Office of Transportation EPA420-F-06-034
and Air Quality June 2006
Environmental Protection
Agency
Technical
Highlights
EPA's Diesel Retrofit SIP and
Conformity Guidance
The U. S. Environmental Protection Agency (EPA) has issued a
guidance document on how to incorporate emission reductions from
retrofits into implementation plans (SIPs) and conformity.
is the
This guidance document will help state and local air quality and trans-
portation planners:
* Quantify the emission reductions from retrofitting diesel vehicles,
engines, and equipment.
* Appropriately include the emission reductions from diesel retrofits
in a state implementation plan (SIP), to help demonstrate progress
toward, attainment of, or maintenance of national ambient air quality
standards.
* Appropriately include emission reductions from diesel retrofits in
transportation conformity or general conformity.
is
Technology is available today to reduce diesel vehicle and engine
emissions in a cost-effective way. Many diesel retrofit projects are
being successfully implemented around the country. Clean diesel
projects already initiated are expected to result in approximately
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20,000 tons of parti culate matter reduced over the life of the projects,
with estimated public health benefits of about $5 billion.
Diesel retrofit technologies reduce pollution from the existing diesel
engine fleet by up to 90% for particulate matter (PM), up to 50% for
nitrogen oxides, and up to 90% for volatile organic compounds.
The ability to use diesel emission reductions for SIP and conformity
purposes gives states and localities additional incentive to implement
diesel retrofit projects.
Retrofit projects provide a unique and cost-effective opportunity for
state and local governments to reduce pollution from highway and
nonroad diesel vehicle and equipment fleets, and as a result, could
assist areas in attaining the 8-hour ozone and PM25 national ambient
air quality standards.
Funding for diesel retrofits is available in the Safe, Accountable,
Flexible, Efficient Transportation Equity Act: A Legacy for Users, or
SAFETEA-LU. SAFETEA-LU continues to provide federal funding
for retrofit of highway diesel vehicles and engines under the exist-
ing Congestion Mitigation and Air Quality Improvement Program
(CMAQ), and expands CMAQ eligibility to include the retrofit of
nonroad diesel vehicles, engines, and equipment. SAFETEA-LU also
placed a priority on distributing CMAQ funds to diesel retrofits and
other cost-effective emission reduction activities while maintaining
the role of states and MPOs in selecting projects.
This guidance also fulfills EPAs requirement to develop guidance for
states to include emission reductions from diesel retrofits, required
by section 795(c) of the Energy Policy Act of 2005.
What does it mean to "retrofit" diesel vehicles and
engines?
The term "retrofit" is broadly defined to include any technology, device,
fuel or system that, when applied to an existing diesel vehicle or engine,
achieves emission reductions beyond that required by EPA regulations
at the time of a vehicle or engine's certification. Retrofit technologies
may include EPA verified emission control technologies and fuels and
CARB-verified emission control technologies. Note that diesel technolo-
gies are verified for specific types of vehicles or engines, defined in the
"applicability" sections of the EPA and CARB verified technology lists.
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(These lists can be accessed from: www.epa.gov/otaq/retrofit/retroveri-
fiedlist.htm)
What type of diesel vehicles and engines can be
retrofitted?
This guidance applies to both highway and nonroad diesel vehicles, en-
gines, and equipment.
• Highway: includes vehicles used on roads for transportation and
freight, such as diesel buses and trucks.
• Nonroad: includes vehicles, engines and equipment used for pur-
poses such as construction, agriculture, industrial operations, and
nonroad transportation.
Does the guidance cover replacement of vehicles,
engines, or equipment?
Yes, this guidance applies to the use of EPA certified engines as engine
replacements, or the early replacement of older vehicles or equipment
with cleaner vehicles or equipment. Emission reductions that result from
replacements that would have occurred through normal attrition are con-
sidered to be the result of normal fleet turnover and are not addressed by
this guidance.
How can emission reductions from diesel retrofits
be quantified for SIPs and conformity?
For states other than California, EPA recommends that the National Mo-
bile Inventory Model (NMEVI) be used for quantifying emission reduc-
tions from retrofits for SIP and conformity purposes. NMIM is a graphi-
cal user interface that contains the MOBILE6.2 and NONROAD2005
models and a database of county-level input information. Chapter 2 of
the guidance provides details on how NMIM can be used for SIP and
conformity purposes, including a summary of key inputs that are nec-
essary (for example, information about the fleet such as vehicle miles
traveled or hours of use) and issues that users may face when developing
input data. Before using NMIM, state and local air quality and transpor-
tation agencies should work together with EPA and the U.S. Department
of Transportation (DOT) to determine whether NMIM is appropriate
given local conditions and modeling methods and to determine what
modifications are needed to NMIM's database.
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EPA also acknowledges that alternative methods are available and others
may be developed. EPA will review any alternative methods for use in
SIPs and conformity on a case-by-case basis.
This guidance does not apply to the quantification of emission reductions
from retrofit projects in California. State and local agencies developing
SIPs and conformity analyses for California should consult with EPA
Region 9 for information on the current version of EMFAC approved for
use in California and for information on how to quantify emission reduc-
tions from retrofit projects.
What if I need to quantify emission reductions from
diesel retrofits for another purpose, like a grant
application?
NMIM could also be used to evaluate retrofit projects for other pur-
poses, such as the development of proposals for retrofit projects. For
these purposes, NMIM users could rely more on default data in NMEVI
or other more simplified methods for using NMIM. Other, more simpli-
fied approaches that do not rely on NMIM may also be appropriate for
non-SIP or conformity uses. Note that simplified approaches may result
in estimates that are not completely consistent with estimates using more
rigorous methods. Consultation between organizations developing proj-
ect proposals and state and local air quality and transportation agencies
about appropriate methods and interpretation of result is important to
ensure that retrofit projects are properly evaluated.
What are the basic requirements for using emission
reductions from diesel retrofits in SIPs?
Chapter 3 of the guidance explains how the basic requirements that all
control measures must meet in order to be included in a SIP - that emis-
sion reductions are quantifiable, surplus, enforceable, permanent, and
adequately supported - can be met with diesel retrofits.
Can diesel retrofits be included in a SIP under the
Voluntary Measures guidance (VMEP)?
Yes. If your retrofit control measure is approved under EPAs VMEP
guidance, the state is responsible for assuring that the reductions cred-
ited in the SIP occur. The state would need to make an enforceable SIP
commitment to monitor, assess and report on the emission reductions
resulting from the voluntary measure and to remedy any shortfalls from
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forecasted emission reductions in a timely manner. See Chapter 3 for
more information.
How can highway diesel retrofits be included in
transportation conformity?
Chapter 4 of the guidance covers this question in detail. Retrofits of
highway vehicles (such as buses and trucks) can be included in transpor-
tation conformity determinations without a SIP revision, by meeting the
requirements in the conformity regulation at 93.122(a).
Can emission reductions from nonroad diesel
retrofits be included in transportation conformity?
Yes, and there are two options that may be used to reflect reductions from
nonroad retrofit projects in transportation conformity determinations:
• Apply nonroad retrofit emission reductions as a "safety margin" to
the on-road motor vehicle emissions budgets through a SIP; or
• Establish a trading mechanism in the SIP to allow emissions to be
traded from one emissions sector to another.
Both of these options are allowed by the current transportation confor-
mity rule and are completed through the SIP process with consultation
among federal, state, and local air quality and transportation agencies.
An area may decide to pursue one of these options if it is anticipated that
emission reductions from nonroad retrofit projects may be needed to as-
sure future transportation conformity determinations. Please see Chapter
4 for additional information.
How is EPA streamlining the processes for using the
emission reductions from nonroad retrofit projects
in conformity?
EPA recognizes the importance of nonroad retrofit projects in reducing
emissions and wants to assist interested state and local air and transpor-
tation agencies. Chapter 4 and Appendices A through C of the guidance
include additional information for crediting nonroad retrofit projects in
the transportation conformity process using the two methods identified.
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Safety Margins
EPA has provided:
• Questions and answers about safety margins, beginning with Ques-
tion 4.6.
Step-by-step process instructions, including a flow chart, for adopting
a safety margin - see Appendix A.
• An example of how a safety margin is applied - see Appendix A.
• A list of areas that have adopted safety margins in the past - see
Question 4.11.
Trading Mechanisms
EPA has provided:
Questions and answers about trading mechanisms, beginning with
Question 4.12.
• Step-by-step process instructions, including a flow chart, for adopting
a trading mechanism - see Appendix B.
• An example of how a trading mechanism would work - see Appen-
dix B.
• A model rule that establishes a trading mechanism that interested
states could adopt through the SIP—see Appendix C. States that are
interested in establishing a trading mechanism merely need to copy
the model rule and fill in the blanks as appropriate (e.g., the appropri-
ate names of state air quality agencies and MPOs must be inserted),
and can adopt it into their SIPs. EPA developed this model rule in
consultation with DOT and state and local air quality and transpor-
tation organizations; therefore, states that adopt the model rule can
expect a streamlined SIP approval.
Could emission reductions from nonroad
diesel retrofits be used in general conformity
determinations?
Yes, emission reductions from nonroad diesel retrofits could be used in a
number of ways in general conformity determinations. See Chapter 5 of
the guidance for more information.
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Who can I contact for further information?
• You can access the guidance document, "Diesel Retrofits: Quantify-
ing and Using Their Benefits in SIPs and Conformity - Guidance for
State and Local Air and Transportation Agencies" (EPA420-B-06-
005, June 2006), on EPA's Office of Transportation and Air Quality
Web site at: www.epa.gov/otaq/stateresources/transconf/policy.htm
• General questions regarding retrofit projects or the application of
verified retrofit technologies for the existing fleet of highway and
nonroad vehicles can be directed to the National Clean Diesel Cam-
paign at cleandiesel@epa.gov.
Technical questions regarding the use of NMIM for calculating emis-
sion reductions from retrofit projects can be directed to mobile@epa.
gov.
• General questions concerning the use of emission reductions from
retrofit projects in SIPs or in transportation conformity can be di-
rected to Meg Patulski at (734) 214-4842, patulski.meg@epa.gov or
Gary Dolce at (734) 214-4414, dolce.gary@epa.gov.
• Questions concerning the use of emission reductions from retrofit
projects in general conformity can be directed to Tom Coda at (919)
541-3037, coda.tom@epa.gov.
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