* — \
*1 PROt^
DOCUMENTATION FOR THE 2008 MOBILE
SOURCE NATIONAL EMISSIONS
INVENTORY

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EPA-454/B-20-028
May 2011
DOCUMENTATION FOR THE 2008 MOBILE SOURCE NATIONAL EMISSIONS
INVENTORY
Prepared by:
E.H. Pechan & Associates, Inc.
3622 Lyckan Parkway, Suite 2005
Durham, NC 27707
Prepared for:
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Air Quality Assessment Division
Emissions Inventory and Analysis Group
Research Triangle Park, NC 27711
Contract No. EP-D-07-097
Work Order No. 4-02
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Air Quality Assessment Division
Research Triangle Park, NC

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May 2011
CONTENTS
Page
TABLES	iv
ACRONYMS	v
1.0 INTRODUCTION	1
1.1	WHAT IS THE PURPOSE OF THIS REPORT?	1
1.2	WHAT CATEGORIES ARE COVERED IN THIS REPORT?	1
1.3	IIOW IS THIS REPORT ORGANIZED?	2
2.0 SUMMARY OF 2008 NONROAD AND ONROAD MOBILE SOURCE
METHODOLOGIES	3
2.1	WHAT ARE THE GENERAL METHODOLOGIES EPA USED TO DEVELOP
PREVIOUS YEAR MOBILE SOURCE \EI" S?	3
2.2	WHAT IS THE BASIS FOR THE 2008 EMISSIONS DATA LOADED INTO THE
EIS?	3
2.3	WHAT IS THE MAGNITUDE OF THE MOBILE SOURCE EMISSIONS
ESTIMATED FOR 2008?	14
3.0 NATIONAL MOBILE INVENTORY MODEL (\ VIIVI)	16
3.1	BACKGROUND	16
3.2	THE \ VIIVI COUNTY DATABASE	 16
3.2.1	Database Structure	16
3.2.2	EPA Default 2008 NCD Inputs	17
3.2.3	State/Local Agency-Submitted Inputs	19
4.0 POST-PROCESSING OF NMIM OUTPUT	23
4.1	POLLUTANT CODE REVISIONS	23
4.2	REMOVAL OF GROUND SUPPORT EQUIPMENT	23
4.3	STAGE II ONRO AD VEHICLE REFUELING	23
5.0 REFERENCES	24
APPENDIX A. TABLES UPDATED WITH EIS SUBMISSIONS	A-l
in

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May 2011
TABLES
Table 2-la. Methods Used to Develop Emission Estimates for Onroad Vehicle Sources	4
Table 2-lb. Methods Used to Develop Emission Estimates for Nonroad Mobile Sources	6
Table 2-2. Summary of Onroad and Nonroad 2008 NMIM Data Submissions	13
Table 2-3. 2008 Onroad Mobile NEI National Emission Totals	15
Table 2-4. 2008 Nonroad Mobile NEI National Emission Totals	15
Table 3-1. Tables in the NMIM County Database (NCD)	17
Table 3-2. Mapping of HPMS Vehicle Categories to NMIM/MOBILE6 and SCC-Level Vehicle
Classes	20
Table 4-1. Pollutant Code Revisions	23
Table A-l. 2008 NMIM County Database Table Updates by Jurisdiction	A-l
Table A-2. Summary of 2008 NEI Vehicle Miles Traveled Data by Jurisdiction	A-3
Table A-3. External Onroad Files Updated for the 2008 NEI	A-5
Table A-4. NONROAD Model Parameters Provided by State Agencies	A-7

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ACRONYMS
AEO
Annual Energy Outlook
CAP
criteria air pollutant
CMV
commercial marine vessel
CNG
compressed natural gas
CO
carbon monoxide
DOE
Department of Energy
DOT
Department of Transportation
EDMS
Emissions and Dispersion Modeling System
EGAS
Emissions Growth Analysis System
EIA
Energy Information Administration
EIS
Emissions Inventory System
EPA
Environmental Protection Agency
ETBE
ethyl tert-butyl ether
ETOH
ethanol
FAA
Federal Aviation Administration
FHWA
Federal Highway Administration
FIPS
Federal Information Processing System
GIS
geographic information system
GSE
ground support equipment
HAPs
hazardous air pollutants
HC
hydrocarbons
HDDV
heavy duty diesel vehicle
HDGV
heavy duty gasoline vehicle
HHDDV
heavy heavy-duty vehicle
HPMS
Highway Performance Monitoring System
I/M
inspection and maintenance
LDDT
light-duty diesel truck
LDGT
light-duty gasoline truck
LDDV
light-duty diesel vehicle
LDGV
light-duty gasoline vehicle
LDV
light-duty vehicle
LEV
low emission vehicle
LHDDV
light heavy-duty diesel vehicle
LPG
liquefied petroleum gas
LTO
landing/take-off
MC
motorcycle
MTBE
methyl tert-butyl ether
NCD
NMIM County Database
NCDC
National Climatic Data Center
NEI
National Emissions Inventory
NGV
natural gas vehicle
nh3
ammonia
NMIM
National Mobile Inventory Model
OTAQ
Office of Transportation and Air Quality
PADDs
Petroleum Administration for Defense Districts

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May 2011
PM
particulate matter
PM10
particulate matter less than or equal to 10 micrometers
PM2.5
particulate matter less than or equal to 2.5 micrometers
RVP
Reid vapor pressure
RFG
reformulated gasoline
see
source classification code
SIC
standard industrial classification code
SIP
State Implementation Plan
S/L/T
State/Local/T rib al
so2
sulfur dioxide
STEEM
Ship Traffic, Energy, and Environmental Model
TAF
Terminal Area Forecast
TAME
tertiary amyl methyl ether
U.S.
United States
VMT
vehicle miles traveled
VOC
volatile organic compound
vi

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May 2011
1.0	INTRODUCTION
The National Emissions Inventory (NEI) is a comprehensive inventory covering criteria
pollutants and hazardous air pollutants (HAPs) for the 50 United States (U.S.), Washington DC,
Puerto Rico, and U.S. Virgin Islands. The NEI is developed by the U.S. Environmental
Protection Agency (EPA)'s Emissions Inventory and Analysis Group in Research Triangle Park,
North Carolina. The EPA is updating the NEI to a new computer system, the Emission
Inventory System (EIS), which supports the collection and distribution of inventory information.
The NEI is used to support air quality modeling, rule development, international reporting, air
quality trends analysis, and other activities. To support these ends, the EPA compiles
comprehensive emissions data in the NEI for criteria and HAPs for nonroad mobile, onroad
mobile, point, and nonpoint sources.
1.1	WHAT IS THE PURPOSE OF THIS REPORT?
This report summarizes the procedures EPA used to estimate annual emissions for the onroad
mobile sector and a portion of the nonroad mobile source sector of EPA's 2008 general release
NEI.
The nonroad sector is comprised of nonroad engines characterized in EPA's National Mobile
Inventory Model (NMIM), as well as other engines not modeled in NMIM, including aircraft,
commercial marine vessel, and locomotive engines. This report only addresses those nonroad
categories included in EPA's NMIM. Methodologies for other nonroad mobile source categories
are documented in the following reports:
•	Documentation for the Commercial Marine Vessel Component of the National Emissions
Inventory Methodology (ERG, 2010);
•	Documentation for Locomotive Component of the National Emissions Inventory
Methodology (ERG, 2011a); and
•	Documentation for Aircraft Component of the National Emissions Inventory
Methodology (ERG, 2011b).
1.2	WHAT CATEGORIES ARE COVERED IN THIS REPORT?
The onroad mobile source category includes motorized vehicles that are normally operated on
public roadways. This includes passenger cars, motorcycles, minivans, sport-utility vehicles,
light-duty trucks, heavy-duty trucks, and buses.
The nonroad categories in NMIM include recreational marine and land-based vehicles, farm and
construction machinery, industrial, commercial, logging, and lawn and garden equipment, and
rail maintenance equipment. These equipment are powered by compression-ignition engines,
which are typically diesel-fueled, as well as spark-ignition (gasoline-fueled) engines.
Compressed natural gas (CNG) and liquefied petroleum gas (LPG) engines may also power
certain types of nonroad equipment. Although included in NMIM, aircraft ground support
equipment (GSE) emissions are modeled separately in the NEI (see Section 4.2 for details).
1

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May 2011
1.3 HOW IS THIS REPORT ORGANIZED?
Section 2 provides an overview of the procedures used to develop the 2008 onroad and nonroad
mobile source emission estimates, as well as a summary of methodologies used for developing
pre-2008 year mobile source emission estimates. Section 3 presents a discussion of EPA's
NMIM, as well as a description of the inputs used in the NMIM County Database (NCD).
Section 4 describes the procedures used to process NMIM results for incorporation in the EIS.
Section 5 presents the references cited in this document. Appendix A displays a detailed listing
of the State/Local agency inputs incorporated into the NCD.
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May 2011
2.0	SUMMARY OF 2008 NONROAD AND ONROAD MOBILE
SOURCE METHODOLOGIES
This section provides an overview of the methods used to develop the EPA estimates in the 2008
NEI. Although the focus of this documentation is on describing the methodologies and data used
to develop 2008 emission estimates, Section 2.1 of this document provides an overview of the
methodologies used to develop pre-2008 year onroad and nonroad mobile source category
emission estimates.
2.1	WHAT ARE THE GENERAL METHODOLOGIES EPA USED TO
DEVELOP PREVIOUS YEAR MOBILE SOURCE NEI'S?
Tables 2.1a and 2.1b summarize the year-specific emission estimation methodologies that EPA
used to develop emission estimates for mobile source categories. Table 2.1a displays the onroad
mobile source emission estimation methodologies, while Table 2.1b presents the nonroad
methodologies. The entries in red boldface type summarize the 2008 NEI methods that are
described in this report.
2.2	WHAT IS THE BASIS FOR THE 2008 EMISSIONS DATA LOADED
INTO THE EIS?
The EPA developed the EIS to support the development of the 2008 and future year NEIs. The
EIS is a data repository that collects and combines data contributions from EPA and
State/Local/Tribal (S/L/T) agencies into a cohesive data set in a transparent manner. One of the
primary tenets of the NEI is that S/L/T agency data take preference over EPA developed data.
Therefore, with some exceptions noted herein, EPA default mobile source data were replaced
with S/L/T submitted data.
For onroad and nonroad mobile source categories, EPA requested that S/L/T agencies submit
model inputs for use in an EPA 2008 NEI run of NMIM. After EPA completed the NMIM runs
for areas that submitted data, EPA then processed the emissions data for loading into the EIS for
S/L/T agency review. If an agency submitted onroad emissions data rather than updated onroad
NMIM inputs, then EPA compiled the vehicle miles traveled (VMT) from this submittal for use
in EPA's NMIM run. As described in Section 3.2.3.1, this situation necessitated EPA efforts to
allocate the SCC-level VMT in these submittals to the level of detail required by NMIM. Table
2-2 identifies the types of NMIM input updates that were provided by each State/Local agency.
The "NCD Files" column indicates that an agency provided updates to the NCD. The NCD is
the database that contains the input data needed by NMIM. The "Onroad SCC-based VMT"
column is used to identify areas that supplied onroad emissions data to the EIS. In these cases,
EPA extracted available SCC-based VMT data from these submittals, and further processed the
VMT data for use in EPA onroad mobile source NMIM runs.
3

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May 2011
Table 2-1 a. Methods Used to Develop Emission Estimates for Onroad Vehicle Sources
Base
Year(s)
Pollutant(s)
Geographic Area
Emission Estimation Method
2008
All Criteria, HAPs US, Puerto Rico, Virgin Islands
2005
All Criteria, HAPs
2002
All Criteria, HAPs
2001
2001
2001
2001
1999
1999
VOC, NOx, CO, S02,
PM10, PM2.5
NH3
All Criteria
All Criteria
All Criteria
VOC, NOx, CO, S02,
PM10, PM2.5
US, Puerto Rico, Virgin Islands
US, Puerto Rico, Virgin Islands
California
California
AL; CO; ME; MA; MS; OR; UT; VA;
WV; Maricopa County, AZ;
Hamilton County, TN
Rest of US
AL; ME; MA; MS; UT; VA; WV;
Maricopa County, AZ; Hamilton
County, TN
California
Emission estimates for all pollutants were developed using EPA's
National Mobile Inventory Model (NMIM), which uses MOBILE6
(specifically, M6203ChcOxFixNMIM.exe) to calculate onroad emission
factors. Where States provided alternate onroad MOBILE6 inputs or
VMT, these data replaced EPA default inputs. Default VMT is based on
FHWA 2008 data and 2008 Census population estimates.
Emission estimates for all pollutants were developed using EPA's NMIM,
which uses MOBILE6 to calculate onroad emission factors. Where States
provided alternate onroad MOBILE6 inputs or VMT, these data replaced EPA
default inputs. Default VMT is based on FHWA 2005 data and 2005 Census
population estimates.
Emission estimates for all pollutants were developed using EPA's NMIM,
which uses MOBILE6 to calculate onroad emission factors. Where States
provided alternate onroad MOBILE6 inputs or VMT, these data replaced EPA
default inputs. California-supplied emissions data which replaced default EPA
emission estimates for this state. Default VMT is based on FHWA 2002 data
and population data from 2000 Census.
Emissions and VMT provided by California at county/vehicle type level; State-
provided emissions expanded to county/SCC level by EPA
Calculated at State/county/SCC level by month using MOBILE6 emission
factors with State-provided VMT data
State-provided VMT grown to 2001; emissions calculated by EPA using
MOBILE6 emission factors
Calculated at State/county/SCC level by month using MOBILE6 and FHWA-
based VMT
Calculated at State/county/SCC level by month using MOBILE6; State-
provided VMT data used
Emissions and VMT provided by California at county/vehicle type level; State-
provided emissions expanded to county/SCC level by EPA
4

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May 2011
Table 2-1 a. Methods Used to Develop Emission Estimates for Onroad Vehicle Sources
Base
Year(s)
Pollutant(s)
Geographic Area
Emission Estimation Method
1999
1999
1999
1999
1999
1999
1999
1997-1998
1990,1996
1991-1995
1988-1989
1979-1986
1978, 1987,
1990, 1996,
2000
1970,1975
NH3
PM10 Exhaust
VOC, NOx, CO, S02,
PM10 brake and tire
wear, PM2.5, NH3
All Criteria
All Criteria
HAPs
HAPs
All Criteria
HAPs
All Criteria
All Criteria
All Criteria
All Criteria
All Criteria
California
Colorado
Colorado
Oregon
Rest of US, Puerto Rico, and US
Virgin Islands
California
Rest of US, Puerto Rico, and US
Virgin Islands
US
US
US
US
US
US
US
Calculated at State/county/SCC level by month using MOBILE6 emission
factors with State-provided VMT data
PM10 emissions and VMT provided by State
Calculated at State/county/SCC level by month using MOBILE6; State-
provided VMT data used
Emissions and VMT provided by Oregon at county/vehicle type level; State-
provided emissions expanded to county/SCC level by EPA
Calculated at State/county/SCC level by month using MOBILE6 and FHWA-
based VMT
HAP emissions and VMT provided by California at county/vehicle type level;
emissions allocated to SCC level by EPA
MOBILE6 emission factors calculated at State/county/SCC level by season;
applied to FHWA-based VMT
2-step linear interpolation at State/count/SCC level based on 1996 and 1999
State/count/SCC level data
MOBILE6 emission factors calculated at State/county/SCC level by season;
applied to Federal Highway Administration (FHWA)-based vehicle miles
traveled (VMT)
Linear interpolation at State/count/SCC level based on 1990 and 1996
State/count/SCC level data
Linear interpolation at State/count/SCC level based on 1987 and 1990
State/count/SCC level data
Linear interpolation at State/count/SCC level based on 1978 and 1987
State/count/SCC level data
Calculated at State/county/source classification code (SCC) level by month
using MOBILE6, no State data incorporated
Linear extrapolation at national vehicle type level based on 1978 and 1987
national data
5

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May 2011
Table 2-1 b. Methods Used to Develop Emission Estimates for Nonroad Mobile Sources
Category
Base Year
Pollutant(s)
Estimation Method*
NONROAD Categories
Nonroad
Gasoline,
Diesel, LPG,
CNG
2008
VOC, NOx, CO, S02,
PM10, PM2.5, NH3i &
HAPs
Emission estimates for NONROAD model engines were developed using EPA's National
Mobile Inventory Model (NMIM), which incorporates NONROAD2008. Where states provided
alternate NMIM nonroad inputs, these data replaced EPA default inputs.
2005
VOC, NOx, CO, S02,
, PM-io, PM25, NH3, &
HAPs
Emission estimates for NONROAD model engines were developed using EPA's NMIM, which
incorporates NONROAD2005. Where States provided alternate nonroad inputs, these data
replaced EPA default inputs.
2002
VOC, NOx, CO, S02,
PM10, PM25, NH3, &
HAPs
Emission estimates for NONROAD model engines were developed using EPA's NMIM, which
incorporates NONROAD2004. Where states provided alternate nonroad inputs, these data
replaced EPA default inputs. State-supplied emissions data also replaced default EPA emission
estimates.
1999
VOC, NOx, CO, S02,
PM-io, PM2 5
Using emission estimates from two emission inventories including: 1) a 1996 county-level
inventory, developed using EPA's October 2001 draft NONROAD model; and 2) an updated 1999
national inventory, based on EPA's draft Lockdown C NONROAD model (dated May 2002). Using
the 1996 county-level emission estimates, seasonal and daily county-to-national ratios were then
developed for application to updated national estimates per season estimated from the Lockdown
C model. Replaced State-submitted data for California for all NONROAD model categories;
Pennsylvania for recreational marine and aircraft ground support equipment, and Texas for select
equipment categories.
1996, 1997,
1998,2000 &
2001
VOC, NOx, CO, S02,
PM-io, PM2 5
Using emission estimates from two emission inventories including: 1) a 1996 county-level
inventory, developed using EPA's October 2001 draft NONROAD model; and 2) updated year-
specific national and California inventories, based on EPA's draft Lockdown C NONROAD model
(dated May 2002). Using the 1996 county-level emission estimates, seasonal and daily county-to-
national ratios and California county-to-state ratios were then developed for application to updated
national estimates per season estimated from the Lockdown C model. California results replace
the diesel equipment emissions generated from prior application of county-to-national ratios.
6

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May 2011
Table 2-1 b. Methods Used to Develop Annual Emission Estimates for
Nonroad Mobile Sources (Continued)
Category
Base Year
Pollutant(s)
Estimation Method*
Nonroad
Gasoline,
Diesel, LPG, and
CNG
(Continued)
1991-1995
VOC, NOx, CO, S02,
PM10, PM25, NH3
Using 1990 and 1996 county-level emissions inventories, estimated emissions using linear
interpolation of national emissions between 1990 and 1996. From these emissions, calculated the
average annual growth rate for each pollutant/SCC combination for each year, and then applied
the growth factors to 1990 county-level emissions to estimate 1991-1995 emissions.
1990
VOC, NOx, CO, S02,
PM-io, PM2 5
Using emission estimates from two emission inventories including: 1) a 1996 county-level
inventory, developed using EPA's October 2001 draft NONROAD model; and 2) updated 1990
national inventory, based on EPA's draft Lockdown C NONROAD model (dated May 2002). Using
the 1996 county-level emission estimates, seasonal and daily county-to-national ratios were then
developed for application to updated national estimates per season estimated from the Lockdown
C model.
1986, 1988, &
1989
VOC, NOx, CO, S02,
PM-io, PM25, NH3
Using 1985 and 1990 county-level emissions inventories, estimated emissions using linear
interpolation of national emissions between 1985 and 1990. From these emissions, calculated the
average annual growth rate for each pollutant/SCC combination for each year, and then applied
the growth factors to 1985 county-level emissions to estimate 1986-1989 emissions.
1987
VOC, NOx, CO, S02,
PM-io, PM2 5
Using EPA's draft Lockdown C NONROAD model (dated May 2002), developed updated national
emissions for 1987 by running 4 seasonal NONROAD model runs to estimate annual criteria
pollutant emissions. Also performed national NONROAD model runs to estimate typical summer
weekday emissions.
1985
VOC, NOx, CO, S02,
PM-io, PM2 5
Using emission estimates from two emission inventories including: 1) a 1996 county-level
inventory, developed using EPA's October 2001 draft NONROAD model; and 2) updated 1985
national inventory, based on EPA's draft Lockdown C NONROAD model (dated May 2002). Using
the 1996 county-level emission estimates, seasonal and daily county-to-national ratios were then
developed for application to updated national estimates per season estimated from the Lockdown
C model.
1970, 1975,
1978, & 1980
VOC, NOx, CO, S02,
PM-io, PM2 5
Using EPA's draft Lockdown C NONROAD model (dated May 2002), developed updated national
emissions for all years by running 4 seasonal NONROAD model runs to estimate annual criteria
pollutant emissions. Also performed national NONROAD model runs to estimate typical summer
weekday emissions.
7

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May 2011
Table 2-1 b. Methods Used to Develop Annual Emission Estimates for
Nonroad Mobile Sources (Continued)
Category
Base Year
Pollutant(s)
Estimation Method*
Nonroad
Gasoline,
Diesel, LPG, and
CNG
(Continued)
1996, 1997,
1998, 1999,
2000,& 2001
nh3
Obtaining national fuel consumption estimates from the Lockdown C NONROAD model,
multiplying by NH3 emission factors, and distributing to counties using 1996 inventory, based on
October 2001 draft NONROAD. NH3 emissions for California were also recalculated using
updated diesel fuel consumption values generated for California-specific runs, and assuming the
1996 county-level distribution.
1985 & 1990
nh3
Obtaining national fuel consumption estimates from the Lockdown C NONROAD model,
multiplying by NH3 emission factors, and distributing to counties using 1996 inventory, based on
October 2001 draft NONROAD.
1987
nh3
Obtaining 1987 national fuel consumption estimates from Lockdown C NONROAD model and
multiplying by NH3 emission factors.
1970, 1975,
1978, & 1980
nh3
Obtaining national fuel consumption estimates from the Lockdown C NONROAD model and
multiplying by NH3 emission factors.
1990, 1996, &
1999
HAPs
Speciation profiles applied to county VOC and PM estimates. Metal HAPs were calculated using
fuel and activity-based emission factors. Some state data were provided and replaced national
estimates. (2003)
Aircraft
Commercial
Aircraft
2008
Criteria and HAPs
Federal Aviation Administration (FAA) Emissions and Dispersion Modeling System (EDMS) -
Version 5.1.was run using BTS T-100 LTO data. (2009)
2002 and 2005
Criteria and HAPs
Federal Aviation Administration (FAA) Emissions and Dispersion and Modeling System (EDMS)
was run for criteria pollutants, VOC and PM emissions were speciated into HAP components.
(2004)
1990, 1996,
1999, 2000,
2001
VOC, NOx, CO, SOx
Input landing and take-off (LTO) data into FAA EDMS. National emissions were assigned to
airports based on airport specific LTO data and BTS GIS data. State data replaced national
estimates. (2003)
1970-1998
VOC, NOx, CO, SOx
Estimated emissions for interim years using linear interpolation between available base years.
(2003)
1990, 1996,
1999
HAPs
Speciation profiles were applied to VOC estimates to get national HAP estimates. State data
replaced national estimates. (2003)
8

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May 2011
Table 2-1 b. Methods Used to Develop Annual Emission Estimates for
Nonroad Mobile Sources (Continued)
Category
Base Year
Pollutant(s)
Estimation Method*
General Aviation,
Air Taxis
2008
Criteria and HAPs
Federal Aviation Administration (FAA) Emissions and Dispersion Modeling System (EDMS) -
Version 5.1.was run using BTS T-100 LTO for aircraft identified as Air taxis. (2010)
Used FAA LTO data from TAF and OTAQ provided activity data for smaller airports derived from
FAA 5010 master plans. EPA approved generic emission factors for criteria estimates. Speciation
profiles were applied to VOC and PM estimates to get national HAP estimates. (2010)

2005
VOC, NOx, CO, S02,
PM-io, PM2 5
2002 emissions for approximately 4,000 largest airports were calculated via EDMS and SIP
guidance and included in the 2005 NEI as point sources. Only airports in FAA's T100 and TAF
databases were included. State point source submittals were incorporated.

1978, 1987,
1990, 1996,
1999, 2000,
2001,& 2002
VOC, NOx, CO, S02,
PM10, PM2 5
Used FAA LTO data and EPA approved emission factors for criteria estimates. Speciation profiles
were applied to VOC estimates to get national HAP estimates. State data replaced national
estimates. (2004)

1970-1998
VOC, NOx, CO, SOx,
PM10, PM2 5
Estimated emissions for interim years using linear interpolation between available base years.
(2003)

1990, 1996,
1999,& 2002
HAPs
Used FAA LTO data and EPA approved emission factors for criteria estimates. Speciation profiles
were applied to VOC estimates to develop national HAP estimates. (2004)

1990, 1996,
1999,& 2002
Pb
Used Department of Energy (DOE) aviation gasoline usage data with lead concentration of
aviation gasoline. (2004)

1996
nh3
Applied NH3 emissions factors to 1996 national jet fuel and aviation gasoline consumption
estimates.
Military Aircraft
2008
VOC, NOx, CO, S02,
PM-io, PM2.5
Used FAA LTO data as reported in TAF and EPA approved emission factors for criteria estimates.
Representative HAP profiles were not readily available, therefore HAP estimates were not
developed. (2010)

2005
VOC, NOx, CO, S02,
PM-io, PM2 5
2002 emissions were included in the 2005 NEI as point sources similar to other TAF reported data.

1978, 1987,
1990, 1996,
1999, 2000,
2001,2002,
2008
VOC, NOx, CO, S02,
PM-io, PM2.5
Used FAA LTO data as reported in TAF and EPA approved emission factors for criteria estimates.
Representative HAP profiles were not readily available, therefore HAP estimates were not
developed.

1970-1998
VOC, NOx, CO, SOx,
PM-io, PM2.5
Estimated emissions for interim years using linear interpolation between available base years.
(2003)
9

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May 2011
Table 2-1 b. Methods Used to Develop Annual Emission Estimates for
Nonroad Mobile Sources (Continued)
Category
Base Year
Pollutant(s)
Estimation Method*
Auxiliary Power
Units and
Ground Support
Equipment
2008
VOC, NOx, CO, S02,
PM-io, PM2.5i HAPs
Federal Aviation Administration (FAA) Emissions and Dispersion and Modeling System (EDMS) -
Version 5.1 .was run using BTS T-100 LTO data. (2009)
2002 and 2005
VOC, NOx, CO, S02,
PM10, PM2.5, HAPs
Computed via NONROAD2005 model runs
1985-2001
VOC, NOx, CO, S02,
PM10, PM2 5
Grew 1996 emissions to each year using LTO operations data from the FAA. Estimation methods
prior to 1996 reported in EPA, 1998.
Unpaved
Airstrips1
1985-2001
PM-io, PM2.5
Grew 1996 emissions to each year using SIC 45-Air Transportation growth factors, consistent with
the current draft version of EGAS. Estimation methods prior to 1996 reported in EPA, 1998.
Aircraft Refueling1
1985-2001
VOC
Grew 1996 emissions to each year using SIC 45-Air Transportation growth factors, consistent with
the current draft version of EGAS. Estimation methods prior to 1996 reported in EPA, 1998.
Commercial Marine Vessel (CMV)
All CMV
Categories
2008
VOC, NOx, CO, SO2,
PM-io, PM2.5
OTAQ provided CAP emission estimates for all CMV categories. Note that the SCCs for this
category have changed such that the Diesel category refers to smaller vessels (Category 1 and 2)
using distillate fuels and the Residual category refers to larger (Category 3) vessels using a blend
of residual fuels. Emissions were allocated to segments using GIS shapefiles and adjusted based
on limited state data (2010)
2008
HAPs
OTAQ's 2008 estimates were speciated into HAP components using EPA profiles (2009)
CMV Diesel
2002 and
2005
VOC, NOx, CO, S02,
PM-io, PM2.5
2001 Estimates carried over. Used state data when provided. (2004)
HAPs
1999 Estimates carried over. Used state data when provided. (2004)
1978, 1987,
1990, 1996,
1999, 2000, &
2001
VOC, NOx, CO, SOx,
PM-io, & PM2.5
Used criteria emission estimates in the background document for marine diesel regulations for
2000. Adjusted 2000 criteria emission estimates for other used based on fuel usage. Emissions
were disaggregated into port traffic and underway activities. Port emissions were assigned to
specific ports based on amount of cargo handled. Underway emissions were allocated based on
Army Corp of Engineering waterway data. State data replaced national estimates. (2003)
1970-1998
VOC, NOx, CO, SOx,
PM-io, PM2 5
Estimated emissions for interim years using linear interpolation between available base years.
(2003)
1990, 1996,
1999
HAPs
VOC and PM emission estimates were speciated into HAP components. State data replaced
national estimates. (2003)
1996
nh3
Applied NH3 emissions factors to 1996 distillate and residual fuel oil estimates (i.e., as reported in
EIA, 1996).
1990-1995
nh3
Estimation methods reported in EPA, 1998.
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May 2011
Table 2-1 b. Methods Used to Develop Annual Emission Estimates for
Nonroad Mobile Sources (Continued)
Category
Base Year
Pollutant(s)
Estimation Method*
CMV Steam
Powered
2005
VOC, NOx, CO, SOx,
PM-io, & PM2 5, HAPs
2002 estimates grown to 2005 (2008).
2002
VOC, NOx, CO, SOx,
PM-io, & PM2 5, HAPs
2002 based estimates were developed for port and underway category 3 (C3) vessels as part of a
rulemaking effort. Emissions were developed separately for near port and underway emissions.
For near port emissions, inventories for 2002 were developed for 89 deep water and 28 Great
Lake ports in the U.S. The Waterway Network Ship Traffic, Energy, and Environmental Model
(STEEM) was used to provide emissions from ships traveling in shipping lanes between and near
individual ports (2008)
1978, 1987,
1990, 1996,
1999, 2000, &
2001
VOC, NOx, CO, SOx,
PM-io, & PM2 5
Calculated criteria emissions based on EPA SIP guidance. Emissions were disaggregated into
port traffic and underway activities. Port emissions were assigned to specific ports based on
amount of cargo handled. Underway emissions were allocated based on Army Corp of
Engineering waterway data. State data replaced national estimates. (2003)
1970-1998
VOC, NOx, CO, SOx,
PM-io, PM2 5
Estimated emissions for interim years using linear interpolation between available base years.
(2003)
1990, 1996, &
1999
HAPs
VOC and PM emission estimates were speciated into HAP components. State data replaced
national estimates. (2003)
Military Marine
1997-2001
VOC, NOx, CO, S02,
PM-io, PM2 5
Applied EGAS growth factors to 1996 emissions estimates for this category.
CMV Coal/ CMV,
Steam powered,
CMV Gasoline2
1997-1998
VOC, NOx, CO, S02,
PM-io, PM2 5
Applied EGAS growth factors to 1996 emissions estimates for this category.
CM Coal, CMV,
Steam powered,
CMV Gasoline,
Military Marine
1991-1995
VOC, NOx, CO, S02,
PM-io, PM2 5
Estimation methods reported in EPA, 1998.
Locomotives
Class 1, II, III and
Yard operations
2008
VOC, NOx, CO,
PM-io, PM2 5 SOx &
HAPs
Criteria emission estimates were provided to EPA by ERTAC. These data were assigned to
individual railway segments using DOT shapefiles and guidance from ERTAC. HAP emissions
were calculated by applying speciation profiles to VOC and PM estimates. (2010)
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May 2011
Table 2-1 b. Methods Used to Develop Annual Emission Estimates for
Category
Base Year
Pollutant(s)
Estimation Method*
Class 1, Class II,
Commuter,
Passenger, and
Yard Locomotives
1978, 1987,
1990, 1996,
1999, 2000,
2000,2002,&
2005
VOC, NOx, CO,
PM-IO, PM2 5
Criteria pollutants were estimated by using locomotive fuel use data from DOE EIA and available
emission factors. County-level estimates were obtained by scaling the national estimates with the
rail GIS data from DOT. State data replaced national estimates. (2004)
1978, 1987,
1990, 1996,
1999, 2000,
2001,2002, &
2005
so2
SOx emissions were calculated by using locomotive fuel use and fuel sulfur concentration data
from EIA. County-level estimates were obtained by scaling the national estimates with the county
level rail activity data from DOT. State data replaced national estimates. (2004)
1970-1998
VOC, NOx, CO, SOx,
PM10, PM2 5
Estimated emissions for interim years using linear interpolation between available base years.
(2003)
1990, 1996,
1999,& 2002
HAPs
HAP emissions were calculated by applying speciation profiles to VOC and PM estimates.
County-level estimates were obtained by scaling the national estimates with the county level rail
activity from DOT. State data replaced national estimates. (2004)
1997-1998
nh3
Grew 1996 base year emissions using EGAS growth indicators.
1996
nh3
Applied NH3 emissions factors to diesel consumption estimates for 1996.
1990-1995
nh3
Estimation methods reported in EPA, 1998.
Notes:
* Dates included at the end of Estimation Method represent the year that the section was revised.
1	Emission estimates for unpaved airstrips and aircraft refueling are included in the nonpoint source NEI, since they represent non-engine emissions.
2	National Emission estimates for CMV Coal and CMV Gasoline were not developed, though states and local agencies may have submitted estimates for these
source categories.
EPA, 1998: U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Emission Factors and Inventory Group, National Air Pollutant
Emission Trends, Procedures Document, 1900-1996, EPA-454/R-98-008. May 1998.
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May 2011
Table 2-2. Summary of Onroad and Nonroad 2008 NMIM Data Submissions



Onroad



SCC-

Data Provided For
NCD
based
State Name
(all counties unless otherwise noted)
Files
VMT
Alabama



Alaska



Arizona
Maricopa County

¦/
Arkansas

¦/

California



Colorado



Connecticut



Delaware



Washington DC

¦/

Florida



Georgia

¦/

Hawaii

¦/

Idaho


¦/
Illinois


¦/
Indiana



Iowa



Kansas

¦/

Kentucky
Jefferson County

¦/
Louisiana

¦/

Maine

¦/

Maryland

¦/

Massachusetts

¦/

Michigan

¦/

Minnesota

¦/

Mississippi

¦/

Missouri

¦/

Montana



Nebraska



Nevada
All counties except Clark and Washoe
¦/

New Hampshire

¦/

New Jersey



New Mexico



New York



North Carolina

¦/

North Dakota



Ohio

¦/

Oklahoma



Oregon



Pennsylvania

¦/

Rhode Island



South Carolina

¦/

South Dakota



Tennessee
Davidson County
¦/

Texas


¦/
Utah



Vermont

¦/

Virginia

¦/

Washington



West Virginia



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May 2011
State Name
Data Provided For
(all counties unless otherwise noted)
NCD
Files
Onroad
SCC-
based
VMT
Wisconsin

¦/

Wyoming



Puerto Rico



Virgin Islands



The EPA developed the 2008 mobile source NEI in multiple phases. In the first phase, EPA ran
NMIM for year 2008 for the entire country. This NMIM run used EPA default modeling inputs
incorporated into "NCD20090327" (the naming convention reflects the NCD's lock-down date).
These default inputs represented EPA's initial assumptions concerning key modeling parameters
such as fuel blends, ambient temperatures, and onroad VMT. The 2008 mobile source emission
estimates from this phase were listed in the EIS under the data set descriptions "EPA Nonroad
using NCD20090327" and "EPA Onroad using NCD20090327." The EPA then discovered a
need to update some of the fuel parameter values from the assumptions used in NCD20090327.
Consequently, EPA developed an updated NCD reflecting the revised values, which was posted
under the name "EPA NMIM Activity NCD20090531." This NCD was then posted for
review/update by S/L/T agencies.
For the second phase, EPA set a deadline of June 1, 2010 for agencies to submit changes to the
NCD20090531 values for their areas. After obtaining any necessary clarification on these
changes from S/L/T agencies, EPA modified the NCD to reflect S/L/T updates, ran NMIM for
2008 for the entire country, and processed annual NMIM emissions output for loading into the
EIS. This 2008 mobile source NEI development phase resulted in the data sets "EPA Nonroad
using NCD20100602" and "EPA Onroad using NCD20100602."
In the third and final phase, agencies were afforded the opportunity to review EPA's emission
estimates and provide additional revisions to NMIM inputs. After updating the NCD to reflect
these revisions, EPA ran NMIM a final time and produced the data sets described as "EPA
Nonroad using NCD20101201" and "EPA Onroad using NCD20101201." This data set only
covers the geographical areas that submitted changes between July 2010 and November 2010.1
2.3 WHAT IS THE MAGNITUDE OF THE MOBILE SOURCE
EMISSIONS ESTIMATED FOR 2008?
Tables 2-3 and 2-4 display the national onroad and nonroad mobile source emission totals
reflecting each area's latest emission estimates (i.e., emissions computed using NCD20101201
for areas for which agencies submitted changes between July 2010 and November 2010, and
emissions computed using NCD20100602 for all other areas). These tables do not reflect any
State/Local agency-submitted 2008 emissions data.
1 Although Lincoln County Nebraska data were provided in time for the June submittal deadline, EPA uploaded the
NMIM results in the NCD20101201 data set rather than the NCD20100602 data set.
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May 2011
Table 2-3. 2008 Onroad Mobile NEI National Emission Totals

Emissions
Pollutant
(tons)
VOC
3,812,673
NOX
4,988,311
CO
41,373,673
PM10-PRI
147,328
PM25-PRI
94,372
so2
44,722
nh3
306,952
Table 2-4. 2008 Nonroad Mobile NEI National Emission Totals
Emissions
Pollutant	(tons)
VOC 2,492,230
NOX 1,882,841
CO 18,214,682
PM10-PRI 185,572
PM25-PRI 176,931
S02 32,214
NH3	2,093
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May 2011
3.0	NATIONAL MOBILE INVENTORY MODEL (NMIM)
3.1	BACKGROUND
This subsection provides a brief overview of EPA's NMIM. Readers that are interested in a
more detailed understanding of NMIM should refer to EPA's NMIM webpage for further model
documentation: http://www.epa.gov/otaq/nmim.htm.
The NMIM is a consolidated emissions modeling system that houses EPA's onroad mobile
source (MOBILE6) and nonroad mobile source (NONROAD) emission models. It was
developed to produce, in a consistent and automated way, national, county-level mobile source
emission inventories. When national inventories have previously been constructed from
MOBILE6 and NONROAD, the necessary input data have been widely scattered in disparate
formats and have required additional specialized software to: convert these data into input files
for MOBILE6 and NONROAD; run the models; integrate the results into a final inventory; and
post-process the results into forms suitable for the national inventories. NMIM is designed to
accomplish these tasks via a single package. Further details on EPA's MOBILE6 and
NONROAD models are available from the following web pages:
http://www.epa.gov/otaq/mobile.htm and http://www.epa.gov/otaq/nonrdmdl.htm, respectively.
3.2	THE NMIM COUNTY DATABASE
3.2.1 Database Structure
The NCD contains all the county-specific information needed to run M0BILE6 and
NONROAD. It also contains the ratios that are applied to M0BILE6/N0NR0AD outputs to
estimate emissions of HAPs, dioxins/furans, and some metals. The NCD is a relational database
management system available from www.mysql.com. Table 3-1 displays the tables that
comprise the NCD.
3.2.1.1 EIS Interface
To speed the interchange of mobile source activity data between S/L/T agencies and EPA, the
EIS was designed to exclude NCD tables that should not generally be revised. Therefore, only
the following tables were required to be included in an EIS mobile source activity data
submission: baseyearvmt, county, countynrfile, countyvmtmonthallocation, countyyear,
countyyearmonth, countyyearmonthhour, diesel, gasoline, natural gas, and state. A separate
folder for the various external files was also required, along with a text file detailing changes that
were made to each table.
To facilitate interaction with S/L/T agencies on the 2008 NEI, the EPA provided NCD activity
data in separate files by State. The EPA then reintegrated the updated data provided by S/L/T
agencies into a single NCD for the 2008 NMIM run. The EPA's instructions for reporting NCD
data to the EIS are available from http://www.epa.gov/ttn/chief/net/neip/section 9.pdf.
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May 2011
Table 3-1. Tables in the NMIM County Database (NCD)
Table
Contents
BaseYearVMT
VMT by year, county, M6Vclass, and HPMSRoadType.
County
For each county, Federal Information Processing System (FIPS) codes for the county
and State, altitude, beginning and end of ozone season, Stage 2 information, Natural
Gas Vehicle (NGV) fraction file name
CountyMap
The representing county for each county/county group, one for NONROAD and one for
MOBILE6.
CountyMonth
Defines the set of possible county-month combinations.
CountyMonthHour
Monthly average hourly temperature and humidity table used if "Use Yearly Weather
Data" option is not selected or data are not available for the requested year in the
CountyYearMonthHour table.
County NRFile
References to external NONROAD files pertaining to a county.
CountyVMTMonthAllocation
Mileage allocation factors for the 12 months of the year, by county.
CountyYear
Stage2 percent input to the NONROAD model, plus external file references for
MOBILE6 and NONROAD.
CountyYearMonth
Gasoline, diesel, and natural gas fuel IDs for each county for each year and month.
CountyYearMonthHour
Historical hourly temperature and relative humidity.
DataSource
Defines the data source identifiers used in other tables.
Diesel
Diesel sulfur content associated with each diesel ID.
EmissionType
Associates emission types (exhaust, evap, brake, tire) with EmissionTypelD used in
other tables
FileType
Defines the set of valid external files and their 3-character extensions.
Gasoline
Detailed fuel properties associated with each gasoline ID.
Hour
Defines the hour identifiers.
HPMSRoadType
Defines the 12 HPMS road type identifiers.
M6Vclass
Defines the 28 vehicle classes used in MOBILE6. These are the valid combinations of
M6Vtype and fuel.
M6Vtype
Defines the fuel-independent vehicle types used in MOBILE6.
NaturalGas
Natural gas sulfur content associated with each natural gas ID.
PollutantCode
Associates NIF pollutant codes and pollutant names with PollutantCodelD used in
other tables.
see
Associates an SCC code and description for each SCCID, and ratios for NH3, PM25,
and for converting between HC forms.
SCCToxics
SCC and fuel property-dependent ratios for calculating HAPs, dioxin/furans, and
metals.
State
Associates State names and abbreviations with State FIPS codes used in other tables.
VMTGrowth
The annual VMT growth rate for a M6Vclass by county and year.
VMTMonthAllocation
Factors for allocating annual VMT to the 12 months, by M6Vtype and HPMSRoadType,
used if there are no county-specific values in CountyVMTMonthAllocation.
3.2.2 EPA Default 2008 NCD Inputs
This section describes how EPA developed default 2008 NCD inputs for the following: vehicle
miles traveled; temperature and humidity; and gasoline and diesel fuel parameters.
3.2.2.1 Vehicle Miles Traveled
The VMT data in the NCD is contained in the BaseYearVMT table. For each county in this
table, VMT data are reported for each of the 12 Highway Performance Monitoring System
(HPMS) functional roadway types and the 28 MOBILE6 vehicle classes, for a total of 336
records per county.
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May 2011
The EPA developed 2008 vehicle miles traveled (VMT) data by allocating Federal Highway
Administration (FHWA) VMT data to the county/road type/vehicle class-level required by
NMIM. The EPA initially developed 2008 VMT data in NCD20090327 by growing 2007 State-
level VMT from FHWA's HPMS to 2008 using VMT growth factors (FHWA, 2007). The 2007
to 2008 growth factors were calculated from the 2007 and 2008 FHWA's Travel Volume Trends
reports (FHWA, 2009a).
For NCD20100602, 2008 HPMS State-level VMT totals by road type were allocated to the
county/road type/vehicle class-level using VMT data submitted for earlier NEIs (FHWA,
2009b). For agencies that submitted data in 2005, the following formula was used:
2008 County VIVITvciass, Road Type ~~
2008 State VMT * (2005 County VMTvaass, Road TyPJ2005 State VMT)
An analogous formula was used for agencies that submitted 2002, but not 2005, VMT data.
If a geographic area did not submit VMT data in either 2005 or 2002, then EPA allocated
FHWA data from its HPMS urban and small urban area data sets, and the Highway Statistics
rural VMT data by State and roadway class, to the county level using 2008 population data
(Census, 2009a and 2009b). The HPMS data sets included VMT by roadway class for urban and
small urban areas, which EPA then allocated to the counties included in these areas using
population data. Rural VMT at the State and roadway class level was obtained from Highway
Statistics and allocated to the rural counties in a State by roadway class using rural interstate
mileage and rural population for the allocations. The EPA allocated the resulting VMT at the
county and roadway class level to each of the 28 MOBILE6 vehicle types based on the default
VMT allocations by vehicle type for 2008 in MOBILE6. See Section 3.2.2.1.2 of the 2005
Mobile NEI Version 2 report for a more detailed explanation of how these default allocations
were performed (EPA/Pechan, 2008).
3.2.2.2 Temperature and Humidity
NMIM requires that each county have both hourly average temperature and hourly relative
humidity values for each month of the year. The NOx emission results from MOBILE6 are
sensitive to humidity levels, and hourly humidity levels are the most accurate way to represent
daily humidity. MOBILE6 allows users to supply daily temperatures as either
minimum/maximum values or as hourly averages. Because MOBILE6 calculates emissions
separately for each hour of the day, user-supplied minimum and maximum temperatures are used
to internally derive hourly temperatures, using a default diurnal temperature profile. MOBILE6
also allows users to supply hourly relative humidity levels.
The NCD contains a full set of default hourly average temperatures and hourly relative humidity
values for each county for each month. These temperature and humidity values were derived
from raw measurement data obtained from the National Climatic Data Center (NCDC). The
procedures used to develop the default NMIM temperature and relative humidity values are
discussed in more detail in the report, "Derivation of By-Month, By-County, By-Hour
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May 2011
Temperature and Relative Humidity with Monthly Data," by Air Improvement Resources, Inc.
(AIR, 2004).
3.2.2.3	Gasoline
The default year 2008 EPA gasoline parameters were generally developed by interpolating
between historical 2005 values compiled in support of the 2005 NEI and 2012 values developed
in support of modeling for the Renewable Fuel Standards established by the Energy
Independence and Security Act of 2007 (RFS2) (EPA, 2009). The following identifies the
instances where EPA deviated from this approach in developing NCD20090531 gasoline
parameter values.
For ethyl tert-butyl ether (ETBE), methyl tert-butyl ether (MTBE), and tertiary amyl methyl
ether (TAME), EPA set 2008 year volume and market share values to zero.2 For gasoline sulfur,
gasoline maximum sulfur, and benzene content, EPA set 2008 values to the 2012 RFS2 values.
For the reformulated gasoline (RFG) and RVP Oxy Waiver fields, EPA retained the 2005 values
for 2008. For ethanol volumes and market shares, EPA used one of two different interpolation
procedures to estimate 2008 values. If RFG was used in the given area, then EPA added the
2005 NEI ETBE, MTBE, and TAME values to the 2005 NEI ethanol values before performing
the interpolation. If RFG was not used, EPA did not include the 2005 values for ETBE, MTBE,
and TAME in the interpolation procedure. Further details on the interpolation procedures are
available in the NMIM ChangeLog under NCD20090531.
3.2.2.4	Diesel
Diesel sulfur values were developed in support of the renewable fuel standard work performed as
part of the 2002 Version 3 Modeling Platform (EPA, 2010). The year 2008 sulfur values were
interpolated from 2005 values developed for the 2005 NEI and 2009 values developed from
Annual Energy Outlook 2007 (additional details are provided in the ChangeLog under
NCD20070727).
3.2.3 State/Local Agency-Submitted Inputs
State/Local agencies were provided the opportunity to provide NCD input data to override EPA
defaults. The EIS performed a number of automated checks on the agency submissions. As
described below, it was necessary for EPA to perform detailed review/manipulation of some S/L
agency data before incorporating the data into the NCD.
3.2.3.1 VMT
If an agency submitted onroad mobile source emissions data, the SCC-level VMT data were
extracted from the submission. Since NMIM maintains 28 vehicle classes and 12 road types
(336 combinations total) to the SCC's 12 vehicle classes and 12 road types (144 combinations
total), some effort was necessary to split SCC-level VMT to the level required by NMIM. Table
2 However, a MOBILE6 anomaly results in a national estimate of onroad MTBE emissions of 0.31 pounds.
19

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May 2011
3-2 shows the mapping between HPMS vehicle categories to both SCC and NMIM/MOBILE6-
level vehicle classes.
Table 3-2. Mapping of HPMS Vehicle Categories to NMIM/MOBILE6 and SCC-
Level Vehicle Classes

SCC-Level
NMIM/MOBILE6
HPMS Vehicle Category
Vehicle Classes
Vehicle Classes
Passenger Cars
LDGV (2201001)
LDDV (2230001)
LDGV
LDDV
Motorcycles
MC (2201080)
MC
Other 2-Axle 4-Tire Vehicles
LDGT1 (2201020)
LDGT1
LDGT2

LDGT2 (2201040)
LDGT3
LDGT4

LDDT (2230060)
LDDT12
LDDT34

HDGV (2201070)
2BHDDV (2230071)
HDGV2B
HDDV2B
Single-Unit 2-Axle 6-Tire or More Trucks
HDGV (2201070)
HDGV3
HDGV4
HDGV5
HDGV6
HDGV7

LHDDV (2230072)
HDDV3
HDDV4
HDDV5

MHDDV (2230073)
HDDV6
HDDV7
Combination Trucks
HDGV (2201070)
HDGV8A
HDGV8B

HHDDV (2230074)
HDDV8A
HDDV8B
Buses
HDGV (2201070)
BUS (2230075)
HDGB
HDDBT
HDDBS
If an agency had submitted VMT data to the 2005 or 2002 NEIs, the most recent NEI data
submission was used to allocate the SCC-level VMT to the NMIM vehicle classes. In the case of
Illinois and Texas there were county-SCC combinations for which VMT data were submitted in
2008 that did not appear in their 2005 submission. Therefore, EPA used default MOBILE6 data
to allocate each State's SCC-level VMT data to the required NMIM vehicle classes. After
performing the allocation to NMIM vehicle classes, the EPA compared the resulting VMT
estimates to EPA's default VMT estimates. The EPA contacted agencies to confirm the validity
of their SCC-level VMT data when estimates differed by more than 10 percent. In several cases,
agencies submitted revised VMT data for use by EPA. Appendix Table A-2 summarizes the data
sources/methods used to develop the VMT data incorporated into the 2008 NCD.
20

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May 2011
3.2.3.2	Temperature and Humidity
Maryland was the only State that submitted temperature and humidity data updates. A review of
the methodology used to generate the temperature data showed that there was no spatial
interpolation performed between airports and neighboring counties, and that the documentation
did not identify how monthly averaging was performed. The EPA decided not to incorporate
Maryland's temperature/humidity data because of these concerns.
3.2.3.3	Gasoline Parameters
The Gasolineld is a code used in the Gasoline table to identify a unique gasoline profile. A
gasoline profile identifies the values for various fuel properties (e.g., the percent by volume of
ethanol in the fuel). The EPA's instructions for reporting new gasoline profiles to the EIS
identifies the naming convention for the Gasolineld field as SSNNNN, where SS indicates the
State's Federal Information Processing System (FIPS) code and NNNNis a unique number
chosen by the State. In cases where agencies submitted a new Gasolineld that did not follow this
numbering convention, EPA revised the Gasolineld to match the convention, starting each
State's new Gasolinelds with "0001" (e.g., two new submittals by Kansas would be assigned
Gasolinelds 200001 and 200002). The countyyearmonth table was also revised to reflect the
revised numbering.
3.2.3.4	CountyYear
The countyyear table is one of the four tables that NMIM uses to determine which (if any)
external files to use when preparing a run. The external files referenced in the countyyear table
are all onroad-specific. The EPA used the description of changes provided in each agency's
submission to identify the columns that should be updated in this table. See Appendix Table A-l
for a list of agencies that supplied updates to the countyyear table.
3.2.3.5	CountyNRFile
The CountyNRFile table is another of the tables NMIM uses to determine which (if any) external
files to use when preparing a run. Files listed in this table are nonroad-specific. Appendix Table
A-4 lists the State specific external files supplied by State agencies (no Local agencies submitted
CountyNRfile updates)—the last column in this table indicates if the file was new in 2008.
3.2.3.6	External Files
External files were included if: (a) agencies noted them in their submission comments; (b) they
were identified in the county, countyyear, countynrfile, or state tables; or (c) if the modified date
on the file was later than the existing file in the NCD. In some cases, NMIM would output an
error flag after running NMIM with the updated external files. When this occurred, EPA
contacted the agency to identify the necessary fix.
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May 2011
In the case of Arkansas and Missouri, NMIM runs with updated external files resulted in
atypically large increases in evaporative VOC emissions relative to previous runs before these
updates. The EPA performed a sample county analysis in each State, and determined that the
large increase occurred due to each State's updated registration distribution file. A review of the
old and new files determined that the average age of vehicles was older in the updated files (on
the order of 2-3 years). Based on this analysis, EPA determined that large evaporative VOC
emission increases seen in other States (e.g., Georgia, Kansas, Minnesota, and Ohio) may also be
attributable to similar registration distribution revisions.
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May 2011
4.0	POST-PROCESSING OF NMIM OUTPUT
Because of specific design decisions in the EIS, it was necessary for EPA to post-process some
of the NMIM output to be able to successfully post the data to the EIS. The following
summarizes the NMIM post-processing procedures that EPA implemented for the 2008 NEI.
4.1	POLLUTANT CODE REVISIONS
Table 4-1 lists the pollutant codes no longer considered valid in the EIS. To prepare the
emissions for loading into the EIS, Pollutant 93 was changed to the valid code 7440382
(Arsenic). The mercury codes (200, 201, and 202) were summed together and reported under the
code 7439976 (Mercury). SOA data were removed completely.
Table 4-1. Pollutant Code Revisions
Pollutant Code
Pollutant Description
Revision
93
Arsenic & compounds
Updated to 7440382 (Arsenic)
200
Mercury (elemental gaseous)
Combined into 7439976 (Mercury)
201
Mercury (divalent gaseous)
202
Mercury (particulate)
SOA
Secondary Organic Aerosols
Removed
4.2	REMOVAL OF GROUND SUPPORT EQUIPMENT
Airport GSE is a category computed by NMIM. The EPA used the Federal Aviation
Administration (FAA)'s Emissions and Dispersion Modeling System (EDMS) - Version 5.1 to
estimate aircraft emissions. This model also calculates GSE emissions using take-off and
landing data. NMIM does not have this level of detail, so emissions for the three GSE SCCs
(2265008005, 2267008005, and 2270008005) were removed before emissions were loaded into
the EIS. Please see "Documentation for Aircraft Component of the National Emissions
Inventory Methodology" for information on how EPA used the EDMS to calculate airport GSE
emissions (ERG, 2011b).
4.3	STAGE II ONROAD VEHICLE REFUELING
Stage II refueling data for onroad vehicles are categorized in the nonpoint source NEI rather than
the mobile source NEI. Therefore, all NMIM onroad refueling emission type records were
removed before loading the NMIM output to the EIS. The nonpoint source NEI documentation
describes the development of Stage II onroad vehicle emission estimates (EPA, 2011).
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May 2011
5.0 REFERENCES
AIR, 2004: "Derivation of By-Month, By-County, By-Hour Temperature and Relative Humidity
with Monthly Data," by Air Improvement Resources, Inc. December 8, 2004.
Census, 2009a: U.S Department of Commerce, Bureau of the Census, "Annual Estimates of the
Resident Population for the United States, Regions, States, and Puerto Rico: April 1,
2000 to July 1, 2008," data file NST-EST2008-01.csv,
http://www.census.gov/popest/states/NST-ann-est.html downloaded on February 23,
2009.
Census, 2009b: U.S Department of Commerce, Bureau of Census, "International Database -
U.S. Virgin Island Total Midyear Population," http://www.census.gov/cgi-
bin/ipc/idbsprd. downloaded on February 23, 2009.
EPA, 2011: U.S. Environmental Protection Agency, "2008 National Emissions Inventory Data
& Documentation," http://www.epa.gov/ttn/chief/net/2008inventory.html (see
Nonpoint/Stage 2 Gasoline Refueling section), accessed March 2011.
EPA, 2010: U.S. Environmental Protection Agency, "2002-Based Modeling Platform,"
http://www.epa.gOv/ttn/chief/emch/index.html#2002. last updated November 2010.
EPA, 2009: U.S. Environmental Protection Agency, "Regulation of Fuels and Fuel Additives:
Changes to Renewable Fuel Standard Program; Proposed Rule,"
http://www.epa.gov/otaq/renewablefuels/rfs2 1 -5.pdf. May 26, 2009.
EPA/Pechan, 2008: U.S. Environmental Protection Agency, Office of Transportation and Air
Quality, and E.H. Pechan & Associates, Inc., "Documentation for the 2005 Mobile
National Emissions Inventory, Version 2," prepared for the U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, December 2008.
ERG, 201 la: Eastern Research Group, "Documentation for Locomotive Component of the
National Emissions Inventory Methodology," prepared under contract to E.H. Pechan &
Associates, Inc., for U.S. Environmental Protection Agency, January 6, 2011.
ERG, 201 lb: Eastern Research Group, "Documentation for Aircraft Component of the National
Emissions Inventory Methodology," prepared under contract to E.H. Pechan &
Associates, Inc., for U.S. Environmental Protection Agency, January 27, 2011.
ERG, 2010: Eastern Research Group, "Documentation for the Commercial Marine Vessel
Component of the National Emissions Inventory Methodology," prepared under contract
to E.H. Pechan & Associates, Inc., for U.S. Environmental Protection Agency, March 30,
2010.
24

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May 2011
FHWA, 2009a: U.S. Department of Transportation, Federal Highway Administration, Office of
Highway Policy Information, "2007 and 2008 Monthly Traffic Volume Trends,"
http://www.fhwa.dot.gov/ohim/tvtw/tvtpage.cfm. downloaded on February 19, 2009.
FHWA, 2009b: U.S. Department of Transportation, Federal Highway Administration, HPMS
2008 Summary Data (summary_dvmt_2008.xls), HPMS 2008 Sample Data
(Sample2008.csv and sample2008.schema), and HPMS2008 Universe Data
(Universe2008.csv and Universe2008.schema) electronic files, 2009.
FHWA, 2008: U.S. Department of Transportation, Federal Highway Administration, HPMS
2007 Summary Data (summary_dvmt_2007.xls), HPMS 2007 Sample Data
(Sample2007.csv and sample2007.schema), and HPMS 2007 Universe Data
(Universe2007.csv and Universe2007.schema), electronic files, December 1, 2008.
25

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May 2011
[This page intentionally left blank.]
26

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May 2011
APPENDIX A. TABLES UPDATED WITH EIS SUBMISSIONS
This Appendix presents tables summarizing the 2008 NCD updates provided by State/Local
agencies. Table A-l lists, for each jurisdiction, the specific NCD tables that were submitted.
Table A-2 identifies the source of the VMT data incorporated into the 2008 NCD by jurisdiction.
The "2008 VMT Allocation Data Source" column should be interpreted as follows:
•	State 2002 indicates that State-supplied 2002 NEI VMT data was used to allocate 2008
VMT data.
•	Local 2002 indicates that Local agency-supplied 2002 NEI VMT data were used to
allocate 2008 VMT data.
•	State 2005 indicates that State-supplied 2005 NEI VMT data was used to allocate 2008
VMT data.
•	MOBILE6 indicates that the State or Local agency did not supply VMT updates in the
2002 or 2005 NEI so MOBILE6 default allocations were used to allocate 2008 VMT
data.
•	n/a indicates that agency-submitted VMT data were provided at the level of detail
required by NMIM—(i.e., it was not necessary for EPA to perform VMT allocations).
Table A-3 lists the MOBILE6-specific external file types submitted by S/L agencies. Table A-4
displays the State agency-supplied external files used by NONROAD. The last column in this
table identifies if the file was submitted for the 2008 NEI.
Table A-1. 2008 NMIM County Database Table Updates by Jurisdiction
Jurisdiction
Base
Year
VMT
County
County
NR File
County
VMT Month
Allocation
County
Year
County
Year
Month
County
Year
Month
Hour
Diesel
Gasoline
Natural
Gas
State
AL











AK











AZ











AZ Maricopa County
see1










AR
¦/



¦/






CA
see1*










CO











CT











DE











DC
¦/



¦/





~
FL











GA
¦/
¦/


¦/






HI
¦/
**



**


**


ID
see1










IL
sec1










IN











IA











KS
¦/



¦/






KY











KY Jefferson County
see1










LA
¦/
¦/

¦/
¦/






ME
¦/
¦/


¦/
¦/


¦/

~
A-l

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May 2011
Jurisdiction
Base
Year
VMT
County
County
NR File
County
VMT Month
Allocation
County
Year
County
Year
Month
County
Year
Month
Hour
Diesel
Gasoline
Natural
Gas
State
MD
¦/
¦/

¦/
¦/
¦/
* * *
¦/
¦/

~
MA

¦/


¦/





~
Ml
¦/

¦/

¦/
¦/


¦/


MN
¦/

¦/

¦/






MS











MO
¦/



¦/






MT











NE











NV
¦/

¦/

¦/
¦/

¦/
¦/


NH
¦/
¦/


¦/






NJ











NM











NY











NC
¦/



¦/
¦/


¦/


ND











OH
¦/



¦/
¦/





OK











OR











PA
¦/


¦/
¦/
¦/


¦/

~
Rl











SC
¦/










SD











TN











TN Davidson County
¦/










TX
see1










UT











VT
¦/



¦/






VA
¦/
¦/


¦/






WA











WV











Wl
¦/

¦/

¦/
¦/


¦/


WY











PR











VI











1 Jurisdiction supplied emissions data, EPA extracted SCC-level VMT data from this submittal.
*Although CA submitted data, the submitted detail (i.e., SCC and pollutants) is substantially different from that used
by other States. Therefore, the VMT submitted in CA's emissions file was not used in NMIM.
** Submitted revisions were inadvertently excluded.
*** MD countyyearmonthhour changes not included due to differences in estimation methodology
A-2

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May 2011
Table A-2. Summary of 2008 NEI Vehicle Miles Traveled Data by Jurisdiction
Jurisdiction
2008 VMT Data
Source
Agency Provided
Level of Detail
2008 VMT Allocation
Data Source
AL
EPA

State 2002
AK
EPA

MOBILE6
AZ Maricopa County
Local
see
Local 2002
AZ - Rest of State
EPA

MOBILE6
AR
State
NMIM
n/a
CA
EPA

State 2005
CO
EPA

State 2005
CT
EPA

MOBILE6
DE
EPA

State 2005
DC
State
NMIM
n/a
FL
EPA

MOBILE6
GA
State
NMIM
n/a
HI
State
NMIM
n/a
ID
State
see
State 2005
IL
State
see
MOBILE6A
IN
EPA

MOBILE6
IA
EPA

MOBILE6
KS
State
NMIM
n/a
KY Jefferson County
Local
see
State 2002
KY - Rest of State
EPA

MOBILE6
LA
State
NMIM
n/a
ME
State
NMIM
n/a
MD
State
NMIM
n/a
MA
EPA

State 2002
Ml
State
NMIM
n/a
MN
State
NMIM
n/a
MS
EPA

State 2002
MO
State
NMIM
n/a
MT
EPA

MOBILE6
NE Lancaster County
EPA

State 2002
NE
EPA

MOBILE6
NV Clark County
EPA

State 2002
NV Washoe County
EPA

MOBILE6
NV - Rest of State
State
NMIM
n/a
NH
State
NMIM
n/a
NJ
EPA

State 2002
NM
EPA

MOBILE6
NY
EPA

State 2002
A-3

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May 2011
Jurisdiction
2008 VMT Data
Source
Agency Provided
Level of Detail
2008 VMT Allocation
Data Source
NC
State
NMIM
n/a
ND
EPA

MOBILE6
OH
State
NMIM
n/a
OK
EPA

MOBILE6
OR
EPA

State 2002
PA
State
NMIM
n/a
Rl
EPA

State 2002
SC
State
NMIM
n/a
SD
EPA

MOBILE6
TN Davidson County
Local
NMIM
n/a
TN - Rest of State
EPA

State 2005
TX
State
see
MOBILE6A
UT
EPA

State 2005
VT
State
NMIM
n/a
VA
State
NMIM
n/a
WA
EPA

State 2002
WV
EPA

State 2005
Wl
State
NMIM
n/a
WY
EPA

MOBILE6
PR
EPA

MOBILE6
VI
EPA

MOBILE6
n/a- not applicable (data supplied at necessary NMIM-level of detail)
A - Pre-2008 state supplied data were available (IL-2002; TX-2005), but could not be used as they did not cover all
required categories.
A-4

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May 2011
Table A-3. External Onroad Files Updated for the 2008 NEI



Reg
VMT
By
Trip
Diesel
Avg
Speed
Dist
NLEV
T2 Exh
Phase
T2 Evap
Phase
T2
Cert
Jurisdiction
ATP
IM
Dist
Hour
Length
Fract
Base
File
In File
In File
File
AL











AK











AZ











AR


¦/








CA











CO











CT











DE











DC
¦/
~
¦/

¦/
¦/
¦/




FL











GA
¦/

¦/








HI











ID











IL











IN











IA











KS


¦/


¦/





KY











KY Jefferson County











LA
¦/
~
¦/








ME
¦/
~





¦/
¦/
¦/
¦/
MD
¦/
~
¦/
¦/

¦/
¦/




MA

~
¦/




¦/
¦/
¦/
¦/
Ml


¦/








MN


¦/








MS











MO


¦/








MT











NE











NV


¦/








NH
¦/
~





¦/



NJ











NM











NY











NC
¦/
~
¦/
¦/


¦/




ND











OH
¦/
~
¦/








OK











OR











PA
¦/
~
¦/
¦/


¦/
¦/
¦/
¦/
¦/
Rl











SC











SD











TN











TN Davidson County











TX











UT











VT











A-5

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May 2011
Jurisdiction
ATP
IM
Reg
Dist
VMT
By
Hour
Trip
Length
Diesel
Fract
Avg
Speed
Dist
Base
NLEV
File
T2 Exh
Phase
In File
T2 Evap
Phase
In File
T2
Cert
File
VA

~
¦/



¦/




WA











WV











Wl

~
¦/



¦/




WY











PR











VI











A-6

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May 2011
Table A-4. NONROAD Model Parameters Provided by State Agencies
State
Description
File
Type
Added in
2008
Colorado
Oil production equipment
allocations.
oil

Delaware
Airport equipment
allocations.
air

Delaware
Golf equipment allocations.
gc

Delaware
Household allocations.
hou

Delaware
Logging equipment
allocations.
log

Delaware
Source populations.
pop

Delaware
Recreational vehicle park
allocations.
rvp

Illinois
Nonroad activity
act

Illinois
Growth rates.
grw

Illinois
Source populations.
pop

Illinois
Seasonal allocations.
sea

Illinois
Inboard watercraft
allocations.
wib

Illinois
Outboard watercraft
allocations.
wob

Indiana
Nonroad activity
act

Indiana
Growth rates.
grw

Indiana
Source populations.
pop

Indiana
Seasonal allocations.
sea

Indiana
Inboard watercraft
allocations.
wib

Indiana
Outboard watercraft
allocations.
wob

Iowa
Nonroad activity
act

Iowa
Seasonal allocations.
sea

Iowa
Inboard watercraft
allocations.
wib

Iowa
Outboard watercraft
allocations.
wob

Michigan
Nonroad activity
act

Michigan
Growth rates.
grw

Michigan
Source populations.
pop

Michigan
Seasonal allocations.
sea

Michigan
Inboard watercraft
allocations.
wib

Michigan
Outboard watercraft
allocations.
wob

Minnesota
Nonroad activity
act

Minnesota
Growth rates.
grw
¦/
Minnesota
Seasonal allocations.
sea

Minnesota
Snowmobile populations.
snm

Minnesota
Inboard watercraft
allocations.
wib

Minnesota
Outboard watercraft
allocations.
wob

Nevada
Census population
cen

Nevada
Wholesale Establishments
com

Nevada
Harvested acres
frm

Nevada
Golf equipment allocations.
gc
¦/
A-7

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May 2011
State
Description
File
Type
Added in
2008
Nevada
Landscaping employment
allocations
wib
¦/
Nevada
Oil production equipment
allocations.
oil
¦/
Nevada
Recreational vehicle park
allocations.
rvp
¦/
Nevada
Commercial snowblower
allocations
sea
¦/
Nevada
Residential snowblower
allocations
sea
¦/
Nevada
Snowmobile populations.
snm
¦/
North
Carolina
Residential snowblower
allocations
sea

Ohio
Nonroad activity
act

Ohio
Growth rates.
grw

Ohio
Source populations.
pop

Ohio
Seasonal allocations.
sea

Ohio
Inboard watercraft
allocations.
wib

Ohio
Outboard watercraft
allocations.
wob

Rhode Island
Source populations.
pop

Washington
Inboard watercraft
allocations.
wib

Washington
Outboard watercraft
allocations.
wob

Wisconsin
Nonroad activity
act

Wisconsin
Growth rates.
grw

Wisconsin
Source populations.
pop

Wisconsin
Seasonal allocations.
sea

Wisconsin
Inboard watercraft
allocations.
wib

Wisconsin
Outboard watercraft
allocations.
wob

A-8

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United States	Office of Air Quality Planning and Standards	Publication No. EPA-454/B-20-028
Environmental Protection	Air Quality Assessment Division	May 2011
Agency	Research Triangle Park, NC

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