 

The Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Appendix D 

North Carolina Reasonable Further Progress Demonstration November 30, 2009 

Table of Contents 

1. INTRODUCTION AND SCOPE ............................................................................................... 1

2. OVERALL METHODOLOGY .................................................................................................. 2

2.1 Source Category Identification ............................................................................................ 2

2.2 Nonroad Mobile Source Emission Estimation Approach .................................................... 2

3. 2002 NONROAD MOBILE SOURCE EMISSION INVENTORY .......................................... 3

3.1 NONROAD Model Sources ................................................................................................ 3

3.2 Aircraft Engines ................................................................................................................... 4

3.3 Railroad Locomotives .......................................................................................................... 5

4. 2008 NONROAD MOBILE SOURCE EMISSION INVENTORY .......................................... 6

4.1 Projection of NONROAD Model Sources ........................................................................... 6

4.2 Projection of Non-NONROAD Model Sources .................................................................. 7
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The Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Appendix D 

North Carolina Reasonable Further Progress Demonstration November 30, 2009 

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Nonroad Mobile Sources Documentation 1 

The Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Appendix D 

North Carolina Reasonable Further Progress Demonstration November 30, 2009 

1. INTRODUCTION AND SCOPE 

The reasonable further progress (RFP) demonstration State Implementation Plan (SIP) for the 

Charlotte-Gastonia-Rock Hill, NC-SC 8-hour ozone nonattainment area (referred to as the 

Metrolina area) is built upon the regional haze modeling done by the Southeast Regional 

Planning Organization, Visibility Improvement State and Tribal Association of the Southeast 

(VISTAS) and the fine particulate matter (PM2.5) and ozone modeling being done by the 

Association of Southeastern Integrated Planning (ASIP). VISTAS and ASIP are run by the ten 

Southeast states (Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South 

Carolina, Tennessee, Virginia and West Virginia). 

The 2002 base year emissions inventory from the attainment demonstration was the starting 

point for the RFP demonstration. The majority of nonroad emission sources were developed for 

both 2002 and 2008 using the NONROAD model. For the other sources that are part of the 

nonroad mobile source category, 2002 emissions were grown using growth and control factors. 

Portions of the emissions inventories were developed by the North Carolina Division of Air 

Quality (NCDAQ) and by the VISTAS/ASIP contractors. In all cases, the emission estimates 

were calculated in tons per year. Tons per average summer day were obtained by processing the 

inventories through the Sparse Matrix Operator Kernel Emissions Modeling System (SMOKE) 

model. Section 3 documents the development of the 2002 base year nonroad mobile source 

emissions inventory. Section 4 documents development of the nonroad mobile source emissions 

inventory for 2008. 
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The Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Appendix D 

North Carolina Reasonable Further Progress Demonstration November 30, 2009 

2. OVERALL METHODOLOGY

2.1 Source Category Identification 

Nonroad mobile sources were identified from the United States Environmental Protection 

Agency (USEPA) guidance document EPA-450/4-91-016, Procedures for the Preparation of 

Emissions Inventories for Carbon Monoxide and Precursors of Ozone (Procedures document). 

Nonroad mobile source emissions are estimated by the methodologies suggested in the USEPA 

document, EPA-454/R-05-001, Emissions Inventory Guidance for Implementation of Ozone and 

Particulate Matter National Ambient Air Quality Standards (NAAQS) and Regional Haze 

Regulations; EPA-450/4-81-026d (Revised), Procedures for Emission Inventory Preparation, 

Volume IV; Mobile Sources (Mobile Source Procedures), and from the USEPA’s 

NONROAD2005c model released March 21, 2006. 

2.2 Nonroad Mobile Source Emission Estimation Approach 

Nonroad mobile sources, sometimes referred to as off-road mobile, are those sources that can 

move but do not use the highway system. They generally have internal combustion engines. 

Nonroad mobile sources are further divided into NONROAD model sources, railroad 

locomotives, aircraft engines, and commercial marine vessels (CMV). The estimation of 

emissions from nonroad mobile sources, like area sources, involves multiplying an activity level 

by an emission factor. 

The majority of the off-road mobile emissions were estimated by using the USEPA’s 

NONROAD2005c model. Direct emissions are generated with this model. For aircraft engine 

emissions see the detailed description below. For railroad locomotive emissions, emission 

factors were obtained from the Mobile Source Procedures document and the activity level was 

obtained from the various railroad companies. There are no CMV emissions in the Metrolina 

nonattainment area. 

Note that emissions are developed as annual values. In order to produce the average summer day 

emissions, the annual emission values are processed through the SMOKE model which applies 

appropriate temporal adjustments. 
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The Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Appendix D 

North Carolina Reasonable Further Progress Demonstration November 30, 2009 

3. 2002 NONROAD MOBILE SOURCE EMISSION INVENTORY 

Development of emission estimates for nonroad mobile sources is documented in the MACTEC, 

Inc. document titled Documentation of the Base G 2002 Base Year, 2009 and 2018, Emission 

Inventories for VISTAS (Appendix G). 

Nonroad mobile sources are those sources that can move but do not use the highway system. 

Examples include lawn mowers, agricultural equipment, construction equipment, aircraft 

engines, railroad locomotives, powerboats, and commercial marine vessels (CMV). All but the 

aircraft engines, railroad locomotive emissions and commercial marine activity were estimated 

using the USEPA’s off-road mobile model NONROAD2005c, which was released March 21, 

2006. Direct emissions are generated with this model. This version incorporates all the USEPA 

final nonroad mobile engine emission standards, including the recreational and large sparkignition engines rules that were published in the Federal Register in November 2002. Although 

this model is considered to be a final model, an updated version is planned that may incorporate 

revised inputs for the small spark-ignition (SI) (<19 kW) and recreational marine SI categories in 

conjunction with additional promulgated nonroad mobile engine standards. 

Nonroad mobile sources calculated through the NONROAD model are discussed in Section 3.1. 

Aircraft and railroad emissions are discussed in Sections 3.2 and 3.3 respectively. There is no 

CMV activity in the Metrolina area. 

3.1 NONROAD Model Sources 

The nonroad mobile source category includes a diverse collection of equipment such as lawn 

mowers, chain saws, tractors, all terrain vehicles, forklifts and construction equipment. The 

USEPA NONROAD2005c model generates emissions directly and includes more than 80 

different types of equipment. To facilitate analysis and reporting, the USEPA grouped the 

equipment types into ten equipment categories. These include: 

Agricultural equipment Lawn and garden equipment 

Airport ground support equipment Logging equipment 

Commercial equipment Railroad maintenance equipment 

Construction equipment Recreational marine equipment 

Industrial equipment Recreational equipment 
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The Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Appendix D 

North Carolina Reasonable Further Progress Demonstration November 30, 2009 

Additionally, the emissions are broken out by five different engine types. These include: 

2-stroke and 4-stroke spark engines, diesel engines, liquid petroleum gas (LPG) and compressed 

natural gas (CNG) fueled engines. 

One of the default input files was edited to reflect North Carolina specific information. In the 

“SEASON.DAT” file, the region representative of North Carolina was changed from MidAtlantic to Southeast. This was done after an evaluation of the meteorological data in the two 

regions and comparing it to that of Charlotte. Default data was used for the remaining input files 

used in the NONROAD model. 

3.2 Aircraft Engines 

Aircraft engines, like other engines, emit pollutants whenever the engines are in operation. 

However, the only emissions that are of concern for this inventory are the portion of the 

operation that occurs below the mixing layer. This is because the emissions tend to disperse 

whenever the aircraft is above the mixing layer and therefore has little or no effect on ground 

level ozone. 

The aircraft operations of interest are termed the landing and takeoff (LTO) cycle. The cycle 

begins when the aircraft approaches the airport, descending below the mixing layer, lands and 

taxis to the gate. It continues as the aircraft idles at the gate and then taxis back out to the 

runway for the subsequent takeoff and climb out as it heads back to cruising altitudes, above the 

mixing layer. 

Aircraft can be categorized by use into four classifications: commercial, air taxis, general 

aviation and military. Commercial aircraft include those used for scheduled service transporting 

passengers and/or freight. Air taxis, or commuter aircraft, also fly scheduled service carrying 

passengers and/or freight but usually are smaller aircraft and operate on a more limited basis than 

commercial carriers. General aviation includes all other non-military aircraft used for 

recreational flying, personal transportation, and various other activities. Military aircraft cover a 

wide range of sizes, uses and operating missions. The military aircraft are treated as a separate 

classification since the LTO operations reported at the airports groups all military aircraft 

together. 

Emission factors are available for the many aircraft and engine combinations that exist. Factors 

for each aircraft exist for four operating modes in the LTO cycle. Emissions are calculated by 

obtaining data for the number of LTO cycles of the various aircraft at each airport in question, 

multiplying by the appropriate factors, and summing the results for the year under consideration. 
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The Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Appendix D 

North Carolina Reasonable Further Progress Demonstration November 30, 2009 

Development of the 2002 aircraft emissions are described in the MACTEC document titled 

Documentation of the Base G 2002 Base Year, 2009 and 2018 Emission Inventories for VISTAS . 

This document refers back to a document titled “Development of the VISTAS Draft 2002 Mobile 

Source Emission Inventory (February 2004 Version)” prepared by E.H. Pechan & Associates, 

Inc. Both of these documents are included in Appendix G. 

The starting point for development of aircraft emissions estimates is the 1999 National Emission 

Inventory (1999 NEI) prepared by the USEPA. These emissions were grown to appropriate 

values for 2002 using growth factors developed by the USEPA for the Clean Air Interstate Rule 

(CAIR). Along the way there was input by the various States including North Carolina to arrive 

at more accurate emission estimates. 

3.3 Railroad Locomotives 

Railroads are categorized by size (Class I, Class 2) and passenger service (Amtrak and North 

Carolina Department of Transportation (NCDOT) Rail Division). Class I railroads are long haul 

operations, consisting of Norfolk Southern Corporation and CSX Corporation in North Carolina. 

Class II and Class III railroads are short lines, serving localized markets. Passenger service is 

provided by Amtrak and the NCDOT Rail Division in North Carolina. These entities lease 

trackage from Class I railroads. 

Development of railroad emissions is described in the MACTEC document titled Documentation 

of the Base G 2002 Base Year, 2009 and 2018 Emission Inventories for VISTAS. The 

VISTAS/ASIP railroad emission estimates started with 1999 emission estimates developed for 

the USEPA’s 1999 NEI Version 2 as base year estimates for the VISTAS region. Additional 

information is provided in “Development of the VISTAS Draft 2002 Mobile Source Emission 

Inventory (February 2004 Version)” prepared by E.H. Pechan & Associates, Inc. 

Projected emissions for 2002 were developed in two steps as described below. For 1999 to 2001, 

State-level rail fuel consumption was obtained from the Department of Energy, Energy 

Information Administration’s (EIA’s) Fuel Oil and Kerosene Sales. For 2001 to 2002, VISTAS 

applied national growth factors developed from fuel consumption projections in EIA’s Annual 

Energy Outlook. A growth factor of 1.4 was used for locomotives and applied to 1999 emissions 

to first develop 2001 emissions. Table 3.3-1 lists the growth factors used to generate 2002 

emissions. 
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The Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Appendix D 

North Carolina Reasonable Further Progress Demonstration November 30, 2009 

Table 3.3-1 2002 National Rail Transportation Energy Use by Fuel Type (Trillion BTU) 

2001 2002 Growth Factor (GF)

Intercity Rail 

(Electric) 

10.17 10.40 1.0226

Intercity Rail (Diesel) 16.60 16.88 1.0169

Transit Rail (Electric) 46.36 47.40 1.0224

Intercity/Transit Rail Average (SCC 2285002008) 1.0206

Commuter Rail 

(Electric) 16.13 16.49 1.0223 

Commuter Rail 

(Diesel) 26.31 26.76 1.0171 

Commuter Rail Average (SCC 2285002009) 1.0197

Freight Rail 

(Distillate) 

(SCCs 2285002000, 

2285002005, 

2285002006, 

2285002007, 

2285002010)

512.81 492.32 0.9600

Source: Department of Energy, Energy Information Administration, Annual Energy Outlook 2003: Table 34. 

Transportation Sector Energy Use by Fuel Type Within a Mode 

4. 2008 NONROAD MOBILE SOURCE EMISSION INVENTORY 

The subsections that follow describe the projection process used to develop 2008 nonroad mobile 

source projection estimates for sources found in the NONROAD model and those sources 

estimated outside of the model (locomotives and airplanes). 

4.1 Projection of NONROAD Model Sources 

NONROAD model input files were prepared based on the 2002 base year inventory input files 

with appropriate updates for the projection year. Other specific updates for the projection year 

for the NONROAD model sources consist of: 

1. Revise the emission inventory year in the model (as well as various output file naming 

commands) to be reflective of the projection year. 

2. Revise the fuel sulfur content for gasoline and diesel powered equipment. 
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North Carolina Reasonable Further Progress Demonstration November 30, 2009 

3. Implement any local control program changes (national control program changes are 

handled internally within the NONROAD model, so explicit input file changes are not 

required). The only change was to designate North Carolina as a Southeastern state 

rather than a Mid Atlantic state in the NONROAD model. This was done because 

climate conditions in North Carolina are more like the other Southeastern states than 

Mid Atlantic states. 

All equipment population growth and fleet turnover impacts are handled internally within the 

NONROAD model, so that explicit input file changes are not required. Diesel fuel sulfur values 

chosen for the land based diesels were 2500 parts per million (ppm) sulfur in 2002 and 500 ppm 

sulfur in 2008. 

4.2 Projection of Non-NONROAD Model Sources 

For the aircraft and railroad emissions for 2008, the 2009 emissions developed for the VISTAS 

modeling was used. This is conservative since airport activity and railroad freight tonnage were 

on upward trends. 

Using the VISTAS 2002 base year emissions inventory for aircraft and locomotives prepared as 

described earlier in this document, corresponding emission projections for 2009 were developed. 

The projection factors were based on growth and control factors developed by MACTEC. A 

detailed description of the process may be found in the MACTEC document titled 

Documentation of the Base G 2002 Base Year, 2009 and 2018 Emission Inventories for VISTAS. 

Briefly, the methodology relies on growth and control factors developed from inventories used in 

support of the USEPA CAIR rulemakings and then matched to the 2002 inventory. The steps in 

this procedure follow: 

(a) Begin with the 2002 base year emission estimates for aircraft and locomotives. 

(b) Detailed inventory data (both before and after controls) for these same emission sources 

for 1996 and 2020 were obtained from the USEPA's CAIR Technical Support Document. 

Using these data, combined growth and control factors for the period 2002-2009 were 

estimated using straight line interpolation between 1996 and 2020 (for 2009). This is 

done at the State-county-SCC-pollutant level of detail. 

(c) The USEPA growth and control data are matched against the 2002 VISTAS base year 

data using State-county-SCC-pollutant as the match key. Ideally, there would be a 

one-to-one match and the process would end at this point. Unfortunately, actual match 
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The Charlotte-Gastonia-Rock Hill, NC-SC 8-Hour Ozone Appendix D 

North Carolina Reasonable Further Progress Demonstration November 30, 2009 

results were not always ideal, so additional matching criteria were required. For 

subsequent reference, this initial (highest resolution) matching criterion is denoted as the 

“CAIR-Primary” criterion. 

(d) A second matching criterion is applied that utilizes a similar, but higher-level SCC (lower 

resolution) matching approach. For example, SCC 2275020000 (commercial aircraft) in 

the 2002 base year inventory data would be matched with SCC 2275000000 (all aircraft) 

in the CAIR data. This criterion is applied to records in the 2002 base year emissions file 

that are not matched using the “CAIR-Primary” criterion, and is also performed at the 

State-county-SCC-pollutant level of detail. For subsequent reference, this is denoted as 

the “CAIR-Secondary” criterion. At the end of this process a number of unmatched 

records continued to remain, so a third level matching criterion was required. 

(e) In the third matching step, the most frequently used SCC in the USEPA CAIR files for 

each of the aircraft and locomotive sectors is averaged at the State level to produce a 

“default” State and pollutant-specific growth and control factor for the sector. The 

resulting factor is used as a “default” growth factor for all unmatched 

county-SCC-pollutant level data in each State. In effect, State-specific growth data are 

applied to county level data for which an explicit match between the VISTAS 2002 base 

year data and the USEPA CAIR data could not be developed. The default growth and 

control SCCs are 2275020000 (commercial aircraft) for the aircraft sector and 

2285002000 (railroad equipment diesel total) for the locomotive sector. Matches made 

using this criterion are denoted as “CAIR-Tertiary” matches. 

 (f) The CAIR matching criteria were overridden for any record for which States provided 

local growth data. Only North Carolina provided these forecasts, as North Carolina has 

provided specific growth factors for airport emissions in four counties. Because the 

provided data were based on forecasted changes in landings and takeoffs at major North 

Carolina airports, the factors were applied only to commercial (SCC 2275020000) and air 

taxi (SCC 2275060000) emissions. Emissions forecasts for military and general aviation 

aircraft operations, as well as all aircraft operations in counties other than the four 

identified in the North Carolina growth factor submission, continued to utilize the growth 

factors developed according to steps (b) through (f) above. The locally generated growth 

factor (2002 to 2009) applied in Mecklenburg County was 1.15.