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OFFICE OF INSPECTOR GENERAL
Catalyst for Improving the Environment
Evaluation Report
Progress Report on EPA's
Nonroad Mobile Source
Emissions Reduction Strategies
Report No. 2006-P-00039
September 27, 2006

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Report Contributors:
John Bishop
Gwen Butler
Jennifer Dwyer
Sarah Fabirkiewicz
Bill Nelson
Rick Beusse
Abbreviations

CO
Carbon Monoxide
EPA
U.S. Environmental Protection Agency
MARPOL
International Convention for the Prevention of Pollution from Ships
NOx
Nitrogen Oxides
OIG
Office of Inspector General
OTAQ
Office of Transportation and Air Quality
PM25
Fine Particulate Matter
PM10
Particulate Matter up to 10 micrometers in diameter
PM
Particulate Matter
PPM
Parts Per Million
SOx
Sulfur Oxides
STAPPA/ALAPCO
State and Territorial Air Pollution Program Administrators/

Association of Local Air Pollution Control Officials
THC
Total Hydrocarbons
VOC
Volatile Organic Compound
Cover photos: Various types of nonroad mobile sources of emissions (photos courtesy EPA).

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U.S. Environmental Protection Agency
Office of Inspector General
At a Glance
2006-P-00039
September 27, 2006
Catalyst for Improving the Environment
Why We Did This Review
Emissions from nonroad
mobile sources can present
significant health and
environmental hazards. The
U.S. Environmental Protection
Agency (EPA) projects that
emissions from these sources
will decrease in some
categories but increase in
others. As such, we examined
EPA's efforts to reduce
nonroad mobile source
emissions, opportunities for
additional reductions, and
challenges to addressing
nonroad emissions problems.
Background
Nonroad mobile sources
include marine vessels,
locomotives, aircraft, farm and
construction machinery, lawn
and garden equipment,
recreational vehicles, and
outdoor power equipment.
Nonroad mobile sources
produce particulate matter and
ozone-forming nitrogen oxides
and volatile organic
compound emissions, as well
as toxic air pollutants, which
contribute to a host of health
and environmental hazards.
For further information,
contact our Office of
Congressional and Public
Liaison at (202) 566-2391.
To view the full report,
click on the following link:
www.epa.aov/oia/reports/2006/
20060927-2006-P-00039.pdf
Progress Report on EPA's Nonroad Mobile
Source Emissions Reduction Strategies
What We Found
EPA has issued nonroad mobile source emissions control regulations that, when
fully implemented, should result in significant reductions in such emissions.
However, more emission reduction efforts are needed and some challenges
remain.
Until the mid-1990s, emissions from nonroad mobile sources were largely
uncontrolled. In the 1990 Clean Air Act Amendments, Congress directed EPA to
study the contribution of nonroad sources to ozone and other air pollutants, and to
issue regulations if problems were found. EPA has since issued 14 regulations to
control pollutants from nonroad mobile sources, with a total of 20 standards for
various nonroad categories. The most recent regulation, the 2004 Nonroad Diesel
Engines rule, is based on a systems approach involving a combination of engine
modifications, reduced sulfur content in diesel fuel, and exhaust controls.
There are approximately 5 million nonroad diesel engines in the United States
today, many of which are not subject to EPA emissions standards. These engines
have the potential to continue to produce high levels of pollution over the next
20 years or more. Agency projections show that substantial emissions reductions
have already been made for some source categories. However, the full benefits of
EPA's regulations may not be realized until 2020-2030, when the standards are
expected to be fully implemented. Projected benefits assume engine turnover and
replacement - activities that may be influenced by cost, lead time, and overall
feasibility. EPA has encouraged emission reductions for existing engines through
voluntary efforts and incentive programs. Although a mandatory retrofit program
may achieve increased health protection sooner, such a requirement from the
Federal level can only come through a change in the Clean Air Act.
EPA faces significant challenges in addressing nonroad emissions, particularly
among the marine, aircraft, and small gasoline engine categories. The role that
other government entities and international communities play in regulating
emissions from these source categories hinders EPA's progress in achieving
reductions. Technical challenges, including the availability of low sulfur fuel, the
diversity of nonroad engines, and the wide range of applications, also must be
addressed to meet air quality standards and emission reduction goals.
This report provides information on the progress of EPA's efforts to address
nonroad emissions and makes no recommendations.

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
OFFICE OF
INSPECTOR GENERAL
September 27, 2006
MEMORANDUM
SUBJECT:
Progress Report on EPA's Nonroad Mobile Source
Emissions Reduction Strategies
Report No. 2006-P-00039
TO:
William L. Wehrum
Acting Assistant Administrator for Air and Radiation
This is a report on the subject evaluation conducted by the Office of Inspector General (OIG) of
the U.S. Environmental Protection Agency (EPA). The report examines current and projected
nonroad mobile source emissions and how Agency actions have affected those emissions to date,
and are projected to affect emissions in the future. This report represents the opinion of the OIG
and the findings in this report do not necessarily represent the final EPA position. Final
determinations on matters in the report will be made by EPA managers in accordance with
established procedures.
The estimated cost of this report - calculated by multiplying the project's staff days by the
applicable daily full cost billing rates in effect at the time - is $453,376.
Action Required
This report does not include recommendations. Therefore, you are not required to respond to
this report.
We appreciate the efforts of EPA managers and staff in working with us to develop this report.
If you or your staff have any questions regarding this report, please contact me at (202) 566-0847
of roderick.bill@epa.gov, or Wade Najjum at (202) 566-0827 or naiiurn. wade@epa.gov.
Sincerely,
—Bitt~A~Roderick
Acting Inspector General

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Progress Report on EPA's Nonroad Mobile Source Emissions Reduction Strategies
Table of C
Chapters
1	Introduction		1
Purpose		1
Background		1
Scope and Methodology		4
2	Despite Regulatory Progress, More Work Needed
to Achieve Emissions Reductions		5
EPA Making Regulatory Progress for New Nonroad Engines		5
EPA Undertakes Non-Regulatory Efforts to Reduce Emissions
from Existing Diesel Engines		6
Data Not Yet Available to Measure Actual Emissions Reductions
and Health Benefits		8
Further Controls Needed In Nonattainment Areas and
for Certain Nonroad Categories		11
Conclusions		12
Agency Response and OIG Evaluation		13
3	Challenges Remain to Achieve Emissions Reductions		14
Challenges Exist to Controlling Emissions from Certain Categories		14
Nonroad Diesel Engines Rule Presents Technical Challenges		17
Conclusions		18
Agency Response and OIG Evaluation		19
Status of Recommendations and Potential Monetary Benefits		20
Appendices
A Details on Scope and Methodology		21
B EPA's Regulatory Schedule for Nonroad Engines		24
C Agency Response to Draft Report		27
D Agency Memo on Projected Near-Term Nonroad Emissions Reductions		28
E Distribution		30

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Chapter 1
Introduction
Purpose
Emissions from nonroad engines contribute significantly to air pollution and
health problems. The U.S. Environmental Protection Agency (EPA) projects that
emissions from some nonroad engines will continue to increase and contribute
large amounts of particulate matter and ozone precursor emissions,1 while
emissions from other source categories have begun to decrease. Concerned with
growth in emissions from these air pollution sources, EPA has issued 14
regulations to control pollutants from nonroad engines, particularly nitrogen
oxides (NOx), a precursor to the formation of ozone, and particulate matter (PM).
Because emissions from existing engines will be a concern for many years, we
reviewed the status of EPA's efforts to reduce emissions from nonroad sources.
Chapter 2 presents EPA's overall approach to reducing nonroad mobile source
emissions, the progress the Agency has made in taking actions to reduce
emissions, and additional opportunities for nonroad ozone and particulate matter
emissions reductions. Chapter 3 notes some of the major challenges EPA faces in
effectively addressing nonroad emissions.
Background
Mobile sources are divided into two categories: onroad and nonroad. The onroad
category includes cars and light trucks, motorcycles, and heavy-duty vehicles,
such as trucks and buses. Nonroad categories cover a variety of engine
configurations and applications and are divided into several sub-categories, as
listed in Table 1-1.
Table 1-1: Nonroad Engine Categories
Category
Application
Land-Based Diesel
Engines
Backhoes, tractors, material handling equipment, airport service vehicles,
generators, and pumps
Land-Based Spark-
Ignition Engines
Small Spark-Ignition Engines: Lawnmowers, string trimmers, leaf blowers, and
chain saws fueled with gasoline
Large Spark-Ignition Engines: Forklifts, generators, compressors, and welders
fueled with liquefied petroleum gas, gasoline, or natural gas
Recreational Vehicles: Off-highway motorcycles, all-terrain vehicles, and
snowmobiles fueled with gasoline
Marine Engines and
Vessels
Marine Spark-Ignition Engines: Outboard engines, personal water craft, and
gasoline-fueled sterndrive and inboard engines
Marine Diesel Engines: Recreational yachts, fishing boats, tug and towboats,
dredgers, and coastal and ocean-going vessels
Locomotives
Diesel-powered engines used in freight and passenger rail, line-haul, local, and
switch-yard service
Aircraft
All types of aircraft (ground support equipment not included)
Source: EPA, Mobile Source Emissions: Past, Present and Future
1 Ozone is formed by a complex atmospheric chemical reaction of oxides of nitrogen (NOx) and volatile organic compounds
(VOCs) in the presence of sunlight and heat. NOx and VOCs are known as precursor emissions for ozone.
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As illustrated in Table 1-1, some nonroad sources operate with the use of diesel
engines and others operate with gasoline, liquefied petroleum gas, or natural gas
(also known as spark ignition engines). Unlike gasoline engines, diesel engines
have no spark plug, but take in air and compress it; the fuel is then injected
directly into a combustion chamber and the heat of the compressed air ignites the
fuel in the engine. While both engines produce air pollutants, diesel engines
produce substantially more NOx and particulates, and spark-ignition engines
generally produce more volatile organic compounds (VOCs).
Until the mid-1990s, emissions from nonroad mobile sources were largely
unregulated. In the 1990 Clean Air Act Amendments, Congress directed EPA to
study the contribution of nonroad sources to ozone and other air pollutants, and to
issue regulations for nonroad sources found to contribute to air pollution. In
1991, EPA concluded that nonroad engines contributed significantly to air quality
problems related to ozone-forming NOx and VOCs, PM, and other pollutants.
Subsequently, in 2001, EPA found that nonroad and onroad engines also
contributed to air pollution from 21 air toxics. EPA defines air toxics as "those
pollutants that are known or suspected to cause cancer or other serious health
effects or adverse environmental effects." From 1994 to 2004, EPA issued 14
regulations to control pollutants from nonroad engines.
Nonroad Emissions Pose Significant Air Quality and Health Concerns
Nonroad engines emit significant amounts of diesel exhaust, which has been
designated a probable human carcinogen. EPA's most recent data2 indicate that
nonroad engines produce about 66 percent of the nation's fine particulate matter
(PM2.5) from all mobile sources. These nonroad engine emissions contribute
significantly to air pollution affecting about 88 million Americans living in areas
that violate PM2.5 air quality standards. Exposure to fine particulate matter has
been linked to premature death rates and the incidence of cardiovascular and
respiratory illnesses. Particulate matter is a mixture of solid particles and liquid
droplets found in air, and comes in a wide range of sizes. Particles less than
2.5 micrometers in diameter are referred to as fine particles, or PM2.5, and because
of their small size pose the greatest health risk compared to other particulates.
These fine particles - about l/30th of the thickness of a human hair - can lodge
deeply into the lungs and may even get into the blood stream. Additionally, fine
particles are the major source of haze. Unless otherwise specified, this report
focuses on PM2.5 when addressing particulate matter.
NOx and VOCs combine in the presence of heat and sunlight to form one of the
most pervasive air pollution problems for major urban areas - ground level ozone.
Ozone pollution is linked to illnesses such as asthma and heart disease.
Environmental effects of ozone include crop damage, damage to trees, decreased
crop yields that cost the agriculture industry billions of dollars, acid deposition,
2 EPA 2005 Technology Transfer Network Clearinghouse for Inventories & Emissions Factors: National Emissions
Inventory Air Pollutant Emissions Trends Data.
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and nutrient overloads in coastal waters. Nonroad engines produce about
36 percent of NOx and 37 percent of VOC emissions,3 two ozone precursors
contributing significantly to air pollution affecting about 159 million Americans
living in areas that exceed EPA's 8-hour ozone standard.
Overall Nonroad Mobile Source Emissions Decreasing,
But Some Categories Continue to Increase
Prior to EPA's 1994 regulations, emissions from nonroad mobile sources (PM,
and ozone-forming NOx and VOCs) were steadily increasing. Since the nonroad
regulations came into effect, PM2.5 and VOC emissions have generally declined,
while NOx emissions have generally begun to level off. However, EPA projects
that emissions from nonroad sources such as aircraft, marine, and locomotive
diesel engines will continue to increase. EPA estimates that by 2030, without
new controls, locomotive and marine diesel engines, as a subset of mobile source
emissions, will contribute about 27 percent of NOx and 45 percent of fine diesel
PM. While aircraft emissions contribute 1 percent of these NOx emissions
nationwide, some cities with greater airport traffic see larger NOx emissions and
these emissions levels are expected to grow.
Figures 1-1 through 1-3 illustrate the NOx, PM2.5, and VOC emissions for nonroad
sources from 1990 to 2002. As shown, emissions for all three steadily increased
prior to EPA's nonroad regulatory actions, which began to be implemented in
1996.
Figure 1-1: Change in Nonroad Mobile	Figure 1-2: Change in Nonroad Mobile
Source NOx Emissions From 1990 to 2002 Source PM2.5 Emissions From 1990 to 2002
Year
3 EPA 2005 Technology Transfer Network Clearinghouse for Inventories & Emissions Factors: National Emissions
Inventory Air Pollutant Emissions Trends Data.
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Figure 1-3: Change in Nonroad Mobile Source
VOC Emissions From 1990 to 2002
Scope and Methodology
3,000
2.900
2,800
O 2,700
2,600
2.500
2,400
Source for Figures 1-1 through 1-3;
EPA, 2005 National Emission Inventory Air Pollutant
Emissions Trends Data
To assess EPA's efforts to reduce nonroad mobile source emissions, we reviewed
EPA reports, regulations, and guidance, and EPA and external stakeholder
analyses and studies of emissions from nonroad diesel engines. We also
performed limited analyses from EPA's National Emissions Inventory Air
Pollutant Emissions Trends Data, and interviewed officials and representatives
from the EPA Office of Air and Radiation's Office of Transportation and Air
Quality (OTAQ), Ann Arbor, Michigan. In addition, we conducted interviews
with external stakeholder organizations, including State and local organizations,
and environmental and industry groups. We also reviewed pertinent sections of
the Clean Air Act, as amended. Our work was conducted from April 2005
through February 2006. We conducted our evaluation in accordance with
Government Auditing Standards, issued by the Comptroller General of the United
States. Additional details on our scope and methodology are in Appendix A.
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Chapter 2
Despite Regulatory Progress, More Work Needed
to Achieve Emissions Reductions
Since 1994, EPA has issued 14 regulations to control emissions from nonroad
mobile sources. A number of these regulations include multiple tiers of standards,
with a total of 20 standards for the various nonroad categories. Twelve of the
standards have already taken effect, seven are in the process of being phased-in,
and one will not begin to phase-in until 2008. There are approximately 5 million
nonroad diesel engines in the United States today, many of which are not subject
to any EPA diesel engine emissions standards. These engines have the potential
to operate for the next 20 to 30 years and continue to produce high levels of
pollution. EPA officials are aware of the need to reduce emissions from these
existing engines, and have encouraged reductions through voluntary initiatives,
grant awards, and technical guidance. EPA and others have identified
locomotive, marine, and aircraft engines as increasingly significant sources of
emissions that will require additional controls. According to EPA, when the full
inventory of older nonroad engines has been replaced, the nonroad diesel program
will annually prevent up to 12,000 premature deaths, 1 million lost work days,
15,000 heart attacks, and 6,000 children's asthma-related emergency room visits.
EPA Making Regulatory Progress for New Nonroad Engines
The first of the 14 regulations that EPA has issued since 1994 to control nonroad
mobile emission sources went into effect in 1996, and the last is to go into effect
in 2008. EPA has generally taken a phased-in approach when adopting these
regulations and has issued multiple tiers for certain engine categories, with a total
of 20 standards promulgated as of April 2006. To illustrate, EPA issued four tiers
of land-based diesel engine emissions standards, with each tier requiring more
stringent emissions reductions than the previous one. For example, Tier 4 of the
land-based standards first goes into effect in 2008 and is expected to take until
2015 to achieve its 90-percent reduction goal. Additional information on EPA's
nonroad emissions regulatory schedule is in Appendix B.
According to OTAQ officials, at least one set of regulations has been issued for
each nonroad category, with the exception of stern-based marine engines.
OTAQ is working on the following nonroad regulations/activities:
•	Implementing land-based diesel engine emission standards (Tiers 3 and 4).
•	Future gasoline control standards.
•	Future standards for locomotive and marine diesel engines.
•	Mobile source air toxics rulemaking.
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•	Sulfur Oxides (SOx) Emission Control Area under the 1997 Amendments
to the International Convention for the Prevention of Pollution from Ships
(MARPOL-Annex VI).
•	Adopting 2004 NOx standards approved for aircraft by the International
Civil Aviation Organization.
•	Pursuing international standards for ocean-going marine vessels.
In 2004, EPA developed the Control of Emissions of Air Pollution From Nonroad
Diesel Engine and Fuel (Tier 4 standards) - commonly referred to as the Nonroad
Diesel Engines rule - to reduce emissions from nonroad diesel engines by
combining engine and fuel controls as a system to increase emissions reductions.
This concept of integrating engine and fuel controls as a system was
unprecedented in nonroad regulations.
The 2004 standards apply to land-based diesel engines, which are typically used
in construction, agricultural, and industrial equipment. The standards are expected
to reduce NOx emissions by 90 percent and PM2.5 emissions by 95 percent. EPA
estimates that by 2030, these reductions will result in a variety of public health
benefits, including the prevention of 12,000 premature deaths, 1 million lost work
days, 15,000 heart attacks, and almost 6,000 emergency room visits by children
due to asthma attacks. The sulfur fuel component of this rule applies to land
based diesel engines, commercial and recreational marine diesel engines, and
locomotives, and is expected to reduce sulfur levels by 99 percent. EPA's
Nonroad Diesel Engines rule calls for a nationwide transition from diesel fuel
containing about 3,000 parts per million (ppm) of sulfur today to 500 ppm of
sulfur in 2007, and eventually to 15 ppm of sulfur by 2010. Low sulfur levels in
diesel fuel will allow engine manufacturers to use advanced emission control
technologies that allow emissions reductions for PM2.5 and NOx, and, more
importantly, address health and environmental risks associated with these
pollutants.
EPA Undertakes Non-Regulatory Efforts to Reduce Emissions
from Existing Diesel Engines
There are approximately 5 million nonroad diesel engines in use in the United
States today. Many of these are not subject to any EPA diesel engine emissions
standards. Because diesel engines are durable and likely to continue operating
over the next 20 years or more, high levels of pollution from these engines will
persist throughout the life of these engines.
An OTAQ official highlighted the need to reduce emissions from these engines,
and noted that EPA had established a goal of reducing emissions from the existing
11 million onroad and nonroad diesel engines by 2014. Reducing emissions from
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these diesel engines is one of three main priorities that OTAQ plans to address.4
According to the EPA Region 9 Administrator, reducing emissions from older
diesel engines is "one of the most important air quality challenges facing the
country." To meet the goal of reducing emissions from existing engines, a
subcommittee of the Clean Air Act Advisory Committee - the Mobile Source
Technical Review Subcommittee Clean Diesel and Retrofit Working Group - was
established to:
•	Address how to assess fleets to determine diesel emissions reduction
strategies suitably,
•	Evaluate in-use performance of retrofit technology,
•	Educate the public on emissions reduction strategies, and
•	Address how to establish national incentives for cleaner diesel strategies.
Voluntary Diesel Retrofit Program and
National Clean Diesel Campaign
To address the challenge of reducing emissions from existing engines, EPA
established the Voluntary Diesel Retrofit Program and the National Clean Diesel
Campaign. Established in 2000, the Voluntary Diesel Retrofit Program verifies
new retrofit technologies, awards grants, and provides technical guidance. In
2004, EPA established the National Clean Diesel Campaign, which promotes
retrofit incentives and technical assistance to help reduce pollution from these
engines and equipment. The campaign also established voluntary programs in the
marine and construction nonroad sectors - the Clean Ports and Clean
Construction USA initiatives - to encourage the use of emissions control
technology, replacement of older equipment, and use of cleaner fuels. Today, the
National Clean Diesel Campaign is the overall umbrella for EPA's diesel retrofit
activities.
The National Clean Diesel Campaign promotes regional collaborations and
partnerships, such as the West Coast Diesel Emissions Reductions Collaborative.
This collaborative is a joint effort with EPA and other Federal, State, local, and
non-profit and private sector partners to reduce air pollution emissions from diesel
engines along the West Coast. The collaborative, for example, supported the
Oregon Construction Equipment Emissions Reduction Project to reduce diesel
emissions from construction equipment in the City of Portland through diesel
engine retrofits, cleaner fuels, and engine idle reduction policies. Although a
mandatory retrofit program may achieve increased health protection sooner, such
a requirement from the Federal level can only come through a change in the Clean
Air Act. Concerned with nonroad emissions, some States have implemented their
own mandatory programs.
4 EPA outlined three priorities for OTAQ: (1) to successfully implement the diesel programs; (2) focus on
locomotives, marine diesel engines, mobile source air toxics rule, and programs for small engines; and (3) focus on
addressing existing diesel engines.
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EPA has worked to encourage emissions reductions through voluntary initiatives,
grants, and technical guidance. Although some funding is currently available to
reduce emissions from existing engines, the Acting Director, Compliance and
Innovative Strategies Division, OTAQ, said additional resources are needed.
OTAQ has also focused on guidance and technical support to encourage
emissions reductions.
Data Not Yet Available to Measure Actual Emissions Reductions
and Health Benefits
The Clean Air Act provides EPA with the authority to establish emissions
standards only for new engines; therefore, nonroad engine emissions standards
phase in over time as older engines undergo turnover and replacement. Twelve of
the standards have already taken effect, seven are in the process of being phased-
in, and one will not begin to phase-in until 2008. Table 2-1 shows the emissions
reductions estimates for some nonroad standards; for a complete list, see
Appendix B.
Table 2-1: Emissions Reductions Estimates for Existing nonroad regulations
Regulation
Implementation
Date
Estimated Results
Tier 1 standards for land-
based diesel engines
1996-2000
By 2025, 30% reduction in
NOxemissions
Phase 1 standards for small
spark-ignition engines
1997
By 2020, 32% reduction in
hydrocarbon emissions
Gasoline outboard & personal
watercraft Phase 1
1998-2006
By 2025, 75% lower
hydrocarbon emissions on
average
Tier 2 standards for land
based diesel engines
2001-2006
By 2020 50% NOx and
40% PM reduction from Tier 1
levels
Tier 2 standards for Category
1 and 2 marine diesel engines
2004-2007
By 2030, 24% reduction in
NOx, 12% reduction in PM
Tier 4 standards for land
based diesel engines
2008-2015
By 2030, 95% reduction PM
and 90% reduction in NOx,
and 99% reduction SOx levels
Source: EPA, Federal Register Environmental Documents and EPA OTAQ
The full benefits of EPA's regulations may not be realized until 2020-2030, when
the standards are expected to be fully implemented. These benefits assume engine
turnover and replacement, behavior which may be influenced by cost and lead
time, and overall feasibility. For example, EPA estimates that the full emissions
reductions from the Phase 1 standards (small spark-ignition engines) will be
achieved by 2020, at which time the existing fleet of engines is expected to have
turned over. An OTAQ official noted that "even during the phase-in of new
standards, emission reductions are being seen, since the engines complying with
the newer standards are being introduced into commerce." OTAQ provided the
OIG with projected near-term emission reductions, presented in Table 2-2.
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Table 2-2: Projected Near-Term Emissions Reductions Resulting from All
EPA Nonroad Standards, Except Aircraft3

2006

2010


Tons
Percent
Tons
Percent
Pollutant
Reduced
Reduced
Reduced
Reduced
THC
1,590,089
33%
2,449,807
47%
NOx
913,055
21%
1,558,322
33%
PM10
73,143
21%
117,147
33%
CO
3,145,113
10%
4,718,399
14%
THC: Total hydrocarbons
PMi0: Particulate matter up to 10 micrometers in diameter
CO: Carbon monoxide
a If the aircraft category was included in Table 2-2, slightly greater emission reductions
would result, in particular for NOx.
Source: EPAOTAQ
The 2004 Nonroad Diesel Engines rule is viewed by environmental, industry, and
State and local stakeholders as a successful EPA rulemaking. Similar to other
nonroad regulations, emissions reductions and the resultant health benefits
continue to phase-in until 2030. EPA has projected that PM2.5 emissions will be
reduced by 95 percent and NOx emissions by 90 percent for the land-based diesel
engine category of nonroad engines by 2030.
According to OTAQ's 2004 Final Regulatory Analysis, the Nonroad Diesel
Engines rule5 will ultimately yield the public health benefits shown in Table 2-3
by 2030. The timeframe for EPA's analysis reflects engine turnover (existing
engines being replaced by new, cleaner ones) beginning in 2007 and extending
through 2030.
Table 2-3: Projected Public Health Benefits When the Fleet of Older Nonroad
Engines Has Fully Turned Over (by 2030)
Full Implementation of Rule Will Annually Prevent
Projected Amount
Premature deaths
12,000
Hospitalizations
8,900
Heart attacks
15,000
Children's asthma-related emergency room visits
6,000
Cases of respiratory problems in children
280,000
Work days lost
1,000,000
Cases of asthma symptoms in children
200,000
Source: EPA, Clean Air Nonroad Diesel Rule - Facts and Figures
5 EPA (2004a), Final Regulatory Analysis: Control of Emissions from Nonroad Diesel Engines, EPA420-R-04-007 (May 2004),
Table 9-16.
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As shown in Figure 2-1, both the monetized health benefits (shown by the pink
line) and the tons of PM2.5 emissions reduced (shown by the blue line) are
projected to appear gradually. EPA projects that health benefits will begin to
appear in 2007, when the first phase of the low-sulfur diesel fuel requirements
takes effect for nonroad engines.
Figure 2-1: Projected PM-2.5 Emissions Reductions and Public Health Benefits Resulting
from the 2004 Nonroad Diesel Rule
Projected tons PM2.5 Reduction and Monetized
Health Benefits
100%
2010 2015 2020 2025 2030
Years
-»- tons reduced % total monetized health benefits
Source: EPA, Final Regulatory Analysis: Control of Emissions from Nonroad Diesel Engines
For the nonroad diesel engine standards, implementation will occur in stages:
reductions in sulfur content of nonroad diesel fuel will occur first, and then
adoption of controls on most new nonroad engines. Because full turnover of the
fleet of nonroad diesel engines will not occur for many years, the emission
reduction benefits of the standards will not be fully realized until many years after
the reduction in fuel sulfur content. According to EPA, the overall quantifiable
benefits will total over $83 billion annually by 2030, with a 30-year net present
value of $805 billion.
EPA's "NONROAD" emission inventory model has limitations that could affect
the validity of emission reduction projections. The NONROAD model is used to
estimate emissions from nonroad equipment. This model calculates past, present,
and future emissions inventories for all nonroad categories, but does not currently
have the capability to estimate emissions from aircraft, commercial marine
vessels, and locomotive engines. Also, the emissions data are based on laboratory
testing instead of actual field testing of in-use applications. In the future, the
aircraft, locomotive, and commercial marine source categories will be included in
EPA's new emissions model - Motor Vehicle Emission Simulator (MOVES) -
which is currently under development.
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According to an OTAQ official, because the regulations are phased in and
projections are long term, it is difficult to capture emissions reductions data in the
short term. Unlike highway vehicles, nonroad engines are not registered, and the
difficulty in measuring the activity of nonroad vehicles creates a challenge for the
Agency and the States to collect sufficient reliable data for the NONROAD
model.
Further Controls Needed In Nonattainment Areas and for
Certain Nonroad Categories
EPA's deadlines to meet ozone and PM2.5 standards by 2010 are critical to
meeting human health goals in nonattainment areas. Also, OTAQ officials and
outside stakeholders identified locomotive, marine, and aircraft engines as sources
of significantly increasing emissions that will require additional emissions
controls.
Nonattainment Areas
Emissions from nonroad diesel engines are significant contributors to the
pollution in areas that do not meet National Ambient Air Quality Standards
(nonattainment areas). EPA's Green Book of nonattainment areas for criteria
pollutants identifies areas of the country where air pollution levels exceed the
national ambient air quality standard and are designated as nonattainment. Recent
data from EPA's Green Book show that about 159 million Americans live in 126
ozone nonattainment areas. Additionally, about 88 million Americans live in 208
counties not meeting EPA's PM2.5 standards, and EPA's deadlines to meet PM2.5
standards by 20106 are critical in these areas.
Nonattainment areas are required to reduce ozone and PM2.5 emissions as part of
State Implementation Plans. The 2004 Nonroad Diesel Engines rule is expected
to begin providing emissions results by 2008, but will not be fully implemented
until 2015. Therefore, these States will need to look elsewhere for additional
ozone-forming NOx and PM2.5 reductions.
Category 1 and 2 Marine Diesel and Locomotive Engine Emissions
EPA estimates that by 2030, without new controls, locomotive and marine
(Category 1 and 2) diesel engines will contribute about 27 percent of mobile
source NOx and 45 percent of mobile source diesel PM emissions. Currently,
marine diesel engines contribute about 8 percent of mobile source NOx and
9 percent of mobile source diesel PM emissions, although their relative
contribution is greater around commercial ports.
6 With appropriate justification, States are allowed an extension of up to 5 years, or until February 2015, to reach full
attainment for PM2 5.
11

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A representative from OTAQ's marine and locomotive group said that because
the first standards for marine diesel engines did not take effect until January 2004,
large projected emissions reductions have not yet been achieved. Additionally,
this representative said that emissions certification data from engine
manufacturers indicate they are producing and distributing cleaner engines to
meet the new standards. However, according to EPA documents, the Tier 1
marine standards are equivalent to the international emissions standards, which
are considered less stringent regulations by key OTAQ officials.
EPA estimates that locomotives currently contribute about 7 percent of NOx and
5 percent of PM mobile source emissions. Typically, a locomotive engine will
remain in service 40 years or more before it is scrapped. During that time an
engine may be remanufactured every 5 to 7 years to restore it to an "as new"
condition and may travel a million miles between remanufactures. According to
EPA, locomotive engines have relatively modest emissions standards, and
continue to emit large amounts of NOx and PM. Emissions requirements issued in
1997 were considered adequate at the time, but EPA is now considering more
protective regulations. EPA included sulfur fuel requirements for locomotives in
the 2004 Nonroad Diesel Engines rule to reduce emissions from these engines and
improve the ability to use advanced aftertreatment systems.
OTAQ reported that they are talking with locomotive and marine engine
manufacturers to develop a strategy to implement more stringent regulations for
both locomotive and marine engines based on advanced aftertreatment
technologies. OTAQ expects to issue a notice of proposed rulemaking by
December 2006 and a final rule in 2007.
Aircraft Engine Emissions
Aircraft engine emissions are increasing at a time when other mobile source
categories are being reduced. Aircraft emissions contribute 0.7 percent of NOx
emissions from mobile sources nationwide, but some cities with greater airport
traffic see a larger contribution of NOx emissions from these engines, and these
emissions are expected to grow. For example, EPA estimates that NOx emissions
from commercial aircraft in the Atlanta, Georgia area are expected to double by
2010 and contribute as much as 10 percent of mobile source NOx emissions in
that area. Nationally, the Federal Aviation Administration projects that
commercial air travel is expected to increase 45 percent from 2002 to 2020.
Conclusions
EPA has issued several nonroad mobile source emissions control regulations that
will require significant reductions in nonroad source emissions. The full benefits
of EPA's regulations may not be realized until 2020-2030 when the standards are
expected to be fully implemented. However, these regulations have already
achieved reductions in emissions from some emission source categories. These
12

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benefits assume engine turnover and replacement - activities which may be
influenced by cost, lead time, and overall feasibility.
According to EPA there are approximately 5 million existing nonroad diesel
engines in the United States, many of which are not subject to EPA diesel engine
emission standards. EPA has acknowledged the need to reduce emissions from
existing engines and has introduced voluntary programs and grants to encourage
emissions reductions from these engines. Although a mandatory retrofit program
may achieve increased health protection sooner, such a requirement from the
Federal level can only come through a change in the Clean Air Act.
This report provides information on the progress of EPA's efforts to address
nonroad emissions and makes no recommendations. We plan to perform
additional reviews of mobile source issues in the future, including an in-depth
review related to existing engines.
Agency Response and OIG Evaluation
In addition to the memorandum sent to the OIG with Agency comments to the
draft report, the Agency also submitted more specific comments on the draft
report. These comments were documented in the margins of the draft. A
summary of the key additional comments follows:
(1)	The draft report should include information on the substantial reductions
that have already occurred as a result of EPA's nonroad emissions
standards. To demonstrate projected emissions reductions in the near-
term, OTAQ prepared data for the OIG using the NONROAD model to
show projected emissions for the years 2006 and 2010.
(2)	Tier 4 standards incorporated a great deal of flexibility to allow
manufacturers the lead time necessary to develop and apply aftertreatment
device technology.
We agree with the Agency's key comments, and revisions to the draft report were
made accordingly. The Agency also provided technical comments to the draft
report; we made changes based on these comments as appropriate. In both its
memorandum as well as the comments it provided within the margins of the draft,
the Agency asked that the OIG include information regarding near-term projected
emissions reductions to demonstrate the progress that has already been made due
to EPA's nonroad emissions standards. To address this comment, the OIG
incorporated data on projected emissions reductions for 2006 and 2010 in
"Table 2-2: Projected Near-Term Emissions Reductions Resulting from All EPA
Nonroad Standards, Except Aircraft" of the report.
The Agency's comments are in Appendix C. Appendix D contains a separate
memo with information that EPA provided to supplement Table 2-2.
13

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Chapter 3
Challenges Remain to Achieve Emissions Reductions
Although EPA has made substantial progress in developing regulations to reduce
nonroad mobile source emissions, challenges remain in regulating the aircraft,
marine, and small gasoline engine categories. These challenges may hinder
EPA's progress in achieving emissions reductions from nonroad engines and in
protecting public health. In particular:
•	EPA faces significant challenges in issuing regulations for aircraft and
large ocean-going marine vessels because other government entities and
international organizations play significant roles in regulating those
categories of nonroad sources.
•	Small gasoline engines are the largest contributor of nonroad gasoline
NOx emissions, and while EPA is required to issue new regulations for
small gasoline engines, technical challenges exist related to lawn and
garden equipment that must be addressed first.
•	Technical challenges also exist related to the diversity of nonroad engines
and the wide range of applications of those engines.
Challenges Exist to Controlling Emissions from Certain Categories
Large Ocean-going (Category 3) Marine Diesel Engine Emission
Challenges
The commercial marine engine sector is particularly challenging because marine
diesel engines have a long service life (as long as 20 to 30 years), and there are
limited Federal incentives for retrofitting these engines prior to the end of their
useful life. Also, most large ocean-going vessels (category 3 diesel engines) are
subject to international standards rather than U.S. standards. EPA estimates that
commercial marine diesel vessels annually emit about 1,000,000 tons of ozone-
forming NOx, 40,000 tons of PM2 5, and 160,000 tons of sulfur dioxide.
EPA has set engine emissions (Tier 1) standards for large ocean-going marine
(Category 3) vessels flagged in the United States. The International Maritime
Organization sets the engine emissions standards for foreign-flagged ocean-going
vessels. As noted in Chapter 2, Tier 1 marine standards are equivalent to the
international emissions standards and considered less stringent. However, OTAQ
staff said that the standards are based on the technology available at the time the
standards were adopted, and there have been technological advancements within
14

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the nonroad diesel sector since then that OTAQ hopes to apply to the marine
sector.
EPA must continue to work with the international community to regulate
emissions from these engines. The International Maritime Organization was
established under the United Nations to address safety, navigation, and pollution
prevention for ships involved in international trade. According to EPA
documents, foreign-flagged vessels account for about 97 percent of calls on
U.S. ports, and it is likely that the contribution of U.S. vessels with Category 3
engines to local air pollution is small compared to foreign vessels. Because most
of these ships are subject to International Maritime Organization standards rather
than U.S. standards, EPA faces significant legal issues regarding its authority to
regulate these vessels under the Clean Air Act.
From an environmental perspective, International Maritime Organization
standards that are particularly useful are the 1997 Amendments to the
International Convention for the Prevention of Pollution from Ships (MARPOL -
Annex VI), which address air emissions such as ozone-depleting substances,
onboard incinerators, emissions from tanker operations, and NOx and SOx
emissions from ship engines. MARPOL-Annex VI went into effect in May 2005,
and 28 countries have signed it. In April 2006, the United States Senate gave its
advice and consent to the ratification of MARPOL-Annex VI, but has not yet
ratified the treaty. According to OTAQ staff, some of the potential benefits of the
United States joining the MARPOL-Annex VI agreement are related to the
designation of SOx Emission Control Areas, since it would help prevent, reduce,
and control air pollution from SOx emissions. Additionally, MARPOL-Annex VI
would give the United States authority to inspect foreign ships entering U.S. ports
for compliance with MARPOL-Annex VI standards.
OTAQ staff also noted they are working with the international community and
other stakeholders to develop a second tier of more stringent marine diesel
standards. In July of 2005, the International Maritime Organization formally
agreed to begin deliberations regarding a potential second tier of emission
standards for ocean-going marine vessels. OTAQ and EPA's Office of
International Affairs staff are actively working with the International Maritime
Organization to establish aggressive future standards for ocean-going vessels,
according to OTAQ representatives.
Aircraft Engine Emissions Challenges
Similar to marine diesel and locomotive engines, the long service life of aircraft
engines is a substantial challenge to reducing these emissions, and there are no
Federal incentives for retrofitting these engines prior to the end of their useful life.
As mentioned in Chapter 2, emissions from commercial aircraft are a growing
segment of mobile source emissions. Some aircraft engines have a life span of
about 30 years and account for about 45 percent of total emissions among all
15

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airport operations. Further, shared authority for regulating aircraft emissions,
both internationally and within the Federal Government, add additional
challenges.
EPA and the Federal Aviation Administration have joint authority for regulating
aircraft emissions. An OTAQ official told us that sharing joint authority has been
challenging because the two agencies have different missions and approaches.
OTAQ officials said the Federal Aviation Administration focuses on aircraft
safety, and their emissions agenda is more consistent with that of the airline
industry than EPA's emissions agenda.
In addition, the International Civil Aviation Organization is the international
governing body for the aviation industry, seeking to ensure safety, equality, and
consistency among the international aircraft community through the development
of standards and procedures for aircraft engines. A final rule for the control of
pollution from aircraft was issued last year to adopt the Organization's current
standards, but an OTAQ official told us that these standards are essentially a
codification of the existing EPA aircraft standards, and are not technology-
forcing. Currently, about 90 percent of aircraft engines in use already meet these
standards. Further, the official said EPA has tried on numerous occasions to
adopt more stringent aircraft emissions regulations but has not been successful.
Small Gasoline Engine Challenges
Small gasoline engines such as lawn and garden equipment are the largest
contributor of nonroad gasoline NOx emissions (44 percent), and the second
largest contributor of PM2.5 emissions (31 percent) among nonroad gasoline
sources nationwide. Thus, small gasoline engines are another nonroad engine
emissions source in need of emissions reductions. One specific challenge,
described next, exists with respect to reducing emissions from small gasoline
engines less than 50 horsepower.
A rider enacted in the 2004 VA-HUD7 appropriations bill preempts any State
(with the exception of California8) from adopting or enforcing standards relating
to the control of emissions from new nonroad spark-ignition engines smaller than
50 horsepower. Section 209(e)(B) of the Clean Air Act Amendments of 1990
provided States flexibility in choosing between Federal emission standards or
7	Appropriations Bill for the Department of Veterans Affairs and the Department of Housing and Urban
Development
8	There appears to be a typographical error in the VA-HUD Appropriation language which states that "[t]he
prohibition in subsection (e) does not apply to or restrict in any way the authority granted to California under
Section 209(e) of the Clean Air Act (42 U.S.C. 7543(e))." Subsection (e) does not expressly contain any
prohibition, but rather contains language regarding the effect of these provisions on the enforcement by States of
California standards enacted prior to September I, 2003. We conclude that in referring to "the prohibition in
subsection (e)," the drafters intended to reference subsection (c), which includes the following prohibition: "[n]o
state or political subdivision thereof may adopt or attempt to enforce any standard or other requirement applicable to
spark ignition engines smaller than 50 horsepower."
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California's more protective standards. Now, because of the 2004 VA-HUD
rider, States are prohibited from adopting (under section 209(e) of the Clean Air
Act Amendments) the stricter California standards for this subset of small
nonroad vehicles or engines.
EPA had previously issued two sets of regulations - Phase 1 and 2 Emissions
Standards Engines at or Below 19 kW- to control emissions from new small
spark-ignition (small gasoline) engines less than 25 horsepower in 1997 and 2000,
and did not intend to issue additional regulations for these engines in the near
future. Since States are preempted from adopting California's regulations for
small engines less than 50 horsepower, Congress directed EPA to issue revised
small gasoline engine emissions regulations by December 2004. EPA did not
meet the 2004 deadline, which an OTAQ official said was unrealistic. In June
2005, the Senate approved a provision requiring EPA to conduct a safety study on
the effects of installing new emission controls on lawnmowers (a small gasoline
engine) and their potential to cause fires and burns, which could have impacted
the development of the revised rule. Congress required EPA to complete the
study by February 2, 2006, and prohibited the Agency from publishing proposed
or final regulations until after the study was complete. EPA completed the study
in March 2006, and concluded that adding emission control technologies would
not increase the risk of fire and burns to consumers. Now EPA can begin the
rulemaking process for the Phase 3 emission standards.
Nonroad Diesel Engines Rule Presents Technical Challenges
The diversity of nonroad engines presents several technical challenges to the
successful implementation of the most recent rule. The 2004 Nonroad Diesel
Engines rule is based on a systems approach in which emissions reductions will
be accomplished through a combination of engine modifications, reduced content
of sulfur in diesel fuel, and exhaust aftertreatment devices. EPA and other key
stakeholders described this systems-based approach as technology-forcing,
requiring technological advancements or new applications, and combinations of
existing technology to meet required emissions standards. To meet these
challenges, EPA will need to address: (1) diversity of nonroad engine
applications, (2) integration of aftertreatment technology, and (3) availability of
low sulfur fuel. Details on each follow.
Diversity of Nonroad Engine Applications
The nonroad diesel engine sector covers a diverse range of equipment and engine
applications, from tractors to generators. EPA believes the emissions reduction
technology currently used for the onroad sector can be transferred to the nonroad
sector, but transferring this technology to the diverse engine types and sizes in the
nonroad sector, in some cases, may be challenging. While onroad engines operate
under a narrow range of sizes and designs, each nonroad diesel engine application
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involves different mechanical and duty cycle demands, resulting in a variety of
engine designs and configurations.
Integration of Aftertreatment Technology
Exhaust aftertreatment technology or retrofit devices are used to control engine
emissions, such as PM and NOx, before they leave the tailpipe. Examples of these
devices include oxidation catalysts, selective catalytic reduction devices,
particulate filters, and NOx catalysts. The integration of aftertreatment devices in
nonroad equipment presents a challenge due to the variation in operating
temperatures and space constraints. For example, PM aftertreatment devices must
be operated above a certain temperature, while NOx aftertreatment devices have
both a low and high temperature requirement. Further, the technology for
controlling PM emissions is more mature than that for controlling NOx.
Nonroad equipment also has safety and visibility requirements that must be taken
into account when designing aftertreatment devices. For example, nonroad
equipment operators must have a clear view of the operating area for equipment
attachments, such as shovels and buckets, without being blocked by the engine
compartment. While some equipment using a particular engine may have
sufficient space to accommodate aftertreatment devices, the same engine used on
another piece of equipment may not have enough room.
To help address these challenges, EPA incorporated flexibilities into the Tier 4
nonroad diesel rule to allow manufacturers the lead time necessary to develop and
apply aftertreatment device technology. In certain cases, this flexibility extends
for some manufacturers until 2020.
Availability of Low Sulfur Fuel
The use of aftertreatment devices to control NOx and PM emissions will depend
on the availability of ultra low sulfur diesel fuel. Currently, diesel fuel contains
sulfur levels of about 3,400 ppm. EPA's sulfur fuel standards in the 2004
Nonroad Diesel Engines rule should enable the use of new technology to reduce
PM and NOx emissions and, more importantly, address health and environmental
risks associated with these pollutants. These standards require refineries to reduce
the sulfur content of diesel fuel to 500 ppm by 2007 and to 15 ppm by 2010.
Thus, the availability of 15 ppm ultra low sulfur diesel fuel is critical.
Conclusions
EPA emissions control regulations exist for almost all nonroad engine categories,
but challenges to reducing emissions from these engines remain. These
challenges involve the development of regulations with other Federal Government
entities and international organizations, as well as other issues generally outside
of EPA's control. These challenges may hinder EPA's progress in achieving
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emissions reductions from nonroad engines and protecting public health.
Technical challenges exist related to the diversity of nonroad engines and the
wide range of applications of those engines, and will require creating a wide
variety of engine designs and sizes to accommodate emissions controls. Further,
operating constraints, varying temperature ranges, and equipment sizes create a
challenge regarding the placement of aftertreatment devices.
Agency Response and OIG Evaluation
See Agency Response and OIG Evaluation section at the end of Chapter 2, along
with Appendices C and D.
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Status of Recommendations and
Potential Monetary Benefits
RECOMMENDATIONS
POTENTIAL MONETARY
BENEFITS (In $000s)
Rec. No.
Page
No.
Subject
Status1
Action Official
Planned
Completion
Date
Claimed Agreed To
Amount Amount
No recommendations
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Appendix A
Details on Scope and Methodology
We conducted our work from April 2005 through February 2006 in accordance with Government
Auditing Standards issued by the Comptroller General of the United States. This report presents
information based on results from preliminary research; field work was not conducted because a
follow-on evaluation is planned in the near future. This report focused on EPA's efforts to
reduce emissions from nonroad sources, and not those of States or environmental and industry
groups. Nonetheless, we interviewed officials from associations representing air pollution
control agencies across the United States, as well as officials from selected State and local
agencies, and environmental and industry groups, to ascertain their views on EPA's nonroad
emissions reduction efforts. We selected these stakeholders based on their involvement in EPA's
nonroad rulemaking efforts and involvement in the nonroad sector.
To review EPA's approach to reducing nonroad mobile source emissions, the progress made, and
what opportunities and challenges exist in implementing actions that could lead to greater
emissions reductions, we reviewed several documents. These documents included applicable
Agency rulemakings, policies, guidance, and other documentation regarding planning,
implementation, and oversight of programs to reduce emissions from nonroad mobile sources.
We also examined external stakeholder reports, including the following:
Policies, Guidance, and Reports Reviewed
•	Clean Air Act Amendments of 1977 and 1990, Sections 110, 209, 213, and 231
•	1991 Nonroad Mobile Sources Study
•	2004 Control of Emissions of Air Pollution From Nonroad Diesel Engines and Fuel Rule
•	Agency Strategic Plans
•	Regulatory announcements for various nonroad diesel engine categories
•	Various State and local environmental group reports pertaining to nonroad diesel engine emissions
•	NONROAD emissions inventory model
•	EPA National Emissions Inventory Air Pollutant Emissions Trends Data, 2005
•	Clean Air Act Advisory Committee, Mobile Sources Technical Review Subcommittee
meeting notes and presentations
•	Clean Air Act Advisory Committee, Mobile Sources Technical Review Subcommittee -
Clean Diesel and Retrofit Working Group
•	National Clean Diesel Campaign
•	EPA Voluntary Diesel Retrofit Program
•	2005 Diesels Emissions Reduction Act
•	Congestion, Mitigation, and Air Quality Program
•	State and local incentive and grant emission reduction programs
•	EPA marine and locomotive regulations
•	International Maritime Organization regulations
•	EPA aircraft regulations
•	Outdoor Power Equipment Institute	
We also interviewed key air program officials and representatives at OTAQ, which is part of
EPA's Office of Air and Radiation. We also interviewed the following external stakeholders
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from State and local environmental organizations, environmental groups and associations, and
industry:
Key Stakeholders Contacted
EPA
•	Clean Air Act Advisory Committee - Clean Diesel and Retrofit Working Group
•	Clean Air Act Advisory Committee - Mobile Sources Technical Review
Subcommittee, Ports Sector Working Group staff
•	OTAQ Officials
¦S Marine Diesel Engine staff
~ NONROAD Model Staff
¦S Voluntary Diesel Retrofit Program
External
• Association of Equipment Manufacturers

• Association of Local Air Pollution Control Officials

• California Air Resources Board

• Diesel Technology Forum

• Engine Manufacturers Association

• Environmental Defense

• Manufacturers of Emission Controls Association

• Natural Resources Defense Council

• Northeast States for Coordinated Air Use Management

• Puget Sound Clean Air Agency

• Resources for the Future

• State and Territorial Air Pollution Program Administrators /

Association of Local Air Pollution Control Officials
To determine EPA's approach to reduce nonroad mobile source emissions and progress made,
we identified EPA's goals and strategies for controlling nonroad emissions from 1994 to the
present. We identified EPA's rulemaking status for all nonroad engine categories, including
effective dates and the expected emission reductions. We reviewed EPA's regulatory authority
to address emissions from new and existing engines. To identify EPA's efforts to address
emissions from new and existing engines, we reviewed EPA regulations and programs to address
emissions from nonroad engines, interviewed Agency staff and interested stakeholders, and
analyzed supporting documentation. We reviewed PM and NOx emission trends.
To answer the question of what additional opportunities exist for nonroad ozone precursor and
PM emission reductions, we interviewed OTAQ staff, State officials, local environmental groups
and associations, and industry stakeholders. This included discussing whether additional
regulations were needed to address nonroad emissions. We reviewed EPA and other reports on
the health and air quality impacts of nonroad sectors identified in need of additional emission
reductions. We reviewed EPA and external documentation to identify nonroad categories with
projected emissions growth. We identified external stakeholder reports on State and local
emission reduction programs. We reviewed several Bills/Laws/Acts, such as:
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•	The Federal Highway Administration's Congestion, Mitigation, and Air Quality program,
signed into law on August 10, 2005, as part of the Safe, Accountable, Flexible, Efficient
Transportation Equity Act.
•	Diesel Emissions Reduction Act of 2005, signed into law August 2, 2005, as part of the
Energy Policy Act of 2005.
To answer the question of what challenges EPA faces in effectively addressing nonroad
emissions, we interviewed key EPA officials and external stakeholders to ascertain their
perspective on the regulations for foreign-flagged (Category 3) marine vessels as well as aircraft,
and the roles of the International Maritime Organization and International Civil Aviation
Organization in addressing harmful emissions. We reviewed documentation on foreign-flagged
marine vessels and aircraft emissions. We interviewed EPA and external stakeholders to
understand EPA's progress in revising rules for small gasoline engines. We reviewed
Congressional reports and documentation regarding small gasoline engines.
This report provides information on the progress of EPA's efforts to address nonroad emissions
and makes no recommendations. We plan to perform additional reviews of mobile source issues
in the future, including an in-depth review related to existing engines.
Management Controls
This report provides information on the status of EPA's efforts to address nonroad emissions,
and makes no recommendations for Agency action due to the limited scope discussed above. As
such, a review of EPA management control systems was not conducted. To fully assess EPA's
nonroad emission reduction strategies related to existing nonroad engines, the Office of Inspector
General plans further work regarding EPA's programs to reduce emissions from nonroad diesel
sources.
Data Quality
We reviewed EPA's 2005 National Emissions Inventory Air Pollutants Emissions Trends Data
for PM2 5, NOx, and VOCs, but did not conduct a data reliability assessment of the inventory as
this was not the focus of our objectives.
Prior Reports
The EPA Office of Inspector General has not issued any reports specific to nonroad emissions
reductions efforts. During the course of our evaluation, we reviewed the following Government
Accountability Office reports related to airport emissions:
•	Aviation and the Environment: Airport Operations and Future Growth Present
Environmental Challenges (GAO/RCED-00-153), August 2000
•	Aviation and the Environment: Strategic Framework Needed to Address Challenges
Posed by Aircraft Emissions (GAO-03-252), February 2003
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Appendix B
EPA's Regulatory Schedule for Nonroad Engines
Equipment
Category
Rule Making and Date
Final Rule Established
Phases/Tiers of
Emissions
Standards
Implementation
Date of
Emissions
Standards
Actual/ Planned
Emissions
Reductions
Land-Based
Diesel Engines





Control of Air Pollution;
Amendments to Emission
Requirements Applicable to New
Nonroad Compression-Ignition
Engines at or Above 37 kW:
Provisions for Replacement
Compression-Ignition Engines and
the Use of On-Highway
Compression-Ignition Engines in
Nonroad Vehicles (published
November 12, 1996)
Tier 1
1996-2000
Tier 1: 30% reduction
in NOx and 37%
reduction by 2025

Control of Emissions of Air Pollution
from Nonroad Diesel Engines
(published October 23, 1998)
Tier 2
Tier 3
2001-2006
2006-2008
Tiers 2 and 3: By 2020
exceed 50% NOx and
40% PM reduction

Control of Emissions of Air Pollution
From Nonroad Diesel Engines
(published June 29, 2004)
Tier 4
2008-2015
By 2030 , 95%
reduction in PM and
90% reduction in NOx
And 99 % reduction
sulfur fuel levels
Land-Based
Spark-Ignition
Engines




Small Spark-
Iqnition





Control of Pollution; Emission
Standards for New Nonroad Spark-
Ignition Engines At or Below 19kW
(published July 3, 1995)
Phase 1: <25 hp
1997
Phase 1: 32%
reduction in HC by
2020

Phase 2 Emission Standards for
new Nonroad Spark-Ignition
Nonhandheld Engines At or Below
19kW (published March 30, 1999)
Phase 2: <25 hp
non-handheld
engines
2001-2007
Phase 2: 60%
reduction in HC and
NOx from Phase 1
level

Phase 2 Emission Standards for
New Nonroad Spark-Ignition
Handheld engines At or Below
19kW and Minor Amendments to
Emission Requirements Applicable
to Small Spark-Ignition Engines and
Marine Spark-Ignition Engines
(published April 25, 2000)
Phase 2: <25 hp
handheld
engines
2002-2007
Phase 2: 70%
reduction in HC and
NOx from Phase 1
level
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Equipment
Category
Rule Making and Date
Final Rule Established
Phases/Tiers of
Emissions
Standards
Implementation
Date of
Emissions
Standards
Actual/ Planned
Emissions
Reductions
Large Spark-
Ignition





Control of Emissions from Nonroad
Large Spark-Ignition Engines, and
Recreational Engines (Marine and
Land Based) (published November
8, 2002)
>25 hp
2004-2007
By 2030, 75%
reduction in HC, 82%
reduction in NOx.
61% reduction CO,
60% reduction in PM
Recreational
Vehicles




ATVs &
Motorcycles
Snowmobiles
Control of Emissions from Nonroad
Large Spark-Ignition Engines, and
Recreational Engines (Marine and
Land Based) (published November
8, 2002)
The regulation
does not include
tiers of standards
2006-2007
(ATVs &
Motorcycles)
2006-2012
(Snow Mobiles)
67% reduction in HC
28% reduction in CO
Marine Engines
and Vessels




Marine Spark-
Ignition





Control of Air pollution for New
Gasoline Spark-Ignition Engines:
Exemptions for New Nonroad
Compression Ignition Engines at or
Above 37 Kilowatts and New
Nonroad Spark-Ignition Engines at
or Below 19 Kilowatts (published
October 4,1996)
Tier 1: Outboard
& personal water
craft
1998-2006
By 2025 ,75% lower
HC emissions on
average
Marine Diesel
Engines




Small Engines
Control of Emissions of Air Pollution
from Nonroad Diesel Engines
(published October 23, 1998)
Tier 1
Tier 2
1999 or 2000a
2004 or 2005a
Tier 1 and Tier 2:
exceed 50% NOx and
40% PM reduction
These are the same
as the Tier 2 and 3
Land Based Diesel
Engine standards
Commercial diesel
marine engines,
Categories 1 and 2
Control of Emission from New
Marine Compression-Ignition
Engines at or Above 30 Liters per
Cylinder (published February 28,
2003)b
Control of Emission of Air Pollution
from New Marine Compression-
Ignition Engines at or Above 37 kW
(published December 29, 1999)
Tier 1
Tier 2
2004
2004-20073
Not available
24% reduction in NOx,
12% reduction in PM
in 2030
Commercial
marine diesel
engines, Category
3 vessels flagged
or registered in the
U.S.
Control of Emission from New
Marine Compression - Ignition
Engines at or Above 30 Liters per
Cylinder (published February 28,
2003)
Tier 1
2004
Not available
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Equipment
Category
Rule Making and Date
Final Rule Established
Phases/Tiers of
Emissions
Standards
Implementation
Date of
Emissions
Standards
Actual/ Planned
Emissions
Reductions
Category 3 vessels
- foreign flagged
vessels
MARPOL-Annex VI
(international marine standards)
The regulation
does not include
tiers of standards
2000
20% NOx reduction
Recreational





Control of Emissions from New
Marine Compression-Ignition
Engines at or Above 30 Liters per
Cylinder (published February 28,
2003)
Tier 1
2004
Not available

Control of Emission from Nonroad
Large Spark-Ignition Engines, and
Recreational Engines (Marine and
land-Based) (published November
8, 2002)
Tier 2
2006-2009
Not available
Locomotives




Emission Standards for
Locomotives and Locomotive
Engines (published April 19,1998)
Tier 0: engines
originally
manufactured
1973-2001
Tier 1: engines
originally
manufactured
and thereafter,
2002-2004
Tier 2: engines
originally
manufactured
2005 or later
2001-2005
By 2040, 59%
reduction in NOx and
(41% reduction by
2010)
46% reduction in PM,
43% reduction in HC
Aircraft





Control of Air Pollution from Aircraft
and Aircraft Engines; Emission
Standards and Test Procedures,
(published November 17, 2005)
The regulation
does not include
tiers of standards
December 19,
2005
Approximately 16%
reduction in NOx
emissions
CO: Carbon Monoxide
HC: Hydrocarbons
a Effective dates depend on Engine Size.
b This rule also applies the Tier 1 standards to Category 1 and Category 2 engines with a displacement of
2.5 liters/cylinder and greater. The Tier 1 standards are equivalent to the MARPOL-Annex VI NOx and
began in 2004. Beginning in 2007, Category 1 and Category 2 engines must comply with the Tier 2
standards.
Source: EPA, Program Update: Reducing Air Pollution from Nonroad Engines, April 2003
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Appendix C
Agency Response to Draft Report
September 8, 2006
MEMORANDUM
SUBJECT: Comments on OIG's "Progress Report on EPA's Nonroad Mobile Source
Emissions Reduction Strategies"
FROM: William L. Wehrum
Acting Assistant Administrator
TO:	J. Rick Beusse, Director
Office of Inspector General
I am writing to provide you with the Office of Air and Radiation's comments on the draft
Inspector General Report, "Progress Report on EPA's Nonroad Mobile Source Emissions
Reduction Strategies," (No. 2005-001206, May 16, 2006). Thank you for the extended
opportunity to review and comment on this report.
The report has identified a number of important challenges for EPA as we try to reduce
air pollution from the few remaining categories of nonroad equipment where we have yet to
effect meaningful control. I am very concerned, however, as I discussed with Acting Inspector
General Bill Roderick on July 31, that the report does not reflect the important progress that we
have achieved thus far.
The first task OIG set out for this report was to determine "the effectiveness of EPA's
efforts to reduce nonroad mobile source emissions, particularly ozone precursor emissions." The
draft report, however, provides little evaluation or analysis of the enormous progress EPA has
made in reducing ozone precursors (and other pollutants) from nonroad sources. Since the Clean
Air Act Amendments of 1990, EPA has implemented standards for nearly every nonroad source
category. Millions of engines, vehicles and equipment have been introduced into commerce in
the past decade that are cleaner because of these standards, resulting in substantial reductions in
air pollution. This has helped states meet the National Ambient Air Quality Standards for ozone,
particulate matter and carbon monoxide, in addition to providing meaningful public health and
welfare benefits. The report does not quantify these reductions, but instead indicates that EPA's
efforts to date will not have any impact for 20 to 30 years. This is an important issue which
should be addressed.
Please see the attached mark-up of the draft report for additional detailed comments.
I trust these comments will be helpful in completing your work on this report. Please feel
free to contact me or Bill Charmley (734-214-4466) if you have any questions about our
comments or if we can provide additional information.
Attachments
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Appendix D
Agency Memo on Projected Near-Term N on road
Emissions Reductions
August 25, 2006
MEMORANDUM
SUBJECT: Impact of EPA Nonroad Rules on Emissions for 2006 and 2010.
FROM: Craig Harvey and Penny Carey
Assessment and Standards division
TO:	John Koupal, Director, Air Quality and Modeling Center
Assessment and Standards Division
This memorandum documents the emission reductions for calendar years 2006 and 2010
projected to occur from all existing EPA nonroad emission standards, except aircraft standards.
The NONROAD emission inventory model was used for all nonroad source categories except
aircraft, commercial marine, and locomotive engines. For the two years selected, 2006 and
2010, NONROAD was used to estimate the national emissions inventory for total hydrocarbons
(THC), oxides of nitrogen (NOx), particulate matter less than 10 micrograms (PM10) and carbon
monoxide (CO). For each year, annual emission inventories were estimated for two scenarios.
First, inventories were estimated with no EPA emission standards in place. Second, emission
inventories were estimated with the current status quo, that is, with all EPA emission standards
which have been finalized as of August, 2006 assumed.
NONROAD does not currently have the capability to estimate emissions from aircraft,
commercial marine and locomotive engines. Emission estimates for these categories have
historically been done using spread-sheet models. For locomotive engines, the uncontrolled fuel-
specific emission factors contained in the 1997 locomotive final rule were used together with the
2006 and 2010 locomotive fuel use estimates in the 2004 Clean Air Nonroad Diesel Rule to
calculate the locomotive inventories with no EPA emission standards in place. The control
inventories in the 2004 Clean Air Nonroad Diesel Rule incorporate all EPA locomotive
standards which have been finalized to date, so these were used directly for the second scenario.
For commercial marine engines, the inventories with no EPA emission standards in place were
taken from the 1999 final rule affecting Category 1 and 2 engines, and the 2003 final rule
affecting Category 3 engines. The control inventories in the 2004 Clean Air Nonroad Diesel
Rule incorporate all EPA commercial marine standards which have been finalized to date, so
these were used directly for the second scenario.
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The inventories for the source categories were then combined for each scenario. The outputs of
these two scenarios were then compared and are summarized in Table 1.
Table 1: Emission reductions from all EPA nonroad standards, except aircraft

2
006
2010
Pollutant
Tons Reduced
Percent Reduced
Tons Reduced
Percent Reduced
THC
1,590,089
33%
2,449,807
47%
NOx
913,055
21%
1,558,322
33%
PM10
73,143
21%
117,147
33%
CO
3,145,113
10%
4,718,399
14%
The results of this analysis show, for example, that in 2006, EPA's existing emission standards
for nonroad sources are projected to have resulted in a 33% reduction in total hydrocarbons, a
reduction of 1.5 million tons, excluding the aircraft category.
In the future, the aircraft, locomotive, and commercial marine source categories will be included
in EPA's new emissions model, MOVES. If the aircraft category was included in Table 1, it
would show slightly greater emission reductions, in particular for NOx.
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Appendix E
Distribution
Office of the Administrator
Acting Assistant Administrator for Air and Radiation
Deputy Assistant Administrator for Air and Radiation
General Counsel
Agency Followup Official (the CFO)
Agency Followup Coordinator
Audit Followup Coordinator, Office of Air and Radiation
Associate Administrator for Congressional and Intergovernmental Relations
Associate Administrator for Public Affairs
Director, Office of Transportation and Air Quality
Deputy Director, Office of Transportation and Air Quality
Audit Liaison, Office of Transportation and Air Quality
Acting Inspector General
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