2011 BASE YEAR EMISSIONS INVENTORY

FOR THE

WASHINGTON DC-MD-VA

2008 OZONE NAAQS NONATTAINMENT AREA

Prepared by:

District Department of the Environment,

Maryland Department of the Environment,

Virginia Department of Environmental Quality,

and

Metropolitan Washington Council of Governments

on behalf of the

Metropolitan Washington Air Quality Committee

July 9, 2014
TABLE OF CONTENTS

1.0 INTRODUCTION ........................................................................................................... 1-1

1.1 Overview and Background .......................................................................................... 1-1

1.2 8-Hour Ozone Nonattainment Geographic Area ......................................................... 1-2

1.3 Temporal Resolution.................................................................................................... 1-2

1.4 Quality Assurance Policy and Objectives.................................................................... 1-3

1.5 Plan Information Sources............................................................................................. 1-3

1.6 Summary of the Base Year Emissions Inventory ........................................................ 1-4

1.7 Document Contents...................................................................................................... 1-4

2.0 POINT SOURCES........................................................................................................... 2-1

2.1 Introduction.................................................................................................................. 2-1

2.2 Compilation and Documentation of Point Source Emissions...................................... 2-1

3.0 AREA AND NONROAD SOURCES............................................................................. 3-1

3.1 Introduction and Scope ................................................................................................ 3-1

3.2 Area Sources................................................................................................................ 3-1

 3.2.1 Emission Estimation Approach.............................................................................. 3-1

 3.2.2 Summary of Emission Results............................................................................... 3-1

3.3 Nonroad Sources........................................................................................................... 3-3

 3.3.1 Non-Nonroad Model Sources................................................................................ 3-3

 3.3.1.1 Emission Estimation Approach........................................................................ 3-3

 3.3.1.2 Summary of Emission Results......................................................................... 3-3

 3.3.2 Nonroad Model Sources ........................................................................................ 3-4

 3.3.2.1 Emission Estimation Approach........................................................................ 3-4

 3.3.2.2 Summary of Emission Results......................................................................... 3-5

4.0 ONROAD MOBILE SOURCES .................................................................................... 4-1

4.1 Introduction.................................................................................................................. 4-1

4.2 Summary of Onroad Mobile Source Emissions........................................................... 4-1

5.0 QUALITY ASSURANCE PROCEDURES................................................................... 5-1

5.0 Quality Assurance Procedures..................................................................................... 5-1

5.1 Reality Check/Peer Review Check .............................................................................. 5-1

5.2 Sample Calculations..................................................................................................... 5-1

5.3 Sensitivity Analysis ..................................................................................................... 5-1

5.4 Standard Range Checks ............................................................................................... 5-2

5.5 Corrective Action Plan................................................................................................. 5-2
List of Tables

1-1 2011 Base Year SIP Emission Inventories........................................................................ 1-4

2-1 2011 Base Year SIP Point Source Emission Inventories .................................................. 2-2

3-1 2011 Base Year SIP Area Source Emission Inventories................................................... 3-2

3-2 2011 Base Year SIP Non-Nonroad Model Source Emission Inventories......................... 3-3

3-3 2011 Base Year SIP Nonroad Model Source Emission Inventories ................................. 3-5

4-1 2011 Base Year SIP Onroad Source Emission Inventories............................................... 4-2

List of Appendices

A. Point Source Inventory Files

B1. Area and Nonroad (Marine Vessels, Airport, Railroad Locomotives) Source Inventory 

Development Document (Maryland)

B2. Area and Nonroad (Marine Vessels, Airport, Railroad Locomotives) Source Inventory 

Development Documents (Virginia)

B3. Area and Nonroad (Marine Vessels, Airport, Railroad Locomotives) Source Inventory 

Development Documents (District of Columbia)

B4. Area and Nonroad (Marine Vessels, Airport, Railroad Locomotives) Source Inventory Files

C. NMIM2008 (NONROAD Model) Input & Output Files

D1. Onroad Mobile Source Development Document

D2. MOVES2010a (Onroad Mobile Model) Input & Output Files

E. Public Hearing Notices, Comments, and Responses
1-1

1.0 Introduction

1.1 Overview and Background

This document contains a detailed explanation of the 2011 base year emissions inventory 

for stationary, area, nonroad, and mobile anthropogenic sources as well as biogenic 

sources in the Washington, DC-MD-VA 2008 ozone National Ambient Air Quality 

Standards (NAAQS) nonattainment area. The inventory will be included as part of the 

region’s State Implementation Plan (SIP) to meet the above NAAQS. Annual 

anthropogenic emissions were estimated for volatile organic compound (VOC), nitrogen 

oxide (NOX), carbon monoxide (CO), fine particles (PM2.5-Pri), sulfur dioxide (SO2), and 

ammonia (NH3). Typical ozone season day emissions were developed for VOC, NOX, 

and CO.

The federal Clean Air Act (CAA), 42 U.S.C.A § 7401 et seq, as amended by the Clean 

Air Act Amendments of 1990, P.L. 101-549, (referred to hereafter as the Act), requires 

all areas of the nation to attain and maintain compliance with the NAAQS. These federal 

standards are designed to protect the public health and welfare from six criteria 

pollutants, one of which is ozone. 

The Washington, DC-MD-VA 2008 ozone NAAQS nonattainment area was designated 

as a marginal nonattainment area by the United State Environmental Protection Agency 

(EPA) effective July 20, 2012 (Federal Register, Vol. 77, No. 98, May 21, 2012). This 

base year inventory is required by the Act at §7502(c)(3):

(3) Inventory – Such plan provisions shall include a comprehensive, 

accurate, current inventory of actual emissions from all sources of the 

relevant pollutant or pollutants in such area, including such period 

revisions as the Administrator may determine necessary to assure that the 

requirements of this part are met. 

The Metropolitan Washington Council of Governments (MWCOG) prepared the nonroad 

and onroad portions of the inventory. MWCOG used EPA’s nonroad mobile emissions 

model, NONROAD2008a (embedded in NMIM2008) to develop all nonroad emissions

except for commercial marine vessels, aircraft, and locomotives. These three sectors 

were developed separately. MWCOG developed the 2011 onroad mobile inventory using 

EPA’s MOVES2010a model. 

Air quality staff of the District Department of the Environment (DDOE), Maryland 

Department of the Environment (MDE), and Virginia Department of Environmental 

Quality (VDEQ), herein referred to as “state air agencies,” in collaboration with 

MWCOG, supplied area and point source emissions estimates.

EPA’s estimates for biogenic emissions for the NEI2011 effort were accepted for the 

purposes of submission of the base year 2011 biogenic inventories. Methodology for 
1-2

developing biogenic inventories is described in detail in the Technical Support Document 

for the NEI2011 effort.1

Emissions inventory data is used in annual trends reports, SIP submittals, compliance 

demonstrations, emissions trading, emissions fee programs, and in modeling activities 

designed to evaluate ambient air concentrations encountered by the general public. For 

the SIP program, the emission inventory is a fundamental building block in developing an 

air quality control and maintenance strategy. Regulatory agencies rely on emission 

inventories as indicators of air quality changes and for setting permit requirements. 

The end use of emission inventories requires that they be of the highest quality 

obtainable. These data are the foundation of air quality decisions. Inventory quality is 

critical to defining realistic regulations and attainment strategies. 

1.2 2008 Ozone NAAQS Nonattainment Area Geography

Effective July 20, 2012, EPA designated the following jurisdictions in the Washington, 

DC-MD-VA area as nonattainment for the 2008 ozone NAAQS.

 District of Columbia

 Calvert County, Maryland

 Charles County, Maryland

 Frederick County, Maryland

 Montgomery County, Maryland

 Prince George's County, Maryland

 Arlington County, Virginia

 Alexandria City, Virginia

 Fairfax County, Virginia (includes the independent cities of Fairfax and Falls 

Church)

 Loudoun County, Virginia

 Prince William County, Virginia (includes the independent cities of Manassas and 

Manassas Park)

1.3 Temporal Resolution

Another step of inventory development is the temporal allocation of emissions. The 

temporal allocation is an accounting of emission variations over time. The simplest 

temporal allocation is for a steady-state emissions source that continually releases 

emissions at the same rate throughout the year. Under actual conditions, however, steadystate emission sources are quite rare. Instead, under actual conditions, emissions sources 

may operate only in the winter, not operate on Sundays, or their activity may peak during 

certain hours of the day. The temporal allocation of emissions must reflect as accurately 

as possible the reality of emissions occurring to the atmosphere. Ozone formation 

depends on the presence of ozone precursors as well as the amount of sunlight and other 

 

1 EPA NEI2011 Web-site - http://www.epa.gov/ttnchie1/net/2011inventory.html
1-3

meteorological impacts. Since ozone is typically a summertime pollutant, emissions 

during the summer months are more important to air quality than are emissions during 

other times of the year. For these reasons, ozone precursor base year emissions are 

represented as typical ozone season daily emissions (ozone season tons per day). 

The planning period for the 2008 ozone NAAQS emissions inventory covers the ozone 

season defined as May through September. For the purpose of submitting the base year 

2011 SIP inventory to EPA, annual emissions are estimated for VOC, NOX, CO, PM2.5-

Pri, SO2, and NH3. Ozone season day emissions are estimated for the ozone precursors of

VOC, NOx, and CO. 

1.4 Quality Assurance Policy and Objectives

In order to provide data of sufficient quality for attainment and maintenance planning 

needs, quality assurance (QA) and quality control (QC) procedures are part of the 

inventory process. The procedures address data quality objectives of accuracy, 

completeness, comparability, and representativeness. The target goals for each objective 

are listed below.

Accuracy: All estimates must be calculated and documented using acceptable methods.

Individual source requirements and availability of data and resources will affect the 

estimation method selection.

Completeness: Completeness is addressed by ensuring that all applicable source 

categories are included in the inventory and that all information required to estimate 

emissions is present.

Comparability: Data will be compared to the most recent base year inventory: 2011

National Emissions Inventory (NEI) for VOC, NOX, and CO. Any discrepancies (data 

outliers) must be verified or corrected.

Representativeness: Actual 2011 annual and the typical ozone season day emissions will 

be calculated for the base year inventory. Local data will be used in inventory 

calculations wherever possible.

1.5 Plan Information Sources

This plan draws upon inventory, quality assurance, and emissions projections guidance 

available from state and federal agencies and partnerships. The effort also draws upon 

experience gained during previous emission inventory reviews.

A primary source of emissions inventory data is the 2011 NEI, which was submitted to 

EPA by the state air agencies. 
1-4

1.6 Summary of the Base Year Emissions Inventory 

Summaries of the ozone precursor emissions in tons per day (TPD) and tons per year 

(TPY) for the Washington, DC-MD-VA 2008 ozone NAAQS nonattainment area are 

shown in Table 1-1. Summaries relating to the individual sections of the inventory, such 

as point sources, may be found at the beginning of the respective section. Slight 

differences between the executive summary table and the section tables are due to 

rounding. 

Table 1-1

2011 Base Year SIP Emission Inventories 

Washington, DC-MD-VA 2008 Ozone NAAQS Nonattainment Area 

Source 

Category

VOC

(TPD)

NOX

(TPD)

CO

(TPD)

VOC

(TPY)

NOX

(TPY)

CO

(TPY)

PM2.5-

Pri

(TPY)

SO2

(TPY)

NH3

(TPY)

Point 6.96 151.57 32.21 1,223.23 14,134.09 4,189.84 1,669.61 14,393.80 53.21

Area 134.86 2.39 31.67 46,333.16 8,827.77 42,671.86 11,582.23 3,910.64 3,573.82

Nonroad 70.80 77.08 841.96 18,661.42 24,036.39 215,002.54 2,018.93 961.98 25.55

On-road 82.35 205.48 894.98 28,981.19 71,099.71 355,846.05 2,771.45 420.83 1,625.23

Anthropogenic 

Subtotal 294.98 436.52 1,800.82 95,199.00 118,097.96 617,710.29 18,042.21 19,687.25 5,277.81

1.7 Document Contents

Chapter 2 Presents the methodology for developing the 2011 ozone precursor 

emissions from point sources. 

Chapter 3 Presents the methodology for developing the 2011 ozone precursor 

emissions from area and nonroad sources. 

Chapter 4 Presents the methodology for developing the 2011 ozone precursor 

emissions from onroad mobile sources. 

Chapter 5 Presents the QA/QC plan for the 2011 ozone precursor emissions 

inventory. 

The point, area, nonroad, and onroad source emissions inventory development 

documentation; detailed emissions by source classification code (SCC); and nonroad and 

onroad model input and output files are presented in Appendices A through D of this 

document. 
2-1

2.0 Point Sources

2.1 Introduction

This section documents the development of the Washington, DC-MD-VA 2008 ozone NAAQS

nonattainment area stationary point source emissions inventory. This section characterizes the 

point source component of the emissions inventory by describing the 2011 ozone season day and 

annual emissions estimation techniques. The point source inventory consists of actual emissions 

for a typical ozone season day and for the entire period in the year 2011. The inventory includes 

sources located within the Washington DC-MD-VA 2008 ozone NAAQS nonattainment area.

The state air agencies are responsible for developing point source emissions inventories and 

maintaining the data. MWCOG compiled the ozone season day and annual emissions data 

provided by the state air agencies for inclusion in this emissions inventory document.

2.2 Compilation and Documentation of Point Source Emissions 

The state air agencies maintain substantial databases of both small and large air emission 

sources. The list of point sources in this inventory was developed by applying the appropriate 

thresholds to the emission levels in the databases to differentiate between point and area 

stationary sources. Sources with emission levels greater than the threshold or sources previously 

included in Periodic Emissions Inventory submittals are by definition point sources while 

sources with emissions levels less than the thresholds are by definition area sources.

For Virginia units, temporal allocation of emissions from annual to ozone season day was 

accomplished using EPA’s generally accepted emissions calculation techniques for all point 

sources other than those units reporting emissions and activity data to the Clean Air Markets 

Division (CAMD) database under 40 CFR Part 75. For units reporting to CAMD, the hourly 

average NOX emission rate for hours operated during the summer months of 2011 (May through 

September) was multiplied by 24 hours per day to calculate a typical ozone season daily rate in 

tons per day. 

Full documentation on point sources and emissions in individual states are maintained by the 

respective state air agency responsible for the state in which the facility or source is located.

Appendix A provides a detailed description of the total point source emissions for the 

Washington, DC-MD-VA 2008 ozone NAAQS nonattainment area.
2-2

Table 2-1

2011 Base Year SIP Point Source Emission Inventories

Washington, DC-MD-VA 2008 Ozone NAAQS Nonattainment Area

1 There are no VOC, NOX, CO, PM2.5-Pri, SO2, and NH3 emissions for the Virginia Independent City of Manassas Park. 

Point Source Emissions – Base Year 2011 SIP Emission Inventory

Metropolitan Washington NAA1 Pollutant Calvert County Charles County Fredrick County

Montgomery 

County

Prince 

George's 

County

Arlington 

County

Fairfax 

County

Fairfax City

Fairs Church 

City

Loudoun 

County

Prince 

William 

County

Manassas 

City

Alexandria 

City

District Of 

Columbia

MD Total

VA Total

NAA Total

Tons per ozone season 

day

VOC 0.07 0.76 0.49 0.36 1.34 0.07 1.37 0.36 0.0002 1.02 0.73 0.14 0.06 0.19 3.02 3.75 6.96

NOX 1.28 28.15 0.68 14.53 50.05 0.87 18.83 0.04 0.01 10.02 12.96 1.03 11.74 1.39 94.70 55.48 151.57

CO 0.43 2.41 0.80 3.28 6.88 0.36 12.12 0.05 0.0005 2.46 1.61 0.29 0.55 0.98 13.79 17.44 32.21

Tons per year

VOC 6 103 125 44 194 9 243 131 0.003 89 156 41 11 70.84 472.42 679.96 1,223.23

NOX 48 1,421 87 2,611 5,020 75 2,149 7 0.07 216 724 21 1,052 702.88 9,187.12 4,244.09 14,134.09

CO 9 698 127 490 942 49 800 16 0.01 207 252 24 136 438.86 2,266.33 1,484.65 4,189.84

PM2.5-Pri 4 595 22 146 578 0.09 28 0.04 - 2 178 10 50 55.44 1,344.75 269.42 1,669.61

SO2 0.25 5,715 14 1,275 5,811 16 141 0.04 0.01 13 320 3 515 569.92 12,815.23 1,008.65 14,393.80

NH3 - 1 - 2 1 - - - - - 43 6 0.23 0.00 4.12 49.09 53.21
 3-1

3.0 Area and Nonroad Sources

3.1 Introduction and Scope

This document contains a detailed explanation of how the 2011 emissions inventory for area 

and nonroad sources of VOC, NOX, CO, PM2.5-Pri, SO2, and NH3 was developed. Emissions 

inventories for area and a few nonroad sources - marine vessels, airport, railroad locomotives

(MAR) - for a typical ozone season day and the entire year in 2011 were prepared by the 

state air agencies. The MWCOG staff developed emissions for remaining nonroad sources 

using NMIM2008 software. The MWCOG staff also compiled this information for inclusion

in this base year inventory document. 

Area sources include stationary sources not part of the states' point source inventories, 

usually because the source type is too small to be tracked individually and is instead tracked 

as a group or category. Nonroad sources include equipment that draws power from engines

for purposes other than movement on the highway system. Examples include lawn and 

garden equipment, construction equipments, recreational boating, etc. 

All questions or comments regarding the area and MAR emissions in this document should 

be directed to the respective state air agency.

3.2 Area Sources

3.2.1 Emission Estimation Approach

The state air agencies provided detailed documentation regarding the development of 

emissions for area sources. This information is located in Appendix B1, B2, and B3 

respectively.

3.2.2 Summary of Emission Results

Table 3-1 lists emissions for the counties and cities in the Washington, DC-MD-VA 2008

ozone NAAQS nonattainment area. Appendix B4 is an electronic attachment that provides 

the detail of these emissions data.
 3-2

Table 3-1

2011 Base Year SIP Area Source Emission Inventories

Washington, DC-MD-VA 2008 Ozone NAAQS Nonattainment Area

Jurisdiction

VOC

(TPD)

NOX

(TPD)

CO

(TPD)

VOC

(TPY)

NOX

(TPY)

CO

(TPY)

PM2.5-Pri

(TPY)

SO2

(TPY)

NH3

(TPY)

District of Columbia 12.98 0.01 0.25 4,212.49 1,357.18 867.30 381.41 981.52 147.06

Calvert County 2.09 0.06 1.93 679.34 94.11 1,024.79 253.26 91.97 45.79

Charles County 3.78 0.16 5.38 1,248.73 227.22 2,622.87 536.67 183.29 69.93

Frederick County 6.59 0.16 5.46 2,141.56 399.37 3,129.81 1,042.75 284.57 1,489.06

Montgomery County 23.03 0.04 1.94 7,458.41 1,555.02 4,869.65 1,867.42 379.72 344.29

Prince George’s 

County 20.24 0.08 2.57 6,592.32 1,271.14 4,721.60 1,261.01 361.60 296.99

Maryland Total 55.73 0.50 17.29 18,120.37 3,546.87 16,368.72 4,961.11 1,301.15 2,246.06

Arlington County 5.50 0.09 0.35 2,130.12 402.11 2,643.68 567.74 158.45 54.56

Fairfax County 30.55 0.89 3.23 11,102.29 1,955.18 11,216.08 2,657.38 802.35 413.07

Fairfax City 1.20 0.02 0.05 399.62 52.38 243.70 82.71 20.39 15.17

Falls Church City 0.43 0.01 0.02 153.61 26.41 142.47 51.63 10.17 10.94

Loudoun County 9.50 0.37 2.73 3,414.28 532.15 3,653.13 1,273.07 225.16 391.60

Prince William County 13.10 0.32 7.25 4,754.46 585.35 6,107.55 1,245.42 258.13 242.86

Manassas City 1.31 0.05 0.12 467.47 75.62 371.29 105.04 31.79 13.52

Manassas Park City 0.44 0.01 0.04 159.42 19.62 125.14 27.05 8.86 4.44

Alexandria City 4.11 0.12 0.34 1,419.04 274.90 932.79 229.67 112.68 34.55

Virginia Total 66.15 1.88 14.13 24,000.30 3,923.72 25,435.84 6,239.71 1,627.97 1,180.71

Region Total 134.86 2.39 31.67 46,333.16 8,827.77 42,671.86 11,582.23 3,910.64 3,573.82
 3-3

3.3 Nonroad Sources 

Emissions for nonroad sources other than MAR were estimated using EPA’s 

NONROAD2008 model embedded in the NMIM2008 software. Emissions estimation 

approaches for both categories of nonroad sources are described below. 

3.3.1 Marine Vessels, Airport, Railroad Locomotives 

3.3.1.1 Emission Estimation Approach 

Detailed documentation for the development of MAR emissions were provided by the state 

air agencies. The state-specific documentation may be found in Appendix B1, B2, and B3,

respectively. 

3.3.1.2 Summary of Emission Results 

Table 3-2 lists emissions for counties and cities in the Washington, DC-MD-VA 2008 ozone 

NAAQS nonattainment area. Detailed emissions breakdowns may be found in electronic 

format in Appendix B4 of this document. 

Table 3-2

2011 Base Year SIP MAR Emission Inventories 

Washington, DC-MD-VA 2008 Ozone NAAQS Nonattainment Area 

Jurisdiction

VOC

(TPD)

NOX

(TPD)

CO

(TPD)

VOC

(TPY)

NOX

(TPY)

CO

(TPY)

PM2.5-Pri

(TPY)

SO2

(TPY)

NH3

(TPY)

District of Columbia 0.23 3.01 2.52 25.64 330.63 62.86 8.67 13.28 0.002

Calvert County 0.09 2.54 0.29 31.94 925.76 105.68 - 500.74 - 

Charles County 0.04 0.08 0.66 15.41 30.72 241.69 0.78 2.23 - 

Frederick County 0.22 1.25 4.39 80.80 456.17 1,603.02 12.16 10.51 - 

Montgomery County 0.09 0.96 1.31 33.00 351.36 478.24 9.95 3.12 - 

Prince George’s 

County

0.24 1.17 1.44 86.38 427.36 525.66 8.54 15.68 - 

Maryland Total 0.68 6.00 8.09 247.54 2,191.37 2,954.29 31.43 532.27 - 

Arlington County 0.57 3.73 6.33 209.40 1360.76 2309.77 34.81 159.37 0.01

Fairfax County 0.06 0.99 0.26 22.61 359.65 95.43 10.38 6.51 0.09

Loudoun County 0.76 5.20 8.47 279.17 1898.57 3089.74 50.08 194.12 - 

Prince William County 0.04 0.80 0.15 15.98 291.55 55.63 8.78 3.67 0.10

Manassas City 0.02 0.04 0.66 8.34 16.21 240.13 5.02 0.95 0.01 

Manassas Park City 0.0002 0.004 0.0006 0.08 1.48 0.24 0.05 0.02 0.0007

Alexandria City 0.02 0.39 0.10 8.90 141.97 35.14 4.18 1.78 0.03

Virginia Total 1.49 11.15 15.96 544.48 4,070.20 5,826.08 113.31 366.42 0.24

Region Total 2.40 20.16 26.58 817.65 6,592.20 8,843.22 153.41 911.97 0.24

Note: The cities of Fairfax and Falls Church, located within the Commonwealth of Virginia, 

did not have any 2011 emissions from the MAR category. 
 3-4

3.3.2 Nonroad Model Sources

Nonroad model sources include a varied collection of equipment using power from engines 

for purposes other than locomotion on highways. Nonroad emissions result from the use of 

fuel in this diverse collection, which includes vehicles and equipments in the following 

categories:

• Recreational vehicles, such as all-terrain vehicles and off-road motorcycles;

• Logging equipment, such as chain saws;

• Agricultural equipment, such as tractors;

• Construction equipment, such as graders and backhoes;

• Industrial equipment, such as fork lifts and sweepers;

• Residential and commercial lawn and garden equipment, such as leaf and snow blowers.

3.3.2.1 Emission Estimation Approach

Except for equipment in the MAR category, the inventory for nonroad mobile sources was

developed using the most current version of EPA’s NONROAD model as embedded in the 

National Mobile Inventory Model (NMIM). The NONROAD model includes more than 80 

basic and 260 specific types of nonroad equipment and further stratifies equipment types by 

horsepower rating. Fuel types include gasoline, diesel, compressed natural gas (CNG), and 

liquefied petroleum gas (LPG). 

EPA’s NMIM2008 software (version NMIM20090504), the revised NMIM County Database 

(NCD20130531_nei2011v1), and the NONROAD2008a model (July 2009 version) were

used to estimate the 2011 annual and average ozone season day emissions for VOC, NOX, 

CO, SO2, PM2.5-Pri, and NH3 for the purposes of creating the base year 2011 emissions 

inventory. The NONROAD2008a model estimates emissions for each specific type of 

nonroad equipment by multiplying the following input data estimates:

• Equipment population for the base year, distributed by age, power, fuel type, and 

application;

• Average load factor expressed as average fraction of available power;

• Available power in horsepower;

• Activity in hours of use per year; and

• Emission factors reflecting deterioration and/or new standards.

The emissions are then temporally and geographically allocated using appropriate allocation 

factors. 

Several input files provide necessary information to the model. These input files include 

information such as: emission factors, base year equipment population, activity, load factors, 

average lifetime, scrappage function, growth estimates, and geographic and temporal 

allocations. Default values are provided for all input files. The user may replace the default 

data files when better information becomes available, either from EPA for national defaults 

or from local sources for locality-specific data.
 3-5

The NMIM2008 software was run for all twelve months in 2011 to develop average ozone 

season day and annual emissions for the cities and counties in the Washington, DC-MD-VA 

2008 ozone NAAQS nonattainment area. All emissions sources in the software (except for 

ground support equipment in Virginia) were included in the run. Ground support equipment 

emissions were provided by the VDEQ staff separately. Average ozone season day emissions 

were estimated by dividing total emissions in July by the total number of days (31) in July. 

Emissions for all twelve months in 2011 were added together to develop annual emissions. 

Model inputs (temperature, fuel, and other parameters) used in this analysis were included in 

the NMIM county database mentioned above and were the same as the inputs used in 

developing the 2011 NEI for the NMIM model sources. The above NMIM county database 

was acquired from EPA’s website (file name ‘2011nei_supdata_nonroad.zip’ under 

“Supporting data and summaries”) for the NEI 2011(ver 1) effort.

1

The 2011 NEI Technical 

Support Document (ver 1) available on the above website provides details of the 

development of various inputs included in the database. 

3.3.2.2 Summary of Emission Results 

Table 3-3 lists emissions for different counties and cities in the Washington, DC-VA-MD 

ozone nonattainment region. Detailed NMIM2008 software input and output files are being 

provided separately in electronic format as Appendix C of this document.

Table 3-3

2011 Base Year SIP Nonroad Model Source Emission Inventories 

Washington, DC-MD-VA 2008 Ozone NAAQS Nonattainment Area 

Jurisdiction

VOC

(TPD)

NOX

(TPD)

CO

(TPD)

VOC

(TPY)

NOX

(TPY)

CO

(TPY)

PM2.5-Pri

(TPY)

SO2

(TPY)

NH3

(TPY)

District of Columbia 5.28 7.52 46.75 1,250.21 2,364.45 11,995.60 203.88 6.21 2.85

Calvert County 2.56 1.51 15.48 494.70 373.37 3,249.72 30.13 0.95 0.50

Charles County 4.22 2.64 24.71 868.47 696.76 5,408.72 62.62 1.81 0.92

Frederick County 4.27 3.57 49.91 1,126.46 1,061.06 12,727.80 115.73 3.03 1.49

Montgomery County 14.37 8.87 184.54 3,858.80 2,733.86 46,762.90 333.43 8.41 4.48

Prince George’s County 9.18 7.78 112.16 2,432.58 2,442.06 28,757.50 257.83 7.04 3.53

Maryland Total 34.59 24.37 386.79 8,781.01 7,307.11 96,906.64 799.74 21.23 10.92

Arlington County 1.58 3.41 19.41 437.65 1,084.95 5,081.42 98.33 2.84 1.32

Fairfax County 13.85 9.34 189.70 3,798.92 2,903.94 48,445.20 345.98 8.87 4.72

Fairfax City 0.42 0.16 6.74 110.12 49.70 1,666.93 7.45 0.18 0.11

Falls Church City 0.25 0.09 3.81 70.06 26.32 970.22 4.48 0.10 0.06

Loudoun County 6.05 6.88 84.38 1,705.36 2,104.36 21,346.70 230.58 5.92 2.96

Prince William County 4.81 4.52 54.81 1,259.37 1,390.18 13,726.70 149.29 3.91 1.96

Manassas City 0.23 0.17 3.58 66.83 60.63 1,018.76 4.84 0.19 0.08

Manassas Park City 0.23 0.08 3.56 65.52 25.71 912.24 4.29 0.10 0.06

Alexandria City 1.10 0.39 15.86 298.73 126.84 4,088.91 16.66 0.45 0.26

Virginia Total 28.53 25.03 381.85 7,812.56 7,772.63 97,257.07 861.89 22.57 11.53

Region Total 68.40 56.92 815.39 17,843.77 17,444.19 206,159.31 1,865.52 50.01 25.31

 

1

 EPA NEI 2011 Website - http://www.epa.gov/ttn/chief/net/2011inventory.html#inventorydoc 
4-1

4.0 Onroad Mobile Sources

4.1 Introduction

The MOVES2010a model was used for developing the onroad mobile annual and average 

ozone season day base year 2011 emissions for the Washington, DC-MD-VA 2008 ozone 

NAAQS nonattainment area. Appendix D1 provides more detailed documentation on 

data sources and methodologies used to develop different inputs. MOVES2010a input 

files, external input files, and output files are provided separately in electronic format as 

Appendix D2.

Metropolitan Washington Air Quality Committee (MWAQC) staff developed 

meteorology inputs and coordinated with the state air agencies to acquire fuel and 

inspection and maintenance program inputs for the MOVES2010a model. MWAQC staff 

provided these inputs to the National Capitol Region Transportation Planning Board 

(TPB) staff who developed other transportation related inputs for the model. TPB staff 

developed emissions using the above model. MWAQC staff reviewed and approved these 

emissions, incorporating them into the base year 2011 inventories.

This on-road mobile emissions analysis process is very similar to the process used during 

the development of previous base year inventories.

4.2 Summary of Onroad Mobile Source Emissions

The table below summarizes the typical ozone season day emissions for VOC, NOX, and 

CO and annual emissions for VOC, NOX, CO, PM2.5-Pri, SO2, and NH3 in the 

Washington, DC-MD-VA 2008 ozone NAAQS nonattainment area.
4-2

Table 4-1

2011 Base Year SIP Onroad Source Emission Inventories

Washington, DC-MD-VA 2008 Ozone NAAQS Nonattainment Area

Washington, DC-MD-VA 2008 Ozone NAAQS Nonattainment Area1 Pollutant Calvert County Charles County Frederick County Montgomery County Prince George's County Arlington County Fairfax 

CountyLoudoun CountyPrince William CountyAlexandria CityDistrict Of ColumbiaMD TotalVA TotalNAA Total

Tons per ozone season 

day

VOC 2.06 3.24 6.05 14.42 16.55 2.54 16.48 4.90 7.34 1.85 6.91 42.33 33.10 82.35

NOX 4.02 7.15 18.54 34.19 43.75 4.98 40.92 13.57 18.77 3.79 15.79 107.65 82.04 205.48

CO 18.64 29.31 72.54 153.61 188.00 29.27 184.19 52.94 76.55 18.64 71.18 462.11 361.69 894.98

Tons per year

VOC 709 1,112 2,065 5,085 5,678 922 5,966 1,768 2,629 675 2,374.05 14,647.98 11,959.16 28,981.19

NOX 1,420 2,531 6,603 11,791 15,217 1,679 14,113 4,743 6,629 1,299 5,073.93 37,562.80 28,462.98 71,099.71

CO 7,335 11,387 25,397 58,166 66,022 13,002 81,863 23,816 34,050 8,919 25,889.76 168,307.25 161,649.04 355,846.05

PM2.5-

Pri 51 97 256 462 562 63 561 198 265 50 206.09 1,428.37 1,136.99 2,771.45

SO2 6 10 27 69 73 16 105 30 39 11 33.82 185.77 201.24 420.83

NH3 26 43 120 288 353 55 342 92 130 33 144.30 829.77 651.15 1,625.23

1

Fairfax County emissions include onroad emissions from Fairfax City and Falls Church City. Prince William County emissions 

include emissions from Manassas City and Manassas Park City.

* Small discrepancies may result due to rounding.
5-1

5.0 Quality Assurance Procedures

Several quality assurance checks were employed by the Washington DC-MD-VA state 

air agencies or, given resource constraints, regionally to address the data quality 

objectives discussed in Chapter 1.4 related to accuracy, completeness, comparability, 

and/or representativeness: reality/peer review checks, sample calculations, sensitivity 

analysis, and range checks. Details on each check are provided below. 

5.1 Reality Check/Peer Review Check

Independent review was conducted by knowledgeable staff to ensure that data, 

assumptions, and procedures are reasonable. The objective of these checks is to ensure 

accuracy, completeness, comparability, and representativeness.

Reasonableness of methods, assumptions, and emissions estimates was assessed by 1) 

comparing data sources used in the final inventory to those used for the 2011 NEI; 2) 

relying on reviewer expertise; and 3) comparing emissions estimates to other inventory 

efforts, particularly the 2002 base year inventory, 2007 attainment year inventory, and the 

2011 NEI (Version 1).

5.2 Sample Calculations

Sample calculations provide verification of values by replicating calculations. The 

benefit is to ensure that calculations are done correctly. The objective is accuracy.

Emissions calculations were duplicated to spot check the accuracy of the arithmetic and, 

therefore, the resulting emissions estimates. Priority was given to those categories 

identified as the largest emissions contributors.

For nonroad and onroad emissions estimates, sample calculations were not used as a 

quality assurance mechanism. Preparing sample calculations for these sectors was not 

possible since the emissions estimates were generated using EPA-approved models.

Rather, these data, which were generated by MWAQC and TPB modeling staff, were 

checked by comparing the results of similar modeling runs conducted by other agencies 

such as state air agencies, state transportation agencies, or MARAMA to ensure the 

results included herein were reasonable.

5.3 Sensitivity Analysis

Sensitivity analysis is the systematic study of how changes in parameters affect data. The 

benefit is to identify the parameters that have the greatest effect on data. All data quality 

objectives are addressed using these checks.

A sensitivity analysis in the form of source category emissions rankings by pollutant was

performed. The ranking helped determine where efforts should be concentrated.
5-2

5.4 Standard Range Checks

Standard range checks address the data quality objective of comparability. The benefit is 

to identify the source categories that have the greatest change in emission levels from 

previous emission estimates. All data quality objectives are addressed using these checks.

The 2011 base year inventory was compared to the most recent inventories (base year 

2002, attainment year 2007 inventory, and the 2011 NEI Version 1). Any discrepancies 

(data outliers) were verified or corrected.

5.5 Corrective Action Plan

Corrective and follow-up actions identified during the quality checking process were

noted and referred to the appropriate staff.