Appendix B 

Emission Inventory Documentation 
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Appendix B.1

Point Source Emissions 

Inventory Documentation
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Point Source Emissions Inventory i

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.1

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TABLE OF CONTENTS

1.0 INTRODUCTION AND SCOPE .................................................................................... 1-1

2.0 OVERALL METHODOLOGY....................................................................................... 2-1

2.1 Source Identification.................................................................................................... 2-1

2.2 Emission Estimation Approach.................................................................................... 2-1

3.0 QUALITY ASSURANCE............................................................................................... 3-1

4.0 TOTAL POINT SOURCES EMISSIONS ...................................................................... 4-1

4.1 Summary of Point Source Emissions........................................................................... 4-1

4.2 Durham County Plant Emissions................................................................................. 4-2

4.3 Wake County Plant Emissions..................................................................................... 4-3

4.4 Forsyth County Plant Emissions.................................................................................. 4-4

4.5 Mecklenburg County Plant Emissions......................................................................... 4-5

LIST OF TABLES

Table 4.1 Summary of Point Source CO Emissions.................................................................... 4-1

Table 4.2 Summary of Plant CO Emissions for Durham County (tons/day)............................... 4-2

Table 4.3 Summary of Plant CO Emissions for Wake County (tons/day) .................................. 4-3

Table 4.4 Summary of Plant CO Emissions for Forsyth County (tons/day) ............................... 4-4

Table 4.5 Summary of Plant CO Emissions for Mecklenburg County (tons/day) ...................... 4-5
Point Source Emissions Inventory ii

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Point Source Emissions Inventory 1-1

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1.0 INTRODUCTION AND SCOPE

The point source inventory consists of emissions from individual facilities. Primarily, these are 

industrial or commercial facilities that require permits issued by the North Carolina Division of 

Air Quality (NCDAQ), the Forsyth County Environmental Affairs Department and Mecklenburg 

Air Quality Section under the Land Use & Environmental Services Agency (LUESA) to emit air 

pollutants. 

The emissions in this report are based on the 2010 National Emissions Inventory (NEI) for

Durham and Wake Counties while Forsyth and Mecklenburg provided emissions to NCDAQ for

this report. Most point source emissions of carbon monoxide (CO) are associated with industrial, 

utility or large institutional boilers. Other CO sources which may be treated as point sources are 

industrial process combustion (such as kilns) and large stationary internal combustion engines.
Point Source Emissions Inventory 2-1

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2.0 OVERALL METHODOLOGY

All permitted sources are required to report emissions annually in the case of larger sources 

while every five years in the case of smaller sources. The emissions data obtained for this report 

were pulled from files maintained by the NCDAQ, Forsyth County Environmental Affairs 

Department and Mecklenburg County Air Quality. This 2010 data also represents submissions 

to the U. S. Environmental Protection Agency (USEPA).

2.1 Source Identification

All facilities required to have permits to operate sources of air pollution are known and are 

required to submit emission inventories. The local programs in Forsyth and Mecklenburg 

counties provided the NCDAQ with county specific point source CO inventory data for 2010.

2.2 Emission Estimation Approach

The emission inventory information reported to the State was transferred to the Integrated Build 

Environment for Application Management (IBEAM) program by both State employees. This 

program helps assure that certain required data elements are not omitted. It also performs 

calculations, thereby minimizing the occurrence of errors. Depending on the particular process 

and facility, emissions may be calculated by various methods. In many cases, emissions are 

estimated using emission factors published in USEPA’s AP-42, Compilation of Air Pollutant 

Emission Factors. For some processes, a mass balance calculation can be employed to estimate 

emissions or direct continuous emissions monitoring (CEM) data can be reported. In a relatively 

few cases, locally produced emission factors may be used. For any particular case, it is possible 

to determine how emissions were calculated by going to the NEI. This material may be 

downloaded from the following USEPA website:

http://www.epa.gov/ttn/chief/net/2008inventory.html.

Annual emissions are reported in the NEI and maintained by NCDAQ, Mecklenburg County Air 

Quality, and Forsyth County Environmental Affairs Department. There is also data for operating 

hours per day and per year, days per week, and the percentage of emissions occurring in the 

winter quarter. Using this information, peak CO season daily emissions were calculated. 

Mecklenburg County and Forsyth County Air Quality provided NCDAQ with 2010 annual 

emissions. For Durham and Wake Counties, the 2010 inventory was obtained from the NCDAQ 

database.
Point Source Emissions Inventory 3-1

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3.0 QUALITY ASSURANCE

The 2010 emission inventory has undergone a number of quality assurance checks to meet the 

standards for the National Emissions Inventory. The IBEAM program helps insure that 

important data elements are present and calculates some of the data fields, which reduces the 

number of errors in the data. In addition, since the State began collecting annual fees for 

emissions from Title V sources, both the State and the facilities ensure that the emissions that are 

reported annually are accurate. 

Calculations of emissions from publicly-owned treatment works (POTWs) and landfills were 

carefully checked for accuracy. Segment level emissions were totaled to ensure they equaled the 

totals for plant level emissions.
Point Source Emissions Inventory 4-1

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4.0 TOTAL POINT SOURCES EMISSIONS

Summaries of the point source emissions data are listed in the following tables. All emissions 

are in tons per winter day.

Table 4.1 Summary of Point Source Emissions

Table 4.2 Summaries of Plant Emissions for Durham County

Table 4.3 Summaries of Plant Emissions for Wake County

Table 4.4 Summaries of Plant Emissions for Forsyth County

Table 4.5 Summaries of Plant Emissions for Mecklenburg County

4.1 Summary of Point Source Emissions

Table 4.1 Summary of Point Source CO Emissions

COUNTY 2010

Raleigh/Durham Maintenance Area 

Durham 0.97

Wake 1.17

TOTAL 2.14

Winston-Salem Maintenance Area

Forsyth 2.22

Charlotte Maintenance Area

Mecklenburg 2.39
Point Source Emissions Inventory 4-2

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4.2 Durham County Plant Emissions

Table 4.2 Summary of Plant CO Emissions for Durham County (tons/day)

Facility ID Location Name NAICS/SIC 2010

3200308 AW North Carolina, Inc. 33635 0.03

3200270 Carolina Sunrock LLC - Muirhead Distribution Center 32732 0.10

3200296 City of Durham Sanitary Landfill 562212 0.07

3200299 Cree Inc - Silicon Dr 334413 0.09

3200144 Duke University 61131 0.36

3200143 Durham Regional Hospital 62211 0.01

3200289 Eisai Inc 325412 0.02

3200295 Federal Medical Center 62211 0.01

3200214 Freudenberg Nonwovens Group 31323 0.03

3200041 G E Aviation - Durham Engine Facility 336412 0.01

3200017 GlaxoSmithKline 325412 0.06

3200055 IBM Corporation 541512 0.02

3200375 MP Durham, LLC 221119 0.02

3200158 NIEHS 92119 0.05

3200251 North Carolina Central University 61131 0.01

3200257 PBM Graphics - A Consolidated Graphics Company 323110 0.01

3200189 SCM Metal Products, Inc. 331423 0.01

3200234 South Durham Water Reclamation Facility 92411 0.03

3200184 The Hamner Institutes for Health Sciences 54171 0.01

3200215 Valassis Communications 323111 0.01

3200154 Veterans Affairs Medical Hospital 62211 0.01

Plant Total 0.97
Point Source Emissions Inventory 4-3

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4.3 Wake County Plant Emissions

Table 4.3 Summary of Plant CO Emissions for Wake County (tons/day)

Facility ID Location Name NAICS/SIC 2010

9200408 Ajinomoto AminoScience, LLC 325414 0.05

9200504 Austin Quality Foods, Inc. 311821 0.02

9200398 Barnhill Contracting Company 324121 0.02

9200566 Biogen Idec US Limited Partnership 325414 0.02

9200208 Cargill Inc - Raleigh 311222 0.06

9200457 Carolina Sunrock, LLC - RDU Distribution Center 324121 0.06

9200599 CP&L - Harris Nuclear Plant 221113 0.01

9200333 Dorothea Dix Campus 62221 0.05

9200550 Fred Smith Company - Holly Springs Asphalt Plant 324121 0.01

9200752 Fred Smith Company - Knightdale Asphalt Plant 324121 0.05

9200259 Fred Smith Company - Westgate plant 324121 0.04

9200570 FUJIFILM Diosynth Biotechnologies U.S.A., Inc. 325414 0.01

9200314 Gelder & Associates Incorporated 324121 0.05

9200443 GSK, Inc. 325412 0.02

9200349 Mallinckrodt LLC 325411 0.04

9200266 Meredith College 61131 0.01

9200592 Metokote Corporation Plant 23 332812 0.01

9200378 Motiva Enterprises LLC 42471 0.01

9200291 NC DOA Central Heating Plant 22133 0.03

9200003 NC DOC - Central Prison 92214 0.01

9200290 NCSU Central Heat Plant 61131 0.14

9200593 North Wake County Landfill Facility 562212 0.06

9200639 PNG Clayton Compressor Station 22121 0.03

9200377 Potters Industries L.L.C. 327215 0.09

9200620 Public Service Company of NC Inc 221119 0.01

9200621 Raleigh-Durham Airport Authority 488119 0.01

9200338 Rea Contracting (Garner) 324121 0.03

9200339 Rea Contracting (Gresham Lake) 324121 0.07

9200341 Rea Contracting (West Raleigh) 324121 0.06

9200343 Rex Healthcare 62211 0.02

9200761 T R Vernal Paving, Inc. 324121 0.02

9200230 WakeMed 62211 0.03

9200617 WakeMed Cary Hospital 62211 0.01

Plant Total 1.17
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4.4 Forsyth County Plant Emissions

Table 4.4 Summary of Plant CO Emissions for Forsyth County (tons/day)

Facility ID Location Name NAICS/SIC 2010

00003 Wake Forest University 61131 0.02

00082 Microfibres, Inc. 3133 0.02

00131 HANES DYE AND FINISHING CO. 313311 0.04

00201 North Carolina Baptist Hospitals, Inc. 6221 0.05

00339 R.J. Reynolds Tobacco Company (Whitaker Park) 31222 0.12

00363 Hanesbrands, Inc. 315111 0.01

00449 Smurfit-Stone Container Corporation 322211 0.01

00460 HIGHLANDS INDUSTRIES 3133 0.01

00464 Larco Construction 324121 0.09

00465 Oracle Flexible Packaging-Phoenix (200) 331315 0.04

00466 Oracle Flexible Packaging-Liberty (604) 322225 0.02

00473 Winston-Salem State University 611310 0.01

00682 Rexam Beverage Can Company 332431 0.02

00732 Corn Products International, Inc. 311221 1.04

00735 Vulcan Materials - East Forsyth Quarry 21239 0.01

00745 R.J. Reynolds Tobacco Co. (Tobaccoville) 31222 0.08

00755 FORSYTH MEMORIAL HOSPITAL 622110 0.03

00784 Deere-Hitachi Construction Machinery Corp. 33312 0.01

00817 ARCHIE ELLEDGE WWTP 221320 0.01

00872 CRES TOBACCO COMPANY 312210 0.01

00884 Salem Energy Systems, L.L.C. 22111 0.12

00910 Cloverleaf Mixing, Inc. 324121 0.02

00914 Piedmont Landfill and Recycling Center 562212 0.30

00990 ARTISTREE 321999 0.01

01062 APAC-Atlantic, Inc., Thompson-Arthur Division, Plant 

#5 Winston Salem

324121 0.02

00878 Muddy Creek Wastewater Treatment Plant 221320 0.08

Plant Total 2.22
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4.5 Mecklenburg County Plant Emissions

Table 4.5 Summary of Plant CO Emissions for Mecklenburg County (tons/day)

Facility ID Location Name NAICS/SIC 2010

0756 ALSCO, Inc. 7213 0.01

0322 Associated Asphalt Charlotte, LLC 5032 0.01

0067 Barnhardt Manufacturing Company 2269 0.01

0909 Barrday Corporation 2221 0.17

0710 C & M Recycling, Inc. 3272 0.08

0069 Cargill, Inc. 2079 0.01

0289 Carolinas Medical Center 8062 0.05

0109 Carolinas Medical Center - Pineville 8062 0.01

0626 Charlotte Pipe & Foundry Company, Inc. 3321 0.01

0020 C-MUD: Franklin Water Treatment Plant 4941 0.01

0937 C-MUD: Lee S. Dukes, Jr. Water Plant 4941 0.02

0764 C-MUD: McAlpine Creek Wastewater Treatment Plant 4953 0.03

0222 D.H. Griffin Infrastructure, LLC 3295 0.02

0004 Davidson College 8221 0.01

0595 Emerald Carolina Chemical, LLC 2821 0.02

0054 General Steel Drum, LLC 3412 0.01

0058 Huntersville Hardwoods 2426 0.02

0590 IGM Resins Charlotte, Inc 2869 0.01

0588 Industrial Container Services - NC, LLC (Matthews) 7699 0.01

0381 International Paper Company 2653 1.62

0999 J.T. Russell & Sons, Inc. 2951 0.01

0087 Lincoln Harris, LLC 6099 0.01

0148 Mallard Creek Polymers, Inc. 2821 0.01

0132 Metrolina Greenhouses, Inc. 0181 0.03

0201 Novant Healthcare's Presbyterian Hospital 8062 0.04

0936 Presbyterian Hospital - Matthews 8069 0.03

0785 Presbyterian Hospital Huntersville 8062 0.01

0134 Rea Contracting (069 Arrowood) 2951 0.02

0668 Red Clay Industries 1499 0.01

0108 RR Donnelley 2752 0.01

0003 SteelFab, Inc. 3441 0.01

0215 University of North Carolina at Charlotte 8221 0.03

0216 US Airways, Four (4) Site Locations 4581 0.03

Plant Total 2.39
Appendix B.2 

Area Source Emissions 

Inventory Documentation 
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TABLE OF CONTENTS 

1.0 INTRODUCTION AND SCOPE ......................................................................................... 1-1

2.0 OVERALL METHODOLOGY ............................................................................................ 2-1

2.1 SOURCE CATEGORY IDENTIFICATION ............................................................... 2-1

2.2 EMISSION ESTIMATION APPROACH .................................................................... 2-1

3.0 QUALITY ASSURANCE MEASURES .............................................................................. 3-1

4.0 DISCUSSION OF AREA SOURCE CATEGORIES .......................................................... 4-1

4.1 MAN MADE AREA SOURCES .................................................................................. 4-1

4.1.1 Forest Fires............................................................................................................. 4-1

4.1.2 Structure Fires ........................................................................................................ 4-2

4.1.3 Vehicle Fires .......................................................................................................... 4-4

4.1.4 Charbroiling ........................................................................................................... 4-6

4.1.5 Open Burning – Municipal Solid Waste and Yard Waste ..................................... 4-7

4.2 SMALL STATIONARY COMBUSTION AREA SOURCES .................................... 4-8

4.2.1 Residential Combustion Sources ........................................................................... 4-9

4.2.2 Commercial and Industrial Combustion Sources ................................................ 4-12

5.0 SUMMARY OF AREA SOURCE EMISSIONS ............................................................... 4-18

LIST OF TABLES 

Table 2.2-1 County Population ................................................................................................... 2-4

Table 4.1.1-1 2007 Acres of Land Burned by Fires ................................................................... 4-1

Table 4.1.1-2 CO Emissions (tpd) from Forest Fires .................................................................. 4-2

Table 4.1.2-1 2009 County Employment .................................................................................... 4-3

Table 4.1.2-2 CO Emissions (tpd) from Structure Fires ............................................................. 4-4

Table 4.1.3-1 2010 Vehicle Miles Traveled ............................................................................... 4-5

Table 4.1.3-2 CO Emissions (tpd) from Vehicle Fires ............................................................... 4-5

Table 4.1.4-1 Charbroiling Emission Factors ............................................................................. 4-6

Table 4.1.4-2 CO Emissions (tpd) from Charbroiling ................................................................ 4-6

Table 4.1.5-1 CO Emissions (tpd) from Open Burning .............................................................. 4-8

Table 4.2-1 2007 Fuel Use in North Carolina............................................................................. 4-9

Table 4.2-2 Residential Combustion CO Emission Factors ....................................................... 4-9

Table 4.2.1-1 Residential Fuel Type ......................................................................................... 4-10

Area Source Emissions Inventory i 

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Table 4.2.1-2 Population Growth Factors for Residential Combustion.................................... 4-11

Table 4.2.1-3 CO Emissions (tpd) for Residential Combustion ............................................... 4-12

Table 4.2.2-1 Commercial and Industrial Combustion Employment ....................................... 4-12

Table 4.2.2-2 Commerical/Industrial Combustion CO Emission Factors ................................ 4-14

Table 4.2.2-3 Growth Factors for Commercial and Industrial Combustion ............................. 4-15

Table 4.2.2-4 CO Emissions (tpd) for Commercial Combustion ............................................. 4-15

Table 4.2.2-5 CO Emissions (tpd) for Industrial Combustion .................................................. 4-16

Table 4.2.2-6 Point Source Commercial Combustion Emissions (tpd) .................................... 4-16

Table 4.2.2-7 Point Source Industrial Combustion Emissions (tpd) ........................................ 4-17

Table 5-1 Total Area Source CO Emissions (tpd) .................................................................... 4-18

 

Area Source Emissions Inventory ii 

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Area Source Emissions Inventory iii 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

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List of Acronyms 

Acronym Definition 

CO Carbon Monoxide 

EIIP Emissions Inventory Improvement Program 

ERTAC Eastern Regional Technical Advisory Group 

LPG Liquid Petroleum Gas 

NAICS North American Industry Classification System 

NCDAQ North Carolina Division of Air Quality 

NCDFR North Carolina Division of Forest Resources 

NCDOT North Carolina Department of Transportation 

NCOSBM North Carolina Office of State and Budget Management 

NCSU North Carolina State University 

NG Natural Gas 

QAPP Quality Assurance Project Plan 

SIC Standard Industrial Classification 

USCBP U.S Census Bureau, County Business Patterns 

USEPA U.S. Environmental Protection Agency 

USFA U.S. Fire Administration 

VMT Vehicle Miles Traveled 

 
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Area Source Emissions Inventory 1-1 

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1.0 INTRODUCTION AND SCOPE 

Area sources represent a collection of many small, unidentified points of air pollution emissions 

within a specified geographical area, emitting less than the minimum level prescribed for point 

sources. Because these sources are too small and/or too numerous to be surveyed and 

characterized individually, all area source activities are collectively estimated. The county is the 

geographic area for which emissions from area sources are compiled, primarily because counties 

are the smallest areas for which data used for estimating emissions is readily available. 

The area source emissions inventory has been developed in order to meet the requirement of the 

carbon monoxide (CO) National Ambient Air Quality Standard, as part of the process of 

demonstrating continued maintenance for the CO National Ambient Air Quality Standard. 

The North Carolina maintenance areas for CO are comprised of Durham, Forsyth, Mecklenburg 

and Wake Counties. Most of the activity data needed to estimate 2010 emissions was not 

available, therefore, the 2007 emissions inventory that has been developed for other purposes 

was grown to the 2010 base year. All emissions are calculated on a ton per winter day basis. 
Area Source Emissions Inventory 2-1 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

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2.0 OVERALL METHODOLOGY 

2.1 SOURCE CATEGORY IDENTIFICATION 

The area source categories were identified from two US Environmental Protection Agency 

(USEPA) guidance documents: EPA-450/4-91-016, Procedures for the Preparation of Emission 

Inventories of Carbon Monoxide and Precursors of Ozone, Vol. 1, from this point on this 

document will be referred to as the Procedures document, and the Emissions Inventory 

Improvement Program (EIIP) Technical Reports, Vol. 3, Area Sources, from this point on this 

document will be referred to as EIIP Tech. Report. 

2.2 EMISSION ESTIMATION APPROACH 

Area source emissions are estimated by multiplying an emission factor by some known indicator 

of collective activity for each source category within the inventory area. An indicator is any 

parameter associated with the activity level of a source that can be correlated with the air 

pollutant emissions from that source, such as production, number of employees, or population. 

In general, one of the following emissions estimation approaches is used to calculate the area 

source emissions: per capita emission factors, employment-related emission factors, commodity 

consumption-related emission factors and level of activity based emission factors. The emission 

factors used were obtained from the EIIP Tech. Report, the USEPA’s AP-42 Compilation of Air 

Pollutant Emission Factors, 5th Edition, referred to as AP-42 or the emissions methods developed 

by E.H. Pechan & Associates, Inc. (Pechan) for the USEPA for the 2008 National Emissions 

Inventory. The methods Pechan developed were based upon the emission factor development 

work conducted by the Eastern Regional Technical Advisory Group (ERTAC) in conjunction 

with the USEPA and states. 

As previously stated, the area source emissions were calculated based on the emissions methods 

developed by Pechan or the USEPA’s EIIP Tech. Report and AP-42. The majority of the area 

source categories were calculated with the methods outlined by Pechan because they incorporate 

the most recent emission factors and activity data available. The remaining area source 

categories were calculated using the USEPA’s EIIP Tech. Report and AP-42 because these 

categories were not included as part of the area source categories Pechan updated. The following 

outlines the area source categories calculated using the emissions methods developed by Pechan: 

• Residential Combustion

• Commercial Combustion

• Industrial Combustion
Area Source Emissions Inventory 2-2 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

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• Charbroiling

• Open Burning.

The remaining area source categories were calculated using the EIIP Tech. Report and AP-42

are: 

• Structure Fires 

• Vehicle Fires 

• Forest Fires. 

There are several methods for estimating the activity level for a specific area source category. 

Some of these methods include treating area sources as point sources, surveying local activity 

levels, apportioning national or statewide activity totals to local inventory areas, or using 

population and employment data. All of these methods were employed to determine the activity 

data needed for the various area source categories. 

For certain categories, there can be overlap between the point sources and the area sources, 

which can lead to double counting of emissions. To avoid double counting of emissions, point 

source emissions were identified so they could be subtracted from the applicable area source 

emissions. 

There are a number of categories where emissions were calculated with emission factors based 

on employment. These emission factors were developed by the USEPA when employment 

reports were organized by Standard Industrial Classification (SIC) code. Since 1997 

employment statistics are organized by the North American Industry Classification System 

(NAICS). 

The employment for the combustion source categories were obtained from the on-line US 

Census Bureau, County Business Patterns (USCBP) for the various NAICS codes at the county 

level for North Carolina. In addition to having employment values (or employment ranges due 

to confidentiality rules) by NAICS, the USCBP breaks down the number of facilities by 

employment categories. The employment categories are 1 – 4, 5 – 9, 10 – 19, 20 – 49, 50 – 99, 

100 – 249, 250 – 499, 500 – 999, >1000 employees. To account for point sources, it was 

assumed that facilities with 100 employees or greater were point sources and were not 

considered in the calculations. 

When a NAICS category gave a number of employees and there were no establishments with 

100 employees or greater, then the value was used, however, in most cases the USCBP gave a 

range of total employees in the county instead of the actual number. When this occurred, facility 

sizes were considered and the mid-range of employees was assumed, in accordance with the EIIP 
Area Source Emissions Inventory 2-3 

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Tech. Report. For example, a NAICS category for a county had a range of employment of 100-

249 with two establishments with 1-4 employees, one with 20-49 employees, and one with 100-

249 employees. Assuming 3 to be the mid-range of 1-4 and 35 to be the mid-range of 20-49, the 

employment used for the area source calculation was estimated as: 

(2 x 3) + (1 x 35) = 41 employees 

The larger establishment was assumed to be a point source and not taken into consideration for 

the area source calculation. 

If a total number of employees was provided and there were establishments with 100 employees 

or greater, then the mid-range of the smaller facilities were used as described above. The 

estimated employment was compared to the value given to ensure that remainder would account 

for the large establishment. In cases where the remainder would not be enough employment to 

account for the larger establishment, the area source employment was adjusted down. For 

example, a NAICS category had 250 employees with one establishment with 20–49 employees 

(mid-range 35), two establishments with 50–99 employees (mid-range 75), and one 

establishment with 100–249 employees. The employment estimated for the area source and the 

remainder employment was estimated as: 

 (1 x 35) + (2 x 75) = 185 employees 

 250 – 185 = 65 employees 

The remainder of 65 employees is not enough to account for an establishment of 100–249 

employees. Therefore, the area source employment was adjusted down by 35 so that there were 

100 employees remaining to account for the large establishment. 

Additionally, many of the categories for the area source emissions use total county population or 

the rural portion of the county population for the activity data. In order to calculate the 

emissions for these categories, the 2010 population was obtained from the North Carolina Office 

of State and Budget Management (NCOSBM). Since the 2010 population was available, 

categories that have population as the activity data were not grown from 2007 but were 

calculated for 2010. The rural portion of the total county population was determined by applying 

a rural percentage to the total county population. The rural percentage was determined from the 

latest census data available, the 2010 census. 
Area Source Emissions Inventory 2-4 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

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Table 2.2-1 contains the total county population for the CO maintenance areas. 

Table 2.2-1 County Population 

County 2010 Population

Durham 267,587 

Forsyth 350,670 

Mecklenburg 919,628 

Wake 900,993 

Table 2.2-2 shows the rural percentage of each county and the corresponding rural population. 

Table 2.2-2 County Rural Population 

County Percentage of 

Rural Population

2010 Rural 

Population 

Durham 5.63 15,065

Forsyth 7.35 25,774

Mecklenburg 1.07 9,840

Wake 6.10 54,961

 

Certain emission categories were adjusted for factors such as control efficiency, rule 

effectiveness and rule penetration. These are discussed in the description of the area source 

categories where they are applicable. 
Area Source Emissions Inventory 3-1 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

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3.0 QUALITY ASSURANCE MEASURES 

The first step in the quality assurance process is to develop a list of area sources in the 

maintenance areas. The Procedures document and the EIIP Tech. Report were the primary 

references used in preparing this list for the emissions inventory. To ensure the accuracy of the 

emissions estimates, the area source emissions inventory team followed the quality assurance 

measures as outlined in the NCDAQ Emissions Inventory Quality Assurance Project Plan 

(QAPP). 

Under the direction of the quality assurance coordinator, emission sources whose contribution 

was either at the high or low end of the range of estimates were scrutinized more closely for 

reasonableness. The accuracy was addressed by performing independent checks of the emissions 

calculations, verifying the activity data and emission factors as well as plotting all of the area 

source categories vs. pollutants. 
Area Source Emissions Inventory 4-1 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

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4.0 DISCUSSION OF AREA SOURCE CATEGORIES 

There are two major area source categories, man made area sources and small stationary 

combustion sources, that produce CO emissions. Sections 4.1 and 4.2 address each of these 

categories and include subsections that correspond to the category. The objective of each 

subsection is to describe the emission estimation and projection procedures. 

4.1 MAN MADE AREA SOURCES 

Man made area sources include forest fires, which encompasses wildfires and prescribed burns, 

structure fires, vehicle fires, charbroiling and open burning. The methodology used to calculate 

the emissions from these sources are described in detail in each subsection. 

4.1.1 Forest Fires 

There are two types of forest fires; wild fires, which are accidental or felonious fires and 

prescribed burns, which are intentionally set for the purpose of forest and/or grassland 

management practice. The number of acres burned in 2007 for each of these categories was 

obtained from the North Carolina Division of Forest Resources (NCDFR) and are listed in 

Table 4.1.1-1. The U.S. Forest Service and U.S. Fish and Wildlife Service also perform 

prescribed burns in North Carolina but none are in the CO maintenance areas. 

Table 4.1.1-1 2007 Acres of Land Burned by Fires 

County Wildfires 

Acres 

Prescribed 

Fires Acres 

Total Acres 

Burned 

Durham 83 531 614 

Forsyth 28 0 28 

Mecklenburg 62 24 86 

Wake 121 665 786 

The makeup of the plant life burned in each fire can vary from woodland to brush to grassland. 

The emission factors for the southern region of the United States were obtained from AP-42, 

Table 13.1-2, were used to estimate the emissions from forest burns. The fuel loading was also 

obtained from the AP-42. The emission factors are 67 tons CO per acre burned for prescribed 

fires and 140 tons of CO per acre burned for wildfires. 

The NCDFR was not able to provide seasonal numbers, so the daily emissions are estimated by 

dividing by 365 days per year. It is assumed that the number of acres burned remains relatively 
Area Source Emissions Inventory 4-2 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

constant; therefore, the 2007 acres will be used to determine the 2010 fire emissions. The 

emissions were calculated using equation 4.1.1-1. 

EM = no. acres burned *fuel loading* EF * (1 year/365 days) 4.1.1-1 

where: 

EM = total daily emissions in tons/day 

Fuel loading = 9 tons/acre 

EF = emission factors, EFPrescribed Fires = 67 tons/acre burned and EFWildfires = 140 tons/acres burned 

The CO emission estimates, in tons/day (tpd), from forest fires for the CO maintenance areas are 

listed in Table 4.1.1-2. 

Table 4.1.1-2 CO Emissions (tpd) from Forest Fires 

County Prescribed Fires 

Emissions 

Wildfires 

Emissions 

Total Forest Fires 

CO Emissions 

Durham 0.44 0.14 0.58 

Forsyth 0.00 0.05 0.05 

Mecklenburg 0.02 0.11 0.13 

Wake 0.55 0.21 0.76 

4.1.2 Structure Fires 

The U.S. Fire Administration (USFA) maintains statistics on the number of fires per county. The 

number of fires per county for 2009 was obtained from the USFA fire statistics website. The 

structure fires category is based on both residential and non-residential structures. A fires per 

person factor was calculated for the residential structures based on the national number of 

residential fires divided by the national population for 2009. The fires per person factor for 

residential structures 0.0012 fires/person. A fires per person factor was also calculated for the 

non-residential structures based on the national number of non-residential fires divided by the 

national employment for 2009. The fires per employee factor for non-residential structures 

0.00078 fires/employee. 

The 2010 county population was obtained from the North Carolina State Demographics and the 

2009 county employment was obtained from the US Census Bureau, County Business Patterns. 

The 2009 county employment is the latest data available. The 2009 employment data is not 

expected to be significantly different from 2010. The fires per person factor was applied to the 

2010 county population to determine the number of residential structure fires per county. 
Area Source Emissions Inventory 4-3 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

Additionally, the fires per employee factor was applied to the 2009 total county employment to 

determine the non-residential structure fires per county. To determine the total emissions from 

structure fires, the sum of the residential and non-residential structure fires were totaled for each 

county. 

The 2010 county population, shown in Table 2.2-1, was used to estimate the emissions for the 

residential portion and the 2009 county employment, shown in Table 4.3.2-1, was used to 

estimate the emissions for the non-residential portion. The estimates of the residential and 

nonresidential portions were summed to obtain the total emissions for the structure fires. 

Table 4.1.2-1 2009 County Employment 

County Employment 

Durham 163,018 

Forsyth 163,419 

Mecklenburg 531,089 

Wake 375,345 

The fuel loading factor, 1.15 tons of material burned per structural fire, was obtained from the 

EIIP Tech. Report, Chapter 18. The CO emission factor was also obtained from the EIIP Tech. 

Report, Table 18.4-1. The emission factor is 60 lbs of CO per ton burned. 

According to the EIIP Tech. Report emissions from this source category occur 365 days per year 

and there is no seasonal adjustment required. 

The structure fires emissions were calculated using equation 4.1.2-1. 

EM = [(cnty pop * FPP) + (cnty empl * FPE)] * CF * EF * (1 year/365 days) 

 2,000 lbs/tons 4.1.2-1 

where: 

EM = total daily emissions in tons/day 

 FPP = fires per person, 0.0012 fires/person 

 FPE = fires per employee, 0.00078 fires/employee 

 CF = conversion factor, 1.15 tons burned/structure fire 

 EF = emission factors, CO = 60 lbs/ton burned/year 

The CO emission estimates, in tons/day, from structure fires are listed in Tables 4.1.2-2. 
Area Source Emissions Inventory 4-4 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

Table 4.1.2-2 CO Emissions (tpd) from Structure Fires 

County CO Emissions 

Durham 0.01 

Forsyth 0.01 

Mecklenburg 0.04 

Wake 0.03 

4.1.3 Vehicle Fires 

Vehicle fire emissions within the maintenance areas are estimated by considering the estimated 

number vehicles burned in the maintenance counties, the amount of material burned (the fuel 

loading) in a vehicle fire, and the emission factors for the open burning of automobile 

components. The method used to calculate the CO emissions from vehicle fires was obtained 

from the EIIP Tech. Report, Vehicle Fires. 

The estimated number of vehicle fires per county was determined by apportioning a national fire 

statistic to the county level using vehicle miles traveled (VMT). The USFA maintains nationallevel fire statistics. The latest available data for vehicle fires are for the year 2007. The number 

of vehicle fires nationwide in 2007 was 258,000. The number of national vehicle fires was 

apportioned to a state-level using a ratio of the 2007 NC VMT to 2007 U.S. VMT (249,698,650 

miles/3,029,822 x 106 miles). The number of statewide vehicle fires was then apportioned to a 

county level based on the ratio of the 2010 county-level VMT to the 2010 NC VMT. The 

nationwide VMT was obtained from the U.S. Department of Transportation, Federal Highway 

Administration website. The statewide and county VMT is Highway Performance Monitoring 

System data that was received from the NCDOT. 

The CO emission factor was also obtained from the EIIP Tech. Report, Vehicle Fires. The CO 

emission factor is 125 lbs of CO per ton burned. This source category can occur 365 days per 

year and there is no seasonal adjustment required. 

The above methodology was employed to calculate the vehicle fire emissions per county. For 

2010, the VMT for the CO maintenance areas are listed in Table 4.1.3-1. 

 
Area Source Emissions Inventory 4-5 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

Table 4.1.3-1 2010 Vehicle Miles Traveled 

County Vehicle Miles 

Traveled 

Durham 3,290,264,636 

Forsyth 3,916,801,397 

Mecklenburg 11,820,712,140 

Wake 10,469,417,080 

Statewide 102,384,967,632 

The amount of vehicle material burned in a vehicle fire was estimated by assuming that an 

average vehicle has 500 lbs. of components (0.25 tons) that can burn in a fire, based on a 3,700 

lbs. average vehicle weight (CARB, 1995). 

The emissions for 2010 were calculated using equation 4.1.3-1. 

EM = US veh fires * CF * EF * (NC VMT2007/US VMT2007)*(cnty VMT2010/NC VMT2010)*(1 yr/365 dys) 

 2,000 lbs/tons 4.1.3-1 

where: 

EM = total daily emissions in tons/day 

 CF = conversion factor, 0.25 tons burned/vehicle fire 

 EF = emission factors, CO = 125 lbs/ton burned year 

 

The CO emission estimates from vehicle fires are listed in Table 4.1.3-2. 

Table 4.1.3-2 CO Emissions (tpd) from Vehicle Fires 

County CO Emissions 

Durham 0.01 

Forsyth 0.01 

Mecklenburg 0.04 

Wake 0.04 
Area Source Emissions Inventory 4-6 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

4.1.4 Charbroiling 

Charbroiling is one of the categories the USEPA revised for the 2008 National Emissions 

Inventory (NEI). The emission factors were developed and reviewed by an ERTAC advisory 

panel composed of state and USEPA personnel. The emission factors were generated by taking 

the 2002 NEI emissions and dividing by the 2002 population to develop per capita emission 

factors. The charbroiling emission factors are shown in Table 4.1.4-1 

Table 4.1.4-1 Charbroiling Emission Factors 

Subcategory CO Emission Factors 

(lb CO/person/year) 

Conveyorized Charbroiling 0.043 

Under-fired Charbroiling 0.135 

Deep Fat Frying 0.000 

Flat Griddle Frying 0.013 

Clamshell Griddle Frying 0.000 

The 2010 emissions were calculated using equation 4.1.4-1. 

EM = county population *EF * (1 year/365 days) 

 2,000 lbs/tons 4.3.4-1 

where: 

EM = total daily emissions in tons/day 

 EF = emission factor per charbroiling subcategory 

 

The CO emission estimates, in tons/day, from charbroiling for the CO maintenance areas are 

listed in Tables 4.1.4-2. 

Table 4.1.4-2 CO Emissions (tpd) from Charbroiling 

County 

Conveyorized 

Charbroiling 

Emissions 

Under-fired 

Charbroiling 

Flat 

Griddle 

Frying 

Total Charbroiling 

CO Emissions 

Durham 0.01 0.03 0.00 0.04 

Forsyth 0.01 0.03 0.00 0.04 

Mecklenburg 0.03 0.10 0.01 0.14 

Wake 0.02 0.07 0.01 0.10 
Area Source Emissions Inventory 4-7 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

4.1.5 Open Burning – Municipal Solid Waste and Yard Waste 

It was assumed that all municipal solid waste (MSW) and yard waste were burned in the open for 

solid waste generated outside the municipal corporate limits. Since it is illegal to burn within the 

corporate limits, only the rural percentage of the total population was used. The rural population 

was calculated by applying the 2010 census rural population percentage to the total 2010 county 

population as shown in Table 2.2-2. The 2010 total population for each county was obtained 

from the North Carolina Office of State Budget and Management, State Data Center. The 

emission factors were developed by the USEPA in consultation with the ERTAC based primarily 

on AP-42. The fraction of leaf yard waste burned, the fraction of waste generated that is burned 

and the per capita waste generated was estimated using data from a report by the USEPA on 

municipal solid waste. 

The 2010 emissions were calculated using equations 4.1.5-1 and 4.1.5-2. 

EMMSW = county rural pop * 0.28 * PCMSW * EF

 2,000 lb/tons 4.1.5-1 

EMYard = county rural pop * 0.25* 0.28 * PCYard * EF 

 2,000 lb/tons 4.1.5-2 

where: 

EM = total daily emissions in tons/day 

fraction of waste generated that is burned = 0.28 

leaf fraction of yard waste = 0.25 

 PCMSW = per capita MSW generated = 0.000993 ton MSW/person/year 

 PCYard = per capita yard waste generated = 0.000295 ton yard waste/person/year 

 EF = CO emission factor for MSW = 85 lbs MSW/ton burned/year and for 

 yard waste = 112 lbs yard waste/ton burned/year 

 

Since the NCDAQ has an open burning regulation that prohibits the burning of man-made 

materials, the emissions estimated for MSW were reduced to account for this rule. The control 

efficiency is 100% since no burning yields no emissions. The rule penetration is also 100% 

since the regulation prohibits the burning of man-made materials statewide. Finally the rule 

effectiveness was set to a conservative 56% for 2010 since the NCDAQ knows that burning of 

man-made materials does occur. The NCDAQ has started an aggressive campaign to make the 

public aware that it is illegal to burn man-made materials. The NCDAQ has sponsored radio ads 

as well as billboard signs in an effort to educate the public. Additionally, the NCDAQ has 

developed an educational video discussing open burning and the State’s regulation. This video 

has been distributed to the fire departments across the State. Finally, at the 2009 and 2010 North 
Area Source Emissions Inventory 4-8 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

Carolina State Fair, the NCDAQ had a booth that allowed staff to talk with the general public 

about the open burning regulations and provide hand outs that discussed what was legal to burn. 

The formula used to apply these controls to the emissions estimates is shown below in 

equation 4.1.5-3. 

EMMSW,Controlled = EMMSW x [1 – (CE x RP x RE)] 4.1.5-3 

where: 

 EMMSW,Controlled = controlled emissions from burning MSW 

 EMMSW = emissions from burning MSW 

 CE = control efficiency 

 RP = rule penetration 

 RE = rule effectiveness 

The CO emission estimates, in tons/day, from the open burning of MSW and yard waste are 

listed in Table 4.1.5-1. 

Table 4.1.5-1 CO Emissions (tpd) from Open Burning 

County 2010 MSW 

Emissions 

2010 Yard Waste

Emissions 

Total Open 

Burning CO 

Emissions 

Durham 0.08 0.02 0.10 

Forsyth 0.13 0.03 0.16 

Mecklenburg 0.05 0.01 0.06 

Wake 0.29 0.06 0.35 

4.2 SMALL STATIONARY COMBUSTION AREA SOURCES 

Combustion sources are comprised of the small stationary combustion sources that are not 

included in the point source emissions inventory. This source category covers emissions from 

natural gas (NG), liquid petroleum gas (LPG), fuel oil, coal and wood combustion in the 

residential, commercial/institutional (referred to as commercial) and industrial sectors. The 

methodology used to calculate the emissions from these sources are described in detail in each 

subsection. 

The 2010 emissions were developed by applying a growth factor to the 2007 emissions for these 

subcategories. 
Area Source Emissions Inventory 4-9 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

The 2007 fuel usage data for North Carolina was obtained from the U.S. Department of Energy, 

Energy Information Administration (EIA) website for fuel consumption. 

The following table shows the fuel usage for the residential, commercial and industrial sectors. 

Table 4.2-1 2007 Fuel Use in North Carolina 

Fuel Units Residential Commercial Industrial 

Natural Gas 106 ft3 58,909 45,861 89,289 

LPG gallons 239,256,678 41,811,847 184,668,990 

Oil gallons 117,527,897 66,949,824 295,999,749 

Coal tons 4,447 40,020 0 

Wood tons 1,466,667

Wood 106 BTU 1,641 75,691 

The emission factors used to estimate the emissions, except residential wood, were obtained 

from E.H. Pechan & Associates, Inc. based on the ongoing emission factor development work 

conducted by the Eastern Regional Technical Advisory Group in conjunction with the USEPA. 

The residential wood emission factors were obtained from a tool developed by the USEPA to 

calculate the emissions generated from residential wood combustion. 

The emission factors used are shown in Table 4.2-2 below. 

Table 4.2-2 Residential Combustion CO Emission Factors 

Fuel Units 

CO 

Emission 

Factors 

Residential

NG lb/106 ft3 40 

LPG lb/103 gal 159.6 

Fuel Oil lb/103 gal 5 

Coal lb/ton 275 

Wood lb/ton 149 

4.2.1 Residential Combustion Sources 

The residential category for the fuel oil, coal, NG and LPG sources fuel usage for the CO 

maintenance areas were calculated by apportioning the State total fuel usage to a county level. 

Fuel usage was apportioned by applying the ratio of the number of households heated with the 
Area Source Emissions Inventory 4-10 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

appropriate fuel type in a county to the total households in the State heated with the appropriate 

fuel type, see equation 4.2.1-1. 

no. gal. fuel per cnty = (no. gal. fuel for State) * (no. housing units heated by fuel per county)

 (no. housing units heated by fuel in State) 4.2.1-1 

The number of households heated with fuel oil, coal, NG and LPG was obtained from the U.S. 

Census Bureau based on the latest census data which is 2000. The number of households heated 

per fuel type is shown in Table 4.2.1-1. 

Table 4.2.1-1 Residential Fuel Type 

Number of Households per Fuel Type 

County Fuel Oil Coal NG LPG Wood 

Durham 4,231 6 35,446 4,569 14

Forsyth 22,223 39 32,646 3,763 18

Mecklenburg 6,568 29 142,812 4,009 0

Wake 4,265 17 100,902 17,686 43

Statewide 368,279 464 757,777 394,275 65,657

For the residential wood combustion emissions, the USEPA developed a tool to generate the 

emissions for this subcategory. The emissions for this subcategory are for housing units with 

fireplaces as their main source of heating. The activity data used in the calculation was also 

obtained from the tool the USEPA developed to calculate residential wood combustion 

emissions. 

For the residential source sectors, the growth factors are based on the population for each county. 

The population growth factors were developed based on the ratio of the 2010 population to the 

2007 population, see equation 4.2.1-2. 

Population Growth Factors = FYpop 4.2.1-2 

 BYpop 

where: 

BYpop = 2007 population per county 

 FYpop = 2010 population per county 

 
Area Source Emissions Inventory 4-11 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

The population growth factors are in Table 4.2.1-2. 

Table 4.2.1-2 Population Growth Factors for Residential Combustion 

County Growth Factors 

Durham 1.0621 

Forsyth 1.0401 

Mecklenburg 1.0566 

Wake 1.0939 

The emissions calculation is shown in equation 4.2.1-3. 

EM2007 = activity data * EF * (1 year/365 days) 4.2.1-3 

 2,000 lbs/ton 

where: 

EM2007 = 2007 daily emissions in tons/day 

EF = emission factors for CO are shown in Table 4.2-2 

activity data = number of households per fuel type. 

The 2010 emissions for residential combustion were calculated using equation 4.2.1-4 

EM2010 = EM2007 * POPGF 4.2.1-4 

where: 

 EM2010 = 2010 emissions in tons/day 

 EM2007 = 2007 emissions in tons/day 

 POPGF = population growth factors. 

The CO emissions estimates for each residential fuel combustion source, in tons/day, for the 

residential source sector are listed in Table 4.2.1-3. 

 
Area Source Emissions Inventory 4-12 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

Table 4.2.1-3 CO Emissions (tpd) for Residential Combustion 

County Coal Fuel Oil NG LPG Wood 

Total Residential 

Combustion CO 

Emissions 

Durham 0.02 0.01 0.16 0.01 0.19 0.39 

Forsyth 0.15 0.04 0.15 0.01 0.20 0.55 

Mecklenburg 0.11 0.01 0.64 0.01 1.04 1.81 

Wake 0.07 0.01 0.45 0.05 0.53 1.11 

4.2.2 Commercial and Industrial Combustion Sources 

Commercial and industrial fuel usage was apportioned according to the number of employees in 

the commercial/industrial business establishments in the State and the CO maintenance counties. 

Fuel usage was apportioned to the county level by applying the ratio of county employment to 

the total State employment, see equation 4.2.2-1. 

no. gal. fuel per county = (no. gal. fuel for State) * (commercial/industrial employment per county)

 (commercial/industrial employment in State) 

 4.2.2-1

The commercial employment data was obtained from the County Business Patterns for NAICS 

codes 42 (wholesale trade) through 81 (other services - except public administration). For 

industrial combustion, the employment data was also obtained from the County Business 

Patterns for NAICS codes 31-33 (manufacturing). The total number of employees for these 

establishments was used to allocate emissions to the county level. The 2007 commercial and 

industrial employment for each county are shown in Table 4.2.2-1. 

Table 4.2.2-1 Commercial and Industrial Combustion Employment 

County 2007 Commercial 

Employment 

2007 Industrial 

Employment 

Durham 66,296 2,225 

Forsyth 81,819 5,932 

Mecklenburg 274,725 14,984 

Wake 224,283 8,688 

Statewide 1,829,856 163,364 
Area Source Emissions Inventory 4-13 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

The emissions for 2007 for each small stationary combustion source were calculated using 

equations 4.2.2-2 through 4.2.2-6. 

EMcoal = no. tons/year coal * EFcoal * (1 year/365 days) – pse 

 2,000 lb/ton 4.2.2-2 

EMNG = no. ft3/year NG * EFNG * (1 year/365 days) - pse 

 2,000 lbs /ton 4.2.2-3 

EMLPG = no. gal/year LPG * EFLPG * (1 year/365 days) - pse 

 2,000 lbs /ton 4.2.2-4 

EMfuel oil = no. gal/year fuel oil * EFoil * (1 year/365 days) - pse 

 2,000 lbs /ton 4.2.2-5 

EMwood = no. ton/year wood * EFwood * (1 year/365 days) - pse 

2,000 lbs /ton 4.2.2-6 

where: 

 EMcoal = daily total coal emissions in tons/day 

 EMNG = daily total Ng emissions in tons/day 

 EMLPG = daily total LPG emissions in tons/day 

 EMfuel oil = daily total fuel oil emissions in tons/day 

 EMwood = daily total wood emissions in tons/day 

 EFcoal = CO emission factor for coal combustion 

 EFNG = CO emission factor for NG combustion 

 EFLPG = CO emission factor for LPG combustion 

 EFoil = CO emission factor for fuel oil combustion 

 EFwood = CO emission factor for wood combustion 

 pse = point source emissions 

The CO emission factors used to estimate the emissions for the commercial and industrial 

stationary sources are shown in Table 4.2.2-2. 
Area Source Emissions Inventory 4-14 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

Table 4.2.2-2 Commerical/Industrial Combustion CO Emission Factors 

Fuel Units 

CO 

Emission 

Factors 

Commercial

NG lb/106 ft3 84 

LPG lb/103 gal 7.97 

Fuel Oil lb/103 gal 5 

Coal lb/ton 5 

Wood lb/106 BTU 0.6 

Industrial

NG lb/106 ft3 84 

LPG lb/103 gal 7.97 

Fuel Oil lb/103 gal 5 

Wood lb/106 BTU 0.6 

The growth factors were developed based on the ratio of the 2010 employment to the 2007 

employment, see equation 4.2.2-7. 

Commercial/Industrial Growth Factors = FYemp 4.2.2-7 

 BYemp 

where: 

BYemp = 2007 employment per county 

 FYemp = 2010 employment per county 

The commercial combustion growth factors were generated from the statewide employment data 

for NAICS codes 42 (wholesale trade) through 81 (other services - except public administration). 

The industrial combustion growth factors were also generated from statewide data using NAICS 

codes 31-33 (manufacturing). The FORECAST function in Microsoft EXCEL was used to 

determine the future year employment data based on the past statewide employment data for 

2005 - 2009. The FORECAST tool uses linear interpolation to project future values based on the 

historic data. 

Table 4.2.2-3 shows the commercial and industrial combustion growth factors. 
Area Source Emissions Inventory 4-15 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

Table 4.2.2-3 Growth Factors for Commercial and Industrial Combustion 

County Commercial Industrial 

Durham 0.9792 0.6786 

Forsyth 0.9795 0.9167 

Mecklenburg 1.0235 0.8717 

Wake 1.0430 0.9142 

The emissions for 2010 for all of the small stationary combustion sources were calculated using 

equation 4.2.2-8 

EM2010 = EMa,2007 * EMPGF 4.2.2-8 

where: 

 EM2010 = 2010 emissions in tons/day 

 EMa,2007 = 2007 emissions in tons/day per combustion source 

 EMPGF = employment growth factors. 

The commercial and industrial small stationary combustion sources CO emission estimates, in 

tons/day, are shown in Tables 4.2.2-4 – 4.2.2-5, respectively. There are no coal combustion 

emissions for the industrial source sector because the emissions generated from coal are 

accounted for in the point sources inventory. 

Table 4.2.2-4 CO Emissions (tpd) for Commercial Combustion 

County Coal Fuel Oil NG LPG Wood 

Total Commercial 

Combustion CO 

Emissions 

Durham 0.01 0.01 0.13 0.04 0.06 0.25 

Forsyth 0.01 0.02 0.16 0.05 0.07 0.31 

Mecklenburg 0.04 0.06 0.56 0.19 0.24 1.09 

Wake 0.03 0.04 0.61 0.16 0.17 1.01 
Area Source Emissions Inventory 4-16 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

Table 4.2.2-5 CO Emissions (tpd) for Industrial Combustion 

County Fuel Oil NG LPG Wood 

Total Industrial 

Combustion CO 

Emissions 

Durham 0.00 0.09 0.03 0.04 0.16 

Forsyth 0.02 0.15 0.05 0.06 0.28 

Mecklenburg 0.05 0.48 0.16 0.21 0.90 

Wake 0.04 0.53 0.14 0.15 0.86 

Point sources are those stationary sources that require an air permit to operate. In general, these 

sources have a potential to emit more than 5 tons per year of CO from a single facility. Point 

sources that meet this criterion are accounted for in the point source emissions inventory. They 

are subtracted from the area source emissions inventory to prevent double counting of emissions. 

The 2007 point source emissions data was subtracted from the overall area source emissions 

calculation. Tables 4.2.2-6 and 4.2.2-7 illustrates the point source emissions that were subtracted 

from the commercial and industrial fuel oil, NG and wood combustion sources. The coal and 

LPG commercial and industrial combustion sources do not have point source emissions for the 

CO maintenance areas. 

Table 4.2.2-6 Point Source Commercial Combustion Emissions (tpd) 

County Fuel Oil NG Wood 

Durham 0.01 0.03 0.00 

Forsyth 0.00 0.03 0.01 

Mecklenburg 0.00 0.19 0.13 

Wake 0.00 0.15 0.00 

 
Area Source Emissions Inventory 4-17 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

Table 4.2.2-7 Point Source Industrial Combustion Emissions (tpd) 

County Fuel Oil NG Wood 

Durham 0.00 0.06 0.00 

Forsyth 0.02 0.23 0.56 

Mecklenburg 0.02 0.28 0.00 

Wake 0.00 0.09 0.00 
Area Source Emissions Inventory 4-18 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.2 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

5.0 SUMMARY OF AREA SOURCE EMISSIONS 

The total area source CO emissions for the maintenance areas are summarized in the table below. 

All of the emissions are in tons per day. 

Table 5-1 Total Area Source CO Emissions (tpd) 

County 2010 

Durham 1.54 

Forsyth 1.41 

Mecklenburg 4.21 

Wake 4.26 
Appendix B.3 

On-road Mobile Source 

Emissions Inventory Documentation 
i

(This page intentionally left blank)
On-road Mobile Source Emissions Inventory i 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.3 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

TABLE OF CONTENTS 

1.0 INTRODUCTION AND SCOPE .......................................................................................... 1-1

2.0 MODELING METHODOLOGY .......................................................................................... 2-1

2.1 MOVES MODELING SCENARIO AND PARAMETERS ......................................... 2-1

3.0 QUALITY ASSURANCE MEASURES ............................................................................... 3-3

4.0 MODELING RESULTS ........................................................................................................ 4-1

4.1 INTRODUCTION AND SCOPE .................................................................................. 4-1

4.2 MOVES INPUT DATA CRITERIA AND ASSUMPTIONS ....................................... 4-2

4.2.1 Vehicle Miles Traveled and Speeds ........................................................................ 4-2

4.2.2 Source Type Population .......................................................................................... 4-8

4.2.3 Source Type Age Distribution .............................................................................. 4-10

4.2.4 Road Type Distribution ......................................................................................... 4-11

4.2.5 Inspection and Maintenance Program ................................................................... 4-13

4.2.6 Fuel Supply and Formulation ............................................................................... 4-14

4.2.7 Meteorological Data .............................................................................................. 4-14

4.3 ESTIMATED EMISSIONS FROM ON-ROAD MOBILE SOURCES ...................... 4-16

LIST OF TABLES 

Table 2.1-1 MOVES Modeling Parameters ................................................................................. 2-2

Table 4.1-0-1 TDM Data Providers ............................................................................................. 4-1

Table 4.2-1 Peak and Off-peak Travel Periods ............................................................................ 4-2

Table 4.2-2 2010 CO Maintenance Area AADVMT by Road Type (miles) ............................... 4-4

Table 4.2-3 2010 CO Maintenance Area Speeds by Road Type (miles/hour) ............................ 4-5

Table 4.2-4 MOVES Source Types and HPMS Vehicle Types .................................................. 4-9

Table 4.2-5 Fraction of VMT on Road Type by Source Type ................................................... 4-12

Table 4.2-6 MOVES I/M Compliance Factors .......................................................................... 4-14

Table 4.2-7 Average Hourly Temperature and Humidity – January 2010 ................................ 4-15

Table 4.3-1 January 2010 On-road Mobile Source CO emissions ............................................ 4-16
On-road Mobile Source Emissions Inventory ii 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.3 

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List of Acronyms 

Acronym Definition 

AADVMT Average Annual Daily Vehicle Miles Traveled 

CO Carbon Monoxide 

HPMS Highway Performance Monitoring System 

MOVES Motor Vehicle Emission Simulator 

NCDAQ North Carolina Division of Air Quality 

NCDOT North Carolina Department of Transportation 

NCOSBM North Carolina Office of State and Budget Management 

QAPP Quality Assurance Project Plan 

RVP Reid Vapor Pressure 

TDM Travel Demand Modeling 

USEPA U.S. Environmental Protection Agency 

VMT Vehicle Miles Traveled 

 
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On-road Mobile Source Emissions Inventory 1-1 

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1.0 INTRODUCTION AND SCOPE 

Carbon monoxide (CO) emissions from on-road mobile sources comprise a large percentage of 

the total man-made CO emissions from all sources in the current North Carolina CO 

attainment/maintenance area. However, on-road mobile source CO emissions have continually 

decreased over the past two decades due to improved vehicle pollution controls and fuel 

economy, implementation of inspection and maintenance programs, and effective transportation 

planning measures. These decreases have been realized in spite of continual increases in vehicle 

miles traveled (VMT), and have led to ambient CO concentrations well below the CO National 

Ambient Air Quality Standard (NAAQS) in recent years. 

These consistently low CO concentrations allow North Carolina the option of implementing a 

limited CO maintenance plan for the four affected counties (Forsyth, Durham, Mecklenburg, and 

Wake Counties). An on-road mobile source CO emissions inventory has been developed as part 

of the limited maintenance plan requirements. This appendix covers the procedures associated 

with the emissions inventory development. 

The CO emissions inventory data includes 2010 daily on-road mobile source CO emissions 

(tons/day) for a typical winter (January) day for each of the four affected counties. Emissions 

data were generated using the United States Environmental Protection Agency (USEPA) Motor 

Vehicle Emissions Simulator (MOVES) model. Monthly CO inventories for January 2010 were 

generated for each county and the average daily CO emissions values were calculated from the 

monthly inventory values. Details of the MOVES modeling process, including input data 

requirements, input data preparation, and modeling parameters and assumptions, are presented 

below. 

 
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2.0 MODELING METHODOLOGY 

2.1 MOVES MODELING SCENARIO AND PARAMETERS 

Mobile source emissions are estimated by the methodologies suggested in the USEPA 

documents Emissions Inventory Guidance for Implementation of Ozone and Particulate Matter 

National Ambient Air Quality Standards (NAAQS) and Regional Haze Regulations, Policy

Guidance on the Use of MOVES2010 for State Implementation Plan Development, 

Transportation Conformity, and Other Purposes (EPA-420-B-09-046, December 2009), and 

Technical Guidance on the Use of MOVES2010 for Emission Inventory Preparation in State 

Implementation Plans and Transportation Conformity (EPA-420-B-10-023, April 2010). 

In December 2009, the USEPA released a new model for mobile sources. MOVES is a 

computer program designed by the USEPA to estimate air pollution emissions from mobile 

sources. MOVES2010a (hereafter referred to as MOVES) replaces the USEPA’s previous 

emissions model for on-road mobile sources, MOBILE6.2. MOVES can be used to estimate 

exhaust and evaporative emissions as well as brake and tire wear emissions from all types of onroad vehicles. 

One important new feature of MOVES is the option to calculate emissions either as inventory 

estimates (total emissions in units of mass) or, emission rates (emissions per unit of distance for 

running emissions or per vehicle for starts, extended idle and resting evaporative emissions) in a 

look-up table format. 

Use of the inventory option simplifies the post-processing of MOVES output, but it requires 

VMT and vehicle population data as an input to MOVES. When using the emission rates option, 

VMT and vehicle population are applied during post-processing external to MOVES. Either 

approach can be used to develop emissions estimates for state implementation plans (SIPs). If 

inventory option is selected, MOVES provides emissions estimates as mass, using VMT and 

vehicle population entered by the user. If emission rate option is selected, MOVES provides 

emission rates as mass per unit of activity. The emission rates option produces a look-up table of 

emission rates that must be post-processed to produce an inventory. The North Carolina Division 

of Air Quality (NCDAQ) is electing to run the model in the inventory mode due to faster model 

run times and fewer post-processing requirements. 

To generate the emissions inventory data required for the limited CO maintenance plan, MOVES 

modeling was performed using the parameters listed ion Table 2.1-1. 
On-road Mobile Source Emissions Inventory 2-2 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.3 

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Table 2.1-1 MOVES Modeling Parameters 

MOVES Model Version MOVES2010a 

Pollutant Carbon Monoxide (CO) 

Modeling Spatial Domains CO Maintenance counties – Durham, 

Forsyth, Mecklenburg, Wake 

Modeling Year 2010 

Required Emissions Time 

Period 

Typical winter day 

Vehicle Types All on-road vehicles 

Inspection and 

Maintenance Program 

Applicability 

As per the North Carolina Inspection and 

Maintenance SIP (includes OBD-II 

inspection of light duty gasoline vehicles) 

While MOVES can model emissions for a weekday and weekend day in a specified month, it 

cannot directly model a single day with specified “typical winter day” conditions. Therefore, to 

calculate emissions for a typical winter day, MOVES was first run to estimate the total on-road 

CO emissions for the month of January 2010 for each of the listed counties. Each monthly 

emissions value (tons CO) was then divided by the number of days in the month (31) to give 

typical winter day emissions (tons CO/day). 

 
On-road Mobile Source Emissions Inventory 3-3 

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3.0 QUALITY ASSURANCE MEASURES 

The quality assurance (QA) for the on-road mobile source category can be broken into two 

components: 1) input files and 2) MOVES outputs/summaries. Each of these components is 

detailed in the paragraphs below. 

After the speed and VMT information is acquired from the North Carolina Department of 

Transportation (NCDOT), the speed information is checked for reasonableness against previous 

sets of speeds for the areas. Once the speeds are deemed reasonable, the NCDAQ enters the 

speed information into MOVES input files. In addition to the speed information, the user enters 

data to characterize local meteorology, fleet and activity information. All input files are checked 

against a “key” with the original source of the information. This QA step is always performed 

by a person other than the one who generated the files. If any discrepancies are found, they are 

noted back to the person who generated the input files for correction. Additionally, a report is 

kept that identifies the person who produced the input file, the person that QA’d the file, and 

where the data originated. Once the input files have passed through the QA procedure, MOVES 

is run to generate emissions. 

MOVES output data from each county is also checked for reasonableness by comparison with 

historical emissions inventory data and by comparison with emissions data from counties with 

similar transportation activity. As with the MOVES input data, MOVES output data summaries 

are also reviewed for accuracy by someone other than the preparer of the summary. 
On-road Mobile Source Emissions Inventory 4-1 

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4.0 MODELING RESULTS 

On-road mobile sources produce emissions of a host of pollutants. For the purpose of this 

maintenance plan, only the CO emissions were estimated. The objective of this section is to 

describe the source category, the input files, and the emissions estimation procedures. This 

section also includes tables summarizing the estimated emissions for the maintenance year 2010 

by county. 

4.1 INTRODUCTION AND SCOPE 

On-road highway mobile sources are considered as those vehicles that travel on public roadways. 

On-road mobile sources are a major contributor to CO emissions in North Carolina. CO is 

emitted from motor vehicles primarily while vehicles are in motion or at idle and only minimally 

while vehicles are parked or during refueling operations. However, emissions from all of these 

emissions processes were estimated to properly reflect the total emissions from this source 

category. 

A very important component of the highway mobile emission estimation process is interagency 

consultation among federal, state, regional and local regulatory and planning agencies. For this 

CO emissions inventory development project, NCDAQ used travel demand modeling data 

provided by three organizations listed below. These organizations executed the travel demand 

modeling (TDM) for their respective counties in the CO nonattainment area and provided speeds 

and vehicle miles traveled (VMT). 

Table 4.1-0-1 TDM Data Providers 

Organization Providing TDM Data County VMT and Speed Data 

Provided 

Mecklenburg-Union Metropolitan Planning 

Organization (MUMPO) Mecklenburg 

Capital Area Metropolitan Planning Organization 

(CAMPO) in coordination with Durham-Chapel HillCarrboro Metropolitan Planning Organization 

(DCHC-MPO) 

Durham, Wake 

Piedmont Authority for Regional Transportation 

(PART) Forsyth 
On-road Mobile Source Emissions Inventory 4-2 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.3 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

4.2 MOVES INPUT DATA CRITERIA AND ASSUMPTIONS 

The following sections describe the input data used for the MOVES CO emissions modeling. 

Due to the size and the complexity of the MOVES input and output files, the MOVES input files 

and output files will be provided electronically. 

4.2.1 Vehicle Miles Traveled and Speeds 

The MOVES model calculates emissions based on several mobile source operating parameters, 

including the number of VMT on specific types of roadways as defined under the Federal 

Highway Administration’s Highway Performance Monitoring System (HPMS). For each of the 

four affected counties, VMT data were obtained from the municipal planning organization 

(MPO) representing that county. Each MPO used travel demand modeling (TDM), based on their 

specific demographic, roadway network, and socioeconomic data and conditions, to estimate the 

average annual daily VMT (AADVMT) and corresponding average speeds categorized by 

twelve HPMS roadway functional classes. For three of the four counties, VMT and speed data 

were furthered categorized by daily travel periods, including morning and afternoon peak 

periods. Table 4.2-1 shows the travel periods for each county. 

Table 4.2-1 Peak and Off-peak Travel Periods 

County AM Peak Period Midday Period PM Peak 

Period 

Off-peak Period 

Durham, 

Wake 

06:00-10:00 

Included as offpeak 

15:00-18:00 

10:00-15:00, 

18:00-23:59, 

00:00-06:00 

Mecklenburg 06:00-09:00 09:00-15:00 15:00-18:00 18:00-23:59, 

00:00-06:00 

Forsyth No peak or off-peak travel periods specified – 

VMT and speeds provided apply to entire day 

VMT and speed data were processed with converter applications to format the data for input into 

MOVES. Annual VMT for each of 6 HPMS vehicle types were tabulated, as well as the hourly 

distribution of VMT for each source type-road type-day type (weekday or weekend) 

combination. 
On-road Mobile Source Emissions Inventory 4-3 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.3 

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Vehicle power, speed, and acceleration have a significant effect on vehicle emissions. MOVES 

models those emission effects by assigning activity to specific drive cycles or operating mode 

distributions. The distribution of vehicle hours traveled (VHT) by average speed was used to 

determine an appropriate operating mode distribution. The Average Speed Distribution importer 

in MOVES calls for a speed distribution in VHT in 16 speed bins, by each road type, source 

type, and hour of the day included in the analysis. The methodology used to develop the 

average speed distribution inputs is documented below. 

TDM-generated VMT and speeds were provided for 2010 for the time periods described above. 

Table 4.2-2 lists the AADVMT by HPMS functional class for each county. Table 4.2-3 

provides a summary of the speeds in miles per hour (mph) for each county. The column 

headings in these tables represent the road types used in the modeling and are listed below. 

RI Rural Interstate UI Urban Interstate 

RPA Rural Other Principle Arterial UF Urban Freeway & Expressway 

RMA Rural Minor Arterial UPA Urban Other Principal Arterial 

RMjC Rural Major Collector UMA Urban Minor Arterial 

RMiC Rural Minor Collector UC Urban Collector 

RL Rural Local UL Urban Local 

 UH Urban HOV 
Table 4.2-2 2010 CO Maintenance Area AADVMT by Road Type (miles) 

County Durham Forsyth Mecklenburg Wake 

HPMS 

Road 

Type AM PM 

Offpeak Daily AM Midday PM Night AM PM Off- peak 

RI 41255 53589 72624 NA NA NA NA NA 14672 29275 29675RPA 8453 11066 17565 123182 37607 45986 42338 27117 53465 70992 92767RMA 40171 50640 68161 160403 17023 20700 19749 13711 23839 38804 44561RMjC 55109 80109 99517 53612 16862 22570 19703 10535 39049 51064 70029RMiC 22082 32599 41498 124168 32474 40495 41432 20832 18482 31274 32964RL 26544 47274 52352 133503 66263 89945 81369 42693 52333 96970 101612UI 493549 671976 1070728 2008312 1736609 2268124 1919704 1315657 1544267 2108059 3169061UF 320433 453358 667984 3393797 1110226 1389995 1282080 723369 499329 710404 945463UPA 245321 340152 522121 380472 1111629 1680204 1284698 944660 1152837 1665360 2513928UMA 315625 518730 740306 1677609 1024878 1553321 1202756 841426 1212659 1947914 2701970UC 119318 209844 274128 1544519 806596 1207264 941722 642619 500159 836279 1056018UL 225973 418299 585970 1131387 1459707 2340210 1736882 1126041 1021962 1838887 2366951UH NA NA NA NA 17763 374 7595 0 NA NA NA

On-road Mobile Source Emissions Inventory 

Charlotte, Raleigh/Durham & Winston-Salem 

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 4-4 

Appendix B.3 

June 29, 2012 
Table 4.2-3 2010 CO Maintenance Area Speeds by Road Type (miles/hour) 

County Durham Forsyth Mecklenburg Wake HPMS Road Type AM PM 

Offpeak Daily AM Midday PM Night AM PM Off- peak 

RI 64.7 69.7 58.7 NA NA NA NA NA 64.3 63.8 47.7 RPA 42.9 44.1 40.3 54.3 36 45 37 49 60.7 60.7 58.2 RMA 46.2 53.1 38.0 49.3 32 43 38 45 47.6 48.9 45.2 RMjC 49.4 50.1 46.7 44.6 30 40 31 46 47.5 48.1 46.1 RMiC 40.7 40.7 39.2 45.4 37 42 36 45 36.8 37.9 35.7 RL 27.5 26.6 26.7 44.2 30 29 30 29 24.7 23.2 24.7 UI 63.5 64.0 55.8 60.6 46 58 42 62 60.0 64.1 52.8 UF 53.8 53.5 48.5 50.3 49 55 47 58 57.5 58.6 49.8 UPA 40.6 39.6 34.1 41.5 24 28 22 37 43.8 45.3 36.6 UMA 39.3 39.1 34.5 41.8 24 28 23 37 39.6 41.2 33.8 UC 40.4 40.0 36.5 38.0 22 27 21 36 38.8 39.8 34.3 UL 21.8 21.5 21.7 36.4 22 21 19 24 25.1 23.9 24.2 UH NA NA NA NA 63 65 66 0 NA NA NA 

On-road Mobile Source Emissions Inventory 

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Appendix B.3 

June 29, 2012 
On-road Mobile Source Emissions Inventory 4-6 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.3 

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MOVES uses four different roadway type categories that are affected by the average speed 

distribution input: rural restricted access, rural unrestricted access, urban restricted access, and 

urban unrestricted access (these road types are discussed in more detail in Section 4.2.6). In 

MOVES, local roadways are included with arterials and collectors in the urban and rural 

unrestricted access roads category. The USEPA recommends that the average speed distribution 

for local roadway activity be included as part of a weighted distribution of average speed across 

all unrestricted roads along with the distribution of average speeds for arterials and connectors. 

When only a single average speed is available for a specific road type and that average speed is 

not identical to the average speed in a particular speed bin, MOVES guidance stipulates that 

users should apply the following formula for creating the appropriate speed distribution among 

two adjacent speed bins. 

The general formula is: 

VHT Fraction A in Speed Bin with closest average speed lower than observed average speed + 

VHT Fraction B in Speed Bin with closest average speed higher that observed average speed = 1 

VHT Fraction A(low bin) = 1 – [(observed average speed – average speed of lower speed bin) / 

(average speed of higher speed bin – average speed of lower speed bin)] 

VHT Fraction B(high bin) = 1- [(average speed of higher speed bin – observed average speed) / 

(average speed of higher speed bin – average speed of lower speed bin)] 

Or more simply: VHT Fraction B = 1 – VHT fraction A 

The following is an example of applying the above equations. If the single average speed for a 

roadway is 58 miles per hour, the average speed distribution will be split between the 55 and 60 

mph speed bins. The appropriate VHT fractions are found with the following equations: 

VHT fraction A(low bin) = 1 – [(58 mph Avg. Speed – 55 mph (Bin Speed)) / (60 mph (Bin Speed) 

– 55 mph (Bin Speed)] = 0.4 

VHT fraction B(high bin) = 1 – [(60 mph (Bin Speed) – 58 mph Avg. Speed) / (60 mph (Bin Speed) 

– 55 mph (Bin Speed)] = 0.6 

VHT Fraction A(low bin) + VHT Fraction B(high bin) = 1 

0.4 + 0.6 = 1 
On-road Mobile Source Emissions Inventory 4-7 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.3 

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As stated above, MOVES uses only four different roadway types: rural restricted access, rural 

unrestricted access, urban restricted access and urban unrestricted access. This means that the 

speeds for multiple roadway types need to be combined into the appropriate speed bins. To 

create the speed bin fractions for combined roadways the VMT for each road way is used to 

weight the speed bin fraction. For example, below are speeds and VMT for urban restricted 

access road types: 

Road type Speed 

(miles/hour) 

VMT 

(hourly miles) 

Urban Interstate 63 250,000 

Urban Freeway 56 100,000 

The first step is to determine the speed bin fractions for each road type separately. For the urban 

interstate road type, the speed 63 is split between the MOVES speed bins of 60 and 65 as 

described above, which results in the VHT fractions of 0.4 and 0.6 for speed bins 60 and 65, 

respectively. Similarly, the speed for the urban freeway road type (56 miles/hour) is split 

between the MOVES speed bins of 55 and 60 and results in the VHT fractions of 0.8 and 0.2, 

respectively. 

The next step requires road type VMT to weigh the VHT Fractions so that the final MOVES 

speed bin fractions can be developed. The VHT Fraction, specific to the road type and speed 

bin, are multiplied by the corresponding hourly VMT. These hourly totals are divided by the 

total VMT for that hour for the road type category (in this example, urban restricted access 

includes urban interstate and urban freeway). The following equation is used to calculate the 

combined speed bin fractions: 

VHT(Speed Bin X) = [∑ (VHT Fraction(RT) × hourly VMT(RT) ] ÷ [∑ hourly VMT(RT) ] 

Where: 

RT = the HPMS road type 

In this example, the HPMS road types are urban interstate (UI) and urban freeway (UF) and the 

speed bins are 55, 60 and 65. The table below summarizes the speed bin fractions for this 

example. 
On-road Mobile Source Emissions Inventory 4-8 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.3 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

HPMS Road Type Speed Bin 55 Speed Bin 60 Speed Bin 65 

Urban Interstate 0.0 0.4 0.6 

Urban Freeway 0.8 0.2 0.0 

Using the equation below, the final MOVES speed bin fractions are calculated for the urban 

restricted access road type. 

VHT(Speed Bin X) = [(VHT Fraction(UI) * hourly VMT(UI)) + (VHT Fraction(UF) * hourly VMT(UF))]

(hourly VMT(UI) + hourly VMT(UF)) 

VHT(Speed Bin 55) = [(0.0 * 250,000) + (0.8 * 100,000)]

(250,000 + 100,000) 

VHT(Speed Bin 55) = 0.2286 

 

VHT(Speed Bin 60) = [(0.4 * 250,000) + (0.2 * 100,000)]

(250,000 + 100,000) 

VHT(Speed Bin 60) = 0.3428 

 

VHT(Speed Bin 65) = [(0.6 * 250,000) + (0.0 * 100,000)]

(250,000 + 100,000) 

VHT(Speed Bin 65) = 0.4286 

The sum of the VHT fractions for all speed bins within a road type category must add up to 1.0. 

The hourly VHT fractions by speed bin and road type are then processed through a MOVES 

supplied converter to develop the speed distribution file by hour and road type. 

4.2.2 Source Type Population 

The MOVES model requires county-level source type (vehicle type) populations grouped by 13 

categories. These data were developed from 2010 North Carolina Department of Motor Vehicles 

vehicle registration data. Counts of the total number of registered vehicles in each county were 

first obtained. The total populations were then broken down into 13 categories using the MOVES 

default source type distribution for each county for the year 2010. 

Source type population is used by MOVES to calculate start and evaporative emissions. In 

MOVES, start and resting evaporative emissions are related to the population of vehicles in an 
On-road Mobile Source Emissions Inventory 4-9 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.3 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

area. Since vehicle type population directly determines start and evaporative emission, users 

must develop local data for this input. 

MOVES uses a vehicle classification system based the Federal Highway Administration’s 

HPMS vehicle classes (as opposed to the classes used with respect to USEPA emissions 

regulations). Since HPMS vehicle class data is commonly available from state transportation 

sources, this makes it easier for users to develop local data for MOVES. MOVES categorizes 

vehicles into 13 source types, which are subsets of 6 HPMS vehicle types in MOVES, as shown 

in the crosswalk in Table 4.2-3. The USEPA believes that states should be able to develop 

population data for many of these source type categories from state motor vehicle registration 

data (e.g., motorcycles, passenger cars, passenger trucks, light commercial trucks) and from local 

transit agencies, school districts, bus companies, and refuse haulers (intercity, transit, and school 

buses, and refuse trucks). The NCDOT supplied the NCDAQ with source population data as 

described in the following section. 

Table 4.2-4 MOVES Source Types and HPMS Vehicle Types

Source 

Type ID 

Source Types HPMS Vehicle 

Type ID 

HPMS Vehicle Type 

11 Motorcycle 10 Motorcycles 

21 Passenger Car 20 Passenger Cars 

31 Passenger Truck 30 Other 2 axle-4 tire vehicles 

32 Light Commercial Truck 30 Other 2 axle-4 tire vehicles 

41 Intercity Bus 40 Buses 

42 Transit Bus 40 Buses 

43 School Bus 40 Buses 

51 Refuse Truck 50 Single Unit Trucks 

52 Single Unit Short-haul Truck 50 Single Unit Trucks 

53 Single Unit Long-haul Truck 50 Single Unit Trucks 

54 Motor Home 50 Single Unit Trucks 

61 Combination Short-haul Truck 60 Combination Trucks 

62 Combination Long-haul Truck 60 Combination Trucks 

Source Type Population – Local Data

MOVES uses allocation factors to distribute emissions and activity (such as vehicle type 

populations) to individual counties. The NCDAQ is committed to using representative local data 

which will over ride MOVES default values through the County Data Manager. This decision 

was based on the fact that default allocation factors used in MOVES are derived from the VMT. 

Since the allocations are based on VMT, the vehicle populations allocated to counties are 
On-road Mobile Source Emissions Inventory 4-10 

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Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

proportional to the VMT being allocated to that county. The NCDAQ corresponded with the 

USEPA Office of Transportation and Air Quality (OTAQ) to arrive at an acceptable method to 

allocate current year as well as to project future year vehicle populations to source type 

populations. The NCDAQ believes that using MOVES default vehicle population to estimate a 

fraction is the best method of taking state specific vehicle registration data and allocating county 

total vehicles to specific vehicle source types. 

MOVES categorizes vehicles into 13 source types, which are subsets of 6 HPMS vehicle types. 

Presently NCDAQ is unable to develop county source type population data for many of these 

source type categories based on how NCDOT collect vehicle registration data. The latest vehicle 

registration data broken down by county and towns is available by January of each year. Since 

the vehicle types database available from NCDOT differs from what MOVES2010a expects, the 

NCDAQ relies on MOVES default fractions and applies these fractions to county total vehicle 

population, minus trailers. It is assumed that trailers do not have engines and do not generate 

VMT. 

4.2.3 Source Type Age Distribution 

The age distribution of vehicle fleets can vary significantly from area to area. Fleets with a 

higher percentage of older vehicles will have higher emissions for two reasons. Older vehicles 

have typically been driven more miles and have experienced more deterioration in emission 

control systems. Additionally, a higher percentage of older vehicles also implies that there are 

more vehicles in the fleet that do not meet newer, more stringent emissions standards. Surveys 

of registration data indicate considerable local variability in vehicle age distributions. 

For SIP and conformity purposes, the USEPA recommends and encourages states to develop 

local age distributions. A typical vehicle fleet includes a mix of vehicles of different ages. 

MOVES covers a 31 year range of vehicle ages, with vehicles 30 years and older grouped 

together. MOVES allows the user to specify the fraction of vehicles in each of 30 vehicle ages 

for each of the 13 source types in the model. 

Local age distributions can be estimated from local vehicle registration data. The vehicle age 

distribution comes from annual registration data for North Carolina from the NCDOT. For this 

analysis, the age distribution was generated based on the 2010 data. The NCDOT provided the 

data based on the number of vehicle types per year from 1974 through 2010. Since MOVES 

categorizes the vehicle fleet into different vehicle classes and more model years, USEPA has 

created data converters that take registration distribution input files created for MOBILE6.2 and 

converts them to the appropriate age distribution input tables for MOVES. Vehicles greater than 
On-road Mobile Source Emissions Inventory 4-11 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.3 

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25 years old were combined and included as the 25th model year. The vehicle count information 

is provided for nine vehicle types; light duty gas vehicles (LDGV), light duty diesel vehicles 

(LDDV), light duty gas trucks 1 (LDGT1), light duty gas trucks 2 (LDGT2), light duty diesel 

trucks 1 (LDDT1), light duty diesel trucks 2 (LDDT2), heavy duty gas vehicles (HDGV), heavy 

duty diesel vehicles (HDDV) and motorcycles (MC). LDDT1 and LDDT2 are combined and 

labeled as light duty diesel trucks (LDDT). 

4.2.4 Road Type Distribution 

The distribution of VMT traveled by each source type over the five MOVES road types was 

determined. The basis of this distribution was the 2009 statewide vehicle mix data provided by 

the NCDOT, which shows, for a given road type, the activity of each source type as a percentage 

of total vehicle activity. The 2009 statewide vehicle mix dataset was the latest data available at 

the time this CO inventory was developed. This data was provided for each of twelve HPMS 

roadway functional classes and thirteen source types. Procedures outlined in USEPA’s Technical 

Guidance on the Use of MOBILE6.2 for EI Preparation (Aug. 2004) were used to re-aggregate 

the mix data from thirteen source types to sixteen source types and to project the 2009 vehicle 

mix data to the future year of 2010. Table 4.2-5 shows the statewide vehicle mix used for each of 

the four counties. Column headings represent road types described in Section 4.2.1. 
Table 4.2-5 Fraction of VMT on Road Type by Source Type 

Source Type* RI RPA RMA RMjC RMiC RL UI UF UPA UMA UC UL LDV 0.3178 0.3463 0.3599 0.3584 0.3668 0.3609 0.3515 0.3613 0.3685 0.3759 0.3809 0.3723 LDT1 0.0798 0.0871 0.0905 0.0901 0.0922 0.0907 0.0884 0.0908 0.0927 0.0945 0.0958 0.0936 LDT2 0.2657 0.2898 0.3012 0.2999 0.3069 0.3018 0.294 0.3023 0.3083 0.3145 0.3187 0.3114 LDT3 0.0819 0.0893 0.0929 0.0925 0.0946 0.093 0.0906 0.0932 0.0951 0.097 0.0982 0.096 LDT4 0.0376 0.0411 0.0427 0.0425 0.0435 0.0428 0.0417 0.0428 0.0437 0.0446 0.0451 0.0441 HDV2 0.0682 0.0453 0.0344 0.0357 0.029 0.0338 0.0412 0.0334 0.0276 0.0218 0.0178 0.0247 HDV3 0.0066 0.0044 0.0034 0.0035 0.0028 0.0033 0.004 0.0033 0.0027 0.0021 0.0017 0.0024 HDV4 0.0056 0.0037 0.0028 0.0029 0.0024 0.0028 0.0034 0.0027 0.0023 0.0018 0.0015 0.002 HDV5 0.0042 0.0028 0.0021 0.0022 0.0018 0.0021 0.0025 0.0021 0.0017 0.0013 0.0011 0.0015 HDV6 0.0152 0.0101 0.0077 0.008 0.0065 0.0075 0.0092 0.0074 0.0062 0.0049 0.004 0.0055 HDV7 0.018 0.012 0.0091 0.0094 0.0077 0.0089 0.0109 0.0088 0.0073 0.0057 0.0047 0.0065 HDV8A 0.0196 0.013 0.0099 0.0102 0.0083 0.0097 0.0118 0.0096 0.0079 0.0062 0.0051 0.0071 HDV8B 0.0698 0.0463 0.0352 0.0365 0.0297 0.0346 0.0422 0.0342 0.0283 0.0223 0.0182 0.0253 HDBS 0.0035 0.0023 0.0018 0.0018 0.0015 0.0017 0.0021 0.0017 0.0014 0.0011 0.0009 0.0013 HDBT 0.0017 0.0012 0.0009 0.0009 0.0007 0.0009 0.0011 0.0009 0.0007 0.0006 0.0005 0.0006 MC 0.0048 0.0053 0.0055 0.0055 0.0056 0.0055 0.0054 0.0055 0.0056 0.0057 0.0058 0.0057 * Source Type Definitions LDV - Light-Duty Vehicles (Passenger Cars) HDV5 - Class 5 Heavy-Duty Vehicles (16,001-19,500 lbs. GVWR) LDT1 - Light-Duty Trucks 1 (0-6,000 lbs. GVWR, 0-3,750 lbs. LVW) HDV6 - Class 6 Heavy-Duty Vehicles (19,501-26,000 lbs. GVWR) LDT2 - Light-Duty Trucks 2 (0-6,000 lbs. GVWR, 3,751-5,750 lbs. LVW) HDV7 - Class 7 Heavy-Duty Vehicles (26,001-33,000 lbs. GVWR) 

LDT3 - Light-Duty Trucks 3 (6,001-8,500 lbs. GVWR, 0-5,750 lbs. ALVW) HDV8A - Class 8a Heavy-Duty Vehicles (33,001-60,000 lbs. GVWR) 

LDT4 - Light-Duty Trucks 4 (6,001-8,500 lbs. GVWR, 5,751 lbs. and greater ALVW) HDV8B - Class 8b Heavy-Duty Vehicles (>60,000 lbs. GVWR) HDV2 - Class 2b Heavy-Duty Vehicles (8,501-10,000 lbs. GVWR) HDBS - School Buses HDV3 - Class 3 Heavy-Duty Vehicles (10,001-14,000 lbs. GVWR) HDBT - Transit and Urban Buses HDV4 - Class 4 Heavy-Duty Vehicles (14,001-16,000 lbs. GVWR) MC - Motorcycles 

On-road Mobile Source Emissions Inventory 

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Appendix B.3 

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Converter applications were used to reallocate the VMT fractions from the twelve functional 

classes to the five MOVES road types described below: 

• Off-Network (road type 1) – all locations where the predominant activity is vehicle starts, 

parking and idling (parking lots, truck stops, rest areas, freight or bus terminals) 

• Rural Restricted Access (road type 2) – rural highways that can only be accessed by an 

on-ramp 

• Rural Unrestricted Access road type 3) – all other rural roads (arterials, connectors, and 

local streets) 

• Urban Restricted Access (road type 4) – urban highways or freeways that can only be 

accessed by an on-ramp 

• Urban Unrestricted Access (road type 5) – all other urban roads (arterials, connectors, 

and local streets) 

The NCDAQ followed the USEPA guidance that states that all SIP and regional conformity 

analyses must include the Off-Network road type in order to account for emissions from vehicle 

starts, extended idle activity, and evaporative emissions (for volatile organic compounds). The 

Off-Network road type is automatically selected when start or extended idle pollutant processes 

are chosen and must be selected for all evaporative emissions to be quantified. Off-Network 

activity in MOVES is primarily determined by the Source Type Population input, which is 

described in Section 4.2.2. Some evaporative emissions are estimated on roadways (i.e., road 

types 2, 3, 4, and 5) to account for evaporative emissions that occur when vehicles are driving. 

All roads types are automatically selected when Refueling emission processes are selected. 

MOVES uses Road Type to assign default drive cycles to activity on road types 2, 3, 4, and 5. 

For example, for unrestricted access road types, MOVES uses drive cycles that assume stop and 

go driving, including multiple accelerations, decelerations, and short periods of idling. For 

restricted access road types, MOVES uses drive cycles that include a higher fraction of cruise 

activity with less time spent accelerating or idling, although some ramp activity is also included. 

4.2.5 Inspection and Maintenance Program 

In 2002, North Carolina implemented a new vehicle emissions inspection program based on 

vehicle onboard diagnostics (OBD-II). This program covers all light duty gasoline powered 

vehicles that are model year 1996 and newer. The program was initially implemented in 9 

counties and was expanded to include a total of 48 counties between July 2002 and January 

2006. Requirements and specifications of the inspection and maintenance program are 

established in the State Implementation Plan (SIP) for the North Carolina Inspection and 

Maintenance (I/M) Program. The I/M SIP specifies a compliance rate of 92%, meaning that at 
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least 92% of vehicles subject to the I/M program must meet the inspection requirements in order 

for the program to meet the desired emissions reduction goals. The I/M SIP also specifies a 5% 

waiver rate. This means the program requirements can be waived for vehicles that cannot pass 

inspection, as long as the total number of waivers issued does not exceed 5% of all subject 

vehicles. 

In developing this emissions inventory, the MOVES model was run with the appropriate 

parameters needed to show the effects of the North Carolina I/M program in reducing emissions. 

For each source type subject to an I/M program, the MOVES model uses a compliance factor 

based on the compliance rate, waiver rate, and “regulatory class coverage adjustment”, which 

accounts for the fraction of vehicles within a source type that are covered by the I/M program. 

Table 4.2-4 lists the MOVES I/M compliance factors based on the prescribed 92% compliance 

rate, 5% waiver rate, and class coverage adjustment for the applicable source types. 

Table 4.2-6 MOVES I/M Compliance Factors 

Source Type Compliance Factor 

Passenger Car 87.4 

Passenger Truck 82.2 

Light commercial Truck 76.9 

4.2.6 Fuel Supply and Formulation 

The MOVES model is populated with monthly default fuel formulations (identified by fuel 

formulation ID) which are fuel year specific. The model incorporates all recent rulemakings 

(Tier 2, ultra low sulfur diesel, etc). The default dataset was exported from MOVES and was 

updated to reflect North Carolina’s monthly Reid Vapor Pressure (RVP) requirements for 

gasoline. For the month modeled (January), an RVP value of 15 was used for all four counties 

modeled. Also, the MOVES default diesel fuel formulation for January 2010 included a fuel 

sulfur level of 43 parts per million (ppm). This value reflects the transition from low sulfur diesel 

fuel, (500 ppm sulfur) to ultra low sulfur diesel (15 ppm sulfur), which was gradually phased in 

over the period from October 15, 2006 to December 1, 2010. 

4.2.7 Meteorological Data 

Local temperature and humidity data are required inputs for SIP and regional conformity 

analyses with MOVES. Ambient temperature is a key factor in estimating emissions for on-road 

vehicles, with substantial effects on most pollutant processes. Relative humidity is also important 
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for estimating NOx emissions from motor vehicles. MOVES requires a temperature (in degrees 

Fahrenheit) and relative humidity (in percent – 0 to 100 scale) for each hour selected in the Run 

Spec. 2010 monthly average (by hour) temperature and relative humidity from three weather 

stations listed in the table below were provided by State Climate Office of North Carolina. 

Table 4.2-7 Average Hourly Temperature and Humidity – January 2010 

County Forsyth Mecklenburg Durham, Wake 

Weather Station KGSO KCLT KRDU

Location Piedmont Triad 

International Airport

Charlotte / Douglas 

International Airport

Raleigh-Durham 

International 

Airport

Hour Temp., 

°F 

Relative 

Humidity, 

% 

Temp., °F 

Relative 

Humidity, 

% 

Temp., 

°F 

Relative 

Humidity, 

% 

12:00 AM-1:00 AM 32.6 68 34.2 70 34.5 66 

1:00 AM-2:00 AM 31.9 69 33.2 72 33.7 68 

2:00 AM-3:00 AM 31.4 70 32.5 73 32.7 70 

3:00 AM-4:00 AM 31.0 71 31.6 75 32.0 72 

4:00 AM-5:00 AM 29.8 72 31.0 77 31.4 73 

5:00 AM-6:00 AM 29.5 72 30.2 79 30.9 74 

6:00 AM-7:00 AM 29.3 71 29.7 79 30.4 75 

7:00 AM-8:00 AM 29.3 71 30.1 79 30.7 74 

8:00 AM-9:00 AM 32.5 67 33.5 74 33.4 70 

9:00 AM-10:00 AM 35.7 59 36.7 65 36.9 62 

10:00 AM-11:00 AM 38.7 52 39.7 56 40.2 53 

11:00 AM-12:00 PM 40.6 48 42.4 50 42.3 48 

12:00 PM-1:00 PM 42.5 45 43.8 47 44.4 45 

1:00 PM-2:00 PM 43.4 43 45.3 44 45.6 43 

2:00 PM-3:00 PM 44.1 43 45.8 43 46.3 42 

3:00 PM-4:00 PM 43.7 43 46.6 43 45.8 43 

4:00 PM-5:00 PM 42.0 45 44.8 46 44.2 45 

5:00 PM-6:00 PM 40.1 48 42.1 51 41.6 49 

6:00 PM-7:00 PM 38.0 53 40.9 53 39.8 52 

7:00 PM-8:00 PM 36.7 56 39.0 58 38.3 56 

8:00 PM-9:00 PM 36.2 57 37.8 60 37.5 57 

9:00 PM-10:00 PM 34.4 61 37.0 62 36.2 60 

10:00 PM-11:00 PM 33.5 63 36.0 64 35.4 62 

11:00 PM-12:00 AM 33.0 65 34.6 67 34.8 63 
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4.3 ESTIMATED EMISSIONS FROM ON-ROAD MOBILE SOURCES 

Table 4.3-1 lists the CO emissions modeling results. The values listed represent CO emissions 

from all vehicle types, as well as all vehicle activity, including off network (vehicle exhaust 

emissions from starts and evaporative emissions) and on-road running exhaust emissions.. 

Table 4.3-1 January 2010 On-road Mobile Source CO emissions 

County 

CO emissions, 

tons/month 

CO emissions, 

tons/day 

Durham 5,766 186.0 

Forsyth 7,569 244.2 

Mecklenburg 22,456 724.4 

Wake 19,932 643.0 

. 
Appendix B.4 

Nonroad Mobile Sources 

Emission Inventory Documentation 
(This page intentionally left blank) 
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Table of Contents 

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

2.0 OVERALL METHODOLOGY .............................................................................................. 1

2.1 SOURCE CATEGORY IDENTIFICATION .................................................................. 1

2.2 EMISSION ESTIMATION APPROACH ....................................................................... 1

3.0 QUALITY ASSURANCE MEASURES ................................................................................. 2

4.0 EMISSIONS AND DETAILED METHODOLOGY .............................................................. 3

4.1 CATEGORIES FROM THE NONROAD MODEL WITHIN THE NMIM MODEL .... 3

4.2 AIRCRAFT ENGINES AND AIRPORT GROUND SUPPORT.................................... 4

4.3 RAILROAD LOCOMOTIVES........................................................................................ 6

4.4 COMBINED NONROAD EMISSIONS ......................................................................... 7

5.0 PROJECTION AND CONTROL FACTORS ......................................................................... 8

5.1 RAILROAD EMISSIONS GROWTH AND CONTROL ............................................... 8

6.0 NMIM RUNSPEC FILE .......................................................................................................... 9

 
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List of Tables 

Table 4-1 CO Emissions for NMIM Equipment Categories ......................................................... 4

Table 4-2 CO Emissions from Airports ......................................................................................... 6

Table 4-3 CO Emissions from Railroads ....................................................................................... 7

Table 4-4 Combined Nonroad CO Emissions ............................................................................... 7

Table 5-1 Railroad CO Growth and Control Factors, 2008 to 2010 .............................................. 8
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1.0 INTRODUCTION AND SCOPE 

Nonroad mobile sources are equipment that can move but are not licensed to use the public roads 

and highways. 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. Emissions from this type of equipment are calculated using the National Mobile 

Inventory Model (NMIM) developed by the United States Environmental Protection Agency 

(USEPA). This category also includes emissions from aircraft, railroad locomotives, and 

commercial marine vessels which are calculated outside of NMIM. No commercial marine 

vessels operate in Durham, Forsyth, Mecklenburg, or Wake counties so there are no emissions 

reported for this sub-category. 

For this maintenance demonstration, emissions of carbon monoxide (CO) are estimated for the 

year of 2010. 

2.0 OVERALL METHODOLOGY 

2.1 SOURCE CATEGORY IDENTIFICATION 

Nonroad mobile sources were identified using the 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); 

from the USEPA’s NMIM model (incorporating NONROAD2008a released July 6, 2009); and 

from the Emissions and Dispersion Modeling System version 5.1.3 (EDMS 5.1.3) model 

developed by the USEPA and the Federal Aviation Administration (FAA). 

2.2 EMISSION ESTIMATION APPROACH 

For the majority of nonroad mobile categories, emissions were estimated using the USEPA’s 

NMIM model. Model runs were performed for each of the four counties for January, February, 

and December of 2010. The county sums of these runs were divided by 90 to produce typical 

winter day emissions for the several nonroad mobile equipment categories for the counties. 
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Aircraft emissions were calculated with activity data for the year 2010 for the most part. Activity 

data for the very small airports was from less year specific FAA data but, in several cases, was 

obtained by phone calls to the airports. Most of the emissions were calculated using the EDMS 

5.1.3 model where the the number of landings and takeoffs for specific aircraft and engine 

combinations are entered. For air taxi activity and general aviation, not calculated with the 

EDMS 5.1.3 model, methods and emission factors described in Documentation for Aircraft 

Component of the National Emission Inventory Methodology (ERG No.: 0245.03.402.001, 

January 27, 2011) were employed. Emission factors developed for military aircraft at military 

airports in North Carolina as part of the 2008 National Emission Inventory (NEI) were used to 

calculate emissions for military aircraft operating at civilian airports. 

Railroad emissions from the 2008 NEI including passenger railroad emissions developed by the 

North Carolina Division of Air Quality (NCDAQ) for the NEI were used as the starting point for 

developing 2010 emissions. Growth factors were based on projected railroad fuel use. Future 

emission reductions due to emission control measures were calculated based on future emission 

factors published in the USEPA document Emission Factors for Locomotives, EPA-420-F-09-

025. Two additional trains were added to the Piedmont route in June, 2010. Emission 

adjustments were made for this to account for extra emissions in December. 

3.0 QUALITY ASSURANCE MEASURES 

For the NMIM model run, the run specification file (file that displays the variables used to setup 

a model run) was reviewed by a second person who did not perform the actual runs. The model 

results (month totals for three winter months) were also evaluated for completeness and 

comparability to a previous annual run. 

For the aircraft portion of the inventory, data was obtained from sources consistent with USEPA 

emission inventory methodology. Data entry for the EDMS model was reviewed. Spreadsheet 

calculations were also reviewed by a second person. NEI 2008 emissions projected to 2010 

(annual numbers) were compared to those directly calculated (mostly seasonal) and were found 

to be comparable. 

Railroad emission calculations and projection methods were reviewed by a second person. 
Nonroad Mobile Sources Documentation 3 

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4.0 EMISSIONS AND DETAILED METHODOLOGY 

4.1 CATEGORIES FROM THE NONROAD MODEL WITHIN THE NMIM MODEL 

The USEPA included more than 80 different types of equipment in the NONROAD model. To 

facilitate analysis and reporting, the USEPA grouped the equipment types into twelve equipment 

categories. These include: 

Agricultural equipment Lawn and garden equipment, commercial 

Commercial equipment Logging equipment 

Construction and mining equipment Pleasure craft (recreational marine) 

Industrial equipment Railroad maintenance equipment 

Lawn and garden equipment, residential Recreational equipment 

The eleventh category, aircraft ground support equipment, was not calculated with the NMIM / 

NONROAD model because the method of calculation performed by the EDMS model was 

judged to be superior. The twelvth category is underground mining equipment; there are no 

underground mining operations in the four counties. Additionally, the emissions are estimated 

for five different engine types. These include: 2-stroke and 4-stroke spark ignition engines, 

diesel engines, liquid propane gas and compressed natural gas fueled engines. 

The NMIM model containing the NONROAD2008a model version was used to estimate 

emissions for the maintenance plan. NONROAD2008a is the latest release of the USEPA 

NONROAD model that was first released in June 2000, and incorporates many revisions to 

improve the model’s predictive ability. Compared to NONROAD2005c, this model revision 

accounts for emission reductions from the Diesel Recreational Marine standards in the 

Loco/Marine final rule published in the Federal Register (FR) (73FR 25098) and the Small Spark 

Ignition and Spark Ignition Recreational Marine final rule (FR 59034). There are a number of 

additional improvements including the ability to model the effects of ethanol blends on fuel tank 

and hose permeation losses. 

The seasonal file for the NONROAD2008a model was modified to place North Carolina in the 

Southeast states group rather than the Mid-Atlantic group. This change was made because the 

NCDAQ had reviewed temperature data of North Carolina compared to states in the Southeast 

and the Mid-Atlantic. The results of this comparison indicated that North Carolina temperatures 

are more in-line with the Southeast States. Meterological data specific for the year 2010 was 

incorporated in the NMIM model by modification of the model’s CountyYearMonthHour table 

For reporting purposes, the resulting emissions were totaled for each equipment category by 

county. 
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The NMIM model was operated through the graphic user interface (GUI). A runspec file was 

created which directed the running of the NONROAD2008a model. A copy of the runspec file is 

in Section 6.0 of this document. The model was run for January, February, and December of 

2010. Values for the three months were summed and then divided by 90 to get tons of CO per 

day. The summary of the model results expressed in tons emitted per typical winter day are 

tabulated in Table 4-1. 

Table 4-1 CO Emissions for NMIM Equipment Categories 

Equipment Categories CO tons/day 

Durham Forsyth Mecklenburg Wake 

Agricultural Equipment 0.00 0.02 0.01 0.03 

Commercial Equipment 4.38 10.76 51.99 27.02 

Construction and Mining 

Equipment 3.44 2.00 11.41 9.51 

Industrial Equipment 4.55 3.68 6.23 3.80 

Lawn and Garden Equipment, 

Commercial 3.33 3.84 24.12 19.36 

Lawn and Garden Equipment, 

Residential 1.79 2.42 5.67 4.98 

Logging Equipment 0.04 0.05 0.04 0.25 

Pleasure Craft (Recreational 

Marine) 0.09 0.04 0.26 0.27 

Railway Maintenance 0.00 0.00 0.01 0.00 

Recreational Equipment 1.37 0.83 3.73 1.93 

Total 18.99 23.64 103.47 67.15 

4.2 AIRCRAFT ENGINES AND AIRPORT GROUND SUPPORT 

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 have little or no effect on ground 

level air pollutant concentrations. 
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The aircraft emissions of interest are produced during 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. Associated with these emissions are emissions from ground support equipment 

(GSE) and auxiliary power units (APU) which are small engines used to maintain aircraft power 

and air conditioning when the main engines are shut off. 

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, freight or both. Air taxis and 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. Air taxis may also be used for unscheduled on-demand flights. 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. Military operations at civilian airports are often associated with National 

Guard, Army Reserve, and Air Force Reserve training. 

Emission estimates were developed by NCDAQ for a typical winter day of 2010 for all airports 

in the four counties. Emission calculations for commercial aircraft were made using the EDMS 

5.1.3 model developed by the USEPA and the FAA. Emissions for air taxi and general aviation 

(both subgrouped into piston engine and turbine engine categories) were made using emission 

factors developed by the USEPA working with the FAA. More detail about this process is found 

in Documentation for Aircraft Component of the National Emissions Inventory Methodology, 

ERG No.: 0245.02.302.001, Contract No.: EP-D-07-097 prepared by Eastern Research Group 

under contract to E.H. Pechan for the EPA. For military operations at civilian airports, emissions 

were calculated using emission factors developed by NCDAQ from surveys of military airports 

in North Carolina for the 2008 National Emission Inventory (NEI). The next paragraph describes 

the general approach to develop these emission factors. 

For the 2008 NEI, requests for counts of operations by aircraft type were sent to the military 

airports in North Carolina. Two Army airports, two Air Force airports, and one Coast Guard 

airport supplied the requested information The Marine Corps failed to supply any requested data. 

From the available data, the EDMS 5.1.3 model was used to calculate the airport’s emissions. 

Seymour Johnson Airforce Base is home to a large number of fighter aircraft. However, it is 

believed that fighter aircraft operations are not common at civilian airports in NC. The NC Air 

National Guard (based in Charlotte) is equipped for airlift operations. The Air Force Reserve 

units based here (at the two Air Force bases) perform refueling and airlift operations. Fighter 

airplanes tend to make a lot of noise yet we don’t hear of strong complaints about noise around 
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our civilian airports. All this considered, it was decided to assume no fighter operations at the 

civilian airports. Military aircraft at military airports often perform touch and go (T&G) 

operations for landing practice (they don’t actually stop so there are no taxi or ground support 

emissions) The assumption was made that military operations at civilian airports would have the 

same proportion of T&Gs to LTOs as at military airports (civilian operations are not considered 

to include touch and go). Considering all the military airports together and excluding the fighter 

aircraft, emission factors for military aircraft and ground support were calculated on a per 

operation basis. 

Activity data for commercial flights was obtained from the Bureau of Transportation Statistics 

(BTS) T-100 Segment data for 2010. This data is reported by month so January, February, and 

December data were used to calculate commercial flight CO tons per day for the Charlotte 

Douglas airport in Mecklenburg County and the Raleigh Durham airport in Wake County. 

December data appeared to be missing for the Smith Reynolds airport in Forsyth County so just 

January and February data were used. For the rest of the operations data at these three airports an 

Airport Operations: Standard Report was generated using the FAA’s Air Trafic Activity Data 

System (ATADS). This data, after adjustment with annual T-100 Segment data, was used to 

calculate emissions from air taxis, general aviation and military flights. For the smallest airports, 

operations data and based aircraft data was obtained through the FAA National Flight Data 

Center form 5010 data. This was additionally supplemented with phone calls to three of the 

small airports because it appeared that the most recent inspection was a number of years in the 

past. Table 4-2 shows airport emissions. 

Table 4-2 CO Emissions from Airports 

Equipment Categories CO tons/day 

Durham Forsyth Mecklenburg Wake 

Aircraft and Auxiliary Power 

Units 0.03 0.31 6.32 2.16 

Aircraft Ground Support 

Equipment 0.00 0.00 4.69 1.26 

Total 0.03 0.31 11.01 3.42 

4.3 RAILROAD LOCOMOTIVES 

Freight railroad companies are categorized by size (Class I, Class II, or Class III). Class I 

railroad companies are long haul operations, consisting of Norfolk Southern Corporation and 

CSX Corporation. Class II and Class III railroad companies are short lines serving localized 
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markets. Amtrak and the North Carolina Department of Transportation (NCDOT) Rail Division 

provide passenger service. 

Railroad locomotive emissions for classes I, II, and III plus rail yards were calculated for all of 

North Carolina as part of the 2008 NEI. This inventory was prepared by the Eastern Regional 

Technical Advisory Committee (ERTAC) Rail Subgroup for the USEPA. Some of the details of 

the ERTAC work are based on proprietary information provided by the railroad companies. The 

calculation methodologies followed procedures acceptable to the USEPA. 

Passenger railroad emissions were developed by NCDAQ for 2008. This was done using 

information supplied by the NCDOT and emission factors from Emission Factors for 

Locomotives, EPA-420-F-09-025. The daily runs of the Piedmont train from Raleigh to Charlotte 

was increased from two trains to four in June, 2010. Emissions were increased based on the 

expected additional fuel use. 

Growth and control factors were produced to project the 2008 emissions to 2010. Railroad 

emissions are shown in Table 4-3 below. 

Table 4-3 CO Emissions from Railroads 

Equipment Categories CO tons/day 

Durham Forsyth Mecklenburg Wake 

Railroad Emissions 0.02 0.02 0.24 0.05 

4.4 COMBINED NONROAD EMISSIONS 

Table 4-4 Combined Nonroad CO Emissions 

County 2010 CO tons/day 

Charlotte Maintenance Area 

Mecklenburg 114.71 

Raleigh/Durham Maintenance Area 

Durham 19.04 

Wake 70.62 

Total 89.66 

Winston-Salem Maintenance Area 

Forsyth 23.97 
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Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

5.0 PROJECTION AND CONTROL FACTORS 

5.1 RAILROAD EMISSIONS GROWTH AND CONTROL 

Railroad growth factors were calculated using national fuel use estimates for freight and for 

intercity passenger service found on table 46 of the Energy Information Administration’s Annual 

Energy Outlook, 2011. Fuel use for 2010 was divided by fuel use for 2008 and the quotient was 

multiplied by the 2008 emissions to adjust for growth.Control factors were calculated by using 

recommended CO emission factors for from Emission Factors for Locomotives, EPA-420-F-09-

025. The control factors were calculated by dividing base year emission factors into the future 

year emission factors. Since the CO emission factors were the same the control factor was 1 in 

all cases. Table 5-1 shows the growth and control factors used and the equation used is below: 

2008 CO emissions * 2010 fuel use * 2010 CO emission factor = 2010 CO emissions 2008 fuel use 2008 CO emission factor 

An additional adjustment was made to passenger train emissions due to two extra runs (one 

round trip) of the Piedmont each day starting in June, 2010. Therefore, miles traveled and 

emissions were greater in December then in January and February. Emissions were originally 

calculated based on known usage of diesel fuel per mile and miles traveled in each county by all 

passenger trains. The estimated annual fuel use for the original two Piedmont runs was 

calculated as was total annual passenger train fuel use in the three counties. Daily emissions were 

found by adding 59/90 of the original daily emissions to 31/90 of the original daily emissions 

times the new annual fuel amount divided by the original: 

CO t * 59 +CO t * Original fuel use + additional fuel * 31 =Adjusted CO t

d 90 d Original fuel use 90 d

Table 5-1 Railroad CO Growth and Control Factors, 2008 to 2010 

Type of Service Control Factor Growth Factor 

Line Haul Locomotives: Class I Operations 1 0.918868646 

Line Haul Locomotives: Class II / III Operations 1 0.918868646 

Line Haul Locomotives: Passenger Trains (Amtrak) 1 1.005665722 

Yard Locomotives 1 0.918868646 
Nonroad Mobile Sources Documentation 9 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.4 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

6.0 NMIM RUNSPEC FILE 

<runspec> 

 <description>CO limited maintenance plan, 2010 inventory</description> 

 <geography mode="3"> 

 <location fipsstateid="37" fipscountyid="63"/> 

 <location fipsstateid="37" fipscountyid="67"/> 

 <location fipsstateid="37" fipscountyid="119"/> 

 <location fipsstateid="37" fipscountyid="183"/> 

 </geography> 

 <months> 

 <month index="1"/> 

 <month index="2"/> 

 <month index="12"/> 

 </months> 

 <weather useYearlyWeatherDataActive="true" 

useYearlyWeatherDataSelected="true"/> 

 <years> 

 <year index="2010"/> 

 </years> 

 <onroad> 

 </onroad> 

 <offroad> 

 <scc fuel="CNG" segment="1"/> 

 <scc fuel="CNG" segment="2"/> 

 <scc fuel="CNG" segment="3"/> 

 <scc fuel="CNG" segment="4"/> 

 <scc fuel="CNG" segment="5"/> 

 <scc fuel="CNG" segment="6"/> 

 <scc fuel="CNG" segment="7"/> 

 <scc fuel="CNG" segment="9"/> 

 <scc fuel="CNG" segment="10"/> 

 <scc fuel="CNG" segment="11"/> 

 <scc fuel="CNG" segment="12"/> 

 <scc fuel="Dies" segment="1"/> 

 <scc fuel="Dies" segment="2"/> 

 <scc fuel="Dies" segment="3"/> 

 <scc fuel="Dies" segment="4"/> 
Nonroad Mobile Sources Documentation 10 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.4 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

 <scc fuel="Dies" segment="5"/> 

 <scc fuel="Dies" segment="6"/> 

 <scc fuel="Dies" segment="7"/> 

 <scc fuel="Dies" segment="9"/> 

 <scc fuel="Dies" segment="10"/> 

 <scc fuel="Dies" segment="11"/> 

 <scc fuel="Dies" segment="12"/> 

 <scc fuel="Gas" segment="1"/> 

 <scc fuel="Gas" segment="2"/> 

 <scc fuel="Gas" segment="3"/> 

 <scc fuel="Gas" segment="4"/> 

 <scc fuel="Gas" segment="5"/> 

 <scc fuel="Gas" segment="6"/> 

 <scc fuel="Gas" segment="7"/> 

 <scc fuel="Gas" segment="9"/> 

 <scc fuel="Gas" segment="10"/> 

 <scc fuel="Gas" segment="11"/> 

 <scc fuel="Gas" segment="12"/> 

 <scc fuel="LPG" segment="1"/> 

 <scc fuel="LPG" segment="2"/> 

 <scc fuel="LPG" segment="3"/> 

 <scc fuel="LPG" segment="4"/> 

 <scc fuel="LPG" segment="5"/> 

 <scc fuel="LPG" segment="6"/> 

 <scc fuel="LPG" segment="7"/> 

 <scc fuel="LPG" segment="9"/> 

 <scc fuel="LPG" segment="10"/> 

 <scc fuel="LPG" segment="11"/> 

 <scc fuel="LPG" segment="12"/> 

 </offroad> 

 <pollutants hydrocarbonunits="VOC"> 

 <pollutant index="10"/> 

 </pollutants> 

 <advanced> 

 <countydb server="" name=""/> 

 <mobile6run path=""/> 

 <mobile6scenario path=""/> 

 <nonroadalt path=""/> 
Nonroad Mobile Sources Documentation 11 

Charlotte, Raleigh/Durham & Winston-Salem Appendix B.4 

Pre-hearing Draft CO Limited Maintenance Plan June 29, 2012 

 </advanced> 

 <onroadretrofit retrofit="false" parametersFile="" fleet="false" 

fleetInformationFile=""/> 

 <offroadretrofit retrofit="false" parametersFile="" fleet="false" 

fleetInformationFile=""/> 

 <output granularity="2" shouldPreAggregateForNIF3="true"> 

 <outputdb server="localhost" name="nmimCO10out"/> 

 </output> 

</runspec>